Biradical radiationless decay channel in adenine and its derivatives
| العنوان: | Biradical radiationless decay channel in adenine and its derivatives |
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| المؤلفون: | Serguei Patchkovskii, Edward C. Lim, Marek Z. Zgierski |
| المصدر: | Canadian Journal of Chemistry. 85:124-134 |
| بيانات النشر: | Canadian Science Publishing, 2007. |
| سنة النشر: | 2007 |
| مصطلحات موضوعية: | décroissance sans rayonnement, ab initio, Chemistry, Organic Chemistry, coupled clusted, biradical, General Chemistry, Ring (chemistry), Internal conversion (chemistry), Potential energy, Molecular physics, Catalysis, radiationless decay, dommage à l'ADN, agrégat couplé, Unpaired electron, Atomic orbital, Excited state, adénine, DNA damage, guanine, Electron configuration, Ground state, adenine |
| الوصف: | Coupled-cluster calculations of increasing accuracy (approximate doubles: CC2; doubles: EOM-CCSD; connected triples: CR-EOM-CCSD(T)) for CIS-optimized potential energy profiles of adenine and its derivatives indicate that the ultrafast internal conversion of the optically excited π π* state occurs through a state switch to a biradical state, which intersects the ground state at a lower energy. The electronic nature of the biradical state is defined by an electronic configuration in which one unpaired electron occupies a π* orbital confined to the five-membered ring. The second unpaired electron is localized very strongly on a p-type C2 atomic orbital of the six-membered ring. The biradical state minimum has a strongly puckered six-membered ring and a C2–H bond, which is twisted nearly perpendicular to the average ring plane. Consistent with the biradical-mediated internal conversion, the π π* state lifetime is extremely short in adenine and 9-methyladenine, which have barrierless crossing to the biradical state. The lifetime is slightly longer in N,N-dimethyladenine, which has a small barrier for the state switch. In 2-aminopurine the biradical state is found above the π π* state, preventing the biradical state switch and dramatically increasing the lifetime. These results, combined with an earlier work on pyrimidine bases, strongly suggest the importance of a direct decay of the doorway π π* state via a biradical state switch in the photophysics of DNA, even though the nature of the biradical state is somewhat different in purines and pyrimidines.Key words: adenine, guanine, DNA damage, radiationless decay, biradical, ab initio, coupled clusted. |
| تدمد: | 1480-3291 0008-4042 |
| الوصول الحر: | https://explore.openaire.eu/search/publication?articleId=doi_dedup___::cd70e42bdee6021502357e1360609d9cTest https://doi.org/10.1139/v07-006Test |
| حقوق: | CLOSED |
| رقم الانضمام: | edsair.doi.dedup.....cd70e42bdee6021502357e1360609d9c |
| قاعدة البيانات: | OpenAIRE |
| تدمد: | 14803291 00084042 |
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