Water-soluble arene ruthenium complexes containing pyridinethiolato ligands: Synthesis, molecular structure, redox properties and anticancer activity of the cations [(eta(6)-arene)Ru(p-SC5H4NH)(3)](2+)

摘要

The cationic complexes [(eta(6)-arene)Ru(SC5H4NH)(3)](2+), arene being C6H6 (1), MeC6H5 (2), p-(PrC6H4Me)-Pr-i (3) or C6Me6 (4), have been synthesised from the reaction of 4-pyridinethiol with the corresponding precursor (eta(6)-arene)(2)Ru-2(mu(2)-Cl)(2)Cl-2 and isolated as the chloride salts. The single-crystal X-ray structure of [4](PF6)(2) reveals three 4-pyridinethiol moieties coordinated to the ruthenium centre through the sulphur atom, with the hydrogen atom transferred from the sulphur to the nitrogen atom. The electrochemical study of 1-4 shows a clear correlation between the Ru(II)/Ru(III) redox potentials and the number of alkyl substituents at the arene ligand (E degrees' (Ru-II/III): 1 > 2 > 3 > 4), whereas the cytotoxicity towards A2780 ovarian cancer cells follows the series 4 > 1 > 3 > 2, the hexamethylbenzene derivative 4 being the most cytotoxic one. The corresponding reaction of the ortho-isomer, 2-pyridinethiol, with (eta(6)-C6Me6)(2)Ru-2(mu(2)-Cl)(2)Cl-2 does not lead to the expected 2-pyridinethiolato analogue, but yields the neutral complex (eta(6)-C6Me6)Ru(eta(2)-SC5H4N)(eta(1)-SC5H4N) (5). The analogous complex (eta(6)-C6Me6)Ru(eta(2)-SC9H6N)-(eta(1)-SC9H6N) (6) is obtained from the similar reaction with 2-quinolinethiol.