Polychromatic femtosecond fluorescence studies of metal-polypyridine complexes in solution

Femtosecond-resolved broadband fluorescence studies are reported for[M(bpy)₃]²⁺ (M = Fe, Ru), RuN3 and RuN719 complexes in solution. We investigated the pump wavelength dependence of the fluorescence of aqueous [Fe(bpy)₃]²⁺ and the solvent and ligand dependence of the fluorescence of Ru-complexes excited at 400 nm. For all complexes, the ¹MLCT fluorescence appears at zero time delay with a mirror-like image with respect to the absorption. It decays in ?30-45 fs due to intersystem crossing to the ³MLCT states, but a longer lived component of ∼190 fs additionally shows up in RuN719 and RuN3. 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 to ?10 fs using the ¹MLCT lifetime as an internal clock.