Characterization of Complicated New Polymorphs of Chlorothalonil by X-ray Diffraction and Computer Crystal Structure Prediction
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- 作者：Maryjane Tremayne ; Leanne Grice ; James C. Pyatt ; Colin C. Seaton ; Benson M. Kariuki ; Helen H. Y. Tsui ; Sarah L. Price ; and Julian C. Cherryman
- 刊名：Journal of the American Chemical Society
- 出版年：2004
- 出版时间：June 9, 2004
- 年：2004
- 卷：126
- 期：22
- 页码：7071 - 7081
- 全文大小：350K
- 年卷期：v.126,no.22(June 9, 2004)
- ISSN：1520-5126
文摘
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 2and 3. The crystal structure prediction study, using a specifically developed anisotropic atom-atom potentialfor chlorothalonil, gave as the global minimum in the lattice energy a structure that was readily refinedagainst powder diffraction data to the known form 1 (P21/a). The structure of form 2 was solved and refinedfrom powder diffraction data, giving a disordered structure in the R
m (166) space group (Z = 3). It couldalso be refined against a P
ordered model, starting from a low-energy hypothetical sheet structure foundin the computational search. This shows that the disorder could be associated with the stacking of orderedsheets. The disordered structure for form 2 was later confirmed by single-crystal X-ray diffraction. Thestructure of form 3, determined from single-crystal diffraction, contains three independent molecules in theasymmetric unit in P21 (4) (Z = 6). Powder diffraction showed that this single-herringbone structure wassimilar to two low-energy structures found in the search. Further analysis confirmed that form 3 has asimilar lattice energy and contains elements from both these predicted structures, which can be consideredas good approximations to the form 3 structure.
m (166) space group (Z = 3). It couldalso be refined against a P ordered model, starting from a low-energy hypothetical sheet structure foundin the computational search. This shows that the disorder could be associated with the stacking of orderedsheets. The disordered structure for form 2 was later confirmed by single-crystal X-ray diffraction. Thestructure of form 3, determined from single-crystal diffraction, contains three independent molecules in theasymmetric unit in P21 (4) (Z = 6). Powder diffraction showed that this single-herringbone structure wassimilar to two low-energy structures found in the search. Further analysis confirmed that form 3 has asimilar lattice energy and contains elements from both these predicted structures, which can be consideredas good approximations to the form 3 structure.