Synthesis, characterization, and the antimicrobial and anthelmintic activities of some metal complexes with a new Schiff base 3-[(Z)-5-amino-1,3,3- trimethyl cyclohexylmethylimino]-1,3-dihydroindol-2-one

Article abstract of DOI:10.1134/S0036023608060168

The complexes of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), dioxouranium(VI), and Th (IV) with a new Schiff base, 3-[(Z)-5-amino-1,3,3- trimethyl cyclohexylmethylimino]-1,3-dihydroindol-2-one formed by the condensation of isatin (Indole-2.3-dione) with isophoronediamine(5-amino-1,3,3- trimethyl-cyclohexane methylamine) (IPDA) was synthesized and characterized by microanalysis, conductivity, UV-visi-ble, FT-IR, 1 H NMR,TGA, and magnetic susceptibility measurements. All the complexes exhibit 1: 1 metal to ligand ratio except for the dioxouranium(VI) and thorium(IV) complexes, where the metal: ligand stoichiometry is 1: 2. The spectral data revealed that the ligand acts as monobasic bidentate, coordinating to the metal ion through the azomethine nitrogen and carbonyl oxygen of the isatin moiety. Tetrahedral geometry for Co(II), Ni(II), Zn(II), Cd(II), and Hg(II) complexes, square planar geometry for Cu(II) complexes, and the coordination numbers 6 and 8 for UO ₂(VI) and Th(IV) complexes, respectively, are proposed. Both the ligand and the metal complexes were screened for their antibacterial activity against Bacillus subtilis, Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Pseudomonas aeruginosa, and the complexes are more potent bactericides than the ligand. The anthelmentic activity of the ligand and its complexes against earthworms was also investigated.

Full text of DOI:10.1134/S0036023608060168

ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2008, Vol. 53, No. 6, pp. 906–912. © Pleiades Publishing, Ltd., 2008.
COORDINATION
COMPOUNDS
Synthesis, Characterization, and the Antimicrobial
and Anthelmintic Activities of some Metal Complexes
with a New Schiff base 3-[(Z)–5-Amino–1,3,3-Trimethyl
Cyclohexylmethylimino]–1,3-Dihydroindol–2-One1
K. Rama Krishna Reddy and K. N. Mahendra
Department of Chemistry, Central College Campus, Bangalore University, Bangalore 560001
e-mail: Mahendra_kadidal@yahoo.co.in
Received June 07, 2007
Abstract—The complexes of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), dioxouranium(VI), and Th (IV) with
a new Schiff base, 3-[(Z)–5-amino–1,3,3-trimethyl cyclohexylmethylimino]–1,3-dihydroindol–2-one formed
by the condensation of isatin (Indole–2.3-dione) with isophoronediamine(5-amino–1,3,3-trimethyl-cyclohex-
ane methylamine) (IPDA) was synthesized and characterized by microanalysis, conductivity, UV-visi-ble, FT-IR,
1H NMR,TGA, and magnetic susceptibility measurements. All the complexes exhibit 1 : 1 metal to ligand ratio
except for the dioxouranium(VI) and thorium(IV) complexes, where the metal : ligand stoichiometry is 1 : 2. The
spectral data revealed that the ligand acts as monobasic bidentate, coordinating to the metal ion through the
azomethine nitrogen and carbonyl oxygen of the isatin moiety. Tetrahedral geometry for Co(II), Ni(II), Zn(II),
Cd(II), and Hg(II) complexes, square planar geometry for Cu(II) complexes, and the coordination numbers 6
and 8 for UO2(VI) and Th(IV) complexes, respectively, are proposed. Both the ligand and the metal complexes
were screened for their antibacterial activity against Bacillus subtilis, Staphylococcus aureus (S. aureus),
Escherichia coli (E. coli), and Pseudomonas aeruginosa, and the complexes are more potent bactericides than
the ligand. The anthelmentic activity of the ligand and its complexes against earthworms was also investigated.
DOI: 10.1134/S0036023608060168
1
Isatin thiosemicarbazone derivatives exhibit inter- were purified by standard methods. Isophoronediamine
esting applications as research tools in physiological (IPDA) (Aldrich Chemicals) and isatin (S.D Fine
studies [1]. Many isatin-derived compounds possess a chemicals) were used.
wide spectrum of medicinal properties and, thus, have
been studied for activity against tuberculosis [2, 3] and
leprosy [4], as well as fungal [5, 6], viral [7], and bac-
terial infections [8, 9], etc. A survey of the literature
reveals that the biological activity of the Schiff base
was enhanced by complexation [10]. In continuation of
our work to synthesize novel isatin Schiff bases [11,
12], we report in this paper the synthesis and character-
ization of a novel Schiff base and complexes of Co(II),
Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), dioxouranium(VI),
and Th(IV).The ligand and its metal complexes were
screened for antibacterial activity against Bacillus sub-
tilis, Staphylococcus aureus (S. aureus), Escherichia coli
(E. coli), and Pseudomonas aeruginosa. Anthelmentic
activity of the compounds was tested on earthworms
(Peretima posthuma).
Preparation of Schiff Base
The Schiff base was prepared by the reported
method [12]. Equimolar ethanolic solution (50 ml each)
of isatin and isophoronediamine were mixed and
refluxed for about 1 h. The reaction mixture was con-
centrated to a small volume and allowed to cool. The
Schiff base precipitated out as faint pink solid. It was
filtered, washed with ethanol and recrystallised from
ethanol. The purity of the Schiff base ligand was mon-
itored by TLC using 1 : 1 ethyl acetate and petroleum
ether as eluant and separated by column chromatogra-
phy, m.p: 117°C (Yield 90%).
Preparation of the Complexes
EXPERIMENTAL
The metal complexes were prepared by adding eth-
anolic solution (50 ml) of the metal salt to the ligand
(100 ml) in 1 : 2 molar ratio and heating under reflux for
about 3 h. The reaction mixture was concentrated to a
small volume. On cooling, the metal complexes crystal-
The chemicals employed for the preparation of
Schiff bases were of AR or LR grade. All the solvents
1
This article was submitted by the authors in English.
906

SYNTHESIS, CHARACTERIZATION
907
lizes out. They were filtered, washed with ethanol and vents but have partial solubility in DMF and DMSO.
dried in vacuo.
Hence, molecular weights could not be determined.
Conductivity Measurements
Antibacterial and Anthelmentic Activity Measurements
The conductivity for 10–3 M solutions of the com-
plexes (Table 1) in DMF show Cu(II) and Th(IV) com-
plexes to be 1 : 1 electrolytes; the other complexes show
non-electrolytic behavior.
The ligand and its complexes with Cu(II), Co(II),
Ni(II), Zn(II), Cd(II), and Hg(II) were screened for
antibacterial activity against Bacillus subtilis, Staphy-
lococcus aureus (S. aureus), Escherichia coli (E. coli),
and Pseudomonas aeruginosa at a concentration of
1 mg/0.02 mL in DMF by the cup plate method [13].
Anthelmentic activity of the compounds was measured
on earthworms (Peretima posthuma) by the reported
method [14].
IR Spectra
The IR spectrum of the free ligand is characterized
mainly by strong bands at 3220, 1717, and 1618 cm–1,
which are attributed to the stretching frequencies of
NH, C=O, and C=N [16] respectively. Upon complex-
ation with the metal ion, the bands due to C=O and NH
disappear with the simultaneous appearance of band at
1280–1310 cm–1, which may be assigned to C–O, sug-
gesting deprotonation of the NH group via the carbonyl
oxygen atom of the isatin moiety through its lactam–
lactim tautomerism [16]. The band at 1618 cm–1 due to
C=N group stretching vibration in the spectrum of the free
Schiff-base ligand shifts, with splitting to lower wave
numbers in all the metal complexes (1590–1615 cm–1),
indicating that the azomethine nitrogen atom is coordi-
nated to the central metal ion [16]. The bands observed
in the region 3150–3200 cm–1 attributed to symmetric
modes of the NH2 group remain at nearly the same posi-
tion in the spectra of the complexes, indicating the non-
participation of this group in coordination. Further,
these chelate spectra exhibit new bands at 520 cm–1,
420–410 cm–1, and 332 cm–1, which may be assigned to
M–O, M–N, and M–Cl stretching modes respectively
in all the complexes [10]. The IR spectra of UO2(VI)
complex showed no absorption bands either due to free
or coordinated nitrate groups. On the other hand, the
spectra of Th(IV) complex showed an absorption band
at 1380 cm–1, where the free nitrate is known to absorb
[17]. The complex exhibited bands at 1512, 1290, 1028,
809, 745, and 720 cm–1 corresponding to the bidentate
nitrate groups [17]. The IR spectra of all the metal com-
plexes under study exhibit a broad band in the 3380–
3550 cm–1 region, which can be attributed to the OH
stretching vibration of water [16, 17], as expected from
elemental analysis.
Analysis and Physical Measurements
The microanalysis of the samples was carried using
Carlo Ebra analyser.The metals were estimated by the
standard methods [15]. The conductivity measurements
were made on a Systronics Conductivity Meter 304
with a dip type conductivity cell with a cell constant of
1 unit. The magnetic susceptibility measurements were
carried out at room temperature using the Faraday bal-
ance. Electronic spectra were recorded in DMF in the
range 350–900 nm using a Shimadzu UV–3101 PC
1
UV-VIS-NIR scanning spectrophotometer. H NMR
spectra of the ligand and its complexes were obtained
using a Bruker AMX 400 MHz FT NMR spectrometer.
IR spectra of samples in KBr pellets were recorded in
the region 4000–600 cm–1 with a Nicolet Impact 400-D
FT-IR spectrometer. The far IR spectra of the com-
plexes in the region 600–250 cm–1 were recorded using
a Perkin Elmer Instruments, Spectrum one FT-IR spec-
trometer. The mass Spectrum of the ligand was
recorded using an ESI-MS Bruker Daltronics mass
spectrometer. TGA studies of the complexes were car-
ried out using a Perkin–Elmer Thermogravimetric anal-
yser TGA 7 with a scan rate of 10°C per minute in nitro-
gen atmosphere.
RESULTS AND DISCUSSION
All the metal complexes are either colored or color-
less solids and are stable towards air and have high
melting points (above 300°C). Analytical data of the
complexes suggest that the metal to ligand composition
is 1 : 1 for Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and
Hg(II) complexes and 1 : 2 for UO2(VI) and Th(IV)
complexes. The complexes have the general formula
[MLCl · H2O] where M = Co(II), Ni(II), Zn(II), Cd(II),
or Hg(II), while the Cu(II) salt yields complexes of the
type [CuL · 2H2O]Cl; with UO2(VI) and Th(IV) salts
complexes of the type [UO2L2] · H2O and [ThL2(NO3) ·
2H2O] NO3, respectively, were obtained. The com-
1H NMR Spectra
The 1H NMR spectrum of the ligand and its diamag-
netic Zn(II), Cd(II), Hg(II), U(VI), and Th(IV) com-
plexes were recorded in DMSO-d6. The 1H NMR spec-
tral data are reported in Table 2. The spectrum of the
Schiff base ligand shows bands in four distinct regions
plexes are insoluble in water and common organic sol- (singlet at δ10.5, multiplet at 6.8–7.5, multiplet at 2.4,
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 53 No. 6 2008

908
RAMA KRISHNA REDDY, MAHENDRA
Table 1. Analytical and physical data of the complexes
(%) Found (Calcd.)
Yield
%
µeff,
Mol. cond.
Compound
HIsIPD (L)
Color
S cm2 mol–1
µB
C
H
N
M
–
90
Pale pink
71.95
(72.14)
49.34
8.33
(8.35)
6.57
13.98
(14.03)
9.52
–
–
1.87
4.54
3.70
–
[CuL · 2H2O]Cl
[CoLCl · H2O]
85
85
80
74
78
80
90
92
Light green
Brown
14.70
(14.72)
14.35
95
12
24
14
07
12
16
96
(49.71)
52.55
(6.67)
6.51
(9.66)
10.11
(10.20)
10.45
(10.41)
10.10
(10.07)
8.98
(52.49)
52.48
(6.56)
6.62
(14.33)
14.20
[NiLCl · H2O]
Brown
(52.53)
52.01
(6.56)
6.21
(14.27)
15.62
[ZnLCl · H2O]
Brown
(51.81)
46.50
(6.24)
5.61
(15.68)
24.31
[CdLCl · H2O]
Reddish
Light white
Yellow
–
(46.55)
39.68
(5.60)
4.55
(9.05)
7.54
(24.23)
36.38
[HgLCl · H2O]
[UO2L2] · H2O
[ThL2(NO3) · 2H2O] NO3
–
(39.13)
48.80
(4.71)
5.92
(7.61)
9.44
(36.33)
26.84
–
(48.75)
43.45
(5.87)
5.63
(9.48)
11.58
(11.44)
(26.86)
23.63
Chilly Red
–
(43.70)
(5.50)
(23.41)
1
Table 2. H NMR Chemical Shifts (δ ppm) for the Schiff base and its complexes
Isatin ring
Side Chain
Ligand/Complex
N–H
Aromatic protons
7.5–6.8 (4H, m)
NH2
Aliphatic protons
1.5–0.65 (18H, m)
HIsIPD (L)
10.5 (1H, s)
2.4 (2H, m)
(C18H24N3O)
[ZnLCl · H2O]
[CdLCl · H2O]
[HgLCl · H2O]
[UO2L2] · H2O
[ThL2(NO3) · 2H2O]NO3
–
–
–
–
–
7.85–6.9 (4H, m)
7.6–6.8 (4H, m)
7.85–6.9 (4H, m)
7.85–6.9 (4H, m)
7.85–6.9 (4H, m)
2.4 (2H, m)
2.38 (2H, m)
2.38 (2H, m)
2.4 (2H, m)
2.42 (2H, m)
1.5–0.65 (18H, m)
1.5–0.65 (18H, m)
1.5–0.65 (18H, m)
1.5–0.65 (18H, m)
1.5–0.65 (18H, m)
t – triplet, m – multiplet, s – singlet, br – broad.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 53 No. 6 2008

SYNTHESIS, CHARACTERIZATION
909
Table 3. TGA data of the complexes
Weight loss %
Temp. °C
Complex
Stage
Species lost
Residue
CuO
Found (% Calc.)
[CuL · 2H2O]Cl
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
3
150–200
370
15.2(16.5)
66.0(68.7)
11.5(13.1)
70.0(72.6)
12.7(13.6)
69.9(70.6)
11.8(12.8)
69.2(71.5)
10.8(11.6)
62.7(64.2)
10.5(9.7)
52.9(54.0)
1.9(2.0)
Coordinated H2O + Cl
Ligand
[CoLCl · H2O]
[NiLCl · H2O]
220–280
370
Coordinated H2O + Cl
Ligand
Co2O3
NiO
220–270
350
Coordinated H2O + Cl
Ligand
[ZnLCl · H2O]
200–260
330–350
180–250
360
Coordinated H2O + Cl
Ligand
ZnO
[CdLCl · H2O]
[HgLCl · H2O]
[UO2L2] · H2O
[ThL2(NO3) · 2H2O]NO3
Coordinated H2O + Cl
Ligand
CdO
HgO
U3O8
ThO2
180–250
350
Coordinated H2O + Cl
Ligand
120
Uncoordinated H2O
Ligand
360
65.0(67.5)
5.8(6.3)
180
Uncoordinated NO3
Coordinated H2O + NO3
Ligand
200–250
330
8.9(9.9)
58.2(60.3)
complex in solution exhibits a broad band at 14790 cm–1,
which can be assigned to a B1g
and multiplet at 0.65–1.5 ppm) corresponding to the
protons of the aromatic NH, aromatic protons of isatin
moiety, NH2 protons of isophoronediamine, and ali-
phatic protons of the amine, respectively. These protons
are shifted downfield due to coordination to the metal
ions [18]. The absence of the peak due to the NH group
2
2A1g transition.
This transition, along with the magnetic moment value
(µ = 1.88 BM), supports a square planar geometry [19,
20]. The electronic absorption spectrum of Co(II) com-
plex is characterized by the highest energy 4A2
4T2
1
in the H NMR spectra of the Zn(II), Cd(II), Hg(II),
(p) transition at 15170 cm–1, which is typical for tetra-
hedral Co(II) complexes; the magnetic moment (µ =
4.57 BM) also suggests tetrahedral geometry [21]. The
electronic absorption spectrum of Ni(II) complex
exhibits two bands at 10 640 cm–1 and 17540 cm–1 which
UO2(VI), and Th(IV) complexes support the deprotona-
tion of this group upon complexation with a metal ion.
Due to limited solubility in DMSO, the 13C NMR spec-
tra of the complexes could not be measured.
3
can be assigned to the allowed transitions T2g(F)
3T1g(P) and 3T1g(F)
3A2g(F), respectively. The mag-
UV-Visible and Magnetic Susceptibility Measurements
netic moment (µ = 3.70 BM) along with spectral data
The electronic spectral data of complexes in DMF are
included in Table 1. The electronic spectrum of Cu (II) suggests tetrahedral geometry [22]. The electronic
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 53 No. 6 2008

910
RAMA KRISHNA REDDY, MAHENDRA
Table 4. Results of antibacterial activity of the Schiff base Table 5. Anthelmentic activity of the Schiff base and its
and its complexes
complexes
Time taken for paralysis
and death of worms
Zone of inhibition (in mm)
Compound
1 mg/0.02 mL
Ligand/Complex
Pseudomo-
E. coli nas aerugi-
nosa
Bacillus S. au-
subtilis reus
Paralysis
(min)
Death
(min)
Blank (normal saline)
Standard(piperazinecitrate)
HIsIPDA (L)
No effect for 10 h
DMF(control)*
HIsIPDA (L)
–
–
–
4
4
4
5
4
4
9
–
2
7
9
8
4
7
3
10
12
5
16
20
7
14
18
28
22
13
13
16
6
[CuL · 2H2O]Cl
[CoLCl · H2O]
[NiLCl · H2O]
[ZnLCl · H2O]
[CdLCl · H2O]
[HgLCl · H2O]
4
11
10
8
[CuL · 2H2O]Cl
[CoLCl · H2O]
9
10
14
6
[NiLCl · H2O]
12
4
[ZnLC · H2O]
10
12
[CdLCl · H2O]
6
8
[HgLCl · H2O]
4
6
spectra of the U(VI) and Th(IV) complexes in DMF
solution gave no bands in the 330–750 nm region. The
absorption bands obtained below 330 nm correspond to
Antibacterial Activity
The ligand and the metal complexes have been
screened for their antibacterial activity and the results
obtained are presented in Table 4. It is observed that all
the metal complexes are more potent bactericides than
the ligand. This enhancement in the activity can be
explained on the basis of chelation theory [23, 24].
the ligand π
π* transitions and are not much help
in determining the geometry around the central ura-
nium and thorium ions. The Zn(II), Cd(II), and Hg(II)
complexes do not exhibit d–d electronic transitions due
to the completely filled d-orbital. The magnetic suscep-
tibility measurements reveal that all these complexes
are diamagnetic as generally expected.
Anthelmentic Activity (in vitro)
The anthelmentic activity was tested on earthworms
(Pheretima Posthuma).The Schiff base exhibits high
activity and increases upon complexation with Cu(II)
and Co(II) ions (Table 5).
Thermogravimetric Studies
TGA studies of the complexes were carried out in
nitrogen atmosphere at a rate of 10° per minute up to
700°C. In the thermal decomposition studies of the com-
plexes of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II),
UO2(VI), and Th(IV), a general pattern is observed where
the water of hydration is lost followed by the loss of unco-
ordinated chloride/nitrate, coordinated chloride/nitrate,
ligand molecules, and the decomposition of the complex
CONCLUSIONS
The Schiff base ligand acts as bidentate monobasic
with azomethine nitrogen and negatively charged oxy-
gen atom as donors. The probable structures are shown
below in Figs. 1–4. The antibacterial activity of the
isatin Schiff base is greatly enhanced upon complex-
to finally give the respective oxides at higher temperatures. ation with metal ions, particularly the Co(II) complex.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 53 No. 6 2008

SYNTHESIS, CHARACTERIZATION
911
CH3
CH3
R
N
OH2
OH2
N CH2
O
Cl
Cu
N
O
CH3
NH2
N
H
Fig. 2. Tentative structure of the Cu(II) complex.
Fig. 1. Structure of the Schiff base ligand.
R
R
O
U
O
N
N
O
Cl
N
M
N
O
N
R
N
O
OH2
Fig. 3. Tentative structure of the Co(II), Ni(II), Zn(II),
Cd(II) and Hg(II) complexes.
Fig. 4. Tentative structure of the UO+22 (II) complex.
O
N
O O
Th
R
N
CH3
CH3
N
NO3 · H2O
R =
CH2
N
O
2N
OH
OH2
R
CH3
NH2
Fig. 5. Tentative structure of the Th(IV) complex.
Fig. 6. Structure of the side chain in the complexes.
The anthelmentic activity of the Schiff base was
enhanced upon complexation with metal ions.
5. S. P. Sing, S. K. Shukla, and L. P. Awasthi, Curr. Sci. 52,
766 (1983).
6. A. Danda, V. Kaur, P. Singh, and J. Indian, Pharm. Sci.
55, 129 (1993).
ACKNOWLEDGMENTS
7. J. C. Logan, M. P. Fox, J. H. Morgan, et al., J. Gen. Virol.
28, 271 (1975).
The authors thank the Sophisticated Instruments
Facility, Indian Institute of Science, Bangalore for pro-
viding the NMR facility, the Raman Research Institute,
Bangalore for CHN analysis, and the UGC for the DRS
and FIP (RKR) programs. Thanks to Dr. D. N. Satya-
narayana, Professor, Department of Inorganic and
Physical Chemistry, Indian Institute of Science, Banga-
lore for valuable suggestions.
8. A. Omar, M. E. Mohsen, H. Nabil, and M. Hassan, Arch.
Pharm. 317 (8), 668 (1984).
9. D. Singh and R. V. J. Singh, Inorg. Biochem. 15, 227
(1993).
10. K. Rama Krishna Reddy, K. Madhusudan Reddy, and
K. N. Mahendra, Ind. J. of Chem., A 45, 377 (2006).
11. K. Rama Krishna Reddy and K. N. Mahendra, Molbank
M516 (2006).
12. K. Rama Krishna Reddy and K. N. Mahendra, Molbank
M517 (2006).
REFERENCES
13. H. W. Seeky and V. Dermak, Microbes in Action (W. H.
Freeman, San Francisco, 1972).
1. D. Singh and R. V. J. Singh, Inorg. Biochem. 15, 227
(1993).
14. K. N. Gaind, R. N. Das, B. N. Chopra, and R. N. Kaul,
2. R. Protivinsky, Antibiot. Chemother. 17, 101 (1971).
Indian J. Farm. 27, 198 (1963).
3. K. C. Joshi, V. N. Pathak, and S. K. Jain, Pharmazie 35
15. A. I. Vogel, A Textbook of Quantitative Inorganic Analy-
sis (ELBS and Longman’s Green, London, 1962).
(11), 677 (1980).
4. R. G. Shepherd, in Medicinal Chemistry, Ed. by A. Burger 16. M. A. Hassan and K. Shehata, Synt. React. Inorg. Met-
(Wiley, New York, 1970). Org.Chem. 23 (5), 815 (1993).
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 53 No. 6 2008

912
RAMA KRISHNA REDDY, MAHENDRA
17. K. Nakamoto, Infrared Spectra of Inorganic and Coor- 21. S. Konstantinovic, C. Radovanovic, Z. Capic, andV. J. Basic,
dination Compounds 2nd edition (Wiley, 1963).
Serb. Chem. Soc. 68 (8–9), 641 (2003).
22. P. P. Hankare, L. V. Gavali, V. M. Bhuse, et al., Ind. J.
18. H. Chohan, A. Pervez Rauf, M. Khan, and T. Supuran,
Chem., A 43, 2578 (2004).
J. Enzyme Inhibition Med. Chem. 19 (5), 417 (2004).
23. K. N. Thimmaiah, W. D. Lloyd, and G. T. Chandrappa,
19. R. S. Joseyphus, C. J. Dhanaraj, and M. S. Nair, Trans.
Inorg. Chim. Acta 106, 81 (1985).
Met. Chem. 31, 699 (2006).
24. W. Levingson, P. Mikeleus, J. Jackson, and W. Kaska,
Inorganic and Nutritional Aspects of Cancer, Ed. by
G.N. Schranzer Plenum, New York, 1978).
20. E. A. Canpolat Yazici and M. Kaya, Trans. Met. Chem.
31, 653 (2006).
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 53 No. 6 2008