Crystal structure of 4-formyl-2-nitrophenyl 4-chloro-2-nitrobenzoate

In the title compound, C14H7ClN2O7, the central ester moiety is essentially planar, with an r.m.s. deviation of 0.0113 Å. The ester group is twisted away from the chloro- and formyl-substituted rings by 84.60 (9) and 88.55 (9)°, respectively. The crystal packing shows intermolecular C—H⋯O interactions. These interactions generate R 2 2(20) and R 4 4(22) edge-fused rings parallel to (20-2).


S2. Experimental
The title molecule was obtained through a two-step reaction: 4-Chloro-2-nitrobenzoic acid (0.200 g, 0.992 mmol) was refluxed with thionyl chloride (5 mL) in acetonitrile for an hour. Then, the thionyl chloride was distilled to purify the 4chloro-2-nitro benzoyl chloride obtained as a pale-yellow translucent liquid. The same reaction flask was rearranged and an equimolar solution of 4-hydroxy-3-nitrobenzaldehyde (0.166 g, 0.992 mmol) in acetonitrile was dropped inside it with 0.03 mL of pyridine. The reaction mixture was taken to room temperature with constant stirring for about an hour. A shiny yellow solid was obtained after leaving the solvent to evaporate. Yellow crystals; m.p 417 (1) K.

S3. Refinement
All H-atoms were located from difference maps and were positioned geometrically [C-H = 0.93 Å for aromatic and were refined using a riding-model approximation with U iso (H) constrained to 1.2 times U eq of the respective parent atom.
Formyl H141 atom was found from fourier difference maps and its coordinates refined freely.  The molecular structure of (I) with displacement ellipsoids drawn at the 50% probability level. H atoms are shown as spheres of arbitrary radius.

Figure 2
Part of the crystal structure of (I), showing the formation of R 2 2 (20) and R 4 4 (22) edge-fused rings parallel to (202).

Special details
Experimental. IR spectra was recorded on a FT-IR SHIMADZU IR-Affinity-1 spectrophotometer. IR (KBr), cm -1 , 3449 and 3090 (aromatic C-H); 1767 (ester, C=O); 1216 (ester C-O); 1040 (ester C8-O6); 1706 (benzaldehyde C=O); 1539, 1349 (nitro-NO 2 aryl ring); 1487, 1277 (nitro-NO 2 acyl ring); 1090 (C=C): 754 (C-Cl). 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 > 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 Cl1 1.36368 (11