Investigation of photostationary state of chromophor/acceptor and related multistep electron relay by in situ visible absorption spectroscopy

In situ visible absorption spectra were measured under photoirradiated state of an aqueous solution involving Ru(bpy)32+ and methylviologen (MV2+). The short-lived viologen cation radical (MV+) was observed under photoirradiated conditions. In the system of ethylenediaminetetraacetic acid (EDTA)/Ru(bpy)32+/Ni-phthalocyaninesulfonate (NiPcS), the reduced species of the NiPcS was not observed, but the coexistence of MV2+ induced the reduction of NiPcS showing that successive electron transfers from the photoexcited Ru(bpy)32+ to MV2+, and then further from the MV+ to NiPcS take place in the mixture. The photochemical evolution of H2 was remarkably enhanced by the presence of the second electron acceptor (NiPcS) in the aqueous mixture of EDTA/Ru(bpy)32+/MV2+/Pt-black.