Crystal structure, Hirshfeld surface analysis and interaction energy, DFT and antibacterial activity studies of (Z)-4-hexyl-2-(4-methylbenzylidene)-2H-benzo[b][1,4]thiazin-3(4H)-one

Abstract

The title compound, C22H25NOS, consists of methylbenzylidene and benzothiazine units linked to a hexyl moiety, where the thiazine ring adopts a screw-boat conformation. In the crystal, inversion dimers are formed by weak C—HMthn...OBnzthz hydrogen bonds and are linked into chains extending along the a-axis direction by weak C—HBnz...OBnzthz (Bnz = benzene, Bnzthz = benzothiazine and Mthn = methine) hydrogen bonds. A Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H...H (59.2%) and H...C/C...H (27.9%) 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...OBnzthz and C—HMthn...OBnzthz hydrogen-bond energies are 75.3 and 56.5 kJ mol−1, respectively. 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. Moreover, the antibacterial activity of the title compound was evaluated against gram-positive and gram-negative bacteria.

Keywords

• crystal structure
• hydrogen bond
• benzothiazine
• antibacterial activity
• hirshfeld surface