Obtaining accurate chemical shifts for all magnetic nuclei (1H, 13C, 17O, and 27Al) in tris(2,4-pentanedionato-O,O′)aluminium(III) — A solid-state NMR case study

2011 ◽  
Vol 89 (9) ◽  
pp. 1087-1094 ◽  
Author(s):  
Alan Wong ◽  
Mark E. Smith ◽  
Victor Terskikh ◽  
Gang Wu
Keyword(s):  
Solid State ◽  
High Resolution ◽  
Solid State Nmr ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Dft Method ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Multiple Quantum ◽  
Isotropic Chemical Shifts

We report a complete set of high-resolution solid-state NMR spectra for all magnetic nuclei (1H, 13C, 17O, and 27Al) in the α-form of tris(2,4-pentanedionato-O,O′)aluminium(III), α-Al(acac)3. These high-resolution NMR spectra were obtained by using a host of solid-state NMR techniques: standard cross-polarization under the magic-angle spinning (CPMAS) method for 13C, 1-D homonuclear decoupling using the windowed DUMBO sequence for 1H, double-rotation (DOR) for 17O and 27Al, and multiple-quantum MAS for 27Al. Some experiments were performed at multiple magnetic fields. We show that the isotropic chemical shifts obtained for 1H, 13C, 17O, and 27Al nuclei in α-Al(acac)3 are highly resolved and accurate, regardless of the nature of the targeted nuclear spins (i.e., spin-1/2 or quadrupolar) and, as such, can be treated equally in comparison with computational chemical shifts obtained from a gauge-including projector-augmented wave (GIPAW) plane-wave pseudopotential DFT method.

A 13C solid-state NMR investigation of four cocrystals of caffeine and theophylline

2017 ◽  
Vol 73 (3) ◽  
pp. 234-243 ◽  
Author(s):  
Nicolas J. Vigilante ◽  
Manish A. Mehta
Keyword(s):  
Solid State ◽  
Chemical Shift ◽  
Solid State Nmr ◽  
Chemical Shifts ◽  
Active Pharmaceutical Ingredient ◽  
Magic Angle Spinning ◽  
Chemical Shift Tensor ◽  
Magic Angle ◽  
Isotropic Chemical Shifts ◽  
Angle Spinning

We report an analysis of the 13C solid-state NMR chemical shift data in a series of four cocrystals involving two active pharmaceutical ingredient (API) mimics (caffeine and theophylline) and two diacid coformers (malonic acid and glutaric acid). Within this controlled set, we make comparisons of the isotropic chemical shifts and the principal values of the chemical shift tensor. The dispersion at 14.1 T (600 MHz 1H) shows crystallographic splittings in some of the resonances in the magic angle spinning spectra. By comparing the isotropic chemical shifts of individual C atoms across the four cocrystals, we are able to identify pronounced effects on the local electronic structure at some sites. We perform a similar analysis of the principal values of the chemical shift tensors for the anisotropic C atoms (most of the ring C atoms for the API mimics and the carbonyl C atoms of the diacid coformers) and link them to differences in the known crystal structures. We discuss the future prospects for extending this type of study to incorporate the full chemical shift tensor, including its orientation in the crystal frame of reference.

High sensitivity and resolution in 43Ca solid-state NMR experiments

2015 ◽  
Vol 93 (8) ◽  
pp. 799-807 ◽  
Author(s):  
Kevin M.N. Burgess ◽  
Frédéric A. Perras ◽  
Igor L. Moudrakovski ◽  
Yijue Xu ◽  
David L. Bryce
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Nmr Spectra ◽  
High Sensitivity ◽  
Magic Angle Spinning ◽  
Signal Enhancement ◽  
Magic Angle ◽  
Multiple Quantum ◽  
Central Transition ◽  
Angle Spinning

A thorough investigation of solid-state NMR signal enhancement schemes and high-resolution techniques for application to the spin-7/2 43Ca nuclide are presented. Signal enhancement experiments employing double frequency sweeps, hyperbolic secant pulses, and rotor-assisted population transfer, which manipulate the satellite transitions of half-integer quadrupolar nuclei to polarize the central transition (m = + 1/2 ↔ –1/2), are carried out on four well-characterized 43Ca isotopically enriched calcium salts: Ca(NO3)2, Ca(OD)2, CaSO4·2H2O, and Ca(OAc)2·H2O. These results, in conjunction with numerical simulations of 43Ca NMR spectra under magic-angle spinning conditions, are used to identify the technique that provides the most uniform (or quantitative) polarization enhancement as well as the largest signal enhancement factors independent of size of the 43Ca quadrupolar coupling constant, which is the most significant source of resonance broadening in 43Ca NMR spectra. These samples are further investigated using 43Ca double-rotation NMR spectroscopy to yield isotropic, or solution-like, NMR spectra with exquisite resolution. In addition, three unique calcium sites are resolved for the hemihydrated form of calcium acetate (unknown structure), Ca(OAc)2·0.5H2O, with double-rotation NMR, whereas the more common, but more time-consuming, multiple quantum magic-angle spinning technique only clearly resolves two calcium sites. The results shown herein will be useful for other NMR spectroscopists attempting to acquire 43Ca solid-state NMR data for unknown and more complex materials with a higher degree of both sensitivity and resolution.

scholarly journals Solid State NMR Studies of the Aluminum Hydride Phases

2006 ◽  
Vol 927 ◽  
Author(s):  
Son-Jong Hwang ◽  
Robert C. Bowman ◽  
Jason Graetz ◽  
J. J. Reilly
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Nmr Spectra ◽  
Aluminum Hydride ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Multiple Quantum ◽  
Nmr Studies ◽  
Α Phase ◽  
Hydride Phases

ABSTRACTSeveral solid state NMR techniques including magic-angle-spinning (MAS) and multiple-quantum (MQ) MAS experiments have been used to characterize various AlH3 samples. MAS-NMR spectra for the 1H and 27Al nuclei have been obtained on a variety of AlH3 samples that include the β- and γ- phases as well as the most stable α-phase. While the dominant components in these NMR spectra correspond to the aluminum hydride phases, other species were found that include Al metal, molecular hydrogen (H2), as well as peaks that can be assigned to Al-O species in different configurations. The occurrence and concentration of these extraneous components are dependent upon the initial AlH3 phase composition and preparation procedures. Both the β-AlH3 and γ-AlH3 phases were found to generate substantial amounts of Al metal when the materials were stored at room temperature while the α-phase materials do not exhibit these changes.

scholarly journals Combination of solid state NMR and DFT calculation to elucidate the state of sodium in hard carbon electrodes

2016 ◽  
Vol 4 (34) ◽  
pp. 13183-13193 ◽  
Author(s):  
Ryohei Morita ◽  
Kazuma Gotoh ◽  
Mika Fukunishi ◽  
Kei Kubota ◽  
Shinichi Komaba ◽  
...  
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Dft Calculation ◽  
Magic Angle Spinning ◽  
The State ◽  
Mas Nmr ◽  
Magic Angle ◽  
Multiple Quantum ◽  
Hard Carbon ◽  
Angle Spinning

We examined the state of sodium electrochemically inserted in HC prepared at 700–2000 °C using solid state Na magic angle spinning (MAS) NMR and multiple quantum (MQ) MAS NMR.

High resolution triple resonance micro magic angle spinning NMR spectroscopy of nanoliter sample volumes

2016 ◽  
Vol 18 (6) ◽  
pp. 4902-4910 ◽  
Author(s):  
J. Ole Brauckmann ◽  
J. W. G. (Hans) Janssen ◽  
Arno P. M. Kentgens
Keyword(s):  
Solid State ◽  
Nmr Spectroscopy ◽  
High Resolution ◽  
Single Crystals ◽  
Solid State Nmr ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Triple Resonance ◽  
Angle Spinning

To be able to study mass-limited samples and small single crystals, a triple resonance micro-magic angle spinning (μMAS) probehead for the application of high-resolution solid-state NMR of nanoliter samples was developed.

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