σ-Hole and LP-Hole Interactions of Pnicogen···Pnicogen Homodimers under the External Electric Field Effect: A Quantum Mechanical Study

Abstract

σ-Hole and lone-pair (lp)-hole interactions within σ-hole···σ-hole, σ-hole···lp-hole, and lp-hole···lp-hole configurations were comparatively investigated on the pnicogen···pnicogen homodimers (PCl 3 ) 2 , for the first time, under field-free conditions and the influence of the external electric field (EEF). The electrostatic potential calculations emphasized the impressive versatility of the examined PCl 3 monomers to participate in σ-hole and lp-hole pnicogen interactions. Crucially, the sizes of σ-hole and lp-hole were enlarged under the influence of the positively directed EEF and decreased in the case of reverse direction. Interestingly, the energetic quantities unveiled more favorability of the σ-hole···lp-hole configuration of the pnicogen···pnicogen homodimers, with significant negative interaction energies, than σ-hole···σ-hole and lp-hole···lp-hole configurations. Quantum theory of atoms in molecules and noncovalent interaction index analyses were adopted to elucidate the nature and origin of the considered interactions, ensuring their closed shell nature and the occurrence of attractive forces within the studied homodimers. Symmetry-adapted perturbation theory-based energy decomposition analysis alluded to the dispersion force as the main physical component beyond the occurrence of the examined interactions. The obtained findings would be considered as a fundamental underpinning for forthcoming studies pertinent to chemistry, materials science, and crystal engineering.

Yet another perspective on hole interactions, part II: lp-hole vs. lp-hole interactions

“…Results of M06-2X/6-311++G(d,p) in terms of distances and energies were also similar to the previously reported result in M05-2X/6-311++G(d,p) level. 8 Another study demonstrated the presence of an lp-hole in PCl 3 and the interactions between their dimers, 29 reporting “σ-hole···lp-hole” and “lp-hole···lp-hole” complexes. But again, the P⋯P distance was significantly higher than the sum of van der Waals radii, making it very unlikely that the lp-hole is involved in the formation of an electrostatically/charge-transfer driven hole interaction.…”

Pd and Pt metal atoms as electron donors in σ-hole bonded complexes

“…The pace of this work continues to accelerate even today. 33–39 Over the years, the investigations of these interactions have moved beyond halogen atoms, hence the development of analogous chalcogen or pnicogen bonds which engender robust study. 36,40–44…”