Cytotoxicity of osmium(II) and cycloosmated half-sandwich complexes from 1-pyrenyl-containing phosphane ligands

Five metal-arene complexes of formula [MX₂(η⁶-p-cymene)(diR(1-pyrenyl)phosphane)] (M = Os or Ru, X = Cl or I, R = isopropyl or phenyl) and symbolized as MRX2 were synthesized and fully characterized, namely OsiPrCl2, OsiPrI2, OsPhCl2, OsPhI2 and RuPhI2. Furthermore, nine cyclometalated half-sandwich complexes of formula [MX-(η⁶-p-cymene)(k²C-diR(1-pyrenyl)phosphane)] (M = Os or Ru, X = Cl or I, R = isopropyl or phenyl) or [M(η⁶-p-cymene)(kS-dmso)(k²C-diR(1-pyrenyl)phosphane)]PF₆ (M = Os or Ru, R = isopropyl or phenyl) and symbolized as c-MRX were prepared; hence, c-OsiPrCl, c-OsiPrI, c-OsiPrdmso, c-OsPhCl, c-OsPhI, c-OsPhdmso, c-RuPhCl, c-RuPhI and c-RuPhdmso were obtained and fully characterized. The crystal structures of ten out of the fourteen complexes were solved. All complexes exhibit notable cytotoxic properties against A549 (Lung Adenocarcinoma) human cells, with IC₅₀ values ranging from 48 to 1.42 μM. In addition, complex c-OsiPrdmso shows remarkable toxic behaviours agains other cell lines, namely MCF7 (breast carcinoma), MCF10A (non-tumorigenic epithelial breast) and MDA-MB-435 (melanoma) human cells, as illustrated by IC₅₀ values of 4.36, 4.71 and 2.32 μM, respectively. Finally, it has been found that OsiPrI2 affects the cell cycle of A549 cells, impeding their replication (i.e., the cell cycle is blocked), whereas OsPhI2 (namely with phenyl groups instead of isopropyl ones) does not induce this effect.