Solution equilibrium studies of anticancer ruthenium(II)-η6- p-cymene complexes of pyridinecarboxylic acids

Éva Sija, Christian G. Hartinger, Bernhard K. Keppler, Tamás Kiss, Éva A. Enyedy

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9 Citations (Scopus)


Stoichiometry and stability of antitumor ruthenium(II)-η6-p- cymene complexes of picolinic acid and its 6-methyl and 6-carboxylic acid derivatives were determined by pH-potentiometry, 1H NMR spectroscopy and UV-Vis spectrophotometry in aqueous solution in the presence or absence of coordinating chloride ions. The picolinates form exclusively mono-ligand complexes in which they can coordinate via the bidentate (O,N) mode and a chloride or a water molecule is found at the third binding site of the ruthenium(II)-η6-p-cymene moiety depending on the conditions. [Ru(η6-p-cymene)(L)(H2O/Cl)] species are predominant at physiological pH in all studied cases. Hydrolysis of the aqua complex or the chlorido/hydroxido co-ligand exchange results in the formation of the mixed-hydroxido species [Ru(η6-p-cymene)(L)(OH)] in the basic pH range. There is no indication for the decomposition of the mono-ligand complexes during 24 h in the ruthenium(II)-η6-p-cymene-picolinic acid system between pH 3 and 11; however, a slight dissociation with a low reaction rate was found in the other two systems leading to the appearance of the dinuclear trihydroxido-bridged species [Ru26-p- cymene)2(OH)3]+ and free ligands at pH > 10. The replacement of the chlorido by an aqua ligand in [Ru(η6-p- cymene)(L)Cl] was also monitored and equilibrium constants for the exchange process were determined.

Original languageEnglish
Pages (from-to)51-58
Number of pages8
Publication statusPublished - Jan 1 2014


  • Antitumor agents
  • Dipicolinic acid
  • Picolinic acid
  • Speciation
  • Stability constants

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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