Two new europium complexes Eu(DBM)_3qp (DBM=dibenzoylmethane, qp=quinoxalino[2,3-i]-1,10-phenathroline) and Eu(DBM) 3pp (DBM=dibenzoylmethane, pp=pyrazino[2,3-i]-1,10-phenathroline) were synthesized and characterized by X-ray diffraction.Both of these complexes crystallized in monoclinic system with space group P2(1)/c.Each Eu³⁺ is eight coordinated with six oxygen atoms from three DBM ligands and two nitrogen atoms from netural ligand, forming a distorted square antiprism.In the crystals of those complexes, every four complex molecules form a block through strong intermolecular π-π stacking interactions between neutral ligands.The emission intensity of Eu(DBM)_3pp is about twelve times of that of Eu(DBM)_3qp, which results from the distinction of energy level between the second ligands.

Key words: europium complex, crystal structure, fluorescence, π-πstacking