Synthesis, characterization, and cytotoxic activity on MCF-7 cell line of some novel metal complexes with substituted benzimidazole ligands

Article abstract of DOI:10.1080/15533174.2012.682691

A series of novel metal complexes with the Schiff base ligands 4-((((1H-benzo[d]imidazol-2-yl)methyl)imino)methyl) benzene-1,3-diol, H ₃L¹, and (((1H-benzo[d]imidazol-2-yl)methyl) thio)propanenitrile, HL², have been synthesized and identified by elemental and spectral (UV-vis, IR, 1H NMR, mass) analyses, molar conductivities, as well asmagnetic moment measurements technique. The ligands behave either as neutral tridentate or bidentate ligand. The antitumor activity of the new compounds was tested against breast cancer cell line MCF-7. Ag and Cu complexes 2, 8 and 9 showed a remarkable smaller value of IC50 than that of the Tamoxifen, the standard. This would provide a new potential antitumor drug that deserves more attention. Copyright Taylor & Francis Group, LLC 2013.

Full text of DOI:10.1080/15533174.2012.682691

This article was downloaded by: [Harvard College]
On: 15 April 2013, At: 10:46
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,
37-41 Mortimer Street, London W1T 3JH, UK
Synthesis and Reactivity in Inorganic, Metal-Organic,
and Nano-Metal Chemistry
Publication details, including instructions for authors and subscription information:
http://www.tandfonline.com/loi/lsrt20
Synthesis, Characterization, and Cytotoxic Activity on
MCF-7 Cell Line of Some Novel Metal Complexes With
Substituted Benzimidazole Ligands
Ahmed M. A. El-Seidy a b , Eman El-Zahany a , Atiat S. Barakat c , Nabil S. Youssef a , Shadia
A. Galal d & Sayed A. Drweesh a
a Inorganic Chemistry Department, National Research Center, Cairo, Egypt
b Department of Chemistry, Faculty of Science, The Imam Muhammad bin Saud Islamic
University, Riyadh, Saudi Arabia
c Inorganic Chemistry Department, Faculty of Science, Zagazig University, El Zagazig, Egypt
d Department of Chemistry of Natural and Microbial Products, Division of Pharmaceutical and
Drug Industries Research, National Research Centre, Cairo, Egypt
Accepted author version posted online: 06 Aug 2012.Version of record first published: 03 Dec
2012.
To cite this article: Ahmed M. A. El-Seidy , Eman El-Zahany , Atiat S. Barakat , Nabil S. Youssef , Shadia A. Galal & Sayed A.
Drweesh (2013): Synthesis, Characterization, and Cytotoxic Activity on MCF-7 Cell Line of Some Novel Metal Complexes With
Substituted Benzimidazole Ligands, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 43:1,
46-56
To link to this article: http://dx.doi.org/10.1080/15533174.2012.682691
PLEASE SCROLL DOWN FOR ARTICLE
Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions
This article may be used for research, teaching, and private study purposes. Any substantial or systematic
reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to
anyone is expressly forbidden.
The publisher does not give any warranty express or implied or make any representation that the contents
will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should
be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims,
proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in
connection with or arising out of the use of this material.

Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 43:46–56, 2013
Copyright ꢀ Taylor & Francis Group, LLC
C
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2012.682691
Synthesis, Characterization, and Cytotoxic Activity
on MCF-7 Cell Line of Some Novel Metal Complexes
With Substituted Benzimidazole Ligands
Ahmed M. A. El-Seidy,1,2 Eman El-Zahany,1 Atiat S. Barakat,3 Nabil S. Youssef,1
Shadia A. Galal,4 and Sayed A. Drweesh1
1Inorganic Chemistry Department, National Research Center, Cairo, Egypt
2Department of Chemistry, Faculty of Science, The Imam Muhammad bin Saud Islamic University,
Riyadh, Saudi Arabia
3Inorganic Chemistry Department, Faculty of Science, Zagazig University, El Zagazig, Egypt
4Department of Chemistry of Natural and Microbial Products, Division of Pharmaceutical and Drug
Industries Research, National Research Centre, Cairo, Egypt
idazoles are very important intermediates in organic reactions.[4]
Cancer is thought to reflect a multistep process, resulting from
an accumulation of inherited and/or acquired defects in genes in-
volved in the positive or negative regulation of cell proliferation
and survival.[5] Breast cancer has been defined as an abnormal
division or proliferation of epithelial cell in lactiferous duct or
lobe and can be classified into ductal carcinoma and lobular
carcinoma.[6] The importance of metal compounds in medicine
dates back to the 16th century with reports on the therapeutic
use of metals or metal-containing compounds in the treatment
of cancer. Now the list of therapeutically prescribed metal-
containing compounds includes platinum (anticancer), silver
(antimicrobial), gold (antiarthritic), bismuth (antiulcer), an-
timony (antiprotozoal), vanadium (antidiabetic), and iron (an-
timalarial).[7] Metal ions are electron deficient, whereas most
biological molecules (proteins and DNA) are electron rich; con-
sequently, there is a general tendency for metal ions to bind to
and interact with many important biological molecules. Metal
ions also have a high affinity for many small molecules (e.g.,
O2) that are crucial to life. These considerations alone have fu-
eled much of the past and current interest in developing novel
means to use metals or metal containing agents to modulate bi-
ological systems.[8] Schiff bases of azomethine nitrogen donor
heterocyclic ligands are well known due to their wide range
of applications in pharmaceutical and industrial fields.[9] Tran-
sition metal complexes of Schiff bases have attracted a lot of
interest due to their potent biological activities such as antifun-
gal, antibacterial, anticancer, and herbicidal applications.[9,10]
These studies have shown that complexation of metals to Schiff
base ligands improves the antimicrobial and anticancer activ-
ities of the ligands.[9,11] A group of complex compounds of
2-aminobenzimidazole derivatives with some metals, such as
cobalt, zinc, and copper, showed also antifungal and antibacte-
rial activity.[12] While complexes with ruthenium were cytotoxic
A
series of novel metal complexes with the Schiff
base ligands 4-((((1H-benzo[d]imidazol-2-yl)methyl)imino)methyl)
benzene-1,3-diol, H3L1, and (((1H-benzo[d]imidazol-2-yl)methyl)
thio)propanenitrile, HL2, have been synthesized and identified by
elemental and spectral (UV-vis, IR, 1H NMR, mass) analyses, mo-
lar conductivities, as well as magnetic moment measurements tech-
nique. The ligands behave either as neutral tridentate or bidentate
ligand. The antitumor activity of the new compounds was tested
against breast cancer cell line MCF-7. Ag and Cu complexes 2,
8 and 9 showed a remarkable smaller value of IC50 than that of
the Tamoxifen, the standard. This would provide a new potential
antitumor drug that deserves more attention.
Keywords benzimidazole complexes, cytotoxic activity, human
breast cancer cell line (MCF-7), Schiff base metal com-
plexes
1. INTRODUCTION
The benzimidazole ring is an important pharmacophore in
modern drug discovery.[1] Benzimidazole derivatives exhibit
significant activity against several viruses such as HIV, her-
pes (HSV-1), RNA, influenza, and human cytomegalovirus
(HCMV).[2] Benzimidazole and its derivatives have been used
to act as topoisomerase inhibitors, selective neuropeptide Y Y
1 receptor antagonists, angiotensin II inhibitors, inhibitors of
HCMV replication, 5-HT3 antagonists in isolated guinea pig
ileum, potential antitumor agents, antimicrobial agents, smooth
muscle cell proliferation inhibitors, a treatment for interstitial
cystitis, and in diverse areas of chemistry.[3] In addition, benzim-
Received 15 March 2012; accepted 31 March 2012.
Address correspondence to Ahmed M. A. El-Seidy, Inorganic
Chemistry Department, National Research Centre, P.O. 12622, Dokki,
Giza, Egypt. E-mail: ahmedmaee2@gmail.com.
46

SYNTHESIS, CHARACTERIZATION, AND CYTOTOXIC ACTIVITY
47
in vitro against SKW-8 cells (human T-lymphoma).[13] The main
target of present work is to study the coordination behavior of
the benzimidazole ligands H3L and HL2 that incorporate many
binding sites towards AgI, CuII, FeIII, PtII, RuIII, NiII, and ZnII
ions. The structures of the ligands and their metal complexes
were elucidated by elemental analysis, IR, 1H NMR, 13C NMR,
UV-vis, mass spectra, conductivity, and magnetic susceptibility
measurements at room temperature. The biological activity of
the present organic ligands and their metal complexes are also
reported. The remarkable smaller value of IC50 of Ag and Cu
complexes 2, 8 and 9, than that of the Tamoxifen would provide
a new potential antitumor drug that deserves more attention.
NMR spectra were obtained on Brucker Avance 300-DRX or
Avance 400-DRX spectrometers. Chemical shifts (ppm) are re-
ported relative to TMS. The electronic spectra of the ligands
and their complexes were obtained in Nujol mulls using a Shi-
madzu UV-240 UV-visible recording spectrophotometer. Molar
conductivities of the metal complexes in DMSO (10–3 M) were
measured using a dip cell and a Bibby Scientific Limited con-
ductimeter MC1 at room temperature. The resistance measured
in ohms and the molar conductivities were calculated according
to the equation: ꢀ = V × K × Mw/g × ꢁ, where ꢀ is molar
conductivity (ohm–1 cm2 mol–1), V is the volume of the complex
solution (mL), K is the cell constant 0.92 cm–1, Mw the molec-
ular weight of the complex, g is weight of the complex, and
ꢁ is resistance measured in ohms. Magnetic moments at 298 K
were determined using the Gouy method with Hg[Co(SCN)4] as
calibrant. Mass spectra of the solid ligand were recorded using
JEUL JMS-AX-500 mass spectrometer.
EXPERIMENTAL
Materials and Methods
All the reagents and solvents employed for the preparation of
the ligand and its complexes were of the best grade available and
used without further purification. 2-aminomethylbenzimida-
zoledihydrochloride and 2,4-dihydroxybenzaldehyde were pre-
pared according to the literature procedures.[14,15]
Synthesis of the Schiff Base Ligands
Synthesis of 4-((((1H-benzo[d]imidazol-2-yl)methyl)imino)me-
thyl)benzene-1,3-diol, H3L1
The methanol solution (40 mL) of 2-aminomethyl-
benzimidazoledihydrochloride (4.42 g, 20.0 mmol) was neu-
tralized by NaOH, then filtrated to remove the sodium chloride
precipitation. The filtrate was then added to the solution of
2,4-Dihydroxybenzaldehyde (2.76 g, 20.0 mmol) in methanol
(20 mL). The reaction mixture was stirred for 1 h. The excess
solvent was evaporated under reduced pressure. The formed
yellow precipitate is washed several times by ethanol and dried
under vacuum over anhydrous CaCl2 (Scheme 1).
Physical Measurements
The ligands and their metal complexes were analyzed for C,
H, N, and S contents at the Microanalytical Laboratory, Faculty
of Science, Cairo University, Egypt, but all other analyses were
carried out at Microanalytical Laboratories, National Research
Centre, Dokki, Giza, Egypt. Analytical and physical data of the
ligands H3L1 and HL2 and their metal complexes are reported
in (Table 1). The metal ion contents of the complexes were also
determined by the previously reported methods.[16–19] IR spectra
of the ligands and their metal complexes were measured using
KBr discs with a Jasco FT/IR 300E Fourier transform infrared
spectrophotometer covering the range 400–4000 cm–1 and in
Synthesis of (((1H-benzo[d]imidazol-2-yl)methyl)thio)
propane-nitrile, HL2
A mixture of 2-thiomethylbenzimidazole (1.64 g, 10 mmol)
the 500–100 cm–1 region using polyethylene-sandwiched Nu- and potassium hydroxide (0.56 g, 10 mmol) in MeOH (50 mL)
jol mulls on a Perkin-Elmer FT-IR 1650 spectrophotometer. 1H was stirred for 15 min then acrylonitrile (0.53 g, 10 mmol) was
SCH. 1. Schematic representation for the formation of the Schiff base ligand H3L1 and its numbering.

48

SYNTHESIS, CHARACTERIZATION, AND CYTOTOXIC ACTIVITY
49
SCH. 2. Schematic representation for the formation of the Schiff base ligand HL2 and its numbering.
added. The reaction mixture was stirred for 2 h. The excess μg/mL), that inhibits proliferation rate of the tumor cells by
solvent was evaporated under reduced pressure. The salt was 50% as compared with control untreated cells.
collected and dissolved in cold water then, acidified by drops
of hydrochloric acid. The solid formed was filtered off and
washed with cold water then, crystallized from methanol as
RESULTS AND DISCUSSION
orange powder (Scheme 2).
Elemental Analysis
The elemental and physical data of the ligands and their com-
plexes (Table 1) showed that the stoichiometry of the complexes
obtained is either 1:1 or 1:2 M/L (metal:ligand).
Synthesis of the Metal Complexes
The following general procedure was used in the synthesis
of all metal complexes. The salts—AgNO3 (0.84 g, 5 mmol),
Cu(CH3COO)2 (0.90 g, 5 mmol), FeCl3.6H2O (1.35 g, 5 mmol),
Ni(CH3COO)2.4H2O (1.24 g, 5 mmol), ZnCl2 (0.68 g, 5 mmol)
and RuCl3·3H2O (1.30 g, 5 mmol)—were dissolved in a hot
(70◦C) methanol solution (25 mL) and the solution was added
to a hot (70◦C), stirred ethanolic solution (25 mL) of the corre-
sponding ligand H3L1 (1.33 g, 5 mmol) and HL2 (1.08 g, 5 mmol
for all complexes except Ni [2.17 g, 10 mmol] was used). The
mixture was left under reflux with continuous stirring for 5 h
and the solid complexes precipitated. The resulting solid was
filtered off, washed several times with methanol and then with
diethyl ether, and dried under vacuum at 50◦C for 5 h. In case of
platinum(II) compounds a stock [PtCl4]2– solution was used by
dissolving PtCl2 (2.66 g, 10 mmol) in concentration HCl (un-
til dissolved) under reflux, and the turbidity of the undissolved
material is then removed by filtration. The solution is then neu-
tralized with Na2CO3 and diluting with distilled water up to
250 mL (pH 6.0–6.5) to yield a solution of 0.04 M [PtCl4]2–,
then (125 mL, 5 mmol) was used.[20]
Mass Spectra of the Ligands
The mass spectra of the Schiff bases H3L1 and HL2 revealed
the molecular ion peaks at m/e 267 and 217, which is coincident
with the formulae weights 267.3 and 217.3, respectively, for
these compounds and supports the identity of their structures.
Conductivity Measurements
All metal complexes are stable in air and insoluble in com-
mon organic solvents but soluble in DMSO. The molar conduc-
tivities of the complexes in DMSO (10–3 M) are listed in Table 1.
Only complex 5 behaved as a 1:1 electrolyte. The elevated value
of the conductance of this complex may be due to partial dissoci-
ation of the coordinated chlorine with the solvent molecules.[22]
The rest of the complexes showed
a non-electrolyte
nature.[23]
Infrared Spectra
The infrared spectra of the ligands showed sharp band in
the 3375–3405 cm–1 region due to NHbenzimidazole, which re-
main unchanged after complexation indicating that it was not
Biological Evaluation
The cytotixic activity was measured in vitro for the newly involved in complex formation. The band due to ν(OH) stretch-
synthesized compounds using the sulfoRhodamine-B stain ing vibration of ligand H3L1 was found as strong band around
(SRB) assay using the method of Skehan at The National Cancer 3230 cm–1,[24] while the sharp band located around 1620 cm–1
Institute, Cairo University, Cairo, Egypt.[21]
was assigned to υ(C N) stretch. The presence of hydrogen
Test compounds were dissolved in DMSO and diluted with bonding between NH of benzimidazole and other electronega-
saline to the appropriate volumes. Different concentrations of tive atoms in ligand is indicated by the appearance of several
the compound under test (5.0, 12.5, 25.50, and 50.0 μg/mL) medium intensity bands in the range 2500–2700 cm–1. These
were added to the cell monolayer. Tamoxifen, a standard and bands are also present in complexes indicating the presence of
well-known anticancer drug, was used as a standard drug to eval- hydrogen bonding in complexes.[25] The IR data of the Schiff
uate the relative cytotoxic efficiency of the tested compounds at bases H3L1 and HL2 and their complexes are listed in (Table 2).
the same concentrations.
The IR spectra of the complexes are compared with those of the
The relation between surviving fraction and drug concentra- free ligand in order to determine the coordination sites that may
tion is plotted to get the survival curve. The results of cytotoxic be involved in chelation. In all complexes of H3L1, the ligand
activity were expressed as an IC50; the dose of compound (in behaved as neutral tridentates ligand coordinating through both

50

SYNTHESIS, CHARACTERIZATION, AND CYTOTOXIC ACTIVITY
51
TABLE 3
imine groups and one hydroxyl group (NNO). These complexes
showed a shift to lower wave number with decreasing intensity
of the bands of both imine’s and one of the hydroxyl groups
indicating they are involved in coordination to the central metal
while the other hydroxyl group almost retained its original po-
sitions indicating it was not involved in coordination.[26,27] The
appearance of two bands due to ν(C-O) one almost at its orig-
inal position while the other was shift to higher wave number
further supports the coordination of only one of the two pheno-
lic oxygen to the central metal.[27] In case of the ligand H3L2
complexes, the ligand behaved as neutral bidentate ligand coor-
dinating through the imine and thio-ether groups. The IR data
of these complexes showed a shift to lower wave number in the
band corresponding to the imine group along with a decrease
in its intensity, indicating its involvement in coordination.[26–30]
The thio-ether band in the free ligand appeared as a split band
at 700 and 645 cm−1. However, this mode is shifted in the
spectra of the complexes and appeared at 670–650 cm−1 and
630–610 cm−1 suggesting the bonding of the metal ion through
sulfur atom of the ligand.[31] The most important absorption oc-
curred at 2251 cm–1 and corresponds to the νas(C≡N) stretching,
which remain unchanged in complexes excluding participation
of this group in complexation.[32] The new bands in spectra
of all complexes in the 435–475, 334–380, and 520–570 cm–1
regions were assigned to υ(M–N), υ(M–S), and υ(M–O) vibra-
tions, respectively.[33,34] The acetato group in complexes 3, 9,
and 10 acted as a monodentate ligand and this is supported by
the appearance of two new bands in the ranges 1580–1560 cm–1
and 1366–1340 cm–1, which may be attributed to νasym.(COO–)
and νsym.(COO–), respectively.[35] The separation value (ꢂ) be-
tween νasym.(COO–) and νsym.(COO–) in these complexes were
more than 200 cm–1 (208–223 cm–1), suggesting the coordina-
tion of carboxylate group in a monodentate fashion.[36] Further,
the complex exhibits δ(COO–) at 750 cm–1, which is consid-
ered diagnostic for monodentate acetates.[35] The broad bands
in 3464–3441 cm–1 region in the spectra of complexes 6, 8, and
9 are due to coordinated water rather than water of crystalliza-
tion. This is supported by the presence of bands at 1585–1595,
925–950, and 600–625 cm–1 due to H2O deformation, H2O
rocking, and H2O wagging, respectively.[37,38] The spectrum of
nitrato complexes 2 and 8 showed bands in 1452–1448 (υ1),
1075–1055 (υ2), 1364–1360 (υ4), and 710–699 (υ5) regions
The electronic absorption spectral bands (nm) and magnetic
moment (B.M.) for the ligands H3L1 HL2 and their metal
complexes
Ligands/
Complexes
λmax (nm) (ε
No.
[mol–1 cm–1])
μeff in BM
1
2
H3L1
312, 381, 462
290, 325, 395,
465, 550
285, 330, 415,
455, 650
290, 320, 430,
465, 750
300, 340, 410,
460
—
—
H3L1AgONO2
3
4
5
6
H3L1Cu(OC(O)
CH3)2
1.74
5.9
H3L1FeCl3
[H3L1PtCl]Cl
—
[H3L1RuCl2
(H2O)]Cl
295, 325, 410,
460, 590, 675
300, 340, 402
310, 330, 365,
420, 468, 560
315, 370, 430,
745
1.85
7
8
HL2
—
—
HL2Ag(ONO2)
(H2O)
9
10
11
12
HL2Cu(OC(O)
CH3)2(H2O)2
1.89
3.45
—
(HL2)2Ni(OC(O) 315, 350, 410,
CH3)2
585, 815
295, 320, 354,
425
290, 325, 360,
440
HL2PtCl2
HL2ZnCl2
—
with υ1–υ4 separation of 88 cm−1, characteristic of monoden-
tate nitrato group.[39]
Electronic Spectra and Magnetic Moments
The structure of the ligand reveals that the two lone pairs
of electrons of azo group are not the only interacting non-
bonding electrons because the ligand contains nitrogen and
oxygen atoms, which also may be extra sources of lone pair
of electrons. Thus, other n→π∗ transition is expected to take
place from these non-bonding orbital to different π∗ molecular
TABLE 4
(a): 1H-NMR spectral data of H3L1 and some of its metal complexes
H(28),
H(31)H(24),
Compound H(21)
H(19), H(20)
H(27)
H(26)
H(29), H(30)
H(25)
H(22), H(23)
H3L1
2
6
13.61br 13.05(s, 1H), 12.67(s, 1H) 8.62(s, 1H)
13.60br 13.04(s, 1H), 12.60(s, 1H) 8.47(s, 1H)
13.61s 13.05(s, 1H), 12.53(s, 1H) 8.39(s, 1H)
7.55(m, 4H)
7.59(m, 4H)
7.59(m, 4H)
7.25(dd, 2H) 6.41(s, 1H)
7.25(dd, 2H) 6.40(s, 1H)
7.15(dd, 2H) 6.47 (s, 1H) 4.93(s, 2H)
4.97(s, 2H)
5.03(s, 2H)

52
A. M. A. EL-SEIDY ET AL.
TABLE 5
1H-NMR spectral data of HL2
Compound
H(12)
H(17), H(22)
7.54 (S, 2H)
H(23), H(24)
7.17 (S, 2H)
H(19), H(21)
4.04(s, 2H)
H(18), H(20), H(25), H(26)
2.86(m, 4H)
HL2
13.40 (br, 1H)
at 650 nm and ascribed to the d-d transition (dxz; dyz→ dx2-
y2). These results are typical of square pyramidal geometry,[47]
while complex 9 exhibited a band at 745 nm range assignable to
orbital extending over such a large molecule. The data (Table 3)
reveal that the ligand comprises three sets of bands in the UV
and visible regions.[40] The first set of the shortest wavelength
is 300–340 nm range, which may be assigned to the π→π∗
transition in the aromatic moiety and intraligand π→π∗ transi-
tion.[41] The second set appears in the 381–402 nm range, which
may be assigned to n→π∗ of the azomethine group.[42] The
band located in the visible region at 462 nm can be assigned to
π→π∗ transition involving the whole electronic system of the
compounds with a considerable charge transfer character arising
mainly from the phenolic moiety.[40,43] The spectral data of the
free ligands and their metal complexes in DMSO are listed in
Table 3. The spectra of the diamagnetic Ag(I) complexes (2, 8)
exhibited two bands in the 550–560, 465–468, and 365–395 nm
ranges; the latter two may arise from charge transfer of the type
may arise from charge transfer of the type ligand (π) → b1g
(Ag+) and ligand (σ) → b1g (Ag+), respectively, in a typically
distorted square planar environment around the metal ion.[44–46]
The electronic spectra of the copper complex 3 showed a band
2
2Eg→ Tg transition, which is the expected band for d9 ion in an
octahedral configuration with low crystal field splitting.[48] The
magnetic moments of the copper complexes at room tempera-
ture lied in 1.74–1.89 B.M. range (Table 3), corresponding to
one unpaired electron.[49] The electronic spectrum of the ferric
complex 4 showed a band at 750 nm, that may be assigned to
4
6A1→ T1(G), indicating distorted octahedral geometry around
Fe(III) ion.[50,51] The magnetic moment of this complex was
found to be 5.9 B.M. and fall within the range observed for
octahedral Fe(III) complexes.[52–54] The ruthenium complex 6
showed two bands at 675 and 590 nm. The ground state of
ruthenium(III) in octahedral environment is 2T2g, arising from
the t5 configuration, and the first excited doublet levels in the
2g
order of increasing energy are 2A2g and 2T1g, arising from the
t42ge1 configuration. Hence, these two bands may correspond
g
2
2
2
2
to T2g → A2g and T2g → T1g. Thus, the pattern of the
TABLE 6
Thermal data for the metal complexes
TGA (wt. loss%),
Temp.
(oC)
DTA
(Peak)
Composition of
the residue
No.
3
Anal. Calcd. (Found)
Assignment
265
325
560
250
315
550
268
290
645
137
260
340
510
245
275
615
270
310
520
Endo
Endo
Exo
Endo
Endo
Exo
Endo
Endo
Exo
Endo
Endo
Endo
Exo
Endo
Endo
Exo
Endo
Endo
Exo
26.31(26.55)
–
17.72(18.09)
24.76(25.04)
–
37.18(37.58)
22.41(22.74)
–
52.69(52.98)
8.28(8.54)
27.15(27.42)
–
18.29(18.38)
19.32(19.58)
–
12.22(12.44)
20.05(20.35)
–
Loss of 2 acetate groups
Melting point
Decomposition and formation of CuO
Loss of three chloride ions
Melting point
Decomposition and formation of Fe2O3
Loss of three chloride ions
Melting point
Decomposition and formation of Ru2O3
Loss of two coordinated water
Loss of two acetate groups
Melting point
Decomposition and formation of CuO
Loss of 2 acetate groups
Melting point
Decomposition and formation of NiO
Loss of two chloride ions
Melting point
[H3L1Cu]
[H3L1Cu]
CuO
4
6
9
[H3L1Fe]
[H3L1Fe]
Fe2O3
[H3L1Ru]
[H3L1Ru]
Ru2O3
[HL2Cu(OC(O)CH3)2]
[HL2Cu]
[HL2Cu]
CuO
10
12
[(HL2)2Ni]
[(HL2)2Ni]
NiO
[HL2Zn]
[HL2Zn]
ZnO
23.02(23.37)
Decomposition and formation of ZnO

SYNTHESIS, CHARACTERIZATION, AND CYTOTOXIC ACTIVITY
53
FIG. 1. The proposed structures of metal complexes.
The 1HNMR spectrum of the ligand H3L1 showed three sig-
nals at 13.61, 13.05, and 12.67 ppm. The former was assigned
to NHimidazole while the other signals were assigned the phe-
nolic OH’s protons. These signals disappeared on the addition
of D2O. The singlet at 8.62 ppm was assigned to CH N pro-
ton. The signals in the 7.55–6.41 ppm range may be due to the
aromatic rings protons. The signal due to the -CH2- appeared
as a singlet at 4.97. The singlet of the NHimidazole showed no
significant shift in the spectrum of all complexes, indicating it
is not involved in complexation. The signals at 12.67 showed
downfield shift in the spectra of complexes 2 and 6 while the
other signal at 13.05 almost retained its original position. This
supports that only on phenolic oxygen is involved in complex
electronic spectra of the ruthenium (III) complex indicates the
presence of an octahedral environment around the ruthenium
(III) ion.[24,53,55–57]
The electronic spectrum of Nickel(II) complex, complex 10,
showed bands at 815 and 585 nm that may be arising from
3
3
3A2g→ T1g(F) and 3A2g→ T1g(P) transitions, respectively in
octahedral geometry.[58–60]
1HNMR Studies of the Ligands and Some of Their
Diamagnetic Complexes
The insolubility of the complexes in the other or-
ganic solvents necessitates recording 1H NMR spectra in
dimethylsulfoxide-d6 (DMSO-d6) (Tables 4 and 5).

54
A. M. A. EL-SEIDY ET AL.
FIG. 2. Cytotoxic activities of ligands and their complexes against human breast cancer cell line (MCF-7).
formation. The singlet at 8.62 ppm showed a downfield shift activity of complexes (3, 4) and (10–12) compared to that of
(ꢂδ = 0.15–0.23 ppm) on complex formation, which indicates ligands (1, 7) could be attributed to their poor solubility than
the coordination of the azomethine nitrogen to the central metal. their respective free ligands.[65] Additionally, the current com-
1
The HNMR spectrum of the ligand HL2 showed a signal at parative study with Tamxifen, and based on the IC50 values
13.40 assigned to NHimidazole. The signals in the 7.54–7.17 ppm
range may be due to the aromatic rings protons. The signals due
to the -CH2- appeared in 4.04–2.86 ppm range.
Thermal analyses (DTA and TGA)
The results of DTA and TGA of complexes 3, 4, 6, 9, 10, and
12 are shown in Table 6. The results showed good agreement
with the theoretical formulae as suggested from the analytical
data.
Biological Activities
This study has shown that the two ligands and their metal
complexes were cytotoxic against human breast cancer cell line
(MCF-7). The cytotoxic activity of the Schiff base ligands H3L1
and HL2 could be attributed to the antiproliferative activity of
hydroxyl group and the occurrence of C≡N moiety, respectively,
which may be an important fragment for hydrogen bonding for-
mation at the receptor site.[61–63] Also, the study has shown that
complexation of metals to the Schiff base ligands improves the
anticancer activities of the ligands (2, 5, 6, 8, and 9). This may be
FIG. 3. Effect of different concentrations of ligand H3L1 and its complexes
on the viability of human breast cancer cell line (MCF-7).
attributed to the lipophilic character of the central metal atom
explained by Tweedy’s chelation theory.[11,64] The decreased

SYNTHESIS, CHARACTERIZATION, AND CYTOTOXIC ACTIVITY
55
and spectral (UV-Vis, IR, 1H NMR, 13C NMR, mass) and mag-
netic moment measurements techniques. The ligands behaved
either as neutral tridentate or neutral bidentate ligands. Conduc-
tance measurements suggest the non-electrolytic nature for all
the metal complexes except complex 5, which behaves as a 1:1
electrolyte. Complexes 2, 8, and 9 showed a remarkable smaller
value of IC50 than that of Tamoxifen, which would provide a
new potential antitumor drug that deserves more attention.
REFERENCES
1. Tebbe, M.J.; Spitzer, W.A.; Victor, F.; Miller, S.C.; Lee, C.C.; Sattelberg,
T.R.; Mckinney, E.; Tang, C.J. J. Med. Chem. 1997, 40, 3937–3946.
2. Tamm, I. Science 1957, 126, 1235–1236.
3. Iyenger, S.; Nuhhauser, M.A.; Thor, K.B. U.S. Patent 1, 1996.
4. Bai, Y.; Lu, J.; Shi, Z.; Yang, B. Synth. Lett. 2001, 544.
5. El-Deeb, I. M.; Lee, S. H. Bioorgan. Med. Chem. 2010, 18, 3860–3874.
6. Lin, Y.-L.; Su, Y.-T.; Chen, B.-H. Eur. J. Pharmacol. 2010, 637, 1–10.
7. Desoize, B. Crit. Rev. Oncol. Hematol. 2002, 42, 213–215.
8. Huang, R.; Wallqvist, A.; Covell, D.G. Biochem. Pharmacol. 2005, 69,
1009–1039.
FIG. 4. Effect of different concentrations of ligand HL2 and its complexes on
the viability of human breast cancer cell line (MCF-7).
obtained with human breast cancer cell line (MCF-7) revealed
that the H3L1 ligand and HL2-silver complexes were between
2.53 and 2.8 and HL2-copper complexes were 3.35 times more
cytotoxic than Tamxifen, whereas the Ag(I) complexes induce
apoptosis (programmed cell death) in cancer cells which may be
a direct result of their action on the cell, while copper complexes
would cause intracellular generation of hydroxyl radicals from
H2O2 produced during normal cellular activities by the reduc-
tion of Cu(II) to Cu(I), leading to a growth inhibition in tumor
cells.[66] The ligand HL2 and its complexes, except complexes 8
and 9, showed a very low reactivity and we can regard the reac-
tivity in case of complexes 8 and 9 to the presence of copper and
silver ions. The very high reactivity in case of complex 9 com-
pared to the low reactivity of complex 3 is due to the presence
of sulfur in the ligand HL2. Since sulfur is a medium-soft base it
stabilizes copper in the low oxidation state and hence facilitates
the reduction of Cu(II) to Cu(I). This reduction will increase the
formation of hydroxyl radicals from H2O2. Oxygen is a hard
base and stabilizes the presences of copper in the high oxidation
state. The close cytotoxic value of H3L1-platinum complex 11
to Tamxifen value supports the use of cisplatin and related plat-
inum complexes as anti-cancer agents, which has stimulated a
search for other active transition metal complexes, which are as
or more effective but with fewer side effects.[63]
9. Karthikeyan, M.S.; Prasad, D.J. Bioorg. Med. Chem. 2006, 14, 7482–7489.
10. Singh, K.; Barwa, M.S.; Tyagi, P. Eur. J. Med. Chem. 2007, 42, 394–402.
11. Creaven, B.S.; Duff, B.; Egan, D.A.; Kavanagh, K.; Rosair, G.; Thangella,
V.R.; Walsh, M. Inorg. Chim. Acta 2010, 363, 4048–4058.
12. Kukalenko, S.S.; Udovenko, V.A.; Borysova, V.P.; Kulugina, N.L.; Bur-
makin, N.M.; Andreeva, E.L.; U.S.S.R. SU 1,636,414. Odkrytiya Izobret
1991, 11, 75–165.
13. Nikolova, D.; Ivanov, R.; Buyukliev, S.; Konstantinov, M.; Karaivanova,
M.; Arzneim-Forsch, A. Drug Res. 2001, 51, 758–762.
14. Mendelson, W.L.; Hayden, S. Synth. Commun. 1996, 26, 603–610.
15. Cescon, L.A.; Day, A.R. J. Org. Chem. 1962, 27, 581.
16. Welcher, F.J. The Analytical Uses of Ethylenediamine Tetraacetic Acid.
Van Nostrand: New York, 1958.
17. Vogel, A.I. Textbook of Practical Organic Chemistry, Including Qualitative
Organic Analysis. Longman: London, 1978.
18. Holzbecher, Z.; Divis, L.; Kral, M.; Sucha, L.; Vracil, F. Handbook of
Organic Reagents in Inorganic Analysis. Wiley: Chichester, England, 1976.
19. El-Sonbati, A.Z.; El-Bindary, A.A.; Al-Sarawy, A.A. Spectrochim. Acta,
Part A 2002, 58, 2771–2778.
20. Kovala-Demertzi, D.; Yadav, P.N.; Demertzis, M.A.; Coluccia, M. J. Inorg.
Biochem. 2000, 78, 347–354.
21. Skehan, P.; Storeng, R.; Scudiero, D.; Monks, A.; Mahon, J.; Vistica, D.;
Warren, J.T.; Bokesch, H.; Kenney, S.; Boyd, M.R. J. Nat. Cancer Ins.
1990, 82, 1107–1112.
22. El-Bindary, A.A. Trans. Met. Chem. 1997, 22, 381–384.
23. Golcu, A.; Tumer, M.; Demirelli, H.; Wheatley, R.A. Inorg. Chim. Acta
2005, 358, 1785–1797.
24. Kannan, S.; Ramesh, R. Polyhedron 2006, 25, 3095.
25. Maurya, M.R.; Chandrakar, A.K.; Chand, S. J. Mol. Catal. A: Chem. 2007,
263, 227–237.
The IC50 values were summarized as shown in Figure 2 and
the effect of different concentrations of the ligands and their
complexes on the viability of human breast cancer cell line
(MCF-7) are shown in Figures 3 and 4.
26. Youssef, N. S.; El-Zahany, E.; El-Seidy, A.M.A.; Caselli, A.; Fantauzzi, S.;
Cenini, S. Inorg. Chim. Acta 2009, 362, 2006–2014.
27. Nakatamato, K. Infrared Spectra of Inorganic and Coordination Com-
pounds. Wiley Interscience: New York, 1970.
28. El-Wahab, Z.H.A.; Mashaly, M.M.; Salman, A.A.; El-Shetary, B.A.; Fa-
heim, A.A. Spectrochim. Acta Part A 2004, 60, 2861–2873.
29. Youssef, N. S.; El-Zahany, E. A.; El-Seidy, A. M. A.; Caselli, A.; Cenini,
S. J. Mol. Catal. A: Chem. 2009, 308, 159–168.
30. El-Tabl, A.S.; El-Saied, F.A.; Al-Hakimi, A.N. Transition Met. Chem. 2007,
32, 689–701.
CONCLUSION
In the present work, we synthesized two novel Schiff base lig-
ands H3L1 and HL2 and their AgI, CuII, FeIII, PtII, RuIII, NiII, and
ZnII. The ligands and their metal complexes have been synthe-
sized and identified by elemental analyses, molar conductivities,
31. Sarkar, S.; Dey, K. Spectrochim. Acta, Part A 2005, 62, 383–393.

56
A. M. A. EL-SEIDY ET AL.
32. Yuste, C.; Armentano, D.; Marino, N.; Canadillas-Delgado, L.; Delgado, 50. Sallam, S.A.; Orabi, A.S.; El-Shetary, B.A.; Lentz, A. Transition Met.
F.S.; Ruiz-Perez, C.; Rillema, D.P.; Lloret, F.; Julve, M. Dalton Trans. 2008,
1583–1596
33. Singh, K.; Barwa, M.S.; Tyagi, P. Eur. J. Med. Chem. 2006, 41, 147–153.
34. Patel, R. N.; Gundla, V.L.N.; Patel, D.K. Polyhedron 2008, 27, 1054–1060.
Chem. 2002, 27, 447–453.
51. Singh, N.K.; Singh, S.B. Transition Met. Chem. 2001, 26, 487–495.
52. Garcia-Friaza, G.; Fernandez-Botello, A.; Perez, J. M.; Prieto, M. J.;
Moreno, V. J. Inorg. Biochem. 2006, 100, 1368–1377.
35. Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coordination 53. El-Tabl, A.S.; El-Saied, F.A.; Al-Hakimi, A.N. Transition Met. Chem. 2007,
Compounds. Wiley: New York, 1986.
36. Boghaei, D.M.; Gharagozlou, M. Spectrochim. Acta
944–949.
32, 689.
A
2007, 67, 54. Singh, N.K. Transition Met. Chem. 2001, 26, 487–495.
55. Balasubramanian, K.P.; Parameswari, K.; Chinnusamy, V.; Prabhakaran,
37. El-Dissouky, A.; Fahmy, A.; Amer, A. Inorg. Chim. Acta 1987, 133,
R.; Natarajan, K. Spectrochim. Acta Part A 2006, 65, 678–683.
56. Nehru, K.; Athappan, P.; Rajagopal, G. Transition Met. Chem. 2001, 26,
652–656.
311–316.
38. Teotia, M.P.; Gurtu, J.N.; Rana, V.B. J. Inorg. Nucl. Chem. 1980, 42,
821–831.
57. El-Tabl, A.S.; Issa, R.M.; Morsi, M.A. Transition Met. Chem. 2004, 29,
543–549.
39. Sonza, P.; Garcia-Vfizquez, A.J.; Masaguer, J.R. Transition Met. Chem.
1985, 10, 410–412.
58. Ali, M.A.; Mirza, A.H.; Bujang, F.H.; Hamid, M.H.S.A.; Bernhardt, P.V.
Polyhedron 2006, 25, 3245–3252.
40. Rageh, N. M.; Mawgoud, A.M.A.; Mostafa, H.M. Chem. Papers 1999, 53,
107–113.
59. Krishnapriya, K.R.; Kandaswamy, M. Polyhedron 2005, 24, 113–120.
41. Raj, B.N.B.; Kurup, M.R.P.; Suresh, E. Spectrochim. Acta, Part A 2008, 71, 60. Gudasi, K.B.; Patil, M.S.; Vadavi, R.S.; Shenoy, R.V.; Patil, S.A.; Nethaji,
1253–1260.
M. Transition Met. Chem. 2006, 31, 580–584.
42. Gup, B.K.R. Spectrochim. Acta, Part A 2005, 62, 1188–1195.
43. R. Gup. Giziroglu, E.; Kirkan, B. Dyes Pigments 2007, 73, 40–46.
44. Sabin, F.; Ryu, C.K.; Fork, P.; Vogler, A. Inorg. Chem. 1992, 31, 1941–
1946.
61. El-Azab, A.S.; Al-Omar, M.A.; Abdel-Aziz, A.A.M.; Abdel-Aziz, N.I.; El-
Sayed, M.A.A.; Aleisa, A.M.; Sayed-Ahmed, M.M.; Abdel-Hamide, S.G.
Eur. J. Med. Chem. 2010, 45, 4188–4198.
62. Moreau, E.; Fortin, S.; Lacroix, J.; Patenaude, A.; Rousseau, J.; Gaudreault,
R.-C. Bioorg. Med. Chem. 2008, 16, 1206–1217.
45. Mostafa, S.I.; Bekheit, M.M. Chem. Pharm. Bull. Jpn. 2000, 48 266–271.
46. Mostafa, S.I.; Ikeda, S.; Ohtani, B. J. Mol. Catal. A: Chem. 2005, 225, 63. Thati, B.; Noble, A.; Creaven, M.W.B.S.; McCann, M.; Kavanagh, K.;
181–188.
Devereux, M.; Egan, D.A. Cancer Lett. 2007, 248, 321–331.
64. Youssef, N.S.; El-Zahany, E.A.; Ali, M.M. Phosphorus, Sulfur Silicon Re-
lat. Elem. 2010, 185, 2171–2181.
65. Gottschaldt, M.; Peiffer, A.; Koth, D.; Gorls, H.; H.-Dahse, M.; Mollmann,
U.; Obata, M.; Yano, S. Tetrahedron 2006, 62, 11073–11080.
47. Matsumoto, K.; Sekine, N.; Arimura, K.; Ohba, M.; Ohba, H.; Sakiyama,
H.; Okawa, H. Bull. Chem. Soc. Jpn. 2004, 77, 1343–1351.
48. Sanmartin, J.; Novio, F.; Garcia-Deibe, A.M.; Fondo, M.; Ocampo, N.;
Bermejo, M.R. Polyhedron 2006, 25, 1714–1722.
49. Mohamed, G.G.; El-Gamel, N.E.A. Spectrochim. Acta, Part A 2004, 60, 66. Byrnes, R. W.A.; W. E. Petering, D.H. Free Rad. Biol. Med. 1992, 13
3141–3154. 469–478.