Synthesis and electroluminescence properties of an organic europium complex

In order to develop new materials for red electroluminescent devices, a novel ligand, 2-phenyl-imidazo[4,5-f]1,10-phenanthroline (L), and an europium (III) complex with dibenzoylmethanate (DBM), Eu(DBM)3L, was synthesized. The crystal structure of Eu(DBM)3L was determined by single crystal X-ray diffraction. The crystal of Eu(DBM)3L belongs to orthorhombic, space group Pbca with cell dimensions of a=2.1655(6) nm, b=2.0834(5) nm, c=2.6469(7) nm, V=11.942(5) nm3, Z=8, Dx=1.307 g/cm3. Each europium atom is coordinated with six oxygen atoms from three bidentate DBM anions and two nitrogen atoms from one bidentate L, forming a distorted square antiprism. The complex is easily evaporated and can be used as a red light emitting material. Upon improvement, the device with a structure of ITO/N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD) (40 nm)/Eu(DBM)3L (50 nm)/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (bathocuproine or BCP) (20 nm)/tris(8-hydroxyquinoline) aluminum (ALQ) (30 nm)/cathode gives off pure red light with luminance of 42 cd/m2 at 16 V