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Magnetic Relaxation (magnetic + relaxation)

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Chemistry83%

Terms modified by Magnetic Relaxation

  • magnetic relaxation dispersion
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    Selected Abstracts

    Coupling Dy3 Triangles Enhances Their Slow Magnetic Relaxation,

    ANGEWANDTE CHEMIE, Issue 36 2010

    Zwei mal drei: Die Kupplung zweier Dy3 -Dreiecke zu einem Dy6 -Komplex (siehe Bild; Dy,blau, Cl,grün, O,rot) erhöht die Barriere für die Magnetisierungsumkehr erheblich. Dieser Effekt wurde auf der Grundlage von Einkristallmagnetometrie-Messungen und Ab-initio-Rechnungen erklärt. [source]

    Heterometallic CoIII,LnIII (Ln = Gd, Tb, Dy) Complexes on a p -Sulfonatothiacalix[4]arene Platform Exhibiting Redox-Switchable Metal-to-Metal Energy Transfer

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 25 2008
    Viktoriya Skripacheva
    Abstract Nuclear magnetic relaxation along with pH metric data have been used to reveal pH-dependent heterometallic CoIII,LnIII (Ln = Gd, Tb, and Dy) complex formation on a p -sulfonatothiacalix[4]arene (TCAS) platform in aqueous solution. The previously obtained 1D and 2D 1H NMR spectroscopic and X-ray data prove the outer sphere binding of the CoIII block with the upper rim of TCAS, whereas the LnIII ion is coordinated with the phenolate groups of the lower rim of TCAS. The inclusive outer-sphere binding of CoIII tris(dipyridyl) and tris(ethylendiaminate) complexes with the upper rim of TCAS favors binding of the inner-sphere lanthanide ions through the lower rim of TCAS, whereas noninclusive binding of CoIII bis(histidinate) provides no effect on the binding of lanthanide ions. The emission properties of [Co(dipy)3]3+,LnIII (Ln = Gd, Tb, Dy) complexes indicate the quenching of 4f luminescence by the 3d block. This quenching can be switched off by electrochemical CoIII/CoII reduction with further switching on by reoxidation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Water Dynamics in Ionomer Membranes by Field-Cycling NMR Relaxometry,

    FUEL CELLS, Issue 1 2006
    J.-C. Perrin
    Abstract The water dynamics of two types of ionomer membranes, the Nafion® and sulfonated polyimides, have been investigated by field-cycling nuclear magnetic relaxation. This technique, applied to samples prepared at different water content, allows to characterize the proton motion at the time scale of the microsecond. The polyimides appear to behave as standard porous materials, whereas in the Nafion®, we have observed two different dynamical regimes related to a complex swelling process. [source]

    Nuclear magnetic relaxation of water in ionic-liquid solutions: determining the kosmotropicity of ionic liquids and its relationship with the enzyme enantioselectivity

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2007
    Hua Zhao
    Abstract The nuclear magnetic relaxations of water in ionic-liquid (IL) solutions were examined at various IL concentrations in order to better understand their hydration behaviors (in terms of nuclear magnetic resonance (NMR) B,-coefficients). From these B,-values of ILs, the individual ion's B,-coefficients were further calculated based on the additivity. These coefficients represent the hydration behavior (,kosmotropicity') of ILs in aqueous solutions. Using these data, a linear correlation was found between enzyme enantioselectivity in aqueous solution and the ,, parameter (difference in NMR B,-coefficients of anion and cation). In general, high enzyme enantiomeric ratios (E) could be achieved in solutions of ILs with high ,, values. Copyright © 2007 Society of Chemical Industry [source]

    Molecular Dynamics of Podand Studied by Broadband Dielectric and Nuclear Magnetic Resonance Spectroscopies,,

    MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 19-20 2007
    Bakyt Orozbaev
    Abstract Nuclear magnetic resonance (NMR) and broadband dielectric spectroscopies (BDS) were used to analyze the molecular dynamics in P10.3H Podand. The temperature studies of NMR line and magnetic spin,lattice relaxation times accompanied by DS investigation enabled us to distinguish three main dynamical processes connected with the motions of the P10.3H Podand chains. In the low-temperature region the magnetic relaxation was associated with fast axial C3 rotation of methyl groups. Moreover, two other independent processes were observed and interpreted as (i) segmental motion of both oxyethylene and ethylene units, and (ii) the overall motion involved in the melting process. [source]

    Metal,Organic Perovskites: Synthesis, Structures, and Magnetic Properties of [C(NH2)3][MII(HCOO)3] (M=Mn, Fe, Co, Ni, Cu, and Zn; C(NH2)3= Guanidinium)

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 44 2009
    Ke-Li Hu
    Abstract We report the synthesis, crystal structures, and spectral, thermal, and magnetic properties of a family of metal,organic perovskite ABX3, [C(NH2)3][MII(HCOO)3], in which A=C(NH2)3 is guanidinium, B=M is a divalent metal ion (Mn, Fe, Co, Ni, Cu, or Zn), and X is the formate HCOO,. The compounds could be synthesized by either diffusion or hydrothermal methods from water or water-rich solutions depending on the metal. The five members (Mn, Fe, Co, Ni, and Zn) are isostructural and crystallize in the orthorhombic space group Pnna, while the Cu member in Pna21. In the perovskite structures, the octahedrally coordinated metal ions are connected by the anti,anti formate bridges, thus forming the anionic NaCl-type [M(HCOO)3], frameworks, with the guanidinium in the nearly cubic cavities of the frameworks. The Jahn,Teller effect of Cu2+ results in a distorted anionic Cu,formate framework that can be regarded as Cu,formate chains through short basal CuO bonds linked by the long axial CuO bonds. These materials show higher thermal stability than other metal,organic perovskite series of [AmineH][M(HCOO)3] templated by the organic monoammonium cations (AmineH+) as a result of the stronger hydrogen bonding between guanidinium and the formate of the framework. A magnetic study revealed that the five magnetic members (except Zn) display spin-canted antiferromagnetism, with a Néel temperature of 8.8 (Mn), 10.0 (Fe), 14.2 (Co), 34.2 (Ni), and 4.6,K (Cu). In addition to the general spin-canted antiferromagnetism, the Fe compound shows two isothermal transformations (a spin-flop and a spin-flip to the paramagnetic phase) within 50,kOe. The Co member possesses quite a large canting angle. The Cu member is a magnetic system with low dimensional character and shows slow magnetic relaxation that probably results from the domain dynamics. [source]