DYNAMICS OF PROTON-TRANSFER REACTIONS IN POLAR-SOLVENT IN THE NONADIABATIC 2-STATE APPROXIMATION - TEST CALCULATIONS FOR CARBON-CARBON REACTION-CENTER

The quantum dynamics of a proton transfer (PT) reaction in a polar sol vent, treated as continuum, is considered taking as an example the PT process Flu(-) + HFlu --> HFlu + Flu(-) in ether, where FluH means flu orene. Using the model three-dimensional free-energy surface (FES) der ived from quantum-chemical SCRF calculations, the dynamical descriptio n is reduced to a two-level stochastic Liouville equation in the two-d imensional subspace spanned by the solute vibrational mode (representi ng a relative motion of heavy atoms constituting the PT reaction centr e) and a solvent collective coordinate. The two quantum states involve d in a reactive event are a pair of lowest proton levels obtained by m eans of quantum-mechanical averaging the basic three-dimensional FES. The new methodology of a direct evaluation of the coupling matrix elem ent is elaborated. The rate calculation involves a treatment of extrem ely small (similar to 10(-5)-10(-10)) transmission factors for which t wo different approximate non-adiabatic approaches are tested. The whol e variety of experimental data on reaction (a) involving both the abso lute values of the rare constant (K-H) and the H/D isotope effect cann ot be consistently described within the present two-level scheme.