Behaviour of the XH-*-π and YX-*-π interactions (X, Y = F, Cl, Br and I) in the coronene π-system, as elucidated by QTAIM dual functional analysis with QC calculations

Abstract

The dynamic and static nature of XH-*-π and YX-*-π in the coronene π-system (π(C₂₄H₁₂)) is elucidated by QTAIM dual functional analysis, where * emphasizes the presence of bond critical points (BCPs) in the interactions. The nature of the interactions is elucidated by analysing the plots of the total electron energy densities H_b(r_c) versus H_b(r_c) − V_b(r_c)/2 [=(ħ²/8m)∇²ρ_b(r_c)] for the interactions at BCPs, where V_b(r_c) are the potential energy densities at the BCPs. The data for the perturbed structures around the fully optimized structures are employed for the plots in addition to those of the fully optimized structures. The plots are analysed using the polar coordinate of (R, θ) for the data of the fully optimized structures, while those containing the perturbed structures are analysed using (θ_p, κ_p), where θ_p corresponds to the tangent line of each plot and κ_p is the curvature. Whereas (R, θ) show the static nature, (θ_p, κ_p) represent the dynamic nature of the interactions. All interactions in X–H-*-π(C₂₄H₁₂) (X = F, Cl, Br and I) and Y–X-*-π(C₂₄H₁₂) (Y–X = F–F, Cl–Cl, Br–Br, I–I, F–Cl, F–Br and F–I) are classified by pure CS (closed shell) interactions and are characterized as having the vdW nature, except for X–H = F–H and Y–X = F–Cl, F–Br and F–I, which show the typical-HB nature without covalency. The structural features of the complexes are also discussed.