An optic/proton dual-controlled fluorescence switch based on novel photochromic bithienylethene derivatives

Article abstract of DOI:10.1002/cjoc.201200139

A simple method for the synthesis of new bithienylethenes bearing a functional group on the cyclopentene moiety is developed. Three new photochromic compounds (4a, 4b, 4c) have been successfully synthesized through this simple method, and exhibit good photochromic properties with alternate irradiation of ultraviolet and visible light. Furthermore, the fluorescence of compound 4a, which bears a quinoline unit on the cyclopentene, can be modulated via optic and proton dual inputs. Upon excitation by 320 nm light, 4a emits a strong fluorescence at 404 nm. After irradiation with 254 nm light, the emission intensity is reduced due to the fluorescence resonance energy transfers (FRET) from quinoline unit to bithienylethene unit. Moreover, on addition of H ⁺, the fluorescence is quenched completely due to the protonation of the quinoline. In addition, both the FRET and protonation process are reversible, which indicates a potential application in molecular switches and logic gates.

Full text of DOI:10.1002/cjoc.201200139

FULL PAPER
DOI: 10.1002/cjoc.201200139
An Optic/Proton Dual-Controlled Fluorescence Switch based
on Novel Photochromic Bithienylethene Derivatives
Zhang, Jiaqi(张佳琦)
Jin, Jiayu(靳家玉)
Zhang, Junji(张隽佶)
Zou, Lei*(邹雷)
Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University
of Science & Technology, Shanghai 200237, China
A simple method for the synthesis of new bithienylethenes bearing a functional group on the cyclopentene moi-
ety is developed. Three new photochromic compounds (4a, 4b, 4c) have been successfully synthesized through this
simple method, and exhibit good photochromic properties with alternate irradiation of ultraviolet and visible light.
Furthermore, the fluorescence of compound 4a, which bears a quinoline unit on the cyclopentene, can be modulated
via optic and proton dual inputs. Upon excitation by 320 nm light, 4a emits a strong fluorescence at 404 nm. After
irradiation with 254 nm light, the emission intensity is reduced due to the fluorescence resonance energy transfers
(FRET) from quinoline unit to bithienylethene unit. Moreover, on addition of H+, the fluorescence is quenched
completely due to the protonation of the quinoline. In addition, both the FRET and protonation process are reversi-
ble, which indicates a potential application in molecular switches and logic gates.
Keywords photochromism, diarylethenes, dual-control, fluorescence
Introduction
structing fluorescent probes and chemosensors. The
combination between 8-quinolinol derivatives and di-
arylethenes is promising in developing a dual-control
fluorescent switch system. Herein, we synthesized a
novel molecule diarylethene 4a linked with a fluoro-
phore 8-methoxyquinoline (8-MQ) on the cyclopentene,
and its optic and proton dual-controlled switch proper-
ties were investigated.
Photochromic compounds have attracted consider-
able attention in recent years[1-3] because of their poten-
tial application in optical data storage[4-6] and molecular
switches.[7-9] Among all photochromic compounds, di-
arylethenes are regarded as the best candidates for such
devices, owing to their excellent thermal stability, fa-
tigue resistance, and rapid response.[10-12] During the
past decades, many achievements on the modification of
diarylethene family have been carried out, such as ex-
panding the branched chain of the aryl,[13-17] and chang-
ing the center ethene bridge.[18-21] However, the modifi-
cation of the perhydrogencyclopentene is rarely seen. In
this paper, a simple route for the synthesis of several
novel bithienylethenes bearing a functional group on the
cyclopentene moiety with two simple initial materials is
developed. The photochromism of diarylethenes 4a, 4b
and 4c are shown in Scheme 1.
Because of their extensively application in chemo-
sensors[22,23] and biological imaging,[24-26] fluorescent
photochromic diarylethenes are among the top study list
of scientific researchers.[27,28] The regulation of the
fluorescence in one molecule using multi-ways, such as
proton, light and electron, is the ultimate aim of the sci-
entists.[29-32] As we all know, 8-quinolinol derivatives are
excellent fluorophores, and they can respond to the pro-
tons and metal ions, which are widely used in con-
Scheme 1 Photochromism of diarylethenes 4a, 4b and 4c
R
R
254 nm
447 nm
Cl
S
S
Cl
S
Cl
Cl
S
4aO
4bO
4cO
4aC
4bC
4cC
O
O
N
N
a
R =
b
R =
R =
c
*
E-mail: zoulei@ecust.edu.cn; Tel.: 0086-021-64252758; Fax: 0086-021-64252758
Received February 14, 2012; accepted April 8, 2012; published online XXXX, 2012.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.201200139 or from the author.
Chin. J. Chem. 2012, XX, 1—7
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Zhang et al.
FULL PAPER
Experimental
General methods
6.81 (d, J＝8.7 Hz, 2H), 3.87—3.82 (m, 1H), 3.77 (s,
3H), 3.16—3.06 (m, 4H), 2.67 (s, 6H); 13C NMR δ:
193.81, 158.25, 147.90, 135.56, 134.95, 128.32, 126.76,
125.30, 114.01, 55.24, 48.05, 36.00, 15.98; HRMS (ESI)
calcd for C22H21O3S2Cl2 (M ＋H) 467.0309, found
467.0303.
5-Chloro-2-methyl-3-acetylthiophene (1) and 5-alde-
hyde-8-hydroxyquinoline were synthesized according to
the literature.[33,34] Other reagents were commercially
available and used without further purification. 1H NMR
and 13C NMR spectra were recorded on a Bruker
AM-400 spectrometer in CDCl3 solutions using tetra-
methylsilane as the internal standard. High resolution
mass spectra (HRMS) were recorded on a Waters LCT
Premier XE spectrometer using standard conditions (ESI,
70 eV). UV-Vis absorption spectra were measured on a
Varian Cary 500 UV-Vis spectrophotometer. Fluores-
cence emission spectra were measured on a Varian Cary
Eclipse Fluorescence spectrophotometer. The optical
switch experiments were carried out using a photo-
chemical reaction apparatus with a 200 W Hg lamp.
Fluorescence quantum yields were recorded on Fluoro-
Max-4 spectrofluorometer with a quanta-Φ integrating
sphere (Horiba Jobin-Yvon).
5-Aldehyde-8-methoxyquinoline (2a) To a stirred
solution of 5-aldehyde-8-hydroxyquinoline (1.73 g, 10
mmol) in DMF (100 mL) at room temperature, K2CO3
(2.76 g) was successively added in batches. After re-
fluxed for 1 h, MeI (1.56 g, 11 mmol) dissolved in DMF
(50 mL) was dropwise added to the reaction mixture.
Continued refluxing for 3 h, the reaction mixture was
cooled, evaporated, and poured into water. The mixture
was extracted with CH2Cl2 (50 mL×3), washed with
water, and dried with anhydrous Na2SO4. After distilla-
tion of solvent, the residue was chromatographed on
silicon using petroleum ether∶ethyl acetate (1∶1) as
eluent. Compound 2a was separated in 70% yield (1.31
g). m.p. 113—115 ℃; 1H NMR δ: 4.20 (s, 3H),
7.17—9.69 (m, 5H), 10.18 (s, 1H).
Diketone (3c) Compound 3c was prepared by an
analogous method similar to that used for 3a and ob-
tained as a white powder in a yield of 40%. m.p.
116—118 ℃; 1H NMR δ: 8.53—8.49 (m, 2H),
7.22—7.18 (m, 2H), 7.17 (s, 2H), 3.97—3.90 (m, 1H),
3.27—3.07 (m, 4H), 2.59 (s, 6H); 13C NMR δ: 192.58,
152.80, 150.06, 148.46, 134.46, 126.46, 125.63, 122.88,
46.64, 35.61, 16.06; HRMS (ESI) calcd for
C20H18NO2S2Cl2 (M＋H) 438.0156, found 438.0165.
1,2-Bis(2-methyl-5-chloro-3-thienyl)-4-(8-metho-
xyl-5-quinolyl)cyclopentene (4a) 5 mL THF and 173
mg Zn powder were put into a two-neck Schlenk tube
under a nitrogen atmosphere. 0.62 mL TiCl4 (5.3 mmol)
was added very cautiously by a glass syringe under 0
℃. The solution turned yellow and was refluxed for 3 h.
After that was cooled in an ice bath, 3a (0.223 g, 0.44
mmol) was added in portions. Then the mixture was
refluxed overnight, subsequently quenched with 10%
K2CO3 (20 mL), filtered, and the filtrate was extracted
with diethyl ether (20 mL×3). The combined organic
phase was washed with H2O (50 mL), saturated NaCl
solution (50 mL), and dried over anhydrous Na2SO4.
The solvent was removed under vacuum. The product
was purified by column chromatography using petro-
leum ether∶ethyl acetate (1∶2) as the eluent to obtain
the target compound 4a (50 mg, 24%). 1H NMR δ: 8.96
(dd, J＝4.1, 1.5 Hz, 1H), 8.44 (dd, J＝8.6, 1.4 Hz, 1H),
7.48 (dd, J＝8.6, 4.1 Hz, 1H), 7.43 (d, J＝8.1 Hz, 1H),
7.01 (d, J＝8.1 Hz, 1H), 6.61 (s, 2H), 4.29—4.21 (m,
1H), 4.09 (s, 3H), 3.32—2.95 (m, 4H), 1.94 (s, 6H); 13C
NMR δ: 154.07, 148.75, 146.28, 134.21, 133.84, 133.33,
133.27, 131.90, 127.53, 126.48, 125.64, 123.24, 121.36,
107.00, 55.96, 45.51, 37.38, 14.29; HRMS (ESI) calcd
for C25H22NOS2Cl2 (M＋H) 486.0520, found 486.0511.
1,2-Bis(2-methyl-5-chloro-3-thienyl)-4-(p-metho-
xyl-phenyl)cyclopentene (4b) Compound 4b was
prepared by an analogous method similar to that used
for 4a and obtained as a colorless solid in a yield of 90%.
1H NMR δ: 7.23 (d, J＝8.6 Hz, 2H), 6.87 (d, J＝8.6 Hz,
2H), 6.60 (s, 2H), 3.80 (s, 3H), 3.66—3.56 (m, 1H),
3.14—2.83 (m, 4H), 1.92 (s, 6H); 13C NMR δ: 157.99,
138.27, 134.46, 133.64, 133.36, 127.69, 126.59, 125.40,
113.92, 55.32, 46.36, 41.83, 14.29; HRMS (ESI) calcd
for C22H21OS2Cl2 (M+H) 435.0411, found 435.0413.
1,2-Bis(2-methyl-5-chloro-3-thienyl)-4-(pyridyl)-
cyclopentene (4c) Compound 4c was prepared by an
analogous method similar to that used for 4a and ob-
tained as a colorless solid in a yield of 60%. 1H NMR δ:
8.56—8.52 (m, 2H), 7.23—7.20 (m, 2H), 6.60 (s, 2H),
3.67—3.57 (m, 1H), 3.21—2.85 (m, 4H), 1.92 (s, 6H);
13C NMR δ: 155.34, 149.79, 134.00, 133.86, 132.98,
126.39, 125.73, 122.27, 45.30, 41.65, 14.31; HRMS
Diketone (3a) To a stirred solution of 2a (0.94 g, 5
mmol) in ethanol (40 mL) and NaOH aqueous solution
(40 mL, 10%) was dropwise added the solution of
5-chloro-2-methyl-3-acetylthiophene (2.1 g, 15 mmol)
in ethanol (50 mL) at 0 ℃, then stirred for 18 h at room
temperature. After evaporated the solvent, the mixture
was extracted with CH2Cl2 (50 mL×3), washed with
water, and dried with anhydrous Na2SO4. After distilla-
tion of solvent, the residue was purified on a silica gel
column using petroleum ether∶ethyl acetate (1∶2) as
the eluent to obtain the target compound 3a (0.906 g,
1
35%). m.p. 250—252 ℃; H NMR δ: 8.93—7.00 (m,
5H), 7.18 (s, 2H), 4.72—4.64 (m, 1H), 4.07 (s, 3H),
3.32—3.19 (m, 4H), 2.49 (s, 6H); 13C NMR δ: 193.47,
154.19, 148.89, 148.19, 140.39, 134.72, 131.68, 131.40,
127.30, 126.61, 125.50, 123.84, 121.69, 107.02, 55.94,
47.78, 35.96, 15.91; HRMS (ESI) calcd for
C25H22NOS2Cl2 (M＋H) 518.0418, found 518.0414.
Diketone (3b) Compound 3b was prepared by an
analogous method similar to that used for 3a and ob-
tained as a white solid in a yield of 40%. m.p. 100—102
1
℃; H NMR δ: 7.17 (s, 2H), 7.14 (d, J＝8.7 Hz, 2H),
2
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Chin. J. Chem. 2012, XX, 1—7

An Optic/Proton Dual-Controlled Fluorescence Switch based on Novel Photochromic Bithienylethene
(ESI) calcd for C20H18NS2Cl2 (M+H) 406.0258, found
406.0258.
shown in Figure 1a. The maximum absorption of com-
pound 4aO is observed at 243 nm. Upon irradiation with
254 nm light, the colorless solution of 4a gradually turns
yellow due to the appearance of a new visible absorption
band centered at 447 nm, which is attributed to the for-
mation of the closed-ring form 4aC. The photo-statio-
nary state is attained after about 7 min. Alternatively, the
yellow solution could be bleached to colorless upon ir-
radiation with visible light (λ＞440 nm), indicating that
4aC returned to the initial state 4aO. Similarly, the col-
orless solutions of 4b and 4c can turn yellow on irradia-
tion with 254 nm UV light, and the color can also dis-
appear upon irradiation with the same visible light (λ＞
440 nm). The corresponding spectra are shown in
Results and Discussion
Synthesis and characterization
In this work, three new photochromic diarylethenes
with functional groups on the cycloethenes were pre-
pared by a simple method and their photochromic be-
haviors were investigated in detail. The synthetic route
used to obtain diarylethene 4 is shown in Scheme 2.
5-Chloro-2-methyl-3-acetylthiophene (1) was synthe-
sized according to the literature method. Aldehyde 2a
was prepared by the methylation of 5-aldehyde-8-hydro-
xyquinoline with MeI. The diketone compound 3 was
synthesized from compound 1 and the corresponding
aldehyde 2 in the presence of NaOH in ethanol. Ac-
cording to a common McMurry reaction, cyclization of
these diketones in the presence of Zn and TiCl4 in anhy-
drous THF gave the corresponding target bithienyle-
thenes 4a, 4b and 4c. The products were purified by
silica-gel-column chromatography. In this way, novel
diarylethenes with multi-modifiable sites in both aryl
and cyclopentene moieties can be easily synthesized,
acquiring only two steps. All of the target compounds
1
were characterized by H NMR, 13C NMR spectro-
scopes and HRMS.
Scheme 2 Synthetic route for the target compounds
O
O
CH3CH2OH
+
H
NaOH
R
Cl
Cl
S
2a - 2c
1
O
R
O
Zn/TiCl4/THF
Cl
S
S
3a - 3c
R
Cl
Cl
S
S
4a - 4c
O
O
N
N
c
a
b
R =
R =
R =
Photochromism of compound 4
Diarylethene 4 can undergo a reversible photochro-
mic reaction in MeCN upon alternating irradiation with
UV and visible light. Changes in the absorption spectra
of compound 4a induced by photo irradiation at room
Figure 1 Changes in the absorption spectra of compounds 4a
(a), 4b (b) and 4c (c) in MeCN at room temperature (2.5×10－
5
mol•L－1). Inset (a): color change of compound 4a upon alternat-
ing irradiation with UV/Vis light in MeCN.
temperature in MeCN (C＝2.5×10－ mol•L－1) are
5
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Zhang et al.
FULL PAPER
Figure 1b and Figure 1c.
work, the emission band (350—500 nm) of quinoline
fluorophore in the open-ring state has certain overlap
with the absorption band (400—500 nm) of the closed-
ring isomer of diarylethene 4a, and the FRET process
can occur. As a result, the fluorescence intensity of qui-
noline was quenched to 15% by the larger π-conjugation
system of the ring-closed isomer. Furthermore, we
measured the fluorescence quantum yields, and the ab-
solute quantum yields of 4aO and 4aC were 0.28 and
0.03, respectively, which were coincident with the
FRET process. The fatigue resistance of 4a was also
investigated in air at room temperature. Solution of 4a
in MeCN was alternately irradiated with UV (λ＝254
nm) and visible light (λ＞440 nm). As shown in Figure
2b, bithienylethene 4a was rather stable in the fluores-
cence emission spectra at photo-stationary state towards
photochemical deposition.
The thermal stability of these diarylethenes was also
investigated. Putting the solutions of diarylethenes 4a,
4b and 4c in MeCN at room temperature in the dark for
more than one week, no changes in their colors and
spectra were observed. Moreover, The cyclization and
cycloreversion quantum yield of these compounds were
measured. The photochromic properties of diarylethenes
4a, 4b and 4c are summarized in Table 1. From these
data, it can be seen that the photochromic features (in-
cluding the absorption maxima, molar absorption coef-
ficients, and quantum yields) of these diarylethenes are
different, which indicates that the different functional
groups on the cyclopentene moiety will affect the
photochromic properities, and the further work is in
progress.Because the diarylethene 4a can emit a strong
fluorescence upon excitation with 320 nm light, we put
emphasis on the switchable fluorescence properties of
4a below.
Table 1 Absorption parameters and photochromic reactivity of
diarylethenes 4a, 4b and 4c in MeCN (2.5×10－5 mol•L－
)
1
λo,maxa/nm
λc,maxb/nm
Φc
Conversion
at PSS
－
－
1
1
Compd [ε/(L•mol • [ε/(L•mol •
cm－1)]
243
cm－1)]
448
Φo-c
Φc-o
4a
4b
4c
0.17
0.12
61%
68%
72%
(5.13×104) (3.94×103)
228
(2.78×104) (4.94×103)
236 445
(2.36×104) (4.77×103)
446
0.20
0.24
0.11
0.09
a Absorption maxima of open-ring isomers. b Absorption maxima
of closed-ring isomers. c Quantum yields of cyclization reaction
(Φo-c) and cycloreversion reaction (Φc-o), respectively.
Optic fluorescence switch of compound 4a
8-Quinolinol derivatives, which are excellent fluoro-
phores, are widely used in OLED and electrolumines-
cence. 8-MQ is strongly fluorescent because of the ex-
isting of the methoxy group preventing the intramolecu-
lar proton transfer process in the excited state compared
with 8-hydroxyquinoline.[10] The fluorescence spectra of
the diarylethene 4a in MeCN at room temperature are
shown in Figure 2a. In MeCN, diarylethene 4a exhibited
strong emission intensity at 404 nm when excited at 320
nm. After irradiation with 254 nm UV light, the fluores-
cence intensity of 4a decreased enormously due to the
formation of ring-closed isomer as a fluorescence quen-
cher. It can also be seen in the inset that the absorption
band of ring-closed form 4aC is well overlapped with
the emission band of the quinoline fluorophore, which
may lead to an efficient FRET process. FRET is a typi-
cal fluorescence energy transfer process from an excited
fluorophore (donor) to another chromophore unit (ac-
ceptor) which required that the characteristic absorption
band of the acceptor overlapped with the emission of the
donor via a link distance of 1—10 nm.[31,35,36] In our
Figure 2 Fluorescent changes (a) and switch cycles (b) of com-
pound 4a upon alternate irradiation with UV/Vis light in MeCN
－
(2.5×10－ mol•L 1) at room temperature. Inset: the overlapping
5
between the absorbance spectrum of the ring-closed form of 4a
and the emission spectrum of quinoline fluorophore.
Proton controlled fluorescence switch of compound
4a
On account of the existing of the N atom in 8-MQ,
4a is responsive to the acid and base. Addition of 1
equiv. trifluoromethanesulfonic acid (TFMSA) to 4a in
MeCN solution, the maximum absorption shifts from
243 to 256 nm. Meanwhile, the absorbance in the region
of the 8-MQ absorption band (270—320 nm) decreases
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An Optic/Proton Dual-Controlled Fluorescence Switch based on Novel Photochromic Bithienylethene
substantially, and a new absorption band is observed at
ca. 379 nm. All the above changes are attributed to the
protonation of 8-MQ. Moreover, the absorption curve
can be recovered with the addition of equal equiv.
triethylamine (TEA) (Figure 3).
Figure 3 Absorption changes of compound 4aO (2.5×10－
5
mol•L－1) in MeCN upon alternating addition with TFMSA and
TEA.
The emission intensity of compound 4a can also be
tuned with proton. The emission spectra of 4a with ex-
citation at 320 nm in MeCN solution after alternating
additions of TFMSA and TEA are shown in Figure 4a.
On addition of TFMSA gradually (0.2 equiv. each time)
up to 1 equiv., the strong fluorescence was quenched
completely because of the protonation of the fluoro-
phore. The gradual back addition of TEA regenerated
the unprotonated form of 8-MQ, while the fluorescence
intensity was restored to its initial state. Figure 4b also
shows the reversible modulation of the fluorescence
emission intensity of compound 4a with alternating ad-
ditions of TFMSA and TEA, which indicates that the
acid/base-controlled fluorescent switch cycles between
4aO and 4aO' are fully reversible and can be repeated
many times in the same solution without appreciable
reduction in fluorescence intensity.
Figure 4 Fluorescent changes (a) and switch cycles (b) of com-
pound 4a (2.5×10－5 mol•L－1) induced by alternate additions of
TFMSA and TEA in MeCN excited at 320 nm at room tempera-
ture.
One should be noted that the photochromic behavior
of 4a is not disturbed upon the addition of TFMSA. Af-
ter irradiation with UV light, the protonated 4a can still
undergo photocyclization, and shows the reversible
change when irradiated with visible light (Figure 5).
Accompanied by the changes of the absorption curve,
the solution alters its color from colorless to yellow.
Figure 5 Absorption changes of compound 4a in the presence
of 1 equiv. of TFMSA (2.5×10－5 mol•L－1) in MeCN upon al-
ternating irradiation with 254 nm ultra-violet light and visible
light (λ＞440 nm).
Logic gate operation of compound 4a
and the chemical reversibility of the UV/Vis and
acid/base switching can be used to obtain an INHIBIT
logic gate, using the 254 nm UV light (I1) and the base
TEA (I2) as the inputs, and fluorescent emission signals
(ΔF404) as the data outputs. An INHIBIT logic gate is a
two-input AND gate with one input carrying a NOT
gate.[37] We set non-fluorescent 4aO' as the initial state,
and the output is “1” when the fluorescence intensity is
more than 50% of 4aO. Without irradiation of UV light
(I1＝0) and addition of TEA (I2＝0), 4aO' did not emit
Owing to the connection with the fluorophore
8-methoxyquinoline, 4a displays strong fluorescence
intensity at 404 nm when excited at 320 nm. After irra-
diation with 254 nm UV light, the fluorescence intensity
was decreased because of the formation of ring-closed
isomer. Also, on addition of H＋, the fluorescence was
quenched completely due to the protonation of the qui-
noline. The structure and fluorescence changes are
shown in Figure 6. This special spectroscopic behavior
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Zhang et al.
FULL PAPER
Figure 6 Structure and fluorescence changes by the optic and proton dual stimuli.
fluorescence (Output＝0, form 4aO'). If the UV light
was turned on (I1＝1) while the whole system remained
in the acid condition (I2＝0), the fluorescence at 404 nm
was still off (Output＝0, form 4aC'). On another occa-
sion, keeping off the UV light (I1＝0) and adding 1
equiv. of TEA into the system (I2＝1), the emission at
404 nm increased significantly to show a highly fluo-
rescent state (output＝1, form 4aO). Finally, we both
turned on the UV light (I1＝1) and added 1 equiv. of
TEA consequently (I2＝1), the fluorescence dropped
below the standard again (output＝0, form 4aC). This
leads to a UV irradiation and protonation modified IN-
HIBIT logic gate. The output (ΔF404) and the truth table
for the INHIBIT gate are exhibited in Figure 7. Because
of the full reversibility of the photoisomerization and
protonation/deprotonation processes, the current IN-
HIBIT gate can operate repeatedly.
I1 254 nm
I2 TEA
Output ΔF404
Molecule structure
0
1
0
1
0
0
1
1
0 (low, 0)
0 (low, 0)
1 (high, 100%)
0 (low, 15%)
4aO'
4aC'
4aO
4aC
Fluorescence changes in the film
Figure 7 Output (ΔF404) and the truth table for the INHIBIT
In order to have a better application in practice, we
also studied the fluorescent properties in polymeric ma-
trices of diarylethene 4a. Compound 4a (2 mg) and
poly(methyl methacrylate) (PMMA) was dissolved in
chloroform (2 mL), and thin film was obtained by
spin-coating the solution onto a quartz plate with a spin
rate of 1000—2000 r/min. Compound 4a displayed high
fluorescence intensity at 390 nm in PMMA film when
excited at 245 nm, which is 14 nm blue-shifted than the
emission in MeCN solution. This difference from the
fluorescence in MeCN solution may be attributed to the
polar effect of the polymer matrix and the stabilization
of molecular arrangement in solid state. While upon
irradiation with 254 nm UV light, fluorescence intensity
of 4a in PMMA decreases, which is similar to that in
gate. The dashed line indicates the detection limit (50%).
MeCN solution (Figure 8a), indicating that the photo-
chromic properties of 4a are conserved in the solid state.
Dipping the film in the TFA atmosphere for 2 min, the
fluorescence exhibits significant quenching (Figure 8b),
and the fluorescence recovers when dipped in the TEA
atmosphere, which are also corresponding to the
changes in MeCN solution. All the phenomena above
promise a possible application in photo-switchable de-
vices.
Conclusions
In summary, we have synthesized a series of novel
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Chin. J. Chem. 2012, XX, 1—7

An Optic/Proton Dual-Controlled Fluorescence Switch based on Novel Photochromic Bithienylethene
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Figure 8 Fluorescence emission spectra changes of 4a doped in
PMMA with the irradiation of alternant 254 nm UV and visible
light (a) and putting in the TFA/TEA atmosphere (b).
photochromic molecules using a simple method, which
exhibit good photochromic properties. The high fluo-
rescence of diarylethene 4a can be reversibly controlled
by both UV/Vis light and protonation/deprotonation. In
this way, we have successfully realized the dual-control
of a fluorescent molecule, which can be used to con-
struct an INHIBIT logic gate. Moreover, the photo-
chromic and fluorescence behaviors of 4a doped in the
PMMA film are similar to that in the solution, which
indicates a potential application in devices. Further in-
vestigations of applications in devices are currently in
progress.
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Acknowledgement
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R.; Howe, R.; Edington, R. A.; Percival, E.; Herington, E. F. G.;
Kynaston, W.; Shingu, T.; Uyeo, S.; Yajima, H.; Dobson, N. A.;
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This work was supported by NSFC/China (No.
21190033), the National Basic Research 973 Program
(No. 2011CB808400) and Scientific Committee of
Shanghai.
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Chin. J. Chem. 2012, XX, 1—7
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