Mechanisms of photoinduced C{sub {alpha}}-C{sub {beta}} bond breakage in protonated aromatic amino acids
- Universite Paris-Sud 91405, LCAM, Bat. 351, Orsay F-9140 (France)
- France
- Universite Paris-Sud 91405, LPPM, Bat. 210, Orsay F-91405 (France)
- CNRS UMR 7538, Villetaneuse F-93430 (France)
- Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark)
Photoexcitation of protonated aromatic amino acids leads to C{sub {alpha}}-C{sub {beta}} bond breakage among other channels. There are two pathways for the C{sub {alpha}}-C{sub {beta}} bond breakage, one is a slow process (microseconds) that occurs after hydrogen loss from the electronically excited ion, whereas the other is a fast process (nanoseconds). In this paper, a comparative study of the fragmentation of four molecules shows that the presence of the carboxylic acid group is necessary for this fast fragmentation channel to occur. We suggest a mechanism based on light-induced electron transfer from the aromatic ring to the carboxylic acid, followed by a fast internal proton transfer from the ammonium group to the negatively charged carboxylic acid group. The ion formed is a biradical since the aromatic ring is ionized and the carbon of the COOH group has an unpaired electron. Breakage of the weak C{sub {alpha}}-C{sub {beta}} bond gives two even-electron fragments and is expected to quickly occur. The present experimental results together with the ab initio calculations support the interpretation previously proposed.
- OSTI ID:
- 21104036
- Journal Information:
- Journal of Chemical Physics, Vol. 128, Issue 16; Other Information: DOI: 10.1063/1.2899648; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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