Synthesis, photophysical and electroluminescent properties of novel iridium (III) complexes based on 5-methyl-2-phenylbenzo[d]oxazole derivatives

• New iridium (III) complexes with 5-methyl-2-phenylbenzo[d]oxazole derivatives were synthesized.
• The photophysical properties of the complexes were investigated in detail.
• 5-Position methyl substitution greatly affected EL performances of the resultant complexes.
• OLEDs based on the doped complexes showed higher EL performances.

A new series of phosphorescent iridium (III) complexes based on 5-methyl-2-phenylbenzo[d]oxazole derivatives as main ligands, i.e. bis(5-methyl-2- phenylbenzo[d]oxazole-N,C2′)iridium(acetylacetonate) [(mpbo)2Ir(acac)], bis(2-(4-fluorophenyl)-5-methylbenzo[d]oxazole-N,C2′)iridium(acetylacetonate) [(fmbo)2Ir(acac)] and bis(5-methyl-2-p-tolylbenzo[d]oxazole-N,C2′) iridium(acetylacetonate) [(mtbo)2Ir(acac)], were synthesized for organic light-emitting diodes (OLEDs), and their photophysical, electroluminescent properties were investigated. All complexes have high thermal stability and emit intense phosphorescence from green to yellow at room temperature with high quantum efficiencies and relatively short lifetimes. The OLED based on (fmbo)2Ir(acac) as dopant emitter showed very high luminance of 26,004 cd m−2 and luminance efficiency of 18.5 cd A−1. The evidences indicated that this series of iridium (III) complexes were potential candidates for applications in organic electroluminescent devices.