Three-coordinate gold(I) N-heterocyclic carbene complexes: a new class of strongly luminescent derivatives.

A selected group of cationic three-coordinate Au(I)-NHC complexes of the form [Au(NHC)(dppbz)]OTf have been prepared from a commercially available bidentate phosphine. All complexes have been fully characterised by NMR and mass spectroscopy. The [Au(NHC)](+) fragment shows a pronounced tendency to form linear complexes which is confirmed by the molecular structure of [Au(IPr)(dppbz)]OTf in the solid state. The complexes are brightly luminescent and present very high quantum yield values in the solid state. The assignments of the electronic transitions involved in the emissions are of a phosphorescent nature and it is proposed that the origin of the emissions is derived from the ligand (dppbz) to metal-ligand (Au-NHC) charge-transfer (LML'CT) transition.