共查询到20条相似文献,搜索用时 15 毫秒
1.
Denis Schneider Helge Toufar Ago Samoson Dieter Freude 《Solid state nuclear magnetic resonance》2009,35(2):87-92
We demonstrate complementary 1H, 17O, 27Al and 29Si measurements for basic low-silica-X zeolites, which were unloaded and pyrrole and formic acid-loaded. It was found that the acid–base-system is not stabile, if the loading exceeds one pyrrole molecule or two formic acid molecules per supercage.17O DOR NMR spectra exhibit at least four lines, which are broadened by a distribution of chemical shifts in a similar extend as the 29Si MAS NMR spectra are broadened by distribution of Si–O–Al angles. A strong cation influence upon 17O shifts was observed. But there was no strong influence of the acid molecules on the mean value of the 17O shift of the spectra. 相似文献
2.
Freude D Loeser T Michel D Pingel U Prochnow D 《Solid state nuclear magnetic resonance》2001,20(1-2):46-60
Multiple-quantum magic-angle spinning and double-rotation NMR techniques were applied in the high field of 17.6 T to the study of oxygen-17-enriched zeolites A and LSX with the ratio Si/Al = 1. A monotonic correlation between the isotropic value of the chemical shift and the Si-O-Al bond angle alpha (taken from X-ray data) could be found. Hydration of the zeolites causes a downfield 17O NMR chemical shift of about 8 ppm with respect to the dehydrated zeolites. Ion exchange of the hydrated zeolites generates stronger chemical shift effects. The increase of the basicity of the oxygen framework of the zeolite LSX is reflected by a downfield shift of approx. 10 ppm going from the lithium to the cesium form, and the substitution of sodium by thallium in the zeolite A causes a shift of 34 ppm for the O3 signal. 17O DOR NMR spectra are superior to 17O 3QMAS NMR spectra, featuring a resolution increase by a factor of 2 and are about equal with respect to the sensitivity. The residual linewidths of the signals in the 17O DOR and 17O 5QMAS NMR spectra can be explained by a distribution of the Si-O-Al angles in the zeolites. 相似文献
3.
《Journal of Magnetic Resonance (1969)》1982,46(3):423-439
A number of optimization techniques were employed to obtain 17O NMR spectra at natural abundance for a variety of inorganic and orgnic phosphates and polyphosphates. 17O chemical shifts and some Jpo coupling constants are reported for the orthophosphate series of ions from H3PO4 to PO43−, the pyrophosphate ion, P2O74−, the linear tripolyphosphate ion, P3O105−, and the cyclic trimetaphosphate ion, P3O93−; and for disodium dl-α-glycerophosphate and monosodium adenosine monophosphate. 17O-depleted water enables much improved results to be obtained in acqueous solutions. 相似文献
4.
《Solid State Ionics》1988,26(2):125-131
Full profile analyses of the digitized 29Si NMR spectra of a potassium zeolite L and a gallosilicate analog are described. Both spectra can be fitted reasonably based on the assumption that they comprise only a single set of SinAl(Ga); n=0−4 peaks, reflecting that the mean T-O-T angles for the two T-sites (T=tetrahedral species, Si, Al or Ga) are similar. 相似文献
5.
de Graaf RA Brown PB Rothman DL Behar KL 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2008,193(1):63-67
Oxygen is an abundant element that is present in almost all biologically relevant molecules. NMR observation of oxygen has been relatively limited since the NMR-active isotope, oxygen-17, is only present at a 0.037% natural abundance. Furthermore, as a spin 5/2 nucleus oxygen-17 has a moderately strong quadrupole moment which leads to fairly broad resonances (T(2)=1-4 ms). However, the similarly short T(1) relaxation constants allow substantial signal averaging, whereas the large chemical shift range (>300 ppm) improves the spectral resolution of (17)O NMR. Here it is shown that high-quality, natural abundance (17)O NMR spectra can be obtained from rat brain in vivo at 11.74 T. The chemical shifts and line widths of more than 20 oxygen-containing metabolites are established and the sensitivity and potential for (17)O-enriched NMR studies are estimated. 相似文献
6.
We report the first 17O NMR studies of a triangular-lattice superconductor Na(1/3)CoO2 x 4/3H(2)O and the host material Na(x)CoO2 (x=0.35 and 0.72). Knight shift measurements reveal that p-d hybridization induces sizable spin polarization in the O triangular-lattice layers. Water intercalation makes CoO2 planes homogeneous and enhances low frequency spin fluctuations near T(c)=4.5 K at some finite wave vectors different from both the ferromagnetic and "120 degree" modes. 相似文献
7.
Perrin A Flaud J Valentin A Camy-Peyret C Gbaguidi H 《Journal of Molecular Spectroscopy》2000,200(2):248-252
Using 0.002 cm(-1) resolution Fourier transform absorption spectra of an (17)O-enriched ozone sample, an extensive analysis of the nu(3) band together with a partial identification of the nu(1) band of the (17)O(16)O(17)O isotopomer of ozone has been performed for the first time. As for other C(2v)-type ozone isotopomers [J.-M. Flaud and R. Bacis, Spectrochim. Acta, Part A 54, 3-16 (1998)], the (001) rotational levels are involved in a Coriolis-type resonance with the levels of the (100) vibrational state. The experimental rotational levels of the (001) and (100) vibrational states have been satisfactorily reproduced using a Hamiltonian matrix which takes into account the observed rovibrational resonances. In this way precise vibrational energies and rotational and coupling constants were deduced and the following band centers nu(0)(nu(3)) = 1030.0946 cm(-1) and nu(0)(nu(1)) = 1086.7490 cm(-1) were obtained for the nu(3) and nu(1) bands, respectively. Copyright 2000 Academic Press. 相似文献
8.
Perrin A Flaud JM Keller F Smith MA Rinsland CP Devi VM Benner DC Stephen TM Goldman A 《Journal of Molecular Spectroscopy》2001,207(1):54-59
Using 0.002 cm(-1) resolution Fourier transform absorption spectra of an (17)O enriched ozone sample, an extensive analysis of the v(1)+v(3) bands of the (16)O(17)O(16)O and (16)O(16)O(17)O isotopomers of ozone has been performed for the first time. The experimental rotational levels of the (101) vibrational states were satisfactorily reproduced using a Hamiltonian matrix that takes into account the observed rovibrational resonances. More precisely, for (16)O(17)O(16)O, as for the other C(2v)-type ozone isotopomers, it was necessary to account for the Coriolis type resonances linking the (101) rotational levels with the levels of the (200) and (002) vibrational states and the Darling-Dennison interaction coupling the levels of (200) with those of (002). For the C(s)-type isotopomer, namely (16)O(16)O(17)O, as for (16)O(16)O(18)O and (16)O(18)O(18)O, it proved necessary to also account for an additional DeltaK(a)&equals+/-2 resonance involving the rotational levels from (101) and (002) (J.-M. Flaud and R. Bacis, Spectrochimica Acta Part A 54, 3-16 (1998)). Using a Hamiltonian matrix which takes these resonances explicitly into account, precise vibrational energies and rotational and coupling constants were deduced, leading to the following band centers: v(0)(v(1)+v(3))=2078.3496 cm(-1) for (16)O(17)O(16)O and v(0)(v(1)+v(3))=2098.8631 cm(-1) for (16)O(16)O(17)O. Copyright 2001 Academic Press. 相似文献
9.
10.
The vibration-rotation spectra of the ν2 fundamental of 12C17O2 and 12C17O18O have been obtained by Fourier transform spectroscopy at 0.05 cm?1 resolution. The data were fitted by a least-squares routine to obtain a number of the molecular constants. The band center for 12C17O2 lies at 662.0716 cm?1 while that for 12C17O18O is at 659.7057 cm?1. The difference bands ν1 - ν2 have also been observed for the two molecular species. 相似文献
11.
1H NMR signal broadening in spectra of alkane molecules adsorbed on MFI-type zeolites 总被引:1,自引:0,他引:1
Romanova EE Krause CB Stepanov AG Wilczok U Schmidt W van Baten JM Krishna R Pampel A Kärger J Freude D 《Solid state nuclear magnetic resonance》2008,33(4):65-71
The anisotropic behavior of C1-C6 alkane molecules adsorbed in MFI zeolite was studied by 1H nuclear magnetic resonance (NMR) using single-pulse excitation, Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence, Hahn echo (HE) pulse sequence, and magic-angle spinning. The molecular order parameter was obtained by both static 2H NMR spectroscopy and molecular simulations. This yields an order parameter in the range of 0.28-0.42 for linear alkanes in MFI zeolite, whereas the parameter equals zero for FAU zeolite with a cubic symmetry. Thus, in the case of a zeolite with a non-cubic symmetry like MFI, the mobility of the molecules in one crystallite cannot fully average the dipolar interaction. As a consequence, transverse nuclear magnetization as revealed in the echo attenuation notably deviates from a mono-exponential decay. This information is of particular relevance for the performance of pulsed field gradient (PFG) NMR diffusion experiments, since the occurrence of non-exponential magnetization attenuation could be taken as an indication of the existence of different molecules or of molecules in different states of mobility. 相似文献
12.
13.
13C and 17O NMR chemical shifts for a series of isobenzopyrylium salts are reported. The oxygen signal range from 300 to 270 ppm as a double bonded carboxylic oxygen, From the 17O and 13C data valuable informations on the conjugative and substituent effects of isobenzopyrylium salts were obtained. 相似文献
14.
Variations in coordination states of extra-framework iron are studied in low iron content ferrisilicates (Si/57Fe ≈ 200) during various in situ treatments. In Fe-LTA complete Fe3+ ? Fe2?+? reversibility is observed. In Fe-MFI extra-framework iron can be stabilized in Fe2?+? state in spite of ambient oxidizing conditions (N2O, 620 K). Further, in Fe-MFI simultaneous stabilization of Fe2?+? and Fe3?+? may take place providing centres for redox catalytic processes. 相似文献
15.
The 17O NMR spectra for a series of saturated diols were investigated. From these studies both hydroxyl induced substituent chemical shift (SCS) effects of hydroxyl oxygen 17O NMR chemical shifts were determined. In addition, linear correlations between the 17O chemical shift of the hydroxyl oxygen (ROH) and the 13C chemical shift for the methyl group in the corresponding hydrocarbon (RCH3) were obtained. 相似文献
16.
Danny T. Davies Richard J. Richards M.C.L. Gerry 《Journal of Molecular Spectroscopy》1980,80(2):307-319
Pure rotational transitions in the ground vibrational state have been measured for H212C18O, H212C17O, H213C18O, and H213C17O in the frequency region 8–75 GHz. These have included both Q- and R-branch transitions, and have permitted accurate evaluation of rotational constants and several quartic centrifugal distortion constants for each species. These in turn have permitted the prediction of several transitions of possible use in radioastronomy. 相似文献
17.
The molecular dynamic behaviour of water molecules in aqueous solution has been determined by oxygen-17 NMR according to the anisotropic reorientation, two-correlation-time model for bound water. Solutions of brain heart infusion (BHI), NaCl and their 1:1 mixture have been analysed. The anisotropic water population was distinguished into a slow (τs bw) and a fast (τf bw) relaxing component. The slow relaxing component was affected by the nature of the solute, while the fast relaxing component was not. NaCl was found to bind water molecules more strongly (higher τs bw) than BHI. Water was more bound in the 1:1 mixture than in the solution containing only BHI. The population of bound water (P bw) was concentration dependent and increased with increasing solids content. BHI, at the suspension point, bound ~50% of the total water, while NaCl at saturation bound only ~10%. The 1:1 mixture bound water in a synergistic manner that resulted in a slightly higher Pbw, than in BHI at each solid concentration. The Pbw correlated well with the amount of unfreezable water (as measured by DSC) present in the BHI samples. 相似文献
18.
Olariu A Mendels P Bert F Duc F Trombe JC de Vries MA Harrison A 《Physical review letters》2008,100(8):087202
We report, through 17O NMR, an unambiguous local determination of the intrinsic kagome lattice spin susceptibility as well as that created around nonmagnetic defects arising from natural Zn/Cu exchange in the S=1/2 (Cu2+) herbertsmithite ZnCu3(OH)6Cl2 compound. The issue of a singlet-triplet gap is addressed. The magnetic response around a defect is found to markedly differ from that observed in nonfrustrated antiferromagnets. Finally, we discuss our relaxation measurements in the light of Cu and Cl NMR data and suggest a flat q dependence of the excitations. 相似文献
19.
Prasad S Clark TM Sharma R Kwak HT Grandinetti PJ Zimmermann H 《Solid state nuclear magnetic resonance》2006,29(1-3):119-124
We report the application of rotor-assisted population transfer (RAPT) to measure the quadrupolar coupling constant (C(q)) for spin 5/2 nuclei. Results from numerical simulations are presented on the magnitude of enhancement factor as a function of frequency offsets, i.e. the RAPT profile. Experimental O17 RAPT profile is traced for the amino acid L-leucine. In addition, results from MQ-MAS experiments are incorporated to determine the quadrupolar asymmetry parameter (eta(q)). Unlike previous reports, the O17 NMR parameters for an amino acid, L-leucine, is reported at a relatively low field of 9.4 T. 相似文献
20.
Flambard A Montagne L Delevoye L Steuernagel S 《Solid state nuclear magnetic resonance》2007,32(2):34-43
Niobiophosphate compounds with a large range of niobium and oxygen environments were studied with (93)Nb and (17)O solid-state NMR. (93)Nb isotropic chemical shift of pure niobate Nb(ONb)(6), pure phosphate Nb(OP)(6) and mixed phosphate-niobate Nb(OP)(x)(ONb)((6-x)) (1相似文献