Cryptates: inclusion complexes of macropolyciclic receptor molecules

Abstract. Molecular receptors use intermolecular interactions for the selective binding of substrates. Macropolycyclic molecules containing appropriate binding sites and cavities of suitable size and shape, may be designed so as to display molecular recognition in the formation of selective inclusion complexes, cryptates, with metal cations, anions and molecules. Macrocyclic receptors which form stable and selective complexes with primary ammonium and guanidinium groups are discussed; they display central and lateral discrimination. Enhanced rates of intramolecular thiolysis and hydrogen transfer have been observed when suitable reactive groups are attached to the receptor. Macrobicyclic ligands form very stable and selective cryptates with alkali and alkaline—earth cations; they may be modified so as to selectively complex toxic heavy metal cations. Binuclear cryptates of two types have been synthesized: macrobicyclic complexes of an ellipsoidal Bis—Tren ligand and cylindrical macrotricyclic complexes. They display interesting properties (like cation—cation interactions, copper protein type spectral parameters etc.) and are suitable for formation of "cascad