It is well known that aromatic acids serve as excellent ligands to effect sensitization of lanthanide fluorescence. 1

3

5-H

3

BTC has three carboxylate groups and displays widely varying coordination manner

functioning as a monodentate

bidentate

bridging or chelating ligand in complexes with metal ions. On the other hand

the rare earth carboxylate complexes are the active area of research due to their fluorescence and application in high-teach industry

the application foreground is very fast. In recent years

there are many studies carrying on the carboxylate complexes in order to look for the good fluorescent materials

one of the major activities in these studies is the enhancement of fluorescence by using of certain rare earth ions

such as La

3+

Y

3+

and Gd

3+

. The published dates on these were mainly focused on benzoic acid and benzene dicar-boxylate acid complexes

the complexes of trimesic acid with europium and lanthanum were comparatively scare. Only europium-trimesic acid fluorescence complexes were studied.Aseries of mixed rare earth complexes La

x

Eu

1-x

(BTC)·nH

2

O ( H

3

BTC=1

3

5-H

3

BTC

x

=0

0.1

0.3

0.5

0.7

0.9) have been synthesized by the reaction of trivalent rare earth chlorides with trimesic acid. The contents of rare earth

Cand Hwere measured by using EDTAtitration method and a Vario ELelemental analyzer

the constitution of these complexes was confirmed respectively as follows: La

x

Eu

1-x

(BTC)·nH

2

O (

x

=0

0.1

0.3

0.5

0.7

0.9

n=0

0.5

1.0).The IRspectra of free ligand and complexes were recorded by FTZR-8900 infrared spectroscopy with KBr pellet in the range of 350~3500 cm

-1

. There is obviously difference between the ligand and complexes. The results show that the similar structures of the complexes and the different coordination functions of the carboxylate groups. Fluorescence spectra were carrying out by using a Hitachi F-4500 fluorescence spectrophotometer. The results indicate that the complex can emit intense characteristic fluorescence from europium ion

the emission peak centered at 578~582 nm (

5

D

0

→7F

0

)

585~600 nm (

5

D

0

→

7

F

1

)

605~630 nm (

5

D

0

→

7

F

2

)

645~660 nm (

5

D

0

→7F

3

)

685~700 nm (

5

D

0

→7F

4

)

the intensity of the fluorescence of the series complexes were greater in

5

D

0

→

7

F

1

and

5

D

0

→

7

F

2

and both the positions show splitting emission peaks. These results show that the coordinating pattern of the carboxylate groups were different. In addition

the fluorescence intensities of europium ions were sensitized by the doping elements lanthanum ions

and the intensity of fluorescence is the best when La

3+

:Eu

3+

=0.3:0.7

but the position of the emission peak does not changed. In conclusion

a series of mixed rare earth complexes La

x

Eu

1-x

(BTC)·nH

2

O (

x

=0

0.1

0.3

0.5

0.7

0.9) have been synthesized by hydrothermal treatment. They can emit strong fluorescence.