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 R 4 ⁴(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.