Synthesis, characterization and luminescence properties of Eu(III) and Tb(III) complexes with novel pyrazole derivatives and 1,10-phenanthroline

Article abstract of DOI:10.1016/j.saa.2009.12.006

Two novel pyrazole-derived ligands, 3-chloro-6-(3,5-dimethyl-1H-pyrazol-1-yl)picolinic acid (CDPA) and 3-chloro-6-(3,5-dimethyl-1H-pyrazol-1-yl)-N-phenylpicolinamide (CDPP) were prepared by 3,6-dichloropicolinic acid (DCPA). Their complexes with terbium(III) and europium(III) were synthesized. The complexes were characterized by elemental analysis, infrared spectra, ¹H NMR and TG-DTG. Furthermore, the above complexes using 1,10-phenanthroline as a secondary ligand were also synthesized and characterized. The luminescence properties of these complexes in solid state were investigated. The results suggested that Tb(III) complexes exhibit more efficient luminescence than Eu(III) complexes and the fluorescence of the complexes with 1,10-phenanthroline as a secondary ligand was prominently stronger than that of complexes without this ligand., and the three ligand (DCPA), (CDPP) and (CDPA) are excellent sensitizers to Eu(III) and Tb(III) ion.

Full text of DOI:10.1016/j.saa.2009.12.006

Spectrochimica Acta Part A 75 (2010) 825–829
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis, characterization and luminescence properties of Eu(III) and Tb(III)
complexes with novel pyrazole derivatives and 1,10-phenanthroline
Fei-Long Hu, Xian-Hong Yin∗, Yan Mi, Shan-Shan Zhang, Wei-Qiang Luo
College of Chemistry and Ecological Engineering, Guangxi University for Nationalities, Nanning 530006, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Two novel pyrazole-derived ligands, 3-chloro-6-(3,5-dimethyl-1H-pyrazol-1-yl)picolinic acid (CDPA)
and 3-chloro-6-(3,5-dimethyl-1H-pyrazol-1-yl)-N-phenylpicolinamide (CDPP) were prepared by 3,6-
dichloropicolinic acid (DCPA). Their complexes with terbium(III) and europium(III) were synthesized.
The complexes were characterized by elemental analysis, infrared spectra, 1H NMR and TG–DTG. Fur-
thermore, the above complexes using 1,10-phenanthroline as a secondary ligand were also synthesized
and characterized. The luminescence properties of these complexes in solid state were investigated. The
results suggested that Tb(III) complexes exhibit more efficient luminescence than Eu(III) complexes and
the fluorescence of the complexes with 1,10-phenanthroline as a secondary ligand was prominently
stronger than that of complexes without this ligand., and the three ligand (DCPA), (CDPP) and (CDPA) are
excellent sensitizers to Eu(III) and Tb(III) ion.
Received 30 April 2009
Received in revised form
25 November 2009
Accepted 1 December 2009
Keywords:
Lanthanide
Fluorescence property
Pyrazole
© 2009 Elsevier B.V. All rights reserved.
1. Introduction
carboxyl group, which would be of potential applications in
time-resolved fluoroimmunoassay and DNA probe. In addition,
Fluorescent compounds have attracted much attention recently
due to their potential applications. When they are fluorescent in
the solid state, they may be good candidates for photoluminescent
or electroluminescent materials [1–3]; when they are fluorescent
in solution, they can be used as fluorescent sensor molecules for
research in biology or environmental science [4,5]. In the develop-
ment of new luminescent materials, organic electroluminescence
(OEL) has been studied extensively for its applications because of
its low drive voltage, suitability for integrated circuit and potential
application for large flat panel display [6,7]. As some lanthanide
ions, e.g. Eu3+ and Tb3+ possess good luminescence characteristics
based on the transitions between the 4f energy levels, a series of
compounds activated Eu3+ and Tb3+ have been studied for practical
application as phosphors and laser materials [8].
we prepared Eu(III) and Tb(III) pyrazole complexes using 1,10-
phenanthroline as a secondary ligand since it is widely used as
assistant antenna groups for photosensitising lanthanide ion. The
luminescence properties of all these complexes in solid state were
investigated in detail. The synthetic route of ligands are listed in
Scheme 1.
2. Experimental
2.1. Materials
3,6-Dichloropicolinic acid and other reagents were purchased
and used as without further purification. Rare earth chlorides were
prepared according to the literature [10].
The investigations into the relationship between the struc-
tures or organic ligands and the energy levels of lanthanide
ions will give evidences for designing high luminescent lan-
thanide organic complexes. In this work, two novel pyrazole-
derived ligands named 3-chloro-6-(3,5-dimethyl-1H-pyrazol-1-
yl)-N-phenylpicolinamide and 3-chloro-6-(3,5-dimethyl-1H-pyra-
zol-1-yl)picolinic acid and their Eu(III) and Tb(III) complexes
were synthesized. Both of the two novel pyrazole ligands have
rigid conjugated planar structure [9], the carboxylate group or
2.2. Methods
Contents of carbon, hydrogen and nitrogen were determined
using an Elementar vario ELanalyzer. Content of Tb(III) was deter-
mined by EDTA titration. Infrared spectra (4000–400 cm−1) were
recorded with samples as KBr discussing a Nicolet NEXUS 670
FTIR spectrophotometer. 1H NMR spectra was measured by using
a Varian Mercury-300 nuclear magnetic resonance spectrometer
with DMSO as solvents and TMS as internal reference. Fluores-
cence measurements were made on a Hitich F-4500 spectrometer.
All the pH measurements were made with a pHS-3 digital pH-
meter (Shanghai REX instrument factory, Shanghai, China) with
∗
Corresponding author. Tel.: +86 771 3064863; fax: +86 771 3260896.
E-mail address: yxhphd@163.com (X.-H. Yin).
1386-1425/$ – see front matter © 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2009.12.006

826
F.-L. Hu et al. / Spectrochimica Acta Part A 75 (2010) 825–829
Scheme 1.
a combined glass-calomel electrode. Thermogravimetric (TG) and
differential thermal gravimetry (DTG) were performed in the nitro-
gen atmosphere using a Shimadzu DTG 40 system at a heating rate
of 10 ◦C min−1 from 30 ◦C to 800 ◦C.
NH), 2.30–2.55 (s, 6H, CH3). Elemental analytical (calc.) C% 62.42
(62.48); H% 4.68 (4.63); N% 17.10 (17.15).
2.3.4. Synthesis of
3-chloro-6-(3,5-dimethyl-1H-pyrazol-1-yl)picolinic acid (5)
Compound (CDPP) (2 g 6.1 mmol) was added to a solution of
sulfuric acid (10.0 ml 50%) under stirring at room temperature for
10 min, and the mixture was heated to 130 ◦C incubated for 3.5 h,
then was cooled to room temperature and sodium bicarbonate
was added until the pH value was 1, a white precipitate formed,
The precipitate was collected by filtration. Recrystallization from
ethanol give the ligand 3-chloro-6-(3,5-dimethyl-1H-pyrazol-1-
yl)picolinic acid (CDPA) (1.15 g). Yield 80%; mp 180–82 ◦C, IR(KBr),
ꢀmax (cm−1): 3400 (OH), 1713 (C O), 1582 (C N), 1572, 1560, 1469,
1382 (skeleton of ph, Py and Pyraz), 1256 (C–N), 1H NMR(DMSO-d6,
ppm), ı 11.05 (s, 1H, OH), 8.15 (d, 1H, Py), 7.94 (d, 1H, Py), 6.16 (s,
1H, Pyraz), 2.21–2.58 (m, 6H, CH3).
2.3. Synthesis of the ligand
2.3.1. Synthesis of 3,6-dichloro-N-phenylpicolinamide (2)
To a solution of 3,6-dichloropicolinic acid (DCPA) (9.55 g,
0.05 mol) in anhydrous CHCl3 (150 mL), sulfuryl dichloride (50 mL)
was added dropwise under nitrogen atmosphere at 0 ◦C with con-
tinuous stirring for 3 h. Excess solvent was removed under reduced
pressure and the residue was cooled to 0 ◦C with ice bath. Aniline
(5.11 g 0.055 mol) added dropwise, triethylamine in acetonitrile
(100 mL) was added to the residue. The solution was stirred for
another 1 h. The solvent was removed and the crude product was
purified by recrystallization from ethanol to give the flaxen solid 2
(12.5 g) after drying in vacuum. Yield: 90%; mp 130–132 ◦C. IR(KBr),
ꢀmax (cm−1): 3350 (N–H), 1690 (C O) 1600, 1525, 1490, 1340
(skeleton of Ph, Py), 1255 (C–N), 1H NMR(DMSO-d6, ppm), ı: 8.02
(d, 1H, Py), 7.84 (d, 1H, Py), 7.27–7.53 (m, 5H, C6H5), 9.80 (s 1H,
NH). Elemental analytical (calc.) C% 53.86 (53.96); H% 3.08 (3.02),
N% 10.39 (10.49).
2.4. Synthesis of the complexes
The complex Eu(DCPA)3·3H2O was prepared according the fol-
lowing steps. A solution of DCPA (0.286 g, 1.5 mmol) in ethanol
(10 ml) was added dropwise to a solution of EuCl3·6H2O (0.148 g,
0.5 mmol) in ethanol (10 ml) under stirring and this mixture was
heated at 60 ◦C for 24 h. Then the pH value of the mixture was
adjusted to 6 by adding an aqueous solution of sodium hydrox-
ide, pale yellow precipitate obtained was separated by filtration,
washed three times with ethanol and dried in vacuum for 48 h. The
yield was about 60% based on the amount of EuCl3 used.
2.3.2. Synthesis of 3-chloro-6-(3,5-dimethyl-1H-pyrazol-1-yl)-N-
phenylpicolinamide
(3)
Hydrazine hydrate (50 ml, 85%) was added to a solution of 2 (5 g)
in toluene under stirring at 110 ◦C for 1 h, then cooled to room tem-
perature and ice water (100 ml) was added to the mixture, a white
precipitate formed. The precipitate was collected by filtration and
washed with water. Recrystallization from ethanol give the com-
pound 3 (2.45 g). Yield: 50%; mp 140–142 ◦C. IR(KBr), ꢀmax (cm−1):
3300 (N–H), 1690 (C O), 1520 (C N), 1500 (C C). 1H NMR(DMSO-
d6, ppm), ı: 7.8 (d, 1H, Py), 7.74 (d, 1H, Py), 7.15–7.41 (m, 5H, C6H5),
9.55 (s 1H, NH). Elemental analytical (calc.) C% 62.96 (62.48); H%
4.68 (4.63), N% 17.39 (17.15).
The complex Eu(DCPA)2(Phen)·H2O was prepared as follows:
1,10-phenanthroline (0.095 g, 0.5 mmol) in ethanol (10 ml) was
added to a solution prepared as described for Eu(DCPA)3·3H2O
above. The mixture was heated under stirring at 80 ◦C for 24 h.
Then the pH value of the mixture was adjusted to 6 by adding an
aqueous solution of sodium hydroxide. The pale yellow precipitate
obtained was filtered, washed three times with ethanol and
dried in vacuum for 48 h, yield: 75%. Similarly, the other com-
plexes Eu(CDPP)3·2H2O, Eu(CDPP)2(Phen)·3H2O, Eu(CDPA)3·4H2O,
Eu(CDPA)2(Phen)·3H2O,
Tb(DCPA)3·4H2O,
Tb(DCPA)2(Phen),
Tb(CDPP)3·3H2O, Tb(CDPA)3·4H2O, Tb(CDPP)2(Phen)·3H2O and
Tb(CDPA)2(Phen) ·3H2O were prepaered.
2.3.3. Synthesis of 3-chloro-6-(3,5-dimethyl-1H-pyrazol-1-yl)-N-
phenylpicolinamide
(4)
All complexes are soluble in DMF, DMSO and methanol, a little
soluble in ethanol, ethyl acetate and acetone, insoluble in benzene,
diethyl ether and THF.
Pentane-2,4-dione (0.91 g 9.1 mmol) was added to solution of
3 (2 g 7.6 mmol) in toluene under stirring and this mixture was
heated at 120 ◦C for 1.5 h. Excess solvent was removed under
reduced pressure and 50 ml ice water was added to the mixture,
a white precipitate formed. The precipitate was collected by filtra-
tion and washed with water. Recrystallization from ethanol (2.5 g).
Yield: 80%: mp 221–223 ◦C. IR(KBr), ꢀmax (cm−1): 3300 (N–H), 1650
(C O), 1610, 1575, 1530, 1450, 1340 (skeleton of Ph, Py and Pyraz),
1250 (C–N), 1H NMR(DMSO-d6, ppm), ı: 8.05 (d, 1H, Py), 7.91 (d,
1H, Py), 7.28–7.55 (m, 5H, C6H5), 6.08 (s, 1H, Pyraz), 9.84 (s 1H,
3. Result and discussion
3.1. Properties of the complexes
Analytical data for the complexes were presented in Table 1.
The results of elemental analysis indicated that the composition

F.-L. Hu et al. / Spectrochimica Acta Part A 75 (2010) 825–829
827
Table 1
Elemental analytical data for the complexes.
Complex
M (%) found (calc.)
C (%) found (calc.)
H (%) found (calc.)
N (%) found (calc.)
Eu(DCPA)3·3H2O
19.50 (19.51)
20.78 (20.76)
13.06 (13.03)
15.12 (15.15)
15.56 (15.54)
17.42 (17.46)
19.73 (19.77)
22.155 (22.04)
13.34 (13.34)
15.23 (15.20)
16.01 (16.13)
17.65 (17.75)
27.76 (27.75)
39.56 (39.37)
52.76 (52.52)
55.18 (55.10)
40.23 (40.53)
46.93 (46.91)
26.43 (26.89)
39.20 (39.97)
51.42 (51.42)
52.83 (52.83)
40.51 (40.24)
45.61 (45.60)
1.53 (1.55)
1.96 (1.93)
4.09 (4.06)
3.96 (3.92)
3.88 (3.81)
3.56 (3.59)
1.56 (1.76)
1.23 (1.68)
4.13 (4.15)
4.15 (4.14)
3.66 (3.79)
3.70 (3.71)
5.39 (5.39)
7.68 (7.65)
Eu(DCPA)2(Phen)·H2O
Eu(CDPP)3·2H2O
14.38 (14.41)
13.99 (13.97)
12.86 (12.89)
12.89 (12.87)
5.28 (5.23)
Eu(CDPP)2 (Phen)·H2O
Eu(CDPA)3·4H2O
Eu(CDPA)2(Phen)·2H2O
Tb(DCPA)3·4H2O
Tb(DCPA)2(Phen)
7.75 (7.77)
Tb(CDPP)3·3H2O
14.12 (14.11)
13.37 (13.39)
12.95 (12.80)
12.50 (12.51)
Tb(CDPP)2 (Phen)·3H2O
Tb(CDPA)3·4H2O
Tb(CDPA)2(Phen)·3H2O
regarded as a combination of C N of the pyridine or pyrazole ring
and aromatic C C stretching vibrations.
In the case of Ln(III) complexes we observed the following
changes. All the complexes exhibited broad medium intensity
bands at about 3300–3500 cm−1, which were assigned to the coor-
dinated water molecule. The high intensity bands appearing around
1713 cm−1 (DCPA), 1721 cm−1 (CDPP) and 1730 cm−1 (CDPA)
which were ascribed to C O downshifted to 1638–1680 cm−1
in Ln(III) complexes, this confirms that the oxygen atoms of
RCOO– coordinated to Ln(III) ions successfully. The high inten-
sity bands appearing around 1561 cm−1 (DCPA), 1586 cm−1 (CDPP)
and 1564 cm−1 (CDPA) which due to C N in pyridine or pyrazole
ring, downshifted to about 1564 cm−1, 1531 cm−1 and 1558 cm−1
in these Ln(III) complexes respectively. The obvious shifts indicated
that the C N groups of the ligands coordinated to the Ln(III) ions
through nitrogen atoms. The complexes showed medium intensity
bands in the region 550–590 cm−1 which were assigned to Ln–N
[11,12] and 423–435 cm−1 assigned to Ln–O modes.
Fig. 1. Chemical structural formula of the complexes.
of the complexes conforms to Eu(DCPA)3·3H2O, Eu(CDPP)3·2H2O,
Eu(DCPA)2(Phen)·H2O, Eu(CDPP)2(Phen)·3H2O, Eu(CDPA)3·4H2O,
Eu(CDPA)2(Phen)·3H2O,
Tb(DCPA)3·4H2O,
Tb(DCPA)2(Phen),
Tb(CDPP)3·3H2O, Tb(CDPA)3·4H2O Tb(CDPP)2(Phen)·3H2O, and
Tb(CDPA)2(Phen)·3H2O. All the complexes were found to be
soluble in H2O, DMSO, DMF, slightly soluble in ethanol.
On the basis of above evidence and analyses, the possible struc-
tural formula of the complexes is shown in Fig. 1.
According to the results above, we reached the conclusion that
the ligands coordinated to the Ln(III) ions via the oxygen atoms
of the carboxyl groups and the nitrogen atoms of the pyridine,
pyrazole and 1,10-phenanthroline. The elemental analysis and IR
spectra results lead us to propose the general chemical composi-
tion.
3.2. IR spectra
The IR spectral data of the ligands and their lanthanide(III) com-
plexes were listed in Table 2. In the ligands of DCPA and CDPA,
broad weak bands at 3445 and 3440 cm−1 were observed, which
can be attributed to the CO–OH. In addition, high intensity sharp
bands are observed at 1713 cm−1 in DCPA and 1730 cm−1 in CDPA
which are attributed to the C O group. The high intensity bands
at 1601 cm−1 (DCPA), 1603 cm−1 (CDPP), 1606 cm−1 (CDPA) were
assigned to C C. These bands confirm the presence of the aromatic
rings. Medium intensity bands in the 1578–1469 cm−1 region were
3.3. Fluorescence studies
The fluorescence characteristics of Eu(III) and Tb(III) complexes
in solid state were measured at room temperature under PMT
voltage 400 V. Under identical experimental conditions, the fluo-
rescence characteristics of all complexes in solid state were shown
in Fig. 2. The excitation peak of the europium complexes is from
307 to 360 nm. The emission peaks are 593 and 617 nm which can
be attributed to the 5D0 → F1, 5D0 → F2 transitions, respectively.
It shows that the energy transfer from the ligand to Eu3+ take place
and exhibits the fluorescent characteristic of Eu3+. In the Eu(III)
7
7
Table 2
Characteristic IR bands (cm−1) of the ligands and their complexes.
complexes, we could see that the emission band 5D0 → F2 is obvi-
7
ously higher than the other emission band 5D0 → F1 (Fig. 2a, c
7
Compounds
ꢀO–H
ꢀC
O
ꢀC
N
ꢀC–N
ꢀM–O
ꢀM–N
and e), which suggesting low symmetry around the Eu3+ ion in
DCPA
CDPP
CDPA
3445
1713
1721
1730
1698
1640
1679
1680
1715
1701
1695
1689
1675
1688
1647
1706
1558
1564
1543
1542
1545
1528
1531
1520
1557
1538
1543
1526
1529
1603
1545
1227
1259
1234
1233
1221
1261
1226
1244
1225
1230
1221
1250
1226
1247
1225
7
the complexes. Because the forbidden 5D0 → F2 electric dipole
transition is the sensitive to the coordinative environment of Eu3+
ion, the asymmetric microenvironment causes the polarization of
Eu3+ ion under the influence of the electric field of the surround-
ing ligands, which increase the probability for the electric dipole
transition. The excitation peak of the europium complexes is from
307 to 360 nm. The emission peaks are 490, 546, 585 and 622 nm
3440
3365
3521
33295
3345
3340
3325
3501
3452
3487
3365
3438
3385
Eu(DCPA)3·3H2O
Eu(DCPA)2(Phen)·H2O
Eu(CDPP)3·2H2O
Eu(CDPP)2 (Phen)·H2O
Eu(CDPA)3·4H2O
Eu(CDPA)2(Phen) ·2H2O
Tb(DCPA)3·4H2O
Tb(DCPA)2(Phen)
Tb(CDPP)3·3H2O
Tb(CDPP)2 (Phen)·3H2O
Tb(CDPA)3·4H2O
Tb(CDPA)2(Phen) ·3H2O
421
421
413
420
412
419
420
420
415
418
422
422
518
496
505
509
505
522
515
500
506
507
503
520
which can be attributed to the 5D4 → F6, 5D4 → F5, 5D4 → F4, and
7
7
7
7
7
5D4 → F3 transitions, respectively. The emission band 5D4 → F5
is distinctly stronger than the other emission bands 5D4 → F6,
7
5D4 → F4 and 5D4 → F3 in the Tb(III) complexes [13,14] (Fig. 2b,
7
7
d and f).

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F.-L. Hu et al. / Spectrochimica Acta Part A 75 (2010) 825–829
Fig. 2. Subparts (a), (c) and (e) represent the Eu(III) complexes with DCPA, CDPP and CDPA, respectively. Subparts (b), (d) and (f) represent the corresponding Tb(III) complexes.
Black line indicate these complexes using 1,10-phenanthroline as a secondary ligand. The excitation and emission slit widths were 5 nm and the PMT voltage was 400 V.
It is shown in Fig. 2 that the complexes show the character-
istic emissions of Eu(III) and Tb(III). Among these complexes, it is
clearly observed that the fluorescence intensity of Tb(III) complexes
are much stronger than that of corresponding Eu(III) complexes.
This is mostly because that the luminescence of Ln(III) complexes
are related to the efficiency of the intramolecular energy trans-
fer between the triplet level of the ligands and the emitting level
of the ions, which depends on the energy gap between the two
levels, probable the energy gap between the ligand triplet level
and the emitting level of Tb(III) favors to the energy transfer pro-
cess compared with Eu(III) complexes. To obtain highly efficient
luminescence, 1,10-phenanthroline was introduced as a sensitizer.
As seen in the spectra, when the phen was introduced into the
Eu(III) and Tb(III) complexes, the intensity of the high-energy bands
enhanced markedly (Fig. 2). This could be due to the superposition
*
of the ␲ → ␲ transiton of phen, implying that the energy transfer
from phen to the Eu(III) and Tb(III) ion strongly enhances emission
from the phen-doped complexes [15–17]. This data implies that
both ligand and phen are binding to the Eu3+ and Tb3+ ion and that
their presence together affords a strong sensitization of the Eu3+
and Tb3+ emission [18].
It is also observed that the fluorescence intensity of Ln(III) com-
plexes with DCPA or CDPA is about three times as that of Ln(III)
complexes with CDPP and these complexes would be considered
as promising candidates for applications in organic light-emitting
devices, sensory materials and luminescent probes.

F.-L. Hu et al. / Spectrochimica Acta Part A 75 (2010) 825–829
829
177 ◦C. The mass loss percentage is near the loss of three DCPA
molecules from the complex (calc.71.25%). And the second stage
of Tb(DCPA)2(phen) with 31.1% mass loss start at 187 ◦C, finishes
at 314 ◦C and reaches the largest rate at 307 ◦C. The mass loss per-
centage is near the loss of the phen molecule from the complex
(cacl. 25.03%). The residual percentage weight (observed 21.17%
for Tb(DCPA)3·4H2O and 26.6% for Tb(DCPA)2(phen)) at the end of
the decomposition of the complex is consistent with the formation
of Tb4O7.
4. Conclusions
The synthesis and fluorescence properties of Eu(III) and
Tb(III) complexes with new pyridine derived ligands, 3,6-
dichloropicolinic acid, 3-chloro-6-(3,5-dimethyl-1H-pyrazol-1-
yl)picolinic acid, 3-chloro-6-(3,5-dimethyl-1H-pyrazol-1-yl)-N-
phenylpicolinamide and 1,10-phenanthroline were reported.
Acccording to the IR spectra data, coordination of the ligands to
Ln(III) ions was occurring at the oxygen atoms of the carbonyl
goups and the nitrogen atoms of the pyridine (pyrazole) ring and
1,10-phenanthroline. The fluorescence data indicate that Tb(III)
complexes with these ligands exhibit much highter emission than
corresponding Eu(III) complexes. It is worth noting that addi-
tion of 1,10-phenanthroline to the Eu(III) and Tb(III) complexes
lead to the formation of complexes with over 30% higher fluo-
rescence emission. In addition, Tb(III) complexes with CDPA emit
stronger green emission than Tb(III) complexes with correspond-
ing CDPP and DCPA complexes. Based on those results, a series of
new pyrazole-derived ligand could be designed and synthesized
to optimize the luminescent properties of these lanthanide ions
complexes.
Fig. 3. TG–DTG curves of Tb(DCPA)3·4H2O under N2 atmosphere with the heating
rate of 10 ◦C min−1
.
Acknowledgements
The authors thank the National Natural Science Foundation of
China (20761002), PR China, The Natural Science Foundation of
Guangxi (0832080).
Fig. 4. TG–DTG curves of Tb(DCPA)2(phen) under N2 atmosphere with the heating
rate of 10 ◦C min−1
.
References
[1] C.F. Peter, C. Elena, B. James, Chem. Rev. 99 (1999) 3625.
[2] J.Y. Lee, Q.D. Liu, D.R. Bai, Y.J. Kang, Y. Tao, S. Wang, Organometallics 23 (2004)
6205.
[3] X.J. Xu, Y. Liao, G. Yu, H. You, C.A. Di, Z.M. Su, D. Ma, Q. Wang, S.Y. Li, S.Q. Wang,
J.P. Ye, Y.Q. Liu, Chem. Mater. 19 (2007) 1740.
[4] S. Banthia, A. Samanta, J. Phys. Chem. B 110 (2006) 6437.
[5] S.J. Toal, K.A. Jones, D. Magde, W.C. Trogler, J. Am. Chem. Soc. 127 (2005)
11661.
[6] R.H. Friend, R.W. Gymer, A.B. Homes, J.H. Buroughes, R.N. Marks, C. Taliani,
D.D.C. Bradley, D.A. Dos Santos, J.L. Brédas, M. Lögdlund, W.R. Salaneck, Nature
397 (1999) 121.
[7] P.K.H. Ho, D.S. Thomas, R.H. Friend, N. Tessler, Science 285 (1999) 233.
[8] N. Filipescu, W.F. Sager, F.A. Serafin, J. Phys. Chem. 68 (1964) 3324.
[9] K. Zhao, X.H. Yin, Y. Feng, J. Zhu, C.W. Lin, Acta Crystallogr. E64 (2008) m407.
[10] A.J. Chandrasekhar, Imaging Technol. 16 (1990) 158.
[11] K. Ueno, A.E. Martell, J. Phys. Chem. 60 (1956) 1270.
[12] G. Percy, Spectrochim. Acta 32A (1976) 1287.
[13] S.M. Ying, J.G. Mao, Cryst. Growth Des. 6 (2006) 964.
[14] M.D. Regulacio, M.H. Pablico, J.A. Vasquez, P.N. Myers, S. Gentry, M. Prushan, S.
Wah, T. Chang, S.L. Stoll, Inorg. Chem. 47 (2008) 1512.
[15] J.G. Kang, H.G. Cho, J.G. Kim, K.S. Choi, Mater. Chem. Phys. 91 (2005) 172.
[16] J.C. Lee, K.S. Choi, H.K. Cho, J.G. Kang, J. Lumin. 127 (2007) 332.
[17] M.D. McGehee, T.B. Bergstedt, C. Zhang, A.P. Saab, M.B. O’Regan, G.C. Bazan, V.I.
Srdanov, A.J. Heeger, Adv. Mater. 11 (1999) 1349.
3.4. Themogravimetric analysis
The two complexes Tb(DCPA)3·3H2O and Tb(DCPA)2(Phen)
were selected to perform thermal decomposition analysis.
Figs. 3 and 4 show the thermogravimetric and differential ther-
mal gravimetry curves obtained by heating Tb(DCPA)3·4H2O and
Tb(DCPA)2phen in nitrogen atmosphere with the heating rate of
10 ◦C min−1. The decomposition takes place between 30 ◦C and
800 ◦C. In the TG–DTG curves, there are two main successive mass
loss stages from 30 ◦C to 800 ◦C for the two complexes. The first
mass loss satge of Tb(DCPA)3·3H2O starts at 50 ◦C, end at 90 ◦C and
reaches the largest rate at 65 ◦C with mass loss percentage of 10.3%,
this stage roughly coincides with the value of 9.0%, calculated for
the loss of four water molecules from the complex. Similarly, the
first mass loss stage of Tb(DCPA)2(phen) starts at 140 ◦C end at
187 ◦C and reaches the largest rate at 171 ◦C with mass loss percent-
age of 44.6%, this stage roughly coincides with the value of 52.9%,
calculated for the loss of two DCPA molecules from the complex.
The second stage of Tb(DCPA)3·4H2O with 68.5% mass loss
starts at 150 ◦C, finishes at 317 ◦C and reaches the largest rate at
[18] S.T. Frey, M.L. Gong, W.D. Horrocks Jr., Inorg. Chem. 33 (1994) 3229.