Wikipedia
thumb|300px|right|Figure showing the metallacrown analogy to the organic crown ether. Ligand substituents are omitted for clarity.a) 12-crown-4 b) 12-MC-4c) 15-crown-5 d) 15-MC-5 Metallacrowns are a unique class of macrocyclic compounds that consist of metal ions and solely or predominantly heteroatoms in the ring. Classically, metallacrowns contain an [M–N–O] repeat unit in the macrocycle. First discovered by Vincent L. Pecoraro and Myoung Soo Lah in 1989, metallacrowns are best described as inorganic analogues of crown ethers. To date, over 600 reports of metallacrown research have been published. Metallacrowns with sizes ranging from 12-MC-4 to 60-MC-20 have been synthesized.
In 2013, the project "Metallacrowns: Metallacrown-based innovative materials and supramolecular devices" has been funded by the European Union Research Executive Agency as a Marie Curie IRSES International Research Staff Exchange Scheme. This mobility project involves researchers from the Universities of Parma, Wrocław, Paris-Sud, Kyiv, and Michigan, and the CNRS in Orléans. This project has been funded by the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 611488.