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Medientyp:
E-Artikel
Titel:
Efficient Deactivation of a Model Base Pair via Excited-State Hydrogen Transfer
Beteiligte:
Schultz, Thomas;
Samoylova, Elena;
Radloff, Wolfgang;
Hertel, Ingolf V.;
Sobolewski, Andrzej L.;
Domcke, Wolfgang
Erschienen:
American Association for the Advancement of Science (AAAS), 2004
Erschienen in:
Science, 306 (2004) 5702, Seite 1765-1768
Sprache:
Englisch
DOI:
10.1126/science.1104038
ISSN:
0036-8075;
1095-9203
Entstehung:
Anmerkungen:
Beschreibung:
We present experimental and theoretical evidence for an excited-state deactivation mechanism specific to hydrogen-bonded aromatic dimers, which may account, in part, for the photostability of the Watson-Crick base pairs in DNA. Femtosecond time-resolved mass spectroscopy of 2-aminopyridine clusters reveals an excited-state lifetime of 65 ± 10 picoseconds for the near-planar hydrogen-bonded dimer, which is significantly shorter than the lifetime of either the monomer or the 3- and 4-membered nonplanar clusters. Ab initio calculations of reaction pathways and potential-energy profiles identify the mechanism of the enhanced excited-state decay of the dimer: Conical intersections connect the locally excited 1 ππ* state and the electronic ground state with a 1 ππ* charge-transfer state that is strongly stabilized by the transfer of a proton.