title: Ultrafast electronic deactivation dynamics of the inosine dimer--a model case for H-bonded purine bases.
abstract: The structural properties and ultrafast electronic deactivation dynamics of the inosine dimer in CHCl3 have been investigated by two-dimensional (1)H NMR and static FTIR spectroscopy and by femtosecond time-resolved transient absorption spectroscopy, respectively. The (1)H NMR and IR spectra show the formation of a well-defined, symmetric dimer with an association equilibrium constant of KI·I = 690 ± 100 M(-1). The excited-state dynamics after photoexcitation at λpump = 260 nm monitored by ultrafast absorption spectroscopy show great similarity with those of the monomer inosine in an aqueous solution and are governed by a decay time of τ = 90 ± 10 fs, which is one of the shortest electronic lifetimes of all nucleobases and nucleobase dimers studied so far. On the basis of these observations, the inosine dimer is expected to follow a similar relaxation pathway as the monomer, involving an out-of-plane deformation of the six-membered ring. The importance of the C(2) position for the electronic deactivation of hypoxanthine and guanine is discussed. The obtained well-determined structure and straightforward dynamics qualify the inosine dimer as an excellent reference case for more complicated systems such as the G·G dimer and the G·C and A·T Watson-Crick pairs.
authors.affiliation: Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstr. 40, D-24098 Kiel, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Röttger
authors.forename: Frank D
authors.initials: FD
authors.lastname: Sönnichsen
authors.forename: Friedrich
authors.initials: F
authors.lastname: Temps
mesh_terms: D002725:Chloroform / Q000737:chemistry; D019281:Dimerization; D004583:Electrons; D006860:Hydrogen Bonding; D007288:Inosine / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D055668:Photochemical Processes; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D007288:Inosine; D002725:Chloroform