Synthesis and genotoxicity of schiff base transition metal complexes

Article abstract of DOI:10.1002/hc.20665

A new ONNO-type azomethine ligand, 2,2′-(ethane-1,2- diylidenedinitrilo)dibenzoic acid, (YLH₂) (1) has been prepared by the condensation of 2-aminobenzoic acid and glyoxal. The coordination compounds [Ni(YL)] (2), [Co(YL)] (3), [Cu(YL)(H_2<

Full text of DOI:10.1002/hc.20665

Heteroatom Chemistry
Volume 22, Number 2, 2011
Synthesis and Genotoxicity of Schiff Base
Transition Metal Complexes
Yasemin Kara,1 Baris Avar,2 Ahmet Kayraldiz,3 Bilgehan Guzel,4
and Mukerrem Kurtoglu1
1Department of Chemistry, Faculty of Science and Arts, Kahramanmaras Sutcu Imam University,
46050, Kahramanmaras, Turkey
2Department of Physics, Faculty of Science and Arts, Kahramanmaras Sutcu Imam University,
46050, Kahramanmaras, Turkey
3Department of Biology, Faculty of Science and Arts, Kahramanmaras Sutcu Imam University,
46050, Kahramanmaras, Turkey
4Department of Chemistry, Faculty of Science and Arts, Cukurova University, 01330,
Adana, Turkey
Received 2 September 2010; revised 7 October 2010
ꢁ
C
genotoxic potential.
2011 Wiley Periodicals, Inc.
ABSTRACT: A new ONNO-type azomethine ligand,
2,2ꢀ-(ethane-1,2-diylidenedinitrilo)dibenzoic
acid,
Heteroatom Chem 22:119–130, 2011; View this article
online at wileyonlinelibrary.com. DOI 10.1002/hc.20665
(YLH2) (1) has been prepared by the condensation
of 2-aminobenzoic acid and glyoxal. The coordi-
nation compounds [Ni(YL)] (2), [Co(YL)] (3),
[Cu(YL)(H2O)] (4), [Zn(YL)] (5), and [Cd(YL)] (6)
of the YLH2 ligand with five transition metal ions,
Ni(II) Co(II), Cu(II), Zn(II), and Cd(II) have been
prepared. The structures of these new azomethine
compounds are proposed on the basis of the elemen-
tal analyses, proton nuclear magnetic resonance,
infrared, ultraviolet–visible spectroscopy, and X-ray
powder diffraction patterns. Elemental analyses
indicate a ligand metal ratio of 1:1 in the coordination
compounds. X-ray powder diffraction parameters
for [Cu(YL)(H2O)] and [Cd(YL)] compounds corre-
spond to orthorhombic and monoclinic structures,
respectively. The ligand acts as a tetradentate ligand
bending through oxygen atoms of the hydroxyl
groups of benzoic acid and nitrogen atoms of the
azomethine groups. In addition, the ligand and its
metal complexes have been studied for their possible
INTRODUCTION
Benzoic acid derivatives substituted by a hydroxy
group or ether-containing oxygen atom have active
bacteriostatic and fragrant properties. They are
typically used in pharmaceutical and perfumery
industry. Anthranilic acid, amino group substi-
tuted benzoic acid at ortho position, is used as
an intermediate for production of dyes, pigments,
and saccharin. It has amino and carboxylic groups
attached in a ring structure. It and its esters are used
in preparing perfumes, pharmaceuticals, and UV-
absorber as well as corrosion inhibitors for metals
and mold inhibitors in soya sauce. Schiff base lig-
ands act as good chelating agents for the transition
and nontransition metal ions [1–4]. Coordination of
these compounds with metal ions, such as copper,
nickel, and iron, often enhances their activities
[5] as has been reported for pathogenic fungi [6].
There is a continuing interest in metal complexes of
Schiff bases. Because of the presence of both hard
nitrogen and oxygen donor atoms in the backbones
Correspondence to: Mukerrem Kurtoglu; e-mail: mkurtoglu@
ksu.edu.tr.
c
ꢀ
2011 Wiley Periodicals, Inc.
119

120 Kara et al.
of these ligands, they readily coordinate with a
wide range of transition metal ions, yielding stable
and intensely colored metal complexes. ONNO-type
Schiff bases are very interesting ligands, since they
have four coordination atoms. They are the oxygen
atoms of the OH or COOH groups and nitrogen
atoms of the CH N groups. Some of which have
been shown to exhibit interesting physical and
chemical properties [7] and potentially useful bio-
logical activities [8]. Many complexes of Schiff-base
ligands with metal ions have been investigated as
models for active sites of enzymes [9,10], including
DNA-cleavage systems [11,12], and as antibacterial
[13–15] and anticancer [16,17] drugs.
Testing of genotoxicity is mandatory and a pre-
liminary step in the safety assessments for the newly
synthesized chemicals including pharmaceuticals,
food additives, and industrial substances [18–20].
The bacterial Ames test, developed by Dr. Bruce
Ames in 1975 [21], is a widely used screening test
for the possible genotoxic effects of chemical com-
pounds (the ability to induce mutation or cancer).
The assay done in Salmonella typhimurium bacteria
gives much faster and less expensive results as com-
pared to standard tests for carcinogenicity done on
animals, which take years to complete and are ex-
pensive to do [22,23]. Test strains of S. typhimurium
(TA 98 and TA 100) that carries different types of mu-
tation in the histidine operon are used in the Ames
test for detecting reverse mutation in the histidine
gene of tester strains that was caused by mutagenic
compounds.
In our laboratory, we have been investigat-
ing the synthesis, spectral and biological properties
of the metal complexes of various bidentate and
or polydentate ligands [24–27]. In this paper, be-
cause of the importance of the azomethine com-
pounds and in continuance of our interest in syn-
theses of azomethine compounds, we report synthe-
ses, complex formation, characterization using dif-
ferent techniques in particular elemental analyses,
infrared and electronic spectra of 2,2ꢀ-(ethane-1,2-
diylidenedinitrilo)dibenzoic acid, which was synthe-
sized by the reaction of glyoxal and anthranilic acid
in EtOH solution at boiling point. We examined its
complexing ability with Ni(II), Co(II), Cu(II), Zn(II),
and Cd(II) salts. The proposed structure of the lig-
and and its metal chelates are given in Figs. 1 and 2,
respectively.
Co(CH3COO)2 and Cu(CH3COO)2·H2O (Merck,
Darmstadt, Germany), Zn(CH3COO)2 and
Cd(CH3COO)2 were used as purchased with no
additional purification. All solvents were reagent
grade and used without further purification.
Physical Measurements
The microanalysis of carbon, hydrogen, and nitro-
gen and proton NMR spectra of the ligand and Zn(II)
metal complex were performed by the TUBITAK
analyses center, Ankara, Turkey. Infrared spectra
(KBr disk) were recorded in the 4000–400 cm−1
range on a Perkin-Elmer RX-1 FT-IR spectrometer.
Electronic spectra were obtained on a Perkin-Elmer
Lambda 25 UV spectrometer. X-ray powder diffrac-
tion analysis was performed by PANanalytical X’Pert
PRO instrument with Cu Kα radiation (wavelength
0.154 nm) operating at 40 kV and 30 mA. Measure-
ments were scanned for diffraction angles (2θ) rang-
ing from 5◦ to 50◦ with a step size of 0.02◦ and a
time per step of 1 s. Melting points were obtained
with an Electrothermal LDT 9200 Apparatus in open
capillaries.
2,2ꢀ-(Ethane-1,2-diylidenedinitrilo)dibenzoic
acid, YLH2
A hot solution (40◦C) of anthranilic acid (5.50 g, 0.04
mol) in 25 mL EtOH was mixed with hot solution
(40◦C) of glyoxal (3.0 g, 0.02 mmol) in the same sol-
vent (15 mL), and the reaction mixture was stirred
magnetically under reflux for a day. The formed dark
yellow product was dissolved in 25 mL EtOH and left
for crystallization at room temperature for a day.
Then dark brown products were collected, washed
with cold EtOH, and dried in a vacuum. Yield, 1.04
g. Elemental analyses for C16H12N2O4(296.28 g/mol);
Calcd.: C, 64.86; H, 4.08; N, 9.46%. Found: C, 62.34;
H, 3.78; N, 10.12%. IR (KBr pellet, cm−1): 3330
(OH), 3078 (aromatic C H), 2900 ( CH CH ), 1714
(C O), 1624 ( CH N ).
Synthesis of [2,2ꢀ-(Ethane-1,2-diylidenedinitrilo)
dibenzoato]nickel(II),
[Ni(YL)]
(2). 1.04
g
(3.5 mmol) of 2,2ꢀ-(ethane-1,2-diylidenedinitrilo)
dibenzoic acid ligand was dissolved in 10 mL abso-
lute EtOH at room temperature (Fig. 1). A solution
of 0.89 g (3.75 mmol) NiCl2·6H2O (15 mL) was
added dropwise into 15 mL of absolute EtOH with
continuous stirring. The stirred mixture was then
heated to the reflux temperature and maintained at
this temperature for 2–3 h. Then, the mixture was
evaporated to a volume of 10 mL in vacuum and left
to cool to the room temperature. The product was
filtered in vacuum and washed with a small amount
EXPERIMENTAL
Reagents
Anthranilic acid and glyoxal were purchased
from Aldrich (Steinbaum, Germany). NiCl2·6H2O,
Heteroatom Chemistry DOI 10.1002/hc

Synthesis and Genotoxicity of Schiff Base Transition Metal Complexes 121
Synthesis of [2,2ꢀ-(Ethane-1,2-diylidenedinitrilo)
dibenzoato]zinc(II), [Zn(YL)] (5). This dark green
compound was prepared by the addition of
Zn(CH3COO)2 (0.76 g, 3.5 mmol) in EtOH (15 mL) to
a refluxing mixture of the ligand 3.5 mmol (1.03 g)
YLH2 (0.34 g, 1 mmol) in absolute EtOH (10 mL).
The dark green compound was separated out on
filtration, washed with cold EtOH, and dried in
vacuo. Yield, 1.02 g (81%). Elemental analyses for
C16H10N2O4Zn (359.65 g/mol); Calcd.: C, 53.43; H,
2.80; N, 7.79%. Found: C, 53.21; H, 2.77; N, 7.51%.
IR (KBr pellet, cm−1): 3047 (Ar C H), 1614 (C N),
1592 (ArC C), 1541 νas(OCO), 1326 νs(OCO), 630
(M – O), 445 (M – N).
FIGURE 1 Conformation of the ligand.
Synthesis of [2,2ꢀ-(Ethane-1,2-diylidenedinitrilo)
dibenzoato]cadmium(II), [Cd(YL)] (6). To a solu-
tion of the YLH2 ligand (1.03 g, 3.5 mmol) in EtOH
(15 mL) was added, a solution of Cd(CH3COO)2 (0.93
g, 3.5 mmol) in EtOH and the resulting solution
was boiled under reflux for 24 h. The precipitated
reddish brown complex was filtered, washed with
cold EtOH, and dried in vacuo.Yield, 1.19 g (83%).
of cold ethanol. The product was recrystallized from
EtOH and it was dried at room temperature. Yield,
0.88 g (54%). mp >300◦C. Elemental analyses for
C16H10N2NiO4 (352.96 g/mol); Calcd.: C, 54.45; H,
2.86; N, 7.94; Ni, 16.63%. Found: C, 53,86; H, 2.98;
N, 7.75; Ni, 17.02%. IR (KBr pellet, cm−1): 3015
(aromatic C H), 1613 ( CH N), 1554 νas (OCO),
1326 νs (OCO), 665 (M – O), 460 (M – N).
◦
mp> 300 C. Elemental analyses for C16H10CdN2O4
(406.67 g/mol); Calcd.: C, 47.25; H, 2.48; N, 6.89%.
Found: C, 47.20; H, 2.61; N, 7.02. IR (KBr pellet,
cm−1): 3047 (Ar C H), 1614 (C N), 1588 (Ar C C),
1535 νas (OCO), 1399 νs (OCO), 645 (M – O), 453
(M – N).
Synthesis of [2,2ꢀ-(Ethane-1,2-diylidenedinitrilo)
dibenzoato]cobalt(II), [Co(YL)] (3). An ethano-
lic solution (15 mL) of Co(CH3COO)2 (0.63 g,
3.18 mmol) was added gradually to an ethanolic so-
lution (35 mL) of the ligand (1.03 g (3.5 mmol). The
solution was stirred for 2 h, and a green precipitate
was formed. The precipitate was filtered, washed
with EtOH and then Et2O, and finally air-dried.
The yield was 0.75 g (60%). mp ꢂ>300◦C. Elemental
analyses for C16H10CoN2O4 (353.19 g/mol); Calcd.:
C, 54.41; H, 2.85; N, 7.93%. Found: C, 54.72; H,
2.45; N, 8.42%. IR (KBr pellet, cm−1): 3045 (ArC H),
1613 ( CH N ), 1538 νas (OCO), 1326 νs (OCO), 680
(M – O), 490 (M – N).
Ames Test
Chemicals. All the test substances (YLH2,
[Ni(YL)], [Co(YL)], [Cu(YL)(H2O)], [Zn(YL)] and
[Cd(YL)]) were suspended in DMSO with the fi-
nal concentrations of 0.25, 0.125, 0.062, 0.031,
and 0.015 mg/plate, for testing mutagenicity. Mu-
tagenicity test tablets containing nicotinamide ade-
nine dinucleotide phosphate (NADP), and glucose-6-
phosphate (G-6-P) were purchased from Boehringer
Mannheim Biochemicals (Mannheim, Germany).
DMSO (D8418), 1-histidine (H8125), d-biotin
(B4501), ampicillin (A6140), sodium azide (SA,
S2002), and 2-aminofluorene (2-AF, A9031) were
purchased from Aldrich; agar (7178) was purchased
from Aquamedia (Darmstadt, Germany); nutrient
broth (NB, B241116) was purchased from Oxoid
(Darmstadt, Germany); 3-methylcholanthrene (200-
276-4) was purchased from Oekanal (Lyon, France).
In this study, 2-AF (dissolved in DMSO), NPD
(4-nitro-o-phenylene diamine) (dissolved in DMSO),
and SA (dissolved in bidistilled water) were used pos-
itive controls.
Synthesis of [2,2ꢀ-(Ethane-1,2-diylidenedinitrilo)
dibenzoato(aqua)]copper(II), [Cu(YL)(H2O)] (4). A
solution of Cu(CH3COO)·H2O (0.49 g, 2.5 mmol)
in EtOH (15 mL) was added to the ligand solution
(3.5 mmol, 1.0370 g) in EtOH (10 mL), and the mix-
ture was refluxed with stirring for 2 h. After strip-
ping off the excess solvent under reduced pressure, a
brown product was obtained. Yield, 0.37 g (38%). El-
emental analyses for C16H12CuN2O5 (393.26 g/mol);
Calcd.: C, 50.22; H, 2.97; N, 7.85%. Found: C, 51.12;
H, 2.61; N, 7.22%. IR (KBr pellet, cm−1): 3427 (OH),
3274, 3047 (ArC H), 1606 (C C), 1553 νas(OCO),
1378 νs (OCO), 825 (coord. H2O), 670 (M – O), 475
(M – N).
Preparations of S9. The albino male rats
(Rattus norvegicus var. albinos) weighing 200 g
Heteroatom Chemistry DOI 10.1002/hc

122 Kara et al.
were pretreated with 80 mg/kg concentration of
3-methylcholanthrene (dissolved in sunflower oil)
for 5 days, and the S9 fraction and S9 mix were pre-
pared following the procedure of Maron and Ames
[28]. S9 fraction (microsome fraction) was prepared
and immediately distributed to small plastic tubes
at 1 mL quantity and then stored at –35◦C. The S9
mix was prepared fresh for each mutagenicity assay.
For preparation of S9 mix, one S9 tablet dissolved
in 18 mL of sterile bidistilled water supplemented
with 2 mL of microsome fraction; 0.5 mL of S9 mix
was used for each plate. S9 mix contains microsome
fraction, NADP, G-6-P, and other salt solutions [28].
O
O
O
N
O
N
M
M = Ni(II), Cu(II)(H2O), Co(II), Zn(II), and Cd(II)
FIGURE 2 Proposed structure of the metal complexes.
metal complexes of the YLH2 ligand were prepared
by adding an ethanolic solution of the metal(II)
salt solution to a solution of the ligand in absolute
ethanol. The ligand and its metal complexes were
formed only in the powder form, which was not
suitable for single X-ray diffraction analysis. Further
attempts to get crystals were not successful. The
YLH2 ligand on interaction with metal(II) salts
yielded complexes corresponding to the general
formula [M(YL)]. The complexes of the ligand
(YLH2) have the stoichiometry [M(YL)] (Ni(II),
Co(II), Cu(II), Zn(II), and Cd(II)) with the Schiff
base ligand. Coordination occurs via the carboxyl
oxygen and the imine nitrogens of the ligand.
The new tetradentate ligand, gave mononuclear
complexes (Fig. 2) with Ni(II), Co(II), Cu(II), Zn(II),
and Cd(II) as follows:
Bacterial Strains. Histidine-deficient (his−)
tester strains TA98 and TA100 of S. typhimurium
were kindly provided by J. L. Swezey (Curator, ARS
Patent Culture Collection, Microbial Genomics and
Bioprocessing Research Unit, Peoria, Illinois). The
TA100 strain is used for the detection of base-pair
substitution mutagens, and TA98 strain is used for
the detection of frameshift mutagens. Each strain
before use in the assay was checked for the presence
of strain-specific marker as described by Maron and
Ames [28].
Mutagenicity Assay. A standard procedure of
plate incorporation assay was carried out by us-
ing TA98 and TA100 strains for examining the
frameshift mutagens and base-pair substitution mu-
tagens, respectively. Using both strains, the Ames
test was performed with metabolic activation (+S9
mix) to obtain a first approximation of mammalian
metabolism, and without metabolic activation
(–S9 mix). The assay was carried out according to
Kayraldiz et al. 2006 [29]. TA98 and TA100 strains
were exposed to a range of concentrations of each
test substance in a soft agar overlay. The number
of revertants observed in each concentration of test
substances and in spontaneous control was scored.
YLH2 + MX2 · nH2O → [M(YL)] + 2HX + nH2O
where YLH2 is 2,2ꢀ-(ethane-1,2-diylidenedinitrilo)
dibenzoic acid and M is Ni(II), Co(II), Zn(II), Cd(II)
and Cu(II)·H2O, X is Cl or CH3COO, and nis 6 and 2.
The level of impurity in the products was
checked by TLC technique. The newly synthesized
tetradentate ONNO donor Schiff base ligand (YLH2)
and its complexes with metal ions are stable at atmo-
spheric temperature and pressure. They are insolu-
ble in organic solvents such as methanol, ethanol,
and acetone whereas these are soluble in coordinat-
ing solvents such as DMF and DMSO. Single crystals
of the new ligand and its transition metal chelates
could not be isolated from any organic solution;
thus, no definite structures could be described. How-
ever, the analytical and spectroscopic data enables
us to predict possible structures as shown in Figs. 1
and 2.
Statistical Significance. The observed differ-
ences between the test substances and control
groups (spontaneous control and positive control)
were analyzed by the t-test. Regression and correla-
tion tests were used for dose–response relationships.
RESULTS AND DISCUSSION
Electronic Spectra
2,2ꢀ-(Ethane-1,2-diylidenedinitrilo)dibenzoic acid
(YLH2) (1) Schiff base ligand was synthesized
by condensing glyoxal (a dialdehyde) and
2-aminobenzoic acid (an amine) in ethanol at
reflux temperature. The crude ligand was purified
by crystallization from ethanol. The mononuclear
The electronic spectra of the azomethine ligand and
its metal chelates were recorded in DMSO between
200 and 800 nm. The UV–vis absorption of the
synthesized azomethine ligand (1) YLH2 displays
mainly three bands observed in the DMSO solution
Heteroatom Chemistry DOI 10.1002/hc

Synthesis and Genotoxicity of Schiff Base Transition Metal Complexes 123
TABLE 1 UV–Visible (nm) Data of the Synthesized Ligand and Its Metal Complexes in DMSO
Absorption
π → π∗ (CH N)
λ
max (nm)
Compound
π → π∗ (Ar. ring)
π → π∗ (Ar. ring)
n → π∗ (CH N)
d → d
(1) YLH2
221
224
226
222
207
233
–
–
–
–
226
–
261
–
–
262
–
–
342
338
332
349
334
332
–
–
–
586
–
–
(2) [Ni(YL)]
(3) [Co(YL)]
(4) [Cu(YL)(H2O)]
(5) [Zn(YL)]
(6) [Cd(YL)]
at room temperature (Table 1). The first band at 221
nm was assigned to the moderate energy π → π*
transition of an aromatic ring, whereas the second
band 261 nm is due to the low-energy π → π* tran-
sition of the CH N group. The third band at
342 in DMSO was assigned n → π* transition of the
CH N azomethine group of the ligand [33]. The
peaks belonging to the azomethine in the spectra
of the [Ni(YL)] (2), [Co(YL)] (3), [Cu(YL)(H2O)] (4),
[Zn(YL)] (5), and [Cd(YL)] (6) mononuclear coordi-
nation compounds were observed at 347, 350, 342,
and 342 nm, respectively (see Figs. 3–5). The elec-
tronic spectrum of Cu(II) complex was characterized
by low-intensity absorption at 586 nm, which can be
associated with d–d transitions. The spectroscopic
data obtained in this work agree well with previous
work.
1H NMR Spectra
1H NMR spectra of the tetradentate Schiff base
ligand and its diamagnetic Zn(II) complex were
recorded in DMSO-D6 at room temperature, and the
important assignment is summarized in Tables 2 and
1
3. The H NMR spectrum of the ligand reveals the
presence of CH N proton signal at 7.85 ppm (s, 2H,
CH N ) and 14.30–11.20 ppm (brs, 1H) [30] due
to the protons of carboxyl group of benzoic acid, and
6.70–7.71 ppm (m, phenyl protons), respectively. All
the other signals were unchanged, except COOH
between 14.30 and 11.20 ppm range disappeared in
the spectrum of the Zn(II) complex, indicating de-
protonation upon complex formation.
TABLE 2 1H NMR Data (ppm) of the Tetradentate YLH2
Ligand in DMSO-D6
14
15
13
Infrared Spectra
The main IR characteristic stretching frequencies
of the tetradentate azomethine ligand and its metal
chelates along with their proposed assignments are
16
O
19
12
22
11
N
OH
10
20
8
9
TABLE 3 1H NMR Data (ppm) of the [Zn(YL)] Metal Complex
N
OH
7
18
in DMSO-D6
1
2
6
5
O
17
O
O
22
21
21
H
H
O
O
17
1
19
11
3
Zn20
N
12
18
2
13
3
4
H
14
N
4
2,2'-[ethane-1,2-diylidenedinitrilo]dibenzoic acid
H
10
7
9
5
6
8
15
16
2,2ꢀ-[Ethane-1,2-diylidenedinitrilo]dibenzoic acid
H
H
H
H
H
H
Chemical Shifts, δTMS (ppm)
Assignmentsa
Chemical Shifts, δTMS (ppm)
Assignmentsa
14,3-11.2
7.85
[s, 2H] (18, 20)
[d, 2H] (8, 9)
[d, 2H] (3, 13)
[t, 4H] (4, 5, 14, 15)
[d, 2H] (6, 16)
7,77
7,14
6.65
6.45
[d, 2H] (8, 9)
[d, 2H] (3, 13)
[t, 4H] (3, 4, 14,15)
[d, 2H] (6, 16)
7.71
7.4
6.7
as, singlet; d, doublet and t, triplet.
as, singlet; d, doublet and t, triplet.
Heteroatom Chemistry DOI 10.1002/hc

124 Kara et al.
5,76
5,5
5,0
4,5
4,0
3,5
3,0
2,5
221,22
2,0
A
1,5
341,92
1,0
0,5
0,0
260,64
200,0
250
300
350
400
450
500
nm
550
600
650
700
750
800,0
FIGURE 3 UV–visible spectrum of 2,2ꢀ-(ethane-1,2-diylidenedinitrilo)dibenzoic acid ligand.
5,77
5,5
5,0
4,5
4,0
3,5
3,0
221,98
205,71
2,5
2,0
1,5
1,0
0,5
0,0
A
586,08
262,20
348,83
200,0
250
300
350
400
450
500
nm
550
600
650
700
750
800,0
FIGURE 4 UV–visible spectrum of [2,2ꢀ-(ethane-1,2-diylidenedinitrilo)dibenzoato]copper(II).
Heteroatom Chemistry DOI 10.1002/hc

Synthesis and Genotoxicity of Schiff Base Transition Metal Complexes 125
6,81
6,5
6,0
5,5
5,0
4,5
4,0
3,5
3,0
2,5
2,0
1,5
1,0
0,5
0,0
226,11
206,73
A
333,70
200,0
220
240
260
280
300
320
340
360
380
400
420
440
460
480
500,0
nm
FIGURE 5 UV–visible spectrum of [2,2ꢀ-(ethane-1,2-diylidenedinitrilo)dibenzoato]cobalt(II).
summarized in the Experimental section. The IR
spectra of the metal complexes are similar to each
other, except for some slight shifts and intensity
changes in a few vibration peaks caused by different
metal(II) ions, which indicates that the metal com-
plexes have similar structure. However, there are
some significant differences between the metal(II)
complexes and its free ligand upon chelation, as ex-
pected.
tion [32]. When the carboxylic acid group in the
azomethine ligand is converted to the metal com-
plexes, the absorption bands of stretching vibration
of the C O group, ν(C O), of the COOH group at
about 1714 cm−1 disappear, whereas the bands as-
signed to asymmetric vibrations νas (OCO) at 1554–
1535 cm−1 and the bands of symmetric vibrations νs
(OCO) at 1399–1325 cm−1 appear. The appearance of
new bands at 490–445 cm−1 and 680–630 cm−1 that
are attributed to ν (M – N) and ν (M – O) vibra-
tions supports the participation of nitrogen atoms
of the azomethine groups and oxygen atoms of the
OH groups of carboxyl groups of the ligand in the
complexation with metal ions.
The sharp band at 3330 cm−1 is attributed to
ν(OH) of the carboxyl groups of the ligand (see
Fig. 6). This band in the spectrum of the ligand
has been disappeared on chelation. The spectrum
of the Cu(II) complex shows a broad band around
3427 cm−1, attributed to the existence of coordi-
natated water molecule. A band of coordinated wa-
ter at 825 cm−1 indicates the binding of water to
the copper(II) ion. The absorption peaks at 3078
and 2900 cm−1 are assigned to the C H stretch-
ing vibrations of aromatic ring and CH CH of
the ligand, respectively. The infrared spectrum of
the Schiff base ligand exhibits a band at 1624 cm−1
assignable to v(C N) of the azomethine groups [31].
This band shifts to lower region by about 15 cm−1
on the chelation with metal ions. This fact can be
explained by the withdrawing of electrons from a
nitrogen atom to the metal ion due to coordina-
X-Ray Powder Diffraction Studies
Figure 7 and 8 show, respectively, x-ray powder
diffraction patterns of [2,2ꢀ-(ethane-1,2-diylidenedi-
nitrilo)dibenzoato(aqua)]copper(II)
and
[2,2ꢀ-
(ethane-1,2-diylidenedinitrilo)dibenzoato] cadmi-
um(II) complexes. These mononuclear complexes
were assessed by the search and match comparison
of X-ray powder diffraction patterns to ICDD-PDF 2
database by using X’Pert HighScore Plus software.
The diffraction of the [Cu(YL)(H2O)] metal complex
consist of 10 reflections between 5 and 50◦ (2θ) with
Heteroatom Chemistry DOI 10.1002/hc

126 Kara et al.
67,9
66
64
62
60
58
56
54
52
50
48
2346,03
2369,80
532,86
593,50
507,16
2900,42
692,08
1001,74
1168,06 1031,60
1212,37
1261,27
1126,89
1082,75
1488,04
1508,37
1283,66
1354,77
746,04
1623,84
46
44
42
40
38
36
34
32
30
28
%T
3330,70
1714,20
25,5
4400,0
4000
3000
2000
1500
1000
450,0
FIGURE 6 IR spectrum of 2,2ꢀ-(ethane-1,2-diylidenedinitrilo)dibenzoic acid.
maxima reflection at 2θ = 6.8369◦, which corre-
The obtained results fit very well in ICDD 51-2387
and 33-1804 patterns for the [Cu(YL)(H2O)] metal
complex and for the [Cd(YL)] metal complex in
ICDD 52-2355 and 49-1945 patterns. Indexing of the
diffraction patterns (Tables 4 and 5) was performed
˚
sponds to d = 12.91836 A. However, the diffraction
of the [Cd(YL)] metal complex consist of 13 reflec-
tions between 5 to 50◦ (2θ) with maxima reflection at
◦
˚
2θ = 6.5854 which corresponds to d = 13.42229 A.
5
10
15
20
25
30
35
40
45
50
5
10
15
20
25
30
35
40
45
50
°
°
2 Theta
2 Theta
FIGURE 7 XRD diffraction patterns of the [Cu(YL)(H2O)]
metal complex.
FIGURE 8 XRD diffraction patterns of the [Cd(YL)] metal
complex.
Heteroatom Chemistry DOI 10.1002/hc

Synthesis and Genotoxicity of Schiff Base Transition Metal Complexes 127
TABLE 4 XRD Data of the [Cu(YL)(H2O)] Metal Complex
2Theta (o) (◦)
2Theta (c) (◦)
d-sp. (A)
2Theta (d) (◦)
Rel. Int. (%)
˚
P. No.
h
k
l
1
2
3
4
5
6
7
8
9
1
2
1
3
1
0
3
6
0
3
0
0
0
1
2
1
2
0
3
0
0
6.8369
19.2997
20.3378
24.0006
25.4021
26.5866
32.1858
34.3904
36.9252
39.8247
6.8753
19.3108
20.3843
24.0207
25.3736
26.5793
32.1734
34.3748
36.9531
39.8151
12.91836
4.595319
4.363053
3.704836
3.503522
3.350053
2.7789
2.605637
2.432375
2.261715
0.0384
0.0111
0.0465
100
−1
−1
−1
0
47.46
44.07
17.67
13
22.59
2.15
5.84
9.58
3.13
0.0201
−0.0285
−0.0073
−0.0125
−0.0156
0.0278
1
−1
−1
0
10
1
−0.0095
using DICVOL91 program [34] included in the High-
Score Plus software. The indexing of the diffrac-
tion patterns yields the Miller indices (hkl), the unit
cell parameters, and the unit cell volume. The unit
cell parameters of the [Cu(YL)(H2O)] metal complex
while [Ni(YL)] complex was strong mutagenic on
S. typhimurium TA98 strain, it was weak mutagenic
in presence of S9 mix. In addition to this, muta-
genic activity of this complex on the TA98 strain was
found to be dose-dependent (Fig. 10; r = 0.9911). The
Ni(II) complex tested and their various metabolites
induced frame shift mutation (TA98). In addition,
metabolites of the complex induced base-pair sub-
stitution mutation (TA100).
˚
˚
˚
are a = 15.51784 A, b = 7.20964 A, c = 4.51752 A,
3
˚
and the cell volume V = 505.41120 A . The unit
cell parameters of the [Cd(YL)] metal complex are
˚
˚
˚
a = 15.76158 A, b = 4.2926 A, c = 10.90618 A, β =
◦
3
˚
119.726 , and cell volume V = 640.789 A . These
parameters indicate an orthorhombic crystal sys-
tem for the [Cu(YL)(H2O)] metal complex and
a monoclinic crystal system for [Cd(YL)] metal
complex.
40
35
30
25
20
15
Mutagenicity of the Synthesized Compounds
y = 5,0711x + 6,2227
10
r = 0.9728
The data from Salmonella Microsome test are given
in Table 6. YLH2 ligand was not mutagenic on
S. typhimurium TA98 and TA100 strains in the
absence of S9 mix. Besides, while the ligand was
weak mutagenic on S. typhimurium TA98 strain, it
was not mutagenic for the TA100 strain in the pres-
ence of S9 mix. In addition, the azomethine ligand
tested and their various metabolites induced frame
shift mutation (TA98).
Mononuclear [Co(YL)] complex was weak mu-
tagenic on S. typhimurium TA98 strain in the ab-
sence of S9 mix. But not mutagenic for the TA100
strain in the absence of S9 mix. In the presence of
S9 mix, it was mutagenic on S. typhimurium TA98
strain but not mutagenic for the TA100 strain. On
the other hand, mutagenic activity of the complex
on the TA98 strain was observed to be dose depen-
dent (Fig. 9; r = 0.9728). The Co(II) complex tested
and their various metabolites induced frame shift
mutation (TA98).
5
0
Control
0.015
0.031
0.062
0.125
0.25
Doses (mg/plate)
FIGURE 9 Dose-dependent increase in the mutagenic ac-
tivity of Co(II) complex on the TA98 strain in the presence of
S9 mix.
160
140
120
100
80
60
40
20
0
y = 23,877x –4,4573
r = 0.9911
Control
0.015
0.031
0.062
0.125
0.25
Doses (mg/plate)
The Ni(II) complex was weak mutagenic
S. typhimurium TA98 strain in absence of S9 mix.
But it was not mutagenic for TA100 strain. Besides,
FIGURE 10 Dose-dependent increase in the mutagenic ac-
tivity of Ni(II) complex on the TA98 strain in the presence of
S9 mix.
Heteroatom Chemistry DOI 10.1002/hc

128 Kara et al.
TABLE 5 XRD Data of the [Cd(YL)] Metal Complex
2Theta (o) (◦)
2Theta (c) (◦)
d-sp. (A)
2Theta (d) (◦)]
Rel. Int. (%)
˚
P. No.
h
k
l
1
2
3
4
5
6
7
8
1
2
3
1
4
1
3
0
3
4
1
2
7
0
0
0
0
0
0
0
1
1
1
0
2
1
0
0
6.5854
13.2226
19.1681
22.4384
23.5017
24.9923
25.7944
27.7902
33.2851
39.3954
41.2251
44.2387
48.2524
6.5817
13.1853
19.1358
22.4914
23.5096
25.0372
25.7976
27.7963
33.2759
39.3797
41.2112
44.2361
48.2588
13.42229
6.69605
4.63041
3.96241
3.78549
3.56298
3.45398
3.2103
2.69182
2.28726
2.18987
2.04755
1.88453
−0.0037
−0.0373
−0.0324
0.053
0.0079
0.0449
0.0031
0.0061
−0.0091
−0.0157
−0.0139
0.0026
100
7.92
32.96
8.72
4.45
9.44
14.51
6.14
6.81
6.3
−2
2
−2
−3
1
2
1
9
10
11
12
13
−4
4
4.85
3.1
1.93
0
−4
0.0064
TABLE 6 Mutagenicity of Ligand and Its Metal Complexes in S. typhimurium TA98 and TA100 Strains in the Absence (–S9)
or Presence (+S9) of S9 Mix
TA98
TA100
Test
Substances
Concentration
(mg/plate)
−S9
+S9
−S9
+S9
Spontaneous control
–
14.50 2.03
3476 215
13.00 1.91
108.30 11.50
106.20 10.40
NPD
2-AF
SA
3653 217
1250 154
813.20 75.70
121.8 10.3
106 6.70
YLH2
0.25
15.33 1.05
18.83 2.32
20.67 2.76
15.66 0.76
21.50 2.40
28.33 3.41*
29.00 2.86**
23.33 2.88*
21.00 3.16
16.67 2.81
24.50 3.55*
29.17 3.94*
20.50 2.83
22.17 2.41*
21.50 3.13
46.83 3.97***
37.83 7.93*
24.33 2.73*
15.00 1.98
9.33 1.33*
69.50 6.90***
57.17 9.20***
42.83 5.28***
45.00 6.59***
43.83 5.21***
105.00 7.31***
112.00 8.04***
76.7 10.6***
63.67 8.25***
44.17 9.65**
23.00 3.93*
18.83 2.34*
18.33 1.36*
12.00 1.15
17.67 3.03
35.00 4.00***
33.00 3.70***
29.33 2.78***
19.83 2.97
13.67 2.06
137.67 5.21***
109.50 3.37***
93.17 3.08***
77.33 5.25***
44.00 6.63**
48.00 4.10***
32.83 5.57*
116.50 8.98
107.67 6.25
113 5.42
103.50 7.52
109.33 6.27
109.00 7.36
87.67 2.80***
98.00 6.14
72.83 6.63***
64.50 7.62***
168.50 7.23***
131.17 7.29**
107.33 4.70
96.50 6.91
68.83 6.89**
198.00 18.8***
120.20 15.5
103.20 11.3
81.83 2.63***
71.67 4.96**
168.20 20.4*
177.00 25.5*
121.70 12.2
101.83 5.10
93.8 17.3
0.125
0.062
0.031
0.015
0.25
0.125
0.062
0.031
0.015
0.25
0.125
0.062
0.031
0.015
0.25
0.125
0.062
0.031
0.015
0.25
0.125
0.062
0.031
0.015
0.25
0.125
0.062
0.031
0.015
119 5.20
106.17 7.17
118.83 5.50
100.50 11.3
93.67 5.06*
110.17 7.82
90.33 4.29***
83.83 9.06*
108.70 12.3
102.17 4.20
99.83 5.32
83.67 4.40**
66.67 6.58**
160.00 18.10*
110.67 9.37
109.00 9.73
88.83 4.22**
80.33 8.20*
163.50 19.9*
181.3 24.9*
126.5 13.8
107.7 13.8
117.2 14.9
142.67 9.02*
112.00 12.30
110.17 7.82
90.33 4.29**
86.33 8.31*
[Co(YL)]
[Ni(YL)]
[Cd(YL)]
24.00 2.94*
14.83 2.02
8.00 0.96**
[Zn(YL)]
88.50 6.33***
64.17 3.95***
56.33 9.25***
50.83 6.70***
48.50 7.63***
117.33 8.35***
100.00 6.42***
75.33 7.14***
53.33 9.42***
33.33 7.54**
[Cu(YL)(H2O)]
168.67 9.74**
110.30 12.4
102.33 8.74
103.00 8.66
92.67 7.11
Abbreviations: NPD: 4-nitro-o-phenylenediamine, 2AF: 2-aminoflourene, SA: sodium azide.
∗P < 0.05; ∗∗P < 0.01; ∗∗∗P < 0.001.
Heteroatom Chemistry DOI 10.1002/hc

Synthesis and Genotoxicity of Schiff Base Transition Metal Complexes 129
100
90
80
70
60
50
40
30
20
10
0
CONCLUSION
Schiff base behaves as (ONNO) tetradentate ligand
and coordinate to metal ions from two benzoic acid
hydroxyl oxygen atoms and two azomethine nitro-
gen atoms. The structure of Ni(II), Co(II), Zn(II),
and Cd(II) complexes is proposed as a tetragonal
geometry. An extra bonding to tetragonal geometry
is provided by the coordinated a water molecule in
the Cu(II) complexes. The proposed structures of
the complexes are shown in Fig. 2. The Miller in-
dices (hkl), the unit cell parameters, and the unit cell
volume of both Cu(II) and Cd(II) complexes were
determined by XRD. The Cu(II) complex has an or-
thorhombic structure, whereas the Cd(II) complex
has a monoclinic structure. The genotoxical activity
results evidently show that our compounds have the
moderate activity against the microorganisms, but
their activities are less than standard antibiotics and
antifungals.
y = 12,286x + 10,554
r = 0.9353
Control
0.015
0.031
0.062
0.125
0.25
Doses (mg/plate)
FIGURE 11 Dose-dependent increase in the mutagenic ac-
tivity of Zn(II) complex on the TA98 strain in the presence of
S9 mix.
While the [Cd(YL)] complex was mutagenic
S. typhimurium TA98 strain both the absence and
presence of S9 mix, it was weak mutagenic for the
TA100 strain.
While Zn(II) and Cu(II) complexes were strong
mutagenic activity on S. typhimurium TA98 strain
both the presence and absence of S9 mix, they were
weak mutagenic activity for TA100 strain. In addi-
tion, mutagenic activity of [Zn(YL)] complex on the
TA98 strain was found to be dose dependent (Fig. 11;
r = 0.9353). Besides, Zn(II) complex tested and their
various metabolites induced both frame shift mu-
tation (TA98) and base-pair substitution mutation
(TA100). Mutagenic activity of the [Cu(YL)(H2O)]
complex on the TA98 strain was found to be dose-
dependent (Fig. 12; r = 0.9992). Besides, the com-
plex tested and their various metabolites induced
both frame-shift mutation (TA98) and base-pair sub-
stitution mutation (TA100).
ACKNOWLEDGMENTS
The authors thank Prof. Musa Go¨gˇebakan of Kahra-
manmaras Su¨tc¸u¨ Imam University for the use of the
X-ray diffractometer, purchased under grant num-
ber 103K-120–730 of Turkish State Planning Orga-
nization (DPT).
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