Enhancement effect of lithium bonding on the strength of π-hole interactions in O2S···NCLi···NCX and O2S···CNLi···CNX complexes (X = H, F, CN, OH and CH3)

Abstract

As with Groups IV and V, some Group VI atoms may exhibit regions of low electronic density that are perpendicular to portions of a molecular framework. These positive regions can interact in a highly directional manner with any negative site, thereby giving rise to a directional interaction. This type of interaction is labelled as ‘π-hole’ bonding. In this study, ab initio calculations are performed to study the cooperativity effects between the π-hole bond and lithium bond interactions in O2S···NCLi···NCX and O2S···CNLi···CNX complexes, where X = H, F, CN, OH and CH3. These effects are investigated in terms of geometric and energetic features of the complexes, which are computed by the MP2/aug-cc-pVTZ method. Cooperative effects are found when S···N(C) and Li···N(C) bonds coexist in the same complex. The results indicate that the interaction energies of lithium and π-hole bonds in the triads are more negative relative to the respective dyads. The interaction energy of the lithium bond is increased by 9%–14%, whereas that of the π-hole interaction by 18%–28%. The electrostatic interaction is found to be a dominant factor in enhancing both types of interactions.