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

The title compound, C24H27Cl2NOS, contains 1,4-benzothiazine and 2,4-dichlorophenylmethylidene units in which the dihydrothiazine ring adopts a screw-boat conformation. In the crystal, intermolecular C - HBnz⋯OThz (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 - HBnz⋯ClDchlphy (Dchlphy = 2,4-dichlorophenyl) hydrogen bonds and C - HDchlphy⋯π (ring) interactions. These double chains are further linked by C - HDchlphy⋯OThz 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 - HDchlphy⋯OThz, C - HBnz⋯OThz and C - HBnz⋯ClDchlphy hydrogen-bond energies are 134.3, 71.2 and 34.4kJmol^-1, respectively. Density functional theory (DFT) optimized structures at the B3LYP/6-311G(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.