Molecular Ratchets

Can one have molecules which are ratchet like and have them rotate in one direction so that they may be used as parts of nanomotors? Recently, the molecule shown in the figure was synthesised by Kelly et. al [Angew. Chem. Int. ED. Engl. 36, 1866 (1997)]. The internal rotation within the molecule in a constant temperature bath was studied using NMR. It was found that the rotation took place in both the directions with equal likelihood - and it was concluded that this is in accordance with the second law of thermodynamics (for a very interesting discussion of why this should happen, see the chapter 44 of the first volume of Feynman Lectures in Physics). We have recently argued (see the reference below) that the experiment by Kelly et. al. is much more. It actually is an experimental verification of the principle of detailed balance for the ratchet! We also suggest ways to cause the ratchet to have a net rotation in one direction. They are:

keep the ratchet at a higher temperature and suddenly lower the temperature of the surroundings.

change its temperature periodically.

For more information, please see the listed publications below

K. L. Sebastian: Molecular Ratchets: verifying the principle of detailed balance and the second law of thermodynamics. Physical Review E, 61, 937 (2000).

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