Cobalt (II), Nickel (II) and Palladium (II) complexes appended terpyridine‐based ligand: Synthesis, spectral characterization, anticancer activity and apoptosis investigation

Abstract

Three new complexes containing 2‐thiophenylterpyridine (TP) ligand, namely, [Co(stpy)2]Cl2 (Co‐TP), [Ni(stpy)Cl2]2 (Ni‐TP) and [Pd(stpy)Cl]Cl (Pd‐TP) were synthesized and subsequently characterized employing various spectroscopic techniques including UV–Visible, IR, 1H NMR, EPR, and ESI‐MS analysis. ESI‐MS spectra suggested the complexes Co‐TP and Ni‐TP to be six coordinated with two ligand units and the complex Pd‐TP to be a four‐coordinated mononuclear square planar complex. The dimeric nature of the complex Ni‐TP (M2L2Cl4) was established by X‐ray diffraction analysis, which confirmed the bridging of two nickel centers by two chloride ions. The ligand and complexes were assessed for their cytotoxic behavior by using MTT colorimetric assay. The compounds TP, Co‐TP, Ni‐TP and Pd‐TP displayed significant antiproliferative activity on A549 (human lung carcinoma) and MM2 (human breast cancer) cell lines and had no toxic effect on human normal embryonic kidney cells (HEK 293). Further, the morphological changes associated with MM2 and A549 cells triggered by the tested compounds due to apoptosis have been validated with the help of AO‐EB and DAPI staining assays.