Acetylacetonato chelated ruthenium organometallics incorporating imine–phenol function: Spectroscopic, structural, electrochemical and cytotoxicity studies

• Acetylacetonato chelated ruthenium(II) organometallic complexes.
• Schiff base ligand has undergone a large rotation due to steric repulsion.
• Geometry optimizations of the complexes were performed in the gas phase.
• Electronic structure and the absorption spectra of the complexes are scrutinized.
• The complexes have growth-inhibitory effect on MCF-7 cells, inducing sub G0 cell-cycle arrest.

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.

A series of acetylacetonato chelated ruthenium(II) organometallic complexes have been prepared and characterized by different spectroscopic techniques and by X-ray crystallography. Acetylacetonato chelation is attended with the cleavage of the Ru–O and Ru–Cl bonds and by the iminium–phenolato to imine–phenol prototropic shift. Density functional theory and time-dependent density functional theory calculations are also reported.Figure optionsDownload as PowerPoint slide