SOLVENT DEPENDENCE OF PYRANINE FLUORESCENCE AND UV-VISIBLE ABSORPTION-SPECTRA

Fluorescence and UV-visible absorption spectra of HPTS (8-hydroxy-1,3, 6-pyrenetrisulphonic acid trisodium salt, pyranine) were measured in a variety of solvents. Fluorescence maxima (in kcal mol(-1)) can be cor related with the Kosower Z parameter (r = 0.901), the Dimroth-Reichard t E-T(30) parameter (r = 0.900) and the Winstein Y parameter (r = 0.91 6) using one-parameter fits. Good correlations (r = 0.98) were obtaine d for HPTS fluorescence in ethanol-water mixtures using the Y, Y-OTs a nd Z parameters. Fluorescence maxima of HPTS in aqueous sulphuric acid solutions gave an excellent correlation with Y-OTs(r = 0.991). Multi- parameter correlations, indicating the significance of specific solven t interactions, were also studied. In addition, fluorescence maxima co rrelate well with maximum/minimum ratios obtained from UV-visible abso rption experiments. Results can be applied in the use of HPTS as a mol ecular probe of solvent environments and for extension of the Y-OTs sc ale in acidic solutions. HPTS is a unique molecular probe, not only be cause of its photoacidic properties and its widespread use as a pH-sen sitive biosensor, but also because of its relative stability in acidic environments. (C) 1998 John Wiley & Sons, Ltd.