Synthesis, crystal structure and thermal decomposition mechanism of complex [Sm(o-MBA)3phen]2

Article abstract of DOI:10.1016/j.tca.2005.09.004

The title complex [Sm(o-MBA)₃phen]₂ (o-MBA, o-methylbenzoate; phen, 1,10-phenanthroline) was prepared and characterized by single crystal X-ray diffraction, elemental analysis, IR spectra and TG-DTG techniques. The results show that the crystal is triclinic, space group P ī with a = 13.1364(10) ?, b = 14.3739(11) ?, c = 17.4356(13) ?; α = 83.1100(10)°, β = 83.7760(10)°, γ = 73.0520(10)°, Z = 2, D_c = 1.568 Mg/m³, F (000) = 1476. The crystal is consisted of two similar types of binuclear molecule. Each Sm³⁺ is nine-coordinated by one bidentate chelating carboxylate group, two bidentate bridging and two tridentate chelating-bridging carboxylate groups, as well as one 1,10-phenanthroline molecule. The thermal decomposition mechanism of [Sm(o-MBA)₃phen]₂ has been determined on the basis of thermal analysis. The dependences of E -α for the first-stage decomposition process were determined by using Ozawa-iterative procedure, which show the E values varied with the extent of conversion. In addition, the lifetime equation at weight-loss of 10% was deduced as ln τ = -25.5547 + 18511.68/T by isothermal thermogravimetric analysis.

Full text of DOI:10.1016/j.tca.2005.09.004

Thermochimica Acta 438 (2005) 172–177
Synthesis, crystal structure and thermal decomposition
mechanism of complex [Sm(o-MBA)3phen]2
Ning Rena,b, Jian-Jun Zhanga,∗, Su-Ling Xua,b
,
Rui-Fen Wangb, Shu-Ping Wangb
a Experimental Center, Hebei Normal University, Shijiazhuang 050016, PR China
b College of Chemistry & Material Science, Hebei Normal University,
Shijiazhuang 050016, PR China
Received 28 June 2005; received in revised form 29 August 2005; accepted 2 September 2005
Available online 6 October 2005
Abstract
The title complex [Sm(o-MBA)3phen]2 (o-MBA, o-methylbenzoate; phen, 1,10-phenanthroline) was prepared and characterized by single
crystal X-ray diffraction, elemental analysis, IR spectra and TG-DTG techniques. The results show that the crystal◦is triclinic, space group P
◦
◦
3
˚
˚
˚
¯ı with a = 13.1364(10) A, b = 14.3739(11) A, c = 17.4356(13) A; α = 83.1100(10) , β = 83.7760(10) , γ = 73.0520(10) , Z = 2, Dc = 1.568 Mg/m ,
F (000) = 1476. The crystal is consisted of two similar types of binuclear molecule. Each Sm3+ is nine-coordinated by one bidentate chelating
carboxylate group, two bidentate bridging and two tridentate chelating-bridging carboxylate groups, as well as one 1,10-phenanthroline molecule.
The thermal decomposition mechanism of [Sm(o-MBA)3phen]2 has been determined on the basis of thermal analysis. The dependences of E −α
for the first-stage decomposition process were determined by using Ozawa-iterative procedure, which show the E values varied with the extent of
conversion. In addition, the lifetime equation at weight-loss of 10% was deduced as ln τ = −25.5547 + 18511.68/T by isothermal thermogravimetric
analysis.
© 2005 Elsevier B.V. All rights reserved.
Keywords: o-Methylbenzoic acid; Crystal structure; 1,10-Phenanthroline; Samarium complex; Thermal analysis
1. Introduction
2. Experimental
The coordination complexes of rare-earth with various car-
boxylic acids have been an important research field in coor-
dination chemistry and structure chemistry, due to the spe-
cial structures and interesting luminescence properties [1–3].
Benzoic acid and its derivatives are always widely used in
the coordination complexes of rare-earth because of their
versatile coordination modes. In previous work, a series of
rare-earth complexes with benzoic acid or its derivatives
and 1,10-phenanthroline have been reported [4–10]. Herein
we report the synthesis and crystal structural of samarium
o-methylbenzoate with 1,10-phenanthroline, and characterize
the complex by elemental analysis, thermal analysis, and IR
spectra.
2.1. Materials
All the regents used were Analar grade and were used without
further purification.
2.2. Synthesis of complex [Sm(o-MBA)3phen]2
SmCl3·6H2O, o-MBA and phen were dissolved in 95%
ethanol in a molar ratio of 1:3:1, respectively. The pH value
of the o-MBA was adjusted to 6–7 by adding 1.0 M NaOH solu-
tion. The ethanol solution of two ligands were mixed and then
added dropwise to the ethanolic SmCl3 solution. At once a large
white precipitate formed. The mixture solution was stirred for
8 h at room temperature and then deposited them for 12 h. Sub-
sequently, the precipitate was filtered out and washed three times
with deionized water and 95% ethanol. The white powdery com-
plex [Sm(o-MBA)3phen]2 was obtained with yield of 80%. A
∗
Corresponding author. Tel.: +86 311 86268405; fax: 86 311 86268405.
E-mail address: jjzhang6@sohu.com (J.-J. Zhang).
0040-6031/$ – see front matter © 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.tca.2005.09.004

N. Ren et al. / Thermochimica Acta 438 (2005) 172–177
173
colorless cubic crystal was grown by slow evaporation of its
3. Results and discussion
solvent for a month and its structure was established by X-ray
crystallography.
3.1. Elemental analysis
The analysis data of the element content are shown in Table 2.
It can be seen the experimental data are in a good accord with
the theoretical values.
2.3. Experimental equipment and conditions
Elemental analysis (C, H, N) were determined by a Carlo-
Erba model 1106 elemental analyzer. The content of samarium
was assayed using EDTA titration method. The infrared spec-
3.2. Infrared spectra
tra in KBr discs were recorded over the range 4000–400 cm−1
,
The band of the COOH group for o-methylbenzoic acid lig-
and at 1684 cm−1, completely disappears in the spectra of the
complex. However, the appearance of slight bands at 1591, 1531,
1519 and 1490 cm−1, 1402 cm−1, 1347 cm−1 were assigned
to asymmetric and symmetric vibrations of the COO− group,
indicating that the carboxyl group is coordinated to Sm(III)
ion in three coordination modes [11], which was confirmed by
X-ray diffraction analysis. In addition, IR spectra of the com-
using Bio-Rad FTS-135 spectrometer. X-ray diffraction data
collection was performed on Bruker Apex II CCD diffractometer
with graphite-monochromated Mo K␣ radiation (λ = 0.71073 A)
˚
at 293 K using φ–ω scan mode. A semi-empirical absorption
correction based on SADABS scan technique was applied.
10893 Unique data (Rint = 0.0142) were used to solve the
structure by direct methods using SHELXS-97 program and
refined on F2 by full-matrix least squares methods using
SHELXL-97 program. All non-H atoms were refined anisotrop-
ically, and the H atoms were included in the structure-factor
calculations. The crystal data and refinement details of the
complex are summarized in Table 1. The TG and DTG
experiments for the title compound were performed using a
Perkin-Elmer’s TGA7 Thermogravimetric Analyzer under a
static air atmosphere. The heating rate used was 3, 5, 7,
10 ◦C min−1 from ambient to 925 ◦C and the sample size was
2.5 0.2 mg.
plex show that the bands of νC=N (1646 cm−1), δC–C(854 cm−1
)
and δC–H(740 cm−1) for phen ligand are observed to move
lower wavenumbers at 1613, 846 and 731 cm−1, respectively,
suggesting the coordination of the nitrogen atoms of the 1,10-
phenanthroline to Sm3+ ion [12].
3.3. Crystal structure
The final atomic coordinates and thermal parameters for the
title complex are presented in Table 3. Selected bond lengths and
angles are listed in Table 4. In the asymmetric part, the two dif-
ferent Sm(o-MBA)3phen units are combined through inversion
with the corresponding units of the closest asymmetric species
respectively, andthusthecrystalofthetitlecomplexhastwosim-
ilar types of binuclear molecules [5], as shown in Fig. 1a and b.
The carboxylate groups are bonded to the samarium(III) ion in
three modes: bidentate chelating, bidentate bridging, tridentate
chelating-bridging. Each Sm3+ ion is coordinated to one biden-
tate chelating carboxylate group, two bidentate bridging and two
tridentate chelating-bridging carboxylate groups, as well as one
1,10-phenanthroline molecule, giving the coordination number
of 9. The coordination polyhedron adopts a distorted mono-
capped square antiprism geometry. The oxygen atom from the
tridentate chelating-bridging carboxylate is at the capped posi-
tion.
Table 1
Crystallographic data and structure refinement for [Sm(o-MBA)3phen]2
Empirical formula
Formula weight
Temperature
C72H58N4O12Sm2
1471.92
293(2) K
˚
Wavelength
0.71073 A
Crystal system, space group
Triclinic, P ¯ı
◦
˚
˚
˚
Unit cell dimensions
a = 13.1364(10) A α = 83.1100(10)◦
b = 14.3739(11) A β = 83.7760(10)◦
c = 17.4356(13) A γ = 73.0520(10)
3
˚
Volume
3117.1(4) A
Z, calculated density
Absorption coefficient
F(000)
2, 1.568 Mg/m3
1.933 mm−1
1476
In the Fig. 1a and b, the Sm–Sm distances are 4.045(4) and
Crystal size
Theta range for data collection
Limiting indices
0.34 × 0.26 × 0.18 mm
1.63–25.03◦
˚
˚
4.019 (4) A. The average Sm–O distances are 2.465 and 2.456 A.
˚
−15 ≤h ≤h 14,
−19 ≤l ≤20
−17 ≤k ≤11,
The mean bond lengths of Sm–N are 2.628 and 2.656 A, respec-
tively. It can be concluded that the differences are probably
caused by steric effects of the different position of the methyl
Reflections collected/unique
Completeness to theta = 25.03
Absorption correction
Maximum and minimum trans-
mission
16606/10893 [R(int) = 0.0142]
98.9%
Semi-empirical from equivalents
1.000000 and 0.742728
Table 2
Elemental analysis data of [Sm(o-MBA)3phen]2 (%)
Refinement method
Full-matrix least-squares on F2
10893/6/905
1.083
Complex [Sm(o-MBA)3phen]2
Mass fraction (%)
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2sigma(I)]
R indices (all data)
C
H
N
Sm
R1 = 0.0246, wR2 = 0.0673
R1 = 0.0328, wR2 = 0.−06399
Experimental data
Theoretical values
58.88
58.69
3.93
3.94
4.28
3.80
20.01
20.43
˚
Largest diff. peak and hole
0.374 and −0.456 e A

174
N. Ren et al. / Thermochimica Acta 438 (2005) 172–177
Table 3
4
2
3
˚
Atomic coordinates (×10 ) and equivalent isotropic displacement parameters (A × 10 ) for the molecules (a) and (b)
x
y
z
U(eq)
x
y
z
U(eq)
Sm(1)
O(1)
O(2)
O(3)
O(4)
O(5)
O(6)
N(1)
N(2)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
5893(1)
5555(2)
6944(2)
5024(2)
4306(2)
5758(2)
6629(2)
7878(2)
6424(2)
8612(3)
9647(4)
9938(4)
9216(3)
9461(4)
8775(4)
7709(4)
6964(5)
5990(5)
5746(3)
7414(3)
8172(3)
6276(3)
6335(3)
7147(4)
7209(5)
6460(5)
5673(5)
5579(4)
4686(5)
4400(3)
3864(7)
4385(6)
3835(7)
2764(7)
2242(6)
2792(7)
2252(7)
6503(3)
7306(2)
7816(3)
8526(4)
8729(4)
8238(3)
7531(3)
7088(3)
3657(1)
2149(2)
1955(2)
3103(2)
4675(2)
5811(2)
4252(2)
3567(2)
3514(2)
3530(3)
3523(4)
3583(4)
3612(3)
3666(3)
3645(3)
3585(3)
3496(3)
3426(4)
3443(3)
3570(2)
3586(2)
1612(2)
545(3)
10385(1)
11011(1)
10174(1)
9413(2)
9463(1)
8885(1)
9176(1)
10581(2)
11812(2)
9989(2)
10069(3)
10765(4)
11412(3)
12177(3)
12784(3)
12696(2)
13314(3)
13178(2)
12416(2)
11950(2)
11298(2)
10596(2)
10589(2)
10123(3)
10037(4)
10415(4)
10879(3)
10988(2)
11529(3)
9172(2)
8500(3)
7762(4)
7132(3)
7240(5)
7978(6)
8608(4)
9457(5)
8774(2)
8101(2)
7770(2)
7117(2)
6810(2)
7127(2)
7789(2)
8139(3)
34(1)
60(1)
53(1)
75(1)
47(1)
50(1)
50(1)
49(1)
48(1)
68(1)
95(2)
93(2)
69(1)
87(2)
81(2)
67(1)
84(2)
85(1)
66(1)
49(1)
50(1)
45(1)
54(1)
75(1)
101(2)
102(2)
89(2)
68(1)
117(2)
56(1)
45(2)
50(3)
83(4)
73(4)
82(4)
66(4)
58(3)
43(1)
43(1)
63(1)
80(1)
78(1)
64(1)
50(1)
72(1)
Sm(2)
O(7)
O(8)
−454(1)
2046(2)
−499(2)
−625(3)
−158(2)
1377(2)
1891(2)
640(2)
−1456(2)
1639(3)
2227(3)
1762(4)
702(3)
1339(1)
2783(2)
3048(2)
1887(2)
302(2)
5376(1)
5264(2)
5324(2)
3986(1)
4133(1)
4905(1)
4668(1)
6551(2)
6768(2)
6461(2)
7069(3)
7799(2)
7932(2)
8691(2)
8788(2)
8148(2)
8225(2)
7596(2)
6874(2)
7402(2)
7286(2)
3718(2)
2880(4)
2769(5)
1986(6)
1371(6)
1512(9)
2308(4)
2478(9)
5239(2)
5091(2)
4769(2)
4649(2)
4838(3)
5152(3)
5289(2)
5673(3)
4679(2)
4371(2)
4022(2)
3678(3)
3716(3)
4094(3)
4418(2)
4836(3)
36(1)
54(1)
54(1)
89(1)
47(1)
49(1)
50(1)
43(1)
50(1)
54(1)
67(1)
68(1)
55(1)
72(1)
68(1)
56(1)
73(1)
76(1)
67(1)
45(1)
44(1)
54(1)
45(3)
35(2)
66(3)
70(4)
85(5)
44(2)
74(4)
39(1)
40(1)
48(1)
63(1)
73(1)
75(1)
58(1)
100(2)
42(1)
50(1)
65(1)
96(2)
109(2)
101(2)
68(1)
95(2)
O(9)
O(10)
O(11)
O(12)
N(3)
903(2)
−663(2)
1466(2)
1498(2)
1487(3)
1523(3)
1538(3)
1535(3)
1575(3)
1603(3)
1583(3)
1643(3)
1629(4)
1555(3)
1518(2)
1500(2)
1096(3)
1033(6)
1029(8)
990(6)
975(10)
983(14)
1008(5)
1056(13)
3363(2)
4446(2)
4989(2)
6002(3)
6455(3)
5923(3)
4912(3)
4386(3)
149(3)
N(4)
C(37)
C(38)
C(39)
C(40)
C(41)
C(42)
C(43)
C(44)
C(45)
C(46)
C(47)
C(48)
C(49)
C(50)
C(51)
C(52)
C(53)
C(54)
C(55)
C(56)
C(57)
C(58)
C(59)
C(60)
C(61)
C(62)
C(63)
C(64)
C(65)
C(66)
C(67)
C(68)
C(69)
C(70)
C(71)
C(72)
120(4)
−899(4)
−1474(3)
−2562(4)
−3063(3)
−2481(3)
−948(3)
154(3)
−426(3)
−672(10)
−1726(8)
−1967(8)
−1165(13)
−289(19)
106(7)
1292(8)
1492(3)
1971(2)
1294(3)
1660(3)
2698(4)
3371(3)
3042(3)
3820(3)
2058(2)
3143(3)
3196(3)
4162(5)
5065(4)
5014(4)
4072(3)
4104(4)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
C(30)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
−5(3)
−970(3)
−1369(4)
−841(3)
119(3)
625(4)
3887(3)
3888(11)
3832(8)
3802(7)
3828(9)
3884(10)
3914(11)
3937(9)
5060(3)
5104(3)
4252(3)
4241(4)
5083(4)
5941(3)
5983(3)
6939(3)
237(3)
1131(3)
1263(5)
459(6)
−419(5)
−562(4)
−1539(4)
substituent on the benzene ring (see Fig. 1). In contrast with the
complex [Eu(o-MBA)3phen]2[4] and [Tb(o-MBA)3phen]2[5],
they all have two types of binuclear molecules in their crystals.
The coordination modes of the title complex are same to the for-
mer, but unlike the latter in which the Tb3+ is eight-coordinated
and there is no tridentate chelating-bridging carboxylate group.
[Sm(o-MBA)3phen]2 can be divided into two stages. The first
weight loss of 28.01% between 256.26 and 484.63 ◦C, corre-
sponding to the release of 2 mol phen and 4 mol CH3. The
IR spectra of the residue at 484 ◦C shows that the absorption
band of C=N disappears at 1613 cm−1. Average band length of
Sm–N distance is longer than that of Sm–O, therefore, Sm–N
bond is less stable and easy to be broken down. The second
weight loss of 48.23% was in the range of 484.63–704.33 ◦C,
in which C44H30O9 was removed. As shown in the IR spectra
of the residue at 704 ◦C, the bands of the asymmetric vibra-
tions at 1607–1537 cm−1 and of the symmetric vibrations at
1489–1285 cm−1 disappeared, and IR spectra of the residue are
same to that of the sample Sm2O3. Therefore, by 704.33 ◦C, the
3.4. Thermal decomposition mechanism
Fig. 2 shows the TG-DTG curves of the title complex at a
heating rate of 5 ◦C min−1 under a static air atmosphere. The
thermalanalytical data are listed in Table 5. As was observed
from the DTG curve, the thermal decomposition process of

N. Ren et al. / Thermochimica Acta 438 (2005) 172–177
175
Table 4
Selected bond lengths (A) and angles ( ) for the molecules(a) and (b)
◦
˚
Sm(1) O(5)#1
Sm(1) O(4)#1
Sm(1) O(6)
Sm(1) O(1)
Sm(1) O(3)
Sm(1) O(2)
Sm(1) O(4)
Sm(1) N(2)
Sm(1) N(1)
O(1) C(13)
O(2) C(13)
O(3) C(21)
O(4) C(21)
O(5) C(29)
O(6) C(29)
2.362(2)
2.378(2)
2.390(2)
2.446(2)
2.465(2)
2.483(2)
2.729(2)
2.625(3)
2.631(3)
1.255(4)
1.257(4)
1.241(4)
1.264(4)
1.246(4)
1.259(4)
Sm(2) O(10)#2
Sm(2) O(12)#2
Sm(2) O(11)
Sm(2) O(8)
Sm(2) O(9)
Sm(2) O(7)
Sm(2) O(10)
Sm(2) N(4)
Sm(2) N(3)
O(7) C(57)
O(8) C(57)
O(9) C(49)
O(10) C(49)
O(11) C(65)
O(12) C(65)
2.346(2)
2.373(2)
2.381(2)
2.431(2)
2.471(2)
2.486(2)
2.706(2)
2.634(3)
2.679(3)
1.251(4)
1.269(4)
1.227(4)
1.254(4)
1.261(4)
1.252(4)
O(5)#1 Sm(1) O(6)
O(4)#1 Sm(1) O(6)
O(5)#1 Sm(1) O(1)
O(4)#1 Sm(1) O(1)
O(6) Sm(1) O(1)
O(5)#1 Sm(1) O(3)
O(4)#1 Sm(1) O(3)
O(6) Sm(1) O(3)
O(1) Sm(1) O(3)
O(5)#1 Sm(1) O(2)
O(4)#1 Sm(1) O(2)
O(6) Sm(1) O(2)
O(1) Sm(1) O(2)
O(3) Sm(1) O(2)
O(5)#1 Sm(1) N(2)
O(4)#1 Sm(1) N(2)
O(6) Sm(1) N(2)
O(1) Sm(1) N(2)
O(3) Sm(1) N(2)
O(2) Sm(1) N(2)
O(5)#1 Sm(1) N(1)
O(4)#1 Sm(1) N(1)
O(6) Sm(1) N(1)
O(1) Sm(1) N(1)
O(3) Sm(1) N(1)
O(2) Sm(1) N(1)
N(2) Sm(1) N(1)
O(5)#1 Sm(1) O(4)
O(4)#1 Sm(1) O(4)
O(6) Sm(1) O(4)
O(1) Sm(1) O(4)
O(3) Sm(1) O(4)
O(2) Sm(1) O(4)
N(2) Sm(1) O(4)
N(1) Sm(1) O(4)
133.53(8)
76.21(8)
75.77(8)
144.52(8)
139.26(8)
90.78(10)
124.20(8)
76.38(9)
75.68(9)
127.96(8)
153.95(8)
90.96(8)
52.54(7)
72.76(9)
76.07(9)
79.42(8)
132.26(9)
74.38(9)
149.43(9)
93.55(9)
134.62(9)
79.97(8)
73.28(8)
107.59(9)
134.45(10)
74.60(8)
62.40(9)
68.45(7)
75.49(8)
69.50(7)
111.38(8)
49.51(7)
121.51(7)
140.62(8)
139.17(8)
O(10)#2 Sm(2) O(11)
O(12)#2 Sm(2) O(11)
O(10)#2 Sm(2) O(8)
O(12)#2 Sm(2) O(8)
O(11) Sm(2) O(8)
O(10)#2 Sm(2) O(9)
O(12)#2 Sm(2) O(9)
O(11) Sm(2) O(9)
O(8) Sm(2) O(9)
O(10)#2 Sm(2) O(7)
O(12)#2 Sm(2) O(7)
O(11) Sm(2) O(7)
O(8) Sm(2) O(7)
77.31(8)
134.42(7)
152.14(8)
128.53(8)
91.26(8)
123.95(8)
87.53(10)
79.77(10)
77.59(9)
144.77(7)
75.68(8)
137.82(8)
52.85(7)
72.03(9)
81.99(8)
75.62(8)
134.05(8)
88.39(9)
144.12(10)
73.18(9)
78.23(8)
131.69(8)
74.02(8)
74.20(8)
140.62(10)
109.82(8)
61.74(8)
74.78(8)
69.01(7)
69.62(7)
125.21(8)
49.30(7)
110.53(7)
141.69(8)
138.42(7)
O(9) Sm(2) O(7)
O(10)#2 Sm(2) N(4)
O(12)#2 Sm(2) N(4)
O(11) Sm(2) N(4)
O(8) Sm(2) N(4)
O(9) Sm(2) N(4)
O(7) Sm(2) N(4)
O(10)#2 Sm(2) N(3)
O(12)#2 Sm(2) N(3)
O(11) Sm(2) N(3)
O(8) Sm(2) N(3)
O(9) Sm(2) N(3)
O(7) Sm(2) N(3)
N(4) Sm(2) N(3)
O(10)#2 Sm(2) O(10)
O(12)#2 Sm(2) O(10)
O(11) Sm(2) O(10)
O(8) Sm(2) O(10)
O(9) Sm(2) O(10)
O(7) Sm(2) O(10)
N(4) Sm(2) O(10)
N(3) Sm(2) O(10)
#1 −x + 1, −y + 1, −z + 2; #2 −x, −y, −z + 1.
Table 5
Thermal decomposition data for [Sm(o-MBA)3phen]2 (β = 5 ◦C min−1
)
Stage Temperature range (◦C) DTG peak temperature (◦C) Mass loss rate (%)
Probable composition of removed groups Intermediate
TG
Theory
28.56
47.68
I
256.26–484.63
484.63–704.33
316.96
565.57
28.01
48.24
76.25a 76.24a
–2phen, –4CH3
–C44H30O9
[Sm(o-MBA)(C6H4COO)2]2
II
Sm2O3
a
Total loss of mass (%).

176
N. Ren et al. / Thermochimica Acta 438 (2005) 172–177
Fig. 1. (a) Molecular structure of [Sm(o-MBA)3 phen]2. (b) Molecular structure of [Sm(o-MBA)3 phen]2.
complex of [Sm(o-MBA)3phen]2 was completely degraded into
Sm2O3, with a total loss of 76.25%. The experimental data of
the mass loss coincide quite well with theoretical calculations
(see Table 5). Based on the thermal analysis above, the thermal
decomposition process may be expressed in the following way.
procedure [13] are shown in Fig. 3. It is clear that the values
of E don’t seem to keep constant in the decomposition process,
but varied with the extent of conversion. This fact indicates that
the first-stage decomposition process is a multiple-step reaction
[14–16]. Therefore, it is difficult to properly interpret the E-
dependences on α by means of kinetic mechanism [16].
[Sm(o − MBA)3phen]2
→ [Sm(o − MBA) (C6H4COO)2]2 → Sm2O3
3.6. Lifetime
3.5. Thermal decomposition kinetics
The general lifetime formula of materials is [17]
a + b
The values of E corresponding to the values of α for the
first-stage decomposition reaction obtained by Ozawa-iterative
ln τ =
(1)
T

N. Ren et al. / Thermochimica Acta 438 (2005) 172–177
177
The lifetime equation is ln τ = −25.5547 + 18511.68/T. Linear
correlation coefficients r is 0.9924.
4. Conclusion
In summary, the title complex has been successfully synthe-
sized. ItscrystalstructurewasdeterminedbysinglecrystalX-ray
diffraction. In the complex each Sm3+ ion is nine-coordinated.
The thermal decomposition mechanism of [Sm(o-MBA)3phen]2
could be expressed by the scheme shown in the text. Meanwhile,
the E values varied with reaction progress, indicating the com-
plexity of the decomposition process. The lifetime equation at
mass-loss of 10% was deduced as ln τ = −25.5547 + 18511.68/T
by isothermal thermogravimetric analysis.
Fig. 2. TG-DTG curves of [Sm(o-MBA)3 phen]2 (β = 5 ◦C min−1).
Acknowledgements
This project was supported by the Natural Science Founda-
tion of Hebei Province and Hebei Education Department.
References
[1] B. Czajka, B. Bocian, W. Ferenc, J. Therm. Anal. Cal. 67 (2002) 631.
[2] A.W.H. Lam, W.T. Wang, S. Gao, G.H. Wen, X.X. Zhang, Eur. J. Inorg.
Chem. (2003) 149.
[3] Y.H. Wan, L.P. Zhang, L.P. Jin, S. Gao, S.Z. Lu, Inorg. Chem. 42 (2003)
4985.
[4] R.F. Wang, M.Z. Wang, L.P. Jin, G.L. Cai, J. Beijing Normal Univ.
(Nat. Sci.) 30 (1994) 241 (in Chinese).
[5] R.F. Wang, S.P. Wang, S.K. Shi, J.J. Zhang, Rare Metals 23 (2004) 103.
[6] R.F. Wang, S.P. Wang, S.K. Shi, J.J. Zhang, J. Coord. Chem. 55 (2002)
215.
Fig. 3. The relation between E and α for the first-stage decomposition reaction
of [Sm(o-MBA)3phen]2.
[7] R.F. Wang, S.P. Wang, J.J. Zhang, J. Mol. Struct. 648 (2003) 151.
[8] R.F. Wang, L.S. Li, L.P. Jin, J. Rare Earths 16 (1998) 149.
[9] J.J. Zhang, R.F. Wang, H.M. Liu, J.B. Li, N. Ren, Z.H. Gao, Chin. J.
Chem. 23 (2005) 646.
Table 6
The lifetime of the [Sm2(o-MBA)6(phen)2] by isothermal temperature TG
T (K)
τ10% (min)
T (K)
τ10% (min)
[10] R.F. Wang, S.P. Wang, S.K. Shi, J.J. Zhang, Chinese J. Struct. Chem.
23 (2004) 1300.
[11] Z.L. Wang, Z.S. Jin, C.J. Niu, J.Z. Ni, J. Rare Earths 10 (1992) 102.
[12] G.Z. Bai, G.D. Chen, Z.M. Wang, L. Yuan, J.W. Kang, J.Z. Gao, J.
Inorga. Chem. 4 (1988) 32, in Chinese.
528.15
538.15
236.99
110.62
548.15
558.15
54.11
37.10
where τ is the lifetime at temperature T(K), a and b are con-
stant. In this paper, the mass-loss of 10% lifetime was measured
by isothermal temperature TG at 528.15, 538.15, 548.15 and
558.15 K and listed in Table 6. On substitution the values in
Table 6 into Eq. (1), the constant a, b and linear correlation
coefficients r were obtained by the linear least squares method.
[13] Z. Gao, M. Nakada, I. Amasski, Thermaochim. Acta 369 (2001) 137.
[14] S. Vyazovkin, Int. Rev. Phys. Chem. 19 (2000) 45.
[15] S. Vyazovkin, C.A. Wight, Thermochim. Acta 340–341 (1999) 53.
[16] Z.R. Lu, Y.C. Ding, Y. Xu, S.H. Chen, Y.P. Yu, J. Therm. Anal. Cal.
73 (2003) 333.
[17] J.J. Zhang, R.F. Wang, S.P. Wang, H.M. Liu, J.B. Li, J.H. Bai, N. Ren,
J. Therm. Anal. Cal. 79 (2005) 181.