Gold(I) N-Heterocyclic Carbene and Carbazolate Complexes

Gold(I) carbene complexes of the type [Au(NHC)Cl], where NHC represents N-heterocyclic carbenes, have been synthesized. Two crystal structures of this type show that the molecules are stacked to form a linear polymer with Au···Au interactions. Luminous [Au(NHC)(cbz)] (cbz = carbazolate) were synthesized from [Au(NHC)Cl]. The crystal structure of one of this series indicates that the carbene and cbz rings are coplanar and two molecules are arranged pairwise in a head-to-tail fashion. While all the compounds prepared exhibit high-energy emission bands at ∼400 nm, [Au(NHC)Cl] complexes display additional low-energy emission bands at 580−650 nm, which are attributed to Au-centered transitions involving Au···Au interactions. On the other hand, the low-energy emission bands of the [Au(NHC)(cbz)] complexes, which appear at 584−592 nm with fine structures, are likely to arise from the transitions involving mainly carbazolate tuned by Au, as also suggested by the density functional calculations. Crystal structures of Au(I)-dicarbenes are also reported.