Naphthoquinones of natural origin: Aqueous chemistry and coordination to half-sandwich organometallic cations.

Half-sandwich organometallic complexes featuring Ru(II), Os(II) and Rh(III) metal centers and naturally occurring bidentate 2-hydroxy-[1,4]-naphthoquinone ligands (lawsone and phthiocol) have been synthesized and characterized in both solid state and solution phase by analytical, spectroscopic, electrochemical and single crystal X-ray diffraction techniques. Comparative studies revealed the influence of the respective metal center (Ru, Os, Rh), leaving group (Cl, Br, I) and arene (p -cymene, toluene, pentamethylcyclopentadienyl), as well as the naphthoquinone ligand on the structural properties and solution speciation. Additionally, cytotoxicity was tested in SW480, CH1/PA-1 and A549 human cancer cell lines showing a broad range of IC 50 values. Image 1 • Single crystal X-ray structure of five half-sandwich phthiocol complexes. • Anticancer activity in three human cancer cell lines. • Solution stability of Ru(II) and Rh(III) complexes of 2-hydroxy-[1,4]-naphthoquinones. • Comparison with other bidentate (O,O) ligands. [ABSTRACT FROM AUTHOR]