Carboxylato-prism[6]arene as a supramolecular catalyst in water: exploiting its deep hydrophobic cavity for green oxidation of aromatic amines

Abstract

The carboxylato-prism[6]arene acts as an efficient catalyst for the oxidation of aromatic amines in water, utilizing hydrogen peroxide (H₂O₂) as a green oxidant. The findings indicate that forming supramolecular endo-cavity complexes between aniline derivatives and the prism[6]arene is essential for catalytic activity. Calorimetric investigations demonstrate that this complex formation is primarily driven by entropic factors associated with expulsing frustrated water molecules from the deep hydrophobic cavity of the prism[6]arene. In silico studies further confirm the presence of these water molecules within the cavity and their subsequent release upon the introduction of aromatic amines. Additionally, a computational approach was employed to elucidate the initial oxidation steps of aniline within the prism[6]arene cavity. This encapsulation process significantly lowers the activation free energy by 34.94 kJ mol⁻¹, thereby enhancing reactivity through hydrogen bonding and solvent effects. The computational results closely align with experimental data, underscoring the critical role of host–guest interactions within the deep cavity of the prism[6]arene in facilitating the oxidation process.