Characterization of complicated new polymorphs of chlorothalonil by X-ray diffraction and computer crystal structure prediction

Maryjane Tremayne, [No Value] [No Value], [No Value] [No Value], Colin Seaton, Benson Kariuki, HH Tsui, SL Price, JC Cherryman

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43 Citations (Scopus)


A simultaneous experimental and computational search for polymorphs of chlorothalonil (2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile) has been conducted, leading to the first characterization of forms 2 and 3. The crystal structure prediction study, using a specifically developed anisotropic atom-atom potential for chlorothalonil, gave as the global minimum in the lattice energy a structure that was readily refined against powder diffraction data to the known form 1 (P2(1)/a). The structure of form 2 was solved and refined from powder diffraction data, giving a disordered structure in the Rm (166) space group (Z = 3). It could also be refined against a P1 ordered model, starting from a low-energy hypothetical sheet structure found in the computational search. This shows that the disorder could be associated with the stacking of ordered sheets. The disordered structure for form 2 was later confirmed by single-crystal X-ray diffraction. The structure of form 3, determined from single-crystal diffraction, contains three independent molecules in the asymmetric unit in P2(1) (4) (Z = 6). Powder diffraction showed that this single-herringbone structure was similar to two low-energy structures found in the search. Further analysis confirmed that form 3 has a similar lattice energy and contains elements from both these predicted structures, which can be considered as good approximations to the form 3 structure.
Original languageEnglish
Pages (from-to)7071-7081
Number of pages11
JournalJournal of the American Chemical Society
Issue number22
Publication statusPublished - 9 Jun 2004


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