Novel N^C^N-cyclometallated platinum complexes with acetylide co-ligands as efficient phosphors for OLEDs

Abstract

Two new cyclometallated platinum(II) complexes have been prepared that incorporate a terdentate N^C^N-coordinating ligand and a monodentate acetylide co-ligand. The complexes, namely [PtL³–CC–C₆H₃F₂] and [PtL⁶–CC–C₆H₃F₂] (where HL³ = 5-methyl-1,3-di(2-pyridyl)benzene; HL⁶ = 5-mesityl-1,3-di(2-pyridyl)benzene; H–CC–C₆H₃F₂ = 3,5-difluorophenylacetylene), were prepared by ligand metathesis from the corresponding chloro complex PtLⁿCl. Both of the new complexes are intensely luminescent in solution, displaying quantum yields superior to PtLⁿCl. OLEDs have been prepared using the new compounds as phosphorescent emitters. Although both lead to efficient devices, the best electroluminescence quantum efficiencies are obtained with the derivative of HL⁶, having the mesityl group on the cyclometallated phenyl ring. The superior performance with this complex can be rationalised in terms of the greater steric hindrance that serves to reduce aggregate-induced quenching.