Crystal structure of (E)-4-methyl-N-{2-[2-(4-nitrobenzylidene)hydrazin-1-yl]-2-oxoethyl}benzenesulfonamide N,N-dimethylformamide monosolvate

The title Schiff base molecule displays a trans configurations with respect to the C=N double bond. Intermolecular N—H⋯O and C —H⋯O hydrogen bonds connect centrosymmetrically related molecules into dimers, forming rings of (11) and (10) graph-set motif stacked along the a axis into a columnar arrangement.

The molecule of the title Schiff base compound, C 16 H 16 N 4 O 5 SÁC 3 H 7 NO, displays a trans conformation with respect to the C N double bond. The C-N and N-N bonds are relatively short compared to their normal bond lengths, indicating some degree of delocalization in the molecule. The molecule is bent at the S atom, with an S-N-C-C torsion angle of 164.48 (11) . The dihedral angle between the two aromatic rings is 84.594 (7) . Intermolecular N-HÁ Á ÁO and C -HÁ Á ÁO hydrogen bonds connect centrosymmetrically related molecules into dimers forming rings of R 3 3 (11) and R 2 2 (10) graph-set motif stacked along the a axis into a columnar arrangement. The molecular columns are further linked into a three-dimensional network by C-HÁ Á Á interactions.

Chemical context
Hydrazones possess a wide variety of biological activities which include anti-inflammatory, analgesic, anticonvulsant, antituberculous, antitumor, anti-HIV and antimicrobial activity. Hydrazones and their derivatives which can be prepared easily are stable and crystalline in nature. These characteristics have made them suitable compounds in recent times for drug design, ligands for metal complexes and for heterocyclic synthesis. Thus, hydrazones derived from N-(ptoluenesulfonyl)amino acids have been studied extensively for their biological and medicinal activities (Tian et al., 2009(Tian et al., , 2011Shedid et al., 2011). The intermolecular interactions of ptoluenesulfonylamide groups lead to supramolecular structures. In continuation of our efforts to explore the potential of N-acylhydrazone derivatives, we report herein the synthesis and crystal structure of the title compound, (E)-4-methyl-N-{2-[2-(4-nitrobenzylidene)hydrazin-1-yl]-2-oxo-ethyl}benzenesulfonamide N,N-dimethylformamide monosolvate.

Supramolecular features
The Schiff base and solvent molecules in the asymmetric unit are linked by N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds (Table 1 and Fig. 2), giving rise to a ring of R 3 3 (11) graph-set  Table 1 Hydrogen-bond geometry (Å , ).

Figure 2
The hydrogen-bonding pattern (dashed lines) in the title compound.

Figure 1
The molecular structure of the title compound, with displacement ellipsoids drawn at the 50% probability level.
motif. These bimolecular units are then linked by a pair of N-HÁ Á ÁO hydrogen bonds, resulting in inversion dimers forming an R 2 2 (10) ring motif (Fig. 3), which are linked into columns running parallel to the a axis by C-HÁ Á ÁO hydrogen bonds involving aromatic C3 and sulfonyl O3 atoms (Fig. 4). Adjacent columns are further connected by C-HÁ Á Á interactions, leading to the formation of a three-dimensional framework (Table 1).

Database survey
Comparison of the C-HÁ Á ÁO interactions observed in the title compound, (I), with those of the 4-methyl derivative of Nacylhydrazone, namely (E)-N-{2-[2-(4-methylbenzylidene)hydrazin-1-yl]-2-oxoethyl}-p-toluenesulfonamide, (II) (Purandara et al., 2015), indicates that the nitro group imparts a strong ability to the aromatic C-H groups to participate in C-HÁ Á ÁO interactions, whereas the methyl substituent in the benzylidene ring of (II) does not activate aromatic protons for participating in intermolecular C-HÁ Á ÁO interactions. An aromatic H atom (C14-H14) of the nitrophenyl moiety of (I) is involved in the formation of intermolecular C-HÁ Á ÁO interactions. The inductive effect of electron-withdrawing nitro group decreases the electronic density on the benzene ring. As a result, the nitrophenyl moiety provides more acidic protons to form C-HÁ Á ÁO hydrogen bonds.

Synthesis and crystallization
solvate was prepared as follows: p-toluenesulfonyl chloride (0.01 mol) was added to glycine (0.02 mol) dissolved in an aqueous solution of potassium carbonate (0.06 mol, 50 ml). The reaction mixture was stirred at 373 K for 6 h, left overnight at room temperature, then filtered and treated with dilute hydrochloric acid. The solid N-(4-methylbenzenesulfonyl)glycine (L1) obtained was crystallized from aqueous ethanol. Sulfuric acid (0.5 ml) was added to L1 (0.02 mol) dissolved in ethanol (30 ml) and the mixture was refluxed. The reaction mixture was monitored by thin-layer chromatography (TLC) at regular intervals. After completion of the reaction, the reaction mixture was concentrated to remove excess ethanol. The product, N-(4-methylbenzenesulfonyl)glycine ethyl ester (L2), was poured into water, neutralized with sodium bicarbonate and recrystallized from acetone. Pure L2 (0.01 mol) was then added in small portions to a stirred solution of 99% hydrazine hydrate (10 ml) in 30 ml ethanol and the mixture was refluxed for 6 h. After cooling to room temperature, the resulting precipitate was filtered, washed with cold water and dried to obtain N-(4-methylbenzenesulfonyl)glycinyl hydrazide (L3). A mixture of L3 (0.01 mol) and p-nitrobenzaldehyde (0.01 mol) in anhydrous methanol (30 ml) and two drops of glacial acetic acid was refluxed for 8 h. After cooling, the precipitated (E)-N-{2-[2-(4-nitrobenzylidene)hydrazine-1-yl]-2-oxoethyl}-4-methylbenzenesulfonamide was collected by vacuum filtration, washed with cold methanol, dried and recrystallized to constant melting point from methanol (522-523 K). The purity of the compound was checked by TLC and characterized by its IR spectrum.  The molecular packing of the title compound, with hydrogen bonding shown as dashed lines.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms bonded to C atoms were positioned with idealized geometry using a riding model, with C-H = 0.93 (aromatic), 0.96 (methyl) or 0.97 Å (methylene). The amino H atoms were freely refined with the N-H distances restrained to 0.86 (2) Å . All H atoms were refined with isotropic displacement parameters set at 1.2U eq (C,N) or 1.5U eq (C) for methyl H atoms. A rotating model was used for the methyl groups.   Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

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.