Crystal structures of three ortho-substituted N-acylhydrazone derivatives

The effect of the nature of substitutions on the structural parameters and hydrogen-bonding interactions in N-acylhydrazone derivatives has been studied by synthesizing and determining the crystal structures of three ortho-substituted N-acylhydrazone derivatives, namely (E)-N-{2-[2-(2-chlorobenzylidene)hydrazinyl]-2-oxoethyl}-4-methylbenzenesulfonamide (I), (E)-N-{2-[2-(2-methylbenzylidene)hydrazinyl]-2-oxoethyl}-4-methylbenzenesulfonamide (II) and (E)-N-{2-[2-(2-nitrobenzylidene)hydrazinyl]-2-oxoethyl}-4-methylbenzenesulfonamide (III).

(2) and À177.1 (3) in (II) and À179.7 (2) and 173.4 (2) in (III). The two phenyl rings on either side of the chain are approximately parallel to each other. In the crystal, the molecules are linked to each other via N-HÁ Á ÁO hydrogen bonds, forming ribbons with R 2 2 (8) and R 2 2 (10) ring motifs. The introduction of electronwithdrawing groups (by a chloro or nitro group) to produce compounds (I) or (III) results in C-HÁ Á ÁO hydrogen-bonding interactions involving the sulfonyl O atoms of adjacent ribbons, forming layers parallel to the ab plane in (I) or a three-dimensional network in (III). In (III), one O atom of the nitro group is disordered over two orientations with refined occupancy ratio of 0.836 (12):0.164 (12).

Chemical context
N-Acylhydrazones belong to the Schiff base family of general structure R 1 -C( O)-N-N CR 3 R 4 . N-Acylhydrazones of aromatic aldehydes find great importance in organic synthesis due to their biological and medicinal activities (Tian et al., 2009(Tian et al., , 2011. The donor sites, carbonyl and imine groups, in the compounds are responsible for the physical and chemical properties of N-acylhydrazones. Their ability to form chelates with transition metals can be effectively utilized to analyse metals selectively as hydrazone complexes. N-Acylhydrazones can exist as Z/E geometrical isomers about the C N bond of the hydrazone moiety (Palla et al., 1986). Crystal-structure studies of N-acylhydrazones revealed that the molecules display an E conformation in the solid state (Purandara et al., 2015a(Purandara et al., ,b,c, 2017Gu et al. 2012), whereas NMR spectroscopic studies showed the duplicate signals for amide and methylene protons, indicating the presence of two isomers in solution (Lacerda et al., 2012;Lopes et al., 2013). As the stereochemistry of the hydrazone is determined by the various substituents in the hydrazone moiety, we thought it would be interesting to synthesize several ortho-substituted N-acylhydrazone derivatives to explore their effects on crystalstructure parameters and hydrogen-bonding interactions. Thus this paper describes the salient features of ortho-chloro-, methyl-and nitro-substituted N-acylhydrazone derivatives, namely, (

Structural commentary
The title compounds (I)-(III) (Figs. 1-3), which differ only in the ortho-substituent, each crystallize in the centrosymmetric space group P1 with one molecule in the asymmetric units and display many common features. Each molecule adopts an E configuration around the imine C N bond. The conformation of the N--H bond in the amide part is syn with respect to the C O bond, the imine C-H bond and the ortho substituent. The sulfonamide bonds are found to be anticlinal, and the torsion angles of the sulfonamide moieties are 98.6 (3), À99.6 (3) and 99.9 (2) in compounds (I), (II), and (III), respectively.
The dihedral angles between the phenyl ring (C10-C15) and the mean plane of the C9/N3/N2/C8/O3 hydrazone fragment are 5.7 (2), 5.54 (18) and 7.90 (17) for (I), (II), and (III), respectively. The N-acylhydrazone portion of the molecules (C N-NH-C O group) is therefore approximately coplanar with the plane of benzylidenephenyl ring (C10-C15) in these compounds, but the sulfonyl glycine part of the molecule is rotated by 40.0 (3) in (I), 40.2 (3) in (II) and 41.4 (2) in (III) with respect to the hydrazone group. The phenyl rings are also approximately parallel to each other, forming dihedral angles ranging from 12.86 (11) to 13.10 (19) . In (III), an intramolecular C-HÁ Á ÁO hydrogen bond involving the nitro group and the imine H atom is observed (Table 3).

Supramolecular features
In all three compounds, the O atom of the carbonyl group is engaged as an acceptor in bifurcated N-HÁ Á ÁO hydrogen bonding with the sulfonamide H atom and the amino H atom of the hydrazide segment of two centrosymmetrically related neighbouring molecules, enclosing rings of R 2 2 (8) and R 2 2 (10) graph-set motif and forming molecular ribbons parallel to the a axis [ Table 1, Fig. 4 for (I), Table 2, Fig. 6 for (II) and Table 3, Fig. 7 for (III)]. In the crystal structure of (II), there are no other significant intermolecular interactions present. Replacement of the methyl group in (II) by the chloro or nitro The molecular structure of compound (II), with displacement ellipsoids drawn at the 50% probability level.

Figure 3
The molecular structure of compound (III), with displacement ellipsoids drawn at the 50% probability level.

Figure 1
The molecular structure of compound (I), with displacement ellipsoids drawn at the 50% probability level. electron-withdrawing groups to produce compound (I) or (III) introduces C-HÁ Á ÁO interactions. In (I), the interactions involving the sulfonyl oxygen atoms and aromatic H atoms of adjacent ribbons (Fig. 5) result in the formation of twodimensional layer networks extending parallel to the ab plane. In (III), the ribbons are further stabilized by intermolecular C-HÁ Á ÁO interactions between methylene H atoms and the O4 oxygen atom of the nitro group. Adjacent ribbons in (III) are further linked into a three-dimensional network by weak hydrogen-bonding interactions occurring between methyl H atoms and the oxygen atom O5 of the nitro group, resulting in the formation of R 2 2 (34) ring motifs (Fig. 8).

Figure 4
Crystal packing of compound (I), showing the formation of molecular ribbons parallel to the a axis through N-HÁ Á ÁO hydrogen bonds (dashed lines).

Figure 5
The C-HÁ Á ÁO interactions (blue dotted lines) observed in the structure of the compound (I). H atoms have been omitted for clarity.

Figure 6
Crystal packing of compound (II), showing the formation of molecular ribbons parallel to the a axis through N-HÁ Á ÁO hydrogen bonds (dashed lines).

Synthesis and crystallization
General procedure for the synthesis of N-(4-methylbenzenesulfonyl)glycinyl hydrazide (L3) 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 6h, 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 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. The 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).
Synthesis of compound (II) A mixture of L3 (0.01 mol) and 2-methylbenzaldehyde (0.01 mol) in anhydrous methanol (30 ml) and two drops of glacial acetic acid was refluxed for 8 h. After cooling, the precipitate was collected by vacuum filtration, washed with cold methanol and dried. It was recrystallized to a constant melting point from methanol (474-475 K). The purity of the compound was checked by TLC and characterized by its IR spectrum. The characteristic absorptions observed are 3186.   Partial crystal structure of compound (III), showing the C-HÁ Á ÁO interaction forming R 2 129. 34, 130.72, 131.86, 136.41, 136.67, 137.21, 137.61, 142.49, 143.07, 145.86, 163.98, 168.81. Prismatic colourless single crystals of (II) employed in the X-ray diffraction study were grown from a DMF solution by slow evaporation of the solvent.
Synthesis of compound (III) A mixture of L3 (0.01 mol) and 2-nitrobenzaldehyde (0.01 mol) in anhydrous methanol (30 ml) and two drops of glacial acetic acid was refluxed for 8 h. After cooling, the precipitate was collected by vacuum filtration, washed with cold methanol and dried. It was recrystallized to a constant melting point from methanol (509-512 K). The purity of the compound was checked by TLC and characterized by its IR spectrum. The characteristic absorptions observed are 3219.  98, 43.22, 44.59, 124.38, 126.60, 128.07, 129.29, 130.29, 133.35, 137.22, 137.72, 139.12, 142.49, 147.86, 148.01, 164.54, 169.23. Rod-shaped light-yellow single crystals of (III) employed in the X-ray diffraction study were grown from a DMF solution by slow evaporation of the solvent.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 4. The amino H atoms were freely refined with the N-H distances restrained to 0.86 (2) Å . H atoms bonded to C were positioned with idealized geometry using a riding model with C-H = 0.93 Å (aromatic), 0.96 Å (methyl), 0.97 Å (methylene). 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. In the structure of (I), the U ij components of atom C16 were restrained to approximate isotropic behavior. In (III), the O5 atom of the nitro group is disordered over two orientations with refined occupancy ratio of 0.836 (12):0.164 (12). The U eq of atom O5 0 was restrained to approximate isotropic behavior. . E73, 1946-1951 research communications SHELXS2013 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXL2014 (Sheldrick, 2015).

(E)-N-{2-[2-(2-Chlorobenzylidene)hydrazinyl]-2-oxoethyl}-4-methylbenzenesulfonamide (I)
Crystal data 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.

(E)-N-{2-[2-(2-Methylbenzylidene)hydrazinyl]-2-oxoethyl}-4-methylbenzenesulfonamide (II)
Crystal data 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.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (