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Synthesis, structural characterization, Hirshfeld surface and DFT calculations of 2-ethyl-2,4,5-trimethyl-2H-1,3-thiazine-6(3H)-thione

Abstract:

2-Ethyl-2,4,5-trimethyl-2H-1,3-thiazine-6(3H)-thione (1) was synthesized from butanone and carbon disulfide and recrystallized from a 1:1 mixture of ethyl acetate-hexane using the slow solvent evaporation technique. MS, FT-IR, and NMR spectroscopy techniques allowed to confirm the skeleton structure of (1), and its crystal structure was characterized by X-ray diffraction. The powder X-ray diffraction data confirm the phase purity of the crystalline sample. Single-crystal X-ray diffraction analysis indicated that this compound crystallizes in the monoclinic space group P21/n (N° 14), with unit cell parameters: a = 6.3710 (16) Å, b = 11.537 (3) Å, c = 14.292 (4) Å, β = 93.842 (6)°, V = 1048.1 (5) Å3. Compound (1) displays a half-chair conformation and, in addition, has a chiral center that indicates the presence of a racemic mixture. X-ray results were compared with DFTB (density-functional tight-binding) theoretical calculations in the solid state, confirming delocalization of electron density in the S1C1C2C3N1 segment of the ring that alters bond distances. The crystalline packing is stabilized by hydrogen bonds of the type N1–H1··S1, which form infinite chains parallel to the b axis and are described by the graph-set symbol C(6). Finally, an analysis of the Hirshfeld surfaces of the compound, allowed to identify additional interactions of the type C–H···π. The most important contributions to the crystal packing correspond to the interactions H·· H, S · H / H·· S and C·· H / H·· C with values of 59.8%; 32.20% and 6.40%; respectively.