Application of Koopmans' theorem in evaluating electron transfer matrix element of long-range electron transfer

This paper has proposed an approach to searching for the minimum of molecul ar orbital (MO) energy splitting factor, and obtaining the electron transfe r (ET) matrix element in long-range electron transfer reactions. This metho d has been applied to the intramolecular electron transfer reactions betwee n biphenyl anion radical and biphenyl as well as naphthalene, mediated by t he 5-alpha-androstane bridge. The electron transfer matrix element can be d etermined by the minimum location of the MO energy splitting factor between the lowest unoccupied molecular orbital and the next lowest unoccupied mol ecular orbital based on Koopmans' theorem, Such a method is of special inte rest for asymmetric electron transfer systems in which the excess electron or hole transfers from one site to another. This paper has investigated the orientation dependence of the MO energy splitting factor for the co-axis s elf-exchange system of biphenyl anion radical and biphenyl. The values of E T matrix elements obtained using Koopmans' theorem have been discussed in c ontrast to the state overlap on the basis of two-state model. (C) 2000 Else vier Science B.V. All rights reserved.