The 5‐halouracils are an important class of compounds with potential applications as antiviral agents, antitumor agents, and radiosensitizers. In this study, we investigated electron attachment to uracil (U) and 5‐halouracil (5‐XU) in the gas and aqueous phases. In the gas phase, dipole‐bound states were characterized using the EOM‐EA‐CCSD level of theory. These dipole‐bound states showed very low electron‐binding energies. We employed a nuclear charge stabilization method with regularized analytic continuation to determine the position and width of the and resonances. The resonance of uracil is stabilized by the substitution of a halogen at the C5 carbon. The resonance appears at a lower energy, indicating the dissociative nature of 5‐bromouracil (5‐BrU). In the aqueous phase, electron attachment showed that the anionic ground state corresponds to a stable state. Excited state analysis from the anionic ground state revealed that the low‐lying states contribute to efficient dissociative electron attachment in bromo‐ and iodo‐substituted compounds, facilitating rapid bond cleavage. Ab initio molecular dynamics simulations in the aqueous phase revealed dissociation of the C─Br and C─I bonds, while the C─F and C─Cl bonds remained nondissociative throughout the simulation. The dissociative nature of 5‐BrU and 5‐IU makes them potential candidates for radiosensitivity.
Kumar et al. (Fri,) studied this question.