Metal complexes of Schiff base derived from terephthalaldehyde and 2-amino-5-ethyl-1,3,4-thiadiazole synthesis, spectral and thermal characterization

Article abstract of DOI:10.1080/15533170903433162

The present study deals with the preparation of Schiff base and its chelates with some transition metal ions, e.g., Co(II), Ni(II), Cu(II) and Fe(II). The structures of the ligand N-(5-ethyl-1,3,4-thiadiazole-2-yl) terephthalaldehyde imine (L) and its com

Full text of DOI:10.1080/15533170903433162

This article was downloaded by: [University of Aberdeen]
On: 23 July 2013, At: 07:13
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer
House, 37-41 Mortimer Street, London W1T 3JH, UK
Synthesis and Reactivity in Inorganic, Metal-Organic,
and Nano-Metal Chemistry
Publication details, including instructions for authors and subscription information:
http://www.tandfonline.com/loi/lsrt20
Metal Complexes of Schiff Base Derived from
Terephthalaldehyde and 2-Amino-5-Ethyl-1,3,4-
Thiadiazole Synthesis, Spectral and Thermal
Characterization
Nevin Turan a & Memet Sekerci b
a Faculty of Arts and Science, Department of Chemistry, University of Muş Alparslan,
Muş, Turkey
b Faculty of Arts and Science, Department of Chemistry, University of Firat, Elazıg,
Turkey
Published online: 14 Dec 2009.
To cite this article: Nevin Turan & Memet Sekerci (2009) Metal Complexes of Schiff Base Derived from Terephthalaldehyde
and 2-Amino-5-Ethyl-1,3,4-Thiadiazole Synthesis, Spectral and Thermal Characterization, Synthesis and Reactivity in
Inorganic, Metal-Organic, and Nano-Metal Chemistry, 39:10, 651-657
To link to this article: http://dx.doi.org/10.1080/15533170903433162
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained
in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of
the Content. Any opinions and views expressed in this publication are the opinions and views of the authors,
and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied
upon and should be independently verified with primary sources of information. Taylor and Francis shall
not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other
liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or
arising out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any substantial or systematic
reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any
form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://
www.tandfonline.com/page/terms-and-conditions

Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 39:651–657, 2009
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533170903433162
Metal Complexes of Schiff Base Derived from
Terephthalaldehyde and 2-Amino-5-Ethyl-1,3,4-Thiadiazole
Synthesis, Spectral and Thermal Characterization
Nevin Turan1 and Memet Sekerci2
1Faculty of Arts and Science, Department of Chemistry, University of Mus¸ Alparslan, Mus¸, Turkey
2Faculty of Arts and Science, Department of Chemistry, University of Firat, Elazıg, Turkey
In this study, we report the synthesis, spectral, and thermal
characterization of a novel Schiff base ligand (L) containing a
ring of the thiadiazole and its Co(II), Ni(II), Cu(II) and Fe(II)
complexes. Thus, in view of this, it has been considered of in-
terest to study a complex containing the thiadiazole moiety.1H-
NMR spectra was obtained to determine the structure of the
Schiff base ligand. The preparation and structure of the ligand
showed as in Figure. 1.
The present study deals with the preparation of Schiff base
and its chelates with some transition metal ions, e.g., Co(II),
Ni(II), Cu(II) and Fe(II). The structures of the ligand N-(5-
ethyl-1,3,4-thiadiazole-2-yl)terephthalaldehyde imine (L) and its
complexes have been synthesized and characterized by IR, 1H-
NMR spectra, elemental analyses, magnetic susceptibility, UV-vis
and thermogravimetry-differential thermal analysis (TGA-DTA).
From the magnetic moment and UV-vis spectra data, it is found
that the geometrical structures of these complexes are octahedral.
RESULTS AND DISCUSSION
Keywords metal complexes, spectroscopy, transition metal com-
The ligand (L) was obtained by condensation of 2-amino-
5-ethyl-1,3,4-thiadiazole (1) with terephthalaldehyde and was
checked by IR, 1H-NMR spectra, and microanalytical data
(Table 1). Co(II), Ni(II), Cu(II) and Fe(II) complexes of lig-
and were air stable and prepared by the stoichiometric reaction
of the corresponding metal(II) chloride with the Schiff base lig-
and, in molar ratio M:L of 1:1, 2:1, 1:2 and 1:2, respectively.
The analytical data are in good agreement with the proposed
stoichiometry of the complexes. All the complexes are soluble
in common organic solvents such as methanol, acetone, chloro-
form and DMF.
According to the elemental analyses, IR, UV-vis, magnetic
susceptibility and thermogravimetric analyses results, the struc-
tures of complexes are suggested to be as shown in Figures 2–5.
The characterization data of ligand and its complexes are given
in Tables 1–4.
pounds
INTRODUCTION
During the last two decades, many kinds of compounds of
substituted 1,3,4-thiadiazoles, which have special structures and
properties have been widely reported in the field of synthesis,
spectroscopic analysis and traditional application of medicine
and pesticide.[1]
The thiadiazole ring is associated with diverse biochem-
ical activity probably by virtue of incorporating a tox-
ophoric N C S linkage, the importance of which has
been well-stressed in many pesticides. Actually various 2-
amino/substituted-amino-1,3,4-thiadiazoles and their Schiff
bases have recently received significant importance because of
their diverse biochemical properties.[2] As a ligand, it also pro-
vides many potential binding sites for complexation of diverse
metal ions (such as Co(II), Ni(II), Cu(II) or Zn(II) among others)
with well established biological roles.[3]
Infrared Spectra
The IR spectral bands of the ligand and its complexes are
listed in Table 2 together with assignments for most of the
important peaks. The position and/or the intensities of these
peaks are expected to be changed upon chelation.
In the IR spectrum of (1) characteristic peaks are at 3287
cm−1υ(NH2)as, 3108 cm−1υ(NH2)s and 1536 cm−1 (N H) out
of plane bending vibrations.[4] There is no N-H band in the IR
spectra of ligand.[5,6]
Received 26 June 2009; accepted 27 July 2009.
The support of the Management Unit of Scientific Research Projects
of Firat University (FUBAP) under research project no 1275 is grate-
fully acknowleged.
Address correspondence to Nevin Turan, Faculty of Arts and
Science, Dept. of Chemistry, University of Mus¸ Alparslan, 49100 Mus¸,
Turkey. E-mail: nevintrn@hotmail.com
IR spectra of the Schiff base reported here showed the ab-
sence of bands at ≈1700 and 3287, 3108 cm−1 due to carbonyl
651

652
N. TURAN AND M. SEKERCI
FIG. 1. Synthesis of the ligand : N-(5-ethyl-1,3,4-thiadiazole -2-yl) terephthalaldehyde imine (L).
the υ(C N), and other shifted two lower frequency 1430 cm−1
,
υ(C O) and υ(NH2) stretching vibrations (present in the start-
ing materials) and the appearance of a strong new band at 1629
cm−1 assigned as azomethine υ(C N) vibration.[7]
arising due to coordinated υ(C N) mode. The splitting of the
υ(>C N N C<) (ring) absorption band suggests that only
one of the ring nitrogen is involved in coordination and other
is free and non-coordinated. This is further supported by a new
band at 470 cm−1 assignable to υ(M-N) in the complex. The
υ(C S C) band in the ligand occurs at 770 cm−1, which re-
mains unaltered in the spectra of the complex indicating the
non-coordination of sulphur atom of the thiadiazole ring.[11]
In the spectra Co(II) and Cu(II) complexes the
υ(>C N N C<) (ring), υ(N N) vibrations remain almost
unchanged indicating, thereby, non-involvement of the ring ni-
trogen in coordination. The υ(C S C) undergoes a negative
shift in the complexes indicating the coordination of ring sul-
phur. The coordination through the azomethine nitrogen and
sulphur is further supported by the occur of new bands at 471,
460 cm−1 in the spectra of the complexes which may be as-
signed to υ(M-N), respectively.[12] The IR spectra of Co(II) and
The spectra of the free ligand display band at 1692 cm−1 due
to υ(C O). The position of υ(C O) is found to be dependent
on the electronic nature of the p-substituents.[8] The υ(C O)
stretching vibration that is useful for diagnosis of coordination
located at 1692 cm−1 for ligand remain at the same position as
in ligand, indicating that the υ(C O) group does not coordinate
with the metal atoms[4]
The solid state IR spectra of the complexes compared with
those of the ligand indicate that the C N band 1629 cm−1 is
shifted to lower values for complexes Co(II), Ni(II), Cu(II) and
Fe(II). The phenomenon appears to be due to the coordinated of
azomethine nitrogen to the metal ion.[9]
The spectra of all complexes exhibited intense broad 3505–
3300 cm−1 due to υ(OH) of hydrate and coordinated water or
ethanol molecule.[10] The presence of hydrate or/and coordi-
nated water molecules or ethanol molecule are also confirmed
by elemental analyses and thermogravimetric analyses.
The infrared spectra of the ligand show bands 1629 and 1498-
1444 cm−1, which may be assigned to be υ(C N) (azomethine
group) and υ(>C N N C<) (ring), respectively. The first
Cu(II) complexes display an additional new bands at 330 cm−1
,
assigned to υ(M-S).[13] In the IR spectrum of the complexes
(M-S) bands could not be observed, that we study in 4000–400
cm−1 range.
In the Ni(II) complex the υ(>C N N C<) (ring), υ(N N)
vibrations shifted to lower frequencies at 1460–1434 and 1050–
943 cm−1, arising due to coordinated ring nitrogen. The band
at 772 cm−1 assigned to the thiadiazole ring υ(C S C) vibra-
tion is also shifted to lower frequency by ≈10 cm−1, which
is indicative of the involvement of the thiadiazole ring sulphur
band is shifted towards the lower frequency region (22 cm−1
)
in the Fe(II) complex indicating the coordination of the azome-
thine nitrogen atom of the Schiff base. However the second band
υ(>C N N C<) (ring) is found to split into two; one almost
located at the original position indicating non-coordinated at
TABLE 1
The colors, formula, formula weight, yields, melting points, magnetic moments and elemental analysis results of the ligand (L)
and the complexes
Elemental analyses/(%) calculated (found)
FW
M.p. Yield
µeff
Compounds
(g/mol) (◦C) (%) (B.M.)a
C
H
N
S
Ligand (orange ) C12H11N3SO
[CoL(H2O)4].2Cl.H2O (Dark red)
C12H21Cl2CoN3SO6
[Ni2LCl4(H2O)4].4H2O (Pale red)
C12H27Cl4Ni2N3SO9
[CuL2Cl2].2H2O (Pale green)
C24H26Cl2CuN6S2O4
[FeL2Cl2].EtOH (Dark red)
C26H28Cl2FeN6S2O3
245
170
60
48
−
58.76 (58.72) 4.49 (4.22) 17.14(17.20) 13.06 (13.32)
464.84 210
648.24 250
660.46 235
662.75 225
4.11 30.98 (31.31) 4.52 (4.88) 9.04(9.18)
6.88 (6.83)
54
58
55
2.59 22.21 (21.55) 4.16 (3.87) 6.48(6.18)
4.94 (4.64)
1.07 43.61 (43.43) 3.94 (4.20) 12.72(12.60) 9.69 (10.11)
4.73 47.08 (47.00) 4.22 (4.25) 12.67(12.30) 9.66 (9.72)
aMagnetic moment at 30◦C.

METAL COMPLEXES OF SCHIFF BASE
653
in chelation. Further evidence of the metal ions was shown by
the appearance of weak low frequency new bands 529 and 460
cm−1, which can be assigned for υ(M-N) and υ(M-O). The IR
spectra of Ni(II) complex display an additional new bands at
360–365 cm−1, assigned to υ(M-S).[13,14] In the IR spectrum
of the complexes (M-S) bands could not be observed, that we
study in 4000–400 cm−1
.
These new bands were observable only in the spectra of the
metal complexes and not in the spectra of the uncomplexed
Schiff base and thus confirm the participation of these het-
eroatoms (N, O or S) in the coordination.[15]
FIG. 2. Suggested structure of the octahedral Co(II) complex of the ligand
(L).
In the spectra Co(II) and Ni(II) complexes, the IR bands at
894-831 and 816 cm−1, respectively, υ(H2O) of coordinated
water is an indication of the binding of the water molecules
to the metal ions. New bands are found in the spectra of the
complexes in the regions 513, 529 cm−1, respectively, which
are assigned to υ(M-O) stretching vibrations.[16]
In the Co(II) complex the chloride ions do not coordinate
with the metal ions. In the CI− test with AgNO3, precipitation
of white AgCI salt is immediately evident.
1H-NMR Spectra
1
The H-NMR spectrum of the free ligand (L) was run in
FIG. 3. Suggested structure of the octahedral Ni(II) complex of the ligand
(L).
dimethylsulfoxide (DMSO-d6) solution using tetramethylsilane
(TMS) as internal standart. All the protons of the ligand were
found to be in their expected region. The conclusions drawn
from these studies lend further support to the mode of bonding
discussed in IR spectra. The number of protons calculated from
the integration curves. The 1H-NMR spectra of the free ligand
showed a singlet at 10.10 ppm due to the aldehide proton, a
singlet at 9.10 ppm due to the azomethine proton, the broad
multiplet in the range 8.20–6.80 ppm due to the aromatic protons
and aliphatic protons at 1.20, 3.40 ppm.[17,18] Since all the metal
1
complexes are paramagnetic, their H-NMR spectra could not
be obtained.
Magnetic Susceptibility and Electronic Spectra
Measurements
FIG. 4. Suggested structure of the octahedral Cu(II) complex of the ligand
(L).
The UV-vis spectra of the ligand and the complexes were
recorded in the DMF solution in the wavelength range from
200 to 1000 nm. The corresponding magnetic susceptibility and
electronic spectra measurements are collected in Tables 1 and 3.
In the spectrum of the ligand (L), the bands 350–390 nm
range are assigned to the n → π∗ transitions of the azomethine
group and thiadiazole ring. During the formation complexes,
these bands are shifted to lower wavelength, suggesting that the
nitrogen atoms of the azomethine group and thiadiazole ring
are coordinated to the metal ion. The values in the 300–350 nm
range are attributed to the π → π∗ transition of the aromatic
and thiadiazole ring. In the spectra of complexes, these bands
are shifted slightly to lower wavelength.[19]
The electronic spectra of the Co(II) complex shows two bands
FIG. 5. Suggested structure of the octahedral Fe(II) complex of the ligand
(L).
4
observed 505, 570 nm which may be assigned 4T1g(F) → T1g(P)

654
N. TURAN AND M. SEKERCI
TABLE 2
Characteristic IR bands (cm−1) of the ligand (L) and its complexes in KBr pellets
Assignment
Ligand
Co(II)
Ni(II)
Cu(II)
Fe(II)
υ(OH)
—
3090–3082
2865–2806
2757
3400–3384
3095
2967–2923
2754
3373
—
2972–2865
2757
3364
3090–3060
2866–2806
2757
3480–3300
3186
2974–2850
2750
Aromatic υ(C H)
Aliphatic υ(C H)
υ(CH) COH
υ(C O)
1692
1693
1687
1692
1690
υ(CH N)
1629
1604
1610
1607
1607
υ(>C N N C<)
υ( N N)
υ(C S C)
υ(M O)
1498–1444
1045–980
772
1496–1440
1050–977
765
1460–1434
1050–943
762
1490–1440
1040–975
766
1494–1430
1044–952
770
—
513
529
—
—
υ(M N)
—
471
460
460
470
4
and 4T1g(F) → A2g(F) transitions, respectively, and are of their
octahedral geometry around the cobalt ion.[20] The magnetic sus-
ceptibility measurement (4.11 B.M.) for the solid Co(II) com-
plex is also indicative of three unpaired electrons per Co(II) ion
suggesting consistency with their octahedral environment.[21]
The electronic spectra of Ni(II) complex shows d-d bands
in the region 544, 578-618, and 944 nm. These are assigned
is compatible with this complex having an octahedral structure.
The proposed structure is supported by magnetic moment (1.07
B.M.) measured for the complex.
The electronic spectra of the Fe(II) complex has a magnetic
moment value 4.73 B.M., which is consistent with two high spin
octahedral geometry. The diffuse reflectance spectrum shows
two absorption bands at 620 and 430 nm which are assigned to
2
5T2g → Eg transition and charge transfer, respectively.[24]
to the transitions 3A2g → T1g(F), 3A2g → T2g(F) and 3A2g(F)
3
3
→ T2g(F),[21,22] respectively, consistent with its well-defined
3
octahedral configuration. The proposed structure is supported
by magnetic moment (2.59 B.M.) measured for the complex.
The electronic spectra of the Cu(II) complex shows a
strong high-energy band at 315 nm and may be assigned to
Thermal Studies
The thermal stability of the ligand and its complexes were
investigated by a combination of TGA and DTA. The TGA
and DTA curves were obtained at a heating rate of 10◦C/min.
in a nitrogen atmosphere over the temperature range of 25–
800◦C. The thermal data are summarized in Table 4. The results
obtained are in good agreement with the theoretical formula
suggested from the elemental analyses. The weight losses for
2B1g → Egtransition.[23] The strong high-energy band, in turn,
2
is assignedto metal → ligandchargetransfer. Thebandobserved
at 431 nm is assigned to ligand → metal charge transfer band.[9]
On the other hand, the Cu(II) complex shows an absorption
2
2
band at 540 nm attributed to the Eg → T2g transition, which
TABLE 3
Electronic spectral data of the ligand (L) and its complexes (nm, ε) (in DMF)
Wavelength in nm (ε)
Compounds
Ligand (L)
304–354, 390 (1400a, 150)
π → π∗,n → π∗
307, 318 (175, 140)
π → π∗
—
—
—
[FeL2Cl2].C2H5OH
324, 430 (125, 100)
n → π∗
620 (50)
5T2g → Eg
2
L → M
[CoL(H2O)4].2Cl.H2O
302, 360 (3000, 2600)
505 (1000)
570 (500)
4
4
π → π∗,n → π∗
4T1g(F) → T1g(P)
4T1g(F) → A2g(F)
[Ni2LCl4(H2O)4].4H2O
[CuL2Cl2].2H2O
302, 370 (2300, 1300)
π → π∗,n → π∗
306 (750)
544 (830)
578–618 (2000, 1000)
944 (500)
3A2g(F) → T2g(F)
540 (25)
3
3
3A2g → T1g(F)
3A2g → T2g(F)
315 (250)
431 (190)
L → M
2
2
π → π∗
2B1g → Eg
2Eg → T2g
ε = molar extinction coefficient (L mol−1 cm−1), amaximum wavelength in 340 nm.

METAL COMPLEXES OF SCHIFF BASE
655
TABLE 4
Proposed decomposition steps and the respective mass losses of ligand (HL)-metal complexes
% Loss in weight
%Found(% calculated),
Equations
Temperature (◦C)
Decomp. products
C12H11N3SO [L]
C12H11N3SO
C10H6N3SO
C9H5N3S
C7H5N
25.50–115.16
115.16–200.36
200.36–300.24
300.24– 620.88
620.88–
—
Thermal stability
CH2CH3
CHO
11.84 (11.85)
11.84 (11.85)
34.29 (34.81)
C2N2S
[CoL(H2O)4].H2O
C12H21Cl2CoN3SO6
C12H19Cl2CoN3SO5
C12H11Cl2CoN3SO
C12H11CoN3SO
50.45–190.64
190.64–330.78
330.78–370.16
370.16–
3.87 (3.70)
15.59 (14.81)
15.25 (15.55)
H2O
4H2O
2Cl
[Ni2LCl4(H2O)4].4H2O
C12H27Cl4Ni2N3SO9
C12H19Cl4Ni2N3SO5
C12H11Cl4Ni2N3SO
C12H11Ni2N3SO
[CuL2Cl2].2H2O
C24H26Cl2CuN6S2O4
C24H22Cl2CuN6S2O2
C24H22CuN6S2O2
[FeL2Cl2].C2H5OH
C26H28Cl2FeN6S2O3
C24H22Cl2FeN6S2O2
C24H22FeN6S2O2
60.85–100.98
100.98–276.42
276.42–400.46
400.46–
11.85 (11.11)
10.37 (11.11)
21.88 (21.48)
4H2O
4H2O
4Cl
67.21–150.72
150.72–334.60
334.60–
5.45 (5.92)
10.73 (10.37)
2H2O
2Cl
50.64–184.46
184.46–334.16
334.16–
6.94 (6.66)
10.10 (10.37)
C2H5OH
2Cl
ligand and complexes were calculated within the corresponding of the coordination water. This assignment was also confirmed
temperature ranges. by the weight loss obtained by the TGA curve. The three stages
The ligand (L) is stable up to 115.2◦C but then decomposes in of the decomposition of Co(II) complex were irreversible.
three steps 115.2–200.4◦C, 200.4–300.2◦C and 300.2–620.8◦C.
The [Ni2LCl4(H2O)4].4H2O complex was stable up to
In the decomposition process of the ligand, the weight losses cor- 60.0◦C and its decomposition started at this temperature. The
respond to the removal of the CH2CH3, CHO and thiadiazole first step in the temperature range 60.9–100.9◦C may account
group at the first, second and third stage of decomposition, re- for the loss of water molecules of hydration (% experimen-
spectively. The DTA curve of the ligand exhibits three endother- tal weight 11.85; calculated weight 11.11). The second step
mic peaks at 104.4◦C, 190.3◦C, 217.3◦C, and one exothermic of decomposition within the temperature range 100.9–276.4◦C
peak at 313.6◦C. The three stages of the ligand decomposition corresponds to the loss of coordinated water molecules (% ex-
are irreversible.[25]
perimental weight 10.37; calculated weight 11.11). In the DTA
[CoL(H2O)4].2Cl.H2O complex a mass loss occur within the curve, sharp endothermic peak observed in range 158.2◦C for
temperature range 50.5–190.6◦C corresponding to the loss of the complex of Ni(II), in conjunction with the mass loss in the
hydrated water molecule (% experimental weight 3.87; calcu- TGA curve corresponding to four water molecules, confirm the
lated weight 3.70) and at the temperature range 190.6–330.8◦C stoichiometry [Ni2LCl4(H2O)4].4H2O for the Ni(II) complex.
corresponding to a loss of coordinated water molecules (% ex- In the temperature range 276.4–400.5◦C a mass loss occured
perimental weight 15.59; calculated weight 14.81). In the tem- corresponding to a loss of Cl ligands (% experimental weight
perature range 330.8–370.2◦C a mass loss occur corresponding 21.88; calculated weight 21.48). In the Ni(II) complex, the en-
to a losses of Cl ions (% experimental weight 15.25; calculated dothermic peak at 360.4◦C is related to the decomposition of Cl
weight 15.55)[26,27]
ligands.[28,29]
The DTA analysis of Co(II) complex also show endothermic
The thermal decomposition of the [CuL2Cl2].2H2O complex
peak around 326.1◦C. For this complex the endothermic peak started at 67.0◦C. The endothermic peak in the 216.2◦C temper-
in the temperature range 326.1◦C is assigned to the desolvation ature range for Cu(II) complex was assigned to the desolvation

656
N. TURAN AND M. SEKERCI
of the hydrated water (% experimental weight 5.45; calculated was refluxed for 8 h. After cooling, the solution of the Schiff
weight 5.92). This is followed by broad more or less strong base was stirred for an additional 10 min. and finally poured
exothermic peaks located at 200.5 and 276.2◦C corresponding into a beaker containing 100 mL of water. The new mixture was
to decomposition of the Cl ligands (% experimental weight allowed to stir for 20 min, and the resulting dark yellow solid
10.73; calculated weight 10.37).[30]
was collected by filtration, washed several times with water and
The decomposition curve of [FeL2Cl2].C2H5OH began by a dried in air for 48 h. The product was recrystallized from ethanol
step at 50.6–184.5◦C displaying 6.66 % weight loss correspond- and washed with cold ethanol. Yield: 0.29 g (60%)
ing to the removal of C2H5OH. The second weight loss stage at
184.5–334.2◦C refers to the removal of Cl ligands[31] (% exper-
Preparation of [CoL(H2O)4].2Cl.H2O
imental weight 10.10; calculated weight 10.37). The DTA curve
A warm methanol solution (20 mL) of ligand 0.74 g
of the Fe(II) complex exhibits endothermic peak at 83.66◦C cor-
(0.003 mol) was added to a magnetically stirred solution of
responding to the loss of C2H5OH and one exothermic peak at
CoCl2.6H2O 0.71 g (0.003 mol) in ethanol (10 mL). The mix-
320.1◦C corresponding to the loss of Cl ligands.
ture was refluxed for 10 h. Then the volume of the obtained so-
The finally products during thermal analysis of the ligand and
lution was reduced to one-half by evaporation and complex was
its complexes were not possible to identify because ligand and
precipitated by the addition of aceton-water (1:1) to give dark
its complexes undergo could not complete decomposition un-
red product. The precipitate was filtered, washed with methanol
til 800◦C temperature. The continuation of the decompositions
then dried at room temperature. Yield: 0.67 g (% 48).
indicate that a higher thermal stability of the complexes. Such
stability may refer to the presence of one or/two five-membered
rings.[32]
Preparation of [Ni2LCl4(H2O)4].4H2O
A quantity of 0.74 g (0.003 mol) of ligand (L) in methanol (20
mL) was added to a solution of 1.43 g (0.006 mol) NiCl2.6H2O
in methanol-water mixture (1:1), 10 mL. The mixture was left
under reflux with continuous stirring for 10 h where upon the
solid complex precipitated. The resulting solid was washed with
water followed by diethl ether and dried in a room temperature.
Yield: 1.05 g (% 54).
Single crystals of the complexes could not be isolated from
any solutions, thus no definite structure could be described.
However, the analytical, spectrospic and magnetic data enable
us to propose the possible structure.
EXPERIMENTAL
Materials and Physical Measurements
Preparation of [CuL2Cl2].2H2O
All solvents were analytical grade reagents, used as
purchased. The metal salts CoCI2.6H2O, CuCI2.2H2O,
NiCI2.6H2O and FeCI2.6H2O and starting materials for the lig-
and were Merck, Aldrich, Fluka and Alfa Aesar products.
Elemental analyses were carried out on a Leco CHNS-O
model 932 elemental analyzer. 1H-NMR spectra were recorded
using a model Bruker GmbH DPX-300 MHz FT spectrome-
ter. IR spectra were recorded Perkin Elmer Precisely Spectrum
One spectrometer on KBr discs in the wavenumber range of
4000–400 cm−1. Electronic spectral studies were conducted on
a Shimadzu model UV-1700 Spectrophotometer in the wave-
length 1000–200 nm. Magnetic susceptibilities measurements
were performed using the standard Gouy tube technique us-
ing Hg[Co(SCN)4] as a calibrant. Thermal analyzers (TGA and
DTA) were carried out in nitrogen atmosphere with a heating
rate of 10◦C/min. using Shimadzu DTG-60 AH (Shimadzu DSC
60 A) thermal analyzers.
1.49 g (0.006 mol) of ligand (L) was dissolved in 20 mL
absolute methanol in a 100 mL round bottom flask. A solution of
0.51 g (0.003 mol) of CuCl2.2H2O in 10 mL absolute methanol-
water mixture (1:1) was added dropwise in a 10 min. period with
continuous stirring at room temperature. The mixture refluxed
overnight. Then the volume of the solutions was reduced to
about 10 mL and complex were precipitated with aceton-water
(1:1) to give pale green product. The precipitate was filtered,
washed with methanol then dried at room temperature. Yield:
1.15 g (% 58).
Preparation of [FeL2Cl2].EtOH
A warm methanol solution (20 mL) of ligand 1.47 g (0.006
mol) was added to a magnetically stirred solution of FeCl2.6H2O
0.70 g (0.003 mol) in ethanol (15 mL). The mixture was refluxed
overnight. Then the volume of the obtained solution was reduced
to one-half by evaporation. One day later, the colored solid of
the complex formed was filtered, the solid washed with ethanol
and methanol, and finally dried at room temperature. Yield: 1.09
g (% 55).
Preparation of Ligand
N-(5-Ethyl-1,3,4-Thiadiazole-2-yl)Terephthalaldehyde
Imine (L, C12H11N3SO)
2-Amino-5-ethyl-1,3,4-thiadiazole 0.26 g (0.002 mol) in
ethanol 20 mL was added to a hot ethanol solution 15 mL
of terephthalaldehyde 0.27 g (0.002 mol). The pH was adjusted
to ≈5 using glacial acetic acid (3 mL) . The resultant solution
REFERENCES
1. Shen, X-Q., Li, Z-J., Zhang, H-Y., Qiao, H-B., Wu, Q-A., Wang, H-Y., Zu,
Y. Structure and thermal behaviors of organic crystals based on substituted

METAL COMPLEXES OF SCHIFF BASE
657
1,3,4-thiadiazoles. Journal of Physics and Chemistry of Solids, 2005, 66,
17. Uc¸an, S.Y., and Uc¸an, M. Synthesis and characterization of new Schiff
bases and their cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II) and
mercury(II) complexes. Synthesis and Reactivity Inorganic, Metal-Organic
and Nano-Metal Chemistry, 2005, 35, 417–421.
18. Refat, M.S., El-Deen, I.M., Ibrahim, H.K., and El-Ghool, S., 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. Spectrochimica Acta Part A, 2006, 65, 1208–1220.
19. Turan, N., C¸ olak, N., and Sekerci, M. Synthesis and characterization
of Cu(II), Ni(II) and Cd(II) complexes with 3,5-diamino-4-(4-bromo-
phenylazo)-1H-pyrazole. International Journal of Natural and Engineering
Sciences, 2008, 2(3), 28–32.
1755–1760.
¨
¨
2. Oztu¨rk, O.F., Cansız, A., and Koparır, M. Preparation and characteriza-
tion of Co(II), Ni(II), and Cu(II) complexes of a ligand containing 1,3,4-
thiadiazole groups. Transition Metal Chemistry, 2007, 32, 224–227.
3. Chohan, H.Z., Pervez, H., Rauf, A., Scozzafava, A., and Supuran, C.T.
Antibacterial Co(II), Cu(II), Ni(II) and Zn(II) complexes of thiadiazole
derived furanyl, thiophenyl and pyrrolvl Schiff bases. Journal of Enzyme
Inhibition and Medicinal Chemistry, 2002, 17(2), 117–122.
4. Balaban, A., Sekerci, M., and Erk, B. Synthesis, physico-chemical char-
acterization and stability constants of metal complexes of pyridine-2-
carbaldehyde thiosemicarbazone. Synthesis and Reactivity Inorganic and
Metal-Organic Chemistry, 2003, 33, 1775–1786.
20. Sivasankaran Nair, M., Selwin and Joseyphus, R. Synthesis and character-
ization of Co(II), Ni(II), Cu(II) and Zn(II) complexes of tridentate schiff
base derived from vanilin and DL-α-aminobutyric acid. Spectrochimica
Acta, 2008, 70, 749–753.
¨
5. Topal, G., Temel, H., Yavuz, O., Cos¸kun, M., and Sekerci, M. Prepara-
tion of new o-carboxyaniliotellurium(IV)bromides and their dyeing proper-
ties. Synthesis Reactivity Inorganic Metal-Organic Chemistry, 2001, 31(6),
1097–1107.
6. Ilhan, S., Temel, H., Yilmaz, I., and Sekerci, M. Synthesis, structural charac-
terization and electrochemical studies of new macrocyclic schiff base con-
taining pyridine head and its metal complexes. Journal of Organometallic
Chemistry, 2007, 692, 3855–3865.
7. Saydam, S. Synthesis and characterization of the new thiazole schiff
base 2-(2-hydroxy)naphthylideneaminobenzothiazole and its complexes
with Co(II), Cu(II), and Ni(II) ions. Synthesis Reactivity Inorganic Metal-
Organic Chemistry, 2002, 32(3), 437–447.
8. Al-Awadi, N., Shuaib, N.M., and El-Dissouky, A. Synthesis and spectro-
scopic characterization of nickel(II) complexes of 1-benzotriazol-yl-[(p-x-
phenyl) hydrazone] propan-2-one. Spectrochimica Acta Part A, 2006, 65,
36–43.
¨
¨
¨
21. Oztu¨rk, O.F., Sekerci, M., and Ozdemir, E. Preparation of complexes of 1-
amino-6,7-0-cyclohexylidene-4-azaheptane with transition metal acetates.
Russian Journal of General Chemistry, 2006, 76, No. 1, 33–36.
22. Patel, N.H., Patel, K.M., Patel, K.N., and Patel, M.N. Coordination chain
polymers of some transition metals with Schiff base. Synthesis and Reac-
tivity Inorganic, Metal-Organic and Nano-Metal Chemistry, 2001, 31(6),
1031–1039.
23. Chohan, Z.H., Pervez, H., Rauf, A., Khan, K.M., and Supuran, C.T. Isatin-
derived antibacterial and antifungal compounds and their transition metal
complexes. Journal of Enzyme Inhibition and Medicial Chemistry, 2004,
19(5), 417–423.
24. Sharaby, C.M. Synthesis, spectroscopic, thermal and antimicrobial stud-
ies of some novel metal complexes of Schiff base derived from [N1-(4-
methoxy-1,2,5-thiadiazol-3-yl)sulfanilamide] and 2-thiophene carboxalde-
hyde. Spectrochimica Acta Part A, 2007, 66, 1271–1278.
9. So¨nmez, M., Levent, A., and Sekerci, M., Synthesis, characterization and
thermal investigation of some metal complexes containing polydentate
ONO-donor heterocyclic Schiff base ligand. Russian Journal of Coordi- 25. Turan, N. Synthesis and Characterization of complexes of Schiff base lig-
nation Chemistry, 2004, 30, 655–659.
ands thiadiazole derivative. Firat University, PhD Thesis, Elazigˇ, Turkey,
2008.
26. Abdel-Latif, S.A., Hassib, H.B., Issa, Y.M., Abdel-Latif, S.A., Hassib, H.B.,
and Issa Y.M. Studies on some salicylaldehyde Schiff base derivatives
and their complexes with Cr(III), Mn(II), Fe(III), Ni(II) and Cu(II). Spec-
trochimica Acta Part A, 2007, 67, 950–957.
10. Abu-El-Wafa, S.M., El-Wakiel, N.A., Issa, R.M., and Mansour, R.A. For-
mation of novel mono- and multi-nuclear complexes of Mn(II), Co(II) and
Cu(II) with bis azo-dianils containing the pyrimidine moiety: Thermal,
magnetic and spectral studies. Journal of Coordination Chemistry, 2005,
58, 683–694.
11. Srivasvata, A.K., Pandey, O.P., and Sengupta, S.K. Synthesis spectral and 27. Sekerci, M., and Tas, E. The Synthesis and characterization of 1,2-O-
antimicrobial studies of bis(cyclopentadienyl)titanium(IV) derivatives with
Schiff base derived from 2-amino-5-phenyl-1,3,4-tihiadiazole. Bioinor-
ganic Chemistry and Applications, 2005, 3, 3–4.
cyclohexylidene-4-aza-8-aminooctane and some of its transition metal com-
plexes. Heteroatom Chemistry, 2000, 11: No. 4. 254–260.
¨
28. Olmez, H., Arslan, F., and Icbudak, H. Spectrothermal studies on Co(II),
12. Nath, M., Kumar, A., and Vashistha, S., Synthesis, spectral and thermal
studies of Co(II), Ni(II), Cu(II) and Zn(II) complexes of schiff bases de-
Ni(II), Cu(II) and Zn(II) salicylato (1,10-phenanthroline) complexes. Jour-
nal of Thermal Analysis and Calorimetry, 2004, 76, 793–800.
rived from 2-amino-5-aryl-1,3,4-thiadiazole. Synthesis Reactivity Inorganic 29. Sekerci, M., and Alkan, C. The synthesis and Co(II), Cu(II), Ni(II)
Metal-Organic Chemistry, 1998, 28(6), 893–906.
and UO2(VI) complexes of 1,2-o-benzal-4-aza-7-aminoheptane. Synthe-
sis Reactivity Inorganic, Metal-Organic Chemistry, 1999, 29(10), 1685–
1697.
13. Masoud, M.S., Soayed, A.A., Ali, A.E., and Sharsherh, O.K. Synthesis and
characterization of new azopyrimidine complexes. J. Coord. Chemistry,
2003, 56, 725–742.
14. Philip, V., Suni, V., Kurup, M.R.P., and Nethaji, M. Copper(II)
complexes derived from di-2-pyridyl ketone N(4),N(4)-(butane-1,4-
diyl)thiosemicarbazone: Crystal structure and spectral studies. Polyhedron,
2006, 25, 1931–1938.
15. Tsai, P.C., and Wang, I.J. Synthesis and solvatochromic properties of some
disazo dyes derived from pyrazolo[1,5-A]pyrimidine derivatives. Dyes and
Pigments, 2005, 64, 259–264.
30. Sekerci, M. Magnetospectral and thermal studies of cobalt(II), nickel(II)
and copper(II) complexes of new asymmetrical 1,2-dihydroxyimino-3,8-
diaza-9-phenylnonane. Russian Journal of Inorganic Chemistry, 2000, 45,
1525–1530.
31. Olar, R., Badea, M., Stanica, N., Cristurean, E., and Marinescu, D. Syn-
thesis, characterisation and thermal behaviour of some complexes with
ligands having 1,3,4-thiadiazole moieties. Journal of Thermal Analysis and
Calorimetry, 2005, 82, 417–422.
16. Vats, S., and Sharma, L.M. Synthesis and spectroscopic investigations of
Mn(II), Co(II), Ni(II), Rh(III), Ru(III) and Ir(III) complexes with 2-furyl(m-
aminophenylenimine)methyl ketone. Synthesis Reactivity Inorganic Metal-
Organic Chemistry, 1997, 27(10): 1565–1579.
32. El-Metwally, N.M., Gabr, I.M., Shallaby, A.M., and El-Asmy, A.A. Syn-
thesis and spectroscopic characterization of new mono- and binuclear com-
plexes of some NH(1) thiosemicarbazides. Journal of Coordination Chem-
istry, 2005, 58, No.13, 1145–1159.