Syntheses, Photoluminescence, and Electroluminescence of a Series of Iridium Complexes with Trifluoromethyl-Substituted 2-Phenylpyridine as the Main Ligands and Tetraphenylimidodiphosphinate as the Ancillary Ligand

Five bis-cyclometalated iridium complexes with tifluoromethyl-substituted 2-phenylpyridine (ppy) at different positions of its phenyl group as the main ligands and tetraphenylimidodiphosphinate (tpip) as the ancillary ligand, 2-6 (1 is a trifluoromethyl-free complex), were prepared, and their X-ray crystallography, photoluminescence, and electrochemistry were investigated. The number and positions of trifluoromethyl groups at the phenyl ring of ppy greatly affected the emission spectra of Ir3+ complexes, and their corresponding emission peaks at 533, 502, 524, 480, and 542 nm were observed at room temperature, respectively. Constructed with complexes 2-6 as the emitters, respectively, the organic light-emitting diodes (OLEDs) with the structure of indium-tin oxide/1,1-bis[4-(di-p-tolylamino)phenyl]cyclohexane (30 nm)/Ir (x wt %):bis[3,5-bis(9H-carbazol-9-yl)phenyl]-diphenylsilane (15 nm)/1,3,5-tris(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl (45 nm)/LiF (1 nm)/Al (100 am) showed good performances. Particularly, device G4 based on 4-trifluoromethyl-substituted complex 4 with x = 8 wt % obtained a maximum luminance of over 39000 cd m(-2) and maximum luminance efficiency (eta(L)) and power efficiency (eta(p)) of 50.8 cd A(-1) and 29.0 lm W-1, respectively. The results suggested that all of the complexes 2-6 would have potential applications in OLEDs.