Competition and cooperativity between hydrogen bond and σ-hole bond in SCS–(HF) n ( n = 1 and 2) systems

Abstract

Quantum chemical calculations have been performed for 1:1 and 1:2 systems of SCS and HF at the MP2/aug-cc-pVTZ level. There are two isomers for SCS–HF dimer. One is combined through a hydrogen bond with SCS as the electron donor; the other is formed by a σ-hole bond with SCS as the electron acceptor. Although the σ-hole bond is weaker than the hydrogen bond, the former is still competitive with the latter in this system. For comparison, the OCO–HF, SeCSe–HF, and SCS–HCl systems have also been analyzed. The most stable structure is the trimer where there are a FH⋯S hydrogen bond and a direct HF–HF contact simultaneously. It is shown that there is a cooperative effect between the hydrogen bond and the σ-hole bond. The band of 3843 cm −1 is assigned to the H–F stretch vibration in the σ-hole-bonded dimer. The natural bond orbital (NBO) and atoms in molecules (AIM) analyses have been performed for a better understanding the interactions.