Pyrrolic and polypyrrolic anion binding agents

This review traces the emergence of pyrrole-based receptors for anion recognition. It outlines how serendipitous findings that the diprotonated form of sapphyrin, a pentapyrrolic expanded porphyrin, formed a centrally-bound complex with fluoride anion made over a decade ago spawned studies of this and other expanded porphyrins as receptors, carriers, and sensors of anions. Further evolutions of the field, including in particular the finding that neutral, non-aromatic oligopyrrole macrocycles, such as the calixpyrroles and calixphyrins, can act as cheap, and easy-to-prepare anion receptors will also be highlighted, as will recent work with acyclic systems, including dipyrrolylquinoxalines (DPQs) and simple derivatives of pyrrole itself. (C) 2003 Elsevier Science B.V. All rights reserved.