Magic-Angle-Turning Experiments for Measuring Chemical-Shift-Tensor Principal Values in Powdered Solids

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.

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Determination of 51V quadrupole and chemical shift tensor orientations in V2O5 by analysis of magic-angle spinning nuclear magnetic resonance spectra

Solid State Nuclear Magnetic Resonance ◽

10.1016/0926-2040(94)90026-4 ◽

1994 ◽

Vol 3 (2) ◽

pp. 79-91 ◽

Cited By ~ 37

Author(s):

C. Fernandez ◽

P. Bodart ◽

J.P. Amoureux

Keyword(s):

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Chemical Shift ◽

Magic Angle Spinning ◽

Chemical Shift Tensor ◽

Magic Angle ◽

Nuclear Magnetic Resonance Spectra ◽

Angle Spinning ◽

Magnetic Resonance Spectra

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An unusually large value of 1J(31P,31P) for a solid triphenylphosphine phosphadiazonium cationic complex: determination of the sign of J from 2D spin-echo experiments

Canadian Journal of Chemistry ◽

10.1139/v96-264 ◽

1996 ◽

Vol 74 (11) ◽

pp. 2372-2377 ◽

Cited By ~ 6

Author(s):

Klaus Eichele ◽

Roderick E. Wasylishen ◽

Robert W. Schurko ◽

Neil Burford ◽

W. Alex Whitla

Keyword(s):

Chemical Shift ◽

Spin Echo ◽

Magic Angle Spinning ◽

Convincing Evidence ◽

Coupling Constants ◽

Spin Coupling ◽

Chemical Shift Tensor ◽

Magic Angle ◽

Molecular Orbital Calculations ◽

Angle Spinning

Phosphorus-31 NMR spectra of a solid triphenylphosphine phosphadiazonium salt, [Mes*NP-PPh3][SO3CF3], have been acquired at 4.7 and 9.4 T. Analysis of the spectra obtained with magic-angle spinning indicates that the two phosphorus nuclei are strongly spin–spin coupled, [Formula: see text], despite the unusually long P—P separation, rP,P = 2.625 Å. Two-dimensional spin-echo spectra provide convincing evidence that 1J(31P,31P) is negative. Semi-empirical molecular orbital calculations at the INDO level support the negative sign for 1J(31P,31P). A large span, 576 ppm, is observed for the chemical shift tensor of the two-coordinate phosphorus centre (δ11 = 307 ppm, δ22 = 174 ppm, δ33 = −269 ppm), which is very similar to the value previously reported for the non-coordinated phosphorus centre in the free Lewis acid, [Mes*NP][AlCl4]. The principal components and orientations of the phosphorus shielding tensors of these compounds are compared with those calculated for [HNP]+ and its phosphine adduct using the ab initio Gauge-Including Atomic Orbitals method. The phosphorus chemical shift tensor of the triphenylphosphine moiety has a relatively small span of 33 ppm. Key words: spin–spin coupling constants, solid-state NMR, 31P NMR, MO calculations, phosphadiazonium cation, P—P bonds.

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Measurement of 13C chemical shift tensor principal values with a magic-angle turning experiment

Solid State Nuclear Magnetic Resonance ◽

10.1016/0926-2040(94)90039-6 ◽

1994 ◽

Vol 3 (4) ◽

pp. 181-197 ◽

Cited By ~ 38

Author(s):

Jian Zhi Hu ◽

Anita M. Orendt ◽

D.W. Alderman ◽

Ronald J. Pugmire ◽

Chaohui Ye ◽

...

Keyword(s):

Chemical Shift ◽

Chemical Shift Tensor ◽

Magic Angle ◽

13C Chemical Shift

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A phosphorus-31 NMR study of solid carbonylhydridotris(triphenylphosphine)rhodium(I). Unusual MAS sideband intensities in second-order NMR spin systems

Canadian Journal of Chemistry ◽

10.1139/v92-114 ◽

1992 ◽

Vol 70 (3) ◽

pp. 863-869 ◽

Cited By ~ 7

Author(s):

Gang Wu ◽

Roderick E. Wasylishen ◽

Ronald D. Curtis

Keyword(s):

Chemical Shift ◽

Spin System ◽

Principal Components ◽

Nmr Spectra ◽

Magic Angle Spinning ◽

Chemical Shift Tensor ◽

Magic Angle ◽

Nmr Spectrum ◽

Chemical Shift Tensors ◽

Nmr Study

The CP/MAS 31P NMR spectrum of carbonylhydridotris(triphenylphosphine)rhodium(I), RhH(CO)(PPh3)3 (1), can be described as a tightly coupled ABMX spin system (X = 103Rh). In contrast to the solution 31P NMR spectrum, the three equatorial phosphorus nuclei are nonequivalent in the solid state and this structural feature allows us to measure the two-bond spin–spin couplings, 2J(31P,31P). A new method is proposed for extracting the principal components of the chemical shift tensor from slow MAS NMR spectra in a tightly J-coupled two-spin system. For compound 1, the principal components of the 31P chemical shift tensors calculated using this method are in good agreement with those obtained from NMR spectra of a static sample. The principal components of the 31P chemical shift tensors determined for 1 are compared with those reported previously for Wilkinson's catalyst, RhCl(PPh3)3. The δ22 component of the 31P chemical shift tensors in 1 shows the largest variation with structure. This is ascribed to differences in the orientation of the P—Cipso bond about the equatorial plane of the trigonal bipyramidal structure. Keywords: rhodium–phosphine compounds, AB spin system, 31P chemical shift tensor, magic-angle spinning, molecular structure.

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Single Crystal Solid-State NMR of Magnetically Oriented Powder

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s205327331408913x ◽

2014 ◽

Vol 70 (a1) ◽

pp. C1086-C1086

Author(s):

Ryosuke Kusumi ◽

Fumiko Kimura ◽

Tsunehisa Kimura

Keyword(s):

Magnetic Field ◽

Solid State ◽

Chemical Shift ◽

Single Crystal ◽

Solid State Nmr ◽

Chemical Shift Tensor ◽

Magic Angle ◽

Full Information ◽

Crystal Rotation ◽

Rotation Method

Solid-state NMR spectroscopy is one of the most widely used methods for investigating crystal structures, along with the X-ray and neutron diffraction methods. Solid-state NMR can provide structural information including isotropic chemical shift, dipolar and quadrupolar couplings, spin diffusion, and chemical shift tensor. Among these, the chemical shift tensor is of particular significance because the electronic environment around a nucleus is directly reflected on the chemical shift tensor. However, full information of the chemical shift tensor, including principal values and axes, is difficult to obtain experimentally because a large single crystal is required for the measurement. On the other hand, we have proposed the use of a magnetically oriented microcrystal array (MOMA) as an alternative to a single crystal.[1,2] A MOMA is a composite in which microcrystals are aligned three-dimensionally, prepared by using a time-dependent magnetic field. We recently demonstrated that the13C chemical shift tensors of L-alanine crystal can be completely determined by application of the standard procedure in the single-crystal rotation method to a MOMA of L-alanine microcrystals,[3] as shown in Figure 1. The L-alanine MOMA produces sharp resonance peaks without resolution enhancement by magic angle spinning (MAS). In addition, we observed that the positions of the13C resonance peaks vary systematically as a function of the angle ψ that is the sample-rotation angle about the axis inclined by the magic angle with respect to the NMR magnetic field. From the ψ-dependence of the chemical shifts,13C chemical shift tensor was completely determined. We confirmed that the combination of MOMA with the single-crystal rotation method can be applied to other nuclei such as31P and15N. These results clearly show that the MOMA method is a powerful tool for obtaining full information of the chemical shift tensor from a microcrystalline powder without MAS.

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