UO2(VI), Sn(IV), Th(IV) and Li(I) complexes of 4-azomalononitrile antipyrine: Synthesis, characterization and thermal studies

Article abstract of DOI:10.1007/s10973-008-9197-6

UO₂(VI), Sn(IV), Th(IV) and Li(I) complexes of 4-azomalononitrile antipyrine (L) have been isolated and characterized based on IR spectra, ¹H NMR, elemental analyses, molar conductance and thermal analysis (DTA/TG). The study revealed that the ligand behaves as a neutral bidentate one and coordination takes place via the carbonyl atom of pyrazolone ring >C=O and the azomethine nitrogen >C=N. The thermal stability of the metal complexes were investigated by thermogravimetry (TG), differential thermal analysis (DTA) techniques and infrared spectra, and correlated to their structure. The thermal study revealed that Th(IV) complexes show lower thermal stability than both UO₂(VI) and Sn(IV) complexes.

Full text of DOI:10.1007/s10973-008-9197-6

Journal of Thermal Analysis and Calorimetry, Vol. 96 (2009) 2, 599–606
UO2(VI), Sn(IV), Th(IV) AND Li(I) COMPLEXES OF 4-AZOMALONO-
NITRILE ANTIPYRINE
Synthesis, characterization and thermal studies
H. A. El-Boraey1*, F. A. El-Saied1 and S. A. Aly2
1Department of Chemistry, Faculty of Science, El-Menoufia University, Shebin El-Kom, Egypt
2Department of Chemistry, Genetic Engineering and Biotechnology Research Institute, El-Menoufia University, Sadat City, Egypt
UO2(VI), Sn(IV), Th(IV) and Li(I) complexes of 4-azomalononitrile antipyrine (L) have been isolated and characterized based on
IR spectra, 1H NMR, elemental analyses, molar conductance and thermal analysis (DTA/TG). The study revealed that the ligand be-
haves as a neutral bidentate one and coordination takes place via the carbonyl atom of pyrazolone ring >C=O and the azomethine ni-
trogen >C=N. The thermal stability of the metal complexes were investigated by thermogravimetry (TG), differential thermal anal-
ysis (DTA) techniques and infrared spectra, and correlated to their structure. The thermal study revealed that Th(IV) complexes
show lower thermal stability than both UO2(VI) and Sn(IV) complexes.
Keywords: complexes, conductivity, IR, synthesis, thermal analysis (DTA/TG)
Introduction
Antipyrine
(2,3-dimethyl-1-phenyl-3-pyrazolin-5-
one) and its derivatives possess a wide variety of po-
tentially useful application, including biological
[1, 2], clinical [3] and pharmacological areas [4].
They are also used as antipyretic, analgesic and
anti-rheumatic materials [5–8]. Antipyrines have also
been used as analytical reagents in determination of
some metal ions [9]. Follow up literature indicate that
considerable study has been devoted to Schiff bases
and azo containing ligands derived from either
4-amino- or 4-formylantipyrine [10–12]. However,
all the reported studies on this type of compounds are
concerning with synthesis, structure and properties.
However, comparatively less is known regarding
their thermal behaviour. The present study extends to
synthesis, characterization and thermal behaviour
studies of UO2(VI), Sn(IV), Th(IV) and Li(I) com-
plexes with 4-azomalononitrile antipyrine (L).
Scheme 1
tate, Sn(IV) diphenyl chloride, Sn(IV) chloride,
Th(IV) nitrate or Li(I) chlorate (VII) with (0.002 or
0.004 mol) 4-azomalononitrile antipyrine (L) in
ca. 50 mL EtOH for periods of 5 h or more. The re-
sulting solids were filtered off, washed several times
with EtOH and dried under vacuum over P4O10. Ele-
mental analysis (C, H and Cl) were performed by the
Microanalytical unit of the University of Cairo,
Egypt. Metal analyses were estimated using standard
methods. IR spectra in the 4000–200 cm–1 range were
performed as KBr discs using a PerkinElmer 1430 re-
cording spectrophotometer. 1H NMR spectra were re-
corded in DMSO-d6 using a 300 MHz Varian NMR
spectrometer. The molar conductivity measurements
were made in DMF solutions (10–3 M) using a
Tacussel conductometer type CD6N. Thermal
analyses (DTA/TG) were carried out under N2 atmo-
sphere using a Schimadzu DT-50 thermal analyzer at
a heating rate of 10°C min–1 in the temperature range
25–800°C using platinum crucibles.
Experimental
Reagent grade chemicals were used without further
purification. The ligand 4-azomalononitrile anti-
pyrine (Scheme 1) was prepared and characterized as
described [13].
The metal complexes were prepared by stirring
magnetically at ca. 60°C an ethanolic solution (0.002
mol) of a metal salt of UO2(VI) chloride, nitrate, ace-
*
Author for correspondence: helboraey@yahoo.com
1388–6150/$20.00
Akadémiai Kiadó, Budapest, Hungary
Springer, Dordrecht, The Netherlands
© 2008 Akadémiai Kiadó, Budapest

EL-BORAEY et al.
Results and discussion
The infrared spectra and mode of bonding:
A study and comparison of the IR spectra of the
4-azomalononitrile antipyrine ligand (L) and its metal
complexes imply that the ligand is bidentate in nature.
With carbonyl-oxygen and azomethine nitrogen, as
two coordination sites. The IR data are presented in
Table 2. Generally, the infrared spectrum of the free
ligand shows four bands at 3190, 2215, 1630 and
1590 cm–1, assigned to nN–H, nCºN, nC=O and nC=N, re-
spectively. The infrared spectra of all metal com-
plexes show a decrease in the energy of nC=O and nC=N
on complexation, consistent with coordination of the
carbonyl oxygen and azomethine nitrogen atoms
[15–17]. The spectra of all complexes show that the
bands corresponding to nN–H and nCºN remain at the
same frequency or are slightly shifted to lower fre-
quencies compared to that of the free ligand, indicat-
ing that the N–H and CºN groups do not participate in
coordination.
The reaction of UO2(VI), Sn(IV), Th(IV) and Li(I)
salts with 4-azomalononitrile antipyrine ligand (L) re-
sults in the formation of three types (1:1, 1:2 and 1:3)
metal complexes. All the complexes are stable under
ordinary conditions; they are only freely soluble in
strong coordinating solvents like DMF and DMSO.
The values of molar conductivities in DMF (10–3 M)
solution (Table 1) show that the complexes are essen-
tially nonelectrolytes indicating non coordination of
the anions except complexes (2, 7 and 8) that behave
as 1:2 electrolyte [14]. The chlorato(VII) complex (9)
behaves as 1:1 electrolyte [14].
1H NMR
1
A review of the literature revealed that the H NMR
spectroscopy has been proven to be useful in estab-
lishing the nature and structure of many organic lig-
ands as well as their complexes in solutions. The
1H NMR of 4-azomalononitrile antipyrine ligand (L)
However some new bands with medium to weak
intensities appear in the 520–450 and 450–380 cm–1
in the spectra of complexes under study, are tenta-
tively assigned to nM–O/nM–N modes [14, 15, 17]. The
chloro-complexes (1, 5 and 6) show an additional
band at 345–325 cm–1 due to nM–Cl mode [14, 18]. The
IR spectra of UO2(VI) complexes show a strong ab-
sorption band near 925–910 cm–1, assigned to
antisymmetric n3O=U=O [19].
1
is reported [13]. The H NMR spectra of the com-
plexes are examined in comparison with that of the
free ligand. It was found that for all complexes the
NH signal that appeared in the spectrum of the free
ligand at 8.8 ppm (s, 1H, NH) does not change upon
complexation. New signals at 14–15 ppm in the spec-
tra of the complexes, (5 and 6), assigned to (s, 1H,
OH). The signal observed at 1.82 ppm for acetato
complex (4) with an integration corresponding to 6
protons, assigned to acetate anions. Also, complexes
(1–9) except (3 and 6) show a signal at 3.4 ppm attrib-
uted to water molecules.
The IR spectra of nitrato complexes (3, 7 and 8)
show two bands n=1006–1103 and 1290–1319 cm–1
which may be assigned to asymmetric and symmetric
stretches n1 and n2 of coordinated nitrate group. We can
conclude that the NO3 group is coordinated in
Table 1 Colour, elemental analysis data and molar conductivities results of 4-azomalononitrile
Analysis/%
Calc. (F)
Decomp.
*
LM
No. Compound
Colour
temp./°C
C
H
M
–
Cl
–
Orange
yellow
L (C14H12N6O)
–
56.4(56.1)
4.7(4.4)
3.3(3.2)
–
Dark
[UO2L2CL2]·2H2O·EtOH
1
240
36.3(36.5)
24.2(24.5)
7.2(7.2)
31
brown
2
3
4
5
6
[UO2L3]·CL2·4H2O
[UO2L2(NO3)2]·EtOH
[UO2L(OAc)2]·2H2O
[SnL(Ph)2Cl(OH)]·0.5H2O
[SnLCl2(OH)2]
Brown
Brown
Brown
Yellow
Yellow
256
277
235
252
250
40.2(40.1)
36.0(36.7)
30.6(31.0)
50.8(50.8)
33.1(33.3)
3.5 (3.4)
3.0(3.0)
3.1(3.0)
3.9(3.9)
2.6(2.8)
18.9(18.9)
23.8(23.8)
33.8(32.8)
19.2(19.20)
5.7(5.7)
136
12
–
–
16
5.7(5.7)
11
23.4(23.4) 14.1(14.0)
13.3
Dark
red
[ThL2(NO3)2]·(NO3)2·2H2O
7
170
30.9(31.2)
2.9(2.6)
21.5(21.3)
–
141
8
9
[ThL3(NO3)2]·(NO3)2·2H2O Red
[LiL2]CLO4·H2O Brown
152
290
37.1(37.1)
49.1(48.7)
2.9(2.9)
3.8(4.1)
17.1(17.9)
1.0(1.0)
–
126
70
5.2(5.0)
*
W
–1 cm2 mol–1 in 10–3 M DMF Soln
600
J. Therm. Anal. Cal., 96, 2009

COMPLEXES OF 4-AZOMALONONITRILE ANTIPYRINE
J. Therm. Anal. Cal., 96, 2009
601

EL-BORAEY et al.
unidentate manner [19, 20]. Complexes (7 and 8) also
complex (9), the presence of (n3) at 1120 and (n4) at
630 cm–1 indicates that the Td symmetry of ClO–4 is
maintained and suggests the presence of ClO–4 outside
the coordination sphere [22, 24].
show new bands at 1380 and 1385 cm–1, respectively,
assigned to the ionic nitrate group [19, 21]. The acetato
ligand may coordinate to a metal center in a
monodentate, bidentate or bridging manner. Then
The infrared spectra of hydroxo-complexes 5
and 6 show one or two new bands at 3390–3270 cm–1,
assigned to nM–OH [14]. The appearance of the broad
strong absorption band at about 3430–3400 cm–1 can
be reasonably attributed to the presence of lattice wa-
ter molecules and/or ethanolic OH group, another
bands observed at 900–844 cm–1 due to bending vi-
bration of H2O [17], indicating that these complexes
(except 3, 6) are hydrated and was supported from
thermal analysis study [25–28]. The above arguments
indicate that the ligand in all complexes behaves as a
neutral bidentate ligand and coordination occurs via
the carbonyl oxygen and azomethine nitrogen atoms.
Based on the obtained results the coordination
behaviour of the ligand is shown in Scheme 2.
a(COO –
)
and n
of the free acetate ions are at ~1560 and
)
s(COO –
1416 cm–1, respectively. In the monodentate coordina-
tion naC=O is found at higher energy than n and
a(COO –
)
nC–O is lower than n
. As a result the separation be-
)
a(COO –
tween the two (C–O) bands is much larger in
monodentate complexes than that of free ion, the acetato
complex (4), reveals two new bands na(CO at
)
2
1615–1605 and ns(CO at 1375 cm–1, respectively. Indi-
)
2
cating monodentate acetates [22, 23]. In chlorato(VII)
Thermal studies (TG and DTA)
Thermal behaviour of the obtained complexes was in-
vestigated by thermogravimetric and differential ther-
mal analysis. Figure 1 shows the recorded DTA and
TG curves of the complexes under nitrogen atmo-
sphere; important data are summarized in Table 3.
Due to the explosive nature of chlorato(VII) com-
plexes, the thermal behaviour of lithium chlorato(VII)
complex, (9) has not been investigated. The correla-
tions between the different decomposition steps of the
complexes with the corresponding mass losses are
discussed in terms of the proposed formulae of the
complexes.
DTA curves (Fig. 1) are generally characterized
by endothermic peaks in the temperature range of
25–270°C (except for complex 6), assigned to loss of
solvents of crystallization as results from TG mass
loss in that temperature range. The lower and wide
range of temperature of desolvation indicates that, the
solvents of crystallization are physically bound [29].
As shown from DTA curves (Fig. 1), the desolvation
process was followed by other asymmetric exother-
mic peaks, assigned to material decomposition. The
initial decomposition temperature has been used as an
indication on the thermal stability of complexes [30].
Dioxouranium(VI) chelates
Careful analysis of DTA and TG curves of UO2(VI)
chelates (1, 3 and 4) (Fig. 1) show the presence of an en-
dothermic DTA peak in the temperature range of
25–270°C, This peak is assigned to desolvation of the
complexes as results from TG mass loss in that tempera-
ture range (Table 3). The DTA curve of complex (2)
Scheme 2 Structural formulae of ligand (L) metal complexes
602
J. Therm. Anal. Cal., 96, 2009

COMPLEXES OF 4-AZOMALONONITRILE ANTIPYRINE
shows that it loses its water of crystallization during
decomposition is UO2Cl2+carbon residue [29, 31] for com-
plex (1), UO2 for complex (2) and UO2+carbon residue
[29, 31] for complexes (3), (4). It is clear that the acetato
complex (4) has lower thermal stability (231°C) than the
chloro one (1) (240° C), which may be interpreted to the
presence of two six-membered chelate rings in complex (1)
relative to one in complex (4). Also, the anions (Cl, OAc)
play an important role in the thermal stability of the two
complexes. The nitrato complex (3) shows higher thermal
stability (270°C), than the chloro complex (2) (240°C) this
decomposition process as indicated from TG data
(Table 3). The higher temperature of dehydration of
complex (2) may be due to strong interaction of wa-
ter molecules in the crystal lattice. The desolvation
process was followed by number of exothermic
events in the temperature range of 231–604°C, as-
signed to the material decomposition as demon-
strated from IR spectra of the complexes and their
thermoproducts in that temperature range. As it re-
sults from TG mass loss, the final residue of thermal
Table 3 DTA and TG data of the investigated complexes
Temp./°C
Mass loss/%
Reaction Leaving species
Calc.(F)
No.
Complex
DTA
TG
25–50*
50–240*
240–552•
25–50
50–240
240–552
at 552
4.7(4.7)
3.6(3.6)
b
a
d
EtOH
2H2O
[UO2L2CL2]·2H2O·EtOH
1
49.8(50.0)
42.0(41.6)o
16.9(16.8)
61.5(62.0)
21.5(21.2)o
4.6(4.6)
1.75L
UO2Cl2+0.25L (º6C)
256–300
300–604•
256–300
300–604
at 604
a+b
d
4H2O+0.5L
(Cl2+2.5L)
ºUO2
[UO2L3]·CL2·4H2O
2
3
25–270*
270–307
307–557
25–270
270–307
307–557
at 646
b
d
EtOH
40.4(40.3)
21.0(21.2)
34.0(33.9)o
5.1(5.0)
(2NO3+L)
0.75L
[UO2L2(NO3)2]·EtOH
d-
UO2+0.25L (º6C)
25–100
231–310
310–600
25–231
231–310
310–600
at 600
a
d
d
2H2O
9.4(9.3)
1.5 (CO2)
[UO2L(OAc)2]·2H2O
4
40.0(40.6)
46.0(45.1)o
1.4(1.4)
L
UO2+Carbon residue (º4C)
25–74*
25–74
a
0.5H2O
252–329
252–329
17.4(17.3)
d
(HCL+0.25L)
[SnL(Ph)2Cl(OH)]·0.5H2O
5
Completion of
329–600
329–585
34.2(34.3)
d
decomposition reaction
46.9(47.0)o
14.5(14.5)
55.66(55.7)
29.8(29.8)o
3.3(3.3)
ºSn(Ph)2O
at 585
250–310
310–670
at 670
250–310
310–670•
d
d
2HCL
L
[SnLCl2(OH)2]
6
ºSnO2
25–170*
170–300
300–340
340–483
27–170
170–300
300–340
340–483
at 483
a
d
d
d
2H2O
11.5(11.6)
26.0(26.2)
26.2(26.2)
33.0(32.7)o
2.7(2.6)
2NO3=(2NO2+O2)
L
[ThL2(NO3)2]·(NO3)2·2H2O
7
L
ºTh(NO3)2
25–152*
152–270
270–500
25–152
152–270
270–500
at 468
a
d
d
2H2O
9.1(9.1)
2NO3=(2NO2+O2)
3L+2NO2
ºThO2
[ThL3(NO3)2]·(NO3)2·2H2O
8
68.7(69.0)
19.5(19.3)o
* – Endo, • – Splitted, o – Final product percent, a – Dehydration, b – Desolvation, d – Decomposition, L=(C14H12N6O)
J. Therm. Anal. Cal., 96, 2009
603

EL-BORAEY et al.
Fig. 1 DTA and TG curves of 1–4 – dioxouranium(VI) complexes, 5, 6 – tin(IV) complexes and 7, 8 – thorium(IV) complexes
*Mass of sample
may be attributed to the distribution of the ligands
around the metal ion as shown in Scheme 3.
(240°C), which may be due to the increasing number
of chelate rings, however, it still shows lower thermal
stability than the nitrato complex (3), which may be
related to the presence of three organic ligands around
the metal ion.
As shown, the chloro complex (1) suffers from
steric hindrance than the nitrato one (3). On the other
hand, the chloro complex (2) shows higher thermal
stability (256°C) than the chloro complex (1)
Tin(IV) chelates
The DTA curves of tin(IV) complexes are shown in
Fig. 1. The data of the thermal analysis are also col-
lected in Table 3. Inspection of the DTA curves show
that Sn complex (5) exhibits an endothermic DTA
peak in the temperature range of 25–74°C, assigned
to loss of 0.5 molecule of water which is in good
agreement with calculated value (Table 3). The
DTA/TG curves also reveal that the thermal stability
Scheme 3
604
J. Therm. Anal. Cal., 96, 2009

COMPLEXES OF 4-AZOMALONONITRILE ANTIPYRINE
of tin(IV) complexes (5 and 6) is about the same.
• The dioxouranium(VI) nitrato complex (3) shows
higher thermal stability than the chloro-analogous
(1), which may be attributed to the distribution of
the ligands around the central metal ion and its ef-
fect on the thermal stability of chelate. Also, the an-
ions (ligands) Cl, and OAc play an important role
in the thermal stability of the two complexes.
• Tin(IV) complexes have nearly the same thermal
stability and start their decomposition by the same
manner.
Complex (5) starts to decompose around 252°C
through losing of one HCl molecule with partial elim-
ination of the organic ligand, while complex (6) starts
to decompose at nearly 250°C through losing of two
HCl molecules per-complex molecule. The final
thermoproducts were analyzed by IR spectroscopy
and were identified as Sn(Ph)2O and SnO2 for com-
plexes (5) and (6), respectively. The higher tempera-
ture of the formation of final product for complex (6)
(670°C) relative to that of complex (5) (585°C) may
be attributed to the presence of two strong M–Cl
bonds in complex (6) which are characterized by their
high covalent character.
• Thorium(IV) complex (8) show lower thermal sta-
bility than thorium(IV) complex (7), which may
correspond to the presence of three organic ligands
around metal ion in complex (8).
• Thorium(IV) complexes decomposed at lower tem-
perature than both UO2(VI) and Sn(IV) complexes.
Thorium(IV) complexes
DTA and TG curves of thorium(IV) complexes (7 and
8) (Fig. 1 and Table 3), show a broad endothermic
peak in the temperature range of 25–170°C, assigned
to loss of two water molecules for both complexes as
indicated from TG mass loss. That was followed by
an exothermic peak (170–300°C), assigned to loss of
nitrate moiety (as 2NO2+O2) which is in good agree-
ment with the calculated value (Table 3). This peak is
followed by exo-DTA peaks, assigned to departure of
the organic ligand and formation of Th(NO3)2 and
ThO2 as final thermoproducts for the complexes (7)
and (8), respectively as indicated from IR spectra.
The formation of different final thermoproduct as
well as the different nature of the decomposition of
the two complexes (vide TG data) may confirm the
different structure of the two complexes.
References
1 T. P. Popova, R. I. Alexandrova, R. Tudose,
E. M. Mosoarca and O.Costrisor, Bulgarian J. Vert. Med.,
9 (2006) 265.
2 N. Raman, J. D. Raja and A. Saklhivel, J. Chem. Sci.,
119 (2007) 303.
3 D. Chiaramonte, J. M. Steiner, J. D. Broussard, K. Baer,
S. Gumminger, E. D Moller, D. A. Williams and
R. Shumway, Can. J. Vet. Res., 67 (2003) 183.
4 T. Hitoshi, N. Tamao, A. Hideyuki, F. Manabu and
M. Takayuki, Polyhedron, (1997) 3787.
5 A. Kandil and A. Hamid, J. Dry Res., 12 (1980) 27.
6 A. M. Farghaly and A. Hozza, Pharmazie, 35 (1980) 596.
7 I. D. Capel, M. Jenner and M. H. Pinnock, Biochem.
Pharm., 27 (1978) 3.
8 E. M. Mosoarca, R. Tudose, R. Alexandrova and
O. Costisor, Chem. Bull., 50 (2005) 1.
In all of the studied complexes, the metal per-
centage calculated from the remain residue were com-
pared with those determined by the analytical metal
content determination [32].
9 K. Saraswathi, N. V. S. Naidu, K. M. Kumari and
K. P. Padmaja, Chem. Environ. Res., 8 (1999) 271.
10 P. M. Selvakumar, E. Suresh and P. S. Subramanian,
Polyhedron, 26 (2007) 749.
11 S. A. Abdel-Latif, H. B. Hassib and Y. M. Issa,
Spectrochim. Acta, 67 (2007) 950.
Conclusions
12 T. Rosu, S. Pasculescu, V. Lazar, C. Chifiriuc and
R. Cernat, Molecules, 11 (2006). 904.
We have synthesized and structurally characterized
UO2(VI), Sn(IV), Th(IV) and Li(I) complexes with
4-azomalononitrile antipyrine (L) in the same way as
that in first row transition metals complexes prelimi-
nary reported [13]. It should be pointed out that
4-azomalononitrile antipyrine (L), acts as bidentate
ligand coordinating to the metal ion through the car-
bonyl atom of pyrazolone ring and azomethine nitro-
gen. The thermal behaviour of the investigated com-
plexes have also been studied, the thermal study
reveals the following points.
13 F. A. El-Saied, M. I. Ayad, R. M. Issa and S. A. Aly,
Pol. J. Chem., 74 (2000) 919.
14 F. A. El-Saied and S. A. Aly, Afinidad, 61 (2004) 516.
15 M. P. Sathisha, V. K. Revankar and K. S. R. Pai,
Metal-based Drugs, (2008) 1.
16 K. B. Gudasi, R. V. Shenoy, R. S. Vadavi, M. S. Pattil and
S. A. Patil, Chem. Pharm. Bull., 53 (2005) 1077.
17 Z. H. Abd El- Wahab, Spectrochim. Acta,
A (67) (2007) 25.
18 K. Nakamoto, Infrared Spectra of Inorganic and
Coordination Compounds, 2nd Ed., NY: Wiley
Interscience, New York 1970.
• The thermal stability of dioxouranium(VI) chelates
increase with increasing number of chelate rings in
the complexes.
19 Z. H. Abd El-Wahab, M. M. Mashaly and A. A. Faheim,
Chem. Pap., 59 (2005) 25.
J. Therm. Anal. Cal., 96, 2009
605

EL-BORAEY et al.
20 T. A. Khan, M. A. Rather, N. Jaham, S. P. Vankey and
28 R. Olar, M. Badea, M. N. Grecu, D. Marinescu, V. Lazar
and C. Balotescu, J. Therm. Anal. Cal., 92 (2008) 239.
29 H. A. El-Boraey, J. Therm. Anal. Cal., 81 (2005) 339.
30 M. Nath and P. Arora, Synth. React. Inorg. Met-Org.
Chem., 23 (1993) 1523.
M. Shakir, Synth. React. Inorg. Met. Org. Chem.,
27 (1997) 843.
21 A. A. Alemi and B. Shaabani, Acta, Chem. Solv.,
47 (2000) 363.
22 R. K. Agarwal, L. Singh and D. K. Sharma, Bioinorg.
Chem. Appl., (2006) 1.
31 N. N. Dass and S. Sarmah, J. Therm. Anal. Cal.,
58 (1999) 137.
23 I. S. Ahuja, C. L. Yadav and S. Tripath, Asian., J. Chem.,
1 (1989) 195.
32 A. M. G. Macdonald and P. Sirichanya, J. Micro Chem.,
14 (1969) 199.
24 K. Nakamoto, Infrared and Raman Spectra of Inorganic
and Coordination Compounds, Wiley-Interscience,
New York 1997.
Received: April 23, 2008
Accepted: July 10, 2008
25 H. A. El-Boraey, A. M. Donia and M. F. El- Samalehy,
J. Anal. Appl. Pyrol., 73 (2005) 204.
Online First: November 11, 2008
26 A. M. Donia, H. A. El-Boraey and M. F. El-Samalehy,
J. Therm. Anal. Cal., 73 (2003) 987.
DOI: 10.1007/s10973-008-9197-6
27 C. K. Modi, S. H. Patel and M. N. Patel, J. Therm. Anal.
Cal., 87 (2007) 441.
606
J. Therm. Anal. Cal., 96, 2009