Electrochemical studies of a dinuclear copper complex with imidazole derivative ligand H3bphenim

Electrochromism and electrochemical properties of complexes of transition metal ions with benzimidazole-based ligand

Six complexes of transition metal ions have been synthesized and characterized. Complexes showed optical properties dependent on redox state of both metal ions and ligand molecule and can be used for the construction of multielectrochromic devices.

[μ-2,8-Dimethyl-1,4,5,6,7,10,11,12-octa-hydro-diimidazo[4,5-h;4',5'-c][1,6]diaze-cine-5,11-diacetato]bis-[diaqua-nitrato-copper(II)] trihydrate

The title compound, [Cu(2)(C(16)H(20)N(6)O(4))(NO(3))(2)(H(2)O)(4)]·3H(2)O, crystallizes with two dinuclear Cu(II) complex mol-ecules, each lying on an inversion center, and six solvent water mol-ecules per unit cell. The central 1,6-diazecine ring adopts the common chair conformation invariably found in the family of complexes bearing such ligands. The Cu(II) atoms have an octa-hedral geometry, with a very strong tetra-gonal distortion due to the Jahn-Teller effect. Axial sites are occupied by a nitrate ion and a water mol-ecule. The Cu⋯Cu separations [7.3580 (9) and 7.3341 (9) Å] are compatible with a potential catecholase activity. Neighboring mol-ecules in the crystal structure are connected via O-H⋯O hydrogen bonds formed by water mol-ecules and carboxyl-ate O atoms. N-H⋯O hydrogen bonds are also present.

Copper(ii) complexes of a polydentate imidazole-based ligand. pH effect on magnetic coupling and catecholase activity

A potentially dodecadentate N8O4-donor ligand obtained from 2,2'-biimidazole and l-valine and its tetranuclear Cu(ii) complexes in different degrees of protonation were characterized by chemical and spectroscopic methods. The extensive solution studies performed reveal that the rise in pH media leads successively to the formation of imidazolato (pKa(1) and pKa(2) and hydroxido (pKa(3) and pKa(4)) bridges. A frozen solution EPR study shows a decrease in the signal intensity until an EPR silent spectrum is observed, upon increasing the basicity of the solution. The catalytic performance of the oxidation of 3,5-di-tert-butylcatechol to its corresponding quinone was studied using UV-Vis-NIR absorption spectroscopic methods in CH3CN-H2O and in CH3OH-H2O at pH = 7.5, 8.0 and 8.5. A marked increase in activity, consistent with the formation of the hydroxide bridged species, is observed at pH = 8.5 in both solvent mixtures, but the activity is significantly higher in CH3OH-H2O.