EQCM STUDIES OF THE REDOX PROCESSES DURING AND AFTER ELECTROPOLYMERIZATION OF FILMS OF TRANSITION-METAL COMPLEXES OF VINYLTERPYRIDINE

The electropolymerization of the transition-metal complexes [M(v-tpy)( 2)z](n+) (M = Fe-II, Ru-II, Os-II, Cr-III, Co-II, Ni-II; v-tpy = 4'-vi nyl-2,2':6',2 ''-terpyridine) and the redox processes of their electro polymerized films have been investigated in acetonitrile solution usin g the electrochemical quartz crystal microbalance (EQCM) and admittanc e measurements of the quartz crystal resonator. From changes in the fr equency, polymerization for each of the complexes was found to be init iated by reduction of the ligand (v-tpy) except for [Ni(v-tpy)(2)](3+) , where the mechanism appears to involve an ostensibly metal-centered reduction. In all cases, the increase in the resistance parameter of t he electrical equivalent circuit of the resonator with potential cycli ng also indicated polymerization onto the electrode surface. The redox processes of the polymerized [M(v-tpy)(2)](n+) films appear to be of the anion-exchange type with changes in the film morphology. A mechani sm for the ''charge-trapping'' process of a uniform coating of poly-[M (v-tpy)(2)](2+) (M Fe, Ru, Os) is proposed in terms of changes in film morphology.