Cyclic voltammetric investigations of copper(II) complexes with various imidazoles in dimethylformamide

Abstract

The cyclic voltammetric behaviour of copper(n) complexes with various imidazoles, viz. imidazole (ImH), 2-methylimidazole (2-Melm), 1,2-dimethylimidazole (1,2-Me 2 Im) and benzimidazole (BzIm) has been investigated in dimethylformamide (DMF) containing 0.1 M tetrabutyl ammonium perchlorate (TBAP) as a supporting electrolyte at a glassy carbon electrode (GCE). All these copper(II) complexes revealed a diffusion-controlled quasi-reversible one-electron transfer process (Cu 2+/+ ). It has been observed that the reduction peak potential becomes less positive (difficult reduction) with increasing concentration of a given ligand. The observed reduction potentials of these complexes become more positive in the order : Im → 2-MeIm → 1,2-Me 2 Im → BzIm. The deviation of reduction potentials from the expected trend based on pK a values of the ligands is attributed to the dominance of steric effects over the electronic effects (i.e. inductive effects) in the case of 2-MeIm and 1,2-Me 2 Im ligands.