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

Host 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 D 2 O/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 1 H NMR and diffusion‐ordered NMR spectroscopy.