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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 10, Number 3
BKCSDE 10(3)
March 20, 1989 

 
Title
Theoretical Studies on the Photochemical Reactions of 5,7-Dimethoxycoumarin with Adenosine. The Electronic States of 5,7-Dimethoxycoumarin and their Photoadducts
Author
Ja Hong Kim*, Goang Lae Han, Young Chil Song, Sung Ho Sohn
Keywords
Abstract
The chemical reactivity of 5,7-dimethoxycoumarine with adenosine has been calculated by the frontier electron and PPP-Cl MO methods. Results suggest that the major reactivity of the 5,7-dimethoxycoumarin is highest at the carbon-4 (position 4), whereas the electrophilic reactivity is generally spread all over the 5,7-dimethoxycoumarin molecule. These results are consistent with the experimental photoaddition reaction products. The small change of bond orders on excitation does not give enough reactivity to triplet states or the efficient intersystem crossing from T1 to S0 inhibits photoaddition of 5,7-dimethoxycoumarine to adenosine. Although the relative intensity of the singlet band appears to be considerably higher than the triplet band intensity, its integrated intensity, i.e. oscillator strength, is comparable to that of the 5,7-dimethoxycoumarin and adenosine bands.
Page
223 - 226
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