Cryptands history

As early as 1969, Pedersen was intrigued by the intense blue colour observed upon dissolution of small quantities of sodium or potassium metal in coordinating organic solvents in the presence of crown ethers. Indeed, the history of alkali metal (as opposed to metal cation) solution chemistry may be traced back to an 1808 entry in the notebook of Sir Humphry Davy, concerning the blue or bronze colour of potassium-liquid ammonia solutions. This blue colour is attributed to the presence of a solvated form of free electrons. It is also observed upon dissolution of sodium metal in liquid ammonia, and is a useful reagent for dissolving metal reductions , such as the selective reduction of arenes to 1,4-dienes (Birch reduction). Alkali metal solutions in the presence of crown ethers and cryptands in etheric solvents are now used extensively in this context. The full characterisation of these intriguing materials had to wait until 1983, however, when the first X-ray crystal structure of an electride salt (a cation with an electron as the counter anion) was obtained by James L. Dye and... 

The history of anion complexation in supramolecular chemistry is almost as long as that of cation binding. However, it developed differently. Whereas the first cation-binding agents (crown ethers, cryptands, etc.) were electroneutral and compatible with organic solvents, the early anion complexers were cationic and highly hydro-... 

The development of cryptands and crown ethers is a relatively new endeavor in the history of chemistry, and has led to the field of supramolecular chemistry. Cryptands and crown ethers have been developed with the intention of selectively chelating with the s-block elements. Some of these are radioactive, and this is one way they can be removed from water supplies. They are called crown ethers because they look like a spiky crown with a central space that can be filled with a metal. An ether s an organic molecule that has... 

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