Fluorescence characteristics of 2,6-diaryl-4-piperidones

The absorption and fluorescence emission spectra of several substituted piperidones have been reported. The shifts in the absorption and fluorescence emission maxima due to the nature and position of the substituent groups were studied. It is known that the carbonyl group attached directly to the heterocyclic ring undergoes Through Bond Interaction (TBI) with the amine moiety. However, the presence of the substituted phenyl groups is expected to modify the fluorescence quantum yield due to the π-electron mobility. Using Stokes' shifts, excited state dipole moments (μe ) are calculated for 2,6-diphenyl-4-piperidone and 3 methyl 2,6-diphenyl-4-piperidone. The ground state dipole moments (μg ) were determined at 2 MHz, using heterodyne beat method. The changes in the ratio of μe/μg are discussed in the light of the structural stability of the substituted piperidones.