Three new strongly chelating heterocyclic ligands containing pyridine, imidazole and triazine rings have been used to make ternary complexes of Europium(III) ions together with trifluoroacetylacetonate. The complex containing 5,6-diplienyl-3-(2-pyridyl)-1,2,3 -triazine produced efficient electroluminescence in an Organic Light Emitting Diode in the presence of Poly(9-vinylcarbazole) and 8-Hydroxyquinoline aluminum salt, used as hole and electron transporters, respectively. The external quantum efficiency of this device was 0.16%. (c) 2005 Elsevier B.V. All rights reserved.