Cyclic voltammetric studies of some bis(phenanthrolines)copper(II) complexes

The electrochemical properties of some bis(phenanthrolines)copper(II) complexes, [Cu(NN)(2)](ClO4)(2) (NN denotes 1,10-phenanthroline (phen); 4,7-diphenyl-1,10-phenanthroline (bathophen); 2,9-dimethyl-1,10-phenanthroline (dmp) and 2,9-diphenyl-1,10-phenanthroline (dpp) have been studied by cyclic voltammetry at a platinum working electrode in dimethyl sulfoxide (DMSO) and dimethyl formamide (DMF) containing 0.1 M tetrabutyl ammonium perchlorate (TBAP) as the supporting electrolyte. All these complexes display a quasireversible Cu2+/+ redox couple. Both the electron-donating methyl groups and electron-withdrawing phenyl groups at the 2,9-positions of the phen ligand elevate the Cu2+/+ redox potentials of the [Cu(dmp)(2)](ClO4)(2) and [Cu(dpp)(2)](ClO4)(2) complexes. The redox potentials of [Cu(dmp)(2)](2+) are nearly 50 mV more positive than that of [Cu(dpp)(2))](2+) in a given solvent. It is found that the Cu2+/+ reduction potential (E-pc) as well as formal potential (E-0') for a given complex all shifted to more positive values in DMF as compared to that in DMSO.