Acetylacetonato chelated ruthenium organometallics incorporating imine-phenol function: spectroscopic, structural, electrochemical and cytotoxicity studies

The heterogeneous phase reaction of Ru(η2-RL)(PPh3)2(CO)Cl, 1 with lithium acetylacetonate (Liacac) afforded the complexes of the type Ru(η1-RL)(PPh3)2(CO)(acac), 2 in excellent yield where η2-RL is C6H2O-2-CHNHC6H4R(p)-3-Me-5 and η1-RL is C6H2OH-2-CHNC6H4R(p)-3-Me-5 and R is H, Me, Cl. The chelation of acac is attended with the cleavage of Ru-O and Ru-Cl bonds and iminium-phenolato → imine-phenol prototropic shift. A sterically controlled change in rotational conformation is involved in the 1 → 2 conversion. The conversion is irreversible and the type 2 species are thermodynamically more stable than the carboxylate, nitrite and nitrate complexes of 1. The crystal structures of Ru(η1-MeL)(PPh3)2(CO)(acac), 2(Me) and Ru(η1-ClL)(PPh3)2(CO)(acac), 2(Cl) are reported. Spectral (UV-Vis, IR, 1H NMR) and electrochemical data of the complexes are also reported. The electronic structure and the absorption spectra of the complexes are scrutinized by the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) analyses. The complexes were also screened in vitro for their antiproliferative properties against the MCF-7 breast cancer cell lines by using the MTT assay. Flow cytometric analysis showed that the complexes arrested the cell cycle in the sub G0 phase.