FEMTOCHEMISTRY IN NANOCAVITIES - REACTIONS IN CYCLODEXTRINS

We present our first studies of the femtosecond dynamics of reactions in confined nanocavities in water solutions. Intramolecular proton tra nsfer and isomerization dynamics of a hydrogen-bonded molecule (HPMO) in liquid solutions and encapsulated in the cavity formed by beta-cycl odextrin (diameter similar to 8 Angstrom) is studied using the techniq ue of fluorescence up-conversion. Our results suggest that the proton transfer in aprotic solvents occurs in much less than 300 fs while upo n encapsulation this initial step is slowed to the subpicosecond time scale. Furthermore, in these aprotic solvents, HPMO undergoes a picose cond twisting motion around the interaromatic single bond, which is no ticeably inhibited when the molecule is inside the nanocavity. Such st udies of condensed-phase femtochemistry in nanocavities offer several promising extensions.