Crystal structure, Hirshfeld surface and crystal void analysis, intermolecular interaction energies, DFT calculations and energy frameworks of 2H-benzo[b][1,4]thiazin-3(4H)-one 1,1-dioxide

In the title molecule, C8H7NO3S, the nitrogen atom has a planar environment, and the thiazine ring exhibits a screw-boat conformation. In the crystal, corrugated layers of molecules parallel to the ab plane are formed by N—H...O and C—H...O hydrogen bonds together with C—H...π(ring) and S=O...π(ring) interactions. The layers are connected by additional C—H...O hydrogen bonds and π-stacking interactions. Hirshfeld surface analysis indicates that the most important contributions for the crystal packing are from H...O/O...H (49.4%), H...H (23.0%) and H...C/C...H (14.1%) interactions. The volume of the crystal voids and the percentage of free space were calculated as 75.4 Å3 and 9.3%. Density functional theory (DFT) computations revealed N—H...O and C—H...O hydrogen-bonding energies of 43.3, 34.7 and 34.4 kJ mol−1, respectively. Evaluation of the electrostatic, dispersion and total energy frameworks indicate that the stabilization is dominated via the electrostatic energy contribution. Moreover, the DFT-optimized structure at the B3LYP/ 6–311 G(d,p) level is compared with the experimentally determined molecular structure in the solid state. The HOMO–LUMO behaviour was elucidated to determine the energy gap.