Synthesis, characterization and in vitro anticancer activity of highly cytotoxic trithiolato diruthenium complexes of the type [(η6-p-MeC6H4iPr)2Ru2(μ2-SR1)2(μ2-SR2)]+ containing different thiolato bridges

•Eighteen new diruthenium trithiolato complexes were synthesized and characterized.•These complexes show high in vitro anticancer activity with nanomolar IC50 values.•The catalytic activity for glutathione oxidation was studied by NMR spectroscopy.

A series of cationic dinuclear p-cymene ruthenium complexes containing three thiolato bridges with different substituents at the sulfur atoms, [(η6-p-MeC6H4iPr)2Ru2(μ2-SR1)2(μ2-SR2)]+ (R1 = CH2Ph, R2 = Ph: 4; R1 = CH2Ph, R2 = p-C6H4iPr: 5; R1 = CH2Ph, R2 = p-C6H4tBu: 6; R1 = CH2Ph, R2 = p-C6H4OH: 7; R1 = CH2Ph, R2 = p-C6H4Br: 8; R1 = CH2Ph, R2 = p-C6H4F: 9; R1 = CH2CH2Ph, R2 = Ph: 10; R1 = CH2CH2Ph, R2 = p-C6H4iPr: 11; R1 = CH2CH2Ph, R2 = p-C6H4tBu: 12; R1 = CH2CH2Ph, R2 = p-C6H4OH: 13; R1 = CH2CH2Ph, R2 = p-C6H4Br: 14; R1 = CH2CH2Ph, R2 = p-C6H4F: 15; R1 = CH2C6H4–p-tBu, R2 = Ph: 16; R1 = CH2C6H4–p-tBu, R2 = p-C6H4iPr: 17; R1 = CH2C6H4–p-tBu, R2 = p-C6H4tBu: 18; R1 = CH2C6H4–p-tBu, R2 = p-C6H4OH: 19; R1 = CH2C6H4–p-tBu, R2 = p-C6H4Br: 20; R1 = CH2C6H4–p-tBu, R2 = p-C6H4F: 21), have been obtained from the reaction of the neutral dithiolato intermediates [(η6-p-MeC6H4iPr)2Ru2Cl2(μ2-SR1)2] (R1 = CH2Ph: 1; R1 = CH2CH2Ph: 2; R1 = CH2C6H4–p-tBu: 3) with the corresponding thiophenol R2SH. All cationic complexes have been isolated as their chloride salts and fully characterized by spectroscopic and analytical methods. All complexes are highly cytotoxic against human ovarian cancer cells, the IC50 values being in the submicromolar range. The highest activity is shown by complex 6 with IC50 values of 48 nM against the A2780 cell line and 42 nM against the cisplatin-resistant line A2780cisR. This family of cationic trithiolato complexes belongs to the most cytotoxic ruthenium compounds ever reported. The catalytic activity selected representatives for the oxidation of glutathione (GSH) to GSSG has been investigated by NMR spectroscopy.

Graphical abstractEighteen cationic dinuclear p-cymene ruthenium complexes containing three thiolato bridges with different substituents at the sulfur atom have been synthesized and characterized. They belong to the most cytotoxic ruthenium complexes reported so far, the IC50 values for A2780 and A2780cisR cell lines being in the nanomolar range.Figure optionsDownload full-size imageDownload as PowerPoint slide