Spectroscopic studies of hydrophobic association of merocyanine dyes in cationic and anionic micelles

Merocyanine dyes exhibit interesting changes in absorption spectra with changes in solvent polarity. For example solutions of 1-methyl-4- (oxocyclohexadienylidene) ethylidene -1,4-dihydropyridine (MOED) are yellow, red, violet, or blue, in water, ethanol, acetone or pyridine respectively.1 More striking effects are observed when aqueous solutions are diluted with various proportions of the organic co-solvents such as pyridine. The color varies across the whole spectrum from golden yellow to blue.These characteristic properties of merocyanine dyes in various organic solvents have been extensively studied and correlations between [see PDF file for formula]max and solvent polarity have been determined. In this work the visible absorption have been determined. In this work the visible absorption properties of merocyanine dyes were studied in cationic and anionic surfactants in order to investigate the behaviour of these dyes in micellar system and to use their electronic spectra as probes of the micellar environment. Since the description of the literature and discussion of the experimental results will involve certain terms and concepts from surfactant chemistry, it is necessary to introduce the subject