The spectral shifts for the first electronic transition of the benzophenone anion radical (Bp(-)) caused by solvent geometrical reorientation have been investigated by means of semiempirical PM3-MO and classical trajectory calculations. A methanol. molecule (MeOH) and the complex composed of Bp(-) and a methanol molecule (Bp(-)... MeOH complex) were chosen as a solvent molecule and a solvated reaction system, respectively. The classical trajectories of the Bp(-)... MeOH complex following vertical electron attachment to the neutral system have been calculated by the Runge-Kutta method on the PM3 multidimensional potential energy surfaces. The calculations suggested that the solvation structure of the neutral Bp ... MeOH complex is largely changed by accepting an excess electron : the binding site of the hydrogen bond of MeOH is changed from the nonbonding to the pi* orbitals in carbonyl C=O. This structural change occurred as a unimolecule within the Bp(-)... MeOH complex. With the change of the solvation structures, the absorption spectra of Bp(-) were gradually blue-shifted as a function of reaction time. The solvation mechanism was discussed on the basis of the theoretical results.