N-(2-Nitrophenyl)thiophene-2-carboxamide

The title compound, C11H8N2O3S, shows two molecules per asymmetric unit, with the dihedral angles between the benzene and thiophene rings of 13.53 (6) and 8.50 (5)° being a notable difference between them. An intramolecular N—H⋯O hydrogen-bond in each molecule generates an S(6) ring motif. The crystal packing shows no classical hydrogen bonds with the molecules being packed to form weak C—H⋯O and C—H⋯S interactions leading to R 2 2(9) and R 4 4(25) rings which are edge-shared, giving layers parallel to (010).

The title compound, C 11 H 8 N 2 O 3 S, shows two molecules per asymmetric unit, with the dihedral angles between the benzene and thiophene rings of 13.53 (6) and 8.50 (5) being a notable difference between them. An intramolecular N-HÁ Á ÁO hydrogen-bond in each molecule generates an S(6) ring motif. The crystal packing shows no classical hydrogen bonds with the molecules being packed to form weak C-HÁ Á ÁO and C-HÁ Á ÁS interactions leading to R 2 2 (9) and R 4 4 (25) rings which are edge-shared, giving layers parallel to (010).

Synthesis and crystallization
The reagents and solvents for the synthesis were obtained from the Aldrich Chemical Co., and were used without additional purification. The title molecule was synthesized using equimolar quantities of 2-thiophenecarbonyl chloride (0.376 g., 2.565 mmol) and 2-nitroaniline (0.354 g). The reagents were dissolved in 10 mL of acetonitrile and the solution was taken to reflux in constant stirring for 1 hour. Yellow crystals of good quality were obtained after leaving the solvent to evaporate. M.pt: 397 (1) K.

Refinement
All H-atoms were positioned at geometrically idealized positions with a C-H distance of 0.95 Å and U iso (H) = 1.2U eq of the atoms to which they were bonded. The H1N and H3N atoms were found from Fourier maps and were refined freely.

Results and discussion
The present compound forms part of a systematic work on N-aromatic amides in our research group. Antibacterial and antifungal activities of different carboxyamide derivatives have been reported (Aytemir et al., 2003). Derivatives of thiophene carboxanilide compounds present genotoxicity in bacterial mammalian and human cells (Hrelia et al., 1995). In the synthesis of the amides, the 2-nitroaniline is taken as a template, in order to study the structural changes and the supramolecular behavior by the reaction of different ligands with this precursor (Moreno-Fuquen et al., 2013). With this aim, the synthesis of N-(2-nitrophenyl)thiophene-2-carboxamide (I) was undertaken. The structure of N-(2-nitrophenyl)furan-2-carboxamide (2NPFC), (Moreno-Fuquen et al., 2013), a similar compound, was taken to compare with the structural parameters of (I).
The title compound shows two molecules (A and B) per asymmetric unit (see Fig. 1). Compound (I) exhibits dihedral angles between the benzene and thiophene rings of 13.53 (6)° and 8.50 (5)° for A and B, respectively. These dihedral angles are very similar to the value presented in the (2NPFC) system [9.71 (5)°]. The other bond lengths and bond angles agree closely with those values presented in its homologous amide (2NPFC), except for the C-S distances, which for obvious reasons are different on the furan rings. The nitro groups form dihedral angles with the adjacent benzene ring of 15.44 (4) and 16.07 (6)° for O2-N2-O3 and O5-N4-O6, respectively.

Figure 1
Molecular conformation and atom numbering scheme for the title compound 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 edge-fused R 2 2 (9) and R 4 4 (25) rings running parallel to (010). 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 > 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.