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Abstract Solid‐state NMR measurements coupled with density functional theory (DFT) calculations demonstrate how hydrogen positions can be refined in a crystalline system. The precision afforded by rotational‐echo double‐resonance (REDOR) NMR to interrogate13C–1H distances is exploited along with DFT determinations of the13C tensor of carbonates (CO32−). Nearby1H nuclei perturb the axial symmetry of the carbonate sites in the hydrated carbonate mineral, hydromagnesite [4 MgCO3⋅Mg(OH)2⋅4 H2O]. A match between the calculated structure and solid‐state NMR was found by testing multiple semi‐local and dispersion‐corrected DFT functionals and applying them to optimize atom positions, starting from X‐ray diffraction (XRD)‐determined atomic coordinates. This was validated by comparing calculated to experimental13C{1H} REDOR and13C chemical shift anisotropy (CSA) tensor values. The results show that the combination of solid‐state NMR, XRD, and DFT can improve structure refinement for hydrated materials.
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Stereochemical revision of xylogranatin F by GIAO and DU8+ NMR calculations
Abstract This manuscript describes predicted NMR shifts for the limonoid natural product xylogranatin F. The1H and13C NMR shifts of four diastereomers were evaluated by GIAO and hybrid DFT/parametric DU8+ methods. The results of the1H and13C NMR calculations for both the GIAO method and the DU8+ calculations suggest the revised structure that was recently reassigned by chemical synthesis. Furthermore, we show that while DU8+ provides superior accuracy with less computation time, GIAO points to the correct structure with more distinguishable data in this case study.
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- Award ID(s):
- 1665342
- PAR ID:
- 10457768
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Chirality
- Volume:
- 32
- Issue:
- 5
- ISSN:
- 0899-0042
- Page Range / eLocation ID:
- p. 515-523
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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