On the proton-bound noble gas dimers (Ng-H-Ng)+ and (Ng-H-Ng')+ (Ng, Ng' = He-Xe): Relationships between structure, stability, and bonding character

The structure, stability, and bonding character of fifteen (Ng-H-Ng)(+) and (Ng-H-Ng')(+) (Ng, Ng' = He-Xe) compounds were explored by theoretical calculations performed at the coupled cluster level of theory. The nature of the stabilizing interactions was, in particular, assayed using a method recently proposed by the authors to classify the chemical bonds involving the noble-gas atoms. The bond distances and dissociation energies of the investigated ions fall in rather large intervals, and follow regular periodic trends, clearly referable to the difference between the proton affinity (PA) of the various Ng and Ng'. These variations are nicely correlated with the bonding situation of the (Ng-H-Ng)(+) and (Ng-H-Ng')(+). The Ng-H and Ng'-H contacts range, in fact, between strong covalent bonds to weak, non-covalent interactions, and their regular variability clearly illustrates the peculiar capability of the noble gases to undergo interactions covering the entire spectrum of the chemical bond.