Combining the Advantages of Powder X-ray Diffraction and NMR Crystallography in Structure Determination of the Pharmaceutical Material Cimetidine Hydrochloride

<p>The crystal structure of the anhydrous phase of cimetidine hydrochloride was determined directly from powder X-ray diffraction data. The material was prepared bydehydration of the readily obtained monohydrate form of cimetidine hydrochloride, the only form for which a crystal structure has previously been reported. As such, solid-state dehydration processes typically yield the product phase as a microcrystalline powder, and structure determination was carried out directly from powder X-ray diffraction data, using the direct-space genetic algorithm technique for structure solution followed by Rietveld refinement. The structure determined from powder X-ray diffraction was further validated by calculating solid-state 13C NMR data for the crystal structure (using first-principles periodic DFT techniques within the GIPAW approach) and assessing the quality of agreement with the corresponding experimental solid-state 13C CPMAS NMR data. This strategy provides a robust vindication of the correctness of the crystal structure by assessing the quality of agreement of the structure both with experimental powder X-ray diffraction data and with experimental solid-state 13C NMR data.<br></p><p>There are three dataset files.</p><p>The first, "Cimetidine HCl 13C NMR", consists of the raw and processed data for the 13C NMR spectrum of cimetidine HCl together with a text version of the processed spectrum.</p><p>The second, "Cimetidine HCl PXRD", consists of the raw and cpi versions of the two powder X-ray diffraction datasets acquired between 4° and 50° (Cimet HCl M) and between 6° and 70° (Cimet_long).</p><p>The third, "Cimetidine HCl magres", consists of the magres file generated by the program CASTEP when calculating NMR parameters from our crystal structure of cimetidine HCl.</p><p>Results derived from the data described here are published at http://dx.doi.org/10.1021/acs.cgd.6b00016<br></p>