An overview of anion coordination by hydroxyl, amine and amide based rigid and symmetric neutral dipodal receptors

Abstract

Abstract The last two decades have witnessed some modified approach in designing supramolecular anion receptors, not only for academic interests but also for their potential applications in biology and environment. Although, most of the tripodal based anion receptors are extensively studied in literature in a compact way, but the systematic and well-documented anion recognition study by dipodal receptors is still unexplored. The review aims to provide a detailed and comprehensive account of reported examples over last two decades of anion coordinated neutral self-assemblies of artificial dipodal receptors that employ several non-covalent interactions offered by specific low coordinating binding sites such as hydroxyl, amine, amide, thiamide, sulfonamide itself as well as from their hybrid functionalities such as amine-amide, amine-hydroxyl, amide-hydroxyl, hydroxyl-sulfonamide, amine-sulfonamide etc. This review specifically targets the rigid as well as symmetric dipodal backbone of anion receptors/sensors that discuss either the solid state structural aspects and/or the solution phase host–guest binding phenomena. Typical examples of anion-coordinated self-assembled supramolecular architectures including molecular barrel, capsules, foldamer, helicates, tetrahedral cages, mechanically interlocked systems as well as some colorimetric, chromogenic and fluorogenic chemosensors developed from covalently connected rigid dipodal low coordinating scaffolds are summarized other than high coordinating urea, thiourea scaffolds. Discussions relating to some potential applications in anion recognition, selective and sensitive anion sensing, cell imaging studies, transmembrane anion transport etc. as demonstrated by some of these dipodal receptors have also been included in this review.