Switching between supramolecular dimer and nonthreaded supramolecular self-assembly of stilbene amide-α-cyclodextrin by photoirradiation

Article abstract of DOI:10.1021/ja7113135

3-trans-Stilbene amide-α-cyclodextrin (3-trans-Sti-α-CD) formed a double-threaded dimer in aqueous solutions. In contrast, the photoisomerization of the stilbene moiety in 3-Sti-α-CD from trans to cis leads to the structural changes from the double-threaded dimer to nonthreaded supramolecular assemblies in aqueous solutions. The structures of these supramolecular complexes have been found to be controllable by photoirradiation. Copyright

Full text of DOI:10.1021/ja7113135

Published on Web 03/13/2008
Switching between Supramolecular Dimer and Nonthreaded
Supramolecular Self-Assembly of Stilbene
Amide-r-Cyclodextrin by Photoirradiation
Kazuhiro Yamauchi, Yoshinori Takashima, Akihito Hashidzume,
Hiroyasu Yamaguchi, and Akira Harada*
Department of Macromolecular Science, Graduate School of Science, Osaka UniVersity,
Toyonaka, Osaka 560-0043, Japan
Received December 21, 2007; E-mail: harada@chem.sci.osaka-u.ac.jp
In biological systems, protein localization and assembly are
controlled by reversible interactions of specific controlled elements,
which have been exploited with supramolecular interactions for
the study of signal transduction,1,2 tubulin stabilization,3 and
transcription factors.4,5 In the field of supramolecular chemistry,
some research groups demonstrated that molecular recognition for
small guest molecules was controlled by structural changes of host
molecules.6–8 More sophisticated supramolecular assemblies have
been achieved by controlling assembly and disassembly using
external stimuli such as light, environment, and exogenous
ligands.9–15 We have undertaken the structural control of supramo-
lecular complexes by photoirradiation.16 Stilbene derivatives are
well-known to show the photoinduced isomerization, which are
isomerized from the trans form to the cis form and from the cis
form to the trans form under irradiation with UV and visible light,
respectively.17 We have chosen stilbene compounds because the
association constant of R-cyclodextrin (CD) for trans-stilbene is
larger than that for cis-stilbene (trans-stilbene, Ka ) 1260 M-1
;
Figure 1. Partial 2D ROESY NMR spectrum of 3-trans-Sti-R-CD in D2O
at 30 °C (500 MHz, mixing time ) 200 ms).
cis-stilbene, Ka ) 360 M-1).18 Herein, we have demonstrated
photochemical switching of supramolecular structures of 3-stilbene
amide-R-CD (3-Sti-R-CD).
1
The H NMR spectra of 3-trans-Sti-R-CD showed that the
peaks of protons of 3-trans-Sti-R-CD shifted with an increase
in the concentration, indicating the formation of supramolecular
complexes in aqueous solutions. However, no peak shift was
observed in organic media due to the dissociation of supramo-
lecular complexes. The 2D ROESY NMR of 3-trans-Sti-R-CD
in an aqueous solution showed that the protons (a-d) of the
stilbene amide group correlated to inner protons (C(3)-H and
C(5)-H) of R-CD (Figure 1). We have obtained a single crystal
of 3-trans-Sti-R-CD that is suitable for X-ray crystallographic
analysis. The X-ray crystallographic analysis showed the
formation of a double-threaded dimer (Figure 2). This result is
in an agreement with the 2D ROESY NMR experiments.
After photoirradiation with visible light (λ ) 340 nm), 85% of
3-trans-Sti-R-CD isomerized to 3-cis-Sti-R-CD (trans:cis ) 15:
85). Although we had expected that 3-cis-Sti-R-CD would not show
peak shifts because the supramolecular complex of 3-cis-Sti-R-
CD is supposed to decompose, the protons of 3-cis-Sti-R-CD
actually showed the peak shifts with an increase in the concentra-
tion. The 2D ROESY NMR spectra of 3-cis-Sti-R-CD did not show
the correlation peaks between inner protons (C(3)H and C(5)H)
of R-CD and protons of the stilbene amide group in aqueous
solutions. The UV spectra of 3-cis-Sti-R-CD showed a red shift
with an increase in the concentration, indicative of the formation
of nonthreaded supramolecular self-assembly. The circular dichro-
ism (cd) spectra showed the negative-positive Cotton band around
Figure 2. Crystal structure of a double-threaded dimer consisting of 3-trans-
Sti-R-CD. Carbon and oxygen of R-CD are shown in gray and red, respectively.
Carbon and oxygen of stilbene amide groups are shown in light green.
300 nm in aqueous solutions, corresponding to the transition band
of the stilbene amide group. This Cotton band is assigned to the
exciton coupling interactions between stilbene amide groups. This
result suggests that two or more excitons are located in relatively
close distance. In contrast, 3-cis-Sti-R-CD did not exhibit the Cotton
band in methanol because of the dissociation of these supramo-
lecular assemblies. The mixture of 3-cis-Sti-R-CD and ꢀ-CD in
an aqueous solution showed the positive Cotton band because the
cis-stilbene amide group is strongly included in the ꢀ-CD cavity.19
These results indicate that 3-cis-Sti-R-CD forms nonthreaded
9
5024 J. AM. CHEM. SOC. 2008, 130, 5024–5025
10.1021/ja7113135 CCC: $40.75
2008 American Chemical Society

C O M M U N I C A T I O N S
Figure 3. Turbo ion spray TOF mass spectrum of 3-cis-Sti-R-CD in an
Figure 4. Schematic illustration of switching between supramolecular dimer
and nonthreaded supramolecular self-assembly consisting of 3-Sti-R-CD
with photoirradiation.
aqueous solution.
supramolecular self-assembly by π-π stacking interactions be-
tween stilbene amide groups.
Acknowledgment. We are grateful to M. Yamazaki (Rigaku
Corporation, Japan) for measuring the single X-ray analysis.
The authors thank Mr. S. Adachi (Osaka University) for PFG-
NMR experiments. This work has been partially supported by
Grant-in-Aid No. A19205014 for Scientific Research and has
been conducted with financial support from the “Stress and
Symbiosis on Supramolecules” program of the Ministry of
Education, Culture, Sports, Science and Technology, Japan.
To estimate the molecular size of the nonthreaded su-
pramolecular self-assembly from 3-cis-Sti-R-CD, self-diffu-
sion coefficients (Ds) were determined by the pulsed field
gradient spin–echo NMR measurements. We have chosen
2-cinnamoyl-R-CD (2-CiO-R-CD) as a reference compound
because 2-CiO-R-CD formed a double-threaded dimer, which
was proved by single-crystal X-ray analysis. The Ds of 2-CiO-
R-CD showed 0.23 × 10-5 cm2 s-1 in the lower concentration
region (10-30 mM). We are not able to determine the Ds of
3-trans-Sti-R-CD because of a high crystallinity and a low-
water solubility. The Ds of 3-cis-Sti-R-CD significantly
decreased with an increase in concentration (<60 mM). It
should be noted that the hydrodynamic radius of 3-cis-Sti-
R-CD is larger than that of 2-CiO-R-CD at the whole region
of the concentration (see Supporting Information). These
results suggest that the size of nonthreaded supramolecular
self-assembly from 3-cis-Sti-R-CD was larger than that of a
double-threaded dimer in aqueous solutions.
The turbo ion spray TOF mass spectrum provides direct
evidence of the formation of nonthreaded supramolecular self-
assembly. Mass spectrum of 3-trans-Sti-R-CD exhibited dimeric
species as a major peak, whereas that of 3-cis-Sti-R-CD showed
polymeric peaks with multivalent species in aqueous solutions
(Figure 3). These results indicate that 3-trans-Sti-R-CD formed
a double-threaded dimer, and 3-cis-Sti-R-CD formed a non-
threaded supramolecular self-assembly with around 15mer in 1
mM aqueous solution.
In conclusion, we have succeeded in controlling formation of a
double-threaded dimer and that of nonthreaded supramolecular self-
assembly consisting of stilbene amide-R-CD by photoirradiation
as shown in Figure 4. First, we thought that 3-trans-Sti-R-CD would
form a supramolecular polymer and then 3-cis-Sti-R-CD would
decompose it after photoirradiation. The facts are contrary to what
we expected. Formations of these supramolecular complexes might
be due to π-π stacking interactions between stilbene amide groups.
These interactions are presumed to inhibit the formation of a
supramolecular polymer. Instead, it created a more interesting
supramolecular system, in other words, “switching between su-
pramolecular dimer and nonthreaded supramolecular self-as-
sembly”. The unit of R-CD and the cis-stilbene group play
important roles to form supramolecular assembly as a hydrophilic
and hydrophobic part, respectively. These interactions and environ-
ment promote the π-π stacking of the cis-stilbene group and affect
cooperatively the formation of the supramolecular assembly. Now,
the photoresponsive properties of supramolecular structures are
under investigation.
Supporting Information Available: Selected NMR data (1D
NMR and ROESY spectrum), the determination of the diffusion
coefficient, UV spectra, cd spectra, and turbo ion spray mass spectra.
This material is available free of charge via the Internet at http://
pubs.acs.org.
References
(1) Spencer, D. M.; Wandless, T. J.; Schreiber, S. L.; Crabtree, G. R. Science
1993, 262, 1019–1024.
(2) Belshaw, P. J.; Spencer, D. M.; Crabtree, G. R.; Schreiber, S. L. Chem.
Biol. 1996, 3, 731–738.
(3) Nicolaou, K. C.; Roschangar, F.; Vourloumis, D. Angew. Chem., Int. Ed.
1998, 37, 2015–2045.
(4) Minter, A. R.; Brennan, B. B.; Mapp, A. K. J. Am. Chem. Soc. 2004, 126,
10504–10505.
(5) Kwon, Y.; Arndt, H. D.; Mao, Q.; Choi, Y.; Kawazoe, Y.; Dervan, P. B.;
Uesugi, M. J. Am. Chem. Soc. 2004, 126, 15940–15941.
(6) Raymo, F. M.; Stoddart, J. F. Switchable Catenanes and Molecular Shuttles.
In Molecular Switches; Feringa, B. L., Ed.; Wiley-VCH: Weinheim,
Germany, 2001; Sec. 7.
(7) Shinkai, S.; Shigematsu, K.; Sato, M.; Manabe, O. J. Chem. Soc., Perkin
Trans. 1 1982, 2735–2745.
(8) Mulder, A.; Jukovic, A.; van Leeuwen, F. W. B.; Kooijman, H.; Spek,
A. L.; Huskens, J.; Reinhoudt, D. N. Chem.sEur. J. 2004, 10, 1114–1123.
(9) Yang, W.-Y.; Ahn, J.-H.; Yoo, Y.-S.; Oh, N.-K.; Lee, M. Nat. Mater. 2005,
4, 399–402.
(10) Sidhaye, D. S.; Kashyap, S.; Sastry, M.; Hotha, S.; Prasad, B. L. V.
Langmuir 2005, 21, 7979–7984.
(11) Rakotondradany, F.; Whitehead, M. A.; Lebuis, A.-M.; Sleiman, H. F.
Chem.sEur. J. 2003, 9, 4771–4780.
(12) (a) Hirose, T.; Matsuda, K.; Irie, M. J. Org. Chem. 2006, 71, 7499–7508.
(13) (a) Mueller, M.; Zentel, R. Macromolecules 1994, 27, 4404–4406. (b)
Maxein, G.; Zentel, R. Macromolecules 1995, 28, 8438–8440. (c) Mueller,
M.; Zentel, R. Macromolecules 1996, 29, 1609–1617. (d) Mayer, S.;
Maxein, G.; Zentel, R. Macromolecules 1998, 31, 8522–8525.
(14) Ciardelli, F.; Fabbri, D.; Pieroni, O.; Fissi, A. J. Am. Chem. Soc. 1989,
111, 3470–3472. (b) Pieroni, O.; Fissi, A.; Viegi, A.; Fabbri, D.; Ciardelli,
F. J. Am. Chem. Soc. 1992, 114, 2734–2736.
(15) Ajayaghosh, A.; Praveen, V. K. Acc. Chem. Res. 2007, 40, 644–656.
(16) (a) Inoue, Y.; Kuad, P.; Okumura, Y.; Takashima, Y.; Yamaguchi, H.;
Harada, A. J. Am. Chem. Soc. 2007, 129, 6396–6397. (b) Tomatsu, I.;
Hashidzume, A.; Harada, A. J. Am. Chem. Soc. 2006, 128, 2226–2227. (c)
Kuad, P.; Miyawaki, A.; Takashima, Y.; Yamaguchi, H.; Harada, A. J. Am.
Chem. Soc. 2007, 129, 12630–12631.
(17) (a) Irie, M. Chem. ReV. 1999, 100, 1685–1716. (b) Takeshita, K.; Irie, M.
J. Org. Chem. 1998, 63, 6643–6649. (c) Takeshita, K.; Irie, M. J. Chem.
Soc., Chem. Commun. 1996, 1807–1808.
(18) Herrmann, W.; Wehrle, S.; Wenz, G. Chem. Commun. 1997, 1709–1710.
(19) Harata, K.; Uedaira, H. Bull. Chem. Soc. Jpn. 1975, 48, 375–378.
JA7113135
9
J. AM. CHEM. SOC. VOL. 130, NO. 15, 2008 5025