Cationic ruthenium(III) maltolato–imidazole complexes — Synthesis, characterization, and antiproliferatory activity** Adapted from the Ph.D. thesis of D.C. Kennedy (see the References section).

The cationic RuIII complexes, trans-[Ru(ma)2(L)2]CF3SO3, where Hma = maltol = 3-hydroxy-2-methyl-4-pyrone; L = imidazole (Im) (complex 2), 1(N)-methylimidazole (N-MeIm) (3), 2-methylimidazole (2-MeIm) (4), and 4-methylimidazole (4-MeIm) (5), were synthesized via the known L = EtOH (complex 1a), and characterized by elemental analysis, 1H NMR and IR spectroscopies, mass spectrometry, cyclic voltammetry, and (for 3 and 4) by X-ray crystallography. The trans-[Ru(ma)2(H2O)2]CF3SO3 complex (1b) was inadvertently isolated and characterized crystallographically, and the monomaltolato species [Ru(ma)(N-MeIm)4][CF3SO3]2 (6) was also isolated and characterized. In vitro antiproliferatory activity of complexes 2-6 against human breast cancer cells (MDA-MB-435S) was tested using an MTT assay: 4 and 5 exhibit the lowest IC50 values,  5 and  15 µmol/L, respectively, whereas cisplatin exhibits an IC50 value of  35 µmol/L against this cell line.