Synthesis and properties of the bipolar triphenylamine-benzimidazole derivatives

Article abstract of DOI:10.1071/CH09336

A series of newly-developed bipolar triphenylamine benzimidazole derivatives, containing both hole-transporting and electron-transporting moieties, have been completely characterized by ¹H and ¹³C NMR and HRMS, as well as their therm

Full text of DOI:10.1071/CH09336

Full Paper
CSIRO PUBLISHING
Aust. J. Chem. 2010, 63, 712–718
www.publish.csiro.au/journals/ajc
Synthesis and Properties of the Bipolar Triphenylamine-
benzimidazole Derivatives
Hai-Ying Wang,A Gang Chen,A Xiao-Ping Xu,A and Shun-Jun JiA,B
AKey Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry,
Chemical Engineering and Materials Science, Suzhou (Soochow) University,
Renai Road, Suzhou Industrial Park, Suzhou 215123, China.
BCorresponding author. Email: chemjsj@suda.edu.cn
A series of newly-developed bipolar triphenylamine benzimidazole derivatives, containing both hole-transporting and
1
electron-transporting moieties, have been completely characterized by H and 13C NMR and HRMS, as well as their
thermal, optical, and electrochemical properties. The results indicate that these compounds exhibit high fluorescence
quantum yields, desirable HOMO levels and high thermal stabilities. Quantum chemical calculations were used to obtain
the optimized ground-state geometries, spatial distributions of the HOMO, and the LUMO levels of these compounds.
The agreement between experimental and calculated data suggests such compounds may have potential applications in
organic light emitting diodes materials.
Manuscript received: 15 June 2009.
Manuscript accepted: 19 January 2010.
Introduction
4,4ꢀ,4ꢀꢀ-tris(5,6-diphenyl-1H-ben-zimidazol-2-yl)-triphenylamine
(TBITPA), 4-(5-(3,4-dimethoxyphenyl)-6-(2-chloro-phenyl)-1H-
benzimidazol-2-yl)-triphenylamine (MeO-BITPA), 4,4ꢀ-di(5-
(3,4-dimethoxyphenyl)-6-(2-chloro-phenyl)-1H-benzimidazol-
2-yl)-tri-phenylamine (MeO-DBITPA), and 4,4ꢀ,4ꢀꢀ-tri(5-(3,4-
dimethoxyphenyl)-6-(2-chloro-ph-enyl)-1H-benzimidazol-2-yl)-
triphenylamine (MeO-TBITPA), all of which combine both
triphenylamine and benzimidazole moieties as shown in
Scheme 1. As expected, the combination of a hole-transporting
triphenylamine moiety and an electron-transporting benzimida-
zole moiety, has resulted in bipolar charge transport properties.
All of these compounds exhibit high fluorescence quantum
yields, favourable HOMO levels (−5.08 to −5.42 eV) and high
thermal stabilities, implying potential application as multifunc-
tional materials in OLEDs.
Since the first application of a multilayer, thin-film struc-
ture in organic light-emitting devices (OLEDs) by Tang et al.,
OLEDs have attracted a great deal of attention due to their
extensive use in full-colour flat-panel displays and solid-state
lighting.[1,2] A balance between the electron and hole cur-
rents of OLEDs is important in order to achieve high device
efficiency.[3] One promising strategy is development of bipolar
molecules containing both an electron-donating moiety (D) and
an electron-accepting moiety (A). The dipolar compounds are
capable of being matched in the charge carrier injection and
acceptance of both holes and electrons.[4] With prudent choice
of the D and A units, the levels of the HOMO and LUMO,
as well as the emission colour of the D–A molecule, can be
controlled to a fine degree,[5] making such systems increas-
ingly attractive for use in single-layer OLEDs.[6] Triphenyl-
amine derivatives are well-known electron-rich compounds,
which are widely employed as hole-transporting materials, light
emitters in the field of optoelectronics, including OLEDs,[7]
organic field-effect transistors,[8] non-linear materials,[9] and
xerography.[10] Recent developments have produced organic
photovoltaic materials based on triarylamines and new synthetic
methods, as well as the application of starburst triarylamines
as the host emitting materials.[11] Star-shaped molecules con-
taining a triphenylamine core and branches of oligophenylenes,
2-phenylthiophene, or fluorene have also been examined.[12] The
benzimidazole units, introduced as electron-accepting (A) sub-
stituentsbecauseoftheirgoodelectrontransportproperties;have
since been widely utilized as an electron transport material for
OLEDs.[13]
Results and Discussion
The syntheses of the 2a–c followed previously reported
procedures of the Vilsmeier–Haack formylation reaction
(Scheme 1).[11d] Compounds 4 and 6 were synthesized by the
reaction of 2 with 3 and 5, respectively (Scheme 2).
Glass transition temperatures (Tg) and decomposition tem-
peratures (Td) were determined using differential scanning
calorimetry (DSC) and thermal gravimetric analysis (TGA),
respectively, at a heating rate of 20◦C min−1.The results of these
experiments are summarized in Table 1. No glass transition was
observed for these compounds by DSC despite heating to 250◦C,
only melting transitions were observed (Table 1). The TGA data
confirmed the thermal stability of these compounds, with ther-
mal decomposition not occurring until 310◦C. Moreover, the
melting point of these compounds increases with increasing
number of π-conjugated branches. The melting points of 6a–c
were higher than that of the corresponding 4a–c. This may be
attributed to a decrease in the symmetry of the molecular
In this article, we report the syntheses and character-
izations of six novel bipolar molecules: 4-(5,6-diphenyl-
1H-benzimidazol-2-yl)-triphenylamine (BITPA), 4,4ꢀ-di(5,6-
diphenyl-1H-benzimidazol-2-yl)-triphenylamine (DBITPA),
© CSIRO 2010
10.1071/CH09336
0004-9425/10/040712

Bipolar Triphenylamine-benzimidazole Derivatives
713
O
O
POCl3
DMF
N
N
N
ꢀ
O
2b
1
2a
O
O
N
POCl3
DMF
2b
O
2c
Scheme 1. Synthetic routes to compounds 2a–c.
O
O
O
O
N
Cl
O
O
NH4CH3COO
CH3COOH
N
2a
ꢀ
NH4CH3COO
CH3COOH
N
H
N
2a
H
ꢀ
N
Cl
O
O
N
3
5
4a
O
O
6a
O
O
O
O
O
O
NH4CH3COO
CH3COOH
N
N
Cl
2b
NH4CH3COO
CH3COOH
ꢀ
N
N
2b
N
N
H
ꢀ
H
N
H
N
3
H
N
Cl
Cl
O
O
O
N
5
O
O
O
4b
6b
N
N
N
N
N
H
N
H
O
O
N
H
N
H
O
O
NH4CH3COO
CH3COOH
Cl
Cl
N
Cl
NH4CH3COO
CH3COOH
N
2c
ꢀ
2c
ꢀ
3
O
O
5
HN
N
HN
N
Cl
O
6c
O
4c
Scheme 2. Synthetic routes to compounds 4 and 6.
structure as a result of the addition of two methoxy groups to
the terminal phenyl rings.Thermal and morphological stabilities
of the organic electroluminescent materials play an important
role in OLEDs. Excellent thermal stability, for example with a
high Td and Tg, generally leads to high-stability OLEDs. This,
in combination with morphological stability, favours improved
performance and OLED lifetime.
The UV-vis absorption and photoluminescent (PL) proper-
ties of compounds 4 and 6 in DMF are presented in Table 1.
As shown in Fig. 1a, no significant change in the UV spectra
suggests weak intermolecular interactions. Two major bands,
from 350 to 374 nm in the absorption spectra, could be
attributed to the charge transfer (CT) of the π–π* transition
(ε > 51000 L mol−1 cm−1) from the HOMO of the electron-
donating triphenylamine moiety to the LUMO of the electron-
accepting benzimidazole moiety.The absorption bands from 296
to 305 nm, most likely result from the locally excited π–π*
transition at the triphenylamine moiety.[13c] In the case of
4a–c, the di- and tri-branched compounds (4b and 4c) are
greatly red-shifted (20–21 nm) when compared to their equiv-
alent mono-derivative 4a. This indicates that the combination of
an electron-donor and an electron-acceptor will further enhance
the π-electron delocalization upon excitation.[14a] Meanwhile,
the molar extinction coefficient (ε) increases with an increase
in the number of π-conjugated branches. The π–π* energy gaps
(Egs) of these compounds were calculated based on the ultra-
violet photoelectron spectra and the optical band gaps, derived
from the lowest-energy absorption edge of the UV-vis absorption
spectra.[14]
As shown in Fig. 1b, 4a–c exhibit similar fluorescence spec-
tra due to their similar structures, especially in the shape of
a strong emission peak centred around a similar wavenumber
(i.e. 406, 412, 423 nm, respectively). Compared with the mono-
derivative 4a, the di- and tri-branched compounds (4b and 4c)

714
H.-Y. Wang et al.
Table 1. Optical, thermal, and electrochemical properties of the compounds 4 and 6
ε [L mol−1 cm−1
]
em [nm]
Φ
Band
gapA
HOMO/
LUMOA [eV]
Eg [eV]
Eox [V]
EHOMO/ELUMO [eV]
Tm/Td [◦C]
B
C
D
E
Prod
Abs.
[nm]
4a
4b
4c
6a
6b
6c
350
370
373
351
370
374
51000
77000
122000
59800
74000
139800
407
412
424
407
414
424
0.51
0.59
0.54
0.49
0.41
0.52
−3.70
−3.47
−3.40
−3.59
−3.44
−3.34
−4.71/−1.01
−4.67/−1.20
−4.64/−1.24
−4.78/−1.19
−4.73/−1.25
−4.68/−1.27
−3.19
−3.05
−3.01
−3.18
−3.04
−2.99
0.76
0.68
0.93
0.89
1.01
1.02
−5.16/−1.97
−5.08/−2.03
−5.33/−2.32
−5.29/−2.11
−5.41/−2.37
−5.42/−2.43
112/310
196/320
220/350
130/320
200/330
228/350
ADFT/B3LYP calculated values.
BDetermined from UV-vis absorption spectra.
COxidation potential in DMF (10−3 M) containing 0.1 M (n-C4H9)4NPF6 with a scan rate of 100 mV s−1
DEHOMO was calculated by Eox + 4.4 eV, and ELUMO = EHOMO − Eg [eV].
.
EMeasured by TG-DTA analysis under N2 at a heating rate of 20◦C min−1
.
(a)
(b)
160000
7000
6000
5000
4000
3000
2000
1000
0
140000
120000
100000
80000
60000
40000
20000
0
4a
4b
4c
6a
6b
6c
4a
4b
4c
6a
6b
6c
300
350
400
450
500
400
450
500
550
Wavelength [nm]
Wavelength [nm]
Fig. 1. The UV-vis absorption and PL emission spectra of compounds 4 and 6 in DMF (∼1 × 10−5 mol L−1). (a) Absorption spectra; (b) emission spectra.
0.0004
6a
6b
6c
0.0003
0.0002
4a
4b
4c
0.0003
0.0002
0.0001
0.0001
0.0000
0.0000
ꢁ0.0001
ꢁ0.0002
ꢁ0.0001
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
0.0
0.3
0.6
0.9
1.2
1.5
1.8
E [V]
E [V]
Fig. 3. Cyclic voltammograms of 6a–c (10−3 mol L−1
Bu4NPF6-CH2Cl2, with a scan rate of 100 mV s−1
)
in 0.1 M
Fig. 2. Cyclic voltammograms of 4a–c in 0.1 M Bu4NPF6-CH2Cl2, with
a scan rate of 100 mV s−1
.
.
are red-shifted (6–17 nm). Similar observations were made for
compounds 6a–c. All of these compounds show a blue PL emis-
sion, with the maximum emissions peak in the range of 406 to
424 nm in DMF.
The fluorescence quantum yields (Φ) were measured in DMF
using quinine sulfate (Φ = 0.55) as a standard.[14c] The photo-
physical data are summarized in Table 1. A Φ value of 0.59 was
obtained for 4b. The PL quantum yields of the other compounds
were in the range of 0.41–0.54.The difference of quantum yields
might result from the process of exciton migration,[15a] possibly
due to the change in molecular size.[15b]
To test the electrochemical properties of these compounds,
cyclic voltammetry (CV) studies were performed in DMF
(∼10−3 mol L−1) using tetrabutyl-ammonium hexafluorophos-
phate (0.10 mol L−1) as the supporting electrolyte. The results
are listed in the Table 1. All CV measurements were recorded
at room temperature with a conventional three-electrode con-
figuration, consisting of a platinum wire working electrode,

Bipolar Triphenylamine-benzimidazole Derivatives
715
C
B
A
B
C
A
D
D
4a
4c
Fig. 4. Optimized ground-state geometry of 4a and 4c with B3LYP/6–31G* in gas phase. Note: A, B, C, and D represent the imidazole ring and benzene
rings, respectively.
a platinum counter electrode, and a Ag/AgCl reference elec-
trode under an argon atmosphere. The electrochemical band
gaps were calculated from the onset potentials of the anodic
and cathodic waves.[16] All these compounds showed a reversible
oxidation process, which is associated with the generation
of a cation radical (Fig. 2 and Fig. 3). The HOMO levels
of these compounds were calculated with reference to fer-
rocene (4.8 eV), and the LUMO levels were estimated by
the values of Eox and the Eg.[16] As shown in Table 1, the
HOMO levels (HOMO = Eox + 4.4 eV) fell in the range of
−5.42 to −5.08 eV, while the corresponding LUMO levels
(LUMO = HOMO − Eg) ranged from −1.97 to −2.43 eV.
These data are consistent with values derived from Gaussian
calculations (−4.78 to −4.64 eV for the HOMO, and −1.27 to
−1.01 eV for the LUMO). The HOMO and LUMO energy levels
are quite close to those of phenylbenzimidazole-based bipolar
molecules, such as TPBI (−6.03, −2.10 eV), TPBI-Cz (−5.72,
2.15 eV), and TBBI (−5.49, −2.41 eV).[13c,13e] The LUMO
value is dependent on the number of acceptor moieties present
in the material.[16d] The HOMO energy level is lower than
that of the widely-used, hole-transporting material, 4,4ꢀ-bis(1-
naphthylphenylamino)biphenyl (NBP) (HOMO = −5.50 eV,
LUMO = −2.4 eV). As a result, these compounds may be appli-
cable to hole injection and transport.[17] Their LUMO levels
represent a small barrier for electron injection from a com-
monly used cathode such as barium, with a work function
of −2.2 eV.[18] Therefore, these compounds hold promise for
use as hole-transporting and electron-transporting materials for
OLEDs.[19]
properties. In fact, the DFT studies of these compounds clearly
indicate that the LUMO remains on the benzimidazole moi-
ety, with similar distributions to that of TPBI. Conversely, the
HOMOs are localized exclusively on the triphenylamine por-
tion (Fig. 5).[13e] Usually, the holes and electrons in OLEDs are
transferred through individual HOMO and LUMO levels.[13c]
As a result, the electronic delocalization is transmitted more effi-
ciently through the imidazole moieties than through the phenyl
groups. Increased delocalization along the imidazaole moieties
leads to lower band gaps, yet the same effect promotes the rate
of charge recombination, which ultimately quenches the excited
state. The HOMO/LUMO energy levels and band gaps of the
dyes are listed in Table 1.
Conclusion
In summary, a series of the novel bipolar, triphenylamine-
benzimidazole derivatives, with both hole transporting (tri-
phenylamine moieties) and electron-transporting units (benz-
imidazole moieties), have been synthesized and characterized
for their photophysical properties. These compounds exhibit
satisfying luminescence properties (high fluorescence quantum
yields) and high thermal stabilities. Moreover, the DFT calcu-
lations suggest a desirable distribution of HOMO and LUMO
densities, suggesting potential for bipolar charge transport. All
of these compounds exhibit favourable HOMO levels (−5.08 to
−5.42 eV), in good agreement with the DFT calculations, and
thus have promising application as multifunctional materials in
OLEDs.
Electronic configurations were further examined using the
theoretical models associated with Gaussian 03.[20] Molecu-
lar geometries were optimized using the B3LYP/6–31G* basis
set. In the case of 4a–c (Fig. 4), the optimized dihedral angles
between the imidazole (A) and benzene rings (B) are 2.81◦,
3.03◦, and 6.84◦, evidence of a near coplanar relationship.
The orientation of the two adjacent phenyl rings (C and D)
are twisted by 71.42◦, 50.91◦, and 51.10◦, respectively; most
likely due to steric hindrance and a non-planar configuration
of the entire molecular structure. Consequently, this may, to
some extent, impede the π–π stacking interactions in solid
state.[13e] As shown in Fig. 5, the HOMO is expected to reside
ontheelectron-richgroups, affordingeffectivehole-transporting
Experimental
Chemicals and Instruments
All reagents were commercially available and used without
further purification. Melting points were recorded on Electro-
thermal digital melting point apparatus and are uncorrected.
1H and 13C NMR spectra were recorded at 295 K on a Varian
INOVA 400 MHz or a Varian NMR System 300 MHz spectro-
meter using CDCl3 or d6-DMSO as solvents and TMS as an
internal standard. UV-vis and emission spectra were recorded on
a UV-1102 spectrometer and a Hitachi FL-2500 luminescence
spectrometer, respectively. Mass spectroscopic (MS) measure-
ments were carried out using the matrix-assisted laser desorption

716
H.-Y. Wang et al.
4c HOMO
6c HOMO
4c LUMO
6c LUMO
Fig. 5. Calculated spatial distributions of the LUMO and HOMO of 4c and 6c.
ionization time-of-flight (Voyager-DE STR MALDI-TOF) tech-
nique. HRMS data were measured using TOF-MS(EI+) with
a micrOTOF-Q(ESI) instrument. Thermal properties were ana-
lyzed on a SDT 2960 and a DSC 2010 instruments at a
20◦C min−1 heating and cooling rate.
4,4ꢀ-Diformyl Triphenylamine (2b)
4,4ꢀ-Diformyl triphenylamine was prepared in accordance with
literature.[11d] Phosphorus oxychloride (46.6 mL, 0.5 mol) was
added dropwise to stirred DMF (77.4 mL, 1 mol) at 0◦C. The
mixture was stirred at 0◦C for 1 h, and then at room temper-
ature for another 1 h. After the addition of 10 g (0.04 mol) of
triphenylamine dissolved in dichloroethane, the mixture was
stirred at 80◦C for 48 h. After cooling, the solution was poured
into cold water. The resulting mixture was neutralized to pH 7
with 5% NaOH and extracted with dichloromethane.The extract
was washed with brine and the solvent removed under reduced
pressure.The residue was chromatographed on a silica gel (ethyl
acetate/hexane = 1/3) to afford 8 g of a yellowish solid, 66%
yield. δH (400 MHz, CDCl3) 9.89 (s, 2H), 7.84 (d, J = 8.4 Hz,
4H), 7.40 (t, J = 7.6 Hz, 2H), 7.26 (t, J = 6.8 Hz, 1H), 7.18–7.20
(m, 6H).
4-(Diphenylamino)benzaldehyde (2a)
4-(Diphenylamino)benzaldehyde was prepared in accordance
with literature.[11d] Phosphorus oxychloride (1.57 mL,
16.82 mmol) was added dropwise to DMF (1.32 mL,
19.50 mmol) at 0◦C, and the mixture was stirred for 1 h at this
temperature. Triphenylamine (3.27 g, 13.33 mmol) was added
and the reaction mixture was heated to 100◦C for 6 h. The mix-
ture was subsequently cooled to room temperature, poured into
ice water and carefully neutralized with NaOH. The solution
wasextractedwithdichloromethane(3 × 150 mL), thenthecom-
bined organic phase was washed with water (2 × 100 mL) and
dried over anhydrous sodium sulfate. After filtration, the solvent
was removed. The crude product was purified by chromato-
graphy on silica gel (ethyl acetate/hexane 1/8) to afford 4.9 g
of a white solid, 80% yield.
Tris-(4-formyl-phenyl)amine (2c)
Tris-(4-formyl-phenyl)amine was prepared in accordance with
literature.[11d] Phosphorus oxychloride (46.6 mL, 0.5 mol) was
added dropwise to stirred DMF (77.4 mL, 1 mol) at 0◦C. The
mixture was stirred at 0◦C for 1 h, and additionally stirred at
room temperature for 1 h. After the addition of 6 g (0.02 mol)
of 2b in dichloroethane, the mixture was stirred at 80◦C for
δH (400 MHz, CDCl3) 9.81 (s, 1H), 7.69 (d, J = 8.8 Hz,
2H), 7.34 (t, J = 8.0 Hz, 4H), 7.17–7.19 (m, 6H), 7.03 (d, J =
8.8 Hz, 2H).

Bipolar Triphenylamine-benzimidazole Derivatives
717
a further 48 h. After cooling, the solution was poured into
water. The resulting mixture was neutralized to pH 7 with 5%
NaOH and extracted with dichloromethane. The extract was
washed with brine and the solvent removed under reduced pres-
sure. The residue was chromatographed on a silica gel (ethyl
acetate/hexane1/1)toafford1.35 gofyellowishsolid, 20%yield.
δH (300 MHz, CDCl3)9.95(s, 3H), 7.86(d, J = 8.7 Hz, 6H), 7.28
(d, J = 8.1 Hz, 6H). δC (75 MHz, CDCl3) 190.8, 151.4, 132.7,
131.8, 124.8.
DMSO-d6) 148.3, 147.5, 146.8, 144.8, 133.7, 132.8, 129.6,
129.5, 127.2, 126.4, 124.8, 124.5, 123.3, 118.1, 111.7, 109.6,
55.4, 54.9. m/z (HRMS) Found 870.2616 (M + H), Anal. Calc.
for C52H43N5O4: M, 869.2536.
4,4ꢀ,4ꢀꢀ-Tri(5-(3,4-dimethoxyphenyl)-6-(2-chloro-phenyl)-
1H-benzimidazol-2-yl)-triphenylamine (6c)
Yield 85%, yellow compound. mp 219◦C. δH (400 MHz, DMSO-
d6) 12.71 (s, 2H), 12.52 (s, 1H), 8.03–8.11 (m, 5H), 7.52–7.66
(m, 13H), 6.89–7.21 (m, 13H), 3.72 (s, 9H), 3.54 (s, 9H). δC
(75 MHz, DMSO-d6) 148.3, 147.6, 146.5, 144.8, 133.8, 132.9,
129.6, 127.3, 126.6, 126.5, 125.2, 123.8, 118.1, 118.1, 118.0,
111.7, 109.6, 55.4, 54.9. m/z (HRMS) Found 1183.3 (M+),Anal.
Calc. for C69H57N7O6: M, 1181.3.
General Procedure for the Synthesis of the
Compounds (4, 6)
Compounds 4, 6 were synthesized by reaction of 2 with
either 3 or 5 as per the following procedure: A mixture of
2 (1.00 mmol) and 3 or 5 (1.00 mmol) and CH3COONH4
(0.20 mL) in CH3COOH (5.00 mL) was refluxed for 6–12 h.The
resulting mixture was cooled and the precipitate filtered to afford
crude products, which were further purified by recrystallization
from EtOH.
Accessory Publication
General experimental methods and spectroscopic and analytical
data for compounds are available on the Journal’s website.
Acknowledgement
4-(5,6-Diphenyl-1H-benzimidazol-2-yl)-
triphenylamine (4a)
We are grateful to Dr Xiao-Peng Chen and Professor Ping Lu in Department
of Chemistry of Zhejiang University for computational assistance. The work
was partially supported by the National Natural Science Foundation of China
(No. 20672079), Nature Science Key Basic Research of Jiangsu Province
for Higher Education (No. 06KJA15007), Natural Science Foundation of
Jiangsu Province (No. BK2006048), Nature Science of Jiangsu Province for
Higher Education (No. 05KJB150116), the Specialised Research Fund for
the Doctoral Program of Higher Education (No. 20060285001), and Key
Laboratory of Organic Synthesis of Jiangsu Province (No. JSK008).
Yield 88%, yellow compound. mp 112◦C. δH (400 MHz, DMSO-
d6) 12.54 (s, 1H), 7.99 (d, J = 8.4 Hz, 2H), 7.32–7.52 (m, 14H),
7.03–7.10 (m, 8H). δC (75 MHz, DMSO-d6) 148.2, 147.8, 146.4,
130.5, 129.3, 127.3, 125.3, 125.2, 124.3, 123.6. m/z (HRMS)
Found 463.2050 (M+),Anal. Calc. for C33H25N3: M, 463.2048.
4,4ꢀ-Di(5,6-diphenyl-1H-benzimidazol-2-yl)-
triphenylamine (4b)
References
Yield 86%, yellow compound. mp 196◦C. δH (400 MHz, DMSO-
d6) 12.58 (s, 2H), 8.04 (d, J = 8.4 Hz, 4H), 7.54 (d, J = 7.2 Hz,
8H), 7.36–7.41 (m, 14H), 7.14 (t, J = 8.0 Hz, 7H). δC (75 MHz,
DMSO-d6) 146.3, 146.0, 144.8, 129.2, 127.8, 125.9, 124.3,
124.1, 122.8. m/z (HRMS) Found 681.2885 (M+), Anal. Calc.
for C48H35N5: M, 681.2892.
[1] C. W. Tang, S. A. Vanslyke, Appl. Phys. Lett. 1987, 51, 913.
doi:10.1063/1.98799
[2] A. J. Berresheim, M. Müller, K. Müllen, Chem. Rev. 1999, 99, 1747.
doi:10.1021/CR970073+
[3] H. Aziz, Z. D. Popovic, N. X. Hu, A. M. Hor, G. Xu, Science 1999,
283, 1900. doi:10.1126/SCIENCE.283.5409.1900
[4] (a) Y. Shirota, M. Kinoshita, T. Noda, K. Okumoto, T. Ohara, J. Am.
Chem. Soc. 2000, 122, 11021. doi:10.1021/JA0023332
(b) J. M. Hancock, A. P. Gifford,Y. Zhu,Y. Lou, S. A. Jenekhe, Chem.
Mater. 2006, 18, 4924. doi:10.1021/CM0613760
4,4ꢀ,4ꢀꢀ-Tris(5,6-diphenyl-1H-benzimidazol-2-yl)-
triphenylamine (4c)
Yield 84%, yellow compound. mp 228◦C. δH (400 MHz, DMSO-
d6) 12.78 (s, 3H), 8.09 (d, J = 8.8 Hz, 6H), 7.54 (d, J = 7.6 Hz,
12H), 7.20–7.39 (m, 24H). δC (75 MHz, DMSO-d6) 149.5,
148.1, 131.3, 130.6, 130.1, 129.6, 127.9, 126.8. m/z (HRMS)
Found 900.4 (M + H), Anal. Calc. for C63H45N7: M, 899.4.
(c) Z. H. Li, M. S. Wong, H. Fukutani,Y.Tao, Org. Lett. 2006, 8, 4271.
doi:10.1021/OL0615477
[5] (a)Y. Zhu,A. P. Kulkarni, S.A. Jenekhe, Chem. Mater. 2005, 17, 5225.
doi:10.1021/CM050743P
(b) C.T. Chen, J. S. Lin, M.V. R. K. Moturu,Y. W. Lin, W.Yi,Y.T.Tao,
C. H. Chen, Chem. Commun. 2005, 3980. doi:10.1039/B506409K
(c) X. Xu, S. Chen, G. Yu, C. Di, H. You, D. Ma, Y. Liu, Adv. Mater.
2007, 19, 1281. doi:10.1002/ADMA.200601919
4-(5-(3,4-Dimethoxyphenyl)-6-(2-chloro-phenyl)-
1H-benzimidazol-2-yl)-triphenylamine (6a)
(d) T. H. Huang, J. T. Lin, L. Y. Chen, Y. T. Lin, C. C. Wu, Adv. Mater.
2006, 18, 602. doi:10.1002/ADMA.200502078
[6] (a) F. Habrard, T. Ouisse, O. Stephan, L. Aubouy, P. Gerbier,
L. Hirsch, N. Huby, A. V. Lee, Synth. Met. 2006, 156, 1262.
doi:10.1016/J.SYNTHMET.2006.09.009
Yield 80%, yellow compound. mp 130◦C. δH (300 MHz, DMSO-
d6) δ 12.62 (s, 1H), 7.96 (d, J = 8.8 Hz, 2H), 7.39–7.50 (m,
4H), 7.34 (t, J = 7.6 Hz, 4H), 7.20 (d, J = 8.4 Hz, 1H), 7.04–
7.08 (m, 8H), 6.87–6.95 (m, 2H), 3.72 (s, 3H), 3.54 (s, 3H). δC
(75 MHz, DMSO-d6) 148.3, 147.2, 146.8, 144.9, 132.8, 132.7,
129.8, 129.5, 126.2, 125.3, 124.4, 124.1, 123.2, 122.7, 118.1,
111.8, 109.7, 55.4, 54.9. m/z (HRMS) Found 559.1860 (M+),
Anal. Calc. for C35H29N3O2: M, 559.1841.
(b) T. H. Lee, K. L. Tong, S. K. So, L. M. Leung, Synth. Met. 2005,
155, 116. doi:10.1016/J.SYNTHMET.2005.06.020
[7] M. Thelakkat, Macromol. Mater. Eng. 2002, 287, 442. doi:10.1002/
1439-2054(20020701)287:7<442::AID-MAME442>3.0.CO;2-H
[8] Y. Shirota, J. Mater. Chem. 2005, 15, 75. doi:10.1039/B413819H
[9] (a) Y. Song, C. Di, X. Yang, S. Li, W. Xu, Y. Liu, L. Yang,
Z. Shuai, D. Zhang, D. Zhu, J. Am. Chem. Soc. 2006, 128, 15940.
doi:10.1021/JA064726S
4,4ꢀ-Di(5-(3,4-dimethoxyphenyl)-6-(2-chloro-phenyl)-
1H-benzimidazol-2-yl)-triphenylamine (6b)
Yield 86%, yellow compound. mp 200◦C. δH (400 MHz, DMSO-
d6) 12.67 (s, 2H), 8.01 (d, J = 8.4 Hz, 3H), 7.36–7.62 (m, 10H),
6.88–7.15 (m, 14H), 3.72 (s, 6H), 3.54 (s, 6H). δC (75 MHz,
(b)A. Cravino, S. Roquet, O.Aleveque, P. Leriche, P. Frere, J. Roncali,
Chem. Mater. 2006, 18, 2584. doi:10.1021/CM060257H
(c) T. P. I. Saragi, T. F. Lieker, J. Salbeck, Adv. Funct. Mater. 2006, 16,
966. doi:10.1002/ADFM.200500361

718
H.-Y. Wang et al.
[10] (a) G. Bordeau, R. Lartia, G. Metge, C. Fiorini-Debuisschert,
F. Charra, M. P. Teulade-Fichou, J. Am. Chem. Soc. 2008, 130, 16836.
doi:10.1021/JA8055112
(e) S. Takizawa, V. A. Montes, P. A. Jr, Chem. Mater. 2009, 21, 2452.
doi:10.1021/CM9004954
[14] (a) T. C. Lin, G. S. He, P. N. Prasad, L. S. Tan, J. Mater. Chem 2004,
14, 982. doi:10.1039/B313185H
(b) S. Roquet,A. Cravino, P. Leriche, O.Alèvêque, P. Frère, J. Roncali,
J. Am. Chem. Soc. 2006, 128, 3459. doi:10.1021/JA058178E
(c) Y. Qian, K. Meng, C. G. Lu, B. P. Lin, W. Huang, Y. P. Cui, Dyes
Pigments 2009, 80, 174. doi:10.1016/J.DYEPIG.2008.07.005
[15] (a)Y. Li, J. Ding, M. Day,Y. Tao, J. Lu, M. Diorio, Chem. Mater. 2004,
16, 2165. doi:10.1021/CM030069G
(b) A. Bhaskar, G. Ramakrishna, Z. Lu, R. Twieg, J. M. Hales, D. J.
Hagan, E. V. Stryland, T. Goodson III, J. Am. Chem. Soc. 2006, 128,
11840. doi:10.1021/JA060630M
(c) J. Lu, P. F. Xia, P. K. Lo, Y. Tao, M. S. Wong, Chem. Mater. 2006,
18, 6194. doi:10.1021/CM062111O
(d) P. Leriche, P. Frère, A. Cravino, O. Alévêque, J. Roncali, J. Org.
Chem. 2007, 72, 8332. doi:10.1021/JO701390Y
[11] (a) Z. Ning, Q. Zhang, W. Wu, H. Pei, B. Liu, H. Tian, J. Org. Chem.
2008, 73, 3791. doi:10.1021/JO800159T
(b) Z. Zhao, X. Xu, Z. Jiang, P. Lu, G.Yu,Y. Liu, J. Org. Chem. 2007,
72, 8345. doi:10.1021/JO7013388
(b) G. K. Paul, J. Mwaura, A. A. Argun, P. Taranekar, J. R. Reynolds,
Macromolecules 2006, 39, 7789. doi:10.1021/MA060808P
(c) Z. Ning, H. Tian, Chem. Commun. 2009, 5483. doi:10.1039/
B908802D
(d) H. J. Lee, J. Sohn, J. Hwang, S. Young, P. H. Choi, M. Cha, Chem.
Mater. 2004, 16, 456. doi:10.1021/CM0343756
(e) K. T. Kamtekar, C. Wang, S. Bettington, A. S. Batsanov, I. F.
Perepichka, M. R. Bryce, J. H. Ahn, M. Rabinal, M. C. Petty, J. Mater.
Chem. 2006, 16, 3823. doi:10.1039/B604543J
[16] (a) S. Janietz, D. D. C. Bradley, M. Grell, C. Giebeler, M. Inbaselatan,
E. P. Woo, Appl. Phys. Lett. 1998, 73, 2453. doi:10.1063/1.122479
(b) J. Pommerehne, H. Vestweber, W. Guss, R. F. Mahrt, H.
Bässler, M. Porsch, J. Daub, Adv. Mater. 1995, 7, 551. doi:10.1002/
ADMA.19950070608
(c) D. P. Hagberg, T. Edvinsson, T. Marinado, G. Boschloo,
A. Hagfeldt, L. Sun, Chem. Commun. 2006, 2245. doi:10.1039/
B603002E
(d) P. Sonar, S. P. Singh, P. Leclere, M. Surin, L. Roberto, T. T.
Lin, A. Dodabalapur, A. Sellinger, J. Mater. Chem. 2009, 19, 3228.
doi:10.1039/B820528K
[12] (a) H. Ohishi, M. Tanaka, H. Kegeyama,Y. Shirota, Chem. Lett. 2004,
33, 1266. doi:10.1246/CL.2004.1266
(b) T. P. I. Saragi, T. Fuhrmann-Lieker, J. Salbeck, Synth. Met. 2005,
148, 267. doi:10.1016/J.SYNTHMET.2004.10.007
[17] G. Yu, S. Yin, Y. Liu, Z. Shuai, D. Zhu, J. Am. Chem. Soc. 2003, 125,
14816. doi:10.1021/JA0371505
(c) M. Sonntag, K. Kreger, D. Hanft, P. Strohriegl, S. Setayesh, D. de
Leeuw, Chem. Mater. 2005, 17, 3031. doi:10.1021/CM047750I
(d) S.Tao, L. Li, J.Yu,Y. Jiang,Y. Zhou, C. S. Lee, S.T. Lee, X. Zhang,
O. Kwon, Chem. Mater. 2009, 21, 1284. doi:10.1021/CM803087C
[13] (a) W. Y. Hung, T. H. Ke, Y. T. Lin, C. C. Wu, T. H. Hung, T. C.
Chao, K. T. Wong, C. I. Wu, Appl. Phys. Lett. 2006, 88, 064102.
doi:10.1063/1.2172708
[18] (a) B. E. Koene, D. E. Loy, M. E. Thompson, Chem. Mater 1998, 10,
2235. doi:10.1021/CM980186P
(b) M. Thelakkat, H. W. Schmidt, Adv. Mater. 1998, 10, 219.
doi:10.1002/(SICI)1521-4095(199802)10:3<219::AID-ADMA219>
3.0.CO;2-6
[19] (a) X. H. Zhang, W. Y. Lai, Z. Q. Gao, T. C. Wong, C. S. Lee,
H. L. Kwong, S. T. Lee, S. K. Wu, Chem. Phys. Lett. 2000, 320,
77. doi:10.1016/S0009-2614(00)00213-X
(b) Y. T. Tao, E. Balasubramaniam, A. Danel, P. Tomasik, Appl. Phys.
Lett. 2000, 77, 933. doi:10.1063/1.1288811
[20] M. J. Frisch, G. W. Trucks, H. B. Schlegel, P. M. W. Gill, B. G.
Johnson, M. A. Robb, Gaussian 03, revision C.01 2004 (Gaussian,
Inc.: Pittsburgh, PA).
(b)Y. L. Liao, C.Y. Lin, K. T. Wong, T. H. Hou, W.Y. Hung, Org. Lett.
2007, 9, 4511. doi:10.1021/OL701994K
(c) Z. Ge, T. Hayakawa, S. Ando, M. Ueda, T. Akiike,
H. Miyamoto, T. Kajita, M. Kakimoto, Chem. Mater. 2008, 20, 2532.
doi:10.1021/CM7035458
(d) C. J. Kuo, T. Y. Li, C. C. Lien, C. H. Liu, F. I. Wu, M. J. Huang,
J. Mater. Chem. 2009, 19, 1865. doi:10.1039/B816327H