Synthesis, Structural Characterization, Optical Properties, and Biological Potency of Co(II), Cu(II), and Cd(II) Complexes With Heterocyclic Thiosemicarbazide Ligand: Insights From Molecular Docking Studies

ABSTRACT A novel heterocyclic thiosemicarbazide ligand, [(Z)‐N‐(2‐oxoindolin‐3‐ylidene)nicotinohydrazide] (H 2 L) , and its Co(II), Cu(II), and Cd(II) metal chelates were synthesized and characterized using a variety of analytical methods, including elemental analysis, FT‐IR, UV–Visible spectroscopy, EI‐mass, fluorescence spectroscopy, X‐ray powder diffraction, and TGA. The structures and geometries of the complexes were determined using these methods as [Co 2 (H 2 L) 2 Cl 2 (H 2 O) 4 ]·2H 2 O, [Cu(H 2 L) 2 Cl 2 (H 2 O) 2 ]·2H 2 O, and [Cd(H 2 L) 2 Cl 2 (H 2 O) 2 ], all having octahedral geometry. The particulate diameters for [Co 2 (H 2 L) 2 Cl 2 (H 2 O) 4 ]·2H 2 O, [Cu(H 2 L) 2 Cl 2 (H 2 O) 2 ]·2H 2 O, and [Cd(H 2 L) 2 Cl 2 (H 2 O) 2 ] were 192.68, 68.48, and 192.74 nm, respectively using Debye–Scherrer equation and FWHM approach. The corresponding FWHM values were 0.0078, 0.0217, and 0.0075, whereas the crystal strain was calculated as ( ε ) = 0.0018, 0.0056, and 0.0054, and the dislocation density ( δ ) as 2.69 × 10 −5 , 2.13 × 10 −4 , 2.69 × 10 −5 Å −2 . Quantum chemical calculations for the ligand and its solid metal complexes were carried out utilizing DFT with the DMOL3 module. Furthermore, the optical sensing response of the free ligand H 2 L to Co(II), Cu(II), and Cd(II) ions was investigated, revealing that the presence of these metal ions enhanced the fluorescence spectra of the ligand. Additionally, the antibacterial effects of these compounds, as well as their cytotoxicity in human cancer cells, were investigated. Compared to its metal complexes, the ligand, H 2 L exhibits increased antibacterial activity against various bacteria. Tests on HepG‐2 and MCF‐7 cells were conducted to evaluate the compounds' anticancer efficacy against the standard, Doxorubicin. The ligand, H 2 L , demonstrated greater cytotoxicity against the HepG‐2 cell line than its metal complexes. Docking experiments were conducted to assess the interaction of the ligand and its complexes with HepG‐2 (PDB ID: 2OH4) and MCF‐7 (PDB ID: 3W2S) cells, using the XP glide technique and Schrödinger suite software.