Green/yellow-emitting diphenylbenzoimidazole-based iridium(III) complexes influenced by ancillary ligands

Two new diphenylbenzoimidazole-based bis-cyclometalated Ir(III) complexes containing different ancillary ligands, namely [(fppbiz)₂Ir(piz)][PF₆] (Ir1) and [(fppbiz)₂Ir(pbiz)][PF₆] (Ir2) (where fppbiz = 2-(4-fluorophenyl)-1-phenyl-1H-benzo[d]imidazole, piz = 2-(pyridin-2-yl)-1H-imidazole and pbiz = 2-(pyridin-2-yl)-1H-benzo[d]imidazole), were synthesized and characterized. The crystal structure of Ir2 was determined by X-ray analysis, revealing intermolecular π-π and C-H···π interactions within the crystal packings. These Ir(III) complexes exhibited green and yellow emission with high photoluminescence quantum yields of 40.9% and 36.3% and short lifetimes of 0.20 and 0.27 μs, respectively. Their photophysical and electrochemical properties were systematically studied to establish the structure–property relationship upon the change of ancillary ligands, and theoretical calculations were used to further support the deduction.