Healable supramolecular polymers as organic metals

Article abstract of DOI:10.1021/ja5044006

Organic materials exhibiting metallic behavior are promising for numerous applications ranging from printed nanocircuits to large area electronics. However, the optimization of electronic conduction in organic metals such as charge-transfer salts or doped conjugated polymers requires high crystallinity, which is detrimental to their processability. To overcome this problem, the combination of the electronic properties of metal-like materials with the mechanical properties of soft self-assembled systems is attractive but necessitates the absence of structural defects in a regular lattice. Here we describe a one-dimensional supramolecular polymer in which photoinduced through-space charge-transfer complexes lead to highly coherent domains with delocalized electronic states displaying metallic behavior. We also reveal that diffusion of supramolecular polarons in the nanowires repairs structural defects thereby improving their conduction. The ability to access metallic properties from mendable self-assemblies extends the current understanding of both fields and opens a wide range of processing techniques for applications in organic electronics.

Full text of DOI:10.1021/ja5044006

Article
pubs.acs.org/JACS
Healable Supramolecular Polymers as Organic Metals
†
†
†
†
†
†
Joseph J. Armao, IV, Mounir Maaloum, Thomas Ellis, Gad Fuks, Michel Rawiso, Emilie Moulin,
,†
and Nicolas Giuseppone*
†SAMS research group, University of Strasbourg, Institut Charles Sadron, CNRS, 23 rue du Loess, BP 84047, 67034 Strasbourg
Cedex 2, France
*
S Supporting Information
ABSTRACT: Organic materials exhibiting metallic behavior are
promising for numerous applications ranging from printed
nanocircuits to large area electronics. However, the optimization
of electronic conduction in organic metals such as charge-transfer
salts or doped conjugated polymers requires high crystallinity,
which is detrimental to their processability. To overcome this
problem, the combination of the electronic properties of metal-like
materials with the mechanical properties of soft self-assembled
systems is attractive but necessitates the absence of structural
defects in a regular lattice. Here we describe a one-dimensional
supramolecular polymer in which photoinduced through-space charge-transfer complexes lead to highly coherent domains with
delocalized electronic states displaying metallic behavior. We also reveal that diffusion of supramolecular polarons in the
nanowires repairs structural defects thereby improving their conduction. The ability to access metallic properties from mendable
self-assemblies extends the current understanding of both fields and opens a wide range of processing techniques for applications
in organic electronics.
INTRODUCTION
density of structural defects was recently obtained by dispersion
synthesis, showing a dramatic transition from an insulating to a
metallic material upon doping, and with an increase in
■
One of the current challenges facing information technologies
is the development of lightweight, low cost, and disposable
20
1
,2
conductivity over 9 orders of magnitude. Still, the poor
solubility of doped polyaniline limits its use for a number of
processing techniques. Another kind of organic metal is based
plastic or paper electronic devices. Conventional inorganic
semiconductors (e.g., silicon) and conductors (e.g., metals) are
expensive and rigid and commonly require multiple etching and
lithographic steps for device fabrication. The discovery of
chemically or electrochemically doped conjugated polymers
and their implementation in organic electronics has been
21
on charge transfer complexes such as TTF-TCNQ salts,
which are single-crystals and lack the processability and
mechanical properties required by flexible electronic devices.
In a third example, our group has recently shown that
chemically tailored triarylamine molecules can be grown in
3
,4
instrumental to overcome some of these problems. Many
soluble and processable semiconducting conjugated and
supramolecular polymers have been synthesized and incorpo-
rated as active layers in devices such as OFETs (organic field
2
2
2
3
the form of one-dimensional supramolecular polymers
directly between electrodes at the 100 nm length scale.
5
6
These nanowires showed increasing conductivity with decreas-
ing temperature down to 1.5 K, both in the bulk and at
effect transistors), OLEDs (organic light emitting diodes),
7
and OPVs (organic photovoltaics). However, metallic organic
polymers sharing the electrical, electronic, magnetic, and optical
3
−1
interface with electrodes (with values >5 × 10 S m ).
However, the crystalline nature of the fibers originating from a
kinetically controlled nucleation/growth process traps struc-
tural defects in the π-stacking structure over larger length scales,
and disconnections of the rigid nanorods produce grain
boundaries which are detrimental for conductivity.
8
properties of metals are still very scarce although very
promising for the development of a number of technologies
9
,10
such as transparent electrodes,
printed electronic circuits
1
1,12
13,14
and interconnects,
thermoelectric materials,
or memory
1
5
devices. To reach such properties, oxidative or reductive
doping should produce unpaired electrons that open a partially
filled conduction band where charge carriers drift with minimal
We herein describe a new class of conducting but very soft
24
and kinetically labile supramolecular triarylamines, i.e., in
which reorganization of the molecular units can take place with
a relatively low activation energy. In such a configuration, the
reversible nature of the supramolecular interactions can in
principle correct structural defects (i.e., lateral or rotational
1
6
scattering as is the case in metals. Defects enormously affect
such conductivity, resulting in localized electronic states which
alter the transport mechanism from band-like to undesired
1
7,18
thermally activated hopping.
As a result, after four decades
of materials developments, only a few number of organic
structures have reached the landmark of metallic conductivity.
For conjugated polymers, chain-ordered polyaniline with a low
19
Received: May 7, 2014
Published: July 23, 2014
©
2014 American Chemical Society
11382
dx.doi.org/10.1021/ja5044006 | J. Am. Chem. Soc. 2014, 136, 11382−11388

Journal of the American Chemical Society
Article
1
Figure 1. Structural characteristics of TATA self-assemblies. (a) (i) Chemical formula of TATA 1, 2, 3 and associated H NMR of TATA 1 in a 5:3
methanol-d :toluene-d mixture, in the presence of CDCl (5 vol %) before (ii) and after (iii) light irradiation (W, M, and T are the residual
4
8
3
resonance peaks for water, methanol, and toluene, respectively). (b) Freeze-fracture TEM image of TATA 1 showing its native form in chloroform.
(
c,d) AFM imaging of TATA 1 at the micrometer scale (c) and at the nanometer scale for a single fiber (d) obtained from a chloroform solution
drop cast on mica. (e) X-ray scattering of a thin film of TATA 1 prepared from a drop cast film on mica. (f) Side view (i) and top view (ii) of the
proposed stacking structure of TATA 1, as obtained from DFT calculations, and with a longitudinal periodicity of 29.1 Å, a nitrogen−nitrogen
distance of 4.85 Å between adjacent molecules, and a dihedral angle of 20° between each plateau.
·
+
misalignments of the stacks) by reaching a lower energetic state
to its radical cation TATA . Aggregation of these radicals at a
critical nucleation concentration promotes the stacking of
2
5,26
under thermodynamic control (self-healing polymers).
We
22
show that a proper balance between order and mobility leads to
materials presenting a unique combination of functionalities,
namely extended metallic character with soft mechanical and
defect-healing properties.
neutral TATA molecules in a subsequent growth process.
The clear signature of this self-assembly is the disappearance of
the a, b, and c resonance signals due to a strong π-stacking
between TATA cores and resulting in an anisotropic columnar
system kept soluble by lateral flexible alkyl chains (Figure
RESULTS AND DISCUSSION
The original molecular units of this study, namely tris-amide
triarylamines with various alkyl side chains (TATA 1−3, Figure
a(i)), were obtained with good yields in a three step process
1
a(iii)). In a variety of pure organic solvents (chloroform,
■
1
acetonitrile, acetone, or toluene), H NMR reveals the direct
self-assembly of TATA 1−3 without the need of light.
Intermolecular hydrogen bonding also participates in the self-
assembly as observed by infrared spectroscopy, which displays
the characteristic shifts of the amide stretching frequencies with
the N−H and CO stretching vibration occurring at 3291 and
1
(
see the Supporting Information for the synthetic procedures).
At a concentration of 5 mM in a deuterated 5:3
methanol:toluene mixture, 1 is soluble and a full NMR
spectrum can be recorded (Figure 1a(ii)). Interestingly, upon
the addition of deuterated chloroform (5 vol %) as an electron
acceptor, it is possible to trigger a self-assembly process by a
pulse of white light which oxidizes a catalytic quantity of TATA
−1
27
1654 cm , respectively. At the macroscopic level and above a
critical concentration, 1 forms a soft physical gel in chloroform
with a melting enthalpy of 7.6 KJ mol− at 35.7 °C. Differential
scanning calorimetry (DSC) also reveals a decreasing critical
1
1
1383
dx.doi.org/10.1021/ja5044006 | J. Am. Chem. Soc. 2014, 136, 11382−11388

Journal of the American Chemical Society
Article
gelation concentration and an increasing melting enthalpy for
longer alkyl chains (TATA 2 and 3; Figure S1 and Table S1).
Insight in the structure of this self-assembly is first given by
freeze fracture transmission electron microscopy (FFTEM) in
the gel state (Figure 1b), and by atomic force microscopy
(
(
AFM) of cast films obtained from dilute chloroform solutions
Figure 1c and Figure S2). Well-defined fibers of more than ten
micrometers long and of high persistence length are character-
istic of such compounds. For TATA 1, high resolution AFM
shows a diameter of 16(±3.0) Å for the individual fibers
(
Figure 1d and Figure S2), which also present a twisted
periodic pattern of 30.0(±2.0) Å along their main axis. A model
of the molecular assembly was built up using complementary
small angle and wide-angle X-ray scattering (SAXS and WAXS;
Figure 1e), together with density functional theory (DFT;
2
8−30
−1
Figure 1f).
Strong 100 scattering peak at 0.215 Å as well
as weaker 200 and 300 reflections are characteristic of a
smectic-type packing with a periodicity of 29.1 Å along the one-
dimensional ordering of the molecules (similar to the
periodicity observed by AFM, Figure 2b). The large peak at
−1
1
.30 Å corresponds to a distance of 4.85 Å between nitrogen
centers of adjacent triarylamines, in agreement with DFT
results. The apparent pitch (which is due to the 3-fold
symmetry of the TATA core), together with the stacking
distance, imply that 7 molecules are contained in a single period
with a dihedral angle of 20° between them, a value also in
agreement with DFT calculations. The broad scattering peak
−1
centered at 1.40 Å corresponds to amorphous packing of the
−1
alkyl chains, and the small peak around 2 Å corresponds to an
aryl π−π stacking distance of 3.1−3.2 Å. DFT predicts a similar
stacking distance due to both the tilt of the aromatic rings and
the dihedral angle between the molecules.
Exposure of preassembled TATA fibers to visible light in
chloroform leads to the appearance of an absorption band in
the near-infrared (NIR), with a complex behavior as a function
of irradiation time (Figure 2a,b). Similar bands have been
described in the literature for mixed valence charge transfer
between bis-triarylamine molecules linked by conjugated
Figure 2. Effect of light irradiation on TATA self-assemblies. (a,b)
Sequential absorbance spectra taken during light irradiation (with a
−2
halogen lamp; 10 W cm ) of a 0.1 mM solution of TATA 1 in
CHCl ; (a) first 6 min of light irradiation, (b) from 7 to 73 min of light
3
3
1
covalent bonds. Interestingly, in our system, the presence of
such a characteristic absorption band (λmax = 1100 nm) can
only arise from an intermolecular through-space charge-transfer
between stacked triarylamine cores. In the literature, mixed-
valence charge transfers have been classified depending on the
nature of the electronic delocalization between the redox
irradiation. (c) Room temperature EPR spectra taken while irradiating
−2
(with a halogen lamp; 10 W cm ) a 1 mM solution of TATA 1 in
CHCl from 1 to 73 min. (d) Room temperature EPR spectra taken
3
for a sample irradiated for 3 minutes, and subsequently put in the dark
for 60 min. (e) Fluorescence emission of TATA 1 upon light
irradiation showing the quenching induced by the polaron formation.
(f) SAXS of nonirradiated (dotted line) and irradiated (full line) thin
films demonstrating a 49% increase in the correlation length
3
2
centers. Class I systems consist of localized redox centers,
while class II are partially delocalized, and class III fully
delocalized. The shape of the charge transfer band can give
insight into the nature of the interaction, with a Gaussian
shaped band expected for a class II charge transfer and an
asymmetric band expected for a class III (see the Supporting
Information). Here, increasing asymmetry observed between 0
and 30 min of irradiation (Figure S16a) indicates an increasing
contribution from fully delocalized class III charge transfers.
The absorption band at 800 nm, starting at 5 min and
increasing in intensity for the remainder of the irradiation
experiment, corresponds to a higher contribution of localized
class I triarylamine cation.
(calculated as 4π/fwhm). (g−h) AFM image of TATA 1 obtained
from the drop cast of a chloroform solution before light irradiation (g)
and after 15 min of light irradiation (h) showing the healing of
structural defects. In (f) and (g) the nonirradiated solutions were kept
15 min in the dark to discriminate the effect of light from a possible
aging effect.
centers, displays an evolution with the time of light irradiation
(Figure 2c and Figures S16b and S17a). Three distinct although
partially overlapped periods are observed with (i) the growth of
a smooth five line signal corresponding to irradiation times
from 15 s to 7 min (0−15 mol % of radicals); (ii) an evolution
toward a one line pattern from 7 to 18 min (15−25 mol % of
radicals), and (iii) the emergence of a 3-line pattern from 23 to
73 min (29−44 mol % of radicals). In the literature, EPR
studies of covalently linked mixed-valence bis-triarylamines
Electronic paramagnetic resonance spectroscopy (EPR)
provides both a quantification of the amount of radicals within
the fibers as well as an alternative means of investigating the
nature of the charge transfer relative to the EPR time scale. The
hyperfine splitting of the EPR signal, arising from a through-
space hyperfine coupling of adjacent triarylamine nitrogen
33
show similar splitting patterns. By analogy, the five line
pattern corresponds to partially delocalized unpaired electrons
1
1384
dx.doi.org/10.1021/ja5044006 | J. Am. Chem. Soc. 2014, 136, 11382−11388

Journal of the American Chemical Society
Article
between two triarylamines; the one line pattern, to a fully
delocalized system with no energetic barrier to charge transfer;
and the three line pattern, to unpaired electrons which are
localized on one triarylamine.
Thus, both EPR and NIR data demonstrate the initial
formation of a mixed population of classes II and III charge
transfers, followed by a transition to a single population of class
III, which then tends to a localized class I as the higher number
of charges in the one-dimensional fiber leads to electrostatic
repulsion. A complementary experiment was performed by
irradiating a solution for 3 min and by then following the
evolution of the radicals in the dark (Figure 2d). Interestingly,
the change of the EPR signal toward a one-line pattern was
observed over 1 h. This indicates that the transformation from
class II to class III charge transfers is not related to the number
of radicals, and suggests an intrinsic structural evolution of the
system with time.
Figure 3. DFT optimized geometry for TATA self-assemblies. (a,b)
Interactions energies determined by DFT for a generic (i.e., with a
single lateral methyl group instead of the alkyl chain) monocationic
dimer of TATA as a function of the Nitrogen−Nitrogen distance (a)
and the dihedral angle (b). (c) (i) HOMO, (ii) SOMO, and (iii)
LUMO orbitals of a generic TATA monocationic dimer, as
determined by DFT calculations in the optimized geometry.
To understand the relationship between the nature of the
charge transfer and the irradiation time, we compared the X-ray
scattering profiles of two thin films; one made from a
nonirradiated solution, and the other one from a solution
irradiated for 15 min (Figure 2f). A Gaussian fit of the peak at
.215 Å− revealed a noticeable decrease in the peak width at
1
0
half-maximum, demonstrating an increase of the fiber
correlation length (ξ) of 49%, going from 163 Å in the dark
to 243 Å upon irradiation (Figure S6). The 300 reflection of
the irradiated sample also displays a noticeable sharpening,
indicating a decreasing cumulative disorder, i.e. a fewer number
34
of structural defects with light. Characterization of numerous
samples using high resolution AFM unambiguously confirmed
the improved ordering of the fibers, as well as the self-healing of
the gel in the 100 nm range, upon light irradiation (Figure 2g,h
and Figures S4 and S5). Altogether, these results strongly
suggest that class III charge transfer occurs between molecules
in a thermodynamic minimum while class II charge transfer
occurs at small structural defects in the self-assembly where the
electronic coupling and reorganization energy are less efficient.
DFT calculations also support a class III delocalized charge
transfer in the optimized assembly geometry within the
framework of Marcus−Hush theory (Figure 3a−c and Figures
3
5,36
S10−S12).
We propose to describe this type of charge transfer complex
migrating through the fibers as a “supramolecular polaron”,
which consists in a “through-space” version of the polarons
observed in conjugated polymers, and associating the radical
16
cation with a lattice deformation. This is also in agreement
with further fluorescence experiments which show exciton
quenching by the supramolecular polarons as is commonly
observed with polarons in conjugated polymers (Figure 2e and
Figure 4. Metallic characteristics of TATA self-assemblies. (a)
Temperature-dependent EPR measurement of TATA 1 displaying a
low-temperature region consisting entirely of localized Curie spins
(see linear behavior) and a higher temperature region displaying a
mixture of Curie and delocalized Pauli spins. (b) Fit of χT vs T with
3
7,38
the Supporting Information).
For TATA 1, DFT
calculations give an optimized binding energy of 16.2 kcal/
mol for the neutral dimer and of 37.1 kcal/mol for the radical
cation dimer, demonstrating a sufficient energetic gain to heal
defects (i.e., lateral or rotational misalignements) in the course
of their diffusion through the columnar stacks.
In the presence of these polarons, the supramolecular
polymer presents unique and clear signatures of metallic
behavior. For instance, temperature-dependent EPR measure-
ments were performed down to 4 K on the powder obtained
from irradiated fibers, and a plot of the inverse EPR signal
versus temperature displays two distinct regions (Figure 4a).
The lower temperature region below 90 K shows a linear
dependence, indicating that the signal is arising from unpaired
2
the Curie−Weiss law for data between 4 and 80 K (r = 0.999). (c)
Relative intensity of the half-field EPR transition versus temperature.
The data were fitted with the Bleaney−Bowers model giving a weak
2
antiferromagnetic coupling with J = −0.48 K (r = 0.998). (d)
Reflectance measurements of an irradiated thin film of TATA 1
displaying a plasma resonance near 1.2 eV, typical of delocalized
metallic electrons and theoretical fit of the reflectance with the Drude
∞
2
p
2
2 2 −1
model (dotted line), ε(ω) = ε − ω τ (1 + ω τ ) . (e) Absorption
spectrum of an irradiated thin film of TATA 1 displaying optical
signatures of polaronic bands. (f) Determined band structure
calculated from absorbance measurements in (e) and showing a
half-filled polaronic band at −4.5 eV.
1
1385
dx.doi.org/10.1021/ja5044006 | J. Am. Chem. Soc. 2014, 136, 11382−11388

Journal of the American Chemical Society
Article
Curie spins within the fibers. Then, starting at 90 K and above,
a deviation from Curie behavior indicates a contribution from
Pauli spins, which should display temperature independent
behavior and which are commonly observed in materials
containing metallic electrons. In particular, a similar transition
between low temperature Curie behavior and higher temper-
ature Pauli or mixed Curie and Pauli behavior has been
39
observed in films of metallic polyaniline. Additionally, by
fitting the curve in the low temperature region using the
Curie−Weiss law, a value of −1.81 K was found for the Weiss
constant which indicates a weak antiferromagnetic interaction
between radicals within the fibers (Figure 4b). The weak half-
field signal (g ≈ 4), observed around 10 K and below,
demonstrates exchange-coupling of the doublet electrons giving
rise to singlet (S = 0) and triplet (S = 1) states. The half-field
signal dependence with temperature was fitted with Bleaney−
4
0
Bowers model to give a value of J = −0.48 K (Figure 4c),
which is also indicative of weak antiferromagnetic exchange-
coupling and of a singlet ground state within the fibers.
Following the method of Eaton, a distance of 3.73 Å was
calculated between coupled spins at cryogenic temperatures
indicating most of the spin density is on the aromatic carbons,
Figure 5. Combined influences of polarons’ formation and diffusion
on the conductivity of TATA self-assemblies. (a) Resistance versus
time for 17 mM TATA samples in tetrachloroethane, and for a
nonassembling tri(bromophenyl)amine as a control molecule. The
gray background corresponds to the light irradiation time (halogen
lamp; 10 W cm ). (b) I−V curves for samples subjected to
electrochemical oxidation. The control tri(bromophenyl)amine was
subjected to an I−V scan up to 2 V to ensure electrochemical
oxidation. (c) I−V curves before and after light-induced fibers
formation of TATA 1 in a mixed solvent system of 5:3
methanol:toluene +5 vol % tetrachloroethane. (d) Dark conductivity
−
2
41
in line with our DFT calculations. Finally, a further signature
of the metallic behavior comes from the reflectance measure-
ments displaying a minimum around 1.2 eV. These data are
well-fitted by the Drude model for a true metallic behavior
which gives the values of the plasma frequency (ω = 1.16 eV)
and of the relaxation time (τ = 1.16 × 10 s; Figure 4d).
In an irradiated thin film, and by using both EPR (Figure S17c)
and absorption spectroscopy (Figure 4e), we observed a high
stability of the radical which remains unchanged for at least six
months. It is striking to observe a classic polaronic absorption
p
increase time (T ) after 15 s irradiation of TATA 1 (halogen lamp; 10
d
−14
20,42
−2
W cm ); the gray background corresponds to the light irradiation
time. Inset displays the dependence of T on the applied voltage (see
d
Figure S19 for the corresponding plots).
43
signature as described for conducting conjugated polymers
irradiation but, instead, by applying a difference of electric
potential comprised between 0.6 and 0.8 V (that is crossing the
oxidation potential of TATA). The I−V curves demonstrate a
transition toward an ohmic behavior upon electrochemical
oxidation, illustrating the change in the conduction mode going
from a semiconducting to a conducting state (Figure 5b). The
nonself-assembling control triarylamine was also oxidized by
performing I−V sweeps up to 2 V, yet no change to the I−V
curve shape was observed. In addition, it was possible to form
the nanowires directly inside the device by first inserting a
solution of nonassembled TATA 1 (5:3 methanol:toluene with
5% tetrachloroethane) and by subsequent light irradiation. The
4 orders of magnitude increase of the conductivity and the
characteristic linear I−V curve remained after the light was
turned off (Figure 5c), demonstrating a self-construction
process in a gap as large as 4 μm between simple commercially
and, from the two main absorptions, a polaronic conduction
band with a half-filled energy level located at 1.1 eV above the
valence band (Figure 4f).
In order to probe the effect of light on the fibers’ conduction
properties directly in a device, we have then used transparent
ITO electrodes separated by a 4 μm gap. Conductivity
measurements were performed with a dc current on fibers
made of TATA 1, 2, and 3 (all at a concentration of 17 mM in
tetrachloroethane), and on a nonself-assembling tri-
(
bromophenyl)amine for control experiments (Figure 5a).
Compared to this control, previous to light irradiation and
under a 0.1 V bias (which is far below the oxidation potential of
the triarylamine derivatives), conductivities of 2 orders of
magnitude higher for 3, and 4 orders of magnitude higher for 1
and 2 are observed, demonstrating conduction through the
preformed fibers. Upon subsequent irradiation for 50 s, an
increase of 2 orders of magnitude in conductivity is observed
for TATA 1 and 2, while the gel of 3 exhibits nearly a four-
orders-of-magnitude increase, leading to a similar conductivity
for the three TATAs after irradiation. This observation can be
correlated to a larger fluorescence quenching in the case of
TATA 3 (Figure S18). The measured conductivity then
remains very stable in the dark, 6 orders of magnitude higher
than the control molecule. We here consider that the
contribution of ionic current is negligible because, in addition
to its stability in the dark under a dc field and to the negligible
response of the control molecule, the measured electronic
conductivity remains unchanged when adding 10% of
tetrabutylammonium chloride to the gel of 1. It was also
possible to affect the conductivity of the organogel without light
23
available ITO plates.
We finally probed the conductivity improvement afforded by
the light-induced healing process in the fibers. After irradiation
of the initial gel of TATA 1 with a short pulse of light (15 s
with the voltage held at 0.1 V), an increase of the conductivity
was measured afterward in the dark, with a gain comprised
between 30 and 50% (Figure 5d and Figure S19). This value
can be correlated with an increase of the coherence length and
a decrease of structural defects in the polymer, as determined
by SAXS and AFM (see above). We also measured a delay time
(T ) between switching the light off and reaching the maximum
d
conductivity value, and interestingly an inverse dependence of
Td on the applied voltage was noticed (inset in Figure 5d). We
postulate that this further increase reflects the supramolecular
optimization of the fibers thanks to the increased photoinduced
1
1386
dx.doi.org/10.1021/ja5044006 | J. Am. Chem. Soc. 2014, 136, 11382−11388

Journal of the American Chemical Society
Article
charge injection linked to the polarons’ diffusion in the electric
field.
(3) Shirakawa, H.; Louis, E. J.; MacDiarmid, A. G.; Chiang, C. K.;
Heeger, A. J. J. Chem. Soc. Chem. Commun. 1977, 578−580.
(
(
04.
4) Heeger, A. J. Rev. Mod. Phys. 2001, 73, 681−700.
5) Koezuka, H.; Tsumura, A.; Ando, T. Synth. Met. 1987, 18, 699−
CONCLUSIONS
■
7
In conclusion, we have described the synthesis and the unique
properties of a new class of soft supramolecular polymers made
of columnar stacks of tris-amide triarylamines. These one-
dimensional fibers can be oxidized to their radical cation by
light (photodoping) or electrochemically. The resulting
presence of delocalized Pauli spins and polaronic absorption
band shows that this supramolecular system has similar charge-
transport characteristics to those observed in metallic
conducting conjugated polymers. This first demonstration
that supramolecular polymers can present electronic, magnetic,
and optical signatures similar to those measured through-bond
in the best conjugated polymers extends the current under-
standing of both fields and unifies them. In addition, we have
shown that the induced through-space mixed-valence charge
transfer within their structure behave as “supramolecular
polarons” which diffuse along the fibers and fix structural
defects of the stacked structure, representing a novel
cooperative healing mechanism thanks to the presence of the
charge carrier itself. The capacity of soft supramolecular self-
(
6) Burroughes, J. H.; Bradley, D. D. C.; Brown, A. R.; Marks, R. N.;
Mackay, K.; Friend, R. H.; Burns, P. L.; Holmes, A. B. Nature 1990,
47, 539−541.
7) Sariciftci, N. S.; Smilowitz, L.; Heeger, A. J.; Wudl, F. Science
992, 258, 1474−1476.
3
(
1
(8) MacDiarmid, A. G. Angew. Chem., Int. Ed. 2001, 40, 2581−2590.
(9) Fabretto, M. V.; Evans, D. R.; Mueller, M.; Zuber, K.; Hojati-
Talemi, P.; Short, R. D.; Wallace, G. G.; Murphy, P. J. Chem. Mater.
2012, 24, 3998−4003.
(
(
10) Xia, Y.; Sun, K.; Ouyang, J. Adv. Mater. 2012, 24, 2436−2440.
11) Singh, M.; Haverinen, H. M.; Dhagat, P.; Jabbour, G. E. Adv.
Mater. 2010, 22, 673−685.
12) Sirringhaus, H.; Kawase, T.; Friend, R. H.; Shimoda, T.;
Inbasekaran, M.; Wu, W.; Woo, E. P. Science 2000, 290, 2123−2126.
13) Bubnova, O.; Khan, Z. U.; Wang, H.; Braun, S.; Evans, D. R.;
(
(
Fabretto, M.; Hojati-Talemi, P.; Dagnelund, D.; Arlin, J.-B.; Geerts, Y.
H.; Desbief, S.; Breiby, D. W.; Andreasen, J. W.; Lazzaroni, R.; Chen,
W. M.; Zozoulenko, I.; Fahlman, M.; Murphy, P. J.; Berggren, M.;
Crispin, X. Nat. Mater. 2014, 13, 190−194.
(
14) Bubnova, O.; Khan, Z. U.; Malti, A.; Braun, S.; Fahlman, M.;
Berggren, M.; Crispin, X. Nat. Mater. 2011, 10, 429−433.
15) Lin, W.-P.; Liu, S.-J.; Gong, T.; Zhao, Q.; Huang, W. Adv. Mater.
014, 26, 570−606.
(16) Bredas, J.-L.; Street, G. B. Acc. Chem. Res. 1985, 18, 309−315.
17) Kaiser, A. B. Adv. Mater. 2001, 13, 927−941.
(18) Hoffmann, S. T.; Jaiser, F.; Hayer, A.; Bassler, H.; Unger, T.;
Athanasopoulos, S.; Neher, D.; Kohler, A. J. Am. Chem. Soc. 2013, 135,
772−1782.
19) Kohlman, R. S.; Zibold, A.; Tanner, D. B.; Ihas, G. G.; Ishiguro,
T.; Min, Y. G.; MacDiarmid, A. G.; Epstein, A. J. Phys. Rev. Lett. 1997,
8, 3915−3918.
20) Lee, K.; Cho, S.; Heum Park, S.; Heeger, A. J.; Lee, C.-W.; Lee,
S.-H. Nature 2006, 441, 65−68.
21) Cohen, M. J.; Coleman, L. B.; Garito, A. F.; Heeger, A. J. Phys.
Rev. B 1974, 10, 1298−1307.
22) Moulin, E.; Niess, F.; Maaloum, M.; Buhler, E.; Nyrkova, I.;
Giuseppone, N. Angew. Chem., Int. Ed. 2010, 49, 6974−6978.
23) Faramarzi, V.; Niess, F.; Moulin, E.; Maaloum, M.; Dayen, J.-F.;
Beaufrand, J.-B.; Zanettini, S.; Doudin, B.; Giuseppone, N. Nat. Chem.
44−46
assemblies to self-optimize their conduction properties
provides alternatives to conventional organic metals in terms of
responsiveness, healing, and processability, which is of interest
for applications in organic electronics and spintronics.
(
2
(
ASSOCIATED CONTENT
Supporting Information
̈
■
̈
*
S
1
(
Synthetic protocols and characterization of TATA 1−3,
organogelation properties, supplementary AFM characteriza-
tions, X-ray scattering data, DFT calculations, local and
extended charge transfer analyses, and additional conductivity
characterizations. This material is available free of charge via the
Internet at http://pubs.acs.org.
7
(
(
AUTHOR INFORMATION
Corresponding Author
giuseppone@unistra.fr
(
■
(
Notes
2
(
(
012, 4, 485−490.
The authors declare no competing financial interests.
24) Aida, T.; Meijer, E. W.; Stupp, S. I. Science 2012, 335, 813−817.
25) Cordier, P.; Tournilhac, F.; Soulie-Ziakovic, C.; Leibler, L.
ACKNOWLEDGMENTS
■
Nature 2008, 451, 977−980.
(26) Yang, Y.; Urban, M. W. Chem. Soc. Rev. 2013, 42, 7446−7467.
The research leading to these results has received funding from
the European Research Council under the European
Community’s Seventh Framework Program (FP7/2007-
(
27) Non-hydrogen-bonded amides have N-H stretching frequency
−1
−1
between 3400 and 3500 cm as opposed to 3350−3100 cm for
hydrogen bonded amides. Likewise the CO stretch shifts from
2
013)/ERC Starting Grant Agreement No. 257099 (N.G.).
−1
around 1685 to 1650 cm upon hydrogen bonding. The IR frequency
shifts we report for both functional groups correspond to the presence
We wish to thank the Centre National de la Recherche
Scientifique (CNRS), the COST action (CM 1304), the
international center for Frontier Research in Chemistry
̈
of hydrogen bonded amides. See: Pretsch, E. Buhlmann, P.;
Badertscher, M. Structure Determination of Organic Compounds, 4th
ed.; Springer: New York, 2009.
(
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 grateful
to ANR (Agence Nationale de la Recherche) for financial
support (projects STANWs and Multiself). We thank Prof. T.
W. Ebbesen for fruitful discussions on this work. We thank Dr.
Marc Schmutz for FFEM replicas preparation.
(28) Zhao, Y.; Truhlar, D. G. Acc. Chem. Res. 2008, 41, 157−167.
(29) Zhao, Y.; Truhlar, D. Theor. Chem. Acc. 2008, 120, 215−241.
(30) Steinmann, S. N.; Piemontesi, C.; Delachat, A.; Corminboeuf, C.
J. Chem. Theory Comput. 2012, 8, 1629−1640.
31) Heckmann, A.; Lambert, C. Angew. Chem., Int. Ed. 2012, 51,
26−392.
32) Robin, M. B.; Day, P. Mixed valence chemistry - A survey and
classification. In Advances in Inorganic Chemistry and Radiochemistry;
Emeleus, H. J., Sharpe, A. G., Eds.; Academic Press Inc.: New York,
1968; Vol. 10, pp 274−422.
(
3
(
REFERENCES
1) Forrest, S. R. Nature 2004, 428, 911−918.
2) Miller, R. D.; Chandross, E. A. Chem. Rev. 2010, 110, 1−2.
■
(
(
́
1
1387
dx.doi.org/10.1021/ja5044006 | J. Am. Chem. Soc. 2014, 136, 11382−11388

Journal of the American Chemical Society
Article
(
33) Lancaster, K.; Odom, S. A.; Jones, S.; Thayumanavan, S.;
Marder, S. R.; Bredas, J.-L.; Coropceanu, V.; Barlow, S. J. Am. Chem.
Soc. 2009, 131, 1717−1723.
(
34) Rivnay, J.; Mannsfeld, S. C. B.; Miller, C. E.; Salleo, A.; Toney,
M. F. Chem. Rev. 2012, 112, 5488−5519.
(
(
(
35) Marcus, R. A. Angew. Chem., Int. Ed. 1993, 32, 1111−1121.
36) Hush, N. S. Electrochim. Acta 1968, 13, 1005−1023.
37) Scheblykin, I. G.; Yartsev, A.; Pullerits, T.; Gulbinas, V.;
Sundstro
38) Lin, H.; Tabaei, S. R.; Thomsson, D.; Mirzov, O.; Larsson, P.-
O.; Scheblykin, I. G. J. Am. Chem. Soc. 2008, 130, 7042−7051.
39) Krinichnyi, V. I.; Konkin, A. L.; Monkman, A. P. Synth. Met.
012, 162, 1147−1155.
40) Bleaney, B.; Bowers, K. D. Proc. R. Soc. London, A 1952, 214,
51−465.
41) Eaton, S. S.; More, K. M.; Sawant, B. M.; Eaton, G. R. J. Am.
̈
m, V. J. Phys. Chem. B 2007, 111, 6303−6321.
(
(
2
(
4
(
Chem. Soc. 1983, 105, 6560−6567.
(
(
42) Lee, K.; Heeger, A. J. Synth. Met. 1997, 84, 715−718.
43) Beljonne, D.; Cornil, J.; Sirringhaus, H.; Brown, P. J.; Shkunov,
M.; Friend, R. H.; Bred
́
as, J.-L. Adv. Funct. Mater. 2001, 11, 229−234.
(
44) Busseron, E.; Ruff, Y.; Moulin, E.; Giuseppone, N. Nanoscale
2
(
(
013, 5, 7098−7140.
45) Giuseppone, N. Acc. Chem. Res. 2012, 45, 2178−2188.
46) Moulin, E.; Cid, J.-J.; Giuseppone, N. Adv. Mat. 2013, 25, 477−
487.
1
1388
dx.doi.org/10.1021/ja5044006 | J. Am. Chem. Soc. 2014, 136, 11382−11388