Spectroscopic and biological approach of Ni(II) and Cu(II) complexes of 2-pyridinecarboxaldehyde thiosemicarbazone

Article abstract of DOI:10.1016/j.saa.2007.05.033

Ni(II) and Cu(II) complexes having the general composition [M(L)₂X₂] [where L = 2-pyridinecarboxaldehyde thiosemicarbazone, M = Ni(II) and Cu(II), X = Cl^-, NO₃^- and 1/2 SO₄^2-] have been synthesized. All the metal complexes were characterized by elemental analysis, molar conductance, magnetic moment, mass, IR, EPR and electronic spectral studies. The magnetic moment measurements of the complexes indicate that all the complexes are of high-spin type. On the basis of spectral studies an octahedral geometry has been assigned for Ni(II) complexes whereas tetragonal geometry for Cu(II) except [Cu(L)₂SO₄] which posseses five coordinated geometry. The ligand and its metal complexes were screened against phytopathogenic fungi and bacteria in vitro.

Full text of DOI:10.1016/j.saa.2007.05.033

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Spectrochimica Acta Part A 69 (2008) 816–821
Spectroscopic and biological approach of Ni(II) and Cu(II) complexes of
2-pyridinecarboxaldehyde thiosemicarbazone
a,∗
b
a
c
Sulekh Chandra , Smriti Raizada , Monika Tyagi , Praveen Kumar Sharma
a
Department of Chemistry, Zakir Husain College (University of Delhi), JLN-Marg, New Delhi 110002, India
b
Department of Chemistry, M.M.H. College Ghaziabad, India
c
Division of Agricultural Chemicals, Indian Agricultural Research Institute (IARI), New Delhi 110012, India
Received 19 February 2007; received in revised form 23 April 2007; accepted 7 May 2007
Abstract
Ni(II) and Cu(II) complexes having the general composition [M(L)
2
X
2
] [where L = 2-pyridinecarboxaldehyde thiosemicarbazone, M = Ni(II)
2−
4
and 1/2 SO ] have been synthesized. All the metal complexes were characterized by elemental analysis, molar
−
−
and Cu(II), X = Cl , NO
3
conductance, magnetic moment, mass, IR, EPR and electronic spectral studies. The magnetic moment measurements of the complexes indicate that
all the complexes are of high-spin type. On the basis of spectral studies an octahedral geometry has been assigned for Ni(II) complexes whereas
tetragonal geometry for Cu(II) except [Cu(L)
against phytopathogenic fungi and bacteria in vitro.
2007 Elsevier B.V. All rights reserved.
2 4
SO ] which posseses five coordinated geometry. The ligand and its metal complexes were screened
©
Keywords: Thiosemicarbazone; Nickel(II); Copper(II); Biological activities
1
. Introduction
ing of 2-pyridinecarboxaldehyde thiosemicarbazone(L) and its
Ni(II) and Cu(II) complexes. The structure of ligand and scheme
for synthesis is shown in Fig. 1.
Thiosemicarbazones and their metal complexes have con-
siderable interest because of their biological activities, such
as antitumour [1,2], antiviral [3,4], anticancer [5,6], antifungal
2. Experimental
[
7,8], antibacterial [9,10] and antimalarial [11,12]. The benefi-
All the chemicals used were of AnalaR grade and procured
cial biological activities of heterocyclic thiosemicarbazones in
mammalian cells is thought to be due to their ability to inhibit
a key enzyme, ribonucleotide diphosphate reductase (RDR),
which catalyzes the synthesis of DNA precursors [13]. Nickel
is the most toxic metal, which shows the toxicity even in low
doses to both plants and animals [14]. It is found that nickel
transport involves ATP dependent Mg(II) transport system and
toxicity of nickel can be prevented by increasing the concen-
tration of Mg(II) relative to nickel. Copper plays a vital role in
the development and performance of the human nervous and
cardiovascular systemsas well as the skin, bone, immune and
reproductive systems including gene transcription [15,16].
In view of the above applications, in this paper, we report
thesynthesis, spectralcharacterization and antimicrobialscreen-
fromSigma–AdlrichandFluka. Metalsaltswerepurchasedfrom
E. Merck and were used as received.
2.1. Synthesis of ligand
Hot ethanolic solution of thiosemicarbazide (4.55 g,
0.05 mol) and 2-pyridinecarboxaldehyde (4.75 mL, 0.05 mol)
were mixed slowly with constant stirring. This mixture was
◦
refluxed at 70–80 C for 2 h. On cooling a cream coloured com-
pound is precipitated out. It was filtered washed with cold EtOH
◦
and dried under vaccum over P O . Yield, 68%, mp 180 C.
4
10
Elemental analysis found (%) C 46.62; H 4.49; N 31.20. Calcu-
lated for C H N S (atomic mass 180) was C 46.67; H 4.45; N
7
8
4
31.11%.
2.2. Synthesis of complexes
∗
Corresponding author.
Hot ethanolic (20 mL) solution of ligand (0.36 g, 0.002 mol)
E-mail addresses: schandra 00@yahoo.com (S. Chandra),
mnk02tyg@yahoo.co.in (M. Tyagi).
and hot ethanolic (20 mL) solution of the corresponding metal
1
386-1425/$ – see front matter © 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2007.05.033

S. Chandra et al. / Spectrochimica Acta Part A 69 (2008) 816–821
817
Fig. 1. Synthesis and structure of the ligand (L).
salts (0.001 mL) were mixed together with constant stirring. The
◦
mixture was refluxed for 3–4 h at 70–80 C. On cooling, colored
complexes were precipitated out. They were filtered, washed
with 50% ethanol and dried under vaccum over P4O10.
2
.3. Physical measurements
Fig. 2. Electron impact mass spectrum of ligand (L).
The C, H and N were analyzed on Carlo-Erba 1106 ele-
mental analyzer. The Nitrogen content of the complexes was
determined using Kjeldahl’s method. Molar conductance was
measured on the ELICO (CM82T) conductivity bridge. Mag-
netic susceptibility was measured at room temperature using
CuSO4·5H2O as callibrant. Electronic impact mass spectrum
was recorded on JEOL, JMS, DX-303 mass spectrometer. IR
spectra (KBr) were recorded on FTIR spectrum BX-II spec-
trophotometer. The electronic spectra were recorded in DMSO
on Shimadzu UV mini-1240 spectrophotometer. EPR spectra of
the Cu(II) complexes were recorded as polycrystalline sample
at room temperature on E4-EPR spectrometer using the DPPH
as the g-marker.
−1
groups. A band at ∼1610 cm in the IR spectrum of the lig-
and is due to ␯(C N)
group. On complex formation
azomethane
position of this band is shifted toward lower side [18]. Another
−1
band in the region ∼559 cm in the free ligand is due to
␯(C N)
group is also shifted toward higher frequency
pyridine
this indicates that the nitrogen atom of the pyridine group is
involved in complex formation [19]. The (C S) vibration at
42 cm of the free ligand is not shifted on complexation which
indicate that the non involvement of sulphur in coordination
20].
These results indicate that the presence of the thiosemicar-
−1
7
[
bazone ligand coordinated to the Ni(II) an Cu(II) ions through
the Nazomethane and Npyridine chelating centres. Thus, it has
been concluded that ligand acts as bidentate chelating agent
3
. Results and discussion
On the basis of elemental analysis, the complexes were found
[21].
to have the composition as shown in Table 1. The molar con-
ductance measurements of the complexes in DMSO correspond
to non-electrolyte [17]. Thus, the complexes may be formulated
3.1. IR bands due to anions
−
−
as [M(L)2X2], where M = Ni(II) and Cu(II) and X = Cl , NO3
and 1/2 SO42 . EI mass spectrum of the ligand (Fig. 2) con-
−
In the IR spectra of nitrato complexes three bands are
−1
appeared at 1420–1475, 1320–1351 and 1016–1043 cm . The
position of these bands suggests that both the nitrate groups are
coordinated to the metal ion in a unidentate fashion [22].
In the IR spectrum of Ni(II) sulphato complex absorption
firms the proposed formula by showing the final peak at 179 u
[
4
(C7H8N4S), calculated atomic mass 180 u] and other peaks like
4, 60, 78, 88, 91, 119 and 135 u may correspond to various
fragments. The intensity of these peaks gives an idea of the sta-
bility of these fragements. The highest frequency band of the
−1
bands are appeared at ∼1106, ∼1066 and ∼1042 cm sug-
gesting bidentate behaviour of the sulphate ion but in the case of
Cu(II) complex absorption bands are appeared at ∼1179, ∼1019
−
1
2-pyridinecarboxaldehyde thiosemicarbazone at 3433 cm can
assigned to the asymmetric ␯(N–H) vibration of the terminal
NH2 group. The other bands at 3261 and 3156 cm may be
due to the symmetric ␯(N–H) vibrations of the imino and amino
−
1
−
1
and ∼942 cm suggesting unidentate behaviour of the sulphate
ion [23].
Table 1
Elemental analysis data of the complexes
◦
Complex
Colour
Yield (%)
mp ( C)
M.W.
Elemental analysis found (calculated) (%)
M
C
H
N
Ligand (C7H8N4S)
Shiny cream
Green
Light brown
Dark brown
Light green
Green
68
62
63
69
69
72
70
176
237
258
230
195
197
205
180
490
543
515
491
544
516
–
46.67 (46.62)
34.28 (34.25)
30.93 (30.91)
32.62 (32.65)
39.10 (39.12)
35.29 (35.26)
37.20 (37.22)
4.45 (4.49)
3.26 (3.22)
2.95 (2.93)
3.10 (3.08)
3.26 (3.27)
2.94 (2.92)
3.10 (3.12)
31.11 (31.20)
22.86 (22.82)
25.78 (25.76)
21.74 (21.72)
17.11 (17.12)
20.59 (20.57)
16.28 (16.24)
[Ni(L)2Cl2] NiC14H16N8S2Cl2
[Ni(L)2(NO3)2] NiC14H16N10S2O6
[Ni(L)2SO4] NiC14H16N8S3O4
[Cu(L)2Cl2] CuC14H16N8S2Cl2
[Cu(L)2(NO3)2] CuC14H16N10S2O6
[Cu(L)2SO4] CuC14H16N8S3O4
11.98 (11.95)
11.81 (11.83)
11.39 (11.36)
13.03 (13.02)
11.76 (11.74)
12.40 (12.38)
Shiny green

8
18
S. Chandra et al. / Spectrochimica Acta Part A 69 (2008) 816–821
4
. Nickel(II) complexes
At room temperature these complexes show magnetic
Table 3
EPR spectral data of the Cu(II) complexes
Complex
Temperature Data as polycrystalline sample
G
moment in the range 2.91–2.95 BM (Table 2). These values are
in tune with a high spin configuration [24].
gꢀ g⊥
giso
[
Cu(L)2Cl2]
[Cu(L)2(NO3)2] RT
[Cu(L)2SO4] RT
RT
2.0641 2.0255 2.0383
2.0773 2.0318 2.0469
2.2115 2.1673 2.1820
2.5137
2.4308
1.2641
Table 2
Magnetic moments and electronic spectral data of the complexes
λmax (cm 1)
−
Complex
μeff (BM)
[
[
[
[
[
[
Ni(L)2Cl2]
2.92
2.91
2.95
1.85
1.83
1.89
11185, 14084, 25575
11235, 14049, 23364
11185, 14925, 24096
10080, 15898, 24038
11098, 15948, 24096
10162, 15847, 24154
Ni(L)2(NO3)2]
Ni(L)2SO4]
Cu(L)2Cl2]
Cu(L)2(NO3)2]
Cu(L)2SO4]
The electronic spectra of the complexes display three absorp-
tion (Fig. 3a) bands in the range 11185–11235, 14049–14925
−
1
and 23364–25574 cm . The ground state of Ni(II) in an octa-
3
hedral coordination is A2g. Thus, these bands may be assigned
3
3
to three spin allowed transitions A2g(F) → T2g (F) (␯1),
3
3
3
A2g(F) → 3T1g (F) (␯2) and A2g (F) → T1g (P) (␯3), respec-
tively. The position of bands indicates that the complexes have
six-coordinated octahedral geometry [25,26] (Fig. 5).
Fig. 3. Electronic spectra of the complexes. (a) [Ni(L)2Cl2] and (b) [Cu(L)2Cl2].
Fig. 5. Suggested structure of the complexes. (a) [M(L)2X2], where M = Ni(II)
−
−
and Cu(II) and X = Cl and NO3 and [Cu(L)2SO4]. (b) [M(L)2SO4], where
M = Ni(II).
Fig. 4. EPR spectrum of Cu(L)2SO4 as polycrystalline state.

S. Chandra et al. / Spectrochimica Acta Part A 69 (2008) 816–821
819
5
. Copper(II) complexes
considerable exchange interaction in the solid complexes. The
complexes reported in this paper gives the ‘G’ value in the range
1.2641–2.5137, which is <4, indicating exchange interaction in
the solid complexes.
The magnetic moments of Cu(II) complexes were recorded
at room temperature. The complexes show magnetic moments
in the range 1.83–1.89 BM corresponding to one unpaired
electron.
6. In vitro bioassays of ligand and Ni(II) and Cu(II)
complexes
The electronic spectra of these complexes display bands
(Fig. 3b) in the range 10080–11098, 15847–15948 and
−
1
2
4038–24154 cm . These bands correspond to the transitions
Cultures of phytopathogenic fungi and bacteria such as
Rhizoctonia bataticola, Alternaria alternata, Fusarium odum,
BacillusmaceransandPseudomonasstriatawereprocuredfrom
Indian type culture, Division of Plant Pathology, Indian Agri-
cultural Research Institute, New Delhi, India, and maintained
on slants of potato dextrose agar (PDA) and nutrient agar (NA)
media.
2
2
2
2
B1g → A1g(d
x2−y
2
→ d
2
)␯1, B1g → B2g(d
2
2
→ dzy)␯2
z
x −y
2
2
and B1g → Eg(d
2
2
→ dzydyz)␯3, respectively. Therefore,
x −y
the complexes may be considered to possess a tetragonal geom-
etry [27].
EPR spectra of the Cu(II) complexes were recorded, at room
temperature as polycrystalline samples (Fig. 4), on the X-band at
9
.1 GHz under the magnetic field range 2800–3000 G. The anal-
ysis of spectra give gꢀ 2.0641–2.2115 and g⊥ 2.0255–2.1673
Table 3). The trend gꢀ > g⊥ > 2.0023, observed for the com-
plexes, under study, indicate that the unpaired electron is
6.1. Antifungal assay
(
The preliminary fungitoxicity screening of the compounds
at different concentrations were performed in vitro against the
test fungi, R. bataticola, A. alternata and F. odum by the food
poision technique [30,31]. Stock solutions of compounds were
prepared by dissolving the compounds (0.064 mg) in DMF.
Chlorothalonil used as commercial fungicide and DMFserved as
control. Appropriate quantities of the compounds in DMF was
added to potato dextrose agar medium in order to get a concen-
localized in the d
2
2
orbital of the Cu(II) ion and the spectral
x −y
figures are characteristic for the axial symmetry. Tetragonally
elongated geometry is thus confirmed for the aforesaid com-
plexes [28].
G = (gꢀ − 2)/(g⊥ − 2), which measure the exchange interac-
tion between the metal centres in a polycrystalline solid has
been calculated. According to Hathaway and Billing [29] if
G > 4 the exchange interaction is neglisible, but G < 4 indicates
−
1
trations of 250, 125, 62.5 ␮g mL of compound in the medium.
Table 4
Antifungal activities of ligand and Ni(II) and Cu(II) complexes
Complex
Fungus tested
Fungal inhibition (%) at concentrations (␮g mL 1)
−
2
50
125
72.7
73.4
70.0
63.5
Ligand (C7H8N4S)
R. bataticola
A. alternata
F. odum
84.4
90.0
80.0
43.3
42.2
41.0
[
[
[
[
Ni(L)2Cl2]
R. bataticola
A. alternata
F. odum
33.3
61.1
49.0
–
43.3
31.0
–
22.2
–
Ni(L)2(NO3)2]
Ni(L)2SO4]
Cu(L)2Cl2]
R. bataticola
A. alternata
F. odum
50.0
61.2
48.0
44.5
48.9
34.0
16.7
20.0
–
R. bataticola
A. alternata
F. odum
35.0
58.0
33.0
–
–
–
–
39.0
224.0
R. bataticola
A.alternata
F. odum
R. bataticola
A. alternata
F. odum
76.6
62.3
72.0
72.2
67.7
64.0
48.8
47.4
45.0
45.5
48.9
46.0
20.0
22.2
–
11.1
11.2
18.0
[
Cu(L)2SO4]
R. bataticola
A. alternata
F. odum
68.0
60.0
58.0
48.5
41.0
33.0
19.0
14.7
–
Chlorothalonil (standard)
R. bataticola
A. alternata
F. odum
90.0
98.0
89.0
76.6
80.0
74.0
49.0
46.0
42.0

8
20
S. Chandra et al. / Spectrochimica Acta Part A 69 (2008) 816–821
Table 5
Antibacterial activities of ligand and Ni(II) and Cu(II) complexes
Complex
Bacteria tested
Diamater (mm) of compounds at concentrations (␮g mL 1)
−
250
125
63.5
Ligand (C7H8N4S)
B. macerans
P. striata
18
12
11
–
–
–
[
[
[
Ni(L)2Cl2]
B. macerans
P. striata
20
17
16
11
–
–
Ni(L)2(NO3)2]
Ni(L)2SO4]
B. macerans
P. striata
22
15
16
9
10
–
B. macerans
P. striata
15
14
8
7
–
–
Cu(L)2Cl2]
B. macerans
P. striata
34
15
25
–
11
–
[
Cu(L)2(NO3)2]
Cu(L)2SO4]
B. macerans
P. striata
20
14
11
7
–
–
[
B. macerans
P. striata
28
15
19
8
12
–
Streptomycin (standard)
B. macerans
P. striata
30
40
25
26
14
16
The medium was poured into a set of two Petriplates under asep-
tic conditions in a laminar flow hood. When the medium in the
plates was solidified, a mycelial discs of 0.5 cm in diameter cut
from the periphery of the 7 days old culture and it was aseptically
inoculated upside down in the centre of the Petriplates. These
equidistant places at a distance of 2 cm from the center in the
inoculated Petriplates. Filter paper disc treated with DMF served
as control and streptomycin used as a standard drug. All deter-
mination were made in duplicate for each of the compounds.
Average of two independent readings for each compounds was
recorded. These Petriplates were kept in refrigerator for 24 h for
◦
treated Petri dishes were incubated at 26 ± 1 C until fungal
◦
growth in the control Petriplates was almost complete.
The mycelial growth of fungi (mm) in each Petriplates was
measured diametrically and growth inhibition (I) were calcu-
lated by using the formula:
pre-diffusion. Finally Petriplates were incubated at 30 C for
24 h.
The antibacterial results (Table 5) show that all the metal
complexes are more active than free ligand [35]. It has also been
observed that concentration plays a vital role in increasing the
degree of inhibition; as the concentration increases, the activity
increases.
ꢀ
ꢁ
C − T
I(%) − CF
100 − CF
I (%) =
× 100,
IC =
× 100
C
IC = corrected percent inhibition, CF = is the correction factor
obtained the equation; CF = ((90 − Co)/Co) × 100.Where 90 is
the diameter (mm) of the Petridish and Co is the growth of
fungus.
Results of the fungicidal screening (Table 4) show that, the
free ligand (L) was highly active than all the Ni(II) and Cu(II)
complexes against all type of fungi [32].
7. Conclusions
The proposed study revealed an octahedral geometry for
Ni(II) complexes whereas tetragonal geometry for Cu(II) com-
plexes except [Cu(L) SO ] which posseses five coordinated
2
4
geometry. Ligandactsasbidentatechelatingagentthroughnitro-
gen of the pyridine ring and ␯(C N) group. The results of
antifungal activity show that ligand is highly fungitoxic than
the complexes against all type of fungi. On the otherhand, the
antibacterial data reveals that that the complexes are superior
than the free ligand. This increases the lipophilic character of
the metal chelate and favours its permeation through the lipoid
layer of the bacterial memberanes. It has also been proposed
that concentration plays a vital role in increasing the degree of
inhibition; as the concentration increases, the activity increases.
6
.2. Antibacterial assay
The antibacterial activities of the ligand and its Cu(II) and
Ni(II) complexes against test bacteria B. macerans (Gram-
positive) and P. striata (Gram-negative) at different conc.
was checked by disc diffusion technique [33,34]. Twenty-five
milliliters of terilized nutrient agar media (NA) was poured
in each Petriplates. After solidification 0.1 mL of test bacteria
spreads over the medium using a spreader. The test compounds
in measured quantities were dissolved in DMF to get con-
Acknowledgements
−
1
centrations of 250, 125 ␮g mL of compounds. The disc of
Whatmann No. 1 filter paper having the diameter 5.00 mm each
containing (1.5 mg cm ) of compounds were placed at four
We are thankful to the Zakir Husain College, for provid-
ing research facilities. ACBR Delhi University, for recording
−
1

S. Chandra et al. / Spectrochimica Acta Part A 69 (2008) 816–821
[15] S. Majumder, P. Dutta, S.K. Choudhari, Med. Chem. 6 (2005) 563.
821
IR spectra RSIC, IIT Mumbai, for recording EPR spectra and
[
[
[
16] D. Chen, Q.C. Cui, H. Yang, Q.P. Dou, Cancer Res. 66 (2006) 10425.
17] W.G. Geary, Coord. Chem. Rev. 7 (1971) 81.
18] S. Chandra, L.K. Gupta, Spectrochim. Acta A 60 (2004) 1563.
DRDO, New Delhi, for financial assistance.
References
[19] M.A. Ali, A.H. Mirza, A.M.S. Hossain, M. Nazimuddin, Polyhedron 20
2001) 1045.
(
[
20] J. Martinez, L.A. Adrio, J.M. Antelo, M.T. Pereira, J.J. Fernandez, J.M.
Vila, Polyhedron 25 (2006) 2848.
21] S. Chandra, L.K. Gupta, J. Saudi Chem. Soc. 7 (2003) 331.
22] M. Shakir, O.S.M. Nasman, A.K. Mohamed, S.P. Varkey, Ind. J. Chem.
[
[
[
1] V.B. Arion, M.A. Jakupec, M. Galanski, P. Unfried, B.K. Keppler, J. Inorg.
Biochem. 91 (2002) 298.
2] J.P. Scovill, D.L. Klayman, C.F. Franchino, J. Med. Chem. 25 (1982)
[
[
1
261.
35A (1996) 710.
3] C.C. Garcia, B.N. Brousse, M.J. Carlucci, A.G. Moglioni, M.A. Mar-
tins, G.Y. Moltrasio, N.B. D’ Accorso, E.B. Damonte, Antivir. Chem.
Chemother. 14 (2003) 99.
[23] K. Nakamoto, Infrared Spectra of Inorganic and Coordination Compounds,
Wiley Interscience, New York, 1970.
[
[
24] F. Athar, F. Arjmand, S. Tabassum, Trans. Met. Chem. 26 (2001) 426.
25] K.B. Gudasi, M.S. Patil, R.S. Yadav, R.V. Shenoy, S.A. Patil, Trans. Met.
Chem. 31 (2006) 580.
[
[
[
[
4] P. Tarasconi, S. Capacchi, G. Pelosi, M. Cornia, R. Albertini, A. Bonati,
P.P. Dall’Aglio, P. Lunghi, S. Pinelli, Bioorg. Med. Chem. 8 (2000) 157.
5] W.X. Hu, W. Zhou, C.N. Xia, X. Wen, Bioorg. Med. Chem. Lett. 16 (2006)
[
[
26] N.V. Thakkar, S.Z. Bootwala, Ind. J. Chem. 34A (1995) 370.
27] A.B.P. Lever, Inorganic Electronic Spectroscopy, Elsevier, Amsterdam,
2
213.
6] Y. Kang, N. Yang, S.O. Kang, J. Ko, C.H. Lee, Y.H. Lee, Organometallics
6 (1997) 5522.
1
984.
28] B. Jezowska, J. Lisowski, A. Vogt, P. Chemielewski, Polyhedron 7 (1988)
37.
1
[
7] E.M. Jouad, G. Larcher, M. Allian, A. Riou, G.M. Bouet, M.A. Khan, X.D.
Thanh, J. Inorg. Biochem. 86 (2001) 565.
3
[
[
[
29] B.J. Hathaway, D.E. Billing, Coord. Chem. Rev. 5 (1970) 143.
30] N. Fahmi, M.K. Biyala, R.V. Singh, Trans. Met. Chem. 29 (2004) 681.
31] A. Hooda, V.K. Garg, N.K. Sangwan, K.S. Dhindsa, Proc. Natl. Acad. Sci.
India 66A (1996) 223.
[
[
8] S. Belwal, N. Seema Fahmi, R.V. Singh, Ind. J. Chem. 38A (1999) 596.
9] O.E. Offiong, S. Martelli, Farmaco 49 (1994) 513.
[
[
[
10] A. Golcu, M. Dolaz, H. Demirelli, M. Diorak, S. Serin, Trans. Met. Chem.
1 (2006) 658.
11] D.L. Klayman, J.P. Scovill, J. Bruce, J.F. Bartosevich, J. Med. Chem. 27
1984) 84.
12] A. Walcourt, M. Loyevsky, D.B. Lovejoy, V.R. Gordeuk, D.R. Richardson,
Int. J. Biochem. Cell. Biol. 36 (2004) 401.
3
[32] N. Raman, A. Kulandaisamy, C. Thangaraja, K. Jeyasubramanian, Trans.
Met. Chem. 28 (2003) 29.
(
[
[
[
33] J.R. Anacona, G.D. Sillva, J. Chil. Chem. Soc. 50 (2005) 447.
34] S. Znanovic, S. Chi, A.F. Draughan, J. Food Sci. 70 (2005) 45.
35] A. Chaudhary, R.V. Singh, Phosphorus Sulfur Silicon Relat. Elem. 178
[
[
13] F.A. French, E.J. Blanz Jr., J. Med. Chem. 13 (1970) 1117.
14] A.H. Roy, J.F. Hartwig, J. Am. Chem. Soc. 125 (2003) 8704.
(
2003) 603.