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Solid-state structural properties of alloxazine determined from powder XRD data in conjunction with DFT-D calculations and solid-state NMR spectroscopy : unraveling the tautomeric identity and pathways for tautomeric interconversion
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Smalley, Christopher J. H., Logsdail, Andrew J., Hughes, Colan E., Iuga, Dinu, Young, Mark T. and Harris, Kenneth D. M. (2022) Solid-state structural properties of alloxazine determined from powder XRD data in conjunction with DFT-D calculations and solid-state NMR spectroscopy : unraveling the tautomeric identity and pathways for tautomeric interconversion. Crystal Growth & Design, 22 (1). pp. 524-534. doi:10.1021/acs.cgd.1c01114 ISSN 1528-7505.
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WRAP-Solid-state-structural-properties-alloxazine-spectroscopy-interconversion-2021.pdf - Published Version - Requires a PDF viewer. Available under License Creative Commons Attribution 4.0. Download (3231Kb) | Preview |
Official URL: https://doi.org/10.1021/acs.cgd.1c01114
Abstract
We report the solid-state structural properties of alloxazine, a tricyclic ring system found in many biologically important molecules, with structure determination carried out directly from powder X-ray diffraction (XRD) data. As the crystal structures containing the alloxazine and isoalloxazine tautomers both give a high-quality fit to the powder XRD data in Rietveld refinement, other techniques are required to establish the tautomeric form in the solid state. In particular, high-resolution solid-state 15N NMR data support the presence of the alloxazine tautomer, based on comparison between isotropic chemical shifts in the experimental 15N NMR spectrum and the corresponding values calculated for the crystal structures containing the alloxazine and isoalloxazine tautomers. Furthermore, periodic DFT-D calculations at the PBE0-MBD level indicate that the crystal structure containing the alloxazine tautomer has significantly lower energy. We also report computational investigations of the interconversion between the tautomeric forms in the crystal structure via proton transfer along two intermolecular N–H···N hydrogen bonds; DFT-D calculations at the PBE0-MBD level indicate that the tautomeric interconversion is associated with a lower energy transition state for a mechanism involving concerted (rather than sequential) proton transfer along the two hydrogen bonds. However, based on the relative energies of the crystal structures containing the alloxazine and isoalloxazine tautomers, it is estimated that under conditions of thermal equilibrium at ambient temperature, more than 99.9% of the molecules in the crystal structure will exist as the alloxazine tautomer.
Item Type: | Journal Article | ||||||||||||||||||||||||
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Subjects: | Q Science > QC Physics Q Science > QD Chemistry T Technology > TA Engineering (General). Civil engineering (General) |
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Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||||||||||||||||||
SWORD Depositor: | Library Publications Router | ||||||||||||||||||||||||
Library of Congress Subject Headings (LCSH): | Solid state physics , X-ray diffraction imaging , Nuclear magnetic resonance spectroscopy , Tautomerism , X-ray crystallography , Crystal growth | ||||||||||||||||||||||||
Journal or Publication Title: | Crystal Growth & Design | ||||||||||||||||||||||||
Publisher: | American Chemical Society (ACS) | ||||||||||||||||||||||||
ISSN: | 1528-7505 | ||||||||||||||||||||||||
Official Date: | 5 January 2022 | ||||||||||||||||||||||||
Dates: |
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Volume: | 22 | ||||||||||||||||||||||||
Number: | 1 | ||||||||||||||||||||||||
Page Range: | pp. 524-534 | ||||||||||||||||||||||||
DOI: | 10.1021/acs.cgd.1c01114 | ||||||||||||||||||||||||
Status: | Peer Reviewed | ||||||||||||||||||||||||
Publication Status: | Published | ||||||||||||||||||||||||
Access rights to Published version: | Open Access (Creative Commons) | ||||||||||||||||||||||||
Date of first compliant deposit: | 7 January 2022 | ||||||||||||||||||||||||
Date of first compliant Open Access: | 10 January 2022 | ||||||||||||||||||||||||
RIOXX Funder/Project Grant: |
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