Electrochemical studies of copper(II) complexes with Schiff-base ligands

Abstract

The electrochemical reduction of copper(II) complexes with salen Schiff-base ligands derived from ethylenediamine or (R,R) or (S,S)-1,2-diphenylethylenediamine and 5-methoxy, 5-bromo and 5-nitrosalicylaldehyde have been studied by cyclic voltammetry in the potential range + 1 to - 2.3 V in dimethyl sulfoxide (DMSO) as a solvent. The resulting voltammograms consist of a single quasi-reversible one-electron transfer attributable to the couple [Cu(II)L]/[Cu(I)L](-). Trends in cathodic peak potential (E-pc) values are observed which can be correlated with the electronic effects of the 5-substituents of the Schiff-base ligands. Changes in the basicity of the ligand groups are determinant for such electrochemical trends.