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 ura cil molecule with a single water molecule. In all cases the excess ele ctron is bound by the the dipole field of the complex. No conventional stable ''valence'' anionic states were found with the theoretical pro cedure used in this work (SCF + second-order perturbation theory corre ctions for the electron correlation effects). The attachment of the ex cess 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 hydro gen-bond lengths and a shifted orientation of the water molecule with respect to the uracil molecule compared to the neutral system.