Abstract
Solid-state molecular motion (SSMM) plays a critical role in enriching material properties and functions, yet visualizing its detailed dynamics including direction, progression, and velocity to thoroughly elucidate its mechanism remains a great challenge. Herein, an intermolecular charge transfer (ICT)-mediated fluorescence strategy is developed to visualize and regulate SSMM in binary cocrystal systems, utilizing 6-methoxy-2-acetylnaphthalene (MA)/1,2,4,5-tetracyanobenzene (TCNB) as modeling platform. This approach leverages the reversible transformation between MA/TCNB = 1/1 (MT1, yellow emission) and MA/TCNB = 1/2 (MT2, green emission) crystalline phases, enabling real-time visualization of detailed SSMM information via localized dichromatic fluorescence signatures. It reveals an unexpected significant disparity in diffusion rates between electron donor MA and electron acceptor TCNB during the diffusion process at their interface, even exhibiting unidirectional diffusion from MA to TCNB within a restricted time. Applications demonstrated include pretreatment-free impurity analysis of MA (a key impurity in naproxen) down to 0.1% leveraging the fluorescence shift, and real-time monitoring of transesterification reactions based on the differing interaction capabilities of various naproxen esterification derivatives with TCNB. This study not only provides fundamental insights into SSMM and cocrystallization mechanisms but also demonstrates the potential of charge transfer cocrystallization for molecular sensing and dynamic reaction monitoring.
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Data availability
Crystallographic data for MT1 and MT2 have been deposited with the Cambridge Crystallographic Data Center (CCDC) under deposition numbers CCDC 2490358 (MT1) and CCDC 2490348 (MT2). These data can be obtained free of charge from the CCDC. The data supporting the findings of this study are available within the Article, Supplementary Information, or Source Data file. Source data are provided for Figs. 2b-e; 3a-d; 4a, c; 5a–c; 7b-d; 8b, c, e-h and Supplementary Figs. S4-S9, S11, S13-S26, S29, S32, S34-S37, S40-S43, S45-S48 in the associated source data file. Source data are provided with this paper. The Data is available from the corresponding authors on request.
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Acknowledgements
This work was supported by the National Natural Science Foundation of China (Nos. 21605125 awarded to P.F.G., 22105057 awarded to Z.Z.), the Natural Science Foundation of Chongqing (No. CSTB2025NSCQ-GPX0506 awarded to P.F.G.), the Anhui Provincial Natural Science Foundation (No. 2508085MB027 awarded to Z.Z.), and the Fundamental Research Funds for the Central Universities (SWU-XDJH202321 awarded to P.F.G. and SWU-KT24010 awarded to P.F.G.). The authors thank Zhulian Wu, College of Chemistry and Chemical Engineering, Southwest University, for helping to acquire MS data. The authors thank Dr. Yanan Zhao, Analytical and Testing Center, Southwest University, for helping to acquire quantum yield data. The authors thank Prof. Binfang Yuan, College of Chemistry and Chemical Engineering, Yangtze Normal University, for DFT calculations.
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P.F.G., J.Z. and Z.Z. designed this project. J.Z. performed most of the experiments, collected and analyzed the data, and prepared the figures. X.Z., W.W., S.X., W.M., S.S., H.N., and Y.J.L. assisted with the experiments and data collection. Z.Z. performed the crystallographic analysis and contributed to structural interpretation. C.Z.H. provided guidance on data analysis and interpretation. P.F.G. and Z.Z. conceived and supervised the project. J.Z., Z.Z. and P.F.G. wrote the manuscript with input from all authors. All authors discussed the results and approved the final version of the manuscript.
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Nature Communications thanks Yanhua Cheng, who co-reviewed with Xiaoxiao Yu, and the other, anonymous, reviewers for their contribution to the peer review of this work. A peer review file is available.
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Zheng, J., Zhu, X., Wang, W. et al. Visualizing molecular diffusion direction and processes in the solid state via dichromatic fluorescent cocrystalization transformation. Nat Commun (2026). https://doi.org/10.1038/s41467-026-70152-5
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DOI: https://doi.org/10.1038/s41467-026-70152-5
