On the cavity model for solvent shifts of excited states - a critical appraisal

We present model investigations on the solvatochromic shift of several organic molecules. The excitation energies are calculated within the INDO/S-CI approach; solvent effects are taken into account self-consistently via a cavity model. A cavity of arbitrary shape is admitted, the corresponding surface charge density being represented by a finite number of point charges. Applying the model at different levels of sophistication, we investigate the effect of the point density on the accuracy of the results and we suggest a method of monitoring their quality. The evaluation of the electronic excitation energies in different solvents demonstrates the partial success of currently used electrostatic cavity methods for modeling solvatochromic shifts of electronic absorptions, but also their inherent deficiencies. Some strategies for improvement of purely electrostatic cavity models are discussed.