Crystal structure and Hirshfeld surface analysis of (E)-N′-benzylidene-4-chlorobenzenesulfonohydrazide and of its (E)-4-chloro-N′-(ortho- and para-methylbenzylidene)benzenesulfonohydrazide derivatives

The crystal structures of (E)-N′-(benzylidene)-4-chlorobenzenesulfonohydrazide (I) and its ortho- and para-methyl-substituted benzylidene derivatives, (E)-N′-(2-methylbenzylidene)-4-chloro-benzenesulfonohydrazide (II) and (E)-N′-(4-methylbenzylidene)-4-chlorobenzenesulfonohydrazide (III), have been studied to investigate the effect of substitution on the structural and supramolecular features of these compounds.

(E)-N 0 -Benzylidene-4-chlorobenzenesulfonohydrazide, C 13 H 11 ClN 2 O 2 S, (I), and its ortho-and para-methylsubstituted derivatives, C 14 H 13 ClN 2 O 2 S, namely (E)-4-chloro-N 0 -(2-methylbenzylidene)benzenesulfonohydrazide, (II), and (E)-4-chloro-N 0 -(4-methylbenzylidene)benzenesulfonohydrazide, (III), have been synthesized, characterized spectroscopically and their crystal structures determined to investigate the effect of the substitution site of the benzylidene group on the structural and supramolecular features in these compounds. Compounds (I) and (II) are isotypic while compound (III) is different. All three molecules are bent at the S atom with C-S-N-N torsion angles of À66.0 (3), À66.0 (3) and À58.4 (2) for (I), (II) and (III), respectively. The hydrazone portions of the molecules, S-N-N C, are slightly twisted from planarity, with a torsion angle of 166.5 (3) in (I), 165.4 (3) in (II) and 157.9 (2) in (III). The two aromatic rings present in the compounds are inclined to each other by 78.4 (2), 74.8 (2) and 76.9 (1) in (I), (II) and (III), respectively. In the crystal structure of the parent compound (I), and of the ortho-methyl derivative (II), an N-HÁ Á ÁO hydrogen bond links the molecules into chains along [001], which are interconnected by weak intermolecular C-HÁ Á ÁO interactions, generating layers lying parallel to the bc plane. In the crystal of the para derivative (III), however, the packing is significantly different. Here molecules are linked by pairs of N-HÁ Á ÁO hydrogen bonds, forming inversion dimers with an R 2 2 (8) ring motif. The dimers are then linked by C-ClÁ Á Á interactions, forming ribbons propagating along [110]. Hirshfeld surface analyses show that the van der Waals interactions constitute the major contribution to the intermolecular interactions in the crystal structures of all three compounds. The fingerprint plots indicate that the HÁ Á ÁH contacts make the largest contributions to the Hirshfeld surfaces.

Chemical context
Schiff bases are an important class of compounds in the field of coordination chemistry and catalysis (Mahfouz et al., 2015). The photochromic and thermochromic properties of Schiff bases make their study interesting (Girisha et al., 2018). They form second-order NLO organic materials, which are being used in computers, optical communication and medical imaging (Zarei et al., 2015). Hydrazones also play an important role in curing diseases effectively with less toxicity. Sulfonyl hydrazones are known for their good enzymatic modulation, analgesic, anti-Alzheimer's, antidepressant and antidiabetic activities (Cunha et al., 2016). To investigate the impact of substitution, and also the variation of the site of substituent, on the structural parameters and the hydrogenbonding interactions, we report herein on the synthesis and crystal structures of (E)-N 0 -(benzylidene)-4-chlorobenzenesulfonohydrazide (I) and its ortho-and para-methylsubstituted benzylidene derivatives, (II) and (III), respectively.

Structural commentary
The title hydrazide (I) and its derivatives, (II) and (III), crystallize in the monoclinic crystal system with space group P2 1 /c for (I) and (II) and P2 1 /n for (III). The molecular structures of compounds (I), (II) and (III) are illustrated in Figs. 1, 2 and 3, respectively. All three molecules adopt an E configuration about the C N bond of the central imine group. In the ortho-methyl-substituted derivative (II), the N-H and C-H bonds in the hydrazide part are anti with respect to the methyl substituent. These parts of the molecules, S-N-N C, show similar bond lengths of 1.258 (5), 1.272 (5) and 1.273 (3) Å for C7 N2 and 1.394 (5), 1.407 (5) and 1.393 (2) Å for N1-N2 in compounds (I), (II) and (III), respectively. These bond lengths are consistent with the C N double-bond and N-N single-bond lengths, respectively. Furthermore, the S-N-N C segments are slightly twisted from planarity, with torsion angles of 166.5 (3) in (I), 165.4 (3) in (II) and 157.9 (2) in (III). All three compounds are bent at the S atom with C-S-N-N torsion angles of À66.0 (3), À66.0 (3) and À58.4 (2) for (I), (II) and (III), respectively. The two aromatic rings present in these compounds are inclined to each other by 78.4 (2), 74.8 (2) and 76.9 (1) in (I), (II) and (III), respectively. Hence the conformations of (I) and (II) are very similar while that of (III) is slightly different.

Supramolecular features
In the crystals of all three compounds, an O atom of the sulfonyl group acts as an acceptor and the amino H atom of the hydrazide segment as a donor in N-HÁ Á ÁO hydrogenbonding interactions with neighbouring molecules (Tables 1, 2 and 3). The patterns of the hydrogen-bonding interactions in the crystal structures of (I) and (II) are very similar, and will be illustrated for compound (II) only. The N-HÁ Á ÁO hydrogen-bonding interactions result in a C(4) graph-set motif generating chains propagating along the c-axis direction (Fig. 4) Molecular structure of (I), showing the atom labelling and displacement ellipsoids drawn at the 30% probability level.

Figure 2
Molecular structure of (II), showing the atom labelling and displacement ellipsoids drawn at the 30% probability level.

Figure 3
Molecular structure of (III), showing the atom labelling and displacement ellipsoids drawn at the 30% probability level. formation of layers lying parallel to the bc plane (Tables 2 and  3, and Fig. 5). On changing the position of the methyl substituent from ortho-to para-the crystal packing changes significantly. Molecules are now linked by pairs of N-HÁ Á ÁO hydrogen bonds, forming inversion dimers enclosing R 2 2 (8) loops (Fig. 6, Table 3). The dimers are linked by a C-ClÁ Á Á interaction, forming ribbons that propagate along the [110] direction (Fig. 6, Table 3).

Figure 4
A partial view along the b axis of the crystal packing of (II), with hydrogen bonds shown as dashed lines. Only the H atoms involved in the intermolecular interactions have been included.

Figure 5
A view along the c axis of the crystal packing of (II), with hydrogen bonds shown as dashed lines. Only the H atoms involved in the intermolecular interactions have been included.

Figure 6
A view along the b axis of the crystal packing of (III), with hydrogen bonds shown as dashed lines. Only the H atoms involved in the intermolecular interactions have been included. The C-ClÁ Á Á interactions are indicated by blue arrows.
compounds were analysed by Hirshfeld surface analysis and two-dimensional fingerprint plots, generated using Crystal-Explorer3.1 (McKinnon et al., 2004;Spackman & Jayatilaka, 2009;Wolff et al., 2012). The Hirshfeld surfaces of the three compounds mapped over d norm are shown in Fig. 7. The N-HÁ Á ÁO interactions between the corresponding donor and acceptor atoms are visualized as bright-red spots and represent the short interatomic interactions in the crystal structures. The presence of two other light-red spots in (I) and (II) correspond to the C-HÁ Á ÁO interactions, which are considered to be weak interactions.
The most significant difference for compounds (I) and (II) compared to compound (III) is the presence of a relatively strong ClÁ Á ÁC/CÁ Á ÁCl interaction in (III), in accordance with the C-ClÁ Á Á interaction in the crystal (Table 3), which makes a contribution of 5.3%, while for (I) and (II) this interaction is not present.

Synthesis and crystallization
Synthesis of 4-chlorobenzenesulfonohydrazide To 4-chlrobenzenesulfonyl chloride (0.01 mol) dissolved in propanol (30 ml), 99% hydrazine hydrate (5 ml) was added at 273 K under constant stirring. The stirring continued for 15 min at 273 K and then at 303 K for 3 h. After completion of the reaction (monitored by TLC), the reaction mixture was concentrated by evaporating the excess propanol. The solid product, 4-chlorobenzenesulfonohydrazide was washed with cold water and dried.

Synthesis of compounds (I), (II) and (III)
The parent, ortho-and para-substituted (E)-N 0 -(benzylidene)-4-chlorobenzenesulfonohydrazides (I), (II) and (III), were synthesized by refluxing mixtures of 4-chlorobenzenesulfonohydrazide (0.01 mol) and benzaldehyde, 2-methylbenzaldehyde or 4-methylbenzaldehyde (0.01 mol), respectively, in ethanol (30 ml) and two drops of glacial acetic acid for 4 h. The reaction mixtures were cooled to room temperature and concentrated by evaporating the excess of solvent. The solid products (I), (II) and (III) obtained were washed with cold water, dried and recrystallized to constant melting points from ethanol to obtain the pure compounds. The purity of the compounds was checked by TLC. Single crystals of the hydrazides suitable for single crystal X-ray diffraction analysis were obtained by slow evaporation of their DMF solutions at room temperature. All three compounds were characterized by measuring their IR, 1 H and 13 C NMR spectra.