ENERGY-TRANSFER AND ELECTRON-TRANSFER SHUTTLING BY A SOLUBLE, BIFUNCTIONAL REDOX POLYMER

A soluble, bifunctional polymer ([PS-An28.5PTZ1.5]) based on derivatized polystyrene was prepared in which there are both energy-transfer acceptors (modified anthracene, An) and electron-transfer donors (derivatized phenothiazene, PTZ). The polymer was successfully incorporated into a photochemical electron-transfer sequence based on [Ru(bpy)3]2+ (bpy is 2,2'-bipyridine) in which separate oxidative and reductive equivalents were generated in solution. In the sequence, sensitized formation of the triplet excited state of the polymer-bound anthryl sites ([PS-3An*An27.5PTZ1.5]) occurred by diffusion and energy transfer from [Ru(bpy)3]2+* following visible excitation of [Ru(bpy)3]2+. In the presence of the oxidative quencher paraquat (PQ2+), a series of electron-transfer steps led, ultimately, to the appearance of [PS-An28.5PTZ+PTZ0.5] and monomeric PQ+ in solution. The recombination rate constant between PQ+ and [PS-An28.5PTZ+PTZ0.5] was reduced by a factor of approximately 7 relative to back electron transfer between the unbound, 10-methylphenothiazene cation (10-MePTZ+) and PQ+.