(E)-{[(Butylsulfanyl)methanethioyl]amino}(4-methoxybenzylidene)amine: crystal structure and Hirshfeld surface analysis

The title hydrazine carbodithioate features an almost planar C2N2S2 chromophore, which is close to co-planar with the terminal methoxybenzene group; the n-butyl group has an extended, all-trans conformation. In the crystal, centrosymmetric, eight-membered {⋯HNCS}2 synthons are formed by thioamide-N—H⋯S(thioamide) hydrogen bonds.

The title hydrazine carbodithioate, C 13 H 18 N 2 OS 2 , is constructed about a central and almost planar C 2 N 2 S 2 chromophore (r.m.s. deviation = 0.0263 Å ); the terminal methoxybenzene group is close to coplanar with this plane [dihedral angle = 3.92 (11) ]. The n-butyl group has an extended all-trans conformation [torsion angles S-C m -C m -C m = À173.2 (3) and C m -C m -C m -C me = 180.0 (4) ; m = methylene and me = methyl]. The most prominent feature of the molecular packing is the formation of centrosymmetric eight-membered {Á Á ÁHNCS} 2 synthons, as a result of thioamide-N-HÁ Á ÁS(thioamide) hydrogen bonds; these are linked via methoxy-C-HÁ Á Á(methoxybenzene) interactions to form a linear supramolecular chain propagating along the a-axis direction. An analysis of the calculated Hirshfeld surfaces and two-dimensional fingerprint plots point to the significance of HÁ Á ÁH (58.4%), SÁ Á ÁH/HÁ Á ÁS (17.1%), CÁ Á ÁH/ HÁ Á ÁC (8.2%) and OÁ Á ÁH/HÁ Á ÁO (4.9%) contacts in the packing. The energies of the most significant interactions, i.e. the N-HÁ Á ÁS and C-HÁ Á Á interactions have their most significant contributions from electrostatic and dispersive components, respectively. The energies of two other identified close contacts at close to van der Waals distances, i.e. a thione-sulfur and methoxybenzenehydrogen contact (occurring within the chains along the a axis) and between methylene-H atoms (occurring between chains to consolidate the threedimensional architecture), are largely dispersive in nature.

Chemical context
The dithiocarbazate dianion, NH 2 NHCS 2À , and its esters such as S-benzyldithiocarbazate  and S-methyldithiocarbazate (Ali et al., 2008), are well-known to function as starting materials for the synthesis of a wide variety of Schiff bases containing both hard nitrogen and soft sulfur donor atoms. Schiff bases derived from S-alkyl esters of dithiocarbazate, NH 2 NHC( S)SR, and their metal complexes have been the subject of many studies because of their ability to act as multidentate ligands to metals and the subsequent enhanced bioactivity upon complexation (Bera et al., 2009;Ali et al., 2012;Begum et al., 2017). Schiff bases derived from the condensation of S-methyl-or S-benzyldithiocarbazate with heterocyclic aldehydes and ketones can complex metals to form five-membered chelate rings with the metal atoms bound to nitrogen and sulfur atoms (Ali et al., 2003) while complexation via two sulfur atoms, resulting in the formation of a four-membered chelate ring, is also possible (Rakha & Bekheit, 2000). It is also known that slight changes in mol-ecular structure can give rise to different coordination geometries (Chan et al., 2008). In a continuation of structural studies of S-alkyl dithiocarbazate esters (Yusof et al., 2015;Low et al., 2016;Omar et al., 2018) and their complexation to metals with accompanying evaluation of biological potential (Low et al., 2016;Ravoof et al., 2017;Yusof et al., 2017), herein the crystal and molecular structures of the title hydrazine carbodithioate ester, (I), along with the calculated Hirshfeld surfaces and computational chemistry are described.

Supramolecular features
With the exception of thioamide-N-HÁ Á ÁS(thioamide) hydrogen bonding between centrosymmetrically related molecules, Table 1, and which sustain a dimeric aggregate via an eight-membered {Á Á ÁHNCS} 2 synthon, the molecular packing is largely devoid of directional interactions (Spek, 2020). The The molecular structure of (I) showing the atom-labelling scheme and displacement ellipsoids at the 35% probability level. dimeric aggregates are connected into a linear supramolecular chain along the a-axis direction via weak methoxy-C-HÁ Á Á(methoxybenzene) interactions, Fig. 2(a), being the only other identified supramolecular association. Globally, chains pack without specific interactions between them, Fig. 2(b). An analysis of the weak non-covalent contacts within and connecting chains is given in the Analysis of the Hirshfeld surfaces.

Analysis of the Hirshfeld surfaces
The calculation of the Hirshfeld surfaces for (I) were conducted as per a literature precedent (Tan et al., 2019) employing Crystal Explorer 17 (Turner et al., 2017). The presence of bright-red spots near the thioamide-S1 and H1N atoms on the Hirshfeld surface mapped over d norm shown in Fig. 3 reflect the intermolecular N-HÁ Á ÁS hydrogen bonding.
The donor and acceptor associated with this interaction are also viewed as the blue and red regions, corresponding to positive and negative electrostatic potentials, respectively, on the Hirshfeld surface mapped over the calculated electrostatic potential in Fig. 4. The intermolecular methoxy-C-HÁ Á Á(methoxybenzene) interaction is also evident in Fig. 4, as the light-blue and light-red regions around the participating atoms. Fig. 5 also illustrates the donors and acceptors of this C-HÁ Á Á contact through the dotted lines connecting the blue bump and red concave regions, respectively, on the Hirshfeld surface mapped with the shape-index property.

Figure 4
A view of the Hirshfeld surface for (I) mapped over the electrostatic potential in the range À0.056 to +0.104 atomic units. Table 1 Hydrogen-bond geometry (Å , ).

Figure 5
A view of the Hirshfeld surface with the shape-index property highlighting the donors and acceptors of the C-HÁ Á Á/Á Á ÁH-C contacts by black dotted lines.  Fig. 6(c), the pair of well-defined spikes at d e + d i $ 2.5 Å arise as a result of the prominent intermolecular N-HÁ Á ÁS interaction. The points corresponding to SÁ Á ÁH/HÁ Á ÁS contacts involving the thione-S1 and methoxybenzene-H4 atoms, occurring within the supramolecular chain shown in Fig. 2(a), albeit at nearly van der Waals separations (S1Á Á ÁH4 = 3.02 Å for 2 À x, 1 À y, 1 À z), and reflected as an electrostatic interaction in the Hirshfeld surface plotted over the electrostatic potential of Fig. 4, are merged within the plot. Although the points in the fingerprint plot delineated into CÁ Á ÁH/HÁ Á ÁC contacts in Fig. 6(d) are at distances equal to or greater than the sum of van der Waals radii, the presence of characteristic wings is the result of the intermolecular methyoxy-C-HÁ Á Á(methoxybenzene) contact. The points corresponding to interatomic OÁ Á ÁH/HÁ Á ÁO contacts illustrated in the corresponding fingerprint plot of Fig. 6(e), also show a pair of forceps-like tips at d e + d i $ 2.8 Å , i.e. at van der Waals distances. The contribution from the other interatomic contacts summarized in Table 2 have negligible influence on the calculated Hirshfeld surface of (I).

Computational chemistry
The pairwise interaction energies between molecules in the crystal of (I) were calculated by summing up four energy components, comprising electrostatic (E ele ), polarization (E pol ), dispersion (E dis ) and exchange-repulsion (E rep ) (Turner et al., 2017); the energies were calculated using the wave function calculated at the B3LYP/6-31G(d,p) level of theory. The nature and strength of the intermolecular interactions in terms of their energies are quantitatively summarized in Table 3. As indicated in Table 3, the electrostatic energy component is most significant for the N-HÁ Á ÁS hydrogen bond but also makes a significant contribution to the thione-S1 and methoxybenzene-H4 contact, nearly as great as the dispersive component. The other two intermolecular interactions listed in Table 3   Symmetry codes: (i) 1 À x, 1 À y, 1 À z; (ii) 1 + x, y, z; (iii) 2 À x, 1 À y, 1 À z; (iv) Àx, 1 À y, 2 À z.  The calculated energy frameworks viewed down the a-axis direction comprising (a) electrostatic potential force, (b) dispersion force and (c) total energy for a cluster about a reference molecule of (I). The energy frameworks were adjusted to the same scale factor of 50 with a cut-off value of 3 kJ mol À1 within 4 Â 4 Â 4 unit cells.
order, are those arising from the N-HÁ Á ÁS and C-HÁ Á Á contacts, compared to the short interatomic SÁ Á ÁH/HÁ Á ÁS and HÁ Á ÁH contacts. The magnitudes of intermolecular energies are also represented graphically in Fig. 7 by energy frameworks in order to view the supramolecular architecture of the crystal through cylinders that connect the centroids of molecular pairs. This is done using red, green and blue colour codes for the E ele , E disp and E tot components, respectively; the radius of the cylinder is proportional to the magnitude of the interaction energies. This is reflected in the relatively thick red cylinders corresponding to the electrostatic interactions via the N-HÁ Á ÁS hydrogen bonding in Fig. 7(a) and the thick green cylinders corresponding to the strong dispersive interactions provided by the methyoxy-C-HÁ Á Á(methoxy-(methoxybenzene) interactions in Fig. 7(b).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 4. The carbon-bound H atoms were placed in calculated positions (C-H = 0.93-0.97 Å ) and were included in the refinement in the riding model approximation, with U iso (H) set to 1.2U eq (C). The N-bound H atom was located in a difference-Fourier map but was refined with a N-H distance restraint of 0.86 (1) Å .    (Farrugia, 2012), DIAMOND (Brandenburg, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).

(E)-{[(Butylsulfanyl)methanethioyl]amino}(4-methoxybenzylidene)amine:
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.