Lariat Ethers in Membranes and as Membranes

Abstract

Lariat ethers are macrocyclic (crown ethers) that have one or more sidearms appended to the ring. The sidearms usually contain Lewis basic donor groups when cation binding properties are desired. By combining both a macroring and a sidearm, the advantages of both three-dimensional encapsulation and flexibility are realized. Flexibility is important because cation transport requires rapid complexation and release, especially the latter if it is to be effective. The structural, cation binding, and transport properties are discussed herein. It is also possible to prepare macrocycles having lipophilic sidearms that do not contain any donor group. If lipophilic is enough, these lariat ethers self-assemble into micelles, niosomes, or vesicles. If appropriately designed, these compounds may assemble into smaller, more readily characterized structures. Examples of all of these cases are illustrated herein.