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.