Thermal, spectroscopic and kinetic characterization of reaction products of copper(II) chloride with photoproducts of octacyanocomplexes of Molybdenum(IV) and Tungsten(IV) with ethylenediamine

Article abstract of DOI:10.1016/s0040-6031(97)00476-0

The thermal dissociation of complexes formed by copper(II) chloride with photoproducts of M(CN)^4-₈ [where M=Mo or W] and ethylenediamine has been studied by thermogravimetry (TG), differential scanning calorimetry (DSC) and IR spectroscopy. The observed IR bands for different groups support the assigned composition. Both Mo(IV) and W(IV) show the same stoichiometric behaviour towards complex formation but a different decomposition behaviour. In case of Mo(IV) decomposition takes place in four steps with cyanide and oxide of copper and tetrachloro molybdenum(IV) as residue, while in case of W(IV) the decomposition occurs only in three steps up to 298°C. The copper cyanide along with tetrachloro tungstate(IV) is found as residue. DSC for Mo complex displays four transitions, two exothermic and two endothermic. In case of W, DSC displays three endothermic transitions corresponding to three decomposition steps with three different ΔH values. On the basis of TG and DSC, mechanism for decomposition of each complex has been proposed. Kinetic parameters like activation energy (E_a), frequency factor (A), entropy of activation (ΔS^#) for each step has been calculated involving differential methods like Doyle, Coats and Redfern and Arrhenius. The heat of the reaction is obtained from DSC curves.

Full text of DOI:10.1016/s0040-6031(97)00476-0

Thermochimica Acta 311 (1998) 173±181
Thermal, spectroscopic and kinetic characterization of reaction products of
copper(II) chloride with photoproducts of octacyanocomplexes of
Molybdenum(IV) and Tungsten(IV) with ethylenediamine
*
S.I. Ali , Kowsar Majid
Department of Chemistry, Jamia Millia Islamia, New Delhi-110 025, India
Received 11 August 1997; received in revised form 25 November 1997; accepted 3 December 1997
Abstract
4�
The thermal dissociation of complexes formed by copper(II) chloride with photoproducts of MꢀCN†8 [where MˆMo or
W] and ethylenediamine has been studied by thermogravimetry (TG), differential scanning calorimetry (DSC) and IR
spectroscopy. The observed IR bands for different groups support the assigned composition. Both Mo(IV) and W(IV) show the
same stoichiometric behaviour towards complex formation but a different decomposition behaviour. In case of Mo(IV)
decomposition takes place in four steps with cyanide and oxide of copper and tetrachloro molybdenum(IV) as residue, while
in case of W(IV) the decomposition occurs only in three steps up to 2988C. The copper cyanide along with tetrachloro
tungstate(IV) is found as residue. DSC for Mo complex displays four transitions, two exothermic and two endothermic. In case
of W, DSC displays three endothermic transitions corresponding to three decomposition steps with three different ÁH values.
On the basis of TG and DSC, mechanism for decomposition of each complex has been proposed. Kinetic parameters like
#
a
activation energy (E ), frequency factor (A), entropy of activation (ÁS ) for each step has been calculated involving
differential methods like Doyle, Coats and Redfern and Arrhenius. The heat of the reaction is obtained from DSC curves.
1998 Elsevier Science B.V.
#
Keywords: Thermal kinetics; Octacyanomolybdate(IV); Octacyanotungstate(IV); Ethylenediamine; Copper(II) complexes
1
. Introduction
matory agents [2]. These biological activities have
promoted the structural activity correlations of its
complexes [3±7]. On the other hand the thermal
behaviour of chromium, molybdenum and tungsten
in their mixed ligand complexes containing carbonyl
and pyridine [8] and also carbonyl and triphenyl
Study of copper(II) complexes is quite interesting
because it is biologically active in its chelating ability
and its positive redox potential allows it to participate
in biological transport reaction [1]. Its complexes
possess a wide biological activity and are among
the most potent antiviral, antitumor and antiin¯am-
phosphine [9] have been reported. Since K M(CN)8
4
(MˆMo or W) is thermally inert but photochemically
active, as a result of which photoexcitation of
4�
MꢀCN†8 involves substitution of cyanide ion by
different entering ligands, the thermal study of which
4�
*
Corresponding author. Fax: 00 91 682 1232.
have been reported [10±15]. Likewise MꢀCN†8 is
0040-6031/98/$19.00 # 1998 Elsevier Science B.V. All rights reserved
P I I S 0 0 4 0 - 6 0 3 1 ( 9 7 ) 0 0 4 7 6 - 0

1
74
S.I. Ali, K. Majid / Thermochimica Acta 311 (1998) 173±181
�
1
reported to form substitution products with ethylene-
diamine [16], but the complex formation and thermal
study of its substituted complexes is not reported so
far. In this paper we report the thermal study of
complex formation between copper(II) chloride
with the photochemically substituted octayano-
molybdate(IV) and -tungstate(IV) with ethylene-
diamine. The kinetics and mechanism along with
the thermodynamic parameters viz. activation energy,
frequency factor and entropy of activation have been
calculated.
the range of 400±4000 cm using KBr disc techni-
que.
2.2. Thermal analysis
Thermogravimetry was performed on Du Pont ther-
mal analyser-2000. The analysis was made in a
dynamic nitrogen atmosphere with a rate of 50 ml/
min between 308C and 8008C at a heating rate of
108C/min. A platinum pan was used. Differential
scanning calorimetry was also carried out on a TA
analyser (Du Pont TA-2000) with a DSC. The scan-
ning rate was 108C/min. Temperature range was from
room temperature to 5008C. An aluminium pan was
used under a dynamic nitrogen atmosphere. The
instrument calibration was done by indium (99.99%
purity). The temperature repeatability of the instru-
ment is Æ0.18C and of ÁH is Æ0.02 mW.
2
. Experimental
K M(CN) [where MˆMo(IV) or W(IV)] was pre-
4
8
pared by the literature method [17]. AR grade Cop-
per(II) chloride and ethylenediamine were provided
by BDH. All the solutions were prepared in doubly
distilled water. An ultra-vitulax lamp was used for
irradiation purpose.
3. Results and discussion
Synthesis of the chloride complex of copper(II)
with the photoproduct of K M(CN)8 [where
The synthesised complex I was analysed for C, H
and N on the basis of which empirical formula was
assigned. Further characterization was done by IR
spectroscopy. The measured infrared spectra are in
conformity with the composition of the complexes and
reveal the presence of individual functional groups.
The presence of the molecule of ethylenediamine and
CN is demonstrated by several characteristic absorp-
tion bands. The strong absorption peaks for the com-
4
MˆMo(IV) or W(IV)] and ethylenediamine was car-
ried out by irradiating equimolar aqueous solution of
K M(CN) and ethylenediamine under UV light till
4
8
the solution turned red. To this solution aqueous
solution of CuCl was added till the precipitation
2
was complete. The precipitates were washed with
water and ethanol and dried over fused CaCl . The
2
complexes were analysed for C, H and N and assigned
the formula:
�
1
plex I at 3400, 1680±1600, 1500 and 1362 cm are
assigned as ꢀ(OH), ꢀ(C±N), ꢀ(NH ) and ꢀ(CH )
Cu [Mo(CN) (OH) (C H N )(H O) ]Cl
2
I
for
2
2
2
2
8
2
2
4
2
2
which the observed C, H and N is 8.83%, 3.00%
and 10.30% respectively against calculated values
as 8.77%, 2.57% and 10.22% respectively. For the
complex Cu [W(CN) (OH) (C H N )(H O) ]Cl II,
the observed percentages are 7.40, 9.05, 2.50 against
the calculated 7.56, 8.82, 2.22 for C, H and N respec-
tively.
respectively. The strong and sharp absorption in the
1
�
region of 2100 and 2200 cm for Mo(IV) and W(IV)
respectively are due to stretching vibrations of
�
1
ꢀ(CꢁN). The band at 2100 cm for Mo implies
2
2
2
2
8
2
2
2
4
the coordination of the terminal cyanide. Moreover,
the absorption of the type ꢀ(C±N) and ꢀ(NH ) are
2
�
1
observed in the region of 1040 and 640±660 cm
respectively. For complex II, the absorption bands of
(OH), ꢀ(CꢁN), ꢀ(C±N), ꢀ(CH ) appear on the same
ꢀ
2
2
.1. Physical measurements
frequencies as that of complex I. The appearance of
�
(NH ) band shows a shift of 80 cm from that of Mo
2
1
ꢀ
Determination of carbon, hydrogen and nitrogen
towards higher energy. Shifting of N±H vibrations
towards the lower frequencies indicate the coordina-
tion of nitrogen atom of the amine group to metal atom
[18].
was carried out by micro analytical methods. The IR
spectra of the solid complexes were recorded on
Perkin-Elmer (S.No. 782) IR Spectrophotometer in

S.I. Ali, K. Majid / Thermochimica Acta 311 (1998) 173±181
175
3
3
.1. Ta studies
a respective transition for each transition observed in
TG curve with different ÁH values with uncertainty of
Æ0.02 (Fig. 2). The ®rst two steps as seen from TG
curve involving loss of water corresponds to an over-
lapping endothermic peak in DSC in the temperature
range of 1048C to 1928C with maximum at 144.48C
giving ÁHˆ57.2 J/g. This endothermic peak is fol-
lowed by a sharp exothermic peak at 2278C which is
due to evolution of ethylenediamine molecule with an
enthalpy change ÁH of 31.5 J/g. The decomposition
of the remaining complex gives two peaks, one
exothermic with maximum at 2638C which is due
to the release of two moles of OH groups with
ÁHˆ7.8 J/g. The last step leading to ®nal residue
corresponds to an endothermic peak of maximum
384.78C due to the release of one mole of cyanide
molecule. The ÁH value observed is higher as com-
pared to rest of the steps. On the basis of these studies,
following scheme may be proposed for thermal
decomposition of I. The percentages with and without
.1.1. Cu [Mo(CN) (OH) (C H N )(H O) ]Cl I
4
2
2
2
2
8
2
2
2
The TG and DTG curves of I are shown in Fig. 1.
The DTG curve indicates four different mass loss
ranges. The ®rst mass loss is a brief one occurring
from 788C to 1008C is due to the loss of one mole of
H O. This step is followed by a similar type of
2
transition from 1348C to 1428C with a DTG maximum
of 138.78C due to the removal of another mole of
water. The third stage involves a signi®cant mass loss
extending from 1818C to 2238C with DTG maximum
of 191.38C corresponding to the removal of 1 mol of
ethylenediamine and one mole of hydroxide ion. The
fourth and the last stage occurs between 3268C and
3
438C and involves the loss of another mole of
hydroxide alongwith one mole of cyanide. This stage
is observed in DTG peak at 341.08C The observed
mass loss at each decomposition step corresponds to
the calculated values (Table 1). The DSC of I displays
Fig. 1. The TG and DTG curves of complex I.

1
76
S.I. Ali, K. Majid / Thermochimica Acta 311 (1998) 173±181
Table 1
Thermoanalytical data for the decomposition of the complexes:Cu
]Cl II
2
2 2 2 8 2 2 2 4 2 2 2 2 8 2 2
[Mo(CN) (OH) (C H N )(H O) ]Cl I Cu [W(CN) (OH) (C H N )(H O)
2
4
Temp.range
Max. temp. in
Obsd. weight
loss in %
Calc. weight
loss in %
Remarks removal of
in 8C
DTG in 8C
Complex I
7
1
1
3
8±100
92.0(1)
138.7(1)
191.3(1)
341.0(1)
2.00
2.40
13.5
7.83
3.2
3.2
1 mol of H
1 mol of H
2
O
O
36±141
81±223
26±343
2
14.0
7.85
1 mol of C
1 mol of OH ‡1 mol of CN residue is CuCN
CuO ‡ MoCl calc.(74.28) obsd.74.27%
2
H
8
N
2
‡1 mol of OH
‡
4
Complex II
141±160
247±261
278±301
147.5(1)
255.5(1)
289.4(1)
12.16
3.47
4.38
12.28
2.83
5.35
1 mol of H
1 mol of H
2
O ‡1 mol of C
2 8 2
H N
2
O
2 mol of OH residue 2CuCN‡WCl
79.51) obsd. 79.39%.
4
calc.
(
Fig. 2. The DSC curve of complex I.

S.I. Ali, K. Majid / Thermochimica Acta 311 (1998) 173±181
177
parentheses correspond to the calculated and observed
values respectively.
with DTG maximum of 147.58C which is due to
removal of one mole of H O alongwith one mole of
2
ethylenediamine. The expected endothermic peak for
the dehydration process is shown from the DSC curve
between the temperature range of 1308C to 1798C
with maximum of 153.888C. The enthalpy observed
(
ÁH) is 39.6 J/g. The decomposition of the remaining
complex occurs in two steps. Second stage occurs in
the temperature range of 2478C to 2618C, with DTG
maximum at 2558C corresponding to the loss of
another mole of water. The DSC curve displays an
endothermic peak with temperature range of 3788C to
4
208C with maximum of 383.08C with an enthalpy
change of ÁHˆ21.9 J/g. The third and the last stage in
TG occurs between 2788C and 3018C and is due to the
release of two moles of hydroxide. In the third transi-
tion of DSC an endothermic peak is displayed between
4718C and 4968C with maximum 484.28C giving
ÁHˆ5.0 J/g. The residue has the composition of
3
.1.2. Cu [W(CN) (OH) (C H N )(H O) ]Cl II
2 2 2 2 8 2 2 2 4
The TG and DSC curves of II are shown in Fig. 3
and Fig. 4 respectively. The TG curve shows that the
compound is thermally stable upto 1408C. The dehy-
dration of the complex starts from 1418C upto 1608C
2CuCN‡WCl with the observed weight 79.51
4
against calculated 79.39%. The observed mass loss
Fig. 3. The TG and DTG curve of complex II.

1
78
S.I. Ali, K. Majid / Thermochimica Acta 311 (1998) 173±181
Fig. 4. The DSC curve of complex II.
percentage corresponds to the calculated values
Table 1). The decomposition temperature of CuCN
for different stages of decomposition of I and II are
listed in Tables 2 and 3 respectively. The form of these
equations is given below:
(
in N being 4738C justi®es it as residue in decom-
2
position processes of both the complexes. The scheme
proposed to explain the thermal decomposition is
shown as:
0
Doyle s method :
(1)
ꢁ
T
Ea
A
log
ˆ
‡ log
W
4:6T
RH
where ꢁ : t/RH: � dw/dt: fraction decomposed at time
T
t, W: weight of the sample at time `t', RH: heating
rate, E : activation energy, A: frequency factor, T:
temperature in kelvin.
a
Coats and Redfern method :
(2)
ꢂꢀ
ꢁꢃ
l� n
ln l � ꢀ1 � ꢂ†
AR
2RT
Ea
Ea
ˆ
ln
1 �
2
ꢀ
1 � n†T
ꢃ � Ea
RT
3
.2. Kinetic parameters
where ꢂ: fraction decomposed at time t, n: order of
reaction, E : activation energy, ꢃ: linear heating rate
and R: gas constant
The kinetic parameters calculated using differential
methods like Doyle, Coats and Redfern and Arrhenius
a

S.I. Ali, K. Majid / Thermochimica Acta 311 (1998) 173±181
179
Table 2
Activation energy, frequency factor and entropy of activation for Cu
2
[Mo(CN)
Doyle
36.0
2
(OH)
2
(C
2
H
8
N
2
)(H
2
O)
2
]Cl
4
I
Stage
I
Parameters
DTG max. temp.in K
Coats and Redfern
Arrhenius
�
1
E
A(s
a
(kJ mol
)
29.8
3.3
37.9
2.3
�
1
)
� 1
365.0
411.7
464.3
614.0
3.1
� 237.3
41.8
#
� 1
ÁS
II
(J k mol )
� 236.9
33.5
� 239.6
41.7
�
1
E
a
(kJ mol
�
)
1
A(s
)
3.7
� 236.7
34.4
2.9
� 238.9
28.9
2.7
� 239.3
38.1
#
� 1
� 1
� 1
� 1
ÁS (J k mol
)
)
)
�
1
III
IV
E
a
(kJ mol
�
)
1
A(s
)
2.8
240.1
18.6
3.5
� 238.3
14.0
2.2
� 242.0
23.5
#
� 1
ÁS (J k mol
�
1
E
a
(kJ mol
�
)
1
A(s
)
0.9
5.3
0.4
#
� 1
ÁS (J k mol
� 251.5
� 237.1
� 257.8
Table 3
Activation energy, frequency factor and entropy of activation for Cu
2
[W(CN) (OH)
2
2
(C
2
H
8
N
2
)(H
2
2 4
O) ]Cl II
Stage
I
Parameters
DTG max. temp. in K
Doyle
Coats and Redfern
Arrhenius
�
1
E
A(s
a
(kJ mol
)
15.7
0.8
8.7
5.7
16.9
0.008
� 288.0
24.4
�
1
)
420.5
528.5
562.4
#
� 1
� 1
� 1
� 1
ÁS (J k mol
)
)
)
� 249.9
20.4
1.2
� 233.4
12.5
5.3
�
1
II
E
A(s
a
(kJ mol
�
)
1
)
0.7
#
� 1
ÁS (J k mol
� 248.2
22.9
� 235.8
15.3
� 253.0
22.3
�
1
III
E
a
(kJ mol
�
)
1
A(s
)
1.3
� 248.2
5.1
� 236.7
0.5
� 256.7
#
� 1
ÁS (J k mol
Arrhenius method :
(3)
where k: Boltzmann constant; h: Planck's constant;
#
(
ture. In the case of I (Table 2), a higher value of
ÁS ): entropy of activation. T : DTG peak tempera-
s
dx
� dt ˆ kx
n
activation energy (E ) is observed in stage II, an
a
where x: amount of the sample undergoing reaction,
n: order of the reaction and k: specific rate constant
The kinetic parameters were calculated by plotting
the left hand side of Eqs. (1)±(3) against 1/T from
intermediate value in stage I and a lower value in
stage IV, the same trend holds good for pre-exponen-
tial factor A(s ) and entropy of activation(ÁS ) for all
the methods involved. The values from Doyle's and
Arrhenius methods are in close agreement with each
other. In case of complex II (Table 3), higher activa-
� 1
#
which the values of E and A are calculated from the
a
slope and intercept respectively (Figs. 5 and 6). The
plot of each stage of the thermal decomposition of I
and II gives linear graph showing the order as unity.
tion energy E is observed in stage III, an intermediate
a
value in stage II and lower energy value in stage I, the
trend being the same with all other parameters and
#
The entropy of activation (ÁS )was calculated from
the equation:
#
methods as well. Entropy of activation (ÁS ) values
ꢀ
ꢁ
ꢀ
ꢁ
for both the complexes are negative indicating a more
ordered structure in the activated state than reactants
and that the reactions are slower than the normal [19].
kTs
h
ÁS#
A ˆ
exp
(4)
R

1
80
S.I. Ali, K. Majid / Thermochimica Acta 311 (1998) 173±181
3
� 1
Fig. 6. (a) Plot of log ꢁ
of Log [� log(1� ꢂ)]/T vs 1/TÂ10 K of complex II.
T
/w vs 1/TÂ10 K of complex II.(b) Plot
2 3 � 1
References
3
� 1
[1] J. Peisach, P. Asen, W. Blumberg (Eds.), The Biochemistry of
Copper, Academic Press, New York, 1966.
Fig. 5. (a) Plot of log ꢁ
2
T
/w vs 1/TÂ10 K of complex I.(b) Plot
3 � 1
of Log[� log(1� ꢂ)]/T vs 1/TÂ10 K of complex I.
[
[
[
[
[
[
[
[
2] W.S. Hangarter, Inflammatory Disease and Copper, in: J.R.J.
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127.
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complexes, lower value of activation energy is
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4] D.R. West, S.B. Padhye, P.B. Sonaware, Structure and
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Fellowship.
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10] V. Balzani, V. Carassiti, Photochemistry of Coordination
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[
[
[
[
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