Two-Component Polymeric Materials of Fullerenes and the Transition Metal Complexes: A Bridge between Metal-Organic Frameworks and Conducting Polymers.

Review pubs.acs.org/CR

Two-Component Polymeric Materials of Fullerenes and the Transition Metal Complexes: A Bridge between Metal−Organic Frameworks and Conducting Polymers Alan L. Balch† and Krzysztof Winkler*,‡ †

Department of Chemistry, University of California, Davis, California 95616, United States Institute of Chemistry, University of Bialystok, Hurtowa 1, 15-399 Bialystok, Poland

‡

ABSTRACT: In this review, we examined the interactions of metal complexes and metal surfaces with fullerenes. That information has been related to the formation of redox-active materials produced by electrochemical reduction of solutions of various transition metal complexes and fullerene or fullerene adducts. These redox-active polymers are strongly bound to electrode surfaces and display electrochemical activity in solutions containing only supporting electrolyte. Extensive studies of the electrochemical behavior of these films have been used to characterize their properties and structure. The process that produces these poly-PdnC60 and poly-PtnC60 films can also produce composite materials that consist of metal nanoparticles interspersed with the poly-PdnC60 and poly-PtnC60 materials. The relationship between these redox-active films and conducting metal organic framework materials has been examined. These insoluble, redox-active polymers have potential utility for the adsorption of various gases, for the construction of capacitors, for sensing, for the preparation of metal-containing heterofullerenes, and for catalysis.

CONTENTS 1. Introduction 2. Brief Overview of η2-C60 Complexes of Transition Metals 3. Interaction of Fullerenes and Transition Metals in the Thin Films Deposited from the Gas Phase 3.1. Fullerene Monolayers at the Transition Metal Monocrystal Surfaces 3.2. Metal Vapor Synthesis 4. Formation and Structure of Two-Component Polymers with C60 and a Transition Metal 4.1. Chemical Synthesis in Solution 4.2. Electrochemical Synthesis 5. Two-Component Polymers of Fullerenes and Transition Metals as a New Class of Conducting Polymers 6. Similarity between Two-Component Polymers of Fullerenes and Transition Metals and MOFs 6.1. General Properties of MOFs 6.2. Redox-Active MOFs 6.3. Comparisons of Redox-Active MOFs and Metal−Fullerene Frameworks 6.4. Progress in Preparing Fullerene-Based MOFs 7. Practical Application of Two-Component Polymers of Fullerenes and Transition Metals 7.1. Charge Storage Materials 7.2. Two-Component Materials Containing C60 and Transition Metal Polymer and p-Type Polymer 7.3. Analytical Application © 2016 American Chemical Society

7.4. Catalytic Properties 7.5. Gas and Vapor Adsorbents 7.6. Heterofullerenes Formation by Laser Ablation from Two-Component Polymers 8. Conclusions Author Information Corresponding Author Notes Biographies Acknowledgments References

3812 3816 3820 3820 3826 3830 3830 3834

3864 3865 3866 3866 3870 3870 3870 3870 3870 3871

1. INTRODUCTION Fullerene polymers represent a large class of materials in terms of their numbers, diversities in compositions, structures, and physicochemical properties. Fullerene polymers have potential applications in many different fields, such as catalysis, adsorption and separation, energy accumulation, electroactive battery material, hydrogen storage, and electronics. Fullerene moieties can either form a main polymeric chain or be included as guests within polymer pores. The most common structures of polymers containing fullerene moieties are shown in Figure 1. Giacalone and Martin reviewed the general field of fullerene-containing organic polymers in 20061 and again in 2010.2 This field was also the subject of several earlier reviews.3−5 In this introduction, we will begin with an

3837 3844 3844 3845 3851 3851 3852 3852

3858 3862

Received: September 28, 2015 Published: February 22, 2016 3812

DOI: 10.1021/acs.chemrev.5b00553 Chem. Rev. 2016, 116, 3812−3882

Chemical Reviews

Review

Figure 4. Selected structures of fullerene complexes of transition metals. Reproduced with permission from ref 79. Copyright 2003 American Chemical Society.

Figure 1. Fullerene-based macromolecular structures.

Figure 2. Schematic structure of transition metal/fullerene polymeric chain.

Figure 3. Structures containing fullerenes determined by the transition metal−fullerene π-electrons bonding.

overview of the fullerene polymer field before moving on to discuss the novel features of redox-active, two-component fullerene polymers. Like alkenes, fullerenes can form homopolymers through [2 + 2] cycloadditions. Formation of these structures can be induced through excitation by photons,6−9 and electrons,10 in plasma discharge,11 under high pressure,12,13 and by reduction of C60 with alkali metals14−19 or electrochemical reduction in solution containing Li+ cations.20 Ball milling of C60 and C70 can be used to form dimers and trimers when nucleophilic

Figure 5. Molecular structures of (a) η2-C60Pt(PPh3)2 (Reproduced with permission from ref 78. Copyright 1991 Science.) and (b) η2-C60Pd(PPh3)2 (Reproduced with permission from ref 88. Copyright 1993 American Chemical Society.). 3813


Chemical Reviews

Review

Figure 7. Structure of (η2-C60)Ir(CO)Cl(PPh3)2 as determined by X-ray crystallography. Reproduced with permission from ref 89. Copyright 1991 American Chemical Society.

Figure 6. Two views of the structure of C60[Pt(PEt3)2]6 as determined crystallographically. (a) Top view shows the C60[Pt(PEt3)2}6 core, while (b) the lower drawing shows space-filling van der Waals contours that show how effectively the surface of the fullerene is covered by the Pt(PEt3)2 groups. Reproduced with permission from ref 80. Copyright 1991 American Chemical Society.

catalysts are present.21,22 Electrochemical oxidation of C60 to the dication also leads to the formation of stable homofullerene polymeric films onto the electrode surface.23 The homopolymer and in-chain polymers form the so-called “pearl necklace” structures, while the side-chain polymer forms “charm bracelet” chains, as shown in Figure 1. These types of polymers can be used to form highly cross-linked, threedimensional structures that are insoluble in most solvents. The formation of side-chain or charm bracelet structures has been widely explored. Such materials can be formed during the polymerization of C60 and p-xylene.24 Free radical copolymerization25,26 and living anionic polymerization27,28 of styrene and C60 were found to result in the formation of in-chain C60-co-styrene polymers. Polyurethanes29 and amino-containing polymers30 are also used in the preparation of cross-linked charm bracelet fullerene containing polymers.

Figure 8. (a) Structure of (η2 -C 60 )Ir(CO)Cl(Ph 2 Pbob) 2 as determined by X-ray crystallography. Reproduced with permission from ref 93. Copyright 1997 American Chemical Society. (b) Stick drawing and a space-filling diagram of two molecules of (η2-C60)Ir(CO)Cl(Ph2Pbob)2 which show how the arms of the Ph2Pbob ligand encircle the fullerene portion of an adjacent molecule. Repetition of this motif creates infinite chains of these molecules in the crystalline solid. Reproduced with permission from ref 92. Copyright 1992 American Chemical Society.

There are two approaches to the formation of charm bracelet polymers: the reaction of a fullerene or fullerene derivative with a preformed polymer or polymerization of a monomer containing a fullerene, which becomes a pendant functional group. 3814


Chemical Reviews

Review

Figure 10. Drawing of the structure of one of the two independent molecules of (η2-C60)RhH(CO)(PPh3)2. The location of the hydrogen atom is presumed to be trans to the carbon monoxide ligand, but it was not located in the crystal structure analysis. Reproduced with permission from ref 95. Copyright 1993 American Chemical Society.

Figure 9. Structures of two different conformations of C60{Ir(CO)Cl(PPhMe2)2}2 as determined by X-ray crystallography in (a) C 6 0 {Ir(CO)Cl(PPhMe 2 ) 2 } 2 ·C 6 H 6 and (b) C 6 0 {Ir(CO)Cl(PPhMe2)2}2·2C6H6. There is a close benzene/C60 contact in the structure of C60{Ir(CO)Cl(PPhMe2)2·C6H6 that is not shown. Reproduced with permission from ref 90. Copyright 1992 American Chemical Society.

The [4 + 2] cycloaddition reaction between a fullerene and sidechain reactive dienes is a common method of C60 introduction into a polymeric backbone. This method was used to synthesize vinyl polymers with different benzocyclobutanone derivatives of C60 in the side chain.31 Poly(vinyl alcohol)s containing C60 were obtained via treatment of the polymer with sodium hydride. The anion that is formed reacts with fullerene cages to produce the charm bracelet structure.32 C60 was also grafted into an ethylene/propylene polymeric chain according to a free-radical mechanism.33 Another approach involves grafting of C60 using Friedel−Crafts reaction to poly(epoxypropyl carbazole).34 The side-chain containing C60 polymers can be formed from fullerene derivatives via chemical or electrochemical polymerization. Bis-hydroxydiphenyl-methanofullerene35−38 and its fluoro derivative39 were used in the synthesis of polyesters, polyurethanes, and polyethers containing C60 in the side chains. C60 containing vinylic monomer was used to incorporate fullerenes into alkylic polymeric chains.40 A variety of different C60 derivative monomers, such as bis(triethylsilyl)methanofullerene41 and biothiophene derivatives of C60,42−52 were used in electrochemical synthesis of C60 side-chain polymers. In these systems, both π-conjugated polymeric chains and fullerene moieties can transfer electrical charge. In end-capped polymers, the fullerene moieties are located at the terminal positions of a polymeric chain. The C60-end-capped poly(ethylene glycol) synthesized by Goh and co-workers53 is

Figure 11. Molecular structure of (η2-C60)Os3(CO)11. Reproduced with permission from ref 116. Copyright 1998 The Royal Society of Chemistry.

an example of such a structure. A variety of C60-end-capped polystyrene polymers were also synthesized.54 These macromolecular systems can exhibit star-like shape with fullerene molecules at the terminal positions.55−57 Fullerene molecules are also used as stoppers in aromatic poly(azomethylene) rotaxanes with cyclodextrin units covering the polymeric chain.58 In the star-shaped macromolecular structures, a small number of flexible polymeric chains are covalently bound to the fullerene cage. Usually the number of linked polymeric chains is limited to six. There are many examples of polystyrene grafted onto C60.59−64 The “living” anionic polymerization has been the method most frequently used for the formation of these systems. Polystyrene−C70-containing, star-shaped polymers have also been produced. 65,66 C 60 -poly(ethylene oxide), 67−71 C 60 -poly(vinylpyrolidine), 72 and C 60 -poly(acrylonitrile)73 systems are other examples of star-like polymers that have been synthesized and studied. The covalent bonding of two polymeric chains from two star-shaped units results in the formation of dumbbell structures. 3815


Chemical Reviews

Review

Figure 12. Structure of Ru3(CO)9(μ3-η2,η2,η2-C60) as determined by X-ray crystallography. Reproduced with permission from ref 118. Copyright 1996 American Chemical Society.

Polymers can also be doped with C60 without the formation of covalent bonds between the fullerene and the polymeric chains. For example, polyvinylcarbazole74 and poly[2-methoxy,5(2-ethylxexyloxy)-p-phenylenevinylene]75 have been doped with fullerene C60 or C70. A number of C60-containing polymeric materials exhibit good conduction properties. The electronic interaction between polymeric backbones which possess electron-donating properties and fullerene moieties that exhibit electron-accepting behavior makes these systems potentially useful in photoelectrical and photoelectrochemical technology.1−5 This review is focused on the formation methods and properties of two-component polymers of fullerenes and transition metal complexes.76,77 This class of coordinating polymers formally belongs to the main-chain cross-linked systems in which fullerene cages are bonded with transition metal atoms or ions to form polymeric backbone (Figure 2). The covalent interaction between fullerene and metal atoms or ions plays an important role in the polymerization process. Therefore, selected aspects of the interactions between fullerenes and transition metals in η2-C60 complexes and in thin fullerene layers deposited on the solid surfaces of transition metals are described (Figure 3). A strong electronic interaction between fullerene moieties is responsible for the good conductivity of polymers formed from fullerenes and transition metal complexes. The properties of these fullerene−transition metal polymeric materials and their practical applications are prominently discussed in this review.

Figure 13. (a) Molecular structure of (μ-η2:η2:η2-C60)Rh6(CO)9(dppm)2. (b) Molecular structure of (μ-η2:η2:η2-C60)2Rh6(CO)9(dppm)2(CNCH2Ph) fullerene dimer (top view), and molecular geometry showing the coordination modes of two dppm ligands. Two C60 ligands and phenyl groups except ipso carbons are removed for clarity (bottom view). Reproduced with permission from ref 121. Copyright 2002 American Chemical Society.

discussed in this section. In particular, the structures of complexes that are important from the point of view of twocomponent polymers of fullerene and transition metals will be considered. The majority of studies of fullerene−transition metal complexes have focused on C60. In the C60 structure, two different carbon−carbon bonds are present: 6:6 ring junction double bonds and 5:6 ring junction single bonds. The fullerene cage acts in a manner that more closely resembles an electrondeficient alkene derivatives than the relatively electron-rich molecules ethene or benzene.78 The chemical reactivity of fullerene C60 is mainly related to the double bonds at 6:6 ring junctions. During reactions with transition metal complexes, the

2. BRIEF OVERVIEW OF η2-C60 COMPLEXES OF TRANSITION METALS The η2-type metal−fullerene bonding is a key factor in the formation of transition metal−fullerene polymers. Therefore, the basic coordination chemistry of fullerenes will be briefly 3816


Chemical Reviews

Review

Figure 14. Cyclic voltammogram of (μ-η2:η2:η2-C60)2Rh6(CO)9(dppm)2(CNCH2Ph) at a scan rate of 10 mV s−1. Reproduced with permission from ref 121. Copyright 2002 American Chemical Society.

metal atoms generally coordinate to these double bonds in η2-fashion. The formation of mixed π−σ complexes is also possible in the case of addition of metal clusters to fullerenes. A selection of the possible structures of C60/transition metal complexes is shown in Figure 4.79 In the case of C60 complexes, multiple addition products may form with up to six metal atoms attached to the fullerene cage.80 The electronic structure of the fullerene cage is changed significantly upon metal complex formation. The metal bonding results in removal of one C−C double bond. In a polyene system that contains 29 remaining double bonds, the conjugation is expected to decrease. As a result, the energy of the LUMO increases and therefore the electron affinity of the fullerene cage decreases. The backbonding electron transfer from the d orbitals of the transition metal into the π* orbitals of fullerene causes an additional increase of the LUMO energy of the fullerene moiety. A consequence of metal coordination to the fullerene is also the change of the geometry of the environment of the carbon atoms involved in complexation. These atoms are pulled away from the surface of the fullerene. The degree of these changes can be described by the angle θ or the distance d in the following diagram. Figure 15. (a) Molecular geometry of Ir4(CO)3(μ4-CH)(PMe3)2(μPMe2)(CNR)(μ-η2,η2-C60)(μ4-η1,η1,η2,η2-C60) (top view) and expanded view of ligated C6 rings of the two C60 ligands (bottom view). (b) Cyclic voltammogram of Ir4(CO)3(μ4-CH)(PMe3)2(μPMe2)(CNR)(μ-η2,η2-C60)(μ4-η1,η1,η2,η2-C60) in chlorobenzene with [(n-Bu)4N]ClO4 as the electrolyte at a scan rate of 10 mV/s. Reproduced with permission from ref 122. Copyright 2003 American Chemical Society.

The binding of fullerenes to transition metals in η2-fashion has been observed for platinum, palladium, and nickel,81−88 iridium, cobalt, and rhodium,89−103 iron, ruthenium, and osmium,97,104,105 manganese,101,106 titanium,107 rhenium and tantalum,97,101 and molybdenum and tungsten.108−115 In particular, low-valent complexes of these transition metals undergo addition to fullerenes. The chemical and thermal stabilities of these complexes depend upon the particular compound added to the fullerene. The monoadduct (η2-C60)Pt(PPh3)2 was synthesized according to the following reaction.78,82 The structure of this platinum

fullerene complex as determined by single-crystal X-ray diffraction is shown in Figure 5a.78 The coordination geometry of the platinum atoms resembles that of the precursor (Ph3P)2Pt(η2-C2H4). The C−C distance between the carbons coordinated to platinum (1.502(30) Å) is considerably longer than the 6:6 carbon ring bond in the pristine cage (1.388(30) Å). The platinum carbon distances are 2.145(24) and 2.115(23) Å. A similar complex can also be formed by reaction of C60 with phosphine complexes of Pt, Pd, and Ni according to the 3817


Chemical Reviews

Review

geometry around the fullerene cage with each platinum atom coordinated to the C−C bond of 6:6 ring junction. The C60Pt6P12 core exhibits nearly ideal Oh symmetry. Such an octahedral arrangement of metal fragments is sterically optimal. Metallofullerene complexes can be also synthesized using Vaska’s complex, Ir(CO)Cl(PPh3)2, as precursor. Ir(CO)Cl(PPh3)2 and related complexes with different phosphine ligands react with C60 to form η2-C60 complexes, as shown in reaction (3).89 This is a reversible process, and the iridium complex can readily dissociate from the fullerene in dilute solution.

The structure of this complex, as determined by X-ray crystallography, is shown in Figure 7.89 Two phenyl rings are oriented parallel to the fullerene surface to make π−π contact, similar to the structure of (η2-C60)Pd(PPh3)2, as shown in Figure 5b. In addition to Ir(CO)Cl(PPh3)2, other Vaska-type iridium complexes have been added to C60.90,92 Synthesis with the complex Ir(CO)Cl(PPh2bob)2 (Figure 8a),93 which contains two phenyl rings in each side chain, results in the formation of singlecrystal supramolecular structure, as shown in Figure 8b.92 In this supramolecular architecture, each fullerene moiety is chelated by two side-chain phenyl rings through π−π interactions. Replacement of the phenyl groups in Vaska’s complex with alkyl groups results in the formation of complexes that are more reactive toward fullerenes. As a consequence, reactions of C60 with an excess of Ir(CO)Cl(PMe2Ph)2, Ir(CO)Cl(Et3)2, and Ir(CO)Cl(PMe3)2 lead to the formation of double addition products that can be crystallized from the solution.90,91 The structures of two of such solids are shown in Figure 9.90 Rhodium complexes of fullerene C60 can also be synthesized as shown in reaction 4.95,98,103Green crystals of (η2-C60)Rh(CO)H(PPh3)2 were obtained. The structure of the adduct Figure 16. Molecular structure of {Ni(Ph3P)}2(C60)2 dimers in {Ni(Ph3P)}2(μ2-η2,η2-C60)2·2C6H4Cl2 in their major orientation, as viewed along (a) and perpendicular (b) to the Ni Ni line. Carbon atoms are indicated in brown, nickel atoms are green, and phosphorus atoms are orange. Solvent molecules are not shown. (c) Bond lengths in the fragment in which two nickel atoms coordinate to two hexagons of the C60 molecules. Reproduced with permission from ref 125. Copyright 2014 Royal Society of Chemistry.

was determined using X-ray diffraction (Figure 10).103 The structure of this complex resembles that of the parent, Rh(CO)H(PPh3)3, with an η2-coordinated fullerene replacing one of the triphenylphosphine ligands. The complexes of fullerenes with transition metal clusters have been prepared by direct thermal reaction of the secondrow transition metal carbonyl clusters with C60 or by chemical activation of the third-row metal carbonyl clusters with Me3NO in acetonitrile followed by reaction with C60. Fullerenes can bind a variety of metal clusters via η2-C60, μ-η2:η2-C60 and μ-η2:η2:η2-C60 π-type bonding modes, acting as 2e−-, 4e−-, and 6e−-donor ligands, respectively. The η2-C60 complexes of Os, Ru, and Fe were produced by heating a toluene solution of C60 and metal carbonyls as shown for Os in eq 5.116,117 The structure of the product is shown in Figure 11.

reaction (2).82,87,88 The X-ray single-crystal diffraction structure of (η2-C60)Pd(PPh3)2 is shown in Figure 5b.88 The overall structure is similar to the platinum analog, with a slightly different location of the phenyl rings. In the case of the palladium complex, two phenyl groups are oriented parallel to the fullerene surface to make π−π contact. In the analogous platinum complex, such contact is absent. The reaction of an excess of Pt(PEt3)4 with C60 produces a stable hexa-addition product.80 C60[Pt(PEt3)2]6 has been crystallized as a single isomer and its structure determined by X-ray diffraction. The structure of this complex is shown in Figure 6.80 The six platinum atoms are arranged in octahedral

heating

Os3(CO)11(NCMe) + C60 ⎯⎯⎯⎯⎯⎯→ (η2‐C60)Os3(CO)11 toluene

(5)

A complex with three nuclear metal centers coordinated to the fullerene unit in μ-η2:η2:η2-fashion can also be synthesized. 3818


Chemical Reviews

Review

Figure 17. Molecular structure of fullerene dimer {Co(Ph3P)(C6H5CN)}2(μ2-η2,η2-C60)2 viewed perpendicular to (a) and along (b) the Co···Co line, coordination surroundings of a cobalt atom and the lengths of the Co−C, Co−P, and Co−N bonds (c), and a view perpendicular to the Co···Co line without Ph3P and C6H5CN ligands (d). Carbon atoms of Ph3P are pink, carbon atoms of C60 and C6H5CN are brown, nitrogen atoms are blue, phosphorus atoms are orange, and cobalt atoms are violet. Solvent molecules are not shown. Reproduced with permission from ref 123. Copyright 2013 American Chemical Society.

In the (μ-η2:η2:η 2-C60)2Rh6(CO)9(dppm) 2(CNCH2Ph) complex, the two fullerene ligands exhibited strong electronic communication.121 The voltammetric curves of this bis-fullerene complex exhibit a sequence of well-separated reversible reduction peaks in the negative potential range, corresponding to the sequential, pairwise transfer of electrons into the C60 centers (Figure 14). Schematically, this electron transfer process can be described by the following reaction

The reaction between C60 and Ru3(CO)12 in refluxing hexane or chlorobenzene leads to the formation of the (μ-η2:η2:η2C60)Ru3(CO)9 with the molecular structure presented in Figure 12.118,119 A similar complex can also be produced from (η2-C60)Os3(CO)11 during its thermolysis.117 The μ-η2:η2:η2-C60 complexes of osmium clusters can be converted to the complexes with μ-η2:η2-C60 coordination (μ‐η2 :η2 :η2 ‐C60)Os5C(CO)11(PPh3) +CO

2

+e

⎯⎯⎯⎯→ (μ‐η :η ‐C60)Os5C(CO)12 (PPh3)

←⎯⎯⎯⎯⎯⎯⎯ −CO

+e

C60−Rh 6−C60 ⇄ C60−−Rh 6−C60 ⇄ C60−−Rh 6−C60−

2

−e

(6)

+e

2−

−e

−

⇄ C60 −Rh 6−C60 ... −e

Metal clusters can also bridge two or more C60 moieties. Such C60−metal cluster sandwich compounds should serve as model systems for the two-component, transition metal/ fullerene polymeric structures considered later in this review. Several dimers in which two fullerene moieties are bridged by zerovalent metal complexes or metal clusters are known.120−123 The first example of a bis-fullerene adduct with a metal cluster bridging two C60 cages was synthesized in the reaction of the hexanuclear Rh complex, (μ-η2:η2:η2-C60)Rh6(CO)9(dppm)2 (Figure 13a), with an excess of C 60 in the refluxing chlorobenzene, followed by treatment with benzyl izocyanide121

(8)

The large peak separation in the three redox pairs of the two C60 ligands reflects very strong electronic communication between the two C60 moieties. Similar behavior was observed for a complex in which two fullerene ligands are bridged by an Ir4 metal cluster (Figure 15)122 and in (C60)2O where again two fullerenes are joined, this time by an oxygen atom and a C−C bond.124 Such interactions with significant delocalization of electrons over fullerene units can be expected between fullerenes in polymeric structures with transition metal atoms or clusters connecting the cages. As a consequence, these materials should exhibit good conducting properties. Fullerenes may also be bridged by a pair of metal complexes as seen in a number of recent studies by Konarev and coworkers.123,125,126 A diamagnetic dimer, {Ni(PPh3)}2(μ2-η2,η2C60)2, has been prepared by reduction of a solution of (η5C5H5)Ni(PPh3)Cl and C60 with zinc dust.125 The structure,

(μ‐η2 :η2 :η2 ‐C60)Rh 6(CO)9 + C60 → (μ‐η2 :η2 :η2 ‐C60)2 Rh 6(CO)9 (dppm)2 (CNCH 2Ph) (7)

The structure of this cluster complex is shown in Figure 13b. 3819


Chemical Reviews

Review

Figure 18. (a) View on the {Co(dppe)}2{μ2-η2:η2-η2:η2-[(C60)2]} dimer in {Co(dppe)}2{μ2-η2:η2-η2:η2-[(C60)2]}·3C6H4Cl2. (b) Selected bond lengths and angles in the coordination environment of cobalt atoms in {Co(dppe)}2{μ2-η2:η2-η2:η2-[(C60)2]}·3C6H4Cl2. Cobalt, carbon, and phosphorus atoms are in violet, brown, and orange, respectively. The ellipsoid probability is 30%. Phenyl substituents of dppe are omitted in b. Reproduced with permission from ref 126. Copyright 2015. American Chemical Society.

which is shown in Figure 16, involves two, three-coordinate nickel centers with bonds to one triphenylphosphine ligand and a double bond at a 6:6 ring junction of each of the two fullerenes present. The fullerene dimer {Co(PPh3)(C6H5CN)}2(μ2-η2:η2-C60)2 with two zerovalent cobalt atoms as bridges was synthesized and structurally characterized as shown in Figure 17.123 It was suggested that in this complex C60 can act as an effective spin coupler between paramagnetic metals. The synthesis involved reduction of a mixture of Co(PPh3)2Br2 and C60 with zinc metal in benzonitrile solution. When a similar synthesis was conducted using Co(dppe)Cl2 (dppe is bis(diphenylphosphino)ethane) instead of Co(PPh3)2Br2 the remarkable dimer {Co(dppe)}2{μ2-η2:η2-η2:η2-[(C60)2]} was formed.126 Its structure is shown in Figure 18. In contrast to the situation in {Co(PPh3)(C6H5CN)}2(μ2-η2:η2-C60)2, two new C−C bonds have formed in {Co(dppe)}2{μ2-η2:η2-η2:η2[(C60)2]}, and these bonds directly link the two cages. The resulting fullerene unit resembles that found by Komatsu and co-workers in the fullerene dimer (C60)2.127 Single metal atoms are also able to bridge two fullerenes. Mononuclear, bis-fullerene complexes of molybdenum and tungsten were also synthesized and characterized using X-ray crystallography.120

Figure 19. Growth of C60 on Pt(111). (a) Clean surface of Pt(111). (b) After deposition of 0.1 monolayer (ML), fullerenes diffuse on the platinum surface until finding steps in which they remain anchored at room temperature to form one-dimensional molecular lines. (c) 0.3 ML of C60, order islands grow on the terraces. (d) 0.5 ML of C60, STM image in which islands with different orientation can be seen. Black arrows indicate the direction of the nearest molecule. (e and f) Height profiles along lines marked in d. Scanned areas: (a−c) 100 × 100 and (d) 50 × 50 nm. Reproduced with permission from ref 128. Copyright 2011 Elsevier.

3. INTERACTION OF FULLERENES AND TRANSITION METALS IN THE THIN FILMS DEPOSITED FROM THE GAS PHASE 3.1. Fullerene Monolayers at the Transition Metal Monocrystal Surfaces

Two approaches to the study of interaction of fullerenes and transition metals in thin layers can be considered: (i) deposition

of fullerene monolayer or multilayer from the gas phase or solution onto the surface of transition metal crystal and 3820


Chemical Reviews

Review

parameters influencing the fullerene adsorption process on a metal surface include (i) the nature of the metallic solid phase, (ii) its crystallographic orientation, (iii) temperature, (iv) the interaction between the fullerene molecules in the monolayer, and (v) the number of monolayers deposited at the metallic surface. The selected structural data reported in the literature for fullerene adsorption at the surface of different metals are presented in Table 1. The structure of the fullerene adlayer is derived from a balance between the C60−C60 van der Waals interactions, which favor a simple hexagonal C60 layer with the nearest-neighbor distance close to 10.04 Å with the fullerene−substrate interaction perturbing this hexagonal structure. Selected structures for fullerene adlayers on the (111) surface of some transition metals are shown in Figure 20. Fullerenes have always chemisorbed onto all of the transition metal surfaces investigated so far.129 The degree of hybridization of the C60 molecular orbitals with the substrate electronic states and amount of charge transfer during fullerene binding depends greatly on the nature of the metal and the surface crystallographic orientation.129 Generally, the degree of charge transferred during fullerene chemisorption depends on the substrate work function. For metallic surfaces with a high work function such as Pt(111) (5.8 eV),158 a covalent interaction with a limited degree of charge transfer from metal to the C60 cage was observed.128,136 The formation of ionic adlayer structures was reported for Ni(110),156 Cu(111),159 Cu(110),159 Cu(100),159 Ag(111),139,140 Ag(001),141,142 and Au(110).149

(ii) codeposition of fullerene and transition metal from the gas phase onto a suitable substrate. To produce a fullerene monolayer on a transition metal surface from the gas phase, the fullerene is sublimed and slowly deposited at the metallic surface under high-vacuum conditions. A multilayer of fullerenes is formed at the metal surface. After subsequent annealing above the temperature of fullerene sublimation, only a monolayer of fullerenes that are strongly interacting with the metallic surface is left. The mechanism of C60 growth at the Pt(111) surface is shown in Figure 19.128 At low surface coverage, the C60 molecules exhibit large mobilities. The C60 molecules diffuse on the platinum surface until finding a step in which they remain anchored to form one-dimensional molecular lines (Figure 19b). The increase of the C60 surface concentration leads to the formation of two-dimensional islands at the metallic terraces. In the case of Pt(111), these islands exhibit two different orientations that are rotated by approximately 30° as shown in Figure 19c. Finally, the second layer grows in a 3-fold hollow position with respect to the first layer before this layer is completed. Similar behavior was observed for fullerene deposition on the Pd(110) surface.129 In the case of C60−transition metal interactions, bonding mechanisms from purely ionic to predominantly covalent can be expected.130 Additionally, a wide range of bonding strengths from diffusing molecules131−135 to strongly bonded species (resulting in well-defined molecular orientation with respect to the metal surface)136−138 can be observed. The most important

Table 1. Structure of Fullerene C60 Adlayer at Different Metal Monocrystal Surfaces metal surface

annealing temperature

structure of fullerene adlayer

Ag(111)

575 K

(2√3 × 2√3)R30° close-packed hexagonal phase

Ag(110)

650 K

Ag(001)

750 K

Ag(100)

∼450 K

Au(111) Au(110)

625 K 500 K

c(4 × 4) disordered close packing of C60 with 2-fold rotational symmetry quasi-hexagonal c(6 × 4) structure having the long axis along the [110] direction of Ag surface fcc (111) close-packed structure with locally disordered rhombic units (2√3 × 2√3) close-packed hexagonal phase P(6 × 5) zigzag structure

Au(001)

Pt(111)

Pd(110)

close-packed fcc(111) structure with some distortion

300 K

two hexagonal-packed domains rotated by 29 ± 3°

300 K

disordered monolayer

600 K

ordered overlayer with two quasi-hexagonal domains rotated by ∼30° ordered rotated-stripe structure

920 K 950 K 1000 K

Cu(111) Cu(110)

470 K

Ni(110)

575 K

Ni(111)

900 K

rectangular (4 × 5) phase rectangular (4 × 8) phase c(4 × 4) structure well-ordered hexagonal structure consists of three equidistant, parallel rows of C60 running along the [113] direction of substrate with C60 periodicity of 11.2 ± 0.1 Å C60 aligned in one-dimensional rows along the [001] direction of the substrate with adjacent rows varying in height rectangular (5 × 3) C60 phase c(4 × 4) close-packing structure 3821

nature of metal and C60 chemical interaction

ref

relatively weak charge transfer interaction with 0.75 e− per C60 exchanged primarily ionic C60−substrate interaction with filling π*-symmetry LUMO orbitals of C60 two kinds of ionic bonding of C60 to metal surface with different orientation and 2e− located at the C60 cage

139, 140 141, 142 132, 143 144

relatively weak interaction with 0.8 e− per C60 molecule transferred stronger ionic bonding in comparison to Au(111) resulting in the metal surface reconstruction charge transfer from substrate to C60 resulting in the strong chemisorption, metal surface reconstruction, and C60 deformation to an ellipsoidal shape strong covalent bonds with charge transfer < 0.8 e− 12 covalent bonds between carbon and 6 Pt atoms around vacancies formed during surface reconstruction charge transfer of ∼2 e− per C60, leading to fullerene immobilization chemisorption with C60 hexagonal rings on the on-top sites of Pt(111) with six carbon atoms to lie in the hollow sites the strong covalent interaction with 5−6 bond facing toward the substrate

145, 146 147−149

covalent bonding between C60 and Cu with 0.8 e− charge transfer per C60 weak chemical adsorption via 5−6 bond bridging between two close-packed rows of Cu crystal; intermolecular van der Waals interactions dominating the structure of adlayer strong C60−Ni interaction dominating the structure of adlayer and causes a nickel surface reconstruction to form (100) microfacets strong covalent interaction with 2 ± 1e− transferred from substrate to C60 strong covalent interaction

139

150

128, 136 151 152 153 154

155

156 156 157


Chemical Reviews

Review

The work function of these metallic surfaces is significantly lower than that of platinum.158 However, the work function is not the only parameter that influences the degree of charge transfer. Charge transfer during the fullerene chemisorption also occurs through the formation of chemical bonds between the adsorbed C60 and the metal surface.149 The effect of the distribution of the energy levels at the metal/C60 interface can be discussed by comparing the fullerene adsorption process at Cu(110) and Ni(110).160 For these two very similar metal surfaces, large differences in the nature of the metal−fullerene bonds and the structure of the fullerene adlayers were observed. For Cu(110), a disordered hexagonal overlayer is formed due to the dominance of the C60 intermolecular forces (Figure 21).160 Thus, the interaction between the metal surface and the adsorbed fullerene molecules is relatively weak. On Ni(110), the strong Ni−C60 covalent interaction dominates with higher charge transfer from the Ni to C60. Such a strong interaction leads to the reconstruction of the Ni(110) surface. The resulting (100) microfacets formed after the surface reconstruction become sites at which C60 are aligned in rows along the [001] direction of the substrate (Figure 22).160 Such differences in the structure of the fullerene adlayer in both cases can be explained on the basis of the electronic energy diagrams for the fullerene metal interphase, as shown in Figure 23.160,161 In the case of the Ni surface, the highest occupied molecular orbital (HOMO) (hu) orbitals of fullerene are close to the Ni 3d band. The interaction between these two bands leads to the covalent bond formation. In addition, the lowest unoccupied molecular orbital (LUMO) (t1u) band of C60 is energetically close to the 3d band of Ni. The strong hybridization interaction of these two bands results in electron transfer between the nickel d orbitals and the C60 LUMO band. For copper, in contrast to Ni, the d band is approximately 1 eV below the energy of the LUMO orbitals of C60, thus preventing effective hybridization of both orbitals. In this case, the interaction between the HOMO (gg + hg) orbitals of the fullerene and the 3d band of Ni is dominant. The changes of the energy of the electron levels due to the C60 adsorption on the metallic surface were measured using electron energy loss spectroscopy (EELS),162 UV photoemission electron spectroscopy (UPS), inverse UV photoemission spectroscopy (IUPS), or X-ray photoemission spectroscopy (XPS).130 The exemplary results of EELS studies of C60 adsorption at the Cu(111) and Ni(111) surfaces are presented in Figure 24.162 The first three energy loss peaks are assigned to the hu → t1u, gg + hg → t1u, and hu → hg transitions. In the case of the Cu(110) surface, the gg + hg orbitals are involved in the fullerene−metal bond formation and a significant change in the energy of the gg + hg → t1u transition in comparison to the fullerene multilayer film is observed (Table 2). The energies of the two other transitions remain unchanged. In the case of the Ni(110) surface, both the HOMO (hu) and LUMO (t1u) orbitals are involved with fullerene chemisorption. Therefore, all three transition peaks are observed at different energy losses in comparison to these of the fullerene multilayer (Table 2). XPS experiments provide quite quantitative information regarding C60−transition metal interactions in a monolayer of adsorbed fullerenes. Figure 25 shows the X-ray C 1s photoemission spectra of C60 on different metal (111) surfaces and the corresponding shake-up satellites.130 The increase of the negative charge state on the fullerene molecule results in shifting the photoemission line toward lower binding energies (Figure 25a). The degree of

Figure 20. (a) Proposed adsorption model of the C60 overlayer on the Cu(111) with a 4 × 4 superlattice. The intermolecular distance (C60−C60) is 10.2 A, equal to 4 times the Cu−Cu nearest neighbor distance. Three pentagonal rings located in thee upper portion of the C60 molecules are shaded for better view in the rotational freedom of each C60 molecule. Four domains are shown in (I), (I’), (II), and (II’), where each C60 occupies the hollow site. Reproduced with permission from ref 131 . Copyright 1993 American Physical Society. (b) Diagram showing the 7 × 7 and 2√3 × 2√3R30° structures for C60 monolayers on Au(111). In the 2√3 × 2√3R30° structure, every C60 molecule is at an atop position; in the 7 × 7 structure, there are in equivalent sites for C60 molecules: atop or bridge. The C60−C60 distances for ideal 7 × 7 and 2√3 × 2√3R30° structures are 10.08 and 9.98 Å, respectively. Reproduced with permission from ref 133. Copyright 2004 American Chemical Society. (c) Structures of Ag(111)−C60 phases. Reproduced with permission from ref 139. Copyright 1995 Elsevier. 3822


Chemical Reviews

Review

Figure 22. (a) 183 × 196 Å image of C60 on Ni, corresponding to a saturation coverage, in which the fullerenes are aligned in rows long the [001] direction of the substrate. The hexagonal structure is outlined on the image. (Inset) Height profile taken along the line indicated on the image. (b) Schematic illustration of the structure formed in a. The formation of added/missing [001] rows of Ni atoms creates the corrugated structure resulting in the formation of (100) facets and an increase in the C60 coordination to the Ni substrate. Reproduced with permission from ref 160. Copyright 1997 The American Physical Society.

Figure 21. (a) STM image (3 263 364 Å2) of the C60 structure formed on Cu(110) following deposition at 470 K. The structure is a distorted hexagonal overlayer in which every third row of C60 molecules is relaxed, thus forming a structure with a (113) periodicity. (Inset) Higher resolution image (783 102 Å2) of this structure in which both the hexagonal structure and (1103 0) periodicity are indicated. (b) Schematic model of the (1103 0) C60 structure formed on Cu(110) with the unit cell outlined. (c) Corresponding LEED pattern observed for this structure (E = 5.58 eV). Reproduced with permission from ref 160. Copyright 1997 The American Physical Society.

The mobility of the fullerene cages adsorbed on the metallic surface also depends on the nature and energy of the bonds formed. A strong interaction results in a reduced value of fullerene mobility. Strong chemisorption of fullerene molecules on the metal surface also prevents cage rotation. The localization of fullerene adsorption sites on the metal surface is fundamental to understanding the chemical nature of the C60-to-substrate bond. The C60 molecules were found to bind in many different orientations.151,153,163−165 In many cases, a six-membered ring of the fullerene faces the substrate. A schematic diagram for the C60 adsorption model for three different metal (111) faces is presented in Figure 26.153 In the case of the Cu(111) surface, two azimuthal orientations differing by 60° were reported. The six-carbon rings are accommodated on the hollow sites.131 Adsorption of C60 at the Pt(111) surface occurs on the top sites of platinum atoms with six carbon atoms

this shift is related to the amount of charge transferred from the metallic surface to the fullerene. The shake-up structure (Figure 25b) corresponds to the core-ionized final state, in which a valence electron is promoted from an HOMO to the LUMO level. The broadening of these structures and the disappearance of shake-up signals can also be regarded as a measure of the bonding interaction between C60 and the metal. For adsorption of C60 on Ni(111), the shake-up structure is broadened to the point of being unobservable, indicating the more covalent character of the C60−Ni bond. 3823


Chemical Reviews

Review

Figure 23. Diagram illustrating the electronic structure of Ni and Cu together with that of the C60 molecule. Adapted with permission from ref 160. Copyright 1997 The American Physical Society. Figure 25. (a) C 1s photoemission spectra for 1 ML C60 on Ni(110), Pt(111), and Ag(111) and for a thick film deposited on Ni(110). (b) Enlargement of the shake-up region for the same samples. Reproduced with permission from ref 130. Copyright 1999 Elsevier.

Figure 26. Schematic picture of the C60 adsorption model for a few (111) fcc surfaces. For the sake of clarity, only the bottom six-carbon ring, facing the surface, is drawn. (Left) Two adsorption sites (hollow) for the ionic C60/Cu(111) system. (Middle) Two adsorption sites (on top) for the covalent C60/Al(111) system. Only the on-top adsorption site is shown for the covalent C60/Pt(111) system. The three panels are drawn to scale. Reproduced with permission from ref 153. Copyright 2003 Elsevier.

coordination of fullerene moieties through the five-carbon ring was postulated.165 As mentioned above for the chemisorption of C60 onto the Ni(110) surface, the strong fullerene−substrate interaction very often results in metal surface reconstruction.160 Reconstruction of the monocrystal metal surface accompanying a strong adsorption of fullerenes was also observed for Pd(110),135,154 Au(110), 147−149 Au(001), 150 Ag(100), 144 Al(111), 166 Pt(111),151 and Pt(110).167 The interaction between the fullerene and the reconstructed metal atoms is much stronger and stabilizes the system. For example, in the case of the Pd(110) surface, the release of the substrate atoms during surface reconstruction results in stronger C60−Pd coordination for the stable C60 species accommodated in the forced microscopic pits.135,154 The results combined in Table 1 also reveal that the interaction between the fullerenes depends on the temperature of annealing. The morphologies of the fullerene layer on the Pd(110) surface at different temperatures are shown in Figure 27.154 Fullerene molecules are relatively weakly adsorbed at temperatures lower than about 700 K. C60 molecules aggregate into clusters, thereby strongly reducing the value of their mobility. At higher temperature, the formation of three,

Figure 24. Electron energy-loss spectra of 1 ML C60/Ni(111), 1 ML C60/Cu(111), and thick C60 film on Cu(111). b1, b2, b3, p, i indicate hu → t1u transition, gg + hg → t1u transition, hu → hg transition, π-plasmon, and ionization energies, respectively. Reproduced with permission from ref 162. Copyright 2003 Elsevier.

Table 2. Values for Selected Transitions Obtained from Electron Energy Loss Spectra162 energy loss (eV) fullerene form

hu → t1u

hu → hg

eg + hg → t1u

C60 multilayer C60 on Cu(110) C60 on Ni(110)

2.2 2.2 2.4

4.8 4.8 5.3

3.7 3.4 3.6

located at the hollow sites and interacting with the second Pt layer.153 Two covalent on-top adsorption sites were reported for Al(111). This orientation enables all six carbon atoms to remain close to the on-bridge sites of the substrate. In this case, only the interaction of fullerene molecules with the upper metallic layer is possible. In the case of the Au(111) and Ag(111) surfaces, 3824


Chemical Reviews

Review

Figure 27. (a) STM image of the triple-stripe phase (multilayer C60 annealed to 1000 K) consisting of alternating bright and two dark rows oriented along [11¯0] In the corresponding LEED pattern (E = 38.1 eV); the simulated spots for a (4 × 8) structure are overlaid. (Bottom) Suggested realspace model: The bright molecular rows seen in STM correspond to C60 molecules adsorbed in a vacancy formed by Pd atoms released out of the first layer. Dark molecular rows correspond to C60 molecules adsorbed in a vacancy formed by Pd atoms released out of the first two layers. The unit cell contains three C60 molecules; the area per C60 molecule amounts to 77.3 Å2. (b) STM image showing domains of alternating bright and dark rows along [11¯0] prepared by submonolayer C60 deposition at 720 K. This structure covers the entire surface when a C60 multilayer film is annealed to T = 950 K. In the corresponding LEED pattern (E = 38.1 eV) the simulated (4 × 5) spots are overlaid. (Bottom) Real-space model: Dark and bright C60 rows can be explained as in the triple-stripe phase. The unit cell contains two C60 molecules; the area per C60 molecule is 107.0 Å2. (c) STM image of the rotated-stripe phase. Alternating bright and dark rows are rotated by about 22° with respect to [11¯ 0] and shifted by one-half a molecular width. In the corresponding LEED pattern (E = 38.1 eV) the simulated spots of the (7/2 × 1/5) structure are overlaid. (Bottom) Realspace model: Dark and bright C60 rows can be similarly explained as in the (4 × 8) structure. The unit cell contains four C60 molecules; the area per C60 molecule amounts to 88.2 Å2. Reproduced with permission from ref 154. Copyright 2001 AIP Publishing LLC.

Figure 29. High-resolution STM image of a self-organized C60 island. C60 molecules imaged as bumps separated by 1 nm show no height variation and no intramolecular relief. Lines indicate close-packed ⟨110⟩ rows of molecules (60° angle). The arrow shows a vacancy within the self-assembled C60 lattice (9 × 15.5 nm2). Reproduced with permission from ref 170. Copyright 2002 Elsevier.

Figure 28. Valence bands for Cr and Ti overlayers on C60. Reproduced with permission from ref 169. Copyright 1993 The American Physical Society.

role in the evolution of these well-ordered fullerene surfaces. C60 is desorbed without decomposition at 1050 K.154 The C60 that is more weakly bonded to the Ag(111) and Au(111) surfaces desorbs at approximately 500 K.146 In the case of the strong covalent bonding of C60 to Pt(111) and Ni(110), the fullerene decomposition to metal carbides was observed upon heating to 1050 and 760 K, respectively.136 In the case of multilayer of fullerenes deposited at the metallic surfaces, the structure of the film changes with the increase of the distance from the substrate surface. For example,

well-ordered fullerene phases was observed. Upon annealing to 920 K, the rotated-stripe phase is formed (Figure 27a). Slow heating to 950 K results in the formation of the (4 × 5) phase (Figure 27b). The rows of C60 are aligned along the close-packed Pd rows. At 1000 K, the monolayer forms the rectangular (4 × 8) structure, with C60 rows aligned parallel to the close-packed Pd rows along [1−10] (Figure 27c). The rearrangement of the palladium substrate atoms plays a crucial 3825


Chemical Reviews

Review

Figure 30. Typical in situ STM images (a) 20 × 20 and (b) 12 × 12 nm2 of C60 adlayers on Au(111) in 0.1 M perchloric acid prepared by the direct transfer method. (b) Conditions were +0.10 V, − 0.05 V, and 0.8 nA for the electrode potential (Es), the tip potential (Et), and the tunneling current (Itip), respectively. (b) Conditions were +0.10 V, − 0.05 V, and 1.0 nA for Es, Et, and Itip, respectively. Reproduced with permission from ref 172. Copyright 2004 American Chemical Society.

C60 is arranged in the fcc structure on Ag(111) surface.139 However, in the range of a few monolayers, the hcp phase of C60 with azimuthal orientation of (100) plane parallel to the Ag(220) plane is preferentially formed.168 The reverse procedure, metal vapor deposition onto a fullerene substrate, was also used to study the C60−metal interaction.169 In Figure 28, the valence-band spectra of a Cr overlayer and a Ti overlayer on C60 are compared.169 The process of metal vapor bulk diffusion and metal−C60 compound formation competes with surface diffusion and metal nucleation. Fullerenes can also chemisorb at the metallic surfaces from liquid solutions. Marchenko and Cousty170 observed the formation of self-assembled hexagonal packing structure (Figure 29) with (2 √3 × 2 √3)R30° arrangement with respect to Au(111) lattice or an in-phase overlayer with ⟨111⟩ to C60 rows parallel to ⟨110⟩ Au during C 60 chemisorption from tetradecane. The formation of a hexagonal pattern of C60 characterized by a unit cell with a = 1.08 ± 0.07 nm at Au(111) was observed when deposition occurred from 1,2,4trichlorobenzene by Kunitake and co-workers.171 The same authors reported similar packing in C60 films prepared by deposition of fullerene Langmuir films from aqueous solution onto Ag(111) (Figure 30).172

Figure 31. HRTEM image of Co/C60 mixture film, including C60based polymeric chains. White arrows indicate several polymeric chains composing the double chains. In the left part of the image symbol “D” denotes two individual chains, coupling in the upper part. Magnified part of the HRTEM image, permitting one to distinguish the individual buckyballs along the chain. Scheme of the chain is shown in the right. Small and large circles correspond to the Co atoms and C60 molecules, respectively. Reproduced with permission from ref 183. Copyright 2006 Elsevier.

using the metal vapor synthesis method. It is clear that ionic interactions between alkali and alkali earth metal cations and fullerene anions are predominant in these fullerides. C60 doped with alkali metals forms a number of distinct and separate fulleride phases which can be donated by the generic formula MxC60.173−181 The number of doping alkali or alkali earth atoms depends on their size. For example, for small Na atoms an x value as high as 10 was reported.175 Fullerides of larger alkali metals (K, Rb, Cs) saturate at x = 6.176,177 Fulleride phases have also been obtained for transition metals. The high cohesive energy of transition metals favors the formation of thermodynamically more stable two-phase systems of metal and fullerene than the formation of ionic fullerides. In this case, the formation of covalent-type bonding between fullerenes and transition metals can stabilize the fulleride phases.

3.2. Metal Vapor Synthesis

The interaction between C60 and transition metals also determines the structure and composition of thin solid films formed using the metal vapor synthesis method. In this case, the fullerene and metal samples are evaporated simultaneously in high-vacuum conditions, and then the vapors condense on the solid surfaces at moderate temperatures. A variety of fullerides of alkali metal and alkali earth metals were formed

Table 3. Composition and Proposed Structure of Transition Metals−Fullerene Phases Formed by the Coevaporation− Deposition Technique metal Fe Co Ti Nb Sm

composition of metal− fullerene phase FexC60 (x = 3−4) TixC60 (x = 0−3.5) Ti4C60 NbxC60 (x = 0−5.5)

structure of metal−fullerene phase

ref

polymeric structure with the metal atoms connected by a η2-bonding to two neighboring C60 molecules one-dimensional polymeric chains −C60−C60−C60− with a complex ionic−covalent interaction between C60 and Co unbranched or branched polymeric chains ionic interaction with 1 electron transferred from Ti to C60 two-phase mixture of NbxC60 and C60; polymeric structure of NbxC60 with η2-bonding of two C60 with Nb C60 valence state of −1, −3, and −5 depending on the relative ratio of C60 and Sm; Sm atoms preferentially bonded to the five-membered ring of the C60 cage

182 183 184 185 186 187

3826


Chemical Reviews

Review

Figure 34. Time of flight mass spectrum of vanadium Vn(C60)m cations, (n = 0−7, m = 1−5). Reproduced with permission from ref 190. Copyright 1997 AIP Publishing LLC.

Figure 32. (a) XPS C 1s spectra for films with different Ti contents, obtained by coevaporating Ti and C60 onto a substrate heated to 100 °C. Ti concentrations (atomic percent) from bottom to top are (1) 0, (2) 2.3, (3) 3.6, (4) 5.5, (5) 8.4, (6) 12, (7) 19, (8) 31, and (9) 46. (b) XPS Ti 2p spectra showing a chemical shift of 0.84 eV for Ti2.4C60 compared to pure Ti. Reproduced with permission from ref 184. Copyright 1998 American Chemical Society.

Figure 33. Raman spectra of Ti-capped TixC60 films (x = 1.3, 2.4, 3.7, 5.6). A spectrum of pristine C60 (bottom) is also shown for comparison. Reproduced with permission from ref 184. Copyright 1998 American Chemical Society.

During the metal vapor synthesis, the formation of separate phases of fullerene and metal as well as a phase containing chemically interacting C60 and metal atoms can be expected to form. The amount of each phase in the deposited material depends on the vapor composition. Selected results obtained for transition metal and rare earth metal−fullerene composite phase formation using metal vapor synthesis method are presented in Table 3.

Figure 35. Proposed geometric structures of (a) V1(C60)2, (b) V2(C60)3, (c) V3(C60)4, and (d) V4(C60)4. Reproduced with permission from ref 190. Copyright 1997 AIP Publishing LLC.

The formation of a polymeric structure was suggested for the iron fulleride FexC60 (x = 3−4) based on the results of Raman 3827


Chemical Reviews

Review

Table 4. Precursors Used for Chemical and Electrochemical Formation of Two-Component Polymers of Fullerene and Transition Metal Complexes polymer chemical polymerization poly-PdnC60 (n = 1−3) poly-PtnC60 (n = 1,2) poly-Ru3C60 poly-[(CH3)3P]2NiC60 electrochemical polymerization poly-PdnC60 poly-PdnC70 poly-PtnC60 poly-PtnC70 poly-PtnC70 poly-RhnC60 poly-RhnC70 poly-IrnC60 poly-IrnC70 poly-AunC60 poly-AgnC60

precursor

ref

Pd2(dibenzylideneacetone)3 CHCl3 Pd(acetylacetonate) Pt(dibenzylideneacetone)2 Pt(1,5-ciclooctadiene)2 Ru3(CO)12 Ru(acetylacetonate) Ni[(CH3)3P]2Cl2 [Pd(CH3COO)2]3 Pd(PhCN)2Cl2 Pd(CH3COO)2 cis-PtCl2(py)2 PtI2(py)2 [Pt(μ-Cl)Cl(C2H4)]2 cis-PtCl2(py)2 [Rh(CO)2Cl2]2 [Rh(CF3COO)2]2 [Rh(CF3COO)2]2 [IrCl(cyclooctane)2]2 Ir(CO)2Cl(p-toluidine) AuCl(AsPh3) Ag(CH3COO)

194 198 195 196 197 198 199 Pd(CH3COO)2 trans-PdCl2(py)2

200, 201 202 203

trans-PtCl2(py)2 [Pt(μ-Cl)Cl(C2H4)]2

202 203 200, 202

[Rh(1,1-COD)2SO3CF3 RhCl3(py)3

202 200, 202 202 76 76

Ir(CO)2Cl(p-toluidine) (CH3)2SAuCl

Table 5. Dependence of Poly-PdnC60 Composition on the Conditions of Polymerization molar ratio of polymerization precursors Pd:C60

a

product composition

ref

1:1

Pd1.03C60a

Pd1.04C60b

194

2:1

Pd2.15C60a

Pd2.05C60b

194

3:1

Pd2.84C60

a

Pd2.64C60b

194

4:1

Pd3.57C60a

Pd3.27C60b

194

1:1

Pd1.55C60

c

2:1

Pd3.1C60c

204

3:1

Pd7.2C60c

204

Elemental analysis. metric analysis.

b

204

Electron probe microanalysis. cThermogravi-

interaction was confirmed by XPS (Figure 32) and Raman (Figure 33) spectra. A similar interaction was also postulated for Tix(η2-C60).184 The energy of C−C bonds of the fullerene cage is shifted toward lower energies due to the chemical interaction within the Ti/fullerene phase, for x < 3.5. An additional peak observed at approximately 284.8 eV is attributed to the formation of carbides in films containing higher amounts of Ti as shown in Figure 32a. Also, the XPS Ti 2p spectrum shows a chemical shift of 0.84 eV for Ti2.4C60 in comparison to metallic titanium (Figure 32b). In the Raman spectrum (Figure 33), line broadening of the peaks observed for TinC60 is ascribed to the distortion of the C60 cage. The energy of the Ag(2) mode at 1469 cm−1 shifts to lower wavenumbers as additional titanium atoms are added to the cage. These effects are related to charge transfer and covalent bond formation between the fullerene and Ti. Talyzin and co-workers suggested, however, that Ti atoms are intercalated into the fullerene crystal structure, similar to alkali metal fullerides, or that Ti atoms serve as a bridge in the formation of C60−Ti−C60 dimers.185

Figure 36. TGA plots for C60−Pd nanoparticles synthesized in benzene solution containing (a) 0.48 mM C60 and 0.73 mM Pd2(dba)3·CHCl3, (b) 0.48 mM C60 and 0.48 mM Pd2(dba)3· CHCl3, and (c) 0.48 mM C60 and 0.24 mM Pd2(dba)3·CHCl3. (Inset) First derivative in the temperature range of nanoparticles decomposition. Reproduced with permission from ref 204. Copyright 2014 Elsevier.

and XPS C 1s spectroscopy.182 Polymeric one-dimensional chains were also observed using a high-resolution, transmission electron microscope in material deposited from the gas phase of cobalt and fullerene (Figure 31).183 The EELS spectra confirmed the covalent bonding between Co and C60 with partial charge transfer from the metal to the fullerene cage. A strong covalent 3828


Chemical Reviews

Review

Figure 37. Schematic representation of the poly-PdnC60 (n = 1−3) formation. Reproduced with permission from ref 194. Copyright 1992 The Royal Society of Chemistry.

Figure 38. Diagrams of the proposed C60Pd3 structure: (a) the nearbcc unit cell (C60 not drawn to scale) and (b) the arrangement of C60Pd linear chains. (c) Distances of palladium to neighboring carbon atoms of C60.

Similar structure and bonding behavior was observed for Nbx(η2-C60).186 The fulleride phase was formed at x < 5.5, and fullerene decomposition to niobium carbide was observed when a larger amount of metal atoms was codeposited in the material. During the codeposition of Sm and C60, three different fulleride phases were detected with the valence state of the fulleride equal to −1, −3, and −5.187 Zhao and coauthors187 postulated that the five-membered rings of C60 are involved in bonding Sm to form a ferrocene-like structure. In the case of Ag−C60188 and Sn−C60189 films formed by the metal vapor synthesis method; two separate phases of fullerene and metal were formed. Silver is incorporated into the fullerene structure in the form of nanoparticles. Fullerenes doped with a metallic phase exhibit higher conductivity. The formation of transition metal/fullerene binary clusters was also accomplished using gas-phase, laser vaporization methods.190−193 The time-of-flight mass spectrum of the V−C60

Figure 39. SEM images of films formed from chemically synthesized polyPdnC60 in solutions containing a (a) 1:1, (b) 1:2, and (c) 1:3 ratio of C60:Pd. (Inset in b) Size distribution of cubic crystalline superficial structures. Reproduced with permission from ref 209. Copyright 2013 Springer.

system is presented in Figure 34. It shows the formation of a number of Vn(C60)m clusters with different compositions.190 Chain and ring structures were proposed for these clusters (Figure 35). Similar behavior was also observed for the Sc−C60,191 Ti−C60,191 Cr−C60,191 and Ag−C60192 systems. From the ionization energies, it was suggested that M−C60 binding in the clusters arises from the interaction between metal d orbitals and π electrons of the six-membered rings of the fullerene. 3829


Chemical Reviews

Review

Figure 40. TEM images of chemically synthesized poly-PdnC60 in benzene solution containing (a) 0.48 mM C60 and 0.24 mM Pd2(dba)3·CHCl3, (b) 0.48 mM C60 and 0.48 mM Pd2(dba)3· CHCl3, and (c) 0.48 mM C60 and 0.73 mM Pd2(dba)3·CHCl3. (d) Size distribution of poly-PdnC60 nanoparticles formed in benzene solution containing (1) 0.48 mM C60 and 0.24 mM Pd2(dba)3·CHCl3, (2) 0.48 mM C60 and 0.48 mMPd2(dba)3·CHCl3, and (3) 0.48 mM C60 and 0.73 mM Pd2(dba)3·CHCl3. Reproduced with permission from ref 204. Copyright 2014 Elsevier.

4.1. Chemical Synthesis in Solution

Figure 41. (a) TEM image of chemically synthesized poly-PdnC60 in benzene containing 0.48 mM C60 and 0.73 mM Pd2(dba)3·CHCl3. Arrows indicate palladium metallic nanoparticles. (b) TEM image of nanoparticles spot used for EDX analysis. (c) EDX spectrum of spot A of nanoparticle. (d) EDX spectrum of spot B of nanoparticles. (e) Changes of the intensity of palladium EDX signals along the l line. Reproduced with permission from ref 204. Copyright 2014 Elsevier.

Two-component polymers composed of C60 and a transition metal can be synthesized chemically in solution or through electrochemical deposition at the electrode surface. In the

chemical synthesis, a low-valent transition metal complex reacts with the fullerene to obtain polymeric poly-MnC60 material.

4. FORMATION AND STRUCTURE OF TWO-COMPONENT POLYMERS WITH C60 AND A TRANSITION METAL

3830


Chemical Reviews

Review

Figure 43. (a) Raman spectra recorded from samples with various initial Pd:C60 loading. (b) Expanded part of the spectra shown in a for the region near the Ag(2) mode of C60. Reproduced with permission from ref 211. Copyright 2007 Elsevier.

Figure 42. SEM images of poly-PtnC60 formed in solutions containing (a) [C60]:[Pt] = 1:1, (b) [C60]:[Pt] = 1:2, and (c) [C60]:[Pt] = 1:3 molar ratios.

In general, these polymers are insoluble in common organic solvents as well as water. The formation, structure, and properties of poly-PdnC60 were the most intensively investigated.194,198 The polymer is formed according to the following reaction

Table 6. IR Absorptions of C60, Poly-Pd3C60, and PolyPt1C60 compound

vibrations (cm−1)

F1u normal modes 528, 577, 1183, 1429 C60 poly-Pd3C60 Pd−C bond vibrations 280, 358, 426, 484 deformation vibrations 527, 560, 577, 670, 695, 733, 753, 778 vibrations of CC bond 1183, 1370, 1429, 1455, 1465 poly-Pt1C60 Pd−C bond vibrations 433, 462, 487 deformation vibrations 525, 558, 562, 578, 667, 695, 726, 736, 755, 775, 796 vibrations of CC bond 1184, 1183, 1425, 1457

C60 + n/2Pd 2(dba)3 CHCl3

ref 212 210

→ poly‐Pd nC603n/2dba + n/2CHCl3

(9)

The composition and structure of the product depend on the ratio of C60 to the metal complex used in the synthesis.194,204 Thermogravimetric analysis (Figure 36) indicates, however, that the amount of palladium in the deposited material is higher than that in the solution used for synthesis.204 The results obtained for the study of composition of polymeric material as a function of concentration of polymerization precursors in growth solution is summarized in Table 5. A mechanism for formation of poly-PdnC60 (n = 1−4) is schematically presented in Figure 37.194 With a large excess of palladium complex, a composite of poly-Pd3C60 and palladium nanoparticles is produced. Electron diffraction and highresolution electron microscopy studies demonstrated that poly-Pd3C60 exhibits an ordered body-centered cubic (bcc) structure of fullerene units with a slight rhombohedral distortion.205 The fullerene cage is octahedrally coordinated by six palladium atoms. Each palladium atom is bonded to two C60 units. The proposed structure of poly-Pd3C60 is shown in Figure 38a. The lattice parameter for this structure is a0 = 11.3 Å. The C60 molecules are closer to one another in the polymer than in the pure fullerene crystal face-centered cubic

196

The precursors used in chemical synthesis of two-components polymers of fullerene and transition metals are presented in Table 4. Nagashima and co-workers194,195 devoted much effort in the synthesis and study of the poly-PtnC60 (n = 1 and 2) and poly-PdnC60 (n = 1−3) macromolecular systems. These polymers were formed via reaction of fullerene with dibenzylideneacetone (dba) complexes of Pt(0), Pt(dba)2, and Pd(0), Pd2(dba)3CHCl3. The poly-PtnC60 polymer was also produced via reaction of C60 with Pt(1,5-cyclooctadiene)2.196 A carbonyl complex Ru3(CO)12 was used to synthesize polyRu3C60.197 The formation of C60−metal compounds was also reported for the doping of C60 with a small amount of palladium and ruthenium using metal acetylacetonates.198 3831


Chemical Reviews

Review

Figure 45. Energy diagram of frontier Kohn−Sham orbitals for the 1Ag state of {Ni(Me3P)2}4(C60)5 calculated at the RCAM-B3LYP/ LanL2DZ/6-31G(d,p) level of theory. Reproduced with permission from ref 199. Copyright 2014 American Chemical Society.

Figure 44. Structure of the nickel−fullerene polymeric chain in {Ni(Me3P)2}4(C60)5 at 280 K viewed along the c and a axes (a and b, respectively). View of the crystal structure of {Ni(Me3P)2}4(C60)5 along the polymeric chains and the b axis (c). Short interfullerene C···C contacts are shown by green dashed lines. Only the major orientation of C60 is shown. (d) Two types of coordination surrounding nickel atoms in the major (left) and minor (right) orientations of C60 at 280 K. Reproduced with permission from ref 199. Copyright 2014 American Chemical Society.

(fcc) structure, which has a lattice parameter of a = 14.13 Å. The orientational ordering of fullerene molecules with strong bonding to palladium atoms prohibits their free rotation, in contrast to fullerenes in pure crystals. EXAFS studies indicated that the Pd atoms are located at the center of the CC bond between two hexagons of the fullerene cage (Figure 38b). The distances to the neighboring carbon atoms are 2.27(3) and 2.37(5) Å.206 The XPS spectra of poly-Pd3C60 indicate that charge is transferred from the metal atoms to the C60 moieties during bond formation.207 Chemically formed poly-Pd3C60 reacts with tertiary phosphines to produce monomeric (η2-C60)Pd(PR3)2.208 The ability to extract the (η2-C60)Pd unit from the polymers via reaction with ligands constitutes significant evidence for the presence of the C60−Pd covalent interaction in the polymer. In the XRD pattern of poly-PdnC60 (n = 1−5), only certain broad and weak features are observed, indicating that the sample is nearly amorphous. Additionally, broad, low-intensity peaks from metallic palladium were found for materials with a molar ratio of Pd:C60 higher than 2:1. The morphology of the chemically synthesized poly-PdnC60 containing different ratios of fullerene to palladium is shown in Figure 39.209 When the Pd complex to C60 ratio was lower than 3:1, the product precipitated from the solution to form irregular

Figure 46. Multicyclic voltammograms for (a) 0.25 mM C60 and 0.85 mM Pd(ac)2 and (b) 0.25 mM C70 and 0.85 mM Pd(ac)2 in acetonitrile/toluene (1:4, v:v) containing 0.1 M (n-C4H9)4NClO4 recorded at gold disk Au (1.5 mm diameter). Sweep rate was 100 mV s−1. Reproduced with permission from ref 202. Copyright 2008 Springer.

cubic particles with size ranges from 20 to 80 μm. The cubic structures that are formed during chemical synthesis are 3832


Chemical Reviews

Review

The morphology of poly-PtnC60 is very similar to the morphology of the palladium analog. The polymer is deposited in the form of large cubic structures that are composed of nanometer-size spherical particles (Figure 42). The polymers of C60 and platinum can be also formed using low-valent Pt(1,5cyclooctadiene)2 in the synthesis.196 The IR and Raman spectra of poly-PtnC60 and poly-PdnC60 exhibit a large number of vibration modes compared to pure C60 due to the lowering of the Ih symmetry of the fullerene cage upon metal coordination.196,210,211 The IR vibration modes obtained for poly-Pt1C60 and poly-Pd3C60 are presented in Table 6. The vibration at 1370 cm−1 for poly-Pd3C60 may be attributed to the vibrations of the coordinated CC bond. The low intensity of this signal indicates that palladium is coordinated symmetrically at the center of this bond. The increase in the frequency of the doublet related to CC bonds not involved in complexation with metal atoms at 1420− 1465 cm−1 is related to the increase of the negative charge at the fullerene cage. Four bands observed in the low-frequency range are related to the tilting and stretching vibrations of the C60−M−C60 bonds. In Figure 43, the Raman spectra of poly-PdnC60 (n = 1−5) are compared.211 There is almost no effect of sample composition in the spectra. However, close examination of the frequency range of the Ag(2) mode (1300−1600 cm−1) can provide some qualitative information on the polymer structure. The Ag(2) vibration in pristine C60 is observed at 1469 cm−1. The presence of different Raman vibrations for the polymer indicates that different polymeric structures, such as chains, branched chains, and four-coordinated structures, can be found in the synthesized material.211 Zerovalent metal−carbonyl complexes can also be considered as good candidates for precursors of metal−fullerene polymers. In most cases, however, the carbonyl ligand substitution leads to the formation of (CO)mM(η2-C60) complexes.213−215 The formation of amorphous phase with a ruthenium:C60 molar ratio of 3:1 was reported for the reaction of Ru3(CO)12 with C60 in refluxing toluene.197 The air-stable solids formed from this reaction consist of an amorphous matrix embedding small ruthenium metal particles of an average size of 2−5 nm. An interesting approach to the formation of a polymeric network composed of fullerenes and transition metal complexes was recently published by Saito and co-workers.199 They obtained a one-dimensional polymeric chain in which C60 moieties are bonded with Ni[P(CH3)3]2 units in η2-fashion by chemical reduction of Ni[(CH3)3P]2Cl2 with metallic zinc. The structure of this polymer was determined by singlecrystal X-ray diffraction as shown in Figure 44. There are two orientations of C60. The lengths of Ni−C bonds are 2.107(1) and 2.132(1) Å for the major fullerene orientation and 2.121(1) and 2.116(1) Å for the minor orientation. These values are shorter than the distances between Pd and neighboring carbon atoms in poly-Pd3C60.206 The fullerene moieties approach each other very closely in the chain with a 9.693 Å center-to-center distance. These polymer chains are densely packed in a crystal with a 9.92 Å center-to-center distance between chains. The electronic structure of the nickelbridged C60 polymer was examined using density functional theory.199 The electronic diagram of an oligomer composed of five fullerene units is shown in Figure 45. The HOMO is located around the nickel and phosphorus atoms in the

Figure 47. Energy-dispersive X-ray fluorescence spectra of the polyPdnC60 films electropolymerized onto the Au foil electrode under cyclic voltammetry conditions. Molar concentration ratios of Pd:C60 in solutions and their mole ratios in films are indicated. Reproduced with permission from ref 216. Copyright 2003 The Royal Society of Chemistry.

Scheme 1. Formation of Poly-PdnC60 and Poly-PtnC60 by Electropolymerization

composed of smaller 160 ± 10 nm nanoparticles (inset in Figure 39) and can be easily converted into spherical nanoparticles with high-energy ultrasound. TEM images of the nanoparticles produced from large cubic particles of polyPd3C60 are shown in Figure 40.204 The size of the nanoparticles depends on the concentration of polymerization precursors, time of polymerization, temperature, and stirring conditions. TEM images also reveal the presence of smaller (ca. 2−50 nm in diameter) and more dense nanoparticles of metallic palladium (Figure 41). The size of these metallic nanoparticles expands with an increase in the ratio of Pd(0) complex to C60 concentration in the growth solution. Dispersions of polyPd3C60 nanoparticles are stable in many organic protic and aprotic solvents. The Hansen dispersive force parameter and the dipole−dipole interaction parameter govern the stability of these poly-Pd3C60 dispersions.204 The polymer of platinum and C60 obtained the same way exhibits only one composition, poly-Pt1C60.195 To obtain material with a higher molar ratio of Pt to C60, poly-Pt1C60 was heated in xylene to induce the following disproportionation reaction195 xylene,reflux for 24 h

2poly‐Pt1C60 ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯→ poly‐Pt 2C60 + C60

(10) 3833


Chemical Reviews

Review

Figure 48. TEM images and EDX spectra of the polymeric materials formed under cyclic voltammetry conditions in acetonitrile/toluene (1/4, v/v) solution containing (a) 0.27 mM C60, 3.56 mM Pd(ac)2, and 0.1 M (n-C4H9)4NClO4 and (b) 27 mM C60, 9.8 mM Pd(ac)2, and 0.1 M (n-C4H9)4NClO4. Arrows indicate palladium metallic nanoparticles. Reproduced with permission from ref 218. Copyright 2014 American Chemical Society.

voltammetry conditions) or by the time of deposition under potentiostatic or amperostatic conditions. The precursors used in the electrochemical synthesis of two-component polymers of fullerene and transition metals are presented in Table 4. The voltammograms of poly-PdnC60 and poly-PdnC70 deposition are shown in Figure 46.202 Under the same conditions, the yield of poly-PdnC60 formation is much higher than that of poly-PdnC70. Similar to the chemically grown material, the composition of the electrochemically formed polymer depends on the ratio of the concentration of precursors in growth solution. Figure 47 shows the XPS spectra of poly-PdnC60 formed in solution containing different molar ratios of Pd to C60.216 An increase of the concentration of Pd(ac)2 results in an increase in the Pd to C60 ratio in polymeric material. The electropolymerization process can be described by reactions presented in Scheme 1.217 Electroreduction of the Pt(II) and Pd(II) complexes and the formation of metal zerovalent intermediates, M0−C60, initiates the growth of the poly-MnC60 (M = Pt and Pd) film on the electrode surface (path B in Scheme 1), with the subsequent polymer growth stage involving many individual steps. Simultaneously, the deposition of the

Ni[P(CH3)3]2 units. The LUMO and LUMO+1 are localized mainly on the outer C60 cages. The theoretical calculations also indicate that the (CH3)3P ligands are slightly positively charged and that the negative charge is located on the fullerene units. The nickel centers are nearly neutral. The paper of Saito and co-workers199 opens a new area for chemical synthesis of twocomponent polymeric materials from fullerenes and transition metal complexes based on chemical reduction of metal complex to the low-valence state, which can coordinate fullerene cages. 4.2. Electrochemical Synthesis

The two-component polymers of fullerenes and transition metal atoms or ions can also be produced under electrochemical conditions. The potentiostatic, galvanostatic, or potentiodynamic reduction performed in solution containing a fullerene and certain transition metal complexes leads to the formation of dark colored films at the electrode surface. These films are insoluble in the solution from which they were grown and adhere strongly to the electrode surface on which they form. The amount of polymer deposited at the electrode surface and the thickness of the film can be controlled by the number of cycles (if the film is formed under cyclic 3834


Chemical Reviews

Review

Figure 49. (a) TEM image of poly-Pd3C60/Pd composite, and (b) changes of the intensity of palladium L and carbon K EDX signals along the l line. Reproduced with permission from ref 218. Copyright 2014 American Chemical Society.

Figure 50. (a) High-resolution transmission electron microscopy image and (b) selected area diffraction pattern of the poly-PdnC60 sample electropolymerized under multicyclic voltammetry conditions from 1.25 mM [Pd(ac)2]3 and 0.25 mM C60 with 0.10 M (n-C4H9)4NClO4 in a mixed acetonitrile/toluene (1/4, v/v) solution. Reproduced with permission from ref 216. Copyright 2003 The Royal Society of Chemistry.

metallic phase may occur (Path A in Scheme 1). The relative amount of the two products depends on the ratio of Pd(II) or Pt(II) complex to that of the fullerene in solution. At high concentration of metal complexes, the deposition of a metallic phase at the electrode surface occurs. The polymeric film morphology also depends on the ratio of polymerization precursors in solution.216,218,219 Figure 48 shows TEM images of material electrodeposited from solutions with two different ratios of concentrations of the polymerization precursors.218 The poly-PdnC60 polymer electrodeposited from the solution containing a lower concentration of Pd(ac)2 forms spherical particles of ca. 100 nm in diameter. For a high molar ratio of Pd to C60, relatively smooth films of uniform thickness are grown. TEM images of material formed from a solution containing a large excess of palladium(II) acetate reveal the presence of two different types of nanoparticles. Large poly-PdnC60 particles of ca. 200 nm in diameter along with small size (ca. 2−10 nm) and more dense nanoparticles (indicated by arrows in the inset of Figure 48) are formed. The changes of intensity of the fluorescence carbon K line and palladium L line during electron beam scanning along the diameter of the nanoparticles are shown in Figure 49.218 The palladium fluorescence signals measured along line l (Figure 49) abruptly change intensity when the electron beam approaches the edge of dense clusters. At the same time, the intensity of the carbon line remains unchanged. These results clearly indicate that the black spherical spots observed in the TEM images in Figure 48b represent palladium nanoparticles deposited on the surface of the polymer. The amount and size of the palladium nanoparticles expands with an increase of the [Pd]/[C60] ratio in the growth solution. In Figure 50,

Figure 51. Structure proposed for poly-RhnC60.

a high-resolution transmission electron microscopy image and a selected-area electron diffraction pattern are shown.216 A cubic crystalline phase of palladium metal is present in the film. The sample exhibits lattice planes with an interplanar distance of 0.22 nm and a mean palladium grain size in the range of 4 to 8 nm. The XPS studies of poly-PdnC60 films show evidence for direct covalent interaction between the palladium atoms and fullerenes, with approximately 0.8 e− per C60 transferred from the metal to the fullerene cage.216 Electrochemically formed 3835


Chemical Reviews

Review

Figure 53. Multicyclic voltammograms (a) and curves of the frequency changes vs potential simultaneously recorded at the same Au/quartz electrode in acetonitrile/toluene (1:4, v:v) containing 0.1 M (n-C4H9)4NClO4 and 0.25 mM C70 and 0.85 mM Pd(ac)2. Sweep rate was 25 mV s−1. Reproduced with permission from ref 202. Copyright 2008 Springer.

cages are apparently bridged by Rh2(CF3CO2)2 or Ir(CO)2 moieties.200,202 The expected two-dimensional structure of poly-RhnC60 is shown in Figure 51. The proposed structure resembles the architecture of typical metal−organic frameworks (MOFs). Such metal−fullerene framework (MFF) shown in Figure 51 can be modified to produce more complex structures via derivatization of the trifluoroacetic units. Poly-IrnC60 and poly-RhnC60 are formed at negative potentials, which is required for the formation of C602− ions. Voltammograms acquired during the formation of these polymers are shown in Figure 52.202 In the potential range of polymer deposition, the iridium and rhodium complexes are electrochemically inactive. The nuclephilic, double-negatively charged fullerene ions initiate the polymerization process. In the presence of a ligand that competes for occupation of the axial coordination sites of Rh2(CF3CO2)4, growth of polyRhnC60 is inhibited. Such behavior was observed in a solution containing pyridine. Two-component polymeric films of the larger fullerene C70 and transition metal complexes were also produced under electrochemical conditions using the same transition metal precursors.202 The yields of these films are higher than the yields of the C60 analogs. In the case of poly-PdnC70 and polyPtnC70, the mechanism of polymeric phase formation can also be described by Scheme 1. The electrochemical quartz microbalance technique (EQCM) can be very useful for mechanical studies of the electropolymerization processes. This technique allows one to monitor changes of the mass of the electrode related to the polymer deposition as a function of potential, time, or the charge corresponding to the polymerization process. Exemplary results obtained for the process of poly-PdnC70 deposition are shown in Figure 53.202 Upon repeated scanning of the potential in the negative range, an increase of the current related to the fullerene moiety reduction is observed with the increase of the scan

Figure 52. (a) Multicyclic voltammograms for (1) 0.25 mM C60 and 0.85 mM [Rh(CF3COO)2]2 and (2) 0.25 mM C70 and 0.85 mM [Rh(CF3COO)2]2 in acetonitrile/toluene (1:4, v:v) containing 0.1 M (n-C4H9)4NClO4 recorded at Au (1.5 mm). Sweep rate was 100 mV s−1. (b) Multicyclic voltammograms for (1) 0.25 mM C60 and 0.85 mM IrCl(CO)2(p-toluidine) and (2) 0.25 mM C70 and 0.85 mM IrCl (CO)2(p-toluidine) in acetonitrile/toluene (1:4, v:v) containing 0.1 M (n-C4H9)4NClO4 recorded at Au (1.5 mm). Sweep rate was 100 mV s−1. Reproduced with permission from ref 202. Copyright 2008 Springer.

poly-PdnC60 and poly-PtnC60 films, react with phosphines to produce the monomeric complexes, (η2-C60)M(PPh3)2 (M = Pt and Pd).203 This behavior is similar to the reactions observed for the chemically prepared poly-PdnC60 and poly-PtnC60 materials.195 In films prepared by reduction of fullerene in the presence of Rh2(CF3CO2)4 or Ir(CO)2Cl(p-toluidine), the fullerene 3836


Chemical Reviews

Review

Scheme 2. Schematic Structures of Functionalized Fullerene Polymers

Figure 54. Dependences of the mass of poly-Pd3C70 (Δm) deposited on the Au/quartz electrode under EQCM conditions on the charge of reduction (Q). The grown acetonitrile/toluene (1:4, v:v) solution contained 0.25 mM C70, 0.85 mM Pd(ac)2, and 0.1 M (n-C4H9)4NClO4. Sweep rate was 25 mV s−1. Reduction charge was calculated by integration of voltammetric curve shown inset. Arrows indicate potentials corresponding to the charges of the change of Q−Δm slope. Reproduced with permission from ref 202. Copyright 2008 Springer.

number (Figure 53a). A simultaneous decrease of the frequency response of an Au/quartz resonator indicates that a new solid phase is deposited on the electrode surface (Figure 53b). Figure 54 shows the dependence of the mass of poly-PtnC70 polymer, Δm, deposited onto the electrode surface on the charge of reduction, Q, obtained for the first voltammetric reduction sweep of the polymer deposition.202 The initial high mass increase is related to the metallic palladium deposition. The potential for palladium ion reduction process is approximately 50 mV less negative than the potential of the C70 reduction. At more negative potentials where the first fullerene reduction step occurs, the slope of the Q−Δm relation decreases due to the formation of the poly-Pd3C70 polymer and the inhibition of palladium deposition. At even more negative potentials corresponding to the second fullerene reduction step, a significant increase of the Q−Δm relation slope is observed. The increase of the negative charge on fullerene during its reduction favors the bonding of metal atoms to the fullerene, thereby increasing the rate of polymerization. The two-component polymers of palladium and a variety of fullerene adducts shown in Scheme 2 were also synthesized under electrochemical conditions. These adducts include the following: C60 with covalently attached ferrocene redox couples, 2-4;220−222 a C60−metal porphyrin dyad, 5;223 C60 with a covalently attached crown ether moiety having ion-exchange

properties, 6;224 C60 with an attached pyrrolidine unit, 7; and the C60/piperazine adduct, 8.225 Examples of voltammograms for the formation of two-component polymers of palladium with C60 adducts are shown in Figure 55. Polymerization occurs in the negative potential range. The films formed from these fullerene adducts are relatively flat and have uniform thickness. In all cases, the yields of polymerization from these C60 adducts are significantly lower than the yield of polymerization involving pristine C60.

5. TWO-COMPONENT POLYMERS OF FULLERENES AND TRANSITION METALS AS A NEW CLASS OF CONDUCTING POLYMERS Depending on the nature of the charge carriers, conducting polymers fall into two categories. The first group includes electroactive polymers in which electron transfer is responsible for charge mobility within the polymeric material. The second group involves ionic conducting polymers. In this case, the movement of ions incorporated within the polymeric chain is responsible for its conductivity. The electroactive polymers can be also divided into two groups: (i) redox polymers, which consist of an electronically insulating polymer matrix with attached redox sites, and (ii) conjugated polymers containing 3837


Chemical Reviews

Review

extended π-electron systems from which electrons can be withdrawn or into which additional electrons can be injected. These classes of conducting polymeric materials and their most common examples are described in Scheme 3. Electron transport through the redox polymers is governed by two major forces: the electric field and the gradients of concentration of the oxidized and reduced sites within the polymeric film.226,227 The elementary step in electron transport within the polymeric material is the transition from an occupied state (electron donor) to an unoccupied state (electron acceptor). The electron hopping is a bimolecular process between neighboring mixed-valence states. Depending on the structure of polymeric material, two mechanisms of electron transfer can be considered. Typical conducting polymers, such as polyaniline, polypyrrole, polythiophene, and their derivatives, behave as an insulator in the uncharged state. Oxidation or reduction of these polymers creates mobile charge carriers that are delocalized over several monomer units, which leads to continuous displacement of the electronic state densities. The motion of mobile charges along the polymeric chain is responsible for the conductivity of the polymeric material. Such systems with the energies of the states spread over a range of levels are called conjugated polymers. In the case of polymers with redox systems attached to the polymeric chain, the electron-donor and -acceptor sites are located at these redox-active moieties. These sites have identical energy levels. The charge transfer process can be described as an electron exchange between mixed-valence redox centers. In such redox polymers, the charge transfer is described by the electron-hopping model. The formation of additional charge on the main or side polymeric chain during the reduction or oxidation process is always accompanied by the transport of counterions from the solution to the polymeric phase. Most of the conjugated polymers exhibit p-doped properties. They undergo oxidation with simultaneous anion doping, as schematically described for polypyrrole in Figure 56. Polymers that exhibit n-doped properties are much less common. Investigation of n-doped polymers is more difficult compared to p-doped polymeric materials. Usually the very negative potentials are required for n-doping, and the reduced materials are very reactive and sensitive to traces of oxygen and water. Two-component polymeric materials of fullerenes and transition metals exhibit behavior very similar to that observed for conjugated organic polymers. One of the most remarkable properties of fullerenes is their electron-accepting ability, which allows them to form stable multianions.228 The fullerene moieties incorporated into the polymeric materials retain their electrochemical activity. Therefore, two-component films of fullerene and transition metal complexes or atoms exhibit electrochemical activity in the negative potential range.200−204 Behavior that is typical for conjugated conducting polymers with a large capacitance component is observed. The electrochemical properties of these two-component polymeric materials depend on the method of the film formation, the film morphology and composition, and the solvent and supporting electrolyte used. Examples of the voltammetric behavior of electrochemically synthesized poly-Pd3C60 recorded in solution containing different tetra(n-alkyl)ammonium (TAA+) perchlorates are shown in Figure 57.229 The reduction steps recorded at negative potentials are related to the reduction of the fullerene moieties. The electrode processes involving a solid phase deposited at the electrode surface are associated with the

Figure 55. (a) Cyclic voltammograms obtained for (1) 0.16 mM Fc−C60, (2) 0.16 mM Fc−C60 and 3.55 mM Pd(ac)2, (3) 0.16 mM bis-Fc−C60, and (4) 0.16 mM bis-Fc−C60 and 3.55 mM Pd(ac)2 in acetonitrile/toluene (1:4, v:v) containing 0.1 M (n-C4H9)4NClO4. (b) Sweep rate was 100 mV s−1. (b) SEM images of the poly-Pd3C60-Fc and (c and d) poly-Pd3C60-bis-Fc films formed on gold foil under cyclic voltammetric conditions after (a and c) 10 and (b and d) 40 in solution described above. Reproduced with permission from ref 222. Copyright 2011 Elsevier. 3838


Chemical Reviews

Review

Scheme 3. Classification of Conducting Polymers

plex to C60.209 The electrochemical activity of the chemically formed materials is similar to that reported for electrochemically synthesized poly-PdnC60. However, the electrochemical response of the chemically prepared material is not as reversible as the response of the polymeric films formed under electrochemical conditions. Additionally, the yield of reduction of the polymeric material is much lower in the case of the chemically synthesized polymer. The electrochemical reversibility and stability are among the most important factors determining practical application of redox-active materials. Differences between the reduction and the oxidation potentials and between the charge corresponding to the reduction and the oxidation processes can reflect the reversibility of the charge transfer process. These values are listed in Table 7.209 There is a decrease with an increase of the [Pd]:[C60] concentration ratio in the following order: 1:1, 2:1, and 3:1. For films formed in solution with [Pd]/[C60] higher than 3:1, a significant decrease in the reversibility of the electron transfer processes was reported. In solutions with a [Pd]/[C60] ratio higher than 3:1, composites of polymer and metallic palladium are formed. Such materials are less porous, and the transport of counterions during electroreduction becomes more difficult.216,219 This situation results in a lower

transport of ions of the supporting electrolyte in and out of the polymer to balance the charge within the solid phase. In the case of polymers formed from pristine C60, the cations of the supporting electrolyte participate in the electrode processes according to the following reaction

The current response of poly-PdnC60 depends on the size of the supporting electrolyte (Figure 57). The charges related to the polymer reduction and reoxidation processes decrease with an increase of the size of doping ions. The incorporation of the large tetra(alkyl)ammonium cations into the polymeric structure results in the lowering of its stability. Therefore, the reduction potential of the polymer is shifted toward less negative values with the increase in the size of the supporting electrolyte cation. The effect of film morphology is particularly important in the case of the electrochemical behavior of chemically synthesized material.209 Figure 58 shows the voltammetric behavior of the films formed from as-prepared poly-PdnC60 formed in solutions containing different concentration ratios of the palladium com3839


Chemical Reviews

Review

Figure 56. Schematic representation of charge transfer during polypyrrole electrooxidation.

Figure 58. Cyclic voltammograms of Au (1.5 mm diameter) electrode covered with chemically synthesized poly-PdnC60 at 100 mV s−1 in acetonitrile containing 0.10 M (n-C4H9)4NClO4. Mass of polymer deposited was 12.5 μg. The polymer was obtained in solution containing (a) 0.48 mM C60 and 1.46 mM Pd2(dba)3·CHCl3, (b) 0.48 mM C60 and 0.73 mM Pd2(dba)3·CHCl3, (c) 0.48 mM C60 and 0.48 mM Pd2(dba)3·CHCl3, and (d) 0.48 mM C60 and 0.24 mM Pd2(dba)3·CHCl3. Reproduced with permission from ref 209. Copyright 2013 Springer.

removal of electroactive material from the electrode surface. As a result, the current decreases almost to the background value observed for a bare gold electrode. Similar voltammetric behavior was also observed for polymers formed by electrochemical deposition from C70. Examples of the voltammetric responses of polymeric films containing C70 cages are shown in Figure 60.202 These films exhibit higher porosity in comparison to their C60 analogs. They also exhibit more reversible voltammetric behavior upon reduction at negative potentials. In addition, these films exhibit a higher potential range of electrochemical stability. Much more complex behavior is observed for polymers of fullerene adducts and transition metals than for polymers form from unmodified C60. The redox behavior of these materials is related to the electrochemical properties of both the fullerene cage and the functional groups attached to the C60 sphere. Figure 61 shows the electrochemical behavior of an electrode coated with thin films of poly-PdnC60Fc, compound 3 in Scheme 2, and poly-PdnC60Fc2, compound 4 in Scheme 2. The broad peaks observed at negative potentials are related to the fullerene-involved electrode process described by reaction 12.220,222

Figure 57. Multicyclic voltammograms of electrochemically generated poly-Pd3C60 films obtained in acetonitrile containing (a) 0.1 M (C2H5)4NClO4, (b) 0.1 M (n-C4H9)4NClO4, and (c) 0.1 M (n-C6H13)4NClO4. Sweep rate was 100 mV s−1.

rate of polymer formation when a composite of the polymer and metallic palladium is present. The electrochemical stability upon potential cycling also decreases with a decrease of the palladium(0) complex concentration (Table 7). The multicyclic voltammogram recorded over the large potential range for poly-Pd3C60 is shown in Figure 59.209 A slow decomposition process is observed when the potential approaches very negative values. Starting from the second voltammetric cycle, the reduction and reoxidation currents of the film slowly decrease. As the potential becomes more negative, the decomposition process becomes more rapid. In this case, multicycling of the potential results in the complete 3840


Chemical Reviews

Review

Table 7. Comparison of the Electrochemical Properties of Chemically Synthesized Poly-PdnC60 Films in Benzene Solutions Using Different Ratios of [Pd]:[C60]209 [Pd]/[C60] ratio in benzene solution

polymer composition

current density of R1 peak (μA μg−1)

difference of R1 and O1 peak potentials (mV)

negative potential limit of electrochemical stability (V)

slope of current−potential response (μA mV−1)

1:1 2:1 3:1 6:1

poly-PdC60 poly-Pd2C60 poly-Pd3C60 poly-Pd3C60 + Pd

5.41 4.05 2.70 0.95

210 150 110

1.3 1.5 1.7

0.221 0.216 0.170

Figure 60. Cyclic voltammograms of (a) poly-Pd3C60 and (b and c) poly-Pd3C70 films in acetonitrile containing 0.10 M (n-C4H9)4NClO4 (a and b) and 0.10 M (C2H5)4NClO4 (c) recorded at Au (1.5 mm). Sweep rate was 100 mV s−1. Poly-Pd3C60 and poly-Pd3C70 films were grown under cyclic voltammetry conditions in acetonitrile/toluene (1:4, v:v) containing 0.10 M (n-C4H9)4NClO4, 0.25 mM C60 or C70, and 0.85 mM Pd(ac)2. Reproduced with permission from ref 202. Copyright 2008 Springer.

Figure 59. Multicyclic voltammograms recorded at Au (1.5 mm diameter) electrode covered with chemically formed poly-PdnC60 in acetonitrile containing 0.10 M (n-C4H9)4NClO4 for different potential ranges. Sweep rate was 100 mV s−1. Mass of polymer deposited was 12.5 μg. The polymer was obtained in benzene solution containing (a) 0.48 mM C60 and 0.73 mM Pd2(dba)3·CHCl3, (b) 0.48 mM C60 and 0.48 mM Pd2(dba)3·CHCl3, and (c) 0.48 mM C60 and 0.24 mM Pd2(dba)3·CHCl3. Reproduced with permission from ref 209. Copyright 2013 Springer.

anions of the supporting electrolyte from the solution to the polymeric film (p-doping).220,222 The shape of the polymer oxidation peak with a lowcapacitance component is typical for a redox polymer using an electron-hopping model to describe the charge transport through the polymeric film. The mechanism of electron transport through the layer in both the negative and the positive potential ranges is schematically described in Figure 62. Polymers formed from pyrrolidine and piperazine derivatives of C60 also exhibit interesting electrochemical properties.225 The redox behavior of films formed from the C60 piperazine adduct, 8 in Scheme 2, is similar to that of the ferrocene derivatives of the C60. Thus, these films exhibit electrochemical activity in both the negative and the positive potential ranges. At positive potentials, the oxidation of piperazine adducts occurs. The number of oxidation steps observed depends on the number of addends attached to the fullerene cage. The electrochemical behavior of the polymers of pyrrolidine derivatives of C60 depends on the number of alkyl groups attached to the nitrogen.225 Poly-Pd3C60-pyr-CH3 exhibits redox properties similar to the properties of the polymer containing

The changes of frequency of the quartz crystal microbalance in the negative potential range are related to the transport of cations of the supporting electrolyte into the solid phase (n-doping). The sharp and symmetrical peaks that appear at positive potentials are related to the oxidation of ferrocene groups according to reactions 13 and 14. The electron transfer process in this case is accompanied by the transport of the

3841


Chemical Reviews

Review

Figure 61. Cyclic voltammograms of (a) poly-Pd3C60-Fc and (b) poly-Pd3C60-bis-Fc deposited in acetonitrile containing 0.10 M (n-C4H9)4NClO4 recorded at Au (1.5 mm). Sweep rate was 100 mV s−1. Polymeric films were grown under cyclic voltammetric conditions (20 cycles) in the potential range from +0.6 to −1.1 V in acetonitrile/toluene (1:4, v:v) containing (a) 0.16 mM C60−Fc or (b) 0.16 mM C60−bis-Fc, 3.55 mM Pd(ac)2, and 0.1 M (n-C4H9)4NClO4. Sweep rate was 100 mV s−1. Reproduced with permission from ref 222. Copyright 2011 Elsevier.

Figure 63. (Top) Cyclic voltammograms of poly-Pd3C60-pyr-(CH3)2+ in acetonitrile containing (a) 0.10 M (C2H5)4NClO4, (b) 0.10 (n-C4H9)4NClO4, and (c) 0.10 M (n-C6H13)4NClO4 recorded at Au (1.5 mm). Sweep rate was 100 mV s−1. Poly-Pd3C60-pyr-(CH3)2+ films were grown under cyclic voltammetry conditions in N,N-dimethylformamide containing 0.10 M (n-C4H9)4NClO4, 0.37 mM [C60-pyr(CH3)2]I, and 4.05 mM Pd(ac)2. (Bottom) Curve of the frequency change vs potential (a) and cyclic voltammogram (b) simultaneously recorded at the same Au/quartz electrode covered with poly-Pd3C60pyr-(CH3)2+ film in acetonitrile containing 0.10 M (n-C4H9)4NClO4. Sweep rate was 50 mV s−1. Reproduced with permission from ref 225. Copyright 2010 Elsevier.

Figure 62. Schematic representation of electron transfer processes during poly-Pd3C60‑Fc oxidation and reduction.

electrolyte. Such a film exhibits complex electrochemical properties in the potential range of the first reduction step.225 In this case, the electrochemical reduction depends on the nature of both the cations and the anions of the supporting electrolyte (Figure 63). In the potential range of the first reduction step, two voltammetric peaks are observed (Figure 63a). The mass of the polymeric film initially decreases and then increases during the film reduction (Figure 63b). The proposed

pristine C60. The electrochemical activity of this material is related to the reduction of the fullerene moiety, and the polymer reduction process is accompanied by the transport of cations from the electrolyte to the solid phase deposited at the electrode surface.225 The polymerization that occurs in solution containing C60-pyr-(CH3)2+, 7 in Scheme 2, results in the formation of the polymeric film doped with anions of the supporting 3842


Chemical Reviews

Review

reactions involving both anions and cation transport for the film reduction are given in eqs 15 and 16. In the case of polymers formed from a crown ether covalently modified C60 (shown as 6 in Scheme 2) and palladium complexes, alkali metal cations are complexed by the crown ether moieties and participate in electron transfer processes.224 The voltammetric response and the EQCM frequency changes obtained for the polymeric layer in tetra(n-butyl)ammonium perchlorate and LiClO4 in acetonitrile are shown in Figure 64. The opposite trends in the frequency changes in both cases are related to the complexation properties of the polymeric material. In the case of Li+ cations, which are easily coordinated by the crown ether moieties, the polymer reduction process can be described by reaction 17.

In the case of acetonitrile-containing tetra(alkyl)ammonium cations, which are too large to be coordinated by the crown ether moieties, the tetra(alkyl)ammonium cations are involved in the electrode charge transfer process, leading to the increase of the mass of material deposited at the electrode surface as shown in reaction 18.

The polymers of crown ether derivatives of fullerene can also behave as ionic conducting polymers. They can selectively complex alkali metal ions from the solution. Such process creates cationic charge carriers within the polymeric material. The movement of these ions forced by the electric field is responsible for the ionic conductivity of this material (Figure 65). Similar to the behavior reported for typical organic conjugated polymers, the conductivity of two-component polymers of transition metals and fullerenes depends on their oxidation state. Detailed studies of the in situ conductivity changes during the polymer reduction were determined for poly-PdnC60 using interdigitated arrays (IDA) electrodes.218 The IDA electrode was covered with C60−Pd polymer. The polymeric material connects neighboring bands of the IDA electrode. The conductivity was measured using the fourelectrode system shown in Figure 66. A small fixed potential, called the “drain potential” (VD), was maintained between two microelectrodes, called the source and the drain. At the same time, the potential of the “source” electrode (EG) was varied, thereby leading to the changes of the oxidation state of the

Figure 64. (a) Cyclic voltammograms of Au (1.5 mm) covered with (1) poly-Pdnbenzo-15-crown-5-fulleropyrrolidine containing 0.10 M LiClO4, (2) poly-Pdnbenzo-18-crown-6-fulleropyrrolidine in acetonitrile containing 0.10 M LiClO4, (3) poly-Pdnbenzo-18-crown-6fulleropyrrolidine in acetonitrile containing 0.10 M LiBF4, and (4) poly-Pdnbenzo-18-crown-6-fulleropyrrolidine in acetonitrile containing 0.10 M (n-C4H9)4NClO4. Sweep rate was 100 mV s−1. (b) Curves of the frequency changes vs potential recorded at the Au/quartz electrode coated with poly-Pdnbenzo-15-crown-5-fulleropyrrolidine film in acetonitrile containing 0.10 M LiClO4. Sweep rate was 20 mV s−1. (c) Curves of the frequency changes vs potential recorded at the Au/quartz electrode coated with poly-Pdnbenzo15-crown-5-fulleropyrrolidine film in acetonitrile containing 0.10 (n-C4H9)4NClO4. Sweep rate was 20 mV s−1. Films were grown under cyclic voltammetric conditions in acetonitrile/toluene (1:4, v/v) containing 0.10 M (n-C4H9)4NClO4, 3.10 mM Pd(ac)2, and 0.27 mM 15-crown-5-fulleropyrrolidine or 0.11 mM benzo-16-crown-6-fulleropyrrolidine. Reproduced with permission from ref 224. Copyright 2012 Springer. 3843


Chemical Reviews

Review

Figure 65. Schematic representation of alkali metal ion transfer within the polymer of crown ether covalently modified C60.

of magnitude of those for typical organic p-doped polymers. In Table 9, the conducting properties of selected organic conjugated polymers and poly-Pd3C60 are compared The presence of metallic nanoparticles within the polymeric phase influences the material’s conductivity. Figure 69a shows the dependence of the poly-Pd3C60/Pd composite conductivity on the potential EG for different values of VD. In this case, the increase of ID with increasing VD is also observed in a potential range that is less negative then the potential of fullerene reduction (range A in Figure 69a). In both potential ranges (A and B in Figure 69a), the conductivity linearly depends on VD, as shown in Figure 69b. The total resistance of the composite can be represented by two resistors connected in parallel, as shown in Scheme 4, where RPd represents the palladium nanoparticles-involved charge transfer resistivity and RC60−Pd is related to the conductivity of reduced polymeric phase of the composite. The values of both components and the total capacitance of the poly-Pd3C60/Pd composite are presented in Table 10. The palladium nanocrystals are significantly involved in the charge transfer process in the total conductivity of the composite material. The conductivity of poly-Pd3C60/Pd material in the potential range of fullerene cage reduction (potential range B in Figure 69a) depends on the size of the tetra(n-alkyl)ammonium cations. However, the supporting electrolyte does not affect the conducting properties of the composite at less negative values of the potential with respect to the potentials of polymeric phase reduction. The effect of the supporting electrolyte on the conducting properties of C60-Pd/Pd composite is shown in Figure 70.

Figure 66. Overview of the in situ conductivity setup.

polymeric film. The drain current (ID) measured as a function of ED potential provides the relative in situ conductivity. Figure 67 shows the conductivity changes of poly-Pd3C60 film deposited on top of the IDA as a function of the applied potential EG for different VD recorded in acetonitrile solution containing different tetra(alkyl)ammonium perchlorates. Upon reduction, the in situ conductivity of the C60−Pd film reveals initially a transition from a low-conductivity (range A in Figure 67a) to a conductive state, which is followed by the plateau of conductivity (range C in Figure 67a). The formation of the plateau of the in situ conductivity is most pronounced in the case of film doping with smaller tetra(ethyl)ammonium cations. The changes in conductivity correlate very well with the changes in the film reduction current recorded under voltammetric conditions. The conductivity depends linearly on the VD (Figure 68). The specific conductivities and electron diffusion coefficients obtained for poly-PdnC60 doped with different tetra(n-alkyl)ammonium cations are reported in Table 8.218 The conductivities and diffusion coefficients are within the order

6. SIMILARITY BETWEEN TWO-COMPONENT POLYMERS OF FULLERENES AND TRANSITION METALS AND MOFS 6.1. General Properties of MOFs

Metal−organic frameworks (MOFs) can be described as infinite crystalline networks resulting from the bonding of metal ions with polyfunctional organic ligands. They are stable nanoporous materials with high surface area and mechanical and thermal stability. MOF structures contain two main components: (i) metal center building units which acts as “joins” in MOF architecture and (ii) organic linkers which can be considered as “struts” that bridge metal centers. Metal centers in MOF structures are usually metal clusters, such as metal−carboxylate clusters,241 metal−azolate clusters,242 metal atoms, or rod-shaped clusters.243 The organic linkers are multidentate organic ligands, which are 3844


Chemical Reviews

Review

Figure 68. Dependence of the drain current on the drain potential for poly-Pd3C60 doped with (1) (C2H5)4N+, (2) (n-C4H9)4N+, and (3) (n-C6H13)4N+ cations at a gate potential of −1.3 V. Reproduced with permission from ref 218. Copyright 2014 American Chemical Society.

framework to leave free spaces available for another guest molecules. The removing of solvent molecules should not change the structure of MOF. Such structures are called as “open frameworks”. Most of the reported MOFs exhibit a microporous structure with a pore size lower than 2 nm.248−258 The number of compounds with a mesoporous structure (pore size, 2−50 nm) is limited.259−261 The formation of such materials requires the use of longer ligands, but MOFs built from large ligands have a tendency to collapse after solvate molecules or guest molecules are removed. As a result, the size of the pores is reduced and the entrance of large molecules to the MOF limited. The construction of mesoporous MOFs must be devised to extend the ligand size while inhibiting interpenetration and reinforcing the framework against disintegration upon guest removal.262 Due to the porous structure, MOFs can be very useful in gas storage,263 adsorption-based gas/vapor separation,264 selective catalysis,265 and drug storage and delivery.266,267 There are also numerous MOF applications in electroanalysis and electrotechnology.268 Due to the content of this review, we will focus on the electrochemical properties of MOFs and selected related applications.

Figure 67. Simultaneously recorded cyclic voltammograms and drain current, ID, at the gate potential EG, reflecting the in situ C60−Pd film conductivity changes in acetonitrile containing (a) 0.1 M (C2H5)4NClO4, (b) 0.1 M (n-C4H9)4NClO4, and (c) 0.1 M (n-C6H13)4NClO4. Drain current changes were measured for various drain potentials, VD, for which the values are given in the figure. Reproduced with permission from ref 218. Copyright 2014 American Chemical Society.

6.2. Redox-Active MOFs

Several reviews expressing interest in the expectations for electrically conducting MOFs are available.268−270 In the case of MOFs, both ion transfer and electron transfer can be responsible for the conductivity of these materials. MOFs have been recognized for their easy design as ionic component carriers. They could have highly concentrated mobile ions with dynamic behavior. From this point of view, MOFs can be considered as solid-state ionic conductors. Thus far, much of research in this area has been focused on ionic conductivity related to proton transfer. In the case of hydrophilic materials, the proton conductivity is mediated by water. For maximal performance, the framework should retain a large number of water molecules and the accommodated water should exhibit high mobility. This kind of proton conductivity was reported for the 2-D layer-type structure of R2dtoaCu (R = H, C2H4O,

usually carboxylates, azoles, nitriles, and others.244 The properties of metal centers and organic linkers determine the structure and function of target material, like porosity, pore size, pore distribution, and physicochemical properties.245 If the components of the network are well defined, the structure of MOF can be predicted.246,247 The large porosity is the main advantage of MOFs. Most of the practical applications of these materials require high and welldefined porosity. During MOF formation, solvent molecules may be incorporated into the crystal structure. The bonding energy of solvent molecules is the key factor determining the porosity of the framework structure. The MOF materials should contain highly disordered, weakly bonded solvent molecules that appear to flow freely through the void spaces of the well-defined 3845


Chemical Reviews

Review

Table 8. Conductivity Properties of C60−Pd Film in Acetonitrile Containing Different Tetra(alkyl)ammonium Cations218 cation of supporting electrolyte

yield of polymer reduction at −1.3 V

charge carrier density at −1.3 V (C·cm−3)

specific conductivity at −1.3 V σ (S·cm−1)

specific conductivity for Q = 8 C·cm−3 σ (S·cm−1)

electron diffusion coefficient γDe (cm2·s−1)

(C2H5)N+ (n-C4H9)N+ (n-C6H13)N+

0.65 0.33 0.13

45 23 8

0.7 0.25 0.1

0.25 0.075 0.04

2.4 × 10−7 6.4 × 10−8 3.5 × 10−8

Table 9. Specific Conductivities of Selected Conducting Polymers polymer polypyrrole (p-doped) polianiline (p-doped)

poly(N-substituted alkylpyrrole)s (p-doped) polythiophene (p-doped) poly(bithiophene) (p-doped) poly(trithiophene) (p-doped) poly(3,4-dimethylthiophene) (p-doped) poly(3-butylthiophene) (p-doped) poly(3-izobutylthiophene) (p-doped) poly(3,4-ethylenedioxythiophene) (p-doped)

poly(3,4-ethylenedioxythiophene) (n-doped) C60-Pd (n-doped)

conditions

specific conductivity (S·cm−1)

ref

(n-C4H9)4NPF6 in acetonitrile (C2H5)4NClO4 in acetonitrile (C2H5)4NClO4 in acetonitrile HCl + NaCl in water HCl in water (n-C4H9)4NClO4 in acetonitrile (n-C4H9)4NPF6 in acetonitrile (n-C4H9)4NPF6 in acetonitrile LiClO4 in acetonitrile (n-C4H9)4NClO4 in acetonitrile (n-C4H9)4NPF6 in acetonitrile (n-C4H9)4NPF6 in acetonitrile (C2H5)4NBF4 in acetonitrile (n-C4H9)4NClO4 in acetonitrile (C2H5)4NCF3NF3 in acetonitrile (n-C4H9)4NPF6 in acetonitrile Li(CF3SO2)2N in propylene carbonate LiBF4 in propylene carbonate LiClO4 in propylene carbonate (n-C4H9)4NClO4 in propylene carbonate (n-C4H9)4NPF6 in acetonitrile (n-C4H9)4NPF6 in acetonitrile (C2H5)4NClO4 in acetonitrile (n-C4H9)4NClO4 in acetonitrile (n-C6H13)4NClO4 in acetonitrile

1−10 5 × 10−6 24 2.2 220 0.005−0.3 10 0.6 0.2 1 150 10 ∼280 ∼420 ∼200 ∼180 13 5 3.4 0.7 ∼10 ∼0.05 0.68 0.23 0.07

230 231 232 233 234 235 236 236 236 235 237 237 238 238 238 238 239 239 239 239 240 240 218 218 218

transferred by hopping between different basic sites in guest molecules. In the structure of Na3(2,4,6-trihydroxy-1,3,5benzenetrisulfonate (Figure 72b), 1,2,4-triazole acts as a proton carrier.283 Proton carriers responsible for the anhydrous H+ conductivity can be also introduced in the structure of MOFs. In the 2-D layered structure of Zn(H2PO4)2(1,2,4-triazole)2, both ligands are coordinated to metal centers to form the MOF.284 The crystal shows anhydrous H+ conductivity in the range of 10−4 S cm−1 at 150 °C. Proton hopping is promoted by the rotation of the phosphate ligands. The crystal also shows anisotropy of conductivity. Ionic conductivity related to the transfer of other ions within the MOFs crystals has been also reported. The 1-D structures of Mg2(dobdc) (dobdc = 1,4-dioxida-2,5-benzenedicarboxylate) with honeycomb-like pores can transport Li+ ions.285 Counterions present in the ionic MOF can be also responsible for the conducting properties. [Co2Na(bptc)2](emim)3 (bptc = 2,2′,4,4′-biphenyltetraxarboxylate and emim = 1-ethyl-3-methylimidazolium) is example of such framework. In this case, the emim cations are responsible for charge transport, resulting in conductivity of 2.6 × 10−5 S cm−1.286 Much less attention has been paid to the electron transfer processes in MOFs. Such a mechanism for conductivity should be expected for frameworks with mixed-multivalent metal centers (Fe2+/3+, Cu+/2+, Ru2+/3+, and others)287 or electroactive linkers.288−290 In this case, the electron can be exchanged between neighboring redox centers of different valence.

C3H6O, C2H5; dtoa = dithiooxanide anion) shown in Figure 71.271−274 This material exhibits proton conductivity on the order of 10−5−10−6 S cm−1. A similar mechanism of proton transfer was observed in the 1-D chains of M(dhbq)· nH2O (M = Mg, Mn, Co, Ni, Zn; dhbq = 2,5-dihydroxy-1,4benzoquinone)275 and in the 2-D layered structure of Zn3(btp)(H2O)2·2H2O (btp = 1,3,5-benzenetriphosphonate).276 In these structures, well-ordered chains of water present in the interlayer or interchain spaces form a protonhopping path. Water-mediated proton exchange was also reported for M(OH)(bdc) (M = Al, Fe; bdc = 1,4benzenedicarboxylate).277 The conductivity of such systems can be enhanced by using a 2-substituted (−Br, −NH2, NO2, −SO3H) 1,4-benzenedicarboxylate.278−280 When one-half of bdc is replaced with 2-SO3H-bdc in the Al(OH)(bdc) framework, conductivity as high as 10−3 S cm−1 was observed under humid conditions. Anhydrous proton conductivity in MOFs is achieved by incorporation of protic organic molecules within the porous framework. Such systems exhibit conductivity at high temperatures (100−400 °C). Some exemplary systems that exhibit anhydrous proton conductivity are presented in Figure 72. The highly rotational imidazole in the channels of Al(OH)(ndc) (ndc = 1,4-naphthalenedicarboxylate) provides anhydrous proton conductivity in the range of 10−5 S cm−1.281 The same framework with histamine incorporated exhibits conductivity in the range of 10−3 S cm−1.282 In this case, the proton is 3846


Chemical Reviews

Review

achieved by incorporation of electroactive redox centers into the organic linker291,292 or as a guest within the pores.293−297 The electrochemical behavior of the electrochemically active MOFs depends on the framework conductivity and the nature of the solution. Usually the polymeric network exhibits poor electron−conductive properties. In this case, electrochemical reactions occur at the three-phase (electrode/MOF/solution) border, and it is followed by the surface transport of electrons. Figure 74 shows the voltammetric response of the [Al(OH)(bdc-NH2)1−x{bdc-NHC(O)Fc}x] in water and dichloroethane.292 In organic media, well-defined and stable redox behavior was observed. Rapid hopping of charges across the MOF surface was proposed to account for such reversible behavior. In aqueous media, the voltammetric response for ferrocene exhibits rapid decay due to dissolution of the MOF framework. In both cases, the anions are involved in the redox process due to compensation of the positive charge from the interstitial ferrocenium ions. Due to their unique porosity, flexibility, and electrochemical properties, MOFs have been successfully used as electroactive materials in lithium batteries,298−300 electrocatalysts,301−318 electroactive and conductive materials in fuel cells,319 electrode materials for supercapacitors,320−326 and inhibitors of corrosion.327−329 MOFs can be used as both positive and negative electrode materials. In either case, lithium-ion insertion into pores of the framework is used. For example, the mixture of carbon and Fe(OH)0.8F0.2(bdc)·H2O can incorporate up to 0.6 Li+ cations during lithium-ion battery discharge.298 MOFs that utilize the formate ion, such us Zn3(HCOO)6, Co3(HCOO)6, and Zn1.5Co1.5(HCOO)6, were used as negative electrode materials in Li-ion batteries. The best Li-storage properties were reported for Zn3(HCOO)6. The following conversion mechanism was proposed for this material during battery discharge300

Figure 69. (a) Simultaneously recorded cyclic voltammograms and drain current, ID, at the gate potential EG, reflecting the in situ polyPd3C60 + Pd film conductivity changes in acetonitrile containing 0.1 M (n-C4H9)4NClO4. Drain current changes were measured for various drain potentials, VD, for which the values are given in the figure. (b) Dependence of the drain current on the drain potential at gate potentials of (1) −0.5 and (2) −1.1 V. The composite of the polyPd3C60 polymer and palladium nanoparticles was synthesized under cyclic voltammetry conditions (20 cycles) in 0.27 mM C60, 9.8 mM Pd(ac)2, and 0.1 M (n-C4H9)4NClO4 in an acetonitrile/toluene (1/4, v/v) solution. Reproduced with permission from ref 218. Copyright 2014 American Chemical Society.

Zn3(HCOO)6 + Li+ + 6e− ⇄ 3Zn + 6HCOOLi

(19)

3Zn + 3Li+ + 3e− ⇄ 3LiZn

(20)

MOFs were also used as precursors for metal oxide nanoparticles formation suitable for application as electroactive materials in lithium-ion batteries.330,331 For example, calcination of Co3(ndc)3(dmf)4 (ndc = 2,6-naphtalenedicarboxylate, dmf = N,N′-dimethylformamide) leads to the formation of Co3O4 spherical nanoparticles with controlled structure and texture.330 Pyrolysis of ZnMn2−ptcda (ptcda = perylene3,4,9,10-tetracarboxylic dianhydride) MOFs precursors results in formation of ZnMnO4 novel anode materials as shown in Figure 75.331 MOFs with lithium ion incorporated into their pores were used also as a solid separator for lithium-ion batteries. The framework of Zn(II) bridged with benzenetribenzoate,332 Cu(II) bridged with triazolate,333 and Mg2(dobdc)285,334 were immersed in a solution containing lithium cations. Frameworks with lithium ion incorporated exhibit conductivity in the range from 10−7 to 10−4 S m−1. Much higher conductivity of 3.1 × 10−2 S m−1 was obtained for Mg2(dobdc) functionalized with Li isopropoxide, LiOPR) and next soaked with lithium cations in ethylene carbonate and diethyl carbonate mixture of LiBF4.285 MOFs can also catalyze many very important electrochemical reactions. Polyoxomethylate-based metal organic frameworks (POMOF) were found to be effective catalysts for hydrogen

Scheme 4. Equivalent Circuit for the Resistance of the C60−Pd/Pd Composite

Such electrochemically induced process in which electrochemically active metal centers are involved is schematically shown in Figure 73. The electrochemical activity of MOFs can be also 3847


Chemical Reviews

Review

Table 10. Conductivity Properties of poly-Pd3C60/Pd Film in Acetonitrile Containing Different Tetra(alkyl)ammonium Cations218 cation of supporting electrolyte

total specific conductivity at −1.1 V σ (S·cm−1)

specific conductivity at −0.5 V σPd/(S·cm−1)

specific conductivity at −1.1 V σC60−Pd (S·cm−1)

1.15 0.8 0.7

0.6 0.6 0.65

0.5 0.2 0.1

+

(C2H5)N (n-C4H9)N+ (n-C6H13)N+

Figure 72. (a) Structure of Al(OH)(1,4-ndc) (1,4-ndc =1,4naphthalenedicarboxylate) with guest imidazole. (b) Structure of [Na3(2,4,6-trihydroxy-1,3,5-benzenetrisulfonate)] with guest 1,2,4triazole. Reproduced with permission from ref 270. Copyright 2013 American Chemical Society.

Figure 70. Dependence of the drain current on the gate potential for a poly-Pd3C60/Pd film in acetonitrile containing (1) 0.1 M (C2H5)4NClO4, (2) 0.1 M (n-C4H9)4NClO4, and (3) 0.1 M (n-C6H13)4NClO4. Drain potentials were equal to 30 and −30 mV. Reproduced with permission from ref 218. Copyright 2014 American Chemical Society.

Figure 73. Schematic representation of the electron transfer process between mixed-valence redox centers in MOFs.

Various MOFs can also catalyze oxygen electroevolution. Zr6O4(OH)4(bpdc)6 doped with different iridium complexes shows catalytic activity upon water electrooxidation to form O2 in acidic aqueous media.302 Catalytic activity for anodic water splitting in alkaline media was observed for Fe(btc) MOF.303 MOFs can be used directly as catalysts or as precursor of catalysts in electrochemical oxygen reduction. MOFs with porphyrins as buildings blocks304 and Cu−bipy-btc MOF305 can be directly used as catalysts for oxygen reduction. The electrocatalytic effect of Cu−bipy-btc is shown in Figure 76. The catalytic process of oxygen reduction is observed in the potential range of the Cu(II)/Cu(I) redox step. The pyrolysis of various MOFs precursors, such as Co(II) and Zn(II) zeolitic− imidazolate frameworks, results in formation of effective oxygen reduction catalysts.335−338 Recently, Afsahi and Kaliaguine used a Fe-based MOF as precursor for a very effective electrocatalyst.338 The MOF exhibited a truncated octahedal structure which consisted of six [Fe4Cl]7+ squares and eight BTT3− ligands (H 3 BTT = 1,3,5-tris(2H-tetrazol-5yl)benzene) (Figure 77). In order to prepare this electrocatalyst, the Febased MOF was heat treated at temperatures ranging between 700 and 1000 °C. Upon pyrolysis, iron−nitrogen-containing carbon active sites (Fe/N/C) were formed in parallel with development of an electronically conductive carbon medium. This material shows catalytic activity upon oxygen electroreduction. It was also tested as a cathode in an H2/air fuel cell.

Figure 71. Structure of H2dtoaCu (H is omitted for the sake of clarity). Reproduced with permission from ref 271. Copyright 2003 Elsevier.

electroreduction.301 The following mechanism of hydrogen evolution was proposed for this material POMOF + 2e− + 2H+ → H 2POMOF

(21)

H 2POMOF2e− + 2Li(H 2O)n+ [Li 2(H 2O)2n POMOF] + H 2 (22) +

[Li 2(H 2O)2n POMOF] + 2H → H 2POMOF + 2Li(H 2O)n

+

(23) 3848


Chemical Reviews

Review

Figure 76. (a) Coordination geometry of Cu atoms in Cu−bipy-BTC. (b) XRD patterns of the as-prepared Cu−bipy-BTC (red curve) and the simulated one (black curve). (c) Typical SEM image of fully crystallized Cu−bipy-BTC sample. (d) SEM image of Cu−bipy-BTC after being immersed in water for 24 h. (e) Typical CVs obtained at the Cu−bipy-BTC-modified GC electrodes in 0.10 M phosphate buffer (pH 6.0) saturated with N2 (dotted curve) or O2 (solid curve). Scan rate, 20 mV s−1. (f) Typical RRDE voltammograms obtained with bare (black curves) and Cu−bipy-BTC-modified (red curves) GC electrodes as disk electrodes (solid curves) and platinum ring electrode (dotted curves) in 0.10 M phosphate buffer (pH 6.0) under airsaturated O2. Electrode rotation rate, 400 rpm. Scan rate, 10 mV s−1. Reproduced with permission from ref 305. Copyright 2012 Elsevier.

Figure 74. (a) Cyclic voltammograms (scan rate 20 mV s−1) for the oxidation of [Al(OH)(bdc-NH2)1−x{bdc-NHC(O)Fc}x] powder immobilized at a basal plane pyrolytic graphite electrode and immersed into aqueous phosphate buffer pH 9. Cyclic voltammograms (scan rate 15 mV s−1, pH (i) 5, (ii) 7, (iii) 9) for the oxidation of [Al(OH)(bdcNH2)1−x{bdc-NHC(O)Fc}x] in phosphate. (b) Cyclic voltammograms (scan rate (i) 10, (ii) 20, (iii) 50, and (iv) 100 mV s−1) for the oxidation of [Al(OH)(bdc-NH2)1−x{bdc-NHC(O)Fc}x] powder immobilized at basal plane pyrolytic graphite and immersed into dichloroethane with 0.1 M (n-C4H9)4NPF6. (c) Schematic description of the ferrocenyl MOF reactivity in aqueous and organic media. (d) Drawing of the pore redox process involving (i) removal of one electron, (ii) fast expulsion of one proton, and (iii) attack of the hydroxide on the framework. Reproduced with permission from ref 292. Copyright 2012 The Royal Society of Chemistry.

Figure 75. Illustration of the two-step process for the preparation of spinel ZnMn2O4 using ZnMn2−ptcda as a precursor by an “escape-bycrafty scheme” strategy. Reproduced with permission from ref 331. Copyright 2012 The Royal Society of Chemistry.

Figure 77. Crystal structure of an Fe−MOF, a cube of eight sodalitelike truncated-octahedral cages sharing square faces. Fe, yellow; C, gray; N, blue and Cl, green. Reproduced with permission from ref 338. Copyright 2014 The Royal Society of Chemistry. 3849


Chemical Reviews

Review

Figure 79. (a) Co−MOF-71 structure with the blue octahedral representing the Co(II) centers, the red ball oxygen atoms, and the black ball carbon atoms. (b) Life cycle of Co−MOF film in 1 M LiOH electrolytes. (Inset) Percent of specific capacitance retention (R). Reproduced with permission from ref 320. Copyright 2012 Elsevier.

are related to the material surface area (double-layer capacitance) and possibility of faradaic reactions (pseudocapacitance). Due to the highly porous structure and presence of metal-ion or linker redox centers, MOFs are potential candidates as electrode materials for electrochemical capacitors with improved energy density. Cobalt- and zinc-based MOFs were tested for their capacitance properties. Specific capacitances in the range of 150−200 F g−1 were reported for the Co-based MOF, Co(bdc)(DMF), in alkaline water solution.320 The structure of this framework consists of infinite chains of corner-sharing CoO6 octahedra, with each chain linked to four parallel chains via bdc linkers as is shown in Figure 79a. This material also exhibits excellent stability upon repeated charging and discharging (Figure 79b). Marken and co-workers demonstrated that in alkaline solution surface hydrolysis of Co(bdc)(DMF) leads to the transformation of the MOF into a porous cobalt hydroxide with high pseudocapacitance activity.339 The capacitance properties of Co-based MOFs can be manipulated by the molecular length of organic linkers.322 Different aromatic acids (benzendicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4-biphenylcarboxylic acid) were used in the synthesis of porous MOF materials whose SEM images are presented in Figure 80a. The capacitance properties of these materials were examined. Galvanostatic charge/discharge curves are shown in Figure 80b. The molecular length of the linker influences the pore diameter, surface area, and surface morphology. For synthesized materials, the specific capacitance, energy density, and power density were found to range from

Figure 78. (a) Illustration of the 2D structure of Co−MOCP (without guest molecules). (b) CVs of Co−MOCP/CPE in the absence (dotted line) and presence (solid line) of 5 mMGSH in pH 5.5 PBS. (c) Amperometric sensing of GSH by successive addition of GSH at Co−MOCP/CPE at 0.4 V in pH 5.5 PBS. (Inset) Plot of amperometric response versus the concentration of GSH from 2.5 μM to 0.95 mM. Reproduced with permission from ref 315. Copyright 2014 Elsevier.

MOFs were also used as catalysts for alcohols electrooxidation,306,307 nitrite reduction to N2O,308−311 bromate reduction,308,311 hydrogen peroxide reduction,311 hydrogen peroxide oxidation in alkaline media,312 selective electrochemical reduction of carbon dioxide,313 hydrazine electrooxidation,314 and redox catalysts for benzene oxidation with aqueous hydrogen peroxide to phenol. MOFs can also catalyze a variety of electrochemical processes involving biologically active molecules, such as electrooxidation of glutathione,315 316 L-cysteine, ascorbic acid,317 and NADH.318 Some of these reactions, for example oxygen reduction or alcohols oxidation, can be conducted in fuel cells. Other MOFs catalysts are used in electrochemical and electrobiochemical sensors construction. The analytical performance of a [Co(tib)2]·2NO3-based sensor for glutathione is shown in Figure 78.315 Many electrochemical studies of MOFs were focused on their capacitance properties.320−326 Charge storage properties 3850


Chemical Reviews

Review

shown in Figure 82c. The maximum specific capacitance of 250 F g−1 was reported for cyclic voltammetry conditions at low sweep rate. The symmetric capacitors based on the mesoporous carbon nanoparticles featured a specific energy of 10.9 W h kg−1 and specific power of 225 W kg−1. The mesoporous carbon materials formed from MOF-5-furfuryl alcohol composite also show excellent capacitance performance and stability in both aqueous basic and acidic solutions.341 A specific capacitance of ca. 200 F g−1 was reported for the material produced by pyrolysis of ZIF-8/furfuryl alcohol composite (ZIF-8 = Zn[N2C4H6]2).342 The heat treatment of MOFs results in formation of the metal or metal oxide nanoparticles embedded in a carbon matrix.344−350 Various metal oxides exhibit excellent capacitance properties.351,352 Cobalt oxide Co3O4 obtained by calcination of Co(bdc)2 MOF was tested as an electroactive material for electrochemical capacitors.353 The material shows a 3D structure of micrometer size and is composed of spheroidal particles 30−100 nm in diameter. Such a structure is responsible for its large specific surface area, 21 m2 g−1. The specific capacitance of this material was about 200 F g−1. 6.3. Comparisons of Redox-Active MOFs and Metal−Fullerene Frameworks

Two-component coordination polymers of fullerenes and transition metals (metal−fullerene frameworks (MFFs)) exhibit some structural similarities to those observed in MOFs. In these MFFs, the organic linkers are replaced with fullerenes, which can coordinate up to six metal centers to form polymeric networks. Such metal−fullerene frameworks exhibit highly porous structures similar to their metal−organic analogs. MFF structures in which fullerene cages are connected to metal atoms (Pd and Pt) or metal complexes (IrI, RhI, Ni0) were formed. In the second case, the metal centers are additionally coordinated by both organic and inorganic ligands. It can be also expected that similar to fullerene complexes of metal clusters,116−123 MFFs with metal clusters bonded to fullerene cages can also be produced. There are two major advantages to using fullerenes in place of organic polydentate ligands to form polymeric structures. The large sizes of fullerenes would seem to favor the formation of highly porous framework structures with large empty spaces available for guest molecules and ions. The π-electrons of the fullerene cage can also interact with d electrons of the metal center to form delocalized, conducting bands. Therefore, MFFs can exhibit good conductivity that is particularly important for their practical application in electrotechnology. The mechanism of charge transfer in MFFs is similar to that described for MOFs. In the case of polymers formed from fullerenes with attached electrochemically active groups, structures 2−5 and 8 in Scheme 2, the electron transfer occurs according to an electron-hopping model. The MFFs formed from crown ether derivatives of fullerenes exhibit ionic conductivity (structure 6 in Scheme 2) similar to MOFs. The practical applications of two-component polymeric materials described in the next section of this review are very similar to the practical applications of MOFs described above.

Figure 80. SEM images and galvanostatic charging−discharging cycles in 0.5 M aqueous LiOH electrolyte at 50 μA cm−2 of (a) Co−BDC, (b) Co−NDC, and (c) Co−BPDC metal−organic frameworks film. Reproduced with permission from ref 322. Copyright 2013 Elsevier.

132 to 179 F g−1, from 21 to 31 Wh kg−1, and from 3.9 to 5.6 kW kg−1, respectively.322 Recently, very high specific capacitances up to 600 F g−1 were reported for Ni−isonicotinic acid MOF.324 A large specific capacitance of ca. 725 F g−1 was also reported for thin films formed from Ni3(btc)2·12H2O.325 This material also displays very good electrochemical stability under cyclic voltammetry conditions. Asymmetric supercapacitors built using this nickelbased MOF as positive electrode and activated carbon as negative electrode exhibit good capacitance performance with an energy density of 16.5 W h kg−1. The structure of Ni3(btc)2· 12H2O MOF and capacitance performance of the electrode covered with thin film of this material are shown in Figure 81.325 It was also shown that nanocrystals of different MOFs can be doped with graphene and successfully incorporated into supercapacitors devices.323 A zirconium MOF exhibits an exceptionally high capacitance of ca. 5 mF cm−2, about 6 times that of the capacitance of commercial activated carbon materials. MOFs were also used as templates for the formation mesoporous carbon materials that can be used as electrochemical double-layer capacitors.340−343 The proper selection of a MOF allows mesoporous carbon with desired pores size, uniform distribution, and high surface area to be made. Pyrolysis of MOFs also leads to formation of metal oxides that can exhibit excellent capacitance properties. Direct carbonization of ZIT-8 MOF in which Zn clusters were connected by 2-methylimidazole linkers results in formation of nanoporous carbon materials with a very high specific area of 1523 m g−1 and an average pore diameter of ca. 1 nm (Figure 82a).340 The capacitance performance of thin films formed from such nanoparticles is

6.4. Progress in Preparing Fullerene-Based MOFs

Incorporating fullerenes into polymeric solid structures is currently an area of active investigation but one where there are considerable challenges. One of the earliest such compounds, C60{Ag(NO3)}5, was obtained by simply diffusing a solution of silver nitrate into a benzene solution of C60.354,355 Black crystals 3851


Chemical Reviews

Review

Figure 81. (a) Ni-based MOF chain, present as the building block in crystalline Ni3(btc)3·12H2O. (b) 2D sheet motif formed by interchain hydrogen bonds. Hydrogen bonding contacts are shown by the striped bonds. (Lower right corner) Photograph of as-prepared Ni-based MOF. (c) CV curves at different scan rates. (d) Cycle life of the Ni-based MOF electrode at a current density of 1 A g−1 in KOH electrolyte. Reproduced with permission from ref 325. Copyright 2014 Elsevier.

present in this polymer. The reaction of C60N(CH2CH2)2N with the rhodium(II) acetate dimer produces another polymeric chain, {Rh2(O2CCH3)4N(CH2CH2)2NC60}n·2nCS2, whose structure is shown in Figure 86.365 These chains are arranged so that the fullerenes protrude alternately on either side. This arrangement allows the chains to pack in an interdigitated fashion so that two C60 cages from an adjacent chain surround each C60 cage in the original chain. When C60N(CH2CH2)2N reacts with the rhodium(II) acetate dimer in the presence of free C60 or C70, these free fullerenes are incorporated into the polymer.365 The lower part of Figure 86 shows the structure of one of the solids obtained in this way, {Rh2(O2CCH3)4N(CH2CH2)2NC60}n·nC60·2nCS2. In this solid the free C60 cages are also interdigitated into the spaces between the protruding fullerenes on either side of the main chain. These free C60 molecules undergo rather free thermal motion, which increases as the temperature is raised.

containing a curved network of silver and nitrate ions, which completely encapsulated the fullerene, formed and were characterized by X-ray diffraction. This structure, which involves some examples of η1-coordination of silver to the fullerene, is shown in Figure 83. Another curved network has been obtained by combining a terpyridine ligand, NiCl2·6H2O, and C60.356 The formation of other coordination polymers has relied upon the use of functionalized fullerenes that have added Lewis base sites attached to facilitate coordination to metal ions and complexes. Figure 84 shows one of the first examples of this approach. Khlobystov, Schröder and co-workers prepared a fullerene functionalized so that two pyridyl groups were available for coordination.357 Treatment of this ligand with silver hexafluorophosphate produced the linear polymer shown in Figure 84. Several other polypyridal-functionalized fullerenes have been prepared and converted into linear and 2-dimensional networks.358,359 The adduct, C60N(CH2CH2)2N, which may be prepared by a photolytic reaction of C60 with piperazine, is a versatile synthon for the formation of new fullerene-containing polymers.360−363 Figure 85 shows the ligand and one of the polymeric materials obtained from it by reaction with silver trifluoroacetate. The linear chain seen in {[C60(N(CH2CH2)2N)][Ag(O2CCF3)]2}n involves both silver coordination to the nitrogen atom of pip−C60 and to carbon atoms of the cage in η1-fashion.364 The chain seen in Figure 85 is also connected to an adjacent chain through bridging trifluoroacetate ligands, but no voids are

7. PRACTICAL APPLICATION OF TWO-COMPONENT POLYMERS OF FULLERENES AND TRANSITION METALS 7.1. Charge Storage Materials

Conducting polymers are widely used as materials for charge storage.366−369 The suitability of polymers for charge storage depends on their capacitance. The capacitance of redox-active polymeric films can be divided into two components: doublelayer capacitance at the polymeric chain/solution interface and 3852


Chemical Reviews

Review

Figure 82. (a) Method of synthesis, (b) SEM images, and (c) capacitance performance of Zn[N2C4H6]2-derived mesoporous carbon. Reproduced with permission from ref 340. Copyright 2014 The Royal Society of Chemistry.

rectangular shape is related to the faradaic process of film reduction/reoxidation and the film resistance. A linear relationship between the capacitance current and the sweep rate was observed as seen in Figure 87. The specific pseudocapacitance depends on the size of the cation in the supporting electrolyte. The Nyquist plots presented in Figure 88, recorded in the potential range of the fullerene cage reduction, also exhibit a shape typical for electroactive pseudocapacitors.370 A small semicircle corresponding to the polymer reduction process is observed in the high-frequency range. Before the semicircle becomes closed, the imaginary part of the semicircle increases. A very short part of the Nyquist plot, with a phase angle close to 40°, represents the process of counterion diffusion inside the polymeric film. At low frequencies, the imaginary part of the impedance increases rapidly with a decrease in frequency. Such behavior is typical for electrochemical capacitors. The polymer/ electrolyte interface can be represented by the equivalent circuit

faradaic pseudocapacitance related to the reduction/oxidation step of the polymeric material. In the case of typical conjugated polymers, the faradaic component dominates the capacitance. The capacitance properties of the two-component polymers of fullerenes and palladium or platinum depend on the composition of the polymeric material.370 A faradaic pseudocapacitor is formed in solution with a relatively low ratio of the concentration of palladium and platinum complex to the concentration of fullerene (C60 or C70) in the growth solution. In the case of a composite of polymer and metal nanoparticles formed when a solution contains a large excess of the metal complex in the growth solution, the material exhibits doublelayer capacitor properties.370 Voltammograms of the films of poly-PdnC60 and poly-PdnC70 recorded in the negative potential range exhibit a pseudorectangular shape that is typical for electrochemical capacitors as shown in Figure 87.202 The slight departure from the ideal 3853


Chemical Reviews

Review

Composites of poly-PdnC60 and palladium nanoparticles exhibit a wider range of electrochemical activity.370 Due to the metallic palladium contribution to the conductivity, these materials are conductive at potential values that are less negative than the potentials of fullerene cage reduction. In this potential range, these composites exhibit typical double-layer capacitance properties. The cyclic voltammograms recorded for the poly-PdC60/Pd composite are shown in Figure 89.370 The Nyquist plots of the poly-Pd3C60/Pd composite (Figure 90) are dominated by the capacitive behavior. In the low-frequency range, the electrode process can be represented by resistance R(ω) and capacitance C(ω) as a function of pulsation (ω), as shown in Scheme 6. The specific capacitances of the polyPdnC60/Pd composite in different supporting electrolytes are reported in Table 11. The lower values of the specific conductivity are related to the lower permeability of the ions of the supporting electrolyte. However, the material becomes conductive in the higher potential range, where it exhibits increased stability. The capacitance properties of chemically deposited polyPdnC60 depend on the material morphology.204,209 Films formed from as-prepared large poly-Pd3C60 particles exhibit much lower capacity in comparison to the capacitance of thin films of electropolymerized material. Capacitance properties of the electrochemically and chemically prepared poly-PdnC60 are compared in Figure 91. The limiting value of approximately 30 F g−1 was obtained for low sweep rates.209 The capacitance properties also depend on the composition of this material. The capacitance of chemically synthesized poly-PdnC60 increases with a decrease in the particle size. In the case of poly-Pd1C60 nanoparticles, the specific capacitance reaches the value of that obtained for electrochemically prepared poly-Pd3C60 film.

Figure 83. Structure of C60{Ag(NO3)}5 with van der Waals contours for the various atoms, only one fullerene shown in the uppermost layer. Silver is shown as light gray, oxygen red, nitrogen dark blue, and carbon dark gray. Reproduced with permission from ref 354. Copyright 1999 Wiley.

shown in Scheme 5. R1 is the resistance of the ionic conductivity of the electrolyte, Cdl is the capacitance of the external polymer/electrolyte interface, Rct is the charge transfer resistance related to the poly-PdnC60 electroreduction, ZW is the Warburg impedance, which represents the transport of counterions during the process of polymer reduction, and CL is the capacitance of the internal polymer chain/electrolyte interface in the polymer micropores. Values of the specific capacitance of poly-PdnC60 and poly-PdnC70 pseudocapacitors are presented in Table 11. The highest value of 375 F g−1 was reported for poly-PdC60 in acetonitrile containing CsAsF6 as a supporting electrolyte.370 The capacitance of poly-Pd3C70 is similar to the capacitance of poly-Pd3C60.202

Figure 84. Pyridyl-functionalized fullerene and the coordination polymer it forms after treatment with Ag(PF6). Reproduced with permission from ref 357. Copyright 2007 Wiley.

Figure 85. Structure of pip−C60 and a portion of the structure of {[C60(N(CH2CH2)2N)] [Ag(O2CCF3)]2}·CS2. Reproduced with permission from ref 364. Copyright 2009 American Chemical Society. 3854


Chemical Reviews

Review

Figure 87. Cyclic voltammograms of (a) poly-Pd3C60 and (c) polyPd3C70 films in acetonitrile containing 0.10 M (n-C4H9)4NClO4 recorded at Au/quartz electrode. Sweep rate was 20 mV s−1 for trace 1, 50 mV s−1 for trace 2, 100 m V s−1 for trace 3, and 200 mV s−1 for trace 4. Dependence of the pseudocapacitive current on the sweep rate for (b) poly-Pd3C60 and (d) poly-Pd3C70. Films were grown under cyclic voltammetry conditions in acetonitrile/toluene (1:4, v:v) containing 0.10 M (n-C4H9)4NClO4, 0.25 mM C60 or C70, and 2.0 mM Pd(ac)2. Reproduced with permission from ref 202. Copyright 2008 Springer.

Figure 86. (Top) Structure of polymeric crystalline {Rh2(O2CCH3)4N(CH2CH2)2NC60}n·2nCS2 with interdigitation of the fullerenes. (Bottom) Structure of {Rh2(O2CCH3)4N(CH2CH2)2NC60}n·nC60· 2nCS2 at 90 K. Note the free fullerenes interdigitate between spaces on either side of the {Rh2(O2CCH3)4N(CH2CH2)2NC60}n chain. Reproduced with permission from ref 365. Copyright 2014 The Royal Society of Chemistry.

The total capacitance C is mainly limited by the component of smaller capacitance, which contributes more in the total capacitance due to the reciprocal dependence. In Table 12, typical values of the specific capacitances of selected organic polymeric materials are reported. These values are comparable to the values of specific capacitance obtained for poly-PdnC60 and poly-PdnC70 (Table 11). To enhance the capacitance performance of fullerene polymers, composites of carbon nanoparticles and poly-PdnC60 were synthesized.381−385 The composites of conducting polymers and carbon nanoparticles, such us single- and multiwall carbon nanotubes or graphene, combine properties of both components, resulting in materials of high electrical conductivity and large surface area.386 In these composites, the charge storage mechanism of redox pseudocapacity of a conducting polymer is combined with the electrostatic attraction and outstanding mechanical properties of carbon nanoparticles.387 The porous

Most of the polymeric materials used in charge storage devices exhibit p-doped properties. The charge is accumulated in these materials due to the electrooxidation process. Two-component polymers of fullerenes and transition metals exhibit n-doped properties and can be used as a complementary electrode material for p-doped polymers in asymmetric charge storage devices. The charging process of such a device containing poly-PdnC60 is schematically shown in Figure 92. The total capacitance C of the device depends on the cathode CC and anode CA capacitance in the following way.

1/C = 1/CC + 1/CA

(24) 3855


Chemical Reviews

Review

Table 11. Capacitance Properties of Poly-PdnC60 and Poly-PdnC70 in Acetonitrile Containing Different Supporting Electrolytes

Figure 88. Nyquist plots of poly-Pd3C60 films in acetonitrile containing 0.10 M (n-C4H9)4NClO4 at (a) −800 mV. Solid lines represent simulated data. (b) Z′−Z′′ dependences in the frequency range of semicircle formation at −750, − 800, − 850, − 900, and −1100 mV. Poly-Pd3C60 films were grown under cyclic voltammetry conditions in acetonitrile−toluene (1:4, v:v) containing 0.10 M (n-C4H9)4NClO4, 0.27 mM C60, and 4.65 mM Pd(ac)2. Reproduced with permission from ref 370. Copyright 2007 The Electrochemical Society.

polymer composition

formation conditions

supporting electrolyte

specific capacitance (F g−1)

ref

poly-Pd3C60 poly-Pd3C60 poly-Pd3C60 poly-Pd3C60 poly-Pd3C60 poly-Pd3C60 poly-Pd3C60/Pd poly-Pd3C70 poly-Pd3C70 poly-Pd3C70 poly-Pd3C60a poly-Pd3C60b poly-Pd2C60b poly-Pd1C60b

cyclic voltammetry cyclic voltammetry cyclic voltammetry cyclic voltammetry cyclic voltammetry cyclic voltammetry cyclic voltammetry cyclic voltammetry cyclic voltammetry cyclic voltammetry chemical synthesis chemical synthesis chemical synthesis chemical synthesis

(C2H5)4NClO4 (n-C4H9)4NClO4 (n-C6H13)4NClO4 LiClO4 KPF6 CsAsF6 (n-C4H9)4NClO4 (C2H5)4NClO4 (n-C4H9)4NClO4 (n-C6H13)4NClO4 (n-C4H9)4NClO4 (n-C4H9)4NClO4 (n-C4H9)4NClO4 (n-C4H9)4NClO4

145 255 105 200 70 135 300 289 375 25 185 125 80 35 90 125 195

202, 370 202, 370 202, 370 370 370 370 370 202 202 202 209 204 204 204

Thin film formed from as-prepared polymeric material. bThin film formed from polymeric nanoparticles. a

are shown in Figure 94 for different sweep rates.381 The pseudocapacitance current depends linearly on the sweep rate. The composition of the composite material also affects the capacitance properties of the composites. Figure 95 shows the impedance responses of the MWCNTs/poly-PdnC60 composites for different ratios of the mass of the MWCNTs to the mass of poly-PdnC60.381 The mass of the polymer in the composite was kept nearly constant, while the mass of MWCNTs was altered. The equivalent electrical circuit representing the behavior of the MWCNTs/poly-PdnC60 thin film electrode is shown in Scheme 4. Such an equivalent circuit can also be used to describe the charging processes of other composites containing carbon nanostructures and polymers of C60 and transition metal complexes. A higher charge transfer resistance, RCT, value for the composite corresponds to a higher amount of MWCNTs. The resistance of the film decreases with an increase in the mMWCNT:mpoly‑PdnC60 ratio. The opposite effect is observed in the potential range that is less negative than the value of the potential of poly-PdnC60 electroreduction (inset in Figure 95). The Z′−Z′′ response of the film containing a small amount of carbon nanotubes is dominated by the high RCT value of the oxidized form of poly-PdnC60. This high RCT value is represented by the large semicircle. Because MWCNTs are responsible for charge transfer at a potential range that is less negative than the value of the potential of poly-PdnC60 reduction, the semicircular region shrinks with an increase in the amount of MWCNTs in the composite. Due to the high specific capacitance, composites of poly-PdnC60 can be effectively used as a negatively charged electrode material in charge storage devices. The capacitance properties of a composite of SWCNTs and two-component polymer of Pd and C60 with a ferrocene moiety covalently linked to it (structure 2 in Scheme 2) were also investigated.389 Such composites can be used as redox-active materials for both positively and negatively charged electrodes of the electrochemical capacitor. The faradaic redox processes that occur during capacitor charging are described by eqs 12 and 13. The highest values of specific capacitance of 300 and 120 F g−1 were reported for the reduction and oxidation of this material, respectively. The charging/discharging

Scheme 5. Equivalent Electrical Circuit Representing Behavior of the Poly-PdnC60 Film Electrode in an Electrolyte Solution

structure of the carbon material immobilized in the polymeric matrix increases the accessibility of the electrochemically active surface to counterions, thereby enhancing the charge/discharge process and increasing capacity.388 The structure of the composite depends on the carbon nanoparticles used for its formation. The composite formed from single-walled carbon nanotubes (SWCNTs) and poly-Pd3C60 exhibits a porous structure with the polymeric material coating the carbon nanotubes (Figure 93a).384 A similar structure was observed for a composite based on multiwalled carbon nanotubes (MWCNTs).381,384 Much more compact films were obtained for a composite of carbon nano-onions (CNOs) and poly-Pd3C60 (Figure 93b).384 All of these composites are electrochemically active at negative potentials due to fullerene reduction and exhibit good electrochemical stability under multicyclic voltammetry conditions. Both the mechanical and the electrochemical stabilities increase significantly compared to the pure poly-Pd3C60 polymer. The composites also provide rapid current responses upon potential changes. The limiting values of ca. 1000, 750, and 300 F g−1 were found for SWCNTs/poly-Pd3C60, MWCNTs/poly-Pd3C60, and CNOs/ poly-Pd3C60, respectively.384 These values are much larger than the specific capacitance of pure poly-PdnC60.202,204,209,370 The voltammetric responses of MWCNTs/poly-PdnC60 composite 3856


Chemical Reviews

Review

Figure 89. (a) Cyclic voltammograms of poly-Pd3C60/Pd films in acetonitrile containing 0.10 M (n-C4H9)4NClO4. Sweep rate was (1) 20 mV s−1, (2) 50 mV s−1, (3) 100 m V s−1, (4) and 200 mV s−1. (b) Dependence of the capacitive current on the sweep rate. PolyPd3C60/Pd films were grown under cyclic voltammetry conditions in acetonitrile−toluene (1:4, v:v) containing 0.27 mM C60, 8.46 mM Pd(ac)2, and 0.10 M (n-C4H9)4NClO4. Reproduced with permission from ref 370. Copyright 2007 The Electrochemical Society.

chronopotentiometric curves of the symmetrical capacitor formed from a composite of SWCNTs, and the two-component polymer of Pd and a ferrocene derivative of C60 exhibit a typical shape for electrochemical capacitors (Figure 96).389 The poly-PdnC60 was also mixed with p-doped polymers in a composite containing SWCNTs to obtain material electrochemically active in both positive and negative potentials.390 Figure 97 shows voltammetric response of a composite composed of SWCNTs electrochemically coated with poly-PdnC60 and polybithiophene.390 In the negative potential range, reduction of fullerene moieties is observed. The current recorded at positive potentials corresponds to the polybithiophene oxidation. The high capacitance background current is related to the large area of the porous structure of the SWCNTs. The galvanostatic charging/discharging of the composite material is also very fast. Due to the strong interaction of fullerenes and transition metals, solid fullerene films were used as support for highly dispersed metallic nanoparticles catalysts.391 Because of remarkable methanol oxidation activity, they were tested for catalysis of methanol oxidation in fuel cells.392 Catalysts were formed in 1,2-hexadecanediol and benzyl ester containing Pt(acetylacetonate)2, Ru(acetylacetonate)2, and C60. Due to the poor electrical conductivity of C60, carbon black as support had to be added into this material. A large enhancement of the methanol oxidation current is observed for Pt/C 60 and PtRu/C60 in comparison to commercially available E-TEK/Pt and

Figure 90. Nyquist diagrams obtained at (a) −550 mV and (b) −1100 mV, and dependence of the (c) real part of capacitance, (d) imaginary part of capacitance, and (e) phase angle on frequency for poly-Pd3C60/Pd film in acetonitrile containing 0.10 M (n-C4H9)4NClO4. The film was formed under cyclic voltammetry conditions in acetonitrile−toluene (1:4, v:v) containing 0.27 mM C60, 9.13 mM Pd(ac)2, and 0.10 M (n-C4H9)4NClO4. Reproduced with permission from ref 370. Copyright 2007 The Electrochemical Society.

E-TEK/PtRu catalysts (Figure 98). A polypyrrole-modified fullerene-supported Pd nanoparticles catalyst for formic acid electrooxidation was also prepared.393 The polypyrrole−C60 composite was synthesized by in situ chemical oxidative polymerization of pyrrole monomer on the surface of fullerene powder. In the next step, Pd nanoparticles were deposition 3857


Chemical Reviews

Review

Scheme 6. Equivalent Electrical Circuit Representing Behavior of the Poly-Pd3C60/Pd Film Electrode in an Electrolyte Solution

during Pd2+ reduction. Obtained material shows a good electrocatalytic activity and stability for the oxidation of formic acid. 7.2. Two-Component Materials Containing C60 and Transition Metal Polymer and p-Type Polymer

The electron-donor/acceptor approach is an effective way to convert solar energy into electrical energy in organic photovoltaic solar cells.394−396 Usually such cells are constructed from two polymeric layers, which exhibit electron-donor (p-type) and electron-acceptor (n-type) properties. The energy transfer at the p−n interface of two conducting polymers is schematically shown in Figure 99a. The sunlight absorption in the p-type polymer results in the excitation of the polymer. The excitons formed diffuse to the p−n interface, and then the electron is transferred from the LUMO orbital of the p-type material to the LUMO orbital of n-type polymer. The charge separation at the interface generates a potential difference at the p−n junction. Typically, the excitation diffusion length is limited to approximately 10 nm in organic polymeric conductors.397 The excitons generated far away (>10 nm) from the p−n interface do not participate in the formation of free charge carriers.

Figure 92. Asymmetrical electrochemical capacitor composed of n-doped poly-PdnC60 cathode and p-doped polymer anode.

Therefore, the thickness of the p−n photovoltaic devices should be less than approximately 20 nm. As a consequence, the power conversion efficiency in such systems is very low. To overcome these limitations, the concept of bulk-heterojunction photovoltaic devices was introduced (Figure 99b).395 In such systems, nanocomposites of electron-donor and electronacceptor materials are used. The mechanism of solar energy light transformation remains the same. However, the area of the p−n junction in such systems is substantially increased, thereby resulting in much higher power conversion efficiency.

Figure 91. Cyclic voltammograms of Au (1.5 mm diameter) electrode covered with (a) electrochemically and (b) chemically formed poly-Pd3C60 polymer in acetonitrile containing 0.10 M (n-C4H9)4NClO4. Mass of deposited polymer was (a) 1.06 and (b) 0.99 μg. Sweep rate was (1) 20, (2) 50, (3) 100, and (4) 200 mV s−1. Dependence of specific capacitance on the sweep rate for Au (1.5 mm diameter) electrode covered with electrochemically (c) and chemically (d) formed poly-Pd3C60. The mass of the polymer deposited at the surface was (1) 0.53, (2) 1.06, and (3) 2.12 μg. Reproduced with permission from ref 209. Copyright 2013 Springer. 3858


3859

210

485

polythiophene (p-doping) poly(3-methylthiophene) (p-doping) poly(3-methylthiophene) (n-doping) poly(3-p-fluoro-phenylthiophene) (p-doping) poly(3-p-fluoro-phenylthiophene) (n-doping) poly(3-(4-fluoro-phenyl)thiophene) (p-doping) poly(3-(3,4-difluoro-phenyl)thiophene) (p-doping) poly(3,4-ethylene-dioxythiophene) (p-doping)

From ref 368.

750

polyaniline (p-doping)

a

620

220 165 95 80 244 212 103

532

228

240 65−75

∼100

151

355

281

270 220 403

theoretical specific measured specific capacitancea (F g−1) capacitance (F g−1)

polypyrrole (p-doping)

polymer −

conditions of capacitance measurements

chemical oxidation with FeCl3 in aqueous solution chemical oxidation with FeCl3 in aqueous solution chemical oxidation with FeCl3 in aqueous solution

CV CV CV CV CV CV CV

in in in in in in in

propylene carbonate containing (C2H5)4NBF4 propylene carbonate containing (C2H5)4NBF4 propylene carbonate containing (C2H5)4NBF4 propylene carbonate containing (C2H5)4NBF4 acetonitrile containing (C2H5)4NBF4 acetonitrile containing (C2H5)4NBF4 acetonitrile containing (C2H5)4NBF4

CV in H2O containing Cl CV in H2O containing Cl− galvanostatic charge/discharge in H2O containing SO42− pulse galvanostatic deposition in H2O containing p-TOS galvanostatic charge/discharge in H2O containing NO3− chemical polymerization in H2O containing p-TOSNa and CV in acetonitrile containing BF4− FeCl3 chemical polymerization in diethyl ether containing CV in acetonitrile containing BF4− p-TOSNa and FeCl3 galvanostatic charge/discharge in symmetric redox chemical synthesis of polyaniline doped with LiPF6 capacitor CV in H2SO4 aqueous solution CV in H2SO4 aqueous solution galvanostatic deposition HCl aqueous solution galvanostatic charge/discharge in symmetric redox capacitor in HBF4 aqueous solution galvanostatic charge/discharge in H2SO4 aqueous CV in H2SO4 aqueous solution solution mesoporous polyaniline formed under CV conditions in galvanostatic charge/discharge in H2SO4 aqueous H2SO4 aqueous solution containing Brij 98 surfactant solution

conditions of polymer formation CV in H2O containing KCl CV in H2O containing LiClO4 pulse galvanostatic deposition in H2O containing p-TOS

Table 12. Capacitance Properties of Selected Conjugated Conducting Polymers

379 379 379 379 380 380 380

378

378

376 377

374, 375

373

373

372

371 371 372

ref

Chemical Reviews Review


Chemical Reviews

Review

Figure 94. (a) Cyclic voltammograms of the MWCNT/poly-Pd3C60 film containing 4.25 μg of MWCNTs and 0.90 μg of poly-Pd3C60 in 0.10 M (n-C4H9)4NClO4, in acetonitrile. Potential sweep rate was (1) 10, (2) 20, (3) 50, and (4) 100 mV s−1. (b) Dependence of the current at −0.95 V on the potential sweep rate for the MWCNT/polyPd3C60 film. Reproduced with permission from ref 381. Copyright 2009 Elsevier.

A poly-Pd3C60 and polypyrrole interface was formed and examined as a model system for p−n junction. Three types of such structures are schematically shown in Figure 101. Bilayers of conducting polymers (Figure 101a) can serve as a chargetrapping system.401−405 Such devices exhibit rectifying characteristics. The limitation of current flow across the bilayer depends on the polymerization sequence, the potential difference between redox levels of the polymeric components, and the permeability of each polymer to ion transport. Poly-Pd3C60 is conductive in the negative potential range when the polymer is partially reduced. In contrast, polypyrrole exhibits conducting properties at positive potentials when it is partially oxidized. The voltammetric responses of both polymers indicate that there is a narrow overlapping potential range of conduction levels of the two individual components (Figure 102). This behavior allows the electrochemical deposition of bilayers (Figure 101a).406 The electrochemical response of such a bilayer depends on the sequence of polymeric materials electrodeposited on the electrode surface. In the case of electrode/ polypyrrole/poly-Pd3C60, the high permeability of the polyPd3C60 film for the supporting electrolyte ions allows the oxidation of the polypyrrole inner layer to occur. A very broad potential range of bilayer electrochemical activity is observed in this case. In the case of the electrode/poly-C60Pd/polypyrrole bilayer, the outer polypyrrole layer inhibits the reduction of the poly-Pd3C60 inner layer. The low permeability of this polypyrrole film for supporting electrolyte cations is responsible for such behavior. The voltammetric responses of both systems are shown in Figure 102.406

Figure 93. TEM images of (a) SWCNT/poly-Pd3C60 and (b) ox-CNO/poly-Pd3C60. poly-Pd3C60 was deposited under cyclic voltammetry conditions in acetonitrile:toluene (1:4, v:v) mixture containing 0.27 mM C60, 3.56 Pd(ac)2, and 0.10 M (n-C4H9)4NClO4. Reproduced with permission from ref 384. Copyright 2013 Elsevier.

Conjugated polymers such as polyphenylenevinylene398 and polythiophene399,400 and their derivatives have been widely used as donor constituents. However, their band gaps are not sufficiently low for effective light harvesting. Recently, donor materials with much lower band gaps have been used, such as copolymers constructed from the fragments of thiophene, fluorine, or pyrazine. Dye-sensitized p-type polymers have also been used for photovoltaic device construction. Materials based on fullerenes and their derivatives are very good candidates for the electron-accepting constituents of these cells. The polymers of C60 and transition metals can also be considered as effective electron-accepting materials for photovoltaic devices. Figure 100 shows the voltammetric responses of C60 and poly-Pd3C60 recorded under the same conditions. The reduction potential of C60 incorporated into the polymeric matrix is shifted by approximately 50 mV toward less negative potentials in comparison to the potential of C60 reduction in solution. As a consequence, the electron affinity of the fullerene cage increases, making the polymeric material more suitable for application in photovoltaic devices. 3860


Chemical Reviews

Review

Figure 96. Voltage vs time curves of charging at +0.72 mA cm−2 and discharging at −0.72 mA cm−2 for the pyr-SWCNTs/poly-PdnC60−Fc film-coated 4 mm Au disk electrodes in a two identical electrode system in a 0.1 M M (n-C4H9)4NClO4 acetonitrile solution for a voltage limit of (1) 0.15, (2) 0.35, (3) 0.45, (4) 0.65, (5) 0.75, (6) 2.5, and (7) 2.7 V. Reproduced with permission from ref 389. Copyright 2013 American Chemical Society.

Composites of poly-Pd3C60 and polypyrrole, i.e., polyPd3C60/polypyrrole (Figure 101b), and core−shell nanoparticles, i.e., poly-Pd3C60@polypyrrole (Figure 101c), were prepared by sequential chemical polymerization of both components.408 These systems can be used for modeling the charge transfer processes in bulk-heterojunction solar devices. The SEM images of poly-Pd3C6/polypyrrole are shown in Figure 104a.408 Both components in the composites are clearly visible on these images. The voltametric response of the amorphous poly-Pd3C60/polypyrrole composite is shown in Figure 104b.408 The process of poly-Pd3C60 electroreduction becomes inhibited (Figure 104b, curve 2). The small current at −1.35 V corresponds to the reduction of poly-Pd3C60, which is partially covered with polypyrrole. In this case, reduction occurs at the part of the surface in direct contact with the solution. For a higher amount of polypyrrole in the composite, the process of poly-Pd3C60 electroreduction is completely blocked. The core−shell poly-Pd3C60@polypyrrole nanoparticles are particularly interesting from a practical point of view. The morphology of these nanoparticles was investigated with scanning and transmission electron microscopy (Figure 105a) and X-ray fluorescence spectroscopy (Figure 105b).408 These measurements clearly show the core−shell structure of the nanoparticles. The presence of both components in core−shell nanoparticles was also confirmed by infrared and Raman spectroscopy. Electrochemical measurements were performed on solid films of poly-Pd3C60@polypyrrole nanoparticles (Figure 106). The outer polypyrrole layer is easily oxidized at potentials corresponding to the potentials of pure polypyrrole oxidation. The poly-Pd3C60 core reduction is shifted toward more negative potentials in comparison to the potential of reduction of film composed from pure poly-Pd3C60. The degree of outer layer influence on the process of poly-Pd3C60 reduction depends on the polypyrrole layer thickness. The poly-Pd3C60-Fc@polypyrrole film with an outer polypyrrole layer thinner than about 20 nm can be potentially used in solar energy conversion electrochemical

Figure 95. (a) Complex-plane impedance plots for the MWCNT/ poly-Pd3C60 films (4.25 μg of MWCNTs and 0.90 μg of poly-Pd3C60) in 0.10 M (n-C4H9)4NClO4, in acetonitrile, at (1) −0.30, (2) −0.825, (3) −0.90, (4) −1.00, and (5) −1.10 V. (b) Nyquist plots for the MWCNT/poly-Pd 3C 60 films in 0.10 M (n-C4 H9)4 NClO4, in acetonitrile, at −0.825 and −0.30 V (inset). Film composition was (1) 4.25 μg of MWCNTs and 0.90 μg of poly-Pd3C60, (2) 2.12 μg of MWCNTs and 0.75 μg of poly-Pd3C60, and (3) 1.05 μg of MWCNTs and 0.66 μg of poly-Pd3C60. Frequency was in the range from 10 kHz to 100 mHz. Solid curves represent simulated data according to the equivalent circuit presented in Scheme 3. Reproduced with permission from ref 381. Copyright 2009 Elsevier.

The electrochemical properties of a bilayer composed of poly-Pd3C60 and poly-Pd3C60-Fc were also investigated.407 In this system, the poly-Pd3C60-Fc film exhibits both p- and n-doped properties. The bilayer electrode process also depends upon the polymerization sequence. For the electrode/ poly-Pd3C60-Fc/poly-Pd3C60 system, where poly-Pd3C60-Fc is initially deposited at the electrode surface, followed by a layer of poly-Pd3C60, the processes of both fullerene reduction and ferrocene oxidation are observed. In the case of a bilayer electrode poly-Pd3C60Pd/poly-Pd3C60-Fc, the inner polyPd3C60 layer is not conductive in the potential range of ferrocene oxidation of the outer poly-Pd3C60-Fc layer. As a consequence, the inner poly-Pd3C60 film inhibits the oxidation process of the other layer. Incorporation of metallic palladium particles into the inner poly-Pd3C60 layer results in an increase of its conductivity. The oxidation of the outer poly-Fc-C60Pd layer is possible in such a system. The voltammetric responses of the bilayers described above are shown in Figure 103.407 3861


Chemical Reviews

Review

Figure 97. (a) Cyclic voltammograms for (1) the film of the pyr-SWCNTs/poly-Pd3C60-PBT in 0.1 M (n-C4H9)4NClO4 in acetonitrile and (2) 0.34 mM C60 in 0.1 M (n-C4H9)4NClO4 in 1,2dichlorobenzene. The film in 1 was deposited from the 0.27 mM C60, 3.56 mM Pd(ac)2, 1 mM bithiophene, and 0.1 M (n-C4H9)4NClO4 solution of toluene/acetonitrile (4:1, v/v) on the Au-quartz/pyrSWCNT film-coated electrode. (b) Charge−discharge curves for the pyr-SWCNTs/poly-Pd3C60-PBT film-coated Au electrode in 0.1 M (n-C4H9)4NClO4 in acetonitrile at a constant current of 90 μA for the voltage limit of (1) 1.40, (2) 1.80, and (3) 2.30 V. Reproduced with permission from ref 390. Copyright 2009 American Chemical Society.

devices. In such systems, the polypyrrole layer has to be doped with light-harvesting molecules, such as metalloporphyrins409 or ruthenium dyes.410 The small thickness of the outer layer prevents free charge carriers recombination. On the other hand, the large area of the p−n nanojunction in nanostructured material should increase efficiency of solar energy conversion and overcome the limitation of a thin polypyrrole layer. The electric charge formed at the p−n nanojunction can be also transferred from the poly-Pd3C60 inner sphere to the metallic collector. 7.3. Analytical Application

Poly-PdnC60 can be also used as an electrochemical sensor. The electrochemical behavior of this polymeric material is altered when either carbon monoxide or imidazole is added. The electrochemical response of an electrode covered with poly-PdnC60 film becomes more reversible in the presence of carbon monoxide, and the reduction potential of the treated film shifts toward less negative values (Figure 107). A similar effect was also observed in solution containing imidazole. Presumably,

Figure 98. TEM images of (a) Pt/C60 and (b) PtRu/C60 hybrid nanoparticles embedded on Vulcan carbon after acetic acid treatment, and linear sweep voltammograms (scan rate = 0.050 V s−1) of (c) Pt/ C60 hybrid nanoparticles on Vulcan carbon, (d) E-TEK Pt catalyst, (e) PtRu/C60 hybrid nanoparticles on Vulcan carbon, and (f) E-TEK PtRu catalyst. Reproduced with permission from ref 392. Copyright 2009 The Royal Society of Chemistry. 3862


Chemical Reviews

Review

Figure 101. Schematic picture of polypyrrole/poly-PdnC60 interphases. Figure 99. Schematic picture of (a) thin layer heterojunction and (b) bulk heterojunction solar cells.

Figure 102. Cyclic voltammograms recorded at a Au (1.5 mm diameter) electrode coated with (a) poly-Pd3C60 (60 nm thick) and (b) polypyrrole (60 nm thick) in acetonitrile containing 0.10 M (n-C4H9)4N ClO4. Sweep rate was 100 mV s−1. Reproduced with permission from ref 406. Copyright 2004 The Royal Society of Chemistry. Figure 100. Cyclic voltammograms of poly-Pd3C60 film deposited at Au electrode and C60 in o-dichlorobenzene containing 0.1 M (n-C4H9)4NClO4 at 0.1 V.

for the observed catalytic effect. The same polymer has been also used as a matrix for the molecularly imprinted polymeric sensor of adenosine-5′-triphosphate (ATP).412 The concept of this sensor formation is shown in Scheme 7. The fullerene was derivatized with uracil, amide, and carboxy addend for recognition ATP. The ATP complex with all the functional monomers was electropolymerized in solution containing Pd(acetate)2. After polymerization, the template was extracted from the solid phase. The poly-PdnC60-ATP imprinted

the changes of the redox response of the poly-PdnC60 film are related to the coordination of the carbon monoxide or imidazole to the palladium atoms within the polymer. The poly-PdnC60 film was also used as a catalyst for the cytochrome c elecroreduction.411 The incorporation of the cytochrome c into the structure of polymeric film is responsible 3863


Chemical Reviews

Review

Figure 103. (a) Cyclic voltammogram of (a) electrode/poly-Pd3C60-Fc/poly-Pd3C60, (b) electrode/poly-Pd3C60/poly-Pd3C60-Fc, and (c) electrode/ poly-Pd3C60+Pd/poly-Pd3C60-Fc bilayer in acetonitrile containing 0.1 M (n-C4H9)4N ClO4. Sweep rate was 100 mV s−1. Reproduced with permission from ref 407. Copyright 2007 The Royal Society of Chemistry.

polymer deposited at the electrode surface was used as a sensor for ATP. The piezoelectric microgravimetry (Figure 108a) and faradaic impedance (Figure 108b) were used as detecting methods. Polymers of C60 with covalently linked crown ether voids (6, Scheme 2) can be used as sensors of alkali metal cations.224 The formal potential of the polymer reduction is described by the following equation Ef = Ef0 +

[poly‐Pd mC60‐Crown] RT RT ln ln[C+] + n− nF [poly‐Pd mC60 F ‐Crown(C+)n ] (25)

+

where C is an alkali metal cation. The potential at the polyPdnC60−Crown/solution interface depends on the concentration of the alkali metal cations in solution and the formation constant. Due to the selective complexation of alkali metal cations by crown ethers with different cavity size, the films of polymers of fullerene with different crown ethers covalently attached to the fullerene moiety can be used for selective determination of alkali metals. Exemplary results for K+- and Li+-ion detection at the gold electrode surface covered with benzo-18-crown-6-C60-Pd are shown in Figure 109.224 The larger shift of potential in the case of K+ is related to the much higher formation constant of K+/crown ether complex in comparison to the Li+/crown ether complex. 7.4. Catalytic Properties

Monomeric complexes of fullerenes and transition metals such as (η2-C60)Pd(PPh3)2 have been shown to function as catalysts for hydrogenation of olefins and acetylenes.413 Chemically synthesized poly-PdnC60 and poly-PtnC60 were also used as a catalyst for hydrogenation of olefins and acetylenes at room temperature under an atmosphere of dihydrogen.414 The catalytic properties of these materials depend on their composition. It appeared that only the polymer containing metallic palladium or platinum particles could effectively catalyze these hydrogenation reactions. An increase in the content of the metallic phase in the polymer matrix resulted in an increase in the hydrogenation rate. The effect of the poly-PdnC60 film

Figure 104. (a) SEM images the poly-Pd3C60/polypyrrole composite, and (b) cyclic voltammograms of thin films of poly-Pd3C60/polypyrrole composite deposited onto the Au electrode (1.5 mm diameter) in acetonitrile containing 0.1 M (n-C4H9)4NClO4. Sweep rate was 100 mV/s. Poly-Pd3C60 was synthesized in benzene containing 0.48 mmol dm−3 C60 and 0.73 mmol dm−3 Pd2(dba)3·CHCl3, and polypyrrole was deposited in water containing (1) 0.010 mol dm−3 pyrrole and (2) 0.010 mol dm−3 FeCl3. Reproduced with permission from ref 408. Copyright 2015 Wiley. 3864


Chemical Reviews

Review

Figure 105. (a) SEM (top panels) and TEM (bottom panels) images of poly-Pd3C60@polypyrrole core−shell nanoparticles. Poly-Pd3C60 nanoparticles were initially deposited from benzene containing 0.48 mmol dm−3 C60 and 0.73 mmol dm−3 Pd2(dba)3·CHCl3 and then coated with a polypyrrole layer in water containing 0.020 mol dm−3 pyrrole, 0.020 mol dm−3 FeCl3, and 0.315 mmol dm−3 SDS. (b) EDX spectra corresponding to poly-Pd3C60 core and polypyrrole shell of the nanoparticle. Reproduced with permission from ref 408. Copyright 2015 Wiley.

hydrogen desorption from such compounds is a major drawback for fullerenes as hydrogen storage materials. Additionally, different concomitants, such as methane422,423 or polycyclic aromatic hydrocarbons,424,425 are released during hydrogen desorption. Decoration of fullerenes with metal atoms (including alkali metals, alkaline-earth metals, and transition metals) leads to the formation of an extensive set of materials for hydrogen storage. The theoretical exploration of alkali metal fullerides as hydrogen storage materials focused on intercalated or dispersed alkali metal ions in a negatively charged, polycrystalline fullerene matrix.426−430 It was shown that more than one hydrogen atom can be associated with each alkali metal cation according to the charge polarization mechanism. Experimentally, it was shown that hydrogen can be reversibly stored in the NaAlH4/C60, LiBH4/C60, and LiAlH4/C60 systems.431−434 In these systems, hydrogen is bonded to alkali metal intercalated fullerenes (Mx−C60−Hx, where M = Na and Li). Similar behavior was observed for the lithium-doped fullerene formed from LiH and C60 via solvent-assisted mixing.435 The ability of lithiumdoped fullerene−C60 to bond hydrogen is a function of LiXC60 composition.435 The Li:C60 material with a molar ratio of 6:1 can reversibly absorb up to 5% of H2 with a low onset of temperature of ca. 270 °C. Similar behavior was observed for NaxC60.436 For example, at 200 bar H2 and a temperature of 200 °C, up to 3.5% by mass of hydrogen is reversibly absorbed to form NaxC60Hy hydrofullerenes.436 The intercalated alkali metal ions serve a dual purpose in the charge storage mechanism.435 They assist in the formation of a polymeric network material that

composition on the catalytic hydrogenation of diphenylacetylene is shown in Table 13. The results obtained for the catalytic hydrogenation of selected olefins and acetylenes by the polyPdnC60 and metallic palladium composite are summarized in Table 14. Hor and co-workers have shown that the poly-PdnC60 exhibits similar conversion yields but shorter reaction times than a commercial sample of 10% Pd/C catalyst.415 The better catalytic properties of fullerene-based catalyst are probably related to hydrogenation catalysts, which may be applied to many stubborn substrates. The influence of the fullerene on the catalytic properties of ruthenium in hydrogenation reactions was also observed.197,416 The catalytic material with a formal stoichiometry of Ru3C60 consisted of amorphous fullerene matrix embedding small ruthenium metal particles. This material was shown to have catalytic activity for the hydrogenation of cyclohexane in the gas phase or hydrogenation or cyclohexenone in solution. The catalytic activity of Ru3C60 is comparable to those of established, commercially available catalysts.197 7.5. Gas and Vapor Adsorbents

Hydrogen is considered as one of the best alternative and renewable fuels due to its abundance, easy synthesis, and nonpolluting nature.417,418 Hydrogen-base technology requires safe storage materials. Different carbon materials can be used for this purpose.419−421 Hydrogen can be covalently bonded to the fullerene cage leading to the compounds with high hydrogen content (C60H36 contains 4.8 wt % of hydrogen). However, the high temperature (above 500 °C) required for 3865


Chemical Reviews

Review

of H2)) and improved kinetics of the absorption process were reported. It was postulated that platinum and palladium aggregates exhibit catalytic activity toward dissociation of the hydrogen molecule. Fullerene hydrides with high contents of hydrogen (24−26 hydrogen atoms per fullerene molecule) were obtained by hydrogenation of solid-phase mixtures of fullerite with intermetallic compounds (LaNi5, LaNi4.65Mn0.35, CeCo3) or V and Pd metals under relatively mild conditions (1−2.5 MPa and 570−670 K).441 The formation of the mixture of metalhydrides and hydrofullerenes was observed under these conditions. Hydrogen evolves under heating the material up to 800 K. Hydrogen sorption was also postulated for palladium- and ruthenium-doped C60 formed by the incipient wetness impregnation technique.442 The hydrogen storage properties were also examined for chemically synthesized poly-PtnC60 material formed from C60 and H2PtCl6.443 In both cases, the hydrogen sorption isotherms show the enhancement of hydrogen uptake, but the nature of the isoterms is rather odd. Due to the presence of transition metal atoms or transition metal nanocrystals, polymers of fullerenes and transition metals can be used as gas adsorbents. Toluene is adsorbed within chemically formed poly-PdnC60 and poly-PtnC60.444 The amount of toluene adsorbed by these polymers depends on their composition. It has been suggested that interaction between the π-electrons of toluene and the Pd or Pt atoms involved in formation of the polymeric chain is responsible for adsorption phenomena (Figure 110). 7.6. Heterofullerenes Formation by Laser Ablation from Two-Component Polymers

Laser ablation of the electrochemically synthesized poly-MnC60 (M = Pt or Ir(CO)2) results in fullerene fragmentation and gas-phase formation of heterofullerenes such as C59M+ and C58M−.445−447 Mass spectra obtained by laser ablation of polyIrnC60 film are shown in Figure 111a. When laser ablation studies were conducted on poly-IrnC60 films in the presence of 2-butene adducts such as [C59Ir(2-butene)]−, [C58Ir(2-butene)]−, [C57Ir(2-butene)]−, and [C56Ir(2-butene)]− were detected. The ability to bind an added ligand like 2-butene indicates that species such as C59Ir, C58Ir, etc., are heterofullerenes and not endohedral fullerenes. The structures of these heterofullerenes, with metal sites incorporated into carbon cage networks, have been explored by computational procedures using density functional theory. Calculated structures with the metal atoms substituted for one or two carbon atoms within the fullerene cage are shown in Figure 111b. The formation of heterofullerenes in bulk from these polymeric materials remains as a major challenge. These heterofullerenes could combine the oneelectron redox properties of the fullerene cage with the catalytic activity inherent in low-coordinate metal complexes in a novel and useful fashion.

Figure 106. Cyclic voltammograms of (a) chemically synthesized poly-Pd3C60 nanoparticles, (b) polypyrrole nanoparticles, and (c) poly-Pd3C60@polypyrrole core−shell nanoparticles with 235 nm diameter and 175 nm C60−Pd core diameter, (2) 255 nm diameter and 175 nm C60−Pd core diameter, and (3) 280 nm diameter and 175 nm C60−Pd core diameter, deposited onto the Au electrode (1.5 mm diameter) in acetonitrile containing 0.1 M (n-C4H9)4NClO4. Sweep rate was 100 mV s−1. Reproduced with permission from ref 408. Copyright 2015 Wiley.

is able to reversibly store hydrogen. Moreover, charge transfer from the alkali metal atoms to the fullerenes results in the destabilization of the C−H bonds, which leads to lowering the temperature needed for hydrogen desorption. The storage hydrogen properties of fullerenes can be also promoted by transition metals. It was predicted that a single Ti atom affixed to fullerene cage can adsorb up to four hydrogen molecules.437−439 The binding energy of 0.3−0.5 eV for hydrogen adsorption was reported for scandium and titanium. The origin of this molecular chemisorption is explained by a combination of Dewar coordination and Kubas interaction. The transition metals are chemically bonded to fullerenes through hybridization of fullerene LUMO with d orbitals of transition metals (Dewar coordination). The resulting complex binds multiple molecular hydrogens through hybridization between the H2-σ* orbital and transition metal d orbitals (Kubas interaction). The influence of platinum and palladium on the storage properties of the lithium-intercalated C60 was studied by Ricco and co-workers.440 For Li6Pt0.11C60 and Li6Pd0.07C60, an 18 wt % increase of H2 absorbed (with respect to pure Li6C60 (5.9 wt %

8. CONCLUSIONS In this review, three different systems based on transition metal−fullerene interactions are described: (i) transition metal complexes of fullerenes, (ii) metal surfaces with adsorbed fullerenes, and (iii) redox-active, polymeric materials of various metal complexes and fullerenes or fullerene adducts. In all these systems, covalent interactions between the transition metal and the fullerene moieties are crucial for their formation, stability, and properties. These materials can be used in basic and applied research. The presence of fullerene cages in the polymer 3866


Chemical Reviews

Review

Figure 107. Cyclic voltammograms of the poly-Pd3C60 film electropolymerized from Pd(ac)2 and C60 in acetonitrile containing 0.10 M (C2H5)4NClO4 (a) before and (b) after treatment with carbon monoxide. Sweep rate was 100 mV s−1.

components of the polymeric materials. It will be interesting to see whether procedures to incorporate such clusters into suitable fullerene-based polymers can be developed. Fullerene dimers in which C60 moieties are linked by metal complexes can be considered as bridged model systems between simple complexes and networks of coordination polymers. Recently, new dimers with zerovalent Ni and Co bridges were synthesized.123,125,126 These studies open a field of new polymeric materials synthesis. Preliminary work has already been done to produce a one-dimensional polymeric chain in which C60 moieties are bonded with Ni[P(CH3)3]2 units.199 The interactions between fullerenes and transition metal surfaces are also described in this review. In this case, covalent bonding between the fullerene monolayer and the metallic surface is dominant in determining the structure and stability of resulting materials. Fullerenes can be chemisorbed onto the metallic surfaces from both the gas and the liquid phase. Such systems can be used as a platform to immobilize other molecules for sensing and biosensing applications. One of the approaches to the gas-phase deposition of metal/ fullerene films involves the simultaneous condensation of fullerene and metal vapors under low-pressure conditions. During this synthesis, transition metal−fullerene polymeric phase formation was observed for iron,182 cobalt,183 titanium,184 and niobium.186 These studies require additional work to optimize the conditions for polymer phase formation with designed structure and composition. They also open the possibility of further investigation of systems involving other metals. The solvent-free procedure is a major advantage of this approach. This review is mainly focused on the two-component, polymeric materials formed from fullerenes and transition metals, frequently through electrochemical deposition. The information about transition metal complexes of fullerenes and the interactions between transition metals surfaces and monolayers

Scheme 7. Schematic Illustration of the Concept of PolyPdnC60-ATP-Imprinted Polymer Sensor for ATP412

materials provides a large variety of structures with unique physical and chemical properties. Transition metal complexes can serve as model systems for the more complicated structures found in fullerene films chemisorbed on metal surfaces or in coordination polymers comprised of fullerenes and transition metals. The nature of the covalent bonding between fullerenes and transition metal centers in the simple complexes is also expected to be present in the polymeric materials. Many of the structures involving transition metals in particular (Pd0, Pt0, IrI, RhI) that are covalently bonded to a fullerene cage can also serve as linkers in polymeric networks. However, a variety of transition metal− fullerene complexes exist which do not have polymeric analogs. Some of these, for example, fullerene complexes of osmium or rhodium clusters, are particularly interesting as model 3867


Chemical Reviews

Review

Figure 108. (a) Time dependence of the capacity change due to consecutive injections of ATP solutions of concentrations indicated at peaks, recorded at the ATP-extracted MIP-ATP film-coated 1 mm diameter Pt disk electrode at 0.20 V vs Ag/AgCl and 20 Hz, except of 2. (Inset) Calibration plots for (1) ATP, (2) ATP at NIP, (3) GTP, (4) TTP, (5) ADP, (6) AMP, (7) guanosine, (8) adenine, (9) phosphate, and (10) CTP. (b) Time dependence of the resonant frequency change due to consecutive injections of ATP solutions of concentrations indicated at peaks recorded at the ATP-extracted MIP-ATP-coated Au electrode of 10 MHz QCR, except of 2. (Inset) Calibration plots for (1) ATP, (2) ATP at NIP, (3) GTP, (4) TTP, (5) ADP, and (6) CTP. Reproduced with permission from ref 412. Copyright 2014 Elsevier.

Table 13. Catalytic Hydrogenation of Diphenylacetylene with Poly-PdnC60/Pd414 catalyst composition

presence of metallic Pd nanoparticles

reaction half-life time (min)

C60Pd1.44 C60Pd2.46 C60Pd2.58 C60Pd2.71 C60Pd2.78 C60Pd3.37 C60Pd4.23 C60Pd6.99

no no no no yes yes yes yes

no reaction no reaction no reaction no reaction 330 45 20 13

Table 14. Hydrogenation of Olefins and Acetylenes over Poly-PdnC60/Pd414

Figure 109. Changes of the potential of gold electrode (1.5 mm diameter) covered with the poly-Pd3(benzo-18-crown-6-C60) film immersed in acetonitrile containing 0.1 M (n-Bt4N)ClO4 during addition of a solution containing either LiClO4 or KPF6. The benzo18-crown-6-fulleropyrrolidine/Pd film was grown under cyclic voltammetric conditions in acetonitrile/toluene (1:4, v/v) containing 0.10 M (n-Bt4N)ClO4, 0.30 mM benzo-18-crown-6-fulleropyrrolidine, and 3.10 mM Pd(ac)2. Reproduced with permission from ref 224. Copyright 2012 Springer.

of fullerenes gives a strong background for the description of the process of polymeric phase formation and properties of the polymeric materials. These systems can be considered both as conducting polymers and as metal−fullerene frameworks that are similar to metal−organic frameworks in which organic

linkers are replaced with fullerene cages. These materials bridge a gap between conducting polymers and MOFs. Thus far, most of the studies of two-component, polymeric materials have been 3868


Chemical Reviews

Review

Figure 111. (a) Mass spectra (negative-ion mode) obtained by laser ablation of the electrochemically deposited poly-PtnC60 and poly[Ir(CO)2]nC60 film after ejection of the [C60]− ion. (Insets) Expansions of the multiplets observed for [C56Pt2]−, [C57Pt2]−, and [C56Pt2O] and [C58Ir]−, [C59Ir]−, and [C58IrO]− and comparisons with the calculated spectra. (b) Two orthogonal views of the calculated structures of C59M: the C2v isomer of C58M (6:6 C−C bond substitution) and the Cs isomer of C58M (6:5 substitution). Reproduced with permission from ref 446. Copyright 2004 American Chemical Society.

Figure 110. Computed structures of toluene adsorbed on C60−Pd− C60 using the semiempirical MOPAC2002/AM1 method. (a) Idealized structures of C60−Pd−C60/toluene. (b) Surface electron density plot. (c) Example of orbital surface plots. Reproduced with permission from ref 444. Copyright 2004 The Royal Society of Chemistry.

potential application of these materials in batteries, fuel cells, capacitors, and electrochemical sensors. However, the number of conducting MOFs is still very limited. The formation of new metal−fullerene−organic frameworks may significantly increase a number of such materials for electrotechnological application. Both chemical and electrochemical procedures were described for synthesis of a variety of polymers containing C60 or C60 derivatives and transition metals. Electrochemical deposition results in the formation of thin polymeric films directly on the conducting substrate. The chemical synthesis allows the production of polymeric material on a much larger scale. Due to the number of fullerene derivatives suitable for polymeric film formation, there is ample opportunity to create new polymers with varying functionality attached to the fullerene cages. Additionally, polymeric materials that involve

devoted to the exploration of their electrochemical properties, which are related to research on more conventional conducting polymers. Studies related to metal−organic−fullerene frameworks are much less advanced. In part, progress here has been hampered by the difficulty in preparation of suitably functionalized fullerenes that can coordinate metals complexes in a suitable way to form polymers. Introduction of organic linkers into transition metal−fullerene frameworks may lead to a number of structures with novel material architectures and unique and tunable properties. Recent work of the Saito group has opened this large research area.199 In the past decade, the electrical and ionic conductivity aspects of MOF have been a prime focus of research due to 3869


Chemical Reviews

Review

nanostructures containing fullerene polymers are also very promising as components of the light-harvesting devices. Hydrogen production and storage are another important topic for energy production. It has been shown that the presence of transition metals can significantly improve the hydrogen storage ability of fullerene materials and decrease the energy needed for hydrogen release. Polymers of fullerenes and transition metals, particularly palladium-based polymers, can be very useful for these applications. The controlled changes of the structure and composition of poly-PdxC60 and the possibility of incorporation of palladium nanoparticles into polymeric network are big advantages of these systems for hydrogen storage. Fullerene polymers have been used as catalysts in organic reactions, components of biosensors, and reagents for metallofullerenes. These aspects are also highlighted in this review. These areas of studies have been much less explored. However, results obtained to date are highly promising and have suggested new avenues for future investigations. In summary, the fullerene−transition metal interaction can result in the formation of a variety of different structures and materials. These materials can play a leading role in both basic and applied areas of research. We believe that the variety of molecular and polymeric materials containing covalent interactions between transition metals and fullerenes will continue to inspire research on this topic.

endohedral metallofullerenes present an interesting target for synthesis and investigation. Considering the significant changes of the fullerene moiety redox properties when metal atoms reside inside the cage and the decrease in the HOMO−LUMO gap in endohedral fullerenes, polymeric materials obtained from such endohedral fullerenes may be expected to exhibit promising electrochemical and photooptical properties. Polymers of fullerenes and transition metals can serve as model systems for charge transfer processes. Polymers with untouched fullerene moieties behave as typical π-conjugated conducting polymers. However, in contrast to most of the organic conducting polymers, they exhibit n-doped properties. The charge transfer process that involves redox-active groups bonded to the fullerene cage can be described by the hopping model of the electron exchange between mixed-valence redox centers. A number of studies have utilized functionalized fullerene moieties with covalently attached redox-active centers. Due to the charge conduction in two different potential windows, such polymers of fullerenes with covalently bonded redox-active groups are so-called “double-cable” materials. Most of the potential applications of these materials are related to their electrochemical activity. Fullerenes exhibit a relatively high ability to accept electrons and to form stable anions. They also retain these properties after incorporation into the polymeric structure. Attention has been focused on potential applications of these materials in charge storage devices and solar light conversion systems. The important advantage of using fullerenes as an electron transfer moieties is the small reorganization energy associated with electron exchange leading to the high rate of charge transfer and electrochemical reversibility of electrode processes in fullerene polymers. Both pure polymeric materials as well as composites of carbon nanostructures containing polymers of C60 and transition metals exhibit high ability for charge accumulation that is comparable to those reported for typical ptyped organic conjugated conducting polymers. Therefore, fullerene polymers can be used as one of the components in all-polymeric asymmetrical capacitors. However, there are still many unresolved issues related to the potential for practical applications of these materials such as mechanical, thermal, and electrochemical stability, voltage limits in which they can operate, the solvent and electrolyte used for capacitor fabrication, and many others. More attention should be focused on the molecular architecture of materials used for supercapacitors fabrication. Well-ordered, multicomponent systems should exhibit more efficient charge storage properties and have the ability to tune their properties. Some progress in this area has been recently achieved by using nanostructural polymeric materials. Although progress has occurred in the synthesis of charge accumulation materials based on transition metal−fullerene polymers, production of these materials in bulk is very challenging. Fullerenes are also used in solar light converting systems. They can effectively separate charge carriers in different types of solar cells. A large part of basic and applied studies of fullerene polymers is devoted to this area of science and technology. However, the coordination polymers of fullerenes and transition metal complexes have not been investigated for such photoelectrical applications. Thus far, the search of novel and better fullerene polymeric materials based on novel fullerene derivatives could result in the development of more efficient solar cells. The polymers of palladium with C60 covalently bonded with lightharvesting moieties, such as metalloporphyrins, seem to be particularly suitable for this kind of application. The core−shell

AUTHOR INFORMATION Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest. Biographies Alan L. Balch is Distinguished Professor in the Department of Chemistry, University of California, Davis. He obtained his B.A. degree from Cornell University in 1962 and Ph.D. degree from Harvard University in 1967. He joined the University of California faculty in 1966. He is a fellow of the American Chemical Society and received that organization’s F. Albert Cotton Award in Synthetic Inorganic Chemistry. His research interests include the chemistry and structure of fullerenes, chemically modified fullerenes, and endohedral fullerenes as well as the study of transition metal complexes, particularly those showing luminescent properties. Krzysztof Winkler obtained his M.Sc. (1982) and Ph.D. (1989) degrees in Chemistry from the Warsaw University, Poland. He was a postdoctoral fellow at the University of Saskatchewan, Saskatoon (1989−1991) and University of California, Davis (1995−1997). He is currently a professor in the Institute of Chemistry, University of Bialystok, Poland. He served four terms as Head of this Institute (2004−2016). His research interests include kinetics of electrochemical processes, electrodeposition and properties of low-dimensional crystals, and the synthesis, properties, and application of fullerene-based polymers.

ACKNOWLEDGMENTS Portions of this material that were based on research at UC Davis were supported by the U.S. National Science Foundation (most recently, grant CHE-1305125). Portions of the results obtained at the University of Bialystok and used in this paper were supported by the National Center of Science (grants 2011/01/B/ST5/06270 and N 204 374 733). Dr. Monika 3870


Chemical Reviews

Review

(22) Komatsu, K. The Mechanochemical Solid-State Reaction of Fullerenes. Top. Curr. Chem. 2005, 254, 185−206. (23) Bruno, C.; Marcaccio, M.; Paolucci, D.; Castellarin-Cudia, C.; Goldoni, A.; Streletskii, A. V.; Drewello, T.; Barison, S.; Venturini, A.; Zerbetto, F.; Paolucci, F. Growth of p- and n-Dopable Films from Electrochemically Generated C60 Cations. J. Am. Chem. Soc. 2008, 130, 3788−3796. (24) Loy, D. A.; Assink, R. A. Synthesis of a Fullerene C60-p-Xylylene Copolymer. J. Am. Chem. Soc. 1992, 114, 3977−3978. (25) Nayak, P. L.; Yang, K.; Dhal, P. K.; Alva, S.; Kumar, J.; Tripathy, S. K. Polyelectrolyte-Containing Fullerene I: Synthesis and Characterization of the Copolymers of 4-Vinylbenzoic Acid with C60. Chem. Mater. 1998, 10, 2058−2066. (26) Huang, Y.; Peng, H.; Lam, J. W. Y.; Xu, Z.; Leung, F. S. M.; Mays, Y. W.; Tang, B. Z. Linear or Branched Structure? Probing Molecular Architectures of Fullerene−Styrene Copolymers by Size Exclusion Chromatographs with Online Right-angle Laser-light Scattering and Differential Viscometric Detectors. Polymer 2004, 45, 4811−4817. (27) Nuffer, R.; Ederle, Y.; Mathis, C. Preparation of Networks with C60 Knots using Anionic Polymers. Synth. Met. 1999, 103, 2376−2377. (28) Chen, Y.; Zhao, Y.; Cai, R.; Huang, Z. E.; Xiao, L. Anionic Copolymerization of [60]Fullerene with Styrene Initiated by Sodium Naphthalene. J. Polym. Sci., Part B: Polym. Phys. 1998, 36, 2653−2663. (29) Chiang, L. I.; Wang, L. Y.; Kuo, C. S. Polyhydroxylated C60 Cross-Linked Polyurethanes. Macromolecules 1995, 28, 7574−7576. (30) Manolova, N.; Rashkov, I.; Beguin, F.; van Damme, H. Amphiphilic Derivatives of Fullerenes Formed by Polymer Modification. J. Chem. Soc., Chem. Commun. 1993, 1725−1727. (31) Wang, Z. Y.; Kuang, L.; Meng, X. S.; Gao, J. P. New Route to Incorporation of [60]Fullerene into Polymers via the Benzocyclobutenone Group. Macromolecules 1998, 31, 5556−5558. (32) Chen, Y.; Tsai, C. H. Reversible Photoreaction of C60Containing Poly(vinyl alcohol). J. Appl. Polym. Sci. 1998, 70, 605−611. (33) Patil, A. O.; Brois, S. J. Fullerene Grafted Hydrocarbon Polymers. Polymer 1997, 38, 3423−3424. (34) Audouin, F.; Nuffer, R.; Mathis, C. Synthesis of Di- and TetraAdducts by Addition of Polystyrene Macroradicals onto Fullerene C60. J. Polym. Sci., Part A: Polym. Chem. 2004, 42, 3456−3463. (35) Okamura, H.; Terauchi, T.; Minoda, M.; Fukuda, T.; Komatsu, K. Kinetic Analysis of Polymerization Rate Acceleration During the Formation of Polymer/Smectic Liquid Crystal Composites. Macromolecules 1997, 30, 5279−5284. (36) Okamura, H.; Minoda, M.; Fukuda, T.; Miyamoto, T.; Komatsu, K. Solubility Characteristics of C60 Fullerenes with Two Well-Defined Polystyrene Arms in a Polystyrene Matrix. Macromol. Rapid Commun. 1999, 20, 37−40. (37) He, J. D.; Wang, J.; Li, S. D.; Cheung, M. C. New Synthetic Method for Soluble Starlike C60-Bonding Polymers. J. Appl. Polym. Sci. 2001, 81, 1286−1290. (38) Scamporrino, E.; Vitalini, D.; Mineo, P. Synthesis and Characterization of Some Copolyformals Containing, in the Main Chain, Different Amounts of Fullerene Units. Macromolecules 1999, 32, 4247−4253. (39) Berrada, M.; Hashimoto, Y.; Miyata, S. Preparation and Characterization of Poly(arylamine sulfones) and Poly(arylether sulfones) Carrying the C61 Fulleroid Pendant Group. Chem. Mater. 1994, 6, 2023−2025. (40) Zhang, X.; Sieval, A. B.; Hummelen, J. C. Hessen, B. Polyethene with Pendant Fullerene Moieties. Chem. Commun. 2005, 1616−1618. (41) Anderson, H. L.; Boudon, C.; Diederich, F.; Gisselbrecht, J. P.; Gross, M.; Seiler, P. 61,61-Bis(trimethylsilylbutadiynyl)-1,2-dihydro1,2-methanofullerene[60]: Crystal Structure at 100 K and Electrochemical Conversion to a Conducting Polymer. Angew. Chem., Int. Ed. Engl. 1994, 33, 1628−1632. (42) Yassar, A.; Hmyene, M.; Loveday, D. C.; Ferraris, J. P. Synthesis and Characterization of Polythiophenes Functionalized by Buckminsterfullerene. Synth. Met. 1997, 84, 231−232.

Wysocka-Zolopa is acknowledged for assistance in the preparation of the figures.

REFERENCES (1) Giacalone, F.; Martin, N. Fullerene Polymers: Synthesis and Properties. Chem. Rev. 2006, 106, 5136−5190. (2) Giacalone, F.; Martin, N. New Concepts and Applications in the Macromolecular Chemistry of Fullerenes. Adv. Mater. 2010, 22, 4220− 4248. (3) Eklund, P. C.; Rao, A. M. Fullerene Polymers and Fullerene Polymer Composites; Springer: Berlin, 1999. (4) Wang, C.; Guo, Z.-X.; Fu, S.; Wu, W.; Zhu, D. Polymers containing Fullerene or Carbon Nanotube Structures. Prog. Polym. Sci. 2004, 29, 1079−1141. (5) Chiang, L. Y.; Wang, L. Y. Polimer Derivatives of Fullerenes. In Fullerenes: Chemistry, Physics, and Technology; Kadish, K. M., Ruoff, R. S., Eds.; Wiley: New York, 2000; Chapter 7. (6) Yeretzian, C.; Hansen, K.; Diederichi, F. N.; Whetten, R. L. Coalescence Reactions of Fullerenes. Nature 1992, 359, 44−47. (7) Ito, A.; Morikawa, T.; Takahashi, T. Photo-induced Polymerization and Oxidation of C60 Observed by Photoelectron Spectroscopy. Chem. Phys. Lett. 1993, 211, 333−336. (8) Zhou, P.; Dong, Z. H.; Rao, A.; Eklund, P. C. Reaction Mechanism for the Photopolymerization of Solid Fullerene C60. Chem. Phys. Lett. 1993, 211, 337−340. (9) Rao, A. M.; Zhou, P.; Wang, K. A.; Hager, G. T.; Holden, J. M.; Wang, Y.; Lee, W. T.; Bi, X. X.; Eklund, P. C.; Cornett, D. S.; Duncan, M. A.; Amster, I. J. Photoinduced Polymerization of Solid C60 Films. Science 1993, 259, 955−957. (10) Zhao, Y. B.; Poirier, D. M.; Pechman, R. J.; Weaver, J. H. Electron Stimulated Polymerization of Solid C60. Appl. Phys. Lett. 1994, 64, 577−579. (11) Takahashi, N.; Dock, H.; Matsuzawa, N.; Ata, M. PlasmaPolymerized C60/C70 Mixture Films: Electric Conductivity and Structure. J. Appl. Phys. 1993, 74, 5790−5798. (12) Yamawaki, H.; Yoshida, M.; Kakudate, Y.; Usuba, S.; Yokoi, H.; Fujiwara, S.; Aoki, K.; Ruoff, R.; Malhotra, R.; Lorents, D. C. Infrared Study of Vibrational Property and Polymerization of Fullerene C60 and C70 under Pressure. J. Phys. Chem. 1993, 97, 11161−11163. (13) Iwasa, Y.; Arima, T.; Fleming, R. M.; Siegrist, T.; Zhou, O.; Haddon, R. C.; Rothberg, L. J.; Lyons, K. B.; Carter, H. L., Jr.; Hebard, A. F.; Tycko, R.; Dabbagh, G.; Krajewski, J. J.; Thomas, G. A.; Yagi, T. New Phases of C60 Synthesized at High Pressure. Science 1994, 264, 1570−1572. (14) Stephens, P. W.; Bortel, G.; Faigel, G.; Tegze, M.; Janossy, A.; Pekker, S.; Oszlanyi, G.; Forro, L. Polymeric Fullerene Chains in RbC60 and KC60. Nature 1994, 370, 636−639. (15) Huq, A.; Stephens, P. W.; Bendele, G. M.; Ibberson, R. M. Polymeric Fullerene Chains in RbC60 and KC60. Chem. Phys. Lett. 2001, 347, 13−22. (16) Launois, P.; Moret, R.; Llusca, E.; Hoene, J.; Zettl, A. Polymer Chain Orientations in KC60 and RbC60: Structural Analysis and Relation with Electronic Properties. Synth. Met. 1999, 103, 2354− 2357. (17) Pekker, S.; Forro, L.; Mihaly, L.; Janossy, A. Orthorhombic A1C60: A Conducting Linear Alkali Fulleride Polymer? Solid State Commun. 1994, 90, 349−352. (18) Schober, H.; Renker, B. Spectroscopic Characterization of Phase Transformations in KC60. Solid State Commun. 1998, 106, 581−585. (19) de Swiet, T. M.; Yarger, J. L.; Wagberg, T.; Hone, J.; Gross, B. J.; Tomaselli, M.; Titman, J. J.; Zettl, A.; Mehring, M. Electron Spin Density Distribution in the Polymer Phase of CsC60: Assignment of the NMR Spectrum. Phys. Rev. Lett. 2000, 84, 717−720. (20) Strasser, P.; Ata, M. Electrochemical Synthesis of Polymerized LiC60 Films. J. Phys. Chem. B 1998, 102, 4131−4134. (21) Wang, G.-W.; Komatsu, K.; Murata, Y.; Shiro, M. Synthesis and X-ray Structure of Dumb-Bell-Shaped C120. Nature 1997, 387, 583− 586. 3871


Chemical Reviews

Review

(43) Cravino, A.; Zerza, C.; Maggini, M.; Bucella, S.; Svensson, M.; Andersson, M. R.; Neugebauer, H.; Sariciftci, N. S. A Novel Polythiophene with Pendant Fullerenes: Toward Donor/Acceptor Double-Cable Polymers. Chem. Commun. 2000, 2487−2488. (44) Cravino, A.; Zerza, C.; Neugebauer, H.; Bucella, S.; Maggini, M.; Menna, E.; Svensson, M.; Andersson, M. R.; Sariciftci, N. S. Electropolymerization and Spectroscopic Properties of a Novel Double-Cable Polythiophene with Pendant Fullerenes for Photovoltaic Applications. Synth. Met. 2001, 121, 1555−1556. (45) Cravino, A.; Zerza, C.; Neugebauer, H.; Maggini, M.; Bucella, S.; Menna, E.; Svensson, M.; Andersson, M. R.; Brabec, C. J.; Sariciftci, N. S. Electrochemical and Photophysical Properties of a Novel Polythiophene with Pendant Fulleropyrrolidine Moieties: Toward “Double Cable” Polymers for Optoelectronic Devices. J. Phys. Chem. B 2002, 106, 70−76. (46) Benincori, T.; Brenna, E.; Sannicolo, F.; Trimarco, L.; Zotti, G.; Sozzani, P. The First “Charm Bracelet” Conjugated Polymer: an Electroconducting Polythiophene with Covalently Bound Fullerene Moieties. Angew. Chem., Int. Ed. Engl. 1996, 35, 648−651. (47) Murata, Y.; Suzuki, M.; Komatsu, K. Synthesis and Electropolymerization of Fullerene−Terthiophene Dyads. Org. Biomol. Chem. 2003, 1, 2624−2625. (48) Yamazaki, T.; Murata, Y.; Komatsu, K.; Furukawa, K.; Morita, M.; Maruyama, N.; Yamao, T.; Fujita, S. Synthesis and Electrolytic Polymerization of the Ethylenedioxy-Substituted Terthiophene−Fullerene Dyad. Org. Lett. 2004, 6, 4865−4868. (49) Sonmez, G.; Shen, C. K. F.; Rubin, Y.; Wudl, F. The Unusual Effect of Bandgap Lowering by C60 on a Conjugated Polymer. Adv. Mater. 2005, 17, 897−900. (50) Roncali, J. Electrogenerated Functional Conjugated Polymers as Advanced Electrode Materials. J. Mater. Chem. 1999, 9, 1875−1893. (51) Blanchard, P.; Huchet, L.; Levillain, E.; Roncali, J. Cation Template Assisted Electrosynthesis of a Highly π-Conjugated Polythiophene containing Oligooxyethylene Segments. Electrochem. Commun. 2000, 2, 1−5. (52) Perepichka, I.; Besbes, M.; Levillain, E.; Salle, M.; Roncali, J. Hydrophilic Oligo(oxyethylene)-Derivatized Poly(3,4-ethylenedioxythiophenes): Cation-Responsive Optoelectroelectro-chemical Properties and Solid-State Chromism. Chem. Mater. 2002, 14, 449−457. (53) Huang, H. D.; Goh, S. H.; Lee, S. Y. Miscibility of C60-EndCapped Poly(ethylene oxide) with Poly(p-vinylphenol). Macromol. Chem. Phys. 2000, 201, 2660−2665. (54) Ford, W. T.; Lary, A. L.; Mourey, T. H. Addition of Polystyryl Radicals from TEMPO-Terminated Polystyrene to C60. Macromolecules 2001, 34, 5819−5826. (55) Cloutet, E.; Fillaut, J. L.; Gnanou, Y.; Astruc, D. C60 EndCapped Polystyrene Stars. Chem. Commun. 1996, 1565−1566. (56) Cloutet, E.; Fillaut, J. L.; Astruc, D.; Gnanou, Y. Star Block Copolymers and Hexafullerene Stars via Derivatization of Star-Shaped Polystyrenes. Macromolecules 1999, 32, 1043−1054. (57) Zhou, P.; Chen, G. Q.; Li, C. Z.; Du, F. S.; Li, Z. C.; Li, F. M. Synthesis of Hammer-Like Macromolecules of C60 with Well-Defined Polystyrene Chains via Atom Transfer Radical Polymerization (ATRP) using a C60-Monoadduct Initiator. Chem. Commun. 2000, 797−798. (58) Nepal, D.; Samal, S.; Geckeler, K. E. The First FullereneTerminated Soluble Poly(azomethine) Rotaxane. Macromolecules 2003, 36, 3800−3802. (59) Zheng, J.; Goh, S. H.; Lee, S. Y. Miscibility of C60-containing Poly(methyl methacrylate)/Poly(vinylidene fluoride) Blends. J. Appl. Polym. Sci. 2000, 75, 1393−1396. (60) Zheng, J.; Goh, S. H.; Lee, S. Y. Miscibility of Poly(vinylidene fluoride) with C60-Containing Poly(ethyl methacrylate), Poly(methyl acrylate), or Poly(ethyl acrylate). Fullerene Sci. Technol. 2001, 9, 487− 495. (61) Wang, Z. Y.; Kuang, L.; Meng, X. S.; Gao, J. P. New Route to Incorporation of [60] Fullerene into Polymers via the Benzocyclobutenone Group. Macromolecules 1998, 31, 5556−5558.

(62) Wang, C.; Tao, Z.; Yang, W.; Fu, S. Synthesis and Photoconductivity Study of C60-Containing Styrene/Acrylamide Copolymers. Macromol. Rapid Commun. 2001, 22, 98−103. (63) Chen, Y.; Tsai, C. H. Reversible Photoreaction of C60containing Poly(vinyl alcohol). J. Appl. Polym. Sci. 1998, 70, 605−611. (64) Patil, A. O.; Brois, S. J. Fullerene Grafted Hydrocarbon Polymers. Polymer 1997, 38, 3423−3424. (65) Chen, Y.; Wang, J.; Lin, Y.; Cai, R.; Huang, Z. E. Synthesis and Characterization of Polystyrene-Substituted [70]Fullerene. Polymer 2000, 41, 1233−1236. (66) Shen, J.; Chen, Y.; Cai, R.; Huang, Z. E. Covalent Incorporation of [70]Fullerene into Poly(p-methylstyrene) by Anionic Copolymerization. Polymer 2000, 41, 9291−9298. (67) Song, T.; Dai, S.; Tam, K. C.; Lee, S. Y.; Goh, S. H. Aggregation Behavior of Two-Arm Fullerene-Containing Poly(ethylene oxide). Polymer 2003, 44, 2529−2536. (68) Bedrov, D.; Smith, G. D.; Li, L. Molecular Dynamics Simulation Study of the Role of Evenly Spaced Poly(ethylene oxide) Tethers on the Aggregation of C60 Fullerenes in Water. Langmuir 2005, 21, 5251− 5255. (69) Ederle, Y.; Mathis, C.; Nuffer, R. Reaction of “Living” Poly(ethylene oxide) Chains with C60. Synth. Met. 1997, 86, 2287− 2288. (70) Delpeux, F.; Beguin, F.; Benoit, R.; Erre, R.; Manolova, N.; Rashkov, I. Fullerene Core Star-Like Polymers 1. Preparation from Fullerenes and Monoazidopolyethers. Eur. Polym. J. 1998, 34, 905− 915. (71) Delpeux, F.; Beguin, F.; Manolova, N.; Rashkov, I. Fullerene Core Star-like Polymers 2. Preparation from Fullerenes and Linear or Cyclic Monoaminopolyethers. Eur. Polym. J. 1999, 35, 1619−1628. (72) Yevlampieva, N.; Nazarova, O.; Bokov, S.; Dmitrieva, T.; Filippov, S.; Panarin, E.; Rjumtsev, E. Star-Like Fullerene Containing Poly(vinylpyrrolydone) Derivatives: Chloroform Solution Properties. Fullerenes, Nanotubes, Carbon Nanostruct. 2004, 12, 353−359. (73) Chen, Y.; Huang, W. S.; Huang, Z. E.; Cai, R. F.; Yu, H. K.; Chen, S. M.; Yan, X. M. Synthesis and Characterization of a Soluble and Starlike C60(CH3)x(PAN)x Copolymer. Eur. Polym. J. 1997, 33, 823−828. (74) Wang, Y. Photoconductivity of Fullerene-Doped Polymers. Nature 1992, 356, 585−587. (75) Sariciftci, N. S.; Smilowitz, L.; Heeger, A. J.; Wudl, F. Photoinduced Electron Transfer from a Conducting Polymer to Buckminsterfullerene. Science 1992, 258, 1474−1476. (76) Balch, A. L.; Winkler, K. Electrochemically formed TwoComponent Films comprised of Fullerene and Transition-Metal Components. C. R. Chim. 2006, 9, 928−943. (77) Winkler, K.; Balch, A. L.; Kutner, W. Electrochemically Formed Fullerene-Based Polymeric Films. J. Solid State Electrochem. 2006, 10, 761−784. (78) Fagan, P. J.; Calabrese, J. C.; Malone, B. The Chemical Nature of Buckminsterfullerene (C60) and the Characterization of a Platinum Derivative. Science 1991, 252, 1160−1161. (79) Lee, K.; Song, H.; Park, J. T. [60] Fullerene-Metal Cluster Complexes: Novel Bonding Modes and Electronic Vommunication. Acc. Chem. Res. 2003, 36, 78−86. (80) Fagan, P. J.; Calabrese, J. C.; Malone, B. A Multiply-substituted Buckminsterfullerene (C60) with an Octahedral Array of Platinum Atoms. J. Am. Chem. Soc. 1991, 113, 9408−9411. (81) Chase, B.; Fagan, P. J. Substituted C60 Molecules: a Study in Symmetry Reduction. J. Am. Chem. Soc. 1992, 114, 2252−2256. (82) Lerke, S. A.; Parkinson, B. A.; Evans, D. H.; Fagan, P. J. Electrochemical Studies on Metal Derivatives of Buckminsterfullerene (C60). J. Am. Chem. Soc. 1992, 114, 7807−7813. (83) Brady, F. J.; Cardina, D. J.; Domin, M. New Organometallic Complexes of Buckminsterfullerene having π-bondend Nickel, Palladium, or Platinum with Triorganophosphite Ligands, and Their Characterisation. J. Organomet. Chem. 1995, 491, 169−172. 3872


Chemical Reviews

Review

σ-Carboranyl Complex of Iridium. Eur. J. Inorg. Chem. 2002, 2002, 2565−2567. (101) Thompson, D. M.; Bengough, M.; Baird, M. C. Anionic Fullerene-60 Complexes of Manganese(−I), Cobalt(−I), and Rhenium(−I): Thermal and Photoinduced Electron Transfer Processes between Metal Carbonylate Anions and C60. Organometallics 2002, 21, 4762−4770. (102) Song, L. C.; Liu, P. C.; Hu, Q. M.; Lu, G. L.; Wang, G. F. Synthesis, Characterization and Properties of New Organocobalt Complexes Containing η5-functionally Substituted Cyclopentadienyl and [60]Fullerene Ligands. J. Organomet. Chem. 2003, 681, 264−268. (103) Usatov, A. V.; Blumenfeld, A. L.; Vorontsov, A. L.; Vinogradova, L. E.; Novikov, Y. N. Organometallic Hydrides as Reactants in Fullerene Chemistry. Synthesis and Configuration of (η2Cn)RhH(CO)(PPh3)2 (n = 60,70) Complexes. Mendeleev Commun. 1993, 3, 229−230. (104) Rasinkangas, M.; Pakkanen, T. T.; Pakkanen, T. A. The First Ruthenium Carbonyl Derivative of Fullerene: (η2-C60)Ru(CO)4. J. Organomet. Chem. 1994, 476, C6−C8. (105) Usatov, A. V.; Martynova, E. V.; Neretin, I. S.; Slovokhotov, Y. L.; Peregudov, A. S.; Novikov, Y. N. The First Mononuclear η2-C60 Complex of Osmium: Synthesis and X-ray Crystal Structure of [(η2C60)Os(CO)(tBuNC)(PPh3)2]. Eur. J. Inorg. Chem. 2003, 2003, 2041−2044. (106) Bengough, M. N.; Thompson, D. M.; Baird, M. C.; Enright, G. D. Synthesis and Structures of the Novel Manganese(−I) Fullerene[60] Complexes M[Mn(CO)4(η2-C60)] (M = Na, PPN). Organometallics 1999, 18, 2950−2952. (107) Burlakov, V. V.; Usatov, A. V.; Lyssenko, K. A.; Antipin, M. Y.; Novikov, Y. N.; Shur, V. B. Synthesis and Structure of the First Fullerene Complex of Titanium Cp2Ti(η2-C60). Eur. J. Inorg. Chem. 1999, 1999, 1855−1857. (108) Song, L. C.; Zhu, Y. H.; Hu, Q. M. The Chemical Reactivity of Fullerene C60 towards fac-Mo(CO)3 (MeCN)(dppe) and Mo(CO)4(dppe). Synthesis, Characterization and Reactions of the Novel Fullerene Molybdenum Derivative fac-Mo(CO)3(dppe)(η2C60). Polyhedron 1998, 17, 469−473. (109) Song, L. C.; Zhu, Y. H.; Hu, Q. M. The First Fullerene Tungsten Complex Containing a Dppb Ligand fac/mer-W(CO) 3 (dppb)(η 2 -C 60 ) via Displacement Reaction of fac-W(CO)3(MeCN)(dppb). Polyhedron 1997, 16, 2141−2143. (110) Tang, K.; Zheng, S.; Jin, X.; Zeng, H.; Gu, Z.; Zhou, X.; Tang, Y. Syntheses and Structural Characterizations of Novel Tungsten and Molybdenum Complexes of Fullerene [M(η2-C60)(CO)2(phen)(dbm)]· 2C6H6·C5H12 (M = W or Mo, phen = 1,10-phenanthroline, dbm = dibutyl maleate). J. Chem. Soc., Dalton Trans. 1997, 3585−3587. (111) Song, L. C.; Liu, J. T.; Hu, Q. M.; Weng, L. H. Synthesis and Crystal Structures of Two Isomerically Pure Organotransition-Metal [60]Fullerene Derivatives Containing dppb Ligands: mer-M(CO)3(dppb)(η2-C60) (M = Mo, W). Organometallics 2000, 19, 1643−1647. (112) Song, L. C.; Liu, J. T.; Hu, Q. M.; Wang, L. H.; Zanello, P.; Fontani, M. Synthesis, Characterization, and Electrochemical Properties of Organotransition Metal Fullerene Derivatives Containing Dppf Ligands. Crystal Structures of fac-Mo(CO)3(dppf)(CH3CN), W(CO)4(dppf), and mer-W(CO)3(dppf)(η2-C60). Organometallics 2000, 19, 5342−5351. (113) Song, L. C.; Liu, J. T.; Hu, Q. M. Synthesis and Characterization of Group 6 Transition-Metal [70]Fullerene Derivatives Containing Dppb Ligands.: Crystal Structure of fac-Mo(CO)3(dppb)(CH3CN). J. Organomet. Chem. 2002, 662, 51−58. (114) Song, L. C.; Liu, P. C.; Liu, J. T.; Su, F. H.; Wang, G. F.; Hu, Q. M.; Zanello, P.; Laschi, F.; Fontani, M. Synthesis, Characterization and Electrochemical Properties of Optically Active [60]Fullerene Organotransition Metal Complexes mer-[(η2-C60)M(CO)3{(−)DIOP}] (M = Mo, W), mer-[(η2-C60)M(CO)3{(+)-DIOP}] (M = Mo, W) and [(η2-C60)M{(−)-DIOP}] (M = Pd, Pt) − Crystal Structure of [(η2-C60)Pt{(−)-DIOP}]. Eur. J. Inorg. Chem. 2003, 2003, 3201−3210.

(84) Pandolfo, L.; Maggini, M. Reaction of trans-[Pt(H)2(PCy3)2] with C60 Reductive Elimination of H2 and Formation of [Pt(PCy3)2(η2-C60)]. J. Organomet. Chem. 1997, 540, 61−65. (85) Bashilov, V. V.; Magdesieva, T. V.; Kravchuk, D. N.; Petrovskii, P. V.; Ginzburg, A. G.; Butin, K. P.; Sokolov, V. I. A New Heterobimetallic Palladium−[60]Fullerene Complex with Bidentate Bis-1,1′-[P]2-ferrocene Ligand. J. Organomet. Chem. 2000, 599, 37−41. (86) Song, L. C.; Wang, G. F.; Liu, P. C.; Hu, Q. M. Synthetic and Structural Studies on Transition Metal Fullerene Complexes Containing Phosphorus and Arsenic Ligands: Crystal and Molecular Structures of (η2-C60)M(dppf) (dppf = 1,1′-Bis(diphenylphosphino)ferrocene; M = Pt, Pd), (η2-C60)Pt(AsPh3)2, (η2-C60)Pt(dpaf) (dpaf = 1,1′-Bis(diphenylarsino)ferrocene), and (η2-C70)Pt(dpaf). Organometallics 2003, 22, 4593−4598. (87) Fagan, P. J.; Calabrese, J. C.; Malone, B. Metal Complexes of Buckminsterfullerene (C60). Acc. Chem. Res. 1992, 25, 134−142. (88) Bashilov, V. V.; Petrovskii, P. V.; Sokolov, V. I.; Lindeman, S. V.; Guzey, I. A.; Struchkov, Y. T. Synthesis, Crystal, and Molecular Structure of the Palladium(0)-Fullerene Derivative (η2-C60) Pd (PPh3)2. Organometallics 1993, 12, 991−992. (89) Balch, A. L.; Catalano, V. J.; Lee, J. W. Accumulating Evidence for the Selective Reactivity of the 6−6 Ring Fusion of Fullerene, C60. Preparation and Structure of (η2-C60)Ir(CO)Cl(PPh3)2·5C6H6. Inorg. Chem. 1991, 30, 3980−3981. (90) Balch, A. L.; Lee, J. W.; Noll, B. C.; Olmstead, M. M. A Double Addition Product of C60: C60{Ir(CO)Cl(PMe2Ph)2}2. Individual Crystallization of Two Conformational Isomers. J. Am. Chem. Soc. 1992, 114, 10984−10985. (91) Balch, A. L.; Lee, J. W.; Noll, B. C.; Olmstead, M. M. Multiple Additions of Vaska-Type Iridium Complexes to C60. Preferential Crystallization of the ″Para″ Double Addition Products: C60{Ir(CO)Cl(PMe3)2}2·2C6H6 and C60{Ir(CO)Cl(PEt3)2}2·C6H6. Inorg. Chem. 1991, 33, 5238−5243. (92) Balch, A. L.; Catalano, V. J.; Lee, J. W.; Olmstead, M. M. Supramolecular Aggregation of an (η2-C60) Iridium Complex Involving Phenyl Chelation of the Fullerene. J. Am. Chem. Soc. 1992, 114, 5455− 5457. (93) Catalano, V. J.; Parodi, N. Reversible C60 Binding to DendrimerContaining Ir(CO)Cl(PPh2R)2 Complexes. Inorg. Chem. 1997, 36, 537−541. (94) Koefod, R. S.; Hudgens, M. F.; Shapley, J. R. Organometallic Chemistry with Buckminsterfullerene. Preparation and Properties of an Indenyliridium(I) Complex. J. Am. Chem. Soc. 1991, 113, 8957− 8968. (95) Balch, A. L.; Lee, J. W.; Noll, B. C.; Olmstead, M. M. Structural Characterization of {(η2-C60)RhH(CO)(PPh3)2}: Product of the Reaction of Fullerene C60 with the Hydrogenation Catalyst Carbonylhydridotris(triphenylphosphine)rhodium. Inorg. Chem. 1993, 32, 3577−3578. (96) Usatov, A. V.; Peregudova, S. M.; Denisovich, L. I.; Vorontsov, E. V.; Vinogradova, L. E.; Novikov, Y. N. Exohedral Mono- and Bimetallic Hydride Complexes of Rhodium and Iridium with C60 and C70: Syntheses and Electrochemical Properties. J. Organomet. Chem. 2000, 599, 87−96. (97) Chernega, A. N.; Green, M. L. H.; Haggitt, J.; Stephens, A. H. H. New Transition-Metal Derivatives of the Fullerene C60. J. Chem. Soc., Dalton Trans. 1998, 755−768. (98) Usatov, A. V.; Kudin, K. N.; Vorontsov, E. V.; Vinogradova, L. E.; Novikov, Y. N. Organometallic Hydrides as Reactants in Fullerene Chemistry. Interaction of the Fullerenes C60 and C70 with HM(CO)(PPh3)3 (M = Rh and Ir) and HIr(C8H12)(PPh3)2. J. Organomet. Chem. 1996, 522, 147−153. (99) Lee, J. W.; Olmstead, M. M.; Vickery, J. S.; Balch, A. L. A Dumbbell Shaped Fullerene Dimer with An Inorganic Linker. Addition of C60 and Tetracyanoethylene to Ir2(CO)2Cl2(Ph2P(CH2)nPPh2)2 (n = 5 or 7). J. Cluster Sci. 2000, 11, 67−77. (100) Usatov, A. V.; Martynova, E. V.; Dolgushin, F. M.; Peregudov, A. S.; Antipin, M. Y.; Novikov, Y. N. Fullerene and Carborane in One Coordination Sphere: Synthesis and Structure of a Mixed η2-C60 and 3873


Chemical Reviews

Review

(134) Wang, L. T.; Cheng, H. P. Rotation, Translation, Charge Transfer, and Electronic Structure of C60 on Cu(111) Surface. Phys. Rev. B: Condens. Matter Mater. Phys. 2004, 69, 045404. (135) Weckesser, J.; Barth, J. V.; Kern, K. Mobility and Bonding Transition of C60 on Pd(110). Phys. Rev. B: Condens. Matter Mater. Phys. 2001, 64, 161403. (136) Cepek, C.; Goldoni, A. Modest, S. Chemisorption and Fragmentation of C60 on Pt(111) and Ni(110). Phys. Rev. B: Condens. Matter Mater. Phys. 1996, 53, 7466−7472. (137) He, H.; Swami, N.; Koel, B. E. Control of the Growth of Ordered C60 Films by Chemical Modification of Pt(111) Surfaces. Thin Solid Films 1999, 348, 30−37. (138) Casarin, M.; Forrer, D.; Orzali, T.; Petukhov, M.; Sambi, M.; Tondello, E.; Vittadini, A. Strong Bonding of Single C60 Molecules to (1 × 2)-Pt(110): an STM/DFT Investigation. J. Phys. Chem. C 2007, 111, 9365−9373. (139) Sakurai, T.; Wang, X. D.; Hashizume, T.; Yurov, V.; Shinohara, H.; Pickering, H. W. Adsorption of Fullerenes on Cu(111) and Ag(111) Surfaces. Appl. Surf. Sci. 1995, 87-88, 405−413. (140) Tjeng, L. H.; Hesper, R.; Heessels, A. C. L.; Heeres, A.; Jonkman, H. T.; Sawatzky, G. A. Development of the Electronic Structure in a K-doped C60 Monolayer on a Ag(111) Surface. Solid State Commun. 1997, 103, 31−35. (141) Magnano, E.; Vandre, S.; Cepek, C.; Goldoni, A.; Laine, A. D.; Curro, G. M.; Santaniello, A.; Sancrotti, M. Substrate-Adlayer Interaction at C60/Ag(110) Interface Studied by High-Resolution Synchrotron Radiation. Surf. Sci. 1997, 377−379, 1066−1070. (142) David, T.; Gimzewski, J. K.; Purdie, D.; Reihl, D.; Schlittler, R. R. Epitaxial Growth of C60 on Ag(110) Studied by Scanning Tunneling Microscopy and Tunneling Spectroscopy. Phys. Rev. B: Condens. Matter Mater. Phys. 1994, 50, 5810−5813. (143) Cepek, C.; Giovanelli, L.; Sancrotti, M.; Costantini, G.; Boragno, C.; Valbusa, U. Electronic Structure and Growth Mode of the Early Stages of C60 Adsorption at the Ag(001) Surface. Surf. Sci. 2000, 454−456, 766−770. (144) Pai, W. W.; Hsu, C. L. Ordering of an Incommensurate Molecular Layer with Adsorbate-Induced Reconstruction: C60/Ag(100). Phys. Rev. B: Condens. Matter Mater. Phys. 2003, 68, 121403. (145) Tzeng, C. T.; Lo, W. S.; Yuh, J. Y.; Chu, R. Y.; Tsuei, K. D. Photoemission, Near-Edge X-Ray-Absorption Spectroscopy, and LowEnergy Electron-Diffraction Study of C60 on Au(111) Surfaces. Phys. Rev. B: Condens. Matter Mater. Phys. 2000, 61, 2263−2272. (146) Altman, E. I.; Colton, R. J. Nucleation, Growth, and Structure of Fullerene Films on Au(111). Surf. Sci. 1992, 279, 49−67. (147) Gimzewski, J. K.; Modesti, S.; Schlittler, R. R. Cooperative SelfAssembly of Au Atoms and C60 on Au(110) Surfaces. Phys. Rev. Lett. 1994, 72, 1036−1039. (148) Pedio, M.; Felici, R.; Torrelles, X.; Rudolf, P.; Capozi, M.; Rius, J.; Ferrer, S. Study of C60/Au(110)−p(6 × 5) Reconstruction from InPlane X-Ray Diffraction Data. Phys. Rev. Lett. 2000, 85, 1040−1043. (149) Maxwell, A. J.; Bruhwiler, P. A.; Nilsson, A.; Martensson, N.; Rudolf, P. Photoemission, Autoionization, and X-Ray-Absorption Spectroscopy of Ultrathin-Film C60 on Au(110). Phys. Rev. B: Condens. Matter Mater. Phys. 1994, 49, 10717−10725. (150) Kuk, Y.; Kim, D. K.; Suh, Y. D.; Park, H. K.; Noh, H. P.; Oh, S.J.; Kim, S. K. Stressed C60 Layers on Au(001). Phys. Rev. Lett. 1993, 70, 1948−1951. (151) Felici, L.; Pedio, M.; Borgatti, F.; Iannotta, S.; Capozi, M.; Ciullo, G.; Stierle, A. X-Ray-Diffraction Characterization of Pt(111) Surface Nanopatterning Induced by C60 Adsorption. Nat. Mater. 2005, 4, 688−692. (152) He; Swami, N.; Koel, B. E. Control of the Growth of Ordered C60 Films by Chemical Modification of Pt(111) Surfaces. Thin Solid Films 1999, 348, 30−37. (153) Giovanelli, L.; Cepek, C.; Floreano, L.; Magnano, E.; Sancrotti, M.; Gotter, R.; Morgante, A.; Verdini, A.; Pesci, A.; Ferrari, L.; Pedio, M. Molecular Orientation of C60 on Pt (111) Determined by X-Ray Photoelectron Diffraction. Appl. Surf. Sci. 2003, 212−213, 57−61.

(115) Thompson, D. M.; Jones, M.; Baird, M. C. Anionic Cyclopentadienyl C60 Complexes of Molybdenum and Tungsten; The Strange Case of Iron. Eur. J. Inorg. Chem. 2003, 2003, 175−180. (116) Park, J. T.; Cho, J.-J.; Song, H. Triosmium Cluster Derivatives of [60]Fullerene. J. Chem. Soc., Chem. Commun. 1995, 15−16. (117) Park, J. T.; Song, H.; Cho, J.-J.; Chung, M.-K.; Lee, J.-H.; Suh, I.-H. Synthesis and Characterization of η2-C60 and μ3-η2,η2,η2-C60 Triosmium Cluster Complexes. Organometallics 1998, 17, 227−236. (118) Hsu, H.-F.; Shapley, J. R. Ru3(CO)9(μ3-η2,η2,η2-C60): A Cluster Face-Capping, Arene-Like Complex of C60. J. Am. Chem. Soc. 1996, 118, 9192−9193. (119) Chen, C.-H.; Aghabali, A.; Suarez, C.; Olmstead, M. M.; Balch, A. L.; Echegoyen, L. Synthesis and Characterization of BisTriruthenium Cluster Derivatives of an All Equatorial [60]Fullerene Tetramalonate. Chem. Commun. 2015, 51, 6489−6492. (120) Jin, X.; Xie, X.; Tang, K. Syntheses and X-ray Crystal Structures of Dumbbell-Shaped Bis-Fullerene Tungsten and Molybdenum Complexes. Chem. Commun. 2002, 750−751. (121) Lee, K.; Song, H.; Kim, B.; Park, J. T.; Park, S.; Choi, M. G. The First Fullerene−Metal Sandwich Complex: An Unusually Strong Electronic Communication between Two C60 Cages. J. Am. Chem. Soc. 2002, 124, 2872−2873. (122) Lee, G.; Cho, Y. J.; Park, B. K.; Lee, K.; Park, J. T. Two Metal Centers Bridging Two C60 Cages as a Wide Passage for Efficient Interfullerene Electronic Interaction. J. Am. Chem. Soc. 2003, 125, 13920−13921. (123) Konarev, D. V.; Troyanov, S. I.; Nakano, Y.; Ustimenko, K. A.; Otsuka, A.; Yamochi, H.; Saito, G.; Lyubovskaya, R. N. Magnetic Coupling in the Fullerene Dimer {Co(Ph3P)(C6H5CN)}2(μ2-η2:η2C60)2 with Two Zerovalent Cobalt Atoms as Bridges. Organometallics 2013, 32, 4038−4041. (124) Balch, A. L.; Costa, D. A.; Fawcett, W. R.; Winkler, K. Electronic Communication in Fullerene Dimers. Electrochemical and Electron Paramagnetic Resonance Study of the Reduction of C120O. J. Phys. Chem. 1996, 100, 4823−4827. (125) Konarev, D. V.; Troyanov, S. I.; Nakano, Y.; Otsuka, A.; Yamochi, H.; Saito, G.; Lyubovskaya, R. N. Molecular Structure and Spectroscopic Properties of a Nickel-Bridged {Ni(Ph3P)}2(μ2−η2, η2C60)2 Dimer. Dalton Trans. 2014, 43, 17920−17923. (126) Konarev, D. V.; Sergey, I.; Troyanov, S. I.; Ustimenko, K. A.; Nakano, Y.; Shestakov, A. F.; Otsuka, A.; Yamochi, H.; Saito, G.; Lyubovskaya, R. N. Formation of {Co(dppe)}2{μ2-η2:η2-η2:η2[(C60)2]} Dimers Bonded by Single C−C Bonds and Bridging η2Coordinated Cobalt Atoms. Inorg. Chem. 2015, 54, 4597−4599. (127) Wang, G.-W.; Komatsu, K.; Murata, Y.; Shiro, M. Synthesis and X-Ray Structure of Dumb-Bell-Shaped C120. Nature 1997, 387, 583−586. (128) Otero, G.; Mendez, J.; Martin-Gago, J. A. STM Study of C(60) Overlayers on Pt(111) Surfaces. Vacuum 2011, 85, 1059−1062. (129) Weckesser, J.; Cepek, C.; Fasel, R.; Barth, J. V.; Baumberger, F.; Greber, T.; Kern, K. Binding and Ordering of C60 on Pd(110): Investigations at the Local and Mesoscopic Scale. J. Chem. Phys. 2001, 115, 9001−9009. (130) Pedio, M.; Hevesi, K.; Zema, N.; Capozi, M.; Perfetti, P.; Gouttebaron, R.; Pireaux, J.; Caudano, R.; Rudolf, P. C60/Metal Surfaces: Adsorption and Decomposition. Surf. Sci. 1999, 437, 249− 260. (131) Hashizume, T.; Motai, K.; Wang, X. D.; Shinohara, H.; Saito, Y.; Maruyama, Y.; Ohno, K.; Kawazoe, Y.; Nishina, Y.; Pickering, H. W.; Kuk, Y.; Sakurai, T. Intramolecular Structures of C60 Molecules Adsorbed on the Cu(111)-(1 × 1) Surface. Phys. Rev. Lett. 1993, 71, 2959−2962. (132) Giudice, E.; Magnano, E.; Rusponi, S.; Boragno, C.; Valbusa, U. Morphology of C60 Thin Films Grown on Ag(001). Surf. Sci. 1998, 405, L561−L565. (133) Guo, S.; Fogarty, D. P.; Nagel, P. M.; Kandel, S. A. Thermal Diffusion of C60 Molecules and Clusters on Au(111). J. Phys. Chem. B 2004, 108, 14074−14081. 3874


Chemical Reviews

Review

(154) Weckesser, J.; Cepek, C.; Fasel, R.; Barth, J. V.; Baumberger, F.; Greber, T.; Kern, K. Binding and Ordering of C60 on Pd(110): Investigations at the Local and Mesoscopic Scale. J. Chem. Phys. 2001, 115, 9001−9009. (155) Fasel, R.; Agostino, R. G.; Aebi, P.; Schlapbach, L. Unusual Molecular Orientation and Frozen Librational Motion of C60 on Cu(110). Phys. Rev. B: Condens. Matter Mater. Phys. 1999, 60, 4517− 4520. (156) Hunt, M. R. C.; Modesti, S.; Rudolf, P.; Palmer, R. E. Charge Transfer and Structure in C60 Adsorption on Metal Surfaces. Phys. Rev. B: Condens. Matter Mater. Phys. 1995, 51, 10039−10047. (157) Kiguchi, M.; Iizumi, K.; Saiki, K.; Koma, A. Atomic and Electronic Structures of Heteroepitaxial C60 Film Grown on Ni(111), Cu(111). Appl. Surf. Sci. 2003, 212−213, 101−104. (158) Michaelson, H. B. The Work Function of the Elements and its Periodicity. J. Appl. Phys. 1977, 48, 4729−4733. (159) Rowe, J. E.; Rudolf, P.; Tjeng, L. H.; Malic, R. A.; Meigs, G.; Chen, C. T.; Chen, J.; Plummer, E. W. Synchrotron Radiation and Low Energy Electron Diffraction Studies of Ultrathin C60 Films Deposited on Cu (100), Cu (111) and Cu (110). Int. J. Mod. Phys. B 1992, 6, 3909−3913. (160) Murray, P. W.; Pedersen, M. O.; Laegsgaard, E.; Stensgaard, I.; Besenbacher, F. Growth of C60 on Cu(110) and Ni(110) Surfaces: C60-Induced Interfacial Roughening. Phys. Rev. B: Condens. Matter Mater. Phys. 1997, 55, 9360−9363. (161) Haddon, R. C.; Brus, L. E.; Raghavachari, K. Electronic Structure and Bonding in Icosahedral C60. Chem. Phys. Lett. 1986, 125, 459−464. (162) Kiguchi, M.; Iizumi, K.; Saiki, K.; Koma, A. Atomic and Electronic Structures of Heteroepitaxial C60 Film Grown on Ni(111), Cu(111). Appl. Surf. Sci. 2003, 212−213, 101−104. (163) Fasel, R.; Aebi, P.; Agostino, R. G.; Naumovic, D.; Osterwalder, J.; Santaniello, A.; Schlapbach, L. Orientation of Adsorbed C60 Molecules Determined via X-Ray Photoelectron Diffraction. Phys. Rev. Lett. 1996, 76, 4733−4736. (164) Cepek, C.; Fasel, R.; Sancrotti, M.; Greber, T.; Osterwalder, J. Coexisting Inequivalent Orientations of C60 on Ag(001). Phys. Rev. B: Condens. Matter Mater. Phys. 2001, 63, 125406. (165) Altman, E. I.; Colton, R. J. Determination of the Orientation of C60 Adsorbed on Au(111) and Ag(111). Phys. Rev. B: Condens. Matter Mater. Phys. 1993, 48, 18244−18249. (166) Maxwell, A. J.; Bruhwiler, P. A.; Andersson, S.; Arvanitis, D.; Hernnas, B.; Karis, O.; Mancini, D. C.; Martensson, N.; Gray, S. M.; Johansson, M. K. J.; Johansson, L. S. O. C60 on Al(111): Covalent Bonding and Surface Reconstruction. Phys. Rev. B: Condens. Matter Mater. Phys. 1995, 52, R5546−R5549. (167) Orzali, T.; Forrer, D.; Sambi, M.; Vittadini, A.; Casarin, M.; Tondello, E. Temperature-Dependent Self-Assemblies of C60 on (1 × 2)-Pt(110): A STM/DFT Investigation. J. Phys. Chem. C 2008, 112, 378−390. (168) Yoshida, Y.; Tanigaki, N.; Yase, K. In Situ Observation of the In-Plane Structure of C60 Thin Films on Metal Substrates Prepared by Molecular Beam Deposition. Thin Solid Films 1996, 281−282, 80−83. (169) Ohno, T. R.; Chen, Y.; Harvey, S. E.; Kroll, G. H.; Benning, P. J.; Weaver, J. H.; Chibante, L. P. F.; Smalley, R. E. Metal-Overlayer Formation on C60 for Ti, Cr, Au, La, and In: Dependence on MetalC60 Bonding. Phys. Rev. B: Condens. Matter Mater. Phys. 1993, 47, 2389−2393. (170) Marchenko, A.; Cousty, J. C60 Self-Organization at the Interface Between a Liquid C60 Solution and a Au(111) Surface. Surf. Sci. 2002, 513, 233−237. (171) Uemura, S.; Samori, P.; Kunitake, M.; Hirayama, C.; Rabe, J. P. Crystalline C60 Monolayers at the Solid−Organic Solution Interface. J. Mater. Chem. 2002, 12, 3366−3367. (172) Uemura, S.; Sakata, M.; Hirayama, C.; Kunitake, M. Fullerene Adlayers on Various Single-Crystal Metal Surfaces Prepared by Transfer from L Films. Langmuir 2004, 20, 9198−9201. (173) Haddon, R. C.; Hebard, A. F.; Rosseinsky, M. J.; Murphy, D. W.; Duclos, S. J.; Lyons, K. B.; Miller, B.; Rosamilla, J. M.; Fleming, R.

M.; Kortan, A. R.; Glarum, S. H.; Makhija, A. V.; Muller, A. J.; Eick, R. H.; Zahurak, S. M.; Tycko, R.; Dabbagh, G.; Thiel, F. A. Conducting Films of C60 and C70 by Alkali-Metal Doping. Nature 1991, 350, 320− 322. (174) Haddon, R. C.; Perel, A. S.; Morris, R. C.; Chang, S. H.; Fiory, A. T.; Hebard, A. F.; Palstra, T. T. M.; Kochanski, G. P. Electrical Resistivity and Stoichiometry of KxC60, RbxC60, and CsxC60 Films. Chem. Phys. Lett. 1994, 218, 100−106. (175) Yildirim, T.; Zhou, O.; Fischer, J. E.; Bykovetz, N.; Strongin, R. A.; Cichy, M. A.; Smith, A. B., III; Lin, C. L.; Jelinek, R. Intercalation of Sodium Heteroclusters into the C60 Lattice. Nature 1992, 360, 568− 571. (176) Stephens, P. W.; Mihaly, L.; Wiley, J. B.; Huang, S. M.; Kaner, R. B.; Diederich, F.; Whetten, R. L.; Holczer, K. Structure of RbxC60 Compounds. Phys. Rev. B: Condens. Matter Mater. Phys. 1992, 45, 543− 546. (177) Zhou, O.; Fischer, J. E.; Coustel, N.; Kycia, S.; Zhu, Q.; McGhie, A. R.; Romanow, W. J.; McCauley, J. P., Jr.; Smith, A. B., III; Cox, D. E. Structure and Bonding in Alkali-Metal-Doped C60. Nature 1991, 351, 462−464. (178) Poirier, D. M.; Owens, D. W.; Weaver, J. H. Alkali-MetalFulleride Phase Equilibria. Phys. Rev. B: Condens. Matter Mater. Phys. 1995, 51, 1830−1843. (179) Koller, D.; Martin, M. C.; Stephens, P. W.; Mihaly, L.; Pekker, S.; Janossy, A.; Chauvet, O.; Forro, L. Air Stability of Single Crystal Rb1C60 from Infrared Reflectivity Measurements. Appl. Phys. Lett. 1995, 66, 1211−1213. (180) Stephens, P. W.; Mihaly, L.; Lee, P.; Whetten, R. L.; Huang, S. M.; Kaner, R. B.; Deiderich, F.; Holczer, K. Structure of Single-Phase Suprconducting K3C60. Nature 1991, 351, 632−634. (181) Kortan, A. R.; Kopylov, N.; Fleming, R. M.; Zhou, O.; Thiel, F. A.; Haddon, R. C.; Rabe, K. M. Novel A15 Phase in Barium-Doped Fullerite. Phys. Rev. B: Condens. Matter Mater. Phys. 1993, 47, 13070− 13073. (182) Talyzin, A. V.; Jansson, U. A Comparative Raman Study of Some Transition Metal Fullerides. Thin Solid Films 2003, 429, 96− 101. (183) Lavrentiev, V.; Abe, H.; Naramoto, H.; Sakai, S.; Narumi, K. Polymeric Chains in C60 and Co Mixture. Chem. Phys. Lett. 2006, 424, 101−104. (184) Norin, L.; Jansson, U.; Dyer, C.; Jacobsson, P.; McGinnis, S. On the Existence of Transition-Metal Fullerides: Deposition and Characterization of TixC60. Chem. Mater. 1998, 10, 1184−1190. (185) Talyzin, A. V.; Jansson, U.; Usatov, A. V.; Burlakov, V. V.; Shur, V. B.; Novikov, Y. N. Comparative Raman Study of the Ti Complex Cp 2Ti(η2-C60)·C6H5CH3 and TixC60 Films. Phys. Solid State 2002, 44, 483−485. (186) Talyzin, A. V.; Jansson, U. Deposition and Characterisation of NbxC60 Films. Thin Solid Films 2002, 405, 42−49. (187) Zhao, W.; Tang, J.; Falster, A. U.; Simmons, W. B., Jr.; Sweany, R. L. Infrared Transmission Study of Lanthanide Fullendes SmxC60 Prepared by Metal Vapor Synthesis. J. Alloys Compd. 1997, 249, 242− 246. (188) Singhal, R.; Agarwal, D. C.; Mishra, Y. K.; Mohapatra, S.; Avasthi, D. K.; Chawla, A. K. Swift Heavy Ion Induced Modifications of Optical and Microstructural Properties of Silver−Fullerene C60 Nanocomposite. Nucl. Instrum. Methods Phys. Res., Sect. B 2009, 267, 1349−1352. (189) Ke, N.; Cheung, W. Y.; Wong, S. P.; Peng, S. Q. Electrical and Defect Properties of Sn-Doped C60 Thin Films. Carbon 1997, 35, 759−762. (190) Nakajima, A.; Nagao, S.; Takeda, H.; Kurikawa, T.; Kaya, K. Multiple Dumbbell Structures of Vanadium-C60 Clusters. J. Chem. Phys. 1997, 107, 6491−6494. (191) Nagao, S.; Kurikawa, T.; Miyajima, K.; Nakajima, A.; Kaya, K. Formation and Structures of Transition Metal−C60 Clusters. J. Phys. Chem. A 1998, 102, 4495−4500. 3875


Chemical Reviews

Review

(211) Talyzin, A. V.; Dzwilewski, A.; Pudelko, M. Formation of Palladium Fullerides and their Thermal Decomposition into Palladium Nanoparticles. Carbon 2007, 45, 2564−2569. (212) Kratschmer, W.; Fostiropoulos, K.; Huffman, D. R. The Infrared and Ultraviolet Absorption Spectra of Laboratory-Produced Carbon Dust: Evidence for the Presence of the C60 Molecule. Chem. Phys. Lett. 1990, 170, 167−170. (213) Douthwaite, R. E.; Green, M. L. H.; Stephens, A. H. H. Transition Metal-Carbonyl, -Hydrido and -η-Cyclopentadienyl Derivatives of the Fullerene C60. J. Chem. Soc., Chem. Commun. 1993, 1522−1523. (214) Zhang, S.; Brown, T. L.; Du, Y. Metalation of Fullerene (C60) with Pentacarbonylrhenium Radicals. Reversible Formation of C60{Re(CO)5}2. J. Am. Chem. Soc. 1993, 115, 6705−6709. (215) Rasinkangas, M.; Pakkanen, T. T.; Pakkanen, T. A. The First Ruthenium Carbonyl Derivative of Fullerene: (η2-C60)Ru(CO)4. J. Organomet. Chem. 1994, 476, C6−C8. (216) Winkler, K.; Noworyta, K.; de Bettencourt-Dias, A.; Sobczak, J. W.; Wu, C. T.; Chen, L. C.; Kutner, W.; Balch, A. L. Structure and Properties of C60−Pd Films Formed by Electroreduction of C60 and Palladium(II) Acetate Trimer: Evidence for the Presence of Palladium Nanoparticles. J. Mater. Chem. 2003, 13, 518−525. (217) Winkler, K.; de Bettencourt-Dias, A.; Balch, A. L.; Kutner, W.; Noworyta, K. Recent Advances in the Electrochemistry of Fullerene/ Transition Metal Co-polymers. In Fullerenes-Electrochemistry and Photochemistry; Fukuzumi, S., D’Souza, F., Guldi, D. M., Eds.; The Electrochemical Society, Inc.: Pennington, 2000; Vol. 8, pp 31−42. (218) Gradzka, E.; Wysocka-Zolopa, M.; Winkler, K. In Situ Conductance Studies of Two-Component C60-Pd Polymer. J. Phys. Chem. C 2014, 118, 14061−14072. (219) Winkler, K.; de Bettencourt-Dias, A.; Balch, A. L. Electrochemical Studies of C60/Pd Films Formed by the Reduction of C60 in the Presence of Palladium(II) Acetate Trimer. Effects of Varying C60/ Pd(II) Ratios in the Precursor Solutions. Chem. Mater. 2000, 12, 1386−1392. (220) Plonska, M. E.; de Bettencourt-Dias, A.; Balch, A. L.; Winkler, K. Electropolymerization of 2‘-Ferrocenylpyrrolidino-[3‘,4‘;1,2][C60]fullerene in the Presence of Palladium Acetate. Formation of an Electroactive Fullerene-Based Film with a Covalently Attached Redox Probe. Chem. Mater. 2003, 15, 4122−4131. (221) Plonska, M. E.; Makar, A.; Winkler, K.; Balch, A. L. Electrochemical Formation of Two-Component Films from 2′Ferrocenyl-pyrrolidino[3′, 4′;1,2][C60]fullerene and Transition Metal Complexes. Polym. J. Chem. 2004, 78, 1431−1441. (222) Wysocka-Zolopa, M.; Winkler, K.; Caballero, R.; Langa, F. Formation and Properties of Electroactive Fullerene based Films with a Covalently Attached Ferrocenyl Redox Probe. Electrochim. Acta 2011, 56, 5566−5574. (223) Plonska, M.; Winkler, K.; Gadde, S.; D’Souza, F.; Balch, A. L. Redox Active Two-Component Films of Palladium and Covalently Linked Zinc Porphyrin−Fullerene Dyad. Electroanalysis 2006, 18, 841−848. (224) Wysocka-Zolopa, M.; Winkler, K.; Gadde, S.; D’Souza, F. TwoComponent Polymer Films of Palladium and Fullerene with Covalently Linked Crown Ether Voids: Effect of Cation Binding on the Redox Behavior. J. Solid State Electrochem. 2012, 16, 65−74. (225) Wysocka-Zolopa, M.; Winkler, K.; Thorn, A. A.; Chancellor, C. J.; Balch, A. L. Electrochemical Properties of Two-Component Polymers of Palladium and Pyrrolidine and Piperazine Derivatives of C60. Electrochim. Acta 2010, 55, 2010−2021. (226) Kaufman, F. B.; Schroeder, A. H.; Engler, E. M.; Kramer, S. R.; Chambers, J. Q. Ion and Electron Transport in Stable, Electroactive Tetrathiafulvalene Polymer Coated Electrodes. J. Am. Chem. Soc. 1980, 102, 483−488. (227) Chidsey, C. E. D.; Murray, R. W. Electroactive Polymers and Macromolecular Electronics. Science 1986, 231, 25−31. (228) Xie, Q.; Perez-Cordero, E.; Echegoyen, L. Electrochemical Detection of C606‑ and C706‑: Enhanced Stability of Fullerides in Solution. J. Am. Chem. Soc. 1992, 114, 3978−2980.

(192) Reddic, J. E.; Robinson, J. C.; Duncan, M. A. Growth and Photodissociation of AgxC60 Cation Complexes. Chem. Phys. Lett. 1997, 279, 203−208. ( 19 3 ) H u a n g , Y . ; F r e i s e r , B . S . S y n t h e s i s o f B i s (buckminsterfullerene)nickel Cation, Ni(C60)2+, in the Gas Phase. J. Am. Chem. Soc. 1991, 113, 8186−8187. (194) Nagashima, H.; Nakaoka, A.; Saito, Y.; Kato, M.; Kawanishi, T.; Itoh, K. C60Pdn: The First Organometallic Polymer of Buckminsterfullerene. J. Chem. Soc., Chem. Commun. 1992, 377−379. (195) Nagashima, H.; Kato, Y.; Yamaguchi, H.; Kimura, E.; Kawanishi, T.; Kato, M.; Saito, Y.; Haga, M.; Itoh, K. Synthesis and Reactions of Organoplatinum Compounds of C60, C60Ptn. Chem. Lett. 1994, 1207−1210. (196) Herbst, M. H.; Pinhal, N. M.; Demetrio, F. A. T.; Dias, G. H. M.; Vugman, N. V. Solid-State Structural Studies on Amorphous Platinum−Fullerene[60] Compounds [PtnC60] (n = 1,2). J. Non-Cryst. Solids 2000, 272, 127−130. (197) Wohlers, M.; Herzog, B.; Belz, T.; Bauer, A.; Braun, T.; Ruhle, T.; Schlogl, R. Ruthenium-C60 Compounds: Properties and Catalytic Potential. Synth. Met. 1996, 77, 55−58. (198) Saha, D.; Deng, S. Hydrogen Adsorption on Pd- and RuDoped C60 Fullerene at an Ambient Temperature. Langmuir 2011, 27, 6780−6786. (199) Konarev, D. V.; Khasanov, S. S.; Nakano, Y.; Nakano, Y.; Otsuka, A.; Yamochi, H.; Saito, G.; Lyubovskaya, R. N. Fullerene at an Ambient Temperature Linear Coordination Fullerene C60 Polymer [{Ni(Me3P)2}(μ-η2,η2-C60)]∞ Bridged by Zerovalent Nickel Atoms. Inorg. Chem. 2014, 53, 11960−11965. (200) Balch, A. L.; Costa, D. A.; Winkler, K. Formation of RedoxActive, Two-Component Films By Electrochemical Reduction of C60 and Transition Metal Complexes. J. Am. Chem. Soc. 1998, 120, 9614− 9620. (201) Winkler, K.; Noworyta, K.; Kutner, W.; Balch, A. L. Study of Redox Active C60/Pd Films by Simultaneous Cyclic Voltammetry and Piezoelectric Microgravimetry at an Electrochemical Quartz Crystal Microbalance. J. Electrochem. Soc. 2000, 147, 2597−2603. (202) Grodzka, E.; Grabowska, J.; Wysocka-Zolopa, M.; Winkler, K. Electrochemical Formation and Properties of Two-Component Films of Transition Metal Complexes and C60 or C70. J. Solid State Electrochem. 2008, 12, 1267−1278. (203) Hayashi, A.; de Bettencourt-Dias, A.; Balch, A. L.; Winkler, K. Redox-Active Films formed by Electrochemical Reduction of Solutions of C60 and Platinum Complexes. J. Mater. Chem. 2002, 12, 2116−2122. (204) Brancewicz, E.; Gradzka, E.; Basa, A.; Winkler, K. Chemical Synthesis and Characterization of the C60-Pd Polymer Spherical Nanoparticles. Electrochim. Acta 2014, 128, 91−101. (205) Cowley, J. M.; Liu, M. Q.; Ramakrishna, B. L.; Peace, T. S.; Wertsching, A. K.; Pena, M. R. A New Type of Metal-Fulleride Structure: C60Pd3. Carbon 1994, 32, 746−748. (206) Chernov, V. A.; Ivanova, V. N.; Kozhevnikova, A. N. EXAFS Study of the Organometallic Polymers PdnC60 Structure. Nucl. Instrum. Methods Phys. Res., Sect. A 1995, 359, 250−253. (207) Shulga, Y. M.; Lobach, A. S.; Ivleva, I. N.; Spektor, W. N. XRay Photoelectron Spectra and Magnetic Susceptybility of the Palladium-Fullerides C60Pdn (n = 1−4.9). Dokl. Ross. Akad. Nauk 1996, 348, 783. (208) Nagashima, H.; Yamaguchi, H.; Kato, Y.; Saito, Y.; Haga, M.; Itoh, K. Facile Cleavage of Carbon-Palladium Bonds in C60Pdn with Phosphines and Phosphites. An Alternative Route to (η2-C60)PdL2 and Discovery of Fluxionarity Suggesting the Rotation of C60 on the PdL2 Species in Solution. Chem. Lett. 1993, 2153−2156. (209) Brancewicz, E.; Grądzka, E.; Winkler, K. Comparison of Electrochemical Properties of Two-Component C60-Pd Polymers Formed under Electrochemical Conditions and by Chemical Synthesis. J. Solid State Electrochem. 2013, 17, 1233−1245. (210) Ivanova, V. N. Fullerene Compounds with Transition Metals MnC60: Preparation, Struture, and Properties. J. Struct. Chem. 2000, 41, 135−148. 3876


Chemical Reviews

Review

(229) Winkler, K.; de Bettencourt-Dias, A.; Balch, A. L. Charging Processes in Electroactive C60/Pd Films: Effect of Solvent and Supporting Electrolyte. Chem. Mater. 1999, 11, 2265−2273. (230) Zhou, M.; Pagels, M.; Geschke, B.; Heinze, J. Electropolymerization of Pyrrole and Electrochemical Study of Polypyrrole. 5. Controlled Electrochemical Synthesis and Solid-State Transition of Well-Defined Polypyrrole Variants. J. Phys. Chem. B 2002, 106, 10065−10073. (231) Mao, H.; Pickup, P. G. In Situ Measurement of the Conductivity of Polypyrrole and Poly[1-methyl-3-(pyrrol-1-ylmethyl)pyridinium]+ as a Function of Potential by Mediated Voltammetry. Redox Conduction or Electronic Conduction? J. Am. Chem. Soc. 1990, 112, 1776−1782. (232) Patil, R.; Harima, Y.; Yamashita, K.; Komaguchi, K.; Itagaki, Y.; Shiotani, M. Charge Carriers in Polyaniline Film: a Correlation between Mobility and In-Situ ESR Measurements. J. Electroanal. Chem. 2002, 518, 13−19. (233) Mu, S.; Kan, J. The Effect of Salts on the Electrochemical Polymerization of Aniline. Synth. Met. 1998, 92, 149−155. (234) Zaidi, N. A.; Foreman, J. P.; Tzamalis, G.; Monkman, S. C.; Monkman, A. P. Alkyl Substituent Effects on the Conductivity of Polyaniline. Adv. Funct. Mater. 2004, 14, 479−486. (235) Zotti, G.; Zecchin, S.; Schiavon, G.; Vercelli, B.; Berlin, A.; Dalcanale, E.; Groenedaal, L. B. Potential-Driven Conductivity of Polypyrroles, Poly-N-Alkylpyrroles, and Polythiophenes: Role of the Pyrrole NH Moiety in the Doping-Charge Dependence of Conductivity. Chem. Mater. 2003, 15, 4642−4650. (236) Roncali, J.; Garnier, F.; Lemaire, M.; Garreau, R. Poly Mono-, Bi- and Trithiophene: Effect of Oligomer Chain Length on the Polymer Properties. Synth. Met. 1986, 15, 323−331. (237) Roncali, J.; Garreau, R.; Yassar, R.; Marque, P.; Garnier, F.; Lemaire, M. Effects of Steric Factors on the Electrosynthesis and Properties of Conducting Poly(3-alkylthiophenes). J. Phys. Chem. 1987, 91, 6706−6714. (238) Aubert, P. H.; Groenendaal, L.; Louwet, F.; Lutsen, L.; Vanderzande, D.; Zotti, G. In Situ Conductivity Measurements on Polyethylenedioxythiophene Derivatives with Different Counter Ions. Synth. Met. 2002, 126, 193−198. (239) Morvant, M. C.; Reynolds, J. R. In Situ Conductivity Studies of Poly(3,4-ethylenedioxythiophene). Synth. Met. 1998, 92, 57−61. (240) Ahonen, H. J.; Lukkari, J.; Kankare, J. n- and p-Doped Poly(3,4-ethylenedioxy-thiophene): Two Electronically Conducting States of the Polymer. Macromolecules 2000, 33, 6787−6793. (241) Dinca, M.; Yu, A. F.; Long, J. R. Microporous Metal−Organic Frameworks Incorporating 1,4-Benzeneditetrazolate: Syntheses, Structures, and Hydrogen Storage Properties. J. Am. Chem. Soc. 2006, 128, 8904−8913. (242) Chen, B. L.; Ockwig, N. W.; Millward, A. R.; Contreras, D. S.; Yaghi, O. M. High H2 Adsorption in a Microporous Metal−Organic Framework with Open Metal Sites. Angew. Chem., Int. Ed. 2005, 44, 4745−4749. (243) Rosi, N. L.; Kim, J.; Eddaoudi, M.; Chen, B. L.; O’Keeffe, M.; Yaghi, O. M. Rod Packings and Metal−Organic Frameworks Constructed from Rod-Shaped Secondary Building Units. J. Am. Chem. Soc. 2005, 127, 1504−1518. (244) Yaghi, O. M.; O’Keeffe, M.; Ockwig, N. W.; Chae, H. K.; Eddaoudi, M.; Kim, J. Reticular Synthesis and the Design of New Materials. Nature 2003, 423, 705−714. (245) Kitagawa, S.; Kitaura, R.; Noro, S. Functional Porous Coordination Polymers. Angew. Chem., Int. Ed. 2004, 43, 2334−2375. (246) O’Keeffe, M.; Eddaoudi, M.; Li, H. L.; Reineke, T.; Yaghi, O. M. Frameworks for Extended Solids: Geometrical Design Principles. J. Solid State Chem. 2000, 152, 3−20. (247) Noro, S.; Kitaura, R.; Kondo, M.; Kitagawa, S.; Ishii, T.; Matsuzaka, H.; Yamashita, M. Framework Engineering by Anions and Porous Functionalities of Cu (II)/4,4’-bpy Coordination Polymers. J. Am. Chem. Soc. 2002, 124, 2568−2583.

(248) Rosi, N. L.; Eddaoudi, M.; Kim, J.; O’Keeffe, M.; Yaghi, O. M. Infinite Secondary Building Units and Forbidden Catenation in MetalOrganic Frameworks. Angew. Chem., Int. Ed. 2002, 41, 284−287. (249) Kitaura, R.; Onoyama, G.; Sakamoto, H.; Matsuda, R.; Noro, S.; Kitagawa, S. Immobilization of a Metallo Schiff Base into a Microporous Coordination Polymer. Angew. Chem., Int. Ed. 2004, 43, 2684−2687. (250) Forster, P. M.; Eckert, J.; Chang, J. S.; Park, S. E.; Fermy, G.; Cheetham, A. K. Hydrogen Adsorption in Nanoporous Nickel (II) Phosphates. J. Am. Chem. Soc. 2003, 125, 1309−1312. (251) Rosi, N. L.; Eckert, J.; Eddaoudi, M.; Vodak, D. T.; Kim, J.; O’Keeffe, M.; Yaghi, O. M. Hydrogen Storage in Microporous MetalOrganic Frameworks. Science 2003, 300, 1127−1129. (252) Pan, L.; Sander, M. B.; Huang, X.; Li, J.; Smith, M.; Bittner, E.; Bockrath, B.; Johnson, J. K. Microporous Metal Organic Materials: Promising Candidates as Sorbents for Hydrogen Storage. J. Am. Chem. Soc. 2004, 126, 1308−1309. (253) Eddaoudi, M.; Kim, J.; Rosi, N.; Vodak, D.; Wachter, J.; O’Keeffe, M.; Yaghi, O. M. Systematic Design of Pore Size and Functionality in Isoreticular MOFs and their Application in Methane Storage. Science 2002, 295, 469−472. (254) Loiseau, T.; Serre, C.; Huguenard, C.; Fink, G.; Taulelle, F.; Henry, M.; Bataille, T.; Férey, G. A Rationale for the Large Breathing of the Porous Aluminum Terephthalate (MIL-53) Upon Hydration. Chem. - Eur. J. 2004, 10, 1373−1382. (255) Dybtsev, D. N.; Chun, H.; Yoon, S. H.; Kim, D.; Kim, K. Microporous Manganese Formate: A Simple Metal−Organic Porous Material with High Framework Stability and Highly Selective Gas Sorption Properties. J. Am. Chem. Soc. 2004, 126, 32−33. (256) Dybtsev, D. N.; Chun, H.; Kim, K. Rigid and Flexible: A Highly Porous Metal−Organic Framework with Unusual GuestDependent Dynamic Behavior. Angew. Chem., Int. Ed. 2004, 43, 5033− 5036. (257) Kesanli, Y.; Cui, M.; Smith, R.; Bittner, R. W.; Bockrath, B. C.; Lin, W. Highly Interpenetrated Metal−Organic Frameworks for Hydrogen Storage. Angew. Chem., Int. Ed. 2005, 44, 72−75. (258) Lee, E. Y.; Suh, M. P. A Robust Porous Material Constructed of Linear Coordination Polymer Chains: Reversible Single-Crystal to Single-Crystal Transformations upon Dehydration and Rehydration. Angew. Chem., Int. Ed. 2004, 43, 2798−2801. (259) Koh, K.; Wong-Foy, A. G.; Matzger, A. J. A Crystalline Mesoporous Coordination Copolymer with High Microporosity. Angew. Chem., Int. Ed. 2008, 47, 677−680. (260) Park, Y. K.; Choi, S. B.; Kim, H.; Kim, K.; Won, B. H.; Choi, K.; Choi, J. S.; Ahn, W. S.; Won, N.; Kim, S.; Jung, D. H.; Choi, S. H.; Kim, G. H.; Cha, S. S.; Jhon, Y. H.; Yang, J. K.; Kim, J. Crystal Structure and Guest Uptake of a Mesoporous Metal−Organic Framework Containing Cages of 3.9 and 4.7 nm in Diameter. Angew. Chem., Int. Ed. 2007, 46, 8230−8233. (261) Ferey, G.; Serre, C.; Mellot-Draznieks, C.; Millange, F.; Surble, S.; Dutour, J.; Margiolaki, I. A Hybrid Solid with Giant Pores Prepared by a Combination of Targeted Chemistry, Simulation, and Powder Diffraction. Angew. Chem., Int. Ed. 2004, 43, 6296−6301. (262) Wang, X. S.; Ma, S. Q.; Sun, D. F.; Parkin, S.; Zhou, H. C. A Mesoporous Metal-Organic Framework with Permanent Porosity. J. Am. Chem. Soc. 2006, 128, 16474−16475. (263) Li, J.-R.; Kuppler, R. J.; Zhou, H. C. Selective Gas Adsorption and Separation in Metal-Organic Frameworks. Chem. Soc. Rev. 2009, 38, 1477−1504. (264) Chen, B. L.; Xiang, S. C.; Qian, G. D. Metal−Organic Frameworks with Functional Pores for Recognition of Small Molecules. Acc. Chem. Res. 2010, 43, 1115−1124. (265) Lee, J. Y.; Farha, O. K.; Roberts, J.; Scheidt, K. A.; Nguyen, S. B. T.; Hupp, J. T. Metal−Organic Framework Materials as Catalysts. Chem. Soc. Rev. 2009, 38, 1450−1469. (266) Meek, S. T.; Greathouse, J. A.; Allendorf, M. D. Metal-Organic Frameworks: A Rapidly Growing Class of Versatile Nanoporous Materials. Adv. Mater. 2011, 23, 249−267. 3877


Chemical Reviews

Review

(267) An, J.; Geib, S. J.; Rosi, N. L. Cation-Triggered Drug Release from a Porous Zinc−Adeninate Metal−Organic Framework. J. Am. Chem. Soc. 2009, 131, 8376−8377. (268) Morozan, A.; Jaouen, F. Metal Organic Frameworks for Electrochemical Applications. Energy Environ. Sci. 2012, 5, 9269−9290. (269) D’Alessandro, D. M.; Kanga, J. R. R.; Caddy, J. S. Towards Conducting Metal-Organic Frameworks. Aust. J. Chem. 2013, 64, 718− 722. (270) Horike, S.; Umeyama, D.; Kitagawa, S. Ion Conductivity and Transport by Porous Coordination Polymers and Metal−Organic Frameworks. Acc. Chem. Res. 2013, 46, 2376−2384. (271) Kitagawa, H.; Nagao, Y.; Fujishima, M.; Ikeda, R.; Kanda, S. Highly Proton-Conductive Copper Coordination Polymer, H2dtoaCu (H2dtoa = dithiooxamide anion). Inorg. Chem. Commun. 2003, 6, 346− 348. (272) Nagao, Y.; Fujishima, M.; Ikeda, R.; Kanda, S.; Kitagawa, H. Highly Proton-Conductive Copper Coordination Polymers. Synth. Met. 2003, 133−134, 431−432. (273) Nagao, Y.; Ikeda, R.; Iijima, K.; Kubo, T.; Nakasuji, K.; Kitagawa, H. A. A New Proton-Conductive Copper Coordination Polymer, (HOC3H6)2dtoaCu (Dtoa = Dithiooxamide). Synth. Met. 2003, 135−136, 283−284. (274) Nagao, Y.; Kubo, T.; Nakasuji, K.; Ikeda, R.; Kojima, T.; Kitagawa, H. Preparation and Proton Transport Property of N, N′diethyldithiooxamidatocopper Coordination Polymer. Synth. Met. 2005, 154, 89−92. (275) Yamada, T.; Morikawa, S.; Kitagawa, H. Structures and Proton Conductivity of One-Dimensional M(dhbq)·nH2O (M = Mg, Mn, Co, Ni, and Zn, H2(dhbq) = 2,5-Dihydroxy-1,4-benzoquinone) Promoted by Connected Hydrogen-Bond Networks with Absorbed Water. Bull. Chem. Soc. Jpn. 2010, 83, 42−48. (276) Taylor, J. M.; Mah, R. K.; Moudrakovski, I. L.; Ratcliffe, C. I.; Vaidhyanathan, R.; Shimizu, G. K. H. Facile Proton Conduction via Ordered Water Molecules in a Phosphonate Metal− Organic Framework. J. Am. Chem. Soc. 2010, 132, 14055−14057. (277) Shigematsu, A.; Yamada, T.; Kitagawa, H. Wide Control of Proton Conductivity in Porous Coordination Polymers. J. Am. Chem. Soc. 2011, 133, 2034−2036. (278) Kandiah, M.; Nilsen, N. H.; Usseglio, S.; Jakobsen, S.; Olsbye, U.; Tilset, M.; Larabi, C.; Quadrelli, E. A.; Bonino, F.; Lillerud, K. P. Synthesis and Stability of Tagged UiO-66 Zr-MOFs. Chem. Mater. 2010, 22, 6632−6640. (279) Garibay, S. J.; Cohen, S. M. Isoreticular Synthesis and Modification of Frameworks with the UiO-66 Topology. Chem. Commun. 2010, 46, 7700−7702. (280) Foo, M. L.; Horike, S.; Fukushima, T.; Hijikata, Y.; Kubota, Y.; Takata, M.; Kitagawa, S. Ligand-Based Solid Solution Approach to Stabilisation of Sulphonic Acid Groups in Porous Coordination Polymer Zr6O4(OH)4(BDC)6 (UiO-66). Dalton Trans. 2012, 41, 13791−13794. (281) Bureekaew, S.; Horike, S.; Higuchi, M.; Mizuno, M.; Kawamura, T.; Tanaka, D.; Yanai, N.; Kitagawa, S. One-Dimensional Imidazole Aggregate in Aluminium Porous Coordination Polymers with High Proton Conductivity. Nat. Mater. 2009, 8, 831−836. (282) Umeyama, D.; Horike, S.; Inukai, M.; Hijikata, Y.; Kitagawa, S. Confinement of Mobile Histamine in Coordination Nanochannels for Fast Proton Transfer. Angew. Chem., Int. Ed. 2011, 50, 11706−11709. (283) Hurd, J. A.; Vaidhyanathan, R.; Thangadurai, V.; Ratcliffe, C. I.; Moudrakovski, I. L.; Shimizu, G. K. Anhydrous Proton Conduction at 150 °C in a Crystalline Metal−Organic Framework. Nat. Chem. 2009, 1, 705−710. (284) Umeyama, D.; Horike, S.; Inukai, M.; Itakura, T.; Kitagawa, S. Inherent Proton Conduction in a 2D Coordination Framework. J. Am. Chem. Soc. 2012, 134, 12780−12785. (285) Wiers, B. M.; Foo, M. L.; Balsara, N. P.; Long, J. R. J. A Solid Lithium Electrolyte via Addition of Lithium Isopropoxide to a Metal−Organic Framework with Open Metal Sites. J. Am. Chem. Soc. 2011, 133, 14522−14525.

(286) Chen, W. X.; Xu, H. R.; Zhuang, G. L.; Long, L. S.; Huang, R. B.; Zheng, L. S. Temperature-Dependent Conductivity of Emim+ (Emim+ = 1-Ethyl-3-methyl imidazolium) Confined in Channels of a Metal−Organic Framework. Chem. Commun. 2011, 47, 11933−11935. (287) Rodriguez-Albelo, L. M.; Ruiz-Salvador, A. R.; Sampieri, A.; Lewis, D. W.; Gomez, A.; Nohra, B.; Mialane, P.; Marrot, J.; Secheresse, F.; Mellot-Drazniecks, C.; Biboum, R. N.; Keita, B.; Nadjo, L.; Dolbecq, A. Zeolitic Polyoxometalate-Based Metal−Organic Frameworks (Z-POMOFs): Computational Evaluation of Hypothetical Polymorphs and the Successful Targeted Synthesis of the Redox-Active Z-POMOF1. J. Am. Chem. Soc. 2009, 131, 16078− 16087. (288) Mulfort, K. L.; Hupp, J. T. Chemical Reduction of MetalOrganic Framework Materials as a Method to Enhance Ggas Uptake and Binding. J. Am. Chem. Soc. 2007, 129, 9604−9605. (289) Nguyen, T. L. A.; Devic, T.; Mialane, P.; Riviere, E.; Sonnauer, A.; Stock, N.; Demir-Cakan, R.; Morcrette, M.; Livage, C.; Marrot, J.; Tarascon, J. M.; Ferey, G. Reinvestigation of the MII (M = Ni, Co)/ Tetrathiafulvalenetetracarboxylate System Using High-Throughput Methods: Isolation of a Molecular Complex and Its Single-Crystalto-Single-Crystal Transformation to a Two-Dimensional Coordination Polymer. Inorg. Chem. 2010, 49, 10710−10719. (290) Qin, Y. R.; Zhu, Q. Y.; Huo, L. B.; Shi, Z.; Bian, G. Q.; Dai, J. Tetrathiafulvalene-Tetracarboxylate: An Intriguing Building Block with Versatility in Coordination Structures and Redox Properties. Inorg. Chem. 2010, 49, 7372−7381. (291) Horikoshi, R.; Mochida, T.; Eur, J. Ferrocene-Containing Coordination Polymers: Ligand Design and Assembled Structures. Eur. J. Inorg. Chem. 2010, 2010, 5355−5371. (292) Halls, J. E.; Hernan-Gomez, A.; Burrows, A. D.; Marken, F. Metal−Organic Frameworks Post-Synthetically Modified with Ferrocenyl Groups: Framework Effects on Redox Processes and Surface Conduction. Dalton Trans. 2012, 41, 1475−1480. (293) Hermes, S.; Schroder, F.; Amirjalayer, S.; Schmid, R.; Fischer, R. Loading of Porous Metal−Organic Open Frameworks with Organometallic CVD Precursors: Inclusion Compounds of the Type [LnM]a@MOF-5. J. Mater. Chem. 2006, 16, 2464−2472. (294) Muller, M.; Lebedev, O. I.; Fischer, R. A. Gas-Phase Loading of [Zn4O(btb)2] (MOF-177) with Organometallic CVD-Precursors: Inclusion Compounds of the Type [LnM]a@MOF-177 and the Formation of Cu and Pd Nanoparticles Inside MOF-177. J. Mater. Chem. 2008, 18, 5274−5281. (295) Meilikhov, M.; Yusenko, K.; Fischer, R. A. The Adsorbate Structure of Ferrocene inside [Al(OH)(bdc)]x (MIL-53): A Powder X-ray Diffraction Study. Dalton Trans. 2009, 38, 600−602. (296) Meilikhov, M.; Yusenko, K.; Fischer, R. A. Incorporation of Metallocenes into the Channel Structured Metal−Organic Frameworks MIL-53 (Al) and MIL-47 (V). Dalton Trans. 2010, 39, 10990− 10999. (297) Bell, S. R.; Groves, J. T. A Highly Reactive P450 Model Compound I. J. Am. Chem. Soc. 2009, 131, 9640−9641. (298) Ferey, G.; Millange, F.; Morcrette, M.; Serre, C.; Doublet, M. L.; Greneche, J. M.; Tarascon, J. M. Mixed-Valence Li/Fe-Based Metal−Organic Frameworks with Both Reversible Redox and Sorption Properties. Angew. Chem., Int. Ed. 2007, 46, 3259−3263. (299) Saravanan, K.; Nagarathinam, M.; Balaya, P.; Vittal, J. J. Lithium Storage in a Metal Organic Framework with Diamondoid Topology−a Case Study on Metal Formates. J. Mater. Chem. 2010, 20, 8329−8335. (300) Li, X.; Cheng, F.; Zhang, S.; Chen, J. Shape-Controlled Synthesis and Lithium-Storage Study of Metal-Organic Frameworks Zn4O(1,3,5-benzenetribenzoate)2. J. Power Sources 2006, 160, 542− 547. (301) Nohra, B.; Moll, H. E.; Rodriguez Albelo, L. M.; Mialane, P.; Marrot, J.; Mellot-Draznieks, C.; O’Keeffe, M.; Biboum, R. N.; Lemaire, J.; Keita, B.; Nadjo, L.; Dolbecq, A. Polyoxometalate-Based Metal Organic Frameworks (POMOFs): Structural Trends, Energetics, and High Electrocatalytic Efficiency for Hydrogen Evolution Reaction. J. Am. Chem. Soc. 2011, 133, 13363−13374. 3878


Chemical Reviews

Review

at 150 C in a Crystalline Metal−Organic Framework. Nat. Chem. 2009, 1, 705−710. (320) Lee, D. Y.; Yoon, S. J.; Shrestha, N. K.; Lee, S. H.; Ahn, H.; Han, S. H. Unusual Energy Storage and Charge Retention in Co-Based Metal−Organic-Frameworks. Microporous Mesoporous Mater. 2012, 153, 163−165. (321) Diaz, R.; Orcajo, M. G.; Botas, J. A.; Calleja, G.; Palma, J. Co8MOF-5 as Electrode for Supercapacitors. Mater. Lett. 2012, 68, 126− 128. (322) Lee, D. Y.; Shinde, D. V.; Kim, E. K.; Lee, W.; Oh, I. W.; Shrestha, N. K.; Lee, J. K.; Han, S. H. Supercapacitive Property of Metal−Organic-Frameworks with Different Pore Dimensions and Morphology. Microporous Mesoporous Mater. 2013, 171, 53−57. (323) Choi, K. M.; Jeong, H. M.; Park, J. H.; Zhang, Y. B.; Kang, J. K.; Yaghi, O. M. Supercapacitors of Nanocrystalline Metal−Organic Frameworks. ACS Nano 2014, 8, 7451−7457. (324) Liao, C.; Zuo, Y.; Zhang, W.; Zhao, J.; Tang, B.; Tang, A.; Sun, Y.; Xu, J. Electrochemical Performance of Metal-Organic Framework Synthesized by a Solvothermal Method for Supercapacitors. Russ. J. Electrochem. 2013, 49, 983−986. (325) Kang, L.; Sun, S. X.; Kong, L. B.; Lang, J. W.; Luo, Y. C. Investigating Metal-Organic Framework as a New Pseudo-capacitive Material for Supercapacitors. Chin. Chem. Lett. 2014, 25, 957−961. (326) Gao, Y.; Wu, J.; Zhang, W.; Tan, Y.; Gao, J.; Zhao, J.; Tang, B. Synthesis of Nickel Oxalate/Zeolitic Imidazolate Framework-67 (NiC2O4/ZIF-67) as a Supercapacitor Electrode. New J. Chem. 2015, 39, 94−97. (327) Etaiw, S. E. H.; Fouda, A. E. A. S.; Abdou, S. N.; Elbendary, M. M. Structure, Characterization and Inhibition Activity of New Metal− Organic Framework. Corros. Sci. 2011, 53, 3657−3665. (328) Massoud, A. A.; Hefnawy, A.; Langer, V.; Khatab, M. A.; Ohrstrom, L.; Abu-Yousesef, M. A. M. Synthesis, X-Ray Structure and Anti-Corrosion Activity of Two Silver(I) Pyrazino Complexes. Polyhedron 2009, 28, 2794−2802. (329) Etaiw, S. E. H.; Fouda, A. E. A. S.; Amer, S. A.; Elbendary, M. M. Structure, Characterization and Anti-Corrosion Activity of the New Metal−Organic Framework [Ag(qox)(4-ab)]. J. Inorg. Organomet. Polym. Mater. 2011, 21, 327−335. (330) Liu, B.; Zhang, X.; Shioyama, H.; Mukai, T.; Sakai, T.; Xu, Q. Converting Cobalt Oxide Subunits in Cobalt Metal-Organic Framework into Agglomerated Co3O4 Nanoparticles as an Electrode Material for Lithium Ion Battery. J. Power Sources 2010, 195, 857−861. (331) Zhao, J.; Wang, F.; Su, P.; Li, M.; Chen, J.; Yang, Q.; Li, C. Spinel ZnMn2O4 Nanoplate Assemblies Fabricated via “Escape-byCrafty-Scheme” Strategy. J. Mater. Chem. 2012, 22, 13328−13333. (332) Chae, H. K.; Siberio-Perez, D. Y.; Kim, J.; Go, Y.; Eddaoudi, M.; Matzger, A. J.; O’Keeffe, M.; Yaghi, O. M. A Route to High Surface Area, Porosity and Inclusion of Large Molecules in Crystals. Nature 2004, 427, 523−527. (333) Demessence, A.; D’Alessandro, D. M.; Foo, L. M.; Long, J. R. Strong CO2 Binding in a Water-Stable, Triazolate-Bridged Metal− Organic Framework Functionalized with Ethylenediamine. J. Am. Chem. Soc. 2009, 131, 8784−8786. (334) Caskey, S. R.; Wong-Foy, A. G.; Matzger, A. J. Dramatic Tuning of Carbon Dioxide Uptake via Metal Substitution in a Coordination Polymer with Cylindrical Pores. J. Am. Chem. Soc. 2008, 130, 10870−10871. (335) Goenaga, G.; Ma, S.; Yuan, S.; Liu, D. J. New Approaches to Non-PGM Electrocatalysts using Porous Framework Materials. ECS Trans. 2010, 33, 579−586. (336) Ma, S.; Goenaga, G. A.; Call, A. V.; Liu, D. J. Cobalt Imidazolate Framework as Precursor for Oxygen Reduction Reaction Electrocatalysts. Chem. - Eur. J. 2011, 17, 2063−2067. (337) Proietti, E.; Jaouen, F.; Lefevre, M.; Larouche, N.; Tian, J.; Herranz, J.; Dodelet, J. P. Iron-Based Cathode Catalyst with Enhanced Power Density in Polymer Electrolyte Membrane Fuel Cells. Nat. Commun. 2011, 2, 416.

(302) Wang, C.; Xie, Z.; deKrafft, K. E.; Lin, W. Doping Metal− Organic Frameworks for Water Oxidation, Carbon Dioxide Reduction, and Organic Photocatalysis. J. Am. Chem. Soc. 2011, 133, 13445− 13454. (303) Babu, K. F.; Kulandainathan, M. A.; Katsounaros, I.; Rassaei, L.; Burrows, A. D.; Raithby, P. R.; Marken, F. Electrocatalytic Activity of Basolite TM F300 Metal-Organic-Framework Structures. Electrochem. Commun. 2010, 12, 632−635. (304) Jahan, M.; Bao, Q.; Loh, K. P. Electrocatalytically Active Graphene−Porphyrin MOF Composite for Oxygen Reduction Reaction. J. Am. Chem. Soc. 2012, 134, 6707−6713. (305) Mao, J.; Yang, L.; Yu, P.; Wei, X.; Mao, L. Electrocatalytic Four-Electron Reduction of Oxygen with Copper (II)-Based MetalOrganic Frameworks. Electrochem. Commun. 2012, 19, 29−31. (306) Yang, L.; Kinoshita, S.; Yamada, T.; Kanda, S.; Kitagawa, H.; Tokunaga, M.; Ishimoto, T.; Ogura, T.; Nagumo, R.; Miyamoto, A.; Koyama, M. A Metal−Organic Framework as an Electrocatalyst for Ethanol Oxidation. Angew. Chem., Int. Ed. 2010, 49, 5348−5351. (307) Jia, G.; Gao, Y.; Zhang, W.; Wang, H.; Cao, Z.; Li, C.; Li, C.; Liu, J. Metal-Organic Frameworks as Heterogeneous Catalysts for Electrocatalytic Oxidative Carbonylation of Methanol to Dimethyl Carbonate. Electrochem. Commun. 2013, 34, 211−214. (308) Wang, X.; Zhao, H.; Lin, H.; Liu, G.; Fang, J.; Chen, B. Renewable New Copper Complex Bulk-Modified Carbon Paste Electrode: Preparation, Electrochemistry, and Electrocatalysis. Electroanalysis 2008, 20, 1055−1060. (309) Wei, W.; Yu, K.; Su, Z.; Yu, Y.; Zhou, B.; Zhu, C. A Novel Copper Molybdate Inorganic−Organic Hybrid Network Synthesized by In-situ Generation of Pyridine-4-carboxylic Ion from 1, 3-Bis(4pyridyl)propane Precursor. Inorg. Chem. Commun. 2012, 17, 21−25. (310) Yang, Y.; Liu, S.; Li, C.; Li, S.; Ren, G.; Wei, F.; Tang, Q. A Metal−Organic Framework Based on Wells−Dawson Polyoxometalates [As2W18O62]6−Template. Inorg. Chem. Commun. 2012, 17, 54. (311) Lin, H.; Wang, X.; Hu, H.; Chen, B.; Liu, G. A Novel Copper(II) Complex Constructed with Mixed Ligands of Biphenyl4,4′-dicarboxylic Acid (H 2 bpdc) and Dipyrido[3,2-d:2′,3′-f]quinoxaline (Dpq): Synthesis, Structure, Electrochemistry and Electrocatalysis. Solid State Sci. 2009, 11, 643−650. (312) Zhang, C.; Wang, M.; Liu, L.; Yang, X.; Xu, X. Electrochemical Investigation of a New Cu-MOF and Its Electrocatalytic Activity towards H2O2 Oxidation in Alkaline Solution. Electrochem. Commun. 2013, 33, 131−134. (313) Kumar, R. S.; Kumar, S. S.; Kulandainathan, M. A. Highly Selective Electrochemical Reduction of Carbon Dioxide using Cu Based Metal Organic Framework as an Electrocatalyst. Electrochem. Commun. 2012, 25, 70−73. (314) Hosseini, H.; Ahmar, H.; Dehghani, A.; Bagheri, A.; Fakhari, A. R.; Amini, M. M. Au-SH-SiO2 Nanoparticles Supported on MetalOrganic Framework (Au-SH-SiO2@Cu-MOF) as a Sensor for Electrocatalytic Oxidation and Determination of Hydrazine. Electrochim. Acta 2013, 88, 301−309. (315) Yuan, B. Q.; Zhang, R. C.; Jiao, X. X.; Li, J.; Shi, H. Z.; Zhang, D. J. Amperometric Determination of Reduced Glutathione with a New Co-based Metal-Organic Coordination Polymer Modified Electrode. Electrochem. Commun. 2014, 40, 92−95. (316) Hosseini, H.; Ahmar, H.; Dehghani, A.; Bagheri, A.; Tadjarodi, A.; Fakhari, A. R. A Novel Electrochemical Sensor Based on MetalOrganic Framework for Electro-catalytic Oxidation of L-cysteine. Biosens. Bioelectron. 2013, 42, 426−429. (317) Zhang, Y. F.; Nsabimana, A.; Zhu, L. D.; Bo, X. J.; Han, C.; Li, M.; Guo, L. P. Metal Organic Frameworks/Macroporous Carbon Composites with Enhanced Stability Properties and Good Electrocatalytic Ability for Acid and Hemoglobin. Talanta 2014, 129, 55−62. (318) Zhang, Y. F.; Bo, X. J.; Luhana, C.; Wang, H.; Li, M.; Guo, L. P. Facile Synthesis of a Cu-based MOF Confined in Macroporous Carbon Hybrid Material with Enhanced Electrocatalytic Ability. Chem. Commun. 2013, 49, 6885−6887. (319) Hurd, J. A.; Vaidhyanathan, R.; Thangadurai, V.; Ratcliffe, C. I.; Moudrakovski, I. L.; Shimizu, G. K. H. Anhydrous Proton Conduction 3879


Chemical Reviews

Review

(338) Afsahi, F.; Kaliaguine, S. Non-precious Electrocatalysts Synthesized from Metal−Organic Frameworks. J. Mater. Chem. A 2014, 2, 12270−12279. (339) Miles, D. O.; Jiang, D.; Burrows, A. D.; Halls, J. E.; Marken, F. Conformal Transformation of [Co(bdc)(DMF)] (Co-MOF-71, Bdc = 1,4-Benzenedicarboxylate, DMF = N,N-dimethylformamide) into Porous Electrochemically Active Cobalt Hydroxide. Electrochem. Commun. 2013, 27, 9−13. (340) Salunkhe, R. R.; Kamachi, Y.; Torad, N. L.; Hwang, S. M.; Sun, Z.; Dou, S. X.; Kim, J. H.; Yamauchi, Y. Fabrication of Symmetric Supercapacitors Based on MOF-derived Nanoporous Carbons. J. Mater. Chem. A 2014, 2, 19848−19854. (341) Liu, B.; Shioyama, H.; Jiang, H.; Zhang, X.; Xu, Q. Metal− Organic Framework (MOF) as a Template for Syntheses of Nanoporous Carbons as Electrode Materials for Supercapacitor. Carbon 2010, 48, 456−63. (342) Jiang, H. L.; Liu, B.; Lan, Y. Q.; Kuratani, K.; Akita, T.; Shioyama, H.; Zong, F.; Xu, Q. From Metal−Organic Framework to Nanoporous Carbon: Toward a Very High Surface Area and Hydrogen Uptake. J. Am. Chem. Soc. 2011, 133, 11854−11857. (343) Chaikittisilp, W.; Hu, M.; Wang, H.; Huang, H. S.; Fujita, T.; Wu, K. C.; Chen, L. C.; Yamauchi, Y.; Ariga, K. Nanoporous Carbons through Direct Carbonization of a Zeolitic Imidazolate Framework for Supercapacitor Electrodes. Chem. Commun. 2012, 48, 7259−7261. (344) Das, R.; Pachfule, P.; Banerjee, R.; Poddar, P. Metal and Metal Oxide Nanoparticle Synthesis from Metal Organic Frameworks (MOFs): Finding the Border of Metal and Metal Oxides. Nanoscale 2012, 4, 591−599. (345) Su, C. Y.; Goforth, A. M.; Smith, M. D.; Pellechia, P. J.; zur Loye, H. C. Exceptionally Stable, Hollow Tubular Metal−Organic Architectures: Synthesis, Characterization, and Solid-State Transformation Study. J. Am. Chem. Soc. 2004, 126, 3576−3586. (346) Liu, X. Zinc Oxide Nano- and Microfabrication from Coordination-Polymer Templates. Angew. Chem., Int. Ed. 2009, 48, 3018−3021. (347) Cho, W.; Park, S.; Oh, M. Coordination Polymer Nanorods of Fe-MIL-88B and Their Utilization for Selective Preparation of Hematite and Magnetite Nanorods. Chem. Commun. 2011, 47, 4138−4140. (348) Thakuria, H.; Borah, B. M.; Das, G. ZnO Nanoparticles from a Metal-Organic Framework Containing ZnII Metallacycles. Eur. J. Inorg. Chem. 2007, 2007, 524−529. (349) Xiong, Y. J.; Xie, Y.; Li, Z. Q.; Wu, C. Z. Growth of WellAligned γ-MnO2 Monocrystalline Nanowires through a CoordinationPolymer-Precursor Route. Chem. - Eur. J. 2003, 9, 1645−1651. (350) Cho, W.; Lee, Y. H.; Lee, H. J.; Oh, M. Systematic Transformation of Coordination Polymer Particles to Hollow and Non-hollow In2O3 with Pre-defined Morphology. Chem. Commun. 2009, 4756−4758. (351) Lang, X. Y.; Hirata, A.; Fujita, T.; Chen, M. W. Nanoporous Metal/Oxide Hybrid Electrodes for Electrochemical Supercapacitors. Nat. Nanotechnol. 2011, 6, 232−236. (352) Jiang, J.; Li, Y. Y.; Liu, J. P.; Huang, X. T.; Yuan, C. Z.; Lou, X. W. Recent Advances in Metal Oxide-Based Electrode Architecture Design for Electrochemical Energy Storage. Adv. Mater. 2012, 24, 5166−5180. (353) Zhang, F.; Hao, L.; Zhang, L.; Zhamg, X. Solid-state Thermolysis Preparation of Co3O4 Nano/Micro Superstructures from Metal-Organic Framework for Supercapacitors. Int. J. Electrochem. Sci. 2011, 6, 2943−2954. (354) Olmstead, M. M.; Maitra, K.; Balch, A. L. Formation of a Curved Silver Nitrate Network That Conforms to the Shape of C60 and Encapsulates the FullereneStructural Characterization of C60{Ag(NO3)}5. Angew. Chem., Int. Ed. 1999, 38, 231−233. (355) Shrestha, L. K.; Sathish, M.; Hill, J. P.; Miyazawa, K.; Tsuruoka, T.; Sanchez-Ballester, N. M.; Honma, I.; Ji, Q. M.; Ariga, K. Alcoholinduced Decomposition of Olmstead’s Crystalline Ag(I)−Fullerene Heteronanostructure Yields ‘Bucky Cubes’. J. Mater. Chem. C 2013, 1, 1174−1181.

(356) Constable, E. C.; Zhang, G.; Housecroft, C. E.; Zampese, J. A. Bucky-blocks: Templating a Coordination Network with C60. CrystEngComm 2012, 14, 1770−1774. (357) Fan, J.; Wang, Y.; Blake, A. J.; Wilson, C.; Davies, E. S.; Khlobystov, A. N.; Schröder, M. Controlled Assembly of Silver(I)Pyridylfullerene Networks. Angew. Chem., Int. Ed. 2007, 46, 8013− 8016. (358) Peng, P.; Li, F. F.; Bowles, F. L.; Neti, V. S. P. K.; MettaMagana, A. J.; Olmstead, M. M.; Balch, A. L.; Echegoyen, L. High Yield Synthesis of a New Fullerene Linker and Its Use in the Formation of a Linear Coordination Polymer by Silver Complexation. Chem. Commun. 2013, 49, 3209−3211. (359) Peng, P.; Li, F. F.; Neti, V. S. P. K.; Metta-Magana, A. J.; Echegoyen, L. Design, Synthesis, and X-Ray Crystal Structure of a Fullerene-Linked Metal−Organic Framework. Angew. Chem., Int. Ed. 2014, 53, 160−163. (360) Kampe, S.-D.; Egger, N.; Vogel, M. Diamino and Tetraamino Derivatives of Buckminsterfullerene C60. Angew. Chem., Int. Ed. Engl. 1993, 32, 1174−1176. (361) Kampe, K.-D.; Egger, N. Reaktionen von Diaminen mit Fulleren C60. Liebigs Ann. Chem. 1995, 1995, 115−124. (362) Balch, A. L.; Cullison, B.; Fawcett, W. R.; Ginwalla, A. S.; Olmstead, M. M.; Winkler, K. Structural and Electrochemical Characterization of the Products of the C60−Piperazine Reaction. J. Chem. Soc., Chem. Commun. 1995, 2287−2288. (363) Balch, A. L.; Ginwalla, A. S.; Olmstead, M. M.; Herbst-Irmer, R. Structural Analysis of Products from the C60-Piperazine Reaction. Consistent Geometric Distortions of the Fullerene Core upon Adduct Formation. Tetrahedron 1996, 52, 5021−5032. (364) Chancellor, C. J.; Olmstead, M. M.; Balch, A. L. Formation of Crystalline Polymers from the Reaction of Amine-Functionalized C60 with Silver Salts. Inorg. Chem. 2009, 48, 1339−1345. (365) Aghabali, A.; Olmstead, M. M.; Balch, A. L. Zipping up Fullerenes into Polymers Using Rhodium(II) Acetate Dimer and N(CH2CH2)2NC60 as Building Blocks. Chem. Commun. 2014, 50, 15152−15155. (366) Hou, Y.; Cheng, Y.; Hobson, T.; Liu, J. Design and Synthesis of Hierarchical MnO2 Nanospheres/Carbon Nanotubes/Conducting Polymer Ternary Composite for High Performance Electrochemical Electrodes. Nano Lett. 2010, 10, 2727−2733. (367) Frackowiak, E.; Khomenko, V.; Jurewicz, K.; Lota, K.; Béguin, F. Supercapacitors Based on Conducting Polymers/Nanotubes Composites. J. Power Sources 2006, 153, 413−418. (368) Snook, G. A.; Kao, P.; Best, A. S. Conducting-Polymer-Based Supercapacitor Devices and Electrodes. J. Power Sources 2011, 196, 1− 12. (369) Inagaki, M.; Konno, H.; Tanaike, O. Carbon Materials for Electrochemical Capacitors. J. Power Sources 2010, 195, 7880−7903. (370) Winkler, K.; Grodzka, E.; D’Souza, F.; Balch, A. L. TwoComponent Films of Fullerene and Palladium as Materials for Electrochemical Capacitors. J. Electrochem. Soc. 2007, 154, K1−K10. (371) Wang, J.; Xu, Y.; Chen, X.; Du, X.; Li, X. Effect of Doping Ions on Electrochemical Capacitance Properties of Polypyrrole Films. Acta Phys. Chim. Sin. 2007, 23, 299−304. (372) Zhang, J.; Li, L. B.; Kong, H.; Luo, Y. C.; Kang, L. Synthesis of Polypyrrole Film by Pulse Galvanostatic Method and Its Application as Supercapacitor Electrode Materials. J. Mater. Sci. 2010, 45, 1947− 1954. (373) Noh, K. A.; Kim, D. W.; Jin, C. S.; Shin, K. H.; Kim, J. H.; Ko, J. M. Synthesis and Pseudo-capacitance of Chemically-prepared Polypyrrole Powder. J. Power Sources 2003, 124, 593−595. (374) Ryu, K. S.; Kim, K. M.; Park, N. G.; Park, Y. J.; Chang, S. H. Symmetric Redox Supercapacitor with Conducting Polyaniline Electrodes. J. Power Sources 2002, 103, 305−309. (375) Ryu, K. S.; Kim, K. M.; Park, Y. J.; Park, N. G.; Kang, M. G.; Chang, S. H. Redox Supercapacitor using Polyaniline Doped with Li Salt as Electrode. Solid State Ionics 2002, 152−153, 861−866. 3880


Chemical Reviews

Review

(394) Guenes, S.; Neugebauer, H.; Sariciftci, N. S. Conjugated Polymer-Based Organic Solar Cells. Chem. Rev. 2007, 107, 1324− 1338. (395) Delgado, J. L.; Bouit, P.-A.; Filippone, S.; Herranz, M. A.; Martín, N. Organic Photovoltaics: a Chemical Approach. Chem. Commun. 2010, 46, 4853−4865. (396) Delgado, J. L.; Martín, N.; de la Cruz, P.; Langa, F. Pyrazolinofullerenes: a Less Known Type of Highly Versatile Fullerene Derivatives. Chem. Soc. Rev. 2011, 40, 5232−5241. (397) Shtein, M.; Peumans, P.; Benziger, J. B.; Forrest, S. R. Micropatterning of Small Molecular Weight Organic Semiconductor Thin Films using Organic Vapor Phase Deposition. J. Appl. Phys. 2003, 93, 4005−4016. (398) Gettinger, C. L.; Heeger, A. J.; Drake, J. M.; Pine, D. J. A Photoluminescence Study of Poly(phenylene vinylene) Derivatives: the Intrinsic Persistence Length. J. Chem. Phys. 1994, 101, 1673−1678. (399) Roncali, J. Conjugated Poly(thiophenes): Synthesis, Functionalization, and Applications. Chem. Rev. 1992, 92, 711−738. (400) Kim, Y.; Cook, S.; Tuladhar, S. M.; Choulis, S. A.; Nelson, J.; Durrant, J. R.; Bradley, D. D. C.; Giles, M.; McCulloch, I.; Ha, C.-S.; Ree, M. A Strong Regioregularity Effect in Self-organizing Conjugated Polymer Films and High-efficiency Polythiophene: Fullerene Solar Cells. Nat. Mater. 2006, 5, 197−203. (401) Denisevich, P.; Willman, K. W.; Murray, R. W. Unidirectional Current Flow and Charge State Trapping at Redox Polymer Interfaces on Bilayer Electrodes: Principles, Experimental Demonstration, and Theory. J. Am. Chem. Soc. 1981, 103, 4727−4737. (402) Torres, W.; Fox, M. A. Rectifying Bi-layer Electrodes: Layered Conducting Polymers on Platinum. Chem. Mater. 1990, 2, 306−311. (403) Kaneto, K.; Takeda, S.; Yoshino, K. Characteristics of Heterojunction Consisting of Conducting Polymers of Polythiophene and Polypyrrole. Jpn. J. Appl. Phys. 1985, 24, L553−L555. (404) Aizawa, M.; Yamada, T.; Shinohara, T.; Akagi, K.; Shirakawa, H. Electrochemical Fabrication of a Polypyrrole−Polythiophene p−n Junction Diode. J. Chem. Soc., Chem. Commun. 1986, 1315−1317. (405) Miyauchi, S.; Goto, Y.; Tsubata, I.; Sorimachi, Y. Heterojunction Devices Consisting of Conducting Polymers. Synth. Met. 1991, 41, 1051−1056. (406) Wysocka, M.; Winkler, K.; Balch, A. L. The Electrochemical Formation and Properties of Bilayers Composed of Polypyrrole and C60-Pd Films. J. Mater. Chem. 2004, 14, 1036−1042. (407) Winkler, K.; Grodzka, E.; Sobczak, J. W.; Balch, A. L. Charge Transfer Processes in Bilayers and Co-polymers Composed of C60/Pd and 2′-Ferrocenylpyrrolidino-[3′,4′;1,2] C60/Pd Two-component Polymers. J. Mater. Chem. 2007, 17, 572−581. (408) Brancewicz, E.; Gradzka, E.; Wilczewska, A. Z.; Winkler, K. Polymeric p−n Nanojunctions: Formation and Electrochemical Properties of C60-Pd@Polypyrrole Core−Shell Nanoparticles. ChemElectroChem 2015, 2, 253−262. (409) Bedioui, F.; Devynck, J.; Bied-Charreton, C. Immobilization of Metalloporphyrins in Electropolymerized Films: Design and Applications. Acc. Chem. Res. 1995, 28, 30−36. (410) Saito, Y.; Azechi, T.; Kitamura, T.; Hasegawa, Y.; Wada, Y.; Yanagida, S. Photo-sensitizing Ruthenium Complexes for Solid State Dye Solar Cells in Combination with Conducting Polymers as Hole Conductors. Coord. Chem. Rev. 2004, 248, 1469−1478. (411) D’Souza, F.; Rogers, L. M.; O’Dell, E. S.; Kochman, A.; Kutner, W. Immobilization and Electrochemical Redox Behavior of Cytochrome c on Fullerene Film-modified Electrodes. Bioelectrochemistry 2005, 66, 35−40. (412) Noworyta, K.; D’Souza, F.; Kutner, W. Fullerene Derived Molecularly Imprinted Polymer for Chemosensing of Adenosine-5′triphosphate (ATP). Anal. Chim. Acta 2014, 844, 61−69. (413) Sulman, E.; Matveeva, V.; Semagina, N.; Yanov, I.; Bashilov, V.; Sokolov, V. Catalytic Hydrogenation of Acetylenic Alcohols Using Palladium Complex of Fullerene C60. J. Mol. Catal. A: Chem. 1999, 146, 257−263.

(376) Talbi, H.; Just, P. E.; Dao, L. H. Electropolymerization of Aniline on Carbonized Polyacrylonitrile Aerogel Electrodes: Applications for Supercapacitors. J. Appl. Electrochem. 2003, 33, 465−473. (377) Belanger, D.; Ren, X.; Davey, J.; Uribe, F.; Gottesfeld, S. Characterization and Long-Term Performance of Polyaniline-Based Electrochemical Capacitors. J. Electrochem. Soc. 2000, 147, 2923−2929. (378) Khdary, N. H.; Abdesalam, M. E.; Enany, G. E. Mesoporous Polyaniline Films for High Performance Supercapacitors. J. Electrochem. Soc. 2014, 161, G63−G68. (379) Mastragostino, M.; Arbizzani, C.; Soavi, F. Conducting Polymers as Electrode Materials in Supercapacitors. Solid State Ionics 2002, 148, 493−498. (380) Villers, D.; Jobin, D.; Soucy, C.; Cossement, D.; Chahine, R.; Breau, L.; Belanger, D. The Influence of the Range of Electroactivity and Capacitance of Conducting Polymers on the Performance of Carbon Conducting Polymer Hybrid Supercapacitor. J. Electrochem. Soc. 2003, 150, A747−A752. (381) Grodzka, E.; Pieta, P.; Dluzewski, P.; Kutner, W.; Winkler, K. Formation and Electrochemical Properties of Composites of the C60− Pd Polymer and Multi-Wall Carbon Nanotubes. Electrochim. Acta 2009, 54, 5621−5628. (382) Pieta, P.; Grodzka, E.; Winkler, K.; Venukadasula, G. M.; D’Souza, F.; Kutner, W. Preparation and Selected Properties of a Composite of the C60-Pd Conducting Polymer and Single-Wall Carbon Nanotubes. Phys. Status Solidi B 2008, 245, 2292−2295. (383) Pieta, P.; Grodzka, E.; Winkler, K.; Warczak, M.; Sadkowski, A.; Ż ukowska, G. Z.; Venukadasula, G. M.; D’Souza, F.; Kutner, W. Conductive, Capacitive, and Viscoelastic Properties of a New Composite of the C60−Pd Conducting Polymer and Single-Wall Carbon Nanotubes. J. Phys. Chem. B 2009, 113, 6682−6691. (384) Gradzka, E.; Winkler, K.; Borowska, M.; Plonska-Brzezinska, M. E.; Echegoyen, L. Comparison of the Electrochemical Properties of Thin Films of MWCNTs/C60-Pd, SWCNTs/C60-Pd and ox-CNOs/ C60-Pd. Electrochim. Acta 2013, 96, 274−284. (385) Gradzka, E.; Brancewicz, E.; Winkler, K. Morphology and Capacitance Properties of Nanostructured Composites of Carbon Nanostructures and C60-Pd Nanoparticles. ECS J. Solid State Sci. Technol. 2013, 2, M3151−M3155. (386) Zhang, Y.; Feng, H.; Wu, X.; Wang, L.; Zhang, A.; Xia, T.; Dong, H.; Li, X.; Zhang, L. Progress of Electrochemical Capacitor Electrode Materials: A Review. Int. J. Hydrogen Energy 2009, 34, 4889− 4899. (387) Frackowiak, E.; Khomenko, V.; Jurewicz, K.; Lota, K.; Beguin, F. Supercapacitors Based on Conducting Polymers/Nanotubes Composites. J. Power Sources 2006, 153, 413−418. (388) Wang, J.; Xu, Y.; Chen, Y.; Sun, X. Capacitance Properties of Single Wall Carbon Nanotube/Polypyrrole Composite Films. Compos. Sci. Technol. 2007, 67, 2981−2985. (389) Pieta, P.; Obraztsov, I.; Sobczak, J. W.; Chernyayeva, O.; Das, S. K.; D’Souza, F.; Kutner, W. A Versatile Material for a Symmetrical Electric Energy Storage Device: A Composite of the Polymer of the Ferrocene Adduct of C60 and Single-Wall Carbon Nanotubes Exhibiting Redox Conductivity at Both Positive and Negative Potentials. J. Phys. Chem. C 2013, 117, 1995−2007. (390) Pieta, P.; Venukadasula, G. M.; D’Souza, F.; Kutner, W. Preparation and Selected Properties of an Improved Composite of the Electrophoretically Deposited Single-Wall Carbon Nanotubes, Electrochemically Coated with a C60-Pd and Polybithiophene Mixed Polymer Film. J. Phys. Chem. C 2009, 113, 14046−14058. (391) Roth, C.; Hussain, I.; Bayati, M.; Nichols, R. J.; Schiffrin, D. J. Fullerene-Linked Pt Nanoparticle Assemblies. Chem. Commun. 2004, 1532−1533. (392) Lee, G.; Shim, J. H.; Kang, H.; Nam, K. M.; Song, H.; Park, J. T. Monodisperse Pt and PtRu/C60 Hybrid Nanoparticles for Fuel Cell Anode Catalysts. Chem. Commun. 2009, 5036−5038. (393) Bai, Z.; Yang, L.; Guo, Y.; Zheng, Z.; Hu, C.; Xu, P. Highefficiency Palladium Catalysts supported on Ppy-modified C60 for Formic acid Oxidation. Chem. Commun. 2011, 47, 1752−1754. 3881


Chemical Reviews

Review

(436) Mauron, P.; Remhof, A.; Bliersbach, A.; Borgschulte, A.; Züttel, A.; Sheptyakov, D.; Gaboardi, M.; Choucair, M.; Pontiroli, D.; Aramini, M.; Gorreri, A.; Riccò, M. Reversible Hydrogen Absorption in Sodium Intercalated Fullerenes. Int. J. Hydrogen Energy 2012, 37, 14307−14314. (437) Yildirim, T.; Iń ̃iguez, J.; Ciraci, S. Molecular and Dissociative Adsorption of Multiple Hydrogen Molecules on Transition Metal Decorated C60. Phys. Rev. B: Condens. Matter Mater. Phys. 2005, 72, 153403. (438) Sun, Q.; Wang, Q.; Jena, P.; Kawazoe, Y. Clustering of Ti on a C60 Surface and Its Effect on Hydrogen Storage. J. Am. Chem. Soc. 2005, 127, 14582−14583. (439) Durgun, E.; Ciraci, S.; Zhou, W.; Yildirim, T. Transition-MetalEthylene Complexes as High-Capacity Hydrogen-Storage Media. Phys. Rev. Lett. 2006, 97, 226102. (440) Aramini, M.; Milanese, C.; Pontiroli, D.; Gaboardi, M.; Girella, A.; Bertoni, G.; Ricco, M. Addition of Transition Metals to Lithium Intercalated Fullerides Enhances Hydrogen Storage Properties. Int. J. Hydrogen Energy 2014, 39, 2124−2131. (441) Tarasov, B. P.; Fokin, V. N.; Moravsky, A.vP.; Shul’ga, Y. M.; Yartys, V. A. Hydrogenation of Fullerenes C60 and C70 in the Presence of Hydride-Forming Metals and Intermetallic Compounds. J. Alloys Compd. 1997, 253−254, 25−28. (442) Saha, D.; Deng, S. Hydrogen Adsorption on Pd- and RuDoped C60 Fullerene at an Ambient Temperature. Langmuir 2011, 27, 6780−6786. (443) Wang, X. L.; Tu, J. P. Characterization and Hydrogen Storage Properties of Pt-C60 Compound. Appl. Phys. Lett. 2006, 89, 064101. (444) Hayashi, A.; Yamamoto, S.; Suzuki, K.; Matsuoka, T. The First Application of Fullerene Polymer-like Materials, C60Pdn, as Gas Adsorbents. J. Mater. Chem. 2004, 14, 2633−2637. (445) Poblet, J. M.; Munoz, J.; Winkler, K.; Cancilla, M.; Hayashi, A.; Lebrilla, C. B.; Balch, A. L. Geometric and Electronic Structure of Metal-Cage Fullerenes, C59M (M = Pt, Ir) Obtained by Laser Ablation of Electrochemically Deposited Films. Chem. Commun. 1999, 493− 494. (446) Hayashi, A.; Xie, Y.; Poblet, J. M.; Campanera, J. M.; Lebrilla, C. B.; Balch, A. L. Mass Spectrometric and Computational Studies of Heterofullerenes ([C58Pt]−, [C59Pt]+) Obtained by Laser Ablation of Electrochemically Deposited Films. J. Phys. Chem. A 2004, 108, 2192− 2198. (447) Campanera, J. M.; Bo, C.; Balch, A. L.; Ferre, J.; Poblet, J. M. Prediction of Heterofullerene Stabilities: A Combined DFT and Chemometric Study of C56Pt2, C57Pt2 and C81Pt2. Chem. - Eur. J. 2005, 11, 2730−2742.

(414) Nagashima, H.; Nakaoka, A.; Tajima, S.; Saito, Y.; Itoh, K. Catalytic Hydrogenation of Olefins and Acetylenes over C60Pdn. Chem. Lett. 1992, 1361−1364. (415) Yu, R.; Liu, Q.; Tan, K. L.; Xu, G. Q.; Ng, S. C.; Chan, H. S. O.; Hor, T. S. A. Preparation, Characterisation and Catalytic Hydrogenation Properties of Palladium Supported on C60. J. Chem. Soc., Faraday Trans. 1997, 93, 2207−2210. (416) Braun, T.; Wohlers, M.; Belz, T.; Schlogl, R. Fullerene-Based Ruthenium Catalysts: a Novel Approach for Anchoring Metal to Carbonaceous Supports. II. Hydrogenation Activity. Catal. Lett. 1997, 43, 175−180. (417) Demirdöven, N.; Deutch, J. Hybrid Cars Now, Fuel Cell Cars Later. Science 2004, 305, 974−976. (418) Crabtree, G. W.; Dresselhaus, M. S.; Buchanan, M. V. The Hydrogen Economy. Phys. Today 2004, 57, 39−44. (419) Strobel, R.; Garche, J.; Moseley, P. T.; Jorissen, L.; Wolf, G. Hydrogen Storage by Carbon Materials. J. Power Sources 2006, 159, 781−801. (420) Jena, P. Materials for Hydrogen Storage: Past, Present, and Future. J. Phys. Chem. Lett. 2011, 2, 206−211. (421) Zü t tel, A.; Sudan, P.; Mauron, P.; Kiyobayashi, T.; Emmenegger, C.; Schlapbach, L. Hydrogen Storage in Carbon Nanostructures. Int. J. Hydrogen Energy 2002, 27, 203−212. (422) Talyzin, A. V.; Shulga, Y. M.; Jacob, A. Comparative Studies of Hydrofullerides C60Hx Synthesized by Direct and Catalytic Hydrogenation. Appl. Phys. A: Mater. Sci. Process. 2004, 78, 1005−1010. (423) Brosha, E. L.; Davey, J.; Garzon, F. H.; Gottesfeld, S. J. Irreversible Hydrogenation of Solid C60 with and without Catalytic Metals. J. Mater. Res. 1999, 14, 2138−2146. (424) Luzan, S. M.; Tsybin, Y. O.; Talyzin, A. V. Reaction of C60 with Hydrogen Gas: In situ Monitoring and Pathways. J. Phys. Chem. C 2011, 115, 11484−11492. (425) Talyzin, A. V.; Sundqvist, B.; Shulga, Y. M.; Peera, A. A.; Imus, P.; Billups, W. E. Gentle Fragmentation of C60 by Strong Hydrogenation: a Route to Synthesizing New Materials. Chem. Phys. Lett. 2004, 400, 112−116. (426) Sun, Q.; Jena, P.; Wang, Q.; Marquez, M. First-Principles Study of Hydrogen Storage on Li12C60. J. Am. Chem. Soc. 2006, 128, 9741−9745. (427) Chandrakumar, K. R. S.; Ghosh, S. K. Alkali-Metal-Induced Enhancement of Hydrogen Adsorption in C60 Fullerene: An ab Initio Study. Nano Lett. 2008, 8, 13−19. (428) Yoon, M.; Yang, S.; Wang, E.; Zhang, Z. Charged Fullerenes as High-Capacity Hydrogen Storage Media. Nano Lett. 2007, 7, 2578− 2583. (429) Rabilloud, F. Structure and Electronic Properties of Alkali−C60 Nanoclusters. J. Phys. Chem. A 2010, 114, 7241−7247. (430) Rao, B. K.; Jena, P. Hydrogen Uptake by an Alkali Metal Ion. Euro. Phys. Lett. 1992, 20, 307. (431) Berseth, P. A.; Harter, A. G.; Zidan, R.; Blomqvist, A.; Araujo, C. M.; Scheicher, R. H.; Ahuja, R.; Jena, P. Carbon Nanomaterials as Catalysts for Hydrogen Uptake and Release in NaAlH4. Nano Lett. 2009, 9, 1501−1505. (432) Wellons, M. S.; Berseth, P. A.; Zidan, R. Novel Catalytic Effects of Fullerene for LiBH4 Hydrogen Uptake and Release. Nanotechnology 2009, 20, 204022. (433) Teprovich, J. A., Jr.; Knight, D. A.; Wellons, M. S.; Zidan, R. Catalytic Effect of Fullerene and Formation of Nanocomposites with Complex Hydrides: NaAlH4 and LiAlH4. J. Alloys Compd. 2011, 509, S562−S566. (434) Shane, D. T.; Corey, R. L.; Rayhel, L. H.; Wellons, M. S.; Teprovich, J. A., Jr.; Zidan, R.; Hwang, S.; Bowman, J. R.C.; Conradi, M. S. NMR Study of LiBH4 with C60. J. Phys. Chem. C 2010, 114, 19862−19866. (435) Teprovich, J. A., Jr.; Colón-Mercado, H. R.; Ward, P. A.; Peters, B.; Giri, S.; Zhou, J.; Greenway, S.; Compton, R. N.; Purusottan, J.; Zidan, R. Synthesis and Characterization of a Lithium-Doped Fullerane (Lix-C60-Hy) for Reversible Hydrogen Storage. Nano Lett. 2012, 12, 582−589. 3882


Metal-metalloporphyrin frameworks: a resurging class of functional materials.

Metal-organic frameworks as sensory materials and imaging agents.

Evaluation of Stability of Amylose Inclusion Complexes Depending on Guest Polymers and Their Application to Supramolecular Polymeric Materials.

Water adsorption in porous metal-organic frameworks and related materials.

Coordination Polymers into Functional Nanostructured Materials: Experimental Approaches Based on Mechanistic Insights.

Transition metal complexes and the activation of dioxygen.

Metal-organic frameworks as cathode materials for Li-O2 batteries.

Metal-Organic Frameworks as Active Materials in Electronic Sensor Devices.

Metal-phosphate bonding in transition metal-nucleotide complexes. The crystal and molecular structures of the polymeric copper(II) complex of guanosine 5'-monophosphate.

Versatile structures of group 13 metal halide complexes with 4,4'-bipy: from 1D coordination polymers to 2D and 3D metal-organic frameworks.

Correlation between oxygen adsorption energy and electronic structure of transition metal macrocyclic complexes.

Transition metal complexes of L-cysteine containing di- and tripeptides.

Structure and reactivity of late transition metal η³-benzyl complexes.

Symmetric nested complexes of fullerenes.

N-heterocyclic carbene-phosphinidyne transition metal complexes.

Nonlinear d(10)-ML2 Transition-Metal Complexes.

Nonlinear d(10)-ML2 Transition-Metal Complexes.

Hydrophosphination reactions with transition metal ferrocenylphosphine complexes.

An insight into fluorescent transition metal complexes.

Computing pK(A) values of hexa-aqua transition metal complexes.

Bis-amide transition metal complexes: isomerism and DNA interaction study.

First-row transition-metal-diborane and -borylene complexes.

Tuning the electronic properties in ruthenium-quinone complexes through metal coordination and substitution at the bridge.

Transition metal complexes with oligopeptides: single crystals and crystal structures.