Photoinduced gas-phase electron transfer reactions.

The electron transfer quenching process, when a reactive excited state is singlet or triplet, for gas-phase systems (benzophenone and anthraquinone with amines and pyridine as well as carbazole with halomethanes) was systematically investigated using time-resolved fluorescence. Bimolecular rate constants were obtained. Variable-temperature measurements were performed for eight donor-acceptor pairs. It was found that under solvent-free conditions various quenchers differing in photochemical reactivity led to change in quenching rates by almost three orders of magnitude. Positive and negative temperature dependences for the electron transfer rate constants were observed. The data were analyzed in terms of the Marcus-Jortner theory.