N-Heterocyclic Carbene Coinage Metal Complexes as Intense Blue-Green Emitters

The reaction of N-methyl (Me) or N-benzyl (Bn) imidazole with 9-chloroacridine (9-ClAcr) gives the corresponding imidazolium salts, [(RimAcr)H]Cl (R = Me, Bn), which can further react with AgBF4 or [Au(C6F5)(tht)], affording the new salts [(RimAcr)H]BF4 or [(RimAcr)H][Au(C6F5)Cl]. Silver(I) carbene complexes of the form [AgCl(RimAcr)] or [Ag(RimAcr)(2)]BF4 are synthesized by reaction of the corresponding imidazolium salts with Ag2O or Ag2O and NaOH. Transmetalation reactions allow the synthesis of the gold and copper derivatives [MCl(RimAcr)] (M = Au, Cu) and [Au(RimAcr)(2)]BF4. Treatment of [(RimAcr)H]{Au(C6F5)Cl] with NaH affords the synthesis of the carbene complexes [Au(C6F5)(RimAcr)]. The crystal structures of these complexes show interesting pi center dot center dot center dot pi stacking interactions between the acridine and/or the pentafluorophenyl groups. The imidazolium salts and the gold and silver complexes are intense blue-green emitters.