Preferential solvation of 1,4-dimethoxy-2,3-dimethyl-9,10-anthraquinone--a spectrophotometric and fluorometric study

Electronic absorption and fluorescence emission spectra of DMDMAQ (1,4-dimethoxy-2,3-dimethyl-9,10-anthraquinone) have been studied as a function of solvent composition in some binary mixtures and in different neat solvents. The binary mixtures consist CCl(4) (Carbon tetrachloride)-DMSO (Dimethylsulfoxide), EtOH (Ethanol)-DMSO, and CCl(4)-EtOH combination of single solvents. The wavelength maxima of the absorption band for DMDMAQ are quite solvent sensitive in aprotic solvents. But, in protic solvent, there is no marked shift in absorption and emission maximum which shows the absence of specific interaction. Excited state shows increasing shift with increasing solvent polarity compared to ground state. The ratio of dipole moment in the excited state to that in the ground state was calculated. Different criteria were considered to analyse preferential solvation characteristics in different binary mixtures, viz., local mole fraction (X(2)(L)), solvation index (delta(S2)) and exchange constant (K(12)).