Synthesis, spectroscopic characterization and antimicrobial studies of Co(II), Ni(II), Cu(II) and Zn(II) complexes with Schiff bases derived from 5-bromo-salicylaldehyde

Article abstract of DOI:10.1016/j.molstruc.2013.06.017

In this study, the new Schiff base ligands derived from condensation of amine and 5-bromo-salicylaldehyde were characterized. All compounds, the Schiff bases and the metal complexes, were characterized by elemental analyzes, FT-IR, ¹H NMR, ¹³C NMR and magnetic susceptibility measurements. The synthesized ligands, along with their metal (II) complexes, were screened for their in vitro antibacterial activity against four Gram-negative (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Salmonella enteritidis) and four Gram-positive (Streptococcus pyogones, Bacillus cereus, Staphylococcus aureus and Methicillinresistant S. aureus) bacterial strains by using disc diffusion and broth microdilution techniques. The minimum inhibitory concentration (MIC) values were calculated by microplate reader at 620 nm to optimum result. It was found that all compounds showed mild to moderate antibacterial activity and the Schiff base ligands had a better antibacterial activity than their complexes.

Full text of DOI:10.1016/j.molstruc.2013.06.017

Journal of Molecular Structure 1048 (2013) 476–481
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis, spectroscopic characterization and antimicrobial studies
of Co(II), Ni(II), Cu(II) and Zn(II) complexes with Schiff bases derived
from 5-bromo-salicylaldehyde
a
b
b
Ahmed Nuri Kursunlu a, , Ersin Guler , Fatih Sevgi , Birol Ozkalp
⇑
a Department of Chemistry, Selcuk University, Campus, 42075 Konya, Turkey
b Vocational School of Health Services, Selcuk University, Campus, 42075 Konya, Turkey
h i g h l i g h t s
ꢀ
ꢀ
ꢀ
The Schiff bases derived from salicylaldehyde containing bromine have an important situation for antimicrobial studies.
The antibacterial properties of the Schiff bases and their metal complexes are illuminated.
The results of this study can be useful to researchers attempting for future work to study the antifungal activities.
a r t i c l e i n f o
a b s t r a c t
Article history:
In this study, the new Schiff base ligands derived from condensation of amine and 5-bromo-salicylaldehyde
were characterized. All compounds, the Schiff bases and the metal complexes, were characterized by ele-
mental analyzes, FT-IR, 1H NMR, 13C NMR and magnetic susceptibility measurements. The synthesized
ligands, along with their metal (II) complexes, were screened for their in vitro antibacterial activity against
four Gram-negative (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Salmonella enteri-
tidis) and four Gram-positive (Streptococcus pyogones, Bacillus cereus, Staphylococcus aureus and Methicillin-
resistant S. aureus) bacterial strains by using disc diffusion and broth microdilution techniques.
The minimum inhibitory concentration (MIC) values were calculated by microplate reader at 620 nm to
optimum result. It was found that all compounds showed mild to moderate antibacterial activity and the
Schiff base ligands had a better antibacterial activity than their complexes.
Received 12 April 2013
Received in revised form 15 May 2013
Accepted 7 June 2013
Available online 14 June 2013
Keywords:
Schiff base
Metal complex
Disc diffusion
Microdilution
Antibacterial activity
Ó 2013 Published by Elsevier B.V.
1. Introduction
applicability [6–9]. The chelating ligands containing O and N donor
atoms show broad biological activity and have special interest on
In the past decades, the problem of multi-drug resistant micro-
organisms has reached on alarming level around the world. There-
fore, the synthesis of new compounds that are used for the
effective treatment of microbial infections without side effects is
a biomedical problem [1]. The synthesis of new Schiff base com-
plexes becomes widespread due to their potential application in
chemistry, biochemistry, medicine and technology [2]. The synthe-
sis, characterizations and structure–activity relations of Schiff
bases were studied previously by some researchers [3]. It is well
known that several Schiff base complexes are used as anti-inflam-
matory, anti-pyretic, chemosensor, anti-diabetic, anti-bacterial,
anti cancer and anti-HIV [1,4]. Schiff bases containing halogen
groups and their metal complexes have a special interest due to
their antimicrobial properties [5]. Schiff bases derived from substi-
tuted salicylaldehydes and various amines and their metal com-
plexes have been widely investigated because of their wide
bonding to metal ions [10,11]. It is also reported that salicylalde-
hyde derivatives, with one or more halo-atoms in the aromatic
ring, shows biological activities like antitumor, antibacterial and
antifungal activities [12,13].
These investigations led to the conception that the Schiff bases
of 5-bromo-salicylaldehyde would possess potential antimicrobial
properties. In this study, the synthesis-spectroscopic characteriza-
tion of the new Schiff bases derived from 5-bromo-salicylaldehyde
and their metal complexes and their antibacterial properties were
reported. The results of this study can be useful to researchers
attempting to gain more understanding of the antimicrobial activ-
ity of Schiff base ligands and their metal complexes.
2. Experimental
2.1. Instruments
⇑
The melting points of the ligands and the metal complexes were
measured by a Buchi-B-540 melting point apparatus. The pH val-
Corrosponding author. Tel.: +90 332 223 3876.
E-mail address: ankursunlu@gmail.com (A.N. Kursunlu).
0022-2860/$ - see front matter Ó 2013 Published by Elsevier B.V.
http://dx.doi.org/10.1016/j.molstruc.2013.06.017

A.N. Kursunlu et al. / Journal of Molecular Structure 1048 (2013) 476–481
477
ues were measured with a WTW pH, 537 pH meter. The IR spectra
were recorded by using KBr pellet technique in a Mattson-1000 FT-
IR spectrophotometer. The percentages of carbon, hydrogen, nitro-
gen and metal in all compounds were determined using a TruSpec
elemental analyzer. 1H NMR and 13C NMR measurements of Schiff
bases were obtained on a Varian, 400 MHz spectrometer at room
temperature. The mass spectra for ligands were obtained with a
Varian MAT 711 spectrometer. The magnetic measurements of
the metal complexes were carried out by Sherwood Scientific Mag-
netic Susceptibility Balance in solid state at room temperature. The
35.01; H, 3.03; N, 4.33. 1H NMR [400 MHz, CDCl3] d 3.68 (2H, t,
CH2), 3.82 (2H, t, CH2), 6.92(1H, d, ArH), 7.41 (2H, m, ArH),
8.44(1H, s, CH@N), 13.00 (1H, s, ArOH). 13C NMR [400 MHz, CDCl3]
d 34.0, 68.9, 112.5, 119.5, 122.8 136.0, 137.5, 159.2, 166.0. Anal.
Calc. MS (ESI) m/z 306.90 (M+); Found: 307.58.
2.4. Synthesis of complexes
The metal complexes were prepared by the addition of a hot
methanol solution of ligand to an equimolar amount (5 mmol) of
the metal salts [(Cu(CH3COO)2ÁH2O, Co(CH3COO)2Á4H2O, Ni(CH3-
COO)2Á4H2O, Zn(CH3COO)2Á2H2O]. The appropriate reaction mix-
tures were stirred and refluxed at 80 °C for 3 h under nitrogen.
The separated complexes were filtered off, washed several times
with ethanol, and dried under vacuum in the presence of anhy-
drous CaCl2 (Tables 1 and 2).
The general reaction for the preparation of the complexes of
Schiff base ligands are: MX2. nH2O + L ? ML2. n1H2O where
M = Cu(II), Co(II), Ni(II), Zn(II) (X = CH3COOÀ), n = 0–4 and n1 = 0–
2 (see Fig. 1).
MIC values were measured by Bio-Tek lQuant microplate reader.
2.2. Materials
All chemicals used were of the analytical reagent grade and of
highest purity available. 2-Chloroethylamine hydrochloride (Flu-
ka), 2-bromooethylamine hydrobromide (Fluka)5-bromo-2-
hydroxybenzaldehyde (Merck) and triethylamine (Merck) were
used for the synthesis of the ligands and copper(II)acetate mono-
hydrate (Fluka); cobalt(II)acetate dihydrate (Fluka) and
nickel(II)acetate tetrahydrate (Sigma); zinc(II)acetate dihydrate
(AcrosOrganics) were used to make their complexes. The absolute
methanol, ethylacetate, ethanol (Riedel-de Haen) and diethylether
(Merck) were used as organic solvents.
2.5. Biological activity
The test microorganisms; Escherichia coli RSKK 340, Klebsiella
pneumoniae RSKK 06017, Pseudomonas aeruginosa RSKK 06021, Sal-
monella enteritidis RSKK 96046, Streptococcus Pyogones RSKK 413/
214, Bacillus cereus RSKK 1122, Staphylococcus aureus RSKK 96090
were obtained from the Refik Saydam National Public Health
Agency. Methicillin-resistant S. aureus (MRSA) is clinically isolated.
The organisms were maintained on agar slope at 4 °C and sub-cul-
tured for 24 h before use.
Ceftriaxone (CRO) 30 mcg (Bio Disc) was used as a positive con-
trol for disc diffusion tests. Ceftriaxone (Eczacıbaßsı), was used as a
positive control for broth microdilution test. DMSO (Merck) was
used as a negative control. 96-well microtiter plates (TPP 92096)
were used for microdilution tests. Nutrient broth (Difco) and Muel-
ler Hinton Agar (Difco) were used.
2.3. The preparation of (E)-4-bromo-2-((2-
chloroethylimino)methyl)phenol (L1) and (E)-4-bromo-2-((2-
bromoethylimino)methyl)phenol (L2)
A 1:1 equimolar methanolic solution of 2-chloroethylamine
hydrochloride (30 mmol) and 5-bromo-2-hydroxybenzaldehyde
(30 mmol) were mixed and gently heated for 30 min with constant
stirring. 4.2 cm3 of triethylamine (30 mmol) was gradually added
to this mixture to remove the hydrochloride salt of 2-chloro ethyl-
amine. Stirring was continued for an additional 30 min. The yellow
precipitate was washed with ethylacetate and dried under vacuo.
The obtained yellowish residue was recrystallized from a mixture
of hot ethanol and diethylether (1:2) and was dried overnight in
a vacuum desiccator [14]. It was named as (E)-4-bromo-2-((2-chlo-
roethylimino)methyl)phenol (L1). Anal. Calc. for (%) C9H9NOBrCl
(L1) (262.53 g/mol): C, 41.17; H, 3.46; N, 5.34; Found: C, 41.07;
H, 3.37; N, 5.41. 1H NMR [400 MHz, CDCl3] d 3.80 (2H, t, CH2),
3.92 (2H, t, CH2), 6.88(1H, d, ArH), 7.39 (2H, m, ArH), 8.31(1H, s,
CH@N), 13.02 (1H, s, ArOH).13C NMR [400 MHz, CDCl3] d 44.0,
60.9, 110.4, 119.3, 120.1 134.0, 135.5, 160.3, 166.1. Anal. Calc.
MS (ESI) m/z 262.95 (M+); Found: 262.63.
2.5.1. Antibacterial testing by disc diffusion
The antibacterial activities of ligands and their metal complexes
in dimethylsulfoxide (DMSO) were performed in vitro by the disc
diffusion method [15]. The bacterial inoculums were prepared
from overnight grown cultures (24 h) in Nutrient broth (Difco)
and turbidity was adjusted equivalent to 0.5 McFarland units
(approximately 108 cfu/ml). Aliquots (100
lL) of inoculums were
spread over the (Difco) plates with a sterile glass spreader. The
The (E)-4-bromo-2-((2-bromoethylimino)methyl)phenol (L2)
was prepared according to same procedure. Anal. Calc. for (%) C9H9-
NOBr2 (L2) (306.98 g/mol): C, 35.21; H, 2.96; N, 4.56; Found: C,
sterilized paper discs (Oxoid, 6 mm diameter) were wetted with
10
l
L of a solution of each compound to be tested, in the concen-
g per disc) in DMSO. Ceftriaxone and
tration of 0.02 g/ml (200
l
Table 1
Analytical and physical data of the Schiff base ligands and their complexes.
Compound
Color
Yield (%)
m.p (°C)
Elemental analysis found (calcd.) (%)
leff (B.M.)
C
H
N
M
–
L1
L2
Bright yellow
Bright yellow
85
83
93
41.07 (41.17)
35.01 (35.21)
3.46 (3.37)
3.03 (2.96)
5.34 (5.41)
4.33 (4.56)
–
–
102
–
L1
Co(II)
Dark green
Bright green
Med. green
Yellow–white
55
57
62
63
183
220
228
203
34.75 (34.98)
37.16 (37.19)
36.86 (36.72)
36.74 (37.08)
3.33 (3.26)
2.77 (3.01)
2.75 (2.95)
2.74 (2.87)
4.42 (4.53)
4.82 (4.74)
4.78 (4.46)
4.76 (4.71)
9.74 (9.54)
1.67
Dia.
1.80
Dia.
Ni(II)
Cu (II)
Zn(II)
10.09 (10.46)
10.83 (10.95)
11.12 (11.56)
L2
Co(II)
Ni(II)
Cu(II)
Zn(II)
Brown
59
62
57
61
192
229
242
225
30.58 (30.76)
32.24 (32.44)
32.01 (32.19)
31.92 (32.32)
2.85 (2.64)
2.40 (2.27)
2.39 (2.44)
2.38 (2.34)
3.96 (3.78)
4.18 (4.07)
4.15 (4.12)
4.14 (4.09)
8.34 (8.46)
8.75 (9.04)
9.41 (9.66)
9.66 (9.97)
1.72
Dia.
1.76
Dia.
Bright green
Med. green
Yellow–white

478
A.N. Kursunlu et al. / Journal of Molecular Structure 1048 (2013) 476–481
Table 2
Characteristic IR (cmÀ1) bands of ligands and their complexes.
Compounds
v(C@N)
1635
v(OH)
3453
3338
v(CH2)
v(CACl)
823
v(CABr)
654
v(MAN)
L1
L2
L1
2852–2894
2892–2964
–
–
1641
887
677
Co(II)
Ni(II)
Cu(II)
Zn(II)
1612
1612
1620
1620
3480
2887–2929
2941–2964
2894–2925
2925–2960
831
819
823
827
684
692
688
684
554
550
550
569
–
–
–
L2
Co(II)
Ni(II)
Cu(II)
Zn(II)
1612
1612
1620
1620
3480
2887–2929
2941–2964
2894–2925
2925–2960
831
819
823
827
684, 671
692, 677
688, 670
684, 666
554
550
550
569
–
–
–
solution of compounds (2.048 mg/ml DMSO). An equal volume of
bacterial inoculum was added to each well on the microtiter plate.
In this manner final concentration of compounds range from 512,
256, 128. . .to 0.5
l
g/mL and 5 Â 105 cfu/ mL bacteria in each well
(last wells are broth only control well). Then, the inoculated micro-
titer plates were incubated at 37 °C for 24 h, and the growths were
spectrophotometrically recorded at 620 nm by using a microplate
reader (lQuant, BioTek). The MIC values were defined as the low-
est concentration of compounds whose absorbances were compa-
rable to the negative control wells (broth only, without inoculum).
Ceftrioxane was used for comparative purposes and quality control
of the method. The MIC values are reported as the mean of three
experiments.
3. Results and discussion
Fig. 1. The general scheme of the complexes.
3.1. Infrared and elemental analysis
DMSO were used as controls. The plates were incubated at 37 °C
for 24 h and the zone diameters of exact growth inhibition were
measured. The values are reported in Table 3 as a mean of three
replicates.
In the IR spectra of the Schiff base ligands, a sharp C@N band
was observed in the range of 1635–1641 cmÀ1, respectively (Ta-
ble 2) [17]. The other series of weak bands between 2852 and
2894 cmÀ1 are related to
m
(CAH) modes of vibrations. The ligands
also display bands at 3453 and 1366 cmÀ1 which are assigned to
(OH) and (CAO) stretching vibrations of the phenolic-OH,
2.5.2. Determination of minimum inhibitory concentration (MIC)
The minimal inhibitory concentrations (MIC) were determined
by broth microdilution methods [16]. For MIC determination, the
inoculums were prepared like the following procedure: the broth
culture of each bacterial strains was adjusted to a turbidity equiv-
alent to a 0.5 McFarland standard for 4–6 h and were diluted in
Nutrient broth media to give concentration of ꢁ106 cfu/mL for bac-
teria. Twofold serial dilutions of compounds and Ceftrioxane were
prepared in Nutrient broth in 96-well plates starting from a stock
m
m
respectively. Additionally, the peaks were observed between 877
and 654 cmÀ1 that attributed to chlorine and bromine.
After complexation, the vibration bands of the Schiff bases were
decreased in intensity and shifted towards higher area about 15–
30 cmÀ1 in the metal complexes [18]. This shift to lower wavenum-
bers or disappearance of peaks support complex formations [19].
Moreover, the
m(MAN) band for the complexes are appeared in
the wave number range 550–569 cmÀ1 [20].
Table 3
Inhibitory zone (diameter) mm of compounds against tested bacterial strains by the disc diffusion Gram-negative Gram-positive method.
Compounds
E. coli
K. pneumoniae
P. aeruginosa
S. enteritidis
S. pyogones
B. cereus
S. aureus
MRSA
L1
16
10
10
9
15
9
11
8
16
8
10
8
13
8
10
8
20
12
14
8
17
8
10
8
19
9
11
9
12
–
9
–
9
Co(L1)2 (H2O)2
Ni(L1)2
Cu(L1)2
Zn(L1)2
10
10
10
11
15
9
10
L2
16
9
9
8
10
28
13
10
12
8
10
29
17
7
9
9
11
17
18
9
10
8
12
28
14
11
13
9
16
25
21
8
8
10
14
26
11
9
12
10
12
33
Co (L2)2 (H2O)2
Ni(L2)2
Cu(L2)2
Zn(L2)2
CRO
–
8
–
9
–
DMSO
–
–
–
–
–
–
–
–

A.N. Kursunlu et al. / Journal of Molecular Structure 1048 (2013) 476–481
479
Fig. 2. The NMR spectra of L1-Ni(II), L1-Zn(II) complexes and L2, respectively.
Fig. 3. UV–Vis spectra of L1-Co(II), L1-Ni(II), L1-Cu(II) and L1-Zn(II) complexes.

480
A.N. Kursunlu et al. / Journal of Molecular Structure 1048 (2013) 476–481
Table 4
Minimal inhibitory concentration (MIC) in
l
g/mL of compounds against tested bacterial strains by microdilution method.
Compounds
E. coli
K. pneumoniae
P. aeruginosa
S. enteritidis
S. pyogones
B. cereus
S. aureus
MRSA
L1
64
NT
64
NT
128
NT
64
NT
64
NT
32
NT
32
NT
16
NT
Co(L1)2
(H2O)2
Ni(L1)2
Cu(L1)2
Zn(L1)2
128
NT
64
128
NT
64
256
NT
256
64
NT
128
64
NT
64
64
NT
32
64
NT
32
128
NT
64
L2
Co
64
NT
128
NT
128
NT
128
NT
32
NT
32
NT
32
NT
16
NT
(L2)2(H2O)2
(H2O)2
Ni(L2)2
Cu(L2)2
Zn(L2)2
128
NT
64
128
NT
64
256
NT
128
128
NT
256
128
NT
128
64
NT
32
64
NT
32
256
NT
64
<0.5
<0.5 Ceftriaxone
128
32
<0.5
<0.5
<0.5
512
NT: not tested because of insolubility in DMSO/media.
3.2. NMR and mass spectral analysis
[22]. The Zn(II) and Ni(II) complexes are diamagnetic as expected
and their geometries are probably tetrahedral [23].
The NMR spectra confirm the identity of the newly prepared li-
gands. In order to identify the solution structures of the Schiff base
ligands, 1H and 13C NMR spectra were recorded in chloro-
form(CDCl3) as a solvent. The 1H NMR and 13C NMR spectra of
the ligands show no evidence of unreacted carbonyl or amine com-
pound. On the basis of NMR spectra, the new Schiff base ligands
were judged to be greater than 98% pure and were used without
further purification.
The triplets at 3.82–3.92 and 3.68–3.82 ppm in the proton NMR
spectra of the L1 and L2 can be attributed to the protons of the
ACH2 groups, respectively. The singlet peaks at 7.41 and the two
doublets at 6.89–6.92, 7.39–7.41 ppm range may be assigned to
the protons of the benzene ring. The protons of azomethine group
(HC@N) are observed at 8.31–8.44 ppm as singlet. In addition, the
chemical shifts of the proton on phenolic hydroxy groups are
around 13.00 ppm.
3.4. UV–Vis studies
The UV–Vis spectra of all complexes were recorded in DMSO
from 250 to 650 nm (Fig. 3). The low intense bands between 350
and 800 nm are due to d–d transitions and the intensity bands in
the 250–300 nm range are assigned to the intraligand
p–
pà and
n–pà transitions. The cobalt complexes of L1 and L2 have two bands
in the visible region at 560–573 nm. The cobalt(II) octahedral com-
plexes generally show three transitions in the visible region
4T1g ? 4T2g and 4A2g ? 4T1g [16]. [Ni(L1)2] and [Ni(L2)2] exhibit
three spectral bands at 335–367, 410–425 and 625–653 nm due
to 3T1f ? 3T1p. The spectra of the copper complexes show two
absorption at 370–382 and 650–665 nm, which can be assigned
to 2B1g ? 2B2g and 2B1g ? 2Eg transition corresponding to a square
planar structure. Two of these transitions are indicated by weaker
shoulders in the absorption spectrum [23]. For copper complexes,
the absorption bands in the range of 370–382 and 410–425 nm
are assigned to M ? L charge–transfer (MLCT) or L ? M charge–
transfer (LMCT) [24]. The absorption bands observed at lower en-
ergy and in lower intensities between 625–653 nm may be attrib-
uted to the d–d transitions. The d–d transitions were not observed
in the visible region for zinc(II) complexes of L1 and L2 consistent
with the d10 configuration of the Zn(II) ion [25].
The 13C NMR spectra of the L1 and L2 have similar properties. In
13C NMR, the signal due to the azomethine carbon atom was ob-
served at 160.3–166.3 ppm, respectively. The ligands give also sig-
nals at 44.0–34.0 and 60.9–68.9 ppm that are due to the carbon
atoms of ACH2 groups. In the spectra of the ligands, the signals
were observed in the 110.4–112.5, 119.3–119.5, 120.1–122.8,
134.0–136.0, 135.5–137.5 and 166.1–166.0 ppm range may be
attributed to the carbon atoms of the benzene ring and the hydro-
xyl groups. Similarly, The LC–MS (ESI+) spectra of the Schiff base
ligands were investigated and the molecular ions (m/z) were
found: 262.63–307.58, respectıvely. So, these results show that
the goal ligands were synthesized.
Fig. 2 shows that the NMR spectra of L1-Ni(II), L1-Zn(II) com-
plexes and L2, respectively. The shift of the peaks indicated that
the complexation reactions were successful for L1 and similarly
for L2. So, it is well known that Schiff bases derived from salicylal-
dehyde are a good ligand for complex formation [6–9].
3.5. Biological activity
The in vitro antibacterial activity was tested by disc diffusion
method [15] and broth microdilution technique [16] using patho-
genic strains of E. coli RSKK 340, K. pneumoniae RSKK 06017, P.
aeruginosa RSKK 06021, S. enteritidis RSKK 96046, S. pyogones RSKK
413/214, B. cereus RSKK 1122, S. aureus RSKK 96090 and Methicil-
lin-resistant S. aureus (MRSA). Ceftriaxone was used as positive
control and quality control of assays. The zone of inhibition and
MIC’s values are listed in Tables 3 and 4, respectively. Since Cu(II)
and Co(II) complexes of ligands are not soluble enough in DMSO
media, their antimicrobial activity have not been determined by
the microdilution method; these compounds screened only on disc
diffusion method (see Fig. 4).
3.3. Magnetic susceptibility measurements
The structures of the complexes are supported by magnetic mo-
ment data. The magnetic moment of the Cu(II) complexes were ob-
served in the range of 1.80–1.76 B.M. which corresponds to a single
unpaired electron with a very slight orbital contribution. The
geometry of the Cu(II) complexes is a square-planar or a distorted
tetrahedral [21]. The Co(II) complexes reported herein are high
spin at room temperature magnetic moment values of 1.67–
1.72 B.M, respectively. These results indicate that, the complexes
of Co(II) have a six coordinate and probably octahedral geometry
The screening data indicate that ligands are more active than
their metal complexes. While MIC value of control antibiotic has
512
2-((2-chloroethylimino)methyl)phenol
bromoethylimino)methyl)phenol, showed potent inhibitory activity
with 16 g/mL MIC value. The ligands showed moderate activity
lg/mL against MRSA; surprisingly the ligands, (E)-4-bromo-
and (E)-4-bromo-2-((2-
l

A.N. Kursunlu et al. / Journal of Molecular Structure 1048 (2013) 476–481
antimicrobial active terminal
481
antimicrobial active terminal
X
Br
N
Y
Y
N
O
M
O
Br
antimicrobial active terminal
X
antimicrobial active terminal
Fig. 4. The antimicrobial active terminals of the complexes.
[2] M.M. Omar, G.G. Mohamed, A.A. Ibrahim, Spectrochim. Acta A 73 (2009) 358–
369.
[3] G.S. Huang, Y.M. Liang, X.L. Wu, W.M. Liu, Y.X. Ma, Appl. Organomet. Chem. 17
(2003) 706–710.
all of the Gram-positive and Gram-negative strains with MIC
ranges (16–128 g/mL). The Co(II) and Cu(II) complexes of the li-
gands had no valuable inhibitory activity with low inhibition
zones. The Ni(II) and Zn(II) complexes generally have a strong anti-
microbial effect against studies bacteria’s (Tables 3 and 4).
l
[4] M. Aslantasß, E. Kendi, N. Demir, A.E. Sßabik, M. Tümer, M. Kertmen, Spectrochim.
Acta A 74 (2009) 617–624.
[5] K.F. Ansari, C. Lal, Eur. J. Med. Chem. 44 (2009) 2294–2299.
[6] E. Canpolat, M. Kaya, J. Coord. Chem. 57 (2004) 1217–1223.
[7] P.J.K. Inba, B. Annaraj, S. Thalamuthu, M.A. Neelakantan, Spectrochim. Acta A
104 (2013) 300–309.
4. Conclusion
[8] H. Keypour, M. Shayesteh, M. Rezaeivala, F. Chalabian, Y. Elerman, O.
Buyukgungor, J. Mol. Struct. 1032 (2013) 62–68.
[9] E. Canpolat, M. Kaya, A. Yazici, Spectrosc. Lett. 38 (2005) 35–45.
[10] R.C. Maurya, P. Patel, S. Rajput, Synth. React. Inorg. Met. 33 (2003) 817–836.
[11] U. Bohme, B. Gunther, Inorg. Chem. Commun. 10 (2007) 482–484.
[12] L.C. Felton, J.H. Brewer, Science 105 (1947) 409–410.
We synthesized the new Schiff base ligands containing bromine
and chlorine derived from salicylaldehyde. Then, Cu(II), Co(II),
Ni(II) and Zn(II) complexes of these Schiff base ligands were ob-
tained in appropriate conditions. Among the synthesized com-
pounds, the Schiff base ligands (L1 and L2) with chlorine, bromine
and AOH substituents showed moderate inhibition activity against
some Gram-positive and Gram-negative bacteria including MRSA.
The Zn(II) and Ni(II) complexes of the prepared ligands have a
strong antimicrobial effect upon the studies bacterias. The results
of this study can be useful to researchers attempting for future
work to study the antifungal activities of the Schiff base complexes.
Based on the results obtained, slight modifications of the L1 and L2
might produce potent and potential compounds which could be
used as antimicrobial agents such as Ceftriaxone.
[13] P. Noblıa, M. Vieites, B.S. Parajo´n-Costa, E.J. Baran, H. Cerecetto, P. Draper, M.
´
´
´
Gonzalez, O.E. Piro, E.E. Castellano, A. Azqueta, A.L. Cerain, A. Monge-Vega, D.
Gambino, J. Inorg. Biochem. 99 (2005) 443–451.
[14] A.N. Kursunlu, E. Guler, H. Dumrul, O. Kocyigit, I.H. Gubbuk, Appl. Surf. Sci. 255
(2009) 8798–8803.
[15] A.W. Bauer, W.M.M. Kirby, J.C. Sherris, M. Turck, Am. J. Clin. Pathol. 45 (1996)
493–496.
[16] J.H. Jorgensen, J.D. Turnidge, Susceptibility test methods: dilution and disk
diffusion methods, in: P.R. Murray, E.J. Baron, J.H. Jorgensen, M.A. Pfaller, R.H.
Yolken (Eds.), Manual of Clinical Microbiology, eighth ed., American Society for
Microbiology, Washington, DC, 2003, pp. 1108–1127.
[17] Y. Sun, Q. Zeng, S. Gou, W. Huang, C. Duan, J. Yao, J. Incl. Phenom. Macro. 42
(2002) 131–135.
[18] H. Okawa, J. Nishio, M. Ohoba, M. Tadokoro, N. Matumastsumoto, M. Koikawa,
S. Kaida, D.E. Fenton, Inorg. Chem. 32 (1993) 2949–2957.
[19] Z.Y. Yang, R.D. Yang, F.S. Li, K.B. Yu, Polyhedron 19 (2000) 2599–2604.
[20] D.X. West, J.K. Swearingen, J.V. Martinez, S.H. Ortega, A.K. El-Sawaf, F.V. Meurs,
A. Castineiras, I. Garcia, E. Bermejo, Polyhedron 18 (1999) 2919–2929.
[21] H. Köksal, M. Dolaz, M. Tümer, S. Serin, Synth. React. Inorg. Met. 31 (2001)
1141–1162.
Acknowledgments
The authors gratefully would like to thank Selcuk University Re-
search Foundation (SUBAP) for financial support (under Projects
FBE 2009, 09401038).
[22] F.A. Cotton, G. Wilkinson, C.A. Murillo, M. Bochmann, Advanced Inorganic
Chemistry, sixth ed., Wiley, New York, 1999.
[23] A.B.P. Lever, Inorganic Electronic Spectroscopy, second ed., Elsevier, New York,
1968.
[24] E. Tas, V.T. Kasumov, O. Sahin, M. Ozdemir, Transition Met. Chem. 27 (2002)
442–446.
References
[1] R.K. Rawal, R. Tripathi, S.B. Kati, C. Pannecouque, E. De Clercq, Bioorg. Med.
Chem. 15 (2007) 1725–1731.
[25] C.M. Sharaby, Spectrochim. Acta, Part A 66 (2007) 1271–1278.