Complex polymorphic system of gallic acid-five monohydrates, three anhydrates, and over 20 solvates

Doris E Braun, Rajni M. Bhardwaj, Alastair J. Florence, Derek A. Tocher, Sarah L. Price

Research output: Contribution to journalArticlepeer-review

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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.
Original languageEnglish
Pages (from-to)19-23
Number of pages5
JournalCrystal Growth and Design
Issue number1
Early online date27 Nov 2012
Publication statusPublished - 2 Jan 2013


  • monohydrate crystal
  • gallic acid
  • anhydrate polymorphs

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