Photoinduced electron transport across a lipid bilayer mediated by C70

Electron transport across a membrane is central to photosynthesis, to mitochondrial respiration and to the design of molecular systems for solar energy conversion. Relatively few synthetic molecules, however, have been shown to facilitate transport of electrons across a lipid bilayer. We report here that C70 can act as both a photosensitizer for electron transfer from a donor molecule and a mediator for electron transport across a lipid bilayer membrane. The steady-state photocurrent density obtained from the C70-bilayer system is about 40 times higher, at comparable light intensities, than that of the carotene-porphyrinquinone system, previously the most efficient artificial system. The C70-bilayer system has a quantum yield of about 0.04, while the stability (tens of minutes) and turnover number (electrons transported per C70 before decay) of 10(3) are one to three orders of magnitude greater than those of other systems. We anticipate that other higher fullerenes may also provide the basis for efficient transmembrane electron-transport systems.