Synthesis And Luminescent Properties Of Several Novel Iridium Complexes

Three ancillary ligands containing electron-transporting [l,3.4]oxadiazole moieties,2-(5-phenyl-[1,3,4]oxadiazol-yl)-phenol (HPOP),2-[5-(4-fluoro-phenyl)-[1,3,4]oxadiazol-yl]-phenol (HFPOP),2-[5-(4-trifluoromethyl-phenyl)-[1,3,4] oxadiazol-yl]-phenol (HCF3POP) and their corresponding iridium complexes with2-(3.4,6-trifluorophenyl)pyridine(F3.4.6ppy) as main ligand. Ir(F3.4.6ppy)2POP, Ir(F3.4.6ppy)2FPOP and Ir(F3,4,6ppy)2CF3POP were synthesized and characterized with thermal analysis.’H NMR and MS spectra along with the X-ray crystal structure analysis. The TG-DSC data reveal that all the complexes have good thermal stability with the melting temperatures of291-326℃and the initial decomposition temperatures of393-408℃. In the absorption spectra, the three complexes showed the spin-allowed ligand-centered charge transfer (tâ†'>Ï€*(L) IL) bands and metal-to-ligand charge-transfer (dÏ€(Ir)â†'Ï€*MLCT) bands. The three complexes have strong green emission with maximum peaks in the range of503-521nm with quantum efficiency yields of18.04,12.05and12.87%, respectively. The lifetimes of complexes are in the range of microseconds (1.83-2.14μs in CH2Cl2solution). In the CV spectra, one irreversible oxidation process in the range of0.60-1.20V exists in each of the complexes which is assigned to the metal oxidation. Ir3+-eâ†'Ir4+. The HOMO/LUMO levels are calculated as-5.59/-2.95,-5.58/-2.92and-5.582/-2.91eV, respectively. Five green-emitting heteroleptic indium complexes with2-(4-fluorophenyl)-pyridine (F4ppy),2-(4.5.6-trifluorophenyl)pyridine (F3.-4.5ppy).2-(3.4.6-trifluoro phenyl)pyridine (F3.4.6ppy) or2-(3.4.5-trifluorophenyl)pyridine (F4.5.6PPy) as main ligands and tetraphenylimidodiphosphinate acid (Htpip) or tetra-(4-trifluoromethyl pheny)limidodiphosphinate acid (Htfmtpip) as the ancillaiy ligands were synthesized and fully characterized. The numbers and positions of fluorine atoms on phenyl ring can affect the complexes’ emission properties. Because the application of Htpip as the ancillary ligand can improve the electron mobilities of the complexes to comparable to that of popular electron transport material of Alq3under the same electric fields, the organic light-emitting diodes (OLEDs)(ITO/TAPC (1,1-bis(4-(di-p-tolyl-amino)phenyl)cyclohexane,30nm)/Ir-complex (x wt%):mCP (N.N-dicarbazolyl-3,5-benzene,15nm)/TPBi (1,3,5-tri(1-pheny1-1H-benzo[d] imidazol-2-yl)phenyl.45nm)/LiF (1nm)/Al (100nm)) based on the above phosphorescent emitters exhibited good performances. The device doped (Ir(F3,4,6ppy)2tpip with8wt%concentration showed superior performances with a peak current efficiency (ηc) of66.36cd A’1and a peak external quantum efficiency (ηext,EQE) of25.7%at5.8V.a maximun power efficiency (ηp) of48.20lm W-1at4.4V and a maximum luminance (Lmax) of47627cd m-2at12.6V. It is worth noting that the EL efficiency roll-off effects at relatively high current density in all devices are very mild, which are helpful to obtain high efficiency and brightness. The results suggested that the complexes would have potential applications in OLED.