Dimethyl 3,3′-di­meth­oxy­biphenyl-4,4′-di­carboxyl­ate

In the title compound, C₁₈H₁₈O₆, the biphenyl moiety is twisted with a dihedral angle of 29.11 (10)°. The carbometh­oxy groups form C—C—C—O torsion angles of −18.3 (3) and −27.7 (3)° with the attached rings, as a result of steric hindrances from the nearby meth­oxy groups. In the absence of stacking inter­actions and with no H...O contacts shorter than 2.7 Å, the packing is dominated by weaker van der Waals inter­actions.

Methyl 5-iodo-2-meth­oxy­benzoate

In the title compound, C₉H₉IO₃, the mol­ecules are close to planar [maximum deviation from benzene ring plane = 0.229 (5) Å for the methyl carboxylate C atom] with the methyl groups oriented away from each other. In the crystal, mol­ecules form stacked layers parallel to the ab plane, where every layer has either the iodine or meth­oxy/methyl carboxyl­ate substituents pointing towards each other in an alternating fashion.

4,4′-Dimeth­oxybi­phenyl-3,3′-di­car­box­ylic acid

The title compound, C₁₆H₁₄O₆, was recrystallized under solvothermal conditions. The mol­ecules are located on inversion centres, with one complete mol­ecule generated from the asymmetric unit by inversion. There are intra­molecular O—H...O hydrogen bonds involving the carb­oxy­lic acid group and the O atom of the adjacent meth­oxy group. In the crystal, mol­ecules are linked via O—H...O hydrogen bonds, forming chains propagating along [100]. The chains are linked via C—H...O hydrogen bonds, forming sheets parallel to (001).