Polychromatic femtosecond fluorescence studies of metal–polypyridinecomplexes in solution

Femtosecond-resolved broadband fluorescence studies are reported for[M(bpy)3]2+ (M = Fe, Ru), RuN3and RuN719 complexes in solution. We investigated the pump wavelength dependence of the fluorescenceof aqueous [Fe(bpy)3]2+ and the solvent and ligand dependence of the fluorescence of Ru-complexesexcited at 400 nm. For all complexes, the 1MLCT fluorescence appears at zero time delay with amirror-like image with respect to the absorption. It decays in 630–45 fs due to intersystem crossing tothe 3MLCT states, but a longer lived component of 190 fs additionally shows up in RuN719 andRuN3. No solvent effects are detected. The very early dynamics are characterized by internal conversion(IC) and intramolecular vibrational redistribution (IVR) processes on a time scale which we estimate to610 fs using the 1MLCT lifetime as an internal clock.