The uracil dimer and trimer covalent anions: An ab initio study

In this work, we present new structures for both the uracil dimer anion (U2-) and trimer anion (U3-) calculated at the MP2/6-31++G** level of theory. In these systems, the excess electron is localized at only one uracil unit in a π-state and that molecule shows some off-plane distortion leading to higher anion stabilization. In both structures excess electron attachment leads to the formation of a stable covalent anion, with electron affinity values of 0.25, 0.05 eV for U2 and U3, respectively. Experimental implications in relation to the calculated data are also discussed.