Synthesis, characterisation and biological properties of gold(iii) compounds with modified bipyridine and bipyridylamine ligands

Square planar gold(III) complexes that contain functionalised bipyridine ligands of general formula [Au(N⁁N)Cl2][PF6] [where N⁁N = 2,2′-bipyridine, 4,4′-dimethyl-2,2′-bipyridine, 4,4′-dimethoxy-2,2′-bipyridine and 4,4′-diamino-2,2′-bipyridine] have been prepared and characterised by NMR spectroscopy and mass spectrometry. Two of the complexes have also been characterised in the solid state by X-ray crystallography. In addition, a gold(III) compound bearing a dipyridin-2-ylamine ligand was also prepared and characterised. The complexes were found to undergo hydrolysis under pseudo-physiological conditions. Moreover, the complexes showed moderate to good cytotoxicity in vitro towards the A2780 human ovarian carcinoma cell line and the cisplatin resistant variant A2780cisR. Reactivity studies with biomolecules, such as reducing agents, plasmid DNA and a model protein (ubiquitin) were also performed to provide tentative insights into the mode of action of the complexes.