Photoresponsive nanoassemblies of a dithienylethene organogelator

Article abstract of DOI:10.1080/15421400590946226

A 1,2-Bisdithienylperfluorocyclopentene covalently linked to aggregative gelling moieties based on a synthetic aminoacid unit have been synthesized. This rationnally designed molecular target lead to the spontaneous organisation of nanosized fibers which in turn form a 3D-network. The photoinduced ring-closure process involved in the photochromism of diarylethene suppresses the self-assembling properties. The system reversibly reverts back to the Gel state upon Visible irradiation.

Full text of DOI:10.1080/15421400590946226

This article was downloaded by: [McMaster University]
On: 05 January 2015, At: 11:40
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954
Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,
UK
Molecular Crystals and Liquid
Crystals
Publication details, including instructions for
authors and subscription information:
http://www.tandfonline.com/loi/gmcl20
Photoresponsive
Nanoassemblies of a
Dithienylethene Organogelator
Jiaan Gan a , Jean-Luc Pozzo a & Fritz Vögtle b
a Photochemistry for Nanoscience, CNRS , UMR
Bordeaux , Talence, France
b Kekulé Institute, Department of Chemistry and
Biochemistry, University of Bonn , Germany
Published online: 31 Aug 2006.
To cite this article: Jiaan Gan , Jean-Luc Pozzo & Fritz Vögtle (2005) Photoresponsive
Nanoassemblies of a Dithienylethene Organogelator, Molecular Crystals and Liquid
Crystals, 430:1, 99-106, DOI: 10.1080/15421400590946226
To link to this article: http://dx.doi.org/10.1080/15421400590946226
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the
information (the “Content”) contained in the publications on our platform.
However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness,
or suitability for any purpose of the Content. Any opinions and views
expressed in this publication are the opinions and views of the authors, and
are not the views of or endorsed by Taylor & Francis. The accuracy of the
Content should not be relied upon and should be independently verified with
primary sources of information. Taylor and Francis shall not be liable for any
losses, actions, claims, proceedings, demands, costs, expenses, damages,
and other liabilities whatsoever or howsoever caused arising directly or

indirectly in connection with, in relation to or arising out of the use of the
Content.
This article may be used for research, teaching, and private study purposes.
Any substantial or systematic reproduction, redistribution, reselling, loan,
sub-licensing, systematic supply, or distribution in any form to anyone is
expressly forbidden. Terms & Conditions of access and use can be found at
http://www.tandfonline.com/page/terms-and-conditions

Mol. Cryst. Liq. Cryst., V o l. 4 3 0 , p p . 9 9 – 1 0 6 , 2 0 0 5
C o p y r i g h t # T ay l o r & F r a n ci s I n c.
I S S N : 1 54 2- 1 4 06 p r i n t =1 5 6 3 - 5 2 8 7 o n l i n e
D O I : 1 0. 10 8 0/ 1 5 421 4 00 5 9 0 9 4 6 2 2 6
Photoresponsive Nanoassemblies of a Dithienylethene
Organogelator
Jiaan Gan
Jean-Luc Pozzo
P h o t o c h e m i s tr y f o r N an o s c i e nc e, C N R S, U M R B o r d e a u x ,
T a l e nc e , F r a n c e
¨
Fritz Vogtle
´
K e k ul e I ns t i t u t e , D ep a r t m e nt o f C h em i s t r y a n d B i o c h e mi s t r y,
U n i v e r si t y o f B o nn , G er ma n y
A 1,2-Bisdithienylperfluorocyclopentene covalently linked to aggregative gelling
moieties based on a synthetic aminoacid unit have been synthesized. This rationn-
ally designed molecular target lead to the spontaneous organisation of nanosized
fibers which in turn form a 3D-network. The photoinduced ring-closure process
involved in the photochromism of diarylethene suppresses the self-assembling
properties. The system reversibly reverts back to the Gel state upon Visible
irradiation.
Keywords: d i t h i e n y le t he ne ; g e ls ; n a no a s se mb li e s ; p ho t o c h r om i sm
INTRODUCTION
R e c e n t l y , a w i d e v ar i e t y o f l o w m o l e c u l ar w e i gh t o r g a n o g e l a t o r s h a v e
e m e r g e d a s a f a s c i n a t in g c l a s s o f t h e r m o r e ve r s i b l e s e l f - a s s e m b l i n g
m a t e ri a l s [ 1 ] . S i n c e t h e r e a r e m a n y a s p e c t s o f g e l a t i o n r e m a in u n c l e a r
[ 2] , i t i s s t i l l d i f f i c u l t t o p r e d ic t w h i c h m o le c u l a r s t r u c t u r e s w i l l a c t a s
a n e f f i c i e n t g el a t o r m o l e c u l e . L o w m o le c u l a r m a s s o r g a n o g e l a t o r s
( L M OG s ) a r e a bl e t o s e lf - as s o c ia t e t o f o r m f i b r e - li k e s t r u c t u r e s ,
e n t r a p p i n g s ol v e n t m o le c u l e s w i th i n t h e i r v o i d s p a c e d r i v e n b y
T h e p r e s e n t r e se a r ch w a s f in a c ia l ly s u p po r t ed b y C N R S a n d C O S T D - 1 1 S u pr a -
m ol e c u l ar p r o j e c t D 1 1=0 0 0 1 5=9 9 .
A d d r e s s c o r r e s p o nd en c e t o J ea n - L u c P o z z o, P h ot o c h e mi s t r y f o r N a n o s c i en c e, C N R S,
U M R 5 8 0 2 B o r d e a ux 1 , 3 5 1 c ou r s l ib e ra t i on , T a l en c e, 3 3 4 0 5 , F ra n c e. E - m a i l : j l . p o z z o @
l c o o . u - b o r d ea u x 1 . f r
9 9

1 0 0
J. Gan et al.
i n t e rm o l e c u l a r i n t e r a c t i o n t h r o u g h h y d r o g e n b o n d i n g , pꢀp s t a c k in g
a n d v a n d e r v a a l s i n t e r a c t i o n s [ 3] .
I t i s a t re m e n d o u s c h a l le n g in g t a s k t o d e s i g n c o n t r o l l e d g e l a t i o n
s y st e m s b a s ed o n i s o m e r is at i o n c h a n g e s o f a g e l a t o r m o l e c u l e i n d u c e d
b y e xt e r n a l s t i m u li [ 4] . I n t r o d u c t i o n o f a p h o t o r e s p o n s i v e g r o u p o n t o
t h e s e l f - a ss e m b l i n g u n i t i s o n e o f t h e p r o m i si n g a p p r o a c h t o w a r d s u c h
s m a r t g e l s [ 5 ] . M ic r o s p h e r e -t o -G e l f ib r e m o r p h o l o g i c a l t r a n s i t i o n c a n
b e i n d u c e d b y t h e p h o t o is o m e r i z a t io n o f a m a l i c a c i d a m i d e t o a
f u m a r i c a c i d a m id e [ 6] . S o m e o r g an o g e l a t o r s w i t h p h o t o c h r o m ic u n i t s
h a v e b e e n r e po r t e d f o r t h e d e s ig n o f s p e c i al s u p r a m o l e c u l a r m a t e r i a ls
[ 7 , 8 ] . D i a r y l e t h e n e d e r iv a t i ve s a r e t h e m o s t p r o m i s i n g p h o t o c h r o m i c
c o m p o u n d s b e c a u s e o f t h e ir t h e r m a ll y i r r e v e r s i b l e a n d f a t i g u e r e s is t -
a n t p h o t o c h r o m i c p e r f o r m a n c e [ 9] . I n d e e d , t h e p h o t o c h r o m i c r e a c t i o n s
o f 1 , 2 - b i s- t h i e n y l c y c l o p e n t e n e s f u n c t i o n al i z e d w i t h t w o a m i d e g r o u p s
h a v e b e e n r ep o r t e d t o l ar ge ly i n fl u e n c e t h e m e d i u m v i s c o s i t y [ 1 0 ] .
M o r e r e ce n t l y , t h e s e d e r iv a t i ve s i n c o r p o r a t i n g a c h i r a l m o i e t y h a v e
b e e n s h o w n t o r e ve r s i bl y c o n t r o l s u p r a m o l e c u l a r c h i r a l i t y s w i t c h i n g
b e t w e e n d i f f e r en t c h i r a l a gg r e g at e s i n t h e g e l p h a s e [ 1 1 ] .
I n t h i s s t u d y , w e d e s ig n e d a n d s y n t h e s i ze d a p h o t o c h r o m ic
d i t h i e n y l e t h e n e d e r iv a t i ve w it h t w o N - ac y l - 1 , x- a m i n o a c i d m o i e t i e s
a s s i d e- a r ms ( S c h e m e 1 ). T h e p h o t o c h r o m i c p r o p e r t i e s o f t h i s o r g a n o -
g e l a t o r a r e k e p t a n d a n e f f ic ie n t G e l - t o - S o l p h a s e t r a n s i t i o n p r o c e s s i s
o b s e rv e d u p o n i r r ad i a t io n w it h 2 54 n m U V l i gh t .
RESULTS AND DISCUSSION
Molecular Design and Synthesis
P h o t o c h r o m i c c o m p o u n d s b as e d o n d i ar y l e t h e n e d e r i v a t i v e s h a v e
a t t r a c t e d m u c h a t t e n t i o n f o r o p t o e l e c t r o n i c d e v i c e s b e c a u s e b o t h i s o -
m e r s o f t h e c om p o u n d s a r e s t a b le a n d t h e c o l o r a t i o n =d e c o lo r a t i o n
4
c
y
c
l
e
s
c
a
n
b
e
r
e
p
e
a
t
e
d
a
s
h
i
g
h
a
s
1
0
t
i
m
e
s
.
P
r
e
v
i
o
u
s
l
y
,
w
e
s
u
c
c
e
s
s
-
f u l l y p r ep a re d p h o t o c h r o m i c m u lt i a d d r e s s a bl e s e l f - a s s e m b l i n g
n a p h t h o p yr a n g e l a t o r s . I n c o r p o r a t io n o f t h e n a p h t h o p y r a n u n i t i n
t h e s u p ra m o l e c u l ar s y s t e m c o u ld l e a d t o s m a r t g e l s s e n s i t i ve t o l i gh t,
t e m p e r a t u r e a n d a c i d it y a n d t h i s s t r u c t u r a l m o d i f i c at i o n d i d n o t p r e -
v e n t g el a t i o n [ 1 2 ] . I n t h i s s t u d y , a s i m p l e 1 , 2 - B i s ( 2 - m e t h y l t h i e n - 3 - yl )
p e rf l u o r oc y c l o p e n t e n e w a s s e le c t e d a s t h e p h o t o c h r o m i c c o r e w h i c h
h a s t w o d i f f er e n t i n t e r c o n ve r t i b le i s o m e r s : t h e c o l o r l e s s o p e n f o r m
( O F ) a n d t h e c o l o r e d c l o s e d f o r m ( CF ) a s d e p ic t e d i n S c h e m e 2 . T h e
p h o t o ge n e r a t e d c o lo r e d f o r m a r e s t a b le i n t h e d a r k a n d c a n b e c o n -
v e r t e d b a ck t o t h e o p e n f o r m w i th a v is ib l e l i gh t . T h e p h o t o c h r o m ic
u r e t h a n e d e ri v a t i v e w a s p r e p a r e d t h r o u g h t h e c o n d e n s a t i o n o f t h e

Photoresponsive Nanoassemblies of a Dithienylethene Organogelator
1
0
1
=
=
SCHEME 1 ( i ) N a B H ; ( i i ) O C Nꢀ( C H 2 )1 0 ꢀC O O M e , T E A=T H F ; ( i i i ) L i O H
4
t
h
e
n
1
N
H
C
l
;
(
i
v
)
N
a
O
H
1
N
.
d i t h i e n y l e t h en e d i al c o h o l 2 w i th a n a p p r o p r i a t e i s o c y a n a t e . T h e d i a c i d
4 w a s o b t a i n e d b y t h e s a p o n if i c a ti o n o f t h e u r e t h a n e e s t e r w i t h a m i l d
l i t h i u m h y d r ox i d e b as e . O n e c o u ld e x p e c t t h a t t h e g e l l i n g a b i li t y i s
r e t a i n e d w h e n t h e 1 , 2 -B i s ( 2- m e t h y lt h i e n - 3 - y l ) p e r f l u o r o c y c l o p e n t e n e
p h o t o ch ro mi c u n i t i s i n t r o d u c e d t o t h e u r e t h a n e d e r i v a t i v e s .
SCHEME 2

1 0 2
J. Gan et al.
Photochromic Properties
T h e c o mp a r i s o n o f t h e U V -v i s a bs o r pt i o n s p e c t r a o f d i a lc o h o l 2
a n d d i s a l t 5 i n m e t h a n o l a t i d e n t i c a l c o n c e n t r a t i o n w e r e s h o w n i n
F i g u r e 1 a n d l i s te d i n T a b le 1 . U p o n i r r a d i a t i o n w i t h 2 5 4 - n m l i gh t ,
t h e c o l o rl e s s s ol u t i o n o f 2 a n d 5 g r a d u a ll y t u r n e d r e d . T h e a b s o r p t i o n
b a n d a t 2 9 6 n m f o r t h e o p e n f o r m o f 2 d e c r e a s e d a n d t w o n e w a b s o r p -
t i o n b a n d s i n t h e p r e s e n c e o f a n i s o s b e s t i c p o i n t a t 3 0 8 n m a p p e a r e d .
S i m i l a r s pe c t ra l c h a n g e s w e r e o b s e r v e d f o r c o m p o u n d 5. T h e i s o s b e s t i c
p o i n t h a s b e e n m e a s u r e d a t 3 06 n m a n d t h e t w o m a x i m a a b s o r p t i o n
b a n d s f o r t h e c l o s e d f o r m o f 5 w e r e c e n t e r e d a t 3 4 0 a n d 5 1 7 n m . T h e s e
r e su l t s i n c l u d i n g t h e a p p e a r a n c e o f a n i s o s b e s t i c p o i n t i n d i c a t e t h a t
t h e i n c or p o ra t i o n o f t h e g e l a t io n u n i t h a s n o t a l t e r e d t h e p h o t o c h r o m i c
p ro p e r ti e s o f t h e 1 , 2 - B i s (2 - m e t h y lt h ie n - 3- yl ) p e r f l u o r o c yc l o p e n t e n e
s u b u n i t . B o t h p h o t o s t a t io n a r y s t a t e s f o r c o m p o u n d s 2 a n d 5 i n m e t h -
a n ol s o l u t i o n w e r e a t t ai n e d a t t h e s a m e t i m e , i .e . a f t e r 1 6 5 s e c o n d s
i r ra d i a t i on . U p o n v is ib l e l ig h t ( k > 5 30 n m ) i r r a d i a t i o n , t h e r e d c o l o r
a n d t h e t w o a b s o r p t io n b an d s w h i c h w a s a s c r i b e d t o t h e c l o s e d f o r m
o f b o t h 2 a n d 5 d i s a p pe a r e d i n d ic a t i n g t h at t h e d e s i g n e d L M O G
r e ve rt s b a ck t o t h e i n it i a l o p e n r i n g i s o m e r .
D i s a l t 5 i s a n e f f i c i e n t g e l a t o r o f p o l a r o r g a n i c s o l v e n t s s u c h a s D M F
a n d D M S O . T h e p h o t o c h r o m i s m o f d i al c o h o l 2 a n d d i s a l t 5 i n D M F f o r
c o mp a r i s o n w e r e i n v e s t ig at e d a n d t h e r e s u l t s w e r e s h o w n i n F i gu r e 2
a n d l i s t e d i n T a bl e 1 . U p o n i r r a d i a t io n w i th 2 5 4 - n m l i gh t , d i a lc o h o l 2
i n D MF e xh i b i t t h e s a m e p h o t o c h r o m i c b e h a v io u r a s i n m e t h a n o l i c
s o l u t i o n s . T h e a p p e a r a n c e o f t h e i s o s b e s ti c p o i n t a n d t h e t w o n e w
FIGURE 1 C h a n ge s i n t h e U V - vi s a bs o r p t i o n s p e c t r a o f d i a l c o h o l 2 ( a ) a n d
d i s a l t 5 ( b ) i n m e t h a n o l ( 2 , 2 ꢁ 1 0ꢀ4 M ) w h en i r r a d i a t e d w i t h 2 5 4 n m l i g h t .
I r r a d i a t i o n p e r i o d s f o r t h e s o l ut i o n s t u d i e d a r e 0 , 1 5 , 4 5 , 7 5 , 1 0 5 , 1 3 5 , 1 6 5 s .

Photoresponsive Nanoassemblies of a Dithienylethene Organogelator
1
0
3
TABLE 1 U V - V i s D at a a n d P h ot o c h e mi c a l C o n v e r s i on o f C o m p ou n d s a
3
1
1
km x=n m (e ꢁ 1 0ꢀ L m olꢀ c mꢀ
)
a
I
s
o
s
b
e
s
t
i
c
C o m p o u n d
O pe n f or m
C lo s e d f o rm
p o i n t=n m
2 i n M e O H
5 i n M e O H
2 i n D M F
5 i n D M F
2 9 6b ( 4 . 6 8 )
2 9 8b ( 4 . 8 9 )
3 0 1b ( 4 . 4 4 )
3 0 9b ( 5 . 5 9 )
3 3 9 ( 6 . 8 2 ) 5 1 3 ( 4 . 6 8 )
3 4 0 ( 6 . 6 8 ) 5 1 7 ( 5 . 0 3 )
3 3 9 ( 5 . 3 6 ) 5 2 2 ( 3 . 2 1 )
3 6 0 ( 5 . 1 7 ) 5 4 1 ( 1 . 5 1 )
3 0 8
3 0 6
3 1 0
–
aU V=V i s s p e c t r o sc o pi c d a t a w er e o bt a i n ed a t a mb i ent t e m pe r a t u r e. T he p h ot o st a ti o n -
a
r
y
s
t
a
t
e
w
e
r
e
o
b
t
a
i
n
e
d
b
y
i
r
r
a
d
i
a
t
i
o
n
o
f
t
h
e
s
o
l
u
t
i
o
n
o
f
t
h
e
o
p
e
n
f
o
r
m
w
i
t
h
a
h
a
n
d
-
h
e
l
d
2
2 54 n m U V ( 4 7 0 mW=c m ) l am p .
bs h o u l d e r .
a b s o rp t i on b a n d s f o r t h e c l o s e d f o r m w e r e o b s e r v e d . T h e p h o t o s t at i o n -
a r y s ta t e o f t h e d i al c o h o l 2 i n D M F w a s p r o l o n g e d t o 7 3 5 s e c o n d s a n d
t h e i s o s b e st i c p o i n t w a s r e m a i n e d . T h e d i ff e r e n c e o f t h e p h o t o c h r o m ic
p r op e r ti e s w a s a s s i g n e d t o s o lv e n t e f f e c t .
U n d e r t h e s a m e i r r a d i a t io n c o n d it i o n a n d a t i d e n t i c a l c o n c e n -
t r a t io n a s d i a l co h o l 2 i n D M F , n o i s o s be s t i c p o i n t w a s o b s e r v e d f o r
d i s a l t 5 i n D M F . T w o n e w b r o a d b an d s a t 3 2 0 –5 0 0 a n d 5 0 0 –
6 0 0 n m c or r e s po n d t o t h e c l o s e d f o r m i s o m e r . T h e p h o t o s t a ti o n a r y
s t a t e o f t h e d i s al t i n D M F a t t ai n e d a t 3 75 s e c o n d s . U p o n b l e a c h i n g
FIGURE 2 C h a n g e s i n t h e U V - Vi s a bs o r p t i o n s p e c t r a o f d i a l c o h o l 2 ( a ) a n d
d i s a l t 5 ( b ) i n D M F ( 2 , 2 ꢁ 1 0ꢀ4 M ) w h en i r r a d i a t e d w i t h 2 5 4 n m l i g h t .
I r r a d i a t i o n p e r i o d s f o r ( a ) a n d ( b ) a r e 0 , 1 5, 4 5, 7 5 , 1 3 5 , 1 9 5 , 2 5 5 , 3 1 5 , 3 7 5 ,
4 9 5 , 6 1 5 , 7 3 5
s
a n d 0 , 1 5, 4 5, 7 5, 1 3 5 , 1 9 5 , 2 5 5 , 3 1 5 , 3 7 5
s
r e s p e

1 0 4
J. Gan et al.
w it h v i si b l e l i g h t (>5 30 n m ), t h e t w o a bs o r p t i o n b a n d s d i s a p p e a r e d
a n d r e tu rn e d t o a c o lo r l e s s s t a t e . T h o u g h t h e r e v e r s a l p r o c e s s w a s
r a t h e r s l o w, t h e l o w e s t c y c l o c o n v e r s i o n f r o m t h e c l o s e d f o r m t o t h e
o p e n f o r m c o u l d b e a t t r ib u t e d t o t h e a gg r e g a t i o n s t a t e o f t h e d i s a l t
o rg a n o g e l a t o r s d r i v e n b y s p e c i fi c u n k n o w n n o n c o l v a l e n t i n t e r m o l e c u -
l a r f o r c e s s u ch a s h y d r o ge n b o n d i n g , h yd r o p h o b ic i n t e r a c t i o n s ,
d i p o l e – d i p ol e i n t e r a c t i o n s , v an d e r v aa l s i n t e r a c t i o n s o r m e t a l c o o r d i -
n a ti on b o n d f o r m a t io n . I r i e [ 13 ] h a s r e p o r t e d t h a t t h e c y c l o r e v e r s i o n
o f a d i a ry l e t h e n e d e r iv a t i ve w a s s t r o n g ly d e p e n d a n t o n s o l v e n t v i s -
c o s i t y . I n t h e 3 D g e l n e t w o r k , t h e r o t a t i o n a l f r e e d o m a b o u t t h e
CꢀC b o n ds b e t w e e n t h e t h i o p h e n e a n d c y c l o p e n t e n e r i n g s m a y b e
d e cr e a s e d d u e t o t h e a gg r e g at i o n s t a t e a n d o n e c a n e x p e c t t h a t t h e
r i n g - o p e n p ro c e s s b e s u p p r e s s e d .
Gelation Properties and Gel-to-Sol Phase Transition Process
T h e g el a t i o n b e h a v io r w a s i n ve s t i ga t e d v i a t h e i n v e r t e d t e s t t u b e
m e t h od a n d t h r o u g h r h e o l o g ic al m e a s u r e m e n t s . D i s a l t 5 h a s b e e n
f ou n d t o b e s o l u bl e i n v ar i o u s a l c o h o l i c s o l v e n t s a n d w a t e r , w h e r e a s
i t i s i n s o l u b l e i n a ll o f a p o l a r s o lv e n t s a n d m o s t o f t h e l o w p o l a r s o l -
v e n t s s u ch a s d i c h l o r o m e t h a n e a n d c h l o r o f o r m e t c . , R e m a r k a bl y c o r r e -
s p o n d i n g d i a ci d 4 w a s e a s i ly d i s s o l v e d i n s u c h m e d i a . D i s a l t 5 i s
s p a r i n g l y s ol u b le i n D M F a n d D M S O . U p o n h e a t i n g a t 8 0 – 11 0 ꢂC ,
t h e f i n e p o w d e r o f d i s al t 5 g r a d u a ll y d i s s o l v e d . A f t e r c o o li n g t o
t h e a m b i e n t t e m p e r a tu r e , g e l s w e r e r e a d i ly o b t a i n e d w h i c h a r e
t h e n s ta b l e f o r m o n t h s . T r an s i t io n t e m p e r a t u r e ( T ) o f t h e g e l i n
g
e
l
D MF a s a f u n c t i o n o f o r ga n o g e l a t o r c o n c e n t r at i o n w e r e s h o w n
i n F i gu r e 3 . T h e G e l - t o - S o l p h a s e t r a n s i t i on t e m p e r a t u r e o f D M F i n
ꢂ
ꢀ
2
a
c
o
n
c
e
n
t
r
a
t
i
o
n
o
f
1
%
w
t
=
v
o
l
(
1
.
1
ꢁ
1
0
M
)
i
s
a
s
h
i
g
h
a
s
1
2
0
C
,
w
h
i
c
h
i s c l o se t o a s u p e r g e l a t o r [ 14 ] .
ꢀ
A
s
t
r
o
n
g
g
e
l
o
f
d
i
s
a
l
t
5
i
n
D
M
F
w
i
t
h
a
c
o
n
c
e
n
t
r
a
t
i
o
n
o
f
3
.
7
ꢁ
1
0
M
3
i n a n i n v e r te d c e ll ( T ¼ 9 6ꢂC ), w a s i r r a d i a t e d u s i n g a h a n d - h e ld
g
e
l
2 5 4 n m l a mp . T h e c o lo r l e s s g e l t u r n e d t o b r o w n r e d a n d t h e n b e g a n
t o f l o w u p o n i r r a d i a t io n f o r 4 m i n a s s h o w n i n F ig u r e 4 . T h e G e l - t o -
S o l p r oc e s s s ta r t i n g f r o m t h e u p p a r t o f t h e i n v e r t c e l l t h e n t o t h e
w h o l e c e l l c a n b e o b s e r v e d c l e a r l y , b e c au s e t h a t t h e s o l u t i o n p a r t
w a s d e e p l y c o l o r e d a n d t h e g e l p a r t w a s s t i l l c o l o r l e s s .
T h e r e ve rs a l b le a c h i n g p r o c e s s f o r t h e c l o s e d f o r m o f t h e g e l
3
( 3 . 7 ꢁ 1 0ꢀ M ) i n D M F w a s r a t h e r l o w t h a n t h a t o f t h e d i s a l t 5 i n
4
D MF s o l u t i o n ( 2 ꢁ 1 0ꢀ M ). S t r o n g v is ib l e i r r a d i a t i o n ( k > 5 3 0 n m )
o f t h e s o l g a ve r i s e t o t h e p h o t o c y c l o r e v e r s io n t o r e f o r m 5 i n a
g e l p h a se . T h i s r e p r e s e n t s t h e f ir s t e x a m p l e o f a G e l - t o - S o l p h a s e
t r a n s i t i o n t h a t c o u ld b e p h o t o s w it c h e d i n b o t h d i r e c t i o n s u s i n g

Photoresponsive Nanoassemblies of a Dithienylethene Organogelator
1 0 5
FIGURE 3 G e l - t o - So l p h a se t r a n s i t i on t e mp e r a t u r e s a s a f u n c t i o n 5 c o n c e n -
t r a t i o n i n D M^F ) ( a n d D M S.O) .
(
a p p r op r i a t e w a v e le n g th . D i ff e r e n t c y c l e s h a v e b e e n r e a l i s e d s h o w i n g
t h a t T ge l v a l u e s d e c r e a s e a s a f u n c t i o n o f t h e n u m b e r o f U V =V i s .
i r ra d i a t i on p r oc e s s e s . I n t h e s e c o n d it i o n s n o p h o t o d e g r a d a t i o n t a k e s
p l a c e a s t h e i n i t i a l T g e l v al u e i s r e c o v e r e d b y s i m p l y h e a t i n g a n d t h e n
c o o l i n g t h e u n c o l o u r e d p h a s e . T h e n e t w o r k s t r u c t u r e i s o n l y p a r t i a l l y
r e c o n s t ru c t e d a t 3 0 ꢂC a n d i s t o t a l ly r e g e n e r a t e d u s i n g t h e t h e r m a l
p r oc e ss .
I n c o n cl u s i o n , w e h a v e p r e p a r e d a n o v e l l o w m o l e c u l a r m a s s
o r g a n o ge l a t or u s i n g d i th ie n y l e t h e n e u n i t a s p h o t o c h r o m ic c o r e . T h i s
c o m p o u n d s h o w e d t y p i c a l p h o t o c h r o m i c b e h a v i o r o f a d i a r y l e t h e n e
FIGURE 4 P ho t o c o nt r ol l e d G el - t o - So l p h a s e t r an s i t i o n p r o c e s s . L e f t : g e l
b e f o r e i r r a d i a t i on , M i d d l e : p h o t or eg e ne r a t e d g e l w i t h v i s i b l e l i g h t >5 3 0 n m
a n d R i g h t: s o l u t i o n a f t er i r r a d i a t i on .

1
0
6
J. Gan et al.
d e r i v a t i v e i n s o l u t i o n s a n d a c t e d a s a n e f f i c i e n t g e l a t o r f o r p o l a r
o r g a n i c f l u i d . P ho t o c o n t r o l l e d G e l - t o - S o l t r a n s i t i o n p r o c e s s o f a D M F
g e l w a s u n d o u b t e d l y o b s e r v e d . T h i s d i th i e n y l e t h e n e o r g a n o g e l a t o r
s h o w e d g re a t p o t e n t i al f o r t h e a p p li c a t i o n o f a d v a n c e d o p t i c a l
m a t e r i a l s a n d d e v i c e u s i n g s o l- g e l t e c h n o l o g y .
REFERENCES
[ 1 ] T e r e ch , P . & W e is s , R . G . ( 1 99 7 ) . Chem. Rew., 97, 3 1 3 3 .
[ 2 ] O d a, R . , H u c, I . , & C a nd a u , S . J . ( 1 99 8 ) . Angew. Chem. Int. Ed., 37, 2 6 8 9 .
[ 3 ] S h u m b u r o , A . & B ie we r, M . C . ( 2 00 2 ) . Chem. Mater., 14, 3 7 4 5 .
[ 4 ] v a n E s c h , J . , S c h oo n b ee k, F . , D e L o os , M . , V ee n, E . M . , K e l l o g g, R . M . , & F er i n g a,
B . L . ( 1 9 9 9 ) . Supramolecular science: where it is and where it is going; N a t o A S I
S e ri e s C , M a t h em ati ca l a n d p hy s i ca l s c i en c es , K l u w e r A c a de m i c : D o rd r e c h t ,
V o l . 5 2 7, p 2 3 3 .
[ 5 ] P o z z o , J . L . , C l a v i er , G . , & D es v e rg n e , J . P . ( 19 9 8 ). J. Mater. Chem., 8, 2 5 7 5 .
[ 6 ] F r k a n e c, L . , J o k ic , M . , M a k a r evi c, J . , W o ls pe rg er , K . , & Z i n i c , M . ( 2 0 0 2 ). J. Am.
Chem. Soc. , 124, 9 7 1 6 .
[ 7 ] P o z z o , J . L . , C l a v i er , G . , R us t m e y er , F . , & B ou a s - La ur e n t , H . ( 2 0 0 0 ). Mol. Cryst.
Liq. Cryst., 344, 1 0 1 .
[ 8 ] D e L o o s , M . , v a n E s c h, J . , K el lo g g , R . M . , & F e ri n g a , B . L . ( 2 0 0 1 ). Angew. Chem.
Int. Ed., 40, 6 1 3 .
[ 9 ] I r i e , M . ( 2 0 0 0 ) . Chem. Rev. , 100, 1 6 8 5 .
[ 1 0 ] L u ca s , L . N . , v a n E s c h , J . , F e ri n g a , B . L . , & K el lo gg , R . M . ( 2 0 0 1 ). Chem. Comm. ,
7 5 9 .
[ 1 1 ] d e J o n g , J . , L u c a s , L . N . , K el lo g g , R . M . , v a n E s c h , J . , & F er i n g a , B . L . ( 2 0 0 4 ).
Science, 304, 2 7 8 .
[ 1 2 ] A h m ed , S . , S a l le na v e , X . , F a g e s , F . , M i ed e n- Gu nd e rt , G . , M u¨ l l er , W . M . , M u¨ l l er , U . ,
¨
V
o
g
t
l
e
,
F
.
,
&
P
o
z
z
o
,
J
.
L
.
(
2
0
0
2
)
.
L
a
n
g
m
u
i
r
,
1
8
,
7
0
9
6
.
[ 1 3 ] M i y a s a k a , H . , N o b ut o, T . , M u r a ka m i, M . , I t a y a , A . , T a m a i , N . , & I r i e , M . ( 2 0 0 2 ).
J. Phys. Chem. A, 106, 8 0 9 6 .
[ 1 4 ] G r o n w a l d , O . & S h i nk a i , S . ( 20 0 1 ) . Chem. Eur. J. , 7, 4 3 2 9 .