Novel: Cis -[(NHC)1(NHC)2(L)Cl]platinum(II) complexes-synthesis, structures, and anticancer activities

Article abstract of DOI:10.1039/c6dt02350a

A general synthesis of novel platinum(ii) complexes bearing two different, cis-oriented, N-heterocyclic carbene (NHC) ligands is presented. Easily accessible cis-[Pt^II(NHC)(DMSO)] precursor complexes were converted to either cis-[Pt^II(NHC)₂Cl₂] complexes such as 5a and 5b, or to novel mixed cis-[Pt^II(NHC)¹(NHC)²Cl₂] complexes such as 5c-h by successive introduction of the individual carbene ligands. The 'symmetric' complexes 5a and 5b were also converted to cationic cis-[Pt^II(NHC)₂(PPh₃)Cl]⁺Cl^- complexes 8a and 8b. The structures of the ten new complexes, comprising benzylated and alkylated imidazol-2-ylidene ligands, were analysed by ¹H, ¹³C and ¹⁹⁵Pt NMR spectroscopy and also by X-ray diffraction for 5a, 5d, 5h, and 8a. The neutral complexes 5 were cytotoxic against a panel of seven human cancer cell lines with IC₅₀ values in the low micromolar range, while the cationic complexes 8 reached even nanomolar IC₅₀ values. Complex 5h carrying the substitution pattern of the natural antitumoral agent Combretastatin A-4 showed a conspicuous specificity for cancer cell lines sensitive to this drug. In electrophoretic mobility shift assays, the cis-biscarbene complexes 5b and 8b led to an unwinding or aggregation of plasmid DNA, while the trans-biscarbene complex 1b showed no such effect.

Full text of DOI:10.1039/c6dt02350a

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DOI: 10.1039/C6DT02350A
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ARTICLE
1
2
Novel cis-[(NHC) (NHC) (L)Cl]platinum(II) complexes –
†
synthesis, structures, and anticancer activities
Received
a
a
a
b
b
Tobias Rehm, Matthias Rothemund, Julienne K. Muenzner, Awal Noor, Rhett Kempe,
a
and Rainer Schobert *
A general synthesis of novel platinum(II) complexes bearing two different, cis-oriented, N-heterocyclic carbene
II
(
NHC) ligands is presented. Easily accessible cis-[Pt (NHC)(DMSO)] precursor complexes were converted to
Accepted
II
II
1
2
either cis-[Pt (NHC)
2 2 2
Cl ] complexes such as 5a and 5b, or to novel mixed cis-[Pt (NHC) (NHC) Cl ] complexes
such as 5c–h by successive introduction of the individual carbene ligands. The ‘symmetric’ complexes 5a and 5b
DOI: 10.1039/x0xx00000x
www.rsc.org/
II
+
–
2 3
were also converted to cationic cis-[Pt (NHC) (PPh )Cl] Cl complexes 8a and 8b. The structures of the ten new
1
13
complexes, comprising benzylated and alkylated imidazol-2-ylidene ligands, were analysed by H and C NMR
spectroscopy and also by X-ray diffraction for 5a, 5d, 5h, and 8a. The neutral complexes 5 were cytotoxic
against a panel of seven human cancer cell lines with IC50 values in the low micromolar range, while the cationic
complexes 8 reached even nanomolar IC50 values. Complex 5h carrying the substitution pattern of the natural
antitumoral agent Combretastatin A-4 showed a conspicuous specificity for cancer cell lines sensitive to this
drug. In electrophoretic mobility shift assays, the cis-biscarbene complexes 5b and 8b led to an unwinding or
aggregation of plasmid DNA, while the trans-biscarbene complex 1b showed no such effect.
II
Unlike complexes trans-[Pt (NHC)
2
Cl
2
] 1, featuring a poor
complexes cis-
] 2 which bear a well accessible
Introduction
NHC
II
leaving
Pt (DMSO)(NHC)Cl
group,
the
[
2
Metal complexes of N-heterocyclic carbenes (NHCs)
were reported as early as 1968 by Wanzlick et al. and
chlorido leaving ligand, had bound to DNA as expected.
Substitution of DMSO for PPh gave complexe 3 which
1,2
3
others. But it was not until the isolation of a crystalline
3
carbene by Arduengo et al. in 1991 that NHCs turned
still, though to a lesser extent, bound coordinatively to
DNA but also initiated some DNA aggregation. The
from mere curiosities into applicable chemical reagents.
Nowadays, they are routinely used as organocatalysts for
4
a wide range of established reactions. NHC metal
II
trans-[Pt (PPh
+
(NHC)Cl] Cl
-
cationic
complex
3
)
2
4,
featuring a sterically shielded chlorido ligand, exclusively
induced DNA aggregation (Figure 1).
complexes are among the most efficient catalysts for
5
reactions such as olefin metathesis and Pd-catalysed
6
,7
coupling reactions.
aspects came to the fore. With the successful history of
More recently, their medicinal
8,9
10
anticancer active platinum compounds
bioactive NHC complexes were devised of metals such
in mind,
11
12
13
14
15
16
as Pd, Ag, Cu, Ru, Au, and Pt. Meanwhile, a
general picture of structure-activity correlations for such
complexes is unfolding, allowing a prediction of the
influence of the central metal, the NHC substituents, the
charge, the lipophilicity, and the sterical encumbrance
around the metal centre on their biological properties. We
recently studied the influence of the latter factor, sterical
17
congestion, in a series of platinum complexes.
Fig. 1 NHC-platinum(II) complexes with spectator ligands of
increasing bulkiness and their modes of DNA interaction.
1
7
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Results and discussion
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DOI: 10.1039/C6DT02350A
Synthesis and characterisation
The key intermediates for our new synthesis are cis-
II
[
Pt (NHC)(DMSO)L
sised by Rourke et al. in 2007. This group found that
using DMSO instead of CH Cl as the solvent for the
carbene transfer from silver NHC complexes to suitable
sources of the desired metal, e.g. K PtCl , led to the
2
] complexes such as 2, first synthe-
21
2
2
2
4
formation of monocarbene complexes of type 2 rather
than to the formation of trans-biscarbene complexes of
type 1. The DMSO ligand can then be substituted by a
1
7,21
more electron-rich ligand such as a phosphane,
detailed in this work, a second NHC ligand.
or, as
II
We prepared eight new cis-[Pt (NHC) (NHC) Cl
1
2
2
]
complexes 5 with six different NHCs as ligands via DMSO
precursor complexes 2. Since the two NHC ligands are
introduced one at a time, complexes with two different
Scheme 1 Syntheses of cis-bis(NHC) complexes of platinum(II) NHCs can be synthesised starting from two different
1
9
20
18
1
2 22-26
by a) Nolan et al., b) Nolan et al., c) Röschenthaler et al.,
imidazolium salts 6 (ImH ) and 7 (ImH )
We employed imidazolium chlorides that were 1,3-
For a more nuanced assessment of such steric effects we benzylated, or -alkylated. For the synthesis of cis-
(Scheme 2).
II
1
2
2
and a new access to complexes cis-[Pt (NHC) (NHC) Cl ] 5.
II
1
2
now developed an access to platinum(II) complexes with [Pt (NHC) (NHC) Cl
two different, cis-positioned NHC ligands (Scheme 1). complex cis-[Pt (DMSO)(NHC) Cl
2
]
complexes
1
5
] 2 was treated with
the respective
II
2
II
2
t
2
Complexes cis-[Pt (NHC)
2
L
2
] with two identical NHC ImH Cl 7 and KO Bu to generate NHC . The resulting
Cl for 16 hours by which
], time the DMSO had been completely substituted by NHC
] as precursors. Displacement and the pure product complexes 5 were obtained by
of the leaving ligands DMSO or cod, respectively, by precipitation in yields of up to 93%. Replacing the base
ligands had been synthesised before by Röschenthaler et mixture was stirred in dry CH
2
2
18
19,20
2
al.,
and Nolan et al.
], or [Pt(cod)Me
2
2 2
using cis-[Pt(DMSO) Cl
[
Pt(cod)Cl
2
t
2 3 2
two equivalents of the free or masked NHC led to the KO Bu by K CO , NaOMe or CaH had little influence on
desired cis-biscarbene complexes. However, these the yields as had the use of acetonitrile as a solvent.
protocols do not allow the synthesis of mixed cis-
II
1
2
[
2
Pt (NHC) (NHC) L ] complexes.
Scheme 2 General synthesis and structures of complexes 5a-h.
2
| Dalton Trans. 2016, 00, 1-9
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ARTICLE
1 13
The cis configuration of complexes 5 was confirmed by H Further evidence is provided by the C NMR shifts of the
View Article Online
1
3
and C NMR spectroscopy. In line with a previous carbene carbon signals ranging from 147.8 to 149 ppm,
DOI: 10.1039/C6 D. 9T 02350A
1
7
1
study of the complexes 2a and 3, the H NMR spectra typical of carbon atoms in a cis-NHC-L-PtCl
2
environ-
While the symmetric complexes 5a and 5b
group (one facing showed only one carbene carbon signal, the mixed
17,21,27
of complexes 5 showed an inequivalency of the two ment.
geminal protons of each benzylic CH
2
the neighbouring chlorine, the other the second NHC) and complexes gave rise to two inequivalent signals for the
their splitting up into two doublets. These corresponding different NHC ligands.
1
signals are 0.44 to 1.13 ppm apart and couple with Complexes 5g and 5h showed distinct H NMR spectra
2
2
J
AB = 14.34 to 14.95 Hz. This corroborates the cis with coupling constants
configuration of the NHC ligands as well as the overall more complex spectra as each CH
perpendicular orientation of the imidazole ring relative to different surrounding and thus a distinctive shift. In the
J
AB = 15.11 to 15.26 Hz and
2
proton has a
13
the plane spanned by the PtCl
2
fragment (Figure 2).
C NMR spectrum of 5g the carbene carbon of the N-
methylated NHC ligand peaks at 146.6 ppm.
We also prepared cationic complexes 8 from the
symmetric complexes 5a and 5b by substitution of a
chlorido for a triphenylphosphane ligand (Scheme 3).
Scheme 3 Synthesis of cationic phosphane complexes 8 from cis-
II
[
Pt (NHC)
2 2
Cl ] complexes 5a and 5b.
1
2
Their H NMR spectra showed more complex CH signals
due to the additional asymmetry. Their carbene carbon
13
signals in the C NMR spectra appeared as doublets with
2
J
CP = 10 Hz (cis to PPh
3
) and 151 Hz (trans to PPh
3
),
respectively. The P– Pt coupling of JPPt = 2366 Hz
8a) and 2361 Hz (8b) was visible as were the phosphane
31
195
1
(
1
Fig. 2 Relevant H NMR signals of inequivalent benzylic CH
of complexes 5 proving the cis configuration.
2
protons
31
signals at 13.09 (8a) and 13.34 ppm (8b) in the P NMR
spectra.
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DOI: 10.1039/C6DT02350A
IC50 (72h) ["M]
Cell line
18A2 6.2 ± 0.4 7.9 ± 0.4 5.6 ± 0.2 6.1 ± 0.5 5.2 ± 0.3 7.1 ± 0.5
HT-29 14.6 ± 1.4 11.1 ± 2.0 13.9 ± 1.4 21.6 ± 1.5 4.1 ± 0.4 6.6 ± 0.5
5a
5b
5c
5d
5e
5f
5g
5h
8a
8b
CDDP
5
39.0 ± 1.0
39.7 ± 2.0
6.5 ± 0.2
0.86 ± 0.05 0.60 ± 0.15
5.3 ± 0.4
> 100
11.1 ± 0.7 0.82 ± 0.06 0.45 ± 0.03
DLD-1 4.7 ± 1.4 3.2 ± 0.1 5.1 ± 0.6 4.0 ± 0.2 5.7 ± 1.4 11.1 ± 0.9 30.2 ± 5.2 0.39 ± 0.07 0.77 ± 0.04 0.66 ± 0.02
32.6 ± 2.4
4.0 ± 0.3
4.8 ± 0.7
10.6 ± 0.7
> 100
U87 7.2 ± 0.2 7.7 ± 0.5 9.0 ± 1.1 5.0 ± 0.3 4.5 ± 0.4 7.3 ± 0.3
Panc-1 3.5 ± 0.7 2.9 ± 0.0 3.0 ± 0.1 4.2 ± 0.4 6.7 ± 1.3 6.0 ± 0.1
> 50
38.8 ± 3.7 0.24 ± 0.05 0.36 ± 0.00 0.39 ± 0.03
37.1 ± 5.6 0.43 ± 0.01 0.52 ± 0.03
35.5 ± 1.3 7.3 ± 1.2 6.0 ± 0.3
0.4 ± 0.08 0.48 ± 0.01 0.72 ± 0.03
6.1 ± 2.1
0.89 ± 0.19 0.95 ± 0.21
MCF7/Topo 8.6 ± 2.0 4.0 ± 0.2 11.1 ± 5.6 7.6 ± 0.9 3.2 ± 0.5 13.7 ± 0.9 42.1 ± 2.7
Kb-V1/Vbl 11.7 ± 0.8 13.9 ± 1.1 16.1 ± 0.8 18.1 ± 2.6 43.5 ± 2.1 21.0 ± 1.0 > 50
Ea.Hy926 6.8 ± 1.6 4.2 ± 0.4 5.6 ± 1.9 7.6 ± 0.2 3.2 ± 0.5 13.4 ± 0.5 45.3 ± 1.2
17.3 ± 1.9
4, showing IC50 concentrations in the low nanomolar
range.
X-ray crystallography
Crystals suitable for X-ray diffraction analyses were
grown by slow infusion of hexane into saturated solutions
As we have already shown in previous work, exchange of
one chlorido for a phosphane ligand can enhance the
cytotoxicity significantly, probably due to an increase in
2 2
of 5a, 5d, 5h, or 8a in CH Cl kept at 4 °C. Figure 3
17
shows their molecular structures. The characteristic bond
lengths and angles were similar for all four complexes.
The distances between the platinum and the carbene
carbon atoms were in the range of 1.97!1.99 Å, only in
the phosphane complex 8a the distances were slightly
longer with 2.02 Å and 2.07 Å. The Pt–Cl distances lay
between 2.35 and 2.36 Å, while the Pt–P bond of 8a was
lipophilicity, solubility and thus of cellular uptake. This
was observed here as well when going from the neutral
dichlorido complexes 5a-b to the phosphane complexes
8
a-b which are typical ‘delocalised lipophilic cations’
DLCs). They were efficacious with submicromolar IC50
(
values against most of the cell lines. Again, the KbV1/Vbl
cells were least responsive requiring single-digit
micromolar IC50 concentrations (8a: 7 "M; 8b: 6 "M).
2
.31 Å long. The C–Pt–C angles ranged from 93.7° (8a)
to 96.4° (5d) for those complexes that bore 1,3-
dibenzylimidazol-2-ylidene ligands. In the case of 5h the
C–Pt–C angle was reduced to 90.4°.
In vitro DNA interaction
II
We investigated the DNA interaction of trans-[Pt (NHC)
2
Cl
2
]
complex 1b, the isomeric cis-complex 5b, and its cationic
Anticancer activity
II
+
–
2 3
analogue cis-[Pt (NHC) (PPh )Cl] Cl 8b by means of an
Complexes 5 and 8 were investigated for their cytotoxicity
against a panel of seven human cancer cell lines of six
entities and an endothelial cell line using the MTT-based
electrophoretic mobility shift assay (EMSA) with circular
pBR322 plasmid DNA (Fig. 4). The trans configured complex
1
b did not alter the DNA morphology, i.e. the ratio of open
28,29
viability assay.
72 h) values. All complexes 5a-h showed remarkable
efficacies with low micromolar IC50 values against all cell
Table 1 summarises the resulting IC50
circular (oc) and covalently closed circular (ccc) forms. In
contrast, its cis isomer 5b led to a distinct unwinding of the
plasmid DNA in a concentration-dependent manner, as is also
typical of cisplatin, apparent from a pronounced band shift with
a maximum at a concentration of 10 "M of 5b. At this
concentration the DNA also seems to aggregate to adducts
that remain in the gel pocket during electrophoresis, not able
to permeate the pores of the gel. The same phenomenon was
observed for 8b, yet to a greater extent. It initiated immediate
aggregation of the plasmid DNA without any conversion of its
topological oc and ccc isomers. Such effects had previously
(
30
lines, save for the cisplatin resistant HT-29 colon and
the multidrug-resistant (mdr) KB-V1/Vbl cervix
31
carcinoma cell line. The latter, which overexpresses the
detoxifying efflux transporter protein p-gp1, was
surprisingly unresponsive to all complexes, especially to
5h that bears the structural motif of the natural anticancer
drug combretastatin A-4 (CA-4). Complex 5h was also
less active than most other test compounds against the
32
17
mdr MCF7/Topo mamma carcinoma cell line which
overexpresses the efflux transporter BCRP34 (breast
cancer resistance protein). This is an indication for 5h
being a substrate of these drug efflux pumps.
been observed
and corroborated by light scattering
experiments and studies of the DNA binding kinetics for
complexes 3 and 4. They suggest that the mode of DNA
interaction is mainly governed by the sterical shielding of the
chlorido leaving ligand or the metal centre.
Against CA-4 sensitive cancer cell lines such as DLD-1
colon carcinoma and Panc-1 pancreatic cancer, and also
against the hybrid endothelial Ea.Hy926 cells, complex
5
h retained the activity of the natural lead compound CA-
4
| Dalton Trans. 2016, 00, 1-9
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DOI: 10.1039/C6DT02350A
Experimental
Materials and methods
All chemicals and reagents were purchased from Sigma
Aldrich, Alfa Aesar, or ABCR and were used without
further purification. Melting points are uncorrected; NMR
spectra were run on a 500 MHz spectrometer; chemical
shifts are given in ppm (#) and referenced relative to the
1
95
internal solvent signal;
Pt NMR shifts are quoted
195
relative to $( Pt) = 21.496784 MHz, K PtCl was used
2
4
as external standard (# = –1612.81); mass spectra: direct
inlet, EI, 70 eV; elemental analyses: Vario EL III and
HEKAtech EA 3000 elemental analysers; X-ray
diffractometers: STOE-IPDS II and STOE-STADIVARI. All
biotested compounds were >95% pure by elemental
Fig. 4 Modification of gel electrophoretic mobility of pBR322
plasmid DNA when incubated for 24 h with different concentrations
of DMF solutions of cisplatin, 1b, 5b, and 8b (oc = open circular, analysis. N-methyl- and N-benzylimidazolium salts were
ccc = covalently closed circular DNA form; the red arrows mark
DNA aggregates).
prepared according to literature procedures (cf.
22-25
Supporting Information),
3‘,4‘,5‘-trimethoxyphenyl)-5-(4’’-methoxyphenyl)imidazolium
as were 1,3-dimethyl-4-
(
iodide and complex 2a. Complex 1b was prepared
Conclusions
26
17
17
We have developed a new synthetic protocol that gives analogously to 1a and is described in the Supporting
II
1
2 1 2
access to cis-[Pt (NHC) (NHC) L L ] complexes with two Information.
different NHC ligands. Ten complexes were prepared,
Syntheses and characterisation
structurally elucidated, and screened for antiproliferative
activity against human tumour cells. Their activity was
surprisingly high on average, with a considerable degree
of structure-dependent cell line specificity. For some
complexes we observed a breach of the cisplatin and
multidrug resistance of certain cancer cell lines.
Mechanistically, DNA seems to be a major target of these
new platinum complexes, albeit in a more differentiated
way when compared to cisplatin. In EMSA experiments
with circular plasmid DNA, the neutral cis-biscarbene
complex 5b bound coordinatively to it leading to its
unwinding. Apparently, complex 5b also initiated the
aggregation of this form of DNA to some extent. This
needs to be confirmed by further experiments. The
cationic cis-biscarbene complex 8b seems to have led
exclusively to DNA aggregation. The trans-biscarbene
complex 1b showed no such effects. Obviously, the mode
of DNA interaction is correlated to the replaceability and
sterical accessibility of the leaving ligand, and the overall
charge of the complex.
cis-[Dichlorido-(1,3-di(4-methoxybenzyl)imidazol-2-
ylidene)(dimethylsufoxide)]platinum(II) (2b). A mixture of
1
5
,3-di(4-methoxybenzyl)imidazolium chloride (177 mg,
13 "mol) and CH Cl (10 mL) was treated with silver(I)
2
2
oxide (59 mg, 257 "mol) and stirred for 24 h at room
temperature. Solids were filtered off and the silver NHC
complex was precipitated by addition of hexane. After
decanting and drying in vacuo this intermediate complex
(
200 mg, 443 "mol) was dissolved in DMSO (7.5 mL),
treated with K PtCl (184 mg, 443 "mol), and the mixture
was stirred at 60 °C for 24 h. CH Cl was added, the
reaction mixture was filtered, and the filtrate was washed
with water and dried over Na SO . The volatiles were
removed in vacuo and the remainder was recrystallised
from CH Cl /hexane to yield 225 mg (78 %) of white
crystals of m.p. 206 °C. H NMR (CDCl
.26 (s, 6H, CH , DMSO), 3.81 (s, 6H, OCH
J=15.3 Hz, 4H, CH ), 6.78 (s, 2H, CH, imidazole), 6.92 (d,
J=8.5 Hz, 4H, Ar), 7.33 (d, J=8.5 Hz, 4H, Ar); C NMR
2
4
2
2
2
4
2
2
1
3
, 500 MHz): !
3
3
3
), 5.60 (virt. t,
2
13
(
(
CDCl
3
, 126 MHz): ! 45.6 (DMSO), 53.9 (CH
), 114.3 (Ar), 121.0 (CH, imidazole), 126.9 (Ar),
29.7 (Ar), 143.8 (NCN), 159.7 (Ar); EI-MS: m/z 502 (5%,
Cl , –DMSO), 416 (9), 401 (7), 308 (10), 241 (8), 188
2
), 55.3
Another interesting aspect is the retention of intrinsic
ligand bioactivity in the complexes, e.g. for the CA-4
derived complex 5h. This should allow a high degree of
liberty in devising new pleiotropic anticancer complexes
with various combinations of NHC ligands, spectator
OCH
3
1
–
2
(
10), 121 (100), 78 (12).
ligands, and leaving groups that contribute their inherent cis-[Dichlorido-(1,3-dimethyl-4-(3’,4’,5’-trimethoxyphenyl)-
activity and so influence the overall pharmacological 5-(4’’-methoxyphenyl)imidazol-2-
properties. Likewise, our new access to cis-biscarbene ylidene)(dimethylsufoxide)]platinum(II) (2c). Analogously to
complexes, which is very likely not restricted to platinum, 2b, complex 2c (155 mg, 78%) was obtained from 1,3-
will be of interest to catalysis chemists as it offers a way dimethyl-4-(3’,4’,5’-trimethoxyphenyl)-5-(4’’-methoxyphenyl)-
to fine-tune the stereoelectronic properties of NHC imidazolium iodide (143 mg, 287 "mol), silver(I) oxide
complex catalysts more minutely than before.
2 4
(33 mg, 144 "mol), K PtCl (119 mg, 287 "mol), and
1
DMSO (6 mL) as white crystals of m.p. 143 °C. H NMR
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CDCl
Dalton Transactions
3
, DMSO), 3.71 (s, cis-[Dichlorido-(1,3-dibenzylimidazol-2-ylidene)(1,3-di(4-
(
3
, 500 MHz): ! 3.59 (s, 6H, CH
H, 3’-, 5’-OCH ), 3.79 (s, 3H, 4’’-OCH
), 3.90 (s, 3H, NCH ), 3.94 (s, 3H, NCH
View Article Online
6
3
3
), 3.83 (s, 3H, 4’- methoxybenzyl)imidazol-2-ylidene)]pl aD tOi nI : u1 0m. 1 (0 I 3I )9 /C6DT02 (355 c0 )A .
), 6.33 (s, Complex 2a (104 mg, 176 "mol), 1,3-di(4-
OCH
3
3
3
2
H, Ar), 6.86 (d, J=8.4 Hz, 2H, Ar), 7.10 (d, J=8.8 Hz, 2H, methoxybenzyl)imidazolium chloride (61 mg, 176 "mol), and
13
t
Ar); C NMR (CDCl
3
, 126 MHz): ! 36.2 (N-CH
DMSO), 55.3 (4’’-OCH ), 56.2 (3’-, 5’-OCH ), 60.9 (4’- crystals of m.p. 243 °C. Elemental analysis (%): calc. for
), 107.8 (Ar, C-2’, -6’), 114.3 (Ar, C-2’’, -6’’), 119.5 PtCl (822.69): C, 52.56; H, 4.41; N, 6.81. Found:
3
), 46.3 KO Bu (24 mg, 211 "mol) gave 78 mg (54%) of 5c as white
(
3
3
OCH
3
C
36
H
36
O
2
N
4
2
1
(
Ar, C-1’’), 122.7 (Ar, C-1’), 131.5 (C-4, -5, imidazole), C, 52.18; H, 4.81; N, 6.98; H NMR (CDCl
3
, 500 MHz): ! 3.77
), 5.06 (d, J=14.3 Hz, 2H, CH ), 5.41 (d, J=14.3
), 5.96 (2 & d, J=14.3 Hz, 4H, CH ), 6.45 (s, 2H,
2
35 (2, –DMSO), 562 (2, –Cl , –DMSO), 415 (6), 369 imidazole CH), 6.59 (s, 2H, imidazole CH), 6.80 (d, J=8.5 Hz,
1
31.8 (Ar, C-3’’, -5’’), 138.6 (Ar, C-4’), 142.5 (NCN), 153.3 (s, 6H, OCH
3
2
+
(
Ar, C-3’, -5’), 160.2 (Ar, C-4’’); EI-MS: m/z 712 (M , 1%), Hz, 2H, CH
2
2
6
(
(
11), 355 (67), 340 (34), 78 (56), 63 (56), 50 (100), 36 4H, Ar), 7.12 (d, J=8.5 Hz, 4H, Ar), 7.16 (m, 4H, Ar), 7.29 (m,
13
98).
6H, Ar); C NMR (CDCl
5.3 (OCH ), 114.3 (Ar), 120.2 (imidazole CH), 120.6
imidazole CH), 126.8 (Ar), 128.2 (Ar), 128.4 (Ar), 128.9 (Ar),
29.9 (Ar), 134.9 (Ar), 147.9 (NCN), 149.3 (NCN), 159.6 (Ar);
3 2 2
, 126 MHz): ! 53.6 (CH ), 54.1 (CH ),
5
3
General procedure for the preparation of cis-
II
1
2
(
[
Pt (NHC) (NHC) Cl
2
] complexes 5. Complex 2 (1 equiv) and
1
the respective imidazolium chloride 7 (1 equiv) were dissolved
195
+
t
Pt NMR (CDCl
8, –Cl), 749 (27, –Cl
57 (30), 121 (100), 91 (79).
3
): ! –3603.0; EI-MS: m/z 822 (M , 6%), 786
in dry CH
2
Cl
2
(60 mL/mmol) and treated with KO Bu
(
2
), 502 (9), 441 (22), 307 (11), 247 (38),
(
1.2 equiv) under an atmosphere of dry argon. After stirring at
1
room temperature for 16 h solids were filtered off and the pure
product 5 was precipitated by adding diethyl ether at 4 °C.
cis-[Dichlorido-(1,3-dibenzylimidazol-2-ylidene)(1,3-di(4-
fluorobenzyl)imidazol-2-ylidene)]platinum(II) (5d). Complex
cis-[Dichlorido-bis(1,3-dibenzylimidazol-2-ylidene)]
platinum(II) (5a). Complex 5a (60 mg, 93%) was obtained 2a (80 mg, 135 "mol), 1,3-di(4-fluorobenzyl)imidazolium
t
from 2a (50 mg, 84.4 "mol), 1,3-dibenzylimidazolium chloride chloride (43 mg, 135 "mol), and KO Bu (18 mg, 162 "mol)
t
(
(
(
24 mg, 84.4 "mol), and KO Bu (11 mg, 101 "mol) yield 60 mg afforded 57 mg (53%) of 5d as white crystals of m.p. 241 °C.
93 %) as white crystals of m.p. 287 °C. Elemental analysis Elemental analysis (%): calc. for C H N F PtCl (798.62): C,
34
30
4
2
2
1
%): calc. for C34
H
32
N
4
PtCl
.35. Found: C, 53.04; H, 4.48; N, 7.39. H NMR (CDCl
00 MHz): ! 5.27 (d, J=14.6 Hz, 4H, CH ), 5.99 (d, J=14.6 Hz, (d, J=15.0 Hz, 2H, CH ), 5.92 (d, J=15.0 Hz, 2H, CH ), 6.08
H, CH
.27–7.33 (m, 12H, Ar); C NMR (CDCl
2
(762.63): C, 53.55; H, 4.23; N, 51.13; H, 3.79; N, 7.02. Found: C, 50.61; H, 3.66; N, 7.04; H
1
7
5
4
7
3
,
3 2
NMR (CDCl , 126 MHz): ! 4.96 (d, J=14.3 Hz, 2H, CH ), 5.48
2
2
2
2
), 6.52 (s, 4H, imidazole CH), 7.12–7.19 (m, 8H, Ar), (d, J=14.3 Hz, 2H, CH ), 6.45 (s, 2H, imidazole CH), 6.63 (s,
2
13
3
, 126 MHz): ! 54.1 2H, imidazole CH), 6.98 (t, J=8.7 Hz, 4H, Ar), 7.13–7.18 (m,
(
CH
2
), 120.5 (imidazole CH), 128.2 (Ar), 128.9 (Ar), 134.9 (Ar), 4H, Ar), 7.21 (dd, J=8.7, 5.2 Hz, 4H, Ar), 7.28–7.34 (m, 6H,
195
13
1
49.0 (NCN);
3
3 2 2
Pt NMR (CDCl ): ! –3605.3; EI-MS: m/z 762 Ar); C NMR (CDCl , 126 MHz): ! 53.4 (CH ), 54.1 (CH ),
+
2
(
M , 7%), 726 (11, –Cl), 689 (24, –Cl
2
), 441 (18), 247 (51), 115.9 (d, JCF=21.8 Hz, Ar), 120.4 (imidazole CH), 120.8
1
57 (29), 91 (100).
(imidazole CH), 127.9 (Ar), 128.4 (Ar), 129.0 (Ar), 130.3 (d,
3
Crystal data: C34
H
32
N
4
PtCl
2
, M=762.62, monoclinic, space
JCF=8.2 Hz, Ar), 130.6 (Ar), 134.8 (Ar), 149.0 (NCN), 149.1
1
195
group P2(1)/c, a=7.5380(3), b=33.6480(12), c=12.1810(5) Å, (NCN), 162.7 (d, JCF=248 Hz, Ar);
"
3
Pt NMR (CDCl ): ! –
3
+
=#=90°, $=95.951(3)°, V=3072.9(2) Å , Z=4, %=0.71069 Å, 3605.2; EI-MS: m/z 798 (M , 8%), 761 (28, –Cl), 725 (100, –
–1
!=4.77 mm , T=133 K; 12924 reflections measured, 6540 Cl ), 477 (24), 441 (33), 283 (45), 247 (81), 109 (60), 91 (44).
2
2
unique; final refinement to convergence on F gave R=0.0276 Crystal data: C H N F PtCl , M=796.59, monoclinic, space
34
28
4
2
2
and Rw=0.0601, GOF=0.766. CCDC 1481381.
group C2/c, a=15.6790(6), b=14.1220(6), c=15.1390(8)
3
Å, "=#=90°, $=113.895(5)°, V=3064.8(3) Å , Z=4, %=0.71069
cis-[Dichlorido-bis(1,3-di(4-methoxybenzyl)imidazol-2-
ylidene)]platinum(II) (5b). Complex 2b (88 mg, 135 "mol),
–1
Å, !=4.80 mm , T=133 K; 19249 reflections measured, 3070
2
unique; final refinement to convergence on F gave R=0.0267
1
1
,3-di(4-methoxybenzyl)imidazolium
chloride
(47 mg,
t
and Rw=0.0639, GOF=0.984. CCDC 1481378.
35 "mol), and KO Bu (18 mg, 162 "mol) yielded 74 mg (62%)
of 5b as white crystals of m.p. 211 °C. Elemental analysis (%): cis-[Dichlorido-(1,3-di(4-fluorobenzyl)imidazol-2-
calc. for C38 PtCl (882.74): C, 51.70; H, 4.57; N, 6.35. ylidene)(1,3-di(4-methoxybenzyl)imidazol-2-
Found: C, 51.75; H, 4.46; N, 6.39. H NMR (CDCl
3.77 (s, 12H, OCH ), 5.19 (d, J=14.3 Hz, 4H, CH
J=14.3 Hz, 4H, CH ), 6.53 (s, 4H, imidazole CH), 6.77–6.83 fluorobenzyl)imidazolium chloride (43 mg, 135 "mol), and
d, J=8.5 Hz, 8H, Ar), 7.08–7.16 (d, J=8.5 Hz, 8H, Ar);
NMR (CDCl , 126 MHz): ! 53.7 (CH ), 55.3 (OCH ), 114.3 Elemental analysis (%): calc. for C H N O F PtCl (858.67):
Ar), 120.3 (imidazole CH), 126.9 (Ar), 129.9 (Ar), 148.2 C, 50.36; H, 3.99; N, 6.52. Found: C, 49.91; H, 4.13; N, 6.32;
H
40
O
4
N
4
2
1
3
, 500 MHz): ylidene)]platinum(II) (5e). Complex 5e (13 mg, 11%) was
), 5.93 (d, obtained
from 2b (88 mg, 135 "mol), 1,3-di(4-
!
3
2
2
13
t
(
C
KO Bu (18 mg, 162 "mol) as white crystals of m.p. 223 °C.
3
2
3
36
34
4
2
2
2
(
(
1
95
1
NCN), 159.6 (Ar); Pt NMR (CDCl
3
): ! –3601.0; EI-MS: m/z
3 3
H NMR (CDCl , 500 MHz): ! 3.77 (s, 6H, OCH ), 5.13 (d,
+
8
3
82 (M , 2%), 845 (4, –Cl), 809 (18, –Cl ), 502 (16), 379 (9), J=14.6 Hz, 2H, CH ), 5.22 (d, J=14.3 Hz, 2H, CH ), 5.88 (d,
07 (11), 187 (11), 121 (100).
2
2
2
2 2
J=14.3 Hz, 2H, CH ), 6.04 (d, J=14.6 Hz, 2H, CH ), 6.54 (s,
2
H, imidazole CH), 6.56 (s, 2H, imidazole CH), 6.80 (d, J=8.5
6
| Dalton Trans. 2016, 00, 1-9
This journal is © The Royal Society of Chemistry 20xx
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Page 7 of 10
Plea sD ea ldt oo nn To rt a an ds j au cs tti om n as rgins
Journal Name
ARTICLE
Hz, 4H, Ar), 6.97 (t, J=8.7 Hz, 4H, Ar), 7.12 (d, J=8.5 Hz, 4H, Elemental analysis (%): calc. for C38
H
40
N
4
O
4
PtCl
2
(882.74): C,
View Article Online
13
1
Ar), 7.21 (dd, J=8.7, 5.2 Hz, 4H, Ar); C NMR (CDCl
3
,
51.70; H, 4.57; N, 6.35. Found: C, 51.51 D; OH I :, 1 40 .. 61 09 3 9; / NC 6, D6 T. 02 26 3; 50 HA
), 114.3 (Ar), NMR (CDCl , 500 MHz): ! 3.66 (s, 6H, OCH ), 3.73 (s, 3H,
CF=21.8 Hz, Ar), 120.5 (imidazole CH), 120.5 NCH ), 3.79 (s, 3H, OCH ), 3.81 (s, 3H, NCH ), 3.82 (s, 3H,
), 5.77 (d, J=15.3 Hz, 1H CH ), 5.87 (d, J=15.3 Hz, 1H,
), 5.95 (2 & d, J=15.6 Hz, 2H, CH ), 6.07 (s, 2H, Ar), 6.71
): ! – (d, J=2.1 Hz, 1H, imidazole CH), 6.73 (d, J=2.1 Hz, 1H,
601.7; EI-MS: m/z 858 (M , 6%), 822 (10, –Cl), 786 (39, – imidazole CH), 6.82 (m, 4H, Ar), 7.11 (dd, J=8.0, 1.8 Hz, 2H,
), 663 (8), 502 (12), 477 (27), 283 (31), 175 (25), 121 (100), Ar), 7.21 (dd, J=8.0, 1.8 Hz, 2H, Ar), 7.29–7.37 (m, 6H, Ar);
1
1
26 MHz): ! 53.4 (CH
2
), 53.6 (CH
2
), 55.3 (OCH
3
3
3
2
15.9 (d,
J
3
3
3
3
(
imidazole CH), 126.7 (Ar), 129.7 (Ar), 130.3 (d, JCF=8.2 Hz, OCH
3
2
4
Ar), 130.6 (d,
J
CF=2.7 Hz, Ar), 147.8 (NCN), 149.0 (NCN), CH
2
2
1
195
1
3
59.7 (Ar), 162.7 (d, JCF=249 Hz, Ar); Pt NMR (CDCl
3
+
Cl
2
13
1
09 (98).
C NMR (CDCl
CH ), 54.3 (CH
07.7 (Ar), 114.1 (Ar), 119.8 (Ar), 120.7 (imidazole CH), 120.9
3
, 126 MHz): ! 36.2 (NCH
3
), 36.3 (NCH
3
), 54.2
(
2
2
), 55.3 (OCH ), 56.2 (OCH
3
3
), 60.9 (OCH
3
),
cis-[Dichlorido-(1,3-dibenzylimidazol-2-ylidene)(1,3-
1
bis(3,5-dimethoxybenzyl)imidazol-2-ylidene)]platinum(II)
(
imidazole CH), 123.0 (Ar), 127.6 (Ar), 127.9 (Ar), 128.3 (Ar),
(
5f). Complex 5f (35 mg, 26%) was obtained from 2a (90 mg,
53 "mol), 1,3-bis(3,5-dimethoxybenzyl)imidazolium chloride
1
29.0 (Ar), 131.1 (Ar), 131.5 (Ar), 135.2 (Ar), 138.5 (Ar), 146.6
1
195
t
(NCN), 149.3 (NCN), 153.1 (Ar), 160.0 (Ar);
Pt NMR
(
62 mg, 153 "mol), and KO Bu (21 mg, 184 "mol) as white
crystals of m.p. 237 °C. Elemental analysis (%): calc. for
PtCl (882.74): C, 51.70; H, 4.57; N, 6.35. Found:
C, 51.41; H, 5.18; N, 6.43; H NMR (CDCl
s, 12H, OCH ), 5.05 (d, J=14.3 Hz, 2H, CH
Hz, 2H, CH ), 5.97 (dd, J=14.6, 1.8 Hz, 4H, CH
+
(
CDCl
19 (39, –Cl
91 (47).
Crystal data: C38
space group
c=12.1160(4) Å, "=#=90°, $=101.539(3)°, V=3935.5(3) Å ,
3
): ! –3616.9; EI-MS: m/z 882 (M , 1%), 847 (8, –Cl),
8
2
), 690 (5), 561 (4), 369 (12), 247 (100), 157 (7),
C
38
H
40
O
4
N
4
2
1
3
, 500 MHz): ! 3.73
), 5.32 (d, J=15.0
), 6.35 (t,
H
40
N
4
O
4
PtCl
2
&CH
2
Cl
2
, M=967.65, monoclinic,
b=29.7780(14),
(
3
2
P2(1)/c,
a=11.1330(4),
2
2
3
J=2.4 Hz, 2H, Ar), 6.42 (d, J=2.4 Hz, 4H, Ar), 6.52 (s, 2H,
imidazole CH), 6.60 (s, 2H, imidazole CH), 7.17 (m, 4H, Ar),
–1
Z=4, %=0.71069 Å, !=3.88 mm , T=133 K; 23066 reflections
2
13
measured, 7701 unique; final refinement to convergence on F
7
.28–7.33 (m, 6H, Ar); C NMR (CDCl
3
, 126 MHz): ! 54.1
gave R=0.058 and Rw=0.1494, GOF=0.934. CCDC 1481379.
(
CH ), 54.1 (CH ), 55.6 (OCH ), 100.3 (Ar), 106.3 (Ar), 120.6
2
2
3
(
imidazole CH), 120.8 (imidazole CH), 128.2 (Ar), 128.4 (Ar), General procedure for the preparation of cis-
II
+
–
1
1
29.0 (Ar), 135.0 (Ar), 137.3 (Ar), 148.9 (NCN), 148.9 (NCN), [Pt (NHC)
2
(PPh
): ! –3604.0; EI-MS: m/z 882 triphenylphosphane (5 equiv) and complex 5 (1 equiv) in
), 689 (17), 561 (13), CH Cl (100 mL/mmol) was stirred at room temperature for
42 (16), 367 (37), 247 (100), 157 (22), 91 (74).
16 h. The solvent was removed in vacuo, and the residue was
recrystallised from CH Cl /hexane.
3
)Cl] Cl
complexes 8.
A
solution of
195
61.2 (Ar);
Pt NMR (CDCl
3
+
(
M , 4%), 846 (14, –Cl), 809 (17, –Cl
2
2
2
4
2
2
cis-[Dichlorido-(1,3-dibenzylimidazol-2-ylidene)(1-benzyl-
-methylimidazol-2-ylidene)]platinum(II) (5g). Complex 5g
29 mg, 50%) was obtained from 2a (50 mg, 84,4 "mol), 1-
cis-[Chlorido-bis(1,3-dibenzylimidazol-2-ylidene)(triphenyl
phosphane)]platinum(II) chloride (8a). Complex 8a (32 mg,
3
(
9
5%) was obtained from 5a (25 mg, 32.8 "mol) and
benzyl-3-methylimidazolium chloride (18 mg, 84,4 "mol), and
t
triphenylphosphane (43 mg, 164 "mol) as colourless crystals
KO Bu (15 mg, 127 "mol) as white crystals of m.p. 243 °C.
of m.p. 173 °C. Elemental analysis (%): calc. for
Elemental analysis (%): calc. for C28
H
28
N
4
PtCl
2
(686.54): C,
1
C
52
H
47
N
4
PPtCl
2
(1024.92): C, 60.94; H, 4.62; N, 5.47. Found:
4
8.98; H, 4.11; N, 8.16. Found: C, 48.55; H, 3.80; N, 7.83; H
1
C, 60.74; H, 4.58; N, 5.37; H NMR (CDCl
3
, 500 MHz): ! 4.68
), 4.96 (d, J=14.0 Hz, 2H, CH ), 5.69
), 5.92 (d, J=14.0 Hz, 2H, CH ), 6.68
s, 2H, imidazole CH), 7.02 (d, J=7.6 Hz, 4H, Ar), 7.12 (t,
NMR (CDCl
3
, 500 MHz): ! 3.92 (s, 3H, CH
), 5.71–5.83 (2 & d,
), 6.08 (d, J=14.5 Hz, 1H, CH ), 6.50 (d,
3
), 5.23 (m, 2H,
(
(
(
d, J=14.6 Hz, 2H, CH
2
2
CH
2 2
), 5.61–5.71 (d, J=15.1 Hz, 1H, CH
d, JJ=14.6 Hz, 2H, CH
2
2
J=15.1 Hz, 2H, CH
2
2
J=1.4 Hz, 1H, imidazole CH), 6.52 (d, J=1.4 Hz, 1H, imidazole
CH), 6.64 (d, J=1.4 Hz, 1H, imidazole CH), 6.67 (d, J=1.4 Hz,
J=7.6 Hz, 4H, Ar), 7.19–7.25 (m, 4H, imidazole CH, Ar), 7.25–
7
.29 (m, 5H, Ar), 7.31–7.42 (m, 17H, Ar, PPh
3
), 7.47–7.53 (m,
1
7
5
1
H, imidazole CH), 7.02–7.09 (m, 2H), 7.11–7.19 (m, 4H),
13
13
3H, PPh
3
); C NMR (CDCl
3
, 126 MHz): ! 54.0 (CH ), 54.3
2
.25–7.34 (m, 9H); C NMR (CDCl
3.8 (CH ), 54.0 (CH ), 54.1 (CH
20.4 (imidazole CH), 120.9 (imidazole CH), 122.4 (imidazole
3
, 126 MHz): ! 37.9 (CH
3
),
(
CH
2
), 121.8 (imidazole CH), 123.2 (imidazole CH), 128.1 (Ar),
2
2
2
), 120.0 (imidazole CH),
1
1
28.7 (Ar), 128.8 (Ar), 129.0 (d, JCP=55 Hz, PPh ), 129.0 (d,
3
3
J
4
CP=11 Hz, PPh
3
), 129.1 (Ar), 131.4 (d, JCP=2.7 Hz, PPh
3
),
CH), 127.7 (Ar), 127.8 (Ar), 128.3 (Ar), 128.9 (Ar), 128.9 (Ar),
29.0 (Ar), 134.8 (Ar), 135.0 (Ar), 148.1 (NCN), 149.0 (NCN);
2
1
33.7 (Ar), 134.2 (d, JCP=11 Hz, PPh
3
), 134.3 (Ar), 144.9 (d,
1
1
2
2
31
95
+
JCP-cis=10 Hz, NCN), 162.8 (d, JCP-trans=151 Hz, NCN);
P
Pt NMR (CDCl
9, –Cl), 613 (21, –Cl
71 (80), 158 (16), 91 (100).
3
): ! –3610.7; EI-MS: m/z 686 (M , 3%), 650
1
195
NMR (CDCl
CDCl ): ! –4098.7 / –4120.8 (d, JPtP = 2377 Hz); EI-MS: m/z
62 (11%, –PPh ), 726 (14, –Cl, –PPh ), 689 (42, –Cl , –
), 597 (9), 441 (33), 350 (11), 262 (99), 247 (100), 183
3
, 202 MHz): ! 13.1 ( JPPt=2366 Hz);
Pt NMR
(
2
), 441 (8), 365 (18), 284 (7), 247 (43),
(
3
1
7
3
3
2
cis-[Dichlorido-(1,3-dibenzylimidazol-2-ylidene)(1,3-
dimethyl-4-(3’,4’,5’-trimethoxyphenyl)-5-(4’’-
methoxyphenyl)imidazol-2-ylidene)]platinum(II)
PPh
3
(
52), 157 (34), 91 (95).
(5h).
Crystal data: C52H N PPtCl , CH Cl , 2H O, M=1145.84,
47 4 2 2 2 2
Complex 5h (19 mg, 73%) was obtained from 2c (21 mg, 30
mol), 1,3-dibenzylimidazolium chloride (9 mg, 30 "mol), and
triclinic, space group P-1, a=11.4460(4), b=11.7520(4),
c=19.7120(8) Å, "=75.959(3)°, $=74.604(3)°, #=73.708(3)°,
"
t
KO Bu (4 mg, 35 "mol) as white crystals of m.p. 266 °C.
3
–1
V=2412.88(16) Å , Z=2, %=0.71069 Å, !=3.21 mm , T = 133
This journal is © The Royal Society of Chemistry 20xx
Dalton Trans. 2016, 00, 1-9 | 7
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Plea sD ea ldt oo nn To rt a an ds j au cs tti om n as rgins
Page 8 of 10
Paper
Dalton Transactions
K; 34049 reflections measured, 9655 unique; final refinement mM stock solutions in DMF (5 mM in DMSO for 5Vgiew, 1Ar0ticlme OMnlinine
2
to convergence on F gave R=0.0582 and Rw=0.1538, DMSO for CDDP) with water, and add eD dO It :o10 e. 1a0 c3 h9 / Cw 6 eD l Tl 0o 2f3 5t h0 eA
GOF=0.994. CCDC 1481380.
microtiter plates with working concentrations ranging from 100
M to 25 nM. DMF or DMSO was used as a negative control.
Treatment of the cells with 5a-h and 8a-b lasted for 72 h at
7 °C. The culture medium was replaced with a solution of
MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium-
"
cis-[Chlorido-bis(1,3-di(4-methoxybenzyl)imidazol-2-
ylidene)(triphenylphosphane)]platinum(II) chloride (8b).
Complex 8b (23 mg, 88%) was obtained from 5b (20 mg,
3
2
2.7 "mol) and triphenylphosphane (30 mg, 114 "mol) as
colourless crystals of m.p. 138 °C. Elemental analysis (%):
calc. for C56 PPtCl (1145.02): C, 58.74; H, 4.84; N,
.89. Found: C, 58.39; H, 4.98; N, 4.93; H NMR (CDCl
00 MHz): ! 3.71 (s, 6H, OCH ), 3.79 (s, 6H, OCH ), 4.55 (d,
), 5.00 (d, J=14.3 Hz, 2H, CH ), 5.52 (d,
), 5.84 (d, J=14.3 Hz, 2H, CH ), 6.56–6.64
d, J=8.5 Hz, 4H, Ar), 6.71 (s, 2H, imidazole CH), 6.84–6.90
bromide] (0.05 % in PBS) and the cells were incubated for
another 2 h. The MTT solution was discarded and the water-
insoluble formazan crystals, formed by metabolically viable
cells, were dissolved in SDS/DMSO. The absorbance of the
formazan solution was measured at 630 nm, the background
absorbance at 570 nm. Means ± SDs were calculated from
four independent values.
H
55
N
4
O
4
2
1
4
5
3
,
3
3
J=14.3 Hz, 2H, CH
J=14.3 Hz, 2H, CH
2
2
2
2
(
(
d, J=8.5 Hz, 4H, Ar), 6.90–6.96 (d, J=8.5 Hz, 4H, Ar), 7.12 (s, Electrophoretic mobility shift assay (EMSA assay)
2
H, imidazole CH), 7.22–7.26 (d, J=8.5 Hz, 4H, Ar), 7.29–7.41
The complexes 1b, 5b, and 8b were tested for their interaction
13
(
m, 12H, PPh
3
), 7.47–7.52 (m, 3H, PPh
26 MHz): ! 53.6 (CH ), 53.9 (CH ), 55.3 (OCH
), 114.4 (Ar), 114.5 (Ar), 121.6 (imidazole CH), 122.7
3
); C NMR (CDCl
3
,
with circular pBR322 plasmid DNA in electrophoretic mobility
33
1
2
2
3
), 55.3
shift assays according to a general method by Huq et al..
(
(
OCH
3
Briefly, 1.5 "g pBR322 plasmid DNA in freshly sterile-filtrated
TE buffer (10 mM Tris/HCl, 1 mM EDTA, pH 8.0) were
incubated with 0 "M (TE buffer with plasmid DNA), 5 "M, 10
3
imidazole CH), 125.4 (Ar), 126.3 (Ar), 129.0 (d, JCP=10 Hz,
1
J
PPh
3
), 129.1 (d,
CP=55 Hz, PPh
CP=2.7 Hz, PPh ), 134.2 (d,
CP-cis=10 Hz, NCN), 162.6 (d,
, 202 MHz): ! 13.3 ( JPPt=2360 Hz);
): ! –4097.4 / –4119.3 (d, JPtP = 2361 Hz);
EI-MS: m/z 848 (6%, –Cl, –PPh ), 809 (21, –Cl , –PPh ), 687
6), 501 (19), 379 (10), 307 (14), 262 (86), 183 (97), 121
100).
3
), 129.9 (Ar), 130.1 (Ar),
4
2
1
1
31.3 (d,
44.0 (d,
J
J
3
3
JCP=10 Hz, PPh ),
"
M, 25 "M and 50 "M of the complexes or cisplatin as a
positive control for 24 h at 37 °C. Agarose gel electrophoresis
1%) was conducted at 66 V for 4 h. DNA bands were
2
2
JCP-trans=151 Hz,
1
31
NCN); P NMR (CDCl
3
(
195
Pt NMR (CDCl
3
visualised via staining with 10 "g/mL ethidium bromide in 0.5x
TBE buffer (900 mM Tris/HCl, 900 mM boric acid, 25 mM
EDTA, pH 8.3) for 30 min at room temperature. The stained
DNA was documented by UV excitation. EMSA assays were
performed at least twice for each of the tested complexes.
3
2
3
(
(
X-ray data collection and structural determination
Data collection and cell refinement by X-AREA-STOE. The
single crystal samples were irradiated with Mo-K% at 133 K.
The structures were solved by direct methods using SIR 97
Acknowledgements
2
We thank the Deutsche Forschungsgemeinschaft (grant
Scho402/12), the COST Action CM1105 ‘Functional metal
complexes that bind to biomolecules’, and the University
Bayreuth Graduate School for financial support.
and refined by full matrix least-squares on F for all data using
SHELXL 2014. All hydrogen atoms were added at calculated
positions and refined using a riding model. Anisotropic thermal
displacement parameters were used for all non-hydrogen
atoms. For 5d, the two fluorine atoms on the phenyl rings
were disordered and the corresponding hydrogens could not
be located, yet detected in the 1H NMR spectrum. For further
details cf. Supporting Information. The crystallographic data
were deposited with The Cambridge Crystallographic Data
Centre CCDC under no. 1481381 (5a), 1481378 (5d),
Notes and references
1
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| Dalton Trans. 2016, 00, 1-9
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DOI: 10.1039/C6DT02350A
Platinum(II) complexes bearing two different, cis-oriented, N-heterocyclic carbene
ligands are readily accessible for catalysis or as selective, pleiotropic anticancer
agents