Mechanical molecular brake

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]. 

Molecular systems that exhibit controlled or coordinated rotary motion are discussed in this chapter. These systems represent a reproduction of a variety of macroscopic mechanical devices on the molecular scale. From gears to a motor, passing through a turnstile, a brake and a ratchet, we describe their design, synthesis and dynamic behavior. The importance of molecular motors in the biological realm and possible applications in nanotechnology are also discussed. 

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