On the Origin of the Ultrafast Internal Conversion of Electronically Excited Pyrimidine Bases

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DOIResolve DOI: http://doi.org/10.1021/jp054158nS1089-5639(05)04158-7
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TypeArticle
Journal titleThe Journal of Physical Chemistry A
ISSN1089-5639
Volume109
Issue42
Pages93849387; # of pages: 4
AbstractThe ultrafast radiationless decay of photoexcited uracil and cytosine has been investigated by ab initio quantum chemical methods based on CIS and CR-EOM-CCSD(T) electronic energy calculations at optimized CIS geometries. The calculated potential energy profiles indicate that the S1 S0 internal conversion of the pyrimidine bases occurs through a barrierless state switch from the initially excited 1* state to the out-of-plane deformed excited state of biradical character, which intersects the ground state at a lower energy. This three-state nonradiative decay mechanism predicts that replacement of the C5 hydrogen by fluorine introduces an energy barrier for the initial state switch, whereas replacement of the C6 hydrogen by fluorine does not. These predictions are borne out by the very different fluorescence yields of 5-fluorinated bases relative to the corresponding 6-fluorinated bases. It is concluded from these results that the origin of the ultrafast radiationless decay is the same for the two pyrimidine bases.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada; NRC Steacie Institute for Molecular Sciences
Peer reviewedYes
Identifier16891788
NPARC number12333589
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Record identifiercfb4754c-39ff-4322-8288-7ad905f79c5d
Record created2009-09-10
Record modified2017-03-23
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