Metallacrown nomenclature has been developed to mimic the nomenclature of crown ethers, which are named by the total number of atoms in the ring, followed by "C" for "crown,"  and the number of oxygen atoms in the ring. For example, 12-crown-4 or 12-C-4 describes Figure 2a.  When naming metallacrowns, a similar format is followed.  However, the C becomes "MC" for "metallacrown" and the "MC" is followed by the ring metal, other heteroatom, and the ligand used to make the metallacrown.  For example, metallacrown b in the figure above is named [12-MC-4], where "shi" is the ligand, salicylhydroxamic acid.