Solvent effect on vertical electronic transitions by the polarizable continuum model

A recent extension of the polarizable continuum solvation model (PCM) to excited electronic states is applied to the study of solvent effects on electronic transitions, accounting for both electrostatic and nonelectrostatic solute-solvent interactions. A general formalism for nonequilibrium electrostatic solvation is developed, applicable to all PCM versions, and a recent procedure for the quantum-mechanical computation of dispersion and repulsion solute-solvent interactions is implemented and used for the first time in this context. The procedure is applied to the study of the n -->pi* transition of acetone in aqueous and nonaqueous solvents: nonequilibrium effects are very important in polar environments; also, the inclusion of dispersion and repulsion is mandatory to obtain the correct trend of the solvatochromic shifts. The effect of adding some explicit solvent molecules is also analyzed. (C) 2000 American Institute of Physics. [S0021-9606(00)53205-X].