Robust and highly efficient blue light-emitting hosts based on indene-substituted anthracene

Article abstract of DOI:10.1039/c000092b

Two new unsymmetrically indene-substituted 10-naphthylanthracene derivatives, 9-(4-(1,1′-dimethylinden-3-yl)phenyl)-10-(1-naphthyl) anthracene (DMIP-1-NA) and 9-(4-(1,1′-dimethylinden-3-yl)phenyl)-10-(2- naphthyl)anthracene (DMIP-2-NA), were easily synthesized. Both of them show intense fluorescence and good thermal stability. Three-layer organic light-emitting devices (OLEDs) using these anthracene derivatives as blue host materials and diphenyl-[4-(2-[1,1′;4′,1′′]terphenyl-4- yl-vinyl)-phenyl]amine (BD-1) as the dopant emitter have been fabricated. Highly efficient and color stable OLEDs were achieved under the range of doping concentration from 3% to 7%. A further optimized device structure based on DMIP-2-NA exhibited a maximum power efficiency of 8.39 lm W^-1 (7.6 cd A^-1 at 2.90 V) with a pure blue emission at CIE_x,y coordinates of (0.14, 0.18).

Full text of DOI:10.1039/c000092b

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PAPER
www.rsc.org/materials | Journal of Materials Chemistry
Robust and highly efficient blue light-emitting hosts based on
indene-substituted anthracene†
Zhen-Yuan Xia,a Zhi-Yun Zhang,a Jian-Hua Su,a Qiong Zhang,a Ka-Man Fung,b Mei-Ki Lam,b King-Fai Li,b
c
b
a
Wai-Yeung Wong, Kok-Wai Cheah, He Tian and Chin H. Chencd
*
*
Received 6th January 2010, Accepted 1st March 2010
First published as an Advance Article on the web 12th March 2010
DOI: 10.1039/c000092b
Two new unsymmetrically indene-substituted 10-naphthylanthracene derivatives, 9-(4-(1,10-
dimethylinden-3-yl)phenyl)-10-(1-naphthyl)anthracene (DMIP-1-NA) and 9-(4-(1,10-dimethylinden-3-yl)
phenyl)-10-(2-naphthyl)anthracene (DMIP-2-NA), were easily synthesized. Both of them show
intense fluorescence and good thermal stability. Three-layer organic light-emitting devices (OLEDs)
using these anthracene derivatives as blue host materials and diphenyl-[4-(2-[1,10;40,100]terphenyl-4-yl-
vinyl)-phenyl]amine (BD-1) as the dopant emitter have been fabricated. Highly efficient and color
stable OLEDs were achieved under the range of doping concentration from 3% to 7%. A further
optimized device structure based on DMIP-2-NA exhibited a maximum power efficiency of 8.39 lm
Wꢀ1 (7.6 cd Aꢀ1 at 2.90 V) with a pure blue emission at CIEx,y coordinates of (0.14, 0.18).
(EL) devices, a wider band-gap host with appropriate energy level
Introduction
is necessary for efficient generation of blue dopant emission.
Therefore, blue-doped emitter systems with all the desirable
attributes of high luminance efficiency, long operational lifetime,
and saturated blue color are still rare.14 Recently, anthracene-
based molecules show great promise as stable and efficient blue
host materials.15–18 Lee et al. reported 2-methyl-9,10-di(2-naph-
thyl)anthracene (MADN) doped with an unsymmetrical
Organic light-emitting devices (OLEDs) based on small mole-
cules have attracted intense attention due to their potential as
flat-panel displays. Among the three primary-color emitters (red,
green and blue) in OLEDs, blue-light emitting materials are of
particular importance. Due to the intrinsic wide band-gap of blue
materials, they are not only essential components for full-color
display applications but also hosts for suitable lower-energy
dopants to generate nearly all colors.1–5
mono(styryl)amine
fluorescent
dopant,
diphenyl-[4-(2-
[1,10;40,100]terphenyl-4-yl-vinyl)-phenyl]amine (BD-1) in which
the device produced an EL efficiency of 5.4 cd Aꢀ1 and 2.5 lm/W
with a saturated blue CIEx,y of (0.14, 0.13) and a normalized
operational lifetime of 9700 h at an initial brightness of 100 cd mꢀ2
with the introduction of a composite hole-transport layer
(c-HTL).2 Gao et al. also used BD-1 as the blue dopant and
unsymmetrical 9-(a-naphthyl)-10-(b-naphthyl)-anthracene (a,b-
ADN) as the hostmaterial to achievean ELefficiency of 4.9 cdAꢀ1
with a deep blue CIEx,y coordinate of (0.15, 0.13) by adding a hole
injection layer and inserting a buffer layer between the emitter and
Alq3.19
To date, much effort has been devoted to developing new blue
phosphorescent or fluorescent materials. However, blue phos-
phorescent materials are restricted to the instability and color
saturation issues.6 Many blue fluorescent materials and their
non-doped devices have also been reported,7–12 but only few of
them have their device stability being mentioned.
It is well-known that a guest-host doped emitter system can
significantly improve the device efficiency and operational life-
time.13 Highly efficient green and red electroluminescent
(EL) devices are easily obtained by doping the dyes in
some commercially used host materials, like tris-(8-hydroxy-
quinolinato)aluminium (Alq3). Asfor the blue electroluminescent
Although the BD-1 doped emitting system based on
a dinaphthylanthracene host can achieve saturated blue color
and high current yield, the complicated multilayer structures of
these devices hamper charge injection into the emissive layer, and
then cause relatively lower power efficiencies. Also the optimal
doping concentration should be precisely controlled in a narrow
range, which limits its application.
aKey Laboratory for Advanced Materials and Institute of Fine Chemicals,
East China University of Science & Technology, Shanghai, 200237, China.
E-mail: tianhe@ecust.edu.cn; Fax: (+86) 21-64252288
bCentre for Advanced Luminescence Materials, Department of Physics,
Hong Kong Baptist University, Kowloon Tong, Hong Kong, China
cCentre for Advanced Luminescence Materials, Department of Chemistry,
Hong Kong Baptist University, Kowloon Tong, Hong Kong, China. E-mail:
rwywong@hkbu.edu.hk
dDisplays & Lighting Center, National Engineering Lab of TFT-LCD
Materials and Technologies, Shanghai Jiao Tong University, Shanghai,
200240, China
† Electronic supplementary information (ESI) available: 1H NMR
spectra and 13C NMR spectra, high resolution mass spectra, cyclic
voltammograms, DSC and TGA data for target compounds. CCDC
reference number 767308. For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/c000092b
Indene derivatives are important intermediates for medica-
ments.20 However, there is little report on the application of
indene in the field of OLEDs.21 In this paper, we adopted an
indene building block incorporated into the classical anthracene
chromophores through a convenient synthetic approach. The 4-
(1,10-dimethylinden-3-yl)phenyl group is end-capped at the C-9
position of the 10-naphthylanthracene core to prevent the close-
packing of the molecules in the solid state and thus facilitate the
formation of amorphous films. Two new unsymmetrical robust
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blue host materials, 9-(4-(1,10-dimethylinden-3-yl)phenyl)-10-(1-
naphthyl)anthracene (DMIP-1-NA) and 9-(4-(1,10-dimethy-
linden-3-yl)phenyl)-10-(2-naphthyl)anthracene (DMIP-2-NA),
were successfully synthesized and applied in BD-1 doped three-
layer blue OLEDs with high efficiency, low power consumption
and good device stability in the range of doping concentrations
from 3% to 7%.
Results and discussion
Fig. 1 X-Ray structure of DMIP-1-NA, with the thermal ellipsoids
drawn at the 25% probability level.
Synthesis and characterization
The synthetic routes for the two new compounds, DMIP-1-NA
and DMIP-2-NA, are shown in Scheme 1. The mono-bromo
indene derivative 2 was easily prepared from two steps. In the
first step, acid-promoted Friedel–Crafts alkylation of benzene
with 3-methylcrotonic acid afforded indanone 1 with a high
yield. The following Grignard reaction of 1 and (4-bromo-
phenyl)magnesium bromide formed the indene-substituted
compound 2. 9-Naphthylanthrancene boronic acid intermediates
(3a, 3b) were obtained according to our previous report.22
Subsequent Pd-catalyzed Suzuki cross-coupling reaction
between the boronic acid 3 and monobromide 2 afforded the
unsymmetrical target compounds. Unlike the other anthracene
derivatives, these indene-substituted anthracenes dissolve well in
some common organic solvents. Good solubility of the target
compounds facilitates their purification procedure.
ring and the 1-naphthyl (or phenyl) group is 102.6ꢂ (or 80.6ꢂ),
while that between the phenyl plane and the indene ring is 39.0ꢂ.
According to its crystal packing, it is obvious that the molecules
tend not to aggregate in the ground state.
Thermal, optical and electrochemical behavior
The thermal properties of the new compounds were determined
by differential scanning calorimetry (DSC) and thermogravi-
metric analysis (TGA) measurements (Table 1). The two indene
derivatives, DMIP-1-NA and DMIP-2-NA, exhibit high thermal
stabilities with decomposition temperatures (5% weight-loss)
over 400 ꢂC. Tg and Tm of DMIP-1-NA and DMIP-2-NA are
132 ꢂC, 262 ꢂC and 138 ꢂC, 298 ꢂC, respectively. The Tg and Tm
data are stable after repeated heating and cooling cycles. Higher
Tg and Tm of DMIP-1-NA than DMIP-2-NA may be explained
by the higher steric hindrance of the 1-naphthyl ring compared to
the 2-naphthyl group.18 The good Tg values of these two
compounds suggest stable morphological properties, which is
desirable for OLEDs with high stability and efficiency.
All compounds were purified by the silica column chromato-
graphic method or recrystallization. Further purification was
readily accomplished by train sublimation under vacuum (10ꢀ6
Torr). The target compounds were characterized by NMR
spectroscopy and high-resolution mass spectrometry.
Cyclic voltammetry (CV) analyses were carried out to identify
the electrochemical behaviors of these two materials. Both
DMIP-1-NA and DMIP-2-NA show a reversible one-electron
oxidation event. The 2-naphthyl-containing DMIP-2-NA has
a lower oxidation potential (Eox) and a smaller energy gap than
the one with 1-naphthyl group DMIP-1-NA, which might be
caused by the stronger donor ability of 2-naphthyl group.22 The
HOMO levels of the two compounds were derived from the Eox
data. The LUMO values were calculated from the optical band
gap (estimated from the absorption edge) and the HOMO values.
Fig. 2 illustrates the frontier molecular orbitals of DMIP-1-
NA and DMIP-2-NA. Their electron density distribution of the
highest occupied molecular orbital (HOMO) and the lowest
unoccupied molecular orbital (LUMO) are primarily localized
on the anthracene moiety, indicating that the indene-substituted
group does not influence the blue emission of the anthracene
unit. Also the non-coplanar structures of unsymmetrically
indene-substituted anthracene molecules can effectively prevent
intermolecular interactions in the solid state and then improve
the thin-film stability, which is consistent with the X-ray struc-
tural results.
X-Ray crystal structure
In order to look at the conformation of these compounds, the
crystal structure of DMIP-1-NA was determined (Fig. 1). Each
of the four rings appears to be nearly coplanar (mean deviations
ꢀ
ꢁ0.0082–0.0193 A). The dihedral angle between the anthracene
Fig. 3 shows the absorption and PL spectra of the two
compounds in dilute dichloromethane solution (see Table 1).
They have similar absorption peaks in the range from 350 to
400 nm, and these characteristic vibronic bands are assigned to
the p–p* transitions of the anthracene core. Additionally, the
two absorption bands in the region from 220 to 260 nm are
Scheme 1 Synthesis of compounds DMIP-1-NA and DMIP-2-NA.
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Table 1 The optical, photophysical and thermal properties of DMIP-1-NA and DMIP-2-NA
lmax a/nm
PLmax a/nm
PLmax film b/nm
Solution c Ff
Eg/eV
Tg, Tm, Td/ꢂC
HOMO/LUMO/eV
DMIP-1-NA
DMIP-2-NA
228, 263, 376, 397
229, 261, 376, 397
421, 433
425
422, 436
429, 434
0.68
0.63
3.05
3.04
138, 298, 441
132, 262, 400
5.58/2.53
5.55/2.51
a
The absorption and PL spectra in CH2Cl2. b The solid state emission spectra of DMIP-1-NA and DMIP-2-NA thin films were made by spin coating
c
with poly(methyl methacrylate) (PMMA). PL quantum yield relative to 9,10-diphenylanthracene (DPA) in cyclohexane (Ff ¼ 0.90).
devices and chemical structures of some relevant compounds are
shown in Scheme 2, where indium tin oxide (ITO) was used as the
anode, CFx was the hole-injection layer, 4,40-bis[N-(1-naphthyl)-
N-phenyl-l-amino]biphenyl (NPB) was used as the hole trans-
porting layer, Alq3 or MADN doped CsF was used as the
electron transporting layer, and LiF was used as the electron
injecting layer. Type I and II devices are the conventional blue
OLED structures with different host emitters (type I: DMIP-1-
NA, type II: DMIP-2-NA) doped with BD-1. Type III device
replaced the electron-transporting and injecting layer of Type II
with n-doped (MADN: 20% CsF) material.
Detailed EL performance of the type I and II devices with
various BD-1 doping concentrations are summarized in Table 2.
The optimal BD-1 concentration of the two types of devices are
about 7%. The two unsymmetrical blue hosts exhibit deep-blue
emission without the dopant (CIEx,y (0.155, 0.104) for DMIP-1-
Fig. 2 Conformational structures of DMIP-1-NA and DMIP-2-NA
NA and CIEx,y (0.151, 0.097) for DMIP-2-NA), but the lumi-
(DFT calculations with B3LYP/6-31G).
nance yield is relatively low. Upon adding the BD-1 dopant, the
device efficiency improved dramatically with a wide range of
doping levels from 3% to 7%. The bulky indene group attached to
anthracene core effectively suppresses intermolecular inter-
actions and alleviates self-quenching of the dopant at high
doping levels. Both type I and II devices show a main EL peak at
460 nm and a shoulder peak (484 nm for DMIP-1-NA and
488 nm for DMIP-2-NA) with a full width at half maximum
(FWHM) of about 60 nm (see Fig. 5).
The difference in the shoulder peaks results in a better blue
color purity of type I than type II devices. We assume that it
Fig. 3 The absorption and PL spectra of DMIP-1-NA and DMIP-2-NA.
attributed to the peripheral indene and naphthyl groups. Upon
irradiation at 380 nm, the PL spectra of DMIP-1-NA and DMIP-
2-NA in solution were found to exhibit excellent blue emission
with the peak maxima at lmax ¼ 421, 433 nm for DMIP-1-NA
and lmax ¼ 425 nm for DMIP-2-NA. Their PL spectra in thin
films are similar to the spectra in solution, which implies that the
intermolecular interactions are almost negligible.
Electroluminescent properties
To investigate the EL performance of the two blue host mate-
rials, three different types of blue-emitting devices have been
fabricated. The detailed device architectures of the three type
Scheme 2 Chemical structures of some relevant compounds and the
device architectures.
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Table 2 EL performances of blue-emitting devices at the current density of 20 mA cmꢀ2
Device
Dopant (x %)
Voltage/V
Yield/cd Aꢀ1
Efficiency/lm Wꢀ1
EQE (%)
CIEx,y coordinaes
I
I
I
I
II
II
II
II
III
0
3
5
7
0
3
5
7
7
5.80
5.73
5.58
5.47
5.77
5.63
5.58
5.40
4.59
0.88
4.26
5.13
5.20
1.17
5.15
5.40
5.87
6.27
0.48
2.33
2.88
2.98
0.64
2.87
3.04
3.41
4.29
1.0
3.1
3.7
3.7
1.4
3.5
3.7
4.0
4.6
(0.155, 0.104)
(0.146, 0.178)
(0.145, 0.180)
(0.145, 0.185)
(0.151, 0.097)
(0.145, 0.196)
(0.145, 0.195)
(0.144, 0.197)
(0.144, 0.176)
could come from the conformational change of the dopant
material in the excited state of the two hosts. There is no residual
peak of host emitters from the EL spectra in Fig. 4, which
Alq3 as the electron-transporting layer. The energy level of
MADN (HOMO: 5.5 eV; LUMO: 2.5 eV) is similar to those of
the hosts, and this may eliminate the accumulated charge carriers
and then reduce the undesirable polarization effect. As shown in
Fig. 5, the intensity of the shoulder peak at 488 nm in type III
device is lower compared to the type II. Also the n-doped elec-
tron transporting layer is capable of lowering the driving voltage
and enhancing the efficiency of the device (see Fig. 6). The
maximum current and power efficiencies of type III device are
7.6 cd Aꢀ1 (EQE of 5.6%) and 8.39 lm/W, respectively, with pure
blue CIEx,y coordinates of (0.14, 0.18). Although there is a roll-
off in EL efficiency at high current density, the power efficiency
of device III is still among the best of the reported doped blue-
emitting devices.
€
indicates that complete Forster energy transfer from the host to
the dopant molecule (BD-1) takes place.
It is worthwhile that both type I and II doped devices show
a near flat EL efficiency versus current density response. For
example, the efficiency of 7% doped type II device is maintained
at 5.5 cd Aꢀ1 even at 200 mA cmꢀ2. In addition, there is almost no
EL color shift with varying drive currents as the CIEx,y color
coordinates only shifted from (0.145, 0.201) at 1 mA cmꢀ2 to
(0.144, 0.195) at 300 mA cmꢀ2 with DCIEx,y ¼ (0.001, 0.006). The
other type I and II devices also showed similar behavior. It
suggests that the electron-hole pairs for recombination are well
confined in the blue emitter region. The stable EL efficiency and
color coordinates of the DMIPNA based devices with a broad
range of doping levels indicate its potential use for the
commercial application in full-color displays.
Fig. 7 shows the operational lifetime of the two optimized
doped blue devices at a constant current density of 20 mA cmꢀ2
after encapsulation in the nitrogen-purged dry-box. The t1/2 (the
time for the luminance to drop to 50% of the initial luminance)
and initial luminance (L0) of 7% doped type I and II devices were
We noticed that the color purity of both optimal doped devices
is not as pure blue as expected. This phenomenon might be
caused by the charge-induced polarization effect. The solvent-
induced bathochromic shift of BD-1 emission is a major cause for
the higher CIEy value.19 The large energy barriers between the
host and the electron/hole transporting layers might lead to the
accumulation of charge carriers, which would form considerable
dipolar region between the interface and also introduce addi-
tional polarization. Consequently, the emission of type I and II
BD-1 doped devices suffered from a bathochromic shift near this
region. In this case, we adopted MADN doped CsF to replace
734 h at L0 ¼ 1173 cd mꢀ2, and 1205 h at L0 ¼ 1039 cd mꢀ2
,
respectively. The driving voltage of the two devices at half-decay
lifetime increased only 1.1 V for type I and 0.9 V for type II
device. Assuming the scalable law of Coulombic degradation
driving at a L0 value of 100 cd mꢀ2 23
, the half-lives (t1/2) of type I
and II devices without consideration of any accelerating factor
Fig. 5 EL efficiency vs. current density characteristics of 7% doped type
I,II and III devices. Inset: EL spectra of three types devices with optimal
Fig. 4 EL spectra of different BD-1 doping concentrations in type I and
type II devices.
concentration at 20 mA cmꢀ2
.
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Experimental
Characterization
1H and 13C NMR spectra were recorded on a Bruker-AF301 AT
400 MHz spectrometer. Mass spectrometric measurements were
recorded by a Finnigan-SSQ 710 fast atom bombardment (FAB)
mass spectrometry. High resolution mass spectrometric
measurements were carried out using a Bruker autoflex MALDI-
TOF mass spectrometer. UV-vis spectra were obtained on
a Varian Cary 200 spectrophotometer. Fluorescence spectra were
obtained on a Perkin Elmer LS55 luminescence spectrometer.
The differential scanning calorimetry (DSC) analysis was per-
formed under a nitrogen atmosphere on a TA Instruments DSC
2920. Thermogravimetric analysis was undertaken using a TGA
instrument. To measure the fluorescence quantum yields (FF),
degassed solutions of the compounds in CH2Cl2 were prepared.
The concentration was adjusted so that the absorbance of the
solution would be lower than 0.1. The excitation was performed
at 380 nm, and 9,10-diphenylanthracene (DPA) in the solution of
cyclohexane, which has Ff ¼ 0.9, was used as a standard. Cyclic
voltammetric (CV) measurements were carried out in a conven-
tional three electrode cell using a Pt button working electrode of
2 mm in diameter, a platinum wire counter electrode, and a SCE
reference electrode on a computer-controlled EG&G Potentio-
stat/Galvanostat model 283 at room temperature. Reduction CV
of all compounds was performed in dichloromethane containing
Bu4NPF6 (0.1 M) as the supporting electrolyte.
Fig. 6 Current density-voltage-luminance characteristics of type I, II
and III devices.
Device fabrication
Prior to the deposition of organic materials, indium-tin-oxide
(ITO)/glass was cleaned with a routine cleaning procedure and
pretreated with oxygen plasma. Devices were fabricated under
about 10ꢀ6 Torr base vacuum in a thin-film evaporation coater
following a published protocol.23 The current–voltage–lumi-
nance characteristics were measured with a diode array rapid
scan system using a Photo Research PR650 spectrophotometer
and a computer-controlled, programmable, direct-current (DC)
source.
Fig. 7 Device operational stability of devices I and II.
are projected to be 12500 h and 8600 h, respectively. The longer
lifetime of type I devices may be attributed to the better thermal
stability of DMIP-1-NA.
Single-crystal X-ray analysis
Conclusions
Diffraction data were collected at 293 K using graphite mono-
ꢀ
In summary, we have synthesized two unsymmetrical indene-
substituted 10-naphthylanthracene derivatives as robust blue
hosts by a high-yield convenient synthetic route. The efficient
chromated Mo-Ka radiation (l ¼ 0.71073 A) on a Bruker Axs
SMART 1000 CCD diffractometer. The collected frames were
24
processed with the software SAINT+
and an absorption
correction (SADABS) 25 was applied to the collected reflections.
26
The structure was solved by the Direct methods (SHELXTL)
€
Forster energy transfer from those wide band-gap hosts to the
blue dopant BD-1 ensures excellent device performance under
various doping concentrations. The EL efficiencies with optimal
BD-1 doped devices are 5.20 cd Aꢀ1 (2.98 lm/W at 5.5 V) for
DMIP-1-NA and 5.87 cd Aꢀ1 (3.41 lm/W at 5.4 V) for DMIP-2-
NA at 20 mA cmꢀ2. Also the high thermal and morphological
stabilities of the two hosts offer long operational lifetime of the
devices. The efficiency and color purity of DMIP-2-NA based
devices were further optimized by the use of n-doped MADN
electron transporting layer, which exhibited maximum power
efficiency of 8.39 lm/W (7.6 cd Aꢀ1 at 2.9 V) with blue CIEx,y
coordinates of (0.14, 0.18).
in conjunction with standard difference Fourier techniques and
subsequently refined by full-matrix least-squares analyses on F2.
Crystallographic data for DMIP-1-NA: C41H30, Mr ¼ 522.65,
crystal dimension 0.32 ꢃ 0.28 ꢃ 0.23, monoclinic, space group
ꢀ
ꢀ
ꢀ
C2/c, Z ¼ 8, a ¼ 40.541(6) A, b ¼ 7.356(1) A, c ¼ 23.412(3) A,
ꢂ
ꢂ
ꢂ
3
ꢀ
a ¼ 90 , b ¼ 123.363(2) , g ¼ 90 , U ¼ 5831(2) A , T ¼ 293 K, rc
¼ 1.191 g cmꢀ3, m(Mo-Ka) ¼ 0.067 mmꢀ1, F(000) ¼ 2208. A total
of 13567 reflections were measured in the range 2.41 # q # 25.00
(hkl indices: ꢀ48 # h # 47, ꢀ8 # k # 8, ꢀ27 # l # 25),
5055 unique reflections. The structure was refined on F2 to
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R1 ¼ 0.0526, wR2 ¼ 0.1312 (2789 reflections with I > 2s(I), GOF
¼ 1.025 on F2 for 371 refined parameters).
tetrakis(triphenylphosphine)palladium(0) (80 mg, 0.06 mmol),
compound 2 (1.1 g, 3.7 mmol), tetrahydrofuran (50 mL), and
ꢂ
2.0 M K2CO3 (20 mL) were heated at 80 C with magnetic stir-
ring under nitrogen atmosphere. After 12 h, the mixture was
cooled to room temperature and the organic layer was dried with
anhydrous Na2SO4 and filtered. Then the solvent was evaporated
under reduced pressure, and the residue was purified through
a silica gel column (20% CH2Cl2–hexane) to give the product
DMIP-1-NA. Yield 75%. 1H NMR: (400 MHz, CDCl3, d): 8.01–
8.08 (m, 2H, J ¼ 8.2 Hz), 7.84–7.90 (m, 4H, J ¼ 8.12 Hz), 7.58–
7.76 (m, 5H, J ¼ 8.2 Hz), 7.45–7.49 (m, 4H, J ¼ 7.34 Hz),
7.30–7.36 (m, 4H, J ¼ 7.3 Hz), 7.20–7.26 (m, 4H, J ¼ 7.45 Hz),
6.63 (s, 1H), 1.48 (s, 6H). 13C NMR (400 MHz, CDCl3, d): 24.80,
48.50, 120.80, 121.63, 125.12, 125.20, 125.48, 125.61, 126.01,
126.27, 126.45, 126.66, 127.08, 127.65, 128.10, 128.22, 129.20,
129.96, 130.64, 131.58, 133.58, 133.68, 135.07, 136.77, 137.24,
138.29, 140.61, 141.70, 144.39, 154.55. MALDI-TOF-MS m/z
calculated for C41H30: 522.2342, Found [M+]: 522.2357.
Synthesis
3,3-Dimethyl-1-indanone (1). A solution of 3-methylcrotonic
acid (9.5 g, 0.095 mol) in benzene (50 mL) was added to
aluminium chloride (38 g, 0.285 mol, 3 equiv) and the mixture
was heated for 5 h under reflux and then poured into iced
hydrochloric acid. The oil was washed with sodium carbonate
solution and the organic layer was collected. After removing the
solvent, the residue was purified by distillation under reduced
pressure to give 11 g (0.076 mol) of compound 1. Yield 80%. 1H
NMR: (400 MHz, CDCl3, d): 7.73–7.71 (d, 1H, J ¼ 7.4 Hz), 7.66–
7.62 (t, 1H, J ¼ 7.8 Hz), 7.53–7.51 (d, 1H, J ¼ 7.8 Hz), 7.41–
7.37(t, 1H, J ¼ 7.8 Hz), 2.64 (s, 2H), 1.45 (s, 6H). FAB+-MS: 160.
1,1-Dimethyl-3-(4-bromo-phenyl)-indene (2).
A
Grignard
reagent prepared from 4.4 g (18.5 mmol) of p-dibromobenzene in
20 mL of dry THF was added to a solution of 2.26 g (15.4 mmol)
of 3,3-dimethyl-1-indanone in 200 mL of THF solvent. The
9-(4-(1,10-Dimethylinden-3-yl)phenyl)-10-(2-naphthyl)-anthra-
1
cene (DMIP-2-NA). H NMR: (400 MHz, CDCl3, d): 8.08–8.10
ꢂ
reaction was heated at 50 C for 2 h. The reaction mixture was
(m, 3H, J ¼ 8.37 Hz), 7.92–7.95 (m, 1H, J ¼ 8.6 Hz), 7.82–7.89
(m, 4H, J ¼ 8.36 Hz), 7.73–7.75 (d, 3H, J ¼ 7.85 Hz), 7.64ꢀ7.58
(m, 5H, J ¼ 8.89 Hz), 7.46–7.48 (d, 1H, J ¼ 7.35 Hz), 7.26–7.40
(m, 6H), 6.63 (s, 1H), 1.48 (s, 6H). 13C NMR (400 MHz, CDCl3,
d): 24.80, 48.50, 120.80, 121.63, 125.09, 125.14, 125.49, 126.22,
126.43, 126.45, 127.06, 127.67, 127.91, 127.97, 128.10, 129.57,
129.96, 130.07, 130.25, 131.55, 132.77, 133.42, 135.08, 136.60,
136.96, 137.05, 138.32, 140.64, 141.72, 144.36, 154.56. MALDI-
TOF-MS m/z calculated for C41H30: 522.2342, Found [M+]:
522.2357.
hydrolyzed with dilute hydrochloric acid. The upper organic
layer was separated and washed with water, dried over Na2SO4
and the solvent was evaporated under reduced pressure. The
compound was purified through a silica gel column (5% EtOAc–
hexane) to give 3 g of 1,1-dimethyl-3-(4-bromo-phenyl)-indene.
Yield 65%. 1H NMR: (400 MHz, CDCl3, d): 7.57–7.55 (m, 2H, J
¼ 8.2 Hz), 7.47–7.38 (m, 4H, J ¼ 8.5 Hz), 7.28–7.27 (m, 2H, J ¼
7.4 Hz), 6.42 (s, 1H), 1.40 (s, 6H). FAB+-MS: 298.
9-(1-Naphthyl)anthracene-10-boronic acid (3a). To a slurry
containing dry 9-(1-naphthyl)-10-(bromo)anthracene (6.5 g,
17 mmol) in 80 mL of dry THF under nitrogen atmosphere in
a 250 mL three-necked round flask cooled in a dry ice-acetone
bath was added dropwise 11 mL of 1.6 M n-butylithium solution
in hexane with stirring within a period of 30 min. Stirring was
continued for another 2 h. Tri(isopropyl)borate (22 mmol,
1.3 equiv) was added in 20 min, then the mixture was equilibrated
to room temperature and stirred for an additional 12 h. The
mixture was then cooled in a dry ice bath and quenched with
20 mL of 2 M HCl. The organic layer was extracted with diethyl
ether (2 ꢃ 25 mL) and dried with anhydrous Na2SO4. The solvent
was concentrated under reduced pressure and the residue was
recrystallized from diethyl ether–hexane mixture to give 1a. Yield
75%. 1H NMR (400 MHz, CDCl3, d): 8.96 (s, 2H), 8.17 (d, 1H, J
¼ 4.4 Hz), 7.09–8.16 (m, 3H), 7.75–7.77 (m, 1H), 7.47–7.50 (m,
4H), 7.22–7.31 (m, 5H), 6.84–6.86 (m, 1H). MALDI-TOF-MS
m/z calculated for C24H17BO2: 348.1320, Found [M+]:348.1308.
Acknowledgements
This work is financially supported by NSFC/China, National
Basic Research 973 Program (2006CB806200). W.Y.W. would
like to thank the Hong Kong Research Grants Council (HKBU
202106) and the Hong Kong Baptist University (FRG2/08-09/
111) for financial support.
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