Syntheses of ruthenium(II)-4,4'-biimidazole complexes and their potential anti-tumour activity

Synthesis and characterization of the RuII complexes, [Ru(N-N)3][CF3SO3]2, where N-N is 4,4'-biimidazole (complex 1a) or 2,2'-dimethyl-4,4'-biimidazole (1b), and the dimethylsulfoxide complexes RuCl2(DMSO)2(N-N) are reported. The air-stable, water-soluble complexes were characterized by elemental analysis, 1H NMR and IR spectroscopies, mass spectrometry, and solution conductivity. Evidence is presented also for the existence of the diruthenium complexes Ru2Cl4(DMSO)4(N-N), but there are insufficient data for elucidation of their structure. The complexes (and cisplatin) were tested against human breast-cancer cells (MDA-MB-435S) using an in vitro MTT assay, a colorimetric determination of cell viability: 1a and 1b exhibit the lowest IC50 values of 18 +/- 5 and 36 +/- 5 mol/L, respectively, with cisplatin exhibiting an IC50 value of 35 +/- 5 mol/L. Isolation of DNA from cells treated with a solution of the Ru species showed no evidence of DNA-binding to the metal, although examination of the cells indicated that Ru was being taken up into the cells.