A series of dinuclear half-sandwich Ru(II), Os(II) and Ir(III) complexes [Ru
2(μ-L
n)(η
6-
pcym)
2Cl
2](PF
6)
2 ( 1 , 4 ), [Os
2(μ-L
n)(η
6-
pcym)
2Cl
2](PF
6)
2 ( 2 , 5 ) and [Ir
2(μ-L
n)(η
5-Cp*)
2Cl
2](PF
6)
2 ( 3 , 6 ), based on 4,4′-biphenyl-based bridging Schiff base ligands
N,N′-(biphenyl-4,4′-diyldimethylidyne)bis-2-(pyridin-2-yl)methanamine (L
1; for 1 – 3 ) and
N,N′-(biphenyl-4,4′-diyldimethylidyne)bis-2-(pyridin-2-yl)ethanamine (L
2; for 4 – 6 ) is reported;
pcym = 1-methyl-4-(propan-2-yl)benzene, Cp* = pentamethylcyclopentadienyl. The complexes were characterized by relevant analytical techniques (i.e. elemental analysis, FT-IR, NMR, ESI-MS), and their
in vitro cytotoxicity was assessed at six cancerous and two non-cancerous (healthy) human cell lines. Overall, complexes 4 – 6 , containing the L
2 bridging ligand, revealed higher cytotoxicity as compared with 1 – 3 and, thus, they were studied in greater detail. The best-performing complex 6 exceeded at least twice the
in vitro cytotoxicity of
cisplatin and showed high selectivity towards the cancer cells over the normal ones, including the primary culture of human hepatocytes. In contrast to
cisplatin, complexes 4 – 6 did not induce the cell cycle modification of the treated A2780 human ovarian carcinoma cells (studied by flow cytometry and Western blot analysis). High levels of superoxide anion were induced by complexes 4 – 6 at the A2780 cells. The levels of activated forms of Caspase-3 and Caspase-8 at the A2780 cells treated by Ru(II) complex 4 were comparable with
cisplatin, while complexes 5 and 6 had only a minor effect on activation of these caspases.
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