Computational Study of the Formation of Short Centrosymmetric N–H···S Supramolecular Synthon and Related Weak Interactions in Crystalline 1,2,4-Triazoles

A comprehensive analysis of the crystal packing and the energetic features of a series of four biologically active molecules belonging to the family of substituted 4-(benzylideneamino)-3-(4-fluoro-3-phenoxyphenyl)-1<i>H</i>-1,2,4-triazole-5-(4<i>H</i>)-thione derivatives have been performed based on the molecular conformation and the supramolecular packing. This involves the formation of a short centrosymmetric <b>R</b>_<b>2</b>^<b>2</b><b>(8)</b> N–H···S supramolecular synthon in the solid state, including the presence of C–H···S, C–H···O, C–H···N, C–H···F, C–H···Cl, C–F···F–C, C–Cl···Cl–C, and C–H···π intermolecular interactions along with π–π stacking to evaluate the role of noncovalent interactions in the crystal. The presence of such synthons has a substantial contribution toward the interaction energy (−18 to −20 kcal/mol) as obtained from the PIXEL calculation, wherein the Coulombic and polarization contribution are more significant than the dispersion contribution. The geometrical characteristics of such synthons favor short distance, and the population of related molecules having these geometries is rare as has been obtained from the Cambridge Structural Database (CSD). Furthermore, their interaction energies have been compared with those present in our molecules in the solid state. The topological characteristics of the N–H···S supramolecular synthon, in addition to related weak interactions, C–H···N, C–H···Cl, C–F···F–C, and C–Cl···Cl–C, have been estimated using the quantum theory of atoms in molecules (QTAIM). In addition, an analysis of the Hirshfeld surface and associated fingerprint plots of these four molecules also have provided a platform for the evaluation of the contribution of different atom···atom contacts, which contribute toward the packing of the molecules in solids