Synthesis, spectral characterization and biological activities of Mn(II) and Co(II) complexes with benzyloxybenzaldehyde-4-phenyl-3-thiosemicarbazone

Article abstract of DOI:10.1016/j.saa.2011.01.029

Mn(II) and Co(II) complexes of benzyloxybenzaldehyde-4-phenyl-3- thiosemicarbazone have been synthesized and characterized by the investigations of electronic and EPR spectra and X-ray diffraction. Based on the spectral studies, an octahedral geometry is

Full text of DOI:10.1016/j.saa.2011.01.029

Spectrochimica Acta Part A 79 (2011) 39–44
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis, spectral characterization and biological activities of Mn(II) and Co(II)
complexes with benzyloxybenzaldehyde-4-phenyl-3-thiosemicarbazone
B. Prathimaa, Y. Subba Raoa, G.N. Ramesha, M. Jagadeesha, Y.P. Reddyb,
P.V. Chalapathia, A. Varada Reddya,∗
a Analytical Division, Department of Chemistry, Srivenkateswara University, Tirupati 517502, India
b Department of Physics, Sri Padhmavati Mahila Visva Vidyalayam (Women’s University), Tirupati 517502, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Mn(II) and Co(II) complexes of benzyloxybenzaldehyde-4-phenyl-3-thiosemicarbazone have been syn-
thesized and characterized by the investigations of electronic and EPR spectra and X-ray diffraction. Based
on the spectral studies, an octahedral geometry is assigned for the Mn(II) and Co(II) complexes. X-ray
powder diffraction studies reveal that Mn(II) and Co(II) complexes have triclinic crystal lattices. The unit
Received 8 November 2010
Received in revised form 8 January 2011
Accepted 17 January 2011
◦
◦
˚
˚
˚
cell parameters of the Mn(II) complex are a = 11.0469 A, b = 6.2096 A, c = 7.4145 A, ˛ = 90.646 , ˇ = 95.127 ,
Keywords:
◦
3
˚
˚
˚
˚
ꢀ = 104.776 , V = 489.7 A and those of Co(II) complex are a = 9.3236 A, b = 10.2410 A, c = 7.8326 A,
Thiosemicarbazone
Electronic spectra
EPR spectra
◦
◦
◦
3
˚
˛ = 90.694 , ˇ = 99.694 , ꢀ = 100.476 , V = 724.2 A . When the free ligand and its metal complexes are
subjected to antibacterial activity, the metal complexes are proved to be more active than the ligand.
However with regard to in vitro antioxidant activity, the ligand exhibits greater antioxidant activity than
its metal(II) complexes.
X-ray powder diffraction
© 2011 Elsevier B.V. All rights reserved.
1. Intoduction
2. Experimental methods
Thiosemicarbazones usually act as chelating ligands with tran-
sition metal ions, bonding through the sulphur and hydrazine
nitrogen atoms. Thiosemicarbazones and their complexes have
received considerable attention because of their pharmacological
activities [1]. The metal complexes show more pharmacological
activities as compared to the free thiosemicarbazones and semicar-
bazones [2]. The thiosemicarbazones have numerous applications
like antitumour [3], fungicides and antibacterial [4], antiviral [5],
antifungal [6], anti HIV [7], anticancer [8] and other biological
activities [9]. Particularly the thiosemicarbazones can be used as
reagents for Co(II), Ni(II), Cu(II) and Pd(II) for high performance
liquid chromatography and diverse biological activities [10–13].
Thiosemicarbazones have also been used as analytical reagents for
the analysis of metals [14] and as devices for optical storage and
optical information processing [15]. Novak et al. have reported that
salicylaldehyde-4-phenylthiosemicarbazone belongs to an impor-
tant class of biologically active thiosemicarbazone compounds that
possess anticancer, antivirial, antibacterial, antiinflammatory and
antifungal activity [16].
2.1. Materials
All the chemicals used are of analytical grade. Organic chem-
icals such as thiobarbituric acid (TBA), trichloroaceticacid (TCA),
␣-tocopherol, butylated hydroxy toluene (BHT), 1,1-diphenyl-2-
picryl hydrazyl (DPPH), 4-phenyl thiosemicarbazide and dimethyl
formamide (DMF) are procured from Sigma–Aldrich and all metal
salts are procured from E. Merck Chemical Company.
2.2. Physical measurements
The IR spectra of the compounds are recorded on a Nikolet FT-
IR 560 Magna spectrometer using KBr (neat). The Bruker 300 MHz
NMR spectrometer is used to obtain the 1H NMR spectrum of the
ligand. A mass spectrum is recorded in a Quattro LC-Micro mass.
Elemental analysis is obtained from vario-micro qub elementar
analyzer. The electronic spectra of the complexes are recorded on
a Perkin Elmer UV-Visible Lambda 950. EPR spectra are recorded
on an EPR spectrometer (JEOL FE-1X), operating in the X-band
frequencies with a modulation frequency of 100 kHz. For EPR mea-
surements, 100 mg of each compound is taken in a quartz tube. The
magnetic field is scanned from 2200 to 4200 G, with a scan speed
of 250 G min−1. Absorbance is measured using Systronics UV/VIS
spectrometer-117. A digital pH meter (model L1-10 Elico, India)
is used for measuring pH. X-ray diffractometer (PHILIPSPW3710)
∗
Corresponding author. Tel.: +91 877 2249666x303; fax: +91 877 2249611.
E-mail address: ammireddyv@yahoo.co.in (A. Varada Reddy).
1386-1425/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2011.01.029

40
B. Prathima et al. / Spectrochimica Acta Part A 79 (2011) 39–44
˚
2.5. DPPH scavenging activity
using CuK␣ (1.5418 A) radiation operated at 45 kV and 25 mA is used
in X-ray investigations.
The principle for the reduction in DPPH free radicals is that the
antioxidant reacts with stable free radical DPPH and converts it
to 1,1-diphenyl-2-picrylhydrazine. The ability to scavenge the sta-
ble free radical DPPH is measured by decrease in the absorbance
at 517 nm. Solutions ligand and its Mn(II) and Co(II) complexes
at 100 ␮M concentrations are added to 100 ␮M DPPH and kept
in ethanol tubes. The tubes are kept at ambient temperature for
20 min and absorbances are measured at 517 nm. For positive con-
trol, ␣-tocopherol is used [20]. These measurements are run in
triplicate. The percentage of scavenging activity is calculated as
follows:
2.3. Synthesis of the ligand and their metal complexes
Equal volumes of hot ethanolic solution containing 2.12 g of
benzyloxybenzaldehyde and hot ethanolic solution containing
1.67 g of 4-phenyl-3-thiosemicarbazide are mixed. The mixture
obtained is refluxed for an hour, then stirred for 3½ h at 60–70 ◦C
and kept at room temperature for a day. The resulting intense
yellow colored precipitate is filtered, washed with ethanol and
dried. The schematic structure is depicted below [17].
-
H2O
S
O
N
HN
S
+
H2N
O
N
N
HN
H
H
O
Benzyloxybenzaldehyde
4-Phenyl-3-thiosemicarbazide Benzyloxybenzaldehyde-4-phenyl-
3-thiosemicarbazone
ADPPH − ATEST
scavenging activity (%) =
ADPPH
2.3.1. Synthesis of metal complexes
× 100
(1)
A mixture of hot ethanolic solution (10 ml) of free ligand
(0.002 mol) and hot ethanolic solution (10 ml) of (0.001 mol) the
metal solutions [MnCl2·4H2O/CoCl2·6H2O] was refluxed for 3–4 h
and 6–7 h at 50–60 ◦C, respectively. The resulting solutions are
allowed to stand at room temperature and upon slow evaporation
gives cream colored crystals of Mn(II) complex and brick red col-
ored crystals of Co(II)complex. The crystals are collected, washed
with 50% ethanol and dried. The purity of the complex is checked
by TLC.
where ADPPH is the absorbance of DPPH without test sample (con-
trol) and ATEST is the absorbance of DPPH in the presence of test
sample.
2.6. Inhibition of lipid peroxidation in rat brain homogenate
2.6.1. Preparation of rat brain homogenate
For the present study, Albino Wistar rats (180–200 g) are
selected. Prior to decapitation and removal of the brain, the
animals are anesthetized with ether and perfused transcardially
with ice-cold normal saline to prevent contamination of brain
tissue with blood. The collected tissues are weighed and their
homogenates 10% w/v are prepared in 0.15 M KCl and centrifuged at
800 rpm for 10 min. The supernatants are used immediately for the
study [21].
2.4. Antibacterial screening
In vitro antibacterial screening is performed by the agar disc
diffusion method [18,19]. The bacterial species used in the screen-
ing are gram-negative bacteria such as Klebsiella pneumoniae and
Escherichia coli and gram-positive bacteria such as Staphylococ-
cus aureus and Bacillus subtilis. Stock cultures of the test bacterial
species are maintained on nutrient agar media (Hi-media labo-
ratories, Mumbai) by subculturing in Petri dishes. The media are
prepared by adding the components as per manufacturer’s instruc-
tions and sterilized in the autoclave at 121 ◦C and atmospheric
pressure for 15 min. Each medium is cooled to 45–60 ◦C and 20 ml
of it is poured into a Petri dish and allowed to solidify. After solidi-
fication, Petri plates with media are spread with 1.0 ml of bacterial
suspension prepared in sterile distilled water. The wells are bored
with cork borer and the agar plugs are removed. To each agar well,
100 ml of the compound reconstituted in DMF of concentration
1.0 mg/ml is added. DMF is used as a negative control and in sim-
ilar way, antibiotics such as ampicillin and tetracycline are used
as positive control standards. All the plates are incubated at 37 ◦C
for 24 h and they are observed for the growth inhibition zones. The
presence of clear zones around the wells indicate that both the lig-
and and complexes are active. The diameter of zone of inhibition is
calculated in millimeters. The well diameter is deducted from the
zone diameter to get the actual zone of inhibition diameter and the
values are tabulated.
2.6.2. Iron(III) induced lipid peroxidation
The incubation mixtures contain a final volume of 1.5 ml brain
homogenate (0.5 ml of 10% (w/v)), KCl (0.15 M) and ethanol (10 ␮l)
or test compound dissolved in ethanol. Peroxidation is initiated
by adding ferric chloride (100 ␮M) to give the final concentration
stated. After incubation for 20 min at 37 ◦C, reactions are stopped
by adding 2 ml of ice-cold 0.25 M HCl containing 15% trichloroaceti-
cacid (TCA), 0.38% thiobarbituric acid (TBA) and 0.05% butylated
hydroxy toluene (BHT). The samples are heated at 80 ◦C for 15 min,
cooled and centrifuged at 1000 rpm for 10 min. The absorbances
of the supernatant solutions are measured at 532 nm. Percentage
inhibition ofthiobarbituricacidreactivesubstances (TBARS)formed
by test compounds was calculated by comparing with the con-
trol. Iron(III) solutions are prepared afresh in distilled water and
other solutions are prepared in 0.15 M KCl. Since most buffers trap
hydroxyl radical or interfere with iron conversion, the reactions are
carried out in unbuffered 0.15 M KCl solution [22,23].
The inhibition percentages of the selected ligand and its metal
complexes are evaluated using lipid peroxidation method. The fol-

B. Prathima et al. / Spectrochimica Acta Part A 79 (2011) 39–44
41
305
1.50
1.45
1.40
1.35
1.30
1.25
1.20
1.15
1.10
325
361
408
443
562
300
350
400
450
500
550
600
WAVELENGTH(nm)
Fig. 1. Powder X-band EPR spectrum of Mn(II) at room temperature (ꢁ = 9.205 GHz).
Fig. 2. Solid state electronic spectrum (nm) of Mn(II)complex.
lowing formula is used in calculating inhibition percentages:
ACONT − ATEST
magnitude of hyperfine splitting constant provides a measure of
the bonding between Mn(II) ions and its surrounding ligands [27].
In case of d5 transition metal ions, it is known that axial distor-
tion of octahedral symmetry gives rise to three Kramer’s doublets
inhibition percentage =
× 100
(2)
ACONT
where ACONT is the absorbance of the control reaction and ATEST is
the absorbance in the presence of the test sample.
|
5/2ꢀ, | 3/2ꢀ and | 1/2ꢀ [28]. Application of Zeeman field lifts the
spin degeneracy of the Kramer’s doublets [29]. As the crystal field
splitting is normally much greater than the Zeeman field, the reso-
nances observed are due to transitions within the Zeeman field split
Kramer’s doublets. The resonance at g ∼ 2.0 is due to Mn(II) ions in
an environment close to octahedral symmetry [30] and is known
to arise from the transition between the energy levels of the lower
doublet. The magnitude of hyperfine splitting constant (A) provides
a measure of covalency between the Mn(II) ion and the ligand.
The strength of the hyperfine splitting depends on the matrix into
which the ion is dissolved and is mainly determined by the electro
negativity of the neighbors. This means a qualitative measure of the
covalency of the bonding in the matrix which can be determined
from the value of A; the smaller the splitting, the more covalent the
bonding of the anion. It is also noted that the g-value for the hyper-
fine splitting was indicative of the nature of bonding in the complex.
If the g-value shows a negative shift with respect to 2.0023, then
the bonding is ionic and conversely, if the shift is positive, then
the bonding is more covalent in nature. In the present work, from
the measured negative shift in the g-value, with respect to 2.0023,
it is apparent that the Mn(II)ion is in an ionic environment. The g
value calculated is 2.0183. The hyperfine coupling constant value
is 102 G.
3. Results and discussion
3.1. Characterization of the ligand
Benzyloxybenzaldehyde-4-phenyl-3-thiosemicarbazone
is
analyzed by IR and 1H NMR spectroscopy. The IR spectrum of
ligand exhibits absorption bands around 1543.18 cm−1 (C N),
1253.18 cm−1(C S) and 3307.85 cm−1(–NH). The 1H NMR
(300 MHz, ı (ppm), CDCl3) investigations provide the following
information 8.0–7.15 (m, 14H, Ar–H), 11.66 (s, NH), 5.13 (s, N CH),
3.12 (s, OCH2). Elemental analysis gives C 69.78; H 5.30; N 11.63; S
8.87; Calcd: C 69.32; H 5.043; N11.35; S 8.725%. The mass spectrum
of ligand shows a molecular ion peak at 362.1, corresponding to
the species [C21H19N3OS]+, which confirms the proposed for-
mula. Benzyloxybenzaldehyde-4-phenyl-3-thiosemicarbazone is
a yellow solid with a melting point of 150–152 ◦C.
3.2. Electron paramagnetic resonance spectrum of the Mn(II)
complex
The EPR spectrum of Mn(II) complex is shown in (Fig. 1). EPR
spectrum of Mn(II) exhibits sextet, superimposed on a broad line.
The sextet slowly broadened leaving behind a single broad line due
to dipole–dipole interaction. The EPR spectrum of Mn(II), in general,
can be analyzed using the spin-Hamiltonian [24,25]:
3.3. Electronic spectrum of the Mn(II) complex
The electronic spectrum of Mn(II) complex is shown in Fig. 2.
The spectrum consists of six bands at 562, 443, 408, 361, 325
and 305 nm that are characteristics of Mn(II) in octahedral sym-
metry. The characteristic broad bands at longer wavelengths 562
and 443 nm are assigned, respectively to the low lying transi-
H = gˇB · S + SAI + SDS
where g is the isotropic factor, ˇ is the Bohr magneton, B is the
external magnetic field, S is the vector operator of the electron spin
momentum, A is the hyperfine interaction parameter, I is the vector
operator of nuclear spin momentum and D is the zero field splitting
parameter. Investigations of the EPR spectrum of Mn(II) complex
have shown that it has been characterized by an intense resonance
signal at around g = 2.0 with six line hyperfine pattern, which is a
characteristic of ions with a nuclear spin, I = 5/2 [26].
6
4
6
4
tions A1g(S) → T1g(G) and A1g(S) → T2g(G). With the help of
the Tanabe–Sugano diagram Other bands at 408, 361, 325 and
4
305 nm are assigned to the transitions 6A1g(S) → A1g(G) + 4Eg(G),
4
4
4
6A1g(S) → T2g(D), 6A1g(S) → Eg(D) and 6A1g(S) → T1g(P), respec-
tively [31]. The energy matrices for d5 configuration with Trees
correction (free ion term ˛ = 76 cm−1) are solved for various values
of the crystal field parameter (Dq) and Racah parameters (B and C).
The values Dq = 890, B = 870 and C = 3000 cm−1 give a reasonably
The ability to observe the 55Mn hyperfine structure has two tan-
gible benefits: (i) it generally allows unambiguous assignments of
positions of complex resonance lines to manganese and (ii) the

42
B. Prathima et al. / Spectrochimica Acta Part A 79 (2011) 39–44
Table 1
Observed and calculated band positions of Mn(II) complex.
Transition Observed band position
Calculated wave number (cm−1
)
Wave length (nm)
Wave numbers (cm−1
)
4
6A1g(S) → T1g(G)
562
443
408
361
325
305
17,789
22,567
24,503
27,693
30,761
32,777
17,816
22,536
25,207
28,331
30,272
32,815
4
6A1g(S) → T2g(G)
4
6A1g(S) → A1g(G),4Eg(G)
6A1g(S) → 4T2g(D)
6A1g(S) → 4Eg(D)
4
6A1g(S) → T1g(P)
good fit between observed and calculated values of the band head
data Table 1.
3.4. Electron paramagnetic resonance spectrum of the Co(II)
complex
EPR spectrum for Co(II)complex is not observed at normal lab
temperature. This might be because of the broadening of the line
due to rapid spin lattice relaxation of Co(II) at higher temperature
[32]. Therefore EPR spectrum of Co(II) complex is recorded at liquid
nitrogen temperature (LNT) and the calculated value of g is 2.1785.
3.5. Electronic spectrum of the Co(II) complex
The electronic spectrum of Co(II) complex exhibits three
absorption bands at 1130, 600 and 520 nm. For Co(II) (d7)
in octahedral field without considering spin orbit interaction,
4
4
4
4
three spin allowed transitions T1g(F) → T2g(F), T1g(F) → A2g(F)
Fig. 4. XRD spectrum of Mn(II) complex.
4
4
and T1g(F) → T1g(P) are to be expected. Of these transitions,
4T1g(F) → A2g(F) involves the promotion of two electrons and is
4
3.6. Surface morphological studies
expected to be weak [33]. Accordingly the two bands observed
at 1130 nm (8847 cm−1) and 520 nm (19226 cm−1) are attributed
to spin allowed transitions 4T1g(F) → T2g(F) and 4T1g(F) → T1g(P),
4
4
X-ray powder diffraction (XRD) of samples are depicted in
Figs. 4 and 5, respectively. The observed diffraction data is given in
Tables 3 and 4. Using trial and error methods, the unit cell param-
where as the band observed at 600 nm (16662 cm−1) is attributed
to4T1g(F) → A2g(F). In octahedral symmetry, theoretically, the
4
4
4
˚
˚
eters of Mn(II) complex◦are found to◦be a = 11.0469 A, b = 6.2096 A,
ratio of the energies of the transitions T1g(F) → A2g(F) (ꢁ2) and
◦
4T1g(F) → T2g(F) (ꢁ1) are almost invariable at 1.9–2.2 [34]. From
4
˚
c = 7.4145 A, ˛ = 90.646 , ˇ = 95.127 , ꢀ = 104.776 and cell vol-
ume V = 489.7 A . For Co(II) complex, a = 9.3236 A, b = 10.2410 A,
c = 7.8326 A, ˛ = 90.694 , ˇ = 99.694 , ꢀ = 100.476 and cell volume
V = 724.2 A . This data of the complexes support triclinic systems.
3
˚
˚
˚
the band positions Table 2, the ratio of ꢁ2/ꢁ1 is 1.9. The cubic field
energy matrices (d7) are solved for different sets of parameters Dq
and B. The parameters which give good fit of the calculated and
◦
◦
◦
˚
3
˚
observed band positions are Dq = 920 and B = 820 cm−1
.
The observed X-ray pattern of the free ligand sample studied in
Fig. 3. XRD spectrum of free ligand.
Fig. 5. XRD spectrum of Co(II) complex.

B. Prathima et al. / Spectrochimica Acta Part A 79 (2011) 39–44
43
Table 2
Observed and calculated band positions of Co(II) complex.
Transition
Observed band position
Calculated wave numbers (cm−1
)
Wave length (nm)
Wave number (cm−1
)
4
4T1g(F) → T2g(F)
1130
600
520
8847
16,662
19,226
8090
17,290
19,280
4
4T1g(F) → A2g(F)
4
4T1g(F) → T1g(P)
Table 3
Powder X-ray diffraction data of Mn(II) complex.
˚
Peak number
d-spacing (A)
2ꢂ values
ꢃ 2ꢂ
(h k l)
Observed
Calculated
Observed
Calculated
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
6.0038
5.9141
5.8270
4.7370
4.6859
4.6314
4.0795
3.9576
3.5779
3.5463
3.4574
3.3991
3.1887
3.0054
2.9616
2.7121
6.0038
5.9141
5.8270
4.7370
4.6859
4.6314
4.0795
3.9008
3.5889
3.5463
3.4648
3.3953
3.1867
3.0019
2.9570
2.7138
14.74
14.97
15.19
18.72
18.92
19.15
21.79
22.45
24.86
25.09
25.75
26.19
27.96
29.70
30.15
33.00
14.74
14.97
15.19
18.72
18.92
19.15
21.77
22.78
24.86
25.09
25.69
26.22
27.97
29.74
30.20
33.98
0.000
0.000
0.000
0.000
0.000
0.000
0.023
0.331
−0.078
−0.001
0.056
−0.030
−0.018
−0.035
−0.047
0.022
(0 1 0)
(1 0 1)
¯
(1 0 1)
(1 1 0)
¯
(0 1 1)
(0 1 1)
¯ ¯
(1 1 1)
(1 1 1)
¯
(1 0 2)
(3 0 0)
¯
(3 1 0)
(1 0 2)
¯
(1 1 2)
(0 2 0)
¯
(2 2 0)
(1 2 0)
Table 4
Powder X-ray diffraction data of Co(II) complex.
˚
Peak number
d-spacing (A)
2ꢂ values
ꢃ 2ꢂ
(h k l)
Observed
Calculated
Observed
Calculated
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
10.0605
7.4455
6.4426
6.2559
5.9949
5.6795
5.0249
4.5504
4.0808
3.8638
3.5502
3.2149
3.1019
3.0802
2.7723
2.6567
10.0605
7.4455
6.4426
6.2559
5.9949
5.6795
5.0302
4.5146
4.0825
3.8588
3.5492
3.2165
3.0994
3.0804
2.7799
2.6561
8.78
11.88
13.73
14.15
14.76
15.59
17.64
19.49
21.76
23.00
25.06
27.73
28.76
28.96
32.26
33.71
8.78
11.88
13.73
14.15
14.76
15.59
17.62
19.65
21.75
23.03
25.07
27.71
28.78
28.96
32.17
33.71
0.000
0.000
0.000
0.000
0.000
(0 1 0)
¯
(1 1 0)
¯
(1 0 1)
¯
(0 1 1)
(0 1 1)
¯
0.000
0.019
(1 1 1)
(0 2 0)
(2 0 0)
(1 2 0)
(2 1 0)
(0 1 2)
−0.156
0.009
−0.030
−0.007
0.015
¯
(2 2 1)
¯
−0.024
(1 3 1)
¯
0.002
(1 2 2)
¯
0.090
−0.008
(3 2 1)
(1 2 2)
the present investigation indicates amorphous nature (Fig. 3). To
evaluate the crystallite size of the synthesized complexes, D is
determined using Debye–Scherer formula [35,36] given by
where ˇ is the full width at half maximum of the predominant peak
and ꢂ is the diffraction angle and ꢄ is the wavelength of light. The
sizes of the crystallites of the Mn(II) and Co(II) complexes are found
to be 50 nm and 55 nm.
0.94ꢄ
D =
ˇ cos ꢂ
3.7. Antibacterial activity
Antibacterial activity of these metal complexes is tested against
different micro-organisms using only one concentration of these
metal complexes and their activities are compared with standard
antibiotics such as ampicillin and tetracycline (Table 5). The com-
plexes of Mn(II) and Co(II) with free ligand have shown a strong
activity against gram-negative bacteria (E. coli and K. pneumoniae)
and gram-positive bacteria (S. aureus and B. subtilis).
The synthesized ligand and its metal complexes have been
screened for reduction in DPPH free radicals and inhibition of
iron(III) induced lipid peroxidation at 100 ␮m concentration. The
Table 5
Antibacterial screening data of the ligand and its Mn(II) and Co(II) complexes (diam-
eter of zone of inhibition in mm).
Compound
K. pnuemoniae
E. coli
B. subtilis
S. aureus
Ligand (L)
–
30
26
43
32
–
21
16
40
33
–
23
20
43
30
–
18
20
42
32
Mn(II) complex
Co(II)complex
Ampicillin
Tetracycline

44
B. Prathima et al. / Spectrochimica Acta Part A 79 (2011) 39–44
Table 6
Effect of ligand and its metal complexes on scavenging of DPPH and Fe3+ induced lipid peroxidation at 100 ␮M concentration.
Compound
DPPH scavenging (%)
Fe3+ induced lipid peroxidation
Ligand (L)
42
–
38
53
60
–
41
65
Mn(II) complex
Co(II) complex
␣-Tocopherol
free ligand and Co(II) complex show comparable activity in DPPH
scavenging and ferric ion induced lipid peroxidation as seen in the
case of standard antioxidant ␣-tocopherol, but Mn(II) complex has
not shown any activity (Table 6).
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In this paper, the ligand benzyloxybenzaldehyde-4-phenyl 3-
thiosemcarbazone is synthesized and its structure is investigated.
The Mn(II) and Co(II) complexes are prepared with the ligand and
they are characterized with analytical and spectral techniques. The
EPR and electronic spectral studies of both the complexes indicate
near octahedral site symmetry for the metal ions. The ligand does
not exhibit any antibacterial activity but both the complexes give
considerable antibacterial activity. Free ligand and the Co(II) com-
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lipid peroxidation but the Mn(II) complex does not exhibit these
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Acknowledgements
Two of the authors B. Prathima and Y. Subba Rao are highly
grateful to the UGC, Government of India, and New Delhi for finan-
cial assistance in the form of an award of Meritorious Research
Fellowship. We sincerely thank Prof. J. Lakshmana Rao, Department
of Physics, S. V. University, Tirupati, for his help in EPR studies.
We also thank K. Madhavi, Institute of Pharmaceutical Technology,
Sri Padhmavati Mahila VisvaVidyalayam, Tirupati, for her help in
biological studies.
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