Introduction
Blue, especially deep-blue, emitters are crucial for the development of organic light-emitting
diodes (OLEDs) not only because they can act as hosts for other color materials,[1 ] but also they can be directly used as luminescent materials to reduce the power
consumptions of full-color OLEDs.[2 ] In order to achieve high external quantum efficiency (EQE), a large number of high-performance
blue phosphorescent and thermally activated delayed fluorescence (TADF) materials
have been exploited. However, the severe efficiency roll-offs induced by long exciton
lifetimes and low maximum luminance strictly confine their applications.[3 ] To make things worse, TADF and phosphorescent emitters always show broad emission
spectra due to the intramolecular charge-transfer state (ICT) or metal-to-ligand charge
transfer (MLCT) character.[4 ] Consequently, only few TADF and phosphorescent OLEDs can meet the blue standard
of Commission International de L'Eclairage (CIE) chromaticity coordinate of (0.15,
0.06) required for the International Telecommunication Union Recommendation (ITU-R)
BT.709. Therefore, the development of efficient deep-blue emitters is still an urgent
need.
Apart from TADF and phosphorescent mechanisms, Ma and Yang's group put forward the
hybridized local and charge-transfer (HLCT) state mechanism that can also achieve
100% electricity-generated exciton utilization.[5 ] In HLCT materials, the exciton in the triplet state Tm (m ≥ 2) can convert into the singlet state Sn (n ≥ 1) through inverse intersystem crossing. Based on this mechanism, many blue
emitters have been developed. In 2012, they reported a TPA-PPI -based device with CIE coordinates of (0.15, 0.11) and a maximum EQE of 5.02%.[6 ] Not long after that they demonstrated that introducing a strong electron-withdrawing
cyano group to the nitrogen-substituted benzene ring of TPM can effectively improve exciton utilization efficiency (EUE).[7 ] Based on the above results, Yang's group developed cyano-substituted TPA-PPI , i.e., TBPMCN , which achieves an EQE of 7.8%, an EUE of 97%, and a CIE of (0.16, 0.16).[8 ] Recently, by introducing anthracene as a bridge between the donor and acceptor units
in PAC , Ma et al . realized the first OLED based on the HLCT mechanism with over 10% EQE.[9 ] Besides these high-performance emitters, a variety of excellent OLEDs utilizing
HLCT host materials have been reported,[10 ] proving the versatility of HLCT molecules.
Although incorporating cyano or anthracene improves the performances of phenanthro[9,10-d]imidazole
(PPI) derivative-based OLEDs, it also inevitably leads to poor color purities due
to the enhanced charge-transfer (CT) state and electron coupling effects. Moreover,
the strong CT states are usually accompanied by reduced fluorescence quantum yield
(ϕ
pl ), which leads to low EQE. Aiming at solving the above issues, we introduced fluorine
atoms into the two meta -positions of the nitrogen-substituted phenyl groups of PPI derivatives to delicately
regulate the properties of the excited-state. Fluorine is the most electronegative
element in the periodic table, and it has been proven that the fluorine atoms can
alter energy levels without sacrificing bandgaps and improve molecular ordering by
introducing supramolecular interactions.[11 ] In this contribution we show how the HLCT state mixing status was greatly improved
by introducing fluorine into PPI derivative. We also show that the corresponding non-doped
OLEDs with deep-blue emissions were achieved and their performances were among the
best of HLCT materials.
Results and Discussion
Synthesis and Thermal Stability
As shown in [Scheme 1 ], all target molecules were synthesized within two facile steps with high yields
(>70%). PPI-brominated derivatives and 2FPPIDPA were synthesized through a one-pot cyclization reaction with phenanthraquinone, aromatic
aldehydes, aromatic amine, and ammonium acetate, and then the brominated PPI reacted
with 4-(diphenylamino)phenylboronic acid by the Suzuki coupling reaction to produce
2FPPImTPA and 2FPPITPA . The final products were further purified by a vacuum sublimation approach and fully
characterized by 1 H NMR, mass spectrometry (ESI-ITMS), elemental analysis, and single-crystal X-ray
analysis. Thermal stability of the target molecules was investigated through thermogravimetric
analysis (TGA; [Figure S1a ]) and differential scanning calorimetry (DSC; [Figure S1b ]). All these materials show high decomposition temperatures (T
d corresponding to 5% mass loss) of more than 417 °C, suggesting excellent thermal
stability in the device fabrication process by vacuum thermal deposition. The glass-transition
temperatures (T
g ) of 2FPPImTPA and 2FPPITPA are 118 and 131 °C, respectively. High T
g is advantageous in avoiding crystallization of the material to maintain long-term
stability of the device.
Scheme 1 Synthetic routes and chemical structures of 2FPPImTPA , 2FPPITPA , and 2FPPIDPA . Note that 2FPPIDPA was directly synthesized in the first step.
Investigation of Fluorine Influences
Firstly, the electronic structures of 2FPPImTPA , 2FPPIDPA , and 2FPPITPA were investigated by density functional theory (DFT) calculations. DFT calculations
demonstrate that compared to their counterparts without fluorine substituents ([Figure S2 ]), the fluorine atoms cause more decrease in the LUMOs than the HOMOs ([Figure 1 ]). Furthermore, the fluorine atoms also induce more LUMO orbital distributions on
the nitrogen-substituted phenyl groups of the PPI moiety, which brings more CT components
to the S0 →S1 transitions as indicated by time-dependent DFT (TD-DFT) calculations. Reports reveal
that increased CT components are beneficial to the “state mixing” of high-lying triplet
states and singlet states.[8 ]
[12 ] To further explore their excited-state characteristics, “hole–electron” analyses
of some transitions were analyzed using Multiwfn 3.6,[13 ] and the detailed information is given in [Table S1 ], [Table S2 ], and [Figure S3 ]. Different CT and locally excited (LE) components and distribution characteristics
in S1 and Tn with similar energy ([Figure S3 ]) are beneficial for the reverse intersystem crossing process according to the El-Sayed
rule.[14 ] From the “hole–electron” analyses we can see that the excited-state transitions
of 2FPPImTPA , 2FPPIDPA , and 2FPPITPA are consistent with the characteristics of the HLCT state. The CT component of the
S0 →S1 transition decreases while the LE component increases in the order of 2FPPImTPA , 2FPPIDPA , and 2FPPITPA as shown by the three indexes in [Table S2 ]. For 2FPPImTPA , the CT component is dominant, while for 2FPPITPA , the LE component is highlighted, and 2FPPIDPA displays a balanced LE and CT component ratio. More importantly, the energy bandgaps
of S0 →S1 transitions drop negligibly (<0.02 eV) for 2FPPIDPA and 2FPPITPA and only 0.2 eV for 2FPPImTPA ( see E
g values in [Figures 1 ] and [S2 ]). Owing to the meta -connection which reduces the degree of conjugation, 2FPPImTPA is still the bluest emitter among the three molecules. Theoretical calculations distinctly
confirm that the fluorine atoms located on the meta -positions of the nitrogen-substituted phenyl groups can effectively influence the
excited-state properties of PPI derivatives, while maintaining deep-blue emission
simultaneously.
Figure 1 Frontier molecular orbital distributions and energy levels of target molecules calculated
by B3LYP-D3/6-311(g, d). E
g represents the vertical transition energy based on S0 geometries of S0 →S1 transition calculated by TD-DFT, and C represents the contribution ratios of HOMO→LUMO to S0 →S1 transitions. The unit of HOMO, LUMO, and E
g is eV.
Crystal-Structure Analyses
Single crystals were grown for these materials to investigate their molecular structures
and packing modes. In the 2FPPImTPA crystal ([Figure 2a ]): C–H…F hydrogen bonds were formed between the hydrogen of triphenylamine (TPA)
and the adjacent molecule fluorine at a distance of 2.593 Å; C–H…π interactions assembled
between the hydrogen of the difluorophenyl group and phenanthrene at a distance of
2.469 Å and C–H…π interactions between the hydrogen of the difluorophenyl group and
phenylene bridge at a distance of 2.858 Å were established. In the 2FPPIDPA crystal ([Figure 2b ]), molecules are arranged layer by layer along the plane formed by the a and c crystallographic axes, and the molecules in the same layer are assembled in the same
direction but those in adjacent layers are antiparallel. Two 2FPPIDPA molecules of adjacent layers formed “dimers” through mutual C–H…N hydrogen bonds
(2.682 Å), and C–H…F hydrogen bonds formed between the hydrogen of phenanthrene and
fluorine (2.647 Å). In the 2FPPITPA crystal ([Figure 2c ]), the C–H…F hydrogen bonds between the hydrogen of phenanthrene and fluorine are
2.598 Å in length; there are also C–H…π interactions linked between adjacent TPA groups
(2.772 Å) and the hydrogen of the difluorophenyl group and phenanthrene (2.506 Å).
The introduction of fluorine makes our PPI derivatives pile up more compact compared
with their counterparts as indicated by their bigger crystal density (see [Table S3 ], ρ column), which will reduce the excited nonradiative decay by molecular vibration
and increase ϕ
pl in the solid state.[15 ] Meanwhile, the twisted molecular structures resulting from the propeller TPA and
nitrogen-substituted phenyl with large torsional angles are beneficial for suppressing
the formation of excimers and exciplexes in the solid state.[16 ]
Figure 2 The oak ridge thermal ellipsoid plots (ORTEPs) with important dihedral angle marked
and major intermolecular interactions in crystals of (a) 2FPPImTPA , (b) 2FPPIDPA , and (c) 2FPPITPA .
Photophysical Properties
UV-visible absorption spectra and photoluminescence (PL) spectra of all target molecules
in dilute dichloromethane solution (10−5 mol L−1 ) are shown in [Figure 3 ]. 2FPPITPA and 2FPPIDPA show similar absorption spectra, and their longest-wavelength absorption peaks are
at 363 nm, which are attributed to the S0 →S1 transition with the mixing of CT and LE state as revealed by TD-DFT. 2FPPImTPA also has a shoulder peak at 358 nm with a relatively lower extinction coefficient,
which is attributed mainly to the CT characteristics resulting from the meta -substitution of TPA to PPI. Absorption peaks in the 300–335 nm range are attributed
to the π–π* transitions of PPI moieties. The absorption spectra of their films are
the same as the solutions ([Figure S4 ]).
Figure 3 UV-visible absorption spectra and fluorescence spectra measured in dichloromethane.
Although introduction of fluorine induces stronger CT properties, these molecules
all showed deep-blue emissions both in solutions and in nondoped films, which is in
good agreement with the DFT results. Some key physical properties of the target molecules
are listed in [Table 1 ]. The triplet energy levels of these molecules are all about 2.4 eV, estimated from
the highest-energy-vibration sub-bands of phosphorescence (PH) spectra in toluene
at 77 K ([Figure S5 ]). The fluorescence quantum yields (ϕ
pl ) of all target molecules are very high in dichloromethane solution, which are 71%
for 2FPPImTPA , 76% for 2FPPIDPA , and 90% for 2FPPITPA , respectively. However, their ϕpl values in the film state are only about half of those in solution, resulting from
an aggregation-caused quenching effect.[17 ] 2FPPITPA has a higher ϕ
pl than the other two molecules, which originates from the increased degree of conjugation
and frontier orbital overlap ([Table S2 ]).
Table 1
Summary of key physical properties
λ
em
[a ]
[nm]
E
T
[b ]
[eV]
HOMO/LUMO
[eV][c ]
ϕ
pl
[%][d ]
T
g
[e ]/T
d
[f ]
[°C]
2FPPImTPA
424/405
2.48
−5.3/−2.2
71/35
118/441
2FPPIDPA
430/433
2.36
−5.2/−2.2
76/33
no/417
2FPPITPA
453/461
2.40
−5.2/−2.3
90/52
131/457
a Emission maximum in dichloromethane (left) and in nondoped film (right).
b The triplet energy levels were estimated from the highest-energy-vibration sub-bands
of PL spectra in toluene at 77 K.
c HOMO and LUMO levels were measured by cyclic voltammetry based on the oxidation potential
of ferrocene (4.8 eV) as the reference.
d Fluorescence quantum yield in dichloromethane solution (left) and in film state (right).
e The glass-transition temperatures.
f The thermal decomposition temperatures corresponding to 5% weight loss.
In order to further explore the luminescence properties, solvation effect tests of
all target molecules were carried out, and the results are listed in [Figure S6 ]. Their visible absorption spectra show nearly no change in different solvents, while
their fluorescence spectra showed a significant redshift when solvent polarities were
increased [e.g., hexane to dimethyl sulfoxide (DMSO)]. The redshift of 2FPPIDPA (41 nm) is smaller than those of 2FPPITPA and 2FPPImTPA (>65 nm), resulting from the short CT distance of 2FPPIDPA as revealed by the “hole–electron” analyses (D index in [Table S2 ]). In addition, the fluorescence spectra of 2FPPITPA and 2FPPIDPA exhibit fine vibrational structures with LE properties in low polarity solvents,
but are structureless with CT properties in high polarity solvents, which attests
again to their HLCT characteristics.[18 ]
Energy Levels and Single-Carrier Devices
Before applying our materials to OLEDs, their electrochemical energy levels were investigated
by cyclic voltammetry using ferrocene as a reference ([Figure S7 ]). The HOMOs of these materials are all about −5.2 eV, which is attributed to the
oxidation of the TPA group, and their LUMOs are all about −2.2 eV, which is attributed
to the reduction of the PPI group.[19 ] To check the carrier-transporting properties of 2FPPImTPA , 2FPPITPA , and 2FPPIDPA , single-carrier devices with the structures of [indium-tin oxide (ITO)/1,4-bis[(1-naphthylphenyl)amino]-biphenyl
(NPB) (10 nm)/target materials (80 nm)/NPB (10 nm)/Al (100 nm)] for hole-only devices,
and [ITO/1,3,5-tris(N-phenylbenzimidazol-2-yl) benzene (TPBi) (10 nm)/target materials
(80 nm)/TPBi (10 nm)/LiF (1 nm)/Al (100 nm)] for electron-only devices were fabricated.
Here, NPB and TPBi are used to prevent electron and hole injection from the cathode
and anode, respectively. [Figure 4 ] depicts the current density–voltage plots of all our fabricated single-carrier devices
and comparison of NPB hole-only devices, from which we can see that as the molecular
conjugates increase, the difference in their electron and hole transport abilities
decrease. Since PPI itself is a bipolar transport material with similar electron and
hole transport capabilities,[19b ] the incorporation of TPA with good hole transport ability enhances hole mobility
over electron mobility for all target materials. Intriguingly, the hole transport
abilities of our target materials are approximately equal to that of NPB or even better
than NPB, which may have resulted from the compact packing of these fluorine-substituted
PPI derivatives.
Figure 4 The current density–voltage (J –V ) plots of all single-carrier devices. The dash line represents a comparison of NPB
hole-only device with a structure of [ITO/NPB (100 nm)/Al (100 nm)].
OLED Performances
We fabricated multilayer nondoped OLEDs via a vacuum evaporation technique with the
device structure of [ITO/NPB (40 nm)/TCTA (5 nm)/emitting layer (20 nm)/TPBi (35 nm)/LiF
(0.8 nm)/Al (100 nm)]. TCTA stands for 4,4′,4"-tris(carbazol-9-yl)triphenylamine.
Since the hole transport capability of our material is far superior to the corresponding
electron transport capability, TCTA acted as a block layer to slow the hole mobility
and was utilized for its deeper HOMO, which can further block the excitons due to
its high triplet energies and broad bandgap.[20 ] The energy-level diagrams and molecular structures of the materials used in these
devices are shown in [Figure S8 ] and the performances of these multilayer OLEDs are depicted in [Figure 5 ] and [Table 2 ]. These OLEDs have very low turn-on voltages of no more than 3 V, resulting from
low carrier-injection barriers. The peaks of their electroluminescence (EL) spectra
are below 440 nm and are located in the deep-blue region. The CIE coordinates of 2FPPImTPA and 2FPPIDPA devices are (0.160, 0.038) and (0.156, 0.046), respectively, which can meet the ITU-R
BT.709 blue standard without any color filter. The EQEs of 2FPPImTPA , 2FPPIDPA , and 2FPPITPA multilayer devices are 4.12, 6.49, and 8.47%, respectively, which are far superior
to those of their counterparts ([Table S3 ]) and are among the best of deep-blue materials with similar CIE coordinates.[19b ]
[21 ] What's more, the efficiency roll-offs are less than 20% at 1000 cd m−2 for 2FPPImTPA and 2FPPITPA devices, since there are no detrimental intermolecular interactions as indicated
by the molecule packing modes in crystals ([Figure 2a, b ]). However, the efficiency roll-off of 2FPPIDPA is 33%, which is attributed to the antiparallel “dimer”-like packing mode that can
lead to intermolecular CT ([Figure 2c ]).[22 ]
Figure 5 (a) Current density–voltage–luminance (J–V–L ) plots, (b) EQEs versus luminance curves with EL spectra at 100 cd m−2 as an inset, and (c) power efficiencies (PEs) and current efficiencies (CEs) versus
luminance curves for multilayer OLEDs.
Table 2
Summary of OLED performances in this study
Emitter
V
on
[V][a ]
λ
em
[nm]
L
max
[cd m−2 ][b ]
PEmax
[lm W−1 ][c ]
CEmax
[cd A−1 ][d ]
CIE
(x , y )[e ]
EQEmax/1000
[%][f ]
2FPPImTPA (m )
3.0
416
15560
0.93/0.36
1.10/0.81
0.160, 0.038
4.12/3.30
2FPPIDPA (m )
2.8
430
4916
2.83/0.93
2.58/1.72
0.156, 0.046
6.49/4.36
2FPPITPA (m )
2..8
440
3798
7.00/3.66
6.47/5.30
0.152, 0.083
8.47/6.90
2FPPImTPA (d )
3.0
404
1417
0.93/0.27
0.99/0.55
0.159, 0.047
4.10/2.32
2FPPIDPA (d )
2.8
420
3822
3.40/0.93
3.02/1.80
0.156, 0.055
6.73/4.01
2FPPITPA (d )
2.8
440
13870
6.64/4.28
6.55/5.94
0.154, 0.128
6.10/5.54
Note: The m in parentheses represents the multilayer device structure, and d represents the double-layer device structure.
a Turn-on voltage at 1 cd m−2 .
b The maximum luminance.
c The maximum power efficiency and power efficiency at 1000 cd m−2 .
d The maximum current efficiency and current efficiency at 1000 cd m−2 .
e CIE coordinates recorded at 100 cd m−2 .
f The maximum EQEs and EQEs at 1000 cd m−2 .
Conventionally, the EQE of OLEDs can be expressed by the following equation[23 ]:
EQE = η
eu × γ × η
out × ϕ
pl (Equation 1)
where η
eu is the EUE for singlet and triplet excitons to generate photons, γ is the carrier balance ratio of holes and electrons, which reaches close to unity
for a multilayer device, and η
out is the light out-coupling efficiency, which is considered to be about 20–30% without
additional external light-extracting strategy.[24 ] Assuming a η
out of 30%, the EQE of 2FPPITPA with the highest ϕ
pl (52% in nondoped film) is only 3.9% according to Equation 1. Therefore, the η
eu of 2FPPImTPA , 2FPPIDPA , and 2FPPITPA devices exceeds the 25% limit of traditional fluorescent materials.[25 ] Since these molecules have a linear molecular configuration, they tend to accumulate
parallel to the substrate with a horizontal transition dipole moment, which is conducive
to the increase of η
out . The transition-dipole anisotropies of these molecules in nondoped films were investigated
by florescence polarization experiments as described in our previous study.[19b ] As shown in [Figure S9 ], the emission intensity of the sample film excited by a fixed-intensity laser source
gradually changed upon rotation of the polarizer, which indicates anisotropy of their
transition dipole. Ratios of maximum-to-minimum emission intensity of 2FPPImTPA , 2FPPIDPA , and 2FPPITPA are 1.23, 1.62, and 1.47, respectively. 2FPPITPA possesses the strongest transition dipole anisotropy and the highest ϕ
pl among these three materials, which explains why it has the highest EQE. However,
both ϕ
pl values and ratios of maximum-to-minimum emission intensity of these materials are
smaller compared to those in our previous report,[19b ] but their EQEs are very close, indicating that these materials have higher exciton
utilization ratios. The higher exciton utilization ratios originate from the HLCT
mechanism of these materials, which has been demonstrated in the above analyses. The
η
eu of 2FPPIDPA is about 66% assuming a η
out of 30%, which is attributed to the molecular-structure fine-tuning resulted LE and
CT component ratio equilibrium revealed by the “hole–electron” analyses. The high
η
eu values of these materials manifest our success in improving the HLCT state mixing
by fluorine substitution.
Encouraged by the excellent OLED performances and outstanding hole transport ability,
we also fabricated simplified double-layer nondoped OLEDs without the hole-transport
layer. The structure of the double-layer OLEDs is [ITO/emitting layer (50 nm)/TPBi
(35 nm)/LiF (0.8 nm)/Al (100 nm)]; the performances of these double-layer OLEDs are
also listed in [Table 2 ]. [Figure 6 ] shows the EQE versus luminance curves with EL spectra as an inset for these double-layer
OLEDs, and other information is shown in [Figure S10 ]. The spectrum profiles and the peaks of their EL spectra for these double-layer
devices are similar to those of their multilayer OLEDs, proving that they all originate
from the luminescence of our target molecules. The maximum power efficiencies (PEs)
and maximum current efficiencies (CEs) of 2FPPImTPA and 2FPPITPA double-layer devices are nearly the same as their multilayer OLEDs, but their maximum
EQEs decreased due to the increase of spectrum full-width at half-maximum (FWHM).
Surprisingly, the 2FPPIDPA double-layer device performance exceeded its corresponding multilayer OLED, which
implies a huge potential for its application in OLEDs with simple device structures.
Figure 6 The EQE versus luminance curves with EL spectra at 100 cd m−2 as an inset for the double-layer OLEDs.
Experimental Section
All reagents were bought from Energy Chemical Co. and/or J&K scientific Ltd. Co . and immediately used without further purification. The Schlenk technique was strictly
performed under a nitrogen atmosphere in all reactions. The synthesis process is shown
below in detail. The final products were first purified by column chromatography,
then further purified by temperature-gradient vacuum sublimation.
Procedures
Reaction I : this is the general information for cyclization reactions. Phenanthrene-9,10-dione
(1 eq.), 3,5-difluoroaniline (3 eq.), aromatic aldehyde (1.06 eq.), and ammonium acetate
(5 eq.) were dissolved in acetic acid and refluxed in a nitrogen atmosphere for 6 hours.
After cooled to room temperature, the system was poured into an equal volume of water
and then separated by vacuum suction filtration. The filter cake was purified via
column chromatography using dichloromethane and ethyl acetate as the eluent.
Reaction II : this is the general information for Suzuki coupling reactions. PPI-brominated derivatives
(1 eq.), (4-(diphenylamino)phenyl)boronic acid (1.1 eq.), Pd(PPh3 )4 (0.04 eq.), 2 mol L−1 K2 CO3 (3 eq.), tetrabutylammonium bromide (TBAB, 0.1 eq.), and toluene were refluxed in
a nitrogen atmosphere for 12 hours. After cooled to room temperature, the system was
poured into water and extracted with dichloromethane. Then the crude product was purified
via column chromatography using dichloromethane and ethyl acetate as the eluent.
2a : phenanthrene-9,10-dione (1.25 g, 6 mmol), 3,5-difluoroaniline (2.32 g, 18 mmol),
1a (1.18 g, 6.36 mmol), and ammonium acetate (2.31 g, 30 mmol) were used as reactants
according to Reaction I to give 2a . A white powder, mass: 2.39 g, yield: 82%. 1 H NMR (500 MHz, chloroform-d ): δ = 8.79 (ddd, J = 18.8, 8.2, 1.3 Hz, 2 H), 8.73–8.65 (m, 1 H), 7.75 (ddd, J = 8.0, 7.0, 1.2 Hz, 1 H), 7.67 (ddd, J = 8.4, 7.0, 1.5 Hz, 1 H), 7.55 (ddd, J = 8.4, 7.0, 1.3 Hz, 1 H), 7.51–7.39 (m, 4 H), 7.35 (ddd, J = 8.3, 7.0, 1.2 Hz, 1 H), 7.20 (dd, J = 8.4, 1.3 Hz, 1 H), 7.17–7.05 (m, 3 H). ESI–ITMS, m/z : 484.32 and 486.33 [M+ ]. Calcd: 484.04 and 486.04.
2b : phenanthrene-9,10-dione (1.25 g, 6 mmol), 3,5-difluoroaniline (2.32 g, 18 mmol),
1b (1.18 g, 6.36 mmol), and ammonium acetate (2.31 g, 30 mmol) were used as reactants
according to Reaction I to give 2b . A white powder, mass: 2.30 g, yield: 79%. 1 H NMR (500 MHz, DMSO-d
6 ): δ = 8.96 (d, J = 8.4 Hz, 1 H), 8.90 (d, J = 8.3 Hz, 1 H), 8.69 (dd, J = 8.0, 1.4 Hz, 1 H), 7.86–7.66 (m, 6 H), 7.66–7.59 (m, 2 H), 7.54 (dt, J = 7.8, 1.3 Hz, 1 H), 7.51–7.45 (m, 1 H), 7.38 (t, J = 7.9 Hz, 1 H), 7.19 (dd, J = 8.3, 1.2 Hz, 1 H). ESI–ITMS, m/z : 484.30 and 486.31 [M+ ]. Calcd: 484.04 and 486.04.
2FPPIDPA: phenanthrene-9,10-dione (1.25 g, 6 mmol), 3,5-difluoroaniline (2.32 g, 18 mmol),
1c (1.74 g, 6.36 mmol), and ammonium acetate (2.31 g, 30 mmol) were used as reactants
according to Reaction I to give 2FPPIDPA . A white powder, mass: 2.51 g, yield: 73%. 1 H NMR (500 MHz, methylene chloride-d
2 ): δ = 8.86 (d, J = 8.4 Hz, 1 H), 8.79 (d, J = 8.3 Hz, 1 H), 7.84 (s, 1 H), 7.77 (s, 1 H), 7.60 (d, J = 46.5 Hz, 4 H), 7.44 (t, J = 7.6 Hz, 1 H), 7.37 (t, J = 7.7 Hz, 4 H), 7.29–7.14 (m, 10 H), 7.02–6.98 (m, 2 H). 19 F NMR (471 MHz, methylene chloride-d
2 ): δ = −106.75. ESI–ITMS: m/z : 573.13 [M+ ]. Calcd: 573.20. Elem. Anal. Calcd. (%) for C39 H25 N3 F2 : C, 81.66; H, 4.39; N, 7.33. Found: C, 81.28; H, 4.62; N, 7.29.
2FPPImTPA: 2b (1.94 g, 4 mmol) and (4-(diphenylamino)phenyl)boronic acid (1.27 g 4.4 mmol) were
reacted according to Reaction II to give 2FPPImTPA . A white powder, mass: 2.31 g, yield: 89%. 1 H NMR (500 MHz, methylene chloride-d
2 ): δ = 8.90–8.81 (m, 2 H), 8.77 (d, J = 8.3 Hz, 1 H), 7.92 (t, J = 1.8 Hz, 1 H), 7.84–7.77 (m, 1 H), 7.72 (ddd, J = 8.4, 6.9, 1.5 Hz, 1 H), 7.65 (dt, J = 7.8, 1.6 Hz, 1 H), 7.60 (ddd, J = 8.3, 6.9, 1.3 Hz, 1 H), 7.53 (dt, J = 7.7, 1.5 Hz, 1 H), 7.48–7.39 (m, 4 H), 7.37–7.32 (m, 6 H), 7.27–7.15 (m, 10 H),
7.13–7.09 (m, 2 H). 19 F NMR (471 MHz, methylene chloride-d
2 ): δ = −106.61. ESI–ITMS: m/z : 649.17 [M+ ]. Calcd: 649.23. Elem. Anal. Calcd. (%) for C45 H29 N3 F2 : C, 83.19; H, 4.50; N, 6.47. Found: C, 82.95; H, 4.70; N, 6.40.
2FPPITPA: 2a (1.94 g, 4 mmol) and (4-(diphenylamino)phenyl)boronic acid (1.27 g 4.4 mmol) were
reacted according to Reaction II to give 2FPPITPA . A pale yellow powder, mass: 2.39 g, yield: 92%. 1 H NMR (500 MHz, methylene chloride-d
2 ): δ = 8.87 (t, J = 11.6 Hz, 2 H), 8.79 (d, J = 8.3 Hz, 1 H), 7.84–7.79 (m, 1 H), 7.76–7.68 (m, 3 H), 7.66–7.60 (m, 3 H), 7.58–7.55
(m, 2 H), 7.43 (ddd, J = 8.2, 6.9, 1.2 Hz, 1 H), 7.35–7.30 (m, 5 H), 7.27–7.19 (m, 3 H), 7.19–7.14 (m, 6
H), 7.13–7.07 (m, 2 H). 19 F NMR (471 MHz, methylene chloride-d
2 ): δ = −106.60. ESI–ITMS: m/z : 649.73 [M+ ]. Calcd: 649.23. Elem. Anal. Calcd. (%) for C45 H29 N3 F2 : C, 83.19; H, 4.50; N, 6.47. Found: C, 82.97; H, 4.69; N, 6.41.
