One-pot synthesis of homoleptic iridium (III) dyes created using alkoxo-functionalized bipyridine ligands and these dyes' applications for organic light-emitting diodes

A facile, one-pot synthetic method to prepare alkoxo-functionalized homoleptic cyclometalated Ir (III) compounds with facial geometry has been developed. The reaction of Ir(COD)₂BF₄ with two bipyridine ligands, 2',6'-dimethoxy-4-methyl-2,3'-bipyridine and 2',6',4-trimethoxy-2,3'-bipyridine, afforded the homoleptic Ir (III) compounds Ir[(RO)₂(Me)pypy]₃ (1) and Ir[(RO)₃pypy]₃ (2) in good yields. The reaction conditions highly selectively produced the aforementioned Ir (III) compounds with facial geometry. The decomposition temperatures of 1 and 2 were 387 °C and 368 °C, respectively. Both compounds exhibited intense blue phosphorescence (λ_max = 452–458 nm) with excellent quantum efficiencies (Φ_PL = 0.45–0.52). Phosphorescent organic light-emitting diodes (PHOLEDs) that used these compounds as the dopant material and 9-(3-(9H-carbazol-9-yl)phenyl)-9H-carbazol-3-yl)diphenylphosphine oxide as the host material have been fabricated. The electroluminescent device created using compound 1 at a doping level of 5 wt% exhibited the best performance, with an external quantum efficiency of 15.7–15.5% at a brightness of 10–100 cd/m² and color coordinates of (0.16, 0.28) at 100 cd/m².