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 nm) 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 (ηL) and power efficiency (ηp) 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.