Rare earth complex materials have been widely used in cathodoluminescent display phosphor screens

lasers and lamps because their photoluminescence (PL) exhibits high quantum efficiencies and very sharp spectral bands. The luminescence process of the rare earth complex is as follows:the electrons in excited single state of the ligand move to the triplet state by intrasystem relaxation process

followed by the energy transfers from the triplet state of the ligand to the nearest resonance level of the rare earth ion.In the luminescence process

the single state and triplet state can only be used.Theoretically

the internal quantum efficiency can reach 100％

which is four times than that of other fluorescent materials.When europium ion chelates with some organic ligands

such as benzoic acid(BA)

the emissions of rare earth Eu

3+

ion exhibits highly pure red color and strong luminescence intensity. The intensity of sensitized luminescence of central lanthanide ions in a rare earth organic chelate depends on three factors.Firstly

the suitability of the energy gap between the excited triplet energy level of the ligands and the lowest excited energy level of rare earth ions. Secondly

the rigidity and planarity of the structure of the chelate molecule.Thirdly

the existence of a suitable secondary ligand which may increase the rigidity and the stability of the chelate molecule.In this paper

1

10-phenanthroline (phen) derivative

2-phenyl-imidazo [4

5-f] 1

10-phenanthroline (PIP) were synthesized.With benzoic acid(BA) as the first ligand and PIP as the secondary ligand

a new ternary organic europium complex Eu(BA)

3

PIP was prepared.In the same condition

with the same first ligand and phen as the secondary ligand

Eu(BA)

3

phen was also prepared. The structures and compositions of the ligand PIP

Eu(BA)

3

PIP and Eu(BA)

3

phen were confirmed by elemental analysis

IR spectra

TG analyses

the fluorescence properties [JP2]of the two complexes were also studied. Elemental analysis demonstrates that the compositions of the ternary[JP]

complexes are PIP

Eu(BA)

3

PIP and Eu(BA)

3

phen. IR spectra indicate that rare earth Eu

3+

ion is coordinated with six oxygen atoms of three benzoic acid ligands and two nitrogen atoms of the second ligand.The emission spectra demonstrate that two kinds of ternary organic europium complex exhibit characteristic fluorescence of rare earth Eu

3+

and the second ligand PIP has larger conjugation system

and under UV excitation

energy absorbed by the ligands in the complex can be transfed to the rare earth Eu

3+

ion

so that it can emit characteristic luminescence of Eu

3+

and the luminescence intensity of Eu(BA)

3

PIP is obviously higher than that of Eu(BA)

3

phen. The luminescence of complex was greatly sensitized by appropriate secondary ligand. TG analyses show that the thermal decomposition temperature of Eu(BA)

3

PIP are higher than that of Eu(BA)

3

phen. Thus the secondary ligand of 2-phenyl-imidazo [4

5-f] 1

10-phenanthroline(PIP) obviously enhanced the fluorescent intensity of Eu

3+

and the thermal stability of europium complex. So

the new ternary organic europium complex of Eu(BA)

3

PIP is an excellent red-emitting material.