which is favoured by the extended conformation of the TEG
chains, induced by the hydrophilic solvent. In addition, the
solvophobically favourable interactions between the TEG
indebted to MEC for a FPU studentship. The authors are
gratefully acknowledged to Prof. N. Martın and his
´
research group.
16,17
chains
—which have been experimentally proven by the
1
VT H NMR experiments—likely gives rise to a complex
framework of the OPE 1 that finally yields spherical hollow
vesicles (Scheme S1w).
Notes and references
1 (a) G. M. Whitesides and M. Boncheva, Proc. Natl. Acad.
Sci. USA, 2002, 99, 4769; (b) J. M. Lehn, Science, 2002, 295,
Considering the dependence of the NMR features and K
a
2
4
400; (c) A. Ajayaghosh and V. K. Praveen, Acc. Chem. Res., 2007,
0, 644.
values for 1 on solvent polarity, we have also visualized that
the morphology of the self-assembly of 1 can be modulated by
using solvents other than polar acetonitrile or acetonitrile–
2
(a) R. M. Capito, H. S. Azevedo, Y. S. Velichko, A. Mata and
S. I. Stupp, Science, 2008, 319, 1812; (b) J. P. Hill, W. S. Jin,
A. Kosaka, T. Fukushima, H. Ichihara, T. Shimomura, K. Ito,
T. Hashizume, N. Ishii and T. Aida, Science, 2004, 304, 1481; (c) F.
J. M. Hoeben, L. M. Herz, C. Daniel, P. Jonkheijm, A. P. H.
J. Schenning, C. Silva, S. C. J. Meskers, D. Beljonne, R. T. Phillips,
R. H. Friend and E. W. Meijer, Angew. Chem., Int. Ed., 2004, 43,
H
2
O mixtures. AFM images obtained upon dropcasting a
À6
freshly prepared solution of 1 in chloroform (B10 M) onto
mica showed the presence of a network with irregular holes
(
Fig. 3(c) and S10w), similarly to that observed for freshly
1
976.
(a) L. C. Palmer and S. I. Stupp, Acc. Chem. Res., 2008, DOI:
0.1021/ar8000926; (b) D. E. Discher and A. Eisenberg, Science,
prepared acetonitrile. The lack of vesicles or other curved
objects, together with the average profile height for the net-
work (B2 nm), suggests the p-stacking of a very few molecules
coplanar to the mica surface and intertwined with other
molecules of 1 by the TEG chains. This molecular organiza-
tion, probably influenced by the hydrophilic character of the
mica surface, induces the network growing in-plane but not in
height (Scheme 1 and S1w). However, for the case of dropcast-
ing a benzene solution, AFM images display long wires of
different heights, ranging from B3.5 to B100 nm (Fig. 3(d)
and S11w). SEM images also prove the formation of wires
under equivalent conditions (Fig. S12w). According to these
dimensions, non-polar benzene induces the coiling of the
hydrophilic TEG chains which, in turn, rotates the molecules
of 1—an effect that has been confirmed by concentration
3
4
1
2002, 297, 967.
(a) V. Percec, A. E. Dulcey, V. S. K. Balagurusamy, Y. Miura,
J. Smidrkal, M. Peterca, S. Nummelin, U. Edlund, S. D. Hudson,
P. A. Heiney, H. Duan, S. N. Magonov and S. A. Vinogradov,
Nature, 2004, 430, 764; (b) Y. Li, B. S. Lokitz and
C. L. McCormick, Angew. Chem., Int. Ed., 2006, 45, 5792;
(c) C. Park, J. Lim, M. Yun and C. Kim, Angew. Chem., Int.
Ed., 2008, 47, 2959.
5
(a) J.-H. Ryu, D.-J. Hong and M. Lee, Chem. Commun., 2008,
1043; (b) A. Ajayaghosh, P. Chithra and R. Varghese, Angew.
Chem., Int. Ed., 2007, 46, 230.
6
7
8
X. Zhang, Z. Chen and F. Wu
4
¨
rthner, J. Am. Chem. Soc., 2007, 129,
886.
J.-H. Ryu, H.-J. Kim, Z. Huang, E. Lee and M. Lee, Angew.
Chem., Int. Ed., 2006, 45, 5304.
(a) S. H. Seo, J. Y. Chang and G. N. Tew, Angew. Chem., Int. Ed.,
2006, 45, 7526; (b) A. Ajayaghosh, R. Varghese, S. Mahesh and
V. K. Praveen, Angew. Chem., Int. Ed., 2006, 45, 7729;
(c) A. Ajayaghosh, R. Varghese, V. K. Praveen and S. Mahesh,
Angew. Chem., Int. Ed., 2006, 45, 3261.
1
dependent H NMR experiments in deuterated benzene—that
self-assemble by p–p interactions to form wire-like assemblies.
In summary, the self-assembly ability of a radial OPE amphi-
phile, readily available in only four synthetic steps from
commercial reagents, is reported. A number of techniques
9
Intermolecular and Surface Forces, ed. J. N. Israelachvili,
Academic Press, London, 1992.
0 C. A. Hunter, K. R. Lawson, J. Perkins and C. J. Urch, J. Chem.
1
1
1
(
MALDI-TOF, variable concentration and temperature
Soc., Perkin Trans. 2, 2001, 651.
1 (a) R. B. Martin, Chem. Rev., 1996, 96, 3043; (b) D. Zhao and
J. S. Moore, Org. Biomol. Chem., 2003, 1, 3471.
1
H NMR studies, dilution UV-Vis experiments, and DLS
measurements) demonstrates the association of amphiphile 1.
The high value for the calculated association constant (B3.2 Â
2 F. Wu
J., 2001, 7, 2245.
13 A similar K value has been recently reported for referable
-symmetric systems. See: T. Haino, M. Tanaka and
¨
rthner, C. Thalacker, S. Diele and C. Tschierske, Chem. Eur.
5
0 M in acetonitrile) accounts for the strong tendency of 1 to
À1
1
a
C
3
self-assemble as a consequence of the contribution of several
classes of non-covalent forces, namely, p–p stacking, van der
Waals and solvophobic interactions. AFM images demonstrate
the morphological changes produced in the self-association of 1
by modifying the solvent polarity. Thus, the dimensionality of
the ensembles obtained from 1 is directly proportional to the
polarity of the solvent and rods, networks or vesicles can be
unambiguously observed.
Y. Fukazawa, Chem. Commun., 2008, 468.
1
1
4 The dissimilar diameter values observed for the vesicles in solution
or onto a surface is a well-known phenomenon. For recent
examples, see refs. 5b and 8c.
5 (a) H.-J. Butt, R. Guckenberger and J. P. Rabe, Ultramicroscopy,
¨
1992, 46, 375; (b) P. Samorı, V. Francke, T. Mangel, K. Mullen
´
and J. P. Rabe, Opt. Mater., 1998, 9, 390. The radius of the tip
(Veeco probes, MPP-11100-10) has been considered as 12.5 nm.
For the case of MeCN–H O and MeCN AFM images, the
2
rc ea sl cp ue cl at ti ve de ly t. ip broadening factors are 51 Æ 2 and 46 Æ 1 nm,
6 (a) T. F. A. de Greef, M. M. L. Nieuwenhuizen, P. J. M. Stals,
C. F. C. Fitie, A. R. A. Palmans, R. P. Sijbesma and E. W. Meijer,
´
Work is in progress to explore the self-assembly of com-
pound 1 in other conditions as well as for the synthesis of new
amphiphilic congeners of 1 useful to attain vesicles and other
supramolecular objects.
1
Chem. Commun., 2008, 4306; (b) I. Yoshikawa, J. Sawayama and
K. Araki, Angew. Chem., Int. Ed., 2008, 47, 1038.
We are thankful to A. Soubrie
A. Cortes (Centro de Microscopı
microscopy imaging; Unidad de Espectrocopı
Raman-Correlacion (UCM) for DLS experiments, and Dr M.
´
, A. Go
a y Citometrı
a de Infrarrojo-
´
mez, L. Alonso and
1
7 The participation of large functional groups in the self-assembly of
molecules by p–p interactions suggests that other non-covalent
forces, such as van der Waals or solvophobic ones, play a key role
in the final supramolecular structure. See: (a) ref. 10;
´
´
´
a, UCM) for
´
´
´
(
b) M. T. Stone, J. M. Heemstra and J. S. Moore, Acc. Chem.
Alonso (UAM) for MALDI-TOF spectra. This work has been
supported by UCM (UCM-SCH-PR34/07-15826). G. F. is
Res., 2006, 39, 11; (c) L. Zang, Y. Che and J. S. Moore, Acc. Chem.
Res., 2008, DOI: 10.1021/ar800030w.
This journal is ꢀc The Royal Society of Chemistry 2008
Chem. Commun., 2008, 6567–6569 | 6569