Mv. Basilevsky et al., DYNAMICS OF PROTON-TRANSFER REACTIONS IN POLAR-SOLVENT IN THE NONADIABATIC 2-STATE APPROXIMATION - TEST CALCULATIONS FOR CARBON-CARBON REACTION-CENTER, Chemical physics, 208(2), 1996, pp. 267-282
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.