Tetraurea Macrocycles: Template-Directed One-Pot Synthesis and Anion Binding Properties

Given the significance of anion in life, study of anion recognition attracted great attentions in the past decades. Macrocyclic receptors display intriguing anion binding properties; however, the synthesis of macrocycles is challenging. Here, we reported a new strategy of making tetraurea in one-step. By using 1-butyl-3-methylimidazolium ([hmim][X], X = anion) as the solvent and template reagent, tetraurea macrocycle comprised of bis(urea) binding moiety and hexyl chain spacers is selectively formed with high yield. The obtained macrocycles displayed interesting anion binding properties as indicated by single crystal X-ray diffraction structures and computational modelling.