INVESTIGATION OF CARBAZOLE DERIVATIVES AND THEIR VAN-DER-WAALS COMPLEXES IN THE JET BY LASER-INDUCED FLUORESCENCE SPECTROSCOPY

Laser-induced fluorescence (LIF) spectra of jet-cooled carbazole, N-et hylcarbazole (EC), N-phenylcarbazole (PC), N-(4-cyanophenyl)carbazole (CPC) and N-anthrylcarbazole (AC) are presented and analysed. Perpendi cularity is proposed in the ground state geometry of PC and CPC, in co ntrast with the twisted angle in AC, and these ground state configurat ions of PC and CPC are preserved on electronic excitation, but not in AC. The electron distribution on the nitrogen atom in the carbazole mo iety is used as a basis to explain the differences in the spectral shi fts of the substituted carbazoles with respect to the bare carbazole c hromophore. PC complexes with argon atoms, non-polar and polar molecul es were investigated and compared with those of CPC and EC. Intermolec ular vibrational modes were observed in several PC complexes. The simi larity of the spectral shifts of PC complexes to those of CPC indicate s that they have very similar properties under jet conditions, in cont rast with observations in acetonitrile solution. No twisted intramolec ular charge transfer (TICT) took place for PC and CPC, where the perpe ndicularity is preserved on electronic excitation, which is in agreeme nt with the fact that TICT fluorescence emission was not observed in t he jet for CPC-acetonitrile complexes.