The synthesis, structural characterization, and in vitro anti-cancer activity of chloro(p-cymene) complexes of ruthenium(II) containing a disulfoxide ligand

Two diruthenium(II) complexes [RuCl2(p-cymene)]2(μ-BESE) (1), [RuCl2(p-cymene)]2(μ-BESP) (2), and the mononuclear salt [RuCl(p-cymene)(BESE)]PF6 (3), containing the disulfoxides BESE and BESP, were synthesized and characterized by elemental analysis, and NMR and IR spectroscopies, and were shown to contain S-bound sulfoxide groups; the disulfoxides are EtS(O)(CH2)nS(O)Et, where n=2 (BESE) or 3 (BESP). Complexes 1 and 3 were also characterized by X-ray crystallography. Preliminary in vitro tests of 1 and 3 were conducted using the MTT assay, which measures mitochondrial dehydrogenase activity as an indication of cell viability; these complexes showed in vitro anti-cancer activity against a human mammary cancer cell line (MDA-MB-435s) with IC50 values of 360 and 55 μM, respectively.