Novel pnicogen bonding interactions with silylene as an electron donor: covalency, unusual substituent effects and new mechanisms

Theoretical study on the noncovalent interactions involving triplet diphenylcarbene

The properties of some types of noncovalent interactions formed by triplet diphenylcarbene (DPC³) have been investigated by means of density functional theory (DFT) calculations and quantum theory of atoms in molecule (QTAIM) studies. The DPC³···LA (LA = AlF₃, SiF₄, PF₅, SF₂, ClF) complexes have been analyzed from their equilibrium geometries, binding energies, and properties of electron density. The triel bond in the DPC³···AlF₃ complex exhibits a partially covalent nature, with the binding energy - 65.7 kJ/mol. The tetrel bond, pnicogen bond, chalcogen bond, and halogen bond in the DPC³···LA (LA = SiF₄, PF₅, SF₂, ClF) complexes show the character of a weak closed-shell noncovalent interaction. Polarization plays an important role in the formation of the studied complexes. The strength of intermolecular interaction decreases in the order LA = AlF₃ > ClF > SF₂ > SiF₄ > PF₅. The electron spin density transfers from the radical DPC³ to ClF and SF₂ in the formation of halogen bond and chalcogen bond, but for the DPC³···AlF₃/SiF₄/PF₅ complexes, the transfer of electron spin density is minimal.

Comparison of pnicogen and tetrel bonds in complexes containing CX2 carbenes (X = F, Cl, Br, OH, OMe, NH2, and NMe2)

The similarities and differences of pnicogen and tetrel bonds formed by carbenes CX₂ with H₃AsO and H₃SiCN were investigated by carrying out ab initio calculations in association with topological analysis of electron density.

Modulating of the pnicogen-bonding by a H⋯π interaction: An ab initio study

An ab initio study of the cooperativity in XH₂P⋯NCH⋯Z and XH₂P⋯CNH⋯Z complexes (X=F, Cl, Br, CN, NC; Z=C₂H₂,C₆H₆) connected by pnicogen-bonding and H⋯π interactions is carried out by means of MP2 computational method. A detailed analysis of the structures, interaction energies and bonding properties is performed on these systems. For each set of the complexes considered, a favorable cooperativity is observed, especially in X=F and CN complexes. However, for a given X or Z, the amount of cooperativity effects in XH₂P⋯CNH⋯Z complexes are more important than XH₂P⋯NCH⋯Z counterparts. Besides, the influence of a H⋯π interaction on a P⋯N (C) bond is more pronounced than that of a P⋯N (C) bond on a H⋯π bond. The quantum theory of atoms in molecules shows that ternary complexes have increased electron densities at their bond critical points relative to the corresponding binary systems. The results also indicate that the strength of the P⋯N(C) and H⋯π interactions increases in the presence of the solvent.

Comparison of tetrel bonds and halogen bonds in complexes of DMSO with ZF3X (Z = C and Si; X = halogen)

A theoretical study of the complexes formed by dimethylsulfoxide (DMSO) with ZF₃X (Z = C and Si; X = halogen) has been performed at the MP2/aug-cc-pVTZ level.

Comparison of π-hole tetrel bonding with σ-hole halogen bonds in complexes of XCN (X = F, Cl, Br, I) and NH3

In addition to the standard halogen bond formed when NH₃approaches XCN (X = F, Cl, Br, I) along its molecular axis, a perpendicular approach is also possible, toward a π-hole that is present above the X–C bond.

Theoretical study of the cooperative effects between the triel bond and the pnicogen bond in BF3···NCXH2···Y (X = P, As, Sb; Y = H2O, NH3) complexes

The interplay between the triel bond and the pnicogen bond in BF3···NCXH2···Y (X = P, As, Sb; Y = H2O, NH3) complexes was studied theoretically. Both bonds exhibited cooperative effects, with shorter binding distances, larger interaction energies, and greater electron densities found for the ternary complexes than for the corresponding binary ones. The cooperative effects between the triel bond and the pnicogen bond were probed by analyzing molecular electrostatic potentials, charge transfer, and orbital interactions. The results showed that the enhancement of the triel bond can mainly be attributed to the electrostatic interaction, while the strengthening of the pnicogen bond can be ascribed chiefly to the electrostatic and orbital interactions. In addition, the origins of both the triel bond and the pnicogen bond were deduced via energy decomposition.