Light-induced electron-transfer reactions at electrodes coated with macromolecular thionine and ruthenium systems

Abstract

Thiazine dyes have been condensed with the macromolecules poly(N-methylolacrylamide), poly(N-methylolacrylamide-co-acrylic acid) and poly(N-methylolacrylamide-co-vinylpridine). Cyclic voltammograms of polymeric thionine-coated electrodes indicate the formation of a complex by the dye with ferric and ferricyanide ions at the electrode. The peak potential of quinone is not affected by the polymer-dye-coated electrode. When the electrode is exposed to light cathodic behaviour at the electrode is observed, indicating a change in the polarity of the electrode in comparison with the reaction at a platinum electrode with thionine and iron(II) present in the homogeneous solution. It is proposed that the generation of a charge-separated thionine–iron complex is stabilised by the macromolecular network. As a comparison polymeric ruthenium(II) bipyridyl complexes have been prepared and their cyclic-voltammetric and photoelectrochemical behaviour has been investigated. The nature of the polymeric network and of the dye bound to it appears to be an important factor for efficient charge transfer at the electrode.