Photophysics of 2,6-bis(4′-diethylaminobenzylidene)cyclopentanone in a polymer matrix containing carboxyl groups

The photophysics of a photosensitizer, 2,6-bis(4'-diethylaminobenzylidene)cyclo (DBC) in solvents and polymer matrices containing carboxyl groups is reported. In acetic acid, the fluorescence spectrum of DEC showed two bands of fluorescence with individual lifetimes. Two emitting species were also observed in polymer matrices containing carboxyl groups. The shorter and longer wavelength fluorescence bands are assigned to the emission from DBCs hydrogen bonded (HB) and protonated (PR) with the carbonyl group, respectively. As the concentration of DEC increased, the ratio of PR fluorescence intensity to HE fluorescence intensity increased, and the lifetime of HE fluorescence decreased. The energy level of HE in the excited state is dispersive depending on the magnitude of hydrogen bonding, resulting in the gradual red-shift of fluorescence spectra with the increase of carboxyl content and DEC concentration. Efficient energy transfer was observed from the HE to PR-DEC which acts as an energy trap in the polymer matrix containing carboxyl groups. (C) 2000 Elsevier Science S.A. All rights reserved.