Hwang, F.-M.F.-M.HwangChen, H.-Y.H.-Y.ChenChen, P.-S.P.-S.ChenLiu, C.-S.C.-S.LiuChi, Y.Y.ChiShu, C.-F.C.-F.ShuWu, F.-I.F.-I.WuPI-TAI CHOUSHIE-MING PENGLee, G.-H.G.-H.Lee2018-09-102018-09-102005http://www.scopus.com/inward/record.url?eid=2-s2.0-20044379930&partnerID=MN8TOARShttp://scholars.lib.ntu.edu.tw/handle/123456789/315176Rational design and syntheses of four iridium complexes (1-4) bearing two substituted quinoxalines and an additional 5-(2-pyridyl) pyrazolate or triazolate as the third coordinating ligand are reported. Single-crystal X-ray diffraction studies of 1 reveal a distorted octahedral geometry, in which two dpqx ligands adopt an eclipse configuration, for which the quinoxaline N atoms and the C atoms of orthometalated phenyl groups are located at the mutual trans- and cis-positions, respectively. The lowest absorption band for all complexes consists of a mixture of heavy-atom Ir(III)-enhanced 3MLCT and 3pipi* transitions, and the phosphorescent peak wavelength can be fine-tuned to cover the spectral range of 622-649 nm with high quantum efficiencies. The cyclic voltammetry was measured, showing a reversible, metal-centered oxidation with potentials at 0.76-1.03 V, as well as two reversible reduction waves with potentials ranging from -1.61 to -2.06 V, attributed to the sequential addition of two electrons to the more electron-accepting heterocyclic portion of two distinctive cyclometalated C/N ligands. Complex 1 was used as the representative example to fabricate the red-emitting PLEDs by blending it into a PVK-PBD polymer mixture. The devices exhibited the characteristic emission profile of 1 with peak maxima located at 640 nm. The maximum external quantum efficiency was 3.15% ph/el with a brightness of 1751 cd/m2 at a current density of 67.4 mA/cm2, and the maximum brightness of 7750 cd/m2 was achieved at the applied voltage of 21 V and with CIE coordinates of (0.64, 0.31).journal article10.1021/ic04894432-s2.0-20044379930WOS:000227346300033