Mechanisms of ultrafast excited-state deactivation in adenosine

Deniz Tuna, Andrzej L. Sobolewski, Wolfgang Domcke

Research output: Contribution to journalArticlepeer-review

80 Scopus citations

Abstract

Recently, resonant two-photon ionization experiments on isolated adenine and adenosine suggested that adenosine exhibits a significantly shorter excited-state lifetime than adenine, which indicates the existence of an efficient excited-state deactivation mechanism in adenosine that is not existent in adenine. We report on ab initio investigations on a syn and an anti conformer of adenosine exhibiting an intramolecular O- H···N3 hydrogen bond. For both conformers, we have identified the existence of a barrierless excited-state deactivation mechanism that involves the forward-backward transfer of a proton along the intramolecular hydrogen bond and ultrafast radiationless deactivation through conical intersections. The S1/S0 conical intersection associated with the proton-transfer process is lower in energy than the known S 1/S0 conical intersections associated with the excited-state deactivation processes inherent to the adenine moiety. These results support the conjecture that the photochemistry of hydrogen bonds plays a decisive role for the photostability of the molecular building blocks of RNA and DNA, which have been selected at the earliest stages of the chemical evolution of life.

Original languageEnglish
Pages (from-to)122-127
Number of pages6
JournalJournal of Physical Chemistry A
Volume118
Issue number1
DOIs
StatePublished - 9 Jan 2014

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