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

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 X₃/X atom(s) of the NC-C₆H₂-X₃ and NCX Lewis bases (LB) with F, Cl, Br, or I. In Set II, the W-C-F₃ and F-C-X₃ (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-F₃∙∙∙NC-C₆H₂-X₃ complexes compared with the F-C-F₃∙∙∙NCX analogs. Moreover, significant E_int was recorded for Set I complexes, along with decreasing the electron-withdrawing power of the X₃/X atom(s). Among Set I complexes, the highest negative E_int was ascribed to the F-C-F₃∙∙∙NC-C₆H₂-I₃ complex with a value of -1.23 kcal/mol. For Set II complexes, E_int values of F-C-X₃ 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-F₃ analogs. However, V_s,max quantities exhibited higher values in the case of W-C-F₃ molecules compared with F-C-X₃; preferable negative E_int were ascribed to the F-C-X₃ bearing complexes. These findings were delineated as a consequence of the promoted contributions of the X₃ 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.