Single-crystal XRD, Hirshfeld surfaces, 3D energy framework calculations, and DFT studies of 4,5-diphenyl-1,3,4-thiadiazole-2-thiolate: A mesoionic compound

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The single crystal of mesoionic 4,5-diphenyl-1,3,4-thiadiazolium-2-thiolate 2 was obtained by the solvent evaporation method. The compound was characterized by spectroscopic and analytical techniques. The structure-property relationship of the mesoionic compound 2 was elucidated by single-crystal X-ray diffraction (XRD) data and density functional theory (DFT) methods. The XRD studies showed that compound 2 crystallized in monoclinic, P21/n space group. In the mesoionic ring, the exocyclic C14-S1 bond length was 1.676 (2) Å and the ring C1-S2 bond length was 1.705 (2) Å as a characteristic feature of the existence of dual charges. The crystal packing of the compound showed an interesting zig-zag type pattern of arrangement of molecules when viewed along [101]. The highest percentage of intercontact was found between sulfur and hydrogen in the Hirshfeld surface analysis. The computational studies were performed using the DFT method for the determination of the molecular and electronic properties. The frontier molecular orbitals give an idea of the delocalization of electrons in the molecule, and the energy gap describes the electron transport potential and excitation for reactivity of the molecule. The charge distribution in the compound was visualized using the molecular electrostatic potential surface diagram. Mulliken atomic charges were calculated to study the chemical nature of the molecule. The computational investigations suggested that mesoionic 4,5-diphenyl-1,3,4-thiadiazolium-2-thiolate is electrophilic and dipolar.