Two series of Eu

3+

Tb

3+

heteronuclear doped complexes with terephthalic acid(L) and 18-crown-6(L') have been synthesized.Elemental analysis

IR

UV absorption spectra

rare earth complexometry and fluorescence spectra have been studied respectively.The compositions of the complexes were confirmed to be Eu RELL'2(ClO

4

)

4

·nH

2

O and TbRELL'2(ClO

4

)

4

·nH

2

O(RE=Ce

3+

Pr

3+

Nd

3+

Sm

3+

Eu

3+

Tb

3+

Dy

3+

Ho

3+

Er

3+

Yb

3+

;n=2

3

4).Terbium series complexes show that there is an excitation characteristic peak

which is a wide band from 230 to 340 nm

and a maximum peak is at 300 nm.To europium series complexes the band from 220 to 330 nm and maximum peak is at 261 nm.The excitation characteristic peaks are assigned to the ligands-metal energy transfer band through -COO-RE-OOC-.So 300 nm and 261 nm were chosen as excitation wavelength respectively to measure the fluorescence spectra of europium and terbium complexes.We all know that the UV absorption of 18-C-6 is weak

the

5

D

0

energy of Eu

3+

is 17250

but 20430 cm

-1

for the 5D4 energy of Tb

3+

and 25160 cm

-1

for the triplet energy of terephthalic acid.The triplet energy of terephthalic acid is higher a little than the excitation energy of Tb ion

but more higher than Eu

3+

ion's

the lowest excitation energy of Tb

3+

ion matchs well with the triplet state energy of the ligand each other.Thus it is possible that energy transfer from terephthalic acid ligand to Tb

3+

through -COO-RE-OOC- bonds more effectively.Absorbing energy of organic ligands are effectively transfered to the rare earth ion in the luminescence center

and producing a characteristic spectrum.Some non-fluorescence rare earth ions can absorb the energies of triplet organic ligand too

and then transfer them to Eu

3+

or Tb

3+

in this way the fluorescence intensity was enhanced.If the transition energy of non-fluorescence rare earth ions is lower than the

5

D

4

energy of Tb

3+

or

5

D

0

energy of Eu

3+

the luminescence will be quenched.Another way

the high-energy vibration of the OH of H

2

O molecules will heavily quench the luminescence of RE ions

so 18-crown-6 was introduced to replace some coordination H

2

O molecular.These results will provide relatively reliable criteria for the prediction of luminescence properties of rare earth complexes and for seeking excellent luminescent materials.