Visualising crystal packing interactions in solid-state NMR: Concepts and applications

Abstract

In this article, we introduce and apply a methodology, based on density functional theory and the gauge-including projector augmented wave approach, to explore the effects of packing interactions on solid-state nuclear magnetic resonance (NMR) parameters. A visual map derived from a so-termed "magnetic shielding contribution field" can be made of the contributions to the magnetic shielding of a specific site-partitioning the chemical shift to specific interactions. The relation to the established approaches of examining the molecule to crystal change in the chemical shift and the nuclear independent chemical shift is established. The results are applied to a large sample of 71 molecular crystals and three further specific examples from supermolecular chemistry and pharmaceuticals. This approach extends the NMR crystallography toolkit and provides insight into the development of both cluster based approaches to the predictions of chemical shifts and for empirical predictions of chemical shifts in solids.

NMR Spectroscopy Reveals Adsorbate Binding Sites in the Metal–Organic Framework UiO-66(Zr)

“…The 13 C carbonyl chemical shifts at low loadings (7.5 and 16% mass ratio) appeared at higher frequencies compared to the neat acetone carbonyl chemical shift (Figure 3). Similar to the 1 H experiments, a secondary carbonyl resonance emerged at higher loadings (21,40, and 63% mass ratio), supporting the inference of pore saturation. The 13 C chemical shift of the second peak (at lower frequencies relative to the initial peak present at low loadings) matched the carbonyl chemical shift of the neat acetone (see Table S1 in the Supporting Information).…”

An XRD and NMR crystallographic investigation of the structure of 2,6-lutidinium hydrogen fumarate

“…44 By comparing the parameters in the full crystal structure with those for the isolated molecule, insight is provided into the intermolecular interactions responsible for maintaining the crystal structure. 45…”

Improving Confidence in Crystal Structure Solutions Using NMR Crystallography: The Case of β-Piroxicam

“…16,[21][22] Furthermore, the wide range of NMR-active nuclei potentially included within a NMR crystallography study increases the range of systems that can be studied. The accuracy of a proposed model can be gauged from a comparison between chemical shift values, [23][24] and for spin >½ nuclei, the quadrupolar interaction can also be determined, using experiment and calculation. [25][26][27] Insight into intermolecular packing configurations can be provided by 2D correlation experiments, where an observed correlation between atoms is due to through-space or through-bond couplings.…”