Synthesis, photo- and electro-luminescent properties of novel ternary europium(III) complexes

With two azatriphenylene-type ligands, two novel ternary europium(III) complexes Eu(DBM)(3)L-1 and Eu(DBM)(3)L-2 (DBM = dibenzoylmethanato; L-1, L-2 = azatriphenylene-type ligands) have been synthesized and characterized by elemental analysis, IR and UV-Vis spectra. Photo-luminescent studies show that the synergistic complexation of the second ligand has indeed led to the construction of efficiently emitting europium(III) complexes, and as a result both complexes exhibit intense emission typical of Eu3+ ion. Using TPD as hole transporting material and Gd(DBM)(3)bath (bath = bathophenanthroline) as electron transporting material, three layer devices with the emitting layer formed by codeposition of luminescent complex and TPD were fabricated: ITO/TPD (30 run)/ Eu(DBM)(3)L-1 (L-2): TPD(1:2) (50 nm)/Gd(DBM)(3)bath(30 nm)/Mg : Ag. Based on the EL measurement results, it can be concluded that those ternary europium complexes possess excellent electron-transporting abilities, and the azatriphenylene-type second ligands play an important role in improving the electron-transporting abilities of the complexes. OEL devices with Eu(DBM)(3)L-1 and Eu(DBM)(3)L-2 as emitting materials have low onset driving voltage of 3 V, and the maximum pure red Eu (III)-based luminance of 148 cd.m(-2) and 110 cd.m(-2) were observed at 12 V, 52 mA.cm(-2) and 13 V, 42 mA.cm(-2) respectively.