Effects of Counter Anions on Intense Photoluminescence of 1-D Chain Gold(I) Complexes

A series of cationic carbene complexes of Au(I) with different types of counteranions, [Au{C(OMe)NHMe}2]+(X−) (X− = CF3SO3−, PF6−, CF3CO2−, ClO4−, and I−), was synthesized, and their intense photoluminescence was studied. These complexes crystallize in the same space group, and the X-ray crystallographic data of these samples revealed the short Au(I)−Au(I) aurophilic distances (3.263−3.335 Å), where planar carbene Au(I) complexes are organized into linear stacks. The aurophilic Au(I)−Au(I) interactions found in the crystalline state give rise to phosphorescence with relatively high emission quantum efficiencies, whereas [Au{C(OMe)NHMe}2]+(X−) complexes show no appreciable emission in solutions. The Au(I)−Au(I) distances in the crystal of [Au{C(OMe)NHMe}2]+(X−) vary depending on the type of counteranions because the carbene ligands of Au(I) cations are linked through hydrogen bonds with adjacent counteranions. The effects of counteranions on the Au(I)−Au(I) aurophilic interactions allow one to modulate the intense photoluminescence color from blue to yellow by adjusting the counteranions of [Au{C(OMe)NHMe}2]+(X−) complexes.