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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
Crystal structure and Hirshfeld surface analysis of a third polymorph of 2,6-di-meth-oxy-benzoic acid
1Chemistry Department, "Sapienza" University of Rome, P. le A. Moro 5, I-00185 Rome, Italy.
Abstract:
A third crystalline form of the title compound, C9H10O4, crystallizing in the centrosymmetric monoclinic space group P21/c, has been identified during screening for co-crystals. The asymmetric unit comprises a non-planar independent mol-ecule with a synplanar conformation of the OH group. The sterically bulky o-meth-oxy substituents force the carb-oxy group to be twisted away from the plane of the benzene ring by 74.10 (6)°. The carb-oxy group exhibits the acidic H atom disordered over two sites between two O atoms. A similar situation has been found for the second tetra-gonal polymorph reported [Portalone (2011 ▸). Acta Cryst. E67, o3394-o3395], in which mol-ecules with the OH group in a synplanar conformation form dimeric units via strong O-H⋯O hydrogen bonds. In contrast, in the first ortho-rhom-bic form reported [Swaminathan et al. (1976 ▸). Acta Cryst. B32, 1897-1900; Bryan & White (1982 ▸). Acta Cryst. B38, 1014-1016; Portalone (2009 ▸). Acta Cryst. E65, o327-o328], the mol-ecular components do not form conventional dimeric units, as an anti-planar conformation adopted by the OH group favors the association of mol-ecules in chains stabilized by linear O-H⋯O hydrogen bonds.
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