Criteria to average out the chemical shift anisotropy in solid-state NMR when irradiated with BABA I, BABA II, and C7 radiofrequency pulse sequences

2013 ◽  
Vol 55-56 ◽  
pp. 63-72 ◽  
Author(s):  
Eugene Stephane Mananga
Keyword(s):  
Solid State ◽  
Chemical Shift ◽  
Solid State Nmr ◽  
Chemical Shift Anisotropy ◽  
Pulse Sequences ◽  
Radiofrequency Pulse

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

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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