Role of Exact Exchange and Relativistic Approximations in Calculating <sup>19</sup>F Magnetic Shielding in Solids Using a Cluster <i>Ansatz</i>

Alkan, Fahri; Holmes, Sean T.; Dybowski, Cecil

doi:10.1021/acs.jctc.7b00555

Cited by 22 publications

(46 citation statements)

References 113 publications

(276 reference statements)

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“…It should also be noted, that periodic structure calculations do not yield better agreement with experiment, and large cluster calculations using appropriately constructed symmetryadapted molecular clusters and high level of theory appear to be necessary, as we have demonstrated previously for fluorine in a wide variety of environments. 27…”

Section: Methodsmentioning

confidence: 99%

¹⁹F Magic Angle Spinning NMR Spectroscopy and Density Functional Theory Calculations of Fluorosubstituted Tryptophans: Integrating Experiment and Theory for Accurate Determination of Chemical Shift Tensors

Sarkar

Wang

et al. 2018

J. Phys. Chem. B

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The F chemical shift is a sensitive NMR probe of structure and electronic environment in organic and biological molecules. In this report, we examine chemical shift parameters of 4F-, 5F-, 6F-, and 7F-substituted crystalline tryptophan by magic angle spinning (MAS) solid-state NMR spectroscopy and density functional theory. Significant narrowing of theF lines was observed under fast MAS conditions, at spinning frequencies above 50 kHz. The parameters characterizing the F chemical shift tensor are sensitive to the position of the fluorine in the aromatic ring and, to a lesser extent, the chirality of the molecule. Accurate calculations ofF magnetic shielding tensors require the PBE0 functional with a 50% admixture of a Hartree-Fock exchange term, as well as taking account of the local crystal symmetry. The methodology developed will be beneficial for F-based MAS NMR structural analysis of proteins and protein assemblies.

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Section: Methodsmentioning

confidence: 99%

¹⁹F Magic Angle Spinning NMR Spectroscopy and Density Functional Theory Calculations of Fluorosubstituted Tryptophans: Integrating Experiment and Theory for Accurate Determination of Chemical Shift Tensors

Sarkar

Wang

et al. 2018

J. Phys. Chem. B

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“…In the previous benchmarking study [182], hybrid functionals give a shift/shielding fitting gradient for 19 F that was significantly closer to the expected -1. A follow-up study [184] showed that increasing the fraction of Hartree-Fock exchange to 50% (compared to 25% in PBE0) further improved the regression slope, although the RMSDs (not calculated) did not seem to significantly improve. This is consistent with the idea the systematic limitations of DFT are often due to "self-interaction / delocalisation" errors [84] associated with the exchange energy correlation functional, which are reduced by decreasing the contribution of the PBE functional.…”

Section: Limitations Of Current Dft Functionalsmentioning

confidence: 97%

NMR crystallography of molecular organics

Hodgkinson

2020

Progress in Nuclear Magnetic Resonance Spectroscopy

116

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“…In this context, Dybowski and co-workers have identified that such discrepancies arise in DFT calculations of 19 F magnetic shielding. 75 …”

Section: Results and Discussionmentioning

confidence: 99%

Synergy of Solid-State NMR, Single-Crystal X-ray Diffraction, and Crystal Structure Prediction Methods: A Case Study of Teriflunomide (TFM)

Pawlak

Sudgen

Bujacz

et al. 2021

Crystal Growth & Design

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In this work, for the first time, we present the X-ray diffraction crystal structure and spectral properties of a new, room-temperature polymorph of teriflunomide (TFM), CSD code 1969989. As revealed by DSC, the low-temperature TFM polymorph recently reported by Gunnam et al. undergoes a reversible thermal transition at −40 °C. This reversible process is related to a change in Z’ value, from 2 to 1, as observed by variable-temperature 1 H– 13 C cross-polarization (CP) magic-angle spinning (MAS) solid-state NMR, while the crystallographic system is preserved (triclinic). Two-dimensional 13 C– 1 H and 1 H– 1 H double-quantum MAS NMR spectra are consistent with the new room-temperature structure, including comparison with GIPAW (gauge-including projector augmented waves) calculated NMR chemical shifts. A crystal structure prediction procedure found both experimental teriflunomide polymorphs in the energetic global minimum region. Differences between the polymorphs are seen for the torsional angle describing the orientation of the phenyl ring relative to the planarity of the TFM molecule. In the low-temperature structure, there are two torsion angles of 4.5 and 31.9° for the two Z’ = 2 molecules, while in the room-temperature structure, there is disorder that is modeled with ∼50% occupancy between torsion angles of −7.8 and 28.6°. These observations are consistent with a broad energy minimum as revealed by DFT calculations. PISEMA solid-state NMR experiments show a reduction in the C–H dipolar coupling in comparison to the static limit for the aromatic CH moieties of 75% and 51% at 20 and 40 °C, respectively, that is indicative of ring flips at the higher temperature. Our study shows the power of combining experiments, namely DSC, X-ray diffraction, and MAS NMR, with DFT calculations and CSP to probe and understand the solid-state landscape, and in particular the role of dynamics, for pharmaceutical molecules.

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Role of Exact Exchange and Relativistic Approximations in Calculating ¹⁹F Magnetic Shielding in Solids Using a Cluster Ansatz

Cited by 22 publications

References 113 publications

¹⁹F Magic Angle Spinning NMR Spectroscopy and Density Functional Theory Calculations of Fluorosubstituted Tryptophans: Integrating Experiment and Theory for Accurate Determination of Chemical Shift Tensors

¹⁹F Magic Angle Spinning NMR Spectroscopy and Density Functional Theory Calculations of Fluorosubstituted Tryptophans: Integrating Experiment and Theory for Accurate Determination of Chemical Shift Tensors

NMR crystallography of molecular organics

Synergy of Solid-State NMR, Single-Crystal X-ray Diffraction, and Crystal Structure Prediction Methods: A Case Study of Teriflunomide (TFM)

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Role of Exact Exchange and Relativistic Approximations in Calculating 19F Magnetic Shielding in Solids Using a Cluster Ansatz

Cited by 22 publications

References 113 publications

19F Magic Angle Spinning NMR Spectroscopy and Density Functional Theory Calculations of Fluorosubstituted Tryptophans: Integrating Experiment and Theory for Accurate Determination of Chemical Shift Tensors

19F Magic Angle Spinning NMR Spectroscopy and Density Functional Theory Calculations of Fluorosubstituted Tryptophans: Integrating Experiment and Theory for Accurate Determination of Chemical Shift Tensors

NMR crystallography of molecular organics

Synergy of Solid-State NMR, Single-Crystal X-ray Diffraction, and Crystal Structure Prediction Methods: A Case Study of Teriflunomide (TFM)

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Role of Exact Exchange and Relativistic Approximations in Calculating ¹⁹F Magnetic Shielding in Solids Using a Cluster Ansatz

¹⁹F Magic Angle Spinning NMR Spectroscopy and Density Functional Theory Calculations of Fluorosubstituted Tryptophans: Integrating Experiment and Theory for Accurate Determination of Chemical Shift Tensors

¹⁹F Magic Angle Spinning NMR Spectroscopy and Density Functional Theory Calculations of Fluorosubstituted Tryptophans: Integrating Experiment and Theory for Accurate Determination of Chemical Shift Tensors