Regioselective Substitution at the 1,3- and 6,8-Positions of Pyrene for the Construction of Small Dipolar Molecules

Article abstract of DOI:10.1021/acs.joc.5b02128

This article presents a novel asymmetrical functionalization strategy for the construction of dipolar molecules via efficient regioselective functionalization along the Z-axis of pyrene at both the 1,3- and 6,8-positions. Three asymmetrically substituted

Full text of DOI:10.1021/acs.joc.5b02128

Article
pubs.acs.org/joc
Regioselective Substitution at the 1,3- and 6,8-Positions of Pyrene
for the Construction of Small Dipolar Molecules
Xing Feng,†,‡ Hirotsugu Tomiyasu,‡ Jian-Yong Hu,*,§ Xianfu Wei,† Carl Redshaw,∥ Mark R. J. Elsegood,⊥
Lynne Horsburgh,⊥ Simon J. Teat,# and Takehiko Yamato*,‡
†Beijing Institute of Graphic Communication, Beijing 102600, P. R. China
‡Department of Applied Chemistry, Faculty of Science and Engineering, Saga University, Honjo-machi 1, Saga 840-8502, Japan
§School of Materials Science and Engineering, Shannxi Normal University, Xi’an, 710062 Shannxi, P. R. China
∥Department of Chemistry, The University of Hull, Cottingham Road, Hull, Yorkshire HU6 7RX, U.K.
⊥Chemistry Department, Loughborough University, Loughborough, Leicestershire LE11 3TU, U.K.
#Advanced Light Source, Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, United States
S
* Supporting Information
ABSTRACT: This article presents a novel asymmetrical functionalization strategy for the construction of dipolar molecules via
efficient regioselective functionalization along the Z-axis of pyrene at both the 1,3- and 6,8-positions. Three asymmetrically
substituted 1,3-diphenyl-6,8-R-disubsituted pyrenes were fully characterized by X-ray crystallography, photophysical properties,
electrochemistry, and density functional theory calculations.
-accepting strength on the emission color of dipolar molecules,
or the regio-chemical relationship between donor and acceptor
units.
Recently, the Kim group and the Lee group developed a set
of tetrakis-substituted pyrenes functionalized with electron
donor and electron acceptor moieties located at the 1,6- and
3,8-positions randomly in nature, respectively.10 However,
reports focusing on regioselectively substituted pyrene
derivatives for bipolar materials are scant, because of the lack
of straightforward strategies for modifying the pyrene core.
INTRODUCTION
■
The construction of dipolar molecules with donor−acceptor
(D−A) type structures are of interest given their potential
application in organic optoelectronic devices.1 Such dipolar
architectures can, via a suitable choice of the D−A units, fine-
tune the electron redistribution, facilitate simultaneous
manipulation of the HOMO−LUMO energy gap and the
emission color by intramolecular charge transfer (ICT),2
control crystallinity,3 and be used to self-assemble molecular
morphologies.4
Pyrene5 belongs to a family of polycyclic aromatic hydro-
carbons (PAHs) with a natural electron-donating role and an
electron-accepting role.6 Apart from other PAHs like
anthracene7 and fluorene,8 pyrene that possess the equivalent
activity of the sites at the 1-, 3-, 6-, and 8-positions, it is
different challenge to develop an effectively rational synthetic
strategy for the asymmetric functionalization of pyrene.
Typically, tetrabromopyrene and pyrene tetraone derivatives
as key precursors were extensively utilized in the construction
of PAHs for semiconductor applications, via the introduction of
terminal moieties.5,9 Until now, few examples of pyrene
chemistry have focused on constructing a “push−pull” system
or investigating the effect of the electron-donating and
Mullen et al. reported the selective asymmetric functionaliza-
̈
tion of pyrene at the K-region for use in organic field-effect
transistors via a two-step chemical functionalization.11 Mean-
while, Bodwell et al. reported a regioselective synthesis of 4,5-
dialkoxy-1,8-dibromopyrenes for preparing 1,8-pyrenylene-
ethynylene macrocycles.12 After that, a series pyrene derivatives
with D−A substituents of the pyrene derivative in the K-region
was presented as follows.13 Very recently, both strong donors
and acceptors were introduced into the K-region and the 2,7-
positions, respectively, via 2,7-dibromo- and 2,7-diiodopyrene-
Received: September 10, 2015
© XXXX American Chemical Society
A
DOI: 10.1021/acs.joc.5b02128
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a
Scheme 1. Synthetic Route for the Preparation of 5 and 6
a
(a) Nafion-H, o-xylene, 160 °C, 24 h; (b) BTMABr3 (benzyltrimethylammonium tribromide), CH2Cl2/MeOH, rt, 12 h; (c) NHPh2F, Pd(OAc)2/
(tBu)3P/K2CO3, toluene, 100 °C, 24 h; (d) 4-ethynyl-1,1′-biphenyl, [PdCl2(PPh3)2], CuI, PPh3, Et3N/DMF (1:1), 48 h, 100 °C; (e) CuCN, NMP,
48 h, 180 °C; (f) phenylboronic acid, Pd(PPh3)4, K2CO3, toluene, 90 °C, 24 h.
4,5,9,10-tetraones as the key intermediates.14 Such novel
synthetic procedures at the pyrene core not only greatly enrich
our knowledge of synthetic chemistry but also stimulate further
research into semiconductor materials.
6,8-positions of pyrene shows potential advantages. (a) More
artificial dipolar pyrene-based molecules would be synthesized
from bromopyrene intermediations than by Pd-catalyzed forms.
(b) Introduction of the substitutions at 1,3,6,8-positions would
lead to a special influence on both the S2 ← S0 and S1 ← S0
transition18,19 compared with other substitution patterns. (c)
This strategy is beneficial for tuning the band gap of the dipolar
architectures to realize color control by introducing the
substitution groups. For comparison, 1,3,6,8-tetraphenylpyrene
(TPPy, 6)20 was synthesized.
Suitable single crystals were obtained by slow evaporation of
a CH2Cl2/hexane solvent for 2,16 5b (CCDC 1025083), and 6
(CCDC 1025084) and a CH2Cl2/acetone solvent for 3
(CCDC 1025085) at rt. The crystal structures are presented
in Figure 1 and the Supporting Information. Generally, the
Unlike the previously mentioned studies, our interest stems
from exploring new effective strategies for preparing asym-
metrically substituted pyrene along the Z-axis to be used in
high-performance electroluminescence material applications.
Previously, we have released a novel approach for modifying
both at active position of 1,3- and K-region of 4,5,9,10-position
using classical methods from 1,3-dibromo-7-tert-butylpyrene in
considerable yield;15 in this case, a tert-butyl group plays a role
in protecting the ring against electrophilic attack at the 6- and
8-positions.16 Herein, we further present a novel synthetic
strategy for realizing regioselective substitution at the 1,3- and
6,8-positions of pyrene for the construction of dipolar
molecules.
RESULTS AND DISCUSSION
■
Assuming that the tert-butyl group can be removed by an
effective approach, the effective approach to regioselective
substitution at the 1,3- and 6,8-positions of pyrene would be
achievable. On the basis of our knowledge, the bulky tert-butyl
group can be removed by using Nafion-H as a catalyst.17
Following this inspiration, 1,3-diphenylpyrene (3) was
successfully synthesized in 85% yield from 7-tert-butyl-1,3-
diphenylpyrene, which is a key step for building dipolar
architectures along the Z-axis.18 The detailed synthetic
procedure is illustrated in Scheme 1. Further bromination of
3 afforded 1,3-dibromo-6,8-diphenylpyrene (4) in high yield
(79%).19 Compound 4 is a novel bromide precursor used for
synthesizing the desired dipolar architectures (5). This is the
first example of the regioselective, stepwise, and asymmetric
substitution of pyrene at the active 1,3- and 6,8-positions.
Compared with that along the short axis (4-, 5-, 9-, and 10-
position) or at 2,7-positions, and introduction of a dipole to
pyrene as well, asymmetric functionalization at both 1,3- and
Figure 1. X-ray structures of molecules 3 and 5b.
packing of the structures and the molecular conformation in the
crystal were influenced by short intermolecular interactions or
the π-stacking present. For instance, the phenyl moieties
located at the pyrene 1,3-positions in 2 are all twisted with
torsion angles in the range of 45−65° relative to the pyrene
plane, which is arranged in a herringbone motif with a slip angle
of 28°.16 Molecules of 3 are held together by strong face-to-face
π···π stacking interactions with a shortest separation of 3.31 Å.
B
DOI: 10.1021/acs.joc.5b02128
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Figure 2. (a) Absorption and (b) fluorescence spectra of 3, 5, and 6 in CH2Cl2. (c) PL spectra and (d) cyclic voltammograms of 5.
Table 1. Photophysical and Electrochemical Properties of Compounds 3, 5, and 6
a
a
λ(S1←S0) (nm)
λ(S2←S0) (nm)
b
c
d
[ε
[ε
λmax Abs
Stokes
HOMO (IP)
energy gap
(eV)
c
R
(M−1 cm−1 L)] (M−1 cm−1 L)]
(nm)
λmax PL (nm) shift (nm)
Φf
(eV)
LUMO (eV)
a
b
a
b
e
f
c
g
3
357 (28000)
433 (18500)
437 (12900)
411 (46100)
394 (29500)
286 (41000)
285 (27000)
332 (48400)
296 (41000)
304 (41200)
359
438
455
425
400
396 (462)
39 (103)
55 (31)
25 (55)
45 (112)
0.27 (0.03)
0.92 (0.42)
0.90 (0.44)
0.96 (0.32)
0.87 (052)
−5.14 (−5.83)
−4.84 (−5.70)
−4.93 (−5.77)
−5.90 (−)
−1.58 (−2.76)
3.56 (3.07)
5a
5b
5c
6
488 (469)
462 (510)
456 (537)
−1.88 (−3.15)
−2.12 (−3.24)
−2.69 (−)
2.97 (2.55)
2.80 (2.53)
3.21 (2.69)
421 (464)
b
27 (64)
−5.01 (−5.76)
−1.69 (−2.93)
3.32 (2.83)
e
a
c
d
Measured in dichloromethane at room temperature. As a thin film. DFT/B3LYP/6-31G* using Gaussian. Determined using AC-3. LUMO =
Eg + HOMO. LUMO (eV) = Eg − IP. Calculated from λedge in a thin film. IP > 6.2 eV.
f
g
Dipolar molecule 5b exhibited a π-stacked packing motif with
π−π distances in the range of 3.38−3.51 Å, but no π···π
stacking was observed in 6 (see the Supporting Information).
Interestingly, 5b is remarkably planar with a twist angle of
approximately of 40.49(3)° between the adjacent rings of the
biphenyl moiety, which is consistent with reported values.21
The intriguing conformations of the dipolar molecules can also
lead to special optical properties.
The effects on the photophysical properties of a series of 1,3-
diphenyl 6,8-donor/acceptor asymmetrically substituted pyr-
enes 3, 5, and 6 are discussed. Figure 2 exhibits the absorption
spectra of 3, 5, and 6 in dilute dichloromethane. In the D-π-A
type molecules, with a strong -NPh2F donor in 5a, the
absorption spectra exhibited a weak but broad band in the low-
energy absorption (375−400 nm), which indicated a charge-
transfer (CT) excitation between the donor and acceptor
moieties. For 5b, a broad band around 332 nm is mainly due to
a localized π−π* excitation of the biphenylethynyl group with
high extinction coefficients (ε = 48400 mol−1 cm−1 L). In
contrast, the strong -CN acceptor group in 5c has a strong
influence on both the S1 ← S0 and S2 ← S0 excitations,
consistent with the large extinction coefficients with oscillator
strengths. However, compounds 3 and 6 exhibited a similar
absorption pattern with little influence on the S1 ← S0 or S2 ←
S0 excitation, as reflected in the similar extinction coefficients
(Table 1). Obviously, with an electron-withdrawing group
asymmetriclly substituted at the 6,8-positions, the S1 ← S0
excitation has high extinction coefficients, while the electron
donors play a significant role in influencing both the S1 ← S0
and S2 ← S0 excitations by decreasing the extinction
coefficients.
The emission maxima of 3, 5, and 6 were in the range of
396−488 nm in dilute dichloromethane solutions with a
systematic bathochromic shift following the order 3 < 6 < 5c <
5b < 5a, suggesting that the energy gap could be fine-tuned
between the ground and excited states by choosing the
substituent group. The fluorescence of 5a exhibited pro-
nounced positive solvatochromism with an intramolecular
charge-transfer (ICT) state, in which the emission wavelength
displays a large red shift from 464 nm (in cyclohexane) to 503
nm (in DMF) (see the Supporting Information), whereas the
D-π-A conjugated compound 5b displayed a maximal emission
peak at 462 nm with a shoulder at 488 nm and contributed to
an efficient mesomeric intramolecular charge-transfer (MICT)
C
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emission, due to the twist angle [40.49(3)°] of the Franck−
Condon vertical state between the diphenyl moieties.22 The
spectroscopic and photophysical properties of dipolar mole-
cules 5 exhibit a solvent dependency. The linear relationship of
the Stokes shift (ΔVst) versus the solvent parameters (ε and n)
of 5 was determined by a Lippert−Mataga plot.16 Obviously,
the MICT of the solvent polarity dependence of the
fluorescence bands is weaker than for the TICT case (see the
Supporting Information).
Compounds 5b and 5c as films exhibited green emission and
displayed λfilm,max values of 510 and 537 nm, respectively, which
are significantly red-shifted relative to those of their solutions
because of the planar structure of the molecule that tends to
form dimers. However, the maximum of 5a was blue-shifted by
19 nm compared with the measurement in solution, because of
the presence of the bulky electron donor -NPh2F moiety that
not only plays a role in suppressing aggregation in the solid but
also affects the conformation of the electronic structures,
therefore, can tune the energy gap. Additionally, in solution,
dipolar molecules 5 have similar PL quantum yields (>0.90) in
solution, suggesting they display excited state ICT character.
The red-shifted emission with decreased quantum yields of 5
(0.32−0.44) in the solid state is attributed to the π−π stacking
interactions, whereas 3, both in solution and in thin films,
exhibited the lowest PL efficiencies, which can be attributed to
the strong molecular aggregation.
Figure 3. Computed molecular orbital plots (B3LYP/6-31G*) of 5a−
c.
The electrochemical properties of 5 were investigated by
cyclic voltammetry (CV). The oxidation of 5a and 5b displayed
a quasi-reversible oxidation process with HOMO energy levels
of −5.15 and −5.51 eV, respectively. For compound 5c, the
oxidation wave was not clearly observed because of the
presence of the strongly electron-withdrawing -CN group. The
result was further confirmed by photoelectron spectroscopy.
The ionization potentials of 3, 5a, 5b, and 6 are measured in a
thin film, and their IP values are 5.83, 5.70, 5.77, and 5.76 eV,
respectively (Table 1). However, in the presence of the strong
electron-withdrawing -CN group in 5c, the maximal IP range
was greater than the instrument full scale (6.2 eV). The optical
gaps of 3, 5, and 6 were calculated from the absorption spectra
of their thin films at 3.07, 2.55, 2.53, 2.69, and 2.83 eV.
The energy gap was further evaluated by density functional
theory (DFT) calculations. As shown in Figure 3, obviously,
because of the substituents asymmetrically located at the 1,3-
and 6,8-positions, the HOMO of 5a is mainly spread over the
-NPh2F moiety and the pyrene ring, whereas the LUMO
extended on the pyrene core and the phenyl rings, which
implies a partial charge separation between the donor (-NPh2F
moiety) and acceptor (phenyl moiety). For 5b, the HOMO
and LUMO were delocalized in the pyrene moiety. However,
with strong acceptor -CN in 5c, the HOMO is located over the
entire molecular skeleton and the LUMO mostly existed at the
pyrene and cyano groups. Obviously, the ICT states would be
formed in molecules 5a and 5c along the Z-axis with a strong
donor at the 1,3-positions and an acceptor at the 6,8-positions.
The calculated HOMO−LUMO gap of 5a−c is 2.97, 2.81, and
3.21 eV, respectively. In addition, the fully optimized structure
of 5b is shown to exhibit a C21−C22−C25−C26 twist angle of
36°, very close to that of the X-ray structure.
introduced into the 1,3- and 6,8-positions along the Z-axis of
the pyrene core by regioselective substitution was explored. X-
ray analysis has confirmed the novel asymmetric substitution of
the pyrene core. The small dipolar molecule pyrene-based
compounds possess a fine ICT state between the donor and
acceptor units in the ground state. This article presents a
revolutionary methodology for the functionalization of the
pyrene core and has potential application in organic photonics.
EXPERIMENTAL SECTION
■
1
General. All melting points are uncorrected. H and 13C NMR
spectra were recorded on a FT-NMR spectrometer (300 and 400
MHz, respectively) and referenced to 7.26 and 77.0 ppm, respectively,
for chloroform-d solvent with SiMe4 as an internal reference. J values
are given in hertz. IR spectra were measured for samples as KBr pellets
in a FT-IR spectrophotometer. Mass spectra were obtained with a
mass spectrometer at 75 eV using a direct-inlet system. UV/vis spectra
were recorded with a UV/vis/NIR spectrometer in various organic
solvents. Fluorescence spectroscopic studies were performed in various
organic solvents in a semimicro fluorescence cell with a spectropho-
tometer. Fluorescence quantum yields were measured using absolute
methods. Differential scanning calorimetry (DSC) was performed
under a nitrogen atmosphere at a heating rate of 10 °C min−1.
Photoluminescence spectra were recorded using a luminescence
spectrometer. The ionization potential was determined by atmospheric
photoelectron spectroscopy. Electrochemical properties of HOMO
levels were determined with an electrochemical analyzer. Cyclic
voltammetry was performed in 0.10 M tetrabutylammonium
perchlorate in anhydrous dichloromethane and THF at a scan rate
of 100 mV s−1 at room temperature. The quantum chemistry
calculations were performed with the Gaussian 03W (B3LYP/6-31G*
basis set) software package. Crystallographic data were collected using
graphite monochromated Mo Kα radiation (λ = 0.71073 Å) in the ω
scan mode. Data (excluding structure factors) for the structures
reported here have been deposited with the Cambridge Crystallo-
graphic Data Centre. CCDC 1025083−1025085 contain the
supplementary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
CONCLUSION
■
In summary, a facile synthetic strategy for the construction of
dipolar architectures in which the asymmetric unit, including
phenyl rings and NPh2F/biphenylethynyl/CN moieties, is
D
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Film Preparation. The thin films were prepared by a solution
process. A 10 mg sample is dissolved in 1 mL of a toluene solution,
and the solution is placed on the substrate, which is then rotated at
high speed to spread the fluid by centrifugal force.
Material. Unless otherwise stated, all other reagents used were
purchased from commercial sources and were used without further
purification. The preparations of 2-tert-butylpyrene23 and 7-tert-butyl-
1,3-dibromopyrene16 were described previously.
CH2Cl2, washed with a brine solution, and dried over MgSO4.
Evaporation of the solvent under vacuum resulted in a solid residue.
The residue was adsorbed on a silica gel and purified by column
chromatography using hexane as the eluent and recrystallized from
from ethyl acetate to afford the corresponding desired compound 5a as
1
a green powder (125 mg, 56%): mp 161.1−162.5 °C; H NMR (400
MHz, CDCl3) δ 6.84−6.94 (m, 20H), 7.40−7.44 (m, 2H), 7.49 (t, J =
7.4 Hz, 8H), 7.53 (s, 1H), 7.56 (d, J = 7.2 Hz, 8H), 7.94 (s, 1H), 8.00
(d, J = 9.6 Hz, 2H), 8.03 (d, J = 9.6 Hz, 2H); 13C NMR (100 MHz,
CDCl3) δ 159.27, 156.86, 144.67, 144.65, 141.56, 140.63, 137.89,
130.47, 129.97, 128.48, 128.34, 128.04, 127.40, 126.55, 125.60, 123.19,
123.11, 122.80, 116.07, 115.85; FABMS m/z 760.31 (M+). Elemental
Anal. Calcd for C52H32F4N2 (760.82): C, 82.09%; H, 4.24%; N, 3.68%.
Found: C, 82.16%; H, 4.39%; N, 3.55%.
Synthesis of 7-tert-Butyl-1,3-diphenylpyrene (2).16 A mixture of 7-
tert-butyl-1,3-dibromopyrene (1) (200 mg, 0.5 mmoL), phenylboronic
acid (250 mg, 2.0 mmoL) in toluene (12 mL), and ethanol (4 mL) at
room temperature was stirred under argon, and K2CO3 (250 mg, 1.8
mmoL) and Pd(PPh3)4 (70 mg, 0.06 mmol) were added. After the
mixture had been stirred for 30 min at room temperature under argon,
the mixture was heated to 90 °C for 24 h while being stirred. After the
mixture had been cooled to room temperature, the reaction was
quenched with water, and the mixture was extracted with CH2Cl2 (2 ×
30 mL) and washed with water and brine. The organic extracts were
dried with MgSO4 and evaporated. The residue was purified by
column chromatography eluting with a 1:1 CH2Cl2/hexane mixture to
give 2 as white prisms (1:2 CH2Cl2/hexane) (124 mg, 63%): mp 186
°C; IR (KBr) νmax 2958, 2900, 2866, 1766, 1597, 1484, 1462, 1442,
1396, 1360, 1227, 1151, 875, 837, 810, 764, 702, 613, 503, 457 cm−1;
1H NMR (300 MHz, CDCl3) δ 1.59 (s, 9H), 7.44−7.69 (m, 10H),
7.94 (s, 1H), 8.01 (d, J = 9.2 Hz, 2H), 8.18 (d, J = 9.2 Hz, 2H), 8.20
(s, 2H); 13C NMR (75 MHz, CDCl3) δ 149.23, 141.14, 137.11,
131.16, 130.63, 128.97, 128.35, 127.75, 127.64, 127.22, 125.32, 125.11,
123.42, 122.25, 35.19, 31.89; MS m/z 410.2 [M]+. Elemental Anal.
Calcd for C32H26 (410.2): C, 93.62%; H, 6.38%. Found: C, 93.81%; H,
6.19%.
Synthesis of 1,3-Bis[(3-biphenyl)ethynyl]-6,8-diphenylpyrene
(5b). A mixture of 1,3-dibromo-6,8-diphenylpyrene (50 mg, 0.10
mmoL), PdCl2(PPh3)2 (21 mg, 0.03 mmoL), CuI (10 mg, 0.05
mmoL), PPh3 (20 mg, 0.08 mmoL), and 4-ethynyl-1,1′-biphenyl (53
mg, 0.30 mmoL) was added to a degassed solution of triethylamine (5
mL) and N,N-dimethylmethanamide (5 mL) under an argon
atmosphere. The resulting mixture was stirred at 100 °C for 48 h.
After the mixture had cooled to room temperature, the reaction was
quenched with water, and the mixture was extracted with CH2Cl2 (2 ×
30 mL) and washed with water and brine. The organic extracts were
dried with MgSO4 and evaporated. The residue was purified by
column chromatography eluting with a 2:1 CH2Cl2/hexane mixture to
give 5b as a dark yellow powder (1:2 CH2Cl2/hexane) (28 mg, 40%):
1
mp 263.1−264.9 °C; H NMR (400 MHz, CDCl3) δ 7.39 (m, 1H),
7.49 (m, 5H), 7.58 (m, 5H), 7.65−7.71 (m, 13H), 7.77 (d, J = 8.2 Hz,
4H), 8.06 (s, 1H), 8.38 (d, J = 9.3 Hz, 2H), 8.50 (s, 1H), 8.67 (d, J =
9.3 Hz, 2H); 13C NMR (100 MHz, CDCl3) δ 141.92, 141.19, 140.64,
140.31, 140.06, 138.57, 133.31, 132.91, 132.08, 131.98, 130.67, 128.87,
128.41, 128.11, 127.82, 127.66, 127.51, 127.13, 127.07, 127.00, 125.43,
122.22, 120.60, 117.65, 95.38, 88.72; FABMS m/z 706.33 (M+).
Elemental Anal. Calcd for C56H34 (706.87): C, 95.15%; H, 4.85%.
Found: C, 95.07%; H, 5.03%.
Synthesis of 1,3-Diphenylpyrene (3). A mixture of 1,3-diphenyl-7-
tert-butylpyrene (2) (410 mg, 0.09 mmoL), Nafion-H (400 mg), and
o-xylene (4 mL) was refluxed for 24 h and then cooled to room
temperature. The solid was removed in vacuo and the mother solution
collected. The crude product was purified by column chromatography
using hexane as an eluent to afford a yellow solid (300 mg, 85%): mp
136.5−137.2 °C; 1H NMR (300 MHz, CDCl3) δ 7.45−7.50 (m, 2H),
7.53−7.58 (m, 4H), 7.66−7.68 (m, 4H), 8.00 (d, J = 8.8 Hz, 2H), 8.05
(d, J = 2.9 Hz, 2H), 8.16 (s, 1H), 8.20 (d, J = 2.9 Hz, 2H), 8.22 (s,
1H); 13C NMR (100 MHz, CDCl3) δ 141.01, 137.30, 131.28, 130.65,
129.35, 128.40, 127.93, 127.46, 127.32, 126.13, 125.27, 125.16, 124.98;
FABMS m/z 354.22 (M+). Elemental Anal. Calcd for C28H18 (354.44):
C, 94.88%; H, 5.12%. Found: C, 94.85%; H, 5.11%.
Synthesis of 1,3-Dicyano-6,8-diphenylpyrene (5c). A mixture of
1,3-dibromo-6,8-diphenylpyrene (2) (100 mg, 0.20 mmoL), CuCN
(42 mg, 0.49 mmoL), and N-methyl-2-pyrrolidone (10 mL) was
stirred for 24 h and then cooled to room temperature. The solid was
removed in vacuo and the mother solution collected. Water was added
to the solution and the mixture extracted with CH2Cl2 (2 × 30 mL)
and washed with water and brine. The organic extracts were dried with
MgSO4 and evaporated. The residue was purified by column
chromatography eluting with a 4:1 CH2Cl2/hexane mixture to give
Synthesis of 1,3-Dibromo-6,8-diphenylpyrene (4). To a mixture of
1,3-diphenylpyrene 3 (300 mg, 0.85 mmol) in dry CH2Cl2 (30 mL)
was added dropwise a solution of BTMABr3 (benzyltrimethylammo-
nium tribromide) (1.0 g, 2.6 mmol) in CH2Cl2 (10 mL) and methanol
(5 mL) at 0 °C for 1 h under an argon atmosphere. The resulting
mixture was allowed to slowly warm to room temperature and stirred
overnight. The reaction mixture was poured into ice−water (60 mL)
and neutralized with an aqueous 10% Na2S2O3 solution. The mixture
solution was extracted with dichloromethane (2 × 20 mL). The
organic layer was washed with water (2 × 20 mL) and saturated brine
(20 mL), and then the solution was dried (MgSO4) and condensed
under reduced pressure. The crude compound was washed with hot
hexane to afford pure 1,3-dibromo-6,8-diphenylpyrene 3 (330 g, 79%)
1
5c as a yellow powder (43 mg, 54%): mp ≤300 °C; H NMR (400
MHz, CDCl3) δ 7.56−7.67 (m, 10H), 8.24 (s, 1H), 8.50 (d, J = 9.6
Hz, 2H), 8.56 (s, 1H), 8.63 (d, J = 8.8 Hz, 2H); 13C NMR (100 MHz,
CDCl3) δ 141.95, 139.34, 135.60, 133.55, 131.94, 131.44, 130.71,
128.76, 128.34, 127.41, 124.34, 123.69, 123.58, 117.11, 105.60;
FABMS m/z 404.35 (M+). Elemental Anal. Calcd for C30H16N2
(404.46): C, 89.09%; H, 3.99%; N, 6.93%. Found: C, 89.19%; H,
3.69%; N, 6.53%.
Synthesis of 1,3,6,8-Tetraphenylpyrene (6).9 1,3,6,8-Tetrabromo-
pyrene (200 mg, 0.386 mmoL), phenylboronic acid (254 mg, 2.08
mmoL), Pd(PPh3)4 (50 mg, 0.04 mmol), and 2.0 M aqueous NaOH
(2 mL) were mixed in a flask containing argon-saturated toluene (10
mL). The reaction mixture was stirred at 90 °C for 20 h. After it was
cooled to room temperature, the reaction mixture was extracted with
dichloromethane (2 × 40 mL). The combined organic extracts were
dried with anhydrous MgSO4 and evaporated. The crude product was
purified by column chromatography using a 1:4 hexane/dichloro-
methane mixture as the eluent to provide a pale powder and
recrystallized from hexane to afford 1,3,6,8-tetraphenylpyrene 6 as a
light yellow powder (146 mg, 74%): mp 300.1−301.8 °C; IR νmax
(KBr) 2952, 1608, 1513, 1494, 1459, 1286, 1245, 1176, 1106, 1035,
1
as a yellow solid: mp 184−186 °C; H NMR (400 MHz, CDCl3) δ
7.49 (m, 2H), 7.53−7.57 (m, 4H), 7.62−7.67 (m, 4H), 8.03 (s, 1H),
8.29 (d, J = 9.2 Hz, 2H), 8.33 (d, J = 9.6 Hz, 2H), 8.49 (s, 1H); 13C
NMR (100 MHz, CDCl3) δ 140.41, 138.61, 133.60, 130.58, 130.47,
129.29, 128.45, 127.91, 127.61, 127.17, 127.10, 125.70, 124.30, 119.24;
FABMS m/z 510.05 (M+). Elemental Anal. Calcd for C28H16Br2
(512.23): C, 65.65%; H, 3.15%. Found: C, 65.35%; H, 3.34%.
Synthesis of 1,3-Bis[di(4-fluorophenyl)amino]-6,8-diphenylpyr-
ene (5a). The corresponding 1,3-dibromo-6,8-diphenylpyrene (150
mg, 0.29), bis(4-fluorophenyl)amine (180 mg, 0.87 mmoL), Pd-
(OAc)2 (40 mg, 0.18 mmoL), (t-Bu)3P (0.05 mL), sodium tert-
butoxide (200 mg, 2.05 mmoL), and toluene (10 mL) were mixed
together and heated at 100 °C for 24 h. The reaction was quenched
with water (30 mL) and the organic layer taken into 100 mL of
1
835, 549, 476 cm−1; H NMR (400 MHz, CDCl3) δ 7.43−7.47 (m,
2H), 7.53 (t, J = 7.6 Hz, 8H), 7.66 (d, J = 8.0 Hz, 8H), 8.00 (s, 2H),
8.17 (s, 4H); 13C NMR (100 MHz, CDCl3) δ 141.04, 137.22, 130.61,
129.50, 128.31, 128.10, 127.26, 125.91, 125.28; FABMS m/z 506.30
E
DOI: 10.1021/acs.joc.5b02128
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
(M+). Elemental Anal. Calcd for C40H26 (506.63): C, 94.83%; H,
5.17%. Found: C, 94.77%; H, 5.29%.
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ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.joc.5b02128.
■
R.; Mullen, K. Chem. Commun. 2011, 47, 6960−6962.
̈
S
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1H and 13C NMR data, complete photophysical and
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Crystallographic data (CIF)
Crystallographic data (CIF)
Crystallographic data (CIF)
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AUTHOR INFORMATION
Corresponding Authors
*E-mail: yamatot@cc.saga-u.ac.jp.
*E-mail: hujianyong@snnu.edu.cn.
Notes
■
The authors declare no competing financial interest.
(18) Crawford, A. G.; Dwyer, A. D.; Liu, Z.-Q.; Steffen, A.; Beeby, A.;
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ACKNOWLEDGMENTS
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13349−13362.
(19) Sato, T.; Uejima, M.; Tanaka, K.; Kaji, H.; Adachi, C. J. Mater.
Chem. C 2015, 3, 870−878.
This work was performed under the Cooperative Research
Program of “Network Joint Research Center for Materials and
Devices (Institute for Materials Chemistry and Engineering,
Kyushu University)”. We thank the EPSRC (travel grants to
C.R.), The Royal Society of Chemistry, The Scientific Research
Foundation for the Returened Overseas Chinese Scholars, the
State Education Ministry, and The Scientific Research
Common Program of Beijing Municipal Commission of
Education (18190115/008) for financial support. The
Advanced Light Source is supported by the Director, Office
of Science, Office of Basic Energy Sciences, of the U.S.
Department of Energy under Contract DE-AC02-05CH11231.
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