temperature in the dark. The reaction mixture was stirred at
room temperature for 24 h, the resulting solution treated with
HCl (0.1 M, 10 mL), neutralized with NaHCO , and then
extracted with chloroform several times. After filtration and
solvent evaporation, the residual solid was recrystallized from
1
hexane, to give a white crystalline solid (yield 56%). H NMR
Characterization methods
1
The H NMR spectra were recorded on a AVANCE 500
spectrometer at 298 K with deuterated chloroform or dimethyl
sulfoxide (DMSO) as the solvent and tetramethylsilane (TMS)
as the standard. The compounds were characterized on a Flash
EA 1112 CHNS–O elemental analysis instrument. IR spectra
3
(
1
500 MHz, CDCl
H, ArH), 7.650–7.634 (d, 1H, ArH), 7.546–7.531 (d, 1H,
ArH), 7.510–7.491 (d, 2H, ArH), 7.398–7.368 (t, 1H, ArH),
.342–7.310 (t, 1H, ArH), 3.890 (s, 2H, ArCH Ar). Anal.: calcd
for C13 Br: C, 63.70; H, 3.70; found: C, 63.59; H, 3.76.
3
): d ~ 7.766–7.751 (d, 1H, ArH), 7.682 (s,
were recorded on a Perkin–Elmer spectrophotometer in the
4
21
00–4000 cm region using a powdered sample on a KBr
plate. The LC–MS and MS–TOF mass spectra were recorded
using a Applied Biosystems QSTAR instrument. UV–Vis
absorption spectra were recorded on a UV-3100 spectro-
photometer. Fluorescence measurements were carried out with
a RF-5301PC instrument. Differential scanning calorimetry
7
2
H
9
Synthesis of 2-bromo-9,9’-dihexylfluorene (3)
Compound 2 (1 g, 4.08 mmol), 1-bromohexane (1.7 mL,
2 mmol), tert-butylammonium bromide (0.129 g, 0.4 mmol)
and NaOH (0.48 mL, 50% w/w) were mixed in a 100 mL round-
bottomed flask under a nitrogen atmosphere. The mixture was
heated at 90 uC for 24 h. After the mixture was cooled to room
temperature, water was added to the resulting solution and it
was extracted with chloroform several times. The organic phase
was dried over anhydrous magnesium sulfate. After filtration
and solvent evaporation, the yellow liquid was purified by
(
DSC) analysis was carried out using a NETZSCH (DSC-204)
2
1
instrument at 10 uC min
whilst flushing with nitrogen.
Electrochemical measurements were performed with a Bioa-
nalytical Systems BAS 100 W instrument, using a glassy carbon
working electrode, a platinum wire auxiliary electrode with a
porous ceramic wick, and a Ag/Ag reference electrode,
standardized for the redox couple ferricinium/ferrocene. Cyclic
voltammetric studies of TFB were carried out in MeCN
containing 0.1 M NBu PF (tetra-n-butylammonium hexa-
4 6
fluorophosphate) as the supporting electrolyte. The electro-
chemical investigations on the oligomer were carried out on a
1
1
column chromatography (silica gel, cyclohexane) to afford a
1
colorless oil (yield 41%). H NMR (500 MHz, CDCl ): d ~
thin layer of material deposited on glassy carbon from a CHCl
solution.
3
3
7
1
1
6
.670–7.651 (m, 1H, ArH), 7.560–7.542 (d, 1H, ArH), 7.469 (s,
H, ArH), 7.336–7.275 (m, 4H, ArH), 1.95–1.92 (m, 4H, CH2),
.12–1.09 (m, 4H, CH ), 1.04–1.03 (m, 8H, CH ), 0.78–0.75 (m,
Devices fabricated by spin-coating
2
2
H, CH
3 2
), 0.59–0.57 (m, 4H, CH ) ppm.
The typical device configuration fabricated by spin-coating was
ITO/PEDOT/TFB/Ba/Al. Indium–tin oxide (ITO)-coated glass
2
1
with a sheet resistance of v50 V % was used as the substrate.
Pre-treatment of ITO included a routine chemical cleaning
using detergent and alcohol in sequence, followed by oxygen
plasma cleaning. The PEDOT (3,4-polyethylenedioxythiophene–
polystyrenesulfonate) layer was deposited onto the ITO-coated
substrate as the buffer layer. The TFB film was formed on the
PEDOT layer by spin-coating a toluene solution with a
Synthesis of 9,9’-dihexylfluorene-2-carbaldehyde (4)
Compound 3 (0.413 g, 1 mmol) was dissolved in THF (15 mL)
and the flask purged with nitrogen. A 15% solution of n-BuLi
in hexane (0.7 mL, 1.4 mmol) was added dropwise at
278 uC. After 3 h at this temperature, dry degassed DMF
(
0.4 mL) was added, and the reaction was allowed to continue
2
1
concentration of 5 mg mL to give a film thickness of 50–
0 nm. The Ba cathode was deposited by thermo-evaporation
and was followed by a thick Al capping layer.
for an additional 12 h at 0 uC. The resulting solution was
evaporated under reduced pressure, and solid residue was
7
2
1
stirred with 10 mL CH
temperature for 20 min. The organic layer was separated,
washed with saturated NaHCO , dried with Na SO , and the
2 2
Cl and 10 mL HCl (3 mol L ) at room
Devices fabricated by vacuum evaporation
3
2
4
solvent removed under reduced pressure. The crude product
was purified by column chromatography using dichloro-
The typical device configuration fabricated by vacuum
evaporation was ITO/NPB/TFB/BCP/LiF/Al. The organic
1
2
6
methane as solvent to give a colorless oil (yield 66%).
H
layer was deposited by high vacuum (10
Torr) thermal
NMR (500 MHz, DMSO): d ~ 10.05 (s, 1H, CHO), 8.05–8.04
d, 1H, ArH), 7.97 (s, 1H, ArH), 7.96–7.94 (d, 1H, ArH), 7.93–
.91 (d, 4H, ArH), ), 7.52–7.51 (d, 1H, ArH), 7.44–7.38 (m, 2H,
evaporation onto a cleaned ITO glass substrate. The layer
thickness of the deposited material was monitored in situ using
an oscillating quartz thickness monitor. Finally a LiF buffer
layer and Al cathode were vapor-deposited onto the organic
films at a background pressure of 10 Torr. The EL spectra
´
and Commission Internationale de l’Eclairage (CIE) coordi-
(
7
ArH), 2.07–2.02 (m, 4H, CH ), 1.03–0.95 (m, 12H, CH ), 0.72–
2
2
2
6
0
.69 (m, 6H, CH ), 0.47–0.44 (m, 4H, CH ) ppm.
3
2
nates of these devices were measured by a PR650 Spectroscan
spectrometer. The luminance–current density–voltage charac-
teristics were recorded simultaneously with the EL spectra by
combining the spectrometer with a Keithley model 2400
programmable voltage–current source. All measurements
were carried out at room temperature under ambient
conditions.
Synthesis of 2,5,2’,5’-tetra(9,9’-dihexylfluorenyl)biphenyl (TFB)
Compound 4 (0.217 g, 0.6 mmol) and tetra(phosphonate) 5
(
0.158 g, 0.1 mmol) were dissolved in a mixture of anhydrous
ethanol (10 mL) and THF (10 mL) in a 100 mL oven-dried
round-bottomed flask, equipped with a magnetic stirring bar
and capped with a rubber septum. A freshly prepared 5%
solution of sodium ethoxide in ethanol (0.090 g, 0.8 mmol) was
added dropwise to the reaction flask via a syringe at room
temperature. The reaction mixture was stirred at room
temperature under an argon atmosphere. The resulting
solution was twice precipitated from methanol to give a light
Results and discussion
Synthesis and characterization of TFB
As shown in Scheme 1, the oligo(phenylenevinylene) dimer
TFB containing a biphenyl linkage center and fluorene end
segments was prepared by a Wittig reaction. The structure of
1
yellow solid (yield 60%). H NMR (500 MHz, DMSO): d ~
7
.78–7.28 (m, 42H), 2.09–1.93 (m, 16H, CH
8H, CH ), 0.71–0.62 (m, 24H, CH ), 0.60–0.49 (m, 16H, CH )
2
), 0.98–0.85 (m,
1
4
ppm.
2
3
2
TFB was identified by FT-IR, H NMR and HPLC mass
spectrometry. The FT-IR spectrum of TFB is shown in Fig. 1.
2
7 3 6
J . M a t e r . C h e m . , 2 0 0 4 , 1 4 , 2 7 3 5 – 2 7 4 0