An investigation of supramolecular synthons in 1,2,4-triazole-3(4H)-thione compounds. X-ray crystal structures, energetic and Hirshfeld surface analysis

A series of four closely related 1,2,4-triazole-3-thione (1-4) compounds was obtained by heterocyclization of thiosemicarbazides under basic catalytic conditions. The crystal structures of the 4-alkyl-5-(substituted-phenyl)-2H-1,2,4-triazole-3(4H)-thione derivatives [4-alkyl = 4-ethyl-5-phenyl (1), 4-hexyl-5-phenyl (2), 4-hexyl-5-p-tolyl (3), and 4-ethyl-5-(2,4,6-trimethoxyphenyl) (4)] have been determined. PIXEL lattice energy calculations revealed that dispersion components make the major contributions, with the coulombic terms also contributing significantly to the total energy. Interaction energies for the inversion dimers involving N–H⋯S=C hydrogen bonds indicate a dominant contribution to packing stabilization coming from the coulombic energy component. Hirshfeld surfaces and 2D-fingerprint plots allowed us to visualize different intermolecular contacts and their relative contributions to the total surface in each compound. The comprehensive analysis of the crystal packing and the energetic features demonstrate the key role of the R 2 2 ( 8 ) supramolecular synthon of the type (···HNCS)2 in the solid state structures of these 1,2,4-triazole-3-thiones.