2,2′-(Biphenyl-4,4′-diyldioxy)diacetic acid N,N-dimethylformamide solvate

In the crystal struture of the title compound, C16H14O6·C3H7NO, the two crystallographically independent benzene rings are coplanar [dihedral angle = 1.00 (2)°]. The crystal structure is stabilized by O—H⋯O hydrogen bonds between the diacid and the solvate dimethylformamide molecule, resulting in the formation of a zigzag chain structure extending parallel to [001].

In the crystal struture of the title compound, C 16 H 14 O 6 Á-C 3 H 7 NO, the two crystallographically independent benzene rings are coplanar [dihedral angle = 1.00 (2) ]. The crystal structure is stabilized by O-HÁ Á ÁO hydrogen bonds between the diacid and the solvate dimethylformamide molecule, resulting in the formation of a zigzag chain structure extending parallel to [001].
The molecular structure of the title compound is shown in Fig. 1. The two crystallographically independent benzene rings are coplanar (dihedral angle = 1.00 (2)°) and the two carboxylic acid groups are oriented in different directions. There are no unusual bonds lengths and angles. The C1-O1 and C16-O5 distances in the title compound are 1.197 (3)Å and 1.184 (4)Å, respectively, typical of double bonds.
The crystal structure is further stabilized by weak intermolecular hydrogen bonding interactions between the diacids, thus forming a sandwich structure as represented in Fig. 3.

Refinement
All H atoms were placed in calculated positions and were allowed to ride on their parent atoms; C-H = 0.93 (aromatic C-H), 0.97 (methylene) and 0.96 (methyl) and O-H = 0.82 (hydroxyl) Å; U iso (H) = 1.2 U eq (aromatic and methylene C), U iso (H) = 1.5 U eq (methyl C) and U iso (H) = 1.5 U eq (O). In the absence of anomalous scatterers and using Mo radiation Friedel pairs were merged prior to refinement.
supplementary materials sup-2 Figures Fig. 1. The molecular structure of the title compound with displacement ellipsoids at the 50% probability level. All H atoms are drawn as spheres of arbitrary radius.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.