Synthesis and spectroscopic properties of photochromic dithienylethene-functionalized subphthalocyanine conjugate

Article abstract of DOI:10.1142/S108842461650067X

A subphthalocyanine-dithienylethene dyad has been synthesized and characterized by ¹H-, ¹³C-NMR, HR-MS, UV-visible and emission spectroscopy. The results show that photoinduced isomerization of dithienylethene moiety from close-form to opened form can be achieved under visible light using subphthalocyanine as a light-harvesting unit and the fluorescence properties of subphthalocyanine could be modulated by the isomerization state of the dithienylethene moiety.

Full text of DOI:10.1142/S108842461650067X

Journal of Porphyrins and Phthalocyanines
J. Porphyrins Phthalocyanines 2016; 20: 1–8
DOI: 10.1142/S108842461650067X
Published at http://www.worldscinet.com/jpp/
Synthesis and spectroscopic properties of photochromic
dithienylethene-functionalized subphthalocyanine conjugate
Maohu Shi, Jingzhi Chen and Zhen Shen*◊
State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing
University, Nanjing 210093, China
Dedicated to Professor Tomás Torres on the occasion of his 65th birthday
Received 27 January 2016
Accepted 1 March 2016
ABSTRACT: A subphthalocyanine-dithienylethene dyad has been synthesized and characterized by
1H-, 13C-NMR, HR-MS, UV-visible and emission spectroscopy. The results show that photoinduced
isomerization of dithienylethene moiety from close-form to opened form can be achieved under
visible light using subphthalocyanine as a light-harvesting unit and the fluorescence properties of
subphthalocyanine could be modulated by the isomerization state of the dithienylethene moiety.
KEYWORDS: subphthalocyanine, dithienylethene, dyad, photochromic, fluorescence.
that from closed-form to open form was accomplished by
INTRODUCTION
irradiation Q-band of porphyrin moiety, but the change
Dithienylethene (DTE) derivatives [1] are well-known
was very weak in the UV-vis absorption spectrum. And
photochromic compounds, in which diarylethenes with
phthalocyanine-DTE[10–14]complexesdisplayedsolvent-
heterocyclic aryl groups can be interconverted between
dependent and ultraviolet photocontrolable J-aggregation
colorless open and colored closed form under UV and
behavior. Subphthalocyaninatoboron (SubPc) complexes
visible light irradiation, respectively. The spectrum of ring
opened isomer is similar to a substituted thiophene, since
p-conjugation is localized in each thiophene ring. While the
spectrumofringclosedisomershiftstoalongerwavelength,
[15] are ring contracted congener of phthalocyanines
consisting of three N-fused diiminoisoindoline units
arranged around a central four-coordinate boron atom.
Due to the 14 p-electron aromatic system, it shows
because the p-conjugation delocalizes throughout the
intense absorption (550–600 nm) and fluorescence in the
molecule. The structural differences between the two
visible region and makes it possible to be an excellent
states result in a large difference such as luminescence
light-harvesting unit [16, 17]. Due to easily axial ligand
[2–6], color [7], refractive index [8] and conformational
exchange [18], multi-functional subphthalocyanines not
flexibility [9]. Based on the light harvesting ability of
only apply to organic photodetectors [19, 20], molecular
conjugated macrocycle molecules (such as porphyrins,
cages [21, 22], organic solar cells [23–28] and organic
phthalocyanines and subphthalocyanines) in visible region,
light-emitting diodes [29, 30], but also photodynamic
the light energy could be delivered to covalent attached
therapy (PDT) [31, 32] and probes [19, 20]. The previous
DTE unit. Therefore it is possible to modulate the switching
research of subphthalocyanine-DTE [33] complex only
properties of DTE molecule depending on the covalently
illustrated that closed form was obtained with UV light.
linked moieties. Porphyrin-DTE [6] complex showed
In this work close-form and opened form isomerization
of a novel subphthalocyanine-DTE complex was studied
in detail. Importantly, close-form to opened form can be
◊ SPP full member in good standing
achieved under visible light using subphthalocyanine as a
light-harvesting unit.
*Correspondence to: Zhen Shen, email: zshen@nju.edu.cn,
fax: +86-25-89682309
Copyright © 2016 World Scientific Publishing Company

2
M. SHI ET AL.
anhydrous THF (20 mL) was added n-BuLi (1.6 M, 4 mL)
dropwise at -78°C for 30 min. Then B(OBu)3 (1.12 g,
1.32 mL, 4.86 mmol) was added and stirred for 1 h at
-78°C, then for 2 h at room temperature and used for
further reaction without any workup.
EXPERIMENTAL
Synthesis
Preparation of 1,5-bis(5-chloro-2-methylthiene-3-
yl)pentane-1,5-dione (2). 1,5-Bis(5-chloro-2-methyl-
thiene-3-yl)pentane-1,5-dione was prepared in a manner
somewhat similar to the method reported previously
[34]. Anhydrous AlCl3 (8 g, 60 mmol) was added to
dichloroethane (50 mL) at 0°C with vigorous stirring.
Glutaryl dichloride (4.23 g, 25 mmol) in dichloroethane
(5 mL) and 2-chloro-5-methylthiophene 1 (5.97 g, 45
mmol) in dichloroethane (5 mL) were added dropwise
to the solution successively, and the color of the solution
was observed to turn aubergine. The resulting mixture
was stirred for 3 h at room temperature. Then the crude
product was poured into the mixture solution of ice-cold
concentrated hydrochloric acid, and the water layer was
extracted with dichloromethane. The combined organic
phase was neutralized using the saturated aqueous
NaHCO3, then subsequently washed with water and
saturated brine, dried over Na2SO4, and the solvent was
removed under reduced pressure. The crude residue
was purified by silica gel chromatography (1:9 (v/v)
ethyl acetate/petroleum ether) and crystallized from
dichloromethane/methanol to give 2 as a white solid.
Preparation of 2-(4-iodo-phenoxy)tetrahydropyran
(5). 2-(4-Iodo-phenoxy)tetrahydropyran was prepared
in a manner somewhat similar to the method reported
previously [34]. 4-Iodophenol (2.20 g, 10 mmol) was
stirred for 30 min in dry CH2Cl2 (50 mL) and then
pyridinium p-toluenesulfonate (PPTS) (251 mg, 1 mmol)
was added into the solution and stirred for 10 min. 3,4-
Dihydro-2H-pyran (1.37 mL, 15 mmol) in dichloroethane
(5 mL) was added dropwise to the solution and stirred
for 2.5 h at room temperature. The reaction mixture was
diluted with diethyl ether and washed once with saturated
brine. The organic layer was dried over anhydrous
Na2SO4 and the solvent was removed under reduced
pressure. The crude residue was purified by silica gel
chromatography (1:9 (v/v) ethyl acetate/petroleum ether)
to afford 5 as a white solid. Yield 2.9 g (95%). 1H NMR
(500 MHz; CDCl3-d, Me4Si): dH, ppm 7.55 (d, 3J = 8.8 Hz,
2H, Ar), 6.83 (d, 3J = 8.8 Hz, 2H, Ar), 5.38–5.37
(t, 3J = 3.2 Hz, 1H, CH), 3.88–3.83 (m, 1H, CH2), 3.61–
3.57 (m, 1H, CH2), 2.00–1.95 (m, 1H, CH2), 1.85–1.84
(m, 1H, CH2), 1.71–1.56 (m, 4H, CH2). MS (ESI): m/z
305.33 (calcd. for [M + H]+ 305.00).
1
Yield 4.06 g (50%). H NMR (400 MHz; CDCl3-d1,
Preparation of 1,2-bis[2-methyl-5-[(p-((tetrahydro-
pyran-2-yl)oxy)phenyl]-3-thienyl]cyclopentene (6).
1,2-Bis[2-methyl-5-[(p-((tetrahydropyran-2-yl)oxy)
phenyl]-3-thienyl]cyclopentene was prepared in a manner
somewhat similar to the method reported previously
[34]. A mixture of 2-(4-iodo-phenoxy)tetrahydropyran
(1.48 g, 4.86 mmol) and Pd(PPh3)4 (57.7 mg, 0.05 mmol)
in THF (20 mL) was added to 4, and the resulting solution
was stirred for 15 min at room temperature. Then, 2 M
aqueous Na2CO3 (10 mL) was added and the reaction
mixture was refluxed for 30 min. 1,2-Bis[5-(dibutoxybory)-
2-methylthien-3-yl]cyclopentene was added and refluxed
for 12 h. The mixture was cooled to room temperature
and extracted with ether, washed with water, dried over
anhydrous Na2SO4. The solvent was removed under reduced
pressure. The crude residue was purified by silica gel
chromatography [1:9 (v/v) ethyl acetate/petroleum ether] to
afford 5 as a brownish solid.Yield 745 mg (69%). 1H NMR
(400 MHz; CDCl3-d1, Me4Si): dH, ppm 7.41–7.35 (m, 4H,
Ar), 7.02 (d, 3J = 8.8 Hz, 2H, Ar), 6.90 (d, 3J = 7.8 Hz, 2H,
Ar), 6.79 (d, 3J = 8.6 Hz, 2H, thienyl-H), 5.43–5.41 (t, 3J =
3.0 Hz, 1H, CH2), 4.93–4.86 (m, 1H, CH2), 4.00–3.81 (m,
2H, CH2), 3.63–3.63 (m, 2H, CH2), 2.84 (t, J = 7.4 Hz, 4H,
CH2), 2.14–1.93 (m, 10H, CH2), 1.93–1.80 (m, 4H, CH2),
1.75–1.58 (m, 6H, CH3).
Me4Si): dH, ppm 7.18 (2H, s, thienyl-H), 2.86 (4H, t,
3J = 7 Hz, CH2), 2.66 (6H, s, CH3), 2.03–2.10 (2H, m,
CH2). MS (ESI): m/z 361.17, 383.25 (calcd. for [M + H]+
360.99, [M + Na]+ 382.97).
Preparation of 1,2-bis(5-chloro-2-methylthien-
3-yl)cyclopentene (3). 1,2-Bis(5-chloro-2-methylthien-
3-yl)cyclopentene was prepared in a manner somewhat
similar to the method reported previously [34]. A mixture
TiCl4 (THF)2 (4 g, 11.6 mmol) and activated Zn dust
(1.14 g, 17.4 mmol) in dry THF (50 mL) was stirred and
heated to reflux for 3 h under argon. After cooling to
room temperature, 2 (2.09 g, 5.8 mmol) in THF (5 mL)
was added to the solution and heated to reflux for 4 h.
The reaction mixture was cooled to room temperature
and a 20% aqueous solution of NaHCO3 was added. The
mixture was filtered. The filter cake was extracted with
ethyl ether and the organic layer was dried over Na2SO4.
The solvent was removed under reduced pressure. The
crude residue was purified by silica gel chromatography
(petroleum ether) and crystallized from dichloromethane/
methanol to give 3 as a white solid. Yield 917 mg (48%).
1H NMR (400 MHz; CDCl3-d1, Me4Si): dH, ppm 6.57
3
(2H, s, thienyl-H), 2.71 (4H, t, J = 7.4 Hz, CH2), 2.66
(6H, s, CH3), 1.98–2.05 (2H, m, CH2). MS (ESI): m/z
330.42 (calcd. for [M + H]+ 329.00).
Preparation of 1,2-bis[2-methyl-5-(4-hydroxy-
phenyl)-3-thienyl]cyclopentene (7). 1,2-Bis[2-methyl-5-
(4-hydroxyphenyl)-3-thienyl]cyclopentene was prepared
in a manner somewhat similar to the method repor-
ted previously [34]. A solution of 6 (612 mg, 1 mmol)
Preparation of 1,2-bis[5-(dibutoxybory)-2-methyl-
thien-3-yl]cyclopentene (4). 1,2-Bis[5-(dibutoxybory)-
2-methylthien-3-yl]cyclopentene was prepared in a
manner somewhat similar to the method reported previ-
ously [34]. To a solution of 3 (800 mg, 2.43 mmol) in
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SYNTHESIS AND SPECTROSCOPIC PROPERTIES OF PHOTOCHROMIC DITHIENYLETHENE-FUNCTIONALIZED
3
and pyridinium p-toluenesulfonate (PPTS) (20 mg,
0.08 mmol) in MeOH−CH2Cl2 (20 mL) was stirred at
room temperature over night. The solvent was removed
under reduced pressure. The crude residue was purified
by silica gel chromatography (1:1 (v/v) ethyl acetate/
petroleum ether) to afford 7 as a brownish solid. Yield
otherwise indicated. The NMR spectra were measured
on a Bruker 600 or 500 or 400 MHz spectrometer.
UV-visible absorption spectra were measured on a
Shimadzu UV-2550 double beam spectrophotometer.
Fluorescence emission spectra were measured on a
Hitachi F-4600 fluorescence spectrophotometer with
a 150 W-xenon arc lamp used as the light source
with a working voltage of 700 V. The emission
slit was set at 5 nm. Fluorescence quantum yield
(FF) was determined by the comparative method
and the absorbance values of the solutions were
between 0.04 and 0.05 at the excitation wavelength.
Fluorescence lifetime was measured using a time
correlated single photon counting (TCSPC) setup
(Single Photon Avalanche Diodes, PDM series,
PicoQuant GmbH). The excitation source was a diode
laser (LDH-P-C-405 with 10 MHz repetition rate,
70 ps pulse width). MALDI-TOF mass spectra (MS)
were collected using Bruker Daltonics autoflexII
MALDI-TOF MS spectrometer. The MS analysis was
carried out on a Thermo scientific LCQ Fleet mass
spectrometer (Thermo, USA) with ESI and the X
calibur 2.1 software work station. ESI-Q-TOF-MS was
collected using Model 6540 Agilent high definition
quadrupole time-of-flight mass spectrometer.
1
222 mg, (50%). H NMR (400 MHz; CDCl3-d1, Me4Si):
3
dH, ppm 7.37 (d, J = 8.6 Hz, 4H, Ar), 6.90 (s, 2 H,
3
3
thienyl-H), 6.80 (d, J = 8.6 Hz, 4H, Ar), 2.82 (t, J =
7.4 Hz, 4H, CH2), 2.06 (q, 3J=7.4 Hz, 2H, CH2), 1.98 (s, 6H,
CH3). MS (ESI): m/z 443.25 (calcd. for [M – H]- 443.11).
Preparation of boron subphthalocyanine chloride
(8). Boron subphthalocyanine chloride was prepared
in a manner somewhat similar to the method reported
previously [35]. In a 50 mL two-neck round bottom
flask, 2 mL of 1.0 M solution of BCl3 (234 mg,
2 mmol) in dichloromethane was added to a solution of
phthalonitrile (256 mg, 2 mmol) in p-xylene (15 mL).
The mixture was heated to remove the dichloromethane
through distillation using a Dean–Stark condenser. After
distillation the flask was heated to reflux for 3 h under
argon. The mixture was then cooled and the solvent was
removed under reduced pressure. The resultant solid
was thoroughly washed with methanol until the filtrate
became colorless to afford 8 as a golden solid. Yield
1
158 mg (55%). H NMR (400 MHz, CDCl3-d1, Me4Si):
dH, ppm 8.90–8.93 (m, 6H, Ar), 7.95–7.97 (m, 6H, Ar).
MS (MALDI-TOF): m/z 430.931, 395.067 (calcd. for
[M + H]+ 430.091, [M – Cl]+ 395.122).
RESULTS AND DISCUSSION
Preparation of subphthalocyanine-dithienylethene
dyad (9). Subphthalocyanine-dithienylethene dyad was
prepared in a manner somewhat similar to the method
reported previously [33]. In a 15 mL pressure vessel,
compound 7 (66.7 mg, 0.15 mmol) was added to a
solution of compound 8 (21.5 mg, 0.05 mmol) in dry
toluene and heated at 130°C for 16 h. The solvent was
evaporated under reduced pressure. The resultant solid
was thoroughly washed with methanol until the filtrate
became colorless. The crude residue was purified by
neutral alumina column chromatography (THF) to afford
Synthesis and characterization
The synthetic procedure for 1,2-bis[2-methyl-5-(4-
hydroxyphenyl)-3-thienyl]cyclopentene 7 and the novel
subphthalocyanine-dithienylethene dyad 9 was outlined
in Scheme 1. 7 was prepared starting from 2-chloro-5-
methylthiophene 1, which was reacted with glutaryl
dichloride in dichloroethane to give 1,5-bis(5-chloro-2-
methylthiene-3-yl)pentane-1,5-dione2.2wastreatedwith
TiCl4(THF)2 and Zn in THF to get dithienylcyclopentene
3 which was reacted with B(OBu)3 and n-BuLi to give
bis-(boronic) ester 4 followed by the Suzuki coupling
reaction with protected p-iodophenol 5 and Pd(PPh3)4 to
obtain intermediate 6. After removal of tetrahydropyran-
protected group in MeOH−CH2Cl2, diphenol 7 was
reacted with boron subphthalocyanine chloride 8 in dry
toluene (closed ampoule) to afford the target compound
9. 7 and 9 were characterized by 1H NMR and UV-visible
1
9 as a cardinal red solid. Yield 42 mg (60%). H NMR
(400 MHz, CDCl3-d1, Me4Si): dH, ppm 8.56 (s, 1H,
Ar-OH), 8.87–8.84 (m, 6H, Ar), 8.03–8.01 (m, 6H, Ar),
7.30 (d, 3J = 8.6 Hz, 2H, Ar), 7.00–6.97 (m, 2H, thienyl-
3
3
H), 6.93 (d, J = 8.6 Hz, 2H, Ar), 6.74 (d, J = 8.6 Hz,
2H, Ar), 5.31 (d, 3J = 8.4 Hz, 2H, Ar), 2.80–2.71 (m, 4H,
CH2), 2.00–1.95 (m, 2H, CH2), 1.81 (d, 3J = 5.6 Hz, 6H,
CH3). 13C NMR (125 MHz, (CD3)2SO-d6, Me4Si): dC,
ppm 157.37, 151.66, 138.88, 136.95, 134.54, 130.82,
130.61, 126.70, 125.97, 122.80, 122.50, 119.92, 116.20,
38.52, 22.70, 14.38. HR-MS (ESI) m/z 861.2253 (calcd.
for [M + Na]+ 861.2254).
1
absorption. In the H NMR spectra, the benzene ring
protons of 7 were located at 7.37 and 6.80 ppm as typical
double peaks, and the protons on the thiophene moiety
were at 6.90 ppm as a singlet peak. While the benzene
ring protons of 9 on the dithienylethene (DTE) moiety
were located at 7.30, 6.93, 6.74 and 5.31 ppm as typical
double peaks, the protons on the thiophene moiety were
at 7.00–6.97 ppm. Molecular ion peaks were observed
by MS at m/z 443.25 [M – H]- for 7 and 861.2253 [M +
Na]+ for 9.
Materials and equipment
All reagents were obtained from commercial
suppliers and used without further purification, unless
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M. SHI ET AL.
N
N
N
B
S
N
S
Cl
O
S
HO
N
N
(1)
(9)
i
Cl
N
N
O
O
N
B
N
vi
Cl
N
N
S
Cl
S
(2)
ii
(8)
S
Cl
S
Cl
S
OH
S
HO
(3)
(7)
iii
v
I
O
O
(5)
iv
S
S
O
B(OBu)2
(BuO)2B
S
O
S
O
O
(4)
(6)
Scheme 1. Synthetic route for the subphthalocyanine-dithienylcyclopentene dyad (9). (i) Glutaryl dichloride, AlCl3,
dichloroethane, argon atmosphere; (ii) TiCl4(THF)2, Zn, THF; (iii) n-BuLi, B(OBu)3, THF; (iv) Pd(PPh3)4, aqueous
Na2CO3, THF; (v) pyridinium p-toluenesulfonate(PPTS), CH3OH–CH2Cl2; (vi) toluene, reflux, 16 h
Fluorescence spectroscopy, quantum yield
and lifetime
A and AStd are the absorbance values, and n and nStd are
the refractive indices of the solvents used. Cresyl violet
perchlorate (in methanol) (FF = 0.54) [31, 38] was used
as the standard, exciting at 530 nm. The fluorescence
quantum yield of compound 9 is approximately 0.086
in DMSO. The absorption and fluorescence spectra of
9 in DMSO are shown in Fig. 1. Figure 2 contains the
TCSPC trace for 9 in toluene. A double-exponential
luminescence decay curve with an average tF value of
0.77 ns was observed.
Fluorescence quantum yields (FF) are determined by
the comparative method, using Equation 1 [36, 37]:
Std
2
.
.
F A
.
n
ΦF = ΦSFtd
(1)
FStd A (n
)
Std
2
.
where F and FStd are the integrated areas under the
emission curves for the sample and standard, respectively,
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SYNTHESIS AND SPECTROSCOPIC PROPERTIES OF PHOTOCHROMIC DITHIENYLETHENE-FUNCTIONALIZED
5
Fig. 2. Fluorescence decay curve of 9 in toluene (top) and the
residual of the fit (bottom)
Fig. 1. Normalized absorption and emission spectral of 9 in
DMSO (lex = 530 nm)
Fig. 3. 1H NMR changes of 9 before (top) and after (bottom) UV irradiation (312 nm, 800 mW.cm-2) for 2 h in DMSO-d6
NMR spectra characterization
of photoisomerization process
Fig. 3, a remarkable change occurred for the protons on
the thiophene, which shifted from 7.00–6.97 ppm to 6.54–
6.51 ppm.Theprotons benzenering onthe dithienylethene
(DTE) moiety shifted slightly to the low-field, while the
protons of the cyclopentene core on the DTE moiety and
methyl group moved to high-field after photocyclization.
These changes indicate that part of the open isomer was
When a DMSO-d6 solution of 9 was irradiated by UV
light (312 nm), distinct differences in H NMR signals
were observed between the open form and closed form
both in the high-field and low-field regions. As shown in
1
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M. SHI ET AL.
Fig. 4. 1H–1H COSY spectra of subphthalocyanine-dithienylethene dyad 9 in DMSO-d6
transformed into the closed isomer upon UV irradiation.
By integration in 1H NMR approximately 75% of closure
isomer existed in the photostationary state. 1H–1H COSY
spectra are measured to ascertain the correlation among
these protons. Two dimensional spectra protons region
of 9 is depicted in Fig. 4, where the additional lines are
drawn to specify the correlated peaks. The signals located
at 7.30, 6.93, 6.74 and 5.31 ppm were assigned as protons
from the benzene ring linked to the DTE moiety, while
the signals at 2.80–2.71, 2.00–1.95 and 1.81 ppm were
assigned as the protons from the cyclopentene core on the
DTE moiety and methyl group, respectively.
ring isomer (Fig. 5). The ring closed form exhibits
a maximum absorption at l = 524 nm whereas the
absorption of the ring opened form is located in the
region between ca. 325 and 400 nm.
The photoisomerization between open ring form
and closed ring form of 9 was studied using dilute
sample solutions in DMSO. As can be seen in Fig. 6(a),
conversion of open form to closed form photostationary
state (PSS) was accomplished by irradiating open
form solution with UV light at l = 312 nm, while the
back conversion of the closed form to the open form
was actively driven using visible light at l = 570 nm.
Formation of the closed form caused remarkable
absorption increases in the regions between ca. 340 and
540 nm. In addition, the absorption band of the closed
isomer overlapped with the absorption maximum of the
subphthalocyanine unit was at 565 nm.
Luminescence spectra characterization
of photoisomerization process
The photoisomerization of 7 was investigated in dilute
DMSO solution. Irradiation with UV light (312 nm)
caused the expected spectral change due to an increasing
conversion of the colorless open form to the red closed
Dyad 9 exhibits emission due to the subphthalocyanine
moiety and the respective luminescence maximum
is located at 587 nm. As can be seen in Fig. 6(b), the
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SYNTHESIS AND SPECTROSCOPIC PROPERTIES OF PHOTOCHROMIC DITHIENYLETHENE-FUNCTIONALIZED
7
l = 312 nm, and recovering open form by irradiation at
l = 570 nm could bring back the fluorescence intensity.
The quenching of the fluorescence of 9 by closed form
could be due to the resonant energy transfer [6, 39–46] or
electron transfer [47, 48].
CONCLUSION
Insummary,anovelsubphthalocyanine-dithienylethene
complex has been synthesized by using the corresponding
subphthalocyanine and 1,2-bis[2-methyl-5-(4-hydroxy-
phenyl)-3-thienyl]cyclopentene as the precursors in an
axial exchange reaction. The dyad has been characterized
by NMR, UV-visible absorption, and high resolution MS
spectra. The photoisomerization process of SubPc-DTE
dyad is investigated by UV-visible spectra by irradiating
open form solution at l = 312 nm and closed form solution
at l = 570 nm. Significantly, the decrease and recovery in
the fluorescence intensity of the SubPc moiety were also
observed during photoisomerization of SubPc-DTE dyad,
which verified that the fluorescence emission of SubPc-
DTE dyad could be modulated by the isomerization state
of the DTE moiety.
Fig. 5. The UV-vis spectral changes upon the photo-
isomerization of 7 in DMSO
Acknowledgements
This work was supported by the National Natural
Science Foundation of China (no. 21371090).
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Fig. 6. (a) The UV-vis spectral changes upon the
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