Heterobimetallic PtII-AuI Complexes Comprising Unsymmetrical 1,1-Bis(diphenylphosphanyl)methane Bridges: Synthesis, Photophysical, and Cytotoxic Studies

Article abstract of DOI:10.1002/ejic.201801297

In the present work, a series of aryl-cycloplatinated(II) complexes with general formula [Pt(C^{^}N)(Ar)(κ¹-dppm)], 1, [C^{^}N = 7,8-benzoquinolinyl (bzq) or 2-phenylpyridinyl (ppy); Ar = C₆F₅ or p-MeC₆H₄, dppm = 1,1-bis(diphenylphosphanyl)methane] was employed in the reaction with AuCl(SMe₂) in order to generate heterobimetallic Pt^II-Au^I complexes, [Pt(C^{^}N)(Ar)(μ-dppm)Au(Cl)], 2, featuring a dppm bridge between the metal centers. The expectation was to induce metallophilic character into the excited state and to reduce non-radiative deactivation pathways of the dangling auxiliary κ¹-dppm ligand through molecular motions, to improve the photophysical properties. After characterization of the new complexes by means of NMR spectroscopy and X-ray crystallography technique, the photophysical properties of all the complexes were investigated by UV/Vis and photoluminescence spectroscopy. Both of the monometallic complexes and heterobimetallic products have shown to be luminescent in different states and temperature conditions. However, by addition of Au^I, the impact on the photophysics of the heterobimetallic products in relation to the precursors with dangling dppm is minimal, a finding which can be attributed to the absence of a Pt^II-Au^I bond in these compounds. Indeed, the character of the excited states of the monomer Pt^II complexes and their corresponding bimetallic Pt^II-Au^I ones are similar, as confirmed by density functional theory (DFT) and time resolved DFT (TD-DFT) calculations. The cytotoxic activities of the compounds along with that of [ClAu(μ-dppm)AuCl] were evaluated against human breast cancer (MCF-7), human lung cancer (A549), human ovarian cancer (SKOV3) and non-tumorigenic epithelial breast (MCF-10A) cell lines. The highest activity was found for the heterometallic Pt-Au species, suggesting a cooperative effect of both metallic fragments. The most cytotoxic compound, i.e. [Pt(bzq)(p-MeC₆H₄)(μ-dppm)Au(Cl)], 2b, effectively causes cell death in MCF-7 cancer cell line by inducing apoptosis. Fluorescence microscopy experiments for 2a were performed.

Full text of DOI:10.1002/ejic.201801297

A Journal of
Accepted Article
Title: Heterobimetallic Pt(II)−Au(I) Complexes Comprising
Unsymmetrical 1,1-Bis(diphenylphosphino)methane Bridge:
Synthesis, Photophysical and Cytotoxic Studies
Authors: Hamid R. Shahsavari, Nora Giménez, Elena Lalinde, M.
Teresa Moreno, Masood Fereidoonnezhad, Reza Babadi
Aghakhanpour, Mehri Khatami, Foroogh Kalantari, Zahra
Jamshidi, and Mozhdeh Mohammadpour
This manuscript has been accepted after peer review and appears as an
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To be cited as: Eur. J. Inorg. Chem. 10.1002/ejic.201801297
Link to VoR: http://dx.doi.org/10.1002/ejic.201801297

10.1002/ejic.201801297
European Journal of Inorganic Chemistry
FULL PAPER
Heterobimetallic
Unsymmetrical
Pt(II)Au(I)
Complexes
Comprising
1,1-Bis(diphenylphosphino)methane
Bridge:
Synthesis, Photophysical and Cytotoxic Studies
Hamid R. Shahsavari*[a], Nora Giménez[b], Elena Lalinde*[b], M. Teresa Moreno[b], Masood
Fereidoonnezhad*[c,d], Reza Babadi Aghakhanpour[a], Mehri Khatami[a], Foroogh Kalantari[d], Zahra
Jamshidi[e], and Mozhdeh Mohammadpour[e]
Abstract: In the present work, a series of aryl-cycloplatinated(II)
complexes with general formula [Pt(C^N)(Ar)(κ1-dppm)], 1, [C^N =
7,8-benzoquinolinyl (bzq) or 2-phenylpyridinyl (ppy); Ar = C6F5 or p-
against human breast cancer (MCF-7), human lung cancer (A549),
human ovarian cancer (SKOV3) and non-tumorigenic epithelial breast
(MCF-10A) cell lines. The highest activity was found for the
heterometallic Pt-Au species, suggesting a cooperative effect of both
metallic fragments. The most cytotoxic compound, i.e. [Pt(bzq)(p-
MeC6H4)(-dppm)Au(Cl)], 2b, effectively causes cell death in MCF-7
cancer cell line by inducing apoptosis. Fluorescence microscopy
experiments for 2a were performed.
MeC6H4, dppm
=
1,1-bis(diphenylphosphino)methane] were
employed in the reaction with AuCl(SMe2) in order to generate
heterobimetallic Pt(II)-Au(I) complexes, [Pt(C^N)(Ar)(-dppm)Au(Cl)],
2, featuring
a dppm bridge between the metal centers. The
expectation was to induce metallophilic character into the excited
state and to reduce non-radiative deactivation pathways of the
dangling auxiliary κ1-dppm ligand through molecular motions, to
improve the photophysical properties. After characterization of the
new complexes by means of NMR spectroscopy and X-ray
crystallography technique, the photophysical properties of all the
complexes were investigated by UV-Vis and photoluminescence
spectroscopies. Both of the monometallic complexes and
heterobimetallic products have shown to be luminescent in different
states and temperature conditions. However, by addition of Au(I), the
impact on the photophysics of the heterobimetallic products in relation
to the precursors with dangling dppm is minimal, a finding which can
be attributed to the absence of a Pt(II)-Au(I) bond in these compounds.
Indeed, the character of the excited states of the monomer Pt(II)
complexes and their corresponding bimetallic Pt(II)-Au(I) ones are
similar, as confirmed by density functional theory (DFT) and time
resolved DFT (TD-DFT) calculations. The cytotoxic activities of the
compounds along with that of [ClAu(µ-dppm)AuCl] were evaluated
Introduction
The rational design and synthesis of mixed metal
complexes have been a rising area of interest in recent years.[1]
For example, mixed metal complexes have been successfully
applied in catalysis of sequential reactions in which each metal
center was found to play the role of one catalytic center,[2] and, in
many occasions, the heterometallic complexes exhibited a higher
catalytic activity or selectivity compared with their monometallic
analogues.[3] Furthermore, the combination of two or more metal
centers into a unique structure have been shown to enhance the
anticancer activity of the structure or to induce unique properties
due to the new physicochemical characteristics, coming from
synergic effects between the metal centers.[4] Sometimes, these
complexes display luminescent properties due to presence of
organic luminophores in their structure, what provides the
posibility to be visualized by fluorescence microscopy. In this
context, luminescent heterometallic complexes provide the
opportunity to generate new metal-based structures able of
displaying cytoxic activity and give information about their
internalization mechanism, localization, biodistribution and
biological targets.[4b, 5]
[a]
Dr. H. R. Shahsavari, Dr. R. Babadi Aghakhanpour, M. Khatami;
Department of Chemistry, Institute for Advanced Studies in Basic
Sciences
(IASBS),
Zanjan
45137-66731,
Iran.
E-mail:
shahsavari@iasbs.ac.ir
https://iasbs.ac.ir/personalpage?id=32125&staff=0
ORCID: 0000-0002-2579-2185
The metal centers can be linked by variable spacer ligands
in order to form heterobimetallic complexes; however, no diversity
is observed in these ligands to be appropriate candidates as
spacers mainly due to the difficulty in prohibiting the formation of
undesirable chelate instead of an appropriate bridging ligand or
reorganization processes leading to symmetrical homobimetallic
[b]
[c]
Nora Giménez, Prof. Elena Lalinde, Prof. M. Teresa Moreno;
Departamento de Química-Centro de Síntesis Química de La Rioja,
(CISQ), Universidad de La Rioja, 26006, Logroño, Spain. E-mail:
elena.lalinde@unirioja.es
https://cisq.unirioja.es/en/gmmo.php
Dr. M. Fereidoonnezhad; Toxicology Research Center, Ahvaz
Jundishapur University of Medical Sciences, Ahvaz, Iran. E-mail:
fereidoonnezhad-m@ajums.ac.ir
systems.[5c]
Among
the
linker
ligands,
1,1-
bis(diphenylphosphino)methane (dppm) has a special dignity for
two reasons. First, dppm in its chelated form is under strain due
to the formation of four-membered ring and, this fact facilitates the
binding coordination mode as monodentate ligand with a free
phosphine head. Secondly, due to the presence of a short chain
between the phosphine heads, dppm is able to hold the metal
centers close to each other in which the formation of metal-metal
http://isid.research.ac.ir/Masood_Fereidoonnezhad
[d]
[e]
Dr. M. Fereidoonnezhad, Foroogh Kalantari; Department of Medicinal
Chemistry, Student Research Committee, Ahvaz Jundishapur
University of Medical Sciences, Ahvaz, Iran.
Dr. Z. Jamshidi, Dr. M. Mohammadpour; Chemistry & Chemical
Engineering Research Center of Iran, Tehran, 14968-13151, Iran.
Supporting information for this article is given via a link at the end of
the document.
1
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10.1002/ejic.201801297
European Journal of Inorganic Chemistry
FULL PAPER
bond becomes more probable. These properties of the dppm
make it a good candidate to be located as an unsymmetrical
bridge between two different metal centers particularly in d8-d10 or
d8-d8 heterobimetallic complexes. In the synthesis of such
physiological conditions, avoiding off-target reactions, and,
therefore, simplifies the potential therapeutic applications.[17]
Additionally, recent studies have also demonstrated that the
antiproliferative properties of some of these platinum complexes
improved upon attaching a second Au(I) unit to the organometallic
Pt compound.[18] Because of the mechanisms of action of gold
complexes are likely to be different from those of platinum, in
some cases, the heteronuclear Pt(II)-Au(I) complexes exhibit
antiproliferative properties in vitro in human cancer cells in the
range of cisplatin or higher.[4c, 15j]
complexes, firstly,
a
complex featuring one (or more)
monodentated κ1-dppm ligand is isolated and then reacted with
the second metal center to generate a heterobinuclear structure.
It is worthy to note that some of these heterometallic complexes,
in occasions, exhibit luminescence properties, which have been
associated to the presence of metal-metal bonds.[6]
Cycloplatinated(II) complexes are an important class of
compounds because of their attractive photochemical and
photophysical properties with successful applications in light
emitting devices,[7] dye sensitized solar cell,[8] biosensors, photo-
switches,[9] optoelectronic devices,[10] photocatalysts[11] and
biological imaging.[12] These complexes display very strong Pt-C
bonds that increase the energy of the higher lying metal-centered
d-d states to a level high enough to suppress the thermal
population. Consequently, depending on the auxiliary ligand,
these complexes display highly efficient and tunable
Following our interest on cycloplatinated complexes
featuring an unsymmetrical dppm bridge,[19] in this contribution
some [Pt(C^N)(Ar)(k1-dppm)], 1, complexes with monodentate
dppm ligand were employed as precursors to give a series of
heterobimetallic complexes with general formula [Pt(C^N)(Ar)(µ-
dppm)AuCl], 2. We anticipated that an intra-molecular
metallophilic interaction could be established between Pt(II) and
Au(I) centers, which could influence the optical properties.[14h] In
addition, it is worthy to note that among the new non-platinum
drugs especially gold compounds have gained more attention.[20]
Epidemiological, clinical and experimental studies show that gold
metallodrugs are promising cancer chemotherapeutic agents.[21]
Auranofin, one of the best-known lead structure of gold(I)
complexes, which also incorporates a phosphine ligand, is under
phase I/II clinical trial studies for the treatment of non-small cell
lung cancer,[22] small cell lung cancer,[22] ovarian cancer,[23] and
primary peritoneal cancer.[23] In this context, complexes 1 and 2
offer us the opportunity to investigate the role of the two metallic
fragments in the cytotoxic activity and properties of the final
complexes. A number of reports support the idea that bimetallic
complexes may enable novel and synergic modes of interaction
with biomolecular targets.[24]
3
3
phosphorescence attributed to LC or admixtures LC/3MLCT or
13]
3LLCT/3MLCT states.[10a,
Heteronuclear cycloplatinated
complexes with the metal centers connected via metallophilic
interactions,[14] or remotely connected through a linker ligand[15]
are also an intensively studied research area, mainly due to their
interesting luminescence properties, though in these systems an
straight relationship between structures and emission properties
is still unclear.
In recent years, cycloplatinated(II) complexes have also
attracted growing attention for their possible use as anticancer
drugs and the results are quite promising.[16] These complexes,
possess strong (Pt-C) bonds what increases their stability in
Scheme 1. Synthetic routes for (a) Pt(II)-dppm, (b) Pt(II)-dppmO and (c) Pt(II)-Au(I) complexes, with atom numbering of the C^N ligands.
2
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10.1002/ejic.201801297
European Journal of Inorganic Chemistry
FULL PAPER
respectively, in which, the dppm ligand behaves as
a
monodentate pendant ligand. It should be noted, that the
synthesis and characterization of tolyl complexes, 1b and 1c, has
been previously reported.[19a] The pentafluorophenyl complex, 1a,
is new and it was characterized by different spectroscopic
methods. It was found that the free phosphine head is oxidized
during the crystallization process in the solvent mixture of
CH2Cl2/Et2O, yielding the complex [Pt(bzq)(C6F5)(κ1-dppmO)],
1aO. Finally, the complexes 1a-c were reacted with the Au
precursor complex [AuCl(SMe2)][25] to give the new
heterobimetallic complexes [Pt(C^N)(Ar)(-dppm)AuCl], 2, Ar =
C6F5, C^N = bzq (2a); Ar = p-MeC6H4, C^N = bzq (2b); Ar = p-
MeC6H4, C^N = ppy (2c), respectively.
Results and Discussion
Synthesis and Characterization
The syntheses of the platinum complexes and the
heterobimetallic Pt-Au complexes was carried out as depicted in
Scheme 1. Treatment of the heteroleptic aryl-cycloplatinated
67
complexes
[Pt(C^N)(Ar)(dmso)]
(A-C)66,
with
1,1-
bis(diphenylphosphino)methane (dppm) in acetone, in a 1:1 molar
ratio, provided yellow or greenish solutions, which after workup
afforded
the
corresponding
monodentate
complexes
[Pt(C^N)(Ar)(κ1-dppm)], 1, Ar = C6F5, C^N = bzq (1a); Ar = p-
MeC6H4, C^N = bzq (1b);[19a] Ar = p-MeC6H4, C^N = ppy (1c),[19a]
Figure 1. 31P{1H} NMR spectra of the complexes I) 1a, and II) 2a.
a
The new complexes 1a, 2a-c were analyzed by ESI
(electrospray ionization) mass spectroscopy and characterized by
multinuclear (1H, 31P{1H}, 19F) NMR spectroscopy. The
corresponding ESI (+) mass spectra of the complexes are
depicted in Figures S1-S4. The molecular peak for the complexes
1a, 2a, 2b and 2c are related to [M-C6F5]+, [M + Na]+ and [M + H]+
fragments, respectively. The numerical details for the NMR
spectra are listed in the Experimental Section. The 19F NMR
resonance, Pª appears as doublet (2JP b = 13 Hz) and exhibits
P
one-bond Pt coupling constant of 1963 Hz, comparable to those
found in 1b,c, whereas Pb is resolved as pseudo-triplet due to the
additional coupling to a close o-F of C6F5 group. For 1a-O, the
oxidation of the terminal phosphorus atom causes a remarkable
downfield shift of the Pb signal ( 25.3) and a slight increase of the
three bond 195Pt-31Pb coupling constant (46 Hz). For all the
heterobimetallic complexes 2a-c, the most significant feature is
observed in the Pb resonance, which also shifts downfield, in
relation to the precursors, due to coordination to Au(I), whereas,
spectra of 1a and 1a-O exhibit the typical AA’MXX’ pattern for 2o-
19
F, p-F and 2m-F of the C6F5 ring with relatively high 3J195
F (496
Pt–
1
a
Hz 1a, 490 Hz 1a-O), supporting the trans disposition of the N
relative to the pentafluorophenyl group. As illustration, the 31P{1H}
NMR spectra of complexes 1a/2a and 1c/2c are provided in
Figures 1 and S5, respectively. The 31P{1H} NMR spectrum of 1a
(see Figure 1) compares to those of related 1b,c. It displays the
expected two different signals due to the coordinated ( Pa 12.62)
and free (Pb -25.3) P atoms of dppm, respectively, The low field
interestingly, the JPtP value is slightly reduced (1890 2a; 2032
2b, 1960 Hz 2c vs 1963 1a; 2082 1b, 2015 Hz 1c).
The structures of complexes 1aO, 2a and 2b were
stablished by X-ray crystallography (details in the Supporting
Information). Although complex 1a is completely stable in the solid
state, crystals of 1aO in which the free P head of dppm is oxidized,
were separated during attempts to obtain nanocrystals suitable
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10.1002/ejic.201801297
European Journal of Inorganic Chemistry
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for X-ray for complex 1a in CH2Cl2/Et2O. Figure 2 shows the
ORTEP plot of the complex 1aO and a selection of corresponding
geometrical parameters is given in Table S1. The structure
confirms the square-planar coordination environment for the Pt(II)
atom, whose bond distances and angles were similar to other
related cyclometalated derivatives,[26] as well as the mutually
trans disposition between the nitrogen (N1) atom of the bzq ligand
and the ipso-C (C14) of the C6F5 group. The P2-O1 bond length
[1.484(2) Å] and the O1–P2–C angles [112.7(1)-113.5(1)°] of the
terminal dppm-O ligand are in the range of those observed for
terminal phosphine oxides.[27] The P2-C44-P1 backbone of the
dppm-O ligand is inclined by 63.13° to the Pt coordination,
locating the oxygen atom far away the platinum center [Pt····O
4.858(2) Å]. It is noteworthy that one of the phenyl groups lies
above the cyclopatinated ring close to the Pt atom with a Pt-C43
distance [3.472(4) Å] shorter than the Van der Waals limit (4.09
Å),[28] suggesting some degree of Pt··(phenyl) interaction. As is
typical in this type of complexes, the crystal packing of 1aO
includes extensive intermolecular π···π [bzq···bzq (C···C 3.398
Å) interactions and weak [O···H (2.618 Å), F···H (2.564 Å)]
contacts (Figure S6).
Figure 2. ORTEP view of 1aO. Ellipsoids are drawn at the 50% probability level.
Figure 3. ORTEP views of 2a and 2b. Ellipsoids are drawn at the 50% probability level.
4
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10.1002/ejic.201801297
European Journal of Inorganic Chemistry
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Views of the crystal structures of the complexes 2a and 2b
are given in Figure 3 and a selection of the bond lengths and
angles are also included in Table S1. The crystal structures
confirm the coordination of the AuCl unit to the P of the dppm
ligand of the precursors, which acts as a bringing group between
the Pt chromophore and the Au center. The type of ancillary ligand,
i.e. C6F5 (2a) or MeC6H4 (2b), considerably affects the orientation
of P-Au-Cl moiety in relation to the square planar Pt(II) moiety. In
2a, and likely due to steric constrains of the bulky C6F5 ligand, the
planar Pt(II) and P-Au-Cl moieties are situated in the opposite
sides in relation to each other, whereas, in the case of 2b, the Au-
Cl unit leans towards the Pt center. As a consequence the Au-Pt
distance in 2a (5.375 Å) is remarkably longer than that observed
for 2b (3.539 Å). This later distance is larger than those found in
complexes [Pt(bzq)Me(-dppy)AuCl][2.9850(4) Å][14h] and ([Pt(2-
2-C6X4PPh2)(PPh3)(-2-C6X4PPh2)AuCl] [X = H 3.3902(2), X = F
3.1459(2) Å][29] and longer than the sum of the van der Waals radii
of the two metals (3.41 Å)[28] excluding metallophilic interactions.
The crystal packing of 2a (Figure S7) contains dimers
supported by intermolecular π···π contacts (bzq··bzq 3.268-
3.333 Å) (pink lines), reinforced by HPh···Cl (2.744-2.882 Å),
HPh···FC6F5 (2.550 Å), HPh···CPh and HPh···Cbzq (2.784-2.875 Å)
secondary interactions (blue lines), whereas 2b shows a supra-
molecular packing, being supported by HPh···Cbzq (2.761-2.838 Å)
and Cl···Hbzq (2.764-2.788 Å) short interactions (Figure S8).
Figure 4. a) UV-Vis absorbance spectra of 1-2a, 1-2b and 1-2c in CH2Cl2 solutions (5×10-5 M). b) DRUV (diffuse reflectance UV-Vis) spectra of 1-2a, 1-2b and 1-
2c.
charge transfer from Pt(II) to cyclometalated, and phosphine
ligands in complexes 1 and, additionally, from Au(I) to phosphine
UV-Vis spectra
ligand in complexes 2. Expectedly, the bands for bzq complexes
(a,b) are red-shifted in relation to those of ppy complexes, being
attributed to the extending π-conjugation system in bzq ligand.[30]
As can be seen in Figure 4, the spectra of the heterometallic Pt(II)-
Au(I) complexes (2a-c) are rather similar to their corresponding
precursors (1a-c) not only in CH2Cl2 solution but also in the solid
state (Figure 4b).
The electronic absorption spectra of all complexes recorded
in dilute CH2Cl2 solutions are displayed in Figure 4a, while the
relevant data are summarized in Table S2. The high energy
intense bands with wavelengths below 325 nm can be attributed
1
1
to -* intra-ligand IL or ILʹ transitions mainly centered on the
cyclometalated ligand [L = bzq or ppy] and Lʹ = aryl groups [C6F5
or p-MeC6H4]). In addition to the mentioned transitions, these
bands have also contributions from intra-ligand charge transfer in
the phenyl rings of dppm. With reference to previous assignments
in related complexes,[1a] the low energy absorption bands above
1
325 nm could be attributed to mixed MLCT/1IL transitions, with
some 1L’LCT contribution in the tolyl derivatives as suggested by
theoretical calculations. The 1MLCT transitions can involve
5
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10.1002/ejic.201801297
European Journal of Inorganic Chemistry
FULL PAPER
Table 1. Emission parameters for 1a-c and 2a-c.
λem/nma)
Complex
1a
State (Temp.)
τ/μs
Φ(%)
Solid (298 K)
492max, 519, 558sh
494max, 530, 570sh
478max, 514, 553sh
485max, 520, 565sh
485max, 521, 564sh
484max, 519, 555sh
476max, 509, 538sh
474max, 508, 538sh
480max, 511, 545sh
494max, 524
494max, 533, 571sh
465max, 496, 520sh
478max, 513, 553sh
491max, 526, 574sh
494max, 528, 568sh
485max, 521, 558sh
495, 515max, 554sh
489max, 524, 564sh
478max, 514, 542sh
8.4 (89%), 24.1 (11%)
532 (53%), 311 (47%)
3
Solid (77 K)
CH2Cl2 5×10-5 M (77 K)
1b
1c
2a
Solid (298 K)
30.4
11
95
2
Solid (77 K)
CH2Cl2 5×10-5 M (77 K)
221.1(68%), 68.2 (32%)
Solid (298 K)
11.7
72.3
Solid (77 K)
CH2Cl2 5×10-5 M (77 K)
Solid (298 K)
10.44
380
Solid (77 K)
CH2Cl2 5×10-5 M (298 K)
CH2Cl2 5×10-5 M (77 K)
Solid (298 K)
0.3
2b
32.9
89.4
29.3
3.7
Solid (77 K)
CH2Cl2 5×10-5 M (77 K)
2c
Solid (298 K)
9.6
Solid (77 K)
CH2Cl2 5×10-5 M (77 K)
56.2
a exc 365-380 nm.
Figure 5. Normalized emission (solid lines) and excitation (dashed lines) spectra in the solid state of a) 1a-c at 298 K, b) 2a-c at 298 K, c) 1a-c at 77 K and d) 2a-
c at 77 K.
Photoluminescence Spectra
remarkable quenching of the emission in fluid solution could be
ascribed to ease non-radiative deactivation through molecular
motions and non-covalent intermolecular interactions enhanced
in the monodentate 1-dppm precursors 1, due to the presence of
the dangling free phosphine. Besides, ease thermal access to
All complexes (1a-c, 2a-c) exhibit emission in the green
region, in rigid media, either in the solid state (298, 77 K) or in a
CH2Cl2 glassy matrix at 77 K. Excluding complex 2a, the rest of
complexes are not luminescent in fluid CH2Cl2 solution. The
6
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10.1002/ejic.201801297
European Journal of Inorganic Chemistry
FULL PAPER
non-emissive metal centered d-d excited states and also direct
solvent interactions should not be ruled out.[17a, 31]
emitting excited state. Due to the slight red-shift observed in the
emission from 1c to 2c, the emission maxima at low temperature
for the ppy complex 2c (489 nm) is very close to that of bzq
complexes 2a and 2b (494 nm). The photoluminescence quantum
yields were measured in the solid state and, therefore, solid state
effects cannot discarded. The benzoquinolinyl-pentafluorophenyl
complexes 1a and 2a exhibit similar and relatively low quantum
yields () with values of 3% and 2%, respectively, likely related to
a significant quenching associated to extensive intermolecular
·· interactions. By contrast, complex 1c with the ppy ligand
displays a very high  value (95%), which is drastically reduced to
3.7% by incorporation of the AuCl unit in 2c. In opposition to 1a
and 1c, the quantum yield value for 1b (11 %) is enhanced upon
coordination of the AuCl unit in 2b (29.3%).
As mentioned above, only complex 2a exhibits a weak
emission in CH2Cl2 solution at 298 K (Figure S12). However, in
the glass state at 77 K, all the complexes are strongly emissive
exhibiting well resolved vibronic-structured phosphorescence
emission bands (Figure S9). The bands are slightly blue shifted in
relation to those observed in the solid state (298 K and 77 K) and
are located in a close region (478 – 485 nm) with minimal
differences in their maxima. The emission and excitation profiles
suggest rather similar electronic transitions.
The luminescence spectra obtained in solid at 298 K and at
77K are reported in Figure 5 and those obtained in CH2Cl2 at 77
K are provided in Figure S9. The main photophysical parameters
are listed in Table 1. It should be noted that, for all complexes, the
emission band shapes and wavelengths do not vary by changing
the excitation wavelength. As can be seen in Figure 5, both, the
mononuclear (1a-c) and the Pt-Au (2a-c) complexes display
similar structured emissions in the solid state, with spectral shape
broader at room temperature. The well resolved vibrational
progression and the relatively long lifetimes (Table 1) are
indicative of excited states of mixed 3IL/3MLCT nature. The slight
red shifts observed for the bzq complexes (1a,b) in relation to the
ppy complex (1c) in the precursors is in line with the lower energy
gap for the * orbitals of the more delocalized benzoquinolinyl
ligand. A minimal bathochromic shift can be observed for
emission bands of the heterobimetallic complexes Pt-Au (2), in
relation to the Pt precursors (1), which is marginal for 2a and 2b
and more meaningful for 2c (see Figure S10 for comparison).
From 298 to 77 K, the emission bands become intensified and
more structured (see Figure S11 for comparison) and a
remarkable increase in the luminescence lifetime are observed
(Table 1), thus indicating an increase of the 3IL character for the
Figure 6. DFT-optimized geometries of a) 1a, b) 1b, c) 2a and d) 2b in CH2Cl2. Hydrogen atoms were eliminated for clarity.
mentioned complexes were optimized in CH2Cl2 solvent. The
DFT Calculations
available crystal structures directly or indirectly were used to
make input files for the software. The optimized geometries are
shown in Figure 6 and corresponding geometrical parameters are
collected in Table S3. The calculated structures resemble the
crystal structures of 1b,[19a] 2a and 2b.
The electronic structures of complexes 1a, 1b, 2a and 2b
were investigated by DFT (density functional theory) calculations.
Time-dependent DFT (TD-DFT) calculations were also performed
for simulation of the theoretical UV-Vis spectra and to assist in the
spectral assignment. For this purpose, the ground states of the
7
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10.1002/ejic.201801297
European Journal of Inorganic Chemistry
FULL PAPER
The energy levels and compositions of selected molecular
orbitals for 1a, 1b, 2a and 2b are listed in Tables S4-S7,
respectively. Plots of the highest occupied molecular orbital
(HOMO) and lowest unoccupied molecular orbital LUMO are
shown in Figure 7, whereas the plots of frontier orbitals including
“HOMO to HOMO-10” and “LUMO to LUMO+10”, are provided in
Figures S13-S16, respectively.
Figure 7. Plots of HOMO and LUMO for 1a, 1b, 2a and 2b.
Figure 8. Overlaid experimental (spectra) and theoretical (bars) absorbance for a) 1a, b) 1b, c) 2a and d) 2b.
For 1a, the HOMO is located on bzq (71%) and Pt (26%),
p-MeC6H4 is low in most of MOs, while the contribution of dppm
while in 1b the HOMO is mostly centered on p-MeC6H4 ligand
(54%) with lower contributions of Pt (27%) and bzq (11%).
However, in 1b the composition of the HOMO-1, which is close in
energy (0.086 eV), is similar to the HOMO in 1a (bzq 66%, Pt
28%). In both complexes, the LUMO and L+1 are almost
completely localized on bzq fragment. The contribution of C6F5 or
becomes important in higher LUMOs or lower HOMOs.
In the heterobimetallic complexes 2a and 2b, the
composition of the orbital frontiers is rather similar (see Tables S6
and S7) to their precursors 1a and 1b, respectively. Thus, in 2a
the HOMO is located on the bzq (72%) and Pt (25%) and the
LUMO on the bzq (87%). In 2b, the HOMO and H-1 are also close
8
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10.1002/ejic.201801297
European Journal of Inorganic Chemistry
FULL PAPER
in energy (0.044 eV), being contributed from the bzq, Pt and the
aryl ligand (p-MeC6H4 22% in HOMO and 38% in HOMO-1),
whereas the LUMO is centered on bzq fragment (90%). It should
be noted that for both complexes the contribution Au-Cl fragment
is negligible in most of MOs. However, the contribution of dppm
increases from HOMO to HOMO+10 or LUMO to LUMO-10.To
further understand the electronic properties of these complexes,
TD-DFT calculations were carried out for 1a, 1b, 2a and 2b.
Calculated energies, major contributions, and oscillator strengths
of selected spin-allowed electronic transitions together with their
corresponding assignments are collected in Tables S8-S11. A
comparison of the experimental UV-Vis spectra and the
calculated vertical excitations as bars is presented in Figure 8. For
the pentafluorophenyl complexes 1a and 2a, the first excited state
(S0→S1) is mainly contributed by the HOMO→LUMO transition
(379 nm) having similar oscillator strength of 0.054, and thus can
be described as a mixed ILCT/MLCT (L = bzq, M = Pt) transition.
For 1b the lowest excited state S0→S1 is contributed by HOMO
and H-1 to LUMO, supporting a mixed ILCT/MLCT/LʹLCT (Lʹ = p-
MeC6H4) character. For 2b the lowest transition S0→S1
(HOMO→LUMO 87%) has also mixed ILCT/MLCT/LʹLCT
character. In both complexes, the transition is calculated slightly
red shifted (383 nm) in relation to 1a and 2a, in accordance with
the experimental values (exp. 409 1b, 410 nm 2b vs 407 1a, 404
nm 2a).
As expected, the dppm ligand participates in electronic
transitions at higher energies (MLʹʹCT and LʹʹLCT, Lʹʹ = dppm, see
Tables S8-11), but the ILCT character still has an outstanding
presence. It is worthy to note that Au-Cl fragment in 2a and 2b
does not participate in any electronic transitions. According to the
aryl ligands, in 1a and 2a, C6F5 has a very negligible contribution
in the electronic transitions, while p-MeC6H4 ligand in 1b and 2b
exhibit a relatively more effective contribution.
Figure 9. Flow cytometry-based detection of the apoptotic properties of 2b on MCF-7 cell line. Representative scatter plots show apoptosis of MCF-7 cells after 72
hours of incubation with different concentrations of 2b (1, 2, and 4 µM) using the Annexin V-PE/7AAD detection kit. The percentages of apoptotic cells (Q2: late
apoptotic and Q3: early apoptotic) were determined in Annexin V+ cells. Q1: necrotic cells, Q2: late apoptotic cells, Q3: early apoptotic cells, and Q4: living cells.
As shown in Table 2, 2b, as the best studied compound,
showed a good anti-proliferative activity with an IC50 of 5.47 μM,
Biological activity studies
The in vitro cytotoxic activity of 1a-c and 2a-c were
evaluated on three human cancer cell lines, MCF-7 (breast
cancer), SKOV3 (ovarian cancer), and A549 (non-small cell lung
cancer).
10.73 μM and 2.27 μM, compared to that measured for cisplatin,
which was 9.63 μM, 15.66 μM and 11.34 μM against the A549,
SKOV3 and MCF7 cell lines, respectively. Complex 2c, also
exhibited a higher anti-proliferative activity than cisplatin against
9
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10.1002/ejic.201801297
European Journal of Inorganic Chemistry
FULL PAPER
A549 and MCF-7 cancer cell lines with IC50 of 8.51 μM, and 3.89
μM, respectively.
MCF-10A, non-tumorigenic epithelial breast cell line, was
used to investigate the selectivity between cancer and the normal
cell lines. Results showed good selectivity of the compounds
between the tumorigenic and non-tumorigenic cell lines.
Interestingly, complexes 2b and 2c showed greater specificity for
human breast cancer cell with less damage to normal epithelial
breast cell.
The structure-activity relationship (SAR) studies on these
complexes, revealed that series 2a-c, which contain dppm
bonded to the AuCl, showed considerable antitumor activities
compared to the series 1a-c. The presence of the bzq ligand (in
2b) had a greater effect on the cytotoxicity than the ppy ligand (in
2c). On the other hand, the existence of the p-MeC6H4 as the
aromatic group attached to the Pt(II), as it was clear in 2b, had
considerable more cytotoxic effect than the C6F5 ligand (in 2a).
The IC50 of Auranofin, as the best-known lead structure of
gold(I) complexes, was 6.14 μM, 6.28 μM, and 5.17 μM against
the A549, SKOV3, and MCF7 cell lines, respectively. In
comparison to Auranofin, 2b exhibited higher anti-proliferative
activity on A549 and, MCF-7, while, 2c was also showed a higher
antitumor activity than Auranofin against MCF-7.
Series of 1a-c, which have no gold in their structures, as
well as [ClAu(-dppm)AuCl][25] exhibited low potency in inhibiting
cell proliferation and significantly lower in vitro cytotoxicities
against the studied cancer cell lines,[32] compared to series of 2a-
c. The improvement of the IC50 values of the heterometallic
complexes suggests a cooperative effect of both metal fragments.
Table 2. In vitro cytotoxic activity of the synthesized complexes against three cancerous cell lines (A549, SKOV3 and MCF-7) and non-cancerous cell line (MCF-
10A).
IC50 (μM ± SD)
Name
MCF-10A
A549
SKOV3
MCF-7
1a
1b
>100
>100
>100
>100
90.45 ± 1.06
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
1c
2a
86.32 ± 2.17
5.47 ± 1.32
95.16 ± 2.71
10.73 ± 1.72
78.52 ± 1.38
2.27 ± 0.16
2b
2c
8.51 ± 1.82
9.63 ± 1.39
6.14 ± 1.06
>100
18.92 ± 0.28
15.66 ± 1.34
6.28 ± 0.67
>100
3.89± 0.29
11.34 ± 1.52
5.17 ± 0.34
85.31 ± 1.27
cisplatin
Auranofin
-
-
[ClAu(-dppm)AuCl]
Figure 10. Biological emission and intracellular tracking of compounds 2a in MCF-7 cells. The cells were treated with 1000µM of 2a for 4 hours and investigated
immediately by a fluorescent microscope (See Experimental).
10
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10.1002/ejic.201801297
European Journal of Inorganic Chemistry
FULL PAPER
19F{1H} (376.5 MHz)] were recorded on a Bruker Avance DPX 400 MHz
instrument. The 1H NMR spectra were referenced to the residual peak of
the solvents, i.e CDCl3 and CD3COCD3, while the 31P{1H} NMR and 19F{1H}
NMR spectra were referenced to the external 85% H3PO4 and CFCl3,
respectively. The chemical shifts (δ) being reported as ppm and coupling
constants (J) expressed in Hz. Elemental analyses were carried out with a
Carlo Erba EA1110 CHNS/O microanalyzer. Electrospray ion mass
spectra (ESI-MS) were recorded using a HP-5989B spectrometer using
methanol-water as the mobile phase. The UV-Vis absorption spectra were
Determining apoptotic effect of 2b on MCF-7 cell line
We used BioLegend's PE Annexin V Apoptosis Detection
Kit with 7AAD to specifically determine the dose-dependent
apoptotic effect of 2b on cancerous cells. To determine this,
complex 2b with three concentrations (1, 2 and 4 µM) was applied
on MCF-7 cells. As illustrated in Figure 9, with the increase in the
concentration of 2b from 1 to 4 µM, the percentage of the cells in
early apoptotic phase significantly elevates from 3.18% in
untreated cells to 4.85%, 36.40% and 70.00% in the treated cells,
respectively. This observation indicated that 2b compound, is
able to effectively induce apoptosis in cancerous cells in a dose
dependent manner. It implies that anti-proliferative/cytotoxic
effect observed for 2b in cytotoxic assay, could be mediated
through inducing apoptosis in cancer cells.
carried out in
a Hewlett-Packard 8453 spectrophotometer. Diffuse
reflectance UV-Vis (DRUV) data of pressed powder were recorded on a
Shimadzu (UV-3600 spectrophotometer with a Harrick Praying Mantis
accessory) and recalculated following the Kubelka-Munk function.
Excitation and emission spectra were obtained on a Jobin-Yvon Horiba
Fluorolog 3-11 Tau-3 spectrofluorimeter. The lifetime measurements were
performed in
a Jobin Yvon Horiba Fluorolog operating in the
phosphorimeter mode (with an F1-1029 lifetime emission PMT assembly,
using a 450WXe lamp) or with a Datastation HUB-B with a nanoLED
controller and software DAS6. The nanoLEDs employed for lifetime
measurements were of wavelength 450 nm with pulse lengths of 0.8-1.4
ns. The lifetime data were fitted using the Jobin-Yvon software package.
Quantum yields in solid were measured using an F-3018 Integrating
Sphere mounted on a Fluorolog 3-11 Tau-3 spectrofluorimeter. The
complexes [Pt(bzq)(C6F5)(dmso)], A,[33] [Pt(bzq)(p-MeC6H4)(dmso)], B,[34]
[Pt(ppy)(p-MeC6H4)(dmso)], C,[34] [Pt(bzq)(p-MeC6H4)(κ1-dppm)], 1b,[19a]
[Pt(ppy)(p-MeC6H4)(κ1-dppm)], 1c,[19a] [AuCl(SMe2)][25] and [ClAu(-
dppm)AuCl][25] were prepared as reported in the literature. The chemical
shift assignments are based on the NMR labeling for the ligands as are
shown in Scheme 1.
Fluorescence microscopy cellular localization on 2a
Due to the emissive properties of 2a in solution, its
intracellular localization was assessed by fluorescence
mycroscopy imaging (see experimental for details). As illustrated
in Figure 10, the MCF-7 cells treated with 1000µM of 2a for 4
hours show green-blue light emission. As could be observed, 2a
were efficiently penetrated into the cells, mostly localized in the
nucleus with less dispersion in the cytoplasm of MCF-7 cells.[12b]
Synthesis of the complexes
[Pt(bzq)(C6F5)(κ1-dppm)], 1a. To a yellow suspension of A (0.150 gr,
0.243 mmol) in acetone (25 mL), dppm (0.093 gr, 0.2425 mmol) was added.
After 30 min of stirring, the solution obtained was evaporated to dryness
and treated with hexane (5 mL) and cold isopropanol (2 mL) to afford 1a
as a yellow solid. Yield = 58%. Anal. Calcd. for C44H30F5NP2Pt (924.73):
C, 57.15; H, 3.27; N, 1.51%. Found: C, 56.89; H, 3.53; N, 1.78%. ESI (+):
m/z (%) 757 [M-C6F5]+ (100). NMR data in CD3COCD3: δ (1H): 3.65 (d, 1H,
J = 9, 3JPt-H = 26, CH2P2), 6.92-6.88 (m, 6H), 6.96 (t, 1H, 3JH-H ≈ 4JP-H = 6,
H9, bzq), 7.14 (dd, 1H, J = 8, J = 5, H3, bzq), 7.44-7.39 (m, 3H), 7.36-7.33
(m, 4H), 7.66 (t, 2H, J = 8), 7.53 (m, 4H), 7.88 (m, 5H), 8.25 (t, 4H, J = 5,
Conclusions
To be concluded, a series of closely related cyclometalated
Pt(II) with monodentate dppm (1a-c) and their corresponding
cyclometalated Pt(II)-Au(I) complexes (2a-c) were successfully
prepared and characterized. In the heterobimetallic complexes,
dppm ligand was situated as an unsymmetrical bridge between
the Pt(II) and Au(I) centers. The crystal structures of Pt(II)-Au(I)
complexes showed no Pt(II)-Au(I) bonding interaction in these
heterobimetallic complexes. The absence of these Pt(II)-Au(I)
bonds causes that the electronic structures do not remarkably
change in relation to those of Pt(II) parent complexes, as
evidenced by spectroscopy (absorption and emission) and
supported by DFT and TDDFT calculations on selected 1a, 1b,
2a and 2b complexes. These complexes are only emissive in rigid
media exhibiting typical structured bands with well resolved
vibrational progression and relatively long lifetime’s characteristic
of excited states of mixed 3IL/3MLCT nature with remarkable
strong intraligand (cyclometalated) character. The heterometallic
Pt-Au complexes show an improvement of the in vitro cytotoxic
activity against A549 (lung), SKOV3 (ovarian) and MCF-7 (breast)
cancer cell lines in comparison to complexes 1 and [ClAu(µ-
dppm)AuCl], suggesting a cooperative effect of the metal
fragments. Complex 2b exhibited high potency in inhibiting cell
proliferation compared to cisplatin and Auranofin, and can
effectively induce apoptosis in MCF-7 cells in a dose dependent
manner. Also, the effects of complexes 2b and 2c on the
proliferation of the non-tumorigenic epithelial breast (MCF-10A)
revealed good selectivity among the tumorigenic and non-
tumorigenic cell lines. Fluorescence microscopy revealed
effective localization of 2a into MCF-7 human cells.
3JPt-H = 24, H2, bzq), 8.39 (d, J = 8, H4, bzq); δ (31P{1H}): 12.62 (d, 2JPP
=
13, 1JP-Pt = 1963), -25.3 (dm, 2JPP = 13 Hz, 3JPtP = not resolved); δ (19F{1H}):
-115.7 (dm, JPt-oF = 496, 2o-F, C6F5), from -166.5 to -166.9 (m, 1p-F, 2m-
F, C6F5).
[Pt(bzq)(C6F5)(κ1-dppmO)], 1aO. NMR data in CDCl3: δ (1H): 3.34 (dd, J
= 12, J = 8, 3JPt-H = 33, CH2P2), 6.99-6.93 (m, 2H, H3,9, bzq), 7.14-7.12 (m,
6H), 7.27-7.23 (m, 4H), 7.36-7.32 (m, 2H), 7.44 (td, 1H, J = 7, 5JH-P = 2, H8,
bzq), 7.47 (d , J = 8, 1H), 7.61-7.54 (m, 5H), 7.75 (d, J = 8, 1H), 8.00-7.95
(m, 4H), 8.12 (dd, 1H, J = 8, 4JH-H = 1, H4, bzq), 8.20 (d, 1H, J = 5, 3JPt-H
23, H2, bzq); δ (31P{1H}): 25.30 (d, 2JP-P = 13, 3JP-Pt = 46), 12.75 (d, 2JPP
=
=
13, 1JP-Pt = 1950); δ (19F{1H}): -116.2 (dm, JPt-oF = 490, 2o-F, C6F5), -163.3
(t, 1p-F, C6F5), -163.8 (m, 2m-F, C6F5).
[Pt(bzq)(C6F5)(-dppm)AuCl], 2a. [AuCl(SMe2)] (0.02 gr, 0.093 mmol)
was added to a solution of 1a (0.086 gr, 0.093 mmol) in CH2Cl2 (20 mL) at
-50 ºC. After 10 min of stirring, the yellow solution was evaporated until 5
ml and a yellow solid was precipitated with hexane (~10 mL) to obtain 2a
as a yellow solid. Yield = 44 %. Anal. Calcd. for C44H30F5NP2ClPtAu
(1157.15): C, 45.67; H, 2.61; N, 1.21%. Found: C, 45.28; H, 2.87; N, 1.49%.
ESI (+): m/z (%) 1180 [M + Na]+ (12). NMR data in CDCl3: δ (1H): 3.63 (dd,
3
3
4
J = 11, J = 7, JPt-H = 34, CH2P2), 6.88 (t, 1H, JH-H ≈ JP-H = 6, H9, bzq),
7.12-7.04 (m, 6H), 7.24 (d, 1H, J = 5, H3, bzq), 7.37-7.33 (m, 4H), 7.40 (td,
1H, J = 7, 5JH-P = 2, H8, bzq), 7.48-7.44 (m, 3H), 7.64-7.57 (m, 5H), 7.75-
7.71 (m, 5H), 8.17 (dd, 1H, J = 8, JH-H = 1, H4, bzq), 8.74 (d, 1H, J = 5,
4
3JPt-H = 25, H2, bzq); δ (31P{1H}): 19.07 (d, 2JPP = 4, 3JP-Pt = 23), 12.2 (s br,
2JPP = not resolved, 1JP-Pt = 1890); δ (19F{1H}): -116.6 (dm, JPt-oF = 475, 2o-
F, C6F5), -163.2 (t, 1p-F, C6F5), -163.8 (m, 2m-F, C6F5).
[Pt(bzq)(p-MeC6H4)(-dppm)Au(Cl)], 2b. To a solution of 1b (0.04 gr,
0.05 mmol) in CH2Cl2 (15 mL), [AuCl(SMe2)] (0.014 gr, 0.05 mmol) was
added. The mixture was stirred at room temperature for 3 h under an Ar
atmosphere. After concentration of the solvent, the residue was washed
with diethyl ether. The precipitate was filtered and washed with diethyl
ether to give the product as a yellow solid. Yield: 90%. Anal. Calcd. For
C45H37ClNP2PtAu (1081.23): C, 49.99; H, 3.45; N, 1.30%; Found: C, 50.37;
H, 3.54; N, 1.21%. ESI (+): m/z (%) 1082 [M + H]+ (100). NMR data in
Experimental Section
General procedures and materials
2
3
CDCl3: δ (1H): 2.22 (s, 3H, Me, p-MeC6H4), 3.06 (dd, JPH = 8.1, JPtH
=
The reactions were fully performed in common solvents without any
further purification. All NMR spectra [1H (400 MHz), 31P{1H} (161.9 MHz),
37.5, 2H, CH2P2), 6.74 (d, 3JHH = 7.5, 2H), 6.95 (dd, 3JHH = 7.1, 3JHH = 6.5,
11
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10.1002/ejic.201801297
European Journal of Inorganic Chemistry
FULL PAPER
1H), 7.17-7.45 (m, 15H), 7.50 (m, 3H, Ho and H9, bzq), 7.55-7.61 (m, 2H),
Olympus, Japan). The images were taken at 20× and 40× magnification
and analyzed by the Olympus micro imaging software cellSens (Olympus,
Japan). The emission of compound could be detected at two channels
3
7.62-7.69 (m, 1H), 7.76-7.89 (m, 2H), 7.94-8.03 (m, 4H), 8.16 (d, JHH
=
3
1
2
7.1, JPtH = 59.1, 2H); δ (31P) 18.36 (d, JPtP = 2032.2, JPP = 14.5, 1P),
19.67 (d, 3JPtP = 84.3, 2JPP = 14.6, 1P).
(Excitation=365/10,
Emission=580LP).
Emission=420LP
and
Excitation=535/30,
[Pt(ppy)(p-MeC6H4)(-dppm)Au(Cl)], 2c. To a solution of 1c (0.072 gr,
0.08 mmol), in CH2Cl2 (15 mL), [AuCl(SMe2)] (0.026 gr, 0.08 mmol) was
added. The solution was stirred under an Ar atmosphere for 3 h at room
temperature, then concentrated to a small volume (2 mL) and treated with
diethyl ether (5 mL). The formed precipitate was filtered off, washed with
diethyl ether to give the product as a green-yellow solid. The precipitate
was dried in vacuum. Yield: 92%. Anal. Calcd. For C43H37ClNP2PtAu
(1057.21): C, 48.85; H, 3.53; N, 1.32%; Found: C, 48.93; H, 3.51; N, 1.37%.
ESI (+): m/z (%) 1058 [M + H]+ (100). NMR data in CDCl3: δ (1H) 2.17 (s,
3H, Me, p-MeC6H4), 2.94 (dd, 2JPH = 8.2, 3JPtH = 39.6, 2H, CH2P2), 6.56 (t,
3JHH = 6.5, 1H), 6.65 (d, 3JHH = 7.4, 2H), 7.03-7.40 (m, 17H), 7.45 (m, 3H,
Ho and H3´, ppy), 7.62-7.83 (m, 4H), 7.88-8.00 (m, 5H); δ (31P) 19.00 (d,
1JPtP = 1960.0, 2JPP = 17.1, 1P), 19.75 (d, 3JPtP = 83.7, 2JPP = 17.1, 1P).
CCDC-1860146 (1aO), CCDC-1860147 (2a) and CCDC-1860148 (2b)
contain the supplementary crystallographic data for this paper. This data
can be obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
Supporting Information (see footnote on the first page of this article):
NMR spectra, ESI-MS spectra, crystallographic and computational details.
Acknowledgements
This work was supported by the Institute for Advanced
Studies in Basic Sciences (IASBS) Research Council
(G2018IASBS32629) and the Spanish MINECO (Project
CTQ2016-78463-P). N.G. is grateful for a UR grant. M. F. is
grateful to the Medicinal Chemistry, school of pharmacy, Ahvaz
Jundishapur University of Medical Sciences (GP96075) and the
Iran National Science Foundation (Grant no 96007334).
Biological assay
Cell lines and cell culture
Human cancer cell lines, MCF-7 (breast cancer), SKOV3 (ovarian
cancer), and A549 (non-small cell lung cancer) were purchased from
National Cell Bank of Iran (NCBI, Pasteur Institute, Tehran, Iran). The cells
were grown in complete culture media containing RPMI 1640 (Biosera,
France), 10% fetal bovine serum (FBS; Gibco, USA) and 1%
penicillin−streptomycin (Biosera, France) and kept at 37 °C in a humidified
CO2 incubator. MCF10A cells (human breast epithelial cell line) were
cultured in DMEM/Ham's F-12 (GIBCO-Invitrogen, Carlsbad, CA)
supplemented with 100 ng/ml cholera toxin, 20 ng/ml epidermal growth
factor (EGF), 0.01 mg/ml insulin, 500 ng/ml hydrocortisone, and 5%
chelex-treated horse serum.
Keywords: Heterobimetallic complexes
•
Cycloplatinated
complexes • Photophysical properties • Cytotoxic study
•
Bis(diphenylphosphino)methane ligand.
[1]
[2]
a) J. R. Berenguer, E. Lalinde, M. T. Moreno, Coord. Chem. Rev. 2018,
Cytotoxic activities of the synthesized compounds were investigated
366, 69-90; b) M. Yoshida, M. Kato, Coord. Chem. Rev. 2018, 355, 101-
115.
using
a
standard 3-(4,5-dimethylthiazol-yl)-2,5-diphenyl-tetrazolium
bromide (MTT) assay, as previously described.[35] To do this, the cells with
a density of 0.8 × 104 cells per well were seeded in 96-well microplates
and kept for 24h to recover. The cells were then treated with the
synthesized compounds in different concentrations from 1 to 100 μM in a
triplicate manner and incubated for more 72 hours at 37 °C in humidified
CO2 incubator. Following incubation, the media were completely discarded
and replaced with 150 μl of RPMI 1640 containing 0.5 mg/mL MTT solution
and incubated at room temperature for 3h. To dissolve the formazan
crystals, the media containing MTT was discarded again and 150 μl of
DMSO was added to each well and incubated for more 30 min at 37 °C in
the dark. The absorbance of individual well was then read at 490 nm with
an ELISA reader. The 50% inhibitory concentration of each compound,
representing IC50, was calculated using CurveExpert 1.4. Data are
presented as mean ± SD.
a) A. Zanardi, R. Corberán, J. A. Mata, E. Peris, Organometallics 2008,
27, 3570-3576; b) A. Zanardi, J. A. Mata, E. Peris, J. Am. Chem. Soc.
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Apoptosis assay
BioLegend's PE Annexin V Apoptosis Detection Kit with 7AAD
(Biolegend, USA) was used to assess the apoptotic effect of 2b as
previously described.[35] Briefly, 0.5  105 cells per 1 ml of complete culture
medium were seeded in a 24-well culture plate, treated with 2b compound
in different concentrations (1, 2 and 4 µM) for 72 h. An untreated sample
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then harvested and washed twice with cold BioLegend's Cell Staining
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FACSCalibur flow cytometer (BD Bioscience, USA) with proper setting.
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14
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10.1002/ejic.201801297
European Journal of Inorganic Chemistry
FULL PAPER
Entry for the Table of Contents
FULL PAPER
Hamid R. Shahsavari*, Nora Giménez,
Elena Lalinde*, M. Teresa Moreno,
Masood Fereidoonnezhad*, Reza Babadi
Aghakhanpour, Mehri Khatami, Foroogh
Kalantari, Zahra Jamshidi, and Mozhdeh
Mohammadpour
Heterobimetallic
Comprising
Pt(II)Au(I) Complexes
Unsymmetrical 1,1-
Bis(diphenylphosphino)methane
Bridge:
Synthesis, Photophysical and Cytotoxic
Studies
A series of aryl-cycloplatinated(II) complexes “[Pt(C^N)(Ar)(κ1-dppm)]” featuring dangling
dppm ligand were reacted with AuCl(SMe2) to give the heterobimetallic Pt(II)-Au(I)
complexes with unsymmetrical dppm bridge. The impact of the coordination of AuCl unit
on the optical properties and biological activity of the precursors has been investigated.
15
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