Synthesis and antibacterial activities of mixed ligands complexes of Cu(II) and Zn(II) containing tridentate azo anils ligands and bidentate oxalate ion

Article abstract of DOI:10.14233/ajchem.2015.19030

Mixed ligands complexes of copper(II) and zinc(II) were synthesized using azo anils ((HNPDBAB = 2-({2-hydroxy-5-[(4- nitrophenyl)diazenyl]benzylidene}amino)benzoic acid, HPIMNDP = 2-{[(2-hydroxyphen yl)imino]methyl}-4-[(4-nitrophenyl)diazenyl] phenol) and oxalate ion as a coordinating ligands. Elemental analysis, atomic absorption spectroscopy, FTIR, NMR, UV-visible. were used for the characterizations of synthesized azo anils ligands and their mixed ligands complexes. Distorted octahedral geometry was tentatively proposed for these new mixed ligands M(II) {Cu(II) and Zn(II)} complexes. Gram-positive (Bacillus subtilis and Staphylococcus aureus) and Gram-negative (Enterobacter aerogenes and Escherichia coli) were screen out for antibacterial activities of azo anils ligands, oxalic acid, metal salts and their mixed ligands M(II) complexes. The antibacterial activities were performed to assess the extent of inhibition potential of free ligand and their mixed ligands M(II) complexes. The results revealed that antibacterial activities of azo anils became more pronounced when these were coordinated to central metal atom.

Full text of DOI:10.14233/ajchem.2015.19030

Asian Journal of Chemistry; Vol. 27, No. 11 (2015), 3988-3992
A
SIAN
J
OURNAL OF HEMISTRY
C
http://dx.doi.org/10.14233/ajchem.2015.19030
Synthesis and Antibacterial Activities of Mixed Ligands Complexes of Cu(II) and
Zn(II) Containing Tridentate Azo Anils Ligands and Bidentate Oxalate Ion
1,*
1
1
1
2
1
MUHAMMAD AMEEN , SYEDA RUBINA GILINI , AMINA NASEER , ISHRAT SHOUKAT , SYED DANISH ALI and AYESHA SADIQA
1
2
Department of Chemistry, University of Engineering and Technology, Lahore-54890, Pakistan
Nano Science and Catalysis Division, Nation Centre for Physics, Islamabad-45320, Pakistan
*
Corresponding author: E-mail: ch.ameen86@gmail.com
Received: 17 January 2015; Accepted: 19 February 2015;
Published online: 16 July 2015;
AJC-17388
Mixed ligands complexes of copper(II) and zinc(II) were synthesized using azo anils ((HNPDBAB = 2-({2-hydroxy-5-[(4-
nitrophenyl)diazenyl]benzylidene}amino)benzoic acid, HPIMNDP= 2-{[(2-hydroxyphen yl)imino]methyl}-4-[(4-nitrophenyl)diazenyl]
phenol) and oxalate ion as a coordinating ligands. Elemental analysis, atomic absorption spectroscopy, FTIR, NMR, UV-visible were
.
used for the characterizations of synthesized azo anils ligands and their mixed ligands complexes. Distorted octahedral geometry was
tentatively proposed for these new mixed ligands M(II) {Cu(II) and Zn(II)} complexes. Gram-positive (Bacillus subtilis and Staphylococcus
aureus) and Gram-negative (Enterobacter aerogenes and Escherichia coli) were screen out for antibacterial activities of azo anils ligands,
oxalic acid, metal salts and their mixed ligands M(II) complexes. The antibacterial activities were performed to assess the extent of
inhibition potential of free ligand and their mixed ligands M(II) complexes. The results revealed that antibacterial activities of azo anils
became more pronounced when these were coordinated to central metal atom.
Keywords: Azo anils, Oxalate, Mixed ligands M(II) complexes, Antibacterial activity.
(
chemistry and biology). Binuclear oxalate bridged Cu(II)
INTRODUCTION
24
complexes with Schiff base have been reported .
Azo anils and their complexes with Cu(II) and Zn(II) had
Here we have reported novel mixed ligands complexes of
Cu(II) and Zn(II), synthesized by the coordination of azo anils
ligands and oxalate ion. The metal salt, azo anils and oxalic
acid were mixed in 1:1:1 ratio and resulted to mixed ligands
M(II) complexes. The objective of this study was to determine
how much extent of antibacterial activities of azo anils
increased when they were coordinated to central transition
metal.A pronounce change in antibacterial activities have seen
from azo anils ligands to mixed ligands M(II) complexes.
1
displayed antibacterial and antifungal activities . Azo anils
ligands have been supposed as “fortunate ligands” because
they can be easily synthesized by the condensation of azo dye
2
of salicyladehyde and aromatic amine . Azo Schiff bases can
3
coordinate through azo and azomethine group . Most of the
transition metal forms stable complexes with azomethine
because it has excellent π-donor character . All at once, it is
not possible for both group together to take part in bonding
with central metal ion because –N=N- (azo group) and –C=N
4
-6
(
azomethine group) are far away from each other. So preferen-
tially coordination take place through –C=N group whereas
N=N- group remain free because there is no more room for
EXPERIMENTAL
–
Carbon, hydrogen and nitrogen contents were determined
using 4010-Elemental combustion system (Costech Interna-
tional).Atomic absorption spectroscopy (varian) was performed
to determine exact Cu(II) and Zn(II) contents in synthesized
complexes. Electronic spectra of Cu(II) and Zn(II) complexes
in dimethyl sulfoxide (DMSO) solvent were recorded using
Perkin-Elmer Lambda 25 UV-visible spectrophotometer (800-
200 nm). The IR spectra of synthesized azo anils ligands and
mixed ligands complexes with KBr pellets were recorded on
7-10
azo group to take part in coordination .Azo complexes are very
important compounds and have fascinated more awareness in
both academic and applied researches
The complexes having bridging ligands such as oxalate
ion or mixed ligands complexes with one azo Schiff base and
one oxalate ligands were studied not only due to antiferromagnetic
properties of oxalate group between two paramagnetic centres
1
1-16
.
1
7-20
21-23
of binuclear homo-metallic
lexes but also due to their application in various fields of science
or hetero-metallic
comp-
–
1
Jasco FTIR (4100-typeA) within (4000-400 cm ) range.

Vol. 27, No. 11 (2015)
Synthesis and Antibacterial Activities of Mixed Ligands Complexes of Cu(II) and Zn(II) 3989
1
3
1
1
Nuclear magnetic resonance ( C and H) spectroscopy was
performed using a Bruker 300 MHZ spectrometer. The
antibacterial studies were carried out using diffusion disc
method. The physical parameters of ligands and complexes
are given in Table-1.
500 nm. H NMR(DMSO) δ ppm: 13.50 (1H, S), 12.80 (1H,
S), 8.70 (3H, S), 8.1(1H, S), 7.90 (3H, S), 7.78 (2H, S), 7.60
13
1
(1H, S), 7.25 (1H, S), 6.90 (1H, S). C-{ H} NMR (DMSO) δ
ppm: 113.1, 115.14, 118.21, 119.01, 123.05, 123.05, 123.50,
124.23, 124.50, 124.70, 124.75, 130.90, 136.53, 142.51,
149.40, 151.53, 152.3, 160.41, 165.34, 172.53.
2-{[(2-Hydroxyphenyl)imino]methyl}-4-[(4-nitrophenyl)-
diazenyl]phenol (HPIMNDP): Dark brown solid, Yield:
Reagent grade copper chloride dihydrate, zinc acetate
dihydrate, 4-nitroaniline, 2-aminophenol, 2-aminobenzoic,
oxalic acid were purchased from BDH and absolute solvent
(methanol and ethanol) were received fromAldrich.All chemi-
77 %, m.p.: 287-290 °C. m.f.: C19
H
14
4 4
N O .2H
2
O. Anal. Calc.
cals were used without any further purification, except vacuum
dried over silica gel.
C: 57.28, H: 4.55, N: 14.06 %. Found: C: 57.29, H: 4.56, N:
–1
14.15 %. FTIR spectra (KBr pellets, cm ); 3240-3150 (-OH,
phenolic), 3500-3600 (coordinated water), 3062 (C-H,
aromatic), 1616 (-C=N-, azomethine), 1604 (C=C, aromatic),
Synthesis of starting materials (azo dye): An azo dye
2
-hydroxy-5-[(4-nitrophenyl)diazenyl]benzaldehyde was
25
–1
prepared in accordance with published procedure . Concen-
trated hydrochloric acid (40 mL) and distilled water (20 mL)
were added to 4.14 g (30 mmol) of 4-nitroaniline and heated
up to 80 °C until absolute dissolution occur. Diazotization
occurred below 5 °C when solution of 4-nitroaniline was added
to 2.1 g (30 mmol) of sodium nitrite solution in 10 mL of
distilled water. The chilled diazonium solution slowly poured
into salicyladehyde solution which was prepared by adding
1511 (-N=N-, azo), 1290 (C-O, phenolic) cm . UV-visible:
1
λ
max = 280, 420, 505 nm. H NMR(DMSO) δ ppm: 12.90 (1H,
S), 8.50 (1H, S), 8.40 (2H, S), 7.90 (2H, S), 7.81 (3H, S), 7.60
(1H, S), 7.25 (2H, S), 7.06 (1H, S), 6.91 (1H, S) ppm. C-
{ H}NMR(DMSO) δ ppm: 113.2, 115.21, 118.22, 119.03,
13
1
119.5, 119.71, 123.11, 124.55, 124.70, 124.75, 128, 52, 135.53,
149.50, 151.50, 151.53, 152.21, 153.06, 160.32, 170.33.
Synthesis of mixed ligands M(II) complexes: Methanolic
solution of azo anils (1 mmol) and aqueous solution of oxalic
acid (1 mmol) were blended and added to methanolic solution
3
.2 g (30 mmol) of salicyladehyde in 57 mL water, which also
contain 11.1 g of sodium carbonate, 1.2 g of sodium hydroxide
and stirred over magnetic stirrer for 40 min in ice bath. The
azo dye was obtained using gooch crucible and washed with
of 1 mol of metal salt [CuCl
2
2
·2H O or Zn(CH
3
COO)
2
·2H O].
2
The colour changed occurred after 2-3 min. The reaction
mixture was refluxed for 3-4 h. The precipitated compounds
were obtained using gooch crucible, washed with methanol and
then with water to remove organic and inorganic impurities.
[(HNPDBAB)M(II)(OX)]: Orange red solid,Yield: 70 %,
m.p.: 350 °C and elemental analysis results are given in Table-1.
1
0 % sodium chloride solution. Diazonium reagent coupled
to salicyladehyde (at p-position from –OH group). The final
product was extensively washed with water and ethanol to
remove unreacted substance. m.f.: C13
H N
9
3
O , yellow coloured
4
solid, Yield: 85 %, m.p.: 187-188 °C. The FTIR (KBr pellet,
–
1
–1
–1
cm ): 3103 (-OH), 1661 (-CHO), 1481 (N=N), 1337 (NO
2
)
FTIR (KBr pellets, cm ): 3600-3560 cm (coordinated water).
–1
–1
and 1284 (C-O) cm group. UV-visible: λmax = 395; 551 nm.
A band at -31003150 cm indicates the coordination of phenolic
group with central metal atom. The band at 2750-2640 cm
–1
Synthesis of azo anils ligands: Azo anils ligands were
26
synthesized according to a reported method . For preparation
of azo anils, 50 mL of methanol was added in azo dye (4 mmol)
followed by the addition of corresponding aromatic amine.
Few drops of glacial acetic acid were added to catalyze the
reaction mixture and refluxed for 2-3 h.
correspond coordinated (OH, Carboxylic acid) with central
metal atom. Several bands were observed in the range of 1608-
–
1
1450 cm , matching to the bands of coordinated oxalate,
–1
carboxyl and azomethine group. The band at 1423 cm corres-
pond to (N=N, azo group), 1336 to (C-O, phenolic group)
–
1
–1
2
-({2-Hydroxy-5-[(4-nitrophenyl)diazenyl]benzylidene}-
amino)benzoic acid (HNPDBAB): Dark red solid, Yield:
0 %, m.p.: 280-285 °C. m.f.: C20 ·2H O, Anal Calc:
C: 56.34, H: 4.27, N: 13.14 %. Found: C: 56.32, H: 4.25, N:
cm . The bands at 978, 1109 cm were assigned to ν
s
(C-C)
–1
and band at 754 cm to ν
such as 408, 578 cm correspond to ν(M-N) and ν(M-O) band
respectively. UV-visible: λmax = 387, 481, 558 nm.
s
(OCO, carboxylic group). The band
–1
8
H
14
N O
4 5
2
–1
1
3.10 %. FTIR spectra (KBr pellets, cm ); 3250-3150 (-OH,
[(HPIMNDP)M(II)(OX)]: Brick red solid;Yield: 72 %;
m.p. above 350 °C and elemental analysis results are given in
phenolic), 3600-3500 (coordinated water), 3072 (C-H,
aromatic), 2771-2638 (O-H, carboxylic acid), 1750-1704
–1
Table-1. FTIR (KBr pellets, cm ) Spectrum showed partial
–1
(
correspond to -C=O and (-C=N, azomethine), 1616 (-C=C-,
broad peak at 3600-3550 cm , which correspond to coordi-
–1
aromatic), 1515 (-N=N-, azo group), 1280 (C-O, phenolic),
nated water molecule.A band at 3140-3100 cm indicates the
coordination of phenolic group with central metal atom.
–1
1
329 cm (C-O carboxylic acid). UV-visible: λmax = 285, 383,
TABLE-1
PHYSICAL AND ANALYTICAL DATA OF LIGANDS AND THEIR M(II) COMPLEXES
Elemental analysis (%): Exp. (calcd.)
Colour
Compound
HNPDBAB
m.p. (°C)
C
H
N
M(II)
–
–
Dark red
56.32 (56.34)
57.29 (57.28)
49.09 (49.08)
48.88 (48.90)
49.43 (49.44)
49.20 (49.25)
4.25 (4.27)
4.56 (4.55)
2.74 (2.75)
2.75 (2.74)
2.87 (2.9)
2.85 (2.89)
13.10 (13.14)
14.05 (14.06)
10.8 (10.9)
280-285
287-290
> 350
> 350
> 350
HPIMNDP
Dark brown
[
[
[
[
(HNPDBAB)Cu(II)(OX)] Orange red
(HNPDBAB)Zn(II)(OX)] Orange red
(HPIMNDP)Cu(II)(OX)] Brick red
12.35 (12.37)
12.69 (12.68)
13.09 (13.08)
13.44 (13.41)
10.84 (10.86)
11.54 (11.53)
11.50 (11.49)
(HPIMNDP)Zn(II)(OX)]
Brick red
> 350

3
990 Ameen et al.
Asian J. Chem.
Several bands were appeared in range of 1613-1476 matching
to the bands of coordinated oxalate, azomethine group and
negative bacteria under similar conditions. The thickness of
inhibition zone resulting from DMSO was subtracted from
the thickness of inhibition zone of test compounds and anti-
bacterial activity was calculated as an average of three replicate.
1
420 to (N=N, azo group), 1335 to (C-O, phenolic group).
–1
The following bands such as 1030, 1109 cm are assigned at
the same time as ν
–1
s
(C-C) and band at 747 cm as ν (OCO,
s
–1
RESULTS AND DISCUSSION
carboxylic group). The band such as 412, 589 cm , correspond
to ν(M-N) and ν(M-O) band respectively. UV-visible: λmax
=
FT-IR analysis: The FTIR analysis of synthesized
–1
3
89, 480, 560 nm.
Antibacterial activities measurement: Diffusion disc
compounds was performed over KBr pellet (4000-400 cm ).
–1
The band at 3250-3150 cm relate to –OH (phenolic) group,
2
7-32
–1
method
was used to determine antibacterial activities of
shifted toward lower frequency (25-55 cm ) in complexes
copper chloride, zinc acetate, oxalic acid, azo anils and their
mixed ligands complexes. Glass wares were sterilized at 170 °C
for 1 h. Agar medium was prepared by adding nutrient agar
spectra, indicating the coordination of phenolic group with
central metal atom. The new band in complexes spectra at
–1
589-578 cm appeared indicating presence of M-O bond. The
formation of complex was showed up with increased C-O
(
2.8 g) and agar technical (1 g) in 100 mL distilled water. The
–1
mixture was boiled for 0.5 h and then cooled. The pH of agar
medium was adjusted at 7.4 with the help of dil. HCl and dil.
NaOH solutions. The agar medium was autoclaved for 15 min
stretching vibration (1336 cm ) in complexes as compared to
–1
azo anils ligands (1280 cm ). In HNPDBAB the band at 2771-
2638 correspond to –OH (carboxylic acid) which shifted toward
33
–1
at 121 °C (at 15 psi) . Spread this autoclaved agar (20-25 mL)
on Petri dishes with the help of spreader and incubated for
lower frequency (23-68 cm ) in [(HNPDBAB) M(II)(OX)],
which support the fact that carboxylic acid group is involved
in coordination. In ligands (HNPDBAB and HPIMNDP)
2
4 h at 37 °C. Test compounds in measured quantities were
–1
taken and dissolved in DMSO to get required concentration
of 1000 ppm. The agar media was taken in Petri dishes (9 cm
in diameter). Later than solidifying it, 0.2 mL of Gram-positive
spectra the band at 1616-1603 cm indicates the presence of
34
–C=N (azomethine group) as given in literature . This band is
–1
shifted toward lower frequencies (1608-1597 cm ) upon M(II)
complexes formation. This is an indication for the formation
of M-N bond and it was confirmed by the results obtained
(
Bacillus subtilis and Staphylococcus aureus) and Gram-
negative (Enterobacter aerogenes and Escherichia coli) bacteria
were spread separately over agar medium using sterilized
spreader in different Petri dishes and area of inhibition zone
was measured and given in Table-2. The discs of Whatmann
filter paper no.1 (6 mm in diameter) were soaked in test
compound solutions and then placed on inoculated Petri dishes.
The plates were incubated at 37 °C for 48 h. The sector of
inhibition was measured in millimetres.
3
5-37
from similar complexes . The bands at 412-408 and 589-
–1
578 cm could be assigned to ν(M-N) and ν(M-O) stretching
vibrations respectively and is in accordance with results
38
obtained from comparable complexes . In prepared complexes
–1
the band at 754 cm was assigned to oxalate group (OCO),
which was not appeared in free ligand except HNPDBAB
which contain carboxylic group. A broad band at 3600-3550
–
1
A measured quantity i.e. 0.2 mL of DMSO alone was
also taken as a standard control for Gram-positive and Gram-
cm shows coordinated water molecule. All other bands
appeared in their customary positions and are given in Table-3.
TABLE-2
MEASUREMENT OF INHIBITION ZONE OF TEST COMPOUNDS AGAINST GRAM-POSITIVE AND GRAM-NEGATIVE BACTERIA
Diameter of inhibition zone measured (mm): Bacterial species
Compound
CuCl ·2H O
Volume (µL)
Gram-positive
Staphylococcus aureus
Gram-negative
Enterobacter aerogenes
Bacillus subtilis
4 ± 1.0
Escherichia coli
3 ± 1.0
20
20
20
20
20
20
20
20
20
20
4 ± 1.0
3 ± 1.0
8 ± 1.0
8 ± 1.0
8 ± 1.0
14 ± 1.0
13 ± 1.0
12 ± 1.0
12 ± 1.0
7 ± 1.0
4 ± 1.0
4 ± 1.0
4 ± 1.0
5 ± 1.0
8 ± 1.0
12 ± 1.0
14 ± 1.0
13 ± 1.0
13 ± 1.0
8 ± 1.0
2
2
Zn(CH COO) ·2H O
2 ± 1.0
5 ± 1.0
8 ± 1.0
9 ± 1.0
14 ± 1.0
12 ± 1.0
14 ± 1.0
14 ± 1.0
5 ± 1.0
4 ± 1.0
8 ± 1.0
8 ± 1.0
7 ± 1.0
10 ± 1.0
14 ± 1.0
14 ± 1.0
14 ± 1.0
10 ± 1.0
3
2
2
Oxalic acid
HNPDBAB
HPIMNDP
[
[
[
[
(HNPDBAB)Cu(II)(OX)]
(HNPDBAB)Cu(II)(OX)]
(HPIMNDP)Zn(II)(OX)]
(HPIMNDP)Zn(II)(OX)]
Streptomycin
These values are expressed as a mean of three replicate reading (±)
TABLE-3
FTIR AND ELECTRONIC SPECTRA OF AZO ANILS LIGANDS AND THEIR M(II) COMPLEXES
–
1
Azo anils/M(II)
complexes
FTIR (cm )
UV-visible
(nm)
ν(OH)
ν(C-O)
1280
1290
1336
1335
ν(-C=N)
1704-1750
1616
1580
1575
ν(OCO)
1329
-
ν(M-O)
ν(M-N)
HNPDBAB
HPIMNDP
(HNPDBAB)M(II)(OX)]
(HPIMNDP)M(II)(OX)]
3150-3250
3150-3240
3050-3105
3050-3100
-
-
-
-
285, 383, 500
280, 420, 505
387, 481, 558
389, 480, 560
[
[
754
747
578
589
408
412

Vol. 27, No. 11 (2015)
Synthesis and Antibacterial Activities of Mixed Ligands Complexes of Cu(II) and Zn(II) 3991
1
Electronic spectra of ligands and their metal complexes:
The electronic spectra of azo anils ligands (HNPDBAB and
HPIMNDP), exhibited two absorption bands at 288 nm and
H NMR exhibited peaks at 13.50-12.80 ppm and 8.70-8.20
ppm which could be assigned to phenolic and azomethine
13
proton respectively. In C NMR, peaks emerged in the range
of 113.2-165.34 ppm could be assigned to aromatic C and
signal at 172.53 ppm to azomethine carbon.
5
10 nm were assigned to π→π* (phenyl rings) and n→π*
34
(
H-C=N and azo group) transitions respectively . These
transition bands were also existed in the electronic spectra of
M(II) complexes with different lower intensities, which
confirmed that these groups were involved in coordination. A
weak band in complexes spectra at 380 nm and 480 nm was
observed which correspond to charge transfer (ct). Another
weak band at 480-560 nm corresponds to d-d transition,
Antibacterial activities evaluation: Gram-positive
(Bacillus subtilis and Staphylococcus aureus) and Gram-
negative (Enterobacter aerogenes and Escherichia coli)
bacteria were used to test antibacterial activities of CuCl
2 2
·2H O,
Zn(CH COO) ·2H O, oxalic acid, azo anils and metal {Cu(II)
3
2
2
and Zn(II)} complexes. Streptomycin, an antibacterial drug
was used for the comparison of antibacterial activities under
similar conditions. The results obtained are given in Table-4.
It was concluded from these results that Cu(II) and Zn(II)
complexes displayed higher antibacterial activities as
2
2
2
2
namely B1g → E and B1g → B2g. These transitions suggested
g
39
distorted octahedral geometry for M(II) complexes . The
electronic spectra results are shown in Table-3.
13
1
13
1
C- H NMR spectra of azo anils: C and H NMR
spectroscopy of azo anils was recorded in (DMSO-d ) solvent.
6
compared to CuCl
2
·2H
2
O, oxalic acid, Zn(CH
3
COO)
2
·2H O
2
Scheme-I: Steps involved in the synthesis of azo anils ligands
Scheme-II: Proposed structure of distorted octahedral geometry of mixed ligands complexes containing tridentate azo anils and bidentate
oxalate ion as coordinating ligands

3
992 Ameen et al.
Asian J. Chem.
and azo anils ligands as given in Table-4. The Tweedy’s
chelation theory and Searl’s idea explain the reason of antibac-
terial activities of metal complexes increase .
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RESULTS OF ANTIBACTERIAL STUDY OF
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+++
+++
++++
+++++
++++
+++++
++++
++++
++++
++++
++++
+++++
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[
[
[
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1
1
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Streptomycin
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1
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**
*
Antibacterial activity was measured using disc diffusion method: disc
diameter = 6 mm; inhibition zone = 1-5 mm beyond control limit =
++ (less active); inhibition zone = 6-10 mm beyond control limit =
+++ (moderately active); inhibition zone = 11-15 mm beyond control
limit = +++++ (highly active); inhibition zone = 0 (resistant to
bacteria). Streptomycin: standard antibacterial drug.
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1
*
*
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2
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2
2
2
3
3
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2
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ACKNOWLEDGEMENTS
3
3
The authors are thankful to Department of Biochemistry,
Pakistan Council of Scientific & Industrial Research, Lahore
for their cooperation in the measurement of antibacterial
activities of synthesized compounds.
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