Photocyclization reaction of a diarylmaleimide derivative in polar solvents

Article abstract of DOI:10.1039/b802780c

Photochromism of a symmetric diarylmaleimide derivative, having two thiophene rings (1), and a non-symmetric derivative having a S,S-dioxide thiophene ring and a thiophene ring (2) as the aryl moieties, was studied in various solvents. The photocyclization quantum yield of 1 gradually decreased with increasing the solvent polarity and the reaction was not observed in polar solvents, such as ethanol and acetonitrile; on the other hand, such a strong solvent dependence of the photocyclization reaction was not observed for 2; the different behavior is attributed to the weaker electron donating ability of the S,S-dioxide thiophene ring. The Royal Society of Chemistry.

Full text of DOI:10.1039/b802780c

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Photocyclization reaction of a diarylmaleimide derivative in polar
solventsw
Masato Ohsumi,a Masaki Hazama,a Tuyoshi Fukaminato*a and Masahiro Irie*b
Received (in Cambridge, UK) 19th February 2008, Accepted 21st April 2008
First published as an Advance Article on the web 19th May 2008
DOI: 10.1039/b802780c
Photochromism of a symmetric diarylmaleimide derivative,
having two thiophene rings (1), and a non-symmetric derivative
having a S,S-dioxide thiophene ring and a thiophene ring (2) as
the aryl moieties, was studied in various solvents. The photo-
cyclization quantum yield of 1 gradually decreased with increas-
ing the solvent polarity and the reaction was not observed in
polar solvents, such as ethanol and acetonitrile; on the other
hand, such a strong solvent dependence of the photocyclization
reaction was not observed for 2; the different behavior is
attributed to the weaker electron donating ability of the
S,S-dioxide thiophene ring.
A symmetric diarylmaleimide derivative, having thiophene
rings (1), and a non-symmetric derivative having a S,S-dioxide
thiophene ring and a thiophene ring (2) as the aryl moieties
(Scheme 1), were synthesized and their photochromic proper-
ties in various solvents were studied. Detailed synthetic pro-
cedures are described in the ESI.w Compound 1 was obtained
by a typical condensation procedure in high yield. Compound
2 was prepared by the oxidation of 1 using 3-chloroperoxy-
benzoic acid (m-CPBA)10 in 67% yield. The structures were
1
identified with H NMR, MS spectra and elemental analysisz
(also see ESIw).
Fig. 1(a) shows the absorption spectral change along with
the photochromic reaction of 1 in cyclohexane solution. Upon
irradiation with 405 nm light, the yellow color solution turned
to red–purple, and new absorption bands appeared at 526 and
377 nm. The color change is attributed to the photocyclization
reaction from the open-ring isomer (1a) to closed-ring isomer
(1b). Upon irradiation with visible light (l 4500 nm), the
peaks at 526 and 337 nm gradually decreased and finally
disappeared (i.e. the red–purple solution returned to a yellow
solution).
Recently, photochromic compounds have attracted consider-
able attention as molecular switches to control various func-
tions.1 Among many photochromic compounds, diarylethene
derivatives are the most promising for practical applications
because of their thermal stability and fatigue resistance.2,3 One
of potential applications of the photochromic compounds is as
a biological probe.4 Photochromic chromophores can be used
as an energy acceptor or donor group in FRET, which
provides a tool for resolving molecular interactions in biolo-
gical systems. Photochromic FRET is advantageous for the
quantitative determination of FRET parameters.5 In addition,
photochromic biological probes are also useful as a super-
resolution biological imaging technique.6 For useful applica-
tion, the photochromic compound should undergo photoreac-
tion even in polar solvents. In addition, the photoreaction
should be induced by irradiation with visible light, because in
biological systems UV light is absorbed by proteins, such as
indole residues. Diarylmaleimides7 as well as diarylmaleic
anhydrides8,9 are possible candidates for this application, since
these compounds undergo reversible photochromic reactions
upon irradiation with visible light. One of the drawbacks of
these derivatives is that the photochromic reactions are
strongly suppressed in polar solvents.8 It is strongly desired
to develop a novel diarylethene derivative, in which both
cyclization and cycloreversion reactions take place upon irra-
diation with light in the visible region even in polar solvents.
Here, we report on a diarylmaleimide derivative, which ex-
hibits reversible photochromism in polar solvents.
Remarkable solvent dependence was observed for the
photochromic reaction of 1. The conversion from the
open- to the closed-ring isomer in the photostationary state
under irradiation with 405 nm light decreased with increasing
solvent polarity. The conversion of 54% in cyclohexane
decreased to 42% in toluene, 27% in THF, 7% in
ethanol, and 4% in acetonitrile, respectively (Fig. 1(b) and
Fig. S1 in ESIw). In ethanol and acetonitrile solutions, no
appreciable color change was observed upon irradiation
with 405 nm light, as shown in Fig. 1(c). Table 1 summarizes
the quantum yields of 1 in various solvents. The strong solvent
dependence was observed only in the cyclization reaction. The
cyclization quantum yield of 1a decreases with increasing
solvent polarity. The cyclization quantum yield decreases to
0.097 in THF, 0.029 in ethanol and 0.013 in acetonitrile,
respectively. On the other hand, the photocycloreversion
a Department of Chemistry and Biochemistry, Graduate School of
Engineering, Kyushu University, Motooka 744, Nishi-ku, Fukuoka,
819-0395, Japan. E-mail: tuyoshi@cstf.kyushu-u.ac.jp;
Fax: +81-92-802-2873; Tel: +81-92-802-2873
b Department of Chemistry, Rikkyo University, Nishi-Ikebukuro
3-34-1, Toshima-ku, Tokyo, 171-8501, Japan.
E-mail: iriem@rikkyo.ac.jp; Fax: +81-3-3985-2397;
Tel: +81-3-3985-2397
w Electronic supplementary information (ESI) available: Details of
synthesis of 1 and 2. See DOI: 10.1039/b802780c
Scheme 1 Photochromism of diarylmaleimide derivatives.
Chem. Commun., 2008, 3281–3283 | 3281
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Fig. 2 Absorption spectra of 2 (a) in cyclohexane, (b) in ethanol; the
open-ring isomer (solid line), the photostationary state under irradia-
tion with 405 nm light (dashed line), and the closed-ring isomer
(broken line). (c) Photographs of color changes of 2 upon irradiation
with 405 nm light in various solvents (from left to right: cyclohexane,
toluene, THF, ethanol, acetonitrile): Left: before photoirradiation,
right: after photoirradiation.
Fig. 1 Absorption spectra of 1 (a) in cyclohexane, (b) in ethanol; the
open-ring isomer (solid line), the photostationary state under irradia-
tion with 405 nm light (dashed line), and the closed-ring isomer
(broken line). The inset in Fig. 1(b) shows the absorption spectra
between 400 and 700 nm. (c) Photographs of color changes of 1 upon
irradiation with 405 nm light in various solvents (from left to right:
cyclohexane, toluene, THF, ethanol, acetonitrile): Left: before photo-
irradiation, right: after photoirradiation.
Table 2 Absorption maxima, quantum yields and conversion ratios
from the open- to the closed-ring isomers upon irradiation with
405 nm light of 2 in various solvents
quantum yields are almost the same in cyclohexane, toluene,
THF, ethanol and acetonitrile. These results are similar to the
behavior of diarylmaleic anhydride derivatives previously
reported.8
l
max/nm
Quantum yield
Solvent
2a 2b
2a - 2ba 2b - 2ab Conversion (%)
Fig. 2(a) shows the absorption spectral change along with
photochromic reaction of 2 in cyclohexane solution. Upon
irradiation with 405 nm light, the yellow color solution turned
to red, and new absorption bands appeared at 498 and 331 nm.
The color change is attributed to the photocyclization reaction
from the open-ring isomer (2a) to the closed-ring isomer (2b).
Upon irradiation with visible light (l 4500 nm), the peaks at
498 and 331 nm gradually decreased and finally disappeared
(i.e. the red color solution returned to a yellow solution). The
conversion from 2a to 2b in cyclohexane was 80%, which is
much higher than that of 1a in the same solvent. 2a was
efficiently converted to 2b even in polar solvents such as
ethanol and acetonitrile (Fig. 2(b) and Fig. S2 in ESIw). The
color change along with photochromic reaction was clearly
observed even in polar acetonitrile (Fig. 2(c)). These results
suggest that the solvent polarity scarcely affects the photo-
reaction. The cyclization quantum yields were measured in
various solvents and are summarized in Table 2. As expected,
the cyclization quantum yield of 2a is still high even in
acetonitrile.
Cyclohexane 401 502 0.30
0.031
0.022
0.024
0.030
0.038
80
65
70
63
40
Toluene
THF
Ethanol
Acetonitrile
400 505 0.24
401 498 0.22
405 500 0.17
400 494 0.11
a
b
Irradiation with 405 nm light. Irradiation with 494 nm light.
In a previous paper,8 the solvent dependence of analogous
compounds, 1,2-bis(2,4,5-trimethylthiophene-3-yl)maleic an-
hydride and 1,2-bis(2-methylbenzothiophen-3-yl)maleic anhy-
dride was attributed to the contribution of
a twisted
intramolecular charge transfer interaction (TICT).11 The do-
nor–acceptor interaction between the thiophene and maleic
anhydride moieties play a role to control the reactivity. The
weak solvent dependence observed in 2a can be attributed to
the weak electron donating ability of the S,S-dioxide
thiophene ring.
In conclusion, a non-symmetric derivative having a S,S-
dioxide thiophene ring and a thiophene ring as the aryl
moieties was synthesized and showed high photochromic
reactivity even in polar solvents such as acetonitrile. The weak
electron donating ability of the S,S-dioxide moiety favored the
cyclization reaction even in polar solvents.
Table 1 Absorption maxima, quantum yields and conversion ratios
from the open- to the closed-ring isomers upon irradiation with
405 nm light of 1 in various solvents
This work was partly supported by Grant-In-Aid for Fun-
damental Research Program (S) (No. 15105006), Grant-in-
Aids for Young Scientist (B) (No. 18750119), Grant-in-Aids
for Scientific Research on Priority Areas (471) (No. 19050009)
from the Ministry of Education, Culture, Sports, Science, and
Technology (MEXT) of Japanese Government and also by
Grant-in-Aid for The Global COE Program, ‘‘Future Mole-
cular Systems’’ from the Ministry of Education, Culture,
Science, Sports and Technology of Japan.
l
max/nm
Quantum yield
Solvent
1a 1b
1a - 1ba 1b - 1ab Conversion (%)
Cyclohexane 392 526 0.22
0.16
0.14
0.12
0.13
0.14
54
42
27
7
Toluene
THF
Ethanol
Acetonitrile
398 527 0.13
393 526 0.097
396 528 0.029
388 525 0.013
4
a
b
Irradiation with 405 nm light. Irradiation with 516 nm light.
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This journal is The Royal Society of Chemistry 2008
3282 | Chem. Commun., 2008, 3281–3283

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S. Takami, S. Kobatake, T. Kawai and M. Irie, Chem. Lett.,
2003, 32, 892.
Notes and references
z Analytical data for 1a: 1H NMR (400 MHz, CDCl3): d 1.79 (s, 3H),
1.95–1.96 (m, 6H), 2.11 (s, 3H), 2.26–2.28 (m, 6H), 7.33–7.40 (m, 1H),
7.45–7.54 (m, 4H); MS (FAB+): m/z 422 [M + H]+; Anal. Calc. for
C24H23NO2S2: C, 68.38; H, 5.50; N, 3.32. Found: C, 68.32; H, 5.59; N,
3.32%.
4. R. Ando, H. Mizuno and A. Miyawaki, Science, 2004, 306, 1370;
N. Soh, K. Yoshida, H. Nakajima, K. Nakano, T. Imato,
T. Fukaminato and M. Irie, Chem. Commun., 2007, 5206.
5. L. Giordano, T. M. Jovin, M. Irie and E. Jares-Erijiman, J. Am.
Chem. Soc., 2002, 124, 7481; E. Jares-Erijiman and T. M. Jovin,
Nat. Biotechnol., 2003, 21, 1387.
6. S. W. Hell, S. Jakobs and L. Kastrup, Appl. Phys. A, 2003, 77, 859;
S. W. Hell, Science, 2007, 316, 1153; P. Dedecker, C. Flors, J. Hotta,
H. Uji-i and J. Hofkens, Angew. Chem., Int. Ed., 2007, 46, 8330.
7. K. Uchida and M. Irie, Bull. Chem. Soc. Jpn., 1998, 71, 1101;
T. Yamaguchi and M. Irie, Chem. Lett., 2004, 33, 1398.
8. M. Irie and K. Sayo, J. Phys. Chem., 1992, 96, 7671.
9. H. Miyasaka, T. Nobuto, M. Murakami, A. Itaya, N. Tamai and
M. Irie, J. Phys. Chem. A, 2002, 106, 8096.
10. Y.-C. Jeong, D. G. Park, E. Kim, K. Ahn and S. I. Yang, Chem.
Commun., 2005, 2503.
11. N. Mataga, Y. Kaifu and M. Koizumi, Bull. Chem. Soc. Jpn.,
1956, 29, 465; Z. Grabowski, K. Rotkiewicz and W. Rettig, Chem.
Rev., 2003, 103, 3899.
12. The identification of the molecular structure of compound 2 was
carried out by using the closed-ring isomer (2b), since the 1H
NMR signal of the open-ring isomer (2a) was very complex due to
the non-symmetric molecular structure and the existence of
parallel and anti-parallel conformers.
Analytical data for 2b:12 1H NMR (400 MHz, CDCl3): d 1.54 (s,
3H), 1.82 (s, 3H), 2.23 (d, 3H, J = 0.8 Hz), 2.32 (s, 3H), 2.41 (s, 3H),
2.48 (d, 3H, J = 0.8 Hz), 7.35–7.43 (m, 3H), 7.48–7.52 (m, 2H); MS
(FAB+): m/z 454 [M + H]+; Anal. Calc. for C24H23NO4S2: C, 63.55;
H, 5.11; N, 3.09. Found: C, 63.21; H, 5.32; N, 2.97%.
1. H. Bouas-Laurent and H. Durr, Pure Appl. Chem., 2001, 73, 639;
¨
F. M. Raymo and M. Tomasulo, Chem. Soc. Rev., 2005, 34, 327;
D. Gust, T. A. Moore and A. L. Moore, Chem. Commun., 2006,
1169; W. R. Browne and B. L. Feringa, Nat. Nanotechnol., 2006,
1, 25; N. Katsonis, M. Lubomska, M. M. Pollard, B. L. Feringa
and P. Rudolf, Prog. Surf. Sci., 2007, 82, 407.
2. M. Irie, Chem. Rev., 2000, 100, 1685; M. Irie and K. Uchida, Bull.
Chem. Soc. Jpn., 1998, 71, 985; H. Tian and S. Yang, Chem. Soc.
Rev., 2004, 33, 85; K. Matsuda and M. Irie, J. Photochem.
Photobiol., C, 2004, 5, 169.
3. M. Hanazawa, R. Sumiya, Y. Horikawa and M. Irie, J. Chem.
Soc., Chem. Commun., 1992, 206; M. Irie, T. Lifka, K. Uchida,
S. Kobatake and Y. Shindo, Chem. Commun., 1999, 747;
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