Helical stacking tuned by alkoxy side chains in π-conjugated triphenylbenzene discotic derivatives

Article abstract of DOI:10.1002/chem.200501058

We report on the synthesis and self-assembly of a new series of discotic molecules containing triphenylbenzene as the core and alkoxy side chain with varying length. It was found that compounds 3a-c, 4b and 5b could form stable gels in several apolar solv

Full text of DOI:10.1002/chem.200501058

FULL PAPER
DOI: 10.1002/chem.200501058
Helical Stacking Tuned by Alkoxy Side Chains in p-Conjugated
Triphenylbenzene Discotic Derivatives
Chunyan Bao,[a] Ran Lu,*[a] Ming Jin,[b] Pengchong Xue,[a] Changhui Tan,[a]
Tinghua Xu,[a] Guofa Liu,[a] and Yingying Zhao[a]
Abstract: We report on the synthesis
and self-assembly of a new series of
discotic molecules containing triphenyl-
benzene as the core and alkoxy side
chain with varying length. It was found
that compounds 3a–c, 4b and 5b could
form stable gels in several apolar sol-
vents. Transmission electron microsco-
py (TEM) images revealed that their
morphologies were very different for
the different alkoxy-substituted orga-
nogels. In toluene or hexane, 3b and
3c resulted in both left- and right-
handed helical fibers, whereas 3a re-
sulted in straight rigid fibers; 4b and
5b resulted in most straight fibers with
a few twisted fibers. The results from
FT-IR and UV/Vis absorption spectro-
scopy indicated that the hydrogen
bonding and p–p interactions were the
main driving forces for the formation
of the self-assembled gels. Further de-
tailed analysis of their aggregation
modes were conducted by UV-visible
absorption spectra and X-ray diffrac-
tion (XRD) measurements. Based on
these findings, the influence of these
peripheral alkoxy substituents on the
gel formation and the aggregation
mode were discussed. The special en-
hanced fluorescent emissions, which re-
sulted from aggregation, were also
found in the gel phase.
Keywords: discotic molecules
fluorescence gels helical
structures · self-assembly
·
·
·
Introduction
chitectures found in organogels attracted broad attention for
the preparation of helical fibers or ribbons, in which the
chiral groups (such as chiral alkyl chains,[3] amino acids,[4]
glucose,[5] and cholesterol[6]) in the molecules can influence
the formation of the helices. However, few reports have de-
scribed the formation of an artificial helix from achiral mol-
ecules.[2b,7,8] In these cases, racemic products could be ob-
tained when no optical active species were used. The phe-
nomenon that helical structures can be built by achiral mol-
ecules is known as spontaneous symmetry breaking,[9–11]
which was explained by packing restrictions between differ-
ent parts of the molecules or by the interplay of surface and
volume effects. In this context, a series of organogels con-
sisted of p-conjugated core were designed to obtain the heli-
ces by adjusting the peripheral alkoxy substituents, as the re-
sulting structures could find potential photonics applications
due to their unique optical properties.[12]
Helical architectures are very common in nature and have
always found the wide interest of scientists. Examples are
the DNA double helix, the collagen triple helix, and the a-
helical motifs in proteins. Inspired by the unique functions
of helical superstructures performed by biological systems, a
variety of aesthetically appealing helical supramolecular as-
semblies have been designed with the help of noncovalent
forces, such as hydrogen bonding, p–p interactions, and van
der Waals interactions.[1,2] Recently, the supramolecular ar-
[a] C. Bao, Prof. R. Lu, P. Xue, C. Tan, T. Xu, G. Liu, Y. Zhao
Key Laboratory of Supramolecular Structure and Materials
College of Chemistry, Jilin University, 2519 Jiefang Road
Changchun 130023 (P.R. China)
Fax : (+86)431-892-3907
E-mail: luran@mail.jlu.edu.cn
A new series of C3-symmetrical discotic molecules, in
which alkoxy chains as the side chains connected to the tri-
phenylbenzene cores through amide groups (as seen in
Scheme 1), were synthesized and their self-assembling prop-
erties and optical properties were studied. Most of the com-
pounds, such as 3a–c, 4b, and 5b, could form stable gels in
several apolar solvents; the morphologies and the packing
structures of the organogels were significantly influenced by
[b] Dr. M. Jin
Present address:
Kanagawa Academy of Science and Technology (KSP)
KSP East-412
3-2-1 Sakado, Takatsu-ku, Kawasaki-shi
Kanagawa 213 (Japan)
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author: CPK models for
the molecules, possible packing for the gels, and FT-IR data.
Chem. Eur. J. 2006, 12, 3287 – 3294
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3287

Table 1. Gelation properties of discotic compounds in organic solvents.
the length and the number of the substituted alkoxy chains.
Notably, both left- and right-handed helical fibers with dif-
ferent helical pitches could be generated by tuning the
alkoxy chain due to the steric hindrance of the self-assem-
bled molecules cooperating with the packing of the alkoxy
chains instead of any chiral groups. In particular, the forma-
tion of aggregates for the discotic molecules in gel phase ex-
hibited unusually enhanced fluorescent emission, which was
novel and totally different from those of conventional dis-
cotic supramolecular materials.
Gelator
3a
3b
3c
4b
5b
benzene
toluene
xylene
mesitylene
cyclohexane
hexane
OG
OG
OG
TG
IS
OG
OG
OG
TG
IS
OG
OG
OG
TG
IS
TG
TG
TG
TG
S
S
S
S
S
S
TG
S
IS
PG
IS
PG
IS
PG
S
S
chloroform
OG: opaque gel, TG: transparent gel, S: soluble, IS: insoluble, PG:
partly gel. The low critical gelation concentrations (cgc) of gelators 3a–c
were 0.1 wt% and of 4b, 5b were 1 wt%.
Results
found that compounds 3a–c formed gels in fifteen minutes
after cooling the hot transparent solution to the room tem-
perature, while 4b and 5b formed gels in 24 h. This could be
attributed to the lower tendency to crystallize in 4b and 5b;
also the steric effects hindered and slowed the stacking
process of the discotic molecules.
Synthesis: The synthetic routes for the triamides 3a–c, 4a–c
and 5a–c were shown in Scheme 1. They were prepared
through acylation of 1,3,5-tris(4-aminophenyl) benzene with
the according alkoxybenzoyl chloride. All compounds were
characterized with FT-IR spectroscopy, 1H NMR and
MALDI-TOF spectrometry.
Self-assembled behaviours: The structures of the organogels
in toluene or hexane have been investigated by TEM
(Figure 1). The gels exhibited well-defined fibers with differ-
ent morphologies. For example, gel 3a gave fibers with the
diameter of 100–150 nm with high axial ratios, while gel 3b
generated both right- and left-handed superhelical fibers
with diameter of about 80–120 nm. It seemed that most of
the superhelical fibers in gel 3b were composed of several
thinner twisted fibers with the diameter of 30–50 nm, which
intertwined into helix with non-uniform helical pitch. And
also some single twisted fibers could be observed with the
diameter of 30–50 nm in the gel 3b. In gel 3c, the fibers
formed were similar to those of 3b, but the helical pitch was
longer and even some straight fibers were observed, which
Gelation: The gelation properties of the discotic compounds
were investigated in various solvents. As summarized in
Table 1, the molecules with three alkoxy chains (compound
3a–c) could form stable fibrous gel in benzene, toluene,
xylene, and mesitylene even at 0.1 wt%. As for compounds
4a–c and 5a–c, the increase in size of the alkoxy side chains
induced a good solubility in most solvents; only 4b and 5b
could form gels in apolar solvent at the lowest concentration
of 1 wt%. The formation of self-assembled gels was ther-
moreversible in the organic medium, for example, the gela-
tors were insoluble at room temperature, and then turned
into a clear solution by heating to reflux, upon cooling to
room temperature, the immobile gels appeared. It was also
Scheme 1. Synthesis of discotic molecules 3a–c, 4a–c and 5a–c.
3288
www.chemeurj.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 3287 – 3294

Helical Stacking
FULL PAPER
may be due to the looser packing of 3c which consisted of
longer carbon chains. The TEM images of 4b and 5b
showed much thinner and less helical fibers with the diame-
ter of 30–80 nm, which was similar to the single fibers in 3b
and 3c, but the helical pitch increased and even formed
straight fibers. The results outlined above suggested that the
volume of peripheral alkoxy groups could tune the morphol-
ogies of gels. In these samples, right- and left-handed helices
were present in equal quantities, thus resulting in overall
racemic mixtures. It could be confirmed by the absence of
any CD signal (not shown). In order to reveal the reason
why the achiral molecules can stack into helical fibers in or-
ganogel phase, FT-IR spectra, UV-visible spectra and XRD
measurement were recorded for the gels.
In order to ascertain how the discotic molecules aggregat-
ed into the gels, both FT-IR and UV/Vis investigations were
performed. In THF, the compounds were soluble at all con-
centrations, for example, the FT-IR spectra of compound 3b
in THF showed an H-free N–H stretch band at 3560 cmꢀ1
and an amide I band at 1675 cmꢀ1, respectively. While in the
gel phase, 3b showed an N–H stretch band at 3292 cmꢀ1 and
an amide I band at 1646 cmꢀ1, which was contributed to the
characteristic of H-bonded amides (as shown in Figure 2).
Figure 2. FT-IR spectra of a) a THF solution of compound 3b and
b) a xerogel of compound 3b from toluene.
These results confirmed that hydrogen bonds between the
amide groups contribute to the self-assembly process.[13] The
UV/Vis absorption spectra for the gels were measured and
compared with the corresponding dilute solution 1”10ꢀ6 m,
in which the molecules may be considered in monomer
state. For example (as seen in Figure 3), for the 3b, the peak
assignable to the triphenylbenzene absorption gave a much
broadened and red-shifted band in gel phase than the one in
the monomer state. It suggested that the p–p interaction
also played a key role on the formation of the gels.[14]
To reveal the packing conformations of the molecules in
gel phase, XRD were measured. The XRD patterns (as seen
in Figure 4) of the xerogels 3a and 3b revealed a hexagonal
Figure 1. TEM images for gels a) 3a, b) 3b, c) 3c, d) 4b obtained from
toluene, and e) 5b obtained from hexane. The inset c) shows the ampli-
fied left- and right-handed helical fibers, respectively.
Chem. Eur. J. 2006, 12, 3287 – 3294
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3289

R. Lu et al.
1:1= :1= . This was indeed a very interesting phenomenon
2
3
since it was not expected that the discotic molecules ar-
ranged into a lamellar instead of a columnar architec-
ture.[16,17] For xerogels 3c, only one broad peak in wide-
angle region was observed and it was indicated that the
packing of the alkoxy chains were slight disordered. The
wide peaks in the small-angle region and the absence of
peaks in the wide-angle region for xerogels 4b and 5b (not
shown) suggested the disordered and loose stacking of the
alkoxy chains in 4b and 5b.[18] Given the packing structural
differences between the gels, one can presume that the van
der Waals interaction among alkoxy chains should have a
significant effect on their packing modes.
Moreover, the vibration frequencies for CH2 antisymmet-
ric nas(CH2) and symmetric ns(CH2) stretching as well as the
CH2 scissoring deformation d(CH2) band frequency of the
xerogels would somewhat reflect the packing conformation
of alkyl chains.[5a,19] For the xerogels, both of the nas(CH2)
and ns(CH2) band frequencies appeared at relatively low
wavenumber regions (2920–
Figure 3. UV-visible absorption of gel 3b in toluene at 1.0 wt% (a)
and monomer state 3b in dilute toluene solution at 10ꢀ6 m (c).
2923 and 2850–2852 cmꢀ1, re-
spectively), which suggested
that the alkyl chains adopted
the all-trans conformation. The
d(CH2) band frequency can
give the information on the
packing
chain. As seen in Figure 5, gels
3a, 3b displayed peak at
of
oligomethylene
a
1467 cmꢀ1 with full width at
half-maximum of 5.1, 7.5 cmꢀ1,
respectively, which can be ascri-
bed to a triclinic chain packing
for 3a and slight distorted hex-
agonal packing for 3b; gels 3c,
4b and 5b showed increased
Figure 5. FT-IR spectra of the
d(CH2) band region (1450–
1480 cmꢀ1) for the assembled
full width at half-maximum xerogels.
(>9 cmꢀ1) which suggested the
disordered packing.[20] These re-
Figure 4. Small-angle X-ray diffraction diagrams of the xerogels: a) 3a,
b) 3b, c) 3c, d) 4b, and e) 5b. The insets show the respective wide-angle
X-ray diffraction.
sults agreed well with those from XRD observation.
Combining the above results from the FT-IR spectra and
XRD data as well as the molecular conformation, the
reason for the generation of helical fibers from achiral mole-
cules could be deduced. It was known that the core of the
triphenylbenzene was not planar and the dihedral angle be-
tween the benzene ring was about 358 in the monomeric
state derived from the CPK model, which might induce the
same rotational direction of benzene rings due to the steric
hindrance. It had been proposed that coplanarisation of
chromophores could be induced by aggregation.[21] In the
process for the formation of the gels, the hydrogen bonding
and p–p interactions arranged the molecules to aggregate
into fibrous structure, the coplanarisation of the cores might
be induced to a certain extant. But the cores in the aggre-
gates could not, however, assume a perfect coplanar confor-
mation due to the steric hindrance and hydrogen-bonding
interactions between the amide groups, and the phenyl rings
columnar structure with the column diameters of 2.78 and
2.94 nm in the low angle region with a reciprocal spacing
pffiffiffi pffiffiffi
ratio of 1:1/ 3:1/ 4, respectively; the peaks of 3a in the
small-angle region were narrower than that of 3b, which
suggested more ordered and closed packing in xerogel 3a.
In addition, the diffractions of the wide-angle region for xe-
rogels 3a and 3b gave a series of sharp peaks, which sup-
ported the view that long alkoxy chains presumably packed
into some ordered arrangement due to hydrocarbon crystal-
lization by van der Waals interaction.[15] When the length
and the number of the alkoxy chains increased, the self-as-
sembled structures changed into lamellar ones for xerogels
3c, 4b and 5b with the interlayer distance of 5.66, 3.80 and
4.09 nm, respectively, with a reciprocal spacing ratio of
3290
www.chemeurj.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 3287 – 3294

Helical Stacking
FULL PAPER
might still rotate to some degree to cope with the formation
of the hydrogen bonding, such rotation would preclude the
co-facial alignment of the cores (see Chart S2 in the Sup-
porting Information). Therefore the cores would be aggre-
gated in a propeller-like conformation, which might provide
an induction for the formation of helices. One could think
that such perfect propeller-like conformation would only
induce straight linear packing. Therefore, there must be
some defect in the molecular packing, such as slightly disor-
dered packing of the alkoxy chains, which induced the for-
mation of twist propeller-like conformations and gave mac-
roscopic helical structures. From the XRD and FT-IR re-
sults, the side chains in xerogels 3a were packed tightly and
highly ordered, and this tight propeller-like structure stack-
ing could only cause the straight fibers as shown in Fig-
ure 1s. As for xerogel 3b, the IR spectroscopic analysis sug-
gested that the arrangement of side chains were slightly dis-
torted and the packing of the molecules was not as tight xe-
rogel 3a, which might reflect some defect in the molecular
packing and both right- and left-handed fibers were generat-
ed. When the volume of the side chains was increased, the
amount of helical fibers decreased and the helical pitches in-
creased as in gel 3c, 4b and 5b. From FT-IR and XRD ob-
servation, it was known that the packing of the molecules
were changed from hexagonal to lamellar and the packing
of the alkoxy chains in gels 3c, 4b and 5b were disordered,
in which the van der Waals interactions between the periph-
eral alkoxy chains might play a more important role on the
arrangement of the discotic molecules than the helical in-
ducement of the core, which caused the less helical configu-
ration of fibers. All of above results indicate that the helical
fibers were formed based on the steric hindrance in the
cores cooperating with the packing of the alkoxy chains.
Fluorescent emission spectra: Fluorescence spectroscopy
provides important information on the molecular organiza-
tion of fluorophores,[22] such as triphenylbenzene moieties in
present system. Figure 6 shows emission spectra of the solu-
tions of 3b, 4b, and 5b at concentrations of 1”10ꢀ6 m and
1”10ꢀ4 m, in which the compounds may be considered in the
monomer state and aggregated state, respectively. Com-
pounds 3a, 3b and 3c showed similar fluorescent emission
behaviors, so that we used 3b as an example. When excited
at 300 nm, 3b resulted in an emission peak at 340 nm under
the lex =295 nm in 10ꢀ6 m toluene solution and displayed
purple under an UV lamp at lex =365 nm. When the concen-
tration was increased to 10ꢀ4 m, the fluorescence maximum
shifted to longer wavelength with an obviously broadened
peak and displayed blue color under 365 nm UV light (as
shown in Figure 6a, and inset). The noteworthy difference
for 4b is that an unusual new peak at around 525 nm was
observed at the concentration 10ꢀ4 m under the lex =300 nm,
which was attributed to the excimer emission.[22] The lumi-
nescent property of compound 5b was similar to that of 3b
(lex =310 nm), except that a weak peak at about 450 nm ap-
peared at the concentration of 10ꢀ6 m, which suggested that
aggregates of 5b formed even in the quite dilute hexane sol-
Figure 6. Fluorescence emission spectra of discotic compounds of a) 3b,
b) 4b, and c) 5b. The solid lines represent the emission spectra at con-
centration of 10ꢀ6 m and the dash lines represented those at the 10ꢀ4 m in
the homogeneous solution for compound 3a and 3b in toluene and 3c in
hexane, respectively. The inset in a) shows the photograph illuminated by
365 nm light at 10ꢀ6 m (right) and 10ꢀ4 m (left).
ution. All luminescent emission bands of the aggregates red-
shifted to high wavelength, which could be due to the co-
facial stacking of the cores, in which a better conjugation be-
tween the cores could be obtained, thus lead to red-shift its
emission bands.[23]
Another remarkable phenomenon was that the fluores-
cence enhancement of all the gels obtained here could be
Chem. Eur. J. 2006, 12, 3287 – 3294
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3291

R. Lu et al.
unambiguously observed. As shown in Figure 7, for exam-
ple, when excited at 350 nm, organogel 5b exhibited strong
emission band, while the solution of 5b in THF didnꢁt under
phases to lamellar ones when the volume of the alkoxy
chain of molecules increased. The formation of the helical
fibers was due to the helical inducement of the core cooper-
ating with the packing and arrangement of the alkoxy
chains. The novel fluorescence emission enhancement of the
organogels was discovered, which was induced by the aggre-
gation of the molecules.
Experimental Section
General methods: Dry ethanol was obtained by distillation from Na, and
dry tetrahydrofuran (THF) by distillation from Na/K/benzophenone. The
alkoxybenzoyl chlorides were prepared according to a general procedure
and were used without any further distillation. Other chemicals were
used as received.
Characterization: 1H NMR spectra were determined with Varian-300 EX
and JEOL JNM-500EX. Mass spectral data were obtained by MALDI-
TOF mass spectrometry using a-cyano-4-hydroxycinnamic acid as the
matrix on a spectrometer. UV-visible absorption spectra were recorded
with a Shimadzu UV-2201 UV-visible spectrophotometer. FT-IR spectra
for the samples of xerogels and in THF solutions (10ꢀ2 m) were measured
at 208C (room temperature) on a Nicolet Impact 410 FT-IR spectrome-
ter. X-ray diffraction (XRD) patterns were obtained on a Japan Rigaku
D/max-gA. XRD equipped with graphite monochromatized CuKa radia-
tion (l=1.5418 Š), employing a scanning rate of 0.028sꢀ1 in the 2q range
from 0.7 to 108 and 0.058sꢀ1 in the 2q range from 10 to 508. The sample
was prepared by casting the gels on glass slide and dried at room temper-
ature. Transmission electron microscopy (TEM) was taken with a Hitachi
mode H600 A-2 apparatus. Samples for TEM measurement were pre-
pared by wiping small amount of gel onto a 200-mesh copper grid fol-
lowed by natural evaporating the solvent. Fluorescence spectra were
measured on a Japan Hitachi 850 fluorescence spectrophotometer at
room temperature.
Figure 7. Fluorescence emission spectra of compound 5b in THF solution
(c) and in the hexane gel state (a) at the same concentration
1.0 wt%. The inset shows the photographs of in hexane (left) and in
THF (right) illuminated by 365 nm light.
the same concentration. This novel and significant property
can be explained with the context of the aggregation-in-
duced enhanced fluorescent emission phenomenon, which
has been reported previously.[23] In the gel state, more
planar conformation of the cores was formed due to the in-
termolecular forces, which enhanced the fluorescent emis-
sion, while in THF, 5b was in the monomeric state con-
firmed by FT-IR measurement and the molecules were con-
sidered to be high twisted due to the steric interactions in
triphenylbenzene, which generally suppressed the radiative
decay channel and decreased the fluorescence emission. As
known, the aggregation quenching has been the thorniest
problem in the development of organic light-emitting diodes
with high efficiency, the aggregation-induced emission en-
hancement herein will stimulate new molecular engineering
endeavors in the design of the luminescent organic com-
pounds and polymers with highly emissive aggregation
states.
1,3,5-Tris(4-aminophenyl)benzene (2): SiCl4 (20 mL, 0.18 mol) was added
dropwise to a solution of p-nitroacetophenone (10 g, 0.06 mol) in abso-
lute ethanol (60 mL) at 08C. A yellow precipitate was formed immediate-
ly and then the mixture was refluxed for 10 h. After the mixture was
cooled to room temperature, saturated NH4Cl (100 mL) was added and
stirred for 10 min. The obtained yellow precipitate was filtered and dried,
and added ethanol (100 mL) directly with Pd/C (0.8 g), which was heated
to reflux. Then NH2NH2·H2O (80%, 20 mL) was added dropwise to the
hot solution. After refluxing for 10 h, the precipitate was taken off by fil-
tration and the solution was cooled to room temperature, and the white
precipitate was collected. The solid was recrystallized in ethanol and
dried at vacuum and finally obtained white solid (5.6 g, 80%). M.p.
> 2008C; 1H NMR (CDCl3, 300 MHz): d=7.59 (s, 3H; ArH), 7.50 (m,
6H; ArH), 6.78 (m, 6H; ArH), 3.73 (s, 6H; NH2); FT-IR: n˜ =3420, 3344,
1618, 1592, 1515 cmꢀ1
.
1,3,5-Tris(4-octyloxybenzoylamino)phenylbenzene (3a): A dry THF solu-
tion (10 mL) containing 4-octyloxybenzoyl chloride (0.612 g, 2.3 mmol)
was added dropwise to another dry THF (15 mL) solution consisting of
1,3,5-tris(4-aminophenyl)benzene (2) (0.2 g, 0.57 mmol) and triethyla-
mine (0.42 mL, 3.0 mmol) at 08C. After stirring at room temperature for
12 h, the solution was poured into water (200 mL), and the precipitate
was filtered and recrystallized in CHCl3/THF 4:1 twice, followed by
Conclusion
drying in
a vacuum oven (0.36 g, 60%). M.p. >
2008C; 1H NMR
In this paper, we have designed a new series of achiral dis-
cotic organogelators consisting of triphenylbenzene as core
to prepare well-defined helical fibers by tuning the peripher-
al substituted alkoxy chains. The FT-IR and UV/Vis absorp-
tion revealed that hydrogen bonding and p–p interactions
were the main driving forces for the formation of the self-as-
sembly. The XRD diagrams suggested that the self-assem-
bled structure of the gels changed from hexagonal columnar
(CDCl3, 300 MHz): d=7.86 (m, 9H; ArH), 7.74 (m, 12H; ArH), 6.98 (d,
6H; ArH), 4.02 (t, 6H; OCH2), 1.84(m, 6H; CH2), 1.56–1.43 (m, 30H;
CH2), 0.88 (t, 9H; CH3); FT-IR: n˜ =3435, 3301, 2925, 2854, 1646, 1606,
1513 cmꢀ1; MALDI-TOF MS: m/z: calcd for: 1048.4, found: 1049.2.
1,3,5-Tris(4-dodecyloxybenzoylamino)phenylbenzene (3b): Compound
3b was synthesized according to a similar method as that of 3a; yield:
0.45 g, 65%. M.p. > 2008C; 1H NMR (CDCl3, 300 MHz): d=7.85 (m,
9H; ArH), 7.73 (m, 12H; ArH), 6.97 (d, 6H; ArH), 4.02 (t, 6H; OCH2),
1.85 (m, 6H; CH2), 1.54–1.27 (m, 54H; CH2), 0.87 (t, 9H; CH3); FT-IR:
3292
www.chemeurj.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 3287 – 3294

Helical Stacking
FULL PAPER
n˜ =3431, 3297, 2922, 2852, 1647, 1606, 1514 cmꢀ1; MALDI-TOF MS: m/z:
calcd for: 1216.7, found: 1216.2.
Acknowledgements
The work was financially supported by the National Natural Science
Foundation of China (NNSFC, No. 20574027).
1,3,5-Tris(4-cetyloxybenzoylamino)phenylbenzene (3c): Compound 3c
was synthesized according to a similar method as that of 3a; yield: 0.51 g,
65%. M.p.
>
2008C; 1H NMR (CDCl3, 300 MHz): d=7.86 (m, 9H;
ArH), 7.72 (m, 12H; ArH), 6.97 (d, 6H; ArH), 3.99(t, 6H; OCH2), 1.82
(m, 6H; CH2), 1.52–1.26 (m, 78H; CH2), 0.88 (t, 9H; CH3); FT-IR: n˜ =
3439, 3293, 2921, 2851, 1646, 1606, 1514 cmꢀ1; MALDI-TOF MS: m/z:
calcd for: 1385.4, found: 1385.6.
[1] a) J. C. Nelson, J. G. Saven, J. S. Moore, P. G. Wolyness, Science
1998, 280, 1427–1430; b) A. E. Rowan, R. J. M. Nolte, Angew.
Chem. 1998, 110, 65–71; Angew. Chem. Int. Ed. 1998, 37, 63–68;
c) R. Oda, M. Schmutz, S. J. Candau, F. C. MacKintosh, Nature
1999, 399, 566–568.
[2] a) E. R. Zubrarev, M. U. Pralle, E. D. Sone, S. I. Stupp, J. Am.
Chem. Soc. 2001, 123, 4105–4106; b) E. D. Sone, E. R. Zubrarev,
S. I. Stupp, Angew. Chem. 2002, 114, 1781–1785; Angew. Chem. Int.
Ed. 2002, 41, 1705–1709; c) H. Fenniri, B.-L. Deng, A. E. Ribbe, J.
Am. Chem. Soc. 2002, 124, 11064–11072; d) T. Giorgi, S. Lena, P.
Mariani, M. A. Cremonini, S. Masiero, S. Pieraccini, J. P. Rabe, P.
Samori, G. P. Spada, G. Gottarelli, J. Am. Chem. Soc. 2003, 125,
14741–14749; e) R. Iwaura, K. Yoshida, M. Masuda, M. O. Ka-
meyama, M. Yoshida, T. Shimizu, Angew. Chem. 2003, 115, 1039–
1042; Angew. Chem. Int. Ed. 2003, 42, 1009–1012.
[3] a) L. Brunsveld, H. Zhang, M. Glasbeek, J. A. J. A. Vekemans,
E. W. Meijer, J. Am. Chem. Soc. 2000, 122, 6175–6182; b) J. J. Van
Gorp, J. A. J. A. Vekemans, E. W. Meijer, J. Am. Chem. Soc. 2002,
124, 14759–14769; c) H. Engelkamp, S. Middelbeek, R. J. M. Nolte,
Science 1999, 284, 785–788; d) S. J. George, A. Ajayaghosh, P. Jonk-
heijin, A. P. H. J. Schenning, E. W. Meijer, Angew. Chem. 2004, 116,
3504–3507; Angew. Chem. Int. Ed. 2004, 43, 3422–3425.
[4] a) T. Sagawa, S. Fukugawa, T. Yamada, H. Ihara, Langmuir 2002,
18, 7223–7228; b) L. A. Estroff, A. D. Hamilton, Angew. Chem.
2000, 112, 3589–3592; Angew. Chem. Int. Ed. 2000, 39, 3447–3450.
[5] a) I. Nakazawa, M. Masuda, Y. Okada, T. Hanada, K. Yase, M.
Asai, T. Shimizu, Langmuir 1999, 15, 4757–4764; b) G. John, M.
Masuda, Y. Okada, K. Yase, T. Shimizu, Adv. Mater. 2001, 13, 715–
718; c) G. John, J. H. Jung, H. Minamikawa, K. Yoshida, T. Shimizu,
Chem. Eur. J. 2002, 8, 5494–5500; d) S. Tamaru, S. Uchino, M. Take-
uchi, M. Ikeda, T. Hatano, S. Shinkai, Tetrahedron Lett. 2002, 43,
3751–3755.
1,3,5-Tris(3,5-dioctyloxybenzoylamino)phenylbenzene (4a): 3,5-Diocty-
loxylbenzoylchloride (0.913 g, 2.3 mmol) was dissolved in dry THF
(10 mL), and the solution was added dropwise to the dry THF (15 mL)
solution consisting of 1,3,5-tris(4-aminophenyl)benzene (2) (0.2 g,
0.57 mmol) and triethylamine (0.42 mL, 3.0 mmol) at 08C. After stirring
at room temperature for 12 h, the solution was poured into water
(200 mL), and the product was extracted with CHCl3. After evaporating
the solvent, the product was recrystallized with CHCl3/C2H5OH at
volume ratio of 1:3, and dried in a vacuum (0.41 g, 50%). M.p.>2008C;
1H NMR (CDCl3, 300 MHz): d=7.94 (s, 3H; ArH), 7.74 (m, 12H; ArH),
6.98 (s, 6H; ArH), 6.61 (s, 3H; ArH), 3.98 (t, 12H; OCH2), 1.79 (m,
12H; CH2), 1.60–1.29 (m, 60H; CH2), 0.9 (t, 18H; CH3); FT-IR: n˜ =
3285, 2926, 2855, 1649, 1594, 1512 cmꢀ1; MALDI-TOF MS: m/z: calcd
for: 1433.0, found: 1433.7.
1,3,5-Tris(3,5-didodecyloxybenzoylamino)phenylbenzene (4b): Com-
pound 4b was synthesized according to a similar method as that of com-
pound 4a; yield: 0.65 g, 65%. M.p. 1608C; 1H NMR (CDCl3, 300 MHz):
d=7.85 (s, 3H; ArH), 7.77 (m, 12H; ArH), 6.99 (s, 6H; ArH), 6.62 (s,
3H; ArH), 4.00 (t, 12H; OCH2), 1.88 (m, 12H; CH2), 1.59–1.26 (m,
108H; CH2), 0.88 (t, 18H; CH3); FT-IR: n˜ =3275, 2922, 2851, 1647, 1592,
1518 cmꢀ1; MALDI-TOF MS: m/z: calcd for: 1601.5, found 1601.2.
1,3,5-Tris(3,5-dicetyloxybenzoylamino)phenylbenzene (4c): Compound
4c was synthesized according to a similar method as that of compound
4a; yield: 0.60 g, 60%. 1H NMR (CDCl3, 300 MHz): d=7.83 (s, 3H;
ArH), 7.75 (m, 12H; ArH), 6.89 (s, 6H; ArH), 6.62 (s, 3H; ArH), 3.98 (t,
12H; OCH2), 1.86 (m, 12H; CH2), 1.59–1.26 (m, 156H; CH2), 0.89 (t,
18H; CH3); FT-IR: n˜ =3274, 2923, 2851, 1646, 1592, 1518 cmꢀ1; MALDI-
TOF MS: m/z: calcd for: 1769.7, found 1769.0.
1,3,5-Tris(3,4,5-trioctyloxybenzoylamino)phenylbenzene (5a): A dry THF
solution (10 mL) containing 3,4,5-trioctyloxylbenzoyl chloride (1.2 g,
2.3 mmol) was added dropwise to another dry THF solution (15 mL) con-
sisting of 1,3,5-tris(4-aminophenyl)benzene (2) (0.2 g, 0.57 mmol) and
triethylamine (0.42 mL, 3.0 mmol) at 08C. After stirring at room temper-
ature for 12 h, the solution was poured into water (200 mL), and the pre-
cipitate was filtered and recrystallized in CHCl3/C2H5OH at volume ratio
1:4 twice and dried in a vacuum (0.52 g, 50%). M.p. > 2008C; 1H NMR
(CDCl3, 500 MHz): d=7.92 (s, 3H; ArH), 7.72 (m, 12H; ArH), 7.08 (s,
6H;ArH), 4.03 (m, 18H; OCH2), 1.82 (m, 18H; CH2), 1.59–1.29 (m,
90H; CH2), 0.87 (m, 27H; CH3); FT-IR: n˜ =3268, 2924, 2854, 1644, 1584,
1531, 1511 cmꢀ1; MALDI-TOF MS: m/z: calcd for: 1817.6, found: 1817.5.
[6] a) P. C. Xue, R. Lu, D. M. Li, M. Jin, C. H. Tan, C. Y. Bao, Z. M.
Wang, Y. Y. Zhao, Langmuir 2004, 20, 1123411239; b) E. Snip, K.
Koumoto, S. Shinkai, Tetrahedron 2002, 58, 8863–8873; c) J. H.
Jung, S. Shinkai, T. Shimizu, Chem. Mater. 2003, 15, 2141–2145;
d) P. C. Xue, R. Lu, D. M. Li, M. Jin, C. Y. Bao, Y. Y. Zhao, Z. M.
Wang, Chem. Mater. 2004, 16, 3702–3707; e) S. Kawano, N. Fujita, S.
Shinkai, J. Am. Chem. Soc. 2004, 126, 8592–8593.
[7] a) W. Yang, X. Chai, L. Chi, X. Liu, Y. Cao, R. Lu, Y. Jiang, X.
Tang, H. Fuchs, T. Li, Chem. Eur. J. 1999, 5, 1144–1149; b) U. Sie-
meling, I. Scheppelmann, B. Neumann, A. Stammel, H.-G. Stamm-
ler, J. Frelek, Chem. Commun. 2003, 2236–2237; c) D. Ogata, T. Shi-
kata, K. Hanabusa, J. Phys. Chem. B 2004, 108, 15503–15510; d) T.
Shikata, D. Ogata, K. Hanabusa, J. Phys. Chem. B 2004, 108, 508–
514.
1,3,5-Tris(3,4,5-tridodecyloxybenzoylamino)phenylbenzene (5b): Com-
pound 5b was synthesized according to a similar method as that of com-
pound 5a; yield: 0.86 g, 65%, liquid crystal phase: 60–1408C; 1H NMR
(CDCl3, 500 MHz): d=7.91 (s, 3H; ArH), 7.72 (m, 12H; ArH), 7.08 (s,
6H; ArH), 4.04 (m, 18H; OCH2),1.83(m, 18H; CH2), 1.59–1.29 (m,
162H, CH2), 0.88 (m, 27H, CH3); FT-IR: n˜ =3298, 2923, 2852, 1648,
1585, 1513 cmꢀ1; MALDI-TOF MS: m/z: calcd for: 2322.6, found: 2322.5.
[8] K. Kçhler, G. Fçester, A. Hauster, D B. obner, U. F. Heiser, F.
Ziethe, W. Richter, F. Steiniger, M. Drechsler, H. Stettin, A. Blume,
J. Am. Chem. Soc. 2004, 126, 16804–16813.
[9] A. Jµkli, G. G. Nair, C. K. Lee, R. Sun, L. C. Chien, Phys. Rev. E
2001, 63, 061710/1-5.
1,3,5-Tris(3,4,5-tricetyloxybenzoylamino)phenylbenzene (5c): Compound
5c was synthesized according to a similar method as that of compound
5a; yield: 1.13 g, 70%. M.p. 1588C; 1H NMR (CDCl3, 500 MHz): d=
7.81(s, 3H; ArH), 7.75 (m, 12H; ArH), 7.08 (s, 6H; ArH), 4.04 (m, 18H;
OCH2), 1.82 (m, 18H; CH2), 1.50–1.25 (m, 234H; CH2), 0.87 (m, 27H;
CH3); FT-IR: n˜ =3265, 2920, 2850, 1645, 1584, 1522 cmꢀ1; MALDI-TOF
MS: m/z: calcd for: 2827.6, found:2827.5.
[10] R. Viswanathan, J. A. Zasadzinski, D. K. Schwartz, Nature 1994,
368, 440–443.
[11] D. K. Kondepudi, R. J. Kaufman, N. Singh, Science 1990, 250, 975–
979.
[12] X. Cao, W. Zhang, J. Wang, X. Zhou, H. Lu, J. Pei, J. Am. Chem.
Soc. 2003, 125, 12430–12431.
[13] a) G. Socrates, In Infrared Characteristic Group Frequencies, Wiley,
Chichester, 1994, 2nd ed., pp. 104–107; b) S. J. Lee, C. R. Park, J. Y.
Chang, Langmuir 2004, 20, 9513–9519; c) F. Camerel, C. F. J. Faul,
Chem. Commun. 2003, 1958–1959.
[14] T. Kunitake, Angew. Chem. 1992, 104, 692–710; Angew. Chem. Int.
Ed. Engl. 1992, 31, 709–726, and references therein.
Chem. Eur. J. 2006, 12, 3287 – 3294
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3293

R. Lu et al.
[15] a) J. H. Jung, G. John, K. Yoshida, T. Shimizu, J. Am. Chem. Soc.
2002, 124, 10674–10675; b) J. H. Jung, S. Shinkai, T. Shimizu,
Chem. Eur. J. 2002, 8, 2684–2690.
[16] M. Shitakawa, S. Kawano, N. Fujita, K. Sada, S. Shinkai, J. Org.
Chem. 2003, 68, 5037–5044.
[17] J. Kadam, C. F. J. Faul, U. Scherf, Chem. Mater. 2004, 16, 3867–3871.
[18] M. Masuda, T. Hanada, Y. Okada, K. Yase, T. Shimizu, Macromole-
cules 2000, 33, 9233–9238.
[19] a) M. Masuda, V. Vill, T. Shimizu, J. Am. Chem. Soc. 2000, 122,
12327–12333; b) T. Shimizu, M. Masuda, J. Am. Chem. Soc. 1997,
119, 2812–2818.
[21] M. Levitus, K. Schmieder, H. Ricks, K. D. Shimizu, U. H. F. Bunz,
M. A. Garcia-Garibay, J. Am. Chem. Soc. 2001, 123, 4259–4265.
[22] a) N. J. Turro, Molecular photochemistry, University Science Books,
1991; b) J. B. Brikd, Photophysics of Aromatic Molecules, Wiley-In-
terscience, 1970; c) S. Y. Ryu, S. Kim, J. Seo, Y. W. Kim, O. H.
Kwon, D. J. Jang, S. Y. Park, Chem. Commun. 2004, 70–71.
[23] a) B.-K. An, S.-K. Kwon, S.-D. Jung, S. Y. Park, J. Am. Chem. Soc.
2002, 124, 14410–14415; b) B.-K. An, D.-S. Lee, J.-S. Lee, Y.-S.
Park, H.-S. Song, S. Y. Park, J. Am. Chem. Soc. 2004, 126, 10232–
10233; c) J. Luo, Z. Xie, J. W. Y. Lam, L. Cheng, H. Chen, C. Qiu,
H. S. Kwok, X. Zhan, Y. Liu, D. Zhu, B. Z. Tang, Chem. Commun.
2001, 1740–1741.
[20] N. Garti, K. Sato, Crystallization and Polymorphism of Fats and
Fatty Acids, Marcel Dekker, 1988.
Received: August 29, 2005
Published online: February 7, 2006
3294
www.chemeurj.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 3287 – 3294