Synthesis, characterization, and field-effect transistor properties of carbazolenevinylene oligomers: From linear to cyclic architectures

Article abstract of DOI:10.1002/chem.200800008

Two cyclic carbazolenevinylene dimers 1 and 2 were synthesized by McMurry coupling reactions. A linear compound 3 was also prepared for comparison. Compounds 1-3 were fully characterized by means of NMR spectroscopy, HRMS, elemental analysis, and UV/Vis absorption spectroscopy. Quantum chemical simulations showed that the cyclic compounds possessed smaller HOMO-LUMO gaps and more extended conjugation. The UV/Vis absorption spectra of the cyclic compounds showed blueshifts compared with that of the linear compound 3. Time-dependent DFT (TD-DFT) analysis revealed that this was due to the different selection rules for molecules with cyclic and linear architectures. The cyclic conformation also significantly affected the molecular ordering in the solid state. The X-ray crystal structure of 1 showed partial π-π over-lapping between the adjacent mole-cules. Thin films of 1-3 were fabricated by the vacuum-deposition method on Si/SiO, substrates. Multicrystalline thin films were obtained from compounds 1 and 2, but only amorphous thin films could be obtained for the linear compound 3. Another important difference between the cyclic and linear compounds was the reduced reorganization energy for the cyclic compounds. These two facts have resulted in improved field-effect transistor (FET) mobilities for the cyclic compounds compared with the linear compound. In addition, as the substrate temperature has a significant influence on the morphology and the degree of crystallinity of the thin films deposited, the device performance could be optimized by varying the substrate temperature. The FET devices based on 2 gave the highest mobility of 0.013 cm²V ^-1s^-1. The results showed that carbazole derivatives with cyclic structures might make better FETs.

Full text of DOI:10.1002/chem.200800008

FULL PAPER
DOI: 10.1002/chem.200800008
Synthesis, Characterization, and Field-Effect Transistor Properties of
Carbazolenevinylene Oligomers: From Linear to Cyclic Architectures
Yabin Song,[a, b] Chong-an Di,[a, b] Zhongming Wei,[a, b] Tianyue Zhao,[a, b] Wei Xu,*[a]
Yunqi Liu,*[a] Deqing Zhang,[a] and Daoben Zhu*[a]
Abstract: Two cyclic carbazolenevinyl-
ene dimers 1 and 2 were synthesized
by McMurry coupling reactions.
tures. The cyclic conformation also sig-
nificantly affected the molecular order-
ing in the solid state. The X-ray crystal
structure of 1 showed partial p–p over-
lapping between the adjacent mole-
cules. Thin films of 1–3 were fabricated
by the vacuum-deposition method on
Si/SiO2 substrates. Multicrystalline thin
films were obtained from compounds 1
and 2, but only amorphous thin films
could be obtained for the linear com-
pound 3. Another important difference
between the cyclic and linear com-
pounds was the reduced reorganization
energy for the cyclic compounds. These
two facts have resulted in improved
field-effect transistor (FET) mobilities
for the cyclic compounds compared
with the linear compound. In addition,
as the substrate temperature has a sig-
nificant influence on the morphology
and the degree of crystallinity of the
thin films deposited, the device perfor-
mance could be optimized by varying
the substrate temperature. The FET
devices based on 2 gave the highest
mobility of 0.013 cm2 Vꢀ1 sꢀ1. The re-
sults showed that carbazole derivatives
with cyclic structures might make
better FETs.
ACHTREUNG
A
linear compound 3 was also prepared
for comparison. Compounds 1–3 were
fully characterized by means of NMR
spectroscopy, HRMS, elemental analy-
sis, and UV/Vis absorption spectrosco-
py. Quantum chemical simulations
showed that the cyclic compounds pos-
sessed smaller HOMO–LUMO gaps
and more extended conjugation. The
UV/Vis absorption spectra of the cyclic
compounds showed blueshifts com-
pared with that of the linear compound
3. Time-dependent DFT (TD-DFT)
analysis revealed that this was due to
the different selection rules for mole-
cules with cyclic and linear architec-
Keywords: cyclooligomerization
density functional calculations
·
·
·
films
·
semiconductors
structure–activity relationships
Introduction
layers instead of traditional silicon in field-effect transistors
(FETs).[2] Furthermore, organic materials possess many ad-
vantages over silicon, such as low cost, flexibility, and easier
tailoring of the functional properties of the materials by
modification of their molecular structures.[2] Some organic
semiconductors may be deposited by low temperature solu-
tion processing, which allows industrial methods, such as
spin coating, printing and stamping to be used.[3] Therefore,
they provide alternative approaches towards the realization
of low cost electronics. To date, significant progress has
been made in increasing the performance of organic semi-
conductors in FETs in all respects of charge-carrier mobility,
on/off ratio, and stability.[2,4] However, it is still a major chal-
lenge to understand the relationship between molecular
structures and properties, and there are no definite guide-
lines for molecular designs to facilitate the charge trans-
port.[5]
Organic semiconductors have been the focus of intense in-
vestigation for the past decade because of their potential
electronic applications.[1] Due to their capability of trans-
porting charge, organic semiconductors can act as active
[a] Y. Song, C.-a. Di, Z. Wei, T. Zhao, Dr. W. Xu, Prof. Y. Liu,
Prof. D. Zhang, Prof. D. Zhu
CAS Key Laboratory of Organic Solids
Beijing National Laboratory for Molecular Sciences
Institute of Chemistry, Chinese Academy of Sciences
Beijing 100080 (China)
Fax : (+86)10-6256-9349
E-mail: wxu@iccas.ac.cn
liuyq@iccas.ac.cn
zhudb@iccas.ac.cn
[b] Y. Song, C.-a. Di, Z. Wei, T. Zhao
Graduate School of the Chinese Academy of Sciences
Beijing 100080 (China)
Carbazole-based materials have been widely studied for
their unique electrical and optical properties.[6] They have
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4731

been used as hole-transporting materials in a variety of
fields, such as organic photoconductors,[6] organic light-emit-
ting diodes,[7] and nonlinear optics[8]. Due to their excellent
hole transporting characteristics and air-stability, carbazole
derivatives have also been used in FETs.[2d,9] Recently,
Drolet et al. fabricated organic FETs based on thin films of
2,7-carbazolenevinylene-based oligomers and obtained high
hole mobilities (0.3 cm2 Vꢀ1 sꢀ1).[9d] Ong and co-workers have
also reported a series of indolo
A
that can be used to fabricate high-mobility FETs under am-
bient conditions.[9b,c] This research indicates that carbazole-
based materials can be attractive candidates for FETappli-
cations.
Conjugated macrocyclic oligomers have become a topic of
growing interest in several fields of research, including
supramolecular chemistry, organic materials science, and
nanotechnology.[10] The cyclic structure of these compounds
were fabricated and tested in detail. They all worked as p-
type semiconductors. The film morphologies and molecular
structures were discussed in relation to the device perform-
ances.
represents
a defect-free and well-defined p-conjugated
chain, which ideally combines an infinite polymer with the
structural features of a well-defined oligomer, but without
any perturbing end-effects.[11] Cyclic oligomers based on car-
bazole have been synthesized and investigated.[12] Impor-
tantly, several carbazolylacetylene-derived macrocycles have
been reported that have unique fluorescence-quenching-
based chemical detection,[13] self-assembly,[14] and photoin-
duced charge-transfer properties.[15] However, their synthesis
is always complicated, and their potential use in FETs has
been scarcely studied so far. Furthermore, comparing the
properties of the cyclic oligomers with those of the linear
oligomers will provide useful information for molecular
design in the development of
Results and Discussion
Synthesis: The procedure for the synthesis of compounds 1–
3 is shown in Scheme 1. Compounds 1 and 2 were synthe-
sized by a similar process to that we have reported previous-
ly.[16] Two formyl groups were introduced into carbazole to
give the precursor of 1 in high yield by direct Vilsmeier–
Haack formylation employing DMF and phosphorus oxy-
chloride.[18] However, for phenyl-substituted carbazole 6, the
yield was very low. Thus, 6 was brominated, followed by
novel molecular materials.
Based on previous work on
the synthesis of the triphenyl-
ACHTREUNG
cles,[15,16] we planned to apply
the McMurry reaction for the
synthesis of cyclic carbazolene-
vinylene oligomers. Carbazole
units were linked by two ethyl-
ene groups resulting in two
cyclic dimers (compounds
1
and 2). The introduction of
carbon–carbon double bonds
in organic conductors is
deemed to reduce the band
gap and tune the electrical
properties with an extended p-
conjugated length.[9d,17] For
comparison, a linear carbazole
dimer (compound 3) was also
synthesized. The optical and
electronic properties of 1–3
were fully characterized. To in-
vestigate their hole-transport-
ing properties, FETdevices
Scheme 1. i) TBAI, NaOH; ii) POCl3, DMF; iii) TiCl4, Zn, pyridine, 808C; iv) K2CO3, CuI, [18]crown-6;
v) NBS; vi) ꢀ788C, nBuLi, DMF. TBAI=tetrabutylammonium iodide; NBS=N-bromosuccinimide
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Carbazolenevinylene Oligomers
FULL PAPER
lithiation and reaction with DMF, which afforded the di-
formyl compound 8 in a satisfactory yield. Compounds 1–3
were realized by McMurry coupling reactions.[16,19] The reac-
tions of 9-n-butyl-carbazole-3,6-dicarbaldehyde and 9-
phenyl-carbazole-3,6-dicarbaldehyde with TiCl4, Zn powder,
and pyridine in THF at reflux under nitrogen gave 1 and 2
in yields of 8.1 and 5.6%, respectively. Although the yields
were low, the syntheses were simple and could be operated
on a large scale. Compound 3 was also synthesized by
McMurry reactions in 58.0% yield. Compounds 1 and 3
were soluble in common organic solvents, such as dichloro-
methane and toluene, with a high solubility (>10 mgmLꢀ1),
but
2
had very low solubility in organic solvents
(<1 mgmLꢀ1 in chloroform or toluene at room tempera-
ture). All compounds were characterized by HRMS, NMR
spectroscopy, and elemental analysis. Compound 2 could not
be characterized by 13C NMR spectroscopic analysis due to
its poor solubility. Thermogravimetric analysis (TGA) meas-
urements gave thermal decomposition temperatures (Td) of
466, 406, and 4208C for 1, 2, and 3, respectively. Their melt-
ing points were all above 2008C, which showed that they all
possessed excellent thermal stability.
Crystal structure: Single crystals of 1 for X-ray analysis
were obtained by slow evaporation of its dichloromethane
solution. The crystal belongs to a crystal system of ortho-
rhombic space group Pbca with unit-cell parameters of a=
15.618(3), b=8.4122(17), c=19.403(4) Š. As shown in Fig-
ure 1a, molecule 1 has a symmetric center located at the
center of the cyclic structure. The carbazole moieties band
to a nonplanar comformation with a dihedral angle of about
128 between the five-membered ring and fused six-mem-
bered ring. Molecules stacked in a column along the b-axis
can be observed when the structure is viewed along the c-
axis (Figure 1b). There is partial p–p overlapping between
the adjacent molecules in the same column, as the inter-
plane distance between two N-hetero rings is about 3.25 Š.
This column-stacking manner may favor efficient hole trans-
portation.
Figure 1. a) Molecular structure of compound 1 with 50% possibility el-
lipsoids. b) Stacking pattern of 1 in the crystal view along the c-axis, inter-
molecular p–p interactions are indicated by a (hydrogen atoms were
omitted for clarity).
Cyclic voltammetric measurements have been carried out
on compounds 1–3. We used a conventional three-electrode
cell with Pt working electrodes, a platinum wire counter
electrode, and an Ag/AgCl reference electrode at room tem-
perature. The experiments were calibrated with the ferro-
cene/ferrocenium (Fc/Fc+) redox system. They all showed
two reversible oxidation waves corresponding to the oxida-
tion of each of the nitrogens (Figure 3). The two oxidation
peaks of 1 were found at 0.804 and 1.079 V (vs. Ag/AgCl),
whereas 2 had peaks at 0.928 and 1.142 V. They were all a
little higher than the potentials of 3 (0.791, 1.128 V). The
large separation of the redox potentials indicated that the
two carbazole units were strongly electronically coupled. We
used the onset oxidation potentials to determine the
HOMO levels based on the internal standard ferrocene
value of ꢀ4.8 eV with respect to the zero vacuum level.[20]
Optical and electrochemical properties: The UV/Vis spectra
of 1–3 in dichloromethane and in neat films are shown in
Figure 2. Their spectra in solution showed absorption peaks
at 298, 300, and 343 nm, respectively. In thin films prepared
by the vacuum-deposition method, the absorption maxima
of 1 and 2 were at 304 and 307 nm, exhibiting a small red-
shift and broadening in comparison with that in solution.
This indicated the formation of J-aggregates in the solid
state. The spectrum of compound 3 as a film showed a
smaller shift, which indicated loose congregation. From the
absorption edges of the thin film spectra, optical band gaps
of 1, 2, and 3 were estimated as 3.51, 3.21, and 2.88 eV, re-
spectively. The band gaps in 1 and 2 were much larger than
in the linear analogue 3, which showed that they might be
more stable. This is in conflict with the HOMO–LUMO
gaps (HLGs) obtained from the quantum simulation, which
is discussed below.
The HOMO levels could be estimated by using the equation
onset
ox
HOMO=ꢀ(E
+
4.4) eV.[21] Therefore, the HOMO
levels of 1–3 were estimated by using the oxidation onsets
(0.69 V for 1, 0.82 V for 2, and 0.70 V for 3) and were found
to be ꢀ5.09, ꢀ5.22, and ꢀ5.10 eV, respectively. These values
were very low, which implies high oxidative stability. The
appropriate HOMO level of 1 and 3 also matched well with
the work function of metallic gold (ꢀ5.1 eV). This might en-
hance the hole injection between the electrode and p-chan-
nel type semiconductor, and thus improve the device perfor-
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D. Zhu, Y. Liu, W. Xu et al.
Figure 3. Cyclic voltammograms of 1–3 in dichloromethane at room tem-
perature (scan rate=50 mVsꢀ1).
Figure 4. AFM images of the films of compound 1 on OTS treated Si/
SiO2 deposited at a) 20, b) 40, c) 60, and d) 1008C (~50 nm thickness).
Each image is 5 mm”5 mm.
Figure 2. UV/Vis absorption spectra of a) 1, b) 2, and c) 3 in dichlorome-
thane (c) and as thin films (a). Thin films of 1–3 about 50 nm thick
were fabricated by a vacuum-deposition method on quartz substrates at
room temperature.
films of compound 1 deposited at room temperature (208C)
showed a smoother morphology than those deposited at
higher temperatures, but with a small grain size. While the
grain size grew as the substrate temperature increased, the
films became discontinuous bundlelike structures at 40 and
608C. At a substrate temperature of 1008C, crystalline belts
linking these bundles could be observed. A similar trend in
film morphologies was observed for compound 2. At a sub-
strate temperature of 208C, the film was very even and con-
tinuous. The substrate was covered by the material and a
good network interconnection was formed between the crys-
tallites. When the substrate temperature increased, the films
became very rough and discontinuous. At 608C, besides sep-
arated bundlelike structures at the film surface, a continuous
smooth film could be observed underneath these bulges.
mance. On the contrary, the HOMO level of 2 was a little
larger than the work function of metallic gold.
Thin films: Thin films of 1–3 were fabricated by a
vacuum-deposition method on Si/SiO2 substrates. The Si/
SiO2 substrate was highly n+-doped Si with a 450 nm ther-
mally oxidized SiO2 layer on it. Before the deposition of the
organic semiconductor, an octadecyltrichlorosilane (OTS)
self-assembled monolayer was preformed on the surface of
SiO2. We used several substrate temperatures (Tsub) during
the deposition process. Atomic-force microscopy (AFM)
was used to investigate these films (Figures 4 and 5). The
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Carbazolenevinylene Oligomers
FULL PAPER
Figure 5. AFM images of the films of compound 2 on OTS treated Si/
SiO2 deposited at a) 20, b) 40, c) 60, and d) 1008C (~50 nm thickness).
Each image is 5 mm”5 mm.
This might account for the high mobility observed at this
temperature. At 1008C, the films showed clewlike structures
with bigger boundaries between the clews. For compound 3,
we fabricated thin films at room temperature (208C), and
they showed a similar morphology to that observed for com-
pound 2 at the same Tsub (Figure 6).
These films were also characterized by XRD (Figure 7).
The XRD patterns of thin films of 1 exhibited weak diffrac-
tion peaks at all temperatures, and thus showed low crystal-
linity. Although films obtained at a substrate temperature of
40 and 1008C showed relatively stronger diffractions than
that obtained at 208C, they showed less continuity. This
should account for the higher FETmobility observed in the
films deposited at 208C. For compound 2, diffraction peaks
could only be observed on films deposited at 608C. This in-
dicated that the films with a relatively high degree of order-
ing and crystallinity were formed at this temperature. The
Figure 7. XRD patterns of vacuum-deposited thin films of a) 1 and b) 2
on OTS treated Si/SiO2 substrate at various substrate temperatures
(Tsub).
optimized thin films of 3 exhibited no XRD peaks, and thus
showed amorphous properties.
FET Measurements: FETdevices were fabricated by using
top-contact geometry. The thin films (~50 nm) of 1, 2, and 3
were deposited on OTS treated Si/SiO2 substrates by using
the vacuum-deposition method as noted above. Subsequent-
ly, gold electrodes were deposited by vacuum evaporation
on the organic layer through a shadow mask. The character-
istics of the FETs were obtained at room temperature in air.
The mobilities were extracted in the saturation regime from
the gate sweep by using Equation (1):
mWCi
2L
2
ð1Þ
IDS ¼ ð
ÞðVGꢀVTÞ
in which IDS is the drain-source current, m is the field-effect
mobility, W is the channel width, Ci is the capacitance per
unit area of the gate dielectric layer, L is the channel length,
and VG and VT are the gate voltage and threshold voltage,
respectively. The FET characteristics of the devices based
Figure 6. AFM image of a thin film of compound 3 on OTS treated Si/
SiO2 deposited at 208C (~50 nm thickness). The image is 5 mm”5 mm.
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D. Zhu, Y. Liu, W. Xu et al.
on 1–3 at different substrate temperatures are summarized
in Table 1. As examples, the output and transfer characteris-
tics of the devices are shown in Figure 8. These compounds
all displayed p-type accumulation FETbehaviors. They all
showed well-defined linear and saturation-regime output
characteristics.
in the calculation of transition energies at the B3LYP/6-
31G* level.
In the UV/Vis spectra of compounds 1, 2, and
3
(Figure 2), the first intensive absorptions of cyclic dimers
are blueshifted by about 40 nm with respect to the linear
compound. This conflicts with the HLG determined by
quantum simulation. To understand such phenomena, we
have calculated the transition energy by using TD-DFT. The
results are collected in Table 2. The calculated maxima are
in good agreement with experimental observations. It can be
seen that the transition-energy differences for these com-
pounds are due to the different assignments of these transi-
tions, which mainly belong to HOMOꢀ1–LUMO and
HOMO–LUMO+3 transitions for the cyclic compounds and
to the HOMO–LUMO transition for the linear analogue.
Such different selection rules for linear and cyclic conjugat-
ed oligomers have also been noted by Bäuerle and co-work-
ers in cyclic and linear oligothiophenes.[22]
Table 1. The performance of FETs based on compounds1, 2, and 3 pre-
pared at different deposition temperatures of the substrate (Tsub).
Compound Tsub
[8C]
Mobility
On/Off
ratio
Threshold voltage
[V]
[cm2 Vꢀ1 sꢀ1
]
1
2
3
20
40
60
100
20
40
60
100
20
5.3”10ꢀ3
2.6”10ꢀ4
1.2”10ꢀ4
–
106
105
104
–
ꢀ4.7
ꢀ28.9
ꢀ26.3
–
ꢀ20.4
ꢀ23.6
ꢀ22.0
ꢀ26.8
ꢀ6.4
1.5”10ꢀ4
2.7”10ꢀ3
1.3”10ꢀ2
1.8”10ꢀ3
3”10ꢀ4
104
106
107
106
104
At room temperature, the charge mobility of organic ma-
terials is often determined by a hopping transport process,[23]
and two major parameters determine the charge mobility:
the intermolecular electronic coupling and the reorganiza-
tion integral.[24] In previous work, we found that, for a tri-
phenylamine dimer, the reorganization energy could be sig-
nificantly reduced from a linear molecule to a cyclic archi-
tecture. To validate such a structure–property relationship,
we also calculated the reorganization energy for these car-
bazole derivatives. Similar to that observed for triphenyla-
mine dimers, the cyclic compounds 1 and 2 possess lower re-
organization energy (0.177 and 0.180 eV) compared with
that of linear molecule 3 (0.275 eV). It is known that the re-
organization energy is dependent on the conjugation
degree.[25] From the calculated HLGs of compounds 1, 2,
and 3, we can see that the cyclic molecules possess lower
HLGs referring to an extended conjugation in the cyclic ar-
chitecture. From the difference between the bond lengths of
neutral molecules and cations we can also get some clues
about the trends in the reorganization energies of these car-
bazole derivatives. The bond length changes for compounds
1 and 3 are shown in Figure 9. It can be seen that the bond
length changes upon oxidation for compound 1 are signifi-
cantly smaller (average difference 0.0084 Š) than those of
compound 3 (average difference 0.0172 Š). This is consis-
tent with the reorganization energy difference between com-
pounds 1 and 3. In conclusion, the extended conjugation
and restricted cyclic conformation have limited the confor-
mation changes of the cyclic oligomers before and after oxi-
dation and resulted in the reduction of the reorganization
energy in comparison with that of the linear analogue.
From Table 1, we can see that the carrier mobilities of the
FETs were dependent on the substrate deposition tempera-
tures. With the increase of Tsub, the mobility of compound 1
decreased. This was not surprising because film discontinui-
ties and large gaps increased as well, which had a large neg-
ative effect on charge-transporting ability. No field effect
was found at 1008C, which may result from the discontinuity
of the thin film as mentioned above. For compound 2, the
highest mobility of 0.013 cm2 Vꢀ1 sꢀ1 was measured at a Tsub
of 608C. The on/off current ratio was also excellent with an
order of magnitude of 107. This was because a more ordered
thin film was formed at this temperature, which was evident
from AFM and XRD. The decrease in mobility (1.8”
10ꢀ3 cm2 Vꢀ1 sꢀ1) at a Tsub of 1008C was possibly due to the
large boundaries between grains.
Similar to what was observed with triphenylamine dimers
of linear and cyclic architectures,[16] the FETperformance of
linear compound 3 was worse than that of cyclic compounds
1 and 2. Two facts should account for such differences be-
tween the mobilities for the cyclic and linear compounds.
First, the cyclic structure significantly improved the molecu-
lar ordering and p–p stacking in vapor deposited thin films.
Only amorphous films could be obtained from compound 3
as indicated by XRD analysis. For compound 1 and 2 multi-
crystalline thin films could be prepared by the vapor evapo-
ration method. Second, the cyclic structure led to a signifi-
cant reduction in molecular reorganization energy.[16]
Quantum chemical calculations: To gain an insight into the
relationship between the molecular structures and proper-
ties of these cyclic compounds, we performed quantum-
chemical calculations by using the Gaussian 03 program.[27]
The geometry optimization, frequency, and reorganization
energy were calculated at the DFTlevel by using the
B3LYP functional with 6-31G* basis sets. TD-DFT was used
Conclusion
We have synthesized three carbazolenevinylene oligomers
by McMurry coupling reactions, the linear compound 3 and
the cyclic compounds 1 and 2. They were fully characterized
by means of NMR spectroscopy, HRMS, and elemental
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Carbazolenevinylene Oligomers
FULL PAPER
!
~
*
Figure 8. Plots of drain-to-source current (IDS) versus drain-to-source voltage (VDS) for the FETdevice of a) 1 at Tsub =208C ( : ꢀ40 V, : ꢀ30 V,
:
1/2
&
^
ꢀ20 V, : ꢀ10 V, : 0 V); b) ꢀIDS and (ꢀIDS
)
versus VG plots for the same device as a) at VDS of ꢀ100 V; c) plots of IDS versus VDS for the FETof 2 at
1/2
~
!
&
*
^
T
sub =608C ( : ꢀ100 V, +: ꢀ80 V, : ꢀ60 V, : ꢀ40 V, : ꢀ20 V, : 0 V); d) ꢀIDS and (ꢀIDS
)
versus VG plots for the same device as c) at VDS of
1/2
!
~
&
*
^
ꢀ100 V; e) plots of IDS versus VDS for the FETof 3 at 208C ( : ꢀ40 V, : ꢀ30 V, : ꢀ20 V, : ꢀ10 V, : 0 V); f) ꢀIDS and (ꢀIDS
)
versus VG plots for the
same device as e) at VDS of ꢀ100 V.
Table 2. The calculated HOMO–LUMO gap (HLG), reorganization and transition energies (lmax), oscillator strengths (f), and composition of the first in-
tense transition of compounds 1, 2, and 3.
Compound
HLG
[eV]
Reorganization
energy [eV]
lmax [nm]
f
Composition[a]
Calcd
Exptl
1
2
3
3.48
3.54
3.82
0.177
0.18
0.275
308.13
337.58
356.68
298
300
343
1.1162
0.6899
0.7375
0.44157c(131!133) +0.45203c(132!136)
0.52955c(139!141) + 0.25805c(140!144) +0.28929c(140!148)
0.53878c(126!127) +0.12840c(124!127) + 0.37717c(126!128)
[a] Orbital 131 is the HOMOꢀ1 of compound 1, orbital 139 is the HOMOꢀ1 of compound 2, and orbital 126 is the HOMO of compound 3.
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4737

D. Zhu, Y. Liu, W. Xu et al.
Thermogravimetric (TGA) and differ-
ential thermal (DTA) analyses were
performed by using a Shimadzu DTG
60 Thermal Analyzer. A heating rate
of 108C minꢀ1 under flowing N2 was
used with runs being conducted from
room temperature to 5508C.
UV/Vis spectra were recorded on a
JASCO V-570 spectrometer. Cyclic
voltammetric measurements were re-
corded on a CHI660C voltammetric
analyzer (CH Instruments, USA).
They were carried out in a conven-
tional three-electrode cell by using Pt
button working electrodes of 2 mm
diameter,
a platinum wire counter
electrode, and a Ag/AgCl reference
electrode at room temperature. Con-
ditions: 0.1m (nBu)4NPF6 in dichloro-
methane.
Figure 9. Bond lengths [Š] of neutral and oxidized compounds a) 1 and b) 3.
XRD measurements of thin films
were performed in the reflection mode at 40 kV and 200 mA with CuKa
radiation by using a 2 kW Rigaku X-ray diffractometer.
analysis. Quantum chemical simulations showed that the
cyclic compounds possessed lower HLGs and more extend-
ed conjugation. However the UV/Vis absorption spectra of
the cyclic compounds showed blueshifts compared with that
of linear compound 3. TD-DFT analysis revealed that this
was due to the different selection rules for molecules with
cyclic and linear architectures. The cyclic conformation also
significantly affected the molecular ordering in the solid
state. Only amorphous thin films could be obtained from
compound 3, whereas multicrystalline thin films were ob-
tained from compounds 1 and 2 by using the thermal evapo-
ration method. Another important difference between these
cyclic and linear compounds was the reorganization energy
reduction for the cyclic compounds. These two differences
resulted in improved FETmobilities for the cyclic com-
pounds versus the linear compound. In addition, the sub-
strate temperature has a significant influence on the mor-
phology and the degree of crystallinity of the thin films de-
posited, and the device performance could be optimized by
varying the substrate temperature. The FET devices based
on 2 gave the highest mobility of 0.013 cm2 Vꢀ1 sꢀ1. The mo-
bilities of devices based on 1 and 2 were higher than that of
the linear compound 3. The results showed that the carba-
zole derivatives with cyclic structures might fit better for
FETs.
AFM images of the organic thin films were obtained on a Nanoscope
IIIa AFM (Digital Instruments) in tapping mode.
X-ray structures: X-ray crystallographic data were collected with
a
Bruker Smart CCD diffractometer by using graphite-monochromated
MoKa radiation (l=0.71073 Š). The data were collected at 113 K and the
structure was resolved by the direct method and refined by full-matrix
least-squares on F2 The computation was performed with the SHELXL-
97 program. All non-hydrogen atoms were refined anisotropically.
Rodlike single crystals of 1 were obtained by slow evaporation of its di-
chloromethane solution. Crystallographic data for 1: Crystal size: 0.12”
0.10”0.08 mm3; orthorhombic; Pbca; Z=4; a=15.618(3), b=8.4122(17),
c=19.403(4) Š; V=2549.1(9) Š3; 1calcd =1.289 gcmꢀ3; of 14602 reflec-
tions, 2243 were unique (Rint =0.0943); GOF=1.240; 173 parameters;
R1=0.0840, wR2=0.1529 (for all reflections). CCDC 676722 contains the
supplementary crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
Device fabrication: Thin-film transistors were made in a top-contact
device configuration. Prior to the deposition, 1–3 were purified twice by
vacuum sublimation. The substrate was highly n+-doped Si with a 450 nm
thermally oxidized SiO2 layer on it. Before the deposition of the organic
semiconductor, OTS treatment was performed on the gate dielectrics
which were placed in a vacuum oven with OTS at a temperature of
1208C to form an OTS self-assembled monolayer. Then, the treated sub-
strates were rinsed with heptane, ethanol, and chloroform, and then
dried with nitrogen. Under a base pressure of 4~6”10ꢀ4 Pa, thin films of
1, 2, and 3 about 50 nm thick were deposited on the OTS treated Si/SiO2
at a rate of 1 Šsꢀ1. On the surfaces of the prepared thin films, 20 nm
thick gold was vacuum deposited through a shadow mask to give the
source (S) and drain (D) electrodes. The channel length L was 0.05 mm
and the width W was 3 mm. The FET characteristics of the devices were
obtained at room temperature in air by using a Hewlett–Packard (HP)
4140B semiconductor parameter analyzer.
Experimental Section
General: All air/moisture-sensitive materials were handled under a nitro-
gen atmosphere by using Schlenk techniques. THF was distilled over
sodium/benzophenone. Pyridine was distilled over NaOH. All reagents
were used as received unless otherwise noted. 9-n-Butylcarbazole (4) was
prepared as we have reported previously.[15] 9-Phenyl-carbazole (6) and
3,6-dibromo-9-phenylcarbazole (7) were synthesized according to litera-
ture procedures.[26] Melting points were recorded on a BÜCHI melting
point B-500 apparatus. 1H NMR and 13C NMR spectra were obtained on
Bruker Advance 300 or 400 MHz spectrometers. EIMS measurements
were performed on UK GCT-Micromass or SHIMADZU G-MS-QP2010
Quantum chemical calculations: DFTand TD-DFTcalculations were car-
ried out by using the Gaussian 03 program.[27] All geometries and elec-
tronic properties were calculated by assuming the target molecules to be
isolated molecules in the gas phase.
9-n-Butyl-carbazole-3,6-dicarbaldehyde (5): Phosphorus oxychloride
(51.56 mL, 0.553 mol) was added dropwise to DMF (43.06 mL, 0.559
mol) at 08C, and the mixture was stirred for 1 h at this temperature. 9-n-
Butylcarbazole (6.624 g, 0.0297 mol) was added and the reaction mixture
was stirred at 1008C for 6 h. Then, the mixture was cooled to room tem-
perature, poured into ice water and carefully neutralized with sodium hy-
droxide. The solution was extracted with dichloromethane(3”150 mL).
spectrometers. HRMS measurements were performed on
APEX II FTICRMS spectrometer.
a Bruker
4738
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Chem. Eur. J. 2008, 14, 4731 – 4740

Carbazolenevinylene Oligomers
FULL PAPER
The 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 column chromatography on silica gel
(20% CH2Cl2 in petroleum ether) to give 5 (6.082 g, 73.4%). 1H NMR
(400 MHz, CDCl3): d=10.14 (s, 2H), 8.67 (s, 2H), 8.10 (d, J=8.5 Hz,
2H), 7.57 (d, J=8.5 Hz, 2H), 4.42 (t, J=7.2 Hz, 2H), 1.95–1.87 (m, 2H),
1.48–1.38 (m, 2H), 1.00 ppm (t, J=7.3 Hz, 3H); 13C NMR (100 MHz,
CDCl3): d=191.19, 144.47, 129.35, 127.59, 123.81, 122.83, 109.51, 43.29,
30.75, 20.22, 13.56 ppm; MS (EI): m/z: 279 [M]+; HRMS (GCT-MS):
calcd for C18H17NO2: 279.1259; found: 279.1260 [M]+.
to afford 9 (6.33 g, 66.9%). 1H NMR (400 MHz, CDCl3): d=10.10 (s,
1H), 8.61 (s, 1H), 8.17 (d, J=7.8 Hz, 1H), 8.02 (d, J=8.5 Hz, 1H), 7.55
(t, J=7.8 Hz, 1H), 7.45 (t, J=7.4 Hz, 2H), 7.34 (t, J=7.4 Hz, 1H), 4.36
(t, J=7.2 Hz, 2H), 1.92–1.84 (m, 2H), 1.46–1.37 (m, 2H), 0.98 ppm (t,
J=7.3 Hz, 3H); 13C NMR (100 MHz, CDCl3): d=191.79, 144.05, 141.16,
128.46, 127.12, 126.71, 123.97, 123.02, 122.97, 120.73, 120.29, 109.42,
108.94, 43.16, 31.05, 20.53, 13.87 ppm; MS (EI): m/z: 251 [M]+; HRMS
(GCT-MS): calcd for C17H17NO: 251.1310; found: 251.1313 [M]+.
Compound 3: This compound was prepared according to the general pro-
cedure for
1 by using Zn (5.18 g, 7.97 mmol), TiCl4 (4.415 mL,
40.03 mmol), 9-n-butyl-carbazole-3-carbaldehyde (2 g, 7.97 mmol), and
pyridine (5 mL) in THF (300 mL). Column chromatography was per-
formed on silica gel (CH2Cl2/ petroleum ether 1:2) to give the crude
product. Recrystallization from CH2Cl2/hexane gave 3 (1.086 g, 58.0%)
as a jade-green powder. M.p. 2078C; 1H NMR (400 MHz, CDCl3): d=
8.28 (s, 2H), 8.16 (d, J=7.7 Hz, 2H), 7.74 (d, J=8.5 Hz, 2H), 7.49–7.40
(m, 6H), 7.37 (s, 2H), 7.26–7.23 (m, 2H), 4.34 (t, J=7.1 Hz, 4H), 1.92–
1.85 (m, 4H), 1.47–1.38 (m, 4H), 0.98 ppm (t, J=7.3 Hz, 6H); 13C NMR
(100 MHz, CDCl3): d=129.21, 127.03, 125.69, 124.24, 123.22, 122.95,
120.45, 118.88, 118.26, 108.89, 108.84, 42.97, 31.20, 20.61, 13.94 ppm; MS
(EI): m/z: 470 [M]+; HRMS (GCT-MS): calcd for C34H34N2: 470.2722;
found: 470.2727 [M]+; elemental analysis calcd (%) for C34H34N2: C
86.77, H 7.28, N 5.95; found: C 87.00, H 7.44, N 6.06.
Compound 1: Zn powder (9.32 g, 143 mmol) was suspended in THF
(200 mL) under N2. A solution of TiCl4 (7.76 mL, 71.6 mmol) in CH2Cl2
(50 mL) was added carefully to the suspension with stirring and then the
suspension was heated to reflux at 808C for 1 h. A solution of 5 (2 g,
7.17 mmol) and pyridine (5 mL) in THF (100 mL) was added dropwise to
the reaction mixture. The mixture was stirred and heated at reflux for
10 h, and after cooling to room temperature, saturated aqueous NaHCO3
(200 mL) was added and the reaction mixture was stirred for a further
0.5 h. The reaction mixture was filtered and most of the filtrate was re-
moved under reduced pressure. The residual mixture was extracted with
dichloromethane(3”100 mL) and the combined organic extracts were
dried over anhydrous sodium sulfate, filtered, and concentrated under re-
duced pressure. The residue was purified by flash chromatography on
silica gel (20% CH2Cl2 in petroleum ether) to afford the crude product.
Recrystallization from CH2Cl2/hexane gave
1 as a yellow powder
(135 mg, 8.1%). M.p. 2608C; 1H NMR (400 MHz, CDCl3): d=9.79 (s,
4H), 7.25–7.18 (m, 8H), 6.36 (s, 4H), 4.20 (t, J=7.1 Hz, 4H), 1.90–1.82
(m, 4H), 1.49–1.40 (m, 4H), 1.00 ppm (t, J=7.3 Hz, 6H); 13C NMR
(100 MHz, CDCl3): d=140.85, 129.71, 128.08, 127.75, 123.54, 119.93,
108.78, 42.86, 30.95, 20.43, 13.77 ppm; MS (EI): m/z: 494 [M]+; HRMS
(GCT-MS): calcd for C36H34N2: 494.2722; found: 494.2720 [M]+; elemen-
tal analysis calcd (%) for C36H34N2: C 87.41, H 6.93, N 5.66; found: C
87.19, H 7.01, N 5.80.
Acknowledgement
The authors are grateful for financial support from the National Natural
Science Foundation of China (Grant Nos 20572113, 20632020, 20721061),
the
State
Key
Basic
Research
Program
(2006CB9321001,
2006CB806201), and the Chinese Academy of Sciences.
9-Phenyl-carbazole-3,6-dicarbaldehyde (8): A hexane solution of nBuLi
(2.5m, 5.76 mL, 14.4 mmol) was added slowly by using a syringe to a solu-
tion of 7 (3 g, 7.48 mmol) in freshly distilled THF (150 mL) at ꢀ788C
under N2. The resulting mixture was stirred at this temperature for 1 h.
Then, DMF (5.76 mL, 74.7 mmol) was added and the mixture was stirred
for another 1 h at ꢀ788C. After this time, the mixture was gradually
warmed to room temperature and stirred overnight. Saturated aqueous
NH4Cl (100 mL) was added. The mixture was extracted with dichlorome-
thane (2”100 mL). The combined organic extracts were dried over anhy-
drous sodium sulfate, filtered, and the solvent was removed under re-
duced pressure. The residue was purified by flash chromatography on
[1] Y. Shirota, H. Kageyama, Chem. Rev. 2007, 107, 953.
[2] a) T. W. Kelley, P. F. Baude, C. Gerlach, D. E. Ender, D. Muyres,
M. A. Haase, D. E. Vogel, S. D. Theiss, Chem. Mater. 2004, 16, 4413;
b) Y. Sun, Y. Liu, D. Zhu, J. Mater. Chem. 2005, 15, 53; c) J. E. An-
thony, Chem. Rev. 2006, 106, 5028; d) A. R. Murphy, J. M. J. FrØchet,
Chem. Rev. 2007, 107, 1066; e) A. Facchetti, Mater. Today 2007, 10,
28.
[3] a) H. Sirringhaus, T. Kawase, R. H. Friend, T. Shimoda, M. Inbase-
karan, W. Wu, E. P. Woo, Science 2000, 290, 2123; b) Z. Bao, Adv.
Mater. 2000, 12, 227; c) S. R. Forrest, Nature 2004, 428, 911; d) H.
Sirringhaus, Adv. Mater. 2005, 17, 2411; e) M. Berggren, D. Nilsson,
N. D. Robinson, Nat. Mater. 2007, 3; f) E. Menard, M. A. Meitl, Y.
Sun, J. U. Park, D. J. Shir, Y. S. Nam, S. Jeon, J. A. Rogers, Chem.
Rev. 2007, 107, 1117.
[4] For example: a) Z. Wang, C. Kim, A. Facchetti, T. J. Marks, J. Am.
Chem. Soc. 2007, 129, 13362; b) S. Handa, E. Miyazaki, K. Takimiya,
Y. Kunugi, J. Am. Chem. Soc. 2007, 129, 11684; c) P.-L. T. Bou-
dreault, S. Wakim, N. Blouin, M. Simard, C. Tessier, Y. Tao, M. Le-
clerc, J. Am. Chem. Soc. 2007, 129, 9125; d) H. Pan, Y. Li, Y. Wu, P.
Liu, B. S. Ong, S. Zhu, G. Xu, J. Am. Chem. Soc. 2007, 129, 4112;
e) M. Zhang, H. N. Tsao, W. Pisula, C. Yang, A. K. Mishra, K.
Mullen, J. Am. Chem. Soc. 2007, 129, 3472; f) T. Yamamoto, K. Ta-
kimiya, J. Am. Chem. Soc. 2007, 129, 2224; g) T. Okamoto, M. L.
Senatore, M.-M. Ling, A. B. Mallik, M. L. Tang, Z. Bao, Adv. Mater.
2007, 19, 3381; h) X. Gao, Y. Wang, X. Yang, Y. Liu, W. Qiu, W.
Wu, H. Zhang, T. Qi, Y. Liu, K. Lu, C. Du, Z. Shuai, G. Yu, D. Zhu,
Adv. Mater. 2007, 19, 3037; i) L. Li, Q. Tang, H. Li, X. Yang, W. Hu,
Y. Song, Z. Shuai, W. Xu, Y. Liu, D. Zhu, Adv. Mater. 2007, 19,
2613.
silica gel (dichloromethane) to afford product
8 (1.504 g, 67.2%).
1H NMR (400 MHz, CDCl3): d=10.16 (s, 2H), 8.73 (s, 2H), 8.03 (d, J=
8.5 Hz, 2H), 7.71 (t, J=7.4 Hz, 2H), 7.62 (t, J=7.4 Hz, 1H), 7.55 (d, J=
7.3 Hz, 2H), 7.46 ppm (d, J=8.5 Hz, 2H); 13C NMR (100 MHz, CDCl3):
d=191.47, 145.36, 135.85, 130.42, 129.09, 128.13, 127.18, 124.13, 123.44,
110.88 ppm; MS (EI): m/z: 299 [M]+; HRMS (GCT-MS): calcd for
C20H13NO2: 299.0946; found: 299.0944 [M]+.
Compound 2: This compound was prepared according to the general pro-
cedure for
1 by using Zn (4.347 g, 66.9 mmol), TiCl4 (3.62 mL,
33.4 mmol), 8 (1 g, 3.34 mmol), and pyridine (2.33 mL) in THF (300 mL).
Column chromatography was performed on silica gel (dichloromethane)
to get the crude product. This was then further purified by gradient subli-
mation. Compound 2 (about 50 mg, 5.6%) was obtained as a yellow
solid. M.p. 3638C; 1H NMR (400 MHz, CDCl3): d=9.80 (s, 4H), 7.65–
7.58 (m, 8H), 7.52–7.46 (m, 2H), 7.29 (d, J=7.3 Hz, 4H), 7.19 (d, J=
8.5 Hz, 4H), 6.43 (s, 4H); MS (EI): m/z: 534 [M]+; HRMS (GCT-MS):
calcd for C40H26N2: 534.2096; found: 534.2103 [M]+; elemental analysis
calcd (%) for C40H26N2: C 89.86, H 4.90, N 5.24; found: C 89.59, H 4.88,
N 5.29.
9-n-Butyl-carbazole-3-carbaldehyde (9): This compound was prepared ac-
cording to the general procedure for 5 by using 9-n-butylcarbazole
(3.345 g, 13.33 mmol), phosphorus oxychloride (1.568 mL, 16.82 mmol),
and DMF (1.319 mL, 19.50 mmol). The mixture was purified by flash
chromatography on silica gel (50% dichloromethane in petroleum ether)
[5] K. Takimiya, Y. Kunugi, T. Otsubo,Chem. Lett. 2007, 36, 578.
[6] a) J.-F. Morin, M. Leclerc, D. Ad›s, A. Siove, Macromol. Rapid
Commun. 2005, 26, 761; b) J. V. Grazulevicius, P. Strohriegl, J. Pieli-
chowski, K. Pielichowski, Prog. Polym. Sci. 2003, 28, 1297.
Chem. Eur. J. 2008, 14, 4731 – 4740
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4739

D. Zhu, Y. Liu, W. Xu et al.
[7] For example: a) K. Brunner, A. Dijken, H. Bçrner, J. J. A. M. Bas-
tiaansen, N. M. M. Kiggen, B. M. W. Langeveld, J. Am. Chem. Soc.
2004, 126, 6035; b) M. H. Tsai, Y. H. Hong, C. H. Chang, H. C. Su,
C. C. Wu, A. Matoliukstyte, J. Simokaitiene, S. Grigalevicius, J. V.
Grazulevicius, C. P. Hsu, Adv. Mater. 2007, 19, 862; c) Y.-C. Chen,
G.-S. Huang, C.-C. Hsiao, S.-A. Chen, J. Am. Chem. Soc. 2006, 128,
8549.
[8] Y. Zhang, T. Wada, H. Sasabe, J. Mater. Chem. 1998, 8, 809.
[9] a) J.-F. Morin, N. Drolet, Y. Tao, M. Leclerc, Chem. Mater. 2004, 16,
4619; b) Y. Wu, Y. Li, S. Gardner, B. S. Ong, J. Am. Chem. Soc.
2005, 127, 614; c) Y. Wu, Y. Li, S. Gardner, B. S. Ong, Adv. Mater.
2005, 17, 849; d) N. Drolet, J.-F. Morin, N. Leclerc, S. Wakim, Y.
Tao, M. Leclerc, Adv. Funct. Mater. 2005, 15, 1671; e) M. Sonntag,
K. Kreger, D. Hanft, P. Strohriegl, S. Setayesh, D. De Leeuw, Chem.
Mater. 2005, 17, 3031.
[17] J. Roncali, Chem. Rev. 1997, 97, 173.
[18] J. Ostrauskaite, V. Voska, J. Antulis, V. Gaidelis, V. Jankauskas, J. V.
Grazulevicius, J. Mater. Chem. 2002, 12, 3469.
[19] a) J. E. McMurry, Chem. Rev. 1989, 89, 1513; b) Z. Hu, J. L.
Atwood, M. P. Cava, J. Org. Chem. 1994, 59, 8071.
[20] M. Thelakkat, H.-W. Schmidt, Adv. Mater. 1998, 10, 219.
[21] X. Gao, W. Wu, Y. Liu, S. Jiao, W. Qiu, G. Yu, L. Wang, D. Zhu, J.
Mater. Chem. 2007, 17, 736.
[22] M. Bednarza, P. Reinekera, E. Mena-Osteritzb, P. Bäuerle. J. Lumi-
nescence 2004, 110, 225.
[23] a) N. F. Mott, E. A. Davis, Electronic Processes in Non-Crystalline
Materials, 2nd ed., Oxford University Press, Oxford, 1979; b) J. A.
Reedijk, H. C. F. Martens, S. M. C. van Bohemen, O. Hilt, H. B.
Brom, M. A. J. Michels, Synth. Met. 1999, 101, 475; c) A. J. Epstein,
W. P. Lee, V. N. Prigodin, Synth. Met. 2001, 117, 9.
[10] For recent reviews, see: a) J. S. Moore, Acc. Chem. Res. 1997, 30,
402; b) S. Hçger, J. Polym. Sci., Part A: Polym. Chem. 1999, 37,
2685; c) M. M. Haley, J. J. Pak, S. C. Brand, Top. Curr. Chem. 1999,
201, 81; d) C. Grave, A. D. Schlꢁter, Eur. J. Org. Chem. 2002, 3075;
e) D. Zhao, J. S. Moore, Chem. Commun. 2003, 807; f) Y. Yamagu-
chi, Z. I. Yoshida, Chem. Eur. J. 2003, 9, 5430; g) S. Hçger, Chem.
Eur. J. 2004, 10, 1320; h) Acetylene Chemistry, (Eds.: F. Diederich,
P. J. Stang, R. R. Tykwinsky), Wiley-VCH, Weinheim, 2005; i) W.
Zhang, J. S. Moore, Angew. Chem. 2006, 118, 4524; Angew. Chem.
Int. Ed. 2006, 45, 4416.
[24] a) R. A. Marcus, Rev. Mod. Phys. 1993, 65, 599; b) N. E. Gruhn,
D. A. da Silva Filho, T. G. Bill, M. Malagoli, V. Coropceanu, A.
Kahn, J.-L. BrØdas, J. Am. Chem. Soc. 2002, 124, 7918; c) J. L.
BrØdas, J. P. Calbert, D. A. da Silvo Filho, J. Cornil, Proc. Natl.
Acad. Sci. USA 2002, 99, 5804.
[25] G. R. Hutchison, M. A. Ratner, T. J. Marks, J. Am. Chem. Soc. 2005,
127, 2339.
[26] a) S. W. Cha, J. I. Jin, J. Mater. Chem. 2003, 13, 479; b) M. Park, J. R.
Buck, C. J. Rizzo, Tetrahedron 1998, 54, 12707.
[27] Gaussian 03 (Revision B.05), M. J. Frisch, G. W. Trucks, H. B. Schle-
gel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A. Montgomer-
y, Jr., T. Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyen-
gar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N.
Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K.
Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda,
O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian,
J. B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann,
O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y.
Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg,
V. G. Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O.
Farkas, D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B. Fores-
man, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski,
B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L.
Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Na-
nayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen,
M. W. Wong, C. Gonzalez, J. A. Pople, Gaussian, Inc., Pittsburgh
PA, 2003.
[11] P. Bäuerle, Adv. Mater. 1992, 4, 102.
[12] a) S. Maruyama, Y. D. Zhang, T. Wada, H. Sasabe, J. Chem. Soc.
Perkin Trans. 1 1999, 41; b) S. Maruyama, X. T. Tao, H. Hokari, T.
Noh, Y. D. Zhang, T. Wada, H. Sasabe, H. Suzuki, T. Watanabe, S.
Miyata, J. Mater. Chem. 1999, 9, 893; c) S. Maruyama, H. Suzuki,
X. T. Tao, T. Wada, H. Sasabe, S. Miyata, T. Kamata,Phys. Chem.
Chem. Phys. 2000, 2, 3565; d) S. Maruyama, H. Hokari, X. T. Tao,
A. Gunji, T. Wada, H. Sasabe, Chem. Lett. 1999, 731; e) W. Zhang,
J. S. Moore, J. Am. Chem. Soc. 2004, 126, 12796.
[13] T. Naddo, Y. Che, W. Zhang, K. Balakrishnan, X. Yang, M. Yen, J.
Zhao, J. S. Moore, L. Zang, J. Am. Chem. Soc. 2007, 129, 6978.
[14] K. Balakrishnan, A. Datar, W. Zhang, X. Yang, T. Naddo, J. Huang,
J. Zuo, M. Yen, J. S. Moore, L. Zang, J. Am. Chem. Soc. 2006, 128,
6576.
[15] T. Zhao, Z. Liu, Y. Song, W. Xu, D. Zhang, D. Zhu, J. Org. Chem.
2006, 71, 7422.
[16] 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; b) Y. Song,
C. Di, W. Xu, Y. Liu, D. Zhang, D. Zhu, J. Mater. Chem. 2007, 17,
4483.
Received: January 3, 2008
Published online: April 2, 2008
4740
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Chem. Eur. J. 2008, 14, 4731 – 4740