Solvatochromism in the aromatic ketone benzo[b]fluorenone

Spectroscopic studies on benzo[b]fluorenone (BF) solvatochromism in several pure aprotic and alcoholic solvents are reported. Fluorescence quenching was not observed in pure ethanol, unlike the related aromatic ketone 9-fluorenone (9-FL). Results in the more strongly hydrogen bonding alcohol 2,2,2-trifluoroethanol (TFE) demonstrate fluorescence quenching, a red shift in emission, and indicate the presence of at least two ground state species in BF–TFE solutions. These results suggest BF has less ability to hydrogen bond with ethanol than 9-FL; this appears to relate to the difference in aromaticity between these two compounds.