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

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.