The Search for Selective, Neutral Anion Receptors

Difficult, but not impossible! Though anions are large and coordinatively saturated—and therefore slow to form adducts—they do form complexes selectively and efficiently with the novel coronands and cryptands specially tailored to be large enough and to contain ionic, Lewis acidic, or dipolar groups. These host molecules can be, for instance, modified carboranes and crown ethers or tricyclic borane–amine adducts (as in the formation of 1).