Crystal structure, Hirshfeld surface analysis and DFT study of (2Z)-2-(4-fluorobenzylidene)-4-(prop-2-yn-1-yl)-3,4-dihydro-2H-1,4-benzothiazin-3-one

The title compound, C ₁₈ H ₁₂ FNOS, is built up from a 4-fluorobenzylidene moiety and a dihydrobenzothiazine unit with a propynyl substituent, with the heterocyclic portion of the dihydrobenzothiazine 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- H _Flurphen · · ·F _Flurphen (Flurphen = fluorophenyl) hydrogen bonds link the molecules 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%) interactions. Hydrogen bonding and van der Waals interactions are the dominant interactions 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 molecular structure in the solid state. The HOMO-LUMO behaviour was elucidated to determine the energy gap.