Crystal structure, Hirshfeld surface analysis and interaction energy and DFT studies of 3-{(2Z)-2-[(2,4-dichlorophenyl)methylidene]-3-oxo-3,4-dihydro-2H-1,4-benzothiazin-4-yl}propanenitrile

In the title compound, the dihydrobenzothiazine moiety is folded about the S1⋯N1 axis. In the crystal, inversion dimers, generated by C—HBnz⋯NPrpnit (Bnz = benzene, Prpnit = propanenitrile) hydrogen bonds, are linked into stepped ribbons extending parallel to [110] by C—HPrpnit⋯OThz (Thz = thiazine) hydrogen bonds. The ribbons are joined into pairs by inversion-related C=O⋯Cl interactions.


Figure 2
A partial packing diagram viewed along the c-axis direction with the C-HÁ Á ÁO and C-HÁ Á ÁN hydrogen bonds shown, respectively, as black and blue dashed lines.

Hirshfeld surface analysis
In order to visualize the intermolecular interactions in the crystal of the title compound, a Hirshfeld surface (HS) analysis (Hirshfeld, 1977;Spackman & Jayatilaka, 2009) was carried out by using CrystalExplorer17.5 (Turner et al., 2017. In the HS plotted over d norm (Fig. 4), the white surface indicates contacts with distances equal to the sum of 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 brightred spots 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  A partial packing diagram viewed along the a-axis direction with hydrogen bonds depicted as in Fig. 2, and C OÁ Á ÁCl interactions as green dashed lines.

Figure 5
View of the three-dimensional Hirshfeld surface of the title compound plotted over electrostatic potential energy in the range À0.0500 to 0.0500 a.u. using the STO-3 G basis set at the Hartree-Fock level of theory. Hydrogen-bond donors and acceptors are shown as blue and red regions around the atoms corresponding to positive and negative potentials, respectively.

Figure 4
View of the three-dimensional Hirshfeld surface of the title compound plotted over d norm in the range À0.2386 to 1.2893 a.u.

Figure 6
Hirshfeld surface of the title compound plotted over shape-index.

Figure 7
The full two-dimensional fingerprint plots for the title compound   Fig. 8a-f, respectively.

DFT calculations
The optimized structure of the title compound in the gas phase was generated theoretically via density functional theory (DFT) using standard B3LYP functional and 6-311 G(d,p) basis-set calculations (Becke, 1993) as implemented in GAUSSIAN 09 (Frisch et al., 2009). The theoretical and experimental results were in good agreement. The highestoccupied 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 electron transition from the HOMO to the LUMO energy level is shown in Fig. 9. The energy band gap of the title compound. A search in the Cambridge Structural Database (Groom et al., 2016;updated to March 2019), for compounds containing the fragment II (R 1 = Ph, R 2 = C), gave 14 hits. With R 1 = Ph and R 2 = CH 2 C CH IIa (Sebbar et al., 2014a), CH 2 COOH IIb , IIc  and IIf (Sebbar et al., 2015b), there are other examples with R 1 = 4-FC 6 H 4 and R 2 = CH 2 C CH IIa (Hni et al., 2019a), R 1 = 4-ClC 6 H 4 and R 2 = CH 2 Ph2 IId  and R 1 = 2-ClC 6 H 4 , R 2 = CH 2 C CH IIa (Sebbar et al., 2017). In all these compounds, the configuration about the benzylidene C CHC 6 H 5 bond is Z, and in the majority of these, the heterocyclic ring is quite non-planar with the dihedral angle between the plane defined by the benzene ring plus the nitrogen and sulfur atoms and that defined by nitrogen and sulfur and the other two carbon atoms separating them ranging from ca 29 (IIa) to 36 (IIf). The other three (IIa, IIc) have the benzothiazine unit nearly planar with a corresponding dihedral angle of ca 3-4 .

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. C-bound H atoms were positioned geometrically (C-H = 0.95 Å for aromatic and methine H atoms and 0.99 Å for methylene H atoms) and constrained to ride on their parent atoms, with U iso (H) = 1.2U eq (C).

Funding information
The support of NSF-MRI grant No. 1228232 for the purchase of the diffractometer and Tulane University for support of the Tulane Crystallography Laboratory are gratefully acknowledged. TH is grateful to the Hacettepe University Scientific Research Project Unit (grant No. 013 D04 602 004) for support.

3-{(2Z)-2-[(2,4-Dichlorophenyl)methylidene]-3-oxo-3,4-dihydro-2H-1,4-benzothiazin-4-yl}propanenitrile
Crystal data where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.25 e Å −3 Δρ min = −0.35 e Å −3 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. Hatoms attached to carbon were placed in calculated positions (C-H = 0.95 -0.99 Å) and included as riding contributions with isotropic displacement parameters 1.2 -1.5 times those of the attached atoms.