Photo-induced intramolecular electron transfer will be studied in ruthenium(II) and osmium(II) complexes containing chelating ligands with nitrogen donors. The goal of the research is to elucidate the role of solvent dynamics in controlling the rate of excited state electron transfer when both internal and solvent-induced reaction barriers exist. Reaction rates will be determined in solvents with different relaxation rates and the experimental results compared to theoretical predictions of the contribution of inner- and outer-sphere reaction barriers. Photoexcitation will place the system at its transition state where, if theoretical predictions prove valid, non-exponential dynamics will be observed. Excited state electron transfer between ligands will be observed in both symmetric and assymmetric complexes using picosecond absorption polarization spectroscopy. In addition, studies will be carried out concerning solvent effects on excited state proton transfer reactions in porphyrin complexes. The experimentally determined rates, activation energies, and preexponential factors will be interpreted using theories constructed by analogy to excited state electron transfer kinetics. %%% In this project in the Inorganic, Bioinorganic, and Organometallic program, Dr. David F. Kelley of Department of Chemistry at Colorado State University will excite various transition metal complexes photochemically and measure the subsequent rapid rates of electron transfer within the excited molecules. While this work is of a very fundamental nature, the results are relevant to development of a theoretical framework for utilization of solar energy.
