The field of molecular machines, i.e. multicomponent systems able to undergo large amplitude motions under the action of an external signal, has experienced a spectacular development since the beginning of the 1990s. Transition metal complexes have played an important role in this context, often as components of catenanes and rotaxanes. The present tutorial review will discuss a few systems of this type, taken from the contributions of our group or from others. The stimulus responsible for the controlled motion of the machine can be chemical, electrochemical, or photochemical. Examples of these three categories will be considered.

Organic chemistry Z 0200 Transition Metal Complexes as Molecular Machine Prototypes -[34 refs.]. -(CHAMPIN, B.; MOBIAN, P.; SAUVAGE*, J.-P.; Chem. Soc. Rev. 36 (2007) 2, 358-366; Lab. Chim. Org.-Miner., Univ. Louis Pasteur, F-67070 Strasbourg, Fr.; Eng.) -Lindner 21-232

A new highly rigid ditopic ligand has been prepared which consists of a terpy fragment connected through its 4 0 position to the 3 position of a phen nucleus via a 1,4-phenylene linker. The chemical structure of the presently reported two-chelate ligand is such that the coordination axes of the two chelates are orthogonal to one another. The reaction of this phen-terpy conjugate with Zn 21 affords in good yield a dimeric structure, as shown by ES-MS and 1 H NMR spectroscopies.