Spectral, conformational and photochemical analyses of photochromic dithienylethene: Cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethene revisited

Article abstract of DOI:10.1002/ejoc.201301143

The conformational equilibrium and thermodynamic parameters of cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethene (1a) and its trans derivative 1c are presented. Irradiation of both compounds was carried out by using 365 nm light, which affects the cis/trans isomerisation process, whereas irradiation with 405 nm light preferentially promotes the formation of the cyclised product. Prolonged irradiation of 1a at 365 nm leads to the formation of a new derivative showing photochromic properties. Evidence for the formation of the novel derivative is presented, and details of its photochromic properties were investigated; a tentative mechanism has also been proposed. The equilibrium between parallel and antiparallel forms of cis- and trans-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethene was studied by NMR spectroscopy. Photocyclisation or cis/trans isomerisation was induced by irradiation with 405 or 365 nm light. Extended irradiation of the cis compound generated two peroxy derivatives that thermally convert into a new coloured compound with its own photochromic properties. Copyright

Full text of DOI:10.1002/ejoc.201301143

FULL PAPER
DOI: 10.1002/ejoc.201301143
Spectral, Conformational and Photochemical Analyses of Photochromic
Dithienylethene: cis-1,2-Dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethene
Revisited
Firealem G. Erko,[a] Jérôme Berthet,[a] Abhijit Patra,[b][‡] Régis Guillot,[c]
Keitaro Nakatani,[b] Rémi Métivier,[b] and Stéphanie Delbaere*[a]
Keywords: Conformation analysis / Photochromism / Photochemistry / Dithienylethene / Peroxides
The conformational equilibrium and thermodynamic param-
eters of cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)eth-
ene (1a) and its trans derivative 1c are presented. Irradiation
of both compounds was carried out by using 365 nm light,
which affects the cis/trans isomerisation process, whereas ir-
radiation with 405 nm light preferentially promotes the for-
mation of the cyclised product. Prolonged irradiation of 1a at
365 nm leads to the formation of a new derivative showing
photochromic properties. Evidence for the formation of the
novel derivative is presented, and details of its photochromic
properties were investigated; a tentative mechanism has also
been proposed.
hibited reversible photoisomerisation upon light irradia-
tion.[2] Its reversible photocyclisation induced with 405 nm
light involves an open-ring isomer (open form 1a) and a
closed-ring isomer (closed form 1b, see Scheme 1). The
open form exists in two conformations, namely the parallel
and the antiparallel conformers. The former conformer has
both thienyl groups in mirror symmetry, whereas the latter
conformer has C2 symmetry, which is the only form able to
photocyclize according to the Woodward–Hoffmann rules.
Introduction
Since their discovery in 1988, 1,2-dithienylethene deriva-
tives have emerged as a unique class of photochromic func-
tional materials.[1,2] They have received great attention due
to their fascinating properties, such as thermal stability, fa-
tigue resistance, high sensitivity and short response times.
Active research has subsequently developed due to their
promising applications in an extensive range of technol-
ogies, from optical data storage to sensors and switches.[3–27]
The photochromic reaction of cis-1,2-dithienylethenes is a
reversible phototransformation between 1,3,5-hexatriene
and cyclohexadiene by a conrotatory mechanism according
to the Woodward–Hoffmann rules.[28] Absorption of light
induces not only photocyclisation but also a cis/trans iso-
merisation of the double bond joining the thienyl groups.
The latter reaction could be avoided by introducing a per-
fluorocyclopentene or maleic anhydride group, which pro-
hibits the cis/trans photoisomerisation, which may compete
with the photocyclisation reaction.[2] cis-1,2-Dicyano-1,2-
bis(2,4,5-trimethyl-3-thienyl)ethene (1a; Scheme 1) was the
first bistable dithienylethene molecule to be found that ex-
[a] Université Lille Nord de France, UDSL, CNRS UMR 8516,
BP83, 59006 Lille, France
Scheme 1. Photochromic reactions of cis-1,2-dicyano-1,2-bis(2,4,5-
trimethyl-3-thienyl)ethene in its open cis isomer (1a), closed isomer
(1b), and open trans isomer (1c).
E-mail: stephanie.delbaere@univ-lille2.fr
http://lasir.univ-lille1.fr
[b] PPSM, ENS Cachan, CNRS, UMR8531,
61 av. Président Wilson, 94235 Cachan cedex, France
[c] Institut de Chimie Moléculaire et des Matériaux d’Orsay,
UMR8182 CNRS, Université Paris-Sud,
The photochromism of 1a has been investigated by UV/
Vis and IR spectroscopy,[29] cyclic voltammetry, fast-sweep
voltammetry and in situ electrochemical absorptiometry,[30]
in colloidal solutions and amorphous films,[18] in amorph-
ous solids,[31] polymer matrices,[32] and in nanoscale thin
layers[33,34] to construct photoswitchable materials.
Bât 420, 91405 Orsay Cedex, France
[‡] Present address: Department of Chemistry, Indian Institute of
Science Education and Research Bhopal,
Bhopal 462030, Madhya Pradesh, India
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201301143.
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NMR spectroscopic analysis of 1a in CCl4 was reported mined from the simulation of the spectra by using DNMR
by Irie,[2] before photoirradiation and at the photostation- software.[35,36] Simulated spectra with the corresponding
ary state under irradiation with 405 nm light. The six lines rate constants, along with matching experimental spectra at
observed before photoirradiation indicate the existence of different temperatures, are shown in the Supporting Infor-
two conformations in the compound. The broadening of mation. The rate constant found from the DNMR software
the six methyl signals is explained by the interconversion of is the rate of exchange between the parallel and antiparallel
the two conformers, which is induced by rotation of the forms and is represented as k = kparallel + kantiparallel. Since
thiophene rings. The conversion of the cis form into the the concentration ratio of parallel vs. antiparallel conform-
cyclised form (1b) in the photostationary state was observed ers was found to be independent of the temperature (1:1.03,
to be 60% and the cis (1a) into the trans (1c, Scheme 1) parallel/antiparallel), the rate constant for both is approxi-
isomerisation was considered to be rather negligible under mately equal, with kparallel = kantiparallel = k/2. Then the k
these irradiation conditions.
values can be used to calculate the activation energy by
In this paper, we detail the structural, conformational using the Eyring plot and the Arrhenius plot. The acti-
and photochemical properties of the three isomers 1a, 1b, vation parameters for the rotation of the thienyl units in 1a
and 1c by a combination of UV/Vis, X-ray diffraction and were found to be ΔH϶
= =
71.2 kJmol–1, ΔS϶
NMR spectroscopy. In addition to the expected photochro- +28.4 Jmol–1 K–1 and Ea = 73.5 kJmol–1. In 1c, the acti-
mic behaviour, upon extended irradiation, the formation of vation parameters were calculated to be ΔH϶
a new photoproduct, being also photochromic, has been 77.5 kJmol–1, ΔS϶ +43.1 Jmol–1 K–1 and Ea
=
=
=
underlined and characterised.
79.9 kJmol–1. Then, in both molecules, the rotational en-
ergy barriers are comparable, and these activation energies
for the conformational changes are in complete agreement
with values reported by Uchida et al. for benzo derivatives
of 1a (67 and 71 kJmol–1).[37]
Results and Discussion
To obtain a preliminary insight into the rotation behav-
iour of the thienyl units, H NMR spectra were carefully
The UV/Vis absorption spectrum of 1a in chloroform
(Figure 2) shows three main bands at 304, 324, and 375 nm.
When irradiated at 365 or 405 nm, the 1a isomer (open cis
form) is converted into isomer 1b (closed form). The latter
is characterised by an extended absorption spectrum from
1
examined. At room temp., 1a (300 MHz, CD3CN, Fig-
ure 1a) displays six broad resonances due to the coexistence
of the antiparallel and parallel conformations. Compound
1c exhibits three resonances at ambient temperature (Fig-
ure 1b) that are split upon decreasing the temperature
(300 MHz, CD3CN). Repeating the measurement of 1c in
[D8]toluene at room temp. revealed the existence of five
broad signals for six methyl groups (two signals are at the
same position), thus indicating the existence of two con-
formers, observed separately by NMR spectroscopy.
the visible region, with a large band located at λmax
=
522 nm, to the UV region, with a band maximum at 359 nm
(Figure 2). The ring-closure reaction 1a Ǟ 1b is reversible;
when irradiated at 546 nm, the ring-opening reaction 1b Ǟ
1a occurs, and the open cis isomer is fully recovered. How-
ever, UV irradiation of 1a in chloroform (365 or 405 nm)
does not produce solely the 1b isomer. Indeed, a noticeable
proportion of open trans isomer 1c is present at the photo-
stationary state (PSS), as observed by simple thin-layer
chromatography. Separation and purification of isomer 1c
by column chromatography allowed its absorption spec-
trum to be recorded, which showed two main bands at 325
and 380 nm. Determination of its absorption coefficient
Figure 1. 1H NMR spectra of (a) pure 1a, (b) pure 1c, and (c) mix-
ture after irradiation with 405 nm light.
Variable-temperature NMR studies of 1a and 1c were
conducted to determine the rates of rotation of the thienyl
units. NMR spectra were recorded in the range 229–333 K
for 1a. The coalescence temperatures of 303 and 292 K
(300 MHz, CD3CN) were deduced for 1a and 1c, respec-
Figure 2. Molar absorption coefficient curves (ε in Lmol–1 cm–1) of
tively. The rate of rotation of the thienyl groups was deter- 1a, 1b and 1c isomers in CHCl3.
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cis-1,2-Dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethene Revisited
provided a value that was slightly lower than that of isomer
The same procedure was applied by starting from a solu-
tion of trans isomer 1c, irradiated with 365 and 405 nm
light (Figure 5). Similarly, 45% of the cyclised form 1b and
1a (ε325nm
= =
5600 Lmol–1 cm–1 for 1c vs. ε304nm
7600 Lmol–1 cm–1 for 1a).
The X-ray diffraction of single-crystals of 1a, 1b, and 1c 18% of trans isomer 1c were formed upon 405 nm irradia-
provided the structures of the three isomers, as depicted in tion, and 10% of 1b and 20% of 1c were obtained upon
Figure 3. In the crystalline state, the open cis form 1a is in 365 nm irradiation. It can then be confirmed that the
the antiparallel conformation. The distance between the cis/trans photoisomerisation is favoured with 365 nm light,
two carbon atoms involved in the cyclisation is 3.496 Å, whereas 405 nm irradiation preferentially induces the cyclis-
which is in agreement with the distance required for photo- ation.
chromism in the solid state. Compound 1b has a typical,
During the photochemical investigation of 1a with
more planar structure that is compatible with an extended 365 nm light, we extended the time of irradiation and were
π-conjugated system, and 1c shows thienyl rings tilted from intrigued to observe the formation of a new product desig-
the plane of the ethene bridge, with dihedral angles of nated as 1d (Figure 6a).
121.38° and 126.90° for the two thiophene rings.
We isolated an appreciable amount of compound 1d by
irradiation at 365 nm of a 300 mL solution of CHCl3 con-
taining 30 mg of compound 1a for 6 h (by means of a
closed-loop recirculation system equipped with a suitable
2 mm quartz cell) and further purified by column
chromatography. Mass analysis allowed a formula of
C18H18N2O2S to be determined. 1H NMR spectra, re-
corded in CDCl3, showed six methyl signals for 1d from δ
= 1.50 to 2.70 ppm (Figure 6b). Of the signals of the 18
carbon atoms observed in the 13C NMR spectrum, two
Figure 3. ORTEP views of 1a, 1b and 1c (ellipsoid probability at
50% level, hydrogen atoms have been omitted).
showed high chemical shift values (δ
= 200.9 and
208.2 ppm) that were not observed in either of the pre-
The photochemical behaviour of 1a and 1c was then in- viously characterised open (1a) or closed form (1b). This
vestigated by NMR spectroscopy. Figure 4 shows the con- indicates that two carbonyl groups might be present in 1d.
centration/time profiles of 1a under photoirradiation with 1H-13C HMBC spectra were recorded with an optimised
1
365 and 405 nm light, followed by H NMR spectroscopy. coupling constant of 8 Hz (2J-3J) and 1 Hz (4J). These sig-
2
Irradiations led to a decrease in the initial amount of 1a nals underlined the J correlation between a CH3 group (δ
and the formation of two sets of resonances, assigned to the = 2.69 ppm) and of a highly deshielded carbon atom (δ =
closed isomer 1b (Figure 1c) and to the trans isomer 1c. 200.9 ppm). In addition, the second deshielded carbon
Under our conditions, 62% of the cyclised form 1b and atom (δ = 208.2 ppm) correlated with a CH3 group (δ =
20% of the trans isomer 1c (Scheme 1) were reached upon 2.31 ppm) and a second CH3 group (δ = 1.75 ppm). Two
irradiation with 405 nm light, whereas 10% 1b and 30% 1c carbon atoms resonating at δ = 62.8 and 64.5 ppm were also
were produced upon irradiation with 365 nm light.
detected, which were characterised as bridged sp3 carbon
Figure 4. Time-evolution concentration of 1a upon irradiation with 365 nm (left) and 405 nm light (right). Circles: 1a; squares: 1b;
diamonds: 1c.
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S. Delbaere et al.
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Figure 5. Time-evolution concentration of 1c upon irradiation with 365 nm (left) and 405 nm light (right). Circles: 1a; squares: 1b;
diamonds: 1c.
Scheme 2. Photochromic reaction of 1d and 1e derivatives; 1H and
13C NMR chemical shifts.
Figure 6. 1H NMR spectra of (a) a mixture after 365 nm irradiation
of 1a at room temp. for 30 min; (b) pure 1d; (c) 1d after irradiation
with 546 nm light; (d) 1a after irradiation with 365 nm at 253 K for
2 h.
atoms in a configuration of the cyclohexadiene. All these
observations are in agreement with the structure of 1d dis-
played in Scheme 2. Because 1d contains a 1,3-cyclohexa-
diene, it is expected to be opened if a suitable wavelength
of irradiation is applied. The absorption spectrum of 1d
Figure 7. UV/Vis spectra of 1d and 1e in acetonitrile.
shows a band maximum in the visible range (475 nm), char-
acteristic of closed diarylethenes (Figure 7). Irradiation at
To understand the mechanistic pathway leading to the
546 nm of 1d at room temp. for 5 min resulted in the forma- formation of 1d, a fresh sample of 1a was irradiated for
tion of a new product that was fully characterised by 1D 120 min, in periods of 10 min; between each irradiation
and 2D NMR spectroscopy as the colourless open form, step, NMR spectra were recorded (Figure 6d). The presence
namely 1e (see Scheme 2 and Figure 6c). Subsequent irradi- of two additional sets of signals characterising two photo-
ation at 365 nm of a sample containing 1e, led to its conver- products (I1 and I2), which thermally evolved towards 1d,
sion into closed 1d, thus revealing further photochromic was underlined. Cooling of the solution enabled 2D NMR
properties.
spectra to be recorded to assign these signals to two isomers
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cis-1,2-Dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethene Revisited
of peroxy intermediates, as depicted in Scheme 3. This as-
The presence of two peroxy intermediates is suggested to
signment is in agreement with the suggestion of endoperox- result from singlet oxygen approaching the thiophene ring
ide formation on the thiophene cycle reported by Taniguchi from endo and exo sides. The similarities between the NMR
et al.[38]
spectroscopic data of the two intermediates are a further
indication that the two peroxy derivatives have similar
chemical linkages. Thus, considering the experimental evi-
dence, and also that they contain 1,3-cyclohexadiene, it is
possible to devise a plausible mechanism for the formation
of 1d from 1a (Scheme 4). However, in the course of our
studies, we did not succeed in detecting the presence of the
two peroxy derivatives with open diarylethenes (I1Ј and I2Ј),
which are expected to be the respective precursor of the two
peroxy derivatives with cyclised diarylethenes (I1 and I2).
The peroxides thermally decompose to 1d with extrusion of
sulfur, as previously reported by some authors.[39–41]
Conclusions
The equilibrium between parallel and antiparallel con-
formations of cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thi-
enyl)ethene (1a) and its trans derivative (1c) has been quan-
tified with the determination of the thermodynamics pa-
rameters. The photochromic reaction was studied by using
two irradiation wavelengths. At 405 nm, the main reaction
is the photocyclisation into 1b, whereas irradiation at
365 nm favours cis/trans isomerisation between 1a and 1c.
The three structures were characterised by NMR and X-ray
analyses.
Scheme 3. Structures of the two intermediates I1 (top) and I2 (bot-
1
tom) with H and 13C NMR chemical shifts.
In addition to the conventional photochromic reactions
occurring with dithienylethene derivatives (ring-opening/
ring-closure reactions, cis/trans isomerisation), we have ob-
tained evidence for the formation under 365 nm light irradi-
ation of a new coloured compound, 1d, showing its own
photochromic properties. This species has been fully iden-
tified and could be decyclised with visible light into the
colourless compound 1e, which is able to yield back com-
pound 1d. The formation of 1d from 1a upon extended irra-
diation time involved two peroxy derivatives that are ther-
mally converted into 1d. A plausible mechanism was pro-
posed. The intricate reaction pathways of the 1a derivative
under light activation, involving open cis, open trans, closed
isomers, and, additionally, these latter photoproducts 1d
and 1e, result in a very complex photochromic pattern. Al-
though this dithienylethene compound is used in a wide
range of applications, such properties were not described
until now. Multiple photochromic routes that depend on
the irradiation wavelengths, as described for this simple
compound, could be advantageously employed to reach
several molecular states by a light trigger, with reversible
or irreversible locking/unlocking behaviour, in the field of
organic electronic devices.
Experimental Section
NMR spectra (1H, 13C, HMBC and HSQC) were recorded with
Bruker 500 or 300 MHz spectrometers equipped with TXI or QNP
probes. Samples were irradiated directly in the NMR tube (5 mm)
Scheme 4. Proposed mechanism for the photoreaction from 1a to
1d under irradiation at 365 nm.
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[11] M. Irie, Chem. Rev. 2000, 100, 1685–1716.
by using a 1000 W Xe-Hg high-pressure filtered short-arc lamp
(Oriel), equipped with suitable filters. Monochromatic UV light
was obtained by passing the light through a first filter (Schott
11FG09: 259 Ͻ λ Ͻ 388 nm with λmax = 330 nm, T = 79%), then
through an interferential filter (λ = 365 nm and T = 30%). Mono-
chromatic visible light was obtained by passing the light through a
first filter (Schott SCFIKG1503: 295 Ͻ λ Ͻ 800 nm with T = 50%
at λ = 330 and 700 nm), then through an interferential filter (λ =
405 nm and T = 49%, λ = 546 nm and T = 15%).
[12] H. Tian, S. Wang, Chem. Commun. 2007, 781–792.
[13] S. J. Lim, B. K. An, S. D. Jung, M. A. Chung, S. Y. Park, An-
gew. Chem. 2004, 116, 6506; Angew. Chem. Int. Ed. 2004, 43,
6346–6350.
[14] Z. Tian, W. Wu, A. D. Q. Li, ChemPhysChem 2009, 10, 2577–
2591.
[15] I. Yildiz, E. Deniz, F. M. Raymo, Chem. Soc. Rev. 2009, 38,
1859–1867.
[16] Q. Chen, Y. Feng, D. Q. Zhang, G. X. Zhang, Q. H. Fan, S. N.
Sun, D. B. Zhu, Adv. Funct. Mater. 2010, 20, 36–42.
[17] Y. N. He, Y. Yamamoto, W. S. Jin, T. Fukushima, A. Saeki, S.
Seki, N. Ishii, T. Aida, Adv. Mater. 2010, 22, 829–832.
[18] K. Kasatani, S. Kambe, M. Irie, J. Photochem. Photobiol. A:
Chem. 1999, 122, 11–15.
[19] N. Tagawa, A. Masuhara, H. Kasai, H. Nakanishi, H. Oikawa,
Cryst. Growth Des. 2010, 10, 2857–2859.
[20] F. Sun, F. Zhang, F. Zhao, X. Zhou, S. Pu, Chem. Phys. Lett.
2003, 380, 206–212.
[21] A. Spangenberg, R. Métivier, J. Gonzalez, K. Nakatani, P. Yu,
M. Giraud, A. Leaustic, R. Guillot, T. Uwada, T. Asahi, Adv.
Mater. 2009, 21, 309–313.
[22] N. Tagawa, A. Masuhara, T. Onodera, H. Kasai, H. Oikawa,
J. Mater. Chem. 2011, 21, 7892–7894.
[23] J. Piard, R. Métivier, M. Giraud, A. Léaustic, P. Yu, K. Nakat-
ani, New J. Chem. 2009, 33, 1420–1426.
UV/Vis absorption spectra were recorded with a Cary 5000 spectro-
photometer from Agilent Technologies. Production of 1d in large
amounts was performed by using a circulation system with a Mes-
terflex peristaltic pump, PTFE tube and a circulation quartz cu-
vette under in situ continuous irradiation by means of an Hg/Xe
lamp (Hamamatsu, LC6 Lightningcure, 200 W) equipped with a
narrow-band interference filter (Semrock Hg01-365-25 for λirr
=
365 nm).
X-ray diffraction data were collected with a Kappa X8 APPEX II
Bruker diffractometer with graphite-monochromated Mo-Kα radia-
tion (λ = 0.71073 Å). Crystals were mounted on a CryoLoop
(Hampton Research) with Paratone-N (Hampton Research) as cry-
oprotectant and then flash-frozen in a nitrogen gas stream at
100 K.
[24] A. Patra, R. Métivier, J. Piard, K. Nakatani, Chem. Commun.
2010, 46, 6385–6387.
Supporting Information (see footnote on the first page of this arti-
cle): NMR spectra, details of DNMR, MS, and X-ray data.
[25] R. O. Al-Kaysi, C. J. Bardeen, Adv. Mater. 2007, 19, 1276–
1280.
[26] F. Di Benedetto, E. Mele, A. Camposeo, A. Athanassiou, R.
Cingolani, D. Pisignano, Adv. Mater. 2008, 20, 314–318.
[27] H. Ishitobi, Z. Sekkat, M. Irie, S. Kawata, J. Am. Chem. Soc.
2000, 122, 12802–12805.
Acknowledgments
[28] R. B. Woodward, R. H. Hoffmann, The Conservation of Orbital
Symmetry, Verlag Chemie, Germany, 1970.
[29] A. Spangenberg, J. A. P. Perez, A. Patra, J. Piard, A. Brosseau,
R. Metivier, K. Nakatani, Photochem. Photobiol. Sci. 2010, 9,
188–193.
The NMR facilities were funded by the Region Nord-Pas de Calais
(France), the Ministere de la Jeunesse, de l’Education Nationale et
de la Recherche (MJENR) and the Fonds Europeens de De-
veloppement Regional (FEDER). Part of this collaborative work
was realised within the framework GDRI CNRS 93 “Phenics”
(Photoswitchable Organic Molecular Systems & Devices). PRES
UniverSud is acknowledged for providing a post-doctoral fellow-
ship to A. P. The authors acknowledge S. Meuret for her experi-
mental contribution.
[30] T. Koshido, T. Kawai, K. Yoshino, J. Phys. Chem. 1995, 99,
6110–6114.
[31] T. Kawai, T. Koshido, K. Yoshino, Appl. Phys. Lett. 1995, 67,
795–797.
[32] S. Murase, M. Teramoto, H. Furukawa, Y. Miyashita, K. Ho-
rie, Macromolecules 2003, 36, 964–966.
[33] A. Spangenberg, A. Brosseau, R. Metivier, M. Sliwa, K. Naka-
tani, T. Asahi, T. Uwada, J. Phys. Org. Chem. 2007, 20, 985–
991.
[34] H. Furukawa, M. Misu, K. Ando, H. Kawaguchi, Macromol.
Rapid Commun. 2008, 29, 547–551.
[35] http://www.chem.wisc.edu/areas/reich/plt/windnmr.htm.
[36] H. J. Reich, J. Chem. Educ.: Software Ser. D 1996, 3.
[37] K. Uchida, Y. Nakayama, M. Irie, Bull. Chem. Soc. Jpn. 1990,
63, 1311–1315.
[1] M. Irie, M. Mohri, J. Org. Chem. 1988, 53, 803–808.
[2] S. Nakamura, M. Irie, M. Mohri, J. Org. Chem. 1988, 53,
6136–6138.
[3] B. L. Feringa, in Molecular Switches, Wiley-VCH, Weinheim,
2001.
[4] H. Tian, S. J. Yang, Chem. Soc. Rev. 2004, 33, 85–97.
[5] G. Y. Jiang, Y. L. Song, X. F. Guo, D. Q. Zhang, D. B. Zhu,
Adv. Mater. 2008, 20, 2888–2898.
[6] V. W. W. Yam, J. K. W. Lee, C. C. Ko, N. Y. Zhu, J. Am. Chem.
Soc. 2009, 131, 912–913.
[7] A. J. Myles, T. J. Wigglesworth, N. R. Branda, Adv. Mater.
2003, 15, 745–748.
[38] H. Taniguchi, A. Shinpo, T. Okazaki, F. Matsui, M. Irie, Nip-
pon Kagaku Kaishi 1992, 1138–1139.
[39] K. Gollnick, A. Griesbeck, Tetrahedron Lett. 1984, 25, 4921–
4924.
[8] T. J. Wigglesworth, A. J. Myles, N. R. Branda, Eur. J. Org.
Chem. 2005, 1233–1238.
[40] M. G. Matturro, R. P. Reynold, Tetrahedron Lett. 1987, 28,
4981–4984.
[9] S. Kobatake, M. Irie, Annu. Rep. Prog. Chem. Sect. C 2003, 99,
[41] C. N. Skold, R. H. Schlessinger, Tetrahedron Lett. 1970, 11,
277–313.
791–794.
[10] F. Sun, F. Zhang, F. Zhao, X. Zhou, S. Pu, Chem. Phys. Lett.
2003, 380, 206–212.
Received: July 30, 2013
Published Online: October 9, 2013
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Eur. J. Org. Chem. 2013, 7809–7814