SOLVENT EFFECTS ON THE FLUORESCENCE OF THIOXANTHONE - INTERPRETATION BY SOLVATOCHROMIC PARAMETERS PI, ALPHA AND BETA

Solvent effects on thioxanthone (TX) fluorescence were investigated in terms of variation versus E(T)(30) and Kamlet, Aboud and Taft's pi*, alpha, beta solvatochromic parameters. The solvatochromic equation describing the effects of solvent polarity/dipolarizability (pi*), solvent hydrogen bond donor acidity (alpha) on lambda-f and PHI-f works quite satisfactorily except for water, trifluoroethanol and hexafluoroisopropanol. However the consideration of two distinct rate constants for internal conversion leads to a good correlation of PHI-f with pi*, alpha over the total range of solvent polarity, from hexane to hexafluoro-isopropanol.