Search results for "magnetism."
showing 10 items of 1879 documents
Oxalate‐Based 3D Chiral Magnets: The Series [Z II (bpy) 3 ][ClO 4 ][M II Fe III (ox) 3 ] (Z II = Fe, Ru; M II = Mn, Fe; bpy = 2,2'‐Bipyridine; ox = O…
2005
The synthesis, structure, and physical properties of the oxalate-based molecular magnets with the formula [ZII(bpy)3][ClO4][MIIFeIII(ox)3] (ZII = Fe, Ru; MII = Mn, Fe; bpy = 2,2'-bipyridine; ox = oxalate dianion) are presented here. All compounds are isostructural and crystallize in the chiral cubic space group P4132, and contain three-dimensional dimetallic networks formed by alternating MII and MIII ions that are connected by oxalate anions. These compounds exhibit strong antiferromagnetic interactions that give rise to magnetic ordering as ferrimagnets or weak ferromagnets, with critical temperatures of up to 20 K, which is twice as high as those found for the isostructural magnets based…
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.
New hexanuclear FeIII clusters with the gem-diol hydrated form of di(2-pyridyl)ketone and carboxylato ligands: Crystal structures and magnetic proper…
2019
Abstract The hexanuclear compounds [Fe6O2Cl2{(py)2CO2}2(pyOH)2(pyCOO)2(ButCOO)6] (1) and [Fe6O2{(py)2CO2}2(pyCOO)4(ButCOO)6] (2) were obtained by condensation of the trinuclear μ3-oxo-centered iron(III) pivalate [Fe3O(ButCOO)6(H2O)3]+ in the presence of di(2-pyridyl)ketone [(py)2CO] in MeCN at ambient temperature. Both complexes contain an analogous core which can be described as two {Fe3O}7+ units joined by gem-diolato (py)2CO22− bridges. Variable-temperature magnetic susceptibility measurements in polycrystalline samples of 1 and 2 reveal strong antiferromagnetic couplings between the iron(III) ions leading to S = 0 ground states.
Structural and magnetic properties of polynuclear oximate copper complexes with different topologies
2017
Abstract Two new copper(II) complexes containing the methyl(2-pyridyl)ketone oxime ligand (mpkoH) [Cu3(OH)(ClO4)2(mpko)3]·CH3OH (1) and [Cu(ClO4)(mpko)(mpkoH)]n (2) have been prepared from Cu(ClO4)2 and mpkoH in different metal-to-ligand molar ratios. In addition, the compound [Cu{(mpko)2BF2}(H2O)](BF4) (3) [(mpko)2BF2 is the fluoroboration product of the oxime] has been obtained when replacing Cu(ClO4)2 by Cu(BF4)2. Compound 1 is an isolated triangle with a {Cu3(µ3-OH)}5+ core, whereas 2 is a chain of CuII ions linked by anionic mpko− bridges. 1 exhibits strong antiferromagnetic competing interactions, as well as antisymmetric exchange. On the other hand, very weak ferromagnetic interactio…
Exchange coupling in a thiocyanato-bridged copper(II) chain: Computational approach to magnetostructural correlations
2021
Abstract In this article we report the synthesis and magneto-structural characterization of two new copper(II) compounds with thiocyanato and methyl(2-pyridil) ketone oxime (mpkOH), namely [Cu(NCS)(mpkO)(mpkOH)] (1) and [Cu(µ-NCS)(NCS)(mpkOH)]n (2). Compound 1 is a mononuclear complex that crystallizes as discrete units. Conversely, compound 2 is a single equatorial-axial end-to-end thiocyanato bridged polymeric chain of Cu(II) with the oxime as a co-ligand. The coordination geometry around the Cu(II) centers is distorted square pyramidal for 1 and 2. The magnetic susceptibility data for 2 reveal weak intrachain antiferromagnetic coupling, with J value −0.74(3) cm−1 and g = 2.10(1). The ap…
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…
Reversible Solvent‐Exchange‐Driven Transformations in Multifunctional Coordination Polymers Based on Copper‐Containing Organosulfur Ligands
2014
The preparation by simple direct synthesis of a series of coordination polymers based on copper with chloride or bromide and dipyrimidinedisulfide is reported. The structural characterisations of these compounds reveal a rich structural variety as a result of the number of coordination modes available to the organosulfur ligand, in combination with the bridging capabilities of the halides. Interestingly, some of the polymers displayed fully reversible solvent exchange/removal crystal-to-crystal 2D to 0D and 2D to 2D transformations. These materials show multifunctional electronic properties. Thus, some of them are semiconductors and present weak antiferromagnetic interactions, and the CuI/C…
Discrete unusual mixed-bridged trinuclear CoIII2CoII and pentanuclear NiII coordination complexes supported by a phenolate-based ligand: theoretical …
2021
Two new complexes [CoIII2CoII(μ-OL)2(μ-OOCCH3)2(μ-N3)2(N3)2]·Et2O (1·Et2O) and [NiII5(μ-OL)4(μ-OOCCH3)2(OOCCH3)2(μ-N3)2]·CH3CN (2) (HOL = 2-((2-(pyridin-2-yl)ethylamino)methyl)phenol) have been synthesized and characterized by elemental analysis, IR, and UV/Vis spectroscopy. Structural analysis revealed that 1 is a discrete trinuclear and 2 is a discrete pentanuclear coordination complex. In complex 1, terminal metal (CoIII) is in a distorted octahedral MN4O2 environment where coordination is satisfied by two nitrogen atoms and one oxygen atom of the ligand, and an oxygen atom from the acetate group and two nitrogen atoms from azide (one each from the bridging and terminal ones). The centra…
Chiral Molecular Magnets: Synthesis, Structure, and Magnetic Behavior of the Series [M(L-tart)] (M = MnII, FeII, CoII, NiII;L-tart = (2R,3R)-(+)-tart…
2006
A new series of layered magnets with the formula [M(L-tartrate)] (M = Mn(II), Co(II), Fe(II), Ni(II); L-tartrate = (2R,3R)-(+)-tartrate) has been prepared. All of these compounds are isostructural and crystallize in the chiral orthorhombic space group I222, as found by X-ray structure analysis. Their structure consists of a three-dimensional polymeric network in which each metal shows distorted octahedral coordination bound to four L-tartrate ligands, two of which chelate through an alcohol and a carboxylate group and the other two bind terminally through a monodentate carboxylate group. The chirality of the ligand imposes a Delta conformation on all metal centers. Magnetically, the paramag…