Dimethyl 2,2′-dinitrobiphenyl-4,4′-dicarboxylate

The title compound, C16H12N2O8, exhibits two near-planar aromatic ester groups with aryl–ester dihedral angles of 2.1 (2) and 4.2 (3)°. The dihedral angle between the aromatic rings is 58.0 (1)°. The two nitro groups are tilted slightly from the plane of the aromatic rings, making dihedral angles of 14.1 (1) and 8.2 (2)°. In the crystal, molecules are connected by weak C—H⋯O interactions, forming a three-dimensional network.

The title compound, C 16 H 12 N 2 O 8 , exhibits two near-planar aromatic ester groups with aryl-ester dihedral angles of 2.1 (2) and 4.2 (3) . The dihedral angle between the aromatic rings is 58.0 (1) . The two nitro groups are tilted slightly from the plane of the aromatic rings, making dihedral angles of 14.1 (1) and 8.2 (2) . In the crystal, molecules are connected by weak C-HÁ Á ÁO interactions, forming a three-dimensional network.

Comment
Biphenyl-4,4′-dicarboxylate and its derivatives are widely used in metal-organic frameworks (MOFs) as linkers. One of the many advantages of MOFs is the ability to incorporate different functional groups within their pores. As a part of our efforts in this field, we prepared the previously reported dimethyl 2,2′-dinitrobiphenyl-4,4′-dicarboxylate (Ol'khovik et al. 2008) and report its structure herein.
The molecular structure of the title compound is shown in Figure 1. The structure demonstrates two near planar aromatic ester groups with aryl-ester dihedral angles of 2.1 (2)° and 4.2 (3)°. The two aromatic rings demonstrate a dihedral angle of 58.0 (1)°. The nitro groups are skewed slightly with aryl-nitro dihedral angles of 8.2 (2)° and 14.1 (1)°.
No π-π interactions were noted between the aromatic rings. The packing for the title compound is shown in Figure 2.

Experimental
The compound was prepared by literature procedure (Ol'khovik et al. 2008). Crystals suitable for single-crystal X-ray analysis were grown by slow evaporation of an ethanol solution.

Refinement
All non-hydrogen atoms refined anisotropically by full matrix least squares on F 2 . All hydrogen atoms were placed in calculated positions and then refined with riding model with C-H lengths of 0.95 Å for (CH) and 0.98 Å for (CH 3 ) and with isotropic displacement parameters set to 1.20 and 1.50 times U eq of the parent C atom.   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 > σ(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq O1 0.28379 (14