Ruthenium(II) Sulfoxide−Maltolato and −Nitroimidazole Complexes: Synthesis and MTT Assay

RuII sulfoxide−maltolato complexes, Ru(ma)2(L)2 (L = DMSO (1a) and TMSO (1b) or L2 = BESE (1c)), were
synthesized, as well as the analogous ethylmaltolato derivatives, Ru(etma)2(L)2 (2a−c) (ma = 3-hydroxy-2-methylpyran-4-onate, etma = 2-ethyl-3-hydroxypyran-4-onate, TMSO = tetramethylene sulfoxide, BESE = 1,2-bis(ethylsulfinyl)ethane). A RuII bidentate sulfoxide−metronidazole complex, RuCl2(BESE)(metro)2 (3), was also
synthesized (metro = metronidazole = 2-methyl-5-nitroimidazole-1-ethanol). The complexes were characterized
generally by 1H NMR, UV−vis, and IR spectroscopies, as well as MS, elemental analysis, solution conductivity,
and cyclic voltammetry. The molecular structures of Ru(ma)2(S,R-BESE) (1c) and trans-RuCl2(R,R-BESE)(metro)2
(3) were determined by X-ray crystallography. All sulfoxide ligands are S-bonded. The complexes were tested
against human breast cancer cells (MDA-MB-435S) using an in vitro MTT assay, a colorimetric determination of
cell viability:  2a,b exhibit the lowest IC50 values of 190 ± 10 and 220 ± 10 μM, respectively. Cisplatin exhibits an
IC50 value of 30 ± 5 μM.