Electroactive nanorods and nanorings designed by supramolecular association of π-conjugated oligomers

Article abstract of DOI:10.1002/chem.200701638

In investigations into the design and isolation of semiconducting nano-objects, the synthesis of a new bisureido π-conjugated organogelator has been achieved. This oligo(phenylenethienylene) derivative was found to be capable of forming one-dimensional supramolecular assemblies, leading to the gelation of several solvents. Its self-assembling properties have been studied with different techniques (AFM, EFM, etc.). Nano-objects have successfully been fabricated from the pristine organogel under appropriate dilution conditions. In particular, nanorods and nanorings composed of the electroactive organogelator have been isolated and characterized. With additional support from an electrochemical study of the organogelator in solution, it has been demonstrated by the EFM technique that such nano-objects were capable of exhibiting charge transport properties, a requirement in the fabrication of nanoscale optoelectronic devices. It was observed that positive charges can be injected and delocalized all along an individual nano-object (nanorod and nanoring) over micrometers and, remarkably, that no charge was stored in the center of the nano-ring. It was also observed that topographic constructions in the nanostructures prevent transport and derealization. The same experiments were performed with a negative bias (i.e., electron injection), but no charge derealization was observed. These results could be correlated with the nature of 1, which is a good electrondonor, so it can easily be oxidized, but can be reduced only with difficulty.

Full text of DOI:10.1002/chem.200701638

FULL PAPER
DOI: 10.1002/chem.200701638
Electroactive Nanorods and Nanorings Designed bySupramolecular
Association of p-Conjugated Oligomers
Olivier J. Dautel,*[a] Mike Robitzer,[a] Jean-Charles Flores,[a] Denis Tondelier,[b]
FranÅoise Serein-Spirau,[a] Jean-Pierre L›re-Porte,*[a] David GuØrin,[b]
StØphane Lenfant,[b] Monique Tillard,[c] Dominique Vuillaume,*[b] and
Jol J. E. Moreau[a]
Abstract: In investigations into the
design and isolation of semiconducting
nano-objects,the synthesis of a new
tive organogelator have been isolated
and characterized. With additional sup-
port from an electrochemical study of
the organogelator in solution,it has
been demonstrated by the EFM tech-
nique that such nano-objects were ca-
pable of exhibiting charge transport
properties,a requirement in the fabri-
cation of nanoscale optoelectronic de-
vices. It was observed that positive
charges can be injected and delocalized
all along an individual nano-object
(nanorod and nanoring) over microme-
ters and,remarkably,that no charge
was stored in the center of the nano-
bis
has been achieved. This oligo(phenyl-
enethienylene) derivative was found to
A
C
A
be capable of forming one-dimensional
supramolecular assemblies,leading to
the gelation of several solvents. Its self-
assembling properties have been stud-
ied with different techniques (AFM,
EFM,etc.). Nano-objects have success-
fully been fabricated from the pristine
organogel under appropriate dilution
conditions. In particular,nanorods and
nanorings composed of the electroac-
graphic constructions in the nanostruc-
tures prevent transport and delocaliza-
tion. The same experiments were per-
formed with a negative bias (i.e.,elec-
tron injection),but no charge
delocalization was observed. These re-
sults could be correlated with the
nature of 1,which is a good electron-
donor,so it can easily be oxidized,but
can be reduced only with difficulty.
Keywords: nanorings · nanorods ·
pi-conjugated oligomers
·
self-
assembly
chemistry
·
supramolecular
Introduction
[a] Dr. O. J. Dautel,Dr. M. Robitzer,Dr. J.-C. Flores,
Prof. F. Serein-Spirau,Prof. J.-P. L›re-Porte,Prof. J. J. E. Moreau
Architectures MolØculaires et MatØriaux NanostructurØs
Institut Charles Gerhardt Montpellier,UMR CNRS 5253
Ecole Nationale SupØrieure de Chimie de Montpellier
8 rue de l’Ecole Normale
34296 Montpellier Cedex 05 (France)
Fax : (+33)467-147-212
E-mail: olivier.dautel@enscm.fr
One of the most promising “bottom-up” approaches in
nanoelectronics is to assemble p-conjugated molecules to
build nano-sized electronic and opto-electronic devices in
the 5–100 nm length scale. This field of research,called
“supramolecular electronics” by Meijerꢀs group,bridges the
gap between molecular electronics and bulk “plastic” elec-
tronics.[1] In this context,the design and preparation of
nanowires are of considerable interest for the development
of nano-electronic devices such as nanosized transistors,[2]
sensors,[3] logic gates,[4] light-emitting diodes,[5] and photovol-
taic devices.[6]
jean-pierre.lere-porte@enscm.fr
[b] Dr. D. Tondelier,Dr. D. GuØrin,Dr. S. Lenfant,Dr. D. Vuillaume
Molecular Nanostructures and Devices group
Institut d’Electronique,de Micro-Ølectronique et de Nanotechnologie
CNRS UMR 8520,BP0069,Avenue Poincare
59652 Villeneuve d’Ascq,cedex (France)
Of all the noncovalent interactions,hydrogen bonds have
been most extensively used to construct supramolecular ar-
chitectures,as they are highly selective and directional not
only in solution but also on surfaces. Numerous nanostruc-
tures such as nanorods,nanotubes,or nanorings have been
obtained by this approach. In particular,the use of organo-
gelators as directors to control the morphologies of the ag-
gregates has been explored recently. Cholesterol- and phos-
pholipid-tethered trans-stilbenes are able to gelate different
Fax : (+33)320-197-884
E-mail: dominique.vuillaume@iemn.univ-lille1.fr
[c] Dr. M. Tillard
AgrØgats,Interfaces,MatØriaux pour l ’Énergie
Institut Charles Gerhardt,UMR 5253 CNRS UM2,CC015
UniversitØ de Montpellier 2,Sciences et Techniques du Languedoc
2 Place Eug›ne Bataillon
34095 Montpellier Cedex 5 (France)
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author.
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4201

organic solvents in which the steroid and lipid units serve as
templates to form one-dimensional stacks.[7] However,orga-
nogelators based on p-conjugated systems,unlike systems
based on dyes,are relatively rare. Ajayaghosh et al. extend-
ed this concept to oligophenylenevinylene (OPV) deriva-
tives and reported a completely thermoreversible self-as-
sembly process in a series of hydrocarbon solvents from
single OPV molecules to fibers and ultimately to an entan-
gled network structure.[8] The absorption and emission prop-
phenylene fragments destabilizes the HOMO levels of the
oligomer. This type of compound therefore exhibits a low
oxidation potential and a relatively low HOMO–LUMO
gap. This fully p-conjugated core was disubstituted with two
urea moieties in order to take advantage of their self-assem-
bly properties,resulting from the strong directional abilities
of hydrogen bonds. With regard to previous work,[14] a pro-
pylene arm spacer was adopted to favor the self-association
of neutral or oxidized p segments.
erties
showed
dramatic
changes during gelation,which
is an indication of strong inter-
molecular
p electronic cou-
pling of the ordered OPV seg-
ments. In a similar way,van
Esch et al. have shown by the
pulse-radiolysis time-resolved
microwave conductivity (PR-
TRMC) technique on solid-
state powder samples that high
charge carrier mobilities can
be achieved in gel networks
based on thiophene and bithiophene derivatives modified
with bisurea units. The thiophene moieties formed closely
packed arrays enforced by the urea hydrogen-bonding units,
thereby creating an efficient pathway for charge trans-
port.[9,10] The two-dimensional self-assembly of the bisurea
1,2-thiophene has been studied on solid substrates. Elongat-
ed twisted fibers with lengths of 20–100 mm and widths of 2–
10 mm were observed on SiO2. These fibers are strongly bire-
fringent,indicating a high degree of molecular ordering.
After annelation,extended mono-layers consisting of up-
right 1D arrays standing side-by-side are formed. On highly
orientated pyrolytic graphite,1D arrays lying flat on the sur-
face were obtained. Scanning tunneling spectroscopy indi-
cated that effective conjugation in the p stacks exists,as the
band gap of the thiophene was decreased.[11] As pointed out
by Shenning and Meijer,it would be of great interest if we
were able to study such types of fibers made up of mole-
cules containing longer conjugated p fragments.[12]
Furthermore,progress needs to be achieved in order to
demonstrate that individual nano-objects might be capable
of exhibiting electronic properties such as charge transport,
a requirement in the fabrication of nanoscale optoelectronic
devices.
In this context,here we report the synthesis of 1,a se-
quence of five 1,4-dialkoxyphenylene and thiophene units
functionalized with two urea moieties. The p-conjugated
core is defined by the regular alternation of thienylene and
1,4-dialkoxyphenylene. We have demonstrated by PES/UV
spectroscopy correlated with DFT calculations that thio-
phene and dialkoxyphenylene fragments are suitable for the
construction of fully p-conjugated oligomers. Because of
noncovalent S···O interactions the fragments are coplanar,
while in addition,the energy levels of the p-molecular orbi-
tals are close.[13] As a result,a strong interaction between
the molecular orbitals of the thiophene and the dialkoxy-
In order to increase the solubility of the compound and to
improve the supramolecular organization through van der
Waals interactions,two alkoxy chains were also grafted onto
each benzene ring. This oligo(phenylenethienylene) deriva-
tive was found to be capable of forming one-dimensional
supramolecular assemblies,leading to gelation of several
solvents. Its self-assembling properties have been studied by
different techniques.
To confirm the influence of the urea moieties on the
supramolecular organization of 1 in the solid state,the oth-
erwise identical unsubstituted conjugated segment 2 was
prepared,and the structural and optical properties of the
two compounds were established and compared. Nano-ob-
jects were successfully fabricated from the pristine organo-
gel of 1 under appropriate dilution conditions. In particular,
nanorods and nanorings composed of the electroactive orga-
nogelator were isolated and characterized. With additional
support from an electrochemical study of the solution,it
was possible to demonstrate by the EFM technique that
such nano-objects were capable of exhibiting charge trans-
port properties. Unlike PR-TMC experiments,this tech-
nique can provide direct evidence of charge delocalization
on an individual nano-object. Because of the ultrahigh fre-
quencies (GHz) and low field strengths (about 10 Vcmꢀ1)
used,the mobility values obtained by PR-TMC experiments
mainly reflect the mobilities of charge carriers within the
best organized domains (i.e.,highest mobility) within a ma-
terial.[15] The use of nanosecond time resolution ensures in
addition that in most cases the charge carriers are probed
prior to their diffusional drift to intrinsic chemical or physi-
cal trapping sites. On the other hand,EFM images of an in-
dividual object will reflect how far charge carriers move
within the object and the influence of defects (grain and
domain boundaries) on their mobility.
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Electroactive Nanorods and Nanorings
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Results and Discussion
(1058C) should allow examination of the energy required to
break the hydrogen bond system of the urea function.
The organogel was prepared as follows: compound 1
(5 mgmLꢀ1,0.3 wt%) was dissolved in hot tetrachloroethyl-
Synthesis of the organogelator: Compound 1 was synthe-
sized in ten steps from 1,4-dioctyloxybenzene (3) and 2,5-di-
octyloxy-1,4-phenylenediboronic
acid
as
shown
in
N
Scheme 1.[16] In a Friedel–Crafts acylation reaction,com-
pound 3 was converted into the corresponding ketone 4 in
85% yield. In two steps, 4 was then transformed into phenol
5 in 80% yield by a Baeyer–Villiger reaction followed by a
saponification.[17,18] O-Alkylation of 5 with N-(3-bromopro-
pyl)phthalimide (72%) and iodination with N-iodosuccini-
mide (NIS) in the presence of 0.3 equiv of trifluoroacetic
acid as a catalyst[19] gave 7 in 95% yield. Suzuki cross-cou-
pling of 7 with thiophene-2-boronic acid afforded 8 in 71%
yield. Iodination with NIS gave an 89% yield of 9,which on
Suzuki cross-coupling with 2,5-dioctyloxy-1,4-phenylenedi-
boronic acid afforded 10 in 53% yield. The last two steps
consisted of cleaving the two phthalimides by hydrazinolysis
to recover the diamine (96%),which reacted with 2.2 mol
equivalents of dodecyl isocyanate to afford the bisurea 1 in
95% yield. This multi-step synthesis of compound 1 consti-
tutes a versatile and general procedure by which to func-
tionalize p-conjugated oligomers with urea moieties.
Studyof the organogel : Compound 1 is soluble in common
solvents (THF,toluene,dichloromethane,etc.). When solu-
tions of 1 (10 mg) in toluene or dichloromethane (1 mL)
were heated,however,organogels were formed upon cool-
ing the solution to ꢀ208C. After their formation,the differ-
ent organogels were stable at room temperature. In the
same way, 1 gelatinized toluene,THF,and even the nonpo-
lar and hydrophobic tetrachloroethylene at concentrations
as low as 0.2 wt%. Tetrachloroethylene was the solvent
chosen for the organogel studies for two major reasons: i) it
does not absorb infra-red radiation,which is essential in
order to permit study of the contribution of the hydrogen
bond interaction by FTIR,and ii) its high boiling point
Scheme 1. Synthesis of 1. a) 2 equiv acetyl chloride,1.2 equiv AlCl ,CH Cl2,40 8C,16 h,85%; b) peracetic acid,AcOEt,40 8C,16 h; c) 4 equiv KOH,2 equiv EtOH,
3
2
H2O,80 8C,1 h 30,then 4 equiv HCl (1.5 n), ꢀ308C,80%; d) K CO3, N-(3-bromopropyl)phthalimide,acetonitrile,21 8C,72%; e) NIS,0.3 equiv CF 3COOH,CH Cl2,
2
2
218C,95%; f) thiophene-2-boronic acid,[Pd 2dba3],PPh 3,Na 2CO3,THF/H 2O,70 8C,71%; g) NIS,CH 2Cl2,21 8C,89%; h) Pd 2dba3,PPh 3,Na 2CO3,THF/H 2O,70 8C,
53%; i) NH2NH2·H2O,THF,66 8C,96%; j) 2.2 equiv dodecylisocyanate,CH 2Cl2,40 8C,95%. Overall yield 15%.
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O. J. Dautel,J.-P. L›re-Porte,D. Vuillaume et al.
3357 and sym nNH =3325 cmꢀ1),the C =O stretch called the
“amide I band” (nCO ꢂ1627 cmꢀ1),and a combination of the
ꢀ
ꢀ
N H deformation and of the C N stretch called the “ami-
de II band” (dNH+nCN ꢂ1576 cmꢀ1). The intensities and the
wavenumbers of those three bands are directly related to
the hydrogen bond strength of the system. In the case of a
ꢀ
transition from an associated urea to a free urea,the N
H
stretch and amide I bands are shifted to higher wavenum-
bers and the amide II band to lower wavenumbers. In this
context,a tetrachloroethylene gel of 1 (5 mgmLꢀ1,0.3 wt%)
was introduced into a sealed KBr cell and the FTIR spectra
were recorded at different temperatures (Figure 1).
At room temperature,the amide I and the amide II
bands,found at 1627 and 1576 cm ꢀ1,respectively,are repre-
sentative of an associated urea function. With increasing
temperature,the intensities of the two bands are lowered
and two new bands appear at 1694 and 1515 cmꢀ1. The oc-
currence of an isobestic point at 1657 cmꢀ1 demonstrated
the presence of one-mode association alternation of urea
functions and of equilibrium between the free and the asso-
ciated species. At ꢂ60–658C,in the temperature range cor-
responding to the Tgel max previously determined by both
methods,no more association between urea moieties is ob-
served.
~
&
Figure 2. Percentages of free (%FAI, ) and associated (%AAI, ) urea
in an organogel of 1 (5 mgmLꢀ1,0.3 wt%) in tetrachloroethylene as a
function of temperature.
The percentage of free urea increases gradually with the
temperature. For temperatures close to the Tgel (ꢂ508C for
a 0.3 wt% gel of 1 in C2Cl4),the percentage of free urea is
about 35% and the slope of the curve is nearly constant up
to 658C. At 658C,almost all H-bonds are broken. Consis-
tently with the van’t Hoff equation,a linear evolution of
lnK as a function of 1/T is found between 308C and 508C.
A DH8 value of 87 kJmolꢀ1 can be deduced from the slope
(ꢀDH8/R). This value,corresponding to the dissociation of
We deduced the percentages of free and associated urea
by integration of the free amide I band (1694 cmꢀ1) and the
associated amide I band (1627 cmꢀ1),assuming that the inte-
grated molar extinction coefficients are constant with the
temperature. We investigated the evolution of the ratio be-
tween free amide I (%FAI) and associated amide I
(%AAI) as a function of the temperature. For each temper-
ature,areas of these two bands can be deduced by deconvo-
lution of FTIR spectra. An example of a deconvoluted
FTIR spectrum and area determination of %FAI and
ꢀ
four N H···O=C hydrogen bonds,is in good agreement with
the 46 kJmolꢀ1 reported by Jadzyn et al. for the formation
of two N H···O=C hydrogen bonds in diethylurea.[24] Finally,
ꢀ
%AAI of an organogel of
1
(5 mgmLꢀ1) in
above Tꢂ658C almost all H-bonds are broken and the mol-
tetrachloroethylene at T=508C is given in the Supporting
ACHTREUNG
ecules exist in an isolated state.
Information. From these data,the concentrations of the two
species can be calculated and plotted (Figure 2).
From the FTIR study of 1 as an organogel,it is clear that
the urea functions play the role of structure directing agents
Figure 1. FTIR spectra of an organogel of 1 (5 mgmLꢀ1,0.3 wt%) in tetrachloroethylene as a function of the temperature.
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Electroactive Nanorods and Nanorings
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through hydrogen bonds. The design of the molecule being
functionalized by two urea functions should drive the supra-
molecular organization toward 1D assembly with an opti-
mized overlapping of the p-conjugated segment. In the solid
state,the influence of the urea moieties on the supramolec-
ular organization of 1 was revealed by comparison of the
optical properties of 1 and 2 (see Supporting Information).
Interestingly,the UV/Visible absorbance of 1 was blue-shift-
ed from 413 nm in solution to 406 nm in the solid state,ac-
companied by a broadening and decrease in intensity of the
p–p* absorption bands. These spectral changes can be at-
tributed to a strong exciton coupling between the phenyl-
ready determined by the test tube “tilting” method or by
FTIR measurements. Upon aggregation,the strong p–p in-
teraction leads to quenching of emission of individual mole-
cules. In a remarkable way,these spectroscopic phases and
their temperatures could be correlated to the hydrogen
bond strength and relative orientational transitions of the
urea functions determined by FTIR. This spectroscopic be-
havior observed for 1 upon gelation (blue-shifted absorp-
tion,red-shifted and quenched emission) can be attributed
to H-aggregation,[27,28,29] which is reasonable to expect from
an anticipated “card pack” orientation of the phenylene-
A
N
A
directed by the urea.
A
More information about the two different supramolecular
organizations exhibited by 1 and 2 was provided by the de-
termination of the crystal structure of 2 (Figure 4a and b).
Recrystallization of 2 from acetone furnished orange paral-
lelepipedic single crystals suitable for X-ray diffraction in-
tensity recording on an Xcalibur CCD (Oxford Diffraction)
diffractometer. Compound 2 crystallizes in a triclinic system
stacked H-aggregates.[25] On the other hand,the red shift
from 405 to 434 nm observed for 2 suggests a different
supramolecular organization with the formation of J-aggre-
gates.[26]
The H-aggregation of the bisurea deduced from the blue-
shifted absorption of its freeze-dried gel was confirmed by
study of the emission behavior of the organogelator in tetra-
chloroethylene as a function of the temperature. An organo-
gel of 1 in tetrachloroethylene (5 mgmLꢀ1) was heated at
1158C (above the Tgel) and irradiated at 400 nm. Emission
spectra were recorded during the cooling of the sample
(Figure 3).
From Figure 3,two types of spectroscopic behavior can be
identified. At 1158C, 1 exhibits the same emission properties
as in dilute solution,with a fluorescence maximum found at
462 nm. The chromophores are perfectly isolated from each
other. From 115 to 578C,almost no evolution in the shape
and the intensity of the spectra is observed. Below 578C,a
red shift of the emission maximum and a decreased intensity
can be seen (see Supporting Information for intermediate
temperatures). This transition corresponds to the Tgel as al-
¯
with a P1 space group. The molecule is located at the inver-
sion centre,and the asymmetric unit is then defined with a
half-molecule. As attested to by the crystal structure,the
three benzene rings and the two thiophene rings are mostly
coplanar,due to the S···O interactions,which favor a small
dihedral angle between benzene and thiophene rings and
consequently a good p orbital overlap.[13] In the solid state, 2
forms stacks separated by the octyl chains lying perpendicu-
larly to the chromophore long axis (Figure 4a). The interlac-
ing of lateral chains stabilized by van der Waals interactions
produces a longitudinal and a lateral slip of the molecules in
a given stack toward a J-aggregation with a pitch angle of
P2 =568 and a roll angle of R2 =488 (Figure 4b).[30] The pitch
and roll angles are used to assess the molecular slipping
along the long and the short axes of a molecule. Although
the p-stack undergoes a pitch
angle distortion of 568,the mo-
lecular p-systems of molecules
could still overlap. However
with a roll angle distortion of
488,the adjacent molecules
slide completely out from
under one another and there is
little remaining p-overlap be-
tween them.
From the conformation of
the p-conjugated core and the
lateral aliphatic chains posi-
tions obtained from the crystal
structure of 2,and taking into
account that bisureas are well
known to self-assemble in one-
dimensional fashion,it was
possible to propose a molecu-
lar model (Figure 4c and d).
Figure 3. Emission spectra of an organogel of 1 (5 mgmLꢀ1) in tetrachloroethylene irradiated at 400 nm as a
In that case,both urea
function of temperature.
groups form hydrogen bonds
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O. J. Dautel,J.-P. L›re-Porte,D. Vuillaume et al.
Figure 4. Crystal structure of 2. a) View of the packing in 2,as seen down the a axis. This illustration shows six molecules,stacked two deep. b) J stacks
running along the a axis (octyl chains have been omitted for clarity) and molecular model proposed for the supramolecular assemblies formed by 1.
c) Infinite chains of hydrogen-bonded urea moieties. d) Face-to face-arrangement of the phenylenethienylene moieties along the same direction as the in-
finite hydrogen-bonded chains (octyl chains have been omitted for clarity).
with urea groups of neighboring molecules,and thereby par-
ticipate in the formation of infinite chains of hydrogen-
bonded urea moieties (Figure 4c). The average repeat dis-
tance along the direction of the hydrogen-bonded chains is
4.5 Š,in accordance with the average value of 4.6 Š found
for crystal structures of urea compounds.[31] The phenylene-
thienylene moieties adopt a face-to-face arrangement along
the same direction as the infinite hydrogen-bonded chains
(Figure 4d). A modest pitch angle (P1 =98) and a very small
roll displacement (R1 =48) are consistent with an H-aggrega-
tion in which adjacent molecules of 1 retain appreciable p-
overlap.
cerning the supramolecular assemblies structuring the orga-
nogel was provided by scanning electron microscopy (SEM)
and transmission electron microscopy (TEM) images of a
freeze-dried gel of 1 (10 gLꢀ1 in dichloromethane). As ex-
pected,the entire sample is comprised of fiber-like struc-
tures with one-dimensional architectures (see Supporting In-
formation).
With the intention of isolating fibers,a gel of 1 (10 gLꢀ1)
was diluted to 0.5 gLꢀ1 in dichloromethane prior to being
dropcast on a silicon wafer covered by a dry silicone dioxide
film (thickness 250 nm). Atomic force microscopy (AFM)
showed an interdigitated network of nanorods formed by as-
sociation of 1 as a result of hydrogen bonding of urea
groups (Figure 5a). When diluted ten times more,however,
two different types of nano-objects were obtained,depend-
Shapes of the aggregates: The formation of a gel suggests
self-assembly of 1 into nanostructures. Further insight con-
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Electroactive Nanorods and Nanorings
FULL PAPER
ing on their location on the substrate. Dispersion of nano-
rods was found at the periphery of the drop (Figure 5b)
whereas nanorings could be observed in the center of the
drop (Figure 5c). Sizing of the different nano-objects leads
us to postulate two different processes for the formation of
the nanorods and the nanorings. Indeed,on the one hand,
nanorods obtained after dilution of the gel (Figure 5b) ex-
hibited the same dimensions as those present in the pristine
organogel (typical height 4 nm,typical width 70 nm,and
typical length 2 mm),suggesting that they had originated
from the dispersion of the preexisting nanorods (Figure 5a).
On the other hand,the nanorings (Figure 5c) had the same
width (70 nm) but much greater height (12 nm). This obser-
vation indicates that they are the product of a dewetting
process. During the drying of the drop,the concentration of
unassociated molecules increases considerably in its center,
to form new supramolecular assemblies around nanodrops
of solvent or water. Their diameters lie between 200 and
300 nm.
The nano-objects were deposited on a highly-doped n-type
silicon wafer (resistivity of ꢂ10ꢀ3 Wcm),covered by ꢂ4 nm
thick thermal oxide grown in dry O2 at 7308C. The SiO2 sur-
face roughness (rms) is ꢂ0.15 nm (AFM measurements).
The SiO2 surfaces were cleaned by a piranha attack and
rinsed in deionized water before the nanoring deposition.
Local charge injections and EFM experiments were per-
formed with the aid of a Dimension 3100 microscope (Digi-
tal Instruments) under air. We used PtIr-coated cantilevers
with a free oscillating frequency f0 ꢂ60 kHz and a spring
constant k ꢂ1–3 Nmꢀ1. To inject charges into the nano-
object locally,the EFM tip was biased at Vinj with respect to
the silicon wafer,its oscillation frequency was set to zero,
and the tip was gently contacted to the nano-object with a
typical 2 nN contact force for two minutes (Figure 6). Image
analyses were performed with the DI software or WSxM.[34]
EFM measurements were first carried out on a nanorod
measuring 2 mm long,with an average thickness of 2.5 nm
and a width of ꢂ50–100 nm determined by AFM in tapping
mode (Figures 5b and 7a). A first EFM image (Figure 7b)
was performed before local application of a bias voltage
Electrical force microscopyexperiments : The electronic be-
havior of the nano-objects was studied by electrical force
microscopy (EFM). We have recently described the use of
the EFM technique to study organic nanostructures[32] or
DNA samples[33] in previous papers. It is a powerful tool
with which to investigate the electrical transport properties
of nano-objects. Charge carriers were locally injected by the
apex of an atomic force microscope tip,and the resulting
distribution and concentration of injected charges were mea-
sured by electrical force microscopy (EFM) experiments.
Vinj =+2 V (i.e.,hole injection) over 2 minutes by the apex
of the tip. Then,after the hole injection,another EFM
image (Figure 7c) was taken under the same scan conditions.
It was observed that positive charges (inducing a negative
shift of the cantilever frequency biased at VEFM =ꢀ2 V ap-
pearing dark in the EFM image; see below) were delocal-
ized all along the nanorod over micrometers,attesting that
molecules inside the nano-objects are reasonably well organ-
ized (a more detailed discussion is given below).
Figure 5. AFM topographic images (taping mode,SiO substrate) and cross-sections (along the black lines) of drop-cast films of the gels of 1 diluted in
2
dichloromethane at: a) 0.5 gLꢀ1,b) 0.05 gL periphery of the drop,and c) 0.05 gL ꢀ1 center of the drop.
ꢀ1
Chem. Eur. J. 2008, 14,4201 – 4213
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4207

O. J. Dautel,J.-P. L›re-Porte,D. Vuillaume et al.
spectively, e the electron charge, z the tip–substrate distance,
VEFM the EFM bias,and VS the surface potential,which is
negligible in our case.[35]
g
a
ðs=eRÞ e z
ð1Þ
R ¼ ꢀ
Figure 6. Schematic representation of charge injection and detection by
EFM. The silicon substrate is covered by an oxide (thickness tox—in light
grey). The nano-object (in black) has a height h. In the EFM mode,the
tip is set at a distance z from the substrate. Vinj is the tip bias for injecting
charges (electrons at Vinj < 0,and holes at Vinj > 0). VEFM is the tip bias
for the EFM measurements.
e0ðVEFMꢀVSÞ
The factors g and a are two geometric factors associated
with the tip and the substrate (aꢂ1.5 and gꢂ3.5).[32,35,36]
The average frequency shifts DfC and DfQ are estimated
from the profile sections of the EFM images before and
after injection,respectively
(Figure 9).
According
to
Eq. (1),with eR ꢂ3 (a common
value for most organic materi-
als),the maximum charge den-
sity is 1.4”105 holesmmꢀ2. We
observe that this maximum
arises at the injection point
and that charge density slowly
decreases along the nanorods.
We also note (Figure 7c)
that the EFM signal extends
Figure 7. a) Topographic image of a nanorod. b) EFM image before charge injection,c) EFM image after hole
injection (at the point marked by the arrow in Figure 7a) in the same nanorod at Vinj =+2 V for 2 minutes.
d) After electron injection at Vinj =ꢀ3 V for 3 min. EFM image conditions: VEFM =ꢀ2 V,lift z=50 nm.
The distribution of charges injected into the nanorods was
characterized by EFM,in which electric force gradients
acting on the tip biased at VEFM (here ꢀ2 V) shift the EFM
cantilever oscillation frequency. For this measurement,the
tip–substrate distance was typically z=50 nm (otherwise
specified). EFM images are sensitive to two distinct interac-
tions. Firstly,the capacitive interaction associated with the
local increase in the tip–substrate capacitance when the
EFM tip is moved over the nanorings leads to weak nega-
tive frequency shifts,which appear as weak dark features in
Figure 7b. The second interaction is the interaction between
the charge Q stored in the nanoring and the capacitive
charge at the tip apex. This additional frequency shift is
either positive or negative,and varies as Q”VEFM. When >0
(repulsive interaction),this corresponds to a positive fre-
quency shift,leading to bright features in the EFM images.
In contrast, <0 (attractive interaction) corresponds to a neg-
ative frequency shift and thus dark features in the EFM
images (as shown in Figure 7c).
A control experiment was performed,in which charges
were injected and measured,under the same conditions,di-
rectly in the oxide without any nanorod. In that case,the
charges stayed localized in the oxide (Figure 8a),and the
EFM image showed an isotropic 2D distribution with an
average diameter of about 150–200 nm.
To quantify the amount of charge injected into the nano-
rod,we followed the same protocol as in our recent paper
on EFM on pentacene nanostructures,[32] in which the ratio
R of the frequency shift DfQ due to the charge in the nanor-
ing over the one DfC coming from the capacitance effect is
related to the surface charge density s by Equation (1),with
e0 and eR being the vacuum and nanorod permittivity,re-
Figure 8. a) EFM image of charges (electrons at Vinj =ꢀ2 V (right hand-
side) and holes at Vinj =+2 V (left hand-side)) directly injected into the
naked 4 nm thick SiO2 layer (as grown oxide). b) EFM image of hole in-
jection under the same conditions as in Figure 7c (Vinj =+3 V for 2 mi-
nutes) in the oxide,away from the nanorod,after the nanorod deposition
process. All EFM image conditions: VEFM =ꢀ2 V,lift z=50 nm.
widely over the nanorod in the perpendicular direction
(ꢂ500 nm on each side). This cannot be explained by convo-
lution with the tip size and shape (radius of 15–20 nm),nor
by the intrinsic spatial resolution of the EFM (ꢂ50 nm
under our experimental conditions).[37] In the present case,
this also cannot be explained by charge injection into the
oxide through the nanorod,because the blank experiment
(Figure 8a) shows that charge injected (under the same con-
ditions) into the oxide spreads over a smaller distance.
While it is likely that charges have also been injected into
the oxide (as in our previous experiments on pentacene
monolayer islands),[32] we surmise that charges can also
spread away from the nanorod as a result of the presence of
residual organic materials left on the substrate by the dip-
ping process. To test this hypothesis,we injected holes under
the same conditions into the oxide substrate,away from a
nanorod (Figure 8b). We clearly observed an isotropic diffu-
4208
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Electroactive Nanorods and Nanorings
FULL PAPER
Figure 9. Topographic (a) and EFM (b–c) profiles along the nanorods.
The profiles are taken along a curved line following the long axis of the
nanorods. b) EFM before hole injection and c) after hole injection (same
Figure 10. Cyclic voltammogram of a solution of 1 in THF (10ꢀ3 molLꢀ1
)
&
conditions as in Figure 7). EFM profile ( ) for hole injection in the oxide
containing Bu4NPF6 (0.1 molLꢀ1) as a supporting electrolyte at a scan
rate of 100 mVsꢀ1,referenced vs. SCE.
substrate after the deposition of the nanorods (from Figure 8b),net EFM
~
signal due to charges in the nanorod ( ) obtained by subtracting the
&
oxide contribution ( ) from the measured profile after injection
(curve c).
the nanoring. Figure 11b and d represent the EFM images
before and after hole injection at Vinj =+2 V for 2 min. It is
clear that the injected holes have been delocalized along the
nanoring,while more charges have been injected in the
right-hand part of the nanoring close to the injection point.
It is also clear that some charges have spread away from the
nanoring due to the presence of residual materials on the
substrate around the nanoring (as clearly shown in the topo-
graphic image).
sion of charges,as in the naked substrate (Figure 8a),but
with a larger diffusion distance (ꢂ1 mm).[38] The correspond-
ing EFM profile is also shown in Figure 9 (line with
squares). To distinguish the respective contributions of
charge in the nanorod and in the oxide substrate in Fig-
A
raw EFM profile shown in Figure 9c. The resulting EFM
signal due to the net charges in the nanorod is shown by the
line with triangles in Figure 9. We can conclude that the in-
jected holes in the nanorod are almost homogeneously
spread along the nanorod over a distance of ꢂ1 mm,and
that their density slowly decreases near the edges. The EFM
plateau at ꢂꢀ10 Hz corresponds to ꢂ5.8”104 holesmmꢀ2.
The same experiments with negative bias (i.e.,electron in-
jection) were carried out,but no charge delocalization was
noted (Figure 7d). We only observed a weak bright isotropic
spot (diameter of about 250–300 nm). By comparison with
the blank experiment (Figure 8a),this probably corresponds
to electron injection into the oxide underneath.
These results could be correlated with electrochemical
measurements performed on 1. Figure 10 shows a full-scan
cyclic voltammogram of
a
solution of
1
in THF
(10ꢀ3 molLꢀ1) containing Bu4NPF6 (0.1 molLꢀ1) as a sup-
porting electrolyte. At a scan rate of 100 mVsꢀ1 referenced
vs. SCE, 1 exhibits an irreversible wave under cathodic
sweep and the reduction takes place at ꢀ1.56 V vs. SCE.
The oxidation process exhibits a pseudo-reversible wave
when swept anodically,and the onset potential of oxidation
for 1 is located at 0.63 V vs. SCE. Thus,it is easier to inject
holes into the HOMO of 1,which is a good electron-donor,
than to inject electrons in the LUMO.
Further experiments were performed on the nanorings
shown in Figure 5c. Figure 11a and c show the topographic
images before and after the charge injection (done at the
point marked by an arrow). By comparing the two images,
we checked that the injection protocol had not deformed
Figure 11. a) and c) Topographic images of the nanoring before and after
hole injection at Vinj =+2 V over 2 min at the point indicated by the
arrow. b) and d) Corresponding EFM images recorded at VEFM =ꢀ2 V
and z=50 nm. e) 3D topographic image (from a) showing two constric-
tions marked by the arrows.
Figure 12 shows three different profiles of the nanoring
taken along the lines I,II,and III (as shown in Figure 11),
before (in blue) and after (in red) hole injections (topo-
graphic profiles are also shown along the same lines). From
these EFM profiles,and by using eRꢂ3 (a common value
[39]
for organic materials),we can deduce
that ꢂ1.8–2.1”
Chem. Eur. J. 2008, 14,4201 – 4213
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4209

O. J. Dautel,J.-P. L›re-Porte,D. Vuillaume et al.
104 holesmmꢀ2 have been in-
jected into the right-hand part
of the nanoring (profiles I and
II) and ꢂ7.5”103 holesmmꢀ2
into the left-hand part (profile
III). In view of the shape and
size of the nanoring (Figure 11
and topographic profile along
I in Figure 12),with an inter-
nal radius of ꢂ50 nm and an
external radius of ꢂ250 nm,
these values correspond to
ꢂ3.3–4.2”103
and
ꢂ1.5”
103 holes,respectively. The fact
that fewer charges have been
delocalized on the left-hand
side of the nanoring may be
related to the presence of “de-
fects”. From the 3D image
(Figure 11e),we can observe
two constrictions (shown by
the arrows) in the nanoring,
separating its left- and right-
hand parts. These constrictions
partly prevent the diffusion of
charge from the right-hand
part of the nanoring to the
left.
Other
experiments
on
nanorings without defects (Fig-
ure 13a) showed a more uni-
form charge distribution all
over the nanoring (Figure 13b
and c).
Figure 12. Profiles along the lines I,II and III as shown in Figure 11. Left-hand images: AFM heights. Right-
hand images: EFM frequency shift measured before the hole injection (blue,from EFM image in Figure 11b)
and after the hole injection (red,from EFM image in Figure 11d).
Conclusion
In summary,we have synthesized
a
p-conjugated
oligo(phenylenethienylene) capable of forming one-dimen-
ACHTREUNG
sional supramolecular assemblies,leading to gelation of sev-
eral solvents. From the FTIR study of 1 as an organogel,it
was shown that the urea functions play the role of structure
directing agents through hydrogen bonds. The H-aggrega-
tion of the bisurea deduced from the blue-shifted absorption
of its freeze-dried gel was confirmed by the study of the
emission behavior of the organogelator in tetrachloroethyl-
ene as a function of temperature. As suggested by the for-
mation of an organogel,supramolecular architectures were
imaged by scanning electron microscopy of a freeze-dried
gel. As expected,the entire sample is comprised of fiber-
like structures with one-dimensional architectures. Nano-ob-
jects were successfully isolated under special conditions of
dilution of the organogel. Two different types of nano-ob-
jects were obtained,depending on their location on the sub-
strate. A dispersion of nanorings was found in the center of
the drop,whereas nanorods could be observed at the pe-
Figure 13. a) Topographic and b) EFM image of a defect-free nanoring.
c) EFM profile along the line in b). Hole injection and EFM conditions
as in Figure 11.
4210
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Electroactive Nanorods and Nanorings
FULL PAPER
extraction of the product with dichloromethane,a brown solid was ob-
tained and purified by column chromatography (silica gel,gradient of cy-
clohexane/dichloromethane) to yield an orange powder (260 mg,
0.2 mmol,28%). M.p. 88 8C; 1H NMR (200 MHz,CDCl 3): d=7.52 (m,
riphery. Sizing of the different nano-objects leads us to pos-
tulate two different processes for the formation of the nano-
rods and the nanorings. Isolated nanorods are certainly the
result of the dispersion of preexisting nanorods,while nano-
4H),7.26 (m,4H),6.89 (dd,
(d, 3J
(H,H)=3.9 Hz,2H),1.70–2.00 (m,12H),4.01 (m,12H),1.20–1.65
(m,60H),0.88 ppm (m,18H);
13C NMR (50 MHz,CDCl 3): d=153.2,
3J
A
N
rings could be the product of a dewetting process. Their
AHCTREUNG
electronic properties such as positive charges transport have
been demonstrated by the EFM technique. It was observed
that positive charges were nonuniformly delocalized all
along an isolated nano-object over micrometers. In particu-
lar,no charge was stored in the centers of the nanorings.
The observed negative frequency shift corresponds to about
1.5–4”103 injected charges in the nanoring. The same ex-
periments have been performed with negative bias (i.e.,
electrons injection),but no charge delocalization was noted.
These results could be correlated with the nature of 1,which
is a good electron-donor,so it can be easily oxidized,but re-
duced only with difficulty. It was observed that topographic
constrictions in the nanostructures prevent the charge trans-
port and delocalization. Organic nanorings could be very in-
teresting for persistent-current experiments.[40]
149.6,149.5,139.3,125.8,125.6,124.6,123.2,114.4,114.2,113.9,112.9,
69.7,68.7,31.8,29.4,29.4,29.2,26.2,26.2,26.1,22.6,14.1 ppm; IR (KBr):
n˜ =3082,2952,2923,2868,2852,1603,1535,1497,1466,1221,800 cm
elemental analysis (%) calcd for: C 76.37,H 9.87,O 8.25; found: C
75.93,H 9.80,O 8.17.
ꢀ1
;
1-(2,5-Dioctyloxyphenyl)ethan-1-one (4): 1,4-Dioctyloxybenzene (3,
20.4 g,60.9 mmol) and acetyl chloride (2 equiv,9.7 g,138.8 mmol) were
mixed in CCl4 (75 mL) at 58C. AlCl3 (1.2 equiv,9.7 g,73.2 mmol) was
then carefully added to this yellow solution by spatula in small portions
over 30 min. After the addition,the dark red solution was heated to
room temperature for 16 h and became black. During the reaction HCl
was released; the acidic overpressure was neutralized by bubbling
through a KOH solution. The medium was quenched with a water/ice
mixture,and the organic layer was washed three times with water,dried
over Na2SO4,and filtered,and the solvent was removed under vacuum.
The product was purified by column chromatography (silica gel,gradient
of pentane/dichloromethane 10:0 ! 7:3). Compound 4 was isolated as a
white solid (19.3 g,51.3 mmol,85%). 1H NMR (200 MHz,CDCl 3): d=
7.28 (d, 4J
3.1 Hz,1H; Ar),6.85 (d, 3J
6.5 Hz,2H; OCH 2),3.91 (d, 3J
A
3J
(H,H)=9.1, 4J
ACHTREUNG
H
ACHTREUNG
AHCTREUNG
Experimental Section
CH3),1.90–1.65 (m,4H),1.55–1.35 (m,4H),1.28 (brs,16H),0.95–
0.80 ppm (m,6H).
General information and techniques: All synthetic experiments were per-
formed under nitrogen by conventional Schlenk line techniques. The re-
agents 2,5-dioctyloxyphenyleneboronic acid,[41] 1,4-dioctyloxybenzene
(3),[16] 2,5-dioctyloxy-1,4-phenylenediboronic acid,[16] and 1,4-bis(2’-thien-
yl)-2,5-dioctyloxybenzene[42] were prepared by known procedures. 2,5-Di-
octyloxyphenol (5) was prepared by our modification of the protocol de-
scribed in References [16] and [17]. The analytical data for 5 were in
good accordance with the literature. N-(3-Bromopropyl)phthalimide,1-
dodecyl isocyanate,and thiophene-2-boronic acid were purchased from
Acros, N-bromosuccinimide (NBS) and N-iodosuccinimide (NIS) from
2,5-Dioctyloxyphenol (5): A solution of peracetic acid in AcOEt (61%,
2 equiv,17.0 mL,102.6 mmol) was slowly added over 30 min at 40 8C to a
solution of 4 (19.9 g,51.2 mmol) in AcOEt (15 mL). The brownish solu-
tion turned reddish and was stirred for an additional 16 h. The crude
product was washed with brine (150 mL),and the aqueous layer was ex-
tracted twice with AcOEt. The organic layers were combined,washed
once with H2O,dried over Na SO4,and filtered,and the solvent was care-
2
fully removed under vacuum. KOH (4 equiv, ꢂ0.2 mol) and EtOH
(2 equiv, ꢂ0.1 mol) were mixed with the crude product in water (50 mL),
and the mixture was heated to 808C and stirred for 1 h 30. The solution
Alfa Aesar. Dichloromethane was distilled over CaH2,THF over LiAlH
4
was then cooled to ꢀ308C,and HCl (1.5 n,ca 0.2 mol) was added (pH
<
then sodium/benzophenone under nitrogen. Melting points were deter-
mined on an electrothermal apparatus (IA9000 series) and are uncorrect-
ed. 1H and 13C NMR spectra in solution were recorded on Bruker
AC 200 and AC 250 spectrometers at room temperature with deuterated
chloroform for solvent and TMS as internal reference. IR data were ob-
tained on a Perkin–Elmer 1000 FT-IR spectrophotometer. Mass spectra
were measured on JEOL MS-SX 102 and Autospec EQ mass spectrome-
ters. SEM images were obtained with JEOL 6300F microscopes.
2). The organic layer was washed twice with brine,dried over Na 2SO4,
and filtered through Celite,and the solvent was removed under vacuum.
The product was recrystallized from MeOH at ꢀ308C. Compound 5 was
isolated as a white solid (14.4 g,41.1 mmol,80%). M.p. 5 8C; 1H NMR
(200 MHz,CDCl 3): d=6.74 (d, 3J
4J(H,H)=2.9 Hz,1H; Ar),6.35 (dd, 3J
Ar),4.9 (brs,1H; OH),3.96 (d, (H,H)=6.5 Hz,2H; OCH 2),3.87 (d,
3J
3J
(H,H)=6.6 Hz,2H; OCH ),1.85–1.65 (m,4H),1.60–1.35 (m,4H),1.29
(brs,16H),0.95–0.85 ppm (m,6H);
(H,H)=8.8 Hz,1H; Ar),6.55 (d,
4
A
G
N
AHCTREUNG
AHCTREUNG
2
1,4-Bis(5-bromothien-2-yl)-2,5-dioctyloxybenzene: 1,4-Bis(thien-2-yl)-2,5-
dioctyloxybenzene (1.5 g,3 mmol) was added to a solution of NBS (1.1 g,
6.2 mmol) in dichloromethane (30 mL). The mixture was then stirred for
5 h. After aqueous workup the solvent was removed under vacuum to
yield a yellow powder,which was purified by flash chromatography
(silica gel,gradient of cyclohexane/dichloromethane) (1.7 g,2.7 mmol,
13C NMR (50 MHz,CDCl 3): d=
153.9,146.6,140.1,112.7,105.1,102.2,69.7,68.4,32.5,31.7,29.3,29.2,
29.1,26.0,25.9,22.6,14.0 ppm.
N-[3-(2,5-Dioctyloxyphenoxy)propyl]phthalimide (6): Compound
5
(1.48 g,4.2 mmol) was added to a solution of N-(3-bromopropyl)phthal-
imide (1.13 g,4.2 mmol) and K 2CO3 (0.88 g,6.3 mmol) in acetonitrile
(50 mL). The mixture was then stirred for 2 days. After aqueous workup
and extraction of the product with dichloromethane,a dark brown oil
was obtained and purified by column chromatography (silica gel,gradient
89%). M.p. 898C; 1H NMR (200 MHz,CDCl 3): d=7.22 (d, 3J
3.9 Hz,2H),7.09 (s,2H),7.03 (d, (H,H)=3.9 Hz,2H),4.01 (t,
3J
3J
A
AHCTREUNG
A
6H); 13C NMR (50 MHz,CDCl 3): d=148.9,140.4,129.2,124.5,122.4,
113.1,111.1,69.8,31.9,29.42,29.4,26.3,22.7,14.2 ppm; IR (KBr):
3084,2944,2919,2867,2848,1537,1491,1462,1210,1064,786 cm
n˜ =
of cyclohexane/dichloromethane) to yield
3.3 mmol,72%). M.p. 91 8C; 1H NMR (250 MHz,CDCl 3): d=7.76 (m,
4H),6.77 (d, 3J(H,H)=8.9 Hz,1H),6.48 (d, 4J
(H,H)=2.8 Hz,1H),6.37
(dd, 3J(H,H)=8.9, 4J(H,H)=2.8 Hz,1H),4.03 (t, 3J
(H,H)=6.1 Hz,2H),
a white powder (1.64 g,
ꢀ1
;
HRMS (FAB+): m/z: calcd for C30H40Br2O2S2: 654.0836 [M]+; found:
A
ACHTREUNG
654.0833.
A
N
ACHTREUNG
3.87 (m,6H),2.20 (m,2H),1.73 (m,4H),1.2–1.5 (m,20H),0.88 ppm
1,4-Bis[5-(2,5-dioctyloxyphenyl)thien-2-yl]-2,5-dioctyloxybenzene (2):
mixture of 1,4-bis(5-bromothien-2-yl)-2,5-dioctyloxybenzene (520 mg,
0.8 mmol),25,-dioctyloxyphenylboronic acid (640 mg,1.6 mmol),K 3PO4
(1 g,4.8 mmol),Pd 2dba3 (35 mg,35 mmol),and triphenylphosphine
(35 mg,280 mmol) in DMF (40 mL) was heated under nitrogen at 808C
for 3 days. The DMF was then evaporated. After aqueous workup and
A
(m,6H); 13C NMR (50 MHz,CDCl ): d=168.2,154.1,150.0,143.4,133.8,
3
132.2,123.2,116.1,105.3,103.2,70.6,68. 4,66.8,35.3,31.8,29.5,29.4,
29.2,29.2,28.6,26.1,26.0,22.6,14.0 ppm; IR (KBr):
n˜ =3076,2940,2869,
ꢀ1
2854,1773,1712,1226,722 cm
; HRMS (FAB+): m/z: calcd for
C33H47NO5: 537.3454 [M]+; found: 537.3448.
Chem. Eur. J. 2008, 14,4201 – 4213
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4211

O. J. Dautel,J.-P. L›re-Porte,D. Vuillaume et al.
N-[3-(4-Iodo-2,5-dioctyloxyphenoxy)propyl]phthalimide (7): Compound
6 (1.02 g,1.89 mmol) was added to a solution of NIS (0.45 g,1.99 mmol)
and trifluoroacetic acid (65 mg,0.6 mmol) in dichloromethane (40 mL).
The mixture was then stirred for 2 h. After aqueous workup and extrac-
tion of the product with dichloromethane,the solvent was removed
under vacuum to yield a yellow powder (1.2 g,1.8 mmol,94%). M.p.
868C; 1H NMR (250 MHz,CDCl 3): d=7.77 (m,4H),7.20 (s,1H),6.49
1,4-Bis[5-(4-(3-aminopropoxy)-2,5-dioctyloxyphenyl)thien-2-yl]-2,5-di-
A
lution of 10 (200 mg,0.12 mmol) in THF (10 mL). The mixture was then
stirred at 508C overnight. After workup with aqueous sodium hydroxide
(1n) and extraction of the product with dichloromethane,a bright yellow
powder (150 mg,0.11 mmol,96%) was obtained. M.p. 122 8C; 1H NMR
(250 MHz,CDCl 3): d=7.45 (d, 3J
A
ACHTREUNG
(s,1H),4.05 (t, 3J
(m,4H),1.2–1.5 (m,20H),0.88 ppm (m,6H);
ACHTREUNG
AHCTREUNG
0.88 ppm (m,18H); 13C NMR (50 MHz,CDCl 3): d=150.1,149.5,148.2,
143.3,139.6,138.2,125.5,124.6,123.1,116.4,115.0,112.8,101.5,70.4,
69.9,69.7,67.9,39.5,33.1,31.8,29.6,29.5,29.5,29.4,29.3,28.7,26.2,26.1,
22.7,14.1 ppm; IR (KBr): n˜ =3390,3054,2952,2924,2868,2854,1210,
CDCl3): d=168.2,152.7,149.9,144.6,133.9,132.1,125.1,123.2,102.4,
75.5,10.5,70.3,67.6,35.3,31.8,29.3,29.2,28.6,26.1,26.0,22.6,14.1 ppm;
IR (KBr): n˜ =3058,2948,2921,2866,2852,1772,1710,1213,710 cm
ꢀ1
;
HRMS (FAB+): m/z: calcd for C33H46NO5: 663.2421 [M]+; found:
794 cmꢀ1
; HRMS (FAB+): m/z: calcd for C80H128N2O8S2: 1309.9190
663.2448.
[M+H]+; found: 1309.9210; elemental analysis (%) calcd for: C 73.43,H
N-[3-(4-Thienyl-2,5-dioctyloxyphenoxy)propyl]phthalimide (8):
A mix-
8.47,N 1.78,S 4.08; found: C 73.13,H 8.55,N 1.86,S 4.42.
ture of (1.1 g,1.73 mmol),thiophene-2-boronic acid (330 mg,
7
1,4-Bis[5-(4-(3-dodecylureidopropoxy)-2,5-dioctyloxyphenyl)thien-2-yl]-
2,5-dioctyloxybenzene (1): 1-Dodecyl isocyanate (60 mg,0.27 mmol) was
added under nitrogen to a solution of 11 (160 mg,0.12 mmol) in dry THF
(20 mL). The mixture was then stirred for 2 h. The solvent was evaporat-
ed,and the yellow precipitate was washed several times with pentane
(155 mg,89 mmol,73%). M.p. 145 8C; 1H NMR (250 MHz,CDCl 3): d=
2.60 mmol),Na 2CO3 (400 mg,3.46 mmol),Pd 2dba3 (36 mg,36 mmol),and
triphenylphosphine (36 mg,285 mmol) in THF (20 mL) and water
(10 mL) was heated under nitrogen at 508C overnight. The THF was
then evaporated. After aqueous workup and extraction of the product
with dichloromethane,a brown solid was obtained and purified by
column chromatography (silica gel,gradient of cyclohexane/dichlorome-
thane) to yield a white powder (760 mg,1.2 mmol,71%). M.p. 93 8C;
7.52 (d, 3J
N
N
2H),7.23 (s,2H),6.58 (s,2H),5.17 (m,2H),4.41 (m,2H),4.00–4.20 (m,
16H),3.45 (m,4H),3.13 (m,4H),1.75–2.00 (m,16H),1.2–1.5 (m,
100H),0.88 ppm (m,24H); 13C NMR (50 MHz,CDCl 3): d=158.4,150.4,
149.5,148.7,142.9,139.3,138.4,125.5,124.7,123.1,116.8,115.3,124.7,
123.1,116.8,115.3,112.8,101.2,70.9,69.9,69.7,68.9,40.6,39.0,31.8,30.3,
1H NMR (250 MHz,CDCl 3): d=7.77 (m,4H),7.37 (dd, 3J
ACHTREUNG
4J
A
3J
G
ACHTREUNG
7.04 (dd, 3J
(H,H)=5.3, 3J
4.10 (t, J
ACHTREUNG
1.2–1.5 (m,20H),0.88 ppm (m,6H);
168.2,150.0,149.1,143.5,139.6,133.8,132.2,126.5,124.4,124.0,123.2,
116.5,115.8,102.2,70.7,69.7,67.6,35.4,31.1,29.5,29.4,29.3,29.2,29.2,
29.4,29.3,26.2,26.1,26.0,22.6,14.0 ppm; IR (KBr):
2923,2870,2852,1627,1577,1212,799 cm
n˜ =3352,3051,2954,
ꢀ1; HRMS (FAB+): m/z: calcd
for C106H179N4O10S2: 1732.3062 [M+H]+; found: 1732.3068; elemental
analysis (%) calcd for: C 73.48,H 10.35,N 3.23,S 3.70; found: C 73.10,
H 10.41,N 3.46,S 3.21.
28.7,26.2,26.0,22.6,14.2 ppm; IR (KBr):
n˜ =3068,2939,2923,2870,
ꢀ1
2855,1770,1706,1216,721 cm
; HRMS (FAB+): m/z: calcd for
C37H49NO5S: 619.3331 [M]+; found: 619.3320.
X-raycrystal structure determination : Diffracted intensities were mea-
sured over a full sphere of the reciprocal space on an Xcalibur CCD
(Oxford Diffraction) diffractometer with use of monochromated MoKa
radiation (l=0.71073 Š). CrysAlisCCD and CrysAlisRed software pack-
ages[43] were used for data acquisition,extraction,and reduction. The
structure was solved by direct methods as provided by SHELXS-97[44]
and subsequent Fourier analyses. Refinement of atomic positions and
anisotropic displacement parameters for all non-hydrogen atoms were
carried out by full-matrix,least-squares methods based on F2 (program
SHELXL-97[45]). Hydrogen atoms attached to carbon were placed in geo-
metrically idealized positions and constrained to ride on their parent
atoms. They were each given an isotropic displacement parameter equal
to 1.2 times the Ueq of their C parent.
N-[3-(4-(5-iodothiophen-2-yl)-2,5-dioctyloxyphenoxy)propyl]phthalimide
(9): Compound 8 (300 mg,0.48 mmol) was added to a solution of NIS
(110 mg,0.48 mmol) in dichloromethane (15 mL). The mixture was then
stirred for 2 h. After aqueous workup and extraction of the product with
dichloromethane,the solvent was removed in vacuum to yield a yellow
powder (350 mg,0.45 mmol,89%). M.p. 84 8C; 1H NMR (250 MHz,
CDCl3): d=7.77 (m,4H),7.20 (d, 3J
7.05 (d, 3J
(H,H)=3.2 Hz,1H),6.59 (s,1H),4.12 (t,
2H),4.03 (t, 3J(H,H)=5.3 Hz,2H),3.95 (t, 3J
(H,H)=5.4 Hz,4H),2.23
ACHTREUNG
A
ACHTREUNG
A
ACHTREUNG
(m,2H),1.90 (m,2H),1.77 (m,2H),1.2–1.5 (m,20H),0.88 ppm (m,
6H); 13C NMR (50 MHz,CDCl 3): d=168.2,149.8,149.5,143.5,133.8,
132.2,124.4,123.2,115.7,114.8,101.8,73.0,70.7,69.8,67.5,35.3,31.8,
¯
Crystal data for 2: C74H114O6S2, M=1163.77,triclinic, P1, a=7.9650(6),
29.5,29.3,29.2,28.6,26.2,26.0,22.6,14.0 ppm; IR (KBr):
n˜ =3059,2951,
2925,2868,2851,1770,1706,1216,720 cm
ꢀ1; HRMS (FAB+): m/z: calcd
b=9.549(1), c=23.781(2) Š, a=82.94(1)8, b=80.60(1), g=79.70 (1)8,
V=1747.5(3) Š3, T=173 K, Z=1, 1calcd =1.106 gcmꢀ3,orange parallel-
for C37H49NO5S: 745.2298 [M]+; found: 745.2463.
A
1,4-Bis[5-(4-(3-phthalimid-N-yl)propoxy)-2,5-dioctyloxyphenyl)thien-2-
yl]-2,5-dioctyloxybenzene (10): A mixture of 8 (540 mg,0.73 mmol),25, -
dioctyloxy-1,4-phenylenediboronic acid (212 mg, 0.36 mmol), Na2CO3
(150 mg,1.44 mmol),Pd 2dba3 (15 mg,15 mmol),and triphenylphosphine
(15 mg,120 mmol) in THF (25 mL) and water (5 mL) was heated under
nitrogen at 508C overnight. The THF was then evaporated. After aque-
ous workup and extraction of the product with dichloromethane,a dark
brown solid was obtained and purified by column chromatography (silica
(qmax =258),6150 unique. Final R1 =0.0552 and wR2 =0.1211 for 370 re-
fined parameters using 4156 observed reflections with I > 2s(I). Good-
ꢀ3
ness of fit=0.982,electron density residuals =0.327/ꢀ0.212 eŠ
.
CCDC 661776 contains the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
gel,gradient of cyclohexane/dichloromethane) to yield a orange powder
1
(300 mg,0.19 mmol,53%). M.p. 119 8C; H NMR (250 MHz,CDCl ): d=
3
7.79 (m,8H),7.45 (d, 3J
A
N
Acknowledgements
2H),7.26 (s,2H),7.23 (s,2H),6.64 (s,2H),3.80–4.20 (m,20H),2.25 (m,
4H),1.94 (m,8H),1.79 (m,4H),1.2–1.5 (m,60H),0.88 ppm (m,18H);
13C NMR (50 MHz,CDCl 3): d=168.3,150.1,149.5,149.0,143.6,139.5,
138.3,133.9,132.2,125.5,124.6,123.2,123.1,116.9,115.5,112.8,102.4,
70.6,69.8,69.7,67.6,35.4,31.8,29.6,29.29.4,29.4,29.3,28.7,26.2,26.1,
22.7,14.1 ppm; IR (KBr): n˜ =3054,2951,2924,2868,2853,1773,1715,
1213,719,711 cm ꢀ1; HRMS (FAB+): m/z: calcd for C96H133N2O12S2:
1569.9299 [M+H]+; found: 1569.9289.
We are grateful to the CNRS,“La RØgion Languedoc Roussillon” and
the “AC Nanofilum” program for financial support.
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4212
www.chemeurj.org
ꢁ 2008 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
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Received: October 16,2007
Published online: March 25,2008
Chem. Eur. J. 2008, 14,4201 – 4213
ꢁ 2008 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
www.chemeurj.org
4213