FLUORESCENCE AND DOLE BURNING DEPLETION SPECTRA OF JET-COOLED 1-(1-ANTHRYL)-3-(M-(N,N-DIMETHYLAMINO)PHENYL)PROPANES AND 1-(9-ANTHRYL)-3-(M-(N,N-DIMETHYLAMINO)PHENYL)PROPANES - MULTICONFORMATIONS AND EXCIPLEX FORMATION

Fluorescence excitation and hole burning depletion spectra of jet-cooled bichromophoric compounds, 1-(9- and 1-anthryl)-3-(m-(N,N-dimethylamino)phenyl)propanes (9-An-m-DMA and 1-An-m-DMA), indicate that two isomeric conformations of these compounds are involved in the ground state. Two distinct conformers (9a and 9b) of 9-An-m-DMA exhibit roughly equal intensity of excitation spectra, while one conformer is major (1a) and another is minor (1b) in 1-An-m-DMA. These ground-state conformers exhibit remarkably different excess vibrational energy (Delta E) dependence of the intramolecular charge transfer in the singlet excited state: the Delta E dependence of the exciplex fluorescence and decay times are considerably different between the two conformations. The facts seem attributable to the torsional conformation of the m-(N,N-dimethylamino)phenyl moiety concerning the trimethylene (An-C-1-C-2-C-3-m-DMA) of these compounds in the ground state, from which the geometrical transformations take place to the favorable conformers' for the intramolecular charge transfer.