Search results for "Spin Crossover"
showing 10 items of 379 documents
1H NMR studies of paramagnetic ferricytochrome c-551 from Pseudomonas aeruginosa at high pH: The role of histidine 16 in the spin transition
2005
Abstract Cytochrome c-551 from the mesophile Pseudomonas aeruginosa is an electronic transfer protein that contains 82 amino-acid residues and a c-type heme as the prosthetic group with low spin Fe(II) in the reduced form and low spin Fe(III) in the oxidized form of cytochrome c-551. We have studied the electronic properties of ferricytochrome c-551 from P. aeruginosa at high pH (9–11.4) by means of paramagnetic 1H NMR spectra and the T1 and T2 values of isotropically shifted proton resonances. We have also analyzed the temperature dependence of the hyperfine-shifts. Resonance assignment of some signals was based on 2D saturation transfer experiments, EXSY. These results indicate the existe…
Insertion of FeII complexes with Schiff base ligands derived from imidazole or pyridine into 3D bimetallic oxalate-based ferromagnets
2013
Abstract The syntheses, structures and magnetic properties of the compounds [FeII(imid2-trien)][MnII(CH3OH)CrIII(ox)3]2·(CH3OH)4(CH3CN)(H2O) (1), [FeII(tren(6-Me-py)3)][MnIICrIII(ox)3][MnII(CH3OH)0.58(H2O)0.42CrIII(ox)3]·(CH3OH)2(CH3CN)0.5(H2O)0.42 (2) and [FeII(tren(imid)3)]2[Mn2.5(CH3OH)3Cr3(ox)9]·(CH3OH)4.75·(H2O)4.25 (3) are reported. They are prepared by the insertion of FeII-Schiff base complexes derived from imidazole and pyridine into bimetallic oxalate networks. Different types of 3D oxalate networks are obtained for each templating cation. Thus, [FeII(imid2-trien)]2+ and [FeII(tren(6-Me-py)3)]2+ give rise to unusual 3D achiral bimetallic oxalate networks with heptacoordinated MnII…
2D Bimetallic Oxalate‐Based Ferromagnets with Inserted [Fe(4‐Br‐sal 2 ‐trien)] + and [Fe(3‐R‐sal 2 ‐trien)] + (R = Br, Cl and CH 3 O) Fe III Spin‐Cro…
2012
The syntheses, structures and magnetic properties of the compounds of formula [FeIII(4-Br-sal2-trien)][MnIICrIII(ox)3]0.67Cl0.33·CH3OH_solvate (1), [FeIII(3-Br-sal2-trien)][MnIICrIII(ox)3]·(CH3CN)2 (2), [FeIII(3-Cl-sal2-trien)][MnIICrIII(ox)3]·(CH3OH)2·(CH3CN)2 (3) and [FeIII(3-CH3O-sal2-trien)][MnIICrIII(ox)3]·(CH3OH)·(H2O)1.5·(CH2Cl2)0.5 (4) are reported. The four structures present a 2D honeycomb anionic layer formed by MnII and CrIII ions linked through oxalate ligands and a cationic layer of the FeIII complexes intercalated between the 2D oxalate network. The main differences compared with previous 2D oxalate-based structures are the presence of double layers of cations in compounds 1,…
Spin crossover FeII complexes as templates for bimetallic oxalate-based 3D magnets
2007
Abstract We present the synthesis and structural characterization of the salt [Fe(bpp)2][MnCr(ox)3]2 · bpp · CH3OH. It crystallizes in the monoclinic space group. This material contains an anionic [MnCr(ox)3]− 3D 10-gon ferromagnetic network, that orders below 3.0 K. The channels created by this architecture are filled by the spin crossover cations [Fe(bpp)2]2+ (bpp = 2,6(bispyrazol-3-yl)pyridine), free ligand and solvent molecules. No spin transition has been observed at ambient pressure.
Hofmann-Like Frameworks Fe(2-methylpyrazine)n[M(CN)2]2 (M = Au, Ag) : Spin-Crossover Defined by the Precious Metal
2020
Hofmann-like cyanometalates constitute a large class of spin-crossover iron(II) complexes with variable switching properties. However, it is not yet clearly understood how the temperature and cooperativity of a spin transition are influenced by their structure. In this paper, we report the synthesis and crystal structures of the metal–organic coordination polymers {FeII(Mepz)[AuI(CN)2]2} ([Au]) and {FeII(Mepz)2[AgI(CN)2]2} ([Ag]), where Mepz = 2-methylpyrazine, along with characterization of their spin-state behavior by variable-temperature SQUID magnetometry and Mössbauer spectroscopy. The compounds are built of cyanoheterometallic layers, which are pillared by the bridging Mepz…
Spin state switching in iron coordination compounds
2013
The article deals with coordination compounds of iron(II) that may exhibit thermally induced spin transition, known as spin crossover, depending on the nature of the coordinating ligand sphere. Spin transition in such compounds also occurs under pressure and irradiation with light. The spin states involved have different magnetic and optical properties suitable for their detection and characterization. Spin crossover compounds, though known for more than eight decades, have become most attractive in recent years and are extensively studied by chemists and physicists. The switching properties make such materials potential candidates for practical applications in thermal and pressure sensors …
Unravelling the chemical design of spin-crossover nanoparticles based on iron(ii)–triazole coordination polymers: towards a control of the spin trans…
2015
A systematic study of the key synthetic parameters that control the growth of spin-crossover (SCO) nanoparticles (NPs) using the reverse micelle technique has been undertaken in the system [Fe(Htrz)2(trz)](BF4)·H2O, (Htrz = 1,2,4-triazole). This has permitted us to modulate the physical properties of the NPs in a controlled and reproducible manner. In particular, a control over the size of the NPs (in the range 4 to 16 nm) has been achieved by varying the water to surfactant molar ratio. The consequences of this size variation on the cooperativity of the spin transition are discussed. Finally, this approach has been extended to the chemical alloy [Fe(Htrz)2.95(NH2trz)0.05](ClO4)2 in order t…
A Combined Top-Down/Bottom-Up Approach for the Nanoscale Patterning of Spin-Crossover Coordination Polymers
2007
Molecular spin-crossover complexes of 3d–3d transitionmetal ions have been the focus of many researchers’ work because of their fascinating properties associated with the bistability of their electronic states (high spin (HS) or low spin (LS)). Although the origin of the spin-crossover phenomenon is purely molecular, the macroscopic behavior of these systems in the solid state is strongly determined by the interactions, of mainly elastic origin, between the transition-metal ions. Recently, remarkable progress has been made in the area of spin-crossover complexes with infinite one-, two-, or three-dimensional (1D, 2D, 3D) networks, the so-called coordination polymers. The purpose of this app…
Inside Front Cover: A Combined Top-Down/Bottom-Up Approach for the Nanoscale Patterning of Spin-Crossover Coordination Polymers (Adv. Mater. 16/2007)
2007
The background scanning electron microscopy image shows nanometric patterns of the 3D spin crossover coordination polymer Fe(pyrazine)[Pt(CN)4] (see schematic structure in the circle), which have been fabricated using a combination of lift-off and multilayer sequential assembly methods. These patterns, reported by Gabor Molnar, Azzedine Bousseksou, and co-workers on p. 2163, exhibit a bistability of their electronic states (1A1 ⇌ 5T2), and thus represent a novel platform for a wide array of potential applications.
Electrical Voltage Control of the Pressure-Induced Spin Transition at Room Temperature in the Microporous 3D Polymer [Fe(pz)Pt(CN)4]
2019
Fine control and direct monitoring of the spin crossover properties driven by pressure at room temperature are reported for the porous three-dimensional coordination polymer {Fe(pz)[Pt(CN)4]} by us...