Tautomers of the N-centered radical generated by reaction of SO4˙– with N1-substituted cytosines in aqueous solution. Calculation of isotropic hyperfine coupling constants by a density functional method

2001 ◽  
pp. 1648-1653 ◽  
Author(s):  
Sergej Naumov ◽  
Knut Hildenbrand ◽  
Clemens von Sonntag
Keyword(s):  
Aqueous Solution ◽  
Density Functional ◽  
Hyperfine Coupling ◽  
Density Functional Method ◽  
Functional Method ◽  
Coupling Constants ◽  
Hyperfine Coupling Constants ◽  
Isotropic Hyperfine Coupling ◽  
Isotropic Hyperfine Coupling Constants

Article

1998 ◽  
Vol 76 (12) ◽  
pp. 1817-1826
Author(s):  
Leif A Eriksson ◽  
C Magnus Jansson ◽  
Donald R Arnold ◽  
Russell J Boyd
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Hyperfine Coupling ◽  
Coupling Constants ◽  
Functional Theory ◽  
Hyperfine Coupling Constants ◽  
Isotropic Hyperfine Coupling ◽  
Ionization Processes ◽  
Cleavage Reactions ◽  
Isotropic Hyperfine Coupling Constants

The cleavage reactions of the 1-butene and 4,4-dimethyl-1-pentene molecules and their cations, to form neutral and charged hydrocarbon products, are investigated using hybrid Hartree-Fock/density functional theory. In comparison with previous theoretical results (Du et al.), the density functional cleavage and ionization energies, including zero-point vibrational energy, lie in better agreement with experimental and thermochemical data. Assuming vertical ionization processes the mean absolute deviation (MAD) compared with experiment is 3.4 kcal/mol for the reaction sequences studied. Using adiabatic ionization processes instead gives a MAD of 5.2 kcal/mol. The largest deviation from experiment occurs for the cleavage reactions of the neutral parent molecules, where the difference between theory and experiment is up to 12.8 kcal/mol. In addition to reaction energies we also report optimized ground-state structures, and for the radicals studied, isotropic hyperfine coupling constants that are compared to experimental data. It is found that the experimental hyperfine properties of the 1-butene cation can be explained by rotational averaging caused by the flat potential surface for rotation about the C2-C3 bond.Key words: density functional theory (DFT), alkenes, radical cations, bond cleavage, isotropic hyperfine coupling constants.

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