Syntheses and fluorescence properties of two novel lanthanide (III) perchlorate complexes with bis(benzylsulfinyl)methane

Article abstract of DOI:10.1007/s10895-011-1001-5

A novel ligand with double sulfinyl groups, bis (benzylsulfinyl)methane, was synthesized by a new method and its two lanthanide (III) complexes were synthesized and characterized by element analysis, molar conductivity, coordination titration analysis, IR

Full text of DOI:10.1007/s10895-011-1001-5

J Fluoresc (2012) 22:651–658
DOI 10.1007/s10895-011-1001-5
ORIGINAL PAPER
Syntheses and Fluorescence Properties of Two
Novel Lanthanide (III) Perchlorate Complexes
with Bis(benzylsulfinyl)methane
Wen-Xian Li & Ying-Jie Li & Wen-Juan Chai & Tie Ren &
Yu Liu & Jing Zhang & Bo-Yang Ao
Received: 1 June 2011 /Accepted: 14 October 2011 /Published online: 21 October 2011
#
Springer Science+Business Media, LLC 2011
Abstract A novel ligand with double sulfinyl groups, bis
benzylsulfinyl)methane, was synthesized by a new method
Introduction
(
and its two lanthanide (III) complexes were synthesized and
characterized by element analysis, molar conductivity,
coordination titration analysis, IR, TG-DSC, HNMR and
In last decades, many rare earth complexes had been given
much attention for investigation. An attractive feature of
lanthanide complexes was their line-like emission, which
resulted in a high color purity of the emitted light [1].
Photoluminescence of lanthanide complexes could be an
efficient process. However, direct excitation of lanthanide
ions was not efficient enough due to its inherently small
absorption cross section. In 1942, Weissman discovered
that metal-centered luminescence could be observed for
lanthanide complexes with organic ligands [2]. Because of
the absorption bands of organic chromophores, much more
light could be absorbed by the organic ligands than by the
lanthanide ion itself. Subsequently, the excitation energy
was transferred from the organic ligands to the lanthanide
ion by intramolecular energy transfer.
The structure of the ligands could greatly affect the
luminescence of the rare earth ions, therefore, many
fluorescent complexes had been synthesized. The major
ligands included β-diketon, aromatic carboxylic acid
and heterocyclic ligands [3–6]. These complexes had
special characteristics, such as extremely narrow emission
bands and high internal quantum efficiencies, which were
more suitable to be used as the luminescent materials [7].
Consequently, the rare earth complexes were applied to
many areas, such as fluorimetric determination, electro-
luminescent devices and as fluorescence probes and
labels in a variety of biological and chemical applications
1
UV spectra. The results indicated that the composition of
these complexes was REL2.5(ClO ) ·3H O (RE=Tb (III),
4 3
2
Dy (III), L=C H CH SOCH SOCH C H ). The FT-IR
6
5
2
2
2 6 5
results revealed that the perchlorate group was bonded
with the lanthanide ion by the oxygen atoms, and the
coordination was bidentate. The fluorescent spectra
illustrated that both the Tb (III) and Dy (III) complexes
displayed characteristic fluorescence in solid state,
especially for the Tb (III) complex, the peak of
5
7
D → F of the Tb (III) ion in 544 nm was stronger than
4
5
that of others. It indicated that the Tb (III) complex could
emit purer green fluorescence. By analysis fluorescence
and phosphorescence spectra, it was found that the ligand
had the advantage to absorb energy and transfer it to the
Tb (III) and Dy (III) ions. The phosphorescence spectra
and fluorescence lifetimes of the complexes were also
measured.
Keywords Rare earth complexes
.
.
Bis(benzylsulfinyl)methane Fluorescence
Phosphorescence
:
:
:
:
:
:
W.-X. Li (*) Y.-J. Li W.-J. Chai T. Ren Y. Liu J. Zhang
B.-Y. Ao
[
8–10].
In recent years, W.X. Li etal had found that rare-earth
College of Chemistry and Chemical Engineering,
Inner Mongolia University,
Hohhot 010021, People’s Republic of China
e-mail: nmglwx@163.com
sulphoxide complexes containing an aromatic ring not only
had good luminescent properties, but also had good

6
52
J Fluoresc (2012) 22:651–658
Fig. 1 The synthesis scheme of
bis(benzylsulfinyl)methane
−
1
solubility and stability. So sulfoxide organic ligands
containing aromatic ring were a good class of organic
ligands for sensitizing the luminescence of rare-earth ions
400 cm ) were determined by the KBr pressed discmethod
on a Nicolet NEXUS-670 FT-IR spectrophotometer. The
ultraviolet spectra (200–350 nm) of the ligands and the
complexes were recorded on a Shimadzu TU-1901 double
beam spectrophotometer and DMF was used as a reference
[
11–17]. The object of this study was to seek new
fluorescence materials that had strong luminescence, high
thermodynamic stability and good solubility. Thus, a novel
ligand bis(benzylsulfinyl)methane with two sulfoxide
groups had been synthesized, and the corresponding
luminescent lanthanide complexes were synthesized and
characterized. The luminescence properties of the synthe-
sized complexes had been studied in the solid state.
1
and solvent. HNMR spectra were measured on Bruker
AC-300 spectrometer in DMSO-d . Fluorescence excitation
6
and emission spectra were determined on a Hitachi RF-
3010 fluorescence photometer with the slit width was 3 nm.
The phosphorescence spectra were monitored by F-4500
FL spectrophotometer at room temperature. Fluorescent
decay curves were recorded by FLS920 Combined Steady
State and Lifetime Spectrometer.
Experiment
Synthesis of the Ligand
Materials
The synthesis scheme was shown in Fig. 1.
Synthesis of the Sulfide
The purity of lanthanide oxide exceeded 99.99%. The rare
earth (III) perchlorates were prepared by dissolving their
oxide (99.99%) in HClO (2 mol/L). The purity of benzyl
4
mercaptan exceeded 99%. All other chemicals used were of
analytical grade.
The sulfide was synthesized according to the method of
Shriner et al [18].
Sodium hydroxide was dissolved in alcohol. The
mechanical stirrer was started and benzyl mercaptan was
added in a slow but steady stream. Then dibromomethane
was run in drop by drop. The mixture was refluxed, with
stirring, on a steam-bath for one and one-half hours. The
hot solution was immediately poured on ice powder. A light
yellow solid was precipitated, filtered and dried in vacuum.
The sulfide was a light yellow crystalline substance which
was purified by recrystallization from alcohol. Yield: 60~
70%, mp: 46~48. Anal. calcd. For C H S : C, 69.23%;
Physical Measurements
Elemental analysis was carried out on a HANAU analyzer.
Conductivity measurement was made using a 10 mol ·L
−3
−1
solution in DMF on a DDS-11D conductivity meter at room
temperature. Rare-earth contents of the complexes were
determined by EDTA titration using Xylenol-orange as
indicator. The thermal behavior was monitored on
SDTQ600 differential scanning calorimeter and thermal
gravimetric analyzer. The infrared spectra (IR, ν=4,000–
1
5 16 2
H, 6.154%; found: 69.20 C,%; H, 6.353%.
2
-1
Table 1 Composition analysis (%) and molar conductivities (S•cm •mol ) of the rare earth complexes (25 °C)
1m(a) (S•cm •mol−1)
2
Complexes
TbL2.5(ClO
M
Anal.calcd.(found)(%)
C
H
RE
4
)
3
·3H
2
O
1,231.4
1,245.0
36.43(36.25)
35.91(36.14)
3.88(3.71)
3.71(3.70)
13.23(12.91)
13.34(13.05)
148.5
150.5
DyL2.5(ClO
4
)
3
·3H
2
O
(
L=C CH
6
H
5
2
SOCH
2
SOCH
2
6
C H
5
)

J Fluoresc (2012) 22:651–658
653
white precipitate formed. The mixture was stirred for 0.5 h
and precipitate was filtered. The products were washed with
ether for several times, and then dried in drying oven. It
looked like white powder (yield>90%).
Results and Discussion
Properties of the Complexes
Analytical data for the complexes, presented in Table 1,
conformed to REL2.5 (ClO ) ·3H O. All the complexes
4 2
2
were white powder, stable in atmospheric condition and
soluble in DMF and DMSO. The molar conductivity values
of the complexes in DMF were in accord with them being
formulated as 1:2 electrolytes [19].
4 3 2
Fig. 2 The TG-DSC curves of TbL2.5(ClO ) ·3H O
Synthesis of the Sulfoxide
TG-DSC Studies
Bis(benzylthio)methane was dissolved in acetic acid, then
0% hydrogen peroxide was added to it at once. The
mixture was stirred continuously at room temperature for
4 h. After the reaction, the mixture was extracted with
ether until the pH of mixture was 7. Then a white solid was
precipitated, filtered and dried in vacuum. Yield: 80%, mp:
3
The TG-DSC analyses were carried out up to 1,000 °C in
−1
N at a heating rate of 10 °C min . All the TG-DSC curves
2
2
of rare earth (III) complexes were similar. The curve of Tb
(III) complex was depicted in Fig. 2. The TG curve of Tb
(III) complex showed the first mass loss occurred between
37.0~114.0 °C and mass loss percentage was 4.21%. The
result was coincided with the release of all the three water
content (4.35%) well. At the same time, DSC curve showed
small endothermic peak at 94.2 °C when losing water. In
addition, there were two exothermic peaks in DSC curve
which were attributed to the decomposition of ligands, as
well as two obvious weight losses occurring on the TG
curve. The final product was found to be Tb O (or Dy O )
2
12~214 °C. Anal. calcd. For C H S O : C, 61.64%; H,
15 16 2 2
5
.479%; found: C, 61.33%; H, 5.485%.
Preparation of the Complexes
An ether solution containing 3 mmol rare earth perchlorates
was added drop by drop in an ether solution containing
5
mmol bis(benzylsulfinyl)methane. After a few minutes a
4
7
2 3
Fig. 3 IR absorption spectrum
of ligand

6
54
J Fluoresc (2012) 22:651–658
Fig. 4 IR absorption spectrum
of TbL2.5 (ClO ·3H
4
)
2
2
O
when the temperature was near 1,000 °C, and the total
weight loss of the complexes was found to be close to the
calculated values. The results are consistent with element
analyses.
In addition, the IR frequencies of the perchlorate group
were listed in Table 3. When the perchlorate group wasn’t
coordinated, it was Td symmetry. The strong band assigned
to the ν mode of its group, which appeared at 1,085~
3
−
1
1,090 cm . It indicated the presence of ionic perchlorate
Infrared Spectra
groups in the complexes. The IR spectra of the complexes
showed three strong absorptions about at 1,144, 1,116 and
1,030 cm , which were assigned respectively to ν , ν and
8 6
ν1 vibrations of the coordinating C2ν perchlorate group
[20]. Therefore, the perchlorate group in these complexes
was bonded with the lanthanide ion by the oxygen atoms,
and the coordination was bidentate.
−
1
The most important IR assignments in the spectra of the
ligands and the complexes could be seen in the Figs. 3 and
4
and Tables 2 and 3.
In the ligand IR spectra, the S=O group stretching
modes appeared at 1,038 cm . However, the S=O
stretching frequency of the two complexes shifted to lower
−
1
−1
wave number which appeared at 1,011 and 1,008 cm
UV Spectra
respectively, it suggested that rare earth ions bonded with
oxygen atom in sulfinyl group.
The UV spectra of the ligand and Tb (III) complex were
recorded in Fig. 5. In Fig. 5a, the free ligand exhibited one
absorption band at 266 nm, which was attributed to π→π*
transition. In Fig. 5b, there was only one band at 267 nm in
the absorption spectra of Tb (III) complex which was no
significant shift. It indicated that the center cation didn’t
affect energy of the ligand. The UV absorption of Tb (III)
Table 2 Some main IR data of ligand and the rare earth complexes
Assignment (cm−
1
)
Ligand
Tb
Dy
ν
ν
ν
δ
O-H(H
C=C(C
C-H(C
2
O)
–
3,426
1,625
3,061
770
3,380
1,624
3,061
770
6
H
5
)
1,619
3,062
769
6 5
H )
Table 3 IR absorption bands of the perchlorate group of rare earth
C-H(C
6
H
5
)
−1
complexes (cm
)
7
01
702
702
Ln
C
2v
3 2
Td ν (T )
ν
ν
δ
S=O
1,038
2,964
1,406
3,032
1,454
1,011
2,965
1,406
3,033
1,454
1,008
2,965
1,406
3,030
1,453
C-H (C
C-H(C
C-H (-SO-CH
C-H (-SO-CH
6
H
5
-CH
2
-SO-)
ν
8
(B
2
)
ν
6
(B
1
)
ν
1
(A
1
)
ν
2
(A
1
)
7 1
ν (B )
6
H
5
-CH
2
-SO-)
ν
δ
2
-SO-)
Tb
1,144
1,147
1,116
1,116
1,030
1,024
924
922
625
627
1,084
1,083
2
-SO-)
Dy

J Fluoresc (2012) 22:651–658
655
Fig. 5 The UV absorption
spectra of a bis(benzylsulfinyl)
methane, b the Tb(III) complex
complex was mainly come from the ligand absorption.
Therefore, the ligand transferred energy to Tb (III) ion
effectively when complex was formed.
temperature. According to the spectra of the complexes that
were reported in Fig. 6 and Table 5, we could see that the
complexes had excellent luminescent property.
The excitation spectra were obtained by monitoring the
emission of the Tb (III) complex at 547 nm and Dy (III)
complex at 484 nm, the maximum peak at 378 and 441 nm,
respectively. The emission peaks of the Tb (III) complex
1
HNMR Spectra
1
The HNMR spectra data of bis(benzylsulfinyl)methane
and its complexes in DMSO-d could be seen from the
Table 4. The HNMR of the ligand showed the proton
resonance of two phenyl group peaks was at δ7.279~
5
7
(Fig. 6a) were assigned to the characteristic D → F (J=
4 J
6
1
6, 5, 4, 3) transitions of Tb (III) at 488, 544, 583 and
622 nm. The fluorescence emission spectrum of Tb (III)
complex under the excitation of 378 nm showed that the
strongest emission peak was at 544 nm which corresponded
7
.379 ppm, and the integral intensities showed that it had
ten protons. The proton resonance of two methylene group
peaks was at δ4.246~4.452 ppm, the integral intensities of
peaks showed that it had four protons. There was also one
methylene group in the ligand and the proton resonance of
its peaks was at δ3.311~4.143 ppm, and the integral
intensities showed that it had two protons.
5
7
with the characteristic emission for the D → F transition
4
5
of the Tb (III) ion. In Fig. 6b, the emission peaks of the Dy
4
6
(III) complex were assigned to the characteristic F9 → H
/2
J
(J=15/2 and 13/2) transitions of Dy (III) at 486 and
580 nm, respectively, and the strongest fluorescence
emission intensity was at 486 nm, which was considered
1
The HNMR spectra of the complexes were similar. The
4
6
proton resonances peaks of phenyl and methylene group
were very clear, which shifted to low field at different
degree. It resulted from the bond between ligand and rare
earth ions, which produced the remove shielded effect, it
led to the proton resonances peaks shifting to a lower field.
to the characteristic emission for the F → H
transi-
9
/2
15/2
tion of the Dy (III) ion. The strongest characteristic
emission intensity of the Tb (III), Dy (III) complexes were
8021 (a.u.) and 2089 (a.u.), respectively. Both the two
complexes had good luminescence properties, especially
5
7
the Tb (III) complex, the peak of D → F of the Tb (III)
4
5
Fluorescence Spectra
ion in 544 nm was stronger than others. It indicated that the
Tb (III) complex could emit pure green fluorescence.
Therefore, Tb (III) complex could be applied to green
luminescent materials.
The excitation spectra and emission spectra of Tb (III), Dy
(
III) complexes were measured in solid state at room
Table 4 Chemical shift data of HNMR spectra (1×10−6
1
)
1
Ligand and complexes
HNMR
-
CH
2
-
-CH
2
-(×2)
6 5
-C H -(×2)
C
6
H
5
CH
TbL2.5(ClO
DyL2.5−(ClO
2
SOCH
·3H
·3H
2
SOCH
2 6
C H
5
3.311~4.143 (s, 2 H)
3.846~4.176 (s, 2 H)
3.838~4.153 (s, 2 H)
4.246~4.452 (s, 4 H)
4.256~4.482 (s, 4 H)
4.238~4.465 (s, 4 H)
7.279~7.379 (m, 10 H)
7.316~7.371 (m, 10 H)
7.298~7.364 (m, 10 H)
4
)
3
2
O
4
)
3
2
O

6
56
J Fluoresc (2012) 22:651–658
Fig. 6 Fluorescent excitation
and emission Spectra of binary
Tb(III) (a) and Dy(III) (b)
complexes
The fluorescence decay curves of the Tb (III), Dy (III)
complexes were also measured. Figure 7 showed the
fluorescence decay curve and linear fit curve of the Tb
two energy transfer processes: one was the transition from
the triplet state energy level of ligand to the excited states of
the Tb (III) and Dy (III) ions by Dexter’s resonant exchange
interaction [23], the other was just an inverse energy
transfer process through the thermal deactivation mecha-
nism [24]. Based on the theory, conclusion could be drawn
that an optimal value of energy states could be calculated
out from the spectra, and energy level difference was an
important factor to influence the two energy transfer
processes; therefore, an appropriate energy level difference
could make the triplet state of ligand energy level and the
excited state of rare earth ions energy match able.
Otherwise, if the difference of energy level was too large
or too small, it would not be conducive to energy transfer.
In Fig. 8, two bands could be seen clearly at 519 and
471 nm which corresponded to the triplet state energy level
(
III) complex. The fluorescence lifetime values of Tb (III),
Dy (III) complex were calculated by the single exponential
mode. From the results, the lifetime of the Tb (III) ion was
determined to be 760.12 μs, and the lifetime of the Dy (III)
ion was determined to be 9.27 μs. This result showed that
the lifetime of the Tb (III) ion was longer than that of Dy
(
III) ion. In the fluorescence spectrum (Fig. 6), the
fluorescence intensity of Tb (III) complex was stronger
than that of the Dy (III) complex. So we could infer that the
life time getting long properly was helpful to increasing the
fluorescence intensity in our experimental system.
Phosphorescence Spectra
−1
of the ligand of Gd (III) complex T (19,268 cm ) and T
1
2
−1
The phosphorescence spectrum of Gd (III) complex
(21,231 cm ), respectively. The triplet state energy level
5
(
GdL2.5(ClO ) ·3H O) was measured by F-4500 FL spec-
T2 was appropriately higher than D4 of Tb (III) ion
4 3
2
−
1
4
−1
trophotometer in solid state. The spectrum was listed in
Fig. 8. It was known that the energy of the triplet state (T)
of the ligand was sensitive to ligand coordination to the
metal ion; therefore, the complex of gadolinium was
prepared and its phosphorescence spectrum was registered
to examine the triplet states of the ligand. According to the
intra-molecular energy transfer mechanism [21, 22], intra-
molecular energy transfer efficiency chiefly depended on
(20,430 cm ) [25] and F of Dy (III) ion (21,100 cm )
9/2
5
[26]. The energy level difference between T and D of Tb
(III) ion was 801 cm and the energy level difference
2
4
−
1
4
−1
between T2 and F9/2 of Dy (III) ion was 131 cm .
According to the fluorescence spectrum, the strongest
characteristic emission intensity of Tb (III) complex was
higher than that of the Dy (III) complex, so the triplet state
energy level of ligand and the excited state energy of Tb
Table 5 Fluorescent data of Tb
Complexes
TbL2.5(ClO
1
EX (nm)
1
EM (nm)
Intensity (a.u.)
Energy state transitions
(
III), Dy(III) complexes in soild
at room temperature
5
5
5
5
4
4
7
4
)
3
·3H
2
O
378
488
1,724
8,021
1,271
995
D
D
D
D
4
4
4
4
→ F
6
5
4
3
7
5
5
6
44
83
22
→ F
7
→ F
7
→ F
6
DyL2.5(ClO
4
)
3
·3H
2
O
441
486
80
2,089
1,231
F
9/2→ H15/2
6
5
F
9/2→ H13/2

J Fluoresc (2012) 22:651–658
657
Fig. 7 Fluorescence decay
curve and fitted curve of binary
Tb(III) complex
(
III) ion matched each other very well, and the ligand could
complexes displayed characteristic RE (III) ion fluores-
cence. Therefore, the ligand had a suitable conjugated
system to efficiently sensitize RE (III) ion fluorescence.
Meantime, the luminous type of Tb (III) and Dy (III) ions
in complexes was the type of L-M.
absorb and transfer energy effectively to Tb (III) ion as
well. Meanwhile, the luminous type of Tb (III) and Dy (III)
ions in complexes was the type of L-M.
From the experimental results of fluorescence emission,
5
7
Conclusion
we had known that the peak of D → F of the Tb (III) ion
4 5
in 544 nm was stronger than others. It indicated that the Tb
(III) complex could emit pure green fluorescence. There-
fore, the Tb (III) complex had application potential as green
luminescent materials and so on. Hence, based on these
factors, more luminescent materials could be obtained in
the future.
In this paper, a novel ligand bis(benzylsulfinyl)methane and
its two complexes were successfully synthesized and
characterized. The composition of the complexes were
proved to be REL2.5(ClO ) ·3H O (RE=Tb (III), Dy (III),
4 3
2
L=C H CH SOCH SOCH C H ).
6
5
2
2
2 6 5
The photophysical properties of complexes had been
studied with ultraviolet spectra, excitation and emission
spectra, fluorescence lifetimes and phosphorescence spec-
tra. Both Tb (III) and Dy (III) complexes had good
solubility in DMF and DMSO. In these complexes, the
perchlorate group was bonded with the lanthanide ion by
the oxygen atom, and the coordination was bidentate. The
fluorescence spectra showed that both Tb (III) and Dy (III)
Acknowledgements This work is supported by the financial
supports from the National Natural Science Foundations of China
Research project (20861005), Natural Science Foundations of
Inner Mongolia Science Foundation (2010 MS 0204) and
supported by Inner Mongolia Yili Industrial Group Co. horizontal
joint project.
References
1
2
3
. Binnemans K (2009) Lanthanide-based luminescent hybrid
materials. Chem Rev 109:4283–4374
. Weissman SI (1942) Intramolecular energy transfer the fluores-
cence of complexes of europium. J Chem Phys 10:214–217
. Luo YM, Li J, Tang RR, Tang XC (2009) Synthesis,
characterization and fluorescence properties of Eu(III) and
Tb(III) complexes with novel mono-substituted β-diketon
ligands and 1,10-phenanthroline. Spectrochim Acta Part A
7
2:703–708
4
5
6
. Xi P, Gu XH, Chen CF, He YX, Huang XA (2007) Synthesis,
characterization and fluorescence properties of new highly
luminescent organic ligand and complexes of trivalent rare earth.
Spectrochim Acta Part A 66:667–671
. Singh AK, Singh SK, Mishra H, Prakash R, Rai SB (2010)
Structural, thermal, and fluorescence properties of Eu
(
DBM)
3 χ
Phen complex doped in PMMA. J Phys Chem B
114:13042–13051
. Song XQ, Zheng JR, Liu WS, Ju ZH (2008) Synthesis, structure
and spectroscopic properties of rare earth complexes with a new
aryl amide 2,2′-bipydine derivative. Spectrochimica Acta Part A
69:49–55
4 3 2
Fig. 8 The phosphorescence spectrum of GdL2.5(ClO ) ·3H O

6
58
J Fluoresc (2012) 22:651–658
7
. Lv YG, Zhang JC, Cao WL, Fu YL (2009) Enhanced lumines-
cence of novel rare earth complexes Eu(3,5-DNBA) Phen in
nano-TiO . Spectrochim Acta Part A 72:22–25
16. Li WX, Chai WJ, Sun XJ, Ren T, Shi XY (2010) Synthesis and
luminescence properties of two novel lanthanide (III) perchlorate
complexes with Bis(benzoylmethyl) sulfoxide and benzoic acid. J
Fluoresc 20:873–880
17. Chai WJ, Li WX, Sun XJ, Ren T, Shi XY (2011) Fluorescence
enhancement of lanthanide(III) perchlorate by 1,10-phenanthroline in
bis(benzoylmethyl) sulfoxide complexes and luminescence mecha-
nism. J Luminesc 131:225–230
3
2
8
. Wang L, Chen JG, Chen HQ, Zhou CL, Ling B, Fu J (2011) A
sensitive fluorimetric method for determination of trace amounts
of nitrite based on luminescence energy transfer. J Luminesc
1
31:83–87
9
. Kukhta A, Kolesnik E, Grabchev I, Sali S (2006) Spectral and
luminescent properties and electroluminescence of polyvinylcar-
bazole with 1, 8-naphthalimide in the side chain. J Fluoresc
18. Shriner RL, Struck HC, Jorison WJ (1930) The preparation and
properties of certain sulfoxide and sulfones. Chem Soc 52:2060–
2069
1
6:375–378
1
0. Zamotaiev OM, Postupalenko VY, Shvadchak VV, Pivovarenko
VG, Klymchenko AS, Mely Y (2011) Improved hydration-
sensitive dual-fluorescence labels for monitoring peptide-nucleic
acid interactions. Bioconjugate Chem 22:101–107
19. Greary WJ (1971) The use of conductivity measurements in
organic solvents for the characterisation of coordination com-
pounds. Coord Chem Rev 7:81–122
20. Zhang RH, Zhang QW, Kong DL (1991) Studies of DIsulfoxide
complexes of lanthanide. J Rare Earths 9:85–89
11. Shi XY, Li WX, Qin CH, Guo L, Sun XJ, Sun XL, Geng GQ (2008)
Synthesis and characterization of quaternary complexes of light rare
earth perchlorate with diphenyl sulfoxide, benzoic acid and studies
on fluorescence of Eu3+ complex. Chinese J Luminesc 29:772–778
2. Li WX, Guo L, Chen LJ, Shi XY (2008) Synthesis and
fluorescence properties of lanthanide (III) perchlorate complexes
with bis(benzoylmethyl) sulfoxide. J Fluoresc 18:1043–1049
3. Guo L, Li WX, Shi XY, Sun XJ, Sun XL (2009) Enhanced
luminescence of rare-earth Tb (III) by Tm (III) in bis(benzoyl-
methyl)sulfoxide complexes and intra-molecular energy transfer. J
Luminesc 129:639–644
21. Yan B, Zhang HJ, Wang SB, Ni JZ (1998) Spectroscopic study of
luminescence and intramolecular energy transfer of binary
andternary rare earth complexes with aromatic carboxylic acids
and 1, 10-phenanthroline. Spectro Lett 31:603–608
22. Yan B, Zhang HJ, Wang SB, Ni JZ (1998) Intramolecular energy
transfer echanism between ligands internary complexes with
aromatic acids and 1, 10-phenanthroline. J Photochem Photobiol
A Chem 116:209–214
1
1
23. Dexter DL (1953) A theory of sensitized luminescence in solids. J
Chem Phys 21:836–841
1
4. Li WX, Zheng YS, Sun XJ, Shi XY, Chai WJ, Ren T (2010)
Synthesis and fluorescence properties of lanthanide (III) perchlorate
complexes with naphthyl-naphthalinesulphonylpropyl sulfoxide. J
Fluoresc 20:235–241
5. Sun XJ, Li WX, Chai WJ, Ren T, Shi XY (2010) The studies of
enhanced fluorescence in the two novel ternary rare-earth complex
systems. J Fluoresc 20:453–461
24. Dean CRS, Shepherd TM (1975) Evaluation of the intramolecular
4
energy transfer rate constants in crystalline Eu(hfaa) ButNH31. J
Chem Soc Faraday Trans II 71:146–152
25. Gerisler HF, Hellwege KH (1953) Spectrum and luminescent
mechanism of crystal Tb(BrO . Physik 136:293–295
1
3 3
)
26. Gerisler HF, Hellwege KH (1953) Zeitschrift für Physik A
Hadrons and Nuclei 136:293–302