DOI: 10.1002/chem.201402021
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Synthesis, Characterization, and Metal Ion Coordination of a Multichromophoric Highly Luminescent Polysulfurated Pyrene Andrea Fermi,[a, b] Paola Ceroni,[a] Myriam Roy,[b] Marc Gingras,*[b] and Giacomo Bergamini*[a]
Abstract: We have designed a new multichromophoric system based on a tetra(phenylthio)pyrene core appended with four terpyridine units. The system behaves as a molecular antenna that collects light with the peripheral units and funnels the energy to the very highly luminescent core. The
addition of metals ions to the investigated system can not only switch the direction of the intramolecular energy transfer, but also control the formation of three-dimensional nanoscopic objects in a dual function.
Introduction In the last 20 years, increasing attention has been devoted to multichromophoric systems capable of operating as light-harvesting antennae.[1] The purpose is to construct organized multicomponent systems in which different chromophoric molecular units are in close contact to favor the energy and/or the electron transfer, so that the excitation energy can be funneled to a specific acceptor. If one of these chromophores is also a good ligand for metal ions, new interesting properties can arise in a supramolecular system: 1) By changing the bound metal ion, it can change the energy of the lowest excited states and control (direct) the energy/electron transfer processes, and 2) by using metal ions that form complexes in a 2:1 ligand to metal stoichiometry, it becomes possible to generate supramolecular architectures and coordination polymers in which the “monomers” Scheme 1. Synthetic sequence to the tetra(phenylthio-terpyridine)pyrene 2 and chemical are glued by the metal ions. structure of model compound PyrS. DMI = 1,3-Dimethyl-2-imidazolidinone. In this paper we report the synthesis, characterization, and metal ion coordination of a new multichromophoric tetra(terpyridine) ligand, for making new supramolecular systems with tailor-made photophysical prop2,2’:6’,2’’-terpyridine units (1-SH), hereafter named compound erties and aggregation states. It is composed of a 1,3,6,8-tetra2 (Scheme 1). (phenylthio)pyrene core, with four appended mercaptophenylIn the design of this molecule, a 1,3,6,8-tetrasubstituted pyrene core has been chosen because of its geometry and its valuable photophysical and electrochemical properties. A pre[a] Dr. A. Fermi, Prof. Dr. P. Ceroni, Dr. G. Bergamini cursor, namely 1,3,6,8-tetrabromopyrene, has facilitated the Department of Chemistry “G. Ciamician” synthesis of many pyrene derivatives having direct carbonUniversity of Bologna, Via Selmi 2, 40126, Bologna (Italy) pyrene bonds.[2] Pyrene and those derivatives have thus been Fax: (+ 39) 051-2099456 widely used in several technological fields such as organic E-mail: [email protected] light-emitting devices,[3] ion sensors,[4] biological markers,[5] [b] Dr. A. Fermi, Dr. M. Roy, Prof. Dr. M. Gingras Aix-Marseille Universit, CNRS, CINaM UMR 7325 field-effect transistors,[6] liquid crystals,[7] and conformational 163 Ave. de Luminy, 13288 Marseille (France) probes.[8] As for pyrene derivatives with sulfur-pyrene bonds, Fax: (+ 33) 491829155 1,3,6,8-tetra(thio)pyrenes are still an underdeveloped and unE-mail: [email protected] derused family of compounds. However, they are known to be Supporting information for this article is available on the WWW under good organic p-conductors when doped,[9, 10] to stabilize http://dx.doi.org/10.1002/chem.201402021. Chem. Eur. J. 2014, 20, 1 – 9
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Full Paper charged species, and to give rise to complexes with thiophilic metal ions and charge-transfer complexes with organic molecules.[11] We previously reported the synthesis and the remarkable luminescent and electrochromic properties of a family of dendrimers consisting of a polysulfurated pyrene core with poly(thiophenylene) dendrons.[12] In this work, we decorated a polysulfurated pyrene core with terpyridine ligands. The terpyridine unit exhibits strong chelating activity towards various metal ions with a well-defined stoichiometry and very high association constants.[13] As a consequence, we modulated the electronic and the physicochemical properties of tetra(phenylthio)pyrene 2 from metal coordination. Additionally, 2,2’:6’,2“-terpyridyl (terpy) complexes have already been used as linkage elements for the construction of supramolecular architectures and coordination polymers[14] with a precise shape and size in solution and in the solid state.[15] We have demonstrated that the addition of metals ions to a solution of a highly luminescent multichromophoric molecular antenna can not only switch the direction of the energy transfer but can also control the formation of three-dimensional nanoscopic objects.
Figure 1. Absorption spectra of 1 (g) in CH2Cl2 and 2 (c) in CHCl3 and PyrS (b) in CH2Cl2. The absorption spectrum of 1 has been multiplied by four for comparison purposes.
Results and Discussion Synthesis and characterization Tetra-substituted derivatives of pyrene are conveniently prepared from 1,3,6,8-tetrabromopyrene, as we already reported.[12] The (phenylthio)terpyridine motif acts as a ligand to build the external periphery of the tetrasulfurated pyrene core. A classical synthetic path to provide similar molecules was reported in the literature.[16] We used an optimized protocol[17] to afford 1 in acceptable yields. Two equivalents of 2-acetylpyridine undergo condensation with 4-(methylthio)benzaldehyde in a basic media for building the terpyridyl skeleton. Following a quite known and efficient demethylation strategy,[18, 19] a deprotection to the free thiol 1-SH was performed. We found it was convenient to use solid tBuOK as a strong base, for obtaining 1-SH in a good yield on a gram scale. We succeeded in the tetrasulfuration of 1,3,6,8-tetrabromopyrene by using simple nucleophilic aromatic substitutions with the thiolate from 1-SH in polar aprotic solvents.[20] Compound 2 was obtained in good yields after purifying the crude product by trituration in warm toluene.
Figure 2. Emission spectra of 1 (g) in CH2Cl2, PyrS (b) in CH2Cl2, 2 (c) in CHCl3 and 2 solid (d). lex = 300 nm.
The emission spectrum of 1 recorded in CH2Cl2 presents a maximum at 390 nm, which can be ascribed to the radiative deactivation of the terpy-like excited state (Figure 2). The fluorescence quantum yield is rather high (F = 0.33) with a lifetime (t) of 1.40 ns. The observed band is slightly redshifted and more intense compared with that of the p-tolylterpy (lem = 350 nm, F = 0.08), this is probably due to the effect of the MeS being directly attached to the phenyl group.[21] The emission spectra of 2 obtained exciting both in the UV, in which most of the light is absorbed by the terpy moieties, and in the visible, where only the core absorbs, are identical. The intense florescence band of the tetra(p-tolylthio)pyrene PyrS with a maximum at 460 nm is shown in Figure 2.[12] The fact that no terpy emission has been detected in compound 2 indicates that the lowest excited state of the terpy units is completely quenched by the lower excited state of the pyrene core. The excitation spectrum of 2, fixing the lem = 460 nm, perfectly overlaps the absorption spectrum, indicating that intramolecular (due to low concentration in solution and ns-lifetime
Photophysical properties The absorption spectra of 1 in CH2Cl2 and 2 in CHCl3 are reported in Figure 1. Compound 1 has been studied in CH2Cl2 because of the different solubility compared with 2. The spectrum of 2 presents the typical features of tetra(ptolylthio)pyrene PyrS between 380 and 470 nm[11] and the band at 295 nm of model compound 1 (see the comparison in Figure 1). This result points out that there is no significant interaction between the pyrene and the terpyridine chromophores in the ground state, so that compound 2 can be considered a supramolecular species. &
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Full Paper Table 1. Emission properties of the investigated compounds and the respective metal complexes. Compound
lmax [nm]
F
t [ns]
1[a] 2[b] [Zn(1)2]2 + [a] 2·Zn2[b] 2·Nd2[b]
390 460 490 540 1064
0.33 0.51 0.32 0.01 0.0017[c]
1.4 1.3 4.1 1.4 –
[a] In CH2Cl2. [b] In CHCl3. [c] Fem = het hNd.
of the luminescent excited state) energy transfer takes place from the peripheral chromophores to the core with 100 % efficiency. The emission quantum yield has been estimated to 51 % (quinine sulfate in H2SO4 0.5 m was used as a standard) and the fluorescence lifetime is 1.3 ns (Table 1). As shown in Figure 2, compound 2 is fluorescent also in the solid state with a broader emission band centered at 505 nm.
Figure 3. Absorption spectra of a 1.1 10 5 m solution of 1 in CH2Cl2 upon titration with [Fe(CF3SO3)2]: 0 (c), 0.8 equiv (b). Inset shows normalized absorption changes at 298 (*), and 575 nm (~).
Photophysical properties of the metal complexes As mentioned in the introduction, 2,2’:6’,2’’-terpyridine derivatives (tpy) exhibit strong chelating affinity towards various metal ions.[14] In particular, with transition-metal ions such as iron, zinc, and neodymium, a very strong [M(tpy)2]n + complex can be obtained. We report the titration of compound 2, and compound 1 for comparison, with Zn2 + , Fe2 + , and Nd3 + ions. In each experiment, the changes in the absorption and emission spectra were monitored. We have first investigated the complexation properties of the model compound 1 with [Fe(CF3SO3)2] in CH2Cl2 solution. The absorption spectra show a redshift of the lowest energy band of the free ligand and the appearance of a band in the visible region centered at 575 nm due to a metal-to-ligand charge-transfer (MLCT) transition. Upon excitation at the isosbestic point, complete quenching of the fluorescence band at 390 nm was observed. The emission quenching was expected on the basis of the fast non-radiative decay observed for the lowest energy MLCT excited state of the pristine [Fe(tpy)2]2 + complex.[15, 22] The plots of the normalized absorption changes at 298 nm and at 580 nm reach a plateau at 0.5 equivalents of metal ion per 1 (Figure 3, inset). These results demonstrate a 2:1 ligand-to-metal stoichiometry with an association constant logb > 15, estimated by global fitting of the absorption spectra.[23] The same experiment has been carried out with molecule 2. Upon titration of a 4.5 10 6 m solution of 2 in CHCl3 with [Fe(CF3SO3)2]. We observed similar spectral changes in the absorption and emission spectra, as those recorded for 1 (Figure 4). In addition, there is a decrease of the emission band of the tetra(thio)pyrene indicating that the complexation of the metal by the external terpyridine quenches the luminescence of the core. By exciting at the isosbestic point at 410 nm, the emission band at 460 nm decreases upon additions of Fe2 + , reaching a complete quenching at two equivalents of metal ions. Chem. Eur. J. 2014, 20, 1 – 9
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Figure 4. Absorption spectra of a solution of 2 (4.5 10 6 m) in CHCl3 upon titration with [Fe(CF3SO3)2]: 0 (c), 2.5 equiv (b). Inset shows normalized absorption changes at 445 (*) and 575 nm (~).
Those results prove the formation of metal complexes in a ratio of 1:2 of ligand 2 to metal ions. Due to the fact that four terpyridine moieties are present in each molecule, the stoichiometry of terpy to metal ion is 2:1, as for the model compound 1. Considering that two terpy units of the same molecule cannot cooperate to bind a single metal ion because the structure of the molecule confines them too far apart and not in the right geometry, it follows that two molecules are linked together by intermolecular complexation of Fe2 + ions. Thereby, it forms an oligomeric structure ([Fe2n(2)n]4n + or 2·Fe2) in which a Fe2 + ion bridges two terpy units from two different molecules 2 (see the representation of the self-assembled, polymeric architecture involving 2, below). Continuing the investigations on the interactions of 1 and 2 with metal ions, we performed a similar titration with [Zn(CF3SO3)2]. The changes in the absorption spectra are similar to that observed in the case of iron except for the band at 575 nm. Concerning the emission spectra (Figure 5), in the 3
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case of 1 we observed the decreasing of the band at 390 nm and the appearance of a band at 490 nm ascribable to the formation of the [Zn(1)2]2 + metal complex.[24] The emission spectra of 2 during the addition of Zn2 + show a decrease of the band of the core at 460 nm, and the appearance of a very weak Zn-terpy emission band at 540 nm, compared with the emission of the [Zn(1)2]2 + complex. The quenching can be attributed to a thermodynamically favored[12, 25] photoinduced electron transfer from the terpy-metal complex to the tetra(phenylthio)pyrene core. After fixing the emission wavelength at 540 nm, the excitation spectrum perfectly match the absorption spectrum of 2, pointing out a 100 % energy transfer from the tetra(phenylthio)pyrene core to the Zn-terpy complexes at the periphery (see later, Figure 9). In the case of Zn2 + , the stoichiometry obtained by the titration also suggests the formation of complexes with one metal and two terpyridine units. As already stated, since it is not possible that two terpy of the same molecule coordinate the same metal ion, the formation of a “polymeric” structure is proposed.
Figure 5. Emission spectra upon titration with [Zn(CF3SO3)2]: a) 1 in CH2Cl2 (0 (c); 0.7 equiv (b)) lex = 315 nm; and b) 2 in CHCl3 (0 (c); 2 equiv (b)) lex = 305 nm. The dashed line represents the final emission of 2 after the addition of 2.2 equiv of Zn2 + multiplied by 25. Inset shows normalized emission changes at 460 nm (&).
an average diameter of 50 nm (Figure 7), which is in good agreement with the results obtained from DLS experiments. To obtain luminescent supramolecular assemblies, we performed a titration of 2 with Nd3 + . The latter ion is well known to be an infrared emitter and to have a good affinity with very high binding constants with terpyridine.[26] The addition of a CH3CN solution of [Nd(CF3SO3)3] to a CHCl3 solution of 2 causes changes in the absorption spectra, similar to those observed for the other metal ions (Figure 8 a); a complete
Structural characterization
To confirm and to evaluate the dimension of the supramolecular, metal-coordinated, polymeric structure, we carried out dynamic light scattering (DLS) experiments. The DLS analysis shows the presence of nanoparticles whose dimension increases upon metal ion addition up to two equivalents (Figure 6 b). Upon addition of 2.5 equivalents of Zn2 + , the DLS experiment indicates the formation of an aggregate with an average hydrodynamic diameter of 65 nm, with a low polydispersity index (PDI) of about 0.065. Further additions of metal ions show minor changes (even at 250 equiv: d = 76 nm, PDI = 0.216), demonstrating a stability in the particles size. Topological characterization using AFM of the 2·Zn2 solution ([2] = 2 10 6 m) and 2.5 equiv of [ZnFigure 6. a) Size distribution of the aggregates formed upon addition of Zn2 + (from 0.5 (CF3SO3)2] spin-coated onto freshly cleaved mica to 2.5 equiv); b) Plot of the changes of the particles diameter during the addition of [Znsheets indicated the formation of nanoparticles with (CF3SO3)2]. &
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Figure 7. AFM peak force mode images of height from a solution of 2·Zn2 spin-coated on mica.
quenching of the emission from the tetra(phenylthio)pyrene core together with an increase of the sensitized emission of the Nd3 + ions in the NIR is observed (Figure 8 b). It is worth remembering that the emission quantum yield calculated and reported in Table 1 is the product of the intrinsic emission quantum yield of the [Nd(tpy)2]3 + unit and the energy transfer efficiency from molecule 2 (Fem = het hNd). To evaluate which absorption wavelengths are responsible of the sensitized emission, we recorded the excitation spectrum at the lem = 1064 nm. The spectrum obtained perfectly matches the absorption spectrum of 2 after addition of 2.3 equiv of [Nd(CF3SO3)3], proving the 100 % energy transfer from the molecule to the emissive metal ion (Figure 9).
Figure 8. a) Absorption spectra of 2 upon titration with [Nd(CF3SO3)3] (0 (c); 2.7 equiv (b)); the inset shows the normalized absorption changes at 350 (~) and at 445 nm (*); b) Emission spectrum of 2 + 2.7 equiv of [Nd(CF3SO3)3], lex = 405 nm.
Conclusion We have synthesized a new multichromophoric, supramolecular polymeric system based on a tetra(thio)pyrene core appended with four phenylated terpyridine units. Compound 2, and model ligand 1, exhibit very interesting photophysical properties; in particular, the fluorescence quantum yield of 2 is remarkably high and the excitation of the terpyridine units at the periphery leads to a quantitative energy transfer to the core. Metal ion complexes are formed with the addition of iron(II), zinc(II), and neodymium(III) salts in diluted solutions. The stoichiometry observed and the geometry of the molecule suggest the formation of “super” oligomeric structures built on [M(tpy)2]n + interactions. The dimensions of these nanoparticles have been characterized by DLS and AFM measurements. In the case of 2·Nd2 the assemblies obtained are also good emitters in the infrared region and the emission of Nd is sensitized by all the chromophoric units present in 2, which undergo Chem. Eur. J. 2014, 20, 1 – 9
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Figure 9. Absorption spectrum of 2 in CHCl3 (solid line), excitation spectrum of 2 after the addition 2.2 equiv of [Zn(CF3SO3)2] (dotted line, lem = 540 nm), and excitation spectrum of 2 after the addition of 2.3 equiv of [Nd(CF3SO3)3] (dashed line, lem = 1064 nm).
a 100 % energy transfer as confirmed by the excitation spectrum. 5
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ammonium acetate (75.98 g, 0.990 mol, 32.9 equiv) in ethanol (540 mL) was then added, followed by a gentle heating at reflux for 4 h with the use of a heating mantle. During this time, a yellow-orange color appeared. After cooling at room temperature, the solvent was evaporated to 1/3 of its starting volume. Pale-yellow crystals were then formed, collected on a fritted glass after filtration, and rinsed with EtOH. More crystals were formed from the mother liquors. All crops of crystals were combined (9 g), and vigorously stirred in warm EtOH (120 mL). After cooling, the solid was filtered and recovered. A recrystallization from a warm CH2Cl2/EtOH mixture was achieved to afford 1 as pale-yellow crystalline needles (4.85 g, 13.7 mmol, 45 % yield). M.p. 173–175 8C (lit. 173–174 8C[5] ; 176 8C[2]); Rf = 0.50 (SiO2, petrol. ether/EtOAc: 4:1 v/v); HPLC: reverse-phase HPLC analysis of crystalline 1 indicated an excellent purity > 98 % (Chromatorex C18, 15 cm, CH3CN/H2O: 80:20 as mobile phase, UV detection 254 nm); 1H NMR (250.13 MHz, CDCl3): d = 2.55 (s, 3 H; SCH3), 7.35 (ddd, 4J(H,H) = 1.1 Hz, 3J(H,H) = 4.9 Hz, 3J(H,H) = 7.4 Hz, 2 H; tpySCH3(5,5II)), 7.38 (dapp, 3J(H,H) = 8.6 Hz, 2 H; Ph(3,5)], 7.85 (dapp, 3J(H,H) = 8.6 Hz, 2 H; Ph(2,6)), 7.88 (ddd, 3J(H,H) = 7.8 Hz, 3J(H,H) = 7.8 Hz, 4J(H,H) = 1.8 Hz, 2 H; tpySCH3(4,4II)), 8.67 (dapp,3J(H,H) = 7.9 Hz, 2 H; tpySCH3(3,3II)), 8.73 (s, 2 H; tpySCH3(3I,5I)), 8.74 ppm (bd, 3J(H,H) = 5.0 Hz, 2 H; tpySCH3(6,6II)); 13 C NMR (62.90 MHz, CDCl3): d = 15.5 (CH3), 118.3 (CH; tpySCH3(3I,5I)), 121.3 (CH; tpySCH3(3,3II)), 123.8 (CH; tpySCH3(5,5II)), 126.5 (CH; Ph(3,5)), 127.6 (CH; Ph(2,6), tpy(5,5II)), 134.9 (C), 136.8 (CH; tpySCH3(4,4II)), 140.0 (C), 149.1 (CH; tpySCH3(6,6II)), 149.5 (C), 155.9 (C), 156.2 ppm (C); MS-ESI (matrix: CH2Cl2, NH4Ac 3 mm, + mode): m/z calcd for C22H17N3S: 355.4; found: 356.2 [M + H] + ; 384.2.
Instruments for the characterization of compounds 1
H (250.13 MHz) and 13C NMR (62.90 MHz) spectra were recorded on a Bruker Avance 250 spectrometer at 293 K in CDCl3 (dried over activated 4 molecular sieves). Me4Si at d = 0.00 ppm or residual proton signals for CHCl3 at d = 7.26 ppm served as internal references. As for 13C NMR spectra, the central triplet resonance for CDCl3 at d = 77.36 ppm was used as internal reference. The multiplicities in 1H NMR spectra are described as: “s” (singlet), “d” (doublet), “t” (triplet), “q” (quartet), “m” multiplet, or “b” broad. MALDI-TOF-MS analyses were performed on an Autoflex MALDI-TOF Bruker spectrometer. LRMS (EI) spectra were recorded on a Shimazu GC-MS QP2010SE equipped with a DI2010 direct introduction unit and an electron impact ionization source at 70 eV. LRMS (ESI) spectra were recorded on a 3200QTRAP (Applied Biosystems SCIEX) equipped with an atmospheric ionization source (API). The samples were also ionized under ESI with an electrospray voltage of 5500 V; orifice voltage at 20 V, and an air pressure of the nebulizer at 10 psi. A linear ion trap analyzer in a positive mode was used for QTRAP. FTIR absorption spectra were recorded on a Spectrum 100 PerkinElmer instrument, with a Universal ATR accessory (contact crystal: diamond).
Chromatography TLC analyses were performed on precoated silica gel (Alugram SilG/UV254gel) aluminium plates from Macherey–Nagel. Compounds were visualized with UV light (254 or 365 nm) and detected with TLC developers: p-anisaldehyde/conc. H2SO4/EtOH (1/1/18 v/v/v) followed by heating or a molybdenum/cerium solution (100 mL H2SO4, 900 mL H2O, 25 g [Mo7O24H2O(NH4)6], 10 g [Ce(SO4)2]) followed by heating with a heat gun. Flash chromatography was performed over silica gel 60, Merck type 230–400 mesh (40–63 mm). HPLC analyses were performed with a Jasco system fitted with a PU 980 intelligent pump equipped with a LG 980–02 tertiary gradient unit, a DG 980–50 line degasser, a 7725i Rheodyne injection valve with a 20 mL loop, a UV 975 intelligent UV/Vis detector. The acquisition data were processed on a Borwin 1.21.60 version acquisition software (JMBS developments, Grenoble, France).
4’-[4-(Mercapto)phenyl]-2,2’;6’,2’’-terpyridine (1-SH):[27] An ovendried round-bottom flask fitted with a reflux-condenser was charged with tpy-SMe (1) (501.5 mg, 1.41 mmol, 1.00 equiv), and tBuOK (1.190 g, 10.61 mmol, 7.52 equiv) under an argon atmosphere. Anhydrous DMF (10.0 mL) was added through a syringe and the yellow mixture was stirred until complete dissolution. tBuSH (640 mg, 800 mL, 7.10 mmol, 5.04 equiv) was injected to the mixture and heated at 160 8C for 15 h under Ar. After cooling at 5–8 8C (ice-bath temperature), the red mixture was poured in a quasi-saturated ammonium chloride aqueous solution (75 mL, pH 5) and a pale-yellow solid precipitated. This product was then collected on a fritted glass after a filtration, and washed several times with cold distilled water to provide tpy-SH (1-SH). After drying, a paleyellow powder was obtained (447.8 mg, 1.31 mmol, 93 % yield). M.p. 169–171 8C (lit. 166–168 8C); 1H NMR (250.13 MHz, CDCl3, ppm): d = 3.57 (s, 1 H; SH), 7.34 (ddd, 3J(H,H) = 7.5 Hz, 3J(H,H) = 4.8 Hz, 4J(H,H) = 1.2 Hz, 2 H; tpySH(5,5II)), 7.40 (dapp, 3J(H,H) = 8.5 Hz, 2 H; Ph(3,5)), 7.79 (d, 3J(H,H) = 8.5 Hz, 2 H; Ph(2,6)), 7.86 (ddd, 3 J(H,H) = 7.6 Hz, 3J(H,H) = 7.6 Hz, 4J(H,H) = 1.8 Hz, 2 H; tpySH (4,4II)), 8.66 (d,3J(H,H) = 8.0 Hz, 2 H; tpySH(3,3II)), 8.70 (s, 2 H; tpySH(3I,5I)), 8.72 ppm (bd, 3J(H,H) = 4.8 Hz, 2 H; tpySH(6,6II)); 13C NMR (62.90 MHz, CDCl3): d = 118.8 (CH; tpySH(3I,5I)), 121.7 (CH; tpySH(3,3II)), 124.2 (CH; tpySH(5,5II)), 128.2 (CH; Ph(2,6)), 129.9 (CH; Ph(3,5)), 132.8 (C), 136.1 (C), 137.2 (CH; tpySCH3(4,4II)), 149.5 (CH; tpySCH3(6,6II)), 149.7 (C), 156.3 (C), 156.6 ppm (C); FTIR (ATR diamond contact; solid sample): n˜ = 2552.3 cm 1 ( SH stretching, weak); MS-EI: m/z (%): 308 (50.9) [M SH], 340 (20.6) [M H], 341 (100) [M], 342 (26.6) [M + H] + , 343 (7.7) [M + 2 H]2 + .
Syntheses Reagents were purchased from Sigma–Aldrich or Alfa Aesar and used as received. Solvents were purchased from Sigma–Aldrich, Acros Organics (Fisher Scientific) or Carlo Erba. Their purity was analytical or reagent grade, with a low water content or extra dry, and stored for many days over freshly activated 3 molecular sieves (3 h at 250 8C). DMF was dried over CaH2 overnight, distilled under reduced pressure and kept over freshly activated 3 sieves. 1,3-Dimethyl-2-imidazolidinone (DMI) was used as received and kept over 3 sieves. The synthesis of 1,3,6,8-tetrabromopyrene has been previously reported.[12, 20] 4’-[4-(Methylthio)phenyl]-2,2’;6’,2’’-terpyridine (1):[27] Potassium tert-butoxide (11.19 g, 99.7 mmol, 3.31 equiv), followed by anhydrous THF (150 mL), were added into an oven-dried, two-necked, 2L-round-bottom flask equipped with a condenser and kept under argon. After stirring the solid suspension for 30 min, 2-acetylpyridine (7.67 g, 63.3 mmol, 2.10 equiv) was slowly added through a syringe at 20 8C. 4-(Methylthio)benzaldehyde (4.58 g, 30.1 mmol, 1.00 equiv) was also injected within 5 min in a dropwise manner, while stirring vigorously. The resulting ruby-red mixture was further stirred for 2.5 days at room temperature (22 8C). A suspension of
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1,3,6,8-Tetrakis((4-([2,2’:6’,2’’-terpyridin]-4’-yl)phenyl)thio)pyrene (2): 1,3,6,8-tetrabromopyrene[12, 20] (181.4 mg, 0.350 mmol, 1.00 equiv), 4’-[4-(mercapto)phenyl]-2,2’;6’,2’’-terpyridine (1-SH) (507.0 mg, 1.48 mmol, 4.23 equiv), and Cs2CO3 (590.1 mg, 1.81 mmol, 5.17 equiv) were introduced in an oven-dried round bottom flask, and the content was further dried under high vacuum. Under argon, DMI (3.0 mL) was injected through a syringe
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Full Paper and the mixture was stirred at 60 8C for 6.5 days. After being cooled to RT, an aqueous NaOH solution (2 m, 30 mL) was poured into the mixture. A bright-yellow solid precipitated, which was separated by filtration and washed with H2O (2 5 mL). Stirring the solid in absolute ethanol (20 8C, 18 h) was followed by a second trituration in warm toluene (100 8C, 24 h). The product was filtrated, collected, and dried under high vacuum to afford a yellow powder (413 mg, 76 % yield). M.p. 335–336 8C (dec.); 1H NMR (250.13 MHz, CDCl3): d = 8.70 (s, 4 H; pyrene), 8.59 (m, 8 H; tpy), 8.53 (s, 8 H; tpy), 8.46 (dapp, 3J(H,H) = 7.8 Hz, 8 H; SPh), 8.02 (s, 2 H; tpy), 7.79–7.74 (m, 16 H; tpy), 7.42 (dapp, 3J(H,H) = 7.8 Hz, 8 H; SPh), 7.17 ppm (m, 8 H; tpy); 1H NMR (250.13 MHz, CDCl2CDCl2): d = 8.72 (s, 4 H; pyrene), 8.61 (m, 8 H; tpy), 8.53 (s, 8 H; tpy), 8.47 (dapp, 3 J(H,H) = 7.8 Hz, 8 H; SPh), 8.07 (s, 2 H; pyrene), 7.75–7.83 (m, 16 H; tpy), 7.46 (dapp, 3J(H,H) = 7.8 Hz, 8 H; SPh), 7.29 ppm (m, 8 H; tpy); 13 C NMR (62.90 MHz, CDCl2CDCl2): d = 155.6, 155.5, 148.9, 148.7, 137.4, 136.5, 136.0, 131.5, 131.2, 128.2, 125.3, 123.6, 121.0, 118.4, 103.6 ppm; FTIR (ATR, diamond contact, solid): n˜ = 3050 (CH arom), 3017 (CH arom), 1583 (C=C), 1564 (C=C), 1466 (C=C), 1382 (C=C), 1075 (CH), 1037 (CH), 826, 789 (CH, strong), 734 (CH), 660 cm 1 (CH); MALDI-TOF MS (DCTB-NaI matrix, l = 337 nm): m/z calcd for C100H62N12S4 :1558.4 [M] + , 1581.3 [M + Na] + ; found: 1558.3 [M] + , 1581.3 [M + Na] + ; elemental analalysis calcd (%) for C100H62N12S4 : C 77.00, H 4.01, N 10.78, S 8.22; found: C 74.76, H 3.87, N 10.21, S 7.85.
Aix-Marseille Universit. A.F. is grateful to the French–Italian University for a PhD scholarship from the Vinci program. We thank Dr. Guy Flix for helpful discussions on HPLC and the Spectropole of Marseille for some MS and EA data. Keywords: antenna effect · chromophores · energy transfer · supramolecular chemistry · UV/Vis spectroscopy [1] See, for example: a) S. L. Gilat, A. Adronov, J. M. J. Frchet, Angew. Chem. 1999, 111, 1519; Angew. Chem. Int. Ed. 1999, 38, 1422; b) P. D. Frischmann, K. Mahata, F. Wrthner, Chem. Soc. Rev. 2013, 42, 1847; c) A. Sautter, B. K. Kaletas, D. G. Schmid, R. Dobrawa, M. Zimine, G. Jung, I. H. M. van Stokkum, L. De Cola, R. M. Williams, F. Wrthner, J. Am. Chem. Soc. 2005, 127, 6719; d) V. Balzani, G. Bergamini, P. Ceroni, E. Marchi, New J. Chem. 2011, 35, 1944. [2] For a few examples of 1,3,6,8-tetra-C-substituted pyrenes, see: a) J. B. Shaik, V. Ramkumar, B. Varghese, S. Sankararaman, Beilstein J. Org. Chem. 2013, 9, 698; b) J.-y. Hu, M. Era, M. R. J. Elsegood, T. Yamamoto, Eur. J. Org. Chem. 2010, 72; c) T. M. Figueira-Duarte, S. C. Simon, M. Wagner, S. I. Druzhinin, K. A. Zachariasse, K. Mllen, Angew. Chem. 2008, 120, 10329; Angew. Chem. Int. Ed. 2008, 47, 10175; d) S. Bernhardt, M. Kastler, V. Enkemann, M. Baumgarten, K. Mllen, Chem. Eur. J. 2006, 12, 6117. [3] See, for example: a) K. L. Chan, J. P. F. Lim, X. Yang, A. Dodabalapur, G. E. Jabbour, A. Sellinger, Chem. Commun. 2012, 48, 5106; b) Y.-J. Pu, M. Higashidate, K. Nakayama, J. Kido, J. Mater. Chem. 2008, 18, 4183; c) J. N. Moorthy, P. Natarajan, P. Venkatakrishnan, D.-H. Huang, T. J. Chow, Org. Lett. 2007, 9, 5215; d) Y. Sagara, T. Mutai, I. Yoshikawa, K. Araki, J. Am. Chem. Soc. 2007, 129, 1520; e) Y. Oyamada, S. Akiyama, M. Yahiro, M. Saigou, M. Shiro, H. Sasabe, C. Adachi, Chem. Phys. Lett. 2006, 421, 295. [4] For recent examples, see: a) D. Maity, C. Bhaumik, D. Mondal, S. Baitalik, Inorg. Chem. 2013, 52, 13941; b) V. Amendola, G. Bergamaschi, M. Boiocchi, L. Fabbrizzi, L. Mosca, J. Am. Chem. Soc. 2013, 135, 6345; c) L. Liu, D. Zhang, G. Zhang, J. Xiang, D. Zhu, Org. Lett. 2008, 10, 2271; d) H. J. Kim, S. Y. Park, S. Yoon, J. S. Kim, Tetrahedron 2008, 64, 1294; e) A. Ben Othman, J. W. Lee, J.-S. Wu, J. S. Kim, R. Abidi, P. Thuery, J. M. Strub, A. Van Dorsselaer, J. Vicens, J. Org. Chem. 2007, 72, 7634. [5] a) J. Huang, Y. Wu, Y. Chen, Z. Zhu, X. Yang, C. J. Yang, K. Wang, W. Tan, Angew. Chem. 2011, 123, 421; Angew. Chem. Int. Ed. 2011, 50, 401; b) L. Zeng, J. Wu, Q. Dai, W. Liu, P. Wang, C.-S. Lee, Org. Lett. 2010, 12, 4014; c) H.-W. Rhee, C.-R. Lee, S.-H. Cho, M.-R. Song, M. Cashel, H. E. Choy, Y.-J. Seok, J.-I. Hong, J. Am. Chem. Soc. 2008, 130, 784; d) A. A. Marti, S. Jockusch, N. Stevens, J. Ju, N. J. Turro, Acc. Chem. Res. 2007, 40, 402. [6] See, for example: a) J. Kwon, J.-P. Hong, S. Noh, T.-M. Kim, J.-J. Kim, C. Lee, S. Lee, J.-I. Hong, New J. Chem. 2012, 36, 1813; b) L. Zçphel, D. Beckmann, V. Enkelmann, D. Chercka, R. Rieger, K. Mllen, Chem. Commun. 2011, 47, 6960; c) H. Zhang, Y. Wang, K. Shao, Y. Liu, S. Chen, W. Qiu, X. Sun, T. Qi, Y. Ma, G. Yu, D. Zhu, Chem. Commun. 2006, 755. [7] For recent examples, see: a) Y. Sagara, T. Kato, Angew. Chem. 2008, 120, 5253; Angew. Chem. Int. Ed. 2008, 47, 5175; b) S. Diring, F. Camerel, B. Donnio, T. Dintzer, S. Toffanin, R. Capelli, M. Muccini, R. Ziessel, J. Am. Chem. Soc. 2009, 131, 18177; c) M. J. Sienkowska, H. Monobe, P. Kaszynski, Y. Shimizu, J. Mater. Chem. 2007, 17, 1392; d) A. Hayer, V. De Halleux, A. Koehler, A. El-Garoughy, E. W. Meijer, J. Barbera, J. Tant, J. Levin, M. Lehmann, J. Gierschner, J. Cornil, Y. H. Geerts, J. Phys. Chem. B 2006, 110, 7653. [8] For recent examples, see: a) M. E. Østergaard, P. Cheguru, M. R. Papasani, R. A. Hill, P. J. Hrdlicka, J. Am. Chem. Soc. 2010, 132, 14221; b) D. Honcharenko, C. Zhou, J. Chattopadhyaya, J. Org. Chem. 2008, 73, 2829; c) L. Le Guyader, C. Le Roux, S. Mazeres, H. Gaspard-Iloughmane, H. Gornitzka, C. Millot, C. Mingotaud, A. Lopez, Biophys. J. 2007, 93, 4462; d) P. Storm, L. Li, P. Kinnunen, A. Wieslander, Eur. J. Biochem. 2003, 270, 1699. [9] For tetra(methylthio)derivatives: a) G. Heywang, S. Roth, Angew. Chem. 1991, 103, 201; Angew. Chem. Int. Ed. Engl. 1991, 30, 176; b) G. Heywang, L. Born, S. Roth, Synth. Met. 1991, 41, 1073. [10] For other poly(thio)pyrene derivatives: a) J.-S. Lee, K.-C. Huang, W.-J. Wang, G.-H. Lee, Synth. Met. 1995, 70, 1231 and references therein; b) T. Li, R. Giasson, J. Am. Chem. Soc. 1994, 116, 9890.
Photophysical experiments The experiments were carried out in air-equilibrated CHCl3 and CH2Cl2 solution at 298 K. UV/Vis absorption spectra were recorded with a PerkinElmer l40 spectrophotometer, using quartz cells with path length of 1.0 cm. Fluorescence spectra were obtained with a PerkinElmer LS-50 spectrofluorimeter, equipped with a Hamamatsu R928 phototube. Fluorescence lifetime measurements were performed by an Edinburgh FLS920 spectrofluorimeter equipped with a TCC900 card for data acquisition in time-correlated single-photon counting experiments (0.5 ns time resolution) with a D2 lamp and a LDH-P-C-405 pulsed diode laser. Fluorescence quantum yields were measured following the method of Demas and Crosby.[28] Global fitting of absorption and emission spectra has been performed by Specfit software.[23] The estimated experimental errors are: 2 nm on the band maximum, 5 % on the molar absorption coefficient and log K values, 10 % on the fluorescence quantum yield. AFM imaging was performed using a Nanoscope Multimode 8 (Bruker, Santa Barbara, USA) equipped with a 15 mm piezoelectric scanner.
Structural characterization The AFM was operated in tapping mode and in peak-force tapping mode. DLS measurements were performed with a Malvern Nano ZS instrument with a 633 nm laser diode; samples were taken in a quartz cuvette of 1 cm optical path length using CHCl3 as solvent. The width of DLS hydrodynamic diameter distribution is indicated by the polydispersion index (PDI).
Acknowledgements We gratefully acknowledge the European Research Council ERC-StG (PhotoSi, 278912) and MIUR (FIRB RBAP11C58Y, PRIN 2010N3T9M4) for financial support. M.G., M.R., and A.F. thank the French National Center for Scientific Research (CNRS) and Chem. Eur. J. 2014, 20, 1 – 9
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Full Paper [11] G. Heywang, F. Jonas, Eur. Pat. Appl., 1989, pat no. EP0339419A3. [12] M. Gingras, V. Placide, J.-M. Raimundo, G. Bergamini, P. Ceroni, V. Balzani, Chem. Eur. J. 2008, 14, 10357. [13] a) U. S. Schubert, H. Hofmeier, G. R. Newkome, Modern Terpyridine Chemistry, Wiley-VCH, Weinheim, 2006; b) T. Bauer, Z. Zheng, A. Renn, R. Enning, A. Stemmer, J. Sakamoto, A. D. Schlter, Angew. Chem. 2011, 123, 8025; Angew. Chem. Int. Ed. 2011, 50, 7879; c) J.-L. Wang, X. Li, X. Lu, I.-F. Hsieh, Y. Cao, C. N. Moorefield, C. Wesdemiotis, S. Z. D. Cheng, G. R. Newkome, J. Am. Chem. Soc. 2011, 133, 11450; d) S. Li, C. N. Moorefield, C. D. Shreiner, P. Wang, R. Sarkare, G. R. Newkome, New J. Chem. 2011, 35, 2130; e) G. Schwarz, T. K. Sievers, Y. Bodenthin, I. Hasslauer, T. Geue, J. Koetz, D. G. Kurth, J. Mater. Chem. 2010, 20, 4142. [14] a) T. Bauer, A. D. Schlter, J. Sakamoto, Synlett 2010, 6, 877; b) J. K. Molloy, P. Ceroni, M. Venturi, T. Bauer, J. Sakamoto, G. Bergamini, Soft Matter 2013, 9, 10754. [15] P. S. Braterman, J.-I. Song, R. D. Peacock, Inorg. Chem. 1992, 31, 555 and references therein. [16] F. Krçhnke, Synthesis 1976, 1. [17] N. Tuccitto, V. Torrisi, M. Cavazzini, T. Morotti, F. Puntoriero, S. Quici, S. Campagna, A. Licciardello, ChemPhysChem 2007, 8, 227. [18] A. Pinchart, C. Dallaire, A. Van Bierbeek, M. Gingras, Tetrahedron Lett. 1999, 40, 5479. [19] A. Pinchart, C. Dallaire, M. Gingras, Tetrahedron Lett. 1998, 39, 543. [20] a) K. Ogino, S. Iwashima, H. Inokuchi, Y. Harada, Bull. Chem. Soc. Jpn. 1965, 38, 473; b) H. Vollmann, H. Becker, M. Corell, H. Streeck, G. Langbein, Liebigs Ann. Chem. 1937, 531, 1. [21] A. Wild, A. Winter, F. Schltter, U. S. Schubert, Chem. Soc. Rev. 2011, 40, 1459 and references therein.
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[22] V. Balzani, V. Carassiti, Photochemistry of Coordination Compounds, Academic Press, London, 1970. [23] a) R. A. Binstead, SPECFIT; Spectrum Software Associates: Chapell Hill, NC, 1996; b) H. Gampp, M. Maeder, CJ. Meyer, A. Zuberbulher, Talanta 1985, 32, 257. [24] G. Albano, V. Balzani, E. C. Constable, M. Maestri, D. R. Smith, Inorg. Chim. Acta 1998, 277, 225. [25] X. Chen, Q. Zhou, Y. Cheng, Y. Geng, D. Ma, Z. Xie, L. Wang, J. Lumin. 2007, 126, 81. [26] E. S. Andreiadis, R. Demadrille, D. Imbert, J. Pcaut, M. Mazzanti, Chem. Eur. J. 2009, 15, 9458. [27] a) D.-Q. Feng, G. Liu, W. Zheng, T. Chen, D. Li, J. Mater. Chem. B: Mater. for Biol. and Med. 2013, 1, 3057; b) R. B. Romashkina, A. G. Majouga, E. K. Beloglazkina, D. A. Pichugina, M. S. Askerka, A. A. Moiseeva, R. D. Rakhimov, N. V. Zyk, Russ. Chem. Bull. 2012, 61, 2265; c) C. H.-H. Traulsen, E. Darlatt, S. Richter, J. Poppenberg, S. Hoof, W. E. S. Unger, C. A. Schalley, Langmuir 2012, 28, 10755; d) E. C. Constable, C. E. Housecroft, E. Medlycott, M. Neuburger, F. Reinders, S. Reymann, S. Schaffner, Inorg. Chem. Commun. 2008, 11, 518; e) A. Winter, A. M. J. van den Berg, R. Hoogenboom, G. Kickelbick, U. S. Schubert, Synthesis 2006, 2873; f) J. Wang, G. S. Hanan, Synlett 2005, 1251. [28] a) G. A. Crosby, J. N. Demas, J. Phys. Chem. 1971, 75, 991; b) M. Montalti, A. Credi, L. Prodi, M. T. Gandolfi in Handbook of Photochemistry, 3rd ed., Taylor & Francis, London 2006, Chapter 10.
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FULL PAPER & Supramolecular Chemistry
Alternating one-way: We report the synthesis, characterization, and photophysical behavior of a highly luminescent supramolecular antenna based on a tetra(thio)pyrene core appended with four phenylated terpyridine units (see figure). The coordination of metals ions can not only switch the direction of the intramolecular energy transfer, but can also can control the formation of threedimensional nanoscopic objects in a dual function.
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A. Fermi, P. Ceroni, M. Roy, M. Gingras,* G. Bergamini* && – && Synthesis, Characterization, and Metal Ion Coordination of a Multichromophoric Highly Luminescent Polysulfurated Pyrene
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Synthesis, Characterization, and Metal Ion Coordination of a Multichromophoric Highly Luminescent Polysulfurated Pyrene Andrea Fermi,[a, b] Paola Ceroni,[a] Myriam Roy,[b] Marc Gingras,*[b] and Giacomo Bergamini*[a]
Abstract: We have designed a new multichromophoric system based on a tetra(phenylthio)pyrene core appended with four terpyridine units. The system behaves as a molecular antenna that collects light with the peripheral units and funnels the energy to the very highly luminescent core. The
addition of metals ions to the investigated system can not only switch the direction of the intramolecular energy transfer, but also control the formation of three-dimensional nanoscopic objects in a dual function.
Introduction In the last 20 years, increasing attention has been devoted to multichromophoric systems capable of operating as light-harvesting antennae.[1] The purpose is to construct organized multicomponent systems in which different chromophoric molecular units are in close contact to favor the energy and/or the electron transfer, so that the excitation energy can be funneled to a specific acceptor. If one of these chromophores is also a good ligand for metal ions, new interesting properties can arise in a supramolecular system: 1) By changing the bound metal ion, it can change the energy of the lowest excited states and control (direct) the energy/electron transfer processes, and 2) by using metal ions that form complexes in a 2:1 ligand to metal stoichiometry, it becomes possible to generate supramolecular architectures and coordination polymers in which the “monomers” Scheme 1. Synthetic sequence to the tetra(phenylthio-terpyridine)pyrene 2 and chemical are glued by the metal ions. structure of model compound PyrS. DMI = 1,3-Dimethyl-2-imidazolidinone. In this paper we report the synthesis, characterization, and metal ion coordination of a new multichromophoric tetra(terpyridine) ligand, for making new supramolecular systems with tailor-made photophysical prop2,2’:6’,2’’-terpyridine units (1-SH), hereafter named compound erties and aggregation states. It is composed of a 1,3,6,8-tetra2 (Scheme 1). (phenylthio)pyrene core, with four appended mercaptophenylIn the design of this molecule, a 1,3,6,8-tetrasubstituted pyrene core has been chosen because of its geometry and its valuable photophysical and electrochemical properties. A pre[a] Dr. A. Fermi, Prof. Dr. P. Ceroni, Dr. G. Bergamini cursor, namely 1,3,6,8-tetrabromopyrene, has facilitated the Department of Chemistry “G. Ciamician” synthesis of many pyrene derivatives having direct carbonUniversity of Bologna, Via Selmi 2, 40126, Bologna (Italy) pyrene bonds.[2] Pyrene and those derivatives have thus been Fax: (+ 39) 051-2099456 widely used in several technological fields such as organic E-mail: [email protected] light-emitting devices,[3] ion sensors,[4] biological markers,[5] [b] Dr. A. Fermi, Dr. M. Roy, Prof. Dr. M. Gingras Aix-Marseille Universit, CNRS, CINaM UMR 7325 field-effect transistors,[6] liquid crystals,[7] and conformational 163 Ave. de Luminy, 13288 Marseille (France) probes.[8] As for pyrene derivatives with sulfur-pyrene bonds, Fax: (+ 33) 491829155 1,3,6,8-tetra(thio)pyrenes are still an underdeveloped and unE-mail: [email protected] derused family of compounds. However, they are known to be Supporting information for this article is available on the WWW under good organic p-conductors when doped,[9, 10] to stabilize http://dx.doi.org/10.1002/chem.201402021. Chem. Eur. J. 2014, 20, 1 – 9
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Full Paper charged species, and to give rise to complexes with thiophilic metal ions and charge-transfer complexes with organic molecules.[11] We previously reported the synthesis and the remarkable luminescent and electrochromic properties of a family of dendrimers consisting of a polysulfurated pyrene core with poly(thiophenylene) dendrons.[12] In this work, we decorated a polysulfurated pyrene core with terpyridine ligands. The terpyridine unit exhibits strong chelating activity towards various metal ions with a well-defined stoichiometry and very high association constants.[13] As a consequence, we modulated the electronic and the physicochemical properties of tetra(phenylthio)pyrene 2 from metal coordination. Additionally, 2,2’:6’,2“-terpyridyl (terpy) complexes have already been used as linkage elements for the construction of supramolecular architectures and coordination polymers[14] with a precise shape and size in solution and in the solid state.[15] We have demonstrated that the addition of metals ions to a solution of a highly luminescent multichromophoric molecular antenna can not only switch the direction of the energy transfer but can also control the formation of three-dimensional nanoscopic objects.
Figure 1. Absorption spectra of 1 (g) in CH2Cl2 and 2 (c) in CHCl3 and PyrS (b) in CH2Cl2. The absorption spectrum of 1 has been multiplied by four for comparison purposes.
Results and Discussion Synthesis and characterization Tetra-substituted derivatives of pyrene are conveniently prepared from 1,3,6,8-tetrabromopyrene, as we already reported.[12] The (phenylthio)terpyridine motif acts as a ligand to build the external periphery of the tetrasulfurated pyrene core. A classical synthetic path to provide similar molecules was reported in the literature.[16] We used an optimized protocol[17] to afford 1 in acceptable yields. Two equivalents of 2-acetylpyridine undergo condensation with 4-(methylthio)benzaldehyde in a basic media for building the terpyridyl skeleton. Following a quite known and efficient demethylation strategy,[18, 19] a deprotection to the free thiol 1-SH was performed. We found it was convenient to use solid tBuOK as a strong base, for obtaining 1-SH in a good yield on a gram scale. We succeeded in the tetrasulfuration of 1,3,6,8-tetrabromopyrene by using simple nucleophilic aromatic substitutions with the thiolate from 1-SH in polar aprotic solvents.[20] Compound 2 was obtained in good yields after purifying the crude product by trituration in warm toluene.
Figure 2. Emission spectra of 1 (g) in CH2Cl2, PyrS (b) in CH2Cl2, 2 (c) in CHCl3 and 2 solid (d). lex = 300 nm.
The emission spectrum of 1 recorded in CH2Cl2 presents a maximum at 390 nm, which can be ascribed to the radiative deactivation of the terpy-like excited state (Figure 2). The fluorescence quantum yield is rather high (F = 0.33) with a lifetime (t) of 1.40 ns. The observed band is slightly redshifted and more intense compared with that of the p-tolylterpy (lem = 350 nm, F = 0.08), this is probably due to the effect of the MeS being directly attached to the phenyl group.[21] The emission spectra of 2 obtained exciting both in the UV, in which most of the light is absorbed by the terpy moieties, and in the visible, where only the core absorbs, are identical. The intense florescence band of the tetra(p-tolylthio)pyrene PyrS with a maximum at 460 nm is shown in Figure 2.[12] The fact that no terpy emission has been detected in compound 2 indicates that the lowest excited state of the terpy units is completely quenched by the lower excited state of the pyrene core. The excitation spectrum of 2, fixing the lem = 460 nm, perfectly overlaps the absorption spectrum, indicating that intramolecular (due to low concentration in solution and ns-lifetime
Photophysical properties The absorption spectra of 1 in CH2Cl2 and 2 in CHCl3 are reported in Figure 1. Compound 1 has been studied in CH2Cl2 because of the different solubility compared with 2. The spectrum of 2 presents the typical features of tetra(ptolylthio)pyrene PyrS between 380 and 470 nm[11] and the band at 295 nm of model compound 1 (see the comparison in Figure 1). This result points out that there is no significant interaction between the pyrene and the terpyridine chromophores in the ground state, so that compound 2 can be considered a supramolecular species. &
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Full Paper Table 1. Emission properties of the investigated compounds and the respective metal complexes. Compound
lmax [nm]
F
t [ns]
1[a] 2[b] [Zn(1)2]2 + [a] 2·Zn2[b] 2·Nd2[b]
390 460 490 540 1064
0.33 0.51 0.32 0.01 0.0017[c]
1.4 1.3 4.1 1.4 –
[a] In CH2Cl2. [b] In CHCl3. [c] Fem = het hNd.
of the luminescent excited state) energy transfer takes place from the peripheral chromophores to the core with 100 % efficiency. The emission quantum yield has been estimated to 51 % (quinine sulfate in H2SO4 0.5 m was used as a standard) and the fluorescence lifetime is 1.3 ns (Table 1). As shown in Figure 2, compound 2 is fluorescent also in the solid state with a broader emission band centered at 505 nm.
Figure 3. Absorption spectra of a 1.1 10 5 m solution of 1 in CH2Cl2 upon titration with [Fe(CF3SO3)2]: 0 (c), 0.8 equiv (b). Inset shows normalized absorption changes at 298 (*), and 575 nm (~).
Photophysical properties of the metal complexes As mentioned in the introduction, 2,2’:6’,2’’-terpyridine derivatives (tpy) exhibit strong chelating affinity towards various metal ions.[14] In particular, with transition-metal ions such as iron, zinc, and neodymium, a very strong [M(tpy)2]n + complex can be obtained. We report the titration of compound 2, and compound 1 for comparison, with Zn2 + , Fe2 + , and Nd3 + ions. In each experiment, the changes in the absorption and emission spectra were monitored. We have first investigated the complexation properties of the model compound 1 with [Fe(CF3SO3)2] in CH2Cl2 solution. The absorption spectra show a redshift of the lowest energy band of the free ligand and the appearance of a band in the visible region centered at 575 nm due to a metal-to-ligand charge-transfer (MLCT) transition. Upon excitation at the isosbestic point, complete quenching of the fluorescence band at 390 nm was observed. The emission quenching was expected on the basis of the fast non-radiative decay observed for the lowest energy MLCT excited state of the pristine [Fe(tpy)2]2 + complex.[15, 22] The plots of the normalized absorption changes at 298 nm and at 580 nm reach a plateau at 0.5 equivalents of metal ion per 1 (Figure 3, inset). These results demonstrate a 2:1 ligand-to-metal stoichiometry with an association constant logb > 15, estimated by global fitting of the absorption spectra.[23] The same experiment has been carried out with molecule 2. Upon titration of a 4.5 10 6 m solution of 2 in CHCl3 with [Fe(CF3SO3)2]. We observed similar spectral changes in the absorption and emission spectra, as those recorded for 1 (Figure 4). In addition, there is a decrease of the emission band of the tetra(thio)pyrene indicating that the complexation of the metal by the external terpyridine quenches the luminescence of the core. By exciting at the isosbestic point at 410 nm, the emission band at 460 nm decreases upon additions of Fe2 + , reaching a complete quenching at two equivalents of metal ions. Chem. Eur. J. 2014, 20, 1 – 9
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Figure 4. Absorption spectra of a solution of 2 (4.5 10 6 m) in CHCl3 upon titration with [Fe(CF3SO3)2]: 0 (c), 2.5 equiv (b). Inset shows normalized absorption changes at 445 (*) and 575 nm (~).
Those results prove the formation of metal complexes in a ratio of 1:2 of ligand 2 to metal ions. Due to the fact that four terpyridine moieties are present in each molecule, the stoichiometry of terpy to metal ion is 2:1, as for the model compound 1. Considering that two terpy units of the same molecule cannot cooperate to bind a single metal ion because the structure of the molecule confines them too far apart and not in the right geometry, it follows that two molecules are linked together by intermolecular complexation of Fe2 + ions. Thereby, it forms an oligomeric structure ([Fe2n(2)n]4n + or 2·Fe2) in which a Fe2 + ion bridges two terpy units from two different molecules 2 (see the representation of the self-assembled, polymeric architecture involving 2, below). Continuing the investigations on the interactions of 1 and 2 with metal ions, we performed a similar titration with [Zn(CF3SO3)2]. The changes in the absorption spectra are similar to that observed in the case of iron except for the band at 575 nm. Concerning the emission spectra (Figure 5), in the 3
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case of 1 we observed the decreasing of the band at 390 nm and the appearance of a band at 490 nm ascribable to the formation of the [Zn(1)2]2 + metal complex.[24] The emission spectra of 2 during the addition of Zn2 + show a decrease of the band of the core at 460 nm, and the appearance of a very weak Zn-terpy emission band at 540 nm, compared with the emission of the [Zn(1)2]2 + complex. The quenching can be attributed to a thermodynamically favored[12, 25] photoinduced electron transfer from the terpy-metal complex to the tetra(phenylthio)pyrene core. After fixing the emission wavelength at 540 nm, the excitation spectrum perfectly match the absorption spectrum of 2, pointing out a 100 % energy transfer from the tetra(phenylthio)pyrene core to the Zn-terpy complexes at the periphery (see later, Figure 9). In the case of Zn2 + , the stoichiometry obtained by the titration also suggests the formation of complexes with one metal and two terpyridine units. As already stated, since it is not possible that two terpy of the same molecule coordinate the same metal ion, the formation of a “polymeric” structure is proposed.
Figure 5. Emission spectra upon titration with [Zn(CF3SO3)2]: a) 1 in CH2Cl2 (0 (c); 0.7 equiv (b)) lex = 315 nm; and b) 2 in CHCl3 (0 (c); 2 equiv (b)) lex = 305 nm. The dashed line represents the final emission of 2 after the addition of 2.2 equiv of Zn2 + multiplied by 25. Inset shows normalized emission changes at 460 nm (&).
an average diameter of 50 nm (Figure 7), which is in good agreement with the results obtained from DLS experiments. To obtain luminescent supramolecular assemblies, we performed a titration of 2 with Nd3 + . The latter ion is well known to be an infrared emitter and to have a good affinity with very high binding constants with terpyridine.[26] The addition of a CH3CN solution of [Nd(CF3SO3)3] to a CHCl3 solution of 2 causes changes in the absorption spectra, similar to those observed for the other metal ions (Figure 8 a); a complete
Structural characterization
To confirm and to evaluate the dimension of the supramolecular, metal-coordinated, polymeric structure, we carried out dynamic light scattering (DLS) experiments. The DLS analysis shows the presence of nanoparticles whose dimension increases upon metal ion addition up to two equivalents (Figure 6 b). Upon addition of 2.5 equivalents of Zn2 + , the DLS experiment indicates the formation of an aggregate with an average hydrodynamic diameter of 65 nm, with a low polydispersity index (PDI) of about 0.065. Further additions of metal ions show minor changes (even at 250 equiv: d = 76 nm, PDI = 0.216), demonstrating a stability in the particles size. Topological characterization using AFM of the 2·Zn2 solution ([2] = 2 10 6 m) and 2.5 equiv of [ZnFigure 6. a) Size distribution of the aggregates formed upon addition of Zn2 + (from 0.5 (CF3SO3)2] spin-coated onto freshly cleaved mica to 2.5 equiv); b) Plot of the changes of the particles diameter during the addition of [Znsheets indicated the formation of nanoparticles with (CF3SO3)2]. &
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Figure 7. AFM peak force mode images of height from a solution of 2·Zn2 spin-coated on mica.
quenching of the emission from the tetra(phenylthio)pyrene core together with an increase of the sensitized emission of the Nd3 + ions in the NIR is observed (Figure 8 b). It is worth remembering that the emission quantum yield calculated and reported in Table 1 is the product of the intrinsic emission quantum yield of the [Nd(tpy)2]3 + unit and the energy transfer efficiency from molecule 2 (Fem = het hNd). To evaluate which absorption wavelengths are responsible of the sensitized emission, we recorded the excitation spectrum at the lem = 1064 nm. The spectrum obtained perfectly matches the absorption spectrum of 2 after addition of 2.3 equiv of [Nd(CF3SO3)3], proving the 100 % energy transfer from the molecule to the emissive metal ion (Figure 9).
Figure 8. a) Absorption spectra of 2 upon titration with [Nd(CF3SO3)3] (0 (c); 2.7 equiv (b)); the inset shows the normalized absorption changes at 350 (~) and at 445 nm (*); b) Emission spectrum of 2 + 2.7 equiv of [Nd(CF3SO3)3], lex = 405 nm.
Conclusion We have synthesized a new multichromophoric, supramolecular polymeric system based on a tetra(thio)pyrene core appended with four phenylated terpyridine units. Compound 2, and model ligand 1, exhibit very interesting photophysical properties; in particular, the fluorescence quantum yield of 2 is remarkably high and the excitation of the terpyridine units at the periphery leads to a quantitative energy transfer to the core. Metal ion complexes are formed with the addition of iron(II), zinc(II), and neodymium(III) salts in diluted solutions. The stoichiometry observed and the geometry of the molecule suggest the formation of “super” oligomeric structures built on [M(tpy)2]n + interactions. The dimensions of these nanoparticles have been characterized by DLS and AFM measurements. In the case of 2·Nd2 the assemblies obtained are also good emitters in the infrared region and the emission of Nd is sensitized by all the chromophoric units present in 2, which undergo Chem. Eur. J. 2014, 20, 1 – 9
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Figure 9. Absorption spectrum of 2 in CHCl3 (solid line), excitation spectrum of 2 after the addition 2.2 equiv of [Zn(CF3SO3)2] (dotted line, lem = 540 nm), and excitation spectrum of 2 after the addition of 2.3 equiv of [Nd(CF3SO3)3] (dashed line, lem = 1064 nm).
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ammonium acetate (75.98 g, 0.990 mol, 32.9 equiv) in ethanol (540 mL) was then added, followed by a gentle heating at reflux for 4 h with the use of a heating mantle. During this time, a yellow-orange color appeared. After cooling at room temperature, the solvent was evaporated to 1/3 of its starting volume. Pale-yellow crystals were then formed, collected on a fritted glass after filtration, and rinsed with EtOH. More crystals were formed from the mother liquors. All crops of crystals were combined (9 g), and vigorously stirred in warm EtOH (120 mL). After cooling, the solid was filtered and recovered. A recrystallization from a warm CH2Cl2/EtOH mixture was achieved to afford 1 as pale-yellow crystalline needles (4.85 g, 13.7 mmol, 45 % yield). M.p. 173–175 8C (lit. 173–174 8C[5] ; 176 8C[2]); Rf = 0.50 (SiO2, petrol. ether/EtOAc: 4:1 v/v); HPLC: reverse-phase HPLC analysis of crystalline 1 indicated an excellent purity > 98 % (Chromatorex C18, 15 cm, CH3CN/H2O: 80:20 as mobile phase, UV detection 254 nm); 1H NMR (250.13 MHz, CDCl3): d = 2.55 (s, 3 H; SCH3), 7.35 (ddd, 4J(H,H) = 1.1 Hz, 3J(H,H) = 4.9 Hz, 3J(H,H) = 7.4 Hz, 2 H; tpySCH3(5,5II)), 7.38 (dapp, 3J(H,H) = 8.6 Hz, 2 H; Ph(3,5)], 7.85 (dapp, 3J(H,H) = 8.6 Hz, 2 H; Ph(2,6)), 7.88 (ddd, 3J(H,H) = 7.8 Hz, 3J(H,H) = 7.8 Hz, 4J(H,H) = 1.8 Hz, 2 H; tpySCH3(4,4II)), 8.67 (dapp,3J(H,H) = 7.9 Hz, 2 H; tpySCH3(3,3II)), 8.73 (s, 2 H; tpySCH3(3I,5I)), 8.74 ppm (bd, 3J(H,H) = 5.0 Hz, 2 H; tpySCH3(6,6II)); 13 C NMR (62.90 MHz, CDCl3): d = 15.5 (CH3), 118.3 (CH; tpySCH3(3I,5I)), 121.3 (CH; tpySCH3(3,3II)), 123.8 (CH; tpySCH3(5,5II)), 126.5 (CH; Ph(3,5)), 127.6 (CH; Ph(2,6), tpy(5,5II)), 134.9 (C), 136.8 (CH; tpySCH3(4,4II)), 140.0 (C), 149.1 (CH; tpySCH3(6,6II)), 149.5 (C), 155.9 (C), 156.2 ppm (C); MS-ESI (matrix: CH2Cl2, NH4Ac 3 mm, + mode): m/z calcd for C22H17N3S: 355.4; found: 356.2 [M + H] + ; 384.2.
Instruments for the characterization of compounds 1
H (250.13 MHz) and 13C NMR (62.90 MHz) spectra were recorded on a Bruker Avance 250 spectrometer at 293 K in CDCl3 (dried over activated 4 molecular sieves). Me4Si at d = 0.00 ppm or residual proton signals for CHCl3 at d = 7.26 ppm served as internal references. As for 13C NMR spectra, the central triplet resonance for CDCl3 at d = 77.36 ppm was used as internal reference. The multiplicities in 1H NMR spectra are described as: “s” (singlet), “d” (doublet), “t” (triplet), “q” (quartet), “m” multiplet, or “b” broad. MALDI-TOF-MS analyses were performed on an Autoflex MALDI-TOF Bruker spectrometer. LRMS (EI) spectra were recorded on a Shimazu GC-MS QP2010SE equipped with a DI2010 direct introduction unit and an electron impact ionization source at 70 eV. LRMS (ESI) spectra were recorded on a 3200QTRAP (Applied Biosystems SCIEX) equipped with an atmospheric ionization source (API). The samples were also ionized under ESI with an electrospray voltage of 5500 V; orifice voltage at 20 V, and an air pressure of the nebulizer at 10 psi. A linear ion trap analyzer in a positive mode was used for QTRAP. FTIR absorption spectra were recorded on a Spectrum 100 PerkinElmer instrument, with a Universal ATR accessory (contact crystal: diamond).
Chromatography TLC analyses were performed on precoated silica gel (Alugram SilG/UV254gel) aluminium plates from Macherey–Nagel. Compounds were visualized with UV light (254 or 365 nm) and detected with TLC developers: p-anisaldehyde/conc. H2SO4/EtOH (1/1/18 v/v/v) followed by heating or a molybdenum/cerium solution (100 mL H2SO4, 900 mL H2O, 25 g [Mo7O24H2O(NH4)6], 10 g [Ce(SO4)2]) followed by heating with a heat gun. Flash chromatography was performed over silica gel 60, Merck type 230–400 mesh (40–63 mm). HPLC analyses were performed with a Jasco system fitted with a PU 980 intelligent pump equipped with a LG 980–02 tertiary gradient unit, a DG 980–50 line degasser, a 7725i Rheodyne injection valve with a 20 mL loop, a UV 975 intelligent UV/Vis detector. The acquisition data were processed on a Borwin 1.21.60 version acquisition software (JMBS developments, Grenoble, France).
4’-[4-(Mercapto)phenyl]-2,2’;6’,2’’-terpyridine (1-SH):[27] An ovendried round-bottom flask fitted with a reflux-condenser was charged with tpy-SMe (1) (501.5 mg, 1.41 mmol, 1.00 equiv), and tBuOK (1.190 g, 10.61 mmol, 7.52 equiv) under an argon atmosphere. Anhydrous DMF (10.0 mL) was added through a syringe and the yellow mixture was stirred until complete dissolution. tBuSH (640 mg, 800 mL, 7.10 mmol, 5.04 equiv) was injected to the mixture and heated at 160 8C for 15 h under Ar. After cooling at 5–8 8C (ice-bath temperature), the red mixture was poured in a quasi-saturated ammonium chloride aqueous solution (75 mL, pH 5) and a pale-yellow solid precipitated. This product was then collected on a fritted glass after a filtration, and washed several times with cold distilled water to provide tpy-SH (1-SH). After drying, a paleyellow powder was obtained (447.8 mg, 1.31 mmol, 93 % yield). M.p. 169–171 8C (lit. 166–168 8C); 1H NMR (250.13 MHz, CDCl3, ppm): d = 3.57 (s, 1 H; SH), 7.34 (ddd, 3J(H,H) = 7.5 Hz, 3J(H,H) = 4.8 Hz, 4J(H,H) = 1.2 Hz, 2 H; tpySH(5,5II)), 7.40 (dapp, 3J(H,H) = 8.5 Hz, 2 H; Ph(3,5)), 7.79 (d, 3J(H,H) = 8.5 Hz, 2 H; Ph(2,6)), 7.86 (ddd, 3 J(H,H) = 7.6 Hz, 3J(H,H) = 7.6 Hz, 4J(H,H) = 1.8 Hz, 2 H; tpySH (4,4II)), 8.66 (d,3J(H,H) = 8.0 Hz, 2 H; tpySH(3,3II)), 8.70 (s, 2 H; tpySH(3I,5I)), 8.72 ppm (bd, 3J(H,H) = 4.8 Hz, 2 H; tpySH(6,6II)); 13C NMR (62.90 MHz, CDCl3): d = 118.8 (CH; tpySH(3I,5I)), 121.7 (CH; tpySH(3,3II)), 124.2 (CH; tpySH(5,5II)), 128.2 (CH; Ph(2,6)), 129.9 (CH; Ph(3,5)), 132.8 (C), 136.1 (C), 137.2 (CH; tpySCH3(4,4II)), 149.5 (CH; tpySCH3(6,6II)), 149.7 (C), 156.3 (C), 156.6 ppm (C); FTIR (ATR diamond contact; solid sample): n˜ = 2552.3 cm 1 ( SH stretching, weak); MS-EI: m/z (%): 308 (50.9) [M SH], 340 (20.6) [M H], 341 (100) [M], 342 (26.6) [M + H] + , 343 (7.7) [M + 2 H]2 + .
Syntheses Reagents were purchased from Sigma–Aldrich or Alfa Aesar and used as received. Solvents were purchased from Sigma–Aldrich, Acros Organics (Fisher Scientific) or Carlo Erba. Their purity was analytical or reagent grade, with a low water content or extra dry, and stored for many days over freshly activated 3 molecular sieves (3 h at 250 8C). DMF was dried over CaH2 overnight, distilled under reduced pressure and kept over freshly activated 3 sieves. 1,3-Dimethyl-2-imidazolidinone (DMI) was used as received and kept over 3 sieves. The synthesis of 1,3,6,8-tetrabromopyrene has been previously reported.[12, 20] 4’-[4-(Methylthio)phenyl]-2,2’;6’,2’’-terpyridine (1):[27] Potassium tert-butoxide (11.19 g, 99.7 mmol, 3.31 equiv), followed by anhydrous THF (150 mL), were added into an oven-dried, two-necked, 2L-round-bottom flask equipped with a condenser and kept under argon. After stirring the solid suspension for 30 min, 2-acetylpyridine (7.67 g, 63.3 mmol, 2.10 equiv) was slowly added through a syringe at 20 8C. 4-(Methylthio)benzaldehyde (4.58 g, 30.1 mmol, 1.00 equiv) was also injected within 5 min in a dropwise manner, while stirring vigorously. The resulting ruby-red mixture was further stirred for 2.5 days at room temperature (22 8C). A suspension of
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1,3,6,8-Tetrakis((4-([2,2’:6’,2’’-terpyridin]-4’-yl)phenyl)thio)pyrene (2): 1,3,6,8-tetrabromopyrene[12, 20] (181.4 mg, 0.350 mmol, 1.00 equiv), 4’-[4-(mercapto)phenyl]-2,2’;6’,2’’-terpyridine (1-SH) (507.0 mg, 1.48 mmol, 4.23 equiv), and Cs2CO3 (590.1 mg, 1.81 mmol, 5.17 equiv) were introduced in an oven-dried round bottom flask, and the content was further dried under high vacuum. Under argon, DMI (3.0 mL) was injected through a syringe
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Full Paper and the mixture was stirred at 60 8C for 6.5 days. After being cooled to RT, an aqueous NaOH solution (2 m, 30 mL) was poured into the mixture. A bright-yellow solid precipitated, which was separated by filtration and washed with H2O (2 5 mL). Stirring the solid in absolute ethanol (20 8C, 18 h) was followed by a second trituration in warm toluene (100 8C, 24 h). The product was filtrated, collected, and dried under high vacuum to afford a yellow powder (413 mg, 76 % yield). M.p. 335–336 8C (dec.); 1H NMR (250.13 MHz, CDCl3): d = 8.70 (s, 4 H; pyrene), 8.59 (m, 8 H; tpy), 8.53 (s, 8 H; tpy), 8.46 (dapp, 3J(H,H) = 7.8 Hz, 8 H; SPh), 8.02 (s, 2 H; tpy), 7.79–7.74 (m, 16 H; tpy), 7.42 (dapp, 3J(H,H) = 7.8 Hz, 8 H; SPh), 7.17 ppm (m, 8 H; tpy); 1H NMR (250.13 MHz, CDCl2CDCl2): d = 8.72 (s, 4 H; pyrene), 8.61 (m, 8 H; tpy), 8.53 (s, 8 H; tpy), 8.47 (dapp, 3 J(H,H) = 7.8 Hz, 8 H; SPh), 8.07 (s, 2 H; pyrene), 7.75–7.83 (m, 16 H; tpy), 7.46 (dapp, 3J(H,H) = 7.8 Hz, 8 H; SPh), 7.29 ppm (m, 8 H; tpy); 13 C NMR (62.90 MHz, CDCl2CDCl2): d = 155.6, 155.5, 148.9, 148.7, 137.4, 136.5, 136.0, 131.5, 131.2, 128.2, 125.3, 123.6, 121.0, 118.4, 103.6 ppm; FTIR (ATR, diamond contact, solid): n˜ = 3050 (CH arom), 3017 (CH arom), 1583 (C=C), 1564 (C=C), 1466 (C=C), 1382 (C=C), 1075 (CH), 1037 (CH), 826, 789 (CH, strong), 734 (CH), 660 cm 1 (CH); MALDI-TOF MS (DCTB-NaI matrix, l = 337 nm): m/z calcd for C100H62N12S4 :1558.4 [M] + , 1581.3 [M + Na] + ; found: 1558.3 [M] + , 1581.3 [M + Na] + ; elemental analalysis calcd (%) for C100H62N12S4 : C 77.00, H 4.01, N 10.78, S 8.22; found: C 74.76, H 3.87, N 10.21, S 7.85.
Aix-Marseille Universit. A.F. is grateful to the French–Italian University for a PhD scholarship from the Vinci program. We thank Dr. Guy Flix for helpful discussions on HPLC and the Spectropole of Marseille for some MS and EA data. Keywords: antenna effect · chromophores · energy transfer · supramolecular chemistry · UV/Vis spectroscopy [1] See, for example: a) S. L. Gilat, A. Adronov, J. M. J. Frchet, Angew. Chem. 1999, 111, 1519; Angew. Chem. Int. Ed. 1999, 38, 1422; b) P. D. Frischmann, K. Mahata, F. Wrthner, Chem. Soc. Rev. 2013, 42, 1847; c) A. Sautter, B. K. Kaletas, D. G. Schmid, R. Dobrawa, M. Zimine, G. Jung, I. H. M. van Stokkum, L. De Cola, R. M. Williams, F. Wrthner, J. Am. Chem. Soc. 2005, 127, 6719; d) V. Balzani, G. Bergamini, P. Ceroni, E. Marchi, New J. Chem. 2011, 35, 1944. [2] For a few examples of 1,3,6,8-tetra-C-substituted pyrenes, see: a) J. B. Shaik, V. Ramkumar, B. Varghese, S. Sankararaman, Beilstein J. Org. Chem. 2013, 9, 698; b) J.-y. Hu, M. Era, M. R. J. Elsegood, T. Yamamoto, Eur. J. Org. Chem. 2010, 72; c) T. M. Figueira-Duarte, S. C. Simon, M. Wagner, S. I. Druzhinin, K. A. Zachariasse, K. Mllen, Angew. Chem. 2008, 120, 10329; Angew. Chem. Int. Ed. 2008, 47, 10175; d) S. Bernhardt, M. Kastler, V. Enkemann, M. Baumgarten, K. Mllen, Chem. Eur. J. 2006, 12, 6117. [3] See, for example: a) K. L. Chan, J. P. F. Lim, X. Yang, A. Dodabalapur, G. E. Jabbour, A. Sellinger, Chem. Commun. 2012, 48, 5106; b) Y.-J. Pu, M. Higashidate, K. Nakayama, J. Kido, J. Mater. Chem. 2008, 18, 4183; c) J. N. Moorthy, P. Natarajan, P. Venkatakrishnan, D.-H. Huang, T. J. Chow, Org. Lett. 2007, 9, 5215; d) Y. Sagara, T. Mutai, I. Yoshikawa, K. Araki, J. Am. Chem. Soc. 2007, 129, 1520; e) Y. Oyamada, S. Akiyama, M. Yahiro, M. Saigou, M. Shiro, H. Sasabe, C. Adachi, Chem. Phys. Lett. 2006, 421, 295. [4] For recent examples, see: a) D. Maity, C. Bhaumik, D. Mondal, S. Baitalik, Inorg. Chem. 2013, 52, 13941; b) V. Amendola, G. Bergamaschi, M. Boiocchi, L. Fabbrizzi, L. Mosca, J. Am. Chem. Soc. 2013, 135, 6345; c) L. Liu, D. Zhang, G. Zhang, J. Xiang, D. Zhu, Org. Lett. 2008, 10, 2271; d) H. J. Kim, S. Y. Park, S. Yoon, J. S. Kim, Tetrahedron 2008, 64, 1294; e) A. Ben Othman, J. W. Lee, J.-S. Wu, J. S. Kim, R. Abidi, P. Thuery, J. M. Strub, A. Van Dorsselaer, J. Vicens, J. Org. Chem. 2007, 72, 7634. [5] a) J. Huang, Y. Wu, Y. Chen, Z. Zhu, X. Yang, C. J. Yang, K. Wang, W. Tan, Angew. Chem. 2011, 123, 421; Angew. Chem. Int. Ed. 2011, 50, 401; b) L. Zeng, J. Wu, Q. Dai, W. Liu, P. Wang, C.-S. Lee, Org. Lett. 2010, 12, 4014; c) H.-W. Rhee, C.-R. Lee, S.-H. Cho, M.-R. Song, M. Cashel, H. E. Choy, Y.-J. Seok, J.-I. Hong, J. Am. Chem. Soc. 2008, 130, 784; d) A. A. Marti, S. Jockusch, N. Stevens, J. Ju, N. J. Turro, Acc. Chem. Res. 2007, 40, 402. [6] See, for example: a) J. Kwon, J.-P. Hong, S. Noh, T.-M. Kim, J.-J. Kim, C. Lee, S. Lee, J.-I. Hong, New J. Chem. 2012, 36, 1813; b) L. Zçphel, D. Beckmann, V. Enkelmann, D. Chercka, R. Rieger, K. Mllen, Chem. Commun. 2011, 47, 6960; c) H. Zhang, Y. Wang, K. Shao, Y. Liu, S. Chen, W. Qiu, X. Sun, T. Qi, Y. Ma, G. Yu, D. Zhu, Chem. Commun. 2006, 755. [7] For recent examples, see: a) Y. Sagara, T. Kato, Angew. Chem. 2008, 120, 5253; Angew. Chem. Int. Ed. 2008, 47, 5175; b) S. Diring, F. Camerel, B. Donnio, T. Dintzer, S. Toffanin, R. Capelli, M. Muccini, R. Ziessel, J. Am. Chem. Soc. 2009, 131, 18177; c) M. J. Sienkowska, H. Monobe, P. Kaszynski, Y. Shimizu, J. Mater. Chem. 2007, 17, 1392; d) A. Hayer, V. De Halleux, A. Koehler, A. El-Garoughy, E. W. Meijer, J. Barbera, J. Tant, J. Levin, M. Lehmann, J. Gierschner, J. Cornil, Y. H. Geerts, J. Phys. Chem. B 2006, 110, 7653. [8] For recent examples, see: a) M. E. Østergaard, P. Cheguru, M. R. Papasani, R. A. Hill, P. J. Hrdlicka, J. Am. Chem. Soc. 2010, 132, 14221; b) D. Honcharenko, C. Zhou, J. Chattopadhyaya, J. Org. Chem. 2008, 73, 2829; c) L. Le Guyader, C. Le Roux, S. Mazeres, H. Gaspard-Iloughmane, H. Gornitzka, C. Millot, C. Mingotaud, A. Lopez, Biophys. J. 2007, 93, 4462; d) P. Storm, L. Li, P. Kinnunen, A. Wieslander, Eur. J. Biochem. 2003, 270, 1699. [9] For tetra(methylthio)derivatives: a) G. Heywang, S. Roth, Angew. Chem. 1991, 103, 201; Angew. Chem. Int. Ed. Engl. 1991, 30, 176; b) G. Heywang, L. Born, S. Roth, Synth. Met. 1991, 41, 1073. [10] For other poly(thio)pyrene derivatives: a) J.-S. Lee, K.-C. Huang, W.-J. Wang, G.-H. Lee, Synth. Met. 1995, 70, 1231 and references therein; b) T. Li, R. Giasson, J. Am. Chem. Soc. 1994, 116, 9890.
Photophysical experiments The experiments were carried out in air-equilibrated CHCl3 and CH2Cl2 solution at 298 K. UV/Vis absorption spectra were recorded with a PerkinElmer l40 spectrophotometer, using quartz cells with path length of 1.0 cm. Fluorescence spectra were obtained with a PerkinElmer LS-50 spectrofluorimeter, equipped with a Hamamatsu R928 phototube. Fluorescence lifetime measurements were performed by an Edinburgh FLS920 spectrofluorimeter equipped with a TCC900 card for data acquisition in time-correlated single-photon counting experiments (0.5 ns time resolution) with a D2 lamp and a LDH-P-C-405 pulsed diode laser. Fluorescence quantum yields were measured following the method of Demas and Crosby.[28] Global fitting of absorption and emission spectra has been performed by Specfit software.[23] The estimated experimental errors are: 2 nm on the band maximum, 5 % on the molar absorption coefficient and log K values, 10 % on the fluorescence quantum yield. AFM imaging was performed using a Nanoscope Multimode 8 (Bruker, Santa Barbara, USA) equipped with a 15 mm piezoelectric scanner.
Structural characterization The AFM was operated in tapping mode and in peak-force tapping mode. DLS measurements were performed with a Malvern Nano ZS instrument with a 633 nm laser diode; samples were taken in a quartz cuvette of 1 cm optical path length using CHCl3 as solvent. The width of DLS hydrodynamic diameter distribution is indicated by the polydispersion index (PDI).
Acknowledgements We gratefully acknowledge the European Research Council ERC-StG (PhotoSi, 278912) and MIUR (FIRB RBAP11C58Y, PRIN 2010N3T9M4) for financial support. M.G., M.R., and A.F. thank the French National Center for Scientific Research (CNRS) and Chem. Eur. J. 2014, 20, 1 – 9
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Received: February 3, 2014 Published online on && &&, 2014
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Full Paper
FULL PAPER & Supramolecular Chemistry
Alternating one-way: We report the synthesis, characterization, and photophysical behavior of a highly luminescent supramolecular antenna based on a tetra(thio)pyrene core appended with four phenylated terpyridine units (see figure). The coordination of metals ions can not only switch the direction of the intramolecular energy transfer, but can also can control the formation of threedimensional nanoscopic objects in a dual function.
Chem. Eur. J. 2014, 20, 1 – 9
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These are not the final page numbers! ÞÞ
A. Fermi, P. Ceroni, M. Roy, M. Gingras,* G. Bergamini* && – && Synthesis, Characterization, and Metal Ion Coordination of a Multichromophoric Highly Luminescent Polysulfurated Pyrene
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2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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