Metal-organic magnets with large coercivity and ordering temperature up to 242°C

Towards next-generation molecule-based magnets

Magnets are to be found everywhere in our daily lives, whether in satellites, telephones or on fridge doors. However, they are made up of heavy inorganic materials whose component elements are, in some cases, of limited availability.

Now, researchers from the CNRS, the University of Bordeaux and the ESRF (European Synchrotron Radiation Facility in Grenoble) have developed a new lightweight molecule-based magnet, produced at low temperatures, and exhibiting unprecedented magnetic properties. This compound, derived from coordination chemistry, contains chromium, an abundant metal, and inexpensive organic molecules.  This is the first molecule-based magnet that exhibits a ‘memory effect’ (i.e. it is capable of maintaining one of its two magnetic states) up to a temperature of 240°C. This effect is measured by what is known as a coercive field, which is 25 times higher at room temperature for this novel material than for the most efficient of its molecule-based predecessors.  This property therefore compares well with that of certain purely inorganic commercial magnets. The discovery, published on 30 October in Science, opens up highly promising prospects, which could lead to next-generation magnets complementary to current systems.

Reference & authors: P. Perlepe, I. Oyarzabal, A. Mailman, M. Yquel, M. Platunov, I. Dovgaliuk, M. Rouzières, P. Négrier, D. Mondieig, E. A. Suturina, M.A. Dourges, S. Bonhommeau, R. A. Musgrave, K. S. Pedersen, D. Chernyshov, F. Wilhelm, A. Rogalev, C. Mathonière, R. Clérac, Metal-organic magnets with large coercivity and ordering temperatures up to 242°C”, Science, Vol. 370, Issue 6516, pp. 587-592, (2020) – 10.1126/science.abb3861Abstract – Reprint Full text

Online comments and publications

Acknowledgments: This work was supported by the University of Bordeaux, the Région Nouvelle Aquitaine, Quantum Matter Bordeaux, the Basque Government, the University of the Basque Country, the Villum Fonden, the University of Jyväskylä, the Academy of Finland, the Centre National de la Recherche Scientifique (CNRS) and the ESRF-The European Synchrotron.

Contact: clerac@crpp-bordeaux.cnrs.fr

MagLAB is talking about us… “Molecular magnetic building blocks”

This study reports the first transition metal compounds featuring mixed fluoride–cyanide ligands. A significant enhancement of the magnetic anisotropy, as compared to the pure fluoride ligated compounds, is demonstrated by combined analysis of high-field electron paramagnetic resonance (HF-EPR) spectroscopy and magnetization measurements.

What did scientists discover?

This study reports the first transition metal molecules featuring both fluorine and cyanide ligands (see “branches” attached to the metal atom (M) in the molecules at the top of the figure). A strong and significant enhancement of the non-uniformity of the magnetism, the “magnetic anisotropy” for the trans-[ReIVF4(CN)2]2– complex (shown in the upper right) was discovered by combined high-field magnetization and electron paramagnetic resonance (EPR) spectroscopy (see lower Figure).

Why is this important?

This research highlights an efficient new strategy for synthesizing molecular building blocks based on heavier transition metals that feature relatively large magnetic moments and very strong magnetic anisotropy. Such building blocks may form the basis for future high-performance magnetic materials used in high-density information storage applications.

Read more on MagLab website:

https://nationalmaglab.org/user-facilities/emr/emr-publications/highlights-emr/molecular-magnetic-building-blocks

M3 research in the news: Uranium (IV) magnetism

Rodolphe Clérac’s research has been recently cited by the CNRS Institute of Chemistry.  

L’origine du magnétisme atypique de l’ion actinide Uranium(IV) enfin comprise

Les ions de terres rares et d’actinides, qui présentent des propriétés magnétiques remarquables étant données leurs structures électroniques, sont de bons candidats pour entrer dans la composition des aimants de nouvelle génération. Mais alors pourquoi, de manière atypique, l’uranium au degré oxydation IV n’est que faiblement magnétique, alors qu’au regard de sa structure électronique, ses propriétés devraient être comparables aux autres analogues de terres rares ou d’actinides?

Read the rest of the article here

Fabien Durola’s work featured in l’Actualité Chimique

Des molécules aromatiques et torsadées

Fabien Durola's work featured in l'Actualité Chimique

“La chimie organique est régie par de nombreuses règles
établies au fil des expériences. Aujourd’hui, les chimistes
explorent les limites de ces lois. Comme Fabien Durola et son
équipe du Centre de recherche Paul Pascal (CNRS/Université
de Bordeaux), qui prouvent avec leur cyclo-tris-[5]hélicène
qu’un composé aromatique peut être triplement torsadé,
esthétique et atypique, de par ses propriétés électroniques
induites.”

Read more (in French)

M3 research has been recently highlighted by the CNRS Institute of Chemistry

This work demonstrates the possibility of modulating the spin state of the FeII sites and subsequently the magnetic properties of a [2×2] FeII grid-like complex by variation of the degree of deprotonation of the hydrazine-based N-H sites of the ligand in the complex. Evidence has been provided, both in the solid state and in solution, towards understanding the strong influence of the spin-crossover process on the pKas of the grid ligands, which exhibit a unique deprotonation pattern. The present study provides a demonstration of the effect of spin state switching of a chemical property, here on ligand pKa in a metallosupramolecular grid.

modulating the spin state of the FeII sites and subsequently the magnetic properties of a [2x2] FeII  grid-like complex

Sébastien Dhers, Abhishake Mondal, David Aguilà, Juan Ramírez, Sergi Vela, Pierre Dechambenoit, Mathieu Rouzières, Jonathan R. Nitschke, Rodolphe Clérac & Jean-Marie Lehn. Spin State Chemistry: Modulation of Ligand pKa by Spin State Switching in a [2×2] Iron(II) Grid-Type Complex J. Am. Chem. Soc. 2018, 140 (26), pp 8218–8227 DOI : 10.1021/jacs.8b03735

See also the Institut de Chimie website of the CNRS

M3 research on MEMS cited by the CNRS Institute of Chemistry

Incorporating functional molecules into sensor devices is an emerging area in molecular electronics that aims at exploiting the sensitivity of different molecules to their environment and turning it into an electrical signal. Among the emergent and integrated sensors, microelectromechanical systems (MEMS) are promising for their extreme sensitivity to mechanical events. However, to bring new functions to these devices, the functionalization of their surface with molecules is required. Herein, we present original electronic devices made of an organic microelectromechanical resonator functionalized with switchable magnetic molecules. The change of their mechanical properties and geometry induced by the switching of their magnetic state at a molecular level alters the device’s dynamical behavior, resulting in a change of the resonance frequency. We demonstrate that these devices can be operated to sense light or thermal excitation. Moreover, thanks to the collective interaction of the switchable molecules, the device behaves as a non-volatile memory. Our results open up broad prospects of new flexible photo- and thermo-active hybrid devices for molecule-based data storage and sensors.

Incorporating functional molecules into sensor devices is an emerging area in molecular electronics

Matias Urdampilleta, Cedric Ayela, Pierre-Henri Ducrot, Daniel Rosario-Amorin, Abhishake Mondal, Mathieu Rouzières, Pierre Dechambenoit, Corine Mathonière, Fabrice Mathieu, Isabelle Dufour et Rodolphe Clérac
Molecule-based microelectromechanical sensors
Scientific Reports – Mai 2018
DOI: 10.1038/s41598-018-26076-2

See also the Institut de Chimie website of the CNRS

Fabien Durola, Jean-Marie Lehn and Jean-Pierre Sauvage on the 2016 Nobel Prize in Chemistry

Listen to three generations of scientists discuss the 2016 Nobel Prize in Chemistry for “for the design and synthesis of molecular machines”, awarded to Jean-Pierre Sauvage, Sir J. Fraser Stoddart and Bernard L. Feringa on “La Une de la Science” at France Inter.

Fabien, who did his thesis research with J.-P. Sauvage, gives a particularly lucid explanation and history of molecular machines. J.-P. Sauvage describes some of his most important discoveries, rotaxane and molecular muscles. The thesis director of J.-P. Sauvage, J.-M. Lehn, himself winner of the Nobel Prize in Chemistry in 1987, offers his congratulations and advice on living with the Nobel Prize.

Listen to the entire interview at https://www.franceinter.fr/emissions/la-une-de-la-science/la-une-de-la-science-05-octobre-2016

CNRS INC Focus on Molecular Magnet…

En direct des laboratoires de l’institut de Chimie

Vers une synthèse rationnelle d’aimants moléculaires

L’intérêt des aimants moléculaires pour de nombreuses applications telles que la spintronique, le stockage des données ou encore l’information quantique n’est plus à démontrer. Mais aucune stratégie de synthèse ne paraît totalement satisfaisante car il est toujours très complexe de prédire leur anisotropie magnétique, propriété intimement liée à leurs applications. Des chercheurs de l’Institut des sciences moléculaires de Marseille (CNRS, AMU) et du Département de chimie moléculaire à Grenoble (CNRS, Université Grenoble Alpes) en collaboration avec le Centre de recherche Paul Pascal (CNRS, Université de Bordeaux) ont étudié cette anisotropie magnétique pour une série de complexes de cobalt en combinant des données expérimentales et des calculs de chimie quantique. Ils ont ainsi pu définir l’origine physique de l’anisotropie magnétique. Ces travaux sont publiés dans Chemistry-A European Journal.

Read more: http://www.cnrs.fr/inc/communication/direct_labos/orio.htm