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Published October 7, 2023 | Published
Journal Article Open

Naphthopyran molecular switches and their emergent mechanochemical reactivity

  • 1. ROR icon California Institute of Technology


Naphthopyran molecular switches undergo a ring-opening reaction upon external stimulation to generate intensely colored merocyanine dyes. Their unique modularity and synthetic accessibility afford exceptional control over their properties and stimuli-responsive behavior. Commercial applications of naphthopyrans as photoswitches in photochromic ophthalmic lenses have spurred an extensive body of work exploring naphthopyran–merocyanine structure–property relationships. The recently discovered mechanochromic behavior of naphthopyrans has led to their emergent application in the field of polymer mechanochemistry, enabling advances in the design of force-responsive materials as well as fundamental insights into mechanochemical reactivity. The structure–property relationships established in the photochemical literature serve as a convenient blueprint for the design of naphthopyran molecular force probes with precisely tuned properties. On the other hand, the mechanochemical reactivity of naphthopyran diverges in many cases from the conventional photochemical pathways, resulting in unexpected properties and opportunities for deeper understanding and innovation in polymer mechanochemistry. Here, we highlight the features of the naphthopyran scaffold that render it a powerful platform for the design of mechanochromic materials and review recent advances in naphthopyran mechanochemistry.

Copyright and License

This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence.


This article is part of the themed collection: 2023 Chemical Science Perspective & Review Collection. 

Financial support from an NSF CAREER award (CHE-2145791) and the Rose Hills Foundation is gratefully acknowledged. M. E. M. and A. C. O. were supported by NSF Graduate Research Fellowships (DGE-1745301) and Barbara J. Burger Graduate Fellowships from Caltech. Support from an Institute Fellowship at Caltech (A. C. O.) is also gratefully acknowledged. M. J. R. gratefully acknowledges the Alfred P. Sloan Foundation for a Sloan Research Fellowship and the Camille and Henry Dreyfus Foundation for a Camille Dreyfus Teacher-Scholar Award. 

All publication charges for this article have been paid for by the Royal Society of Chemistry. 


M. E. M. wrote the first draft of the manuscript with contributions from R. W. B. and A. C. O. M. J. R. provided direction and edited the manuscript.

Conflict of Interest

There are no conflicts to declare.


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Additional details

October 2, 2023
December 22, 2023