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1991 (1)
1988 (1)
1976 (1)
1Author    Sn Bakalova, L. Biczók, T. BércesRequires cookie*
 Title    Photophysical and Photochemical Properties of 2,3-Dihydro-4(l H)- quinolinones. Part II. Rates and Mechanism of Primary Processes  
 Abstract    Fluorescence quantum yields, singlet lifetimes and triplet yields for 2-methyl-2,3-dihydro-4(1 H)-quinolinone and N -m ethyl-2,3-dihydro-4(l H)-quinolinone were determined as a func­ tion o f temperature. In non-polar solvents, an efficient non-radiative process identified as an indirect singlet —* • triplet transition occurring through S2(n,jr*) was found to depopulate the lowest S 1(7t,7E*) state. In polar solvents, direct singlet —> triplet intersystem crossing appears to dominate. Photochemical dehydrogenation produced the corresponding 4(1 H)-quinolinone with a yield o f few times 10"2. This was shown to be the only traceable reaction route. 
  Reference    Z. Naturforsch. 46c, 549 (1991); received March 16/A pril4 1991 
  Published    1991 
  Keywords    Dihydroquinolinones, Triplet Yields, Fluorescence Quantum Yields, Photochemical D ehy­ drogenation, Singlet Lifetimes 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0549.pdf 
 Identifier    ZNC-1991-46c-0549 
 Volume    46 
2Author    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 
3Author    Dieter Oelkrug, Klaus Rempfer, Ellen Prass, Herbert MeierRequires cookie*
 Title    F Investigations on the Fluorescence of Distyrylbenzenes  
 Abstract    lu o re s z e n z -U n te rs u c h u n g e n a n D is ty ry lb e n z o le n The absorption and fluorescence of three isomeric distyrylbenzenes are investigated as function of temperature. From the fluorescence decay times and fluorescence quantum yields two classes of oligostyrylarenes can be distinguished. A decisive criterion for this classification is, whether the first excited singlet state Sj belongs to an allowed or forbidden transition S0— >Sj. 
  Reference    Z. Naturforsch. 43a, 583—590 (1988); eingegangen am 25. Februar 1988 
  Published    1988 
  Keywords    o-, m-, p-Distyrylbenzenfes, Fluorescence Lifetimes, Fluorescence Quantum Yields, Photoreactivity 
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 TEI-XML for    default:Reihe_A/43/ZNA-1988-43a-0583.pdf 
 Identifier    ZNA-1988-43a-0583 
 Volume    43