title: Dynamics of dipole- and valence bound anions in iodide-adenine binary complexes: A time-resolved photoelectron imaging and quantum mechanical investigation.
abstract: Dipole bound (DB) and valence bound (VB) anions of binary iodide-adenine complexes have been studied using one-color and time-resolved photoelectron imaging at excitation energies near the vertical detachment energy. The experiments are complemented by quantum chemical calculations. One-color spectra show evidence for two adenine tautomers, the canonical, biologically relevant A9 tautomer and the A3 tautomer. In the UV-pump/IR-probe time-resolved experiments, transient adenine anions can be formed by electron transfer from the iodide. These experiments show signals from both DB and VB states of adenine anions formed on femto- and picosecond time scales, respectively. Analysis of the spectra and comparison with calculations suggest that while both the A9 and A3 tautomers contribute to the DB signal, only the DB state of the A3 tautomer undergoes a transition to the VB anion. The VB anion of A9 is higher in energy than both the DB anion and the neutral, and the VB anion is therefore not accessible through the DB state. Experimental evidence of the metastable A9 VB anion is instead observed as a shape resonance in the one-color photoelectron spectra, as a result of UV absorption by A9 and subsequent electron transfer from iodide into the empty π-orbital. In contrast, the iodide-A3 complex constitutes an excellent example of how DB states can act as doorway state for VB anion formation when the VB state is energetically available.
authors.affiliation: Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 København Ø, Denmark.
authors.forename: Anne B
authors.initials: AB
authors.lastname: Stephansen
authors.affiliation: Department of Chemistry, University of California, Berkeley, California 94720, USA.
authors.forename: Sarah B
authors.initials: SB
authors.lastname: King
authors.affiliation: Department of Chemistry, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama City, Saitama 338-8570, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Yokoi
authors.affiliation: Department of Chemistry, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama City, Saitama 338-8570, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Minoshima
authors.affiliation: Department of Chemistry, University of California, Berkeley, California 94720, USA.
authors.forename: Wei-Li
authors.initials: WL
authors.lastname: Li
authors.affiliation: Department of Chemistry, University of California, Berkeley, California 94720, USA.
authors.forename: Alice
authors.initials: A
authors.lastname: Kunin
authors.affiliation: Department of Chemistry, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama City, Saitama 338-8570, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Takayanagi
authors.affiliation: Department of Chemistry, University of California, Berkeley, California 94720, USA.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Neumark
mesh_terms: D000225:Adenine / Q000737:chemistry*; D000838:Anions / Q000737:chemistry*; D004583:Electrons; D005740:Gases / Q000737:chemistry; D007454:Iodides / Q000737:chemistry*; D008956:Models, Chemical; D015394:Molecular Structure; D055668:Photochemical Processes; D017785:Photons; D011789:Quantum Theory; D013057:Spectrum Analysis
chemical_list: D000838:Anions; D005740:Gases; D007454:Iodides; D000225:Adenine