Cyclic voltammetric and spectral studies of some mixed-ligand copper(II) complexes involving 2,2'-bipyridine/1,10-phenanthroline and amino acids

Department of Chemistry, University of Allahabad, Allahabad-211 002, Uttar Pradesh, India E-mail : dr_krishna_s@yahoo.co.in; drjagdish_p@yahoo.co.in Manuscript received 10 September 2007, revised 24 October 2008, accepted 27 October 2008 Cyclic voltammetric and electronic spectral studies of some mixed ligand copper(n) complexes, viz. [Cu(bipy)(glu)), 1; [Cu(bipy)(tyro))CI, 2; [Cu(phen)(asp)), 3; [Cu(phcn)(glu)].2H2O, 4 and [Cu(phen)(tyro))CI H2O, 5 (where, bipy = 2,2'-bipyridine, phen = 1,10-phenanthroline, asp = L-aspartate dianion, glu = L-glutamate dianion and tyro = L-tyrosinate anion) have been studied in aqueous medium at pH 5.0. All these complexes displayed a single-electron redox couple (Cu2+/+) in the potential range + 1000 to -400 m V vs Ag/ AgCI. The cathodic peak potential shifts positively with Increasing scan rate (V) and peak current ratio (lpa/lpc) is greater than 1.0, representing a decrease in dissolved CuI species near the electrode surface because of weak adsorption of the reduced species at the surface of working electrode in the case of phen mixed ligand complexes, 3 to S. It is important to note that for a given amino acid, the reduction potential (Epc) of these mixed ligand Cull complexes is less negative for the phen complex than the bipy complex (1 vs 4 and 2 vs 5), owing to the stronger π-acceptor character of phen over bipy