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Published June 2, 2021 | Supplemental Material
Journal Article Open

Generation of an Elusive Permanent Merocyanine via a Unique Mechanochemical Reaction Pathway


We report the discovery of a 2H-naphtho[1,2-b]pyran mechanophore that produces a permanent merocyanine dye upon mechanochemical activation, in contrast to the reversible product generated photochemically. Experiments suggest that the irreversibility of the mechanically generated merocyanine is due to a unique reaction in which the scission of an ester C–O bond reveals a β-hydroxy ketone that locks the merocyanine through an intramolecular H-bonding interaction. In addition to demonstrating the reactivity using solution-phase ultrasonication, permanent merocyanine generation is also achieved in solid polymeric materials. The permanent coloration achieved with the naphthopyran mechanophore affords unique opportunities for sensing and force-recording applications as well as fundamental studies limited by the reversibility of typical colorimetric force probes.

Additional Information

© 2021 American Chemical Society. Received 13 April 2021. Published online 19 May 2021. Financial support from Caltech is gratefully acknowledged. M.E.M. was supported by an NSF Graduate Research Fellowship (DGE-1745301). We thank the Molecular Materials Research Center and the Center for Catalysis and Chemical Synthesis of the Beckman Institute at Caltech for access to equipment. We also thank Dr. Bruce Brunschwig, Dr. Mona Shahgholi, and Dr. David VanderVelde for technical assistance. The authors declare no competing financial interest.

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August 20, 2023
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