Synergistic Cyclic Cooperativity Govern 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 this HB in the respective dimer, provides an accurate estimation of its energy in an actual molecular cluster. For this purpose, the molecular tailoring approach (MTA)-based method was utilized to estimate the CCs of these cycles. The HB energies calculated in this fashion (E_HB^Synergetic) were in excellent agreement with their actual cluster counterparts (E_HB^Cluster). In this work, 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) and sulphur dioxide (SO₂) are employed. These microhydrated clusters exhibits TBs, PBs and CBs with the surrounding water molecules. The energy of these NCBs calculated using synergetic cyclic cooperativity (E_NCB^Synergetic) approach were found to be in excellent agreement with their full cluster counterpart (E_NCB^Cluster) calculated by the MTA-based method. The difference in two values were found to be less than 0.6 kcal/mol. 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 these cyclic structures common them.