SOLVATOCHROMIC STUDIES ON REVERSED-PHASE LIQUID-CHROMATOGRAPHIC PHASES .1. SYNTHESIS AND SOLVENT EFFECTS OF A NEW MEROCYANINE DYE, CHLORO-2-[2-(1-METHYL-4-PYRIDINIO)VINYL]-PHENOLATE

A new merocyanine dye with a stilbazolium betaine structure has been s ynthesized and characterized by its UV-visible absorption. This compou nd, ichloro-2-[2-(1-methyl-4-pyridinio)vinyl]phenolate (DCMPVP), has a n absorption wavelength shift of 166 nm across 13 polar solvents, with peak positions ranging from 454.8 nm in water to 620.9 nm in ethyl ac etate, Correlation of the absorption energy of DCMPVP by least-squares fitting with the Kamlet-Taft dipolarity/polarizability, pi, and hydr ogen-bond-donating ability, alpha, yields a regression equation of Del ta E(max) (kcal/mol) = (9.0 +/- 1.1)pi + (10.1 +/- 0.5)alpha + (41.8 +/- 0.8), The pK(a) value of 6.26 is lower than those for other non-ch lorinated derivatives of stilbazolium dyes. This dye is a suitable ind icator for a variety of neutral and weak acidic media, including chrom atographic phases.