Using resonance Raman spectroscopy to examine vibrational barriers to electron transfer and electronic delocalization

A time-dependent approach to the interpretation of resonance Raman scatteri ng intensities has been used to obtain quantitative vibrational mode displa cement information from scattering intensities associated with charge-trans fer excitation. The displacements and associated frequencies are the key pa rameters needed to understand Franck-Condon effects in electron-transfer ki netics, and to delineate in a mode-specific way the composition of vibratio nal reorganization energies. Application of the approach to a number of typ es of electron-transfer reactions is described, including symmetrical and u nsymmetrical intervalence electron transfers in inorganic and organic redox systems, metal-to-ligand charge-transfer reactions, and interfacial electr on-transfer reactions. Also described is how the approach can be used to el ucidate mechanisms for valence delocalization in strongly interacting redox systems.