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  • Title: Solid-state 13C NMR study of indomethacin polymorphism.
    Author: Masuda K, Tabata S, Kono H, Sakata Y, Hayase T, Yonemochi E, Terada K.
    Journal: Int J Pharm; 2006 Aug 02; 318(1-2):146-53. PubMed ID: 16675172.
    Abstract:
    The purpose of this study was to analyze the difference in the molecular conformation packed in the crystal lattice between the meta-stable alpha-form and stable gamma-form of indomethacin on the basis of solid-state (13)C NMR spectral patterns. The chemical shifts of each resonance of the alpha-form were distinctly different from the gamma-form. Each carbon nucleus of the gamma-form showed a single signal with no splitting. In contrast, carbon nuclei of the alpha-form showed a complicated set of resonances for each carbon. For some carbons of the alpha-form, four signals assigned to one carbon were observed at 203 K. Two of these four signals were merged between the temperature range from 203 to 343 K without a transformation in the crystal structure. It was found that solid-state (13)C NMR can be a powerful tool to estimate the number of molecular conformations as well as configurational differences in the packing of molecules in a unit cell.
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