STRUCTURE AND DYNAMICS OF SOLVENT LANDSCAPES IN CHARGE-TRANSFER REACTIONS

The dynamics of solvent polarization plays a major role in the control of charge-transfer reactions. Although in principle solvent dynamics looks extremely complicated, the success of Marcus theory describing t he solvent influence via a single collective quadratic polarization co ordinate has been remarkable. Onuchic and Wolynes have recently propos ed (J. Chem. Phys. 1993, 98 (3), 2218) a simple solvent model demonstr ating how a many-dimensional complex system composed of several dipole moments (representing solvent molecules or polar groups in proteins) can be reduced under the appropriate limits into the Marcus model. Thi s work presents a dynamical study of the same model. It is shown that an effective potential, obtained by a thermodynamic approach, provides an appropriate dynamical description. At high temperatures, the syste m exhibits effective diffusive one-dimensional dynamics in this effect ive potential, where the Born-Marcus limit is recovered. At low temper atures, a glassy phase emerges with a slow non-self-averaging dynamics . At intermediate temperatures, we will discuss the concept of equival ent diffusion paths and polarization-dependent effects. The equivalent paths are necessary to seduce the problem into the Marcus picture. A discussion of how these different regimes affect the rate of charge tr ansfer is presented.