Solution Equilibrium Studies on Anticancer Ruthenium(II)–eta6-p-cymene Complexes of 3-Hydroxy-2(1H)-pyridones

Enyedy, Éva Anna and Bognár, Gabriella M. and Kiss, Tamás and Hanif, Muhammad and Hartinger, Christian G. (2013) Solution Equilibrium Studies on Anticancer Ruthenium(II)–eta6-p-cymene Complexes of 3-Hydroxy-2(1H)-pyridones. JOURNAL OF ORGANOMETALLIC CHEMISTRY, 734. pp. 38-44. ISSN 0022-328X

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Abstract

Ru-II(eta(6)-p-cymene) complexes of bidentate (0,0) alkoxycarbonylmethyl-3-hydroxy-2(1H)-pyridone ligands exhibit in vitro antitumor activity. We determined the stoichiometry and stability in aqueous solution of two examples by pH-potentiometry, H-1 NMR spectroscopy and UV-vis spectrophotometry and also characterized the proton dissociation processes of the ligands. Formation of mono-ligand complexes with moderate stability was found to predominate in the physiological pH range. Moreover, the chlorido/aqua co-ligand exchange processes of the [Ru-II(eta(6)-p-cymene)(L)(H2O)](+) species were also monitored and 55-65% of the aqua ligand was found to be replaced by chloride in 0.2 M KCl-containing aqueous solutions. Under basic conditions, the complexes decompose to dinuclear tri-hydroxido-bridged [Ru-2(I)(eta(6)-p-cymene)(2)(OH)(3)](+) and metal-free ligand and also a hydroxido species [Ru-II(eta(6)-p-cymene)(L)(OH)] was found. Furthermore, the ligands contain an ester functional group, which may hydrolyze at basic pH, which is however negligible at acidic or neutral pH.

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