Solvent effects on electronic transitions of fluorenone and 4-hydroxyfluorenone

The solvation characteristics of the ground and excited states of fluorenone and 4-hydroxyfluorenone were investigated in neat and binary solvent mixtures. The spectral shifts are correlated by the Kamlet-Taft parameters (π*, β, and α). Multiple linear regression analysis indicates that both non-specific dipolar interaction and specific hydrogen-bonding interaction play an important role in the position of the absorption and fluorescence maxima in neat solvents. The behavior of the fluorenone and 4-hydroxyfluorenone in methylcyclohexane-tetrahydrofuran and methylcyclohexane-ethanol solvent mixtures has been explained in terms of preferential solvation. Index of preferential solvation has been calculated as a function of solvent composition. These results along with our previous studies [M. Józefowicz, J.R. Heldt, Chem. Phys. 294 (2003) 105] indicate that strong non-linear dependence of the solvatochromic shifts on the mole fraction of ethanol in methylcyclohexane-ethanol mixtures for molecules under study is attributed to formation of hydrogen-bond between solute and solvent in addition to preferential solvation.