Preparation and properties of rotaxanes formed by dimethyl-β- cyclodextrin and oligo(thiophene)s with β-cyclodextrin stoppers

Article abstract of DOI:10.1021/jo061834o

Novel cyclodextrin rotaxanes with oligothiophene as an axis molecule have been prepared by the Suzuki coupling reaction of 6-O-(4-iodophenyl)-β-CD (6-I-Ph-β-CD) with di(1,3,2-dioxaborolan-2-yl)-oligothiophene (oligothiophene diboric ethylene glycol esters

Full text of DOI:10.1021/jo061834o

Preparation and Properties of Rotaxanes Formed by
Dimethyl-â-cyclodextrin and Oligo(thiophene)s with â-Cyclodextrin
Stoppers
Kazuya Sakamoto, Yoshinori Takashima, Hiroyasu Yamaguchi, and Akira Harada*
Department of Macromolecular Science, Graduate School of Science, Osaka UniVersity, Toyonaka,
Osaka 560-0043, Japan
harada@chem.sci.osaka-u.ac.jp
ReceiVed September 6, 2006
Novel cyclodextrin rotaxanes with oligothiophene as an axis molecule have been prepared by the Suzuki
coupling reaction of 6-O-(4-iodophenyl)-â-CD (6-I-Ph-â-CD) with di(1,3,2-dioxaborolan-2-yl)-oligo-
thiophene (oligothiophene diboric ethylene glycol esters) in aqueous solutions of dimethyl-â-cyclodextrin
(DM-â-CD). These reactions gave [2]rotaxanes and [3]rotaxanes, which were isolated by reversed phase
chromatography. The fluorescence intensities of rotaxanes are higher than those of dumbbell-shaped
molecules (without DM-â-CD) in aqueous solutions. The inclusion ratio and chain length of rotaxanes
have been found to relate to the emission properties and emission intensities of oligothiophene. In aqueous
solutions, fluorescence quantum yields of rotaxanes are higher than those of dumbbell-shaped molecules.
The increase in the fluorescence efficiency of rotaxane is caused by suppression of intermolecular
interactions, indicating the effect of insulated oligothiophene with DM-â-CD. â-CD at the both ends of
rotaxanes functions not only as bulky stoppers but also as the recognition site for guest molecules, as
verified by fluorescence quenching experiments.
Introduction
ping ends of CDs-polymer complex with covalently bound
stoppers.3 Recently, conjugated poly(rotaxane)s, in which the
conjugated polymer backbone is covered at the molecular level
by wrapping macrocyclic molecules, such as cyclophanes,4
CDs,5,6 and zeolites,7 have been studied as insulated molecular
Poly(thiophene)s (PTs) and oligo(thiophene)s have attracted
widespread interest due to their applications as single-molecule
electronics devices and light-emitting diodes,1 whereas mechani-
cally interlocked molecules, rotaxanes and catenanes, are
expected to become the prototype for the design and construction
of controllable molecular switches and actuators.2 Previously,
we prepared cyclodextrin (CD)-based poly(rotaxane)s by cap-
(3) (a) Harada, A.; Li, J.; Kamachi, M. Nature 1992, 356, 325-327. (b)
Harada, A.; Li, J.; Nakamura, T.; Kamachi, M. J. Org. Chem. 1993, 58,
7524-7528. (c) Harada, A.; Li, J.; Kamachi, M. J. Am. Chem. Soc. 1994,
116, 3192-3196. (d) Okada, M.; Harada, A. Macromolecules 2003, 36,
9701-9703. (e) Okada, M.; Harada, A. Org. Lett. 2004, 6, 3192-3196. (f)
Okada, M.; Takashima, Y.; Harada, A. Macromolecules 2004, 37, 7075-
7077.
(4) (a) Anderson, S.; Aplin, R. T.; Claridge, T. D. W.; Goodson, T.;
Maciel, A. C.; Rumbles, G.; Ryan, J. F.; Anderson, H. L. J. Chem. Soc.,
Perkin Trans. 1 1998, 2383-2397. (b) Buey, J.; Swager, T. M. Angew.
Chem., Int. Ed. 2000, 39, 608-612. (c) Sauvage, J.-P.; Kern, J.-M.; Bidan,
G.; Divisia-Blohorn, B.; Vidal, P.-L. New J. Chem. 2002, 26, 1287-1290.
(5) (a) Shimomura, T.; Akai, T.; Abe, T.; Ito, K. J. Chem. Phys. 2002,
116, 1753-1756. (b) Yoshida, K.; Shimomura, T.; Ito, K.; Hayakawa, R.
Langmuir 1999, 15, 910-913.
* Corresponding author. Phone: +81-6-6850-5445. Fax +81-6-6850-5445.
E-mail: harada@chem.sci.osaka-u.ac.jp.
(1) (a) Shirakawa, H. Angew. Chem., Int. Ed. 2001, 40, 2574-2580. (b)
MacDarmid, A. G. Angew. Chem., Int. Ed. 2001, 40, 2581-2590. (c)
Heeger, A. J. Angew. Chem., Int. Ed. 2001, 40, 2591-2611. (d) Kraft, A.;
Grimsdale, A. C.; Holmes, A. B. Angew. Chem., Int. Ed. 1998, 37, 402-
428.
(2) (a) Sauvage, J. P.; Dietrich-Buchecker. C. Molecular catenanes,
rotaxanes, and knots; VCH-Wiley: Weinheim, 1999. (b) Harada, A. Acc.
Chem. Res. 2001, 34, 456. (c) Balzani, V.; Credi, A.; Raymo, F. M.;
Stoddart, J. F. Angew. Chem., Int. Ed. 2000, 39, 3348-3391.
10.1021/jo061834o CCC: $37.00 © 2007 American Chemical Society
Published on Web 12/22/2006
J. Org. Chem. 2007, 72, 459-465
459

Sakamoto et al.
SCHEME 1. Preparation of DM-â-CD-Oligothiophene-Based Rotaxanes with the End Stopper of â-CDs
wires by many research groups. We also reported the formation
and crystal structure of the â-cyclodextrin (â-CD)-bithiophene
inclusion complex and polymerization of the corresponding
inclusion complexes in a selective way to give pseudo-poly-
(rotaxane)s.8 Although a few poly(rotaxane)s containing π-con-
jugated polymer have been reported, discussion on the use of
monodisperse poly(rotaxane)s has not been reported yet.9 Here
we prepare 2,6-dimethyl-â-cyclodextrin (DM-â-CD)-based poly-
(rotaxane)s using oligothiophene as an axis molecule and
isolated rotaxanes having various contents of DM-â-CD and
oligothiophene. These poly(rotaxane)s have â-CD as bulky
stoppers at the end of oligothiophene axis molecules to prevent
DM-â-CD from slipping off the axis molecules. We investigated
the fluorescence of these poly(rotaxane)s with different polymer
chain lengths and CD coverages.
DMF. These rotaxanes and dumbbell-shaped molecules were
purified by preparative reversed phase chromatography.
NMR Studies of Rotaxanes with Oligothiophene. Figure
1 shows the 1H NMR spectra of 2T-dumbbell, 2T-[2]rotaxane,
3T-dumbbell, and 3T-[2]rotaxane in DMSO-d6. The aromatic
protons of dumbbell-shaped molecules showed simple peaks,
indicating formation of symmetric structure. However, the
aromatic protons of [2]rotaxanes showed splitting and peak
shifts, caused by the asymmetric structure included in the DM-
â-CD cavity. The ROESY NMR spectra of rotaxanes showed
that the peaks of thienylene protons correlated with the inner
protons (C(3)-H and C(5)-H) of DM-â-CD in DMSO-d6
(Figures 2 and S12). pseudo-Rotaxane did not show any
correlation peaks between inner protons of CDs and the protons
of axis molecules because of dethreading in DMSO-d6. These
results show formation of [2]rotaxane with interlocked DM-â-
CD. The aromatic protons of [3]rotaxanes, 4T-[3]rotaxane and
6T-[3]rotaxane (Figure 1e and f), gave more complicated peaks
which can be ascribed to the inclusion complex of two DM-
â-CDs with an axis molecule. These [3]rotaxanes have three
isomers which have different direction of threading DM-â-CDs
or head-to-head, head-to-tail, and tail-to-tail fashioned isomers.
Results and Discussion
Preparation of Rotaxanes with Oligothiophenes. Bithio-
phene-[2]rotaxane (2T-[2]rotaxane) and terthiophene-[2]rotaxane
(3T-[2]rotaxane) were prepared by the Suzuki coupling reaction
of 6-O-(4-iodophenyl)-â-CD (6-I-Ph-â-CD) with di(1,3,2-di-
oxaborolan-2-yl)-oligothiophene (oligothiophene diboric ethyl-
ene glycol esters) in an aqueous solution of DM-â-CD (Scheme
1). The crude product was found to contain dumbbell-shaped
molecules, [2]rotaxanes, and [3]rotaxanes by MALDI-TOF
mass spectroscopy. 4T-[3]Rotaxane and 6T-[3]rotaxane were
produced at the same time during the preparation of 2T-[2]-
rotaxane and 3T-[2]rotaxane, respectively. Dumbbell-shaped
molecules, 2T-dumbbell and 3T-dumbbell, were prepared in
Absorption and Fluorescence Properties of Dumbbell-
Shaped Molecules and Rotaxanes. The absorption and fluo-
rescence spectra of dumbbell-shaped molecules and rotaxanes
were measured in aqueous solutions at 15 µM (Figure 3). The
absorption spectra of [2]rotaxanes showed higher absorption than
those of dumbbell-shaped molecules. The fluorescence intensi-
ties of [2]rotaxanes in aqueous solutions are stronger than those
of dumbbell-shaped molecules. The intensities of [2]rotaxane
and dumbbell-shaped molecule of 3T as an axis molecule
showed greater difference than that of 2T. The fluorescence
intensities of dumbbell-shaped molecules and [2]rotaxanes were
comparable in methanol (Figure S13). It was suggested that in
comparison to dumbbell-shaped molecules, the greater absorp-
tion and fluorescence intensities of rotaxanes in aqueous
solutions were due to suppression of the intermolecular interac-
tions of oligothiophenes by insulation of oligothiophene with
DM-â-CD.
Figure 4 shows the absorption and fluorescence spectra of
rotaxanes with various lengths of thiophenes. The absorption
maximum wavelength (λmax) and fluorescence maximum wave-
length shifted to a longer wavelength with an increase in the
conjugation length (λmax ) 378 (2T), 407 (3T), 438 (4T), and
449 nm (6T); fluorescence maxima ) 423 (2T), 481 (3T), 500
(4T), and 539 nm (6T)). Table 1 shows the quantum yields of
(6) Okumura, H.; Kawaguchi, Y.; Harada, A. Macromol. Rapid Commun.
2002, 23, 781-785.
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1694. (b) Lin, V. S.-Y.; Radu, D. R.; Han, M.-K.; Deng, W.; Kuroki, S.;
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Cardin, D. J.; Constantine, S. P.; Gilbert, A.; Lay, A. K.; Alvaro, M.;
Galletero, M. S.; Garcia, H.; Marquez, F. J. Am. Chem. Soc. 2001, 123,
3141-3142. (d) Cardin, D. J. AdV. Mater. 2002, 14, 553-563. (e) Wu,
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(8) (a) Takashima, Y.; Oizumi, Y.; Sakamoto, K.; Miyauchi, M.;
Kamitori, S.; Harada, A. Macromolecules 2004, 37, 3962-3964. (b)
Takashima, Y.; Sakamoto, K.; Oizumi, Y.; Yamaguchi, H.; Kamitori, S.;
Harada, A. J. Inclusion Phenom. Macrocycl. Chem. 2006, 56, 45-53.
(9) (a) Cacialli, F.; Wilson, J. S.; Michels, J. J.; Daniel, C.; Silva, C.;
Friend, R. H.; Severin, N.; Samor`ı, P.; Rabe, J. P.; O’Connell, M. J.; Taylor,
P. N.; Anderson, H. L. Nat. Mater. 2002, 1, 160-164. (b) Michels, J. J.;
O’Connel, M. J.; Taylor, P. N.; Wilson, J. S.; Cacialli, F.; Anderson, H. L.
Chem. Eur. J. 2003, 9, 6167-6176. (c) Terao, J.; Tang, A.; Michels, J. J.;
Krivokapic, A.; Anderson, H. L. Chem. Commun. 2004, 56-57.
460 J. Org. Chem., Vol. 72, No. 2, 2007

Preparation and Properties of Rotaxanes
FIGURE 1. 1H NMR spectra of (a) 2T-dumbbell, (b) 2T-[2]rotaxane, (c) 3T-dumbbell, (d) 3T-[2]rotaxane, (e) 4T-[3]rotaxane, and (f) 6T-[3]-
rotaxane in DMSO-d6 at 30 °C.
rotaxanes and dumbbell-shaped molecules in aqueous solutions
calculated using 0.1 N H2SO4 solution of quinine sulfate as a
standard.10 The inclusion ratios of DM-â-CD were calculated
from the space-filling models. The quantum yields of rotaxanes
increased with an increase in the inclusion ratio of DM-â-CD.
The absorption and fluorescence spectra of phenyl end-capped
â-nonsubstituted oligothiophene (T, 2T, 3T, 4T)11 (in CH2Cl2)
are similar in shape to the spectra of the series of rotaxanes in
aqueous solutions. The spectrum of phenyl end-capped 6T could
not be measured because of the poor solubility of this
compound.12 Cyclophane end-capped 6T13 was reported as the
only example of spectroscopic measurement of phenyl end-
capped â-nonsubstituted 6T derivative. 6T-[3]Rotaxane was
dissolved in an aqueous solution as well as in an organic solvent
like methanol. It was the first example of a water-soluble long
oligothiophene rotaxane.
Fluorescence Quenching Using TNBS. The recognition
ability of â-CD in the rotaxanes was investigated by fluorescence
(10) (a) Melhuish, W. H. J. Phys. Chem. 1961, 65, 229-235. (b)
Rusakowicz, R.; Testa, A. C. J. Phys. Chem. 1968, 72, 793-796.
(11) Lee, S. A.; Hotta, S.; Nakanishi. F. Phys. Chem. A 2000, 104, 1827-
1833.
(12) Hotta, S. J. Heterocycl. Chem. 2003, 40, 845-850.
FIGURE 2. 2D ROESY NMR spectrum of 3T-[2]rotaxane in DMSO-
d6.
(13) Guyard, L.; Dumas, C.; Miomandre, F.; Pansu, R.; Renault-MeLallet,
R.; Audebert, P. New J. Chem. 2003, 27, 1000-1006.
J. Org. Chem, Vol. 72, No. 2, 2007 461

Sakamoto et al.
FIGURE 3. Absorption (a) and fluorescence (b) spectra of dumbbell-shaped molecules and rotaxanes in 15 µM aqueous solution (λex ) 378 nm
for 2T and 407 nm for 3T).
FIGURE 4. Absorption (a) and fluorescence (b) spectra of rotaxanes with various conjugation lengths (λmax ) 378 nm for 2T, 407 nm for 3T, 438
nm for 4T, 449 nm for 6T).
TABLE 1. Quantum Yields of Rotaxanes and Dumbbell-Shaped Molecules and Inclusion Ratio of Rotaxanes
2T-[2]rotaxane
3T-[2]rotaxane
4T-[3]rotaxane
6T-[3]rotaxane
2T-dumbbell
0.15
3T-dumbbell
0.06
a
ΦH2O
inclusion ratio/%b
0.21
63
0.15
50
0.24
83
0.17
61
a Calculated using 0.1 N H2SO4 solution of quinine sulfate as a standard. b Calculated from 3D models.
quenching measurements. We chose 2,4,6-trinitrobenzene sul-
fonic acid sodium salt (TNBS Na) as a quencher because TNBS
Na could be included in the â-CD cavity.14 The 1H NMR spectra
of the mixture of rotaxane and TNBS Na showed that the
aromatic protons of TNBS Na shifted upfield, indicating
formation of the inclusion complex between â-CD and TNBS
Na (Figure S14). Figure 5 shows the Stern-Volmer plots for
the fluorescence quenching of 2T-[2]rotaxane with TNBS Na.
Fluorescence intensity dependence on quencher concentration
is given by the Stern-Volmer equation (eq 1)
I0/I ) 1 + ksv[Q]
(1)
where [Q] is the quencher concentration, I0 and I are the
fluorescence intensities in the absence and presence of a
quencher, respectively, and ksv is the Stern-Volmer constant.
FIGURE 5. Stern-Volmer plots for the fluorescence quenching of
2T-[2]rotaxane with TNBS Na in the absence of AdCA (0) and
presence of excess (50 equiv) AdCA (O) (in H2O, 15 µM).
(14) Miyauchi, M.; Hoshino, T.; Yamaguchi, H.; Kamitori, S.; Harada,
A. J. Am. Chem. Soc. 2005, 127, 2034-2035.
462 J. Org. Chem., Vol. 72, No. 2, 2007

Preparation and Properties of Rotaxanes
1H NMR (500 MHz, in DMSO-d6, 30 °C) δ 7.55 (d, 2H, C2H of
Ph, J ) 9.0 Hz), 6.79 (d, 2H, C3H of Ph, J ) 9.0 Hz), 5.76-5.62
(m, 14H, O2,3H of â-CD), 4.87 (d, 1H, phenyl-substituted C1H of
glucopyranose, J ) 3.2 Hz), 4.78-4.75 (m, 6H, C1H of â-CD),
4.45-4.34 (m, 5H, O6H of â-CD), 4.32-3.90 (m, 4H, phenyl-
substituted C3,4,5,6H of glucopyranose), 3.74-3.47 (m, C3,4,5,6H of
â-CD). 13C NMR (125 MHz, in DMSO-d6, 30 °C) δ 158.4 (C1 of
Ph), 137.8 (C2 of Ph), 117.4 (C3 of Ph), 102.0 (C1 of â-CD), 83.1
(C4 of Ph), 81.6 (C4 of â-CD), 73.1 (C6 of â-CD), 72.5 (C2 of
â-CD), 72.0 (C5 of â-CD), 60.0 (C3 of â-CD). MALDI-TOF MS
(matrix: DHBA) [M + K]+ ) 1376.0 (calcd 1376.1). Anal. Calcd
for (C48H73O35I)(H2O)3: C, 41.45; H, 5.72. Found: C, 41.37; H,
5.64.
Upon addition of TNBS Na to the solution of 2T-[2]rotaxane,
fluorescence intensities decreased with an increase in the
concentration of TNBS Na. When 50 equiv of adamantane
carboxylic acid (AdCA) per â-CD moiety, which is strongly
bound to the â-CD cavity,15 was added to the solution of
rotaxanes with TNBS Na, the fluorescence quenching of the
mixture of 2T-[2]rotaxane, TNBS Na, and AdCA was sup-
pressed as compared with that of the mixture of 2T-[2]rotaxane
and TNBS Na. Suppression of the fluorescence quenching in
the mixture of 2T-[2]rotaxane, TNBS Na, and AdCA is caused
by formation of the inclusion complex between â-CD and
AdCA.
Preparation of 5,5′-Di-(1,3,2-dioxaborolan-2-yl)-2,2′-bithiophene
(2T Diboric Ethylene Glycol Ester)16 (eq 3). At -78 °C,
Conclusion
A series of novel DM-â-CD-oligothiophene-based rotaxanes
has been prepared by the palladium-catalyzed coupling reaction.
[2]Rotaxanes and [3]rotaxanes which have various chain lengths
and inclusion ratios of DM-â-CD were isolated from the crude
products using preparative reversed phase chromatography.
Their photochemical properties have been investigated by UV-
vis and fluorescence measurements. The inclusion ratio and
chain length of rotaxanes have been found to relate to the
emission properties and emission intensities of oligothiophene.
In aqueous solutions, fluorescence quantum yields of rotaxanes
were higher than those of dumbbell-shaped molecules. The
increase in the fluorescence efficiency of rotaxane is caused by
suppression of intermolecular interactions, indicating the effect
of insulated oligothiophene with DM-â-CD. We studied the
ability of â-CD stoppers of the rotaxanes with TNBS Na to
form inclusion complexes by the fluorescence quenching
experiment. Quenching by the inclusion complex formation of
2T-[2]rotaxane with TNBS Na was observed. Now, we are
investigating the preparation of supramolecular polymers using
the CD-oligothiophene rotaxanes as ditopic host molecules. The
supramolecular polymers will cause an increase in the conjuga-
tion length. Application of the supramolecular polymers as
extended molecular wires is expected.
n-butyllithium (n-hexane solution, 20.4 mL, 49.9 mmol) was added
dropwise to 2,2′-bithiophene (3.62 g, 21.8 mmol) in 50 mL of THF.
The reaction mixture was stirred for 1 h at -78 °C and allowed to
stir for 2 h at room temperature. After the prescribed time, tri-O-
isopropyl borate (20.5 g, 109 mmol) in 20 mL of THF was added
to the reaction mixture quickly via cannula and stirred for 1 h at
-78 °C. After additional stirring for 12 h, the reaction mixture
was neutralized with 150 mL of 2 N HCl. After separation of the
aqueous phase, the aqueous phase was washed twice with diethyl
ether. The combined organic phase was evaporated and dissolved
in 100 mL of toluene. Ethylene glycol (20 mL) was added to the
solution, and the mixture was stirred overnight at 80 °C. The organic
phase was evaporated, and the residue was recrystallized with hot
toluene to give 2T diboric ethylene glycol ester as green crystalline
solid in a yield of 53.0% (3.60 g).
1H NMR (500 M Hz, in CDCl3, 30 °C) δ 7.53 (d, 2H, C4,4′H, J
) 3.6 Hz), 7.53 (d, 2H, C3,3′H, J ) 3.6 Hz), 4.37 (s, 8H, -CH2-).
MALDI-TOF MS (nonmatrix) [M + H]+ ) 306.9 (calcd 307.0).
Anal. Calcd for C12H12B2O4S2: C, 47.10; H, 3.95. Found: C, 47.29;
H, 3.85.
Experimental Section
Preparation of 5,5′′-Di-(1,3,2-dioxaborolan-2-yl)-2,2′-5,2′′-
terthiophene (3T Diboric Ethylene Glycol Ester) (eq 4). 3T
Preparation of 6-O-(4-Iodophenyl)-â-cyclodextrin (eq 2). A
solution of potassium carbonate (10.0 g, 72.4 mmol) and 4-io-
dophenol (10.0 g, 45.5 mmol) in 40 mL of DMF was stirred at
room temperature. After 2 h, 6-O-toluenesulfonyl-â-CD (9.77 g,
7.89 mmol) in 40 mL of DMF was added to the reaction mixture
and stirred for 24 h at 80 °C. After the prescribed time, the reaction
mixture was neutralized by 250 mL of 1 N HCl. Ethyl acetate (250
mL) was added to the reaction mixture. White powder was collected
by filtration. The crude product was recrystallized with hot water
to give 6-O-(4-iodophenyl)-â-cyclodextrin in a yield of 44.9% (4.59
g).
diboroic ethylene glycol ester was prepared in a manner similar to
2T diboroic ethylene glycol ester using 2,2′-5,2′′-terthiophene (2.00
g, 8.05 mmol), n-butyllithium (n-hexane solution, 7.56 mL, 18.4
mmol), tri-O-isopropyl borate (7.57 g, 40.3 mmol), and ethylene
glycol (25 mL). 3T diboric ethylene glycol ester was obtained as
a yellowish green crystalline solid in a yield of 34.0% (1.06 g).
mp 190-191 °C.
1H NMR (500 MHz, in CDCl3, 30 °C) δ 7.53 (d, 2H, C4,4′′H, J
) 3.6 Hz), 7.53 (d, 2H, C3,3′′H, J ) 3.6 Hz), 7.15 (s, 2H, C3′,4′H),
4.35 (s, 8H, -CH2-). MALDI-TOF MS (nonmatrix) [M + H]+ )
390.0 (calcd 389.0). Anal. Calcd for C16H14B2O4S3: C, 49.52; H,
3.64. Found; C, 49.40; H, 3.52.
(15) (a) Zhang, B.; Breslow, R. J. Am. Chem. Soc. 1993, 115, 9353-
9354. (b) Weickenmeter, M.; Wenz, G. Macromol. Rapid Commun. 1996,
17, 731-736.
(16) Oliga, T.; Destri, S.; Porzio, W. Macromol. Chem. Phys. 1997, 198,
1091-1107.
Preparation of Dumbbell-Shaped Molecules (eq 5). (a) 2T-
Dumbbell Molecule (n ) 0). Palladium acetate (8.40 mg, 0.0374
mmol), potassium carbonate (138 mg, 1.12 mmol), and 6-O-(4-
J. Org. Chem, Vol. 72, No. 2, 2007 463

Sakamoto et al.
7.1 Hz), 5.68 (m, 28H, O2,3H of â-CD), 4.92 (d, 7H, C1H of DM-
â-CD, J ) 2.1 Hz), 4.88 (s, 7H, O3H of DM-â-CD), 4.82 (d, 14H,
C1H of â-CD, J ) 3.0 Hz), 4.42 (m, 14H, O6H of â-CD), 4.42-
4.13 (m, 8H, C3′,4′,5′,6′H of â-CD), 3.96 (bs, 2H, C2′H of â-CD),
3.8-3.5 (m, C3,4,5,6H of CDs), 3.47 (s, 21H, O2Me of DM-â-CD),
3.15 (s, 21H, O6Me of DM-â-CD). 13C NMR (125 MHz, in DMSO-
d6, 30 °C) δ 158.5 (p-phenyl carbon next to thienylene ring at CD
second rim), 158.3 (p-phenyl carbon next to thienylene ring at CD
first rim), 142.6 (C5 of thienylene at CD first rim), 141.8 (C5′ of
thienylene at CD second rim), 134.9 (C2′ of thienylene at CD second
rim), 134.5 (C2 of thienylene at CD first rim), 126.6 (o-phenyl
carbon thienylene side at CD second rim), 126.1 (o-phenyl carbon
thienylene side at CD first rim), 126.0 (p-phenyl carbon next to
ether bond), 123.9 (C3 of thienylene at CD first rim), 123.6 (C3′ of
thienylene at CD second rim), 122.6 (C4 of thienylene at CD first
rim), 122.4 (C4′ of thienylene at CD second rim), 115.1 (m-phenyl
carbon ether bond side at CD first rim), 115.0 (m-phenyl carbon
ether bond side at CD second rim), 102.3 (C1′ of â-CD), 101.9 (C1
of â-CD), 100.0 (C1 of DM-â-CD), 82.6 (C4 of DM-â-CD), 81.9
(C4′ of â-CD), 81.7 (C4 of â-CD), 73.0 (C3 of DM-â-CD), 72.7
(C3 of â-CD), 72.4 (C2 of â-CD), 72.0 (C5 of â-CD), 70.5 (C6 of
DM-â-CD), 69.9 (C5 of DM-â-CD), 69.7 (C3′ of â-CD), 59.9 (C6
of â-CD), 59.6 (O2Me of DM-â-CD), 58.0 (O6Me of DM-â-CD).
MALDI-TOF MS (matrix: DHBA) [M + Na]+ ) 3954.8 (calcd
3955.2). Anal. Calcd for (C160H248O105S2)(H2O)19: C, 45.13; H,
6.77. Found: C, 45.04; H, 6.70. UV-vis: λmax ) 378 nm.
(b) 4T-[3]Rotaxane. 1H NMR (500 MHz, in DMSO-d6, 30 °C)
δ 7.55 (m, 4H, phenyl proton next to thienylene ring), 7.11-7.00
(m, 12H, thienylene proton and phenyl proton next to ether bond),
5.77 (m, 28H, O2,3H of â-CD), 4.96 (m, 14H, C1H of DM-â-CD),
4.93 (s, 14H, O3H of DM-â-CD), 4.82 (bs, 14H, C1H of â-CD),
4.41 (m, 14H, O6H of â-CD), 4.32-4.10 (m, 8H, C3′,4′,5′,6′H of
â-CD), 3.99 (bs, 2H, C2′H of â-CD), 3.8-3.5 (m, C3,4,5,6H of CDs),
3.48 (s, 42H, O2Me of DM-â-CD), 3.13 (m, 42H, O6Me of DM-
â-CD). MALDI-TOF MS (matrix: DHBA) [M + Na]+ ) 5421.9
(calcd 5433.8). Anal. Calcd for (C224H350O140S4)(H2O)28: C, 45.48;
H, 6.92. Found: C, 45.09; H, 6.62. UV-vis: λmax) 438 nm.
Preparation of 3T-[2]Rotaxane and 6T-[3]Rotaxane. 3T-[2]-
rotaxane and 6T-[3]rotaxane were synthesized in the same manner
as 2T-[2]rotaxane and 4T-[3]rotaxane using 5.00 mL of an aqueous
solution of the inclusion complex between 3T diboric ethylene
glycol ester (72.5 mg, 0.187 mmol) and DM-â-CD (1340 mg, 1.00
mmol). The crude product was purified by HPLC (eluent; water:
acetonitrile) to give 3T-[2]rotaxane and 6T-[2]rotaxane in a yield
of 23.2% (173.4 mg) and 2.8% (15.1 mg), respectively.
(a) 3T-[2]Rotaxane. 1H NMR (500 MHz, in DMSO-d6, 30 °C)
δ 7.62 (d, 2H, phenyl proton next to thienylene ring at CD first
rim, J ) 7.0 Hz), 7.53 (d, 2H, phenyl proton next to thienylene
ring at CD second rim, J ) 7.0 Hz), 7.32 (d, 1H, C4′′H of thienylene
at CD second rim, J ) 2.9 Hz), 7.26 (d, 1H, C4H of thienylene at
CD first rim, J ) 2.9 Hz), 7.21 (d, 1H, C3H of thienylene at CD
first rim, J ) 2.9 Hz), 7.12 (d, 1H, C3′′H of thienylene at CD first
rim, J ) 2.8 Hz), 7.09 (d, 1H, C3′H of thienylene at CD second
rim, J ) 2.7 Hz), 7.06 (d, 1H, C4′H of thienylene at CD second
rim, J ) 2.9 Hz), 7.03 (d, 2H, phenyl proton next to ether bond at
CD second rim, J ) 7.2 Hz), 6.99 (d, 2H, phenyl proton next to
ether bond at CD first rim, J)7.2 Hz), 5.8-5.6 (m, 28H, O2,3H of
â-CD), 4.93 (d, 7H, C1H of DM-â-CD, J ) 2.5 Hz), 4.88 (s, 7H,
O3H of DM-â-CD), 4.82 (d, 14H, C1H of â-CD, J ) 3.1 Hz), 4.41
(m, 14H, O6H of â-CD), 4.32-4.14 (m, 8H, C3′,4′,5′,6′H of â-CD),
3.97 (bs, 2H, C2′H of â-CD), 3.8-3.5 (m, C3,4,5,6H of CDs), 3.47
(s, 21H, O2Me of DM-â-CD), 3.16 (s, 21H, O6Me of DM-â-CD).
13C NMR (125 MHz, in DMSO-d6, 30 °C) δ 158.4 (p-phenyl carbon
next to thienylene ring at CD second rim), 158.3 (p-phenyl carbon
next to thienylene ring at CD first rim), 143.0 (C5 of thienylene at
CD first rim), 142.3 (C5′′ of thienylene at CD second rim), 135.5
(C2′ of thienylene at CD first rim), 134.9 (C5′ of thienylene at CD
second rim), 134.2 (C2′′ of thienylene at CD second rim), 133.9
(C2 of thienylene at CD first rim), 126.6 (o-phenyl carbon thienylene
iodophenyl)-â-cyclodextrin (500 mg, 0.374 mmol) dissolved in 20
mL of DMF were stirred for 2 h. 2T diboric ethylene glycol ester
(57.2 mg, 0.187 mmol) in 10 mL of DMF was added dropwise to
the reaction mixture and stirred for 24 h at 80 °C. After
neutralization by 1 N HCl, the reaction mixture was centrifuged
(3500 rpm, 10 min) and the supernatant evaporated to give the crude
product. The crude product was purified by HPLC (eluent; water:
acetonitrile) to give 2T-dumbbell molecule in a yield of 10.6% (51.6
mg).
1H NMR (500 MHz, 30 °C, in DMSO-d6) δ 7.56 (d, 4H, Ph on
thienylene side, J ) 8.5 Hz), 7.35 (d, 2H, C4H of thienylene, J )
3.8 Hz), 7.27 (d, 2H, C3H of thienylene, J ) 3.7 Hz), 7.00 (d, 4H,
Ph on ether side, J ) 9.0 Hz), 5.78-5.60 (m, 28H, O2,3H of â-CD),
4.96-4.82 (m, 14H, C1H of â-CD), 4.50-3.90 (m, 6H, phenyl
substituted glucopyranose of â-CD), 3.75-3.50 (m, C3,4,5,6H of
â-CD). MALDI-TOF MS (matrix: DHBA) [M + K]+ ) 2625.6
(calcd 2623.8). Anal. Calcd for (C104H150O70S2)(H2O)18: C, 42.95;
H, 6.45. Found: C, 42.92; H, 6.27.
(b) 3T-Dumbbell Molecule (n ) 1). 3T-Dumbbell molecule was
prepared in the a manner similar to 2T-dumbbell molecules using
3T diboric ethylene glycol ester (72.5 mg, 0.187 mmol), after
purification by HPLC (eluent; water:acetonitrile) to give 3T-
dumbbell molecule in a yield of 20.1% (100.2 mg).
1H NMR (500 MHz, in DMSO-d6,30 °C) δ 7.57 (d, 4H, Ph on
thienylene side, J ) 8.6 Hz), 7.37 (d, 2H, C4,4′′H of thienylene, J
) 3.9 Hz), 7.31 (d, 2H, C3,3′′H of thienylene, J ) 3.7 Hz), 7.28 (s,
2H, C3′,4′H of thienylene), 7.00 (d, 4H, Ph on ether side, J ) 9.0
Hz), 5.74-5.63 (m, 28H, O2,3H of â-CD), 4.92-4.79 (m, 14H,
C1H of â-CD), 4.46-3.94 (m, 6H, phenyl substituted glucopyranose
unit of â-CD), 3.78-3.52 (m, C3,4,5,6H of â-CD). MALDI-TOF MS
(matrix: DHBA) [M + Na]+ ) 2688.5 (calcd 2689.5). Anal. Calcd
for (C108H152O70S3)(H2O)16: C, 43.90; H, 6.28. Found: C, 43.83;
H, 6.06.
Preparation of 2T-[2]Rotaxane and 4T-[3]Rotaxane. Pal-
ladium acetate (8.40 mg, 0.0374 mmol), potassium carbonate (138
mg, 1.12 mmol), and 6-O-(4-iodophenyl)-â-cyclodextrin (500 mg,
0.374 mmol) dissolved in 50 mL of water were stirred for 2 h. An
aqueous solution (5 mL) of the inclusion complex between 2T
diboric ethylene glycol ester (57.2 mg, 0.187 mmol) and DM-â-
CD (996 mg, 0.748 mmol) was added dropwise to the reaction
mixture. The reaction mixture was allowed to stir for 24 h at room
temperature. After neutralization by 1 N HCl, the reaction mixture
was centrifuged (3500 rpm, 10 min) and the supernatant solution
evaporated to give the crude product. The crude product was
purified by HPLC (eluent; water:acetonitrile) to give 2T-[2]rotaxane
and 4T-[3]rotaxane in a yield of 22.7% (166.9 mg) and 3.0% (15.2
mg), respectively.
(a) 2T-[2]Rotaxane. 1H NMR (500 MHz, in DMSO-d6, 30 °C)
δ 7.55 (d, 2H, phenyl proton next to thienylene ring at CD second
rim, J ) 6.9 Hz), 7.48 (d, 2H, phenyl proton next to thienylene
ring at CD first rim, J ) 6.6 Hz), 7.22 (d, 1H, C4H of thienylene
at CD first rim, J ) 3.0 Hz), 7.14 (m, 1H, C4′H of thienylene at
CD second rim), 7.12 (m, 1H, C3H of thienylene at CD first rim),
7.03 (d, 2H, phenyl proton next to ether bond at CD first rim, J )
7.1 Hz), 7.02 (m, 1H, C3′H of thienylene at CD second rim), 6.99
(d, 2H, phenyl proton next to ether bond at CD second rim, J )
464 J. Org. Chem., Vol. 72, No. 2, 2007

Preparation and Properties of Rotaxanes
side at CD second rim), 126.2 (o-phenyl carbon thienylene side at
CD first rim), 125.9 (p-phenyl carbon next to ether bond), 124.7
(C3 of thienylene at CD first rim), 124.3 (C3′′ of thienylene at CD
second rim), 123.6 (C3′ of thienylene at CD first rim), 123.4 (C4′
of thienylene at CD second rim), 122.9 (C4′′ of thienylene at CD
second rim), 122.8 (C4 of thienylene at CD first rim), 115.1 (m-
phenyl carbon ether bond side at CD second rim), 115.0 (m-phenyl
carbon ether bond side at CD first rim), 102.2 (C1′ of â-CD), 101.9
(C1 of â-CD), 100.0 (C1 of DM-â-CD), 82.6 (C4 of DM-â-CD),
81.9 (C4′ of â-CD), 81.6 (C4 of â-CD), 73.0 (C3 of DM-â-CD),
72.7 (C3 of â-CD), 72.4 (C2 of â-CD), 72.0 (C5 of â-CD), 70.5 (C6
of DM-â-CD), 69.9 (C5 of DM-â-CD), 69.6 (C3′ of â-CD), 59.9
(C6 of â-CD), 59.5 (O2Me of DM-â-CD), 58.0 (O6Me of DM-â-
CD). MALDI-TOF MS (matrix: DHBA) [M + Na]+ ) 4020.9
(calcd 4020.9). Anal. Calcd for (C164H250O105S3)(H2O)21: C, 45.01;
H, 6.73. Found: C, 44.59; H, 6.29. UV-vis: λmax ) 407 nm.
(b) 6T-[3]Rotaxane. 1H NMR (500 MHz, in DMSO-d6, 30 °C)
δ 7.60 (d, 3H, Ph, J ) 8.7 Hz), 7.52 (d, 3H, Ph, J ) 7.8 Hz), 7.48
(d, 1H, Ph, J ) 8.7 Hz), 7.40 (d, 1H, Ph, J ) 8.6 Hz), 7.33-6.97
(m, 30H, thienylene and phenyl protons), 6.74 (d, 1H, Ph, J ) 9.0
Hz), 6.53 (d, 1H, Ph, J ) 9.0 Hz), 5.79-5.62 (m, 56H, O2,3H of
â-CD), 4.93 (d, 28H, C1H of DM-â-CD, J ) 5.3 Hz), 4.89 (s, 28H,
O3H of DM-â-CD), 4.84 (d, 28H, C1H of â-CD, J ) 5.3 Hz), 4.44-
4.34 (m, 28H, O6H of â-CD), 4.31-4.15 (m, 16H, C3′,4′,5′,6′H of
â-CD), 3.97 (bs, 4H, C2’H of â-CD), 3.8-3.5 (m, C3,4,5,6H of CDs),
3.47 (s, 84H, O2Me of DM-â-CD), 3.17 (m, 84H, O6Me of DM-
â-CD). MALDI-TOF MS (matrix: DHBA) [M + K]+ ) 5614.8
(calcd 5610.9). Anal. Calcd for (C242H348O146S6)(H2O)36: C, 45.17;
H, 6.58. Found: C, 45.25; H, 6.66. UV-vis: λmax ) 449 nm.
Acknowledgment. This work has been partially supported
by Grant in-Aid No. S14103015 for Scientific Research and
conducted with financial support from the 21st Century COE
(Center of Excellence) program of the Ministry of Education,
Culture, Sports, Science and Technology, Japan.
Supporting Information Available: General experimental
details, 1H and 13C NMR spectra of compounds, MALDI TOF mass
spectra of rotaxanes, 2D ROESY NMR spectrum of 2T-[2]rotaxane,
absorption and fluorescence spectra of [2]rotaxanes and dumbbell-
shaped molecules, and 1H NMR spectrum of mixture of TNBS Na
and 2T-[2]rotaxane. This material is available free of charge via
the Internet at http://pubs.acs.org.
JO061834O
J. Org. Chem, Vol. 72, No. 2, 2007 465