Luminescence of Amphiphilic PtII Complexes Controlled by Confinement

Article abstract of DOI:10.1002/chem.201802743

The formation of hybrid silica-based systems to study the effect of the confinement on the emission properties of self-assembled platinum(II) complexes is reported. The complexes behave as surfactants since they possess a hydrophobic moiety and, on the ancillary ligand, a relatively long hydrophilic chain terminated with a positively charged group. The compounds, soluble in water, self-assemble, even at very low concentration, in supramolecular structures which display an orange luminescence. The properties of the assemblies have been studied in detail and in order to stabilize these supramolecular architectures and to enhance their emission properties hybrid silica porous nanoparticles have been prepared. In particular the Pt^II complexes have been employed as co-surfactant for the template formation of mesoporous silica nanoparticles (MSNs) using a sol gel synthesis. Interestingly, upon encapsulation in the silica pores, the platinum aggregates exhibit an emission profile similar in energy to the complexes assembled in solution, but the photoluminescence quantum yields of the hybrid systems are significantly higher (up to 45 %), and the excited state lifetimes much longer than those recorded in solution. Such enhancement of the photophysical properties together with the possibility to process the hybrid silica nanomaterials can pave the way to new type of emitters.

Full text of DOI:10.1002/chem.201802743

A Journal of
Accepted Article
Title: Luminescence of amphiphilic Pt(II) complexes controlled by
confinement
Authors: Luisa De Cola, Youssef Atoini, Eko Adi Prasetyanto, Pengkun
Chen, Simone Silvestrini, and Jack Harrowfield
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Chem. Eur. J. 10.1002/chem.201802743
Link to VoR: http://dx.doi.org/10.1002/chem.201802743
Supported by

Chemistry - A European Journal
10.1002/chem.201802743
FULL PAPER
Luminescence of amphiphilic Pt(II) complexes controlled by
confinement
[
a]
[a][b]
Pengkun Chen,[a] Simone Silvestrini,[a] Jack Harrowfield,[c]
Youssef Atoini, Eko Adi Prasetyanto,*
Luisa De Cola*[a],[d]
Dedication ((optional))
Abstract: The formation of hybrid silica-based systems to study the
effect of the confinement on the emission properties of self-assembled Introduction
platinum(II) complexes is reported. The complexes behave as a
surfactant since they possess a hydrophobic moiety and, on the
ancillary ligand, a relatively long hydrophilic chain terminated with a
positively charged group. The compounds, soluble in water, self-
assemble, even at very low concentration, in supramolecular
structures which display an orange luminescence. The properties of
the assemblies have been studied in detail and in order to stabilize
these supramolecular architectures and to enhance their emission
properties hybrid silica porous nanoparticles have been prepared. In
particular the Pt(II) complexes have been employed as co-surfactant
for the template formation of mesoporous silica nanoparticles (MSNs)
via a sol gel synthesis. Interestingly, upon encapsulation in the silica
pores, the platinum aggregates exhibit an emission profile similar in
energy to the complexes assembled in solution, but the
photoluminescence quantum yields of the hybrid systems are
significantly higher (up to 45%), and the excited state lifetimes much
longer than those recorded in solution. Such enhancement of the
photophysical properties together with the possibility to process the
hybrid silica nanomaterials can pave the way to new type of emitters.
The design of amphiphilic molecules incorporating luminescent
transition metal complexes (TMCs) has been a growing field of
research.[1] The advantage of amphiphilic TMCs is that they
combine the features of ordinary surfactant molecules with those
of TMCs and interesting emerging properties, not present in the
simple single components, can be used in different applications.
For example, amphiphilic TMCs have been studied for their
electric,[2] magnetic,[3] catalytic,[4] and luminescence properties.[5]
For some amphiphilic emitters, an enhancement of the
photoluminescence quantum yield (PLQY) and elongation of their
excited state lifetime have been observed. Even energy transfer
processes in mixed metal assemblies have been reported, when
two different TMCs are used as structure directing agent
(surfactant), leading to a control of the emission colour.[
Regarding amphiphilic Pt(II) complexes, reports related to
5a, 5c, 6]
[7]
[8]
applications in catalysis, or on the synthesis of aggregates,
as well as their spectroscopic properties in micellar systems have
appeared in the literature. Interestingly, besides the aggregation
induced by the amphiphilic nature of the complexes, the Pt(II)
[
9]
compounds can undergo to the formation of a Pt---Pt bond
resulting in new photophysical properties. [
10]
A way to stabilize the aggregates, as well as to control their size,
could be their entrapment in porous materials. [11] Mesoporous
silica nanoparticles (MSNs) can therefore constitute an interesting
host due to their tuneable shape and pore size, large surface area,
their narrow pore distribution, and their high pore volume.[12]
There are several ways to encapsulate TMCs in porous silica. For
[
a]
Dr. Y. Atoini, Dr. E. A. Prasetyanto, Dr. P. Chen, Dr. S. Silvestrini,
Prof. L. De Cola
Laboratoire de Chimie et des Biomatériaux Supramoléculaires,
Institut de Science et d’Ingénierie Supramoléculaires (ISIS - UMR
instance, a direct covalent bonding between silica and a complex
[12-13]
is possible,
but the absence of selective binding sites inside
7
006)
Université de Strasbourg - CNRS.
Rue Gaspard Monge, 67000 Strasbourg, France
the pores as distinct from the outer surface (both the pores and
the outer surface contain only silanol groups), makes the regio-
selectivity difficult to control. Another way to load TMCs into silica
is by sublimation, but the problem is that often charged or heavy
system are not volatile and therefore this technique is relatively
complicated to perform. An interesting strategy relies on the use
of the metal complexes as template (or embedded in the
template) for the formation of mesoporous silica, resulting in their
entrapment in the pores. This encapsulation can lead to an
enhancement of their stability and/or of their photophysical
properties, due to the increase rigidity of the system vs solution,
isolation from the environment and even interaction with the silica
wall that can prevent or reduce vibrational modes. Our group has
already successfully encapsulated amphiphilic Ru(II) and Ir(III)
complexes into mesoporous silica nanoparticles, using them as
structure directing agent (surfactant), for enhancement of
8
E-mail: decola@unistra.fr
Dr. E. A. Prasetyanto
[
[
b]
c]
Faculty of Medicine, Atma Jaya Catholic University of Indonesia
Jl. Pluit Raya 2, 14440 Jakarta, Indonesia
E-mail: prasetyanto@atmajaya.ac.id
Prof. J. Harrowfield
Laboratoire de Chimie Supramoléculaire, Institut de Science et
d’Ingénierie Supramoléculaires (ISIS - UMR 7006)
Université de Strasbourg - CNRS.
8
Rue Gaspard Monge, 67000 Strasbourg, France
[d]
Prof. L. De Cola
Hybrid Nanomaterials Unit, Institute for Nanotechnology,
Karlsruhe Institute of Technology
Campus North, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-
Leopoldshafen, Germany
Supporting information for this article is given via a link at the end of
the document.
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
10.1002/chem.201802743
FULL PAPER
luminescent properties or for controlling the emission colour. [5-6]
Prodi et al. have used a similar approach to entrap luminescent
metal complexes in silica nanoparticles for bio-analytical
applications.[14] Herein, we report the synthesis and the
spectroscopic properties of surfactant-type platinum complexes.
We describe luminescent supramolecular self-assembled
structures and their use as a co-surfactant in the template
synthesis of porous silica nanoparticles. To achieve the
amphiphilic design Pt(II) complexes containing a terdentate
N^N^N dianionic ligand resulting in a hydrophobic moiety, are
combined with a coordinated pyridine para-substituted with an
alkyl chain terminated with a pyridinium substituent acting as the
hydrophilic moiety (Scheme 1). The assemblies and the silica
containing Pt complexes have been investigated in details and the
enhancement of the emission properties of the Pt complexes,
once entrapped in the silica pores, is described.
1
∙cm ) attributed to the triazole moieties. In addition, a shoulder
-1
-1
-1
at 295 nm, (ε between 5000 and 3000 L∙mol ∙cm ) raises from
pyridine located transitions. In general, all these transitions are
assigned to -* or ligand centred ( LC) and metal-perturbed
ligand centred states. Broad, less intense bands between 350 nm
and 500 nm (ε between 1500 and 1000 L∙mol ∙cm ) are attributed
to dz2 –*, metal to ligand charge transfer ( MLCT) as well as to
the metal-metal-ligand charge transfer, MMLCT transitions rising
from the formation of aggregates already present at this
concentration. Indeed, the formation of a metallophilic interaction
(Pt-Pt) results in the destabilization of the dz2 orbitals and the new
HOMO is raised in energy as also observed in the low energy
1
-1
-1
1
1
3
emission spectra (Figure 2) attributed to MMLCT transitions.
Indeed due to the presence of the heavy atom, the Pt ion, the
strong spin orbit coupling causes a very efficient intersystem
crossing to the triplet state.
Scheme 1. Synthetic route for the preparations of complexes 5a-e. For sake of
clarity the complex 5a contain a C2 chain, the 5b a C5, the 5c a C8, the 5d a
C11 and the 5e a C14, between the pyridine and the prydinium moieties.
Figure 1. Absorption spectra of complexes 5a (black trace),5b (red
trace),5c (blue trace), 5d (pink trace) and 5e (green trace) in water
at 5.10 M.
Results and Discussion
-
5
The syntheses of all the ligands are summarised in scheme
S1, while scheme 1 shows the final complexation step. [10b,
1
5]
The use of different carbon chain lengths was dictated by
two reasons. Firstly, it is known that pyridinium salts are very
efficient phosphorescence quenchers, due to their very
strong electron withdrawing behaviour.[16] Therefore, the
distance between the complex and the quencher could affect
the emission properties. Secondly, we wanted to study the
supramolecular assembly of the molecules and investigate
the correlation between the nature and morphology of the
assembly and the luminescence properties of the system. A
long carbon chain should lead to an enhanced stability of the
assembly and even a different shape or size than a short
hydrophobic chain. The structures of the different ancillary
ligands are shown in Scheme S2, and all the
characterisations ( H, NMR, 13C NMR, 19F NMR, HR-MS
spectra) are depicted in Figures S1-S14.
1
The absorption spectra of the complexes, in water solutions at a
concentration of 5∙10-5 M at room temperature, are shown in
Figure 1. They all present the same profile, with a sharp band at
Figure 2. Excitation (λem = 600nm) and Emission (λexc = 400nm) spectra of
complexes 5a (black trace), 5b (blue trace), 5c (-green trace), 5d (red trace) and 5e
-1
-1
2
24 nm (ε between 30000 and 25000 L∙mol ∙cm ) and two other
-
5
(
orange trace) in water at 5∙10 M. Inset, photographs of sample 5a under UV light
-
bands at lower energy (255 nm, ε between 12000 and 9000 L∙mol
(Exc= 366 nm in water, 10-3M, left; and 5∙10-5 M, right).
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
10.1002/chem.201802743
FULL PAPER
Table 1. Photophysical properties of complexes 5 in water at 5∙10-
5M
Complex
em, nm,
Φ(%)
1
τ (µs)
(
exc= 400nm)
5a
593
0.304 (71%)
0
.063 (29%)
0.308(47%)
.094(53%)
0.367 (73%)
.108 (26%)
0.402 (35%)
.115 (65%)
0.442 (56%)
.141 (44 %)
5
b
590
590
587
587
1
0
5
c
6
0
5d
11
14
0
5
e
0
Table 2. Photophysical properties of complexes 5 in solid state
Figure 3. Excitation (em = 600 nm) and Emission (exc = 400 nm) spectra of complexes
Complex
em, nm
Φ(%)
 (µs)
5
a (black trace), 5b (blue trace), 5c (green trace), 5d (red trace) and 5e (orange trace)

exc= 400nm
in solid state. Inset: image of sample 5a in solid state under UV light (exc = 366 nm).
5a
590
4
0.546 (47%)
0.180 (53%)
5
b
590
591
591
593
7
0.260 (48%)
0.112 (52%)
0.332 (43%)
The emission and excitation spectra of all the complexes in water
-5
(
5∙10 M) and in the solid state are depicted in Figures 2 and 3.
5
c
7
Strikingly, they display the same excitation and emission profiles
independently of the state (solid or solution). All the excitation
spectra display an intense band at 500 nm, which confirms the
0.186 (57%)
5d
11
14
0.396(51%)
0.146(49%)
0.452 (57%)
0.140 (43%)
1
appearing of the MMLCT transition induced by Pt---Pt
5
e
interactions, and other bands at higher energy attributed to
1
1
MLCT or LC transitions, as already discussed for the absorption
spectra. The emission profiles show a broad, featureless band at
To estimate the effect of the pyridinium unit, the dependence of
the emission on the distance between the emitter (platinum
complex) and the quencher was studied. Experiments carried out
in dichloromethane at 5∙10-5 M, where we observe only the
monomeric species in solution, revealed that upon excitation of all
the complexes at the isoabsorptive wavelength, 375 nm, the
intensities increased with increasing the length of the chain and
reached a plateau for C11 (Figure S15). We can conclude that the
pyridinium unit can effectively quench the platinum emission in
the monomeric species when the chain is shorter than 11 units.
The different PLQYs are also observed for all the complexes in
water at 5∙10-5 M (Figure S16), where the compounds are
aggregated. These data corroborate the different quenching
related to the donor-acceptor distance, since the trend is identical
to the monomeric species. However, we cannot rule out that a
different packing morphology might also contribute to the variation
of the emission quantum yields. The quenching is also reflected
in the excited state lifetimes in solution (Table 1). The decays are
all biexponential, which is also common for platinum aggregates,
5
85 nm typical, for these type of Pt(II) complexes, to the
3
aggregated form and attributed to MMLCT transitions as already
reported for similar compounds. [10b, 17] In order to prove that such
low energy emission is indeed due to aggregation a spectrum in
dichloromethane, at the same concentration, has been recorded.
This required an anion exchange of the chloride counterion with
hexafluorophosphate, to obtain complexes soluble in
dichloromethane (see SI). The emission spectrum exhibits a blue
emission, due to the monomeric species, with bands at 461 nm,
89 nm and 525 nm as also observed in analogue complexes. [17a,
4
1
8]
All the complexes are therefore aggregated in water also at
high dilution. The orange-red emission observed mirrors the
strong electronic coupling between the platinum centres. The
absence of shift in the emission maxima for the different
compounds indicates that the length of the carbon chain on the
ancillary pyridine does not have any influence on the
luminescence energy. However, we see a correlation between the
emission quantum yields and the length of the hydrophobic chain.
Indeed, upon increasing the chain length the intensity of the
luminescence increases (Table 1). In the series of the compounds
going from complex 5a (n=0) to complex 5e (n= 12), the PLQY
varies from only 1%, to 14%, in water solution. This change may
result from two factors: i) the pyridinium can quench the platinum
emission due to an electron transfer process. Such photoinduced
reaction depends on the distance between the donor and the
acceptor unit; ii) different complexes can pack in a variety of
morphologies which possess different emission quantum yields.
[
19]
and their value increases, from 300 to about 450 ns, with the
elongation of the length of the chain (5a to 5e).
Interestingly, our complexes show a very high tendency to
aggregate, leading to the yellow-orange luminescence
characteristic of a short distance Pt-Pt distance (<3.5 Å). To
monitor this behaviour, even at low concentrations, the emission
spectrum of complex 5e in water was acquired at 10-7 M (Figure
S17) and, as can be seen, it still shows the emission of the
aggregated form.
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
10.1002/chem.201802743
FULL PAPER
TMCs molecules in the formation of the silica nanoparticles and
the photophysical properties of the resulting hybrid materials,
different ratios of complex/CTAB were used (Table 3, Table S1)
to template the growth of a constant amount of silica (45 mM
TEOS was used throughout the experiments).
Table 3. Studied systems, at different ratios complex/CTAB
[Pt(II) Complex](mM)
[CTAB](mM)
-
3
Sample 5e-a/5d-a
Sample 5e-b/5d-b
Sample 5e-c/5d-c
Sample 5e-d/5d-d
10
2.75
2.75
2.25
2
Orange emissive
aggregates
0.02
0.1
0.2
The materials obtained were characterized by SEM, TEM,
thermogravimetric analysis (TGA) and sorption. The
N
2
photophysical properties were also studied in order to compare
them before and after the silica growth. When appropriate, the
results were compared to those for the empty porous silica, MCM-
Figure 4. Schematic illustration of the formation of self-assembled structures of
the studied complexes according to the different concentrations.
41. SEM pictures (Figure 5 left, Figures S22 and S23 for more
examples) show a spherical shape for all the hybrid materials. The
particles prepared using TMCs are bigger than those prepared in
the same conditions and lacking the metal complexes in the
surfactant formulation, MCM-41 (Figure S24).
This is most probably due to the higher ethanol concentration
used in the mother solution for dissolving the platinum complex.
TGAs of the materials were performed between 20 and 1100°C,
and the results are shown in Figure 6. All the nanoparticles
already lost around 8% of their weight at 150°C, corresponding to
the remaining traces of water. Between 200°C and 500°C,
degradation of the complexes inside the hybrid materials was
evident. Mesoporous silica containing complex 5e had a larger
weight loss than samples 5d, (between 40 and 55 % for samples
Further studies to confirm aggregation in solution were performed
using dynamic light scattering (DLS) and SEM on complex 5e,
(
8
Figures S19, S20 and S21) with concentrations between 10-6 and
.10-4 M. From these experiments, as the scattering intensity
starts at the lowest concentration we can confirm that the
aggregates are already formed below 10-6 M. Other DLS
experiments were performed at different concentrations (1 µM, 10
µM, 100 µM, 500 µM). The field correlation function versus the
diffusion time was measured at these concentrations. From this,
-1
we can determine relaxation rate (ms ) according to the
scattering vector q. Subsequently, the hydrodynamic radius of
these assemblies was determined (Figure S20) (for more details:
see ESI). The most dilute sample has the lower diffusion rate (10
ms), and the higher the concentration, the faster the aggregates
diffuse. This is consistent with the assumption that at lower
concentrations, below the CMC, the assembly formed is actually
a supramolecular polymer driven by π-π stacking and Pt---Pt
interactions and hence displaying a bigger hydrodynamic radius;
and when the concentration increases, the assembly takes a
spherical micelle shape induced by hydrophobic interactions in
water. Obviously, the supramolecular polymer has a much bigger
hydrodynamic radius than the micelles. This assumption was then
confirmed by SEM (Figure S21) that shows the different
morphologies at different concentrations. This concept, of the
supramolecular assembly, is pictorially illustrated in Figure 4.
5e, between 25 and 45% for samples 5d), attributed to the higher
molecular mass of 5e vs 5d. At higher temperature, the profiles
displayed a plateau, and no weight change was observed from
500°C to 1100°C.
After TGA analysis, the calcinated samples were re-analysed
using transmission electron microscopy, TEM. Representative
images for sample 5d-a can be observed in Figure 5 (right), with
more examples reported in the SI (Figures S25 and S26).
2.
Encapsulation of amphiphilic Pt(II) complexes in
mesoporous silica nanoparticles
The previous experiments demonstrated the effect of the self-
assembly of the complexes on the photophysical properties in a
dynamic environment. In order to "freeze" the aggregates and
retain their photophysical properties upon changes in their
surrounding environment, they were encapsulated inside
mesoporous silica nanoparticles, MSNs. To this end,
hexadecyltrimethylammonium bromide, CTAB, was employed as
the templating agent for the condensation of silica nanoparticles,
and complexes 5d and 5e, whose length closely match that of
CTAB, were added as co-surfactants. To study the effect of the
Figure 5. SEM (left) and TEM (right, inset: zoom) images of sample 5d-a.
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
10.1002/chem.201802743
FULL PAPER
Figure 7. Pore size distribution of: MCM-41 (black trace); 5d-a (green trace);
5d-b (blue trace); 5d-c (magenta trace); 5d-d (red trace).
Notwithstanding the similarities in emission profiles, confinement
in the micelles brought an important increase in PLQY, from the
original 14 and 11% in water for 5e and 5d, respectively, to 26%.
The excited state lifetimes increased likewise, suggesting that
non-radiative relaxation decay pathways are being effectively
suppressed. The hybrid micelles have then used to template the
silica, as described above, and the resulting photophysical
properties of the particles are shown in Figures 8 and 9. The
figures depict the excitation and emission spectra of the hybrid
materials made by TMCs 5e and 5d. Hybrid materials having a
relatively high concentration of complex (5e/5d, -b, -c and -d
samples), display also the same emission profile as the
complexes aggregates. On the contrary, samples prepared from
a dilute solution of TMCs
Figure 6. TGA profile of the materials: 5e (top) and 5d (bottom).
-6
(
10 M) show a slight hypsochromic effect (576 nm) and narrow
As for the SEM pictures, a primary observation is that MSNs made
by TMC/CTAB mixtures are bigger than particles prepared with
pure CTAB as a surfactant. The parallel arrangement of pores,
having a size of a few nanometres, is evident up to 10% molar
ratio of TMCs relative to CTAB. The addition of TMCs into the
system does not disturb the formation of ordered mesopores.
bands at higher energies (481 and 505 nm), also observed for the
3
3
monomeric forms, and attributed to LC or MLCT transitions.
Exact determination of the size of the pores was carried out by N
2
adsorption-desorption experiments (Figures S27 and 7). In
comparison with the MCM-41 reference particles, which displayed
a pore size of 2.3 nm, MSNs synthesized with TCM/CTAB
mixtures have a pores size, around 3.5 nm. A possible
explanation for this effect lies in the larger size of TMC molecules
relative to CTAB leading to micelles bigger in size due to the
presence of the Pt(II) complexes. The micelles that grow laterally
to template the pores, during the formation of the silica backbone,
lead to larger pores than CTAB alone.
Before analysing the influence of MSN-encapsulation on the
photophysical properties of TMCs, we investigated the effect of
the confinement of the complexes inside the CTAB micelles. The
data reported in table S2 (TMC@CTAB line) refer to the emission
maxima, PLQYs and excited state lifetimes of mixtures of 5d and
Figure 8. Solid state emission (full line, exc = 400nm) and excitation (dashed
line, em = 600nm) of the hybrid materials made from complex 5e.
5e with CTAB, prepared in the same conditions used to template
the growth of MSNs for samples 5d-d and 5e-d, respectively. The
TMCs inside the micelles display emission profiles that resemble
those recorded in aqueous solution (cf. Figure 2), with a broad,
featureless band at around 590 nm, typical for Pt(II) complexes in
their aggregated state.
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
10.1002/chem.201802743
FULL PAPER
Complex
e-a
e-b
e-c
λem (nm, λexc =
00nm)
Φ(%)
τ (µs)
4
5
481-510-576**
n.d.*
38
0.171(39%)**
0
.010(61%)**
0.911 (42%)
.405 (58%)
0.936(34%)
.386(66%)
0.961(40%)
.363(60%)
0.160(31%)**
.008(69%)**
1.247 (19%)
.706 (81%)
1.325 (19%)
.754 (81%)
0.991(63%)
.218(37%)
5
587
587
0
5
37
0
5
e-d
d-a
589
41
0
5
476-590**
590
n.d.*
44
0
5
d-b
d-c
d-d
0
5
590
45
0
Figure 9. Solid state emission (full line, exc= 400nm) and excitation (dashed
line, em = 600nm) of the hybrid materials made from complex 5d.
5
590
39
0
*
not determined due to instrument limitations
*
* λexc = 350nm
It is interesting to compare the emission spectra of TMCs in
samples 5d-a and 5e-a with those of 1 µM aqueous solutions of
5
d and 5e. In the latter case, we only have emission from
Conclusions
aggregates, while in the former, the emission from non-
aggregated TMCs dominates. This is peculiar, since the hybrid
materials were prepared from 1 µM TMC solutions and the metal
complexes were confined into the pores by interaction with CTAB,
presumably increasing their local concentrations above 1 μM.
This suggests therefore that CTAB is preventing metal-metal
interactions inside MSNs when the concentration is low, efficiently
separating the platinum complexes. The confirmation that the
emission comes from the particles was obtained by confocal
microscopy analysis performed for each sample, and an image is
shown in the ESI (Figure S28, sample 5e-d.)
The PLQYs and excited state lifetimes of the hybrid materials
show a more performant behaviour compared to their micellar
counterparts, as shown in Table 4. Indeed, upon encapsulation in
MSNs, the PLQYs recorded for 5e and 5d are up to three times
higher in comparison with its water solutions and solid state, and
the excited state lifetimes are mirroring the same increase. The
confinement provided by the MSNs, due to the increase in rigidity
of the system, immobilization of the complexes, as well as the
protection from dioxygen quenching have an undeniably
beneficial effect on the photophysical properties.
The amphiphilic Pt(II) complexes described in this work, are
strongly aggregated in aqueous solution and even at very low
concentrations display the emission of their self-assembled
structures. These aggregates can be stabilised by their inclusion
within mesoporous silica, employing the complexes as templates,
in association with CTAB, for formation of the porous silica
framework. The confinement provided by the silica is superior to
that conferred by the micelles in solution as demonstrated by the
enhancement of the photophysical properties. High emission
quantum yields for the hybrid nanoparticles have been recorded
and the change in the external environment does not influence
the emission properties. The higher performance can be
rationalized considering the restriction in vibrational and rotational
motion of the aggregates within the pores lattice and protection of
the aggregate from dioxygen.
Such findings could open the way to the construction of very
efficient and easy to store and process emitting materials.
Experimental Section
Table 4. Solid state photophysical properties of the hybrid
materials made from complexes 5e and 5d
The full experimental section is reported in the SI.
Acknowledgements
The authors acknowledge the financial support by the European
Union FP7-SACS Project (Grant agreement no. 2012-310651).
SS acknowledges the financial support by the European Union’s
Horizon 2020 research and innovation programme under the
Marie Skłodowska-Curie grant agreement No 707944.
Keywords: Pt(II) complexes • Amphiphiles • Aggregation
induced emission• Encapsulation • Mesoporous silica
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
10.1002/chem.201802743
FULL PAPER
[
14] a) L. Petrizza, M. Collot, L. Richert, Y. Mely, L. Prodi, A. S. Klymchenko,
RSC Advances 2016, 6, 104164-104172; b) S. Bonacchi, D. Genovese, R. Juris,
M. Montalti, L. Prodi, E. Rampazzo, N. Zaccheroni, Angew. Chem. Int. Ed. 2011,
5
0, 4056-4066.
References
[
15] a) J.-P. Collin, J. Frey, V. Heitz, J.-P. Sauvage, C. Tock, L. Allouche, J. Am.
Chem. Soc. 2009, 131, 5609-5620; b) B. J. Coe, S. P. Foxon, E. C. Harper, M.
Helliwell, J. Raftery, C. A. Swanson, B. S. Brunschwig, K. Clays, E. Franz, J.
Garín, J. Orduna, P. N. Horton, M. B. Hursthouse, J. Am. Chem. Soc. 2010, 132,
1706-1723.
[
1] a) Y. Sagara, T. Komatsu, T. Ueno, K. Hanaoka, T. Kato, T. Nagano, J. Am.
Chem. Soc. 2014, 136, 4273-4280; b) T. Owen, A. Butler, Coord. Chem. Rev.
2
2
5
011, 255, 678-687; c) N. Giri, S. L. James, Chem. Commmun. 2011, 47, 245-
47; d) C. N. Verani, J. Driscoll, P. H. Keyes, M. J. Heeg, Inorg. Chem. 2014,
3, 5647-5655.
[
16] a) H. J. Pownall, L. C. Smith, Biochemistry 1974, 13, 2590-2593; b) M. M.
Velazquez, S. M. B. Costa, J. Chem. Soc., Faraday Trans. 1990, 86, 4043-4048.
17] a) M. Mauro, A. Aliprandi, C. Cebrian, D. Wang, C. Kubel, L. De Cola,
[
[
2] W. L. D., M. Shivnath, K. K. K., S. R. J., S. H. Bernhard, C. N. Verani, Chem.
Eur. J. 2016, 22, 10786-10790.
3] C. Gandolfi, T. Cotting, P. N. Martinho, O. Sereda, A. Neels, G. G. Morgan,
M. Albrecht, Dalton Trans. 2011, 40, 1855-1865.
4] a) H. Mao, H. Yu, J. Chen, X. Liao, Sci. Rep. 2013, 3, 2226; b) C. Boucher-
Jacobs, M. Rabnawaz, J. S. Katz, R. Even, D. Guironnet, Nat. Commun. 2018,
, 841.
5] a) M. de Barros e Silva Botelho, J. M. Fernandez-Hernandez, T. B. de
Queiroz, H. Eckert, L. De Cola, A. S. S. de Camargo, J. Mater. Chem. 2011, 21,
829-8834; b) D. Dominguez-Gutierrez, G. De Paoli, A. Guerrero-Martinez, G.
Ginocchietti, D. Ebeling, E. Eiser, L. De Cola, C. J. Elsevier, J. Mater. Chem.
008, 18, 2762-2768; c) M. Mauro, G. De Paoli, M. Otter, D. Donghi, G.
D'Alfonso, L. De Cola, Dalton, Trans. 2011, 40, 12106-12116.
6] a) A. Guerrero-Martínez, Y. Vida, D. Domínguez-Gutiérrez, R. Q.
Chem. Commmun. 2014, 50, 7269-7272; b) M. Mydlak, M. Mauro, F. Polo, M.
Felicetti, J. Leonhardt, G. Diener, L. De Cola, C. A. Strassert, Chem. Mater.
[
2011, 23, 3659-3667.
[
[18] A. I. Solomatina, D. V. Krupenya, V. V. Gurzhiy, I. Zlatkin, A. P. Pushkarev,
M. N. Bochkarev, N. A. Besley, E. Bichoutskaia, S. P. Tunik, Dalton Trans. 2015,
44, 7152-7162.
9
[
19] S. Sinn, F. Bidermann, L. De Cola, Chem. Eur. J. 2017, 23, 1965-1971.
[
8
2
[
Albuquerque, L. De Cola, Inorg. Chem. 2008, 47, 9131-9133; b) B. Manimaran,
P. Thanasekaran, T. Rajendran, R.-J. Lin, I. J. Chang, G.-H. Lee, S.-M. Peng,
S. Rajagopal, K.-L. Lu, Inorg. Chem. 2002, 41, 5323-5325; c) Y. Li, L. Chen, Y.
Ai, E. Y.-H. Hong, A. K.-W. Chan, V. W.-W. Yam, J. Am. Chem. Soc. 2017, 139,
13858-13866.
[
7] a) A. A. Karasik, R. N. Naumov, A. S. Balueva, Y. S. Spiridonova, O. N.
Golodkov, H. V. Novikova, G. P. Belov, S. A. Katsyuba, E. E. Vandyukova, P.
Lönnecke, E. Hey-Hawkins, O. G. Sinyashin, Heteroat. Chem. 2006, 17, 499-
5
13; b) A. Swami, A. Kumar, R. Pasricha, A. B. Mandale, M. Sastry, J. Colloid
Interface Sci. 2004, 271, 381-387.
8] a) M. Castriciano, A. Romeo, R. Romeo, L. Monsu′Scolaro, Eur. J. Inorg.
[
Chem. 2002, 2002, 531-534; b) T. Taira, Y. Suzaki, K. Osakada, Chem. Asian
J. 2008, 3, 895-902; c) N. Kimizuka, N. Oda, T. Kunitake, Inorg. Chem. 2000,
39, 2684-2689.
[
[
9] V. M. Miskowski, V. H. Houlding, Inorg. Chem. 1991, 30, 4446-4452.
10] a) S. Sinn, L. Yang, F. Biedermann, D. Wang, C. Kübel, J. J. L. M.
Cornelissen, L. De Cola, J. Am. Chem. Soc. 2018, 140, 2355-2362; b) A.
Aliprandi, M. Mauro, L. De Cola, Nat. Chem. 2016, 8, 10-15; c) A. Aliprandi, C.
M. Croisetu, M. Mauro, L. De Cola, Chem. Eur. J. 2017, 23, 5957-5961; d) K. Li,
G. S. Ming Tong, Q. Wan, G. Cheng, W.-Y. Tong, W.-H. Ang, W.-L. Kwong, C.-
M. Che, Chem. Sci. 2016, 7, 1653-1673.
[
11] a) L. Donato, Y. Atoini, E. A. Prasetyanto, P. Chen, C. Rosticher, C. Bizzarri,
K. Rissanen, L. De Cola, Helv. Chim. Acta 2018, 101, DOI:
0.1002/hlca.201700273; b) K. W. K. Mori, M. Kawashima, M. Che, and H.
1
Yamashita, J. Phys. Chem. C 2011, 115, 7; c) M. Yoshida, K. Saito, H.
Matsukawa, S. Yanagida, M. Ebina, Y. Maegawa, S. Inagaki, A. Kobayashi, M.
Kato, J. Photochem. Photobiol. A: Chem. 2018, 358, 334-344.
[
[
12] F. Tang, L. Li, D. Chen, Adv. Mater. 2012, 24, 1504-1534.
13] C. Ezquerro, A. E. Sepulveda, A. Grau-Atienza, E. Serrano, E. Lalinde, J.
R. Berenguer, J. Garcia-Martinez, J. Mater. Chem.C 2017, 5, 9721-9732.
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
10.1002/chem.201802743
FULL PAPER
Entry for the Table of Contents (Please choose one layout)
Layout 2:
FULL PAPER
Youssef Atoini, Eko Adi Prasetyanto,*
Pengkun Chen, Simone Silvestrini, Jack
Harrowfield, Luisa De Cola*
Page No. – Page No.
Title: Luminescence of amphiphilic
Pt(II) complexes controlled by
confinement
Water soluble platinum complexes undergo self-assembly and are used as co-
surfactant for the synthesis of mesoporous silica nanoparticles. Their confinement
in the pores leads to an enhancement of the photophysical properties.
This article is protected by copyright. All rights reserved.