Star-shaped perylene-oligothiophene-triphenylamine hybrid systems for photovoltaic applications

Article abstract of DOI:10.1039/b515657b

A series of novel star-shaped donor-acceptor systems is described. These molecules consist of three head-to-tail coupled oligo(3-hexylthiophene) arms covalently linked to a triphenylamine core which acts as the donor part. At the termini perylene monoimid

Full text of DOI:10.1039/b515657b

View Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/materials | Journal of Materials Chemistry
Star-shaped perylene–oligothiophene–triphenylamine hybrid systems for
photovoltaic applications
Jens Cremer and Peter B a¨ uerle*
Received 3rd November 2005, Accepted 29th November 2005
First published as an Advance Article on the web 21st December 2005
DOI: 10.1039/b515657b
A series of novel star-shaped donor–acceptor systems is described. These molecules consist of
three head-to-tail coupled oligo(3-hexylthiophene) arms covalently linked to a triphenylamine
core which acts as the donor part. At the termini perylene monoimide moieties are attached as
acceptors. These hybrid molecules, which differ by the length of the oligothiophene units, were
effectively synthesized via palladium-catalyzed Suzuki-type couplings. Their optical and
electrochemical properties were determined and structure–property relationships were established,
clearly demonstrating the influence of the length of the integrated oligothiophene chains on the
electronic nature of these hybrid systems.
attached to the termini of the OT chains should provide
Introduction
high absorptivity in the visible region as well as electron
p-Donor p-acceptor systems are considered to be promising
accepting properties. Furthermore, the intrinsic three-fold
candidates for applications in organic electronics, in particular
excess of acceptor over donor units present in these star-
in photovoltaic applications, converting sunlight into electrical
shaped molecules should facilitate photoinduced charge trans-
energy. The field of organic photovoltaics has made
1
fer and better meet the requirements found for conjugated
tremendous progress over the last ten years accompanied by
polymer– or oligomer–fullerene bulk-heterojunction solar cells
2
a rapid increase in energy conversion efficiencies. To
where the power conversion efficiency strongly depends on the
contribute to this field of research, we recently reported the
ratio of donor and acceptor in the photoactive layer and the
11
fullerene derivative typically is used in excess. The dependence
synthesis of linear perylenyl–oligothiophene dyad and triad
3
molecules which combine the outstanding electronic pro-
of the optical and electrochemical properties of the star-shaped
systems on the OT chain length, which varied from two to six
thiophene units in each branch, was investigated. Based on
these optical and electrochemical characterization structure–
property relationships have been established.
4
perties and thermal stability of perylene (Per) dyes with those
5
of structurally defined oligo(3-hexylthiophene)s. This novel
type of donor acceptor system is characterized by a broad
absorption within the terrestrial sun spectrum and correspond-
ing bulk-heterojunction photovoltaic devices showed promis-
3
ing power conversion efficiencies and are superior to
6
previously reported organic solar cells based on perylenes.
Results and discussion
Triphenylamine and its derivatives have been widely investi-
gated for the use in organic electronics, because they are
characterized by good optical properties and p-type charge
Synthesis
In the series of perylene-functionalized head-to-tail coupled
oligo(3-hexylthiophene)s, iodinated Per-OTs 4, 6, and 8 were
employed as intermediate products for the elongation of the
OT chain and were accessible via an effective mercury-
7
transport mobilities, allowing their use as hole-transport
8
layers in organic field-effect transistors (OFET) or organic
9
light emitting diodes (OLED). In this respect, p-type con-
3
a
mediated iodination procedure. In this approach, we utilized
iodinated Per-OTs 4, 6, and 8 as starting materials for an
optimized palladium-catalyzed Suzuki reaction, furnishing
star-shaped Per-OT-TPAs 5, 7, and 9 in good yields. Prior
to their synthesis, TPA boronic ester 3 as the core building
block had to be prepared. The synthetic route started from
commercially available TPA 1 which was reacted with bromine
ductive star-shaped molecules have been recently synthesized
combining triphenylamines (TPA) and oligothiophene (OT)
1
0
chains attached to the central core.
Here, we report the synthesis of a series of star-shaped
perylenyl–oligothiophene–triphenylamines (Per-OT-TPA) 5, 7,
and 9. In contrast to our original linear perylenyl–oligothiophenes
3
a
(
Per-OT), this novel type of p-donor p-acceptor hybrid system
in chloroform at 0 uC to give tris(4-bromophenyl)amine 2 in
was designed in a way that an extended donor part consisting of
a TPA core and OT arms should preserve the typical p-type
charge transport properties in the solid state, whereas the perylene
12
6% yield after recrystallization. Next, it was converted into
8
the corresponding TPA boronic ester 3 by firstly treating
tris(4-bromophenyl)amine 2 with n-butyllithium (n-BuLi) in
THF at 280 uC. Subsequent addition of 2-isopropoxy-4,4,5,5-
tetramethyl-[1,3,2]dioxaborolane afforded boronic ester 3 in
units,
[N-(2,6-diisopropylphenyl)]-perylene-3,4-dicarboximide,
Department Organic Chemistry II (Organic Materials and
Combinatorial Chemistry), University of Ulm, Albert-Einstein-Allee 11,
89081 Ulm, Germany. E-mail: peter.baeuerle@uni-ulm.de;
Fax: (+49) 731-50-22840
5
4% yield after recrystallization, making this synthetic route
superior in comparison with the literature procedure which
1
reported a yield of only 18%.
3
8
74 | J. Mater. Chem., 2006, 16, 874–884
This journal is ß The Royal Society of Chemistry 2006

View Online
In order to obtain Per-OT-TPAs 5, 7, and 9 a thoroughly
In order to thoroughly elucidate the physical properties of
Per-OT-TPAs 5, 7, and 9 reference system 2T-TPA 13 has
been synthesized in which the terminal reactive a-positions of
the bithiophene units were blocked by a methyl group in order
to prevent oxidative coupling processes. The synthesis was
optimized three-fold palladium-catalyzed Suzuki-type reaction
3a
was carried out. In this respect, iodinated Per-OTs 4, 6, and 8
were reacted with TPA boronic ester 3 in DME at 80 uC, using
a 2 M aqueous sodium hydroxide solution as base and 15 mol%
3
a
Pd(PPh
2% yield.
The higher homologues, quaterthiophene 7 and sexithio-
3
)
4
as catalyst, furnishing star-shaped Per-OT-TPA 5 in
derived from brominated bithiophene 10
which firstly
6
was treated with n-BuLi in THF at 280 uC and secondly
was reacted with trifluoromethansulfonate to give methylated
bithiophene 11 in 70% yield after distillation in vacuo. Next, 11
was selectively brominated at the free a-position with NBS in
DMF at 0 uC. After filtration over silica, bithiophene 12 was
accessible in 97% yield.
phene 9, were accessible under the same conditions in 54%
and 45% yield, respectively. The obtained yields correspond to
7
7–85% efficiency per coupling step.
These materials show high melting points ranging from
45–146 uC (9) to 192–193 uC (7) and to 247–248 uC (5). The
1
In the third step, Suzuki coupling of TPA boronic ester 3
and bromobithiophene 12 was carried out at room tempera-
highest melting point of the shortest representative Per-2T-
TPA 5 is due to the predominant influence of the perylene
units which as a pristine material is likely to form crystalline
ture in the presence of the catalytic system Pd
16
2
(dba)
3
/
3 4
H[P(t-Bu) ]BF ,
yielding 74% of 2T-TPA 13 after column
1
4
phases with high phase transition temperatures.
With
chromatography.
increasing length of the integrated oligothiophene chains in 7
and 9 the attached hexyl side chains aggravate the tendency of
the perylene moieties to crystallize. In this respect, an increased
number of alkyl side chains in these hybrid systems signifi-
cantly decreases the corresponding melting points. In addition,
it is well known that triphenylamine and its derivatives form
Optical properties
For the series of Per-OT-TPAs 5, 7, and 9 and reference
compound 13 optical and redox properties were determined
and an energy level diagram of the frontier orbitals was
deduced from the data set. The absorption and emission
maxima, fluorescence quantum yields and the optical energy
gaps for the series are given in Table 1 and compared to the
1
5
amorphous phases. However, detailed DSC investigations on
the hybrid systems 5, 7 and 9 showed no glass transitions and
accordingly they do not possess amorphous character.
This journal is ß The Royal Society of Chemistry 2006
J. Mater. Chem., 2006, 16, 874–884 | 875

View Online
8
76 | J. Mater. Chem., 2006, 16, 874–884
This journal is ß The Royal Society of Chemistry 2006

View Online
3a
parent linear Per-OTs. The energy gaps were determined
from the onset of the longest wavelength absorption band
of the hybrid molecules. This set of data allows for the
establishment of clear structure–property relationships which
typically depend on the inverse chain length of the correspond-
1
7
ing conjugated p-systems.
The absorption spectra of Per-OT-TPAs 5, 7 and 9 are
dominated by intense and weakly structured absorption bands
arising from the perylene units on one hand and the TPA-OT
donor unit on the other hand (Fig. 1). The bands at lowest and
highest energy originate from the excitation of the perylene
abs
3
abs
moieties. Their maxima (l
= 520–519 nm, l
1
= 266 nm)
are practically identical for all three compounds and indepen-
dent of the chain length of the OT branches resulting in a
constant optical band gap of DEopt = 2.11 eV. This behaviour
is directly comparable to that of the parent linear Per-OTs
(
Table 1) and indicates that donor and acceptor units are
electronically decoupled which is due to steric interactions. As
expected, these bands are completely missing in reference
2
T-TPA 13. Whereas the perylene absorption band at high
energies does not alter in shape, with increasing chain length
of the OT branches the vibronic distribution of the low energy
p–p* transition is changed. This effect arises from the
superposition of the third band in the absorption spectra in
the region between 350 and 500 nm which come from the p–p*
transition of the donor part. With increasing OT chain length
abs
their maxima are bathochromically shifted (l
2
= 404–
4
38 nm) as well in comparison to the parent linear Per-OTs
abs
(Dl
= 104–30 nm). These strong shifts which become
2
gradually less pronounced on going from 5 to 7 to 9 clearly
indicate that the TPA core and the OT branches are in full
p-conjugation and have to be considered as the donor system.
This assumption is further supported, firstly, by the absence of
absorption around 300 nm that can be ascribed to pristine
abs
TPA (l = 304 nm) and, secondly, by the comparison of the
intensities of the donor absorptions with those of the parent
linear Per-OTs and reference compound 2T-TPA 13. The
latter exhibits similar optical properties to those of the donor
system of 5. We note that the extinction coefficients for the
Fig. 1 UV-Vis spectra of perylenyl–oligothiophene–triphenylamines
5
, 7, and 9 and reference compound 13 in chloroform (c = 5 6
25 21
1
0
mol l ).
This journal is ß The Royal Society of Chemistry 2006
J. Mater. Chem., 2006, 16, 874–884 | 877

View Online
star-shaped systems are more than three times higher than
expected and arise from the extension of the Per-OT p-system
by the TPA unit. This effect is most pronounced for the
smallest homologue, Per-OT-TPA 5, exhibiting a value of
luminescence is an indication for photoinduced charge transfer
processes occurring within these hybrid systems and has been
confirmed by time-resolved emission and transient absorption
2
0
spectroscopy. This finding is in full accordance with the
parent linear Per-OTs which also have been extensively investi-
21
2
1
21
e = 79000 L mol cm which is by a factor of 4.9 higher than
2
1
21
for parent linear Per-OTs (e = 16100 L mol cm ).
For the solid-state absorption spectra of Per-OT-TPAs 5, 7,
and 9 thin films were spin-coated onto glass substrates from
gated by time-resolved optical measurements. Furthermore,
reference compound 2T-TPA 13 without acceptor moieties
shows an intense emission at 460 nm and a relatively high
22
fluorescence quantum yield of 65%.
2
1
the corresponding toluene solutions (c = 20 mg ml ). The
absorption spectra in the solid state (Fig. 2) show the same
trends as the solution spectra. In general, broadening and red-
shifts of the bands are visible, resulting in smaller band gaps
by 0.10 eV. No displacement is observed for the perylene
absorption maxima, whereas a shift of the p–p* transition of
the donor part is observed for Per-4T-TPA 7 (Dlmax = 17 nm)
and Per-6T-TPA 9 (Dlmax = 27 nm). This behaviour is very
Electrochemical properties
Oxidation and reduction potentials of Per-OT-TPAs 5, 7, 9
and reference compound TPA-2T 13 were measured by cyclic
voltammetry (CV) in dichloromethane using tetrabutylammo-
nium hexafluorophosphate as the supporting salt and are
referenced to the internal standard ferrocene/ferrocenium
+
Fc/Fc ) (Fig. 3). The redox potentials and the electrochemi-
3
18
typical for oligo- and polythiophenes and very favourable
for applications in solar cells, because in particular the larger
members 7 and 9 in the series cover a broad range of the visible
spectrum between 250 and 650 nm with high optical densities.
In contrast, Per-2T-TPA 5 shows only a small displacement
(
cally determined band gaps DECV, measured as the potential
difference between the onset of the first oxidation and the first
reduction wave, respectively, are given in Table 2. In order to
deduce structure–property relationships the individual redox
waves of 5, 7, and 9 are compared to those of the parent linear
of the donor absorption maximum in the solid-state (Dlmax
nm), which is in accordance with reference 2T-TPA 13
exhibiting an identical solid-state absorption maximum
=
4
3a
Per-OTs and reference 13.
Per-OT-TPAs 5, 7, and 9 exhibit two reversible reductions
(lmax = 404 nm).
(Eured1 = 21.43 V, Eured2 = 21.88 V) irrespective of the OT
Corrected emission spectra for the whole series of com-
chain length, indicating the formation of stable radical anions
and dianions, respectively, at the perylene moieties. Due to the
electron withdrawing nature of the carbonyl oxygens, the
pounds were measured in chloroform (Table 1). Per-OT-TPAs
, 7, and 9 exhibit very weak, non-structured and broad
5
emission bands. With increasing length of the oligothiophene
units the fluorescence maxima are gradually blue-shifted, as
bithiophene 5 reveals an emission maximum at lmax = 630 nm,
quaterthiophene 7 at lmax = 595 nm and sexithiophene 9 at
23
anions are mainly located at the imide groups. The high
currents observed during the reductions give rise to a transfer
of three electrons, simultaneously generating a stable radical
lmax = 573 nm. This rather unexpected behaviour has already
been found for the parent linear Per-OTs and will be discussed
1
9
in detail in a forthcoming paper. Irrespective of the OT
chain length the fluorescence quantum yields are extremely
low with values around 1%. The quenching of the acceptor
Fig. 3 Electrochemical characterization of the perylenyl–oligothio-
phene–triphenylamines 5, 7, and 9 and reference compound 13 in
Fig. 2 Solid-state UV-Vis spectra of thin films of the perylenyl–
oligothiophene–triphenylamines 5, 7, and 9 and reference compound
2
dichloromethane/TBAHFP (0.1 M), scan speed 100 mV s , potentials
1
+
vs. Fc/Fc . Dashed lines correspond to redox processes of the perylene
13 spin-coated on glass (normalized to the maximum of the perylene
absorption band).
unit, dotted lines to those of the oligothiophene unit.
8
78 | J. Mater. Chem., 2006, 16, 874–884
This journal is ß The Royal Society of Chemistry 2006

View Online
Table 2 Electrochemical properties of perylenyl–oligothiophene–triphenylamines 5, 7, 9 and reference compound 13. P denotes perylene, D donor
(triphenylamine + oligothiophene)
a
a
a
a
a
a
a
b
Compound Eured2 (P)/V
Eured1 (P)/V
Euox5 (P)/V
Euox1 (D)/V
Euox2 (D)/V
Euox3 (D)/V
Euox4 (D)/V
DECV/V
1
5
7
9
a
3 (2T)
(2T)
(4T)
0.23
0.29 (0.71)
0.24 (0.43)
0.22 (0.31)
0.49
0.56 (1.20)
0.38 (0.71)
0.29 (0.45)
0.66
0.77
0.44
0.79
0.96
0.64
0.73
c
21.88 (21.87)
d
e
f
c
21.43 (21.42)
d
e
f
c
1.20 (1.06)
d
d
d
e
f
1.55 (2.02)
1.48 (1.70)
1.47 (1.59)
c
21.89 (21.87)
c
21.44 (21.42)
c
1.11 (1.17)
e
f
e
e
c
21.88 (21.88)
c
21.43 (21.42)
c
0.97 (1.01)
f
f
f
g
(6T)
0.41 (1.19)
+
(0.1 M) vs. Fc/Fc at 100 mV s
21 b
.
In dichloromethane/n-Bu Determined by DECV = E9ox1 2 E9red1 (E9 is the potential at which the
e
redox process starts). Three electron process. For comparison in parentheses values for the parent linear perylenyl–bithiophene. perylenyl-
4
NPF
6
c
d
f
3a
quaterthiophene. perylenyl-sexithiophene.
anion and dianion on each perylene moiety, respectively. A
direct comparison to the parent linear Per-OTs reveals that the
reduction waves are located at exactly the same potentials
revealing that the electronic properties of the perylene subunits
in 5, 7 and 9 are in excellent agreement with those of the linear
Per-OTs. Since these values are very close to those of pure
electron-withdrawing perylene units by the weakly donating
methyl groups, which stabilize the various cationic species
generated during the oxidation steps.
In the case of the higher homologues, Per-OT-TPAs 7 and 9,
similar electrochemical properties of the donor systems can be
found. The CVs also show four oxidation waves demonstrat-
ing full p-conjugation within the OT-TPA donor systems
which, as a result of the more extended p-systems, gradually
decline in potential the longer the OT chain length becomes.
A comparison of the first oxidation potentials (Euox1) of the
OT units in parent linear Per-OTs with those of the donor
units in corresponding Per-OT-TPAs 5, 7, and 9, reveals that
in the latter cases Euox1 is considerably shifted to lower
potentials. This potential shift is most pronounced in the case
of bithiophene 5 (DEuox1 = 0.42 V) and gradually decreases
3
perylenes, in accordance with the optical measurements, a full
electronic decoupling from the donor system and no influence
of the OT-TPA core on the electronic properties of the
perylene subunits can be noted. As expected from the large
optical band gap DEopt., reference compound 2T-TPA 13
shows no reduction waves in the negative potential regime.
In the positive potential regime, all Per-OT-TPAs 5, 7 and 9
show complex CVs and multiple redox waves, because there is
interference and complicated mutual influence of the perylene
with the OT-TPA oxidation processes. The detailed analysis
of the various redox transitions and the assignment of the
individual redox waves becomes possible by comparison to
the CVs of parent linear Per-OTs and to those of reference
with increasing oligothiophene chain length (7: DEuox1
=
0.19 V; 9: DEuox1 = 0.09 V) indicating a diminished electronic
influence of the TPA core with increasing size of the
conjugated donor systems.
2
T-TPA 13.
Oxidation of the perylene moieties in Per-OT-TPAs 5, 7,
and 9 is found at more positive potentials than the OT waves
(Euox = 1.20 V (5), 1.11 V (7), 0.97 V (9)) in which the process
is facilitated with increasing OT chain length. The values are
Per-2T-TPA 5 shows five reversible oxidation waves at
Euox1 = 0.29 V, Euox2 = 0.56 V, Euox3 = 0.77 V, Euox4 = 0.96 V
and Euox5 = 1.20 V. The first four oxidation processes are
single-electron transfers and can be assigned to the oxidation
of the OT-TPA donor moiety, whereas the fifth originates
from the oxidation of the terminal perylene acceptors. The first
oxidation wave is significantly negatively shifted with respect
to pristine TPA (DEuox = 0.24 V) and to the linear Per-2T
3a
comparable to those of the parent linear and dimeric Per-
3b
OTs. This mutual influence originates from an electronic
interaction occurring during the subsequent oxidation pro-
cesses in which the OT-TPA donor system is oxidized prior to
the perylene unit and accordingly an electron-withdrawing
tetracation is formed. Compared to the oxidation of pristine
(
DEuox = 0.42 V). This result indicates, in accordance with the
3
a
optical properties, that the donor system of 5 is characterized
by a strong p-conjugation between the TPA core and the
adjacent bithiophene units. Moreover, the absence of an
additional oxidation wave at around 0.5 V due to the
oxidation of the pure TPA unit also alludes to a completely
p-conjugated OT-TPA donor system. If the donor system
would be decoupled and divided into a TPA core and three
discrete OT subunits, then oxidation waves similar to those of
the linear Per-OTs but corresponding to the transfer of three
electrons plus one for the oxidation of pure TPA as a one-
electron process would be observed.
perlyene monoimide PDCI (Euox = 0.95 V) this effect is
most pronounced for Per-OT-TPAs 5 (DEuox = 0.21 V)
because the tetracation is delocalized on the smallest donor
system and therefore has the highest charge density. For the
higher homologues 7 and 9 corresponding tetracations are
delocalized over larger p-systems reducing their electron
withdrawing capacity and therefore show smaller potential
differences (DEuox = 0.12 V (7), 0.02 V (9)).
The electrochemical band gaps DECV were determined from
the CVs by taking the difference between the onset of the first
oxidation and reduction process, respectively (Table 2). In this
series the band gap is almost constant and shows only a weak
decrease from Per-2T-TPA 5 (DECV = 1.55 eV) to Per-6T-TPA
9 (DECV = 1.47 eV) reflecting the decreasing oxidation
potential of the OT subunit. The electrochemically determined
band gaps deviate from the optically determined gaps, because
they take donor oxidation and perylene reduction into
account, whereas the latter ones represent the electronic
properties of the decoupled perylene unit.
A mimic of the electrochemical behaviour of the donor
system can be found in reference 2T-TPA 13, showing four
reversible oxidation waves at Euox1 = 0.23 V, Euox2 = 0.49 V,
Euox3 = 0.66 V, and Euox4 = 0.79 V, as well as a fifth
irreversible wave at Euox5 = 1.17 V. The oxidation processes
in 2T-TPA 13 are slightly facilitated in comparison to Per-2T-
TPA 5 (DEuox1 = 0.06 V, DEuox2 = 0.07 V, DEuox3 = 0.11 V,
DEuox4 = 0.17 V) due to the replacement of the terminal
This journal is ß The Royal Society of Chemistry 2006
J. Mater. Chem., 2006, 16, 874–884 | 879

View Online
in energy to inject electrons to both, the LUMO of PCBM
and of the aluminium anode. It is also evident from the
energy diagram that the LUMO of reference TPA-2T 13
lies significantly higher in energy compared to those of
Per-OT-TPAs 5, 7, and 9 due to the absence of the perylene
acceptors.
In a standardized setup, a first bulk-heterojunction device
was manufactured, consisting of a PEDOT : PSS-covered ITO
cathode, a 1 : 4 mixture of Per-4T-TPA 7 and [6,6]-phenyl-C61
-
butyric acid methyl ester (PCBM) as the photoactive layer and
a top anode of aluminium. This device exhibited a photo-
response with an open-circuit voltage of V = 0.60 V, a short-
OC
22
circuit current of ISC = 1.4 mA cm and a fill factor of FF =
Fig. 4 MO energy level diagram scheme for the perylenyl–oligothio-
phene–triphenylamines 5, 7, and 9 and reference compound 13.
0.29, resulting in a power conversion efficiency of 0.25% under
2
2
)
calculated standard test conditions (AM 1.5 G, 1000 W m
(
Fig. 5). These solar cells are not yet fully optimized and their
MO energies
stability under sunlight has not yet been determined.
MO energy diagrams are very helpful for the construction and
understanding of organic devices in which the fundamental
processes are decisively determined by charged states and their
Conclusions
2
4
We synthesized a series of star-shaped hybrid systems with a
novel molecular architecture consisting of three terminal
perylene monoimides covalently attached to an extended
donor system which itself is delocalized over a triphenylamine
core and three adjacent head-to-tail coupled oligo(3-hexylthio-
phene)s. While the type of perylene acceptor remained
unchanged the oligothiophene donor system was system-
atically varied in length from a bithiophene to a sexithiophene.
These novel donor–acceptor systems were obtained by an
optimized palladium-catalyzed Suzuki-type reaction. Detailed
investigations of the electronic properties of the series in
solution and in the solid state clearly revealed that there is a
systematic change in the spectral range of absorption, redox
potentials and energy gaps. Clear structure–property relation-
ships of the novel type of donor–acceptor molecules provide a
valuable data set for their application in organic solar cells.
The fabrication and characterization of a first corresponding
photovoltaic device based on a blend of Per-4T-TPA 7 with
PCBM revealed a non-optimized power conversion efficiency
of 0.25% under a simulated terrestrial sun spectrum.
corresponding energy level in the active organic layer. In
order to calculate the absolute energies of the HOMO and
LUMO levels of Per-OT-TPAs 5, 7, 9 and reference compound
2
T-TPA 13 with respect to the vacuum level, the redox data are
standardized to the ferrocene/ferrocenium couple which has a
5
calculated absolute energy of 24.8 eV.
2
In the energy diagram (Fig. 4), Per-OT-TPAs 5, 7, 9 and
reference 13 are related to the electrode work functions
commonly used for the fabrication of standard photovoltaic
devices. The HOMO–LUMO band gaps of the hybrid systems
5, 7 and 9 only slightly decrease with increasing chain length
of the OT unit which is due to a gradual decrease of the
HOMO energy level while those of the LUMO stay constant.
The HOMO levels of the hybrid molecules are lower in energy
with respect to the work function of a PEDOT-covered ITO
electrode, therefore allowing holes to be easily injected
from the cathode into the photoactive layer. In order to fulfil
the requirement for the fabrication of single-layer or fullerene
bulk-heterojunction photovoltaic devices, hybrid molecules
5, 7, and 9 exhibit LUMO levels which are sufficiently high
Fig. 5 Linear (left) and logarithmic (right) U/I characteristic of the photovoltaic device fabricated from 7 and PCBM (1 : 4 w/w ratio of 7 : PCBM).
8
80 | J. Mater. Chem., 2006, 16, 874–884
This journal is ß The Royal Society of Chemistry 2006

View Online
Experimental
Tris(4-bromophenyl)amine (2)
Triphenylamine 1 (10.6 g, 43 mmol) was dissolved in 43 ml of
chloroform and cooled down to 0 uC prior to the dropwise
addition of bromine (20.7 g, 0.130) under light protection.
After complete addition of the bromine the resulting green
solution was stirred for another hour and the crude product
was precipitated by addition of 100 ml of an ethanol–water
mixture [1 : 1]. The white solid was filtered off and dissolved in
General
1
H NMR spectra were recorded in CDCl on a Bruker AMX
3
1
3
4
00 at 400 MHz. C NMR spectra were recorded in CDCl
3
on a Bruker AMX 400 at 100 MHz. Chemical shifts are
denoted in d units (ppm), and were referenced to internal
tetramethylsilane (0.0 ppm). The splitting patterns are
designated as follows: s (singlet), d (doublet), t (triplet),
2
0 ml of hot chloroform. After addition of 50 ml hot ethanol
and m (multiplet) and the assignments are Pery (perylene),
1
the product was allowed to crystallize overnight at 218 uC,
before the precipitate was filtered off and dried in vacuum.
Ph (phenyl), Th (thiophene), TPA (triphenylamine) for
H
1
Tris(4-bromophenyl)amine 2 (18.0 g, 86% [lit: 90%] ) was
2
NMR. Mass spectra were recorded with a Varian Saturn
000 GC-MS and with a MALDI-TOF MS Bruker Reflex 2
dithranol as matrix). Elemental analyses were performed
1
2
2
obtained as white crystals: mp 143–144 uC (lit: 144–146 uC);
1
(
H NMR (CDCl ): d = 7.35 (approx. d, J = 8.7 Hz, 6H,
3
1
3H,5H), 6.92 (approx. d, J = 8.8 Hz, 6H, 2H,6H); C NMR
3
on a Perkin-Elmer EA 2400. Melting points were determined
with a B u¨ chi B-545 melting point apparatus and are not
corrected. Gas chromatography was carried out using a
Varian CP-3800 gas chromatograph. HPCL analyses were
performed on a Shimadsu SCL-10A equipped with a SPD-
M10A photodiode array detector and a SC-10A solvent
delivery system using a LiChrosphor column (Silica 60, 5 mm,
Merck). Thin-layer chromatography was carried out on Silica
Gel 60 F254 aluminium plates (Merck). Developed plates
were dried and examined under a UV lamp. Preparative
column chromatography was carried out on glass columns
of different sizes packed with silica gel Merck 60 (40–63 mm).
UV-Vis spectra were taken on a Perkin-Elmer Lambda 19 in
(CDCl ): d = 146.06, 132.52, 125.62, 116.07.
3
Tris{4-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolane)phenyl}amine
(3)
To a solution of tris(4-bromophenyl)amine 2 (0.96 g, 2 mmol)
in 40 ml dry THF at 280 uC was added n-butyllithium (3.77 ml,
6
mmol). After stirring at 280 uC for one hour 2-isopropoxy-
,4,5,5-tetramethyl-[1,3,2]dioxaborolane (1.24 g, 6.6 mmol)
4
was added to the resulting suspension. The solution was
allowed to warm up to room temperature prior to the removal
of the solvent. The residue was suspended in chloroform and
was poured into water. The water phase was extracted with
chloroform. Next, the combined organic phases were dried
with magnesium sulfate and the solution was concentrated
in vacuo (1 ml). After the addition of hot ethanol (10 ml) the
product was allowed to crystallize over night at 218 uC. The
resulting colorless crystals were filtered off and dried in
1
cm cuvettes. Thin uniform films for solid-state spectra
were obtained on a POLOS wafer spinner from a toluene
2
1
solution (20 mg ml ) at 5000 rpm onto a glass substrate.
Fluorescence spectra were measured with a Perkin-Elmer LS
5
5 in 1 cm cuvettes. Fluorescence quantum yields were deter-
mined with respect to N-(2,6-diisopropylphenyl)perylene-3,4-
13
vacuum, yielding 700 mg (54% [lit: 20%] ) of the boronic ester
13 1
2
6
dicarboxmide (PDCI) (W = 0.9 in chloroform ). Cyclic
voltammetry experiments were performed with a computer-
controlled EG&G PAR 273 potentiostat in a three-electrode
single-compartment cell (5 ml). The platinum working
electrode consisted of a platinum wire sealed in a soft
3
3. Mp 334–335 uC (lit: >300 uC); H NMR (CDCl ): d = 7.68
(
approx. d, J = 8.4 Hz, 6H, 3H,5H), 7.07 (approx. d, J =
13
8
.4 Hz, 6H, 2H,6H), 1.34 (s, 36H, –CH
3 3
); C NMR (CDCl ):
d = 149.81, 135.93, 123.50, 83.68, 24.88.
2
glass tube with a surface of A = 0.785 mm , which was
General procedure for the synthesis of the star-shaped perylenyl–
oligothiophene–triphenylamines (5, 7, 9)
polished down to 0.5 mm with Buehler polishing paste
prior to use in order to obtain reproducible surfaces. The
counter electrode consisted of a platinum wire and the
reference electrode was an Ag/AgCl secondary electrode. All
potential were internally referenced to the ferrocene/ferroce-
A
solution of the iodinated perylenyl–oligothiophenes
(
1 equivalent) and the boronic ester 3 (0.33 equivalents) in
dry DME was carefully degassed. After addition of tetrakis-
(triphenylphosphine)palladium(0) (15 mol%) and a 2 M
deaerated, aqueous sodium hydroxide solution (3 equivalents)
the resulting emulsion was carefully degassed. After the
reaction mixture had been stirred at 80 uC for 24 hours it
was poured into water and the aqueous phase was extracted
with dichloromethane. The combined organic phases were
dried with magnesium sulfate and the solvent was taken off.
The crude product was purified by column chromatography.
2
5
nium couple.
2
For the measurements concentrations of
of the electroactive species were used in
3
21
1
0
mol l
freshly distilled and deaerated dichloromethane (Lichrosolv,
Merck) and 0.1 M tetrabutylammonium hexafluorophos-
phate (TBAHFP, Fluka) which was twice recrystallized
from ethanol and dried under vacuum prior to use. Solvents
and reagents were purified and dried by usual methods
prior to use and typically used under inert gas atmosphere.
The following starting materials were purchased and
used without further purification: n-butyllithium (1.59 M in
n-hexane, Merck), pinacol (Aldrich), tri(isopropyl)borate
Tris{4-[8-(2-(2,6-diisopropylphenyl)-1H-benzo[5,10]anthra-
[2,1,9-def]isoquinoline-1,3(2H)-dione)]-4,39-dihexyl-2,29-bithien-
2
7
59-yl]phenyl}amine (5)
(
Merck). Tetrakis(triphenylphosphino)palladium(0)
and
2
8
2
-isopropoxy-4,4,5,5-tetramethyl-[1,3,2]dioxaborolane
were
Following the general procedure, 188 mg (0.2 mmol) perylenyl–
prepared according to literature procedures.
bithiophene 4, 42 mg (67 mmol) of boronic ester 3, 24 mg
This journal is ß The Royal Society of Chemistry 2006
J. Mater. Chem., 2006, 16, 874–884 | 881

View Online
(
0.6 mmol) sodium hydroxide and 35 mg (0.03 mmol)
Tris{4-[8-(2-(2,6-diisopropylphenyl)-1H-benzo[5,10]anthra-
tetrakis(triphenylphosphine)palladium(0) in 60 ml DME were
[2,1,9-def]isoquinoline-1,3(2H)-dione)]-4,39,30,3-,39-,30--
hexahexyl-2,29;59,20;50,2-;5-,29-;59-,20--sexithien-50--yl]-
phenyl}amine (9)
reacted at 80 uC for 24 hours to give 5 (110 mg, 62%) as a black
solid after column chromatography (dichloromethane : petrol
1
ether [5 : 1]): mp 247–248 uC; H NMR (CDCl
J = 8.0 Hz, 6H, Pery-1H,6H), 8.50–8.40 (m, 12H, Pery-
3
): d = 8.64 (d,
Following the general procedure, 48 mg (0.03 mmol) perylenyl-
sexithiophene 8, 6 mg (0.01 mmol) of boronic ester 3, 2.4 mg
2H,5H,7H,12H), 8.00 (d, J = 8.5 Hz, 3H, Pery-8H), 7.67 (d, J =
7.7 Hz, 3H, Pery-10H), 7.62 (t, J = 7.8 Hz, 3H, Pery-11H),
7.55 (d, J = 8.6 Hz, 6H, TPA-3H,5H), 7.48 (t, J = 7.8 Hz, 3H,
(
(
0.06 mmol) sodium hydroxide and 7 mg (6 mmol) tetrakis-
triphenylphosphine)palladium(0) in 1 ml DME were reacted
at 60 uC for 24 hours to give 9 (20 mg, 43%) as a black
solid after column chromatography (dichloromethane : petrol
Ph-4H), 7.34 (d, J = 7.8 Hz, 6H, Ph-3H,5H), 7.20–7.10 (m,
2H, TPA-2H,6H,Th-3H,49H), 2.92–2.81 (m, 6H, Ph-CH-
CH ), 2.78 (t, J = 6.8 Hz, 6H, Th-a9-CH ), 2.46 (t, J =
.5 Hz, 6H, Th-a-CH ), 1.81–1.70 (m, 6H, Th-b9-CH ), 1.64–
1
1
ether [5 : 1]): mp 145–146 uC; H NMR (CDCl ): d = 8.68 (d,
3
(
3
)
2
2
J = 7.8 Hz, 6H, Pery-1H,6H), 8.57–8.49 (m, 12H, Pery-
7
1
1
2
2
2H,5H,7H,12H), 8.01 (d, J = 8.4 Hz, 3H, Pery-8H), 7.70 (d, J =
7.8 Hz, 3H, Pery-10H), 7.65 (t, J = 8.0 Hz, 3H, Pery-11H),
7.51 (d, J = 8.7 Hz, 6H, TPA-3H,5H), 7.48 (t, J = 7.8 Hz, 3H,
.50 (m, 6H, Th-b-CH ), 1.50–1.40 (m, 6H, Th-c9-CH ),
2
2
.40–1.08 (m, 30H, -CH
2
-), 1.21 (d, J = 6.8 Hz, 36H Ph-CH-
), 0.78 (t, J = 6.9 Hz,
): d = 163.84, 146.43, 145.64,
(
CH
3
)
2
), 0.89 (t, J = 6.9 Hz, 9H, Th9-CH
3
Ph-4H), 7.34 (d, J = 7.7 Hz, 6H, Ph-3H,5H), 7.18–7.10 (m,
1
3
9
1
1
1
1
3
2
H, Th-CH
3
); C NMR (CDCl
3
1
2H, TPA-2H,6H,Th-3H,49H), 7.02 (s, 3H, Th0-4H), 7.01 (s,
H, Th-4-H), 6.98 (s, 3H, Th-49-H), 2.90–2.75 (m, 36H, Ph-
41.87, 141.41, 140.56, 137.39, 137.12, 136.20, 134.85, 133.81,
33.72, 131.92, 130.99, 130.39, 130.28, 129.48, 129.34, 129.31,
29.27, 128.95, 128.17, 127.19, 126.99, 126.78, 126.44, 125.57,
24.38, 123.91, 122.99, 121.05, 120.99, 120.29, 120.20, 31.62,
1.40, 30.51, 30.37, 29.62, 29.20, 29.09, 28.96, 28.83, 23.93,
3
CH-(CH
a-CH ), 1.80–1.50 (m, 72H), 1.41–1.10 (m, 72H), 1.19 (d, J =
.8 Hz, 36H, Ph-CH-(CH ) ), 0.95–0.85 (m, 45H, Th9-Th0--
3 2 2
) , Th-a9-a0--CH ), 2.46 (t, J = 7.6 Hz, 6H, Th-
2
6
3
2
13
CH ), 0.78 (t, J = 7.6 Hz, 9H, Th-CH ); C NMR (CDCl3):
3
3
+
2.54, 22.38, 14.00, 13.89; MALDI-TOF m/z = 2680 (M + H );
d = 163.86, 145.65, 142.84, 141.88, 140.50, 139.84, 139.79,
Anal. Calcd for C180H174N O S : C 80.56, H 6.61, N 2.09;
4 6 6
1
1
1
1
1
1
2
2
37.50, 137.23, 136.70, 135.77, 134.86, 134.09, 133.93, 133.86,
33.77, 133.74, 132.02, 131.98, 131.96, 131.89, 130.96, 130.46,
30.31, 129.51, 129.38, 129.35, 129.32, 129.30, 128.53, 128.50,
28.48, 128.44, 128.36, 128.21, 127.22, 127.13, 126.90, 126.37,
24.32, 123.96, 123.89, 123.84, 12.01, 121.09, 121.02, 120.36,
20.32, 120.28, 31.58, 31.37, 30.45, 30.39, 30.34, 30.30, 29.53,
9.40, 29.37, 29.23, 29.14, 29.08, 29.04, 28.92, 28.79, 23.89,
Found: C 80.38, H 6.72, N 2.12%.
Tris{4-[8-(2-(2,6-diisopropylphenyl)-1H-benzo[5,10]anthra-
[
2,1,9-def]isoquinoline-1,3(2H)-dione)]-4,39,30,3-0-tetrahexyl-
,29;59,20;50,2--quaterthien-5--yl]-phenyl}amine (7)
2
Following the general procedure, 191 mg (0.15 mmol)
perylenyl–quaterthiophene 6, 31 mg (0.05 mmol) of boronic
ester 3, 12 mg (0.3 mmol) sodium hydroxide and 35 mg
+
2.53, 22.36, 13.98, 13.86; MALDI-TOF m/z = 4673 (M + H );
Anal. Calcd for C300H342N O S : C 77.01, H 7.41, N 1.20;
6 18
4
Found: C 77.22, H 7.54, N 1.31%.
,39-Dihexyl-5-methyl-2,29-bithiophene (11)
(
0.03 mmol) tetrakis(triphenylphosphine)palladium(0) in 15 ml
DME were reacted at 80 uC for 24 hours to give 7 (100 mg,
4%) as a black solid after column chromatography (dichloro-
4
5
1
methane : petrol ether [5 : 1]): mp 192–193 uC; H NMR
To bithiophene 10 (1.24 g, 3 mmol) in THF (6 ml) at 280 uC
was added n-BuLi (1.9 ml, 3 mmol). After stirring at 280 uC
for 15 min methyl trifluoromethanesulfonate (0.54 g, 3.3 mmol)
was added and the solution was allowed to warm up to room
temperature. Next, 0.5 ml of a 1 molar sodium hydroxide
solution was added to deactivate the excessive methyl triflate
before the solvent was completely removed by rotary evapora-
tion. The remaining residue was suspended in 20 ml n-hexane
and the resulting suspension was poured into 100 ml water.
The water phase was extracted with n-hexane (three times
20 ml) and subsequently, the combined organic phases were
washed with water and were dried over sodium sulfate. Next,
the solvent was removed by rotary evaporation and the crude
product was distilled in vacuo to yield methylated thiophene 11
(0.73 g, 70%) as a pale yellow, viscous liquid. Bp 147 uC (1.1 6
(
CDCl
3
): d = 8.66 (d, J = 7.9 Hz, 6H, Pery-1H,6H), 8.51–8.44
(
m, 12H, Pery-2H,5H,7H,12H), 8.00 (d, J = 8.6 Hz, 3H, Pery-
8
H), 7.70 (d, J = 7.8 Hz, 3H, Pery-10H), 7.65 (t, J = 7.9 Hz,
H, Pery-11H), 7.51 (d, J = 8.6 Hz, 6H, TPA-3H,5H), 7.49 (t,
3
J = 7.8, 3H, Ph-4H), 7.34 (d, J = 7.8 Hz, 6H, Ph-3H,5H), 7.17–
7
.10 (m, 12H, TPA-2H,6H,Th-3H,49H), 7.03 (s, 3H, Th-40H),
.01 (s, 3H, Th-4-H), 2.90–2.75 (m, 24H, Ph-CH-(CH
7
3 2
) ,
Th-a9-a--CH ), 2.46 (t, J = 7.5 Hz, 6H, Th-a-CH ), 1.80–1.69
2
2
(
m, 18H, Th-b9-b--CH ), 1.65–1.41 (m, 30H, -CH -), 1.41–1.10
2 2
(
m, 48H, -CH
2
-), 1.20 (d, J = 6.8 Hz, 36H, Ph-CH-(CH
.95–0.85 (m, 27H, Th9-Th--CH ), 0.78 (t, J = 7.6 Hz, 9H,
): d = 163.85, 146.37, 145.65,
3 2
) ),
0
3
1
3
3 3
Th-CH ); C NMR (CDCl
1
1
1
1
1
3
2
41.88, 141.31, 140.53, 139.85, 137.45, 137.18, 135.80, 134.84,
34.15, 133.93, 133.83, 131.93, 130.98, 130.43, 130.28, 130.11,
29.50, 129.34, 129.31, 128.91, 128.50, 128.36, 128.19, 127.21,
27.13, 126.83, 126.38, 125.53, 124.33, 123.95, 123.90, 123.00,
21.07, 121.00, 120.33, 120.24, 31.61, 31.59, 31.38, 30.47,
0.43, 30.41, 30.36, 29.56, 29.43, 29.40, 29.17, 29.06, 28.94,
2
2
1
10 mbar); H NMR (CDCl ): d = 7.11 (d, J = 5.2 Hz, 1H,
3
59-H), 6.90 (d, J = 5.2 Hz, 1H, 49-H), 6.81 (s, 1H, 3-H), 2.72 (t,
J = 7.8 Hz, 2H, a9-H), 2.49 (t, J = 7.7 Hz, 2H, a-H), 2.34 (s, 3H,
T-CH ), 1.65–1.55 (m, 4H, b,b9-H), 1.42–1.28 (m, 12H, -CH -),
3
2
1
0.92–0.85 (m, 6H, -CH3); C NMR (CDCl ): d = 138.82,
3
8.82, 23.91, 22.54, 22.53, 22.37, 14.01, 14.00, 13.98, 13.87;
+
3
MALDI-TOF m/z = 3677 (M + H ); Anal. Calcd for
138.73, 132.70, 131.31, 131.24, 129.82, 127.82, 122.90, 31.72,
C
240
H
258
N
4
O
6
S
12: C 78.34, H 7.07, N 1.52; Found: C 79.58,
31.67, 30.70, 40.41, 29.22, 29.15, 29.09, 28.23, 22.63, 22.61,
+
14.07, 14.06, 12.86; EI m/z (M ) = 348; Anal. Calcd for
H 7.23, N 1.42%.
8
82 | J. Mater. Chem., 2006, 16, 874–884
This journal is ß The Royal Society of Chemistry 2006

View Online
C
21
H
32
S
2
: C 72.35, H 9.25, S 18.39; Found 72.41, H: 9.37,
for providing 9-bromo-N-(2,6-diisopropylphenyl)perylene-
S: 18.23%.
3,4-dicarboximide. We are grateful to Dr Andreas Hinsch
(
Fraunhofer Institute for Solar Energy Systems, Freiburg) for
5
-Bromo-3,49-dihexyl-59-methyl-2,29-bithiophene (12)
the fabrication and characterization of photovoltaic devices.
J.C. would like to thank the ‘‘Fonds der Chemischen
Industrie’’ and the German Ministry for Education and
Research (BMBF) for a Kekul e´ -Grant.
Bithiophene 5 (696 mg, 2 mmol) was dissolved in 2 ml dry
DMF and was cooled down to 0 uC. In the absence of light a
NBS solution (356 mg, 2 mmol dissolved in 3 ml dry DMF)
was added and the reaction mixture was stirred for another
hour at 0 uC. Then, it was poured into 20 ml of a 1 molar
potassium hydroxide solution. The water phase was extracted
with n-hexane (three times 10 ml) and the combined organic
phases were washed with a 1 molar potassium hydroxide
solution (20 ml). After the organic phase was dried over
sodium sulfate, the solvent was removed by rotary evaporation
and the crude product has been filtrated over a short column
References
1 A. M. Ramos, S. C. J. Meskers, P. A. Van Hal, J. Knol,
J. C. Hummelen and R. A. Janssen, J. Phys. Chem. A, 2003, 107,
9
269–9283.
(a) C. Winder and N. S. Sariciftci, J. Mater. Chem., 2004, 14,
077–1086; (b) J. Nelson, Curr. Opin. Solid State Mater. Sci., 2002,
6, 87–95; (c) H. Hoppe and N. S. Sariciftci, J. Mater. Res., 2004,
9, 1924–1945.
2
1
1
3
4
5
(a) J. Cremer, E. Mena-Osteritz, N. G. Pschierer, K. M u¨ llen and
P. B a¨ uerle, Org. Biomol. Chem., 2005, 3, 985–995; (b) J. Cremer
and P. B a¨ uerle, Eur. J. Org. Chem., 2005, 3715–3723.
(
silica/n-hexane) to yield brominated bithiophene 12 (830 mg,
1
7%) as a pale yellow, viscous liquid. H NMR (CDCl
9
3
):
(a) H. Langhals, Heterocycles, 1995, 40, 477–500; (b) H. Langhals,
Chem. Ber., 1985, 188, 4641–4645; (c) A. J. Breeze, A. Salomon,
D. S. Ginley and B. A. Gregg, Appl. Phys. Lett., 2002, 81, 3085–3087.
(a) T. Kirschbaum, R. Azumi, E. Mena-Osteritz and P. B a¨ uerle,
New J. Chem., 1999, 23, 241–250; (b) C. A. Briehn and P. B a¨ uerle,
Synth. Met., 2001, 119, 121–122; (c) R. S. Loewe, S. M. Khersonsky
and R. D. McCullough, Adv. Mater., 1999, 11, 250–253; (d)
R. D. McCullough and P. C. Ewbank, Handbook of Conducting
Polymers, 2nd edn, Marcel Dekker, New York, 1998, pp. 225–258.
(a) H. Tian, P.-H. Liu, W. Zhu, E. Gao, D.-J. Wu and S. Cai,
J. Mater. Chem., 2000, 10, 2708–2715; (b) J. Hua, F. Meng,
F. Ding, F. Li and H. Tian, J. Mater. Chem., 2004, 14, 1849–1853.
(a) S. R. Forrest, P. E. Burrows and M. E. Thompson, Chem. Ind.,
1998, 1022–1027; (b) S.-C. Chang, J. Liu, J. Nharathan, Y. Yang,
J. Onohara and J. Kido, Adv. Mater., 1999, 11, 734–739; (c)
E. Ueta, H. Nakano and Y. Shirota, Chem. Lett., 1994, 12, 2397;
d = 6.84 (s, 1H, 39-H), 6.75 (s, 1H, 4-H), 2.65 (t, J = 7.8 Hz,
2
1
0
1
3
1
5
H, a9-H), 2.48 (t, J = 7.7 Hz, 2H, a-H), 2.34 (s, 3H, T-CH
.61–1.50 (m, 4H, b,b9-H), 1.38–1.25 (m, 12H, -CH -), 0.91–
): d = 139.45, 138.87,
3
),
2
1
3
3 3
.85 (m, 6H, -CH ); C NMR (CDCl
33.39, 132.82, 132.46, 130.02, 128.24, 109.47, 31.72, 31.63,
0.57, 30.39, 29.10, 29.08, 28.20, 22.63, 22.59, 14.08, 14.06,
+
2.89; EI m/z = 427 (M ); Anal. Calcd for C21
H
31BrS
2
: C
6
7
9.00, H 7.31, S 15.00; Found 59.21, H: 7.42, S: 14.79%.
Tris-[4-(3,49-dihexyl-59-methyl-2,29-bithien-5-yl)-phenyl]-amine
13)
(
A solution of bromobithiophene 12 (141 mg, 0.33 mmol) and
boronic ester 3 (62 mg, 0.1 mmol) in 3 ml DME was carefully
degassed prior to the addition of 0.45 ml (0.9 mmol) of a
(
9
d) T. Noda, I. Imae, N. Noma and Y. Shirota, Adv. Mater., 1997,
, 239–241; (e) C. Jonda, A. B. R. Mayer, M. Thelakkat,
H. W. Schmidt, A. Schreiber, D. Haarer and D. Terell, Adv.
Mater. Opt. Electron., 1999, 9, 117–128; (f) U. Bach, K. De Cloedt,
H. Spreitzer and M. Gr a¨ tzel, Adv. Mater., 2000, 12, 1060–1063.
C. D. Dimitrakopoulos and P. Malenfant, Adv. Mater., 2002, 14,
99–117.
U. Mitschke and P. B a¨ uerle, J. Mater. Chem., 2000, 10, 1471–1507.
2
molar tripotassium phosphate solution. The resulting
emulsion was degassed and the catalyst (Pd dba [1.6 mg,
.5 mmol], [HP(t-Bu) ]BF [0.9 mg, 3 mmol]) was added. Next,
2
3
8
9
1
3
4
the mixture was degassed and was stirred at room temperature
for 6 hours. Then it was poured into water (30 ml) and was
extracted with dichloromethane (three times 10 ml). The
organic phase was dried with magnesium sulfate and the
solvent was taken off before the crude product was purified
10 (a) I. Tabakovic, Y. Kunugi, A. Canavesi and L. L. Miller, Acta
Chem. Scand., 1998, 52, 131–136; (b) K. R. J. Thomas, J. T. Lin,
Y.-T. Tao and C.-W. Ko, Chem. Mater., 2002, 14, 1354–1361; (c)
K. R. J. Thomas, J. T. Lin, M. Velusamy, Y.-T. Tao and
C. H. Chuen, Adv. Funct. Mater., 2004, 14, 83–90.
by column chromatography (silica/n-hexane : dichloromethane
1
10 : 1]) to yield 13 (95 mg, 74%) as an orange wax. H NMR
11 C. J. Brabec, N. S. Sariciftci and J. C. Hummelen, Adv. Funct.
Mater., 2001, 11, 15–25.
[
1
2 T. N. Baker, W. P. Doherty, W. S. Kelley, W. Newmeyer,
J. E. Rogers, R. E. Spalding and R. I. Walter, J. Org. Chem., 1965,
30, 3714–3718.
(
CDCl
Ph-2H,6H), 7.05 (s, 3H, 39-H), 6.85 (s, 3H, 4-H), 2.73 (t, J =
.8 Hz, 6H, a9-H), 2.49 (t, J = 7.7 Hz, 6H, a-H), 2.35 (s, 9H,
T-CH ), 1.66 (quin, J = 7.6 Hz, 6H, b9-H), 1.58 (quin, J =
.6 Hz, 6H, b-H), 1.41–1.26 (m, 36H, -CH -), 0.91–0.87 (m,
3
): d = 7.48–7.44 (m, 6H, Ph-3H,5H), 7.11–7.08 (m, 6H,
1
3 N. Nicolas, B. Fabre, J. M. Chapuzet, J. Lessard and J. Simonet,
J. Electroanal. Chem., 2000, 482, 211–216.
7
3
1
4 (a) B. A. Gregg, J. Sprague and M. W. Peterson, J. Phys. Chem. B,
7
1
1
1
2
2
1
997, 101, 5362–5369; (b) A. J. M a¨ kinen, A. R. Kelnyk,
S. Schoemann, R. L. Headrick and Y. Gao, Phys. Rev. B, 1999,
0, 14683.
1
3
8H, -CH3); C NMR (CDCl ): d = 146.32, 140.68, 139.68,
3
6
38.82, 132.65, 131.48, 130.37, 129.13, 127.51, 126.36, 125.37,
1
5 (a) Y. Shirota, J. Mater. Chem., 2000, 10, 1–26; (b) P. Strohriegl
and J. V. Grazulevivius, Adv. Mater., 2002, 14, 1439–1452.
24.36, 31.75, 31.71, 30.62, 30.44, 29.48, 29.28, 29.12, 28.26,
+
2.65, 14.10, 12.90; MALDI-TOF m/z = 1284 (M + H ); Anal.
16 (a) M. R. Netherton and G. C. Fu, Org. Lett., 2001, 3, 4295–4298;
b) A. F. Littke and G. C. Fu, Angew. Chem., 1998, 110,
586–3587; (c) A. F. Littke, C. Dai and G. C. Fu, J. Am. Chem.
(
3
Calcd for C H NS : C 75.70, H 8.24, N 1.09; Found 75.86,
6
8
1
105
H: 8.31 N: 1.13%.
Soc., 2000, 122, 4020–4028.
1
7 (a) P. B a¨ uerle, Adv. Mater., 1992, 4, 102–107; (b) R. E. Martin,
U. Gubler, C. Bondon, V. Gramlich, C. Bosshard,
J. P. Gisselbrecht, P. G u¨ nther and F. Diederich, Chem. Eur. J.,
Acknowledgements
1
997, 3, 1505–1512; (c) H. Meier, J. Gerold, H. Kolshorn and
We would like to thank the German Ministry for Education
and Research (BMBF Netzwerk ‘‘Polymere Solarzellen’’)
for funding and the group of Professor Klaus M u¨ llen
B. M u¨ hling, Chem. Eur. J., 2004, 10, 360–370.
8 T.-A. Chen, X. Wu and R. D. Rieke, J. Am. Chem. Soc., 1995, 117,
233–244.
1
This journal is ß The Royal Society of Chemistry 2006
J. Mater. Chem., 2006, 16, 874–884 | 883

View Online
19 A. Petrella, J. Cremer, L. De Cola, P. B a¨ uerle and R. M. Williams,
J. Phys. Chem. A, in press.
24 A. Kraft, A. C. Grimsdale and A. B. Holmes, Angew. Chem., Int.
Ed., 1998, 37, 402–428.
2
2
0 E. Mena-Osteritz, J. Cremer and P. B a¨ uerle, to be published.
1 E. Fron, M. Lor, R. Pilot, G. Schweitzer, S. De Feyter, J. Cremer,
P. B a¨ uerle, K. M u¨ llen, M. Van der Auweraer and F. C. de
Schryver, Photochem. Photobiol. Sci., 2005, 4, 61–68.
2 The individual subsystems, TPA and bithiophene itself,
typically show very weak fluorescence and low quantum yields
25 J. Pommerehne, H. Vestweber, W. Guss, R. F. Mahrt, H. B a¨ ssler,
M. Porsch and J. Daub, Adv. Mater., 1995, 7, 551–554.
26 T. Gensch, J. Hofkens, A. Herrmann, K. Tsuda, W. Verheijen,
T. Vosch, T. Christ, T. Basch e´ , K. M u¨ llen and F. C. De Schryver,
Angew. Chem., Int. Ed., 1999, 38, 3752–3756.
27 I. C. G. Coutts, H. R. Goldschmidt and O. C. Musgrave, J. Chem.
Soc., 1970, 488–489.
28 R. Smoum, A. Rubinstein and M. Srebnik, Bioorg. Chem., 2003,
31, 464–474.
2
2
(0–5%).
3 S. K. Lee, Y. Zu, A. Herrmann, Y. Geerts, K. M u¨ llen and
A. J. Bard, J. Am. Chem. Soc., 1999, 121, 3513–3520.
8
84 | J. Mater. Chem., 2006, 16, 874–884
This journal is ß The Royal Society of Chemistry 2006