Comparative investigation of interactions of hydrogen, halogen and tetrel bond donors with electron-rich and electron-deficient π-systems

Abstract

Recently, noncovalent interactions in complexes and crystals have attracted considerable interest. The current study was thus designed to gain a better understanding of three seminal types of noncovalent interactions, namely: hydrogen, halogen and tetrel interactions with p-systems. This study was performed on three models of Lewis acids: X 3 -C-H, F 3 -C-X and F-T-F 3 (where X ¼ F, Cl, Br and I; andT ¼ C, Si, Ge and Sn) and three p-systems as Lewis bases: benzene (BZN), 1,3,5-trifluorobenzene (TFB) and hexafluorobenzene (HFB). Quantum mechanical calculations, including geometrical optimization, molecular electrostatic potential (MEP), maximum positive electrostatic potential (V s,max ), Point-of-Charge (PoC), potential energy surface (PES), quantum theory of atoms in molecules (QTAIM) and noncovalent interaction (NCI) calculations, were carried out at the MP2/aug cc-pVDZ level of theory.The binding energies were additionally benchmarked at the CCSD(T)/CBS level. The results showed that:(i) the binding energies of the X 3 -C-H/p-system complexes were unexpectedly inversely correlated with the V s,max values on the hydrogen atom but directly correlated with the X atomic sizes; (ii) the binding energies for the F 3 -C-X/p-system and F-T-F 3 /p-system complexes were correlated with the s-hole magnitudes of the X and T atoms, respectively; and (iii) for the F 3 -C-F/p-system complexes, the binding energy was as strong as the p-system was electron-deficient, indicating the dominating nucleophilic character of the fluorine atom. NCI analysis showed that the unexpected trend of X 3 -C-H/p-system binding energies could be attributed to additional attractive interactions between the X atoms in the X 3 -C-H molecule and the carbon atoms of the p-system. Furthermore, the I 3 -Sn-H molecule was employed as a case study of hydrogen, halogen and tetrel interactions with p-systems. It was found that hydrogen and halogen interactions of the I 3 -Sn-H molecule correlated with the electron-richness of the p-system. In contrast, tetrel interactions correlated with the electron deficiency of the p-system.

±π‐Hole Interactions: A Comparative Investigation Based on Boron‐Containing Molecules

“…For example, the most favorable interaction energies were observed for complexes included BI 3 , where the interaction energies of BI 3 ⋅⋅⋅F 3 N, ⋅⋅⋅Cl 3 N, ⋅⋅⋅Br 3 N, and ⋅⋅⋅I 3 N complexes were observed with values of −1.45, −3.81, −4.46, and −5.18 kcal/mol, respectively. Accordingly, it might be concluded that the + π‐hole interactions of BX 3 with lp‐hole‐containing molecules are exclusive not only to the repulsive/attractive electrostatic interactions but also to the van der Waals interactions with X 3 atoms in X 3 N. These findings match those previously observed, demonstrating the crucial role of X 3 atoms in the interactions of lp‐hole‐containing molecules [21] …”

“…Accordingly, it might be concluded that the + π-hole interactions of BX 3 with lp-hole-containing molecules are exclusive not only to the repulsive/attractive electrostatic interactions but also to the van der Waals interactions with X 3 atoms in X 3 N. These findings match those previously observed, demonstrating the crucial role of X 3 atoms in the interactions of lp-hole-containing molecules. [21] Compared to the previously reported tetrel + σ-hole analogs, the triel + π-hole interactions showed low negative interaction energies. [17] These results outlined the favorable contribution of the three coplanar X 3 atoms of tetrahedral structure in the strength of tetrel interactions than their candidates of the trigonal planar structure of the boron trihalide.…”

“…Furthermore, the B⋅⋅⋅PoC distance effect on the given electrostatic interactions was studied through distances ranging from 2.5 Å to 5.0 Å along x‐axis with step size of 0.1 Å and X‐B⋅⋅⋅PoC angle of 90° (see Figure 1). The strength of the π‐hole interaction was estimated in terms of molecular stabilization energy ( E stablization ) according to the following equation: [21,28a, 19a, 17, 19b, 28b] …”

σ-Hole and Lone-Pair Hole Interactions in Chalcogen-Containing Complexes: A Comparative Study

“…The value of the employed PoC to investigate the Chal···PoC distance effect was made equal to the one used in optimization. The strength of the σ-hole and lp hole interactions was estimated in terms of the molecular stabilization energy ( E stablization ) according to the following equation: 12 , 13 , 18 , 34 , 35 …”

“…The σ-hole and lp hole interactions will first be investigated from the electrostatic perspective via the point-of-charge (PoC) approach. 12 , 13 , 18 , 34 , 35 In addition, the PoC approach will be utilized to precisely define lp, lp hole, and σ-hole locations. Moreover, the Lewis basicity effect on the strength of the σ-hole and lp hole interactions will be also examined.…”