Macrocycle

A macrocycle is, as defined by IUPAC, "a cyclic macromolecule or a macromolecular cyclic portion of a molecule." In the chemical literature, organic chemists may consider any molecule containing a ring of nine or more atoms to be a macrocycle. Coordination chemists generally define a macrocycle more narrowly as a cyclic molecule with three or more potential donor atoms that can coordinate to a metal center.