Molecular orbital modeling of solvent effects on excited states of organic molecules

The excited states of organic molecules are considerably affected in most cases by their environment. A simple example of this phenomenon is the blue-shift effect shown by n pi* bands upon increasing the polarity of the solvent. The purpose of the current paper is to simulate the solvent effect on the excited states of two organic systems: furfural and 1-(N-methyl pyridyl) 2-(p-quinoyl) ethylene (also known as stilbazonium), by creating a set of clusters solute-(solvent)(n) compounded by distributing solvent molecules around the solute at random. These clusters were subsequently optimized using the semiempirical PM3 method to explore such multiple minima hypersurface of the supermolecular system. The minimal energy sets of each system were selected for the calculation of excited states by the CNDOL method combined with a procedure for singly excited configuration interaction. (C) 1998 Elsevier Science B.V. All rights reserved.