Progress in the synthesis and exploitation of catenanes since the Millennium.

Catenanes - molecules consisting of interlocked macrocyclic rings - have been prepared by templation strategies for some thirty years. The utilization of Cu(I) cation, aromatic donor-acceptor interactions and hydrogen bonding assisted self-assembly strategies has led to the construction of numerous examples of these aesthetically pleasing species. This review seeks to discuss key developments in the synthesis and functional application of catenanes that have occurred since the Millennium. The much expanded range of metal cation templates; the genesis and growth of anion templation, as well as the use of alternative supramolecular interactions (halogen bonding and radical templation) and thermodynamically controlled reactions to synthesize catenanes are detailed. The class of catenanes that may be described as "molecular machines" are then highlighted and to conclude, attempts to fabricate catenanes onto surfaces and into metal organic frameworks (MOFs) are discussed.