Synthesis, characterization, X-ray structure and in vitro antimycobacterial and antitumoral activities of Ru(II) phosphine/diimine complexes containing the “SpymMe2” ligand, SpymMe2 = 4,6-dimethyl-2-mercaptopyrimidine

The reaction of cis-[RuCl2(dppb)(N–N)], dppb = 1,4-bis(diphenylphosphino)butane, complexes with the ligand HSpymMe2, 4,6-dimethyl-2-mercaptopyrimidine, yielded the cationic complexes [Ru(SpymMe2)(dppb)(N–N)]PF6, N–N = bipy (1) and Me-bipy (2), bipy = 2,2′-bipyridine and Me-bipy = 4,4′-dimethyl-2,2′-bipyridine, which were characterized by spectroscopic and electrochemical techniques and X-ray crystallography and elemental analysis. Additionally, preliminary in vitro tests for antimycobacterial activity against Mycobacterium tuberculosis H37Rv ATCC 27264 and antitumor activity against the MDA-MB-231 human breast tumor cell line were carried out on the new complexes and also on the precursors cis-[RuCl2(dppb)(N–N)], N–N = bipy (3) and Me-bipy (4) and the free ligands dppb, bipy, Me-bipy and SpymMe2. The minimal inhibitory concentration (MIC) of compounds needed to kill 90% of mycobacterial cells and the IC50 values for the antitumor activity were determined. Compounds 1–4 exhibited good in vitro activity against M. tuberculosis, with MIC values ranging between 0.78 and 6.25 μg/mL, compared to the free ligands (MIC of 25 to >50 μg/mL) and the drugs used to treat tuberculosis. Complexes 1 and 2 also showed promising antitumor activity, with IC50 values of 0.46 ± 0.02 and 0.43 ± 0.08 μM, respectively, against MDA-MB-231 breast tumor cells.