APPLICATION OF THE CONFIGURATION-INTERACTION METHOD FOR QUANTUM-CHEMICAL CALCULATIONS OF SOLVATION EFFECTS

A configuration interaction (CI) version of the self-consistent reaction field theory is formulated in order to treat solvation problems in the framework of the continuum medium model. The problem of an optimal selection of the truncated configurational basis set for large molecular solutes is considered. For the description of solvation effects most important arc found to be the charge transfer electronic configurations which can be treated on the background of incompletely convergent total CI expansions because the contributions of local excitations are mutually canceled with a high accuracy under the conditions of a solvent effect calculation. The free energy changes in two reacting chemical systems are studied by this technique. The first one, the disproportionation reaction of substituted pyridinyl radicals yielding the respective cation and anion, is fairly well described in aprotic solvents, such as dimethylformamide. In other solvents (acetonitrile, H2O) strong specific solvation effects are revealed. The second example treats the energetics of the electron transfer in the excimer complex of excited pyrene singlet with dimethylphthalate. The perspectives of application of the CI methodology in the theory of solvation are discussed.