Model Compounds for Size Selection of Singly Charged Cations

For transport in biological systems, alkali ions are bound by special ligands, called ionophores. These ligands show remarkable ion selectivity, which is usually determined by the size of the corresponding cations.

Similar selectivity can be observed by crown ether complexes, which selectively bind different alkali metal ions depending on the ring size.

Click on the pictures of the ions to see the structures of the complexes.