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

The title compound, C₁₈ H₁₂ Cl₂ N₂ OS, consists of a dihydrobenzothiazine unit linked by a -CH group to a 2,4-dichlorophenyl substituent, and to a propanenitrile unit is folded along the S...N axis and adopts a flattened-boat conformation. The propanenitrile moiety is nearly perpendicular to the mean plane of the dihydrobenzothiazine unit. In the crystal, C - H Bnz ...N Prpnit and C - H Prpnit ...O Thz (Bnz = benzene, Prpnit = propanenitrile and Thz = thiazine) hydrogen bonds link the molecules into inversion dimers, enclosing R 2 2 (16) and R²² (12) ring motifs, which are linked into stepped ribbons extending along [110]. The ribbons are linked in pairs by complementary C=O...Cl interactions. π-π contacts between the benzene and phenyl rings, [centroid-centroid distance = 3.974 (1) Å] may further stabilize the structure. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H...H (23.4%), H...Cl/Cl...H (19.5%), H...C/C...H (13.5%), H...N/N...H (13.3%), C...C (10.4%) and H...O/O...H (5.1%) interactions. Hydrogen bonding and van der Waals interactions are the dominant interactions in the crystal packing. Computational chemistry calculations indicate that the two independent C - H Bnz ...N Prpnit and C - H Prpnit ...O Thz hydrogen bonds in the crystal impart about the same energy (ca 43 kJ mol -1). Density functional theory (DFT) optimized structures at the B3LYP/6-311 G(d,p) level are compared with the experimentally determined molecular structure in the solid state. The HOMO-LUMO behaviour was elucidated to determine the energy gap.