Photodriven transmembrane charge separation and electron transfer by a carotenoporphyrin-quinone triad

Photochemical transmembrane electron transfer processes are an integral part of natural photosynthetic solar energy conversion and are also central to the design of biomimetic energy conversion schemes^1-6. Here we report the synthesis and membrane-associated photoelectrochemical properties of carotenoporphyrin-quinone triad (I), a compound containing a photochemically active porphyrin and electron donor and acceptor moieties, and with the molecular architecture necessary to span a phospholipid bilayer. On excitation of compound 1 by visible light, charge is separated across a planar phospholipid bilayer membrane (BLM) in an intramolecular step; in the presence of suitable electron donor and acceptor species in the aqueous phases, a steady-state photo-current is observed in an external circuit bridging the BLM. Artificial membranes containing I thus mimic key features of the photodriven transmembrane electron transfer processes characteristic of photosynthetic organisms.