Synthesis, Structure, and OLEDs Application of Cyclometalated Iridium(III) Complexes Utilizing Substituted 2‐Phenylpyridine

The syntheses, structures, photophysical, and electroluminescent properties of three green emitting heteroleptic cyclometalated iridium(III) complexes, (ptfmppy) 2Ir(pic) (Ir1), (dfptfmppy) 2Ir(pic) (Ir2), and (tfptfmppy) 2Ir(pic) (Ir3) [ptfmppy = 5-(trifluoromethyl)-2-(phenyl)pyridine, dfptfmppy = 5-(trifluoromethyl)-2-(2,4-difluorophenyl) pyridine, tfptfmppy = 5-(trifluoromethyl)-2-(2,3,4-difluorophenyl)pyridine, and picH = picolinic acid] and the results of an investigation on their suitabilities for phosphorescent organic light-emitting diodes (phOLEDs) applications are reported. X-ray single crystal structures showed that iridium(III) cations in Ir1 and Ir2 adopted six-coordinated geometries involving two C and two N atoms from substituted-ppy, and one N and one O atom from pic, which produced a distorted octahedral geometry. Photoluminescence (PL) spectra revealed that the synthesized iridium(III) complexes exhibited emissions at 497 ~ 534 nm in dichloromethane with high photoluminescence quantum yield (PLQY) ranging from 60 to 67%, and TGA experiments showed that they had good thermal stabilities. In Ir3, the conjugation effect rather than the electronic effect of the 3-positioned fluorine atom on phenyl ring of ppy increased the HOMO energy level causing bathochromic shifts. Electroluminescent devices of ITO(110 nm)/PEDOT:PSS (40 nm)/PVK:TCTA:OXD-7:Ir (80 nm)/TmPyPB (20 nm)/Al (100 nm) were fabricated using the iridium(III) complexes as phosphors in an emitting layer, and their electroluminescent performances were investigated.