Some studies of benzenoid-quinonoid resonance. Part 2.—The effect of solvent polarity on the structure and properties of merocyanine dyes

Abstract

The SCF π-electron theory with bond length optimization, described in part 1, has been used to calculate the effects of solvent polarity on the structure and spectroscopic properties of a simple merocyanine dye. The calculations predict a minimum in energy and oscillator strength of the first absorption band over the range of solvent parameters used, but these extrema should not occur at the same solvent compositions. The measured u.-v. spectra can be interpreted from these results, and the n.m.r. chemical shifts, which change with solvent, can be correlated with calculated net atom charges.