Crystal structure, Hirshfeld surface analysis, inter-action energy and DFT studies of (2)-2-(2,4-di-chloro-benzyl-idene)-4-nonyl-3,4-di-hydro-2-1,4-benzo-thia-zin-3-one.

The title compound, CHClNOS, contains 1,4-benzo-thia-zine and 2,4-di-chloro-phenyl-methyl-idene units in which the di-hydro-thia-zine ring adopts a screw-boat conformation. In the crystal, inter-molecular C-H⋯O (Bnz = benzene and Thz = thia-zine) hydrogen bonds form chains of mol-ecules extending along the -axis direction, which are connected to their inversion-related counterparts by C-H⋯Cl (Dchlphy = 2,4-di-chloro-phen-yl) hydrogen bonds and C-H⋯π (ring) inter-actions. These double chains are further linked by C-H⋯O 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%) inter-actions. Hydrogen-bonding and van der Waals inter-actions are the dominant inter-actions in the crystal packing. Computational chemistry indicates that in the crystal, C-H⋯O, C-H⋯O and C-H⋯Cl hydrogen-bond energies are 134.3, 71.2 and 34.4 kJ mol, respectively. Density functional theory (DFT) optimized structures at the B3LYP/6-311 G(d,p) level are compared with the experimentally determined mol-ecular 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.