Unveiling the Nature and Strength of Selenium-Centered Chalcogen Bonds in Binary Complexes of SeO2 with Oxygen-/Sulfur-Containing Lewis Bases: Insights from Theoretical Calculations

Abstract

Among various non-covalent interactions, selenium-centered chalcogen bonds (SeChBs) have garnered considerable attention in recent years as a result of their important contributions to crystal engineering, organocatalysis, molecular recognition, materials science, and biological systems. Herein, we systematically investigated π-hole-type Se∙∙∙O/S ChBs in the binary complexes of SeO₂ with a series of O-/S-containing Lewis bases by means of high-level ab initio computations. The results demonstrate that there exists an attractive interaction between the Se atom of SeO₂ and the O/S atom of Lewis bases. The interaction energies computed at the MP2/aug-cc-pVTZ level range from -4.68 kcal/mol to -10.83 kcal/mol for the Se∙∙∙O chalcogen-bonded complexes and vary between -3.53 kcal/mol and -13.77 kcal/mol for the Se∙∙∙S chalcogen-bonded complexes. The Se∙∙∙O/S ChBs exhibit a relatively short binding distance in comparison to the sum of the van der Waals radii of two chalcogen atoms. The Se∙∙∙O/S ChBs in all of the studied complexes show significant strength and a closed-shell nature, with a partially covalent character in most cases. Furthermore, the strength of these Se∙∙∙O/S ChBs generally surpasses that of the C/O-H∙∙∙O hydrogen bonds within the same complex. It should be noted that additional C/O-H∙∙∙O interactions have a large effect on the geometric structures and strength of Se∙∙∙O/S ChBs. Two subunits are connected together mainly via the orbital interaction between the lone pair of O/S atoms in the Lewis bases and the BD*(OSe) anti-bonding orbital of SeO₂, except for the SeO₂∙∙∙HCSOH complex. The electrostatic component emerges as the largest attractive contributor for stabilizing the examined complexes, with significant contributions from induction and dispersion components as well.

Keywords: binary clusters; chalcogen bonds; quantum chemical calculations; π–hole interactions.

Figure 1

The MEP diagrams of the SeO₂ and O-/S-containing Lewis bases. The positive and negative electrostatic potentials are represented by the red and blue regions, respectively. The maximum electrostatic potential (V_S,max) and the minimum electrostatic potential (V_S,min) are given in kcal/mol.

Figure 2

The optimized geometries of the global minima of the studied chalcogen-bonded complexes. The purple and green dotted lines denote the chalcogen bonds and hydrogen bonds, respectively, revealed by conducting an NCIplot analysis.

Figure 3

The QTAIM diagrams for the studied complexes. The orange dots indicate (3, −1) critical points, which are called bond critical points (BCPs), and the yellow dots indicate (3, +1) critical points, which are called ring critical points (RCPs). The bond paths (BPs) are indicated by the brown lines.

Figure 4

NCI isosurfaces and scatter diagrams of the RDG versus sign(λ₂)ρ associated with chalcogen bonds and hydrogen bonds within the sixteen investigated complexes. A 0.55 a.u value was used to create the NCI isosurfaces. The blue and green isosurfaces represent the strongly and weakly attractive interactions, respectively, and red isosurface denotes the repulsive interactions.

Figure 5

The diagrams of the NBOs associated with the LP(O/S) → BD*(OSe) orbital interactions for the eight selected complexes.