Several substituted phenanthrolines (L=pyrazino[2,3-f][1,10]phenanthroline (PyPhen), 2-methylpyrazino[2,3-f][1,10]phenanthroline (MPP), dipyrido[3,2-a:2',3'-c]phenazine (DPPz), 11-methyldipyrido[3,2-a:2',3'-c]phenazine (MDPz), 11,12-dimethyidipyrido[3,2-a:2',3'-c]phenazine (DDPz), and benzo[i]dipyrido[3,2-a:2,3-c]phenazine (BDPz)) were successfully prepared and europium, complexes Eu(TTA)(3)L (Eu-L) based on these ligands were synthesized from EUCl3, 2-thenoyltrifluoroacetone (TTA) and L in good yields. Irradiation at the absorption band between 320-390 nm of all these europium complexes, except Eu-BDPz, in solution or in the solid state leads to the emission of a sharp red band at similar to 612 nm, a characteristic Eu3+ emission due to the transition D-5(0) --> F-7(2). No emission from the ligands was found. The result indicates that complete energy transfer from the ligand to the center Eu 3, ion occurs for these europium complexes. In contrast, the photoluminescence spectrum of Eu-BDPz exhibits a strong emission at around 550 nm from the coordinated BDPz ligand and a weak emission at 612 nm from the central europium ion. Incomplete energy transfer from the ligand to the central Eu3+ ion was observed for the first time. Several electroluminescent devices (A-I) using Eu-PyPhen, Eu-MPP, Eu-DPPz, and Eu-DDPz as dopant emitters with the device configuration: TPD or NPB (50 nm)/Eu:CBP (1.7-7 %, 30 nm)/BCP (20-30 nm)/Alq (25-35 mn) (where TPD: 4,4'-bis[N-(p-tolyl)-N-phenylamino]biphenyl; NPB: 4,4'-bis[1-naphthylphenylamino]biphenyl; CBP: 4,4'-N,N'-dicarbazole biphenyl; BCP: 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline; Alq: tris[8-hydroxyquinoline]aluminum) were fabricated. Some of these devices emit saturated red light and are the only europium. complex-based devices that show a brightness of more than 1000 cd m(-2).