Synthesis of new [2]rotaxane including a macrocyclic receptor and a photochromic unit

Article abstract of DOI:10.1016/j.tetlet.2008.03.110

The novel photochromic [2]rotaxane based on chromene molecule introduced into a crown-containing macrocyclic receptor was synthesized. The photochemical properties of rotaxane could be modified by the complexation of the crown ether moiety.

Full text of DOI:10.1016/j.tetlet.2008.03.110

Available online at www.sciencedirect.com
Tetrahedron Letters 49 (2008) 3453–3457
Synthesis of new [2]rotaxane including a macrocyclic
receptor and a photochromic unit
Ekaterina A. Shilova a,b,*, Valery P. Perevalov b, Vasily V. Suslov b, Corinne Moustrou a,*
a Universite´ de la Me´diterrane´e, UPR CNRS 3118, CINaM, Faculte´ des Sciences de Luminy, Case 901, 13288 Marseille Cedex 09, France
b Department of Technology of Organic Intermediates and Dyestuffs, Mendeleev University of Chemical Technology, Moscow, Russia
Received 3 January 2008; revised 17 March 2008; accepted 21 March 2008
Available online 28 March 2008
Abstract
The novel photochromic [2]rotaxane based on chromene molecule introduced into a crown-containing macrocyclic receptor was
synthesized. The photochemical properties of rotaxane could be modified by the complexation of the crown ether moiety.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords: [2]Rotaxane; Chromene; Naphthopyran; Crown ether
The design and the synthesis of organic molecular mate-
rials in which structure and macroscopic properties can be
controlled by external triggers, are of major importance in
emerging optoelectronic and nanotechnologies.1 In this
context, the photochromic crown compounds which com-
bine properties of ion-selective binding and photo-induced
switching are of particular interest.2 Furthermore, a
Fig. 1. New rotaxane which can be controlled by metallocomplexation.
number of crown-containing [2]rotaxanes with salt-binding
properties were developed.3 The incorporation of a photo-
new targeted [2]rotaxane system consists of a binaphtho-
pyran light-sensitive axle 1 and the macrocyclic receptor
23 (Scheme 1), the last one was synthesized by Smith and
co-workers. The constituents of both units are rather
convenient starting materials for the synthesis. 18-
Dibenzo-crown-6 ether is a reasonable price compound;
hydroxynaphthopyrans can be easily obtained4 through
the condensation of commercially available 1,1-diphenyl-
propyn-1-ol with hydroxynaphthalene.
Computer modeling was used to predict the conforma-
tion of the receptor-wheels and the chromene-axles. It dem-
onstrated that the dimensions of the stoppers efficiently
prevent the axles to escape from the wheels and at the same
time they are suitable to allow a complexation. Modeling
study was realized with Ampac 8.15 using semi-empirical
AM1 force field5 (Fig. 2).
chromic unit into such molecule can allow control of its
dynamics by color changing because of metal cations and
anions binding. In the present work, we report a conve-
nient synthetic approach to introduce chromene molecules
into crown-containing macrocyclic receptor with a forma-
tion of [2]rotaxane possessing photochromic metal-ion
sensitive properties.
The aim of the present study is a rotaxane including
chromene and crown units: the motions of such system
have good perspectives to be controlled by metallocom-
plexation between crown ether and the merocyanine form
of a chromene under the light irradiation (Fig. 1). The
*
Corresponding authors. Tel.: +3 349 182 9154; fax: +3 349 182 9301.
E-mail address: shilova@discoverylab.eu (E. A. Shilova).
0040-4039/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2008.03.110

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E. A. Shilova et al. / Tetrahedron Letters 49 (2008) 3453–3457
Scheme 1. Structures of the light-sensitive axle 1 and the macrocyclic receptor 2.
At the beginning of our study, the synthesis of free chro-
mene-axle was accomplished to confirm its photochemical
properties. Binaphthopyran unit 1 was obtained6 by the
condensation of 3,3-diphenyl-9-hydroxy-3H-naphtho[2,1-b]-
pyran with isophthaloyl dichloride (Scheme 2) in 98% yield.
The novel compound showed absorbance in the UV
spectra region but it was transparent in the visible spectra
region (Fig. 3). After the irradiation of UV light7 during
Fig. 2. Modeled conformation of rotaxane 3.
Fig. 3. Absorption spectra of
1
(acetonitrile solutions, C =
0.84 ꢀ 10ꢁ5 M) under dark condition (closed form) and after UV-
Scheme 2. Synthesis of binaphthopyran unit 1.
irradiation during 1 min (open form.)

E. A. Shilova et al. / Tetrahedron Letters 49 (2008) 3453–3457
3455
Scheme 3. Formation of rotaxane 3.
10 s, the absorbance of closed form of chromene decreased,
while a new absorption peak was found in 400 nm region
indicating that the pyran moiety isomerizes to its mero-
cyanine form. Binaphthopyran acetonitrile solution chan-
ged rapidly from transparent to orange saturated color.
Wheel constituent 2 for [2]rotaxane was synthesized
according to the procedure described by Smith and co-
workers.3 For [2]rotaxane synthesis, we used the anion-
templated methodology recently introduced by Vo¨gtle.8
Macrocycle 2 (1 M equiv) was treated with 3,3-diphenyl-
9-hydroxy-3H-naphtho[2,1-b]pyran
(2 M equiv)
and
tenfold excess of K2CO3 at 0 °C in THF–DMF mixture
(5:1) for 15–30 min. The bulky complex anion was formed
due to the hydrogen bonding between the NH-groups of
isophthalamide part of macrocycle and Oꢁ of naphtholate
anion (Scheme 3).
This molecular recognition was the driving force for the
formation of [2]rotaxane 3. Upon single addition of isoph-
thaloyl dichloride (1 M equiv), the bulky anion was alkyl-
ated through the cavity of the macrocycle. Formed
chloromethyl ether then reacted in situ with a second
potassium naphtholate anion producing the target [2]rotax-
ane 3. Formation of the rotaxane competed with the
formation of the free axles. Targeted rotaxane 3 was
obtained9 in 19% yield by thin-layer chromatography.
The independent spot of compound revealed photochromic
properties and was different from the spots of starting
reagents and free axels.
The formation of the rotaxane was confirmed by a com-
parative analysis of NMR spectra of compounds 1, 2 and
3. The signals of a, b, c, and h-carbons can be observed
in compound 3 in 20–90 ppm 13C NMR spectra region
(Fig. 4).
Fig. 4. Partial 13C NMR (acetone-d6, 250 MHz, 273 K) spectra of 1, 2,
and 3. Peak labels are defined in Scheme 1.
The presence of all characteristic signals of both wheel
and axle ester carbons d, e, and j was observed in 160–
190 ppm region of 13C NMR spectra of targeted rotaxane
1
3 (Fig. 5). The H and 13C chemical shifts of key points
of rotaxane are collected in Table 1.
We further studied the binding properties of the rotax-
ane. The addition of tenfold excess of Na+ to a solution
of 3 in acetonitrile induced changes in photochemical
behavior. The increase in absorbance, the broadening of
the spectra signal, and the slight shift of kmax of the open
form were seen (Fig. 6). At the same time, the absorbance

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E. A. Shilova et al. / Tetrahedron Letters 49 (2008) 3453–3457
Fig. 6. Absorption-spectral changes of open forms of 3 (acetonitrile
solutions, C = 0.84 ꢀ 10ꢁ5 M) and 3–Na+ system after UV-irradiation
during 2 min.
Acknowledgments
Grants from the French-Russian Framework for Edu-
cation and Research (MENESR-DREIC) have been
obtained for the realization of this work. We thank
Professor Stephanie Delbaere (UMR CNRS 8009, Lille,
France) for helpful comments, and we are very much
indebted to Dr. Jerome Courcambeck (Genoscience,
Marseille, France) for generous assistance. We thank
Fig. 5. Partial 13C NMR (acetone-d6, 250 MHz, 273 K) spectra of 1, 2 and
3. Peak labels are defined in Schemes 1 and 3.
Table 1
1H, 13C assignments for rotaxane 3 in C3D6O
´
Spectropole (Universites Aix-Marseille I et III, Marseille,
Position
dH (ppm)
dC (ppm)
France) for mass spectrometry study and Professor
Smuchkevich (Mendeleev University, Moscow, Russia)
for help in spectral analysis interpretation.
a
b
c
d
e
1.84
3.50–3.49
3.93–3.91
—
20.1
63.9
65.1
167.4
166.9
131.7
131.2
125.9,129.0
83.5
130.9
165.3
—
—
Supplementary data
f
8.23
8.32
8.72
—
6.23
—
f0
g,g0
h
i
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.tetlet.2008.
03.110.
j
k
7.92
References and notes
1. (a) Molecular Electronics; Ashwell, G. J., Ed.; John Wiley and Sons:
New York, NY, 1992; (b) Lehn, J.-M. Supramolecular Chemistry,
Concepts and Perspectives; VCH: Weinheim, 1995; (c) Chemosensors of
Ion and Molecule Recognition; Desvergnes, J. P., Czarnik, A. W., Eds.;
NATO ASI Series; Kluwer Academic: Dordrecht, 1997.
of closed form of chromene in 3–Na+ system is decreased.
These results suggest that the optical properties of com-
pound 3 could be modified by the complexation of the
crown ether moiety.
2. (a) Kimura, K.; Sakamoto, H.; Kado, S.; Arakawab, R.; Yokoyama, S.
Analyst 2000, 125, 1091; (b) Kimura, K.; Teranishi, T.; Yokoyama, M.;
Yajima, S.; Miyake, S.; Sakamoto, H. J. Chem. Soc., Perkin Trans. 2
1999, 199; (c) Fedorov, Y.; Fedorova, O.; Shepel, N.; Alfimov, M.;
Turek, A. M.; Saltiel, J. Photochem. Photobiol. 2006, 82, 1108.
3. (a) Shukla, R.; Deetz, M. J.; Smith, B. D. Chem. Commun. 2000, 2397;
(b) Deetz, M. J.; Shang, M.; Smith, B. D. J. Am. Chem. Soc. 2000, 122,
6201.
In summary, the novel photochromic [2]rotaxane based
on chromene molecule introduced into macrocyclic recep-
tor was efficiently synthesized. The binding of Na+ showed
that the optical properties of rotaxane could be modified by
the complexation of the crown ether moiety. Further exper-
iments are in progress to gain more details about the ion-
selective binding properties of this molecule. New [2]rotax-
ane could be a good basis for the creation of artificial
molecular machines with salt-dependent properties.
4. (a) Frigoli, M.; Moustrou, C.; Samat, A.; Guglielmetti, R. Eur. J. Org.
Chem. 2003, 2799; (b) Frigoli, M.; Moustrou, C.; Samat, A.;
Gugliemetti, R. Helv. Chim. Acta 2000, 83, 3043.

E. A. Shilova et al. / Tetrahedron Letters 49 (2008) 3453–3457
5. (a) Dewar, M. J. S.; Zoebisch, E.; Healy, E. F.; Stewart, J. J. P. J. Am.
3457
3H-naphtho[2,1-b]pyran (20.3 mg, 0.058 mmol) in 18 mL of anhy-
drous THF–DMF mixture (5:1). The solution was cooled to 0 °C,
then solid isophthaloyl dichloride (5.9 mg, 0.029 mmol) was added
and the reaction was stirred for 4 days at room temperature. After
the removal of the solvent, the residue was purified on silica column
by dichloromethane–methanol (100:0?90:10) to remove the binaphto-
´
Chem. Soc. 1985, 107, 3902; (b) Fradera, X.; Marquez, M.; Smith, B.
D.; Orozco, M.; Luque, F. J. J. Org. Chem. 2003, 68, 4663.
6. Bis-(3,3-biphenyl-3H-benzo[f]chromene-9-yl) isophthalic acid ether
(binaphtopyrane unit 1): A sample of 3,3-diphenyl-9-hydroxy-3H-
naphtho[2,1-b]pyran (30.1 mg, 0.086 mmol) was dissolved in 6 mL of
anhydrous THF–DMF mixture (5:1). The solution was cooled to 0 °C,
then isophthaloyl dichloride (8.7 mg, 0.043 mmol) and triethylamine
(0.012 mL, 0.086 mmol) were added. The mixture was stirred at room
temperature for 12 h, at which time the starting material was consumed
according to TLC analysis. The reaction was extracted with EtOAc
(3 ꢀ 15 mL), washed with H2O (2 ꢀ 20 mL), brine (2 ꢀ 20 mL), dried
over Mg2SO4, and purified by column chromatography with dichloro-
methane–methanol (100:0?90:10) to give 98% of binaphtopyrane 1
(34.9 mg, 0.042 mmol). 1H NMR (acetone, ppm): d 9.12 (s, 1H, H-2,
COC6H3CO), 8.50 (dd, J = 7.74, 1.74, 2H, H-4, H-6, COC6H3CO),
7.86–7.82 (m, 7H, 4H-4, C6H5, H-5, COC6H3CO, 2H-7), 7.50–7.47 (m,
8H, 4H-5, 4H-3, C6H5), 7.40–7.20 (m, 18H, 4H-6, 4H-2, C6H5, 2H-1,
2H-5, 2H-6, 2H-8, 2H-10), 6.26 (d, J = 9.95, 2H, H-2). 13C NMR
(acetone, ppm): d 163.4 (2C, CO), 150.2 (2C, C-4a), 148.4 (2C, C-9),
143.6 (4C, C-1, C6H5), 134.0 (2C, C-10a), 130.8 (1C, C-2, COC6H3CO),
129.5 (2C, C-6), 129.3 (2C, C-4, C-6, COC6H3CO), 129.1 (2C, C-7),
128.7 (2C, C-3, C-1, COC6H3CO), 128.1 (1C, C-5, COC6H3CO), 127.1
(8C, 4C-3, 4C-5, C6H5), 126.9 (2C, C-2), 126.6 (4C, 4C-4, C6H5), 126.5
(2C, C-6a), 125.9 (8C, 4C-2, 4C-6, C6H5), 118.3 (2C, C-8), 117.6 (2C,
C-1), 117.3 (2C, C-5), 113.1 (2C, C-10b), 111.9 (2C, C-10), 81.7 (2C,
C-3). TOF MS ES+: 832 [M+H]+.
pyrane unit
1 and unreacted hydroxychromene to obtain 19%
1
of rotaxane 3 (8.9 mg, 0.006 mmol). H NMR (acetone, ppm; A-Axle,
M-Macrocycle constituents): d 8.72 (s, 2H, H-2, COC6H3CO, A);
H-3, COC6H3CO, M, 8.32 (d, J = 7.74, 2H, H-4, H-6, COC6H3CO,
A), 8.23 (d, J = 7.74, 2H, H-5, H-1, COC6H3CO, M), 7.92 (s, 2H,
2NH, M), 7.81–7.64 (m, 10H, 4H-4, C6H5, H-5, COC6H3CO,
2H-1, 2H-7, A; H-6, COC6H3CO, M), 7.44–7.13 (m, 38H,
4H-6, 4H-2, 4H-5, 4H-3, C6H5, 2H-5, 2H-6, 2H-8, 2H-10, A; H-3,
H-13, C6H3, H-4, H-12, H-1, H-15, C6H3, 2H-2, 2H-6, 2H-3, 2H-5,
C6H4, M), 6.23 (d, J = 9.95, 2H, 2H, H-2, A), 3.93-3.91 (m, 8H,
2CH2-18, 9, 20, 7, M), 3.50-3.49 (m, 8H, 2CH2-17, 10, 21, 6, M), 1.84
(s, 6H, 2CH3, M). 13C NMR, (acetone, ppm; A-Axle, M-Macrocycle
constituents): d 167.4 (2C, 2CONCH3, M), 166.9 (2C, 2CONH, M),
165.3 (2C, CO, A), 152.3 (2C, C-4a, A), 151.1 (2C, C-9, A),
149.4 (2C, C-22a, C-15a, M), 146.1 (4C, 4C-1, C6H5, A), 135.7 (2C,
C-4a, C-11a, C6H3, M), 135.6 (2C, 2C-4, C6H4, M), 135.2 (2C, C-2,
C-14 C6H3, M), 132.5 (2C, C-10a, A), 132.3 (2C, C-2, C-4,
COC6H3CO, M), 131.9 (2C, 2C-1, C6H4, M), 131.7 (2C, C-5,
C-1, COC6H3CO, M), 131.4 (2C, C-6, A), 131.2 (2C, C-4, C-6,
COC6H3CO, A), 130.9 (2C, C-2, A), 130.4 (2C, C-7, A), 129.6 (4C,
2C-2, 2C-6, C6H4, M), 129.4 (1C, C-6, COC6H3CO, M), 129.2
(8C, 4C-3, 4C-5, C6H5, A), 129.0 (1C, C-2, COC6H3CO, A), 128.7
(2C, C-3, C-1, COC6H3CO, A), 128.6 (4C, 4C-4, C6H5, A), 127.9
(1C, C-5, COC6H3CO, A), 127.8 (8C, 4C-2, 4C-6, C6H5, A), 126.7
(2C, C-6a, A), 125.9 (1C, C-3, COC6H3CO, M), 120.4 (2C, C-4, C-12,
C6H3, M), 119.6 (2C, C-8, A), 119.3 (2C, C-1, A), 116.4 (2C, C-5, A),
115.5 (2C, C-10b, A), 114.8 (2C, C-10, A), 114.7 (2C, C-3, C-13,
C6H3, M), 114.4 (4C, 2C-3, 2C-5, C6H4, M), 102.1 (2C, C-1,
C-15, C6H3, M), 83.5 (2C, C-3, A), 65.1 (4C, C-18, C-9, C-20, C-7,
CH2, M), 63.9 (4C, C-21, C-6, C-17, C-10, CH2, M), 20.1 (2C, 2CH3,
M). TOF MS ES+: 1278 [M+H]+; 769 [M+H]+, 786 [M+NH4]+
(ring—H2O).
7. Photochemical measures were performed in acetonitrile solutions
(C = 0.84 ꢀ 10ꢁ5 M) of spectrometric grade at 20°. The analysis cell
was placed in a sample chamber in Cary 50 Scan spectrophotometer.
Solutions were stirred continuously during the experiments. An Oriel-
150-W-high-pressure Xe lamp was used for irradiation, 520 mW/cm2.
8. (a) Hubner, G. M.; Glaser, J.; Seel, C.; Vogtle, F. Angew. Chem., Int.
Ed. 1999, 38, 383; (b) Reuter, C.; Wienand, W.; Hubner, G. M.; Seel,
C.; Vogtle, F. Chem. Eur. J. 1999, 5, 2692; (c) Seel, C.; Vogtle, F.
Chem. Eur. J. 2000, 6, 21.
9. Rotaxane 3: K2CO3 (14.1 mg, 0.116 mmol) was added to a solution of
macrobicycle 2 (22.7 mg, 0.029 mmol) and 3,3-diphenyl-9-hydroxy-