Abstract
Circularly polarized phosphorescence (CPP) is a spin-forbidden radiative process, and its underlying mechanism is not comprehensively understood, mainly due to the limited examples of efficient triplet emission from small chiral organic molecules with well-defined structures. Here we investigate a pair of chiral enantiomers, R- and S-BBTI, that feature highly distorted spiral ring-locked heteroaromatics with heavy iodine atoms. These chiral molecules are found to exhibit large dissymmetry factors up to 0.013 and emit near-infrared CPP with an efficiency of 4.2% and a lifetime of 119 μs in dimethyl sulfoxide solution excited by ultraviolet irradiation. Their crystals show efficient CPP with 7.0% quantum efficiency and a lifetime of 166 μs. Extensive experimental chiroptical investigations combined with theoretical calculations reveal an efficient spin-flip process that modulates the electron and magnetic transition dipole moments to enhance CPP performance. Moreover, the phosphorescence of R/S-BBTI is oxygen-sensitive and photoactivatable in dimethyl sulfoxide. Therefore, R/S-BBTI can be applied for hypoxia imaging in cells and tumours, expanding the application scope of CPP materials.
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Data availability
All data that support the findings of this study are reported in the main text and Supplementary Information. The data that support the findings of this study are available from the corresponding author upon reasonable request, and data for all figures can be found via figshare at https://figshare.com/s/2c6dc3e1e94795e4c29b (ref. 48). The X-ray crystallographic coordinates for structures reported in this study have been deposited at the Cambridge Crystallographic Data Centre under deposition numbers 2329575, 2329576 and 2329577. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Source data are provided with this paper.
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Acknowledgements
We thank the Materials Characterization and Preparation Center, The Chinese University of Hong Kong, Shenzhen, for materials characterization, and we are grateful to X. Li and G. Liu for their help with high-resolution mass and high-performance liquid chromatography measurements. This work was supported by the National Key Research and Development Program of China (2023YFB3810001 (to Z.Z.)); the National Natural Science Foundation of China grant (52273197 (to Z.Z.), 52333007 (to B.Z.T.), 52250410355 (to P.A.), 22305204 (to D.L.) and 52303382 (to Z.Q.)); the Shenzhen Key Laboratory of Functional Aggregate Materials (ZDSYS 20211021111400001 (to B.Z.T., Z.Z. and Z.Q.)); the Science, Technology, and Innovation Commission of Shenzhen Municipality (JCYJ 2021324134613038 (to Z.Z.), JCYJ20220530143805012 (to Z.Q.), KQTD 20210811090142053 (to B.Z.T.), GJHZ 20210705141810031 (to Z.Z.) and JCYJ20220818103007014 (to B.Z.T.)); and the Innovation and Technology Commission (ITCCNERC14SC01 (to B.Z.T.)).
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Z.Q., Z.Z. and B.Z.T. supervised the project. D.L. designed and synthesized the molecules and carried out the measurements of the photophysical characteristics. W.-J.W. performed the cell and animal experiments. D.L., Z.Y. and B.W. performed theoretical calculations. K.W., L.Z., Y.X., S.C., B.W., Q.W. and P.A. contributed to the discussions. D.L., P.A., Z.Q. and Z.Z. contributed to the manuscript writing. All authors discussed the progress of the research and reviewed the manuscript.
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Supplementary Information
Supplementary Discussion, Figs. 1–51 and Tables 1–7.
Supplementary Video 1
The process of writing ‘AIE’ with a UV pen.
Crystallographic Data 1
CCDC 2329575 (R-BBT).
Crystallographic Data 2
CCDC 2329576 (R-BBTI).
Crystallographic Data 3
CCDC 2329577 (S-BBTI).
Source data
Source Data Fig. 2
Photophysical properties in crystalline state.
Source Data Fig. 3
Photoluminescent and chiroptical properties of R/S-BBTI in solution.
Source Data Fig. 4
CPP mechanistic investigations.
Source Data Fig. 5
Photoactivated performance of R/S-BBTI in DMSO solution (10−5 M).
Source Data Fig. 6
Dynamic light scattering data of S-BBTI-based nanoparticles.
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Liu, D., Wang, WJ., Alam, P. et al. Highly efficient circularly polarized near-infrared phosphorescence in both solution and aggregate. Nat. Photon. 18, 1276–1284 (2024). https://doi.org/10.1038/s41566-024-01538-4
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DOI: https://doi.org/10.1038/s41566-024-01538-4
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