Crystal structure, Hirshfeld surface analysis and DFT study of (2Z)-2-(2,4-di-chloro-benzyl-idene)-4-[2-(2-oxo-1,3-oxazolidin-3-yl)eth-yl]-3,4-di-hydro-2H-1,4-benzo-thia-zin-3-one.

The title compound, C20H16Cl2N2O3S, is built up from a di-hydro-benzo-thia-zine moiety linked by -CH- and -C2H4- units to 2,4-di-chloro-phenyl and 2-oxo-1,3-oxazolidine substituents, where the oxazole ring and the heterocyclic portion of the di-hydro-benzo-thia-zine unit adopt envelope and flattened-boat conformations, respectively. The 2-carbon link to the oxazole ring is nearly perpendicular to the mean plane of the di-hydro-benzo-thia-zine unit. In the crystal, the mol-ecules form stacks extending along the normal to (104) with the aromatic rings from neighbouring stacks inter-calating to form an overall layer structure. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (28.4%), H⋯Cl/Cl⋯H (19.3%), H⋯O/O⋯H (17.0%), H⋯C/C⋯H (14.5%) and C⋯C (8.2%) inter-actions. Weak hydrogen-bonding and van der Waals inter-actions are the dominant inter-actions in the crystal packing. 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.