CALCULATIONS OF INTRAMOLECULAR REORGANIZATION ENERGIES FOR ELECTRON-TRANSFER REACTIONS INVOLVING ORGANIC-SYSTEMS

The determination of intramolecular reorganization energies for self-e xchange outer-sphere electron-transfer (ET) reactions is presented usi ng a recently published method. From ab initio calculations, the elect ronic structure and equilibrium geometry, q, for the neutral, q(eq)(0) , and monocharged, q(eq)(+/-), organic molecules are obtained along wi th the force constant matrix F. A projected force constant f is determ ined as f = (Delta q(T)F Delta q)/\Delta q\(2), where Delta q = q(eq)( 0) - q(eq)(+/-). The intramolecular reorganization energy is obtained as lambda(i) = ((f((0))f((+/-)))/(f((0)) + f((+/-))))\Delta q\(2). It is shown that, due to the inclusion of the coupling between the variou s vibrational coordinates, this approach is an improvement compared to conventional methods for calculating the intramolecular reorganizatio n energy. The method is tested on the reductive ET of aromatic hydroca rbons, the oxidative ET of substituted benzenes, and oxidative/reducti ve ET of benzyl radicals.