2-Methoxybenzylidenepyruvatewith heavier trivalent lanthanides and yttrium(III): Synthesis and characterization

Article abstract of DOI:10.1007/s10973-007-8699-y

Solid-state Ln(2-MeO-BP) compounds, where Ln stands for trivalent Eu to Lu and Y(III) and 2-MeO-BP (which is 2-methoxybenzylidenepyruvate) have been synthesized. Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanni

Full text of DOI:10.1007/s10973-007-8699-y

Journal of Thermal Analysis and Calorimetry, Vol. 92 (2008) 3, 953–959
2-METHOXYBENZYLIDENEPYRUVATE WITH HEAVIER TRIVALENT
LANTHANIDES AND YTTRIUM(III)
Synthesis and characterization
E. Y. Ionashiro1*, G. Bannach1, A. B. Siqueira1, C. T. de Carvalho1, E. C. Rodrigues2 and
M. Ionashiro1
1Instituto de Química, UNESP, C.P. 355, CEP 14801-970 Araraquara, SP, Brasil
2Funda¸±o Educacional de Barretos, CEP 14780-000 Barretos, SP, Brazil
Solid-state Ln(2-MeO-BP) compounds, where Ln stands for trivalent Eu to Lu and Y(III) and 2-MeO-BP (which is 2-methoxy-
benzylidenepyruvate) have been synthesized. Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential
scanning calorimetry (DSC), X-ray powder diffraction, infrared spectroscopy and other methods of analysis were used to characterize and
to study these compounds. On the base of the obtained results an Ln(2MeO-BP)3·nH2O general formula can be established.
Keywords: characterization, heavier lanthanides, yttrium, 2-methoxybenzylidenepyruvate, thermal behaviour
Introduction
Experimental
Materials
Synthesis of benzylidenepyruvic acid (HBP), as well as
of phenyl-substituted derivatives of HBP have been re-
ported in [1, 2]. These acids are of continuous interest as
intermediates in pharmacological, industrial and chemi-
cal syntheses, in development of enzyme inhibitors and
drugs, as model substrates of enzymes, etc. [2–7].
Synthesis and investigation of several metal ion
complexes of phenyl-substituted derivatives of BP, have
been carried out in aqueous solutions [8] and in
solid-state [9–18]. In aqueous solutions these works re-
ported mainly the thermodynamic stability (b1) and
spectroscopic parameters (e1max, lmax), associated with
1:1 complex species, analytical applications of the lig-
ands, e.g. in gravimetric analysis and as metallochromic
indicator. In solid-state the establishment of the stoi-
chiometry and detailed knowledge of the thermal be-
haviour of ligands and their metal ion compounds have
been the main purposes of these studies.
Sodium salt of 2-methoxybenzylidenepyruvic acid
(Na-2-MeO-BP) was prepared following the same
procedure as described in [19]. Aqueous solution with
0.1 mol L–1 concentration of Na-2-MeO-BP was pre-
pared by direct weighing of the salt.
Lanthanides and yttrium 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 dis-
solved in distilled water and the solutions were again
evaporated to near dryness to eliminate the excess of
hydrochloric acid. The residues were redissolved in
distilled water, transferred to a volumetric flask and di-
luted in order to obtain ca. 0.1 mol L–1 solutions, whose
pH were adjusted to 5 by adding diluted sodium hy-
droxide or hydrochloric acid solutions.
The solid-state compounds were prepared by add-
ing slowly with continuous stirring, the solution of the
ligand to the respective metal chloride solutions, until
total precipitation of metal ions. The precipitates were
washed with distilled water until elimination of chlo-
ride ion, filtered through and dried on Whatman n° 42
filter paper and kept in a desiccator over anhydrous
calcium chloride under reduced pressure.
In the present paper, solid-state compounds of
heavier trivalent lanthanides (Eu to Lu) and yttri-
um(III)
with
2-methoxybenzylidenepyruvate
(2-CH3–O–C6H4–CH=CH–COCOO–) were prepared.
The compounds were investigated by complexo-
metry, elemental analysis, X-ray powder diffracto-
metry, infrared spectroscopy, simultaneous thermo-
gravimetry 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 includ-
ing their thermal stability, thermal decomposition,
ligand’s denticity and crystallinity.
Methods
After igniting the compounds to the respective
lanthanide or yttrium oxides and dissolving them in a
hot solution of concentrated hydrochloric acid their
metal ions contents were determined by complexo-
*
Author for correspondence: massaoi@iq.unesp.br
1388–6150/$20.00
Akadémiai Kiadó, Budapest, Hungary
Springer, Dordrecht, The Netherlands
© 2008 Akadémiai Kiadó, Budapest

IONASHIRO et al.
metric titration with standard EDTA solution using xy-
metry of these compounds, which are in agreement with
the Ln(2-MeO-BP)3·nH2O general formula where Ln
represents trivalent lanthanides or yttrium, 2-MeO-BP is
2-methoxybenzylidenepyruvate and n=1.5 (Gd, Dy,
Lu); 2 (Eu, Tb, Ho, Er, Yb); 2.5 (Y) and 3 (Tm).
lenol orange as indicator [20]. The lanthanides and yt-
trium contents of the compounds were also estimated
from their corresponding TG curves. The dehydration of
the compounds was also estimated from their corre-
sponding TG curves. The dehydration of the compounds
was firstly pointed out by their DTA curves and subse-
quently confirmed by the broad endothermic peaks cen-
tered at 90–120°C in the respective DSC curves. The
water contents were then determined from the corre-
sponding mass losses observed in the TG curves. Next,
the ligands’ content was also assessed from TG curves.
Simultaneous TG-DTA and DSC curves were
recorded in models SDT 2960 and Q 10, both from
TA instruments. The purge gas was an air flow of
100 mL min–1 for TG-DTA and 50 mL min–1 for DSC.
A heating rate of 20°C min–1 was adopted with
samples weighing about 7 mg for TG-DTA and 5 mg
for DSC. Alumina and aluminum crucibles, the latter
with perforated covers, were used for TG-DTA and
DSC, respectively.
The X-ray diffraction powder patterns show that
all the compounds were obtained in the amorphous
state. The amorphous state is undoubtedly related to
the low solubility of these compounds, as already ob-
served in the lanthanides and yttrium compounds with
other phenyl substituted derivatives of BP [8]. All at-
tempts at growing good single crystals of the pres-
ently investigated compounds or at obtaining them, as
polycrystalline powders were unsuccessful. Their
amorphous state, the absence of definite melting
points and insolubility in a wide variety of solvents
suggest that these compounds might be polymeric in
nature. It is known that high molecular mass metal co-
ordination polymers bearing oxygen or sulfur as do-
nor atoms are generally hard, fiber or film-like materi-
als, stable at relatively elevated temperatures (i.e., up
to 400°C) [21, 22]. The presently prepared com-
pounds do not display these features. So if polymeric,
they should be almost certainly of low nuclearity.
Infrared spectroscopic data on 2-methoxy-
benzylidenepyruvate and its compounds with the
metal ions considered in this work are shown in Ta-
ble 2. The investigation was focused mainly within
the 1700–1400 cm–1 range because this region is po-
tentially the most informative in attempting to assign
coordination sites. In 2-MeO-BP (sodium salt) strong
band at 1679 cm–1 and a medium intensity band lo-
cated at 1479 cm–1 are attributed to the anti-symmetri-
cal and symmetrical frequencies of the carboxylate
groups, respectively [23, 24]. The band centered at
1713 cm–1 is typical of a conjugated ketonic carbonyl
group [23–25]. For all the compounds the bands as-
signed to the anti-symmetrical stretching carboxylate
Carbon and hydrogen microanalysis were per-
formed by using EA 1110, CHNS-O Elemental Ana-
lyzer (CE Instruments).
X-ray powder patterns were obtained by using a
Siemens D-5000 X-Ray Diffractometer, employing
CuKa radiation (l=1.541 ) and settings of 40 kV and
20 mA. Infrared spectra for Na–2-MeO-BP as well as
for its trivalent lanthanides and yttrium compounds
were recorded on a Nicolet mod. Impact 400 FT-IR in-
strument, within the 4000–400 cm–1 range. The solid-
state samples were pressed into KBr pellets.
Results and discussion
The analytical and thermoanalytical (TG) data are
shown in Table 1. These results establish the stoichio-
Table 1 Analytical data for the Ln(L)3·nH2O compounds
Ln/%
Ligand lost/%
Water/%
C/%
calcd.
H/%
calcd.
Final
residue
Compound
calcd.
TG
EDTA calcd.
TG
calcd.
TG
EA
EA
Eu2O3
Eu(L)3·2H2O
18.91
19.66
19.60
20.18
20.20
20.42
20.14
20.98
21.35
12.01
18.79
19.75
19.63
20.25
19.90
20.40
20.04
20.95
21.58
12.13
18.62
19.42
20.04
19.81
20.02
21.02
20.30
21.05
21.09
12.14
73.62
73.96
72.48
73.48
72.45
72.24
70.54
71.74
72.40
79.88
73.84
73.84
72.41
73.36
72.61
72.13
70.50
71.75
72.25
79.29
4.48
3.38
4.45
3.36
4.41
4.40
6.45
4.37
3.31
4.87
4.40
3.40
4.50
3.46
4.60
4.54
6.50
4.40
3.20
5.00
49.31
49.35
48.90
49.23
48.54
48.40
47.26
48.06
48.50
52.88
48.80
49.88
49.10
49.12
48.32
48.66
47.34
47.66
48.80
53.04
3.90
3.79
3.86
3.76
3.83
3.82
3.97
3.80
3.71
4.31
4.20
Gd(L)3·1.5H2O
Tb(L)3·2H2O
Dy(L)3·1.5H2O
Ho(L)3·2H2O
Er(L)3·2H2O
3.92 Gd2O3
3.69 Tb4O7
3.69 Dy2O3
3.64 Ho2O3
3.41 Er2O3
3.20 Tm2O3
3.12 Yb2O3
3.87 Lu2O3
4.22 Y2O3
Tm(L)3·3H2O
Yb(L)3·2H2O
Lu(L)3·1.5H2O
Y(L)3·2.5H2O
Ln: heavier trivalent lanthanides and yttrium(III); L: 2-methoxybenzylidenepyruvate
954
J. Therm. Anal. Cal., 92, 2008

CHARACTERIZATION OF 2-METHOXYBENZYLIDENEPYRUVATE COMPOUNDS
40
35
30
25
20
15
10
5
110
100
90
80
70
60
50
40
30
20
TG
TG
25
20
15
10
5
100
80
60
40
20
b
a
0
0
DTA
DTA
–5
–5
200
200
200
400
600
Temperature/oC
800
1000
1200
200
400
600
Temperature/oC
800
1000
1200
100
80
5
4
3
2
1
0
110
100
90
80
70
60
50
40
30
20
TG
3.0
2.5
2.0
1.5
1.0
0.5
0.0
–0.5
TG
c
d
60
40
20
DTA
DTA
200
400
600
800
1000
1200
400
600
800
1000
1200
Temperature/oC
Temperature/oC
100
90
80
70
60
50
40
30
20
110
100
90
80
70
60
50
40
30
20
TG
2.5
2.0
1.5
1.0
0.5
0.0
–0.5
2.5
2.0
1.5
1.0
0.5
0.0
–0.5
e
TG
f
DTA
DTA
400 600
Temperature/oC
800
1000
1200
200
400 600
Temperature/oC
800
1000
1200
5
4
3
2
1
5
4
3
2
1
110
100
90
80
70
60
50
40
30
20
110
100
90
80
70
60
50
40
30
20
TG
TG
g
h
0
0
DTA
200
DTA
200
400
600
800
1000
1200
400
600
800
1000
1200
Temperature/oC
Temperature/oC
5
4
3
2
1
110
100
90
80
70
60
50
40
30
20
TG
3.0
TG
100
80
60
40
20
0
j
2.5
2.0
1.5
1.0
0.5
0.0
–0.5
i
0
DTA
DTA
200
400
600
Temperature/oC
800
1000
1200
200
400
600
Temperature/oC
800
1000
1200
Fig. 1 Simultaneous TG-DTA curves: a – Eu(2-MeO-BP)3·2H2O, m=7.0514 mg; b – Gd(2-MeO-BP)3·1.5H2O, m=7.216 mg;
c – Tb(2-MeO-BP)3·2H2O, m=7.1450 mg; d – Dy(2-MeO-BP)3·1.5H2O, m=6.9983 mg; e – Ho(2-MeO-BP)3·2H2O,
m=6.92 mg; f – Er(2-MeO-BP)3·2H2O, m=7.0970 mg; g – Tm(2-MeO-BP)3·3H2O, m=6.932 mg; h – Yb(2-MeO-BP)3·2H2O,
m=7.0593 mg; i – Lu(2-MeO-BP)3·2H2O, m=7.0279 mg; j – Y(2-MeO-BP)3·1.5H2O, m=7.0836 mg; heating rate: 20°C min–1;
air flow: 100 mL min–1
J. Therm. Anal. Cal., 92, 2008
955

IONASHIRO et al.
60
40
20
0
60
50
40
30
20
10
0
b
a
–10
–20
–20
100
200
300
400
500
600
100
200
300
400
500
600
Temperature/oC
Temperature/oC
60
50
60
50
40
30
20
10
0
40
30
20
10
d
0
c
–10
–20
–10
100
100
100
200
200
200
300
400
500
500
500
600
600
600
100
200
300
Temperature/oC
400
500
600
Temperature/oC
60
50
80
60
40
40
30
20
20
10
0
f
e
0
–20
–40
–10
–20
300
400
100
200
300
400
500
600
Temperature/oC
Temperature/oC
60
50
40
30
20
10
0
70
60
50
40
30
20
g
10
h
0
–10
–20
–10
300
400
100
200
300
400
500
600
Temperature/oC
Temperature/oC
70
60
80
60
40
20
0
50
40
30
20
10
i
j
0
–10
–20
–20
100
200
300
400
500
600
100
200
300
400
500
600
Temperature/oC
Temperature/oC
Fig. 2 DSC curves of the compounds a – Eu(2-MeOBP)3·2H2O; b – Gd(2-MeOBP)3·2H2O; c – Tb(2-MeOBP)3·2H2O;
d – Dy(2-MeOBP)3·2H2O; e – Ho(2-MeOBP)3·2H2O; f – Er(2-MeOBP)3·2H2O; g – Tm(2-MeOBP)3·2H2O;
h – Y(2-MeOBP)3·2H2O; i – Lu(2-MeOBP)3·2H2O; j – Y(2-MeOBP)3·2H2O
956
J. Therm. Anal. Cal., 92, 2008

CHARACTERIZATION OF 2-METHOXYBENZYLIDENEPYRUVATE COMPOUNDS
frequencies, as well as that assigned to the ketonic
consecutive steps through a fast processes with for-
mation of europium oxide as can be seen in Fig. 1a.
For the other compounds (Gd to Lu, Y) the mass
losses also occur in two steps and the change in the
slope above 300–350°C that occurs in the first step of
the TG curves is ascribed to the increase in the reaction
rates. The similarity among these curves suggests that
the decomposition mechanism should be the same for
the aforementioned compounds. Test with hydrochlo-
ric acid solution on these samples heated above
350°C (Gd), 375°C (Er), 380°C (Tb, Tm, Yb, Y) and
390°C (Dy, Ho, Lu), evolution of CO2 and presence of
carbonaceous residue was observed. The evolution of
CO2 shows that in this step the formation of carbonate
or a carbonate derivative occurs. In agreement with the
mass losses in this step the DTA curves show small
exothermic peaks for the Gd, Ho to Lu and Y com-
pounds. For the Tb and Dy compounds this peak is not
observed and this is probably due to balance between
exothermic process (oxidation of carbonaceous resi-
due) and an endothermic one (decomposition of the
metal dioxycarbonate) resulting net heats produce only
small exothermic peak or no thermal events.
For all compounds, the final thermal decomposi-
tion residues were the respective oxides, Tb4O7 and
Ln2O3 (Ln=Gd, Dy–Lu, Y) as proven by X-ray pow-
der diffractometry.
The mass losses, temperature ranges and the
peak temperatures observed for each step of the
TG-DTA curves are shown in Table 3.
The DSC curves of the compounds are shown in
Fig. 2. These curves show endothermic and exother-
mic peaks that all are in agreement with mass losses
observed in the TG curves.
carbonyl are shifted to lower values relative to the
corresponding frequencies in 2-MeO-BP itself (so-
dium salt). This behaviour indicates that both groups
act as coordination centres in the metal compounds
[25, 26]. The data displayed in Table 2 show that
these shifts are dependent on the metal ions.
Simultaneous TG-DTA curves of the com-
pounds are shown in Fig. 1. These curves exhibit
mass losses in three consecutive and/or overlapping
steps and thermal events corresponding to these
losses. Two patterns of thermal behaviour are ob-
served up to 300°C. Firstly, a close similarity is noted
concerning the TG-DTA profiles of the europium and
holmium compounds Figs 1a and e. On the other
hand, Gd, Tb, Dy, Er to Lu and Y compounds display
another set of very similar TG-DTA profiles,
Figs 1b–d and f–j.
For all compounds the first mass loss (in the
60–110°C range) associated to endothermic peaks at
95–100°C is ascribed to the dehydration, which occurs
in a single step. For the europium and holmium com-
pounds the TG curves show that the anhydrous com-
pounds are stable up to 160°C, while for the Gd, Tb,
Dy, Er to Lu and Y compounds the mass losses occur
without evidence concerning the formation of stable
anhydrous compounds and as previously stressed, the
temperature corresponding to the mass losses due to
dehydration were depicted from the DTA curves.
Once dehydrated, the mass losses above 160°C
(Eu, Ho) and 110°C (Gd, Tb, Dy, Er to Lu, Y) corre-
sponding to exothermic events are attributed to the
oxidation of the organic matter. Only for the euro-
pium compound the oxidation of the organic matter
occurs with combustion with the mass losses in two
Table 2 IR spectroscopic data for sodium 2-methoxybenzylidenepyruvate (2-MeO-BP) and for compounds with heavier triva-
lent lanthanides or yttrium (cm–1)
nO–H
n
Dn
n
sym(COO –
)
nC=O
DnC=O
Compound
as(COO–
)
as(COO–
–
)
2-MeOBP-Na
Eu(L)3·2H2O
Gd(L)3·1.5H2O
Tb(L)3·2H2O
Dy(L)3·1.5H2O
Ho(L)3·2H2O
Er(L)3·2H2O
Tm(L)3·3H2O
Yb(L)3·2H2O
Lu(L)3·1.5H2O
Y(L)3·2.5H2O
3488m
3507m
3416m
3416m
3428m
3380m
3429m
3412m
3418m
3399m
3387m
1679s
1575s
1588s
1589s
1589s
1588s
1632s
1630s
1652s
1658s
1624s
1479m
1479m
1485m
1487m
1488m
1485m
1558m
1557m
1559m
1558m
1549m
1713s
1641s
1642s
1642s
1642s
1642s
1709s
1706s
1703s
1711s
1704s
–
72
71
71
71
71
4
104
91
90
90
91
47
49
7
27
10
2
21
55
9
L=2-methoxybenzylidenepyruvate; s: strong; m: medium; nO–H=hydroxyl group stretching frequency; n
and
)
as(COO–
n
Dn
=symetrical and anti-symetrical vibrations of the COO– group, respectively; nC=O=ketonic carbonyl stretching frequency.
sym(COO–
)
=n
-n
; Dn(C=O) =n(C=O)(Na salt ) -n(C=O)(metal complex)
as(COO– )(metal complex)
as(COO–
)
as(COO– )(Na salt )
J. Therm. Anal. Cal., 92, 2008
957

IONASHIRO et al.
Table 3 Temperature ranges q, mass losses (%) and peak temperatures observed for each step of TG-DTA curves of the compounds
Steps
Compound
first
second
third
q/°C
loss/%
peak/°C
60–110
4.4
100 (endo)
160–400
38.2
360 (exo)
400–490
35.6
490 (exo)
Eu(L)3·2H2O
Gd(L)3·1.5H2O
Tb(L)3·2H2O
Dy(L)3·1.5H2O
Ho(L)3·2H2O
Er(L)3·2H2O
Tm(L)3·3H2O
Yb(L)3·2H2O
Lu(L)3·1.5H2O
Y(L)3·2.5H2O
q/°C
loss/%
peak/°C
60–110
3.4
95 (endo)
110–350
62.7
360 (exo)
350–700
11.2
540 (exo)
q/°C
loss/%
peak/°C
60–110
4.5
100 (endo)
110–380
62.5
380 (exo)
380–600
9.9
440, 460 (exo)
q/°C
loss/%
peak/°C
60–110
3.5
95 (endo)
110–390
62.9
390 (exo)
390–700
10.5
500 (exo)
q/°C
loss/%
peak/°C
60–110
4.6
95 (endo)
160–390
62.1
390 (exo)
390–700
10.6
475 (exo)
q/°C
loss/%
peak/°C
60–110
4.5
95 (endo)
110–375
62.1
375 (exo)
375–700
10.1
505 (exo)
q/°C
loss/%
peak/°C
60–110
6.5
95 (endo)
110–380
59.9
380 (exo)
380–650
10.6
520 (exo)
q/°C
loss/%
peak/°C
60–110
4.4
95 (endo)
110–380
64.4
380 (exo)
380–600
7.3
500 (exo)
q/°C
loss/%
peak/°C
60–110
3.2
95 (endo)
110–390
62.7
390 (exo)
390–600
9.6
510 (exo)
q/°C
loss/%
peak/°C
60–110
5.0
95 (endo)
110–380
66.1
380 (exo)
380–700
13.2
510 (exo)
Acknowledgements
The endothermic peak at 95–100°C is assigned to
the dehydration, which occurs in a single step. The dehy-
dration enthalpies found for these compounds (Eu to Lu
and Y) were: 236.9, 133.4, 228.8, 119.2, 280.5, 127.5,
123.4, 99.8, 125.3 and 93.7 kJ mol–1, respectively.
The authors thank to FAPESP (Proc. 97/12646-8), CAPES
and CNPq Foundations (Brazil) for financial support.
References
Conclusions
1 E. D. Stecher, M. J. Incorvia, B. Kerben, D. Lavine,
M. Oen and E. Suhl, J. Org. Chem., 38 (1973) 4453
and references therein.
From TG curves, elemental analysis and complexo-
metry results a general formula could be established
for these compounds in solid-state.
2 A. J. L. Cooper, J. Z. Ginos and A. Meister, Chem. Rev.,
83 (1983) 321.
The infrared spectroscopic data suggest that
2-MeO-BP acts as a bidentate ligand, both by
a-ketonic carbonyl and carboxylate groups of the
ligand towards the metal ions considered in this work.
The TG-DTA, TG/DTG and DSC curves pro-
vided previously unreported information concerning
the thermal behaviour and thermal decomposition of
these compounds.
3 A. K. Datta and T. C. Daniels, J. Pharm. Sci.,
52 (1963) 905.
4 W. Mayer, H. Rudolph and E. de Cleur,
Angew. Makromol. Chem., 93 (1981) 83.
5 A. I. Baba, W. Wang, W. Y. Kim, L. Strong and
R. H. Schmehl, Synth. Commun., 24 (1994) 1029.
6 G. Dujardin, M. Maudet and E. Brown, Tetrahedron Lett.,
38 (1997) 1555.
7 G. Dujardin, S. Leconte, A. Benard and E. Brown, Synllet,
1 (2001) 147 and references therein.
958
J. Therm. Anal. Cal., 92, 2008

CHARACTERIZATION OF 2-METHOXYBENZYLIDENEPYRUVATE COMPOUNDS
8 R. N. Marques, C. B. Melios, N. C. S. Pereira,
20 M. Ionashiro, C. A. F. Graner and J. Zuanon Netto,
Ecl. Quim., 8 (1983) 29.
O. S. Siqueira, M. de Moraes, M. Molina and
M . Ionashiro, J. Alloys Compd., 249 (1997) 102,
and references therein.
21 K. V. Martin, J. Am. Chem. Soc., 80 (1958) 233.
22 J. E. Mark, H. R. Allcock and R. West. Inorganic
Polymers, Prentice-Hall, Englewood Cliffs, N. J.,
USA 1992, p. 256.
9 L. C. S. Oliveira, C. B. Melios, C. A. Ribeiro,
M. S. Crespi and M. Ionashiro, Thermochim. Acta,
219 (1993) 215.
23 G. Socrates, Infrared Characteristic Group Frequencies,
2nd Ed., Wiley, New York 1994, pp. 91 and 236–237.
24 R. M. Silverstein and F. X. Webster, Spectrometric
Identification of Organic Compounds, 6th Ed., Wiley,
New York 1998, pp. 92, 93, 96 and 97.
10 M. H. Miyano, C. B. Melios, C. A. Ribeiro, H. Redigolo
and M. Ionashiro, Thermochim. Acta, 221 (1993) 53.
11 N. S. Fernandes, M. A. S. Carvalho Filho, C. B. Melios
and M. Ionashiro, J. Therm. Anal. Cal., 59 (2000) 63.
12 R. N. Marques, C. B. Melios and M. Ionashiro,
J. Alloys Compd., 344 (2002) 88.
25 F. A. Cotton, The Infrared Spectra of Transition Metal
Complexes in Modern Coordination Chemistry, J. Lewis
and R. G. Wilkins, Eds, Interscience, New York 1960,
pp. 379–386.
13 R. N. Marques, C. B. Melios and M. Ionashiro,
Thermochim. Acta, 395 (2003) 145.
14 N. S. Fernandes, M. A. S. Carvalho Filho, C. B. Melios
and M. Ionashiro, J. Therm. Anal. Cal., 73 (2003) 307.
15 G. Bannach, R. A. Mendes, E. Y. Ionashiro, A. E. Mauro,
E. Schnitzler and M. Ionashiro, J. Therm. Anal. Cal.,
79 (2005) 329.
26 K. Nakamoto. Infrared and Raman Spectra of Inorganic
and Coordination Compounds, Part B, 5th Ed., Wiley,
New York 1997, pp. 58–61.
Received: September 6, 2007
Accepted: January 11, 2008
16 E. Y. Ionashiro, F. L. Fertonani, C. B. Melios and
M. Ionashiro. J. Therm. Anal. Cal., 79 (2005) 299.
17 G. Bannach, E. Schnitzler, O. Treu Filho, V. H. S. Utuni
and M. Ionashiro, J. Therm. Anal. Cal., 83 (2006) 233.
18 I. A. Petroni, F. L. Fertonani, C. B. Melios and
M. Ionashiro, Thermochim. Acta, 400 (2003) 187.
19 M. Reimer and M. Howard, J. Am. Chem. Soc.,
50 (1928) 2506.
DOI: 10.1007/s10973-007-8699-y
J. Therm. Anal. Cal., 92, 2008
959