Abstract
The reversible interconversion between spiropyran and merocyanine constitutes one of the most intensively investigated photochromic systems, enabling diverse applications in stimuli-responsive materials and optical imaging. Here, we report pyridine-substituted merocyanines (PMCs) as a class of photochromic molecules. Upon visible light irradiation, these compounds undergo an uncommon photoinduced C-N bond formation to yield spiroindolizine (SIZ) structures, accompanied by the color fading. The SIZs can thermally revert to the colored PMC form. This photochromism is marked by rapid response, high photo-switching ratio, robust water compatibility, and fatigue resistance. Furthermore, we have synthesized quinoline-substituted merocyanines and found that they can be bidir…
Abstract
The reversible interconversion between spiropyran and merocyanine constitutes one of the most intensively investigated photochromic systems, enabling diverse applications in stimuli-responsive materials and optical imaging. Here, we report pyridine-substituted merocyanines (PMCs) as a class of photochromic molecules. Upon visible light irradiation, these compounds undergo an uncommon photoinduced C-N bond formation to yield spiroindolizine (SIZ) structures, accompanied by the color fading. The SIZs can thermally revert to the colored PMC form. This photochromism is marked by rapid response, high photo-switching ratio, robust water compatibility, and fatigue resistance. Furthermore, we have synthesized quinoline-substituted merocyanines and found that they can be bidirectionally switched by 660 nm and 500 nm light to form SIZ and PMC structures. Finally, we showed the photochromism of these molecules in solid matrices and demonstrated a light-controlled sequential switching function, highlighting their potential for advanced photonic applications.
Data availability
The data generated in this study are provided in Source Data file. Crystallographic data for the structures reported in this article have been deposited at the Cambridge Crystallographic Data Centre. Deposition numbers for compounds: PMC1 (2455320), PMC2 (2455316), PMC3 (2455317), PMC5 (2455318), PMC6 (2455319). These data can be obtained free of charge from The Cambridge Crystallographic Data Center via (https://www.ccdc.cam.ac.uk/structures/). Coordinates for computational experiments are provided as Supplementary Data 1. All data are available from the corresponding author upon request. Source data are provided with this paper.
References
Mollick, S. & Tan, J. C. Organic solid-state photochromism using porous scaffolds. Nat. Rev. Mater. 10, 519–535 (2025).
Becker, J. et al. Optical control of TRPM8 channels with photoswitchable menthol. Angew. Chem. Int. Ed. 64, e202416549 (2025).
Eisenreich, F. et al. A photoswitchable catalyst system for remote-controlled (co)polymerization in situ. Nat. Catal. 1, 516–522 (2018).
Welleman, I. M., Hoorens, M. W., Feringa, B. L., Boersma, H. H. & Szymanski, W. Photoresponsive molecular tools for emerging applications of light in medicine. Chem. Sci. 11, 11672–11691 (2020).
Gao, M. et al. New molecular photoswitch based on the conformational transition of phenothiazine derivatives and corresponding triplet emission properties. J. Am. Chem. Soc. 147, 2653–2663 (2025).
Zhang, X. et al. Optical control of gene expression using a DNA G quadruplex targeting reversible photoswitch. Nat. Chem. 17, 875–882 (2025).
Rifaie-Graham, O. et al. Photoswitchable gating of non-equilibrium enzymatic feedback in chemically communicating polymersome nanoreactors. Nat. Chem. 15, 110–118 (2023).
Cardano, F., Marquez Garcia, R. & Szymanski, W. Manipulation of chemistry and biology with visible light using tetra-ortho-substituted azobenzenes and azonium ions. Angew. Chem. Int. Ed. 64, e202423506 (2025).
Kortekaas, L. & Browne, W. R. The evolution of spiropyran: fundamentals and progress of an extraordinarily versatile photochrome. Chem. Soc. Rev. 48, 3406–3424 (2019).
Sassmannshausen, T. et al. Wavelength selective photocontrol of hybrid azobenzene-spiropyran photoswitches with overlapping chromophores. Angew. Chem. Int. Ed. 63, e202314112 (2024).
Ai, Q., Lan, K., Li, L., Liu, Z. & Hu, X. Beyond photochromism: alternative stimuli to trigger diarylethenes switching. Adv. Sci. 11, 2410524 (2024).
Petermayer, C. & Dube, H. Indigoid photoswitches: visible light responsive molecular tools. Acc. Chem. Res. 51, 1153–1163 (2018).
Shao, B., Qian, H., Li, Q. & Aprahamian, I. Structure property analysis of the solution and solid-state properties of bistable photochromic hydrazones. J. Am. Chem. Soc. 141, 8364–8371 (2019).
Shao, B., Fu, H. & Aprahamian, I. A molecular anion pump. Science 385, 544–549 (2024).
Helmy, S. et al. Photoswitching using visible light: a new class of organic photochromic molecules. J. Am. Chem. Soc. 136, 8169–8172 (2014).
Fang, L. et al. Ultrafast and reversible photoswitching in bulk polymers enabled by octupolar molecule design. Angew. Chem. Int. Ed. 63, e202402349 (2024).
Puthoff, D., Kuttiyil, H. & Peterson, J. A. Stenhouse salts: visible light photoswitches for protic environments. J. Am. Chem. Soc. 146, 34008–34013 (2024).
Peng, P., Strohecker, D. & Liao, Y. Negative photochromism of a TCF chromophore. Chem. Commun. 47, 8575–8577 (2011).
Shi, Z., Peng, P., Strohecker, D. & Liao, Y. Long-lived photoacid based upon a photochromic reaction. J. Am. Chem. Soc. 133, 14699–14703 (2011).
Hatano, S., Horino, T., Tokita, A., Oshima, T. & Abe, J. Unusual negative photochromism via a short-lived imidazolyl radical of 1,1’-binaphthyl-bridged imidazole dimer. J. Am. Chem. Soc. 135, 3164–3172 (2013).
Mutoh, K. & Abe, J. Fast photochromism of helicene-bridged imidazole dimers. Chem. Sci. 15, 13343–13350 (2024).
Ito, H., Mutoh, K. & Abe, J. Bridged-imidazole dimer exhibiting three-state negative photochromism with a single photochromic unit. J. Am. Chem. Soc. 145, 6498–6506 (2023).
Hamatani, S., Kitagawa, D. & Kobatake, S. Diarylethene photoswitches undergoing 6π azaelectrocyclic reaction: disrotatory thermal cycloreversion of the closed-ring isomer. J. Phys. Chem. Lett. 14, 8277–8280 (2023).
Sacherer, M. & Dube, H. Second generation zwitterionic aza-diarylethene: photoreversible C-N bond formation, three-state photoswitching, thermal energy release, and facile photoinitiation of polymerization. Angew. Chem. Int. Ed. 64, e202415961 (2025).
Wang, X. Y. et al. Light-triggered regionally controlled n-doping of organic semiconductors. Nature 642, 599–604 (2025).
Abeyrathna, N. & Liao, Y. Stability of merocyanine-type photoacids in aqueous solutions. J. Org. Chem. 30, e3664 (2017).
Dhahri, N., Taoufik, B. & Goumont, R. Kinetics of alkaline hydrolysis of p-substituted benzylidenemalononitriles in 50% aqueous acetonitrile: substituent effects and quantification of the electrophilic reactivity. J. Phys. Org. Chem. 27, 484–489 (2014).
Malkin, Y. N., Krasieva, T. B. & Kuzmin, V. A. Quantitative study of the photostability of spiropyrans. J. Photochem. Photobiol. A 49, 75–88 (1986).
Görner, H., Atabekyan, L. S. & Chibisov, A. K. Photoprocesses in spiropyran-derived merocyanines: singlet versus triplet pathway. Chem. Phys. Lett. 260, 59–64 (1996).
Kortekaas, L., Chen, J., Jacquemin, D. & Browne, W. R. Proton-stabilized photochemically reversible E/Z isomerization of spiropyrans. J. Phys. Chem. B 122, 6423–6430 (2018).
Tian, Z. et al. Spirooxazine to merooxazine interconversion in the presence and absence of zinc: approach to a bistable photochemical switch. J. Phys. Chem. A 114, 11900–11909 (2010).
Kubinyi, M. et al. Metal complexes of the merocyanine form of nitrobenzospyran: Structure, optical spectra, stability. J. Mol. Struct. 1000, 77–84 (2011).
Becker, E. D. et al. High Resolution NMR: Theory And Chemical Applications, Ch. 2 (Elsevier Ltd. Press 1999). 1.
Han, Z., He, M., Wang, G., Lehn, J. M. & Li, Q. Visible-light-driven solid-state fluorescent photoswitches for high-level information encryption. Angew. Chem. Int. Ed. 63, e202416363 (2024).
Xie, Y. et al. Hydrogen bond-associated photofluorochromism for time-resolved information encryption and anti-counterfeiting. Angew. Chem. Int. Ed. 64, e202414846 (2025).
Andreasson, J. et al. All-photonic multifunctional molecular logic device. J. Am. Chem. Soc. 133, 11641–11648 (2011).
Zhang, J., Zou, Q. & Tian, H. Photochromic materials: more than meets the eye. Adv. Mater. 25, 378–399 (2013).
Kobauri, P., Dekker, F. J., Szymanski, W. & Feringa, B. L. Rational design in photopharmacology with molecular photoswitches. Angew. Chem. Int. Ed. 62, e202300681 (2023).
Balmond, E. I. et al. Comparative evaluation of substituent effect on the photochromic properties of spiropyrans and spirooxazines. J. Org. Chem. 81, 8744–8758 (2016).
Benchimol, E., Tessarolo, J. & Clever, G. H. Photoswitchable coordination cages. Nat. Chem. 16, 13–21 (2024).
Liu, D. K. et al. Near-infrared II cyanine fluorophores with large stokes shift engineered by regulating respective absorption and emission. Nat. Commun. 16, 4911 (2025).
Gong, Q. Y., Shi, W., Li, L. H. & Ma, H. M. Leucine aminopeptidase may contribute to the intrinsic resistance of cancer cells toward cisplatin as revealed by an ultrasensitive fluorescent probe. Chem. Sci. 7, 788–792 (2016).
Gao, X. H., Li, X. H., Li, L. H., Zhou, J. & Ma, H. M. A simple fluorescent off-on probe for the discrimination of cysteine from glutathione. Chem. Commun. 51, 9388–9390 (2015).
Zhou, J. et al. Detection of misdistribution of tyrosinase from melanosomes to lysosomes and its upregulation under psoralen/ultraviolet A with a melanosome-targeting tyrosinase fluorescent probe. Anal. Chem. 88, 4557–4564 (2016).
Resch-Genger, U., Grabolle, M., Cavaliere-Jaricot, S., Nitschke, R. & Nann, T. Quantum dots versus organic dyes as fluorescent labels. Nat. Methods 5, 763–775 (2008).
Zhao, Y. & Truhlar, D. G. The M06 suite of density functionals for main group thermochemistry, thermochemical kinetics, noncovalent interactions, excited states, and transition elements: two new functionals and systematic testing of four M06-class functionals and 12 other functionals. Theor. Chem. Acc. 120, 215–241 (2008).
Weigend, F. & Ahlrichs, R. Balanced basis sets of split valence, triple zeta valence and quadruple zeta valence quality for H to Rn: design and assessment of accuracy. Phys. Chem. Chem. Phys. 7, 3297–3305 (2005).
Lu, T. & Chen, F. Multiwfn: a multifunctional wavefunction analyzer. J. Comput. Chem. 33, 580–592 (2012).
Lu, T. A comprehensive electron wavefunction analysis toolbox for chemists. Multiwfn. J. Chem. Phys. 161, 082503 (2024).
Acknowledgements
We thank the financial support from the NSF of China (22474147, 22174148, 22374153, 22474144, 22174147). We thank Dr. Qian Li for 2D NMR analysis. We also thank Dr. Tongling Liang and Shuang You for single-crystal structure analysis.
Author information
Authors and Affiliations
Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
He Li, Ya Liu, Feifan Sun, Zixu He, Sijia Lu, Quan Tang, Xiaohua Li, Huimin Ma & Wen Shi 1.
University of Chinese Academy of Sciences, Beijing, China
He Li, Xiaohua Li, Huimin Ma & Wen Shi 1.
Institute of Advanced Displays and Imaging, Henan Academy of Sciences, Zhengzhou, China
Ya Liu 1.
Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
Shiquan Lin
Authors
- He Li
- Ya Liu
- Feifan Sun
- Shiquan Lin
- Zixu He
- Sijia Lu
- Quan Tang
- Xiaohua Li
- Huimin Ma
- Wen Shi
Contributions
W.S. and Y.L. conceived the project. H.L. designed and performed most experiments, analyzed the data, and wrote the original manuscript. F.S., Z.H., S.L. (Sijia Lu), and Q.T. carried out partial experiments. S.L. (Shiquan Lin) performed partial theoretical calculations. X.L. and H.M. contributed to manuscript revision. W.S. supervised the research and finalized the manuscript. All authors discussed the results and approved the final version of the manuscript.
Corresponding author
Correspondence to Wen Shi.
Ethics declarations
Competing interests
The authors declare no competing interests.
Peer review
Peer review information
Nature Communications thanks the anonymous reviewers for their contribution to the peer review of this work. A peer review file is available.
Additional information
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
About this article
Cite this article
Li, H., Liu, Y., Sun, F. et al. Photochromism of pyridine-substituted merocyanine through reversible C-N bond formation. Nat Commun (2025). https://doi.org/10.1038/s41467-025-67626-3
Received: 16 July 2025
Accepted: 04 December 2025
Published: 26 December 2025
DOI: https://doi.org/10.1038/s41467-025-67626-3