Stable Cyclometallated Palladium Complexes of Arylamides: Synthesis, Redox and Anticancer Activities

Air-stable cyclometalated palladium(II) complexes with benzamide ligands were synthesized in high yields and characterized by X-ray diffraction analysis, CVA, ¹H NMR, ¹³C NMR spectroscopy, MALDI-MS, and ESI-MS. The electrochemical oxidation of the complexes is reversible in the presence of a quinoline substituent in the ligand and gives Pd (III) species that do not undergo reductive elimination and are detectable by ESR spectroscopy. The complexes showed high cytotoxicity against cervical cancer (M-HeLa) and duodenal adenocarcinoma (HuTu 80), a human mammary ductal adenocarcinoma line (MCF-7) and a human lung carcinoma cell line (A549). The possibility of generating reactive oxygen species in solution (such as OH−radicals), which can be responsible for the antitumor activity of the studied complexes, using the ESR method was shown.