Interaction of superoxide O2- with water hexamer clusters

A variety of the bonding scenarios that are performed on the potential energy surface of interaction between the superoxide radical anion and the lower-energy water hexamers such as ring, chair, prism, and cage are proposed and elaborated. It is demonstrated that the superoxide anion significantly restructures the hydrogen bonding network of water hexamer and is capable to break weak intramolecular hydrogen bonds of water hexamer, and to therefore form the ionic water-superoxide hydrogen bonds with “free” OH-groups, thus admitting either an “internal” or “surface solvation”. The former solvation regime is however distinguishably different from the hydrogen bonding patterns of the first hydration shell of superoxide. Two bonding scenarios between the superoxide anion and the cage water hexamer leads to the formation of the quasi-linear proton-limited structures that exhibit a substantial long-range behaviour. The bonding scenarios are furnished with the computed IR spectra of the resultant water-superoxide complexes in the O-H stretching region.