Redox properties of anion-exchangeable polypyrrole substituted by (ferrocenylmethyl)ammonium groups and their binding interaction with solution-dissolved calix[6]arene-p-hexasulfonate

This report describes charge transport in a (ferrocenylmethyl)ammonium group-substituted anion-exchangeable polypyrrole and discusses the binding interaction of the ferrocenyl group with solution-dissolved calix[6]arene-p-hexasulfonate. The impedance response of 0.8–1.1 μm thick film modified electrodes corresponded with the behavior expected from the diffusional charge-transport model for thin films. Since the charge-compensating counterions diffused rapidly in the polyelectrolyte film, the rate of intermolecular electron hopping limited that of charge transport. The polycationic film effectively extracted the calixarene from its dilute aqueous solutions. It shifted the half-wave potential of the ferrocenyl group to less positive values, indicating the greater binding affinity of the anionic host for ferrocenium cations than for uncharged ferrocenes. The inclusion complexation decreased the concentrations of the free redox couple; thus the host of 1-mM concentration increased the interfacial charge-transfer resistance by a factor of 70. Since the rates of the coupled chemical reactions were fast, they influenced the electrode kinetics insignificantly.