Crystal structure, Hirshfeld surface analysis and interaction energy and DFT studies of (2Z)-4-benzyl-2-(2,4-dichlorobenzylidene)-2H-1,4-benzothiazin-3(4H)-one

The title compound contains 1,4-benzothiazine and 2,4-dichlorobenzylidene units, where the dihydrothiazine ring adopts a screw-boat conformation. In the crystal, intermolecular C—HBnz⋯OThz (Bnz = benzene and Thz = thiazine) hydrogen bonds form corrugated chains extending along the b-axis direction which are tied into layers parallel to the bc plane by intermolecular C—HMethy⋯SThz (Methy = methylene) hydrogen bonds, enclosing (22) ring motifs.


Figure 1
The molecular structure of the title compound with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. Table 1 Hydrogen-bond geometry (Å , ).

Hirshfeld surface analysis
In order to visualize the intermolecular interactions in the crystal of (I), a Hirshfeld surface (HS) analysis (Hirshfeld, 1977;Spackman & Jayatilaka, 2009) was carried out using CrystalExplorer (Version 17.5; Turner et al., 2017). In the HS plotted over d norm (Fig. 3), the white surface indicates contacts with distances equal to the sum of the van der Waals radii, and the red and blue colours indicate distances shorter (in close contact) or longer (distinct contact) than the van der Waals radii, respectively (Venkatesan et al., 2016). The bright-red spots appearing near atoms O1, S1 and H4 indicate their roles as the respective donors and/or acceptors; they also appear as blue and red regions corresponding to positive and negative potentials on the HS mapped over electrostatic potential (Spackman et al., 2008;Jayatilaka et al., 2005), as shown in View of the 3D Hirshfeld surface of the title compound, plotted over d norm in the range À0.1634 to 1.5051 a.u.

Figure 4
View of the 3D Hirshfeld surface of the title compound, plotted over electrostatic potential energy in the range À0.0500 to 0.0500 a.u., using the STO-3G basis set at the Hartree-Fock level of theory. Hydrogenbond donors and acceptors are shown as blue and red regions around the atoms corresponding to positive and negative potentials, respectively.

Figure 5
Hirshfeld surface of the title compound plotted over shape-index.
relative contributions to the Hirshfeld surface. The most important interaction is HÁ Á ÁH, contributing 29.1% to the overall crystal packing, which is reflected in Fig. 6(b) as widely scattered points of high density due to the large hydrogen content of the molecule with the tip at d e = d i = 1.17 Å , due to the short interatomic HÁ Á ÁH contacts (Table 2). In the presence of C-HÁ Á Á interactions, the pairs of characteristic wings resulting in the fingerprint plot delineated into HÁ Á ÁC/ CÁ Á ÁH contacts (Fig. 6c), with a 27.5% contribution to the HS, arises from the HÁ Á ÁC/CÁ Á ÁH contacts (Table 2) and are viewed as pairs of spikes with the tips at d e + d i = 2.82 and 2.78 Å for thin and thick spikes, respectively. The pair of scattered points of the wings resulting in the fingerprint plots delineated into HÁ Á ÁCl/ClÁ Á ÁH (Fig. 6d), with a 20.6% contribution to the HS, has a symmetrical distribution of points with the edges at d e + d i = 2.78 Å arising from the HÁ Á ÁCl/ClÁ Á ÁH contacts ( Table 2). The pair of characteristic wings resulting in the fingerprint plot delineated into OÁ Á ÁH/ HÁ Á ÁO contacts (Fig. 6e), with a 7.0% contribution to the HS, arises from the OÁ Á ÁH/HÁ Á ÁO contacts (Table 2) and is viewed as a pair of spikes with the tips at d e + d i = 2.35 Å . The CÁ Á ÁC contacts (Fig. 6f) have an arrow-shaped distribution of points with the tip at d e = d i = 1.7 Å . Finally, the characteristic wings resulting in the fingerprint plots delineated into SÁ Á ÁH/HÁ Á ÁS and ClÁ Á ÁC/CÁ Á ÁCl contacts (Figs. 6g and 6h), with 4.0 and 2.2% contributions to the HS, arise from the SÁ Á ÁH/HÁ Á ÁS and ClÁ Á ÁC/CÁ Á ÁCl contacts (Table 2)

DFT calculations
The optimized structure of (I) in the gas phase was generated theoretically via density functional theory (DFT) using standard B3LYP functional and 6-311G(d,p) basis-set calculations (Becke, 1993), as implemented in GAUSSIAN09 (Frisch et al., 2009). The theoretical and experimental results were in good agreement (Table 3). The highest-occupied molecular orbital (HOMO), acting as an electron donor, and the lowest-unoccupied molecular orbital (LUMO), acting as an electron acceptor, are very important parameters for quantum chemistry. When the energy gap is small, the molecule is highly polarizable and has high chemical reactivity. The DFT calculations provide some important information on the reactivity The energy band gap of the title compound.  and site selectivity of the molecular framework. E HOMO and E LUMO clarifying the inevitable charge exchange collaboration inside the studied material, electronegativity (), hardness (), potential (), electrophilicity (!) and softness () are recorded in Table 4. The significance of and is to evaluate both the reactivity and stability. The electron transition from the HOMO to the LUMO energy level is shown in Fig. 8. The HOMO and LUMO are localized in the plane extending from the whole molecule. The energy band gap (ÁE = E LUMO -E HOMO ) of the molecule was about 5.3364 eV, and the frontier molecular orbital (FMO) energies, E HOMO and E LUMO , were À8.2479 and À2.9115 eV, respectively.

Refinement
The experimental details, including the crystal data, data collection and refinement, are summarized in Table 5. H atoms were located in a difference Fourier map and refined freely.

sup-1
Acta Cryst. 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. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.  (7) 0.0333 (7) 0.0271 (7) 0.0065 (6) 0.0104 (5) 0.0039 (5)  C19 0.0385 (8) 0.0330 (7) 0.0476 (9) 0.0061 (6) 0.0232 (7) 0.0101 (6) C20 0.0270 (7) 0.0262 (7) 0.0630 (10) −0.0002 (5) 0.0123 (6) (18) C8-S1-C1 100.14 (6) C11-C12-C13 118.49 (12)