Synthesis, Characterization And Properties Of Diazine Phosphorescent Iridium(Ⅲ) Complexes

In recent decades, organic light-emitting diodes (OLEDs) based on phosphorescentcomplexes have attracted increasing attention due to their potential application in full-color flatpanel displays.Among these phosphorescent complexes, iridium cyclometalates often exhibitfavorable photoproperties for OLEDs including short phosphorescent lifetimes, high quantumeffciencies and good stability.In this dissertation, a series of diazine ligands and their iridium(III) diazine complexes weresynthesized and characterized. This dissertation is comprised of the following four parts.(1) Iridium(III) complexes of (MPPM)2Ir(pic)、(MPPM)2Ir(acac)、(DFPPM)2IrN4、(MDFPPM)2Ir(pic) and (MDFPPM)2IrN4have been designed and synthesized [MPPM=2-phenyl-4,6-dimethyl pyrimidine、DFPPM=2-(2,4-difluoro phenyl) pyrimidine、MDFPPM=2-(2,4-difluorophenyl)-4,6-dimethyl pyrimidine, acac=acetylacetone、pic=picolinate、N4=5-(2-Pridyl)-1H-tetrazole].Their structures were characterized by nuclear magnetic resonance (1HNMR) and IR spectroscopy.(2) Iridium(III) complexes of (DFPPM)2Ir(acac)、(DPPF)2Ir(acac)、(DPP)2Ir(acac)、(MDFPPM)2IrN4、(MDFPPM)2Ir(acac) and(MDPP)2Ir(acac) have been characterized by X-raysingle crystal diffraction. X-ray diffraction studies have revealed that (DPP)2Ir(acac) belongs to thespace groups of P21/n and P-1;(DPPF)2Ir(acac) belongs to the space groups of C2/c and P-1;(MDPPF)2Ir(acac) belongs to the space groups of P-1；(MDPP)2Ir(acac) belongs to the spacegroups of P2(1)/c；(MDFPPM)2IrN4belongs to the space groups of P21/c；(DFPPM)2Ir(acac)belongs to the space groups of P-1. We can see the structure of complexes clearly via iridiumcomplexes ellipsoid chart.(3) Photophysical and electrochemical properties of these complexes were investigated. Theresults of UV spectra showed that all of these iridium complexes had intense absorption peaksfrom metal-to-ligand charge transfer (MLCT) transitions, which indicates these diazine iridium(III)complexes should be used as novel electrophosphorescent materials. Photoluminescence spectrastudies have shown that these iridium(III) complexes have strong phosphorescence emission at room temperature. Electrochemical studies have shown that this kind of iridium(III) complexeshave good redox reversibility. In addition, the influences of chemical structure of ligands on thephotophysical and electrochemical properties of complexes were investigated in detail.(4) Two iridium complexes were used as dopants to fabricated electrophosphosrescentorganic light-emitting devices (OLEDs). The device based on (MDPPF)2Ir(acac)with turn-onvoltage of4.0V has electroluminescent emission peak at585nm, maximum brightness of23080cd/m2, current efficiency of64.1cd/A, and power efficiency of50.4lm/W. The device of(DFPPM)2Ir(acac) with turn-on voltage of5.0V has electroluminescent emission peak at494nm,maximum brightness of21400cd/m2, current efficiency of12.0cd/A, power efficiency of5.4lm/W. The results show that (MDPPF)2Ir(acac) and (DFPPM)2Ir(acac) are good phosphorescentmaterials for highly efficient organic electrophosphorescent devices.