A binuclear aluminum(III) complex: Thermal stability, photophysical, electrochemical and electroluminescent properties

A novel binuclear aluminum(III) complex with acylpyrazolone derivative as ligands, bis(salicylidene-o-aminophenol)-bis(4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one)-bis-aluminum(III) [Al2(saph)2(PMBP)2] was designed and synthesized. A detailed study was carried out on its thermal stability, photophysical, electrochemical and electroluminescent properties. It was found that the introduction of 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (PMBP) ligands improved the thermal stability remarkably. Organic light-emitting diodes (OLEDs) based on this Al complex as the sole emitter and the host for red dopant were fabricated. Bright green-yellow emission was observed from the device using Al2(saph)2(PMBP)2 as the emitter and the electron transporting layer. Pure red emission peaked at 632 nm was obtained from the Al2(saph)2(PMBP)2 doped with DCJTB [4-(dicyanomethylene)-2-tertbutyl-6(1,1,7,7,-tetramethyljulolidyl-9-enyl)-4H-pyran] device with a luminance efficiency of 1.51 cd/A at 200 A/m2. No light from Al2(saph)2(PMBP)2 was found, indicating that the matched energy levels provide an efficient red emission system in Al2(saph)2(PMBP)2 device. Those results demonstrated that Al2(saph)2(PMBP)2 might be a promising material for OLEDs.