Electrochemical and spectroelectrochemical studies of cobalt phthalocyanine polymers

Spectroscopic and electrochemical properties of cobalt phthalocyanine (CoPc) polymers, which are believed to have two- and three-dimensional structures, have been studied and the results are reported. The spectral bands are shifted and a significant band broadening is observed as expected. The cyclic voltammetric results suggest that there are two energetically different Co ions in the three-dimensional polymer. The spectroscopic and electrochemical results indicate that the Co ion on the polymers appears to be in a partially reduced state in solution phases, as evidenced by the presence of the metal-ligand charge-transfer band. When adsorbed onto the carbon surface, this band becomes more prominent even in the formally unreduced state, perhaps due to the coordination of pi-electron clouds of carbon into the coaxial axis of the complex, resulting in the partially reduced Co ion. As a result of this partial reduction, the electron transfer from CoPc polymers appears to be enhanced, which becomes the basis for the catalytic activities observed for this class of compounds.