Solution equilibria of anticancer ruthenium(II)-(η6-p-cymene)-hydroxy(thio)pyr(id)one complexes: Impact of sulfur vs. oxygen donor systems on the speciation and bioactivity

A comparative study on the antitumor ruthenium(II)−η6-p-cymene complexes of bidentate (O,O) hydroxypyrone and (O,S) hydroxythiopyr(id)one type ligands revealed that the hydroxythiopyr(id)one ligands form complexes of significantly higher stability compared with the hydroxypyrones; their complexes are biologically more active. The simultaneous bi- and monodentate coordination of the ligands in the bis complexes (ML2 and ML2H) was also demonstrated.