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Spectroscopy and decay dynamics of jet-cooled carbazole and N-ethylcarbazole and their homocyclic analogues

1986; Elsevier BV; Volume: 103; Issue: 1 Linguagem: Inglês

10.1016/0301-0104(86)85111-4

1873-4421

Andrew R. Auty, Anita C. Jones, D. Phillips,

Spectroscopy and Quantum Chemical Studies

Fluorescence excitation spectra of supersonic jet-cooled carbazole (C) and N-ethylcarbazole (EC) are reported together with those of their homocyclic analogues fluorene (F) and 9-ethylfluorene (EF). Fluorescence spectra of C and EC have been measured following excitation at energies up to ≈ 1300 cm−1 above the S1 origin and reveal that the onset of intramolecular vibrational redistribution occurs at around 900 cm−1 for both molecules, with redistribution being more extensive in the ethylated molecule. In C and EC, a number of modes are active in vibronically coupling the S1 and S2 states and Duschinsky mixing of these modes is apparent in the spectra. The fluorescence lifetimes of both C and EC show a slowly decreasing trend with increasing excitation energy in the range 0–1500 cm−1 excess vibrational energy; vibrational redistribution does not appear to enhance the rate of non-radiative decay in either molecule. Comparison of lifetime values under supersonic jet conditions with solution phase results indicates that solvation produces a considerable increase in the rate of intersystem crossing in these molecules.