Strong and symmetric hydrogen bonding in the hydrogen di-superoxide anion

The structure of the triplet state of the hydrogen di-superoxide anion, [O2–H–O2]−, has been investigated by ab initio quantum chemical geometry optimizations. The anion has two short hydrogen bonds that are symmetry connected. At the highest level of theory considered (B3LYP/AUC-cc-pVTZ) the O–O bond length is 1.332 Å, the hydrogen bond length is 1.220 Å, the strength of the hydrogen bond is 155 kJ/mol and the standard enthalpy of formation of the anion is estimated to be −199±4 kJ/mol at 25°C.