Molecular modelling crown ether-cation complexes

Pedersen prepared Corey-Pauling-Koltun molecular models of his new complexing agents and observed that they bound cations in a manner similar to the crowning of a regal head. He called the compounds crown ethers, inspired by the observation that they crown cations, and in part because their systematic names are impossibly cumbersome. 

Crystals of salt composed of sodium anion and a complex sodium cation. The molecular models show the complex of an alkali metal cation (Na or K ) with an organic compound called crown ether. The large green sphere is the alkali metal anion. 

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