A theoretical investigation of the competition between σ- and π-holes on the stability of cyclic complexes resulting from the interaction between PO₂Cl and HSX molecules (X = F, Cl, Br, and I)

This research theoretically examined the interactions between PO₂Cl and HSX molecules (X = F, Cl, Br, I) at the MP2/aug-cc-pVTZ(PP) computational level. The MEP analysis showed that the PO₂Cl-C₂v symmetry had two π- and σ-hole regions contributing to the PnB and XB interactions, while the HSX molecules, with maximum potential regions on the H and S atoms participated in the HB-ChB interactions. Geometry optimization revealed three types of cyclic complexes: PnB -HB (Structure-I), ChB-ChB (Structure-II), and XB-XB (Structure-III). The interaction energy results demonstrated that structure-I complexes were the most stable, whereas structure-III complexes were the least stable. This stability could be attributed to the ability of π- and σ-holes to pull the electron cloud of electron-donating species toward themselves. The EDA analyses confirmed the key role of electrostatic and orbital interactions in the stability of the complexes. Various methods were used to thoroughly examine the properties of the complexes.