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Solution-phase synthesis of Clar’s goblet and elucidation of its spin properties

Nature Chemistry volume 17, pages 924–932 (2025)Cite this article

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Abstract

In the traditional view, spin pairing occurs between two electrons in a chemical bond where the bonding interaction compensates for the penalty of electrostatic repulsion. It is a mystery whether spin pairing can occur between two non-bonded electrons within a molecular entity. Unveiling this type of spin entanglement (that is, pairing between two spatially segregated spins) at the molecular scale is a long-standing challenge. Clar’s goblet, proposed by Erich Clar in 1972, provides an ideal platform to verify this unusual property. Here we report the solution-phase synthesis of Clar’s goblet and experimental elucidation of its spin properties. Magnetic studies reveal that the two spins are spatially segregated with an average distance of 8.7 Å and antiferromagnetically coupled in the ground state with an ΔES–T of −0.29 kcal mol−1. Our results provide insight into the spin entanglement in Clar’s goblet and may inspire the design of correlated molecular spins for quantum information technologies.

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Fig. 1: Illustration of the concept of spin entanglement in a graphene fragment, Clar’s goblet, along with the achieved molecular design and properties in this work.
Fig. 2: Molecular design and synthesis of cg-1 and cg-2.
Fig. 3: Single-crystal structure and super-structure of cg-2.
Fig. 4: Deciphering the spin ground state of cg-2 and the dipolar interaction between the two radicals.
Fig. 5: Redox behaviour of cg-2 and characterization of its different oxidation states, revealing the spin/charge spatial segregation property.

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Data availability

All data supporting the findings of this study are available within the article and its Supplementary Information. Crystallographic data for the structures reported in this article have been deposited at the Cambridge Crystallographic Data Centre, under deposition numbers CCDC 2376440 (5) and 2376442 (cg-2). Copies of the data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures/. Source data are provided with this paper.

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Acknowledgements

J.W. acknowledges the financial support from Singapore MOE Tier 2 projects (project nos. MOE‐T2EP10222‐0003 and MOE-T2EP10221-0005) and A*STAR MTC IRG grant (grant no. M22K2c0083). S.-D.J. thanks the Natural Science Foundation of China (grant nos. 22488101, 22325503 and 22250001), the Fundamental Research Funds for the Central Universities (grant no. 2024ZYGXZR004) and Guangdong Provincial Quantum Science Strategic Initiative (grant no. GDZX2301002).

Author information

Authors and Affiliations

  1. Department of Chemistry, National University of Singapore, Singapore, Singapore

    Tianyu Jiao, Shaofei Wu & Jishan Wu

  2. Spin-X Institute, School of Chemistry and Chemical Engineering, Guangdong-Hong Kong-Macao Joint Laboratory of Optoelectronic and Magnetic Functional Materials, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, China

    Cong-Hui Wu, Yu-Shuang Zhang & Shang-Da Jiang

  3. Zhejiang Key Laboratory of Precise Synthesis of Functional Molecules, Instrumentation and Service Center for Molecular Sciences and Research Center for Industries of the Future, Westlake University, Hangzhou, China

    Xiaohe Miao

  4. Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area, Shenzhen-Hong Kong International Science and Technology Park, Shenzhen, China

    Shang-Da Jiang

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  1. Tianyu Jiao
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Contributions

T.J. and J.W. conceived the project, designed the research and prepared the paper. T.J. carried out most of the experiments and analysed the data. J.W. supervised the project. C.-H.W. and Y.-S.Z. contributed to the pulse-EPR measurements. X.M. and S.W. contributed to the X-ray crystallographic analyses. S.-D.J. supervised the EPR and magnetic studies. All authors discussed and commented on the paper.

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Correspondence to Shang-Da Jiang or Jishan Wu.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–32.

Supplementary Data 1

Crystallographic data for structure 5 (CCDC 2376440).

Supplementary Data 2

Crystallographic data for structure cg-2 (CCDC 2376442).

Supplementary Data 3

Cartesian coordinates for the calculated structures.

Source data

Source Data Fig. 4

Source data for Fig. 4. Pulse- and cw-EPR spectra and SQUID data.

Source Data Fig. 5

Source data for Fig. 5. CV and DPV traces, UV–vis–NIR absorption spectra, cw-EPR spectrum and NMR spectrum.

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Jiao, T., Wu, CH., Zhang, YS. et al. Solution-phase synthesis of Clar’s goblet and elucidation of its spin properties. Nat. Chem. 17, 924–932 (2025). https://doi.org/10.1038/s41557-025-01776-1

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