Molecular dynamics simulations of reorganization energy for electron transfer reactions

The reorganization energies of electron transfer reactions were calculated for radical cations and anions of a complex organic molecule in water. The charge distributions in the initial and final system states were determined at the level of the AM1 semiempirical method. Molecular dynamics simulations were performed using standard Lennard-Jones parameters that were not adjusted to reproduce the energy characteristics of solvation. The role of the solvent was played by the SPC water model. The very strong nonlinear effect observed earlier for a model two-pole system was found to decrease to a realistic value of 4-5 kcal/mol for the real chemical solute. The temperature dependence of the reorganization energy obtained at the molecular level of calculations was in qualitative agreement with experiment.