Molecular orbital studies of electron-transfer reactions

Abstract

Our previous AM1 semiempirical molecular orbital studies on the electron self-exchange reaction between p-diaminobenzene (PPD) and its radical cation have been extended to include dynamics calculations of the inner-sphere vibrational frequency, ν_i, and a configuration interaction (Cl) study of the distance dependence of the transfer-integral, V₁₂. These and our previous results for the reorganization energy, λ, and the classical activation barrier to electron transfer have been used to calculate a unimolecular gas-phase rate constant, K_et, of (3–7)× 10¹⁰ s^–1, compared with an experimental value in acetonitrile of 2 × 10⁸ s^–1. The solvent is thus suggested to lower K_et by a factor of 150–3350 for this reaction.