A Visible-Light-Induced Dynamic Mechanical Bond as a Linkage for Dynamic Materials

Article abstract of DOI:10.1002/anie.201906761

Exploring dynamic bonds and their applications in fabricating dynamic materials has received great attention. A photoinduced [2]rotaxane-based dynamic mechanical bond (DMB) features visible-light-triggered dynamic bonding behavior that is essentially dist

Full text of DOI:10.1002/anie.201906761

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Accepted Article
Title: Visible Light Induced Dynamic Mechanical Bond as A New Type
of Linkage for Dynamic Materials
Authors: Kang-Da Zhang, Yong Fei Yin, Meng Yan Yun, Li Wu, Hong
Yin Duan, Xia Min Jiang, Tian Guang Zhan, Jie Cheng Cui,
and Li Juan Liu
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201906761
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10.1002/anie.201906761
Angewandte Chemie International Edition
RESEARCH ARTICLE
Visible Light Induced Dynamic Mechanical Bond as A New Type
of Linkage for Dynamic Materials
Yong-Fei Yin,+ Meng-Yan Yun,+ Lin Wu,+ Hong-Ying Duan, Xia-Min Jiang, Tian-Guang Zhan,*
Jiecheng Cui, Li-Juan Liu, and Kang-Da Zhang*
Abstract: Exploring new dynamic bonds and their applications in
fabricating novel dynamic materials have received great attention
recently. Here we describe a unique photoinduced [2]rotaxane-
based dynamic mechanical bond (DMB), featuring with special
visible light triggered dynamic bonding behavior that is essentially
distinguished from conventional dynamic chemical bonds. In this
DMB, a photoisomerizable ortho-fluoroazobenzene unit is introduced
as a steric-controllable stopper, whose visible-light-induced dynamic
wagging movement enables the photo-regulated threading of the
macrocycle. This makes reversibly in situ de-/reforming of the
mechanical bond realized for the first time, without involving dynamic
chemical linkage. Moreover, the prepared DMB-crosslinked
polymeric gel exhibits interesting photoinduced degradation behavior
upon visible light irradiation. Benefiting from the distinctive dual
dynamic nature of reversible bonding behaviors and mechanical
interlocked structure, this DMB is expected to serve as a new type of
dynamic bond that can be promisingly applied in designing novel
dynamic soft materials.
necessity to break new ground in the development of new type
of dynamic bonds which are distinguished from current dynamic
chemical bonds.
Besides chemical bonds, the mechanical bond (MB),
[15]
as a
physical bond, has provided another accessible means in
constructing molecular entities. In the past decades, MBs have
been widely utilized in the fabrication of various dynamic
molecular systems, by taking advantages of the stimuli-
responsive dynamic behaviors between the entangled
components.[16-17] The main concerns in this vital research field
have been focused on designing functional systems by using the
dynamic nature of the mechanically interlocked molecules (MIMs)
themselves. However, in view of that the nature of mechanical
bonds is entirely different from the chemical bonds, as well as
the unique dual dynamic nature of the dynamic mechanical
bonds (DMBs) including the reversible MB de-/reformation and
the relative motion between components, the DMBs are
supposed to exhibit great potential to become a new type of
dynamic bond for the construction of dynamic materials.
Although the DMBs have been reported in achieving efficient
synthesis of MIMs, they were actually based on dynamic
chemical linkers.18 From a bonding point of view, these reported
DMBs are not new dynamic bonds that are distinguished from
current available dynamic chemical bonds in real sense. So far,
to the best of our knowledge, there is no attempt has ever been
made to construct dynamic materials by utilizing the DMBs.
Therefore, we propose to rationally built a DMB which is not
based on dynamic chemical linkers, moreover, it could serve as
a new type of dynamic bond for constructing dynamic materials.
To demonstrate this idea, here we have designed and
synthesized a dumbbell shaped molecule (1 in Scheme 1a),
which contains a dihydroxynaphthalene (DNP) unit as the
recognition site, as well as a visible light (λ > 500 nm) induced
photoisomerizable ortho-fluoroazobenzene unit playing the role
of size-tunable stoppering group. The CBPQT4+ macrocycle is
capable of threading on 1E thermodynamically to generate a
pseudo[2]rotaxane (P1E in Scheme 1b). Upon irradiation with
yellow light, the E-isomeric azobenzene in P1E can be
photoisomerized to the Z-isomeric stopper, whose increased
steric hindrance prohibits the dethreading of CBPQT4+
macrocycle. This leads to the conversion of P1E to the
corresponding [2]rotaxane (R1Z in Scheme 1b) in which
mechanical bond is formed. More importantly, the reversible
deformation/reformation of MB in R1Z can be achieved at the
photostationary state, due to the dynamic wagging movement of
the azobenzene-based stopper under continuous light irradiation.
Notably, the dynamic chemical linkage is not involved during the
whole dynamic MB de-/re-formation cycling. Owing to the
excellent anti-photooxidation and fatigue resistance properties of
the ortho-fluoroazobenzene module, this visible light responsive
DMB is endowed with outstanding anti-photooxidation and
fatigue resistance features which are not readily available by the
means of photoresponsive dynamic chemical linkers. This
makes such DMB a good dynamic linking site in the construction
Introduction
Introducing dynamic bonds into the molecular networks as
dynamic linkers can produce dynamic materials, which
represents one of the most vibrant research fields in materials
science in recent years.[1] Benefiting from the reversible de-/re-
formation of the incorporated dynamic bonds, unprecedented
properties including self-healing,[2] malleability or recyclability,[3]
[5]
shape memory,[4] as well as tunable stiffness
could be
obtained. So far, a set of reversible chemical bonds, including
[6]
[8]
dynamic covalent bonds (DCBs)
such as imine,[7] disulfide
or diselenide,[9] (boronic) ester bond,[10] Diels-Alder adducts,[11]
[12]
olefin metathesis
and others,[13] as well as some dynamic
[14]
coordination bonds
are actively exploited as the “living
linkers” in the fabrication of dynamic materials. Generally, the
nature of the dynamic bonds has great impact on determining
the properties of the dynamic materials, and the exploration of
new dynamic bonds will bring appealing properties or functions
as well as unexplored applications for these emerged materials,
which represents one of the core researches in the field of
dynamic materials. Therefore, it is of great significance and
[*]
Y.-F. Yin,[+] M-Y. Yun,[+] L. Wu,[+] H.-Y. Duan, X.-M. Jiang, Dr. T.-G.
Zhan, Dr. J. Cui, Dr. L.-J. Liu, Prof. Dr. K.-D. Zhang
Key Laboratory of the Ministry of Education for Advanced Catalysis
Materials
College of Chemistry and Life Science
Zhejiang Normal University
688 Yingbin Road, Jinhua 321004 (P. R. China)
E-mail: Kangda.Zhang@zjnu.cn, tgzhan@zjnu.cn
[+]
These authors contributed equally to this work.
Supporting information for this article is given via a link at the end of
the document.
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10.1002/anie.201906761
Angewandte Chemie International Edition
RESEARCH ARTICLE
of photoresponsive dynamic materials. As a showcase, a DMB-
crosslinked dynamic polymeric gel is fabricated, which exhibits
interesting visible light induced dissolution behaviors in the
solution as we expected.
trigger the E→Z photoisomerization of azobenzene stopper of
P1E, leading to the formation of [2]rotaxane R1Z (Figure S5b,
S6b). The resulting PSSZ mixture contained 71% Z-isomer and
29% E-isomer, which suggested that the complexation of
CBPQT4+ with the DNP recognition unit has hardly influence on
the E/Z photoisomerization ability of the azobenzene unit.
Notably, a long t1/2(1Z→1E) of 113 days (Figure S4) was found
for the 1Z molecule. This hints to excellent thermal stability of 1Z
in the solution, which will be highly beneficial for the next
intensive investigation of the photoinduced reversible MB
formation and deformation.
The complexation thermodynamics and kinetics of 1E and
CBPQT4+ in CH3CN were further investigated (section 4 in SI).
When the CBPQT4+ macrocycle was added to the PSSE
mixtures of 1, a new set of significant up-field shifted aromatic
proton signals for DNP unit (Figure S7) and down-field shifted
fluorine signals (Figure S8) of ortho-fluoroazobenzene unit could
be observed, indicating that CBPQT4+ macrocycle can pass
through
the
E-isomeric
azobenzene
unit
to
form
pseudo[2]rotaxane P1E (Scheme 1b). From the recorded 1H
NMR (Figure S7) and 19F NMR (Figure S8) spectra of the low-
concentration solution of PSSE mixtures of 1 mixed with
equivalent amount of CBPQT4+ macrocycle, the association
constant Ka(P1E) could be determined as 4.10 × 104 M-1. The
association rate constant kon(P1E) of 1E and CBPQT4+ in forming
P1E could be calculated as 18.4 M-1∙s-1 by nonlinear fitting the
time-varied UV/Vis absorption changes at 555 nm (Figure S9).
Then, the dissociation rate constant koff(P1E) of P1E at PSSE
could be calculated as 4.49 × 10-4 s-1. From these observations
we are pleased to find that the CBPQT4+ macrocycle can pass
through the E-isomeric azobenzene unit quickly to form P1E with
an appreciable association constant, which is beneficial for the
establishment of dynamic mechanical bond.
Scheme 1. a) Chemical structure of the axis molecule (1) incorporated with
photoswitchable azobenzene stopper; and b) the schematic representation of
the construction of [2]rotaxane-based visible light induced dynamic mechanical
bond (DMB).
The photoinduced formation of the mechanical bond was then
investigated. When the PSSZ mixtures of 1 were mixed with
excess CBPQT4+ macrocycle in CD3CN, no new proton signals
(Figure S14a) corresponding to the DNP unit as well as fluorine
signals (F-cZ′ in Figure 1a) referring to the ortho-fluoro-
azobenzene unit in R1Z could be observed even after treatment
at 25 oC in darkness for 2 hours (Figure 1b, S14b). Only a small
amount of R1Z could be found while extending the darkness
treatment to 184 hours (Figure S10), based on which the
association rate constant of R1Z could be calculated as kon(R1Z)
= 1.16 × 10-5 M-1∙s-1 (see section 5 in SI for the calculation). This
suggested that the formation of R1Z molecule (with mechanical
bond) was very slow under the non-light irradiation condition,
which could be attributed to the steric hindrance of the Z-
isomeric azobenzene stopper prevented the CBPQT4+
macrocycle from threading on the free 1Z. Conversely, once the
R1Z was generated, the Z-isomeric azobenzene stopper was
reliable enough on maintaining the mechanical bond in the dark
as revealed by the dramatically small dissociation rate constant
of koff (R1Z) ≈ 2.83 × 10-10 s-1 as well as the relative long half-life
Results and Discussion
To shed light on the photoinduced DMB, investigations were
carried out firstly to reveal the visible light induced
photoisomerization behaviors of the dumbbell molecule 1 (see
SI for detailed synthesis) in CH3CN. After irradiating the solution
1
of 1 with blue light (λ = 410 nm), the recorded H NMR (Figure
S1a) and 19F NMR (Figure S2a) spectra revealed a mixture of 1
at photostationary state (PSSE) was obtained, in which the 1E/1Z
(93/7) ratio could be calculated based on the integration of the
methyl protons (dE/dZ). Exposing the PSSE mixture of 1 to the
yellow light (λ > 500 nm), the E→Z photoisomerization of 1 could
be triggered as supported by the significantly enhanced proton
(Figure S1b) and fluorine (Figure S2b) signals for 1Z in the
resulting PSSZ mixture of 1 (1Z/1E = 72/28). This could also be
evidenced by the observation of dramatically absorption
increasing and blue-shifted of n-π* band (Figure S3).
Pseudo[2]rotaxane P1E could be further generated when
CBPQT4+ macrocycle was mixed with the blue-light (λ = 410 nm)
irradiated PSSE mixture of 1 (1E/1Z = 94/6) (Figure S5a, S6a).
Irradiating the obtained P1E solution with yellow light could
off
time (t1/2 ≈ 77 years) for R1Z (section 5 in SI). Moreover, not
any signals for the macrocycle-detached free 1Z molecule could
be observed from the time-dependent 1H NMR (Figure S11) and
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RESEARCH ARTICLE
19F NMR (Figure S12) spectra even after the excess competitive
guest molecule of 1, 5-Bis(2-(2-methoxyethoxy)ethoxy)napht-
halene (denoted as DNP-DEG) was added to the solution of R1Z
for 154 days in dark. These results indicated that the MB in R1Z
is not easily formed or deformed in dark.
Figure 1. Partial 19F NMR spectra (564 MHz, CD3CN, 25 oC) of a) a 2:1
mixture of CBPQT4+•4PF6- (4.0 mM) and PSSZ mixtures of 1 (2.0 mM); b) after
treatment at 25 oC in dark for 2 h; c) after irradiation by a yellow light (λ > 500
nm, 22 mW / cm2) for 6 min; and d) after irradiation by a yellow light (λ > 500
nm, 22 mW / cm2) for 9 h. F-cZ refers to the fluorine signal of 1Z, F-cE′ refers to
the fluorine signal of P1E, and F-cZ′ refers to the fluorine signal of R1Z.
Figure 2. a) The schematic representation of the yellow light induced MB
formation; and b) the evolution of the MB formation upon yellow light
irradiation as determined by measuring the concentrations of R1Z, P1E and 1Z
in the solution from the time-dependent 19F NMR spectra of the mixture of
-
CBPQT4+•4PF6 (4.0 mM) and PSSZ mixtures of 1 (2.0 mM) in CD3CN under
yellow light off/on illumination (Figure S15).
However, upon the irradiation with yellow light (λ > 500 nm),
the solution of CBPQT4+ and PSSZ mixtures of 1 immediately
exhibited significant proton (Figure S14c) and fluorine (F-cZ′ in
Figure 1c) signals of R1Z, indicating the formation of mechanical
bond. Following up the component variations in the solution
(Figure S13, S15), it was found that the concentration of R1Z
(red dotted line in Figure 2b) increased while the concentration
of free 1Z (black dotted line in Figure 2b) decreased dramatically
upon the continuous yellow light irradiation, during which the
concentration of P1E (green dotted line in Figure 2b) remained
almost unchanged. After the yellow-light irradiation for 9 hours,
most of the free 1Z molecules were interlocked with CBPQT4+
macrocycle to form the MB-embedded R1Z as reflected by the
hardly observed signals of free 1Z in the solution (Figure 1d,
S14d). These observations clearly sopke for the dynamic E/Z
photoisomerization behaviors of the azobenzene stopper was
successfully in allowing the CBPQT4+ macrocycle to thread
through the stopper, thus forming the photoinduced dynamic
mechanical bond (Figure 2a).
and fluorine (F-cE′ in Figure 3b) signals of P1E, as well as the
simultaneously generated signals of free 1E in the solution (H-dE
and H-eE in Figure S17b, F-cE in Figure 3b). In stark contrast,
the signals of R1Z (with MB) remained constant (Figure 3c,
S17c), indicating that the presence of DNP-DEG has almost no
impact on R1Z without yellow light irradiation.
To further reveal the reversed photoinduced DMB breaking,
the excess competitive guest molecule of DNP-DEG was added
to the solution of R1Z for capturing the CBPQT4+ ring which
released from R1Z under yellow light irradiation (Figure 4a). In
the absence of yellow-light irradiation, the addition of DNP-DEG
into the PSSZ mixtures of 1 and CBPQT4+ could convert P1E
(without MB) to the host-guest complex of DNP-DEG@CBPQT4+
through the competitive encapsulation of CBPQT4+ and DNP-
DEG molecule, which was evidenced by the observation of
dramatically decreased proton (H-dE′ and H-eE′ in Figure S17b)
Figure 3. Partial 19F NMR spectra (564 MHz, CD3CN, 25 oC) of a) the PSSZ
mixtures of CBPQT4+•4PF6- (4.0 mM) and 1 (2.0 mM); b) the PSSZ mixtures of
CBPQT4+•4PF6- (4.0 mM) and 1 (2.0 mM) after DNP-DEG (28 mM) was added;
c) after 2 h of rest at 25 oC in dark; d) after irradiation by a yellow light (λ > 500
nm, 22 mW / cm2) for 28 min; and e) after irradiation by a yellow light (λ > 500
nm, 22 mW / cm2) for 6 h 50 min. F-cE refers to the fluorine signal of 1E, F-cZ
refers to the fluorine signal of 1Z, F-cE′ refers to the fluorine signal of P1E, and
F-cZ′ refers to the fluorine signal of R1Z.
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However, when the solution was irradiated by yellow light (λ >
500 nm), significant proton (H-dZ in Figure S17d) and fluorine (F-
cZ in Figure 3d) signals of the free 1Z were generated
accompanied by the decreasing of the R1Z signals. Furthermore,
extending the yellow light irradiation time to 6 hours and 50 min,
it was found that most of the MB-embedded R1Z has been
disassociated to free 1Z (Figure 3e, S17e). This observation
suggested that the CBPQT4+ macrocycle in R1Z was detached
from the dumbbell, resulting in the breakage of the mechanical
bond. To get more insight into the mechanism of the
photoinduced dynamic MB deformation behavior, the time-
dependent 1H NMR (Figure S16) and 19F NMR (Figure S18)
spectra were further recorded and the component variations in
the systems were carefully monitored, which gave a clear
evolution picture of the dynamically MB deforming process. As
showed in Figure 4b, when exposing the mixed solution
containing R1Z and DNP-DEG guest to the yellow light (λ > 500
nm), the concentration of R1Z (with MB) decreased significantly
guest complex of DNP-DEG@CBPQT4+ in the solution (Figure
4a), resulting in restraining the CBPQT4+ macrocycle from
recomplexing with 1Z. This photo-induced MB breakage behavior
could be owed to the yellow light triggered dynamically
reversible E/Z photoisomerizaion of the azobenzene stopper,
which enabled the dethreading of CBPQT4+ macrocycle from the
dumbbell (Figure 4a).
As it became clear that the introduction of photoiosmerizable
azobenzene unit as a steric hindrance photocontrollable stopper
was indeed a feasible strategy to achieve the in situ deforming
and reforming of mechanical bond, further exploration was
conducted to verify whether such visible-light-induced DMB
could be applied as dynamic linkage to fabricate dynamic
materials. To this end, linear polymer incorporated with
CBPQT4+ macrocycle side chains (P1 in Figure 5a), as well as a
four-armed cross-linker with azobenzene terminus (2 in Figure
5a) were prepared (see SI for the synthesis). By mixing P1 and 2
in acetonitrile, supramolecular polymeric gel (Gel-E in Figure 5b)
could be obtained, whose red color could be attributed to the
charge transfer (CT) absorption originated from the host-guest
interaction between the DNP unit and the electron-deficient
CBPQT4+ macrocycle. This indicated that the linear P1 chains in
Gel-E were noncovalently cross-linked by 2 through host-guest
Figure 4. a) The schematic representation of the yellow light induced MB
deformation; and b) the evolution of the MB deformation upon yellow light
irradiation as determined by measuring the concentrations of R1Z, P1E and 1Z
in the solution from the time-dependent 19F NMR spectra of the mixture of
DNP-DEG (28 mM) and PSSZ mixtures of CBPQT4+•4PF6- (4.0 mM) and 1 (2.0
mM) in CD3CN under yellow light off/on illumination (Figure S18b-u).
(red dotted line in Figure 4b), while the concentration of free 1Z
dramatically increased (black dotted line in Figure 4b). Notably,
the concentrations of 1E (blue dotted line in Figure 4b) and P1E
(green dotted line in Figure 4b) were almost constant during the
photoinduced MB deformation process. This hinted to the fact
that the detached CBPQT4+ macrocycle was further complexed
with the excess competitive guest of DNP-DEG to form the host-
Figure 5. a) Chemical structures of the CBPQT4+-incorporated polymer (P1)
and the four-armed cross-linker (2) with azobenzene terminus. The schematic
representation of b) the fabrication of supramolecular polymeric Gel-E and
Gel-Z; and c) the behaviors of the DMB in Gel-Z upon yellow light irradiation.
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10.1002/anie.201906761
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RESEARCH ARTICLE
preparation procedures for the polymeric gel of Gel-E can be found in the
Supporting Information.
interactions. Further irradiating the Gel-E with yellow light could
trigger the E→Z photoisomerizaion of the azobenzene stopper,
resulting in the generation of Gel-Z in which the mechanically
bonded cross-linkages were formed (Figure 5b).
Acknowledgements
When Gel-E was soaked in CH3CN for about one hour at 25
oC, a homogeneous solution could be obtained (Figure S20a),
indicating that Gel-E was completely dissolved owing to the
deformation of noncovalent crosslinkages in the gel networks.
Nevertheless, for Gel-Z, lots of swollen gel could still be found
even after soaking in the CH3CN for 24 hours (Figure S20b).
This observation could be attributed to the kinetic stability of
mechanically bonds-based cross linkages in Gel-Z networks that
prevented the MB-crosslinked gel from degradation in the
solution. However, when the Gel-Z (soaked in CH3CN) was
exposed to the yellow light (λ > 500 nm) for 1.5 hours, clear
solution could be generated (Figure S20c). This hinted to the
fact that the reversible E/Z photoisomerization of the
azobenzene stoppers were triggered successfully upon yellow
light irradiation, resulting in the switching on of the “static” MB-
The National Natural Science Foundation of China (21602205),
Natural
Science
Foundation
of
Zhejiang
Province
(LQ19B020006) and Zhejiang Normal University are
acknowledged for their financial supports to this research.
Conflict of interest
The authors declare no conflict of interest.
Keywords: mechanical bond • rotaxanes • dynamic bond •
dynamic materials • photo-responsiveness
[1]
a) S. Otto, Acc. Chem. Res. 2012, 45, 2200-2210; b) A. Wlison, G.
Gasparini, S. Matile, Chem. Soc. Rev. 2014, 43, 1948-1962; c) N. Roy,
B. Bruchmann, J.-M. Lehn, Chem. Soc. Rev. 2015, 44, 3786-3807; d)
W. Denissen, J. M. Winne, F. E. Du Prez, Chem. Sci. 2016, 7, 30-38; e)
J. F. Reuther, S. D. Dahlhauser, E. V. Anslyn, Angew. Chem. Int. Ed.
2019, 58, 74-85; Angew. Chem. 2019, 131, 76-88.
based cross linkages in the Gel-Z networks to be “living” ones
[1d]
with associative dynamics (Figure 5c),
which enabled the
photoinduced dissolution of the DMB-crosslinked polymeric gel
in the solution.
[2]
[3]
a) S. Burattini, B. W. Greenland, D. Chappell, H. M. Colquhoun, W.
Hayes, Chem. Soc. Rev. 2010, 39, 1973-1985; b) Y. Yang, M. W.
Urban, Chem. Soc. Rev. 2013, 42, 7446-7467; c) J. Dahlke, S. Zechel,
M. D. Hager, U. S. Schubert, Adv. Mater. Interfaces 2018, 5, 1800051.
a) D. Montarnal, M. Capelot, F. Tournilhac, L. Leibler, Science 2011,
334, 965-968; b) Z. Q. Pei, Y. Yang, Q. M. Chen, E. M. Teretjev, Y. Wei,
Y. Ji, Nat. Mater. 2014, 13, 36-41; c) Y. Nishimura, J. Chung, H.
Muradyan, Z. Guan, J. Am. Chem. Soc. 2017, 139, 14881-14884.
a) Z. Pei, Y. Yang, Q. Chen, Y. Wei, Y. Ji, Adv. Mater. 2016, 28, 156-
160; b) G. G. Zhang, W. J. Peng, J. J. Wu, Q. Zhao, T. Xie, Nat.
Commun. 2018, 9, 4002.
Conclusion
In summary, we have illustrated a facile strategy to construct
a
novel [2]rotaxane-based visible light induced dynamic
mechanical bond (DMB), whose working mechanism is
essentially different from the dynamic chemical bonds. In this
DMB, the incorporated photoisomerizable azobenzene unit is
able to play the role of a steric-controllable stoppering group.
Systematically experimental investigations have revealed that
the resulting DMB whose dynamically in situ deformation and
reformation behaviors could be achieved through the E/Z
photoisomerization of the azobenzene-derived stopper upon
visible light irradiation. What’s more, a case study has showed
that such DMB could be applied as dynamic crosslinkage in the
construction of DMB-crosslinked polymeric gel, which exhibited
photoinduced dissolution behaviors in the solution. Although
photoinduced dynamic covalent bonds have been successfully
applied in the fabrication of photoresponsive dynamic materials,
[4]
[5]
a) J. A. Neal, N. J. Oldenhuis, A. L. Novitsky, E. M. Samson, W, J.
Thrift, R. Ragan, Z. Guan, Angew. Chem. Int. Ed. 2017, 56, 15575-
15579; Angew. Chem. 2017, 129, 15781-15785; b) J. V. Accardo, J. A.
Kalow, Chem. Sci. 2018, 9, 5987-5993.
[6]
a) S. J. Rowan, S. J. Cantrill, G. R. L. Cousins, J. K. M. Sanders, J. F.
Stoddart, Angew. Chem. Int. Ed. 2002, 41, 898-952; Angew. Chem.
2002, 114, 938-993; b) A. W. Jackson, D. A. Fulton, Polym. Chem.
2013, 4, 31-45; c) W. Zhang, Y. Jin, Dynamic Covalent Chemistry:
Principles, Reactions, and Applications, Wiley-VCH, Weinheim, 2017.
a) M. E. Belowicha, J. F. Stoddart, Chem. Soc. Rev. 2012, 41, 2003-
2024; b) P. Taynton, K. Yu, R. K. Shoemaker, Y. Jin, H. J. Qi, W.
Zhang, Adv. Mater. 2014, 26, 3938-942; c) T. Wei, J. H. Jung, T. F.
Scott, J. Am. Chem. Soc. 2015, 137, 16196-16202.
[7]
[8]
[9]
[9, 20]
most of whose dynamic bonding behaviors were not
resistant to photooxidation or light fatigue. [9a, 20b, 21] However, the
influence of these intractable problems could be limited greatly
in the DMB-incorporated dynamic systems. In light of all this, we
envision the unique photoinduced DMB established in this work
may serve as a new type of promising dynamic bond in a broad
application of novel dynamic materials such as self-healing
polymers, vitrimers, dynamic interface and so on.
a) N. Sakai, S. Matile, J. Am. Chem. Soc. 2011, 133, 18542-18545; b)
G. A. Barcan, X. Y. Zhang, R. M. Waymouth, J. Am. Chem. Soc. 2015,
137, 5650-5653; c) Y. Lai, X. Kuang, P. Zhu, M. Huang, X. Dong, D.
Wang, Adv. Mater. 2018, 30, 1802556.
a) S. Ji, W. Cao, Y. Yu, H. Xu, Adv. Mater. 2015, 27, 7740-7745; b) F.
Fan, S. Ji, C. Sun, C. Liu, Y. Yu, Y. Fu, H. Xu, Angew. Chem. Int. Ed.
2018, 57, 16426-16430; Angew. Chem. 2018, 130, 16664-16668.
[10] a) O. R. Cromwell, J. Chung, Z. Guan, J. Am. Chem. Soc. 2015, 137,
6492-6495; b) M. Rçttger, T. Domenech, R. van der Weegen, A.
Breuillac, R. Nicolay, L. Leibler, Science 2017, 356, 62-65.
Experimental Section
[11] a) X. Chen, M. A. Dam, K. Ono, A. Mal, H. Shen, S. R. Nutt, K. Sheran,
F. Wudl, Science 2002, 295, 1698-1702; b) S. Billiet, K. D. Bruycker, F.
Driessen, H. Goossens, V. Van Speybroeck, J. M. Winne, F. E. D. Prez,
Nat. Chem. 2014, 6, 815-821.
The experimental details on the synthesis and characterization of new
compounds, additional NMR and UV/Vis spectra, as well as the
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[12] a) Y.-X. Lu, F. Tournilhac, L. Leibler, Z. Guan, J. Am. Chem. Soc. 2012,
134, 8424-8427; b) H. Liu, A. Z. Nelson, Y. Ren, K. Yang, R. H. Ewoldt,
J. S. Moore, ACS Macro Lett. 2018, 7, 933-937.
[13] a) H. Ying, Y. Zhang, J. Cheng, Nat. Commun. 2014, 5, 3218; b) Y.
Ren, L. You, J. Am. Chem. Soc. 2015, 137, 14220-14228; c) M. M.
Obadia, B. P. Mudraboyina, A. Serghei, D. Montarnal, E. Drockenmuller,
J. Am. Chem. Soc. 2015, 137, 6078-6083; d) D. Zha, L. You, ACS. Appl.
Mater. Interfaces. 2016, 8, 2399-2405; e) W.-X. Liu, C. Zhan, H. Zhang,
N. Zhao, Z.-X. Yu, J. Xu, J. Am. Chem. Soc. 2017, 139, 8678-8684; f) L.
Chen, R. Liu, X. Hao, Q. Yan, Angew. Chem. Int. Ed. 2019, 58, 264-
268; Angew. Chem. 2019, 131, 270-274.
[14] a) M. Burnworth, L. Tang, J. R. Kumpfer, A. J. Duncan, F. L. Beyer, G.
L. Fiore, S. J. Rowan, C. Weder, Nature 2011, 472, 334-337; b) P.
Chen, Q. Li, S. Grindy, N. Holten-Andersen, J. Am. Chem. Soc. 2015,
137, 11590-11593; c) L. Yang, G. Zhang, N. Zheng, Q. Zhao T. Xie,
Angew. Chem. Int. Ed. 2017, 56, 12599-12602; Angew. Chem. 2017,
129, 12773-12776.
[15] C. J. Bruns, J. F. Stoddart, The Nature of the Mechanical Bond: From
Molecules to Machines, John & Wiley, New Jersey, 2016.
[16] a) J.-P. Sauvage, Acc. Chem. Res. 1998, 31, 611-619; b) S. Erbas-
Cakmak, D. A. Leigh, C. T. McTernan, A. L. Nussbaumer, Chem. Rev.
2015, 115, 10081-10206; c) A. Goujion, E. Moulin, G. Fuks, N.
Giuseppone, CCS Chem. 2019, 1, 83-96.
[17] a) C. P. Collier, G. Mattersteig, E. W. Wong, Y. Luo, K. Beverly, J.
Sampaio, F. M. Raymo, J. F. Stoddart, J. R. Heath, Science 2000, 289,
1172-1175; b) Z.-J. Zhang, H-Y. Zhang, H. Wang, Y. Liu, Angew. Chem.
Int. Ed. 2011, 50, 10834-10838; Angew. Chem. 2011, 123, 11026-
10030; c) M. Galli, J. E. M. Lewis, S. M. Goldup, Angew. Chem. Int. Ed.
2015, 54, 13545-13549; Angew. Chem. 2015, 127, 13749-13753; d) Q.
Zhang, S.-J. Rao, T. Xie, X. Li, T.-Y. Xu, D.-W. Li, D.-H, Qu, Y.-T. Long,
H. Tian, Chem 2018, 4, 2670-2684; e) ; X. Zheng, Y. Zhang, N. Cao, X.
Li, S. Zhang, R. Du, H. Wang, Z. Ye, Y. Wang, F. Cao, H. Li, X. Hong,
A. C.-H. Sue, C. Yang, W.-G. Liu, H. Li, Nat. Commun. 2018, 9, 1961; f)
H. V. Schröder, F. Stein, J. M. Wollschläger, S. Sobottka, M. Gaedke, B.
Sarkar, C. A. Schalley, Angew. Chem. Int. Ed. 2019, 58, 3496-3500;
Angew. Chem. 2019, 131, 3534-3538.
[18] a) K.-i. Yamashita, M. Kawano, M. Fujita, J. Am. Chem. Soc. 2007, 129,
1850-1851; b) N. Ponnuswamy, F. B. L. Cougnon, J. M. Clough, G. D.
Pantoş, J. K. M. Sanders, Science 2012, 338, 783-785; c) L. Shen, N.
Cao, L. Tong, X. Zhang, G. Wu, T. Jiao, Q. Yin, J. Zhu, Y. Pan, H. Li,
Angew. Chem. Int. Ed. 2018, 57, 16486-16490; Angew. Chem. 2018,
130, 16724-16728.
[19] a) D. Bléger, J. Schwarz, A. M. Brouwer, S. Hecht, J. Am. Chem. Soc.
2012, 134, 20597-20600; b) C. Kine, M. Utecht, F. Zhao, H. Kulla, S.
Kovalenko, A. M. Brouwer, P. Saalfrank, S. Hecht, D. Bléger, Chem.
Eur. J. 2014, 20, 16492-16501.
[20] a) R. J. Wojtecki, M. A. Meador, S. J. Rowan, Nat. Mater. 2011, 10, 14-
27; b) H. Frisch, D. E. Marschner, A. S. Goldmann, C. Barner-Kowollik,
Angew. Chem. Int. Ed. 2018, 57, 2036-2045; Angew. Chem. 2018, 130,
2054-2064.
[21] a) Y. Amamoto, H. Otsuka, A. Takahara, K. Matyjaszewski, Adv. Mater.
2012, 24, 3975-3980; b) D. Ahn, S. R. Zavada, T. F. Scott, Chem.
Mater. 2017, 29, 7023-7031; c) H. Frisch, J. P. Menzel, F. R. Bloesser,
D. E. Marschner, K. Mundsinger, C. Barner-Kowollik, J. Am. Chem. Soc.
2018, 140, 9551-9557.
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Entry for the Table of Contents (Please choose one layout)
RESEARCH ARTICLE
Yong-Fei Yin,+ Meng-Yan Yun,+ Lin
Wu,+ Hong-Ying Duan, Xia-Min, Jiang,
Tian-Guang Zhan,* Jiecheng Cui, Li-
Juan Liu, and Kang-Da Zhang*
Page No. – Page No.
Visible Light Induced Dynamic
Mechanical Bond as A New Type of
Linkage for Dynamic Materials
A visible light induced dynamic mechanical bond (DMB) has been constructed whose photoinduced dynamic bonding behaviors
enabled the fabrication of novel DMB-crosslinked dynamic polymeric gel.
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