Synthesis, characterization and in vitro anticancer activity of 18-membered octaazamacrocyclic complexes of Co(II), Ni(II), Cd(II) and Sn(II)

Article abstract of DOI:10.1016/j.molstruc.2014.06.073

An effective series of 18 membered octaazamacrocyclic complexes of the type [MLX₂], where X = Cl or NO₃ have been synthesized by template condensation reaction of oxalyl dihydrazide with dibenzoylmethane and metal salt in 2:2:1 molar

Full text of DOI:10.1016/j.molstruc.2014.06.073

Journal of Molecular Structure 1075 (2014) 17–25
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis, characterization and in vitro anticancer activity
of 18-membered octaazamacrocyclic complexes of Co(II),
Ni(II), Cd(II) and Sn(II)
Abdul Kareem a, Hina Zafar a, Asif Sherwani b, Owais Mohammad b, Tahir Ali Khan a,
⇑
a Division of Inorganic Chemistry, Department of Chemistry, Aligarh Muslim University, Aligarh 202002, India
b Interdisciplinary Biotechnology Unit, Aligarh Muslim University, India
g r a p h i c a l a b s t r a c t
h i g h l i g h t s
ꢀ
18-Membered Schiff base polyaza
macrocyclic complexes of the type
[MLX2] have been synthesized.
Synthesis by template condensation
reaction of oxalyl dihydrazide with
dibenzoylmethane and metal salt.
The complexes have been
characterized by different techniques.
Anticancer activity by using MTT
assay, against different human cancer
cell lines.
ꢀ
ꢀ
ꢀ
ꢀ
These complexes showed good
in vitro anticancer activity.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 13 April 2014
Received in revised form 24 June 2014
Accepted 24 June 2014
Available online 30 June 2014
An effective series of 18 membered octaazamacrocyclic complexes of the type [MLX2], where X = Cl or
NO3 have been synthesized by template condensation reaction of oxalyl dihydrazide with dibenzoylme-
thane and metal salt in 2:2:1 molar ratio. The formation of macrocyclic framework, stereochemistry and
their overall geometry have been characterized by various physico-chemical studies viz., elemental anal-
ysis, electron spray ionization–mass spectrometry (ESI–MS), I.R, UV–Vis, 1H NMR, 13C NMR spectroscopy,
X-ray diffraction (XRD) and TGA/DTA studies. These studies suggest formation of octahedral macrocyclic
complexes of Co(II), Ni(II), Cd(II) and Sn(II). The molar conductance values suggest nonelectrolytic nature
for all the complexes. Thermogravimatric analysis shows that all the complexes are stable up to 600 °C.
All these complexes have been tested against different human cancer cell lines i.e. human hepatocellular
carcinoma (Hep3B), human cervical carcinoma (HeLa), human breast adenocarcinoma (MCF7) and nor-
mal cells (PBMC). The newly synthesized 18-membered octaazamacrocyclic complexes during in vitro
anticancer evaluation, displayed moderate to good cytotoxicity on liver (Hep3B), cervical (HeLa) and
breast (MCF7) cancer cell lines, respectively. The most effective anticancer cadmium complex (C34H28N10-
CdO10) was found to be active with IC50 values, 2.44 1.500, 3.55 1.600 and 4.82 1.400 in micro-molar
on liver, cervical and breast cancer cell lines, respectively.
Keywords:
Octaazamacrocyclic complexes
Dibenzoylmethane
Oxalyl dihydrazide
MTT assay
Anticancer activity
Ó 2014 Elsevier B.V. All rights reserved.
Introduction
The family of complexes with aza macrocyclic ligands has
remained a focus of scientific attention for many decades [1]. schiff
⇑
Corresponding author. Tel.: +91 9027798610.
E-mail address: Takhan213@gmail.com (T.A. Khan).
http://dx.doi.org/10.1016/j.molstruc.2014.06.073
0022-2860/Ó 2014 Elsevier B.V. All rights reserved.

18
A. Kareem et al. / Journal of Molecular Structure 1075 (2014) 17–25
base metal complexes have been widely studied because they
have industrial, antifungal, antibacterial, anticancer and herbicidal
applications [2]. A number of macrocyclic complexes with tetra aza
macrocyclic ligands, such as cyclen, cyclam and bicyclam have
been reported to exhibit antitumor activity [3]. The design and
synthesis of the macrocyclic complexes of oxalyl dihydrazide is a
field of interest because of their applications as anticancer, antivi-
ral, antibacterial and antifungal agents [4–6]. Extensive research
work has been carried out on platinum-based chemotherapeutic
compounds [7,8]. Despite of their remarkable success with high
efficiency against human testicular, ovarian, bladder, head and
neck carcinomas, several side effect such as limited water solubil-
ity and the dose-dependent toxicities, mainly nephrotoxicity, cyto-
toxicity and emetogenesis are the major drawbacks associated
with these drugs [8–10]. Moreover, the importance of aza-macro-
cyclic transition metal complexes is due to the role they play as
models for protein metal binding sites in biological systems, as
synthetic ionophores [11], electrocatalyst in fuel cells [12], M.R.I
contrast agents [13,14], luminescent sensors [15], anticancer drugs
[16] and radioimmunotherapeutic agents [17]. These extensive
applications have been worth investigating for the design of new
macrocyclic ligands and their metal complexes for biological and
industrial applications [18]. Coordination compounds containing
macrocyclic ligands have been studies in recent decades owing to
their wide applications in biological and sensor field. The first
non-platinum complex tested in clinical trials was cis-[(CH3CH2O)2
(bzac)2Ti(VI)] used against a wide variety of ascites and solid
tumors [19,20]. One of the potential approaches in anticancer
chemistry is focused on the design of new macrocyclic metal
complexes with different substituent and labile sites which may
increase their cytotoxicity, especially to cancer cells. In this
context, a wide range of macrocyclic metal complexes have been
synthesized and their in vitro anticancer activity has been tested
against different cancerous cell lines along with normal cells. The
Pd(II) complexes have been derived from a salen ligand and tested
against a human hepatoma cancer cell line [21]. Tin based com-
plexes exhibit a broad spectrum of biological activity which
includes organotin derivatives having bactericidal, fungicidal, anti-
tumor and acricidal activity [22]. Recently, a number of metal com-
plexes have been synthesized and some of these complexes were
also tested for their cytotoxicities on various cancer cell lines and
their results showed moderate to good anticancer activity [23].
In this present work we have reported the synthesis and character-
ization of octaazamacrocyclic complexes of Co(II), Ni(II), Cd(II) and
Sn(II) derived from oxalyl dihydrazide and dibenzoylmethane
which were also studied for their in vitro anticancer activity. The
evaluation of in vitro anticancer activity of these complexes was
carried out against different human cancer cell lines (Hep3B, HeLa
and MCF7) by using MTT assay [24].
out by template condensation method. The condensation of oxalyl
dihydrazide and dibenzoylmethane in the presence of the
CoX2ꢁ6H2O, (X = Cl or NO3), in methanol takes place easily. It was
carried out by stirring a hot methanolic solution (50 mL) of oxalyl
dihydrazide (1.181 gm, 10 mmol) with the divalent metal salt of
cobalt (5 mmol) dissolved in minimum quantity of methanol
(ꢂ20 mL). The content of reaction mixture was boiled under reflux
for 0.5 h. after that dibenzoylmethane (2.25 g, 10 mmol) in 20 mL
methanol was added in the refluxing mixture and refluxing was
continued for 8–10 h. Now the mixture was concentrated to half
of its volume and kept in desiccator for ꢂ16 h. The solid product
thus produced was filtered washed several times with methanol
and then with acetone and dried in vacuo.
Synthesis of nickel complexes
In the synthesis of dichloro/dinitrato (7,9,16,18-tetraphenyl-
3,4,12,13-tetraoxa-1,2,5,6,10,11,14,15-octaazacyclooctadecane-6,
9,15,18-tetraene) nickel (II) complexes, [NiLX2], a similar proce-
dure was adopted as above except that in place of the cobalt salts
now nickel salts NiX2ꢁ6H2O (X = Cl or NO3) were used.
Synthesis of cadmium complex
A similar procedure was adopted for the synthesis of cadmium
complex, [CdL(NO3)2], as above except that in place of the nickel
salts now cadmium salt Cd(NO3)2ꢁ4H2O was used.
Synthesis of tin complex
In the synthesis of tin macrocyclic complex, [SnLCl2], here also
the similar procedure was adopted as above except that in place
of the cadmium salt now tin salt SnCl2ꢁ6H2O was used.
MTT assay
The MTT assay is a colorimetric assay for measuring the cellular
growth that reduces the tetrazolium yellow dye, MTT, to its insol-
uble formazan (purple color) by mitochondrial dehydrogenases of
living cells. MTT is used to determine the cytoxicity of potential
drugs and other toxic compounds [24,25]. The insoluble purple for-
mazan product is dissolved into a colored solution by the addition
of a suitable solvent. At certain wavelength, the absorbance of this
colored solution can be measured. The potency of the drug in
causing cell death can be concluded through the production of
dose–response curves when the amount of purple formazan pro-
duced by untreated control cells. The Hep3B cell line was main-
tained in RPMI 1640 culture medium supplemented with 10%
heat-inactivated fetal calf serum. The cells were plated at a density
of 5 ꢃ 103 cells per well in a 96-well plate and cultured for 24 h at
37 °C. Stock solutions of the synthesized steroids were prepared in
a 1:1 mixture of DMSO and THF. The cells were subsequently
exposed to drugs. The plates were incubated for 48 h, and cell pro-
Experimental
Materials and methods
liferation was measured by adding 20 lL of MTT dye (5 mg/mL in
The metal salts CoX2ꢁ6H2O, NiX2ꢁ6H2O, Cd(NO3)2ꢁ4H2O and
SnCl2ꢁ2H2O (X = Cl or NO3), dibenzoylmethane (all E. Merck chemi-
cals) and oxalyl dihydrazide (Acros organics) were used as received.
All the reactions were carried out under anhydrous condition.
phosphate-buffered saline) per well. The plates were incubated
for a further 4 h at 37 °C in a humidified chamber containing 5%
CO2. Formazan crystals formed due to reduction of dye by viable
cells in each well were dissolved in 150 lL dimethyl sulfoxide
and absorbance was read at 570 nm. The absorption values were
expressed as the percent cell viability, according to the control
group as 100%.
Synthesis of the complexes
Synthesis of cobalt complexes
For the other cell lines i.e. HeLa and MCF7, all the procedure are
the same as described above for Hep3B cell lines. Doxorubicin
(Doxo) and 5-Fluorouracil (5-Fu) were used as cytotoxic drugs of
reference.
The synthesis of dichloro/dinitrato (7,9,16,18-tetraphenyl-
3,4,12,13-tetraoxa-1,2,5,6,10,11,14,15-octaazacyclooctadecane-6,
9,15,18-tetraene) cobalt (II) complexes, [CoLX2], has been carried

A. Kareem et al. / Journal of Molecular Structure 1075 (2014) 17–25
19
Scheme 1.
compounds in DMSO were recorded on a Pye-Unicam 8800 spectro-
photometer at room temperature. The electrical conductivities
were obtained with a systronics type 302 conductivity bridge
equilibrated at 25 0.01 °C using 10ꢄ3 M DMSO solution at room
temperature. The TGA and DTA were performed on a Schimadzu
Thermal Analyzer under nitrogen atmosphere using alumina
powder as reference. The XRD pattern and different parameters
were collected with a Rigaku, Mini Flex II powder diffractometer
using X-ray radiation. Peripheral Blood Mononuclear Cell (PBMC)
isolation was done by fresh blood (10–15 mL) which was kindly
Materials and physical measurements
The elemental analyses for carbon, hydrogen and nitrogen were
obtained from the Central Drug Research Institute (Lucknow, India).
The 1H NMR was recorded on a JEOL GSX 300 MHz FX-1000 spec-
trometer using DMSO-d6 as a solvent and tetramethylsilane (Me4Si)
as an internal standard. The IR spectra (4000–400 cmꢄ1) were
recorded as KBr discs on the Perkin Elmer – 2400 spectrometer.
Metal and chloride ions were determined volumetrically [26] and
gravimetrically [27], respectively. The electronic spectra of the
Table 1
Elemental analyses, m/z values, colors, yields, molar conductance and melting points of the metal complexes.
Compounds
m/z (Calc.) Yield (%) Anal. found (calc.) %
Molar conductivity
Color (M.p. °C)
(ohmꢄ1 cm2 molꢄ1
)
M
Cl
C
H
N
[CoLCl2] C34H28N8O4 CoCl2
[CoL(NO3)2]
742.40
(742.49)
65
67
66
74
69
70
7.80
(7.94)
9.60
55.50
3.74
15.10
18
Light pink (240 °C)
Light salmon (235 °C)
Powder blue (252 °C)
Sky blue (250 °C)
(9.55) (55.99) (3.80) (15.09)
795.31
(795.59)
7.50
(7.41)
–
51.40
3.60
17.50
19
20
21
22
21
C
34H28N10CoO10
(51.33) (3.55) (17.61)
[NiLCl2] C34H28N8O4 NiCl2
741.95
(742.25)
7.5
(7.90)
9.41
55.20 3.50 14.98
(9.56) (55.01) (3.80) (15.09)
[NiL(NO3)2] C34H28N10NiO10 795.10
(795.35)
7.6
(7.38)
–
51.00
3.41
17.63
(51.35) (3.55) (17.61)
[CdL(NO3)2]
849.10
(849.07)
13.10
(13.24)
–
47.90 3.40 16.30
(48.10) (3.33) (16.40)
51.10 3.50 13.80
Creamy white
(254 °C)
C
34H28N10CdO10
[SnLCl2] C34H28N8O4 SnCl2
802.30
14.51
8.75
Light yellow (260 °C)
(802.25)
(14.79) (8.84) (50.90) (3.52) (13.96)

20
A. Kareem et al. / Journal of Molecular Structure 1075 (2014) 17–25
Table 2
IR spectral data of the complexes (cmꢄ1).
S. no.
Compounds
m
(NAH)
m
(C@N)
m
(CAH)
d(CAN)
d(CAH)
m
C@O(free) [COANH] moiety
m(MAN)
1
2
3
4
5
6
C
C
C
C
34H28N8O4 CoCl2
34H28N10CoO10
34H28N8O4 NiCl2
34H28N10NiO10
3260 (s)
3182 (s)
3281 (s)
3285 (s)
3284 (s)
3286 (s)
1607
1642
1615
1511
1612
1591
3260
3182
3281
3285
3284
3285
1200
1381
1269
1385
1388
1353
1503
1511
1527
1520
1535
1527
1667
1666
1670
1674
1686
1682
418
460
420
424
421
425
C34H28N10CdO10
34H28N8O4 SnCl2
C
provided by Blood bank of Jawaharlal Nehru Medical College,
A.M.U, Aligarh (India). The blood sample was diluted with the same
volume of phosphate buffered saline (PBS). The diluted blood sam-
ple was carefully layered on Ficoll-Histopaque (Sigma Aldrich,
USA). The mixture was centrifuged under at 900g for 10 min at
20–22 °C. The undisturbed lymphocyte layer was carefully trans-
ferred out. The lymphocyte was washed and pelleted down with
three volumes of PBS for twice and resuspended RPMI-1640 media
Fig. 1. 1H NMR spectra of macrocyclic complex, [SnLCl2].
Fig. 2. 13C NMR spectra of macrocyclic complex, [SnLCl2].

A. Kareem et al. / Journal of Molecular Structure 1075 (2014) 17–25
21
1200
1000
800
600
400
200
0
Infrared spectra
In all the complexes the presence of a single band in the region
3185–3285 cmꢄ1 may be assigned to
(NAH) stretching [30–33]. It
was observed that a pair of bands corresponding to (NH2) at 3300
m
m
and 3310 cmꢄ1 which were present in the i.r. spectrum of oxalyl
dihydrazide were absent in the infrared spectra of all the com-
plexes. The disappearance of these bands and appearance of
absorption bands near 1605–1642 cmꢄ1 which are assignable to
imine
m(C@N) stretching vibration is consistent [34] with the mac-
rocyclic structure given in Scheme 1. The value of
m(C@N) is lower
than that usually found for azomethine linkage which may be
explained on the basis of drift of lone pair density of azomethine
nitrogen towards the metal atom [35,36] indicating the involve-
10
20
30
40
2θ0
50
60
70
80
ment of the
p electrons throughout the macrocyclic framework.
This fact confirm that coordination takes place through nitrogen
Fig. 3. X-ray diffraction (XRD) pattern of macrocyclic complex, [SnLCl2].
of C@N groups. The bands present in the region ꢂ3000 to
3183 cmꢄ1 may be assigned to
m(CAH) stretching [30]. The strong
band present in the region 1660–1685 cmꢄ1 may be assigned to
the C@O group of the COANH moiety [35] in these complexes.
The bands present in the range of 1100–1270 cmꢄ1 an all com-
(Sigma Aldrich, USA) with 10% antibiotic and antimycotic solution
(Sigma Aldrich, USA) and v/v fetal calf serum (FCS) (Sigma Aldrich,
USA). Cell counting was performed to determine the PBMC cell
number with equal volume of trypan blue [28]. The Hep3B (human
hepatocellular carcinoma), MCF7 (human breast adenocarcinoma)
and Hela (human cervical carcinoma) cell lines are procured from
Cell Repository–National Centre for Cell Science, Pune (India).
plexes are assigned to m(CAN) stretching [37]. The far IR spectra
show bands in the region ꢂ410 to 460 cmꢄ1 corresponding to
m
(MAN) vibrations [38,39]. The presence of bands in all the com-
plexes in the region 418–460 cmꢄ1 originate from
m(MAN) vibra-
tional modes and gives idea about coordination of azomethine
nitrogen [40]. However, no bands characteristics free amines were
observed which strongly supports the proposed structure of all
these complexes (Table 2).
Results and discussion
1H and 13C NMR spectroscopic analyses
A new series of octaazamacrocyclic Schiff base complexes
[MLX2] (M = Co(II), Ni(II), Cd(II) and Sn(II); X = Cl or NO3) have been
prepared by the template reaction of respective metal ions, with
oxalyl dihydrazide and dibenzoylmethane in a 1:2:2 molar ratio
as shown in Scheme 1. All the complexes were stable in atmosphere
and soluble in DMF (dimethylformamide) and DMSO (dimethyl
sulfoxide). Their color and melting points are given in Table 1. Their
thermal stabilities (TGA/DTA) were also studied which are
discussed in Section ‘Thermal analyses’. The molar conductivities
of the complexes were recorded in DMSO at room temperature.
As reported by Sears et al. the molar conductance values for 1:1
The 1H NMR as well as 13C NMR spectra of tin complex [SnLCl2]
fully suggest the structure of complexes as given in Scheme 1. The
1H NMR spectrum (Fig. 1) in DMSO-d6 shows broad signal at
7.231–7.472 ppm range due to amide (ACONH) protons
[37,41,42]. The multiplet in the region 6.692–6.984 ppm may be
assigned to aromatic protons [43,44].
A singlet observed at
3.5745 ppm is assigned to methylene protons of [N@C(Ph)ACH2
A(Ph)C@N] moiety. The 13C NMR spectrum of tin complex was also
recorded in DMSO-d6. The signals observed in the region 124.38–
136.60 ppm have been assigned to aromatic carbon attached to
nitrogen atoms. Carbon atoms which have a distance from nitrogen
atoms show upfield shift. A signal observed at 173.264 ppm may
be assigned to carbonyl (˜C@O) carbon. Similarly a band appeared
in the region 125.356–126.027 ppm due to carbon of two methy-
lene group in the complex as shown in Fig. 2.
electrolyte in this solvent ranges from ꢂ23 to 42 ohmꢄ1 cm2 molꢄ1
.
However, Greenwood et al. have suggested 50–70 ohmꢄ1 cm2
molꢄ1 as the range for 1:1 electrolyte in this solvent [29]. For newly
synthesized complexes the recorded molar conductivity values
(18–22 ohmꢄ1 cm2 molꢄ1) are quite low which indicate that Clꢄ
or NOꢄ3 groups are not ionized remaining intact in the coordination
sphere being attached with central metal atom. The metal to ligand
stoichiometry of the complexes was ascertained on the basis of ele-
mental analyses and position of molecular ion peaks in the mass
spectra (Table 1). The analytical data for elemental analyses suggest
that the proposed macrocyclic complexes have 1:1 metal to ligand
stoichiometry.
UV–Vis studies
The UV–Vis absorption spectra of Co(II) and Ni(II) complexes
were recorded in the 8300–30,000 cmꢄ1 range in dimethyl sulfox-
ide solution (10ꢄ3 M). The UV–Vis spectra of cobalt complexes
shows absorption in the region ca. 8300–9200 cmꢄ1
(m
1), 12,600–
15,800 cmꢄ1 2) and 18,800–20,650 cmꢄ1
(m (m3), respectively. These
values resemble to the reported octahedral complexes [45,46]. The
ESI-mass spectra
various bands are assignable to: 4T2g(F) 4T1g, (
m
1), 4A2g(F) 4T1g
,
4
(m
2) and T1g(P) 4T1g, (
m3) transitions, respectively. These transi-
Mass spectra of all the synthesized macrocyclic complexes of
Co(II), Ni(II), Cd(II) and Sn(II) showed m/z peaks at 742.40,
795.31, 741.95, 795.10, 849.10 and 802.30 that corresponded
tions suggest that the symmetry of these complexes is not ideal
octahedral i.e. D4h. The electronic spectra of Ni(II) complexes exhi-
bit a well discernable band on the low energy side and the other
to
C34H28N8O4CoCl2, C34H28N10CoO10
,
C34H28N8O4NiCl2, C34H28
bands are observed in the region ca. 16,600–17,300 cmꢄ1
(m2)
N10NiO10, C34H28N10CdO10 and C34H28N8O4SnCl2 moieties, respec-
tively. The proposed molecular formulae of synthesized complexes
was confirmed by comparing their molecular formula weights with
respective m/z values (Table 1) that are in good agreement for
aforementioned complexes.
and 26,900–28,000 cmꢄ1
(
m
m
3), which are assigned to 3TIg(F) 3A2g
3
(
(
m
m
2), and T1g(P) 3A2g, (
3), respectively. The low energy band
1), splits into two bands in the range ꢂ9500 to 10,000 and
11,500–12,500 cmꢄ1, which can be assigned to 3Eg 3B1g and
3B2g 3B1g, assuming the effective symmetry to be D4h. The

22
A. Kareem et al. / Journal of Molecular Structure 1075 (2014) 17–25
Table 3
representative [SnLCl2] complex was scanned in the range 5–80°
The XRD parameters of the value of Sn(II) complex.
at wavelength 1.540 Å. The diffractogram and associated data
depict the 2h value for each height, relative strength and inter-
planar spacing (d-values). The diffractogram of [SnLCl2] complex
had 12 reflections with maxima at 2h = 10.356° and its intensity
is 1057 a.u. corresponding to d value 8.53495 Å. The above index-
ing method also yields Miller indices (hkl), unit cell parameters.
The unit cell of [SnLCl2] complex yielded values of lattice constants,
a = 6.987 Å, b = 6.987 Å and c = 8.876 Å. In conjunction with these
Identification of the complex
[SnLCl2]
Empirical formula
Formula weight
Wave length
Crystal system (powder)
Lattice parameter
Lattice parameter
2h Min–max
C34H28N8O4 SnCl2
802.30 (g molꢄ1
1.540598 Å
)
Hexagonal
a = 6.987 Å, b = 6.987 Å and c = 8.876 Å
Alpha = 90°, Beta = 90° and Gamma = 120°
5.00–80.00
cell parameters, the conditions such as a = b – c and
a = b = 90,
Lattice type
P
c
= 120 required for samples to be hexagonal were tested and base
to be acceptable (Table 3). Hence, it can be reasoned that [SnLCl2]
complex has a hexagonal crystal system. The average crystallite
size (D) of [SnLCl2] complex was calculated by following the
Debye–Scherrer formula:
spectral results are consistent with distorted octahedral nature of
these complexes [46,47].
D ¼ 0:9k=b ꢁ cos h
X-ray diffraction analysis
where constant 0.9 is the shape factor, k is the X-ray wave-
The [SnLCl2] complex was also characterized by X-ray diffrac-
tion technique. The X-ray powder diffraction (XRD) was used to
determine the type of structure ordering of 18-membered
octaazamacrocyclic complex (Fig. 3). The X-ray diffraction of the
length of Cu Ka radiation (1.54 Å), h is the Bragg diffraction angle
and b is the full-width at half-maximum (FWHM) of the (001)
plane diffraction peak. The calculated average particle size was
found to be ꢂ27.6 nm.
(a) [CoLCl2]
(b) [NiLCl2]
(c) [CdL(NO3)2
(d) [SnLCl2]
Fig. 4. (A–D) TGA/DTA curve of the synthesized macrocyclic complexes.

A. Kareem et al. / Journal of Molecular Structure 1075 (2014) 17–25
23
Thermal analyses
decomposition (Tmax) is between ca. 275 °C and 300 °C in these
complexes.
Thermal stabilities of all the metal complexes were studied by
thermogravimetric analyses (TGA and DTA) in N2 atmosphere at a
heating rate of 20 °C minꢄ1 in the temperature range 20–700 °C.
The thermal analyses show that these compounds undergo three
steps of weight loss (Fig. 4). There are two endothermic peaks
in the DTA curve of these complexes, the first is the melting point
of the complexes and the second corresponds to decomposition of
the complexes. The TG studies of [CoLCl2], [NiLCl2], [CdL(NO3)2]
and [SnLCl2] complexes showed no weight loss upto 140 °C indi-
cating the absence of coordinated water molecules in all these
macrocyclic complexes. The weight loss below 140 °C can be
attributed to the evaporation of the lattice water molecules. Initial
thermal decomposition temperature (IDT) of the complex is found
to be ca. 140 °C. The second weight loss about 50% occurs
between 140 and 370 °C; the temperature of maximum rate
Cytotoxic potential of inhouse synthesized macrocyclic complexes
The cytotoxic potential of the inhouse synthesized macrocyclic
complexes against Hep3B, HeLa and MCF7 cell lines was assessed
by determining the number of viable cells surviving after incuba-
tion with the macrocyclic complexes for the stipulated time period
using the MTT method as given in Section ‘MTT assay’. The cytotox-
icity assay suggests a variable cytotoxicity of inhouse synthesized
complexes for Hep3B, HeLa as well as MCF7 cell lines which can
be attributed to the intrinsic anticancer property of these macrocy-
clic complexes. Curves of dose-dependent effects of all the com-
plexes on cell viability of different human cancer cell lines
(Hep3B, MCF7 and HeLa) and normal cells (PBMC) are displayed
in Fig. 5(a–f). Experiments revealed that there was substantial
Fig. 5. (a–f) Dose-dependent curve of newly prepared Schiff base macrocyclic metal complexes; (a) C34H28N8O4CoCl2, (b) C34H28N10CoO10, (c) C34H28N8O4NiCl2, (d)
34H28N10NiO10, (e) C34H28N10CdO10 and (f) C34H28N8O4SnCl2, against different human cancer cell lines (Hep3B, HeLa and MCF7) and normal cells (PBMC).
C

24
A. Kareem et al. / Journal of Molecular Structure 1075 (2014) 17–25
Table 4
IC50 values in
lM of the macrocyclic complexes.
S. no.
Complexes
Hep3B
HeLa
MCF7
PBMC
1.
2.
3.
4.
5.
6.
7.
8.
C
C
C
C
34H28N8O4 CoCl2
34H28N10CoO10
34H28N8O4 NiCl2
34H28N10NiO10
3.90 0.700
4.86 0. 639
10.50 1.910
6.39 0.280
2.44 1.500
7.85 2.401
2.15 1.700
3.95 1.802
7.36 2.060
3.95 0.162
7.36 2.988
4.49 2.190
3.55 1.600
3.36 2.801
2.32 1.600
3.92 2.800
5.12 2.540
7.54 0.810
4.46 1.200
3.56 1.150
4.82 1.400
3.44 1.702
1.56 2.700
3.18 1.600
12.40 0.900
14.08 1.500
21.5 2.400
11.34 1.300
10.12 2.300
13.41 2.900
8.87 1.800
9.91 2.900
C34H28N10CdO10
34H28N8O4 SnCl2
C
Doxo
FU
ꢀ
Doxo ¼ Doxorubicin
FU ¼ 5 ꢄ Fluorouracil
As reference drugs ꢄ
.
increase in cytoxicity in the cell lines with increasing exposure to
drug concentration. The absorption values were expressed as the
cell viability in percent, according to the control group as 100%.
Assays were performed in triplicate on three independent
experiments. The concentration required for 50% inhibition of cell
viability (IC50) was calculated using the software ‘‘Prism 3.0’’. For
each of the tested complexes IC50 was calculated and the results
are summarized in Table 4. The obtained results were revealed that
compounds C34H28N8O4CoCl2, C34H28N10CoO10, C34H28N8O4NiCl2,
antitumor chemotherapy and could probably be lead to more
active complexes in the area of cancer chemotherapy.
Acknowledgements
The authors wish to thank the Chairman, Department of
Chemistry, Aligarh Muslim University for providing research facil-
ities. We also thank Department of Applied Physics, A.M.U, Aligarh,
India for XRD analysis and Cell Repository–National Centre for Cell
Science, Pune (India) for providing cancer cell lines. The coauthor
Abdul Kareem also thanks UGC, New Delhi for financial assistance.
C34H28N10NiO10, C34H28N10CdO10 and C34H28N8O4SnCl2 showed
remarkable inhibitory activities against different human cancer
cell lines. It is apparent from the IC50 values that all the tested com-
plexes show moderate to good cytoxicity against different human
cancer cell lines. The cobalt complex, [CoLCl2], led to remarkable
increase in potency against human hepatocellular carcinoma
References
[1] N.E. Borisova, M.D. Rshetova, Y.A. Ustynyuk, Chem. Rev. 46 (2007).
[2] H. Sahebalzamania, S. Ghammamya, K. Mehrania, F. Salimib, Der Chem. Sin. 1
(1) (2010) 67–72.
[3] A.S. Pedrares, N. Camina, J. Romero, M.L. Duran, J.G. Vazquez, A. Sousa,
Polyhedron 27 (2008) 3391.
[4] S.G. Teoh, G.Y. Yeap, C.C. Loah, L.W. Foorg, S.B. Teo, H.K. Fun, Polyhedron 16
(1997) 2213.
[5] M.P. Suh, W. Shin, K. Kim, S. Kim, Inorg. Chem. 23 (1984) 618–620.
[6] N.J. Wheate, S. Walker, G.E. Craig, R. Oun, J. Chem. Soc. Dalton Trans. 39 (2010)
8113–8127.
[7] A.G. Quiroga, F.J. Ramos-Lima, A. Alvarez-Valdés, M. Font-Bardía, A. Bergamo,
G. Sava, C. Navarro-Ranninger, Polyhedron 30 (2011) 1646–1650.
[8] D.G. Mccollum, L. Hall, C. White, R. Ostrander, A.L. Rheingold, J. Whelan, B.
Bosnich, Inorg. Chem. 33 (1994) 924–933.
[9] M. Shakir, S.P. Varkey, O.S.M. Nasman, Polyhedron 14 (1995) 1283–1288.
[10] S.M. Peng, V.L. Goedken, J. Chem. Soc. Chem. Commun. 3 (1973) 62–63.
[11] A.J.M. Xavier, M. Thakur, J.M. Marie, J. Chem. Pharm. Res. 4 (2) (2012) 986–990.
[12] M. Shakir, H.N. Chishti, Y. Azim, P. Chingsubam, M.Y. Siddiqi, Synth. React.
Inorg. Met. Org. Chem. 33 (2003) 1569–1583.
[13] M. Zinic, V. Skaric, J. Organomet. Chem. 53 (1988) 2582.
[14] H. Behret, W. Clauberg, G. Sandstede, J. Electroanal. Chem. 74 (1976) 393.
[15] R. Hovland, C. Gloyard, A.J. Aasen, J. Klaveness, J. Chem. Soc. Perkin Trans. 2
(2001) 929.
[16] S.J.A. Pope, A.M. Kenwright, V.A. Boote, S. Faulkner, J. Chem. Soc. Perkin Trans.
(2003) 3780.
(Hep3B) cells with IC50 values of 3.90 0.700
2.540 M (against MCF7 cell lines) and 7.36 2.060
l
M, 5.12
l
lM (against
HeLa cell lines). The another complex of cobalt, [CoL(NO3)2], is
more effective against human cervical carcinoma (HeLa) cells with
IC50 values of 3.95 0.162
[NiL(NO3)2] are more effective against breast cancer (MCF7) cells
with IC50 values of 4.46 1.200 M and 3.56 2.400 M respec-
lM. The complexes [NiLCl2] and
l
l
tively. Among all these complexes the cadmium complex,
[CdL(NO3)2], exhibits very good cytotoxicity against all cancerous
cells with IC50 values of 2.44 1.500
lM against Hep3B cell lines,
3.55 1.600 against HeLa cell lines and 4.82 1.400 lM
lM
against MCF7 cell lines, respectively. Present study showed that
among the three human cancer cell lines tested, HeLa cell lines
were found to be sensitive to most of the tested compounds while
Hep3B and MCF7 cell lines were found to be sensitive to some
selected compounds. Moreover, cadmium complex is relatively
more sensitive for all the tested cancer cell lines.
[17] A. Beeby, L.M. Bushby, D. Maffeo, J.A.G. Willams, J. Chem. Soc. Perkin Trans.
(2002) 4854.
Conclusion
[18] J.H. Jeong, M.W. Chun, W.K. Chung, Korean J. Med. Chem. 6 (1996) 47.
[19] M.J. Clarke, F. Zhu, D.R. Frasca, Chem. Rev. 99 (1999) 2511.
[20] T. Schilling, B.K. Keppler, M.E. Heim, Invest. New Drugs 13 (1995) 327.
[21] M. Azam, Z. Hussain, I. Warad, S.I. Al-Resayes, M.S. Khan, M. Shakir, A.
Trzesowska-Kruszynski, R. Kruszynski, J. Chem. Soc. Dalton Trans. 41 (2012)
10854–10864.
[22] K. Sharma, S.C. Joshi, R.V. Singh, Met.-Based Drugs 7 (2000) 237–243.
[23] (a) S. Amer, N. El-Wakiel, H. El-Ghamry, J. Mol. Struct. 1049 (2013) 326–335;
(b) M.A. Abdel-Nasser Alaghaz, A.H. Bayoumi, A.Y. Ammara, A.S. Aldhlmani, J.
Mol. Struct. 1035 (2013) 383–399;
In the present study an effective series of dichloro/dinitrato
(7,9,16,18-tetraphenyl-3,4,12,13-tetraoxa-1,2,5,6,10,11,14,15-octa
azacyclooctadecane-6,9,15,18-tetraene) metal (II) complexes of
cobalt, nickel, copper, cadmium and tin were derived from oxalyl
dihydrazide and dibenzoylmethane and studied for their biological
evaluation of cytotoxic activity. The results of cytotoxic study by
MTT assay revealed that all the macrocyclic complexes (1–6)
showed a considerable broad spectrum of anticancer activity
against the three tested human cancer cell lines. In particular the
cadmium, (C34H28N10CdO10), was the most proficient cytotoxic
(c) M. EL-Amane, M. Bouhdada, Int. J. Chem. Technol. Res. 6 (2) (2014) 1430–
1439;
(d) S.A. Khan, A.M. Asiri, K. Al-Amry, M.A. Malik, Sci. World J. 10 (2014) 1155;
(e) A. Magro, L. Crociani, C. Prinzivalli, P.A. Vigato, P.L. Zanonato, S. Tamburini,
Inorg. Chim. Acta 410 (2014) 29–38;
agent with IC50 values below 5.00 lM in all the three tested human
(f) H. Gopinathan, N. Komathi, M.N. Arumugham, Inorg. Chim. Acta. 416 (2014)
93–101.
cancer cell lines i.e. Hep3B, HeLa and MCF7. On the basis of these
observations, it could be the topic of further investigations for
searching potential anticancer metal based complexes. Ultimately,
it is comprehensible that further development of macrocyclic
complexes of different metals can serve as new templates for
[24] Shamsuzzaman, H. Khanam, A. Mashrai, A. Sherwani, M. Owais, N. Siddiqui,
Steroids 78 (2013). 1263–127.
[25] T. Mosmann, J. Immunol. Meth. 65 (1–2) (1983) 55–63.
[26] A.I. Vogel, A Text Book of Quantitative Inorganic Analysis, third ed., Longmans,
1961.

A. Kareem et al. / Journal of Molecular Structure 1075 (2014) 17–25
25
[27] C.N. Reilly, R.W. Schmidt, F.A. Sadek, J. Chem. Ed. 36 (1959) 619.
[28] K. Arif, A.K. Aijaz, D. Varun, G.A. Manzoor, H. Seema, et al., Mol. Med. 13 (5–6)
(2007) 266–276.
[37] A. Chaudhary, R.V. Singh, Indian J. Chem 43 (A) (2004) 2529–2535.
[38] M. Shakir, K.S. Islam, A.K. Mohamed, M. Shagufta, S.S. Hasan, Trans. Met. Chem.
24 (1999) 577–580.
[29] W.J. Geary, Coord. Chem. Rev. 7 (1971) 81.
[30] T.A. Khan, S.S. Hasan, S.P. Varkey, M.A. Rather, N. Jahan, M. Shakir, Trans. Met.
Chem. 22 (1997) 4–8.
[39] F.M.A.M. Aqra, Trans. Met. Chem. 24 (1999) 337–339.
[40] V.B. Rana, D.P. Singh, P. Singh, M.P. Teotia, Trans. Met. Chem. 7 (1982) 174–
177.
[31] T.A. Khan, M.A. Rather, N. Jahan, S.P. Varkey, M. Shakir, Trans. Met. Chem. 23
(1998) 283–285.
[32] A. Bansal, R.V. Singh, Bol. Soc. Chil. Quim. 45 (2000) 479–487.
[33] A.K. Singh, A. Panwar, R. Singh, S. Beniwal, Trans. Met. Chem. 28 (2003) 160.
[34] M. Shakir, S.P. Varkey, D. Kumar, Synth. React. Inorg. Met.-Org. Chem. 24
(1994) 941.
[35] S. Chandra, S.D. Sharma, Trans. Met. Chem. 27 (2002) 732–735.
[36] C. Lodeiro, R. Basitida, E. Bertolo, A. Macias, R. Rodriguez, Trans. Met. Chem. 28
(2003) 388–394.
[41] A. Chaudhary, R. Swaroop, R. Singh, Bol. Soc. Chil. Quim. 47 (2002) 203.
[42] Z.A. Siddiqi, S.M. Shadab, Indian J. Chem. 43 (A) (2004) 2274.
[43] D.P. Singh, R. Kumar, Eur. J. Med. Chem. 44 (2009) 1731–1736.
[44] K. Sharma, N. Fahmi, R.V. Singh, Indian J. Chem. 38A (1999) 1293.
[45] V.B. Rana, D.P. Singh, P. Singh, M.P. Teotia, Trans. Met. Chem. 6 (1981) 36;
V.B. Rana, D.P. Singh, P. Singh, M.P. Teotia, Polyhedron 1 (1982) 377.
[46] D.P. Singh, R. Kumar, V. Malik, Trans. Met. Chem. 32 (2007) 1051–1055.
[47] A.B.P. Lever, Inorganic Electronic Spectroscopy, Elsevier, Amsterdam, 1968.