Synthesis and characterization of phosphorescent iridium complexes containing trifluoromethyl-substituted phenyl pyridine based ligands

Several iridium complexes containing trifluoromethyl-substituted phenyl pyridine based ligands have been synthesized and characterized to try to investigate the effect of trifluoromethyl group and its position on physical properties. The complexes have the general structure of (C–N)2Ir(LX), where the C–N are 2-phenylpyridine (ppy), 2-(3,5-bis-trifluoromethylphenyl)pyridine (fmppy), 2-(3,5-bis-trifluoromethylphenyl)-4-methylpyridine (fmpmpy), 2-(3,5-bis-trifluoromethylphenyl)-5-trifluoromethylpyridine (tfmppy) and the LX are 2-picolinic acid (pic) and acetylacetonate (acac). The (tfmppy)2Ir(pic) was characterized using X-ray crystallography. The absorption, emission, and thermostability of the complexes were systematically investigated. Introduction of CF3 substituents into 2-phenylpyridine in (ppy)2Ir(pic) lead to some decrease in the sublimation temperature, which is more suitable to devices fabrication. The experimental results revealed that the emissive colors of these complexes could be finely tuned by suitable incorporation of trifluoromethyl substituents on the 2-phenylpyridine ligand, obtaining bright green-blue emission λmax values from 471 to 489 nm in CH2Cl2 solution at room temperature, with high solution quantum efficiencies ranging from 0.37 to 1.89 relative to Ir(ppy)3.