N‐Alkyl Ammonium Resorcinarene Chloride Receptors for Guest Binding in Aqueous Environment

Abstract

AbstractHost systems with guest binding ability in water and/or biological fluids are a current challenge in supramolecular host–guest chemistry. Here we present the first syntheses of water‐soluble N‐ethanol ammonium resorcinarene chlorides (NARCls) with terminal hydroxyl groups at the upper rim. The NARCls possess deep cavities and are shown to bind a variety of guest molecules such as linear and cyclic alkanes, linear halogenated alkanes, and aromatic fluorophores (naphthalene, p‐(phenylazo)phenol) in water through hydrophobic interactions, as well as 1,4‐dioxane (a water soluble guest) via hydrogen bonds. The receptors are monomeric in aqueous media and form 1:1 host–guest complexes with binding constants of up to 559 m−1 in D2O/MeOD (9:1, v/v) at 298 K. Solid‐state analysis in purely organic media, reveals a dimeric 2:2 capsule and a self‐included dimer of nanometer dimensions. The host–guest complexes are analyzed in solid state by single‐crystal X‐ray diffraction and in solution by 1H NMR and diffusion‐ordered NMR spectroscopy.