The Influence of Amine Functionalities on Anion Binding in Polyamide-Containing Macrocycles

Mixed amide/amine macrocyclic anion hosts of varying sizes and with different amine substituents have been synthesized and characterized. Host 2, containing a 28-membered ring and secondary amines, has shown selective binding for HSO4− over other oxo anions and halides in DMSO-d6 using NMR titrations. Crystal structures of SO42−, HPO42−, H2PO4−, and H2P2O72− with the 28-membered ring hosts indicate different macrocyclic conformations depending on the N-substituent. Anion affinities appear to be correlated with macrocycle conformation.