Quantum chemical calculations with the AIM approach applied to the π-interactions between hydrogen chalcogenides and naphthalene

Abstract

The nature of the π–interactions in the 1 : 1 and 2 : 1 adducts of EH₂ with the naphthalene π-system (E = O, S, Se and/or Te) is elucidated by applying QTAIM-DFA (QTAIM dual functional analysis). The H–*–π interactions are detected in EH₂–*–π(C₁₀H₈) and (EH₂)₂–*–π(C₁₀H₈) for E = S, Se and Te, whereas E–*–π interactions are in OH₂–*–π(C₁₀H₈), (OH₂)₂–*–π(C₁₀H₈) and HE–H–*–π(C₁₀H₈) (denoted by HHE–*–C₁₀H₈) (E = S, Se and Te). Asterisks * emphasize the existence of bond critical points (BCPs) on the interactions in question. H_b(r_c) are plotted versus H_b(r_c) − V_b(r_c)/2 at the BCPs in QTAIM-DFA. Plots for the fully optimized structures are analyzed using the polar coordinate (R, θ) representation. Those containing the perturbed structures are by (θ_p, κ_p): θ_p corresponds to the tangent line of the plot and κ_p is the curvature. While (R, θ) describe the static nature, (θ_p, κ_p) represent the dynamic nature of interactions. The θ and θ_p values are less than 90° for all interactions in question, examined in this work, except for θ_p = 90.6° for HHTe–*–π(C₁₀H₈). Therefore, all interactions examined are classified by the pure-CS (closed shell) interactions and predicted to have vdW-nature, except for HHTe–*–π(C₁₀H₈), which should have the character of the typical HB-nature without covalency. The π–EB interaction in HHS–*–C₁₀H₈ is predicted to have the border character between the vdW-nature and the typical HB-nature without covalency, since θ_p = 89.8°. The nature of four interactions appeared between 2H in TeH₂ and C₁₀H₈ in TeH₂–*–π(C₁₀H₈) is also clarified well using QTAIM-DFA.