Structures and electron detachment energies of uracil anions

Uracil and its radical anions were studied with second-order, many-body perturbation theory, coupled-cluster theory and electron propagator methods with large, diffuse, atom-centered basis sets. All structures were optimized and two minima were found for anionic forms: one corresponding to a 2A′, diffuse-bound state and another corresponding to a 2A, non-planar, covalent-bound state. The optimized 2A′ anionic structure is lower in energy than the neutral form. The vertical electron detachment energy (VEDE) of this structure is very close to the experimentally observed value. A large, positive VEDE was found for the 2A, covalent-bound anion.