INTERMOLECULAR INTERACTIONS OF MEROCYANINE DYES STUDIED BY VISIBLE ABSORPTION, RESONANCE RAMAN AND INFRARED SPECTROSCOPIES

Intermolecular interactions of merocyanine dyes, thyl-ethylidene]-3-et hyl-2-thioxo-3-thiazolidinone (Et(Me)MD) and ene)-ethylidene]-3-ethyl- 2-thioxo-4-thiazolidinone (EtMD), in various solvents were studied. Th e spectra of the dyes in an argon matrix-isolated state and in a thin- film state were also measured. In addition to the well-known solvent e ffects appearing in visible absorption spectra, the solvent dependence of resonance Raman and infrared absorption spectra was examined. The visible absorption bands shift to the longer wavelength region as the polarity of the solvent increases, while the C=O and C=C stretching ba nds shift to the lower frequency region. Correlation between the visib le absorption maximum and the C=C stretching vibrational frequency was found, for the first time. The solvent effects on the spectra are exp lained in terms of intermolecular interactions between merocyanine dye s and solvent molecules. (C) 1997 Elsevier Science B.V.