Synthesis, characterization and thermal behaviour of solid-state tartrates of heavy trivalent lanthanides and yttrium(III)

Article abstract of DOI:10.1007/s10973-011-1370-7

Solid state Ln₂-L₃ compounds, where Ln stands for heavy trivalent lanthanides (terbium to lutetium) and yttrium, and L is tartrate [(C₄H₄O₆)^-2] have been synthesized. Simultaneous thermogra

Full text of DOI:10.1007/s10973-011-1370-7

J Therm Anal Calorim (2011) 105:867–871
DOI 10.1007/s10973-011-1370-7
Synthesis, characterization and thermal behaviour of solid-state
tartrates of heavy trivalent lanthanides and yttrium(III)
•
B. Ambrozini P. R. Dametto M. Ionashiro
•
ESTAC2010 Conference Special Issue
´
´
Ó Akademiai Kiado, Budapest, Hungary 2011
Abstract Solid state Ln2-L3 compounds, where Ln stands
for heavy trivalent lanthanides (terbium to lutetium) and
yttrium, and L is tartrate [(C4H4O6)-2] have been synthe-
sized. Simultaneous thermogravimetry and differential
thermal analysis, differential scanning calorimetry, X-ray
powder diffractometry, infrared spectroscopy, elemental
analysis and complexometry were used to characterize and
to study the thermal behaviour of these compounds. The
results provided information concerning the stoichiometry,
crystallinity, ligand’s denticity, thermal stability and ther-
mal behaviour of these compounds.
Sm(III) and Tb(III) tartrates [5], thermal decomposition
behaviour of lanthanium (III) tris–tartrato lanthanate (III)
decahydrate [6], studies on kinetics and mechanism of
thermal decomposition of yttrium tartrate trihydrate crys-
tals [7] and kinetics and mechanism of thermal decompo-
sition of strontium tartrate crystals [8] and thermal
behaviour of solid-state tartrate of some trivalent metal
ions have also been described [9].
In this article, solid-state compounds of heavy trivalent
lanthanides (Tb to Y) with tartrate [(C4H4O6)-2] were
synthesized. The compounds were investigated by
complexometry, elemental analysis, X-ray powder diffrac-
tometry, infrared spectroscopy, simultaneous thermogravi-
metry and differential thermal analysis (TG-DTA) and
differential scanning calorimetry (DSC). The results allowed
us to acquire information concerning these compounds in the
solid state including their thermal stability and crystallinity.
This article is a continuation of the study of reference [9].
Keywords Heavy lanthanides Á Tartrate Á
Characterization Á Thermal behaviour
Introduction
Tartaric acid (dihydroxybutanedioic acid) is an organic
compound which has not an ample utilization as citric and
malic acids, but it has a great importance in the provision
industry. It is used as acidulant in some food [1].
Experimental
Tartaric acid (C4H6O6) is found in grapes in the form L
(?). Amongst all the organic acids present in grapes it is
found in greater quantities than the others [2].
The sodium tartrate with 99% purity was obtained from
Sigma-Aldrich. Aqueous solution of sodium tartrate
0.20 mol L-1 was made by direct weighing of the solid salt.
Aqueous solutions of bivalent metal ions 0.20 mol L-1 were
prepared by dissolving the corresponding chlorides.
Heavy lanthanide chlorides were prepared from the
corresponding metal oxides by treatment with concentrated
hydrochloric acid. The resulting solutions were evaporated
to near dryness; the residues were again dissolved in dis-
tilled water, transferred to a volumetric flask and diluted
into obtain ca. 0.1 mol L-1 solutions, whose pH were
adjusted to 5.0 by adding diluted sodium hydroxide or
hydrochloric acid solutions.
A survey of literature shows that the thermal studies
involving compounds derivate of tartrate, the studies
reported the thermal decomposition and kinetics of dehy-
dration of praseodimium (III), neodymium (III) and gado-
linium (III) tartarates [3, 4], TG and DSC studies on
B. Ambrozini Á P. R. Dametto (&) Á M. Ionashiro
´
Instituto de Quımica, UNESP, C. P. 355, Araraquara, SP CEP
14801-970, Brazil
e-mail: pdametto@gmail.com
123

868
B. Ambrozini et al.
Table 1 Analytical data for the Ln2(L)3ÁnH2O
Compounds
Water/%
Ligand lost/%
Metal oxide/%
Carbon/%
Calcd.
Hydrogen/%
Residue
Calcd.
TG
8.06
Calcd.
TG
Calcd.
TG
EDTA
E.A.
Calcd.
E.A.
Tb2(L)3Á4H2O
Dy2(L)3Á4H2O
Ho2(L)3Á3H2O
Er2(L)3Á4H2O
Tm2(L)3Á5H2O
Yb2(L)3Á4H2O
Lu2(L)3Á5H2O
Y2(L)3Á5H2O
8.07
7.65
54.90
55.21
54.57
54.65
55.37
54.48
54.97
68.10
54.47
54.31
53.76
53.82
54.98
54.80
54.69
67.66
45.10
45.34
45.43
45.14
44.62
44.78
45.03
31.90
45.72
45.52
45.80
45.62
45.02
45.14
45.29
32.32
45.53
45.65
46.23
45.68
45.48
45.22
44.35
32.64
17.39
17.30
17.33
17.08
16.66
16.64
16.31
20.36
17.23
17.00
17.04
16.84
16.59
16.75
16.18
20.42
2.44
2.42
2.18
2.37
2.57
2.33
2.51
3.14
2.42
2.39
2.15
2.33
2.55
2.34
2.50
3.12
Tb4O7
Dy2O3
Ho2O3
Er2O3
Tm2O3
Yb2O3
Lu2O3
Y2O3
7.64
6.53
6.93
7.68
7.49
9.55
9.34
8.72
8.74
10.13
12.73
10.20
12.12
Ln heavy lanthanides (III) and yttrium (III), L tartrate (C4H4O6-2
)
The solid-state compounds were prepared by adding
slowly, with continuous stirring, the solution of the ligand
to the respective metal chloride until total precipitation of
the metal ions. The precipitates were washed with distilled
water until elimination of chloride ions (qualitative test
with AgNO3/HNO3 solution), filtered through and dried on
Whatman no 42 filter paper and kept in a desiccator over
anhydrous calcium chloride.
Table 2 Spectroscopic data for sodium tartrate and compounds with
heavy trivalent lanthanides
Compounds
m
as(COO-)/cm-1
m
s(COO-)/cm-1 m(mas–ms)/cm-1
Na(L)
1622s
1595s
1409s
1388s
1391s
1391s
1419s
1408s
1412s
1414s
1410s
213
207
206
206
203
192
190
188
192
Tb2(L)3Á4H2O
Dy2(L)3Á4H2O 1597s
Ho2(L)3Á3H2O 1597s
Er2(L)3Á4H2O
1622s
In the solid-state compounds hydration water, ligand and
metal ion content were determined from TG curves. The
metal ions were also determined by complexometric titra-
tions with standard EDTA solution using xylenol orange as
indicator after igniting the compounds to the respective
oxides and their dissolution in hydrochloric acid [10].
X-ray powder patterns were obtained by using a
SIEMENS D-5000 X-ray diffractometer employing CuKa
Tm2(L)3Á5H2O 1600s
Yb2(L)3Á4H2O 1602s
Lu2(L)3Á5H2O
Y2(L)3Á5H2O
1602s
1602s
s strong; L tartrate (C4H4O6-2
)
m
s(COO-) and mas(COO-) symmetrical and anti-symmetrical vibrations
of the COO- structure
˚
radiation (k = 1.541 A) and setting of 40 kV and 20 mA.
The attenuate total reflectance infrared spectra for
sodium tartrate and for its metal-ion compounds were run
on a Nicolet iS10 FT-IR spectrophotometer, using an ATR
accessory with Ge window.
establish the stoichiometry of these compounds, which are
in agreement with the general formula Ln2(C4H4O6)3Á
nH2O, where Ln represents trivalent heavy lanthanides (Tb
to Lu) or Y and n = 3.0 (Ho), 4.0 (Tb, Dy, Er and Yb) or
5.0 (Tm, Lu and Y).
Simultaneous TG-DTA and DSC curves were obtained
with two thermal analysis systems, models 2960 and Q10
both from TA Instruments, respectively. The purge gas was
an air flow of 100 mL min-1 (TG-DTA) and 50 mL min-1
(DSC). A heating rate of 20 K min-1 and with samples
weighing about 7 mg (TG-DTA) and about 5 mg (DSC).
Alumina and aluminium crucibles, the latter with perfo-
rated cover were used for TG-DTA and DSC, respectively.
Carbon and hydrogen contents were determined by
microanalytical procedures with an EA 1110 CHNS-O
Elemental Analyser from CE Instruments.
X-ray powderpatternsshowedthatall the compounds were
obtained in amorphous state. The amorphous state is
undoubtedly related to the low solubility of these compounds.
Infrared spectroscopic data on sodium tartrate
(Na2C4H4O6) and its compounds with the metal ions con-
sidered in this study are shown in Table 2. The investiga-
tion was focused mainly within the 1700–1400 cm-1 range
because the region is potentially most informative in
attempting to assign coordination sites. In the Na2C4H4O6,
strong bands located at 1622 and 1409 cm-1 are attributed
to anti-symmetrical (mas) and symmetrical (msym) frequen-
cies of the carboxylate groups, respectively [11, 12]. For
the synthesized compounds the band assigned to the anti-
symmetrical stretching carboxylate frequencies are shifted
to lower values and the symmetrical ones to higher, relative
to the corresponding frequencies in C4H6O6. The Dm (mas–
Results and discussion
The analytical, thermoanalytical (TG) and elemental
analysis results are shown in Table 1. These results
123

Synthesis, characterization and thermal behaviour of solid-state tartrates
869
ms) for these compounds is indicative that these lanthanides
are linked to the carboxylate group by a bidentate bond
with an incomplete equalization of bond lengths in the
carboxylate anion [13].
Simultaneous TG-DTA curves of the compounds are
shown in Fig. 1. These curves exhibit mass losses in four
(Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) steps between 303 and
1263 K. The first mass loss between 303 and 463 K (Tb–
Fig. 1 TG-DTA curves of:
a Tb2(L)3Á4H2O;
TG
DTA
TG
DTA
b Dy2(L)3Á4H2O;
(e)
(a)
c Ho2(L)3Á3H2O;
d Er2(L)3Á4H2O;
e Tm2(L)3Á5H2O;
f Yb2(L)3Á4H2O;
(f)
g Lu2(L)3Á5H2O;
(b)
h Y2(L)3Á5H2O. L tartrate
(C4H4O-6 2
)
(c)
(g)
Exo up
Exo up
(d)
(h)
473
673
873
1073
1273
473
673
873
1073
1273
Temperature/K
Temperature/K
Table 3 Temperature ranges (T), mass losses (%) and peak temperature observed for each step of the TG-DTA curves of the compounds
Ln2(L)3ÁnH2O where Ln trivalent lanthanides and yttrium, L tartrate
Compounds
Steps
First
Second
Third
Fourth
Tb2(L)3Á4H2O
T (K)
303–453
8.07
453–663
23.40
573
663–688
16.54
683
688–1263
6.46
Loss (%)
Peak (K)
T (K)
393
823
Dy2(L)3Á4H2O
Ho2(L)3Á3H2O
Er2(L)3Á4H2O
Tm2(L)3Á5H2O
Yb2(L)3Á4H2O
Lu2(L)3Á5H2O
Y2(L)3Á5H2O
303–453
7.65
453–668
21.81
568
668–698
14.54
693
698–1048
10.11
Loss (%)
Peak (K)
T (K)
383
873
303–423
6.93
423–673
24.32
570
673–698
11.35
687
698–1063
11.15
Loss (%)
Peak (K)
T (K)
393
910
303–443
7.68
443–673
24.07
573
673–703
12.04
691
703–1063
10.03
Loss (%)
Peak (K)
T (K)
396
933
303–463
9.55
463–673
27.61
572
673–703
9.80
703–1053
8.02
Loss (%)
Peak (K)
T (K)
390
686
938
303–433
8.72
433–663
21.39
568
663–703
14.26
683
703–1063
10.43
Loss (%)
Peak (K)
T (K)
390
943
303–463
10.13
393
463–668
20.47
566
668–708
12.04
688
708–1088
12.05
Loss (%)
Peak (K)
T (K)
964
303–463
12.12
393
463–673
27.60
573
673–708
13.46
691
708–1070
14.48
Loss (%)
Peak (K)
967
123

870
B. Ambrozini et al.
Fig. 2 DSC curves of:
a Tb2(L)3Á4H2O;
DSC
DSC
b Dy2(L)3Á4H2O;
c Ho2(L)3Á3H2O;
d Er2(L)3Á4H2O;
e Tm2(L)3Á5H2O;
f Yb2(L)3Á4H2O;
(a)
(e)
(f)
g Lu2(L)3Á5H2O;
h Y2(L)3Á5H2O. L tartrate
(C4H4O-6 2
)
(b)
(c)
(g)
(d)
(h)
Exo up
Exo up
473
673
873
473
673
873
Temperature/K
Temperature/K
Y) corresponding to the endothermic peak at 393 K (Tb),
383 K (Dy), 393 K (Ho), 396 K (Er), 390 K (Tm), 390 K
(Yb), 393 K (Lu) and 393 K (Y) is due to dehydration,
which occurs in a single step.
assigned to the dehydration, which occurs in single step.
The dehydration enthalpies found for the compounds (Tb–
Y) were: 145.8, 157.9, 102.9, 165.7, 159.6, 181.2, 176.8
and 208.6 kJ mol-1, respectively.
After dehydration the mass losses observed above 453 K
(Tb), 453 K (Dy), 423 K (Ho), 443 K (Er), 463 K (Tm),
433 K (Yb), 463 K (Lu) and 463 K (Y) are due to the
thermal decomposition of the anhydrous compounds; these
take place in consecutive and/or overlapping steps with
partial losses which are characteristic for each compound.
For theses compounds the mass loss up to 1263 K (Tb),
1048 K (Dy), 1063 K (Ho), 1063 K (Er), 1053 K (Tm),
1063 K (Yb), 1088 K (Lu) and 1070 K (Y) corresponding
to endothermic or exothermic peaks attributed to the
thermal decomposition being the exothermic events due to
the oxidation of the organic matter (Fig. 1). Calculations
based on the total mass losses observed in the TG curves
are in agreement with the formation of the respective
oxides, Tb4O7, Ln2O3 (L = Dy, Ho, Er, Tm, Yb, Lu and
Y). The mass losses, temperature ranges and the peak
temperatures observed in each step of the TG-DTA curves
are shown in Table 3.
Conclusions
From analytical and thermoanalytical (TG) results a general
formula could be established for these compounds in the
solid state.
The X-ray powder patterns showed that all the com-
pounds synthesized showed low crystallinity degree.
The infrared spectroscopic data suggest that the C4H4O6
acts as a ligand towards the metal ions.
The TG-DTA and DSC curves provided previously
underported information concerning the thermal behaviour
and thermal decomposition of these compounds.
Acknowledgements The authors thank FAPESP, CAPES and
CNPq Foundations (Brazil) for financial support.
The DSC curves of the compounds are shown in Fig. 2.
These curves show endothermic and exothermic peaks that
all are in agreement with the mass losses observed in the
TG curves. The endothermic peak at 383–443 K is
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