SOLVENT POLARITY INDICATORS - FLEXIBLE STYRYLPYRIDINIUM AND QUINOLINIUM FLUORESCENCE PROBES FOR MEDIUM FREE-VOLUME

Fluorescence properties are studied for four structurally related flex ible styrylpyridinium and quinolinium dyes of electron donor-acceptor type in glycerol at different temperatures. The response of the fluore scence quantum yield (phi(f)) to viscosity-temperature changes (eta(T) function) is a sensitive function of dye structure. Probe rotational relaxation dynamics are accurately described in terms of the free-volu me hypothesis. An intriguing gauge of the interplay between average me dium microviscosity/free-volume and some molecular properties such as rotor size and flexibility is developed for potential analytical appli cation as fluorescence probes for medium viscosity. (C) 1997 Elsevier Science B.V.