Mechanical Conformers of Keyring Catenanes

Interlocked molecules exhibit structural isomerization that is different from that of molecules whose connectedness is solely through covalent bonds. A mechanical bond, or the interlocking of components, provides a rich conformational landscape. The ability of synthetic chemists to design directional motion between these mechanical conformers suggests mechanical bonds as building blocks in the design of synthetic molecular motors and machines. Here we examine the complexity of mechanical conformers of radial catenanes with n anisotropically repulsive rings (coined "keyrings") threaded onto a single central ring for n ≤ 10. For a given number of rings, n, the ratio of the key length to the main ring radius, λ, determines the mechanical conformer. We show that this system displays symmetrical in-plane conformers for short keys and co-conformers of lower symmetry where the keys lie out of the plane for longer keys.