Synthesis, Characterizations, Crystal structure, DFTand Hirshfeld surface analysis of4-cyclohexyl-1-(thiophene-2-carbonyl)thiosemicarbazide

The crystal structure of the thiosemicarbazide derivative 4-cyclohexyl-1-(thiophene-2-carbonyl)thiosemicarbazide (ChtcTSC), C 12 H 17 N 3 OS 2 , is reported here. The title compound ChtcTSC has been characterized by various physicochemical techniques viz UV-vis., Infrared, and NMR. It crystallizes in the monoclinic system having space group P 2 1 /c. The dihedral angle between the thiophene and cyclohexyl rings is 60.7(4) ° . The crystal packing is established by intermolecular N-H∙∙∙O packing interactions involving a three-center donor hydrogen bond between the keto oxygen atom of the thiophene group and H atoms belonging to the hydrazine group which links the molecules into chains along the (011) plane of the unit cell. Hydrogen bonds between the hydrazine hydrogen atom and one of the thiophene groups and C-H∙∙∙Cg π-ring interactions provide added stability to the crystal packing. The fingerprint plots associated with Hirshfeld surface analysis indicate that there are different types of weak interactions viz. O···H-C, O···H-N and S···H-C. The geometry optimization has been performed using the DFT method, and geometrical parameters thus obtained for ChtcTSC correlate with the single-crystal X-ray data. The TD-DFT studied showed a small HOMO and LUMO energy gap of 2.869 eV. The electronic transition from the ground state to the excited state due to a transfer of electrons from HOMO to LUMO levels is mainly associated with the n→π* transition.