Facile synthesis and optoelectronic properties of N,N- difluorenevinylaniline-based molecules

Article abstract of DOI:10.1039/c2nj40051k

A series of RGB molecules (FXs) with a tuneable light-emitting core and difluorenylamino-based peripheries were synthesized through the Heck coupling reaction in good yields. The intramolecular energy transfers and antenna effects were verified in this series of compounds. Strong photoluminescence (PL) from deep blue (～415 nm) to saturated red (～645 nm) was observed. The FXs exhibit good solubility and stability, high fluorescence quantum efficiency (up to 93% in THF and 73% in film), short lifetime (1.3-2.6 ns), and high charge injection and transport properties, revealed by both experimental measurements and theoretical calculations. The preliminary organic light-emitting diode devices exhibit only slightly blue-shifted electroluminescence in comparison with PL without stack characters. This full-colour emitting and solution-processable D-π-X-π-D star-burst molecules are highly attractive for organic optoelectronics. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2012.

Full text of DOI:10.1039/c2nj40051k

View Article Online / Journal Homepage / Table of Contents for this issue
Dynamic Article Links
NJC
Cite this: New J. Chem., 2012, 36, 1512–1518
www.rsc.org/njc
PAPER
Facile synthesis and optoelectronic properties of
N,N-difluorenevinylaniline-based moleculesw
Zhao-Min Lin,a Chao Zheng,a Jian-Jian Xiao,a Run-Feng Chen,*a Ping Zhao,b
Juan Song,a Zhong-Fu An,a He Tianb and Wei Huang*a
Received (in Montpellier, France) 21st January 2012, Accepted 18th April 2012
DOI: 10.1039/c2nj40051k
A series of RGB molecules (FXs) with a tuneable light-emitting core and difluorenylamino-based
peripheries were synthesized through the Heck coupling reaction in good yields. The
intramolecular energy transfers and antenna effects were verified in this series of compounds.
Strong photoluminescence (PL) from deep blue (B415 nm) to saturated red (B645 nm) was
observed. The FXs exhibit good solubility and stability, high fluorescence quantum efficiency
(up to 93% in THF and 73% in film), short lifetime (1.3–2.6 ns), and high charge injection
and transport properties, revealed by both experimental measurements and theoretical
calculations. The preliminary organic light-emitting diode devices exhibit only slightly
blue-shifted electroluminescence in comparison with PL without stack characters.
This full-colour emitting and solution-processable D–p-X–p-D star-burst molecules are
highly attractive for organic optoelectronics.
owing to their good solubility and appropriate viscosity.
Introduction
Moreover, the aggregation of the emissive chromophore cores
can be effectively suppressed by the introduced arms to ensure
color purity.8 However, such big size molecules require high
synthetic cost.
Organic light-emitting diodes (OLEDs) have achieved considerable
progress1 in applications of flat-panel displays and solid-state
lighting since Tang and VanSlyke’s report in 1987.2 Many red,
green, and blue (RGB) light-emitting organic materials, either
fluorescent or phosphorescent, have been developed,3 but highly
efficient materials based on simple structure with emission tunable
over the entire visible spectrum and good processability are still
rare.4 To address such issues, starburst molecules, in which several
linear arms stretch in different orientations of a central core, have
attracted much attention recently for applications in OLEDs.5 With
respect to their small molecular and polymer counterparts,6
starburst molecules present the advantages of monodisperse
unequivocal chemical structures, potentially better reproducibility
of synthesis and purification, more straightforward analysis of
structure–properties relationships, and good film-forming
properties for device fabrications (solution-processable).7 Starburst
molecules with emitting cores can also be solution-processed
One molecular architectural design strategy of the starburst
molecule for OLEDs is to mimic the natural photosynthetic
bacteria, which involve chlorophyll as the light harvesting
antenna that captures the sunlight and funnels the electronic
excitation cascading into the photosynthetic reaction center,
where the photon energy is converted into electronic energy.9
In such a light-harvesting or charge-harvesting antenna
complex, the excitation energy is delocalized and transferred
effectively from the surrounding arms to the light-emitting
core, resulting in the accumulated energy at the core and the
high quantum yield of photoluminescence. This enhanced light
emission due to the efficient energy transfer and antenna
effects, the good reproducibility and processability of the
starburst molecules, and the independently determined emitting
color and charge injection and transport properties by the
central core and the surrounding arms of the starburst molecule
are ideal for high-performance OLEDs as well as other organic
electronic devices.10
a Key Laboratory for Organic Electronics & Information Displays,
Institute of Advanced Materials, Nanjing University of Posts &
Telecommunications, Nanjing 210046, China.
E-mail: wei-huang@njupt.edu.cn, iamrfchen@njupt.edu.cn;
Fax: (+)86 25 8586 6999
In this paper, a facile synthesis of a series of anisomerous
‘‘Y’’ or symmetrical ‘‘H’’ shaped binuclear starburst molecules
in which the oligo(p-phenylene vinylene)s or an analogical unit
is employed as the center, and a bis(dibutylfluorenyl)amino
group as a light-harvesting (or charge-harvesting) branching
unit has been developed through the Heck coupling reaction in
good yields. Such triarylamine-based molecular design takes
b Key Laboratory for Advanced Materials and Institute of Fine
Chemicals, East China University of Science & Technology,
Shanghai 200237, China
w Electronic supplementary information (ESI) available: Computa-
tional details, NMR spectra, ESI-TOF HRMS spectra, fluorescence
decay profile and cyclic voltammograms. See DOI: 10.1039/
c2nj40051k
c
1512 New J. Chem., 2012, 36, 1512–1518
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2012

View Article Online
advantage of triarylamine units which have the prominent
electron donating ability and hole-transport properties,11 of
the oligo(p-phenylene vinylene)s-like cores which are actively
investigated for use in OLEDs and solar cells due to their high
stability and luminescent efficiency,12 and of the 9,90-dibutyl-
fluorene arms which act as the antenna and provide good
solubility and film-forming abilities of the material.13 From
N,N,-bis(9,9-dibutyl-fluoren-2-yl)-4-vinylaniline (F) which is a
starburst electron donor (D), DFPh, DFTh, and DFTb were
obtained with a binuclear starburst molecular architecture of
D–p-X–p-D, where D is F and X is phenyl, thiophenyl, and
benzothiadiazolyl respectively. By slightly changing X with the
same synthetic method, these D–p-X–p-D molecules (FXs)
show strong photoluminescence from deep blue (B415 nm) to
saturated red (B645 nm) in both dilute THF solution and thin
solid film. In comparison with the conventional red (DCM,
4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran;
DCJTB, 4-(dicyanomethylene)-2-tert-butyl-6(1,1,7,7-tetramethyl-
julolidyl-9-enyl)-4H-pyran; and RD3, tetraphenyldibenzo-
periflanthene), green (AlQ3, 8-hydroxylquinoline aluminium;
with high stereo- and regio-selectivity, the E-configured double
bonds of FXs were confirmed from the values of the coupling
constant (J) between vinyl protons (ca. 16 Hz).15 FXs are
highly soluble in common organic solvents and uniform films
can be fabricated by spin coating. The thermal stability of FXs
was investigated by differential scanning calorimetry (DSC)
and thermogravimetric analysis (TGA). The melting points
(Tm) of F, DFPh, DFTh, DFTb were 60, 103, 131 and 136 1C,
respectively. The temperatures with 5% weight loss (Td) for F,
FF, DFPh, DFTh, DFTb were 320, 397, 403, 318, and 388 1C,
respectively (see Table 1), which are good enough for applications
in optoelectronic devices.
The photophysical properties of FXs were investigated both
in dilute solutions and in thin films as shown in Fig. 1 and
Table 1. Except for the Y-shaped F and FF, the dumbbell-like
(H-shaped) FXs show two distinct absorption bands in the
range of 300–400 and 400–600 nm, respectively, in both THF
and solid film, which contribute from the rupture of conjugated
structure of FXs by twisting the C–N bond. The first absorption
band is due to the bis(9,9-dibutyl-fluoren-2-yl)amine group which
is the main peripheral component of the FXs. All of FXs have a
similar absorption band with maximum in a narrow range
(361–375 nm) both in solution and film. Furthermore,
this absorption peak is consistent with those reported for
poly(9,9-dioctylfluorene) (383 nm in THF),16 and can be attributed
to the fluorene segments in the compounds. The second absorption
band varies in a wide range from 400–600 nm according to the
different aryl incorporation of cores. In dilute THF solution, FF
just has a weak shoulder around 420 nm, DFPh shows a clear peak
at 429 nm, DFTh exhibits a peak at 460 nm and a shoulder around
500 nm, and DFTb’s absorption peak is at 540 nm. This signifi-
cantly red-shifted second absorption band is assigned to the p–p*
transition of the core part of the dumbbell-shaped molecules. Both
absorption bands are almost identical in solution and solid film due
to the Y- and H-shaped molecular architectures which significantly
prevent the intermolecular interaction in the solid state and
improve the luminescent efficiency of the materials, as widely
observed in the star-shaped molecules.17
C545T,
10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetra-
hydro-1H,5H,11H-benzo[l]pyrano
[6,7,8-ij]quinolizin-11-one),
and blue (DPAVBi, 4,40-bis[4-(di-p-tolylamino)styryl]biphenyl)
dyes, these emission-tunable molecules of FXs exhibit larger
molecular weight from 900 to 1500, wider emission spectra
coverage, and better solution processability. These facilely
synthesized starburst D–p-X–p-D molecules are very attractive
for solution processable full-color displays.
Results and discussion
FXs were synthesized according to Scheme 1. The key step is
the synthesis of F, which is not only one of the target
compounds but also the starting material for other FXs. With
4-vinylaniline, which was prepared facilely in two steps with good
yields, the Pd-catalyzed amination14 of 2-bromo-9,9-dibutylfluorene
under inert conditions produces F in good yield. The other
FXs were prepared via Heck coupling reactions of F with
dibromoaryls in high yields. Since the Heck reaction proceeds
The photoluminescent (PL) spectra of FXs have only one
peak from deep blue (B415 nm, F) to saturated red (B645 nm,
DFTb) in dilute THF solution and thin film, under excitation at
the longest absorption peak wavelength, i.e. at the first absorption
peak for F and FF and at the second for others. In order to further
investigate the light emission and energy transfer of this particular
molecular system, PL spectra excited at the first absorption peak
wavelength of 370 nm, which is believed to be aroused by
the absorption of bis(9,9-dibutyl-fluoren-2-yl)amine, were also
performed (see Fig. 1b and d). Interestingly, the same emission
spectra of FXs were observed (except for DFTb), suggesting the
identical luminophore at the different exciting wavelengths and a
highly efficient intermolecular energy transfer process (B100%)
from peripherial fluorene segments to the central luminophore was
expected. The efficient energy transfer is also facilitated by the
short distance between the energy donor (periphery) and
the energy accepter (core). Consequently, an antenna system
for light-harvesting was formed in this molecular system. The
surrounding fluorene segments can also act as protecting groups
for the inner luminophore to prevent the formation of excimer,
electromer, or other intermolecular interactions, enabling FXs as
Scheme 1 Synthetic route of FXs.
c
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2012
New J. Chem., 2012, 36, 1512–1518 1513

View Article Online
Table 1 Thermal, optical, and electrochemical properties of FXs
Thermal analysisa PL in solutionb
PL in thin filmb
Energy levels from CVc
te
EHOMO
ELUMO
cvEg
d
c
d
Tm
Td
labs
lem
FPL
labs
lem
optEg
FPL
Compd
F
FF
DFPh
60
—
103
320
397
403
363
375
373
428
372
457
375
540
413
476
494
60
64
48
93
48
67
72
83
361
368
373
429
370
460
371
535
420
486
513
3.00
2.75
2.54
24
41
27
34
12
16
49
73
2.03
1.35
1.53
ꢀ5.50
ꢀ5.48
ꢀ5.54
ꢀ2.40
ꢀ2.76
ꢀ2.91
3.10
2.72
2.63
DFTh
DFTb
131
136
318
388
524
554
640
2.36
2.00
2.12
2.64
ꢀ5.44
ꢀ5.56
ꢀ2.92
ꢀ3.09
2.52
2.47
422
648
a
b
The melting point (Tm) and decomposition temperature (Td) (1C). The maximum of absorption (labs) and emission (lem) spectra (nm).
c
d
HOMO (EHOMO) and LUMO (ELUMO) energy levels and optical (optEg) and electrochemical (cvEg) band-gaps (eV). Photofluorescence
e
quantum yields (FPL) measured by using an integrating sphere when excited at corresponding labs in the same row (%). Lifetime (t, ns) measured
using a time-correlated photon-counting instrument when excited at 370 nm; the fitting coefficiencies (w2) were 1.002 for F, 1.190 for FF, 1.085 for
DFPh, 1.072 for DFTh, and 1.265 for DFTb respectively.
Fig. 2 FXs excited at 365 nm in (a) film and (b) THF solution with
(c) the corresponding CIE(1931) coordinates (J: solution; ’: film).
sphere (see Table 1). Higher FPLs were recorded in THF solutions
than in films, as found in many conjugated systems. The relatively
lower FPL of DFTh in solid film is due to the heavy atom
quenching effect of sulfur in the light-emitting core (thiophene).
The high FPLs of FXs suggest that this kind of material is highly
luminescent and attractive for light-emission related applications.
Fig. 1 Absorption and PL spectra of FXs in THF (a and b) and film
The energy transfer process of this material system can be also
(c and d). PL spectra were recorded under excitation at 363–375 nm.
investigated via FPL. For FXs with dual absorption character,
higher FPLs were obtained when excited at the second absorption
potential high performance OLED materials. For DFTb in
dilute solution, residual fluorescence in the short wavelength
region corresponding to the emission of F segment was
observed due to its incomplete intramolecular energy transfer,
while in the solid state, this energy transfer process is enhanced
and only the red emission of the central luminophore was
detected, which may contribute from the intermolecular
energy transfer due to the shorter distance between molecules.
In thin solid films, F has a very narrow PL spectrum peaked
at 420 nm with deep blue Commission International de
L’Eclairage (CIE, 1931) chromaticity coordinates of (0.16,
0.08); DFPh shows a green emission with CIE (0.25, 0.60);
and DFTb emits red light at 640 nm with CIE (0.58, 0.28)
(see Fig. 2). These three typical RGB emissions are well
corresponding to the normative three element RGB colour.
The deep blue (F), blue (FF), green (DFPh), yellow (DFTh),
and red (DFTh) light emission of FXs (see Fig. 2) that realized
simply by changing the connecting aryl group with F via Heck
coupling with similar components and molecular architecture
suggests the great potential of this dumbbell-shaped molecules
in solution-processable OLEDs for full-color displays.
band than at the first one. From Fig. 1, almost 100% energy
transfer in solid film was observed. However 20–30% of them
were lost during the transfer. In other words, the antenna energy
collecting effects of DFPh, DFTh, and DFTb were 80%, 75%,
and 68% respectively.18
The fluorescence lifetimes of FXs in films were measured
using a time-correlated single photon-counting instrument
(see Table 1 and Fig. S22, ESIw). The decay of the emission
maximum of FXs was found to be well-fitted by a mono-
exponential decay function when excited at 370 nm (the first
absorption band). The short lifetime (o3 ns) indicates the
highly efficient and very fast energy cascade process in which
the final emission came from the nuclear chromophore for the
‘‘H’’ shaped binuclear starburst molecules. This short lifetime
also justifies the high FPLs of FXs.
The electrochemical properties of FXs were investigated by
cyclic voltammetry (CV) measurements (see Fig. S23, ESIw).
Reversible oxidation of FXs was observed, but their reduction
processes are quasi-reversible. From the onset of oxidative or
reductive potentials, HOMO and LUMO energy levels of FXs
were obtained and listed in Table 1. FXs show close HOMOs
(ꢀ5.50 ꢁ 0.06 eV), while their LUMOs vary in a relatively
large range, exhibiting independent modification of HOMO
The fluorescence quantum yields (FPL) of FXs both in dilute
solution and in thin film were measured by an integrating
c
1514 New J. Chem., 2012, 36, 1512–1518
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2012

View Article Online
and LUMO of this material, which is very useful for the molecular
design of optoelectronic materials. DFTh has the highest HOMO
and DFTb has the lowest LUMO, indicating their highest hole
and electron injection and transport properties, respectively, due to
the corresponding electron donating and accepting properties of
thiophene and benzothiadiazole. The highest electrochemical
band-gap was found for F, while DFTb has the lowest, which
are in accordance with the optical band-gap (optEg). In comparison
with PFO,10 FXs have higher HOMO and lower LUMO (except
for F), suggesting their good charge injection and transport
properties for optoelectronic devices.
The photophysical properties of FXs were also studied by DFT
calculations19 as shown in Fig. 3. The simulated HOMOs of FXs
were very close in value (ꢀ4.53 ꢁ 0.08 eV), and the changing trend
of LUMO and the energy band-gap (calEg) were also in good
accordance with the experimental results. From the isodensity plots
of the frontier molecular orbitals of FXs, it is observed that the
LUMOs of the molecules are mainly dominated by the p* orbital
contribution of the inner core (except for F), which explains why
the LUMO can be significantly modified by the introduction of
different aryl rings. The HOMOs are dominated by both the inner
core and the surrounding fluorene segments, resulting in similar
HOMOs due to the higher contribution of the difluorenylamino
segments in the compounds. The complete HOMO and LUMO
separation cannot be observed in this molecular system, and the
facile HOMO 2 LUMO transition on the inner core offers large-
scale shifted and highly efficient light emission of FXs, without a
distinct intramolecular charge transfer (ICT) process.
Fig. 4 Energy diagram of FXs and the connecting aryl rings.
than DFPh, since thiophene has lower LUMO and HOMO
barriers for F. Whilst in DFTb, benzothiadiazole has lower LUMO
than F and after their connection, the electron transfer from F to
benzothiadiazole will be resulted. As a result, the LUMO of DFTb
is even lower than that of benzothiadiazole. Based on this simple
selection of the connection aromatic rings with specific HOMO and
LUMO, the dumbbell-like FXs show controllable optoelectronic
properties that may find applications in many fields.
Three OLEDs were fabricated using FF, DFPh and DFTb
films as emitting layers, which were directly spin-coated from
their solutions. The device structure was simple: ITO/PEDOT/
FXs/Ba/Al.20 From the electroluminescence (EL) spectra in
Fig. 5, the EL peaks of FXs were only slightly blue-shifted,
without distinct redundant stack character in comparison with
their corresponding PL spectra (see Table 1). The non-optimized
OLED devices based on FF, DFPh, and DFTb exhibit red, green,
and blue emission around 451, 484/513, and 638 nm with a turn-on
voltage of 6.5, 6.0 and 4.5 V respectively (see Table 2). The ‘‘new’’
emission of DFPh emerged at 484 nm in the EL spectrum possibly
comes from LUMO + 1 - HOMO ꢀ 1 transition of the
periphery (see discussions in Scheme S1, ESIw). The decreasing
turn-on voltage is due to the decreasing LUMO of the corre-
sponding emitter, which reduces the electron injection and transport
barrier since that of hole is fairly good with the HOMOs of FXs
(around ꢀ5.50 eV) close to that of ITO/PEDOT (ꢀ5.0 eV). These
preliminary device results show that FXs are attractive solution
processable fluorophores for OLEDs and full-color displays.
To gain further insight into the band-gap engineering of this
molecular system, the calculated energy diagram of FXs and the
connecting aryl rings are illustrated in Fig. 4. F is the main building
block of FXs, while phenyl, thiophenyl, and benzothiadiazolyl are
the connecting aryl rings. In DFPh and DFTh, benzene and
thiophene act as barriers for both hole (HOMO) and electron
(LUMO) delocalization of F. The lower the barrier, the
more significant the HOMO increases and the LUMO decreases.
Consequently, DFTh has the lower LUMO and higher HOMO
Conclusion
In conclusion, we have facilely synthesized a new family of
bisdibutyl-fluorenyl amino-based D–p-X–p-D binuclear starburst
organic molecules with a light-emitting core encapsulated with
peripheries capable of light-harvesting and carrier-transporting.
Interesting energy transfer and antenna effects were verified for
these compounds, and strong photoluminescence from deep blue
(B415 nm) to saturated red (B645 nm) was observed. The
FXs exhibit high fluorescence quantum yields (max up to 0.93
in THF solution and 0.73 in film) and short lifetime (1.3–2.6 ns).
The band-gap engineering of this molecular system was investigated
Fig. 3 Isodensity surface plots of the HOMO and LUMO of FXs
calculated with B3LYP/6-31G*.
c
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2012
New J. Chem., 2012, 36, 1512–1518 1515

View Article Online
rate of 5 1C minꢀ1 and a nitrogen flow rate of 50 cm3 minꢀ1
.
Ultraviolet-visible (UV-vis) spectra were recorded on a UV-3600
Shimadzu UV-vis-NIR spectrophotometer. Fluorescent spectra
were obtained using a RF-5301PC spectrofluorophotometer with
a xenon lamp as a light source. The fluorescence lifetime was
measured via the time-correlated single-photon counting method
by using an Edinburgh FLS-920 fluorescence spectrophotometer
at room temperature. The fluorescence quantum yields (FPL
)
were measured by an integrating sphere. The concentrations of
these compounds in solution (in THF) were adjusted to about
0.01 mg mLꢀ1 or less. The thin solid films were prepared by spin-
coating on quartz substrates from solutions in THF at a spin
rate of 3500 rpm. The energy gap (Eg) was obtained from the
absorption edge of spin-coated films (Eg = hc/lonset). The
highest occupied molecular orbital (HOMO) and the lowest
unoccupied molecular orbital (LUMO) were measured by
cyclic voltammetry (CV), which was performed at room
temperature on the CHI660E system in a typical three-electrode
cell with a working electrode (glass carbon), a reference electrode
(Ag/Ag+, referenced against ferrocene/ferrocenium (FOC)), and a
counter electrode (Pt wire) in acetonitrile solution of Bu4NPF6
(0.10 M) at a sweeping rate of 100 mV sꢀ1. The HOMO/LUMO
energy levels of the material were estimated based on the reference
energy level of ferrocene: HOMO/LUMO = ꢀ [Eonset ꢀ (0.155)] ꢀ
5.1 eV, where the value of 0.155 is for FOC vs. Ag/Ag+ and Eonset is
the onset potential.
Fig. 5 Electroluminescence spectra of FXs with the simple device
structure of ITO/PEDOT/FXs(FF, DFPh or DFTb)/Ba/Al.
Table 2 The preliminary EL performance of FXs
EL a
l
max
c
Compd
CIE (x,y)b
Vturn-on
FF
DFPh
DFTb
451
484, 513
638
(0.18, 0.19)
(0.25, 0.47)
(0.64, 0.33)
6.5
6.0
4.5
a
b
The emission maximum of EL spectra (nm). Turn-on voltage (V).
c
Commission International de I’Eclairage coordinates 1931.
via DFT calculations, which suggest that the optoelectronic
properties of the dumbbell-like FXs can be facilely controlled
by the simple selection of the connection aromatic rings. These
easily synthesized RGB starburst FXs with good processability
and property tunability are good molecular systems for high-
performance full-color displays as well as other aspects in
organic electronics.
Device fabrication and measurement
In a general procedure, ITO-coated glass substrates were
etched, patterned, and washed with detergent, deionized
water, acetone, and ethanol in turn. A layer of PEDOT was
spin-coated on the precleaned ITO glass substrates as a hole-
transport layer and then baked at 80 1C in air for 40 minutes.
Organic layers were dissolved in dichlorobenzene (concentration
15 mg mLꢀ1) and filtered with a 0.2 mm filter. A thin film of the
desired material (FF/DFPh/DFTb) was coated at a spin rate of
3000 rpm for 30 seconds and then baked at 80 1C in air for
20 minutes. Finally, a layer of Ba–Al (3.5 nm : 100 nm) was
thermally evaporated as a cathode in a vacuum chamber (under a
pressure of less than 2.5 ꢂ 10ꢀ5 Torr). The layer thickness and
the deposition rate were monitored in situ by an oscillating quartz
thickness monitor. Electroluminescent (EL) spectra and
Commission Internationale de L’Eclairage (CIE) coordinates
of the devices were measured by a PR650 spectroscan spectrometer.
The luminance–voltage and current–voltage characteristics
were measured simultaneously with a programmable Keithley
2400 voltage-current source.
Experimental section
Materials
All chemicals and reagents were used as received from commercial
sources without further purification. Solvents for chemical synthesis
were purified according to the standard procedures. All chemical
reactions were carried out under an inert atmosphere. The
intermediates 4-vinylaniline and 2-bromo-9,9-dibutylfluorene
were prepared according to the literature procedures. FXs were
synthesized in our laboratory following a literature method.
Measurements
Nuclear magnetic resonance (NMR) spectra were collected on
a Bruker Ultra Shield Plus 400 MHz instrument with d-chloro-
form as the solvent and tetramethylsilane (TMS) as the
internal standard. The quoted chemical shifts are in ppm
and J values are expressed in Hz. The signals have been
designated as follows: s (singlet), d (doublet), t (triplet),
q (quartet), dd (doublet of doublets), and m (multiplets).
MALDI-TOF-MS was determined on a Buker Daltonics
flexAnalysis. Mass spectrometric data were obtained on a LCT
Premier XE (Waters) mass spectrometer and an ESI-TOF
HRMS spectrometer. Thermogravimetric analyses (TGA) were
conducted on a DTG-60 Shimadzu thermal analyst system under
a heating rate of 10 1C minꢀ1 and a nitrogen flow rate of
50 cm3 minꢀ1. Differential scanning calorimetry (DSC) was run
on a DSC-60A Shimadzu thermal analyst system under a heating
Synthetic procedures
1
Synthesis of 4-vinylaniline
(1) 1-Nitro-4-vinylbenzene. A total of 1.00 g (4.67 mmol)
1-(bromomethyl)-4-nitrobenzene and 1.23 g (4.69 mmol)
triphenylphosphine were dissolved under inert conditions in
10 mL of chloroform. After vigorous stirring for 30 min, the
mixture was poured into ether and the phosphonium salt was
precipitated and collected by filtration. The following Wittig
reaction was performed by dispersing the dry phosphonium
c
1516 New J. Chem., 2012, 36, 1512–1518
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2012

View Article Online
salt in formaldehyde with exquisite stirring and slow addition
of 3.0 mL 25% sodium carbonate aqueous solution at room
temperature. After reaction for 4 h, the mixture was hydrolyzed
with water and extracted with dichloromethane. The combined
organic layers were collected, dried over anhydrous sodium sulfate
(Na2SO4), filtered and evaporated to remove the solvent. The
resulted crude product was chromatographed on a silica gel
(2) 1-[N,N-Bis(9,9-dibutyl-fluoren-2-yl)]-2-(9,9-dibutyl-
fluoren-2-yl)-ethene (FF). Anhydrous palladium acetate (1.20 mg,
0.005 mmol), N,N,-bis(9,9-dibutyl-fluoren-2-yl)-4-vinylaniline
(168.0 mg, 0.250 mmol), 2-bromo-9,9-dibutyl-fluorene (89.3 mg,
0.250 mmol), and potassium phosphate (85.4 mg, 0.350 mmol)
were dissolved in 30 mL dry DMA and stirred at 140 1C under a
nitrogen atmosphere overnight. Then the reaction mixture was
washed with water and extracted with dichloromethane. The
combined organic layers were collected, dried over anhydrous
sodium sulfate (Na2SO4), filtered and evaporated to remove the
solvent. The resulted crude product was chromatographed on a
silica gel column with petroleum ether as eluent and recrystallized
several times from methanol to afford an olivine powder. Yield:
47%. 1H NMR (400 MHz, CDCl3): d = 0.73 (30H), 1.10
(m, 12H), 1.87 (m, 12H), 7.07 (d, J = 2.0, 1H), 7.09 (d, J =
2.0, 1H), 7.14 (d, J = 8.8, 2H), 7.164 (s, 1H), 7.21 (d, J = 2.0,
2H), 7.25–7.37 (10H), 7.44 (d, J = 8.4, 2H), 7.47 (s, 1H), 7.50
(d, J = 2.0, 1H), 7.59 (d, J = 8.2, 2H), 7.64 (d, J = 7.6, 1H), 7.68
ppm (t, J = 4.0, 2H).13C NMR (100 MHz, CDCl3): d = 13.83,
13.91, 13.96, 14.14, 22.71, 23.07, 23.10, 26.11, 29.38, 29.68, 29.72,
31.95, 40.02, 54.99, 119.12, 119.60, 119.86, 120.33, 120.56, 122.73,
122.77, 122.85, 123.00, 123.28, 123.44, 125.33, 126.27, 126.35,
126.79, 126.94, 127.20, 127.46, 136.29, 136.48, 136.60, 140.65,
140.91, 140.93, 146.76, 150.53, 158.58, 150.94, 151.23,
152.10 ppm. MALDI-TOF, m/z cacld for C71H81N, 947.637;
found, 948.114. HRMS (EI) calcd for C71H81N [M + H]+:
948.6447; found, 948.6442.
1
column with petroleum ether as eluent. Yield: 91%. H NMR
(400 MHz, CDCl3): d = 5.49 (d, J = 10.8, 1H), 5.93 (d, J =
17.2, 1H), 6.73 (q, 1H), 7.52 (d, J = 8.4, 2H), 8.15 ppm (d, J =
8.0, 2H). 13C NMR (100 MHz, CDCl3): d = 118.60, 123.92,
126.81, 134.96, 143.84, 147.16 ppm.
(2) 4-Vinylaniline. To the mixture of 0.8 g iron powder,
0.1 mL concentrated hydrochloric acid, and 3 mL water was
added 5 mL ethanol solution of 1-nitro-4-vinylbenzene at 0 1C.
The resulting mixture was stirred at this temperature for 2 h
and then the mixture was filtrated to remove the iron mud.
The filtrate was hydrolyzed with water and extracted with
dichloromethane. The collected organic layers were dried over
anhydrous sodium sulfate (Na2SO4), filtered, and evaporated to
remove the solvent. The resulted crude product was chromato-
graphed on a silica gel column with petroleum ether–ethyl acetate
(5 : 1) as eluent. Yield: 89%. 1H NMR (400 MHz, CDCl3): d =
3.71 (s, 2H), 5.05 (d, J = 10.8, 1H), 5.56 (d, J = 17.4, 2H),
6.62 (m, 1H), 6.64 (d, J = 8.4, 2H), 7.24 ppm (d, J = 8.4 Hz,
2H). 13C NMR (100 MHz, CDCl3): d = 110.02, 115.03,
127.39, 128.37, 136.58, 146.25 ppm.
(3) 1,4-Bis(4-[N,N-bis(9,9-dibutyl-fluoren-2-yl)aniline]-
vinyl)-benzene (DFPh). Anhydrous palladium acetate (1.20 mg,
0.005 mmol), N,N,-bis(9,9-dibutyl-fluoren-2-yl)-4-vinylaniline
(168.0 mg, 0.250 mmol), 1,4-dibromobenzene (23.6 mg,
0.10 mmol) and potassium phosphate (85.4 mg, 0.350 mmol)
were dissolved in 30 mL dry DMA and stirred at 140 1C under a
nitrogen atmosphere overnight. Then the reaction mixture was
washed with water and extracted with dichloromethane. The
combined organic layers were collected, dried over anhydrous
sodium sulfate (Na2SO4), filtered and evaporated to remove the
solvent. The resulted crude product was chromatographed on a
silica gel column with petroleum ether as eluent and recrystallized
several times from methanol to afford a yellow powder. Yield:
54%. 1H NMR (400 MHz, CDCl3): d = 0.63–0.90 (40H), 1.10
(m, 16H), 1.89 (m, 16H), 7.00 (s, 1H), 7.04 (s, 2H), 7.07–7.09
(5H), 7.14 (d, J = 8.0 Hz, 4H), 7.22 (d, J = 2 Hz, 4H),
7.25–7.34 (12H), 7.42 (d, J = 8.8 Hz, 4H), 7.50 (s, 4H), 7.59
(d, J = 8 Hz, 4H), 7.64 ppm (d, J = 7.2 Hz, 4H). 13C NMR
(100 MHz, CDCl3): d = 13.97, 14.15, 22.72, 23.06, 26.12,
29.39, 29.69, 29.73, 31.95, 40.02, 54.99, 119.14, 119.21, 120.35,
122.78, 122.93, 123.49, 126.37, 126.50, 126.64, 126.80, 127.27,
127.93, 131.17, 136.53, 136.73, 140.90, 146.72, 147.73, 150.60,
2
Synthesis N,N,-bis(9,9-dibutyl-fluoren-2-yl)-4-vinylaniline
based D–p-X–p-D molecules (FXs)
(1) N,N,-Bis(9,9-dibutyl-fluoren-2-yl)-4-vinylaniline
(F).
A total of 0.160 g (1.35 mmol) 4-vinylaniline and 1.00 g
(3.00 mmol) of 2-bromo-9,9-dibutylfluorene were dissolved
under inert conditions in 50 mL of toluene using the Schlenk
tube technique. To this solution were added 0.020 g (0.022 mmol)
of Pd2(dba)3, 0.070 g (0.242 mmol) of P(t-Bu)3BF4, and finally
0.405 g (4.05 mmol) of sodium tert-butoxide. The reaction
mixture was stirred under nitrogen for 10 h at 110 1C. After
cooling to room temperature, the reaction mixture was washed
with water and extracted with petroleum ether. The combined
organic layers were collected, dried over anhydrous sodium
sulfate (Na2SO4), filtered and evaporated. The resulted crude
product was chromatographed on a silica gel column with
petroleum ether as eluent and recrystallized several times from
ethanol or dichloromethane–hexane to afford the pure
compounds. Yield: 63%. 1H NMR (400 MHz, CDCl3): d =
0.71 (t, 12H), 0.6–0.71 (m, 8H), 1.08 (m, 8H), 1.87 (m, 8H),
5.18 (d, J = 10.8, 1H), 5.63 (d, J = 17.4, 1H), 6.70 (m, 1H), 7.04
(d, J = 2.0, 1H), 7.06 (d, J = 2.0, 1H), 7.10 (d, J = 8.8, 2H),
7.18 (d, J = 2.0, 2H), 7.21–7.33 (8H), 7.56 (d, J = 8.0, 2H),
7.63 ppm (d, J = 2.0, 2H). 13C NMR (100 MHz, CDCl3): d =
13.94, 23.05, 26.09, 40.00, 54.97, 119.10, 120.30, 122.75, 122.93,
123.34, 126.32, 126.74, 126.96, 128.05, 128.34, 131.44, 136.25,
136.34, 140.90, 146.79, 147.87, 150.57, 152.06 ppm. MALDI-
TOF, m/z cacld for C36H22N2S, 671.449; found, 671.578. HRMS
(EI) calcd for C36H22N2S [M + H]+: 672.4569; found, 672.4575.
152.12 ppm. MALDI-TOF, m/z cacld for
C106H116N2,
1416.914; found, 1417.463. HRMS (EI) calcd for
106H116N2 [M + H]+: 1417.9217; found, 1417.9213.
C
(4) 2,5-Bis(4-[N,N-bis (9,9-dibutyl-fluoren-2-yl)aniline]vinyl)-
thiophene (DFTh). DFTh was prepared similarly as that of
DFPh. Yield: 32%. 1H NMR (400 MHz, CDCl3): d =
0.63–0.89 (40H), 1.10 (m, 16H), 1.89 (m, 16H), 6.85 (s, 1H),
6.89 (s, 1H), 6.91 (s, 2H), 7.05 (d, J = 2 Hz, 2H), 7.06 (s, 1H),
c
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2012
New J. Chem., 2012, 36, 1512–1518 1517

View Article Online
7.07 (d, J = 2 Hz , 2H), 7.10 (d, J = 2 Hz, 3H), 7.12 (s, 2H),
7.19 (d, J = 2 Hz, 4H), 7.24–7.34 (16H), 7.56 (s, 2H), 7.59
(s, 2H), 7.62 (d, J = 2 Hz, 2H), 7.64 ppm (s, 2H). 13C NMR
(100 MHz, CDCl3): d = 13.95, 14.13, 22.70, 23.05, 26.10,
29.37, 29.67, 29.71, 31.94, 40.00, 54.98, 119.14, 119.25, 120.35,
122.76, 122.81, 123.52, 126.37, 126.60, 126.79, 127.07, 127.94,
130.68, 136.58, 140.87, 141.85, 141.90, 146.64, 147.71, 150.59,
152.11 ppm. MALDI-TOF, m/z cacld for C104H114N2S,
1422.870; found, 1423.441. HRMS (EI) calcd for
Notes and references
1 (a) M. G. Helander, Z. B. Wang, J. Qiu, M. T. Greiner, D. P. Puzzo,
Z. W. Liu and Z. H. Lu, Science, 2011, 332, 944; (b) S. F. Chen,
L. Deng, J. Xie, L. Peng, L. H. Xie, Q. L. Fan and W. Huang,
Adv. Mater., 2010, 22, 5227; (c) R. Capelli, S. Toffanin, G. Generali,
H. Usta, A. Facchetti and M. Muccini, Nat. Mater., 2010, 9, 496.
2 C. W. Tang and S. A. VanSlyke, Appl. Phys. Lett., 1987, 51, 913.
3 A. J. Heeger, Chem. Soc. Rev., 2010, 39, 2345.
4 (a) M. A. McCarthy, B. Liu, E. P. Donoghue, I. Kravchenko, D. Y.
Kim, F. So and A. G. Rinzler, Science, 2011, 332, 570; (b) D. Astruc,
E. Boisselier and C. Ornelas, Chem. Rev., 2010, 110, 1857.
5 (a) S. C. Lo, T. D. Anthopoulos, E. B. Namdas, P. L. Burn and
I. D. W. Samuel, Adv. Mater., 2005, 17, 1945; (b) W. Y. Lai,
Q. Q. Chen, Q. Y. He, Q. L. Fan and W. Huang, Chem. Commun.,
2006, 1959; (c) H. Huang, Q. Fu, S. Zhuang, Y. Liu, L. Wang,
J. Chen, D. Ma and C. Yang, J. Phys. Chem. C, 2011, 115, 4872.
6 S.-C. Lo and P. L. Burn, Chem. Rev., 2007, 107, 1097.
7 (a) J. Q. Ding, B. H. Zhang, J. H. Lu, Z. Y. Xie, L. X. Wang,
X. B. Jing and F. S. Wang, Adv. Mater., 2009, 21, 4983; (b) P. Tyagi,
A. Venkateswararao and K. R. J. Thomas, J. Org. Chem., 2011,
76, 4571.
C
104H114N2S [M + H]+: 1423.8781; found, 1423.8824.
(5) 4,7-Bis(4-[N,N-bis(9,9-dibutyl-fluoren-2-yl)aniline]vinyl)
benzothiadiazole (DFTb). DFTb was synthesized according to
the standard procedure illustrated in the preparation of DFPh.
Yield: 71%. 1H NMR (400 MHz, CDCl3): d = 0.63–0.90
(40H), 1.10 (m, 16H), 1.89 (m, 16H), 7.08 (d, J = 2.4 Hz, 2H),
7.10 (d, J = 2.4 Hz, 2H), 7.16 (d, J = 8.8 Hz, 4H), 7.22 (d,
J = 2 Hz, 4H), 7.25–7.34 (12H), 7.52 (s, 2H), 7.54 (d, J = 2
Hz, 3H), 7.58 (s, 1H), 7.59 (s, 2H), 7.60 (s, 2H), 7.63 (d, J =
1.2 Hz, 2H), 7.65 (s, 2H), 7.67 (s, 2H), 7.95 (s, 1H), 7.99 ppm
(s, 1H). 13C NMR (100 MHz, CDCl3): d = 13.97, 14.14, 22.71,
23.07, 26.12, 29.38, 29.68, 29.72, 31.95, 40.01, 55.01, 119.17,
119.37, 120.39, 122.64, 122.79, 123.66, 126.42, 126.51, 126.81,
127.74, 129.26, 131.22, 132.51, 136.70, 140.87, 146.61, 148.16,
150.61, 152.15, 154.03 ppm. MALDI-TOF, m/z cacld for
8 C. M. Zhong, C. H. Duan, F. Huang, H. B. Wu and Y. Cao, Chem.
Mater., 2011, 23, 326.
9 K. R. Thomas, T. H. Huang, J. T. Lin, S. C. Pu, Y. M. Cheng,
C. C. Hsieh and C. P. Tai, Chem.–Eur. J., 2008, 14, 11231.
10 (a) C.-H. Chen, J. T. Lin and M.-C. P. Yeh, Org. Lett., 2006,
8, 2233; (b) J. L. Wang, Y. Zhou, Y. F. Li and J. J. Pei, J. Org.
Chem., 2009, 74, 7449.
11 S. Kim, D. Kim, H. Choi, M. S. Kang, K. Song, S. O. Kang and
J. Ko, Chem. Commun., 2008, 4951.
12 C. Kim, H. Choi, S. Kim, C. Baik, K. Song, M. S. Kang,
S. O. Kang and J. Ko, J. Org. Chem., 2008, 73, 7072.
13 Y. Wei, S. Samori, S. Tojo, M. Fujitsuka, J. S. Lin, C. T. Chen and
T. Majima, J. Am. Chem. Soc., 2009, 131, 6698.
C
106H114N4S, 1474.877; found, 1475.773. HRMS (EI) calcd
for C106H114N4S [M + H]+: 1475.8844; found, 1475.8842.
14 A. Maier, R. Rabindranath and B. Tieke, Adv. Mater., 2008, 21, 959.
15 (a) L. H. Feng and Z. B. Chen, Polymer, 2005, 46, 3952;
(b) X. F. Wu, P. Anbarasan, H. Neumann and M. Beller, Angew.
Chem., Int. Ed., 2010, 49, 9047.
Acknowledgements
16 R. F. Chen, Q. L. Fan, S. J. Liu, R. Zhu, K. Y. Pu and W. Huang,
Synth. Met., 2006, 156, 1161.
17 J. Cremer and C. A. Briehn, Chem. Mater., 2007, 19, 4155.
18 P. K. Dutta, R. Varghese, J. Nangreave, S. Lin, H. Yan and
Y. Liu, J. Am. Chem. Soc., 2011, 133, 11985.
19 (a) J. Yin, S. L. Zhang, R. F. Chen, Q. D. Ling and W. Huang, Phys.
Chem. Chem. Phys., 2010, 12, 15448; (b) J. Yin, R. F. Chen, S. L. Zhang,
Q. D. Ling and W. Huang, J. Phys. Chem. A, 2010, 114, 3655.
20 S. J. Evenson, M. J. Mumm, K. I. Pokhodnya and
S. C. Rasmussen, Macromolecules, 2011, 44, 835.
We thank the National Basic Research Program of China
(2009CB930601), National Natural Science Foundation of China
(20804020, 60976019 and 20974046), The Ministry of Education of
China (No. IRT1148), National Natural Science Foundation of
Jiangsu Province (BK2011751), Scientific Research Foundation of
Nanjing University of Posts and Telecommunications (NY210017,
NY210046), and Program for Postgraduates Research Innovations
in University of Jiangsu Province (CXZZ11_0412).
c
1518 New J. Chem., 2012, 36, 1512–1518
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2012