MULTIPLE EMITTING SPECIES AND COMPETING INTRAMOLECULAR FLUORESCENCE QUENCHING IN 9,9'-DIANTHRYLMETHANOL AND MODEL COMPOUNDS

In addition to the anthracene-type emission, 9,9'-dianthrylmethanol (A l(OH)A) shows a structureless long-wavelength fluorescence band, which undergoes a red-shift as well as an increase of its relative intensit y with increasing solvent polarity. A parallel intramolecular fluoresc ence quenching process is investigated by the study of two reference c ompounds, 9-hydroxymethylanthracene and 9-ethoxymethylanthracene. In s pite of the lack of the additional fluorescence band in this case, the quenching still persists. It might be caused by the formation of an i ntramolecular nonemissive exciplex but it cannot be the source for the observed additional red-shifted structureless emission band of the bi chromophoric compound. The latter has been accounted for by a polar ex cited state product resulting from a charge separation process.