Received 21 November 2011
In the title molecule, C28H18O10, the two central benzene rings form a dihedral angle of 31.0 (1)°. In the phthalic acid fragments, the carboxy groups in the meta positions are approximately coplanar with the attached benzene rings, being inclined to their planes at 2.7 (1) and 10.3 (1)°, while the carboxy groups in the ortho positions are twisted from the benzene ring planes by 83.5 (1) and 75.4 (1)°. In the crystal, O-HO hydrogen bonds link the molecules into layers parallel to the bc plane. Weak C-HO hydrogen bonds and - interactions between the aromatic rings [centroid-centroid distance = 3.7674 (3) Å] further consolidate the crystal packing.
For applications of metal-organic frameworks with semi-rigid carboxylic acid ligands, see: Li et al. (2008); Chen et al. (2008). For background to the synthesis of various semi-rigid multicarboxylate ligands, see: Maglio et al. (1997).
Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: CV5208 ).
This project was supported by the National Natural Science Foundation of China (grant No. 21101013) and the Foundation of University of Science and Technology Beijing (grant Nos. 00009805 and 06113004).
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