Effects of solvent polarity and hydrogen bonding on the fluorescence properties of trans-4-hydroxy-4′-nitrostilbenes

The excited singlet state properties of 4′-nitro- and 2′,4′-dinitro-substituted trans-4-hydroxystilbenes were studied in various solvents. The fluorescence quantum yield (Φf) of the former compound in solvents unable to form strong hydrogen bonds goes through a maximum as a function of the solvent polarity parameter E T N , reaching the highest value of 0.31 in butyronitrile. In contrast, a monotonous diminution of Φf and moderate changes were found in hydrogen bonding media. The addition of nitrogen-heterocyclic compounds leads to both dynamic and static fluorescence quenching due to excited-state proton transfer along the hydrogen bond. trans-2′,4′-Dinitro-4-hydroxystilbene emits only weak fluorescence in all solvents studied.