Cation Recognition by Crown Ethers and Analogs

This review describes recent developments in the molecular design of crown ethers and analogs, which include lariat ethers, bis(crown ether)s, cryptands, and the corresponding open-chain derivatives.Attention was especially paid to the host compounds for alkali metal and alkaline earth metal cations.The complexation properties were discussed based on the stability constants in methanol, characteristic absorptions in the UV spectrum, the extractabilities, or the transport abilities.