Molecular ratchet

All of these devices show a certain degree of restriction in the movement of their molecular components, but rotation occurs randomly with no control over directionality. In an attempt to achieve directional motion Kelly investigated the dynamic behavior of a so-called molecular ratchet , 6 [21,22],... 

Fig.3 Schematic representation of a macroscopic ratchet, structure of the molecular ratchet 6 and calculated enthalpy changes for rotation of the triptycene wheel around the helicene pawl [21,22]...

For the very interesting and provocative example of a "molecular ratchet," see the chapter by Carpenter (Chapter 12). 

Kelly, T. Ross, Tellitu, Imanol, Perez Sestelo, Jose. 1997. "In Search of Molecular Ratchets."... 

In designing a molecular ratchet we envisioned continuing with a triptycene, which would act as the ratchet wheel, and using helicenes [40] to simultaneously serve as pawls and springs. The two molecular ratchets proposed are 36 and 37 (Fig. 13). Both systems have essentially the same components, but can be differentiated by the length of the helicene. 

Several examples that may be considered mechanical molecular devices have been reported including die rotaxane based molecular shuttle [16], the chir-optical molecular switch [17], light-activated bianthrone molecules [18], mole-eular brakes [19], molecular ratchets [20], molecular propellers [21], and eonformationally invertable columnar mesophases [22]. 

Growp 15 ligands. The structure of [Fe3()i-dppe)( i-CO)2(CO)8] has been reported, and CO fluxionality re-examined, in order to determine whether the chirality of the cluster induces CO mobility preferentially in a single direction, a so-called molecular ratchet . It was found, however, that the carbonyls on the... 

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