Extended π-conjugated molecules derived from naphthalene diimides toward organic emissive and semiconducting materials

Article abstract of DOI:10.1021/jo302677k

In this paper, a new synthetic way to modify naphthalene diimide (NDI) at shoulder positions is reported. The key step of the transformation is the intramolecular cyclization involving ethynyl and imidecarbonyl groups. The structure of the intermediate pyrylium cation was confirmed by X-ray crystal structural analysis. New conjugated molecules 1a-g were successfully synthesized in acceptable yields. Their absorption and fluorescence spectra were measured. Among them 1c-f are strongly emissive in solutions. Furthermore, 1b-f are also fluorescent in their solid states; in particular, 1b exhibits a typical aggregation-induced enhanced emission feature. Yellow-emissive microfibrils of 1d show potential optical waveguide behavior. HOMO/LUMO energies of 1a-f were determined based on their cyclic voltammograms. The results also reveal that HOMO/LUMO energies of these new conjugated molecules are influenced by the two flanking moieties. Notably, the thin film of 1c that is emissive shows p-type semiconducting behavior with hole mobility up to 0.0063 cm ² V^-1 s^-1 based on the transfer and output characteristics of the OFET (organic field effect transistor).

Full text of DOI:10.1021/jo302677k

Article
pubs.acs.org/joc
Extended π‑Conjugated Molecules Derived from Naphthalene
Diimides toward Organic Emissive and Semiconducting Materials
Yonghai Li, Guanxin Zhang,* Ge Yang, Yunlong Guo, Chong’an Di, Xin Chen, Zitong Liu, Huiying Liu,
Zhenzhen Xu, Wei Xu, Hongbing Fu, and Deqing Zhang*
Beijing National Laboratory for Molecular Sciences, Organic Solids Laboratory and Photochemistry Laboratory, Institute of
Chemistry, Chinese Academy of Sciences, Beijing 100190, China
S
* Supporting Information
ABSTRACT: In this paper, a new synthetic way to modify naphthalene
diimide (NDI) at “shoulder” positions is reported. The key step of the
transformation is the intramolecular cyclization involving ethynyl and
imidecarbonyl groups. The structure of the intermediate pyrylium cation
was confirmed by X-ray crystal structural analysis. New conjugated
molecules 1a−g were successfully synthesized in acceptable yields. Their
absorption and fluorescence spectra were measured. Among them 1c−f are
strongly emissive in solutions. Furthermore, 1b−f are also fluorescent in
their solid states; in particular, 1b exhibits a typical aggregation-induced
enhanced emission feature. Yellow-emissive microfibrils of 1d show
potential optical waveguide behavior. HOMO/LUMO energies of 1a−f
were determined based on their cyclic voltammograms. The results also
reveal that HOMO/LUMO energies of these new conjugated molecules are
influenced by the two flanking moieties. Notably, the thin film of 1c that is
emissive shows p-type semiconducting behavior with hole mobility up to 0.0063 cm2 V−1 s−1 based on the transfer and output
characteristics of the OFET (organic field effect transistor).
Scheme 1. Illustration of Chemical Modification Manners of
NDI to Extended Conjugated Molecules
INTRODUCTION
■
It is well-known that development of new π-conjugated
molecules is crucial for optoelectronic materials including
light-emitting materials, organic semiconductors, and photo-
voltaic materials.1−11 This is mainly owing to the electronic
structure of π-systems, which can lead to extensive delocaliza-
tion of electrons throughout the molecules. In principle,
HOMO/LUMO energies and their intermolecular interactions
(thus self-assembly structures) of π-conjugated molecules can
be tuned by modifying their chemical structures. In this
manner, emissive and electronic properties of π-conjugated
molecules in the solid states are critically determined by their
chemical structures. More and more results reveal that
extended π-conjugated molecules are promising for optoelec-
tronic materials of high performances. Accordingly, extended π-
conjugated molecules have received increasing attention in
recent years.12−15
1,4,5,8-Naphthalenediimide (NDI) and its derivatives have
been intensively investigated for organic optoelectronic
materials.16−18 Organic semiconductors and photovoltaic
materials have been constructed on the basis of NDI
framework.19,20 In order to enhance the performance of NDI-
based materials, various chemical modifications of the NDI
framework were reported. As depicted in Scheme 1, these can
be mainly classified as follows: (i) connection of electron-
withdrawing or -donating moieties to the NDI core via single
bonds;21−25 (ii) fusion of additional rings to NDI at core
positions;26−30 (iii) chemical modification of the imide groups
of NDI and formation of additional rings at “head”
positions;31−35 (iv) transformation of the imide groups of
NDI into additional rings at “shoulder” positions.36,37
A number of NDI-derived conjugated molecules were
prepared via manner i. For instance, incorporation of
electron-withdrawing −CN groups at the core positions of
NDI led to air-stable n-type semiconductors.21,22 Facchetti et al.
reported the alternating NDI-bithiophene polymer, and the
resulting OFETs exhibited electron mobilities up to 0.85 cm2
V−1 s−1 (n-type) under ambient conditions.23−25 Chemical
modification of NDI via manner ii also led to various π-
Received: December 14, 2012
Published: March 5, 2013
© 2013 American Chemical Society
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a
Scheme 2. Chemical Structures and Synthetic Approaches for Compounds 1a−g, 2a−g, and 3a−g
a
Reagents and conditions: (i) respective tin reagents, Pd(PPh3)4, toluene, reflux, 2.5 h; yields: for 2a, 81%; for 2b, 84%; for 2c, 86%; for 2d, 89%; for
2e, 85%; for 2f, 76%; for 2g, 83%; (ii) TFSIH (bis(trifluoromethane)sulfonamide), CH2Cl2, N2, for 2a−d and 2g, rt 0.5−6.0 h; for 2e,f, reflux, 48 h;
(iii) NH3·H2O, CH3OH, reflux, 1.0 h; yields based on 2a−g, respectively: for 1a, 47%; for 1b, 42%; for 1c, 60%; for 1d, 52%; for 1e, 46%; for 1f,
59%; for 1g, 58%.
conjugated molecules for organic semiconductors of high
mobilities. Gao et al. reported core-expanded NDI derivatives
containing 2-(1,3-dithiol-2-ylidene)malonitrile groups (elec-
tron-withdrawing), and the resulting OFETs exhibit electron
derivatives, which can react with hydrazine to afford 2,6-
diacylnaphthalene-1,8:4,5-bis(dicarboximides).36 This modi-
fied-NDI framework has been also incorporated into ladder-
polymers by Luscombe et al., and these electronic polymers
exhibit electron mobilities as high as 0.0026 cm2 V−1 s−1 (n-
type).37
In this paper, we report a new synthetic approach to modify
NDI at “shoulder” positions to yield new extended conjugated
molecules 1a−g (Scheme 2). Spectroscopic and electro-
chemical studies were performed to determine their HOMO/
LUMO levels. Most of these new conjugated molecules were
found to be emissive both in solutions and solid states.
Moreover, thin-film OFET (organic field-effect transistor) of 1c
was successfully fabricated, which behaved as a p-type
semiconductor with hole mobility up to 0.0063 cm2 V−1 s−1.
These studies clearly manifest that these new NDI-derived
conjugated molecules are interesting building blocks to
construct new optoelectronic materials.
mobilities up to 1.2 cm2 V−1 s−1 in air (n-type).26−28 Wurthner
̈
et al. disclosed p-type and ambipolar semiconductors based on
core-expanded NDI.29 Some of us have very recently described
NDI derivatives entailing electron-donating tetrathiafulvalene
or 1,3-dithole-2-thione (-one) moieties, and they behave as
either n-type or p-type or ambipolar materials depending on the
substitution groups.30
Chemical transformations of the imide groups of NDI were
also explored to generate new conjugated molecules (via
manners iii and iv). Perinone derivatives as industrially
important pigments were synthesized via manners iii many
decades ago.31 However, in recent years, this type of modified
NDI framework is getting more attention from other areas. For
example, Jenekhe and co-workers introduced them into ladder-
polymers which exhibit n-type semiconducting properties.32,33
Langhals et al. reported naphthalene iminoimides by either
condensation of NDI with ethylenediamine or simultaneous
condensation of naphthalene dianhydride, a primary amine, and
ethylenediamine.34 Marks et al. have recently disclosed a family
of naphthaleneamidinemonoimide-fused oligothiophenes that
exhibit n-type or ambipolar semiconducting behaviors.35
However, fusion of rings to NDI at the “shoulder” positions
was seldom reported. Marder and co-workers have just recently
described the transformation of NDI into the 2,6-diacyl
RESULTS AND DISCUSSION
■
Synthesis. The synthesis of 1a−f started from the
respective NDI compounds 2a−f with substituted acetylene
moieties which were prepared by Stille coupling of the
respective tin reagents and 2BrNDI (dibromonaphthalene
diimide, N-C20H41).38 Compounds 2a−f were allowed to react
with TFSIH [bis(trifluoromethane)sulfonamide] under nitro-
gen atmosphere to afford colored solids after removal of
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solvents. As to be discussed below, these colored solids were
the products from intramolecular cyclization involving ethynyl
and imidecarbonyl groups in CH2Cl2. These colored solids
were dissolved in dry methanol and treated with NH3·H2O
under reflux. After separation with column chromatography,
1a−f were obtained in acceptable yields. Their structures were
characterized by NMR and MS data, and their purities were
confirmed by elemental analysis.
It is interesting to note that the transformation of 2a−c with
electron-donating groups at the end of ethynyl groups into the
colored solids can be completed after stirring at room
temperature for less than 1 h. The transformation of 2d can
also easily proceed after stirring at room temperature for about
6.0 h. However, the transformation of 2e and 2f required
heating the CH2Cl2 solutions to reflux for about 48 h. These are
indeed in agreement with the formation of intermediate
compounds 3a−f since the electron-donating groups will
stabilize the pyrylium cations, whereas electron-accepting
groups would not be favorable for the formation of the
respective pyrylium cations. Crystals of good quality were not
obtained for the colored solids 3a−f. Instead, the analogous
compound 1g with short alkyl chains (−n-C8H17) at the N-
positions was synthesized by following the same procedures as
for 1a. The crystal structure of 3g was successfully determined.
As depicted in Figure 1, the formation of the pyrylium cation
pentadienyl) rings in two flanking ferrocene moieties are almost
coplanar with the central core. The bond lengths and angles of
3g are all in the normal region (see the Supporting
Information). To conclude briefly, the crystal structure of 3g
provides solid evidence for the formation of the pyrylium cation
through the intramolecular cyclization involving the ethynyl
and imidecarbonyl groups.
Although Nishihara and co-workers reported protonation-
induced cyclization of 1-arylethynylanthraquinones and rele-
vant molecules,39−41 the intramolecular reaction between
ethynyl and imidecarbonyl groups to form pyrylium cation in
the presence of acid was not reported before, to the best of our
knowledge. This new reaction will not only provide a new
approach to modify NDI at “shoulder” positions but also
enlarge the scope of this type of cyclization reaction reported
initially by Nishihara.41 This versatile reaction allows the
formation of two pyridine rings and simultaneous introduction
of different functional groups, which can be either electron-
withdrawing or donating, to generate new extended conjugated
molecules.
Spectroscopic Studies. The solutions of 1a−g are
colorful, ranging from red to yellow. The absorption spectra
of 1a−g42 were measured (see Figure S1, Supporting
Information), and the respective low-energy absorption maxima
and the coefficients are shown in Table 1. Compound 1f with
two methyl groups shows the absorption maximum at 466 nm.
In comparison, the absorptions of 1b−d are red-shifted. For 1a
with two electron-donating ferrocene moieties the absorption is
extended to 620 nm. These results reveal that absorption
spectra of 1a−d are influenced by the flanking groups. This can
be understood as follows: (1) the flanking moieties in 1a−d are
electron-donating, whereas the central cores are electron-
accepting; (2) thus, intramolecular interactions between the
respective electron-donating and -accepting moieties in 1a−d
are anticipated; (3) absorption spectra of 1a−d are expected to
be influenced by such intramolecular interactions.43 The
introduction of electron-withdrawing (p-trifluoromethyl)phenyl
moieties in 1e will weaken the intramolecular electron donor−
acceptor interactions, and as a result the absorptions of 1e are
slightly hypsochromically shifted compared to those of 1c and
1d as depicted in Figure S1 (Supporting Information).
Both 1a and 1g are almost nonfluorescent in solutions.
Figure 2a shows the fluorescence spectra of 1b−f including
Figure 1. Crystal structure of 3g and the intermolecular arrangements
in the crystal.
3g was clearly confirmed. The central part of 3g flanked by two
ferrocene moieties was completely planar. Two Cp (cyclo-
Table 1. Absorption and Fluorescence Data of 1a−f
fluorescence
a
absorption
solution fluorescence
solid-state fluorescence
b
c
d
e
f
compd
λmax (nm) (ε/M−1cm−1
)
λmax (nm)
Φ
τ (ns)
λmax (nm)
Φ
τ1 (ns)
τ2 (ns)
<τ> (ns)
1a
1b
1c
1d
1e
1f
453 (22400)
515 (16000)
504 (25500)
480 (28500)
472 (27700)
466 (35600)
637
521
490
482
476
0.06
0.40
605
614
545
538
543
0.24
0.05
0.30
0.10
0.08
15.26
1.04
1.44
0.88
7.96
15.26
3.44
5.47
1.95
4.02
3.84
7.04
4.47
8.15
3.15
0.94
>0.99
>0.99
>0.99
4.26
10.32
a
b
The absorption spectra were measured with the respective CH2Cl2 solutions; the concentration of each solution was 1.0 × 10−5 M. Lowest energy
c
absorption maxima. The fluorescence spectra were measured with the respective CH2Cl2 solutions, and the concentration of each solution was 1.0 ×
d
10−5 M; the excitation wavelengths were 515 nm for 1b, 475 nm for 1c, 455 nm for 1d, 440 nm for 1e, and 430 nm for 1f, respectively. The
e
solution quantum yields were measured using rhodamine 101 (Φ = 100% in ethanol) as standard. The quantum yields in the solid states were
f
measured using the absolute integrating sphere method. An apparent decay time constant <τ> (average fluorescence lifetime) was determined by
using the relation <τ = ∑ni=1ai × τi/∑in=1ai> (n = 1−2), where τi and ai, respectively, represent the individual exponential decay time constant and the
corresponding preexponential factor.55
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and the emission quantum yield is enhanced (see Table 1). As
shown in Figure 3, the CH2Cl2 solution of 1b is just weakly
Figure 3. Fluorescence spectra of 1b (1.0 × 10−5 M) in the mixture of
CH2Cl2 and n-hexane with different fractions of n-hexane (fw); the
excitation wavelength was 500 nm. When only n-hexane was used as
the solvent, it was found that a small amount of 1b precipitated out
and as a result the fluorescence intensity was slightly reduced.
Figure 2. (a) (Left) Solution fluorescence spectra of 1b−f in CH2Cl2;
the concentration of each solution was 1.0 × 10−5 M. (Right)
Corresponding solution photos of 1b−f (1.0 × 10−3 M in CH2Cl2)
under UV light (365 nm) irradiation; (b) solid-state fluorescence
spectra of 1b−f in the form of powders; (c) photoluminescence (PL)
images of microfibrils of 1d.
emissive; but after the addition of n-hexane to induce the
aggregation of 1b the fluorescence spectrum is gradually
hypsochromically shifted and fluorescence intensity is simulta-
neously enhanced. For instance, the emission maximum is
shifted from 637 to 551 nm and the intensity increases by 46.5-
fold when the volume content of n-hexane reaches 90%. Such
“unexpected” fluorescent behavior of 1b may be ascribed to the
free-rotation of phenyl fragments within triphenylamine
moieties which will lead to weak fluorescence of 1b in
solution;48 however, these rotations can be inhibited in the
solid state (after aggregation), resulting in fluorescence
enhancement according to previous reports.49−53 The blue-
shift of the emission maximum in the solid state (after
aggregation) is probably due to the fat that 1b adopts a more
twisting conformation in the solid state; as a result, the
intramolecular electron donor−acceptor interactions are
weakened and the emission is hypsochromically shifted.54
Electrochemical and Theoretical Studies. Cyclic
voltammgrams of 1a−f were measured, and their redox
potentials are shown in Table 2. As shown in Figure S9
(Supporting Information), 1a and 1b each possess one quasi-
reversible oxidation wave due to ferrocence and triphenylamine
moieties, respectively;56 both of them also exhibit one quasi-
reversible reduction wave and one irreversible reduction wave.
In comparison, 1c−f each exhibit an irreversible oxidation wave
at potentials higher than 1.30 V (vs Ag/AgCl), but they each
also possess one quasi-reversible reduction wave and one
irreversible reduction wave. On the basis of the respective onset
oxidation and reduction potentials, HOMO and LUMO
energies of 1a−f were estimated with the following equations:
photos of their solutions under UV light, and Table 1
summarizes their emission maxima and quantum yields.
Obviously, the emissive properties of 1b−f are influenced by
the features of the flanking groups. The emission maxima are
red-shifted in the following order: 1f < 1e < 1d < 1c < 1b. The
solutions of 1d−f show bright yellow-green fluorescence, and
their emission quantum efficiencies reach that of Rhodamine
101. The solution of 1b emits red light with low quantum
efficiency, whereas the solution of 1c is yellow-emissive with
relatively high quantum efficiency. The fluorescence lifetimes of
1c−f are in the nanosecond region, being in agreement with
their high quantum efficiencies. These results reveal that the
emission properties of 1a−g can be tuned by the flanking
groups: (1) when the flanking groups such as ferrocene in 1a
and 1g and triphenylamine in 1b are electron-donating the
fluorescence will be largely quenched due to the photoinduced
electron transfer;44 (2) the incorporation of electron-donating
groups will also red-shift the emission.
The solid-state fluorescence spectra were also measured (see
Figure 2b), and the respective emission quantum yields and
fluorescence lifetimes including average fluorescence lifetimes
are listed in Table 1. Again, 1a and 1g are not emissive in the
solid state either.45 Other compounds are fluorescent in their
solid states. Among these compounds, 1b and 1d are strongly
emissive with relatively high emission quantum yields in the
solid states. This is consistent with the observation that 1b and
1d show longer average fluorescence lifetimes than those of 1c,
1e, and 1f. In comparison with the fluorescence behaviors of
1c−f in solutions, their emission maxima are red-shifted and
emission quantum yields are reduced in their solid states. This
may be attributed to the intermolecular π−π interactions in
solid states of 1c−f according to previous reports.46
ox1
red1
HOMO = −(Eonset +4.41) eV, LUMO = −(Eonset +4.41)
eV.57,58 As listed in Table 2, HOMO energies of 1a and 1b are
−4.91 and −5.30 eV, respectively, which lie higher than those
of 1c−f. This is likely owing to the presence of two electron-
donating groups in 1a and 1b. LUMO energies of 1c and 1e lie
lower than those of 1a, 1b, 1d, and 1f. The incorporation of
electron-withdrawing groups (p-trifluoromethylphenyl) in 1e is
beneficial for lowering its LUMO energy. Theoretical
calculation (see below) indicates that the two thiophene rings
in 1c are almost coplanar with the central core. Such coplanar
conformation favors electron delocalization, and accordingly it
Yellow-emissive microfibrils of 1d were obtained and
characterized with photoluminescence microscopy. Notably,
the tips of these microfibrils exhibit even brighter yellow-
emission as depicted in Figure 2c. Therefore, microfibrils of 1d
are potentially useful for optical waveguides.47
However, compared to those of 1b in solution, the emission
maximum of 1b in the solid state is hypsochromically shifted
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a
Table 2. Redox Potentials and Experimental/Calculated HOMO/LUMO Energies of 1a−f
experimental data
DFT calculations
red1
ox1
red1
ox1
cv
compd
Ep (V)
Ep (V)
Eonset (V)
Eonset (V)
HOMO (eV)
LUMO (eV)
Eg (eV)
HOMO (eV)
LUMO (eV)
1a
1b
1c
1d
1e
1f
−1.37
−1.27
−1.32
−1.36
−1.23
−1.32
0.74
1.09
1.53
1.74
1.79
1.66
−1.20
−1.16
−1.09
−1.14
−1.00
−1.18
0.50
0.89
1.35
1.52
1.65
1.52
−4.91
−5.30
−5.76
−5.93
−6.06
−5.93
−3.21
−3.25
−3.32
−3.27
−3.41
−3.23
1.70
2.05
2.44
2.66
2.65
2.70
−5.54
−5.69
−6.03
−5.80
−2.67
−2.65
−2.93
−2.59
a
The redox potentials were presented in reference to Ag/AgCl, which was calibrated.
Figure 4. Calculated structures, dihedral angles, and HOMO/LUMO orbitals of 1c−f based on DFT calculations; the alkyl chains were replaced by
methyl groups in the calculations.
is understandable that the HOMO and LOMO energies of 1c
were slightly enhanced and lowered, respectively, in compar-
ison with those of 1d. Therefore, for this type of modified-NDI
conjugated molecules their HOMO/LUMO energies can be
tuned by varying the respective two flanking moieties.
expected for the thin film of 1c. For this reason, OFET with
thin a film of 1c was fabricated to demonstrate the potential
application of these new conjugated molecules as organic
semiconductors. The fabrication details of OFET are discussed
in the Experimental Section. Figure 5 shows the transfer and
output characteristics of the bottom-gate bottom-contact
OFET with thin-film of 1c. Obviously, IDS increases by
applying the negative VGS. Thus, it can be concluded that the
thin film of 1c behaves as a p-type semiconductor. As depicted
in Table S1 (Supporting Information), hole mobilities of
OFETs with thin films of 1c increase after annealing the thin
films of 1c at 80 and 100 °C. For instance, the OFETs with thin
films of 1c exhibit hole mobility up to 0.0063 cm2 V−1 s−1
(0.0054 cm2 V−1 s−1 on average) with on/off ratios up to 106
after annealing at 100 °C. But, the performance of OFETs of 1c
becomes poor after further increasing the annealing temper-
ature to 120 °C (see Table S1, Supporting Information).
Further optimization of OFET fabrication is underway to
improve the OFET performance.
The structures of 1c−f were investigated with theoretical
calculations based on density functional theory (DFT).59 It is
expected that the alkyl chains at the N,N′-positions of the new
π-expanded NDI core should not have a significant influence on
their electronic structures. Thus, the alkyl chains were replaced
by methyl groups for the DFT calculations. As depicted in
Figure 4, the central core of 1c−f is completely planar. The two
thiophene rings in 1c are almost coplanar with the central core,
but the respective two flanking moieties in 1d and 1e form
dihedral angles of ca. 158° with the central core. HOMO
orbitals of 1c−f are delocalized on both the central core and the
respective flanking groups, whereas LUMO orbitals are mostly
localized on the central core (see Figure 4). The calculated
HOMO/LUMO energies of 1c−f (see Table 2) are different
from those based on their cyclic voltammograms,60 but the
results do indicate that HOMO/LUMO energies of these new
extended conjugated molecules are affected by the respective
two flanking moieties.
XRD studies reveal that the crystallinity of the thin film of 1c
is improved upon annealing. The as-prepared thin-film
exhibited no diffraction peaks, and weak diffraction peaks at
2θ = 6.1° and 2θ = 12.2° appeared after annealing at 80 °C.
However, intensities of diffraction peaks at 2θ = 6.1° and 2θ =
12.2° increased, and new peaks at 2θ = 9.1, 21.4, and 23.8°
emerged after annealing at 100 °C (see Figure S11, Supporting
Organic Field-Effect Transistor with Thin Film of 1c.
Theoretical calculations reveal that 1c prefers to adopt a planar
conformation; thus, intermolecular π−π interactions are
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emissive behaves as a p-type semiconducting behavior with hole
mobility up to 0.0063 cm2 V−1 s−1.
It is expected that this new NDI-derived conjugated
framework is promising for constructing new optoelectronic
materials since different functionalities can be easily introduced
to this framework. Alternatively, compounds 1c and 1d can be
transformed into the corresponding 1c-2Br and 1d-2Br (see
Chart 1), which can be utilized as new building blocks to
Chart 1
prepare new conjugated D−A molecules and polymers toward
electronic materials of high performance. Therefore, this new
conjugated framework that is easily accessible from NDI
deserves further studies.
EXPERIMENTAL SECTION
■
2BrNDI (N-n-C8H17, N-C20H41) were synthesized according to the
reported procedures.65 The corresponding tin reagents were
synthesized according to the reported procedures and used directly
without further purification.66
Synthesis of 2a. A solution of 2BrNDI (N-C20H41) (108 mg, 0.11
mmol), tributyl(2-ferrocenylethynyl)stannane (165 mg, 0.33 mmol),
and a catalytic amount of Pd(PPh3)4 in toluene (30 mL) was refluxed
for 2.5 h under nitrogen atmosphere. After the reaction, the solvent
was evaporated under vacuum and the residue was subjected to silica
gel column chromatography with petroleum ether (60−90 °C)/
CH2Cl2 (v/v, 1/1) as eluent. Compound 2a was obtained as a dark
green solid (110 mg, 0.088 mmol) in 81% yield: mp 149.3−150.1 °C;
1H NMR (400 MHz, CDCl3) δ 8.80 (s, 2H), 4.72 (br, 4H), 4.42 (br,
4H), 4.33 (s, 10H), 4.18 (d, J = 6.6 Hz, 4H), 2.04 (br, 2H), 1.35−1.23
(m, 64H), 0.86 (m, 12H); 13C NMR (100 MHz, CDCl3) δ 162.8,
162.1, 137.4, 127.5, 126.4, 124.8, 105.0, 87.3, 72.6, 70.7, 70.4, 64.1,
45.0, 36.7, 32.1, 31.9, 30.2, 29.8, 29.5, 26.6, 22.8, 14.3; MS (MALDI-
TOF) m/z 1243.0 (M+). Anal. Calcd for C78H102Fe2N2O4: C, 75.35;
H, 8.27; N, 2.25. Found: C, 75.38; H, 8.29; N, 2.35.
Synthesis of 2b. Compound 2b was synthesized as for compound
2a and obtained as a blue solid in 84% yield: mp 170.8−172.1 °C; 1H
NMR (400 MHz, CD2Cl2): δ 8.64 (s, 2H), 7.46 (d, J = 8.3 Hz, 4H),
7.25 (m, 8H), 7.06 (m, 12H), 6.94 (d, J = 8.3 Hz, 4H), 4.03 (d, J = 6.7
Hz, 4H), 1.92 (br, 2H), 1.34−1.12 (m, 64H), 0.78−0.73 (m, 12H);
13C NMR (100 MHz, CDCl3) δ 162.7, 162.0, 149.5, 146.9, 137.2,
134.0, 129.7, 127.2, 126.5, 125.7, 124.9, 124.5, 124.3, 121.4, 114.8,
104.4, 90.3, 44.9, 36.5, 32.0, 31.7, 30.2, 29.8, 29.5, 26.5, 22.8, 14.3; MS
(MALDI-TOF) m/z 1361.7 (M+). Anal. Calcd for C94H112N4O4: C,
82.90; H, 8.29; N, 4.11. Found: C, 82.80; H, 8.24; N, 4.13.
Figure 5. Transfer characteristics (a) and output characteristics (b) for
OFET of 1c after annealing at 100 °C; the channel width (W) and
length (L) were 1440 and 50 μm, respectively.64.
Information). The crystallinity enhancement observed for the
thin film of 1c agrees well with the observation that hole
mobility increases after annealing. AFM images were also
measured for the thin ilm of 1c after annealing at different
temperatures (see Figure S11, Supporting Information). Thin-
film morphology is obviously altered after annealing the thin-
film of 1c. Relatively large domains which are interconnected
are formed after annealing at 100 °C.61 According to previous
reports,62,63 such thin-film morphology is beneficial for
enhancing carrier mobility.
CONCLUSION
■
In conclusion, we disclose a new synthetic approach to
transform NDI into extended conjugated molecules. The key
step of the transformation is the intramolecular cyclization
involving ethynyl and imidecarbonyl groups. New conjugated
molecules 1a−f were successfully synthesized in acceptable
yields. The structure of the intermediate pyrylium cation was
confirmed by X-ray crystal structural analysis. Except for 1a,
compounds 1b−f are emissive in solutions and their emission
characters can be tuned by varying the respective two flanking
moieties. Furthermore, 1b−f are also fluorescent in their solid
states; in particular, 1b exhibits aggregation-induced enhanced
emission. Yellow-emissive microfibrils of 1d show potential
optical waveguide behavior. The results also reveal that
HOMO/LUMO energies of 1a−f, which were determined on
the basis of their cyclic voltammograms, are influenced by the
two flanking moieties. Notably, the thin film of 1c that is
Synthesis of 2c. Compound 2c was synthesized as for compound
1
2a and obtained as a red solid in 86% yield: mp 142.8−143.4 °C; H
NMR (400 MHz, CDCl3) δ 8.79 (s, 2H), 7.56 (d, J = 1.9 Hz, 2H),
7.49 (d, J = 4.5 Hz, 2H), 7.12 (br, 2H), 4.15 (d, J = 6.7 Hz, 4H), 2.03
(br, 2H), 1.43−1.22 (m, 64H), 0.85−0.89 (m, 12H); 13C NMR (100
MHz, CDCl3) δ 162.5, 161.9, 136.9, 134.9, 130.6, 127.8, 126.8, 126.6,
125.2, 124.8, 122.7, 96.6, 94.3, 45.0, 36.6, 32.1, 31.8, 30.2, 29.8, 29.5,
26.5, 22.8, 14.3; MS (MALDI-TOF) m/z 1038.9 (M+). Anal. Calcd for
C66H90N2O4S2: C, 76.25; H, 8.73; N, 2.69. Found: C, 75.93; H, 8.69;
N, 2.76.
Synthesis of 2d. Compound 2d was synthesized as for compound
2a and obtained as an orange solid in 89% yield: mp 120.1−120.6 °C;
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1H NMR (400 MHz, CDCl3) δ 8.84 (s, 2H), 7.75 (br, 4H), 7.45 (br,
6H), 4.16 (d, J = 6.7 Hz, 4H), 2.04 (br, 2H), 1.44−1.22 (m, 64H),
0.86−0.85 (m, 12H); 13C NMR (100 MHz, CDCl3) δ 162.5, 161.9,
137.4, 132.8, 130.0, 128.7, 127.3, 126.6, 125.5, 125.2, 122.7, 103.0,
89.7, 45.0, 36.6, 32.1, 31.8, 30.2, 29.8, 29.5, 26.5, 22.8, 14.3; MS
(MALDI-TOF) m/z 1027.0 (M+). Anal. Calcd for C70H94N2O4: C,
81.82; H, 9.22; N, 2.73. Found: C, 81.83; H, 9.11; N, 2.56.
Synthesis of 2e. Compound 2e was synthesized similarly as for
compound 2a and obtained as an orange-yellow solid in 85% yield: mp
119.6−120.5 °C; 1H NMR (400 MHz, CDCl3) δ 8.77 (s, 2H), 7.83 (d,
J = 8.0 Hz, 4H), 7.68 (d, J = 8.1 Hz, 4H), 4.13 (d, J = 7.1 Hz, 4H),
2.00 (br, 2H), 1.42−1.21 (m, 64H), 0.87−0.82 (m 12H); 13C NMR
(150 MHz, CDCl3) δ 162.1, 161.5, 137.1, 132.9, 126.7, 126.3, 125.9,
125.6, 125.3, 124.8, 100.8, 91.2, 45.1, 36.6, 32.1, 31.8, 30.2, 29.8, 29.8,
29.5, 26.5, 22.8, 14.2; MS (MALDI-TOF) m/z 1162.7 (M+). Anal.
Calcd for C72H92F6N2O4: C, 74.32; H, 7.97; N, 2.41. Found: C, 73.99;
H, 8.07; N, 2.49.
Synthesis of 2f. Compound 2f was synthesized as for compound
2a and obtained as a yellow solid in 76% yield: mp 117.8−118.2 °C.
1H NMR (400 MHz, CDCl3) δ 8.68 (s, 2H), 4.11 (d, J = 7.4 Hz, 4H),
2.32 (s, 6H), 2.00 (br, 2H), 1.39−1.22 (m, 64H), 0.93−0.87 (m,
12H); 13C NMR (100 MHz, CDCl3) δ 162.4, 162.1, 138.0, 128.2,
126.2, 125.5, 125.0, 101.6, 80.0, 45.1, 36.5, 32.0, 31.7, 30.2, 29.8, 29.5,
26.5, 22.8, 14.2; MS (MALDI-TOF) m/z 902.8 (M+). Anal. Calcd for
C60H90N2O4: C, 79.77; H, 10.04; N, 3.10. Found: C, 79.69; H, 10.24;
N, 3.15.
109.0, 84.1, 70.6, 70.0, 68.0, 46.2, 36.7, 32.0, 30.3, 29.8, 29.5, 29.4,
27.1, 22.8, 14.25; MS (MALDI-TOF) m/z 1240.9 (M+). Anal. Calcd
for C78H104Fe2N4O2: C, 75.47; H, 8.44; N, 4.51. Found: C, 75.61; H,
8.58; N, 4.52.
Synthesis of 1b. Compound 1b was synthesized similarly and
obtained as a red solid (42% yield based on compound 2b): mp
1
208.1−209.2 °C; H NMR (400 MHz, CD2Cl2) δ 8.76 (s, 2H), 8.03
(d, J = 8.2 Hz, 4H), 7.95 (s, 2H), 7.26−7.22 (m, 8H), 7.12−7.07 (m,
12H), 7.04−7.00 (m, 4H), 4.41 (d, J = 6.4 Hz, 4H), 2.09 (br, 2H),
1.24−1.01 (m, 64H), 0.75−0.68 (m, 12H); 13C NMR (100 MHz,
CDCl3) δ 162.5, 152.1, 149.3, 147.5, 135.3, 132.0, 129.6, 128.3, 125.6,
125.3, 123.8, 122.6, 121.5, 111.0, 109.2, 46.0, 36.7, 32.0, 31.9, 30.2,
29.8, 29.7, 29.5, 29.4, 26.9, 22.8, 22.8, 14.2; MS (MALDI-TOF) m/z
1359.4 (M+). Anal. Calcd for C94H114N6O2: C, 83.02; H, 8.45; N, 6.18.
Found: C, 82.94; H, 8.51; N, 6.25.
Synthesis of 1c. Compound 1c was synthesized similarly and
obtained as a orange solid (60% yield based on compound 2c): mp
202.1−203.3 °C; 1H NMR (400 MHz, CDCl3) δ 8.82 (s, 2H), 7.92 (s,
2H), 7.79 (br, 2H), 7.47 (br, 2H), 7.20 (br, 2H), 4.48 (d, J = 5.2 Hz,
4H), 2.16 (br, 2H), 1.36−1.15 (m, 64H), 0.84−0.81 (m, 12H); 13C
NMR (100 MHz, CDCl3) δ 162.0, 149.1, 148.0, 145.0, 135.0, 128.5,
128.4, 125.3, 121.4, 109.9, 109.1, 46.2, 36.5, 32.0, 31.8, 30.3, 29.8, 29.5,
26.7, 22.8, 14.2; MS (MALDI-TOF) m/z 1037.0 (M+). Anal. Calcd for
C66H92N4O2S2: C, 76.40; H, 8.94; N, 5.40. Found: C, 76.40; H, 8.99;
N, 5.37.
Synthesis of 1d. Compound 1d was synthesized similarly and
obtained as a yellow solid (52% yield based on compound 2d): mp
142.5−143.4 °C; 1H NMR (400 MHz, CDCl3) δ 8.92 (s, 2H), 8.27 (d,
J = 7.3 Hz, 4H), 8.14 (s, 2H), 7.60−7.52 (m, 6H), 4.52 (d, J = 6.6 Hz,
4H), 2.16 (br, 2H), 1.35−1.13 (m, 64H), 0.86−0.79 (m, 12H); 13C
NMR (100 MHz, CDCl3) δ 162.3, 152.4, 149.2, 138.7, 135.2, 129.6,
129.1, 128.4, 127.5, 125.5, 121.4, 111.9, 109.3, 46.1, 36.7, 32.0, 30.3,
29.8, 29.5, 26.9, 22.8, 22.8, 14.2; MS (MALDI-TOF) m/z 1025.0
(M+). Anal. Calcd for C70H96N4O2: C, 81.98; H, 9.44; N, 5.46. Found:
C, 81.88; H, 9.43; N, 5.45.
Synthesis of 2g. Compound 2g was synthesized as for 2a and
1
obtained as a deep green solid in 71% yield: mp 260.0 °C dec; H
NMR (400 MHz, CDCl3) δ 8.79 (s, 2H), 4.74 (br, 4H), 4.43 (br, 4H),
4.33 (s, 10H), 4.22 (br, 4H), 1.78 (br, 4H), 1.45−1.29 (m, 20H), 0.88
(br, 6H); 13C NMR (100 MHz, CDCl3) δ 162.4, 161.8, 137.4, 127.4,
126.4, 124.8, 124.7, 105.2, 87.4, 72.7, 70.7, 70.5, 64.1, 41.1, 32.0, 29.5,
29.4, 27.3, 22.8, 14.3; MS (MALDI-TOF) m/z 906.7 (M+). Anal.
Calcd for C54H54Fe2N2O4: C, 71.53; H, 6.00; N, 3.09. Found: C,
71.20; H, 6.13; N, 3.14.
Synthesis of 1e. Compound 1e was synthesized similarly and
obtained as a yellow solid (46% yield based on compound 2e): mp
159.5−160.3 °C; 1H NMR (400 MHz, CDCl3) δ 8.98 (s, 2H), 8.32 (d,
J = 8.0 Hz, 4H), 8.16 (s, 2H), 7.81 (d, J = 8.1 Hz, 4H), 4.54 (d, J = 7.0
Hz, 4H), 2.16 (br, 2H), 1.23−1.13 (m, 64H), 0.85−0.78 (m, 12H);
13C NMR (150 MHz, CDCl3) δ 162.1, 150.9, 149.6, 141.8, 135.3,
128.6, 127.6, 126.1, 125.2, 123.3, 121.7, 112.6, 109.8, 46.1, 36.7, 32.0,
32.0, 30.3, 29.8, 29.7, 29.4, 26.9, 22.8, 14.2, 14.2; MS (MALDI-TOF)
m/z 1160.6 (M+). Anal. Calcd for C72H94F6N4O2: C, 74.45; H, 8.16;
N, 4.82. Found: C, 74.51; H, 8.36; N, 4.80.
Synthesis of 1f. Compound 1f was synthesized similarly and
obtained as a yellow solid (59% yield based on compound 2f): mp
160.1−161.1 °C; 1H NMR (400 MHz, CDCl3) δ 9.09 (s, 2H), 7.71 (s,
2H), 4.69 (d, J = 6.4 Hz, 4H), 2.87 (s, 6H), 2.25 (br, 2H), 1.48−1.19
(m, 64H), 0.87−0.81 (m, 12H); 13C NMR (100 MHz, CDCl3) δ
162.6, 154.1, 149.2, 135.0, 127.5, 125.6, 121.5, 114.6, 108.7, 45.6, 36.6,
32.0, 30.2, 29.8, 29.8, 29.5, 26.7, 25.3, 22.8, 22.8, 14.2; MS (MALDI-
TOF) m/z 900.4 (M+). Anal. Calcd for C60H92N4O2: C, 79.95; H,
10.29; N, 6.22. Found: C, 79.98; H, 10.29; N, 6.25.
Synthesis of 3a−d. TFSIH (39 mg, 0.14 mmol) was added to a
solution of 2a (70 mg, 0.056 mmol) in CH2Cl2 (5.0 mL) under
nitrogen atmosphere. The solution was stirred for 30 min at room
temperature. The solvent was removed under reduced pressure to give
3a as a purple solid. Compound 3a was used for next step without
further purification. Compounds 3b−d were synthesized similarly, and
they all were used for the next step without further purification.
Synthesis of 3e,f. TFSIH (280 mg, 1.0 mmol) was added to a
solution of 2e (233 mg, 0.20 mmol) in CH2Cl2 (15 mL) under
nitrogen atmosphere. The solution was refluxed for 24 h. The solvent
was removed under reduced pressure to give 3e as a red solid.
Compound 3e was used for the next step without further purification.
Compound 3f was synthesized similarly as for compound 3e and used
for the next step without further purification.
Synthesis of 3g. Compound 3g was synthesized similarly as for
compound 3a. However, after the reaction, deep purple crystals were
filtered and washed with n-hexane to give 3g in 90% yield: mp 240.0
1
°C dec; H NMR (400 MHz, CD3CN): δ 9.11 (s, 2H), 8.07 (s, 2H),
5.32 (br, 4H), 5.11 (br, 4H), 4.61 (br, 4H), 4.42 (s, 10H), 1.66 (br,
4H), 1.51−1.35 (m, 20H), 0.91 (br, 6H). Anal. Calcd for
C58H56F12Fe2N4O12S4: C, 47.42; H, 3.84; N, 3.81. Found: C, 47.13;
H, 3.88; N, 3.94.
Synthesis of 1g. Compound 1g was synthesized similarly and
obtained as a red solid (58% yield based on compound 2g): mp 296.0
1
°C dec; H NMR (400 MHz, CDCl3) δ 9.15 (s, 2H), 7.91 (s, 2H),
Synthesis of 1a. To a dry CH3OH solution (15 mL) of compound
3a (obtained without further purification, 0.056 mmol) was added
NH3·H2O (0.25 mL, 6.5 mmol). The color immediately changed from
deep purple to red, and the solution was refluxed for 1.0 h. Then, the
mixture was diluted with water (30 mL) and extracted with CH2Cl2 (3
× 20 mL). The organic layer was dried with MgSO4 and concentrated
by rotary evaporation. The crude was purified by silica gel column
chromatograph with petroleum ether (60−90 °C)/CH2Cl2 (v/v, 2/1)
as eluent to give 1a as a red solid (33.5 mg) in 47% yield: mp 178.0 °C
5.18 (br, 4H), 4.85 (br, 4H), 4.55 (br, 4H), 4.08 (s, 10H), 2.03 (br,
4H), 1.64 (br, 4H), 1.39−1.26 (m, 16H), 0.89 (br, 6H); 13C NMR (75
MHz, 1,2-dichlorobenzene-d4, 100 °C) δ 161.8, 155.5, 149.3, 135.3,
133.3, 131.0, 122.1, 110.6, 109.4, 84.5, 70.3, 69.8, 68.0, 41.9, 31.9, 29.6,
29.3, 28.4, 27.6, 22.5, 13.8; MS (MALDI-TOF) m/z 904.4 (M+). Anal.
Calcd for C54H56Fe2N4O2: C, 71.69; H, 6.24; N, 6.19. Found: C,
71.31; H, 6.12; N, 6.12.
Fabrication of OFETs. Bottom-gate bottom-contact OFETs were
fabricated. A heavily doped Si wafer and a layer of dry oxidized SiO2
(300 nm) were used as a gate electrode and gate dielectric layer,
respectively. The drain-source (D-S) gold contacts were fabricated by
photolithography. The substrates were cleaned in water, deionized
water, ethanol, and rinsed in acetone. Then, the surface was modified
1
dec; H NMR (400 MHz, CDCl3) δ 8.96 (s, 2H), 7.77 (s, 2H), 5.14
(br, 4H), 4.63 (d, J = 6.8 Hz, 4H), 4.53 (br, 4H), 4.03 (s, 10H), 2.33
(br, 2H), 1.47−1.19 (m, 64H), 0.86−0.78 (m, 12H); 13C NMR (100
MHz, CDCl3) δ 162.7, 155.2, 149.2, 134.9, 128.0, 125.7, 121.7, 110.9,
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with n-octadecyltrimethoxysilane (OTS). After that, the substrates
were cleaned in n-hexane and CHCl3 and C2H5OH. Compound 1c
were dissolved in CHCl3 (about 10 mg/mL) and spin-coated on the
substrate at 2000 rpm. The annealing processes were carried out in
vacuum condition for 60 min at each temperature.
The field-effect mobility of holes (μh) was calculated by fitting a
straight line to the plot of the square root of IDS vs VG (saturation
region), according to the expression IDS = (W/2L)μhCi(VG − VTH)2,
where IDS is the drain electrode collected current; L and W are the
channel length and width, respectively; μh is the mobility of the device;
Ci is the capacitance per unit area of the gate dielectric layer; VG is the
gate voltage;and VTH is the threshold voltage.
(10) (a) Liu, Y.; Zhan, X. Macromol. Chem. Phys. 2011, 212, 428−
443. (b) Zhang, Y.; Zou, J.; Cheuh, C.; Yip, H.; Jen, A. K.-Y.
Macromolecules 2012, 45, 5427−5435. (c) Gao, Y.; Yip, H.; Chen, K.;
O’Malley, K.; Acton, O.; Sun, Y.; Ting, G.; Chen, H.; Jen, A. K.-Y. Adv.
Mater. 2011, 23, 1903−1908.
(11) Yue, W.; Lv, A.; Gao, J.; Jiang, W.; Hao, L.; Li, C.; Li, Y.;
Polander, L. E.; Barlow, S.; Hu, W.; Motta, S.; Negri, F.; Marder, S. R.;
Wang, Z. J. Am. Chem. Soc. 2012, 134, 5770−5773.
(12) Brabec, C. J.; Heeney, M.; McCullochb, I.; Nelsonc, J. Chem.
Soc. Rev. 2011, 40, 1185−1199.
(13) Sergeyev, S.; Pisula, W.; Geerts, Y. H. Chem. Soc. Rev. 2007, 36,
1902−1929.
(14) Zhou, J.; Wan, X.; Liu, Y.; Long, G.; Wang, F.; Li, Z.; Zuo, Y.; Li,
C.; Chen, Y. Chem. Mater. 2011, 23, 4666−4668.
(15) Chen, H.; Guo, Y.; Yu, G.; Zhao, Y.; Zhang, J.; Gao, D.; Liu, H.;
Liu, Y. Adv. Mater. 2012, 24, 4618−4622.
ASSOCIATED CONTENT
* Supporting Information
■
S
General information, UV−vis absorption, femtosecond tran-
sient absorption spectra, fluorescence decay curves, cyclic
voltammograms, XRD patterns and AFM images, TGA
analysis, X-ray crystallographic data, theoretical calculations
(16) Bhosale, S. V.; Bhargava, S. K. Org. Biomol. Chem. 2012, 10,
6455−6468.
(17) Sakai, N.; Mareda, J.; Vautheyb, E.; Matile, S. Chem. Commun.
2010, 46, 4225−4237.
1
data, and H NMR and 13C NMR specra. This material is
(18) Wurthner, F.; Stolte, M. Chem. Commun. 2011, 47, 5109−5115.
̈
available free of charge via the Internet at http://pubs.acs.org.
(19) Zhan, X.; Facchetti, A.; Barlow, S.; Marks, T. J.; Ratner, M. A.;
Wasielewski, M. R.; Marder, S. R. Adv. Mater. 2011, 23, 268−284.
(20) (a) Alam, M. M.; Jenekhe, S. A. Chem. Mater. 2004, 16, 4647−
4656. (b) Ahmed, E.; Ren, G.; Kim, F. S.; Hollenbeck, E. C.; Jenekhe,
S. A. Chem. Mater. 2011, 23, 4563−4577. (c) Fabiano, S.; Chen, Z.;
Vahedi, S.; Facchetti, A.; Pignataro, B.; Loi, M. A. J. Mater. Chem.
2011, 21, 5891−5896. (d) Schubert, M.; Dolfen, D.; Frisch, J.; Roland,
S.; Steyrleuthner, R.; Stiller, B.; Chen, Z.; Scherf, U.; Koch, N.;
Facchetti, A.; Neher, D. Adv. Energy Mater. 2012, 2, 369−380.
(21) Chopin, S.; Chaignon, F.; Blart, E.; Odobel, F. J. Mater. Chem.
2007, 17, 4139−4146.
AUTHOR INFORMATION
Corresponding Author
*E-mail: (G.Z.) gxzhang@iccas.ac.cn, (D.Z.) dqzhang@iccas.ac.
■
cn.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
The present research was financially supported by NSFC, the
State Basic Program, and the Chinese Academy of Sciences.
■
(22) Chang, J.; Ye, Q.; Huang, K.; Zhang, J.; Chen, Z.; Wu, J.; Chi, C.
Org. Lett. 2012, 14, 2964−2967.
(23) Chen, Z.; Zheng, Y.; Yan, H.; Facchetti, A. J. Am. Chem. Soc.
2009, 131, 8−9.
REFERENCES
■
(24) Yan, H.; Chen, Z.; Zheng, Y.; Newman, C.; Quinn, J. R.; Dotz,
̈
(1) (a) Li, L.; Gao, P.; Schuermann, K. C.; Ostendorp, S.; Wang, W.;
Du, C.; Lei, Y.; Fuchs, H.; Cola, L. D.; Mullen, K.; Chi, L. J. Am. Chem.
F.; Kastler, M.; Facchetti, A. Nature 2009, 457, 679−686.
(25) Baeg, K.; Khim, D.; Jung, S.; Kang, M.; You, I.; Kim, D.;
Facchetti, A.; Noh, Y. Adv. Mater. 2012, 24, 5433−5439.
(26) Gao, X.; Di, C.; Hu, Y.; Yang, X.; Fan, H.; Zhang, F.; Liu, Y.; Li,
H.; Zhu, D. J. Am. Chem. Soc. 2010, 132, 3697−3699.
(27) Zhao, Y.; Di, C.; Gao, X.; Hu, Y.; Zhang, L.; Liu, Y.; Wang, J.;
Hu, W.; Zhu, D. Adv. Mater. 2011, 23, 2448−2453.
̈
Soc. 2010, 132, 8807−8809. (b) Dasgupta, D.; Srinivasan, S.; Rochas,
C.; Thierry, A.; Schroeder, A.; Ajayaghosh, A.; Guenet, J. M. Soft
Matter 2011, 7, 2797−2804. (c) Ajayaghosh, A.; J.George, S. J. Am.
Chem. Soc. 2001, 123, 514−517.
(2) (a) Henson, Z. B.; Mullen, K.; Bazan, G. C. Nature Chem. 2012,
̈
4, 699−704. (b) Chen, L.; Hernandez, Y.; Feng, X.; Mullen, K. Angew.
̈
(28) Hu, Y.; Gao, X.; Di, C.; Yang, X.; Zhang, F.; Liu, Y.; Li, H.; Zhu,
D. Chem. Mater. 2011, 23, 1204−1215.
Chem., Int. Ed. 2012, 51, 7640−7654.
(3) (a) Liu, W. J.; Zhou, Y.; Ma, Y. G.; Cao, Y.; Wang, J.; Pei, J. Org.
Lett. 2007, 9, 4187−4189. (b) Lei, T.; Cao, Y.; Fan, Y.; Liu, C.-J.;
Yuan, S.-C.; Pei, J. J. Am. Chem. Soc. 2011, 133, 6099−6101.
(4) (a) Okamoto, T.; Senatore, M. L.; Ling, M. M.; Mallik, A. B.;
Tang, M. L.; Bao, Z. Adv. Mater. 2007, 19, 3381−3384. (b) Mei, J.;
Kim, D. H.; Ayzner, A. L.; Toney, M. F.; Bao, Z. J. Am. Chem. Soc.
2011, 133, 20130−20133.
(29) Suraru, S. L.; Zschieschang, U.; Klauk, H.; Wurthner, F. Chem.
̈
Commun. 2011, 47, 11504−11506.
(30) (a) Tan, L.; Guo, Y.; Zhang, G.; Yang, Y.; Zhang, D.; Yu, G.; Xu,
W.; Liu, Y. J. Mater. Chem. 2011, 21, 18042−18048. (b) Tan, L.; Guo,
Y.; Yang, Y.; Zhang, G.; Zhang, D.; Yu, G.; Xu, W.; Liu, Y. Chem. Sci.
2012, 3, 2530−2541.
(31) (a) Herbst, M.; Hunger, K. Industrial Organic Pigments; VCH:
New York, 1993. (b) Herbst, W.; Hunger, K. Industrial Organic
Pigments, Production, Properties, Applications; Wiley-VCH: Weinheim,
1997.
(5) (a) Qu, Y.; Hua, J.; Tian, H. Org. Lett. 2010, 12, 3320−3323.
(b) Ning, Z.; Zhang, Q.; Wu, W.; Pei, H.; Liu, B.; Tian, H. J. Org.
Chem. 2008, 73, 3791−3797.
(6) (a) Wang, C.; Dong, H.; Hu, W.; Liu, Y.; Zhu, D. Chem. Rev.
2012, 112, 2208−2267. (b) Li, R.; Hu, W.; Liu; Zhu, D. Acc. Chem.
Res. 2010, 43, 529−540.
(7) (a) Cao, Y.; Liu, S.; Shen, Q.; Yan, K.; Li, P.; Xu, J.; Yu, D.;
Steigerwald, M. L.; Nuckolls, C.; Liu, Z.; Guo, X. Adv. Funct. Mater.
2009, 19, 2743−2748. (b) Cao, Y.; Steigerwald, M. L.; Nuckolls, C.;
Guo, X. Adv. Mater. 2010, 22, 20−32.
(32) Quinto, M.; Jenekhe, S. A.; Bard, A. J. Chem. Mater. 2001, 13,
2825−2834.
(33) Babel, A.; Jenekhe, S. A. J. Am. Chem. Soc. 2003, 125, 13656−
13657.
(34) Langhals, H.; Jaschke, H. Chem.Eur. J. 2006, 12, 2815−2824.
(35) Ortiz, R. P.; Herrera, H.; Seoane, C.; Segura, J. L.; Facchetti, A.;
Marks, T. J. Chem.Eur. J. 2012, 18, 532−536.
(36) Polander, L. E.; Pandey, L.; Romanov, A.; Fonari, A.; Barlow, S.;
(8) (a) Osaka, I.; Abe, T.; Shinamura, S.; Takimiya, K. J. Am. Chem.
Soc. 2011, 133, 6852−6860. (b) Osaka, I.; Abe, T.; Shinamura, S.;
Miyazaki, E.; Takimiya, K. J. Am. Chem. Soc. 2010, 132, 5000−5001.
́
Seifried, B. M.; Timofeeva, T. V.; Bredas, J.; Marder, S. R. J. Org. Chem.
2012, 77, 5544−5551.
(9) (a) Wurthner, F. Angew. Chem., Int. Ed. 2001, 40, 1037−1039.
̈
(37) Durban, M. M.; Kazarinoff, P. D.; Segawa, Y.; Luscombe, C. K.
(b) Schmidt, R.; Ling, M. M.; Oh, J. H.; Winkler, M.; Konemann, M.;
̈
Bao, Z.; Wurthner, F. Adv. Mater. 2007, 19, 3692−3695.
Macromolecules 2011, 44, 4721−4728.
̈
2933
dx.doi.org/10.1021/jo302677k | J. Org. Chem. 2013, 78, 2926−2934

The Journal of Organic Chemistry
Article
(38) (a) Chopin, S.; Chaignon, F.; Blart, E.; Odobel, F. J. Mater.
(53) Deans, R.; Kim, J.; Machacek, M. R.; Swager, T. M. J. Am. Chem.
Soc. 2000, 122, 8565−8566.
Chem. 2007, 17, 4139−4146. (b) Wurthner, F.; Suraru, S.-L. Synthesis
̈
(54) Efforts were made to prepare the single crystals of 1b to
determine the structure of 1b in the solid state, but failed.
(55) (a) Wu, Y.; Li, J.; Ai, X.; Fu, L.; Zhang, J.; Fu, Y.; Zhou, J.; Li, L.;
Bo, Z. J. Phys. Chem. A 2007, 111, 11473−11479. (b) Liu, H.; Jia, H.;
Wang, L.; Wu, Y.; Zhan, C.; Fu, H.; Yao, J. Phys. Chem. Chem. Phys.
2012, 14, 14262−14269.
2009, 2009, 1841−1845.
(39) (a) Kondo, M.; Uchikawa, M.; Namiki, K.; Zhang, W.; Kume, S.;
Nishibori, E.; Suwa, H.; Aoyagi, S.; Sakata, M.; Murata, M.; Kobayashi,
Y.; Nishihara, H. J. Am. Chem. Soc. 2009, 131, 12112−12124.
(b) Kondo, M.; Uchikawa, M.; Kume, S.; Nishihara, H. Chem.
Commun. 2009, 45, 1993−1995.
(56) Compared to the oxidation potentials of free ferrocene and
triphenylamine (see Figure S10, Supporting Information), the
oxidation potentials of 1a and 1b were positively shifted by 0.10 and
0.04 V, respectively. This is probably due to the respective
intramolecular electron donor−acceptor interactions within 1a and 1b.
(57) De Leeuw, D. M.; Simenon, M. M. J.; Brown, A. R.; Einerhand,
R. E. F. Synth. Met. 1997, 87, 53−59.
(58) Usta, H.; Facchetti, A.; Marks, T. J. J. Am. Chem. Soc. 2008, 130,
8580−8581.
(59) Because of the limitation of calculation capacity, the DFT
calculations were not performed for 1a and 1b.
(40) Rao, K.; Kusamoto, T.; Toshimitsu, F.; Inayoshi, K.; Kume, S.;
Sakamoto, R.; Nishihara, H. J. Am. Chem. Soc. 2010, 132, 12472−
12479.
(41) Kondo, M.; Uchikawa, M.; Zhang, W.; Namiki, K.; Kume, S.;
Murata, M.; Kobayashi, Y.; Nishihara, H. Angew. Chem., Int. Ed. 2007,
46, 6271−6274.
(42) Compound 1g shows almost the same absorption spectra (see
Figure S1, Supporting Information) as 1a. This is understandable as
they contain the same conjugated moieties.
(43) As an example, the absorption spectrum of 1b was measured in
solvents of different polarities (see Figure S3, Supporting Informa-
tion). The absorption spectrum of 1b was slightly red-shifted in polar
solvents. Moreover, the fluorescence spectrum of 1b was largely red-
shifted in acetone and ethyl acetate compared to that in hexane. These
results provide the support for existence of intramolecular interactions
between the respective electron-donating and -accepting moieties in
1a−d.
(44) As an example, the femtosecond transient absorption spectra of
1b in benzonitrile were measured after irradiation. Figures S6−S8
(Supporting Information) show the absorption spectra at different
delay times, the time profile of the transient absorption at 540 nm, and
the time profile of the transient absorption at 650 nm. According to
previous reports, the absorption at 650 nm should be due to the
radical cation of triphenylamin: Oyama, M.; Nozaki, K.; Okasaki, S.
Anal. Chem. 1991, 63, 1387−1392. De la Fuente, J.; Neira, V.; Saitz,
C.; Jullian, C.; Sobarzo-Sanchez, E. J. Phys. Chem. A 2005, 109, 5897−
5904. Therefore, the formation of the radical cation of triphenylamine
upon photoirradiation provides direct evidence for the photoinduced
electron transfer between the triphenylamine moieties and the central
core in 1b upon light irradiation. In addition, the free-rotation of
phenyl fragments within triphenylamine moieties will also lead to weak
fluorescence of 1b in solution.
(60) The differences may result from the fact that the solvent effects
were not included in the calculations.
(61) However, domain sizes decrease after further annealing at 120
°C. Also, XRD diffraction peaks become weak. These are in agreement
with the observation that hole mobility of OFETs of 1c decreases after
further annealing at 120 °C (see Table S1, Supporting Information).
(62) Meng, H.; Bao, Z.; Lovinger, A. J.; Wang, B. C.; Mujsce, A. M. J.
Am. Chem. Soc. 2001, 123, 9214−9215.
(63) Wu, Y.; Li, Y.; Gardner, S.; Ong, B. S. J. Am. Chem. Soc. 2005,
127, 614−618.
(64) The existence of contact resistance is probably due to the fact
that the HOMO level of 1c (−5.76 eV) does not match the work
function of gold electrodes, and thus, the injection barrier is induced.
(65) Chaignon, F.; Falkenstrom, M.; Karlsson, S.; Blart, E.; Odobel,
̈
F.; Hammarstrom, L. Chem. Commun. 2007, 43, 64−66.
̈
(66) Dallairel, C.; Brook, M. A. Organometallics 1993, 12, 2332−
2338.
(45) This can be again attributed to the intramolecular photoinduced
electron transfer between ferrocene moieties and the electron-
accepting central conjugated core.
(46) (a) Kuwabara, J.; Yamagata, T.; Kanbara, T. Tetrahedron 2010,
66, 3736−3741. (b) Mei, J.; Wang, J.; Sun, J.; Zhao, H.; Yuan, W.;
Deng, C.; Chen, S.; Sung, H. H. Y.; Lu, P.; Qin, A.; Kwok, H.; Ma, Y.;
Williams, I. D.; Tang, B. Chem. Sci 2012, 3, 549−558.
(47) Lei, T.; Chen, H.; Yin, J.; Huang, S.; Zhu, X.; Pei, J. Org.
Electron. 2011, 12, 453−460.
(48) Both photoinduced electron-transfer and free rotations of
phenyl fragments within triphenylamine moieties contribute to the
weak fluorescence of 1b in solution. In the solid state, 1b may adopt a
more twisting conformation, and as a result the intramolecular electron
donor−acceptor interactions may be weakened; accordingly, the
photoinduced electron transfer may become less effective in
comparison with that in solution. More importantly, the free rotations
can be inhibited in the solid state (after aggregation). These synergic
effects may lead to fluorescent enhancement for 1b in the solid state
(after aggregation).
(49) Dong, Y.; Lam, J. W. Y.; Qin, A.; Li, Z.; Sun, J.; Sung, H. H.-Y;
Williams, I. D.; Tang, B. Chem. Commun. 2007, 43, 40−42.
(50) Hong, Y.; Lam, J. W. Y.; Tang, B. Chem. Soc. Rev. 2011, 40,
5361−5388.
(51) Qi, X.; Li, H.; Lam, J. W. Y.; Yuan, X.; Wei, J.; Tang, B.; Zhang,
H. Adv. Mater. 2012, 24, 4191−4195.
(52) Zeng, Q.; Li, Z.; Dong, Y.; Di, C.; Qin, A.; Hong, Y.; Ji, L.; Zhu,
Z.; Jim, C. K. W.; Yu, G.; Li, Q.; Li, Z.; Liu, Y.; Qin, J.; Tang, B. Chem.
Commun. 2007, 43, 70−78.
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