The mutual interactions based on amphipathic tetraoxacalix[2]arene[2]triazine: recognition cases of anion and cation investigated by a computational study

Abstract

The nature of anion⋯π (anion X_1–4⁻ = SCN⁻, PF₆⁻, BF₄⁻ and NO₃⁻, respectively) interactions with electron-deficient and cavity self-tunable macrocyclic host tetraoxacalix[2]arene[2]triazine 1 as electron-acceptor (J. Am. Chem. Soc., 2013, 135, 892) have been theoretically investigated with the density functional theory (B3LYP, M06-2X, M06-L, M06, M05-2X, M05, DFT-D3) and the second-order Møller–Plesset perturbation theory (MP2) using a series of basis sets. The binding energies calculated are in good quantitative agreement with the experiments. The LMO-EDA (local molecular orbital energy decomposition analysis) results show that the major contributors of anion⋯π are electrostatic. The alkali metal cations M⁺ (Na⁺, K⁺) and alkaline earth metal cations M²⁺ (Mg²⁺, Ca²⁺) can also interact with 1 and, the cation⋯π binding of M²⁺⋯1 is stronger than that of M⁺⋯1, as well as their strength is gradually decreased along with an increase in the radius of M^+,2+. The investigation of interplay between the anion⋯π and the cation⋯π shows that the interactions among three-body, X⁻, 1 and M⁺ is varied with different phases. The polar solvent can strongly reduce the strength of the interaction, and the more increased the solvent polarity, the more reduced is the binding energy.