Crystal structure and Hirshfeld surface analysis of (E)-N′-[4-(piperidin-1-yl)benzylidene]arylsulfonohydrazides

New Schiff bases containing piperidine and arylsulfonohydrazide moieties have been synthesized, characterized and their crystal structures determined to study the effect of substituents on the structural parameters. Their crystal structures are stabilized by N—H⋯O, C—H⋯O and O—H⋯O interactions. Two-dimensional fingerprint plots show that the largest contributions come from H⋯H interactions.

The crystal structures and Hirshfeld surface analyses of three Schiff bases, namely (E)-N 0 -[4-(piperidin-1-yl)benzylidene]benzenesulfonohydrazide, C 18 H 21 N 3 O 2 S, (I), (E)-4-methyl-N 0 -[4-(piperidin-1-yl)benzylidene]benzenesulfonohydrazide, C 19 H 23 N 3 O 2 S, (II), and (E)-4-chloro-N 0 -[4-(piperidin-1yl)benzylidene]benzenesulfonohydrazide, C 18 H 20 ClN 3 O 2 S, (III), derived from arylsulfonohydrazides and 4-(piperidin-4-yl)benzaldehyde have been analysed to investigate the effect of substituents on the structural parameters. All three structures crystallize in monoclinic crystal systems, in the space groups P2 1 /c for (I) and (II), and C2/c for (III). Compound (III) contains two independent molecules in the asymmetric unit and sixteen molecules per unit cell, while (I) and (II) both have one and four molecules, respectively, in their asymmetric units and unit cells. In all cases, the central part of the molecule is twisted at the S atom. In the crystals, the molecules are linked via N-HÁ Á ÁO hydrogen bonds, forming chains. Two-dimensional fingerprint plots of various interatomic contacts show that the major contributions are from HÁ Á ÁH interactions.

Structural commentary
All three of the title compounds (Figs. 1-3) crystallize in the monoclinic crystal system but in space group P2 1 /c for (I) and (II), and space group C2/c for (III). The asymmetric units of compounds (I) and (II) each contain one molecule whereas there are two independent molecules in the asymmetric unit of (III). All the three compounds display an E-configuration about the C N bond (Purandara et al., 2017;Gu et al., 2012), and a chair conformation of the piperidine ring.

Supramolecular features
In all the three crystal structures, the amino H atom of the sulfonohydrazide segment acts as a donor and the sulfonyl O atom acts as an acceptor in N-HÁ Á ÁO hydrogen-bonding interactions that generate C4 chains propagating parallel to the b axis (Tables 1-3 ,. Substitution at the para position by a methyl or chloro group to produce compounds (II) and (III) has no remarkable effect on the hydrogenbonding pattern. Hydrogen-bonding pattern in (I) with hydrogen bonds shown as dashed lines. Symmetry code as in Table 1.

Figure 5
Hydrogen-bonding pattern in (II) with hydrogen bonds shown as dashed lines. Symmetry code as in Table 2.

Figure 6
Hydrogen-bonding pattern in (III) with hydrogen bonds shown as dashed lines.

Figure 7
Molecular packing of (I).

Database survey
Although there are several reports on the crystal structures of piperidine or sulfonylhydrazides derivatives, reports on the crystal structures of 4-(piperidin-1-yl)benzaldehyde functionalized with sulfonylhydrazides are very few. Comparison of the present data with those of thiophene/phenyl-piperidine hybrid chalcones (Parvez et al., 2014) reveals that the compounds also adopt E configuration around the C N bond and the piperidine rings exhibit a chair conformation. A chair conformation of the piperidine ring is also found in 5-nitro-2-(piperidin-1-yl)benzaldehyde (N'Gouan et al., 2009) and (5-nitro-2-piperidino)benzylidene p-toluenesulfonylhydrazone (Yapo et al., 2008).

Hirshfeld surface analysis
Hirshfeld surfaces (HS) and 2D fingerprint plots were generated using CrystalExplorer17 (Turner et al., 2017;McKinnon et al., 2007;Spackman & Jayatilaka, 2009). The terms such as d norm , d i and d e are defined in the usual way (Shit et al., 2016). The function d norm is a ratio enclosing the distances of any surface point to the nearest interior (d i ) and exterior (d e ) atom and the van der Waals radii of the atoms (Hirshfeld, 1977;Soman et al., 2014). The function d norm will be equal to zero when intermolecular distances are close to van der Waals contacts. They are indicated by a white colour on the HS, while contacts longer than the sum of van der Waals radii with positive d norm values are coloured in blue. The surface images and plots for d norm (Fig. 10) were generated using a high standard surface resolution over a colour scale of À0.3495 to 1.3559, À0.4124 to 1.6768 and À0.3876 to 1.5649 a.u. for (I), (II) and (III), respectively.

Synthesis and crystallization
Synthesis of benzenesulfonohydrazide and 4-methyl and 4-chloro-benzenesulfonohydrazides To solutions of hydrazine hydrate (99%) (0.03mol) in THF at 273 K under stirring, a solution of benzenesulfonyl chloride, 4-methylbenzenesulfonyl chloride or 4-chlorobenzenesulfonyl chloride (0.02 mol) in THF was added dropwise. Three separate reaction mixtures were kept under stirring at 273 K for 1 h and stirring continued for 24 h at room temperature. The formation of the products was monitored by TLC. After completion of the reactions, the reaction mixtures were poured separately onto ice-cold water. The separated solids, benzenesulfonohydrazide, 4-methylbenzenesulfonohydrazide or 4-chlorobenzenesulfonohydrazide, were filtered off and dried. The products were recrystallized from ethanol solution to get the pure products.
The purity of the compounds was checked by TLC and they were characterized by their IR spectra. They were further characterized by 1 H and 13 C NMR spectra. The characteristic IR absorptions and 1 H and 13 C NMR signals are as follows: Benzenesulfonohydrazide

Synthesis of the title compounds (I), (II) and (III):
Mixtures of 4-(piperidin-1-yl)benzaldehyde (0.001 mol) and benzenesulfonohydrazide, 4-methylbenzenesulfonohydrazide or 4-chlorobenzenesulfonohydrazide (0.001 mol) in ethanol (10 ml) and two drops of glacial acetic acid were stirred at room temperature for 2 h. The formation of the products was monitored by TLC. The reaction mixtures were separately poured on crushed ice and the solids that formed were washed and dried. The products were recrystallized to constant melting points from an acetonitrile:DMF (5:1 v:v) mixture. The purity of the compounds was checked by TLC and they were characterized by their IR spectra. They were further characterized by 1 H and 13 C NMR spectra. The characteristic IR absorptions and 1 H and 13 C NMR signals are as follows Compound ( 147.31, 138.89, 133.62, 130.94, 129.91, 128.27, 124.97, 112.76, 48.54, 24.82, 23.93.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 4. H atoms bonded to C were positioned with idealized geometry and refined using a riding model with the aromatic C-H = 0.93, 0.96 (methyl), or 0.97 Å (methylene). H atoms of the NH groups were located in a difference map and their positions refined. All H atoms were refined with U iso (H) = 1.2U eq (C-aromatic, C-methylene, N) or 1.5U eq (C-methyl). In compound (III), the U ij components of atoms C14, C15, C17, and C18 were restrained to approximate isotropic behaviour. under its PURSE Program and BTG thanks the University Grants Commission, Government of India, New Delhi, for a special grant under a UGC-BSR one-time grant to faculty. SHELXS2013/1 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014/6 (Sheldrick, 2015); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXL2014/6 (Sheldrick, 2015).

(E)-N′-[4-(Piperidin-1-yl)benzylidene]benzenesulfonohydrazide (I)
Crystal data (7)   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.