New heteroleptic Tris-cyclometalated iridium complex for red electrophosphorescent light-emitting diodes

New heteroleptic Tris-cyclometalated iridium complex having two different (C boolean AND N) ligands, [Ir(dpq)(2)(dpq-3F)] (dpq=2,4-diphenylquinoline, dpq-3F=2-(3'-fluorophenyl)-4-phenyl quinoline), have been synthesized and characterized for an efficient red organic light-emitting diodes (OLEDs). The iridium phosphors emit bright red light with its maximum at 615 nm. The heteroleptic Tris-cyclometalated iridium complex [Ir(dpq)(2)(dpq-3F)] is shown to be a more efficient electrophosphor than the homoleptic, Tris-cyclometalated iridium complex [Ir(dpq-3F)(3)] to avoid the triplet-triplet (T-T) annihilation by decreasing the number of the luminescent ligand. The highest occupied molecular orbital (HOMO) energy level of Ir(dpq-3F)(3) is lower than that of Ir(dpq)(3). Thus, the luminescence of the heteroleptic Ir(dpq)(2)(dpq-3F) occurs mainly at the dpq-3F ligand because the Ir(dpq-3F)(3) has more MLCT characteristic. To analyze luminescent mechanism, we calculated these complexes theoretically by using computational method. (C) 2007 Elsevier B.V. All rights reserved.