Binary Supramolecular Chirality “1/0” Switched by Hierarchical Photoisomerization of a Flower-Like Compound with a Binaphthol Core and Alkyl-Functionalized Azobenzene Side Chains

Article abstract of DOI:10.1002/cplu.202000049

Chiral supramolecular assemblies are abundant in nature, but controlling the chirality of artificial systems still remains a challenge. In this work, we developed a system where supramolecular chirality can be controlled between chiral and achiral states, namely a chiral “1/0” switch using a flower-like azobenzene compound with a binaphthol core. Upon photoisomerization by ultraviolet irradiation, the terminal alkyl tails envelop the chiral “centre” with a reduction in the dihedral angle of the binaphthol moiety from 76.1° to 61.4°, like “closing petals”. In the doped liquid crystal E7 matrix, this hierarchical conformational transition prevents the transfer of chirality to the host liquid crystal, resulting in a degradation from cholesteric phase (HTP value: 13.84 μm^?1) to an achiral nematic phase.

Full text of DOI:10.1002/cplu.202000049

Accepted Article
Title: Binary Supramolecular Chirality “1/0” Switched by Hierarchical
Photoisomerization of Flower-like Compound with a Binaphthol
Core and Alkyl-Functionalized Azobenzene Side Chains
Authors: Hao Li, Jiaxin Hou, Jinglun Liao, Yancong Feng, Ben L.
Feringa, Jiawen Chen, and Guofu Zhou
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Binary Supramolecular Chirality “1/0” Switched by Hierarchical
Photoisomerization of Flower-like Compound with a Binaphthol
Core and Alkyl-Functionalized Azobenzene Side Chains
Jiaxin Hou[a],[b], Jinglun Liao[a],[b], Yancong Feng[a],[b], Ben L. Feringa[a],[b], Jiawen Chen[a],[b]*, Hao Li[a],[b]*
and Guofu Zhou[a],[b]
,
[
a]
J. Hou, J. Liao, Prof. Y. Feng, Prof. B. L. Feringa, Prof. J. Chen, Prof. H. Li, and Prof. G. Zhou
Guangdong Provincial Key Laboratory of Optical Information Materials and Technology & Institute of Electronic Paper Displays,
South China Academy of Advanced Optoelectronics,
South China Normal University, Guangzhou 510006, China
E-mail: Lihao@m.scnu.edu.cn
[
b]
J. Hou, J. Liao, Prof. Y. Feng, Prof. B. L. Feringa, Prof. J. Chen, Prof. H. Li, and Prof. G. Zhou
National Center for International Research on Green Optoelectronics,
South China Normal University, Guangzhou 510006, China
E-mail: j.chen@m.scnu.edu.cn
Abstract: Chiral supramolecular assemblies are abundant in nature,
additives, are needed to realizing the chirality control process.
Light is usually regarded as one of the best options because of its
high accurance, non-invasiveness and feasiblity.[1,4] In most
cases, light-actived compound, such as azobenzene, is
and serve as inspiration for most of the man-made systems, but the
control on chirality of artificial systems still remains a challenge. In this
work, we developed a system where supramolecular chirality can be
controlled between chirality and achirality, namely chiral “1/0” using a
flower-like azobezene compound. Upon the photoisomerization by
ultraviolet irradiation, terminal alkyl tails envelop the chiral “centre”
with decreasing dihedral angle of the binaphthol moiety from 76.1° to
introduced into liquid crystal (LC) molecule 5-7], chiral dopant
[
[8-13]
,
polymer[14], and other systems, to obtain photo-controllability by
its light-triggered conformational transformation. Other
photochromic groups, e.g., diarylethenes 15], dithienylethenes[16,17],
and oligobipyridyl ligands[ , are aslo embedded to dynamically
self-assemble or disassemble into various helicates under light
irradiation. In most of the cases, direct chiral reversal between R
[
18]
61.4°, like “closing petals”. In the doped E7 matrix, this hierarchical
conformational transition prevents from transferring charity to the host
liquid crystal, resulting in a degradation from cholesteric phase (HTP
-1
and S[9-11], cis- and trans-[5,7,8,11], or others[13,16,17], as well as
value: 13.84 μm ) to achiral nematic phase.
amplification[
14,19]
, are focused. Chiral on–off switching of the
whole supramolecular system induced by light are with few
examples.
Introduction
In this work, we designed and synthesized a flower-like binaphthyl
compound bearing azobenzene moities, and used it as a chiral
dopant to switch the supramolecular chirality of the liquid crystal
system. By ultraviolet light (UV) irradiation, the azobenzene units
of the compound can induce dramatic trans–cis isomerization, as
a result, the conformation of the compound changes. The side
chains of the compound envelop chiral binaphthyl “centre”, and
the whole molecule appears like a flower “closing”, and the
interaction with the surrounding achiral LC hosts are therefore
covered and the whole system shows no supramolecular chirality.
Reversibly, visible light (Vis) can make it “blossoming”, as opuntia
flower behaves in day and night, and the chirality of the LC system
is regained.
In nature, chiral supramolecular assemblies are abundant in
numerous creatures from microscopic units (e.g., DNA, protein,
and biomembrane) to macroscopic structures (e.g., plant tissues,
arthropod cuticle, and sea shells) and these chiral structures are
bases of a lot of beautiful propeties. Therefore, chirality is crucial
to structure, conformation, property, function. Supramolecular
chirality of the whole system comes from interactions between
chiral and achiral components, and the nonsymmetrical
arrangement of achiral molecules via noncovalent intereations.1
It is very important to develop artificial chiral supramolecular
systems for applications in areas of chemistry, biology, physics
and materials.[2]
There are two key issues for supramolecular chirality: (1) transfer
of chirality from molecular scale along all the length scales to
macroscopical scale; (2) control of chirality for modulating
macroscopic properties. In particular, the latter is viewed as an
important challenge that is “still in its infancy” but “exciting in the
future”.[3] Due to complexity and flexibility of noncovalent
interactions, it is difficult to change the self-assembly via direct
conformational control of chiral units inside the supramolecular
system. Some external factors such as solvent, temperature,
sonication, photoirradiation, redox potential, and chemical
Results and Discussion
In this work, we integrated chiral moiety and photosensitizer in
one compound to form a flower-like photo-controllable switch. For
the choice of chiral moiety, cholesterol[
20]
and binaphthyl
[21]
derivatives are two mostly used moieties. As reported previously,
binaphthyl derivatives can induce large βm value up to hundreds
-1 [22, 23],
um
and behaved much better than cholesterol-modified
azobenzenes[ . In the molecular structures of these binaphthyl
24]
derivatives, steric hindrance may induce the carbon–carbon
1
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ChemPlusChem
10.1002/cplu.202000049
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bridged bond between 1 and 1’ position rotating to form different
dihedral angles (θ) of the two naphthyl rings, and therefore induce
some changes in helical structure and therefore affect the helical
irradiated by 365 nm light (A); irradiated by 455 nm light (B);
absorbance-changing curve at 360 nm upon alternating
irradiation of 365 and 455 nm light with duration of 3 minutes (C).
[
25-27]
twisting power (HTP, evaluated by βm value).
As
is more
[28-30[
chromophore moiety, the selected azobenzene
fulgides[
31]
diarylethenes[32-34],
Photochemical properties of compound
1
were firstly
commonly
used
than
,
spiropyrans[ , and other photochromic moieties
35[
[36,37]
characterized in dimethyl sulfoxide (DMSO) solution by UV-Vis
spectroscopy. Figure 1A showed a strong absorption band with
the maximum absorption wavelength (λ max) of 360 nm. Upon UV
irradiation, this band decreased in intensity and two new adjacent
bands appeared simultaneously in the region around 325 and 450
nm. Subsequent irradiation with 455 nm weakened the newly
formed bands in intensity again, and the original band reappeared
. It can
rapidly undergo trans–cis isomerization by ultraviolet (UV)
exposure (~360 nm), to change the helical twisting power (HTP,
value) of the host LC system.[
38-40]
evaluated by β
m
We introduced
four photochromic azobenzene groups on both sides of the
binaphthyl centre, to form a highly symmetric and flower-like
dopant (i.e. compound 1 in Scheme 1) for the control of the
(
see Figure 1B), which is a characteristic behavior of the
supramolecular chirality of LC system.
azobenzene compound. The variation in absorbance at 360 nm
was repeated three times via. alternating irradiation of 365 and
4
55 nm light (see Figure 1C). The photochemical switching
process can be reproduced several times without significant
fatigure.
1H-NMR spectroscopic study
Scheme 1 Synthetic route of compound 1
UV-Vis spectroscopic study
Figure 2 Progressive formation and conversion of the compound
1
stereoisomers in the form of 1H-NMR spectral changes with
increasing irradiation time at 365 nm.(A) (500 MHz; 298K; CD
Enlarged views of partial 1H-NMR spectra (500 MHz; 298K;
CD Cl ): PSS mixture of E-1 after irradiated at 365 nm for 1.5
hours (B), and PSS mixture of Z-1 after irradiated at 455 nm for
.5 hours (C).
2 2
Cl )
2
2
Figure 1 UV-Vis spectra of the DMSO solution of compound 1
with the fixed concentration of 1.7×10-5 mol·dm at 25 C:
-3
o
1
2
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1
The switching process of compound 1 was monitored by H-NMR
spectrospcopy in CD Cl as well (see Figure 2A). The spectra
The switching process of compound 1 was investigated by CD
spectroscopy as depicted in Figure 4 as well. UV irradiation
resulted in the disappearance of the CD signal around 360 nm,
and the appearance of a new CD signal around 440 nm. This
variation within the region from 250 to 550 nm indicates that, the
photoisomerization of the side azobenzene moieties alters the
dihedral angle of binaphthol centre. Vis irradiation can have a
reverse effect on the conformation of compound 1. When
alternated irradiation applied, the CD signal can be regained, in
2
2
were recorded every 5 minutes upon UV light irradiation till no
further change was observed. Starting from the solution
containing only the trans-isomer (E-isomer) of compound 1,
irradiation of 365 nm light resulted in appearance of new signals
in both the aromatic and the aliphatic region. The NMR signals
with the shift are corresponding to the protons adjacent to the
azobenzene unit that undergo the photo-induced isomerization.
There were some observed changes in the aliphatic region. In
1
accordance with the changing process of the H-NMR curve in
detail, the triplet at 4.10 ppm (i.e. H
to 3.95 ppm under UV irradiation (see Figure 2B). The integrals
of the H signal at 4.10 and 3.95 ppm indicates that the trans-cis
E→Z) photostationary state (PSS) is above 88%. Subsequent
visible light (Vis) irradiation of the sample at PSS resulted in 60%
reversion of the cis-(Z) stereoisomers to E azobenzene units (see
Figure 2C). The incomplete Z→E switch may attribute to the
above-mentioned fatigue of UV absorbance.
a
in Figure 2A) shifted upfield
Figure 1C (see Figure 4B). But the unavoidable molecular
fatigue still hinders complete conformational recovery.
a
(
Concentration dependence
Kinetic analyses
Figure 3 360 nm Absorbance-time curves of the DMSO solution
of compound 1 with the fixed concentration of 1.7×10-5 mol·dm-3
at different temperatures (A), and related linear fitting according
to Eyring kinetic equation (B).
Figure 3A shown UV-Vis absorbance-time variations during the
heat-induced Z-to-E isomerization. By Eyring plot analysis, the
activation parameters for thermal cis-trans (Z→E) inversion of
compound 1 were obtained (see Figure 3B): the enthalpy of
-1
activation (ΔH) is 165.73 kJ mol , and the entropy of activation
ΔS) is 187.08 J mol- K . According to Gibbs equation, the free
1
-1
(
-1
energy of activation (ΔG) at 293.15 K is 110.89 kJ mol and
correspond to a half-life of the thermal step at 293.15 K (i.e. 20 ℃)
1
817.2 hours. It demonstrates that the Z isomers of compound 1
is very stable at room temperature.
1
Figure 5 H-NMR spectra (500 MHz, 298K, CD
2
Cl
2
; A) and UV
CD spectroscopic study
absorbances of compound 1 with different concentration (356 nm,
DCM; B).
Compound 1 was prepared as a series of solution ranging from
0 to 2.5 mmol•L-1 and all the chemical shifts of H-NMR signals
1
4
remain unchanged (see Figure 5A), indicating no self-
aggregation. Similarly, UV absorbance at 356 nm shown with
good linear relationship at lower concentration. Both results set a
solid stage for the application in LC within a wide range of
concentrations.
HTP transition
Figure 4 Experimental CD spectra of E-1 and Z-1 isomers of
compound 1 in DCM (A) and related CD signal-changing curve at
3
21 nm upon alternating irradiation of 365 and 455 nm light with
In CLC system, compound 1 was used as photosensitive chiral
dopant, to tune the helicity and the phase state of the host LC by
the interaction with the host and the guest molecules. The HTP
every irradiation period of 3 minutes (B).
3
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(
ꞵ) of compound 1 and its changes under photoirradiation were
Figure
7
Computational simulation of compound 1’s
determined by the Grandjean–Cano method. By measurement,
conformations after 365 and 455 nm photoirradiation: half
symmetrical molecule (A), whole symmetrical molecule (B) and its
photo-switched ‘blossoming-closing’ mechanism.
the initial value of HTP on weight percentage in cholesteric E7 is
-1
1
3.84 μm . Once UV light was irradiated for one hour, all the
stripes completely disappeared (see Figure 6A). It indicates that
the cholesteric phase of E7 change into nematic phase. In other
words, the chirality of the whole CLC system disappears after UV
irradiation. This change can be ascribed to the trans-cis (E→Z)
isomerization of the azobenzene moieties. Reversibly, when Vis
light was irradiated for one hour, these stripes reappeared and the
measured HTP was 10.95 μm . The recovered ꞵ value is lower
than the initial one because of the PSS of the azobenzene. Just
like the above mentioned, here is incomplete recovery originated
from molecular fatigue.
In order to study the mechanism in more detail, we performed
DFT calculation to simulate the conformational change of
compound 1. The naphthalene and two side azobenzene
branches were entitled as three vertexes of triangle shape,
repsepctively. The original symmetrical compound 1 acts like a
blossoming “quatrefoil” with the “centre” dihedral angle of 76.1°.
When UV light irradiates, the symertirc chiral dopant can
isomerize from trans- to cis- conformation, and the benzene rings
overturn and get close to the central naphthalene ring. At this
conformation, the terminal alkyl chains seem to envelop this
-1
“
centre” like “closing petals”. At the same time, the dihedral angle
between two naphthalene ring decreases to a smaller angle of
1.4°.
6
Figure 6. POM images of stripe-wedge Grandjean-Cano cell filled
with 2 wt.% of compound 1 in E7 upon UV (365 nm) and Vis (455
nm) irradiation.(A) Reflection color POM images of 5 μm-thick
planar cell filled with 2 wt.% of compound 1 in E7 upon UV (365
nm) and Vis (455 nm) irradiation.(B)
Furthermore, a mixture of 2 wt.% of compound 1 in E7 was
capillary-filled into a 5 μm thick planar glass cell coated with a
polyimide alignment layer. As shown in Figure 6B, the LC cell
went from initial purple color to dark green color at PSS upon UV
irradiation. UV light irradiation leads to the degradation of
cholesteric E7 system, as well as a sharp decrease of LC
reflection. The newly form state is thermally stable and can be
further photochemically switched back with Vis irradiation. The
regain of the color is the result of the reversed cis-trans (Z→E)
isomerization upon Vis irradiation.
Scheme 2 Chiral “1/0” photo-switching mechanism of compound
1 in E7.
Based on the above analyses, it can be found that, both the
chromophore moiety and its alkyl tails are far away from the
binaphthol “centre” before UV irradiation. Akagi et al. previously
reported that, E7 with biphenyl moiety can interact with binaphthol
by π–π interaction, suggesting to align parallelly to the axis of
binaphthol.[ These intermolecular interactions may enhance the
compatibility between the guest chiral dopants and the host LC,
Mechanism analyses
41]
and therefore induce chirality transferring to host LC for
modulating HTP.[
42-44]
In our case, after UV irradiation, 4
azobenzene moieties isomerized from E to Z, pushing the
chromophore moiety and the terminal alkyl tails to align crowdedly,
so E7 molecules were extruded out of the enveloped binaphthol
“
“
centre”. The weakened π–π interaction between E7 and chiral
centre” makes the host LC far from the guest dopant molecules.
Thus, the chirality of dopant cannot be transferred to the host LC,
and resulted in a dramatic decrease of HTP. As a result, the
doped CLC system changes from CLC phase to nematic phase,
along with increasing pitch to infinity and the HTP appears to be
0
(see Scheme 2).
We use
a
single-molecular photoswitch to control the
supramolecular chirality and achirality of the LC system. The
chromophoric switch we used can transit its own chirality to the
host LC, and when irradiation is applied, it can drive the linked
alkyl tails to envelop the chiral center so the chirality transferring
to host LC is prevented. In other words, the conversion between
4
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“
blooming” and “closing” state is a reversible process and control
solution was neutralized with saturated sodium carbonate
the LC system from chiral and “achiral” .
(
Na
aqueous phase with ethyl acetate (100 mL). Anhydrous sodium
sulfate (Na SO ) powders were added to dry the organic phase
2 3
CO ) solution. The product was extracted twice from the
2
4
Conclusion
and then removed by filtration. Ethyl acetate was removed under
vacuum to yield 2 as light-yellow solid (10 g, 50 mmol; 76%).
A symmetric photo-responsive chiral dopant, bearing axial
binaphthol moiety as chiral center and azobenzene moieties as
chromophore, was designed and synthesized in this work. Based
on various characterizations, the chiral dopant shown reversible
photoisomerization process and the Z-isomer is thermally stable
at room temperature. In CLC system, a reversible change from
cholesteric to nematic phase can be controlled when UV/Vis light
was irradiated. The HTP and the pitch of CLC system can be
controlled at the same time. Thus its optical property, e.g.
reflectivity, can be reversiblly switched by photoirradiation.
(
b) Synthesis
of
methyl
(3):
3,5-bis((E)-(4-
Methyl 3,5-
hydroxyphenyl)diazenyl)benzoate
diaminobenzoate (2) (5 g, 25 mmol) was dissolved in an aqueous
solution of diluted hydrochloric acid (HCl; 0.75 M, 80 mL). After
cooled to 0 C, the resulting solution was gradually mixed with 16
2
mL of iced solution of sodium nitrite (NaNO ; 4.5 g, 65 mmol) by
dropwise addition. Subsequently, the obtained brown diazotized
mixture was added dropwise into a mixture of phenol (11.32 g,
1
o
o
20 mmol), NaOH (4.8 g, 120 mmol) and water (150 mL) at 0 C
for coupling. The crude product was neutralized with HCl (1 M)
aqueous solution, and then filtered and washed with distilled
water. The final orange-red product was pufified by column
According to computational simulation and molecular geometry
optimization, photo-responsive azobenzene group can envelope
the chiral “centre” like “closing petals” using terminal alkyl tails and
induce the decreased dihedral angle of binaphthol moiety during
E→Z isomerization. The reported single-molecular binary
photoswitch in this work can control the supramolecular chirality
2
chromatography (SiO , pentane/EA=1:3), to yield 3 as orange-red
solid (1.22g, 3.25 mmol; 13%)
“
1/0” of the whole system, and we are now working on developing
advanced LC optics.
(c) Synthesis
hexyloxy)phenyl)diazenyl)benzoate (4): 1.22 g (3.25 mmol) of
the orange-red precipitate (3) was added to a mixture of
potassium carbonate (K CO ; 2.01 g, 14.5 mmol), bromohexane
1.2g, 7.2 mmol) and tetrabutylammonium iodide (TBAI; 0.3 g, 0.8
of
methyl
3,5-bis((E)-(4-
(
Experimental Section
2
3
(
mmol) in 30 mL of acetonitrile at nitrogen atmosphere. The
reaction mixture was heated at reflux overnight. After cooled down
to room temperature, the organic layer of the mixture was filtrated.
After the removal of solvent, the residue was dissolved in
dichloromethane (DCM). The organic phase was washed three
Materials: All the chemicals were provided by Sigma˗Aldrich
without any further purity. Vertically aligned polyimide (PI; DL-
4
018) was purchased from Shenzhen Dalton Electronic Materials
Coo., Ltd.. And all organic solvents were analyticly pure, and dried
or redistilled before using. For column chromatography, silica gel
times with brine, dried with anhydrous Na
concentrated under reduced pressure. The obtained orange oil
2
was purified by column chromatography (SiO ,
2 4
SO powders, and
(
Silicycles Siliaflash P60, 40˗60 μm, 230˗400 mesh) was used in
all cases. Separation was carried out on silica gel 60 (silicon
dioxide, SiO ; Merk, Germany) and kieselguhr F254 (celite; Merk,
2
Germany) for thin-layer chromatography (TLC), and visualization
was accomplished by stain.
pentane/DCM=2:1). The solvent was removed in vacuum to yield
4 as a yellow solid (870 mg, 1.63 mmol; 50%).
In Grandjean-Cano wedge method, the wedge cells (KCRK-07,
tanθ = 0.0196) were provided by Japan EHC Co., Ltd.. For the
generation of the planar anchoring, a glass substrate was
thoroughtly cleaned and spin-coated with PI alignment layer.
Another cover glass plate was sticked together with the spacing
distance of 5 μm fixed by the UV-curing spacer (Suzhou
Nanomicro Technology Co., Ltd), to construct the LC cell.
(d) Synthesis
of
3,5-bis((E)-(4-
(hexyloxy)phenyl)diazenyl)benzoic acid (5): Compound 4 (130
mg, 0.238 mmol) was hydrolyzed in the mixed solution of sodium
hydroxide (NaOH; 0.26 M, 6 mL), tetrahydrofuran (THF; 10 mL)
and methanol (10 mL) by vigorous stirring at reflux, and the
process was monitored with TLC. After cooled down to room
temperature, the mixture was neutralized with HCl (1 M) aqueous
solution. After removal of the organic solvent under reduced
pressure, 20 mL of DCM was added. The organic layer was
seperated . Compound 5 was obtained as a red solid after
removal of the organic solvent. The crude product was used
without further purification.
Synthesis: The target molecule, [1,1'-binaphthalene]-2,2'-diyl
bis(3,5-bis((E)-(4-(hexyloxy)phenyl)diazenyl)benzoate),
was
synthesized in a five-step process as shown in Scheme 1. All the
detailed procedures are given below.
(
(
e) Synthesis of [1,1'-binaphthalene]-2,2'-diyl bis(3,5-bis((E)-
4-(hexyloxy)phenyl)diazenyl)benzoate) (1): solution of
(
a) Synthesis of methyl 3,5-diaminobenzoate (2): 3,5-
A
Diaminobenzoic acid (10 g, 65 mmol) and sulfuric acid (5 mL)
were mixed in methanol (75 mL). The solution was heated at
reflux overnight. After the mixture was cooled down to room
temperature, the solvent was removed by rotary evaporation. The
residue was diluted with 50 mL of ultrapure water. Afterward, the
compound 5 (125 mg, 0.235mmol) in chloroform (20 mL) was
added to the mixture of (R)-(+)-1,1'-bi-2-naphthol (33.4 mg, 0.117
mmol), dicyclohexylcarbodiimide (DCC; 60.56 mg, 0.294 mmol)
and 4-dimethylaminopyridine (DMAP; 8.9 mg, 0.0735 mmol)
under the protection of dry argon. The mixture was stirred at room
5
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FULL PAPER
temperature overnight. After removal of the solvent, the residue
the 111 Project. All the calculation and modelling were supported
by Chem Cloud Computing of Beijing University of Chemical
Technology.
was
purified
by
column
chromatography
2
(SiO ,
pentane/DCM=2:3). The organic solvent was removed in vacuum
to yield 1 as a red solid (40 mg, 0.035 mmol; 30%).
Keywords: azobenzene • chirality • host-guest systems • liquid
1
crystals • photoswitches
Characterizations: H˗NMR spectra were recorded on a Varian
AMX-500 (500 MHz), a Varian AMX-400 (400 MHz). Kinetic and
concentration-dependent 1H˗NMR studies were recorded on a References
Varian AMX-500 (500 MHz) in dichloromethane-d (CD Cl ). The
2 2
corresponding chemical shifts were reported in δ values (ppm)
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; 1H δ=7.25, 13C δ=77.2): H
1
[2] L.Zhang, T.Wang, Z.Shen, M. Liu, Adv. Mater. 2016, 28, 1044–1059.
[3] S.M.Morrow, A.J.Bissette, S.P.Fletcher, Nat. Nanotechnol. 2017, 12, 410.
relative to deuterochloroform (CDCl
3
1
3
1
δ=5.32, C δ=54. For H˗NMR, the signals were assigned as
following: singlet (s), doublet (d), double doublet (dd), triplet (t),
quartet (q) and multiplet (m).
[
[
4] Z.Lv, Z.Chen, K.Shao, G.Qing, T.Sun, Polymers. 2016, 8, 310.
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6021.
[
[
[
[
[
6] S.W.Choi, H.Takezoe, Soft Matter. 2016, 12, 7937–7942.
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Proton magnetic resonance spectroscopy (HMRS) was measured
using a double focusing high-resolution mass spectrometer (MS-
9
02, AEI). Ultraviolet-visible (UV-Vis) spectra were obtained with
JASCO V-630 spectrophotometer in a 1 cm quartz cuvette at
room temperature. Solution circular dichroism (CD) spectra were
[11] S.Iamsaard,
S.P.Fletcher, N.Katsonis, Nat. Chem. 2014, 6, 229.
[12] H.Nishikawa, D.Mochizuki, H.Higuchi, Y.Okumura,
ChemistryOpen. 2017, 6, 710–720.
S.J.Aßhoff,
B.Matt,
T.Kudernac,
J.J.Cornelissen,
recorded on
a JASCO J-715 spectropolarimeter at room
H.Kikuchi,
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7
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Table of Contents
Please ensure an appropriate text (60-80 words).
Upon ultraviolet light-induced isomerization, terminal alkyl tails of flower-like azobenzene compound
envelop the chiral “centre” with decreasing dihedral angle of the binaphthol moiety, like “closing petals”.
This variation in hierarchical conformation prevents from transferring charity from the guest molecule to
the host liquid crystal matrix, resulting in a supramolecular chirality 0. And the transition is reversible
under visible light irradiation.
8
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