Chemical-shift analysis of O Kα by EPMA color-mapping method for BiSrCaCuO superconductive specimen

The chemical shifts of x-ray spectra are now frequently observed with EPMA (Electron Probe Microanalysis). The conventional method of chemical-shift analysis with EPMA is to compare the peak shapes and peak positions of standard spectra with those of unknown spectra. We reported that O-Kα peak shapes detected by using a TAP (Thallium acid phthalate) crystal reflect their crystal structures. Fig. 1 shows these O-Kα spectral peaks. In the present study, concerning the BiSrCaCuO superconductor made by the sintering method, it was observed that the O-Kα spectra of several kinds of phases reflected their crystal structures. Moreover, it is now possible to observe these chemical shifts of spectra by using the color mapping method in EPMA.

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Understanding 125Te NMR chemical shifts in disymmetric organo-telluride compounds from natural chemical shift analysis

Physical Chemistry Chemical Physics ◽

10.1039/c9cp05934b ◽

2020 ◽

Vol 22 (4) ◽

pp. 2319-2326 ◽

Cited By ~ 1

Author(s):

Ewa Pietrasiak ◽

Christopher P. Gordon ◽

Christophe Copéret ◽

Antonio Togni

Keyword(s):

Chemical Shift ◽

Chemical Shifts ◽

Lone Pair ◽

Magnetic Coupling ◽

Nmr Chemical Shifts ◽

Shift Analysis ◽

Theoretical Investigations ◽

Chemical Shift Analysis

Magnetic coupling of the lone pair: theoretical investigations reveal the origin of 125Te chemical shift in disymmetric organotellurides

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New NMR experiments for RNA nucleobase resonance assignment and chemical shift analysis of an RNA UUCG tetraloop

Journal of Biomolecular NMR ◽

10.1023/b:jnmr.0000012863.63522.1f ◽

2004 ◽

Vol 28 (1) ◽

pp. 69-79 ◽

Cited By ~ 44

Author(s):

Boris Fürtig ◽

Christian Richter ◽

Wolfgang Bermel ◽

Harald Schwalbe

Keyword(s):

Chemical Shift ◽

Resonance Assignment ◽

Shift Analysis ◽

Chemical Shift Analysis

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Are the amide bonds in N-acyl imidazoles twisted? A combined solid-state 17O NMR, crystallographic, and computational study

Canadian Journal of Chemistry ◽

10.1139/cjc-2014-0397 ◽

2015 ◽

Vol 93 (4) ◽

pp. 451-458 ◽

Cited By ~ 7

Author(s):

Xianqi Kong ◽

Aaron Tang ◽

Ruiyao Wang ◽

Eric Ye ◽

Victor Terskikh ◽

...

Keyword(s):

Solid State ◽

Chemical Shift ◽

Crystal Structures ◽

Computational Study ◽

Chemical Shifts ◽

Amide Bond ◽

Chemical Shift Tensors ◽

Amide Bonds ◽

Bond Rotation ◽

Quadrupole Coupling

We report synthesis of 17O-labeling and solid-state 17O NMR measurements of three N-acyl imidazoles of the type R-C(17O)-Im: R = p-methoxycinnamoyl (MCA-Im), R = 4-(dimethylamino)benzoyl (DAB-Im), and R = 2,4,6-trimethylbenzoyl (TMB-Im). Solid-state 17O NMR experiments allowed us to determine for the first time the 17O quadrupole coupling and chemical shift tensors in this class of organic compounds. We also determined the crystal structures of these compounds using single-crystal X-ray diffraction. The crystal structures show that, while the C(O)–N amide bond in DAB-Im exhibits a small twist, those in MCA-Im and TMB-Im are essentially planar. We found that, in these N-acyl imidazoles, the 17O quadrupole coupling and chemical shift tensors depend critically on the torsion angle between the conjugated acyl group and the C(O)–N amide plane. The computational results from a plane-wave DFT approach, which takes into consideration the entire crystal lattice, are in excellent agreement with the experimental solid-state 17O NMR results. Quantum chemical computations also show that the dependence of 17O NMR parameters on the Ar–C(O) bond rotation is very similar to that previously observed for the C(O)–N bond rotation in twisted amides. We conclude that one should be cautious in linking the observed NMR chemical shifts only to the twist of the C(O)–N amide bond.

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