Photochromic properties of diarylethene maleimide derivatives in polar solvents

Article abstract of DOI:10.1246/cl.2004.1398

Diarylmaleimide derivatives having methoxy, phenyl, or cyano group as a nitrogen substituent were synthesized in an attempt to prepare photochromic compounds which exhibit photochromic reactivity even in polar solvents. Although the derivatives having methoxy or phenyl group did not undergo photochromism in polar solvents, the derivative having a cyano group showed photochromism even in polar solvents.

Full text of DOI:10.1246/cl.2004.1398

1398
Chemistry Letters Vol.33, No.10 (2004)
Photochromic Properties of Diarylethene Maleimide Derivatives in Polar Solvents
Tadatsugu Yamaguchiꢀ and Masahiro Irieꢀy
Chemical and Textile Industry, Fukuoka Industrial Technology Center,
3-2-1 Kamikoga, Chikushino, Fukuoka 818-8540
yDepartment of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University,
6-10-1Hakozaki, Higashi-ku, Fukuoka 812-8581
(Received July 29, 2004; CL-040895)
Diarylmaleimide derivatives having methoxy, phenyl, or
cyano group as a nitrogen substituent were synthesized in an
attempt to prepare photochromic compounds which exhibit
photochromic reactivity even in polar solvents. Although the
derivatives having methoxy or phenyl group did not undergo
photochromism in polar solvents, the derivative having a cyano
group showed photochromism even in polar solvents.
NC
Me
Cl
Me
Me
Ph
Ph
Ph
S
S
S
7
5
6
ClOC
Me
HOOC
Me
Ph
S
Ph
S
8
Various kinds of diarylethenes that undergo thermally irre-
versible and fatigue-resistant photochromic reactions have been
developed.1–3 One of potential application fields of photochro-
mic compounds is a fluorescent probe in biological systems,
such as a FRET probe.4 For such application the photochromic
compound should have sensitivity in visible region and the reac-
tions should take place even in polar solvents, because UV light
induces the damages of the biological systems. Diarylmalei-
mides5,6 as well as diarylmaleic anhydrides7–9 exhibit reversible
photoisomerization reactions upon irradiation with visible light.
However, their photochromic reactions are strongly prohibited
in polar solvents. This is due to an intramolecular electron trans-
fer (TICT) from the donor aryl moiety to the electron acceptor
maleic anhydride or maleimide moiety.5,8 In this work, the di-
arylmaleimide derivatives having methoxy, phenyl, or cyano
groups as a nitrogen substituent were synthesized in an attempt
to control photochromic reactivity in polar solvents. Methoxy
substituent was also introduced at 2-position of benzothiophene
to decrease the cycloreversion quantum yield.10
9
O
O
NHR
S
S
OMe
OMe
11: R = Ph
12: R = OMe
13: R = CN
10
11-13
R
N
O
O
O
O
9
NHR
Me
OMe
1-3
Ph
S
S
S
OMe
11-13
1: R = Ph
2: R = OMe
3: R = CN
Scheme 1. Synthesis of diarylethene maleimide derivatives
1–3.
R1
N
R1
N
h
ν
O
O
O
S
O
S
Ref. 6. The coupling reaction of 9 with N-alkylglycoxylamide
(11–13) gave diaryethenes 1–3 in 12–20% yields. A nitrophenyl
derivative 4 was also synthesized to improve the photoreactivity.
The synthetic route of 4 was the same as that of 1. 2-methyl-
5-(4-nitrophenyl)thiophene was used instead of 2-methyl-5-
phenylthiophene.
hν'
Me
Me
OMe
S
S
OMe
R2
R2
1b-4b
1a-4a
Table 1 summarizes conversions from the open to the
1: R1 = CN, R2 = H
2: R1 = Ph, R2 = H
3: R1 = OMe, R2 = H
4: R1 = CN, R2 = NO2
Table 1. Converision rates of 1–4 from open-ring to closed-ring
isomer upon irradiation with 436-nm or 365-nm light in various
solvents
Diarylmaleimide derivatives 1a–3a were synthesized ac-
cording to Scheme 1. The detail procedure has been reported
in Ref 6. 2-Methyl-5-phenylthiophene was reacted with chloro-
methyl methylether and with sodium cyanide to give compound
7 in 47% yields. The carboxylic acid 8 was obtained by the hy-
drolysis of 7 in 95% yields. N-alkylglycoxylamide derivatives
(11–13) were synthesized from 10. Cyanamide, methoxyamide
or aniline was prepared by the same procedure as used in
Conversion Rate/%
Wavelength Hexane Toluene DMF Acetonitrile Ethanol
Irradiation
a
1
2
3
4
4
436 nm
436 nm
436 nm
436 nm
365 nm
—
43
45
—
—
45
28
26
70
82
13
0
0
43
73
5
0
0
16
70
3
0
0
10
30
a
a
ainsoluble.
Copyright Ó 2004 The Chemical Society of Japan

Chemistry Letters Vol.33, No.10 (2004)
1399
Table 2. Absorption characteristics and photoreactivity of
diarylethene in toluene
0.8
"/103 dm3 molꢃ1 cmꢃ1
Quantum yield
Compound
Open
Form
Closed-ring
Form
0.6
0.4
0.2
0.0
Cyclization Cycloreversion
1
2
3
4
3.24
(410 nm)
3.08
(412 nm)
4.02
(422 nm)
3.03
(415 nm)
4.78
(547 nm)
4.30
(550 nm)
5.76
(542 nm)
4.55
(570 nm)
0.27
(436 nm)
0.27
(436 nm)
0.17
(436 nm)
0.20
(436 nm)
0.49
(547 nm)
0.20
(550 nm)
0.42
(542 nm)
0.068
(550 nm)
sion quantum yield of 4b was very small (ꢀ ¼ 0:068). Both cy-
ano and nitro substituent contribute to increase the conversion
rate.
300
400
500
600
700
Wavelength / nm
Figure 1. Absorption spectra of 4a (solid line) 4b (dashed line)
and in the photostationary state under irradiation with 436-nm
light (dotted line) and 365-nm light (dott-dashed line) in aceto-
nitrile solution (1:72 ꢂ 10ꢃ5 mol/L).
References and Notes
1
H. Durr and H. Bouas-Laurent, ‘‘Photochromism Molecules
¨
and Systems,’’ Elsevier, Amsterdam (1990).
M. Irie, ‘‘Photo-Reactive Materials for Ultrahigh-Density
Optical Memory,’’ Elsevier, Amsterdam (1990).
M. Irie, Chem. Rev., 100, 1685 (2000).
L. Giordano, T. M. Jovin, M. Irie, and E. A. Jares-Erijman,
J. Am. Chem. Soc., 124, 7481 (2002).
T. Yamaguchi, K. Uhida, and M. Irie, J. Am. Chem. Soc.,
119, 6066 (1997).
K. Uchida, Y. Kido, T. Yamaguchi, and M. Irie, Bull. Chem.
Soc. Jpn., 71, 1101 (1998).
closed-ring isomers at the photostationary state in various sol-
vents. Upon irradiation with 436-nm light, the open-ring isomer
1a converted to the closed-ring isomer 1b, which has the absorp-
tion maximum at 547 nm. The conversion rate of 1 was 45% in
toluene. The blue color disappeared upon irradiation with >560-
nm light. In polar solvents such as acetonitrile the rate was
decreased to 5%.
Compounds 2 and 3 underwent reversible photoisomeriza-
tion reactions upon irradiation with 435-nm and >560-nm light
in hexane and toluene solutions. The conversion rates of 2 and 3
were dramatically decreased by changing the solvent from hex-
ane to toluene. These compounds did not show any spectral
change upon irradiation with any wavelength in acetonitrile.
The result suggests that the reactivity in polar solvents is depend-
ent on the nitrogen substituent. The cyano group is the best sub-
stituent for the photoreaction in polar solvents.
In order to improve the photoreactivity in polar solvents,
an electron withdrawing nitro group was introduced at the para-
position of the phenyl group. The electron withdrawing group is
known to decrease the photocycloreversion quantum yield.11
Figure 1 shows the absorption spectral change of 4 in acetoni-
trile. Upon irradiation with 436 nm, the open-ring isomer 4a con-
verted to the closed ring isomer 4b with the absorption band at
570 nm. The conversion rate of 4 was 30%. Upon irradiation
with >560-nm light, the closed-ring isomer returned back to
the open-ring isomer. The conversion rate was increased to
70% under irradiation with 366 nm, at which the absorption
coefficient of the open-ring isomer is larger than that of the
closed-ring isomer.
2
3
4
5
6
7
8
9
M. Irie and M. Mohri, J. Org. Chem., 53, 803 (1988).
M. Irie and K. Sayo, J. Phys. Chem., 96, 7671 (1992).
K. Uchida, Y. Nakayama, and M. Irie, Bull. Chem. Soc. Jpn.,
63, 1311 (1990).
10 K. Shibata, S. Kobatake, and M. Irie, Chem. Lett., 2001,
618.
11 K. Matsuda, Y. Shinkai, T. Yamaguchi, K. Nomiyama,
M. Isayama, and M. Irie, Chem. Lett., 32, 1178 (2003).
12 1a: Orange crystals; mp. 84–85 ꢁC; H NMR (200 MHz) ꢀ
1
2.57 (s, 3H), 3.70 (s, 3H), 6.79–7.87 (m, 10H). EIMS m=z
456 (Mþ). Anal. Calcd for C25H16N2O3S2: C 65.77, H
3.53, N 6.14%. Found: C 65.75, H 3.53, N 6.06%.
13 2a: Orange crystals; mp.78–79 ꢁC; 1H NMR (200 MHz) ꢀ
2.52 (s, 3H), 3.72 (s, 3H), 6.84–7.73 (m, 15H). EIMS m=z
507 (Mþ); Anal. Calcd for C30H21NO3S2: C 70.98, H 4.17,
N 2.76%. Found: C 70.97, H 4.21, N 2.72%.
14 3a: Orange crystals mp. 159–160 ꢁC; 1H NMR (200 MHz) ꢀ
2.50 (s, 3H), 3.72 (s, 3H), 4.07 (s, 3H), 6.77–8.11 (m, 10H).
EIMS m=z 461 (Mþ). Anal. Calcd for C25H19NO4S2: C
65.06, H 4.15, N 3.03%. Found: C 65.16, H 4.22, N 2.89%.
15 4a: Orange crystals; mp.78–80 ꢁC; 1H NMR (200 MHz) ꢀ
2.46 (s, 3H), 3.80 (s, 3H), 6.83–8.20 (m, 10H). EIMS m=z
501 (Mþ); Anal. Calcd for C25H15N3O5S2: C 59.87, H
3.01, N 8.38%. Found: C 59.97, H 3.07, N 8.25%.
The quantum yields, the absorption maxima of the open-
and the closed-ring isomers, and their absorption coefficients
are summarized in Table 2. The cyclization quantum yields of
1–4 are relatively high in toluene. As expected, the cyclorever-
Published on the web (Advance View) September 25, 2004; DOI 10.1246/cl.2004.1398