Quantum crystallography and NMR crystallography

Paul Hodgkinson^a, Paul Niklas Ruth^b

^aDepartment of Chemistry, Durham University, UK; ^aAdvanced Research Computing, Durham University, UK

e-mail: paul.hodgkinson@durham.ac.uk

As a highly local probe of atomic environments, solid-state NMR is a highly complementary tool to diffraction-based analysis. Traditionally often limited to fingerprinting different solid forms, e.g. polymorphs, amorphous vs. crystalline forms, the field of “NMR crystallography”[1,2] has developed as DFT calculations now allow NMR spectra to be predicted efficiently from trial structures. NMR can then be used to resolve questions of disorder or distinguishing between alternative structural models[3]. In particular, the ¹H chemical shift is extremely sensitive to position, allowing questions of hydrogen positioning, e.g. salt vs. co-crystal forms to be readily resolved.

A weakness of current NMR crystallography for organic solids is the relatively poor positioning of H by independent atom modelling in XRD refinement. In order to obtain reasonable agreement with NMR data, it is essential to use DFT to optimise H positions in XRD-derived structures prior to calculating NMR parameters, which introduces subtle systematic errors. There is clear potential for more accurate structures provided by quantum crystallography to provide better starting points for NMR crystallography.

This talk will discuss other questions of common interests, such as the effects of temperature on NMR parameters via vibrational modes, i.e. dynamic NMR crystallography. These areas of overlap are especially useful to explore as the UK Collaborative Computational Project in NMR Crystallography[4], a key developer of tools for NMR crystallography, plans its roadmap for future funding.

References:

[1] P.Hodgkinson, NMR crystallography of molecular organics, Prog. Nucl. Magn. Reason. Spectrosc. 118–119 (2020) 10.

[2] Modern NMR Crystallography: Concepts and Applications, Ed. D. L. Bryce, RSC Publishing (2025).

[3] C. M. Widdifield, J. D. Farrell, J. C. Cole, J. A. K. Howard and P. Hodgkinson, Resolving alternative organic crystal structures using density functional theory and NMR chemical shifts, Chem. Sci., 11 (2020) 2987.

[4] Collaborative Computational Project for NMR Crystallography, www.ccpnc.ac.uk