A hydration function scheme of electron transfer kinetics for hydrated redox couples in solution and its application in the Cr2+(aq)Cr3+(aq) system

This paper presents a hydration potential function scheme for the accurate determination of various electron transfer kinetics parameters. By comparing the common features of the electron transfer process and the hydration process of an ion, two hydration potential functions are determined in terms of the experimental spectroscopic and hydration thermodynamic data, and are then used to depict the energy dependence of the reacting system on the separation between the central ion and the innersphere water molecules and the solvent reorganization. The activation energy is obtained in terms of the proposed new activation model and the hydration potential functions, and is calibrated using the corresponding experimental value extracted from the experimental rate constant, and is also compared with those from other methods. The electronic transmission coefficient is calculated using the Landau-Zener formalism. The involved slopes of the potential energy surfaces are obtained from the proposed accurate hydration potential functions. The coupling matrix element is calculated using the two-state model and the numerical integral method over Slater-type double-zeta wave functions obtained using the perturbation method. The theoretical value of the electron transfer rate is calculated and compared with the experimental value. The applicability of the relevant models is also discussed.