화학공학소재연구정보센터
Journal of Physical Chemistry B, Vol.101, No.36, 7180-7190, 1997
Simulation of Proton-Transfer Reaction-Rates - The Role of Solvent Electronic Polarization
A simulation method suitable for the prediction of the rate of a proton transfer reaction of the form A-H-B -->A-H-Bi, where -denotes a hydrogen bond, is presented. The method is based on a golden rule formulation, where the coupling between the two proton states is obtained by solution of Schrodinger’s equation for the proton states in a double-well potential whose shape is determined, in part, by the solvent’s electronic polarization. The reaction activation energy is determined by solvent fluctuations, as well as flanking group (A and B) vibrational motion. The surfaces for the AB vibrational motion with the proton in its initial and final states are also modified by the coupling to the solvent’s electronic polarization. Consequently, the matrix elements of the proton coupling between the AB vibronic states with the proton in its initial and final state, as well as the reaction’s activation energy, are dependent upon the coupling to the solvent’s electronic polarization. The rate constant for proton transfer in a representative phenol-amine hydrogen-bonded solute immersed in a polar/polarizable model for dichloromethane is simulated. The rate constant can be quite large, in the ps(-1) range, as the proton coupling can be large for smaller AB distances, and the AB vibration provides a number of channels for proton transfer.