Title: Femtosecond to Nanosecond Switching in Photochromic Ruthenium Sulfoxide Complexes

Abstract: Photochromic compounds are molecular devices which convert photonic energy to potential energy, which is employed in excited state bond rupture and bond construction. Our examination of ruthenium and osmium polypryridine complexes containing sulfoxide ligands demonstrate that S-to-O isomerization is efficient, and can occur rapidly both in the solid state and solution. Picosecond transient absorption spectroscopic data show that S-to-O isomerization time constants may be as fast as 80 ps. Recent studies of ruthenium polypyridine complexes containing chelating sulfoxides illustrate that two different colors of light may be used to trigger between the two ground states. In conjunction with these results, structural and electrochemical data will be presented as well as a structural model to understand the photochemistry and photophysics of these compounds.