Synthesis, crystal structure and solution studies of gold(III) complexes with 1,1-dimethylbiguanide

Two novel gold(III) complexes with biologically active 1,1-dimethylbiguanide have been synthesized and structurally characterized. The reactivity of the neutral complex in solution has been studied. [Display omitted] •Metal complexes with 1,1-dimethylbiguanide are important for biomedical applications.•Synthesis and crystal structures of two novel gold(III) complexes with 1,1-dimethylbiguanide are reported.•The substitution of Cl– by OH – and the redox interaction with glutathione and cysteine in aqueous solution have been studied for [Au(dmbg)Cl2]. New gold(III) complexes of the composition [Au(dmbgH)Cl2][AuCl4] · H2O and [Au(dmbg)Cl2], where dmbgH is 1,1-dimethylbiguanide and dmbg is deprotonated 1,1-dimethylbiguanide, were synthesized. The resulting compounds were characterized by elemental analysis, IR spectroscopy, 1H NMR spectroscopy, X-ray single crystal and X-ray powder diffraction analyses. In both compounds, 1,1-dimethylbiguanide, regardless of its charge (0 or −1), is bidentately coordinated to gold(III) through the nitrogen atoms of the imino groups. The processes occurring in solutions for the neutral [Au(dmbg)Cl2] complex were studied: the equilibrium of substitution of Cl– by OH– and the redox interaction with glutathione and cysteine in an aqueous solution at t = 25 °C and I = 0.2 M (NaCl).