Dendritic oligothiophenes terminated with tris(alkyloxy)phenylethynyl tails: Synthesis, physical properties, and self-assembly

Article abstract of DOI:10.1002/chem.201002198

Three-dimensional (3D) π-conjugated dendritic oligothiophenes up to a third generation have been functionalized with tris(decyloxy)phenylethynyl tails at the periphery. The first-generation compounds (3a T-p-Ph-C10 and 6a T-p-Ph-C10) were synthesized by p

Full text of DOI:10.1002/chem.201002198

FULL PAPER
DOI: 10.1002/chem.201002198
Dendritic Oligothiophenes Terminated with TrisACTHNUTRGENUG(N alkyloxy)phenylethynyl
Tails: Synthesis, Physical Properties, and Self-Assembly
Chang-Qi Ma,*[a] Wojciech Pisula,[b] Cornelia Weber,[a] Xin-Liang Feng,[b]
Klaus Mꢀllen,[b] and Peter Bꢁuerle*[a]
Abstract: Three-dimensional (3D) p-
conjugated dendritic oligothiophenes
up to a third generation have been
tammetry. The results revealed that the
terminal tris(alkyloxy)phenylethynyl
eration compounds 3T-p-Ph-C10 and
6T-p-Ph-C10 displayed columnar
ACHTUNGTRENNUNG
groups are conjugated to the branched
oligothiophene core, yielding redshifted
absorption and fluorescence spectra
and reduced optical band gaps relative
to the dendritic oligothiophene core. A
structural study revealed a close rela-
tionship between the type of supra-
molecular organization and the size of
the oligothiophene core. The first-gen-
phases in the bulk state, which was
confirmed by two-dimensional wide-
angle X-ray scattering (2D WAXS)
measurements. The self-assembly into
columnar stacks has mainly been at-
tributed to phase separation between
the rigid thiophene cores and the flexi-
ble side-chains assisted by minor p-
stacking interactions between the con-
jugated dendritic oligothiophene units.
The high-generation compounds, how-
ever, showed less ordered structures in
the solid state.
functionalized
with
tris-
ACHTUNGTRENNUNG(decyloxy)phenylethynyl tails at the pe-
riphery. The first-generation com-
pounds (3T-p-Ph-C10 and 6T-p-Ph-
C10) were synthesized by palladium-
catalyzed Sonogashira coupling reac-
tions, whereas the higher generation
products were synthesized by palladi-
um-catalyzed Suzuki coupling reactions
in a divergent approach. The optical
and electrochemical properties were in-
vestigated by UV/Vis absorption, fluo-
rescence spectroscopy, and cyclic vol-
Keywords: dendrimers
crystals oligothiophenes
pi conjugation · self-assembly
·
liquid
·
·
Introduction
tion and self-organization of the molecules in the bulk
state.[2a,5] In this respect, p-conjugated liquid crystalline
(LC) molecules are very interesting because they have the
potential to form highly ordered nanostructures in the bulk
state through noncovalent p–p interactions of the conjugat-
ed units, which provides efficient electronic pathways for
charge-carrier transport.[6] Many reviews have described the
recent development of one-dimensional (1D) linear and
two-dimensional (2D) planar p-conjugated liquid crystalline
organic semiconductors.[7]
The development of conjugated oligomers and polymers has
been one of the most active research fields in the last few
decades because of their potential applications in organic
electronic devices[1] such as organic field-effect transistors
(OFET),[2] organic light-emitting diodes (OLED),[3] and or-
ganic solar cells (OSC).[3b,4] Device performance is to a large
extent determined by the charge-carrier mobility of the sem-
iconducting material, which strongly depends on the orienta-
Three-dimensional (3D) p-conjugated molecules,[8] for ex-
ample, star-shaped,[9] X-shaped,[10] cruciform,[11] and den-
drimers,[12] have been developed for various electronic appli-
cations. Among them, p-conjugated dendrimers belong to a
class of macromolecules that have the advantage of high-
molecular weights and defined and monodisperse chemical
structures[13] and thus they have recently attracted much at-
tention. Examples of 3D p-conjugated dendrimers include
phenyl-ring-based systems such as polyphenylenes,[13,14] phe-
nylenevinylenes,[15] phenyleneethynylenes,[16] and truxenes[17]
or heterocyclic aromatic systems such as thiophenes,[18] car-
bazoles,[19] and phenothiazines.[20] In such conjugated den-
[a] Dr. C.-Q. Ma, C. Weber, Prof. Dr. P. Bꢀuerle
Institute of Organic Chemistry II and Advanced Materials
Ulm University, Alberti-Einstein-Allee 11
89081 Ulm (Germany)
Fax : (+49)731-50-22840
E-mail: changqi.ma@uni-ulm.de
peter.baeuerle@uni-ulm.de
[b] Dr. W. Pisula, Dr. X.-L. Feng, Prof. Dr. K. Mꢁllen
Max Planck Institute for Polymer Research
Ackermannweg 10, 55128 Mainz (Germany)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201002198.
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drimers, the conformational flexibility is mostly limited.
Therefore these p-conjugated dendrimers are considered as
shape-persistent 3D molecules.[21] Interestingly, even though
these conjugated dendrimers are structurally nonplanar and
do not have any electrostatic or hydrogen-bonding interac-
tions, they show a great tendency for aggregation.[22] The
driving forces seem to be solvophobic interactions associat-
ed with strong interdigitation of the molecules.[23]
Results and Discussion
Synthesis: TrisACTHNUTRGNEUNG(alkyloxy)phenyl has been widely used as a
pro-mesogenic unit in the development of liquid crystalline
molecules.[31] To reduce steric hindrance between two pe-
ripheral tris
duced as
ACHTUNGTRENNUNG
a
a
AHCTUNGTREG(NNUN decyloxy)phenylethynylene (Ph-C10-H, see Scheme 2)
As a very important class of organic semiconducting ma-
terials, oligo- and polythiophenes have been extensively in-
vestigated in the last few decades.[24] Owing to their high
charge-carrier mobility and chemical stability, thiophene-
based materials have shown strong performances in organic
electronic devices.[2,25] On the other hand, the moderate re-
activity of the thiophene a position allows good access to
differently substituted and functionalized oligo- and poly-
thiophenes leading to a broad structural variation and there-
by tuning of the physical properties of the materials accord-
ing to certain application requirements. To date, oligothio-
phenes with different structural geometries, from 1D linear,
2D cyclic, to 3D dendritic, have been developed.[24a]
The first all-thiophene dendrimer series up to a 30-mer
was synthesized by Advincula and co-workers by palladium-
catalyzed Stille coupling reactions.[18a,26] These all-thiophene
dendrons and dendrimers showed intriguing optical, elec-
tronic, and self-assembly properties.[26] Following from this,
various dendrimers based on branched oligothiophene units
have been accessed. The properties and applications of
these materials in organic electronic devices have also been
reported.[18b,27]
Recently we developed a novel synthetic strategy for
large all-thiophene dendrimers.[18b,22d] By using trimethylsilyl
(TMS) groups as terminal protecting groups, thiophene den-
drimers up to a 90-mer were successfully synthesized in
good yields. In addition, this novel synthetic strategy al-
lowed functionalization of dendritic oligothiophenes (DOT)
with, for example, dyes[28] or redox-active[29] or other func-
tional groups at core or periphery positions.[30] Strong inter-
molecular interactions were also found in these highly
branched thiophene dendrimers,[22d,30a] which were attributed
to solvophobic interactions or intermolecular p–p interac-
tions.
building block was synthesized in four steps from 3,4,5-tri-
methoxy-1-bromobenzene according to a literature method
(see the Supporting Information)[32] and the dendritic oligo-
thiophene precursors 3T-I, 6T-I, 9T-I, and 18T-Br were syn-
thesized according to procedures established in our labora-
tory.[18b,22d] Reactions involved in this work include palladi-
um-catalyzed Sonogashira and Suzuki coupling reactions
(see Schemes 2 and 3).
The trisACHTNUTRGNE(UNG decyloxy)phenylethynyl (TDPE)-tailed G1 den-
dron 3T-p-Ph-C10 and the corresponding dendrimer 6T-p-
Ph-C10 were synthesized by palladium-catalyzed Sonoga-
shira coupling of Ph-C10-H and 3T-I and 6T-I in yields of
86 and 97%, respectively (Scheme 2). The products are
highly soluble in organic solvents and were purified by chro-
matography on silica gel. Lithiation of 3T-p-Ph-C10 with
nBuLi was completed within 1 h at ꢀ788C. Reaction of lithi-
ated 3T-p-Ph-C10 with 2-isopropyloxy-4,4,5,5-tetramethyl-
1,3,2-dioxaborolane gave terthiophene boronic ester B-3T-
p-Ph-C10 in 88% yield. Oxidative homocoupling of the
lithiated G1 dendron with CuCl2 gave the corresponding
dendrimer 6T-p-Ph-C10 in a yield of only 17%. Because
lithiation of 3T-p-Ph-C10 with nBuLi is very efficient, the
low yield may be attributable to the inefficient oxidative
coupling step, which has also been observed in other thie-
noacetylene systems.[33]
G2 and G3 TDPE-terminated thiophene dendrons and
dendrimers were synthesized by Suzuki coupling of B-3T-p-
Ph-C10 with different core units under mild reaction condi-
tions (Scheme 3). All coupling reactions gave high yields of
products. Except for the G3 dendrimer 42T-p-Ph-C10,
which was purified by semipreparative recycling gel permea-
tion chromatography (GPC), the other three compounds,
9T-p-Ph-C10, 18T-p-Ph-C10, and 21T-p-Ph-C10, were puri-
fied by preparative size-exclusion chromatography (SEC,
Bio-Rad Beads SX-1).
In this report we describe the synthesis, physical, and self-
assembly properties of all-thiophene dendrons and dendrim-
ers with trisACHTUNGTRENNUNG(decyloxy)phenylethynyl tails at the periphery
(Scheme 1). Such a modification of the chemical structure
creates two different parts of the molecule: A rigid p-conju-
gated core and flexible alkyl side-chains. The self-organiza-
tion of these functionalized 3D dendrimers in the solid state
is elucidated with the supramolecular motif changing from a
highly anisotropic columnar arrangement to an isotropic or-
ganization by increasing the size of the oligothiophene core.
The chemical structures of the TDPE-terminated thio-
phene dendrimers (DOT-p-TDPE) were fully characterized
by NMR spectroscopy, MALDI-TOF mass spectrometry,
and elemental analysis. The characteristic proton resonances
of the b-H of the joint thiophene units as well as the correct
integration ratios between these characteristic peaks unam-
biguously confirmed their chemical identity (see the Sup-
1
porting Information for the H and 13C NMR spectra). For
all compounds, the MALDI-TOF MS clearly revealed the
monodisperse character of the products. For instance, the
MALDI-TOF MS of 42T-p-Ph-C10, obtained through a re-
flection mode, shows the peak mass of the molecule, which
correlates well with the proposed molecular structure. Inter-
estingly, a few high-mass peaks were also found when the
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Dendritic Oligothiophenes
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Scheme 1. Chemical structures of trisACTHUNTGRNEUNG(decyloxy)phenylethynyl-functionalized all-thiophene dendrons (left column) and dendrimers (right column).
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C.-Q. Ma, P. Bꢀuerle et al.
Scheme 2. Synthesis of first-generation dendron 3T-p-Ph-C10 and dendrimer 6T-p-Ph-C10. Reagents and conditions: i) [Pd
diisopropylamine; ii) 1. nBuLi/THF; 2. 2-isopropyloxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane; iii) 1. nBuLi/THF; 2. CuCl2.
ACHTUGNTRENUN(GN PPh3)2Cl2] (4%)/CuI (2%)/
mass spectrum was recorded in linear mode. These peaks
can be assigned to the aggregates of 42T-p-Ph-C10 (see the
Supporting Information, Figure S1). This result suggests that
these TDPE-terminated thiophene dendrimers have a high
tendency to form aggregates in the solid state.
corresponding data for the G2 all-thiophene dendron 9T
and dendrimer 18T are also included in Table 1.
Figure 1a and b depict the absorption spectra of TDPE-
functionalized dendrons and dendrimers, respectively.
Except for the G1 dendron 3T-p-Ph-C10, which shows a
maximum absorption peak (labsmax) at 331 nm and a shoulder
(labsshoulder) at 370 nm, all other TDPE-modified DOTs dis-
play similar broad and structureless absorption bands with a
UV/Vis and fluorescence spectroscopy: The optical proper-
ties of these TDPE-terminated thiophene dendrons and
dendrimers were investigated by UV/Vis absorption and
fluorescence spectroscopy in dichloromethane solution. The
optical data are summarized in Table 1. For comparison, the
max
shoulder
labs
at around 340 nm and a labs
at around 410 nm,
respectively. No redshift of the maximum absorption wave-
length was observed with increasing molecular size, which
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Dendritic Oligothiophenes
FULL PAPER
Scheme 3. Synthesis of higher-generation compounds under Suzuki coupling conditions: [Pd2dba3]·CHCl3/HPACHTUNGTRNE(NUG tBu)3BF4/K2CO3/THF, 08C to room temper-
ature, 12 h.
can be understood in terms of the fact that the absorption
spectrum is a superimposition of the absorption of multiple
chromophores of different conjugation lengths.[22e] In con-
trast, the absorption onset wavelength (labsonset) is redshifted
to longer wavelengths for larger dendrons and dendrimers,
which indicates a smaller optical band gap (Eg) for bigger
molecules, which can be attributed to the larger p-conjugat-
ed oligothiophene core. Molar extinction coefficients at the
absorption maximum are linearly correlated with the molec-
ular weight (Figure 2). The molecular extinction coefficients
normalized for the molecular weights of these TDPE-termi-
nated DOTs were determined to be 29.3 cmLgꢀ1, which is
much smaller than that of the nonfunctionalized
(52.2 cmLgꢀ1) and TMS-protected DOTs (40.4 cmLgꢀ1).[22e]
This is due to the large volume of the insulating tris-
AHCTUNGTRENNUNG
Table 1. Electronic data for the trisACTHNUGTRNEUNG(decyloxy)phenylethynyl-terminated DOTs and 9T and 18T.
max
shoulder
onset
max
opt
0
onset
Compounds
labs
[nm][a]
labs
[nm][a]
labs
[nm][a]
e
lfl
Ffl
[%][a,d]
Eg
Eox
Eox
[V][f]
EHOMO
ELUMO
[cmLmolꢀ1
]
[nm][a,c]
[eV][e]
[V][f,g]
[eV][h]
[eV][i]
[b]
3T-p-Ph-C10
9T-p-Ph-C10
21T-p-Ph-C10
6T-p-Ph-C10
18T-p-Ph-C10
42T-p-Ph-C10
9T[o]
331
370
420
422[k]
420
420
425[m]
–
428
43800
87300
184200
78600
169000
369100
37500
78000
487
13
8
2.90
2.53
2.41
2.47
2.34
2.33
2.69
2.35
0.69
0.61
ꢀ5.71
ꢀ5.55
ꢀ5.46
ꢀ5.59
ꢀ5.42
ꢀ5.44
ꢀ5.61
ꢀ5.52
ꢀ2.74
ꢀ2.95
ꢀ3.05
ꢀ2.99
ꢀ3.01
ꢀ3.15
ꢀ2.92
ꢀ3.17
344
490
529
0.55[j]
0.43[l]
0.57
0.45[j]
0.36[l]
0.49
342[k]
344
514[k]
502
556[k]
525
7[k]
14
9
340
530
564
0.45[j]
0.43[l,n]
0.57
0.32[j]
0.34[l]
0.51
341[m]
373
532[m]
460
577[m]
520
6[m]
11
9
18T[o]
392
–
528
554
0.46
0.42
[a] In dichloromethane, [M]=1.0ꢃ10ꢀ6 molLꢀ1. [b] At labsmax. [c] Excited at labsmax. [d] Fluorescein in 0.1m NaOH as standard (Ffl =0.79). [e] Calculated
onset
from Eg (eV)=1240/labs
(nm). [f] In CH2Cl2, [M]=1.0ꢃ10ꢀ3 molLꢀ1, TBAPF6 (0.1m), 295 K, scan rate=100 mvsꢀ1 vs. Fc/Fc+. [g] Determined from
DPV measurements. [h] Calculated from EHOMO =ꢀ(Eoxonset+5.10). [i] Calculated from ELUMO =EHOMO +Egopt. [j] At [M]=5.0ꢃ10ꢀ4 molLꢀ1. [k] At [M]=
3.4ꢃ10ꢀ7 molLꢀ1. [l] At [M]=3.5ꢃ10ꢀ4 molLꢀ1. [m] At [M]=1.8ꢃ10ꢀ7 molLꢀ1. [n] Shoulder peak. [o] From ref. [22e].
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C.-Q. Ma, P. Bꢀuerle et al.
18T-p-Ph-C10 (Figure 1b). The absorption spectrum of a
thiophene dendrimer can be considered a superimposition
of the absorption of multiple chromophores that correlate
onset
to different conjugation lengths.[18b,27] Therefore the labs
is an indication of the longest p-conjugated unit within the
max
molecule, whereas the labs shows the most abundant chro-
onset
mophore unit in a molecule. The redshifted labs
for the
TDPE-functionalized thiophene dendrimer indicates that
the peripheral TDPE units are conjugated to the branched
oligothiophene core. On the other hand, the blueshifted
max
labs for the TDPE-terminated dendrimer suggests that the
outer terthiophene units are more twisted as a result of the
bulky TDPE groups. The optical band gaps (Eg) of these
compounds were calculated to be 2.90–2.33 eV from the ab-
sorption onsets (Table 1), which are slightly smaller than
those of the nonprotected DOTs.
The fluorescence spectra of the DOT-p-TDPEs along with
those of 9T and 18T in dichloromethane are also shown in
Figure 1. The maximum emission wavelengths (lflmax) of the
DOT-p-TDPEs are gradually redshifted with increasing mo-
lecular size, revealing a more expanded p-conjugated system
for the larger molecules, which is in accordance with the
trend of the UV/Vis absorption onset wavelength. In com-
parison with 9T and 18T, the maximum emission wave-
lengths (lflmax) of the TDPE-functionalized dendron 9T-p-
Ph-C10 and dendrimer 18T-p-Ph-C10 show a 10 nm redshift,
which suggests an extension of the conjugated length due to
the phenylethynyl units. Similarly to their parent nonfunc-
tionalized DOTs, the shapes of the fluorescence spectra of
the DOT-p-TDPEs are independent of the excitation wave-
length, which indicates an efficient intramolecular energy
transfer. The fluorescence quantum efficiencies of these
DOT-p-TDPEs are in the range 6–14%, which is rather low
and can be attributed to the heavy-atom effect of sulfur
leading to highly efficient intersystem crossing to the triplet
state.
Figure 1. UV/Vis absorption and normalized fluorescence spectra of tris-
ACHTUNGTRENNUNG(decyloxy)phenylethynyl-functionalized dendrons (a) and dendrimers (b)
in dichloromethane. For comparison, the absorption and emission spectra
of 9T and 18T are also shown. The fluorescence spectra were obtained
max
by excitation at labs
.
Electrochemical properties: The electrochemical properties
of the DOT-p-TDPEs were investigated by cyclic voltamme-
try (CV) and differential pulse voltammetry (DPV) in di-
chloromethane with Bu4NPF6 as supporting electrolyte. All
potentials reported herein were calibrated with the ferro-
cene/ferrocenium couple (Fc+/Fc) as internal standard. Oxi-
dation potentials (Eox0), oxidation onset potentials (Eoxonset),
as well as HOMO/LUMO energy levels were determined by
a combined analysis of the CV and absorption data and are
listed in Table 1. Figure 3a shows the cyclic and differential
pulse voltammograms of the TDPE-functionalized dendrons.
As can be seen, the TDPE-terminated dendrons show a
broad and ill-defined redox response in the cyclic voltam-
metric measurements. The first oxidation potentials (Eox0) of
these compounds were determined to be 0.69 V for 3T-p-
Ph-C10, 0.55 V for 9T-p-Ph-C10, and 0.43 V for 21T-p-Ph-
C10 by DPV. Although there is one free inner a-H in the
dendron derivatives, neither dimerization nor polymeri-
zation was found during potential sweeping (see the Sup-
porting Information, Figure S2). Figure 3b shows the cyclic
Figure 2. Linear correlation between the molar excitation coefficients
and the molecular weights of the tris
ized dendrons and dendrimers.
ACHTUNGTRENN(UNG decyloxy)phenylethynyl-functional-
onset
tionalized compounds show redshifts for labs
but blue-
shifts for labsmax. As an example, the onset absorption wave-
length of 9T-p-Ph-C10 (490 nm) is redshifted by 30 nm rela-
tive to that of 9T (460 nm), whereas the maximum absorp-
tion wavelength of 9T-p-Ph-C10 (344 nm) is blueshifted by
29 nm with respect to that of 9T (373 nm, Table 1). A simi-
lar but relatively weaker effect was found for G2 dendrimer
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Dendritic Oligothiophenes
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trend that the electronic band gaps of the compounds
become narrower with increasing molecular size. This is in
good agreement with the optical data and can be understood
in terms of the larger p-conjugated systems of the higher
generation molecules.
onset
ð1Þ
ð2Þ
EHOMO ¼ ꢀðEox
þ5:10Þ
opt
ELUMO ¼ EHOMOþEg
Structural study: The assembly of oligothiophenes with flex-
ible alkyloxyl groups at periphery in the solid state play a
fundamental role in determining the materialꢄs bulk and
device properties.[24a] Therefore the superstructures and
phase formation of the DOT-p-TDPEs in the bulk were in-
vestigated. Wide-angle X-ray scattering experiments with a
2D detector (2D WAXS) were performed to gain an insight
into the packing of the DOT-p-TDPEs. For this study the
samples were extruded into a macroscopically aligned fiber,
which was mounted vertically towards the 2D X-ray detec-
tor. In addition, optical textures obtained by polarized opti-
cal microscopy (POM) of thin films, which were cooled
from the isotropic phase, provided additional information of
the corresponding phase.
A POM image of 3T-p-Ph-C10 (inset Figure 4b) recorded
with cross-polarizers revealed birefringent spherulitic do-
mains, which are a characteristic of crystalline materials.[35]
The red-blue color distribution of quarters of the spherulite
due to a l-plate suggests an edge-on arrangement of the
molecules towards the surface of the substrate in the opti-
cally negative spherulites (the refractive index parallel to
the radial direction is smaller than that perpendicular to it;
Figure 4b).[36] The 2D X-ray pattern of 3T-p-Ph-C10 is char-
acteristic of a columnar assembly (Figure 4a).[7e,37] The equa-
torial small- and middle-angle scattering intensities corre-
spond to the intercolumnar arrangement, which is in this
case attributed to a 2D cubic lattice with a=3.02 nm. Thus,
the columnar structures are oriented along the extrusion di-
rection of the fiber. The large number of higher-order reflec-
tions confirmed the crystallinity of the compound. The meri-
dional wide-angle reflections have been assigned to molecu-
lar packing in the stacks with a molecular distance of
0.47 nm, the broad shape of these scattering intensities im-
plying a relatively weak molecular interaction and low intra-
columnar order (Figure 4a). This intracolumnar arrange-
ment is attributed to the nonplanarity of the aromatic unit.
Therefore we assume that the columns are assembled
mainly as a result of a phase separation between the rigid
thiophene cores and the flexible side-chains assisted by
minor p-stacking interactions between the thiophene units.
A schematic model for the organization of 3T-p-Ph-C10 is
illustrated in Figure 4c.
Figure 3. Cyclic and differential pulse voltammograms of TDPE-function-
alized dendrons (a) and dendrimers (b).
and differential pulse voltammograms of the TDPE-func-
tionalized dendrimers. For the small dendrimer 6T-p-Ph-
C10, two reversible oxidation processes were detected. By
DPV measurement the corresponding oxidation potentials
were determined to be 0.57 and 0.66 V, respectively. DPV
measurement of the G2 dendrimer 18T-p-Ph-C10 gave the
first oxidative potential at 0.45 V. Similarly, a shoulder peak
at 0.43 V, which corresponds to the first oxidation potential
of 42T-p-Ph-C10, was found by DPV measurement of the
G3 dendrimer. In all cases, the oxidation potentials of the
DOT-p-TDPEs were negatively shifted compared with those
of the corresponding DOTs. This has been attributed to the
extended p-conjugation as well as to the electron-donating
properties of the trisACTHNUTRGNE(UNG alkyloxy)phenyl groups.
The HOMO/LUMO energy levels were calculated versus
the vacuum level according to Equations (1) and (2, see
onset
opt
below) in which Eox
and Eg represent the onset oxida-
tion and energy band gap determined by optical spectrosco-
py. The onset oxidation was measured relative to the Fc+/Fc
couple for which an energy level of ꢀ5.10 eV versus vacuum
was assumed.[34] The energy level data are summarized in
Table 1. These electrochemical results clearly show the
DOT-p-TDPE 6T-p-Ph-C10 assembled in a similar colum-
nar organization as 3T-p-Ph-C10 (Figure 5a). The derived
columnar unit cell for the crystalline phase is monoclinic
with the parameters a=3.81 nm and b=2.10 nm distorted
laterally by an angle of g=1038 relative to each other. The
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C.-Q. Ma, P. Bꢀuerle et al.
case we assume an out-of-plane tilt of the thiophenes. Inter-
estingly, the POM image of a thin layer crystallized between
glass slides from the isotropic melt shows a liquid crystalline
fan-shaped focal conic texture (Figure 5c) although the 2D
WAXS pattern clearly points towards a crystalline state of
6T-p-Ph-C10. A dark POM image without birefringence be-
tween cross-polarizers was observed after cooling the film
slowly at 0.18Cminꢀ1 (Figure 5d). The lack of birefringence
is characteristic of a homeotropic alignment, as reported for
various discotics,[39] in which the columnar axis is oriented
perpendicular to the surface. 2D WAXS of the aligned film
confirmed the homeotropic phase and revealed a typical
hexagonal arrangement of the columns. This unit cell also
differs from the lattice derived for the bulk fiber sample. In
the case of 6T-p-Ph-C10, the processing seems to play an es-
sential role in phase formation. Whereas the thin film is ob-
tained from the isotropic melt, the powder used for fiber ex-
trusion is precipitated from solution. To confirm this as-
sumption, the powder was first slowly cooled from the melt
and subsequently extruded. The 2D pattern of the melt-pro-
cessed fiber in Figure 5b is different to the initial one and in-
dicates less crystallinity and lower intracolumnar ordering.
The unit cell corresponds to the hexagonal columnar ar-
rangement (parameter ahex =4.06 nm) observed also for the
homeotropically aligned film. In conclusion, a crystalline or
liquid crystalline state is obtained for 6T-p-Ph-C10 depend-
ing on the processing conditions.
Figure 4. a) 2D WAXS and b) POM image with a l-plate at 258C (Inset:
without l-plate; scale bars: 100 mm) of a thin film of 3T-p-Ph-C10 cooled
at 0.18Cminꢀ1 from the isotropic melt. c) Schematic model for the organ-
ization. In the side view the intracolumnar packing is indicated and in
the top view the unit cell is shown. The yellow color highlights the aro-
matic core and the green color represents the aliphatic part in the periph-
ery. In the drawing the molecular arrangement is very simplified as a
higher disorder is present within the stacks.
Compounds with a larger thiophene core than 6T re-
vealed a different organization to that described above.
Figure 6 shows two representative 2D patterns for 9T-p-Ph-
C10 and 42T-p-Ph-C10, whereby 18T-p-Ph-C10 and 21T-p-
Ph-C10 give identical results. In all cases, a single small-
angle isotropic reflection was observed. In addition, POM
Figure 6. 2D WAXS of an extruded fiber of a) 9T-p-Ph-C10 and b) 42T-
p-Ph-C10.
Figure 5. Fiber 2D WAXS of an extruded powder of 6T-p-Ph-C10 ob-
tained from a) solution and b) the isotropic melt. POM images of a thin
film cooled from the isotropic melt at c) 1.0 and d) 0.18Cminꢀ1 (Inset:
2D WAXS of the film; scale bars: 100 mm).
images of the compounds remained black even at cooling
rates of 0.018Cminꢀ1. Both results imply the formation of
an isotropic superstructure. Indeed, it has been reported
that dendritic molecules with an extended size arrange into
isotropic or spherical shapes resulting in 3D cubic phases
and thus an isotropic organization.[40] For this series we
assume that above a critical size of 6T-p-Ph-C10, due to
high nonplanarity, the molecules assemble into such 3D
cubic lattices. However, the appearance of only a single re-
meridional reflection corresponds to an intracolumnar
period of 0.49 nm. The pronounced meridional arcs might
result from overlapping off-meridional reflections, which are
characteristic of the tilting of molecular units or of the
whole building block towards the stacking axis.[38] In this
1514
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ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 1507 – 1518

Dendritic Oligothiophenes
FULL PAPER
afterwards heated above the melting point using a heating stage. The 2D
WAXS experiments were performed by using a rotating anode (Rigaku
18 kW) X-ray beam with pinhole collimation and a two-dimensional Sie-
mens detector. A double-graphite monochromator for the CrKa radiation
(l=0.154) was used. The samples were prepared as thin filaments of
0.7 mm diameter by filament extrusion using a home-made miniextruder.
The sample was positioned perpendicular to the incident X-ray beam and
vertical to the 2D detector.
flection does not allow a detailed analysis of the X-ray scat-
tering data.
Conclusion
A series of peripherally trisACHTNUTRGNE(UNG decyloxy)phenylethynyl-func-
Syntheses: Phenylethyne Ph-C10-H was synthesized according to a litera-
ture procedure starting from 5-bromo-1,2,3-trimethoxybenzene (see the
Supporting Information).[32] 2-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxa-
borolane,[42] 2-bromo-5-trimethylsilylthiophene,[43] 3T-I (Scheme 2), 6T-I
(Scheme 2), 9T-I (Scheme 3), 18T-Br (Scheme 3) were prepared accord-
ing to literature procedures.[18b,22d]
tionalized thiophene dendrons and dendrimers have been
successfully synthesized by palladium-catalyzed Sonogashira
and Suzuki coupling reactions. Spectroscopic investigations
revealed that the trisACHTUNRGTNE(NUG decyloxy)phenylethynyl groups are
conjugatively linked to the oligothiophene core yielding in-
creased HOMO energy levels and smaller optical band gaps.
The self-assembly of these compounds in the bulk state
depend on the size and conformation of the conjugated den-
dritic oligothiophene cores. The lower-generation com-
pounds 3T-p-Ph-C10 and 6T-p-Ph-C10 form anisotropic col-
umnar stacks whereas the larger dendrons and dendrimers
assemble in isotropic 3D cubic structures owing to the in-
creased nonplanarity of the core unit. These results indicate
that the self-assembly of this type of p-conjugated molecule
can be controlled by a fine-tuning of the structure of the p-
conjugated unit. Characterization of these novel dendritic
structures in organic solar cells is underway in our laborato-
ries and will allow a better understanding of how specific
self-organization influences the usual structure–property re-
lationships.
General Sonogashira coupling reaction to 3T-p-Ph-C10 and 6T-p-Ph-C10
(Procedure A): A pre-degassed solution of Ph-C10-H in diisopropyla-
mine was added to a mixture of 3T-I or 6T-I, CuI (2%, per reaction
point), and [PdACTHNUTRGNEUNG(PPh3)2Cl2] (4%, per reaction point) in well-degassed dii-
sopropylamine. The reaction mixture was stirred at room temperature
overnight. The mixture was quenched with aqueous HCl (20 mL) and the
aqueous layer was extracted three times with diethyl ether. The com-
bined organic layers were dried over Na2SO4. The organic solvent was
then removed under reduced pressure and the residue was purified by
column chromatography.
General Suzuki coupling reaction to yield DOT-p-TDPEs (Procedure B):
Halogenated dendritic oligothiophene precursors (3T-I, 6T-I, 9T-I, and
18T-Br), B-3T-p-Ph-C10, [Pd2ACHTUNGRTNE(NUNG dba)3]·CHCl3 (2%, per reaction point),
and HP(tBu)3BF4 (4%, per reaction point) were mixed in THF and the
AHCTUNGTRENNUNG
resulting mixture was carefully degassed prior to the addition of well-de-
gassed aqueous K2CO3 solution (1m, 4 equiv per reaction point) at 08C.
Then the reaction mixture was warmed to room temperature and stirred
overnight. After that, the reaction mixture was quenched with ice-water
and the mixture was extracted with diethyl ether. The organic phases
were combined and the solvent was removed under vacuum. The residue
was purified by column chromatography.
3T-p-Ph-C10 (Scheme 1): Following general procedure A: Compound
3T-I (100 mg), Ph-C10-H (3.0 equiv, 340 mg), and diisopropylamine
(15 mL) were used. The product (237 mg, 86%) was obtained as a yellow
viscous solid after chromatography through a silica gel column with
CH2Cl2/hexane (1:5) as eluent. 1H NMR (CDCl3, 400 MHz): d=7.30 (d,
J=5.2 Hz, 1H), 7.15–7.16 (m, 2H), 7.16 (d, J=5.2 Hz, 1H), 7.03 (d, J=
3.6 Hz, 1H), 6.98 (d, J=5.2 Hz, 1H), 6.71 (brs, 4H), 3.97 (brt, 12H),
1.72–1.81 (m, 12H), 1.43–1.49 (m, 12H), 1.28–1.34 (m, 72H), 0.87–
0.90 ppm (brt, 18H); 13C NMR (CDCl3, 100 MHz): d=153.026, 139.420,
139.350, 138.544, 135.940, 131.963, 131.890, 131.795, 131.450, 129.812,
127.906, 126.725, 125.225, 124.806, 123.596, 117.149, 117.023, 109.998,
94.870, 94.394, 81.334, 81.109, 73.546, 69.178, 31.911, 30.329, 29.731,
29.671, 29.630, 29.586, 29.393, 29.343, 26.087, 22.680, 14.095 ppm; MS
(MALDI-TOF, DCTB): calcd for C88H136O6S3 [M+H]+: 1385.96; found:
1385.4; elemental analysis calcd (%) for C88H136O6S3: C 76.25, H 9.89, S
6.94; found: C 76.09, H 9.98, S 6.72.
Experimental Section
General procedures and instrumentation: Chemicals were purchased and
used without further purification: BBr3 (Merck), tetrabutylammonium
fluoride hydrate (TBAF, Merck), [Pd
A
ACHTUGNRTNE(NUNG PPh3)2Cl2]
(Merck), CuI (Merck), [Pd2dba3]·CHCl3 (Aldrich), HPAHCTUNGTRENNNUG
drich), nBuLi (1.6m in hexane, Aldrich), CuCl2 (Merck), and K2CO3
(Merck). Solvents were purified and dried by the usual methods prior to
use and typically used under an inert gas atmosphere.[41] Column chroma-
tography was performed on silica gel 60 (particle size 0.040–0.063 mm,
Merck 9385) and thin-layer chromatography (TLC) on Merck alumini-
um-backed plates coated with silica gel 60 F254 (layer thickness 0.2 mm).
Semipreparative recycling GPC purification of 42T-p-Ph-C10 was per-
formed on a Shimadzu SCL-8A CE equipped with an SPD-20A UV/VIS
detector CE (LV) and a LC-8A solvent delivery pump using two GPC
columns connected in series (SDP2060055E2 and SDP2060051E3, PSS,
Mainz). The columns were eluted with pure, freshly distilled THF on the
HPLC system. Gas chromatography was carried out by using a Varian
CP-3800 gas chromatograph. Routine NMR spectra were recorded on a
Bruker AMX 400 spectrometer (400 MHz for 1H, 100 MHz for 13C).
Chemical shifts (d) are given as ppm and are referenced to solvent sig-
nals as internal reference. The splitting patterns are designated as fol-
lows: s (singlet), d (doublet), t (triplet), and m (multiplet). Mass spectra
were recorded with a Varian Saturn 2000 GCMS and with a MALDI-
TOF MS Bruker Reflex 3 instrument using 1,8,9-trihydroxyanthrancene
(dithranol), trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-properylidene]ma-
lononitrile (DCTB), or tetracyanoquinodimethane (TCNQ) as matrix.
Elemental analyses (CHN) were performed on a Perkin–Elmer EA 2400
instrument. Melting points were determined with a Bꢁchi B-545 melting
point apparatus and are uncorrected. The mesophase behavior was inves-
tigated by using a ZEISS polarizing optical microscope (POM) equipped
with a UNKAM TMS 591 digital temperature control system. Each
sample was sandwiched between glass slides to form a thin film and was
6T-p-Ph-C10 (Scheme 1): Following general procedure A: Compound
6T-I (100 mg), Ph-C10-H (6.0 equiv, 340 mg) and diisopropylamine
(15 mL) were used. The product (270 mg, 97%) was obtained as a brown
viscous solid after column chromatography through a silica gel column
1
with CH2Cl2/hexane (1:4) as eluent. H NMR (CDCl3, 400 MHz): d=7.22
(s, 2H), 7.19 (d, J=3.72 Hz, 2H), 7.16 (d, J=3.80 Hz, 2H), 7.07 (d, J=
3.80 Hz, 2H), 7.03 (d, J=3.72 Hz, 2H), 6.72 (s, 4H), 6.71 (s, 4H), 3.95–
3.98 (brt, 24H), 1.83–1.70 (m, 24H), 1.42–1.50 (m, 24H), 1.20–1.40 (m,
144H), 0.86–0.89 ppm (brt, 36H); 13C NMR (CDCl3, 100 MHz): d=
152.996, 139.293, 139.238, 137.675, 135.341, 135.010, 132.090, 131.993,
131.954, 131.256, 127.762, 127.311, 126.784, 124.947, 124.105, 117.013,
116.903, 109.823, 95.281, 94.631, 81.177, 81.055, 73.530, 69.090, 31.934,
31.905, 30.305, 29.732, 29.671, 29.629, 29.584, 29.388, 29.349, 29.298,
26.074, 22.700, 22.684, 14.120 ppm; MS (MALDI-TOF, DCTB): calcd for
C176H270O12S6 [M+H]+: 2768.89; found: 2768.9; elemental analysis calcd
(%) for C176H270O12S6: C 76.30, H 9.82, S 6.94; found: C 76.04, H 9.91, S
6.78.
Chem. Eur. J. 2011, 17, 1507 – 1518
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
1515

C.-Q. Ma, P. Bꢀuerle et al.
Synthesis of 6T-p-Ph-C10 by oxidative homocoupling with BuLi/CuCl2:
Terthienyl 3T-p-Ph-C10 (237 mg, 0.17 mmol) was dissolved in dry THF
(4 mL). The reaction mixture was cooled to ꢀ788C and then nBuLi
(0.2 mL) was added dropwise. The reaction mixture was then stirred at
ꢀ788C for another hour. Then CuCl2 (92 mg, 0.68 mmol) was added di-
rectly. The reaction mixture was then allowed to slowly warm to room
temperature and stirred overnight. The solvent was removed on a rotary
evaporator and the residue was purified by chromatography on silica gel
with CH2Cl2/hexane (1:4) as eluent to yield the product (38 mg, 17%) as
a brown viscous solid. Starting material 3T-p-Ph-C10 (143 mg) was recov-
ered.
136.012, 135.670, 135.512, 135.434, 135.084, 133.857, 132.047, 132.005,
131.993, 131.938, 131.898, 130.960, 130.905, 130.613, 128.791, 128.147,
127.666, 127.645, 127.283, 127.238, 126.468, 126.227, 124.813, 124.757,
124.602, 124.570, 124.047, 123.993, 117.024, 116.931, 109.772, 95.222,
95.184, 94.595, 94.576, 81.217, 81.203, 81.092, 73.505, 69.056, 31.929,
31.902, 30.309, 29.730, 29.670, 29.627, 29.584, 29.392, 29.347, 29.298,
26.077, 22.694, 22.680, 14.115 ppm; MS (MALDI-TOF, DCTB): calcd for
C376H550O24S18 [M+H]+, average: 6031.7; found: 6031; elemental analysis
calcd (%) for C376H550O24S18: C 74.87, H 9.19, S 9.57; found: C 74.58, H
9.31, S 9.43.
21T-p-Ph-C10 (Scheme 1): Following general procedure A: Compound
9T-I (31 mg, 25 mmol), B-3T-p-Ph-C10 (171 mg, 85%, 96 mmol), [Pd2-
B-3T-p-Ph-C10 (Scheme 2): nBuLi (1.6m in hexane, 0.4 mL, 0.64 mmol)
was added dropwise to a solution of 3T-p-Ph-C10 (630 mg, 0.45 mmol) in
THF (40 mL) at ꢀ788C under argon. The reaction mixture was stirred at
this temperature for 2 h and then 2-isopropyloxy-4,4,5,5-tetramethyl-
1,3,2-dioxaborolane (144 mg, 0.77 mmol) was added dropwise. The reac-
tion was allowed to warm to room temperature and stirred overnight.
The reaction was quenched with saturated aqueous NH4Cl (15 mL) and
the organic layer was separated. The aqueous phase was extracted with
diethyl ether (3ꢃ15 mL) and the combined organic extracts were washed
with brine, water, and then dried over Na2SO4. After removal of the sol-
vent, the residue was used directly in further coupling reactions; 760 mg
of B-3T-p-Ph-C10 were obtained (1H NMR indicated a purity of 95%),
which corresponds to a yield of 88%. 1H NMR (CDCl3, 500 MHz): d=
7.63 (s, 1H), 7.17 (d, J=3.75 Hz, 1H), 7.15 (d, J=3.75 Hz, 1H), 7.05 (d,
J=3.75 Hz, 1H), 6.98 (d, J=3.75 Hz, 1H), 6.72 (s, 2H), 6.71 (s, 2H),
3.99–3.96 (m, 12H), 1.82–1.71 (m, 12H), 1.55–1.45 (m, 12H), 1.40–1.28
(m, 72H), 0.90–0.87 ppm (m, 18H); 13C NMR (CDCl3, 125 MHz): d=
152.997, 139.721, 139.376, 139.288, 138.461, 138.295, 135.975, 132.649,
131.966, 131.936, 127.745, 126.951, 124.939, 123.715, 117.148, 116.991,
109.953, 95.071, 94.326, 84.478, 81.342, 81.110, 73.518, 69.140, 67.937,
31.899, 30.314, 29.719, 29.659, 29.619, 29.574, 29.381, 29.333, 26.074,
24.735, 22.685, 22.669, 14.086 ppm; MS (MALDI-TOF, DCTB): calcd for
C93H145BO8S3 [M+H]+: 1497.03; found: 1497.5; elemental analysis calcd
(%) for C93H145BO8S3: C 74.56, H 9.76, S 6.42; found: C 74.80, H 9.93, S
5.93.
ACHTUNGRENN(UG dba)3]·CHCl3 (1.9 mg, 1.84 mmol), and HPAHCTUNGTREN(NUNG tBu)3BF4 (1.1 mg, 3.79 mmol)
were used. The product (96 mg, 61%) was obtained as a dark-red viscous
solid by size-exclusion chromatography (SEC, Bio-Rad Beads, SX-1)
eluting with THF. 1H NMR (CDCl3, 400 MHz): d=7.31 (d, J=5.28 Hz,
1H), 7.19–7.15 (m, 10H), 7.13–7.07 (m, 15H), 7.05–7.04 (m, 3H), 7.02–
7.01 (brd, 4H), 7.00–6.98 (brd, 4H), 6.71 (brs, 8H), 6.70 (brs, 8H), 3.98–
3.94 (m, 48H), 1.71–1.83 (m, 48H), 1.44–1.48 (m, 48H), 1.28–1.42 (m,
288H), 0.87–0.90 ppm (m, 72H); 13C NMR (CDCl3, 100 MHz): d=
152.955, 139.212, 139.155, 137.849, 137.749, 137.293, 137.240, 137.165,
137.007, 136.433, 136.411, 136.395, 136.324, 136.229, 136.080, 136.050,
136.035, 135.908, 135.727, 135.704, 135.522, 135.439, 134.383, 134.102,
134.014, 131.960, 131.926, 131.873, 131.637, 131.168, 130.784, 130.757,
130.492, 130.321, 130.069, 128.800, 128.543, 127.970, 127.645, 127.608,
127.264, 127.216, 126.348, 126.330, 126.128, 124.756, 124.691, 124.546,
124.524, 124.004, 123.943, 117.030, 116.935, 109.739, 95.200, 95.175,
94.582, 81.256, 81.229, 81.126, 81.107, 73.487, 69.032, 31.900, 30.312,
29.730, 29.669, 29.628, 29.586, 29.394, 29.348, 29.300, 26.080, 22.678,
14.111 ppm; MS (MALDI-TOF, DCTB): calcd for C388H556O24S21
[M+H]+, average: 6279.1; found: 6278; elemental analysis calcd (%) for
C388H556O24S21: C 74.23, H 8.93, S 10.73; found: C 74.41, H 9.02, S 12.98.
42T-p-Ph-C10 (Scheme 1): Following general procedure B: Compound
18T-Br (21 mg, 10 mmol), B-3T-p-Ph-C10 (174 mg, 85%, 98 mmol), [Pd2-
ACHTUNGRENN(UG dba)3]·CHCl3 (2.2 mg, 2.13 mmol), and HPAHCTUNGTREN(NUNG tBu)3BF4 (1.2 mg, 4.14 mmol)
were used. The product (85 mg, 68%) was obtained as a dark-red viscous
solid by recycling semipreparative GPC. 1H NMR ([D8]THF, 500 MHz,
300 K) d=7.55 (s, 2H), 7.43 (s, 2H), 7.42 (s, 2H), 7.34–7.36 (m, 12H),
7.28–7.29 (m, 12H), 7.21–7.22 (m, 8H), 7.16–7.18 (m, 16H), 7.11–7.13 (m,
16H), 3.91–3.93 (m, 96H), 1.46–1.51 (m, 96H), 1.30–1.45 (m, 576H),
0.81–0.89 ppm (m, 144H) (note: resonance peaks of b-H of the decyloxy
chain overlap with the solvent peak of THF); 13C NMR ([D8]THF,
100 MHz, room temperature) d=154.318, 140.851, 140.771, 138.714,
138.626, 138.509, 138.452, 137.657, 137.615, 137.351, 136.963, 136.325,
136.297, 136.219, 135.115, 135.070, 133.560, 133.511, 133.010, 132.928,
131.733, 131.430, 131.244, 130.514, 130.259, 130.220, 129.322, 129.266,
128.885, 128.817, 127.786, 127.723, 127.595, 127.292, 127.259, 126.336,
126.272, 125.904, 125.526, 125.500, 118.059, 117.924, 110.833, 96.608,
95.949, 81.828, 81.808, 81.639, 81.622, 73.923, 69.910, 33.151, 33.128,
31.610, 31.007, 30.926, 30.895, 30.838, 30.633, 30.580, 27.379, 27.340,
23.818, 14.724 ppm; MS (MALDI-TOF, TCNQ): calcd for C776H1110O48S42
[M+H]+, average: 12555; found: 12554; elemental analysis calcd (%) for
C776H1110O48S42: C 74.24, H 8.91, S 10.73; found: C 74.31, H 9.01, S 9.53.
9T-p-Ph-C10 (Scheme 1): Following general procedure B: Compound
3T-I (140 mg, 280 mmol), B-3T-p-Ph-C10 (920 mg, 614 mmol), [Pd2-
ACHTUNGTRENNUNG(dba)3]·CHCl3 (25 mg, 24 mmol), and HPAHCUTGNTREN(NUGN tBu)3BF4 (13 mg, 46 mmol) were
used. The product (690 mg, 82%) was obtained as a brown viscous solid
by size-exclusion chromatography (SEC, Bio-Rad Beads, SX-1) eluting
with THF. 1H NMR (CDCl3, 400 MHz): d=7.33 (d, J=5.28 Hz, 1H), 7.18
(d, J=5.28 Hz, 1H), 7.16–7.18 (m, 4H), 7.14–7.15 (m, 3H), 7.12–7.13 (d,
J=3.80 Hz, 1H), 7.10–7.09 (d, J=3.80 Hz, 1H), 7.03–7.05 (m, 3H), 7.00–
7.01 (brd, 2H), 6.71 (s, 4H), 6.70 (s, 4H), 3.97–3.95 (brt, 24H), 1.70–1.83
(m, 24H), 1.42–1.47 (m, 24H), 1.29–1.40 (m, 144H), 0.86–0.89 ppm (m,
36H); 13C NMR ([D8]THF, 100 MHz): d=152.982, 139.253, 139.198,
137.935, 137.845, 137.293, 137.053, 136.203, 136.059, 135.884, 135.609,
135.523, 134.422, 133.112, 132.004, 131.960, 131.914, 131.678, 131.197,
130.699, 130.445, 128.824, 127.652, 127.599, 127.530, 127.237, 127.212,
126.374, 126.123, 125.332, 124.764, 124.684, 124.608, 124.572, 123.985,
123.940, 117.041, 116.939, 109.796, 95.170, 95.129, 94.554, 94.535, 81.229,
81.115, 81.100, 73.520, 69.074, 31.935, 31.907, 30.308, 29.733, 29.673,
29.630, 29.587, 29.391, 29.351, 29.298, 22.701, 22.686, 14.122 ppm; MS
(MALDI-TOF, DCTB): calcd for C188H276O12S9 [M+H]+: 3014.86; found:
3014.6; elemental analysis calcd (%) for C188H276O12S9: C 74.85, H 9.22, S
9.57; found: C 74.75, H 9.32, S 9.72.
Acknowledgements
18T-p-Ph-C10 (Scheme 1): Following general procedure A: Compound
6T-I (39 mg, 39 mmol), B-3T-p-Ph-C10 (330 mg, 85%, 185 mmol), [Pd2-
ACHTUNGTRENNUNG(dba)3]·CHCl3 (3.5 mg, 3.38 mmol), and HPCAHTUNGTREN(NUNG tBu)3BF4 (1.8 mg, 6.31 mmol)
We acknowledge the financial support from the Deutsche Forschungsge-
meinschaft (DFG).
were used. The product (183 mg, 78%) was obtained as a brown viscous
solid by size-exclusion chromatography (SEC, Bio-Rad Beads, SX-1)
eluting with THF. 1H NMR (CDCl3, 400 MHz): d=7.27 (s, 2H), 7.19 (s,
2H), 7.18–7.16 (m, 8H), 7.15–7.14 (m, 8H), 7.10–7.11 (d, J=3.68 Hz,
2H), 7.05–7.04 (m, 4H), 7.02–7.10 (m, 4H), 6.71 (brs, 8H), 6.70 (brs,
8H), 3.97–3.94 (brt, 48H), 1.83–1.70 (m, 48H), 1.46–1.42 (m, 48H), 1.40–
1.22 (m, 288H), 0.89–0.86 ppm (m, 72H); 13C NMR (CDCl3, 100 MHz):
d=152.971, 139.243, 139.190, 137.844, 137.744, 137.492, 136.640, 136.169,
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