All-Visible-Light-Activated Dithienylethenes Induced by Intramolecular Proton Transfer

Article abstract of DOI:10.1021/jacs.9b07357

The fast light-responsive dithienylethenes (DTEs) are one of the most attractive photochromic families because of their excellent thermal irreversibility and fatigue resistance. However, the all-visible-light-activated DTE system still remains challenging because most of them require the harmful high-energy ultraviolet light to trigger their photocyclization reaction. Here, we have for the first time borrowed a specific intramolecular proton transfer (IPT) process and rationally designed a series of all-visible-light-driven DTEs. Incorporating the IPT-functional group to DTE unit gives rise to an extra absorption band with a distinct red shift, which enables the photocyclization of DTEs under stimuli of visible light at 450 nm, as well as ensuring the desirable photoswitching efficiency. The isomerization from OH form to NH form induced by IPT can decrease the energy gap for excitation and photocyclization, thereby affording the all-visible-light-triggered photochromic performance, which can not only work well in a polar solvent system but also show its effectiveness in polymeric gel systems. In this regard, we can provide a general and reliable platform to construct all-visible-light-driven DTEs with excellent reversible photoswitching and broad applicability, especially with avoiding the use of harmful ultraviolet light to induce their photocyclization.

Full text of DOI:10.1021/jacs.9b07357

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Article
All-Visible-Light Activated Dithienylethenes
Induced by Intramolecular Proton Transfer
Hancheng Xi, Zhipeng Zhang, Weiwei Zhang, Mengqi Li, Cheng Lian, Qianfu Luo, He Tian, and Wei-Hong Zhu
J. Am. Chem. Soc., Just Accepted Manuscript • Publication Date (Web): 28 Oct 2019
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All-Visible-Light Activated Dithienylethenes Induced by
Intramolecular Proton Transfer
Hancheng Xi,§ Zhipeng Zhang,§ Weiwei Zhang,§ Mengqi Li, Cheng Lian, Qianfu Luo, He Tian, and Wei-
Hong Zhu*
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Key Laboratory for Advanced Materials and Joint International Research Laboratory of Precision Chemistry and Molecular
Engineering, Feringa Nobel Prize Scientist Joint Research Center, Shanghai Key Laboratory of Functional Materials
Chemistry, Institute of Fine Chemicals, School of Chemistry and Molecular Engineering, East China University of Science &
Technology, Shanghai 200237, China.
E-mail: whzhu@ecust.edu.cn
KEYWORDS Photochromism, Dithienylethene, All-visible-light photoswitching, Intramolecular proton transfer
ABSTRACT: The fast light-responsive dithienylethenes (DTEs) are one of the most attractive photochromic families due to their
excellent thermal irreversibility and fatigue resistance. However, all-visible-light induced DTE system still remains challenging since
most of them require the harmful high-energy ultraviolet light to trigger their photocyclization reaction. Here, we have for the first
time borrowed a specific intramolecular proton transfer (IPT) process, and rationally designed a series of all-visible-light driven
DTEs. Incorporating the IPT-functional group to DTE unit gives rise to an extra absorption band with a distinct redshift, which
enables the photocyclization of DTEs under stimuli of visible light at 450 nm, as well as ensuring the desirable photoswitching
efficiency. The isomerization from OH-form to NH-form induced by IPT can decrease the energy gap for excitation and
photocyclization, thereby affording the all-visible-light triggered photochromic performance, which can not only work well in polar
solvent system, but also show its effectiveness in polymeric gel systems. In this regard, we can provide a general and reliable platform
to construct all-visible-light driven DTEs with excellent reversible photoswitching and broad applicability, especially with avoiding
the use of harmful ultraviolet light to induce their photocyclization.
contribution of the excited singlet state to the photo-responsive
central hexatriene unit.37 As an alternative approach, Yam and
coworkers put forward the visible light excitation via
modification of the central ethene bridge (Figure 1a, right).42,43
Nevertheless, the photochromic behavior of these systems was
hampered by the interaction between the additional π-
conjugation and the photoswitchable backbone. Recent work
has clearly demonstrated that the mismatched combination
would lead to complete loss of photochromic activity,44 thus
making it rather difficult to predict the photo-responsive
performance of the resulting DTE via ethene bridge
modification. As a consequence, it is still challenging to obtain
a general all-visible-light DTE platform, and sometimes
calculations is necessary to find out a suitable structure.32
Therefore, efficient and reliable strategies for building up all-
visible-light activated DTEs still remain to be unexplored.
INTRODUCTION
Molecular photoswitches1-3 have drawn much attention due to
their excellent reversible photoresponse performance in optic-
electronic devices,4,5 liquid crystal,6 molecular motor7,8 and
other light-regulated functional materials.9-15 Among them,
dithienylethene (DTE) derivatives have been widely
investigated for their excellent thermal stability, rapid
photoresponse and robust fatigue resistance.16-21 In general,
ultraviolet (UV) light is necessary to switch DTEs from open
form to close form, while the reverse process relies on the
visible light.16 However, high-energy UV light irradiation may
generate undesired by-products in photoreactions18 and would
be detrimental to biological tissues, severely restricting to
burgeoning bio-applications, such as super-resolution
bioimaging,22,23
bioactivity
. Therefore, all-visible-light driven
controls24
and
photopharmacology25,26
photoswitchable systems27-31 are urgently demanded.
Intramolecular proton transfer (IPT) is an important feature
of hydrogen bonded systems,45,46 which is crucial for the
thermo- and solvatochromism of salicylidene Schiff base and
derivatives.47,48 The IPT process in these systems has been well
investigated as follows: the equilibrium exists between two
tautomers, the one with hydrogen bond proton covalently
bonded to the oxygen (OH-form) and the other with the proton
bonded to the nitrogen (NH-form, Figure 1b).49 It is of great
concern that the two tautomers possess different electronic
absorption properties, the NH-form absorbs at longer
wavelength.49-51 Herein we have for the first time exploited the
IPT characteristic, and designed a series of novel DTEs by
For DTE derivatives, much efforts have been devoted to
induce absorption in visible region,32-35 including the
uncommon inverse type of DTE with 2-position of heterorings
connected to the ethene bridge.36,37 For the normal type DTE, in
which 3-position of thiophene is tethered with the ethene
backbone, extending π-conjugation through the side thiophene
rings was broadly utilized to shift the excitation wavelength to
visible region.38-41 However, most of these systems displayed
extremely low photo reaction quantum yields (Φo-c < 1%)
because the additional π-systems could decrease the
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Figure 1. Strategies for designing all-visible-light activated DTEs. (a) Extending π-conjugation on the thiophene ring or the ethene
bridge of DTE unit. (b) General platform exploiting IPT process to induce all-visible-light response: schematic illustration of IPT-based
DTE, target system DTE-1 as well as reference system DTE-OMe.
incorporating IPT-functional groups into DTE unit (Figure 1b).
With the typical IPT process in targeted DTEs, all-visible-light
photochromic performance has successfully realized with the
following extraordinary features: i) exhibiting an additional
red-shifted absorption band induced by the specific IPT
process, ii) achieving an unprecedented photocyclization of
DTE with a visible light of 450 nm, iii) providing a reliable
platform to build up all-visible-light activated DTEs, and iv)
being widely applicable in polar/protic solvents and polymeric
gel systems.
with the λmax located at 325 and 337 nm, respectively, while an
extra absorption band in 400-475 nm visible region was found
for DTE-1. To test their essential photochromic behavior, DTE-
1 and DTE-OMe in solution were irradiated with 365 nm UV
light, a new low-energy absorption band in 500-700 nm
appeared along with the decreasing absorbance at UV region.
These features are consistent with typical photochromic
performance of DTEs switching from open form to close
form.16,19 The preliminary test reveals that the DTE-1 and DTE-
OMe possess similar electronic absorption spectra and
photochromic peformance due to their similar chemical
structures. Thus we infer the additional absorption band in
visible light region of 400-475 nm for open form DTE-1 may
be associated with the IPT process.
RESULTS AND DISCUSSION
Rational Design of Introducing IPT Characteristic into
DTE. To borrow the IPT process in salicylidene Schiff base, we
designed a specific system DTE-1 bearing two functional units:
the photoswitching DTE core and the salicylidene-propylamine
moiety attached to the thiophene rings. The target DTE-1 was
readily synthesized by condensation of propylamine with the
aldehyde intermediate which was obtained through Suzuki-
It has been well recognized that solvent effect is very crucial
to the IPT equilibrium.52-54 Thus we further investigated the
absorption spectra of DTE-OMe and DTE-1 in different aprotic
and protic solvents (Figure 2b-2d). Interestingly, when
increasing the solvent polarity, a new absorption band at 420
nm became emerged and gradually enhanced for DTE-1.
Moreover, this absorption band became quite noticeable in
protic solvents such as methanol. In contrast, no additional
absorption band can be observed for methyl-protected DTE-
OMe upon solvent change. The absorption spectra of DTE-1 are
closely related with the combined interaction of solvent
polarization and protonation. Given the fact that the NH-form
in IPT equilibrium system exhibits longer wavelength
absorption than OH-form,49-51 the emerged absorption band in
visible region was attributed to the NH-form of DTE-1
generated by the IPT process: the acidic proton shift from
oxygen to nitrogen (from OH-form to NH-form, Figure 2e). The
NH-form can be stabilized with increase of the solvent polarity
Miyaura reaction of
a dibromo-substituted DTE and
salicylaldehyde borate. DTE-OMe was also prepared as
reference compound via the similar synthetic procedures
(Figure 1b and Scheme S1 in the Supporting Information), the
introduction of methoxy group into the phenol functionality
would inhibit IPT characteristic. All target products and
1
intermediates have been characterized by H and 13C NMR
spectra as well as HRMS spectra.
Endowing a Visible Absorption Band with Tuning IPT
Equilibrium. With DTE-1 and DTE-OMe in hand, we firstly
compared the absorption spectra of their open form in
acetonitrile solution. As depicted in Figure 2a, both DTE-1 and
DTE-OMe exhibited an obvious absorption band in UV region
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Figure 2. Effect of IPT unit on absorption and 1H NMR spectra. (a) Absorption spectra of open-form DTE-1 and DTE-OMe as well as
their photostationary state spectra irradiated with 365 nm light in acetonitrile solution; (b, c and d) Absorption spectra of open-form
DTE-1 and DTE-OMe in different solvents (10 μM, 293 K); (e) Partial 1H NMR (400 MHz) spectra of DTE-1 in benzene-d6 at 293 K
in the presence of trifluoroethanol (TFE): R stands for the molar ratio of TFE to DTE-1. The chemical structure shows the attribution of
hydrogen atoms during the IPT process in DTE-1.
or proton donating ability,49 thereby increasing its contribution
to the IPT equilibrium (Table S1 in Supporting information).
nm (Figure 3a). Interestingly, this photochromic behavior is
similar to that of 365 nm UV light driven as shown above. To
exclude the possibility that this absorption spectra change was
caused by the trans-cis isomerization of imine bond,56 the pure
close form DTE-1c was synthesized (Scheme S2). As shown in
Figure 3a, the absorption spectra of DTE-1 at photostationary
state (PSS) was in accordance with its pure close form,
demonstraing the formation of DTE-1c via the visible light
activated photocyclization. 1H NMR studies were also
performed and confirmed this result (Figure S22-S23). The
absorption spectra of pure DTE-1c in different solvents were
depicted in Figure S8, showing identical IPT characteristic as
open form DTE-1 that the absorption band at around 420 nm
increases upon solvent polarity or proton donating ability
increasing. Irradiating with 600 nm light can induce the
photocycloreversion of DTE-1c (Figure S9). These results turn
out an unprecedented pathway for switching IPT-based DTE-1
with all visible light (Figure 3b): with the IPT progress
generated in open form DTE-1, the proton-transferred NH-form
absorbs the visible light and undergo photocyclization, then
photocycloreversion of closed form can be induced by longer-
wavelength visible light. Thus UV light can be replaced by
visible light in this IPT-based DTE system. We further
investigated this visible light photochromic behavior in more
solvents. As summarized in Figure S6 and Table S3, DTE-1 can
achieve photochromic behavior upon irradiation with 450 nm
light in various solvents including less polar toluene. In
contrast, the reference system DTE-OMe shows no visible light
1H NMR study was performed to confirm the IPT-induced
transformation from OH-form to NH-form. The increasing of
the proton donating ability of the NMR solvent was achieved
through gradual addition of trifluoroethanol (TFE), which is a
polar solvent with strong proton donating ability, into the
benzene-d6 solution of DTE-1. As shown in Figure 2e, upon
increasing the molar ratio of TFE/DTE-1 from 0 to 1, the signal
of hydroxyl proton showed upfield along with the peak shape
turning from sharp to broad, and the signal of hydrogen adjacent
to the hydroxyl exhibited upfield shift synchronously. These
changes can be attributed to IPT process and formation of the
NH-form of DTE-1, along with the proton transferring from
oxygen to nitrogen, which strengthens the interaction with
nitrogen atom and changes the chemical environment. The
results were in exact accordance with the typical feature of IPT
process,47,54,55 indicative of the possible IPT channel in DTE-1.
All-Visible-Light Driven Photochromic Behavior of IPT-
Based DTE. The IPT induced absorption band emerged in
visible region inspired us to explore the visible light
photochromic behavior of DTE-1. In dark condition, we
irradiated the open form of DTE-1 in acetonitrile solution with
450 nm blue light, and recorded its absorption spectra at every
30 s until the spectra did not changed. After the irradiation, the
color turned from pale yellow to blue, a broad absorption band
at 500-700 nm became grown, and the absorption peak at 325
nm became decreased, along with a clear isosbestic point at 360
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Figure 3. Visible light photochromic performance based on IPT strategy and related mechanism study. (a) Absorption spectra of DTE-
1 upon irradiation with 450 nm blue light (10 μM in acetonitrile, 293 K, inset shows the color changes); (b) Related reactions of this all-
visible-light photochromic DTE system conferred by IPT process; (c) Spatial plots of HOMOs and LUMOs as well as corresponding
energy level of OH- and NH-form of open-form DTE-1; (d) Schematic description of the IPT strategy for visible-light-actived DTE
(blue arrow) and the ESIPT pathway for fluorescence emission (violet arrow).
photochromic behavior at all (Figure S10). These results turn
the IPT-based DTE-1 to be a novel all-visible-light induced
photoswitch. There is also an interesting phenomenon that
DTE-1 exhibits obvious fluorescence emission while DTE-
OMe has no emission at all (Figure S15), which may result from
the IPT process in DTE-1.
OH-form to NH-form induced by IPT in ground state can
decrease the energy gap for excitation and photocyclization,
thereby affording the unusual all-visible-light triggered
photochromic performance; and (ii) the fluorescence property
of DTE-1 can also be attributed to IPT process (Figure S16-
S17), including the OH-form excitation at 360 nm via the
excited-state intramolecular proton-transfer (ESIPT, 57,58 violet
arrow) and the IPT-induced NH-form excitation at 450 nm (blue
arrow).
To delineate the nature of the ground and excited states in
OH- and NH-forms of the open form DTE-1, the calculations
with quantum density functional theory (DFT) were performed.
The HOMO and LUMO profiles for OH- and NH-forms of
DTE-1 were shown in Figure 3c. The HOMOs of OH-form
mainly localize at the peripheral pendant while the LUMOs
localize at the thiophene and perfluorocyclopentene bridge
group. For IPT generated NH-form, the profiles of HOMOs and
LUMOs closely resemble those of OH-form. Both the OH- and
NH- form are suitable for the photocyclization reaction since
the LUMOs distribute throughout the photo responsive central
hexatriene part of DTE-1.19,37 It is worth noting that the HOMO
energy level increases by 0.79 eV upon transformation from
OH-form to NH-form, which results in a narrower energy gap
between LUMO and HOMO by 0.81 eV. Herein the decreased
energy gap is exactly corresponding to the 95 nm red-shifted
absorption band for the NH-form of DTE-1 (from 325 to 420
nm). And the energy difference between the HOMO of OH-
form and NH-form is only 0.02 eV.
Exploring IPT-Based Structure as a General and Reliable
Platform to Design All-Visible-Light Activated DTEs. In
general, a molecular system can exhibit IPT characteristic when
incorporating an intramolecular hydrogen bonding interaction
between proton donor and proton acceptor.59 We expect that the
IPT-based structure in model DTE-1 could serve as a flexible
platform to build up more all-visible-light activated DTEs.
Therefore, we further developed DTE-2, DTE-3 and DTE-4,
containing phenolic hydroxyl group as proton donor and
various nitrogen-containing group as proton acceptor (Figure 4
and Scheme S3). It was found that, all DTE-2, DTE-3 and DTE-
4 exhibit analogical absorption behaviors as DTE-1, showing
an extra absorption band in visible region under the combined
polarization and protonation effect of the solvent (Figure S11),
indicating the formation of corresponding NH-forms. Their
photochromic performance is very similarly as investigated
with 450 nm visible light. As shown in Figure 4, a broad
absorption band in the range of 500-800 nm grows gradually,
The DFT calculation results unambiguously support the IPT
mechanism as depicted in Figure 3d: (i) the isomerization from
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Figure 4. Platform for constructing all-visible-light activated DTEs based on IPT strategy. (a) Modified derivatives of DTE-2, DTE-3,
DTE-4 and IPT process in target systems; (b, c and d) Absorption spectra changes of DTE-2, DTE-3 and DTE-4 with visible light
excitation at 450 nm (solvent for DTE-2: MeOH, for DTE-3 and DTE-4: DMSO, 10 μM, 293 K).
accompanied by the absorption decreasing in UV region. There
observed a clear isosbestic point, indicating the generation of
the closed form of DTEs via photocyclization. Identically,
photocycloreversion of these close forms can be triggered by
irradiating with longer wavelength light (Figure S13). These
IPT-based DTEs also show fluorescence emission property due
to ESIPT mechanism, and the emission intensity can also be
switched by 450 nm visible light irradiation (Figure S18-S20).
DFT calculations for DTE-2, DTE-3 and DTE-4 manifest the
same all-visible-light induced photochromism as the model
compound DTE-1 (Figure S28-S30, and Table S6): the
corresponding NH-form show a narrower HOMO-LUMO
energy gap with respect to OH-form, and the LUMOs
distributions also keep suitable for the photocyclization
reaction. It is notable that the pH value has effect on the
performance of photo-switching. In strong base condition, the
phenol group (-OH) in salicylidene Schiff base turns to
phenoate anion (-O-), which terminates the IPT process. Also in
acidic condition, the possible protonation of nitrogen can inhibit
the IPT process to some extent, and thus resulting in the lower
conversion than that in neutral condition (Supporting
Information, Figure S14). Hence, we choose neutral condition
during the whole investigation. These results demonstrate the
all-visible-light photochromic performances induced by IPT is
not an individual phenomenon, but provides a reliable strategy
to activate photochromic DTEs, especially without requiring
Table 1. Photochromic Data of IPT-Based DTEsa
conversion
photocyclization photocycloreversion
compoundb
at PSS
CRo-c[%]
95.6
λirr[nm] Φo-c[%]c λirr[nm] Φc-o[%]d
365
450
365
450
365
450
365
450
46.5
31.9
38.1
25.0
37.5
26.7
44.4
28.4
DTE-1
DTE-2
DTE-3
DTE-4
600
600
600
600
7.3
6.2
7.5
8.4
94.9
85.1
61.6
89.8
76.7
89.3
68.9
adata collected at 293 K; bsolvent for DTE 1-2: MeOH, for DTE 3-4:
DMSO; cferrioxalate was used as chemical actinometer; daberchrome
670 was used as chemical actinometer.
the harmful high-energy UV light to trigger their
photocyclization.
Excellent Photoreaction Yields and Preferable Fatigue
Resistance Achieved by IPT Strategy. In addition, the typical
criteria for photochromic compounds, such as photoconversion
ratios, quantum yields, fatigue resistance as well as the
thermostability of ring-closed isomers32 were also determinated
to evaluate this IPT-based DTE platform. The photocyclization
quantum yields (Φo-c) at 450 nm was measured to be 31.9% for
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The photochromic fatigue resistance was also checked under
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alternate irradiation at 450 and 600 nm, as shown in Figure 5a,
IPT-based DTE-3 displays no apparent loss of photochromic
activity over 20 cycles in DMSO solution. To further reveal the
superiority of this visible light photochromic behavior, a
contrast test was also performed with alternate irradiation at 365
and 600 nm. When anatomizing the two set of data in the
histogram depicted in Figure 5b, an obvious tendency can be
observed, that the reversible photoswitching under 450 nm
excitation exhibits better photostability than UV light does,
demonstrating the IPT pathway for all-visible-light
photochromism could reduce side reactions and enhance the
fatigue resistance of DTE systerms. In addition, all these IPT-
based DTEs show excellent thermostability at room
temperature, their absorption at PSS showed no decrease for
over 2000 min (Figure 5c). Obviously, the outstanding
photochromic performance renders the IPT-based DTE
platform to be an efficient and reliable protocol for constructing
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Figure 5. Preferable fatigue resistance realized by IPT
strategy. (a) Absorption changes of DTE-3 at 635 nm upon
alternate irradiation with 450 and 600 nm for 20 cycles; (b)
Comparison of the fatigue resistance of DTE-3 under UV light
excitation or visible light excitation (one cycle equal to
irradiating with shorter-wavelength light for 10 s and then
longer-wavelength light for 120 s); (c) Thermal decay plot of
absorbance versus time for IPT-based DTEs monitored at λmax
at 293 K.
Figure 6. IPT-based DTE platform work in in-situ formed gel
system. (a) Schematic illustration of the formation of IPT-
based polymer gel system; (b) Photographs of the component
and the resulting gel system, as well as its all-visible-light
response.
DTE-1, along with an execellent open-to-close conversion ratio
(CRo-c) as high as 94.9% (Table 1). For DTE-2, DTE-3 and
DTE-4, desirable photoswitching efficiencies (Φo-c > 25% and
CRo-c > 60%) were also achieved upon irradiation with visible
light at 450 nm. These photocyclization quantum yields
measured at 450 nm are one third less than those at 365 nm UV
light, and the photocycloreversion quantum yields are 6.2-8.4%.
Moreover, the photocyclization quantum yield is independent
with solvent although the photoconversion ratio shows a
dependency on solvent (Table S3 and S4). These solid data
prove the high efficiency of such IPT-based DTE platform.
the bottlenecked all-visible-light activated dithienylethene
systems.
Enabling IPT-Based DTE Platform Work in in-situ
Formed Gel System. Given that the IPT strategy proposed here
provides a new method for designing all-visible-light activated
DTE systems, we anticipate that such IPT-based DTE platform
could also become a reliable matrix for constructing more
functional visible-light-responsive materials. By virtue of the
mild reaction conditions and high reaction rates during the
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Journal of the American Chemical Society
formation of imine bond,60 we designed an in-situ formed gel
Shanghai Municipal Science and Technology Major Project (Grant
1
2
3
4
5
6
7
8
2018SHZDZX03), the Innovation Program of Shanghai Municipal
Education Commission, Scientific Committee of Shanghai
(15XD1501400), Programme of Introducing Talents of Discipline
to Universities (B16017), and China Postdoctoral Science
Foundation (2019M651418).
system to prove the effectiveness of the IPT-based DTE
platform in such soft materials.61 By mixing the aldehyde-
containing
intermediate
(DTE-CHO)
with
amino-
functionalized siloxane polymer (AS-NH2), a viscous gel was
formed at room temperature immediately (Figure 6). Then
irradiating it with visible light at 450 nm, a significant color
change from yellow to deep blue can be observed, indicating
the IPT-based DTE platform can not only work well in
polar/protic solvent environment, but also is applicable in
polymeric gel systems. Given that the imine bond have been
widely exploited in the fields of supramolecular system,
polymer networks and covalent organic framworks (COF),62-64
we expect the further development of the IPT-based DTE
platform to construct versatile all-visible-light modulated
materials.
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CONCLUSIONS
This work focuses on how to settle the bottleneck of the
traditional photochromic DTE series that need harmful UV light
to trigger the photocyclization. Given that the interplay between
the π-conjugation and the photoswitchable backbone severely
affects the photochromic behavior, we have well demonstrated
a novel strategy with the specific IPT process to building up all-
visible-light driven DTE series. The structural transformation
from OH-form to NH-form in IPT-based DTEs can
significantly decrease the energy gap, resulting in an extra
absorption band in visible light region with a dramatic redshift
up to 95 nm, thereby making a breakthrough to afford all-
visible-light photochromic DTE system without requiring the
harmful stimuli of UV light. This novel system can not only
work well in polar solvent system, but also show its
effectiveness in polymeric gel systems. The IPT-based DTE
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structures can provide
a reliable platform to address
multifunctional all-visible-light modulated materials. Based on
the unprecedented IPT-based DTEs, further insights into the
proton donor group and ethene bridge are now in progress.
ASSOCIATED CONTENT
More detailed experimental procedures, characterizations,
supplementary optical spectra and figures can be found in
Supporting Information. This material is available free of charge
via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
* whzhu@ecust.edu.cn
Author Contributions
§
H. X., Z. Z. and W. Z. contributed equally.
Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENT
This work was supported by NSFC/China for the Science Center
Program (21788102), Creative Research Groups (21421004) and
Key Project (21636002), NSFC/China (21905091), National Key
Research and Development Program (2016YFA0200300),
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Table of contents (TOC)
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All-Visible-Light Activated Dithienylethenes Induced by
Intramolecular Proton Transfer
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Hancheng Xi,§ Zhipeng Zhang,§ Weiwei Zhang,§ Mengqi Li, Cheng Lian, Qianfu Luo, He Tian, and Wei-
Hong Zhu*
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