FLUORESCENCE AND HOLE-BURNING DEPLETION SPECTRA OF JET-COOLED 4-(2',3'-DIMETHYLBUTENYLOXY)METHYL-1-CYANONAPHTHALENE - MULTICONFORMATIONS AND INTRAMOLECULAR EXCIPLEX FORMATION

Fluorescence excitation and hole burning depletion spectra of jet-cooled 4-(2',3'-dimethylbutenyloxy)methyl-1-cyanonaphthalene (CDMB-CNN) indicate that three types of chain conformations are involved in the ground state. These conformers were tentatively ascribed to trans, syn-gauche, and anti-gauche conformers concerning the C-1-O torsional conformation of the ether bonding in 4-DMB-CNN. One of them exhibits a considerable red shift of the 1-cyanonaphthyl (1-CNN) moiety fluorescence, which gradually shifts to the intramolecular exciplex fluorescence (lambda(max) 410-420 nm) with increasing excess vibrational energy. The second conformation shows a similar exciplex fluorescence depending on the excess vibrational energy, while the third one exhibits only 1-CNN moiety fluorescence within the excess vibrational energy <1100 cm(-1). However, no significant difference for the exciplex formation was observed between these conformations in the excess vibrational energy region >1100 cm(-1). These three types of ground-state conformations are tentatively discussed in terms of the torsional conformation of the C-1-O-C-2 chain in 4-DMB-CNN.