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A comparative study has been attempted on 1-substituted 2-(pyridin-2-yl)-1H-benzo[d]imidazole ligand-coordinated copper and cobalt metal complex electrolytes Cu+/2+[nbpbi]2(PF6–)1/2, Cu+/2+[npbi]2(...

Several six-coordinate iron(II) carbene tetra(pentafluorophenyl)porphyrin (TFPP) complexes, [Fe(TFPP)(CPh2)(1-EtIm)] (1-EtIm = 1-ethylimidazole) and [Fe(TFPP)(CPh2)(1,2-Me2Im)] (1,2-Me2Im = 1,2-dimethylimidazole), are isolated and studied by UV–vis, single-crystal X-ray, and Mossbauer spectroscopies. The single-crystal structural studies revealed noteworthy features including strong and “hard” axial carbene bonds (Fe–C) but “flexible” trans ligand bonds (Fe–NIm). The Mossbauer spectra of [Fe(TFPP)(CPh2)(1-EtIm)] and [Fe(TFPP)(CPh2)(1,2-Me2Im)] are obtained on solid-state samples between 25 and 295 K, which give very large ΔEQ values (1.8–1.9 mm/s), suggesting a weak effect of the trans imidazole ligands. Comparisons with diatomic carbon-donor ligands (CO, CS, and CN–) demonstrate considerably stronger π bonding of the :CPh2 carbene.

The synthesis and characterization of several electron-poor iron(II) porphyrin (FeTFPPBr8) complexes with axial imidazole ligands are reported. The single-crystal X-ray structures have been studied by a combination of crystal packing and Hirshfeld surface calculations, which explained the unusual axial-ligand geometries, e.g., the strong tilt of the Fe–NIm bonds and the imidazole planes. The six-coordinate [Fe(TFPPBr8)(1-MeIm)2] was studied by multiple-temperature solid-state Mossbauer spectroscopy, which suggested that it is a low-spin complex with δ ∼ 0.32–0.38 mm/s and ΔEQ ∼ 1.0 mm/s.

Three peroxomanganese(III) complexes [Mn(III)(O(2))(mL(5)(2))](+), [Mn(III)(O(2))(imL(5)(2))](+), and [Mn(III)(O(2))(N4py)](+) supported by pentadentate ligands (mL(5)(2) = N-methyl-N,N',N'-tris(2-pyridylmethyl)ethane-1,2-diamine, imL(5)(2) = N-methyl-N,N',N'-tris((1-methyl-4-imidazolyl)methyl)ethane-1,2-diamine, and N4py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine) were generated by treating Mn(II) precursors with H(2)O(2) or KO(2). Electronic absorption, magnetic circular dichroism (MCD), and variable-temperature, variable-field MCD data demonstrate that these complexes have very similar electronic transition energies and ground-state zero-field splitting parameters, indicative of nearly identical coordination geometries. Because of uncertainty in peroxo (side-on η(2) versus end-on η(1)) and ligand (pentadentate versus tetradentate) binding modes, density functional theory (DFT) computations were used to distinguish between three possible structures: pentadentate ligand binding with (i) a side-on peroxo and (ii) an end-on peroxo, and (iii) tetradentate ligand binding with a side-on peroxo. Regardless of the supporting ligand, isomers with a side-on peroxo and the supporting ligand bound in a tetradentate fashion were identified as most stable by20 kcal/mol. Spectroscopic parameters computed by time-dependent (TD) DFT and multireference SORCI methods provided validation of these isomers on the basis of experimental data. Hexacoordination is thus strongly preferred for peroxomanganese(III) adducts, and dissociation of a pyridine (mL(5)(2) and N4py) or imidazole (imL(5)(2)) arm is thermodynamically favored. In contrast, DFT computations for models of [Fe(III)(O(2))(mL(5)(2))](+) demonstrate that pyridine dissociation is not favorable; instead a seven-coordinate ferric center is preferred. These different results are attributed to the electronic configurations of the metal centers (high spin d(5) and d(4) for Fe(III) and Mn(III), respectively), which results in population of a metal-peroxo σ-antibonding molecular orbital and, consequently, longer M-O(peroxo) bonds for peroxoiron(III) species.

This Article reports the syntheses, structural characterization, and magnetic studies of four different Cu(II)-azido compounds based on imidazole or substituted imidazole ligand. The compounds, [Cu2(μ1,1-N3)2(EtimiH)4(ClO4)2] (1) (EtimiH = 2-ethylimidazole), [Cu2(μ-Meimi(-))(MeimiH)2(μ1,1-N3)2(μ1,3-N3)]n (2) (MeimiH = 2-methylimidazole; μ-Meimi(-) is the bridging mononegative anion of 2-methylimidazole), [Cu2(μ-imi(-))(imiH)2(μ1,1-N3)2(μ1,3-N3)]n (3), and [{Cu2(μ1,1-N3)2(μ1,3-N3)(μ-imi(-))(imiH)3}·H2O]n (4) (imiH = imidazole; μ-imi(-) = bridging mononegative anion of imidazole), have been synthesized by the self-assembly of Cu(II) salts, azide ion, and the corresponding imidazole bridging ligands. By changing the substitution on the second linker (imidazole or substituted imidazole) and varying synthetic conditions, diverse structural and magnetic features have been achieved in compounds 1-4. Compound 1 has a double end-on azido bridged dinuclear core, while the other compounds (2-4) have 2D networks. Compound 2 and 3 contain 1D chains with alternate μ1,1-N3 and μ-Meimi(-) bridging, and such chains are further connected through a μ1,3-N3 bridge to result in the formation of the 2D network. Compound 4 is a novel 2D coordination polymer consisting of a zigzag 1D coordination chain having (μ1,1-N3)2, μ-imi(-), and (μ1,3-N3)2 bridging groups and the chains undergo bridging through a μ1,3-N3 group resulting in the 2D network. Temperature dependent magnetic measurements show diverse magnetic properties of 1-4. Such versatile magnetic behaviors have been correlated to the respective bridging mode of azide and the corresponding imidazole bridging ligands.

Reactions of [WES3]2- (E = S, O) with CuX (X = NCS, CN, I) in the presence of bix (bix = 1,4-bis(imidazole-1-ylmethyl)benzene) in DMF or CH3CN resulted in the formation of two novel 2D --3D interpenetrating coordination polymers [S2W2S6Cu4(bix)2]n (1) and {[WS4Cu4(NCS)2(bix)3].CH3CN}n (2), a noninterpenetrating 3D polymer {[WS4Cu2(bix)].DMF}n (3), and two 2D sheet polymers [WS4Cu3(CN)(bix)]n (4) and {[OWS3Cu3(bix)2][I].DMF.2H2O}n (5), depending on the reaction temperature and the reagents used. Compound 1 contains a hexagonal prism of W2Cu4S6 cluster core, which serves as a 4-connecting node to link equivalent nodes via bix ligands, forming a 2D (4,4) net. In 2, a WCu4S4 core, which also acts as a 4-connecting node, connects the neighboring nodes either through single or double bix bridges, affording a different 2D (4,4) sheet. Inclined interpenetration occurs between two stacks of 2D sheets in the total structure of 1, while 2 involves a parallel interpenetration between the adjacent layers, both creating a 3D network. Compounds 1 and 2 represent the first examples of interpenetrating (4,4) frameworks with clusters as nodes and bidentate pyridyl-based ligands as linkers. Unlike 1 and 2, compound 3 has a noninterpenetrating 3D network, which is composed of the inorganic 1D (WS4Cu2)n chains linked by cis and trans bix ligands. Compound 4 features an inorganic 1D (WS4Cu3)n chain structure, which is linked by CN groups and bix ligands to form an infinite 2D network. Compound 5 is a 2D layer polymer with large inner cavities.

The synthesis and characterization of the new imidazole ligand bis(1-methyl-4,5-diphenylimidaz-2-oyl)(benzyloxy)methane (BimOBz) and its copper(II) complexes [Cu(BimOBz)(2)][BF(4)](2).2H(2)O (1.2H(2)O), [Cu(BimOBz)(NO(3))(2)].CH(2)Cl(2) (2.CH(2)Cl(2)) and [Cu(BimOBz)Cl(2)].2EtOH (3.2EtOH) are presented. The X-ray crystallographic parameters determined are as follows: 1.solv (solv = petroleum ether) C(84)H(66)N(8)B(2)CuF(8)O(2), 1456.65, monoclinic space group (P2(1)/a), a = 20.862(8) Å, b = 19.110(5) Å, c = 22.452(9) Å, beta = 110.09(3) degrees, Z = 4, R = 0.129, and R(w) = 0.139. 2.CH(2)Cl(2), C(41)H(36)N(6)Cl(2)O(7), 859.22, monoclinic space group (P2(1)/c), a = 9.748(1) Å, b = 14.157(5) Å, c = 17.209(2) Å, beta = 103.709(8) degrees, Z = 4, R = 0.066, and R(w) = 0.087. 3.2EtOH, C(44)H(38)N(4)Cl(2)CuO(2), 789.26, monoclinic space group (P2(1)/a), a = 17.171(5) Å, b = 13.988(3) Å, c = 17.897(5) Å, beta = 112.52(2) degrees, Z = 4, R = 0.084, and R(w) = 0.092. The geometry at these Cu(II) centers is distorted tetrahedral in 1 and 3 and essentially square-planar in 2, and this difference is reflected in their EPR spectra, especially the value of A(z)(); 1 (solid, g(x)() = 2.06, g(y)() = 2.13, g(z)() = 2.30, A(z)() = 94 x 10(-)(4) cm(-)(1)), 3 (CH(2)Cl(2), 77 K, g(x)() = g(y)() = 2.06, g(z)() = 2.37, A(z)() = 75 x 10(-)(4) cm(-)(1)), 2 (solid, g(x)() = g(y)() = 2.06, g(z)() = 2.28, A(z)() = 169 x 10(-)(4) cm(-)(1)). 1 displays a reversible, one-electron Cu(II)/Cu(I) couple in CH(2)Cl(2) and MeCN at potentials of +0.62 and +0.49 V vs SCE, respectively.