The Ratio of Quantum Yields of Fluorescence and Phosphorescence of Some N-Heterocyclic Compounds in Solutions at 77 K
Measurements were made of the ratio of quantum yields of fluorescence and phosphorescence (ɳf/ ɳp), the position of the 0–0 transition of the fluorescent and phosphorescent spectrum and the lifetime of phosphorescence in the molecules (free base) and cations (conjugate acid) of seven nitrogen containing heterocyclic compounds (5,6- and 7,8-henzoquinoline, 2-, 4- 6-, 7- and 8-methylquinoline) dissolved in n-hexane and ethanol at different concentrations at 77 K. The n-hexane and ethanol solutions of henzoquinoline have a ɳf/ɳp between 0.5 and 6; the cation, between 2.5 and 17. In pure hydrocarbon solvents at 77 K, methylquinolines show only phosphorescence (ɳf/ɳp < 0.01). In alcohol solvents at 77 K there occurs both fluorescence and phosphorescence (in ethanol ɳf/ɳp = 0.8 to 4.5).
KeywordsQuantum Yield Luminescence Spectrum Free Base Electronic Ground State Conjugate Acid
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