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

Nature Chemistry (2025)Cite this article Metrics details In the traditional view, spin pairing occurs between two electrons in a chemical bond where the bonding interaction compensates for the penalty

Nature Chemistry (2025)Cite this article

Metrics details

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.

This is a preview of subscription content, access via your institution

Access Nature and 54 other Nature Portfolio journals

Get Nature+, our best-value online-access subscription

$29.99 / 30 days

cancel any time

Subscribe to this journal

Receive 12 print issues and online access

$259.00 per year

only $21.58 per issue

Buy this article

Prices may be subject to local taxes which are calculated during checkout

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.

Clar, E. & Mackay, C. C. Circobiphenyl and the attempted synthesis of 1:14, 3:4, 7:8, 10:11-tetrabenzoperopyrene. Tetrahedron 28, 6041–6047 (1972).

Article CAS Google Scholar

Lieb, E. H. Two theorems on the Hubbard model. Phys. Rev. Lett. 62, 1201–1204 (1989).

Article CAS PubMed Google Scholar

Ovchinnikov, A. A. Multiplicity of the ground state of large alternant organic molecules with conjugated bonds: (do organic ferromagnetics exist?). Theor. Chim. Acta 47, 297–304 (1978).

Article CAS Google Scholar

Morita, Y., Suzuki, S., Sato, K. & Takui, T. Synthetic organic spin chemistry for structurally well-defined open-shell graphene fragments. Nat. Chem. 3, 197–204 (2011).

Article CAS PubMed Google Scholar

Zeng, W. & Wu, J. Open-shell graphene fragments. Chem 7, 358–386 (2021).

Article CAS Google Scholar

Kubo, T. Syntheses and properties of open-shell π-conjugated molecules. Bull. Chem. Soc. Jpn 94, 2235–2244 (2021).

Article CAS Google Scholar

Xiang, Q. & Sun, Z. Doublet open-shell graphene fragments. Chem. Asian J. 17, e202200251 (2022).

Article CAS PubMed Google Scholar

Ahmed, J. & Mandal, S. K. Phenalenyl radical: smallest polycyclic odd alternant hydrocarbon present in the graphene sheet. Chem. Rev. 122, 11369–11431 (2022).

Article CAS PubMed Google Scholar

Yokoi, H., Hiroto, S. & Shinokubo, H. Reversible σ-bond formation in bowl-shaped π-radical cations: the effects of curved and planar structures. J. Am. Chem. Soc. 140, 4649–4655 (2018).

Article CAS PubMed Google Scholar

Jiao, T. et al. Synthesis of monolayer and persistent bilayer graphene fragments by using a radical-mediated coupling approach. Nat. Synth. 2, 1104–1115 (2023).

Article CAS Google Scholar

Pal, S. K. et al. Resonating valence-bond ground state in a phenalenyl-based neutral radical conductor. Science 309, 281–284 (2005).

Article CAS PubMed Google Scholar

Kubo, T. et al. Synthesis, intermolecular interaction, and semiconductive behavior of a delocalized singlet biradical hydrocarbon. Angew. Chem. Int. Ed. 44, 6564–6568 (2005).

Article CAS Google Scholar

Pariyar, A. et al. Switching closed-shell to open-shell phenalenyl: toward designing electroactive materials. J. Am. Chem. Soc. 137, 5955–5960 (2015).

Article CAS PubMed Google Scholar

Rudebusch, G. E. et al. Diindeno-fusion of an anthracene as a design strategy for stable organic biradicals. Nat. Chem. 8, 753–759 (2016).

Article CAS PubMed Google Scholar

Mukherjee, A., Sau, S. C. & Mandal, S. K. Exploring closed-shell cationic phenalenyl: from catalysis to spin electronics. Acc. Chem. Res. 50, 1679–1691 (2017).

Article CAS PubMed Google Scholar

Kushida, T. et al. Boron-stabilized planar neutral π-radicals with well-balanced ambipolar charge-transport properties. J. Am. Chem. Soc. 139, 14336–14339 (2017).

Article CAS PubMed Google Scholar

Ravat, P., Šolomek, T., Häussinger, D., Blacque, O. & Juríček, M. Dimethylcethrene: a chiroptical diradicaloid photoswitch. J. Am. Chem. Soc. 140, 10839–10847 (2018).

Article CAS PubMed PubMed Central Google Scholar

Lombardi, F. et al. Quantum units from the topological engineering of molecular graphenoids. Science 366, 1107–1110 (2019).

Article CAS PubMed Google Scholar

Jousselin-Oba, T. et al. Excellent semiconductors based on tetracenotetracene and pentacenopentacene: from stable closed-shell to singlet open-shell. J. Am. Chem. Soc. 141, 9373–9381 (2019).

Article CAS PubMed Google Scholar

Imran, M., Wehrmann, C. M. & Chen, M. S. Open-shell effects on optoelectronic properties: antiambipolar charge transport and anti-kasha doublet emission from a N-substituted bisphenalenyl. J. Am. Chem. Soc. 142, 38–43 (2019).

Article PubMed Google Scholar

Zong, C. et al. Isomeric dibenzoheptazethrenes for air‐stable organic field‐effect transistors. Angew. Chem. Int. Ed. 60, 16230–16236 (2021).

Article CAS Google Scholar

Prajapati, B. et al. Tetrafluorenofulvalene as a sterically frustrated open-shell alkene. Nat. Chem. 15, 1541–1548 (2023).

Article CAS PubMed PubMed Central Google Scholar

Wang, W. et al. A triply negatively charged nanographene bilayer with spin frustration. Angew. Chem. Int. Ed. 62, e202217788 (2023).

Article CAS Google Scholar

Wang, W. L., Yazyev, O. V., Meng, S. & Kaxiras, E. Topological frustration in graphene nanoflakes: magnetic order and spin logic devices. Phys. Rev. Lett. 102, 157201 (2009).

Article PubMed Google Scholar

Fajtlowicz, S., John, P. E. & Sachs, H. On maximum matchings and eigenvalues of benzenoid graphs. Croat. Chem. Acta 78, 195–201 (2005).

CAS Google Scholar

Borden, W. T. & Davidson, E. R. Effects of electron repulsion in conjugated hydrocarbon diradicals. J. Am. Chem. Soc. 99, 4587–4594 (1977).

Article CAS Google Scholar

Lineberger, W. C. & Borden, W. T. The synergy between qualitative theory, quantitative calculations, and direct experiments in understanding, calculating, and measuring the energy differences between the lowest singlet and triplet states of organic diradicals. Phys. Chem. Chem. Phys. 13, 11792–11813 (2011).

Article PubMed Google Scholar

Inoue, J. et al. The first detection of a Clar’s hydrocarbon, 2,6,10-tri-tert-butyltriangulene: a ground-state triplet of non-Kekulé polynuclear benzenoid hydrocarbon. J. Am. Chem. Soc. 123, 12702–12703 (2001).

Article CAS PubMed Google Scholar

Pavliček, N. et al. Synthesis and characterization of triangulene. Nat. Nanotechnol. 12, 308–311 (2017).

Article PubMed Google Scholar

Arikawa, S., Shimizu, A., Shiomi, D., Sato, K. & Shintani, R. Synthesis and isolation of a kinetically stabilized crystalline triangulene. J. Am. Chem. Soc. 143, 19599–19605 (2021).

Article CAS PubMed Google Scholar

Valenta, L. et al. Trimesityltriangulene: a persistent derivative of Clar’s hydrocarbon. Chem. Commun. 58, 3019–3022 (2022).

Article CAS Google Scholar

Dowd, P. Trimethylenemethane. Acc. Chem. Res. 5, 242–248 (1972).

Article CAS Google Scholar

Hund, F. Zur deutung verwickelter spektren, insbesondere der elemente scandium bis nickel. Z. Phys. 33, 345–371 (1925).

Article CAS Google Scholar

Dowd, P. Tetramethyleneethane. J. Am. Chem. Soc. 92, 1066–1068 (1970).

Article CAS Google Scholar

Kollmar, H. & Staemmler, V. Violation of Hund’s rule by spin polarization in molecules. Theor. Chim. Acta 48, 223–239 (1978).

Article CAS Google Scholar

Salem, L. The sudden polarization effect and its possible role in vision. Acc. Chem. Res. 12, 87–92 (1979).

Article CAS Google Scholar

Karafiloglou, P. The double (or dynamic) spin polarization in π diradicals. J. Chem. Educ. 66, 816–817 (1989).

Article CAS Google Scholar

Burkard, G. Spin-entangled electrons in solid-state systems. J. Phys. Condens. Matter 19, 233202 (2007).

Article Google Scholar

Troiani, F. & Affronte, M. Molecular spins for quantum information technologies. Chem. Soc. Rev. 40, 3119–3129 (2011).

Article CAS PubMed Google Scholar

Liu, J. & Feng, X. Synthetic Tailoring of graphene nanostructures with zigzag‐edged topologies: progress and perspectives. Angew. Chem. Int. Ed. 59, 23386–23401 (2020).

Article CAS Google Scholar

Mishra, S. et al. Topological frustration induces unconventional magnetism in a nanographene. Nat. Nanotechnol. 15, 22–28 (2020).

Article CAS PubMed Google Scholar

Zhao, C. et al. Tailoring magnetism of graphene nanoflakes via tip-controlled dehydrogenation. Phys. Rev. Lett. 132, 046201 (2024).

Article CAS PubMed Google Scholar

Zhao, C. et al. Tunable topological phases in nanographene-based spin-1/2 alternating-exchange Heisenberg chains. Nat. Nanotechnol. 19, 1789–1795 (2024).

Article CAS PubMed Google Scholar

Pogodin, S. & Agranat, I. Clar goblet and related non-Kekulé benzenoid LPAHs. A theoretical study. J. Org. Chem. 68, 2720–2727 (2003).

Article CAS PubMed Google Scholar

Ortiz, R. et al. Exchange rules for diradical π-conjugated hydrocarbons. Nano Lett. 19, 5991–5997 (2019).

Article CAS PubMed Google Scholar

Gil‐Guerrero, S., Melle‐Franco, M., Peña‐Gallego, Á. & Mandado, M. Clar goblet and aromaticity driven multiradical nanographenes. Chem. Eur. J. 26, 16138–16143 (2020).

Article PubMed Google Scholar

Xiang, Q. et al. Stable olympicenyl radicals and their π-dimers. J. Am. Chem. Soc. 142, 11022–11031 (2020).

Article CAS PubMed Google Scholar

Wei, H. et al. A facile approach toward 1, 2-diazabenzo [ghi] perylene derivatives: structures and electronic properties. Chem. Commun. 53, 6740–6743 (2017).

Article CAS Google Scholar

Li, Y. et al. Bay-and ortho-octasubstituted perylenes. Org. Lett. 19, 5094–5097 (2017).

Article CAS PubMed Google Scholar

Abe, M. Diradicals. Chem. Rev. 113, 7011–7088 (2013).

Article CAS PubMed Google Scholar

Eaton, S. S., More, K. M., Sawant, B. M. & Eaton, G. R. Use of the ESR half-field transition to determine the interspin distance and the orientation of the interspin vector in systems with two unpaired electrons. J. Am. Chem. Soc. 105, 6560–6567 (1983).

Article CAS Google Scholar

Moise, G. et al. The electronic spin state of diradicals obtained from the nuclear perspective: the strange case of Chichibabin radicals. ChemPhysChem https://doi.org/10.1002/cphc.202400707 (2025).

Bleaney, B. & Bowers, K. D. Anomalous paramagnetism of copper acetate. Proc. R. Soc. Lond. Ser. A 214, 451–465 (1952).

Article CAS Google Scholar

Kubo, T. Recent progress in quinoidal singlet biradical molecules. Chem. Lett. 44, 111–122 (2014).

Article Google Scholar

Zeng, Z. et al. Pro-aromatic and anti-aromatic π-conjugated molecules: an irresistible wish to be diradicals. Chem. Soc. Rev. 44, 6578–6596 (2015).

Article CAS PubMed Google Scholar

Gopalakrishna, T. Y., Zeng, W., Lu, X. & Wu, J. From open-shell singlet diradicaloids to polyradicaloids. Chem. Commun. 54, 2186–2199 (2018).

Article Google Scholar

Wu, J. Diradicaloids (Jenny Stanford Publishing, 2022).

Hu, X. et al. Air stable high-spin blatter diradicals: non-Kekulé versus Kekulé structures. J. Mater. Chem. C 7, 6559–6563 (2019).

Article CAS Google Scholar

Borissov, A., Chmielewski, P. J., Gómez García, C. J., Lis, T. & Stępień, M. Dinor [7] helicene and beyond: divergent synthesis of chiral diradicaloids with variable open‐shell character. Angew. Chem. Int. Ed. 62, e202309238 (2023).

Article CAS Google Scholar

Wu, H. et al. Stable π-extended thio[7]helicene-based diradical with predominant through-space spin–spin coupling. J. Am. Chem. Soc. 146, 7480–7486 (2024).

Article CAS PubMed Google Scholar

Konishi, A. et al. Synthesis and characterization of teranthene: a singlet biradical polycyclic aromatic hydrocarbon having Kekulé structures. J. Am. Chem. Soc. 132, 11021–11023 (2010).

Article CAS PubMed Google Scholar

Sanvito, S. Molecular spintronics. Chem. Soc. Rev. 40, 3336–3355 (2011).

Article CAS PubMed Google Scholar

Gaita-Ariño, A., Luis, F., Hill, S. & Coronado, E. Molecular spins for quantum computation. Nat. Chem. 11, 301–309 (2019).

Article PubMed Google Scholar

Lombardi, F. et al. Synthetic tuning of the quantum properties of open-shell radicaloids. Chem 7, 1363–1378 (2021).

Article CAS Google Scholar

Zhang, D. et al. An air-stable carbon-centered triradical with a well-addressable quartet ground State. J. Am. Chem. Soc. 146, 21752–21761 (2024).

Article PubMed Google Scholar

Download references

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).

Department of Chemistry, National University of Singapore, Singapore, Singapore

Tianyu Jiao, Shaofei Wu & Jishan Wu

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

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

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

Shang-Da Jiang

You can also search for this author in PubMed Google Scholar

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.

Correspondence to Shang-Da Jiang or Jishan Wu.

The authors declare no competing interests.

Nature Chemistry thanks the anonymous reviewers for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary Figs. 1–32.

Crystallographic data for structure 5 (CCDC 2376440).

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

Cartesian coordinates for the calculated structures.

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

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

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and permissions

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

Download citation

Received: 18 September 2024

Accepted: 12 February 2025

Published: 17 March 2025

DOI: https://doi.org/10.1038/s41557-025-01776-1

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

Baystreet.ca - Why Nvidia's GTC could be a negative for Marvell and other optical stocks

VIAVI Launches Advanced 800G Field Testing Module for Network Testing | VIAV Stock News