Quantum-Chemical Study of Relation of Spectral and Luminescent Properties of Positively Solvatochromic Malononitrile-Based Merocyanine Dyes with Their Structure

摘要

The electronic structure, the spectra, and the efficiency of photophysical processes of energy deactivation are calculated by a semiempirical method for three positively solvatochromic merocyanine dyes with different polymethine chain lengths. The electronic structure and spectra calculated by different modifications of the INDO method at different molecular geometries are compared, and the optimum geometry of the isolated molecule is chosen. The absorption spectra of dyes are interpreted, including the short-wavelength bands related to transitions to highest excited states. The possibility of a specific electrophilic solvation of these compounds in the ground and fluorescent states, as well as the contribution of specific intermolecular interactions to the total interaction with the medium, is estimated. The role played by the trans--cis isomerization of isolated merocyanine molecules in the deactivation of their excited states is considered.