The Experts below are selected from a list of 293454 Experts worldwide ranked by ideXlab platform
Lyndon Emsley - One of the best experts on this subject based on the ideXlab platform.
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Spin-State selection in solid-State NMR
Journal of magnetic resonance (San Diego Calif. : 1997), 2003Co-Authors: Luminita Duma, Sabine Hediger, Anne Lesage, Lyndon EmsleyAbstract:Spin-State selection in solid-State NMR is demonstrated, using similar pulse sequences as used in liquid-State NMR. The different transitions of all three carbon resonances in fully 13C-labeled L-alanine are separated in different spectra. By selecting Spin-States, the contribution of the J-coupling to the linewidth is removed, leading to a considerable enhancement in resolution. The Spin-State-selective technique is demonstrated for magic-angle Spinning frequencies from 6 to 35kHz. Other experimental conditions affecting the sensitivity of the experiments are discussed. Sensitivity losses due to the introduction of the Spin-State-selective filter are shown to be acceptable. Finally, Spin-State selection was used to experimentally confirm the differential broadening expected for the two transitions of the CH3 resonance.
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Resolution Enhancement in Multidimensional Solid-State NMR Spectroscopy of Proteins using Spin-State Selection
Journal of the American Chemical Society, 2003Co-Authors: Luminita Duma, Sabine Hediger, Bernhard Brutscher, Anja Böckmann, Lyndon EmsleyAbstract:A new experimental approach is introduced which leads to significant resolution enhancement in multidimensional 13C-13C correlation experiments of microcrystalline systems. Spin-State-selective techniques, adapted for solid-State NMR, are used for removing the J-coupling contribution to the 13C lineshapes. Combination of the Spin-State-selective elements and standard ZQ or DQ solid-State NMR mixing sequences allows to perform a Spin-State-selective polarization transfer. In addition to the resolution improvement, the new technique enables to distinguish "direct" cross peaks involving covalently bound nuclei from "relayed" cross peaks.
Ichiro Terasaki - One of the best experts on this subject based on the ideXlab platform.
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Impurity-Induced Spin-State Crossover in La0.8Sr0.2Co1−xAlxO3
Crystals, 2018Co-Authors: Ichiro Terasaki, Masamichi Ikuta, Takafumi D. Yamamoto, Hiroki TaniguchiAbstract:We have prepared a set of polycrystalline samples of La 0.8 Sr 0.2 Co 1 − x Al x O 3 ( 0 ≤ x ≤ 0.2 ), and have measured the magnetization as functions of temperature and magnetic field. We find that the average Spin number per Co ion ( S Co ) evaluated from the room-temperature susceptibility is around 1.2–1.3 and independent of x. However, we further find that S Co evaluated from the saturation magnetization at 2 K is around 0.3–0.7, and decreases dramatically with x. This naturally indicates that a significant fraction of the Co 3 + ions experience a Spin-State crossover from the intermediate- to low-Spin State with decreasing temperature in the Al-substituted samples. This Spin-State crossover also explains the resistivity and the thermopower consistently. In particular, we find that the thermopower is anomalously enhanced by the Al substitution, which can be consistently explained in terms of an extended Heikes formula.
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Enhanced thermopower via Spin-State modification
Physical Review B, 2018Co-Authors: Hidefumi Takahashi, Ryuji Okazaki, Shintaro Ishiwata, Yukio Yasui, Ichiro TerasakiAbstract:We investigated the effect of pressure on the magnetic and thermoelectric properties of ${\mathrm{Sr}}_{3.1}{\mathrm{Y}}_{0.9}{\mathrm{Co}}_{4}{\mathrm{O}}_{10+\ensuremath{\delta}}$. The magnetization is reduced with the application of pressure, reflecting the Spin-State modification of the ${\mathrm{Co}}^{3+}$ ions into the nonmagnetic low-Spin State. Accordingly, with increasing pressure, the Seebeck coefficient is enhanced, especially at low temperatures, at which the effect of pressure on the Spin State becomes significant. These results indicate that the Spin-orbital entropy is a key valuable for the thermoelectric properties of the strongly correlated cobalt oxides.
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Spin State control of the perovskite Rh/Co oxides
Materials, 2010Co-Authors: Ichiro Terasaki, S. Shibasaki, Shin Yoshida, Wataru KobayashiAbstract:We show why and how the Spin State of transition-metal ions affects the thermoelectric properties of transition-metal oxides by investigating two perovskite-related oxides. In the A-site ordered cobalt oxide Sr3YCo4O10.5, partial substitution of Ca for Sr acts as chemical pressure, which compresses the unit cell volume to drive the Spin State crossover, and concomitantly changes the magnetization and thermopower. In the perovskite rhodium oxide LaRhO3, partial substitution of Sr for La acts as hole-doping, and the resistivity and thermopower decrease systematically with the Sr concentration. The thermopower remains large values at high temperatures (>150 μV/K at 800 K), which makes a remarkable contrast to La1-xSrxCoO3. We associate this with the stability of the low Spin State of the Rh3+ ions.
Luminita Duma - One of the best experts on this subject based on the ideXlab platform.
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Spin-State selection in solid-State NMR
Journal of magnetic resonance (San Diego Calif. : 1997), 2003Co-Authors: Luminita Duma, Sabine Hediger, Anne Lesage, Lyndon EmsleyAbstract:Spin-State selection in solid-State NMR is demonstrated, using similar pulse sequences as used in liquid-State NMR. The different transitions of all three carbon resonances in fully 13C-labeled L-alanine are separated in different spectra. By selecting Spin-States, the contribution of the J-coupling to the linewidth is removed, leading to a considerable enhancement in resolution. The Spin-State-selective technique is demonstrated for magic-angle Spinning frequencies from 6 to 35kHz. Other experimental conditions affecting the sensitivity of the experiments are discussed. Sensitivity losses due to the introduction of the Spin-State-selective filter are shown to be acceptable. Finally, Spin-State selection was used to experimentally confirm the differential broadening expected for the two transitions of the CH3 resonance.
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Resolution Enhancement in Multidimensional Solid-State NMR Spectroscopy of Proteins using Spin-State Selection
Journal of the American Chemical Society, 2003Co-Authors: Luminita Duma, Sabine Hediger, Bernhard Brutscher, Anja Böckmann, Lyndon EmsleyAbstract:A new experimental approach is introduced which leads to significant resolution enhancement in multidimensional 13C-13C correlation experiments of microcrystalline systems. Spin-State-selective techniques, adapted for solid-State NMR, are used for removing the J-coupling contribution to the 13C lineshapes. Combination of the Spin-State-selective elements and standard ZQ or DQ solid-State NMR mixing sequences allows to perform a Spin-State-selective polarization transfer. In addition to the resolution improvement, the new technique enables to distinguish "direct" cross peaks involving covalently bound nuclei from "relayed" cross peaks.
Marcel Swart - One of the best experts on this subject based on the ideXlab platform.
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Spin-State-corrected Gaussian-type orbital basis sets.
The journal of physical chemistry. A, 2010Co-Authors: Marcel Swart, Mireia Güell, Josep M. Luis, Miquel SolàAbstract:Recently, we reported that the basis set has a profound influence on the computed values for Spin-State splittings [J. Phys. Chem. A 2008, 112, 6384]. In particular, small Gaussian-type orbital (GTO) basis sets were shown to be unreliable for the prediction of them. Here, we report simple modifications of the small Pople-type Gaussian-type orbital basis sets (3-21G, 3-21G*, 6-31G, 6-31G*), which correct their faulty behavior for the Spin-State energies. We have investigated the basis sets for a set of 13 first-row transition-metal complexes for which reliable reference data have been obtained at the OPBE/TZ2P(STO) level. For several systems, we have used single and double Spin-contamination corrections to avoid ambiguity of the results because of Spin contamination, that is, the energies and geometries were obtained for the pure Spin States. The Spin ground States as predicted by the Spin-State-corrected GTO basis sets (s6-31G, s6-31G*) are in complete agreement with the reference Slater-type orbital (STO...
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Spin-State splittings of iron(II) complexes with trispyrazolyl ligands
Polyhedron, 2010Co-Authors: Mireia Güell, Miquel Solà, Marcel SwartAbstract:Abstract We report a computational study at the OPBE/TZP level on the chemical bonding and Spin ground-States of mono-nuclear iron(II) complexes with trispyrazolylborate and trispyrazolylmethane ligands. We are in particular interested in how substitution patterns on the pyrazolyl-rings influence the Spin-State splittings, and how they can be rationalized in terms of electronic and steric effects. One of the main observations of this study is the large similarity of the covalent metal–ligand interactions for both the borate and methane ligands. Furthermore, we find that the Spin-State preference of an individual transition-metal (TM) complex does not always concur with that of an ensemble of TM-complexes in the solid-State. Finally, although the presence of methyl groups at the 3-position of the pyrazolyl groups leads to ligand–ligand repulsion, it is actually the loss of metal–ligand bonding interactions that is mainly responsible for shifts in Spin-State preferences.
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Importance of the basis set for the Spin-State energetics of iron complexes.
The journal of physical chemistry. A, 2008Co-Authors: Mireia Güell, Josep M. Luis, Miquel Solà, Marcel SwartAbstract:We have performed a systematic investigation of the influence of the basis set on relative Spin-State energies for a number of iron compounds. In principle, with an infinitely large basis set, both Slater-type orbital (STO) and Gaussian-type orbital (GTO) series should converge to the same final answer, which is indeed what we observe for both vertical and relaxed Spin-State splittings. However, we see throughout the paper that the STO basis sets give consistent and rapidly converging results, while the convergence with respect to the basis set size is much slower for the GTO basis sets. For example, the large GTO basis sets that give good results for the vertical Spin-State splittings of compounds 1−3 (6-311+G**, Ahlrichs VTZ2D2P) fail for the relaxed Spin-State splittings of compound 4 (where 1 is Fe−(PyPepS)2 (PyPepSH2 = N-(2-mercaptophenyl)-2-pyridinecarboxamide), 2 is Fe(tsalen)Cl (tsalen = N,N′-ethylenebis-(thiosalicylideneiminato)), 3 is Fe(N(CH2−o-C6H4S)3)(1-Me-imidazole), and 4 is FeFHOH). Very d...
Sabine Hediger - One of the best experts on this subject based on the ideXlab platform.
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Spin-State selection in solid-State NMR
Journal of magnetic resonance (San Diego Calif. : 1997), 2003Co-Authors: Luminita Duma, Sabine Hediger, Anne Lesage, Lyndon EmsleyAbstract:Spin-State selection in solid-State NMR is demonstrated, using similar pulse sequences as used in liquid-State NMR. The different transitions of all three carbon resonances in fully 13C-labeled L-alanine are separated in different spectra. By selecting Spin-States, the contribution of the J-coupling to the linewidth is removed, leading to a considerable enhancement in resolution. The Spin-State-selective technique is demonstrated for magic-angle Spinning frequencies from 6 to 35kHz. Other experimental conditions affecting the sensitivity of the experiments are discussed. Sensitivity losses due to the introduction of the Spin-State-selective filter are shown to be acceptable. Finally, Spin-State selection was used to experimentally confirm the differential broadening expected for the two transitions of the CH3 resonance.
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Resolution Enhancement in Multidimensional Solid-State NMR Spectroscopy of Proteins using Spin-State Selection
Journal of the American Chemical Society, 2003Co-Authors: Luminita Duma, Sabine Hediger, Bernhard Brutscher, Anja Böckmann, Lyndon EmsleyAbstract:A new experimental approach is introduced which leads to significant resolution enhancement in multidimensional 13C-13C correlation experiments of microcrystalline systems. Spin-State-selective techniques, adapted for solid-State NMR, are used for removing the J-coupling contribution to the 13C lineshapes. Combination of the Spin-State-selective elements and standard ZQ or DQ solid-State NMR mixing sequences allows to perform a Spin-State-selective polarization transfer. In addition to the resolution improvement, the new technique enables to distinguish "direct" cross peaks involving covalently bound nuclei from "relayed" cross peaks.
