Correlation between19F Environment and Isotropic Chemical Shift in Barium and Calcium Fluoroaluminates

2004 ◽  
Vol 43 (8) ◽  
pp. 2474-2485 ◽  
Author(s):  
M. Body ◽  
G. Silly ◽  
C. Legein ◽  
J.-Y. Buzaré
Keyword(s):  
Chemical Shift ◽  
Isotropic Chemical Shift

Aluminum Siting in the ZSM-22 and Theta-1 Zeolites Revisited: A QM/MM Study

2008 ◽  
Vol 73 (6-7) ◽  
pp. 909-920 ◽  
Author(s):  
Stepan Sklenak ◽  
Jiří Dědeček ◽  
Chengbin Li ◽  
Fei Gao ◽  
Bavornpon Jansang ◽  
...  
Keyword(s):  
Experimental Data ◽  
Chemical Shift ◽  
Nearest Neighbor ◽  
Membered Ring ◽  
Mas Nmr ◽  
Isotropic Chemical Shift ◽  
Reaction Space ◽  
Ring Channel ◽  
T1 And T2 ◽  
Nmr Signals

The Al siting in the silicon rich ZSM-22 and Theta-1 zeolites of the TON structure was investigated analyzing already published 27Al 3Q MAS NMR experimental data using QM/MM calculations. The results of our computations show that Al atoms can be located in 6 framework T positions because the two eightfold sites (T1 and T2) split into four fourfold T sites after an Al/Si substitution. The observed resonance at 55.5 ppm corresponds to the T4 site which is predominantly occupied by Al. This site is not located on the surface of the TON ten-membered ring channel and thus the protonic sites related with the majority of Al atoms in the TON structure exhibit a significantly limited reaction space. The 27Al NMR signals centered at 57.6 and 58.7 ppm correspond to either the T2 and T3 sites, respectively, or only to T2. The T2 and T3 sites accommodate some 40% and up to 10%, respectively, of Al while the T1 site is unoccupied by Al. Isotropic shifts of 61.1 and 61.6 ppm were calculated for Al atoms located in the T1-1 and T1-2 sites, respectively. The effect of a silanol "nest" as a next-next-nearest neighbor on the 27Al isotropic chemical shift of Al located in the T4 site is calculated to be less than 1 ppm.

An isotropic chemical shift–chemical shift anisotropic correlation experiment using discrete magic angle turning

2009 ◽  
Vol 198 (1) ◽  
pp. 105-110 ◽  
Author(s):  
Jian Zhi Hu ◽  
Jesse A. Sears ◽  
Ja Hun Kwak ◽  
David W. Hoyt ◽  
Yong Wang ◽  
...  
Keyword(s):  
Chemical Shift ◽  
Magic Angle ◽  
Isotropic Chemical Shift ◽  
Correlation Experiment

scholarly journals On the preparation and NMR spectroscopic characterization of potassium aluminium tetrahydride KAlH4

2019 ◽  
Vol 21 (23) ◽  
pp. 12576-12584 ◽  
Author(s):  
Bodo Zibrowius ◽  
Michael Felderhoff
Keyword(s):  
Nmr Spectroscopy ◽  
Chemical Shift ◽  
Spectroscopic Characterization ◽  
Mas Nmr ◽  
Isotropic Chemical Shift ◽  
Quadrupole Coupling ◽  
Coupling Parameters

Conventional 1D 27Al MAS NMR spectroscopy allows the isotropic chemical shift and the quadrupole coupling parameters of Pnma KAlH4 to be determined precisely.

scholarly journals Determination of the Full 207Pb Chemical Shift Tensor of Anglesite, PbSO4, and Correlation of the Isotropic Shift to Lead–Oxygen Distance in Natural Minerals

Crystals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 43 ◽  
Author(s):  
Otto Zeman ◽  
Jennifer Steinadler ◽  
Rupert Hochleitner ◽  
Thomas Bräuniger
Keyword(s):  
Chemical Shift ◽  
Single Crystal ◽  
Polycrystalline Sample ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Isotropic Chemical Shift ◽  
Natural Minerals ◽  
Angle Spinning ◽  
Data Acquisition And Processing

The full 207 Pb chemical shift (CS) tensor of lead in the mineral anglesite, PbSO 4 , was determined from orientation-dependent nuclear magnetic resonance (NMR) spectra of a large natural single crystal, using a global fit over two rotation patterns. The resulting tensor is characterised by the reduced anisotropy Δ δ = ( - 327 ± 4 ) ppm, asymmetry η C S = 0 . 529 ± 0 . 002 , and δ i s o = ( - 3615 ± 3 ) ppm, with the isotropic chemical shift δ i s o also verified by magic-angle spinning NMR on a polycrystalline sample. The initially unknown orientation of the mounted single crystal was included in the global data fit as well, thus obtaining it from NMR data only. By use of internal crystal symmetries, the amount of data acquisition and processing for determination of the CS tensor and crystal orientation was reduced. Furthermore, a linear correlation between the 207 Pb isotropic chemical shift and the shortest Pb–O distance in the co-ordination sphere of Pb 2 + solely surrounded by oxygen has been established for a large database of lead-bearing natural minerals.

scholarly journals Electronegativity and location of anionic ligands drive yttrium NMR for molecular, surface and solid-state structures

2020 ◽  
Vol 11 (26) ◽  
pp. 6724-6735 ◽  
Author(s):  
Lukas Lätsch ◽  
Erwin Lam ◽  
Christophe Copéret
Keyword(s):  
Solid State ◽  
Chemical Shift ◽  
Molecular Surface ◽  
Isotropic Chemical Shift ◽  
Key Factors ◽  
Anionic Ligands ◽  
Solid State Structures

The yttrium chemical shift signature of molecular and solid-state structures is determined by two key factors: electronegativity (isotropic chemical shift) and pyramidalization (anisotropy) of the anionic ligands.

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