A theoretical study of 5-halouracils: electron affinities, ionization potentials and dissociation of the related anions

The gas phase and solution electron affinities and ionization potentials of uracil, thymine and a series of 5-halouracils (5XU, X = F, Cl, Br) are investigated with B3LYP. Halogen substitution has a smaller effect on the IP than the EA of U. The EAs are calculated to increase according to T < U < 5FU < 5CIU < 5BrU. The calculated barriers for the dissociation of the resulting 5XU anions to X- plus uracil-centered radicals decrease along the series 5FU(-) > 5CIU(-) > 5BrU(-). The calculated trends are consistent with suggestions that 5XUs enhance the sensitivity of deoxyribonucleic acid, DNA (ribonucleic acid, RNA) to ionizing radiation and that 5BrU leads to the greatest enhancement. (C) 2001 Elsevier Science B.V. All rights reserved.