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

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—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.