Exited state electron and energy transfer in molecular assemblies

The metal-to-ligand charge transfer (MLCT) excited states of polypyridyl complexes of the d6 ions Ru(II), Os(II), and Re(I) have provided the basis for many studies on photochemical electron and energy transfer. In this account, a brief review of photochemical electron transfer by [Ru(bpy)3]2+* is given, followed by an update on MLCT excited state molecular and electronic structure, and an introduction to photochemical electron and energy transfer in molecular assemblies. The majority of the account is devoted to describing the evolution of two approaches to preparing complex molecular assemblies for the study of photochemical electron and energy transfer both inspired by the demands of achieving artificial photosynthesis. The first approach involves the derivatization of preformed polystyrene by added chromophores and electron or energy transfer donors or acceptors and three generations of polymers differing in polymer content and linkage strategies. The second approach has exploited solid-state peptide synthesis and the stepwise preparation of oligopeptides with spatial control of added groups and alignment on the resulting helical scaffolds.