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

Two new cyclometallated platinum(II) complexes have been prepared that incorporate a terdentate (NCN)-C-boolean AND-N-boolean AND-coordinating ligand and a monodentate acetylide co-ligand. The complexes, namely [PtL3-C C-C6H3F2] and [PtL6-C C-C6H3F2] (where HL3 = 5-methyl-1,3-di(2-pyridyl)benzene; HL6 = 5-mesityl-1,3-di(2-pyridyl)benzene; H-C C-C6H3F2 = 3,5-difluorophenylacetylene), were prepared by ligand metathesis from the corresponding chloro complex (PtLCl)-Cl-n. Both of the new complexes are intensely luminescent in solution, displaying quantum yields superior to (PtLCl)-Cl-n. 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.