Vol.2, No.8, 817-827 (2010) Natural Science
http://dx.doi.org/10.4236/ns.2010.28103
Synthesis and thermal studies of mixed ligand
complexes of Cu(II), Co(II), Ni(II) and Cd(II) with
mercaptotriazoles and dehydroacetic acid
Dina M. Fouad*, Ahmed Bayoumi, Mohamed A. El-Gahami, Said A. Ibrahim, Abbas M. Hammam
Chemistry department, Faculty of Science, Assiut University, Assiut, Egypt; *Corresponding Author:
Received 15 January 2010; revised 25 February 2010; accepted 2 March 2010.
ABSTRACT
A series of new mixed ligand complexes of
cobalt(II), nickel(II), copper(II) and cadmium(II)
have been synthesized with 3-benzyl-1H-4-[(2-
methoxybenzylidine) amino]-1, 2, 4-triazole-5-
thione (MBT), 3-bezyl-1H-4-[(4-chlorobenzylidine)
amino]-1, 2, 4-triazole-5-thione (CBT), 3-benzyl-
1H-4-[(4-nitrobenzylidine)amino]-1, 2, 4-triazole-
5-thione (NBT) and dehydroacetic acid sodium
salt (Nadha). The mixed ligand complexes have
been characterized by elemental analysis, spec-
troscopic spectral measurements (IR, UV-Vis.),
molar conductance, magnetic measurements and
thermal studies. The stoichiometry of these com-
plexes is M:L1:L2 = 1:1:1, 1:2:1 or 1:1:2 where L1
= NBT, CBT and MBT and L2 = Nadha. Tetrahe-
dral structure was proposed for all Cd(II) mixed
ligand complexes while the square planar ge-
ometry was proposed for Cu(II) mixed ligand
complex with NBT. Octahedral structure was
proposed for Ni(II), Co(II) mixed ligand complexes
and Cu(II) mixed ligand complexes with CBT
and MBT ligands. The thermal decomposition
study of the prepared complexes was monitored
by TG, DTG and DTA analysis in dynamic nitro-
gen atmosphere. TG, DTG and DTA studies con-
firmed the chemical formulations of theses
complexes. The kinetic parameters were deter-
mined from the the thermal decomposition data
using the graphical methods of Coats-Redfern
and Horwitz-Metzger. Thermodynamic parame-
ters were calculated using standard relations.
Keywords: Mix Ligand Complexes; Mercaptotriazoles;
Dehydroacetic Acid
1. INTRODUCTION
3-acetyl-6-methyl-2H-pyran-2, 4(3H)-dione, a commer-
cially available compound usually obtained through the
auto condensation of ethyl acetoacetate [1], it has been
shown to posses modest antifungal properties [2]. The
importance of similar pyrones as potential fungicides is
reinforced by the existence of several natural fungicides
possessing structures analogous to 5, 6-dihydro dehy-
droacetic acid, like alternaric acid, the podoblastins and
lachnelluloic acid [3-5], studies have shown that such
compounds and their complexes have very interesting
biological properties[6-13]. Like dehydroacetic acid,
mercaptotriazoles and their complexes have been shown
to posses enhanced biological activities [14-27]. The
work of the present paper is devoted to the synthesis and
characterization of some new mixed ligand complexes
containing mercaptotriazoles and dehydroacetic acid.
The mercaptotriazole ligands containing the thioamide
groups which are capable of undergoing thione-thiol
(HN – C = S N = C – SH) tautomerism and can
coordinate to the metal atom through both nitrogen and
sulphur atoms. While the sodium salt of dehydroacetic
acid behaves as a monobasic bidentate ligand through
two oxygen atoms. Hence the present paper reports the
thermal analysis studies of some mixed ligand com-
plexes. The associated thermal decomposition mecha-
nisms are reported.
2. EXPERIMENTAL
2.1. Materials and Measurements
All chemicals used in the preparative work were of ana-
lytical grade, they include the following: dehydroacetic
acid sodium salt (Nadha), carbon disulphide, potassium
hydroxide, absolute ethanol, methanol, Dimethylforma-
mide (DMF), phenylacetic acid, o-methoxy benzaldehyde,
p-nitrobenzaldehyde, p-chlorobenzaldehyde, CuCl2·2H2O,
NiCl2· 6H2O, CoCl2· 6H2O, CdCl2· 2.5H2O. They were
used without further purification.

D. M. Fouad et al. / Natural Science 2 (2010) 817-827
818
2.2. Synthesis of the Mercaptotriazole
Ligands
The ligands 3-benzyl-1H-4-[(2-methoxybenzylidine)
amino]-1, 2, 4-triazole-5-thione (MBT), 3-benzyl-1H
-4-[(4-chlorobenzylidine)amino]-1, 2, 4-triazole-5-thione
(CBT) and 3-benzyl-1H-4-[(4-nitrobenzylidine)amino]-
1, 2, 4-triazole-5-thione (NBT) were synthesized ac-
cording to literature survey [28-30]. The purity of the
ligands was checked by elemental analysis (Table 1).
The structures of ligands are shown in Figure 1.
2.3. Synthesis Cu(II) Mixed Ligand
Complexes
To a solution of copper chloride 1 mmol in 10 mL me-
thanol, a solution of the (MBT, CBT or NBT) ligands (1
mmol in 25 mL hot methanol was added dropwise with
constant stirring in one direction. When the precipitate
was formed, 2 mmols in 10mL methanol of
(Nadha) ligand was added. Refluxing of the resulting
solution carried for 8 hours. The product obtained was
left overnight, filtered through sintered glass, washed
with methanol and dried in vacuum over anhydrous
CaCl2.
2.4. Synthesis of Co(II), Ni(II) and Cd(II)
Mixed Ligand Complexes
To 1 mmol of CoCl2.6H2O/NiCl2.6H2O or CdCl2.2.5H2O
and 2 mmols of sodium acetate in 25 mL methanol, a
solution of MBT, CBT or NBT (1 mmol in 25 mL hot
methanol) was added dropwise with constant stirring in
one direction. When the precipitate was formed, 2
mmols: 0.3802 grams in 10mL methanol of Nadha was
added. Refluxing of the resulting solution carried for 8
hours. The mixed ligand complex appears on cooling the
solution after 4-6 hours. The product obtained was left
overnight, filtered through sintered glass, washed with
methanol and dried in vacuum over anhydrous CaCl2.
Table 1. The Analytical data for the mercaptotriazole ligands.
Analytical Data
% Found (Calculated)
Free ligand
(Empirical formula)
Formula weight C H N S
MBT
(C17H16N4OS)
M.Wt.= 324.401
63.09
(62.94)
5.11
(4.97)
17.47
(17.27)
9.71
(9.88)
NBT
(C16H13N5O2S)
M.Wt.= 339.379
56.55
(56.62)
3.282
(3.86)
19.82
(20.63)
9.39
(9.44)
CBT
(C16H13N4SCl)
M.Wt.= 328.820
58.79
(58.44)
4.10
(3.98)
17.04
(17.03)
9.64
(9.75)
N
N
N
S
H
H2
C
CHAr
N
triazole ligands
where Ar is:
OCH3
, 3-benzyl-4-[(2-methoxybenzylidene)amino]-1H-1,2,4-triazole-5-thione (MBT)
O2N,3- benzyl-4-[(4-nitrobenzylidene)amino]-1H-1,2,4-triazole-5-thione(NBT)
Cl , 3-benzyl-4-[(4-chlorobenzylidene)amino]-1H-1,2,4-triazole-5-thione(CBT)
OO
O
ONa
Dehydroacetic acid(Sodium salt)
Figure 1. structures for the ligands.

D. M. Fouad et al. / Natural Science 2 (2010) 817-827
819
2.5. Physical Measurements
The carbon, hydrogen, nitrogen and sulfur of the solid
complexes were determined by Elementar analyzer sys-
tem Gmbh Vario El. Conductivity measurements for the
various complexes were carried out using Jenway 4320
meterlab conductivity meter in DMF solutions at 10-3 M
concentrations at room temperature. Electronic spectra
of the solid complexes were run on perkin Elmer
UV/VIS spectrophotometer Lambda 40 using 1-cm
matched silica cells. Magnetic susceptibility measure-
ments were carried out at room temperature using a
magnetic susceptibility balance of the type MSB-Auto.
Molar susceptibilities were corrected for diamagnetism
of the component atoms by the use of Pascal’s constants.
The calibrant used was Hg[Co(SCN)4]. The infrared
spectra of the free ligands and the metal complexes were
recorded on a shimadzu 470 infrared spectrophotometer
(4000-400 cm-1) using KBr discs. Thermogravimetric
studies of the various complexes was carried out using a
shimadzu DTG-60Hz thermal analyzer, at heating rate
10oC min-1 in dynamic nitrogen atmosphere.
3. RESULTS AND DISCUSSION
3.1. Elemental Analyses and Conductivity
Measurements
The analytical data of the metal complexes are given in
Table 2. The data reveal the formation of complexes
having 1:1:1, 1:1:2 or 1:2:1 (metal ion: mercaptotriazole
ligand: Nadha) ratio with Co(II), Ni(II), Cu(II) and
Cd(II). The methods used for the preparation and isola-
tion of the mixed ligand complexes give materials of
good purity as supported by their analyses. All the mixed
ligand complexes are colored except Cd(II) complexes
are white. They are stable in air and nonhygroscopic.
The synthesized complexes are sparingly soluble in the
common organic solvents but they are completely solu-
ble in DMF or DMSO.
The molar conductance values for complexes (2,
4-9) recorded as DMF solutions are within the range
8.14-30.9 Ohm-1cm2mol-1 (Table 2) which indicates the
nonelectrolyte nature of these complexes. While the
mixed ligand complexes (1, 3, 10-12) show molar
conductance values within the range 71.0-84.9 Ohm-1
cm2mol-1 indicating that these complexes are 1:1 elec-
trolytes [31].
3.2. UV-Visible Spectra and Magnetic
Susceptibility Measurements
The electronic spectra of the Cu(II), Ni(II),Co(II) and
Cd(II) mixed ligand complexes have been recorded as
DMF solutions in the wavelength range 250-1100 nm.
The υmax in kK. and εmax in cm2mol-1 are depicted in Ta-
ble 3. The corrected magnetic moment (μeff) in Bohr
magneton units of the mixed ligand complexes are given
in Table 2.
Table 2. Analytical and physical data for the complexes.
Analytical Data
% Found (Calculated)
No.
Complex
[Empirical formula]
(Formula weight)
Color
C H N S
Λo
ohm-1 cm2 mol-1
μeff
(BM)
1 [Cu(NBT)(dha)]Cl
CuC24H20N5O6SCl(605.51)
Red 47.59
(47.60)
3.10
(3.32)
11.92
(11.56)
4.43
(5.29)
79.83 -
2 [Cu(CBT)(dha)Cl(H2O)]
CuC24H22N4O5SCl2(612.97)
Green47.45
(47.02)
4.02
(3.61)
9.43
(9.14)
5.81
(5.23)
16.47 -
3 [Cu(MBT)2(dha)]Cl.H2O
CuC42H41N8O7S2Cl(932.95)
Green54.85
(54.07)
3.58
(4.42)
11.43
(12.01)
6.38
(6.87)
71.0 -
4 [Co(NBT)(dha)2].H2O
CoC32H29N5O11S(750.59)
Green51.08
(51.20)
3.92
(3.89)
9.20
(9.33)
4.18
(4.27)
24.2 5.12
5 [Co(CBT)(dha)Cl(H2O)].H2O
CoC24H24N4O6SCl2(626.37)
Grey 46.56
(46.01)
3.72
(3.86)
9.12
(8.94)
5.38
(5.11)
30.9 4.86
6 [Co(MBT)(dha)Cl(H2O)]
CoC25H25N4O6SCl(603.94)
Grey 49.63
(49.71)
4.60
(4.17)
9.16
(9.27)
5.49
(5.30)
8.14 4.55
7 [Ni(NBT)(dha)2].2H2O
NiC32H31N5O12S(768.37)
Green49.96
(50.02)
3.90
(4.06)
8.96
(9.11)
4.09
(4.17)
22.6 3.16
8 [Ni(CBT)(dha)Cl(H2O)].H2O
NiC24H24N4O6SCl2(626.13)
Green46.21
(46.03)
4.24
(3.86)
8.19
(8.94)
5.34
(5.12)
14.3 2.98
9 [Ni(MBT)(dha)Cl(H2O)]
NiC25H25N4O6SCl(603.70)
Green49.25
(49.73)
4.02
(4.17)
8.83
(9.28)
5.26
(5.31)
17.2 3.05
10 [Cd(NBT)(dha)]Cl.H2O
CdC24H22N5O7SCl(672.39)
White42.70
(42.87)
3.10
(3.29)
9.65
(10.41)
4.84
(4.76)
71.8 -
11 [Cd(CBT)(dha)]Cl.H2O
CdC24H22N4O5SCl2(661.83)
White43.88
(43.55)
3.23
(3.35)
12.72
(8.46)
4.66
(4.84)
84.9 -
12 [Cd(MBT)(dha)]Cl
CdC25H23N4O5SCl(639.40)
White 47.35
(46.96)
3.67
(3.62)
8.93
(8.76)
4.93
(5.01)
75.2 -
-: diamagnetic

D. M. Fouad et al. / Natural Science 2 (2010) 817-827
820
Table 3. Electronic spectral data of the synthesized mixed ligand complexes.
No. Complex υ(k.K)
(εmaxcm2mol-1) assignment
1 [Cu(NBT)(dha)]Cl
33.17(35140.84)
25.80(5948.31)
12.40(29.60)
Intraligand
LMCT
2B1g2A1g
2 [Cu(CBT)(dha)Cl(H2O)]
36.27(23049.82)
34.29(21219.11)
15.44(26.69)
Intraligand
Intraligand
2B1g2B2g,
2B1g2A1g,
2B1g2Eg
3 [Cu(MBT)2(dha)]Cl.H2O
36.93(53248.13)
30.79(25121.52)
13.33(48.33)
Intraligand
Intraligand
2B1g2B2g,
2B1g2A1g,
2B1g2Eg
4 [Co(NBT)(dha)2].H2O
34.85(84126.39)
26.91(20410.62)
17.24(143.6)
Intraligand
LMCT
4T1g(F) 4A2g(υ2),
4T1g(F)4T1g(P)(υ3)
5 [Co(CBT)(dha)Cl(H2O)].H2O
37.09(57420.32)
15.62(131.05)
Intraligand
4T1g(F) 4A2g(υ2),
4T1g(F)4T1g(P)(υ3)
6 [Co(MBT)(dha)Cl(H2O)]
36.76(38944.24)
31.21(55761.13)
15.71(131.62)
Intraligand
Intraligand
4T1g(F) 4A2g(υ2),
4T1g(F)4T1g(P)(υ3)
7 [Ni(NBT)(dha)2].2H2O
32.30(45142.33)
22.42(56013.97)
15.89(118.74)
Intraligand
LMCT
3A2g(F)3T1g(F)
8 [Ni(CBT)(dha)Cl(H2O)].H2O 34.39(12535.04)
15.64(26.70)
Intraligand
3A2g(F)3T1g(F)
9 [Ni(MBT)(dha)Cl(H2O)]
35.66(12174.10)
31.42(14453.81)
15.02(12.30)
Intraligand
Intraligand
3A2g(F)3T1g(F)
10 [Cd(NBT)(dha)]Cl.H2O
37.12(16417.18)
33.46(8509.42)
29.47(5046.47)
Intraligand
Intraligand
LMCT
11 [Cd(CBT)(dha)]Cl.H2O
36.92(46607.37)
32.11(12100.81)
29.54(6728.32)
Intraligand
Intraligand
LMCT
12 [Cd(MBT)(dha)]Cl 37.10(115683.04)
30.96(78832.13)
Intraligand
Intraligand
Three sets of bands could be recognized in the elec-
tronic spectra of the obtained mixed ligand complexes as
listed in Table 3. The first set with υmax in the range
30.79-37.12 kK., could be attributed to intraligand
charge transfer transitions [32]. The second set of in-
cludes bands having υmax in the range 22.42-29.54 kK.
These bands are assigned as LMCT transitions [32].
The third set of bands of Cu(II) complexes 2 and 3
have υmax at 15.44, 13.33 kK. and is assigned for a d-d
transition which is typical for distorted octahderal Cu(II)
complexes [33]. These bands are assigned to all the three
transitions 2B1g2B2g, 2B1g2A1g and 2B1g2Eg [33].
While complex (1) shows an absorption d-d band at
12.40 kK. which has been attributed to 2B1g2A1g tran-
sition suggesting square planar geometry [33,34].
The d-d transition bands observed for Co(II) mixed
ligand complexes(4-6) are found to have υmax in the
range 15.62-17.24 kK. could be attributed to 4T1g(F)
4A2g(υ2) and 4T1g(F)4T1g(P)(υ3) transitions, suggesting
distorted octahedral environment around Co(II) ions
[33,34].
The d-d transition bands observed for Ni(II) mixed li-
gand complexes (7-9) are found to have υmax in the range
15.02-15.89 kK. could be attributed to 3A2g(F) 3T1g(F)
transitions, suggesting octahedral geometry for the Ni(II)
complexes [33].
All the mixed ligand Cd(II) complexes are diamag-
netic as expected for d10 electronic configuration. On the
basis of elemental analyses, infrared spectra, molar con-
ductance values and thermal analyses, tetrahedral ge-
ometry is proposed for all the complexes.
The corrected magnetic moment values for Cu(II),
Co(II) and Ni(II) mixed ligand complexes are reported in
Table 2. All the Cu(II) mixed ligand complexes (1-3)
display a dimagnetic nature which is attributed either to
their polymeric nature or super exchange interaction [35]

D. M. Fouad et al. / Natural Science 2 (2010) 817-827
821
in the complex molecules and/or high polarizability [36]
of the ligands which supplies more electron density to
copper ion and consequently the ions interact more
strongly. The room temperature magnetic moment values
of the Co(II) mixed ligand complexes (4-6) are within
the range 4.55-5.12 B.M. expected for octahedral Co(II)
complexes [35,37]. These lower magnetic moment val-
ues of the complexes may be attributed to the presence
of low symmetry component in the ligand field as well
as the covalent nature of the metal ligand bonds [38].
The room temperature magnetic moment values of Ni(II)
mixed ligand complexes (7-9) are 3.16, 2.98 and 3.05
B.M., respectively suggesting octahedral geometry [37,39].
3.3. IR Spectra
Relevant IR bands that provide considerable structural
evidence for the formation of mixed ligand complexes
are reported in Table 4.
The IR spectrum of the free (Nadha) ligand exhibit a
series of significant IR absorption bands appearing in the
vibrational regions at 1713, 1642 and 1252 cm-1 have
been ascribed to the stretching vibrations of υ(C=O)
lactone, υ(C=O)carbonyl and υ(C–O) phenolic, respec-
tively [40,41]. In all the complexes υ(C=O) lactone re-
mains unaltered while the other two peaks shift to lower
frequency. This shift has been attributed to the coordina-
tion of the ligand to form the mixed ligand complexes.
NBT, CBT and MBT ligands show four bands at
1565-1588, 1275-1340, 1008-1040 and 780-815 cm-1
which are assignable to thioamide I, II, III, IV vibrations,
respectively [42]. Theses bands have contributions from
δ(C-H) + δ(N-H), υ(C=S) + υ(C-N) + δ(C-H), υ(C-N) +
υ(C-S) and υ(C=S) modes of vibrations, respectively.
These bands are expected to be affected differently by
the modes of coordination to the metal ions. In the com-
plexes, these bands shift to lower frequency suggesting
the coordination of the sulfur atom to the metal ions [43].
All the ligands and their complexes show a band
within the range 3102-3030 cm-1 which is attributed to
υ(NH) vibration, indicating that the mercaptotriazole
ligands and the complexes are in the thione form. The
strongest bands observed in the range 1619-1625 cm-1 in
the IR spectra of NBT, CBT and MBT ligands can be
assigned to υ(C=N) vibrations of the azomethine group.
This band in the complexes shifts to lower frequency
indicating the coordination of the azomethine nitrogen to
the metal ions. The bands observed in the region 480-
520 cm-1 may be assigned to υ(M-N) vibration [44].
The IR spectra of the mixed ligand complexes con-
taining hydration and/or coordination water molecules
display a broad band within the range 3340-3489 cm-1
due to υ(OH) vibrational modes of the water molecules
[45] and this was confirmed by the results of thermal
analysis. Figure 2 shows the Proposed structure for
some mixed ligand complexes.
3.4. Thermal Decomposition Studies
The measured curves obtained during TGA scanning
were analysed to give the percentage mass loss as a
function of temperature .The different kinetic parameters
were computed from thermal decomposition data using
Coats-Redfern. And Horwitz-Metger methods [46,47].
Thermodynamic parameters: entropy (ΔS#), enthalpy
(ΔH#) and free energy (ΔG#) of activation were calcu-
lated as shown in Table 5 using the following standard
relations [48].
Table 4. Relevant IR Spectral data for the complexes.
Thioamide Bands dha characterstic bands
Compound
υ(O-
H)
(H2O)
I
δ(C-H)+
δ(N-H)
II
υ(C=S)+
υ(C-N)+
δ(C-H)
III
υ(C-N)+
υ(C-S)
IV
υ(C=S)
υ(C=O)
carbonyl υ(C–O)
[Cu(NBT)(dha)]Cl - 1550 1240 1000 790 1630 1240
[Cu(CBT)(dha)Cl(H2O)] - 1550 1240 1000 790 1630 1240
[Cu(MBT)2(dha)]Cl.H2O 3350 1550 1260 1000 780 1630 1230
[Co(NBT)(dha)2].H2O 3300 1550 1270 1000 790 1640 1220
[Co(CBT)(dha)Cl(H2O)].H2O 3350 1540 1260 1010 800 1640 1240
[Co(MBT)(dha)Cl(H2O)] 3350 1560 1250 1020 770 1620 1240
[Ni(NBT)(dha)2].2H2O 3400 1560 1270 1000 810 1630 1240
[Ni(CBT)(dha)Cl(H2O)].H2O 3350 1560 1270 1010 780 1600 1200
[Ni(MBT)(dha)Cl(H2O)] 3350 1550 1180 1000 770 1620 1250
[Cd(NBT)(dha)]Cl.H2O 3400 1540 1250 990 810 1630 1190
[Cd(CBT)(dha)]Cl.H2O 3440 1560 1260 1010 760 1620 1220
[Cd(MBT)(dha)]Cl - 1570 1250 1010 750 1620 1230

D. M. Fouad et al. / Natural Science 2 (2010) 817-827
822
O
S
N
M
O
Cl .xH2O
O
OH2 S
N
M
O
Cl
xH2O
M = Cu(II), Co(II), Ni(II) or Cd(II); x = 0 or 1
Figure 2. The Proposed structure for some mixed ligand complexes.
3.4.1. Thermal Analysis of [Cu(NBT)(dha)]Cl
The TGA of the square planar complex [Cu(NBT)-
(dha)]Cl gave three steps (Figure 3, 4). The first step (T
= 26.04-291.4oC, E# = 98.78 KJ/mol) is assignable to
removal of C15H13N5O2S moiety (calcd. = 54.063%;
found = 53.829%). Step two (T = 291.61-392.12oC, E# =
211.85 KJ/mol) is assignable to removal of chlorine
atom and COCH3 moiety (calcd. = 12.986%; found =
12.666%). The third step (T = 394.14-751.73oC, E# =
160.68 KJ/mol) is assignable to removal of carbon atom
and C6H4O3 moiety (calcd. = 22.477%; found =
23.102%). The residual product is assignable to be Cu
(calcd. = 10.494%; found = 10.403%).
[Cu(NBT)(dha)]Cl
[Cu(C)(C6H4O3)]
I, -C15H13N5O2S
III, -C, -C6H4O3
[Cu(C)(dha)]Cl
II,-Cl, -COCH3
Cu
3.4.2. Thermal Analysis of Some Complexes
The TGA of the complexes 1, 2, 3, 4, 5, 6, 7, 10 gave
three steps. The first step (T = 29.69-208.26oC, E# =
17-178.34 KJ/mol) is assignable to removal of one water
molecule. Step two (T = 169.55-388.84oC, E# = 35.48-
430 KJ/mol) is assignable to removal of C15H13N4Cl
moiety. The third step (T = 321.16-751.62oC, E# = 93-
261 KJ/mol ) is assignable to removal of C8H7O3 moiety
and chlorine atom giving CuO + CS as residual prod-
ucts:
[Cu(CBT)(dha)Cl(H2O)]
I, -H2O
III, -Cl, -C8H7O3
II, -C15H13N4Cl
CuO + CS [Cu(CS)(dha)Cl]
[Cu(CBT )(dh a)C l]
Figure 3. TG-DTG curves of complex 1.

D. M. Fouad et al. / Natural Science 2 (2010) 817-827
823
Figure 4. Coats-Redfern and Horwitz-Metzger plots of complex 1(a: 1st step, b: 2nd step, c: 3rd step).
The TGA of the complexes 8, 9, 12 gave four steps. The
first step (T = 27.51-316oC, E# = 42.69-58 KJ/mol) is
assignable to removal of two water molecules. Step two
(T = 191.98-339.03oC, E# = 53.18-205.84 KJ/mol) is
assignable to removal of C8H7O3 moiety and chlorine
atom. The third step (T = 318-529.38.57oC, E# = 136-
205.91 KJ/mol) is assignable to removal of C6H4Cl moi-
ety. The fourth step (T = 444.59-751.64oC, E# = 62.35-
196.92 KJ/mol) is assignable to removal of C10H9N4
moiety giving NiO + S as residual products.
[Ni(CBT)(dha)Cl(H2O)].H2O
[Ni (CBT)(O)]
I, -2H2O
III, -C6H4Cl
II, -C8H7O3, -Cl
IV, -C10H9N4
NiO + S
[Ni(C10H9N4S)(O)]
[Ni(CBT)(dh a)Cl]
3.4.3. Thermal Analysis of [Cd(CBT)(dha)]Cl.H2O
The TGA of the tetrahedral complex [Cd(CBT)(dha)]Cl.
H2O gave five steps. The first step (T = 37.43-173.98oC,
E# = 94.16 KJ/mol) is assignable to removal of one water
molecule (calcd. = 2.722%; found = 2.322%). Step two
(T = 175.18-218.69oC, E# = 67.71 KJ/mol) is assignable
to removal of chlorine atom (calcd. = 5.356%; found =
5.289%). The third step (T = 219.89-284.97oC, E# =
194.96 KJ/mol) is assignable to removal of C7H5N2Cl
moiety (calcd. = 23.054%; found = 23.186%). The
fourth step (T = 286.97-475.42oC, E# = 78.45 KJ/mol) is
assignable to removal of C6H7O2 and CHN2 moieties
(calcd. = 22.988%; found = 22.154%). Step five (T =
477.41-751.71oC, E# = 193.02 KJ/mol) is assignable to
removal of sulphur atom and CO and C8H7 moieties
(calcd. = 24.661%; found = 23.154%) giving CdO + C
as residual products (calcd. = 21.216%; found =
20.804%).
[Cd(CBT)(dha)]Cl.H2O
I, -H2O
III, -C7H5N2Cl IV,-CHN2 -C6H7O2
II, -Cl
[Cd(C9H8N2S)(dha)]
[Cd(CBT)(dha)]Cl [Cd(CBT)(dha)]
[Cd(C8H7S)(C2O2)]
V, -CO, -S, -C8H7CdO + C
3.5. Thermal Stability
Comparing the values of the initial decomposition tem-
peratures (Ti,dec.) of the organic part or the activation
energy data for the prepared mixed ligand complexes the
following data is obtained:
MBT rather than CBT and NBT forms the most stable
complexes with Cu(II), Co(II) and Cd(II) while the most
stable Ni(II) complex in presence of CBT as a S, N do-
nor ligand (Figure 5).
For complexes containing the same mercaptotriazole
ligand; Cd(II) have been found to form the most stable
complexes in presence of NBT or MBT ligands. While
in case of presence of CBT ligand, Cu(II) forms the most
stable complex.
100/ T K-1

D. M. Fouad et al. / Natural Science 2 (2010) 817-827
824
Figure 5. Relationships between the activation energy for the first decomposition step for the mixed ligand com-
plexes and the S, N donor ligand: Cu(II)(A) and Ni(II)(B) complexes.
Table 5. Kinetic and thermodynamic parameters for the thermal decomposition of the synthesized complexes.
Coats-Redfern equation
(Kinetic Pararmeters) (Thermodynamic parameters)
Horwitz-Metzger equation
(Kinetic Pararmeters) (Thermodynamic parameters)
Comp-
lex
No.
Step n
r E Z ΔS ΔH ΔG r E Z ΔS ΔH ΔG
1 1.0 1.0000 98.78 1578.17 –188.10 103.00 198.39 0.999 107.204.75 × 108 –83.20 111.39153.59
2 2.0 0.9991 211.85 3407.68 –183.36217.00 330.53 0.9988222.271.97 ×
1017 80.12 227.39177.77
1
3 2.0 0.9997 160.68 2566.76 –188.02167.48 321.12 0.9997174.503.85 × 108 –88.92 181.25253.92
1 0.0 0.9998 58.56 937.11 –188.9861.35 124.63 1.0000 64.25 2.69 × 107 –103.6 67.02 101.72
2 0.0 1.0000 85.48 1369.69 –189.4789.79 188.10 1.0000 94.41 8.91 × 106 –116.4 98.70 159.13 2
3 2.0 1.0000 257.51 4138.54 –181.58262.56 372.78 0.9999267.553.06 ×
1021 160.51 272.5 175.14
1 1.0 0.9995 76.98 1232.71 –189.1480.71 165.59 0.9992 84.60 3.81 × 107 –103.1 88.32 134.61
2 2.0 0.9988 453.67 7256.60 –176.09458.25 555.15 0.9602336.077.15 ×
1029 321.52 340.62163.69
3
3 0.5 1.0000 57.76 935.37 –195.6663.97 210.04 1.0000 70.52 158.19 –210.44 76.69 233.80
1 0.5 1.0000 58.72 941.80 –190.3762.03 137.71 0.9999 65.35 2.52 ×
106 –124.73 68.63 118.22
2 1.0 1.0000 29.71 482.62 –198.3334.13 139.38 0.9999 38.66 11.10 –229.69 43.05 164.94 4
3 1.0 1.0000 102.44 1652.87 –192.18109.65 276.47 1.0000117.1329439.29 –168.24 124.31270.34
1 2.0 0.9999 28.06 454.21 –196.4331.36 109.42 1.0000 34.74 117.06 –207.70 38.02 120.56
2 0.0 0.9990 51.59 833.72 –194.0456.14 162.42 0.9997 60.77 1181.68 –191.14 65.30 169.99
3 1.0 1.0000 90.97 1463.43 –190.9396.46 222.67 0.9999101.533.70 ×
105 –144.91 107.00 202.79
5
4 1.0 1.0000 266.18 4280.90 –182.62272.10 402.03 0.9998276.692.06 ×
1018 98.47 282.57212.51
1 2.0 0.9995 178.34 2771.21 –182.18181.97 261.54 0.9923185.693.54 ×
1020 145.31 189.31125.84
2 2.0 0.9986 268.70 4316.30 –180.55273.35 374.39 0.9981278.432.58 ×
1023 198.06 283.06172.22
6
3 0.0 0.9863 93.38 1505.70 –192.24 100.00 253.12 0.9904106.4918225.42 –171.51 113.07249.68
1 0.33 1.0000 17.13 555184.60 –138.2720.83 82.38 1.0000 24.41 1.40 –245.41 28.09 137.33
2 0.0 0.9984 35.86 581.46 –197.0340.41 148.25 0.9995 44.84 23.76 –223.62 49.36 171.757
3 2.0 0.9970 186.82 2965.89 –186.33193.23 336.75 0.9967199.692.30 ×
1011 –35.28 206.06233.24
8 1 0.0 0.9914 42.69 688.84 –193.3646.16 126.77 0.9953 49.72 4726.17 –177.35 53.17 127.10

D. M. Fouad et al. / Natural Science 2 (2010) 817-827
825
2 0.5 1.0000 60.18 970.55 –192.8464.77 171.16 0.9999 69.22 9083.61 –174.25 73.78 169.92
3 2.0 0.9986 205.91 3316.03 –185.51212.41 357.28 0.9984218.871.19 ×
1012 –21.71 225.33242.29
4 2.0 0.9999 196.92 3172.60 –187.12204.46 374.11 1.0000212.761.03 ×
1010 –62.43 220.25276.86
1 0.0 0.9999 58.40 934.77 –188.9961.18 124.38 1.0000 64.07 1.86 ×
107 –106.69 66.84 102.51
2 0.0 0.9982 53.00 856.16 –193.5057.38 159.3460.999261.76 1959.32 –186.62 66.11 164.44
3 2.0 0.9996 136.12 2170.36 –187.74141.67 267.04 0.9994146.752.00 ×
109 –73.54 152.28201.39
9
4 0.0 0.9968 122.46 1965.60 –189.79128.90 275.86 0.9977135.863.05 ×
106 –128.70 142.26 241.92
1 0.33 0.9993 23.05 373.88 –198.9726.74 115.11 0.999930.34 10.10 –228.99 34.01 135.72
2 2.0 0.9938 496.60 7928.71 –174.71500.83 589.74 0.9951506.271.48 ×
1051 730.26 510.48138.8610
3 2.0 1.0000 261.18 4197.54 –181.55266.29 377.74 0.9547271.432.06 ×
1021 157.11 276.50180.06
1 0.0 0.9999 94.16 1516.85 –186.8797.65 176.19 1.0000101.221.31 ×
1010 –54.07 104.70127.42
2 1.0 1.0000 67.71 1088.20 71.70 –190.73 163.28 0.9998 75.49 7.75 ×
105 –136.12 79.46 144.81
3 2.0 0.9957 194.96 3136.70 –183.48199.77 305.84 0.9952204.541.29 ×
1016 58.05 209.32175.76
4 0.5 1.0000 78.45 1265.17 –192.7384.34 221.06 1.0000 89.88 12913.82 –173.41 95.74 218.75
11
5 0.5 0.9997 193.02 3109.77 –186.37199.77 351.11 0.9948256.829.27 ×
1013 14.14 263.54252.05
1 2.0 0.9982 511.43 8173.13 –175.35516.15 615.49 0.9988522.151.12 ×
1047 650.47 526.84158.30
2 1.0 0.9997 323.45 5192.46 –179.77328.55 438.69 0.9995333.736.93 ×
1026 262.93 338.79177.70
3 0.5 1.0000 205.84 3314.81 –185.32212.18 353.47 1.0000218.726.68 ×
1012 –7.20 225.02230.51
12
4 0.0 0.9944 62.35 1012.09 –196.8870.13 254.30 0.9946 80.32 24.03 –227.98 88.05 301.31
3.6. Conclusions
Studying the TGA and DTA curves for the complexes
indicates that there is a series of thermal changes on the
DTA curves associate the weight loss in the TGA curves.
This study leads to the following conclusions:
1) The presence of more than one exothermic peak in
the DTA curves of all the complexes reveals that the
pyrolysis occurs in several steps [49].
2) The difference in the shape of the DTA curves of
the complexes containing the same metal ion with re-
spect to each other may be attributed to the structural
features of the ligand or the strength of the chelation
between the metal ion and the ligand; this also led to the
variety in the thermal behaviour of the complexes [50].
3) The thermal behaviour of the complexes displays
an observable difference with respect to each other. This
difference indicates that the thermal behaviour of these
complexes depends mainly on the type of the ligands
rather than the type of the metal ion.
4) Most complexes having DTA curves characterized
by the presence of main sharp and strong exothermic
peaks in their ends. These peaks are associated with a
weight loss on the TGA curves corresponding to the de-
composition of one stable intermediate compounds into
the corresponding final residue [50].
5) The entropy values for all degradation steps of all
degradation steps of all complexes were found to be
negative, which indicates a more ordered activated state
that may be possible through the chemisorption of some
decomposition products [51-53].
6) The relatively low values of values of ΔH# for the
prepared complexes confirm the M-S or M-N bond rup-
ture [54,55]
7) The high values of the free energy of activation
(ΔG#) for most of the steps in the decomposition reac-
tions of the complexes mean that the decomposition re-
actions are slower than that of the normal ones [48].
8) In general there are no obvious trends in the values
of ΔH# and ΔS# for the studied complexes. This may be
attributed to the fact that the thermal decomposition of
the complexes is controlled not only by the structure of
the ligands but also by the configuration of the coordina-
tion sphere [56,57].
9) The values of the free energy of activation (ΔG#) of
a given complex, generally increase significantly for the
subsequent decomposition stages. This is due to the in-
crease TΔS# values significantly from one step to an-
other which overrides the values of ΔH# [48].
10) Increasing the ΔG# values for the subsequent of a

D. M. Fouad et al. / Natural Science 2 (2010) 817-827
826
given complex reflects that the rate of removal of a
given species will be lower than that of the precedent
one [48]. This may be attributed to the structure rigidity
of the remaining complex.
11) There is much closeness in the enthalpy (ΔH#)
values obtained by Coats-Redfern equation and Horwitz-
Metzger equation, indicating that the thermal degrada-
tion of these complexes follow the standard methods.
REFERENCES
[1] Arndt, F. (1955) Org. Synth. Coll. II, 231.
[2] Rao, D.S., Ganorkar, M.C.D., Rao, L.S. and John, V.T.
(1978) Natl. Acad. Sci. Lett., 1, 402.
[3] Bartels-Keith, J.R. (1960) J. Chem. Soc., 1662.
[4] Miyakado, M., Inoue, S., Tanabe, Y., Watanabe, K., Ohno,
N., Yoshioka, H. and Mabay, T.J. (1982) Chem. Lett.,
1539.
[5] Figueroa-Villar, J.D., Ayer, W.A. and Migaj, B. (1988)
Can. J. Chem., 66, 506-512.
[6] Reddy, G.S.R. and Rao, N.R. (1994) Indian J. Chem. B,
33, 113.
[7] Chalaca, M.Z., Figueroa-Villar, J.D., Ellena, J.A. and
Castellano, E.E. (2002) Inorg. Chim. Acta, 328, 45.
[8] Kureshy, R.I., Khan, N.H., Abdi, S.H.R., Iyer, P. and
Patel, S.T. (1999) Polyhedron, 18, 1773.
[9] Kureshy, R.I., Khan, N.H., Abdi, S.H.R. and Iyer, P.
(1997) J. Mol. Catal., 124, 91.
[10] Rao, P.V. and Narasaiah, A.V. (2003) Indian J. Chem. A,
42, 1896.
[11] Puerta, D.T. and Cohen, S.M. (2003) Inorg. Chem., 42,
3423.
[12] Battaini, G., Monzani, E., Casella, L., Santagostini, L.
and Pagliarin, R. (2000) J. Biol. Inorg. Chem., 5, 262.
[13] Thaisrivongs, S., Romero, D.L., Tommasi, R.A., Janaki-
raman, M.N., Strohbach, J.W., Turner, S.R., Biles, C.,
Morge, R.R., Johnson, P.D., Aristoff, P.A., Tomich, P.K.,
Lynn, J.C., Horng, M.M., Chong, K.T., Hinshaw, R.R.,
Howe, W.J., Finzel, B.C. and Watenpaugh, K.D. (1996) J.
Med. Chem. 39, 4630.
[14] Eweiss, N., Bahajaj, A. and Elsherbini, E. (1986)
Heterocycl. Chem., 23, 1451.
[15] Holla, B., Poojary, K., Kalluraya, B. and Gowda, P.
(1996) Farmaco, 51, 793.
[16] Jantova, S., Greif, G., Pavlovicova, R. and Cipak, L.
(1998) Folia Microbiol.(Prague), 43, 75.
[17] Awad, I., Abdel-Rahman, A. and Bakite, E. (1991) J.
Chem. Technol. Biotechnol., 51, 483.
[18] Kucukguzel, I., Kucukguzel, S.G., Rollas, S. and Kiraz,
M. (2001) Bioorg.Chem. Lett., 11, 1703.
[19] Bala, S., Gupta, R.P., Sachedeva, M.L., Lal, M., Singh,
A.K. and Pujari, H.K. (1978) Ind. J. Chem., 16B, 481.
[20] Jantova, S., Greif, G., Pavlovicova, R. and Cipak, L.
(1998) Folia Microbiol., 43, 75.
[21] Sadadudam, Y.S., Shetty, M.M. and Dlawan, P.V. (1992)
Eur. J. Med. Chem., 27, 87.
[22] Bermejo, E., Carballo, R., Castineiras, A., Dominguez,
R., Maichle-Mossmer, C., Strahle, J. and West, D. (1999)
Polyhedron, 18, 3695.
[23] Almajan, G.L., Barbuceanu, S., Almajan, E., Draghici, C.
and Saramet, G. (2008) European Journal of Medicinal
Chemistry, 1-7.
[24] Joshi, S.D., Vagdevi, H.M., Vaidya, V.P. and Gadagina-
math, G.S. (2008) European Journal of Medicinal Chem-
istry, 43, 1989-1996.
[25] Akbar Ali, M. and Livingstone, S.E. (1974) Coord. Chem.
Rev., 13, 101.
[26] Severin, K., Bergs, R. and Beck, W. (1998) Angew.
Chem., Int. Ed., 37, 1722.
[27] Shikkargol, R.K., Angadi, S.D. and Kulkami, V.H. (1996)
Orient. J. Chem., 1172.
[28] Cansiz, A., Koparir, M. and Demitdag, A. (2004) Mole-
cules, 9, 204.
[29] Ragenovic, K.C., Dimova, V., Kakurinov, V., Molnar, D.
G. and Buzarovska, A. (2001) Molecules, 6, 815.
[30] Reid, J.R. and Heindel, D. (1976) J. Heterocyclic Chem.,
13, 925.
[31] Geary, W.J. (1971) Coord. Chem. Rev., 7, 81.
[32] Macias, B., Villa, V.M. and Gallego, R.R. (1995) Tran.
Met. Chem., 20, 347.
[33] Lever, A.B.P. (1984) Inorganic electronic spectroscopy.
Elsevier Amsterdam, 4th Edition.
[34] Dubey, S.N. and Kaushik, B. (1985) Indian J. Chem.,
24A(11), 950-953.
[35] Kishita, M., Inoue, M. and Kubo, M. (1964) Inorg.
Chem., 3, 237.
[36] Dubey, S., Handa, R. and Vaid, B. (1994) Monatsh.
Chem., 125, 395-401.
[37] Earnshow, A. (1968) Introduction to magnetochemistry.
Academic Press, London.
[38] Beena, K. and Dubey, S.N. (1989) Indian. J. Chem.,
28A(5), 425-427.
[39] Figgis, B.N. and Lewis, J. (1960) Modern coordination
chemistry. In: Lewis, J. and Wilkins, R.G., Eds., Inter-
science, New York, 403-406.
[40] Chalaca, M. Z., Villar, J.D.F., Ellena, J.A., Castellano, E.
E. (2002) Inorg. Chim. Acta, 328, 45.
[41] Chitrapriya, N., Mahalingam, V., Zeller, M., Jayabalan,
R., Swaminathan, K. and Natarajan, K. (2008) Polyhe-
dron, 27, 939-946.
[42] Gupta, B.K., Gupta, D.S., Dikshit, S.K. and Agarwala, V.
Ind. J. Chem. (1977) 15A, 624.
[43] Subramanian, M.S. and Viswanatha, A.J. (1969) Inorg.
Nucl. Chem., 31, 2575.
[44] Issleib, K. and Batz, G.Z. (1969) Anorg. Allg. Chem., 369,
83.
[45] Nakamoto, K. (1978) Infrared spectra and raman spectra
of inorganic and coordination compounds. 3rd Edition,
John Wiley, New York.
[46] Coats, A.W. and Redfern, J.P. (1964) Nature, 20, 68.
[47] Horwitz, H.H. and Metzger, G. (1963) Anal. Chem., 35,
1464.
[48] Kandil, S.S., El-Hefnawy, B.G. and Baker, A.E. (2004)
Thermochim. Acta, 414, 105.
[49] Ali, F.B., Al-Akramawi, S.W., Al-Obaidi, H.K. and
Al-Karboli, H.A. (2004) Thermchim. Acta, 419, 39.
[50] Said, A.A. and Hassan, M.R. (1993) Poly. Degard. Stab.,
39, 393.
[51] Madhusudanan, M.P., Yusuff, M.K.K. and Nair, R.G.C.
(1975) J. Therm. Anal., 8, 31.
[52] Gudasi, K.B., Maravalli, P.B. and Goudar, T.R. (2005) J.
Serb. Chem. Soc., 70, 643.

D. M. Fouad et al. / Natural Science 2 (2010) 817-827
827
[53] Maravalli, P.B., Gudasi, K.B. and Goudar, T.R. (2000)
Transition Met. Chem., 25, 411.
[54] Dakternieks, R.D. and Gradon, P.D. (1971) Aust. J.
Chem., 24, 2509.
[55] Shetty, S.P. and Fernando, Q. (1970) J. Am. Chem. Soc.,
92, 3964.
[56] Hill, O.J., Murrary, P.J. and Patil, C.K. (1994) Rev. Inorg.
Chem., 363, 14.
[57] Roman, P., Beitia, I.J., Luque, A. and Miralles, G.C.
(1994) Polyhedron, 13, 2311.