Novel blue-phosphorescent platinum(II) ternary complexes with β-diketonate and fluorinated phenylimidazole for organic light-emitting diodes

In this study, the one-pot synthesis of two novel Pt(II) β-diketonate compounds, namely Pt(tpim)(O^O) (1) and Pt(mtpim)(O^O) (2) (tpim = 1-([1,1′:3′,1′′-terphenyl]-2′-yl)-2-(4-fluorophenyl)-1 H-imidazole, mtpim = 2-(4-fluorophenyl)-1-(5′-methyl-[1,1′:3′,1′′-terphenyl]-2′-yl)-1 H-imidazole, and O^O = acetylacetonato), was achieved. Both compounds had a distorted square-planar geometry without direct intermolecular Pt(II)—Pt(II) interactions, which was attributed to the bulky terphenyl group of the C^N chelate as well as strong intermolecular Pt(II)—H(terphenyl/imidazole) interaction. Compounds 1 and 2 exhibited bright sky-blue-phosphorescent emission with a λ max = 490 nm and photoluminescence quantum yields of 0.50 and 0.47, respectively. The time-dependent density functional theory calculations revealed that the electronic transitions of both compounds were attributed to the combination of intraligand charge transfer (π (phenylimidazole) –π* (terphenyl) ) and ligand-to-ligand charge transfer (π (acac) –π* (terphenyl) ), in addition to a contribution from the metal-to-ligand charge transfer (Pt d –π* (terphenyl) ). Compounds 1 and 2, as the dopants, and 3′-di(9 H-carbazol-9-yl)-1,1′-biphenyl:9-(3'-carbazol-9-yl-5-cyano-biphenyl-3-yl)-9 H-carbazole-3-carbonitrile, as the mixed host were used to fabricate multilayer phosphorescent organic light-emitting diodes. Compound 1 doped in the emissive layer at a 10% doping level demonstrated a maximum current efficiency of 21.7 cd A −1 at 100 cd m −2 .