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

A configuration interaction (CI) version of the self-consistent reacti on 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 molecu lar solutes is considered. For the description of solvation effects mo st important arc found to be the charge transfer electronic configurat ions which can be treated on the background of incompletely convergent total CI expansions because the contributions of local excitations ar e mutually canceled with a high accuracy under the conditions of a sol vent effect calculation. The free energy changes in two reacting chemi cal systems are studied by this technique. The first one, the dispropo rtionation reaction of substituted pyridinyl radicals yielding the res pective cation and anion, is fairly well described in aprotic solvents , such as dimethylformamide. In other solvents (acetonitrile, H2O) str ong specific solvation effects are revealed. The second example treats the energetics of the electron transfer in the excimer complex of exc ited pyrene singlet with dimethylphthalate. The perspectives of applic ation of the CI methodology in the theory of solvation are discussed.