Synthesis, spectral, thermal and biological studies of Co(III) and binuclear Ni(II) complexes with a novel amine-imine-oxime ligand

Article abstract of DOI:10.1134/S1070363208090260

Two different metal complexes of [Co(HL)(L)(Ac)₂]?4H ₂O (I) and [Ni₂(L)₂(Ac)₂] ?4H₂O (II), have been synthesized with newly prepared amine-imine-oxime ligand [HL = 3-(4′-aminobiphenyl-4-ylimino)-butan-2-one oxime, Ac = CH₃COO^-]. This ligand HL was prepared by the condensation of diacetylmonoxime with benzidine. The structure of the ligand and complexes have been proposed by elemental analyses, IR, ¹H, and ¹³C NMR, electronic spectra, magnetic susceptibility measurements, mass spectra, molar conductivity and thermo gravimetric analysis. The molar conductance measurements of the complexes in DMF solution correspond to non electrolytic nature for the complexes. Octahedral and tetrahedral geometries have been determined to the complexes of Co(III) and binuclear Ni(II) respectively. The ligand and its metal complexes were tested in vitro for their biological effects. Their activities against two gram-positive (Bacillus subtilis and Staphylococcus aureus) and one fungal specie (Candida albicans) were found. They were inactive against tested gram negative bacteria.

Full text of DOI:10.1134/S1070363208090260

ISSN 1070-3632, Russian Journal of General Chemistry, 2008, Vol. 78, No. 9, pp. 1808–1815. © Pleiades Publishing, Ltd., 2008.
Synthesis, Spectral, Thermal and Biological Studies
of Co(III) and Binuclear Ni(II) Complexes
with a Novel Amine–Imine–Oxime Ligand1
Muharrem Kayaa, Cengiz Yenikayaa, Alper Tolga Colaka, and Ferdag Colakb
aDumlupınar University, Faculty of Science and Arts, Departmenot tested of Chemistry,
Kütahya, 43100 Turkey
e-mail: mhrkaya@yahoo.com; yenikaya@dumlupinar.edu.tr
phone: +90 274 265 20 51
fax: +90 274 265 20 56
bDepartment of Biology, Faculty of Arts and Sciences, Dumlupinar University, Kütahya, Turkey
Received April 14, 2008
Abstract—Two different metal complexes of [Co(HL)(L)(Ac)2].4H2O (I) and [Ni2(L)2(Ac)2].4H2O (II), have
been synthesized with newly prepared amine-imine-oxime ligand [HL = 3-(4'-aminobiphenyl-4-ylimino)-
butan-2-one oxime, Ac = CH3COO-]. This ligand HL was prepared by the condensation of diacetylmonoxime
1
with benzidine. The structure of the ligand and complexes have been proposed by elemental analyses, IR, H,
and 13C NMR, electronic spectra, magnetic susceptibility measurements, mass spectra, molar conductivity and
thermo gravimetric analysis. The molar conductance measurements of the complexes in DMF solution
correspond to non electrolytic nature for the complexes. Octahedral and tetrahedral geometries have been
determined to the complexes of Co(III) and binuclear Ni(II) respectively. The ligand and its metal complexes
were tested in vitro for their biological effects. Their activities against two gram-positive (Bacillus subtilis and
Staphylococcus aureus) and one fungal specie (Candida albicans) were found. They were inactive against
tested gram negative bacteria.
DOI: 10.1134/S1070363208090260
pared by the condensation of diacetylmonoxime with
benzidine. The structure of the ligand and complexes
have been proposed by elemental analyses, IR, 1H, and
13C NMR, electronic spectra, magnetic susceptibility
measurements, mass spectra, molar conductivity and
thermo gravimetric analysis.
INTRODUCTION
Oximes and their complexes have played a
remarkably role in the development of transition metal
chemistry [1–8]. Oxime and dioxime derivatives are
very important compounds in the chemical industry
and medicine [9]. They have a broad pharmacological
activity spectrum, encompassing antibacterial,
antidepressant and antifungal activities [10–12]. Some
oxime complexes have also anti-carcinogenic activities
[9, 13, 14]. Although the numerous oximes and their
metal complexes have been investigated, there have
been few amine-imine-oxime complexes reported in
the literature [15].
Some literatures [16–18] indicated that in some
transition metal complexes with heterocyclic or
biheterocyclic are biologically more active than the
free ligands. Therefore, the biological activities of the
ligand HL and their metal complexes of the Co(III)
and Ni(II) are tested against six strains of bacteria (i.e.
four gram-positive and two gram-negative bacteria)
and against four fungal species (one yeast and three
molds).
In this study, novel metal complexes of [Co(HL)(L)·
(Ac)2]·4H2O (I) and [Ni2(L)2(Ac)2]·4H2O (II), have
been synthesized with newly prepared amine-imine-
oxime ligand [HL = 3-(4'-aminobiphenyl-4-ylimino)-
butan-2-one oxime, Ac = CH3COO–]. HL was pre-
EXPERIMENTAL
All chemicals and solvents used for the synthesis
were of reagent grade. Benzidine, diacetylmonoxime,
Co(CH3COO)2·4H2O, Ni(CH3COO)2·4H2O (Aldrich)
were used as received.
1 The text was submitted by authors in English.
1808

SYNTHESIS, SPECTRAL, THERMAL AND BIOLOGICAL STUDIES
Table 1. Molar conductance and elemental analysis data of the complexes
1809
Elemental analysis
Calculated, %
Molar
Mass
Compound
Formula
conductance
spectrum,
(Fw) g mol–1
Found, %
(W–1cm2 mol–1)
M+, m/z
C
H
M
–
C
H
N
M
–
N
HL
C16H17N3O
(267.33)
268.0 (M + 1)
267.0 (M+)
1.7
6.4
4.0
71.89
6.41
15.72
71.76 6.43 15.36
C36H47CoN6O10
(782.73)
55.24
51.46
6.05
5.52
10.74
7.53
55.23 5.50 11.52 7.03
I
C36H46N6Ni2O10
(840.17)
II
10.00 13.97 51.54 5.71 9.87 13.89
temperature to a solution of Co(CH3COO)2·4H2O or Ni
(CH3COO)2·4H2O (0.25 g, 1 mmol) in water (20 ml).
The mixture was stirred for 30 min at room
temperature. The product formed was filtered, washed
with warm water, methanol and finally with
trichloromethane and dried under vaccum over P4O10
to obtain reddish brown complex Co(HL)(L)(Ac)2]·4H2O
(I) (Yield 58%; decomp. 255°C) or brown complex
[Ni2(L)2(Ac)2]·4H2O (II) (Yield 45 %; decomp. 272°C).
Synthesis of Ligand (HL)
A solution of diacetylmonoxime (10 mmol, 10.11 g)
in ethanol (30 ml) was added drop wise to a solution of
benzidine (10 mmol, 18.42 g) in ethanol. After 1 hour
stirring, glacial acetic acid (1.5 ml) was added drop
wise to the mixture and refluxed for 24 h. On cooling,
the crude product was filtered, washed with water and
then recrystallized from ethanol to obtain th ligand as
pale yellow crystals (Scheme 1).
The elemental data and molar conductance of the
metal complexes are given in Table 1. In Table 2
magnetic moments and electronic spectral data, in
Table 3 characteristic IR bands and in Table 5 thermo
gravimetric spectral data of the metal complexes are
listed respectively. Schemes 2 and 3 show the pro-
posed structures for the metal complexes I and II res-
pectively according to the spectral and analytical
results. Thermo gravimetric spectra for the complexes I
and II are also presented in Figs. 2 and 3, respectively.
Scheme 1. Synthesis of HL
H3C
CH3
+
H2N
NH2
O
N OH
Ethanol
−H2O
20
10
11
9
3
7
4
6
HO
1
2
8
14
N
5
H2N
N19
15
16
Physical Measurements
13 12
H3C
CH3
The carbon, hydrogen and nitrogen analyses were
obtained using a Carlo Erba 1106 auto elemental
18
17
Yield 65% ; mp 238°C; MS (m/z) (g mol–1) = 268.0
(M + 1), 267.0 (M+), 250.0, 208.9, 168.0, 104.5, 83.5
(Fig. 1).
Table 2. Magnetic moment and electronic spectral data of
the ligand and metal complexes
The elemental data and molar conductance of the
ligand are given in Table 1. In Table 2 electronic
spectral data, in Table 3 characteristic IR bands and in
λmax, nm(ε, l mol–1 cm–1)
μeff
Compound
(BM)
d–d/CT
n–π* azomethine
1
Table 4 the H NMR and 13C NMR spectra of the
HL
I
378 (189)
–
–
ligand are listed respectively.
585 (164)
415 (145)
335 (195)
Synthesis of the Metal Complexes
0.88
A solution of HL (0.27 g, 1 mmol) in ethanol-water
(1:1; 20 ml) was added dropwise with stirring at room
2.86
601 (195)
II
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 9 2008

1810
KAYA et al.
Scheme 2. Structures of Co(HL)(L)(Ac)2]·4H2O (I)
H3C
N
CH3
O
N
N
H2N
OOCCH3
.
Co
4H2O
H3CCOO
NH2
N
HO
H3C
CH3
I
Scheme 3. Structures of Ni2(L)2(Ac)2]·4H2O (II)
H3C CH3
H2N
N
N
O
O
H3CCOO
H3CCOO
.
4H2O
Ni
H2N
Ni
N
N
H3C
CH3
II
analyzer. The complexes were analyzed for their metal
contents by Perkin Elmer Optima 4300 DW ICP-OES.
Magnetic susceptibility measurements at room
temperatures were performed using a Sherwood
Scientific MK1 model Gouy magnetic balance. UV-
vis. spectrum was obtained in the methanol solutions
(10-3 mol l–1) of the complex with a Unicam UV2
and TMS was used as an internal standard. The mass
spectrum of HL was recorded by Thermo Finnigan
Trace DSQ mass spectrometer interfaced with gas
chromatography (GC–MS). FT–IR spectra were
recorded in the 4000–400 cm–1 region with a Mattson
1000 FT–IR spectrometer using KBr pellets. Thermal
analysis curves (DTA, TG and DTG curves) were
recorded simultaneously under nitrogen atmosphere
with a Shimadzu DTA 50 thermal analyzer. The molar
conductivities of the complexes (ΛM) were recorded
using a WTW model 315i conductivity meter.
1
spectrometer in the range of 900–190 nm. The H
NMR and 13C NMR spectra were recorded on a Varian
Mercury Plus 400 MHz FT–NMR spectrometer,
utilizing deuterated dimethylsulphoxide as a solvent
267.0
100
208.9
80
168.0
60
250.0
40
83.5 104.5
115.0
184.0
195.0
139.0
165.9
20
0
210.0
226.1
268.0
269.1
90.9
43.9 70.1
125.0
280.8 319.2 326.9
362.2 390.7
60
80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400
m/z
Fig. 1. Mass spectrum of HL.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 9 2008

SYNTHESIS, SPECTRAL, THERMAL AND BIOLOGICAL STUDIES
Table 3. Characteristic IR bands (cm–1) of the ligand and the complexes
1811
ν(C–H)
aromatic
aliphatic
ν(O–H)
oxime
ν(C=O)
acetate
ν(C=N)
azomethine
ν(C=N)
oxime
Compound
ν(NH2)
ν(N–O)
1020 m
1010 m
1090 m
ν(M–O)
–
ν(M–N)
3340 s
3296 s
3020 w
2920 w
HL
I
3428 s
–
1625 vs
1610 vs
1605 vs
1598 s
1591 s
1593 s
–
3290 s
3261 s
3040 w
2920 w
–
–
1700 m
1699 w
540 w
503 w
444 w
474 w
3321 s
3276 s
3020 w
2890 w
II
broad medium intensity band appearing at ~3400 cm–1
is assigned to the characteristic OHoxime absorption for
the HL ligand. The bands at 3340 and 3296 cm–1 may
be assigned to ν(N–H) stretching vibrations of NH2
group of HL ligand. The relatively weak bands at 3020
and 2920 cm–1 are due to the aromatic and aliphatic
ν(C–H) vibrations respectively. The absorption bands cor-
responding to azomethine ν(C=N)azomet and ν(C=N)oxime
group is distinct and appears at 1625 and 1598 cm–1 of
HL ligand. The broad medium intensity band in the
region of 1020 cm–1 is due to the (N–O) stretching
vibrations.
Biological Screening
A total of 10 microbial species including 6 bacteria,
3 molds and 1 yeast were used as test organisms in this
study. These microorganisms Staphylococcus aureus
ATCC 6538, Enterococcus fecalis ATCC 29212,
Escherichia coli ATCC 25922, Salmonella
typhimurium ATCC 14028, Aspergillus niger ATCC
10949, were obtained from American Type Culture
Collection. Bacillus subtilis NRRL –B-209, Bacillus
cereus NRRRL B-3711, Candida albicans NRRL Y–
12983, Aspergillus flavus NRRL 1957, A. parasiticus
NRRL 465 were also obtained from USDA,
Agriculture Research Service, Peria, USA. Bacterial
and fungal cultures of test organisms were maintained
on Nutrient Agar and Malt Extract Agar slants at 4°C,
respectively, and were sub cultured in Petri dishes
prior to use.
The absorption bands at 3290–3261cm–1 and 3321–
3276 cm–1 are attributed to ν(NH2) vibrations of
complex I and II respectively. The weak absorption
bands at 3040 and 2920 cm–1 and 3020 and 2890 cm–1
indicate the aromatic and aliphatic ν(C–H) vibrations
of I and II complexes respectively. The bands at 1610
and 1605 cm–1 may be assigned to ν(C=N)azomet and
1591 and 1593 cm–1 stretching vibrations to ν(C=N)oxime
The ligand and its metal complexes were tested for
their antimicrobial activity against six species of
bacteria, and four fungal species using agar well
diffusion method. Each compound (100 µl) were
poured into the wells and the diameters of inhibition
zones (mm) were measured at the end of an incubation
period of 24 hours at 37°C for bacteria, and 4 days at
28°C for fungi [19]. Discs saturated with DMSO are
used as solvent control. Tetracycline 30 µg/disc and
Kanamycine 30 µg/disc were used as reference
substance for bacteria.
TG, %
100
DTA/μV, mg
exo
4
3
80
2
1
60
40
10
0
RESULTS AND DISCUSSION
–1
200 400 600
800 1000
Temperature, °C
FT–IR Measurements
The tentative assignment of the most characteristic
IR bands were observed and given in Table 3. The
Fig. 2. Thermo gravimetric spectrum for the Co(HL)(L)(Ac)2]·
4H2O (I).
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 9 2008

1812
KAYA et al.
DTA/μV, mg
TG, %
respectively. In addition, complex 1 exhibits medium
band at 1010 cm–1, complex II exhibits medium band
at 1090 cm–1 corresponding to ν(N-O) vibrations. The
ν(N–O) vibration for II (1090 cm–1) is shifted upper
frequency compared with HL (1020 cm–1) [24] indi-
cating that oxime group coordinated to Ni(II) via oxy-
gen atom to give tetrahedral geometry as indicated in [25].
exo
4
100
80
3
60
40
10
2
1
0
1H NMR and 13C NMR Spectral Measurements
In order to understand the solution structure of the
200 400 600
800 1000
Temperature, °C
1
13
novel HL ligand H NMR and C NMR spectra have
been employed. The 1H NMR assignments are listed in
Table 4 and the spectral data for HL are as expected
(Scheme 1). The 1H signals were assigned on the basis
of chemical shifts, multiplicities and coupling
constants. The two CH3 protons of HL are easily
distinguishable, and they are observed at 2.2 and 2.1 ppm
as singlets. In addition, all aromatic protons of HL are
also distinguishable and their peaks are between 7.58–
6.64 ppm as doublets, in which those have three bond-
coupling constants, ~ca. 8.40 Hz. Furthermore, the
singlet at 5.2 ppm and 12.05 ppm in the ligand HL are
attributed to NH2 and OH protons respectively.
Fig. 3. Thermo gravimetric spectrum for the Ni2(L)2(Ac)]·4H2O
(II).
for I and II. When the spectra of the complexes are
compared with those of the uncomplexed imine-amine-
oxime ligand, the ν(C=N) band are shifted to lower
frequency [20,21]. This indicates that the imine
nitrogen is coordinated to the metal ion which leads to
new absorption bands for ν(M–N) [22, 23]. The acetate
groups as coordinated groups to metal ions show
carbonyl absorption peaks at the region of 1700 cm–1
and which also leads new ν(M–O) bands [20]. The
weak bands in the region of 540–503 cm–1 are due to
the M–O, and 444–474 cm–1 are due to the M–N
stretching vibrations for the complexes I and II
13
The C NMR spectrum of HL has showed a series
of resonance peaks which are in accordance with the
1
Table 4. The H NMR and 13C NMR spectra of the HL
(DMSO-d6)
Table 5. TG–DTG data of complexes
Weight loss
1H NMR spectrum
13C NMR spectrum
δ, ppm
12.05 s, 1H
7.58 d, 2H
J, Hz
assignment
δ, ppm
166.31
158.07
assignment
C15
Comp.
no.
DTGmax
,
Assignment
ºC
OH
8.44
CH3,7
C16
7.37 d, 2H
6.79 d, 2H
6.64 d, 2H
5.2 s, 2H
8.43
8.47
8.14
CH4,6
150.17
149.77
137.77
129.06
C11
C2
C8
C5
25–186
98, 113,
145
8.95
9.19
four crystal
water
molecules
I
CH10,12
CH9,13
186–345 214, 255
83.10
83.25 two HL
ligands and
1
NH2
two acetate
anions
metallic
cobalt
four crystal
water
molecules
17
2.2 s, 3H
2.1 s, 3H
CH3
128.57
127.55
121.43
116.13
C10,12
C9,13
C3,7
7.95
7.56
8.62
18
CH3
20–145
102, 109, 9.46
120, 135
II
C4,6
145–386 189, 345
386–645 415, 448
63.62
13.58
13.34
63.48 two HL
ligands
14.02 two acetate
anions
13.88 metallic
nickel
17.17
11.01
C18
C17
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 9 2008

SYNTHESIS, SPECTRAL, THERMAL AND BIOLOGICAL STUDIES
1813
number of carbon atoms of the ligand. All of the
possible carbon peaks are observed from the 13C NMR
spectral data as expected (Scheme 1 and Table 4).
related to the decomposition of coordinated acetate
anions as an extremely exothermic effect (found, %:
13.58, calculated, %: 14.02; DTGmax= 415, 448°C).
The final decomposition product is metallic nickel
(found, %: 13.34, calculated, %: 13.88) [27].
Thermal Analyses
In addition, the molecular ion peak [267.0 (M+)] has
been observed in mass spectrum as based peak (Table 1
and Fig. 1).
TG–DTG and DTA curves obtained for
experiments at 5°C/min under nitrogen atmosphere. In
Fig. 2, the first endothermic stage, at 25–186ºC
temperature range of I (DTGmax = 98, 113, 145ºC),
corresponds to the loss of the four crystal water
molecules (found, %: 8.95, calculated, %: 9.19). The
second stage, between 186–345°C, is response to the
endothermic decomposition of the two HL ligand and
two acetate anions (found, %: 83.10, calculated, %:
83.25; DTGmax= 214, 255°C). The final decomposition
product is metallic cobalt (found, %: 7.95, calculated,
%: 7.56) [26].
UV–Vis Spectra, Magnetic Moment and Molar
Conductivity Measurements
The molar conductance of the complexes of I and
II in 10–3 M solutions in DMF lies in the range 6.4 and
4.0 Ω–1 cm2 mol–1 (Table 1), consistent with non-
electrolytes [28].
Complex 1 shows magnetic moment 0.88 BM at
room temperature corresponding to low spin d6 system
for Co(III) which suggest octahedral geometry
(Scheme 2 and Table 2). Complex II shows magnetic
moment 2.86 BM per metal at room temperature
corresponding to d8 system with two unpaired electrons
which lies in the range reported for a tetrahedral
geometry around Ni(II) ions (Scheme 3 and Table 2)
[29].
In Fig. 3, the first endothermic stage, at 20–145ºC
temperature range of II (DTGmax = 102, 109, 120,
135ºC), also corresponds to the loss of the four crystal
water molecules (found, %: 9.46, calculated, %: 8.62).
The second stage, between 145–386°C, is response to
the endothermic decomposition of the two HL ligand
(found, %: 63.62, calculated, %: 63.48; DTGmax= 189,
345°C). Following last stage, between 386–645ºC, is
Table 6. Effect of the ligand and its Co(III) and Ni(II) complexes on the growth of Bacteria and Fungi (zone of inhibition in
mm) (well Ø 10mm)a
Ligand
500µg/well
Co(III) complex
500µg/well
Ni(II) complex
500µg/well
Tetracycline
30µg/disc
Kanamycine
30µg/disc
Test microorganisms
Gram-positive bacteria
Bacillus subtilis
–
–
–
–
12 1.2
–
35
30
30
15
25
20
26
22
B. cereus
–
–
20 1.0
–
Staphylococcus aureus
Enterobacter fecalis
–
–
Gram-negative bacteria
Escherichia coli
–
–
–
–
–
28
20
28
28
Salmonella typhimirium
–
Fungi
Candida albicans
Aspergillus niger
A. flavus
–
–
–
–
12 1.7
12 1.5
not tested
not tested
not tested
not tested
not tested
not tested
not tested
not tested
–
–
–
–
–
–
A. fumigatus
a (–) No zones of inhibition were observed. The tests were carried out in triplicate.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 9 2008

1814
KAYA et al.
3. Mehrotra, R.C., in: Comprehensive Coordination Chem-
The electronic spectra of the ligand and complexes
istry, Wilkinson, G., Gillard, R.D., and McCleverty, J.A.,
Eds.,Vol. 2, Oxford: Pergamon Press, 1987, p. 269.
were recorded in DMF at room temperature. The UV–
vis. spectral data of the ligand and complexes are given
in Table 2. The aromatic band of the ligand at 271 nm
is attributed to benzene rings π–π* transition. The band
approach 378 nm is due to the n–π* transition of the
non-bonding electrons present on the nitrogen of the
azomethine groups in the amine-imine-oxime ligand.
4. Smith, A.G., Tasker, P.A., and White, D.J., Coord.
Chem. Rev., 2003, vol. 241, p. 61.
5. Chaudhuri, P., Coord. Chem. Rev., 2003, vol. 243,
p. 143.
6. Kukushkin, Yu.V., Tudela, D., and Pombeiro, A.J.L.,
Coord. Chem. Rev., 1999, vol. 181, p. 147.
The solution state UV–Vis absorption spectrum of
the complex I shows strong absorptions at 585, 415
and 335 nm. These absorptions correspond to d–d
transitions typical for octahedral low spin cobalt(III)
complexes [30]. These transitions are from 1A1g ground
state of cobalt(III) to singlet state 1T1g (low energy) and
from A1g ground state to T2g (higher energy). In the
complexes of the type CoA4B2 (cis or trans) the T1g
state split, the splitting in trans isomer being more
[31], thus justifying trans geometry with the three
absorption peaks in the complex I.
7. Pombeiro, A.J.L. and Kukushkin, Yu.V., in Com-
prehensive Coordination Chemistry II, McCleverty, J.A.,
and Meyer, T.C., Eds., vol. 1, Amsterdam: Elsevier,
2004, p. 631.
8. Kaya, M., Demir, I., and Yenikaya, C., Asian J. Chem.,
2008, vol. 20, no. 3, p. 2221.
1
1
9. Sevagapandian, S., Rajagopal, G., Nehru, K., and
1
Athappan, P., Trans Metal Chem, 2000, vol. 25, p. 388.
10. Forman, S.E.J., Org Chem., 1964, vol. 29, p. 3323.
11. Holan, G., Johnson, W.M.P., Rihs, K., and Virgona, C.T.,
Pest. Sci, 1984, vol. 15, p. 361.
The band observed at 601 nm for the complex II is
in accordance with a tetrahedral configuration and
assigned to the 3T1 → 3T1(P) d–d transition [32].
12. Balsamo, A., Macchia, B., Martinelli, A., Orlandini, E.,
Rossello, A., Macchia, F., Bocelli, G., and Domiano, P.,
Eur. J. Med. Chem., 1990, vol. 25, p. 227.
13. Barybin, M.V., Diaconescu, P.L., and Cummins, C.C..,
Biological Activity
Inorg. Chem., 2001, vol. 40, p. 2892.
The ligand HL and its Co(III) and Ni(II) complexes
were screened in vitro for their antibacterial activity
against microorganisms. The results of the anti-
bacterial and antifungal activities are summarized in
Table 6. Tested microorganisms showed diameters of
zone inhibition ranging between 12 and 20 mm. Co(III)
complex investigated showed antimicrobial activity
against one gram positive bacteria (Bacillus subtilis).
Ni(II) complex also inhibited one gram positive
bacteria (Staphylococcus aureus) while HL ligand does
not present antimicrobial activity against all tested
gram positive bacteria. In addition, they were resistant
against all gram negative bacteria. The complexes
showed activity against only C. albicans from fungi.
14. Srivastava, R.M., Brinn, I.M., Machura-Herrera, J.O.,
Faria, H.B., Carpenter, G.B., Andrade, D., Venkatesh, C.G.,
and Morais, L.P.F., J Mol Struct., 1997, vol. 406,
p. 159.
15. Otter, C.A. and Hartshorn, R.M., J. Chem. Soc., Dalton
Trans, 2002, p. 4193.
16. Liberta, A.E. and West, D.X., BioMetal, 1992, vol. 5(2),
p. 121.
17. Rodriguez-Fernandez, E., Manzano, J.L., Benito, J.J.,
Hermosa, R., Monte, E., and Criado, J.J., J. Inorg.
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The authors gratefully acknowledge the support
provided by Dumlupınar University, Turkey, (under
grant N.24 of the University Research Fund).
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