SOLVATOCHROMIC SHIFTS - THE INFLUENCE OF THE MEDIUM ON THE ENERGY OF ELECTRONIC STATES

The displacement of electronic absorption and luminescence spectra (solvatochromic shifts) are related to the solute-medium interactions. These interactions can be non-specific (dielectric interactions) when they depend only on multiple and polarizability properties of the solute and solvent molecules; but specific associations such as hydrogen bonding can also be important. A number of examples of solvatochromic shifts are shown and discussed according to the various solute-medium interactions. The properties of solvent mixtures and those of rigid media are considered, as well as the "thermochromic shifts" which result from the change in the temperature of the medium. The use of solvatochromic shifts for the determination of the dipole moment and of the polarizability of electronically excited molecules has been important for an understanding of electron distribution changes in such states; examples of such determinations are given, together with references to the original literature. In the final section some limitations of the theories of solvent shifts and possible improvements are discussed. © 1990.