SOLVATOCHROMISM OF A TYPICAL MEROCYANINE DYE - FURTHER INVESTIGATIONS

This paper reports on the solvatochromism of a new typical merocyanine dye of stilbazolium betaine. Solvatochromic absorption and fluorescence energy shifts of 2-(4-hydroxystyryl)-1-methylpyridinium betaine {4-[2-(1-methyl-2-pyridinio)vinyl]phenolate), M, in 10 polar solvents are 15.0 and 6.0 kcal mol-1 (1 cal = 4.184), respectively. Absorption and fluorescence energies vary rectilinearly with Dimroth-Reichardt's empirical solvent polarity parameter, E(T)(30). Depending on the nature of solvent, the non-specific dipole-dipole interactions and specific hydrogen bonding are described on the basis of the least-squares fitting of the absorption and fluorescence energies to multilinear equations with Taft's pi* (solvent polarity) and alpha (hydrogen bond donor ability) parameters.