The influence of solvent dynamics on the lifetime of solute-solvent hydrogen bonds

The lifetimes of the hydrogen bonds formed between resorufin and the solvents ethanol, ethylene glycol, and 1,3-butanediol are measured as a function of temperature. The results show that the hydrogen-bond breaking reaction is strongly influenced by the dynamics of the solvent, in violation of traditional transition-state theory. The relevant solvent dynamics are not well described by the viscosity of the solvent, but do correlate with the dielectric relaxation time. We propose a model in which the hydrogen bond initially breaks to form a poorly solvated, ''dangling'' hydrogen bond, which has a high probability of geminate recombination. The product is not stabilized until the solvent hydrogen-bond structure can reorganize to incorporate the ''dangling'' bond. The same reorganization determines the dielectric relaxation time. (C) 1996 American Institute of Physics.