Relating absorption, emission, and resonance Raman spectra with electron transfer rates in photoinduced charge transfer systems: promises and pitfalls

In molecules or complexes in which a photoinduced electronic transition corresponds to a formal electron transfer process, there exists a close relationship between the theoretical expressions for the absorption, fluorescence, and resonance Raman spectra and the nonphotochemical return electron transfer rate in the coupling limit. In this paper, the theoretical expressions cast in both the sum-over-vibrational-eigenstates picture and the equivalent time-domain picture are reviewed. Several recent efforts by ourselves and other groups to make use of such relationships in the analysis of experimental spectroscopic and electron transfer rate data are then described and critiqued. Finally, prospects for the further development of this approach are discussed, as are some of its limitations and potential pitfalls.