Self-Assembled Cofacial Zinc–Porphyrin Supramolecular Nanocapsules as Tuneable 1O2 Photosensitizers

Article abstract of DOI:10.1002/chem.201705531

We demonstrate the benefits of using cofacial Zn–porphyrins as structural synthons in coordination-driven self-assembled prisms to produce cage-like singlet oxygen (¹O₂) photosensitizers with tunable properties. In particular, we describe the photosensitizing and emission properties of palladium- and copper-based supramolecular capsules, and demonstrate that the nature of the bridging metal nodes in these discrete self-assembled prisms strongly influences ¹O₂ generation at the Zn–porphyrin centers. The Pd^II-based prism is a particularly robust photosensitizer, whereas the Cu^II self-assembled prism is a dormant photosensitizer that could be switched to a ON state upon disassembly of the suprastructure. Furthermore, the well-defined cavity within the prisms allowed encapsulation of pyridine-based ligands and fullerene derivatives, which led to a remarkable guest tuning of the ¹O₂ production.

Full text of DOI:10.1002/chem.201705531

A Journal of
Accepted Article
Title: Self-assembled Cofacial Zinc Porphyrin Supramolecular
Nanocapsules as tuneable 1O2 Photosensitizers
Authors: Cédric Colomban, Carles Fuertes-Espinosa, Sébastien Goeb,
Marc Sallé, Miquel Costas, Lluís Blancafort, and Xavi Ribas
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.201705531
Link to VoR: http://dx.doi.org/10.1002/chem.201705531
Supported by

Chemistry - A European Journal
10.1002/chem.201705531
FULL PAPER
Self-assembled Cofacial Zinc Porphyrin Supramolecular
1
Nanocapsules as tuneable O Photosensitizers
2
[
a]
[a]
[b]
[b]
[a]
Cédric Colomban , Carles Fuertes-Espinosa , Sébastien Goeb , Marc Sallé , Miquel Costas , Lluis
[
a]
[a]
Blancafort* and Xavi Ribas*
6
Abstract: Here we demonstrate the benefits of using cofacial Zn-
porphyrins, used as structural synthons in coordination-driven self-
assembled prisms, to produce cage-like singlet oxygen
photosensitizers having tuneable photosensitizing properties. In
particular, we describe the photosensitizing and emission properties
of palladium and copper-based supramolecular capsules 1 and 2
derivative with bulky noncovalent building blocks. To enhance
1
the
O
2
productivity, another strategy consists in using
5
7
phthalocyanine or porphyrin-based conjugated microporous
polymers. Furthermore, porphyrinic-based metal-organic
frameworks (MOFs) have been reported as efficient tools for
1
8
reversible control over the
2
O generation or selective photo-
9
and demonstrate that the nature of the bridging metal nodes in these
oxidation. In light of these recent examples, controlling the
second coordination sphere of porphyrinic derivatives appears
as a powerful strategy for the development of innovative
photosensitizers.
1
discrete self-assembled prisms strongly influence the O
2
generation
at the Zn-porphyrin centers. On one hand, the Pd(II)-based prism 1
was found to be a particularly robust photosensitizer, while on the
II
other hand the Cu self-assembly 2 is a dormant photosensitizer that
On the other hand, porphyrin based supramolecular cages have
recently attracted lots of attention. The self-assembly of
can be switched to a ON state upon disassembly of the supra-
10
structure. Furthermore, the well-defined cavity within 1 and 2 allow
molecular barrels with porphyrin walls, coordination prisms with
11
for the encapsulation of pyridine-based ligands and fullerene
porphyrin faces, supramolecular arrays of one porphyrin and
1
12
derivatives, leading to
production.
a
remarkable guest tuning of the
O
2
one phthalocyanine linked by rotaxane nodes, and even
13
multiporphyrin cages, have been successfully described using
different bridging metals (Pd, Pt, Zn). The usefulness of
porphyrin-based capsules for versatile applications ranging from
14
15
binding and separation of fullerenes, spin crossover,
cooperative binding of anionic and neutral guest species, to
Introduction
16
17
water solubilisation of hydrophobic cargo, and preparation of
1
Singlet oxygen ( O
2
), the lowest excited state of oxygen plays an
18
breathing flexible cages,
have been recently established.
important role in many biological oxidative processes (e.g.
natural biological defence processes and cytotoxic agent in
Furthermore, the well-defined cavity found in these systems has
also been used as a scaffold for the isolation of metallo-catalysts
1
phototherapies). This reactive oxygen species (ROS) is not only
19,20,21
aiming at performing catalysis in confined space.
Porphyrin
highly desired because of its applications in photodynamic
cancer therapy (PDT) but is also a very convenient oxidant for
and Zn-porphyrin moieties are commonly considered as inert
building blocks in these supramolecular architectures and few
precautions are usually taken regarding their exposure to natural
2
, 3 , 4
wastewater treatments or organic photoredox reactions.
Porphyrin derivatives are currently the most used
photosensitizers due to their high quantum yield in
1
O
O
2
2
light. However, porphyrins and metalloporphyrins are well-known
1
1
photosensitizers and the production of reactive O
2
might impact
5
generation and high light-absorption capability.
The
the way that both host-guest chemistry and catalysis proceeds
within theses cargos. Very few examples of self-assembled
nanocages used as homogeneous photosensitizers are
described in the literature. Ruthenium-based self-assembled
porphyrin prisms were studied as phototoxic agents by Therrien
1
construction of optimized
O
2
photosensitizers with high
1
2
efficiency, stability and control over O production is a topic of
intensive research and many efforts have been devoted recently
in this direction. For example, the suppression of self-quenching
of the excited state, observed upon formation of porphyrin
aggregates, could be prevented by decorating a porphyrin
22
and co-workers. They reported octanuclear ruthenium arene
metalla-cubes composed of cofacial tetrapyridyl porphyrin
23
panels, as chemotherapeutics in cancer cells. In any case, the
effect of the prismatic structure toward the stability, emission
and photosensitizing properties of the porphyrin center were not
investigated.
[
a]
b]
Dr. C. Colomban, C.Fuertes-Espinosa, Dr. M. Costas, Dr. L.
Blancafort, Dr. X. Ribas.
Institut de Química Computatcional i Catàlisi (IQCC) and
Departament de Química, Universitat de Girona,
Campus Montilivi, Girona, E17003, Catalonia, Spain
E-mail: xavi.ribas@udg.edu ; lluis.blancafort@udg.edu
Dr. S. Goeb, Prof. M. Sallé
Herein we present
a
novel approach to build
photosensitizers integrating the principles of self-assembly,
host-guest chemistry and photochemistry. We report the study
of the singlet oxygen photosensitization efficiency of two self-
assembled metal-organic capsules. In order to vary the nature of
the metal-nodes we studied the self-assembled tetragonal
prismatic compounds 1 and 2, where two cofacial Zn-porphyrins
are bound by four bridging macrocyclic walls respectively
[
Université d’Angers, CNRS UMR 6200
Laboratoire MOLTECH-Anjou
2
bd Lavoisier, 49045 Angers Cedex (France)
Supporting information for this article is given via a link at the end of
the document.
II
II
interconnected by Pd or Cu –carboxylate bonds (Figure 1). We
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
10.1002/chem.201705531
FULL PAPER
discovered that the nature of the metal nodes in the
Indeed, while the encapsulation of (m-Py)exTTF by 1 in dark
conditions leads to the formation of the (m-Py)exTTF⊂1
1
supramolecular structures determines their ability to produce O
2
.
1
24
More remarkably, guest binding can also modify the
O
2
complex in a 1:1 stoichiometry, its exposure to natural light
production efficiency. This work is of fundamental nature and
aims at giving a proof of concept for the potential benefits of the
under aerobic atmosphere (during 5 and 90 min) yields to the
2 3
progressive formation of the keto products P and P arising
development of self-assembled Zn-porphyrin supramolecular
from the photo-oxidation of the C=C bond of (m-Py)exTTF.
1
capsules as
O
2
photosensitizers or dormant-photosensitizer
Interestingly, both products were detected by ESI-HRMS as
under supramolecular control.
host-guest adducts P
Upon longer exposition time (270 min) P
major species, while only trace amount of P
Figure S6, S7). These observations strongly suggest that P
generated during the early stage of the reaction is further
oxidized into P . Natural light and air exposure of the authentic
sample of P ⊂1, prepared independently, confirms this proposal
Figure S8). It is worth noting that cage 1, natural light, and
2
⊂1 and P
3
⊂1 (Figure 1b-c, Figure S1-S5).
⊂1 was present as the
⊂1 was detected
2
3
(
3
Results and Discussion.
1
Palladium-based prism 1 as O
2
sensitizer
of
tetrathiafulvalene-based switchable guest, (m-Py)exTTF in the
2
3
The
redox-controlled
encapsulation
an
extended
(
dioxygen were all necessary for this reaction to take place. In
the absence of any of these components, either none or only
24
cavity of 1 has been recently described. On the other hand
25
extended
tetrathiafulvalene derivatives are able to rapidly quench
produced by photosensitizer, by degradation into
corresponding quinone products, making them interesting
(exTTF)
and
superextended
(sExTTF)
traces of the oxidation products P
2 3
and P were detected (Figure
26
1
O
2
S9, S10). Furthermore, performing the reactions in the presence
a
18
18
of
18
O
2
lead to the incorporation of
O
2
in the oxidized products
1
O
2
18
O-P
were conducted in the presence of
2 3
and O-P (Figure 1 and S11). Finally, when reactions
sensors. On this basis, we envisioned that the encapsulated
18
16
H
2
O
under
a
O
2
ligand in the (m-Py)exTTF⊂1 supra-structure (Figure 1a) might
18
atmosphere, no O was incorporated into products (Figure S12),
1
react with the putative O
2
produced at the Zn-porphyrin centers
discarding the hypothesis of a reaction involving a photo-
of 1.
•+
induced
π
radical cation species (m-Py)exTTF which is
27
subsequently trapped by O
2
2
or H O. Altogether, these results
strongly suggest that the oxidizing species is coming from an
3
1
activation of molecular oxygen
Oxidation of (m-Py)exTTF under natural light and air, in CH
CH Cl
was followed by H NMR. Interestingly, upon 16 h of light
exposure, a 65% conversion of the substrate, to yield P , P and
anthraquinone (AQ) products, was observed (Figure 2). By
increasing the catalyst loading to 4.0 mol% complete
O
2
into the reactive
2
O .
3
CN
/
2
2
1:9, in presence of a catalytic amount of 1 (1.0 mol %)
1
3
2
a
conversion of (m-Py)exTTF into P and AQ was reached after 3
2
1
hours of light exposure indicating a continuous production of O
2
28
by 1.
Figure 1. (a) Schematic representation of the building blocks used for the
synthesis of the nanocapsule 1 together with the envisioned structure of (m-
Py)exTTF⊂1. (b) Schematic representation of the envisioned structure of the
P ⊂1 host-guest adduct with the respective ESI-HRMS spectra obtained
3
18
2 2
under air or O-labeled O atmosphere. (c) idem for P ⊂1.
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
10.1002/chem.201705531
FULL PAPER
33
experimental triplet energy of ZnTPP is 1.59 eV, in good
agreement with the calculation.
1
Figure 2. H NMR monitoring of the photocatalytic oxidative cleavage of (m-
Py)exTTF, a) in the absence of light, no degradation was observed, b) in the
presence of 1 (1.0 mol%) after 16h of light exposure and c) in the presence of
1
(4.0 mol%) after 3 hours of light exposure.
The ability of cage 1 to generate singlet oxygen was then
monitored upon irradiation with a 575 nm lamp by using 9,10-
1
diphenylanthracene (DPA) as O
2
quencher. In the presence of
catalytic amounts of 1 (1.3 mol%), a decay in absorbance occurs
at 340, 356, 375 and 393 nm (corresponding to the absorption
bands of DPA, Figure 3a) as a consequence of the formation of
the corresponding endoperoxide which does not absorb, (Figure
1
29
3
2
b) confirming the generation of O .
-
3
As a control experiment, DPA (0.1 x 10 M) alone was
irradiated under air in CH Cl /CH CN 9:1. A limited decrease in
the absorbance of DPA was observed, revealing its stability
2
2
3
30
under the experimental conditions (Figure S14). On the other
hand, zinc−tetraphenylporphyrin (ZnTPP), is a widely used
1
photosensitizer which displays high quantum yield toward
O
2
generation, good solubility in organic solvent, and a well-studied
31
photochemistry. ZnTPP was therefore chosen as reference
photosensitizer in the present study. Reactions carried out with
the same catalyst loading (1.3 mol%) of 1 and ZnTPP displayed
1
identical DPA decay, revealing similar efficiency in
O
2
generation per molecular system (Figure 3c). However it should
1
be noted that the O
2
production rate per Zn-porphyrin center is
32
for 1 is half the one observed for monomeric ZnTPP.
1
According to the accepted mechanism,
energy transfer from the T state of the photosensitizer to
The calculated triplet energies for 1 and ZnTPP, are respectively
.65 and 1.63 eV (Table 1 and S1, see ESI for computation
details). These roughly similar triplet energies are in line with the
2
O is generated by
3
-3
1
O
2
.
Figure 3. a) Time-dependent absorption spectra of DPA (0,1 x 10 M) in
CH
2
Cl
2 3
/CH CN (9:1) under air, upon irradiation at 575 nm in the presence of 1
(
9
1.3 mol%); the band at 424 nm corresponds to the Soret of 1, b) Reaction of
1
1
,10-diphenylanthracene (DPA) with
O
2
yielding its corresponding
endoperoxide and c) comparison of the decay rate of DPA in the presence of 1
(1.3 mol%, blue circle) or ZnTPP (1.3 mol%, purple triangle). d) Kinetics of the
1
similar activities towards O
2
generation observed for the single
photooxidation of DPA in CH
circles) and ZnTPP (purple squares)
2 2 3
Cl /CH CN 9:1. kobs vs. concentration of 1 (blue
molecular photosensitizers 1 and ZnTPP. For comparison, the
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
10.1002/chem.201705531
FULL PAPER
Figure 4. Time-dependent absorption spectra of (a) 1 and (b) ZnTPP (1.7 x
Kinetic experiments were performed by monitoring the bleaching
-
6
1
0
2 2 3
M), in CH Cl /CH CN (9:1) under air upon irradiation at 575 nm, c)
2 2 3
of the absorption band of DPA in CH Cl /CH CN 9:1 as a
corresponding decay rate of Soret bands of 1 (blue) and ZnTPP (green).
function of the irradiation time and at several concentrations of 1
and ZnTPP. The resulting kinetic profiles were linear over time
for both photosensitizers, attesting for a zero-order dependence
-6
Since
1
and ZnTPP (1.7
x
10
M) display similar
1
on [DPA], typical of the photooxidation of DPA by
2
O (Figure
photosensitization activities (Figure 3), their respective stability
34
S15 and S16). Observed constants kobs were extracted from
these data. Interestingly for the oxidation of DPA sentitized by
increasing amounts of 1 the kobs increase linearly in the
1
cannot be explained by the amount of
2
O produced over the
1
experiment time. According to the literature, the attack of O
2
at
the meso-position of the porphyrin is a major degradation
-
6
concentration range 0,84 - 5.6 x 10 M. In the case of ZnTPP
the kobs value response does not increase linearly, but instead
two different linear regimes are observed. From [ZnTPP] = 0.84
36
pathway. It has been reported that porphyrin can be protected
1
from attack by O
2
by sterically shielding the meso-positions of
the porphyrin ring with blocking substituents (fluorine, chlorine,
-
6
-6
x 10 M to 3 x 10 M, the increase and kobs values overlay with
methoxy groups) on the 2- and 6- positions of the aryl rings
those obtained with 1. However, a slower increase is observed
31,37
groups.
Furthermore, It has already been demonstrated that
-
6
at high concentration (3.0 – 5.6 x 10 M, Figure 3d). Similar
trends are observed by ploting the kobs values versus the
concentration of Zn-porphyrin center for both photosensitizers
the presence of appropriate electron-withdrawing substituents
on tetraphenyl-based porphyrin macrocycles can limit their
38
photo-oxygenation at the meso position.
The remarkable
(
1
Figure S17). The concentration dependent deactivation of the
stability of 1 toward bleaching can be therefore explained by the
conjunction of two factors: a) the sterical hindrance arising from
the supramolecular coordination of the Pd-macrocyclic wall at
the meso-position of the Zn-porphyrin units and b) the electronic
effects due to the presence of four coordination bonds (Pd-
carboxylate) in each porphyrin, which strongly decrease their
electron density. A comparison of the electrochemical behavior
of 1 and ZnTPP confirms that the first porphyrin oxidation is
shifted to higher potential (ΔE= +186 mV) in the case of the
supramolecular cage 1 (Figure S19, S20).
O
2
production observed in the case of ZnTPP might be
explained by a difference in the stability toward photobleaching,
which is more pronounced at higher concentrations of the
photosensitizer.
Stability towards photobleaching
Despite their wide use as photosensitizer, the photostability of
1
metallo-porphyrins is strongly limited by their reaction with O
2
,
35
resulting in a self-destruction by photo-oxygenation. Therefore,
1
stability toward O
2
attack and intrinsic light stability, are highly
The photocatalytic robustness of 1 and ZnTPP were then
-
6
desirable properties. The bleaching of ZnTPP and 1 (1.7 x 10
investigated toward the simple C=C bond cleavage of P
3
(into P
and AQ) through recycling experiments. A solution of P (4.2 x
CN 9:1 was irradiated for
5 min in the presence of catalytic amount (4.0 mol%) of
2
M) were compared by following the decay of their Soret bands
by UV-vis, upon irradiation at 575 nm, under air in
39
3
-5
-8
1
4
2 2 3
0 M; 8.4 x 10 mol) in CH Cl / CH
2 2 3
CH Cl /CH CN (9:1) (Figure 4). Interestingly, the decay rate of
cage 1 is much slower than the reference ZnTTP. After 8 h of
irradiation, 91% of the initial Soret band intensity degrades in the
case of ZnTPP, whereas only a 24% decrease is observed for 1
photosensitizers 1 or ZnTPP. After this irradiation time, fresh P
substrate was added to each solution in order to reach the initial
quantity of P . The procedure was repeated to obtain five
3
3
(
Figure 4c). Furthermore, It should be noted that a similar trend
was observed by comparing the bleaching of and the
tetracarboxyphenyl zinc porphyrin (Zn-TCPP), indicating that the
enhanced resistance of should be attributed to the
catalytic cycles (Figure 5). Interestingly, ZnTPP showed a strong
deactivation after the first recycle run (from 38 % to 6.5%
conversion), while 1 displayed a much more robust behaviour
with respectively 46, 39, 31, 20 and 8.5 % conversion upon five
catalytic cycles.
1
1
nanocapsule stability and not solely to the carboxylate
substituents (Figure S18).
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
10.1002/chem.201705531
FULL PAPER
1
Figure 5. (a) Reaction of P
anthraquinone, (b) comparison of the decay rate of P
ZnTPP (4.0 mol%; green) or 1 (4.0 mol%; blue) upon successive additions of
substrate (arrows represents adjusted additions of P to recover the initial
amount of substrate; c represents the P conversion) and (c) comparison of
the average decay rate of P within a 45 min irradiation time, upon recycling
3
with
O
2
yielding to the formation of P
2
and
absorbance, fluorescence and triplet energies upon
encapsulation of 4,4'-bipy is 0.1 - 0.15 eV (Table 1). This is in
agreement with the experimental trend, although the
experimental shift of approximately 0.02 eV in absorbance and
3
in the presence of
3
3
3
fluorescence is somewhat overestimated. The ability to generate
experiments, using 1 (blue), ZnTPP (green).
1
2
O will be favoured, among other factors, by a porphyrin triplet
energy that should be higher, but as close as possible, to the
singlet triplet energy gap of oxygen, which is 0.98 eV (1269 nm),
Following this argumentation, the lower triplet energy calculated
1
Guest-dependent tuning of O
2
production.
Taking advantage of the well-defined cavity present in prism 1,
1 1
for 4,4’-bipy⊂1 (T = 1.50 eV) compared to 1 (T = 1.65 eV)
1
we investigated the
O
2
production efficiency upon guest
implies a higher probability of oxygen sensitization, which is
consistent with the experimental data. In addition, the calculated
oscillator strength for the lowest excited states of 4,4’-bipy⊂1 is
approximately twice as high as that of the empty capsule (see
ESI for details), which is also consistent with the stronger
absorption of 4,4’-bipy⊂1 observed in the spectra.
encapsulation. Pyridine-based ligands like 4,4’-bipy and (m-
Py)exTTF are strongly accommodated within the cavity of 1 via
the ability of the Zn-porphyrin to interact with their pyridine
2
0,24
moieties.
presence and absence of 4,4’-bipy reveal a higher consumption
by a factor 1.4) when the host-guest adduct 4,4’-bipy⊂1 was
Time-dependent plots of the absorbance of DPA in
(
a
Table 1. Experimental and computed (TD-CAM-B3LYP/SDD) photophysical
used as photosensitizer (Figure 6) with a conversion of 40%
data (S
1 1 1
absorption and fluorescence bands, and adiabatic S and T
after 20 min while only 28% conversion were observed for 1.
energies) of prism 1 and the 4,4’-bipy⊂1 complex.
Experimental
TD-CAM-B3LYP/SDD
λ [nm]
E
rel [eV]
E
rel [eV]
2.32
2.27
2.30
1.65
2.23
2.18
2.21
1.50
b
1
Absorption 552, 592
2.24, 2.09
2.06, 1.90
b
Fluorescence 601, 652
c
1
S adiabatic
d
1
T adiabatic
b
4
,4’-bipy⊂1
Absorption 560, 597
2.21, 2.08
2.04, 1.88
b
Fluorescence 606, 659
c
1
S adiabatic
d
1
T adiabatic
Figure 6. (a) Comparison of the decay rate of DPA in CH
2
Cl
2
/CH
3
CN (9:1)
a
-6
-1
Concentration 1·10 mol·l ; fluorescence spectra obtained with excitation at
-
3
under air upon irradiation at 575 nm (0.1 x 10 M), in the presence of 1 (1.3
mol%; blue), 4,4-bipy⊂1 (1.3 mol%; pale blue) and ZnTPP (1.3 mol%)
together with 4,4-bipy (2.6 mol%; purple) (b) Comparison of the average decay
rate of DPA within a 45 min irradiation time, using 1 (blue) or ZnTPP (purple)
as photosensitizers with or without additions of 4,4-bipy (2 equiv.) to the
reaction mixture.
b
C
5
60 nm. Experimental data in CH
2
Cl
2
.
Difference between S
d
1
and S
0
energies at their corresponding geometries. Difference between T
energies at their corresponding geometries.
1
and S
0
Using the ZnTPP photosensitizer in combination with 4,4’-bipy
Figuree 4 and S24) or (m-Py)exTTF (Figure S25) did not affect
(
1
the rates of
2
O generation in comparison with ZnTPP alone
(
Figure 6). This result can be correlated with the lack of
Similar experiments were carried out with (m-Py)exTTF⊂1 and
modification of the UV-vis absorption spectra of ZnTPP in the
presence of 4,4’-bipy (Figure S26). These observations
highlight the crucial role of the cage nature of 1 that allows for a
strong axial ligation of pyridine-based ligands simultaneously to
P
3
⊂1 (Figure S23). Both host-guest systems exhibit identical
results to those obtained with 4,4’-bipy⊂1 (Figure S24),
1
suggesting similar rates of
2
O generation. Therefore, the axial
binding of a pyridine moiety to each of the Zn-porphyrin centers
2
0
1
both Zn-porphyrins moieties, even in highly diluted conditions
of 1 plays an essential role in the observed increase of
production. As expected, the ditopic binding of 4,4’-bipy within 1
in CH Cl leads to bathochromic shifts of both the Soret (422-
26 nm) and the Q-band a (550-559 nm) together with an
increase of the intensity of both Q-bands (α and β) (Figure S26).
O
2
-
6
41
(
1.3 x 10 M).
2
2
4
40
We therefore assume that such modifications of the
absorption features result in improved photosensitization
efficiency. The observed increase in fluorescence quantum yield
(
by a factor 1.6) when 4,4’-bipy is bound within 1 confirmed this
assumption (Figure S27).
The bathochromic shift and higher band intensity in 4,4’-
bipy⊂1 compared to 1 is confirmed by the TD-CAM-B3LYP data.
Figure 7 shows the sensitization mechanism and the energy
levels involved. The calculated bathochromic shift for the
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
10.1002/chem.201705531
FULL PAPER
Figure 7.
Energy levels involved in the singlet oxygen sensitization
mechanism by 1 and 4,4’-bipy⊂1 (blue and red figures, respectively).
1
II
2
pH-dependent O production: the Cu -based prism 2.
The use of a metal-organic capsule as photosensitizer raises the
question of the influence of metallic centers over the
photochemistry of the suprastructure. Indeed, a recent study on
II
a BODIPY-based metal-organic capsule (Fe
4
L
6
) photosensitizer
showed a modest quantum yield of singlet oxygen generation
compared to well-established BODIPY photosensitizers. It was
II
proposed that Fe metal centers could be responsible for the
1
lowering of the quantum yield of O
2
generation by reducing the
42
spin-orbit coupling necessary for efficient intersystem crossing.
II
II
II
Furthermore, several transition-metal complexes (Ni , Cu , Ag )
are reported in the literature as moderate to excellent excited-
43
II
9
state quenchers. In particular, the paramagnetic Cu , with its d
valence electron configuration, is paramagnetic, which has been
shown to increase the quenching efficiency. The Zn-porphyrin
2
+
(
ZnP) fluorescence quenching upon binding of Cu ions to the
periphery of the porphyrin has been reported through the
44
synthesis of porphyrin-metal receptor dyads.
Steady-state
fluorescence and lifetime measurements have demonstrated
1
that the photo-excited singlet state of ZnP, (ZnP)*, is quenched
II
by a pendant [Cu (edta)] complex tethered to the ZnTPP
chromophore through intramolecular photo-induced ET
45
reaction.
Furthermore, the significant quenching of the
emission and photosensitizing properties of the Zn-TCPP
moieties of a metal–organic framework nanoparticle, have been
2
+
very recently achieved by using Cu ions as metal nodes of the
46
network.
To investigate the effect of the bridging metal ion in our self-
assembled Zn-porphyrin prismatic capsules, the
photosensitizing properties of Cu -based prism 2, the copper-
II
47
analogue of 1 (Figure 8), were tested. As expected, the time-
dependent plot of DPA absorbance in the presence of the
soluble 2 (1.3 mol%) displayed a negligible decay rate, similar to
the one observed in the absence of photosensitizer (Figure S28).
Furthermore no degradation of (m-Py)exTTF was observed
upon its exposition to light and air in the presence of 2 (4.0
1
mol%, 3 h, Figure S29), confirming the lack of O
2
production.
Figure 8. a) Schematic illustration of the “ON” and “OFF“ states of the
1
photosensitized production of
2
O respectively found in 1 and 2 (ET: Electron
Transfer). b) Superimposed fluorescence emission spectrums of 1 and 2 in
-
6
3
CH CN under Argon atmosphere (1 x 10 M, excitation at 560 nm). c)
Representative orbitals involved in the lowest excited states of 1 and 2.
The quenching of the excited states of the Zn-porphyrin
moieties by the Cu(II)-macrocycle, was further confirmed by
studying the fluorescence emission of 2, which revealed a
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
10.1002/chem.201705531
FULL PAPER
severe quenching resulting in a very low quantum yield value in
CH
3 F
CN (Φ = 0.00075) (Figure 8, S30). Finally, it should be
1
noted that the quenching of the O
2
production observed for 2 is
not affected by the encapsulation of 4,4’-bipy (Figure S28).
The quenching mechanism in the Cu(II)-based capsule 2 is
due to the existence of a manifold of low-lying excited states
9
below the porphyrin Q-bands which are associated to the d
configuration of the Cu(II) atoms. According to TD-CAM-B3LYP
calculations, the lowest excited states of 2 are a group of CT
states from the porphyrin A1u- and A2u-like orbitals to the empty d
orbitals of the Cu atoms (see representative orbitals in Figure
8
c) at 0.25 - 0.27 eV, followed by a group of d-d metal centred
states at 0.33 eV, and a group of ligand(biphenyl)-to-metal(Cu)
charge transfer states of the side ligands between 1.35 and 1.39
eV (see Table S5). There are further groups of states around 2
eV. This suggests that the quenching of the porphyrin states in 2
occurs through decay to the low-lying states involving the Cu(II)
atoms ultimately leading to electron transfer. Triplet sensitization
is no more possible, energetically, from these states.
A common strategy to obtain activatable photosensitizers (a-PS)
consists of maintaining the photosensitizer in a quenched state
prior to a molecular activation that turns ON the photosensitizer.
Quenching through Förster resonance energy transfer (FRET),
induced electron transfer, and self-quenching are particularly
-
3
Figure 9. Time dependent decay rate of DPA (8.27x10 M in CH
1:2.5)), in the presence of 2 (1.1 mol%), upon sequential additions of Et
and CF SO H, irradiation at 575 nm under air atmosphere.
2 2
Cl /DMF
(
3
N
48
useful strategies for efficient a-PS design. The Zn-porphyrin
moieties of are in quenched state (OFF-state) that
generation and fluorescence. Contrary to a rigid
3
3
2
a
1
deactivates O
2
covalent assembly, the “tunable” nature of metal-coordination
Control experiments using the monomeric photosensitizer Zn-
II
bonds in 2 might allow for a reversible liberation of the porphyrin
TCPP in combination with the copper(II) salt Cu (OTf)
2
were
units. The latter would no longer held in close proximity to the
conduced under identical experimental conditions. Addition of
1
II
metal centers and should therefore produce O
2
(ON-state). The
Cu (OTf)
form (deprotonated by Et
1:2.5) solvent mixture, instantly led to the precipitation of the
porphyrin which might result from the formation of insoluble
2
(4 equiv.) to a solution of Zn-TCPP in its carboxylate
reversible disassembly/reassembly of cage 2 was monitored by
3
N, 4 equivalents) in a DMF/CH Cl
2
2
1
H-NMR (Figure S31), ESI-HRMS (Figure S32) and UV-vis
(
(
3
Figure S33) upon addition of triflic acid and Et N respectively.
II
To confirm ON/OFF switching of the photosensitization
oligomers [(Zn-TCPP)-Cu ]
equiv. of CF SO H to the latter mixture did not recover the
soluble Zn-TCPP. Interestingly, addition of Cu (OTf)
to a solution of the carboxylic-acid form of Zn-TCPP did not
n
. Furthermore, the addition of 4
capability, (m-Py)exTTF was exposed to natural light and air in
3
3
II
a CH
presence of 2 (4.0 mol%) and Et
equiv.). In the presence of Et N, no photo-oxidation of (m-
Py)exTTF could be detected. Interestingly, in the presence of
triflic acid, (m-Py)exTTF was fully converted into P , P and AQ
production (Figure S34).
3
CN/DMF/CH
2
Cl
2
1:2:20 solvent mixture for one hour in the
2
(4 equiv.)
3
N (8 equiv.) or CF SO H (8
3
3
1
3
quench the
2
O production upon mixing but the favoured Cu-
carboxylate complexation occurred after 10 minutes affording
1
2
3
the same precipitate and totally quenching the
O
2
production
1
oxidation products, accounting for a O
We thus monitored the ability of 2 to reversibly generate
upon its disassembly/reassembly, by tracking the rate of the
2
(
Figure S36). The behavior of 2 is markedly different as both the
1
O
2
cage
2
and the protonated Zn-TCPP and macrocyclic
dicopper(II) complex arising from its reversible disassembly,
were fully soluble, illustrating the benefits of the well-defined
supra-structure of 2, which prevent the formation of insoluble
oligomeric species. Futhermore, it should be noted that identical
1
reaction of
DPA (8.27x10 M) and 2 (1.1 mol%) in a DMF/CH
solvent mixture, was irradiated at 575nm under air upon
subsequent additions of Et and CF SO H. The DPA
absorption intensity was followed by UV-vis measurements
Figure S35). Interestingly, the DPA consumption clearly reveals
2
O with DPA (Figure 9). A solution containing both
-
3
2
2
Cl (1:2.5)
3
N
3
3
control experiments (Zn-TCPP in combination with 4 equivalents
II
of Cu (OTf)
2
) were conducted in the presence of 4 equivalents of
nitrogenated chelating ligand N,N,N’,N’,N”-
pentamethyldiethylenetriamine. Addition of this ligand prevents
(
the
1
that the O
2
production can be controlled through the addition of
1
acid and base (Figure 9).
the formation of the insoluble oligomers and quench the
production (Figure S36). However, in this case, the
O
O
2
1
2
production is not turned-on upon addition of 4 equivalents of
CF CO H and the addition of 8 equivalents of acid only lead to a
3
3
very weak photooxidation of the DPA (15% convertion after 26
min). Clearly, this system (which mimics the structure of cage 2
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
10.1002/chem.201705531
FULL PAPER
but in a monomeric way) fails at reproducing the fine-tuning of
soluble cargo for the C70 photosensitizers without quenching its
1
1
O
2
production as observed for 2.
O
O
2
production efficiency. Finally, it should be noted that similar
1
Finally, since both cages 1 and 2 are reported as efficient
2
generation rates were observed for the empty capsule 1 or
54
receptors of fullerene derivatives with remarkably strong binding
the C70⊂1 host-guests adduct (Figure S39).
4
7,49
constants for C70
,
we posed ourselves the question of what
would be the effect of combining the dormant photosensitizer 2
1
50
with another
O
2
photosensitizer such as C70
.
Cage 2, which Conclusion
1
1
does not produce
2 2
O , was used as a host to study the O
photosensitization ability of the encapsulated C70 in C70⊂2.
Interestingly, the use of catalytic amount of C70⊂2 (1.3 mol%) in
We have shown that the self-assembled cofacial Zn-porphyrin
1
prisms 1 and 2 can be respectively used as robust
O
2
CH
3 2 2
CN/CH Cl (9:1) leads to a DPA decay similar to the one
photosensitizers and activatable photosensitizer. Indeed, the
1
II
II
observed for 1 (Figure 10, S37). C70 can therefore produce O
2
bridging metals Pd and Cu found in 1 and 2, respectively, led
even when encapsulated inside the porphyrin-based nano-
capsule. The use of C70 as photosensitizer is usually limited by
its lack of solubility in common organic solvent. Inclusion of
fullerene inside self-assembled mettalosupramolecular receptors
is known as an efficient strategy in order to increase their
to the formation of markedly different supramolecular
photosensitizers with distinct photosensitizing properties. The
1
production of
2
O was studied through the oxygenation of two
1
anthracene-based substrates, the
2
O quencher DPA and the
extended-TTF guest (m-py)exTTF.
51
II
solubility. The particularly high affinity of 2 toward C70 (K
a
≈ 1.8
The Pd -based supra-structure of 1 appears as a good
7
-1 47
1
0
M )
allows for solubilisation and transport of C
70
compromise between efficiency and stability towards
photosensitizer into organic solvent such as CH
3
CN or CH
2 2
Cl ,
photobleaching.
1 displays a very similar photosensitizing
-
6
even in highly diluted conditions (1.3 x 10 M). The ability of
efficiency comparing to the ZnTPP reference but with
1
C
70⊂2 to generate
monitored by DPA trapping. The oxygen generation efficiency of
70⊂2 and 70 in toluene/CH CN (9:1) are modest with
2
O in different solvent mixtures has been
remarkably enhanced photostability, thus being a particularly
1
robust catalyst for singlet oxygen production. The improved O
2
C
C
3
resistance observed for 1 compared to ZnTPP can be explained
owing to both the reduction of the electron density and increase
of the sterical hindrance at the porphyrin centers. This self-
assembly approach avoids tedious purification steps and
synthesis redesign of the porphyrin subunit. It therefore provides
an additional tool to prevent porphyrins self-decompositon.
respectively 4% and 7 % conversion after 35 min of irradiation.
According to the literature, the lifetime of singlet oxygen shows a
1
strong solvent dependence. The reported O
2
lifetime in toluene,
CH
3
CN and CH
2
Cl
2
at room temperature, are respectively 29, 75
Cl replaced toluene, a
2
O generation efficiency of C70⊂2 was observed
52
and 91 µs. Interestingly, when CH
2
2
1
II
much higher
On the other hand, the Cu -carboxylate coordination bonds
with 26% conversion of DPA (Figure 10, S38). C70 alone is not
soluble in the later solvent mixture.
involved in 2 allow for an adaptive system with switchable
properties. In the prism, the photosensitization is switched off by
II
electron transfer to the Cu atoms. We have demonstrated that 2
1
can be used as a dormant
2
O photosensitizer that can be
turned ON/OFF upon the reversible disassembly of the supra-
structure by protonation/deprotonation of the carboxylate
moieties and liberation of the tetra-carboxyphenyl zinc porphyrin
moieties in the carboxylic form (Zn-TCPP). Such switching
behavior can not be reproduced using Zn-TCPP unit in
II
combination with simple Cu (OTf)
2
due to the formation of
insoluble structures, highlighting the crucial role of the supra-
structure in 2. Sensitizers that allow for reversible switching
55
between ON and OFF states have attracted growing attention,
and pH-based approaches have the potential to induce tumor-
selective damages due to the higher acidity of tumor tissue
5
6
comparing to normal tissue.
approach to exert control over the O
a supramolecular cage might be of significant importance as it
This novel pH-dependent
1
2
generation upon breaking
Figure 10. (a) Schematic representation of the
photosensitizer. (b) Average decay rate of DPA (0.1 x 10 M) within a 45 min
C
70⊂2 host-guest
1
-
3
opens the door to systems merging
O
2
production and drug
delivery.
irradiation time, using 1, C70⊂1 , 2, C70⊂2, or C70 as photosensitizers (1.3
mol%) in toluene/CH
3
CN (9:1) (purple) or CH
2
Cl
2
/CH
3
CN (9:1) (blue).
Contrariwise
to
conventional porphyrin-based
photosensitizers, nanocages 1 and 2 allow for strong host-guest
interactions that open new opportunities for a challenging guest-
1
This strong solvent effect can therefore be explained by the
control over
O
2
generation. When pyridine-based ligands are
1
53
longer lifetime of O
2
in CH
2
Cl
2
compared to toluene. Aiming at
encapsulated through the axial binding of both Zn-porphyrin of 1,
1
avoiding the solvent quenching effect of toluene, the Zn-
the
2
O production is significantly enhanced by a factor 1.4
porphyrin-based nanocapsule 2 can therefore be used as a
through a shift of the energy levels involved in the sensitization.
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
10.1002/chem.201705531
FULL PAPER
1
2
Finally, despite cage 2 can not produce O in its OFF form, C70
can be encapsulated and the photosensitization ability of C70
itself is not altered by its encapsulation in 2, making it interesting
cargo for transport and delivery of organic photosensitizers.
Indeed, the association between fullerene and porphyrin is
considered as a promising strategy toward the development of
therapeutic weapons having both drug-delivery and imaging
[
15] N. Struch, C. Bannwarth, T. K. Ronson, Y. Lorenz, B. Mienert, N. Wagner,
M. Engeser, E. Bill, R. Puttreddy, K. Rissanen, J. Beck, S. Grimme, J. R.
Nitschke, and A. Lgtzen, Angew. Chem. Int. Ed. 2017, 56, 4930 – 4935.
16] F. J. Rizzuto and J. R. Nitschke, Nat. Chem. 2017, 9, 903 – 908.
17] E. G. Percastegui, J. Mosquera, and J. R. Nitschke, Angew. Chem. Int.
Ed. 2017, 56, 9136 - 9140
[
[
57
[18] L. Schoepff, L. Kocher, S. Durot, and V. Heitz, J. Org. Chem. 2017, 82,
845−5851
capabilities.
5
Since self-assembled prims based on porphyrin subunit and
metallo-macrocycle can be easily obtained, we envision that
library of such supramolecular photosensitizers may be rapidly
built. In particular, the use of alternative building blocks allowing
for water solubility will be of particular interest to further extend
the research perspectives of porphyrin-based nanocages toward
photodynamic therapy.
[
19] (a) S. H. A. M. Leenders, R. Gramage-Doria, B. and J. N. H. Reek, Chem.
Soc. Rev. 2015, 44, 433; (b) P. F. Kuijpers, M. Otte, M. Dürr, I.Ivanović-
Burmazović, J. N. H. Reek, and B. de Bruin, ACS Catal. 2016, 6,
3
106−3112 ; (c) M. Otte, P. F. Kuijpers, O. Troeppner, I. Ivanovic´-
Burmazovic´, J. N. H. Reek, and B. de Bruin, Chem. Eur. J. 2014, 20,
4880 – 4884
[20] C. García-Simón, R. Gramage-Doria, S. Raoufmoghaddam, T. Parella, M.
Costas, X. Ribas and J. N. H. Reek, J. Am. Chem. Soc. 2015, 137, 2680-
2
687.
[
[
21] X. Wang, S. S. Nurttila, W. I. Dzik, R. Becker, J. Rodgers, and J. N. H.
Reek, Chem. Eur. J. 2017, 23, 14769 – 14777
Acknowledgements
22] F. Schmitt, N. P.E. Barry, L. Juillerat-Jeanneret, B. Therrien, Bioorg. Med.
Chem. Lett. 2012, 22, 178–180
We thank Spanish MINECO (CTQ2015-70795-P, CTQ2016-
7
7989-P, CTQ2015-69363-P), the Agence Nationale de la
[
[
[
23]
F. Schmitt, P. Govindaswamy, O. Zava, G. Süss-Fink, L. Juillerat-
Recherche (ANR-14-CE08-0001 JCJC BOMBER to S.G.), and
the Generalitat de Catalunya (2014 SGR 862, 2014SGR-1202
and posdoctoral grant to C.C.). X.R. and M.C. are also grateful
for ICREA-Acadèmia awards. We thank STR UdG for technical
support. Calculations were carried out at the Consorci de
Serveis Universitaris de Catalunya.
Jeanneret and B. Therrien, J Biol Inorg Chem. 2009, 14, 101–109
24] C. Colomban, G. Szaloki, M. Allain, L. Gomez, S. Goeb, M. Sallé, M.
Costas and X. Ribas, Chem. Eur. J. 2017, 23, 3016 - 3022
25] A. E. Jones, C. A. Christensen, D. F. Perepichka, A. S. Batsanov, A;
Beeby, P. J. Low, M. R. Bryce, and A. W. Parker, Chem. Eur. J. 2001, 7,
5, 973-978.
[
[
26] J.-B. Giguere and J.-F. Morin, J. Org. Chem. 2015, 80, 6767−6775.
27] M. Yoshizawa, S. Miyagi, M. Kawano, K. Ishiguro, and M. Fujita, J. Am.
Chem. Soc. 2014, 126, 9172-9173.
Keywords: porphyrin-based metallocages • self-assembly •
supramolecular photosensitizers • host-guest chemistry •
singlet oxygen
[
28] It should be noted that the same catalytic behaviour was observed when
zinc−tetraphenylporphyrin (ZnTPP) was used as photosensitizer instead
of 1 (Figure S13)
[
29] a) S. Martins, J.P.S. Farinha, C. Baleizao and M.N. Berberan-Santos,
Chem.Commun. 2014, 50, 3317-3320. b) J. Hynek, J. Rathousky, J.
Demel and K. Lang, RSC Adv.,2016, 6, 44279-44287.
ꢀ
[
[
[
[
[
[
1]
P.R. Ogilby, Chem. Soc. Rev. 2010, 39, 3181.
2]
3]
4]
5]
6]
A. A. Ghogare and A. Greer, Chem. Rev. 2016, 116, 9994−10034.
N. A. Romero and D. A. Nicewicz, Chem. Rev. 2016, 116, 10075–10166.
M. Klaper and T. Linker, J. Am. Chem. Soc. 2015, 137, 13744−13747.
X.Ding and B.-H. Han, Angew. Chem. Int. Ed. 2015, 54, 6536 – 6539.
K.Liu, Y. Liu, Y. Yao, H. Yuan, S. Wang, Z. Wang, and X. Zhang, Angew.
Chem. Int. Ed. 2013, 52, 8285-8289.
[30] Irradiation of DPA (0,1 mM) in the presence of (m-Py)exTTF (6,5 mol%)
afford the same observation indicating that (m-Py)exTTF itself is not able
to generate singlet oxygen (Figure S14).
[31] L. Hou, X. Zhang, T. C. Pijper, W.R. Browne and B. L. Feringa, J. Am.
Chem. Soc. 2014, 136, 910−913.
[
32] The lower activity per Zn-porphyrin center for 1 can be explained by the
fact that, due to symmetry, the S state at the ground-state minimum of 1
[
[
[
[
[
[
7]
8]
9]
J. Hynek, J. Rathousky, J. Demel and K. Lang, RSC Adv. 2016, 6, 44279
1
−
44287.
J. Park, D. Feng, S. Yuan and H.C. Zhou, Angew. Chem. Int. Ed. 2015,
4, 430 − 435.
Y.Z. Chen, Z. U. Wang, J. Lu, S. H. Yu, H. L. Jiang, J. Am. Chem. Soc.
017, 139, 2035−2044.
10] A. K. Bar, S. Mohapatra, E. Zangrando and P. S. Mukherjee, Chem. Eur. [34] M. I. Burguete, F. Galindo, R. Gavara, S. V. Luis, M. Moreno, P. Thomasc
is distributed over the two porphyrin units, and upon relaxation, the
excitation localizes on one of the porphyrin units (see Table S1 and
related comment).
5
2
[33] S. J. Kim and E. T. Kool, J. Am. Chem. Soc. 2006, 128, 6164-6171
J. 2012, 18, 9571 – 9579
and D. A. Russell, Photochem. Photobiol. Sci. 2009, 8, 37–44
35] J.A.S. Cavaleiro, H. Görner, P. S.S. Lacerda, J. G. MacDonald, G. Mark,
M.G.P.M.S. Neves, R. S. Nohr, H. P. Schuchmannb, C. V. Sonntag and
11] Y. Shi, I. Sanchez-Molina, C. Cao, T. R. Cook, and P. J. Stang, J. Proc.
Natl. Acad. Sci. U. S. A. 2014, 111, 9390
[
12] N. Mihara, Y. Yamada, and K. Tanaka, Bull. Chem. Soc. Jpn. 2017, 90,
A. C. Toméa, J. Photochem. Photobiol. A Chem. 2001, 144, 131–140.
36] R. Bonnett and G. Martinez, tetrahedron 2001, 57, 9513-9547.
37] (a) T. Nakazono, A. R. Parent and K. Sakai, Chem. Eur. J. 2015, 21,
6723-6726. (b) T. Nakazono and K. Sakai, Dalton Trans. 2016, 45, 12649
– 12652.
4
27-435
13] T. Nakamura, H. Ube, M. Shiro, and M. Shionoya, Angew. Chem. Int. Ed.
013, 52, 720 –723
14] W. Brenner, T. K. Ronson, and J. R. Nitschke J. Am. Chem. Soc. 2017,
39, 75−78
[
[
[
[
2
1
[38] A. M. S. Silva, M.G. P.M. S. Neves, R. R. L. Martins, J. A. S. Cavaleiro, T.
Boschi and P. Tagliatesta, J. Porphyr. Phthalocyanines 1998, 2, 45–51.
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
10.1002/chem.201705531
FULL PAPER
[
39] The conversion of P
3
upon irradiation (575nm), in CH
2
Cl
2
/CH
3
CN 9:1, [49] C. García-Simón, M. Garcia-Borràs, L. Gómez, T. Parella, S. Osuna, J.
under air, was followed by UV-vis. In the absence of photosensitizer only
negligible decrease in the absorbance of P was observed (Figure S21).
Juanhuix, I. Imaz, D. Maspoch, M. Costas and X. Ribas, Nat. Commun.
2014, 5, 5557.
3
In the presence of 1 (4 mol%) or ZnTPP (4 mol%), the oxidative cleavage [50] R. Kumar, E. H. Gleibner, E. Gabrielle V. Tiu, and Y. Yamakoshi, Org.
of P
3
(0.042 mM) into P
(at 355 and 458 nm) with clean isosbestic points (Figure S21). After
showed
conversion of 83% when ZnTPP shows a lower conversion of 55%
Figure S22).
2
and AQ show a decay of the absorbance bands
Lett. 2016, 18, 184−187.
of P
3
[
[
51] C. García-Simón, M. Costas and X. Ribas, Chem. Soc. Rev., 2016, 45,
1
45 min of irradiation time, the experiments with
1
a P
3
4
0-62.
52] (a) R. Schmidt, J. Am. Chem. Soc. 1989, 111, 6983. (b) F. Wilkinson, W.
P. Helman, A. B. Ross, J. Phys. Chem. Ref. Data 1995, 24, 663. (c) A.
A.Gorman, M. A. J. Rodgers, Singlet Oxygen; Scaiano, J. C., Ed.; CRC
Press: BocaRaton, Florida, 1989; Vol. II, pp 229.
(
[
[
[
40] H. L. Kee, J. Bhaumik, J.R. Diers, P. Mroz, M. R. Hamblin, D.F. Bocian, J.
S. Lindsey, and D. Holten, J Photochem Photobiol A Chem. 2008, 200,
3
46–355.
6
41] The reported affinity constant of 1 toward pyridine-based ligands (K
a
> 10 [53] C. Schweitzer and R. Schmidt, Chem. Rev. 2003, 103, 1685-1757.
-
1
1
M ), is three orders of magnitude higher than that the one of monomeric
[
54] The similar O
2
generation rates observed for 1, C70⊂1 and C70⊂2
3
-1 20
a
analogues ZnTPP (K ≈ 10 M ).
suggest an inhibition of the photosensitization at the Zn-porphyrin centers
of 1 upon fullerene encapsulation. The strong quenching of the
fluorescence of the Zn-porphyrin units of 1 upon C70 encapsulation is
42] P. P. Neelakandan, A. Jiménez, J. D. Thoburn, and J. R. Nitschke,
Angew. Chem. Int. Ed. 2015, 54, 14378 –14382.
[
[
43] J. R. McCarthy and R. Weissleder, ChemMedChem 2007, 2, 360 – 365.
44] (a) Y. Q. Weng, F. Yue, Y. R. Zhong, and B. Ye, Inorg. Chem. 2007, 46,
4
9
indeed reported, confirming this proposal. We therfore suggest that the
putative inhibition of photosensitization at the porphyrin centers of C70⊂1
7
2
749-7755. (b) Y. Ding, W.-H. Zhu, and Y. Xie, Chem. Rev. 2017, 117,
203−2256.
1
is balanced by the O
2
production by the C70 guest itself.
[
[
[
[
45] H. Takashima, H. Kawahara, M. Kitano, S. Shibata, H. Murakami and K. [55] H. Horiuchi, R. Kuribara, A. Hirabara, and T. Okutsu, J. Phys. Chem. A.
Tsukahara, J. Phys. Chem. B 2008, 112, 15493–15502.
2016, 120, 5554−5561.
46] Y. Ma, X. Li, A. Li, P. Yang, C. Zhang, and B. Tang, Angew. Chem. Int. [56] T. Torring, R. Toftegaard, J. Arnbjerg, P. R. Ogilby, and K.V. Gothelf,
Ed. 2017, 56, 13752 – 13756
Angew. Chem. Int. Ed. 2010, 49, 7923 –7925.
47] C. Fuertes-Espinosa, C. García-Simón, E. Castro, M. Costas, L. [57] C. Constantin, M. Neagu, R. M. Ion, M. Gherghiceanu and C. Stavaru,
Echegoyen, and X. Ribas, Chem. Eur. J. 2017, 23, 3553 – 3557.
Nanomedicine 2, 2010, 5 (2).
48] J. F. Lovell, T. W. B. Liu, J. Chen, and G. Zheng, Chem. Rev. 2010, 110,
ꢀ
ꢀ
ꢀ
2
839-2857.
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
10.1002/chem.201705531
FULL PAPER
Entry for the Table of Contents (Please choose one layout)
Layout 2:
FULL PAPER
Cédric Colomban, Carles Fuertes-
Espinosa, Sébastien Goeb, Marc Sallé,
Miquel Costas, Lluis Blancafort* and
Xavi Ribas*
Page No. – Page No.
Self-assembled Cofacial Zinc Porphyrin
Supramolecular Nanocapsules as
Text for Table of Contents
The benefits of using self-assembled cofacial Zn-porphyrins prisms as cage-like
photosensitizers with tuneable photosensitizing properties are reported.
1
tuneable O
2
Photosensitizers
This article is protected by copyright. All rights reserved.