Control over nanostructures and associated mesomorphic properties of doped self-assembled triarylamine liquid crystals

Article abstract of DOI:10.1002/chem.201405567

We have synthesized a series of triarylamine-cored molecules equipped with an adjacent amide moiety and dendritic peripheral tails in a variety of modes. We show by ¹H NMR and UV/Vis spectroscopy that their supramolecular self-assembly can be p

Full text of DOI:10.1002/chem.201405567

DOI: 10.1002/chem.201405567
Full Paper
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Liquid Crystals |Hot Paper|
Control over Nanostructures and Associated Mesomorphic
Properties of Doped Self-Assembled Triarylamine Liquid Crystals
Yuya Domoto,[a, b] Eric Busseron,[a, c] Mounir Maaloum,[a] Emilie Moulin,[a] and
Nicolas Giuseppone*[a]
Abstract: We have synthesized a series of triarylamine-cored
molecules equipped with an adjacent amide moiety and
dendritic peripheral tails in a variety of modes. We show by
1H NMR and UV/Vis spectroscopy that their supramolecular
self-assembly can be promoted in solution upon light stimu-
lation and radical initiation. In addition, we have probed
their molecular arrangements and mesomorphic properties
in the bulk by integrated studies on their film state by using
differential scanning calorimetry (DSC), variable-temperature
polarizing optical microscopy (VT-POM), variable-tempera-
ture X-ray diffraction (VT-XRD), and atomic force microscopy
(AFM). Differences in the number and the disposition of the
peripheral tails significantly affect their mesomorphic prop-
erties associated with their lamellar- or columnar-packed
nanostructures, which are based on segregated stacks of the
triphenylamine cores and the lipophilic/lipophobic periphery.
Such structural tuning is of interest for implementation of
these soft self-assemblies as electroactive materials from so-
lution to mesophases.
Introduction
amine-based materials have been reported and implemented
in electronic devices including organic light-emitting diodes
(OLEDs),[6c] organic field-effect transistors (OFETs),[6e] and organ-
ic photovoltaic cells (OPVs),[6b,d] but also as non-linear optical
(NLO) materials[7a,b] and as photoconductors for the Xerox pro-
cess in laser printers and photocopiers.[6a] Most of the triaryla-
mines were used in the solid state, although a few examples
of triarylamines in the liquid[8] and liquid crystalline[9] state
have also been studied in the context of pursuing higher
device processability and device performance. However, only
very few examples of triarylamine self-assembled structures
and their associated properties have been described, including
those for which the self-assembled properties are brought by
their conjugation with other structuring p-functional groups.[10]
Recently, we have discovered a new type of light-triggered
self-assembly by using triarylamine cores substituted with
amide lateral groups.[11] The detailed mechanism of this unique
supramolecular polymerization is very complex,[11h] but it can
be summarized for compound A as follows (Figure 1): i) the ox-
idation of a catalytic quantity of triarylamines to their radical
The precise control over molecular organization by using
supramolecular self-assemblies has risen to prominence in
order to access organic materials and devices displaying im-
proved (or even emergent) functional properties.[1,2] For in-
stance, focusing on organic electronics and p-type (semi)con-
ductors, self-assemblies of oligothiophenes,[3] phthalocya-
nines,[4] and of various polycyclic aromatic hydrocarbons,[5]
when substituted by appropriate solubilizing groups, can pro-
duce 1D and 2D nanostructures with improved structure–prop-
erty relationships both in the bulk and in solution. Still in the
field of organic electronics, triarylamine molecules are among
the most promising hole transporting units.[6] From their mo-
nomer or covalent polymer derivatives, various types of triaryl-
[a] Dr. Y. Domoto, Dr. E. Busseron, Prof. Dr. M. Maaloum, Dr. E. Moulin,
Prof. Dr. N. Giuseppone
SAMS research group
University of Strasbourg
Institut Charles Sadron, CNRS
23 rue du Loess, BP 84047
cations A +, with concomitant reduction of the chlorinated sol-
C
67034 Strasbourg Cedex 2 (France)
E-mail: giuseppone@unistra.fr
vent producing chloride counterions, ii) the formation (above
a critical concentration of 10 nm) of a nucleus of at least six tri-
arylammonium radicals in a double columnar arrangement in-
volving hydrogen bonds, iii) the stacking of neutral triaryla-
mines onto the nucleus and subsequent growth of the primary
fibril, and iv) the lateral secondary aggregations of fibrils by
van der Waals forces to reach larger bundles of fibers.
[b] Dr. Y. Domoto
Present address:
Department of Applied Chemistry
School of Engineering, 7-3-1, Hongo
Bunkyo-ku, Tokyo (Japan)
[c] Dr. E. Busseron
Present address:
PCAS Expansia, Route d’Avignon
30390 Aramon (France)
In addition to this unique supramolecular polymerization
process, we measured outstanding conductivities[11c] higher
than 5ꢀ103 Smꢀ1 for these nanostructured fibers, whereas
Akande et al. have determined theoretical mobilities as high as
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201405567.
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dendritic moieties to surround the triphenylamine core. 3,4,5-
Tri(dodecyloxy)-benzene[17] and tris(tetraethyleneglycol mono-
methylether)-benzene[18] groups were chosen due to their suc-
cessful use in previous reports on supramolecular liquid crystal
materials. Triarylamines with different numbers, n, of the 3,4,5-
tri(dodecyloxy)-benzene moiety (G1–G3 with n=1, 2, 3, re-
spectively) were prepared starting from the previously report-
ed compounds 1, 2, and 4,[11a] respectively (Scheme 1). The
nitro group of triarylamine 1 was initially reduced with tin
chloride and the resulting amine was then treated with 3,4,5-
tris(dodecyloxy)benzoyl chloride to give compound G1
equipped with one dendritic tail positioned on the amide.
Starting from compound 2 and after deprotection of the
benzyl groups and concomitant reduction of the nitro group
by using palladium on charcoal, a first introduction of the den-
dritic tail was achieved following a similar procedure as report-
ed for compound G1 and leading to compound 3. Two more
tails were then attached after reaction with (3,4,5-tris(dodec-
yloxy)phenyl)methanol under Mitsunobu conditions[16] to
afford G3. The synthesis of G3DT was carried out in a similar
Figure 1. Schematic and simplified representation of the hierarchical self-as-
sembly process for compound A under light irradiation in chlorinated sol-
vents. The supramolecular polymerization starts by the oxidation of neutral
+
C
molecule A to its radical cation A (i), a critical number of radicals then ag-
gregate in a nucleation structure (ii) from which double columnar fibrils
grow by supramolecular association of neutral molecule A (iii), finally, fibrils
are bundled in larger and stiffer fibers by lateral associations (iv).
12 cm2 Vꢀ1 sꢀ1.[11d] These self-assembly process and related op-
toelectronic properties were also exploited recently by the
group of Kumar et al. to improve the efficiency of OPVs.[11f] We
have also probed the physical reasons for such a conductivity
in these wires by studying their electronic, optical, and mag-
netic signatures, which were fully explained by the formation
of highly efficient charge-transfer complexes (characterized as
supramolecular polarons) between triarylammonium radicals
and neutral triarylamines in the stacked structures.[11g] By inves-
tigating the scope and limitations for a successful light-trig-
gered supramolecular polymerization, we have found that the
existence of long alkyl chains at the peripheral moieties of the
triarylamine core is one of the favored choices together with
an amide hydrogen-bonding site for stabilizing the assembled
form in the harmony of multiple non-covalent interactions.[11a,g]
Interestingly, one can expect that such a molecular shape is
also in common with general requirements for designing func-
tional soft materials including organic gelators[12] and plastic-
or liquid-crystalline organics[13] composed of a p-conjugated
core surrounded by soft peripheral moieties. A systematic
study on the rarely known controlled self-assembly of triaryla-
mines is thus supposed to provide us with a beneficial insight
for their implementation as functional materials. Here, we
report on the synthesis of triarylamine-cored dendritic mole-
cules containing an amide group and on some of their supra-
molecular polymerization and functional properties in solution
and in the bulk. In particular, we focus on the control of their
nanostructures in the liquid-crystal phase by modifying their
peripheral groups, which are further related to their character-
istic mesomorphic properties.
Results and Discussion
Synthesis of triarylamine-cored dendritic molecules G1–G3
and G3DT
Scheme 1. Synthesis of triarylamine-cored molecules G1–G3 and G3DT.
a) R=C8H17: 1) SnCl2, EtOH/CH3CN, 2) Ar-COCl, Et3N, THF (G1: 84%, two
steps); R=Bn: 1) H2, Pd/C, MeOH/AcOEt, 2) Ar-COCl, Et3N, THF (3: 45%, two
steps), b) Ar-CH2OH or Ar’-CH2OH, diisopropyl azodicarboxylate (DIAD), PPh3,
THF (G3: 41%; G3DT: 46%), c) Ar-CH2OH, DIAD, PPh3, THF (G2: 43%).
Ar=aryl, Bn=benzyl.
To investigate potential liquid crystal properties of triaryla-
mine-based molecules equipped with an amide moiety and
soft peripheral tails, we have introduced a variable number of
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way from compound 3 with the introduction of two tris(tetrae-
thyleneglycol monomethylether)-benzene tails. Triarylamine G2
with two tails on the phenolic moieties was also readily syn-
thesized under the similar Mitsunobu conditions from com-
pound 4. With a series of the dendritic molecules G1–G3 and
G3DT in hand, we investigated their light-triggered self-assem-
bly properties in solutions, their supramolecular organization
in the bulk and their related mesomorphic properties.
20 min of light irradiation, disappearance of the specific
1H NMR signals assigned to the triphenylamine core was ob-
served, which amounts for their strong anisotropic stacking
and radical migration through the supramolecular columns
and as demonstrated in previous studies (Figures 2a and S1–
S4 in the Supporting Information).[11] After keeping these irradi-
ated solutions in the dark for three days, the proton resonan-
ces of the triphenylamine core partly reappear as broad signals
for G1, G3, and G3DT indicating partial disassembly. The rever-
sible character of the present light-triggered self-assembly pro-
cess is shown by the additional 10 min irradiation, which leads
again to the disappearance of the signals (Figures S1–S4 in the
Supporting Information). In the particular case of G2, at room
temperature and after three days in the dark, the absence of
resonance signals for the triphenylamine core indicates stron-
ger supramolecular interactions, which are explained by the
less hindered character of the amide substituent compared to
other derivatives (Figures 2a and S2 in the Supporting
Information).
Light-triggered supramolecular polymerization of G1–G3
and G3DT from solution and photophysical properties of
their self-assemblies
Because of the presence of an amide bond in their immediate
periphery, we have first studied the possibility to light-trigger
the self-assemblies of triarylamines G1–G3 and G3DT in chloro-
form. Indeed, it was found earlier that the support by the
amide hydrogen-bonding network is critical for the success of
the self-assembly in solution, which is also in harmony with
van der Waals interactions due to peripheral alkyl chains or
phenyl rings.[11]
The response of the system followed by UV/Vis/NIR spectros-
copy also indicates a self-assembly process, which is in agree-
ment with our previous studies.[11h] Two typical absorption
bands appear upon irradiation: one in near-infrared (NIR) (l=
800–830 nm), which is characteristic of the stabilized radical
cation in the self-assembly (and importantly confirming the
doped nature of the assembly), and one in the blue region
(l=400–450 nm), which accounts for the stacking of the triar-
To generate triarylammonium radicals, 2 mm chloroform sol-
utions of G1–G3 and G3DT were exposed to a 20 W halogen
lamp (10 Wcmꢀ2) at room temperature. The subsequent signa-
tures of the self-assembly process initiated by a catalytic quan-
1
tity of radical cations were monitored by H NMR, UV/Vis/NIR,
and photoluminescence spectroscopy. In all cases, after 10–
Figure 2. a) 1H NMR spectra of a 2 mm solution of G2 in CDCl3 before light irradiation and after 10 min irradiation by using a 20 W power white light lamp.
b) UV/Vis/NIR spectra for a 0.1 mm solution of G2 in CHCl3 upon light irradiation for 15 min, absorption spectra were detected by using a 10 mm quartz cuv-
ette. c) Photoluminescence spectra (lex =400 nm) for a 0.1 mm solution of G2 upon light irradiation in chloroform. d) Plots of maximum emission wavelength
(lem) for G1, G2, G3, and G3DT as a function of light irradiation time in chloroform.
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ylamine core (Figures 2b and S5
in the Supporting Information).
The accumulation of the radical
cationic species saturates at
roughly the same time scale
than the one monitored by
1H NMR
spectroscopy
(10–
20 min for G1 and G2, ꢁ60 min
for G3 and G3DT).
Finally, light irradiation of G1–
G3 and G3DT in chloroform also
led to a strong enhancement of
the emission intensities ob-
served in the green region (l=
480–537 nm) as revealed by
photoluminescence spectrosco-
py (Figures 2c and S6 in the
Supporting Information). This
characteristic behavior of such
triarylamines can be explained
as a sort of aggregation-induced
emission (AIE),[11g,19] which is
likely contributing by the restric-
tion of intramolecular rotations
in aggregates to lessen the non-
radiative decay of the photo-ex-
Figure 3. DSC thermograms for the triarylamines a) G1, b) G2, c) G3, and d) G3DT with a heating/cooling rate of
58Cminꢀ1. Data are taken from the second heat and cool. Dashed lines correspond to data recorded during the
first heat.
cited states. The enhanced emission peaks are expected to
appear in the higher wavelength region compared to the
weak emission from the molecularly dissolved triarylamines
(ꢁ450 nm with structural bands corresponding to p–p*
transitions[4b,20]).
However, POM observations on a film made of G1 at room
temperature show a high degree of birefringence with spheru-
lite textures typical for a highly ordered structure of discotic
assemblies[22] (Figures 4a and S10 in the Supporting Informa-
tion), suggesting that the crystalline phase is kept over this
transition. Additionally, VT-POM revealed a second phase tran-
sition at 538C, accompanied by complete disappearance of bi-
refringence (Figure S11 in the Supporting Information).[23,24]
The DSC curve of G2 shows two phase transition peaks in
the second heating cycle (Figure 3b), which correspond to the
transition from the initial crystalline phase into the highly or-
dered mesophase at ꢀ168C, characterized by focalconic-like
POM textures (Figure S12 in the Supporting Information),[25a]
and further transition to another mesophase at 448C. The
waxy nature of the film indicates that the first mesophase can
be classified as plastic,[22b,26] whereas a liquid crystalline (LC)
property was found for the second mesophase due to a fluid
character of the film as shown by shearing between two glass
plates (Figure S13c in the Supporting Information). VT-POM ex-
periments show that the second mesophase finally transits to
an isotropic phase at 778C (Figures 4b and S13a–c in the Sup-
porting Information), as also supported by observation of
This is the case for G3, G3DT, and G2 showing a significant
redshift by 50, 33, and 10 nm, respectively (Figure 2d). It is ob-
served, however, that the emission of G1 is blueshifted by
14 nm upon continuous light irradiation. Although the reason
for this tendency is unclear, differences in the stacking configu-
ration of the triarylamine cores may affect the excited state of
aggregates influencing the AIE properties as it is the case for
other systems in the literature.[21] To better understand such
fine effects, we turned to a precise structural analysis of these
self-assemblies in the bulk after evaporation of the previously
irradiated solutions.
Differential scanning calorimetry and polarized optical mi-
croscopy experiments
The thermal behavior of the dendritic molecules G1–G3 and
G3DT in the bulk were first studied by differential scanning cal-
orimetry (DSC) measurements at a scan rate of 58Cminꢀ1. Vari-
able-temperature polarized optical microscopy (VT-POM) ex-
periments were then carried out on films made from these
molecules. The films were sandwiched between two glass
plates and fabricated either 1) by drop-cast of chloroform solu-
tions followed by slow evaporation of the solvent or 2) by
thermal annealing of neat materials. The DSC curve of G1
shows reversible phase transition at 6.5 and ꢀ7.38C in the
second heating and cooling cycle, respectively (Figure 3a).
a
peak by mDSC analysis at a slower heating rate of
0.28Cminꢀ1 (Figure S9 in the Supporting Information).
The combined data from the DSC and VT-POM measure-
ments show that the outline of the thermal behavior of G3 is
similar to that of G2 (Figures 3c, 4c–d, S14, and S15 in the
Supporting Information). Two independent non-fluid phases
were defined (with a transition at ꢀ4.18C), followed by the LC
phase over a range comprised between 64 and 728C. Typical
pseudo focalconic textures[25b] were observed for the second
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over a larger range (7–238C), whereas VT-POM shows a plate-
like texture instead of a fan-shaped one (Figures 4e–f and S17
in the Supporting Information). In the literature, similar tex-
tures can be seen for LC phases with lamellar packing,[26d,e] in-
dicating the possible existence of a layered molecular order in
the film made of G3DT.
We subsequently carried out variable-temperature (VT) X-ray
diffraction XRD experiments to shed light on the detailed
supramolecular organizations for compounds G1–G3 and
G3DT in the film state. The combined results of the DSC, VT-
POM, and VT-XRD experiments are presented in Table 1.
X-ray diffraction (XRD) studies
XRD were measured for films of G1–G3 and G3DT fabricated
in between two mica substrates in a similar manner to the
POM experiments described above.
XRD of G1 at 238C shows a diffraction pattern containing
three sets of periodical (1, 1/2, 1/3,…) peaks (37.31, 18.82,
12.35, 9.27; 33.77, 16.89, 11.34, 8.23; 29.44, 14.64 in [ꢂ]), indi-
cating a lamellar-like molecular arrangement (Figures 5a and
S18 and Table S2 in the Supporting Information) in the film
state.[27]
Figure 4. Cross-polarized optical micrographs for thin films made from light-
irradiated solutions of a) triarylamine G1 at room temperature after anneal-
ing, b) triarylamine G2 at 658C, c) triarylamine G3 at room temperature with-
out annealing, d) triarylamine G3 at room temperature after annealing, e) tri-
arylamine G3DT at room temperature after annealing, and f) triarylamine
G3DT at room temperature after annealing and further shearing.
For the as-prepared film of G2 at room temperature, a 2D
hexagonal lattice is observed with ahex =58.8 ꢂ, characterized
p
p
by typical diffraction peaks in the ratio of 1:1/ 3:1/2:1/ 7 for
d spacing (Figures 5b and S19 and Table S3 in the Supporting
Information). The estimated number of molecules per colum-
nar disk (Z=4.83) suggests a pentameric arrangement of G2
forming a disk in the columnar assembly. The observed d11
value of 29.0 ꢂ, corresponding to the radius of the disk in the
columnar hexagonal (Colh) arrangement, is slightly smaller
than the estimated radius of fan-shaped G2 (33 ꢂ, Figure S31
in the Supporting Information). We therefore assume a “pizza-
like” assembly as illustrated in Figure S19b in the Supporting
Information, as it fits well with partial intercalation of the pe-
ripheral chains between one another. In contrast, it was found
that thermal annealing over the melting point of G2 changes
the molecular order in the film. After annealing, variable-tem-
crystalline (or plastic) phase, with their birefringent colors and
shapes changing measurably at the LC phase (Figures S14 and
S15 in the Supporting Information). The transition from the
plastic to the LC phase was also revealed by shearing experi-
ments between two glass plates (Figure S16 in the Supporting
Information). For G3DT, in which the alkyl chains of the periph-
eral tails are partially replaced by tetraethylene glycol chains,
a different thermal behavior is observed compared with the
original G3 (Figure 3d). A DSC experiment indicates that the
LC phase of G3DT appeared at a much lower temperature and
Table 1. Phase properties of the triarylamines G1–G3 and G3DT.
Thermal behavior[a]
Lattice parameters
Cr1 6.6 (18.8)
G1
G2
G3
Cr2 (Lam) (238C): d=37.3, 33.8, and 29.4 ꢂ[d]
Cr2 53 (–[b]) Iso
Colhp (238C): a=58.8 ꢂ, Z=4.83[g]
Cr ꢀ15 (8.4) Colhp 45 (1.4) Col[f] 77 (–[b]) Iso
Cr ꢀ4.1 (33.6) Colhrp 64 (1.2) Col 73 (–[b]) Iso
(annealed) Lam (658C) d=53.5 ꢂ (658C)
Colhrp (238C): a=39.4 ꢂ (hexagonal), a=68.2 ꢂ, b=39.4 ꢂ (rectangular), Z=1.53[g]
Col (688C) d=32.1 ꢂ
Coltet (128C): a=73.6 ꢂ, Z=5.78[g]
G3DT
Cr 7 (23.4) Coltet; Lam (Colh)[e] 23 (25.1[c]) Iso
Lam: (238C) d=63.1 ꢂ
Colh (238C)[e]: a=65.2 ꢂ, Z=3.95[g]
[a] The phase transition temperatures (in [8C]) and the enthalpies (in parentheses, in [kJmolꢀ1]) were determined during the 2nd heating cycle of DSC ex-
periments at 58Cminꢀ1. [b] Not detectable during the 2nd heating cycles by DSC. The phase transition was observed with VT-POM. [c] Total value integrat-
ing multiple transition peaks observed on the 2nd heating cycle. [d] Taken from the largest d spacings of three periodical peak sets (Table S2 in the Sup-
porting Information). Cr=crystalline, Lam=lamellar order possessing phase, Colh =hexagonal columnar phase, Colhrp =pseudo-hexagonal columnar phase,
Coltet =tetragonal columnar phase, p=plastic phase, r=rectangular packing. [e] After continuous XRD detections for a few days. [f] Suggested by VT-POM
(Figure S13 in the Supporting Information). [g] Number of molecules per columnar disk, see the Supporting Information for details.
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Even at 238C, the diffraction pattern shows only slight differen-
ces, suggesting that the thermal transition from Colh to Lam is
an irreversible process. An interlayer distance of 55.2 ꢂ (i.e., d
at 238C) is almost comparable to the inter-columnar distance
(i.e., ahex) of the Colh packing observed for the as-prepared
film; thus we can assume that the oligomeric structure de-
scribed above for self-assembled G2 in each disk is retained
also in the Lam phase.
For G3 at 238C, a 2D hexagonal lattice is observed with a=
39.4 ꢂ (Figures 5c and S20 and Table S4 in the Supporting In-
formation), which is significantly smaller than that for G2 form-
ing a pentameric assembly in the columnar disk as described
above. In this case, a single molecular columnar assembly is
the most likely explanation for G3 from the lattice parameter
(Z=1.53).[28] Interestingly, in this diffraction pattern, a 2D rec-
tangular lattice was concurrently observed with a=68.2 ꢂ, b=
39.4 ꢂ (i.e., a (hexagonal)). Thus the phase is denoted as the
[29]
pseudo-hexagonal columnar phase (Colhrp
)
with a 2D hexag-
onal packing arrangement for the whole molecules and a 2D
rectangular symmetry for the cores. As illustrated in Figure S21
in the Supporting Information, such a molecular arrangement
is reasonable for G3, having two different linkers (an amide
and two ether groups) adjacent to the triarylamine core,
whereas the whole molecular shape presents a high symmetry
due to the three-directional deposition of the same peripheral
tails. VT-XRD at the LC phase (688C) shows only a diffraction at
d=32.1 ꢂ and disappearance of following peaks in the wider
angle region (Figure S20 in the Supporting Information),
whereas only a slight thermal change in the birefringent tex-
tures on VT-POM was observed up to this temperature as men-
tioned above. These results suggest that the LC phase of G3
maintains less ordered columnar packing (Col) possessing only
orientational order with an average inter-columnar distance
(d).
Triethylamine G3DT, in which the peripheral dodecyl-oxy
chains of G3 were partially altered by tetraethylene glycol
chains, exhibits more complicated phase changes (Figures 5d
and S22 and Table S5 in the Supporting Information). At 128C,
a tetragonal columnar (Coltet) phase was determined with a rel-
atively large column size (a=73.6 ꢂ). The middle angle diffrac-
tion then changes to a periodical pattern (1, 1:2, 1:3, 1:4,…),
which can be attributed to a phase possessing a lamellar order
and with an inter-layer distance of 63.1 ꢂ. Although the phase
transition between Coltet and the lamellar phase (Lam) is a re-
versible process, the additional transition from Lam towards
Colh (a=65.2 ꢂ) is also observed when XRD detection was con-
tinued at 238C for a few days (Figures S22 and S23 in the Sup-
porting Information). Existence of these different phases can
be rationally supported by the observation of multiple phase
transition peaks at around 238C on the DSC analysis for G3DT
(Figure 3d). Interestingly, even in the isotropic phase, two
broadened diffractions are observed at the small angle region
(Figure S22 f in the Supporting Information). This indicates that
the columnar aggregates of G3DT remain in the isotropic
phase and confirms the existence of the amide hydrogen-
bonding network through the columnar stacks even with very
bulky substituents. This self-assembled structure is also likely
Figure 5. SAXS/WAXS patterns for films prepared by drop-casting light-irradi-
ated solutions of a) G1, b) G2, c) G3 at room temperature, and d) G3DT at
various temperatures.
perature XRD at 658C shows a relatively strong diffraction
peak at d=53.5 ꢂ with the following d-spacing ratio of 1:2,
1:3, 1:4, and 1:6, indicating the existence of an ordered lamellar
(Lam) packing (Figure S19c in the Supporting Information).
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reinforced by the phase-separation of co-existing hydrophobic
dodecyl-oxy chains and hydrophilic tetraethylene glycol chains
at the periphery of G3DT.[30] The decreasing average inter-col-
umnar distance from 63.1 (at 238C) to 57.0 (by heating at
408C) and 55.2 ꢂ (by heating at 688C), might be attributed to
the partial interdigitation of these peripheral chains between
the columns due to their higher disorder at higher
temperatures.
character of the molecular arrangement estimated by XRD, as
described above. Several observations can then be combined:
1) the thickness of each sheet is 3.5 nm (Figure S24c in the
Supporting Information), a value comparable to the molecular
size of G1 in the lamellar packing as previously estimated by
XRD, 2) according to strongly birefringent spherulites observed
by POM, the molecular surface of G1 should not be in parallel
but rather perpendicular to the substrate in the as-prepared
film, 3) the layer stacks form larger scale of superstructures in
a radial fashion similar to the observation by POM without
a cross-polarizer (Figures S24b and S10c in the Supporting In-
formation). By combining these three observations, one can es-
timate that the sheets consist in assembled monolayers of G1
as illustrated in Figure S24d in the Supporting Information.
In contrast, AFM images of films made of G2 show fibrillar
objects with an average diameter of 30 nm, which further ag-
gregate into densely packed bundles (Figures 6b and S25 in
the Supporting Information). The flexible aspect of these mi-
crometric fibers accounts satisfyingly for the soft character of
columnar plastic phase observed for G2 by XRD and POM at
this temperature.
In the wide angle region, overlaps of several diffractions
were observed at 4.2–5.4 ꢂ for G1 and G2. These peaks can be
identified as two orders in the lattice: 1) distances between
the nitrogen centers of adjacent triphenylamine cores
(4.8 ꢂ)[11g,h] in the columnar stacks and 2) typical distances be-
tween peripheral alkyl chains (4.2–4.9 ꢂ).[25,26,31] The broadness
of this halo with the order of G1<G2<G3, and G3DT at room
temperature indicates enhanced “fluidity” of the peripheral
moieties according to an increased number of the side chains.
Observation of additional peaks at twice distance (8.2–9.6 ꢂ)
for G1–G3 is consistent with a period in the stack involving
two triphenylamine disks with alternated orientations and han-
dedness,[26d,f] and named as the “snow-flake” molecular ar-
rangement according to our previous experimental and theo-
retical studies.[11h]
Similarly to the case of G1, nanosheets forming terrace
structures are observed for G3 (Figures 6c and S26 in the Sup-
porting Information), whereas the surface elastic modulus
image (Figure 6d) shows more distinct microstructures,[32] indi-
cating that the thin layers further consist of fibrous compo-
nents. The morphological differences observed for the nano-
structures of G2 and G3, exhibiting both Colh phases, can pos-
sibly be attributed to the respective compositions of the col-
umnar structures. On the one hand, the columns of G2 have
a high 2D symmetry due to the pentameric assembly of the
G2 molecules in each composing disks (Figures S19b and c in
the Supporting Information), consequently bundling into thick
fibers omnidirectionally. On the other hand, G3 forms single
molecular columns bearing less 2D symmetry (because of its
two different linkers) and leading to a pseudo-hexagonal pack-
ing (Figure S21 in the Supporting Information). Such a molecu-
lar arrangement is thought to result in spread sheet structures
rather than individually completed fibers and bundles.
Atomic force microscopy (AFM) measurements
To further understand the supramolecular organizations of the
present assembled systems, AFM was performed on films pre-
pared by drop-casting irradiated chloroform solutions of G1–
G3 on mica substrates, followed by evaporation of the solvent.
As shown in Figure 6a, stacked layers of multiple nanosheets
are observed for G1 when imaged at room temperature. For-
mation of such a structure is in good agreement with a lamellar
Summary of the self-assembled structures and of their relat-
ed mesomorphic properties
Compounds G1–G3 and G3DT readily self-assemble by light ir-
radiation in solution and variation of the peripheral tails at-
tached to the triarylamine core dramatically affect the modes
and properties of the supramolecular materials in the bulk, as
summarized in Figure 7.
Lamellar-like arrangement is preferred in the case of G1
equipped with a single dendritic moiety containing three do-
decyl chains, resulting in a layer-by-layer stack of the monolay-
er nanosheets. Introduction of two identical dendritic tails at
the peripheral positions, in contrast, induces the pentameric
assembly of G2 in a hexagonally packed columnar stack, which
finally leads to thick bundles of nanofibers with micrometer-
scale lengths. However, thermal annealing of the as-prepared
film produces an irreversible transition to the lamellar molecu-
Figure 6. AFM height images obtained for a) G1, b) G2, and c) G3. d) AFM
surface elastic modulus image obtained for G3.
Chem. Eur. J. 2014, 20, 1 – 12
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posed of tetraethylene glycol chains having higher flexibility
and electrically repulsive character.[34]
We can also correlate the morphology in the bulk and films
with our spectroscopic analyzes in solution. Interestingly, the
nanosheet structure for G1 can be correlated with its 14 nm
blue-shifted emission upon continuous light irradiation in solu-
tion. In contrast, G2, G3, and G3DT form columnar structures
that align the triarylamine core,[11h] and show significant red-
shifts in solution. In addition, for all these derivatives, the char-
acteristic NIR absorption bands (Figure S7 in the Supporting In-
formation) and fluorescent emissions (Figure S8 in the Support-
ing Information) were also observed in the film state at similar
maximum wavelengths to those in light-irradiated solution
(Table S1 in the Supporting Information). This tendency indi-
rectly indicates that the light-triggered self-assembly in solu-
tion can take place in a similar manner with organizations ex-
plained in the film state for the present triarylamines.[35] This is
also of particular interest to produce doped self-assemblies in
the liquid crystal state.
Figure 7. Summary of the proposed supramolecular self-assemblies of G1–
G3 and G3DT. [a] After thermal annealing of the as-prepared film. [b] Under
heated conditions. [c] Observed for as-prepared films at RT.
lar order. Furthermore, when all the three corners of the triaryl-
amine core are occupied by the dendritic tails, triethylamine
G3 forms unimolecular columns further bundled into a nano-
sheet structure. This is likely due to an anisotropic alignment
of the triarylamine cores mono-substituted by an amide
moiety in a pseudo-hexagonal molecular packing. The colum-
nar alignment of G3 is also maintained in the LC phase, where-
as the lateral positional order of the columns is lost at these
temperatures as indicated by VT-XRD measurements. Triaryla-
mine G3DT shows a complex phase behavior with columnar
phases transiting between tetragonal, lamellar, and hexagonal
packing at ambient temperature. This property can reflect the
soft nature of the assemblies due to partial wrapping of the
core by flexible tetraethylene glycol chains. The Gemini-type
amphiphilic structure[33] of G3DT also affects the composition
of the columnar structures as estimated by XRD analysis; triar-
ylamine G3DT tends to form an oligomeric assembly (Zꢁ4 to
6) in the disks, whereas G3 prefers a single-molecular columnar
stacking. Indeed, two poorly compatible peripheral chains (i.e.,
hydrocarbons and ethylene glycols) substituting a discotic mol-
ecule are often segregated in distinct layers, inducing super-
structures with multi-columnar orders.[33d]
Conclusion
To summarize, we have designed and synthesized a series of
amide-containing triphenylamine-cored dendritic molecules by
tuning their peripheral moieties. Self-assembly can be trig-
gered from solution and their doped character, as well as their
characteristic stacked structures, remain in the bulk after sol-
vent evaporation as investigated by DSC, VT-POM, VT-XRD, and
AFM. By combining these multidimensional analyses, we ob-
tained some insights into the controlled self-assembly of triar-
ylamines: 1) triphenylamine cores can be aligned into ordered
supramolecular organizations in the bulk by introducing ap-
propriate peripheral moieties leading to multiple non-covalent
interactions, 2) modification of the peripheral moieties
(number, positional relationships with the amide moiety, and
their variation) largely defines the molecular packing of lamel-
lar and columnar assemblies of triarylamines, further affecting
the formation of various supramolecular nanostructures,
3) such structural differences also change their mesomorphic
properties exhibiting characteristic phase transition behaviors
across crystalline states and plastic/liquid crystalline mesophas-
es. The structure–property relationships revealed here provide
us with useful orientations for the design of soft materials for
optoelectronics based on the framework of doped supramolec-
ular conducting nanostructures.
With respect to the mesomorphic properties, G1–G3 and
G3DT show unique characteristics, influenced by their structur-
al differences: 1) G1 displays two independent crystalline
phase, 2) both G2 and G3 display two independent mesophas-
es with a columnar plastic phase at ambient temperature and
LC phases upon heating, 3) G3DT displays a LC phase at room
temperature. Noteworthy, the transition temperature into the
LC phase was by 208C lower for G2 (having only two peripher-
al tails in a molecule) than for G3 (in which the tails cover all
three corners of the core); this is explained by the difference in
the molecular arrangement of the respective columnar packing
and the resulting number of aggregation of flexible alkyl
chains. Additionally, the drastic lowering of the LC transition
below room temperature for G3DT can be attributed to the
relatively disordered character of the peripheral stacks com-
Experimental Section
All reagents and solvents were purchased at the highest commer-
cial quality and used without further purification unless otherwise
noted. Dry solvents were obtained by using a double column
SolvTech purification system. Microscope glass slides (soda-lime,
76ꢀ26 mm, 1 mm thickness) and cover slips (20ꢀ20 mm) for the
fabrication of thin films (for POM, UV/Vis/NIR, and photolumines-
cence experiments) were purchased from the Carl Roth GmbH.
Wet column chromatography was performed by using silica gel
(high-purity grade, pore size 60 ꢂ, 230–400 mesh, 40–63 mm parti-
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cle size, Fluka). UV/Vis-NIR spectra were recorded on Cary 5000 UV/
Vis/NIR spectrometer (Agilent Technology). Fluorescence spectra
were recorded on FluoroMax-4 spectrofluorometer (HORIBA-JOBIN
YVON). FTIR spectra were recorded on a VERTEX70 FT-IR spectrom-
eter (Bruker) and are reported as wave number n˜ in [cmꢀ1] with
band intensities as “s” (strong), “m” (medium), or “w” (weak). Polar-
izing optical microscopy (POM) experiments were done by using
a Leica DMR polarization microscope (Leica) equipped with a digital
camera (COOLPIX995, Nikon). Temperature-variable POM experi-
ments were done by using a temperature-controlled stage (Linkam
Scientific Instruments). Differential scanning calorimetry was per-
formed on a DSC 8500 (PerkinElmer). X-ray diffraction (XRD) experi-
ments have been performed with two setups: an Elexience spec-
trometer with a distance sample to detector of 1.5 m with a wave-
length of l=1.54 ꢂ and a Nanostar spectrometer (Bruker-Anton
Paar) that operates with a pinhole collimator and a wire propor-
tional gas detector. Atomic force microscopy (AFM) images were
obtained by scanning the samples by using a Nanoscope 8
(Bruker) operated in peak-force tapping mode. 1H NMR spectra
were recorded on a Bruker Avance 400 spectrometer at 400 MHz
and 13C NMR spectra at 100 MHz at room temperature. The spectra
were internally referenced to the residual proton solvent signal.
For 1H NMR assignments, the chemical shifts are given in [ppm].
Spin multiplicities are reported as a singlet (s), doublet (d), triplet
(t), and quartet (q) with coupling constants (J) listed in [Hz], or
multiplet (m). Hydrogen multiplicities of 13C signals were assigned
with the help of DEPT 135 and HSQC measurements, and are re-
ported as s (C), d (CH), t (CH2), and q (CH3).
celite and rinsed with methanol. The solvent was evaporated to
give the reduced intermediate amino-triarylamine (2.3 g), which
was used without further purification. To a solution of 3,4,5-tris(do-
decyloxy)benzoyl chloride[14] (0.85 g, 1.2 mmol) in THF (3 mL) was
added a solution of amino-triarylamine (0.29 g, 0.98 mmol) and
triethylamine (0.17 mL, 1.2 mmol) in THF (7 mL) dropwise at 08C.
The mixture was stirred for 20 h while warmed slowly to room
temperature. The reaction mixture was diluted with EtOAc and
washed with saturated aqueous NH4Cl solution and brine. The or-
ganic layer was dried over Na2SO4 and the solvent was then re-
moved in vacuum. The residue was purified by column chromatog-
raphy (dichloromethane to dichloromethane/EtOAc/methanol
70:3:3; Rf =0.50 with dichloromethane/EtOAc/methanol 70:3:2) to
give compound 3 (0.42 g, 45%) as a pale yellow solid. 1H NMR
(400 MHz, CDCl3): d=7.75 (brs, 1H), 7.40 (dd, 3J=8.8, 4J=2.0 Hz,
2H), 7.05 (s, 2H), 6.98–6.93 (m, 6H), 6.76–6.74 (m, 4H), 4.06–4.01
(m, 6H), 1.85–1.74 (m, 8H), 1.51–1.47 (m, 6H), 1.38–1.28 (m, 46H),
0.91–0.88 ppm (m, 9H); 13C NMR (100 MHz, CDCl3/MeOD 97:3): d=
166.2 (s), 153.1 (s), 152.4 (s), 146.2 (s), 141.4 (s), 140.4 (s), 130.0 (s),
129.6 (s), 126.5 (d), 122.3 (d), 120.8 (d), 116.2 (d), 106.0 (d), 73.6 (t),
69.4 (t), 31.9 (t), 30.3 (t), 29.7 (4ꢀt), 29.6 (t), 29.4 (3ꢀt), 26.1 (2ꢀt),
22.7 (t), 14.1 ppm (q) (Signals for the two non-equivalent dodec-
yloxy groups are partially overlapped.); IR (neat): n˜ =3535 (br),
3367 (br), 2919 (s), 2850 (s), 1682 (w), 1617 (w), 1592 (m), 1585 (s),
1539 (w), 1493 (s), 1338 (m), 1228 (s), 1121 (s), 829 cmꢀ1 (s).
Compound G3DT: To
a mixture of triarylamine 3 (0.14 g,
0.15 mmol), Ar’-CH2OH[15] (0.35 g, 0.49 mmol), and triphenylphos-
phine (0.13 g, 0.49 mmol) in THF (5 mL) was added a solution of
DIAD (90 mL, 0.45 mmol) in THF (1 mL) dropwise at 08C. The mix-
ture was warmed to room temperature and then stirred at 608C
for 24 h. The solvent was then removed in vacuum, and the resi-
due was purified by column chromatography (dichloromethane to
dichloromethane/methanol 20:1, Rf =0.39 with dichloromethane/
methanol 10:1) to give compound G3DT (0.16 g, 46%) as a yellow
Compounds 1, 2, and 4 were prepared following procedures re-
ported in the literature.[11a]
Compound G1: A mixture of triarylamine 1 (0.12 g, 0.22 mmol) and
tin(II) chloride dihydrate (0.61 g, 2.7 mmol) in ethanol (4 mL) and
acetonitrile (5 mL) was stirred while heating to reflux overnight.
The reaction mixture was then treated with EtOAc and aqueous
NaHCO3 solution. After filtration, the separated organic layer was
dried over Na2SO4. The solvent was then evaporated to give the
amine as a solid, which was used without further purification. To
1
solid. M.p. 238C; H NMR (400 MHz, CDCl3): d=7.66 (s, 1H), 7.43 (d,
3
3J=9.2 Hz, 2H), 7.03–6.96 (m, 8H), 6.86 (d, J=8.8 Hz, 4H), 6.66 (s,
4H), 4.89 (s, 4H), 4.17–4.12 (m, 12H), 4.04–3.98 (m, 6H), 3.84 (t,
3
3J=5.2 Hz, 8H), 3.78 (t, J=5.2 Hz, 4H), 3.72–3.69 (m, 12H), 3.66–
a
solution of 3,4,5-tris(dodecyloxy)benzoyl chloride[14] (0.31 g,
3.61 (m, 48H), 3.54–3.51 (m, 12H), 3.36–3.35 (m, 18H), 1.84–1.70
(m, 6H), 1.50–1.43 (m, 6H), 1.34–1.25 (m, 48H), 0.87 ppm (t, 3J=
6.8 Hz, 9H); 13C NMR (100 MHz, CDCl3): d=165.5 (s), 154.7 (s), 153.2
(s), 152.8 (s), 145.3 (s), 141.5 (2ꢀs), 138.2 (s), 132.5 (s), 131.6 (s),
130.1 (s), 125.8 (d), 122.4 (d), 121.5 (d), 115.7 (d), 107.3 (d), 105.9
(d), 73.6 (t), 72.3 (t), 71.9 (t), 70.8 (t), 70.6 (2ꢀt), 70.5 (t), 69.7 (t),
69.5 (t), 68.9 (t), 59.0 (q), 31.9 (2ꢀt), 30.3 (t), 29.7 (4ꢀt), 29.64 (3ꢀ
t), 29.40 (3ꢀt), 26.1 (t), 22.7 (t), 14.1 ppm (q) (Aliphatic signals as-
signed to the dodecyloxy and tetraethylene glycol monomethyl-
ether chains are not completed due to overlaps of the signals for
non-equivalent chains.); IR (neat): n˜ =3515 (br), 3350 (br), 2922 (s),
2854 (s), 1690 (w), 1662 (w), 1640 (w), 1585 (m), 1528 (w), 1502 (s),
1466 (m), 1436 (m), 1332 (m), 1230 (m), 1103 (s), 827 cmꢀ1 (m).
0.44 mmol) in THF (4 mL) was added a solution of amine (0.12 g,
0.22 mmol) and triethylamine (93 mL, 0.67 mmol) in THF (4 mL)
dropwise at 08C. After stirring for 2 h at 08C, the mixture was
warmed to room temperature and further stirred for 3 h. The reac-
tion mixture was concentrated in vacuum and the residue was pu-
rified by column chromatography (cyclohexane to cyclohexane/
EtOAc 96:4; Rf =0.48 with cyclohexane/AcOEt 95:5) to give com-
1
pound G1 (0.22 g, 84%) as a pale brown solid. M.p. 538C; H NMR
3
(400 MHz, CDCl3): d=7.86 (s, 1H), 7.36 (d, J=9.6 Hz, 2H), 7.08 (s,
3
3
3
2H), 6.94 (d, J=8.8 Hz, 4H), 6.89 (d, J=8.4 Hz, 2H), 6.73 (d, J=
8.8 Hz, 4H), 3.98–3.91 (m, 6H), 3.85 (t, 3J=6.6 Hz, 4H), 1.78–1.65
(m, 12H), 1.43–1.34 (m, 12H), 1.27–1.24 (m, 60H), 0.83–0.79 ppm
(m, 15H); 13C NMR (100 MHz, CDCl3): d=163.9 (s), 155.2 (s), 152.2
(s), 149.8 (s), 145.0 (s), 141.0 (s), 129.9 (s), 126.0 (d), 121.8 (d), 121.3
(d), 117.1 (s), 115.3 (d), 109.8 (d), 74.3 (t), 74.0 (t), 69.1 (t), 66.3 (t),
32.0 (t), 30.3 (t), 30.2 (t), 29.8 (t), 29.7 (3ꢀt), 29.6 (t), 29.5 (t), 29.4
(4ꢀt), 29.2 (t), 26.1 (2ꢀt), 26.0 (t), 22.7 (t), 14.1 ppm (q) (Signals for
the two non-equivalent dodecyloxy groups and the two octoxy
groups are partially overlapped.); IR (neat): n˜ =3229 (br), 3043 (w),
2918 (s), 2850 (s), 1796 (w), 1650 (m), 1583 (w), 1507 (s), 1466 (m),
1417 (m), 1343 (m), 1235 (s), 1109 (s), 823 cmꢀ1 (m).
Compound G3: To a mixture of triarylamine 3 (0.26 g, 0.28 mmol),
(3,4,5-tris-(dodecyloxy)phenyl)methanol[16] (0.45 g, 0.68 mmol), and
triphenylphosphine (0.19 g, 0.71 mmol) in THF (8 mL) was added
a solution of DIAD (0.14 mL, 0.71 mmol) in THF (1 mL) dropwise at
08C. The mixture was warmed to room temperature and then
stirred at 608C for 22 h. The solvent was then removed in vacuum
and the residue was purified by column chromatography (cyclo-
hexane to cyclohexane/EtOAc 20:1; Rf =0.22 with cyclohexane/
EtOAc 7:1) and preparative thin-layer chromatography (cyclohex-
ane/EtOAc 20:1) to give compound G3 (0.25 g, 41%) as a pale
Compound 3: A mixture of triarylamine 2 (4.1 g, 8.1 mmol) and
palladium on carbon (0.40 g, 10 wt%) in methanol (50 mL) and
EtOAc (100 mL) was stirred under a hydrogen gas atmosphere at
room temperature for 21 h. The reaction mixture was filtered on
1
orange solid. M.p. 728C; H NMR (400 MHz, CDCl3): d=7.56 (s, 1H),
3
3
7.42 (d, J=8.8 Hz, 2H), 7.03–7.01 (m, 5H), 6.97 (d, J=9.6 Hz, 2H),
Chem. Eur. J. 2014, 20, 1 – 12
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6.88 (d, 3J=9.2 Hz, 4H), 6.61 (s, 4H), 4.89 (s, 4H), 4.02–3.94 (m,
18H), 1.79–1.77 (m, 18H), 1.53–1.44 (m, 18H), 1.34–1.23 (m, 144H),
0.88–0.85 ppm (m, 27H); 13C NMR (100 MHz, CDCl3): d=165.4 (s),
154.9 (s), 153.3 (2ꢀs), 145.4 (s), 141.6 (s), 141.5 (s), 138.1 (s), 131.9
(s), 131.5 (s), 130.0 (s), 125.9 (d), 122.3 (d), 121.4 (d), 115.7 (d), 106.3
(d), 105.9 (d), 73.6 (t), 73.5 (t), 70.8 (t), 69.5 (t), 69.2 (t), 32.0 (t), 31.9
(t), 30.4 (t), 29.8 (t), 29.7 (tꢀ2), 29.4 (tꢀ3), 26.2 (t), 26.1 (2ꢀt), 22.7
(t), 14.1 ppm (q) (Aliphatic signals assigned to four non-equivalent
dodecyloxy groups are not completed due to overlaps of the sig-
nals for four non-equivalent dodecyl chains.); IR (neat): n˜ =3285
(br), 3038 (w), 2920 (s), 2851 (s), 1639 (w), 1585 (m), 1508 (s), 1474
(m), 1434 (m), 1378 (w), 1335 (m), 1231 (s), 1117 (s), 1003 (m),
824 cmꢀ1 (m).
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Compound G2: To a mixture of triarylamine 4 (80 mg, 0.24 mmol),
(3,4,5-tris-(dodecyloxy)phenyl)methanol[16] (0.33 g, 0.50 mmol), and
triphenylphosphine (0.14 g, 0.53 mmol) in THF (7 mL) was added
DIAD (0.10 mL, 0.53 mmol) dropwise at 08C. The mixture was
stirred for 26 h while warmed slowly to room temperature, and the
solvent was removed in vacuum. The residue was purified by
column chromatography (cyclohexane to cyclohexane/EtOAc
75:25; Rf =0.46 with cyclohexane/EtOAc 70:30) to give compound
G2 (0.17 g, 43%) as a pale brown solid. M.p. 778C; 1H NMR
(400 MHz, CDCl3): d=7.29–7.27 (m, 2H), 7.01–6.98 (m, 4H), 6.93–
6.91 (m, 2H), 6.88–6.86 (m, 4H), 6.61 (s, 4H), 4.89 (s, 4H), 3.98–3.92
(m, 12H), 1.82–1.70 (m, 12H), 1.47–1.44 (m, 12H), 1.33–1.25 (m,
96H), 0.89–0.85 ppm (m, 18H); 13C NMR (100 MHz, CDCl3): d=
168.1 (s), 154.8 (s), 153.3 (s), 145.3 (s), 141.5 (s), 138.1 (s), 132.0 (s),
131.4 (s), 125.8 (d), 122.3 (d), 121.3 (d), 115.6 (d), 106.3 (d), 73.5 (t),
70.8 (t), 69.2 (t), 32.0 (t), 30.4 (q), 29.8 (t), 29.7 (2ꢀt), 29.5 (t), 29.4
(tꢀ2), 26.2 (t), 22.7 (t), 14.1 ppm (q) (Aliphatic signals assigned to
two non-equivalent dodecyloxy groups are not completed due to
overlaps of the signals for two non-equivalent dodecyl chains.); IR
(neat): n˜ =3290 (br), 3038 (w), 2917 (s), 2851 (s), 1654 (w), 1641 (w),
1591 (m), 1498 (s), 1466 (m), 1437 (m), 1373 (m), 1333 (m), 1313
(m), 1231 (s), 1211 (s), 1112 (s), 996 (m), 853 (w), 834 (m), 823 (m),
811 cmꢀ1 (w).
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The research leading to these results has received funding
from the European Research Council under the European Com-
munity’s Seventh Framework Program (FP7/2007-2013)/ERC
Starting Grant agreement no. 257099 (N.G.). We are also grate-
ful to ANR (Agence Nationale de la Recherche) for funding the
STANWs and Multiself projects. We also wish to thank the
Centre National de la Recherche Scientifique (CNRS), the COST
action (CM 1304), the international center for Frontier Research
in Chemistry (icFRC), the Laboratory of Excellence for Complex
System Chemistry (LabEx CSC), the University of Strasbourg
(UdS), and the Institut Universitaire de France (IUF). We are
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Keywords: light-responsive materials · liquid crystals · self-
assembly · supramolecular chemistry · triarylamines
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Received: October 8, 2014
Published online on && &&, 0000
Chem. Eur. J. 2014, 20, 1 – 12
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11
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Full Paper
FULL PAPER
Changing by packing: Chemically tai-
lored triarylamine derivatives readily
self-assemble upon visible light irradia-
tion (see figure) to produce doped
liquid crystals with complex mesophase
behaviors.
&
Liquid Crystals
Y. Domoto, E. Busseron, M. Maaloum,
E. Moulin, N. Giuseppone*
&& – &&
Control over Nanostructures and
Associated Mesomorphic Properties of
Doped Self-Assembled Triarylamine
Liquid Crystals
Self-assembled stacks of…
…triarylamines are generated by simple light irradia-
tion. These p-doped columnar arrangements can
produce a variety of liquid crystalline mesophases,
which strongly depend on the lateral substitutions. For
more information, see the Full Paper by Giuseppone
and co-workers on page && ff.
&
&
Chem. Eur. J. 2014, 20, 1 – 12
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12
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!