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

Abstract

The title compound, C18H12Cl2N2OS, 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—HBnz...NPrpnit and C—HPrpnit...OThz (Bnz = benzene, Prpnit = propanenitrile and Thz = thiazine) hydrogen bonds link the molecules into inversion dimers, enclosing R 2 2(16) and R 2 2(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—HBnz...NPrpnit and C—HPrpnit...OThz 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.