Journal of Applied Crystallography

Volume 46, Part 1 (February 2013)


research papers



J. Appl. Cryst. (2013). 46, 99-107    [ doi:10.1107/S0021889812048133 ]

Cimetidine, C10H16N6S, form C: crystal structure and modelling of polytypes using the superspace approach

A. Arakcheeva, P. Pattison, A. Bauer-Brandl, H. Birkedal and G. Chapuis

Abstract: The H2 antagonist cimetidine forms many polymorphs, several of which have resisted structural analysis thus far. Using single-crystal X-ray measurements obtained from synchrotron radiation, the crystal structure of cimetidine form C has been solved. This layered structure crystallizes in space group C2/c with an unusually large lattice parameter, a = 82.904 Å. The thickness of each layer L is equal to a' = a/6 = 13.82 Å, and a = 6a' originates from a sixfold LLLL'L'L' sequence with L and L' differing by 0.5b. This packing is reminiscent of polytypic stacking in metals. A (3 + 1)-dimensional superspace model is derived and used to explain and predict many polytypic modifications. This model is characterized by (i) the (3 + 1)-dimensional symmetry group X2/c([alpha]0[gamma])00, where X = 0\textstyle{1 \over 2}0\textstyle{1 \over 2}; (ii) the lattice parameter a' and modulation vector q = 1/n(a'*); (iii) the atomic positions of a single molecule of cimetidine form C; (iv) the primary variable, 1/n. The model reproduces the previously solved structure, the 6M polytype, and generates the related polytypes nM with lattice parameter anM = na' for n = 1, 2, 3, 4 and 5. A comparison of powder X-ray diffraction patterns available for cimetidine form C with those simulated for the nM polytypes suggests that the powder samples published previously probably contain a mixture of various polytypes.

Keywords: cimetidine; crystal structure; polymorphism; polytypism; superspace modelling; synchrotron radiation.


cmldisplay filedownload file

Chemical Markup Language (CML) file (1.7 kbytes)
[ doi:10.1107/S0021889812048133/he5576Isup3.cml ]
Supplementary material


pdfdisplay filedownload file

Portable Document Format (PDF) file
[ doi:10.1107/S0021889812048133/he5576sup4.pdf ]
Supporting information


Notes:

To open or display or play some files, you may need to set your browser up to use the appropriate software. See the full list of file types for an explanation of the different file types and their related mime types and, where available links to sites from where the appropriate software may be obtained.

The download button will force most browsers to prompt for a file name to store the data on your hard disk.

Where possible, images are represented by thumbnails.

 bibliographic record in  format

  Find reference:   Volume   Page   
  Search:     From   to      Advanced search

Copyright © International Union of Crystallography
IUCr Webmaster