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1.
A.V. Soloninin A.V. Skripov A.L. Buzlukov A.P. Stepanov 《Journal of solid state chemistry》2009,182(9):2357-2361
In order to study the atomic jump motions in the high-temperature solid phase of LiBH4, we have measured the 1H and 11B nuclear magnetic resonance (NMR) spectra and the 1H, 7Li and 11B spin–lattice relaxation rates in this compound over the resonance frequency range of 14–34.4 MHz. In the temperature range 384–500 K, all the spin–lattice relaxation data are satisfactorily described in terms of a thermally activated jump motion of Li ions with the pre-exponential factor τ0=1.1×10−15 s and the activation energy Ea=0.56 eV. The observed frequency dependences of the spin–lattice relaxation rates in this temperature range exclude a presence of any distributions of the Li jump rate or any other jump processes on the frequency scale of 107–1010 s−1. The strong narrowing of the 1H and 11B NMR lines above 440 K is consistent with the onset of diffusive motion of the BH4 tetrahedra. 相似文献
2.
V. Paul-Boncour M. Latroche A. Percheron-Guégan 《Journal of solid state chemistry》2006,179(10):3224-3228
The magnetic properties of the RY2Ni9 ternary alloys (R=La, Ce) and their hydrides have been investigated. Both LaY2Ni9 and CeY2Ni9 are ferromagnets with TC=15 and 92 K, respectively. Upon H absorption LaY2Ni9H12 becomes a Pauli paramagnet, whereas CeY2Ni9H8 remains ferromagnetic with an additional magnetic contribution of trivalent Ce atoms belonging to the MgZn2 units occupied by hydrogen atoms. 相似文献
3.
M Latroche V Paul-Boncour A Percheron-Guégan 《Journal of solid state chemistry》2004,177(7):2542-2549
The crystal structure of two deuterides RY2Ni9Dx (R=La; x=12.8 and R=Ce; x=7.7) have been investigated by means of neutron powder diffraction and X-ray absorption spectroscopy. The structures are best described in the space group . The deuterium location has been determined for both compounds. The nature and the occupancy factors of the different D sites are presented. Comparisons are made between the La-based deuteride and the Ce-one in relation with the crystal structure of the intermetallic compounds. Differences in site occupancies within the RM2 and RM5 building units of the PuNi3-type structure are discussed and heterogeneous mixed valence state is reported for the cerium compound. 相似文献
4.
The present article reviews and discusses proton magnetic resonance studies on metalloporphyrins which provide good models
for heme proteins in their physical and chemical properties. Emphasis is given on the discussion of the1Hnmr work done in our laboratory. 相似文献
5.
Hydrogenation of tetragonal InPd3 in the ZrAl3 type structure (four-fold ccp superstructure) yields a hydride with a cubic AuCu3 type structure (one-fold ccp superstructure). Deuterium can be located by neutron powder diffraction in octahedral voids surrounded exclusively by palladium, [Pd6], which are 88.5(6)% occupied in a statistical manner. The resulting deuteride InPd3D0.89 thus crystallizes in a cubic anti-perovskite type structure (space group Pm3¯m (no. 221), a=402.25(1) pm at 299(2) K). The Pd-D distance of 201.13(1) pm is typical for interstitial hydrides with palladium. Inelastic neutron scattering on the hydride InPd3H0.89, which shows a spectrum similar to that of binary palladium hydride, confirms the cubic site symmetry of hydrogen in [Pd6] interstices. This is also confirmed by the absence of any quadrupole splitting in the 2D-NMR signal of the deuteride. 1H NMR spectra of InPd3H0.89 do not show any motional narrowing. Values found for the H jump rate τ−1 in InPd3H0.89 remain below 106 s−1 in the studied temperature range 28-360 K, indicating a small hydrogen mobility in InPd3H0.8 as compared with binary palladium hydride, PdH≤1. This can be attributed to the large spatial separation of the [Pd6] sites. 相似文献
6.
Mikhail Ryazanov Reinhard K. Kremer Hansjürgen Mattausch 《Journal of solid state chemistry》2005,178(7):2339-2345
We have studied the effect of hydrogen insertion in GdI2 on its magnetic and electrical properties. The ferromagnetic layered metal GdI2 reversibly absorbs hydrogen with the formation of GdI2Hx which exhibits a range of homogeneity 0?x?1. These phases crystallize with the hexagonal MoS2-type heavy atom arrangement. Variation of the hydrogen content is accompanied by a monotonic change in the lattice parameters, and a decreases from 4.074(1) to 4.023(1) Å whereas c increases from 15.050(5) to 15.394(5) Å for x=0-0.97. The molar volume passes through a maximum at x≈0.35. Magnetization and resistance measurements reveal a substantial change in the physical properties of GdI2Hx as a function of the hydrogen content, particularly as x approaches a critical value of ∼1/3. The Curie temperature rapidly decreases with increasing hydrogen content, and the long-range magnetic ordering is destroyed for x>0.33. The phases GdI2Hx with 0.42?x?0.69 exhibit characteristics of a spin-glass below the magnetic freezing temperatures Tf=24 and 3 K for x=0.42 and 0.69, respectively. The hydride halides GdI2Hx (x>0.19) show thermally activated conduction, accompanied by a steep increase of the activation energy at x≈0.33. The anomalies observed can be understood by assuming an ordering of the hydrogen atoms for x=1/3 within each layer. 相似文献
7.
Nuclear magnetic resonance spectroscopic study on ionic liquids of 1-alkyl-3-methylimidazolium salts
Chemical shifts of 1H and 13C NMR of series of methylimidazolium salts (MIM+, X=Br−, BF4− and PF6−) function on the length of alkyl groups on the ring, type of solvents and the concentration. The bromides series demonstrate more chemical shift variation on H2 upon the change of solvents and concentration. Unexpected H-D exchange reactions were also observed in the MIM+Br− by using CD3OD and D2O. The exchange rates strongly depend on the length of the alkyl group, which could cause more steric factor to reduce the interaction between deuterium atom from solvent and C2 of the ring. 相似文献
8.
Ortner K Sivanandam VN Buchberger W Müller N 《Analytical and bioanalytical chemistry》2007,388(1):173-177
Enzymatically cleaved glycans from sub-milligram quantities of erythropoietin (EPO) and ovalbumin have been analyzed, without
further purification, by two-dimensional diffusion-ordered nuclear magnetic resonance spectroscopy. At NMR sample concentrations
below 50 μmol L−1 the major components of the oligosaccharide fractions could be distinguished by their anomeric proton chemical shift and
their size-dependent diffusion coefficients.
Figure
1H NMR diffusion decay curves of anomeric protons in the EPO glycan fraction 相似文献
9.
Gemma M. Kirwan Timothy Hancock Kathryn Hassell Julie O. Niere Dayanthi Nugegoda Susumu Goto Michael J. Adams 《Analytica chimica acta》2013
Blood plasma collected from adult fish (black bream, Sparidae) exposed to a dose of 5 mg kg−1 17β-estradiol underwent metabonomic profiling using nuclear magnetic resonance (NMR). An extension of the orthogonal 2 projection to latent structure (O2PLS) analysis, tO2PLS, was proposed and utilized to classify changes between the control and experimental metabolic profiles. As a bidirectional modeling tool, O2PLS examines the (variable) commonality between two different data blocks, and extracts the joint correlations as well as the unique variations present within each data block. tO2PLS is a proposed matrix transposition of O2PLS to allow for commonality between experiments (spectral profiles) to be observed, rather than between sample variables. tO2PLS analysis highlighted two potential biomarkers, trimethylamine-N-oxide (TMAO) and choline, that distinguish between control and 17β-estradiol exposed fish. This study presents an alternative way of examining spectroscopic (metabolite) data, providing a method for the visual assessment of similarities and differences between control and experimental spectral features in large data sets. 相似文献
10.
Shigenobu Hayashi 《Journal of solid state chemistry》2003,170(1):82-93
Ti0.33V0.67HxDy (x+y≈0.9) alloys have been studied by means of X-ray powder diffraction (XRD), differential scanning calorimetry (DSC) and 1H and 2H NMR. The crystal structures are body-centered-cubic (bcc) dominantly, being mixed with a face-centered-cubic (fcc) phase. A phase transition similar to that from the δD phase to the αD phase in the V-D system is observed in all the samples except for the protide. H and D are considered to occupy tetrahedral sites. The temperature and frequency dependence of spin-lattice relaxation times T1 of 1H and 2H has been analyzed by Bloembergen-Purcell-Pound equations with a distribution of correlation times, and parameters of hydrogen diffusion are estimated. The mean activation energy for D diffusion (ED) is higher than that for H diffusion (EH). EH is constant while ED increases slightly with the [D]/[H] ratio. The distribution of the correlation times increases as the [D]/[H] ratio decreases. 相似文献
11.
R.V. Denys V.A. Yartys Masashi Sato R.G. Delaplane 《Journal of solid state chemistry》2007,180(9):2566-2576
A new intermetallic deuteride Ce2Ni7D4.7 with an anomalous volume expansion has been studied. Its structure was solved on the basis of in situ neutron diffraction data. Expansion proceeds along the c-axis and within the CeNi2 slabs only. All D atoms are located inside these slabs and on the border between CeNi2 and CeNi5. Ordering of D atoms in the bulk of CeNi2 is accompanied by substantial deformation of these slabs thus lowering the hexagonal symmetry to orthorhombic [space group Pmcn (No. 62); a=4.9251(3) Å, b=8.4933(4) Å, c=29.773(1) Å]. Inside the CeNi2 layer the hydrogen sublattice is completely ordered; all D-D distances exceed 2.0 Å. Local coordination of Ni by D inside the CeNi2 blocks is of “open”, saddle-like type. Hydrogen ordering is mainly determined by Ce-H and H-H interactions. The pressure-composition-temperature measurements yielded the following thermodynamic parameters of the formation of the hydride: ΔH=−22.4 kJ/molH, ΔS=−59.9 J/(K molH). 相似文献
12.
Shigenobu Hayashi 《Journal of solid state chemistry》2004,177(3):824-833
Sites and dynamics of deuterium in VD0.50 as well as in VD0.40 and VD0.57 have been studied by means of X-ray diffraction, differential scanning calorimetry and 2H NMR. VD0.40 consists of the body-centered-cubic (bcc) αD and body-centered-tetragonal (bct) βD phases at room temperature and only the octahedral (O) sites are occupied in the βD phase. On the other hand, in VD0.50, consisting of the bctβD phase at room temperature, the O site is dominantly occupied with a small occupancy of the tetrahedral (T) sites in the βD phase. VD0.57 is composed of the bccα′D (a high-deuterium-concentration phase of the αD phase) and bctβD phases at room temperature, and the occupancy of the T sites is observed. The mean activation energy (ED) of the deuterium diffusion is much larger for the O sites than for the T sites, and the diffusion is also much slower in the O sites. The mean ED values for the O sites are almost the same in the βD phase of VD0.40 and VD0.50, although the distribution of the mean residence time is much larger in VD0.50 than in VD0.40. 相似文献
13.
Edmund J. Cussen 《Journal of solid state chemistry》2007,180(2):474-483
A series of perovskite phases have been prepared from the appropriate carbonates and oxides by heating under reducing conditions at temperatures up to 1300 °C. Complete ordering between ErO6 and MoO6 octahedra and a disordered distribution of Sr2+ and Ba2+ occur in all compounds. Neutron powder diffraction experiments show that the substitution of Sr2+ into Ba2ErMoO6 introduces a progressive reduction in symmetry from Fm3¯m (x=0) to I4/m (x=0.5, 0.8) to P21/n (x=1.25, 1.75, 2.0). Magnetic susceptibility measurements indicate that all of these compounds show Curie-Weiss paramagnetism and that for x<1.25 this behaviour persists down to 2 K. The monoclinically distorted compounds show magnetic transitions at low temperature and neutron diffraction has confirmed the presence of long-range antiferromagnetic order below 2.5 and 4 K in Ba0.25Sr1.75ErMoO6 and Sr2ErMoO6, respectively. Ba0.75Sr1.25ErMoO6, Ba0.25Sr1.75ErMoO6 and Sr2ErMoO6 do not undergo structural distortion on cooling from room temperature. 相似文献
14.
The cohesive interaction among polymer chains in a polyacrylamide (PAAm)–D2O solution has been studied by NMR relaxation. The NMR relaxation times of PAAm in the good solvent D2O were measured at different temperatures. The results show that the solution system has a high local viscosity and that its
relaxation characteristic is soft-solid-like. The temperature dependence of the relaxation behavior of the solution is obviously
different from that of ordinary polymer solutions. The difference lies in the relaxation behavior of the methylene protons
in the main chain of PAAm, as shown by analyzing the relaxation process with single exponential and biexponential decays.
As the temperature increases, the solvation is weakened, leading polymer chains to form curling coils, thus hindering the
movement of the methylene protons among the main chains. It can be expected from the existence of 80% fast-relaxing protons
that there are a zhigh number of entanglements among the polymer chains in PAAm solution. The information about entanglements
among the polymer chains can be deduced from the biexponential dependence of the spin–spin relaxation on the concentration
of the polymer solutions.
Received: 14 April 1999/Accepted in revised form: 12 October 1999 相似文献
15.
Crystal structure and hydrogenation properties of pseudo-binary Mg6Pd0.5Ni0.5 complex metallic alloy
The crystal structure of the Ni-substituted Mg6.10(2)Pd0.52(2)Ni0.41(2) complex metallic alloy has been determined by X-ray and neutron powder diffraction. The reaction of this compound at 573 K towards deuterium absorption for pressures up to 23 bar has also been studied. The crystal structure of Mg6.10(2)Pd0.52(2)Ni0.41(2) compound was determined in the light of Samson's [Acta Crystallogr. B 28 (1972) 936) and Makongo's (Philos. Mag. 86 (2006) 427] models for the binary Mg6Pd compound. It crystallizes in space group with lattice parameter 20.13331(7) Å. The refined unit-cell composition is Mg342(1)Pd29(1)Ni23(1) with Z=56. Nickel by palladium substitution is not fully random. Nickel atoms preferentially locate on Pd sites with low coordination number due to steric effects. Deuterium uptake is 9.6 D/f.u. under the given conditions of pressure and temperature. Upon absorption, the intermetallic compound disproportionates into MgD2, Mg5Pd2 and Mg2NiD4 phases. The Mg2NiD4 phase is observed to crystallize in the orthorhombic LT2 modification for which an averaged crystal structure in the Pcc2 space group is proposed. 相似文献
16.
R.V. Denys A.B. Riabov V.A. Yartys Masashi Sato 《Journal of solid state chemistry》2008,181(4):812-821
The present work is focused on studies of the influence of magnesium on the hydrogenation behaviour of the (La,Mg)2Ni7 alloys. Substitution of La in La2Ni7 by Mg to form La1.5Mg0.5Ni7 preserves the initial Ce2Ni7 type of the hexagonal P63/mmc structure and leads to contraction of the unit cell. The system La1.5Mg0.5Ni7-H2 (D2) was studied using in situ synchrotron X-ray and neutron powder diffraction in H2/D2 gas and pressure-composition-temperature measurements. La replacement by Mg was found to proceed in an ordered way, only within the Laves-type parts of the hybrid crystal structure, yielding formation of LaMgNi4 slabs with statistic and equal occupation of one site by La and Mg atoms. Mg alters structural features of the hydrogenation process. Instead of a strong unilateral anisotropic expansion which takes place on hydrogenation of La2Ni7, the unit cell of La1.5Mg0.5Ni7D9.1 is formed by nearly equal hydrogen-induced expansions proceeding in the basal plane (Δa/a=7.37%) and along [001] (Δc/c=9.67%). In contrast with La2Ni7D6.5 where only LaNi2 layers absorb hydrogen atoms, in La1.5Mg0.5Ni7D9.1 both LaNi5 and LaMgNi4 layers become occupied. Nine types of sites were found to be filled by D in total, including tetrahedral (La,Mg)2Ni2, (La,Mg)Ni3, Ni4, tetragonal pyramidal La2Ni3 and trigonal bipyramidal (La,Mg)3Ni2 interstices. The hydrogen sublattice around the La/Mg site shows formation of two co-ordination spheres of D atoms: an octahedron MgD6 and a 16-vertex polyhedron LaD16 around La. The interatomic distances are in the following ranges: La-D (2.28-2.71), Mg-D (2.02-2.08), Ni-D (1.48-1.86 Å). All D-D distances exceed 1.9 Å. Thermodynamic PCT studies yielded the following values for the ΔH and ΔS of hydrogenation/decomposition; ΔHH=−15.7±0.9 kJ (molH)−1 and ΔSH=−46.0±3.7 J (K molH)−1 for H2 absorption, and ΔHH=16.8±0.4 kJ (molH)−1 and ΔSH=48.1±1.5 J (K molH)−1 for H2 desorption. 相似文献
17.
The synthesis and complete characterisation of the fluorescent ligand, 4-acridinol-1-sulphonic acid (the acridine analogue of 8-quinolinol-5-sulfonic acid) is described. Using a judicious array of nuclear magnetic resonance spectroscopy experiments, the structural elucidation and full assignment of all proton and carbon chemical shifts were afforded. The 4-acridinol-1-sulphonic acid was found to behave in a similar manner to 8-quinolinol-5-sulphonic acid, forming fluorescent complexes with magnesium(II) and zinc(II). The uncorrected emission maxima for the metal-acridinol complexes were found to be at around 620 nm compared to 505 nm for the respective quinolinol complexes. Unfortunately, preliminary spectrofluorimetric analytical figures of merit revealed that the detection limits of the new acridinol metal complexes were one and a half orders of magnitude poorer than those attained with the corresponding quinolinol ligand. However, in contrast to 8-quinolinol-5-sulphonic acid, the 4-acridinol-1-sulphonic acid ligand showed considerable selectivity for magnesium(II) and zinc(II) over aluminium(III). 相似文献
18.
Gloria Uccello-Barretta Letizia VanniFederica Balzano 《Journal of chromatography. A》2010,1217(7):928-940
NMR spectroscopy represents a valuable tool for obtaining information about structure and dynamics at a molecular level on the diastereoisomeric complexes formed by enantiomeric substrates and chromatographic chiral selectors or modifiers. Some examples collected from the literature show the potentialities of solution NMR spectroscopy in the rationalization of chromatographic enantiorecognition processes and the different NMR approaches needed according to the chiral selector features. 相似文献
19.
The proton-carbon correlation spectra, HMBC (heteronuclear multiple bond correlation) and HMQC (heteronuclear multiple quantum correlation), respectively, provide direct and remote connectivity information with high sensitivity. Their combination enables carbon-carbon proximity relationships to be deduced, which are formally identical to those produced by a fictitious INADEQUATE-2D experiment, where correlations would be established exclusively between atoms linked by one or two bonds. The CASA program uses these relationships, as well as DEPT spectra and elementary chemical-shift considerations to assign the 13C spectrum of a compound if its structure is known or assumed. If the structure conflicts with the experimental data, no assignment is produced. The CASA program serves as an aid to either spectral assignment or structural elucidation. 相似文献
20.
A structural, magnetic and electronic study of the cobaltocuprate CoSr2Y2−xCexCu2O9±δ (x=0.5-0.8) has been performed. All materials crystallise in the orthorhombic Cmcm symmetry space group in which chains of corner linked CoO4 tetrahedra run parallel to the 1 1 0 direction. An antiferromagnetic transition is observed for x=0.5-0.8; TM increases with x. A change in the dimensionality of the magnetic order occurs at x=0.8 as the interchain distance increases to a critical value. There is charge transfer between the cuprate planes and cobaltate layer as Ce doping increases, so that Co3+ is partially oxidised to Co4+ with a concomitant reduction in the valence of Cu. Superconductivity is not observed in any of the samples and a crossover from Mott to Efros and Shklovskii variable range hopping behaviour is evidenced as x increases from 0.5 to 0.8. 相似文献