The back and forth motions of a crown-ether based wheel along the axis of a bistable rotaxane are triggered by the decarboxylation of 2-cyano-2-phenylpropanoic acid and detected by the oscillation of the EPR nitrogen splitting of a dialkyl nitroxide function mounted within the macrocyclic ring. When the -Cl derivative of the acid is used, back and forth motions are accelerated. Conversely, with CH and -OCH derivatives, the back motion is strongly inhibited by the insurgence of collateral radical reactions.
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