3,3′-[Biphenyl-4,4′-diylbis(oxy)]diphthalic acid

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—H⋯O hydrogen bonds link the molecules into layers parallel to the bc plane. Weak C—H⋯O hydrogen bonds and π–π interactions between the aromatic rings [centroid–centroid distance = 3.7674 (3) Å] further consolidate the crystal packing.

In the title molecule, C 28 H 18 O 10 , 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-HÁ Á ÁO hydrogen bonds link the molecules into layers parallel to the bc plane. Weak C-HÁ Á ÁO hydrogen bonds and interactions between the aromatic rings [centroidcentroid distance = 3.7674 (3) Å ] further consolidate the crystal packing.

Related literature
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).
In the title molecule ( Fig.1), two central benzene rings form a dihedral angle of 31.0 (1)°. In the phthalic acid fragments, the carboxy groups in meta positions are approximately coplanar with the attached benzene rings being inclined to their planes at 2.7 (1) and 10.3 (1)°, respectively, while carboxy groups in ortho positions are twisted from the benzene rings at 83.5 (1) and 75.4 (1)°, respectively. In the crystal structure, intermolecular O-H···O hydrogen bonds (Table 1) link the molecules into layers parallel to bc plane. Weak intermolecular C-H···O hydrogen bonds (Table 1) and π-π interactions between the aromatic rings [centroid-centroid distance of 3.7674 (3) Å] consolidate further the crystal packing.

Experimental
To a solution of 4,4'-biphenol(1.62 g,0.01 mol) and anhydrous Na2CO3(2.12 g,0.02 mol) in DMF(25 ml)stirred for 30 min, 3-nitropthalonitrile(3.46 g,0.02 mol) was added.The resulting mixture was stirred for 48 h. Then the mixture was poured into water (500 ml), and a slightly yellow solid was yielded and isolated by filtration. The crude product was dried in air, yielding 3,3'-(4,4'-biphenylenebis(oxy))diphthalonitrile. The mixture of 3,3'-(4,4'-biphenylenebis(oxy))diphthalonitrile (3.6 g, 0.01 mol) and NaOH (3.2 g, 0.08 mol) in distilled water (150 ml) was refluxed until the solution turned clear Then, the solution was cooled drown to room temperature and filtered. After the pH value of the filtrate was adjusted to about 4-5 with HCl (6.0 mol/L), the filtrate was kept undisturbed at room temperature. After about one day, a large amount of yellow solid of (I) was collected by filtration. A mixture containing Zn(NO 3 ) 2 .6H 2 O (0.0595 g, 0.2 mmol), (I)(0.0514 g, 0.1 mmol), and H 2 O (15 ml) was sealed in a Teflon-lined stainless steel reactor and heated at 120 for 3 days. Unfortunately, X-ray quality single crystals of (I) were only obtained.

Refinement
All hydrogen atoms were positioned geometrically and included in the refinement using a riding-model approximation