New molecular materials for hole injection: The synthesis and in situ ESR-UV/Vis/NIR spectroelectrochemistry of 2-diarylaminothiophene-based starburst compounds

Article abstract of DOI:10.1039/b711328e

A series of 2-diarylaminothiophene-based starburst compounds 14-16 with a central triphenylamino-, benzene-, and 1,3,5-triphenylbenzene moiety, respectively, were prepared at moderate yields by a palladium-catalysed coupling reaction. Their electrochemical, optical and magnetic properties were studied with respect to their application as hole transport materials, using cyclic voltammetry and in situ ESR-UV/Vis/NIR spectroelectrochemistry. Although all prepared 2-diarylaminothiophene-based starburst compounds are structurally related, their electrochemical properties differ in their dependence on the central moiety. The number of reversible voltammetric peaks is diminished upon changing the central triphenylamino moiety of the starburst compounds to a central benzene or 1,3,5-triphenylbenzene moiety. The simultaneous multiple electron transfer as well as the location of the spins on the core moieties was detected in the oxidation of the 1,3,5-triphenylbenzene based starburst compound. The stability of the charged states increased substantially upon the incorporation of a thiophene moiety between the central moieties and the side groups. The Royal Society of Chemistry 2007.

Full text of DOI:10.1039/b711328e

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/materials | Journal of Materials Chemistry
New molecular materials for hole injection: the synthesis and in situ
ESR-UV/Vis/NIR spectroelectrochemistry of 2-diarylaminothiophene-
based starburst compounds
Peter Rapta,ab Ahacene Tabet,c Horst Hartmannc and Lothar Dunsch*a
Received 24th July 2007, Accepted 2nd October 2007
First published as an Advance Article on the web 19th October 2007
DOI: 10.1039/b711328e
A series of 2-diarylaminothiophene-based starburst compounds 14–16 with a central
triphenylamino-, benzene-, and 1,3,5-triphenylbenzene moiety, respectively, were prepared at
moderate yields by a palladium-catalysed coupling reaction. Their electrochemical, optical and
magnetic properties were studied with respect to their application as hole transport materials,
using cyclic voltammetry and in situ ESR-UV/Vis/NIR spectroelectrochemistry. Although all
prepared 2-diarylaminothiophene-based starburst compounds are structurally related, their
electrochemical properties differ in their dependence on the central moiety. The number of
reversible voltammetric peaks is diminished upon changing the central triphenylamino moiety of
the starburst compounds to a central benzene or 1,3,5-triphenylbenzene moiety. The simultaneous
multiple electron transfer as well as the location of the spins on the core moieties was detected in
the oxidation of the 1,3,5-triphenylbenzene based starburst compound. The stability of the
charged states increased substantially upon the incorporation of a thiophene moiety between the
central moieties and the side groups.
such candidates (Scheme 1). They have been prepared from
Introduction
the parent 2-diphenylaminothiophene 5a (Scheme 2) by an
oxidative dimerisation5 (for 60) or by a palladium- or copper-
Organic p-conjugated compounds which exhibit a good glass-
catalysed coupling reaction with dibromo(het)arylenes,6
forming tendency, accompanied by a pronounced facility to be
4,49,40-trisbromobenzene7 and hexabromobenzene.8They are
transformed into charged species by their oxidation, have
claimed to be promising hole transport materials.9 We have
received a lot of interest in recent years. Among these
compounds triphenylamine 1 and several of its derivatives
used the parent 2-diphenylaminothiophene 5a and the
(Scheme 1), such as the benzidine compound 2 (TPD) and
derivatives 5b and 5c as educts for preparing the heterocyclic
the starburst compounds 3 (DATA) and 4 (TDAPB), play a
analogues 14–16 of the above-mentioned carbocyclic starburst
crucial role in the search for new materials in different
applications1 like charge transport materials for several
compounds 3 and 4 and studied their electrochemical pro-
perties with respect to their application as hole transport
types of optoelectronic devices, such as organic light-emitting
materials. Besides the electrochemical characterisation the
diodes, organic solar cells, and data storage devices.2 In
charged states in the compounds were studied by in situ
common, they can be easily prepared by a heavy-metal
catalysed C,N- or C,C-coupling reaction3 starting from
UV/VIS/NIR and ESR spectroscopy.
suitable building blocks.
Results and discussion
Recently it was demonstrated that 2-diarylaminothiophenes
5 as heterocyclic triarylamine analogues have similar proper-
ties to the triarylamines themselves. Thus, 2-diarylaminothio-
phenes are able to vitrify very easily and to form stabilised
radical cations and dications by oxidation.4 Due to these
properties 2-diarylaminothiophenes were used as building
blocks for preparing compounds with promising charge
transport properties. For instance, the compounds 6n–8 are
Synthesis and characterization of 2-diarylaminothiophene based
starburst compounds 14–16
The synthesis of starburst compounds with 2-diaryl-
aminothiophene moieties follows the routes for preparing
2-diarylamino-substituted oligothiophenes such as the a,v-
bis(diphenylamino)-substituted oligothiophenes 6.8 It starts
with the transformation of the 2-diarylaminothiophenes 5a–5c
into their metallated species 9a–9c and 10a–10c and ends
up in a palladium-catalysed C,C-coupling reaction of the
tributylstannyl compounds 10a–10c with the tribromo com-
pounds 11–13 (Scheme 2). Thus, the starburst-like compounds
14a–14c, 15a–15c, and 16a–16c can be prepared in moderate
yields. The synthesis of the starting compounds 5a–5c has
been published previously.6 It consists of a heterocyclisation
procedure starting from acyclic 1-chlorotrimethinium salts
aIFW Dresden, Leibniz-Institute of Solid State Research, Department of
Electrochemistry and Conducting Polymers, Helmholtzstrasse 20,
D-01069 Dresden, Germany
bSlovak University of Technology, Faculty of Chemical and Food
Technology, Department of Physical Chemistry, Radlinske´ho 9, SK-812
37 Bratislava, Slovak Republic
cUniversity of Technology Dresden, Institute of Applied Photophysics,
D-01062 Dresden, Germany
4998 | J. Mater. Chem., 2007, 17, 4998–5007
This journal is ß The Royal Society of Chemistry 2007

View Article Online
Scheme 1
which react with alkylthioglycolates giving rise to the
formation of 2-diarylamino-substituted alkyl thiophene-5-
carboxylates10 from which the desired 2-diphenylaminothio-
phenes 5 have been prepared by saponification and subsequent
decarboxylation of the 2-aminothiophene-5-carbonic acids
primarily formed.
properties differ to a certain extent. Similar electrochemical
properties were observed for the triphenylamine-based
compounds 14a–14c. In the cyclic voltammetry of these
compounds, measured in dichloromethane containing tetra-
butylammonium tetrafluoroborate (TBABF4) as supporting
electrolyte, four reversible one-electron processes during
oxidation at a scan rate of 0.1 V s21 are recorded. For
compound 14a, the half-wave potentials E1/2 vs. ferrocene/
ferrocenium redox couple (Fc/Fc+) were evaluated to be
0.07, 0.18, 0.35 and 0.54 V, respectively (see Fig. 1a and
Table 1). Remarkably, the peak separation DE between
neighbouring voltammetric peaks increases with the number
The structures of the prepared starburst compounds 14–16
which are, apart from compounds 14a7 and 15a,11 unknown
till now, were confirmed by elemental analyses, mass spectra,
and NMR data. Thus, all of these 2-amino-5-thienyl starburst
compounds exhibit in their mass spectra an intense molecular
1
ion peak. The H NMR spectra of the compounds 14–16 give
2
of electrons transferred from 0.11 V (E1/2 2 E1/21) to 0.19 V
characteristic signals at about 6.7–6.8 and 7.6–7.8 ppm. These
signals are not hidden under the signals of the protons at the
N-aryl moieties and appear as doublets or singlets. They can be
unambiguously attributed to the protons at the thiophene ring
and, for compounds 15 and 16, to the central benzene moieties.
As expected, some of the starburst compounds prepared
exhibit a high tendency to form amorphous glasses after
cooling their melts. These properties were checked by DSC
measurements. The compounds 15a, 15b, and 15c exhibit a
glass transition at 82 uC, 100 uC, and 88 uC, respectively, in a
second heating of their cooled melts.
4
(E1/2 2 E1/23) indicating a strong charge delocalisation in
this molecule.
During the in situ study of the oxidation of 14a by
ESR-UV/Vis/NIR spectroelectrochemistry at
a platinum
mesh electrode (scan rate v = 3 mV s21) two optical transitions
arise at 2.19 eV (566 nm) and 0.98 eV (1265 nm) at the
electrode potential of the first electron transfer (Fig. 2a).
Simultaneously, broad unresolved ESR spectra with
a
g-value of 2.0027 were observed (Fig. 2b). The shape of
ESR spectrum indicates the presence of a large set of
unresolved splittings by the central triphenylamine moiety
of the molecule.12 This assumption was confirmed by the
spectroelectrochemical investigation of 14c and 14b under the
same experimental conditions. In 14c the diphenylamino
Spectroelectrochemistry
Although all the 2-diarylaminothiophene-based starburst com-
pounds 14–16 are structurally related, their electrochemical
This journal is ß The Royal Society of Chemistry 2007
J. Mater. Chem., 2007, 17, 4998–5007 | 4999

View Article Online
Scheme 2
moiety of 14a is replaced by a phenothiazinyl moiety and in
14b an additional thiophene moiety is inserted into the bridge
between the central triphenylamine and the 2-aminothiophene
fragments. Similarly to the oxidation of 14a, the cyclic
voltammetry of a solution of 14c gives four reversible one-
electron processes at a scan rate of 0.1 V s21 (Fig. 1b, Table 1).
However, the peak separation DE is much smaller than
for 14a. The first and the second voltammetric peak are
coincident and the third and fourth electron transfer reactions
proceed at higher potentials. In the first oxidation step of 14c
very similar optical transitions (at 2.19 eV (566 nm) and
1.07 eV (1159 nm) (Fig. 2c) were observed and identical ESR
spectra (see broad ESR lines at g = 2.0027 in Fig. 2d) as
compared to the detected cation radical of 14a. These
observations confirm a spin delocalisation on the central
triphenylamino moiety in the monocation of 14c which is the
same as in compound 14a.
By increasing the electrode potential to the value of the
second electron transfer a slight shift of low optical energy
transitions was observed only for both compounds 14a and 14c
(see transitions at y0.97 eV (1278 nm) in Fig. 2a and at
1.04 eV (1192 nm) in Fig. 2c). At the electrode potentials of the
third and the fourth electron transfer significant changes in the
optical as well as the ESR spectra were observed for 14c.
Here, new absorptions arise at 2.37 eV (523 nm) and 1.68 eV
(738 nm). Simultaneously, intense ESR spectra with strongly
shifted g-values (g = 2.0056) were observed. The ESR spectra
change their shape going from the third to the fourth oxidation
peak (Fig. 2d). In the potential region of the third oxidation
peak a line broadened ESR spectrum with a dominant ESR
5000 | J. Mater. Chem., 2007, 17, 4998–5007
This journal is ß The Royal Society of Chemistry 2007

View Article Online
Fig. 1 Cyclic voltammograms of 1 6 1023 mol L21 (a) 14a and (b) 14c in CH2Cl2 + 0.1 mol L21 TBABF4 at a platinum wire electrode (scan rate:
v = 100 mV s21).
splitting constant caused by one nitrogen atom with aN
=
that of ferrocene at the same concentration the height of the
ferrocene peak was approximately 3 times smaller than that of
the peaks of 16a and 16c. Therefore, three strongly over-
lapping one electron processes are proposed at this potential
for both starburst compounds 16a and 16c. The in situ
spectroelectrochemical study of the oxidation of 16c at the first
voltammetric peak (Fig. 3a, scan rate v = 3 mV s21) gives the
same ESR spectra (see inset in Fig. 3b) as for the oxidation of
14c at electrode potentials of the third electron transfer.
Simultaneously well defined optical transitions were observed
at 2.56 eV (484 nm), 1.77 eV (701 nm), and 1.50 eV (827 nm),
respectively (Fig. 3b). By increasing the electrode potential line
broadened ESR spectra were observed indicating a strong
interaction of spins. Such an effect is well known for biradicals
and triradicals formed during the oxidation of structures
where a dipolar coupling of the electron spins strongly
broadens the ESR spectra.12 Similar optical transitions at
2.54 eV (488 nm) and 1.58 eV (784 nm) were observed for the
oxidation products of 16a, where the phenothiazinyl moieties
are replaced by a diphenylamino group. Broad unresolved
ESR spectra at a g-value of 2.0027 similar to that of the
oxidation products of 14a were observed in the oxidation
of 16a indicating the localisation of the spin density at the
diphenylamino-thiophene arm moieties.
0.58 mT was observed (see ESR spectrum at 0.6 V in Fig. 2d).
A number of neighbouring hydrogen nuclei having different
hyperfine coupling constants cause strong line broadening.
The high g-value as well as the shape of ESR signal point to
the localisation of the additional charge and spin on the
phenothiazinyl moiety. Consequently, new optical transitions
are observed at the third and fourth electron transfer stages.
They can be attributed to the charged phenothiazinyl moiety
in which significant charge localisation obviously occurs. The
ESR spectra observed in the region of the fourth electron
transfer (see ESR spectrum at 0.9 V in Fig. 2d) can be
simulated with two equivalent nitrogen spitting constants
2aN = 0.3 mT confirming the charging of the further
phenothiazinyl moiety and indicating strong electronic
coupling between the charged arm moieties.
The number of reversible voltammetric peaks is diminished
for the starburst compounds 16 with the central 1,3,5-
triphenylbenzene moiety. Thus, for compounds 16a and 16c
only one reversible oxidation peak is observed at E1/2 = 0.32 V
and E1/2 = 0.40 V vs. Fc/Fc+, respectively. Comparing the peak
currents of these structures in their cyclic voltammograms with
Table 1 Cyclic voltammetry data (in volts vs. Fc/Fc+ redox couple)
for compounds 14–16 in oxidation (CH2Cl2 + 0.1 mol L21 TBABF4,
platinum working electrode, scan rate v = 0.1 V s21). E1/2i (i = 1–4) are
the half-wave potentials in volts vs. Fc/Fc+ for the corresponding
oxidation peaks
In cyclic voltammetry of compound 14b some multistep
reversible electron transfer processes were observed at a
scan rate of 0.1 V s21 (Table 1, Fig. 4a). The peak separation
for the first two peaks is relatively small (DE = 0.15 V), while
the peak separation of the second and third peaks is large
(DE = 0.33 V). Two new optical transitions arise at 0.94 eV
(1319 nm) and 1.84 eV (674 nm) at the electrode potential
of the first electron transfer, as measured by in situ ESR-UV/
VIS/NIR spectroelectrochemistry at a scan rate of 3 mV s21
(Fig. 4a). By increasing the potential to that of the second
electron transfer the absorption peaks shift to 0.98 eV
(1265 nm) and 2.17 eV (571 nm), respectively. For the third
redox reaction an absorption peak at 1.39 eV (892 nm) is
detected (Fig. 4a). Intense and broad singlet ESR spectra with
1
2
3
4
Sample
E1/2
E1/2
E1/2
E1/2
14a
14b
14c
16a
16b
16c
15a
15b
15c
a
0.07
0.17
0.23
0.32
0.19
0.40
0.36a
0.26
0.44a
0.18
0.32
0.33
0.35
0.65
0.45
0.54
0.53
0.49
0.62
Follow-up reactions.
This journal is ß The Royal Society of Chemistry 2007
J. Mater. Chem., 2007, 17, 4998–5007 | 5001

View Article Online
Fig. 2 UV/Vis/NIR spectra and ESR spectra measured during the oxidation of 14a (a,b) and 14c (c,d) in 0.2 mol L21 TBABF4–CH2Cl2 (platinum
mesh working electrode, scan rate v = 3 mV s21). Identically colored ESR and optical spectra correspond to the potential in volts vs. Fc/Fc+ marked
in the figure with the same trace.
g y2.003 and a line width of 0.7 mT were observed for the
species generated in the first electron transfer.
thiophene units in the molecule. Broad voltammetric peaks
at electrode potentials of about 0.4 V vs. Fc/Fc+ have been
detected for compounds 15a, 15c and 15b (Table 1). At this
electrode potential a low intensity ESR signal with a rich
hyperfine splitting was observed in oxidation of 15a (Fig. 5a).
Simultaneously new absorption peaks at 1.55 eV (800 nm),
2.36 eV (525 nm), and 2.95 eV (420 nm) were detected during
the voltammetric scan (Fig. 5a). However the intensity of the
most intense absorption peak at 1.55 eV (800 nm) does not
correlate with the intensity of the ESR signal simultaneously
measured in a voltammetric scan. This new band is slightly
shifted to lower energies compared to the cation radical band
(1.69 eV) (734 nm) and decreases during the back scan (see
dashed lines in Fig. 5a). Obviously, the dimerisation of the ion
radicals generated by the electrochemical oxidation occurs
with the relatively short p-conjugated system13 and therefore
this band can be attributed to a dimerisation product. Very
similar behaviour was observed in the oxidation of 15c where
the diphenylamino moiety of 15a is replaced by a phenothia-
zinyl moiety. In this case, a very intense optical band at 1.56 eV
Similar redox behaviour was observed for the electro-
chemical oxidation of 16b (Fig. 4b), in which the conjugated
p-system is extended by the insertion of a thiophene moiety
between each of the core diphenylamino group and the central
1,3,5-triphenylbenzene moiety. Compound 16b exhibits rever-
sible voltammetric peaks at 0.19 V and 0.62 V vs. Fc/Fc+
(Table 1, Fig. 4b). The species generated in the first oxidation
peak gives rise to an absorption maximum at 1.53 eV (810 nm)
which shifts under further oxidation to 1.43 eV (867 nm), while
a new absorption band arises simultaneously at 2.12 eV
(585 nm). The species generated at the second oxidation peak,
the potential of which is strongly shifted to higher values, give
rise to an absorption maximum at 1.70 eV (729 nm) (Fig. 4b).
Negligible ESR intensity is caused by the formation of ESR
silent dicationic species.
The starburst compounds 15a–15c with a central benzene
core exhibit different cyclovoltammetric as well as spectro-
electrochemical behaviour depending on the number of
5002 | J. Mater. Chem., 2007, 17, 4998–5007
This journal is ß The Royal Society of Chemistry 2007

View Article Online
groups is an advantageous strategy to enhance the stability of
charged states in the hole transporting starburst compounds.
Subsequent dimerisation reactions of cation radicals of
2-diarylaminothiophene-based starburst compounds with
short p-conjugation were eliminated by this strategy.
Theoretical studies concerning the charge distribution and
the intramolecular charge transfer within the newly prepared
star-shaped molecules taking into account recent efforts in this
field12,14 are under way.
Conclusion
We have demonstrated by an in situ spectroelectrochemical
study the effects of structure on electrochemical and spectro-
electrochemical behaviour of 2-diarylaminothiophene-based
starburst compounds, which exhibit a high tendency to form
amorphous glasses after cooling their melts. Four distinct
reversible one-electron processes during oxidation of 2-diaryl-
aminothiophene-based starburst compounds with the central
triphenylamino moiety, 14, were observed and the spin
delocalisation on the central triphenylamino moiety in the
monocation was confirmed. On the other hand the starburst
compounds with the central 1,3,5-triphenylbenzene moiety, 16,
exhibit three strongly overlapping one-electron processes and
the location of the spins on the core moieties was indicated at
the first oxidation peak. The stability of the charged states was
increased substantially by the incorporation of a thiophene
moiety between the central moieties and the side groups for
2-diarylaminothiophene-based starburst compounds 15 with a
central benzene moiety. This represents an advantageous
strategy to enhance the stability of charge states in the hole
transporting starburst compounds.
Experimental
Fig. 3 In situ ESR-UV/Vis/NIR spectroelectrochemistry of 16c in
CH2Cl2 + 0.2 mol L21 TBABF4 at a platinum electrode. a) Cyclic
voltammogram (v = 3 mV s21, inset: structure of 16c). b) UV/Vis/NIR
spectra measured during a CV scan (inset: the corresponding ESR
spectra measured at the marked potentials in volts vs. Fc/Fc+).
General
The following instruments and analytical techniques were
used. Melting points: Kofler hot-stage microscope, corrected;
NMR: Inova 500 ‘‘max 2’’. Varian 300 MHz spectrometer
Gemini 300; CDCl3 was used as solvent; elemental analysis:
LECO analyzer CHNS 932; MS: AMO spectrometer 402
(70 eV, EI); cyclic voltammetry: all cyclovoltammetric (CV)
experiments were performed at room temperature with a PAR
273 potentiostat (EG&G, U.S.) in a glove-box (oxygen and
water content below 1 ppm). A standard three-electrode
arrangement with a platinum wire as a working electrode, a
platinum coil as a counter electrode and a silver wire as a
pseudo-reference electrode was used. Ferrocene (Fc) was
added as the internal standard for a final voltammetric cycle
and all potentials are referred to the Fc/Fc+ couple. The
concentration of the samples ranges from 561024 to
161023 mol L21: spectroelectrochemistry: the ESR spectra
were recorded using an EMX X-Band ESR spectrometer
(Bruker, Germany) and the optical spectra by using a UV/Vis/
NIR spectrometer system TIDAS (J&M, Aalen, Germany).
Both the ESR spectrometer and UV-Vis-NIR spectrometer
were triggered by a HEKA potentiostat PG 285 and the
triggering was performed using software package PotPulse
8.53 (HEKA Electronic, Germany). As the supporting
(795 nm), which corresponds to the follow-up reaction of the
cation radical of 15c, dominates the optical spectrum during
anodic oxidation.
By incorporation of a thiophene moiety between the central
benzene moiety and the diphenylamino-thiophene side frag-
ments, resulting in compound 15b, the extended structure
results in the formation of stable charged states. Thus two well
defined absorption maxima at 1.44 eV (694 nm) and 2.16 eV
(574 nm) were found for the ion radicals generated from
compound 15b at the first oxidation peak. In contrast to 15a
for which an irreversible cyclovoltammetric response was
measured in situ at a scan rate of 3 mV s21 in an ESR flat cell,
reversible behaviour was observed for 15b at the same scan
+
?
rate (Fig. 6). The ESR intensity of the cation radical 15b
correlates well with the intensity of both optical bands in
their potential dependence (Fig. 5b). During the voltammetric
cycling an identical spectroelectrochemical response is
observed for each cycle indicating that the incorporation of
the thiophene moiety between the central moiety and its side
This journal is ß The Royal Society of Chemistry 2007
J. Mater. Chem., 2007, 17, 4998–5007 | 5003

View Article Online
Fig. 4 UV/Vis/NIR spectroelectrochemistry of (a) 14b and (b) 16b in CH2Cl2 + 0.2 mol L21 TBABF4 (UV/VIS/NIR spectra taken in forward scan
are shown for clarity; the potentials marked are in volts vs. Fc/Fc+; for 14b UV/VIS/NIR spectra taken during the second cyclovoltammetric scan
are shown in (a)).
electrolyte tetrabutylammonium tetrafluoroborate (TBABF4)
was used, which was dried under reduced pressure at 340 K
for 24 h and stored in a glove box prior to use. The
concentration of TBABF4 in dichloromethane ranges from
The organic layer was dried with sodium sulfate, filtrated, and
evaporated in vacuo. The remaining product 9 was used
without further purification for the next step.
(b) The tributylstannyl compound 10 (25 mmol) obtained
was dissolved in absolute toluene (75 mL) and mixed under
argon and under stirring, with an appropriate tribromoaryl
compound 11, 12, or 13 (6 mmol) and Pd(PPh3)4 (0.06 mmol,
0.07 g). After heating the resulting mixture was treated at 80 uC
for 8 h and the solvent was removed at reduced pressure. The
residue was purified by column chromatography using silica as
adsorbent and cyclohexane–toluene as eluent. The products
14–16 were thus obtained.
0.1 to 0.2 mol L21
.
Materials
The 5-diarylamino-substituted thiophenenes 5a and 5b as
well as 5-diphenylamino-2,29-bithiophene 5c used as starting
materials for the oxidative coupling reactions were prepared
accordingly to ref. 6.
2-Diarylaminothienyl-substituted starburst compounds 14–16
(general procedure)
4,49,40-Tris(2-diphenylamino-5-thienyl)triphenylamine (14a).
From 5a and 11 in a yield of 18% and a mp of 90 uC. 1H
NMR (in CDCl3), d values (assignment): 6.69 (d, J = 4.2 Hz,
3H), 7.02 (d, J = 8.7 Hz, 6H), 7.07–7.11 (m, 18H), 7.22 (d, J =
3.9 Hz, 3H), 7.29–7.35 (m, 12H), 7.49 (d, J = 8.1 Hz, 6H). 13C
NMR (in CDCl3), d values: 121.6, 122.8, 123.2, 123.6, 125.2,
126.7, 129.8, 130.0, 138.8, 146.8, 148.4, 150.9. Calculated for
C66H48N4S3 (993.31) C, 79.80; H, 4.87; N, 5.64, S, 9.68; found
C, 79.83; H, 4.81; N, 5.70; S, 9.60%. m/z: 993.
(a) To a solution of a 2-diarylaminothiophene 5 (25 mmol) in
absolute THF (310 mL) a solution (1.6 M) of BuLi in n-hexane
(20 mL) was added dropwise under argon at 270 uC. After
warming the reaction mixture to room temperature tributyl-
stannyl chloride (10 mL, 0.1 M) was added. After standing of
this mixture overnight it was poured into water (100 mL) and
the product formed extracted by dichloromethane (100 mL).
5004 | J. Mater. Chem., 2007, 17, 4998–5007
This journal is ß The Royal Society of Chemistry 2007

View Article Online
Fig. 5 Spectroelectrochemistry of (a) 15a and (b) 15b in CH2Cl2 + 0.2 mol L21 TBABF4 at a platinum mesh electrode in the potential range from
20.55 V to 0.45 V vs. Fc/Fc+. Identically colored ESR and optical (full lines - forward scan, dashed lines - back scan) spectra were taken at the same
time during cyclovoltammetric scan (v = 3 mV s21). The potentials are marked in Volts vs. Fc/Fc+.
Fig. 6 Cyclic voltammograms of (a) 15a and (b) 15b in CH2Cl2 + 0.2 mol L21 TBABF4 at a platinum mesh electrode (v = 3 mV s21).
This journal is ß The Royal Society of Chemistry 2007
J. Mater. Chem., 2007, 17, 4998–5007 | 5005

View Article Online
4,49,40-Tris(59-diphenylamino-2,29-bithien-5-yl)triphenyl-
amine (14b). From 5b and 11 in a yield of 29% and a mp of
212 uC (decomp.). 1H NMR (in CDCl3), d values (assignment):
6.60 (d, J = 4.2 Hz, 3H), 6.96 (d, J = 3.9 Hz, 3H), 7.00 (d, J =
3.6 Hz, 3H), 7.03–7.08 (m, 6H), 7.11–7.14 (m, 9H), 7.17–7.21
(m, 12H), 7.27–7.31 (m, 12H) 7.47–7.50 (m, 6H). 13C NMR (in
CDCl3), d values: 121.9, 122.7, 123.5, 123.8, 124.0, 124.4,
125.1, 127.2, 129.8, 129.9, 132.1, 137.3, 142.8, 147.1, 148.3,
151.2. Calculated for C78H54N4S6 (1239.69) C, 75.57; H, 4.39;
N, 4.52, S, 15.52; found C, 75.02; H, 4.91; N, 3.83; S, 15.03%.
m/z: 1239.
7.04 (t, J = 7.2 Hz, 6H), 7.14 (d, J = 3.9 Hz, 3H), 7.18 (d, J =
7.2 Hz, 9H), 7.24–7.30 (m, 15H), 7.50 (s, 3H). 13C NMR (in
CDCl3), d values: 120.6, 121.4, 122.3, 122.7, 123.1, 129.2,
135.6, 137.0, 147.6, 151.4. Calculated for C54H39N3S3 (825.11)
C, 78.51; H, 4.76; N, 5.09, S, 11.64; found C, 77.86; H, 5.15; N,
4.63; S, 11.53%. m/z: 825.
1,3,5-Tris(5-phenothiazin-10-yl-2-thienyl)benzene (15c).
From 5c and 12 in a yield of 18% and a mp of 245 uC. 1H
NMR (in CDCl3), d values (assignment): 6.84 (d, J = 8.1 Hz,
6H), 6.91 (t, J = 7.5 Hz, 6H), 7.02 (t, J = 7.8 Hz, 6H), 7.08 (d,
J = 6.6 Hz, 9H), 7.43 (d, J = 3.9 Hz, 3H), 7.78 (s, 3H). 13C
NMR (in CDCl3), d values: 117.8, 122.6, 123.2, 123.5, 124.5,
127.5, 127.8, 129.3, 136.3, 142.7, 144.4, 144.5. Calculated for
C54H33N3S6 (916.26) C, 70.79; H, 3.63; N, 4.59, S, 21.00; found
C, 69.95; H, 4.19; N, 4.40; S, 19.45%. m/z: 916.
4,49,40-Tris[5-(phenothiazin-10-yl)thien-2-yl]triphenylamine
(14c). From 5c and 11 in a yield of 17% and a mp of 275 uC. 1H
NMR (in CDCl3), d values (assignment): 6.80 (d, J = 4.2 Hz,
6H), 6.89 (t, J = 7.2 Hz, 6H), 6.98 (d, J = 7.5 Hz, 6H), 7.02–
7.06 (m, 9H), 7.17 (d, J = 8.7 H, 6H), 7.30 (d, J = 3.9 Hz, 3H),
7.57 (d, J = 6.6 Hz, 6H). 13C NMR (in CDCl3), d values: 117.2,
12.6, 123.4, 124.8, 126.9, 127.4, 129.4, 129.7, 142.3, 143.6,
144.2, 147.1. Calculated for C66H42N4S6 (1083.46) C, 73.16; H,
3.91; N, 5.17, S, 17.76; found C, 72.34; H, 4.06; N, 5.15; S,
17.14%. m/z: 1084.
1,3,5-Tris(59-diphenylamino-2,29-bithien-5-yl)benzene (15b).
From 5b and 12 in a yield of 25% and a mp of 108 uC.
1H NMR (in CDCl3), d values (assignment): 6.57 (d, J =
4.2 Hz, 3H), 6.97 (d, J = 3.9 Hz, 3H), 7.00–7.06 (m,
9H), 7.15–7.18 (m 12H), 7.23–7.29 (m, 15H), 7.61 (s, 3H).
13C NMR (in CDCl3), d values: 121.5, 122.0, 123.0, 123.5,
124.0, 124.2, 125.0, 129.9, 131.5, 136.0, 138.5, 141.8, 148.2,
151.5. Calculated for C66H45N3S6 (1072.48) C, 73.91; H, 4.23;
N, 3.92, S, 17.94; found C, 73.93; H, 4.34; N, 3.83; S, 17.57%.
m/z: 1072.
1,3,5-Tris[4-(2-diphenylamino-5-thienyl)phenyl]benzene (16a).
1
From 5a and 13 in a yield of 16% and a mp of . 320 uC. H
NMR (in CDCl3), d values (assignment): 6.69 (d, J = 3.9 Hz,
3H), 7.06 (t, J = 7.2 Hz, 6H), 7.17–7.30 (m, 27H), 7.65 (dd, J =
8.2 Hz, 12H), 7.78 (s, 3H). 13C NMR (in CDCl3), d values:
122.3, 122.5, 123.4, 123.8, 125.1, 126.2, 128.3, 129.8, 134.6,
138.1, 140.1, 142.4, 148.4, 151.9. Calculated for C72H51N3S3
(1053.39) C, 82.02; H, 4.88; N, 3.99, S, 9.12; found C, 81.16; H,
4.88; N, 4.08; 8.99%. m/z: 1054.
Acknowledgements
Financial support by the Deutsche Forschungsgemeinschaft,
by the Alexander von Humboldt Foundation (Projekt 3
Fokoop DEU/1063827) and the Slovak Scientific Grant
Agency (1/3579/06) for P. R. is duly acknowledged.
1,3,5-Tris[4-(5-phenothiazin-10-yl-2-thienyl)phenyl]benzene
(16c). From 5c and 13 in a yield of 22% and a mp of 286 uC
(decomp.). 1H NMR (in CDCl3), d values (assignment):
6.84 (d, J = 8.1 Hz, 6H), 6.91 (t, J = 7.52 Hz, 6H), 7.01 (t,
J = 7.7 Hz, 6H), 7.06–7.09 (m, 9H), 7.40 (d, J = 3.9 Hz,
3H), 7.76 (m, 12H), 7.86 (s, 3H). 13C NMR (in CDCl3), d
values: 117.8, 122.5, 122.7, 124.1, 125.56, 126.9, 127.5, 127.8,
128.6, 129.7, 134.3, 141.1, 142.5, 143.8, 143.9, 144.6.
Calculated for C72H45N3S6 (1144.54) C, 75.56; H, 3.96;
N, 3.67, S, 16.81; found C, 75.47; H, 4.10; N, 3.71; S,
16.20%. m/z: 1145.
References
1 T. Fuhrmann and J. Salbeck, Adv. Photochem., 2002, 27, 83–166;
P. Strohrigl and J. V. Graulevicius, Adv. Mater., 2002, 14,
1439–1452.
2 Handbook of Organic Conductive Molecules and Polymers, ed.
H. S. Nalwa, John Wiley, New York, 1997, vol. 1–4; Y. Shirota,
J. Mater. Chem., 2005, 15, 75–93; Y. Shirota, J. Mater. Chem.,
2000, 10, 1–25.
3 J. F. Hartwig, Angew. Chem., 1998, 110, 2154–2174; J. F. Hartwig,
Angew. Chem., Int. Ed., 1998, 37, 2047–2067; A. S. Guram,
R. A. Rennels and S. L. Buchwald, Angew. Chem., 1995, 107,
1456–1458; A. S. Guram, R. A. Rennels and S. L. Buchwald,
Angew. Chem., Int. Ed. Engl., 1995, 34, 1348–1350; E. Lukevics,
P. Arsenyan and O. Pudova, Heterocycles, 2003, 60, 663.
4 H. Hartmann, P. Gerstner and D. Rohde, Org. Lett., 2001, 3,
1673–1675; D. Rohde, L. Dunsch, A. Tabet, H. Hartmann and
J. Fabian, J. Phys. Chem. B, 2006, 110, 8223–8231; P. Rapta,
D. Rohde, H. Hartmann and L. Dunsch, Tetrahedron Lett., 2006,
47, 7587–7590.
1,3,5-Tris[4-(59-diphenylamino-2,29-bithien-5-yl)phenyl]ben-
zene (16b). from 5b and 13 in a yield of 21% and a mp of
1
112 uC. H NMR (in CDCl3), d-values (assignment): 6.60 (d,
J = 3.6 Hz, 6H), 6.99 (d, J = 3.9 Hz, 3H), 7.03–7.09 8m, 9H),
7.19–7.21 (m, 12H), 7.24–7.32 (m, 12H), 7.69 (s, 12H), 7.79 (s,
3H). 13C NMR (in CDCl3), d-values: 121.8, 122.9, 123.4, 123.9,
124.4, 124.5, 125.3, 126.6, 128.4, 129.9, 131.8, 134.1, 138.1,
140.5, 142.4, 142.5, 148.2, 151.4. Calculated for C84H57N3S6
(1300.77) C, 77.56; H, 4.42; N, 3.23, S, 14.79; found C, 76.87;
H, 4.43; N, 3.19; S, 14.17. m/z: 1301.
5 O. Zeika and H. Hartmann, Tetrahedron, 2004, 60, 8213–8219;
O. Zeika, H. Hartmann, K. Leo and M. Pfeiffer, DE 10343757,
Chem. Abstr., 2005, 142, 411349.
6 A. Tabet and H. Hartmann, Synthesis, 2005, 610–616.
7 I.-Y. Wu, J. T. Lin, Y.-T. Tao, E. Balasubrumaniam, Y. Z. Su and
C.-W. Ko, Chem. Mater., 2001, 13, 2626–2631.
8 I.-Y. Wu, J. T. Lin, Y.-T. Tao and E. Balasubrumaniam, Adv.
Mater., 2000, 12, 668–669; J. T. Lin, I.-Y. Wu, Y.-T. Tao and
E. Balasubrumaniam, US Pat. 2002115870, Chem. Abstr., 2002,
137, 185321.
1,3,5-Tris(59-diphenylamino-2-thienyl)benzene (15a). From
1
5a and 12 in a yield of 17% and a mp of 209 uC. H NMR
(in CDCl3), d values (assignment): 6.55 (d, J = 3.9 Hz, 3H),
5006 | J. Mater. Chem., 2007, 17, 4998–5007
This journal is ß The Royal Society of Chemistry 2007

View Article Online
9 A. Kanitz, J. Schumann, M. Scheffel, S. Rajoelson,
W. Rogler, H. Hartmann and D. Rohde, Chem. Lett., 2002,
896–897.
12 Y. Hirao, A. Ito and K. Tanaka, J. Phys. Chem. A, 2007, 111,
2951–2956; Y. Hirao, H. Ino, A. Ito and K. Tanaka, J. Phys.
Chem. A, 2006, 110, 4866–4872.
10 C. Heyde and I. Zug. H. Hartmann, Eur. J. Org. Chem., 2000,
3273–3278.
11 S. Liu, K. S. Lin, V. M. Churikov, Y. Z. Su, J. T. Lin, T. H. Huang
and C. C. Hsu, Chem. Phys. Lett., 2004, 390, 433–439.
13 P. Rapta, N. Schulte, A.-D. Schlu¨ter and L. Dunsch, Chem.–Eur.
J., 2006, 12, 3103–3113 and references cited therein.
14 S. Amthor, C. Lambert, S. Du¨mmler, I. Fischer and J. Schelter,
J. Phys. Chem. A, 2006, 110, 5204–5214.
This journal is ß The Royal Society of Chemistry 2007
J. Mater. Chem., 2007, 17, 4998–5007 | 5007