Search results for "Magnetization"

Polarization transfer via field sweeping in parahydrogen-enhanced nuclear magnetic resonance.

2019

<div><br></div><div><table><tr><td>We show that in a spin system of two magnetically inequivalent protons coupled to a heteronucleus such as 13C, an adiabatic magnetic field sweep, passing through zero field, transfers proton singlet order into magnetization of the coupled heteronucleus. This effect is potentially useful in parahydrogen-enhanced nuclear magnetic resonance, and is demonstrated on singlet-hyperpolarized [1-13C]maleic acid, which is prepared via the reaction between [1-13C]acetylene dicarboxylic acid and para-enriched hydrogen gas. The magnetic field sweeps are of microtesla amplitudes, and have durations on the order of seconds. We sh…

Molecular Engineering To Control the Magnetic Interaction between Single-Chain Magnets Assembled in a Two-Dimensional Network

2012

International audience; Two two-dimensional (2D) systems having the formula [{Fe-III(dmbpy)(CN)(4)}(2)(CoL)-L-II](n) [L = pyetNO (1), tvpNO (2)] and consisting of single-chain magnets connected through organic ligands (L) have been prepared, and their magnetic properties have been investigated. The overall magnetic behavior depends on the capacity of the organic pillars to transmit long-range magnetic interactions. 1 is the first example of a 2D compound exhibiting double relaxation of the magnetization, whereas 2 behaves as a metamagnet.

Field-Induced Hysteresis and Quantum Tunneling of the Magnetization in a Mononuclear Manganese(III) Complex

2013

International audience

Magnetic hysteresis up to 80 kelvin in a dysprosium metallocene single-molecule magnet

2018

Breaking through the nitrogen ceiling Single-molecule magnets could prove useful in miniaturizing a wide variety of devices. However, their application has been severely hindered by the need to cool them to extremely low temperature using liquid helium. Guo et al. now report a dysprosium compound that manifests magnetic hysteresis at temperatures up to 80 kelvin. The principles applied to tuning the ligands in this complex could point the way toward future architectures with even higher temperature performance. Science , this issue p. 1400

Field-induced slow relaxation of magnetization in a mononuclear Co(II) complex of 2,6-bis(pyrazol-1-yl)pyridine functionalized with a carboxylic acid

2018

Abstract Combining Co(II) with the 2,6-bis-(pyrazol1-yl)pyridine ligand functionalized with a carboxylic acid group (bppCOOH) results in the compound [CoII(bppCOOH)2](ClO4)2·2Me2CO, which shows a field-induced slow relaxation of magnetization as a result of the magnetic anisotropy of the distorted octahedral coordination of high-spin Co(II). Co(II)/Fe(II) solid solutions of bppCOOH have been prepared to study the influence of Co(II) on the spin crossover properties of Fe(II). Magnetic characterization of [Fe0.92Co0.08(bppCOOH)2](ClO4)2 indicates that the Cobalt dopant leads to a reduction of T1/2 and a loss of cooperativity of the spin transition.

2017

Eight coordination compounds of formulae [FeII(L˙)2][ReIVCl6] (1a), [FeII(L˙)2][ReIVBr6] (1b), [CoII(L˙)2][ReIVCl6]·CH3CN (2a), [CoII(L˙)2][ReIVBr6] (2b), [NiII(L˙)(CH3CN)3][ReIVCl6]·CH3CN (3a), [NiII(L˙)(CH3CN)3][ReIVBr6]·3CH3CN (3b), [CuII(L˙)2][ReIVCl6] (4a) and [CuII(L˙)2][ReIVBr6] (4b), where L˙ is the aminoxyl radical chelating ligand, 4,4′-dimethyl-2,2′-di(2-pyridyl)oxazolidine-N-oxide, have been synthesised. Structural and magnetic studies reveal metal–radical intramolecular antiferromagnetic interactions in the [MII(L˙)2]2+ cations in the iron, cobalt and copper based compounds (1a, 1b, 2a, 2b, 4a and 4b) with the central metal ion low-spin in the case of iron (1a and 1b) and a gra…

The glass transition in (KI)0.5(ND4I)0.5 mixed crystals as studied by deuteron spin-lattice relaxation

1993

Abstract Nuclear spin resonance has been used to study the deuteron magnetization recovery in (KI)0.5(ND4I)0.5 mixed crystals. At high temperatures the spin-lattice-relaxation is exponential. For T ⪅ 45 K deviations from this simple behaviour occur, signalling the onset of spatial inhomogeneities due to the formation of an orientational glass. The results demonstrate that the transition of (KI)0.5(ND4I)0.5 into the glassy state is driven by the freezing of random bonds.

Hybrid Organic/Inorganic Molecular Materials Formed by Tetrathiafulvalene Radicals and Magnetic Trimeric Clusters of Dimetallic Oxalate‐Bridged Compl…

2003

The first examples of trimeric, dimetallic, pure oxalate-bridged complexes [ox = (C2O4)2−] have been synthesized and characterized structurally and magnetically for the two new series of crystalline molecular assemblies formulated as (TTF)4{MII(H2O)2[MIII(ox)3]2}·nH2O [for MIII = Cr; MII = Mn (1), Fe (2), Co (3), Ni (4), Cu (5) and Zn (6); for MIII = Fe; MII = Mn (7), Fe (8), Co (9), Ni (10) and Zn (11)]. Both series (Cr2M and Fe2M) are isostructural. The crystal structure of (TTF)4{Mn(H2O)2[Cr(ox)3]2}⋅14H2O (1) [monoclinic, space group C2/c (no. 15), a = 13.240(5) A, b = 19.450(5) A, c = 27.690(5) A, β = 97.63(5)°, V = 7068(3) A3 and Z = 4] shows alternating layers of the organic radical T…

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…

Langmuir–Blodgett films based on inorganic molecular complexes with magnetic or optical properties

2005

Langmuir and Langmuir–Blodgett (LB) films of a great variety of molecular metal complexes with interesting magnetic or optical properties have been prepared in the last few years. Some of the results obtained by our group and others are summarized in this article. (i) LB films of polyoxometalates (POM) were first prepared taking advantage of the adsorption properties of these cluster anions along a positively charged monolayer of an organic surfactant spread in water. A correct choice of the POM allowed the preparation of LB films with magnetic, electrochromic, or luminescent properties. Besides this semiamphiphilic method, two new methods to prepare LB films of POMs have been developed by …