Photoinduced electron transfer across membranes

Abstract

Vectorial photoinduced electron transfer (PET) across bilayer lipid and surfactant membranes provides a unique opportunity for the spatial separation of photochemically generated oxidants and reductants. In this chapter a review is given of the data on vectorial PET across the membranes of vesicles and planar bilayer membranes. The key steps that determine the efficiency of PET across membranes are discussed, i.e. (i) primary photochemical charge separation processes, (ii) secondary recombination reactions and (iii) electron transfer across membranes that provides stabilization of the charges generated in step (i). Step (iii) can be performed by three mechanisms: (1) via the diffusion of electron (or hole) carrier through the membrane, (2) via reactions of electron exchange between molecules located in different monolayers of a bilayer membrane and (3) via intramolecular electron transfer along bridging molecules, molecular wires and ultrafine semiconductor particles embedded into membranes. The possibility of conjugating PET across membranes with catalytic redox reactions is discussed with the emphasis on the water cleavage.