Tautomeric Polymorphism of 4-Hydroxynicotinic Acid

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• 作者：Sihui Long ; Mingtao Zhang ; Panpan Zhou ; Faquan Yu ; Sean Parkin ; Tonglei Li
• 刊名：Crystal Growth & Design
• 出版年：2016
• 出版时间：May 4, 2016
• 年：2016
• 卷：16
• 期：5
• 页码：2573-2580
• 全文大小：500K
• 年卷期：0
• ISSN：1528-7505

文摘

4-Hydroxynicotinic acid (4-HNA) was discovered to exist in the solid state as either 4-HNA or its tautomer 4-oxo-1,4-dihydropyridine-3-carboxylic acid (4-ODHPCA) in three polymorphs and two hydrates. Packing motifs differ as each of the three oxygen atoms acts as the hydrogen-bond acceptor, respectively, in the anhydrate forms, while in the hydrate forms, water molecules participate in hydrogen bonding with 4-HNA. Phase behaviors of the forms were characterized by differential scanning calorimetry (DSC), hot-stage microscopy (HSM), and thermogravimetric analysis (TGA). It was found that anhydrates I and II converted into III during heating; the two hydrate forms dehydrated at different temperatures and eventually transformed into anhydrate III, and sublimation of all five forms led to form III when the crystals were heated. Quantum mechanical calculations were performed providing further insight into the polymorphism.