Synthesis And Property Of Some Novel Iridium Complexes

Seven iridium(Ⅲ) phosphors with the structure of (tfinppy)2Ir(L1～L7) were de-signed and synthesized, where tfinppy is 4-trifluoromethylphenylpyridine and L1-L7 are fluorine or trifluoromethyl substituted N-(diphenylphosphoryl)benzamide deriva-tives ancillary ligands. These complexes were fully characterized and investigated by 1H NMR, high-resolution MS, X-ray single crystal diffraction, cyclic voltammetry and theoretical calculation. All the complexes are all green emitters with the emission peaks around 520 nm. Their emission decay times were about 2μs at ambient temper-ature and the quantum efficiencies were in the range of 37.5-61.2%.Sixteen blue and greenish-blue Ir(Ⅲ) phosphors with the structure of (dfp-py)2Ir(NHC) were prepared, where NHC is N-heterocyclic carbene cyclometalated ligand and dfppy is 2-(2,4-difluorophenyl)pyridine. The Ir(Ⅲ) complexes display typical phosphorescence in the range of 455-485 nm with quantum yields up to 0.73 and lifetimes of 1.7-2.1μs. By modifying the phenyl moiety in the NHCs with elec-tron-withdrawing substituents (-F or -CF3) or replacing it with N-hetero-aromatic rings (pyridine or pyrimidine), the HOMO-LUMO gaps are broadened and the emis-sions shift to the more blue region accordingly. Furthermore, to extend the application scope of NHCs as the second cyclometalated ligands, five other Ir(Ⅲ) complexes with different emissions from blue to red were synthesized with different first cy-clometalated ligands. Finally, the organic light-emitting diodes (OLEDs) using Ir5b exhibit a maximum current efficiency of 37.83 cd A-1, an external quantum efficiency of 10.3% and a maximum luminance of 8709 cd m-2. It is one of the best performanc-es for OLEDs using carbene based Ir(Ⅲ) complex as emitter in the blue-light-emitting region. The results demonstrate that the second cyclometalated NHCs are good can- didates for efficient phosphorescent Ir(Ⅲ) complexes and corresponding devices.