Synthesis and spectroscopic studies of some transition metal complexes of a novel Schiff base ligands derived from 5-phenylazo-salicyladehyde and o-amino benzoic acid

Article abstract of DOI:10.1016/j.saa.2006.01.049

Cu(II), Mn(II), Ni(II), and Zn(II) metal complexes with novel heterocyclic Schiff base derived from 5-phenyl azo-salicyladehyde and o-amino benzoic acid have been synthesized and characterized on the basis of elemental analyses, electronic, IR, and ¹H NMR spectra, and also by aid of scanning electron microscopy (SEM), X-ray powder diffraction, molar ratio measurements, molar conductivity measurements, and thermogravimetric analyses. It has been found that the Schiff base behaves as neutral tridentate (ONO) ligand forming chelates with 1:1 (metal:ligand) stoichiometry.

Full text of DOI:10.1016/j.saa.2006.01.049

Spectrochimica Acta Part A 65 (2006) 1208–1220
Synthesis and spectroscopic studies of some transition metal complexes of
a novel Schiff base ligands derived from 5-phenylazo-salicyladehyde
and o-amino benzoic acid
Moamen S. Refata,∗, Ibrahim M. El-Deena, Hassan K. Ibrahimb, Samir El-Ghoola
a Department of Chemistry, Faculty of Education, Port Said, Suez Canal University, Mohamed Ali Street, Port Said, Egypt
b Department of Chemistry, Faculty of Science, Ismalia, Suez Canal University, Ismalia, Egypt
Received 31 October 2005; accepted 23 January 2006
Abstract
Cu(II), Mn(II), Ni(II), and Zn(II) metal complexes with novel heterocyclic Schiff base derived from 5-phenyl azo-salicyladehyde and o-
amino benzoic acid have been synthesized and characterized on the basis of elemental analyses, electronic, IR, and 1H NMR spectra, and
also by aid of scanning electron microscopy (SEM), X-ray powder diffraction, molar ratio measurements, molar conductivity measurements,
and thermogravimetric analyses. It has been found that the Schiff base behaves as neutral tridentate (ONO) ligand forming chelates with 1:1
(metal:ligand) stoichiometry.
© 2006 Elsevier B.V. All rights reserved.
Keywords: 5-Phenyl azo-salicyladehyde; o-Amino benzoic acid; Transition metals; Infrared spectra; Thermogravimetric analyses
1. Introduction
reported herein the syntheses and spectroscopic studies as well
as thermal investigation of a novel Schiff base derivatives ligand
(H2L) (L1 = 2-[5-phenyl azo-2-hydroxy benzylidene amino]-
benzoic acid; L2 = 2-[5-(2-chlorophenyl) azo-2-hydroxy benzyl
idene amino] benzoic acid; L3 = 2-[5-(4-methyl phenyl) azo-
2-hydroxy benzylidene amino] benzoic acid) and its Cu(II),
Mn(II), Ni(II), and Zn(II) complexes. Mass spectra and 1H NMR
spectra were obtained to determine the structure of the ligands
HL1, HL2, and HL3.
During the past two decades, considerable attention has been
paid to the chemistry of the transition metal complexes of Schiff
bases containing nitrogen and other donors [1–4]. The ligands,
derivedbythecondensationofaprimaryamineandanactivecar-
bonylgroup, containtheazomethinegroup[5,6]. Schiffbasesare
a class of important compounds in medicinal and pharmaceuti-
cal field. They show biological activities including antibacterial
[7–10], antifungal [11,12], anticancer [13–15], and herbicidal
[16] activities. Furthermore, Schiff bases are utilized as start-
ing material in the synthesis of industrial [17] and biological
compounds such as ␤-lactons [18]. Azo compounds have been
used for a long time as dyes in industry [19]. In addition, azo
compounds are used in analytical chemistry as indicators in
pH, redox, or complexometric titration [20,21]. Some azo com-
pounds have shown a good antibacterial activity [22,23]. The
existence of an azo moiety in different types of compounds
has caused them to show pesticidal activity [16]. Based on the
mentioned properties for Schiff bases and azo compounds, we
2. Experimental
2.1. Materials
o-Chloroaniline, o-amino benzoic acid, p-toluidine, salicy-
ladehyde, aniline, metal salts (Cu(CH3COO)2·3H2O, NiSO4·
7H2O, MnSO4·4H2O, and ZnSO4·7H2O), and other chemicals
were obtained from Porlabo (reagent grade).
2.2. Synthesis of the azo compounds
Aniline (4.65 ml, 50 mmol), o-chloroaniline (6.40 ml,
50 mmol), or p-toluidine (5.35 g, 50 mmol) was mixed with
hydrochloric acid (37%, 6.0 ml, 40 mmol) in distilled water
∗
Corresponding author.
E-mail address: msrefat@yahoo.com (M.S. Refat).
1386-1425/$ – see front matter © 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2006.01.049

M.S. Refat et al. / Spectrochimica Acta Part A 65 (2006) 1208–1220
1209
(30 ml) and diazotized below 5 ◦C with sodium nitrite
(40.0 mmol, 2.8 g) in distilled water (30 ml). The diazotized ani-
line, o-chloroaniline, or p-toluidine compounds were coupled
with salicyladehyde in alkaline media below 5 ◦C. The pH value
during the coupling was kept fixed between 7 and 9. Coupling to
the salicyladehyde occurred in basic media at the para position
to the hydroxyl group (Scheme 1) [24].
All diazo compounds were recrystallized several times from
ethyl alcohol (95%) and the addition of hydrochloric acid to pH
3. All organic impurities were then extracted by washing with
small portion of diethyl ether. The precipitated compounds were
dried under vacuum at 70 ◦C. The other, all diazo compounds (L2
and L3) were synthesized in the same manner. The purity of all
diazo compounds was evaluated by thin layer chromatography.
solution of the Schiff base was filtered, and the solid was washed
several times with methanol. All organic impurities were then
extracted by washing with small portions of diethyl ether. The
ligands were dried in vacuo over calcium chloride, and were
recrystallized several times from ethyl alcohol. The purity of the
ligands was evaluated by thin layer chromatography. Elemental
analysis CHN, IR, UV–vis, mass, and 1H NMR spectra confirm
the composition of the ligands. The formulas of the azo-linked
Schiff base ligands are given in Scheme 1.
2.4. Synthesis of metal complexes
Allofthecomplexesweresynthesizedbyaddingoftheappro-
priate metal salts (1.0 mmol, in 20 ml ethyl alcohol–water (1:1))
to a hot solution of the ligands (1.0 mmol, in 30 ml ethyl alco-
hol (95%)). The pH was adjusted to 6.00–7.00 using alcoholic
sodium hydroxide (0.01 M). The resulting solutions were stirred
and heated on a hot plate at 70 ◦C for 30 min. The volume of the
obtained solution was reduced to one-half by evaporation. One
day later, the colored solid of the complexes formed was filtered,
thesolidswashedwithethanolanddiethylether, andfinallydried
under vacuum. The synthesized complexes were recrystallized
from ethanol–water (1:1). The purity of all complexes was evalu-
ated by thin layer chromatography. All complexes were prepared
by the same method and isolated as powdered material. Elemen-
2.3. Synthesis of the Schiff base ligand
The Schiff base ligands were synthesized according to
the known condensation method [25]. The methanol solution
(50 ml) of o-amino benzoic acid (6.85 g, 50 mmol) was mixed
with a solution of the derivatives of 5-phenyl azo-salicyladehyde
(11.3 g, 50 mmol, L1; 13.02 g, 50 mmol, L2; 12.0 g, 50 mmol,
L3) in water (100 ml). The mixture was refluxed and stirred
magnetically for 2 h at 70 ◦C on a hot plate. After cooling, the
1
tal analysis CHN, IR, mass spectra, UV–vis, H NMR, XRD,
SEM, and thermogravimetric analyses as well as atomic absorp-
tion spectra confirmed the composition of metal complexes.
2.5. Apparatus and experimental conditions
2.5.1. Elemental analysis and metal percentage
Elemental analyses (C, H, and N) were performed using a
Perkin-Elmer CHN 2400 elemental analyzer. Percentages of
the metal ions of the complexes were determined using PYE-
UNICAM SP 1900 atomic absorption spectrophotometer sup-
plied with the corresponding lamp used for this purpose.
2.5.2. Infrared spectra
IR spectra (4000–400 cm−1) were recorded as KBr pellets on
Perkin-Elmer spectrum RXI FT-IR system spectrophotometer.
2.5.3. Electronic spectra
UV spectra were measured with a Jenway 6405 spectropho-
tometer, using 1 cm Quartz cell, slit fixed at 2 nm. The range of
wavelength was from 200 to 800 nm. The concentrations of lig-
ands (H2L1, H2L2, and H2L3) were 5 × 10−4 mol/l (pH 7), each
of these ligands was added into five 5 ml cuvettes, each contain-
ing 1 ml of this solution, then metal ions (Cu(II), Mn(II), Ni(II),
or Zn(II)) solutions of 5 × 10−4 mol/l (regulated at pH 7) from
0 to 4.00 ml were added into cuvettes, respectively, and diluted
to 5 ml with ethanol (95%). The final concentration of ligands
was 10−4 mol/l in each cuvette, the final concentrations of metal
ions were 0.00, 0.25 × 10−4, 0.50 × 10−4, 0.75 × 10−4, 1.00 ×
10−4, 1.50 × 10−4, 2.00 × 10−4, 2.50 × 10−4, 3.00 × 10−4
,
3.50 × 10−4, and 4.00 × 10−4 mol/l. Until equilibrium was
reached, each UV absorption was recorded.
Scheme 1. Azo-linked Schiff base ligands.

1210
M.S. Refat et al. / Spectrochimica Acta Part A 65 (2006) 1208–1220
2.5.4. 1H NMR spectra
Tetradentatecomplexeswereobtaineduponreactionbetween
metal ions and H2L1, H2L2, and H2L3 ligands at 1:1 molar
ratio. The ligands H2L1, H2L2, and H2L3, on reaction
with Cu(CH3COO)2·3H2O, NiSO4·7H2O, MnSO4·4H2O, and
ZnSO4·7H2O salts, yield complexes corresponding to the gen-
eral formula [CuL1]·2H2O (1), [MnL1]·4H2O (2), [NiL1]·3H2O
(3), [ZnL1]·5H2O (4), [CuL2]·4H2O (5), [MnL2]·3H2O
(6), [NiL2]·4H2O (7), [ZnL2]·4H2O (8), [CuL3]·3H2O (9),
[MnL3]·4H2O (10), [NiL3]·2H2O (11), and [ZnL3]·3H2O (12).
The newly synthesized Schiff base ligands and its com-
plexes are very stable at room temperature in the solid state.
The ligands are insoluble in common organic solvents in cold
or hot conditions. But the ligands and its metal complexes
are generally soluble in DMF and DMSO. The colors, yield,
melting/decomposition points, elemental analyses, and molar
conductances of H2L1, H2L2, H2L3, and 1–12 complexes are
presented in Table 1. The analytical data are in a good agree-
ment with the proposed stoichiometry of the complexes.
The metal-to-ligand ratio in the Cu(II), Mn(II), Ni(II), and
Zn(II) complexes was found to be 1:1. All the complexes (1–12)
have two, three, four, or five molecules of water of crystalliza-
tion.
The structures of ligands (H2L1, H2L2, and H2L3) and com-
plexes were elucidated using a Varian Gemini 200 MHz 1H
NMR spectrometer. The solvent used was DMSO. The inter-
nal reference was the peak due to the solvent. Ligands and solid
complex were added into sample tubes and dissolved in DMSO,
respectively. The 1H NMR was done at 25 ◦C.
2.5.5. Thermal analysis (TG) and DTG techniques
Thermogravimetric analyses (TG) were carried out in the
temperature range from 25 to 800 ◦C in a steam of nitrogen
atmosphere by Shimadzu TGA 50H thermal analysis. The exper-
imental conditions were: aluminum crucible with 1 mg sample,
nitrogen atmosphere with a 30 ml/min flow rate, and a heating
rate 15 ◦C/min.
2.5.6. Mass spectra
The purity of (H2L1, H2L2, and H2L3) is checked from mass
spectra at 70 eV by using AEI MS 30 mass spectrometer.
2.5.7. X-ray powder diffraction
The X-ray powder diffraction analyses were carried out by
using Rigku Model ROTAFLEX Ru-200. Radiation was pro-
vided by copper target (Cu anode 2000 W) high intensity X-ray
tube operated at 40 kV and 35 MA. Divergence slit and the
receiving slit were 1 and 0.1, respectively.
The molar conductivity values for all the complexes in
aqueous medium (10−3 M) were in the range of 4–15 ꢀ−1
cm2 mol−1, suggesting them to be non-electrolytes (Table 1).
The ligands decomposed at temperatures higher than 200 ◦C,
while all complexes decomposed at temperatures higher than
250 ◦C. All of the new complexes and Schiff base seemed to
have dye character due to the high molar extinction constant.
Elemental analyses were in good agreement with those required
for the purpose of formula. According to the elemental anal-
2.5.8. Scanning electron microscope
The scanning electron microscope (SEM) images were taken
in JEOL-840 equipment, with an accelerating voltage of 15 kV.
3. Results and discussion
1
yses, IR, UV–vis, H NMR, and thermogravimetric data, the
complexes of the tridentate ligands had one coordinated water
molecule. Analytical data for all ligands and complexes are
listed in Table 1.
Condensation of the 5-phenyl azo salicyladehyde and its
derivatives with o-amino benzoic acid readily gives rise to the
corresponding imine H2L1, H2L2, and H2L3, which was easily
identified by its IR, 1H NMR and mass spectra.

M.S. Refat et al. / Spectrochimica Acta Part A 65 (2006) 1208–1220
1211
Table 1
Elemental analyses and physical data of ligands H2L1, H2L2, H2L3, and their complexes 1–12
Complexes
Empirical formula
Molecular
weight
(g/mol)
Color
Melting
point
Content ((calculated) found)
Yield
Λm
(ꢀ cm2 mol−1
)
%C
%H
%N
H2L1
H2L2
H2L3
C20H14N3O3
C20H13N3O3Cl
C21H16N3O3
344
378.5
358
Pink
Red
236
252
262
(69.77) 69.82
(63.41) 63.11
(70.39) 70.13
(54.35) 54.70
(51.18) 51.03
(52.78) 52.90
(48.25) 48.10
(46.87) 46.80
(49.44) 49.17
(47.32) 47.11
(46.79) 46.53
(53.21) 52.91
(52.18) 51.70
(55.91) 55.73
(53.01) 52.84
(4.07) 4.02
(3.43) 3.38
(4.47) 4.41
(3.62) 3.57
(4.62) 4.18
(3.96) 3.88
(4.42) 4.37
(3.71) 3.65
(3.50) 3.44
(3.74) 3.66
(3.69) 3.56
(4.22) 4.09
(4.55) 4.51
(3.99) 3.89
(4.21) 4.18
(12.71) 12.18
(11.10) 10.59
(11.73) 11.64
(9.51) 9.36
(8.95) 8.79
(9.23) 9.11
(8.44) 8.33
(8.20) 8.10
(8.65) 8.56
(8.28) 8.16
(8.17) 8.08
(8.87) 8.77
(8.69) 8.54
(9.32) 9.13
(8.83) 8.67
73
77
71
64
63
62
66
63
60
66
64
67
65
65
62
2.7
3.1
2.4
5.3
4.2
10.3
12.5
11.7
13.3
14.9
10.2
11.2
12.2
14.1
13.7
Orange
Olivey green
Violet
Yellow
Orange
Olivey green
Violet
Orange
Orange
Olivey green
Violet
Yellow
Yellow
[CuL1]·2H2O
[MnL1]·4H2O
[NiL1]·3H2O
[ZnL1]·5H2O
[CuL2]·4H2O
[MnL2]·3H2O
[NiL2]·4H2O
[ZnL2]·4H2O
[CuL3]·3H2O
[MnL3]·4H2O
[NiL3]·2H2O
[ZnL3]·3H2O
C20H16N3O5Cu
C20H20N3O7Mn
C20H18N3O6Ni
C20H22N3O8Zn
C20H19N3O7ClCu
C20H17N3O6ClMn
C20H19N3O7ClNi
C20H19N3O7ClZn
C21H20N3O6Cu
C21H22N3O7Mn
C21H18N3O5Ni
C21H20N3O6Zn
441.55
468.94
454.70
497.38
512.05
485.44
507.20
513.88
473.55
482.94
450.70
475.38
>387
>350
>400
>400
>392
>400
>400
>400
>322
>400
>400
>400
3.1. Infrared spectra
of electrons from nitrogen atom to the metal ion due to coordi-
nation. The infrared spectra of the complexes exhibited broad
bands at 3425–3394 cm−1 that are attributed to OH of the crys-
tal water molecules, while the bands observed at approximately
839–819 cm−1 are assigned to coordinated water molecule [27].
The infrared spectra of azo-linked Schiff base ligands showed
bands around 1285–1260 cm−1 assigned to the phenolic C–O
vibration. However, in the spectra of the metal complexes, the
C–O band shifted to the lower region (∼1200 cm−1). In the
infrared spectra of the complexes, bands assigned to M–N and
M–O were identified at 564–496 and 435–415 cm−1, respec-
tively [28] (Figs. 1–3).
Table 2 presents the most important IR spectral bounds for
H2L1, H2L2, H2L3, and all the metal complexes. The func-
tional groups of the azo-linked Schiff base ligands and the metal
complexes have been appeared by infrared spectra, as given in
Figs. 1–3. When the carboxylic acid group in the ligands is
converted to the complexes, the absorption bands of stretch-
ing vibration of C O group, ν(C O), of COOH group at about
∼1700 cm−1 disappear, whereas the bands assigned to asym-
metric vibrations νas(OCO) at 1560–1523 cm−1 and the bands
of symmetric vibrations νs(OCO) at 1395–1333 cm−1 appear.
The bands at 1627–1620 cm−1 were assigned to the stretching
vibration of the azomethine group of the ligands H2L1, H2L2,
and H2L3. This band is shifted in the complexes toward lower
frequencies because of the coordination of the nitrogen to the
metal ion [26]. This fact can be explained by the withdrawing
3.2. Molar conductivities of metal chelates
Conductivity measurements in non-aqueous solutions have
frequently been used in structural studies of metal chelates
Table 2
Infrared spectral data for the azo-linked Schiff base ligands and their complexes (cm−1
)
Compounds
ν(OH)
hydrated water
ν(OH)
coordinated H2O
ν(C O)
COOH−
ν(C N)
νas(C O)
COO−
νs(C O)
COO−
ν(C O)
phenolic
ν(M N)
ν(M O)
H2L1
3472br
3421br
3425br
3424br
3424br
3444br
3425s
3425br
3394br
3425br
3424br
3424br
3424br
3425br
3423br
–
1682mw
–
–
–
1620vs
1616vs
1618vs
1615vs
1618vs
1621vs
1609vs
1618vs
1613s
1591vs
1627vs
1624vs
1623vs
1620vs
1593vs
–
–
1260w
1191ms
1186ms
1184ms
1186s
1285ms
1247w
1254vw
1257w
1262w
1285w
1246w
1252vw
1255ms
1221ms
–
–
[CuL1]·2H2O
[MnL1]·4H2O
[NiL1]·3H2O
[ZnL1]·5H2O
H2L2
[CuL2]·4H2O
[MnL2]·3H2O
[NiL2]·4H2O
[ZnL2]·4H2O
H2L3
[CuL3]·3H2O
[MnL3]·4H2O
[NiL3]·2H2O
[ZnL3]·3H2O
837s
837s
837ms
819s
–
837s
836ms
838s
825s
–
1523ms
1526s
1540s
1538vs
–
1554s
1558s
1532vs
1537vs
–
1392vs
1395vs
1379s
1379s
–
1394s
1395s
1388vs
1379s
–
529w
518w
523vw
496w
–
527w
536w
524s
532s
–
423ms
424w
415vw
435vw
–
426ms
418vw
416w
423vw
–
–
1700w
–
–
–
–
1698w
838s
838ms
839s
825s
–
–
–
–
1552vs
1560w
1528s
1537vs
1382vs
1394s
1333s
1377s
519s
517vs
516ms
546ms
422s
419s
423vw
433vw

1212
M.S. Refat et al. / Spectrochimica Acta Part A 65 (2006) 1208–1220
Fig. 2. Infrared spectra of: (A) H2L2, (B) [CuL2]·4H2O (5), (C) [MnL2]·3H2O
(6), (D) [NiL2]·4H2O (7), and (E) [ZnL2]·4H2O (8).
Fig. 1. Infrared spectra of: (A) H2L1, (B) [CuL1]·2H2O (1), (C) [MnL1]·4H2O
(2), (D) [NiL1]·3H2O (3), and (E) [ZnL1]·5H2O (4).
given by the relation:
within the limits of their solubility. They provide a method of
testing the degree of ionization of the complexes, the molar ions
that a complex liberates in solution, the higher will be its molar
conductivity and vice versa. The non-ionized complexes have
negligible value of molar conductance. The molar conductivities
of the solid chelates are measured for 10−3 mol solution of 1:1
complexes in DMSO. The conductivity data reported for these
complexes are given in Table 1. The product of the cell constant
and the measured conductance of a solution gives the specific
conductivity K. The molar conductance (ꢀ−1 cm2 mol−1) is
K
Λm
=
× 1000
C
where C (mol/l) is the concentration of the solution. It is clear
from the conductivity data that the complexes present behave as
weak electrolytes. Also the molar conductance values indicate
that the anions may be present inside the coordination sphere
or absent. This result was confirmed from the chemical analysis
where CH3COO− or SO4 ions are not precipitated colored
2−

M.S. Refat et al. / Spectrochimica Acta Part A 65 (2006) 1208–1220
1213
Fig. 4. Electronic spectra of H2L3 and its copper complex.
Fig. 5. The relationship of absorption of H2L1 with the addition of Cu(II) [1],
Mn(II) [2], Ni(II) [3], and Zn(II) [4] solution.
Fig. 3. Infrared spectra of: (A) H2L3, (B) [CuL3]·3H2O (9), (C) [MnL3]·4H2O
(10), (D) [NiL3]·2H2O (11), and (E) [ZnL3]·3H2O (12).
by addition of FeCl3 or BaCl2 solutions, respectively. All the
complexes did not show electrolytic properties. This fact eluci-
2−
dated that the CH3COO− and SO4 are absent, and that one
of the water molecules completes the coordination sphere of the
studied complexes.
3.3. Electronic spectra
Table 3 shows the absorption values of L1, L2, and L3
at ∼370 nm with the addition of Cu(II), Mn(II), Ni(II), and
Zn(II) solution to it. UV spectra (Fig. 4) clearly indicated a
Fig. 6. The relationship of absorption of H2L2 with the addition of Cu(II) [5],
Mn(II) [6], Ni(II) [7], and Zn(II) [8] solution.

1214
M.S. Refat et al. / Spectrochimica Acta Part A 65 (2006) 1208–1220
Table 3
Absorption data of ligands (L1, L2, and L3) solution with the addition of metal M2+ (M2+ = Cu, Mn, Ni, and Zn) solution, where [CuL1]·2H2O (1), [MnL1]·4H2O (2),
[NiL1]·3H2O (3), [ZnL1]·5H2O (4), [CuL2]·4H2O (5), [MnL2]·3H2O (6), [NiL2]·4H2O (7), [ZnL2]·4H2O (8), [CuL3]·3H2O (9), [MnL3]·4H2O (10), [NiL3]·2H2O
(11), and [ZnL3]·3H2O (12)
Molar ratio, Concentration of
Concentration of
M2+ (10−4 ml/l)
1
2
3
4
5
6
7
8
9
10
11
12
L:M2+
Ln (10−4 ml/l)
0
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
0
0.131 0.153 0.167 0.155 0.159 0.144 0.181 0.203 0.147 0.182 0.211 0.191
0.134 0.158 0.169 0.158 0.163 0.148 0.183 0.207 0.149 0.186 0.214 0.195
0.137 0.160 0.173 0.163 0.170 0.150 0.187 0.209 0.153 0.189 0.216 0.194
0.141 0.162 0.176 0.166 0.174 0.153 0.191 0.212 0.155 0.191 0.219 0.201
0.150 0.167 0.183 0.169 0.180 0.160 0.194 0.215 0.158 0.193 0.221 0.205
0.152 0.170 0.184 0.170 0.181 0.161 0.194 0.215 0.162 0.193 0.222 0.206
0.153 0.170 0.184 0.170 0.182 0.162 0.195 0.216 0.162 0.193 0.222 0.206
0.153 0.171 0.185 0.171 0.182 0.162 0.196 0.216 0.163 0.194 0.222 0.207
0.154 0.172 0.185 0.171 0.183 0.163 0.196 0.217 0.163 0.195 0.222 0.207
0.154 0.174 0.185 0.171 0.183 0.163 0.197 0.217 0.163 0.195 0.223 0.207
0.155 0.175 0.186 0.171 0.183 0.163 0.197 0.217 0.164 0.195 0.223 0.207
1:0.25
1:0.50
1:0.75
1:1.00
1:1.50
1:2.00
1:2.50
1:3.00
1:3.50
1:4.00
0.25
0.50
0.75
1.00
1.50
2.00
2.50
3.00
3.50
4.00
bathochromic shift (red shift) for the two detected peaks in
the L3 as one of the studied ligands from 340 and 280 to 370
and 300 nm. We plot the curves according to the data listed in
Table 3. From Table 3 and Figs. 5–7, we can see absorption
values were enhanced with increasing concentration of Cu(II),
Mn(II), Ni(II), and Zn(II) at the beginning and then formed a
platform, when L:M2+ is about 1:1. This fact illustrated that
1 mol ligand (L1, L2, and/or L3) molecules will coordinate with
1 mol of M2+ (M2+ = Cu, Mn, Ni, and/or Zn).
3.4. Mass spectra
The purity of ligands L1, L2, and L3 is checked from
mass spectra (Fig. 8A–C) where the spectra showed that a
clearly base peaks (m/e) molecular weights and the intensity
(%) of the three ligands (L1 = 2-[5-phenyl azo-2-hydroxy ben-
zylidene amino]-benzoic acid, L2 = 2-[5-(2-chlorophenyl)azo-
Fig. 7. The relationship of absorption of H2L3 with the addition of Cu(II) [9],
Mn(II) [10], Ni(II) [11], and Zn(II) [12] solution.
2-hydroxy benzylidene amino] benzoic acid, and L3 = 2-[5-(4-
Fig. 8. Mass spectra of: (A) H2L1, (B) H2L2, and (C) H2L3 compounds.

M.S. Refat et al. / Spectrochimica Acta Part A 65 (2006) 1208–1220
1215
Fig. 9. 1H NMR spectra of: (A) H2L3 and (B) [CuL3]·3H2O compounds.
1
methylphenyl)azo-2-hydroxybenzylideneamino]benzoicacid)
at 345 (75%), 379 (80%), and 359 (83%), respectively.
its Cu(II) complex are shown in Fig. 9. The H NMR spectra
of the ligand, HL3, and the Cu(II) complex were recorded using
1
DMSO-d6 as a solvent. As a result of the H NMR spectral
3.5. 1H NMR spectra
studies, important class concerning the geometry of azo-linked
Schiff base ligands was obtained. The 1H NMR spectrum of HL3
showed a singlet at 2.50 ppm that was assigned to the protons of
methyl group, and multiplets at 6.50–8.20 ppm were assigned to
1
For instance, the H NMR spectra of HL3 (2-[5-(4-methyl
phenyl) azo-2-hydroxy benzylidene amino] benzoic acid) and
Fig. 10. XRD diagrams of: (A) [CuL3]·3H2O (9), (B) [MnL3]·4H2O (10), (C) [NiL3]·2H2O (11), and (D) [ZnL3]·3H2O (12).

1216
M.S. Refat et al. / Spectrochimica Acta Part A 65 (2006) 1208–1220
Fig. 11. SEM diagrams of: (A) [CuL3]·3H2O (9), (B) [MnL3]·4H2O (10), (C) [NiL3]·2H2O (11), and (D) [ZnL3]·3H2O (12).
Table 4
Thermal decomposition of the metal complexes (1–12)
Complexes
Step
ꢁT (◦C)
Weight loss (calculated/found) (%)
Residue (calculated/found) (%)
CuO (18.02/19.41)
[CuL1·H2O]·H2O (1)
1
2
60–150
150–550
4.08/3.83
77.9/76.76
[MnL1·H2O]·3H2O (2)
[NiL1·H2O]·2H2O (3)
[ZnL1·H2O]·4H2O (4)
[CuL2·H2O]·3H2O (5)
1
2
50–167
167–600
7.68/7.02
73.78/72.98
MnO2 (18.54/19.35)
NiO (16.43/15.79)
ZnO (16.36/17.36)
CuO (15.54/15.63)
1
2
50–208
208–550
7.92/7.05
75.65/77.16
1
2
90–250
250–600
14.47/14.07
69.17/68.57
1
2
3
60–170
170–260
260–600
3.52/3.37
7.03/7.86
73.91/73.14
[MnL2·H2O]·2H2O (6)
[NiL2·H2O]·3H2O (7)
[ZnL2·H2O]·3H2O (8)
[CuL3·H2O]·2H2O (9)
[MnL3·H2O]·3H2O (10)
1
2
55–235
235–665
7.41/8.01
74.68/73.56
MnO2 (17.91/18.43)
NiO (4.73/15.52)
1
2
75–260
260–620
10.65/10.35
74.62/74.13
1
2
50–220
220–627
3.50/3.48
80.66/80.12
ZnO (15.84/16.40)
CuO (16.80/17.27)
MnO2 (18.00/18.13)
1
2
50–275
275–640
7.60/7.27
75.60/75.46
1
2
3
50–200
200–300
300–600
3.72/3.77
7.45/7.54
70.83/70.56
[NiL3·H2O]·H2O (11)
[ZnL3·H2O]·2H2O (12)
1
2
50–220
220–615
3.99/2.26
79.44/81.26
NiO (16.57/16.48)
ZnO (17.14/17.24)
1
2
70–300
300–625
7.57/7.83
75.31/74.93

M.S. Refat et al. / Spectrochimica Acta Part A 65 (2006) 1208–1220
1217
the aromatic protons. The singlet at 9.07 ppm was attributed to
the proton of the azomethine group [3]. The signal of the OH-
proton in the salicyladehyde ring was observed at 10.37 ppm.
A broad peak at 11.43 ppm was attributed to the OH-proton of
carboxylic acid. By making comparison between the 1H NMR
data of HL3 and its Cu(II) complex the mode of coordination in
between the ligands and metal ions was clarified. Through the
discussion of 1H NMR spectrum of Cu(II) complex, we find that
the peaks (signals) specialized to OH-proton of carboxylic acid
and OH-proton in salicyladehyde ring disappeared and notified
the appearance of new strong broad peak at 3.38 ppm; this can
be assigned to the H-proton of H2O, which attached to the Cu(II)
metal to complete the coordination sphere as follows:
Fig. 12. TGA diagrams of: (A) [CuL1]·2H2O (1), (B) [MnL1]·4H2O (2), (C) [NiL1]·3H2O (3), (D) [ZnL1]·5H2O (4), (E) [CuL2]·4H2O (5), (F) [MnL2]·3H2O (6),
(G) [NiL2]·4H2O (7), (H) [ZnL2]·4H2O (8), (I) [CuL3]·3H2O (9), (J) [MnL3]·4H2O (10), (K) [NiL3]·2H2O (11), and (L) [ZnL3]·3H2O (12).

1218
M.S. Refat et al. / Spectrochimica Acta Part A 65 (2006) 1208–1220
Fig. 12. (Continued )
3.6. X-ray powder diffraction
Single crystals of the complexes could not be isolated from
any solutions; thus, no definitive structure can be described.
However, the spectroscopic data and elemental analysis of CHN
enable us to predict possible structures (1–10).
X-ray powder diffraction patterns in the 5◦ < 2θ < 90◦ of
the compounds were carried in order to obtain an idea about
the lattice dynamics of the compound. By comparison of the
obtained X-ray powder diffraction patterns shown in Fig. 10,
the X-ray powder diffraction pattern throws light only on the
fact that each solid represents a definite compound of a defi-
nite structure which is not contaminated with starting materials.
This identification of the complexes was done by the known
method [29]. Such facts suggestthattheprepared compoundsare
amorphous.
3.8. Thermal studies
The thermal degradation of all the metal complexes (1–12)
was studied using thermogravimetric techniques and a temper-
ature range of 25–800 ◦C (Fig. 12). The thermal stability data
are listed in Table 4. The data from the thermogravimetric anal-
ysis clearly indicated that the decomposition of the complexes
proceeds in two or three steps. Water molecules were lost in
between 50 and 300 ◦C and metal oxides were formed above
600 ◦C for Cu(II), Mn(II), Ni(II), and Zn(II) complexes. For
these complexes, the removal of water can proceed in two steps.
All complexes lost hydration water between 50 and 300 ◦C, and
then the coordinated water molecule was lost above ≥300 ◦C.
The decomposition was complete at ≥600 ◦C for all complexes.
The degradation pathway for all complexes may be represented
3.7. Scanning electron microscopy
Purity and morphology of the complexes obtained were stud-
ied by SEM. The obtained SEM micrographs, shown in Fig. 11,
allow to verify that the copper, manganese, nickel, and zinc(II)
complexes are the ones with the well-formed amorphous shape.
Such facts are in agreement with the obtained X-ray results.

M.S. Refat et al. / Spectrochimica Acta Part A 65 (2006) 1208–1220
1219
Fig. 12. (Continued ).
as follows:
[ML(H2O)] · nH2O 50–300 C
[9] A.H. El-masry, H.H. Fahmy, S.H.A. Abdelwahed, Molecules 5 (2000)
1429.
[10] M.A. Baseer, V.D. Jadhav, R.M. Phule, Y.V. Archana, Y.B. Vibhute, Orient.
J. Chem. 16 (3) (2000) 533.
−→◦ [ML(H2O)] + nH2O
◦
[11] S.N. Pandeya, D. Sriram, G. Nath, E. De Clercq, IL Farmaco 54 (1999)
624.
[ML(H2O)]300−–→665 C–H2O + [MO or MO2]
[12] W.M. Singh, B.C. Dash, Pesticides 22 (11) (1988) 33.
[13] E.M. Hodnett, W.J. Dunn, J. Med. Chem. 13 (1970) 768.
[14] S.B. Desai, P.B. Desai, K.R. Desai, Hetrocycl. Commun. 7 (1) (2001) 83.
[15] P. Pathak, V.S. Jolly, K.P. Sharma, Orient. J. Chem. 16 (1) (2000) 161.
[16] S. Samadhiya, A. Halve, Orient. J. Chem. 17 (1) (2001) 119.
[17] F. Aydogan, N. Ocal, Z. Turgut, C. Yolacan, Bull. Korean Chem. Soc. 22
(2001) 476.
[18] A.E. Taggi, A.M. Hafez, H. Wack, B. Young, D. Ferraris, T. Lectka, J. Am.
Chem. Soc. 124 (2002) 6626.
[19] K. Hansongnern, S. Tempiam, J.C. Liou, F.L. Laio, T.H. Lu, Anal. Sci. 19
(2003) x13.
[20] P.L. Coort, M. Johansson, Electroanalysis 12 (2000) 565.
[21] D. Choi, S.K. Lee, T.D. Chung, H. Kim, Electroanalysis 12 (2000) 477.
[22] P. Alka, P. Vinod, V.S. Jolly, Orient. J. Chem. 10 (1) (1994) 73.
[23] A. Halve, A. Goyal, Orient. J. Chem. 12 (1) (2001) 87.
[24] A.A. Khandar, Z. Rezvani, Polyhedron 18 (1999) 129.
where MO = CuO, NiO, ZnO; MO2 = MnO2.
References
[1] X. Tai, X. Yin, Q. Chen, M. Tan, Molecules 8 (2003) 439.
[2] M. Sonmez, A. Levent, M. Sekerci, Russ. J. Coord. Chem. 30 (9) (2004)
655.
[3] M. Tuncel, S. Serin, Synth. React. Inorg. Met. Org. Nano Met. Chem. 35
(2005) 203.
[4] A.A. Khandar, K. Nejati, Z. Rezvani, Molecules 10 (2005) 302.
[5] A.D. Garnovskii, I.S. Vasil Chenko, Russ. Chem. Rev. 71 (2002) 943.
[6] A.D. Garnovskii, A.L. Nivorozhkin, V.I. Minkin, Coord. Chem. Rev. 126
(1993) 1.
[7] F.D. Karia, P.H. Parsania, Asian J. Chem. Soc. 11 (3) (1999) 991.
[8] P.G. More, R.B. Bhalvankar, S.C. Pattar, J. Indian Chem. Soc. 78 (9) (2001)
474.

1220
M.S. Refat et al. / Spectrochimica Acta Part A 65 (2006) 1208–1220
[25] R.J. Fessenden, J.S. Fessenden, Inorganic Chemistry, vol. 13, fourth ed.,
Cole Publishing Company, California, 1990, pp. 587–648.
[26] M. Mikuraya, T. Sasaki, A. Anjiki, S. Ikemoae, T. Tokh, Bull. Chem. Soc.
Jpn. 65 (1992) 334.
[28] H. Koksal, M. Tumer, S. Seria, Synth. React. Inorg. Met. Org. Chem. 26
(1996) 1577.
[29] B.D. Cullity, Elements of X-ray Diffraction, second ed., Addison-Wesley
Inc., 1993.
[27] G.G. Mohamed, Spectrochim. Acta Part A 57 (2001) 411.