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

Abstract 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.