Experimental electron density and neutron diffraction studies on the polymorphs of sulfathiazole

Sovago, I., Gutmann, M. J., Hill, J. G., Senn, H. M. , Thomas, L. H., Wilson, C. C. and Farrugia, L. J. (2014) Experimental electron density and neutron diffraction studies on the polymorphs of sulfathiazole. Crystal Growth and Design, 14(3), pp. 1227-1239. (doi: 10.1021/cg401757z)

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High resolution X-ray diffraction data on forms I–IV of sulfathiazole and neutron diffraction data on forms II–IV have been collected at 100 K and analyzed using the Atoms in Molecules topological approach. The molecular thermal motion as judged by the anisotropic displacement parameters (adp’s) is very similar in all four forms. The adp of the thiazole sulfur atom had the greatest amplitude perpendicular to the five-membered ring, and analysis of the temperature dependence of the adps indicates that this is due to genuine thermal motion rather than a concealed disorder. A minor disorder (1–2%) is evident for forms I and II, but a statistical analysis reveals no deleterious effect on the derived multipole populations. The topological analysis reveals an intramolecular S–O···S interaction, which is consistently present in all experimental topologies. Analysis of the gas-phase conformation of the molecule indicates two low-energy theoretical conformers, one of which possesses the same intramolecular S–O···S interaction observed in the experimental studies and the other an S–O···H–N intermolecular interaction. These two interactions appear responsible for “locking” the molecular conformation. The lattice energies of the various polymorphs computed from the experimental multipole populations are highly dependent on the exact refinement model. They are similar in magnitude to theoretically derived lattice energies, but the relatively high estimated errors mean that this method is insufficiently accurate to allow a definitive stability order for the sulfathiazole polymorphs at 0 K to be determined.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Farrugia, Dr Louis and Hill, Dr John and Sovago, Ms Ioana and Senn, Dr Hans and Thomas, Dr Lynne
Authors: Sovago, I., Gutmann, M. J., Hill, J. G., Senn, H. M., Thomas, L. H., Wilson, C. C., and Farrugia, L. J.
College/School:College of Science and Engineering > School of Chemistry
Journal Name:Crystal Growth and Design
Publisher:American Chemical Society
ISSN (Online):1528-7505
Copyright Holders:Copyright © 2014 American Chemical Society
First Published:First published in Crystal Growth and Design 14(3):1227-1239
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
430141Understanding the energetics in polymorphsLouis FarrugiaEngineering & Physical Sciences Research Council (EPSRC)EP/F021348/1CHEM - CHEMISTRY