title: Theoretical Study of the Photophysics of 8-Vinylguanine, an Isomorphic Fluorescent Analogue of Guanine.
abstract: Paving the way for the application of the algebraic-diagrammatic construction scheme of second-order (ADC(2)) to systems based on the guanine chromophore, we demonstrate the this excited-state electronic structure method provides a realistic description of the photochemistry of 9H-guanine, in close agreement with the benchmark provided by the CASPT2 method. We then proceed to apply the ADC(2) method to the photochemistry of 8-vinylguanine (8vG), a minimally modified analogue of guanine which, unlike the naturally occurring nucleobase, displays intense fluorescence, indicative of a much longer-lived excited electronic state. The emissive electronic state of 8vG is identified as an ππ*-type intramolecular charge transfer (ICT) state, in which a charge of roughly -0.2 e is transferred from the guanine moiety onto the vinyl substituent. The main radiationless deactivation pathway competing with fluorescence is predicted to involve the molecule leaving the minimum on the ICT ππ* state, and reaching a region of the S1 adiabatic state where it resembles the La ππ* state of unmodified 9H-guanine. The topology of the La ππ* region of the S1 state favors subsequent internal conversion at a crossing seam with the ground electronic state. The sensitivity of this process to environment polarity may explain the experimentally observed fluorescence quenching of 8vG upon incorporation in single- and double-stranded DNA.
authors.affiliation: Max Planck Institute for the Structure and Dynamics of Matter and Hamburg Centre for Ultrafast Imaging , Bldg. 99 (CFEL), Luruper Chaussee 149, 22761 Hamburg, Germany.
authors.forename: Michał A
authors.initials: MA
authors.lastname: Kochman
authors.affiliation: Max Planck Institute for the Structure and Dynamics of Matter and Hamburg Centre for Ultrafast Imaging , Bldg. 99 (CFEL), Luruper Chaussee 149, 22761 Hamburg, Germany.|Institut für Theoretische Physik, Universität Hamburg , Jungiusstraße 9, 20355 Hamburg, Germany.
authors.forename: Martina
authors.initials: M
authors.lastname: Pola
authors.affiliation: Max Planck Institute for the Structure and Dynamics of Matter and Hamburg Centre for Ultrafast Imaging , Bldg. 99 (CFEL), Luruper Chaussee 149, 22761 Hamburg, Germany.|Department of Chemistry and Physics, University of Toronto , 80 St. George Street, Toronto, Ontario M5S 3H6, Canada.
authors.forename: R J Dwayne
authors.initials: RJ
authors.lastname: Miller
mesh_terms: D005456:Fluorescent Dyes / Q000737:chemistry*; D006147:Guanine / Q000031:analogs & derivatives / Q000737:chemistry*; D015394:Molecular Structure; D055668:Photochemical Processes; D011789:Quantum Theory
chemical_list: D005456:Fluorescent Dyes; D006147:Guanine