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Updated: Aug 6, 2026

The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes
Published on: April 10, 2015
Oxygen-Bridged Boron NHC-Based Red-Emitting Iridium Complexes Exhibiting Tri-Charge (0, -1, -2) Ligands
Wenqing Yu1, Fuzheng Zhang1, Zhenghao Zhang2
1School of Environmental and Chemical Engineering, Jiangsu University of Science and Technology, Zhenjiang212003, P. R. China.
Abstract:
Phosphorescent iridium complexes bearing N-heterocyclic carbenes (NHCs) have attracted significant attention for violet and blue emission, yet red-emitting variants remain challenging. This study introduces two rigid oxygen-bridged boron NHC ligands (Bpmi and Bpmb) as monoanionic (-1) ligands into an iridium system with tri-charge (0, -1, -2) ligands, with biphenyl (bp) as the dianionic (-2) ligand and bipyridine (bpy) or phenanthroline (phen) as the neutral (0) ligand, affording four neutral complexes: Ir(Bpmi)bpy, Ir(Bpmi)phen, Ir(Bpmb)bpy, and Ir(Bpmb)phen. Single-crystal structures reveal that the carbon atom of the oxygen-bridged boron unit exhibits a trans-C-C arrangement with that of the biphenyl ligand, while the NHC carbon atom shows a trans-C-N arrangement with the nitrogen atom of the neutral (0) ligand, with π-π, C-H···π, and C-H···O intermolecular interactions present. All complexes exhibit efficient red luminescence (637-650 nm), with phen and Bpmb ligands enhancing efficiency through greater rigidity. As OLED dopants, Ir(Bpmi)phen, Ir(Bpmb)bpy, and Ir(Bpmb)phen achieved maximum EQEs of 9.8%, 4.3%, and 10.3% with emission peaks at 632, 629, and 624 nm (CIE: 0.65,0.34; 0.63,0.36; 0.62,0.37), respectively. This research provides significant insights for the design and optoelectronic applications of red phosphorescent iridium complexes based on oxygen-bridged boron fused-ring NHC ligands.
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