Synthesis, characterization, photophysical and electrochemical properties of new phosphorescent dopants for OLEDs

New heteroleptic iridium(III) complexes of 2-(p-substituted-phenyl)-pyridine were synthesized and characterized. These complexes have two cyclometalated ligands (C^∧N) and a bidentate ancillary ligand (LX), that is, (C^∧N)₂Ir(LX). LX was either acetylacetonate or 5-nitro-8-hydroxy quinolate. Substitution on the p-phenyl of C^∧N ligands was used to alter the electronic properties of these complexes. The (C^∧N)₂Ir(acac) complexes show phosphorescence with good quantum yields and microsecond lifetimes and also show photoluminescence over a wide visible range (λ_max = 503-620 nm). The HOMO level and triplet energy level of these complexes were also determined. These data indicate their potential use as emitting materials for organic light emitting diodes, OLEDs.