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

The title compound, C22H15Cl2NOS, contains 1,4-benzo­thia­zine and 2,4-di­­chloro­benzyl­idene units, where the di­hydro­thia­zine ring adopts a screw-boat conformation. In the crystal, inter­molecular C—HBnz⋯OThz (Bnz = benzene and Thz = thia­zine) hydrogen bonds form corrugated chains extending along the b-axis direction which are connected into layers parallel to the bc plane by inter­molecular C—HMethy⋯SThz (Methy = methyl­ene) hydrogen bonds, en­closing R44(22) ring motifs. Offset π-stacking inter­actions between 2,4-di­­chloro­phenyl rings [centroid–centroid = 3.7701 (8) Å] and π-inter­actions which are associated by C—HBnz⋯π(ring) and C—HDchlphy⋯π(ring) (Dchlphy = 2,4-di­chloro­phen­yl) inter­actions may be effective in the stabilization of the crystal structure. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (29.1%), H⋯C/C⋯H (27.5%), H⋯Cl/Cl⋯H (20.6%) and O⋯H/H⋯O (7.0%) inter­actions. Hydrogen-bonding and van der Waals inter­actions are the dominant inter­actions in the crystal packing. Computational chemistry indicates that in the crystal, the C—HBnz⋯OThz and C—HMethy⋯SThz hydrogen-bond energies are 55.0 and 27.1 kJ mol−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.