Catenane

Catenanes are substances composed of two or more mechanically (like links in a chain ) linked rings - mostly macrocycles - exist. These rings can not be separated without breaking at least one covalent bond ring a macrocyclic ring. The term Catenanes goes back to the Latin word catena, meaning " chain ". In addition to the catenanes are rotaxanes and molecular knots to the group of mechanically interlocked molecular architectures.

Synthesis

For the synthesis of catenanes there are two different methods. When performing a cyclization reaction can hope that the rings be arranged before the second and further cyclization so that creating the desired catenane. This is the so- called "statistical approach " which led to the first synthesis of a catenane. However, this method is very inefficient. Possibly at high dilution of the reactants in the mechanical link, and a large excess of the first macrocyclic ring previously formed, this technique works tolerably well. This synthetic approach has mainly historical significance.

The second method is based on supramolecular preorganization of the macrocyclic precursor taking advantage of hydrogen bonds, the coordination of metals, hydrophobic forces or Coulomb interactions. These non- covalent interactions compensate for the entropic disadvantages of the Association and direct the reactants at favorable sites for the formation of the desired Catenanes the last ring closure. This " template-directed " approach can simultaten with the application of high pressure, result in yields of about 90 % to catenanes.

• Catenated families

Brezelane (→ pretzel )

" Handcuffs " catenanes

Special catenanes

In 1994, researchers James Fraser Stoddart and David Amabilino and their research groups succeeded in the synthesis of a catenane that they called Olympiadane ( German Olympiadan ), in line with the five Olympic rings. The Olympiadan has no explicit purpose, but is merely a contribution to basic research, the synthesis should examine the feasibility of such syntheses.