Syntheses, Crystal Structures and Spectroscopic Studies of Bis[1-methyl-3-(methoxycarbonylmethyl)-benzimidazolium]~(2+) [CuBr4]~(2-) and [ZnBr4]~(2-) Compounds

摘要

X-ray diffraction structure of two new bis [1-methyl-3-(methoxycarbonylmethyl) benzimidazolium]~(2+) [CuBr4]~(2-) and [ZnBr4]~(2-) compounds has been determined. Zn-crystal is monoclinic with perfect Td symmetry of the ZnBr4 tetrahedron, whereas the Cucompound is orthorhombic with D_(2d) symmetry of CuBr4 tetrahedron. The difference in these structures is described as due to the static Jahn-Teller effect. Vibrational spectroscopy (1800–3200 cm~(-1)) identified hydrogen bond network. NIR-UVVis spectra (5000–50000 cm~(-1)) are dominated by ligand-tometal bands with d-d transition contribution. EPR results (Qband) analyzed in terms of the MO-theory showed a very strong delocalization of unpaired electron density on ligands accompanied by the Cu(II) 4pz orbital contribution. This effect is partially compensated by charge transfer transitions to the EPR g-factor.