(E)-N′-(2-Chlorobenzylidene)-1-methyl-4-nitro-1H-pyrrole-2-carbohydrazide

In the title compound, C13H11ClN4O3, the phenyl and pyrrolyl ring are linked by an acyl–hydrazone (R 2C=N—N—CO—R) group, forming a slightly bent molecule: the dihedral angle subtended by the the phenyl and pyrrolyl rings is 8.46 (12)°. In the crystal, the three-dimensional supramolecular structure is assembled by N—H⋯O hydrogen bonding. Molecular sheets are formed parallel to (101) in a herringbone arrangement by weak van der Waals interactions; weak π–π [centroid–centroid phenyl–phenyl and pyrrolyl–pyrrolyl distances of 3.7816 (3) and 3.8946 (2) Å, respectively] interactions occur between neighbouring sheets.

In the title compound, C 13 H 11 ClN 4 O 3 , the phenyl and pyrrolyl ring are linked by an acyl-hydrazone (R 2 C N-N-CO-R) group, forming a slightly bent molecule: the dihedral angle subtended by the the phenyl and pyrrolyl rings is 8.46 (12) . In the crystal, the three-dimensional supramolecular structure is assembled by N-HÁ Á ÁO hydrogen bonding. Molecular sheets are formed parallel to (101) in a herringbone arrangement by weak van der Waals interactions; weak -[centroid-centroid phenyl-phenyl and pyrrolyl-pyrrolyl distances of 3.7816 (3) and 3.8946 (2) Å , respectively] interactions occur between neighbouring sheets.   Table 1 Hydrogen-bond geometry (Å , ).

Comment
A great number of aroylhydrazones (AH) have triggered wide interest because of their diverse spectra of biological and pharmaceutical properties (Raja, et al., 2012). In our lab, the AH compound (E)-N′-(2-hydroxybenzylidene)-1-methyl-4nitro-1H-pyrrole-2-carbohydrazide (L) and its transition metal complexes were obtained and characterized. The interaction of these compounds with CT-DNA and pBR322 DNA has been explored (Wang, et al., 2014). The present report is an extension of our earlier studies in this area.
As shown in Figure 2, the herringbone molecular sheet of the title compound is formed by weak van-der-Waals interactions along (101) plane.

Experimental
Single crystals of the title compound were obtained accidentally in the attempted synthesis of a Ni complex. (E)-N′-(2hydroxybenzylidene)-1-methyl-4-nitro-1H-pyrrole-2-carbohydrazide (L) was synthesized according to literature procedures (Wang et al., 2014). Sodium methoxide (250 µL, 3%, g/V) was added to solution of L (0.50 mmol, 0.144 g) in 15 ml MeOH and was heated to reflux. NiCl 2 ·6H 2 O (0.50 mmol, 0.119 g) was then added to the refluxing mixture and further refluxed for 2 h. The reaction mixture was cooled and was allowed to stir at room temperature overnight. The mixture was filtered and washed with methanol. The L-Ni complex is not achieved as predicted. However, orange single crystals of the title compound suitable for X-ray analysis were obtained after several days from the mother liquor by slow evaporation.

Refinement
H atoms attached to C atoms are placed in geometrically idealized position, with N-H=0.86 Å, C-H=0.93 and 0.96 Å, for CH and CH 3 groups, respectively, and with U iso (H) = k × U eq (parent C-atom), where k = 1.5 for CH 3 H-atoms and =1.2 for other H-atoms.

Figure 1
The molecular structure of the title compound with the atom numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. H atoms are presented as small spheres of arbitrary radius.

Figure 2
The two-dimensional herringbone layer in the crystal structure of title compound.  Packing of the title compound viewed along the b axis. The three-dimensional supramolecular structure is assembled by N-H···O hydrogen bonding (pink dotted lines) and weak π···π interactions (black dotted lines) between the neighbouring molecular sheets (all distances in Å).

(E)-N′-(2-Chlorobenzylidene)-1-methyl-4-nitro-1H-pyrrole-2-carbohydrazide
Crystal data where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.23 e Å −3 Δρ min = −0.33 e Å −3 Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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.