Synthesis and phosphorescent properties of two novel iridium(III) complexes bearing bulky tert-butyl substituents

The synthesis and phosphorescence properties of two novel Ir(III) complexes bearing tert-butyl substituents, bis(4-tert  -butyl-2-phenylbenzothiozolato-N,C2′C2′) iridium(III) (acetylacetonate) [(tbt)2Ir(acac)] and bis(4-tert-butyl-1-phenyl-1H  -benzimidazolato-N,C2′C2′) iridium(III) (acetylacetonate) [(tpbi)2Ir(acac)], are reported, their molecular structures are confirmed by 1H NMR, ESI-MS and elementary analysis. Photoluminescence (PL) studies revealed that they can emit strong green and orange phosphorescence in high quantum yields. Compared to their prototypes lacking of tert-butyl substituents, the two novel iridium(III) complexes both have shorter lifetimes and improved or nearly similar PL quantum efficiencies, implying that the exciton quenching is inhibited effectively when molecular steric hindrance increases. The two chelates have great potential to be used as electrophosphorescent materials.