A solution-processable bipolar molecular glass as a host material for white electrophosphorescent devices

Article abstract of DOI:10.1039/b804192j

A solution-processable bipolar material tBu-OXDTFA comprising an electron-rich triphenylamine core and electron-deficient oxadiazole/fluorene peripheries was synthesized. This dendrimer-like molecule not only possesses a high triplet energy (2.74 eV) but also exhibits excellent film-forming properties upon solution processing. We achieved highly efficient white electrophosphorescent OLEDs (22.3 cd A^-1, 11.6%) through solution processing, wherein the single white emitting layer was readily formed after spin-coating a solution of blue- and red-phosphor co-dopants containing tBu-OXDTFA as the host matrix.

Full text of DOI:10.1039/b804192j

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/materials | Journal of Materials Chemistry
A solution-processable bipolar molecular glass as a host material for
white electrophosphorescent devices
a
a
a
a
Chen-Han Chien, Liang-Rern Kung, Chen-Hao Wu, Ching-Fong Shu, Sheng-Yuan Changb and
*
b
*
Yun Chi
Received 11th March 2008, Accepted 16th May 2008
First published as an Advance Article on the web 16th June 2008
DOI: 10.1039/b804192j
A solution-processable bipolar material tBu-OXDTFA comprising an electron-rich triphenylamine
core and electron-deficient oxadiazole/fluorene peripheries was synthesized. This dendrimer-like
molecule not only possesses a high triplet energy (2.74 eV) but also exhibits excellent film-forming
properties upon solution processing. We achieved highly efficient white electrophosphorescent OLEDs
(22.3 cd Aꢀ1, 11.6%) through solution processing, wherein the single white emitting layer was readily
formed after spin-coating a solution of blue- and red-phosphor co-dopants containing tBu-OXDTFA
as the host matrix.
Introduction
Organic light-emitting diodes (OLEDs) have attracted consid-
erable interest because of their potential applications in flat-panel
displays and in solid state lighting.1 Phosphorescent emitters are
considered to be superior to their fluorescent counterparts at
improving the efficiency of electroluminescent (EL) devices;
because they can harvest both singlet and triplet excitons, their
internal quantum efficiencies can reach theoretical levels as high
as 100%.2 In phosphorescent OLEDs, the triplet emitters are
normally used as emitting guests in a host material to reduce the
self-quenching associated with the relatively long excited state
lifetimes of triplet emitters and triplet–triplet annihilation;3
consequently, the choice of host materials is of vital importance
for the preparation of efficient phosphorescent OLEDs.
Presently, most electroluminescent devices are fabricated using
vacuum deposition, which is a complicated and expensive
manufacturing process. In contrast, solution processing
methods, such as spin-coating and ink-jet printing, are relatively
inexpensive and can be utilized for the preparation of large-area
displays.4 Most studies have employed solution-processable
polymeric host materials, such as poly(9-vinylcarbazole) and
polyfluorenes, blended with phosphorescent emitters as the
emitting layer (EML).5 Nevertheless, several issues—such as
aggregation or phase separation of the phosphor in the macro-
molecular matrix and the intrinsic difficulty in purifying the
polymeric materials—can hamper the applicability of polymeric
hosts.6
In this paper, we report the design and synthesis of a solution-
processable, bipolar molecular glass, namely tBu-OXDTFA, for
use as a host material in electrophosphorescent devices. As
shown in Scheme 1, tBu-OXDTFA comprises a triphenylamine
(TPA) core and fluorene/oxadiazole (OXD) peripheries. These
individual building blocks each exhibit a high triplet energy
Scheme 1 Synthesis route to tBu-OXDTFA and chemical structures of
Flrpic and Os(fppz).
aDepartment of Applied Chemistry, National Chiao Tung University,
Hsin-Chu, Taiwan 30050
bDepartment of Chemistry, National Tsing Hua University, 300 Hsinchu,
Taiwan
(ET > 2.9 eV)7 and are connected through the sp3-hybridized C-9
atoms to effectively interrupt any extended p-conjugation. This
structural feature endows tBu-OXDTFA with an adequately high
This journal is ª The Royal Society of Chemistry 2008
J. Mater. Chem., 2008, 18, 3461–3466 | 3461

View Article Online
value of ET for efficient confinement of the triplet excitons
primarily on the guest, blue-emitting phosphors. In addition, the
built-in bipolar functionalities, arising from the electron-rich
TPA core and electron-deficient OXD pendent units, may facil-
itate and balance the hole and electron injection and transport,
respectively.8 Moreover, the three-dimensional, rigid, and
asymmetric structure of tBu-OXDTFA hinders its close packing
and suppresses its crystallizability, leading to an amorphous
material exhibiting pronounced thermal stability. We prepared
highly efficient white electrophosphorescent OLEDs (22.3 cd
Aꢀ1, 11.6%) through solution processing; the single white EML
was formed simply through spin-coating of a solution of
blue- and red-phosphor co-dopants containing tBu-OXDTFA as
the host matrix.
Fig. 2 AFM topographic images (tapping mode) of (a) neat tBu-
OXDTFA and (b) tBu-OXDTFA doped with 14 wt% FIrpic and 0.1 wt%
Os(fppz). The films were prepared through spin-coating from chloro-
benzene solutions onto silicon wafers.
Results and discussion
weight losses occurred at 408 and 426 ꢁC, respectively. DSC
revealed that tBu-OXDTFA exhibited an extremely high glass
transition temperature of 207 ꢁC with no detectable values of Tc
and Tm at temperatures up to 370 ꢁC. This observation indicates
the prominent stability of the amorphous glass state of tBu-
OXDTFA, which we attribute to the presence of its rigid fluorene
and OXD peripheries and its high molecular weight. In addition,
the presence of the propeller-like TPA core hinders close packing
of tBu-OXDTFA, suppressing its crystallizability.12 To investi-
gate its morphology, we prepared thin films of tBu-OXDTFA
through spin-coating from a chlorobenzene solution onto silicon
wafers and imaged them using atomic force microscopy (AFM;
Fig. 2). The surface topographies clearly revealed that the spin-
coated films exhibited fairly smooth and pinhole-free surface
morphologies, with a root-mean-square (RMS) surface rough-
ness of 0.306 nm. For a spin-coated, white-emitting tBu-
OXDTFA film doubly doped with 14 wt% FIrpic and 0.1 wt%
Os(fppz),13 we calculated the RMS surface roughness to be 0.359
nm; there was no phase separation or any aggregated domains.
These results demonstrate that tBu-OXDTFA is capable of
forming amorphous films through solution processing, with
organometallic triplet emitters dispersed homogeneously.
Synthesis
Scheme 1 illustrates the synthesis route followed for the prepa-
ration of tBu-OXDTFA. The Grignard reaction of fluorenone
with m-tolylmagnesium bromide gave the corresponding alcohol,
9-(m-tolyl)fluoren-9-ol (1), the tolyl group of which was then
oxidized using KMnO4 in H2O/pyridine to provide the carbox-
ylic acid 2. Subsequent Friedel–Crafts-type substitution of
triphenylamine with 2 yielded compound 3. This reaction pro-
ceeded through the initial formation of a transitory carbocation
from the protonated 9-fluorenol group,9 which in turn underwent
electrophilic substitution exclusively at the electron-rich para
carbon atom of the TPA phenyl group. The formation of the
OXD moiety commenced from the acid 3 in a two-step protocol:
the acylhydrazide and 3 were coupled under amide bond-forming
conditions, followed by cyclodehydration mediated by CBr4 and
Ph3P.10 Finally, the oxadiazole 5 was subjected to another Frie-
del–Crafts reaction with 9-(4-tert-butylphenyl)-9-fluorenol (6)11
to afford the desired host material tBu-OXDTFA. The structure
of tBu-OXDTFA was characterized using 1H and 13C NMR
spectroscopy, elemental analysis, and high-resolution mass
spectrometry.
Electrochemistry
Thermal properties
We employed cyclic voltammetry (CV) to investigate the elec-
trochemical behavior of tBu-OXDTFA, using ferrocene as the
internal standard. During the anodic scan in CH2Cl2, a reversible
We used thermogravimetric analysis (TGA) and differential
scanning calorimetry (DSC) to investigate the thermal properties
of tBu-OXDTFA (Fig. 1). TGA indicated that its 5 and 10%
oxidative process occurred at 0.42 V (Eo ), originating from the
0
oxidation of the electron-rich TPA core. Upon the cathodic
sweep in THF, we detected a reversible reductive process at
ꢀ2.60 V (Eo ), attributable to reduction of the peripheral elec-
0
tron-deficient OXD units (Fig. 3). This reversible reductive and
oxidative behavior indicates that tBu-OXDTFA can be utilized
as both a hole and an electron transporter. Moreover, such
pronounced electrochemical stability, which improves the life-
time of electroluminescent devices, makes tBu-OXDTFA
a desirable host material for use in light-emitting applications.
Photophysical properties
Fig. 1 TGA trace of tBu-OXDTFA recorded at a heating rate of 10 ꢁ
minꢀ1. Inset: DSC measurement recorded at a heating rate of 10 ꢁC minꢀ1
C
Fig. 4a displays the absorption and PL spectra of tBu-OXDTFA
.
in various organic solvents. In CH2Cl2, the absorption spectrum
3462 | J. Mater. Chem., 2008, 18, 3461–3466
This journal is ª The Royal Society of Chemistry 2008

View Article Online
than that reported for the common triplet blue-emitter FIrpic
(2.65 eV).15 Accordingly, this value of ET is sufficiently high to
effectively confine the triplet excitons on the guest and prevent
back energy transfer to the host molecules; thus, we expected that
tBu-OXDTFA would serve as an appropriate host for short-
wavelength dopants, such as FIrpic, as well as long-wavelength
dopants.16
Electroluminescence properties of OLEDs
To assess the utility of this solution-processable compound as
a host material in OLEDs, we fabricated a white light-emitting
device having the configuration ITO/PEDOT (35 nm)/EML (60–
80 nm)/1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI,
Fig. 3 Cyclic voltammogram of tBu-OXDTFA recorded at a scanning
rate of 50 mV sꢀ1
˚
30 nm)/LiF (15 A)/Al (100 nm). The EML—a tBu-OXDTFA film
.
doped with blue-emitting FIrpic (14 wt%) and red-emitting
Os(fppz) (0.1 wt%)—was prepared readily through spin-coating
from a chlorobenzene solution consisting of the co-dopants and
the host material. The TPBI layer was employed as an electron-
transporting and hole-blocking layer. As illustrated in Fig. 5, the
EL spectrum exhibits dual emissions—with equalized blue and
red emission intensities—covering the whole visible region. The
Commission Interationale d’Eclairage (CIE) chromaticity coor-
dinates of the EL emission at a bias of 11 V were (0.37, 0.39), i.e.,
in the white light region and close to the equienergy white point.
When we increased the driving voltage to 17 V, the CIE coor-
dinates of the emission color remained almost constant and the
EL spectrum barely changed. Fig. 6a presents the current
density–voltage–luminance (I–V–L) curves of the tBu-OXDTFA-
based device, which was turned on at 5.9 V (corresponding to 1
cd mꢀ2) and had a maximum brightness of 20 280 cd mꢀ2. As
revealed in Fig. 6b, the maximum external quantum efficiency
(max. hext) of this white-emitting device was 11.6% (953 cd mꢀ2
,
Fig. 4 (a) UV-Vis absorption and (b) PL spectra of tBu-OXDTFA in
various organic solvents. (c) Normalized phosphorescence spectrum
(77 K) of tBu-OXDTFA in 2-MeTHF.
4.27 mA cmꢀ2), and the corresponding luminance and power
efficiencies were 22.3 cd Aꢀ1 and 5.0 lm Wꢀ1. Even at brightnesses
beyond 10 000 cd mꢀ2, 80% of the peak efficiency (9.2%) was
sustained, along with a luminescence efficiency of 17.6 cd Aꢀ1
.
We attribute this high performance to the presence of both
electron-rich TPA and electron-deficient OXD units in tBu-
OXDTFA, which may improve and balance charge injection and
transport, leading to efficient charge recombination. Moreover,
the short triplet excited lifetime of Os(fppz) (ca. 0.7 ms)13 assists in
this high performance because it prevents undesired T–T and P–
T annihilation from occurring under high current densities.3
of tBu-OXDTFA is almost a superimposed image of the
absorptions of the fluorene-substituted TPA group and the OXD
unit, suggesting that negligible interactions occur between the
TPA and OXD moieties in the ground state. Furthermore, in all
the solvents studied, the features in the absorption spectra were
nearly identical and independent of the solvent polarity, indi-
cating that the Franck–Condon excited state of tBu-OXDTFA
was subject to a rather small dipolar change with respect to the
ground state. In contrast, the PL spectra exhibit a strong
dependence on the solvent polarity, with the emission band red-
shifting significantly upon increasing the solvent polarity
(Fig. 4b). We attribute this phenomenon to a mechanism
involving a fast photoinduced electron transfer between the
designed donor (TPA)–acceptor (OXD) pairs, leading to a large
change in the dipole moment in the excited state; a subsequent
solvent relaxation process results in the solvent polarity-depen-
dent emission.14 To evaluate the potential of utilizing tBu-
OXDTFA as a host material in phosphorescent OLEDs, we
measured its phosphorescence spectrum in a frozen 2-methylte-
trahydrofuran (2-MeTHF) matrix at 77 K (Fig. 4c). We used the
highest-energy 0–0 phosphorescent emission, located at 2.74 eV,
to calculate the ET gap of tBu-OXDTFA, giving a value higher
Fig. 5 EL spectra of a tBu-OXDTFA-based device co-doped with 14
wt% FIrpic and 0.1 wt% red-emitting Os(fppz), recorded at various
driving voltages.
This journal is ª The Royal Society of Chemistry 2008
J. Mater. Chem., 2008, 18, 3461–3466 | 3463

View Article Online
a DuPont TGA 2950 instrument. The thermal stabilities of the
samples under a nitrogen atmosphere were determined by
measuring their weight losses while heating at a rate of 10 ꢁC
minꢀ1. UV-Vis spectra were measured using an HP 8453 diode-
array spectrophotometer. PL spectra were obtained using
a Hitachi F-4500 luminescence spectrometer. The low-tempera-
ture phosphorescence spectrum was obtained using a composite
spectrometer containing a monochromator (Jobin Yvon, Triax
190) coupled to a liquid nitrogen-cooled charge-coupled device
(CCD) detector (Jobin Yvon, CCD-1024 ꢂ 256-open-1LS).
Cyclic voltammetry (CV) measurements were performed using
a BAS 100 B/W electrochemical analyzer; 0.1 M tetrabuty-
lammonium hexafluorophosphate (TBAPF6) was the supporting
electrolyte. The potentials were measured against an Ag/Ag+
(0.01 M AgNO3) reference electrode with ferrocene as the
internal standard. Atomic force microscopy measurements were
performed in the tapping mode under ambient conditions using
a Digital Nanoscope IIIa instrument.
Device fabrication
PEDOT was spin-coated directly onto indium tin oxide (ITO)
glass and dried at 80 ꢁC for 12h under vacuum to improve both the
hole injection capability and the smoothness of the substrate. The
light-emitting layer was spin-coated on top of the PEDOT layer
using chlorobenzene as the solvent; the sample was then dried for
3 h at 60 ꢁC in vacuo. Prior to film casting, the solution was filtered
through a Teflon filter (0.45 mm). The TPBI layer, which was used
as an electron-transporting layer that would also block holes and
confine excitons, was grown through thermal sublimation in
a vacuum of 3 ꢂ 10ꢀ6 Torr. The cathode was completed through
Fig.
6 (a) Current density–voltage–luminance and (b) luminance
efficiency–current density–external quantum efficiency plots of the tBu-
OXDTFA-based device.
Conclusions
In conclusion, we have synthesized and characterized a bipolar
host material, tBu-OXDTFA, containing both hole- and elec-
tron-transporting functionalities. This dendrimer-like structure
exhibits not only a high triplet energy but also good film-forming
properties for solution processing. We achieved highly efficient
white electrophosphorescent OLEDs (22.3 cd Aꢀ1, 11.6%)
through solution processing, wherein the single white EML was
readily formed after spin-coating a solution containing tBu-
OXDTFA and two co-dopants [blue-emitting FIrpic and red-
emitting Os(fppz)]. In this paper we demonstrate that utilizing
a dendritic small molecule, tBu-OXDTFA, as a host co-doped
with organometallic phosphors allows the ready fabrication of
white electrophosphorescent OLEDs possessing simple device
structures, yet exhibiting high efficiency and luminance.
˚
thermal deposition of LiF (15 A)/Al (100 nm). The current–
voltage–luminance relationships were measured under ambient
conditions using a Keithley 2400 source meter and a Newport
1835C optical meter equipped with an 818 ST silicon photodiode.
9-(m-Tolyl)fluoren-9-ol (1)
3-Bromotoluene (5.0 mL, 41.2 mmol) was added dropwise over
2 min to a stirred mixture of Mg (1.34 g, 54.9 mmol) and dry
ether (60 mL) at ambient temperature under nitrogen. The
resulting mixture was gently heated for 3 h and then 9-fluorenone
(4.95 g, 27.5 mmol) in dry THF (10 mL) was added dropwise
over 5 min. The solution was then heated under reflux for 12 h.
After cooling, aqueous NH4Cl solution was added and the
mixture was extracted with EtOAc. The organic extracts were
washed with water and brine and then dried (MgSO4) The
solvent was removed under reduced pressure and the residue was
purified through column chromatography (hexane–EtOAc, 10 :
1) to obtain 1 (7.17 g, 96%). 1H NMR (300 MHz, CDCl3): d 2.27
(s, 3 H), 7.01–7.03 (m, 1 H), 7.13 (dd, J ¼ 3.9, 0.9 Hz, 2 H), 7.20–
Experimental
General directions
All chemicals were purchased from Aldrich, TCI, and Acros
Organics and used without further purification. Column chro-
matography was performed on silica gel (E. Merck Art. 7734
silica gel, 60 particle size, 70–230 mesh ASIM). NMR spectra
were recorded on Varian UNITY INOVA 500 MHz, Varian
Unity 300 MHz, and Bruker-DRX 300 MHz spectrometers.
Chemical shifts are denoted on the scale in ppm, with reference to
CDCl3 or CD3COCD3. Mass spectra were obtained using JEOL
JMS-HX 110 and SX-102A mass spectrometers. Differential
scanning calorimetry (DSC) was performed using a Seiko
EXSTAR 6000 DSC unit operated at heating and cooling rates
of 10 and 50 ꢁC minꢀ1, respectively. The glass transition
temperatures (Tg) were determined from the second heating scan.
Thermogravimetric analysis (TGA) was undertaken using
7.26 (m, 3 H), 7.30–7.37 (m, 4 H), 7.65 (d, J ¼ 7.5 Hz, 2 H). 13
C
NMR (75 MHz, CDCl3): d 21.4, 83.4, 119.9, 122.4, 124.6, 125.8,
127.8, 127.9, 128.2, 128.8, 137.6, 139.4, 143.0, 150.4. HRMS
(m/z): calcd for C20H16O 272.1201; found, 272.1202.
9-(3-Carboxyphenyl)fluoren-9-ol (2)
KMnO4 (61.7 g, 0.31 mol) was added in four portions at intervals
of 12 h to a solution of 1 (7.10 g, 26.1 mmol), pyridine (160 mL),
3464 | J. Mater. Chem., 2008, 18, 3461–3466
This journal is ª The Royal Society of Chemistry 2008

View Article Online
and water (16 mL) under reflux. After a total period of 48 h, the
mixture was filtered and the solids washed with copious hot
water. The filtrate was acidified with 12 N HCl and then
extracted with EtOAc–Et2O (1 : 1). The organic extracts were
washed with water and brine and then dried (MgSO4). The
solvent was evaporated under reduced pressure and the residue
was purified through column chromatography (hexane–Me2CO,
8 : 1) to afford 2 (7.88 g, 75%). 1H NMR (300 MHz,
CD3COCD3): d 7.26–7.41 (m, 8 H), 7.61–7.64 (m, 1 H), 7.81 (d, J
¼ 7.5 Hz, 2 H), 7.94 (d, J ¼ 7.5 Hz, 1 H), 8.19 (s, 1 H). 13C NMR
(75 MHz, CD3COCD3): d 84.3,121.5,126.1,128.1,129.6,129.7,
129.73,130.3,131.5,131.8,141.1,147.0,152.5,168.4. HRMS (m/z):
calcd for C20H14O3 302.0943; found, 302.0937.
(70.0 mg, 90 mmol) in CH2Cl2 (5 mL) at ambient temperature.
The mixture was heated under reflux for 6 h; after cooling,
evaporation of the solvent and column chromatography of the
residue (SiO2; hexane–Me2CO, 3 : 1) afforded 5 (42.4 mg, 62%).
1H NMR (300 MHz, CD3COCD3): d 1.36 (s, 9 H), 6.91–7.0 (m, 4
H), 7.04–7.09 (m, 6 H), 7.19–7.42 (m, 10 H), 7.46 (d, J ¼ 6.0 Hz, 2
H), 7.53 (d, J ¼ 6.0 Hz, 2 H), 7.79 (d, J ¼ 6.0 Hz, 2 H), 7.93–7.97
(m, 1 H), 7.99 (d, J ¼ 6.0 Hz, 2 H), 8.06 (s, 1 H). 13C NMR (75
MHz, CD3COCD3): d 30.1, 35.1, 65.2, 120.8, 121.7, 123.4, 123.5,
124.5, 124.6, 125.4, 126.3, 126.5, 126.9, 128.3, 128.4, 129.3, 129.7,
131.7, 139.5, 140.5, 147.0 148.0, 148.1, 151.0 155.6, 164.4, 164.7.
HRMS (m/z): calcd. for C49H39N3O 685.3093; found, 685.3101.
Anal. Calcd: C, 85.81; H, 5.73; N, 6.13. Found: C, 85.77; H, 5.77;
N, 6.12%.
9-(3-Carboxyphenyl)-9-(4-diphenylaminophenyl)fluorene (3)
Preparation of tBu-OXDTFA
CH3SO3H (40 mL, 660 mmol) was added dropwise under nitrogen
to a solution of 2 (200 mg, 660 mmol) and triphenylamine
(240 mg, 990 mmol) in 1,4-dioxane (3 mL) at 100 ꢁC and then the
mixture was heated at that temperature for 1 h. After this period,
the reaction mixture was cooled and diluted with CH2Cl2. The
CH2Cl2 solution was washed with saturated NaHCO3(aq) and
brine and then dried (MgSO4). Evaporation of the solvent fol-
lowed by silica gel chromatography (hexane–Me2CO, 3 : 1) gave
3 (250 mg, 70%). 1H NMR (300 MHz, CD3COCD3): d 6.92 (d, J
¼ 8.8 Hz, 2 H), 6.98–7.04 (m, 6 H), 7.13 (d, J ¼ 8.8 Hz, 2 H),
7.22–7.54 (m, 12 H), 7.90–7.94 (m, 4 H). 13C NMR (75 MHz,
CD3COCD3): d 65.2, 120.8, 124.6, 124.7, 125.9, 127.7, 129.4,
129.5, 129.6, 130.1, 130.3, 130.5, 130.9, 132.2, 134.2, 140.8, 141.7,
148.2, 148.4, 149.2, 152.4, 168.2. HRMS (m/z): calcd. for
C38H27NO2 529.2042; found, 529.2047.
CH3SO3H (30 mL, 520 mmol) was added dropwise under nitrogen
to a mixture of 5 (170 mg, 260 mmol) and 6 (180 mg, 570 mmol) in
CH2Cl2 (5 mL) at 50 ꢁC and then the resultant mixture was
heated at that temperature for 1 h. Upon cooling, the reaction
mixture was diluted with CH2Cl2 (20 mL), washed with saturated
NaHCO3 solution and water, and then dried (MgSO4). Evapo-
ration of the solvent followed by column chromatography of the
residue (SiO2; hexane–Me2CO, 3 : 1) gave tBu-OXDTFA (240
1
mg, 75%). H NMR (500 MHz, CD3COCD3): d 1.21 (s, 18 H),
1.34 (s, 9 H), 6.84–6.86 (m, 6 H), 7.03 (d, J ¼ 8.5 Hz, 4 H), 7.06 (d,
J ¼ 8.5 Hz, 6 H), 7.22–7.25 (m, 8 H), 7.28–7.35 (m, 6 H), 7.38–
7.41 (m, 6 H), 7.44–7.49 (m, 4 H), 7.60 (d, J ¼ 8.5 Hz, 2 H), 7.83
(d, J ¼ 8.0 Hz, 4 H), 7.89 (d, J ¼ 8.0 Hz, 2 H), 7.95–7.98 (m, 4 H).
13C NMR (75 MHz, CD3COCD3): d 30.8, 31.1, 34.3, 35.1, 64.2,
65.1, 120.5, 120.8, 121.6, 123.3, 124.0, 124.5, 125.4, 125.5, 126.1,
126.5, 126.8, 127.8, 127.9, 128.0, 128.2, 128.3, 129.1, 129.3, 129.7,
131.8, 139.3, 140.3, 140.4, 140.7, 143.3, 146.0, 146.5, 148.0, 149.4,
150.9, 151.6, 155.5, 164.4, 164.7. HRFAB MS (m/z): calcd. for
C95H79N3O 1277.6223; found, 1277.6239. Anal. Calcd: C, 89.24;
H, 6.23; N, 3.29. Found: C, 88.78; H, 6.23; N, 3.37%.
9-{3-[N0-(4-tert-Butylbenzoyl)]-N-benzoylhydrazide}-9-(4-
diphenylaminophenyl)fluorene (4)
N-Methylmorphine (0.57 mL, 5.15 mmol) and isobutyl-
chloroformate (0.68 mL, 5.15 mmol) were added sequentially
under nitrogen to a solution of 3 (2.48 g, 4.68 mmol) in THF
ꢁ
(30 mL) at ꢀ45 C; a white suspension formed during the addi-
tion of iBuOCOCl. The reaction mixture was stirred for 45 min at
ꢀ45 ꢁC before 4-tert-butylbenzhydrazide (0.90 g, 4.68 mmol) was
added. The resulting mixture was stirred at ambient temperature
for an additional 3 h before being filtered through silica gel and
washed with EtOAc. The solvent was evaporated under vacuum;
column chromatography of the residue (SiO2; hexane–Me2CO, 2
: 1) provided 4 (2.04 g, 62%). 1H NMR (300 MHz, CD3COCD3):
d 1.35 (s, 9 H), 6.93 (d, J ¼ 8.6 Hz, 2 H), 6.99–7.05 (m, 6 H), 7.13
(d, J ¼ 8.6 Hz, 2 H), 7.20–7.32 (m, 7 H), 7.36–7.43 (m, 3 H), 7.49–
7.54 (m, 4 H), 7.88ꢀ7.99 (m, 6 H), 9.90 (br, 2 H). 13C NMR (75
MHz, CD3COCD3): d 32.1, 36.1, 66.4, 121.9, 124.5, 124.54,
125.8, 126.8, 127.3, 127.7, 128.6, 128.9, 129.3, 129.4, 129.9, 130.4,
130.8, 131.3, 133.0, 134.4, 140.9, 141.5, 148.0, 148.3, 149.0, 152.3,
156.5, 167.5, 167.7. HRMS (m/z): calcd. for C49H41N3O2
703.3199; found, 703.3204.
Acknowledgements
This study was supported generously by the National Science
Council, Republic of China.
References
1 T. Fuhrmann and J. Salbeck, MRS Bull., 2003, 28, 354.
2 (a) C. Adachi, M. A. Baldo, M. E. Thompson and S. R. Forrest,
J. Appl. Phys., 2001, 90, 5048; (b) Y. Kawamura, K. Goushi,
J. Brooks, J. J. Brown, H. Sasabe and C. Adachi, Appl. Phys. Lett.,
2005, 86, 071104.
3 (a) M. A. Baldo, C. Adachi and S. R. Forrest, Phys. Rev. B, 2000, 62,
10967; (b) F.-C. Chen, Y. Yang, M. E. Thompson and J. Kido, Appl.
Phys. Lett., 2002, 80, 2308.
4 (a) M. T. Bernius, M. Inbasekaran, J. O’Brien and W. Wu, Adv.
´
Mater., 2000, 12, 1737; (b) A. Adronov and J. M. J. Frechet, Chem.
Commun., 2000, 1701; (c) L. Akcelrud, Prog. Polym. Sci., 2003, 28,
875; (d) J. Ding, J. Gao, Y. Cheng, Z. Xie, L. Wang, D. Ma,
X. Jing and F. Wang, Adv. Funct. Mater., 2006, 16, 575; (e)
P. L. Burn, S.-C. Lo and I. D. W. Samuel, Adv. Mater., 2007, 19, 1675.
5 (a) J. Kido, K. Hongawa, K. Okuyama and K. Nagai, Appl. Phys.
Lett., 1994, 64, 815; (b) S. Lamansky, P. I. Djurovich, F. Abdel-
Razzaq, S. Garon, D. L. Murphy and M. E. Thompson, J. Appl.
Phys., 2002, 92, 1570; (c) F.-I. Wu, H.-J. Su, C.-F. Shu, L. Luo,
9-(3-(5-(4-tert-Butylphenyl)-2-oxadiazoyl)phenyl)-9-(4-
diphenylaminophenyl)-fluorene (5)
CBr4 (66.0 mg, 190 mmol) and Ph3P (52.0 mg, 190 mmol) were
added under nitrogen in a single portion to a solution of 4
This journal is ª The Royal Society of Chemistry 2008
J. Mater. Chem., 2008, 18, 3461–3466 | 3465

View Article Online
W.-G. Diau, C.-H. Cheng, J.-P. Duan and G.-H. Lee, J. Mater.
Chem., 2005, 15, 1035.
10 H. A. Rajapakse, H. Zhu, M. B. Young and B. T. Mott, Tetrahedron
Lett., 2006, 47, 4827.
6 (a) T.-H. Kim, H. K. Lee, O. O. Park, B. D. Chin, S.-H. Lee and
J. K. Kim, Adv. Funct. Mater., 2006, 16, 611; (b) H. Kim, Y. Byun,
R. R. Das, B.-K. Choi and P.-S. Ahn, Appl. Phys. Lett., 2007, 91,
093512.
11 E. Weber, N. Doerpinghaus and I. Csoeregh, J. Chem. Soc., Perkin
Trans. 2, 1990, 2167.
´
12 J. C. Sancho-Garaıa, C. L. Foden, I. Grizzi, G. Greczynski, M. P. De
Jong, W. R. Salaneck, J. L. Bredas and J. Cornil, J. Phys. Chem. B,
´
`
7 (a) C. Rulliere and P. C. Roberge, Chem. Phys. Lett., 1983, 97, 247;
2004, 108, 5594.
(b) T. F. Palmer and S. S. Parmar, J. Photochem., 1985, 31, 273;
(c) K. Brunner, A. van Dijken, H. Bo¨rner, J. J. A. M. Bastiaansen,
N. M. M. Kiggen and B. M. W. Langeveld, J. Am. Chem. Soc.,
2004, 126, 6035.
8 (a) C.-F. Shu, R. Dodda, F.-I. Wu, M. S. Liu and A. K.-Y. Jen,
Macromolecules, 2003, 36, 6698; (b) F.-I. Wu, P.-I. Shih, C.-F. Shu,
Y.-L. Tung and Y. Chi, Macromolecules, 2005, 38, 9028.
9 (a) T. Ohta, K. Shudo and T. Okamoto, Tetrahedron Lett., 1983, 24,
71; (b) P.-I. Shih, C.-L. Chiang, A. K. Dixit, C.-K. Chen, M.-C. Yuan,
R.-Y. Lee, C.-T. Chen, E. W.-G. Diau and C.-F. Shu, Org. Lett.,
2006, 8, 2799.
13 Y.-L. Tung, P.-C. Wu, C.-S. Liu, Y. Chi, J.-K. Yu, Y.-H. Hu,
P.-T. Chou, S.-M. Peng, G.-H. Lee, Y. Tao, A. J. Carty, C.-F. Shu
and F.-I. Wu, Organometallics, 2004, 23, 3745.
14 (a) Y.-Y. Chien, K.-T. Wong, P.-T. Chou and Y.-M. Cheng, Chem.
Commun., 2002, 2874; (b) K.-T. Wong, S.-Y. Ku, Y.-M. Cheng,
X.-Y. Lin, Y.-Y. Hung, S.-C. Pu, P.-T. Chou, G.-H. Lee and
S.-M. Peng, J. Org. Chem., 2006, 71, 456.
15 R. J. Holmes, S. R. Forrest, Y.-J. Tung, R. C. Kwong, J. J. Brown,
S. Garon and M. E. Thompson, Appl. Phys. Lett., 2003, 82, 2422.
16 P.-I. Shih, C.-H. Chien, F.-I. Wu and C.-F. Shu, Adv. Funct. Mater.,
2007, 17, 3514.
3466 | J. Mater. Chem., 2008, 18, 3461–3466
This journal is ª The Royal Society of Chemistry 2008