N2O2, N2O2- and N2O22-: structures, energetics and N-N bonding

The density functional theory and the ab initio quantum chemistry methods, Becke3LYP and CASPT2, have been employed to determine structures and energetics of neutral and anionic N2O2 species. When going from a neutral NO dimer to an anionic species the N---N bond lengths decrease drastically and the corresponding N---N frequencies increase. The relative stabilities of the different N2O2− isomers suggest an ONNO structure in a Trans configuration to be the most stable mono valent anion. The formation energies of 1.4–1.7 eV relative to the NO + NO− asymptote are in agreement with experiments. Excitation energies are determined and specific formation channels for three N2O2− isomers are discussed. The hyponitrite ion, N2O22−, is also studied. Its total energy is 2.7–2.8 eV above the total energy of two NO−. In order to connect to an experimental study of NO adsorption on MgO the ability of two NO molecules to form a complex with Mg and Mg+ is investigated