title: Photoinduced charge-transfer dehydrogenation in a gas-phase metal-DNA base complex: Al-cytosine.
abstract: An Al-cytosine association complex has been generated via laser ablation of a mixture of aluminum and cytosine powders that were pressed into a rod form. The ionization energy of the complex is found to be 5.16 +/- 0.01 eV. The photoionization efficiency spectrum of Al-cytosine has also been collected. DFT calculations indicate that binding of Al to cytosine manifests a significant weakening of the N-H bond, predicted to have a strength of 1.5 eV in the complex, and a significant stabilization of the oxo tautomeric form relative to the hydroxy forms. The predicted ionization energy of 5.2 eV agrees well with the experimental value. The threshold for dehydrogenation/ionization of Al-cytosine, forming (Al-cytosine-H)+, is found to occur at photoexcitation energies between 11.4 and 12.8 eV. This is a two-photon process that is proposed to occur via photoinduced electron transfer from Al to an antibonding (sigma) orbital localized on N-H. In the context of this mechanism, this work constitutes the first time charge transfer between a metal and DNA base has been photoinitiated in the gas phase.
authors.affiliation: Steacie Institute for Molecular Sciences, National Research Council of Canada, Ottawa, Ontario, K1A 0R6, Canada. david.pedersen@nrc.ca
authors.forename: David B
authors.initials: DB
authors.lastname: Pedersen
authors.forename: Marek Z
authors.initials: MZ
authors.lastname: Zgierski
authors.forename: Stephane
authors.initials: S
authors.lastname: Denommee
authors.forename: Benoit
authors.initials: B
authors.lastname: Simard
mesh_terms: D000535:Aluminum / Q000737:chemistry*; D003596:Cytosine / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D006865:Hydrogenation; D009942:Organometallic Compounds / Q000737:chemistry; D010777:Photochemistry; D013816:Thermodynamics
chemical_list: D009942:Organometallic Compounds; D003596:Cytosine; D004247:DNA; D000535:Aluminum