Efficient electrophosphorescence based on 2-(9,9-diethylfluoren-2-yl)-5-trifluoromethylpyridine iridium complexes

A novel cyclometalated ligand 2-(9,9-diethylfluoren-2-yl)-5-trifluoromethyl-pyridine (fl-5CF3-py), and its complexes bis[2-(9,9-diethylfluoren-2-yl)-5-trifluoromethyl-pyridinto-C3, N]iridium (acetylacetonate) (fl-5CF3-py)2Ir(acac) (5) and bis[2-(9,9-diethylfluoren-2-yl)-5-trifluoromethylpyridinto-C3, N] iridium (2-picolinic acid) (fl-5CF3-py)2Ir(pic) (6) were synthesized, respectively. Trifluoromethyl group and 2-picolinic acid were incorporated into iridium ligands to tune luminescent color. Emission spectra of 5 and 6 in THF solutions were 589 and 572 nm. Decomposition temperatures (Td) of 5 and 6 were 326 and 360 °C. Multilayer electrophosphorescent devices were fabricated using 5 and 6 as emitter dopants with electroluminescent spectra maximized at around 585 and 571 nm, respectively. The relatively high efficiencies of the devices and their slow rate of decay against increases in current densities indicated that (fl-5CF3-py)2Ir(acac) or (fl-5CF3-py)2Ir(pic) was a promising emitter for practical device applications.