Crystal structure, Hirshfeld surface analysis and DFT study of (2Z)-2-(4-fluoro-benzyl-idene)-4-(prop-2-yn-1-yl)-3,4-di-hydro-2H-1,4-benzo-thia-zin-3-one.

The title compound, C18H12FNOS, is built up from a 4-fluoro-benzyl-idene moiety and a di-hydro-benzo-thia-zine unit with a propynyl substituent, with the heterocyclic portion of the di-hydro-benzo-thia-zine unit adopting a shallow boat conformation with the propynyl substituent nearly perpendicular to it. The two benzene rings are oriented at a dihedral angle of 43.02 (6)°. In the crystal, C-HFlurphen⋯FFlurphen (Flurphen = fluoro-phen-yl) hydrogen bonds link the mol-ecules into inversion dimers, enclosing R 2 2(8) ring motifs, with the dimers forming oblique stacks along the a-axis direction. Hirshfeld surface analysis of the crystal structure indicates that the most important contributions to the crystal packing are from H⋯H (33.9%), H⋯C/C⋯H (26.7%), H⋯F/F⋯H (10.9%) and C⋯C (10.6%) inter-actions. 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.