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Tunable valence tautomerism in lanthanide–organic alloys

Nature Chemistry (2024)Cite this article

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Abstract

The inimitable electronic structures of the lanthanide (Ln) ions are key to advanced materials and technologies involving these elements. The trivalent ions are ubiquitous and are used much more widely than the divalent and tetravalent analogues, which possess vastly different optical and magnetic properties. Hence, alteration of the valence electron count by external stimuli can lead to dramatic changes in materials properties. Compounds exhibiting a temperature-induced complete Ln(III) ⇄ Ln(II) switch, referred to as a valence tautomeric (VT) transition, are rare. Here we present an abrupt and hysteretic VT transition in a lanthanide-based coordination polymer, SmI2(pyrazine)3, driven by the interconversion of Sm(II)–pyrazine(0) and Sm(III)–pyrazine(·−) redox pairs. Alloying SmI2(pyrazine)3 with Yb(II) yields isomorphous Sm1–xYbxI2(pyrazine)3 solid solutions with VT transition critical temperatures ranging widely from 200 K to ∼50 K at ambient pressure. These findings demonstrate a simple strategy to realize thermally switchable magnetic materials with chemically tunable transition temperatures.

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Fig. 1: Single-crystal X-ray diffraction structure of SmI2(pyz)3.
Fig. 2: Magnetic properties of SmI2(pyz)3.
Fig. 3: X-ray absorption spectroscopy.
Fig. 4: Magnetic properties of Sm1–xYbxI2(pyz)3 solid solutions.

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Data availability

All data are available in the main text or in the Supplementary Information. Crystallographic data for the structures reported in this Article have been deposited at the Cambridge Crystallographic Data Centre, under deposition numbers CCDC 2285789 (SmI2(pyz)3 at 230 K), 2285788 (SmI2(pyz)3 at 170 K), 2300988 (YbI2(pyz)3 at 230 K), 2300987 (YbI2(pyz)3 at 170 K) and 2285790 (YbI2(pyz)3 at 120 K). 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

K.S.P. thanks the VILLUM Foundation for a VILLUM Young Investigator+ (42094) grant, the Independent Research Fund Denmark for a DFF-Sapere Aude Starting grant (no. 0165-00073B) and the Carlsberg Foundation for a research infrastructure grant (no. CF17-0637). The X-ray spectroscopy experiments were performed at the ID12 beamline at the European Synchrotron Radiation Facility (Grenoble, France). We thank the Danish Agency for Science, Technology, and Innovation for funding the instrument centre Danscatt.

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Authors and Affiliations

  1. Department of Chemistry, Technical University of Denmark, Kongens Lyngby, Denmark

    Maja A. Dunstan, Anna S. Manvell, Frédéric Aribot & Kasper S. Pedersen

  2. European Synchrotron Radiation Facility, Grenoble, France

    Nathan J. Yutronkie & Andrei Rogalev

  3. Department of Chemistry, University of Copenhagen, Copenhagen, Denmark

    Jesper Bendix

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Contributions

K.S.P. and M.A.D. conceived and planned the research project. M.A.D., F.A. and A.S.M. developed and performed the synthesis and the crystallographic analysis. M.A.D., K.S.P. and J.B. performed the characterization of the magnetic properties. N.J.Y. and A.R. acquired and analysed the X-ray spectroscopic data. J.B. performed the DFT calculations. The manuscript was written by K.S.P. and M.A.D. with input from all coauthors. All authors have given their consent to the publication of the manuscript.

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Correspondence to Maja A. Dunstan or Kasper S. Pedersen.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–13, Tables 1–4 and Discussion 1.

Supplementary Data 1

Crystallographic data for SmI2(pyz)3 at 230 K; CCDC reference 2285789.

Supplementary Data 2

Crystallographic data for SmI2(pyz)3 at 170 K; CCDC reference 2285788.

Supplementary Data 3

Crystallographic data for YbI2(pyz)3 at 230 K; CCDC reference 2300988.

Supplementary Data 4

Crystallographic data for YbI2(pyz)3 at 170 K; CCDC reference 2300987.

Supplementary Data 5

Crystallographic data for YbI2(pyz)3 at 120 K; CCDC reference 2285790.

Supplementary Data 5

Source Data for Supplementary Figs. 1, 2, 4, 5, 7 and 9–13.

Source data

Source Data Fig. 2

Source data for Fig. 2—magnetic data.

Source Data Fig. 3

Source data for Fig. 3—normalized XANES data.

Source Data Fig. 4

Source data for Fig. 4—magnetic data for solid solutions.

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Dunstan, M.A., Manvell, A.S., Yutronkie, N.J. et al. Tunable valence tautomerism in lanthanide–organic alloys. Nat. Chem. (2024). https://doi.org/10.1038/s41557-023-01422-8

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