A dicopper complex with distant metal centers. Structure, magnetic properties, electrochemistry and catecholase activity

Abstract

The crystal structure and magnetic properties of a dinuclear copper(II) complex of the ligand [2,8-dimethyl-5,11-di-(dimethylethyleneamine) 1,4,5,6,7,10,11,12-octahydroimidazo [4,5-h] imidazo [4,5-c] [1,6]diazecine] dimeim have been investigated. Also, its catecholase activity has been explored in different solvent mixtures: MeCN/H2O and OH/H2O, each at several pH values. In CH3OH/H2O, where the activity was superior, the optimal pH value for the catalytic activity was found to be lower than in CH3CN/H2O. The study of the complex's electrochemical behavior (cyclic voltammetry) which was also investigated in these various media, revealed that although an increase in pH in both solvent mixtures results in an increase both in Me oxidizing power (E-1/2) and reversibility (i(pa)/i(pc)) the change of solvent system seems to be a more influencing factor. The superior catalytic activity found in MeOH/H2OpH=8.0, is associated with a significantly more reversible behavior displayed in this medium. Potentiometric determination of the overall formation constant and three successive pK(a)s for the complex, suggest the formation of stable hydroxo complexes which could be the catalytically active species. (C) 2008 Elsevier Inc. All rights reserved.