Cyclopalladated benzophenone imines: Synthesis, cytotoxicity against human breast adenocarcinoma cell lines and DNA interaction

Treatment of benzophenone imine with the stoichiometric amount of Pd(OAc)2 in acetic acid at 60 °C produced the corresponding acetato-bridged five-membered ortho-cyclopalladated dimer [Pd{C6H4CPhdouble bond; length as m-dashNH}(μ-OAc)]2 (1), which was isolated in pure form in a 79% yield. Reaction of 1 with an excess of LiCl in acetone gave rise to the corresponding chlorido-bridged cyclopalladated dimer [Pd{C6H4CPhdouble bond; length as m-dashNH}(μ-Cl)]2 (2) in a 78% yield. Compounds 1–2 reacted with an excess of py-d5 or the stoichiometric amount of PPh3 to give the mononuclear compounds trans-N,L-[Pd{C6H4CPhdouble bond; length as m-dashNH}(X)(L)] [3 (X = OAc, L = py-d5); 4 (X = Cl, L = py-d5); 5 (X = OAc, L = PPh3) and 6 (X = Cl, L = PPh3)]. Compounds 2–3 were prepared in CDCl3/py-d5 solution and were studied by 1H NMR, but were not isolated. In contrast, compounds 5–6 were prepared in acetone and were isolated in pure form in 43 and 79% yields, respectively. Compounds 1, 2, 5 and 6 were characterized by elemental analyses, mass spectrometry, IR, NMR and electronic spectroscopy. Compounds 1, 2, 5 and 6 showed high antiproliferative activity against MDA-MB231 and MCF7 human breast cancer cell lines, especially, compounds 5–6. These two latter compounds presented greater antiproliferative activity than cisplatin and produced IC50 values in the range 1–5 μM. The interaction of compounds 1, 2, 5 and 6 with DNA was also studied by the DNA electrophoretic migration, DNA-ethidium bromide fluorescence quenching and viscometry techniques.