Synthesis and characterization of a series of gold(III) complexes with the 4,4′-dimethyl-2,2′-bipyridine ligand: Counterion influence on the cytotoxicity of gold(III) complexes

A series of Au(III) complexes, [Au(4,4'-dmbipy)X-2]Y-+(-) where X = Cl, Br and Y = [AuCl4], [AuCl2], [ClO4], [AuBr4], were prepared from the reactions of HAuCl4 center dot 3H(2)O/AuBr3 with 4,4'-dimethy1-2,2'-bipyridine (4,4'-dmbipy) in a mixture of alcohol/CH3CN. These complexes were characterized by elemental analysis, IR, UV-Vis, H-1 and C-13 NMR spectroscopy and their structures were studied by the single-crystal diffraction method. The electrochemical behavior of the title complexes were also studied in CH3CN and DMSO using cyclic voltammetry. The cationic parts of the complexes are similar, with a bidentate nitrogenous 4,4'-dmbipy ligand and two halide anions attached to a gold(III) center in a square-planar geometry. However, the effect of the anionic parts of the complexes on the cytotoxic properties was evaluated in four cultures, Vero, A431, HeLa and HT-29 by means of an MTT assay. The results illustrate that the anion part plays an important role in the cytotoxicity of relevant compounds in different cell lines. Complexes 1 and 4, with the similar anion part of [AuX4](-) (X = Cl and Br), displayed good agreement in their anticancer activities toward human cancer cell lines. (C) 2014 Elsevier Ltd. All rights reserved.