A Ruthenium Complex-Porphyrin-Fullerene-Linked Molecular Pentad as an Integrative Photosynthetic Model.

A ruthenium complex, porphyrin sensitizer, fullerene acceptor molecular pentad has been synthesized and a long-lived hole-electron pair was achieved in aqueous solution by photoinduced multistep electron transfer: Upon irradiation by visible light, the excited-state of a zinc porphyrin ((1) ZnP*) was quenched by fullerene (C60 ) to afford a radical ion pair, (1,3) (ZnP(.+) -C60(.-) ). This was followed by the subsequent electron transfer from a water oxidation catalyst unit (Ru(II) ) to ZnP(.+) to give the long-lived charge-separated state, Ru(III) -ZnP-C60(.-) , with a lifetime of 14 μs. The ZnP worked as a visible-light-harvesting antenna, while the C60 acted as an excellent electron acceptor. As a consequence, visible-light-driven water oxidation by this integrated photosynthetic model compound was achieved in the presence of sacrificial oxidant and redox mediator.