Rotaxane-branched dendrimers with enhanced photosensitization

Article abstract of DOI:10.1021/jacs.0c07292

During the past few decades, fabrication of functional rotaxane-branched dendrimers has become one of the most attractive yet challenging topics within supramolecular chemistry and materials science. Herein, we present the successful fabrication of a fami

Full text of DOI:10.1021/jacs.0c07292

Subscriber access provided by CORNELL UNIVERSITY LIBRARY
Article
Rotaxane-Branched Dendrimers with Enhanced Photosensitization
Wei-Jian Li, Zhubin Hu, Lin Xu, Xu-Qing Wang, Wei Wang, Guang-Qiang Yin,
Dan-Yang Zhang, Zhenrong Sun, Xiaopeng Li, Haitao Sun, and Hai-Bo Yang
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.0c07292 • Publication Date (Web): 01 Sep 2020
Downloaded from pubs.acs.org on September 1, 2020
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a service to the research community to expedite the dissemination
of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in
full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully
peer reviewed, but should not be considered the official version of record. They are citable by the
Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore,
the “Just Accepted” Web site may not include all articles that will be published in the journal. After
a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web
site and published as an ASAP article. Note that technical editing may introduce minor changes
to the manuscript text and/or graphics which could affect content, and all legal disclaimers and
ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or
consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W.,
Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 9
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
Rotaxane-Branched Dendrimers with Enhanced Photosensitization
†
§
†,*
†
†
†, #
†
Wei-Jian Li , Zhubin Hu , Lin Xu , Xu-Qing Wang , Wei Wang , Guang-Qiang Yin , Dan-Yang Zhang ,
§
#
§,*
†,*
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Zhenrong Sun , Xiaopeng Li , Haitao Sun , Hai-Bo Yang
†Shanghai Key Laboratory of Green Chemistry and Chemical Processes & Chang-Kung Chuang Institute, School of Chem-
istry and Molecular Engineering, East China Normal University, 3663 N. Zhongshan Road, Shanghai 200062, P. R. China.
§State Key Laboratory of Precision Spectroscopy, School of Physics and Electronic Science, East China Normal University,
5
00 Dongchuan Road, Shanghai 200241, P. R. China
#Department of Chemistry, University of South Florida, Tampa, Florida 33620, United States.
ABSTRACT: During the past few decades, fabrication of functional rotaxane-branched dendrimers has become one of the
most attractive yet challenging topics within supramolecular chemistry and materials science. Herein, we present the suc-
cessful fabrication of a family of new rotaxane-branched dendrimers containing up to twenty-one platinum atoms and forty-
two photosensitizer moieties through an efficient and controllable divergent approach. Notably, the photosensitization
efficiencies of these rotaxane-branched dendrimers gradually increased with the increase of dendrimer generation. For ex-
1
ample, third-generation rotaxane-branched dendrimer PG3 revealed 13.3-fold higher O
2
generation efficiency than its cor-
1
responding monomer AN. The enhanced O
2
generation efficiency was attributed to the enhancement of intersystem crossing
(
ISC) through the simple and efficient incorporation of multiple heavy atoms and photosensitizer moieties on the axles and
wheels of the rotaxane units, respectively, which has been validated by UV-visible and fluorescence techniques, time-depend-
ent density functional theory calculations, photolysis model reactions, and the apparent activation energy calculations. There-
fore, we develop a new promising platform of rotaxane-branched dendrimers for the preparation of effective photosensitizers.
INTRODUCTION
improving the
photosensitization efficiency of
1
1
photosensitizers. Therefore, the incorporation of heavy
atoms such as bromine, iodine, or platinum into a
photosensitizer molecule has been one of the most popular
approaches for improving the photosensitization efficiency
In recent decades, the increasing attention has been paid
to the design and synthesis of diverse mechanically
interlocked molecules (MIMs) because of their impressive
topologies and unique dynamic features, which have
enabled them to be versatile platforms for the construction
1
12
since it can enhance the SOC of photosensitizers.
2
3
Considering the fact that rotaxane-branched dendrimers
usually feature the star-shaped structures and highly
branched topology, we envision that rotaxane-branched
dendrimers might serve as an advantageous platform for
the preparation of the effective photosensitizers for the
following reasons: (i) the simple and efficient incorporation
of multiple heavy atoms could be realized through the
introduction of heavy atoms such as platinum(II) on the
axles of the rotaxane units; (ii) the facile substitution of a
large number of the photosensitizer moieties on the wheels
of rotaxane units may contribute to the enhanced energy
transition channels, which should facilitate the ISC process
of molecular pumps, molecular elevators, molecular
4
5
shuttles, and so on. As a vital subset of MIMs, rotaxane-
branched dendrimers have become one of the most
attractive topics within supramolecular chemistry and
6
materials science. The combination of the characteristics of
both rotaxanes and dendrimers endows the resultant
rotaxane-branched
dendrimers
with
well-defined
7
topological structures and stimulus-responsiveness. More
importantly, the well-defined topological arrangements of
rotaxanes within the dendritic skeleton endow the resultant
rotaxane-branched dendrimers with amplified collective
1
3
8
effects. For instance, we have recently realized a new pro-
9b,14
and then improve the photosensitization efficiency;
(iii)
totype of rotaxane-branched dendrimers with the collective
expansion-contraction motion on each branch for the mimic
of the amplified collective molecular motions in biomolecu-
the spatial steric effect of rotaxane units could reduce the
tendency of photosensitizer moieties to aggregate and
thereby prevent aggregation-caused quenching (ACQ)
9
lar machines.
1
3
effects.
Notably, the development of highly effective
photosensitizers has recently attracted increasing interests
because of their widespread applications in photocatalytic
Based on the above considerations as well as our ongoing
interests in rotaxane-branched dendrimers,
study, a series of new rotaxane-branched dendrimers PG1–
8
,9,13
in this
10
synthetic chemistry and three-dimensional (3-D) printing.
According to the photosensitization process and the
perturbation theory, the enhancement of the spin-orbit
coupling (SOC) can give rise to an increase in the rate
constant of the intersystem crossing (kISC), thereby
ACS Paragon Plus Environment

Journal of the American Chemical Society
incorporating mechanically interlocked anthracene-
Page 2 of 9
(
a)
(b)
Photosensitizers
ISC
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
S
1
containing units on each branch. As shown in Scheme 1, by
employing the copper-catalyzed coupling reaction of the
precursor [2]rotaxane R-AN with the core module 1,3,5-
triethynylbenzene, the first generation of the rotaxane-
branched dendrimer PG1 bearing three rotaxane units with
six alkoxy-substituted anthracene moieties on the branches
was successfully prepared in a good yield of 74%. The
subsequent deprotection of PG1 with tetrabutylammonium
S
1
1O
2
1
O2
1O
2
1
O2
T
1
T
1
Energy Transfer
O2
Rotaxane
Dendrimers
Energy Transfer
3O2
3
3O
2
light
F
P
light
F
3
O2
S
0
S
0
(c)
fluoride trihydrate (Bu
4
NF·3H O) produced the
2
corresponding rotaxane-branched dendrimer intermediate
PG1-YNE with six alkyne groups at the periphery.
Repeating the similar coupling reaction of PG1-YNE and R-
AN gave rise to the second-generation rotaxane-branched
dendrimer PG2 with nine rotaxane units as well as eighteen
alkoxy-substituted anthracene moieties on the branches in
69% yield. Following this iterative deprotection-coupling
growth process, the third-generation rotaxane-branched
dendrimer PG3 was obtained in a good yield of 81%. Very
impressively, PG3 contained twenty-one rotaxane units
with forty-two alkoxy-substituted anthracene units on the
rotaxane branches. Notably, the efficient formation of
platinum-acetylide bonds played significant roles in the
high-yield and structure-controlled synthesis of the
rotaxane-branched dendrimers PG1–PG3. Moreover, all
of the resultant rotaxane-branched dendrimers were
soluble and stable in common organic solvents, which
enabled ready purification by means of column
chromatography and preparative gel permeation
chromatography (GPC).
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
SOC
enhancing
ISC
ISC
S
S
T
T
More ISC transition channels
Figure 1. Working mechanism of photosensitizers and the
design principle of this work. The different photosensitization
processes of the small-molecule photosensitizer (a) and the
rotaxane-branched dendrimer photosensitizer (b). (c)
Enhanced intersystem crossing of rotaxane-branched
dendrimer.
1
5
PG3 containing multiple platinum atoms as the heavy atoms
and alkoxy-substituted anthracene units as the
photosensitizer moieties
have been successfully
The rotaxane-branched dendrimers PG1–PG3 were first
constructed through an efficient and controllable divergent
approach. It should be noted that, within the resultant third-
generation rotaxane-branched dendrimer PG3, twenty-one
platinum atoms and forty-two alkoxy-substituted
anthracene units were spatially distributed on the axles and
wheels of the rotaxane units, thus resulting in the
1
31
characterized by one-dimensional multinuclear ( H and P)
1
NMR spectroscopy (Figures S23-24). As shown in the H
NMR spectra of PG1–PG3, the peaks below 0.0 ppm that are
assigned to the protons on the axles of the rotaxane units
still remained unchanged after the formation of rotaxane-
branched dendrimers PG1–PG3, which indicated that the
rotaxane units remained intact during the synthetic process.
From the first to the third generation of the rotaxane-
branched dendrimers, these peaks became broader
possibly because the rotaxane units on different branches
were slightly nonequivalent in the high-generation
significantly enhanced energy transition channels from S
1
to
T
1
and a remarkable heavy-atom effect (Figure 1). As
expected, compared with their monomer AN and the
precursor [2]rotaxane R-AN, the newly designed rotaxane-
branched dendrimers PG1–PG3 showed much higher
photosensitization
efficiency.
In
particular,
the
31
dendrimers. In the case of P NMR analysis, compared with
the peak ascribed to the PEt ligands around platinum
centers in the precursor [2]rotaxane R-AN, those PEt
photosensitization efficiencies of these rotaxane-branched
dendrimers gradually increased with the increase of
dendrimer generation. Accordingly, we demonstrated for
the first time that rotaxane-branched dendrimers could
serve as a new promising platform for the preparation of
effective photosensitizers.
3
3
ligands in the rotaxane-branched dendrimers PG1, PG2,
and PG3 exhibited a remarkable downfield shift of ~2.9
ppm, respectively, which provided a direct evidence for the
formation of platinum-acetylide bonds during the
dendrimer growth process.
RESULTS AND DISCUSSION
Mass spectrometric investigation of the rotaxane-
branched dendrimers PG1–PG3 was performed by the
matrix-assisted laser desorption/ionization time of flight
mass spectrometry (MALDI-TOF-MS), which provided the
further support for the existence of the desired rotaxane-
branched dendrimers. In the MALDI-TOF-MS spectrum of
the rotaxane-branched dendrimer PG1, the peak of m/z =
Synthesis and Characterization of Rotaxane-Branched
Dendrimers. The key precursor [2]rotaxane R-AN
containing
9-alkoxy-substituted
anthracene
was
synthesized through multistep sequence reactions as
shown in Schemes S1-2. Notably, by employing the
threading-followed-by-stoppering approach, the rotaxane
formation proceeded in a relatively high yield of 84%.
Sequentially, starting from the precursor [2]rotaxane R-AN,
a controllable divergent strategy was used for the synthesis
7
360.3, consistent with the theoretical values of the [PG1 +
+
H] ion (m/z = 7,357.6), was detected (Figure S15). The
MALDI-TOF-MS spectrum of the rotaxane-branched
of
the
targeted
rotaxane-branched
dendrimers
ACS Paragon Plus Environment

Page 3 of 9
Journal of the American Chemical Society
Scheme 1. (a) Synthesis of Rotaxane-Branched Dendrimer PG1. (b) Schematic Representation of A Controllable Divergent
1
2
3
4
5
6
7
8
9
Strategy for the Synthesis of Rotaxane-Branched Dendrimers PG2 and PG3. Reaction Conditions: (I) (i) Bu
4
NF·3H
2
O, THF,
r.t.,
CuI,DCM/Et
2
h; (ii) R-AN, CuI, DCM/Et
NH,r.t.,overnight, 81%.
2
NH, r.t., overnight, 69%; (II) (i) Bu
4
NF·3H
2
O, THF, r.t., 2 h; (ii) R-AN,
2
(
a)
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
CuI, DCM/Et NH
r.t., overnight, 74%
[
2]rotaxane R-AN
PG1
(b)
I
II
PG1
PG2
PG3
conducted to determine their sizes in solution (Figure S29).
dendrimer PG2 exhibited two charged states at m/z =
+
2
[
0,856.7 and 10,437.6 corresponding to [PG2 + K] and
The average hydrodynamic sizes (D ) for PG1, PG2, and
h
2
+
PG2 + K + Na] , respectively, which were close to their
theoretical molecular weights (m/z = 20,854.1 and 10,438.5)
Figure S19). For the rotaxane-branched dendrimer PG3,
MALDI-TOF-MS provided unsatisfactory mass data because
of its high molecular weight (theoretical average M =
PG3 were 2.2 ± 0.1 nm, 3.6 ± 0.2 nm, and 6.2 ± 0.2 nm,
respectively, which indicated that the size progression was
in agreement with that measured by the DOSY technique.
(
With the aim of identifying the morphologies, atomic
force microscopy (AFM) measurements of the resultant
rotaxane-branched dendrimers PG1–PG3 were also carried
out as well. As shown in Figure 2, when the generation of
the dendrimers increased, the averaged height gradually
increased from 2.1 ± 0.1 nm (PG1) to 3.4 ± 0.1 nm (PG2),
and 5.5 ± 0.2 nm (PG3), respectively. These results also
a reasonable evidence for the successful
preparation of high-generation rotaxane-branched
dendrimers.
4
7,781.00 Da) and low ionization efficiency. To determine
the large, monodispersed rotaxane-branched dendrimers,
two-dimensional (2-D) diffusion-ordered spectroscopy
(DOSY) was also exploited to evaluate the resultant
rotaxane-branched dendrimers PG1–PG3 (Figures S26-28).
The observation of a distinct band in the DOSY spectrum of
PG1, PG2, or PG3 indicated the existence of the sole species
provided
of rotaxane-branched dendrimers. Furthermore,
a
significant decrease in the diffusion coefficient (D) from
Photosensitization Efficiencies of Rotaxane-Branched
Dendrimers. After introduction of the anthracene unit as
the photosensitizer, we investigated the photosensitizing
ability of the resultant rotaxane-branched dendrimers
-
9
2
-1
-9
2
-
(
1.38 ± 0.12) × 10 m s (PG1) to (1.02 ± 0.10) × 10 m s
1
-10
2
-1
(
PG2), (6.76 ± 0.15) × 10 m s (PG3) was observed,
which provided further evidence of the progressive size
increase of the obtained rotaxane-branched dendrimers.
Moreover, dynamic light scattering (DLS) investigations of
rotaxane-branched dendrimers PG1–PG3 were also
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 4 of 9
of the mixture solution of SOSG and R-AN or AN for 60 min,
2
.5
(
a)
(b) 2
PG1
1
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
which revealed the very low efficiency of O
R-AN and AN (Figures S35-36). More importantly, the
inverse correlation between Φ and Φ indicated that
generation by
2
.0
1.5
1.0
0.5
0.0
o
f
increasing the generations of rotaxane-branched
dendrimers was an effective way to enhance the ISC in the
above-mentioned cases.
-0.5
0
100 200 300 400 500 600 700
nm
Table 1. Optical and photosensitization properties of the
resultant rotaxane-branched dendrimers PG1–PG3, the
precursor [2]rotaxane R-AN and the monomer AN.
(
(
c)
e)
(
d)
4
3
2
1
0
PG2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1O
malized
yield
2
nor-
Com-
pound
Φ
f
(%)
λabs (nm)
λem (nm)
Ak[a]
0
100 200 300 400 500 600 700
nm
0.5[b]
0.6[b]
AN
R-AN
PG1
PG2
PG3
35.3±2.6
17.1±2.1
10.8±1.3
8.0±1.0
370, 391
371, 391
370, 391
370, 391
371, 391
419
420
420
420
420
18.1±2.4
21.5±2.2
33.3±1.6
82.1±5.0
241.5±4.2
(f)
6
4
2
0
PG3
1.0
2.5
7.3
6.7±0.8
0
200 400 600 800 1000
nm
[
a] The non-linear regression fitting parameters of the 1
O
2
Figure 2. AFM images of the rotaxane-branched dendrimers. (a)
PG1; (b) the height range of PG1 is 2.1 ± 0.1 nm; (c) PG2; (d)
the height range of PG2 is 3.4 ± 0.1 nm; (e) PG3; (f) the height
range of PG3 is 5.5 ± 0.2 nm.
generation rate equation. [b] The very low efficiency of R-AN
1
and AN in O
2
generation.
0.5
350000
280000
210000
140000
70000
0
AN
AN
(b)
(
a)
0.4
0.3
0.2
0.1
R-AN
PG1
PG2
PG3
R-AN
PG1
PG2
PG3
PG1–PG3 as well as the precursor [2]rotaxane R-AN and
the monomer AN. The photophysical data of all compounds
are summarized in Table 1. At the equal anthracene unit
concentrations (0.042 mM) in THF, all compounds
displayed two main absorption peaks at approximately 370
nm and 391 nm with almost the same molar absorption
coefficient and had the similar wavelengths of maximum
photoluminescence (PL) emission at approximately 420 nm.
This observation indicated that the intermolecular or
intramolecular interactions between anthracene groups
and the aggregation of anthracene moieties did not take
place even in the case of PG3, which contained forty-two
anthracene units (Figures 3a-b). However, as the generation
of the dendrimers increased, the fluorescence intensity
decreased progressively accompanied by a decreased
0.0
3
40
360
380
400
420
440
400
450
500
550
600
Wavelength (nm)
Wavelength (nm)
10
8
5
4
0
0
Φo
Φf
(d)
(c)
30
20
10
0
6
4
2
0
AN
R-AN PG1 PG2 PG3
AN R-AN PG1 PG2 PG3
Figure 3. Photosensitization properties of the molecules
investigated in this work. UV-vis spectra (a), PL spectra (b),
1
fluorescence quantum yield (Φ
f
) from 35.3 ± 2.6% (AN) and
7.1 ± 2.1% (R-AN) to 10.8 ± 1.3% (PG1), 8.0 ± 1.0% (PG2),
and then to 6.7 ± 0.8% (PG3), which might be attributed to
the gradual enhancement of the intersystem crossing (ISC)
from AN to PG3 (Figure 3c).
fluorescence quantum yield (c) and O
2
quantum yield (d) of
the resultant rotaxane-branched dendrimers PG1–PG3, the
precursor [2]rotaxane R-AN and the monomer AN.
1
To investigate the mechanism of the enhanced
photosensitization efficiencies of these rotaxane-branched
dendrimers, time-dependent density functional theory (TD-
DFT) calculations were performed on these optimized
molecular models AN, R-ANM and PG1 in both singlet and
triplet excited states (see computational details in the
As one of the most important parameters of
generation efficiency (Φ
PG3, R-AN, and AN was evaluated by using the
1
photosensitizers, the O
2
o
) of PG1–
1
commercially available O
green (SOSG), which could react with the generated O
give green fluorescence with a maximum emission
2
indicator singlet oxygen sensor
17
1
Section E of the SI). According to the perturbation theory-
2
to
based equation, both the energy gap between the singlet
and triplet states (ΔEST) and SOC should be taken into
consideration in studying the ISC since a reduction in ΔEST
or increase in SOC increases the rate constant of ISC (kISC).
As shown in Figure 4 and Table S4-5, AN, R-ANM and PG1
exhibited nearly the same ΔEST because the π-conjugation
length of the anthracene moieties in these compounds was
the same. Since the AN molecule possesses two anthryl
16
wavelength at 550 nm. Interestingly, as shown in Figure
d, along with the increase of dendrimer generation from
PG1 to PG2 and then to PG3, the normalized Φ increased
from 1.0 to 2.5 and then to 7.3. Notably, the third-generation
rotaxane-branched dendrimer PG3 showed approximately
3
o
1
7
-fold higher O generation than that of the first-generation
2
rotaxane-branched dendrimer PG1. Although R-AN and AN
also had anthracene moieties, the change in fluorescence
intensity of SOSG was negligible under the light irradiation
units, the S
is similar to T
1
and S
2
states should be nearly degenerated, that
states. Thus, the energy of the upper
1
and T
2
ACS Paragon Plus Environment

Page 5 of 9
Journal of the American Chemical Society
-
1
excited states (T
excited states (T
n
and S
n
) did not move closer to the lowest
/S ). Analysis of the transition
0.000~0.033 cm . Furthermore, three times the number of
1
2
3
4
5
6
7
8
9
/T and S
ISC channels for PG1M occur accompanying with enhanced
1
2
1
2
configurations of excited states and the corresponding
molecular orbitals for AN, R-ANM and PG1 confirmed the
significant localized excitation (LE) character on
anthracene moieties (Figures S37, S38 and S41). This was
also in good agreement with the measured absorption and
fluorescence spectra. Although the introduction of multiple
anthracene units into the rotaxane-branched dendrimers
did not induce a decrease in ΔEST, it is noteworthy that the
increased number of anthracene units with the increasing
dendrimer generation resulted in the significantly
SOC values between S
1
/S
2
and T
1
/T states (see Table S5).
2
Moreover, the T /T energy levels (1.65 ~ 1.69 eV) of all the
1
2
molecules are found to be close to the excitation energy
(1.627 eV) for the excited singlet O
tosensitization efficiency of O
the energy-level matching principle. Collectively, the simple
introduction of multiple anthracene moieties and platinum
atoms on the axles and wheels of the rotaxane units, which
resulted in the enhanced energy transition channels from
1
17c
2
,
indicating the pho-
1
2
should be efficient due to
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
S
1
/S
2
to T
1
/T and the intramolecular-space heavy-atom
2
enhanced energy transition channels from S
1
/S
2
to T
1
/T ,
2
effect, respectively, played important roles in improving
both the ISC efficiency as well as the
1
which was highly beneficial for the ISC process to facilitate
2
O generation
1
O
2
generation. For instance, unlike AN and R-ANM, which
efficiency. Moreover, because of the existence of many more
ISC processes from singlet to triplet states, the
corresponding nonradiative transition processes became
increasingly competitive. Thus the fluorescence quantum
yield was gradually reduced from AN to R-ANM and then to
PG1–PG3.
each possess only one transition channel from S
1
/S
/S
2
to
to
T
T
1
/T
/T
2
, three times the transition channels from S
occurred in PG1, thus endowing PG1 with a higher
1
2
1
2
photosensitization capability than AN and R-ANM.
Therefore, when the number of anthracene units are further
increased in PG2 and PG3, the energy transition channels
(a)
for ISC from S
a result, the O
1
1
/S
2
2
to T
generation efficiencies of PG2 and PG3
were higher than those AN, R-ANM, and PG1.
1
/T should increase accordingly. As
2
hv
AN
PG1
R-ANM
0.30
0.25
0.20
0.15
2.8
2.4
2.0
AN
2.45
(b)
R-AN
PG1
PG2
PG3
(c)
1.94
1.70
1
.6
.2
0.10
1
1.00
.92
0
0.05
0.8
0
10 20 30 40 50 60
AN R-AN PG1 PG2 PG3
Time (min)
S
1
/S
2
3.0
3.0
2.5
2.0
S
1
/S
2
S
1
/S
2
AN
2.75
(d)
R-AN
PG1
PG2
PG3
(e)
2.5
2.20
2.0
1.5
1.75
T
1
/T
2
T
1
/T
2
1 2
T /T
1.5
1.00
1
.0
.5
ISC Enhancement
1.0 0.85
0
0.5
0
10 20 30 40 50 60
Time (min)
AN R-AN PG1 PG2 PG3
Figure 4. Mechanism of the enhanced photosensitization
efficiencies of rotaxane-branched dendrimers. Optimized
ground-state geometries of model compounds (top) and
calculated excited-state energy levels and possible ISC
channels (bottom).
7
.8 (f)
6.6 (g)
5.88 (h)
7.5
6.4
6.2
6.0
5
.84
5.80
.76
7
.2
.9
6
5.8
6.6
5
5.6
5.4
5.2
6.3
6.0
5.7
5.72
5.68
PG1
PG2
PG3
Subsequently, the heavy-atom effect of platinum, which
makes an important contribution to SOC, was also studied
for AN, R-ANM, and PG1. For AN, the significant ISC pro-
3.15 3.20 3.25- 3.30 3.35
3.15 3.20 3.25 3.30 3.35
3.15 3.20 3.25-1 3.30 3.35
-3
1
×10-3
-1
×10-3
1/T (K
)
1/T (K
)
1/T (K
)
×10
Ea = 69.87 kJ/mol
Ea = 45.19 kJ/mol
Ea = 7.04 kJ/mol
cesses between S
/S
1 2
and T
3
/T
4
are competitive due to the
simultaneous small energy gaps ΔEST (0.220 ~ 0.247 eV)
Acceleration of Photolysis
-
1
and moderate SOC values (0.014 ~ 0.223 cm ) compared to
those between S /S and T /T (ΔEST of 1.890~1.920 eV and
SOC of 0.014~0.099 cm ) as shown in Table S4. The
calculated SOC values of AN between S /S and T /T were
Figure 5. Photolysis of the resultant rotaxane-branched
dendrimers PG1–PG3, the precursor [2]rotaxane R-AN and the
monomer AN. (a) Schematic representation of photolysis of the
rotaxane-branched dendrimer PG3. Absorbance at 391 nm (b)
and normalized photolysis rates (c) upon irradiation at 365 nm
for 1 h (0.042 mM, 25 °C). Absorbance at 391 nm (d) and
normalized photolysis rates (e) upon irradiation at 365 nm for
1 h (0.42 mM, 25 °C). (f-h) Kinetic analysis of the photolysis of
the rotaxane-branched dendrimer PGn (n = 1, 2, 3).
1
2
1
2
-
1
1
2
1
2
relatively small, which is a common phenomenon observed
in pure organic compounds. However, for R-ANM, upon in-
corporation of platinum(II) atom from one side, the ISC
channels are significantly enhanced between S
1
/S
2
and
-
T
1
/T
2
(ΔEST of 1.836~1.906 eV and SOC of 0.022~0.298 cm
/S and T /T
1
), but the channels between S
1
2
3
4
states are
Model Photolysis Reactions for Further Investitaion on
the Enhanced Photosensitization. It has been reported
greatly suppressed due to the vanishing SOC values of
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 6 of 9
that 9-alkoxy-substituted anthracene has the ability to trap
With the aim of exploring the mechanism behind the
accelerated photolysis reaction of the rotaxane-branched
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
1
O and then react with it to decompose anthracene into
2
anthraquinone and alkanol through photolysis reaction,
dendrimers, the apparent activation energy (E
a
) of PG1–
1
which is useful for the detection of
O
2
by directly
PG3 was investigated since the E of chemical reactions
a
monitoring the absorption of 9-alkoxy-substituted
plays a central role in the field of chemical kinetics and
serves as an important tool for analyzing and
1
8
anthracene.
Thus, to further verify the enhanced
1
9
photosensitization efficiencies of rotaxane-branched
dendrimers with the increase of dendrimer generation, the
photolysis of the monomer AN, the precursor [2]rotaxane
R-AN, and the resultant rotaxane-branched dendrimers
PG1–PG3 was investigated. As shown in Figure 5a-e, upon
irradiation of AN (0.042 mM of anthracene unit) at 365 nm
for 60 min, the absorption of the 9-alkoxy-substituted
anthracene moiety in the range of 340-410 nm gradually
decreased. Comparatively, under the same conditions, the
irradiation of rotaxane-branched dendrimer PG1 induced a
significant decrease in the absorption of the 9-alkoxy-
substituted anthracene moiety with a 2-fold normalized
photodecomposition rate higher than that of AN (0.92 for
AN). Along with the increase of the generation of rotaxane-
branched dendrimers, the normalized photodecomposition
rates for R-AN, PG1, PG2, and PG3 increased from 1.00, to
understanding reaction rates. According to the Arrhenius
analysis, E can be calculated based on the following
a
equation:
퐸푎
푅
1
푇
푙푛(t1/2) =
×
+ 푙푛퐶 + 푙푛퐴
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
where the half-life (t1/2), which is highly dependent on
temperature, can be obtained directly from the time-
conversion curves. A, R, and T are the pre-exponential factor,
universal gas constant and temperature, respectively.
Therefore, from the data on half-life (t1/2) at different
temperatures (T), the E values for PG1 and PG2 were
a
-
1
-1
calculated to be 69.87 kJ mol and 45.19 kJ mol , whereas
-
the E value for PG3 was determined to be only 7.04 kJ mol
Figure 5f-h). This result clearly exhibited that increasing
a
1
(
generations of the resultant rotaxane-branched dendrimers
greatly decreased the apparent activation energy by 62.83
1
.70, 1.94, and then to 2.45. Moreover, the concentration of
−
1
kJꢀmol , which might account for the significant
the dendrimers had slight impact on the
a
acceleration of the photolysis reaction.
photodecomposition process. For instance, at higher
anthracene unit concentrations (0.42 mM), the normalized
photodecomposition rates for AN, R-AN, PG1, PG2, and PG3
were determined to be 0.85, 1.00, 1.75, 2.20, and 2.75,
respectively. These results clearly indicated that the
formation of rotaxane was beneficial to the photolysis of
anthracene, which was significantly enhanced after the
formation of the rotaxane-branched dendrimers.
CONCLUSION
In summary, we have developed a novel platform of the
rotaxane-branched dendrimers for the construction of
highly effective photosensitizers. A series of new rotaxane-
branched dendrimers PG1–PG3 containing up to twenty-
one heavy atoms and forty-two photosensitizer moieties
were prepared through an efficient and controllable
divergent approach. Impressively, the first-, second-, and
To probe their photolysis mechanism, the photolytic
products of AN, R-AN, PG1, and PG2 were identified by ESI-
1
MS and H NMR techniques. For example, upon irradiation
third-generation rotaxane-branched dendrimers PG1, PG2,
1
with AN for 60 min, the precipitate product was separated
and PG3 revealed 1.8-, 4.5-, and 13.3-fold higher
O
2
through filtration and confirmed as anthraquinone by ESI-
generation efficiency than their corresponding monomer
1
1
MS and H NMR measurements as shown in Figures S55-56.
AN. The achievement of highly efficient
2
O generation
Moreover, the peak corresponding to the alkanol-
substituted pillararene moiety was also observed in the ESI-
MS spectrum (Figure S57). These results revealed that AN
was decomposed into anthraquinone and alkanol-
substituted pillararene through photolysis reactions, which
efficiencies of PG1-PG3 was atributed to the simple and
effective introduction of numerous anthracene moieties
and multiple heavy atoms on the axles and wheels of the
rotaxane units. These star-shaped, highly topologically
branched, and mechanically interlocked rotaxane-branched
dendrimers are a very promising platform not only for the
preparation of effective photosensitizers but also for the
fabrication of artificial light-harvesting systems,
photolyzable materials, and dynamic smart materials in the
future.
1
8b
was consistent with the reported mechanism. In the cases
of R-AN, PG1, and PG2, the anthraquinone product was also
1
identified by ESI-MS and
H NMR measurements.
1
Furthermore, H NMR analysis demonstrated that the main
skeletons of the resultant rotaxane-branched dendrimers re-
mained intact upon UV irradiation although a residue of
unreacted 9-alkoxy-substituted anthracene at the
periphery of the dendrimers resulted in the generation of
asymmetric dendrimers with some broadened signal peaks
ASSOCIATED CONTENT
Supporting Information. The Supporting Information is avail-
able free of charge on the ACS Publications website.
Additional information concerning the synthesis, characteriza-
tion, and other experimental details.
(
Figures S58-63). By combining all the aforementioned
results, a plausible photolysis mechanism for rotaxane-
branched dendrimers PG1–PG3 was deduced as illustrated
in Scheme S6, where the 9-alkoxy-substituted anthracene at
1
the periphery of the dendrimers reacted with
2
O to
decompose into anthraquinone and the main skeletons of
the resultant rotaxane-branched dendrimers remained
after irradiation.
AUTHOR INFORMATION
Corresponding Author
* hbyang@chem.ecnu.edu.cn (H.-B. Yang)
* lxu@chem.ecnu.edu.cn (L. Xu)
ACS Paragon Plus Environment

Page 7 of 9
Journal of the American Chemical Society
*
htsun@phy.ecnu.edu.cn (H. Sun)
Kitchen, J. A.; Goldup, S. M.; Roessler, M. M. Rotaxane-based transi-
1
2
3
4
5
6
7
8
9
tion metal complexes: effect of the mechanical bond on structure
and electronic properties. J. Am. Chem. Soc. 2019, 141, 879-889. (f)
Denis, M.; Goldup, S. M. A [3]Rotaxane host selects between stere-
oisomers. Angew. Chem. Int. Ed. 2018, 57, 4462-4464. (g) Ogoshi,
T.; Aoki, T.; Shiga, R.; Iizuka, R.; Ueda, S.; Demachi, K.; Yamafuji, D.;
Kayama, H.; Yamagishi, T.-a. Cyclic host liquids for facile and high-
yield synthesis of [2]rotaxanes. J. Am. Chem. Soc. 2012, 134, 20322-
20325. (h) Mitra, R.; Zhu, H.; Grimme, S.; Niemeyer, J. Functional
mechanically interlocked molecules: Asymmetric organocatalysis
with a catenated bifunctional brønsted acid. Angew. Chem. Int. Ed.
2017, 56, 11456-11459. (i) Hardie, M. J. One-pot pentaknot. Nat.
Chem. 2012, 4, 7-8. (j) Nakatani, Y.; Furusho, Y.; Yashima, E.
Amidinium carboxylate salt bridges as a recognition motif for me-
chanically interlocked molecules: Synthesis of an optically active
ORCID
Hai-Bo Yang: 0000-0003-4926-1618
Notes
The authors declare no competing interest.
ACKNOWLEDGMENT
This work was financially supported by the NSFC/China (Nos.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
2
1922506, 21871092, 21625202, 51773073, 11727810, and
1603074), Shanghai Pujiang Program (No. 18PJD015), the In-
[
4
2]catenane and control of its structure. Angew. Chem. Int. Ed. 2010,
9, 5463-5467. (k) Kim, D. H.; Singh, N.; Oh, J.; Kim, E.-H.; Jung, J.;
novation Program of Shanghai Municipal Education Commis-
sion (no. 2019-01-07-00-05-E00012), Projects from Shanghai
Science and Technology Commission (No. 19JC1412200), and
the Fundamental Research Funds for the Central Universities.
Kim, H.; Chi, K.-W. Coordination-driven self-assembly of a molecu-
lar knot comprising sixteen crossings. Angew. Chem. Int. Ed. 2018,
57, 5669-5673. (l) Kim, T.; Singh, N.; Oh, J.; Kim, E.-H.; Jung, J.; Kim,
H.; Chi, K.-W. Selective synthesis of molecular borromean rings: En-
gineering of supramolecular topology via coordination-driven self-
assembly. J. Am. Chem. Soc. 2016, 138, 8368-8371. (m) Goujon, A.;
Lang, T.; Mariani, G.; Moulin, E.; Fuks, G.; Raya, J.; Buhler, E.;
Giuseppone, N. Bistable [c2] Daisy Chain Rotaxanes as Reversible
Muscle-like Actuators in Mechanically Active Gels. J. Am. Chem. Soc.
REFERENCES
(
(
1) (a) Bruns, C. J.; Stoddart, J. F. The Nature of the Mechanical Bond
John Wiley & Sons, Hoboken, 2016). (b) Meng, Z.; Xiang, J.-F.; Chen,
C.-F. Directional molecular transportation based on a catalytic
stopper-leaving rotaxane system. J. Am. Chem. Soc. 2016, 138,
5652- 5658. (c) Goujon, A.; Du, G.; Moulin, E.;Fuks, G.; Maaloum, M.;
Buhler, E.; Giuseppone, N. Hierarchical self-assembly of supramo-
lecular muscle-like fibers. Angew. Chem. Int. Ed. 2016, 55, 703-707.
2
(
017, 139, 14825-14828.
6) (a) Mao, M.; Zhang, X.-K.; Xu, T.-Y.; Wang, X.-D.; Rao, S.-J.; Liu, Y.;
Qu, D.-H.; Tian, H. Towards a hexa-branched [7]rotaxane from a
3]rotaxane via a [2+2+2] alkyne cyclotrimerization Process. Chem.
[
Commun. 2019, 55, 3525-3528. (b) Kwan, C.-S.; Zhao, R.; Hove, M.
A. V.; Cai, Z.; Leung, K. C.-F. Higher-generation type III-B rotaxane
dendrimers with controlling particle size in three-dimensional mo-
lecular switching. Nat. Commun. 2018, 9, 497. (c) Lee, J. W.; Han, S.
C.; Kim, J. H.; Ko, Y. H.; Kim, K. Formation of rotaxane dendrimers
by supramolecular click chemistry. Bull. Korean Chem. Soc. 2007,
28, 1837-1840. (d) Amabilino, D. B.; Ashton, P. R.; Balzani, V.;
Brown, C. L.; Credi, A.; Fréchet, J. M. J.; Leon, J. W.; Raymo, F. M.;
Spencer, N.; Stoddart, J. F.; Venturi. M. Self-assembly of [n]rotax-
anes bearing dendritic stoppers. J. Am. Chem. Soc. 1996, 118,
(
d) Erbas-Cakmak, S.; Leigh, D. A.; McTernan, C. T.; Nussbaumer, A.
L. Artificial molecular machines. Chem. Rev. 2015, 115, 10081-
10206. (e) Mena-Hernando, S.; Pérez, E. M. Mechanically inter-
locked materials. Rotaxanes and catenanes beyond the small mol-
ecule. Chem. Soc. Rev. 2019, 48, 5016-5032. (f) Inthasot, A.; Tung,
S.-T.; Chiu, S.-H. Using alkali metal ions to template the synthesis of
interlocked molecules. Acc. Chem. Res. 2018, 51, 1324-1337.
(
2) (a) Cheng, C.; McGonigal, P. R.; Schneebeli, S. T.; Li, H.; Ver-
meulen, N. A.; Ke, C.; Stoddart, J. F. An artificial molecular pump.
Nat. Nanotechnol. 2015, 10, 547-553. (b) Qiu, Y.; Zhang, L.; Pezzato,
C.; Feng, Y.; Li, W.; Nguyen, M. T.; Chen, C.; Shen, D.; Guo, Q.-H.; Shi,
Y.; Cai, K.; Alsubaie, F. M.; Astumian, R. D.; Stoddart, J. F. A molecular
dual pump. J. Am. Chem. Soc. 2019, 141, 17472-17476.
12012-12020. (e) Leung, K. C.-F.; Lau, K. N. Self-assembly and ther-
modynamic synthesis of rotaxane dendrimers and related struc-
tures. Poly. Chem. 2010, 1, 988-1000. (f) Chen, C.-F. High-genera-
tion organometallic rotaxane dendrimer. Sci. China Chem. 2015, 58,
(
3) (a) Badjic, J. D.; Balzani, V.; Credi, A.; Stoddart, J. F. A molecular
1
089. (g) Kim, S.-Y.; Ko, Y. H.; Lee, J. W.; Sakamoto, S.; Yamaguchi,
elevator. Science 2004, 303, 1845-1849. (b) Zhang, Z.-J.; Han, M.;
Zhang, H.-Y.; Liu Y. A double-leg donor–acceptor molecular eleva-
tor: new insight into controlling the distance of two platforms. Org.
Lett. 2013, 15, 1698–1701.
K.; Kim, K. Toward high-generation rotaxane dendrimers that
incorporate a ring component on every branch: noncovalent
synthesis of a dendritic [10]pseudorotaxane with 13 molecular
components. Chem. -Asian J. 2007, 2, 747-754.
(
4) (a) Anelli, P. L.; Spencer, N.; Stoddart, J. F. A molecular shuttle. J.
(
7) (a) Ho, W. K.-W.; Lee, S.-F.; Wong, C.-H.; Zhu, X.-M.; Kwan, C.-S.;
Am. Chem. Soc. 1991. 113, 5131-5133. (b) Zhu, K.; Baggi, G.; Loeb,
S. J. Ring-through-ring molecular shuttling in a saturated [3]rotax-
ane. Nat. Chem. 2018, 10, 625-630. (c) Chen, S.; Wang, Y.; Nie, T.;
Bao, C.; Wang, C.; Xu, T.; Lin, Q.; Qu, D.-H.; Gong, X.; Yang, Y.; Zhu, L.;
Tian, H. An artificial molecular shuttle operates in lipid bilayers for
ion transport. J. Am. Chem. Soc. 2018, 140, 17992-17998.
Chak, C.-P.; Mendes, P. M.; Cheng, C. H. K.; Leung, K. C.-F. Type III-B
rotaxane dendrimers. Chem. Commun. 2013, 49, 10781-10783. (b)
Elizarov, A. M.; Chiu, S.-H.; Glink, P. T.; Stoddart, J. F. Dendrimer
with rotaxane-like mechanical branching. Org. Lett. 2002, 4, 679-
682. (c) Zeng, Y.; Li, Y.; Li, M.; Yang, G.; Li, Y. Enhancement of energy
utilization in light harvesting dendrimers by the pseudorotaxane
formation at periphery. J. Am. Chem. Soc. 2009, 131, 9100-9106. (d)
Tramontozzi, D. A.; Suhan, N. D.; Eichhorn, S. H.; Loeb, S. J. The effect
of incorporating fréchet dendrons into rotaxanes and molecular
shuttles containing the 1, 2-bis(pyridinium)ethane⊂[24]crown-8
templating motif. Chem. Eur. J. 2010, 16, 4466-4476. (e) Lee, J. W.;
Kim, K. Rotaxane dendrimers. Top Curr. Chem. 2003, 228, 111-140.
(
5) (a) Lim, J. Y. C.; Marques, I.; Félix, V.; Beer, P. D. A chiral halogen-
bonding [3]rotaxane for the recognition and sensing of biologically
relevant dicarboxylate anions. Angew. Chem. Int. Ed. 2018, 57,584–
5
88. (b) Gong, H.-Y.; Rambo, B. M.; Karnas, E.; Lynch, V. M.; Sessler,
J. L. A ‘Texas-sized’ molecular box that forms an anion-induced su-
pramolecular necklace. Nat. Chem. 2010, 2, 406–409. (c) Collin, J.-
P.; Dietrich-Buchecker, C.; Gaviña, P.; Jimenez-Molero, M. C.;
Sauvage, J.-P. Shuttles and muscles: linear molecular machines
based on transition metals. Acc. Chem. Res. 2001, 34, 477-487.(d)
Cai, K.; Shi, Y.; Zhuang, G.-W.; Zhang, L.; Qiu, Y.; Shen, D.; Chen, H.;
Jiao, Y.; Wu, H.; Cheng, C.; Stoddart, J. F. Molecular-pump-enabled
synthesis of a daisy chain polymer. J. Am. Chem. Soc. 2020, 142,
(
f) Zhou, H.-Y.; Zong, Q.; Han Y.; Chen, C.-F. Recent advances in
higher order rotaxane architectures. Chem. Commun. 2020, 56,
916-9936.
9
(8) Wang, X.-Q.; Li, W.-J.; Wang, W.; Wen, J.; Zhang, Y.; Tan, H.; Yang,
H.-B. Construction of type III-C rotaxane-branched dendrimers and
their anion-induced dimension modulation feature. J. Am. Chem.
Soc. 2019, 141, 13923-13930.
10308–10313. (e) Cirulli, M.; Kaur, A.; Lewis, J. E. M.; Zhang, Z.;
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 8 of 9
(
9) (a) Li, W.-J.; Wang, W.; Wang, X.-Q.; Li, M.; Ke, Y.; Yao, R.; Wen, J.;
dendrimers with fourth-generation mechanically interlocked
branches. Proc. Natl. Acad. Sci. U. S. A. 2015, 112, 5597-5601.
(14) (a) Fan, C.; Wu, W.; Chruma, J. J.; Zhao, J.; Yang, C. Enhanced
triplet–triplet energy transfer and upconversion fluorescence
through host–guest complexation. J. Am. Chem. Soc. 2016, 138,
15405-15412. (b) Cekli, S.; Winkel, R. W.; Alarousu, E.; Mohammed,
O. F.; Schanze, K. S. Triplet excited state properties in variable gap
π-conjugated donor–acceptor–donor chromophores. Chem. Sci.
2016, 7, 3621-3631.
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
Yin, G.-Q.; Jiang, B.; Li, X.; Yin, P.; Yang, H.-B. Daisy chain dendrimers:
integrated mechanically interlocked molecules with stimuli-in-
duced dimension modulation feature. J. Am. Chem. Soc. 2020, 142,
8
473-8482. (b) Wang, X.-Q.; Wang, W.; Li, W.-J.; Chen, L.-J.; Yao, R.;
Yin, G.-Q.; Wang, Y.-X.; Zhang, Y.; Huang, J.; Tan, H.; Yu, Y.; Li, X.; Xu,
L.; Yang, H.-B. Dual stimuli-responsive rotaxane-branched den-
drimers with reversible dimension modulation. Nat. Commun.
2
018, 9, 3190.
10) (a) Zhao, J.; Wu, W.; Sun, J.; Guo, S. Triplet photosensitizers:
from molecular design to applications. Chem. Soc. Rev. 2013, 42,
323-5351. (b) Howlader, P.; Mondal, B.; Purba, P. C.; Zangrando,
(
(15) (a) Chan, A. K.-W.; Ng, M.; Wong, Y.-C.; Chan, M.-Y.; Wong, W.-
T.; Yam, V. W.-W. Synthesis and characterization of luminescent cy-
clometalated platinum(II) complexes with tunable emissive colors
and studies of their application in organic memories and organic
light-emitting devices. J. Am. Chem. Soc. 2017, 139, 10750-10761.
(b) Wang, X.; Han, Y.; Liu, Y.; Zou, G.; Gao, Z.; Wang, F. Cooperative
supramolecular polymerization of fluorescent platinum acetylides
for optical waveguide applications. Angew. Chem. Int. Ed. 2017, 56,
12466-12470. (c) Furusho, Y.; Tanaka, Y.; Yashima, E. Double helix-
to-double helix transformation, using platinum(II) acetylide com-
plexes as surrogate linkers, Org. Lett. 2017, 8, 2583–2586. (d) Ito,
H.; Ikeda, M.; Hasegawa, T.; Furusho, Y.; Yashima, E. Synthesis of
complementary double-stranded helical oligomers through chiral
and achiral amidinium-carboxylate salt bridges and chiral amplifi-
cation in their double-helix formation, J. Am. Chem. Soc. 2011, 133,
3419–3432. (e) Leininger, S.; Stang, P. J.; Huang, S. Synthesis and
characterization of organoplatinum dendrimers with 1, 3, 5-tri-
ethynylbenzene building blocks. Organometallics 1998, 17, 3981-
3987. (f) Wang, W.; Yang, H.-B.; Linear neutral platinum–acetylide
moiety: beyond the links. Chem. Commun. 2014, 50, 5171-5186.
(16) (a) Kim, S.; Fujitsuka, M.; Majima, T. Photochemistry of singlet
oxygen sensor green. J. Phys. Chem. B 2013, 117, 13985−13992. (b)
Prasad, A.; Sedlářová, M.; Pospíšil, P. Singlet oxygen imaging using
fluorescent probe singlet oxygen sensor green in photosynthetic
organisms. Sci. Rep. 2018, 8, 13685. (c) Yu, G.; Zhu, B.; Shao, L.;
Zhou, J.; Saha, M. L.; Shi, B.; Zhang, Z.; Hong, T.; Li, S.; Chen, X.; Stang,
P. J. Host−guest complexation-mediated codelivery of anticancer
drug and photosensitizer for cancer photochemotherapy. Proc.
Natl. Acad. Sci. U.S.A., 2019, 116, 6618-6623. (d) Zhao, Y.; Farrer, N.
J.; Li, H.; Butler, J. S.; McQuitty, R. J.; Habtemariam, A.; Wang, F.; Sad-
ler, P. J. De novo generation of singlet oxygen and ammine ligands
by photoactivation of a platinum anticancer complex. Angew. Chem.
Int. Ed., 2013, 52, 13633-13637. (e) Chen, Y.-Z.; Wang, Z. U.; Wang,
H.; Lu, J.; Yu, S.-H.; Jiang, H.-L. Singlet oxygen-engaged selective
photo-oxidation over Pt nanocrystals/porphyrinic MOF: the roles
of photothermal effect and Pt electronic state. J. Am. Chem. Soc.,
2017, 139, 2035-2044. (f) Chen, L.-J.; Chen, S.; Qin, Y.; Xu, L.; Yin,
G.-Q.; Zhu, J.-L.; Zhu, F.-F.; Zheng, W.; Li, X.; Yang, H.-B. Construction
of porphyrin-containing metallacycle with improved stability and
activity within mesoporous carbon. J. Am. Chem. Soc., 2018, 140,
5049-5052. (g) Qin, Y.; Chen, L.-J.; Dong, F.; Jiang, S.-T.; Yin, G.-Q.;
Li, X.; Tian, Y.; Yang, H.-B. Light-controlled generation of singlet ox-
ygen within a discrete dual-stage metallacycle for cancer therapy.
J. Am. Chem. Soc., 2019, 141, 8943-8950.
5
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
E.; Mukherjee, P. S. Self-assembled Pd(II) barrels as containers for
transient merocyanine form and reverse thermochromism of
spiropyran. J. Am. Chem. Soc. 2018, 140, 7952-7960. (c) Acharyya,
K.; Bhattacharyya, S.; Sepehrpour, H.; Chakraborty, S.; Lu, S.; Shi, B.;
Li, X.; Mukherjee, P. S.; Stang, P. J. Self-assembled fluorescent Pt(II)
metallacycles as artificial light-harvesting systems. J. Am. Chem. Soc.
2019, 141, 4565–14569. (d) Hola, E.; Ortyl, J.; Jankowska, M.; Pilch,
M.; Galek, M.; Morlet-Savary, F.; Graff, B.; Dietlinc, C.; Lalevée, J. New
bimolecular photoinitiating systems based on terphenyl
derivatives as highly efficient photosensitizers for 3D printing
application. Polym. Chem. 2020,11, 922-935. (e) Shao, L.; Pan, Y.;
Hua, B.; Xu, S.; Yu, G.; Wang, M.; Liu, B.; Huang, F. Constructing
adaptive photosensitizers via supramolecular modification based
on pillararene host–guest interactions. Angew. Chem. Int. Ed. 2020,
5
9, 11779-11783. (f) Li, D.-H.; Schreiber, C. L.; Smith, B. D. Sterically
shielded heptamethine cyanine dyes for bioconjugation and high
performance near-infrared fluorescence imaging. Angew. Chem. Int.
Ed. 2020, 59, 12154–12161. (g) Wu, W.; Mao, D.; Xu, S.; Kenry, F.;
Hu, Li, X.; Kong, D.; Liu, B. Polymerization-enhanced photosensiti-
zation. Chem 2018, 4, 1937-1951. (h) Liu, S.; Zhang, H.; Li, Y.; Liu, J.;
Du, L.; Chen, M.; Kwok, R. T. K.; Lam, J. W. Y.; Phillips, D. L.; Tang, B.
Z. Strategies to enhance the photosensitization: polymerization
and the donor–acceptor even–odd effect. Angew. Chem. Int. Ed.
2
018, 57, 15189-15193. (i) Peck, E. M.; Collins, C. G.; Smith, B. D.
Thiosquaraine rotaxanes: synthesis, dynamic structure, and
oxygen photosensitization. Org. Lett. 2013, 15, 2762–2765.
(
Cornil, J.; Bazzini, C.; Caronna, T.; Tubino, R.; Meinardi, F.; Shuai, Z.;
Brédas, J.-L. Intersystem crossing processes in nonplanar aromatic
heterocyclic molecules. J. Phys. Chem. A 2007, 111, 10490-10499.
11) (a) Schmidt, K.; Brovelli, S.; Coropceanu, V.; Beljonne, D.;
(b) Espinoza, C.; Trigos, Á .; Medina, M. E. Theoretical study on the
photosensitizer mechanism of phenalenone in aqueous and lipid
media. J. Phys. Chem. A 2016, 120, 6103-6110. (c) Jin, J.; Zhu, Y.;
Zhang, Z.; Zhang, W. Enhancing the efficacy of photodynamic ther-
apy through a porphyrin/POSS alternating copolymer. Angew.
Chem. Int. Ed. 2018, 57, 16354-16358. (d) Wang, Z.; Zhao, J.; Barbon,
A.; Toffoletti, A.; Liu, Y.; An, Y.; Xu, L.; Karatay, A.; Yaglioglu, H. G.;
Yildiz, E. A.; Hayvali, M. Radical-enhanced intersystem crossing in
new bodipy derivatives and application for efficient triplet–triplet
annihilation upconversion. J. Am. Chem. Soc. 2017, 139, 7831-7842.
(
12) (a) Hou, Y.; Liu, Q.; Zhao, J. An exceptionally long-lived triplet
state of red light-absorbing compact phenothiazine-styrylBodipy
electron donor/acceptor dyads: a better alternative to the heavy
atom-effect? Chem. Commun. 2020, 56, 1721-1724. (b) Yu, Q.;
Huang, T.; Liu, C.; Zhao, M.; Xie, M.; Li, G.; Liu, S.; Huang, W.; Zhao,
Q. Oxygen self-sufficient NIR-activatable liposomes for tumor hy-
poxia regulation and photodynamic therapy. Chem. Sci. 2019, 10,
9091-9098. (c) Karges, J.; Basu, U.; Blacque, O.; Chao, H.; Gasser, G.
Polymeric encapsulation of novel homoleptic bis(dipyrrinato)
zinc(II) complexes with long lifetimes for applications as photody-
namic therapy photosensitisers. Angew. Chem. Int. Ed. 2019, 58,
(17) (a) Marques, M. A. L.; Ullrich, C. A.; Nogueira, F.; Rubio, A.;
Burke, K.; Gross, E. K. U. Time-dependent density functional theory
(Springer: Berlin, Germany, 2006, 706). (b) Runge, E.; Gross, E. K.
U. Density-functional theory for time-dependent systems. Phys. Rev.
Lett. 1984, 52, 997−1000. (c) Schweitzer, C.; Schmid, R. Physical
mechanisms of generation and deactivation of singlet oxygen.
Chem. Rev. 2003, 103, 1685−1757.
(18) (a) He, Y.-Q.; Fudickar, W.; Tang, J.-H.; Wang, H.; Li, X.; Han, J.;
Wang, Z.; Liu, M.; Zhong, Y.-W.; Linker, T.; Stang, P. J. Capture and
release of singlet oxygen in coordination-driven self-assembled or-
ganoplatinum(II) metallacycles. J. Am. Chem. Soc. 2020, 142, 2601-
2608; (b) Wang, Y.-X.; Zhang, Y.-M.; Liu, Y. Photolysis of an am-
phiphilic assembly by calixarene-induced aggregation. J. Am. Chem.
Soc. 2015, 137, 4543-4549. (c) Preston, D.; Sutton, J. J.; Gordon, K.
C.; Crowley, J. D. A nona-nuclear heterometallic Pd3Pt6 “donut”-
shaped cage: molecular recognition and photocatalysis. Angew.
14334-14340. (d) Gorman, A.; Killoran, J.; O’Shea, C.; Kenna, T.; Gal-
lagher, W. M.; O’Shea, D. F. In vitro demonstration of the heavy-
atom effect for photodynamic therapy. J. Am. Chem. Soc. 2004, 126,
10619-10631.
(
13) Wang, W.; Chen, L.-J.; Wang, X.-Q.; Sun, B.; Li, X.; Zhang, Y.; Shi,
J.; Yu, Y.; Zhang, L.; Liu, M.; Yang, H.-B. Organometallic rotaxane
ACS Paragon Plus Environment

Page 9 of 9
Journal of the American Chemical Society
Chem. Int. Ed. 2018, 57, 8659-8663. (d) Kim, S.; Tachikawa, T.; Fu-
jitsuka, M.; Majima, T. Far-red fluorescence probe for monitoring
singlet oxygen during photodynamic therapy. J. Am. Chem. Soc.
polyaromatic compounds with alkyl chains for enhanced emission
in the solid state. Angew. Chem. Int. Ed. 2016, 55, 6906 –6910.
(19) (a) Mao, Z.; Campbell, C. T. Apparent activation energies in
complex reaction mechanisms: a simple relationship via degrees of
rate control. ACS Catal. 2019, 9, 9465-9473. (b) Jiao, Y.; Li, W.-L.;
Xu, J.-F.; Wang, G.; Li, J.; Wang, Z.; Zhang, X. A supramolecularly ac-
tivated radical cation for accelerated catalytic oxidation. Angew.
Chem. Int. Ed. 2016, 55, 8933-8937.
1
2
3
4
5
6
7
8
9
2014, 136, 11707-11715. (e) Yoshizawa, M.; Catti, L. Bent anthra-
cene dimers as versatile building blocks for supramolecular cap-
sules. Acc. Chem. Res. 2019, 52, 2392–2404. (f) Sekiguchi, S.; Kondo,
K.; Sei, Y.; Akita, M.; Yoshizawa, M. Engineering stacks of V-shaped
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Insert Table of Contents artwork here
light
1O2
3O2
ACS Paragon Plus Environment