An excess electron bound to urea. III. The urea dimer as an electron trap

Abstract

The possibility of electron binding to urea dimers in the gas-phase was studied at the coupled cluster level with single and double excitations using aug-cc-pVDZ+7s6p5d basis sets. It was found that two kinds of anions can be formed—dipole-bound anions and solvated-electron anions. The global minimum on the ground-state anionic potential energy surface corresponds to the dipole-bound anion whose adiabatic and vertical electron binding energies are 484 and 1443 cm−1, respectively. It was also found that solvated electron structures, which are locally geometrically stable yet thermodynamically unstable, are considerably higher in energy than dipole-bound anions. However, the vertical electron detachment energies of the latter are significantly larger (i.e., 1267, 4129, and 7540 cm−1, depending on whether two canonical, one canonical, and one zwitterionic, or two zwitterionic urea monomers are involved, respectively), so their presence in any experimental source should allow them to be identified.