Synthesis, crystal structure, luminescence and thermal decomposition kinetics of Eu(III) complex with 2,4-dichlorobenzoic acid and 2,2′-bipyridine

Article abstract of DOI:10.1016/j.ica.2009.03.010

The complex of [Eu(2,4-DClBA)₃(bipy)]₂ (2,4-DClBA = 2,4-dichlorobenzoate; bipy = 2,2′-bipyridine) was obtained and characterized by elemental analysis, IR spectra, UV spectra, luminescence spectra, ¹H NMR spectra, single c

Full text of DOI:10.1016/j.ica.2009.03.010

Inorganica Chimica Acta 362 (2009) 3388–3394
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Note
Synthesis, crystal structure, luminescence and thermal decomposition kinetics
of Eu(III) complex with 2,4-dichlorobenzoic acid and 2,20-bipyridine
d
e
Liang Tian a,b, Ning Ren c, Jian-Jun Zhang a, , Hong-Mei Liu , Ji-Hai Bai , Hong-Mei Ye a,b, Shu-Jing Sun a,b
*
a Experimental Center, Hebei Normal University, Shijiazhuang, Hebei 050016, PR China
b College of Chemistry and Material Science, Hebei Normal University, Shijiazhuang 050016, PR China
c Department of Chemistry, Handan College, Handan 056005, PR China
d College of Chemistry and Pharmacy Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, PR China
e Department of Compute, Hebei Normal College of Science and Technology, Qinhuangdao 066600, PR China
a r t i c l e i n f o
a b s t r a c t
The complex of [Eu(2,4-DClBA)3(bipy)]2 (2,4-DClBA = 2,4-dichlorobenzoate; bipy = 2,20-bipyridine) was
obtained and characterized by elemental analysis, IR spectra, UV spectra, luminescence spectra, 1H
NMR spectra, single crystal X-ray diffraction and TG–DTG techniques. Two Eu3+ ions are connected by
four carboxylate groups through bridging bidentate and bidentate chelating-bridging mode. The coordi-
nation number of europium ion is nine. The thermal decomposition behavior of the title complex under a
static air atmosphere can be discussed by TG–DTG, SEM and IR techniques. The non-isothermal kinetics
was investigated by using double equal-double steps method and Starink method. The mechanism func-
Article history:
Received 8 November 2008
Received in revised form 4 March 2009
Accepted 9 March 2009
Available online 16 March 2009
Keywords:
2,4-Dichlorobenzoic acid
Europium complex
Crystal structure
Thermal analysis
Non-isothermal kinetics
Luminescence
tion of the first decomposition step was determined. Meanwhile, the thermodynamic parameters (
G– and S–) and kinetic parameters (activation energy E and the pre-exponential factor A) were also
calculated.
D
H–,
D
D
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
tion mechanism were studied, and the non-isothermal kinetics was
discussed by using double equal-double steps method [23], and
Starink method [24].
Because of the various crystal structures and unique properties
[1–8], the complexes of rare-earth elements with benzoic acid and
some of derivatives have drawn great attention among scholars for
decades. Along with in-depth studies, their application value has
also attracted great attention. What deserves to be mentioned is,
efficient luminescent materials may have several applications: as
new rare-earth fluorescent materials, as luminescent probes in bio-
medical assays [9], as emitters in electroluminescent (EL) devices
[10], etc. In addition, they have been used in many other fields
gradually, such as pharmaceutical industries, functional material
preparation. Meanwhile, thermal analysis techniques are further
developed and widely used to study the thermal behavior and
properties of solid materials. These studies will provide value
information for understanding their potential applications.
In the previous studies [11–22], a series of ternary lanthanide
complexes with benzoic acid or benzoate derivatives and nitro-
gen-containing ligands were prepared, and their crystal structures,
thermal decomposition behaviors and non-isothermal kinetics
were also reported. In this work, on the basis of the previous works,
the complex [Eu(2,4-DClBA)3(bipy)]2 was synthesized. Meanwhile,
the crystal structure, fluorescence spectra and thermal decomposi-
2. Experimental
2.1. Synthesis of [Eu(2,4-DClBA)3(bipy)]2
EuCl3 ꢀ 6H2O (0.2 mmol), 2,4-dichlorobenzoic acid (0.6 mmol)
and 2,20-bipyridine (0.2 mmol) were dissolved, respectively, in
95% C2H5OH solution. The pH of 2,4-dichlorobenizonic acid solu-
tion was controlled in the range of 6–7 by addition of NaOH solu-
tion (1 mol Lꢁ1). The two ligands were mixed and the mixture was
added dropwise to the EuCl3 ꢀ 6H2O solution, stirred continuously
at room temperature for about 10 h and then deposited for 12 h.
Subsequently, the precipitates were collected by filtration and then
dried in desiccator. The colorless single crystals were obtained by
slow evaporation of the mother solution at room temperature
about a month. The Element Anal. Calc.: C, 42.40; H, 1.95; N,
3.19; Eu, 17.30. Found: C, 41.61; H, 1.28; N, 3.10; Eu, 16.85%.
2.2. Chemicals and apparatus
Eu2O3 (P99.99%), 2,4-dichlorobenzoic acid and 2,20-bipyridine
were obtained from commercial sources and used without further
purification.
* Corresponding author. Tel.: +86 031186269386; fax: +86 031186268405.
E-mail address: jjzhang6@126.com (J.-J. Zhang).
0020-1693/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2009.03.010

L. Tian et al. / Inorganica Chimica Acta 362 (2009) 3388–3394
3389
The contents of carbon, hydrogen and nitrogen were acquired
on a Vario-EL III element analyzer, while the metal content was as-
sayed using EDTA titration method. Infrared spectra were recorded
at room temperature from 4000 to 400 cmꢁ1 using a Perkin–Elmer
FTIR-1730 spectrometer with the KBr discs technique. The ultravi-
olet spectra were recorded on a Shimadzu 2501 spectrophotometer
in DMSO. 1H NMR spectra were obtained by a Bruker AVAN-
CE500MHZ-NMR spectrometer. The single crystal X-ray diffraction
data was obtained by a Bruker Apex II CCD diffractometer with
that the coordination of nitrogen atoms of a bipy ligand to Eu3+
ion [28].
3.3. 1H NMR spectra
1H NMR spectra of the ligands and its complex were obtained at
room temperature in deuterated solvent (DMSO). The chemical
shift of 1H NMR spectra of the complex and ligands are displayed
in Table 2. The spectral line of the proton (COOH) of free 2,4,-DClBA
ligand in 1H NMR spectra disappears on complexation. The facts
indicate that the oxygen atoms of the carboxyl group are coordi-
nated to Eu3+ ion [29]. Meanwhile, chemical shift dH of benzol ring
moves to high magnetic field in 1H NMR spectra after coordination.
Because the carboxyl group directly bonded with Eu3+ while coor-
dinating instead of H atom. As a result, electron cloud moved to
benzol ring, making electron density equilibration, which leads to
the moving of the shift dH at benzol ring to high magnetic field.
The chemical shifts of bipy do not change after coordination. It
may be caused by steric effect of bipy. The new Eu–N bonds are
formed via the non-hybridized p orbit of bipy nitrogens share lone
electron pairs with Eu3+. But as the crystal structure of the title
complex shown, 2,4-dichlorobenzoic acids are around to bipy.
And so, there will have large steric hindrance to the two bulky pyr-
idine rings. As a result of it, the bond lengths of the new formed
Eu–N bonds get longer. Because of the weak coordination between
Eu3+ and bipy nitrogen, the electro cloud density of bipy system is
nearly not affected, and this fact results in the unchanged chemical
shift.
graphite-monochromated Mo
Ka radiation (k = 0.71073 Å) at
293 K using u– scan technique in the range of 1.72° 6
x
h 6 26.00°. A semi-empirical absorption correction with the SADABS
was applied. The structure was solved by direct methods using
SHELXS-97 program and refined by Full-matrix least-squares on F2
using SHELXL-97 program to R1 = 0.0722 wR2 = 0.1751. The TG–DTG
experiments were achieved using a Perkin–Elmer TGA7 thermo-
gravimetric analyzer. The heating rate was 3, 5, 7, 10, 15 °C minꢁ1
from ambient to 950 °C under a static air atmosphere. The fluores-
cence spectra were measured on an F-4500 Hitachi spectropho-
tometer in the solid state at room temperature. Small amount of
the sample was dispersed regularly on the sample holder and Au
was sprayed for 15 min with Hitachi IB-5. Then they were observed
by the Hitachi S-570 scanning electron microscope.
3. Results and discussion
3.1. Ultraviolet spectra
The UV spectra data of the ligands and its complex were de-
picted with DMSO solution as reference. The complex and ligands
have the strong
3.4. Luminescent properties
p ?
p* transition absorption. The UV absorption
The luminescence spectrum excited at 396 nm was recorded at
room temperature as shown in Fig. 1. The sample gives rise to red
light emission under UV excitation. The emission spectrum for the
title complex is composed of the characteristic emission peaks of
Eu (III) arising from 5D0 ? 7F0 (579 nm), 5D0 ? 7F1 (592 nm) and
5D0 ? 7F2 (615 nm), respectively. The luminescence intensity of
5D0 ? 7F2 transition emission is strongly dependent on the chemi-
cal environments of Eu3+. And Fig. 1 shows the intensity of
5D0 ? 7F2 electric dipole transition is much greater than that of
5D0 ? 7F1 magnetic dipole transition, indicating that there is no
inversion symmetry at the site of Eu3+ ion [30].
spectra of the complex show maximum absorption peak at
280 nm, while the band for the 2,4-DClBA ligand is about
260 nm. This phenomenon can be explained by the expansion
p-
conjugated system that caused by the metal coordination [25]. In
addition, the maximum absorption band of bipy at 280 nm is sim-
ilar to that in the complex, but it is noteworthy that the molar
extinction coefficient in the same wavelength is greatly enhanced
(from 0.28 to 0.38), suggesting that it has formed bigger conju-
gated system, namely forming chelating ring.
3.2. Infrared spectra
3.5. Crystal structure determination
The characteristic bands of the ligands and its complex are dis-
played in Table 1. The IR spectrum of the complex shows the char-
acteristic absorption of the carboxylate group at 1614 cmꢁ1 for
asymmetric stretching and at 1411 cmꢁ1 for symmetric stretching
The crystal structure of the title complex is displayed in Fig. 2.
Crystallographic data for the title complex are presented in Table
3 and the selected bond lengths and angles listed in Table 4.
Each Eu3+ is nine coordinated to two nitrogen atoms from one
2,20-bipyridine molecule, two oxygen atoms from one bidentate
chelating carboxylate group, two oxygen atoms from two biden-
tate bridging carboxylate groups, and three oxygen atoms from
two bidentate chelating-bridging carboxylate groups. The coordi-
nation polyhedron around Eu3+ shown in Fig. 3 is a capped square
antiprism geometry, and the capping donor atom is O3. The mole-
cules are interlinked by super- molecular network structure along
(
D
= 203 cmꢁ1). While the characteristic band of carboxylate group
at 1699 cmꢁ1 attributed to the free ligand 2,4-DClBA disappears
completely. The results clearly show the oxygen atoms in carbox-
ylate groups participate in coordination to Eu3+ ion [26]. The sepa-
ration (
= 193 cmꢁ1) is considered indicative of bidentate bridging car-
boxylate groups [27]. Furthermore, the appearance of the band of
(Eu–O) at 419 cmꢁ1 also indicates the conclusions above. Mean-
while, the bands of
CN(1578 cmꢁ1) and dCH (992 cmꢁ1, 757 cmꢁ1
D) of the complex similar to corresponding sodium salt
(D
m
m
)
the [1,0,1] direction via
Fig. 4.
p–p stacking interaction as shown in
of a bipy ligand shift to higher wave numbers around at 1588,
1014 and 761 cmꢁ1 in the spectra of the complex, indicating
Table 1
IR absorption for the ligands and complex (cmꢁ1).
Compounds
mCN
dCH
mCO
m
as(COOꢁ)
m
s(COOꢁ)
m(RE–O)
Bipy
2,4-HDClBA
[Eu(2,4-DClBA)3(bipy)]2
1578
992
757
751
1699
1588
1014
1614
1411
419

3390
L. Tian et al. / Inorganica Chimica Acta 362 (2009) 3388–3394
Table 2
1HNMR data for the ligands and complex.
Compounds
d (ppm)
d1
d2
d3
d4
da
db
dc
dd
COOH4
7.88
7.71
7.57
13.53
Cl
3
2
1
Cl
b
c
a
d
7.45
7.46
7.95
7.96
8.40
8.40
8.69
8.70
N
N
[Eu(2,4-DClBA)3(bipy)]2
7.06
6.96
6.53
1000
800
600
400
200
0
525
550
575
600
625
650
675
/nm
Fig. 1. Luminescence spectra of complex [Eu(2,4-DClBA)3(bipy)]2.
In the title complex, the length of Eu–O bond is in the range of
2.353(7)–2.632(8) Å, and the mean bond length is 2.444 Å. While
the length of Eu–N bond between 2.552(9) Å and 2.581(8) Å with
an average length of 2.567 Å is longer than the Eu–O bond, indicat-
ing that Eu–O bond is stronger than Eu–N bond, which is in accor-
dance with the results of thermal decomposition process. In the
binuclear molecule, the Eu–O bond distance of bidentate bridging
carboxyl groups are smaller than those of the chelating carboxyl
groups. The reason is probably due to the stronger strain in the
four-membered ring of chelating coordination [31].
Fig. 2. Molecular Structure of the title complex.
changed from smooth-surface to a crackled crystal. The second
stage occurs at 289.68–871.99 °C with the mass loss of 62.06%
(the theoretical mass loss is 62.18%) and corresponds to the loss
of C42H18Cl12O9. As shown in the IR spectra of the residue, the
3.6. Thermal decomposition of the complex
bands of the asymmetric vibrations
m
as(COOꢁ) at 1614 cmꢁ1 and
symmetric vibrations
m
s(COOꢁ) at 1411 cmꢁ1 disappear. It can be
The TG–DTG curves of [Eu(2,4-DClBA)3(bipy)]2 with a heating
rate of 10 °C minꢁ1 are shown in Fig. 5. The data of thermal decom-
position are listed in Table 5. The SEM pictures of the complex
[Eu(2,4-DClBA)3(bipy)]2 at RT, 289.68 °C and 871.99 °C are given
in Fig. 6a–c.
As is shown from the DTG curve, the thermal decomposition
process of the title complex can be divided into two stages. The
first stage occurs from 137.84 °C to 289.68 °C with the mass loss
of 17.38% (the theoretical mass loss is 17.79%), which is equivalent
to the loss of 2bipy. The IR spectra of the residue at 289.68 °C
shows that the absorption band of C@N at 1588 cmꢁ1 disappears.
Compared with Fig. 6a and b, the appearance of the title complex
seen that the crackled crystal broke up into even smaller granules
from the Fig. 6c. The characteristic absorption band of the residue
as shown in the IR spectra is similar to the standard sample spec-
trum of Eu2O3. Therefore, the final product at 871.99 °C is Eu2O3.
The total weight loss of the thermal decomposition process of
the title complex is 79.44% (the theoretical mass loss is 79.97%).
Based on the analysis above, the thermal decomposition process
of [Eu(2,4-DClBA)3(bipy)]2 can be denoted in the following
scheme:
½Euð2; 4-DClBAÞ3ðbipyÞꢂ2 ! ½Euð2; 4-DClBAÞ3ꢂ2 ! Eu2O3

L. Tian et al. / Inorganica Chimica Acta 362 (2009) 3388–3394
3391
Table 3
Crystal data and structure refinement for [Eu(2,4-DClBA)3(bipy)]2.
Item
Data
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system, space group
Unit cell dimensions
a (Å)
C62H46Cl12Eu2N4O12
1756.25
293(2)
0.71073
monoclinic, P2(1)/n
11.94674(19)
17.2743(3)
16.955(3)
b (Å)
c (Å)
a
(°)
b (°)
(°)
V (Åꢁ3
90
106.600(3)
90
3353.2(10)
2, 1.739
2.394
1720
c
)
Z, calculated density (Mg/mꢁ3
)
)
Absorption coefficient (mmꢁ1
F(000)
Crystal size (mm)
h range for data collection (°)
Limiting indices
0.390 ꢃ 0.252 ꢃ 0.189
1.72–26.00
ꢁ14 6 h 6 12, ꢁ18 6 k 6 21,
ꢁ20 6 l 6 16
17636/6581 [0.1641]
99.9%
Reflections collected/unique [R(int)
Completeness to h = 26.00
Absorption correction
]
Fig. 3. Coordination geometry of Eu3+ ion.
empirical
Maximum and minimum transmission 1.0000 and 0.8338
Refinement method
full-matrix least-squares on F2
Data/restraints/parameters
6581/6/410
0.944
Goodness-of-fit (GOF) on F2
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.07224, wR2 = 0.1751
R1 = 0.1234, wR2 = 0.1937
2.741 and ꢁ1.425
Largest difference peak and hole (e Aꢁ3
)
Table 4
Bond lengths (Å) and angles (°) for [Eu(2,4-DClBA)3(bipy)]2.
Eu(1)#1–O(3)
Eu(1)#1–O(4)
Eu(1)#1–N(1)#1
Eu (1)#1–N(2)#1
2.632(8)
2.517(8)
2.552(9)
2.581(8)
2.353(7)
74.8(2)
135.0(3)
75.2(2)
80.7(3)
85.0(3)
126.8(3)
129.6(3)
81.1(3)
76.8(3)
53.3(3)
87.0(3)
122.5(3)
81.7(3)
145.7(3)
142.4(3)
Eu (1)#1–O(5) #1
Eu (1)#1–O(6) #1
Eu (1)#1–O(1) #1
Eu (1)#1–O(3) #1
2.424(8)
2.428(8)
2.388(7)
2.364(6)
137.2(3)
148.0(3)
79.1(3)
96.6(3)
74.6(3)
146.6(3)
138.1(3)
74.1(3)
72.9(2)
70.3(2)
146.2(3)
142.1(3)
49.8(2)
77.4(3)
98.1(3)
156.2(3)
Eu(1)#1–O(2)
O(2)–Eu(1)#1–N(1)#
O(3)#–Eu(1)#1–N(1)#
O(1)#–Eu(1)#1–N(1)#
O(5)#–Eu(1)#1–N(1)#
O(6)#–Eu(1)#1–N(1)#
O(3)#–Eu(1)#1–N(2)#
O(1)#–Eu(1)#1–N(2)#
O(5)#–Eu(1)#1–N(2)#)
O(3)#–Eu(1)#1–O(3)
O(1)#–Eu(1)#1–O(3)
O(5)#–Eu(1)#1–O(3)
O(6)#–Eu(1)#1–O(3)
O(4)–Eu(1)#1–O(3)
O(2)–Eu(1)#1–C(18)
O(3)#–Eu(1)#1–C(18)
O(5)#–Eu(1)#1–C(18)
O(2)–Eu(1)#1–O(3)#
O(2)–Eu(1)#1–O(1)#
O(3)#–Eu(1)#1–O(1)#
O(2)–Eu(1)#1–O(5)#
O(3)#–Eu(1)#1–O(5)#
O(1)#–Eu(1)#1–O(5)#
O(2)–Eu(1)#1–O(6)#
O(3)#–Eu(1)#1–O(6)#
O(1)#–Eu(1)#1–O(6)#
O(5)#–Eu(1)#1–O(6)#
O(2)–Eu(1)#1–O(4)
O(3)#–Eu(1)#1–O(4)
O(1)#–Eu(1)#1–O(4)
O(5)#–Eu(1)#1–O(4)
O(6)#–Eu(1)#1–O(4)
Fig. 4. Crystal packing diagram of the title complex.
E, A and probable mechanism function can be determined by
means of double equal-double steps method [23]. The Ozawa iter-
ation equation [33] is as follows:
ꢂ
ꢀ
ꢁ
ꢃ
b
0:0048AE
E
RT
ln
¼
ln
ꢁ ln Gð
a
Þ
ꢁ 1:0516
ð2Þ
HðxÞ
R
#1 ꢁx + 2, ꢁy + 2, ꢁz + 2.
expðꢁxÞ
0:0048 expðꢁ1:0516xÞ
HðxÞ ¼
hðxÞ ¼
hðxÞ
3.7. Kinetics of the first decomposition stage
x4 þ 18x3 þ 86x2 þ 96x
x4 þ 20x3 þ 120x2 þ 240x þ 120
The activation energy E of the first decomposition stage has
been calculated by Starink method [24]. The equation is as follows:
ꢄ
ꢅ
0:0048AEHðxÞ
E
RT
ln Gð
a
Þ ¼ ln
ꢁ 1:0516
ꢁ ln b ¼ a þ b ln b
ð3Þ
b
T1f :92
E
RTf
R
ln
¼ ꢁ1:0008
þ C
ð1Þ
where G(
a) is the integral mechanism function, T the absolute tem-
By substituting Tf and b obtained from the experiment into Eq. (1), E
is determined from the slope of plots of ln(b/Tf1.92) versus 1/Tf .
perature, A the pre-exponential factor, R the gas constant, E the
apparent activation energy and b the linear heating rate.
Fig. 7 shows the relationship between E and
activation energy E change slightly with , suggesting the first
decomposition stage is a single step reaction [32]. Therefore, the
a
. The values of
By substituting the values of
sion functions [34] into Eq. (3), using the linear least-squares
method with lnG( ) versus lnb, the linear correlation coefficient
a, b in Table 6 and various conver-
a
a

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L. Tian et al. / Inorganica Chimica Acta 362 (2009) 3388–3394
Fig. 5. TG–DTG curves of the title complex at a heating rate of 10 °C minꢁ1
.
Table 5
Thermal decomposition data for [Eu(2,4-DClBA)3(bipy)]2 (b = 10 °C minꢁ1).
Stage
Temperature range (°C)
DTG peak temperature (°C)
Mass loss (%)
Probable composition of removed groups
Intermediate
TG
Theory
I
II
137.84–289.68
289.68–871.99
245.11
483.32
17.38
62.06
17.79
62.18
2bipy
C42H18Cl12O9
[Eu(2,4-DClBA)3]2
Eu2O3
Fig. 6. SEM pictures of the [Eu(2,4-DClBA)3(bipy)]2 at (a) RT; (b) 289.68 °C and (c) 871.99 °C.
As seen from Table 7, it can be concluded that only the coeffi-
cients r of the function no. 25 is best while the slope b is close to
ꢁ1. So the probable mechanism function of the title complex is
G(a) = a, f(a) = 1. Therefore, it can be decided that the reaction
mechanism in the first stage is the boundary reaction. The kinetic
d
a
A
b
E
equation is
¼
expðꢁ RTÞ.
dt
The activation energy is inaccurate by plots of lnb versus 1/T
based on the traditional isoconversional method, as it neglects
the variation of H(x) against x. However, iterative calculations con-
sidering the change can give the exact value of activation energy by
means of plots of ln(b/H) versus 1/T, no matter how little or how
great the E/RT value of the reaction is. The value of activation en-
ergy is literately calculated by Ozawa iteration method [33]
according to Eq. (2), until the absolute difference of (Ei ꢁ Eiꢁ1) is
less than a defined small quantity such as 0.1 kJ molꢁ1
.
By substituting the values of a, b and T in Table 8 and the cor-
responding mechanism function determined above into Eq. (2),
via the linear least-squares method with lnb/H(x) versus 1/T. The
activation energy E can be calculated from the value of the slope
and the pre-exponential factor A can also be calculated from the
value of the intercept. The results are listed in Table 9.
The thermodynamic parameters of activation can be calculated
from the equations [35,36]:
Fig. 7. The relationship of E and
complex.
a of the first decomposition stage for the title
r, the slope b and the intercept a at the different temperatures were
obtained. The integrant results are listed in Table 7.

L. Tian et al. / Inorganica Chimica Acta 362 (2009) 3388–3394
3393
Table 6
Conversion degrees measured for given the same temperatures on the TG–DTG curves of [Eu(2,4-DClBA)3(bipy)]2 at different heating rates: (Stage I).
T (K)
a
b = 3 °C minꢁ1
b = 5 °C minꢁ1
b = 7 °C minꢁ1
b = 10 °C minꢁ1
b = 15 °C minꢁ1
483.61
489.81
494.27
497.66
500.47
502.87
504.96
0.2878
0.4335
0.5726
0.7014
0.8196
0.9072
0.9603
0.1585
0.2456
0.3358
0.4183
0.5021
0.5849
0.6648
0.1000
0.1500
0.2000
0.2500
0.3000
0.3500
0.4000
0.0770
0.1192
0.1629
0.2034
0.2466
0.2883
0.3294
0.0534
0.0813
0.1098
0.1385
0.1641
0.1943
0.2193
Table 7
Table 9
Integrant of the results from the linear least-squares method at different tempera-
tures for [Eu(2,4-DClBA)3(bipy)]2: (Stage I).
The values of the kinetic parameters computed by use of the plot of lnb/H(x) vs. 1/T.
a
E (kJ molꢁ1
)
A ꢃ 1014 (minꢁ1
)
r
T (K)
Function no.
a
b
r
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
109.03
115.89
117.24
118.94
119.77
119.83
119.94
120.37
120.08
119.75
119.59
118.87
118.91
118.98
118.50
117.71
116.75
2.49
14.91
21.39
33.25
41.33
42.20
43.73
48.83
45.50
42.06
40.27
33.75
33.94
34.34
30.31
24.61
19.07
ꢁ0.9846
ꢁ0.9909
ꢁ0.9906
ꢁ0.9911
ꢁ0.9913
ꢁ0.9915
ꢁ0.9914
ꢁ0.9906
ꢁ0.9902
ꢁ0.9900
ꢁ0.9905
ꢁ0.9915
ꢁ0.9914
ꢁ0.9913
ꢁ0.9916
ꢁ0.9909
ꢁ0.9914
483.61
15
25
35
15
25
35
15
25
35
15
25
35
14
25
35
9
0.2811
ꢁ0.8495
ꢁ1.0491
ꢁ0.8306
ꢁ0.8864
ꢁ1.0431
ꢁ0.7141
ꢁ0.9268
ꢁ1.0309
ꢁ0.6011
ꢁ0.9745
ꢁ1.0149
ꢁ0.5004
ꢁ0.9294
ꢁ1.0045
ꢁ0.4194
ꢁ3.4176
ꢁ0.9677
ꢁ0.3422
ꢁ2.6356
ꢁ0.9313
ꢁ0.2868
ꢁ0.9924
ꢁ0.9943
ꢁ0.9976
ꢁ0.9904
ꢁ0.9934
ꢁ0.9956
ꢁ0.9881
ꢁ0.9925
ꢁ0.9897
ꢁ0.9859
ꢁ0.9926
ꢁ0.9825
ꢁ0.9838
ꢁ0.9931
ꢁ0.9683
ꢁ0.9724
ꢁ0.9928
ꢁ0.9547
ꢁ0.9872
ꢁ0.9924
ꢁ0.9361
ꢁ0.6473
0.2648
0.2112
0.1136
0.3037
0.3588
0.2329
0.2925
0.4888
0.3150
0.2615
0.5581
0.3829
0.2306
1.5713
0.4157
0.1943
0.8097
0.4350
0.1676
489.81
494.27
497.66
500.47
502.87
504.96
25
35
6
25
35
118.13(average)
32.47(average)
Table 10
A expðꢁE=RTÞ ¼
m
expðꢁ
S–
D
G–=RTÞ
ð4Þ
ð5Þ
ð6Þ
The thermodynamic parameters of the title complex.
b (°C minꢁ1
)
D
H– (kJ molꢁ1
)
D
G– (kJ molꢁ1
)
D
S– (J molꢁ1 Kꢁ1
)
TP (K)
D
H– ¼ E ꢁ RT
D
G–
¼
D
H– ꢁ T
D
3
5
7
10
15
113.91
113.89
113.83
113.81
113.76
113.84a
94.23
93.86
93.56
93.45
93.24
93.67a
39.45
39.29
39.17
39.13
39.04
39.22a
500.46
509.89
517.50
520.12
525.68
where
m
is the Einstein Vibration frequency,
D
G– is the Gibbs free
enthalpy of activation,
D
H– is the enthalpy of activation,
D
S– is en-
tropy of activation. The values of entropy, enthalpy and the Gibbs
free energy of activation at the peak temperature acquired on the
basis of Eqs. (4)–(6) are shown in Table 10. As seen in Table 10,
a
An average value.
Table 8
The values of temperatures at the same degree of conversion for the different hating rate on TG curves for the title complex (Stage I).
a
T (K)
b = 3 °C minꢁ1
b = 5 °C minꢁ1
b = 7 °C minꢁ1
b = 10 °C minꢁ1
b = 15 °C minꢁ1
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
466.57
473.51
477.91
481.42
484.25
486.57
488.52
490.40
492.04
493.48
495.02
496.28
497.59
498.81
500.02
501.34
502.59
478.01
482.88
486.98
490.08
492.66
494.91
496.98
498.70
500.36
501.82
503.23
504.60
505.84
507.14
508.26
509.45
510.88
483.61
489.81
494.27
497.66
500.47
502.87
504.96
506.97
508.78
510.38
511.90
513.19
514.57
515.87
517.23
518.64
520.04
487.33
493.24
497.35
500.58
503.47
505.88
507.97
509.86
511.59
513.14
514.81
516.16
517.62
518.83
520.21
521.46
523.05
492.85
498.94
503.42
506.94
509.78
512.33
514.48
516.36
518.23
519.82
521.59
523.27
524.64
526.03
527.44
529.08
530.74

3394
L. Tian et al. / Inorganica Chimica Acta 362 (2009) 3388–3394
G– are more than 0, indicating that the decomposi-
[3] Y. Li, F.K. Zheng, X. Liu, W.Q. Zou, G.C. Guo, C. Z Lu, J.S. Huang, Inorg. Chem. 45
D
the values of
(2006) 6308.
tion reaction for the title complex is not spontaneous reaction.
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4985.
4. Conclusions
[7] G.Q. Li, Y. Li, W.Q. Zou, Q.Y. Chen, F.K. Zheng, G.C. Guo, Chinese J. Struct. Chem.
26 (2007) 575.
The complex was synthesized by the reaction of EuCl3 ꢀ 6H2O,
2,4-dichlorobenzoic acid and 2,20-bipyridine. The crystal structure
of the [Eu(2,4-DClBA)3(bipy)]2 shows that the carboxylic groups
coordinated to Eu3+ with bridging bidentate, bidentate chelating
and bidentate chelating-bridging modes. The coordination number
is nine. The mechanism function of the first step for the title com-
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158 (2008) 157.
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40 (2008) 607.
[21] H.Y. Zhang, J.J. Zhang, N. Ren, S.L. Xu, J.H. Bai, L. Tian, J. Alloy. Compd. 464
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plex is G(
a) = a, f(a) = 1. The activation energy E, the pre-exponen-
tial factor A, the enthalpy of activation
D
H–, the Gibbs free energy
of activation
D
,
G– and the entropy of activation
D
,
S– are
93.67
118.13 kJ molꢁ1
32.47 ꢃ 1014 minꢁ1
,
113.84 kJ molꢁ1
kJ molꢁ1 and 39.22 J molꢁ1 Kꢁ1, respectively.
Acknowledgements
This project was supported by the National Natural Science
Foundation of China (No. 20773034), the Natural Science Founda-
tion of Hebei Province (No. B2007000237) and Science Foundation
of Hebei Normal University (No. L2006Z06).
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Appendix A. Supplementary material
CCDC 686510 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif. Supplementary data associated with this article
can be found, in the online version, at doi:10.1016/j.ica.
2009.03.010.
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Kinetics, 2nd ed., Science Press, Beijing, 2008. p. 151.
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