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'Fluorescence Quantum Yields' in keywords Facet   Publication Year 1976  [X]
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1Author    H. Strähle, W. Seitz, H. GüstenRequires cookie*
 Title    Der Substituenteneinfluß auf die Fluoreszenz des 1.3-Diphenyl-2-pyrazolins* Substituent Effects on the Fluorescence of l,3-Diphenyl-2-pyrazoline  
 Abstract    The electronic absorption spectra, absolute fluorescence spectra and fluorescence quantum yields as well as the fluorescence decay times of nine l,3-diphenyl-2-pyrazolines substituted in the para-position of the 1-phenyl ring and of 19 substituted in the para-position of the 3-phenyl ring were measured in degassed benzene at room temperature. The fluorescence quantum yields are about 0.90 with the exception of the NO2-and J-substituted l,3-diphenyl-2-pyrazolines. The fluorescence decay time ranges from 2 to 4 nsec. The natural fluorescence lifetimes determined experimentally agree well with those calculated from the absorption spectra according to STRICKLER and BERG. A plot of the Hammett r7p-values versus the energies of the absolute fluorescence maxima of the p-substituted 1-and 3-phenyl ring of the 2-pyrazoline system shows a statistically significant linear correlation with moderate precision. The linearity between ground state substituent constants and fluorescence energies reveals that the relative importance of the inductive and the resonance effects of the substituents remains constant during the transition from the ground state to the relaxed excited singlet state. In the excited singlet state of 1,3-diphenyl-2-pyrazoline the p-substituents provide more room for a larger charge displace-ment in the intramolecular charge-transfer. The structural bands in the fluorescence spectra resulting from strong electron accepting substituents in the para-position of the 1-phenyl ring are considered as the result of the ring breathing vibration due to a local excitation of the 1-phenyl ring. 
  Reference    (Z. Naturforsch. 31b, 1248—1255 [1976]; eingegangen am 20. April 1976) 
  Published    1976 
  Keywords    Fluorescence Quantum Yield, Fluorescence Decay Time, l, 3-Diphenyl-2-pyrazolines, Hammett crp-values, Fluorescence Energies 
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 TEI-XML for    default:Reihe_B/31/ZNB-1976-31b-1248.pdf 
 Identifier    ZNB-1976-31b-1248 
 Volume    31