Ab initio investigations of nonadiabatic electron-transfer reactivity of monohydrated transition-metal-ion redox couples M~(2+)-OH_2/M~(3+)-OH_2 (M = V, Cr, Mn and Fe)

摘要

According to the basic features of electron-transfer reactions, a new theoretical model is presented for determining accurately various electron-transfer kinetics parameters. The potential-energy surfaces and relevant geometrical parameters for the monohydrated transition-metal-ion redox pairs, M~(2+)-OH_2/M~(3+)-OH_2 (M = V, Cr, Mn and Fe), have been calculated in terms of the electron correlation method by using second-order Moller-Plesset perturbation theory in the full orbital space at the 6-311 +G~* basis set level (UMP2(full)/6-311 + G~*). The activation energies are obtained in terms of the new activation model and potential-energy surfaces calculated ab initio, and are compared with those from other methods. In the calculation of the electronic transmission coefficient, the slopes of the potential-energy surfaces are obtained from the single-point ab initio calculated data in terms of a fitting method, and the coupling matrix element is determined by use of the two-state model and Slater-type d-electron wave functions. Theoretical values of the electron-transfer rate are determined in the gas phase and also in solution. The applicability of these models is also discussed.