In Silico Study of the π–π Stacking Interactions in Borazine–Borazine, Boroxine–Boroxine, Borazine–Boroxine Complexes and Their Substituted Derivatives

The study investigates the stacking interactions between borazine-borazine, boroxine-boroxine, and borazine-boroxine complexes and their substituted derivatives, obtained by replacing all the hydrogen atoms with the electron-withdrawing -F and the electron-donating -CH₃ groups. The strength of these interactions is rationalized using a composite density functional theory method, r²SCAN-3c. It is found that the staggered conformation is more stable than the eclipsed conformation in all of the cases studied. Noncovalent interaction (NCI) plots and quantum theory of atoms in molecules analysis were carried out to confirm the presence of NCIs in the complexes. Analysis through the symmetry-adapted perturbation theory approach indicates that dispersion is the most significant contributor to the stabilization of the stacking interactions. However, the observation of small, negative charge transfer (CT) energy values demonstrates stabilization due to CT upon complexation; the magnitude of stabilization increases with both -F and -CH₃ substitutions, and the staggered configuration in each case exhibits higher CT than the eclipsed one.