Search for Stable Anions of Uracil−Water Clusters. Ab Initio Theoretical Studies

Abstract

In this work we investigate the ability of the uracil·water complex to form stable anionic systems. As the experimental evidence and theoretical calculations have indicated, the isolated uracil molecule can only attach an excess electron into a diffuse dipole-bound state, while some recent experiments suggest that the uracil· water complex can form a more stable valence-type anion. In this work we demonstrate that it is possible to converge ab initio calculations of uracil·(H2O)3- to an equilibrium structure that is significantly different from the structure of the neutral cluster and that has a positive and remarkably significant vertical ionization potential. Apart from the valence anion, the uracil·(H2O)3 complex can form a stable dipolebound anion, but as the present calculations indicate the electron affinity, which corresponds to this attachment, is very small (13 meV). The structure of the dipole-bound anion is virtually identical with the structure of the neutral complex.