Sessler, Jonathan L. Pyrrole-based anion receptors : binding studies and progress towards attachment to solid support

Anions have a wide range of importance both in chemical, as well as biological, systems; thus, the design and synthesis of novel receptors with the ability to selectively recognize or bind a specific class of anions is a rapidly developing field of supramolecular chemistry. A series of novel, acyclic pyrrole-based anion receptors will be presented. These systems, which are based on pyridine 2,6-dicarboxamides, bind nitrite and carboxylate anions with good selectivity in dichloroethane solution and are also capable of binding cyanide anions weakly. Control systems, incorporating a benzene-1,3-dicarboxamide spacer, or those wherein the connectivity of the amide linkage is "reversed," either failed to act as effective anion receptors or displayed very different selectivities. Such observations provide support for the notion that small perturbations in the structure of these receptors can lead to drastic changes in their anionbinding properties. Furthermore, efforts have been made to attach macrocyclic phosphate-binding receptors developed in the Sessler Group to cellulose solid supports. The idea is that these macrocycles, once bound to cellulose, will be capable of extracting phosphate from solutions. Studies on the macrocyclic loading level and extraction abilities of the receptors are underway, and will be presented herein.