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'Phototautomerism' in keywords
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1980 (1)
1978 (2)
1Author    Walter FabianRequires cookie*
 Title    Semiempirische SCF-Rechnungen an den angeregten Zuständen von Hydroxy Cumarinen Semiempirical SCF-Calculations of the Excited States of Hydroxycoumarines  
 Abstract    Semiempirical SCF-calculations show that the fluorescence bands of 7-hydroxycoumarin at 1.87 • 10 4 -1,92 • 10 4 cm -1 are most probably due to a phototautomeric form. A topo-logical rule is evaluated to explain the dependence of the fluorescence intensity upon the position of the hydroxyl group in the various isomeric hydroxycoumarines. 
  Reference    Z. Naturforsch. 33b, 628—631 (1978); eingegangen am 16. März 1978 
  Published    1978 
  Keywords    Hydroxycoumarines, Fluorescence, Phototautomerism, PPP-Calculations 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0628.pdf 
 Identifier    ZNB-1978-33b-0628 
 Volume    33 
2Author    Walter FabianRequires cookie*
 Title    W. Fabian * Eigenschaften von Molekülen in angeregten Zuständen 348 Properties of Molecules in Excited States  
 Abstract    Using bisisochinolin derivatives and related compounds it is shown that information about the fluorescent state can be obtained by comparison of experimental fluorescence data and calculated energies of the Si-state assuming various geometries. 
  Reference    Z. Naturforsch. 33b, 332—335 (1978); eingegangen am 7. September 1977 
  Published    1978 
  Keywords    Excited States, Fluorescence, PPP-Calculations, Phototautomerism, Bisisochinolin Deri-vatives 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0332.pdf 
 Identifier    ZNB-1978-33b-0332 
 Volume    33 
3Author    Jacek Wierzchowski, M. Arian Szczęśniak, D. Avid ShugarRequires cookie*
 Title    Fluorescence Emission Properties of the Cation of 4-Aminopyrazole(3,4-d) pyrimidine, an Adenine Analogue: Evidence for Phototautomerism  
 Abstract    A study has been made of the emission spectra at room temperature, in aqueous and alcoholic media, of 4-aminopyrazolo(3,4-d)pyrimidine (APP) and some o f its methylated derivatives. The cationic forms APPH+, N 2-methyl-APPH+ and N 7-methyl-APPH+ exhibit intense fluorescence un­ der these conditions, the first two exhibiting excitation spectra which differ from the absorption spectra, pointing to the existence o f a tautomeric equilibrium in the ground state. From the shape o f the excitation spectra, and comparisons with methylated analogues in fixed tautomeric forms, it follows that the emission of APPH+ originates exclusively from the species N (2)-H ,N (7)-H +, the other forms being non-fluorescent. The proportion o f the emitting species, calculated from the ex­ citation wavelength dependence o f the quantum yield, is in good agreement with data for the ground state. The emission spectrum of APPH+ in aqueous medium consists o f two bands with /lmax 360 nm and 430 nm, which exhibit identical excitation spectra, but are quenched to different extents by H30 +. The 430 nm emission band is absent in alcoholic media. A similar behaviour is exhibited by N 7-methyl-APPH+, whereas the neutral form o f this analogue exhibits only the 430 nm band. These results indicate that the long wavelength emission band o f APPH+ originates from the rare tautomeric species N(7)-H formed in the excited state by photodissociation o f the N(2)-H proton from the species N(2)-H ,N(7)-H+. This is further confirmed by results obtained with the aid o f the basicity method, as well as by salt efects in non-aqueous media. Consideration is given to the possibility of such processes occurring in other analogues o f nucleic acid derivatives. 
  Reference    Z. Naturforsch. 35c, 878—8 (1980); received July 28 1980 
  Published    1980 
  Keywords    Fluorescence, Phototautomerism, Pyrazolo(3, 4-d)pyrimidines, Adenine Analogues, Protonation Sites 
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 TEI-XML for    default:Reihe_C/35/ZNC-1980-35c-0878.pdf 
 Identifier    ZNC-1980-35c-0878 
 Volume    35