Disappearing and Reappearing Polymorphism in p-Methylchalcone

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• 作者：Inna Barsky ; Joel Bernstein ; Peter W. Stephens ; Kevin H. Stone ; Eugene Cheung ; Magali B. Hickey ; Jan-Olav Henck
• 刊名：Crystal Growth & Design
• 出版年：2008
• 出版时间：January 2008
• 年：2008
• 卷：8
• 期：1
• 页码：63 - 70
• 全文大小：1290K
• 年卷期：v.8,no.1(January 2008)
• ISSN：1528-7505

文摘

One stable form (Form I) and two metastable forms (Forms II and IV) of p-methylchalcone have been obtained, with Form II having previously been reported to be a disappearing polymorph. To prevent the conversion of Form II, which has a melting point of 89–91 °C, into the stable form it was produced in conditions free from seeds of the stable form. Form IV was discovered serendipitously as a single crystal that appeared in the preparation of a powder of Form II. Forms I and II have also been characterized by optical microscopy, differential scanning calorimetry (DSC), variable temperature powder X-ray diffraction, and spectroscopic analysis. The crystal structures of these three forms have been solved, Forms I and IV by single-crystal methods and Form II from synchrotron powder diffraction. This investigation highlights the fact that the challenges of reproducing experimental results (i.e., the production of a particular crystal form) may be overcome by a systematic search for new conditions under which previously obtained results can be regained.