Photoreversible current ON/OFF switching by the photoinduced bending of gold-coated diarylethene crystals

Article abstract of DOI:10.1039/c5cc00355e

Gold-coated diarylethene crystals exhibited photoreversible bending upon alternating irradiation with ultraviolet (UV) and visible light. The bending behavior can be well explained by the extended bimetal model, which we propose here. Moreover, we have de

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Photoreversible current ON/OFF switching by photoinduced bending of
gold-coated diarylethene crystals
Daichi Kitagawa and Seiya Kobatake*
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
5
DOI: 10.1039/b000000x
Gold-coated diarylethene crystals exhibited photoreversible
improve strength of the crystals, such as fatigue and fracture.
bending upon alternating irradiation with ultraviolet (UV) 50 Although the photochromism of diarylethenes in the crystalline
2
7-29
and visible light. The bending behavior can be well explained
by the extended bimetal model which we propose here.
Moreover, we have demonstrated that it can be used as an
actual electrical circuit photoswitching.
phase has been so far reported,
crystals have never been investigated.
such coated diarylethene
Here we report on the photoinduced bending behavior of the
gold-coated diarylethene crystals. The crystal of 1,2-bis(5-
methyl-2-phenyl-4-thiazolyl)perfluorocyclopentene (1a) before
and after gold deposition shows the photoreversible crystal
bending upon alternating irradiation with UV and visible light.
The crystal thickness dependence of the photoinduced bending
behavior is also investigated before and after gold deposition. The
bending behavior is analyzed by Timoshenko’s bimetal model
and its extended bimetal model. Moreover, we established the
photoreversible current ON/OFF switching using the gold-coated
diarylethene crystal. These results provide not only a new useful
strategy to design for photomechanical actuators but also a new
practical use of photomechanical crystals.
1
0
5
6
6
5
0
5
Photomechanical motions of photoresponsive molecular crystals
have been attracted much attention because they enable us to
convert light energy into mechanical energy in direct without any
contact and electric wires. Various compounds which show
photomechanical behavior in crystal have been reported for
1
2
2
3
3
4
4
5
0
5
0
5
0
5
1
-10
11
12-16
diarylethene,
aniline,
1
furyl fulgide, azobenzene,
salicylidene-
1
7,18
19-22
23
anthracene carboxylates,
,2-bis(4-pyridyl)ethylene
imidazolinone,
4-chlorocinnamic acid,
benzylidenedimethyl-
2
4
salt,
2
5
and so on. Among these compounds,
diarylethene derivatives are the most promising compounds
functioned as photomechanical actuators because of their rapid
2
6,27
response, fatigue resistance, and thermal stability.
There are
various photomechanical motions of diarylethene crystals, such
2,5,10
8
2-4,7,8,10
6
as contraction,
expansion, bending,
fragmentation,
9
and twisting. Among these photomechanical motions, the
bending behavior is the most common motion. The quantitative
and theoretical analysis of the photoinduced bending behavior is
required. We have reported the crystal thickness dependence of
1
a
1b
UV
8
,10
the photoinduced bending behavior of diarylethene crystals.
It
was experimentally clarified that the speed of the bending
depends on the thickness of the crystal. When the thickness is
thin, the crystal is bent rapidly and largely. In order to discuss the
photoinduced bending behavior in the easy-handled model, we
have introduced the Timoshenko’s equation which is known as
Fig. 1. Molecular structure and the photoinduced crystal bending
behavior of diarylethene 1a.
2
,30
8
,10
70
Rod-like crystals of diarylethene 1a
recrystallization from n-hexane. The crystal shape, face indices,
and molecular packing are shown in Fig. S1. Fig. 1 shows the
photoinduced bending behavior upon irradiation with UV light to
the (0 1 0) face. The crystal of diarylethene 1a bends toward the
incident light. This is ascribed to the contraction of the
photoreacted layer in the crystal surface, which is caused by the
photochromic reaction from the open-ring isomer to the closed-
were prepared by
the simplified bimetal model.
The correlation between the
initial speed of the curvature change and the crystal thickness can
be well explained by Timoshenko’s bimetal model in both types
of bending behavior caused by expansion and contraction of the
2
8
,10
photoreacted crystal surface. A mixed crystal composed of two
diarylethene derivatives exhibited actual photomechanical work
to rotate a gearwheel upon controlled irradiation with UV and
75
7
visible light. The two-component co-crystal composed of a
2
ring isomer upon irradiation with UV light.
diarylethene and perfluoronaphthalene with 1-5 mm size in length
could lift a heavy metal ball which is 200-600 times heavier than
the crystal. The crystal can work as a molecular crystal crane in
The crystal thickness dependence of photoinduced bending
behavior was investigated. Fig. S2 shows the curvature change of
the crystals having different crystal thickness by UV irradiation
time. This result indicates that the crystal is bent rapidly and
80
4
the mesoscopic region. These photomechanical crystals may be
used for the photomechanical work by coating other materials to
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largely when the thickness is thin. In order to discuss the bending
(
(
a)
c)
(b)
(d)
speed quantitatively, the initial speed of the bending (Vinit) was
estimated by fitting of the curvature change in a polynomial
function, followed by the differential of the function at t = 0. The
Vinit values of the curvature change of the crystal having the
thickness of 3.22, 4.82, 6.59, 7.36, 8.53, 9.98, 13.95, and 22.48
5

m were determined to be 1.845, 0.918, 0.610, 0.549, 0.467,
−
1
−1
0
.325, 0.176, and 0.076 mm s , respectively, using the
polynomial degree of 6. This result can be theoretically explained
1
0
by Timoshenko’s equation (1) which is well known as a simple
bimetal model illustrated in Fig. S3.
3
1,32
(
e)
Fitting curve using the bimetal model
0
.8
1.0
0.8
2
2
1
1
0
0
.5
.0
.5
.0
.5
.0
h
2
= 1.5 m, 2,init = 0.37% s−1
0.6
0
0
0
.6
.4
.2
h2 h1
Fitting curve using the extended bimetal model
0
0
0
.4
.2
.0
h
= 1.5 m, 2,init = 0.37% s−1
2
h
Au = 7 nm
0.0
25

Au = 0.69
0
5
10
15
20
2 1 Au
h h h
Thickness of gold / nm
4
5
5
0
Fig. 3. Optical photograph of the photoinduced bending behavior upon
irradiation with UV light for 5 s without (a) and with gold deposition with
the gold thickness of 7 (b), 14 (c), and 21 nm (d), respectively. Changes
of curvature and Au value relative to the thickness of gold are shown in
0
5
10
15
20
25
Thickness of crystal / μm
(
e): The crystal thickness is ca. 14 m.
1
2
5
0
Fig. 2. Initial speed of curvature change relative to the crystal thickness
before (red) and after gold deposition (blue). The solid lines show fitting
curve using the bimetal model (red) and the extended bimetal model
blue). The value of error bar was obtained from the difference of the
polynomial degree to determine the Vinit in Fig. S2.
2,init
6m(1 m)
(
Vinit

(3)
2
3
4
h2 1 4m  6m  4m  m
Next, we performed the gold deposition to the diarylethene
1
 1
6mn(1 m)
2
Curvature 


(1)
55 crystals. Fig. S4 shows a gold-coated diarylethene crystal
observed under transparent mode. The gold can be cleanly
deposited to the crystal surface. Fig. S5 shows the relationship
between the thickness of gold and the deposition time. The
thickness of gold was observed by AFM. The thickness of gold
60 after the deposition for 15, 30, 45, and 60 s were determined to be
7, 14, 21, and 28 nm, respectively. The thickness of gold
increased in proportion to the deposition time. Moreover, we
investigated the photoinduced bending behavior of the gold-
coated diarylethene crystals. Fig. 3 shows the photoinduced
2
3
4
2
R
h2 1 4mn 6m n  4m n  m n
2
6m(1 m)
(2)
2
3
4
h 1 4m  6m  4m  m
2
2
3
3
4
5
0
5
0
where R is the curvature radius,  (i = 1, 2) are the actuation
i
strains, h (i = 1, 2) are the layer thicknesses, m = h /h , n = E /E ,
and E (i = 1, 2) are the Young’s moduli. Actuation strain
means the coefficient of expansion or contraction of the layer
in the absence of the other layer upon UV irradiation. In the case
of diarylethene 1a, 2 means the coefficient of contraction
because the crystal bends toward the incident UV light. In the
non-photoreacted layer, the value of actuation strain  is always
zero because the layer cannot expand or contract. Moreover, we
considered that the Young’s modulus E is the same as E in the
initial stage of the bending. As a result, the Timoshenko’s
equation becomes very simple, as shown in equation (2). The
value of h and the initial rate of  (2,init) can be obtained by the
i
1
2
1
2
i

65
bending behavior before and after the gold deposition to the
crystal surface when the crystal thickness is ca. 14 m. UV light
was irradiated to the opposite side of the gold-coated layer. The
curvature of the bending crystal without the gold layer was 0.572
1
−1
1
2
mm . The curvatures of the bending crystal with the gold
−1
70
thickness of 7, 14, and 21 nm were 0.396, 0.271, and 0.209 mm ,
respectively. The crystal tends not to be bent with increasing the
2
2
thickness of the gold layer. This is due to the large Young’s
best fitting curve (equation (3)) to the experimental data, as
33
modulus of the gold (83 GPa) compared with that of the
shown in Fig. 2. The values of h and  were determined to be
2
2,init
diarylethene crystal (ca. 3.0 GPa) which was determined by
−1
1.5 m and 0.37% s , respectively. This result is similar to the
4
75
means of a manual beam-bending test, as shown in Fig. S6. In
8
,10
other diarylethene crystals.
order to discuss the delay of the bending due to the gold-coated
layer, we introduced the Au value. The definition of Au is shown
in equation (4).
2
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(
a)
Fig. 2 shows the experimental data and theoretical calculated
line by the extended bimetal model using the Au value which is
obtained by the above mentioned experiment in Fig. 3. It is
clarified that the experimental data can be well fitted to the
extended bimetal model. This result provides a new useful
strategy to design for photomechanical actuators.
‘
‘ON’’
‘ON’’
‘‘OFF’’
‘‘OFF’’
UV
40
1
mm
1 mm
Vis.
Furthermore, we have demonstrated photoreversible current
ON/OFF switching of an electric circuit using the gold-coated
‘
UV
45 diarylethene crystal, as shown in Fig. S9. In order to flow current
in stable, it is better that the gold thickness on the crystal surface
is thicker. However, it was already clarified that the gold-coated
diarylethene crystal tends not to bend when the gold thickness
increases. Here, we estimated the appropriate gold thickness from
1
mm
1 mm
(
b)
0.6
0.5
0.4
0.3
0.2
0.1
0
5
0
the extended bimetal model. Fig. S10 shows the initial speed of
the curvature change to the crystal thickness in different gold
thickness samples calculated by the extended bimetal model.
From this calculation, the gold-coated diarylethene crystal with
the crystal thickness of ca. 6 m can bend with the adequate
−1 −1
55
speed as much as 0.248 mm s even in the gold thickness of 21
nm. Thus, we use the gold-coated diarylethene crystals with the
gold thickness of 21 nm in the following experiments.
0
50
100
150
200
250
Time / s
Fig. S11 shows the I-V curve of the electric circuit containing
external resistance. The current value becomes large in proportion
Fig. 4. Photoreversible current switching upon alternating irradiation with
UV and visible light. The crystal thickness is 6.2 m. The gold thickness
is 21 nm. The applied voltage is 1.0 V. The external resistance is 2 kΩ.
60 to the applied voltage. When the applied voltage was 0.8 V, the
current value for external resistance of 1 and 2 k were ca. 0.8
and 0.4 mA, respectively. The crystal showed no deformation
even in the current value over 30 mA. This result indicates that
there is no resistance in the gold-coated diarylethene crystal. Fig.
65 S12 shows the current value to the running time. It was clarified
that the current value was very stable. Fig. 4 and Video S1 shows
the photoreversible current ON/OFF switching using the
photoinduced bending behavior of the gold-coated diarylethene
crystals upon alternating irradiation with UV and visible light.
5
Curvaturein the presenceof gold layer
Au

(4)
Curvaturein theabsence of gold layer
1
1
2
2
3
3
0
5
0
5
0
5
The Au values for the crystal having the different gold
thickness of 7, 14, and 21 nm were determined to be 0.69, 0.47,
and 0.36, respectively, as shown in Fig. 3. This result indicates
that the gold thickness brings about the delay of the bending
speed and it reduces the bending motion by half in the presence
of only 14 nm gold layer.
7
0
When the gold-coated diarylethene crystal was irradiated with
UV light, the crystal got away from the tip of electric wire and
the current cannot flow, which means the switch ‘OFF’. Upon
irradiation with visible light, the crystal can contact with the tip
of electric wire and the current can flow again, which means the
switch ‘ON’. The crystals can be bent repeatedly without any
breaking of the gold layer on the crystal and the current can be
switched over 10 cycles only by photoirradiation. This result
provides a new practical use of photomechanical crystals as a
molecular crystal switch.
The crystal thickness dependence of the photoinduced bending
behavior after the gold deposition was also investigated. The
thickness of the gold was fixed to 7 nm. Fig. S7 shows
photoinduced crystal bending of the gold-coated crystals having
different crystal thickness. The bending speed depends on the
crystal thickness as well as that of the non-coated crystals. When
the crystal is thin, the crystal is bent rapidly and largely. The Vinit
values of the curvature change of the gold-coated crystals having
the crystal thickness of 3.22, 4.82, 6.59, 7.36, 8.53, 9.98, and
13.95 m were determined to be 1.010, 0.515, 0.388, 0.259,
75
80
Conclusions
In conclusion, we investigated the photoinduced crystal bending
behavior of 1a before and after gold deposition. The crystals of
1a showed photoreversible crystal bending upon irradiation with
alternating UV and visible light before and after gold deposition.
−1
−1
0
.139, 0.119, and 0.096 mm s , respectively. In order to
explain the relationship between the Vinit values and the crystal
thickness, we have introduced the extended bimetal model which
takes into account the effect of gold by using the Au value. The 85 It was revealed that the relationship between the initial speed of
extended bimetal model consists of three component materials;
the photoreacted layer, the non-photoreacted layer and the gold
layer. The equation and illustration of the extended bimetal model
are shown in equation (5) and Fig. S8.
the curvature change and the crystal thickness was well explained
by Timoshenko’s bimetal model and the extended bimetal model
before and after gold deposition, respectively. Moreover, we have
demonstrated the photoreversible ON/OFF switching of the
electric circuit using the gold-coated diarylethene crystal. The
current could be flowed in the gold layer on the surface of
diarylethene crystal without any resistance. Furthermore, the
90
1
2
6m(1 m)
Curvature 

 Au
4
(5)
2
3
R
h 1 4m  6m  4m  m
2
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photoreversible current switching by the photoinduced bending of 65 23 T. Kim, L. Zhu, L. J. Mueller and C. J. Bardeen, CrystEngComm,
2
012, 14, 7792.
the gold-coated diarylethene crystal could be repeated over 10
cycles upon alternating irradiation with UV and visible light.
These findings bring about not only a new strategy to design for
photomechanical actuators but also a new practical use of
photomechanical crystals.
2
2
4
5
J. K. Sun, W. Li, C. Chen, C. X. Ren, D. M. Pan and J. Zhang,
Angew. Chem. Int. Ed., 2013, 52, 6653.
P. Naumov, J. Kowalik, K. M. Solntsev, A. Baldridge, J.-S. Moon, C.
Kranz and L. M. Tolbert, J. Am. Chem. Soc., 2010, 132, 5845.
M. Irie, Chem. Rev., 2000, 100, 1685.
5
70
2
2
6
7
M. Irie, T. Fukaminato, K. Matsuda, S. Kobatake, Chem. Rev., 2014,
1
14, 12174.
Acknowledgements
2
8
9
S. Pu, C. Zheng, Q. Sun, G. Liu and C. Fan, Chem. Commun., 2013,
49, 8036.
G. Liu, S. Pu and R. Wang, Org. Lett., 2013, 15, 980.
7
8
5
0
This work was partly supported by a Grant-in-Aid for Scientific
Research on Innovative Areas "Photosynergetics" (No.
26107013) from The Ministry of Education, Culture, Sports,
Science and Technology (MEXT), Japan. D.K. appreciates
Research Fellowships of the Japan Society for the Promotion of
Science (JSPS) for Young Scientists. The authors also thank
Nippon Zeon Co., Ltd. for providing octafluorocyclopentene.
2
3
0 K. Uchida, T. Ishikawa, M. Takeshita and M. Irie, Tetrahedron, 1998,
54, 6627.
1 S. Timoshenko, J. Opt. Soc. Am., 1925, 11, 233.
32 M. Christophersen, B. Shapiro and E. Smela, Sens. Actuators. B
Chem., 2006, 115, 596.
1
0
3
3
3
B. Shapiro and E. Smela, J. Intell. Mater. Syst. Struct., 2007, 18, 181.
1
5
Notes and references
Department of Applied Chemistry, Graduate School of Engineering,
Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585,
Japan.
Fax: +81 6 6605 2797; Tel: +81 6 6605 2797;
E-mail: kobatake@a-chem.eng.osaka-cu.ac.jp
2
2
3
3
4
4
5
5
6
0
5
0
5
0
5
0
5
0
†
Electronic Supplementary Information (ESI) available: detailed
experimental data (Fig. S1–S12), and movie of current switching (Video
S1).]. See DOI: 10.1039/b000000x/
1
2
M. Irie, S. Kobatake and M. Horichi, Science, 2001, 291, 1769.
S. Kobatake, S. Takami, H. Muto, T. Ishikawa and M. Irie, Nature,
2
007, 446, 778.
3
K. Uchida, S. I. Sukata, Y. Matsuzawa, M. Akazawa, J. J. D. de Jong,
N. Katsonis, Y. Kojima, S. Nakamura, J. Areephong, A. Meetsma
and B. L. Feringa, Chem. Commun., 2008, 326.
4
5
M. Morimoto and M. Irie, J. Am. Chem. Soc., 2010, 132, 14172.
L. Kuroki, S. Takami, K. Yoza, M. Morimoto and M. Irie,
Photochem. Photobiol. Sci., 2010, 9, 221.
6
7
S. Kobatake, H. Hasegawa and K. Miyamura, Cryst. Growth Des.,
2011, 11, 1223.
F. Terao, M. Morimoto and M. Irie, Angew. Chem. Int. Ed., 2012, 51,
9
01.
8
9
D. Kitagawa and S. Kobatake, J. Phys. Chem. C, 2013, 117, 20887.
D. Kitagawa, H. Nishi and S. Kobatake, Angew. Chem. Int. Ed., 2013,
52, 9320.
1
1
0
1
D. Kitagawa and S. Kobatake, Photochem. Photobiol. Sci., 2014, 13,
7
64.
H. Koshima, H. Nakaya, H. Uchimoto and N. Ojima, Chem. Lett.,
012, 41, 107.
12 H. Koshima and N. Ojima, Dyes Pigm., 2012, 92, 798.
2
1
3
O. S. Bushuyev, T. A. Singleton and C. J. Barrett, Adv. Mater., 2013,
5, 1796.
2
1
4
O. S. Bushuyev, A. Tomberg, T. Friscic and C. J. Barrett, J. Am.
Chem. Soc., 2013, 135, 12556.
15 O. S. Bushuyev, T. C. Corkery, C. J. Barrett and T. Friščić, Chem.
Sci., 2014, 5, 3158.
1
1
1
6
7
8
H. Koshima, N. Ojima and H. Uchimoto, J. Am. Chem. Soc., 2009,
31, 6890.
H. Koshima, R. Matsuo, M. Matsudomi, Y. Uemura and M. Shiro,
Cryst. Growth Des., 2013, 13, 4330.
H. Koshima, K. Takechi, H. Uchimoto, M. Shiro and D. Hashizume,
Chem. Commun., 2011, 47, 11423.
1
1
2
9
0
R. O. Al-Kaysi and C. J. Bardeen, Adv. Mater., 2007, 19, 1276.
L. Zhu, A. Agarwal, J. Lai, R. O. Al-Kaysi, F. S. Tham, T. Ghaddar,
L. Mueller and C. J. Bardeen, J. Mater. Chem., 2011, 21, 6258.
L. Zhu, R. O. Al-Kaysi and C. J. Bardeen, J. Am. Chem. Soc., 2011,
2
2
1
2
1
33, 12569.
L. Zhu, R. O. Al-Kaysi, R. J. Dillon, F. S. Tham and C. J. Bardeen,
Cryst. Growth Des., 2011, 11, 4975.
4
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