Synergistic cyclic cooperativity governs the strength of chalcogen, pnictogen and tetrel bonds in microhydrated clusters

Abstract

It has been demonstrated that the sum of the cooperativity contributions (CCs) of the cyclic structures (common to a referenced hydrogen bond (HB)) when added to the energy of the HB in the respective dimer provides an accurate estimation of its energy in an actual molecular cluster. For this purpose, a molecular tailoring approach (MTA)-based method was utilized to estimate the CCs of these cycles. The HB energies calculated in this fashion (E^Synergetic_HB) were in excellent agreement with those of their actual cluster counterparts (E^Cluster_HB). In this study, the generality of this methodology for estimating the energy of other non-covalent bonds (NCBs), viz. tetrel (TBs), chalcogen (CBs) and pnictogen bonds (PBs), in microhydrated clusters is tested. For this purpose, the microhydrated clusters of carbon dioxide (CO₂), nitrous (N₂O) oxide and sulphur dioxide (SO₂) are employed. These microhydrated clusters exhibit TBs, PBs and CBs with the surrounding water molecules. The energies of these NCBs calculated using the synergetic cyclic cooperativity (E^Synergetic_NCB) approach were found to be in excellent agreement with those of their full cluster counterparts (E^Cluster_NCB) calculated using the MTA-based method. The difference between the two values was found to be less than 0.6 kcal mol⁻¹. It is emphasized here that the variation in the strength of these different NCBs can be nicely explained in terms of the interplay of the nature of the cooperativity exhibited by the cyclic structures common to them.