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 inv estigated with B3LYP. Halogen substitution has a smaller effect on the IP t han the EA of U. The EAs are calculated to increase according to T < U < 5F U < 5CIU < 5BrU. The calculated barriers for the dissociation of the result ing 5XU anions to X- plus uracil-centered radicals decrease along the serie s 5FU(-) > 5CIU(-) > 5BrU(-). The calculated trends are consistent with sug gestions that 5XUs enhance the sensitivity of deoxyribonucleic acid, DNA (r ibonucleic acid, RNA) to ionizing radiation and that 5BrU leads to the grea test enhancement. (C) 2001 Elsevier Science B.V. All rights reserved.