Light blue and green thermally activated delayed fluorescence from 10H-phenoxaborin-derivatives and their application to organic light-emitting diodes

Article abstract of DOI:10.1039/c5tc01380a

New luminescent compounds consisting of 10H-phenoxaboryl groups as electron-accepting units and carbazole (9), 9,9-dimethylacridane (10), or phenoxazine (11) as an electron-donating unit have been synthesized. Compounds 10 and 11 showed thermally activated delayed fluorescence (TADF) with light blue and green emissions, respectively, with very high PL quantum yields (PLQYs), however, compound 9 exhibited only a prompt emission and no delayed component. Photoluminescence studies and quantum chemical calculation based on density functional theory (DFT) and time-dependent density functional theory (TD-DFT) revealed that in comparison with compound 9, the HOMO and LUMO for compounds 10 and 11 are well separated, resulting in lowering of ΔE_ST and effective reverse intersystem crossing (RISC) between a lowest triplet excited state (T₁) and a lowest singlet excited state (S₁). Organic light-emitting diodes (OLEDs) using compounds 10 and 11 exhibited light blue and green emissions with very good maximum η_ext of 15.1% and 22.1%, respectively.

Full text of DOI:10.1039/c5tc01380a

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ARTICLE
Light Blue and Green Thermally Activated Delayed Fluorescence
from 10H-Phenoxaborin-Derivatives and Their Application to
Organic Light-Emitting Diodes†
Received 00th January 20xx,
Accepted 00th January 20xx
a
b
b
b
b
DOI: 10.1039/x0xx00000x
Yuichi Kitamoto,* Taketo Namikawa, Dai Ikemizu, Yasuo Miyata, Takatsugu Suzuki, Hiroshi
c
a,d
a
Kita, Tetsuo Sato, and Shuichi Oi*
www.rsc.org/
New luminescent compounds consisting of 10H-phenoxaboryl group as an electron-accepting unit and carbazole (9), 9,9-
dimethylacridane (10), or phenoxazine (11) as an electron-donating unit have been synthesized. Compounds 10 and 11
showed thermally activated delayed fluorescence (TADF) with light blue and green emissions, respectively, with very high
PL quantum yields (PLQYs), however, compound 9 exhibited only a prompt emission and no delayed component.
Photoluminescence studies and quantum chemical calculation based on density functional theory (DFT) and time-
dependent density functional theory (TD-DFT) revealed that in comparison with compound 9, HOMO and LUMO for
compounds 10 and 11 are well separated, resulting in lowering ꢀEST and effective reverse intersystem crossing (RISC)
1 1
between a lowest triplet excited state (T ) and a lowest singlet excited state (S ). Organic light-emitting diodes (OLEDs)
using compounds 10 and 11 exhibited light blue and green emissions with very good maximum ηext of 15.1% and 22.1%,
respectively.
demonstrated: tripletꢀtriplet annihilation (TTA), which generate
one singlet exciton by annihilative reaction between two triplet
excitons, can totally generate a maximum 62.5% of singlet
excitons. Hybridized local and chargeꢀtransfer (HLCT), which
harvest triplet excitons via the reverse intersystem crossing
Introduction
After pioneering work on multilayer organic lightꢀemitting
diodes (OLEDs) by the research group of Eastman Kodak Ltd.,
OLEDs has been widely developed and applied to smart
phones, flatꢀpanel displays, and lighting applications because
they realized high efficiency, slim design, and flexible form.
Under electrical excitation, 25% of singlet excitons and 75% of
triplet excitons being formed by a spin statistic rule, early
OLEDs using fluorescent materials exhibit theoretically at most
7
1
3
2
(RISC) between highꢀlying triplet CT excited states ( CT
x
) and
1
3
4
singlet CT excited state ( CT
η
x
), can realize theoretically 100%
int. Recently, Adachi et al. have found that OLEDs doped
Sn ꢀporphyrin complexes exhibited thermally activated
8
IV
9
5
delayed fluorescence that enable triplet excitons to upꢀconvert
1
0
to singlet excitons via endothermic RISC. As all of the
excitons generated by electrical excitation can be converted into
fluorescent luminescence, TADF materials such as cuprous
2
5% of internal quantum efficiency (
excitons wasted as a nonꢀradiative decay. In order to improve
int of the OLEDs, phosphorescent materials consisting of
ηint) with the triplet
η
1
1
12
complexes,
molecules
zinc complexes,
and metalꢀfree organic
have been developed in the past few years.
For an effective intersystem upꢀconversion of triplet
organicꢀheavy metal complexes have developed because
intersystem crossing (ISC) from singlet excited states to triplet
excited states and radiative triplet decay rates are effectively
enhanced by high spinꢀorbit coupling induced by the heavy
metal, resulting in theoretical 100%
1
3ꢀ20
excitons from T
gap between S
1
state to S state in TADF process, the energy
and T , ∆EST, play a key role, which depends
1
6
1
1
η
int
.
Fluorescent based
on the overlapping of the frontier molecular orbitals of a
highest occupied molecular orbital (HOMO) and lowest
OLEDs harvesting 75% triplet excitons have also been
1
3a,21
unoccupied molecular orbital (LUMO).
This theory
indicates that the spatial separation of the two orbitals leads to a
2
1a
lowering of ∆
Adachi group has achieved metalꢀfree TADF molecules with a
small ∆ ST and high external quantum efficiency (
E
ST
,
which results in an efficient TADF.
E
ηext) by
introducing donor and acceptor moieties with a suitable steric
hindrance and distance, which enabled to develop efficient
OLEDs without using expensive heavy metals, such as Ir and
1
9b
Pt.
Recently, boronꢀcontaining compounds exhibiting high
electron mobility have jointly reported by Konica Minolta, Inc.
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2
2a
22b
and Shirota group, and Chujo group. Since the electron 10 and 11 were very close to the phosphorescence bands and
mobility originated from a high electron accepting ability of the their experimental values of ∆
boron atom, we imagined that the aromatic moiety
EST were determined to be 0.013
incorporating the boron atom into the
would serve as a new acceptor unit for a TADF molecule.
Herein, we report new TADF molecules consisting of 10
phenoxaboryl group as an electronꢀaccepting unit and
πꢀconjugated system
Hꢀ
2
3
diarylamineꢀderivatives as an electronꢀdonating unit.
Results and discussion
Our strategy of molecular design on the boronꢀcontaining
TADF compounds is shown in Figure 1: electronꢀaccepting and
ꢀ
donating units are crossꢀlinked thorough a phenylene bridge at
the 1,4ꢀpositions. We choose 10 ꢀphenoxaborin unit as an
acceptor and carbazole, phenoxazine, or 9,9ꢀdimethylꢀ9,10ꢀ
dihydroacridine (9,9ꢀdimethylacridane) as donor. We
H
a
supposed that these quasi anthracene and fluorene moieties
would be twisted by the steric repulsion between the hydrogen
atoms of the crossꢀlinking phenylene, donor, and acceptor,
resulting in effective spatial separation of the HOMO and
LUMO and lowering ∆
These molecules were synthesized according to Scheme 1.
Triarylamine halides were synthesized by Cuꢀ or Pdꢀ
catalyzed crossꢀcoupling of carbazole ( ), phenoxazine ( ), or
,9ꢀdimethylacridane with 1,4ꢀdihalobezenes as the
precursors of the donor units. 10 ꢀPhenoxaborinꢀ10ꢀol ( ) and
isopropyl alcohol were subjected to esterification reaction to
synthesize the borinate ester as an intermediate of the
acceptor unit. The borinate ester was used without
ST
E .
4ꢀ6
1
2
9
(3)
H
7
8
8
purification because it was rapidly hydrolyzed under air. Then,
subsequent reaction of lithium triarylamines, which were
prepared from 4-6 and
gave the corresponding NꢀB type products 9-11 in good yield.
The absorption and photoluminescence (PL) spectra of
compounds 11 in toluene are shown in Figure 2. The NꢀB
type compounds having carbazole ( ), acridane (10), and
nꢀbutyl lithium, with borinate ester 8
9
ꢀ
9
phenoxazine (11) as a donor exhibited deep blue, light blue, and
green emission at 300 K, respectively. The order of emission
bands for fluorescence and phosphorescence also maintained at
77 K. The fluorescence bands of compounds 10 and 11
especially showed broad bands, suggesting that the emission
originate from the intramolecular CT excitons. Comparing the
Scheme 1 Synthesis of compounds 9-11: a) i CuI, LiCl, Cs
°C; ii n-BuLi, THF–Et O, −78 °C; iii borinate ester 8, THF–Et
2
Cs CO , DMF, microwave 220 °C; ii n-BuLi, THF–Et O, −78 °C; iii borinate ester 8,
t
2
CO
3
, DMF, microwave, 220
fluorescence and phosphorescence emissions of compound
9
at
2
2
O, −78 °C: b) i CuI, KI,
2
3
77 K, the difference in two onsets of the emissions was 40.9 nm
THF–Et
2
O, −78 °C: c) i Pd
2
(dba)
3
·CHCl
3
, JohnPhos, NaO Bu, toluene, 60 °C; ii n-BuLi,
O, −78 °C: d) i isopropyl alcohol–
and the value of ∆EST was experimentally estimated to be 0.35
THF–Et
2
O, −78 °C; iii borinate ester 8, THF–Et
2
2
4
eV. On the other hand, the fluorescence bands of compounds
benzene, MS3A, reflux.
and 0.028 eV, respectively. The small ∆EST of compounds 10
and 11 suggests that these two NꢀB type molecules, which have
quasi anthracene skeletons as donors, exhibit efficient TADF in
comparison to compound
a donor.
9 having a quasi fluorene skeleton as
To elucidate the delayed fluorescence from the NꢀB type
compounds, we analyzed the PL characteristics of polystyrene
film fabricated with 6 wt% of compounds 9, 10 and 11 by wet
Fig. 1 Molecular design of boron-based TADF molecules.
2
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Fig. 2 Absorption and fluorescence spectra of a) compound 9, b) 10, and c) 11 in
toluene (ex. 290 nm). Green and blue lines represent fluorescence spectra at 300 K
and 77 K, respectively. Black line represents UV-vis spectra. Red dotted line
represents phosphorescence spectra at 77 K.
Fig. 3 Transient photoluminescence of 6 wt% a) compounds 9, b) 10, and c) 11:
polystyrene films fabricated by wet process (YaG laser, λ = 355 nm). The inset shows
prompt (black line) and delayed (red line) photoluminescence spectra of 6 wt% 10
and 11: polystyrene fabricated films.
fourꢀ and threeꢀexponentials for compounds 10 and 11, the
2
process using a streak camera at 300 K under N . Figure 3
weightꢀaverage lifetimes are determined to be 2.36 and 1.87 ꢁs,
shows transient PL decay curves and the prompt and delayed
PL spectra. The PL curves of compounds 10 and 11 are
comprised of sharp and gentlyꢀsloping emissions, which are
attributed to prompt and delayed components, respectively. In
addition, the prompt emission bands for compounds 10 and 11
coincide with the delayed emission bands with peak position at
respectively, showing the effective RISC process occurs. These
shortꢀlived TADF emissions are suitable for OLED emitters
because longꢀlived emissions relating to triples excitons could
cause the tripletꢀtriplet and singletꢀtriplet annihilations,
1
7b,25
resulting in quantum efficiency rollꢀoff.
In contrast with
compounds 10 and 11, the carbazoleꢀbased molecule
9
440 and 482 nm, respectively (inset figures in Figure 3b and
exhibited only a prompt emission and showed no delayed
component.
3
c). These results strongly indicate that the fabricated films
with compounds 10 and 11 exhibit TADF emissions. Fitting
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26b
Fig. 4 The HOMO and LUMO distribution of a) compounds 9, b) 10, and c) 11 calculated at the M06/6-31G* level.
In order to clarify why the TADF characteristics were basis of these observation and calculation, the value of ∆EST is
observed for the phenoxazineꢀ and acridaneꢀbased molecules dependent on the molecular structure of donor and the twist
but not the carbazoleꢀbased molecule, quantum chemical angle between the donor and crossꢀlinking phenylene: for
calculations for S
0
states of compounds 9ꢀ11 were carried out compounds 10 and 11 having acridane and phenoxazine as a
using density functional theory (DFT) at the M06/6ꢀ31G* donor, the steric repulsion between the hydrogen atoms of the
2
6
level. Figure 4 shows the optimized structures and the HOMO donor and crossꢀlinking phenylene causes the large dihedral
and LUMO of compounds 11. The dihedral angle between angles as shown in Figure 1. For compound having carbazole
the phenylene and the acceptor of compound ) is as a donor, on the other hand, the relative small fiveꢀmembered
almost the same as that of compounds 10 and 11 51.8, ring decrease the steric repulsion, resulting in the decrease of
2.2
between the phenylene and the donors are largely different: for making the ∆
compounds 10 and 11, the dihedral angles are calculated to be To evaluate the performance of compounds 10 and 11 as an
8.9 and 87.5, respectively, while compound exhibits much emitter in OLEDs, we examined the electroluminescence (EL)
smaller dihedral angle of 54.7 . For compounds 11, the characteristics of multilayer OLEDs using compounds 10 and
LUMO is mainly distributed on the 10 ꢀphenoxaborin moiety, 11 as the emitters as follows: the device structures are
which indicates that the ꢀconjugated moiety containing boron ITO/PEDOT:PSS (40 nm)/ ꢀNPD (35 nm)/mCP (10
atom serve as an acceptor. The HOMO of compounds 10 and
are wellꢀseparated spatially on the donors, but the HOMO of
compound is predominantly localized not only on the donor
9ꢀ
9
9
(
θ
=
53.6°
(
θ =
5
°
, respectively). On the other hand, the dihedral angles the dihedral angle, overlapping of the HOMO and LUMO, and
ST larger than that of 10 and 11
E
.
8
9
°
9ꢀ
H
π
α
1
1
9
but also on the crossꢀlinking phenylene moiety adjacent to the
acceptor. As these differences in the dihedral angles and degree
of orbital overlap were assumed to affect the value of ∆
then investigated the ∆ ST of compounds 11 using timeꢀ
dependent density functional theory (TDꢀDFT) at the M06/6ꢀ
EST, we
E
9ꢀ
2
6ꢀ28
3
1G* level,
mentioned above. It was found that compounds 10 and 11
exhibit very small ∆ ST of 0.0027 and 0.0036 eV, respectively,
which are much smaller than that of compound (∆ 0.295
eV). This correlation of ∆ ST is in reasonable agreement with
the experimental values for compounds 11 vide supra).
using the optimized ground state geometry
E
9
ST
E =
E
9
ꢀ
(
Although the optimization of excited states for each molecule
was not performed in the present study, these DFT and TDꢀ
DFT calculations give us the important information about the
Fig. 5 The external quantum efficiency-current density characteristic of the OLEDs
using compounds 10 and 11. The inset shows the electroluminescence spectra. The
blue and green plots represent compounds 10 and 11, respectively.
relationship between the molecular structure and ∆EST. On the
4
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nm)/compound 10 (6%):DPEPO (20 nm)/DPEPO (10 OLED layer structure.
nm)/TPBi (40 nm)/Al (100 nm) and ITO/PEDOT:PSS (40 We found that for the devices using compounds 10 and 11
nm)/ ꢀNPD (35 nm)/mCP (10 nm)/compound 11 (6%):mCP current density vs. luminescence plots did not exhibit a
,
α
(20 nm)/PPT (10 nm)/TPBi (40 nm)/LiF (0.5 nm)/Al (100 nm) quadratic increase but a liner increase (Figure 6), indicating that
(
Figure S1). For compounds 10 and 11, the devices exhibited the processes of the luminescence from the triplet excitons are
1
5b,29
light blue and green EL with the peak positions of the EL not the TTA mode but the TADF mode.
It is also noted
spectra at 466 and 503 nm with very good maximum
ηext of that the device based on 10 exhibits a high luminescence of
−
2
15.1 and 22.1%, respectively (Figure 5). These results clearly 8216 cd·m at 8.5 V as shown in Figure 7 and maintains a high
−
2
indicate that the substantial triplet excitons contribute the
luminescence. The PL quantum yields (PLQYs) of 6 wt% characteristics are caused by the small
doped film of compounds 10 and 11 in the corresponding host time of the excitons of the boron containing TADF molecules
η
ext of 14.6% even at a luminescence of 1000 cd·m . These EL
ꢀ
E
ST and the short life
layers under nitrogen were then measured. Compound 10 in 10 and 11
DPEPO and 11 in mCP showed very high PLQYs of 98%
.
(
excited at 300 nm) and 99% (excited at 320 nm), respectively.
Considering a light outcoupling efficiency of 20–30%, an
estimated electroluminescence int of 11 is as high as its PLQY.
In comparison to this, a decline of the electroluminescence
Conclusions
η
In summary, we have demonstrated light blue and green TADF
molecules consisting of the
boron atom as an electronꢀaccepting unit and diarylamine
derivatives as an electronꢀdonating unit. For compounds 10 and
η
ext
πꢀconjugated system containing
of 10, in spite of the high PLQY as 11, indicates that there is
room to improve the choice of the host compound and the
1
1
, phenoxazine and acridane moieties induced suitable twists
between the donors and the crossꢀlinking phenylene, resulting
in a very small ∆ ST and shortꢀlived TADF emissions. OLEDs
constructed with 10 and 11 as dopants exhibited high
E
η
ext and
luminescence, indicating that these molecules are promising
candidate for dopants of OLEDs. Further optimization of the
Fig. 6 Luminance-current density characteristics of the OLEDs using a) compounds
Fig. 7 The OLEDs characteristics using compounds 10, and 11 as an emitter: a)
Current density-voltage characteristics, and b) luminescence-voltage characteristics.
The blue and green plots represent compound 10 and 11, respectively.
1
0, and b) 11 as an emitter. The inset show luminescence-current density
characteristics at the region with low current density. The blue and green plots
represent compound 10 and 11, respectively.
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3
dopant molecular structure as well as the host compound and (dd, 2H,
the multilayer structure would contribute to improve blueꢀ DMSOꢀ
emitting OLEDs using TADF molecules with boron atom.
J = 7.4, 1.7 Hz), 9.88 (brs, 1H); C NMR (100 MHz,
1
1
d
6
)
δ
17.1, 120.3, 122.2, 132.0, 133.3, 160.8; B NMR
(128 MHz, DMSOꢀ 37.9; HRMS (FAB) calcd for
[M] 196.0696, found 196.0697.
6
d ) δ
+
C
12
H
9
BO
-(4-Bromophenyl)-9
according to the literature procedures. A white powder,
NMR (400 MHz, CDCl 7.29 (ddd, 2H, = 7.5, 7.2, 1.2 Hz),
.36–7.41 (m, 4H), 7.44 (d, 2H, = 8.7 Hz), 7.72 (d, 2H,
= 7.5 Hz); C NMR (100 MHz,
109.7, 120.3, 120.5, 121.0, 123.6, 126.2, 128.8,
2
3
1
9
H
-carbazole (4).
4 was prepared
1
Experimental
H
3
)
δ
J
General
7
J
J =
1
3
NMR spectra were recorded on an AVANCE III 400 8.7 Hz), 8.13 (d, 2H,
J
1
spectrometer. H NMR were obtained at 400 MHz and CDCl3)
δ
1
3
+
referenced to tetramethylsilane singlet at 0.00 ppm. C NMR 133.2, 136.9, 140.7; HRMS (FAB) calcd for C H BrN [M]
1
8
12
were obtained at 100 MHz and referenced to the center line of 321.0153, found 321.0152.
the CDCl triplet and DMSOꢀ octet at 77.16 and 39.52 ppm.
9-(4-(10 -phenoxaboryl)phenyl)-9
B NMR were obtained at 128 MHz and referenced to 100 mL twoꢀnecked flask equipped with dropping funnel filled
BF ·OEt at 0.00 ppm as an external standard. Highꢀresolution with MS3A and dimroth condenser was charged with
(166
mass spectra were obtained on a JEOL JMSꢀ700 spectrometer mg, 1.0 equiv, 8.49
10 mmol), and then evacuated with
3
d
6
H
H
-carbazole (9).
A
1
1
3
7
ꢀ1
×
at the Department of Instrumental Analysis of the Technical heating and refilled with N . 50 mL of dry 2ꢀpropanol and 10
2
Division, School of Engineering, Tohoku University. IR spectra mL of dry benzene were added and the reaction mixture was
were recorded on a JASCO FT/IRꢀ350 Fourierꢀtransform refluxed for 48 h. After the solvent was removed in vacuo at 70
infrared spectrometer. Photoluminescence spectra in toluene
were recorded on Hitachi HighꢀTech Fꢀ7000 ml and 4 ml, respectively) to give a solution of the borinate
Spectrophotometer. UVꢀvis spectra in toluene were recorded on ester
. A 50 mL twoꢀnecked flask was charged with (273
Shimazu UVꢀ2500 spectrophotometer. Melting points were mg, 8.49
10 mmol), and then evacuated with heating and
2
°C for 2 h, the residue was dissolved with dry Et O and THF (2
a
8
4
ꢀ1
×
recorded using a Stuart melting point apparatus SMP3. The refilled with N . 4 mL of dry THF and 3 mL of dry Et O were
2
2
transient photoluminescence decay of the films fabricated with added, and then
nꢀbutyllithium (640
ꢁ
L, 1.2 equiv, 1.02 mmol,
TADF molecules were recorded using a Hamamatsu Photonics 1.6 M in
QuantaurusꢀTau C11367ꢀ01 equipped with YaG laser ( 355 at
78 C. The reaction mixture was stirred for 1.0 h at
nm). The prompt and delayed emission spectra were also and then the prepared solution of the borinate ester was added
recorded using Hamamatsu Photonics QuantaurusꢀTau dropwise at
78 C. After stirring at 78 C for 0.5 h, the
C11367ꢀ01 equipped with YaG laser ( 355 nm). PL quantum solution was gradually warmed to room temperature and stirred
n
ꢀhexane) was added dropwise to the stirred solution
78
λ
=
−
°
−
°C
a
−
°
−
°
λ
=
efficiencies were measured using a Hamamatsu Photonics for 24 h at room temperature. The resulting mixture was passed
QuantaurusꢀQY C11347ꢀ01 absolute photoluminescence through a silica gel short column (dichloromethane). After the
quantum yield measurement system. The electroluminescence volatile was removed in vacuo, the product was recrystallized
spectra and current densityꢀvoltageꢀluminance characteristics of from dichloromethane–
the OLEDs were measured using a Konica Minolta CSꢀ2000 washing with
ꢀpentane, the product
Spectroradiometer, and an ADC DC Voltage and Current obtained as white powder. Mp 232.0–233.5
n
ꢀpentane at 0
(178 mg, 58% yield) was
C; IR (KBr)
°C. After filtration and
n
9
°
Source/Monitor.
3020.0, 2986.4, 1592.9, 1575.6, 1476.2, 1449.2, 1431.9,
atmosphere in eggꢀ 1333.5, 1316.2, 1294.0, 1263.2, 1226.5, 910.2, 745.4, 721.3; H
1
All reactions were performed under a N
2
plant shaped flasks unless noted otherwise. Microwaveꢀassisted NMR (400 MHz, CDCl3)
reactions were carried out with a Biotage Initiator Sixty (400 7.38 (ddd, 2H,
= 7.8, 7.4, 1.0 Hz), 7.47 (ddd, 2H,
W, 2.45 GHz) using a Biotage 5 mL vial sealed with a crimp 1.2 Hz), 7.61 (d, 2H,
= 7.8 Hz), 7.66 (d, 2H, = 7.8 Hz), 7.77
= 8.3 Hz), 7.81 (ddd, 2H, = 7.8, 7.7, 1.6 Hz), 7.96
= 8.3 Hz), 8.17 (dd, = 7.6, 1.6 Hz), 8.19 (d, 2H,
110.2, 118.0, 120.1,
20 mm i.d.) and a JAI 120.5, 122.7, 123.7, 124.7, 126.1, 126.3, 134.8, 135.2, 136.6,
δ
7.32 (ddd, 2H,
J
= 7.4, 7.4, 0.9 Hz),
= 7.7, 7.6,
+
J
J
J
J
cap. Colum chromatography was performed using spherical (d, 2H,
silica gel (63–200 m, Kanto Chemical). Recycling preparative (d, 2H,
J
J
J
ꢁ
J
J =
1
3
GPC was performed using preparative columns connecting a 7.4 Hz); C NMR (100 MHz, CDCl3)
JAI JAIGELꢀ1H column (600 mm
JAIGELꢀ2H column (600 mm
CHCl as an eluent.
20
δ
×
1
1
×
20 mm i.d.) in series with 138.1, 139.8, 141.0, 160.2; B NMR (128 MHz, CHCl )
δ
3
+
3
51.3; HRMS (FAB) calcd for C H BNO [M] 421.1638,
3
0
found 421.1635.
,9-Dimethyl-9,10-dihydroacridine (2).
All solvents (including superꢀdehydrated) using in reactions, according to the literature procedures. A white powder,
UVꢀvis, and photoluminescence measurements was purchased NMR (400 MHz, CDCl3)
1.57 (s, 6H), 6.10 (brs, 1H), 6.67
and used as received. Commercially available reagents were (dd, 2H,
= 7.7, 1.3 Hz), 6.91 (ddd, 2H, = 7.7, 7.4, 1.3 Hz),
purchased and used without purification unless noted otherwise. 7.09 (ddd, 2H,
= 7.7, 7.4, 1.3 Hz), 7.37 (dd, 2H, = 7.7, 1.3
was prepared according Hz); C NMR (100 MHz, CDCl3)
30.7, 36.3, 113.5, 120.7,
to the literature procedures. White, fluffy solids, H NMR (400 125.6, 126.9, 129.3, 138.6; HRMS (FAB) calcd for C H N
Materials
32
9
2 was prepared
1
H
δ
J
J
J
J
3
0
13
10
H
-Phenoxaborin-10-ol (7).
7
δ
1
1
5
15
+
MHz, DMSOꢀ = 7.5, 7.4, 0.90 Hz), 7.44 [M] 209.1204, found 209.1206.
d
6
)
δ
7.30 (ddd, 2H,
J
(
d, 2H, = 7.9 Hz), 7.68 (ddd, 2H, J = 7.9, 7.5, 1.7 Hz), 8.16
J
6
| J. Name., 2012, 00, 1-3
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Jou Pr nl e aa ls oe fd Mo an to et r ai ad lj su s Ct hm ea mr g ii sn ts ry C
View Article Online
DOI: 10.1039/C5TC01380A
ARTICLE
ꢀ
2
9
.9-Dimethyl-10-(4-iodophenyl)-9,10-dihydroacridine
butylphosphino)biphenyl (18 mg, 6.0 mol%, 6.00
×
10 mmol),
(209 mg, 1.00 mmol), 1,4ꢀ and NaO Bu (289 mg, 3.0 equiv, 3.00 mmol), and then
. 1.5 mL of dry toluene was
(327 mg, 1.0 equiv, 1.00 added and the reaction mixture was stirred at 60 C until a dark
mmol), KI (332 mg, 2.0 equiv, 2.00 mmol), and dry DMF (2.4 purplishꢀred persisted (for ca. 5 min). 10 ꢀphenoxadine (183
mL). The vial was sealed with a crimp cap, and then the mg, 1.00 mmol), 1ꢀbromoꢀ4ꢀiodobezene (706 mg, 2.5 equiv,
reaction was heated in the microwave reactor at 220 C for 30 2.50 mmol), and dry toluene (1.5 mL) were added, and then the
min. After the reaction mixture was diluted with reaction was stirred at 60 C for 11 h. After the reaction
dichloromethane, the resulting solution was passed through a mixture was diluted with dichloromethane, the resulting
celite short column (dichloromethane). The resulting mixture solution was passed through celite short column
was washed successively with sat. NH Cl aq. and brine, dried (dichloromethane). The resulting mixture was washed
over MgSO , and evaporated. The residue was purified by silica successively with sat. NH Cl aq. and brine, dried over MgSO
gel chromatography with hexaneꢀdichloromethane (7:1) as an and evaporated. The residue was purified by silica gel
eluent to give the product (295 mg, 72% yield) as white chromatography with hexaneꢀdichloromethane (6:1) as an
crystalline solids. Mp 165.8–166.7 C; IR (KBr) 3075.9, eluent to give the product (272 mg, 81% yield) as white
943.2, 1586.2, 1498.4, 1470.5, 1449.2, 1322.0, 1268.9, crystalline solids. Mp 196.5–197.9 C; IR (KBr) 3045.5,
1.67 (s, 6H), 6.25 2886.4, 1590.0, 1483.0, 1335.5, 1291.1, 1272.8, 1208.2,
t
(
5). A 5 mL vial was charged with 2
diiodobenzene (657 mg, 2.0 equiv, 2.00 mmol), CuI (189 mg, evacuated and refilled with N
.0 equiv, 1.00 mmol), Cs CO
2
1
2
3
°
H
3
°
°
a
4
4
4
4
,
5
°
6
2
1
(
6
°
1
008.6, 744.4; H NMR (400 MHz, CDCl
dd, 2H, = 7.8, 1.5 Hz), 6.93 (2H, ddd,
.97 (2H, ddd,
.45 (2H, dd,
3
) δ
1
J
J
= 7.5, 7.4, 1.5 Hz), 1010.5, 736.7; H NMR (400 MHz, CDCl
3
)
δ
5.91 (dd, 2H,
= 8.6 Hz), 7.72
= 8.6 Hz); C NMR (100 MHz, CDCl 113.3,
J =
J
= 7.8, 7.5, 1.8 Hz), 7.09 (2H, d,
J
= 8.5 Hz), 7.8, 1.4 Hz), 6.57–6.70 (m, 6H), 7.23 (d, 2H, J
1
3
13
7
J
= 7.4, 1.8 Hz), 7.95 (2H, d,
J
= 8.5 Hz);
C
(d, 2H,
J
3
) δ
3
NMR (100 MHz, CDCl ) δ 31.4, 36.1, 93.8, 114.1, 120.9, 115.7, 121.7, 122.5, 123.4, 132.9, 134.1, 134.6, 138.2, 144.0;
+
1
25.5, 126.5, 130.2, 133.7, 140.4, 140.7, 141.2; HRMS (FAB) HRMS (FAB) calcd for C18H12BrNO [M] 337.0102, found
+
calcd for C21
H
18IN [M] 411.0484, found 411.0490.
-phenoxaboryl)phenyl)-9,10-
dihydroacridine (10). A solution of borinate ester
prepared as above using 204 mg (1.0 equiv, 1.04 mmol) of
0 mL twoꢀnecked flask was charged with (427 mg, 1.0 flask was charged with
337.0104.
10-(4-(10
was (11). A solution of borinate ester
9
,9-Dimethyl-10-(4-(10
H
H
-phenoxaboryl)phenyl)-10
was prepared as above using
10 mmol) of .A 50 mL twoꢀnecked
(314 mg, 9.31
H-phenoxazine
8
8
ꢀ1
7
. A 182 mg (1.0 equiv, 9.31
×
7
ꢀ1
5
5
6
×
10 mmol), and then
. 4.5 mL of dry THF
O were added, and then ꢀbutyllithium (700
ꢀhexane) was added
C. The reaction mixture
C and then the prepared solution of
78 C. After stirring at 78 C for
C for 0.5 h, the solution was gradually warmed 0.5 h, the solution was gradually warmed to room temperature
to room temperature and stirred for 24 h at room temperature. and stirred for 24 h at room temperature. The resulting mixture
The resulting mixture was passed through a silica gel short was passed through silica gel short column
column (dichloromethane). After volatile was removed in (dichloromethane). After the volatile was removed in vacuo, the
vacuo, the residue was purified by recycling preparative GPC. product was recrystallized from ethylacetate– ꢀhexane at 0 C.
After the volatile was removed in vacuo, the product was After filtration and washing with ꢀpentane, the product 11
recrystallized from dichloromethane– ꢀpentane at 0 C. After (265 mg, 65% yield) was obtained as blight yellow crystals. Mp
filtration and washing with ꢀpentane, the product 10 (305 mg, 242.5–244.4 C; IR (KBr) 3061.4, 2981.8, 1589.1, 1576.5,
5% yield) was obtained as pale light blue crystals. Mp 195.9– 1487.8, 1449.2, 1431.9, 1333.5, 1294.0, 1272.8, 1208.2, 910.2,
equiv, 1.04 mmol), and evacuated with heating and refilled with evacuated with heating and refilled with N
2
N
2
. 4.5 mL of dry THF and 4.5 mL of dry Et
and then ꢀbutyllithium (780 l, 1.2 equiv, 1.25 mmol, 1.6 M in
ꢀhexane) was added dropwise to the stirred solution at 78
The reaction mixture was stirred for 1.5 h at 78 C and then was stirred for 1.5 h at
the prepared solution of was added dropwise at 78 C. After was added dropwise at
stirring at 78
2
O were added, and 2 mL of dry Et
2
n
n
ꢁ
ꢁ
L, 1.2 equiv, 1.11 mmol, 1.6 M in n
n
−
°
C. dropwise to the stirred solution at
−78 °
−
°
−
78
°
8
−
°
8
−
°
−
°
−
°
a
n
°
n
n
°
n
°
6
1
1
1
97.1
431.9, 1334.5, 1266.0, 1205.3, 1135.9, 911.2, 745.4; H NMR 6.66–6.73 (m, 6H), 7.37 (ddd, 2H,
1.73 (s, 6H), 6.47 (dd, 2H, = 7.9, 1.0 (d, 2H, = 8.0 Hz), 7.65 (dd, 2H, J
= 7.6, 7.5, 1.0 Hz), 7.05 (ddd, 2H, = 7.9, 2H, = 8.1, 7.6, 1.7 Hz), 7.94 (d, 2H,
.5, 1.5 Hz), 7.38 (t, 2H, = 7.6 Hz), 7.49 (dd, 2H, = 7.6, 1.5 = 7.5, 1.7 Hz); C NMR (100 MHz, CDCl
Hz), 7.52 (d, 2H, = 8.1 Hz), 7.65 (d, 2H, = 8.0 Hz), 7.80 118.0, 121.5, 122.7, 123.4, 124.6, 130.1, 134.6, 134.9, 136.3,
= 8.0, 7.6, 1.6 Hz), 7.97 (d, 2H,
°
C; IR (KBr) 3065.3, 2931.8, 1590.0, 1573.6, 1475.3, 759.8, 737.6; H NMR (400 MHz, CDCl
3
)
δ
6.10 (br, 2H),
= 7.6, 7.5, 0.73 Hz), 7.52
8.1, 0.73 Hz), 7.80 (ddd,
= 8.0 Hz), 8.10 (dd, 2H,
113.5, 115.6,
1
J
(400 MHz, CDCl
3
)
δ
J
J
=
Hz), 6.96 (ddd, 2H,
7
J
J
J
J
1
3
J
J
J
3
) δ
J
J
J
1
1
(
(
ddd, 2H,
dd, 2H,
J
= 8.1 Hz), 8.16 136.5, 139.3, 141.1, 144.2, 160.2; B NMR (128 MHz, CHCl
3
)
1
3
+
J
= 7.6, 1.6 Hz); C NMR (100 MHz, CDCl
3
)
δ
31.3,
2
δ 50.3; HRMS (FAB) calcd for C30H20BNO [M] 437.1587,
3
1
6.2, 114.3, 118.0, 120.7, 122.7, 124.7, 125.3, 126.5, 130.2, found 437.1587.
1
1
30.6, 134.9, 136.2, 136.6, 140.7, 141.2, 141.6, 160.2;
B
NMR (128 MHz, CHCl
C H26BNO [M] 463.2107, found 463.2106.
33
3
)
δ
50.6; HRMS (FAB) calcd for
+
Acknowledgements
1
0-(4-Bromophenyl)-10
H
-phenoxazine (6). A 100 mL
We thank Prof. T. Hattori (Tohoku University) for courteous
permission to use their instruments and technical guidance.
twoꢀnecked flask was equipped with Pd
2
(dba)
mmol),
3
·CHCl
3
(21 mg,
ꢀ2
2.0
mol%,
2.00
×
10
2ꢀ(diꢀtertꢀ
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
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Journal of Materials Chemistry C
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DOI: 10.1039/C5TC01380A
ARTICLE
Journal Name
Kawata, S. Igawa and M. Yashima, Dalton Trans., DOI:
0.1039/c4dt02853h.
Notes and references
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9
1
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8
| J. Name., 2012, 00, 1-3
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Page 9 of 10
Journal Name
J. Turro, V. Ramamurthy and J. C. Scaiano, Principles of
Jou Pr nl e aa ls oe fd Mo an to et r ai ad lj su s Ct hm ea mr g ii sn ts ry C
View Article Online
DOI: 10.1039/C5TC01380A
ARTICLE
Molecular Photochemistry: An Introduction
, University
Science Books, Sausalito, 2008, Chapter 2.
2 (a) M. Kinoshita, H. Kita and Y. Shirota, Adv. Funct. Mater.
2
,
2012, 12, 780–786; (b) A. Nagai, S. Kobayashi, Y. Nagata,
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Mater. Chem., 2010, 20, 5196–5201.
2
3 During the submission of this paper, Adachi et al. also
reported luminescent materials bearing 10Hꢀphenoxaborin
moieties. M. Numata, T. Yasuda and C. Adachi, Chem.
Commun., DOI: 10.1039/C5CC00307E.
2
2
2
4 Adachi et al. showed how an experimental ∆
determined from onset of emission, see ref. 18a.
5 N. C. Giebink and S. R. Forrest, Phys. Rev. B: Condens.
Matter Mater. Phys., 2008, 77, 235215
EST value was
.
6 (a) M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B.
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Journal of Materials Chemistry C
Page 10 of 10
View Article Online
DOI: 10.1039/C5TC01380A
New luminescent compounds consisting of 10H-phenoxaboryl group show excellent
PLQYs and EQEs.
∆E
ST = S
1
- T
1
: small
1 1
∆EST = S - T : large
RISC
S
1
S
1
Donor
RISC
T
1
ISC
ISC
T
1
X :
X :
EQE = 15.1%
X :
light blue
Acceptor
deep blue
EQE = 22.1%
green
S
0
S
0
Only prompt fluorescence
because of large ∆EST
Prompt and delayed fluorescence
because of small ∆EST