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

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 [nu (12)-(X(1)nu (1)+X(2)nu (2))] serves as a measure of the extent of preferential solvation, where nu 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 (delta(s2)), and exchange constant (k(12)) are evaluated.