Electropolymerized cobalt macro complex-based films for thiols electro-oxidation: effect of the film formation conditions and the nature of the macrocyclic ligand

We report here on the study of the electrocatalytic behavior of adsorbed and thin electropolymerized cobalt porphyrin and phthalocyanine films towards thiols oxidation with a special emphasize on the effect of the anion used for preparing the films and the nature of the macrocyclic ligand on the catalytic activity. Our results show that there are no effects related to the anions used during the preparation of the films on the electrocatalytic activity of the complex coatings, as evaluated by the cyclic voltammetry investigation of various thiols of different sizes. In contrast, the nature of the ligand around the cobalt centre of the macrocyclic complex has a strong effect on the catalytic activity for the oxidation of 2-mercaptoethanol (2-ME). This clearly illustrates the fact that the Co-II/Co-I formal redox potential of the macrocycle needs to be located in a rather narrow window to obtain maximum activity. (C) 2003 Published by Elsevier B.V.