Spectral characterization and antibacterial effect of 2-Methyl-6-(5-H/Me/ Cl/NO2-1H-benzimidazol-2-yl)-phenols and some transition metal complexes

Article abstract of DOI:10.1134/S0036023610020130

2-Methyl-6-(5-H/methyl/chloro/nitro-1H-benzimidazol-2-yl)-phenols (HL _x: x = 1-4) ligands and HL₁ complexes with Fe(NO ₃)₃, Cu(NO₃)₂, AgNO₃, Zn(NO₃)₂ have b

Full text of DOI:10.1134/S0036023610020130

ISSN 0036ꢀ0236, Russian Journal of Inorganic Chemistry, 2010, Vol. 55, No. 2, pp. 215–222. © Pleiades Publishing, Ltd., 2010.
COORDINATION COMPOUNDS
Spectral Characterization and Antibacterial Effect
of 2ꢀMethylꢀ6ꢀ(5ꢀH/Me/Cl/NO2ꢀ1HꢀBenzimidazolꢀ2ꢀyl)ꢀPhenols
and Some Transition Metal Complexes1
Aydin Tavmana, Serkan Ikizb, A. Funda Bagcigilb, N. Yakut Özgürb, and Seyyal Akb
a Istanbul University, Faculty of Engineering, Department of Chemistry, 34320, Avcilar, Istanbul, Turkey
b Istanbul University, Veterinary Faculty, Department of Microbiology, 34320, Avcilar, Istanbul, Turkey
Received July 21, 2008
Abstract—2ꢀMethylꢀ6ꢀ(5ꢀH/methyl/chloro/nitroꢀ1Hꢀbenzimidazolꢀ2ꢀyl)ꢀphenols (HLx : x = 1–4) ligands
and HL1 complexes with Fe(NO3)3, Cu(NO3)2, AgNO3, Zn(NO3)2 have been synthesized and characterized.
The structures of the compounds were confirmed on the basis of elemental analysis, molar conductivity, magꢀ
netic moment, FTꢀIR, 1Hꢀ and 13CꢀNMR. Antibacterial activity of the free ligands, their hydrochloride salts
and the complexes were evaluated using the disk diffusion method in dimethyl sulfoxide as well as the miniꢀ
mum inhibitory concentration dilution method, against nine bacteria. While HL1 ligand has not any activity,
it’s Ag(I) complex show antibacterial effect toward almost to all the bacteria. Zn(II) complex has antibacterial
effect on especially K. pneumoniae
, S. epidermidis and S. aureus bacteria.
DOI: 10.1134/S0036023610020130
1
Investigation of biological activity of complex [2ꢀmethylꢀ6ꢀ(5ꢀmethyl/chloro/nitroꢀ1Hꢀbenzimidaꢀ
compounds is a field that has developed over the years.
In the literature, antimicrobial activity of many metal
complexes is investigated. For example, Ag(I) comꢀ
plexes of quinoxaline, dimethylpyrazine, aminopyriꢀ
dine and nicotinateꢀtype ligands have considerable
antimicrobial activity [1, 2].
Likewise, in the literature some metal complexes
showed a change in the antimicrobial [3] and antifunꢀ
gal effect of the ligands [4].
zolꢀ2ꢀyl)ꢀphenols (HLx):
x = 2–4] and Fe(III),
Cu(II), Ag(I) and Zn(II) nitrate complexes are
reported. Antibacterial activities of the compounds are
evaluated by the disk diffusion method against nine
bacteria. Herein, we discuss the differences of 5ꢀsubꢀ
stituents and metal ion complexes with the free HL1
ligand in their structuralꢀbiological activity relationꢀ
ship.
Cytotoxicity of some trimethylsilylpropyl substiꢀ
tuted benzimidazolinium salts and their metal comꢀ
plexes with CuCl2, ZnCl2, CoCl2, PdCl2, and AgNO3
was tested and it was determined that the cytotoxicity
of the complexes depended on the metal [5].
EXPERIMENTAL
Chemistry
Fe(III), Ag(I), and Hg(II) complexes of some
All chemicals and solvents were reagent grade and
were used as purchased without further purification.
Melting points were determined using an Electrotherꢀ
mal meltingꢀpoint apparatus. Analytical data were
obtained with a Thermo Finnigan Flash EA 1112
analyser. Atomic absorption data were obtained with a
Perkin Elmer Analyst 200 flame spectrometer. Molar
conductivity of the complexes was measured on a
WPA CMD750 conductivity meter in DMSO at 25°C.
1H and 13CꢀNMR spectra were run on a Varian Unity
Inova 500 NMR spectrometer. The residual DMSOꢀ
d6 signal was also used as an internal reference. FTꢀIR
spectra were recorded in KBr disks on a Mattson 1000
FTꢀIR spectrometer. Magnetic measurements were
carried out on a Sherwood Scientific apparatus at
room temperature by Gouy’s method.
5ꢀsubstituted 2ꢀ(2'ꢀhydroxyphenyl)ꢀ1
zoles [6] and Cu(II), Zn(II), Ag(I) complexes of some
2ꢀ and 3ꢀpyridinylꢀ1 ꢀbenzimidazoles have an antiꢀ
Hꢀbenzimidaꢀ
H
bacterial and antifungal effect [7].
Iron, copper and zinc are essential elements and
Fe(III), Cu(II) and Zn(II) ions play important roles in
biochemical systems. Silver compounds are known
have high antimicrobial effect. In our previous work,
2ꢀmethoxyꢀ6ꢀ(5ꢀH/methyl/chloro/nitroꢀ1Hꢀbenzꢀ
imidazolꢀ2ꢀyl)ꢀphenols and some transition metal
complexes were synthesized and characterized. Some
ligands and Cu(II) and Zn(II) complexes showed antiꢀ
bacterial activity against Gram positive bacteria [8]. In
this work, 2ꢀmethylꢀ6ꢀ(1Hꢀbenzimidazolꢀ2ꢀyl)ꢀpheꢀ
nol (HL1), it’s methyl, chloro, nitro derivatives
1
The article is published in the original.
215

216
AYDIN TAVMAN et al.
Synthesis of the Ligands: General Procedure
2ꢀMethylꢀ6ꢀ(1 ꢀbenzimidazolꢀ2ꢀyl)ꢀphenol (HL1).
(CAMBH) with Mg2+ (10 mg Mg2+/mL) and Ca2+
(20 mg Ca2+/L) was used as the medium.
H
The ligands were prepared according to literature proꢀ
cedures [9, 10], by reacting 2ꢀhydroxyꢀ3ꢀmethylbenꢀ
zaldehyde (1.36 g, 10 mmol) and an equivalent
amount of NaHSO3 (1.04 g, 10 mmol) at room temꢀ
perature in EtOH (25 mL) for several h. The mixture
Detection of the Antibacterial Activity
Qualitative antibacterial evaluation. Disc diffusion
method was used for the detection of the antibacterial
effect of the chemical agents, qualitatively [11]. For
this purpose, filter papers (Whatman No. 1) with
6 mm diameter were autoclaved and dried at 37°C for
overnight. Each chemical agent (21.27 mg) was disꢀ
solved in dimethyl sulfoxide and 23.5 μl of this solution
(containing 500 μg chemical agent) were soaked on to
was treated with
oꢀphenylenediamine (1.08 g,
10 mmol) in dimethylformamide (15 mL) and gently
refluxed for 2 h. The reaction mixture was then poured
into iced H2O (500 mL), filtered and crystallized from
EtOH.
the sterile discs. Bacterial suspension with 1–2
×
Synthesis of the Complexes
108 cfu/mL (McFarland 0.5) were prepared from each
[Fe(L1)(OH)(H2O)3](NO3)
ligand HL1 (112 mg, 0.5 mmol) in
was treated with Fe(NO3)3 9H2O (222 mg, 0.55 mmol) surface and incubated at 37°C for 24 h. Chemical
in ꢀPrOH (5 mL) at 60°C for several h. The solution agents with growth inhibition zones were used for the
mixture was allowed to stand at 4°C for several days further examinations.
to precipitate black solid products, which were colꢀ
lected by filtration and dried at 80–90°C
[Cu(L1)2] 2H2O. 112 mg ligand (0.5 mmol) and
133 mg Cu(NO3)2 3H2O (0.55 mmol) were reacted in
10 mL methanol. After 4 h reflux the precipitate was
filtered and dried at 80–90°C
.
A hot solution of the bacterial strain and streaked onto the agar, chemical
i
ꢀPrOH (10 mL) agents impregnated discs were placed onto the agar
⋅
i
∼
∼
Quantitative antibacterial evaluation. For the
detection of the antibacterial effect of the chemical
agents, quantitatively, macro dilution broth method
according to clinical and laboratory standards institute
(formerly NCCLS) were performed [12]. Serial diluꢀ
.
⋅
⋅
.
tions of the chemical agents between 532–0.26 μg/mL
[Ag(HL1)](NO3). 112 mg ligand (0.5 mmol) and with CAMBH were prepared within sterile tubes. Bacꢀ
94 mg AgNO3 (0.55 mmol) was treated 10 mL ethanol terial suspension with 107 cfu/mL final concentration
at room temperature for 6 h with stirring. The precipꢀ was inoculated. Positive (without tested chemical
itate was filtered and dried at 80–90°C
[Zn(L1)(H2O)2](NO3). 112 mg ligand (0.5 mmol)
suspended in ethyl acetate, 164 mg Zn(NO3)2 6H2O
.
agent) and negative (without bacterial suspension)
tubes were used at the end of the each organism tested.
Tubes were incubated at 37°C for 24 h. The MIC value
was defined as the lowest concentration of the chemiꢀ
cal agent giving complete inhibition of visible growth.
⋅
(0.55 mmol) 15 mL ethylacetate was added to the ligand
solution. The mixture was refluxed for 2 h. The dark yelꢀ
low precipitate was filtered and dried at 80–90oC
.
RESULTS AND DISCUSSIONS
Microorganisms
Physical Properties
The antimicrobial activities are evaluated against
Gram positive (Staphylococcus aureus ATCC 29213,
Bacillus cereus ATCC 11778, Bacillus subtilis ATCC
6633, Staphylococcus epidermidis ATCC 12228) and
Gram negative (Escherichia coli ATCC 25922, Klebꢀ
siella pneumoniae ATCC 4352, Pseudomonas aerugiꢀ
nosa ATCC 27853, Salmonella enteritidis KUEN 349,
Proteus mirabilis CCM 1944) bacteria using disk diffuꢀ
sion method as well as the minimum inhibitory conꢀ
centration (MIC) dilution method. The strains were
provided from the Centre for Research and Applicaꢀ
tion of Culture Collections of Microorganisms, Istanꢀ
bul University (KUKENS) were used for the detection
of antibacterial effect of the strains.
The analytical data and physical properties of the
ligands and the complexes are summarized in Table 1.
The molar conductivity values of the complexes are
46, 51 and 37 Ω–1 cm2 mol–1 for Fe(III), Ag(I) and
Zn(II) complexes, respectively. These results are
indicative for 1 : 1 electrolyte complexes. Cu(II) comꢀ
plex has nonꢀionic character according to the molar
conductivity.
The room temperature effective magnetic moment
value of [Fe(L1)(OH)(H2O)3](NO3) is 3.90 BM, indiꢀ
cating stabilization of the species having intermediate
ferric spin (S = 3/2) state. The occurrence of such an
Test Media. MuellerꢀHinton Agar (Fluka 70191) intermediate spin state is typical for the six and five
were used for the detection of the antibacterial effect coordinate ferric complexes (Fig. 4) [13–15]. Magꢀ
qualitatively and to maintain the strains. For the netic moment value of [Cu(L1)2] ⋅ 2H2O complex is
detection of the quantitative antibacterial effect by 1.67 BM, which is in the expected range for a typical
MIC, MuellerꢀHinton broth (Fluka 70192) d9 Cu(II) complex.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 2 2010

SPECTRAL CHARACTERIZATION AND ANTIBACTERIAL EFFECT
217
Table 1. The analytical data and physical properties of the ligands and complexes
Found (calcd.) %
Compound
Yield % * M.p.dec. Color
Λ
–
C
H
N
M
–
HL1
75.3
(75.0)
75.5
5.6
12.1
(12.5)
11.0
60
55
60
60
65
70
65
70
281
232
dirty
white
dirty
white
grey
C14H12N2O
HL2
(5.4)
5.8
–
–
–
–
C15H14N2O
HL3
(75.6)
65.1
(5.9)
4.1
(11.8)
10.6
273
–
C14H11ClN2O
HL4
(65.0)
61.9
(4.3)
4.6
(10.8)
15.6
226
yellow
black
–
C14H11N3O3
(62.4)
40.0
(4.1)
3.9
(15.6)
9.8
[Fe(
C14H18FeN3O8
[Cu( 1)2] 2H2O
L
1)(OH)(H2O)3](NO3)
14.8
(13.6)
11.2
>350
210
46
16
51
37
(40.8)
61.1
(4.4)
4.4
(10.2)
10.8
L
⋅
dark
C28H26CuN4O4
[Ag(HL1)](NO3)
C14H12AgN3O4
(61.6)
42.2
(4.8)
2.8
(10.3)
10.4
(11.6)
24.6
green
light
169
(42.7)
44.2
(3.1)
3.4
(10.7)
11.5
(27.4)
16.0
brown
dark
[Zn(
L
1)(H2O)2](NO3)
>350
C14H15N3O6Zn
(43.5)
(3.9)
(10.9)
(16.9)
yellow
µ
values for [Fe(L )(OH)(H O) ]NO and [Cu(L ) ] ⋅ 2H O are 3.90 and 1.67 BM, respectively.
1 2 3 3 1 2 2
eff
–1
2
–1
* approximately values; dec., decomposed; Λ, molar conductivity, Ω cm mol (25°C).
FTꢀIR Spectra
supports the presence of coordinated water molecules.
The characteristic (C–H) modes of ring residues and
methyl groups are observed in the wave region between
3107–2903 cm–1. The sharp or medium bands at the
900–740 cm–1 range are due to the outꢀofꢀplane
ν
FTꢀIR spectral data of the ligands and the comꢀ
plexes are given in Table 2. The characteristic
and (N–H) vibration frequencies of the HL1, HL2
ν(O–H)
ν
and HL3 ligands exhibit only a single strong band at ca.
3340 cm–1 in the IR spectra, probably caused by douꢀ
bly intramolecular hydrogen bonding between the
phenoxyl hydrogen atom and one of the imine nitroꢀ
gen atom (Table 2, Fig. 2) [16–18]. The 3338 cm–1
band in the HL1 changes significantly upon metal
complexation indicating deprotonation and subseꢀ
quent involvement of the phenoxyl group in metal
deformation bands for the aromatic C
–
H.
The (C
ν
=C) frequencies for the ring residue are
expected to appear at ca. 1625 cm–1 with their own
characteristics for the ligands in the IR spectra. These
frequencies are expected to shift at lower frequency
upon complex formation. Similarly the (C=N) asymꢀ
metric stretching frequencies are expected to appear at
ca. 1600 cm–1
.
coordination [19]. In HL4 spectra ν(O–H) and ν(N–H)
vibration frequencies appear separately because of
weak intramolecular hydrogen bonding.
Appearance of a strong broad band at ca. 3400 cm–1
in the Fe(III), Cu(II) and Zn(II) complexes strongly
Fe(III), Ag(I) and Zn(II) complexes show strong
bands at 1386 cm–1 in their IR spectra, supporting the
presence of uncoordinated nitrate ion, which was also
confirmed by conductivity data [20–22].
H
N
H
N
N
N
R1
R
CH3
HO
CH3
H
O
Fig. 1. Structure of the ligands R = H, HL ; R = CH ,
Fig. 2. The intramolecular hydrogen bonding in the
ligands.
1
3
HL ; R = Cl, HL ; R = NO , HL .
4
2
3
2
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 2 2010

218
AYDIN TAVMAN et al.
H
H
R
N
N
N
N
R
HO
CH3
HO
CH3
Isomer A
Isomer B
Fig. 3. Isomeric structures of HL (R = CH ) and HL (R = NO ).
2
3
4
2
+
+
H
N
H
N
NO3–
NO3–
N
N
CH3
Fe
O
CH3
Zn O
OH2
H2O
H2O
OH
H2O
OH2
H
N
+
H
N
N
NO3–
CH3
Cu
O
O
H3C
N
N
CH3
Ag
O
H
N
H
Fig. 4. The proposal structures for the complexes under study.
NMR Spectra
observation is an evidence for the OH hydrogen’s
eliminating and the phenolic oxygen’s coordinating to
the Zn(II) ion (Fig. 4). In the Ag(I) complex, the sinꢀ
glet at 13.25 ppm shows that the phenolic OH hydroꢀ
gen is not eliminated; however changes in the chemiꢀ
cal shift and the coupling constant values show that a
complex is formed.
1Hꢀ and 13CꢀNMR spectral data and assignments
are given in Tables 3 and 4. According to the 1HꢀNMR
spectra HL2 and HL4 have two isomeric forms (Fig. 3,
Table 3). The isomer structures are observed for the
benzimidazole protons only.
The ligands give two singlets over 13 ppm belonging
to NH (broad singlet) and OH (sharp singlet) protons
(except HL4). These signals are closer each other
because of intraꢀmolecular hydrogen bonding between
the OH hydrogen and the C=N nitrogen atoms.
The phenolic and benzimidazole protons of the
Ag(I) and Zn(II) complexes change their characterisꢀ
tics according to the ligand. In the Zn(II) complex, all
of the multiplet, doublet or triplet peaks change to
broad singlets or broad doublets because of the metal
ion’s strong perturbing effect. It can be said that, on
complexation, acidic character of the benzimidazole
All of the carbon atoms were observed in the
13CꢀNMR (APT) spectra of the HL1 and its Ag(I),
Zn(II) complexes. In the 13CꢀNMR spectra of the HL1
and its Ag(I) and Zn(II) complexes the signal around
152.87, 152.60 and 153.71 ppm belongs to imidazole
C=N (Cꢀ2) carbon atom, respectively. The highest
ppm values of these compounds, 157.18, 156.87 and
164.02, are due to C1' carbon atom (phenolic oxygen
bonded C atoms), respectively. The low ppm signals,
16.53, 16.63 and 18.20 ppm, are assigned to the 2'ꢀ
substituted methyl carbon atoms. C8 and C9 carbon
atoms appear in 130–141 ppm range (Table 4). In HL1
and the phenol moiety protons is increased.
The OH proton signal in the HꢀNMR spectra of 13CꢀNMR spectra, it is expected C4 + C7, C5 + C6
1
the Zn(II) complex is removed as expected. This and C8 + C9 are to be identical, however they are
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 2 2010

SPECTRAL CHARACTERIZATION AND ANTIBACTERIAL EFFECT
Table 2. IR spectral data of the ligands and the complexes
Compound
219
Frequency (cm–1)
HL1
3338 s, 3056 w, 2903 w, 1628 m, 1601 m, 1532 m, 1454 m, 1474 s, 1428 s, 1389 m, 1320 m, 1259 m,
1228 m, 1089 m, 820 m, 743 m, 642 m
[Fe(
L
1)(OH)(H2O)3](NO ) 3407 s,br, 3238 m,br, 3107 m,br, 1624 m, 1605 w, 1559 m, 1463 m, 1386 s, 1262 m, 1031 w, 750 m,
3
666 w
[Cu(L1)2]
⋅
2H2O
3408 m,br, 3215 m,br, 3062 m,br, 2969 w, 1623 m, 1608 m, 1562 m, 1462 m, 1354 m, 1315 m,
1215 m, 1108 m, 1046 m, 831 m, 746 s
[Ag(HL1)](NO3)
3344 m, 3301 m, 3057 m, 2918 w, 1624 m, 1598 m, 1528 m, 1478 s, 1455 s, 1431 m, 1386 s, 1320 m,
1272 m, 1216 m, 1035 m, 819 m, 743 s, 572m
[Zn(
HL2
HL3
HL4
L1)(H2O)2](NO3)
3434 m,br, 3288 s, 3057 w, 2918 w, 1628 w, 1601 m, 1540 m, 1493 m, 1474 s, 1455 m, 1386 s, 1305 s,
1232 m, 1170 m, 1112 m, 1043 m, 904 m, 789 m, 747 m, 716 m
3342 s, 3080 w, 2964 w, 2918 w, 1632 m, 1605 m, 1474 s, 1428 m, 1386 m, 1320 m, 1278 m, 1259 m,
1228 m, 1089 m, 804 m, 750 m
3331 s, 3075 w, 2917 w, 1615 m, 1602 m, 1531 m, 1477 s, 1423 m, 1387 s, 1307 m, 1254 s, 1225 m,
1064 m, 931 m, 810 m, 790 s, 645 m
3420 br, 3328 s, 3078 m, 2927 m, 1624 m, 1597 m, 1523 s, 1497 m, 1455 m, 1352 s, 1212 m, 1089 m,
1035 m, 820 m, 742 m, 550 m
Table 3. 1HꢀNMR spectral data of the ligands and the complexes (in DMSOꢀd6)
Chemical shifts, δH, ppm and coupling constants (
Benzimidazole protons Phenolic protons
H4' H5'
J, Hz)
Compound
H4
H5
H6
H7
NH
H3'
OH CH3
HL
7.71 d
J = 7.8
7.31
m
7.31
m
7.59 d 13.50 7.27 dꢀd
6.92 t
7.88 dꢀd 13.19 2.26
1
J = 7.8 J = 7.3, 1.0 J = 7.8, 7.3 J = 7.8, 1.0
s
s
s
A
B
7.78 d
J=7.8
7.28 t
8.8, 6.3
7.28 t
8.8, 6.3 J = 7.8
7.68 d 13.28 7.30 d 6.97 t 7.88 d,br 13.25 2.26
s
J = 7.3 J = 7.8, 7.3 J = 7.7
s
s
8.95
s,br
8.04
s,br
7.31
d,br
7.60
s,br
13.57
s,br
7.25
s,br
7.25
s,br
7.87
s,br
–
2.07
s
HL2, IsomerA (55%) 7.58 d
J = 8.3
7.11 d
J = 8.3
2.46
s*
7.50
s
13.50
s,br
7.25 d
6.90 t
7.85 d
13.02 2.26
J = 7.3 J = 7.8, 7.3 J = 7.8
s
s
HL2, IsomerB (45%) 7.37
s
2.44
s*
7.09 d
7.46 d 13.50
7.25 d 6.90 t 7.85 d
J = 7.3 J = 7.8, 7.3 J = 7.8
13.02 2.26
J = 8.3 J = 8.3 s,br
s
s
HL3
7.72
s,br
–
7.28 d,br 7.61 13.36
J = 7.3 s,br s,br
7.32
s,br
6.94 t
J = 7.8, 7.8 J = 8.0
7.87 d,br 13.21 2.26
s,br
s
HL4, IsomerA (50%) 8.97
s
–
7.56 d 7.35 d,br 12.57
J = 7.1 J = 7.3 s,br
6.62
s,br
6.93 t
J = 7.6, 7.3
6.62
s,br
–
2.25
s
HL4, IsomerB (50%) 6.83 d
7.96 dꢀd
–
8.01 d 12.57
J = 2.4 s,br
6.62
s,br
6.93 t
J = 7.6, 7.3
6.62
s,br
–
2.25
s
J = 8.9 J = 8.8, 2.4
* 3H (CH ); A: [Ag(HL )]NO ; B: [Zn(L )(H O) ](NO ).
1 2 2 3
3
1
3
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 2 2010

220
AYDIN TAVMAN et al.
Table 4. 13CꢀNMR (APT) spectral data of the HL1 and its Ag(I) and Zn(II) complexes (δC, ppm; in DMSOꢀd6)
The benzimidazole carbons
C4+C7 C5+C6 C8+C9
The phenolic carbons
C3' C4' C5'
Comꢀ
pound
C2
C1'
C2'
C6'
CH3
HL1
152.87 112.15 124.33 141.46 157.18 126.40 133.27 119.26 123.11 112.32
118.58 124.00 133.84
16.53
A
B
152.60 112.71 124.76 141.27 156.87 126.49 133.47 119.47 123.08 112.16
118.55 123.70 133.86
16.63
18.20
153.71 112.16
24.61
140.74 164.02 126.91 133.29 119.16 123.14 111.72
132.34 124.46 133.85
A: [Ag(HL )]NO B: [Zn(
L
)(H O) ](NO )
1
3,
1
2
2
3
H
N
7
5'
4'
6
6'
3'
2
N
5
R
1' 2'
4
HO
CH
3
Table 5. In vitro antimicrobial activity of the compounds (inhibition zone, mm)
Microorganisms
Compound
1
2
3
4
5
6
7
8
9
HL1
HL1
HL2
HL2
HL3
HL3
HL4
HL4
–
–
–
–
–
–
–
–
–
–
10
–
–
–
–
–
–
–
–
–
–
–
8
–
–
–
–
–
–
–
–
8
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
7
–
–
–
–
–
–
–
–
–
8
–
–
–
–
–
–
–
8
–
–
–
–
–
–
–
–
–
–
8
–
–
–
–
–
–
–
<5
–
–
7
⋅
⋅
⋅
⋅
HCl
HCl
HCl
HCl
[Fe(
[Cu(
[Ag(HL1)](NO3)
[Zn( 1)(H2O)2](NO3)
L
1)(OH)(H2O)3](NO3)
8
L
1)2]
⋅
2H2O
–
10
–
–
10
8
–
10
8
14
12
L
–
–
–
– : zone did not form.
appear as separately because of the strong intramolecꢀ
ular hydrogen bonding with phenolic oxygen and
C=N nitrogen atoms in the solvent (Fig. 2). It is likely
that the hydrogen bonding changed the identity of the
benzimidazole ring carbon atoms as in the metal comꢀ
plexes.
Antibacterial Effect
The results concerning in vitro antibacterial activꢀ
ity of the ligand, their hydrochloride salts and the
complexes together with the inhibition zone (mm) and
MIC values are presented in Tables 5 and 6.
The other signals belong to the benzimidazole benꢀ
zen and phenol rings carbon atoms (Table 5).
It is observed that Ag(I) complex is effective toward
almost to all the bacteria. Besides of this, Zn(II) comꢀ
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 2 2010

SPECTRAL CHARACTERIZATION AND ANTIBACTERIAL EFFECT
221
Table 6. In vitro antimicrobial activity of the compounds (MIC,
μ
g/mL)
Microorganisms
Compound
1
2
3
4
5
6
7
8
9
HL1
HL1
HL2
HL2
HL3
HL3
HL4
HL4
–
–
–
–
–
–
–
–
–
–
8.3
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
8.3
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
8.3
*
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
266
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
266
–
–
⋅
⋅
⋅
⋅
HCl
HCl
HCl
HCl
[Fe(
[Cu(
[Ag(H
[Zn( 1)(H2O)2](NO3)
L
1)(OH)(H2O)3](NO3)
L
1)2]
⋅
2H2O
–
16.6
–
133
2.1
*
–
16.6
–
L1)](NO3)
16.6
66.5
33.2
–
L
1. P. aeruginosa ATCC 27853, 2. S. enteriditis KUEN 349, 3. E. coli ATCC 25922
,
4. P. mirabilis CCM 1944, 5. K. pneumoniae ATCC 4352, 6. S. epidermidis ATCC 12228
7. S. aureus ATCC 29213, 8. B. cereus ATCC 11778, 9. B.subtilis ATCC 6633.
– : No antibacterial activity qualitatively.
,
* : MIC value was not detected in the test concentrations (<532 µg/mL).
2. M. A. M. AbuꢀYoussef, R. Dey, Y. Gohar, A. A. Masꢀ
soud, L. Ohrstrom, and V. Langer, Inorg. Chem. 46
(15), 5893 (2007).
plex has antibacterial effect on especially K. pneumoꢀ
niae, S. epidermidis and S. aureus bacteria, while the
ligand has not any activity. Also, Cu(II) complex is
3. B. Dudova, D. Hudecova, R. Pokorny, M. Mikulasova,
M. Palicova, P. Segla, and M. Melnik, Folia Microbiol.
46, 379 (2001).
4. B. Dudova, D. Hudecova, R. Pokorny, M. Mickova,
M. Palicova, P. Segla, and M. Melnik, Folia Microbiol.
47, 225 (2002).
5. E. Lukevics, P. Arsenyan, I. Shestakova, I. Domꢀ
racheva, A. Nesterova, and O. Pudova, Eur. J. Med.
Chem. 36, 507 (2001).
effective selectively on S. epidermidis. It is observed that
Fe(III) complex has antibacterial effect toward E. coli
,
K. pneumoniae and S. aureus considering the zone valꢀ
ues. These observation shows that a metal ion coordiꢀ
nates to the organic compound increases the antimiꢀ
crobial activity probably due to synergic effect.
On the other hand, HL4 is only ligand exhibits
microbial effect among the ligands (on S. aureus). This
may be resulted from the nitro group existence as
reported in the literature [23].
6. B. Ulküseven, A. Tavman, G. Otük, and S. Birteksöz,
Folia Microbiol. 47, 481 (2002).
As a result, it can be said that the antibacterial
activities of these compounds against tested organisms
suggested further investigation on these compounds.
7. A. Tavman, B. Ülküseven, S. Birteksöz, and G. Ötük,
Folia Microbiol. 48, 479 (2003).
8. A. Tavman, S. Ikiz, A. F. Bagcigil, N. Y. Ozgur, and
S. Ak, J. Serb. Chem. Soc. 74, 537 (2009).
9. H. F. Ridley, G. W. Spickett, and G. M. Timmis, J. Het.
Chem. 2, 453 (1965).
10. A. Tavman and B. Ülkuseven, Main Group Met.
In conclusion, the optimized structures for the
complexes in Fig. 3, are in best accord with the anaꢀ
lytical data, molar conductivity, magnetic
moments, FTꢀIR and NMR spectroscopic measureꢀ
ments.
Chem. 24, 205 (2001).
11. Performance Standards for Antimicrobial Disk Susceptiꢀ
bility Tests, 6th Ed.; Approved Standard NCCLS Docꢀ
ument M2ꢀA6 (NCCLS, 940 West Valley Road, Suite
1400, Wayne, Pennsylvania 19087, 1997).
ACKNOWLEDGMENT
12. Methods for Dilution Antimicrobial Susceptibility Tests
for Bacteria That Grow Aerobically, 5th Ed., Approved
Standard NCCLS Document M7ꢀA5 (NCCLS, 940
West Valley Road, Suite 1400, Wayne, Pennsylvania
19087, 2000).
13. A. Tavman, N. M. AghꢀAtabay, A. Neshat, F. Gucin,
B. Dulger, and D. Haciu, Transit. Met. Chem. 31, 194
(2006).
This work was supported by Istanbul University
Research Fund. Project number: 262/23082004.
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