Synthesis, characterization and thermal behaviour of solid-state compounds of light trivalent lanthanide succinates

Article abstract of DOI:10.1016/j.tca.2010.01.001

Characterization, thermal stability and thermal decomposition of light trivalent lanthanide succinates, Ln₂(C₄H₄O₄)₃ ·nH₂O (Ln = La to Gd, except Pm) were investigated employing simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), infrared spectroscopy, TG-FTIR system, elemental analysis and complexometry. The dehydration of the lanthanum and cerium compounds occurs in a single step, while for the praseodymium to gadolinium compounds the dehydration occurs in two consecutive steps. The thermal decomposition of the anhydrous compounds occurs in consecutive and/or overlapping steps, except for the cerium compound, with formation of the respective oxides, CeO₂, Pr₆O₁₁ and Ln₂O₃ (Ln = La, Nd to Gd), as final residue. The results also provided information concerning the denticity of the ligand and thermal behaviour of these compounds.

Full text of DOI:10.1016/j.tca.2010.01.001

Thermochimica Acta 501 (2010) 50–54
Contents lists available at ScienceDirect
Thermochimica Acta
journal homepage: www.elsevier.com/locate/tca
Synthesis, characterization and thermal behaviour of solid-state compounds of
light trivalent lanthanide succinates
a,∗
a
a
b
a
L.S. Lima , F.J. Caires , C.T. Carvalho , A.B. Siqueira , M. Ionashiro
a
Instituto de Química, UNESP, CP 355, 14801-970 – Araraquara, SP, Brazil
Instituto de Ciências Exatas e da Terra, Campus Pontal do Araguaia, UFMT, Rodovia MT-100, 78698-000, MT, Brazil
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Characterization, thermal stability and thermal decomposition of light trivalent lanthanide succinates,
Ln2(C4H4O4)3·nH2O (Ln = La to Gd, except Pm) were investigated employing simultaneous thermo-
gravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), infrared
spectroscopy, TG-FTIR system, elemental analysis and complexometry. The dehydration of the lanthanum
and cerium compounds occurs in a single step, while for the praseodymium to gadolinium compounds the
dehydration occurs in two consecutive steps. The thermal decomposition of the anhydrous compounds
occurs in consecutive and/or overlapping steps, except for the cerium compound, with formation of the
respective oxides, CeO2, Pr6O11 and Ln2O3 (Ln = La, Nd to Gd), as final residue. The results also provided
information concerning the denticity of the ligand and thermal behaviour of these compounds.
Received 3 November 2009
Received in revised form 5 January 2010
Accepted 6 January 2010
Available online 25 January 2010
Keywords:
Light trivalent lanthanides
Succinate
Thermal behaviour
©
2010 Elsevier B.V. All rights reserved.
1
. Introduction
2. Experimental
Coordination polymers of rare-earth metals have received sig-
nificant attention in the current research because of their wide
range of application [1].
The sodium succinate, Na C H O ·6H O, with 99% purity was
1
2
4
4
4
2
−
obtained from Sigma–Aldrich and aqueous solution 0.1 mol L was
prepared by direct weighing of the salt.
Preparation and investigation of several metal-ion succinates
have been investigated in the solid-state using thermoanalytical
techniques, X-ray diffractometry and infrared spectroscopy. The
papers published are concerned with the thermogravimetric study
of rare earth elements, yttrium and scandium malonate and suc-
cinates [2], thermal analysis of lanthanum and cerium succinates
Lanthanide chlorides were prepared from the correspond-
ing oxides (except for cerium) by treatment with concentrated
hydrochloric acid. The resulting solutions were evaporated to near
dryness, the residues redissolved in distilled water, and the solu-
tions again evaporated to near dryness to eliminate the excess
of hydrochloric acid. The residues were again dissolved in dis-
tilled water, transferred to a volumetric flask and diluted in order
[
[
[
3], thermal decomposition of gadolinium fumarate and succinate
4], thermal decomposition of ytterbium fumarate and succinate
5] and thermal studies of praseodymium(III) and dysprosium(III)
−
1
to obtain 0.1 mol L solutions, whose pH was adjusted to 5.0 by
adding diluted sodium hydroxide or hydrochloric acid solutions.
−
1
succinates [6]. In these papers the thermal studies were performed
in a static atmosphere.
Aqueous solution of cerium(III) nitrate 0.1 mol L was prepared
by direct weighing of the salt.
In the present paper, solid-state compounds of light trivalent
lanthanides (i.e. La to Gd, except Pm) with succinate were prepared.
The compounds were investigated by means of complexometry,
elemental analysis, X-ray diffractometry, infrared spectroscopy,
simultaneous thermogravimetry and differential thermal analy-
sis (TG-DTA), differential scanning calorimetry (DSC) and TG-FTIR
system. The thermal studies were performed in dynamical air
atmosphere.
The solid-state compounds were prepared by adding slowly,
with continuous stirring, the solution of the ligand to the hot solu-
tion of the respective lanthanides, until total precipitation of the
metal ions. The precipitates were washed with distilled water until
elimination of chloride (or nitrate) ions, filtered through and dried
on Whatman no. 42 filter paper, and kept in a desiccator over anhy-
drous calcium chloride.
In the solid-state compounds, hydration water, ligand and metal
ion contents were determined from the TG curves. The metal ions
were also determined by complexometric titrations with standard
EDTA solution, using xylenol orange as indicator [7]. Carbon and
hydrogen microanalysis were performed using an EA 1110, CHNS-O
Elemental Analyser (CE Instruments).
∗ Corresponding author. Tel.: +55 16 3301 6617; fax: +55 16 3322 7932.
E-mail address: lispazzapam@yahoo.com.br (L.S. Lima).
0
040-6031/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.tca.2010.01.001

L.S. Lima et al. / Thermochimica Acta 501 (2010) 50–54
51
Table 1
Analytical and thermoanalytical (TG) data for Ln2(L)3·nH2O compounds.
Compound
Lanthanide oxide (%)
L (lost) (%)
Calcd.
H2O (%)
Calcd.
C (%)
H (%)
Final residue
Calcd.
TG
EDTA
TG
TG
Calcd.
E.A.
Calcd.
E.A.
La2(L)3·5H2O
Ce2(L)3·5H2O
Pr2(L)3·4H2O
Nd2(L)3·4H2O
Sm2(L)3·5H2O
Eu2(L)3·4H2O
Gd2(L)3·5H2O
45.50
47.91
48.49
47.54
47.18
48.60
48.15
45.24
47.76
48.38
47.56
47.48
48.45
47.94
45.90
47.75
48.59
47.93
47.43
48.84
48.65
41.92
39.55
41.24
42.29
40.63
41.45
39.89
41.83
39.48
41.52
42.14
40.43
41.35
40.22
12.58
12.54
10.27
10.17
12.19
9.95
12.93
12.76
10.10
10.30
12.09
10.20
11.84
20.12
20.06
20.53
20.33
19.50
19.90
19.16
20.42
20.41
20.35
20.49
20.01
19.40
19.32
3.10
3.09
2.88
2.85
3.01
2.79
2.95
2.80
3.34
2.81
2.50
2.78
3.00
2.80
La2O3
CeO2
Pr6O11
Nd2O3
Sm2O3
Eu2O3
Gd2O3
11.96
L = succinate and Ln = lanthanide.
X-ray powder patterns were obtained by using X-ray
diffractometer Rigaku RINT 2000 with copper rotatory anode
carboxylate frequencies are shifted to lower values and the sym-
metrical ones to higher, relative to the corresponding frequencies
in C H O . The ꢁꢂ (ꢂas − ꢂsym) for these compounds is indicative
(
ꢀ = 1.5406 Å).
4
4
4
The attenuate total reflectance (ATR) spectra for sodium succi-
that the La(III) and Ce(III) are linked to the carboxylate group by a
bridging bond [11].
nate, as well as for its lanthanide compounds were run on a Nicolet
iS10 FT-IR spectrophotometer, using an ATR accessory with Ge win-
dow.
For the praseodymium to gadolinium compounds the anti-
symmetrical and symmetrical stretching carboxylate frequencies
are both shifted to higher values relative to the corresponding fre-
Simultaneous TG-DTA and DSC curves were obtained with two
thermal analysis system, model SDT 2960 and DSC Q10, both from
quencies in C H O (sodium salt). The ꢁꢂ for these compounds
4
4
4
−
1
TA Instruments. The purge gas was an air flow of 100 mL min
suggest that these lanthanides are linked to the carboxylate group
by a bridging bidentate bond [11].
−1
for TG-DTA and 50 mL min for DSC experiments. A heating rate
◦
−1
of 20 C min
was adopted, with samples weighing about 7 mg
The simultaneous TG-DTA curves of the compounds are shown
in Fig. 1. These curves show mass losses in two (Ce), four (La, Eu,
Gd), five (Pr, Sm) and six (Nd) consecutive and/or overlapping steps
and thermal events corresponding to these losses or due to physical
phenomenon.
for TG-DTA and 2 mg for DSC. Alumina and aluminium crucibles,
the latter with perforated cover, were used for TG-DTA and DSC,
respectively.
The measurements of the gaseous products were carried out
using a Thermogravimetric Analyzer Mettler TG-DTA coupled to a
FTIR spectrophotometer Nicolet with gas cell and DTGS KBr detec-
◦
Two patterns of thermal behaviour are observed up to 250 C.
Firstly, a close similarity is noted concerning the TG-DTA profiles
of lanthanum and cerium compounds, Fig. 1a and b, or between
the praseodymium to gadolinium ones (Fig. 1c–g). On the other
hand, praseodymium and samarium compounds (Fig. 1c and e) or
europium and gadolinium ones, Fig. 1f and g show a close similarity
◦
tor. The furnace and the heated gas cell (250 C) were coupled
◦
through a heated (T = 200 C) 120 cm stainless steel line transfer
with diameter 3.0 mm both purged with dry air (50 mL min ).
The FTIR spectra were recorded with 32 scans per spectrum at a
−
1
−1
◦
resolution of 4 cm
.
up to 680 and 720 C, respectively.
Thus the features of each compound are discussed on the base
◦
3
. Results and discussion
of their similar thermal profiles up to 720 C.
The analytical and thermoanalytical (TG) data are shown in
3
.1. Lanthanum compound
Table 1. These results permitted to establish the stoichiometry of
the compounds, which are in agreement with the general formula
Ln(L) ·nH O, where Ln represents lanthanides, L is succinate and
The TG-DTA curves of the lanthanum compound are shown
3
2
◦
in Fig. 1a. The first mass loss up to 190 C, corresponding to an
endothermic peak at 165 C is due to dehydration with loss of 5H O
n = 4 (Pr, Nd, Eu) or 5 (La, Ce, Sm, Gd).
◦
2
The X-ray powder patterns show that all the compounds were
obtained with low crystallinity degree and for the praseodymium,
neodymium and samarium compounds with evidence for forma-
tion of an isomorphous series.
(Calcd. = 12.58%, TG = 12.93%).
After the dehydration the anhydrous compound is stable up
◦
to 365 C and above this temperature the thermal decomposition
The difference in the crystallinity degree of these compounds
undoubtedly is due to the stirring and/or the adding velocity of the
ligand solution to the respective metal chloride or nitrate solutions
that were not rigorously controlled, as already observed for other
compounds [8].
Table 2
Spectroscopic data for sodium succinate (C4H4O4) and its compounds with light
trivalent lanthanides.
−
−1
−
−1
The attenuate total reflectance infrared spectroscopic data on
succinate (sodium salt) and its compounds with the metal ions
considered in this work are shown in Table 2. The investigation
Compound
ꢂas (COO ) cm
ꢂsym (COO ) cm
ꢁꢂ (ꢂas − ꢂsym)
Na2(C4H4O4)·6H2O
La (C H O ) ·5H O
1535 s
1527 s
1528 s
1573 s
1574 s
1401 m
1422 m
1423 m
1403 m
1404 m
1405 m
1406 m
1407 m
134
105
105
170
170
173
174
172
2
4
4
4
3
2
−1
was focused mainly 1700–1400 cm range, because this region is
potentially most informative in attempting to assign coordination
sites.
Ce2(C4H4O4)3·5H2O
Pr2(C4H4O4)3·4H2O
Nd2(C4H4O4)3·4H2O
Sm2(C4H4O4)3·5H2O 1578 s
−
1
In C H O (sodium salt), strong band at 1535 cm
medium intensity band located at 1401 cm
and a
4
4
4
Eu2(C4H4O4)3·4H2O
Gd2(C4H4O4)3·5H2O
1580 s
1579 s
−
1
are attributed to
the anti-symmetrical and symmetrical frequencies of the carboxy-
late groups, respectively [9,10]. For the lanthanum and cerium
compounds the band assigned to the anti-symmetrical stretching
s = strong and m = medium.
−
−
ꢂas (COO ) and ꢂsym (COO ) = anti-symmetrical and symmetrical vibrations of the
−
COO group, respectively.

5
2
L.S. Lima et al. / Thermochimica Acta 501 (2010) 50–54
◦
occurs in three steps between 365–450, 450–525 and 525–800 C,
with losses of 7.64, 19.31 and 14.88%, respectively, corresponding
◦
to the exothermic peaks at 490 and 730 C attributed to oxidation
of the organic matter. No thermal event corresponding to the first
mass loss of the anhydrous compound is observed in the DTA curve
and this is probably due to the heat involved in this step is not
sufficient to produce a thermal event.
◦
The total mass loss up to 800 C is in agreement with the forma-
tion of La O as the final residue (Calcd. = 54.50%, TG = 54.76%).
2
3
3.2. Cerium compound
The TG-DTA curves are shown in Fig. 1b. The first mass loss up
◦
◦
to 170 C corresponding to an endothermic peak at 155 C is due to
dehydration with loss of 5H O (Calcd. = 12.54%, TG = 12.76%). The
2
◦
anhydrous compound is stable up to 340 C and above this tempera-
ture the thermal decomposition occurs in a single step up to 415 C,
corresponding to the exothermic peak at 415 C attributed to the
◦
◦
oxidation reaction of Ce(III) to Ce(IV), together with the oxidation
of the organic matter. The smaller thermal stability of the cerium
compound had already been observed for other cerium compound
[
12,13].
The total mass loss up to 415 C is in agreement with the forma-
◦
tion of CeO as final residue (Calcd. = 52.09%, TG = 52.24%).
2
The thermal decomposition of the anhydrous cerium compound
that occurs without formation of carbonate as intermediate is
in disagreement with the results reported by Sevost’yanov and
Dvornikova [3].
3.3. Neodymium compound
The TG-DTA curves are shown in Fig. 1d. The first two mass losses
◦
between 30–100 and 180–230 C, corresponding to the endother-
◦
mic peaks at 80 and 220 C, are due to dehydration with loss of
2
H O in each step (Calcd. = 5.15%, TG = 5.10 and 5.20%, respectively).
2
◦
The anhydrous compound is stable up to 365 C and above this
temperature the thermal decomposition occurs in four consecu-
tive and/or overlapping steps between 365–425, 425–475, 475–580
and 580–670 C, with losses of 8.10, 21.07, 7.70 and 5.27%, respec-
tively, corresponding to the endothermic peaks at 380, 650 C and
◦
◦
◦
Fig. 1. Simultaneous TG-DTA curves of the compounds: (a) La2L3·5H2O (7.0279 mg);
exothermic ones at 410, 460 and 545 C, which are attributed to the
(
(
b) Ce2L3·5H2O (7.3772 mg); (c) Pr2L3·4H2O (6.9885 mg); (d) Nd2L3·4H2O
7.2812 mg); (e) Sm2L3·5H2O (7.0684 mg); (f) Eu2L3·4H2O (7.1891 mg) and (g)
thermal decomposition and/or oxidation of the products evolved
during the thermal decomposition.
Gd2L3·5H2O (7.2186 mg). L = succinate.
◦
The total mass loss up to 670 C is in agreement with the forma-
tion of Nd O , as final residue (Calcd. = 52.46%, TG = 52.44%).
2
3
◦
◦
Fig. 2. SEM of the samarium compound heated up to (a) 300 C and (b) 360 C.

L.S. Lima et al. / Thermochimica Acta 501 (2010) 50–54
53
3.4. Praseodymium and samarium compounds
The TG-DTA curves are shown in Fig. 1c and e, respectively. The
◦
◦
first two mass losses between 30–100 C (Pr, Sm) and 180–230 C
◦
(
Pr) or 165–225 C (Sm), corresponding to the endothermic peaks at
0 C (Pr, Sm) and 210 C (Pr) or 215 C (Sm), are due to dehydration
◦ ◦ ◦
8
with losses of 2H O in each step (Pr) (Calcd. = 5.14%, TG = 5.00 and
2
5
.10%) or 3 and 2H O (Sm) (Calcd. = 7.31 and 4.88%, TG = 7.30 and
2
4
.79%), respectively.
◦
The anhydrous compounds are stable up to 365 C (Pr) and
◦
3
75 C (Sm) and above these temperatures the thermal decomposi-
tion occurs in three consecutive and/or overlapping steps between
◦
3
4
2
65–430, 430–475 and 475–680 C (Pr) or 375–435, 435–470 and
◦
70–670 C (Sm), with losses of 7.90, 27.69, 5.93% (Pr) and 8.51,
5.0 and 6.92% (Sm), respectively. In correspondence with the mass
losses of the TG curves, the DTA ones show endothermic peaks at
◦
◦
◦
3
4
85 C (Pr) and 400 C (Sm) and exothermic peaks at 465 C (Pr) or
◦
◦
Fig. 3. X-ray powder pattern of the samarium compound heated up to (a) 300
and (b) 360 C.
C
70 and 565 C (Sm), which are attributed to the thermal decom-
position and oxidation of the products evolved during the thermal
decomposition.
The total mass loss up to 680 C (Pr) and 670 C (Sm) is in agree-
ment with the formation of Pr O (Calcd. = 51.51%, TG = 51.62%)
◦
◦
◦
6
11
and Sm O (Calcd. = 52.82%, TG = 52.52%), as final residue.
2
3
The formation of Pr O as final residue of the decomposition of
6
11
praseodymium compound is also in disagreement with the result
reported by Kaul and Sharma [6].
3.5. Europium and gadolinium compounds
The TG-DTA curves are shown in Fig. 1f and g, respectively. The
◦
◦
first two mass losses between 30–100 C (Eu, Gd)) and 160–220 C
◦
(
Eu) or 155–220 C (Gd), corresponding to the endothermic peaks
at 80 and 210 C (Eu, Gd), are due to dehydration with losses of
◦
2
H O in each step (Eu) (Calcd. = 4.98%, TG = 5.20 and 5.00%) or 3 and
2
2
H O (Gd) (Calcd. = 7.18 and 4.78%, TG = 7.10 and 4.74%), respec-
2
tively.
◦
The anhydrous compounds are stable up to 340 C (Eu) and
◦
3
90 C (Gd), and above these temperatures the mass losses occur
◦
in two consecutive steps between 340–430 and 430–690 C (Eu)
or 390–485 and 485–720 C (Gd), with losses of 32.69 and 8.66%
◦
(
Eu) or 33.29 and 6.93% (Gd), respectively. In correspondence with
the mass losses of the TG curves, the DTA ones show an endother-
◦
mic peak at 420 C (Gd), attributed to the thermal decomposition
◦
◦
and exothermic peaks at 420 C (Eu) or 480 and 585 C (Gd) which
are attributed to the oxidation of the products evolved during the
thermal decomposition.
◦
◦
The total mass loss up to 690 C (Eu) and 720 C (Gd) is in agree-
ment with the formation of Eu O3 (Calcd. = 51.40%, TG = 51.55%)
2
and Gd O (Calcd. = 51.85%, TG = 52.06%), as final residue.
2
3
The thermal decomposition temperature, as well as the thermal
stability of the anhydrous gadolinium compound is in disagreement
with the results reported by Sevost’yanov and Dvornikova [4].
The formation of Ln O (Ln = La, Nd to Gd), CeO and Pr O as
2
3
2
6
11
final residue of the TG curve were also confirmed by X-ray powder
diffractometry.
◦
◦
The small exothermic peak at 320 C (Sm, Eu) and 325 C (Gd),
without mass loss in the TG curve is attributed to crystallization
process which was confirmed by X-ray powder diffractometry,
as can be seen in Figs. 2 and 3, as representative of these
compounds.
The DSC curves of the compounds are shown in Fig. 4. These
curves show endothermic and exothermic peaks that all accord
with the thermal events observed in the DTA curves. The endother-
Fig. 4. DSC curves of the compounds: (a) La2L3·5H2O (2.0420 mg); (b) Ce2L3·5H2O
(1.9780 mg); (c) Pr2L3·4H2O (1.9600 mg); (d) Nd2L3·4H2O (2.0220 mg); (e)
◦
◦
◦
mic peaks at 166 C (La), 158 C (Ce), 94 and 227 C. (Pr), 97 and
◦
◦
◦
Sm L ·5H O (2.0450 mg); (f) Eu L ·4H O (2.0000 mg) and (g) Gd L ·5H O
2
34 C (Nd), 101 and 244 C (Sm), 90 and 226 C (Eu) and 92
2
3
2
2
3
2
2
3
2
◦
(2.0240 mg).
and 223 C (Gd) are attributed to dehydration. The dehydration

5
4
L.S. Lima et al. / Thermochimica Acta 501 (2010) 50–54
4. Conclusion
From TG, complexometry and elemental analysis data, a general
formula could be established for the compounds involving the light
trivalent lanthanides and succinate.
The reflectance infrared spectroscopic data suggest that the suc-
cinate act as bridging ligand toward the lanthanum and cerium ions,
and as bridging bidentate ligand for praseodymium to gadolinium
ones.
The TG-DTA and DSC curves show that the lanthanum and
cerium compounds, the dehydration occurs in a single step while
praseodymium to gadolinium ones, the dehydration occurs in
two steps. In the praseodymium to gadolinium compounds, the
high dehydration temperature indicates that the last two water
molecules are coordinated ones.
The TG-DTA and DSC curves also provided previously unre-
ported information about the thermal behaviour of these
compounds in a dynamic air atmosphere.
Acknowledgements
The authors thank FAPESP, CNPq and CAPES Foundations (Brazil)
for financial support.
References
Fig. 5. IR spectra of gaseous products evolved during the decomposition of the
compounds: (a) La2L3·5H2O and (b) Eu2L3·4H2O. L = succinate.
[
[
[
1] S.C. Manna, E. Zangrando, A. Bencini, C. Benelli, N.R. Chaudhuri, Inorg. Chem.
5 (2006) 9114–9122.
2] B.S. Azikov, V.V. Serebrennikov, Z. Neorg. Khim. 12 (1967) 445–449;
B.S. Azikov, V.V. Serebrennikov, Chem. Abstr. 66 (1967) 43327.
3] V.P. Sevost’yanov, L.M. Dvornikova, Z. Neorg. Khim. 16 (1971) 1812–1816;
V.P. Sevost’yanov, L.M. Dvornikova, Chem. Abstr. 75 (1971) 133469.
4
enthalpies found for these compounds were: 135.1 (La), 135.3 (Ce),
3
7.7 and 100.4 (Pr), 60.8 and 121.4 (Nd), 70.0 and 146.3 (Sm), 67.5
−1
and 149.8 (Eu), 66.3 and 153.4 kJ mol (Gd).
For all the compounds, the thermal events above 350 C are due
to the thermal decomposition and/or oxidation of organic matter.
[4] V.P. Sevost’yanov, L.M. Dvornikova, Khim. Khim. Tekh. 14 (1971) 1771–1773;
V.P. Sevost’yanov, L.M. Dvornikova, Chem. Abstr. 76 (1971) 85167.
[
◦
5] V.P. Sevost’yanov, L.M. Dvornikova, Z. Neorg. Khim. 17 (1972) 2884–2887;
V.P. Sevost’yanov, L.M. Dvornikova, Chem. Abstr. 78 (1973) 34380.
◦
The small exothermic peak observed at 325 C for the Sm, Eu
[6] M.L. Kaul, R.M. Sharma, Proc. Natl. Acad. Sci., India, Sec. A: Phys. Sci. 61 (1991)
163–172.
[
[
and Gd compounds is due to crystallization, in agreement with DTA
curves, and the crystallization enthalpy found was 18.6, 24.4 and
7] M. Ionashiro, C.A.F. Graner, J. Zuanon Netto, Ecl. Quim. 8 (1983) 29–32.
8] F.J. Caires, L.S. Lima, C.T. Carvalho, R.J. Giagio, M. Ionashiro, Thermochim. Acta
−
1
2
9.4 kJ mol , respectively.
(
2009).
The gaseous products evolved during the thermal decomposi-
[9] G. Socrates, Infrared Characteristic Group Frequencies, second ed., Wiley, New
York, 1994, pp. 91 and 236–237.
10] R.M. Silverstein, F.X. Webster, Spectrometric Identification of Organic Com-
pounds, sixth ed., Wiley, New York, 1998, pp. 92–93 and 96–97.
tion of the compounds studied in this work were monitored by FTIR,
and it has carbon dioxide as main product due to the decarboxyla-
tion and oxidation of organic matter. The IR spectra of the gaseous
products evolved during the thermal decomposition of lanthanum
and europium, as representative of all the compounds are shown
in Fig. 5.
[
[11] G.B. Deacon, R.J. Phillips, Coord. Chem. Rev. 33 (1980) 227.
[
12] J.R. Locatelli, E.C. Rodrigues, A.B. Siqueira, E.Y. Ionashiro, G. Bannach, M.
Ionashiro, J. Therm. Anal. Calorim. 90 (3) (2007) 737–746.
13] C.T. Carvalho, A.B. Siqueira, O. Treu-Filho, E.Y. Ionashiro, M. Ionashiro, J. Braz.
Chem. Soc., in press.
[