"Synthesis, Characterization, and Biological Activity of Cationic Ruthenium-Arene Complexes with Sulfur Ligands"

Mohammed Zain Aldin, Guillermo Zaragoza, Eva Choquenet, Guillaume Blampain, Gilles Berger, and Lionel Delaude

journal cover 
          source: Journal of Biological Inorganic Chemistry
            year: 2024
          volume: 29
      first page: accepted for publication
       last page: 
             doi:
graphical abstract

Abstract: Five cationic ruthenium-arene complexes with the generic formula [Ru(SAc)(S2C·NHC)(p-cymene)](PF6) (5a-e) were prepared in almost quantitative yields using a straightforward one-pot, two-step experimental procedure starting from [RuCl2(p-cymene)]2, an imidazol(in)ium-2-dithiocarboxylate (NHC·CS2) zwitterion, KSAc, and KPF6. These half-sandwich compounds were fully characterized by various analytical techniques and the molecular structures of two of them were solved by X-ray diffraction analysis, which revealed the existence of an intramolecular chalcogen bond between the oxygen atom of the thioacetate ligand and a proximal sulfur atom of the dithiocarboxylate unit. DFT calculations showed that the C=S...O charge transfer amounted to 2.4 kcal mol-1. The dissolution of [Ru(SAc)(S2C·IMes)(p-cymene)](PF6) (5a) in a DMSO-d6/D2O mixture at room temperature did not cause the dissociation of its sulfur ligands. Instead, p-cymene was slowly released to afford the 12-electron [Ru(SAc)(S2C·IMes)]+ cation that could be detected by mass spectrometry. Monitoring the solvolysis process by 1H NMR spectroscopy showed that more than 22 days were needed to fully decompose the starting ruthenium-arene complex. Compounds 5a-e exhibited a high antiproliferative activity against human glioma Hs683 and human lung carcinoma A549 cancer cells. In particular, the IMes derivative (5a) was the most potent compound of the series, achieving toxicities similar to those displayed by marketed platinum drugs.

Keywords: Cellular Uptake, Chalcogen Bond, Cytotoxicity, 1,1-Dithiolate Ligand, Thioacetate Ligand, Zwitterion

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