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Accueil > Les équipes > Equipe de Recherche en Matériaux Moléculaires et Spectroscopies (ERMMES) > Publications

Publications

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2023



  • J. Glatz, M. Donnart, G. Gontard, Y. Li, et R. Lescouëzec, « Design of Redox-Active Cs⊂{Fe4Ni4} Cyanide-Bridged Cage Complexes Bearing Monodentate Ligands: Synthesis, Structure, and Electronic Properties », Crystal Growth & Design, vol. 23, nᵒ 3, p. 1709-1717, mars 2023.
    Résumé : In recent years, strong efforts have been devoted to the design and crystallization of molecular models of the cyanido-bridged inorganic polymers known as “Prussian Blue Analogues” (PBA). In this work, we more specifically focus on soluble octametallic complexes that represent an elemental unit of the PBA cubic network. The self-assembly of tris-cyanido, the fac-[FeIII(Tp)(CN)3]− (Tp = hydro-tris(pyrazol-1-yl-borate) complex, and Ni(II) salts is shown to lead to {[Fe(Tp)(CN)3]4[Ni(S)3]4} procubes, where the Ni(II) ions are coordinated to labile solvent molecules (S: DMF or CH3CN). 1H and 133Cs paramagnetic NMR studies show that (i) the cubic complex is relatively stable during several days in solution, in particular in acetonitrile and (ii) a Cs+ ion can be inserted inside the cubic cavity as revealed by the presence of a strongly shifted 133Cs paramagnetic signal near −800 ppm at 300 K. The resulting Cs⊂{[Fe(Tp)(CN)3]4[Ni(S)3]4}5+ procube shows an enhanced stability as shown by time dependent 1H and 133Cs paramagnetic NMR spectra collected during several weeks. FT-IR spectra confirm the expected Fe(III) and Ni(II) redox states, with the occurrence of a single characteristic cyanide stretching vibration near 2170 cm–1. The Fe(III) redox state is also confirmed by cyclic voltammetry experiments in acetonitrile, with the occurrence of four pseudoreversible reduction events that can be assigned to the successive reduction of the FeIII ions in the Cs procube. Although these procubes could not be isolated as single crystals, the substitution of the labile coordinated solvent of the Cs-containing procube by N-donor imidazole monodentate ligands allows the crystallization of the novel Cs⊂{[Fe(Tp)(CN)3]4-[NiII(Im)3]4}Cl3 (Im = 1H imidazole) cubic complex by slow diffusion of ether into a DMF mother solution. The analyses of this cube demonstrate that in solution in ambient condition, Fe(III) centers are gradually reduced to Fe(II). The presence of three chlorides as counterions suggests that the cube can be isolated in the FeII2FeIII2NiII4 redox state. The presence of at least two Fe(II) ions is actually confirmed by cyclic voltammetry experiment in DMF and FT-IR spectroscopy. An intermediate state FeIIFeIII3NiII4 can be isolated by isolating fresh crystals (ca. 72 h) as demonstrated by FT-IR, cyclic voltammetry, and the magnetic measurements, that also reveal the presence of paramagnetic ferromagnetic interactions between the low-spin FeIII and NiII ions.
    Mots-clés : ERMMES, POLE 2.
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2022



  • S. De, A. Flambard, B. Xu, L. ‐M. Chamoreau, G. Gontard, L. Lisnard, Y. Li, M. ‐L. Boillot, et R. Lescouëzec, « Molecular Magnetic Materials Based on {Co <sup>III</sup> (Tp*)(CN) <sub>3</sub> } <sup>−</sup> Cyanidometallate: Combined Magnetic, Structural and <sup>59</sup> Co NMR Study », Chemistry – A European Journal, vol. 28, nᵒ 50, sept. 2022.


  • J. Glatz, J. - R. Jiménez, L. Godeffroy, H. J. von Bardeleben, L. Fillaud, E. Maisonhaute, Y. Li, L. - M. Chamoreau, et R. Lescouëzec, « Enlightening the Alkali Ion Role in the Photomagnetic Effect of FeCo Prussian Blue Analogues », Journal of the American Chemical Society, vol. 144, nᵒ 24, p. 10888-10901, juin 2022.


  • P. Kumar, A. Swain, J. Acharya, Y. Li, V. Kumar, G. Rajaraman, E. Colacio, et V. Chandrasekhar, « Synthesis, Structure, and Zero-Field SMM Behavior of Homometallic Dy2, Dy4, and Dy6 Complexes », Inorganic Chemistry, vol. 61, nᵒ 30, p. 11600-11621, août 2022.
    Résumé : The synthesis, structure, and magnetic properties of three DyIII complexes of different nuclearity, [Dy2(H2L)2(NO3)] [NO3]·2H2O·CH3OH (1), [Dy4(HL)2(piv)4(OH)2] (2), and [Dy6(H2L)3(μ3–OH)(μ3–CO3)3(CH3OH)4(H2O)8] 5Cl·3H2O (3) [(H4L) = 6-((bis(2-hydroxyethyl)amino)-N′-(2-hydroxybenzylidene)picolinohydrazide)], are described. This variety of complexes with the same ligand could be obtained by playing with the metal-to-ligand molar ratio, the type of DyIII salt, the kind of base, and the presence/absence of coligand. 1 is a dinuclear complex, while 2 is a tetranuclear assembly with a butterfly-shaped topology. 3 is a homometallic hexanuclear complex that exhibits a propeller-shaped topology. Interestingly, in this complex 3, three atmospheric carbon dioxide molecules are trapped in the form of carbonate ions, which assist in holding the hexanuclear complex together. All of the complexes reveal a slow relaxation of magnetization even in zero applied field. Complex 1 is a zero-field SMM with an effective energy barrier (Ueff) of magnetization reversal equal to 87(1) K and a relaxation time of τ0 = 6.4(3) × 10–9 s. Under an applied magnetic field of 0.1 T, these parameters change to Ueff = 101(3) K, τ0 = 2.5(1) × 10–9 s. Complex 2 shows zero-field SMM behavior with Ueff = 31(2) K, τ0 = 4.2(1) × 10–7 s or τ01 = 2(1) × 10–7 s, Ueff1 = 37(8) K, τ02 = 5(6) × 10–5 s, and Ueff2 = 8(4) by considering two Orbach relaxation processes, while 3, also a zero-field SMM, shows a double relaxation of magnetization [Ueff1 = 62.4(3) K, τ01 = 4.6(3) × 10–8 s, and Ueff1 = 2(1) K, τ02 = 4.6(2) × 10–5 s]. The ab initio calculations indicated that in these complexes, the Kramer’s ground doublet is characterized by an axial g-tensor with the prevalence of the mJ = ±15/2 component, as well as that due to the weak magnetic coupling between the metal centers, the magnetic relaxation, which is dominated by the single DyIII centers rather than by the exchange-coupled states, takes place via Raman/Orbach or TA-QTM. Moreover, theoretical calculations support a toroidal magnetic state for complex 2.
    Mots-clés : ERMMES, POLE 2.
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  • A. Li, L. - M. Chamoreau, B. Baptiste, L. Delbes, Y. Li, F. Lloret, Y. Journaux, et L. Lisnard, « Solvothermal Synthesis, Temperature-Dependent Structural Study, and Magnetic Characterization of a Multipolydentate Oxamate-Based 2D Coordination Network », Crystal Growth & Design, vol. 22, nᵒ 12, p. 7518-7526, déc. 2022.
    Résumé : A multipolydentate N-substituted oxamate ligand bearing an additional carboxylato group has been successfully reacted in solvothermal conditions to form the 2D coordination network (TMA)3[CuMn(paba)2(OAc)]·8H2O (1). This coordination network displays a brick-wall type morphology with, thanks to the augmented connectivity of the ligand, a lower than usual metal ion nuclearity for the building subunit. Temperature-dependent structural studies indicate that the layered structure undergoes dehydration at 90 °C and remains stable up to 200 °C. Magnetic characterizations show that 1 behaves as a ferrimagnet, with a Curie temperature of 2.8 K.
    Mots-clés : ERMMES, POLE 2.
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  • C. Mathonière, D. Mitcov, E. Koumousi, D. Amorin-Rosario, P. Dechambenoit, S. Fatima Jafri, P. Sainctavit, C. Cartier dit Moulin, L. Toupet, E. Trzop, E. Collet, M. - A. Arrio, A. Rogalev, F. Wilhelm, et R. Clérac, « Metal-to-metal electron transfer in a cyanido-bridged {Fe <sub>2</sub> Co <sub>2</sub> } square complex followed by X-ray diffraction and absorption techniques », Chemical Communications, vol. 58, nᵒ 86, p. 12098-12101, 2022.
    Résumé : Combining X-ray diffraction and absorption spectroscopy, a full picture of the thermal-, light- and X-ray-induced metal-to-metal electron transfer in a cyanido-bridged molecular Fe/Co square is obtained, demonstrating the concerted and concomitant role played by the Fe and Co sites. , The switching properties of a cyanido-bridged Fe/Co square molecule were investigated by single-crystal X-ray diffraction and X-ray absorption spectroscopy at both Fe and Co K-edges. Combining these two techniques, a complete picture of the thermal-, light- and X-ray-induced metal-to-metal electron transfer is obtained, illustrating the concerted role played by the Fe and Co sites.
    Mots-clés : ERMMES, POLE 2.
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2021



  • A. Benchohra, Y. Li, L. - M. Chamoreau, B. Baptiste, E. Elkaïm, N. Guillou, D. Kreher, et R. Lescouëzec, « The Atypical Hysteresis of [Fe(C6F5Tp)2]: Overlay of Spin-Crossovers and Symmetry-Breaking Phase Transition », Angewandte Chemie, vol. 133, nᵒ 16, p. 8885-8889, 2021.
    Résumé : The [FeII(C6F5Tp)2] spin-crossover complex is an atypical molecular switch, which can be converted upon annealing between two archetypal spin-crossover behaviours: from an extremely gradual spin-crossover to a broad hysteretic spin-transition (of ca. 65 K). The hysteresis shows an uncommon “rounded shape” that is reproducible upon cycling temperature. In depth structural studies reveal a first crystal phase transition, which occurs upon melting and recrystallizing at high temperature. This first irreversible transition is associated with a radical change in the crystal packing. More importantly, the “rounded and broad” hysteretic transition is shown to occur in a non-cooperative SCO system and is associated with the occurrence of a symmetry-breaking phase transition that appears when roughly ca. 50 % of the SCO complexes are switched.
    Mots-clés : ERMMES, POLE 2, POLYMERES.
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  • J. - R. Jiménez, B. Xu, H. E. Said, Y. Li, J. von Bardeleben, L. - M. Chamoreau, R. Lescouëzec, S. Shova, D. Visinescu, M. - G. Alexandru, J. Cano, et M. Julve, « Field-induced single ion magnet behaviour of discrete and one-dimensional complexes containing [bis(1-methylimidazol-2-yl)ketone]-cobalt(II) building units », Dalton Transactions, vol. 50, nᵒ 44, p. 16353-16363, nov. 2021.
    Résumé : We describe herein the first examples of six-coordinate CoII single-ion magnets (SIMs) based on the β-diimine Mebik ligand [Mebik = bis(1-methylimidazol-2-yl)ketone]: two mononuclear [CoII(Rbik)2L2] complexes and one mixed-valence {CoIII2CoII}n chain of formulas [CoII(Mebik)(H2O)(dmso)(μ-NC)2CoIII2(μ-2,5-dpp)(CN)6]n·1.4nH2O (3) [L = NCS (1), NCSe (2) and 2,5-dpp = 2,5-bis(2-pyridyl)pyrazine (3)]. Two bidentate Mebik molecules plus two monodentate N-coordinated pseudohalide groups in cis positions build somewhat distorted octahedral surroundings around the high-spin cobalt(II) ions in 1 and 2. The diamagnetic [CoIII2(μ-2,5-dpp)(CN)8]2− metalloligand coordinates the paramagnetic [CoII(Mebik)(H2O)(dmso)]2+ complex cations in a bis-monodentate fashion to afford neutral zigzag heterobimetallic chains in 3. Ab initio calculations, and cryomagnetic dc (2.0–300 K) and ac (2.0–12 K) measurements as well as EPR spectroscopy for 1–3 show the existence of magnetically isolated high-spin cobalt(II) ions with D values of 59.84–89.90 (1), 66.32–93.90 (2) and 70.40–127.20 cm−1 (3) and field-induced slow relax

    ation of the magnetization, being thus new examples of SIMs with transversal magnetic anisotropy. The analysis of their relaxation dynamics reveals that the relaxation of the magnetization occurs by the Raman (with values of the n parameter covering the range 6.0–6.8) and direct spin-phonon processes.
    Mots-clés : ERMMES, POLE 2.
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  • A. Li, L. - M. Chamoreau, B. Baptiste, Y. Li, Y. Journaux, et L. Lisnard, « Solvothermal synthesis, structure and magnetic properties of heterometallic coordination polymers based on a phenolato-oxamato co-bidentate-tridentate ligand », Dalton Transactions, vol. 50, nᵒ 2, p. 681-688, janv. 2021.
    Résumé : The use of solvothermal conditions has succesfully led to the preparation of heterometallic 1D coordination polymers from a co-bidentate-tridentate phenolato-oxamato ligand. The reaction of the N-(2-hydoxyphenyl)oxamic acid (ohpma) with acetate salts of transition metal ions at 80 °C has yielded the heterobimetallic [Cu(ohpma)M(OAc)(DMF)2] (M = Co (1); Mn (2)) and the heterotrimetallic [Cu(ohpma)Co0.57Mn0.43(OAc)(DMF)2] (3) chain compounds. Single-crystal and powder diffraction studies show that the polymers are isostructural. Magnetic studies suggest the existence of an inter-chain two-dimensional antiferromagnetic interaction taking place in compounds 1–3.
    Mots-clés : ERMMES, POLE 2.
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  • A. Li, J. Forté, Y. Li, Y. Journaux, et L. Lisnard, « Synthesis, structure and magnetic properties of an oxamate-based 1D coordination polymer built on pentametallic links », Inorganica Chimica Acta, vol. 521, p. 120320, juin 2021.
    Résumé : The solvothermal reaction of the hexadentate 2-(oxamato)benzoic acid ligand (oaba) with copper(II) and cobalt(II) ions has yielded the [Cu4Co3(oaba)4(OH)2(DMF)6]·2(DMF)·1H2O (1) 1D coordination polymer. The single-crystal X-ray diffraction study reveals the formation of a neutral chain built from pentametallic complexes where each multi-polydentate ligand bridges four metal centres. The atypical morphology observed here for an oxamate-based 1D polymer arises from the use of a ligand bearing extra coordination sites. Magnetometry indicates strong dominating antiferromagnetic interactions within the polymer resulting in a non-zero ferrimagnetic state at low temperature.
    Mots-clés : ERMMES, POLE 2.
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  • P. P. Mudoi, A. Choudhury, Y. Li, R. Lescouëzec, R. Marimuthu, et N. Gogoi, « Observation of Protonation-Induced Spin State Switching in a Cyanido-Bridged {Fe2Co2} Molecular Square », Inorganic Chemistry, vol. 60, nᵒ 23, p. 17705-17714, déc. 2021.
    Résumé : The self-assembly of [Co(MeTPyA)(CH3COO)]PF6 (1) and [Fe(bbp)(CN)3]2– affords a cyanido-bridged square-shaped {Fe2Co2} tetranuclear complex, [{Co(MeTPyA)(μ2-NC)2Fe(bbp)(CN)}2]·3H2O (2; MeTPyA = tris((3,5-dimethylpyrazol-1-yl)methyl)amine and H2bbp = bis(2-benzimidazolyl)pyridine). The possibility of inducing an intramolecular electron transfer coupled spin transition in 2 by employing protonation as an external stimulant is explored. UV–visible spectrophotometric measurements, electrochemical and 1H NMR studies establish that a reversible intramolecular electron transfer coupled spin transition can be triggered in 2 upon addition of either acid or base.
    Mots-clés : ERMMES, POLE 2.
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  • L. Zhang, M. - A. Arrio, S. Mazerat, L. Catala, W. Li, E. Otero, P. Ohresser, L. Lisnard, C. Cartier dit Moulin, T. Mallah, et P. Sainctavit, « Magnetic Hysteresis in a Monolayer of Oriented 6 nm CsNiCr Prussian Blue Analogue Nanocrystals », Inorganic Chemistry, vol. 60, nᵒ 21, p. 16388-16396, nov. 2021.
    Résumé : Prussian blue analogue nanocrystals of the CsINiII[CrIII(CN)6] cubic network with 6 nm size were assembled as a single monolayer on highly organized pyrolytic graphite (HOPG). X-ray magnetic circular dichroism (XMCD) studies, at the Ni and Cr L2,3 edges, reveal the presence of an easy plane of magnetization evidenced by an opening of the magnetic hysteresis loop (coercive field of ≈200 Oe) when the magnetic field, B, is at 60° relative to the normal to the substrate. The angular dependence of the X-ray natural linear dichroism (XNLD) reveals both an orientation of the nanocrystals on the substrate and an anisotropy of the electronic cloud of the NiII and CrIII coordination sphere species belonging to the nanocrystals’ surface. Ligand field multiplet (LFM) calculations that reproduce the experimental data are consistent with an elongated tetragonal distortion of surface NiII coordination sphere responsible for the magnetic behavior of monolayer.
    Mots-clés : ERMMES, POLE 2.
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2020



  • A. Benchohra, C. Méthivier, J. Landoulsi, D. Kreher, et R. Lescouëzec, « Electrospray ionization: an efficient approach to deposit polymetallic molecular switches onto gold surfaces », Chemical Communications, vol. 56, nᵒ 48, p. 6587-6589, 2020.
    Résumé : Electrospray ionization (EI) deposition is proven efficient in obtaining monolayers of a polymetallic charge transfer complex on gold surfaces. , Electrospray ionization (EI) deposition is proven efficient in obtaining monolayers of a polymetallic charge transfer complex on gold surfaces. The molecule's integrity is monitored by using PM-IRRAS and XPS. This approach broadens the perspective of molecular magnetic switch deposition, which is currently dominated by the thermal evaporation of monometallic spin crossover (SCO) complexes.
    Mots-clés : ERMMES, POLE 2, POLYMERES.
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  • J. ‐R. Jiménez, J. Glatz, A. Benchohra, G. Gontard, L. ‐M. Chamoreau, J. ‐F. Meunier, A. Bousseksou, et R. Lescouëzec, « Electron Transfer in the Cs⊂{Mn <sub>4</sub> Fe <sub>4</sub> } Cubic Switch: A Soluble Molecular Model of the MnFe Prussian‐Blue Analogues », Angewandte Chemie International Edition, vol. 59, nᵒ 21, p. 8089-8093, mai 2020.


  • A. Li, Y. Li, L. - M. Chamoreau, C. Desmarets, L. Lisnard, et Y. Journaux, « A Bis-Polydentate Oxamate-Based Achiral Ligand That Can Stabilize a Macrocyclic Mixed Valence Compound or Induce a 1D Helical Chain », European Journal of Inorganic Chemistry, vol. 2020, nᵒ 34, p. 3311-3319, 2020.
    Résumé : The reaction of the N-(2-hydroxyphenyl)oxamate ligand (ohpma) has been investigated with cobalt(II) and copper(II) ions. It has led to two coordination compounds, (TMA)3[CoIII(ohpma)2CoII(MeOH)23]·10H2O·5MeOH (1) and (HNEt3)[Cu(ohpma)] (2). Both compounds have been characterized by single-crystal X-ray diffraction and magnetometry. The X-ray diffraction studies have revealed atypical structures that are not commonly observed in oxamate coordination chemistry with a macrocyclic arrangement for the mixed-valence cobalt-based complex 1, and a helical chiral chain for compound 2. In the latter, the bis-polydentate nature of the (ohpma)3– ligand with distinct tridentate and bidentate coordination sites creates a chirogenic center on the copper ion. The investigation of the magnetic properties shows for complex 1 a single-molecule magnet behavior detectable under static field, while antiferromagnetic interactions dominate the behavior of 2.
    Mots-clés : ARC, ERMMES, POLE 1, POLE 2.
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2019



  • J. Besnardiere, B. Ma, A. Torres-Pardo, G. Wallez, H. Kabbour, J. M. González-Calbet, H. J. Von Bardeleben, B. Fleury, V. Buissette, C. Sanchez, T. Le Mercier, S. Cassaignon, et D. Portehault, « Structure and electrochromism of two-dimensional octahedral molecular sieve h’-WO3 », Nature Communications, vol. 10, nᵒ 1, p. 327, janv. 2019.
    Résumé : Octahedral molecular sieves (OMS) are built of transition metal-oxygen octahedra that delimit sub-nanoscale cavities. Compared to other microporous solids, OMS exhibit larger versatility in properties, provided by various redox states and magnetic behaviors of transition metals. Hence, OMS offer opportunities in electrochemical energy harnessing devices, including batteries, electrochemical capacitors and electrochromic systems, provided two conditions are met: fast exchange of ions in the micropores and stability upon exchange. Here we unveil a novel OMS hexagonal polymorph of tungsten oxide called h’-WO3, built of (WO6)6 tunnel cavities. h’-WO3 is prepared by a one-step soft chemistry aqueous route leading to the hydrogen bronze h’-H0.07WO3. Gentle heating results in h’-WO3 with framework retention. The material exhibits an unusual combination of 1-dimensional crystal structure and 2-dimensional nanostructure that enhances and fastens proton (de)insertion for stable electrochromic devices. This discovery paves the way to a new family of mixed valence functional materials with tunable behaviors.
    Mots-clés : ERMMES, POLE 2.
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  • N. Daffé, J. - R. Jiménez, M. Studniarek, A. Benchohra, M. - A. Arrio, R. Lescouëzec, et J. Dreiser, « Direct Observation of Charge Transfer and Magnetism in Fe4Co4 Cyanide-Bridged Molecular Cubes », The Journal of Physical Chemistry Letters, vol. 10, nᵒ 8, p. 1799-1804, avr. 2019.
    Résumé : We have studied the zero-dimensional cubane molecular correspondent of a Prussian blue analogue Cs–Fe4Co4 at low temperature and high magnetic field by means of L-edge X-ray absorption spectroscopy and X-ray magnetic circular dichroism. We probe the magnetic and electronic structures of Fe and Co separately upon light irradiation, which allows us to observe directly the electron transfer coupled to a spin transition phenomenon within the molecular cubes and to investigate the nature of the metastable photoexcited state. The magnetic moments in the photoexcited state are found to be M = 1.3μB (Mspin = 0.59μB with large orbital moment, Morbit = 0.74μB) for low-spin FeIII and M = 1.5μB (Mspin = 1.08μB with orbital moment, Morbit = 0.41μB) for high-spin CoII at 2 K and 6.8 T. From our results, we evidence that a strong antiferromagnetic coupling between the metal ions can be ruled out.
    Mots-clés : ERMMES, POLE 2.
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  • S. De, A. Flambard, D. Garnier, P. Herson, F. H. Köhler, A. Mondal, K. Costuas, B. Gillon, R. Lescouëzec, B. Le Guennic, et F. Gendron, « Probing the Local Magnetic Structure of the [FeIII(Tp)(CN)3]− Building Block Via Solid-State NMR Spectroscopy, Polarized Neutron Diffraction, and First-Principle Calculations », Chemistry – A European Journal, vol. 25, nᵒ 52, p. 12120-12136, 2019.
    Résumé : Abstract The local magnetic structure in the [FeIII(Tp)(CN)3]− building block was investigated by combining paramagnetic Nuclear Magnetic Resonance (pNMR) spectroscopy and polarized neutron diffraction (PND) with first-principle calculations. The use of the pNMR and PND experimental techniques revealed the extension of spin-density from the metal to the ligands, as well as the different spin mechanisms that take place in the cyanido ligands: Spin-polarization on the carbon atoms and spin-delocalization on the nitrogen atoms. The results of our combined density functional theory (DFT) and multireference calculations were found in good agreement with the PND results and the experimental NMR chemical shifts. Moreover, the ab-initio calculations allowed us to connect the experimental spin-density map characterized by PND and the suggested distribution of the spin-density on the ligands observed by NMR spectroscopy. Interestingly, significant differences were observed between the pseudo-contact contributions of the chemical shifts obtained by theoretical calculations and the values derived from NMR spectroscopy using a simple point-dipole model. These discrepancies underline the limitation of the point-dipole model and the need for more elaborate approaches to break down the experimental pNMR chemical shifts into contact and pseudo-contact contributions.
    Mots-clés : ERMMES, POLE 2.
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  • D. Garnier, A. Mondal, Y. Li, P. Herson, L. - M. Chamoreau, L. Toupet, M. Buron Le Cointe, E. M. B. Moos, F. Breher, et R. Lescouëzec, « Tetranuclear [FeII2FeIII2]2+ molecular switches: [FeII(bik)2(N–)2] spin-crossover complexes containing [FeIII(Tp)(CN)3]– metalloligands as N-donor », Comptes Rendus Chimie, mai 2019.
    Résumé : Three novel mixed valence cyanide-bridged {FeIII2FeII2} square complexes were obtained through the self-assembling of [FeIII(Tp)(CN)3]- or [FeIII(Tp*)(CN)3]− cyanido building blocks with the in situ formed [FeII(bik)2(S)2] complex (Tp = hydrotris (pyrazol-1-yl)borate, Tp* = hydrotris (3,5-dimethyl-pyrazol-1-yl)borate, bik = bis(1-methylimidazol-2-yl)ketone, S = solvent). The structures of these three complexes (2, 3 and 4) are reminiscent of that of our previously published square complex {[FeIII(Tp)(CN)3]2 [FeII(bik)2]2}·[FeIII(Tp)(CN)3]2·18H2O·4CH3OH (1). They consist of cyanide-bridged square dicationic complexes, ClO4− (2 and 3) or BF4− (4) counterions and solvate molecules. The FT-IR cyanide stretching vibrations observed at νCN ≈ 2145–60 cm−1 are typical of {FeIII–CN–FeII} moieties. The investigation of the magnetic properties of 2 reveals the occurrence of spin-crossover centered at T1/2 = 227 K. The χMT variation, ca. 7 cm3 mol−1 K, reflects the complete spin-state change occurring on both {FeII(bik)(–NC)2} moieties (–NC represents the cyanido building blocks). The Slichter–Drickamer model leads to a weak cooperativity factor, Γ = 1.6 kJ mol−1 (with Γ < 2RT1/2), which reflects the gradual spin-state change. This is in agreement with the molecular structure of 2, which does not present significant intermolecular interactions. The calculated enthalpy and entropy variations associated with the spin-state equilibrium are ΔH = 24 kJ mol−1 and ΔS = 105 J K−1 mol−1. In contrast, 3 and 4 show only partial spin-crossover in the accessible temperature range (2–400 K) as the T1/2 are shifted toward higher temperatures (ca. T1/2 > 400 K). Although no photomagnetic effect is observed for 3, compound 4 shows a moderate increase in the magnetization upon irradiation at low temperature. This phenomenon is ascribed to the light-induced excited spin-state trapping (LIESST) effect. Interestingly, the complex 2 also shows a remarkable LIESST effect, which is observed with different laser lights covering the visible and near-infrared range. The resulting χMT value obtained in the photoinduced state suggests the occurrence of a ferromagnetic interaction inside the {FeIII–CN–FeII} units. Résumé Trois nouveaux complexes carrés {FeIII2FeII2} à pont cyanure et à valence mixte ont été obtenus par auto-assemblage des précurseurs cyanurés [FeIII(Tp)(CN)3]− ou [FeIII(Tp*)(CN)3]− et du complexe cationique [FeII(bik)2(S)2] formé in situ (Tp = hydrotris (pyrazol-1-yl)borate, Tp* = hydrotris (3,5-dimethyl-pyrazol-1-yl)borate, bik = bis(1-methylimidazol-2-yl)cétone, S = solvant). Les structures de ces trois complexes (2, 3 et 4) sont similaires à celle du complexe {[FeIII(Tp)(CN)3]2[FeII(bik)2]2}[FeIII(Tp)(CN)3]2·18H2O·4CH3OH (1) préalablement publié. Elles sont constituées de complexes carrés dicationiques à pont cyanure, de contre-ions ClO4− (2 and 3) ou BF4− (4) et de molécules de solvant. Les vibrations d’élongation des cyanures, observée en spectroscopie IR à νCN ≈ 2145–60 cm−1, sont caractéristiques d'unités {FeIII–CN–FeII}. L’étude des propriétés magnétiques de 2 révèle un équilibre de spin centré à T1/2 = 227 K. La variation du produit χMT, ca. 7 cm3 mol−1 K, traduit une conversion de spin complète sur chacune des unités {FeII(bik)(–NC)2} du carré (–NC représente le complexe précurseur cyanuré). L'analyse des données par le modèle de Slichter–Drickamer conduit à un faible facteur de coopérativité, Γ = 1.6 kJ mol−1 K (with Γ < 2RT1/2), en accord avec un changement d’état de spin graduel. Ces données sont en accord avec la structure de 2 qui ne montre pas d'interactions intermoléculaires notables. Les valeurs des variations d'enthalpie et d'entropie associées à la conversion de spin sont ΔH = 24 kJ mol−1 et ΔS = 105 J K−1 mol−1. Au contraire de 2, les composés 3 and 4 présentent seulement une conversion de spin partielle dans le domaine de température exploré (2–400 K), avec des valeurs T1/2 déplacées vers les hautes températures (ca. T1/2 > 400 K). Tandis qu'on n'observe pas d'effet photomagnétique pour 3 et seulement un faible effet dans 4, le composé 2 présente une forte augmentation de son aimantation sous irradiation à basse température. Cet effet est dû au piégeage photo-induit d'un état excité de spin (effet « LIESST », Light-Induced Excited Spin-State Trapping). Il est observé avec différentes sources laser couvrant le spectre visible et le proche infrarouge. Les valeurs de χMT obtenues dans l’état photo-induit suggèrent la présence d'une interaction ferromagnétique au sein de la paire {FeIII–CN–FeII}.
    Mots-clés : ERMMES, POLE 2.
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  • A. Harbi, H. Moutaabbid, Y. Li, C. Renero-Lecuna, M. Fialin, Y. Le Godec, S. Benmokhtar, et M. Moutaabbid, « The effect of cation disorder on magnetic properties of new double perovskites La2NixCo1-xMnO6 (x = 0.2–0.8) », Journal of Alloys and Compounds, vol. 778, p. 105-114, mars 2019.
    Résumé : Solid solutions of new double perovskite oxides La2NixCo1-xMnO6 (x = 0.2, 0.25, 0.5, 0.75, 0.8) were synthesized by solid-state reaction method. The X-ray powder diffraction data show that all the compounds crystallize in the monoclinic structure with space group P21/n at room temperature. The elementary composition of the powders was determined by the electron Probe Microanalysis. Raman and IR spectra show strong bands at (520, 650 cm−1) and (426, 600 cm−1) respectively, attributed to the stretching vibration of Ni/Co-O and Mn-O bonds in the structure. The magnetic studies for all the compounds have been performed in both DC and AC magnetic fields in the temperature range from 2 to 300 K. All samples exhibit a main paramagnetic to ferromagnetic (PM-FM) transition between 232 K and 260 K, and their Curie temperature increases rapidly with increasing x values. Three samples with x = 0.2, 0.25 and 0.5 respectively display also a secondary PM-FM transition between 200 K and 208 K. The thermal variation of out of phase component of AC susceptibility presents also frequency-dependent transitions between 65 K and 110 K unfolding the existence of super-paramagnetic mono-domains in all samples. The band gap energy has been calculated and revealing semiconductor behavior for all samples.
    Mots-clés : ERMMES, POLE 2.
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  • M. Okubo, J. Long, D. R. Talham, et R. Lescouëzec, « Solid-state electrochemistry of metal cyanides », Comptes Rendus Chimie, vol. 22, nᵒ 6, p. 483 - 489, 2019.
    Résumé : Efficient energy storage in the form of batteries contributes to building sustainable society. As advanced batteries need positive electrode materials capable of larger capacity, higher voltage, and lower cost, it is important to search for novel electrode materials. Among various inorganic/organic materials, cyanido-bridged coordination compounds are promising candidates for battery electrodes due to their ability to undergo solid-state redox reaction associated with ion (de)intercalation. In this review, recent results about the thermodynamic and kinetic aspects of the solid-state electrochemistry of cyanido-bridged coordination compounds are summarized, providing a fundamental basis toward developing cyanide electrodes for advanced batteries. Résumé Le stockage de l’énergie dans des batteries performantes est un élément clé pour le développement des énergies renouvelables et d'un modèle de société durable. Un des défis pour construire de nouvelles batteries plus performantes est le développement de matériaux d'intercalation pour cathode présentant de plus grandes capacités, de plus grands voltages et des coûts réduits. Parmi les divers matériaux organiques et inorganiques explorés, les polymères de coordination à pont cyanure sont des candidats prometteurs. Ceux ci peuvent s'oxyder et se réduire à l’état solide en (dés)intercalant des ions. Dans cette revue, quelques résultats récents sur les aspects thermodynamiques et cinétiques des propriétés électrochimiques des polymères de coordination à pont cyanure sont résumés, démontrant leur potentiel intérêt comme életcrodes dans de nouvelles batteries.
    Mots-clés : ERMMES, POLE 2.
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  • O. Stetsiuk, V. Synytsia, S. R. Petrusenko, V. N. Kokozay, A. El-Ghayoury, J. Cano, F. Lloret, M. Julve, B. Fleury, et N. Avarvari, « Co-existence of ferro- and antiferromagnetic interactions in a hexanuclear mixed-valence CoIII2MnII2MnIV2 cluster sustained by a multidentate Schiff base ligand », Dalton Transactions, vol. 48, nᵒ 31, p. 11862-11871, 2019.
    Résumé : The successful utilization of the “direct synthesis” approach yielded the unprecedented hexanuclear complex of formula [Co2MnII2MnIV2(L1)4Cl2(μ3-O)2(dmf)4]·2dmf (1) (H3L is the Schiff base derived from the condensation of salicylaldehyde and 3-aminopropane-1,2-diol). Single crystal X-ray analysis revealed that 1 crystallizes in the monoclinic system P21/c and it contains a rare mixed-valence CoIII2MnII2MnIV2(μ2-O)8(μ3-O)2 core where all metal ions are linked through the phenolato and alkoxo groups of the L3− ligand. Besides the charge balance resulting from the X-ray structure, the oxidation state of the metal ions has been confirmed by XPS spectroscopy. Cryomagnetic studies indicate the coexistence of ferro- (MnIV–MnII, J2 = +1.10(3) cm−1, J3 = +2.19(3) cm−1; MnII–MnII, j = +0.283(3) cm−1) and antiferromagnetic interactions (MnIV–MnIV, J1 = −17.31(4) cm−1), with the six-coordinate CoIII ions being diamagnetic. DFT type calculations were carried out to substantiate these values. The energy diagram for the different spin states using the best-fit parameters shows the occurrence of six low-lying spin states (S = 0–5) which are close in energy but clearly separated from the remaining ones, with the ground spin state being S = 5. Complex 1 is found to be the first example where weak ferromagnetic exchange between MnII ions through the long –O–MnIV–O– pathway takes place.
    Mots-clés : ERMMES, POLE 2.
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2018



  • S. De, L. - M. Chamoreau, H. El Said, Y. Li, A. Flambard, M. - L. Boillot, S. Tewary, G. Rajaraman, et R. Lescouëzec, « Thermally-Induced Spin Crossover and LIESST Effect in the Neutral [FeII(Mebik)2(NCX)2] Complexes: Variable-Temperature Structural, Magnetic, and Optical Studies (X = S, Se; Mebik = bis(1

    -methylimidazol-2-yl)ketone) », Frontiers in Chemistry, vol. 6, août 2018.


  • T. Zhang, A. Solé-Daura, S. Hostachy, S. Blanchard, C. Paris, Y. Li, J. J. Carbó, J. M. Poblet, A. Proust, et G. Guillemot, « Modeling the Oxygen Vacancy at a Molecular Vanadium(III) Silica-Supported Catalyst », Journal of the American Chemical Society, vol. 140, nᵒ 44, p. 14903-14914, nov. 2018.
    Résumé : Here we report on the use of a silanol-decorated polyoxotungstate, [SbW9O33(tBuSiOH)3]3– (1), as a molecular support to describe the coordination of a vanadium atom at a single-site on silica surfaces. By reacting [V(Mes)3·thf] (Mes = 2,4,6-trimethylphenyl) with 1 in tetrahydrofuran, the vanadium(III) derivative [SbW9O33(tBuSiO)3V(thf)]3– (2) was obtained. Compound 2 displays the paramagnetic behavior expected for a d2-VIII high spin complex (SQUID measurements) with a triplet electronic ground state (ca. 30 kcal·mol–1 more stable than the singlet, from DFT calculations). Compound 2 proves to be a reliable model for reduced isolated-vanadium atom dispersed on silica surfaces [(≡Si—O)3VIII(OH2)], an intermediate that is often proposed in a Mars–van Krevelen type mechanism for partial oxidation of light alcohols. Oxidation of 2 under air produced the oxo-derivative [SbW9O33(tBuSiO)3VO]3– (3). In compound 2, the d2-electrons are localized in degenerated d(V) orbitals, whereas in the electronically analogous bireduced-[SbW9O33(tBuSiO)3VO]5–, 3·(2e), one electron is localized on d(V) orbital and the second one is delocalized on the polyoxotungstic framework, leading to a unique case of a bireduced heteropolyanion derivative with completely decoupled d1-V(IV) and d1-W(V). Our body of experimental results (EPR, magnetic measurements, spectroelectrochemical studies, Raman spectroscopy) and theoretical studies highlights (i) the role of the apical ligand coordination, i.e., thf (σ-donor) vs oxo (π-donor), in destabilizing or stabilizing the d(V) orbitals relative to the d(W) orbitals, and (ii) a geometrical distortion of the O3VO entity that causes a splitting of the degenerated orbitals and the stabilization of one d(V) orbital in the bireduced compound 3·(2e).
    Mots-clés : E-POM, ERMMES, POLE 2.
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