Photochromism of diarylethene derivatives having an indene unit

Article abstract of DOI:10.1016/j.tetlet.2005.12.074

Photochromic indene derivatives, 1-(2-methyl-1-inden-3-yl)-2-(2-methyl-1- benzothien-3-yl)perfluorocyclopentene and 1-(2-methyl-1-inden-3-yl)-2-(2-methyl- 1-benzofuran-3-yl)perfluorocyclopentene, were synthesized and their photochromic performance was examined.

Full text of DOI:10.1016/j.tetlet.2005.12.074

Tetrahedron
Letters
Tetrahedron Letters 47 (2006) 1267–1269
Photochromism of diarylethene derivatives having an indene unit
*
*
Tadatsugu Yamaguchi and Masahiro Irie
Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, 6-10-1 Hakozaki,
Higashi-ku, Fukuoka 812-8581, Japan
Received 22 October 2005; revised 8 December 2005; accepted 15 December 2005
Available online 9 January 2006
Abstract—Photochromic indene derivatives, 1-(2-methyl-1-inden-3-yl)-2-(2-methyl-1-benzothien-3-yl)perfluorocyclopentene and 1-
(
2-methyl-1-inden-3-yl)-2-(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene, were synthesized and their photochromic perfor-
mance was examined.
2006 Elsevier Ltd. All rights reserved.
ꢀ
Photochromism has attracted considerable attention
because of its potential application to molecular devices,
such as optical memories and switches. Among various
thesized in the past. In this letter, diarylethene deriva-
tives having an indene group were synthesized and the
photochromic performance was compared with a deriv-
ative having benzothiophene aryl groups.
1
thermally irreversible photochromic compounds, diaryl-
ethene derivatives are the most promising compounds
because of their fatigue resistant and thermally irrever-
Diarylethenes 1a and 2a were synthesized according to
Scheme 1. The coupling reaction of 2-methyl-1-indene
2
,3
sible properties. Diarylethene derivatives so far synthe-
4
sized have hetero-aryl moieties such as thiophene, ben-
with
1-(2-methyl-1-benzothien-3-yl)heptafluorocyclo-
5
6
7
9,10
zothiophene, thiazole, crysothiophene, and indole
pentene gave diarylethene 1a
in 24% yield. The
8
rings. Their photochromic performance is strongly
synthetic route of 2a was the same as that for 1a. The
dependent on the aryl moieties. When the aryl groups
have low aromatic stabilization energy, the derivatives
undergo thermally irreversible photochromic reactions.
When benzothiophene rings are used as heterocyclic
groups, it showed fatigue resistant performance (colora-
coupling reaction of 2-methylindene with 1-(2-methyl-
1
1
1-benzofuran-3-yl)heptafluorocyclopentene
4
gave
1
2
diarylethene 2a in 13% yield. Bis(2-methyl-1-benzo-
thiophen-3-yl)perfluorocyclopentene 3a was also synthe-
5
sized as a reference compound.
3
tion/decoloration cycles >10,000). Indene is an attrac-
tive aryl unit because of its low aromatic stabilization
energy and the structure is similar to benzothiophene.
Photochromic indene derivatives have not yet been syn-
Figure 1 shows the absorption spectral change of 1a by
photoirradiation in hexane. At the photostationary state
under irradiation with 313 nm light, 52% of the open-
ring isomer 1a, which has the maxima at 255 nm
F2
F2
F2
hν
F2
F2
F2
X
F2
H C
3
F2
F2
X
CH3
hν'
i)
X
Y
CH3
Y
H C
3
1
2
3
a: X = S, Y=CH2
a: X = O, Y=CH2
a: X = S, Y= S
1b: X = S, Y=CH2
2b: X = O, Y=CH2
3b: X = S, Y= S
ii) or iii)
1
a: X = S
2a: X = O
a, 2a
1
Scheme 1. Synthesis of indene derivatives 1 and 2. Reagents and
conditions: (i) n-BuLi (1.1 equiv), THF at À78 ꢁC and (ii) 1-(2-methyl-
1-benzothiophen-3-yl)heptafluorocyclopentene (24%) or (iii) 1-(2-
methyl-1-benzofuran-3-yl)heptafluorocyclopentene (13%).
Keywords: Photochromism; Diarylethene; Indene.
*
Corresponding authors. Tel.: +81 92 642 3557; fax: +81 92 642 3568
T.Y.); e-mail: tyamagu@cstf.kyushu-u.ac.jp
(
0040-4039/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2005.12.074

1268
T. Yamaguchi, M. Irie / Tetrahedron Letters 47 (2006) 1267–1269
closed-ring isomer returned to original 1a. Both isomers
were stable at 80 ꢁC in decaline for more than 1 day.
0
.4
.3
Just as for 1a, compound 2a underwent photochromism
upon irradiation with UV and visible light in hexane
0
(
Fig. 2). Compound 2a showed the absorption maxi-
4
À1
À1
mum at 281 nm (e: 0.68 · 10 M cm ). Upon irradia-
tion with 313 nm light, the diarylethene transformed
into closed-ring isomer 2b (e: 1.68 · 10 M cm ) at
4
4
À1
À1
0
0
.2
.1
35 nm. The absorption maximum showed a hypsochro-
mic shift as much as 34 nm in comparison with 1b. At
the photostationary state, the conversion ratio from
the open- to the closed-ring isomer was 43%. Upon irra-
diation with light of wavelength longer than 400 nm
light, the closed-ring isomers returned to the original
2a. Both isomers were stable at 80 ꢁC in decaline for
more than 1 day. The coloration/decoloration cycles
of the hexane solution of 1 or 2 could be repeated more
than 100 times without destruction.
0
.0
3
00
400
500
600
700
Wavelength /nm
Figure 1. Absorption spectra of 1a (solid line), 1b (broken line) and at
the photostationary state (dotted line) under irradiation with 313 nm
light in hexane (1.72 · 10 mol/L).
À5
The cyclization and cycloreversion quantum yields were
measured for compounds 1 and 2 (Table 1). The data for
diarylethene 3 are also shown in Table 1. Compounds 1
and 2 gave the same cyclization and cycloreversion
quantum yields. These values are slightly smaller than
4
À1
À1
(
e: 1.73 · 10 M cm ), converted to the closed-ring
isomer 1b, which has the absorption maxima at
69 nm (e: 1.19 · 10 M cm ). The colorless solution
changed to orange. By changing an aryl unit from a benz-
othiophene ring to an indene ring, the absorption max-
imum of the closed-ring isomer is shifted to shorter
wavelength as much as 48 nm. Upon irradiation with
light of wavelength longer than 400 nm light, the
4
À1
À1
4
1
3
the values of 3.
The molar absorption coefficients for the closed-ring
4
À1
À1
isomers 1 and 2 (1: 1.19 · 10 M cm , 2: 1.68 ·
4
À1
À1
10 M cm ) are larger than that of compound 3
0.91 · 10 M cm ). The compounds which absorb
at 400–500 nm range show, in general, low molar
absorption coefficient (e < 1.0 · 10 M cm ).
The closed-ring isomers 1 and 2 have the highest class
of the molar absorption coefficient so far reported.
4
À1
À1
(
4
À1
À1 14–17
0
0
.3
.2
Theoretical calculation for the absorption bands of the
closed-ring isomer 1b, 2b, and 3b was carried out with
1
8
Gaussian 03. The calculated wavelengths of 1b, 2b,
and 3b were 482.71 nm (f = 0.2236), 453.90 nm (f =
0
.4124) and 533.13 nm (f = 0.1918), respectively. The
absorption wavelengths correlate well with those of
experimental ones.
0
0
.1
.0
A single crystal 1a was obtained by recrystallization
from hexane and X-ray crystallographic analysis of
the crystal was carried out. Figure 3 shows the ORTEP
drawing of 1a. The aryl moieties are in an anti-parallel
conformation. As expected C24a carbon has sp3 struc-
ture. Although the aryl groups are in an anti-parallel
conformation, the distance between the reactive car-
bons is 0.451 nm. The distance is too far for the mole-
cule to undergo the photochromic reaction in the
300
400
500
600
700
Wavelength / nm
Figure 2. Absorption spectra of 2a (solid line), 2b (broken line) and at
the photostationary state (dotted line) under irradiation with 313 nm
light in hexane (1.72 · 10 mol/L).
À5
Table 1. Absorption characteristics and photoreactivity of diarylethene derivatives 1–3 in hexane
4
3
À1
À1
Compound
e/10 dm mol cm
Quantum yield
a
b
Cyclization
Cycloreversion
1
2
3
1.73 (255 nm)
0.68 (281 nm)
1.40 (254 nm)
1.19 (469 nm)
1.68 (435 nm)
0.91 (517 nm)
0.32 (313 nm)
0.32 (313 nm)
0.35 (313 nm)
0.25 (469 nm)
0.25 (435 nm)
0.35 (517 nm)

T. Yamaguchi, M. Irie / Tetrahedron Letters 47 (2006) 1267–1269
1269
8
9
. Yagi, K.; Irie, M. Bull. Chem. Soc. Jpn. 2003, 76, 1623.
1
. Compound 1a: colorless crystals; mp 139–140 ꢁC;
H
NMR (200 MHz) d 1.57 (s, 4H), 2.02 (s, 2H), 3.33 (s,
0
2
.67H), 3.51 (s, 1.33H), 6.99–7.22 (m, 6H), 7.38–7.47 (m,
H). Ms (EI) m/z 450 (M ); Anal. Calcd for C24H F S:
16 6
+
C, 63.99; H, 3.58%. Found: C, 64.01; H, 3.54%.
0. Crystal data for 1a: C H F S, MW = 450.43, mono-
1
2
4
16 6
˚
clinic, space group P2 /n, a = 8.0890(17) A, b =
1
˚
˚
1
8.886(4) A, c = 13.144(3) A, a = 90ꢁ, b = 90.882(3)ꢁ,
˚
3
À3
,
c = 90ꢁ, V = 2007.8(8) A , Z = 4, D = 1.490 g cm
c
R
1
= 0.0536 for 2460 observed reflections with I > 2r(I)
from 2881 unique reflections. CCDC deposition number:
91105.
1. Compound 4: colorless liquid; H NMR (200 MHz) d 2.50
s, 3H), 7.13–7.37 (m, 2H), 7.43–7.56 (m, 2H). Ms (EI) m/z
2
1
1
1
(
3
+
20 (M ).
2. Compound 2a: Colorless crystals; mp 105–106 ꢁC;
NMR (200 MHz) d 1.87 (s, 3H), 2.15 (s, 3H), 3.13 (s, 1H),
.37 (s, 1H), 2.47 (s, 4.2H), 7.07–7.34 (m, 6H), 7.37–7.52
1
H
3
+
Figure 3. The ORTEP drawings of 1a. The ellipsoids represent 50%
(m, 2H). Ms (EI) m/z 434 (M ); Anal. Calcd for
displacement of atoms. The arrow indicates a C24a carbon atom.
C H F O: C, 66.36; H, 3.71%. Found: C, 66.49; H,
2
4
16 6
3
.90%.
crystal.19 Any photocoloration was not observed in the
crystal.
13. Uchida, K.; Tsuchida, E.; Aoi, Y.; Nakamura, S.; Irie, M.
Chem. Lett. 1999, 63.
1
1
4. Uchida, K.; Irie, M. J. Inf. Record. 1998, 24, 101.
5. Peter, A.; Vitols, C.; McDonalds, R.; Branda, N. R. Org.
Lett. 2003, 5, 1183.
In conclusion, a new type of photochromic compounds
having an indene unit was synthesized and their photo-
chromic reactivity was examined in hexane.
16. Shrestha, S. J.; Nagashima, H.; Yokokama, Y.; Yoko-
yama, Y. Bull. Chem. Soc. Jpn. 2003, 76, 363.
1
1
7. Saito, M.; Yokoyama, Y.; Yokoyama, Y. Chem. Lett.
003, 806.
2
8. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G.
E.; Robb, M. A.; Cheeseman, J. R.; Montgomery, J. A.,
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Iyengar, S. S.; Tomasi, J.; Barone, V.; Mennucci, B.;
Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.;
Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda,
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Kitao, O.; Nakai, H.; Klene, M.; Li, X.; Knox, J. E.;
Hratchian, H. P.; Cross, J. B.; Bakken, V.; Adamo, C.;
Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.;
Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.;
Ayala, P. Y.; Morokuma, K.; Voth, G. A.; Salvador, P.;
Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich, S.;
Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.;
Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.; Ortiz,
J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.;
Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.;
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Acknowledgments
This work was supported by a Grant-in-Aid for Scien-
tific Research (S) (No. 15105006) from the Ministry of
Education, Culture, Sports, Science and Technology,
Japan.
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