Theoretical study of the inner-sphere energy barrier of the transition-metal complex M(H2O)62+/3+ in electron-transfer process

Two theoretical models, a reorganization model and an activation model, are presented for accurately determining the energy barrier of the type M(H2O)(6)(2+/3+) of the transition-metal complexes in the electron-transfer process. Ab initio calculations are carried out at UMP2/6-311G level for several redox pairs M(H2O)(6)(2+/3+) (M = V, Cr, Mn, Fe, and Co) to calculate their inner-sphere reorganization energies and activation energies according to the models presented in this article. The values of theoretical inner-sphere reorganization energies and activational energies are comparable with the experimental results obtained from the vibration spectroscopic data. The theoretical reorganization energy of the every redox pair is four times as much as its activation energy, which agrees with Marcus' electron-transfer theory. The fact proved that the theoretical models presented in this article are scientific and available for studying the electron-transfer process of the transition-metal complex. (C) 1999 John Wiley & Sons, Inc.