Halogen bonding rotaxanes for nitrate recognition in aqueous media

Targeting the biologically and environmentally important nitrate anion, halogen bonding (XB) has been incorporated into three novel [2]rotaxane structural frameworks via an axle component containing covalently linked 3,5-bis-iodotriazole pyridine–pyridinium motifs. This has enabled the recognition of nitrate in aqueous media containing up to 90% water with equivalent binding affinity to chloride, illustrating the potency of XB for anion recognition in highly competitive aqueous solvent mixtures.