Kinetic analysis of thermogravimetric data of p-toluidino-p-chlorophenylglyoxime and of some complexes

Article abstract of DOI:10.1016/S0040-6031(01)00657-8

Thermogravimetric (TG) and derivative thermogravimetric (DTG) investigations of p-toluidino-p-chlorophenylglyoxime (p-T-p-CPG) and of some complexes (Co(II), Ni(II), and Cu(II)) in dynamic nitrogen atmosphere have been studied to determine their modes of decomposition. All the complexes showed similar TG behaviour. The mass losses in the main decomposition stage indicated conversion of the metal complexes to its oxide. A gas chromatography-mass spectrometry (GC-MS) combined system was used to identify the products during pyrolytic decompositions. The final products of the decompositions were identified by X-ray powder diffraction method. The kinetic parameters (energy, entropy of activation and pre-exponential factor) were calculated from the data of TG curves.

Full text of DOI:10.1016/S0040-6031(01)00657-8

Thermochimica Acta 383 ꢀ2002) 69±77
Kinetic analysis of thermogravimetric data
of p-toluidino-p-chlorophenylglyoxime
and of some complexes
a,*
Hakan Arslan , Nilg uÈ n Ozpozan , Necdet Tarkan
Department of Chemistry, Faculty of Arts and Sciences, Mersin University, Mersin, Turkey
b
a
È
a
b
Department of Chemistry, Faculty of Arts and Sciences, Erciyes University, Kayseri, Turkey
Received 22 January 2000; received in revised form 18 June 2001; accepted 25 June 2001
Abstract
Thermogravimetric ꢀTG) and derivative thermogravimetric ꢀDTG) investigations of p-toluidino-p-chlorophenylglyoxime
p-T-p-CPG) and of some complexes ꢀCoꢀII), NiꢀII), and CuꢀII)) in dynamic nitrogen atmosphere have been studied to
ꢀ
determine their modes of decomposition. All the complexes showed similar TG behaviour. The mass losses in the main
decomposition stage indicated conversion of the metal complexes to its oxide. A gas chromatography±mass spectrometry
ꢀGC±MS) combined system was used to identify the products during pyrolytic decompositions. The ®nal products of the
decompositions were identi®ed by X-ray powder diffraction method. The kinetic parameters ꢀenergy, entropy of activation and
pre-exponential factor) were calculated from the data of TG curves. # 2002 Elsevier Science B.V. All rights reserved.
Keywords:p -Toluidino-p-chlorophenylglyoxime; CoꢀII), NiꢀII) and CuꢀII) complexes; Thermal behaviour; Decomposition kinetics; DTA/TG/
DTG
1
. Introduction
metal complexes are being isolated at an increasing
rate.
The importance of coordination compounds in
p-Toluidino-p-chlorophenylglyoxime ꢀp-T-p-CPG)
and its CoꢀII), NiꢀII) and CuꢀII) complexes have been
studied [4] ꢀsee Fig. 1). After searching the literature
we could not ®nd any thermal decomposition kinetics
data of this type of vic-dioximes. In this study, decom-
position kinetics were investigated for vic-dioxime
complexes and the relation between metal properties
ꢀsuch as radius) and decomposition kinetics data have
also been examined. Thermoanalytical data ꢀthermo-
gravimetric ꢀTG), derivative thermogravimetric ꢀDTG)
and differential thermal analysis ꢀDTA)) of three
typical complexes, i.e. p-T-p-CPG in this paper, inter-
pretation and mathematical analysis of those data and
the energy and entropy of activation, based on the
biological systems, their increased uses in industry
and the reality that they could be used as anti-tumour
agents in chemotherapy have led to an increase in
investigations of these complexes, especially the vic-
dioxime complexes, which are widely used in analy-
tical chemistry to detect many elements as they are
highly selective complexing conformers [1±3]. Today,
new vic-dioximes are being synthesised and transition
*
Corresponding author. Tel.: ‡90-532-707-31-22;
fax: ‡90-324-361-00-47.
E-mail address: arslanh@mersin.edu.tr ꢀH. Arslan).
0040-6031/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 4 0 - 6 0 3 1 ꢀ 0 1 ) 0 0 6 5 7 - 8

70
H. Arslan et al. / Thermochimica Acta 383 +2002) 69±77
Fig. 1. Octahedral and square-planar metal complexes of the p-toluidino-p-chlorophenylglyoxime ligand.
integral method using Coats and Redfern equation in
5] and the approximation method using Horowitz and
Metzger equation are given in [6].
Agaschromatography±massspectrometryꢀGC±MS)
system VG-ZabSpect model DFMS, was used to
identify pyrolysis products evolved during heating.
Melting points were measured using an Electro-
thermal 9200 model digital melting point apparatus.
[
2
. Experimental
2
.1. Preparation of samples
3. Results and discussions
p-T-p-CPG was synthesised and its complexes with
The thermal behaviour of the above ligand and
complexes have been studied elsewhere in detail [4].
The TG curves were redrawn as % mass loss versus
temperature ꢀTG) and also as the rate of loss of mass
versus temperature ꢀDTG) curves. Typical TG±DTG
and DTA curves are presented in Fig. 2ꢀa)±ꢀc),
respectively, and the thermal curves obtainedfor most
of the compounds were very similar in character.
Thermal data of the compounds are summarised in
Table 1 together with the radii of the metal ions.
p-T-p-CPG and its CoꢀII), NiꢀII) and CuꢀII) com-
plexes are thermal stable up to 401, 408, 453, 383 K,
respectively. It was found that pyrolytic decomposi-
tion occurs together with melting in both ligand and its
metal complexes. The ligand decomposes in two
stages and the metal complexes undergo decomposi-
tion in three stages through different mechanisms ꢀsee
Table 1).
CoꢀII), NiꢀII) and CuꢀII) were prepared using a pre-
viously described method [7]. All chemicals used
were of analytical reagent grade or chemically pure.
2
.2. Instrumentation
The thermal studies were carried out on a Shimadzu
DT-40 Thermal Analyser with simultaneous DTA±TG
module. TG and DTA curves were recorded in a
nitrogen furnace atmosphere at a heating rate of
À1
1
and 1823 K with samples varying in mass from 4 to
0 K min in the temperature range between 273
8
mg. a-Al O was used as a reference.
2
3
Infrared spectra were recorded in the region 4000±
À1
4
using KBr pellets.
00 cm
on a Shimadzu 435 spectrophotometer,
X-ray powder diffraction analyses of the ®nal resi-
dues were made with a Siemens F model diffract-
ometer. X-ray generator is Phillips PW-1010 model
ranging from 20 to 40 kV and from 6 to 50 mA while
CuꢀII) and NiꢀII) complexes which have a square-
planar structure undergo similar thermal decomposi-
tion in three stages and produce metal oxides ꢀNiO and
CuO). CoꢀII) complexes which have an octahedral
Ê
using ®ne focus Cu Ka radiation ꢀl ˆ 1:5406 A).

H. Arslan et al. / Thermochimica Acta 383 +2002) 69±77
71
coordination undergo decomposition in three stages
and turn to CoO but yield different intermediate
products. X-ray powder diffraction data, GC±MS data
and TG data con®rm our obtained results.
NiꢀII)
and
CuꢀII)
complexes
produce
CH3C6H4NHCN ‡ 2OH ‡ NO substances at the
®rst stage whereas CoꢀII) complexes produce
CH C H NHCN ‡ 2H O. At the second stage, NiꢀII)
3
6
4
2
Fig. 2. ꢀa) TG±DTG curves of p-toluidino-p-chlorophenylglyoxime ligand and its CoꢀII) complex; ꢀb) TG±DTG curves of NiꢀII)± and
CuꢀII)±p-toluidino-p-chlorophenylglyoxime complexes; ꢀc) DTA curves for p-toluidino-p-chlorophenylglyoxime ligand and CoꢀII)±,
NiꢀII)±, CuꢀII)±p-toluidino-p-chlorophenylglyoxime complexes.

72
H. Arslan et al. / Thermochimica Acta 383 +2002) 69±77
Fig. 2. ꢀContinued ).
and CuꢀII) complexes yield CH C H NCH whereas
3
3.6%; N 13.0%; C H N O Cl Ni requires: C 54.3%,
30 26 6 4 2
6
4
CoꢀII) complexes yield CH C H NCH ‡ 2OH ‡ NO.
H 3.9%; N 12.7%; found: C 53.5%; H 3.6%; N 12.3%;
C H N O Cl ÁCu requires: C 53.9%, H 3.9%; N
3
6
4
At the last stage, the product ꢀClC H CN) is the same
6
4
30 26
6
4
2
for all these complexes. These results were con®rmed
by TG data, GC±MS analysis data ꢀCH C H NHCN
12.6%; found: C 51.2%; H 4.3%; N 12.2%;
C H N O Cl CoÁ2H O requires: C 51.4%; H
3
6
4
30 26
6
4
2
2
ꢀ
m/z)) and micro-analysis data ꢀfound: C 54.6%, H
133 m/z), CH C H NCH ꢀ118 m/z), ClC H CN ꢀ137
4.3%; N 12.0%; found: C 59.3%; H 4.7%; N
13.9%; C H N O Cl requires: C 59.3%; H 4.6%;
3
6
4
6 4
1
5 14 3 2
Fig. 3. IR spectra of NiꢀII)±p-toluidino-p-chlorophenylglyoxime complex.

Table 1
Thermal decomposition data and radii of metal ions
Sample
Radius of
metal ion
Stage
TG results
temperature
range ꢀK)
DTG results DTA results Weight loss ꢀ%) Evolved moiety
temperature
peak ꢀK)
Stage products
temperature
peak ꢀK)
ꢀ
pm)
Found Calcu-
lated
p-T-p-CPG
±
I
401±669
669±973
467
908
481
903
55.12
44.85
54.71
45.29
CH
ClC
3
C
6
H
4
NHCN ‡ 2OH
ClC
±
6 4
H CN
II
H CN
6 4
Cuꢀp-T-p-CPG)
2
70
I
383±567
567±770
770±1080
>1080
487
583
986
470
592
30.34
16.65
41.11
11.90
29.32
17.66
41.13
11.89
CH
CH
3
C
C
6
H
H
4
4
NHCN ‡ 2OH ‡ NO [C22
NCH [C14
H
H
16
N
3
OCl
2
]ÁCu
2
II
III
3
6
8
N
2
OCl
]ÁCu
1034
2ClC
±
6
H
4
CN
CuO
CuO
Residue
Niꢀp-T-p-CPG)
Coꢀp-T-p-CPG)
72
74
I
453±575
575±786
786±1111
>1111
571
631
961
±
571
624
30.77
16.68
40.81
11.74
29.54
17.79
41.42
11.25
CH
CH
3
C
C
6
H
H
4
4
NHCN ‡ 2OH ‡ NO [C22
H
H
16
N
3
OCl
2
]ÁNi
II
3
6
NCH
[C14
NiO
NiO
8
N
OCl
2 2
]ÁNi
III
889±1006
±
2ClC
±
6 4
H CN
Residue
2
2
Á2H O
I
408±557
557±617
617±996
>996
509
591
968
±
506
599
947
±
23.56
25.51
39.93
11.00
24.01
26.01
39.28
10.70
CH
CH
3
C
C
6
H
H
4
NHCN ‡ 2H
NCH ‡ 2OH ‡ NO
CN
2
O
[C22
[C14
H
H
18
N
4
O
4
Cl
2
]ÁCo
2
II
3
6
4
8
N
2
OCl
]ÁCo
III
2ClC
±
6
H
4
CoO
CoO
Residue

74
H. Arslan et al. / Thermochimica Acta 383 +2002) 69±77
Fig. 4. Linearisation curves of Horowitz and Metzger method for p-toluidino-p-chlorophenylglyoxime ligand.
N 13.8%). By considering the mass loss of the com-
plexes and X-ray diffraction data [8] the ®nal products
was indicated to be oxide ꢀNiO, CuO and CoO).
It has been noticed that molecules except CoꢀII)
complex did not contain any hydrate molecules
according to the IR measurements ꢀsee Fig. 3). As
additional evidence there is no dedectable change in
TG curves up to 100 8C. These results were con®rmed
by CHN analysis for all compounds.
From the TG curves, the order n, activation energy
E , entropies DS , and pre-exponential factor A of the
thermal decomposition have been elucidated by the
methods of Coats and Redfern and Horowitz and
Metzger [5,6].
Ã
Ã
Fig. 5. Linearisation curves of Coats and Redfern method for p-toluidino-p-chlorophenylglyoxime ligand.

H. Arslan et al. / Thermochimica Acta 383 +2002) 69±77
75
Fig. 6. Linearisation curves of Horowitz and Metzger method for CoꢀII)±, NiꢀII)±, and CuꢀII)±p-toluidino-p-chlorophenylglyoxime
complexes.
The linearisation curves of ligand that are obtained
by Horowitz and Metzger and Coats and Redfern are
presented in Figs. 4 and 5, respectively. And the
complex curves which obtained by Horowitz and
Metzger and Coats and Redfern are presented in
Figs. 6 and 7, respectively. The results of kinetic
studies of TG±DTG are presented in Table 2.
The value of correlation coef®cients of linearisation
curves of ligand and its complexes are approximately
1. And their reaction orders are 1 for ligand and about
Fig. 7. Linearisation curves of Coats and Redfern method for CoꢀII)±, NiꢀII)±, and CuꢀII)±p-toluidino-p-chlorophenylglyoxime complexes.

76
H. Arslan et al. / Thermochimica Acta 383 +2002) 69±77
Table 2
Kinetic data on the investigated compounds
a
Sample
Stage
Reaction
Parameters
From Coats and
Redfern equation
From Horowitz and
Metzger equation
order ꢀn)
Ã
p-T-p-CPG
I
1.000
E
17.3
8.6 Â 10À2
À269.4
0.9997
17.8
À2
A
12.5 Â 10
Ã
DS
À266.3
0.9998
42.8
r
Ã
II
1.000
E
41.9
7
7
A
7.7 Â 10
8.9 Â 10
Ã
DS
À72.6
À102.0
r
0.9932
0.9962
Ã
Cuꢀp-T-p-CPG)
2
I
0.919
0.916
0.932
E
45.5
236.2
56.6
4018.9
À180.2
0.9991
45.0
A
Ã
DS
À203.7
0.9994
36.2
r
Ã
II
III
E
A
1.0
5.1
Ã
DS
À252.1
0.9910
101.9
À238.4
0.9945
110.1
r
Ã
E
A
571.2
1615.9
À193.4
0.9997
Ã
DS
r
À202.1
0.9991
Ã
Niꢀp-T-p-CPG)
2
I
0.749
0.971
0.990
E
31.2
0.2
46.9
56.6
A
Ã
DS
À262.5
0.9972
34.9
À216.7
0.9981
37.9
r
Ã
II
III
E
A
0.6
1.6
Ã
DS
À255.8
0.9896
96.2
À247.9
0.9955
95.1
r
Ã
E
A
223.8
À209.8
0.9985
247.9
À208.9
0.9995
Ã
DS
r
Ã
Coꢀp-T-p-CPG)
2
Á2H
2
O
I
0.847
0.912
0.837
E
45.0
105.9
53.5
823.3
A
Ã
DS
À184.8
0.9994
161.3
À193.8
0.9986
170.6
r
Ã
II
III
E
12
12
A
1.2 Â 10
À19.3
0.9990
34.7
8.0 Â 10
Ã
DS
À3.7
0.9989
45.1
r
Ã
E
A
0.1
À271.6
0.6
À257.5
0.9991
Ã
DS
r
0.9985
a
Ã
À1
À1
Ã
À1 À1
K ), r: correlation coef®cient of the linear plot, n: order of reaction.
Units of parameters: E ꢀkJ mol ), A ꢀs ), DS ꢀmol

H. Arslan et al. / Thermochimica Acta 383 +2002) 69±77
77
1
for each stage of complexes. The kinetic data
NiꢀII) which decomposes at lower temperatures as 1/r
increase, may decompose by electron transfer from the
oximes to the metal ions. This is supported by the fact
that the electron af®nities of metal ions, in general
increase with increasing effective nuclear charge
[16,17].
reached by both of the methods are in harmony with
each other.
Ã
The values of activation energy E obtained by two
methods for the ligand and for each of its complexes
are given in Table 2. The activation energy of CoꢀII),
NiꢀII) and CuꢀII) complexes is expected to increase
proportional to the decrease in their radius [9]. The
activation energy of NiꢀII) and CuꢀII) complexes
which have been decomposed on a similar mechanism
and have square-planar structure increase proportional
to their radius degrees. E values according to the
average of two methods for these two complexes in the
®rst decomposition stages are 39.1 and 51.1 kJ mol
respectively.
TCu ˆ383 K ꢀrCu ˆ70 pm†<TNi ˆ453 K ꢀrNi ˆ72 pm†
References
Ã
[
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Ã
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