Preparation, characterization and crystal structure of dibromrido(5,5'-dimethyl-2,2'-bipyridine)gold(III)tetrabromridoaurate(III) complex

A new complex of [Au(5,5'-dmbipy)Br2][AuBr4] (1) was prepared from the reactions of AuBr3 with 5,5'-dimethyl-2,2'-bipyridine (5,5'-dmbipy) ligand in a mixture of methanol/acetonitrile. This complex was characterized by elemental analysis, IR, UV–Vis, 1H NMR, 13C{1H}NMR, and luminescence spectroscopy. Furthermore, its structure was determined by the X-ray diffraction method. Crystal data for 1: a=7.7057(3), b=13.9836(3), c=18.9763(9)Å and β =93.554(3)°. The structure of the title complex consists of one [Au(5,5'-dmbipy)Br2] cation and one [AuBr4]– anion. In both of the cation and anion parts, the Au(III) atoms have a distorted square planar coordination. In the crystal structure of the title complex, intermolecular C-H…Br hydrogen bonds and Br…π interactions are effective in the stabilization of the crystal structure. The luminescence spectrum of the title complex shows that the intensity of its emission band is smaller than that of the emission band for the free 5,5'-dmbipy ligand. However, its intensity has shifted towards longer wavelengths.