Introduction of new ancillary ligands to the iridium complexes having 2,3-diphenylquinolinato ligands for OLED

Abstract

We investigated the effect of an ancillary ligand (AL) on the emission color and luminous efficiencies of its complex, Ir(4-Me-2,3-dpq)(2)(AL),where 4-Me-2,3-dpq represents 4-methyl-2,3-diphenylquinolinato ligand. We expected that ancillary ligand modi. cation by introduction of the bulky substituent to the complexes might allow luminous efficiency increase by reduction of T -T annihilation. Furthermore, some ancillary ligands may contribute to. ne-tuning of their complex emission colors by influencing the energy level of Ir d-orbitals upon the orbital mixing. As new ancillary ligands substituting for acac which is a typical AL in the iridium complexes, pyrazolone-based ligands, 4-R-5-methyl-2-phenyl-2,4-dihydropyrazol3- one series (przl-R), were prepared, where R represents C6H5, C6H4CH3 and C6H4Cl. These ligands were chelated to the iridium center to yield a new series of the iridium complexes, Ir(4-Me-2,3- dpq)(2)(przl-R). The X-ray crystal structure of Ir(4-Me-2,3-dpq)(2)(przl-C6H4Cl) was determined. The electrochemical and luminescence properties of the iridium complexes were investigated. The effect of the przl-substituents on the emission colors of the complexes was not significant. On the other hand, the luminous efficiencies of Ir(4-Me-2,3-dpq) 2(przl-C6H5) and Ir(4-Me-2,3-dpq)(2)(przl-C6H4CH3) were higher than that of Ir(4-Me-2,3-dpq)(2)(acac). (C) 2009 Elsevier B.V. All rights reserved.