Cytosine Radical Cations: A Gas-Phase Study Combining IRMPD Spectroscopy, UVPD Spectroscopy, Ion-Molecule Reactions, and Theoretical Calculations.
The radical cation of cytosine (Cyt.+) is generated by dissociative oxidation from a ternary CuIIcomplex in the gas phase. The radical cation is characterized by infrared multiple photon dissociation (IRMPD) spectroscopy in the fingerprint region, UV/Vis photodissociation (UVPD) spectroscopy, ion-molecule reactions, and theoretical calculations (density functional theory and ab initio). The experimental IRMPD spectrum features diagnostic bands for two enol-amino and two keto-amino tautomers of Cyt.+that are calculated to be among the lowest energy isomers, in agreement with a previous study. Although the UVPD action spectrum can also be matched to a combination of the four lowest energy tautomers, the presence of a nonclassical distonic radical cation cannot be ruled out. Its formation is, however, unlikely due to the high energy of this isomer and the respective ternary CuIIcomplex. Gas-phase ion-molecule reactions showed that Cyt.+undergoes hydrogen-atom abstraction from 1-propanethiol, radical recombination reactions with nitric oxide, and electron transfer from dimethyl disulfide.
Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL, 60115, USA.
Michael
M
Lesslie
Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL, 60115, USA.
John T
JT
Lawler
Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, Washington, 98195, USA.
Andy
A
Dang
Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, Washington, 98195, USA.
Joseph A
JA
Korn
Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 166 10, Prague 6, Czech Republic.
Daniel
D
Bím
Laboratoire de Chimie Physique, Université Paris-Sud, UMR8000 CNRS, 91405, Orsay, France.
Vincent
V
Steinmetz
Laboratoire de Chimie Physique, Université Paris-Sud, UMR8000 CNRS, 91405, Orsay, France.
Philippe
P
Maître
Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, Washington, 98195, USA.
Frantisek
F
Tureček
Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL, 60115, USA.
Victor
V
Ryzhov
IRMPD spectroscopy; UVPD spectroscopy; ion-molecule reactions; nucleobases; radical ions