Supramolecularly engineered aggregation of a dipolar dye: Vesicular and ribbonlike architectures

Article abstract of DOI:10.1002/anie.201006117

It's all in the packing: Self-assembly of the title system through hydrogen bonding and then aggregation led to vesicle formation, and capping of the hydrogen-bonding moieties with subsequent aggregation led to ribbons. The resulting self-assembled archit

Full text of DOI:10.1002/anie.201006117

Communications
DOI: 10.1002/anie.201006117
Self-Assembly
Supramolecularly Engineered Aggregation of a Dipolar Dye: Vesicular
and Ribbonlike Architectures**
Shiki Yagai,* Yujiro Nakano, Shu Seki, Atsushi Asano, Takashi Okubo, Takashi Isoshima,
Takashi Karatsu, Akihide Kitamura, and Yoshihiro Kikkawa
Functional dyes have gained increased attention because of
the growing demands for low-cost and low-molecular-weight
materials applicable to organic photovoltaic devices.[1] The
major appealing features of these materials are the variable
optical and electronic properties obtained through intermo-
lecular electronic interactions.[2] Although this feature
demands careful molecular design of the dyes, including
taking their stacking arrangements into consideration for
obtaining the desired optical and electronic properties, it
offers a new possibility for tuning the properties by engineer-
ing specific noncovalent interactions.[1] Furthermore, tailoring
of well-defined nanostructures by the bottom-up approach
based on engineered noncovalent interactions[3] is emerging
as a powerful strategy for increasing the number of potential
applications of functional dyes. Dimension- and shape-
controlled nanostructures consisting of optically and elec-
tronically active elements would show specific functions such
as dimension-controlled transportation of excitons and
charges.[4] Thus, simultaneous control over stacking arrange-
ments and self-assembled architectures of functional dyes
would produce organic optoelectronic materials with
enhanced functionality. The stacking arrangements of various
functional dyes have been controlled by modifying peripheral
substituents,[5] host–guest complexation,[6] and hydrogen
bonding.[7] For functional dyes having a strong dipole
moment such as merocyanines, control of the stacking
arrangement is particularly challenging because aggregation
of this type of chromophore is susceptible to strong dipolar
interactions, thus resulting in antiparallel face-to-face stack-
ing arrangements (H-type aggregation).[8] The head-to-tail
orientation (J-type aggregation) of merocyanine dyes[9] have
been accomplished by Bosshard and co-workers[10] and Marks
and co-workers[11] in vapor-phase deposited films, and by
Wꢀrthner et al.[12] in
a thermodynamically equilibrated
system using hydrogen-bonding interactions. Herein, we
report a novel supramolecular strategy to obtain J- and
H-type aggregates of a dipolar dye using multiple hydrogen-
bonding interactions, thereby leading to the formation of
rationally organized vesicular and ribbonlike self-assembled
architectures[13] with distinct optical and electronic properties
(Scheme 1).
The merocyanine dye 1 bearing a barbituric acid (BA)
group,[14] was synthesized as a hydrogen-bonding dipolar dye
(m = 10.9 D). Previous studies have shown that the BA group
is a useful supramolecular binding moiety that leads to the
assembly of functional building blocks into well-defined
nanostructures through self-complementary hydrogen
bonds.[15] Self-aggregation of dye 1 proceeds through two
intermolecular hydrogen-bonding interactions between each
BA moiety, and subsequent hierarchical organization of the
resulting hydrogen-bonded species through dipolar interac-
tions (J-type aggregation). Upon addition of receptor 2,[16] the
BA group of 1 is capped, thereby shifting its aggregation
mode through dipolar interactions (H-type aggregation).
The hydrogen-bonding pattern of 1 was studied by
scanning tunneling microscopy (STM) at the liquid–solid
interface. Figure 1a shows the STM image of 1 obtained at
1-phenyloctane/highly oriented pyrolytic graphite (HOPG)
interface. Unidirectional lows of bright spots corresponding
to the stilbene moiety of 1 were observed, indicating the
formation of a linear hydrogen-bonding motif.[17] The periodic
distance between the bright spots within the lows is
(1.0ꢀ0.1) nm, which corresponds well to the hydrogen-bond-
ing motif shown in Figure 1b which is among the various
tapelike supramolecular structures found for the single
crystals of barbituric acid derivatives (see Figure S1 in the
Supporting Information).[18] The lows are separated alter-
nately by the darker regions with a width of (1.0 ꢀ 0.1) nm
(L1) and the darkest regions with a width of (1.5 ꢀ 0.1) nm
(L2). The former regions correspond to linear hydrogen-
bonded arrays of barbituric acid moieties, whereas the width
of L2 is in good agreement with the length of dodecyl chains,
suggesting the interdigitation of dodecyl chains between the
hydrogen-bonded tapes (Figure 1b). One of the two alkyl
chains of 1 is thus considered to be not physisorbed to the
[*] Prof. Dr. S. Yagai, Y. Nakano, Prof. Dr. T. Karatsu,
Prof. Dr. A. Kitamura
Department of Applied Chemistry and Biotechnology
Graduate School of Engineering, Chiba University
1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan)
Fax: (+81)43-290-3039
E-mail: yagai@faculty.chiba-u.jp
Prof. Dr. T. Okubo
School of Science and Engineering, Kinki University (Japan)
Dr. T. Isoshima
Flucto-Order Functions Research Team, RIKEN Advanced Science
Institute (RIKEN-ASI) (Japan)
Prof. Dr. S. Seki, A. Asano
Department of Applied Chemistry, Osaka University (Japan)
Dr. Y. Kikkawa
Photonics Research Institute, National Institute of Advanced
Industrial Science and Technology (AIST) (Japan)
[**] This work was partially supported by the Ministry of Education,
Science, Sports and Technology of Japan, Grant-in-Aid for Scientific
Research (B) (No. 20350061).
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201006117.
9990
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2010, 49, 9990 –9994

Angewandte
Chemie
In nonpolar solvents
such as methylcyclohexane
(MCH), hierarchical organ-
ization of the hydrogen-
bonded tapes of 1 could
take place, leading to
a
higher-order structure. 1 is
poorly soluble in MCH (cmax
ꢁ 1 ꢁ 10ꢂ5 m). The absorp-
tion spectrum of the c = 1 ꢁ
10ꢂ6
vibronic
m
solution exhibits
transitions at
lmax = 509 and 541 nm (Fig-
ure 2a). Upon increasing
the concentration to c = 1 ꢁ
10ꢂ5 m, a new band emerged
in the red-shifted region
around l = 600 nm as
a
shoulder. The new band
(J-band) disappeared upon
heating to 908C (data not
shown), suggesting that it
originates
from
J-type
aggregates of 1. Notably,
the observation of the
J-band indicates that the
hierarchical organization of
the hydrogen-bonded tapes
into two-dimensional sheets
occurs through dipolar p–p
stacking
because
interactions
distance
the
between the neighboring
stilbene moieties within the
hydrogen-bonded
exceeds 10 ꢂ.
Cooling of
tapes
a
hot
(1008C),
homogeneous
MCH solution of 1 (c = 3 ꢁ
10ꢂ5 m) to ambient temper-
atures results in a purple
suspension. The absorption
spectrum of the suspension
shows an additional increase
in the intensity of the J-band
(lmax = 595 nm, Figure 2a).
Dynamic light scattering
measurements
demon-
strated that the formation
of particles having uniform
hydrodynamic
diameters
(Dh) at around 600 nm (Fig-
ure 2b). Remarkably, scan-
ning electron microscopy
(SEM) of the particles
revealed a coffee-bean-like
ellipsoidal morphology (Fig-
Scheme 1. Schematic representation of the self-organization process of 1 and subsequent J-aggregation into
vesicles, and the formation of complex 1·2 and subsequent H-aggregation into ribbons.
surface. The interlayer spacing of hydrogen-bonded tapes
ure 2c). The longer diameters of the ellipsoids are approx-
(L3) is estimated to be (4.1 ꢀ 0.1) nm.
imately 1 mm, which is larger than the Dh value in solution.
Angew. Chem. Int. Ed. 2010, 49, 9990 –9994
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org 9991

Communications
parts. Atomic force microscopy (AFM) revealed that the
ellipsoids are between 100 and 200 nm in height with a
concavity of 50 nm in depth (Figure 2e). On the basis of these
microscopic observations, it is most likely that 1 self-
assembles into vesicular (or erythrocytelike) aggregates in
the solvent, which are deformed by the evaporation process.
X-ray diffraction of the vesicular aggregates exhibited
explicit d-spacings at 29.4, 14.6, and 9.6 ꢂ (Figure 2 f), thus
demonstrating that they are constructed by multilamellar
organization of 1. The interlayer spacing of 2.94 nm is shorter
than that of the monolayer (L3) formed at liquid–solid
interface (4.1 nm, Figure 1). Therefore, a tilted packing of the
hydrogen-bonded tapes with respect to the lamellar normal
by an angle of 448 is suggested for a higher-order organization
of 1 (Scheme 1). The tilted packing is rationalized by
observation of the J-band, which indicates an offset stacking
of the tapes along to their short axes. Notably, the J-type
aggregation of 1 is supramolecularly engineered by the
formation of the antiparallel hydrogen-bonded tape which
does not allow face-to-face stacking because of the unfavor-
able parallel orientation of the dipole moments (Scheme 1).
The addition of 0.2 equivalents of the barbituric acid
receptor 2 to the MCH suspension of 1 results in the
dissolution of vesicular aggregates, thus affording a trans-
parent purple solution (Figure 3a). Interestingly, the UV/Vis
spectrum of this solution retained the J-band (lmax = 585 nm;
Figure 3b). This observation implies that a small amount of 2
fragments the large vesicular aggregates into soluble J-type
aggregates. Further addition of 2 resulted in an abrupt
decrease in the intensity of the J-band and an increase in
the intensity of a new absorption band at lmax = 514 nm,
exhibiting a prominent color change from purple to red
(Figure 3a). The intensity of the new band was at a maximum
when [2] = [1], which suggests a 1:1 complexation.
Figure 1. a) STM image of 1 at the 1-phenyloctane/HOPG interface. L1
and L2 show the widths of the barbituric acid and alkyl-tail arrays,
respectively. L3 corresponds to the interlayer spacing of the hydrogen-
bonded tapes. b) Proposed molecular arrangement of 1.
Figure 2. a) UV/Vis absorption spectra of homogeneous MCH solu-
tions of 1 at concentrations of c=1ꢀ10ꢂ6 m (dotted line) and
c=1ꢀ10ꢂ5 m (solid line), and its MCH suspension (purple line,
c=3ꢀ10ꢂ5 m) at 258C. Arrow indicates the J-band. b) Dynamic light
scattering analysis of the MCH suspension (c=3ꢀ10ꢂ5 m). c) SEM
image of vesicular aggregates of 1 drop-cast from the MCH suspen-
sion onto a silicon substrate. d) TEM image of vesicular aggregates of
1 dip-coated from the MCH suspension onto carbon-coated TEM grid.
The sample was sputtered by Ir/Pt at an angle of 458. e) AFM image of
vesicular aggregates of 1 drop-cast from the MCH suspension onto
the HOPG surface. z scale=200 nm. Inset: three-dimensional AFM
image of a single vesicle. f) XRD pattern of vesicular aggregates of 1.
Figure 3. a) Color change of MCH solution of 1 (c=3ꢀ10ꢂ5 m) upon
increasing the equivalents of 2. b) UV/Vis spectra of 1 (c=3ꢀ10ꢂ5 m,
l=1 cm) with 2 in MCH. Arrow indicates the spectral change upon
increasing the amount of 2 (purple to red lines; 0.2!1 equiv). The
normalized spectrum at 0 equiv of 2 (a; vesicular aggregates), and
the normalized spectrum of 1·2 gel (blue line; c=2ꢀ10ꢂ3 m) are
shown. c) Polarized optical micrographic image of the 1·2 gel. Inset:
picture of the gel in a vial. d) Optical and e) polarized optical micro-
scopic images of the dried 1·2 gel.
The morphology of the ellipsoids was also visualized by
transmission electron microscopy (TEM) after sputtering
with Ir/Pt from an angle of 458 on a carbon-coated TEM grid.
The image confirmed the presence of central concavity which
shows a higher degree of penetration of electrons as a result of
a low sputtering efficiency compared to that of the peripheral
9992 www.angewandte.org
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2010, 49, 9990 –9994

Angewandte
Chemie
The supramolecular species absorbing at lmax = 514 nm is
considered to be the hydrogen-bonded complex 1·2 that is
free from dipolar aggregation because of its small red-shifted
absorption maximum from that of the monomeric 1 in MCH
(lmax = 509 nm). The 5 nm red-shift would be a result of the
polarizing effect by hydrogen-bonding interactions.[19] Addi-
tional association of this complex takes place upon increasing
concentration, leading to gelation of the solutions at a
concentration above c = 2 ꢁ 10ꢂ3 m and a blue-shift of the
absorption maximum to lmax = 474 nm (Figure 3b).[20] This
observation illustrates that the packing arrangement of the
merocyanine chromophores is shifted to an H-type arrange-
ment. Polarized optical microscopic observation of the
pristine gels showed a threadlike birefringent texture which
is characteristic of the formation of nematic gels (Fig-
ure 3c).[21] Upon drying the gel between glass substrates,
intertwined macroscopic fibers were generated and showed a
maximum birefringence when they were aligned 458 relative
to the polarizers (Figure 3d,e). This result suggests that
p planes of the discotic complex are almost perpendicular to
the long axis of the fibers.
AFM analysis of the dried gels of 1·2 showed flat
ribbonlike nanostructures with widths of 50–200 nm lying on
top of one another (Figure 4a). Notably, the individual
ribbons are comprised of thinner fibrils arranged in side-by-
side fashion (Figure 4b), consistent with the formation of the
nematic gels. The body-to-body distance between neighbor-
ing fibrils is estimated by cross-sectional analysis to be 6 nm
(Figure 4d; along i), which might correspond to the width of
the fibrils. Remarkably, magnified phase imaging revealed
that the elementary fibrils have either right- (P) or left-
handed (M) helical structures with a regular pitch of 7.5 nm
(Figure 4c and Figure 4d; along ii). Thus, it is strongly
suggested that a rotational displacement of the discotic
complex around the stacking axis occurs, leading to the
formation of twisted ribbons (Scheme 1).[5a,22] The occurrence
of the rotational displacement was supported by the electro-
absorption spectroscopic analysis of the dried gels, which
showed the presence of the transition to a lower-lying exciton
state (at 550 nm), as well as the major transition to a higher-
lying one (at 474 nm).[2] The transition to the theoretically
forbidden lower-lying exciton state in the H-type aggregates
originate from an imperfect H-type stacking arrangement
with a rotational displacement (see Figure S5 in the Support-
ing Information).[23] Since the helical pitch corresponds to a
1808 rotation of the discs, approximately 21 disks are involved
in one pitch by assuming p–p stacking distance of 3.5 ꢂ. Thus,
the rotational angle between the neighboring disks is
calculated roughly to be 98.
Molecular arrangement in semiconducting materials can
have a significant impact on their charge-carrier mobilities
and electrical conductivities.[24] We thus evaluated the mobi-
lities of photogenerated charge carriers of self-assembled
vesicular and ribbonlike aggregates by flash-photolysis time-
resolved microwave conductivity measurement (FP/
TRMC).[25] Upon excitation with a 355 nm laser pulse, the
vesicular aggregates of 1 showed the maximum transient
conductivity (fSm) of 4.4 ꢁ 10ꢂ6 cm2 Vꢂ1 sꢂ1, which is lower
than the fSm of 5.2 ꢁ 10ꢂ6 cm2 Vꢂ1 sꢂ1 observed for the
ribbonlike aggregates of 1·2 (see Figure S6 in the Supporting
Information). The photocarrier generation yields (f) of the
aggregates were determined to be 3.3 ꢁ 10ꢂ3 for 1 and 3.0 ꢁ
10ꢂ3 for 1·2 by photocurrent integration measurements (see
Figure S7 in the Supporting Information). Thus, isotropic
mobilities of photogenerated charge carriers within the
aggregates (Sm) were determined to be 1.3 ꢁ 10ꢂ3 and 1.7 ꢁ
10ꢂ3 cm2 Vꢂ1 sꢂ1 for 1 and 1·2, respectively. Taking into
account the one-dimensional columnar structure of the
latter, charge-carrier transport is assumed to occur along the
one-dimensional stacking axes directed randomly in the
present case. Therefore, Sm of 1·2 was multiplied by a factor
of three,[26] thus giving the one-dimensional mobility (m1D) of
5.1 ꢁ 10ꢂ3 cm2 Vꢂ1 sꢂ1. The higher mobility of the binary
system is consistent with the efficient overlap of p-conjugated
chromophores in the H-type aggregates.
Previous studies have shown that complementary multiple
hydrogen-bonding interactions are a powerful tool for con-
trolling either stacking arrangements[7b,d,g] or self-assembled
structures[27] of functional dyes. Herein we have demonstrated
that not only the aggregation mode of a dipolar dye but also
the resulting self-assembled architectures can be rationally
controlled by this supramolecular approach. As a result,
optical and electronic properties of a single dye component
can be tuned without any synthetic modifications. This study
clearly demonstrates that supramolecularly engineered aggre-
gation of functional dyes enhance the potential utility of these
materials in optoelectronic applications.
Received: September 30, 2010
Published online: November 19, 2010
Figure 4. AFM images of dried MCH gel of 1·2 (c=2ꢀ10ꢂ3 m).
a) Height image, b) amplitude image, c) phase image, and d) cross-
sectional profiles across the lines i and ii in b) and c), respectively. In
c), the right- and left-handed twisted ribbons are designated by “P”
and “M”, respectively.
Keywords: dyes/pigments · hydrogen bonds · nanostructures ·
.
self-assembly · supramolecular chemistry
Angew. Chem. Int. Ed. 2010, 49, 9990 –9994
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org 9993

Communications
e) A. Ajayaghosh, P. Chithra, R. Varghese, K. P. Divya, Chem.
Commun. 2008, 969 – 971.
[14] a) R. Ahuja, P. L. Caruso, D. Moebius, W. Paulus, H. Ringsdorf,
G. Wildburg, Angew. Chem. 1993, 105, 1082 – 1085; Angew.
Chem. Int. Ed. Engl. 1993, 32, 1033 – 1036; b) F. Wꢀrthner, S.
Yao, J. Org. Chem. 2003, 68, 8943 – 8949.
[15] a) X. Huang, C. Li, S. Jiang, X. Wang, B. Zhang, M. Liu, J. Am.
Chem. Soc. 2004, 126, 1322 – 1323; b) S. Yagai, S. Kubota, H.
Saito, K. Unoike, T. Karatsu, A. Kitamura, A. Ajayaghosh, M.
Kanesato, Y. Kikkawa, J. Am. Chem. Soc. 2009, 131, 5408 – 5410;
c) S. Yagai, T. Kinoshita, Y. Kikkawa, T. Karatsu, A. Kitamura,
Y. Honsho, S. Seki, Chem. Eur. J. 2009, 15, 9320 – 9324; d) C.-C.
Chu, G. Raffy, D. Ray, A. D. Guerzo, B. Kauffmann, G. Wantz,
L. Hirsch, D. M. Bassani, J. Am. Chem. Soc. 2010, 132, 12717 –
12723.
[16] a) S. K. Chang, A. D. Hamilton, J. Am. Chem. Soc. 1988, 110,
1318 – 1319; b) A. G. Bielejewska, C. E. Marjo, L. J. Prins, P.
Timmerman, F. de Jong, D. N. Reinhoudt, J. Am. Chem. Soc.
2001, 123, 7518 – 7533.
[1] “Supramolecular Dye Chemistry”: Topics in Current Chemistry,
Vol. 258 (Ed.: F. Wꢀrthner), Springer, Berlin, 2005.
[2] M. Kasha, H. R. Rawls, M. A. El-Bayoumi, Pure Appl. Chem.
1965, 11, 371 – 392.
[3] a) G. M. Whitesides, J. P. Mathias, C. T. Seto, Science 1991, 254,
1312 – 1319; b) J.-M. Lehn, Supramolecular Chemistry: Concepts
and Perspectives, VCH, Weinheim, 1995; c) D. N. Reinhoudt, M.
Crego-Calama, Science 2002, 295, 2403 – 2407.
[4] a) E. W. Meijer, A. P. H. J. Schenning, Nature 2002, 419, 353 –
354; b) A. P. H. J. Schenning, E. W. Meijer, Chem. Commun.
2005, 3245 – 3258; c) L. Zang, Y. Che, J. S. Moore, Acc. Chem.
Res. 2009, 41, 1596 – 1608.
[5] a) A. Ajayaghosh, C. Vijayakumar, R. Varghese, S. J. George,
Angew. Chem. 2006, 118, 470 – 474; Angew. Chem. Int. Ed. 2006,
45, 456 – 460; b) S. Yagai, M. Ishii, T. Karatsu, A. Kitamura,
Angew. Chem. 2007, 119, 8151 – 8155; Angew. Chem. Int. Ed.
2007, 46, 8005 – 8009; c) S. Ghosh, X.-Q. Li, V. Stepanenko, F.
Wꢀrthner, Chem. Eur. J. 2008, 14, 11343 – 11357.
[6] S. Gadde, E. K. Batchelor, J. P. Weiss, Y. Ling, A. E. Kaifer, J.
Am. Chem. Soc. 2008, 130, 17114 – 17119.
[17] S. De Feyter, A. Miura, S. Yao, Z. Chen, F. Wꢀrthner, P.
Jonkheijm, A. P. H. J. Schenning, E. W. Meijer, F. C.
De Schryver, Nano Lett. 2005, 5, 77 – 81.
[18] J. C. MacDonald, G. M. Whitesides, Chem. Rev. 1994, 94, 2383 –
2420.
[19] J. Schmidt, R. Schmidt, F. Wꢀrthner, J. Org. Chem. 2008, 73,
6355 – 6362.
[20] The IR spectra of the gel and the vesicular aggregates also
confirmed the formation of hydrogen bonds between 1 and 2
(see Figure S2 in the Supporting Information).
[21] a) H. von Berlepsch, C. Boettcher, L. Daehne, J. Phys. Chem. B
2000, 104, 8792 – 8799; b) J.-H. Ryu, M. Lee, J. Am. Chem. Soc.
2005, 127, 14170 – 14171.
[22] a) P. Jonkheijm, P. P. A. M. van-der-Schoot, A. P. H. J. Schen-
ning, E. W. Meijer, Science 2006, 313, 80 – 83; b) A. Brizard, R.
Oda, I. Huc, Top. Curr. Chem. 2005, 256, 167 – 218.
[23] U. Rꢃsch, S. Yao, R. Wortmann, F. Wꢀrthner, Angew. Chem.
2006, 118, 7184 – 7188; Angew. Chem. Int. Ed. 2006, 45, 7026 –
7030.
[24] S. Prasanthkumar, A. Saeki, S. Seki, A. Ajayaghosh, J. Am.
Chem. Soc. 2010, 132, 8866 – 8867.
[25] A. Acharya, S. Seki, A. Saeki, Y. Koizumi, S. Tagawa, Chem.
Phys. Lett. 2005, 404, 356 – 360.
[7] a) M. Shirakawa, S. Kawano, N. Fujita, K. Sada, S. Shinkai, J.
Org. Chem. 2003, 68, 5037 – 5044; b) S. Yagai, M. Higashi, T.
Karatsu, A. Kitamura, Chem. Commun. 2006, 1500 – 1502;
c) T. E. Kaiser, H. Wang, V. Stepanenko, F. Wurthner, Angew.
Chem. 2007, 119, 5637 – 5640; Angew. Chem. Int. Ed. 2007, 46,
5541 – 5544; d) S. Yagai, T. Seki, T. Karatsu, A. Kitamura, F.
Wꢀrthner, Angew. Chem. 2008, 120, 3415 – 3419; Angew. Chem.
Int. Ed. 2008, 47, 3367 – 3371; e) Y. Sagara, T. Kato, Angew.
Chem. 2008, 120, 5253 – 5256; Angew. Chem. Int. Ed. 2008, 47,
5175 – 5178; f) F. Wꢀrthner, C. Bauer, V. Stepanenko, S. Yagai,
Adv. Mater. 2008, 20, 1695 – 1698; g) S. Yagai, S. Kubota, K.
Unoike, T. Karatsu, A. Kitamura, Chem. Commun. 2008, 4466 –
4468.
[8] a) F. Wꢀrthner, S. Yao, Angew. Chem. 2000, 112, 2054 – 2057;
Angew. Chem. Int. Ed. 2000, 39, 1978 – 1981; b) F. Wꢀrthner, S.
Yao, U. Beginn, Angew. Chem. 2003, 115, 3368 – 3371; Angew.
Chem. Int. Ed. 2003, 42, 3247 – 3250; c) F. Wꢀrthner, K.
Meerholz, Chem. Eur. J. 2010, 16, 9366 – 9373.
[9] J-aggregation of merocyanine dyes has been also achieved by the
treatment of thin films of an amphiphilic merocyanines on SiO2
electrode with the alkaline aqueous solution: K. Iriyama, F.
Mizutani, M. Yoshimura, Chem. Lett. 1980, 1399 – 1402.
[10] C. Cai, M. M. Bꢃsch, Y. Tao, B. Mꢀller, Z. Gan, A. Kꢀndig, C.
Bosshard, I. Liakatas, M. Jꢄger, P. Gꢀnter, J. Am. Chem. Soc.
1998, 120, 8563 – 8564.
[11] P. Zhu, H. Kang, A. Facchetti, G. Evmenenko, P. Dutta, T. J.
Marks, J. Am. Chem. Soc. 2003, 125, 11496 – 11497.
[12] F. Wꢀrthner, J. Schmidt, M. Stolte, R. Wortmann, Angew. Chem.
2006, 118, 3926 – 3930; Angew. Chem. Int. Ed. 2006, 45, 3842 –
3846.
[13] Guest-induced transition between fibrous and vesicular nano-
structures have been reported: a) A. Ajayaghosh, R. Varghese,
V. K. Praveen, S. Mahesh, Angew. Chem. 2006, 118, 3339 – 3342;
Angew. Chem. Int. Ed. 2006, 45, 3261 – 3264; b) J.-H. Ryu, H.-J.
Kim, Z. Huang, E. Lee, M. Lee, Angew. Chem. 2006, 118, 5430 –
5433; Angew. Chem. Int. Ed. 2006, 45, 5304 – 5307; c) A.
Ajayaghosh, P. Chithra, R. Varghese, Angew. Chem. 2007, 119,
234 – 237; Angew. Chem. Int. Ed. 2007, 46, 230 – 233; d) C. Wang,
S. Yin, S. Chen, H. Xu, Z. Wang, X. Zhang, Angew. Chem. 2008,
120, 9189 – 9192; Angew. Chem. Int. Ed. 2008, 47, 9049 – 9052;
[26] a) F. C. Grozema, L. D. A. Siebbeles, J. M. Warman, S. Seki, S.
Tagawa, U. Scherf, Adv. Mater. 2002, 14, 228 – 231; b) T. Amaya,
S. Seki, T. Moriuchi, K. Nakamoto, T. Nakata, H. Sakane, A.
Saeki, S. Tagawa, T. Hirao, J. Am. Chem. Soc. 2009, 131, 408 –
409.
[27] a) S. Yagai, T. Kinoshita, M. Higashi, K. Kishikawa, T. Naka-
nishi, T. Karatsu, A. Kitamura, J. Am. Chem. Soc. 2007, 129,
13277 – 13287; b) B. J. Jordan, Y. Ofir, D. Patra, S. T. Caldwell, A.
Kennedy, S. Joubanian, G. Rabani, G. Cooke, V. M. Rotello,
Small 2008, 4, 2074 – 2078; c) S. Yagai, S. Mahesh, Y. Kikkawa,
K. Unoike, T. Karatsu, A. Kitamura, A. Ajayaghosh, Angew.
Chem. 2008, 120, 4769 – 4772; Angew. Chem. Int. Ed. 2008, 47,
4691 – 4694; d) S. Yagai, S. Hamamura, H. Wang, V. Stepanenko,
T. Seki, K. Unoike, Y. Kikkawa, T. Karatsu, A. Kitamura, F.
Wꢀrthner, Org. Biomol. Chem. 2009, 7, 3926 – 3929; e) T.
Tazawa, S. Yagai, Y. Kikkawa, T. Karatsu, A. Kitamura, A.
Ajayaghosh, Chem. Commun. 2010, 46, 1076 – 1078; f) S. Yagai,
H. Aonuma, Y. Kikkawa, S. Kubota, T. Karatsu, A. Kitamura, S.
Mahesh, A. Ajayaghosh, Chem. Eur. J. 2010, 16, 8652 – 8661.
9994 www.angewandte.org
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2010, 49, 9990 –9994