Supramolecular chemistry of environmentally relevant anions

This chapter discusses supramolecular chemistry of environmentally relevant anions. The ultimate goal of the studies on the basic chemical aspects of anion receptor design of functional pH-independent systems is to target selective binding of anions of environmental significance. In applications-oriented aspects of the research on the design of separations, strategies for selective and efficient removal of targeted anions have been a major long-term goal. The chapter discusses (1) some of the first synthetic sulfate-selective anion-binding agents; (2) simple, structure-based methods for modifying the intrinsic anion selectivity of a given class of anion receptors; and (3) the first system capable of extracting sulfate anion from acidic, nitrate-containing aqueous media. These initial findings point the way to more effective systems involving receptors with higher selectivity, binding strength, and solubility. The evolution of anion-binding ligands from simple ammonium-based systems through mixed amide/amine and thioamide/amine receptors is reviewed. Thus, the emphasis is largely on synthetic design strategy carried out in the Bowman–James group.