Electrochemical measurement of switchable hydrogen bonding in an anthraquinone-based anion receptor

Conformational Control of Selectivity and Stability in Hybrid Amide/Urea Macrocycles

The anion-binding properties of two similar hybrid amide/urea macrocycles containing either a 2,6-dicarboxamidophenyl or a 2,6-dicarboxamidopyridine group are compared. Significant differences in anion affinity and mode of interaction with anions are attributed to the presence of intramolecular hydrogen bonds in the pyridine system. In fact, remarkably, the phenyl macrocycle undergoes amide hydrolysis under neutral conditions in DMSO/water. The anion binding abilities of the receptors are compared to those of acyclic analogues of the macrocycles that show that the phenyl receptor behaves in a similar fashion to acyclic urea-containing receptors (i.e., showing little selectivity amongst oxo anions), whilst the pyridine-containing receptor shows a high affinity and selectivity for carboxylates.

Structural and molecular recognition studies with acyclic anion receptors

Acyclic molecules containing amides, ureas, and pyrrole groups have proven to be effective and selective anion-binding agents. In this Account, the structural chemistry of isophthalamide anion complexes, ortho-phenylenediamine based bis-ureas, and amidopyrroles, as well as anion-triggered deprotonation processes in neutral anion receptor systems, are discussed.