Synthesis and structureproperty relationships of symmetric ambipolar quaterfluorene-containing oxadiazole as a central core and diphenylamine as end-capping moieties

Article abstract of DOI:10.1071/CH07368

A facile approach for the synthesis of the symmetric ambipolar quaterfluorene, OF(4)OX-NPh, with hole-transporting and electron-transporting moieties by Suzuki cross-coupling as a key reaction has been developed. This novel ambipolar quaterfluorene exhibi

Full text of DOI:10.1071/CH07368

Full Paper
CSIRO PUBLISHING
www.publish.csiro.au/journals/ajc
Aust. J. Chem. 2008, 61, 541–546
Synthesis and Structure–Property Relationships of
Symmetric Ambipolar Quaterfluorene-Containing
Oxadiazole as a Central Core and Diphenylamine
as End-capping Moieties
Fan Yang,A Xiao Ling Zhang,A Mo Jun Xiong,B Zi Jian Cao,A Ping Fang Xia,A
and Zhong Hui LiA,C
ASichuan College of Education, Chengdu, 610041, Sichuan Province, China.
BWest China School of Pharmacy, Sichuan University, Chengdu,
610041, Sichuan Province, China.
CCorresponding author. Email: zhonghli@sohu.com
A facile approach for the synthesis of the symmetric ambipolar quaterfluorene, OF(4)OX-NPh, with hole-transporting
and electron-transporting moieties by Suzuki cross-coupling as a key reaction has been developed. This novel ambipolar
quaterfluorene exhibits high thermal and electrochemical stabilities and is expected to possess potential application as a
double charge-transfer and light-emitting material in the field of single-layer organic emitting diodes.
Manuscript received: 20 October 2007.
Final version: 21 May 2008.
Introduction
devices.[9] We herein report the synthesis and functional proper-
ties of the novel symmetric ambipolar quaterfluorene OF(4)OX-
NPh, in which the hole-transporting, electron-transporting, and
emitting moieties are integrated into a single molecule; this
molecule has the electronic nature of D-π-A-π-D, which is
expected to show novel properties and could be used in fab-
ricating single-layer OLEDs. Furthermore, to compare and to
investigate the structure–property relationships of this series of
compounds, the functional properties of other quaterfluorene
analogues, i.e. OF(4), OF(4)-NPh, and OF(4)OX, are also shown
here (Fig. 1).
Highly electron-rich triarylamines known to have a high hole-
transporting mobility and to form stable cation radicals have
been widely used as hole-transporting materials in light-emitting
diodes (LEDs)[1] and shown potential as molecular magnets.[2]
It has been shown that light-emitting polymers grafted or end-
capped with triarylamine moieties exhibit improved LED device
performance.[3] Furthermore, highly electron-deficient oxadia-
zole (OXA) derivatives have been extensively used as electron-
transporting materials as they have efficient electron-transport
and hole-blocking characteristics and a high stability to high
current density in organic LEDs (OLEDs) devices.[4] However,
monodisperseoligofluorenes(OFs)haverecentlyattractedmuch
attention because of their chemical and thermal stabilities and
the possibility to vary the functional properties of the resulting
compounds via the substitution pattern on the C9 position of the
fluorenyl unit, as well as potential applications for optoelectronic
molecular materials, especially for OLED devices.[5] Recently,
we also found that the incorporation of triarylamines onto
the backbone of oligophenylenes (OPPs)[6] and OFs[7] could
improve the functional properties of the resulting molecules
and device performance of the resulting molecular material-
based OLEDs. In particular, we successfully incorporated the
hole-transporting triphenylamine unit and electron-transporting
oligothienyl moiety into one molecule to afford ambipolar
diphenylamino-end-capped oligofluorenylthiophenes as highly
efficient hole-transporting ambipolar emitters for OLEDs.[8] In
the field of single-layer OLEDs, researchers mainly focus on
combining the three components of hole transporting, electron
transporting and light-emitting into one molecule to simplify
device fabrication and to improve the performance of resulting
Results and Discussion
The strategy for preparation of triphenylamine- and oxadiazole-
based symmetric ambipolar quaterfluorene OF(4)OX-NPh
is outlined in Scheme 1. Monobromination of the 9,9-di
(n-butyl)fluorene[7a] afforded the corresponding 2-bromo-9,9-
di(n-butyl)fluorene in an excellent yield of 98% by controlling
Bu Bu
Bu Bu
Y
X
Y
Bu Bu
X ϭ Ϫ
Bu Bu
OF(4)
Y ϭ H
X ϭ Ϫ
X ϭ
Y ϭ NPh2 OF(4)-NPh
Y ϭ H OF(4)OX
N
N
O
N N
X ϭ
Y ϭ NPh2 OF(4)OX-NPh
O
Fig. 1. Structures of the quaterfluorene derivatives synthesized.
10.1071/CH07368 0004-9425/08/070541
© CSIRO 2008

542
F. Yang et al.
(a)
(b)
(c)
Br
COOH
COCl
98%
98%
56%
Bu Bu
Bu Bu
Bu Bu
Bu Bu
1
2
(d)
(e)
O
O
O
51%
NHHN
97%
N N
Bu Bu
Bu Bu
Bu Bu
Bu Bu
3
4
(f)
O
I
I
87%
N N
5
Bu Bu
Bu Bu
Bu Bu
(HO)2B
6
(g) 53%
O
Bu Bu
H
H
N N
2
2
N
B(OH)2
(g) 85%
Bu Bu
Bu Bu
7
OF(4)OX
Bu Bu
Bu Bu
O
N
N
N N
Bu Bu
Bu Bu
OF(4)OX-NPh
Scheme 1. Synthetic routes of symmetric ambipolar quaterfluorene OF(4)OX-NPh. Reagents and conditions:
(a) N-bromosuccinimide, acetone, 80◦C, overnight. (b) (i) 1.2 equiv. n-BuLi, THF, −78◦C, 1 h; (ii) dry ice, −78◦C–
room temp., 2 h. (c) SOCl2, reflux, 4 h. (d) 0.5 equiv. H2NNH2·H2O, pyridine, CHCl3, 0◦C–room temp., overnight.
(e) SOCl2, reflux, 4 h. (f) I2, HIO4, H2SO4–HOAc, 50◦C, overnight. (g) 5 mol-% Pd(OAc)2:2P(o-tolyl)3, 2 M
K2CO3, toluene/methanol, N2, 75◦C, overnight.
the total amount of N-bromosuccinimide (NBS) and reflux-
ing in acetone solution. Transformation of 2-bromo-9,9-di(n-
butyl)fluorene into 9,9-di(n-butyl)fluorenyl-2-carboxylic acid 1
was carried out in a moderate yield of 56% by lithium–bromine
exchange at low temperature, followed by reaction with dry ice
at room temperature and subsequently acid hydrolysis. Transfor-
mation of the carboxylic acid 1 into the corresponding carbonyl
chloride 2 was carried out in an excellent yield of 98% by
refluxing a mixture of 1 and an excess of thionyl chloride
(SOCl2). Condensation of two equivalents of carbonyl chloride 2
with one equivalent of hydrazine monohydrate (NH2NH2·H2O)
in the presence of a catalytic quantity of pyridine or triethy-
lamine at room temperature afforded the disubstituted hydrazine
3 in a moderate yield of 51%. Then, intramolecular dehydra-
tion of disubstituted hydrazine 3 in the presence of SOCl2
afforded 2,5-bis[9ꢀ,9ꢀ-bis(n-butyl)fluorenyl]-1,3,4-oxadiazole 4
in an excellent yield of 98%. Double-iodination of 4 by
I2/HIO4 gave the corresponding diiodide 5 in a good yield
of 87%. Suzuki cross-coupling between the diiodide 5 and
7-diphenylamino-9,9-di(n-butyl)fluorenyl-2-boronic acid 7[7a]
using Pd(OAc)2:2P(o-tolyl)3 as a catalyst afforded the desired
quarterfluorene derivative OF(4)OX-NPh in a good yield of
85%. OF(4)OX was also prepared in a moderate yield of 53%
by a similar Suzuki cross-coupling between diiodide 5 and
9,9-di(n-butyl)fluorenyl-2-boronic acid 6[7a] as in the synthetic
procedure for OF(4)OX-NPh. The newly synthesized quater-
fluorene derivatives OF(4)OX and OF(4)OX-NPh were fully
OF(4) and OF(4)-NPh, were also synthesized according to our
published procedures[7a] for comparison.
The decomposition temperatures (Tdec) of quaterfluorene
derivatives OF(4), OF(4)-NPh, OF(4)OX, and OF(4)OX-NPh
are 451, 464, 446, and 389◦C, respectively, indicating that
all the quaterfluorene derivatives have good thermal stability
(Table 1 and Fig. 2). It is worth mentioning that Tdec of the
diphenylamino end-capped quaterfluorene OF(4)-NPh remark-
ably improves in comparison with non-end-capped quaterfluo-
rene OF(4); however, the Tdec of ambipolar OF(4)OX-NPh is
lower than that of OF(4)OX, suggesting the ambipolar forma-
tion in one molecule may lower the thermal stability. Although
the quaterfluorene derivative without diphenylamino and oxadi-
azole moieties OF(4) could not form a stable amorphous glass,
the quaterfluorene containing the oxadiazole moiety, OF(4)OX,
exhibited a high (up to 87◦C) glass transition temperature
(Tg) and, more importantly, the glass transition temperature
of ambipolar quaterfluorene OF(4)OX-NPh, which is derived
from the OF(4)OX end-capped by two diphenylamino groups,
is up to 135◦C. All the above indicates that the incorporation
of the oxadiazole moiety onto the backbone of oligofluorene
is necessary for the formation of a stable amorphous glass,
and the incorporation of diphenylamino groups onto the back-
bone of oligofluorene can further enhance the glass transition
temperature.
In view of electronic absorption spectra, the absorption
bands or maxima of diphenylamino double-end-capped ambipo-
lar quaterfluorenes OF(4)OX-NPh and OF(4)-NPh peaked at
393 and 386 nm, and there was a substantial red shift (ꢀ 25 nm)
of the absorption maxima (λmax) on incorporation of strongly
electron-donating diphenylamino groups, which is attributed to
1
characterized by H and 13C NMR spectroscopy, mass spec-
trometry, and elemental analysis and found to be in good
agreement with their structures. Furthermore, the quaterfluo-
rene derivatives without oxadiazole or triphenylamine moieties,

Synthesis of Symmetric Ambipolar Quaterfluorene
543
Table 1. Summaries of measurements of quaterfluorene derivatives
CV, cyclic voltammetry; Fc, ferrocene; HOMO, highest occupied molecular orbitals
abs A
em A,B
E
F
G
H
Compounds
λ
[nm]
λ
[nm]
ΦA,C
τA,D [ns]
HOMOE [eV]
E1/2 [eV]
Eg [eV]
Tg [◦C]
Tdec [◦C]
max
max
(ε × 104 [M−1 cm−1])
OF(4)
361 (8.23)
410
432
0.93
0.94
0.98
0.92
5.53
5.14
0.73
0.95
0.34
0.79
0.94
0.69
1.02
0.37
0.97
3.02
2.76
–
451
464
OF(4)-NPh
386 (14.2)
117
OF(4)OX
368 (7.40)
393 (4.93)
423
472
0.59
0.99
1.79
1.72
5.82
5.17
3.02
2.82
87
446
389
OF(4)OX-NPh
135
AMeasured in CHCl3.
BExcited at the absorption maxima.
CUsing quinine sulfate monohydrate (Φ313 0.48) as a standard.
DUsing nitrogen laser as an excitation source.
EE1/2 v. Fc+/Fc estimated by CV method using platinum disc electrode as a working electrode, platinum wire as a counter electrode, and scanning calomel
electrode (SCE) as a reference electrode with an agar salt bridge connecting to the oligomer solution. All the potentials were calibrated with ferrocene, E1/2
(Fc/Fc+) = 0.45V v. SCE.
FEstimated from the edge of electronic absorption spectra.
GDetermined by differential scanning calorimeter from remelt after cooling with a heating rate of 10◦C min−1 under N2.
HDetermined by thermal gravimetric analyzer with a heating rate of 10◦C min−1 under N2.
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
110
100
90
OF(4)OX-NPh
OF(4)OX
OF(4)-NPh
OF(4)
OF(4)
OF(4)OX
OF(4)OX-NPh
OF(4)-NPh
80
70
60
50
40
30
20
200
400
600
800
1000
300
350
400
450
500
550
Temperature [°C]
Wavelength [nm]
Fig. 2. Thermal gravimetric analysis curves of quaterfluorene derivatives.
Fig. 3. Absorption spectra of quaterfluorene derivatives, measured in
CHCl3.
theasymmetricdestabilizationofthehighestoccupiedmolecular
orbitals (HOMO) and the lowest unoccupied molecular orbital
levels leading to a decrease in the energy gap[10] (Fig. 3 and
Table 1); however, the incorporation of an oxadiazole unit onto
the backbone of oligofluorene causes the resulting molecule
to be more planar than the analogue without the oxadiazole
end-capped triarylamine or at 361 nm corresponding to the
π → π∗ transition of the quaterfluorene core, the emission spec-
tra obtained are identical, suggesting that energy or exciton
can efficiently transfer from the end-capped triarylamine to the
quaterfluorene core. The fluorescence quantum yields (ꢁPL) of
OF(4), OF(4)-NPh, OF(4)OX, and OF(4)OX-NPh measured in
chloroform using quinine sulfate monohydrate as a standard
are 0.93, 0.94, 0.59, and 0.99, respectively,[11] indicating the
incorporation of the oxadiazole moiety onto the backbone of
quaterfluorene perturbs the coplanarity and reduces the fluores-
cence quantum yield of the resulting molecule; however, the
ꢁPL of diphenylamino end-capped quaterfluorene OF(4)OX-
NPh is larger than that of the homologue without diphenylamino
end-capping. This implies that in the excited state, better or
more π-orbital overlap is attained with the incorporation of
end-capping diphenylamino groups onto the backbone of quater-
fluorene. However, the emission spectrum of diphenylamino
unit in its electronic ground state, leading to a slightly red-
abs
max
shifted λ
.
[7a,10] The emission spectra of both non-end-capped
quaterfluorenes OF(4) and OF(4)OX have two peaks, at 410
and 430, and at 401 and 423 nm, respectively; however, the
emission spectra of diphenylamino-end-capped quaterfluorenes
OF(4)OX-NPh and OF(4)-NPh have only one peak at 472
and 432 nm, respectively, and show a significantly red shift
em
max
(ꢀ 22–50 nm) in λ
relative to that of the corresponding
OF(4)OX and OF(4) (Fig. 4 and Table 1). This indicates that
the excitation energy of diphenylamino-end-capped OF(4)OX-
NPh and OF(4)-NPh can be efficiently transferred, whereas
that of non-end-capped OF(4)OX and OF(4) cannot. On exci-
tation either at 324 nm attributed to the n → π∗ transition of

544
F. Yang et al.
OF(4)-NPh
OF(4)
OF(4)OX
OF(4)OX-NPh
OF(4)-NPh
1.0
0.8
0.6
0.4
0.2
0.0
OF(4)OX-NPh
350
400
450
500
550
600
650
0
400
800
1200
1600
2000
Wavelength [nm]
Potential [mV]
Fig. 4. Emission spectra of quaterfluorene derivatives, measured in
CHCl3.
Fig. 6. Cyclic voltammograms of OF(4)OX-NPh and OF(4)-NPh, mea-
sured in CH2Cl2 using a platinum disc electrode as a working electrode,
platinum wire as a counter electrode, and scanning calomel electrode as a
reference electrode.
PL in CHCl3
PL in film
1.0
0.8
onto the quaterfluorene backbone makes the resulting molecule
more stable to electrochemical oxidation. In general, owing to
the easy oxidation of triarylamine to form relatively more sta-
ble radical dications, with the incorporation of triarylamine, the
HOMO energy level of oligofluorenes moves up to ∼5.15 eV
(relative to the vacuum level) as estimated by the electrochem-
ical method. Such a high HOMO energy level greatly reduces
the energy barrier for the hole injection from indium tin oxide
(quantum yield (φ) = 5.0 eV) to the emissive oligofluorenes. As
a result, OF(4)OX-NPh and OF(4)-NPh can also be used as hole
transport or injection materials.
0.6
0.4
0.2
0.0
350
400
450
500
550
600
650
700
Wavelength [nm]
Conclusions
Fig. 5. Emission spectra of diphenylamino-end-capped quaterfluorene
OF(4)OX-NPh measured in CHCl3 and as a film.
A facile approach for synthesis of the symmetric ambi-
polar oligofluorene-containing hole-transporting and electron-
transporting moieties by Suzuki cross-coupling as a key reaction
has been presented. This approach will be applicable for the
construction of other structurally uniform and well-defined
π-conjugated functional ambipolar oligomers. All the quater-
fluorene compounds were characterized by a combination of 1H
and 13C NMR spectroscopy and elemental analysis. The newly
synthesized symmetric ambipolar oligofluorene OF(4)OX-NPh
exhibits good thermal and electrochemical stabilities.The details
of the OLED performance using this material as a charge transfer
and emitting layer will be reported in the future.
end-capped quaterfluorene OF(4)OX-NPh in a solid film is
452 nm, which blue-shifts ∼20 nm relative to its value in chloro-
form solution (Fig. 5). Furthermore, the fluorescence life-times
of all quaterfluorenes are in the nanosecond time-scale, sug-
gesting the emission originates from the singlet excited state to
ground state transition.
The electrochemical behaviours of these quaterfluorene
derivatives are tabulated in Table 1 and Fig. 6. The ambipolar
quaterfluorene OF(4)OX-NPh exhibits similar electrochemical
behaviour to the triphenylamine-based oligomers,[6,7] with one
reversible two-electron anodic redox couple (E1/2 ∼0.37 eV)
that corresponds to removal of electrons from the end-capped
arylamino group of the ambipolar molecule, and another irre-
versible one-electron anodic redox couple (E1/2 ∼0.97 eV) that
corresponds to removal of electrons from the oligofluorene core
containing oxadiazole, forming radical bis-cations and a single
cation, respectively (Fig. 6). The similar oxidation potentials of
the quaterfluorene backbones of OF(4), OF(4)-NPh, OF(4)OX,
andOF(4)OX-NPhare0.95, 0.94, 1.02, and0.97 eV, respectively,
suggesting they are almost unaffected by the structures of the
oligofluorene cores. Furthermore, the first oxidation potential
values (E1/2: 0.37 and 0.34 eV) of OF(4)OX-NPh and OF(4)-
NPh are much smaller than those of the corresponding non-end-
capped OF(4)OX (E1/2 = 1.02 eV) and OF(4) (E1/2 = 0.73 eV)
(Table 1), indicating that incorporation of diphenylamino groups
Experimental
General Procedures and Requirements
All the solvents were dried by the standard methods wher-
ever needed. 1H NMR spectra were recorded using either a
JEOL JHM-EX270 FT NMR spectrometer or a Varian INOVA-
400 FT NMR spectrometer and are referenced to residual
CHCl3 (7.24 ppm) or DMSO (2.5 ppm). 13C NMR spectra were
recorded using a Varian INOVA-400 FT NMR spectrometer and
are referenced to CDCl3 (77 ppm) or [D6]DMSO (39.5 ppm).
Mass spectroscopy (MS) measurements were carried out using
fastatombombardment(FAB)onanAPIASTARPulsarIHybrid
mass spectrometer. Elemental analysis was carried on a CARLO
ERBA 1106 ElementalAnalyzer. Thermal stabilities were deter-
mined with a thermal gravimetric analyzer (PE-TGA6) with

Synthesis of Symmetric Ambipolar Quaterfluorene
545
a heating rate of 10◦C min−1 under N2. Glass transitions and
melting transitions were extracted from the second-run differen-
tial scanning calorimetry (DSC) traces, which were determined
with a DSC (PE Pyris Diamond DSC) with a heating rate of
10◦C min−1 under N2. All the physical measurements were per-
formed in CHCl3 including electronic absorption (UV-visible)
andfluorescencespectra. Electronicabsorption(UV-visible)and
fluorescence spectra were recorded using aVarian Cary 100 Scan
Spectrophotometer and a PTI luminescence spectrophotometer,
respectively. The fluorescence quantum yields in chloroform
were determined by the dilution method using quinine sulfate
monohydrate (λexc 313 nm, Φ 0.48) as a standard. The fluores-
cence decay curves were recorded at room temperature using
a nitrogen laser for excitation. The lifetimes were estimated
from the measured fluorescence decay using an iterative fit-
ting procedure. E1/2 v. ferrocene (Fc)+/Fc was estimated by the
cyclic voltammetric method (Voltammetric Analyzer CV-50W)
using platinum disc electrode as a working electrode, platinum
wire as a counter electrode, and scanning calomel electrode
(SCE) as a reference electrode with an agar salt bridge con-
necting to the oligomer solution dissolved in CH2Cl2, using
0.1 M of Bu4NPF6 as a supporting electrolyte with a scan rate of
100 mV s−1, and all the potentials were calibrated with ferrocene
(E1/2 (Fc/Fc+) = 0.43V v. SCE) as an external standard.
δC (100 MHz, CDCl3) 168.3, 152.2, 151.2, 148.4, 138.9, 131.5,
131.3, 129.2, 127.2, 125.5, 123.1, 121.1, 119.7, 55.4, 39.9, 26.0,
23.0, 13.8. m/z (FAB) 340.5 [M+].
1,2-Bis[9ꢀ,9ꢀ-bis(n-butyl)fluorene-2ꢀ-carbonyl]
Hydrazine 3
To a mixture of 9,9-bis(n-butyl)fluorene-2-carbonyl chloride
2 (1.91 g, 5.6 mmol), pyridine (475 mg, 5.6 mmol) and chlo-
roform (30 mL) was added dropwise a solution of hydrazine
(H2NNH2·H2O, 127 mg, 2.6 mmol) in chloroform (20 mL) in an
ice–water bath while maintaining good magnetic stirring. After
completion of the addition, the reaction mixture was stirred for
another 4 h at room temperature. The reaction mixture was first
poured into water, and then sodium carbonate (2 M) was added
in a dropwise fashion until a neutral solution was obtained and
the solution extracted with dichloromethane (3 × 50 mL). The
combined organic layers were dried over anhydrous Na2SO4
and evaporated to dryness. The crude product was then purified
by silica gel column chromatography using petroleum spirits/
EtOAc as gradient eluent, affording the desired hydrazine 3 as
a white solid (830 mg, 51%). δH (400 MHz, CDCl3) 9.78 (s,
2H), 7.92 (d, J 6.8, 4H), 7.77–7.71 (m, 4H), 7.34 (d, J 5.4, 6H),
2.02–1.96 (m, 8H), 1.06–0.98 (m, 8H), 0.63–0.49 (m, 20H).
δC (100 MHz, CDCl3) 164.4, 151.5, 151.2, 145.5, 139.6, 129.6,
128.2, 126.9, 126.4, 123.0, 121.7, 120.5, 119.8, 55.4, 40.1, 26.0,
23.0, 13.9. m/z (FAB) 641.8 [M+ + 1].
Synthesis
9,9-Bis(n-butyl)fluorene-2-carboxylic Acid 1
2,5-Bis[9ꢀ,9ꢀ-bis(n-butyl)fluorenyl]-1,3,4-oxadiazole 4
To a 100-mL two-necked flask containing 9,9-bis(n-butyl)-
2-bromofluorene (3.80 g, 10.60 mmol) in 20 mL dried THF
equipped with a magnetic stirrer was added dropwise 1.5 M
n-butyl lithium (8.5 mL, 12.73 mmol) under a nitrogen atmo-
sphere with a −78◦C acetone–dry ice bath while maintaining
good stirring. After stirring for 1 h, dry ice (0.70 g, excess) was
added. After stirring for another 2 h, water was added to the
reaction mixture, and then HCl (6 M) was added in a dropwise
fashion until an acidic solution was obtained. The reaction mix-
ture was poured into water and extracted with dichloromethane
(3 × 50 mL).The combined organic layers were dried over anhy-
drous Na2SO4 and evaporated to dryness. The crude product
was then purified by silica gel column chromatography using
petroleum spirits/EtOAc as gradient eluent, affording the desired
carboxylic acid as a white solid (1.08 g, 56%). δH (400 MHz,
CDCl3) 8.14 (dd, J 8.0, 1H), 8.09 (s, 1H), 7.79–7.76 (m, 2H),
7.38–7.35 (m, 3H), 2.08–1.97 (m, 4H), 1.11–1.02 (m, 4H), 0.67–
0.59 (t, J 7.4, 6H), 0.57–0.51(m, 4H). δH (400 MHz, [D6]DMSO)
12.91 (s, 1H), 7.94 (s, 4H), 7.48 (s, 1H), 7.38 (s, 2H), 2.01
(s, 4H), 1.00 (s, 4H), 0.60 (s, 6H), 0.43 (s, 4H). δC (100 MHz,
CDCl3) 172.7, 151.9, 150.8, 146.8, 139.7, 129.6, 128.5, 127.6,
127.0, 124.6, 123.1, 120.7, 119.5, 55.2, 40.0, 25.9, 23.0, 13.8.
m/z (FAB) 322.5 [M+].
After a mixture of 1,2-bis[9ꢀ,9ꢀ-bis(n-butyl)fluorene-2ꢀ-
carbonyl] hydrazine 3 (0.81 g, 1.26 mmol) and thionyl chloride
(SOCl2, 10 mL, excess) was refluxed for 4 h, the excess thionyl
chloride was removed by simple distillation. The residue mix-
ture was poured into ice–water, and dichloromethane (100 mL)
was added to dissolve the solid product, the organic layer was
collected and washed with water first, then sodium carbonate
(2 M) until a neutral solution was obtained, and lastly water. The
organic layer was dried over anhydrous Na2SO4 and evaporated
to dryness, affording the desired pure oxadiazole derivative 4 as a
white solid (766 mg, 97%). δH (400 MHz, CDCl3) 8.16–8.12 (m,
4H), 7.86–7.83 (m, 2H), 7.78–7.76 (m, 2H), 7.38–7.37 (m, 6H).
δC (100 MHz, CDCl3) 165.1, 151.6, 151.4, 144.7, 139.9, 128.3,
127.0, 126.0, 123.0, 122.3, 121.3, 120.4, 120.1, 55.4, 40.1, 25.9,
23.0, 13.8. m/z (FAB) 623.7 [M+ + 1]. Calc. for C44H50N2O C
84.8, H 8.1, N 4.5. Found C 84.9, H 8.2, N 4.5%.
2,5-Bis[9ꢀ,9ꢀ-bis(n-butyl)-2ꢀ-iodofluorenyl]-
1,3,4-oxadiazole 5
A
mixture of 2,5-bis[9ꢀ,9ꢀ-bis(n-butyl)fluorenyl]-1,3,4-
oxadiazole 4 (512 mg, 0.82 mmol), acetic acid (10 mL), water
(1 mL), concentrated sulfuric acid (1 mL), iodine (229 mg,
0.90 mmol), iodic acid (309 mg, 0.90 mmol), and carbon tetra-
chloride (2 mL) was heated at 50◦C overnight with good
magnetic stirring. After the product slurry was cooled to
room temperature, it was poured into water and extracted
with dichloromethane (3 × 50 mL). The combined dark purple
organic layers were decolourized with sodium sulfite, washed
with water, dried over anhydrous Na2SO4, filtered, and evap-
orated to dryness. Purification of the crude product by sil-
ica gel column chromatography using 1:1 petroleum spirits/
dichloromethane afforded the title compound as a yellow solid
with an isolated yield of 87% (624 mg). δH (400 MHz, CDCl3)
8.14 (d, J 8.4, 8H), 7.81 (d, J 8.8, 2H), 7.69 (d, J 8.8, 4H),
9,9-Bis(n-butyl)fluorene-2-carbonyl Chloride 2
After refluxing a mixture of 9,9-bis(n-butyl) fluorene-2-
carboxylic acid 1 (1.80 g, 5.60 mmol) and thionyl chloride
(SOCl2, 10 mL) for 2 h, the excess thionyl chloride was removed
by simple distillation. Benzene (80 mL) was added to the reac-
tion mixture and then was distilled out by simple distillation
to remove the by-product sulfite acid (H2SO3), affording the
colourless liquid residue product with an isolated yield of 98%
(1.91 g). δH (400 MHz, CDCl3) 8.15 (dd, J 8.1, 1H), 8.03 (d, J
1.6, 1H), 7.78 (d, J 8.4, 2H), 7.41–7.34 (m, 3H), 2.04–1.98 (m,
4H), 1.11–1.00 (m, 4H), 0.65 (t, J 7.3, 6H), 0.60–0.51 (m, 4H).

546
F. Yang et al.
7.50 (d, J 8.4, 2H), 2.10–1.94 (m, 8H), 1.13–1.04 (m, 8H), 0.65
(t, J 7.4, 12H), 0.60–0.52 (m, 8H). δC (100 MHz, CDCl3) 165.0,
153.6, 151.0, 143.7, 139.5, 136.2, 132.2, 126.1, 122.8, 122.0,
121.3, 120.3, 94.2, 55.6, 40.0, 25.9, 22.9, 13.8. m/z (FAB) 875.4
[M+ + 1].
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123.5, 122.5, 122.3, 121.4, 121.2, 120.7, 120.2, 119.4, 119.3,
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We are grateful to the Scientific and Technological Support Project of
Sichuan Province (2008GZ0041) for financial support of the present work.