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

The title compound, C 24 H 27 Cl 2 NOS, contains 1,4-benzothiazine and 2,4-dichlorophenylmethylidene units in which the dihydrothiazine ring adopts a screw-boat conformation. In the crystal, intermolecular C—H Bnz ...O Thz (Bnz = benzene and Thz = thiazine) hydrogen bonds form chains of molecules extending along the a -axis direction, which are connected to their inversion-related counterparts by C—H Bnz ...Cl Dchlphy (Dchlphy = 2,4-dichlorophenyl) hydrogen bonds and C—H Dchlphy ...π (ring) interactions. These double chains are further linked by C—H Dchlphy ...O Thz hydrogen bonds, forming stepped layers approximately parallel to (012). The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H...H (44.7%), C...H/H...C (23.7%), Cl...H/H...Cl (18.9%), O...H/H...O (5.0%) and S...H/H...S (4.8%) interactions. Hydrogen-bonding and van der Waals interactions are the dominant interactions in the crystal packing. Computational chemistry indicates that in the crystal, C—H Dchlphy ...O Thz , C—H Bnz ...O Thz and C—H Bnz ...Cl Dchlphy hydrogen-bond energies are 134.3, 71.2 and 34.4 kJ mol −1 , respectively. 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. The two carbon atoms at the end of the nonyl chain are disordered in a 0.562 (4)/0.438 (4) ratio.