Stable Pseudorotaxane

Stable Pseudorotaxane

Author: Andrei Dragan

Rotaxanes and pseudorotaxanes are two different prototypes of molecular machines that have drawn increasing attention in supramolecular chemistry and nanotechnology. Both of them are composed of an axle and a wheel, with the macrocyclic compounds always acting as the wheel component.

Yu Liu, Nankai University, Tianjin, China, and colleagues have constructed a pseudo[2]rotaxane, based on an azobenzene-bridged bis-ferrocene as the axle molecule and α-cyclodextrin as the wheel component. Then, the two ferrocene groups in this pseudo[2]rotaxane were encapsulated by two cucurbit[7]urils to obtain a pseudo[4]rotaxane (pictured). This heteropseudo[4]rotaxane displayed high stability towards harsh temperatures and the isomerization of azobenzene, so it can be regarded as a [2]rotaxane.

In this [2]rotaxane, two macrocyclic cucurbit[7]uril molecules act not only as the wheel components of the heteropseudo[4]rotaxane, but also as its stoppers. This supramolecular stoppering strategy could provide a simpler methodology for the construction of future rotaxanes.


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