Crystal structure of benzyl N′-[(1E,4E)-1,5-bis(4-methoxyphenyl)penta-1,4-dien-3-ylidene]hydrazine-1-carbodithioate

The title compound comprises four crystallographically different molecules that are composed of a 1,5-bis(4-methoxyphenyl)penta-1,4-dien-3-ylidenyl group and a benzyl ring connected by a hydrazine-1-carbodithioate bridge. In the crystal, molecules are connected into a three-dimensional network through C—H⋯O, N—H⋯S and C—H⋯π interactions.


Chemical context
S-benzyl and S-alkyl dithiocarbazates are interesting ligands in coordination chemistry because they can act as N,S-chelating agents because of the presence of soft sulfur and hard nitrogen donor atoms (Takjoo et al., 2016). These types of ligands can form stable metal complexes with five-membered chelate rings, and with transition metals in different stable oxidation states (Centore et al., 2013). Dithiocarbazate Schiff bases and their metal complexes show a wide range of biological activities such as anti-malarial, anti-bacterial, anti-viral and antitumour (Low et al., 2016;Nanjundan et al., 2016;Islam et al., 2016a). S-benzyldithiocarbazate and S-alkyldithiocarbazate Schiff base derivatives formed with aromatic aldehydes and ketones as well as their metal complexes have attracted attention due to their cytotoxicity against many types of cancer cell lines (Yusof et al., 2016;2017a,b;Vijayan et al., 2015;Basha et al., 2012), whereby S-methyl and S-benzyl dithiocarbazate Schiff bases with 2-acetylpyridine show better cytotoxicity against a breast cancer cell line (MDA-MB-231) than their transition-metal complexes (Hamid et al., 2016). Furthermore, Schiff bases synthesized from the reaction of S-benzyldithiocarbazate and m-hydroxyacetophenone as well as their metal complexes exhibit moderate analgesic and good anti-inflammatory activities in comparison with standard ISSN 2056-9890 drugs diclofenac sodium and indomethacin (Mahapatra et al., 2017).
Encouraged by previous findings on various properties of related Schiff base derivatives, we report herein the synthesis and structure determination of the title compound (I). Structural details of (I) are compared with other hydrazinecarbodithioates.
Torsion angles for the minor disorder component were omitted.

Figure 2
Overlay of the four molecules in (I). The r.m.s deviation of A:B = 1.038 Å , A:C = 0.881 Å and A:D = 0.947 Å .
Dihedral angle 1 is the dihedral angle between the mean planes of the 4methoxyphenyl rings; dihedral angle 2 is the dihedral angle between the mean planes of the benzyl (C20-C25) and 4-methoxyphenyl (C1-C6) rings; dihedral angle 3 is the dihedral angle between the mean planes of the benzyl (C20-C25) and the 4-methoxyphenyl (C12-C17) rings.

Figure 3
A partial packing diagram of the title compound, with N-HÁ Á ÁS and C-HÁ Á ÁO interactions (dotted lines). Hydrogen atoms not involved in these interactions were omitted for clarity.

Supramolecular features
In the crystal, molecule A is interconnected to molecule B and molecule C through weak C24A-H24AÁ Á ÁO2B and C21A-H21AÁ Á ÁO1C hydrogen-bonding interactions. Molecules B and C each form inversion-related dimers via C21B-H21BÁ Á ÁO1B and N2C-H3N2Á Á ÁS2C interactions, respectively (Fig. 3a). In addition, molecule C and molecule D are connected through C17C-H17CÁ Á ÁO1D hydrogen bonds (Fig. 3b). The four molecules are linked into an endless chain parallel to [021] through the combination of these hydrogen bonds (Fig. 4). Further interactions, namely N2A-H1N2Á Á ÁS2A, N2B-H2N2Á Á ÁS2D and N2D-H4N2Á Á ÁS2B, link the chains into a three-dimensional network, as shown in Fig. 5. Additional C-HÁ Á Á interactions (Table 3) Fig. 6. Details regarding different substituents (R 1 ) together with the torsion angles for the benzyl hydrazine-1carbothioate moiety in these structures are collated in Table 4. In analogy with the title molecules, the planarity of the hydrazine-1-carbodithioate bridge for these structures is indicated by the 7 , 8 and 9; torsion angles 7 and 9 range from 165.1 to 180.0 and indicate an anti-periplanar conformation whereas torsion angle 8 is indicative of a syn-periplanar conformation (0.0-9.1 ). With respect to torsion angle 10 , most of the structures adopt an anti-periplanar conformation ranging from 159.5 to 180.0 , but there are nine structures that adopt either a syn-clinal or an anti-clinal  Table 3 Hydrogen-bond geometry (Å , ).

Figure 4
A partial packing diagram of the title compound showing molecules linked into chains by N-HÁ Á ÁS and C-HÁ Á ÁO interactions.

Figure 5
The overall packing of the title compound, viewed approximately along the a-axis direction.
Two sets of torsion angles are stated for compounds EXINAB, QORJAK, SIMMUX, VOJGUX and WUPGIX because there are two molecules in their asymmetric units. The molecule with disorder in the structure of compound ZENLIN was omitted from this table.

Synthesis and crystallization
Compound (I) was synthesized following a well-described literature protocol (Ali & Tarafder, 1977;Ravoof et al., 2010;Omar et al., 2014). S-benzyldithiocarbazate (1.98 g, 0.01 mol) was dissolved in absolute ethanol (50 ml) under heating and stirring. The resulting solution was slowly added to a hot solution of di-p-methoxybenzalacetone (2.94 g, 0.01 mol) dissolved in absolute ethanol (50 ml). 3-5 drops of concentrated hydrochloric acid were added to the mixture, which was subsequently heated and stirred for 5 h (Fig. 7). The acidified mixture was allowed to stand overnight, resulting in the formation of red crystals. They were filtered off and recrystallized using the slow evaporation technique from absolute ethanol as solvent.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 5. The labelling of atoms is the same in each molecule, with the molecule indicated by the suffix A, B, C or D. The N-bound H atoms were located in difference-Fourier maps and were refined freely [N-H = 0.81 (3)-0.91 (4) Å ]. The C-bound H atoms were positioned geometrically (C-H = 0.93-0.97 Å ) and refined using a riding model, with U iso (H) = 1.2 or 1.5U eq (C). A rotating-group model was applied to the methyl groups. The 1,5-bis(phenyl)penta-1,4-dien-3-ylidenyl amine moiety in molecule B and the phenylmethyl moiety in molecule D display positional disorder, with refined site occupancy ratios of 0.667 (7):0.333 (7) and 0.653 (15):0.347 (15), respectively (SIMU, DELU and SAME restraints were used). Reaction scheme for the synthesis of (I).

Computing details
Data collection: CrysAlis PRO (Rigaku OD, 2018); cell refinement: CrysAlis PRO (Rigaku OD, 2018); data reduction: CrysAlis PRO (Rigaku OD, 2018); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2015); molecular graphics: SHELXL2013 (Sheldrick, 2015), Mercury (Macrae et al., 2006) and OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: SHELXL2013 (Sheldrick, 2015) and PLATON (Spek, 2009).  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.