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Construction and Systematical Symmetric Studies of a Series of Supramolecular Clusters with Binary or Ternary Ammonium Triphenylacetates
Published on: February 15, 2016
Complex Polymorphic System of Gallic Acid-Five Monohydrates, Three Anhydrates, and over 20 Solvates
Doris E Braun1, Rajni M Bhardwaj, Alastair J Florence
1Department of Chemistry, University College London , 20 Gordon Street, London WC1H 0AJ, U.K. ; Institute of Pharmacy, University of Innsbruck , Innrain 52c, 6020 Innsbruck, Austria.
Abstract:
We report the structure of the fifth monohydrate of gallic acid and two additional anhydrate polymorphs and evidence of at least 22 other solvates formed, many containing water and another solvent. This unprecedented number of monohydrate polymorphs and diversity of solid forms is consistent with the anhydrate and monohydrate crystal energy landscapes, showing both a wide range of packing motifs and also some structures differing only in proton positions. By aiding the solution of structures from powder X-ray diffraction data and guiding the screening, the computational studies help explain the complex polymorphism of gallic acid. This is industrially relevant, as the three anhydrates are stable at ambient conditions but hydration/dehydration behavior is very dependent on relative humidity and phase purity.
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