Synthesis and biochemical activity studies of 2,2'-[propane-1,3- diylbis(oxy)]-2,2'bis-[(benzylideneamino)benzenethiol] ligand and its mononuclear Copper(II), Nickel(II), and Cobalt(II) complexes

Article abstract of DOI:10.1080/15533174.2012.754770

A new hexadentate ligand incorporating Schiff base moities has been synthesized and its copper(II), nickel(II), and cobalt(II) complexes have been prepared and characterized by spectral methods. Elemental analyses and spectroscopic data of the Schiff base ligand and its copper(II), nickel(II), and cobalt(II) complexes are consistent with the formation of the ligand and its metal complexes. In addition to the Schiff base ligand (H₂L) and copper (II), nickel(II), and cobalt(II) complexes (5-7) were tested against the morphology of series bacteria. The copper(II), nickel(II), and cobalt(II) complexes exhibit higher activity than Schiff base ligand (H₂L) under identical experimental conditions. Copyright Taylor and Francis Group, LLC.

Full text of DOI:10.1080/15533174.2012.754770

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Synthesis and Biochemical Activity Studies
of 2,2′-[propane-1,3-diylbis(oxy)]-2,2′bis-
[(benzylideneamino)benzenethiol], ligand and its
mononuclear copper(II), nickel(II) and cobalt(II)
complexes
a
a
a
a
Nevin Karabocek , Pınar Ekmekcioglu , Seda Muhsir & Serdar Karabocek
a
Department of Chemistry, Karadeniz Technical University, Trabzon, 61080, Turkey
Accepted author version posted online: 14 Feb 2013.
To cite this article: Nevin Karabocek , Pınar Ekmekcioglu , Seda Muhsir & Serdar Karabocek (2013): Synthesis and Biochemical
Activity Studies of 2,2′-[propane-1,3-diylbis(oxy)]-2,2′bis-[(benzylideneamino)benzenethiol], ligand and its mononuclear
copper(II), nickel(II) and cobalt(II) complexes, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal
Chemistry, DOI:10.1080/15533174.2012.754770
To link to this article: http://dx.doi.org/10.1080/15533174.2012.754770
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ACCEPTED MANUSCRIPT
Synthesis and Biochemical Activity Studies of 2,2'-[propane-1,3-diylbis(oxy)]-2,2’bis-
[
(benzylideneamino)benzenethiol], ligand and its mononuclear copper(II), nickel(II) and
cobalt(II) complexes
1
1
1
1
Nevin Karabocek , Pınar Ekmekcioglu , Seda Muhsir and Serdar Karabocek *
1
. Department of Chemistry, Karadeniz Technical University, 61080 Trabzon, Turkey
Abstract: A new hexadentate ligand incorporating Shiff base moities has been synthesized and
its copper(II), nickel(II) and cobalt(II) complexes have been prepared and characterized by
spectral methods. Elemental analyses and spectroscopic data of the Schiff base ligand and its
copper(II), nickel(II) and cobalt(II) complexes are consistent with the formation of the ligand and
its metal complexes. In addition to the Schiff base ligand (H
2
L) and copper (II), nickel(II) and
cobalt(II) complexes (5-7) were tested against the morphology of series bacteria. The copper(II),
nickel(II) and cobalt(II) complexes exhibit higher activity than Schiff base ligand (H
identical experimental conditions.
2
L) under
Keywords: Benzenethiol; biological activity; copper(II); nickel(II); cobalt(II) complex.
*
Corresponding author. Tel.: +90 4623772598; fax: +90 4623253195, E-mail:
serdar@ktu.edu.tr
Introduction
1
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[1]
The reaction of primary amines with carbonyl compounds yields Schiff bases. Also the
Schiff base derived from the reaction of diketones with diamines represent an important series of
chelating agents and are now being widely used the synthesise mono-, di-, and polynuclear
transition metal complexes. Schiff bases and their metal complexes play a key role in our
[2]
understanding of the coordination chemistry of transition metal ions. There is considerable
interest in the chemistry of transition metal complexes of ligands containing oxygen, nitrogen
and sulphur donor atoms due to the antitumor, antiviral, antifungal and antibacterial activity and
[3,4]
industrial uses.
In the past years, the synthesis, structure and properties of Schiff base complexes have
been stimulated much interest for their noteworthy contributions in single molecule-based
[5]
magnetism, material science, catalysis of many reaction like carbonylation, hydroformylation,
[6]
reduction, oxidation, epoxidation and hydrolysis. This is due to the fact that Schiff bases offer
opportunities for inducing substrate chirality, tuning the metal centered electronic factor,
enhancing the solubility and stability of either homogeneous or heterogeneous catalyst. The
flexibility of disposition of different donor site is the secret behind their successful performance
in mimicking peculiar geometries around the metal centers, leading to very interesting
[7]
spectroscopic properties with varied magnetic activities.
Copper(II), nickel(II) and cobalt(II)
complexes of Schiff base with pseudohalides are well known for their preparational
[8-
accessibilities, exhibiting the flexibility of the coordination geometry around the metal center.
1
0]
The coordination number usually varies from four to six depending upon the donor site
geometry around the metal and above all the steric constraints imposed by the ligand itself.
2
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This article describes the synthesis and characterization of the new ligand, 2,2'-[propane-
1
,3-diylbis(oxy)]2,2’bis-[(benzylideneamino)benzenethiol], and its copper(II), nickel(II) and
cobalt(II) complexes. The properties of the complexes were investigated by magnetic, physical,
and spectral methods. Furthermore, the free ligand and copper(II), nickel(II) and cobalt(II)
complexes (5-7) were evaluated for antimicrobial activity against one gram-positive bacterium
(
Staphylococcus aureus), a gram-negative bacterium (Escherichia coli), and the fungi
Aspergillus niger and Trichoderma. The free ligand and copper(II), nickel(II) and cobalt(II)
complexes (5-7) exhibit antibacterial activity against both strains.
Results and Discussion
2
,2'-[propane-1,3-diylbis(oxy)]2,2’bis-[(benzylideneamino)benzenethiol], (H2L) was
synthesised in EtOH by condensation 2,2'-[propane-1,3-diylbis(oxy)]dibenzaldehyde, (3) with
-aminothiophenol (Scheme 1). The Schiff base ligand and dialdehyde (3) were characterized by
2
1
13
elemental analysis, H-NMR, C-NMR, IR and mass spectral data. The Cu(II), Ni(II), and
Co(II) complexes of Schiff base (H L) have been prepared and characterized by elemental
analysis, magnetic moment, Uv-Vis, and mass spectral data. In the proposed structure of the
Schiff base ligand (H L), N units available for the octahedral complexation of Cu(II),
2
2
2
S
2
O
2
Ni(II), and Co(II) metal ions.
NMR Spectra
The 1H-NMR spectra of dialdehyde (3) and Schiff base (H
2
L) ligand (in CDCl ) showed
3
1
well-resolved signals as expected. The proton H-NMR spectrum of compound 3 showed the
following signals: C
6
H
4
as multiplet at δ = 7.0-7.85, -CHO singlet at δ = 10.50, -OCH - triplet at
2
δ = 4.33, and -CH
2
- pentet at δ = 2.43 ppm. The proton NMR spectrum of Schiff base ligand
3
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(
-
H
2
L) showed the following signals: C
6
H
4
as multiplet at δ = 7.1-8.1, -N=CH singlet at δ = 8.57,
- pentet at δ = 2.73 ppm. In 8.53 ppm,
SH singlet at δ = 8.53, -OCH - triplet at δ = 4.6 and -CH
2
2
1
the singlet disappears on deuterium exchange. In the H-NMR spectra, integrated data are
1
3
consistent with the formula. Nine resonance signals were observed in the C-NMR spectra of
the dialdehyde (3) and Schiff base ligand (H L), which was also consistent with the formula for
L.
Mass Spectra
The mass spectra of the Schiff base (H
were recorded in pyridine solution. The mass spectra (ESI) exhibited the molecular ion at m/z =
2
H
2
2
L) and its Cu(II), Ni(II), and Co(II) complexes
+
+
2
84 M for compound 3 and m/z = 498 M for the free Schiff base ligand, which indicated
+
formation of compound 3 and ligand. The molecular ion peaks appeared (m/z, ESI) at 560.18 M ,
+
+
at 556.41 [M+1] , and at 555.57 M for the CuL, NiL, and CoL, respectively. The mass spectra
showed the formation of the ligand and its Cu(II), Ni(II), and Co(II) complexes.
IR Spectra
Relevant characteristic IR bands were given in Table 1. In generally, the metal complexes
exhibited very comparable IR features, suggesting that they were similar structure. The certain
bands in the generally complicated IR spectra were used to establish the nature of the metal
-
1
[11]
complexes. The strong band at 1594 cm might be assigned to � (C=N) vibration. In the
Cu(II), Ni((II), and Co(II) complexes � (C=N) vibrations were shifted to lower frequency (≈10
-1
[12]
cm ), suggesting coordination of metal via nitrogen.
Finally, the peaks appearing between
-1
[12, 13]
4
30 and 480 cm are attributed to � (M-N).
The significant shifts in � (C=N) upon
4
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complexation support the concept of coordination of ligand through the Schiff base nitrogen (Fig
1
).
Magnetic properties and Electronic Absorption Spectra
Electronic spectra of the Cu(II), Ni(II), and Co(II) complexes were recorded in DMSO (λ
-1
-1
-1
cm (ε L mol cm )). The experimental values are given in Table 2. Electronic spectra of the
-
1
Cu(II) complex show bands at 13,123 (762), 16,181 (618), and 28,985 (345) cm assignable to a
2
2
E
g
 T2g transition and charge transfer. Electronic spectral data coupled with detected magnetic
[
12, 14]
moment of 1.81 B.M. suggest octahedral geometry.
Ni(II) complex displays bands at 13,422
-1
3
3
3
3
(
1025), 14,285 (700), and 30,303 (355) cm assignable to a A2g T2g(F), A2g T1g(F), and
3
3
A
2g T1g(P), respectively. These electronic transition along with magnetic moment 2.78 B.M.
[
12, 15]
suggest octahedral geometry for Ni(II) complex.
The Co(II) complex shows three bands at
-
1
4
4
4
1
3,450 (750), 14,326 (700), and 33,335 (320) cm assignable to T1g(F) T2g(P), T1g(F)
4
4
4
T
1g(P), and
T
1g(F) A2g transitions, respectively. These transitions and detected magnetic
[
12, 16, 17]
moment of 3.9 B.M. indicate a high-spin octahedral complex.
ligand field splitting energy (10 Dq), Racah interelectronic repulsion parameter (B), covalent
factor (β), ratio v /v , and ligand field stabilization energy (LFSE), given in Table 2, support the
The calculated values of
2
1
proposed geometry for the Cu(II), Ni(II), and Co(II) complexes.
Antimicrobial Activity
The Schiff base ligand (H L) and its metal complexes were evaluated for antimicrobial
2
activity against one gram-positive bacterium (S. aureus), gram-negative bacterium (E. coli), and
fungi fungi A. niger and Trichoderma. The results of these studies are given in Table 3. These
data showing that the Schiff base ligand and its Cu(II), Ni(II), and Co(II) complexes exhibit
5
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antibacterial activity against both strains. The Cu(II), Ni(II), and Co(II) complexes exhibit higher
activity than the Schiff base ligand under identical experimental conditions. Antibacterial
inhibitions were compared with the activity of ciprofloxin as a standard. The Schiff base ligand
(
2
H L) and its metal complexes showed less activity than the standard. The metal salts used for
[
18, 19]
synthesis of metal complexes exhibit negligibly antimicrobial activities.
Enhancement of
activity of the Schiff base after chelation can be explained on the basis of Overtones and
[20]
Tweedy’s concepts.
Antibacterial inhibition was found to increase with increasing
concentration of the metal complexes. The studies showed that the Cu((II) complex exhibits
higher activity against each class of organism. The activity is related to the nature and structure
[21]
of the metal complexes.
The higher activity of the Cu(II) complex may be attributed to its
higher stability constants. The Schiff base and its metal complexes show more activity against
gram–negative E. coli than against gram-positive S. aureus. Antibacterial activity can be ordered
[
12, 22]
as CuL> CoL > NiL, similar to earlier observations.
The Cu(II), Ni(II), and Co(II) metal
complexes don’t show strong concentration dependence of antimicrobial activity as compared to
the antifungal activities of the same complexes. The relation between chelation and toxicity is
very complex, expected to be a function of steric, electronic, and pharmacological factors along
[23]
with mechanistic pathways. Investigation of antifungal activity of the Schiff base ligand and
its Cu(II), Ni(II), and Co(II) metal complexes revealed that all the metal complexes are more
toxic than the ligand. The antifungal activity is enhanced several times on being coordinated with
metal. The metal complexes activity increases as the stability of the complex increases. The
metal complex activities follow the order CuL> CoL > NiL, which is exactly same as the order
of stability constants of these complexes. Comparison of activities shows that the Cu(II) complex
6
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is more active than the Schiff base ligand against A. niger. The Schiff base ligand (H
against Trichoderma increases.
2
L) activity
Conclusions
In this work, we have demonstrated the synthesis and characterization of the 2,2'-
propane-1,3-diylbis(oxy)]2,2’bis-[(benzylideneamino)benzenethiol], and its copper(II),
[
nickel(II) and cobalt(II) complexes. All the metal complexes have been found to be paramagnetic
properties. The metal atom ions were complexed with nitrogen, sulphur and oxygen atoms of the
Schiff base ligand in an octahedral geometry. All of data obtained from spectra supported the
structural properties of ligand and its metal complexes. The Shiff base ligand and its copper(II),
nickel(II) and cobalt(II) complexes (5-7) were evaluated for antimicrobial activity against one
gram-positive bacterium (Staphylococcus aureus), a gram-negative bacterium (Escherichia coli),
and the fungi Aspergillus niger and Trichoderma. The free ligand and copper(II), nickel(II) and
cobalt(II) complexes (5-7) exhibit antibacterial activity against both strains.
Experimental and methods
Reagents and Instruments
1
13
H-NMR and C- NMR spectra were recorded on a Varian Gemini 200 spectrometer. CDCl
3
was used as solvent. Chemical shifts () are reported in ppm relative to tetramethylsilane, using
the solvent signal as internal reference. C, H and N contents were determined microanalytically
on a Hewlett Packard 85 CHN analyzer, and metal contents were estimated
spectrophotometrically. IR spectra were recorded on an ATI Unicam Matson 1000 Model FTIR
spectrophotometer and Uv-Vis spectra on an ATI Unicam UV2 Model UV/Vis
7
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spectrophotometer. Mass spectra [ESI) were recorded on Micromass Quattroo LC-MS/MS
spectrophotometer. Room temperature magnetic susceptibility measurements were done on a
PAR model 155 vibrating sample magnetometer. All chemicals were of the highest quality
available, obtained from local suppliers, and used as received
Sythesis of 2,2'-[propane-1,3-diylbis(oxy)]dibenzaldehyde, (3)
Freshly prepared potassium 2-formylphenolate (3.2 g, 20 mmol) and 1,3-dibrompropane
(
2 g, 10 mmol) were refluxed for 3 h in dimethylformamide (DMF) (25 mL). The solution was
then poured in to ice-water (50 mL) and the solid product filtered off and recrystallised from
o
ethanol with decolourising charcoal. The compound 3, m.p. 120 C, was isolated in 80% yield;
-
1
1
IR (KBr disc.)/cm 1682 (C=O) and 1240(C-O); H-NMR(CDCl
.0-7.85 (m, 8H, aryl), 4.33 (t, 4H, C -OCH ), and 2.44 (p, 2H, -CH
Elementel analysis (%): calculated: C, 72.90; H, 5.82; found: C, 72.70; H, 5.8 for C17
3
)/ppm δ: 10.50 (s, 2H, CHO),
+
7
2
2
-). MS: (ESI) m/z = 284 M .
H
16
4
O .
Sythesis of 2,2'-[propane-1,3-diylbis(oxy)]2,2’bis-[(benzylideneamino)benzenethiol], (H L)
2
A solution of dialdehyde (3) (2.84 g, 10 mmol) and 2-aminothiophenol (2.5 g, 20 mmol)
were refluxed for 10 h in EtOH (25 mL). The solution was then poured in to water (50 mL) and
the solid product filtered off and recrystallised from ethanol with decolourising charcoal. The
o
-1
compound 3, m.p. 154.3 C, was isolated in 60% yield; IR (KBr disc.)/cm 1594 (C=N), and
1
1
238(C-O); H-NMR(CDCl
3
)/ppm δ: 8.57 (s, 2H, N=CH), 8.53 (s, 2H, -SH) 7.1-8.1 (m, 16H,
+
aryl), 4.6 (t, 4H, -OCH
2
), and 2.73 (p, 2H, -CH
2
-). MS: (ESI) m/z = 498 M . Elementel analysis
(
%): calculated: C, 69.8; H, 5.3; found: C, 69.9; H, 5.2 for C29
H
26
N
2
O
2
2
S .
8
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Sythesis of copper(II), nickel(II) and cobalt(II) complexes (5-7)
Metal complexes (5-7) have been prepared by the same method. A solution of
M(ClO
solution in (CH
The products were filtered off, washed with H
4
)
2
.6H
2
O (1 mmol) in (CH
CO (25 mL), and the mixture was boiled under reflux with stirring for 4 h.
O, EtOH, Et O respectively and dried over P O .
3
)
2
CO (25 mL) was added to the ligand (0.5 g, 1 mmol)
)
3 2
2
2
2
5
For C29
H24CuN
2
O
2
S
2
, (5), elementel analysis (%): calculated: C, 62.2; H, 4.3; Cu, 11.3
+
found: C, 62.1; H, 4.2; Cu, 11.2. MS (ESI): m/z = 560.18 M . Yield, a green-brown solid: 0.4 g
(
71%). For C29
H24NiN
2
O
2
S
2
, (6), elementel analysis (%): calculated: C, 62.7; H, 4.4; Ni, 10.6
+
found: C, 62.6; H, 4.5; Ni, 10.5. MS (ESI): m/z = 556.41 [M+1] . Yield, a pale-red solid: 0.35 g
(
63%). For C29
H24CoN
2
O
2
S
2
, (7), elementel analysis (%): calculated: C, 62.7; H, 4.4; Co, 10.6
+
found: C, 62.7; H, 4.4; Ni, 10.7. MS (ESI): m/z = 555.57 M . Yield, a brown solid: 0.4 g (72%).
Antimicrobial Activity
The antimicrobial activity of the Schiff base ligand and its Cu(II), Ni(II), and Co(II)
complexes, the metal salts, and the control (DMSO) was tested in vitro against gram-positive
bacteria (Staphylococcus aureus), and gram-negative bacteria (Escherichia coli) by paper disc
[24].
method.
Sterile (10 mm diameter) Whatman number 42 paper discs were soaked in different
-1
concentrations of ligand and/or complex (0.5 and 1 mg L ) in DMSO, dried, and then placed on
o
nitruent agar plates. The plates were then incubated for 24 h at 37 C and the inhibition zone
around each disc was measured. The results obtained were compared with those of ciprofloxin.
Three replicates were taken and the average value is given in Table 1. The Schiff base ligand
and its Cu(II), Ni(II), and Co(II) complexes, metal salts, and the control (DMSO) were screened
9
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-1
for antifungal activity against the fungi Aspergillus niger and Trichoderma at 0.5 and 1 mg L
[25]
by the mycelia dry weight (MDW) method. The cultures of fungi were purified by single-
spore isolation technique. The glucose nitrate (GN) medium was used for growth of fungi. The
o
mycelia biomass was then dried along with filter paper in an oven at 65±5 C to constant weight,
cooled, and finally weighed. The MDW was obtained by subtracting the weight of mycelium-
[26]
free filter paper from final dry weight.
Three replicates of each treatment were repeated in all
experiments. The MDW was corrected each time by subtracting the dry weight obtained from the
incubated flask under similar experimental conditions. The yields of MDW (mg) are presented in
Table 1. The percentage error was found to be ±0.01. The percent decrease in MDW to the test
compound in each case was calculated and tabulated in terms of average percentage inhibition.
The results indicate that the ligand and its Cu(II), Ni(II), and Co(II) complexes arrested the
growth of fungi.
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5
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2
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document M24-A, 2003.
Acknowledgment: This work was supported by Karadeniz Technical University Research Fund,
and its project code is 8665.
-
1
TABLE 1. Characteristic IR bands of the free ligand and its metal complexes (in cm )
Compound
� (C=O)
� (C=N)
� (C-O)
� (M-N)
3
1682
-
1240
1238
1241
1240
1236
-
H
2
L
-
-
-
-
1594
1574
1580
1578
-
CuL
NiL
CoL
455
430
480
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TABLE 2. Ligand field parameter of the metal complexes
Complex Ligand field splitting
Racah interelectronic
repulsion parameter
Covalent
β
v
2
/v
1
LFSE
-1
-1
energy (Dq cm )
factor (β) (%)
(kcal mol )
-1
(
B cm )
CuL
NiL
CoL
1312,3
1342,2
1345,0
95
-
-
-
37.49
38.34
38.42
1030
971
0.2845
0.5054
6.2 1.06
4.9 1.06
TABLE 3. Antibacterial activities of (diameter inhibition zone in mm) and antifungal activity
weight (mg) (% inhibion) of the ligand and metal complexes
−
1
Antibacteriyal
Antifungal activiteleri (mg mL )
−
1
activiteleri(mg mL )
E. coli S. aureus
A. niger
0.5
74
Trichoderma
Compound
0.5
1
0.5
1
1
0.5
65
1
Ciprofloxin/kontrol 40
45
15
35
15
20
42
10
15
12
15
44
20
25
20
20
72
60
H
2
L
12
20
10
17
70 (15) 65 (10) 45 (25)
50 (45) 15 (80) 35 (50)
50 (40) 20 (80) 30 (50)
55 (30) 25 (75) 40 (60)
30 (50)
25 (70)
25 (65)
25 (64)
5
6
7
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CHO
CHO
CHO
O
O
KOH, EtOH
Br
Br
2
OH
(
1)
(2)
(
3)
SH
EtOH
2
NH2
HC
HC
N
N
SH
O
O
SH
(
4)
Scheme 1. Preparation of ligand, bis-{2-[(E)-(2-propoxybenzylidene)amino]benzenethiol},(H
2
L)
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S
M
S
N
N
O
O
M= Cu(II) (5), Ni(II) (6), Co(II) (7)
Fig. 1. Proposed structures for the copper(II), nickel(II) and cobalt(II) complexes
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