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

Abstract

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.

Spectral Signatures of Protonated Noble Gas Clusters of Ne, Ar, Kr, and Xe: From Monomers to Trimers

“…The predicted bond distance at this level of theory not only captures the trend, but also agrees well with the reported experimental values. Furthermore, our CCSD(T) internuclear distances have reproduced the reported calculations of Borocci et al [ 51 ] Furthermore, our calculated internuclear distances for NeH + and ArH + agrees well with those reported by de Oca-Estévez et al, which were calculated at the CCSD(T)/CBS[56] and MRCI+Q/aug-cc-pV6Z levels of theory and basis [ 31 ].…”

“…As for the nature of the Ng-H + bond, Borocci et al have performed an extensive bonding analysis [ 51 ]. Their findings indicate that the nature of the Ng-H + bond is dominantly covalent.…”

“…On the one hand the dissociation may lead to Ng and H + . The dissociation energy for this pathway is very high (>50 kcal/mol) [ 51 , 57 , 58 , 60 ]. The CCSD(T)/CBS//CCSD(T)/aug-cc-pVTZ dissociation energies are 53.03 kcal/mol for NeH + , 93.64 kcal/mol for ArH + , 104.79 kcal/mol for KrH + , and 120.01 kcal/mol for XeH + [ 60 ].…”

“…We will now consider asymmetric proton-bound noble gas dimers, NgH + Ng’. Based on several studies, these triatomic NgH + Ng’ have a linear structure [ 35 , 37 , 45 , 51 , 60 ]. Compare with their symmetric counterparts (NgH + Ng), these species no longer have a center of inversion, because the Ng atoms sandwiching the H + are now distinct (i.e., Ng ≠ Ng’).…”

“…Early calculations have focused on their structure and characteristic fundamental bands [ 19 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ]. The works of Grabowski et al and Borocci et al have provided valuable insights on the bonding for these complexes [ 50 , 51 ]. Spectral simulations which accounts for the anharmonic effects have also been available recently [ 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ].…”