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Figure 2
Root-mean-square deviations (RMSD) for isotropic chemical shifts (a) δiso(1H) and (b) δiso(13C) between experimental δiso values for a sample of furosemide from Sigma–Aldrich and a recrystallized sample, with those computed using GIPAW DFT on the H-optimized structures indicated. Grey bands correspond to RMSD ranges established using a series of benchmark organic compounds. The 1H RMSD is sensitive to the position of the COOH hydrogen, as shown by RMSD values which include (blue) and do not include (red) this site. (c) A comparison of the calculated [CSD refcodes FURSEM01 (Lamotte et al., 1978BB97) and FURSEM17 (Bolukbasi & Yilmaz, 2012BB98)] and experimental (from Sigma–Aldrich) 1H NMR spectra. Red traces in (c) correspond to the carboxyl H atom from each crystallographically unique furosemide molecule. On the basis of the low RMSDs shown in (a) and (b), the diffraction structures FURSEM01 (and FURSEM-NEW) have been verified by NMR crystallography. From Widdifield et al. (2016BB68). Published by The Royal Society of Chemistry. Used with permission.

IUCrJ
Volume 4| Part 4| July 2017| Pages 350-359
ISSN: 2052-2525
https://doi.org/10.1107/S2052252517006042