Mutual Interplay Between π-Electron Interactions and Simultaneous σ-Hole Interactions: A Computational Study

In this study, the role of interaction of π-electrons on the strength of simultaneous σ-hole interactions (pnicogen, chalcogen and halogen bonds) is investigated using the quantum chemical calculations. X-ben||TAZ∙∙∙Y1,Y2,Y3 complexes (X = CN, F, Cl, Br, CH3, OH and NH2, TAZ= s-triazine and Y1,Y2 and Y3 denote PH2F, HSF and ClF molecules) is introduced as a model. The results show that interaction of π- electrons of X-ben and TAZ rings in X-ben||TAZ∙∙∙Y1,Y2,Y3 complexes are effective in enhancing the strength of simultaneous σ-hole interactions than that in the TAZ∙∙∙Y1,Y2,Y3 complexes. We show that the effect of the substituents on the studied complexes strongly depends on the nature of the substituents on the X-ben ring. The electron-donor and electron-acceptor substituents increase and decrease the stability of complexes, respectively. The electronic properties of the complexes have been analyzed using molecular electrostatic potential (MEP), and the parameters were derived from the quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) methodologies.