Author: Fabrice Wilhelm

0000000000267214

AUTHOR

Fabrice Wilhelm

A Study Using X-ray Absorption and Emission Spectroscopy of Dioxygen-Binding Xerogels Incorporating Cyclam Units Complexed with Copper Salts.

X-ray absorption spectroscopy was used to elucidate how hybrid xerogels complexed with CuCl2 could reversibly bind molecular dioxygen. Difference EXAFS analyses at the Cu K-edge suggest that dioxygen could bridge two Cu atoms in a μ-η1:η1 peroxo-like conformation with unequal Cu···O distances. Only the short distance (RCu–O1 = 1.86 ± 0.01 A) was unambiguously determined and looks typical of a CuII site. The Cu···Cu internuclear distances would be rather long: RCu–Cu ≈ 4.0 A (3.9 A) for the oxygenated (oxygen-free) xerogels. Cl K-edge EXAFS spectra revealed the pre-existence in the oxygen-free xerogels of CuI sites with short Cl–Cu bonds (2.11 ± 0.03 A). Pentacoordinate CuII sites with a lon…

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Structure of Dioxygen Binding Xerogels Incorporating Cyclams Complexed with CuCl2 Salts

X-ray absorption/emission spectroscopies were combined in order to elucidate how hybrid xerogels complexed with CuCl2 could bind reversibly O2. Difference EXAFS analyses at the Cu K-edge revealed the existence of binuclear structures with long Cu...Cu distances, i.e. RCu–Cu ≈ 3.98 A and 3.87 A for the oxygenated and oxygen-free xerogels. In oxygenated xerogels, dioxygen would bridge two Cu atoms in a μ-η1 : η1 peroxo-like conformation. The Cu-O signal found at short distance (RCu−O1 = 1.85 ± 0.01 A) is fully consistent with 40% of O2 molecules being chemisorbed per Cu site. In oxygen-free xerogels, Cl K-edge EXAFS revealed the presence of CuI sites with short Cl-Cu bond lengths (RCl−Cu = 2.…

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X-Ray Detected Magnetic Resonance: A Unique Probe of the Precession Dynamics of Orbital Magnetization Components

X-ray Detected Magnetic Resonance (XDMR) is a novel spectroscopy in which X-ray Magnetic Circular Dichroism (XMCD) is used to probe the resonant precession of local magnetization components in a strong microwave pump field. We review the conceptual bases of XDMR and recast them in the general framework of the linear and nonlinear theories of ferromagnetic resonance (FMR). Emphasis is laid on the information content of XDMR spectra which offer a unique opportunity to disentangle the precession dynamics of spin and orbital magnetization components at given absorbing sites. For the sake of illustration, we focus on selected examples in which marked differences were found between FMR and XDMR s…

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

International audience; Magnets derived from inorganic materials (e.g., oxides, rare-earth–based, and intermetallic compounds) are key components of modern technological applications. Despite considerable success in a broad range of applications, these inorganic magnets suffer several drawbacks, including energetically expensive fabrication, limited availability of certain constituent elements, high density, and poor scope for chemical tunability. A promising design strategy for next-generation magnets relies on the versatile coordination chemistry of abundant metal ions and inexpensive organic ligands. Following this approach, we report the general, simple, and efficient synthesis of light…

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CCDC 1983877: Experimental Crystal Structure Determination

Related Article: Panagiota Perlepe, Itziar Oyarzabal, Aaron Mailman, Morgane Yquel, Mikhail Platunov, Iurii Dovgaliuk, Mathieu Rouzières, Philippe Négrier, Denise Mondieig, Elizaveta A. Suturina, Marie-Anne Dourges, Sébastien Bonhommeau, Rebecca A. Musgrave, Kasper S. Pedersen, Dmitry Chernyshov, Fabrice Wilhelm, Andrei Rogalev, Corine Mathonière, Rodolphe Clérac|2020|Science|6516|587|doi:10.1126/science.abb3861

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CCDC 2007863: Experimental Crystal Structure Determination

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