Effects of solvent and solute polarizability on the reorganization energy of electron transfer

We report Monte Carlo simulations of the effect of solute and solvent polarizability on the solvent reorganization energy of intramolecular electron transfer. In the first set of simulations, the polarizability of the solvent is varied at constant permanent dipole of the solvent molecules (high-frequency dielectric constants is in the range 1-2.5). The reorganization energy is calculated on the solvent configurations around a nonpolar solute (charge separation transition) and around a dipolar solute (charge recombination transition). In both cases, the variation of the solvent reorganization energy does not exceed 30%, a change much smaller than predicted by dielectric continuum models. In the second set of simulations, the solute polarizability in the charge-separated state was varied while keeping the initial state for charge separation at zero dipole moment and polarizability. The gap between the charge-separation and charge recombination reorganization energies widens substantially with increasing difference in the polarizability of the initial and final charge-transfer states. Both the effect of solute and solvent polarizability can be accurately described by analytical theories of solvent reorganization.