Anions of the Hydrogen-Bonded Uracil Dimer. Ab Initio Theoretical Study

Theoretical ab initio calculations have been performed to determine the ability of the hydrogen-bonded uracil dimer to form stable anions. The major conclusions of this work are (i) three of the hydrogen-bonded conformers of the uracil dimer can form stable dipole-bound anions with excess electrons; (ii) uracil dimer can form a covalent anion that has a structure dissimilar from the structures of the neutral dimer; (iii) in the covalent uracil dimer anion the excess electron is localized on one of the uracil molecules and this molecule shows an out-of-plane distortion; (iv) the covalent uracil dimer anion is stable with respect to a vertical electron detachment, but at the level of theory (MP2) used in the calculations the anion is marginally unstable with respect to an adiabatic electron detachment.