Synthesis and photo physical study of iridium complex of new pentafluorophenyl-substituted ligands

New iridium complexes, [Ir(dpq)2(acac), Ir(PF-dpq)2(acac) and Ir(PF-dpq-5F)2(acac)] (dpq = 2,4-diphenylquinoline, dpq-5F = 2-(3′-fluorophenyl)-4-phenylquinoline), PF-dpq-5F = 2-(3-fluoro-phenyl)-6-pentafluorophenyl-4-phenylquinoline and acac = acetylacetonate) have been synthesized and characterized for efficient red organic light-emitting diodes (OLEDs). In order to improve the luminescence efficiency by preventing self-quenching and to tune photoluminescence (PL) and electroluminescence (EL) spectra to a longer wavelength, dpq ligand was fluorinated by -PF and -F moieties. However, the iridium complex of PF-dpq-5F underwent a weak MLCT transition because of the weak coupling between the 5d orbital of the iridium atom and HOMO of the substituted ligand. Thus, the maximum luminous efficiencies of the device using Ir(dpq)2(acac), Ir(PF-dpq)2(acac) and Ir(PF-dpq-5F)2(acac) are 4.36 cd/A, 6.04 cd/A and 4.35 cd/A, respectively.