Cyclometalated Platinum(II) Complexes of Lepidine-Based Ligands as Highly Efficient Electrophosphors

A new series of lepidine-containing-ligand-based cyclometalated platinum(II) complexes 1−7 with general formula [Pt(L)acac] (L = lepidine-based ligand, acac = acetylacetonate) have been synthesized. The complexes have been characterized using spectral and electrochemical techniques. The single-crystal X-ray structures of complexes 2 and 5 have been successfully determined. The effects of substituents on the electronic features and redox potentials of the cyclometalated phenyl ring of the complexes are discussed. Complexes 1−7 are highly phosphorescent in fluid as well as in solid state, covering a rather broad spectral range from yellow to saturated red. These complexes were successfully used as a dopant material to fabricate the electroluminescent device, ITO/NPB (40 nm)/CBP-doped Pt complex (5 wt %) (20 nm)/BCP (10 nm)/Alq3 (20 nm)/LiF (1 nm)/Al (150 nm), which exhibits very promising performance. The device doped with 5 wt % 3 produced a maximum external quantum efficiency of 15.2% with a maximum brightness of 26847 cd m−2 and corresponds to a luminance efficiency of 29.83 cd A−1.