New insights into the redox chemistry of ruthenium metallopharmaceuticals: The electrochemical behaviour of [LH][trans-Ru^IIICl₄L ₂] (L = imidazole or indazole) complexes

Here we report the findings from a study on the electrochemical behaviour of two Ru^III complexes [LH][trans-Ru^IIICl ₄L₂] (L = imidazole, ICR, or indazole, IndCR) in aqueous solution at different pH values. An electrochemically reversible and chemically quasi-reversible one-electron reduction is observed for both compounds. Despite the similarity of the structures, the fate of the electrogenerated Ru ^II species is different; in the case of ICR, imidazole, followed by a chloride ion, is released as the consequence of the reduction, while for IndCR two subsequent water for chloride substitutions take place. Our measurements suggests that the Ru^III complexes under study may serve as pro-drugs, being activated by reduction in a suitable aqueous environment and, therefore, binding biomolecules more rapidly.