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Conformations in solution and in solid-state polymorphs : correlating experimental and calculated nuclear magnetic resonance chemical shifts for tolfenamic acid
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Blade, Helen, Blundell, Charles D., Brown, Steven P., Carson, Jake, Dannatt, Hugh R. W., Hughes, Leslie P. and Menakath, Anjali K. (2020) Conformations in solution and in solid-state polymorphs : correlating experimental and calculated nuclear magnetic resonance chemical shifts for tolfenamic acid. The Journal of Physical Chemistry A, 124 (43). pp. 8959-8977. doi:10.1021/acs.jpca.0c07000 ISSN 1089-5639.
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WRAP-Conformations-solution-solid-state-polymorphs-experimental-Tolfenamic-Acid-Brown-2020.pdf - Accepted Version - Requires a PDF viewer. Download (2532Kb) | Preview |
Official URL: https://doi.org/10.1021/acs.jpca.0c07000
Abstract
A new approach for quantitively assessing putative crystal structures with applications in crystal structure prediction (CSP) is introduced that is based upon experimental solution- and magic-angle spinning (MAS) solid-state NMR data and density functional theory (DFT) calculation. For the specific case of tolfenamic acid (TFA), we consider experimental solution-state NMR for a range of solvents, experimental MAS NMR of polymorphs I and II, and DFT calculations for four polymorphs. The change in NMR chemical shift observed in passing from the solution state to the solid state (ΔδExperimental) is calculated as the difference between 1H and 13C experimental solid-state chemical shifts for each polymorphic form (δSolid expt) and the corresponding solution-state NMR chemical shifts (δSolution expt). Separately, we use the gauge-included projector augmented wave (GIPAW) method to calculate the NMR chemical shifts for each form (δSolid calc) and for TFA in solution (δSolution calc), using the dynamic 3D solution conformational ensemble determined from NMR spectroscopy. The calculated change in passing from the solution state to the solid state, ΔδCalculated, is then calculated as the difference of δSolid calc and δSolution calc. Regression analysis for ΔδCalculated against ΔδExperimental followed by a t-test for statistical significance provides a robust quantitative assessment. We show that this assessment clearly identifies the correct polymorph, i.e., when comparing ΔδExperimental based on the experimental MAS NMR chemical shifts of Form I or II with ΔδCalculated based on calculated chemical shifts for polymorphs I, II, III and IV. Complementarity to the established approach of comparing δSolid expt to δSolid calc is explored. We further show that our approach is applicable if there are no solid-state crystal structure data. Specifically, δSolid calc in ΔδCalculated is replaced by the chemical shift for an isolated molecule with a specific conformation. Sampling conformations at specific 15° angle values and comparing them against experimental 13C chemical shift data for Forms I and II identifies matching narrow ranges of conformations, successfully predicting the conformation of tolfenamic acid in each form. This methodology can therefore be used in crystal structure prediction to both reduce the initial conformational search space and also quantitatively assess subsequent putative structures to reliably and unambiguously identify the correct structure.
Item Type: | Journal Article | ||||||||
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Subjects: | Q Science > QC Physics Q Science > QD Chemistry |
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Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||
Library of Congress Subject Headings (LCSH): | Crystallography, Polymorphism (Crystallography), Nuclear magnetic resonance | ||||||||
Journal or Publication Title: | The Journal of Physical Chemistry A | ||||||||
Publisher: | American Chemical Society | ||||||||
ISSN: | 1089-5639 | ||||||||
Official Date: | 29 October 2020 | ||||||||
Dates: |
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Volume: | 124 | ||||||||
Number: | 43 | ||||||||
Page Range: | pp. 8959-8977 | ||||||||
DOI: | 10.1021/acs.jpca.0c07000 | ||||||||
Status: | Peer Reviewed | ||||||||
Publication Status: | Published | ||||||||
Reuse Statement (publisher, data, author rights): | “This document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of Physical Chemistry A, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see [insert ACS Articles on Request author-directed link to Published Work, see http://pubs.acs.org/page/policy/articlesonrequest/index.html].” | ||||||||
Access rights to Published version: | Restricted or Subscription Access | ||||||||
Copyright Holders: | Copyright © 2020 American Chemical Society | ||||||||
Date of first compliant deposit: | 23 September 2020 | ||||||||
Date of first compliant Open Access: | 15 September 2021 | ||||||||
RIOXX Funder/Project Grant: |
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