Four solid quaternary complexes of light rare earth perchlorate with diphenyl sulfoxide (

L

) and benzoic acid (

L

') have been synthesized and characterized.By elemental analysis

TGA-DTAand themolar conductivities in acetone solution studies

the composition of the complexeswere suggested as [

REL

5

L

'(ClO

4

)](ClO

4

) (

RE

=La

Pr

Nd

Eu;

L

=C

6

H

5

SOC

6

H

5

L

'=C

6

H

5

COO

-

).As shown in IRspectra

the absorption band associated with the S-Ostretching modes in the first ligand diphenyl sulfoxide appears at 1037 cm

-1

while the absorption bands in the complexes appear between 987 cm

-1

and 989 cm

-1

.Ashift of the S-Ostretching frequency towards lowerwave number by about 50 cm

-1

suggests that rare earth ions are bonded with an oxygen atom in sulfoxyl group.In the second ligand benzoate

the absorption band associated with ν

as(COO

-

)

appears at 1550 cm

-1

ν

s(COO

-

)

appears at 1416 cm

-1

.The value of Δn[ν

as(COO

-

)

-ν

s(COO

-

)

] is 134 cm

-1

.Ashift of ν

as(COO

-

)

frequency in complexes towards higherwave number

while a shift of ν

s(COO

-

)

frequency in complexes towards lower wave number.What's more

the value of Δn[ν

as(COO

-

)

-ν

s(COO

-

)

] in complexes is higher than that of Δn[ν

as(COO

-

)

-ν

s(COO

-

)

] in sodium benzoate.This showed that benzoate (

L

') bonded with

RE

3+

ions by one oxygen atom in carboxylgroupwhich coordinate as an unidentate group.One of two perchlorates (ClO

4

-

) is coordinated with

RE

3+

while another is not.Fluorescent spectra of Eu

3+

complex showed thatquaternary complexes have stronger fluorescence than the binary one whose ligand is diphenyl sulfoxide

(the fluorescence intensity of Eu

3+

complex increased by 469%).Phosphorescent spectra of two ligands showed that the lower limit of the triplet state with benzoic acid was overlapped by the upper limit with diphenyl sulfoxide

the energy level range of triplet state was extended.As a result

matching extent of triplet state of ligandswith excited state of the rare earths have been increased by coordination of the second ligand benzoic acid

the transmit efficiency also have been increased.Attributed to the addition of the second ligand

the symmetry of the complexes always have been decreased

as a result

the fluorescence intensitywas increased.