Effect of configuration of viologen-linked porphyrin on photocurrent generation and on photoinduced hydrogen evolution

Abstract

Two types of viologen-linked porphyrin with different configuration between the porphyrin and the bonded viologen have been synthesized and Langmuir–Blodgett (LB) films prepared. The effects of the different configurations on the photoelectric conversion by indium tin oxide (ITO) electrodes modified with the LB films and on photoinduced hydrogen evolution, using the LB films and H ₂ PtCl ₆ as a catalyst in the presence of ethylenediaminetetraacetic acid (EDTA) as a sacrificial electron donor, have been investigated. No effect was detected for the photocurrent generation but photoinduced hydrogen evolution was dependent upon the configuration. These results show that the rate of diffusion of small electrolyte ions is the same in both LB films but diffusion of large EDTA molecules is affected by the configuration. Hence, the molecular structure of viologen-linked porphyrin must be taken into account in order to make diffusion of reactant in the LB film easy and thus to increase the reaction yield.