Cyanide-bridged Fe(III)–Co(II) bis double zigzag chains with a slow relaxation of the magnetisation

Reaction of [FeIII(bipy)(CN)4]¯ with fully solvated MII cations [M = Co (1) and Mn (2)] produces the isostructural bis double zigzag chains [[FeIII(bipy)(CN)4]2MII(H2O)]·MeCN·1/2H2O; 1 exhibits intrachain ferromagnetic and interchain antiferromagnetic couplings, slow magnetic relaxation and hysteresis effects.Luminita Marilena, Toma, [email protected] ; Lescouezec, Alain Francois Rodri, [email protected] ; Lloret Pastor, Francisco, [email protected] ; Julve Olcina, Miguel, [email protected]

A cyanide and hydroxo-bridged nanocage: a new generation of coordination clusters

International audienceCombining serendipitously-formed hydroxo-clusters, [CoII3(OH)(piv)4(L)]+ (where L = MeCN or Hpiv), with assembling cyanide building block, [FeIII(Tp)(CN)3]−, has led to an unprecedented architecture where polymetallic cobalt clusters and blocked tris-cyanide iron complexes define the apexes of a unique magnetic cubic nanocage

Combining Cyanometalates and Coordination Clusters: An Alternative Synthetic Route toward Original Molecular Materials

International audienceWith the discovery of molecules or molecule-based compounds that can display blocked magnetization, magnetic ordering or switchable magnetic bistability, the research efforts devoted to molecular magnetic materials have considerably increased over the past two decades, fully exploiting the advantages of the bottom-up approach. 1-4 This research field focuses on promising properties for potential technological applications such as information storage, quantum computing and spintronics at the molecular scale, but it also provides fundamental insights into original quantum phenomena. 5,6 Coordination chemists have developed efficient synthetic tools for the preparation of interesting magnetic systems

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

International audienceThe local magnetic structure in the [Fe (Tp)(CN) ] 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

Single chain magnet behaviour in an enantiopure chiral cobalt(II)–copper(II) one-dimensional compound

The self-assembly of an enantiomerically pure, chiral dianionic oxamatocopper(II) complex with cobalt(II) ions leads to neutral oxamato-bridged heterobimetallic chains that combine chirality and slow magnetic relaxation, providing thus the first example of ‘‘chiral single chain magnets (CSCMs).Ruiz Garcia, Rafael, [email protected] ; Lloret Pastor, Francisco, [email protected]

switchable molecular magnetic materials

Cette thèse porte sur la synthèse et la caractérisation magnéto-structurale de molécules photomagnétiques. Un des objectifs de ce travail est l étude de systèmes moléculaires (photo)commutables qui pourraient être utilisés comme modèles afin de mieux comprendre les propriétés physiques de systèmes tri-dimensionnels plus complexes, tels que les Analogues du Bleu de Prusse (ABPs) photomagnétiques. L exploration de nouvelles voies de synthèse permettant d obtenir des systèmes moléculaires originaux, ou l obtention de nouvelles paires {M-CN-M } susceptibles de présenter un transfert électronique photo-induit et donc du photomagnétisme représentent également des objectifs importants de ce travail. La stratégie de synthèse que nous avons choisie se base sur l auto-assemblage de complexes cyanurés (les métallo-ligands ) avec des complexes mono- ou poly-métalliques partiellement bloqués. L utilisation de métallo-ligands cyanurés est motivée par plusieurs raisons : Le cyanure est un ligand ambidentate qui donne un accès facile à des matériaux hétéro-métalliques, et donc à des comportements de type ferrimagnétique. Par ailleurs, le cyanure est connu pour transmettre efficacement l interaction d échange magnétique. La chimie de coordination du cyanure est riche et permet d accéder à une variété de métallo-ligands dont les propriétés électroniques et topologiques peuvent être modifiées à volonté . Cette flexibilité représente un grand avantage pour la conception de systèmes magnétiques bistables car elle permet d ajuster finement les propriétés électroniques des briques de départ et donc par la même, des propriétés physiques des matériaux moléculaires qui en découlent. Bien que le rôle du ligand cyanure ne soit pas encore complètement compris, le grand nombre d exemples de complexes cyanurés photomagnétiques semble indiquer que ces systèmes sont particulièrement adaptés à l observation de transfert d électron photo- ou thermo-induitThe work presented in this Ph. D. dissertation focuses on the synthesis and the characterization of new Switchable Molecular Magnetic Materials. The synthesis approach is based on the self-assembly of preformed cyanide-based building blocks with sensitively chosen partially-blocked mono- or poly-nuclear complexes. Various physical techniques are used for investigating the physical properties of these systems, such as (variable temperature) FT-IR and UV-vis (in both solid-state and solution) spectroscopies, TGA, EPR and Mössbauer spectroscopies, single crystal X-Ray Diffraction, and SQUID magnetometry. Molecular Fe-Co model complexes of the so-called Prussian Blue Analogues have been prepared and their physical properties are presented in the second chapter, after the bibliographical introduction (chapter 1). Some of these complexes exhibit a reversible switching of their magnetic properties, between a dia- and a para-magnetic state, under the application of an external perturbation such as a temperature change and/or a light irradiation. The magneto-structural correlations of these switching materials show that an electron transfer coupled to a spin transition (ETCST) is taking place in the Fe-Co pairs. Following a similar strategy, a series of new switchable molecules, which exhibit either photo-induced Spin transition (ST), or photo-induced ETCST have been designed and they are presented in the third and fourth chapters. All these compound shows bistability in their magnetic property. The chapter 3 is devoted to the study of mixed valence FeII-FeIII complexes. The fourth chapter focuses on new octacyanometallate-based photomagnetic molecules. Finally the chapter 5 intends to explore a new synthetic strategy for designing new (switchable) molecular magnetic materials. Our aim is to prepare original multifunctional materials by combining versatile (hydr)oxo clusters and stable cyanide-based building blocksPARIS-BIUSJ-Biologie recherche (751052107) / SudocSudocFranceF

Solid-state electrochemistry of metal cyanides

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