A reaction between a hexadentate pyridine-based ligand (L) [pyridine-2-ylmethylene][2-({2-[(2-{[pyridine-2-ylmethylene]amino}phenyl)thio]ethyl}thio)phenyl]amine with ) gave the complex of [NiL](ClO4)2.H2O. This synthesized complex has been characterized by a variety of physico-chemical techniques. Based on the structural data, the geometry of NiN4S2 cationic complex is slightly distorted-octahedral. The asymmetric unit consisted of one Schiff-base ligand (L), one Ni(II) ion, two disordered perchlorate counterions, and one water molecule. The crystal packing analysis also showed O—H⋯O and C—H⋯O hydrogen-bonding interactions form a three-dimensional (3D) supramolecular structure. Moreover, Hirshfeld surface analysis ratified the effective role of perchlorate anions and water molecules in the formation and stabilization of the crystal packing. Also, density functional theory calculations were used to analyze the electronic structure of the complex which gave us consistent results with the obtained experimental data for the complex.
