Thermal studies of p-toluidino-p-chlorophenylglyoxime and of some corresponding Ni(II), Cu(II) and Co(II) complexes

Article abstract of DOI:10.1016/S0040-6031(99)00004-0

The thermal behaviour of p-toluidino-p-chlorophenylglyoxime (pTpCPG) and its Cu(II), Ni(II), and Co(II) complexes have been studied by DTA and TG. It was found that pyrolytic decomposition undergoes with melting in both ligand and its metal complexes and

Full text of DOI:10.1016/S0040-6031(99)00004-0

Thermochimica Acta 329 (1999) 57±65
Thermal studies of p-toluidino-p-chlorophenylglyoxime and of
some corresponding Ni(II), Cu(II) and Co(II) complexes
Hakan Arslana, NilguÈn Ozpozanb,*, Talat Ozpozanb
aDepartment of Chemistry, Nigde University, Nigde, Turkey
bDepartment of Chemistry, Erciyes University, Kayseri, Turkey
Received 26 August 1998; received in revised form 18 December 1998; accepted 22 December 1998
Abstract
The thermal behaviour of p-toluidino-p-chlorophenylglyoxime (pTpCPG) and its Cu(II), Ni(II), and Co(II) complexes have
been studied by DTA and TG. It was found that pyrolytic decomposition undergoes with melting in both ligand and its metal
complexes and metal oxides remained as end products of the metal complexes. The ligand decomposes in two stages through
two different mechanisms and the metal chelates undergo decomposition in three stages. GC±MS combined system was used
to identify the products during pyrolytic decompositions. The pyrolytic end products were identi®ed by X-ray powder
diffraction. # 1999 Elsevier Science B.V. All rights reserved.
Keywords: p-Toluidino-p-chlorophenylglyoxime; Cu(II)-, Ni(II)- and Co(II)-complexes; Thermal behaviour; Pyrolysis; DTA/
TG/DTG
1. Introduction
B12 and coenzyme B12, since these macromolecules
play important roles in biological mechanisms.
In some recent studies, Pt vic-dioxime complexes
have been tested as anti-tumour agents in chemother-
apy [5]. These complexes have also been used in the
production of semiconductors [6]. Liquid crystal prop-
erties of some vic-dioxime complexes have been
studied [6] and further applications include column
packing material in chromatographic separation of
nucleotides and nucleosides after bonding to natural
resins as functional groups [7].
In the present study, p-toluidino-p-chlorophenyl-
glyoxime (pTpCPG) complexes of Ni(II), Co(II),
and Cu(II) are studied by DTA and TG and the
mechanisms of thermal decomposition have been
determined.
Vic-dioxime metal complexes are important as
coordination compounds. The early studies on oxime
complexes date from 1905 and have been reviewed by
Chakravorty [1] who also studied Ni(II) dimethyl-
glyoximes. Later in 1907, Tschugaeff [2] isolated
dimethylglyoxime complexes of Co(III) which played
an important role as model compounds in the elucida-
tion of some biological and biochemical mechanisms.
Several studies were concentrated on Co vic-diox-
ime complexes in later years [3,4]. These were used as
model compounds to explain the structure of vitamin
*Corresponding author. Fax: +90-352-4374933; e-mail:
ozpozant@erciyes.edu.tr
0040-6031/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved.
P I I : S 0 0 4 0 - 6 0 3 1 ( 9 9 ) 0 0 0 0 4 - 0

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H. Arslan et al. / Thermochimica Acta 329 (1999) 57±65
2. Experimental
2.1. Instrumentation
The ligand pTpCPG and the corresponding Ni(II),
Co(II), and Cu(II) chelates were synthesized from
analytical pure reagents as described in [8].
A Shimadzu model DT-40 simultaneous TG, DTA
thermal analysis system was used over the temperature
range 273±1823 K (0±15508C). The samples were
Fig. 1. DTA/TG/DTG diagram of (a) p-toluidino-p-chlorophenylglyoxime, (b) Ni(II) complex of pTpCPG, (c) Cu(II) complex of pTpCPG,
(d) Co(II) complex of pTpCPG.

H. Arslan et al. / Thermochimica Acta 329 (1999) 57±65
59
Fig. 1. (Continued )
placed in Pt crucibles and a-Al2O3 was used as the
reference material. Heating was performed under a N2
atmosphere and a ¯ow rate of 60 ml/min. The sample
size was limited to 4±8 mg and the heating rate was
adjusted to 10 K/min in all cases.
heating. The residual end products of heating were
identi®ed by X-ray powder diffractometry using a
power generator from Phillips (model PW-1010)
and a goniometer from Siemens (type F). Melting
point determinations were performed with a digital
melting point instrument from Electrothermal model
9200.
A GC±MS system VG-ZabSpec model DFMS, was
used to identify pyrolysis products evolved during

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H. Arslan et al. / Thermochimica Acta 329 (1999) 57±65
3. Results and discussions
From the corresponding DTA pro®le, two exothermic
peaks are noted, the ®rst between 434 and 509 K with
a maximum at 481 K and the second between 820 and
946 K with a maximum at 903 K.
3.1. p-Toluidino-p-chlorophenylglyoxime
pTpCPG melts at 398±399 K with simultaneous
decomposition. The ®rst mass loss was observed at
401 K in the TG pro®le. The DTA/TG/DTG pro®les of
the ligand are shown in Fig. 1(a). From the TG curve,
it appeared that the sample decomposes in two stages
over the temperature range 298±973 K. The ®rst
decomposition occurs between 298 and 669 K with
a mass loss of 55.1% and the second decomposition
starts at 669 K, ends at 973 K with a 44.8% mass loss.
Two different mechanisms of decomposition for the
ligand are possible as shown by Schemes 1 and 2. The
theoretical mechanisms given in Schemes 1 and 2 are
in agreement with that of Burakevich et al. [9], who
studied with phenylglyoxime in 1971. The theoretical
mechanisms dealt with in Schemes 1 and 2 are con-
®rmed by the GC±MS data in Fig. 2(a). The peaks
observed at 303, 287, 270, 256, 138, 133, 118 m/z are
responsible for the evolved radical moiety. The
Scheme 1.
Scheme 2.

H. Arslan et al. / Thermochimica Acta 329 (1999) 57±65
61
Fig. 2. GC±MS spectrum of (a) p-toluidino-p-chlorophenylglyoxime, (b) Ni(II) complex of pTpCPG.
decomposition mechanisms obtained from TG pro®les
are shown in Schemes 3 and 4. The theoretical and the
experimental per cent mass losses obtained from these
decomposition stages are in good agreement.
The mechanism of reaction (1) proceeds in two
stages, the ®rst of which is apparent in reaction (3).
The end-product (Cl±C6H4±C>N:) of this stage under-
goes pyrolysis in the second stage. The second decom-
position mechanism proceeds in two stages, the ®rst of
which is apparent in reaction (4). The end-product
(Cl±C6H4±C>N:) of the second stage undergoes pyr-
olysis in the same way as in the second stage of the
®rst mechanism. The ®rst stages in both suggested
mechanisms correspond to a theoretical mass loss of
54.7%. This percentage was found to be 55.1% from
TG studies. The second stages in both mechanisms

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H. Arslan et al. / Thermochimica Acta 329 (1999) 57±65
Scheme 3.
Scheme 4.
correspond to a theoretical mass loss of 45.3% for
which the experimentally found value is 44.8% from
TG studies. This mass loss corresponds to the mass of
Cl±C6H4±C>N: as observed in GC±MS data
(Fig. 2(a)). The mass losses found experimentally
are very close to the theoretical values.
40.8% mass loss. Three exothermic peaks were
observed in the DTA analysis. The ®rst peak occurs
between 554 and 573 K with a maximum at 571 K.
The second peak occurs between 588 and 693 K with a
maximum at 624 K and the third occurs between 783
and 1121 K and is associated with two maxima at 889
and 1006 K.
3.2. Ni(II) complex
The theoretical mechanisms given in Schemes 5 and
6 are supported by GC±MS data as shown in Fig. 2(b)
and the identi®cation of greenish-black end product of
decomposition is obtained by X-ray diffraction
(Fig. 3). In both studies, it is concluded that the
decomposition of the Ni-complex yields NiO as the
decomposition end product in accordance with reac-
tion (5). The theoretical mass of remaining NiO is
11.2% which corresponds to 11.7% from the TG
studies. 29.5% theoretical mass loss in the ®rst decom-
position corresponds to 30.8% from TG. The same
theoretical mass losses in the second and third stages
It is noted from the TG analysis that the Ni(II)
complex of pTpCPG looses 88.3% of its original mass
between 298 and 1111 K and the 11.7% residue is a
greenish-black coloured solid. The DTA/TG/DTG
data for the Ni complex is shown in Fig. 1(b). The
sample decomposes in three stages. The ®rst decom-
position occurs between 298 and 575 K with 30.8%
mass loss, the second decomposition occurs between
588 and 693 K with 16.7% mass loss and the third
decomposition occurs between 786 and 1111 K with
Scheme 5.

H. Arslan et al. / Thermochimica Acta 329 (1999) 57±65
63
Scheme 6.
Fig. 3. X-ray powder diffraction pattern of NiO.
were 17.8% and 41.4%. These values were experi-
mentally found to be 16.7% and 40.8% from TG data,
respectively.
The DTA curves shows three exothermic peaks. The
®rst peak occurs between 414 and 526 K with a
maximum at 470 K. The second occurs between
569 and 628 K with a maximum at 592 K and the
third occurs between 825 and 1076 K with a maximum
at 1034 K.
3.3. Cu(II) complex
The TG studies on the Cu(II) complex of pTpCPG
showed that the initial mass loss occurs at 383 K.
Decomposition ends with a total of 88.1% mass loss at
1080 K with a black solid residue corresponding to a
mass of 11.9%. DTA/TG/DTG diagrams of the Cu(II)
complex are shown in Fig. 1(c).
It was observed from the TG curve that the sample
decomposes in three stages and it looses 30.34%,
16.55% and 41.13% of its mass in each stage, respec-
tively. The temperature ranges of these decomposi-
tions are found to be 298±567, 567±770 and 770±
1080 K, respectively.
Both DTA/TG and X-ray powder diffraction studies
showed that the residual black solid was CuO which
corresponds to a theoretical mass of 11.9% of the
complex. TG curve of the same complex gave an end-
product having a mass of 11.9%. Hence the Cu(II)
complex decomposes in a similar way to the Ni(II)
complex in three stages in accordance with Scheme 5.
The theoretical and experimental mass losses of
each stage are as follows; 29.3%, 17.7%, 41.1%,
where the corresponding experimental per cent mass
losses are found to be 30.3%, 16.6%, 41.1%, respec-
tively.

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H. Arslan et al. / Thermochimica Acta 329 (1999) 57±65
The TG studies on pTpCPG chelates of both Ni(II)
peak appeared between 452 and 539 K with a max-
imum at 506 K. The second appeared between 558 and
614 K with a maximum at 599 K and the third
appeared between 614 and 987 K with a maximum
at 947 K.
TG analysis showed that the Co(II) complex yields
a pyrolysis solid product of mass 11.0% correspond-
ing to the theoretical mass of 10.7% for CoO. As given
in Scheme 6, the Co(II) complex decomposes in three
stages by losing 24.0%, 26.0% and 39.3% of its mass
theoretically during the pyrolysis, respectively. In
these pyrolytic reactions, the mass losses derived from
TG curve are 23.6%, 25.5% and 39.9%.
It was concluded from TG studies that all the Ni(II),
Cu(II) and Co(II) complexes examined were con-
verted to the corresponding oxides. The ligand decom-
poses in two stages by two different mechanisms, and
the complexes decompose in three stages. The oxides
yielded at the end of pyrolysis were con®rmed by the
X-ray powder diffraction data given in the related
sources [10].
and Cu(II) showed that these two complexes have
similar thermal decomposition mechanisms which is
expected since they both have square-planar structure.
Since the decomposition of both Ni(II) and Cu(II)
complexes undergo the similar thermal decomposition
mechanism, only the GC±MS spectrum and X-ray
powder diffraction patterns of the Ni(II) complex
are included here.
3.4. Co(II) complex
It was found from TG analysis that the sample starts
losing mass at 408 K and ends at 994 K after losing
89.0% of its mass with a greenish-brown residue
which corresponds to 11.0% of the total mass. The
DTA/TG/DTG diagrams of the Co(II) complex are
shown in Fig. 1(d). The examination of TG curve
showed that the sample decomposes in three stages.
The sample loses 23.6% of mass between 298 and
557 K, 25.5% of the mass between 557 and 617 K and
39.9% between 617 and 996 K. The DTA study of the
complex showed three exothermic peaks. The ®rst
The critical data and values deduced from the
present study were summarized in Table 1.
Table 1
DTA/TG data for the Ni(II), Cu(II) and Co(II) complexes of p-toluidino-p-chlorophenylglyoxime
Sample
Stage
Temperature of DTA
peak maximum (K)
TG temperature
range (K)
Mass loss (%)
TG
Theoretical
RE (%)
Ligand
I
481
903
401±669
669±973
55.12
44.85
54.71
45.29
0.75
0.97
(pTpCPG)
II
Cu(II)
I
470
592
1034
±
383±567
567±770
770±1080
>1080
30.34
16.65
41.11
11.90
29.32
17.66
41.13
11.89
3.48
5.72
0.05
0.08
complex
II
III
Last
Ni(II)
I
571
453±575
575±786
786±1111
>1111
30.77
16.68
40.81
11.74
29.54
17.79
41.42
11.25
4.16
6.24
1.47
4.36
complex
II
624
889±1006
±
III
Last
Co(II)
complex
I
506
599
947
±
408±557
557±617
617±996
>996
23.56
25.51
39.93
11.00
24.01
26.01
39.28
10.70
0.09
1.92
1.65
2.80
II
III
Last
Average
2.41
%RE: % relative error.

H. Arslan et al. / Thermochimica Acta 329 (1999) 57±65
65
[6] M.A. Deveci, Ph.D. Thesis, Selc,uk University, Konya-TR,
1994.
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