Electrochemistry of binary and mixed-ligand copper(II) complexes with pyrazineand dicyanamide bridging ligands in aqueous medium

Abstract

The binary copper(II) complexes, viz., [Cu(II) (pyz)n(H2O)n] (1), and [Cu(II)(dca)n(H2O)n] (2), and, mixed ligandcomplex, [Cu(II) (dca)n(pyz)n]. nH2O (3), containing pyrazine (pyz) and dicyanamide (dca) bridging ligands (where n isnumber of ligand attached and it could be 1 to 6 ) are formed in aqueous medium. The electrochemical behavior of binarycomplexes in 1:1, 1:2 and 1:10 (Cu : pyz/dca) molar ratios and mixed ligand complex in 1: 1 :1 and 1:2:1 (Cu:dca:pyz)molar ratios have been carried out by cyclic voltammetry. The binary complex 1 undergoes a quasi-reversible singleelectronredox process (Cu2+/+), while the binary complex 2 exhibits a totally irreversible reduction peak involving twoelectrons corresponding to Cu2+/0 change. The reduction potential becomes positive with increasing concentration of pyz/ordca, clearly indicating that reduction becomes easier with increasing concentration of ligand in binary complexes. Themixed ligand complex 3 involving pyz and dca bridging ligands shows an irreversible reduction peak assigned to Cu2+/0electrode reactions. The UV-vis spectral properties of all the binary and mixed ligand complexes have been studied inaqueous medium.