Deep-blue fluorescent emitter based on a 9,9-dioctylfluorene bridge with a hybridized local and charge-transfer excited state for organic light-emitting devices with EQE exceeding 8%

Article abstract of DOI:10.1039/d0tc02941f

It is indispensable to synthesize deep-blue light emitting materials with high luminous efficiency for realizing full-colour organic light emitting diode (OLED) displays. The hybridized local and charge-transfer (HLCT) state is a special excited state tha

Full text of DOI:10.1039/d0tc02941f

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Materials Chemistry C
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Deep-blue fluorescent emitter based on a
9,9-dioctylfluorene bridge with a hybridized local
and charge-transfer excited state for organic
light-emitting devices with EQE exceeding 8%†
a
Cite this:DOI: 10.1039/d0tc02941f
Xing Liu,‡a Wen Liu,‡a Wu Dongyu,b Xiaozhen Wei,a Long Wang,a Hua Wang,
*
a
c
Yanqin Miao, *a Huixia Xu,
Junsheng Yu
and Bingshe Xu*a
It is indispensable to synthesize deep-blue light emitting materials with high luminous efficiency for
realizing full-colour organic light emitting diode (OLED) displays. The hybridized local and charge-
transfer (HLCT) state is a special excited state that hybridizes the local state and the charge transfer state
to ensure a high fluorescence quantum yield (Zpl). Herein, a blue fluorescent material of TPA-DFCP was
designed and synthesized, with a twisted D–p–A configuration, in which triphenylamine (TPA), benzo-
nitrile (CP) and 9,9-dioctylfluorene serve as the D, A, and p-conjugation unit, respectively. It also exhibits
good solubility and can be dissolved in several organic solvents with different polarities. The non-doped
device, with TPA-DFCP as the emitter, shows excellent electroluminescent (EL) efficiency with a
maximum EQE of 7.74%. Furthermore, the doped device of TPA-DFCP exhibits excellent deep-blue
emission with the EL emission peak at 436 nm and the CIE coordinates at (0.153, 0.077), which are very
close to the NTSC standard blue CIE (x, y) coordinates of (0.140, 0.080). Meanwhile, the doped device
also exhibited excellent EL performance, with a maximum external quantum efficiency (EQE) and
radiative exciton utilization (Zr) of 8.30% and 57.67%, respectively.
Received 21st June 2020,
Accepted 19th August 2020
DOI: 10.1039/d0tc02941f
rsc.li/materials-c
75% triplet excitons is the key to improving the exciton utiliza-
tion rate of the material. As yet, there are three major organic
Introduction
In recent years, organic light emitting diodes (OLEDs) have electroluminescence mechanisms using triplet excitons,
attracted wide attention arising from the advantages of low cost i.e. triplet–triplet annihilation (TTA), thermally activated delayed
of fabrication, diversity of variety and structure, adjustable fluorescence (TADF), and hybridized local and charge-transfer
performance by structural design, and the simple synthesis (HLCT).14,15
process.1–10 In order to realize full-colour OLED displays, it is
In TTA type luminescent materials, when there is a large
indispensable to synthesize new light-emitting materials of energy level difference between the lowest singlet excited state
three primary colours with high luminous efficiency, especially (S1) and the lowest triplet excited state (T1), the TTA process
blue-light materials.11–13 Luminescent materials usually form occurs between the two triplet excitons, and the upper conver-
25% singlet excitons and 75% triplet excitons. However, in sion produces a high-level triplet exciton (Tm) with similar
traditional fluorescent materials, the 75% triplet excitons are energy levels to the high-level singlet (Sn), and then singlet
prone to dissipate by thermal radiation. Hence, the use of the excitons are generated by intersystem crossing (ISC) between Tm
and Sn, leading to high-efficiency fluorescence emission.16–18
However, the theoretical upper limit of the singlet exciton produc-
tion ratio is still less than 62.5% when the TTA process occurs,
corresponding to an external quantum efficiency (EQE) of 12.5%
a Key Laboratory of Interface Science and Engineering in Advanced Materials,
Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, China.
E-mail: wanghua001@tyut.edu.cn, miaoyanqin@tyut.edu.cn, xubs@tyut.edu.cn
b SEDIN Engineering Co., Ltd, Taiyuan 030000, China
c State Key Laboratory of Electronic Thin Films and Integrated Devices,
School of Optoelectronic Information, University of Electronic Science and
Technology of China, Chengdu 610054, China
in the ideal case.16,19 For TADF materials, it is important to realize
the efficient reverse intersystem crossing (RISC) process of
excitons from T1 to S1.20–23 In order to promote the RISC process,
the energy level difference (DEST) between T1 and S1 must be small
enough through the complete separation of the HOMO and
LUMO of the material to enhance the CT state. But, at the same
time, TADF materials are prone to generate quenching of triplet
† Electronic supplementary information (ESI) available. CCDC 2010880. For ESI
and crystallographic data in CIF or other electronic format see DOI: 10.1039/
d0tc02941f
‡ These authors contributed equally to this work.
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excitons, leading to roll-off of the efficiency and a short lifetime of
devices in the process of electroluminescence.24,25 The HLCT state
is a special excited state that hybridizes the local state and the
charge transfer state.26 The LE state ensures that the material has
a high fluorescence quantum yield (Zpl), and the CT state guar-
antees that the material has a high exciton utilization rate.11,27,28
Theoretically, the exciton utilization rate of HLCT materials can
reach 100%. Moreover, the luminescence of the HLCT material
originates from the LE state, so the emission spectrum is
narrower, and the colour purity of the device is higher. The
coexistence of the CT state and the LE state of HLCT materials
requires that the HOMO and LUMO of the material overlap and
separate, and the rigidity of the structure is small. In 2015, Tang
et al. constructed a donor–acceptor (D–A) type molecule named
PMSO with phenanthroimidazole as a weak donor and sulfone as
a moderate acceptor, and achieved a maximum EQE of 6.85%
with an emission peak of 445 nm and CIE coordinates (0.152,
0.077) for the doped device.28 In 2019, Qiu et al. reported HLCT
state materials of 9,9-dimethyl-N,N-diphenyl-7-(1,4,5-triphenyl-1H-
imidazol-2-yl)-9H-fluoren-2-amine (DFPBI) and 4-(9,9-dimethyl-7-
(1,4,5-triphenyl-1H-imidazol-2-yl)-9H-fluoren-2-yl)-N,N-diphenyl-
aniline (TFPBI) with a structure of donor–p–acceptor (D–p–A)
with 9,9-dimethylfluorene as the p-bridge, and achieved a
maximum EQE of the doped device of TFPBI of 6.01%, with
CIE coordinates (0.153, 0.051).29 In summary, HLCT materials
have great potential for the design of deep-blue emitters.
In this work, blue fluorescent material TPA-DFCP was
designed and synthesized, with a twisted D–p–A configuration, in
which triphenylamine (TPA), benzonitrile (CP) and 9,9-dioctyl-
fluorene serve as the D, A, and p-conjugation unit, respectively.
Herein, TPA is a strong electron donor group and has a high
HOMO energy level. More importantly, the molecular space of
TPA has a certain twist angle for avoiding the accumulation
of molecules to construct the intramolecular CT state.30
9,9-dioctylfluorene, known as a common rigid p-conjugated
bridge, provides necessary conjugation to the molecular back-
bone, and thus ensures the satisfactory contribution of the LE
component for the HLCT state and improves Zpl of fluorescent
molecules.31–33 Fortunately, the HLCT state was observed from the
material TPA-DFCP. Meanwhile, the doped device of TPA-DFCP
exhibits excellent deep-blue emission with the EL emission peak
at 436 nm and the CIE coordinates at (0.153, 0.077), which are
very close to the NTSC standard blue CIE (x, y) coordinates of
(0.140, 0.080). Furthermore, the doped device also exhibited
excellent EL efficiency, with a maximum EQE of 8.30%.
Scheme 1 Synthetic route of TPA-DFCP.
Fig. 1 (a) A single molecular structure of the TPA-DFCP crystal; (b) inter-
molecular interactions.
suitable crystal was selected. The crystal system of TPA-DFCP
is monoclinic, the space group is I2/a and there were eight
molecules in one unit cell. As shown in Fig. 1a, the twisted
dihedral angle between the TPA substituents and the central
9,9-dimethylfluorene was 37.491 (y1), and the dihedral angle
between benzonitrile and the central 9,9-dimethylfluorene was
38.891 (y2), which is similar to the dihedral angle from theore-
tical calculations. As presented in Fig. 1b, the N-atom of
benzonitrile and the benzonitrile-H of the adjacent molecules
form C–Hꢀ ꢀ ꢀN hydrogen bonds.
To further explore the relationship between the material
property and molecular structure of TPA-DFCP, the electronic
structure was calculated, and the optimized structures and
frontier molecular orbital distributions are shown in Fig. 2.
As depicted, the HOMO and LUMO of TPA-DFCP are mainly
distributed on the D unit of TPA and the A unit of CP,
respectively. The separation of the electron density distribution
of the HOMO and LUMO indicates the existence of a CT state.
Meanwhile, a certain degree of overlap between the HOMO and
LUMO of TPA-DFCP distributed on the p-conjugation unit of DF
Results and discussion
Structure characteristics
The synthetic routes of TPA-DFCP can be seen in Scheme 1. The
intermediate compound M1 and the target products were
prepared through a palladium catalysed Suzuki coupling reaction,
and then purified by column chromatography on silica gel.
Single crystals of TPA-DFCP were obtained through slow
diffusion of ethanol into methylene dichloride, and then a
Fig. 2 Optimized structures and frontier molecular orbital distributions of
TPA-DFCP.
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indicates a decent radiative transition rate for this material to characteristics. Subsequently, the relationship between the
achieve high Zpl.
Stokes shift (va ꢁ vf) and the orientation polarizability of the
solvent f (e, n) was investigated to estimate the dipole moment
of the S1 state (me), according to the Lippert–Mataga equation as
introduced in previously reported work.
Photophysical properties
In order to investigate the photophysical properties, UV-vis
absorption and PL spectra of TPA-DFCP in different polar
solutions and in a film were measured (Fig. 3, Fig. S3, ESI,†
and Table 1). As shown in Fig. 3a, the UV-vis absorption
spectrum of TPA-DFCP in dilute toluene solution exhibits an
À
Á
2
À
Á
2 me ꢁ mg
0
hcðva ꢁ vf Þ ¼ hc va ꢁ vf0
þ
f ðe; nÞ
3
a0
As presented in Fig. 3b, TPA-DFCP shows two linear relation-
absorption peak at 300 nm, and a maximum absorption peak at ships between the Stokes shift and the orientation polariz-
368 nm, corresponding to the n–p* transition between n ability of solvents. According to the calculation, me of TPA-DFCP
electrons and p electrons on N heteroatoms of triphenylamine, in low polarity solvents (6.36 D) is smaller than the well-known CT
and the p–p* transition of the whole molecule, respectively. The molecule 4-(N,N-dimethylamino)benzonitrile (DMABN) (23 D),
PL spectrum in dilute toluene solution exhibits a maximum and me of TPA(PFCP) in high polarity solvents (31.76 D) is larger
emission peak (lpl) at 433 nm. In the film, the UV-vis absorp- than 23 D, which indicates that the excited state of TPA-DFCP
tion spectrum of TPA-DFCP exhibits similar features as in exhibits a mixed character of LE and CT states: the LE-dominated
dilute solutions: the PL spectrum of TPA-DFCP in the film excited state in low polarity solvents ( f o 0.096), the CT-
shows a 21 nm red-shift relative to that in toluene solution, dominated excited state in high-polarity solvents ( f 4 0.149),
which is owing to molecule aggregation (Fig. 3a).
and an inter-crossed excited state of LE character and CT char-
In addition, for researching the CT characteristic in excited acter in environments with moderate polarity (0.096 o f o 0.149).
states, the photophysical properties of TPA-DFCP in different Moreover, Zpl of TPA-DFCP in different polar solvents was mea-
solvents were examined (Fig. S3, ESI†). As shown, from low- sured (82.76% in hexane; 79.96% in chloroform; 53.17% in
polarity (i.e. hexane, f = 0.0012) to high-polarity solutions acetonitrile), and Zpl showed a significant decreasing trend with
(i.e. acetonitrile, f = 0.305), the emission peaks in the PL spectra increasing solvent polarity, which coincided with the increase of
of TPA-DFCP show a large redshift of 126 nm. The significant the CT states above.
solvation effect originates from CT from the D unit of TPA to
In order to further investigate the excited state properties,
the A unit of CP, which indicates that the TPA-DFCP molecule transient PL decay of TPA-DFCP in different solutions and in a
is more likely to be affected by the solvent polarity during film was measured. As shown in Fig. S4 and Table S2 (ESI†), the
the radiative transition, and the excited states have strong CT spectra illustrate that TPA-DFCP shows short PL decay lifetimes
Fig. 3 (a) UV-vis absorption and PL spectra of TPA-DFCP in toluene solution and in a film; (b) fitted correlation of the Stokes shift as a function of solvent
polarity.
Table 1 The photophysical, electrochemical and thermal properties of TPA-DFCP
lpl [nm]
Solution
433
labs [nm]
Solution
368
b
Compound
Film
454
Film
368
Zpl [%]
HOMO/LUMO [eV]
Td [1C]
Tg [1C]
DEST [eV]
a
TPA-DFCP
66.74
ꢁ5.29/ꢁ2.31
398
—
0.37
a
b
Measured in Not observed. DEST = E(T1) ꢁ E(S1)
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ranging from 1.20 to 3.22 ns in different solvents and a film. DEST = 1240/lFl ꢁ 1240/lPh, DEST between the S1 and T1 states is as
Based on the fluorescence lifetime of TPA-DFCP film (t = 2.26 ns), high as 0.372 eV, indicating that the RISC transition from the T1
the radiative decay rate (kr = Zpl/tf) and non-radiative decay rate to the S1 state is impossible during the PL process. In considera-
(knr = 1/tf ꢁ kr) can be calculated to be 0.295 and 0.147 nsꢁ1
,
tion of the large DEST and short PL decay lifetime, we have
respectively. Obviously, the value of kr is much larger than that of excluded the TADF mechanism for the TPA-DFCP luminescence
knr, which originates from the intramolecular planarization. As process.
illustrated in Fig. S5 (ESI†), the emission peaks of the PL spectra
Moreover, the energy landscape of singlet and triplet excited
at room temperature and phosphorescence spectra at 77 K were states was calculated to observe the excited state performance
located at 467 and 543 nm, respectively. According to the formula of TPA-DFCP (Fig. 4). It can be known from Fig. 4 that the large
energy gap between T2 and T1 (DET –T = 0.42 eV) may signifi-
2
1
cantly prohibit internal conversion from T2 to T1 on the basis of
the energy gap law, and the small energy gap between T2 and S1
(DET –S = 0.05 eV) may be facilitating reverse intersystem
1
1
crossing (RISC) from T2 to S1. Such an energy level landscape
meets the requirement of the ‘‘hot exciton’’ mechanism very
well, leading to a high-lying RISC process from T2 to S1, and an
exciton utilization exceeding 25% under electrical excitation
can be expected.
Electroluminescence performance
To investigate the electroluminescence (EL) performance of
TPA-DFCP, we fabricated a blue OLED with a non-doped
configuration (Fig. 5): ITO/MoO3 (3 nm)/TAPC (40 nm)/TCTA
(10 nm)/TPA-DFCP (20 nm)/TmPyPB (30 nm or 40 nm)/LiF
(1 nm)/Al (120 nm) (named Device A or B), in which MoO3
was employed as the hole-injection layer (HIL), 4,40-cyclo-
hexylidene bis[N,N-bis(p-tolyl)aniline] (TAPC) served as the
Fig. 4 The energy landscape of singlet and triplet excited states for the
BTDF-based compounds of TPA-DFCP.
Fig. 5 EL performance of Device A and Device B: (a) EL spectra, the picture of Device B; (b) J–V–L curve; (c) CE–L–PE curve; (d) EQE–L curve.
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brightness with 8212 cd mꢁ2 compared with Device A (Lmax
=
6540 cd mꢁ2). Meanwhile, Zs of Device A and Device B was
estimated to be 57.99% and 54.99%, which are higher than the
upper limit of Zs (25%) for traditional fluorescent materials.
Higher Zs indicates that the molecule can effectively utilize some
of the triplet excitons to participate in the luminescence, and thus
a higher EQE was obtained, which is in line with our original
intention to design molecules.
To further improve the EL efficiency and colour purity of
Device B, different doped devices were fabricated with 4,40-bis-
(N-carbazolyl)-1,10-biphenyl (CBP) as the host, and TPA-DFCP
as the dopant. Through changing the doping ratio, different
doped devices were obtained: ITO/MoO3 (3 nm)/TAPC (40 nm)/
TCTA (10 nm)/CBP : 5 wt%, 10 wt%, 15 wt%, 30 wt%, 50 wt%,
80 wt% TPA-DFCP (20 nm)/TmPyPB (40 nm)/LiF (1 nm)/Al
(120 nm), where the doping concentrations of 5 wt%, 10 wt%,
15 wt%, 30 wt%, 50 wt% and 80 wt% correspond to Devices B1,
B2, B3, B4, B5, and B6, respectively (Fig. S8 (ESI†) and Fig. 6).
Scheme 2 Schematic energy level diagram of the devices based on TPA-
DFCP.
hole-transporting layer (HTL), 4,40400-tri(N-carbazolyl)-triphenyl As shown in Table S3 (ESI†), compared to the non-doped device B,
amine (TCTA) acted as a buffer for confining excitons within the doped devices B1–B6 exhibit obvious blue-shifted EL spectra,
the emission layer, 1,3,5-tri(m-pyrid-3-ylphenyl)benzene (TmPyPb) and with the decrease of the doping concentration, the blue-shift
acted as the electron-transporting layer (ETL), and LiF acted as the value for the EL spectra presents an increasing trend. This is
electron-injection layer (Scheme 2). For Device A and Device B, the because the interactions between TPA-DFCP molecules in the
ETL has different thicknesses. As shown in Fig. 5, the two devices doped devices are obviously weaker than in the non-doped device
had a deep-blue emission peak at 452 nm, consistent with the PL B, which leads to a relatively large band gap in the doped devices,
emission of the thin film, indicating that the emission was from further inducing blue-shifted EL spectra. The blue-shift of the EL
only TPA-DFCP rather than other layers or any exciplex formed. spectra also causes the reduced luminance and current efficiency
Meanwhile, the two devices exhibited excellent color stability for the corresponding devices. It’s easy to understand because the
since the EL spectra showed nearly no changes with increasing luminance depends on the human vision function, where emis-
driving voltage (Fig. S6, ESI†); the similar CIE coordinates of sion with a peak of 555 nm for the same photonic radiation shows
the devices are located at (0.155, 0.140) (Device A) and (0.156, the strongest emission luminance, and emission with a longer or
0.141) (Device B). As shown in Fig. 5, Device A exhibits higher EL shorter waveband will exhibit reduced luminance for the same
efficiency with a maximum EQE of 7.74%, a turn-on voltage (Von
)
photonic radiation. Especially, as shown in Fig. 6 and Table 2,
of 2.90 V, a maximum current efficiency (CE) of 9.21 cd Aꢁ1 and a Device B1 showed high quality deep blue light emission with the
maximum power efficiency (PE) of 9.17 lm Wꢁ1 relative to those of EL spectral emission peak at 436 nm and the CIE coordinates at
Device B (EQE = 7.34%, Von = 2.9 V, CE = 8.76 cd Aꢁ1, and PE = (0.153, 0.077). Furthermore, Device B1 also exhibited excellent EL
9.17 lm Wꢁ1). Meanwhile, however, Device B has better maximum efficiency, with a maximum EQE, CE and PE of 8.30%, 5.63 cd Aꢁ1
Fig. 6 EL performance of Device B1: (a) EL spectra, the picture of Device B1; (b) EQE–L curve and CIE coordinates.
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Table 2 EL performance of devices based on TPA-DFCP
CEmax [cd Aꢁ1
]
PEmax [lm Wꢁ1
]
Lmax [cd mꢁ2
]
Von [V]
a
TPA-DFCP
lEL [nm]
CIE (x, y)
EQEmax [%]
Device A
Device B
Device B1
452
452
436
(0.155, 0.140)
(0.155, 0.141)
(0.153, 0.077)
7.74
7.34
8.30
9.21
8.76
5.63
9.25
9.17
4.87
6540
8212
2482
2.90
2.90
3.54
a
Turn-on voltage estimated at a brightness of 1 cd mꢁ2
.
Table 3
used as an internal reference for chloroform deuteride. The
crystal was kept at 293.41(10) K during data collection. Using
Olex2, the structure was solved with the SHELXS structure
solution program using direct methods and refined with the
SHELXL refinement package using least squares minimization.
Ultraviolet-visible (UV-vis) absorption and photoluminescence
(PL) spectra were recorded on a Hitachi U-3900 and Horiba
Fluoromax-4 spectrophotometer, respectively. Furthermore,
transient fluorescence and low temperature phosphorescence
spectra were measured using an Edinburgh FLS 980 spectro-
meter with a 375 nm xenon laser source. The HOMOs of the
materials were measured using an ionization energy measure-
ment (IPS) system, and the LUMOs were calculated from the
HOMO and the optical band gap of the material. Thermal
gravimetric analysis (TGA) curves were recorded on a Netzsch
TG 209 F3 at a heating rate of 10 1C minꢁ1 from 40 to 800 1C
under a nitrogen flow.
Compound
lEL (nm)
CIE (x, y)
EQEmax (%)
Ref.
TPA-DFCP
PMSO
DFPBI
TFPBI
TPEA
PIMNA
PyINA
2EHO-CNPE
3a
CzPAF–TFMP
m-BBTPI
Ph–BPA–BPI
436
445
425
440
445
412
440
452
443
436
428
448
(0.153, 0.077)
(0.152, 0.077)
(0.157, 0.039)
(0.153, 0.051)
(0.150, 0.090)
(0.160, 0.034)
(0.157, 0.084)
(0.150, 0.090)
(0.150, 0.080)
(0.155, 0.066)
(0.160, 0.060)
(0.150, 0.080)
8.30
6.85
4.96
6.01
8.00
2.43
3.68
7.06
7.10
5.40
3.63
4.56
This work
28
29
29
34
35
36
36
37
38
39
40
and 4.87 lm Wꢁ1, respectively Table 3 summarized performance of
the reported deep-blue OLEDs. As far as we know, the TPA-DFCP-
based doped device realized a relatively outstanding performance
in deep blue light emission. The excellent EL performance of
Device B1 can be attributed to the addition of CBP, which can
reduce the fluorescence quenching phenomenon caused by mole-
Theoretical calculations
The electronic structure was calculated by TD-DFT calculations
using the Gaussian suite of programs (Gaussian 09-B01 package).
The ground state geometry was optimized at the B3LYP/
6-311G*(d,p) level. The energy landscape of singlet and triplet
excited states was calculated at the level of TD-M062X/
6-31G(d,p) on the BTDF-based compounds.
¨
cular packing, and promote efficient Forster energy transfer from
CBP to TPA-DFCP.
Conclusions
In general, a blue-emitting compound TPA-DFCP was successfully
designed and synthesized, which was based on triphenylamine
and benzonitrile as D and A moieties, and 9,9-dimethyl-
fluorene as the p-conjugation bridge. By theoretical calculations
and experimental results, it is concluded that this material could be
suitable with HLCT state, which possesses highly hybridized LE
and CT excited states. The solvatochromic effect showed that the
emission peak is less influenced by the polarity of the solvent in a
low-polarity solvent, and the excited state shows the LE state
characteristic; the emission peak is influenced by the polarity of
the solvent in a high-polarity solvent, and the characteristic of the
CT state is exhibited. Furthermore, the TPA-DFCP doped device
exhibited high-efficiency deep-blue OLED performance with the EL
spectral emission peak at 436 nm and the CIE coordinates at
(0.153, 0.077) and a maximum EQE of 8.3%.
OLED fabrication and characterization
OLEDs with an area of 3 ꢂ 3 mm2 were fabricated by vacuum
deposition onto indium tin oxide (ITO) glass substrates. Current
density–voltage–luminance (J–V–L) curves were measured on a
Keithley 2400 source meter and BM-7A spot brightness meter.
The electroluminescence (EL) spectra were measured through a
PR-655 Spectra Scan spectrometer with computer control. EQEs
were calculated from the J–V–L curves and EL spectra data.
All the measurements were performed at room temperature.
Synthesis
All the reagents and solvents used for the syntheses and mea-
surements were purchased from commercial suppliers and
were used without further purification unless otherwise noted.
Synthesis of 4-(7-Bromo-9,9-dioctyl-9H-fluoren-2-yl) benzo-
nitrile (M1). The compounds of 2,7-dibromo-9,9-dioctyl-9H-
fluorene (7.5 mmol, 4.125 g), (4-cyanophenyl) boronic acid
(5 mmol, 735 mg) and K2CO3 (2 M) were dissolved in toluene
Experimental section
Materials and methods
All commercially available reagents were not further purified, and stirred at room temperature, to which Pd(PPh3)4 was added
unless otherwise specified. The solvents were purified by conven- under a nitrogen atmosphere. The reaction mixture was refluxed
tional procedures. 1H NMR and 13C NMR spectra were measured for 10 h, and then cooled to room temperature, and extracted
on a Bruker DRX 600 spectrometer where tetramethylsilane was three times with dichloromethane. The combined organic
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phases were washed with water and brine, successively, and
then dried with MgSO4. After filtration and solvent evapora-
tion under reduced pressure, the crude product was purified
by silica gel column chromatography (silica gel, hexane) to
1
afford 1.82 g (yield: 70.1%) as a pale-yellow powder. H NMR
(600 MHz, CDCl3) d = 7.75 (s, 5H), 7.55–7.60 (m, 2H), 7.51 (d, J =
1.3 Hz, 1H), 7.48 (dd, J = 1.8, 6.1 Hz, 2H), 1.95–2.00 (m, 4H), 1.18
(dd, J = 6.9, 14.1 Hz, 4H), 1.01–1.13 (m, 16H), 0.78–0.82 (m, 6H),
0.63 (dt, J = 7.1, 18.1 Hz, 4H).
Synthesis of TPA-DFCP. The compounds of M1 (3 mmol,
1.853 g), (4-(diphenylamino)phenyl)boronic acid (3 mmol,
867 mg) and K2CO3 (2 M) were dissolved in toluene and stirred
at room temperature, to which Pd(PPh3)4 was added under
nitrogen atmosphere protection. Then, the reaction mixture
was refluxed for 4 h, and then cooled to room temperature,
and extracted three times with dichloromethane. The combined
organic phases were washed with water and brine, successively,
and then dried with MgSO4. After filtration and solvent evapora-
tion under reduced pressure, the crude product was purified by
silica gel column chromatography (silica gel, hexane) to afford
1.82 g (yield: 73.7%) as a white powder. 1H NMR (600 MHz, CDCl3)
d = 7.70–7.79 (m, 6H), 7.50–7.58 (m, 6H), 7.26 (t, J = 7.9 Hz, 4H),
7.14 (dd, J = 11.2, 8.2 Hz, 6H), 7.02 (t, J = 7.4 Hz, 2H), 1.96–2.06
(m, 4H), 1.10–1.19 (m, 4H), 0.99–1.10 (m, 16H), 0.76 (t, J = 7.2 Hz,
6H), 0.68 (dd, J = 6.6, 15.8 Hz, 4H). 13C NMR (101 MHz, CDCl3) d
152.01, 151.77, 147.66, 147.24, 146.17, 141.66, 140.09, 139.09,
137.69, 135.34, 132.59, 129.32, 127.82, 127.71, 126.27, 125.70,
124.43, 123.95, 123.00, 121.46, 120.98, 120.32, 120.23, 119.13,
110.52, 55.38, 40.40, 31.77, 29.98, 29.20, 29.18, 23.80, 22.60,
14.07. MS (MALDI-TOF, m/z), found: [M+ matrix]+ 735.46439; calcd
for C54H58N2: [M+ matrix]+ 735.46728. Elemental anal. found:
C, 88.24; H, 7.95; N, 3.81%; C54H58N2: C, 88.78; H, 7.36; N, 3.86%.
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Conflicts of interest
There are no conflicts to declare.
Acknowledgements
This work was financial supported by the National Natural
Scientific Foundation of China (61775155, 61705156), Key R&D
Program of Shanxi Province (201903D121100, 201903D421087),
and Natural Science Foundation of Shanxi Province
(201901D111108). We also thank professor Runfeng Chen in
Nanjing University of Posts and Telecommunications for
calculation data.
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