Dipole-bound electron attachment to uracil-water complexes. Theoretical ab initio study

Ab initio calculations performed in this work found positive electron affinities for all three possible doubly H-bonded complexes of the uracil molecule with a single water molecule. In all cases the excess electron is bound by the the dipole field of the complex. No conventional stable ''valence'' anionic states were found with the theoretical procedure used in this work (SCF + second-order perturbation theory corrections for the electron correlation effects). The attachment of the excess electron lowers the relative energy differences between the three complexes, making their coexistence more probable. Structural changes in the uracil-water complex upon attachment of an electron were also found. The anion's equilibrium geometry had noticeably shortened hydrogen-bond lengths and a shifted orientation of the water molecule with respect to the uracil molecule compared to the neutral system.