Anion binding involving pi-acidic heteroaromatic rings.

Anions are essential species in biological systems and, particularly, in enzyme-substrate recognition. Therefore, the design and preparation of anion receptors is a topical field of supramolecular chemistry. Most host-guest systems successfully developed are based on noncovalent (ionic and hydrogen-bonded) interactions between anions and ammonium-type functionalities or Lewis acid groups. However, since the past 5 years, an alternative route toward the synthesis of efficient anion hosts has emerged, namely, the use of "anion-pi" interactions involving nitrogen-containing electron-deficient aromatic rings, as the result of several favorable theoretical investigations. In this Account, the state of the (new) art in this growing area of anion-binding research is presented and several selected examples from our work and that of other groups will be discussed.