Effects of Lewis Basicity and Acidity on σ-Hole Interactions in Carbon-Bearing Complexes: A Comparative Ab Initio Study.

The effects of Lewis basicity and acidity on σ-hole interactions were investigated using two sets of carbon-containing complexes. In Set I, the effect of Lewis basicity was studied by substituting the X 3 /X atom(s) of the NC-C 6 H 2 -X 3 and NCX Lewis bases (LB) with F, Cl, Br, or I. In Set II, the W-C-F 3 and F-C-X 3 (where X and W = F, Cl, Br, and I) molecules were utilized as Lewis acid (LA) centers. Concerning the Lewis basicity effect, higher negative interaction energies ( E int ) were observed for the F-C-F 3 ∙∙∙NC-C 6 H 2 -X 3 complexes compared with the F-C-F 3 ∙∙∙NCX analogs. Moreover, significant E int was recorded for Set I complexes, along with decreasing the electron-withdrawing power of the X 3 /X atom(s). Among Set I complexes, the highest negative E int was ascribed to the F-C-F 3 ∙∙∙NC-C 6 H 2 -I 3 complex with a value of -1.23 kcal/mol. For Set II complexes, E int values of F-C-X 3 bearing complexes were noted within the -1.05 to -2.08 kcal/mol scope, while they ranged from -0.82 to -1.20 kcal/mol for the W-C-F 3 analogs. However, V s,max quantities exhibited higher values in the case of W-C-F 3 molecules compared with F-C-X 3 ; preferable negative E int were ascribed to the F-C-X 3 bearing complexes. These findings were delineated as a consequence of the promoted contributions of the X 3 substituents. Dispersion forces ( E disp ) were identified as the dominant forces for these interactions. The obtained results provide a foundation for fields such as crystal engineering and supramolecular chemistry studies that focus on understanding the characteristics of carbon-bearing complexes.