Crystal structure of 4,4′-dinitro-[1,1′-biphenyl]-2-amine

In the title biphenyl derivative, the dihedral angle between the benzene rings is 52.84 (10)°. In the crystal, molecules are linked by two pairs of N—H⋯O hydrogen bonds, forming chains propagating along [101].

In the title biphenyl derivative, C 12 H 9 N 3 O 4 , the dihedral angle between the benzene rings is 52.84 (10) . The nitro group attached to the benzene ring is inclined to the ring by 4.03 (2) , while the nitro group attached to the aminosubstituted benzene ring is inclined to the ring by 8.84 (2) . In the crystal, molecules are linked by two pairs of N-HÁ Á ÁO hydrogen bonds, forming chains propagating along [101]. Within the chains, these N-HÁ Á ÁO hydrogen bonds result in the formation of R 2 2 (20) and R 2 2 (14) ring motifs. The latter ring motif is reinforced by a pair of C-HÁ Á ÁO hydrogen bonds, enclosing R 2 1 (6) ring motifs. The chains are linked by a second C-HÁ Á ÁO hydrogen bond, forming a threedimensional supramolecular structure.

Chemical context
Biphenyl and its derivatives have been shown to play an important role in fighting cancer and arteriosclerosis in humans (Umeda et al., 2005). The dihedral angle between the phenyl rings of biphenyl derivatives is associated with their affinity for cellular target molecules and, therefore, can correlate with their toxicity. The parent compound, biphenyl, adopts a planar conformation in the solid state with a dihedral angle of 0 (Trotter, 1961). The calculated dihedral angle for biphenyl derivatives without ortho substituents is ca 41 (Shaikh et al., 2008). Deviations from the energetically most favourable conformation are most likely the result of crystal packing effects, which allow such compounds to adopt an energetically favorable conformation in the solid state by maximizing the lattice energy. Many research groups have calculated the inter-ring torsion angle of biphenyl in the solid state (Brock, 1980;Brock & Minton, 1989;Bastiansen & Samdal, 1985), and in the gas phase (Bastiansen & Traetteberg, 1962). We report here a detailed description of the molecular structure and supramolecular features of the title biphenyl derivative, 4,4 0 -dinitro-[1,1 0 -biphenyl]-2-amine, (I).

Supramolecular features
In the crystal, molecules are linked by two pairs of N-HÁ Á ÁO hydrogen bonds, forming chains propagating along the [101] direction. Within the chains, these N-HÁ Á ÁO hydrogen bonds result in the formation of R 2 2 (20) and R 2 2 (14) ring motifs (Table 1 and Fig. 2). The latter ring motif is reinforced by a pair of C-HÁ Á ÁO hydrogen bonds, enclosing R 1 2 (6) ring motifs (Table 1 and Fig. 2). The chains are linked by a second C-HÁ Á ÁO hydrogen bond (Table 1), forming a three-dimensional supramolecular structure, as illustrated in Figs Table 1 Hydrogen-bond geometry (Å , ).

Figure 2
A view of the N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds (dashed lines; see Table 1), in the crystal of (I), forming chains that propagate along [101].

Figure 3
A view along the b axis of the crystal packing of (I). Hydrogen bonds are shown as dashed lines (see Table 1) and, for clarity, only H atoms H2A, H2B, H6 and H9 have been included.

Figure 4
A view along the a axis of the crystal packing of (I). Hydrogen bonds are shown as dashed lines (see Table 1) and, for clarity, only H atoms H2A, H2B, H6 and H9 have been included.

Figure 1
The molecular structure of the title compound, with the atom labelling. Displacement ellipsoids are drawn at the 40% probability level.

Synthesis and crystallization
The title compound (I), was prepared by a literature procedure (Ol'khovik et al., 2008). Orange prismatic crystals, suitable for single-crystal X-ray analysis, were grown by slow evaporation of a solution in ethanol.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The N-bound H atoms were located in a difference Fourier map and refined with U iso (H) = 1.2U eq (N). The C-bound H atoms were included in calculated positions and refined as riding: C-H = 0.93-0.96 Å with U iso (H) = 1.2U eq (C).    where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.10 e Å −3 Δρ min = −0.12 e Å −3 sup-2 Acta Cryst. (2017). E73, 550-552 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.