Electron spin resonance and intermediate neglect of differential overlap molecular orbital study of the. pi. cations of (hydroxymethyl)uracil and (hydroxymethyl)cytosine. Evidence for internal hydrogen bonding

Journal Article · Thu Feb 17 04:00:00 EST 1983 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100227a023· OSTI ID:5903183

Sevilla, M D; McGlashen, M

The ..pi..-cation radicals of 5-(hydroxymethyl)uracil (HOMeU) and 5-(hydroxymethyl)cytosine (HOMeC) have been produced by Cl/sub 2//sup -/ attack in ..gamma..-irradiated basic 12 M LiCl and photoionization in basic 8 M NaClO/sub 4/ glasses at low temperatures. Analysis of the ESR spectra found for these radicals shows that each of the ..pi..-cation radicals converts to another species probably by a change in a nitrogen protonation state as the temperature is raised. For example, 5-(hydroxymethyl)uracil cation shows a 28.5-G average splitting for the two hydroxymethyl-group ..beta.. protons which convert upon annealing to a 36-G splitting. The splittings and the narrowness of the line widths found after annealing are suggestive of a configuration which is intramolecularly rigid and stabilized by a intramolecular hydrogen bond from the hydroxyl proton to the 4-position oxygen. The ..pi.. cation of 5-(hydroxymethyl)cytosine converts to a radical with substantial spin density on the exocyclic nitrogen which again shows strong evidence for intramolecular hydrogen bonding. Final radicals are found to be produced from the ..pi..-cation radicals of (hydroxymethyl)uracil and (hydroxymethyl)cytosine by deprotonation of a methylene proton. INDO calculations for the ..pi.. cation of (hydroxymethyl)uracil as a function of orientation of the hydroxyl group show that the hydrogen bond to the 4-position oxygen increases in strength by a factor of 3 upon deprotonation at the 3-position nitrogen. The hydrogen bond is therefore predicted to substantially stabilize the ..pi..-cation radical.

• Research Organization: Oakland Univ., Rochester, MI
• OSTI ID: 5903183
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 87:4; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400600* -- Radiation Chemistry
ALKALI METAL COMPOUNDS
AMINES
ANIONS
ANNEALING
AZINES
CATIONS
CHARGED PARTICLES
CHEMICAL BONDS
CHEMICAL RADIATION EFFECTS
CHEMISTRY
CHLORIDES
CHLORINE COMPOUNDS
CYTOSINE
ELECTROMAGNETIC RADIATION
ELEMENTS
GAMMA RADIATION
GLASS
HALIDES
HALOGEN COMPOUNDS
HEAT TREATMENTS
HETEROCYCLIC COMPOUNDS
HYDROGEN
HYDROXY COMPOUNDS
IONIZATION
IONIZING RADIATIONS
IONS
LITHIUM CHLORIDES
LITHIUM COMPOUNDS
LITHIUM HALIDES
MAGNETIC RESONANCE
NONMETALS
NUCLEAR MAGNETIC RESONANCE
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
ORIENTATION
PHOTOIONIZATION
PYRIMIDINES
RADIATION CHEMISTRY
RADIATION EFFECTS
RADIATIONS
RESONANCE
SPIN ORIENTATION
STRUCTURAL CHEMICAL ANALYSIS
TEMPERATURE EFFECTS
URACILS