VB resonance theory in solution. II. I2-[larger_closed_square]I+I- in acetonitrile.

The electronic structure in solution theory developed in the preceding article is applied to the molecular ion I2-[larger_closed_square]I+I- reaction system in the dipolar, aprotic solvent acetonitrile, which illustrates in detail the implementation of the general theory. A two-dimensional, nonequilibrium free energy surface in the nuclear separation and a difference solvent coordinate is constructed via solution of a nonequilibrium solvation, nonlinear Schrödinger equation. The reduction to a single important solvent coordinate—from a manifold of three solvent coordinates—is motivated by an examination of the equilibrium solvation path and an analysis of the harmonic nonequilibrium fluctuations around this path. The evolving solute electronic structure over the basis of two orthogonal valence bond diabatic states—approximately corresponding to -II and II-—is discussed. Comparisons with the limiting Born–Oppenheimer and self-consistent approximations for the solvent electronic polarization are made, with the former proving to be more accurate, and the latter giving a qualitatively inaccurate picture of the electronic structure near the equilibrium geometry. The validity of the dielectric image approximation is also examined. The polarization force associated with the charge shift in the reaction system and important for the system vibrational relaxation is also calculated. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]