Helically Foldable Diphenylureas as Anion Receptors: Modulation of the Binding Affinity by the Chain Length

Using a series of diphenylureas capable of folding to helical conformations, the binding trends have been compared between two anions of different sizes, chloride and sulfate. The binding constant for the sulfate ion steadily increases from monomer to pentamer as the chain length increases, but for the chloride ion it increases up until the trimer and then reaches a plateau