Triple-bridged ferromagnetic nickel(II) complexes: a combined experimental and theoretical DFT study on stabilization and magnetic coupling.

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This article can be cited before page numbers have been issued, to do this please use: A. Ghosh, R. Biswas, C. Diaz, A. Bauzá and A. Frontera, Dalton Trans., 2014, DOI: 10.1039/C3DT52764F.

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Triple-bridged ferromagnetic nickel(II) complexes derived from a tridentate NNO donor Schiff base ligand: A combined experimental and theoretical DFT

Rituparna Biswas,a Carmen Diazb, Antonio Bauzác, Miquel Barceló-Oliverc, Antonio Fronterac* and Ashutosh Ghosha* a

Department of Chemistry, University College of Science, University of Calcutta, 92, A.P.C.

Road, Kolkata-700 009, India; e-mail: [email protected] b

Departament de Química Inorgànica, Universitat de Barcelona, Martí I Franquès 1–11, 08028

Barcelona, Spain c

Departament de Quimica, Universitat de les Illes Balears, Crta. De Valldemossa km 7.5, 07122

Palma de Mallorca (Balears), Spain; E-mail: [email protected] Abstract Two

dinuclear

[Ni2L2(o-(NO2)C6H4COO)2(H2O)]

(1),

[Ni2L2(p-

(NO2)C6H4COO)2(H2O)]·0.5CH3OH (2) and one trinuclear [Ni3L2(p-nitro-C6H4COO)4]·C2H5OH (3) Ni(II) complexes have been synthesized using a tridentate Schiff base ligand, 1-[(3dimethylamino-propylimino)-methyl]-naphthalen-2-ol (HL) along with ortho- and para-nitro benzoate as co-ligands. All these three (1-3) complexes have been characterized by spectral analysis, X-ray crystallography and variable temperature magnetic susceptibility measurements. The structural analyses reveal that complexes 1 and 2 are dinuclear in which two µ2-phenoxido and a water molecule bridge the two Ni(II) centers to make the complexes face sharing bioctahedra. Complex 3 is a linear triple bridged (phenoxido and carboxylato) trinuclear Ni(II) complex. Variable-temperature magnetic susceptibility studies indicate the presence of ferromagnetic exchange coupling in complexes 1-3 with J values of 25.4, 28.1 and 6.2 cm–1 respectively. Theoretically obtained J values of 21.4 cm–1 (for 1), 22.0 cm–1 (for 2) and 9.3 cm–1 (for 3), corroborate very well the experimental results. DFT calculation also shows that stronger H-bonding interactions present in case of carboxylate based coligands stabilise the triple oxidobridged complexes. 1

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study on stabilization and magnetic coupling

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Introduction Nickel(II) complexes of tridentate NNO donor Schiff base ligands have received considerable


magnetism.3 In particular those ligands derived from diamines and salicylaldehyde are extremely useful in the construction of oxido or phenoxido bridged polynuclear Ni(II) compounds.3,4 The single atom oxido/phenoxido bridge are very efficient in mediating the magnetic coupling between the paramagnetic Ni(II) centres.5-8 The coupling can be ferro- or antiferromagnetic depending upon the bridging angles.9 Literature survey reveals that majority of the di-µ2phenoxido bridged Ni(II) complexes are antiferromagnetic9,10 with the average Ni-O-Ni bridging angles in the range 97-101°. However, it has been shown that in some cases the bridging angles can be lowered below 90° to make the compounds ferromagnetically coupled11,12. A closer look into the structural factors that determine the bridging angles reveals that monodentate13,14 or chelated coligands (e.g. nitrite, nitrate etc)9,10 usually form di-µ2-phenoxido bridged complexes with larger bridging angles. In some compounds, a syn-syn carboxylato15,16 or bidentate nitrito ligand17 acts as an additional bridge along with the phenoxido bridges with lower bridging angles but the compounds are still antiferromagnetically coupled as the angle is higher than the critical value. On the other hand, when a single atom (e.g. water, μ11-azido) acts as the additional bridge between the two Ni(II) the bridging angles become lower than the critical one and consequently the compounds become ferromagnetically coupled.9,11,12,18-20 It has also been found that water molecule is the most common among the additional single atom bridging ligands and interestingly such a bridging system exist mostly with carboxylates as coligands.9,11,12 In all such compounds a strong H-bond between the water and carboxylate ion has been found to exist, which is assumed to be responsible for the stability of the triple-bridged structure.9,11,12 However, no theoretical study has been reported till date to calculate the energies of such H-bond formation or to rationalize the formation of different structures depending upon the anionic coligands. In the present work, we report the synthesis of three new nickel(II) complexes [Ni2L2(o(NO2)C6H4COO)2(H2O)] (1), [Ni2L2(p-(NO2)C6H4COO)2(H2O)]·0.5CH3OH (2) and [Ni3L2(pnitro-C6H4COO)4]·C2H5OH (3), where L stands for a tridentate NNO donor Schiff base ligand derived from N,N-dimethyl-1,3-propanediamine and 2-hydroxy-1-napthaldehyde. All the three 2


attention due to their potential applications in the field of biological systems, 1 catalysis2 and

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complexes (1-3) are characterized by X-ray crystallography. Structural analysis reveals that complexes 1 and 2 are dinuclear containing µ2-phenoxido and water bridges. Complex 3 is a


carboxylato) complex in which two different bridging modes of the carboxylate is present. Magnetic characterization has been performed for the three complexes. Density functional theory (DFT) combined with the broken symmetry approach have also been performed to gain insight into the qualitative theoretical interpretation on the overall magnetic behavior of the complexes. We have also performed a DFT study to investigate and rationalize the importance of the intramolecular H-bond formation between the water molecule and the uncoordinated oxygen atoms of the terminal carboxylates on the stability of the complexes. Experimental and theoretical methods Materials. The N,N-dimethyl-1,3-propanediamine and 2-hydroxy-1-napthaldehyde were purchased from Lancaster Chemical Co. The chemicals were of reagent grade and used without further purification. Synthesis of the Schiff-base ligand 1-[(3-dimethylamino-propylimino)-methyl]-naphthalen2-ol (HL): The Schiff base was prepared by the condensation of 2-hydroxy-1-napthaldehyde and N,N-dimethyl-1,3-propanediamine in methanol as reported earlier.11 Synthesis

of

[Ni2L2(o-(NO2)C6H4COO)2(H2O)]

(1),

[Ni2L2(p-

(NO2)C6H4COO)2(H2O)]·0.5CH3OH (2): The monocondensed tridentate Schiff base ligand 1[(3-dimethylamino-propylimino)-methyl]-naphthalen-2-ol (HL) (5 mmol) was allowed to react with Ni(ClO4)2·H2O (1.828 g, 5 mmol), in a methanol solution followed by the addition of a methanolic solution of o-nitro benzoic acid (0.84 g, 5 mmol) (for 1) and p-nitro benzoic acid (0.84 g, 5 mmol) (for 2) in 1:1:1 molar ratios to yield the complexes. Triethylamine (1.4 mL, 10 mmol) was added for deprotonation of the Schiff base ligand and also of the carboxylic acids. Slow evaporation of the resulting green solution gave X-ray quality deep-green single crystals of compounds 1 and 2. Synthesis of [Ni3L2(p-nitro-C6H4COO)4]·C2H5OH (3): Ni(ClO4)2·6H2O (2.740 g, 7.5 mmol), dissolved in 10 mL of methanol, was added to a methanolic solution (10 mL) of the Schiff base 3


linear trinuclear triple bridged (µ2-phenoxido, 1κO:2κO'-carboxylato and 1κO:2κ2OO'-

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(HL) (5 mmol) with constant stirring. After ca. 15 min methanolic solution (10 mL) of p-nitro benzoic acid (2.51 g, 10 mmol) was added with slow stirring followed by addition of


solid was then filtered and redissolved in CH3CN. X-ray quality deep-green single crystals of compound 3 were obtained by slow evaporation of the acetonitrile solution. Complex 1: Yield: 1.71 g, 70%. Anal. Calcd. For C46H48O11N6Ni2 (978.28): C, 56.48; H, 4.95; N, 8.59. Found: C, 56.35; H, 5.01, N, 8.65. IR (KBr pellet, cm-1): 3436(broad) ν(OH), 1622 ν(C=N), 1565 as(C=O), and 1460 s(C=O). λmax (CH3OH), 649 and 1042 nm. Complex 2: Yield: 1.64 g, 65%. Anal. Calcd. For C46.5H50O11.5N6Ni2 (994.31): C, 56.17; H, 5.07; N, 8.45. Found: C, 55.79; H, 5.10, N, 8.28. IR (KBr pellet, cm-1): 3437(broad) ν(OH), 1621 ν(C=N), 1567 as(C=O), and 1457 s(C=O). λmax (CH3OH), 647 and 1045 nm. Complex 3: Yield: 2.35 g, 65%. Anal. Calcd. for C62H60N8Ni3O19 (1397.25): C, 53.29; H, 4.33; N, 8.02. Found: C, 53.20; H, 4.59; N, 7.81. IR (KBr pellet, cm-1): 1626 ν(C=N), 1570 νas(C=O) and 1452 νs(C=O). λmax(CH3OH), 645 and 997 nm. Physical measurements. Elemental analyses (carbon, hydrogen and nitrogen) were performed using a Perkin-Elmer 240C elemental analyzer. IR spectra in KBr (4500-500 cm-1) were recorded using a Perkin-Elmer RXI FT-IR spectrophotometer. Electronic spectra (1400-350nm) in CH3OH (for 1-3) were recorded in a Hitachi U-3501spectrophotometer. Temperaturedependence molar susceptibility measurements of powdered sample of 1-3 were carried out at the “Servei de Magnetoquimica (Universitat de Barcelona)” in a Quantum Design SQUID MPMSXL susceptometer with an applied field of 7000 G and 400 G in the temperature range of 2-300K and 2-30 K, respectively. Theoretical methods. The geometries of all complexes included in the energetic study were fully optimized at the BP86/def2-TZVPD level of theory starting from the crystallographic coordinates within the program TURBOMOLE version 6.4.21 For the magnetic properties, we have used the crystallographic coordinates. The magnetic coupling constants are described using the Heisenberg model. For DFT-based wave functions, a reasonable estimate of the exchange coupling constants can be obtained from the energy difference between the state with highest 4


triethylamine (2.1 mL, 15 mmol). A deep green precipitate appeared immediately. The green

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spin, EHS and the low spin wave function, EBS (namely broken-symmetry solution). The hybrid B3LYP functional22 has been used in all calculations as implemented in Gaussian-09,23 using the


all energy calculations must be performed including the SCF = Tight option of Gaussian to ensure sufficiently well converged values for the calculated energies. The approach used to determine the exchange coupling constants for dinuclear and trinuclear complexes has been described before in the literature.24,25 Crystallographic Data Collection and Refinement. Suitable single crystals of each complex were mounted on a Bruker SMART diffractometer equipped with a graphite monochromator and Mo-Kα (λ = 0.71073 Å) radiation. The structures were solved using Patterson method by using the SHELXS97. Subsequent difference Fourier synthesis and least-square refinement revealed the positions of the remaining non hydrogen atoms. Non-hydrogen atoms were refined with independent anisotropic displacement parameters. Hydrogen atoms were placed in idealized positions and refined riding on their parent atoms except for the hydrogen atoms on O(3) in 1 of the water molecule which were located in the difference Fourier map and refined isotropically. In compound 1, both o-nitro benzoate ligands have been split in two different half-occupancy positions In structure 2, one of the p-nitro benzoate ligands has been split in two different positions and the occupancy of the solvent methanol molecule set as 0.5 and the two hydrogen atoms on O(3) of the water molecule have been introduced in calculated positions. In structure 3, there is one molecule of noncoordinated solvent ethanol between two half-occupancy positions. All calculations were carried out using SHELXS 97,26 SHELXL 2013,26 PLATON 99,27 ORTEP-3228 and WinGX systemVer-1.64.29 Data collection and structure refinement parameters and crystallographic data for the three complexes (1-3) are given in Table 1. Repeated recrystallization failed to produce good-quality crystals of complex 2. The poor quality of the crystals of 2 gave rise to misshapen large spots in the diffraction pattern which in turn led to high R value.

5


6-31+G* basis set for all atoms. Due to the small magnitude of the exchange coupling constant,

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Results and Discussion Synthesis, IR and UV-VIS spectra and structure description of the complexes. The Ni(ClO4)2·6H2O in a methanol solution followed by the addition of o-nitro benzoic acid (for 1) or p-nitro benzoic acid (for 2) in 1:1:1 molar ratios and a methanolic solution of p-nitro benzoic acid in 2:3:4 molar ratio (for 3). Equimolar amount of triethyl amine was added for deprotonation of the Schiff base ligand and respective carboxylic acids. In case of complexes 1 and 2, a solvent water molecule bridges the two Ni(II) along with phenoxido oxygen while carboxylate ion remains as monodentate. A strong H-bond between the uncoordinated oxygen atom of the carboxylate and the bridged water molecule may have important role in stabilizing the structures. Two different types of bridging modes of p-nitro benzoate (1κO:2κO'; 1κO:2κ2OO') in the present complex 3 (Scheme 1) show its coordination flexibility as is found also in two other similar complexes.30,31 Unlike the case of p-nitro benzoate, no similar trinuclear complex could be isolated with o-nitrobenzoate, possibly due to very low solubility of the dinuclear complex 1 which is the sole product even with higher proportion of Ni(II) salt (HL:Ni(II):o-nitro benzoic acid = 2:3:4).

Scheme 1. Synthetic route to complexes 1-3. 6



complexes were synthesized simply by allowing the Schiff base (HL) to react with

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Regarding the IR spectra, a strong and sharp band due to azomethine υ.(C=N) appears at 1622, 1621 and 1626 cm-1 for complexes 1, 2 and 3 respectively. The appearance of a broad band near


1300-1650 cm-1 region are difficult to be attributed due to the appearance of several absorption bands both from the Schiff base and the carboxylate ligands. The strong bands at 1565, 1567 and 1570 cm-1 are likely due to the antisymmetric stretching mode of the carboxylate group, whereas the bands at 1460, 1457 and 1452 cm-1 may be attributed to the symmetric stretching modes of the carboxylate ligands in complexes 1 and 2 respectively.11,12 The absorption bands in the electronic spectra, taken in methanolic solution are very similar for three complexes (1-3). Both of them exhibit a distinct band at 649, 647 and 645 nm for 1, 2 and 3 respectively which can be assigned to the spin-allowed d-d transition 3

T1g(F)←3A2g. Another weaker broad band which is centered at 1042, 1045 and 997 nm for 1, 2

and 3 respectively and is well-separated from the first band is assignable to the transition 3

T2g←3A2g. These values are in agreement with the literature values for octahedral Ni(II)

compounds.10,31 The molecular structures of complexes [Ni2L2(o-(NO2)C6H4COO)2(H2O)] (1) and [Ni2L2(p-(NO2)C6H4COO)2(H2O)]·0.5CH3OH (2) are very similar. The only difference between the two structures is that the terminally coordinated carboxylate group is p-nitrobenzoate in 2 instead of o-nitrobenzoate in complex 1. There is no other significance difference between the two structures. Therefore, we have described only the structure of complex 1 in the main text. The structure description for complex 2 is given in the supporting information. The structure of complex 1 is shown in Figure 1 together with the atomic numbering scheme. Selected bond lengths and angles are summarized in Table 2 and for complex 2 see Table S1. The dinuclear unit is formed by two independent nickel atoms, labeled Ni(1) and Ni(2), bridged by one water molecule O(3) and two µ2-phenoxido oxygen atoms O(1) and O(2). Both metal centers, Ni(1) and Ni(2), present distorted octahedral environment, being coordinated to the deprotonated chelating Schiff base ligand through the secondary amine nitrogen atoms N(1), N(3), the imine nitrogen atoms N(2), N(4) and the phenoxido oxygen atoms O(1) and O(2) respectively in facial configuration with usual bond distances (Table 2).4,9 The carboxylate oxygen atoms O(4) and O(6) of the terminally coordinated monodentate carboxylate ions, the oxygen atom O(3) of the 7


3400 cm-1 indicates the presence of water molecule in both of them. The IR spectral bands in the

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water molecule and the bridging phenoxido atoms O(2) and O(1) complete the hexacoordination of Ni(1) and Ni(2) respectively. Thus two nickel atoms are linked through a triple oxygen bridge


phenoxido bridging angles, Ni(1)–O(1)–Ni(2) and Ni(1)–O(2)–Ni(2) are 85.1(1)°, 85.9(1)° respectively, and the water bridge angle, Ni(1)–O(3)–Ni(2) is of 88.1(1)°. Each bridging phenoxido oxygen atom is asymmetrically bound, with one Ni-O bond slightly longer [Ni(1)O(2) 2.218(2) Å; Ni(2)-O(1) 2.243(2)Å] than the other [Ni(1)-O(1) 2.027(2)Å; Ni(2)-O(2) 2.018(2)Å]. The Ni-O(water) bonds are identical within the experimental error [Ni(1)-O(3) 2.080(2)Å; Ni(2)-O(3) 2.077(2)Å] and these distances are comparable to those found in other reported aqua-bridged dinuclear Ni(II) complexes, which are in the range 2.09–2.25Å.11,18,19 The sets of four donor atoms O(1), N(2), O(4), O(3) describe the basal plane of Ni(1) and the deviations of these coordinating atoms from the least-square mean plane through them are 0.091(2), -0.080(2), 0.077(2), -0.088(2) Å respectively. Ni(1) atom is displaced -0.169(1)Å towards the axially coordinated N(1) atom from the same plane. The basal bond lengths around the Ni(1) atom are in the range of 1.989(2) - 2.080(2)Å. The apical bond lengths are Ni(1)–O(2) 2.218(2)Å, and Ni(1)–N(1) 2.135(2)Å the bond angle O(2)–Ni(1)–N(1) being 172.3(7)°. Similarly in the coordination sphere of Ni(2) the basal plane consists of O(2), N(4), O(6) and O(3) with the bond lengths in the range of 1.993(2)- 2.085(2)Å. The apical bond lengths are Ni(2)-O(1) 2.243(2)Å and Ni(2)–N(3) 2.147(2)Å, the bond angle O(1)-Ni(2)-N(3) being 171.5(7)°. Deviations of the coordinating atoms O(2), N(4), O(6) and O(3) from the least-square mean plane through them are -0.082(2), 0.072(2), -0.068(2), 0.079(2)Å respectively, and that of Ni(2) atom from the same plane is 0.141(1)Å towards the axially coordinated N(3) atom. The two hydrogen atoms H(3WA) and H(3WB) of the bridging water molecule participate in strong intramolecular hydrogen bonding to the oxygen atoms O(5) and O(7) respectively of the terminally coordinated acetate anions with D…A distances of 2.50(2) Å and 2.64(2) Å (Table 3).11, 12

8


to form a face shared bi-octahedron, leading to a Ni-Ni distance of 2.891(1) Å. The two

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Figure 1. Left: ORTEP view of the asymmetric unit of 1 with ellipsoids at the 30% probability level. The intramolecular hydrogen bonds are shown as dotted line of complex 1. Right: the face sharing bi-octahedron presentation of complex 1. The cyan, blue and red balls represent Ni, N and O atoms respectively. The molecular structure of complex [Ni3L2(p-nitro-C6H4COO)4]·C2H5OH (3) consists of a discrete trinuclear unit, see Figure 2. Selected bond lengths and angles are summarized in Table 4. The trinuclear unit is perfectly linear, owing to the presence of a crystallographic inversion center at the central nickel atom Ni(2). All three Ni atoms are six-coordinate with distorted octahedral environments. Each of the two terminal nickel atoms Ni(1) are coordinated by a deprotonated chelating tridentate Schiff base ligand (L) through two nitrogen atoms (N(3) and N(4)) and a phenoxido oxygen atom O(9) in a mer arrangement. In addition, each of the two Ni(1) ions is bonded to one of the oxygen atoms O(6) of a bridging bidentate p-nitrobenzoate ligand and two oxygen atoms O(7) and O(8) of a second chelating p-nitro-tridentate benzoate ligand. The meridionally coordinated Schiff base and the oxygen atom O(7) constitute the equatorial plane with bond distances in the range 1.983(6)-2.144(4) Å (Table 4), similar to the axial ones (2.016(5) and 2.186(5) Å). The main distortion from octahedral geometry is a consequence of the small bite of the chelating p-nitro-benzoate ligand, the O(7)-Ni(1)-O(8) angle 9



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being only 61.1(2)°. The coordination geometry around the central metal ion Ni(2) is also a distorted octahedron involving two bridging phenoxido oxygen atoms, O(9) and O(9)#, two


atoms O(5) and O(5)# from the second bridging bidentate p-nitro-benzoate ligand. Thus one pnitro-benzoate ligand bridges two nickel atoms with O(5) coordinated to Ni(2) and with O(6) (1κO:2κO') to Ni(1), whereas the other p-nitro-benzoate ligand is bidentate to Ni(1) through the O(7) and O(8) atoms and monodentate to Ni(2) through the O(7) atom (1κO:2κ2OO'). Ni(1) and Ni(2) atoms are separated by 3.049(1) Å, indicating the absence of any bond between the two nickel centers. The Ni(1)-O(9)-Ni(2) and Ni(1)-O(7)-Ni(2) bridge angles are 96.6(2) and 91.4(2)°, respectively.

Figure 2. (a) ORTEP view of 3 with ellipsoids at the 30% probability level. All the hydrogen atoms are not shown for clarity.

10


oxygen atoms, O(7) and O(7)# from two bridging p-nitro-benzoate groups and two more oxygen

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Magnetic properties. Temperature-dependent molar susceptibility measurements of powdered samples of complexes 1-3 were carried out in an applied field of 7000 and 400 G in the


in the form of χMT versus T, where χM is the molar susceptibility per Ni2 unit and T the temperature, are depicted in Figure 3. Complexes 1 and 2 show very similar behavior that indicate the presence of ferromagnetic exchange interactions within the Ni(II) dimer together with zero field splitting of the resulting S = 2 spin ground state and/or antiferromagnetic interdimer interactions. The χMT values at 300 K is 2.78 cm3mol-1K (for 1) and 2.92 cm3mol-1K (for 2), higher than that expected for the contribution of two non interacting Ni(II) S = 1 spin centers (the expected spin only value is 2.0 cm3 mol-1 K, g = 2). On cooling, χMT increases to reach a maximum of 3.84 cm3 mol-1 K at around 14 K for 1, and 3.81 cm3 mol-1 K at around 10 K for 2, these values correspond well with a S = 2 ground state stemming from the occurrence of ferromagnetic coupling between the two S = 1 centers. Below to this temperature, χMT decreases to reach a value of 3.07 cm3mol-1K and 3.17 cm3mol-1K at 2 K, for 1 and 2, respectively. To consider the decrease of the χMT curve versus T at low temperatures and taking into account that no classical hydrogen bonds or π-π staking are present into their structures, we have fitted the magnetic properties to full diagonalization formalism, introducing only the single-ion D parameter. Employing the following spin-Hamiltonian:





H   JS1S 2  D S z2  1 / 3( S  1)  gHS z according to which the single-ion anisotropy D is assumed to be the same for the two Ni(II) ions. The best fit parameters to the magnetic data were found to be J = 25.4 cm-1, g = 2.27, D = 3.20 cm-1 and R = 5x10-7 for 1 and J = 28.1 cm-1, g = 2.23, D =2.80 cm-1 and R = 5x10-9 for 2 {R is the agreement factor defined as: R = ∑[(χMT)exp-(χMT)calcd]2/∑(χMT)exp2}, which correspond to the solid line in Figure 3, respectively. The analogous J values agree with the similar structural parameter in both complexes. The ferromagnetic coupling of complexes 1 and 2 lead to S = 2 ground spin state, which is confirmed by the isothermal magnetization measurements at 2 K (figure 3, inset).

11


temperature ranges 2-300 and 2-30 K, respectively. The magnetic behavior of 1 and 2, expressed

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3.4 3.2

M / NB

3.6

3.8 3.6

-1

M / N B

-1

MT/ emu mol K

3.8

5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 -0.5

MT / emu mol K

4.0

3.4

0

3.0

15000

30000 H/G

3.2

45000

5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 -0.5

0

15000

30000 H/G

45000

3.0

2.8

2.8

2.6 0

50

100

150

200

250

0

300

50

100

150

200

250

300

T/K

Figure 3. Thermal dependence of χMT for 1 (a) and for 2 (b). The solid line represents the best-fit curve. The inset shows the field dependence of the magnetization for 1 (a) and for 2 (b) at 2 K. The magnetic behavior of 3, expressed in the form of χMT versus T, where χM is the molar susceptibility per Ni3 unit and T the temperature, are depicted in Figure 4. The χMT value at 300 K is 4.27 cm3mol-1K, value higher than that expected for the contribution of three non interacting Ni(II) S = 1 spin centers (the expected spin only value is 3.0 cm3mol-1K, g = 2). On cooling, χMT increases to reach a maximum of 6.785 cm3mol-1K at around 6 K, this value corresponds well with a S = 3 ground state stemming from the occurrence of ferromagnetic coupling. Below to this temperature, χMT decreases to reach a value of 4.70 cm3mol-1K. The shape of the curve indicates ferromagnetic coupling, together with zero field splitting of the resulting S = 3 spin ground state and/or antiferromagnetic interdimer interactions. Considering the absence of magnetic interaction between the terminal Ni(II) ions in the trinuclear unit, and that no classical hydrogen bonds or - staking are present into its structure experimental data can be fitted using the following spin Hamiltonian:





H   J ( S1 S 2  S 2 S 3 )  D S z2  1 / 3( S  1)  g HS z

according to which the single-ion anisotropy D is assumed to be the same for the three NiII ions. The best fit parameters to the magnetic data were found to be J = 6.2 cm-1, g = 2.33, D =5.75 cm-1 and R=3x10-7 {R is the agreement factor defined as: R= ∑[(χMT)exp-(χMT)calcd]2/∑(χMT)exp2}, which correspond to the solid line in Figure 4. The ferromagnetic coupling leads to S = 3 spin ground state, which is confirmed by the isothermal magnetization measurements at 2 K (Figure 12


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4, inset). The D values obtained for complexes 1-3 are typical for Ni(II) complexes.32 The magnetic susceptibility data treatment of complexes 1-3 were made using the MAGPACK

M / N B

6.5 -1

6.0 5.5 5.0

7 6 5 4 3 2 1 0 0

15000

30000 H/G

45000

4.5 4.0 0

50

100

150

200

250

300

T/K

Figure 4. Thermal dependence of χMT for 3. The solid line represents the best-fit curve. The inset shows the field dependence of the magnetization for 3 at 2 K. The magnetic properties of 1 and 2, which present non centrosymmetric dinuclear structures, are interpreted in terms of different bridges: two µ2-phenoxido and a water molecule. To our knowledge, only six9,12,18,19,35 dinuclear Ni(II) complexes triply bridged by two phenoxido and one water molecule that their magnetic properties have been studied, are reported in the literature. Ferromagnetic behavior has been found in all cases except for RATXIV (Table 5), the authors attributed its antiferromagnetic behavior to the basic character of the terminal carboxylato ligand.35 Correlations of the superexchange coupling in centrosymmetric Ni-O-Ni dinuclear nickel(II) complexes made by Nanda et al.,36 and a quantum chemical ab initio study by Wang et al.37 show that the value of the exchange coupling constant is directly proportional to the Ni-ONi bridge angles or Ni···Ni distance and the ferromagnetic coupling takes place for angles smaller than 97°. Later, Bu et al.38 found that this relation is not linear, and the ferromagnetic coupling appears for angles smaller than 93.5º. DFT calculations show that an additional µ2-H2O ligand plays an important role in the magnetic behavior, in bis-µ2-phenoxido Ni(II) complexes,9 its presence reduces the Ni-O-Ni angles and consequently the Ni···Ni distances and explains its ferromagnetic behavior. 13


7.0

MT / emu mol K


program,33 employed with a non-linear least-square curve-fitting program DSTEP.34

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The Ni-O-Ni bond angles are: Ni(1)-O(1)-Ni(2) = 85.1(1)°, Ni(1)-O(2)-Ni(2) = 85.9(1)°and Ni(1)-O(3)-Ni(2) = 88.1(1)° for 1; and Ni(1)-O(1)-Ni(2) = 86.3(2)°, Ni(1)-O(2)-


complexes 1 and 2 was not unexpected. Their structural parameters and J values are in the same range that those reported in Table 5. The magnetic properties of complex 3, which present centrosymmetric linear trinuclear structure, are interpreted in terms of three different bridges: one µ2- phenoxido, one bidentate carboxylato in syn-syn configuration, and one carboxylato in tridentate 1O:22OO´ mode. A search in the CCDC data base shows four4,15,30,31 related centrosymmetric linear trinuclear complexes, being their magneto structural parameters listed in Table 6. All of these complexes exhibit weak ferromagnetic interaction. These results agree with considering a dominating ferromagnetic behavior from the two oxido bridges in front of the expected small antiferromagnetic coupling through the bidentate syn-syn carboxylato ligand.39 The complexes related in Table 6 present analogous structural parameters and J values of same order. The average Ni-O-Ni bond angles, in the range of 92.5-94.8, are within the expected range for ferromagnetic coupling according to the above mentioned magneto structural correlation established for oxido-bridged Ni(II) complexes; the J values are in the range of 0.42-8.8. No linear relationship is found between J and the average Ni-O-Ni due to the presence of the additional syn-syn carboxylato bridge that could diminish the ferromagnetic effect. The structural parameters of the syn-syn carboxylato ligand shows no significant differences in the Ni-O bond distances but significant differences in the Ni-O-O-Ni torsion angle (Table 6) that affect to its contribution to the magnetic coupling. Theoretical DFT study. As explained above three new Ni(II) compounds have been synthesized. The difference between 1 and 2 is just the position of the nitro substituent group, which is ortho in 1 and para in 2. Since the position of the hydrogen atoms has been determined in 1, we have selected this compound for the theoretical study. The first part of our theoretical study is focused to explain the different behaviour observed in this type of dinuclear Ni(II) complexes that depends on the anionic coligand used, as has been recently described by some of us.9 That is, when a carboxylate is used a water molecule can be inserted as an additional bridge. 14


Ni(2) = 86.9(2)° and Ni(1)-O(3)-Ni(2) = 85.5(2)° for 2, so the ferromagnetic coupling for

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However this bridging water cannot be inserted if other coligand as nitrate or nitrite is used. In addition, the presence/absence of this water molecule modulates the magnetic behavior of the


antiferromagnetic and, curiously, they become ferromagnetic in the presence of an additional bridge. We have performed a DFT energetic study on the different stability of the complexes and the importance of the H-bond formation between the water molecule and the different coligands. The solid state structures of complexes 1 and 2 and the previously reported for acetate and related ligands reveal the presence of a strong hydrogen bond between the bridging water molecule and the uncoordinated oxygen atom of the carboxylate group that plays a key role in stabilizing the structure and facilitating the incorporation of the water molecule in the structure. However, the same hydrogen bonding pattern can be envisaged for the hypothetical complexes with nitrite and nitrate (see DFT optimized complexes in Figure 5). The hydrogen bonding distance is shorter for the optimized structure using formiate (as a model of carboxylate-based coligand) than the other two, indicating a stronger interaction.

Figure 5. Optimized geometries of formiate (top left), nitrate (top right) and nitrite (bottom) complexes at the BP86/def2-TZVPD level of theory. 15


complexes. As aforementioned, the diphenoxido bridged dinuclear Ni(II) compounds are usually

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In order to evaluate the relative strength of the different complexes, we have used some energetic balances using the reactions represented in Scheme 2, where ligand exchange processes


formiato by two nitrito ligands. It can be observed that the process is unfavorable in 10.6 kcal/mol, indicating that the cost of each ligand exchange is approximately 5.3 kcal/mol. The second reaction is also unfavorable (∆E2 = 20.5 kcal/mol) indicating that the replacement of formiato by nitrato is even more unfavorable than the replacement by nitrite. A likely explanation for this energetic behavior is the relative basicity of the three anionic coligands (formiate, nitrate and nitrite), which influences their capability of interaction with both the Ni (II) atom (coordination bond) and the water molecule (hydrogen bond). The highest basicity corresponds to the formiate anion, which is the most stable complex and, conversely, the nitrate anion is the least basic species, thus resulting in the least favorable complex.

Scheme 2. Ligand exchange reactions and their energies at the BP86 /def2-TZVPD level of theory The energetic balances used above are useful to justify in part the experimental finding, however they do not explain why the water molecule is not incorporated in dinuclear Ni(II) complexes with NO2– or NO3– as coligands, they just demonstrate that the carboxylate is a better ligand and hydrogen bond acceptor than the other two. To further analyze this issue we have 16


have been evaluated. In the first one (∆E1), we have computed the energetic cost of replacing two

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computed the relative stability of the dinuclear complexes observed experimentally with the hypothetical complexes incorporating the bridging water molecule for nitrite and nitrate and


summarized in Scheme 3. Theoretically, the incorporation of a bridging water molecule is favorable for all complexes, however it is clear that it is much more favorable for formiate (∆E3) than for either nitrate (∆E4) or nitrite (∆E5), in partial agreement with the experimental results. It should be mentioned that experimentally the water-complex is not formed when nitrito or nitrato coligand is present. A likely explanation is that the different packing forces can easily compensate the 3.6 kcal/mol of nitrito and nitrato-based complexes in the solid state and, conversely, they cannot easily compensate the 11.8 kcal/mol in case of formiate.

Scheme 3. Complexation energies for the incorporation of a water molecule in dinuclear complexes. The second part of the theoretical study is devoted to the rationalization of the magnetic results. The determination of J values was carried out using DFT calculations combined with the broken symmetry approach. The magnetic coupling constants J of the systems are described by the Heisenberg model, and the Heisenberg spin Hamiltonian used for the magnetic fitting was Ĥ = –JŜ1Ŝ2 where Ŝ1 and Ŝ2 present the spins at sites 1 and 2, respectively. For the nickel(II) complexes 1, 2 and 3 (see Figure 6), calculation of the J values has been performed computing the difference between the energy values of the highest spin state and the broken-symmetry state. The theoretical models have been simplified (benzene instead of naphthalene, see Figure 6) in order to keep the size of the system computationally approachable.

17


without the water molecule for formiate. The reactions used and energetic results are

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Figure 6. Theoretical models of compounds 1(left) and 3 (right). The magnetic behavior of this type of complexes has been previously analyzed. In the absence of the additional bridging water molecule, magnetostructural correlation studies for the μ2-oxido/phenoxido-bridged Ni(II) complexes indicate ferromagnetic coupling below the critical Ni–O–Ni angle of 93.5° and above which the exchange coupling is usually antiferromagnetic, as it is observed for most of the reported diphenoxido bridged dinuclear nickel(II) complexes. In contrast, complexes with the additional bridging water molecule show a different behavior exhibiting dominant intramolecular ferromagnetic exchange coupling. This behaviour is also observed in the complexes reported herein. That is, compounds 1 and 2 incorporate in the structure a carboxylate-based ligand that, as aforementioned, induces the incorporation of the bridging water molecule. Both compounds present a ferromagnetic Ni–Ni exchange coupling inside its dimeric structure. In addition, complex 3 exhibits weak ferromagnetic interaction that is likely due to a compensating effect between the dominating ferromagnetic behavior from the two oxido bridges and the antiferromagnetic coupling through the bidentate carboxylato ligand. To better understand the magneto-structural interrelation, we have obtained J values of complexes 1, 2 and 3 theoretically, which are in good agreement with the experimental results. They are 21.4 cm–1 (for 1), 22.0 cm–1 (for 2) and 9.3 cm–1 (for 3), which reveals ferromagnetic coupling in complexes 1 and 2, and weak ferromagnetic coupling in complex 3. In order to demonstrate the key role of the bridging water molecule, we have also computed the magnetic constant J of a model of complex 1 where the water molecule has been eliminated. As a result 18



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the J value changes to -1.7 cm-1, which confirms the dominating ferromagnetic exchange through the μ2-OH2 bridge.

distribution has been analyzed in complexes 1 and 3. In 1, the Mulliken spin population analysis indicates that a significant spin (ca. 0.60 e) is delocalized through the ligands, and the rest (4.4 e) is carried by the central nickel atoms. The spin density plot is shown in Figure 7 for the high spin state of 1. Here, the spin carried by the phenoxido oxygen atoms is ca. 0.085 e in the high-spin state and 0.030 e in the broken-symmetry state of complex 1. In contrast a very small spin density is observed on the water-bridged oxygen atom only in the broken-symmetry state (0.0006 e) indicating a polarization competition between the two nickel atoms with α and β spin density, respectively. The spin carried by the water molecule for the high spin is considerable higher (0.057 e). In octahedral Ni(II) complexes, each orbital (dx2–y2 and dz2) contains an unpaired electron and, as previously described in the literature,9 for the complexes without the μ2-OH2 bridge only the dx2–y2 orbitals of the metal atom along with the local orbitals of the bridging ligands are involved in the super-exchange pathways, whereas for the complexes with the μ2-OH2 bridge both dx2–y2 and dz2 orbitals of nickel(II) and ligand local orbitals participate in super-exchange phenomena. This behavior has been also observed in the present orbital analysis of complex 1. The SOMO involving the dz2 orbitals of nickel(II) metal centers is represented in Figure 7, where can be also observed the participation of the px orbital of the oxygen atom of the μ2-OH2 bridge.

19



In order to further examine the magnetic coupling mechanism, the spin density

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Figure 7. Left: Graphical representation of spin density (contour 0.004 e/Å3) at the ground state (high spin) configuration. Right: Pictorial representation of the SOMO involving the dz2 orbitals of nickel(II) for the high spin state of complex 1. As previously commented, the BS-DFT calculation gives the following value of J = +9.3 cm–1, which agrees well with the experimentally one (J = +6.2 cm–1) for the trinuclear complex 3. It is clear from the SOMO plot (shown in Figure 8) that the d-orbital of each nickel center is orthogonal with the neighboring one that is associated with the bridging angle, as previously observed in similar complexes.11 The spin density distribution (see Figure 8, left) of complex 3 shows a delocalization mechanism in which the Ni atoms carry 86.6% of net spin and the rest part is delocalized through coordinating atoms. The spin density map of the high spin state shows that the spin density carried by the phenoxido-bridged oxygen atom is equally delocalized on both sides of Ni ion (labeled as “b” in Figure 8), whereas the spin density carried by the carboxylate bridged oxygen is localized towards the terminal nickel site (labeled as “a” in the highlighted fragment of Figure 8, bottom). Therefore the phenoxido and carboxylato groups are responsible for creating antiferromagnetic and ferromagnetic interactions, respectively. Interestingly, the spin density computed at the carbon atom of the bridging bidentate carboxylate group C(7) is negative (–0.033 e), indicating a spin polarization mechanism that facilitates the ferromagnetic interaction. In addition the spin density is higher in the phenoxido oxygen (0.098

20



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e) atom compared to the carboxylato oxygen atom (O(7), 0.046 e) which indicates that

Figure 8. Left: Graphical representation of spin density (contour 0.004 e/Å3) at the ground state (high spin) configuration. Right: Pictorial representation of the SOMO for the high spin state of complex 3. The molecule has been rotated in the inset plot to show that spin density is localized towards the terminal nickel site. Conclusion The crystal structures of two triple-bridged (µ-diphenoxido and µ-water) dinuclear Ni(II) complexes with the NNO donor Schiff base ligand, 1-[(3-dimethylamino-propyl imino)-methyl]naphthalen-2-ol (HL) along with anionic coligands o-nitro benzoate and p-nitro benzoate reveal the presence of strong hydrogen bond between the bridging water molecule and the uncoordinated oxygen atoms of the carboxylate groups. With the help of the energetic study, the presence/absence of a bridging water molecule depending on the anionic coligands (carboxylate, nitrate, nitrite, etc.) has been rationalized. It is shown that a delicate energetic balance between their coordination ability and the strength of the two additional hydrogen bonds that are established between the bridging water molecule and the anionic coligand is responsible for the 21



phenoxido bridging is more effective for mediating magnetic exchange than the latter one.

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final structure of the complexes. In case of p-nitrobenzoate, with a higher proportion of Ni(II) a linear trinuclear complex having three different bridges (µ2-phenoxido, syn-syn carboxylato and


water bridges in complexes 1 and 2 favor the ferromagnetic coupling by lowering the Ni-O-Ni bridging angles. In case of complex 3 ferromagnetic interaction occurs through the tridentate carboxylato bridges. This has been corroborated by the spin density and SOMO plots obtained from DFT calculations. Acknowledgements We thank CSIR, Government of India [Senior Research Fellowship to R.B Sanction no.09/028(0746)/2009-EMR-I]. Crystallography was performed at the DST-FIST, India-funded Single Crystal Diffractometer Facility at the Department of Chemistry, University of Calcutta. AB and AF acknowledge the Spanish Ministerio de Economía y Competitividad (MINECO) (Projects, and CONSOLIDER INGENIO 2010, CSD2010-00065, FEDER funds) and the Direcció General de Recerca i Innovació del Govern Balear (project 23/2011, FEDER funds) for financial support.

Electronic supplementary information CCDC reference numbers 963144 (1), 963145 (2) and 963146 (3).

22


a tridentate 1ĸO:2ĸ2OO' bridging mode of carboxylate) has also been isolated. The additional

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References: 1. (a) R. N. Patel, A. Singh, V. P. Sondhiya, Y. Singh, K. K. Shukla, D. K. Patel, R. Pandey, J. Venkatsubramanian, K. Nag, Inorg. Chem. 1994, 33, 5934–5939; (c) S. Ciurli in Metal Ions in Life Sciences (Eds: A. Sigel, H. Sigel, R. K. O. Sigel), John Wiley & Sons, Chichester, 2007, 2, 241–278. 2. (a) K. Yamaguchi, S. Koshino, F. Akagi, M. Suzuki, A. Uehara, S. Suzuki, J. Am. Chem. Soc., 1997, 119, 5752-5753; (b) A. Biswas, L. Kanta Das, M. G. B. Drew, G. Aromí, P. Gamez, A. Ghosh, Inorg. Chem., 2012, 51, 7993−8001. 3. (a) R. Biswas, Y. Ida, M. L. Baker, S. Biswas, P. Kar, H. Nojiri, T. Ishida, A. Ghosh, Chem. Eur. J., 2013, 19, 3943–3953; (b) R. Biswas, S. Mukherjee, P. Kar, A. Ghosh, Inorg. Chem., 2012, 51, 8150−8160. 4. P. Mukherjee, M. G. B. Drew, C. J. Gómez-García, A. Ghosh, Inorg. Chem., 2009, 48, 58485860. 5. W.-W. Sun, C.-Y. Tian, X.-H. Jing, Y.-Q. Wang, E.-Q. Gao, Chem. Commun., 2009, 31, 4741-4743. 6. M. Moragues-Cánovas, M. Helliwell, L. Ricard, E. Rivière, W. Wernsdorfer, E. Brechin, T. Mallah, Eur. J. Inorg. Chem., 2004, 2219-2222. 7. A. Ferguson, J. Lawrence, A. Parkin, J. Sanchez-Benitez, K. V. Kamenev, E. K. Brechin, W. Wernsdorfer, S. Hill, M. Murrie, Dalton Trans., 2008, 6409–6414. 8. C. Ding, C. Gao, S. Ng, B. Wang, Y. Xie, Chem. Eur. J., 2013, 19, 9961–9972. 9. R. Biswas, S. Giri, S. K. Saha, A. Ghosh, Eur. J. Inorg. Chem., 2012, 2916–2927. 10. S. Naiya, M. G. B. Drew, C. Estarellas, A. Frontera, A. Ghosh, Inorg. Chim. Acta, 2010, 363, 3904–3913. 11. R. Biswas, C. Diaz, A. Ghosh, Polyhedron, 2013, 56, 172-179. 12. R. Biswas, P. Kar, Y. Song, A. Ghosh, Dalton Trans., 2011, 40, 5324–5331. 13. M. Dey, C. P. Rao, P. K. Saarenketo, K. Rissanen, Inorg. Chem. Commun., 2002, 5, 924928. 14. J. M. Floyd, G. M. Gray, A. G. V. Spivey, C. M. Lawson, T. M. Pritchett, M. J. Ferry, .C. Hoffman, A. G. Mott, Inorg. Chim. Acta 2005, 358, 3773-3785. 23



Coord. Chem., 2012, 65, 795–812; (b) K. K. Nanda, R. Das, L. K. Thompson, K.

Dalton Transactions

Page 24 of 29

View Article Online

DOI: 10.1039/C3DT52764F

15. P. Mukherjee, M. G. B. Drew, C. J. Gómez-García, A. Ghosh, Inorg. Chem., 2009, 48, 4817– 4827.


2004, 357, 1517-1522. 17. (a) S. Naiya, H.-S. Wang, M. G. B. Drew, Y. Song, A. Ghosh, Dalton Trans., 2011, 40, 2744–2756; (b) J. C. Byun, W. H. Lee, C. H. Han, Inorg. Chem. Commun., 2006, 9, 563-565. 18. S. Banerjee, M. G. B. Drew, C.-Z. Lu, J. Tercero, C. Diaz, A. Ghosh, Eur. J. Inorg. Chem., 2005, 2376–2383. 19. L. Rodríguez, E. Labisbal, A. Sousa-Pedrares, J. A. Garcı´a-Va´zquez, J. Romero, M. L. Durán, J. A. Real, A. Sousa, Inorg. Chem., 2006, 45, 7903-7914. 20. (a) Dey, S. K.; Mondal, N.; Fallah,M. S. E.; Vicente, R.; Escuer, A.; Solans, X.; FontBardı´a, M.; Matsushita, T.; Gramlich, V.; Mitra S. Inorg. Chem., 2004, 43, 2427-2434; (b) Banerjee, A.; Singh, R.; Chopra, D.; Colacio, E.; Rajak, K. K. Dalton Trans., 2008, 6539–6545; (c) Zhang, Y.; Zhang, X.-M.; Liu, T.-F.; Xu, W.-G. Transition Met.Chem. 2010, 35, 851-858; (d) Sasmal, S.; Hazra, S.; Kundu, P.; Dutta, S.; Rajaraman, G.; Sanudo, E. C.; Mohanta, S. Inorg. Chem., 2011, 50, 7257-7267. 21. R. Ahlrichs, M. Bär, M. Hacer, H. Horn, C. Kömel, Chem. Phys. Lett., 1989, 162, 165–169. 22. (a) A. D. Becke, Phys. Rev. A, 1988, 38, 3098-3100; (b) C. T. Lee, W. T.Yang, R. G. Parr, Phys. Rev. B, 1988, 37, 785-789; (c) A. D. Becke, J. Chem. Phys., 1993, 98, 5648-5653. 23. Gaussian 09, RevisionB.01, M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J. A. Montgomery, Jr., J. E. Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Staroverov, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J. M. Millam, M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Martin, K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador, J. J. Dannenberg, S. Dapprich, A. D. Daniels, Ö. Farkas, J. B. Foresman, J. V. Ortiz, J. Cioslowski, and D. J. Fox, Gaussian, Inc., Wallingford CT, 2009. 24


16. S. K. Dey, M. S. El Fallah, J. Ribas, T. Matsushita, V. Gramlich, S. Mitra, Inorg. Chim. Acta,

Page 25 of 29

Dalton Transactions

View Article Online

DOI: 10.1039/C3DT52764F

24. (a) E. Ruiz, J. Cano, S. Alvarez and P. Alemany, J. Comput. Chem.,1999, 20, 1391-1400; (b) E. Ruiz, S. Alvarez, A. Rodríguez-Fortea, P. Alemany, Y. Pouillon and C. Massobrio, in:


Germany, 2001, 2, 5572. 25. (a) E. Ruiz, A.Rodríguez-Fortea, J. Cano, S. Alvarez, P. Alemany, J. Comput. Chem., 2003, 24, 982-989; (b) E. Ruiz, S. Alvarez, J. Cano and V. Polo, J. Chem. Phys., 2005, 123, 164110164117. 26. G. M. Sheldrick, Acta Cryst. 2008, A64, 112-122. 27. A. L. Spek, PLATON, Molecular Geometry Program, J. Appl. Crystallogr., 2003, 36, 7-13. 28. L. J. Farrugia, J. Appl. Crystallogr., 1997, 30, 565-566. 29. L. J. Farrugia, J. Appl. Crystallogr., 1999, 32, 837-838. 30. P. Mukherjee, M. G. B. Drew, V. Tangoulis, M. Estrader, C. Diaz, A. Ghosh, Inorg. Chem. Commun. 2009, 12, 929–932. 31. S. Giri, R. Biswas, A. Ghosh, S. K. Saha, Polyhedron, 2011, 30, 2717–2722. 32. R. Boca, Coord. Chem Rev., 2004, 248, 757-815. 33. J. J. Borrás-Almenar, J. M. Clemente-Juan, E. Coronado, B. S. Tsukerblat, J. Comp. Chem. 2001, 22, 985-991. 34. PROGRAM 66, Quantum Chemistry Program Exchange, Indiana University, Bloomington, IN, 1965. 35. V. K. Bhardwaj, M. S. Hundal, M. Corbella, V. Gomez, G. Hundal, Polyhedron, 2012, 38, 224-234. 36. a) K. K. Nanda, L. K. Thompson; J. N. Bridson, K. Nag, J. Chem Soc., Chem. Commun., 1994, 1337-1338. b) K. K. Nanda, R. Das, K. Venkatsubramanium, P. Paul, K. Nag, Inorg. Chem., 1994, 33, 1188-1193. 37. C. Wang, K. Fink, V. Staemmler, Chem. Phys., 1995, 192, 25-35. 38. X. H. Bu, M. Du, L. Zhang, D. Z. Liao, J. K. Tang, R. H. Zhang, M. Shionoya, J. Chem. Soc. Dalton Trans., 2001, 593-598. 39. A. Rodriguez-Fortea, P. Alemany, S. Alvarez, E. Ruiz, Chem Eur. J. 2001, 7, 627-637.

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Magnetism: Molecules to Materials (Eds.: J. S. Miller, M. Drillon), Wiley-VCH,Weinheim,

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Table 1. Crystallographic data for complexes 1, 2 and 3.


2

Formula

C46H48N6Ni2O11 C46H48N6Ni2O11, 0.5 CH4O C62H60N8Ni3O19

M

978.28

1988.61

1397.25

Crystal System

Triclinic

Monoclinic

Monoclinic

P21/c

P21/c

Space Group



P1

a/Å

12.194(5)

9.691(5)

12.597(5)

b/Å

12.681(5)

30.326(5)

20.605(5)

c/Å

14.833(5)

16.498(5)

14.151(5)

/

99.696(5)

90

90

/

97.420(5)

95.900(5)

108.141(5)

/

91.907(5)

90

90

V/Å3

2238.4(15)

4823(3)

3491(2)

Z

2

2

2

Dc/g cm-3

1.452

1.369

1.329

µ/mm-1

0.909

0.846

0.873

F (000)

1020

2076

1448

R(int)

0.024

0.126

0.041

Total Reflections

15344

32872

14920

Unique reflections 7613

9088

5823

I>2(I)

6208

4324

4285

R1, wR2

0.0327, 0.0873

0.1068, 0.3148

0.0688, 0.2251,

Temp (K)

293

293

293

26

3


1

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Ni(1) – O(1) Ni(1) – O(2) Ni(1) – O(3) Ni(1) – O(4) Ni(1) – N(1) Ni(1) – N(2)

2.027(2) 2.218(2) 2.080(2) 2.061(2) 2.134(2) 1.989(2)

Ni(2) – O(1) Ni(2) – O(2) Ni(2) – O(3) Ni(2) – O(6) Ni(2) – N(3) Ni(2) – N(4)

2.243(2) 2.018(2) 2.076(2) 2.081(2) 2.147(2) 1.993(2)

O(1)-Ni(1)-O(2) O(1)-Ni(1)- O(3) O(1) -Ni(1) - O(4) O(1) -Ni(1) - N(1) O(1) -Ni(1) - N(2) O(2) -Ni(1) - O(3) O(2) -Ni(1) - O(4) O(2) -Ni(1) - N(1) O(2) -Ni(1) - N(2) Ni(1) -O(3)- Ni(2) O(3)- Ni(1) - O(4) O(3) -Ni(1) - N(1) O(3) -Ni(1) - N(2) O(4) -Ni(1) - N(1) O(4) -Ni(1) - N(2) Ni(1)- O(1)- Ni(2) Ni(1)- O(2)- Ni(2) N(1)-Ni(1)-N(2) O(1)-Ni(2)-O(2) O(1)-Ni(2)-O(3)

78.7(1) 80.6(1) 164.1(1) 103.0(1) 90.3(1) 76.1(1) 86.0(1) 172.3(1) 98.6(1) 88.1(1) 91.7(1) 96.6(1) 170.1(1) 91.7(1) 96.3(1) 85.1(1) 85.9(1) 89.0(1) 78.3(1) 75.7(1)

O(1)-Ni(2)-O(6) O(1)-Ni(2)-N(3) O(1)-Ni(2)-N(4) O(2)-Ni(2)-O(3) O(2)-Ni(2)-O(6) O(2)-Ni(2)-N(3) O(2)-Ni(2)-N(4) O(3)-Ni(2)-O(6) O(3)-Ni(2)-N(3) O(3)-Ni(2)-N(4) O(6)-Ni(2)-N(3)

88.4(1) 171.5(1) 99.8(1) 80.7(1) 165.8(1) 99.7(1) 90.0(1) 91.6(1) 95.8(1) 170.3(1) 92.8(1)

Table 3. Hydrogen bonding distances (Å) and angles (º) for the complex 1 Compound D−H…A 1

D—H

O(3)–H(3WA)…O(5) 0.86(3) O(3)–H(3WB)…O(7)

A…H

D—H…A

2.50(2) 1.66(4)

167(3)

0.83(4) 2.64(2) 1.83(4)

165(3)

27

D… A



Table 2. Bond distances (Å) and angles (º) in the metal coordination spheres of complex 1

Dalton Transactions

Page 28 of 29

View Article Online

DOI: 10.1039/C3DT52764F

Ni(1) – O(6) Ni(1) – O(7) Ni(1) – O(8) Ni(1) – N(3) Ni(1) – N(4) Ni(1) – O(9)

2.016(5) 2.144(4) 2.186(5) 2.137(7) 1.983(6) 2.030(5)

Ni(2) – O(5) Ni(2) – O(7) Ni(2) – O(9)

2.025(5) 2.117(4) 2.052(5)

O(6) - Ni(1) - N(3) O(6) - Ni(1) - N(4) O(6) - Ni(1) - O(7) O(6) - Ni(1) - O(8) O(6) - Ni(1) - O(9) O(9) - Ni(1) - N(3) O(9) - Ni(1) - N(4) O(7) - Ni(1) - O(9) N(3) - Ni(1) - N(4) O(7) - Ni(1) - N(3) O(8) - Ni(1) - N(3) O(7) - Ni(1) - N(4) O(8) - Ni(1) - N(4) O(8) - Ni(1) - O(9) O(7) - Ni(1) - O(8)

88.9(2) 92.4(2) 101.9(2) 163.0(2) 90.1(2) 174.0(2) 89.1(2) 80.6(2) 96.9(3) 93.8(2) 91.4(2) 162.3(2) 104.4(2) 87.9(2) 61.1(2)

Ni(1) -O(9) -Ni(2) O(5)#- Ni(2) - O(9) O(7)# - Ni(2) - O(9) O(5)# - Ni(2) - O(7)# Ni(1) -O(7) -Ni(2)

96.6(2) 90.4(2) 99.2(2) 92.4(2) 91.4(2)

Symmetry operation# = 1-x,-y,1-z Table 5. Comparisons of the magneto-structural data for similar complexes triply bridged by two phenoxido and one water molecule.

Compound Ni···Ni (Å) MAQQUR 2.953 JENKUJ A:2.925 B:2.913

Ni−O (Å)a 2.061 A: 2.026 B:2.029

USEWIZ

2.862

2.091

USEWOF

A: 2.866 B: 2.876

A:2.097 B: 2.099

Ni-O-Ni (°)b 91.45 A:92.42 B:91.21 91.69 86.03 86.53 A: 85.51 86.73 B: 87.32 28

Ni-Ow-Ni (°)c J cm-1 Reference 82.48 6.2 18 A: 82.58 9.9 19 B: 81.01 85.93

11.1

12

A: 86.59 B: 86.73

10.9

12



Table 4. Bond distances (Å) and angles (º) in the metal coordination spheres of complex 3

Page 29 of 29

Dalton Transactions

View Article Online

85.42 85.46 87.04 85.82 PARJAV 2.872 2.082 86.30 86.71 87.19 Complex 1 2.891 2.126 85.10 88.10 85.90 Complex 2 2.851 2.078 86.30 85.50 86.90 a)Average Ni-O bond distances. b) Ni-O-Ni angles in the oxido bridge.


RATXIV

2.857

2.010

-1.9

35

19.1

9

25.4

This work

28.1

This work

c) Ni-Ow distances and Ni-Ow-Ni angles in the water bridge.

Table 6. Comparisons of the magneto-structural data for analogous complexes triply bridges by one µ2- phenoxido, one bidentate carboxylato in syn-syn configuration, and one carboxylato in tridentate 12OO´:2O mode.

Compound

Ni-O-Ni (°) 94.63 90.37 97.61 90.86

Ni-O (Å)b 1.996 2.020 2.015 2.029

Ni-O-O-Ni (°)c 12.63

J (cm-1) 6.1

Reference

13.29

8.8

31

2.082

97.64 91.87

2.024 2.044

11.87

0.2

15

A:2.100

A:90.40 97.17 B:90.44 97.14

A:2.038

A:25.79 3.6

30

B:2.016

B:23.17

96.61 91.39

2.014 2.024

10.18

6.2

This work

HOZXIE

Ni···Ni (Å) 3.019

Ni−O (Å)a 2.091

EXUJIR

3.074

2.100

FUSXAT

3.061

GUTGEI

A:3.063

Complex 3

B:3.058

B:2.096

3.047

2.084

4

a) Average Ni-O bond distances in the oxido bridges. b) Ni-O distances in the bidentate carboxylato. c) Dihedral angle in the bidentate carboxylato

29


DOI: 10.1039/C3DT52764F

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