Back and forth motions of the acid-base-operated molecular switch 1 are photo-controlled by irradiation of a solution, which also contains the photolabile pre-fuel 4. The photo-stimulated deprotection of the pre-fuel produces controlled amounts of acid 2, the base-promoted decarboxylation of which fuels the back and forth motions of the Sauvage-type [2]-catenane-based molecular switch. Because switch 1 and pre-fuel 4 do not interact in the absence of irradiation, an excess of the latter with respect to 1 can be added to the solution from the beginning. In principle, photocontrol of the back and forth motions of any molecular machine, the operation of which is guided by protonation/deprotonation, could be attained by use of pre-fuel 4, or of any other protected acid that undergoes deprotection by irradiation with light at a proper wavelength, followed by decarboxylation under conveniently mild conditions.
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http://dx.doi.org/10.1002/chem.201800474 | DOI Listing |
J Org Chem
July 2019
Dipartimento di Chimica "G. Ciamician" , Università di Bologna, Via San Giacomo 11 , I-40126 Bologna , Italy.
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.
View Article and Find Full Text PDFChemistry
July 2018
Dipartimento di Chimica, Istituto CNR di Metodologie Chimiche-IMC, Sezione Meccanismi di Reazione, Università degli Studi di Roma "La Sapienza", P.le A. Moro 5, 00185, Rome, Italy.
Back and forth motions of the acid-base-operated molecular switch 1 are photo-controlled by irradiation of a solution, which also contains the photolabile pre-fuel 4. The photo-stimulated deprotection of the pre-fuel produces controlled amounts of acid 2, the base-promoted decarboxylation of which fuels the back and forth motions of the Sauvage-type [2]-catenane-based molecular switch. Because switch 1 and pre-fuel 4 do not interact in the absence of irradiation, an excess of the latter with respect to 1 can be added to the solution from the beginning.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
June 2016
Dipartimento di Chimica, Università di Roma La Sapienza and Istituto CNR di Metodologie Chimiche (IMC-CNR), Sezione Meccanismi di Reazione, P. le A. Moro 5, 00185, Roma, Italy.
The decarboxylation of 2-cyano-2-phenylpropanoic acid is fast and quantitative when carried out in the presence of 1 molar equivalent of a [2]catenane composed of two identical macrocycles incorporating a 1,10-phenanthroline unit in their backbone. When decarboxylation is over, all of the catenane molecules have experienced large-amplitude motions from neutral to protonated catenane, and back again to the neutral form, so that they are ready to perform another cycle. This study provides the first example of the cyclic operation of a molecular switch at the sole expenses of the energy supplied by the substrate undergoing chemical transformation, without recourse to additional stimuli.
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