Ricerc@Sapienza

Second-order rate constants of the aminolysis of 2-cyano-2-phenylpropanoic anhydride 3 by a series of N-methylanilines differently substituted in the aromatic moiety (4a-d) were measured in dichloromethane. The common reaction product of aminolysis is 2-cyano-2-phenylpropanoic acid 1, which is known to be an effective fuel for acid-base driven molecular machines, but cannot be used in molar excess with respect to the machine.

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 p-Cl derivative of the acid is used, back and forth motions are accelerated. Conversely, with p-CH3 and p-OCH3 derivatives, the back motion is strongly inhibited by the insurgence of collateral radical reactions.