Diphenylamino end-capped oligofluorenes with enhanced functional properties for blue light emission: Synthesis and structure-property relationships

Article abstract of DOI:10.1002/chem.200401152

A novel series of monodisperse asymmetrically and symmetrically substituted diphenylamino end-capped oligofluorenes, OF(2)-NPhR, R = H or An (An = 9-anthryl) and OF(n)-NPh, n = 2-4, has been synthesized by a convergent approach using palladium-catalyzed S

Full text of DOI:10.1002/chem.200401152

FULL PAPER
Diphenylamino End-Capped Oligofluorenes with Enhanced Functional
Properties for Blue Light Emission: Synthesis and Structure–Property
Relationships
Zhong Hui Li,[a] Man Shing Wong,*[a] Ye Tao,*[b] and Jianping Lu[b]
Abstract: A novel series of monodis-
perse asymmetrically and symmetrical-
ly substituted diphenylamino end-
capped oligofluorenes, OF(2)-NPhR,
R = H or An (An = 9-anthryl) and
OF(n)-NPh, n = 2–4, has been synthe-
sized by a convergent approach using
palladium-catalyzed Suzuki cross-cou-
pling. End-capping of oligofluorenes
with diphenylamino group(s) has been
shown to offer advantages in terms of
lowering their first ionization poten-
tials, enhancing thermal stability, and
inducing good amorphous morphologi-
cal stability. By tuning the number of
diphenylamino end-caps and the chain
length, the optimal conjugated length
for optical and luminescence properties
has been determined. Of all the hither-
to reported oligofluorenes capable of
serving as non-doped blue emitters,
OF(3)-NPh, with an optimal conjugat-
ed length, exhibits some of the best
hole-transport and blue-emitting prop-
Keywords: cyclic voltammetry
·
enhanced hole-injection/transport
properties · fluorescence · light-
emitting materials · oligofluorenes
erties.
A
maximum luminance of
7500 cdmꢀ2 and a luminance efficiency
up to 1.8 cdAꢀ1 have been achieved.
Introduction
great promise as highly stable and efficient blue-emissive
materials, have been extensively investigated recently. Nev-
ertheless, OLED performance is significantly affected by the
charge balance of the injected holes and electrons, as well as
by the confinement of carriers and excitons in a device. In
addition, a large hole-injection barrier for fluorene-based
materials often limits their device efficiency. To improve the
hole-injection and transport properties, triarylamines or
their moieties have been blended with[12] or incorporated
into[13,14] fluorene-based polymers, resulting in greatly en-
hanced stability and efficiency of blue-emitting OLEDs
made with these materials. However, this knowledge does
not provide any guidelines for further optimization of fluo-
rene-based materials. Interestingly, there have not been any
reports exploring blue-emissive diarylamine- or triaryl-
amine-substituted fluorene-based molecules/oligomers, even
though morphologically stable triarylamine derivatives have
been widely used as hole-transporting materials.[15,16] Investi-
gations of structure–property relationships in such oligomers
can be expected to provide insight into the functional prop-
erties of the related polymers as well as useful knowledge
for the rational design and optimization of fluorene-based
materials. Furthermore, monodisperse functional p-conju-
gated oligofluorenes with well-defined structure, which can
be easily characterized and obtained in high purity, can be
utilized as active materials in various optoelectronic applica-
tions.
With the advent of first-generation full-color organic light-
emitting diode (OLED) displays in consumer electronics,
for example in digital cameras and mobile phones, interest
in developing highly stable and efficient blue-emissive mate-
rials has intensified, as at present these do not match the far
superior stabilities and device performances of green-emis-
sive materials.[1,2] Furthermore, good wide-energy-gap emis-
sive materials can be used as host matrices to generate a
complete set of primary colors by means of energy transfer
to luminescent dopants or by using color filters.[3,4] Fluo-
rene-based molecules[5–7] and polymers,[8–11] which show
[a] Z. H. Li, Dr. M. S. Wong
Department of Chemistry and Centre for Advanced Luminescence
Materials
Hong Kong Baptist University
Kowloon Tong, Hong Kong SAR (China)
Fax : (+852)3411-7348
E-mail: mswong@hkbu.edu.hk
[b] Dr. Y. Tao, Dr. J. Lu
Institute for Microstructural Sciences
National Research Council of Canada
M-50 Montreal Road, Ottawa, ON, K1A 0R6 (Canada)
Fax : (+1)613-990-0202
E-mail: ye.tao@nrc.ca
Chem. Eur. J. 2005, 11, 3285 – 3293
DOI: 10.1002/chem.200401152
ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3285

As part of our efforts to investigate the structural factors
of functional materials[17–20] that can enhance OLED per-
formance and stability, we report herein the first synthesis
of monodisperse diphenylamino end-capped oligofluorenes,
OF(2)-NPhR, R = H and An and OF(n)-NPh, n = 2–4,
ly, cross-coupling of boronic acid 5 and bromide 4 afforded
the desired symmetrically substituted bifluorene, OF(2)-
NPh, in excellent yield (93%) under the same conditions. It
is important to note that use of the classical catalyst Pd-
(PPh3)4 often resulted in a poor yield. Cross-coupling of bor-
onic acid 5 and 7-(9’-anthryl)-2-bromofluorene 7, which was
prepared by selective cross-coupling of 9-anthrylboronic
acid (6) with 2-bromo-7-iodofluorene (3), afforded OF(2)-
NPhAn in moderate yield (56%). Double palladium-cata-
lyzed cross-coupling of 3 with boronic acid 5 yielded the ter-
fluorene OF(3)-NPh in 81% yield. Using the same conver-
gent approach, double palladium-catalyzed cross-coupling of
boronic acid 5 and 7,7’-diiodobifluorene 10, which was syn-
thesized by cross-coupling of 2 and the corresponding fluo-
renylboronic acid 8 followed by electrophilic iodination,
yielded OF(4)-NPh in 64% yield. All the newly synthesized
1
oligomers were fully characterized by H NMR, 13C NMR,
and an investigation of the influence of diphenylamino end-
caps and chain length on various physical and functional
properties of oligofluorenes, particularly blue-light-emitting
properties. We have unambiguously shown that diphenyl-
amino moieties end-capped onto highly luminescent oligo-
fluorene backbones improve hole-injection/transport proper-
ties, induce morphologically stable amorphous thin-film for-
mation, and increase the thermal stability of the oligomers,
which makes them superior as difunctional blue-emissive
materials. In addition, this systematic investigation has led
to the development of an oligofluorene possessing the opti-
mal conjugated length for highly efficient and stable blue
emission. Importantly, undoped OF(3)-NPh-based multilay-
er OLEDs exhibit excellent device performance and color
chromaticity for practical applications.
MS, and elemental analysis, and the data were found to be
in good agreement with the proposed structures. It is worth
mentioning that the protons of the methyl and third methyl-
ene groups of the butyl chains attached at the C9 position of
fluorene and its derivatives resonate at unexpectedly low
frequencies in the H NMR spectra. This unusual shift sug-
gests that the methyl and methylene groups fall within the
shielding region of the aromatic rings of the fluorene.
1
To probe the end-capping effect, the corresponding un-
substituted OF(n) series was also prepared using the same
convergent synthetic strategy for comparison. End-capping
of one or more diphenylamino functionalities onto oligo-
fluorene cores has pronounced effects on various molecular/
functional properties of the oligomers and OLED device
performance. In the electronic absorption spectra, a substan-
tial red-shift of the absorption maxima (lambasx) of oligofluor-
enes (Dl = 25–54 nm) is seen upon incorporation of strong-
ly electron-donating diphenylamino group(s), which is at-
tributed to an asymmetric destabilization of the HOMO and
Results and Discussion
The syntheses of the monodisperse asymmetrically and sym-
metrically substituted diphenylamino end-capped oligofluor-
enes, OF(2)-NPhR, R = H or An and OF(n)-NPh, n = 2–
4, are outlined in Scheme 1. Palladium-catalyzed Suzuki
cross-coupling was employed to construct the oligofluorene
cores, with 9,9-dibutyl-7-(diphenylamino)-2-fluorenylboronic
acid (5) as a key intermediate in these coupling reactions.
Alkylation of fluorene with nBuI in the presence of NaOH
in DMSO afforded 9,9-dibutylfluorene (1) in 82% yield.
Monobromination of 1 with N-bromosuccinimide (NBS) fol-
lowed by electrophilic iodination with periodic acid/I2 af-
forded 2-bromo-7-iodo-9,9-dibutylfluorene (3) in excellent
yield (92%). Chemoselective Ullmann coupling of 3 with di-
phenylamine using Cu/K2CO3 in triglyme afforded 2-bromo-
7-(diphenylamino)-9,9-dibutylfluorene (4), which was subse-
quently converted to the corresponding boronic acid (5) by
lithium–bromide exchange with nBuLi followed by reaction
with trimethyl borate and then acid hydrolysis. Suzuki cross-
coupling of boronic acid 5 and bromofluorene 2 using Pd-
(OAc)2/2P(o-tol)3 as catalyst afforded the asymmetrically
substituted bifluorene, OF(2)-NPhH, in 76% yield. Similar-
LUMO levels, leading to a decrease in the energy gap.[21]
abs
max
The l
and molar absorptivities (emax) of both the OF(n)
and OF(n)-NPh series increase sequentially with increasing
abs
max
chain length; however, l
values of diphenylamino end-
capped oligofluorenes show evidence of saturation at
386 nm, even though emax increases (Figure 1). This implies
that an effective conjugated length for the energy gap is
reached when n = 3 in the OF(n)-NPh series. The emission
em
max
maxima (l ) of oligofluorenes consistently shift to longer
wavelengths (Dl = 22–44 nm) with the incorporation of di-
phenylamino end-cap(s). Upon excitation at either 310 nm,
corresponding to the n!p* transition of the triarylamine
moiety, or at 386 nm (lmax), corresponding to the p!p*
transition of the oligofluorene core, the emission spectra ob-
tained are identical, suggesting that energy or excitons can
be efficiently transfered from the triarylamine moiety to the
emissive fluorene core. Consistent with the absorption be-
em
max
havior, the l values of the OF(n)-NPh series also show a
tendency for convergence at 432 nm when n = 3, further
supporting the existence of an effective conjugated length
for the energy gap (Figure 1).
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Diphenylamino End-Capped Oligofluorenes
FULL PAPER
Scheme 1. Synthesis of diphenylamino end-capped oligofluorenes, OF(2)-NPhR, R = H or An, and OF(n)-NPh, n = 2–4. Reagents and conditions:
a) nBuI, NaOH, DMSO, 908C; b) NBS, acetone, 608C; c) I2, HIO4, AcOH, H2SO4, 808C; d) Ph2NH, Cu, K2CO3, triglyme, 1808C; e) 1. nBuLi, THF,
ꢀ788C, 2. B(OCH3)3, 3. H+; f) Pd(OAc)2/2P(o-tol)3, K2CO3, CH3OH, 758C.
Chem. Eur. J. 2005, 11, 3285 – 3293
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3287

M. S. Wong, Y. Tao et al.
become saturated on reaching the terfluorene (FFL = 93%)
in the OF(n)-NPh series. The fluorescence lifetimes of all
the diphenylamino end-capped oligofluorenes are in the
nanosecond range, suggesting that the emission originates
from a transition between the singlet excited state and the
ground state.
To prevent aggregation/excimer formation and to induce
an amorphous state for fluorene-based molecular materials,
a widely adopted approach is to introduce either a spiro-
linkage[22–24] or bulky substituent(s) or dendron(s)[25,26] at the
C9-position of the fluorene core. It is important to note that
compounds of the OF(n) series bearing short butyl substitu-
ents exhibit no glass transition temperature (Tg), as deter-
mined by differential scanning calorimetry (DSC); instead,
melting points of 153, 69, and 1098C were recorded for
OF(2), OF(3), and OF(4), respectively, by DSC. On the
other hand, oligofluorenes end-capped with diphenylamino
group(s) show distinct Tg values, which increase with in-
creasing size of the fluorenyl unit (Table 1). These results
suggest that the incorporation of diphenylamino moieties at
the ends of oligofluorenes may also be used as a tool to
induce morphologically stable amorphous thin-film forma-
tion. Furthermore, all of the OF(2)-NPhRs and OF(n)-NPhs
show improved thermal stabilities, with decomposition tem-
peratures, Tdec, in the range 405–4648C.
To examine the electrochemical properties of the oligom-
ers, cyclic voltammetry experiments were carried out in a
three-electrode cell set-up with 0.1m Bu4NPF4 in CH2Cl2 as
the supporting electrolyte. The results are tabulated in
Table 1. In contrast to the OF(n) series and triaryldiamines,
the asymmetrically substituted bifluorenes, OF(2)-NPhRs,
exhibit two reversible one-electron anodic redox couples,
which correspond to the sequential removal of electrons
from the arylamino group and bifluorene core to form radi-
cal cations and dications, respectively (Figure 2). One the
other hand, the symmetrically disubstituted oligofluorenes,
OF(n)-NPhs, exhibit a reversible two-electron anodic redox
couple, corresponding to two arylamine oxidations, as well
as a (ir)reversible one-electron anodic redox couple and an
additional reversible one-electron redox couple for OF(4)-
Figure 1. Absorption and fluorescence spectra of the a) OF(2)-NPhR and
b) OF(n)-NPh series measured in chloroform.
Importantly, end-capping of one or more diphenylamino
functionalities onto the oligofluorene skeleton does not per-
turb the planarity or alter the highly fluorescent nature of
the oligofluorene core (Table 1). The fluorescence quantum
yields measured in chloroform using 9,10-diphenylanthra-
cene as a standard increase with increasing chain length and
Table 1. A summary of the various physical measurements on the OF(2)-NPhR, OF(n)-NPh, and OF(n) series.
[a]
[f]
[h]
l
[a] [nm]
l
[nm]
FFL
t
[a,e] [ns]
E1/2 [V]
HOMO[g] [eV]
Tg [8C]
Tdec[i] [8C]
abs
max
em [a,b]
max
(emax/104 [mꢀ1 cmꢀ1])
OF(2)-NPhH
OF(2)-NPhAn
OF(2)-NPh
OF(3)-NPh
OF(4)-NPh
OF(2)
372 (4.38)
377 (5.88)
384 (7.06)
386 (8.53)
386 (14.2)
330 (4.30)
353 (5.78)
361 (8.23)
423
0.50[c]
0.73[c]
0.67[c]
0.93[c]
0.94[c]
0.71[d]
0.92[d]
0.93[d]
1.06
1.48
4.56
1.23
0.92
0.95
1.04
0.98
0.35, 0.89
0.35, 0.78
0.36, 1.06
0.35, 0.87
0.34, 0.79, 0.94
0.91, 1.19
0.77, 1.01
0.73, 0.95
5.15
5.15
5.16
5.15
5.14
5.70
5.57
5.53
60
93
91
406
446
452
461
464
369
432
451
427
425
432
432
99
117
no
no
no
363, 381
394, 416
410
OF(3)
OF(4)
[a] Measured in CHCl3. [b] Excited at the absorption maxima. [c] Using 9,10-diphenylanthracene (F360 = 0.9) as a standard. [d] Using quinine in 1.0m
H2SO4 (F313 = 0.48) as a standard. [e] Using a nitrogen laser as excitation source. [f] E1/2 versus Fc+/Fc estimated by CV using a platinum disc electrode
as a working electrode, platinum wire as a counter electrode, and SCE as a reference electrode, connected to the oligomer solution through an agar salt
bridge, with ferrocene as an external standard, E1/2 (Fc/Fc+) = 0.45 V versus SCE). [g] Calculated with reference to ferrocene (0.48 eV). [h] Determined
by differential scanning calorimetry with a heating rate of 108Cminꢀ1 under N2. [i] Determined by thermogravimetric analysis with a heating rate of
108Cminꢀ1 under N2.
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Diphenylamino End-Capped Oligofluorenes
FULL PAPER
Figure 3. Thin-film photoluminescence spectra of OF(2)-NPhRs and
OF(n)-NPhs.
fluorenes show great potential for use as hole-transport
blue-emitters in OLEDs. Multilayer OLEDs with the struc-
ture ITO/OF(2)-NPhR or OF(n)-NPh (40 nm)/PBD
(40 nm)/LiF (1 nm)/Al (150 nm) were thus fabricated by
vacuum deposition and subsequently investigated (PBD =
2-biphenyl-4-yl-5-(4-tert-butylphenyl)-1,3,4-oxadiazole). The
EL spectra of these devices generally resemble the PL spec-
tra of the thin films, with blue emission maxima at 420–
436 nm and a shoulder peak at 456–460 nm (Figure 3, Fig-
ure 4a, and Figure 5), with the exception of the EL spectrum
of OF(2)-NPhAn, which exhibits a tailed emission at long
wavelengths. Such a long-wavelength emission may be due
to the formation of aggregates, leading to low-energy trap-
ping sites.[27] In addition, these EL spectra proved to be in-
dependent of the applied voltage, suggesting that the EL
originates purely from the oligomers, without exciplex for-
mation. Importantly, the performance of the device based
on the symmetrically disubstituted bifluorene, OF(2)-NPh,
was found to be superior to those of the devices based on
the asymmetrically substituted bifluorenes, OF(2)-NPhAn
and OF(2)-NPhH (Figure 4), even though the systems pos-
sess comparable molecular properties, such as hole-injection
and transport properties as well as fluorescence quantum
yield. As a result, further studies of device performance
were concentrated on the OF(n)-NPh materials.
Figure 2. Cyclic voltammograms of the OF(2)-NPhR and OF(n)-NPh
series.
NPh, corresponding to oxidation of the oligofluorene skele-
ton (Figure 2). The arylamine oxidation potential is essen-
tially unaffected by the number of end-caps and the length
of the oligofluorene core; however, the second oxidation
proceeds more easily with an increase in conjugated length
as the electrochemically formed radical cation is suitably
predisposed for efficient delocalization and hence is stabi-
lized. In general, upon the incorporation of diphenylamino
end-caps, the HOMO level of oligofluorenes is raised (rela-
tive to the vacuum level) to about 5.15 eV, as estimated by
electrochemical methods (Table 1). Such a high HOMO
level greatly reduces the energy barrier for hole injection
from ITO (f = 5.0 eV) to the emissive oligofluorenes. As a
result, OF(2)-NPhRs and OF(n)-NPhs can also be used as
hole-transport/injection materials.
Thin-film photoluminescence (PL) spectra of all of the di-
phenylamino end-capped oligofluorenes, except OF(4)-NPh,
show more distinct vibronic structures and slightly red-shift-
ed emission maxima (<6 nm) as compared to the solution
PL spectra, indicating the absence of aggregation/excimer
formation in the solid state. On the other hand, the signifi-
cant spectral broadening coupled with a red shift of about
20 nm in the PL spectrum of a vacuum-deposited thin film
of OF(4)-NPh is indicative of intermolecular interactions
between the quaterfluorenyl backbones (Figure 3).
Over a wide operation range, the emission of OF(2)-NPh-
based devices was found to have CIE coordinates (x, y =
0.15, 0.09) very close to those of NTSC blue (x, y = 0.14,
0.08). The emission of OF(3)-NPh-based devices has CIE
coordinates (x, y = 0.16, 0.14), which are also very close to
those of NTSC blue.
Despite the fact that the OF(2)-NPh-based devices exhib-
ited a turn-on voltage of 4.5 V, a maximum luminance of
1000 cdmꢀ2, and a luminance efficiency up to 1.1 cdAꢀ1, and
the OF(3)-NPh-based device exhibited a turn-on voltage of
4.5 V, a maximum luminance of 700 cdmꢀ2, and a luminance
efficiency up to 2.2 cdAꢀ1, these devices broke down at
around 15–16 V (Figure 6). The breakdown of these PBD-
Because of their strong luminescence, low first ionization
potentials, high thermal stabilities, and good amorphous
morphological stabilities, diphenylamino end-capped oligo-
Chem. Eur. J. 2005, 11, 3285 – 3293
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M. S. Wong, Y. Tao et al.
Figure 5. PL spectra of a) OF(2)-NPh and b) OF(3)-NPh, as well as EL
spectra of the corresponding OLEDs.
Figure 4. a) EL spectra of OF(2)-NPhR- and OF(2)-NPh-based devices
and b) luminance–voltage plots of OF(2)-NPhR- and OF(2)-NPh-based
devices. The inset shows plots of external efficiency versus voltage.
0.8 cdAꢀ1, whereas the OF(3)-NPh-based devices exhibited
a maximum luminance of 7500 cdmꢀ2 and a luminance effi-
ciency of up to 1.8 cdAꢀ1. Both devices have a turn-on volt-
age of 7.5 V. The superior device performance of the OF(3)-
NPh-based OLED is attributed to the significantly higher
fluorescence quantum, FFL, of OF(3)-NPh (0.93) compared
to that of OF(2)-NPh (0.67). The HOMO levels of F-TBB
(6.3 eV) and PBD (6.2 eV) are very close, but the LUMO
level of F-TBB (2.4 eV) is much higher than that of PBD
(2.8 eV). Therefore, one trade-off resulting from the use of
F-TBB to obtain higher luminance is increased turn-on vol-
tages and slightly decreased device efficiencies.
In summary, a novel series of monodisperse asymmetrical-
ly and symmetrically substituted diphenylamino end-capped
oligofluorenes, OF(2)-NPhR, R = H or An and OF(n)-
NPh, n = 2–4, has been successfully synthesized by a con-
vergent approach using palladium-catalyzed Suzuki cross-
coupling. We have shown that terfluorene symmetrically
end-capped with diphenylamino groups, OF(3)-NPh, pos-
sesses the optimal conjugated length for optical and lumi-
based devices at high current is most probably due to the
poor morphological stability of the PBD film at device oper-
ating temperatures. To further enhance the device perform-
ance, a hole-blocking amorphous material, 1,3,5-tris(4-fluo-
robiphenyl-4’-yl)benzene (F-TBB),[28] combined with an
Alq3 film as a hole-blocking/electron-transport layer, was
used to replace the PBD layer. The EL spectra of the result-
ing devices showed no apparent difference from those ob-
tained using the PBD layer (Figure 5). The CIE coordinates
of the OF(2)-NPh- and OF(3)-NPh-based devices using F-
TBB as the hole-blocking layer were found to be x, y =
0.16, 0.08, and x, y = 0.17, 0.14, respectively. Remarkably,
the OF(n)-NPh-based devices could be operated at much
higher current/voltage with the use of the F-TBB layer, re-
sulting in a much higher maximum luminance than could be
achieved with a PBD layer (Figure 6). As a result, the
OF(2)-NPh-based devices exhibited a maximum luminance
of 6000 cdmꢀ2 and
a luminance efficiency of up to
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Diphenylamino End-Capped Oligofluorenes
FULL PAPER
whereas the OF(3)-NPh-based device exhibited a maximum
luminance of 700–7500 cdmꢀ2 and a luminance efficiency up
to 1.8–2.2 cdAꢀ1. Our findings provide a useful alternative
approach to the design of stable and efficient blue-emissive
materials.
Experimental Section
EL device fabrication and testing: ITO-glass substrates (15 Wmꢀ2) were
patterned by applying conventional photolithography techniques with an
acid mixture of HCl and HNO3 as the etchant. The active area of each
EL device was 1ꢁ5 mm2. All organic layers were thermally deposited in
a vacuum chamber at a base pressure of 2ꢁ10ꢀ7 Torr. Typically, a diphe-
nylamino end-capped oligofluorene (OF(n)-NPh), functioning as a hole-
transport emissive layer (40 nm), was first deposited on a patterned ITO
substrate. A hole-blocking layer (F-TBB, 20 nm) was then vacuum-depos-
ited on top of the oligofluorene layer, followed by the deposition of an
Alq3 thin film (20 nm). The device fabrication was completed by the
evaporation of LiF (1 nm) and the Al cathode (100 nm). A film of PBD
(40 nm) was used to replace the F-TBB (20 nm) and Alq3 (20 nm) in
some devices for comparison purposes. The devices were tested in air
under ambient conditions with no encapsulation. EL spectra, device lu-
minances, and current–voltage characteristics were recorded using a com-
bination of a Photo Research PR-650 SpectraScan and a Keithley 238
Source meter.
9,9-Bis(n-butyl)fluorene (1): A mixture of fluorene (16.6 g, 0.1 mol), n-
butyl iodide (40 g, 0.22 mol), and sodium hydroxide (12 g, 0.3 mol) in
DMSO (120 mL) was stirred overnight at 908C under an inert atmos-
phere. After cooling to room temperature, the solution was poured into
cold water and the resulting mixture was extracted with dichloromethane
(3ꢁ50 mL). The combined organic layers were washed with water, dried
over anhydrous sodium sulfate, filtered, and concentrated to dryness. The
crude product was then purified by column chromatography on silica gel
using petroleum ether as eluent to afford the desired product as a color-
less solid (23 g, 82% yield). 1H NMR (400 MHz, CDCl3, 258C): d =
7.70–7.69 (m, 2H; ArH), 7.28–7.33 (m, 6H; ArH), 1.94–1.98 (m, 4H;
CH2), 1.03–1.09 (m, 4H; CH2), 0.66 (t, J (H,H) = 7.4 Hz, 6H; CH3),
0.54–0.62 ppm (m, 4H; CH2); 13C NMR (100 MHz, CDCl3, 258C): d =
150.6, 141.1, 127.0, 126.7, 122.8, 119.6, 54.9, 40.2, 25.9, 23.0, 13.8 ppm; MS
(FAB): m/z: 280.2 [M+].
Figure 6. Luminance–voltage plots of a) OF(2)-NPh- and b) OF(3)-NPh-
based devices. The inset shows plots of external efficiency versus voltage.
9,9-Bis(n-butyl)-2-bromofluorene (2): A mixture of 9,9-bis(n-butyl)fluor-
ene (13 g, 46 mmol) and NBS (8.25 g, 46 mmol) in acetone (50 mL) was
stirred under nitrogen at 808C for 3 h. After cooling to room tempera-
ture, the solution was poured into cold water and the resulting mixture
was extracted with dichloromethane (3ꢁ50 mL). The combined organic
layers were washed with water, dried over anhydrous sodium sulfate, fil-
tered, and concentrated to dryness. The crude product was purified by
short-column chromatography on silica gel using petroleum ether as
eluent to afford the desired product as a colorless solid (15.78 g, 96%
yield). 1H NMR (400 MHz, CDCl3, 258C): d = 7.64–7.66 (m, 1H; ArH),
7.50–7.55 (m, 1H; ArH), 7.42–7.45 (m, 2H; ArH), 7.31–7.33 (m, 3H;
ArH), 1.89–1.98 (m, 4H; CH2), 1.02–1.10 (m, 4H; CH2), 0.67 (t, J(H,H)
= 7.4 Hz, 6H; CH3), 0.51–0.62 ppm (m, 4H; CH2); 13C NMR (100 MHz,
CDCl3, 258C): d = 152.9, 150.3, 140.1, 140.0, 129.9, 127.4, 126.9, 126.7,
126.1, 122.9, 121.0, 119.7, 55.3, 40.1, 25.8, 23.0, 13.8 ppm; MS (FAB): m/z:
359.5 [M+].
nescence properties in this series. The diphenylamino end-
caps do not perturb the planarity or alter the highly fluores-
cent nature of the oligofluorene backbone, although the ab-
sorption and emission spectra are red-shifted (20–50 nm).
Furthermore, the presence of diphenylamino end-caps
lowers the first ionization potential (raises the HOMO level
of oligofluorenes to ~5.15 eV), as estimated by cyclic vol-
tammetry experiments, which greatly reduces the energy
barrier for hole injection from ITO to the emissive oligo-
fluorenes. Diphenylamino end-capped oligofluorenes show
enhanced thermal stability and exhibit superior amorphous
morphological stability as compared to those of the corre-
sponding unsubstituted counterparts. Remarkably, undoped
OF(n)-NPh-based multilayer OLEDs exhibit excellent
device performance and color chromaticity. Depending on
the hole-blocking material used (i.e., PBD or 1,3,5-tris(4-flu-
orobiphenyl-4’-yl)benzene (F-TBB)), the OF(2)-NPh-based
9,9-Bis(n-butyl)-2-bromo-7-iodofluorene (3):
A mixture of 9,9-bis(n-
butyl)-2-bromofluorene (15.4 g, 43 mmol), iodine (6.5 g, 25.8 mmol), con-
centrated sulfuric acid (2.3 mL), periodic acid (1.7 g, 25.8 mmol), and
water (7.7 mL) in glacial acetic acid (74 mL) was stirred at 508C for 4 h.
After cooling to room temperature, the solution was poured into ice-
cooled water containing a large amount of sodium sulfite and the result-
ing mixture was extracted with dichloromethane (3ꢁ50 mL). The com-
bined organic phases were washed twice with water, dried over anhy-
drous sodium sulfate, and concentrated to dryness. The crude product
devices exhibited
a
maximum luminance of 1000–
6000 cdmꢀ2 and a luminance efficiency up to 0.8–1.1 cdAꢀ1,
Chem. Eur. J. 2005, 11, 3285 – 3293
www.chemeurj.org
ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3291

M. S. Wong, Y. Tao et al.
was purified by short-column chromatography on silica gel using petrole-
um ether as eluent to yield the desired product as a light-yellow solid
(20.3 g, 97% yield). 1H NMR (400 MHz, CDCl3, 258C): d = 7.62–7.65
(m, 2H; ArH), 7.49–7.51 (m, 1H; ArH), 7.38–7.44 (m, 3H; ArH), 1.86–
1.91(m, 4H; CH2), 1.02–1.11 (m, 4H; CH2), 0.67 (t, J(H,H) = 7.2 Hz,
6H; CH3), 0.50–0.58 ppm (m, 4H; CH2); 13C NMR (100 MHz, CDCl3,
258C): d = 152.7, 152.5, 152.3, 139.7, 139.1, 136.0, 132.1, 132.1, 132.0,
130.1, 130.1, 126.1, 121.5, 121.2, 93.0, 55.5, 40.0, 25.8, 22.9, 13.8 ppm; MS
(FAB): m/z: 485.5 [M+].
7.15 (d, J(H,H) = 7.6 Hz, 10H; ArH), 7.00–7.06 (m, 6H; ArH), 1.88–
1.99 (m, 8H; CH2), 1.07–1.15 (m, 8H; CH2), 0.73 ppm (t, J(H,H)
=
7.4 Hz, 20H; CH2CH3); 13C NMR (100 MHz, CDCl3, 258C): d = 119.3,
152.4, 151.4, 148.0, 147.1, 140.0, 139.6, 136.0, 129.1, 125.9, 123.8, 123.5,
122.5, 121.0, 120.3, 119.4, 55.1, 40.0, 26.1, 23.0, 13.9 ppm; MS (FAB): m/z:
889.0 [M+]; elemental analysis calcd (%) for C66H68N2 (888.5382): C
89.14, H 7.71, N 3.15; found: C 88.82, H 7.72, N 3.29.
2-(Diphenylamino)bis[9,9-bis(n-butyl)fluorene],
OF(2)-NPhH:
The
Suzuki coupling procedure described above was followed using 9,9-bis(n-
butyl)-2-bromofluorene (359 mg, 1 mmol) and 9,9-bis(n-butyl)-2-dipheny-
lamino-7-fluorenylboronic acid (489 mg, 1 mmol). The crude product was
purified by column chromatography on silica gel using petroleum ether/
9,9-Bis(n-butyl)-7-bromo-2-diphenylaminofluorene (4): A mixture of 9,9-
bis(n-butyl)-2-bromo-7-iodofluorene (10.0 g, 20.6 mmol), diphenylamine
(4.2 g, 24.7 mmol), copper bronze (0.7 g, 11 mmol), and potassium car-
bonate (11 g, 82.4 mmol) in triglyme (50 mL) was stirred under an inert
atmosphere at 190–2008C for 24 h. After cooling to room temperature,
the solution was poured into cold water and the resulting mixture was ex-
tracted with dichloromethane (3ꢁ50 mL). The combined organic phases
were washed with water, dried over anhydrous sodium sulfate, and con-
centrated to dryness. The crude product was purified by short-column
chromatography on silica gel using petroleum ether as eluent to afford
the desired product as a white solid (5.8 g, 54% yield), along with 2,7-
bis(diphenylamino)-9,9-di(n-butyl)fluorene as a white solid (2.0 g, 26%).
1H NMR (400 MHz, CDCl3, 258C): d = 7.38–7.51 (m, 4H; ArH), 7.21–
7.25 (m, 4H; ArH), 7.06–7.11 (m, 5H; ArH), 6.98–7.01 (m, 3H; ArH),
dichloromethane (6:1, v/v) as eluent to afford
a light-yellow solid
(549 mg, 76% yield). 1H NMR (400 MHz, CDCl3, 258C): d = 7.80 (d, J-
(H,H) = 7.60 Hz, 1H; ArH), 7.76 (d, J(H,H) = 7.20 Hz, 1H; ArH), 7.72
(d, J(H,H) = 8.40 Hz, 1H; ArH), 7.69–7.61 (m, 5H; ArH), 7.40–7.33 (m,
3H; ArH), 7.28 (t, J(H,H) = 7.20 Hz, 4H; ArH), 7.17 (d, J(H,H) =
7.60 Hz, 5H; ArH), 7.09–7.02 (m, 3H; ArH), 2.08–1.92 (m, 8H; CH2),
1.16–1.09 (m, 8H; CH2), 0.77–0.70 ppm (m, 20H; CH2CH3); 13C NMR
(100 MHz, CDCl3, 258C): d = 152.4, 151.4, 151.3, 150.9, 148.0, 147.1,
140.8, 140.4, 140.2, 140.1, 139.6, 135.9, 129.1, 126.9, 126.8, 126.0, 125.9,
123.8, 123.5, 122.9, 122.5, 121.2, 121.1, 120.4, 119.9, 119.7, 119.4, 119.3,
55.1, 40.2, 40.0, 26.1, 26.0, 23.1, 23.0, 13.9, 13.8 ppm; MS (FAB): m/z =
722.0 [M+]; elemental analysis calcd (%) for C54H59N (721.4647): C
89.82, H 8.24, N 1.94; found: C 89.98, H 8.30, N 1.89.
1.79–1.83 (m, 4H; CH2), 1.02–1.09 (m, 4H; CH2), 0.69 (t, J(H,H)
=
7.4 Hz, 6H; CH3), 0.58–0.64 ppm (m, 4H; CH2); 13C NMR (100 MHz,
CDCl3, 258C): d = 152.8, 151.7, 147.9, 147.5, 140.0, 135.0, 129.9, 129.2,
126.0, 123.9, 123.3, 122.6, 120.4, 120.1, 119.0, 55.2, 39.9, 25.9, 22.9,
13.8 ppm; MS (FAB): m/z: 525.4 [M++H].
9,9-Bis(n-butyl)-7-(9’-anthryl)-2-bromofluorene (7): The Suzuki coupling
procedure described above was followed using 9,9-bis(n-butyl)-2-bromo-
7-iodofluorene (971 mg, 2 mmol) and 9-anthrylboronic acid (444 mg,
2 mmol). The crude product was purified by column chromatography on
silica gel using petroleum ether as eluent to afford a light-yellow solid
9,9-Bis(n-butyl)-2-diphenylamino-7-fluorenylboronic acid (5): A 100-mL
two-necked flask was charged with
a solution of 9,9-bis(n-butyl)-7-
1
(480 mg, 45% yield) and the di-coupling product in 35% yield. H NMR
bromo-2-diphenylaminofluorene (1.3 g, 2.47 mmol) in dry THF (20 mL)
and a magnetic stirrer bar. The solution was cooled to ꢀ788C by immers-
ing the flask in an acetone/dry ice bath, whereupon nBuLi (1.5m, 2.3 mL,
3.71 mmol) was added under nitrogen atmosphere while maintaining
good stirring. After stirring for 1 h, trimethyl borate (0.4 mL, 3.71 mmol)
was added. After stirring for a further 2 h, the reaction mixture was first
quenched with water and then 6m HCl was added in a dropwise fashion
until an acidic solution was obtained. The resulting mixture was poured
into water and extracted with dichloromethane (3ꢁ50 mL). The com-
bined organic layers were dried over anhydrous Na2SO4 and concentrated
to dryness. The crude product was then purified by column chromatogra-
phy on silica gel using CH2Cl2/EtOAc as eluent to afford the desired bor-
(400 MHz, CDCl3, 258C): d = 8.51 (s, 1H; ArH), 8.06 (d, J(H,H) =
8.40 Hz, 2H; ArH), 7.87 (d, J(H,H) = 8.40 Hz, 1H; ArH), 7.72 (t, J-
(H,H) = 4.40 Hz, 2H; ArH), 7.66 (d, J(H,H) = 8.80 Hz, 1H; ArH),
7.52–7.32 (m, 8H; ArH), 1.99–1.95 (m, 4H; CH2), 1.15–1.06 (m, 4H;
CH2), 0.78–0.67 ppm (m, 10H; CH2CH3); 13C NMR (100 MHz, CDCl3;
258C): d = 152.9, 150.3, 140.1, 140.0, 138.3, 138.0, 136.4, 131.8, 131.3,
130.1, 129.8, 127.4, 126.9, 126.1, 126.0, 122.8, 121.1, 121.0, 120.9, 119.7,
55.2, 40.1, 25.8, 22.9, 13.8 ppm; MS (FAB): m/z: 534.5 [M++H].
9-[7-(2’-Diphenylamino-bi(9,9-bis(n-butyl)fluorene))-yl]anthracene,
OF(2)-NPhAn: The Suzuki coupling procedure described above was fol-
lowed using 9,9-bis(n-butyl)-7-(9’-anthryl)-2-bromofluorene (267 mg,
0.5 mmol) and 9,9-bis(n-butyl)-2-diphenylamino-7-fluorenylboronic acid
(367 mg, 0.75 mmol). The crude product was purified by column chroma-
tography on silica gel using petroleum ether/dichloromethane (6:1, v/v)
onic acid as
a
light-yellow solid (976 mg, 81% yield). 1H NMR
(400 MHz, [D6]DMSO, 258C): d = 8.02 (s, 2H; OH), 7.79 (s, 1H; ArH),
7.75 (d, J(H,H) = 7.6 Hz, 1H; ArH), 7.70 (d, J(H,H) = 8.0 Hz, 1H,
ArH), 7.65 (d, J(H,H) = 8.4 Hz, 1H), 7.26 (t, J(H,H) = 7.4 Hz, 4H;
ArH), 7.08 (s, 1H; ArH), 7.00 (d, J(H,H) = 8.0 Hz, 6H; ArH), 6.92 (d,
J(H,H) = 8.0 Hz, 1H; ArH), 1.83–1.85 (m, 4H; CH2), 0.99–1.03 (m, 4H;
CH2), 0.63 (t, J(H,H) = 7.4 Hz, 6H; CH3), 0.49–0.55 ppm (m, 4H; CH2);
13C NMR (100 MHz, CDCl3, 258C): d = 153.1, 150.0, 147.9, 145.3, 135.6,
134.7, 129.4, 129.2, 124.0, 123.9, 123.2, 122.7, 121.1, 119.0, 118.6, 54.9,
39.9, 26.0, 23.0, 13.8 ppm; MS (FAB): m/z: 489.7 [M+].
as eluent to afford
a
yellow solid (251 mg, 56% yield). 1H NMR
(400 MHz, CDCl3, 258C): d = 8.52 (s, 1H; ArH), 8.07 (d, J(H,H) =
8.0 Hz, 2H; ArH), 7.94 (d, J(H,H) = 7.60 Hz, 1H; ArH), 7.88 (d, J-
(H,H) = 7.60 Hz, 1H; ArH), 7.79 (d, J(H,H) = 9.20 Hz, 2H; ArH),
7.73–7.67 (m, 3H; ArH), 7.63 (s, 1H; ArH), 7.60 (d, J(H,H) = 8.40 Hz,
2H; ArH), 7.49–7.42 (m, 4H; ArH), 7.36 (dd, J(H,H) = 7.60 Hz, 2H;
ArH), 7.26 (d, J(H,H) = 7.60 Hz, 4H; ArH), 7.16 (s, 5H; ArH), 7.06–
7.01 (m, 3H; ArH), 2.08–1.91 (m, 8H; CH2), 1.16–1.09 (m, 8H; CH2),
0.76–0.70 ppm (m, 20H; CH2CH3); 13C NMR (100 MHz, CDCl3, 258C): d
= 152.3, 151.6, 151.3, 151.0, 147.9, 147.1, 140.5, 140.1, 140.0, 137.9, 137.5,
137.2, 136.7, 131.3, 130.2, 129.9, 129.1, 128.3, 126.8, 126.4, 126.1, 126.0,
125.2, 125.0, 123.8, 122.4, 121.2, 120.3, 119.9, 119.5, 119.3, 55.3, 55.2, 40.2,
40.1, 26.3, 26.2, 23.1, 23.0, 14.2, 14.0 ppm; MS (FAB): m/z: 898.0 [M+];
elemental analysis calcd (%) for C68H67N (897.5273): C 90.92, H 7.52, N
1.56; found: C 91.25, H 7.68, N 1.65.
2,2’-Bis(diphenylamino)bis[9,9-bis(n-butyl)fluorene], OF(2)-NPh: A 100-
mL round-bottomed flask was charged with a mixture of 9,9-bis(n-butyl)-
7-bromo-2-diphenylaminofluorene (262 mg, 0.50 mmol), 9,9-bis(n-butyl)-
2-diphenylamino-7-fluorenylboronic acid (347 mg, 0.70 mmol), Pd(OAc)2
(11 mg, 5 mol%), and tri(o-tolyl)phosphine (30 mg, 10 mol%), which was
taken up in toluene (20 mL), methanol (10 mL), and 2m aqueous K2CO3
solution (2 mL). The reaction mixture was stirred overnight at 758C
under a nitrogen atmosphere. After cooling to room temperature, it was
poured into cold water and the resulting mixture was extracted with di-
chloromethane (3ꢁ50 mL). The combined organic layers were dried over
anhydrous Na2SO4 and concentrated to dryness. The crude product was
purified by column chromatography on silica gel using petroleum ether/
dichloromethane (6:1, v/v) as eluent to afford the desired product as a
yellow solid (414 mg, 93% yield). 1H NMR (400 MHz, CDCl3, 258C): d
= 7.69 (d, J(H,H) = 7.6 Hz, 2H; ArH), 7.63 (d, J(H,H) = 8.0 Hz, 2H;
ArH), 7.59–7.61 (m, 4H; ArH), 7.27 (d, J(H,H) = 8.0 Hz, 8H; ArH),
2,2’’-Bis(diphenylamino)tris[9,9-bis(n-butyl)fluorene], OF(3)-NPh: The
Suzuki coupling procedure described above was followed using 9,9-bis(n-
butyl)-2-bromo-7-iodofluorene (734 mg, 1.5 mmol) and 9,9-bis(n-butyl)-2-
diphenylamino-7-fluorenylboronic acid (2.20 g, 4.5 mmol). The crude
product was purified by column chromatography on silica gel using pe-
troleum ether/dichloromethane (6:1, v/v) as eluent to afford a light-
yellow solid (944 mg, 81% yield). 1H NMR (400 MHz, CDCl3, 258C): d
= 7.80 (d, J(H,H) = 8.0 Hz, 2H; ArH), 7.63–7.70 (m, 8H; ArH), 7.58–
3292
ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2005, 11, 3285 – 3293

Diphenylamino End-Capped Oligofluorenes
FULL PAPER
7.60 (m, 4H; ArH), 7.25 (d, J(H,H) = 8.0 Hz, 8H; ArH), 7.14 (d, J-
(H,H) = 7.6 Hz, 10H; ArH), 6.99–7.05 (m, 6H; ArH), 2.09–2.11 (m,
4H; CH2), 1.90–1.98 (m, 8H; CH2), 1.10–1.18 (m, 12H; CH2), 0.71–
0.75 ppm (m, 30H; CH2CH3); 13C NMR (100 MHz, CDCl3, 258C): d =
152.4, 151.7, 151.4, 148.0, 147.1, 140.4, 140.2, 139.9, 139.6, 135.9, 129.1,
126.0, 123.8, 123.5, 122.5, 121.3, 121.2, 120.4, 119.9, 119.4, 119.3, 55.2,
55.1, 40.2, 40.0, 26.1, 23.1, 23.0, 13.9, 13.8 ppm; MS (FAB): m/z: 1165.4
[M+]; elemental analysis calcd (%) for C87H92N2 (1164.7260): C 89.64, H
7.95, N 2.41; found: C 89.40, H 8.15, N 2.65.
Acknowledgements
This work was supported by Earmarked Research Grant (HKBU2051/
01P) from the Research Grants Council, Hong Kong SAR, China. We
gratefully acknowledge Dr. K.K. Shiu for his advice on the cyclic voltam-
metric measurements.
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9,9-Bis(n-butyl)-2-fluorenylboronic acid (8): The procedure described for
5
was followed by using 9,9-bis(n-butyl)-2-bromofluorene (7.9 g,
22 mmol), nBuLi (16.5 mL, 26.4 mmol), and trimethyl borate (3.0 mL,
1
26.4 mmol), affording a light-yellow solid in an isolated yield of 81%. H
NMR (400 MHz, [D6]DMSO, 258C): d = 8.05 (s, 2H; OH), 7.83 (s, 1H;
ArH), 7.74–7.81 (m, 3H; ArH), 7.42–7.44 (m, 1H; ArH), 7.31–7.33 (m,
2H; ArH), 1.95–1.98 (m, 4H; CH2), 0.98–1.04 (m, 4H; CH2), 0.60 (t, J-
[6] S. W. Culligan, Y. Geng, S. H. Chen, K. Klubek, K. M. Vaeth, C. W.
Tang, Adv. Mater. 2003, 15, 1176–1179.
(H,H)
=
7.4 Hz, 6H; CH3), 0.43–0.48 ppm (m, 4H; CH2); 13C NMR
(100 MHz, [D6]DMSO, 258C): d = 150.6, 148.9, 142.4, 140.5, 133.0, 128.3,
127.5, 126.8, 122.9, 121.1, 118.8, 54.3, 40.1, 25.8, 22.5, 13.8 ppm.
[7] K.-T. Wong, Y.-Y. Chien, R.-T. Chen, C.-F. Wang, Y.-T. Lin, H.-H.
Chiang, P.-Y. Hsieh, C.-C. Wu, C. H. Chou, Y. O. Su, G.-H. Lee, S.-
M. Peng, J. Am. Chem. Soc. 2002, 124, 11576–11577.
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1997, 9, 798–802.
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Markiewicz, R. Siemens, J. C. Scott, R. D. Miller, Chem. Mater.
1999, 11, 1800–1805.
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Mꢄllen, M. J. D. C. Silva, R. H. Friend, J. Am. Chem. Soc. 2003, 125,
437–443.
Bis[9,9-bis(n-butyl)fluorene] (9): The Suzuki coupling procedure de-
scribed above was followed using 2-bromo-9,9-bis(n-butyl)fluorene (1.0 g,
2.78 mmol), 9,9-bis(n-butyl)-2-fluorenylboronic acid (897 mg, 2.78 mmol),
Pd(OAc)2 (31 mg, 5 mol%), and tri(o-tolyl)phosphine (85 mg, 10 mol%).
The crude product was purified by column chromatography on silica gel
using petroleum ether as eluent to afford the desired product as a white
solid (1.02 g, 76% yield). 1H NMR (400 MHz, CDCl3, 258C): d = 7.71–
7.78 (m, 4H; ArH), 7.61–7.65 (m, 4H; ArH), 7.32–7.36 (m, 6H; ArH),
1.99–2.06 (m, 8H; CH2), 1.06–1.14 (m, 8H; CH2), 0.64–0.71 ppm (m,
20H; CH2CH3); 13C NMR (100 MHz, CDCl3, 258C): d = 151.3, 150.8,
140.6, 140.3, 140.2, 126.9, 126.7, 125.9, 122.8, 121.2, 119.8, 119.6, 55.1,
40.3, 26.1, 23.2, 13.9 ppm; MS (FAB): m/z: 554.6 [M+]; elemental analy-
sis calcd (%) for C42H50 (554.3912): C 90.92, H 9.08; found: C 90.73, H
8.98.
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Ulanski, H. Fujikawa, D. Neher, Appl. Phys. Lett. 2000, 76, 1810–
1812.
2,2’-Diiodo-bis[9,9-bis(n-butyl)fluorene] (10): The iodination procedure
described for the preparation of 3 was followed using bis[9,9-bis(n-butyl)-
2-bromofluorene] (816 mg, 1.47 mmol), iodine (410 mg, 1.62 mmol), con-
centrated sulfuric acid (2.0 mL), water (2.0 mL), and periodic acid
(456 mg, 1.62 mmol). The crude product was purified by column chroma-
tography on silica gel using petroleum ether as eluent to afford the de-
sired product as a white solid (1.01 g, 86% yield). 1H NMR (400 MHz,
CDCl3, 258C): d = 7.74 (d, J(H,H) = 8.0 Hz, 2H; ArH), 7.61–7.68 (m,
6H; ArH), 7.57 (s, 2H; ArH), 7.47 (d, J(H,H) = 8.4 Hz, 2H; ArH),
1.92–2.06 (m, 8H; CH2), 1.06–1.15 (m, 8H; CH2), 0.61–0.71 ppm (m,
20H; CH2CH3); 13C NMR (100 MHz, CDCl3, 258C): d = 153.4, 150.9,
140.8, 140.3, 139.4, 135.9, 132.1, 126.2, 121.5, 121.3, 120.1, 92.5, 55.3, 40.1,
25.9, 23.0, 13.8 ppm; MS (FAB): m/z: 806.5 [M+].
[13] T. Miteva, A. Meisel, W. Knoll, H. G. Nothofer, U. Scherf, D. C.
Mꢄller, K. Meerholz, A. Yasuda, D. Neher, Adv. Mater. 2001, 13,
565–570.
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2,2’’-Bis(diphenylamino)tetrakis[9,9-bis(n-butyl)fluorene], OF(4)-NPh:
The Suzuki coupling procedure described above was followed using 9,9-
bis(n-butyl)-2-diphenylamino-7-fluorenylboronic
0.75 mmol) and 2,2’-diiodo-bis[9,9-bis(n-butyl)fluorene]
acid
(367 mg,
(202 mg,
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0.25 mmol). The crude product was purified by column chromatography
on silica gel using petroleum ether/dichloromethane (4:1, v/v) as eluent
to afford a light-yellow solid (230 mg, 64% yield). 1H NMR (400 MHz,
CDCl3, 258C): d = 7.79–7.82 (m, 4H; ArH), 7.63–7.70 (m, 12H; ArH),
7.58–7.60 (m, 4H; ArH), 7.23–7.26 (m, 8H; ArH), 7.12–7.14 (m, 10H;
ArH), 6.98–7.05 (m, 6H; ArH), 2.08–2.12 (m, 8H; CH2), 1.88–1.96 (m,
8H; CH2), 1.07–1.17 (m, 16H; CH2), 0.70–0.77 ppm (m, 40H; CH2CH3);
13C NMR (100 MHz, CDCl3, 258C): d = 152.4, 151.8, 151.4, 148.0, 147.1,
140.4, 140.3, 140.2, 140.0, 139.9, 139.6, 135.9, 129.1, 126.1, 126.0, 123.8,
123.5, 122.5, 121.4, 121.3, 121.2, 120.4, 119.9, 119.4, 55.2, 55.1, 40.2, 40.0,
26.1, 23.1, 23.0, 13.9, 13.8 ppm; MS (FAB): m/z: 1442.1 [M+]; elemental
analysis calcd (%) for C108H116N2 (1440.9138): C 89.95, H 8.11, N 1.94;
found: C 89.89, H 8.26, N 2.19.
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Received: November 16, 2004
Published online: March 22, 2005
Chem. Eur. J. 2005, 11, 3285 – 3293
www.chemeurj.org
ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3293