Theoretical and Experimental Chemistry

, Volume 6, Issue 1, pp 28–33 | Cite as

Electronic aspects of the photodimerization of pyrimidine bases and their derivatives

  • Yu. A. Kruglyak
  • V. I. Danilov
  • V. A. Kuprievich
  • V. V. Ogloblin
Article

Abstract

Results of calculations for the lower excited triplet and singlet states of pyrimidine bases and a number of their derivatives, calculated by the self-consistent field (SCF) method for open shells and by the configuration interaction (CI) method for self-consistent orbitals, are presented. It is shown that excitation to the T1 and S1 states primarily affects the C5—C6 bond while triplet excitation is almost completely localized on this bond. This leads to exceptionally pronounced weakening of the C5—C6 bond in the T1 state. All other conditions being equal, the conditions in the T1 state are more favorable for the dimerization of the bases than in the S1 state. A correlation between the degree of localization of the triplet excitation at the C5—C6 bond and the ease of photodimerization has been established. The experimental facts associated with the formation of thymine free radicals in DNA are explained.

Keywords

Free Radical Pyrimidine Experimental Fact Thymine Singlet State 

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Copyright information

© Consultants Bureau 1972

Authors and Affiliations

  • Yu. A. Kruglyak
    • 1
    • 2
  • V. I. Danilov
    • 1
    • 2
  • V. A. Kuprievich
    • 1
    • 2
  • V. V. Ogloblin
    • 1
    • 2
  1. 1.Pisarzhevskii Institute of Physical ChemistryAS UkrSSRUSSR
  2. 2.Institute of Microbiology and VirusologyAS UkrSSRKiev

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