White-light emission from a pyrimidine-carbazole conjugate with tunable phosphorescence-fluorescence dual emission and multicolor emission switching

Article abstract of DOI:10.1039/d0cc00251h

A metal-free organic carbazole-pyrimidine dye exhibiting phosphorescence-fluorescence dual emission was developed into a white-light emission-switching system. The two crystal polymorphs obtained by breaking the molecular symmetry responded to the external stimuli of heating, vapor-fuming, and mechanical grinding, resulting in a tricolor switching system that includes white-light emission.

Full text of DOI:10.1039/d0cc00251h

View Article Online
View Journal
ChemComm
Chemical Communications
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: T. Ishi-i, H.
Tanaka, I. S. Park, T. Yasuda, S. Kato, M. Ito, H. Hiyoshi and T. Matsumoto, Chem. Commun., 2020, DOI:
10.1039/D0CC00251H.
Volume 54
This is an Accepted Manuscript, which has been through the
Number
January 2018
Pages 1-112
1
4
Royal Society of Chemistry peer review process and has been
accepted for publication.
ChemComm
Chemical Communications
rsc.li/chemcomm
Accepted Manuscripts are published online shortly after acceptance,
before technical editing, formatting and proof reading. Using this free
service, authors can make their results available to the community, in
citable form, before we publish the edited article. We will replace this
Accepted Manuscript with the edited and formatted Advance Article as
soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes to the
text and/or graphics, which may alter content. The journal’s standard
Terms & Conditions and the Ethical guidelines still apply. In no event
shall the Royal Society of Chemistry be held responsible for any errors
or omissions in this Accepted Manuscript or any consequences arising
from the use of any information it contains.
ISSN 1359-7345
COMMUNICATION
S. J. Connon, M. O. Senge et al.
Conformational control of nonplanar free base porphyrins:
towards bifunctional catalysts of tunable basicity
rsc.li/chemcomm

Please do not adjust margins
Page 1 of 4
ChemComm
View Article Online
DOI: 10.1039/D0CC00251H
COMMUNICATION
White-light emission from a pyrimidine-carbazole conjugate with
tunable phosphorescence-fluorescence dual emission and
multicolor emission switching†
Received 00th January 20xx,
Accepted 00th January 20xx
Tsutomu Ishi-i,*a Honoka Tanaka,ab In Seob Park,c Takuma Yasuda,c Shin-ichiro Kato,d Mitsunori
Ito,e Hidetaka Hiyoshie and Taisuke Matsumotof
DOI: 10.1039/x0xx00000x
A
metal-free organic carbazole-pyrimidine dye exhibiting enhanced intersystem crossing and suppress nonradiative
phosphorescence-fluorescence dual emission was developed into a deactivation, resulting in room-temperature phosphorescence.
white-light emission-switching system. The two crystal polymorphs Recently, interesting examples of white-light emission were
obtained by breaking the molecular symmetry responded to the found in single organic molecules that show dual emission
external stimuli of heating, vapor-fuming, and mechanical grinding, arising from yellow phosphorescence and blue fluorescence.15–
resulting in a tricolor switching system that includes white-light 19 More recently, an interesting white-light emission was found
emission.
in a double blue and yellow phosphorescence system.20
Interestingly, the white-light emission can be switched to
different color emission in a limited number of stimuli-response
White-light emission of metal-free organic materials has
attracted attention because of its scientific interest1 and its
practical applications in materials science, such as organic light-
emitting diodes.2 One of the simple strategies used to achieve
white-light emission is by combining the two complimentary
colors of blue and yellow light,3 which is more easily accessible
compared to a combination of the three primary colors blue,
green, and red light.4 In contrast to systems composed of more
than two fluorescent molecules,3–6 single-molecular systems
have several advantages: they can avoid the drawbacks of
phase separation, color aging, and degradation; moreover, they
lead to enhanced reproducibility and stability as well as easy
device fabrication.7–9 Moreover, phosphorescence emission has
recently been observed in metal-free organic materials even
systems.16–18 However,
a versatile strategy for stimuli-
responsive emission switching is lacking.21 In addition, achieving
multicolor emission switching, including white-light emission, is
a challenging task.
If more than two different crystal states exist in
a
N
N
N
N
N
N
Br
Br
R
R
4A
4B
4W
(phosphorescence-active)
(phosphorescence-inactive)
(white-light emission)
1
2
3
R =H
R =Cl
R =Br
Fig. 1 Molecular structures of compounds 1-4.
under
ambient
atmospheric
conditions
at
room
phosphorescence-fluorescence
dual
emission
system,
temperature.10,11 Specific systems involving crystallization,12
aggregation,13 and noncovalent interactions14 allow for
reversible emission switching can be achieved by external
stimulation. The crystal polymorphs can be created by different
conformation obtained by breaking the symmetry of a
molecular structure.22 In this paper, we report white-light
emission based on phosphorescence-fluorescence dual
emission from a carbazole-pyrimidine conjugate, and its
multicolor switching by external stimulation (Fig. 1). The
phosphorescence, which was achieved by aggregation in the
crystalline state, was enhanced by introducing a heavy atom,
bromine. The meta-substituted bromine derivative bearing
asymmetrical aromatic groups provided two polymorphs, one
active and the other inactive in phosphorescence.
Phosphorescence and fluorescence dual emission can be
regulated reversibly by the external stimuli. In this reversible
emission-switching system, white-light emission can be
a. Department of Biochemistry and Applied Chemistry, National Institute of
Technology, Kurume College, 1-1-1 Komorino, Kurume 830-8555, Japan. E-mail:
ishi-i@kurume-nct.ac.jp
b. Material Engineering Advanced Course, Advanced Engineering School, National
Institute of Technology, Kurume College, 1-1-1 Komorino, Kurume 830-8555,
Japan
c. INAMORI Frontier Research Center (IFRC), Kyushu University, 744 Motooka, Nishi-
ku, Fukuoka 819-0395, Japan
d. Department of Materials Science, School of Engineering, The University of Shiga
Prefecture, 2500 Hassaka-cho, Hikone 522-8533, Japan
e. Research and Development Division, Kumiai Chemical Industry Co., Ltd, 2256
Nakanogo, Fiji 421-3306, Japan
f. Institute for Materials Chemistry and Engineering, Kyushu University, 6-1 Kasuga-
kohen, Kasuga 816-8580, Japan
†Electronic Supplementary Information (ESI) available: [experiment, spectral data
(absorption, fluorescence, and phosphorescence), powder XRD, DSC, single crystal,
computer simulation, and NMR spectra]. See DOI: 10.1039/x0xx00000x
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 2 of 4
COMMUNICATION
Journal Name
obtained by heat stimulation of the active phosphorescence interactions (3.33–3.48 Å) between pairs of moleVciuewleAsrti(cFleigO.nl3inae
state, because of an increase in the phosphorescence and a and Table S4). These -stacking interactiDoOnIs: 1c0o.1n0t3in9/uDe0CinC0a0o25n1eH-
decrease in the fluorescence, leading to multicolor switching dimensional direction. The columnar-type aggregates formed
between three different emission states.
are intertwined through C-H∙∙∙ interactions to constitute an L-
Dyes 1-4 in solution showed a broad absorption band of shaped packing (Fig. 3b), producing the three-dimensional
crystal structure. The whole crystal packing is stabilized through
FL (solution)
FL
Ph
FL (solution)
FL
Ph
FL (solution)
FL
Ph
a)
b)
c)
multiple intermolecular ∙∙∙, C-H∙∙∙, and halogen∙∙∙
interactions (Fig. S22).27 These multiple interactions effectively
work to reduce the vibrational/rotational molecular motions for
restricting the nonradiative channel.12 Similar crystal packing
structures of a one-dimensional aggregate and its intertwining
were found in dyes 1 and 2 (Figs. S20 and S21). In dye 3, in
addition to the internal bromine heavy-atom effect, the
intermolecular halogen∙∙∙ interactions27 work cooperatively to
enhance intersystem crossing and the subsequent radiative
FL (film)

P
P 193 ms
F 6.5%
-

P
P 77 ms
F 9.0%
-


F 3.0%
P 3.8%
P 40 ms
1
2
3
350
450
550
650
750
350
450
550
650
750
350
450
550
650
750
Wavelength (nm)
Wavelength (nm)
Wavelength (nm)
Fig. 2 Steady-state fluorescence spectra in DCM solution, and steady-state fluorescence
and phosphorescence spectra in the crystal solid state, for (a) 1, (b) 2, and (c) 3 (excited
at 350 nm) together with steady-state fluorescence spectrum in the PMMA film state.
around 340–400 nm, which is assigned to a charge-transfer
transition arising from a donor–acceptor chromophore of the
carbazole-pyrimidine conjugate, along with - transition
bands below 340 nm (Fig. S1).23 Upon excitation of the charge-
transfer band, a weak fluorescence emission was observed
around 440–510 nm which showed a weak solvent dependence
(Fig. S2). In the crystalline solid state, the unsubstituted dye 1
produced a fluorescence emission band at 428 nm in the
steady-state fluorescence spectrum (Fig. 2a). This emission
band is similar to that observed in solution. In the
phosphorescence spectrum, a very weak phosphorescence
emission band at 549 nm was found, together with two
additional bands at 598 and 650 nm (Fig. 2a). The introduction
a)
b)
2.79, 2.75 Å (C-H∙∙∙)
3.33-3.48 Å (∙∙∙)
3
c)
3.38 Å
(∙∙∙ )
3.35 Å (∙∙∙ )
3.50 Å
(∙∙∙ )
3
4A
Fig. 3 Single crystal X-ray structures of 3 and 4A: (a) aggregate structure with parallel
stacked arrangement and (b) L-shaped contact structure with perpendicular
arrangement in 3. (c) aggregate structure with anti-parallel stacked arrangement in 4A.
transition, leading to enhanced phosphorescence (Fig. S22g).
Dye 4, which possesses two bromine atoms in the meta-
position, occurs in two different crystal polymorphs.28 One
polymorph, 4A, is white, and is obtained by evaporation of
chloroform solution, whereas the other, 4B, is yellow, and is
of the chlorine atom in dye
2 did not improve the
phosphorescence efficiency (Fig. 2b). Interestingly, a persistent
phosphorescence emission at 547 nm can be detected in the
bromine-substituted dye 3 even in the steady-state mode (Fig.
2c). A relatively high phosphorescence quantum yield (P) of
3.8% was achieved along with a fluorescence quantum yield
(F) of 3.0% (Table S2). The observed phosphorescence lifetime
of 40 ms is acceptably long, although it is shorter than those of
1 (193 ms) and 2 (77 ms) (Table S2). The improved quantum
yield and reduced lifetime could be ascribed to a trade-off,
wherein introduction of the heavy bromine atom resulted in
augmented intersystem crossing and activation of a radiative
channel from the triplet state.24 Also, the shorter lifetime in 3
can be explained by slightly reduced -stacking in the crystal
structure,25 because the 3 molecule has slightly bent structure
compared to the 2 molecule (Table S4). The phosphorescence
emission bands were scarcely affected by the presence or
absence of halogen atoms (Table S2), indicating a negligible
halogen effect on the triplet excited state.19 The monomeric
state of 3, which is formed in polymethylmethacrylate (PMMA)
film, showed only a fluorescence emission band at 439 nm (Fig.
2c), suggesting that aggregation is important for realizing
phosphorescence.26
produced by recrystallization from
a chloroform/hexane
mixture. This polymorph formation is attributed to reduction in
the symmetry of the molecular structure due to the meta-
substituted bromine atom. Dye 4B is inactive in
phosphorescence and shows only a band at 476 nm in the
steady-state fluorescence spectrum. Only very weak
phosphorescence bands could be detected in its
phosphorescence spectrum (Fig. 4b). In contrast, dye 4A is
phosphorescence-active in the steady-state mode (Fig. 4a). A
distinct phosphorescence at 546 nm with a P of 3.3% was
found, together with fluorescence at 431 nm with a F of 5.1%
(Table S2). A persistent yellow phosphorescence with a lifetime
of 79 ms could be seen with the naked eye when the excitation
source was removed (inset photos in Fig. 4a). The
phosphorescence emission bands in 4A and 4B appeared in the
same position, around 546–554 nm, as in the para-isomer 3. In
contrast, the fluorescence emission bands were found at
different positions, with a trend of increasing wavelength from
4A (431 nm) through 3 (442 nm) to 4B (476 nm), leading to a
hypsochromic shift in 4A and a bathochromic shift in 4B.
The aggregate formation was found in a single crystal X-ray
diffraction (XRD) analysis. The molecule of dye 3 adopts a flat
conformation, with dihedral angles of 6.3° between the
pyrimidine and carbazole rings and 11.3° between the
pyrimidine and benzene rings (Table S4). The flat conformation
facilitates parallel stacking through nine short ∙∙∙ contact
Single crystal XRD analysis of 4A was successful in a colorless
prism obtained by recrystallization from 1,1,2,2-
tetrachloroethane/hexane (Figs. 3c and S23). The simulated
powder XRD pattern coincided with the powder XRD pattern of
4A (Fig. S15). In contrast, long, fine, pale yellow fibers could be
obtained from boiling toluene. This fiber sample named as 4B’
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 4
ChemComm
Please do not adjust margins
Journal Name
COMMUNICATION
is inactive in phosphorescence as similar to 4B sample (Fig. S11). crystallinity of 4A is increased by the heatingViaewndArticcloe oOlnilninge
DOI: 10.1039/D0CC00251H
The XRD pattern of 4B’ is relatively similar to that of 4B but not stimulation, leading to a more ordered crystalline state in 4W.
to 4A (Fig. S16). Thus, we used the fiber sample of 4B’ as the By increasing the crystallinity, the intersystem crossing is
sample of X-ray crystallographic analysis.
enhanced, which reduces the fluorescence intensity and
In 4A, a conformational polymorph was given due to the enhances the phosphorescence intensity. As a result of this
orientation of the bromine atoms,22 which are positioned in the spectral change, the whole visible light region can be covered
molecular structure in the conformation called ‘in-in’ (Fig. by the blue fluorescence and yellow phosphorescence to
S25a). In contrast to 3, the 4A molecule has a twisted produce a white-light emission. The Commission Internationale
conformation, with dihedral angles of 15.9° between the de l’Éclairage (CIE) 1931 chromaticity coordinates, (0.30, 0.31),
pyrimidine and carbazole rings, and 26.4° between the
FL
Ph
d)
a)
4A
pyrimidine and benzene rings (Table S4). The hypsochromic
shift in the fluorescence band of 4A can be explained by this
twisted conformation. The twisted molecules are oriented one-
dimensionally with an anti-parallel arrangement through six
∙∙∙ interactions (3.35–3.50 Å) between two molecules (Figs.
3c), which is different from the parallel arrangement of 3. The
one-dimensional aggregate structure has a loose packing,
judging from the twisted conformation, the reduced number of
∙∙∙ contact interactions (six contacts in 4A vs. nine contacts in
3), and the low density (1.66 g cm–3 in 4A vs. 1.74 g cm–3 in 3).
This loose packing can facilitate the stimuli-responsive packing
change between 4A and 4B, as described below. The anti-
parallel arrangement in 4A is a result of the enhanced dipole
moment in the in-in arrangement (Fig. S26), by which the
dipole-dipole interactions work effectively. The intermolecular
halogen∙∙∙ interactions27 found in 4A support active
phosphorescence (Fig. S23e).
Dye 4B’ adopts an out-out conformation with high molecular
planarity to form a parallel arrangement and the one-
dimensional stacked structure (Fig. S24, and Table S4). The one-
dimensional structures are intertwined to give another L-
shaped structure by approaching the bromine-substituted
benzene moieties (Fig. S24f), because the bromine atoms in the
meta-position sterically disturb the L-shaped contact found in
dye 3 (Fig. S25b). The four bromine atoms are oriented
alternatively to minimally reduce the steric repulsion (Fig.
S24g). Thus, this crystal packing structure rules out the
opportunity for intermolecular halogen interactions, leading to
the observed inactivity in phosphorescence. Dye 4B probably
takes similar crystal structure, judging from the photophysical
and morphological similarities with 4B’, as described above. The
4B molecule is likely to adopt more flat conformation to
enhance the -stacking interactions, leading to the
bathochromic shift of its fluorescence band. This enhanced -
stacking is supportive of the bathochromic shift of its excitation
and diffuse reflection bands (Fig. S3) and the enhanced XRD
reflection around 26.5° arising from the -stacking (Fig. S17).
An interesting white-light emission can be obtained by
stimulating 4A by heating it to 210 °C (above the melting point)
and subsequently cooling it to room temperature. The 4W
sample obtained showed enhanced phosphorescence (P
increased from 3.3% to 5.5%) and reduced fluorescence (F
decreased from 5.1% to 3.6%) (Fig. 4c and Table S2). The XRD
pattern exhibited little change after heating (Fig. S15). In
contrast, the differential scanning calorimetry (DSC) traces
showed an increase in enthalpy from –28.5 kJ mol–1 in 4A to –
29.9 kJ mol–1 in 4W at its melting point of 183 °C (Table S3). The
on
off
F 5.1%
P 3.3%


P 79 ms
4W (0.30, 0.31)
4B (0.23, 0.19)
350
450
550
650
750
Wavelength (nm)
FL
Ph
4A (0.19, 0.29)
b)
4B
on
off
F 6.6%

e)
P
-
fuming
(slow)
heat
(210 oC)
P 8 ms
4W
350
450
550
650
750
Wavelength (nm)
fuming (slow) or
heat (170 oC, slow)
FL
Ph
c)
4W
4B
4A
on
off
F 3.6%
P 5.5%
P 77 ms
heat (210 oC)


fuming
(rapid)
or heat
(170 oC, rapid)
grinding
350
450
550
650
750
4Ag
Wavelength (nm)
Fig. 4 Steady-state fluorescence and phosphorescence spectra in the crystal solid state
for (a) 4A, (b) 4B, and (c) 4W. Inset photos are emission images before (on) and after
(off) removal of the excitation source (black light, at 350 nm). (d) CIE 1931 coordinates
of emission of 4A, 4B, and 4W. (e) Emission color switching between 4A, 4B, and 4W
stimulated by heating, chloroform-vapor-fuming, and mechanical grinding.
are very close to those (0.33, 0.33) of pure white color (Fig. 4d).
As described above, dye 4 takes three different crystalline
forms, 4A, 4B, and 4W, which appear violet, blue-green, and
white, respectively (Fig. 4d). A reversible switching between 4A,
4B, and 4W can be obtained by application of the external
stimuli (Fig. 4e). A change from 4B to 4A was accomplished by
heating above the melting point at 210 °C and subsequently
cooling to room temperature (Fig. S6). This transition was
observed even at the slow cooling rate at 0.1 °C min–1 (Fig. S19).
On treatment of 4A with chloroform vapor, a change in the
opposite direction occurred (Fig. S7a), to give 4B, indicating that
4B is thermodynamically stable. This finding is supported by the
higher melting point (191 °C) of 4B and its larger enthalpy
change (–37.8 kJ mol–1) compared to 4A (183 °C and –28.5 kJ
mol–1) (Table S3). The emission switching by heating and fuming
treatments could be repeated for at least three cycles (Fig. S9).
The vapor-fuming change can be accelerated by pretreatment
of 4A with mechanical grinding. The 4Ag sample produced by
this method showed a rapid change to 4B, within 0.5 h,
compared to the slow change by direct vapor-fuming of 4A for
4 h (Fig. S7a and S7b). Another accelerated change from 4A to
4B was produced by heating 4Ag at 170 °C, below its melting
point (Fig. S7d). In contrast, a trace change was produced by
direct heating of 4A without the pretreatment by mechanical
grinding (Figs. S7c and S18, and Table S3). The DSC trace of 4Ag
showed a weak exothermic peak at 140 °C and a melting point
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 4 of 4
COMMUNICATION
Journal Name
7
8
9
(a) Q.-Y. Yang and J.-M. Lehn, Angew. Chem. Int. Ed., 2014, 53,
4572–4577; (b) D. Li, W. Hu J. Wang, DQO. IZ: h10a.n10g3,V9Xi/eD.w-0MACrt.CicC0lea0Oo2n5,l1inXHe.
Ma and H. Tian, Chem. Sci., 2018, 9, 5709–5715.
S. Park, J. E. Kwon, S. H. Kim, J. Seo, K. Chung, S.-Y. Park, D.-J.
Jang, B. M. Medina, J. Gierschner and S. Y. Park, J. Am. Chem.
Soc., 2009, 131, 14043–14049.
corresponding to 4B but not to 4A, indicating a phase transition
from 4A to 4B at 140 °C (Fig. S18). Mechanical grinding probably
gives rise to a defect structure, and this is the driving force for
the phase transition. This defect structure would be reflected in
the broadened fluorescence band, together with a shift to
longer wavelength (Fig. S7b), and in a slight broadening of the
XRD reflections (Fig. S17). An additional route from 4A to 4B
through the 4W state was obtained by heating 4A at 210 °C
followed by vapor-fuming (Fig. S8). The final fuming step was
performed slowly over 1 day, owing to the high crystallinity of
4W. As a result of the foregoing findings, we conclude that
reversible emission switching is achieved from two different
crystal states, in response to the external stimuli of heating,
vapor-fuming, and mechanical grinding (Fig. 4e).
In conclusion, we have demonstrated that white light can be
obtained from a phosphorescence-fluorescence dual emission
system. Room-temperature phosphorescence can be achieved
by aggregation of a carbazole-pyrimidine conjugate assisted by
the bromine heavy-atom effect. Breaking the symmetry of the
molecular structure provides two crystal polymorphs, one
active and the other inactive in phosphorescence. Active
phosphorescence can be stimulated by heating to increase the
phosphorescence and decrease the fluorescence, thereby
leading to white-light emission. Finally, the two polymorphs and
the white light state can respond to the external stimuli,
resulting in a reversible tricolor switching system. This
reversible change of phosphorescence-fluorescence dual
emission, including white-light emission, is a new finding.
We thank Professor Dr. Ichiro Hisaki (Osaka University) for the
helpful discussion. This work was partially supported by the
Cooperative Research Program of Network Joint Research
Center for Materials and Devices (Institute for Materials
Chemistry and Engineering, Kyushu University, No. 20192016).
Z. Xie, C. Chen, S. Xu, J. Li, Y. Zhang, S. Liu, J. Xu and Z. Chi,
Angew. Chem. Int. Ed., 2015, 54, 7181–7184.
10 (a) S. Xu, R. Chen, C. Zheng and W. Huang, Adv. Mater., 2016,
28, 9920–9940; (b) H. Yuasa and S. Kuno, Bull. Chem. Soc. Jpn.,
2018, 91, 223–229.
11 (a) Z. Yang, Z. Mao, X. Zhang, D. Ou, Y. Mu, Y. Zhang, C. Zhao,
S. Liu, Z. Chi, J. Xu, Y.-C. Wu, P.-Y. Lu, A. Lien and M. R. Bryce,
Angew. Chem. Int. Ed., 2016, 55, 2181–2185; (b) M. Shimizu,
R. Shigitani, M. Nakatani, K. Kuwabara, Y. Miyake, K. Tajima,
H. Sakai and T. Hasobe, J. Phys. Chem. C, 2016, 120,
11631−11639; (c) A. Sakai, E. Ohta, Y. Matsui, S. Tsuzuki and
H. Ikeda, Chem. Phys. Chem., 2016, 17, 4033–4036; (d) Y.
Shoji, Y. Ikabata, Q. Wang, D. Nemoto, A. Sakamoto, N.
Tanaka, J. Seino, H. Nakai and T. Fukushima, J. Am. Chem. Soc.,
2017, 139, 2728−2733.
12 (a) W. Z. Yuan, X. Y. Shen, H. Zhao, J. W. Y. Lam, L. Tang, P. Lu,
C. Wang, Y. Liu, Z. Wang, Q. Zheng, J. Z. Sun, Y. Ma and B. Z.
Tang, J. Phys. Chem. C, 2010, 114, 6090–6099; (b) Y. Gong, L.
Zhao, Q. Peng, D. Fan, W. Z. Yuan, Y. Zhang and B. Z. Tang,
Chem. Sci., 2015, 6, 4438–4444.
13 (a) Z. An, C. Zheng, Y. Tao, R. Chen, H. Shi, T. Chen, Z. Wang,
H. Li, R. Deng, X. Lin and W. Huang, Nat. Mater., 2015, 14,
685–6890; (b) L. Gu, H. Shi, M. Gu, K. Ling, H. Ma, S. Cai, L.
Song, C. Ma, H. Li, G. Xing, X. Hang, J. Li, Y. Gao, W. Yao, Z.
Shuai, Z. An, X. Liu and W. Huang, Angew. Chem. Int. Ed., 2018,
57, 8425–8431
14 (a) L. Xiao and H. Fu, Chem. Eur. J., 2019, 25, 714–723; (b) Z.
Chai, C. Wang, J. Wang, F. Liu, Y. Xie, Y.-Z. Zhang, J.-R. Li, Q. Li
and Z. Li, Chem. Sci. 2017, 8, 8336–8344; (c) H. Wu, Y. Zhou, L.
Yin, C. Hang, X. Li, H. Ågren, T. Yi, Q. Zhang and L. Zhu, J. Am.
Chem. Soc., 2017, 139, 785−791.
15 G.-P. Yong, Y.-M. Zhang, .W.-L. She and Y.-Z. Li, J. Mater.
Chem., 2011, 21, 18520−18522.
16 Z. Mao, Z. Yang, Y. Mu, Y. Zhang, Y.-F. Wang, Z. Chi, C.-C. Lo, S.
Liu, A. Lien and J. Xu, Angew. Chem. Int. Ed., 2015, 54, 6270–
6273.
17 B. Xu, H. Wu, J. Chen, Z. Yang, Z. Yang, Y.-C. Wu, Y. Zhang, C.
Jin, P.-Y. Lu, Z. Chi, S. Liu, J. Xu and M. Aldred, Chem. Sci., 2017,
8, 1909–1914.
Conflicts of interest
There are no conflicts to declare.
18 H. Wu, C. Hang, X. Li, L. Yin, M. Zhu, J. Zhang, Y. Zhou, H. Ågren,
Q. Zhang and L. Zhu, Chem. Commun., 2017, 53, 2661–2664.
19 J.-A. Li, J. Zhou, Z. Mao, Z. Xie, Z. Yang, B. Xu, C. Liu, X. Chen,
D. Ren, H. Pan, G. Shi, Y. Zhang and Z. Chi, Angew. Chem. Int.
Ed., 2018, 57, 6449–6453.
20 Z. He, W. Zhao, J. W.Y. Lam, Q. Peng, H. Ma, G. Liang, Z. Shuai
and B. Z. Tang, Nat. Commun., 2017, 18, 416–423.
21 G. Liu and Y. Zhao, Adv. Sci., 2017, 4, 1700021.
22 L. Yu, Acc. Chem. Res., 2010, 43, 1257−1266.
23 S. Kato, Y. Yamada, H. Hiyoshi, K. Umezu and Y. Nakamura, J.
Org. Chem., 2015, 80, 9076−9090.
24 W. Zhao, Z. He, J. W.Y. Lam, Q. Peng, H. Ma, Z. Shuai, G. Bai, J.
Hao and B. Z. Tang, Chem., 2016, 1, 591–602.
25 J. Yang, X. Zhen, B. Wang, X. Gao, Z. Ren, J. Wang, Y. Xie, J. Li,
Q. Peng, K. Pu and Z. Li, Nat. Commun., 2018, 9, 840.
26 S. Cai, H. Shi, J. Li, L. Gu, Y. Ni, Z. Cheng, S. Wang, W.-w. Xiong,
L. Li, Z. An and W. Huang, Adv. Mater., 2017, 29, 1701244.
27 C. Heroven, V. Georgi, G. K. Ganotra, P. Brennan, F. Wolfreys,
R. C. Wade, A. E. Fernández-Montalván, A. Chaikuad and S.
Knapp, Angew. Chem. Int. Ed., 2018, 57, 7220–7224.
28 J. Yang, Z. Ren, B. Chen, M. Fang, Z. Zhao, B. Z. Tang, Q. Peng
and Z. Li, J. Mater. Chem. C, 2017, 5, 9242–9246.
Notes and references
1
2
3
4
5
6
(a) Y. Kubo and R. Nishiyabu, Polymer, 2017, 128, 257−275; (b)
M. Pan, W.-M. Liao, S.-Y. Yin, S.-S. Sun and C.-Y. Su, Chem.
Rev., 2018, 118, 8889−8935.
(a) K. T. Kamtekar, A. P. Monkman and R. M. Bryce, Adv.
Mater., 2010, 22, 572−582; (b) G. M. Farinola and R. Ragni,
Chem. Soc. Rev., 2011, 40, 3467−3482.
(a) C. Vijayakumar, K. Sugiyasu and M. Takeuchi, Chem. Sci.,
2011, 2, 291–294; (b) X. Wang, J. Yan, Y. Zhou and J. Pei, J. Am.
Chem. Soc., 2010, 132, 15872–15874.
R. Abbel, C. Grenier, M. J. Pouderoijen, J. W. Stouwdam, P. E.
L. G. Leclére, R. P. Sijbesma, E. W. Meijer and A. P. H. J.
Schenning, J. Am. Chem. Soc., 2009, 131, 833–843.
(a) X. Zhang, S. Rehm, M. M. Safont-Sempere and F.
Würthner, Nat. Chem., 2009, 1, 623–629; (b) R. Nishiyabu, Y.
Sugino and Y. Kubo, Chem. Commun., 2013, 49, 9869−9871.
S. Haldar, D. Chakraborty, B. Roy, G. Banappanavar, K. Rinku,
D. Mullangi, P. Hazra, D. Kabra and R. Vaidhyanathan, J. Am.
Chem. Soc., 2018, 140, 13367−13374.
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins