Formation of the layered conductive magnet CrCl2(pyrazine)2 through redox-active coordination chemistry

Abstract

The unique properties of graphene, transition-metal dichalcogenides and other two-dimensional (2D) materials have boosted interest in layered coordination solids. In particular, 2D materials that behave as both conductors and magnets could find applications in quantum magnetoelectronics and spintronics. Here, we report the synthesis of CrCl2(pyrazine)2, an air-stable layered solid, by reaction of CrCl2 with pyrazine (pyz). This compound displays a ferrimagnetic order below 55 K, reflecting the presence of strong magnetic interactions. Electrical conductivity measurements demonstrate that CrCl2(pyz)2 reaches a conductivity of 32 mS cm–1 at room temperature, which operates through a 2D hopping-based transport mechanism. These properties are induced by the redox-activity of the pyrazine ligand, which leads to a smearing of the Cr 3d and pyrazine π states. We suggest that the combination of redox-active ligands and reducing paramagnetic metal ions represents a general approach towards tuneable 2D materials that consist of charge-neutral layers and exhibit both long-range magnetic order and high electronic conductivity.

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Fig. 1: Structure of CrCl2(pyz)2.
Fig. 2: XAS at the pre-K-edge region.
Fig. 3: Magnetic properties for CrCl2(pyz)2.
Fig. 4: DFT calculations.
Fig. 5: XMCD at the Cr K-edge.
Fig. 6: Electrical conductivity.

Data availability

All data generated and analysed in this study are included in the Article and its Supplementary Information, and are also available from the authors upon request. Crystallographic information has been deposited in the Cambridge Crystallographic Data Centre under accession codes CCDC 1563526 (CrCl2(pyz)2) and CCDC 1563527 (Cr(iii)).

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Acknowledgements

K.S.P. thanks the VILLUM Foundation for a VILLUM Young Investigator grant (15374). K.S.P. and R.C. thank the Danish Research Council for Independent Research for a DFF-Sapere Aude Research Talent grant (4090-00201), the University of Bordeaux, the Région Aquitaine, the CNRS, the GdR MCM-2: Magnétisme et Commutation Moléculaires and the MOLSPIN COST action CA15128. M.L.A. and J.R.L. thank the National Science Foundation (grant DMR-1611525) for funding support. K.B. is thankful for funding by the Danish National Research Foundation (Center for Materials Crystallography, DNRF93). D.N.W. thanks the Diamond Light Source Ltd for beam time (I11; EE13284). Theory and computation were supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences (Theory FWP) Materials Sciences and Engineering Division (DE-AC02-05CH11231). R.C. and J.R.L. are grateful to the France-Berkeley Fund and the CNRS for PICS no. 06485. Work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under contract no. DE-AC02-05CH11231. J. Bendix, E. Suturina, B. B. Iversen, L. E. Darago, F. Hof, T. Maris and E. Lebraud are thanked for experimental assistance and helpful discussions.

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Contributions

K.S.P. and R.C. conceived, planned and designed the research project. K.S.P., P.P., D.W., A.R. and D.S. executed the syntheses and the chemical and crystallographic analyses. L.V. obtained and analysed the scanning electron microscopy data. M.L.A., M.R., P.P., J.R.L. and R.C. performed and analysed the electrical conductivity experiments. M.R., K.S.P. and R.C. performed and analysed the magnetic susceptibility measurements. Z.L. and K.S.P. obtained and analysed the UPS and NIR–IR data. K.B. and K.S.P. obtained and analysed the Seebeck measurements. S.E.R.-L., J.N. and K.S.P. performed the DFT studies. F.W., A.R., K.S.P., P.P. and R.C. executed the X-ray spectroscopy experiments and analysed the results. All coauthors were involved in the writing of the manuscript and they have all given their consent to its publication.

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Correspondence to Kasper S. Pedersen or Rodolphe Clérac.

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Supplementary information

Supplementary Information

Additional experimental and computation details; structural, magnetic, electronic, spectroscopic and computational data; Supplementary Figures 1–15; Supplementary Table 1 and Supplementary References 1–23

Crystallographic data

CIF for compound CrCl2(pyz)2; CCDC reference: 1563526

Crystallographic data

CIF for compound Cr(iii); CCDC reference: 1563527

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Pedersen, K.S., Perlepe, P., Aubrey, M.L. et al. Formation of the layered conductive magnet CrCl2(pyrazine)2 through redox-active coordination chemistry. Nature Chem 10, 1056–1061 (2018). https://doi.org/10.1038/s41557-018-0107-7

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