Fine tuning of blue photoluminescence from indoles for device fabrication

Article abstract of DOI:10.1039/b821246e

Functionalized indoles were synthesized as blue-light emitting materials through palladium-catalyzed heteroannulation. Fine tuning of their color from violet to blue photoluminescence in solution and thin film was accomplished by placement of electron-don

Full text of DOI:10.1039/b821246e

View Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/materials | Journal of Materials Chemistry
Fine tuning of blue photoluminescence from indoles for device fabrication†
ab
Yung Chang Hsu,a Thainashmuthu Josephrajana and Shwu-Chen Tsayc
*
Jih Ru Hwu,
Received 27th November 2008, Accepted 10th February 2009
First published as an Advance Article on the web 23rd March 2009
DOI: 10.1039/b821246e
Functionalized indoles were synthesized as blue-light emitting materials through palladium-catalyzed
heteroannulation. Fine tuning of their color from violet to blue photoluminescence in solution and thin
film was accomplished by placement of electron-donating and -withdrawing substituents at the C2-,
C3-, and C5-positions. A device of organic light-emitting diodes was made, which exhibited the desired
blue light with the Commission International de L’Eclairage (CIE) coordinates x ¼ 0.18 and y ¼ 0.12.
a methoxycarbonyl group at the C3-position for the possible
Introduction
resonance structure 3, in which the electrons delocalize between
the veratrole and the methoxycarbonyl groups.
Manufacture of low-voltage multicolor displays with high effi-
ciency requires organic light-emitting diodes (OLEDs).1 The high
need for blue-light emitting materials comes from their wide
applicability.2 In addition to being a component in blue-emitting
devices, these materials can be used in light sources to generate
low energy light from green to red with a color-conversion
medium.3 Green and red emitters for organic electrolumines-
cence devices have become readily available nowadays, while
blue light emitting materials with excellent Commission Inter-
national de L’Exclairage (CIE) coordinates are still rare. More-
over, light emitting materials are required for the preparation of
electron-accepting and -transporting materials. These ‘‘n-type’’
materials are needed for use in n-type transistors, as the electron-
accepting components in photovoltaic devices.4
An intriguing part of our design also came from the possibility
that the plane of the C2-veratrole group may not lie in the same
plane as the indole nucleus. Steric congestion between the
COOMe group at the C3 position and hydrogen atoms on the
C2-veratrole group may generate a dihedral angle between these
two planes. As a result, the resonance effect would be discounted.
This possible non-planarity, however, may offer an advantage
for molecules 1 to become ideal OLED materials. This is because
amorphous materials are highly desirable for multilayer
devices.11 Their use can suppress formation of grain boundaries
during operation and strain-driven failure in a thermally stressed
OLED.
Compounds with a single veratrole group often do not exhibit
photo- or electro-luminescence. In the presence of oxidants (such
as chloranil, quinones, and perchlorate) under acidic conditions,
their trimers (i.e., triphenylene derivatives) can be generated
through the para positions of the methoxy groups.12 On the other
hand, veratrole is not appreciably oxidized under typical Scholl
conditions involving nitrobenzene and aluminium chloride.13
Our choice of a C2 veratrole group was based on its capability of
contributing to the resonance shown in 3. This moiety may not be
easily oxidized in compounds 1 because one of the para positions
of the methoxy group is blocked by an indole nucleus. Steric
hindrance resulting from this nucleus can also retard the oxida-
tion from occurring at the other para position.
Pope et al.5 first reported in 1963 that anthracene can give blue
electroluminescence. Up to now, many blue-emitting materials
have been developed, including anthracenes,2 distyrylenes,2
indole derivatives,6 1,3,4-oxadiazoles,7 spirobifluorenes,8 as well
as metal chelates such as aluminium, beryllium, boron, and
lithium complexes.9 Among various light-emitting materials, we
selected the indole nucleus as the basic chromophore for devel-
opment of new OLED materials because it may emit photo-
luminescence (PL) in the blue–UV region with high quantum
efficiency.10 Attachment of appropriate auxochromes at the C2-,
C3-, and C5-positions of indoles 1 may allow us to tune its
emitting light with bathochromic and hypsochromic shifts
through conjugation. A C5-auxochrome with electron-donating
or -withdrawing capability could influence the resonance
contribution between the canonical form 2 and the parent
structure 1 (Scheme 1). Furthermore, we planned to attach
aDepartment of Chemistry, National Tsing Hua University, Hsinchu,
Taiwan, 30013, R.O.C. E-mail: jrhwu@mx.nthu.edu.tw; Fax: +886-35-
721594; Tel: +886-35-725813
bDepartment of Chemistry, National Central University, Jhongli, Taiwan,
32001, R.O.C.
cWell-being Biochemical Corporation, Neihu Technology Park, Taipei,
114, Taiwan, R.O.C.
† Electronic supplementary information (ESI) available: 1H and 13C
NMR spectra of compounds 1a–g and 8a,b. CCDC reference number
718748. For ESI and crystallographic data in CIF or other electronic
format see DOI: 10.1039/b821246e
Scheme 1 The canonical forms of indoles 1.
3084 | J. Mater. Chem., 2009, 19, 3084–3090
This journal is ª The Royal Society of Chemistry 2009

View Online
In continuation of our ongoing research on this topic,14 we
report herein our successful development and syntheses of
indole–veratrole conjugates as new OLED materials with blue
CIE coordinates. More important is the establishment of a way
to tune the blue color of indoles to the desired chromaticity.
Results and discussion
Synthesis of new indoles
We applied the Larock heteroannulation method15 as the key
step for the convergent-type synthesis16 of our desired multi-
substituted indoles 1 (see Scheme 2). Heteroannulation of 5
with various 4-substituted-2-iodo-1-anilines 4 (1.0 equiv) was
performed in the presence of (PPh3)2PdCl2 (0.050 equiv),
n-Bu4NBr (1.0 equiv), and NaOAc in DMF at 100 ꢀC. The target
molecules 1a–g were obtained in 30–65% yields with an H, Me, F,
Cl, CN, COOMe, or NO2 group at the C5 position.
Anthracene possesses electron-donating and electrolumines-
cent properties.2,5 We applied the same synthetic strategy shown
in Scheme 3 for incorporating an anthracene moiety into an
indole nucleus. Consequently, 2-anthracenylindoles 8a,b were
obtained from (dibromovinyl)anthracene 617 through consecu-
tive debromohydrogenation, carbomethoxylation, and Larock
heteroannulation.
Fig. 1 Molecular framework of 1f: (a) ORTEP diagram obtained by
X-ray diffraction analysis; and (b) molecular modeling obtained by
CVFF calculations.
Structures of these potentially new OLED materials 1a–g and
8a,b were fully characterized by 1H NMR, 13C NMR, IR, UV, PL
and mass spectroscopic methods. For example, indole 1f
exhibited two characteristic singlets at 8.86 and 7.21 ppm in its
1H NMR spectrum, for the C4- and C02-aromatic protons,
respectively. In its 13C NMR spectrum, resonance occurred at
145.86 and 104.88 ppm for the C2- and C3-carbons, respectively.
In its IR spectrum, two strong (i.e., 1708 and 1695 cmꢁ1) and one
medium (i.e., 1548 cmꢁ1) absorption bands appeared for the two
C]O and C]C stretching vibrations, respectively. These data
clearly indicate the formation of an a,b-unsaturated ester moiety.
Moreover, we unequivocally confirmed the molecular frame-
work of 1f by single crystal X-ray diffraction analysis (see
Fig. 1(a)). Its monoclinic crystals possessed the space group P21/c
Scheme 2 Synthesis of indoles 1a–g.
˚
with a ¼ 12.396(2), b ¼ 14.120(2), c ¼ 13.920(2) A, b ¼
114.759(4)ꢀ. The dihedral angle was 50.3ꢀ between the indole
nucleus and the dimethoxybenzene moiety. The structure
observed from the solid state is consistent with that obtained
from our CVFF calculations of the molecular geometry of 1f
(i.e., 54.4ꢀ in Fig. 1(b)). Compounds with an asymmetric or
nonplanar structure generally have a lower tendency to pack into
a crystal lattice and hence favor amorphous morphology.11 These
data indicate that the aryl moiety attached at the C2-position is
not co-planar with the indole nucleus and, thus, may increase its
amorphous application during device fabrication. Our molecular
modeling also provides a convenient and reliable protocol for
design and prediction of indole OLED materials to be developed
in the future.
Thermal stability
For regular high performance OLEDs, materials are often
required to possess good thermal stability and the ability to form
amorphous thin films.11 While our single crystal X-ray structure
Scheme 3 Synthesis of indoles 8a,b.
This journal is ª The Royal Society of Chemistry 2009
J. Mater. Chem., 2009, 19, 3084–3090 | 3085

View Online
shown in Fig. 1 discloses valuable information on the possibility
of amorphousness related to indoles 1, it was crucial for us to
obtain amorphous molecular materials with a high glass transi-
tion temperature (Tg). Accordingly, we performed a differential
scanning calorimetry analysis and found that the Tg was 136 ꢀC
for indole 1e. Given our best knowledge through literature
search, it is higher than those of any other indole derivatives
reported (55–126 ꢀC)6 and general organic materials used for
OLEDs ($ 60 ꢀC).18 Furthermore, our synthesized indoles were
found with Tm $ 192 ꢀC and Td $ 274 ꢀC, except 1a, by thermal
gravimetric analysis. For example, the melting point was
measured as 260 ꢀC for compound 8a, which decomposed at
274 ꢀC.
Photo-physical properties
The absorption and photoluminescence (PL) spectral data are
given in Table 1 for indole derivatives 1a–f and 8a. In the solution
of dichloromethane, compounds 1a–f emitted violet light (397–
404 nm) for a variety of substituents (i.e., H, Me, F, Cl, CN and
COOMe) attached to the C5 position. We successfully tuned the
light from violet to blue (444 nm) by incorporating an anthracene
unit at the C2 position (i.e., 8a).
As prepared in solid film where the molecules are fixed, we
found that the emitting light shifted bathochromically by 12–41
nm in comparison with the same samples prepared in solution.
Moreover, by placing a CN or a COOMe substituent at the C5
position, we found that the solid films of 1e and 1f emitted blue
light with wavelengths of 439 and 431 nm, respectively. In
addition, placement of an anthracene substituent at the C2
position allowed 8a to emit blue light at 456 nm. The bath-
ochromic shift caused by CN-, COOMe-, and anthracene-
containing indoles was due to the interactions between these
auxochromes with the chromophore in the excited state.19 The
photoluminescence, however, was not observed at all from indole
1g with a C5 nitro group; thus it has no applicability as an OLED
material. Given the results in Table 1 and the photoluminescence
spectra in Fig. 2(a), we conclude that the wavelengths of emitting
light resulting from indoles can be tuned by following the orders
listed in Fig. 2(b).
Fig. 2 A trend for various substituents for tuning the violet–blue light
emitted by indoles: (a) photoluminescence spectra of indole derivatives
1a–f and 8a; (b) the orders of substituents causing hypsochromic shifts in
dichloromethane solutions and thin film.
Moreover, all of these new indole derivatives exhibited
appealing quantum yields FPL (in dichloromethane) between
0.411 and 0.592. These values are greater than those of reported
indole derivatives.6
Electrochemistry
Table 1 Absorption and photoluminescent data of 1a–f and 8a
Khan, Bredas, Marder, and co-workers20 reported a reliable
method for direct measurements and comparison with experi-
mental and theoretical estimates of electron affinities. The most
direct experimental probes of ionization potentials and electron
affinities are photoelectron spectroscopy and inverse-photoelec-
tron spectroscopy, respectively. On the other hand, cyclic
voltammetry has been applied widely for determination of the
HOMO21 and LUMO levels of organic compounds, particularly
in the area of developing electroluminescent materials and
OLEDs. Thus we recorded the cyclic voltammetry scans against
an Ag/AgCl reference electrode at a scan rate of 0.20 V/sec by
using 0.10 M [NBu4]PF6 as a supporting electrolyte in dry,
abs
soln
film
UV lmax
Indolea C5 group (nm)
PL lmax
(nm)
PL lmax
(nm)
soln
FPL
1a
1b
1c
1d
1e
1f
H
Me
F
306
306
302
308
284, 322
278, 320
290, 305
402
404
398
399
398
397
—
418
416
405
414
439
431
—
0.545
0.567
0.534
0.478
0.592
0.556
—
Cl
CN
COOMe
NO2
Hb
1g
8a
282, 366, 386 444
456
0.411
a
Concentration for UV, PL lmax, and FPL: [M] ¼ 1.0 ꢂ 10ꢁ5 in CH2Cl2
b
at 298 K. C2 with an anthracene moiety.
3086 | J. Mater. Chem., 2009, 19, 3084–3090
This journal is ª The Royal Society of Chemistry 2009

View Online
Table 2 Energy alignment in indole derivatives
Indole
Eox (V)
HOMO (eV)
LUMO (eV)
Energy gap (eV)
1a
1b
1d
1e
1f
1.34
1.37
1.40
1.53
1.46
1.57
ꢁ5.6
ꢁ5.6
ꢁ5.7
ꢁ5.7
ꢁ5.7
ꢁ5.7
ꢁ2.1
ꢁ2.1
ꢁ2.1
ꢁ2.2
ꢁ2.2
ꢁ2.6
3.5
3.5
3.6
3.5
3.5
3.1
8a
degassed CH2Cl2 solution. Ferrocene (4.8 eV) was applied as an
internal reference for calibration of redox potentials.22
We calculated the LUMO energy from the HOMO and the
lowest energy absorption edge of the UV/Vis absorption spectra.
Their first oxidation potential (Eox), HOMO energy, LUMO
energy, and energy gaps are listed in Table 2. These estimated
HOMO and LUMO values fall into the ranges of ꢁ5.6 to ꢁ5.7
eV and ꢁ2.1 to ꢁ2.6 eV, respectively. 4,40-Bis[2-(1,10-diphe-
nyl)vinyl]biphenyl (DPVBI)2,23 is proven as a good blue light
OLED material. Both the HOMO and the LUMO energy levels
of our synthesized compound 8a are very close to those of
DPVBI.
Fig. 3 The electroluminescence spectrum of cyano-containing indole 1e
and its CIE chromaticity coordinates represented by -. They were
obtained by use of a Keithley 2400 Source meter and a Newport 1835C
optical meter equipped with a Newport 818-ST silicon photodiode,
respectively.
(x ¼ 0.18, y ¼ 0.12) in the Commission International de
L’Exclairage (CIE) chromaticity coordinates. These results
indicate our success in the development of an OLED device for
emitting pure blue light. For electroluminescence performance
as an undoped device, we compared 1e with two known blue-
emitters:9,10-bis(4-(2,2-diphenylvinyl)phenylanthracene (DPVPA)
and 2-methyl-9,10-di(2-naphthyl)anthracene (MADN).2 Both
DPVPA and MADN possess greater external quantum efficien-
cies (3% and 1.5%, respectively) than that of 1e (0.87%). However,
DPVPA exhibits a ‘‘greener’’ color with CIE x ¼ 0.14, y ¼ 0.17,
while the ‘‘blue’’ emitter 1e has CIE x ¼ 0.18, y ¼ 0.12. Moreover,
Fabrication of OLED devices and measurement
For device fabrication, we chose 1e as the candidate because of
its higher PL quantum yield (FPL 0.592) and better thermal
stability (e.g., Td 289 ꢀC) than other synthesized indoles.
Accordingly, the OLED device was fabricated by use of vacuum-
deposition of NPB, indole 1e, TPBI, Alq3, and an Mg–Ag
electrode on top of an ITO glass substrate. The device
structure was ITO/NPB (30 nm)/1e (25 nm)/TPBI (10 nm)/Alq3
(40 nm)/Mg–Ag (55 nm), where ITO, NPB, TPBI, Alq3, Mg–Ag
represent indium tin oxide, 4,40-bis[N-(1-naphthyl)-N-phenyl-
amino]biphenyl, 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene,
tris(8-hydroxyquinoline)aluminium, and magnesium–silver alloy
(ꢃ10:1), respectively. NPB and Alq3 were used as the hole and
electron transporting materials, respectively. TPBI functioned as
the hole blocking material.
ꢀ
the Tg values ꢀare higher for indole 1e (136 C) than polyarene
MADN (120 C). Thus the former compound developed by us
possesses better thermal stability.
Conclusions
Use of the Larock heteroannulation method led to a series of
substituted indole derivatives. These new compounds may
possess a 3,4-dimethoxybenzyl or an anthracenyl group at the C2
position, meanwhile, an H, Me, F, Cl, CN, COOMe, or NO2
group at the C5 position. Their emitting photoluminescence from
the thin film can be tuned by attachment of various groups at the
C2 and the C5 positions of indoles following the order from
violet to blue: 5-F < 5-Cl < 5-Me < 5-H < 5-COOMe < 5-CN <
2-anthracene. The device with a configuration ITO/NPB/1e/
TPBI/Alq3/Mg–Ag was prepared, which successfully emitted
blue electroluminescence with good color purity.
The substrate was an indium-tin-oxide (ITO) coated glass
possessing a resistance of < 30 U/square. The ITO glass was
etched for the anode electrode pattern and organic materials
were deposited under vacuum. The thermal evaporation of
organic materials was carried out at a chamber pressure of 10ꢁ6
torr. The deposition rates for organic materials, Mg and Ag were
about 0.10, 0.50, and 0.050 nm/s, respectively. The cathode
Mg1.0Ag0.1 alloy was deposited (55 nm) by co-evaporation and
followed by a thick silver capping layer. Current–voltage–lumi-
nescence (I–V–L) characteristics and CIE color coordinates were
then determined simultaneously.
Experimental
As a result, our fabricated device including 1e had a turn-on
voltage of 6.0 V. Its brightness reached 184 cd/m2 at 20 mA and
8.3 V as well as 783 cd/m2 at 100 mA and 10.2 V. The observed
maximum brightness in this device was at 2417 cd/m2 at 551 mA
and 15.0 V. The external maximum quantum and power effi-
ciency for the device were 0.87% and 0.45 lm/W, which were
achieved at 7.6 V (4.1 mA/cm2, 46 cd/m). The electrolumines-
cence spectrum of a 1e-based device showed the emission
maximum at 443 nm (see Fig. 3). The color of our device was blue
General details
ꢀ
All reactions were carried out in oven-dried glassware (120 C)
under an atmosphere of nitrogen unless as indicated otherwise.
˚
Acetone from Mallinckrodt was dried with 4A molecular sieves
and distilled. Tetrahydrofuran (reagent grade) from Mallinck-
rodt was dried by distillation from sodium and benzophenone
under an atmosphere of nitrogen. N,N-Dimethylformamide
This journal is ª The Royal Society of Chemistry 2009
J. Mater. Chem., 2009, 19, 3084–3090 | 3087

View Online
from Mallinckrodt was dried and distilled from MgSO4 under
reduced pressure and then stored in serum-capped bottles over
˚
4A molecular sieves under nitrogen. Chloroform, dichloro-
minimization. The energies for all conformations were mini-
mized with the consistent valence forcefield (CVFF) until the
maximum derivative was less than 0.001 kcal molꢁ1
A
ꢁ1
ꢀ
.
methane, ethyl acetate, and hexanes from Mallinckrodt Chem-
ical Co. were dried and distilled from CaH2. The following
compounds and reagents were purchased from Aldrich Chemical
Co.: 2-iodoaniline (4a), 4-cyano-2-iodoaniline (4e), methyl
4-amino-3-iodobenzoate (4f), 2-iodo-4-nitroaniline (4g), methyl
chloroformate, and (PPh3)2PdCl2. The following compounds
were synthesized by following the literature methods: 2-iodo-
4-methylaniline24 (4b), 4-fluoro-2-iodoaniline25 (4c), 4-chloro-
2-iodoaniline24 (4d), methyl (3,4-dimethoxyphenyl)propiolate26
(5), and 9-(2,2-dibromovinyl)anthracene17 (6).
Standard procedure for the syntheses of indoles 1a–g and 8a,b.
A solution containing o-iodoaniline (1.0 equiv), an alkyne (1.6–
3.0 equiv), (PPh3)2PdCl2 (0.050 equiv), n-Bu4NBr (1.0 equiv),
and NaOAc (5.0 equiv) in DMF was stirred at 100–120 ꢀC for 30
min (1a–g) or 10 h (8a,b). After the reaction mixture was cooled
to room temperature, it was quenched with water (50 mL),
neutralized with saturated aqueous NH4Cl, and extracted with
Et2O (3 ꢂ 50 mL). The combined organic layers were washed
with saturated aqueous NaCl (10 mL), dried over MgSO4 (s),
filtered, and concentrated under reduced pressure. The residue
was purified by use of gravity column chromatography on silica
gel with 25% EtOAc (except 8a,b with 10% EtOAc) in hexanes as
eluant to provide the desired indoles with purity >99.0%, as
checked by GC.
€
Melting points were obtained with a Buchi 535 melting point
apparatus. Analytical thin layer chromatography (TLC) was
performed on precoated plates (silica gel 60 F-254), purchased
from Merck Inc. Mixtures of ethyl acetate and hexanes were used
as eluants. Gas chromatographic analyses were performed on
a Hewlett-Packard 5890 Series II instrument equipped with a 25
m cross-linked methyl silicone gum capillary column (0.32-mm
i.d.). Nitrogen gas was used as a carrier gas and the flow rate was
kept constant at 14.0 mL/min. The retention time tR was
measured under the following conditions: injector temperature
Methyl 2-(3,4-dimethoxyphenyl)indole-3-carboxylate (1a). The
standard procedure was followed by use of 2-iodoaniline (4a,
165.0 mg, 0.7533 mmol, 1.0 equiv), methyl (3,4-dimethoxy-
phenyl)propiolate (5, 497.2 mg, 2.258 mmol, 3.0 equiv),
(PPh3)2PdCl2 (26.3 mg, 0.0375 mmol, 0.050 equiv), n-Bu4NBr
(242.6 mg, 0.7526 mmol, 1.0 equiv), NaOAc (310.0 mg, 3.779
mmol, 5.0 equiv), and DMF (30 mL) to give 1a (152.2 mg, 0.489
ꢀ
ꢀ
260 C, the initial temperature for column 70 C, duration 2.00
min, increment rate 15 ꢀC/min, and the final temperature for
ꢀ
column 280 C. Gas chromatography and low resolution mass
ꢀ
spectral analyses were performed on an Agilent Technologies
6890N Network GC System equipped with an Agilent 5973
Network Mass Selective Detector and a capillary HP-1 column.
Purification by gravity column chromatography was carried out
by use of Merck Reagents Silica Gel 60 (particle size 0.063–0.200
mm, 70–230 mesh ASTM).
mmol, 65%) as white solids; mp 154.2–154.8 C (from CH2Cl2);
(Rf ¼ 0.35, 20% EtOAc in hexanes); nmax/cmꢁ1 3317 (m, N–H),
2950 (m), 2840 (w), 1682 (s, C]O), 1605 (w), 1584 (w), 1548 (m),
1502 (s), 1456 (s), 1331 (m), 1257 (s) and 1121 (s); dH(500 MHz;
CDCl3) 3.83 (s, 3 H, C(]O)OCH3), 3.86 (s, 3 H, ArOCH3), 3.88
(s, 3 H, ArOCH3), 6.88 (d, J ¼ 8.5 Hz, 1 H, ArH), 7.18–7.25 (m, 4
H, 4 ꢂ ArH), 7.35 (d, J ¼ 6.5 Hz, 1 H, ArH), 8.17 (d, J ¼ 6.0 Hz,
1 H, ArH) and 8.65 (s, 1 H, NH); dC(125 MHz; CDCl3) 50.86,
55.89, 55.96, 103.99, 110.69, 110.87, 113.00, 122.03, 122.07,
122.15, 123.10, 124.39, 127.65, 134.96, 144.51, 148.40, 149.87 and
165.84 (C]O); m/z (EI) 311 (M+, 100), 296 (8), 280 (43), 236
(15), 207 (19), 140 (7); HRMS calcd for C18H17NO4: 311.1157,
found 311.1156.
Photoluminescence spectra were measured on a Hitach F-4500
fluorescence spectrophotometer. Ultraviolet (UV) spectra were
measured on a Hitach U3300 UV-vis spectrophotometer. Cyclic
voltammograms were measured on a CH Instruments, Inc. 600A
Electrochemical Analyzer. Infrared (IR) spectra were measured
on a Jasco FT/IR-5300 Fourier transform infrared spectrometer.
The wavenumbers reported are referenced to the polystyrene
1601 cmꢁ1 absorption. Absorption intensities are recorded by the
following abbreviations: s, strong; m, medium; w, weak. Proton
NMR spectra were obtained on a Varian Unity-400 (400 MHz)
spectrometer by use of chloroform-d as solvent and tetrame-
thylsilane as internal standard. Carbon-13 NMR spectra were
obtained on a Varian Unity-400 (100 MHz) spectrometer by use
of chloroform-d as solvent. Carbon-13 chemical shifts are
referenced to the center of the CDCl3 triplet (77.0 ppm) or
DMSO-d6 pentet (39.54 ppm). Multiplicities are recorded by the
following abbreviations: s, singlet; d, doublet; t, triplet; q, quartet;
m, multiplet; J, coupling constant (hertz). High-resolution mass
spectra were obtained by means of a JEOL JMS-HX110 mass
spectrometer. Electrospray ionization mass spectrometry (ESI-
MS) analyses were performed on a quadrupole ion trap mass
analyzer fitted with an electrospray ionization source (Finnigan
LCQ, Finnigan MAT, San Jose, CA).
Methyl 2-(3,4-dimethoxyphenyl)-5-methylindole-3-carboxylate
(1b). The standard procedure was followed by use of 2-iodo-4-
methylaniline (4b, 175.4 mg, 0.7526 mmol, 1.0 equiv), methyl
(3,4-dimethoxyphenyl)propiolate (5, 500.1 mg, 2.271 mmol, 3.0
equiv), (PPh3)2PdCl2 (26.9 mg, 0.0383 mmol, 0.050 equiv), n-
Bu4NBr (242.0 mg, 0.7507 mmol, 1.0 equiv), NaOAc (308.8 mg,
3.764 mmol, 5.0 equiv), and DMF (30 mL) to give 1b (101.2 mg,
0.301 mmol, 40%) as white solids; mp 211.3–211.5 ꢀC (from
CH2Cl2); (Rf ¼ 0.35, 20% EtOAc in hexanes); nmax/cmꢁ1 3291 (m,
N–H), 2941 (w), 2838 (w), 1698 (s, C]O), 1607 (m), 1585 (m),
1546 (m), 1502 (s), 1442 (s), 1301 (m), 1260 (s), 1247 (s) and 1118
(s); dH(400 MHz; CDCl3) 2.47 (s, 3 H, CH3), 3.82 (s, 3 H,
C(]O)OCH3), 3.86 (s, 3 H, ArOCH3), 3.88 (s, 3 H, ArOCH3),
6.87 (d, J ¼ 8.0 Hz, 1 H, ArH), 7.06 (d, J ¼ 8.0 Hz, 1 H, ArH),
7.16–7.24 (m, 3 H, 3 ꢂ ArH), 7.96 (s, 1 H, C4-ArH) and 8.54 (s, 1
H, NH); dC(100 MHz; CDCl3) 21.61, 50.72, 55.85, 55.92, 103.58,
110.48, 110.74, 113.11, 121.66, 122.09, 124.59, 124.63, 127.92,
131.45, 133.29, 144.44, 148.39, 149.81 and 165.91 (C]O);
m/z (EI) 325 (M+, 100), 294 (32), 278 (6), 250 (12), 223 (4), 207
Computation was performed on a Silicon Graphics O2+
workstation. The program Builder was used for the construction
of 3,5-dimethyl 2-(3,4-dimethoxyphenyl)indole-3,5-dicarbox-
ylate (3f). The program Discover was used for energy
3088 | J. Mater. Chem., 2009, 19, 3084–3090
This journal is ª The Royal Society of Chemistry 2009

View Online
(10), 162 (6); HRMS calcd for C19H19NO4: 325.1314, found
325.1311.
(d, J ¼ 8.4 Hz, 1 H, ArH), 7.48 (d, J ¼ 8.4 Hz, 1 H, ArH), 8.54 (s,
1 H, C4-ArH) and 8.78 (s, 1 H, NH); dC(100 MHz; DMSO-d6)
50.87, 55.75, 55.72, 102.71, 103.55, 111.23, 113.08, 113.83,
120.35, 122.82, 122.90, 125.37, 126.23, 127.25, 137.31, 146.89,
148.05, 150.08 and 164.38 (C]O); m/z (EI) 336 (M+, 100), 321
(9), 305 (35), 261 (9), 203 (5); HRMS m/z calcd for C19H16N2O4:
336.1110, found 336.1107.
Methyl 2-(3,4-dimethoxyphenyl)-5-fluoroindole-3-carboxylate
(1c). The standard procedure was followed by use of 4-fluoro-
2-iodoaniline (4c, 183.9 mg, 0.7759 mmol, 1.0 equiv), methyl
(3,4-dimethoxyphenyl)propiolate (5, 505.5 mg, 2.295 mmol, 3.0
equiv), (PPh3)2PdCl2 (27.2 mg, 0.0387 mmol, 0.050 equiv),
n-Bu4NBr (249.0 mg, 0.7724 mmol, 1.0 equiv), NaOAc (320.0
mg, 3.901 mmol, 5.0 equiv), and DMF (30 mL) to give 1c (102.4
mg, 0.301 mmol, 40%) as white solids; mp 188.5–189.0 ꢀC (from
CH2Cl2); (Rf ¼ 0.35, 20% EtOAc in hexanes); nmax/cmꢁ1 3316 (s,
N–H), 2949 (m), 2838 (w), 1683 (s, C]O), 1586 (m), 1503 (s),
1452 (s), 1300 (m), 1261 (s), 1204 (m), 1122 (s) and 1025 (m);
dH(400 MHz; CDCl3) 3.81 (s, 3 H, C(]O)OCH3), 3.82 (s, 3 H,
ArOCH3), 3.84 (s, 3 H, ArOCH3), 6.82 (d, J ¼ 8.0 Hz, 1 H, ArH),
6.95 (t, J ¼ 10 Hz, 1 H, ArH), 7.14–7.24 (m, 3 H, 3 ꢂ ArH), 7.81
(d, J ¼ 10 Hz, 1 H, ArH) and 8.85 (s, 1 H, NH); dC(100 MHz;
CDCl3) 50.83, 55.85, 55.94, 104.19, 107.38 (d), 110.81, 111.35 (d),
111.63 (d), 113.14, 122.12, 124.12, 128.47 (d), 131.46, 145.99,
148.46, 150.08, 159.22 (d), and 165.54 (C]O); m/z (EI) 329 (M+,
100), 314 (9), 298 (42), 282 (8), 254 (16), 149 (7); HRMS calcd for
C18H16FNO4: 329.1063, found 329.1062.
3,5-Dimethyl 2-(3,4-dimethoxyphenyl)indole-3,5-dicarboxylate
(1f). The standard procedure was followed by use of methyl
4-amino-3-iodobenzoate (4f, 208.4 mg, 0.7522 mmol, 1.0 equiv),
methyl (3,4-dimethoxyphenyl)propiolate (5, 496.2 mg, 2.253
mmol, 3.0 equiv), (PPh3)2PdCl2 (26.6 mg, 0.0379 mmol, 0.050
equiv), n-Bu4NBr (240.8 mg, 0.7470 mmol, 1.0 equiv), NaOAc
(306.9 mg, 3.741 mmol, 5.0 equiv), and DMF (30 mL) to giveꢀ1f
(92.2 mg, 0.250 mmol, 33%) as white solids; mp 192.4–192.8 C
(from CH2Cl2); (Rf ¼ 0.30, 20% EtOAc in hexanes); nmax/cmꢁ1
3305 (m, N–H), 2951 (m), 2839 (w), 1709 (s, C]O), 1695 (s,
C]O), 1619 (m), 1587 (w), 1505 (s), 1441 (s), 1378 (w), 1285 (s),
1257 (s) and 1122 (s); dH(400 MHz; CDCl3) 3.82 (s, 3 H,
C(]O)OCH3), 3.85 (s, 6 H, 2 ꢂ ArOCH3), 3.92 (s, 3 H,
C(]O)OCH3), 6.84 (d, J ¼ 8.0 Hz, 1 H, ArH), 7.18–7.21 (m, 2 H,
2 ꢂ ArH), 7.34 (d, J ¼ 8.4 Hz, 1 H, ArH), 7.91 (d, J ¼ 8.4 Hz, 1
H, ArH), 8.86 (s, 1 H, C4-ArH) and 9.16 (s, 1 H, NH); dC(100
MHz; CDCl3) 51.06, 51.96, 55.87, 55.94, 104.88, 110.75, 110.77,
113.05, 122.23, 123.77, 123.91, 124.49, 124.79, 127.24, 137.63,
145.86, 148.48, 150.14, 165.42 (C]O) and 168.07 (C]O); m/z
(EI) 369 (M+, 100), 338 (42), 294 (9), 281 (9), 207 (18), 169 (11),
131 (12); HRMS calcd for C20H19NO6: 369.1212, found
369.1213.
Methyl 5-chloro-2-(3,4-dimethoxyphenyl)indole-3-carboxylate
(1d). The standard procedure was followed by use of 4-chloro-
2-iodoaniline (4d, 191.2 mg, 0.7545 mmol, 1.0 equiv), methyl
(3,4-dimethoxyphenyl)propiolate (5, 499.1 mg, 2.266 mmol,
3.0 equiv), (PPh3)2PdCl2 (26.5 mg, 0.0378 mmol, 0.050 equiv),
n-Bu4NBr (245.2 mg, 0.7606 mmol, 1.0 equiv), NaOAc
(311.9 mg, 3.802 mmol, 5.0 equiv), and DMF (30 mL) to give 1d
(121.3 mg, 0.351 mmol, 47%) as white solids; mp 196.8–197.2 ꢀC
(from CH2Cl2); (Rf ¼ 0.40, 20% EtOAc in hexanes); nmax/cmꢁ1
3310 (s, N–H), 2949 (m), 2837 (w), 1681 (s, C]O), 1503 (s),
1465 (s), 1441 (s), 1295 (m), 1263 (s), 1206 (s), 1121 (s) and 1025
(m); dH(400 MHz; CDCl3) 3.84 (s, 3 H, C(]O)OCH3), 3.87 (s, 3
H, ArOCH3), 3.89 (s, 3 H, ArOCH3), 6.88 (d, J ¼ 8.0 Hz, 1 H,
ArH), 7.17–7.27 (m, 4 H, 4 ꢂ ArH), 8.14 (s, 1 H, C4-ArH) and
8.65 (s, 1 H, NH); dC(100 MHz; CDCl3) 50.97, 55.93, 56.04,
103.89, 110.84, 111.83, 113.11, 121.72, 122.14, 123.48, 123.92,
127.89, 128.81, 133.30, 145.62, 148.57, 150.22 and 165.32
(C]O); m/z (EI) 345 (M+, 100), 314 (22), 270 (16), 207 (9), 172
(4), 157 (6); HRMS calcd for C18H16ClNO4: 345.0768, found
345.0770.
Methyl 2-(3,4-dimethoxyphenyl)-5-nitroindole-3-carboxylate
(1g). The standard procedure was followed by use of 2-iodo-
4-nitroaniline (4g, 199.5 mg, 0.7555 mmol, 1.0 equiv), methyl
(3,4-dimethoxyphenyl)propiolate (5, 499.2 mg, 2.267 mmol, 3.0
equiv), (PPh3)2PdCl2 (26.8 mg, 0.0382 mmol, 0.050 equiv),
n-Bu4NBr (241.9 mg, 0.7504 mmol, 1.0 equiv), NaOAc (309.5
mg, 3.773 mmol, 5.0 equiv), and DMF (30 mL) to give 1g (79.7
mg, 0.224 mmol, 30%) as yellow solids; mp 241.2–241.6 ꢀC (from
CH2Cl2); (Rf ¼ 0.35, 20% EtOAc in hexanes); nmax/cmꢁ1 3306 (s,
N–H), 2950 (w), 2840 (w), 1694 (s, C]O), 1555 (m), 1503 (s),
1471 (s), 1338 (s), 1264 (s), 1209 (m), 1086 (m) and 1021 (m);
dH(400 MHz; CDCl3) 3.91 (s, 6 H, 2 ꢂ ArOCH3), 3.93 (s, 3 H,
C(]O)OCH3), 6.95 (d, J ¼ 8.4 Hz, 1 H, ArH), 7.25 (d, J ¼ 8.0
Hz, 1 H, ArH), 7.27 (s, 1 H, C20-ArH), 7.42 (d, J ¼ 8.8 Hz, 1 H,
ArH), 8.15 (d, J ¼ 8.8 Hz, 1 H, ArH), 8.84 (s, 1 H, C4-ArH) and
9.08 (s, 1H, NH); dC(100 MHz; DMSO-d6) 51.41, 56.03, 56.04,
104.18, 111.58, 112.71, 113.95, 117.90, 118.34, 123.14, 123.25,
127.25, 139.06, 142.70, 148.29, 148.41, 150.49, and 164.78
(C]O); m/z (EI) 356 (M+, 100), 341 (9), 325 (32), 278 (19), 235
(5), 139 (9), 31 (17); HRMS calcd for C18H16N6O6: 356.1008,
found 356.1009.
Methyl 5-cyano-2-(3,4-dimethoxyphenyl)indole-3-carboxylate
(1e). The standard procedure was followed by use of 4-cyano-2-
iodoaniline (4e, 175.2 mg, 0.7179 mmol, 1.0 equiv), methyl (3,4-
dimethoxyphenyl)propiolate (5, 480.2 mg, 2.181 mmol, 3.0
equiv), (PPh3)2PdCl2 (25.1 mg, 0.0358 mmol, 0.050 equiv), n-
Bu4NBr (238.6 mg, 0.7401 mmol, 1.0 equiv), NaOAc (305.2 mg,
3.720 mmol, 5.0 equiv), and DMF (30 mL) to give 1e (95.8 mg,
0.285 mmol, 38%) as white solids; mp 220.0–220.5 ꢀC (from
CH2Cl2); (Rf ¼ 0.30, 20% EtOAc in hexanes); nmax/cmꢁ1 3296 (s,
N–H), 2954 (w), 2840 (w), 2221 (s), 1694 (s, C]O), 1614 (w),
1505 (s), 1470 (s), 1443 (s), 1375 (m), 1265 (s), 1215 (s) and 1120
(s); dH(400 MHz; CDCl3) 3.88 (s, 3 H, C(]O)OCH3), 3.90 (s, 3
H, ArOCH3), 3.91 (s, 3 H, ArOCH3), 6.94 (d, J ¼ 8.4 Hz, 1 H,
ArH), 7.23 (d, J ¼ 8.6 Hz, 1 H, ArH), 7.25 (s, 1 H, C20-ArH), 7.43
Methyl (9-anthracenyl)propiolate (7). To a solution of 9-(2,2-
dibromovinyl)anthracene (6, 9.05 g, 25.0 mmol, 1.0 equiv) in dry
THF (150 mL) was added n-butyl lithium (1.78 M, 35.4 mL, 62.5
mmol, 2.5 equiv) at ꢁ78 ꢀC. After the solution was stirred at
ꢁ10 ꢀC for 60 min, methyl chloroformate (4.73 g, 50.0 mmol, 2.0
ꢀ
equiv) was then added at ꢁ78 C and the reaction mixture was
This journal is ª The Royal Society of Chemistry 2009
J. Mater. Chem., 2009, 19, 3084–3090 | 3089

View Online
stirred at room temperature for 30 min. The reaction was
quenched with saturated aqueous NH4Cl (125 mL) and extracted
with ether (3 ꢂ 100 mL). The combined organic layers were dried
over MgSO4 (s), filtered, and concentrated under reduced
pressure. The residue was purified by use of gravity column
chromatography on silica gel (1.0% EtOAc in hexanes as eluent)
to give 7 (5.460 g, 21.0 mmol, 84%) as yellow solids: mp 113.8–
Acknowledgements
For financial support, we thank the National Science Council of
R.O.C.
References
1 For recent reviews, see: (a) P. L. Burn, S. C. Lo and I. D. W. Samuel,
Adv. Mater., 2007, 19, 1675; (b) I. F. Perepichka, D. F. Perepichka,
H. Meng and F. Wudl, Adv. Mater., 2005, 17, 2281.
2 For a recent review, see: S. W. Wen, M. T. Lee and C. H. Chen, IEEE
J. Display Technol., 2005, 1, 90.
3 D. Gebeyehu, K. Walzer, G. He, M. Pfeiffer, K. Leo, J. Brandt,
€
A. Gerhard, P. Stoßel and H. Vestweber, Synth. Met., 2005, 148,
205, and references cited therein.
4 J. Jacob, S. Sax, T. Piok, E. J. W. List, A. C. Grimsdale and
K. Mullen, J. Am. Chem. Soc., 2004, 126, 6987.
114.2 ꢀC (from CH2Cl2); (Rf ¼ 0.25, 1% EtOAc in hexanes); nmax
/
cmꢁ1 3057 (w), 2957 (w), 2203 (s), 1716 (s, C]O), 1434 (m), 1358
(m), 1237 (s), 1158 (m), 1085 (m), 738 (m) and 732 (m); dH(400
MHz; CDCl3) 3.94 (s, 3 H, C(]O)OCH3), 7.52 (t, J ¼ 7.4 Hz, 2
H, 2 ꢂ ArH), 7.63 (t, J ¼ 7.2 Hz, 2 H, 2 ꢂ ArH), 8.02 (d, J ¼ 8.4
Hz, 2 H, 2 ꢂ ArH), 8.53 (d, J ¼ 8.8 Hz, 2 H, 2 ꢂ ArH) and 8.54
(s, 1 H, ArH); dC(100 MHz; CDCl3) 52.80 (CH3), 83.73, 91.17,
112.70, 125.92, 126.03, 127.77, 128.81, 130.78, 130.82, 134.11 and
154.77 (C]O); m/z (EI) 260 (M+, 100), 229 (35), 215 (11), 202
(85), 114 (15), 100 (31); HRMS calcd for C18H12O2: 260.0837,
found 260.0837.
5 M. Pope, H. P. Kallmann and P. Magnante, J. Chem. Phys., 1963, 38,
2042.
6 For recent works, see: (a) Y. Li, L. Cao, Z. Ning, Z. Huang, Y. Cao
and H. Tian, Tetrahedron. Lett., 2007, 48, 975; (b) T. S. Yeh,
T. J. Chow, S. H. Tsai, C. W. Chiu and C. X. Zhao, Chem. Mater.,
2006, 18, 832; (c) W. H. Huang, W. L. Jia and S. Wang, Can. J.
Chem., 2006, 84, 477; (d) Q. Fang, B. Xu, B. Jiang, H. Fu, X. Chen
and A. Cao, Chem. Commun., 2005, 1468; (e) C. W. Chiu,
T. J. Chow, C. H. Chuen, H. M. Lin and Y. T. Tao, Chem. Mater.,
2003, 15, 4527; (f) US Pat., 0 137 262, 2004.
7 G. S. Liou, S. H. Hsiao, W. C. Chen and H. J. Yen, Macromolecules,
2006, 39, 6036.
8 C. C. Wu, Y. T. Lin, H. H. Chiang, T. Y. Cho, C. W. Chen,
K. T. Wong, Y. L. Liao, G. H. Lee and S. M. Peng, Appl. Phys.
Lett., 2002, 81, 577.
9 For recent representative works, see: (a) L. M. Leung, W. Y. Lo,
S. K. So, K. M. Lee and W. K. Choi, J. Am. Chem. Soc., 2000, 122,
5640; (b) Y. Liu, J. Guo, J. Feng, H. Zhang, Y. Li and Y. Wang,
Appl. Phys. Lett., 2001, 78, 2300; (c) X. T. Tao, H. Suzuki,
T. Wada, S. Miyata and H. Sasabe, J. Am. Chem. Soc., 1999, 121,
9447; (d) W. B. Im, H. K. Hwang, J. G. Lee, K. Han and Y. Kim,
Appl. Phys. Lett., 2001, 79, 1387.
10 B. M. Krasovitskii and B. M. Bolotin, Organic Luminescent
Materials, VCH, New York, 1988.
11 Y. Shirota, J. Mater. Chem., 2000, 10, 1.
Methyl 2-(9-anthracenyl)indole-3-carboxylate (8a). The stan-
dard procedure was followed by use of 2-iodoaniline (4a, 166.6
mg, 0.7607 mmol, 1.0 equiv), methyl (9-anthracenyl)propiolate
(7, 313.0 mg, 1.203 mmol, 1.6 equiv), (PPh3)2PdCl2 (26.7 mg,
0.0380 mmol, 0.050 equiv), n-Bu4NBr (247.6 mg, 0.7681 mmol,
1.0 equiv), NaOAc (309.0 mg, 3.767 mmol, 5.0 equiv), and DMF
(30 mL) to give 8a (89.9 mg, 0.256 mmol, 34%) as yellow solids;
ꢀ
mp 259.5–260.0 C (from CH2Cl2); (Rf ¼ 0.30, 10% EtOAc in
hexanes); nmax/cmꢁ1 3249 (m, N–H), 3051 (w), 2948 (w), 1674 (s,
C]O), 1543 (w), 1457 (s), 1441 (s), 1424 (m), 1335 (m), 1193 (s)
and 1087 (s); dH(400 MHz; CDCl3) 3.47 (s, 3 H, C(]O)OCH3),
7.33–7.47 (m, 7 H, 7 ꢂ ArH), 7.58 (d, J ¼ 8.8 Hz, 2 H, 2 ꢂ ArH),
8.04 (d, J ¼ 8.0 Hz, 2 H, 2 ꢂ ArH), 8.36 (d, J ¼ 8.0 Hz, 1 H,
ArH), 8.56 (s, 1 H, ArH) and 8.60 (s, 1 H, NH); dC(100 MHz;
DMSO-d6) 50.34 (CH3), 106.96, 111.94, 121.10, 121.57, 122.75,
125.43, 125.44, 125.59, 126.44, 127.31, 127.88, 128.43, 130.44,
130.69, 136.06, 141.47 and 164.40 (C]O); m/z (EI) 351 (M+,
100), 320 (62), 291 (40), 207 (9), 145 (34); HRMS calcd for
C24H17NO2: 351.1259, found 351.1259.
ꢁ
12 E. Weinhold, O. P. Marquez and J. Marquez, Avances en Quımica,
ꢁ
´
2007, 2, 9.
13 I. M. Matheson, O. C. Musgrave and C. J. Webster, Chem. Commun.
(London), 1965, 278.
14 J. R. Hwu, K. S. Chuang, S. H. Chuang and S. C. Tsay, Org. Lett.,
2005, 7, 1545.
15 R.C.Larock,E.K.YumandM.D.Refvik,J. Org. Chem., 1998, 63, 7652.
16 For related works, see: (a) S. H. Watterson, T. G. M. Dhar,
S. K. Ballentine, Z. Shen, J. C. Barrish, D. Cheney, C. A. Fleener,
K. A. Rouleau, R. Townsend, D. L. Hollenbaugh and
E. J. Iwanowicz, Bioorg. Med. Chem. Lett., 2003, 13, 1273; (b)
Y. Kondo, F. Shiga, N. Murata, T. Sakamoto and H. Yamanaka,
Tetrahedron, 1994, 50, 11803.
17 T. R. Kelly, J. P. Sestelo and I. Tellitu, J. Org. Chem., 1998, 63, 3655.
18 H. Aziz and Z. D. Popovic, Chem. Mater., 2004, 16, 4522.
19 S. Wang, W. J. Oldham Jr., R. A. Hudack Jr. and G. C. Bazan, J. Am.
Chem. Soc., 2000, 122, 5695.
Methyl 2-(9-anthracenyl)-5-methylindole-3-carboxylate (8b).
The standard procedure was followed by use of 2-iodo-4-meth-
ylaniline (4b, 175.4 mg, 0.7527 mmol, 1.0 equiv), methyl (9-
anthracenyl)propiolate (7, 311.9 mg, 1.198 mmol, 1.6 equiv),
(PPh3)2PdCl2 (26.2 mg, 0.0373 mmol, 0.050 equiv), n-Bu4NBr
(241.8 mg, 0.7500 mmol, 1.0 equiv), NaOAc (312.3 mg, 3.807
mmol, 5.0 equiv), and DMF (30 mL) to give 8b (82.5 mg, 0.226
mmol, 30%) as yellow solids; mp 215.7–216.1 ꢀC (from CH2Cl2);
(Rf ¼ 0.30, 10% EtOAc in hexanes); nmax/cmꢁ1 3320 (m, N–H),
2954 (w), 1689 (s, C]O), 1450 (s), 1265 (m), 1218 (m), 1149 (s)
and 1079 (s); dH(400 MHz; CDCl3) 2.57 (s, 3 H, CH3), 3.45 (s, 3
H, C(]O)OCH3), 7.17 (d, J ¼ 8.0 Hz, 1 H, ArH), 7.31–7.36 (m, 3
H, 3 ꢂ ArH), 7.44 (t, J ¼ 8.0 Hz, 2 H, 2 ꢂ ArH), 7.58 (d, J ¼ 8.8
Hz, 2 H, 2 ꢂ ArH), 8.04 (d, J ¼ 8.8 Hz, 2 H, 2 ꢂ ArH), 8.16 (s, 1
H, ArH), 8.47 (s, 1 H, NH) and 8.55 (s, 1 H, ArH); dC(100 MHz;
CDCl3) 21.66, 50.63, 108.47, 110.76, 121.52, 124.88, 125.29,
125.83, 126.27, 126.74, 127.17, 128.45, 128.47, 130.97, 131.03,
131.80, 133.90, 141.00 and 165.24 (C]O); m/z (EI) 365 (M+,
100), 334 (47), 319 (16), 306 (25), 253 (14), 191 (10). HRMS calcd
for C25H19NO2: 365.1416, found 365.1421.
20 X. Zhan, C. Risko, F. Amy, C. Chan, W. Zhao, S. Barlow, A. Kahn,
ꢁ
J. L. Bredas and S. R. Marder, J. Am. Chem. Soc., 2005, 127, 9021.
21 S. Miyata and H. S. Nalwa, Organic Electroluminescent Materials and
Devices, Gordon and Breach, Amsterdam, 1997.
22 cf. A method reported in X. Zhan, A. Haldi, C. Risko, C. K. Chan,
W. Zhao, T. V. Timofeeva, A. Korlyukov, M. Yu. Antipin,
S. Montgomery, E. Thompson, Z. An, B. Domercq, S. Barlow,
ꢁ
A. Kahn, B. Kippelen, J. L. Bredas and S. R. Marder, J. Mater.
Chem., 2008, 18, 3157.
23 C. Hosokawa, H. Higashi, H. Nakamura and T. Kusumoto, Appl.
Phys. Lett., 1995, 67, 3853.
24 W. J. Xiao and H. Alper, J. Org. Chem., 1999, 64, 9646.
25 R. Beugelmans and M. Chbani, Bull. Soc. Chim. Fr., 1995, 132, 306.
26 D. H. Wadsworth, S. M. Geer and M. R. Detty, J. Org. Chem., 1987,
52, 3662.
3090 | J. Mater. Chem., 2009, 19, 3084–3090
This journal is ª The Royal Society of Chemistry 2009