Solvatochromism and preferential solvation of 1,4-dihydroxy-2,3-dimethyl-9,10-anthraquinone by UV–vis absorption and laser-induced fluorescence measurements

Abstract

Solvation characteristics of 1,4-dihydroxy-2,3-dimethyl-9,10-anthraquinone ( 1) in pure and binary solvent mixtures have been studied by UV–vis absorption spectroscopy and laser-induced fluorescence techniques. The binary solvent mixtures used as CCl 4 (tetrachloromethane)–DMF ( N, N-dimethylformamide), AN (acetonitrile)–DMSO (dimethylsulfoxide), CHCl 3 (chloroform)–DMSO, CHCl 3–MeOH (methanol), and MeOH–DMSO. The longest wavelength band of 1 has been studied in pure solvents as well as in binary solvent mixtures as a function of the bulk mole fraction. The Vis absorption band maxima show an unusual blue shift with increasing solvent polarity. The emission maxima of 1 show changes with varying the pure solvents and the composition in the case of binary solvent mixtures. Non-ideal solvation characteristics are observed in all binary solvent mixtures. It has been observed that the quantity [ ν ˜ 12 − ( X 1 ν ˜ 1 + X 2 ν ˜ 2 ) ] serves as a measure of the extent of preferential solvation, where ν ˜ and X are the position of band maximum in wavenumbers (cm −1) and the bulk mole fraction values, respectively. The preferential solvation parameters local mole fraction ( X 2 L ), solvation index ( δ s2), and exchange constant ( k 12) are evaluated.