Light Machinery Powered by Light

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Science  21 Sep 2001:
Vol. 293, Issue 5538, pp. 2171
DOI: 10.1126/science.293.5538.2171c

Like macroscopic machines, molecular machines need energy to run. If energy is supplied in the form of chemical fuel, then not only must it be delivered, but waste products that form must be removed. Balzani et al. show that light can be used to power the dethreading and rethreading of a pseudorotaxane, in which a cyclic component moves back and forth over a linear backbone (true rotaxanes have bulky groups at both ends that usually prevent complete dethreading). There are two isomers, E and Z, of the “thread.” Initially, the E isomer forms a pseudorotaxane with its partner cyclophane; irradiation at 365 nanometers then photoisomerizes the E to the Z isomer, which dethreads. Irradiation at 436 nanometers reverses the photoisomerization, and the E isomer rethreads to form the original construct. Such light-powered nanomachine components have the added advantage that they can be switched on and off easily and rapidly. — JU

Chem. Commun. 10.1039/b105160c.

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