Synthesis and thermal characterization of new ternary chelates of piroxicam and tenoxicam with glycine and dl-phenylalanine and some transition metals

Article abstract of DOI:10.1016/j.saa.2005.06.042

The ternary chelates of piroxicam (Pir) and tenoxicam (Ten) with Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) in the presence of various amino acids such as glycine (Gly) or dl-phenylalanine (PhA) were prepared and characterized with different physicochemical methods. IR spectra confirm that Pir and Ten behave as a neutral bidentate ligand coordinated to the metal ions via the pyridine-N and carbonyl group of the amide moiety. Gly molecule acted as a uninegatively monodentate ligand and coordinate to the metal ions through its deprotonated carboxylic group. In addition, PhA acted as a uninegatively bidentate ligand and coordinate to the metal ions through its deprotonated carboxylic and amino groups. The solid reflectance spectra and magnetic moment measurements confirm that all the chelates have octahedral geometrical structures while Cu(II)- and Zn(II)-ternary chelates with PhA have square planar geometrical structures. Thermal behaviour of the complexes is extensively studied using TG and DTA techniques. TG results show that water molecules (hydrated and coordinated) and anions are removed in the first and second steps while Gly, PhA, Pir and Ten are decomposed in the next and subsequent steps. The pyrolyses of the chelates into different gases are observed in the DTA curves as exo- or endothermic peaks. Also, phase transition states are observed in some chelates. Different thermodynamic parameters are calculated using Coats-Redfern method and the results are interpreted.

Full text of DOI:10.1016/j.saa.2005.06.042

Spectrochimica Acta Part A 64 (2006) 216–232
Synthesis and thermal characterization of new ternary chelates of
piroxicam and tenoxicam with glycine and dl-phenylalanine
and some transition metals
M.A. Zayed, F.A. Nour El-Dien, Gehad G. Mohamed∗, Nadia E.A. El-Gamel
Chemistry Department, Faculty of Science, Cairo University, Giza, Egypt
Received 11 March 2005; received in revised form 7 June 2005; accepted 14 June 2005
Abstract
The ternary chelates of piroxicam (Pir) and tenoxicam (Ten) with Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) in the presence of various
amino acids such as glycine (Gly) or dl-phenylalanine (PhA) were prepared and characterized with different physicochemical methods. IR
spectra confirm that Pir and Ten behave as a neutral bidentate ligand coordinated to the metal ions via the pyridine-N and carbonyl group of the
amide moiety. Gly molecule acted as a uninegatively monodentate ligand and coordinate to the metal ions through its deprotonated carboxylic
group. In addition, PhA acted as a uninegatively bidentate ligand and coordinate to the metal ions through its deprotonated carboxylic and
amino groups. The solid reflectance spectra and magnetic moment measurements confirm that all the chelates have octahedral geometrical
structures while Cu(II)- and Zn(II)-ternary chelates with PhA have square planar geometrical structures. Thermal behaviour of the complexes
is extensively studied using TG and DTA techniques. TG results show that water molecules (hydrated and coordinated) and anions are removed
in the first and second steps while Gly, PhA, Pir and Ten are decomposed in the next and subsequent steps. The pyrolyses of the chelates into
different gases are observed in the DTA curves as exo- or endothermic peaks. Also, phase transition states are observed in some chelates.
Different thermodynamic parameters are calculated using Coats–Redfern method and the results are interpreted.
© 2005 Elsevier B.V. All rights reserved.
Keywords: Piroxicam and tenoxicam ternary chelates; IR; Magnetic and diffuse reflectance spectra; Thermal analyses
1. Introduction
catalysed biochemical reactions [3–5]. Rheumatoid arthritis
is a disease characterized by painful disorders in the muscle
and joints. At present, therapeutical treatment, for this illness
are mainly based on non-steroidal anti-inflammatory drugs
(NSAIDs), characterized by rapid and complete uptake in
the blood stream and thus possessing a fast analgesic action
[6]. Piroxicam (4-hydroxy-2-methyl-N-(2-pyridyl)-2H-1,2-
benzothiazine-3-carboxamide 1,1-dioxide) and Tenoxi-
cam (4-hydroxy-2-methyl-N-(2-pyridyl)-2H-thieno[2,3-e]-
1,2-thiazine-3-carboxamide1,1-dioxide), are the most impor-
tant members of oxicams class (Fig. 1) to be strong chelators
for several divalent metal ions. Pir has been found to act as
a monodentate ligand through pyridyl N with Pt(II) [7,8],
a bidentate chelate ligand through its pyridyl N and amide
O with Cd(II) and Cu(II) [6,9] and a tridentate ligand via
the enolic oxygen, the amide nitrogen and pyridyl nitrogen
with the organotin [SnBu2(Pir)]n, complex [10]. Tenoxicam
An intensive number of studies on the formation of mixed
ligand complexes reveal a realization of their growing impor-
tance, particularly in their role in biological process [1]. The
formation of mixed ligand chelates is a general feature of
systems where a metal is present with two or more ligands.
The study of these complexes shows that their formations are
a favoured process over that of simple complexes [2]. The
study of ternary complexes involving an aromatic amine as
the primary ligand, various amino acids and biomolecules
as secondary ligands can serve as useful models for gain-
ing a better understanding of enzyme–metal ion–substrate
complexes, which play an important role in metalloenzyme-
∗
Corresponding author.
E-mail address: ggenidy@hotmail.com (G.G. Mohamed).
1386-1425/$ – see front matter © 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2005.06.042

M.A. Zayed et al. / Spectrochimica Acta Part A 64 (2006) 216–232
217
Fig. 1. Structural formula for piroxicam and tenoxicam.
forms complexes with first row transition metal ions, includ-
ing Cu(II), Cu(Ten)2·2H2O [11]. Spectroscopic and magnetic
properties suggested that Ten can act as a monoanionic lig-
and through the enolate oxygen and amide oxygen atom
[11]. However, Ten forms a stable chelate with Cu(II) by
employing the amide oxygen and pyridyl nitrogen of the drug
molecule [12].
ide were supplied from Prolabo. De-ionized water collected
from all glass equipments was usually used in all prepara-
tions.
2.2. Instrumentation
Elementalmicroanalysisoftheseparatedsolidchelatesfor
C, H, N and S were performed in the Microanalytical Cen-
ter of Cairo University. Infrared spectra were recorded on
a Perkin-Elmer FT-IR type 1650 spectrophotometer in wave
number region 4000–200 cm−1. The spectra were recorded as
KBr pellets. The solid reflectance spectra were measured on
a Shimadzu 3101PC spectrophotometer. The molar magnetic
susceptibility was measured on powdered samples using the
Faraday method. The diamagnetic corrections were made by
Pascal’s constant and Hg[Co(SCN)4] was used as calibrant.
The thermogravimetric analysis (TGA and DTGA) and dif-
ferential thermal analysis (DTA) were carried out in dynamic
nitrogen atmosphere (20 mL min−1) with a heating rate of
10 ◦C min−1 using Shimadzu TGA-50H and DTA-50H ther-
mal analysers, respectively. Metal contents were determined
by titration against standard EDTA after complete decompo-
sition of the complexes with aqua regia in kjeldahl flask.
With the aim to continue the exploration of the coordi-
nation mode adopted by Pir and Ten, we have performed
a preparative and structural work by using Pir and Ten (as
primary ligands) with various amino acids (such as Gly and
PhA) as secondary ligands with some ‘d-block’ metal ions.
The amide oxygen and pyridyl nitrogen of the drug molecules
with deprotonated carboxylate group in unidentate manner
of Gly and uninegatively bidentate through deprotonated car-
boxylate and amino groups of PhA were employed. The solid
chelates are characterized using different physico-chemical
methods like elemental analyses (C, H, N, S and M), IR,
magnetic moment and diffuse reflectance spectra. The ther-
mal behaviour of the complexes (TG and DTA) are the main
objective of this study in order to elucidate their thermal sta-
bility via following their mass loss with temperature as well
as the changes accompanying these weight losses via DTA
technique. Different thermodynamic parameters were calcu-
lated using Coats–Redfern method.
2.3. Synthesis
A hot ethanol solutions (60 ◦C) of the respective metal
chlorides (Fe(II), Fe(III), Co(II) and Ni(II)) or acetate (Cu(II)
and Zn(II)) (1 mmol) in de-ionized water (25 mL) were added
to a mixture of 25 mL hot ethanol solution (60 ◦C) of Pir
(0.331 g, 1 mmol) or Ten (0.337 g, 1 mmol) and 25 mL of
1 mmol Gly (0.075 g in de-ionized water) or 25 mL of 1 mmol
PhA (0.165 g in ethanol) in the molar ratio 1:1:1 (metal
salt:Pir or Ten:Gly or PhA) in total volume 75 mL mixture.
The resulting mixture was stirred under reflux for 30 min. The
complexes were precipitated as microcrystalline powders.
They were removed by filtration, washed with hot ethanol
followed by diethyl ether and dried in a vacuum desiccator
over anhydrous calcium chloride.
2. Experimental
2.1. Materials
All chemicals used were of the analytical reagent grade
(AR), and of highest purity available. They included Pir (an
authentic sample was kindly supplied by Pfizer Company,
Cairo, Egypt) and Ten (sample was supplied by Eipico Com-
pany, Egypt) and their melting points was checked to con-
firm their purity. PhA was supplied from Acros, USA, while
Gly was supplied from Sigma. Copper (II) acetate dihydrate
(Prolabo); cobalt (II) and nickel (II) chlorides hexahydrate
(BDH); zinc acetate dihydrate (Ubichem), anhydrous ferrous
sulphate (Sigma) and ferric chloride hexahydrated (Prolabo).
Zinc oxide, disodium salt of ethylenediaminetetraacetic acid,
EDTA (Analar), ammonia solution (33%, v/v) and ammo-
nium chloride (El-Nasr Pharm. Chem. Co., Egypt). Absolute
ethyl alcohol, diethylether and nitric acid (Analar) were sup-
plied from ADWIC. Hydrogen peroxide and sodium hydrox-
3. Results and discussion
All the solid complexes are coloured products and sep-
arated as crystalline powder. The results of the elemental
analyses of ternary chelates are listed in Tables 1 and 2. It was

Table 1
Analytical and physical data of piroxicam (Pir) and tenoxicam (Ten) ternary chelates with Gly
Compound
Chemical formula
Colour
mp (◦C)
Found (calcd.) (%)
µeff (B.M.)
Λm (ꢀ−1 cm2 mol−1
)
C
H
N
S
M
Piroxicam [Pir]
Tenoxicam [Ten]
[Gly]
C15H13N3O4S
White
Yellow
White
198
210
245 (dec)
193
169
204
218
159
223
189
125
186
161
201
203
54.50 (54.38)
46.35 (46.29)
32.00 (31.80)
42.90 (43.08)
43.15 (43.52)
43.65 (43.35)
43.25 (43.35)
46.60 (46.23)
44.40 (44.31)
37.10 (37.19)
38.83 (38.62)
38.40 (38.14)
38.25 (38.14)
40.05 (39.82)
38.90 (38.63)
3.70 (3.90)
3.55 (3.26)
6.80 (6.60)
4.35 (4.54)
4.20 (4.05)
3.45 (3.61)
3.45 (3.60)
4.55 (4.19)
4.10 (4.17)
4.00 (4.13)
3.50 (3.43)
4.10 (3.92)
3.95 (3.92)
3.55 (3.32)
3.80 (3.76)
12.34 (12.68)
12.20 (12.46)
18.42 (18.66)
11.70 (11.83)
11.86 (11.95)
11.85 (11.90)
11.95 (11.90)
12.75 (12.69)
12.30 (12.29)
11.35 (11.57)
11.87 (12.02)
11.75 (11.86)
11.81 (11.86)
12.41 (12.39)
12.16 (12.02)
9.55 (9.66)
19.25 (18.99)
–
–
–
–
–
–
–
–
–
–
C
13H11N3O4S2
C2H5NO2
Fe(II)–Pir–Gly
Fe(III)–Pir–Gly
Co(II)–Pir–Gly
Ni(II)–Pir–Gly
Cu(II)–Pir–Gly
Zn(II)–Pir–Gly
Fe(II)–Ten–Gly
Fe(III)–Ten–Gly
Co(II)–Ten–Gly
Ni(II)–Ten–Gly
Cu(II)–Ten–Gly
Zn(II)–Ten–Gly
[Fe(Pir)2(Gly)2]·4.5H2O
[Fe(Pir)2(Gly)2]Cl·2H2O
[Co(Pir)2(Gly)2]·4H2O
[Ni(Pir)2(Gly)2]·4H2O
[Cu(Pir)2(Gly)2]·1.5H2O
[Zn(Pir)2(Gly)2]·2H2O
[Fe(Ten)2(Gly)2]·5H2O
[Fe(Ten)2(Gly)2]Cl·H2O
[Co(Ten)2(Gly)2]·3.5H2O
[Ni(Ten)2(Gly)2]·3.5H2O
[Cu(Ten)2(Gly)2]·H2O
[Zn(Ten)2(Gly)2]·2.5H2O
Reddish brown
Reddish brown
Orange
Light green
Olive green
Lemon
Reddish brown
Reddish brown
Orange
Light green
Olive green
Lemon
6.32 (6.76)
6.90 (6.82)
6.75 (6.80)
6.70 (6.80)
7.35 (7.25)
6.98 (7.02)
13.42 (13.22)
13.34 (13.48)
13.52 (13.56)
13.61 (13.56)
14.50 (14.16)
13.50 (13.73)
5.67 (5.91)
5.70 5.97
5.66 (6.27)
6.27 (6.27)
7.62 (7.19)
7.14 (7.28)
5.52 (5.78)
5.76 (6.01)
6.51 (6.25)
6.81 (6.25)
7.55 (7.02)
6.80 (6.98)
5.12
5.92
5.10
2.98
2.0
Diam
4.95
5.60
4.70
3.15
1.95
Diam
17.70
130
29.0
22.0
10.1
25.0
26.8
120
24.0
20.0
9.3
15.3
Table 2
Analytical and physical data of piroxicam (Pir) and tenoxicam (Ten) ternary chelates with PhA
Compound
Chemical formula
Colour
mp (◦C)
Found (calcd.) (%)
µeff (B.M.) Λm (ꢀ 1 cm2 mol−1
)
C
H
N
S
M
[PhA]
C9H11NO2
White
267 (dec) 65.60
6.43 (65.45) 8.60 (6.6)
– (8.48)
– (8.48)
–
–
Fe(II)–Pir–PhA
Fe(III)–Pir–PhA
Co(II)–Pir–PhA
Ni(II)–Pir–PhA
Cu(II)–Pir–PhA
Zn(II)–Pir–PhA
Fe(II)–Ten–PhA
[Fe(Pir)(PhA)(H2O)2]0·5SO4
[Fe(Pir)(PhA)Cl2]·H2O
[Co(Pir)(PhA)(H2O)2]Cl
[Ni(Pir)(PhA)(H2O)2]Cl
[Cu(Pir)(PhA)](Ac)·H2O
[Zn(Pir)(PhA)(H2O)2](Ac)·H2O
Reddish brown 200
Reddish brown 218
45.50 (45.35) 4.21 (4.25)
8.60 (8.82)
8.70 (8.75)
8.85 (8.95)
8.87 (8.95)
8.75 (8.81)
8.44 (8.32)
8.35 (8.38)
8.70 (8.67)
8.50 (8.39)
8.72 (8.87)
8.55 (8.37)
8.26 (8.25)
7.72 (7.56)
8.29 (8.82) 4.91
4.52 (4.38) 5.70
9.60 (9.43) 5.40
9.27 (9.43) 3.40
9.36 (9.99) 1.70
9.32 (9.66) Diam
8.52 (8.38) 5.20
8.96 (9.67) 5.40
8.58 (8.84) 4.20
9.30 (9.34) 2.86
9.41 (9.49) 1.78
9.59 (9.57) Diam
156
15.70
44.95 (45.00) 3.90 (4.06)
46.12 (46.06) 4.45 (4.30)
46.25 (46.04) 4.48 (4.30)
46.20 (49.09) 4.45 (4.40)
46.40 (46.36) 4.80 (4.90)
39.40 (39.50) 4.09 (4.20)
40.83 (40.87) 3.55 (3.40)
39.50 (39.55) 4.15 (4.30)
41.63 (41.80) 3.69 (3.96)
43.45 (43.31) 4.60 (4.48)
42.20 (42.41) 4.72 (4.56)
4.90 (5.00)
5.40 (5.12)
5.25 (5.11)
5.25 (5.03)
4.60 (4.75)
11.78 (11.97)
9.80 (9.91)
9.42 (9.58)
10.18 (10.13)
9.40 (9.57)
9.10 (9.43)
Orange
140
175
170
220
115
105
120
135
174
9.0
120
90
Light green
Olive green
Lemon
[Fe(Ten)(PhA)(H2O)2]0.5SO4·1.5H2O Reddish brown 203
Fe(III)–Ten–PhA [Fe(Ten)(PhA)Cl2]·H2O
Reddish brown 145
Co(II)–Ten–PhA [Co(Ten)(PhA)(H2O)2]Cl·2H2O
Orange
195
180
200
200
Ni(II)–Ten–PhA
[Ni(Ten)(PhA)(H2O)2]Cl
Light green
Olive green
Lemon
Cu(II)–Ten–PhA [Cu(Ten)(PhA)](Ac)·2.5H2O
110
142
Zn(II)–Ten–PhA [Zn(Ten)(PhA)·(H2O)2](Ac)·H2O

M.A. Zayed et al. / Spectrochimica Acta Part A 64 (2006) 216–232
219
of Gly (δNH2) at 1524 cm−1 is slightly shifted to higher or
lower frequencies (1516–1528 cm−1) upon chelation indi-
cating non-participation of the nitrogen atom in bonding to
the metal ions [18]. The shift to higher or lower wave num-
bers may be attributed to the participation of the NH2 group
in intermolecular hydrogen bond. While the band due to
δNH2 of dl-phenylalanine is assigned to a maximum near
1502 cm−1 is red shifted to the extent 10–23 cm−1 in all the
complexes confirming coordination of the NH2 group to the
metal ions [19,20].
The ν(M–N) bands of the pyridyl nitrogen are appeared
in the wave number range 566–590 cm−1 for the divalent
and at 523–597 cm−1 for the trivalent metal ion137. While
the ν(M–N) bands [21] of the PhA ternary chelates are
observed in the region 313–432 cm−1. New peaks of weak
or medium intensity are observed in the wave number range
297–386 cm−1 which are attributed to ν(M–O) vibrations of
ternary chelates [22]. The stretching vibration bands due to
ν(M–O) of amino acids (Gly and PhA) appeared in the region
of 313–54 cm−1, as reported for [Cu(Gly)2] and [Cu(ala)2]
complexes [21,23]. The band at 334–45 cm−1 is assigned
to the M–Cl vibration of Fe(III) ternary complexes with Pir
or Ten and PhA [24]. The vibrations of the sulphate ion in
Fe(II) ternary chelates with PhA appear at 1160–1147 and
630–629 cm−1. These indicate the uncoordinated nature of
sulphate group [25].
seen from Table 1 that ternary chelates of di- and tri-valent
transition metals with Pir or Ten and Gly are formed with
1:2:2 ratio (metal salts:Pir or Ten:Gly). The chelates have the
general formula [M(H2L)2(Gly)2]·yH2O, where M = Fe(II),
Co(II), Ni(II), Cu(II) and Zn(II) and y = 1–5; while Fe(III)
ternary chelates have the formula [Fe(H2L)2(Gly)2]Cl·yH2O,
y = 1–2. The mixed ligand complexes of Pir or Ten and PhA
(Table 2) with the same transition metals are formed with
1:1:1 ratio [metal salts:Pir or Ten:PhA]. The Fe(II), Co(II),
Ni(II), Cu(II) and Zn(II) ternary chelates have the formula
[M(H2L)(PhA)·(H2O)z](x)·yH2O, where x = acetate in case
of Cu(II) (z = 0) and Zn(II) (z = 2); sulphate in case of Fe(II)
(z = 2) or Cl in case of Co(II) (z = 2) and Ni(II) (z = 2) and
y = 1–2.5. Whereas in case of Fe(III) ternary chelates, it have
the formula [Fe(H2L)(PhA)(Cl)2]·H2O.
3.1. IR spectra and mode of bonding
The careful inspection of the of the IR spectra of free
Pir or Ten and their ternary complexes, was made in order
to facilitate the assignment of these bands in the free lig-
and and its metal chelates. The strong bands observed at
1630 and 1636 cm−1 in the free Pir and Ten, respectively,
are assigned to the stretching vibration of the C O group.
In Pir and Ten complexes, these bands are shifted to lower
frequencies (3–36 cm−1) or disappear supporting the partic-
ipation of the carbonyl group in the coordination [13]. The
bands located at 1572 and 1599 cm−1 are assigned to the
ν(C N) stretching vibration of pyridyl nitrogen of Pir and
Ten, respectively. These bands disappeared but it is still diffi-
cult to confirm their participation in chelate formation as they
overlapped with those of the carboxylate group of the amino
acids or the amide II stretching vibration band. Its participa-
tion is confirmed from the band due to in-plane deformation
ρ(py) located at 624 cm−1. After complexation, this band dis-
appeared and a new band at 630–669 cm−1 is found in the
ternary chelates [14].
3.2. Magnetic susceptibility and electronic spectra
measurements
The diffuse reflectance spectra of the Fe(III)-chelates
exhibit a band at 21,930–21,140 cm−1, which may be
6
assigned to the A1g → T2g (G) transition in octahedral
geometry of the complexes [26]. The observed mag-
netic moment values are 5.1–5.92 B.M. which confirm
the octahedral geometry in Fe(III) ion [27]. The diffused
reflectance spectra of the mixed ligand complexes of Fe(II)
ion display two absorption bands at 12,200–11,630 and
Two bands, located at 1351–1330 and 1041–1040 cm−1
,
5
5
are assigned to the asymmetric and symmetric stretching
vibrations of the SO2 group, respectively. These two SO2
bands are shifted to lower or higher frequencies in accor-
dance to the assignment of Cini et al. [9]. As the SO2 group
is not involved in metal binding, this shift to higher fre-
quencies must be related to important hydrogen bonding
effects [15,16]. The bands at the wave number 1594–1586
and 1412–1408 cm−1 regions, in the free amino acids; Gly or
PhA, are assigned to the asymmetric and symmetric stretch-
ing vibrations of the carboxylate group, respectively. The
shiftofthesetwobandstohigherorlowerfrequenciessuggest
theparticipationof COOHgroupincomplexformationafter
deprotonation [17,18]. In the 3500–3000 cm−1 IR region of
the ternary chelates of Pir and Ten, the overlap of the various
ν(NH) vibrations coupled in many cases with molecules of
water of hydration gives rise to very strong absorption. This
prevents the individual recognition of the various bands. The
band due to the in-plane deformation of the amino group
22,220–17,730 cm−1 which are assigned to T2g → Eg
transition and charge transfer, respectively [28]. The
Fe(II)-ternary chelates exhibit magnetic moment values of
4.91–5.80 B.M., which are consistent with a high spin octa-
hedral geometry [29].
The Ni(II)-mixed ligand complexes have magnetic
moment values of 2.86–3.40 B.M.; which are in the
normal range observed for octahedral Ni(II)-complexes
[30]. Their electronic spectra display three bands, in
the solid reflectance spectra at ν1, 12,630–11,610 cm−1
;
3
3
3A2g → T2g, ν2, 15,770–14,640 cm−1
;
3A2g → T1g (F)
3
3
and ␯3, 20,280–19,080 cm−1; A2g → T1g (P). The 10 Dq
values lie in the 11,610–12,630 cm−1 ranges, again con-
firming the octahedral configuration of the chelates [31].
The electronic spectra of the ternary Co(II) complexes
give three bands at 12,270–11,310, 15,040–13,890 and
17,590–16,340 cm−1 wave number regions, respectively. The
third region 18,180–26,060 cm−1 refers to the charge trans-

220
M.A. Zayed et al. / Spectrochimica Acta Part A 64 (2006) 216–232
Gly− and PhA− molecules as different fragments is accom-
panied by the appearance of several endo- and exothermic
peaks in the DTA curves as illustrated in Figs. 2–5. The DTA
curve of chelate 19 shows an endothermic peak at 1118 ◦C,
which may be attributed to a phase transition.
fer band. The bands observed are assigned to the transitions
4
4
4T1g (F) → T2g (F) (ν1), 4T1g (F) → A2g (F) (ν2) and 4T1g
4
(F) → T2g (P) (ν3), respectively, suggesting that there is an
octahedral geometry around Co(II) ion [32]. The magnetic
susceptibility measurements lie in the 4.2–5.4 B.M. range
which is an indicative of octahedral geometry [33].
The thermograms of Fe(III) chelates; 8, 14, 20, show
three decomposition steps within the temperature range
25–890 ◦C. Whereas Fe(III) chelate; 2, show four decom-
position steps within the temperature range 25–700 ◦C. The
first step of decomposition within the temperature range
25–165 ◦C corresponds to the loss of water molecules of
hydration with a mass loss of 3.61% (calcd. for 2H2O;
3.84%), 1.27% (calcd. for H2O; 1.93%), 3.35% (calcd. for
H2O; 2.81%) and 2.25% (calcd. for H2O; 2.78%) for 2, 8, 14
and 20 chelates, respectively. The DTA curves (Figs. 2b–5b
and Tables 3–6) show that this dehydration step gives
endothermic and/or endo- and exothermic peaks within the
temperature of decomposition. The second, third and fourth
steps (from 120 to 890 ◦C) correspond to the removal of Cl2,
Gly−, PhA−, Pir and Ten molecules leaving metal oxide or
sulphide as a residue. The overall weight loss amounts to
83.71% (calcd. 82.93%), 87.65% (calcd. 87.12%), 83.20%
(calcd. 83.75%) and 86.06% (calcd. 86.38%) for 2, 8, 14
and 20 chelates, respectively. The decomposition of Pir,
Ten, Gly−, PhA− and Cl2 molecules is accompanied by the
appearance of several exo- and endothermic peaks as shown
in the DTA curves (Figs. 2b–5b and Tables 3–6). Also, phase
transitions are observed in the DTA curves for the chelates 2,
14 and 20.
The reflectance spectra of Cu(II) ternary chelates in the
presence of Gly (as second ligand) consist of a broad, low
intensity shoulder centered at (17,860–16,340 cm−1) that
forms part of the charge transfer band. The magnetic moment
of 1.95–2.0 B.M. falls within the range normally observed for
octahedral Cu(II) complexes [34]. While, the Cu(II)–ternary
chelates in the presence of PhA (as second ligand) exhibit
a broad band in the region 16,670–15,380 cm−1 assigned
2
to 2Eg → T2g transition and broad band in the region
2
2
14,710–14,160 cm−1 which is assigned to B1g → A1g as
well as a shoulder band in the range 17,540–17,610 cm−1
characteristic of a square planner geometry for Cu(II) com-
plexes [35]. The magnetic moments of the Cu(II)-complexes
are found to be 1.7–1.83 B.M.
In analogy with those described for Zn(II) complexes con-
taining N–O donor Schiff bases [36] and according to the
empirical formulae of these complexes, we proposed an octa-
hedral geometry for the mixed ligand Zn(II) complexes of Pir
and Ten (as primary ligands) and Gly or PhA (as secondary
ligands) with two axial position occupied by the two glycine
molecules or water molecules in case of Pir or Ten mixed
ligand complexes with PhA.
3.3. Thermal analyses (TGA and DTA)
The Co(II) complexes; 3, 9, 15 and 21, exhibit three
to four steps of decomposition as given by TGA analy-
ses (Figs. 2c–5c). The first decomposition step (within the
temperature range 25–195 ◦C) corresponds to the loss of
4H2O (mass loss 7.87%; calcd. 7.65%), 3.5H2O (mass loss
6.65%; calcd. 6.67%), (1/2)Cl2 (mass loss 5.22%; calcd.
5.68%), and (1/2)Cl2 and H2O (mass loss 7.64%; calcd.
8.01%) for 3, 9, 15 and 21 chelates, respectively. The
exo- and endothermic peaks have been observed in the
DTA curves (Figs. 2c–5c) within the temperature range of
this dehydration step. The loss of coordinated water, Pir,
Ten, Gly− and PhA molecules takes place within the tem-
perature range 140–960 ◦C with mass losses of 84.94%
(calcd. 84.38%), 85.07% (calcd. 84.41%), 83.17% (calcd.
82.33%) and 81.60% (calcd. 80.76%) for 3, 9, 15 and 21
chelates, respectively. According to the DTA curves, given in
Figs. 2c–5c, these decomposition steps give several exo- and
endothermic peaks as the result of elimination of the ligand
molecules to different fragments.
The TGA curves of the Ni(II)-ternary chelates, namely 4,
10, 16 and 22, show three to four stages of decomposition
within the temperature range of 25–750 ◦C. The first stage
at 25–210 ◦C corresponds to the loss of water molecules of
hydration and (1/2)Cl2 gas, while the second, third and fourth
stages involve the loss of Pir, Ten, Gly−, PhA− and coordi-
nated water molecules. The overall weight loss amounts to
92.03% (calcd. 92.03%), 91.34% (calcd. 92.06%), 88.63%
The TGA, DTG and DTA curves of the ternary chelates
are shown in Figs. 2–5 and the results are listed in Tables 3–6.
Thermal analyses of ternary chelates elicit the following
points to the light.
The thermograms of Fe(II)-ternary chelates, namely 1,
7, 13 and 19, show three decomposition steps within the
temperature range 25–830 ◦C (Figs. 2a–5a). The first step
of decomposition, within the temperature range 25–200 ◦C,
corresponds to the loss of hydrated water molecules with a
masslossof8.91%(calcd. for4.5H2O;8.55%), 8.96%(calcd.
for 5H2O; 9.29%), 8.0% (calcd. for 0.5SO42−; 7.56%) and
8.15% (calcd. for 0.5SO42− and 0.5H2O; 8.53%) for 1, 7, 13
and 19 chelates, respectively. The DTA curves, illustrated in
Figs. 2a–5a, show that this dehydration step is endothermic
process for chelates 1 and 7, while for chelates 13 and 19,
an exo- and endothermic peaks are appeared as the result
of dehydration and sulphate elimination. The second and
third steps in the temperature range 185–830 ◦C; correspond
to the elimination of coordinated water, Pir, Ten, Gly− and
PhA− molecules leaving metal disulphide (in case of 1 and
7 chelates) or metal oxide (in case of 13 and 19 chelates) as
a residue. The overall weight loss amounts to 87.86% (calcd.
87.33%), 88.17% (calcd. 87.61%), 89.33% (calcd. 88.66%)
and 89.40% (calcd. 89.23%) for 1, 7, 13 and 19 chelates,
respectively. The elimination of coordinated water, Pir, Ten,

M.A. Zayed et al. / Spectrochimica Acta Part A 64 (2006) 216–232
221
Fig. 2. Thermal analyses (TG and DTA) of Pir and Gly mixed ligand chelates: (a) Fe(II), (b) Fe(III), (c) Co(II), (d) Ni(II), (e) Cu(II) and (f) Zn(II).
(calcd. 88.01%) and 85.65% (calcd. 85.59%) for 4, 10, 16 and
22 chelates, respectively. The DTA curves of these chelates
are illustrated in Figs. 2d–5d and the results are listed in
Tables 3–6. The chemical changes accompanying the elimi-
nation of water, anion, and ligand molecules is observed as
exo- or endothermic peaks in the DTA curves.
step in the temperature range 30–155 ◦C (mass loss = 2.96%;
calcd. for 1.5H2O; 3.06%), 25–90 ◦C (mass loss = 2.46%;
calcd. for H2O; 1.99%), 25–170 ◦C (mass loss = 2.64%;
calcd. for H2O; 2.83%) and 45–200 ◦C (mass loss = 6.27%;
calcd. for 2.5H2O; 6.73%) may accounted for the loss of
water molecules of hydration for 5, 11, 17 and 23 chelates,
respectively. As shown in Tables 3–6, the mass losses of the
remaining decomposition steps amount to 90.47% (calcd.
On the other hand the Cu(II) chelates; 5, 11, 17 and 23,
exhibit three decomposition steps (Figs. 2e–5e). The first

222
M.A. Zayed et al. / Spectrochimica Acta Part A 64 (2006) 216–232
Fig. 3. Thermal analyses (TG and DTA) of Ten and Gly mixed ligand chelates: (a) Fe(II), (b) Fe(III), (c) Co(II), (d) Ni(II), (e) Cu(II) and (f) Zn(II).
91.00%), 90.54% (calcd. 91.21%), 88.28% (calcd. 87.49%)
and 88.23% (calcd. 88.11%) for 5, 11, 17 and 23, respectively.
They correspond to the removal of Pir, Ten, Gly−, PhA− and
Ac− molecules leaving CuO as a residue.
The TGA curves of the Zn-ternary chelates, 6, 12, 18
and 24, represent three decomposition steps as illustrated in
Figs. 2f–5f and Tables 3–6. The first step of decomposition
within the temperature range (25–220 ◦C) correspond to the
loss of hydrated water molecules with a mass loss of 4.62%
(calcd. for 2H2O; 3.95%), 4.87% (calcd. for 2.5H2O; 4.83%),
8.81% (calcd. for 3H2O; 8.02%) and 8.44% (calcd. for 3H2O;
7.95%) for 6, 12, 18 and 24, respectively. The DTA curves
show that, this dehydration step is appeared as endothermic
and/or endo- and exothermic peaks. The remaining steps of

M.A. Zayed et al. / Spectrochimica Acta Part A 64 (2006) 216–232
223
Fig. 4. Thermal analyses (TG and DTA) of Pir and PhA mixed ligand chelates: (a) Fe(II), (b) Fe(III), (c) Co(II), (d) Ni(II), (e) Cu(II) and (f) Zn(II).
decomposition within the temperature range 110–1100 ◦C
correspond to the removal of these ligands as gases and this
is accompanied by the appearance of exo- and endother-
mic peaks in the DTA curves and the position of these exo-
and endothermic peaks is given in Tables 3–6. The over-
all weight loss amounts to 89.35% (calcd. 89.14%), 89.51%
(calcd. 89.59%), 88.38% (calcd. 87.96%) and 88.05% (calcd.
88.07%) for chelates 6, 12, 18 and 24 chelates, respectively.

224
M.A. Zayed et al. / Spectrochimica Acta Part A 64 (2006) 216–232
Fig. 5. Thermal analyses (TG and DTA) of Ten and PhA mixed ligand chelates: (a) Fe(II), (b) Fe(III), (c) Co(II), (d) Ni(II), (e) Cu(II) and (f) Zn(II).

Table 3
Thermoanalytical data of Pir–Gly ternary chelates
Complex
Temperature
range (◦C)
Peak temperature in DTA (◦C)
No. of decom-
position steps
% Found (calcd.)
Mass loss
Assignment
Metallic
residue
Total mass loss
[1]
[2]
25–200
200–656
63(+), 130(+), 190(+)
1.0
2.0
8.91 (8.55)
87.86 (87.33)
Loss of 4.5H2O
Loss of Pir and Gly molecules
FeS2
284(+), 430(+), 476(−), 508(+), 621(−),
78.95 (78.78)
654(+), 686(−)
25–165
165–680
105(+), 136(−)
1.0
3.0
3.61 (3.84)
83.71 (82.93)
Loss of 2H2O
Loss of (1/2)Cl2, Pir and Gly molecules
Fe2O3
200(−), 250(−), 282(+), 454(−), 530(+),
573(−), 620(+), 673(−)
80.10 (79.09)
84.94 (84.38)
732(+), 766(+), 790(−), 820(−), 885(+),
1110(−), 1135(+)
Phase transition
[3]
25–195
195–960
66(+), 105(−), 143(+), 200(+)
268(+), 310(−), 343(−), 365(+), 400(−),
430(−), 541(−), 640(+), 883(+)
1040(+), 1070(−), 1177(+)
1.0
2.0
7.87 (7.65)
92.81 (92.03)
Loss of 4H2O
Loss of Pir and Gly molecules
CoO
Phase transition
Loss of 4H2O
Loss of Pir and Gly molecules
Phase transition
Loss of 1.5H2O
[4]
[5]
25–210
210–600
77(+), 107(−), 150(+), 190(−)
270(−), 320(−), 391(+), 440(−), 488(+)
880(+), 958(+), 1154(+)
1.0
2.0
8.20 (7.65)
92.03 (92.03)
NiO
CuO
84.01 (84.38)
87.51 (87.94)
30–155
155–1225
40(+), 80(+)
1.0
2.0
2.96 (3.06)
90.47 (91.00)
181(−), 250(−), 297(+), 398(+), 482(+),
620(+), 699(−), 780(−), 840(−), 880(+),
920(−), 950(+), 1163(+)
Loss of Pir and Gly molecules
[6]
25–110
110–710
50(+), 85(+), 110(+)
1.0
2.0
4.62 (3.95)
89.35 (89.14)
Loss of 2H2O
Loss of Pir and Gly molecules
ZnS
156(+), 200(−), 245(−), 290(+), 370(+),
499(+), 550(+), 584(−), 630(+), 670(+),
722(+), 798(−), 864(+), 1128(+)
84.73 (85.19)
(+) = Endothermic, (−) = exothermic, [1] = [Fe(II)(Pir)2(Gly)2]·4.5H2O, [2] = [Fe(III)(Pir)2(Gly)2]Cl·2H2O, [3] = [Co(II)(Pir)2(Gly)2]·4H2O, [4] = [Ni(II)(Pir)2(Gly)2]·4H2O, [5] = [Cu(II)(Pir)2(Gly)2]·1.5H2O,
[6] = [Zn(II)(Pir)2(Gly)2]·2H2O.

Table 4
Thermoanalytical data of Ten–Gly ternary chelates
Complex
Temperature
range (◦C)
Peak temperature in DTA (◦C)
No. of decom-
position steps
% Found (calcd.)
Mass loss
Assignment
Metallic residue
FeS2
Total mass loss
[7]
25–185
185–830
105(+)
1.0
2.0
8.96 (9.29)
88.17 (87.61)
Loss of 5H2O
Loss of Ten and Gly molecules
220(−), 256(+), 363(+), 445(−),
480(+), 749(+), 778(−), 840(−),
810(+), 870(+), 974(+)
79.48 (78.32)
[8]
25–125
125–890
30(+), 100(+)
1.0
2.0
1.27 (1.93)
87.65 (87.12)
Loss of H2O
Loss of (1/2)Cl2, Ten and Gly molecules
FeS2
150(+), 225(−), 255(+), 320(+),
431(+), 470(−), 700(+), 741(−),
758(+), 782(+), 865(+)
86.38 (85.19)
[9]
25–180
180–710
100(+), 144(−)
1.0
3.0
6.65 (6.67)
91.72 (92.08)
Loss of 3.5H2O
Loss of Ten and Gly molecules
Phase transition
Loss of 3.5H2O
Loss of Ten and Gly molecules
CoO
NiO
626(+), 519(−)
85.07 (85.41)
84.85 (85.39)
860(+), 1111(−)
[10]
25–160
160–750
107(+), 130(−)
1.0
3.0
6.49 (6.67)
91.34 (92.06)
174(−), 261(−), 290(+), 355(+),
390(−), 417(−), 455(+), 517(+),
842(+), 870(−), 930(+), 977(−)
50(+), 101(+)
[11]
[12]
25–90
90–840
1.0
2.0
2.46 (1.99)
90.54 (91.21)
Loss of H2O
Loss of Ten and Gly molecules
CuO
ZnS
137(−), 210(+), 250(−), 281(+),
400(+), 570(−), 536(+), 674(+),
860(+)
88.08 (89.22)
84.64 (84.76)
946(−), 1104(−), 1020(+)
Phase transition
Loss of 2.5H2O
Loss of Ten and Gly molecules
25–130
130–800
60(+), 95(+), 114(−)
1.0
2.0
4.87 (4.83)
89.51 (89.59)
147(+), 163(−), 232(−), 250(+),
290(+), 300(+), 310(−), 410(+),
459(−), 573(−), 714(+), 790(−),
770(+)
851(+), 876(−), 915(−), 1176(+)
Phase transition
(+) = Endothermic, (−) = exothermic, [7] = [Fe(II)(Ten)2(Gly)2]·5H2O, [8] = [Fe(III)(Ten)2(Gly)2]Cl·H2O, [9] = [Co(II)(Ten)2(Gly)2]·3.5H2O, [10] = [Ni(II)(Ten)2(Gly)2]·3.5H2O, [11] = [Cu(II)(Ten)2(Gly)2]·
H2O, [12] = [Zn(II)(Ten)2(Gly)2]·2.5H2O.

Table 5
Thermoanalytical data of Pir–PhA ternary chelates
Complex
Temperature range (◦C)
Peak temperature in DTA (◦C)
No. of decom-
position steps
% Found (calcd.)
Assignment
Metallic residue
Mass loss
Total mass loss
2−
[13]
[14]
30–200
200–560
30–115
120(−)
1.0
2.0
1.0
2.0
81.33 (81.10)
8.00 (7.56)
89.33 (88.66)
3.35 (2.81)
Loss of 0.5SO4
FeO
480(−), 490(+)
Loss of 2H2O, Pir and PhA molecules
Loss of H2O
Loss of Cl2, Pir and PhA molecules
35(+)
79.85 (80.94)
Fe2S3
120–710
240(+), 275(+), 385(+), 450(+),
521(+), 631(+)
83.20 (83.75)
812(+), 1071(+), 1091(−), 1136(+)
Phase transition
Loss of (1/2)Cl2
Loss of 2H2O, Pir and PhA molecules
Phase transition
Loss of (1/2)Cl2
Loss of 2H2O, Pir and PhA molecules
Phase transition
Loss of H2O
[15]
[16]
[17]
25–140
140–605
95(+), 102(−)
1.0
2.0
83.17 (82.33)
83.14 (82.34)
85.64 (84.66)
5.22 (5.68)
88.39 (88.01)
CoO
NiO
CuO
430(+), 455(−), 484(+), 510(−)
1111(+), 1130(−), 1179(+)
95(+), 116(−)
30–170
170–700
1.0
3.0
5.49 (5.67)
88.63 (88.01)
205(−), 411(−), 470(+), 510(+)
878(−), 1095(+), 1183(+)
120(+)
25–170
170–681
1.0
2.0
2.64 (2.83)
88.28 (87.49)
190(−), 200(+), 251(+), 355(+),
380(+), 414(+), 450(+), 520(+),
594(+), 602(−), 638(+), 683(+)
888(−), 922(+), 975(+), 1008(+),
1120(+)
Loss of acetate, Pir and PhA molecules
Phase transition
[18]
30–220
220–762
51(+), 85(+), 201(−)
1.0
2.0
79.57 (79.94)
8.81 (8.02)
88.38 (87.96)
Loss of 3H2O
Loss of acetate, Pir and PhA molecules
ZnO
250(−), 268(+), 320(−), 388(−),
403(+), 583(+), 615(+), 650(+),
665(−)
790(+), 945(+), 1000(−), 1062(−)
Phase transition
(+) = Endothermic, (−) = exothermic, [13] = [Fe(II)(Pir)(PhA)(H2O)2]·0.5SO4, [14] = [Fe(III)(Pir)(PhA)Cl2]·H2O, [15] = [Co(II)(Pir)(PhA)(H2O)2]Cl, [16] = [Ni(II)(Pir)(PhA)(H2O)2] Cl, [17] = [Cu(II)(Pir)
(PhA)](Ac)·H2O, [18] = [Zn(II)(Pir)(PhA)(H2O)2](Ac)·H2O.

Table 6
Thermoanalytical data of Ten–PhA ternary chelates
Complex
Temperature
range (◦C)
Peak temperature in DTA (◦C)
No. of decom-
position steps
% Found (calcd.)
Mass loss
Assignment
Metallic residue
FeO
Total mass loss
2−
[19]
25–200
200–650
102(+), 140(+), 163(−)
230(−), 259(+), 493(−), 600(−),
626(+)
1.0
2.0
8.15 (8.53)
89.40 (89.23)
Loss of 0.5SO4 and 0.5H2O
Loss of 3H2O, Ten and PhA molecules
81.25 (80.70)
1118(+)
Phase transition
[20]
30–140
140–715
–
1.0
2.0
2.25 (2.78)
86.06 (86.38)
Loss of H2O
Loss of Cl2, Ten and PhA molecules
Phase transition
FeS
236(−), 253(+), 510(+), 666(+)
1040(−), 1051(+), 1071(−), 1098(+)
1144(−), 1160(+)
83.81 (83.60)
[21]
[22]
[23]
45–190
190–810
94(+), 150(+)
1.0
3.0
7.64 (8.01)
89.24 (88.77)
Loss of (1/2)Cl2 and H2O
Loss of 3H2O, Ten and PhA molecules
Phase transition
Loss of (1/2)Cl2
Loss of 2H2O, Ten and PhA molecules
CoO
NiS
283(+), 440(+), 555(+), 847.5(−)
1020(+), 1040(−), 1130(+), 1178(+)
102(+), 131(−)
81.60 (80.76)
79.73 (79.97)
81.96 (81.38)
25–160
160–640
1.0
3.0
5.92 (5.62)
85.65 (85.59)
170(+), 200(−), 270(−), 283(+),
426(−), 450(+), 555(+)
98(−), 138(−)
45–200
200–830
1.0
2.0
6.27 (6.73)
88.23 (88.11)
Loss of 2.5H2O
Loss of acetate, Ten and PhA molecules
CuO
229(+), 374(+), 420(+), 467(+),
520(+), 622(+), 670(+), 740(+),
740(+), 820(+)
863(+), 896(+), 943(+), 1178(+)
70(+), 92(+), 109(−), 152(+), 174(−)
220(−), 249(+), 270(+), 400(+),
526(+), 690(−)
Phase transition
Loss of 3H2O
Loss of acetate, Ten and PhA molecules
[24]
30–200
200–870
1.0
2.0
8.44 (7.95)
88.05 (88.07)
79.61 (80.12)
ZnO
952(+), 1057(+), 1097(+)
Phase transition
(+) = Endothermic, (−) = exothermic, [19] = [Fe(II)(Ten)(PhA)(H2O)2]·0.5SO4·1.5H2O, [20] = [Fe(III)(Ten)(PhA)Cl2]·H2O, [21] = [Co(II)(Ten)(PhA)(H2O)2]Cl·2H2O, [22] = [Ni(II)(Ten)(PhA)(H2O)2]Cl,
[23] = [Cu(II)(Ten)(PhA)](Ac)·2.5H2O, [24] = [Zn(II)(Ten)(PhA)(H2O)2](Ac)·H2O.

M.A. Zayed et al. / Spectrochimica Acta Part A 64 (2006) 216–232
229
Scheme 1. Thermal decomposition of Pir and Ten ternary chelates with Gly.
the free energy change of activation (ꢁG*) were calculated
using the following equations:
Accordingly, the thermal decomposition of Pir or Ten in
ternary chelates in the presence of Gly can be summarized as
shown in Scheme 1.
For Pir or Ten ternary chelates with PhA, the thermal
decomposition is shown in Scheme 2.
ꢂ
ꢃ
log Ah
KT
ꢁS∗ = 2.303
R
(2)
ꢁH∗ = E∗ − RT
ꢁG∗ = H∗ − TS∗
(3)
(4)
3.4. Kinetic study
The thermodynamic activation parameters of decompo-
sition processes of dehydrated complexes namely activation
energy (E*), enthalpy (ꢁH*), entropy (ꢁS*) and Gibbs free
energy change of the decomposition (ꢁG*) were evaluated
graphically by employing the Coast–Redfern relation [37]:
where K and h are the Boltzman and Planck constants, respec-
tively. The calculated values of E*, A, ꢁS*, ꢁH* and ꢁG*
for the decomposition steps are given in Tables 7 and 8.
The activation energy for the elimination of water
molecules of hydration or hydrated water from the Fe(II)-
ternary chelates is shown in the range 64–174 kJ mol−1
(Tables 7 and 8). Regarding the Fe(III)-chelates, the
activation energy of the first step is shown in the range
35–77 kJ mol−1. Meanwhile, the data listed in Tables 7 and 8
show that the Co(II)- and Ni(II)-chelates are found to have
activation energy for the elimination of water molecules
of hydration in the range 8–108.3 and 60.55–137 kJ mol−1
for the Co(II) and Ni(II) chelates, respectively. Moreover,
the Cu(II)- and Zn(II)-chelates exhibit an activation energy
in the range 36.21–62.10 and 59.4–76.26 kJ mol−1 for
the elimination of water molecules of hydration for the
Cu(II)- and Zn(II)-chelates, respectively. From the acti-
ꢀ
ꢁ
log(Wf/Wf − W)
log
T2
ꢀ
ꢂ
ꢃꢁ
AR 1 − 2RT
E∗
= log
−
(1)
θE∗
E∗
2.303RT
where Wf is the mass loss at the completion of the reaction,
W the mass loss up to temperature T; R the gas constant,
E* the activation energy in kJ mol−1, θ the heating rate and
*
∼
(1 − (2RT/E )) 1. A plot of the left-hand side of Eq. (1)
=
against 1/T gives a slope from which E* was calculated and
A (Arrhenius factor) was determined from the intercept. The
entropy of activation (ꢁS*), enthalpy of activation (ꢁH*) and
Scheme 2. Thermal decomposition of Pir and Ten ternary chelates with PhA.

230
M.A. Zayed et al. / Spectrochimica Acta Part A 64 (2006) 216–232
Table 7
Kinetic data of the thermal decomposition of Pir–Gly and Ten–Gly mixed ligands
Complex
Decomposition
range (◦C)
E* (kJ mol−1
)
A (S−1
)
ꢁS* (J K−1 mol−1
)
ꢁH* (kJ mol−1
)
ꢁG* kJ mol−1
[Fe(II)(Pir)2(Gly)2]·4.5H2O
25–200
200–326
326–656
128.4
130.5
224.8
1.20 × 1012
2.50 × 1012
9.37 × 1014
−0.41
−0.69
−4.58
127.7
128.5
220.9
127.7
128.7
218.8
[Fe(III)(Pir)2(Gly)2]Cl·2H2O
25–165
165–324
324–440
445–680
21.65
175.9
127.4
192.4
7.68 × 102
1.53 × 1016
1.50 × 109
9.21 × 1011
−32.87
−7.92
−8.59
−2.43
−37.94
−10.37
−7.97
−14.04
−7.61
−3.24
−16.11
−27.38
−15.87
20.95
173.7
124.2
188.3
22.97
171.6
127.5
189.5
[Co(II)(Pir)2(Gly)2]·4H2O
[Ni(II)(Pir)2(Gly)2]·4H2O
[Cu(II)(Pir)2(Gly)2]·1.5H2O
[Zn(II)(Pir)2(Gly)2]·2H2O
[Fe(II)(Ten)2(Gly)2]·5H2O
[Fe(III)(Ten)2(Gly)2Cl]·H2O
[Co(II)(Ten)2(Gly)2]·3.5H2O
25–195
195–355
355–960
99.7
106.6
169.2
5.37 × 1028
1.72 × 108
3.25 × 1016
98.94
104.5
264.7
195.7
97.11
260.5
25–210
210–367
367–600
137.0
112.0
259.6
1.45 × 106
3.02 × 109
3.18 × 1011
136.3
109.9
156.4
137.5
112.1
157.6
30–155
155–380
380–1225
48.90
22.99
134.7
2.68 × 105
7.44 × 103
1.51 × 106
47.80
20.71
130.1
49.85
28.22
138.9
25–110
110–350
350–710
76.26
191.6
25.85
4.81 × 1010
5.28 × 1017
5.01 × 106
−32.00
−11.47
−3.22
75.75
189.4
210.9
75.95
186.4
212.8
25–185
185–502
510–830
64.40
173.8
286.7
1.58 × 107
1.07 × 1017
4.34 × 1019
−12.10
63.28
171.8
282.9
64.91
169.4
276.0
−9.96
−15.34
25–125
125–341
341–890
35.14
151.4
63.61
4.74 × 104
3.63 × 1014
2.6 × 107
−16.97
34.69
149.4
58.67
35.60
148.4
66.44
−4.28
−13.09
25–180
180–300
300–473
475–710
8.67
105.6
90.63
132.4
7.88 × 109
5.80 × 109
1.80 × 106
8.16 × 1020
−5.75
79.69
103.7
87.64
128.0
80.36
105.2
93.12
318.4
−6.72
−15.24
−18.11
[Ni(II)(Ten)2(Gly)2]·3.5H2O
25–160
160–343
347–460
460–750
60.55
125.5
159.0
171.8
5.39 × 106
1.62 × 1011
3.25 × 1011
1.57 × 1010
−13.14
−3.51
−3.23
−6.54
−10.93
−14.14
−16.41
−9.16
−32.71
−9.29
59.46
123.4
155.8
167.6
61.18
124.3
157.0
171.0
[Cu(II)(Ten)2(Gly)2]·H2O
25–90
90–200
200–840
62.10
196.8
89.70
4.29 × 1017
6.98 × 1018
9.39 × 105
61.13
194.8
87.71
62.40
191.4
94.49
[Zn(II)(Ten)2(Gly)2]·2.5H2O
25–130
130–200
200–800
62.46
270.7
182.8
1.89 × 108
8.17 × 1026
1.29 × 109
61.75
268.7
177.3
62.54
260.7
183.4
vation energy values, one can conclude that, the water
and anion molecules are easy to be eliminated from
the ternary chelates according to the following order:
Fe(II)-chelates > Ni(II)-chelates > Co(II)-chelates > Fe(III)-
chelates > Zn(II)-chelates > Cu(II)-chelates.
According to the kinetic data obtained from DTG curves,
all the complexes have negative entropy, which indicates that
activated complexes have more ordered systems than reac-
tants. From Tables 7 and 8, it is obvious that, the nickel com-
plex shows a higher thermal stability than those of copper.
This can be discussed in terms of repulsion among electron
pairs in the valence shell of the central ion. The higher elec-
tronegativity of copper compared to that of nickel leads to a
higher repulsion between bonding pairs in the valence shell
of copper ion giving lower stability [32,38,39].
The lower thermal stability of the cobalt complex may
be attributed to the higher repulsion between the multiple-
bonding electron pairs (six bonds) in the valence shell of
cobalt, as well as to the higher repulsion obtained by the
non-bonded pairs of electrons on the axial donating oxygen
of the water molecule and the bonded electrons [40].
3.5. Structural interpretation of ternary chelates
The structure of the ternary chelates of Pir or Ten and
amino acids (Gly or PhA) with some di- and tri-valent tran-

M.A. Zayed et al. / Spectrochimica Acta Part A 64 (2006) 216–232
231
Table 8
Kinetic data of the thermal decomposition of Pir–PhA and Ten–PhA mixed ligands
Complex
Decomposition
range (◦C)
E* (kJ mol−1
)
A (S−1
)
ꢁS* (J K−1 mol−1
)
ꢁH* (kJ mol−1
)
ꢁG* (kJ mol−1
)
[Fe(II)(Pir)(PhA)(H2O)2]·0.5SO4
30–200
200–311
315–560
77.22
174.2
194.5
1.17 × 109 −7.76
4.8 × 1016 −9.15
7.56 × 1011 −2.67
76.49
172.1
190.2
77.14
169.9
191.5
[Fe(III)(Pir)(PhA)Cl2]·H2O
[Co(II)(Pir)(PhA)(H2O)2]Cl
[Ni(II)(Pir)(PhA)(H2O)2]Cl
32–115
120–468
468–710
35.54
107.1
238.3
3.71 × 104 −17.20
6.05 × 109 −6.74
1.04 × 1015 −4.58
35.10
105.1
233.9
36.03
106.7
231.6
25–140
140–325
325–605
106.0
156.9
160.0
7.85 × 1014 −6.14
9.24 × 1013 −2.78
6.82 × 1011 −2.44
2.34 × 1014 −4.62
1.4 × 109 −8.35
6.77 × 1027−34.36
6.71 × 1019−15.67
105.3
154.6
156.9
104.8
153.9
157.8
30–170
170–356
356–453
460–700
111.9
108.5
363.7
306.6
110.9
106.1
360.5
302.4
110.5
108.5
347.2
294.5
[Cu(II)(Pir)(PhA)](Ac)·H2O
25–170
170–421
424–681
36.21
36.21
211.9
1.09 × 104 −18.75
2.18 × 102 −23.93
6.40 × 1012 −0.533
35.62
34.09
207.6
36.97
40.19
207.9
[Zn(II)(Pir)(PhA)(H2O)2](Ac)·H2O
[Fe(II)(Ten)(PhA)(H2O)2]·0.5S O4·1.5H2O
[Fe(III)(Ten)(PhA)Cl2]·H2O
30–220
220–518
518–762
71.09
86.99
385.0
6.26 × 109 −5.62
3.16 × 107 −12.05
1.25 × 1016 −6.93
70.40
84.84
380.3
70.87
87.95
376.2
25–200
203–311
315–650
77.22
174.2
194.5
1.17 × 109 −7.76
4.8 × 1016 −9.15
7.56 × 1011 −2.67
76.49
172.1
190.2
77.14
169.9
191.5
30–137
140–372
372–712
43.70
192.8
108.1
1.02 × 106 −14.07
5.07 × 1018−13.81
6.48 × 105 −16.64
43.16
190.7
103.8
44.05
187.4
112.4
[Co(II)(Ten)(PhA)(H2O)2]Cl·2H2O
45–190
190–332
332–490
495–810
108.3
216.3
58.44
223.3
2.31 × 1013 −2.20
3.85 × 1020−18.10
2.55 × 1011 −3.40
1.51 × 1020−16.43
107.2
214.2
55.40
318.8
106.9
209.6
56.65
310.1
[Ni(II)(Ten)(PhA)(H2O)2]Cl
25–160
160–340
341–468
473–635
94.75
112.1
185.3
243.9
4.58 × 1011 −1.72
7.41 × 109 −6.61
4.65 × 1013 −1.74
1.34 × 1015 −4.82
93.74
109.9
182.0
239.6
93.95
111.7
181.4
237.2
[Cu(II)(Ten)(PhA)](Ac)·2.5H2O
45–200
200–409
409–830
59.40
200.9
207.5
1.18 × 107 −12.10
58.56
298.7
203.9
59.80
289.0
203.1
3.1 × 1029 −38.61
255 × 1012
−1.48
[Zn(II)(Ten)(PhA)(H2O)2](Ac)·H2O
30–200
200–343
348–870
59.40
294.5
275.5
6.08 × 107 −10.25
2.81 × 1029−38.55
1.88 × 1015 −5.00
58.72
292.5
270.5
59.56
283.0
267.5
sition metal ions (Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and
Zn(II)) were confirmed by the IR, magnetic, solid reflectance
and thermal analyses data. For all the chelates, the chela-
tion is brought by the pyridine nitrogen and C O of amide
groups of Pir or Ten or by the carboxylate and/or the amino
groups of amino acids (Gly or PhA). The valence of the metal
ions in the chelates is neutralized by the displacement of car-
boxylate proton of amino acids in case of ternary chelates.
This is supported by the IR data. IR and thermal analy-
ses confirmed the existence of water molecules of hydration
and/or coordination. From the reflectance spectra and mag-
netic moment measurements, the geometrical structure of the
ternary chelates were proposed and found to be octahedral,
Fig. 6. Suggested structure of Pir or Ten ternary chelates with Gly.

232
M.A. Zayed et al. / Spectrochimica Acta Part A 64 (2006) 216–232
Fig. 7. Suggested structure of Pir or Ten ternary chelates with PhA.
tetrahedral or square planar. As a general conclusion, Pir or
Ten behaves as neutral bidentate ligands in all the ternary
chelates. While, Gly behaves as a monobasic ligand through
the carboxylate group. Whereas, PhA behaves as a dibasic
ligand through the carboxylate and amino groups. The struc-
ture of the ternary chelates is given in Figs. 6 and 7.
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