Pd(ii) complexes bearing NNS pincer ligands: unveiling potent cytotoxicity against breast and pancreatic cancer

Abstract

The continuously increasing rate of breast cancer is one of the major threats to female health worldwide. Recently, palladium complexes have emerged as impressive candidates with effective biocompatibility and anticancer activities. Hence, in the present study, we report a new series of palladium complexes bearing NNS pincer ligands for cytotoxicity studies. The reaction of thiophenol/4-chlorothiophenol/4-methylthiophenol/4-methoxythiophenol with 2-bromo-N-quinolin-8-yl-acetamide in the presence of sodium hydroxide in ethanol at 80 °C gave [C₉H₆N–NH–C(O)–CH₂–S–Ar] [Ar = C₆H₅ (L1), C₆H₄Cl-4 (L2), C₆H₄Me-4 (L3), and C₆H₄–OMe-4 (L4)]. The corresponding reaction of L1–L4 with Na₂PdCl₄ in methanol at room temperature for 3 h resulted in complexes [(L1–H)PdCl] (C1), [(L2–H)PdCl] (C2), [(L3–H)PdCl] (C3), and [(L4–H)PdCl] (C4). All new compounds have been characterized by spectroscopic analyses. The structures of complexes C1, C3, and C4 have also been determined from single-crystal X-ray diffraction data. The cytotoxicities of L1–L4 and C1–C4 have been investigated for breast cancer 4T1 and pancreatic cancer MIA-PaCa-2 cells. The IC50 values for complexes C2 and C3 were observed to be comparable to or higher than those of cisplatin. The stressed morphology and cell death of cancerous cells were successfully observed through cellular morphology analysis and the assessment of cytoskeleton damage.