Rare earth complexes have become excellent luminescence materials

this is related to lanthanide(ions') peculiar characteristics

and have potential use in laser

photoluminescence and electroluminescence.Rare earth complexes with aromatic carboxylic acids are a kind of luminescent materials with good properties. So much attention was paid to the fluorescence properties of these complexes.There are some reports about fluorescence properties of the complexes of a part of rare earth with phthalic acid and terbium with benzoic acid and salicylic acid.However

no report on systemic study of the fluorescence properties concerning rare earth complexes with different aromatic carboxylic acids has been reported.For this purpose

we have synthesized fourteen complexes of Sm

Eu

Tb

Dy with benzoic acid derivatives: RC

6

H

4

COOH(R=o-NH

2

H

p-NH

2

(o-OH)

m-Cl

o-COOH

m-COOH

p-COOH

p-OH

m-NO

2

3

5-Dinitro

p-Br

o-I

2-OH

-

5-SO

3

H)and it is found that the complexes of Sm and Dy with these aromatic acids show little fluorescence

but Eu and Tb with some of these aromatic acids show strong fluorescence under the excitation of UV

and that the complexes of terbium with sulfosalicylic acid have the strongest fluorescence intensity.In the present paper

terbium complexes with aromatic acids were synthesized and their fluorescence properties were investigated.The synthetic process was as follows: The aqueous TbCl

3

solution was slowly added to ligand solution(according) to the molar ratio of Tb

3+

:ligand=1:3 or 2:3(phthalic acid

m-phthalic acid) at 80℃ under(stirring.) The pH of the mixture was adjusted to 6.0～6.5 by addition of sodium hydroxide solution.Thus

white precipitates of the complexes came into being.After another two hours

stop stirring

the mixture was cooled to room temperature.The white precipitates of the complexes were filtered

washed with deionized(water) and ethanol till no chloridion could be found

then dried at 85℃ under vacuum for 4 h.The compositions of samples were identified by elemental analyses.UV

IR of the complexes also have been investigated.The UV spectra indicated that the complexes' ultraviolet absorption was mainly the ligands' absorption

but the location of peak drifted.The IR spectra showed that the IR spectra of complexes are dif-(ferent) from those of free ligands and the band at 400～500cm

-1

due to the stretching vibration of Tb-O

is absent for free ligands.The fluorescence properties were investigated by using luminescence spectroscopy

the results showed that all the six complexes of terbium exhibited excellent luminescence

due to the transition from the lowest excited state

5

D

4

to

7

F

J

ground state manifold

and the complexes of terbium with sulfosalicylic acid had the strongest fluorescence intensity.