Efficient electroluminescent tertiary europium(III) β-diketonate complex with functional 2,2′-bipyridine ligand

A new red electroluminescent complex (2Fphen-bpy)Eu(DBM)₃(2Fphen-bpy: 4-(2,4-difluorophenylene)-2,2′-bipyridine; DBM: dibenzoylmethanate) was designed and synthesized. X-ray single crystal structural analysis shows that the dihedral angles involving the difluorophenylene moiety and two pyridine rings of the 2,2′-bipyridine unit in (2Fphen-bpy)Eu(DBM)₃ are 42° and 51.6°, indicant of non-conjugation between the two segments. The europium complex was incorporated into the doped electroluminescent device: ITO/TPD(40 nm)/(2Fphen-bpy)Eu(DBM)₃:CBP(30 nm, 3%)/BCP(20 nm)/Alq₃(30 nm)/LiF(1 nm)/Al(100 nm). At the brightness of 100 cd/m², the current and power efficiency are about 2.53 cd/A and 0.79 lm/W, respectively. In comparison with the inefficient control device using (2,2′-bipyridine)Eu(DBM)₃ as the red emitter in the same configuration, the introduction of difluorophenylene moiety into the Eu(III) complex could possibly account for the improved performance of the title compound.