Synthesis And Properties Of Iridium Complexes Based On Imidazopyridine Groups And Poly(9-(4-vinylbenzyl)-9H-carbazole)Derivatives

Phosphorescent Ir(Ⅲ)complexes can realize very high luminous efficiency and relatively short phosphorescent lifetime.However,the most outstanding characteristic of this class of complexes might be the variability of the electro-optical properties.Their metal–ligand-based luminescence provides the opportunity to tune the emission color over the whole visible spectrum by varying the attached ligands.All these criteria make iridium(III)complexes highly appealing as phosphors in multicolor organic lightemitting diodes(OLED).The ongoing peak of interest in carbazolecontaining polymers is connected mostly with the discovery of polymeric light emitting diodes and organic photorefractive materials.In all these fields of application photoconductive properties of carbazole-containing polymers and their ability to transport holes are exploited.PVK containing blue,green or orange emitting fluorescent dyes was demonstrated to be useful as hole transport and emitting layer in organic electroluminescent devices.In the chapter 2,we synthesized three novel imidazopyridine-based cyclometalated iridium complexes from 2-cyanopyridine by Grignard,homogeneous Cu-catalyzed decarboxylation,and Nonoyama reactions.The thermal,photophysical and electrochemical properties of iridium complexes were studied by changing the substituents on the benzene ring of the organic ligand C-chelating unit in the iridium complexes.The thermal decomposition temperature of these phosphorescent iridium complexes is about 300 ~oC,and they have good thermal stability.The newly synthesized iridium complexes have high fluorescence quantum efficiency,and their HOMO and LUMO energy levels fall in the energy band gap of1,3-Bis(carbazol-9-yl)benzene(m CP),which is the host material in the electroluminescence(EL)devices,and efficient energy transfer can be achieved between them.They are blue emitters and can be used in blue and white phosphorescent polymer EL devices.In the chapter 3,two monomers M1 and M2 were prepared from carbazole by a series of reactions including phase transfer catalysis,bromination and suzuki coupling.Two homopolymers P1 and P2 and two copolymers P3 and P4 were obtained by adjusting the molar ratio of monomer M1 and M2 in the free radical polymerization mediated by azodiisobutyronitrile(AIBN).The thermal properties,photophysical properties and electrochemical properties of the corresponding polymers were studied.The thermal decomposition temperature of the four polymers is above 210 ~oC,and they have good thermal stability.The glass transition temperature is about 90 ~oC,which is amorphous in nature.They can be used as purple luminescent materials because of their strong violet emission with the maximum fluorescence emission peak of about 400 nm.The newly synthesized polymers have high fluorescence quantum efficiency,and their HOMO and LUMO energy levels are basically similar to those of Poly(N-vinylcarbazole)(PVK),which is the hole-transport materials in EL devices,indicating that these polymers possess the electrochemical properties of hole-transport materials and can be used as hole-transport materials in EL devices.