Synthesis And Optoelectronic Properties Of Novel Iridium Complexes With Deep Red And Near-Infrared Luminescence

The organic materials with the emissive deep-red or near-infrared（NIR）character are highlighted due to their potential applications in night vision,information security display,and medical fields.In this perspective,upon the heavy atomic effect of transition metal complexes with the theoretical quantum efficiency up to 100%,phosphorescent transition-metal iridium（Ⅲ）and platinum（II）complexes for deep red and near-infrared electroluminescent devices are much concerned.In contrast to the relatively heavier efficiency-roll-off for tetrahedral platinum（II）complex with theπ-πstacking effect and the intrinsic longer phosphorescence lifetime,the Ir（Ⅲ）-complex with octahedral configurations and the relative short phosphorescence lifetime shows the trade-off of both good luminous efficiency and weak efficiency-roll-off.Therefore,this thesis is focused on the synthesis of six novel Ir（Ⅲ）-complexes with deep red and near-infrared luminescence,and the relation-ship between the structure and the photo-physical property is deeply investigated.Moreover,using the selected mononuclear or binuclear Ir（Ⅲ）-complex with good NIR luminescence as the guest,their near-infrared polymer light-emitting diodes（NIR-PLEDs）are fabricated.The main contents are shown as follows:（1）By changing the conjugation of the main ligand,1-（benzo[b]thiophen-2-yl）–isoquinolinate（Hiqbt）or 2,3-diphenylbenzo[g]quinoxaline（Hdpbq）,and using8-hydroxyquinolinean as the ancillary ligand,two nevel Ir（Ⅲ）-complexes[Ir（iqbt）₂（8-q）]and[Ir（dpbq）₂（8-q）]were synthesized,respectively.Based on the photophysical and the electrochemical properties of those two Ir（Ⅲ）-complexes,it is proved that the bathochromic shift of the emissive wavelength into the strictive NIR region can be realized after the introduction of the main ligand Hdpbq with a larger conjugated structure,in which,the Ir（Ⅲ）-complex[Ir（iqbt）₂（8-q）]exhibits a deep red emission peaked at 678 nm(deep red;Φ_em=0.16),while[Ir（dpbq）₂（8-q）]shows a typical NIR emission peaked at 786 nm(NIR;Φ_em=0.05).Besides that,the phosphorescence quantum yield of[Ir（dpbq）₂（8-q）]is relatively lower than that of[Ir（iqbt）₂（8-q）].（2）Under the condition of the usage of the same C^N main ligand（Hiqbt）,the approach to asymmetric binuclear Ir（Ⅲ）-complex is founded on the introduction of the bis-β-diketone H₂btp as the ancillary ligand,from which,two novel Ir（Ⅲ）-complexes[（iqbt）₂Ir-（btp）-Ir（iqbt）₂](λ_em=722 nm andΦ_em=0.15)and[（dpbq）₂Ir-（btp）-Ir（dpbq）₂](λ_em=781 nm andΦ_em=0.09),were synthesized,respectively.For comparison,two new mononuclear Ir（Ⅲ）-complexes[Ir（iqbt）₂（btfa）](λ_em=698 nm andΦ_em=0.08)and[Ir（dpbq）₂（btfa）](λ_em=776 nm andΦ_em=0.05)were also prepared,respectively.Their photophysical property result shows that compared with the mononuclear Ir（Ⅲ）-complexes,the emissive wavelength of the dinuclear Ir（Ⅲ）-complexes with asymmetric structure has a certain degree of bathochromic shift,exhibiting both the typical near-infrared luminescence and the improved quantum yield to some extent.（3）Employingthemononuclear[Ir（iqbt）₂（btfa）]orthedinuclear[（iqbt）₂Ir-（btp）-Ir（iqbt）₂]with relatively higher NIR quantum yield,the NIR-PLEDs with the doping into PVK-OXD7(PVK:poly（N-vinylcarbazole and OXD-7:1,3-bis（5-（4-tert-butyl-phenyl）-1,3,4-oxadiazol-2-yl）benzene）as the light-emitting layer were fabricated,respectively.Their electroluminescence properties show that:For the NIR-PLED based on the asymmetric binuclear Ir（Ⅲ）-complex[（iqbt）₂Ir-（btp）-Ir（iqbt）₂](λ_em=720 nm),it gives a maximum external quantum efficiency of 3.11%and a maximum irradiance 0.140W/sr×m²,which are relatively higher than those（1.12%and 0.047 W/sr×m²）for the NIR-PLED from the mononuclear complex[Ir（iqbt）₂（btfa）](λ_em=702 nm).Moreover,the character of their efficiency-roll-off（<5%）is also expected.