Structural, photophysical, and catalytic properties of Au(I) complexes with 4-substituted pyridines

Ionic gold(I) complexes with general formula of Au(Py)2]AuCl2] and Au(Py)2]PF6] (Py = 4-substituted pyridines) have been synthesized. Structures of five Au(I) complexes and a Ag(I) complex were determined by single crystal X-ray diffraction. Evidence for cationic aggregation of Au(py)2]PF6] complexes in solution was obtained by conductivity measurements and by the isosbestic point observed from variable temperature UV-visible absorption spectra. All compounds were luminous in the solid state. Calculations employing density functional theory were performed to shed light on the nature of the electronic transitions. While the Au(4-dmapy)2]AuCl2] (4-dmapy = 4-dimethylaminopyridine) and Au(4-pic)2]AuCl2] (4-pic = 4-picoline) emissions were found to be mainly ligand in nature, their PF6](-) counterparts involved a Au...Au-interaction imbedded in the highest occupied molecular orbital. Au(4-dmapy)2]AuCl2] was found to be an efficient catalyst for Suzuki cross-coupling of aryl bromide and phenylboronic acid.