Mechanism of mediation of the electrochemical oxidation of K4Fe(CN)(6) at poly-[tris(3-{omega-[4-(2,2'-bipyridyl)]alkyl}-thiophene)iron(II)]-film modified electrodes in aqueous solutions

The kinetics of the electrochemical oxidation of K4Fe(CN)(6) at poly-[tris(3-{omega-[4-(2,2'-bipyridyl)]alkyl}thiophene)iron(II)]-film modified electrodes have been investigated in aqueous solutions, using cyclic voltammetry and rotating disk electrode voltammetry. The retro-electrocatalytic reaction of the substrate at the polymer-coated electrodes is dependent on the alkyl chain length between the thiophene and 2,2'-bipyridine moieties and on the concentration of the substrate. The electrodes coated with the films possessing short alkyl chains exhibit more reversible voltammetric behavior and better catalytic activity to the oxidation of [Fe(CN)(6)](4-) species in aqueous solutions compared with those possessing long alkyl chains. Kinetic parameters, calculated on the basis of modified Levich equations, indicate that under most circumstances the mediated reactions are controlled by the chemical step. Copyright (C) 1995 Elsevier Science Ltd.