Synthesis, characterization, and in vitro anti-neoplastic activity of novel vic-dioximes bearing thiosemicarbazone side groups and their mononuclear complexes

Article abstract of DOI:10.1016/j.bioorg.2014.01.003

Two novel vicinal dioxime ligands containing thiosemicarbazone units, (2E)-2-[4-(diethylamino)benzylidene]-N-[(1Z,2E)-N-hydroxy-2-(hydroxyimino) ethanimidoyl]hydrazine carbothioamide (L¹H₂) and (2E)-2-[4-(dimethylamino)benzylidene]-N

Full text of DOI:10.1016/j.bioorg.2014.01.003

Bioorganic Chemistry 53 (2014) 92–98
Contents lists available at ScienceDirect
Bioorganic Chemistry
journal homepage: www.elsevier.com/locate/bioorg
Synthesis, characterization, and in vitro anti-neoplastic activity of novel
vic-dioximes bearing thiosemicarbazone side groups and their
mononuclear complexes
a,
b
a
a
b
⇑
_
Ilknur Babahan , Ali Özmen , Nil Orhan , Didem Kazar , Esin Hafize Deg˘irmenci
a Adnan Menderes University, Faculty of Science and Art, Department of Chemistry, 09010 Aydin, Turkey
b Adnan Menderes University, Faculty of Science and Art, Department of Biology, 09010 Aydin, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 19 July 2013
Available online 31 January 2014
Two novel vicinal dioxime ligands containing thiosemicarbazone units, (2E)-2-[4-(diethylamino)benzyl-
idene]-N-[(1Z,2E)-N-hydroxy-2-(hydroxyimino)ethanimidoyl]hydrazine carbothioamide (L1H2) and (2E)-
2-[4-(dimethylamino)benzylidene]-N-[(1Z,2E)-N-hydroxy-2-(hydroxyimino)ethanimidoyl]hydra-
zinecarbothioamide (L2H2), were synthesized. Using the HL-60 human leukemia cell line, the in vitro
anti-neoplastic activity of these thiosemicarbazone-oxime derivatives was evaluated. Mononuclear
nickel(II), copper(II), and cobalt(II) complexes with a metal:ligand ratio of 1:2 for both the L1H2 and
L2H2 ligands were also synthesized. To characterize these compounds, Fourier transform-infrared
spectroscopy (FT-IR), mass spectrometry (MS), magnetic susceptibility measurements, 1H and 13C nuclear
magnetic resonance (NMR), ultraviolet–visible (UV–Vis) absorption spectroscopy, heteronuclear
multiple-bond correlation (HMQC), and elemental analysis were performed. For L1H2, L2H2, and each
of their derivatives, antiproliferative effects against HL-60 cells were exhibited and the associated IpC50
Keywords:
Vic-dioxime
Thiosemicarbazone
Transition metal complex
Hydrogen-bridge complex
Antiproliferative
Leukemia
values ranged from 5 lM to 20 l
M. Furthermore, L1H2 and its derivatives inhibited the proliferation of
HL-60 cells more effectively than L2H2, and 5
l
M [Cu(L1H)2] exhibited the strongest antiproliferative
activity.
Ó 2014 Elsevier Inc. All rights reserved.
1. Introduction
has been found to include antibacterial, antimalarial, antiviral,
and antitumour activities [12–14]. For example, it has been re-
ported that thiosemicarbazones are potent antitumour agents that
inhibit the enzyme, topoisomerase II(Topo-II). Moreover, in recent
studies, di-2-pyridylketonethiosemicarbazone(DpT) and 2-ben-
zoylpyridinethiosemicarbazone(BpT) ligands were found to exhibit
selective antitumour activity both in vitro and in vivo [15]. The 3,5-
diacetyl-1,2,4-triazolbis(4,4-dimethylthiosemicarbazone) ligand,
H(3)L(1), and its dinuclear platinum complex, [Pt(mu-HL(1))](2),
also exhibited high antiproliferative activity against the human
non-small cell lung cancer line, NCI-H460 [16].
Vic-dioximes are coordination compounds which have been
well studied over the past few decades. Correspondingly, vic-dioxi-
mes have been applied to analytical, biological, pigment, and
medicinal chemistries. In particular, 1,2-dioximes have been found
to play an important role in coordination chemistry, mainly due to
their stable MN4 core [1–4]. The exceptional stability and unique
electronic properties of these complexes have also been attributed
to the planar structure of 1,2-dioximes that is stabilized by hydro-
gen bonding interactions [5–8].
The chemistry of transition metal complexes of thiosemicarba-
zone ligands has also been of interest, primarily due to their bioin-
organic relevance [9–11]. Thiosemicarbazones usually bind to a
metal ion as bidentate N,S-donor ligands via dissociation of the
hydrazinic proton, thereby forming five-membered chelate rings
[9,12]. The potential biological benefits of this class of complexes
While there have been many studies of thiosemicarbazones, as
well as studies of mono- and di-oximes, studies of vic-dioxime
derivatives with thiosemicarbazone side groups have not been re-
ported. Therefore, in this work, vic-dioximes containing thiosemi-
carbazone units (L1H2 and L2H2), and novel mononuclear Ni(II),
Cu(II), and Co(II) complexes of L1H2 and L2H2, were synthesized
and structurally characterized. In addition, the cytotoxic activity
of these complexes and their derivatives were assayed using the
human promyelocytic leukemia cell line, HL60.
⇑
Corresponding author. Fax: +90 256 213 5379.
_
E-mail address: ilknurbabahan@yahoo.com (I. Babahan).
http://dx.doi.org/10.1016/j.bioorg.2014.01.003
0045-2068/Ó 2014 Elsevier Inc. All rights reserved.

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I. Babahan et al. / Bioorganic Chemistry 53 (2014) 92–98
93
Scheme 1. Synthesis of the ligands (L1H2 and L2H2).
2.2. FT-IR spectra, MS, and magnetic susceptibility
2. Results and discussion
The FT-IR spectrum of L1H2 and L2H2 included ANH and AOH
peaks, as well as AC@N peaks for both the oxime and thiosemicar-
bazone groups, and peaks representing the -NO stretching vibra-
2.1. Ligand synthesis
(2E)-2-[4-(diethylamino)benzylidene]hydrazinecarbothioamide
(Scheme 1, 1a) and (2E)-2-[4-(dimethylamino)benzylidene]hydra-
zinecarbothioamide (Scheme 1, 1b) were obtained from
tions (Table 2). For L1H2, these peaks occurred at 3458 cmꢀ1
,
3289 cmꢀ1, 1648 cmꢀ1, 1689 cmꢀ1, and 951 cmꢀ1, respectively.
For L2H2, these peaks occurred at 3461 cmꢀ1 3287 cmꢀ1
a
,
,
condensation reaction of 4-(diethylamino)benzaldehyde and
4-(dimethylamino)benzaldehyde with thiosemicarbazide in the
presence of alcohol [11]. (2E)-2-[4-(diethylamino)benzylidene]-N-
[(1Z,2E)-N-hydroxy-2-(hydroxyimino)ethanimidoyl]hydrazinecar-
bothioamide (L1H2) and (2E)-2-[4-(dimethylamino)benzylidene]-
N-[(1Z,2E)-N-hydroxy-2-(hydroxyimino)ethan imidoyl]hydrazine-
carbothioamide (L2H2) were subsequently prepared from 1a and
1b with anti-chloroglyoxime (1c) [17] in the presence of alcohol.
Ni(II), Cu(II), and Co(II) complexes of L1H2 and L2H2 were also pre-
pared in ethanol using MCl2.xH2O as the metal salt. To characterize
the structures of the metal complexes formed, Fourier transform-
infrared spectroscopy (FT-IR), mass spectrometry (MS), magnetic
susceptibility measurements, 1H and 13C nuclear magnetic reso-
nance (NMR), ultraviolet–visible (UV–Vis) absorption spectros-
copy, heteronuclear multiple-bond correlation (HMQC), and
elemental analysis were performed. Although there were also
attempts to grow X-ray quality single crystals, these attempts were
unsuccessful.
1646 cmꢀ1, 1686 cmꢀ1, and 948 cmꢀ1, respectively [16–24]. The
C@N and OH stretching vibration data for both ligands were also
consistent with those previously reported for vic-dioxime and thi-
osemicarbazone derivatives [16–24]. The absence of bands be-
tween 2700 cmꢀ1and 2500 cmꢀ1 excluded the possibility of a
thione-thiol tautomerism (e.g., HANAC@S, AC@NASH) [20]. How-
ever, the strong
m(C@S) absorption bands that were observed
around 813–812 cmꢀ1 indicate that both ligands achieved a thion
tautomeric form in the solid state (Fig. 1). Moreover, based on
the fast atom bombardment (FAB) mass spectrometry data ob-
tained, with values of 335 [Mꢀ1]+ for L1H2 and 309 [M+1]+ for
L2H2, the structures predicted for both ligands were confirmed.
FT-IR spectra for complexes with the general formula: [M(LH)2],
[M: Ni(II), Cu(II), and Co(II)ꢁ2H2O], exhibited C@Noxime absorptions
at 1640–1632 cmꢀ1. Upon complexation, absorptions at 1648–
1646 cmꢀ1 for the individual ligands were shifted to lower wave
numbers, and the intensity of the bands were also reduced. Taken
Table 1
Physical properties and elemental analyses of the ligands and complexes.
Compounds formula
M.p. (d)b
(°C)
Yield
(%)
Color
leff
(BM)a
–
Calculated (Found)% of
C
H
N
S
L1H2
195
70
Yellow
Red
49.98
5.99
24.98
9.53
(49.94)
46.10
(6.02)
5.25
(24.95)
23.04
(9.48)
8.79
[Ni(L1H2)]
[Cu(L1H2)]
[Co(L1H2)(H2O)2]
L2H2
>300
>300
>300
196
52
40
45
72
60
45
50
Dia.
1.70
3.77
–
(46.23)
45.80
(5.15)
5.22
(23.34)
22.89
(8.91)
8.73
Brown
Brown
Yellow
Red
(45.68)
43.92
(5.35)
5.53
(23.14)
21.95
(8.56)
8.37
(43.46)
46.74
(5.34)
5.23
(21.67)
27.25
(27.50)
24.96
(8.78)
10.40
(10.56)
9.52
(46.70)
42.81
(5.45)
4.49
[Ni(L2H2)]
[Cu(L2H2)]
[Co(L2H2)(H2O)2]
>300
>300
>300
–
(42.67)
42.50
(4.98)
4.46
(24.45)
24.78
(9.30)
9.46
Brown
Brown
1.70
3.75
(42.33)
40.62
(4.68)
4.83
(24.54)
23.68
(10.03)
9.04
(40.97)
(4.65)
(23.54)
(9.51)
a
l
eff: magnetic moment, Dia.: diamagnetic.
b
d: decomposition.

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I. Babahan et al. / Bioorganic Chemistry 53 (2014) 92–98
Table 2
Characteristic IR bands of the ligands and their metal complexes (cmꢀ1, KBr) (1) L1H2 (2) [Ni(L1H)2] (3) [Cu(L1H)2] (4) [Co(L1H)2(H2O)2] (5) L2H2 (6) [Ni(L2H)2] (7) [Cu(L2H)2] (8)
[Co(L2H)2(H2O)2].
Compound
NH
AOH/H2O
C@S
OAHꢁ ꢁ ꢁO
C@Na
C@Nb
NAO
1
2
3
4
5
6
7
8
3458 b
3410 b
3458 b
3458 b
3461b
3465 b
3462 b
3462 b
3289 b
_
_
3285 b
3287 b
_
813 m
813 m
812 m
813 m
812 m
810 m
811 m
811 m
–
1689 s
1686 s
1689 s
1689 s
1686 s
1688 s
1686 s
1686 s
1648 s
1639 s
1632 s
1640 s
1646 s
1639 s
1639 s
1640 s
951 m
953 m
945 m
953 m
948 m
947 m
945 m
948 m
1788 w
1740 w
1765 w
_
1863 w
1871 w
1797 w
-
3289 b
b: board s: Strong, m: medium, w: weak.
a
m
m
(C@N): thiosemicarbazone moiety.
(C@N): oxime moiety.
b
(I)
(II)
(III)
Fig. 1. Thion (I) and thiol (II and III) forms of the ligands (R: ACH2CH3 for L1H2, R: ACH3 for L2H2).
together, these data suggest that L1H2 and L2H2 are N,N0 coordi-
nated with the M(II) ion to form the structures proposed in
Figs. 2a–2b. Moreover, these data suggest that complexation only
involves the C@N bond of the vic-dioximes groups, with N,N0 coor-
dinated with the M(II) ion. The disappearance of functional groups
relating to d OH for the Ni(II), Cu(II), and Co(II) complexes at
3289–3287 cmꢀ1 further indicates that intramolecular hydrogen
bonds form upon complexation, resulting in a peak between
1797 cmꢀ1 and 1740 cmꢀ1
.
Coordination of sulfur with the metal ion present would result
in the displacement of electrons towards the latter, thereby
weakening the (C@S) bond and decreasing the (C@S) stretching
Fig. 2a. trans The structure of metal complexes.
Fig. 2b. cis The structure of metal complexes.

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I. Babahan et al. / Bioorganic Chemistry 53 (2014) 92–98
95
vibrations [19]. However, upon complexation, the 813–812 cmꢀ1
frequencies for the ligands do not shift to lower wave numbers,
and the intensity of the bands do not decrease. Thus, it appears that
a metal-sulfur bond is not formed.
for L2H2, both as singlets [27]. Further evidence of the thion form
of these ligands was supported by the appearance of NH signals
around 7.92–7.69 ppm.
Carbon resonances for the oxime groups of L1H2 and L2H2 were
observed at 157.63 ppm and 129.63 ppm, and at 151.56 ppm and
129.28 ppm, respectively. The detection of these non-equivalent
carbon atoms, particularly when they were associated with
hydroxyimino carbon atoms, confirmed the anti-structures of L1H2
and L2H2 [28,29]. (NMR spectra data are summarized in Table 3).
FAB mass spectral data for the compounds: [Ni(L1H)2], [Cu(L1-
H)2], [Co(L1H)2(H2O)2], [Ni(L2H)2], [Cu(L2H)2], and [Co(L2H)2(H2-
O)2], included values of 730 [M+1]+, 735 [M+1]+, 765 [M]+, 674
[M+1]+, 679 [M+1]+, and 709 [M]+, respectively. In addition, the
MS-determined metal:ligand ratio for these compounds was 1:2
for the Ni(II), Cu(II) and Co(II) complexes. The elemental analysis
data further indicate that the desired compounds were synthesized
(Table 1). Thus, these data confrim that the complexes have a me-
tal:ligand ratio of 1:2 and maintain square planar or octahedral
geometries (Figs. 2a–2b).
2.4. UV–Vis spectra
Electronic spectra of ligands, L1H2 and L2H2, and their Ni(II),
Cu(II), and Co(II) metal complexes, were recorded in the 200–
800 nm range in DMSO. Each ligand and complex exhibited be-
tween two and seven intense absorption bands in both the visible
and ultraviolet regions (e.g., 240–587 nm). This wide distribution
The magnetic moment measurements obtained at room tem-
perature indicate that the Co(II) complexes are paramagnetic and
have magnetic susceptibility values of 3.77 Bohr magneton (BM)
for L1H2 and 3.75 BM for L2H2. These values are within the range
predicted for high spin octahedral cobalt(II) complexes (the
three-spin value is 3.87 BM) [24]. For [Co(L1H)2(H2O)2] and [Co(L2-
H)2(H2O)2], coordinated H2O molecules were identified based on
the detection of a broad OH absorption peak around 3289–
3287 cmꢀ1 that exhibited a constant intensity 24 h after these
ligands were heated above 110 °C [25]. There was also no differ-
ence in the IR spectra of all of the synthesized compounds (L1H2
and L2H2, and their Ni(II), Cu(II), and Co(II) metal complexes) fol-
lowing this heating period and the IR spectra previously obtained
at room temperature. These results demonstrate the stability of
the synthesized complexes.
of bands may be due to both the
p ?
pꢂ, n ? pꢂ, and the d–d tran-
sitions involving the C@N bond, as well as a charge transfer transi-
tion that could arise from p electron interactions between the
metal and ligand. The latter could involve either a metal-to-ligand
or ligand-to-metal electron transfer [30]. The absorption bands
present below 262 nm were practically identical for the ligands
and their complexes, and this can be attributed to the
p ?
pꢂ tran-
sitions that can occur in the aromatic ring or azomethine (AC@N)
groups. Moreover, the absorption bands observed between 397 nm
and 320 nm are most likely due to the n ? pꢂ transition of the
imine group of the ligands and complexes [31]. The absorption
bands between 404 nm and 435 nm are attributed to a M ? L
charge transfer (MLCT) or a L ? M charge transfer (LMCT) and
1A1g ? 1B1g transitions [32], respectively. For the Cu(II) and Co(II)
complexes, the broad bands ranging from 589 to 590 nm were
identified as 2Eg ? 2T2g transitions, which are characteristic of
octahedral or square planar geometries [33]. Lastly, weak d–d tran-
sitions of the square planar Ni(II) complexes were observed be-
tween 435 nm and 431 nm [29a].
The Cu(II) complexes were found to be diamagnetic, and to have
an leff value of 1.70 for L1H2 and a 1.70 BM value for L2H2. These
values are consistent with a spin value of 1.73 BM, despite being
relatively low values for the magnetic moments. It is possible that
the ligands contribute some diamagnetism, thereby leading to a
decrease in the total paramagnetism of the complexes [25].
2.3. NMR spectra
2.5. Antiproliferative activity
In the 1H NMR spectrum, two low intensity proton resonance
singlets were detected at 11.11 ppm and 9.86 ppm for L1H2, and
at 11.14 ppm and 9.90 ppm for L2H2. For both ligands, these two
D2O-exchangeable singlets correspond to two non-equivalent
AOH protons. These data indicate that the AOH groups are in an
anti-configuration relative to each other [26]. The chemical shifts
which represent the ANH protons were observed at 7.90 ppm
To evaluate the antiproliferative activity of L1H2 and L2H2, and
their Ni(II), Cu(II), and Co(II) metal complexes, the human promy-
elocytic leukemia cell line, HL-60, was selected. This cell line has
previously been used in studies of myeloid differentiation and
the effects of various physiologic, pharmacologic, and viral ele-
ments on this process [34]. In the present study, proliferation as-
says were performed at 37 °C for 72 h, and all of the synthesized
compounds exhibited thermal stability during these experiments.
The IpC50 values determined for L1H2 and L2H2 and their complexes
and 7.69 ppm as
a
singlet for L1H2, and at 7.92 ppm and
7.71 ppm as a singlet for L2H2. Moreover, these singlets disap-
peared with D2O exchange. Chemical shifts for the CH@NOH pro-
tons were also observed at 6.26 ppm for L1H2 and at 6.30 ppm
were found to vary from 5 lM to 20 lM (Figs. 3 and 4). Moreover,
Table 3
1H NMR and 13C NMR spectra of the ligandsa,b in DMSO-d6 in d (ppm).
1H NMR spectra of the ligands
AOHc
NHc
ArAH
CH3
ACH2
CH@NOH
CH@NNH
L1H2
L2H2
11.11–9.86 s, 2H
7.90–7.69 s, 2H
7.43 d, 2H
6.60 d, 2H
7.49 d, 2H
6.68 d, 2H
6.26 s, 1H
7.53 s, 1H
7.57 s, 1H
1.07 t, 6H
3.35 q,4H
11.14–9.90 s, 2H
7.92–7.71 s, 2H
6.30 s, 1H
2.91 s, 6H
13C NMR spectra of the ligands
C@S
HNC@NOH
HC@NOH
HC@NNH
ArAC
ACH3
ACH2
L1H2
L2H2
164.21
157.60
157.63
151.56
129.61
129.28
148.82
141.00
128.75–111.69
128.38–109.09
13.11
39.60
44.36
–
a
b
c
Chemical shifts (d) are reported in ppm relative to SiMe4 at 30 °C, s: singlet, d: doublet.
In DMSO-d6.
Disappears on D2O exchange.

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I. Babahan et al. / Bioorganic Chemistry 53 (2014) 92–98
L1H2 and its complexes inhibited the proliferation of HL-60 cells
proliferation more effectively than L2H2, and the strongest
antiproliferative activity was exhibited by the Cu complex of
L1H2 at 5
M (Fig. 3).
l
Fig. 3. Antiproliferative effect of L1H2 and its complexes.
Fig. 4. Antiproliferative effect of L2H2 and its complexes.

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I. Babahan et al. / Bioorganic Chemistry 53 (2014) 92–98
97
Fig. 5. Conformation of trans structure of Ni(II), Cu(II), and Co(II) complexes for L2H2.
Inorganic chemistry is a discipline that is increasingly finding
applications in the field of medicine, with a subset of inorganic
compounds exhibiting anti-tumour or anti-cancer activities. Corre-
spondingly, the novel synthesis of various metal complexes has led
to the development of new pharmaceuticals. In particular, several
thiosemicarbazones have been found to exhibit antitumour activ-
ity against human cancer cells of the breast, bladder, lung, cervix,
liver, and skin. Antitumour activity against hematologic malignan-
cies, laryngeal epithelial cells, and leukemia cells has also been ob-
served. Regarding the latter, platinum (II) complexes with
thiosemicarbazones derived from 2-formyl and 2-acetylpyridine
and Mn(II), Co(II), and Zn(II) complexes with heterocyclic substi-
tuted thiosemicarbazones have been found to be very effective
chemotherapeutic antileukemic agents [35,36].
Both oxime moieties were found to have an E configuration, and
the Ni(II), Cu(II), and Co(II) complexes form intramolecular hydro-
gen bonds. In addition, both ligands can form mononuclear com-
plexes [(LH)2M] with
a metal-to-ligand ratio of 1:2 with
M = Co(II)(H2O)2, Ni(II), and Cu(II). The Co(II) complexes were
found to be octahedral with water molecules as axial ligands, and
the Ni(II) and Cu(II) complexes formed a square planar geometry.
L1H2 and L2H2 and their metal complexes were identified as po-
tent anti-cancer agents based on their antiproliferative activity
against HL-60 cells, with IpC50 values ranging from 5
20
M. L1H2 and its derivatives inhibited the proliferation of HL-
60 cells more effectively than L2H2, and the strongest antiprolifer-
lM to
l
ative activity was exhibited by 5 l
M [Cu(L1H)2].
These antiproliferative data are consistent with the results of
previous studies that have shown some thiosemicarbazone com-
plexes to be more effective than commonly used anti-cancer
agents. For example, when zinc(II) complexes of 2-acetylpyri-
dine1-(4-fluorophenyl)-piperazinylthiosemicarbazone were tested
against four cancer cell lines, the antiproliferative activity of these
complexes was found to be considerably stronger than that of cis-
platin, a commonly used chemotherapy agent [37]. The structures
of these compounds have also been shown to contribute to the
antitumour activity observed as demonstrated in studies of (ꢀ)-al-
pha-bisabolol-based thiosemicarbazones and various human tu-
mour cell lines [38].
Thiosemicarbazone platinum complexes have also exhibited
antitumour activity against various human cancer cell lines
[35,15]. Similarly, thiosemicarbazone derivatives have exhibited
very low toxicity against kidney cells compared to cisplatin [39],
and palladium(II) complexes of thiosemicarbazones have been
found to be effective against human cancer cell lines as well
[40,41]. Terminal dimethylation of thiosemicarbazones also plays
an important role, and has been shown to enhance the anti-cancer
activity of these compounds [42].
Currently, cancer is the second leading cause of death in the
United States. In 2013, it is predicted that over 1.5 million new
cases of cancer will be diagnosed, and over half a million Ameri-
cans will die of cancer [43]. Correspondingly, there continues to
be a need for new anti-cancer drugs to reduce cancer mortality
rates, to avoid the high costs of therapy, and to improve the quality
of life of affected patients. The results of the present study
demonstrate that two new oxime-thiosemicarbazones and their
derivatives represent potential anti-cancer agents. Therefore, fur-
ther studies are needed to elucidate the specific mechanisms of
action mediated by these compounds.
4. Experimental
4.1. Materials and measurements
All reagents used were purchased from Merck. 1H NMR–13
C
NMR spectra (Bruker 400 MHz), I.R spectra (Varian 900), melting
points (Buchi SPM-20) and pH measurements (Orion Expandable
Ion Analyzer EA 940) were used to elucidate the structures of the
products. The magnetic moments of the complexes were measured
by the Gouy method with a Newport type D-104 instrument mag-
net power supply. Mass spectrometry (MS) spectra were recorded
on a Bruker LC/MS/MS-8030 Triple Quadrupole Mass Spectrometer.
(2E)-2-[4-(diethylamino)benzylidene]hydrazinecarbothioamide
(Scheme 1, 1a) and (2E)-2-[4-(dimethylamino)benzylidene]hydra-
zinecarbothioamide (Scheme 1, 1b) [11] were prepared by litera-
ture methods, as was anti-chloroglyoxime (Scheme 1, 1c) [17].
4.2. Synthesis of L1H2 and L2H2
A
solution of (2E)-2-[4-(diethylamino)benzylidene]hydra-
zinecarbothioamide (1a) (1 mmol) or a solution of (2E)-2-[4-
(dimethylamino)benzylidene]hydrazinecarbothioamide (1b) in
absolute ethanol 30 mL was added dropwise to a solution of anti-
chloroglyoxime (1c) (1 mmol) in absolute ethanol 10 mL for a
30 min period. The reaction mixture was stirred overnight at room
temparature. After cooling to 0 °C the pH of the mixture was raised
to 5.0–5.5 with treatment with NaHCO3 dissolved in 5 mL distilled
water, and stirring was continued for one hour. The solution was
poured into 100 mL cold water with stirrring. After the end of
the period, yellow precipitated solid was filtered, washed thor-
oughly with distilled water and dried. The chemical reaction and
molecular structure are shown in Scheme 1.
3. Conclusions
4.3. Synthesis of the Ni(II), Cu(II) and Co(II) complexes of ligands
In this study, novel vic-dioxime ligands (L1H2 and L2H2) con-
taining thiosemicarbazone groups and novel mononuclear com-
plexes [Ni(II), Cu(II), and Co(II)] were synthesized. In addition,
the antiproliferative effects of these compounds on neoplastic cells
were demonstrated using human HL-60 promyelocytic leukemia
cells.
A solution of a metal salt (1 mmol of NiCl2ꢁ6H2O, CoCl2ꢁ6H2O
and CuCl2ꢁ2H2O) in 20 mL of water were added to 2 mmol of the
ligand solution (0.672 g L1H2 or 0.616 g L2H2 in 30 mL of ethanol)
with stirring. An initial sharp decrease in the pH of the solution
from 5.5 to about 3–3.5 is observed. After raising the pH to
5.0–5.5 using 1% aqueous NaOH solution, the reaction mixture

_
98
I. Babahan et al. / Bioorganic Chemistry 53 (2014) 92–98
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in
a vacuum oven. Structure of complexes are shown in
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4.4. Pharmacology
4.4.1. Cell culture
HL-60 promyeloic leukaemia cells were purchased from ATCC.
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½ðC72 h þ drug ꢀ C24 h þ drugÞ=ðC72 h ꢀ drug ꢀ C24 h ꢀ drugÞꢄ
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