SOLVENT DEPENDENCE OF (SUB)PICOSECOND PROTON-TRANSFER IN PHOTO-EXCITED [2,2'-BIPYRIDYL]-3,3'-DIOL

We report on (sub)picosecond fluorescence studies of the mono- to dike to tautomer reaction in photo-excited [2,2'-bi-pyridyl]-3,3'-diol in a protic and protic solvents. In aprotic solvents no influence of the na ture of the solvent, temperature and deuteration of the hydroxyl group s on the proton transfer dynamics was found. In protic solvents, howev er, the proton transfer time is found to change proportionally with th e viscosity coefficient of the solvent. We briefly discuss (i) the for mation of the mono-and diketo forms from the dienol form and (ii) the nature of the vibrational modes assisting in the proton transfer proce ss. (C) 1997 Elsevier Science B.V.