Solvatochromic and thermochromic effects in low-temperature rigid matrices

Abstract

The comparison of electronic of absorption and emission spectra of solute molecules between various liquid and sold media requires a knowledge of the solvatochromic shifts; If spectra taken at different temperatures are to be compared, the thermochromic shifts must be considered as well. There is a considerable body of empirical and theoretical knowledge in this field for solutes in liquid solvents, whereas little systematic work has been performed so far for the case of rigid matrices. In this paper some experimental observation are presented to relate the electronic transition energies of some solute molecules in liquid and solid environments at different temperatures; these observations are correlated with the macroscopic properties (dielectric constant, refractive index) of the medium, as well as with the glassy or crystalline structure of the matrix. Hydrogen bonding between the solute and the solvent is considered, in addition to the general dielectric interactions, and the anomalous behaviour of 1,4-dioxane as a liquid solvent or a rigid matrix is described.