SUPERSONIC JET FLUORESCENCE OF BICHROMOPHORIC PYRENYL AND (N,N-DIMETHYLAMINO)PHENYL SYSTEMS - MULTICONFORMATIONS AND EXCIPLEX AND CT COMPLEX-FORMATION

Intramolecular exciplex and charge transfer (CT) complex fluorescence was investigated in the bichromophoric EDA systems of 1-(1-pyrenyl)-3-(p- and m-(N,N-dimethylamino)phenyl)propanes (Py-p-DMA and Py-m-DNA) in a supersonic free jet. The UV fluorescence excitation spectrum of jet-cooled Py-p-DMA exhibits vibrational structures similar to 1-alkylpyrene, while the visible fluorescence excitation spectrum of this compound has a very broad congested band. The dispersed fluorescence indicates that two types of groundstate conformers are involved; one of them exhibits the CT complex fluorescence, and another has an excess energy dependent exciplex fluorescence. In jet-cooled Py-m-DMA, two types of vibrational structure in the excitation spectra were observed. The excitation of these band series exhibit exciplex fluorescence with a remarkably different excess vibrational energy dependence. In addition to these exciplexes, the ground-state CT complex (probably a closed form) shows a CT fluorescence similar to the exciplex. The remarkably different features of the CT complex and exciplex formations are attributable to multiconformations of these bichrompophoric EDA systems in the ground state.