Evidence for intermolecular hydrogen-bond rearrangement in the electron transfer dynamics of betaine-30 in n-butanol

The electron transfer and ground-state solvation dynamics of betaine-30 (B-30) in n-butanol at low temperatures are investigated by femtosecond pump-probe spectroscopy. Two separate components of the solvent response to solute excitation are observed. At higher temperatures (292-273 K), spectral evolution corresponding to diffusional solvation is evident. However, low-temperature studies (273-193 K) show the presence of a second process characterized by a approximate to 100 ps decay time and weak temperature dependence demonstrating that specific intermolecular hydrogen-bond dynamics are involved in the solvation of B-30 in protic solvents.