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The Role of 1πσ* States in the Formation of Adenine Radical-Cations in DNA Duplexes

Research output: Contribution to journalArticle

Original languageEnglish
Pages (from-to)464-471
Number of pages8
JournalChemical Physics
Early online date11 Aug 2018
DateAccepted/In press - 1 Aug 2018
DateE-pub ahead of print - 11 Aug 2018
DatePublished (current) - 14 Nov 2018


Photoinduced damage of DNA is a well-known but still far from fully understood phenomenon. Electronic structure methods are here employed to investigate potential roles of πσ states in initiating photodamage, and ways in which πσ-state driven photochemistry might evolve with increasing molecular complexity. The study starts with the bare 9H-adenine molecule and progresses through to a model double-helix DNA duplex in aqueous solution. Relative to the gas phase, aqueous solvation is predicted to stabilize the 1πσ states of these systems when exciting at the respective ground state equilibrium geometries, but to have relatively little effect on the asymptotic NH bond strengths. But the study also re-emphasises the potential importance of rival σ ← π excitations, wherein a solute π electron is promoted to a σ orbital localized on an OH bond of a complexing H2O molecule, as a route to forming parent radical cations – as have recently been observed following near UV photoexcitation of double-helix adenine-thymine duplexes in water (Banyasz et al., 2018). The subsequent deprotonation of such radical cations offers a rival low energy route to NH bond fission and radical formation in such duplexes.

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