Efficiently luminescent mononuclear copper iodide complexes with sterically hindered iminephosphine chelating ligands

Phosphorescent four-coordinate Cu(I) complexes (1–3) of the type [CuI(PPh3)(N^P)], N^P = 4-(diphenylphosphanyl)-1,2-diphenylbenzimidazole derivatives, have been synthesized and characterized. Under UV excitation, the title complexes in the solid-state exhibit intense emission with a photoluminescence quantum yield of 35% and a short decay time (τ < 11 μs) at 290 K. The involvement of the methoxy group allows the tuning of the photoluminescent maxima from 568 to 589 nm. The combined experimental and density functional theory results suggest that the luminescence of the complexes represents phosphorescence attributed to the 3(M + X)LCT transitions. The prototype solution-processed devices with the complexes as an emitting dopant realize high electroluminescent performance. In particular, the OLED based on 3 achieves a maximum EQE value of 3.08%, which is equivalent to 52% of the respective theoretical maximum, suggesting that the cheap and environmental cuprous complexes are potential alternatives to the luminescent noble metal complexes.