Theoretical Study Of Electron Transfer In Organic Systems And Non-equilibrium Solvation

This dissertation consists of three parts. The first part, including chapter one and chapter two, tells the fundamental theory of electron transfer. Some specific electron transfer systems, including some self-exchange systems and the effect of external electric field, are investigated at ab initio level in the second part. The theory of non-equilibrium solvation is discussed in the third part.The Fundamental of electron transfer developed during the recent half-century are summarized in chapter one. We discuss the classical Marcus' model, quantum model and semi-classical model in this chapter. The factors that affect the rate constant of electron transfer reaction are discussed based on the classical Marcus' theory.The electronic coupling matrix, which is a very important factor in electron transfer, is discussed in chapter two. The methods of calculations for this factor, which are widely used at present, such as two states variation method, partition technological method, Generalized Muliiken-Hush method and the using of Koopman's theory method, are introduced in this chapter. We introduce the methods of the charge localization in quantum chemistry calculation. These methods include the geometry change of donor and acceptor, inducement of external electric field and the line composition of symmetrical and anti-symmetrical delocalized molecular orbitals. For the using of Koopman's theory, we have suggested a new criterion forselection of molecular orbitals. The electronic coupling matrix for cation system is equal to the half of energy difference between HOMO and H0M0-1 of the neutral system and that for anion system is equal to the corresponding LUMO+1 and LUMO of neutral system in the past. The relationship between Koopman's theory and two-states variation method has been obtained. Through this relationship, a new criterion for selection of molecular orbitals has been proposed. The summation and the difference between the two molecular orbtials which are used in the Koopman's theory should localize on donor and acceptor respectively. In addition, the two molecular orbitals should be frontier orbitals and they are occupied for cation system and unoccupied for anion system. Five different kinds of electron transfer reactions have been calculated to verify our conclusion. They are closed shell cation system, closed shell anion system, open shell cation system, open shell anion system self-exchange reaction and cross reaction. The geometry of the transition state of ET can be found along the linear reaction coordinate by searching for the minimal energy gap based on the new criterion.Two self-exchange electron transfer systems, including durene-bridged system and a U-shaped molecular system, are discussed in chapter three. The effect of conformation on intramolecular electron transfer between durene-bridged aromatic redox centers is discussed. Based on the semi-classical theory of electron transfer, quantum chemical calculations at HF/6-31G level are performed for the study of intramolecular electron transfer between durene-bridged 2,5-dimethoxy-4 -methylphenyl and its cation. Two conformations are adopted. After the geometric optimizations of the electron-localized states, a linear reaction coordinate was introduced to determine the transition state. The electronic transfer matrix elements are calculated by variation principle. The non-equilibrium solvation correction was taken into account. The electron transfer rate and reorganization energy obtained by theoretical calculation are consistent well with the experimental values. The electronic transfer matrix elements at different dihedral angles between bridge and redox centers were obtained. In order to show the different contribution to this value,the electronic transfer matrix elements were divided into two parts: through space and through bond. The latter is further divided into c-bond contribution and bond one. It was concluded that the through bond coupling is proportional to the square of cosine of dihedral angle. This conclusion was explained qualitative...