Determination of the 15 N chemical shift anisotropy in natural abundance samples by proton-detected 3D solid-state NMR under ultrafast MAS of 70 kHz

2019 ◽  
Vol 57 (6) ◽  
pp. 294-303 ◽  
Author(s):  
Federica Rossi ◽  
Nghia Tuan Duong ◽  
Manoj Kumar Pandey ◽  
Michele R. Chierotti ◽  
Roberto Gobetto ◽  
...  
Keyword(s):  
Solid State ◽  
Chemical Shift ◽  
Solid State Nmr ◽  
Chemical Shift Anisotropy ◽  
Natural Abundance ◽  
3D Solid

A solid-state 133Cs nuclear magnetic resonance and X-ray crystallographic study of cesium complexes with macrocyclic ligands

2000 ◽  
Vol 78 (7) ◽  
pp. 975-985
Author(s):  
Alan Wong ◽  
Simon Sham ◽  
Suning Wang ◽  
Gang Wu
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Chemical Shift ◽  
Solid State Nmr ◽  
Chemical Shifts ◽  
Macrocyclic Ligand ◽  
Chemical Shift Anisotropy ◽  
Macrocyclic Ligands ◽  
X Ray

We report solid-state NMR determination of the 133Cs chemical shift anisotropy (CSA) for a series of cesium complexes with macrocyclic ligands. It was found that the isotropic 133Cs chemical shifts are related to the number of oxygen atoms to which the Cs+ ion is coordinated. The 133Cs chemical shifts were found to correlate with average Cs-O distances. We also attempt to use the established correlation to deduce Cs+ coordination environment for compounds with unknown structures. We also report the X-ray determination of the crystal structure for Cs(DB18C6)2SCN•1/2CH3OH•1/2H2O. The compound crystallizes in monoclinic, a = 14.503(2), b = 15.152(3), c = 39.989(6) Å, β = 90.796(8)°, space group P21/c, Z = 8. There are two independent molecules in the asymmetric unit cell where each of the two Cs+ ions is coordinated to two DB18C6 ligand molecules forming a sandwich-type structure.Key words: solid state NMR, alkali metal, 133Cs chemical shift, macrocyclic ligand, crystal structure.

scholarly journals Insight into the local environment of magnesium and calcium in low-coordination-number organo-complexes using 25Mg and 43Ca solid-state NMR: a DFT study

2017 ◽  
Vol 73 (3) ◽  
pp. 208-218 ◽  
Author(s):  
Christel Gervais ◽  
Cameron Jones ◽  
Christian Bonhomme ◽  
Danielle Laurencin
Keyword(s):  
Solid State ◽  
Chemical Shift ◽  
Metal Ions ◽  
Solid State Nmr ◽  
Chemical Shift Anisotropy ◽  
Local Environment ◽  
Coordination Numbers ◽  
Highly Sensitive ◽  
Calcium Complexes ◽  
Insight Into

With the increasing number of organocalcium and organomagnesium complexes under development, there is a real need to be able to characterize in detail their local environment in order to fully rationalize their reactivity. For crystalline structures, in cases when diffraction techniques are insufficient, additional local spectroscopies like 25Mg and 43Ca solid-state NMR may provide valuable information to help fully establish the local environment of the metal ions. In this current work, a prospective DFT investigation on crystalline magnesium and calcium complexes involving low-coordination numbers and N-bearing organic ligands was carried out, in which the 25Mg and 43Ca NMR parameters [isotropic chemical shift, chemical shift anisotropy (CSA) and quadrupolar parameters] were calculated for each structure. The analysis of the calculated parameters in relation to the local environment of the metal ions revealed that they are highly sensitive to very small changes in geometry/distances, and hence that they could be used to assist in the refinement of crystal structures. Moreover, such calculations provide a guideline as to how the NMR measurements will need to be performed, revealing that these will be very challenging.

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