Blue-Phosphorescent Pt(II) Complexes of Tetradentate Pyridyl-Carbolinyl Ligands: Synthesis, Structure, Photophysics, and Electroluminescence.

Blue phosphorescent tetradentate pyridyl-carbolinyl Pt(II) complexes, Pt(ppzOclpy-Me), Pt(ppzOclpy-iPr), and Pt(ppzOclpy-mesi), were purposefully synthesized and investigated with their photophysical and luminescent properties. The complexes, incorporating with carbolinyl moieties, have twisted planar structure. X-ray crystallography revealed that the intraligand N···H-C hydrogen bond reversely turned the twisty pyridyl moiety back into the chelating plane. Computational analyses confirmed that the metal-to-ligand charge-transfer transition character appears in the singlet manifolds. However, the ligand-centered transitions rule in their triplet states, which accounts for the phosphorescent emission. The Pt(II) complexes emit blue light with peak wavelengths (λmax) of 461-481 nm and moderate photoluminescent quantum yields (Φ = 34-46% in dichloromethane and Φ = 44-52% in films). The electroluminescent devices were fabricated by solution processes, giving blue emissions peaking at around 470 nm.