Synthesis and anticancer activities of a novel class of mono- and di-metallic Pt(II)(salicylaldiminato)(DMSO or Picolino)Cl complexes

Article abstract of DOI:10.1039/c4dt03018d

A series of novel Pt(ii) complexes [cis- and trans-Pt(ii)(salicylaldimine)(DMSO)Cl (C-1), trans-Pt(ii)(salicylaldimine)(4-picoline)Cl (C-2), Pt(ii)(salicylaldimine)Cl (C-3), trans- and cis/trans-Pt₂(ii)(salicylaldimine)(DMSO)₂Cl

Full text of DOI:10.1039/c4dt03018d

Dalton
Transactions
View Article Online
View Journal
PAPER
Synthesis and anticancer activities of a novel class
of mono- and di-metallic Pt(II)(salicylaldiminato)-
(DMSO or Picolino)Cl complexes†
Cite this: DOI: 10.1039/c4dt03018d
Faiz-Ur Rahman,a Amjad Ali,b Rong Guo,a Yun-Chang Zhang,a Hui Wang,*a
Zhan-Ting Lia and Dan-Wei Zhang*a
A series of novel Pt(II) complexes [cis- and trans-Pt(II)(salicylaldimine)(DMSO)Cl (C-1), trans-Pt(II)(salicylal-
dimine)(4-picoline)Cl (C-2), Pt(II)(salicylaldimine)Cl (C-3), trans- and cis/trans-Pt2(II)(salicylaldimine)
(DMSO)2Cl2 (C-4), trans-Pt2(II)(salicylaldimine)(4-picoline)2Cl2 (C-5) was synthesized and characterized.
The structures of C-1-cis, C-1-trans and C-3 were determined using a single crystal X-ray analysis. This
class of Pt(II) complexes has been studied for their in vitro cytotoxicity in multiple human cancer cell lines,
including breast (MCF-7), liver (HepG2), lung (A549), colon (HCT116) and cervical (Hela) cancers. C-1-
trans, C-2 and C-4-trans showed significant cytotoxicity to these cancer cells comparable to cisplatin.
A time- and dose-dependent MTT assay revealed that these complexes can suppress cell viability and cell
proliferation. Mechanistically these complexes induced pro-apoptotic gene expression such as BAX,
PUMA and NOXA and thereby enhanced apoptosis. Moreover, PARP cleavage in a dose-dependent
manner indicated their cytotoxic effect against cancer cells. Apoptosis of cancer cells occurred through
apoptotic pathways as explained by the cytometry analysis. The DNA unwinding properties of these active
Pt(II) complexes were studied by gel electrophoresis using pBR322 plasmid DNA as a target. Changes in
the morphology of cancer cells were also observed upon the addition of C-1-trans, C-2 and C-4-trans.
Received 30th September 2014,
Accepted 5th December 2014
DOI: 10.1039/c4dt03018d
www.rsc.org/dalton
researchers to discovering other platinum-based, easily synthe-
sizable, stable and less toxic anticancer agents.20–24 The struc-
Introduction
Cytotoxic chemotherapy is still the mainstay for cancer treat- tures and different functional groups attached to platinum
ment; many groups have shown significant benefits of cyto- play a vital role in the cytotoxic activity as well as in the side
toxic chemotherapy against multiple cancers.1–6 Over the last effects. Thus, a number of new complexes with different
five decades a large number of transition metal complexes attached groups and structural aspects have been investigated
have been investigated for their in vitro and in vivo cytotoxic with improved cytotoxicity and minimal side effects in cancer
activities.7–12 Platinum-based chemotherapeutic agents are a patients.25,26 The main development in these newly syn-
subject of growing interest in preclinical and clinical trials thesized Pt complexes involved the replacement of either one
showing
their
promising
activities
in
cancer NH3 with another monodentate N-donor ligand or both NH3
chemotherapy.13–17 Cisplatin (cis-Pt(NH3)2Cl2) has been clini- with a bidentate ligand.27 The second approach used was the
cally administered for quite a while since its first report in the substitution of Cl− by carboxylate units, as in carboplatin and
1960s.18,19 Its successful clinical applications and its known other similar derivatives.28 The utilization of both strategies
side effects (nephrotoxicity vomiting, neurotoxicity, ototoxicity, has led to the replacement of NH3 and Cl− ligand(s)29 with car-
loss of sensation in the hands, bone marrow suppression, boxylate, as in oxaliplatin.30–32 Similarly, anticancer agents
haemolysis etc. in cancer patients) have directed the interest of derived by the replacement of amine or Cl− ligand(s) of cispla-
tin by other potential drugs were also investigated.33,34
Pt(II) Schiff base complexes are famous phosphorescence
aDepartment of Chemistry, Fudan University, 220 Handan Road, Shanghai 200433,
agents having rigid and stable structures.35 There are fewer
China. E-mail: zhangdw@fudan.edu.cn, wanghui@fudan.edu.cn;
literature reports about their anticancer properties.36 The
Schiff base O^N^N^O donor ligand in the complex was separ-
Tel: +86 21 65643576
bInstitute of Biomedical Sciences, School of Life Sciences, East China Normal
University, 500 Dongchuan Road, Shanghai 200241, China
ated into two bidentate O^N donor ligands using long chain
†Electronic supplementary information (ESI) available: For NMR, ESI-MS
spacers, and highly phosphorescent dinuclear Pt(II) complexes
spectra, and stability analysis spectra. CCDC 1026340 (C-1-trans), 1016359 (C-1-
were prepared.37,38 Using this bidentate O^N donor Schiff base
cis) and 1016409 (C-3). For ESI and crystallographic data in CIF or other elec-
ligand, Pt(II) complexes with O^N^S and O^N^P mixed ligands
tronic format see DOI: 10.1039/c4dt03018d
This journal is © The Royal Society of Chemistry 2014
Dalton Trans.

View Article Online
Paper
Dalton Transactions
have been reported, in which other co-ligands bearing S or P isomers while C-3 was a single compound. The mixture of C-1
were used as electron donor species.39 Related new (salicylaldi- was further transformed into C-2 as a single isomer, and C-4
minato)Pt(II) complexes with cyclooctene co-ligands were also was transformed into C-5. The mixtures of isomers can be sep-
reported. These complexes did not show any good activity in arated using preparative thin layer chromatography. cis- and
human tumors, but have proved to be effective in brain trans-isomers were isolated for C-1 and trans- and cis/trans-
cancer.40
isomers were formed in the case of C-4. All these complexes
1
Here, we have reported the syntheses of novel Pt(II) com- were characterized by H NMR, 13C NMR, positive ESI-MS and
plexes [cis- and trans-Pt(II)(salicylaldimine)(DMSO)Cl (C-1), single crystal X-ray crystallography (for C-1-cis, C-1-trans, and
trans-Pt(II)(salicylaldimine)(4-picoline)Cl (C-2), Pt(II)(salicylaldi- C-3).
mine)Cl (C-3), trans- and cis/trans-Pt2(II)(salicylaldimine)-
C-1-cis was identified from its large JPt–H value (88 Hz) of
(DMSO)2Cl2 (C-4), trans-Pt2(II)(salicylaldimine)(4-picoline)2Cl2 imine proton, while that of C-1-trans was 60 Hz.39,44 The
(C-5)] with gradual structural changes. The cytotoxicities of other substantial differences between C-1-cis and C-1-trans
these complexes were screened. MTT assay studies described were the chemical shifts of DMSO methyl protons: for the cis-
the anticancer activities of these rigidly attached salicylaldi- isomer it was 3.58 ppm and for the trans-isomer it was
mine and easily replaceable N or S donor co-ligands based 3.36 ppm. The imine proton signal for the cis-isomer
mono- and di-metallic Pt(II) complexes. C-1-trans, C-2 and C-4- (7.59 ppm) was observed a little upfield as compared to the
trans showed significant cytotoxicities while the other four trans-isomer (7.74 ppm). An imine proton peak of C-2 was
complexes were inactive. From combined experimental results, observed at 7.66 ppm with a JPt–H value of 56 Hz, which
the structural effect on cytotoxicity was discussed.
suggested the formation of the trans-isomer only. The imine
proton signal of C-3 was observed at 7.67 ppm with a JPt–H
value of 80 Hz, which indicated that Cl− was trans to imine
nitrogen. The 1H NMR of C-4-trans showed only one set of
imine and DMSO signals, which showed that C-4-trans was a
symmetric compound. The imine proton signal of C-4-trans
was observed at 7.61 ppm with a JPt–H value of 52 Hz, proving
DMSO to be attached trans to imine nitrogen. In the case of
C-4-cis/trans two singlet imine proton signals were observed at
7.54 and 7.48 ppm, respectively. Due to the overlap and broad-
ening of the peaks, it was difficult to calculate JPt–H values. The
configuration of this isomer of C-4 was characterized to be
Results and discussion
Synthesis and characterization
The syntheses of complexes C1–5 are shown in Scheme 1.
First, ligands L1–3 were prepared by general imine synthesis
methods from the reaction of aldehydes 1 or 2 with the corres-
ponding primary amine, respectively. Then the ligands were
converted to C-1, C-3, and C-4 by reacting with K2PtCl4 in the
presence of NaOAc.41–43 C-1 and C-4 were configuration
Scheme 1 Preparation of Pt(II) complexes C-1-cis, C-1-trans, C-2, C-3, C-4-trans, C-4-cis/trans and C-5.
Dalton Trans.
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
cis/trans using 2D NOESY spectra. The structure of C-5 was
confirmed by 1H NMR and only one symmetric isomer was
obtained. A JPt–H value of 48 Hz indicated that C-5 possesses a
trans configuration.
Table 1 Selected bond lengths (Å), angles (°) and torsion angles (°) of
C-1-cis, C-1-trans, and C-3
Entry
Bond/angle
C-1-cis
C-1-trans
C-3
1
2
3
4
5
6
7
8
Pt–N1
Pt–O
Pt–S/N2
Pt–Cl
∠N1PtO
∠AcPtAta
∠OPtAt
∠N1PtAc
∠N1PtAt
∠OPtAc
∠C1OPtAc
∠C1OPtAt
∠OPtN1C8
2.015(5)
2.018(5)
2.2035(18)
2.3018(18)
87.9(2)
88.81(7)
85.47(13)
97.76(16)
173.42(16)
173.54(14)
–106.18
2.039(6)
1.963(6)
2.2399(19)
2.294(2)
92.7(3)
89.87(8)
83.96(18)
93.5(2)
176.61(19)
173.39(19)
156.04
177.17
179.66
1.983(13)
1.970(12)
2.088(15)
2.315(4)
92.1(5)
88.2(5)
82.6(4)
Crystallography
X-ray quality crystals of C-1-cis, C-1-trans, and C-3 were
obtained by slow evaporation of CH2Cl2 solutions of these
complexes. The ORTEP diagrams of these complexes are
shown in Fig. 1. Two conformers were detected for C-1-cis and
C-1-trans, respectively (Table 1). C-1-cis was crystallized in
monoclinic pattern, C-1-trans in triclinic pattern, and C-3 in
orthorhombic pattern, whereas Pt got a square planar environ-
ment. For all three complexes, the sum of bond angles around
Pt was ca. 360° (Table 1, entries 5–8). The angle of N–Pt–Ac
(the atom possesses cis configuration to the N atom) was
found to be the biggest of all and that of O–Pt–At (the atom
possesses trans configuration to N) was the smallest one. The
differences in the structure of these three complexes came
from the dihedral angles around the O–Pt bond (Table 1,
entries 11–13). The dihedral angle of C1–O–Pt–Ac is gauche-
like for C-1-cis and anti for C-1-trans and C-3. Compared to the
bond lengths of C-1-cis and C-1-trans, the Pt–S length of C-1-cis
is shorter than that of C-1-trans (Table 1, entry 3). This means
that the coordination of the DMSO ligand with the Pt metal is
weaker in C-1-trans than that of C-1-cis.
97.1(6)
9
174.7(4)
170.7(6)
172.65
166.24
–171.30
10
11b
12b
13b
–133.92
141.48
a Ac represents the atom cis to N1 and At represents the atom trans to
N1. b Dihedral angle.
Anticancer activities
We examined the effect of these complexes on the viability of
five selected human tumor cell lines. These cancer cells were
incubated with Pt(II) complexes C1–5 and cisplatin (as a
control). An MTT assay showed that C-1-trans, C-2 and C-4-
trans decreased the growth of these cancer cells (Fig. 2A). MTT
assay results of C-1 and C-4 showed that, in Pt(II)–ONS mixed
Fig. 2 MTT assay with DMSO and cisplatin (10 µM) as control com-
pounds. (A) Cytotoxicity screening of all seven complexes synthesized in
this study in multiple cancer cells that were incubated at the complex
concentration of 10 µM. (B) MCF-7 incubated with C-1-trans, C-2, and
C-4-trans (10 µM) and a time-dependent MTT assay was performed. (C)
MCF-7 incubated with C-1-trans, C-2 and C-4-trans at different concen-
trations of 0, 5, 10, and 20 µM, respectively, and MTT assay was
performed.
Fig. 1 ORTEP plot of C-1-cis, C-1-trans, and C-3 at 50% probability. For
C-1-cis and C-1-trans only one conformer was presented.
This journal is © The Royal Society of Chemistry 2014
Dalton Trans.

View Article Online
Paper
Dalton Transactions
ligand complexes, only the trans-isomer was active. Similarly,
in this study, C-3 did not show any cytotoxic activity. The active
nature of C-1-trans and C-2 and the non-active nature of C-3
could possibly be explained by the DNA interaction mechan-
ism of these complexes. In the light of the previous published
reports describing the interaction of Pt(II) complexes with
DNA,20,23,45–48 the most important point for an active Pt(II)
complex was: the complex must have two cis labile groups
which could be easily replaced by DNA to form a C–DNA
adduct.25 So we assumed that the DNA interaction mechanism
of these complexes should be the removal of the Cl− ligand to
result in the first DNA-complex attachment and in turn the
removal of DMSO (in the case of C-1-trans and C-4-trans) or
4-picoline (in case of C-2) for the second attachment. Keeping
in view the mechanism and the experimental results it is easy
to predict the inactive nature of C-3. We assumed that C-3
interacts with DNA and gave the first C-3–DNA adduct with the
removal of the ancillary Cl ligand. In principle it should go
through the second DNA interaction, for which there are two
possibilities: firstly the breaking of the Pt–N2 coordinate
covalent bond and secondly the breaking of the Pt–O covalent
bond, but due to the stronger nature of these two bonds neither
of these interactions takes place, so C-3 was inactive. The poss-
ible reason for the non-active nature of C-5 implies a stronger
Pt–picoline bond as compared to its monometallic counterpart
C-2 that inhibits C-5–DNA interaction, so the removal of the
4-picoline from the metal coordination sphere by DNA did not
result; therefore it showed no cytotoxic activities.
Notably the cytotoxic effect observed was comparable to cis-
platin, which showed nearly the same level of cytotoxicity to all
these tested cancer cells. We performed a time-dependent
MTT assay in human breast cancer cell lines. It was observed
that the cytotoxic effect was distinct during 0–24 hours and
then decreasing during 24–72 hours (Fig. 2B) and it was com-
parable to cisplatin at different time intervals.
To determine the maximum effective concentration which
could suppress cell growth, we incubated C-1-trans, C-2 and
C-4-trans of different concentrations with breast cancer cells
and performed a dose-dependent MTT assay. Each complex at
20 µM concentration caused significant cell death (Fig. 2C).
These results also indicated that small concentrations of these
complexes can also produce significant apoptosis.
Table 2 In vitro cytotoxicity against selected human tumor cell lines of
complexes C-1-trans, C-2, and C-4-trans
IC50 (µM)
Complex
MCF-7a
A549b
Cisplatin
C-1-trans
C-2
5.6 0.6
6.1 0.9
7.1 0.7
6.6 0.5
4.8 0.2
6.5 0.5
7.5 0.8
6.9 1.2
C-4-trans
a Human breast carcinoma cell. b Human lung cancer cell.
trans was checked by real-time PCR (RT-PCR) and the mRNA
levels of these genes were detected (Fig. 3). These complexes
induced the expression of these genes to cause genotoxic
stress, which was comparable to cisplatin, while C-1-cis did
not. These results showed their genotoxic stress enhancing
abilities, which is an important property of chemotherapeutic
agents to cause apoptosis.
The PARP protein is an indicator for apoptosis induction.52
PARP cleavage increases with increasing apoptosis. We also
incubated MCF-7 cells with different concentrations of C-1-
trans, C-2, and C-4-trans for 24 hours and an immunoblot was
performed to detect the PARP level. It was observed that PARP
cleavage was enhanced by these complexes in a dose-depen-
dent manner (Fig. 4A–C). Similarly PARP cleavage levels of C-1-
trans and C-4-trans were much stronger than C-2. The PARP
cleavage level at 5 µM for C-4-trans was higher than that for
C-1-trans, suggesting that C-4-trans induces more PARP clea-
vage at this concentration. However the PARP cleavage at
10 µM for these three complexes was nearly the same, and
maximum PARP cleavage was observed at 20 µM. Thus, these
complexes also possess the ability to cleave the PARP protein
and cause DNA damage.
The distribution of cancer cells upon addition of C-1-cis,
C-1-trans, C-2, and C-4-trans was analysed by flow cytometry.
An annexin V/propidium iodide assay was performed in MCF-7
cells by incubating them with these complexes at 20 µM con-
We also determined the IC50 values of these active com-
plexes and cisplatin in breast and lung cancer cells (Table 2).
The IC50 values indicated that the cytotoxicity was nearly
similar to cisplatin. Among these complexes, C-1-trans showed
higher cytotoxicity than C-2 and C-4-trans. In addition, C-4-
trans was more cytotoxic to cancer cells in comparison with
C-2. From these experimental results we found that these novel
complexes possess significant anticancer properties in selected
human cancer cells.
Apoptosis is a programmed cell death operated by anti-
apoptotic and pro-apoptotic genes in response to genotoxic
stress. Several genes are involved in this process including
BAX, NOXA and PUMA.49–51 The enhanced expression of these
Fig. 3 Pro-apoptotic gene expression induced by C-1-cis, C-1-trans,
C-2 and C-4-trans. MCF-7 cells were incubated with these complexes at
the concentration of 10 µM. Total RNA was extracted and RT-PCR was
performed to detect the mRNA expression of different genes after
genes in response to the addition of C-1-trans, C-2, and C-4- 24 hours. Cisplatin (10 µM) was used as a control.
Dalton Trans.
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
Fig. 4 (A–C) (Left panel) Human MCF-7 was incubated with C-1-trans,
C-2 and C-4-trans for the indicated concentrations and PARP cleavage
was detected by immunoblot. B-actin was used as the loading control.
(Right panel) Relative quantification of cleaved PARP levels.
centration for 24 hours and subjecting to a flow cytometric
analysis (Fig. 5). Q1-2 represents unnatural death, Q2-2 rep-
resents necrotic cells, Q3-2 represents normal cells and Q4-2
indicates apoptotic cells upon genotoxic stress. We observed
higher percentage of cell death by C-1-trans, C-2, and C-4-trans.
The cell death percentage of C-1-trans was comparable to cis-
platin. However, the ratio of cell death of C-2 and C-4-trans was
lower than that of C-1-trans and cisplatin. These results
implied that these complexes affect the distribution of cancer
cells and cause cell death.
Fig. 5 Human MCF-7 cells were incubated with the mentioned com-
plexes at the concentration of 20 µM and subjected to flow cytometric
analysis, DMSO and cisplatin were used as controls.
The interaction of C-1-trans, C-2, and C-4-trans with DNA
was studied using pBR322 plasmid DNA as a target. 20 µM each
of these complexes was incubated with pBR322 DNA, and gel
electrophoresis was performed. Fig. 6 clearly shows that DNA
incubated with cisplatin and these active complexes migrated
more slowly than the DNA incubated with DMSO. This con-
firmed the DNA–metal interaction and resulted in a slow
migration of form II of plasmid DNA. In conclusion, a strong
interaction exists between these complexes and DNA and this is
an important property for causing effective apoptosis.
Changes in morphology of cancer cells upon the addition
of some chemotherapeutic agents are common and important
features of most tumor cells.53–55 We studied the changes in
morphological features of cancer cells upon the addition of
C-1-trans, C-2, and C-4-trans. MCF-7 cells were incubated with
20 µM of each of these complexes for 12 hours and a cell mor-
phology assay was performed. Prominent shape changes were
observed in the microscopic images of these cancer cells
(Fig. 7). It was clear that cancer cells treated with DMSO were
healthier and less elongated while the cancer cells treated with
Fig. 6 Interaction with pBR322 plasmid DNA. Cisplatin and other com-
plexes (20 µM) were incubated with pBR322 plasmid DNA and a gel
electrophoresis was performed. DMSO was used as a negative control
and cisplatin as a positive control.
Pt(II) complexes and cisplatin were more elongated and less
healthy. These results indicated the effect of these complexes
on morphological changes of cancer cells and this pheno-
menon may also contribute to cell apoptosis.
Conclusion
In summary, mono- and di-metallic Pt(II)(salicylaldiminato)
(DMSO or Picolino)Cl complexes were synthesized by efficient
procedures. The structures of these complexes were character-
ized by NMR, ESI-MS and single crystal X-ray crystallography. A
cytotoxicity assay of these complexes revealed that three of
This journal is © The Royal Society of Chemistry 2014
Dalton Trans.

View Article Online
Paper
Dalton Transactions
Limited. Preparative thin layer chromatography (TLC) was per-
formed on precoated silica gel plates (0.4–0.5 mm thick). 1H
and 13C NMR analyses were conducted using a Bruker AVANCE
III HD 400 MHz spectrophotometer at room temperature
(298 K) in CDCl3 or DMSO-d6. Positive ion mass spectra
(ESI-MS) were obtained on a Bruker micrOTOF II. X-ray data
were collected on a Bruker APEX DUO diffractometer with
graphite-monochromatized Mo Kα radiation (λ = 0.71073 Å).
Multiscan absorption corrections (SADABS) were applied to
the data. The structure was solved by direct methods using a
beta-test version of SHELX.56 The positions of carbon-bound
hydrogen atoms were calculated and refined as riding on the
parent carbon atoms with UH = 1.2UC.
Preparation and characterization
Synthesis of ligand L1.
2-Hydroxybenzaldehyde (244.2 mg, 2.0 mmol), 2-methyl-1-pro-
panamine (175.0 mg, 2.4 mmol) and anhydrous Na2SO4
(200 mg) were taken in 15 mL of toluene and stirred at 70 °C
for 4 hours. On completion (checked by TLC using 10% ethyl
acetate–n-hexane as an eluent) the reaction mixture was fil-
tered, vacuum evaporated and dried using an oil pump to
afford a yellow oil in quantitative yield. 1H NMR (400 MHz,
CDCl3) δ 13.74 (s, 1H, Hh), 8.31 (s, 1H, Hi), 7.31 (t, J = 7.8 Hz,
1H, H3), 7.26 (d, J = 7.6 Hz, 1H, H2), 6.97 (d, J = 8.0 Hz, 1H,
H5), 6.87 (t, J = 7.8 Hz, 1H, H4), 3.43 (d, J = 6.4 Hz, 2H, H7),
2.04–1.91 (m, 1H, H8), 0.99 (d, J = 6.7 Hz, 6H, H9). 13C NMR
(100 MHz, CDCl3) δ 164.7 [Ci], 161.5 [C1], 132.1, 131.1, 118.8,
118.4, 117.1 [C2–6], 67.5 [C7], 29.6 [C8], 20.5 [C9].
Fig. 7 Human MCF-7 cells were incubated with different Pt(II) com-
plexes (20 µM) for 12 hours and subjected to a microscopic analysis.
DMSO and cisplatin (20 µM) were used as controls.
these complexes (C-1-trans, C-2, and C-4-trans) have good cyto-
toxicity against breast, lung, liver, colon and cervical human
cancer cell lines. 5–20 μM of these complexes showed
maximum activity between 0–24 hours. The low concentration
and short time for the cytotoxic effect indicated their potency
in cytotoxicity. These active complexes enhanced pro-apoptotic
gene expression by following pro-apoptotic pathways. They
enhanced PARP cleavage, which means that they follow the
caspase signalling and lead to cell apoptosis. The C-1-trans,
C-2 and C-4-trans DNA interaction assay using pBR322 plasmid
DNA clearly indicated the formation of the DNA–Pt complex.
Moreover, a flow cytometric analysis and a morphological
change study of cancer cells showed these complexes to be
active cytotoxic agents. This study provided a possible way of
designing Pt(II) complex chemotherapeutic agents.
Synthesis of ligand L2.57
2-Hydroxybenzaldehyde (244.2 mg, 2 mmol) and N,N-dimethyl
propane-1,3-diamine (225 mg, 2.2 eq.) were mixed while the
remaining procedure was the same as that for L1. 1H NMR
(400 MHz, DMSO-d6) δ 13.58 (s, 1H, Hh), 8.53 (s, 1H, Hi), 7.41
(d, J = 7.6 Hz, 1H, H2), 7.34–7.26 (m, 1H, H3), 6.90–6.82 (m,
2H, H4,5), 3.59 (t, J = 6.4 Hz, 2H, H7), 2.24 (t, J = 7.1 Hz, 2H,
H9), 2.11 (s, 6H, H10), 1.79–1.68 (m, 2H, H8).
Synthesis of ligand L3.
Experimental
General
All analytical grade solvents and reagents were purchased from
commercial sources and used without further purification
unless otherwise mentioned. K2PtCl4 was purchased from
Sinopharm Chemical Company. pBR322 plasmid DNA was 4,6-Dihydroxy-5-methyl-1,3-benzenedicarboxaldehyde (180 mg,
purchased from Beijing Think-Far Technology Company 1 mmol), 2-methyl-1-propanamine (175 mg, 2.4 eq.), and
Dalton Trans.
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
Na2SO4 (200 mg) were taken in 20 mL of anhydrous CH2Cl2. 160.6 [Ci], 135.5, 134.3, 119.7, 119.3, 117.1 [C2–6], 70.2 [C7],
The mixture was stirred under reflux for 4 hours (checked by 41.5 [Cd], 30.0 [C8], 19.5 [C9].
TLC, 20% ethyl acetate–n-hexane as an eluent). On reaction
completion, the mixture was cooled to room temperature and
filtered to remove the undissolved solid which was further
washed with CH2Cl2. The filtrate was vacuum evaporated to
afford an orange gummy material that was redissolved in
10 mL of n-hexane and put in a freezer overnight. The crystal-
line solid precipitated was filtered, further washed with cold
n-hexane and vacuum dried to afford a yellow solid in 83%
yield (241.0 mg, 0.83 mmol). 1H NMR (400 MHz, CDCl3)
δ 14.68 (s, 2H, Hh), 8.10 (s, 2H, Hi,i′), 6.99 (s, 1H, H2), 3.36 (d,
J = 6.4 Hz, 4H, H7,7′), 2.15 (s, 3H, H10), 2.04–1.79 (m, 2H, H8,8′),
0.99 (d, J = 6.7 Hz, 12H, H9,9′). 13C NMR (100 MHz, CDCl3)
δ 166.2 [C1,3], 163.7 [Ci,i′], 133.9 [C2], 112.5 [C4,6], 111.0 [C5],
65.6 [C7,7′], 29.6 [C8,8′], 20.4 [C9,9′], 7.3 [C10]. HRMS (ESI): Calcd
for C17H27N2O2: 291.2072 [M + H]+, Found: 291.2091.
Preparation of C-2.
A C-1-cis/trans mixture (24.2 mg, 0.05 mmol) was dissolved in
3 mL of CH2Cl2 in a 5 mL glass vial, and 4-picoline (9.3 mg,
0.1 mmol, 2 eq.) was added to it, capped tightly and stirred at
room temperature for two days till completion (checked by TLC
developed with 20% ethyl acetate–n-hexane). The mixture was
filtered through a 5 × 1.3 cm silica column rinsed in CH2Cl2.
The filtrate collected was rotary evaporated. The pure yellow
solid C-2 was obtained in 83% yield (20.1 mg, 0.040 mmol). 1H
NMR (400 MHz, CDCl3) δ 8.68 (d, J = 6.4 Hz, 2H, H10), 7.66 (s,
JPt–H = 56 Hz, 1H, Hi), 7.35 (t, J = 7.7 Hz, 1H, H3), 7.29 (d, J = 7.8
Hz, 1H, H2), 7.17 (d, J = 6.4 Hz, 2H, H11), 6.89 (d, J = 8.5 Hz, 1H,
H5), 6.63 (t, J = 7.2 Hz, 1H, H4), 3.85 (d, J = 6.8 Hz, 2H, H7),
2.59–2.45 (m, 1H, H8), 2.41 (s, 3H, H13), 0.94 (d, J = 6.7 Hz, 6H,
H9). 13C NMR (100 MHz, CDCl3) δ 162.4 [C1], 158.5 [Ci], 151.6
[C10], 150.2 [C12], 134.2 [C2], 133.8 [C3], 125.6 [C11], 120.4 [C6],
119.6 [C4], 116.3 [C5], 72.1 [C7], 29.8 [C13], 21.1 [C8], 19.6 [C9].
HRMS (ESI): Calcd for C17H22ClN2OPt: 500.1068 [M + H]+,
Found: 500.1078. Anal. found (Calcd) for C17H22ClN2OPt: C,
40.35 (40.84); H, 4.28 (4.23); N, 5.49 (5.60).
Synthesis of Pt(II) complexes
Preparation of C-1-cis and C-1-trans.
L1 (17.7 mg, 0.1 mmol), K2PtCl4 (41.5 mg, 0.1 mmol), and
NaOAc (8.2 mg, 0.1 mmol) were reacted in 10 mL MeOH–
DMSO (20 : 1). After stirring for 18 h at reflux the yellow reac-
tion mixture was evaporated to dryness; the yellow gummy
material obtained was dissolved in CH2Cl2, washed thoroughly
with deionized water, dried using Na2SO4 and vacuum evapor-
Preparation of C-3.
ated to afford
a yellow solid. HRMS (ESI): Calcd for
C13H21ClNO2PtS: 485.0629 [M + H]+, Found: 485.0643. Anal.
found (Calcd) for C13H21ClNO2PtS: C, 32.05 (32.20); H, 4.19
(4.16); N, 2.82 (2.89). The cis/trans mixture was further sub-
jected to preparative thin layer chromatography developed with
a 0.5% MeOH–CH2Cl2 mixture. The two main bands of the
preparative TLC were scratched separately and washed with a L2 (10.3 mg, 0.05 mmol), K2PtCl4 (20.75 mg, 0.05 mmol), and
1% MeOH–CH2Cl2 mixture. The top band contained C-1-cis NaOAc (4.1 mg, 0.05 mmol) were reacted in 10 mL of MeOH–
and the down band consisted of C-1-trans with an isomeric DMSO (20 : 1) for 18 h at reflux. After evaporation the yellow
ratio of 24 : 76. The overall cis/trans yield recovered was 62% gummy material obtained was dissolved in CH2Cl2, washed
(30.1 mg, 0.062 mmol). C-1-cis: 1H NMR (400 MHz, CDCl3) with deionized water, dried and vacuum evaporated to afford a
δ 7.59 (s, JPt–H = 88 Hz, 1H, Hi), 7.39 (t, J = 7.9 Hz, 1H, H3), 7.23 yellow solid, which was filtered through a 5 × 1.3 cm silica
(d, J = 7.9 Hz, 1H, H2), 7.10 (d, J = 8.5 Hz, 1H, H5), 6.68 (t, J = column rinsed in a 1% MeOH–CH2Cl2 mixture. The filtrate col-
8.4 Hz, 1H, H4), 4.01 (d, J = 7.0 Hz, 2H, H7), 3.58 (s, 6H, Hd), lected was vacuum evaporated. Pure C-3 was obtained in 69%
2.40–2.24 (m, 1H, H8), 0.97 (d, J = 6.7 Hz, 6H, H9). 13C NMR yield (15.1 mg, 0.035 mmol) as a yellow solid. 1H NMR
(100 MHz, CDCl3) δ 163.0 [C1], 161.5 [Ci], 136.0, 133.0, 120.4, (400 MHz, CDCl3) δ 7.67 (s, JPt–H = 80 Hz, 1H, Hi), 7.32 (t, J =
120.3, 117.2 [C2–6], 71.8 [C7], 47.3 [Cd], 32.3 [C8], 19.7 [C9]. C-1- 6.9 Hz, 1H, H3), 7.04 (d, J = 8.6 Hz, 1H, H2), 7.00 (d, J = 8.4 Hz,
1
trans: H NMR (400 MHz, CDCl3) δ 7.74 (s, JPt–H = 60 Hz, 1H, 1H, H5), 6.51 (t, J = 7.3 Hz, 1H, H4), 3.81 (t, J = 7.9 Hz, 2H, H7),
Hi), 7.39 (t, J = 8.0 Hz, 1H, H3), 7.29 (d, J = 8.0 Hz, 1H, H2), 6.98 3.11 (s, 6H, H10), 2.72–2.56 (m, 2H, H9), 2.01–1.91 (m, 2H, H8).
(d, J = 8.1 Hz, 1H, H5), 6.70 (t, J = 8.0 Hz, 1H, H4), 3.88 (d, J = 13C NMR (100 MHz, CDCl3) δ 162.7 [C1], 158.5 [Ci], 134.5,
6.8 Hz, 2H, H7), 3.36 (s, 6H, Hd), 2.45–2.29 (m, 1H, H8), 0.92 132.8, 121.0 [C2–4], 119.6 [C6], 116.1 [C5], 66.0 [C7], 60.9 [C9],
(d, J = 6.7 Hz, 6H, H9). 13C NMR (100 MHz, CDCl3) δ 162.1 [C1], 55.4 [C10], 26.2 [C8]. HRMS (ESI): Calcd for C12H18ClN2OPt:
This journal is © The Royal Society of Chemistry 2014
Dalton Trans.

View Article Online
Paper
Dalton Transactions
436.0755 [M + H]+, Found: 436.0765. Anal. found (Calcd) for 4H, H11,11′), 7.45 (s, JPt–H = 48 Hz, 2H, Hi,i′), 7.23 (s, 1H, H2),
C12H18ClN2OPt: C, 32.92 (33.07); H, 3.94 (3.93); N, 6.32 (6.43).
Preparation of C-4-trans and C-4-trans/trans.
7.15 (d, J = 6.5 Hz, 4H, H12,12′), 3.75 (d, J = 6.7 Hz, 4H, H7,7′),
2.57–2.43 (m, 2H, H8,8′), 2.40 (s, 6H, H14,14′), 1.92 (s, 3H, H10),
0.94 (d, J = 6.7 Hz, 12H, H9,9′). 13C NMR (100 MHz, CDCl3) δ
164.2 [C1,3], 158.2 [Ci,i′], 151.5 [C11,11′], 150.2 [C2], 141.0
[C13,13′], 125.6 [C4,6], 125.4 [C12,12′], 115.3 [C5], 71.5 [C7,7′], 29.8
[C14,14′], 21.1 [C8,8′], 19.6 [C9,9′], 9.6 [C10]. HRMS (ESI): Calcd for
C29H39Cl2N4O2Pt2: 935.1746 [M + H]+, found: 935.1703. Anal.
found (Calcd) for C29H39Cl2N4O2Pt2: C, 36.90 (37.22); H, 4.11
(4.09); N, 5.89 (5.99).
Stability of Pt(II) complexes
L3 (14.5 mg, 0.05 mmol), K2PtCl4 (41.4 mg, 0.1 mmol), and
NaOAc (8.2 mg, 0.1 mmol) were taken in 15 mL of MeOH– The stability of a chemotherapeutic agent is crucial in a cyto-
toxic study, so we checked the stabilities of C-1-trans and C-2
DMSO (20 : 1). After stirring for 18 hours at reflux the reaction
mixture was cooled to room temperature. A yellow solid separ-
using 1H NMR techniques in the same solvent in which the
ated from the reaction mixture was filtered, washed with biological study was conducted. The comparative spectra are
given in the ESI† which showed that these compounds are
quite stable under the mentioned conditions.
methanol and dried. The product was a mixture of two main
isomers of trans and cis/trans geometry (from TLC). HRMS
(ESI): Calcd for C21H36Cl2N2O4Pt2S2K: 943.0426 [M + K]+,
Found: 943.0402. Anal. found (Calcd) for C21H36Cl2N2O4Pt2S2:
C, 27.65 (27.85); H, 4.13 (4.01); N, 2.94 (3.09). The trans and
Biological study
Real time PCR (RT-PCR). RT-PCR was performed as
cis/trans mixture was further applied to preparative TLC develo- described previously.58 Total RNA from cells was isolated using
TRIZOL (Invitrogen) following the manufacturer’s protocol.
Briefly, 0.5–1 µg of total RNA was reverse transcribed in a total
ped with a 3% MeOH–CH2Cl2 mixture. The top layer of the pre-
parative TLC was scratched and washed with 3% MeOH–
CH2Cl2, which resulted in C-4-cis/trans, while the bottom layer volume of 25 µL, including 132 units of Moloney-murine-
leukemia virus reverse transcriptase, 26.4 units of the RNase
inhibitor, 0.6 µg of (dT)15 primer, 2 µM dNTPs, and 1×
gave C-4-trans. Two isomers were separated in a 23 : 77 ratio
with an overall yield of 73% (33.1 mg, 0.036 mmol). C-4-trans:
1H NMR (400 MHz, CDCl3) δ 7.61 (s, JPt–H = 52 Hz, 2H, Hi,i′), Moloney-murine-leukemia virus RT buffer provided by
7.32 (s, 1H, H2), 3.81 (d, J = 6.8 Hz, 4H, H7,7′), 3.40 (s, 12H, Hd),
Promega (Madison, WI). Aliquots of the RT products were
2.43–2.28 (m, 2H, H8,8′), 2.15 (s, 3H, H10), 0.94 (d, J = 6.7 Hz,
used for RT-PCR analysis. For semi-qRT-PCR, 2 µL of RT pro-
8H, H9,9′). 13C NMR (100 MHz, CDCl3) δ 164.41 [C1,3], 159.94 ducts was brought to a volume of 25 µL containing 1.5 mM
[Ci,i′], 142.71 [C2], 114.63 [C5], 69.69 [C7,7′], 42.25 [Cd], 29.91
MgCl2, 0.25 mM of each dNTP, 0.5 µM of both the upstream
[C8,8′], 19.58 [C9,9′], 10.62 [C10]. C-4-cis/trans: 1H NMR (400 MHz,
and downstream PCR-primers, and 1× Taq reaction-buffer and
CDCl3) δ 7.54 (s, 1H, Hi), 7.48 (s, 1H, Hi′), 7.20 (s, 1H, H2), 3.91 1.25 units of Taq DNA polymerase, provided by Promega. PCR
(d, J = 7.0 Hz, 2H, H7′), 3.78 (d, J = 7.0 Hz, 2H, H7), 3.56 (s, 6H,
products were visualized by electrophoresis on a 2% agarose
gel in 0.5 × TBE buffer after staining with 0.5 µg mL−1 ethi-
Hd′), 3.36 (s, 6H, Hd), 2.38–2.27 (m, 2H, H8,8′), 2.18 (s, 3H, H10),
0.97 (d, J = 6.7 Hz, 6H, H9′), 0.90 (d, J = 6.7 Hz, 6H H9). 13C NMR dium bromide. For qRT-PCR, 2 µL of reverse transcribed cDNA
(100 MHz, CDCl3) δ 161.3 [C1], 161.0 [C3], 161.0 [Ci], 159.7 [Ci′],
was subjected to RT-PCR using a mastermix with SYBR-green
(BIORAD) and the Mx3005P-quantitative RT-PCR system (Stra-
tagene). Each reaction consisted of SYBR green (1 : 60 000 final
concentration), 40 nM of both sense and antisense primers,
2 µL of cDNA and H2O to a final volume of 20 µL. Each experi-
ment was performed in duplicates and repeated thrice.
140.9 [C2], 125.8 [C5], 71.3 [C7′], 69.7 [C7], 47.2 [Cd], 42.0 [Cd′],
31.9 [C8′], 29.9 [C8], 19.7 [C9′], 19.6 [C9], 10.2 [C10].
Preparation of C-5.
Preparation of total cell extract and Western blot analysis.
A Western blot analysis was performed as described pre-
viously.59 Cells were washed with phosphate buffered saline
and treated with an extraction buffer (50 mM Tris-HCl, pH 7.4,
1% Nonidet P-40, 0.25% sodium deoxycholate, 150 mM NaCl,
and 1 mM EDTA) supplemented with 1 mM phenylmethane-
sulfonyl fluoride, 1 mM sodium orthovanadate (Na3VO4),
0.1 mM dithiothreitol, 0.4 µg mL−1 leupeptin/pepstatin). The
C-4-trans and C-4-cis/trans mixture (22.6 mg, 0.025 mmol) and cell extract was stored at −20 °C until required. Protein
4-picoline (9.3 mg, 0.1 mmol, 4 eq.) were reacted, and the samples were subjected to electrophoresis on 10% SDS poly-
remaining procedure was the same as that followed for C-2. acrylamide-gel. Separated proteins were electroblotted to nitro-
C-5 was recovered in 87% yield (19.7 mg, 0.021 mmol) as a cellulose membranes (Bio-Rad), and the blot was blocked for
1
yellow solid. H NMR (400 MHz, CDCl3) δ 8.73 (d, J = 6.5 Hz, 1 hour at room temperature with the blocking buffer 0.1%
Dalton Trans.
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
PBST with 5% fat-free dried milk powder. The blot was then the agarose gel (up to 1% w/v) containing ethidium bromide
incubated with primary antibodies (1 : 1000 dilutions) at 4 °C was prepared with TA buffer (50 mM Tris-acetate, pH 7.5). The
overnight. The blot was washed with 0.1% TBST three times, mixtures with loading buffer (1 μL) underwent electrophoresis
and incubated with secondary antibodies (mouse, rabbit) on agarose gel in TA buffer at 120 V for 40 min. Bands were
(1 : 5000 dilution) for 1 hour. The blot was washed again three imaged using a Molecular Imager (Bio-Rad) under UV light.
times and exposed to an Odyssey LI-COR-scanner.
Cell culture. Five human solid tumor cell lines, HepG-2
(human hepatocellular carcinoma), MCF-7 (human breast car-
cinoma), A549 (human non-small cell lung cancer), HCT-116
Acknowledgements
(human colorectal cancer) and Hela (human cervical cancer)
The authors acknowledge the Ministry of Science and Techno-
were used. They were cultured in DMEM medium sup-
logy of China (2013CB834501), the Science and Technology
plemented with 10% fetal bovine serum (FBS), 100 μg mL−1
Commission of Shanghai Municipality (13M1400200), the
penicillin, and 100 μg mL−1 streptomycin under an atmos-
National Natural Science Foundation of China (no. 21102017),
phere containing 5% CO2 at 37 °C.
and China Postdoctoral Association for providing a post-
In vitro cytotoxicity assay. The IC50 values of all complexes
doctoral fellowship.
were determined by an MTT assay. This assay is based on the
cleavage of the yellow tetrazolium salt (3-(4,5-dimethylthiazol-
2-yl)-2,5-diphenyl tetrazolium bromide; MTT, Sigma), forming
purple formazan crystals by viable cells. The cells were plated
in 96-well culture plates at a density of 3000 cells per well and
Notes and references
incubated for 24 hours at 37 °C in a 5% CO2 incubator. All
compounds were dissolved in DMSO and then diluted to the
required concentration with culture medium. The diluted com-
plexes were then added to the wells, and cells were incubated
at 37 °C under 5% CO2 for 48 hours. Afterwards, the cells were
treated with 20 μL of MTT dye solution (5 mg mL−1) for four
hours of cultivation. The media with MTT were removed and
replaced with DMSO (100 μL). The absorbance was measured
at λ = 540 nm. IC50 values were determined by plotting cell via-
bility (%) against the dose of complex added (μM).
Cell apoptosis study by flow cytometry. Apoptosis induced
by Pt(II) complexes was determined by flow cytometry using an
AnnexinV-FITC apoptosis detection kit. After the induced
apoptosis of selected cell lines (MCF-7) by the addition of
20 μM selected compounds and positive controls including cis-
platin (20 μM) for 24 hours, cells were collected by centrifu-
gation (5 min, 25 °C, 2000 rpm). The cells were then washed
twice with cold water and resuspended in AnnexinV-FITC
binding buffer at a concentration of 1 × 106 cells mL−1. Cells
were stained with 5 μL of AnnexinV-FITC and incubated in the
dark at 25 °C for 10 min. The cell suspension was centrifuged
for 5 min (25 °C, 2000 rpm), and cells were resuspended in
AnnexinV-FITC binding buffer. Propidium iodide (10 μL) was
added, and the tubes were placed on ice away from light. The
fluorescence was measured using a flow cytometer. The results
were analyzed using FCSExpress software and are expressed as
the percentage of normal and apoptotic cells at various stages.
1 L. A. Carey, E. C. Dees, L. Sawyer, L. Gatti, D. T. Moore,
F. Collichio, D. W. Ollila, C. I. Sartor, M. L. Graham and
C. M. Perou, Clin. Cancer Res., 2007, 13, 2329.
2 D. A. Berry, C. Cirrincione, I. C. Henderson, M. L. Citron,
D. R. Budman, L. J. Goldstein, S. Martino, E. A. Perez,
H. B. Muss and L. Norton, JAMA, 2006, 295, 1658.
3 D. P. Silver, A. L. Richardson, A. C. Eklund, Z. C. Wang,
Z. Szallasi, Q. Li, N. Juul, C.-O. Leong, D. Calogrias,
A. Buraimoh, A. Fatima, R. S. Gelman, P. D. Ryan,
N. M. Tung, A. De Nicolo, S. Ganesan, A. Miron, C. Colin,
D. C. Sgroi, L. W. Ellisen, E. P. Winer and J. E. Garber,
J. Clin. Oncol., 2010, 28, 1145.
4 Z. C. Wang, M. Lin, L.-J. Wei, C. Li, A. Miron, G. Lodeiro,
L. Harris, S. Ramaswamy, D. M. Tanenbaum and
M. Meyerson, Cancer Res., 2004, 64, 64.
5 R. Rouzier, C. M. Perou, W. F. Symmans, N. Ibrahim,
M. Cristofanilli, K. Anderson, K. R. Hess, J. Stec, M. Ayers
and P. Wagner, Clin. Cancer Res., 2005, 11, 5678.
6 W. D. Foulkes, I. M. Stefansson, P. O. Chappuis,
L. R. Bégin, J. R. Goffin, N. Wong, M. Trudel and
L. A. Akslen, J. Natl. Cancer Inst., 2003, 95, 1482.
7 K. D. Mjos and C. Orvig, Chem. Rev., 2014, 114, 4540.
8 N. Muhammad and Z. Guo, Curr. Opin. Chem. Biol., 2014,
19, 144.
9 P. Chellan, T. Stringer, A. Shokar, P. J. Dornbush,
G. Vazquez-Anaya, K. M. Land, K. Chibale and G. S. Smith,
J. Inorg. Biochem., 2011, 105, 1562.
Gel electrophoresis. The DNA binding produced by C-1- 10 A. A. Bekhit, O. A. El-Sayed, T. A. Al-Allaf, H. Y. Aboul-
trans, C-2, C-4-trans and cisplatin was investigated by agarose
Enein, M. Kunhi, S. M. Pulicat, K. Al-Hussain, F. Al-Kho-
dairy and J. Arif, Eur. J. Med. Chem., 2004, 39, 499.
gel electrophoresis. pBR322 plasmid DNA (50 ng μL−1) was
used as the target. Appropriate dilutions of the tested com- 11 W. M. Motswainyana, M. O. Onani and A. M. Madiehe,
pounds were made, and the required volumes of solutions Polyhedron, 2012, 41, 44.
were added to achieve a set of concentrations in the range of 12 A. R. Kapdi and I. J. Fairlamb, Chem. Soc. Rev., 2014, 43,
20 μM. pBR322 DNA (5 μL, 0.20 μg) was added to each tube, 4751.
and the mixtures of these complexes and pBR322 plasmid 13 S. E. Karp, P. N. Tonin, L. R. Bégin, J. J. Martinez, J. C. Zhang,
DNA were then incubated at 37 °C for 24 hours. Afterwards,
M. N. Pollak and W. D. Foulkes, Cancer, 1997, 80, 435.
This journal is © The Royal Society of Chemistry 2014
Dalton Trans.

View Article Online
Paper
Dalton Transactions
14 J. N. Marcus, P. Watson, D. L. Page, S. A. Narod, 37 N. Komiya, T. Muraoka, M. Iida, M. Miyanaga,
G. M. Lenoir, P. Tonin, L. Linder-Stephenson, G. Salerno,
K. Takahashi and T. Naota, J. Am. Chem. Soc., 2011, 133,
T. A. Conway and H. T. Lynch, Cancer, 1996, 77, 697.
16054.
15 F. Eisinger, J. Jacquemier, C. Charpin, D. Stoppa-Lyonnet, 38 N. Komiya, M. Okada, K. Fukumoto, D. Jomori and
B. Bressac-de Paillerets, J.-P. Peyrat, M. Longy, T. Naota, J. Am. Chem. Soc., 2011, 133, 6493.
J.-M. Guinebretière, R. Sauvan and T. Noguchi, Cancer Res., 39 F. Zheng, A. T. Hutton, C. G. van Sittert, J. R. Moss and
1998, 58, 1588. S. F. Mapolie, Dalton Trans., 2013, 42, 11163.
16 D. Kovala-Demertzi, A. Papageorgiou, L. Papathanasis, 40 A. E. Patterson, J. J. Miller, B. A. Miles, E. L. Stewart,
A. Alexandratos, P. Dalezis, J. R. Miller and
M. A. Demertzis, Eur. J. Med. Chem., 2009, 44, 1296.
17 D. Talancon, C. Lopez, M. Font-Bardia, T. Calvet, J. Quirante,
J.-M. E. J. Melanson, C. M. Vogels, A. M. Cockshutt,
A. Decken, P. Morin Jr. and S. A. Westcott, Inorg. Chim.
Acta, 2014, 415, 88.
C. Calvis, R. Messeguer, R. Cortes, M. Cascante, L. Baldoma 41 V. Y. Kukushkin, A. J. L. Pombero, C. M. P. Ferreira and
and J. Badia, J. Inorg. Biochem., 2013, 118, 1.
18 B. Rosenberg, L. Vancamp, J. E. Trosko and V. H. Mansour,
Nature, 1969, 222, 385.
19 B. Lippert, Cisplatin: Chemistry and Biochemistry of a
Leading Anticancer Drug, Verlag Helvetica Chimica Acta
Zurich, Switzerland, 1999.
L. I. Elding, in Dimethylsulfoxide Complexes of Platinum(II):
K[PtCl3 (Me2SO)], cis-[PtCl2L(Me2SO)] (L = Me2SO, MeCN),
[PtCl(μ-Cl)(Me2SO)]2, and [Pt(Me2SO)4](CF3SO3)2, ed. D. Cou-
couvanis, John Wiley & Sons, Inc., New York, 2002, vol. 33,
pp. 189–196.
42 J. H. Price, A. N. Williamson, R. F. Schramm and
B. B. Wayland, Inorg. Chem., 1972, 11, 1280.
20 B. W. Harper, A. M. Krause-Heuer, M. P. Grant,
M. Manohar, K. B. Garbutcheon-Singh and J. R. Aldrich- 43 R. Cini, A. Donati and R. Giannettoni, Inorg. Chim. Acta,
Wright, Chem. – Eur. J., 2010, 16, 7064. 2001, 315, 73.
21 R. E. Windsor, S. J. Strauss, C. Kallis, N. E. Wood and 44 M. Crespo, R. Martín, T. Calvet, M. Font-Bardía and
J. S. Whelan, Cancer, 2012, 118, 1856. X. Solans, Polyhedron, 2008, 27, 2603.
22 N. Milosavljevic, C. Duranton, N. Djerbi, P. H. Puech, 45 J. Reedijk, Eur. J. Inorg. Chem., 2009, 2009, 1303.
P. Gounon, D. Lagadic-Gossmann, M. T. Dimanche-Boitrel, 46 J. Reedijk, Pure Appl. Chem., 1987, 59, 181.
C. Rauch, M. Tauc, L. Counillon and M. Poet, Cancer Res., 47 H. Baruah, C. L. Rector, S. M. Monnier and U. Bierbach,
2010, 70, 7514. Biochem. Pharmacol., 2002, 64, 191.
23 P. J. Loehrer and L. H. Einhorn, Ann. Intern. Med., 1984, 48 K. Samper, V. Rodríguez, E. Ortega-Carrasco, S. Atrian,
100, 704.
J. Maréchal, N. Cutillas, A. Zamora, C. de Haro,
M. Capdevila, J. Ruiz and Ò. Palacios, BioMetals, 2014, 1.
49 J. Stallock, K. Molyneaux, K. Schaible, C. M. Knudson and
C. Wylie, Development, 2003, 130, 6589.
24 R. S. Aroney, J. A. Levi and D. N. Dalley, Br. Med. J., 1981,
282, 2003.
25 S. E. Sherman and S. J. Lippard, Chem. Rev., 1987, 87, 1153.
26 F. Arnesano and G. Natile, Coord. Chem. Rev., 2009, 253, 50 K. Nakano and K. H. Vousden, Mol. Cell, 2001, 7, 683.
2070.
51 E. Oda, R. Ohki, H. Murasawa, J. Nemoto, T. Shibue,
T. Yamashita, T. Tokino, T. Taniguchi and N. Tanaka,
Science, 2000, 288, 1053.
52 Y. Yang, S. Zhao and J. Song, Int. J. Biochem. Cell Biol.,
2004, 36, 223.
27 J. Zhao, S. Gou and G. Xu, Inorg. Chim. Acta, 2014, 409, 310.
28 N. J. Wheate, S. Walker, G. E. Craig and R. Oun, Dalton
Trans., 2010, 39, 8113.
29 A. Mishra, S. Chang Lee, N. Kaushik, T. R. Cook,
E. H. Choi, N. Kumar Kaushik, P. J. Stang and K. W. Chi, 53 A. I. Goranov, A. Gulati, N. Dephoure, T. Takahara,
Chem. – Eur. J., 2014, 20, 1.
30 L. Dvořák, I. Popa, P. Štarha and Z. Trávníček, Eur. J. Inorg.
Chem., 2010, 2010, 3441.
T. Maeda, S. P. Gygi, S. Manalis and A. Amon, Curr. Biol.,
2013, 23, 1269.
54 B. Brandhagen, C. Tieszen, T. Ulmer, M. Tracy,
A. Goyeneche and C. Telleria, BMC Cancer, 2013, 13, 35.
31 S. J. Berners-Price, Angew. Chem., Int. Ed., 2011, 50, 804.
32 P. Virag, M. Perde-Schrepler, E. Fischer-Fodor, C. Tatomir, 55 M. Sekimata, Y. Kabuyama, Y. Emori and Y. Homma,
S. A. Dorneanu, V. I. Cernea and A. Irimie, Anti-Cancer
Drugs, 2012, 23, 1032.
33 S. Kemp, N. Wheate, S. Wang, J. G. Collins, S. Ralph,
J. Biol. Chem., 1999, 274, 17757.
56 G. Sheldrick, Acta Crystallogr., Sect. A: Fundam. Crystallogr.,
2008, 64, 112.
A. Day, V. Higgins and J. Aldrich-Wright, J. Biol. Inorg. 57 J. Chakraborty, M. Nandi, H. Mayer-Figge, W. S. Sheldrick,
Chem., 2007, 12, 969.
L. Sorace, A. Bhaumik and P. Banerjee, Eur. J. Inorg. Chem.,
2007, 2007, 5033.
58 A. Ali, Z. Wang, J. Fu, L. Ji, J. Liu, L. Li, H. Wang, J. Chen,
C. Caulin, J. N. Myers, P. Zhang, J. Xiao, B. Zhang and
X. Li, Nat. Commun., 2013, 4, 2667.
59 G.-H. Lee, D.-S. Kim, H.-T. Kim, J.-W. Lee, C.-H. Chung,
T. Ahn, J. M. Lim, I.-K. Kim, H.-J. Chae and H.-R. Kim,
J. Biol. Chem., 2011, 286, 24743.
34 S. Roy, K. D. Hagen, P. U. Maheswari, M. Lutz, A. L. Spek,
J. Reedijk and G. P. van Wezel, ChemMedChem, 2008, 3, 1427.
35 C. M. Che, C. C. Kwok, S. W. Lai, A. F. Rausch,
W. J. Finkenzeller, N. Zhu and H. Yersin, Chem. – Eur. J.,
2010, 16, 233.
36 M. Proetto, W. Liu, A. Hagenbach, U. Abram and R. Gust,
Eur. J. Med. Chem., 2012, 53, 168.
Dalton Trans.
This journal is © The Royal Society of Chemistry 2014