Red Phosphorescent Bis-Cyclometalated Iridium Complexes with Fluorine-, Phenyl-, and Fluorophenyl-Substituted 2-Arylquinoline Ligands

Article abstract of DOI:10.1002/chem.201504392

Red phosphorescent iridium(III) complexes based on fluorine-, phenyl-, and fluorophenyl-substituted 2-arylquinoline ligands were designed and synthesized. To investigate their electrophosphorescent properties, devices were fabricated with the following structure: indium tin oxide (ITO)/4,4′,4′′-tris[2-naphthyl(phenyl)amino]triphenylamine (2-TNATA)/4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB)/4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP): 8 % iridium (III) complexes/bathocuproine (BCP)/tris(8-hydroxyquinolinato)aluminum (Alq₃)/8-hydroxyquinoline lithium (Liq)/Al. All devices, which use these materials showed efficient red emissions. In particular, a device exhibited a saturated red emission with a maximum luminance, external quantum efficiency, and luminous efficiency of 14200 cd m^-2, 8.44 %, and 6.58 cd A^-1 at 20 mA cm^-2, respectively. The CIE (x, y) coordinates of this device are (0.67, 0.33) at 12.0 V. Dopant in red: Nine iridium complexes with fluorine-, phenyl-, and fluorophenyl-substituted 2-arylquinoline ligands for red phosphorescence organic light-emitting diodes were prepared. A device based on (2,4-pentanedionato)bis[2-(9,9-dimethyl-9 H-fluoren-2-yl)-5-(4-fluorophenyl)quinolinyl]iridium(III) showed an efficient deep red emission with an external quantum efficiency of 8.44 % at 20 mA cm^-2.

Full text of DOI:10.1002/chem.201504392

DOI: 10.1002/chem.201504392
Full Paper
&
OLEDs
Red Phosphorescent Bis-Cyclometalated Iridium Complexes with
Fluorine-, Phenyl-, and Fluorophenyl-Substituted 2-Arylquinoline
Ligands
Jwajin Kim,[a] Kum Hee Lee,[a] Seok Jae Lee,[b] Ho Won Lee,[b] Young Kwan Kim,*[b]
Young Sik Kim,*[c] and Seung Soo Yoon*[a]
Abstract: Red phosphorescent iridium(III) complexes based
on fluorine-, phenyl-, and fluorophenyl-substituted 2-arylqui-
noline ligands were designed and synthesized. To investigate
their electrophosphorescent properties, devices were
fabricated with the following structure: indium tin oxide
(ITO)/4,4’,4’’-tris[2-naphthyl(phenyl)amino]triphenylamine (2-
TNATA)/4,4’-bis[N-(1-naphthyl)-N-phenylamino]biphenyl
(NPB)/4,4’-bis(N-carbazolyl)-1,1’-biphenyl (CBP): 8% iridium
(III) complexes/bathocuproine (BCP)/tris(8-hydroxyquinolin-
ato)aluminum (Alq3)/8-hydroxyquinoline lithium (Liq)/Al. All
devices, which use these materials showed efficient red
emissions. In particular, a device exhibited a saturated red
emission with a maximum luminance, external quantum
efficiency, and luminous efficiency of 14200 cdmÀ2, 8.44%,
and 6.58 cdAÀ1 at 20 mAcmÀ2, respectively. The CIE (x, y)
coordinates of this device are (0.67, 0.33) at 12.0 V.
Introduction
Many researchers have designed and synthesized a series of
iridium(III) complexes, which have substituted 2-phenylpyri-
dines as the cyclometalating ligands. By changes of the sub-
stituent position and the electronic nature of the substituents
in the aromatic ligands, the emissive colors of the iridium com-
plexes could be fine-tuned.[9–15] As early as 2001, the 2-phenyl-
quinoline (pq) ligand was applied to the synthesis of phos-
phorescent cyclometalated iridium complexes called [Ir(p-
q)2(acac)] (acac=acetylacetonate) that presents an orange-red
emission at l=597 nm.[16] In order to get deep-red emission,
modified pq ligands with a variety of aromatic segments were
designed and cyclometalated iridium complexes, which use
these ligands have been prepared. In accordance with the
structures of the quinoline ligands, iridium complexes emitting
phosphorescence from orange to red with an emission
wavelength range from l=590 to 660 nm have been devel-
oped.[17–19]
Recently, in both industry and academia, organic light-emitting
diodes (OLEDs) are focused on the next generation flat-panel
displays and solid-state lighting.[1,2] In OLEDs, holes and elec-
trons are injected and recombined at the emitting layer (EML)
when it is operated electrically. During this process, singlet and
triplet excitons occur statistically in a ratio of 1:3. OLEDs that
use only fluorescence can only use singlet excitons for emis-
sion, but phosphorescence OLEDs (PHOLEDs) can use both sin-
glet and triplet excitons, and thus, their internal quantum effi-
ciency can be four times higher than that of fluorescence
OLEDs. Their ability of using triplet excitons for emission is ori-
ginated from spin–orbital coupling derived from third-row
transition-metal elements, such as Ir or Pt.[3,4] PHOLEDs, which
use iridium complexes with an efficient emission of the whole
visible area have been reported for several years.[5–8]
As continuing efforts to search for the efficient deep-red
phosphorescent emitters for OLEDs, the iridium(III) complexes
1–9 based on fluorine-, phenyl-, and fluorophenyl-substituted
2-arylquinoline ligands were designed and synthesized, and
their photophysical and electrophosphorescent properties
were investigated. In the ligands of iridium complexes 2, 3, 5,
6, and 9 the electron-withdrawing fluorine atoms were intro-
duced to tune the band gap of the iridium complexes by the
control of the HOMO or LUMO energy levels.[20,21]
[a] J. Kim, Dr. K. H. Lee, Prof. S. S. Yoon
Department of Chemistry, Sungkyunkwan University
2066, Seobu-ro, Jangan-gu, Suwon-si, Gyeonggi-do (Korea)
Fax: (+82)031-290-7075
E-mail: ssyoon@skku.edu
[b] Dr. S. J. Lee, Dr. H. W. Lee, Prof. Y. K. Kim
Department of Information Display, Hongik University
94, Wausan-ro, Mapo-gu, Seoul (Korea)
Fax: (+82)2-3141-8928;
Furthermore, fluorine atoms in the ligands would affect to
carrier transporting abilities, molecular packing tendencies,
and luminescent properties of the corresponding iridium
complexes,[21] which play significant roles in the electro-
luminescence (EL) performances of the devices, which use
these materials. The additional phenyl groups in the quinoline
E-mail: kimyk@hongik.ac.kr
[c] Prof. Y. S. Kim
Department of Information Display, Hongik University
94, Wausan-ro, Mapo-gu, Seoul (Korea)
Fax: (+82)2-3142-0335
E-mail: youngkim@hongik.ac.kr
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moiety of the iridium complexes 1–9 and the fluorene moieties
of the iridium complexes 4–6 would extend the p-conjugation
length of these complexes, and thus induce the red shifts of
the phosphorescent emissions of the corresponding complexes
to the saturated red region in comparison with [(pq)2Ir(acac)].
Multilayered organic light-emitting diodes were fabricated
to explore their electroluminescent properties by employing
the complexes as a dopant. This study revealed that these
iridium(III) complexes (i.e., complexes 1–9) had highly
efficient red electroluminescent properties. The influence of
the systematic changes of the substituent in the ligands of
these iridium complexes to their photophysical properties and
the electrophosphorescent properties will be discussed.
Results and Discussion
Synthesis of iridium complexes
Figure 1 shows the structures of the iridium complexes 1–9
and Scheme 1 exhibits their synthetic routes. Detail conditions
of each synthesis are explained in the Experimental Section
(see below). Newly synthesized red-emitting materials (set 1:
complexes 1, 2, and 3; set 2: complexes 4, 5, and 6; and set 3:
complexes 7, 8, and 9) were purified further by train sublima-
tion at a reduced pressure, below 10À3 Torr, and fully character-
Figure 1. Structures of the iridium(III) complexes 1–9.
1
ized by using H and 13C NMR as well as infrared (IR) spectros-
solutions. All complexes exhibit a strong UV/Vis absorption in
copy, and low- and high-resolution mass spectrometry. High-
performance liquid chromatography (HPLC) analysis revealed
that the purity of the orange- to red-emitting materials (i.e.,
complexes 1–9) was at least 99.0%.
the range of l=250–400 nm with distinct vibronic features,
1
which were assigned to the spin-allowed p–p* transition of
the cyclometalated ligands in the complexes.[22] In the range of
l=400–470 nm, the weak absorption from spin-allowed
metal-to-ligand charge-transfer (1MLCT) transitions of all the
complexes 1–9 are exhibited.[23]
Physical and photophysical properties of the complexes
Over l=470 nm, according to the band position and size,
all iridium complexes have weak absorptions due to spin-
forbidden metal-to-ligand charge-transfer (3MLCT) and 3p–p*
Figure 2 shows the UV/Vis absorption and photoluminescence
(PL) emission spectra of the iridium complexes 1–9 in CH2Cl2
Scheme 1. Synthetic route of the ligands L1–L9 and the corresponding iridium(III) complexes 1–9. Reaction conditions: i) [Pd(PPh3)4], 2m Na2CO3, ethanol,
toluene, heating to reflux for two hours at 908C; ii) peracetic acid, CHCl3, heating to reflux for four hours at 708C; iii) POCl3, heating to reflux for one hour at
1008C; iv) IrCl3·H2O, H2O, 2-ethoxyethanol, heating to reflux for 24 h at 1208C; v) 2,4-pentanedione, Na2CO3, 2-ethoxyethanol, heating to reflux for six hours at
1008C, 6 h;[16] vi) sulfuric acid, acetic acid.
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transitions caused by spin–orbital coupling.[24] As shown in
Table 1, all complexes 1–9 show totally slightly red-shifted
absorption spectra compared with the absorption spectrum of
[(pq)2Ir(acac)] due to the extended p-conjugation lengths of
the ligands by substitution of the aryl groups in complexes
1 and 3–9, and the electron- withdrawing effect of the fluorine
atom of the ligand in complex 2. Particularly, the absorption
spectra of complexes 4–6 and 9 show more red-shifted maxi-
mum absorption wavelengths than the other complexes 1–3,
7, and 8 due to the fluorene unit in complexes 4–6 and the
additional phenyl units in complex 9, which make the
p-conjugation lengths longer than those of complexes 1–3, 7,
and 8.
The maximum emission wavelength lmax for the complexes
1–9 ranged from l=603 to 622 nm in the red region of the
visible spectra. The trends in the emission spectra of com-
plexes 1–9 are similarly observed in the absorption spectra of
complexes 1–9. For examples, the PL spectra of all the
complexes 1–9 are red shifted compared with [(pq)2Ir(acac)],
and those of complexes 4–6 and 9 show largely red-shifted
maximum emission wavelengths in comparison with the other
complexes 1–3, 7, and 8.
By using [Ir(ppy)3] (ppy=4-pyrrolidinopyridine) as a standard
material with a quantum yield (F) of 0.4,[24] the quantum
yields for all complexes 1–9 were measured and are summar-
ized in Table 1 together with the other physical properties of
complexes 1–9. Especially, complex 6 showed a highly lumi-
nescent capability with the value of F as high as 0.67. This ob-
servation indicates that it can be a promising phosphorescent
dopant for high-performance PHOLEDs. The highest occupied
molecular orbital (HOMO) energy levels of complexes 1–9
were measured with an AC-2 photoelectron spectrometer, and
the lowest unoccupied molecular orbital (LUMO) energy levels
were calculated by subtracting the corresponding optical
band-gap energies from the HOMO values. The HOMO and
LUMO energy levels for complexes 1–9 varied from À5.24 to
À5.57 eV and from À2.96 to À3.30 eV, respectively.
Figure 3 shows the cyclic voltammogram of complex 1 in
CH2Cl2 solution. Cyclic voltammetry (CV) was used to examine
Figure 2. UV/Vis absorption and PL emission spectra of a) set 1, b) set 2, and
c) set 3.
Table 1. Optical properties of the iridium complexes 1–9.
[b]
[b]
[f]
Sample
lAbs [nm] (e)
lEm [nm] FWHM[b] [nm] F[c] HOMO[d]/LUMO[e] [eV] Eg [eV] HOMO[g]/LUMO[g] [eV]
1
2
3
4
5
6
7
8
9
262 (9.87), 348 (3.32), 434 (1.05), 472 (0.79)
262 (15.0), 434 (0.93), 473 (0.85)
279 (8.80), 428 (0.75), 473 (0.71)
283 (2.89), 316 (3.28), 370 (2.56), 487 (0.35)
284 (6.20), 313 (7.04), 326 (6.88), 371 (6.47), 489 (0.85) 622
607
609
600
614
73
70
69
52
56
53
66
65
70
66
0.47 À5.26/À2.99
0.37 À5.57/À3.30
0.49 À5.37/À3.08
0.34 À5.25/À3.06
0.24 À5.40/À3.22
0.67 À5.33/À3.13
0.45 À5.24/À2.96
0.46 À5.42/À3.15
0.58 À5.44/À3.20
0.86 À5.11/À2.50
2.27
2.27
2.29
2.19
2.18
2.20
2.28
2.27
2.24
2.61
À4.79/À1.76
À4.95/À1.92
À4.87/À1.85
À4.72/À1.80
À4.87/À1.95
À4.79/À1.88
À4.81/À1.83
À4.88/À1.91
À4.76/À1.85
À4.81/À1.77
286 (18.6), 314 (11.0), 374 (8.81), 487 (1.27)
280 (18.6), 353 (6.67), 407 (1.39), 477 (1.46)
279 (11.6), 353 (4.06), 407 (0.87), 477 (0.86)
283 (12.1), 359 (4.51), 484 (1.04)
618
603
603
618
596
reference[a] 270 (10.6), 425 (0.93), 464 (0.89)
[a] [(pq)2Ir(acac)]. [b] Measured in CH2Cl2 at a concentration of 10À5 m. The molar extinction coefficient (e) values (in [104 mÀ1 cmÀ1]) are shown in paren-
theses. [c] In degassed CH2Cl2 relative to fac-[Ir(ppy)3] (F=0.40), lex =470 nm. [d] Measured with a low-energy photo-electron spectrometer (Riken-Keiki,
AC-2). [e] Calculated by subtracting the corresponding optical band gap energies from the HOMO energy values. [f] Determined from the intersection of
the absorption and PL spectra. [g] Calculated values by using the Gaussian 03 program.[34]
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deep-red emissions with maximum emission wavelengths lmax
of 614, 622 and 618 nm, respectively.
DFT calculations
DFT calculations of the iridium complexes 1–9 were performed
by using the Gaussian 03 program.[34] To obtain their HOMO/
LUMO energy levels and to optimize the molecular structures
of the iridium(III) complexes, the B3LYP density functional
theory was employed, by using the LANL2DZ and 6-31G(d)
basis sets[35] for iridium and the other atoms in the iridium
complexes 1–9, respectively.
Figure 3. Cyclic voltammogram of complex 1.
Geometry optimizations were performed on all possible iso-
mers of the iridium complexes. Ideally, there would be three
diastereomers of the iridium complexes. From the geometry
optimization of the iridium complexes 1–9, the structures with
“N–N trans and C–C cis” relations between the iridium and the
nearest carbon/nitrogen atoms were the most stable ones. As
shown in Figure 4, the HOMOs of all iridium complexes are
mainly localized on the phenyl ring of the pq ligand and the
centric iridium atom. Especially, the donation of the d orbital
of the iridium atom is significant. The LUMOs of all iridium
complexes are seen to be localized on the quinoline ring of
the pq ligand. The calculated HOMO and LUMO levels are
given in Table 1, in comparison with the experimental ones.
It can be clearly seen that the HOMO and LUMO energy
levels become lower by introduction of a fluorine atom in the
pq ligands. Thus, the iridium complexes 2 and 5 showed lower
HOMO/LUMO energy levels in comparison with those of com-
plexes 1 and 4. The iridium complexes 3, 6, and 8, due to sub-
stitution of the aryl group with the electron-withdrawing fluo-
rine atom, also exhibit lower HOMO/LUMO energy levels in
comparison with those of complexes 1, 4 and 7, respectively.
The HOMO and LUMO energy levels of the iridium complexes
3 and 6 decreased by the relatively small amounts in compari-
son with iridium complexes 2 and 5. This implies that the elec-
tron-withdrawing effect of the fluorine atom decreased with
extending the conjugation length of the heteroaromatic ring
of the cyclometalating compound. Although the experimental-
ly obtained energy levels are somewhat different from the cal-
culated ones, their trends are almost consistent. The calculated
HOMO and LUMO levels are slightly influenced by the substitu-
tion of the aryl group and the fluorine atom and this is also
consistent with the experimental results.
the electrochemical behavior as well as the HOMO energy
level of complex 1.
The conventional three-electrode cell with ferrocene as the
internal standard, allowed an estimation of the electrochemical
behavior of complex 1. The cyclic voltammogram was record-
ed in a single compartment glass cell in CH2Cl2 with ferrocene
as the internal standard and nBu4NPF6 as a supporting electro-
lyte. The CV curve of this complex showed a clean reversible
one-electron oxidation wave at EO1=X2 =0.50 V versus the Fc/Fc+
(ferrocene/ferrocenium) couple reference, indicating the good
electrochemical stability of the complex. Based on the onset
potentials of the oxidation, the respective HOMO energy level
of complex 1 was estimated to be À5.30 eV, with regard to
ferrocene (À4.80 eV in vacuum).[25,26] This suggests that the
estimation of the HOMO energy levels by using AC-2 photo-
electron spectroscopy (À5.26 eV in Table 1) and the electro-
chemical study (À5.30 eV) is comparable to each other within
the experimental error.
The introduction of substituents with the different electronic
properties in the ligands of the iridium complexes has an
effect on the HOMO and LUMO energy levels. In this kinds of
iridium complexes, the electronic properties of IrÀcarbon-coor-
dinated aromatic groups/hetero aromatic rings of the cyclo-
metalating ligands have major effects on the HOMO/LUMO
energy levels, respectively.[11,25] The iridium complexes 1–3 and
7–9 with the substituent at the heteroaromatic ring of the cy-
clometalating ligands exhibit lower LUMO energy levels than
[(pq)2Ir(acac)] due to the extended p-conjugation lengths of
the ligands by substitution of the aryl groups in complexes 1,
3, and 7–9, and the electron-withdrawing effect of the fluorine
atom of the ligand in complex 2. Compared to [(pq)2Ir(acac)],
the HOMO energy levels of the iridium complexes 1–3 and 7–
9 also decreased by the relatively small amounts in comparison
with those of the LUMO energy levels. This implies that the
substituent at the heteroaromatic ring of the cyclometalating
ligand have great effects on the LUMO energy levels of the iri-
dium complexes. However, there are small influences on the
HOMO energy levels due to the conjugation between the two
aromatic groups in the ligands of the iridium complexes. In
the iridium complexes 4–6, the substitutions at both the aro-
matic groups in the ligands and the resulting conjugation and
electronic effects would lead to large decreases in the
band-gap energies of complexes 4–6 in comparison with
[(pq)2Ir(acac)]. Therefore, the iridium complexes 4–6 showed
Electrophosphorescent characterization of the PHOLEDs
To investigate the performances of the iridium(III) complexes
1–9 in devices, the multilayered PHOLEDs A–I and the refer-
ence device J (the corresponding dopants and devices are rep-
resented in Table 2) were fabricated by using a thin hole and
exciton blocking layer (HBL) composed of bathocuproine (BCP)
placed between 4,4’-bis(N-carbazolyl)-1,1’-biphenyl (CBP) (as
EML), and aluminum-tris(8-hydroxychinolin) (Alq3) (as ETL). The
performances of the devices are summarized in Table 2.
As shown in Figure 5, the devices A–J, which are based on
the iridium complexes 1–9 and [(pq)2Ir(acac)] show electrolumi-
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nescence emission in the red region around l=602–627 nm.
Among the devices A–J, the devices E and F exhibit excellent
values of the Commission Internationale de l’Eclairage (CIE) co-
ordinates with (0.67, 0.32) and (0.67, 0.33) at 12 V, respectively.
These values are well matching with the National Television
System Committee (NTSC) standard red, that is, (0.67, 0.33).
The trend in the EL spectra of the devices is similar to that in
the PL spectra of the iridium complexes 1–9, which are used
as dopants in the corresponding devices. This similarity
between the PL and EL emission spectra indicates that the EL
emission is originating from the phosphorescence of the
iridium dopants.[27]
Figure 6 shows plots of a) the current density J and the lumi-
nance L versus the voltage V (J–V–L), b) the luminous efficiency
(LE) and the power efficiency (PE) versus the current
density, and c) the external quantum efficiency versus the cur-
rent density plots of the devices A–J. The EL efficiency data of
the devices A–J showed interesting trends upon changes in
the structures of the dopants in the emitting layer. In the devi-
ces A–C, which are built from the iridium complexes 1–3
based on pq ligands with substituents at the C-5 atom of the
quinoline moiety, the external quantum efficiencies at
20 mAcmÀ2 increased in the order B<C<A. The devices A–C
as well as the devices D–I have large hole-injection barriers
(0.5 eV) as shown in Figure 7, in comparison with the electron-
injection barriers (0.1 eV).[28] These suggest that the direct hole
trapping from HTL into the dopants in the emitting layers
would play an important role in the EL efficiencies of devices,
which use the corresponding dopants. Interestingly, the HOMO
energy levels of the dopants 1–3 increased in the order 2
(À5.57 eV)<3 (À5.37 eV)<1 (À5.27 eV).
This implies that the direct hole trapping into the dopants
in the devices A–C becomes effective in the order B<C<A.
This trend is well compatible with that of the EL efficiencies of
the devices A–C.
In the devices G and H, which are built from the iridium
complexes based on pq ligands with substituents at the C-6
atom of the quinoline moiety, the trend in the external quan-
tum efficiencies at 20 mAcmÀ2 (G>H) is well compatible with
that of the HOMO energy levels of the corresponding dopants
[i.e., 7 (À5.24 eV)>8 (À5.42 eV)]. This suggests that the effec-
tive direct hole trapping into the dopant 7 in device G would
Figure 4. Calculated spatial distributions of the HOMOs and LUMOs of
complexes 1–9.
Table 2. EL performance characteristics of the devices A–J.
EL
[a]
Device
Dopant
lmax [nm]
Von [V]
L[b] [cdmÀ2
]
LE[c]/[d] [cdAÀ1
]
PE[c]/[d] [lmWÀ1
]
EQE[c]/[d] [%]
CIE[e] (x,y)
A
B
C
D
E
F
G
H
I
1
2
3
4
5
6
7
8
9
604 (73)
613 (76)
606 (77)
623 (52)
627 (52)
612 (71)
611 (70)
616 (70)
624 (74)
605 (78)
4.0
4.2
4.1
4.4
4.2
3.7
3.6
4.1
3.9
3.7
18800
12100
14200
9930
11 400
14200
22600
13100
12300
35700
9.24/8.36
7.40/6.95
7.74/7.12
4.42/3.90
4.99/4.31
9.69/6.54
12.7/9.31
12.1/8.52
9.69/7.15
17.9/16.0
4.90/2.69
5.15/2.18
4.45/2.16
3.19/1.31
6.50/1.38
6.86/2.11
8.09/3.15
7.98/2.55
4.61/2.20
10.9/5.18
6.93/6.88
12.5/5.50
10.0/6.68
5.96/4.42
12.4/5.91
15.9/8.44
12.4/8.10
14.5/7.99
13.9/6.25
13.7/11.3
(0.61, 0.38)
(0.63, 0.37)
(0.62, 0.37)
(0.61, 0.31)
(0.67, 0.32)
(0.67, 0.33)
(0.64, 0.36)
(0.64, 0.36)
(0.66, 0.33)
(0.61, 0.39)
J
(pq)2Ir(acac)
[a] Turn-on voltage at 1 cdmÀ2.[b] Maximum value at 16.0 V. [c] Maximum value. [d] At 20 mAcmÀ2. [e] At 12.0 V.
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Figure 5. Normalized EL emission spectra of the devices a) A–C, b) D–F, and
c) G–J.
lead to improved EL efficiencies of the device G compared
with the device H. Compared to [(pq)2Ir(acac)], the low HOMO
energy level and the resulting ineffective hole trapping ability
of the iridium complex 9 reduced the external quantum
efficiency of the device I in comparison with the device J.
Intriguingly, the external quantum efficiencies of the device
D–F, which were built from the iridium complexes based on
fluorenylquinoline ligands showed an incompatible trend with
the HOMO energy levels of the iridium complexes 4–6, which
were used as dopants. Among the complexes 4–6, the highest
phosphorescent quantum yield of complex 6 would contribute
the most efficient EL properties of the device F compared with
Figure 6. a) Current density and luminance versus voltage plot and b) lumi-
nous efficiency, c) power efficiency and d) external quantum efficiency
versus current density plots of the devices A–J.
the devices D and E. This suggests that the phosphorescent
quantum yields as well as the direct hole trapping tendencies
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fluoro-quinoline (13),[28] 2-amino-5-bromobenzaldehyde,[31] 2-
amino-5-bromobenzophenone,[32] and 6-bromo-2,4-diphenylquino-
line (16)[33] were synthesized as previously reported. The solvents
were dried by using standard procedures. All reagents were used
as received from commercial sources, unless otherwise stated. All
1
reactions were performed under a N2 atmosphere. H- and 13C NMR
spectra were obtained by using a Varian (Unity Inova 300NB) or
Varian (Unity Inova 500NB) spectrometer at 300 and 500 MHz, re-
spectively. FTIR spectra were recorded by using a Thermo Nicolet
Avatar 320 FTIR spectrometer. Low- and high-resolution mass spec-
tra were recorded by using a Jeol JMS-AX505WA spectrometer in
the FAB mode or a Jeol JMS-600 spectrometer in the EI mode. Ele-
mental analyses (EA) were determined by a Flash 2000 auto ana-
lyzer. The UV/Vis absorption measurements of the materials in di-
chloromethane (10À5 m) were acquired with a Scinco S-3100 in
a quartz cuvette (1.0 cm path length).The PL spectra were mea-
sured on an AMINCO-Bowman Series 2 Luminescence Spectrome-
ter. The phosphorescence quantum yields were determined in
Figure 7. Device structure and energy diagrams of the materials used in the
devices.
CH2Cl2 solutions at 293 K against [Ir(ppy)3] as reference (Fph
=
0.40).[24] Electrochemical measurements were made by using a CHI
600C potentiostat (CH Instruments) at a scan rate of 100 mVsÀ1. A
conventional three-electrode configuration consisting of a glassy
carbon working electrode and a Pt wire as counter and reference
electrodes was used. The supporting electrolyte was 0.1m of tetra-
n-butylammoniumhexafluorophosphate (nBu4NPF6) solution in
anhydrous CH2Cl2. The HOMO energy levels were determined by
using a low-energy photoelectron spectrometer (Riken-Keiki, AC-2).
The energy band gaps were determined from the intersection of
the absorption and the PL spectra. The LUMO energy levels were
calculated by subtracting the corresponding optical band-gap
energies from the HOMO energy values.
of the iridium complexes 1–9 would significantly contribute to
the EL efficiencies of devices, which use them.
For example, in the devices A–C, the higher phosphorescent
quantum yield of complexes 1 and 3 would contribute to the
improved efficient EL properties of the devices A and C com-
pared with device B. Also, the higher phosphorescent quan-
tum yield of [(pq)2Ir(acac)] compared to complex 9 provides
the more efficient EL properties of the devices J than device I.
These observations reflect the very complex natures of the
EL emission processes in phosphorescent OLEDs (i.e., devices
A–J). Presumably, the subtle combinations of the intrinsic lumi-
nescent capability and the carrier trapping property of the iri-
dium complexes 1–9 and [(pq)2Ir(acac)] would control the EL
efficiencies of devices, which use them. These factors would
affect the complex trends in the EL efficiencies of the devices
A–J.
The ligands L1–L6 were synthesized by using Suzuki cross cou-
pling reactions with moderate yields. Three 2-arylquinoline derived
ligands, L7, L8, and L9 were conveniently synthesized by using the
acid-catalyzed Friedländer condensation reaction[19,33] of acetophe-
none with the corresponding 2-aminobenzaldehyde compounds.
General procedures for the Suzuki cross-coupling reaction: Aryl-
boronic acid (1.2 mol), the corresponding aryl bromide derivatives
(1.0 mol), [Pd(PPh3)4] (0.04 mol), aqueous 2.0m solution of K2CO3
(10.0 mol), ethanol, and toluene were mixed in a flask, and the mix-
ture was heated to reflux for 4 h. After the reaction was complete,
the reaction mixture was extracted with ethyl acetate and washed
with water. The combined organic layers were dried with anhy-
drous MgSO4 and evaporated to dryness. The crude product was
further purified by silica gel column chromatography with 6:1
CH2Cl2/hexane as eluent.
Conclusion
A series of red phosphorescent iridium(III) complexes were syn-
thesized and their electroluminescent properties were exam-
ined. By using these red phosphorescent iridium(III) complexes
as dopants (i.e., complexes 1–9), the efficient red phosphores-
cent OLEDs were demonstrated. Particularly, a device, which
uses an iridium complex based on 2-(9,9-dimethyl-9H-fluoren-
2-yl)-5-(4-fluorophenyl)quinoline ligand, showed a maximum
1
5-Phenylquinoline (10): Yield: 98%; H NMR (500 MHz, CDCl3): d=
8.93 (d, J=3.5 Hz, 1H), 8.24 (d, J=7.8 Hz, 1H), 8.13 (d, J=8.5 Hz,
1H), 7.76 (t, J=8.5 Hz, 1H), 7.52–744 (m, 5H), 7.35 (dd, J=4.2,
8.5 Hz, 1H), 7.17 ppm (d, J=4.5 Hz, 1H); 13C NMR (125 MHz,
CDCl3): d=150.5, 148.8, 140.7, 139.6, 134.6, 130.3, 129.2, 129.1,
128.7, 127.9, 127.5, 126.9, 121.3 ppm; MS (EI): m/z: 205 [M+]; HRMS
(EI+): m/z calcd for C15H11N: 205.0891; found: 205.0889.
5-(4-Fluorophenyl)quinoline (11): Yield: 57%; 1H NMR (300 MHz,
CDCl3): d=8.93 (dd, J=1.6, 4.1 Hz, 1H), 8.20–8.16 (m, 1H), 8.15–
8.12 (m, 1H), 7.75 (t, J=7.0 Hz, 1H), 7.48 (dd, J=1.2, 7.2 Hz, 1H),
7.42 (dd, J=5.4, 8.3 Hz, 2H), 7.36 (dd, J=4.1, 8.5 Hz, 1H), 7.20 ppm
(t, J=8.7 Hz, 2H); 13C NMR (75 MHz, CDCl3): d=162.7 (d, J(F,C)=
247.1 Hz), 150.6, 148.8, 139.6, 135.5 (d, J(F,C)=3.3 Hz), 134.3, 131.8
(d, J(F,C)=7.7 Hz), 129.4, 129.1, 127.6, 127.0, 121.4, 115.7 ppm (d,
J(F,C)=21.6 Hz); FTIR (ATR): n˜ =3041, 2970, 1739, 1512, 1366, 1228,
798 cmÀ1; MS (EI): m/z: 223 [M+]; HRMS (EI+): m/z calcd for
C15H10NF: 223.0797; found: 223.0796.
luminance of 14200 cdmÀ2,
a
luminous efficiency of
6.58 cdAÀ1, and an external quantum efficiency of 8.44% at
20 mAcmÀ2, with CIE coordinates of (0.67, 0.33), a saturated
red region. In comparison with the other red emitters,[29] this
material has a high potential to be a candidate for an efficient
red emitter in PHOLEDs in terms of the EL efficiencies and
color purities.
Experimental Section
Materials and measurements: Phenylboronic acid, 4-fluorophenyl-
boronic acid, 5-bromo-quinoline, and acetophenone were used as
received from Aldrich or TCI. 5-Phenylquinoline,[30] 2-chloro-5-
Chem. Eur. J. 2016, 22, 4036 – 4045
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1
1
2,5-Diphenylquinoline (L1): Yield: 89%; H NMR (300 MHz, CDCl3):
2,6-Diphenylquinoline (L7): Yield: 78%; H NMR (300 MHz, CDCl3):
d=8.28 (d, J=8.7 Hz, 1H), 8.24 (d, J=8.5 Hz, 1H), 8.21–8.17 (m,
2H), 8.02–7.99 (m, 2H), 7.92 (d, J=8.5 Hz, 1H), 7.77–7.74 (m, 2H),
7.55–7.48 (m, 5H), 7.44–7.39 ppm (m, 1H); 13C NMR (125 MHz,
CDCl3): d=157.6, 147.9, 140.7, 139.9, 139.3, 137.2, 130.4, 129.6,
129.6, 129.2, 129.1, 127.9, 127.8, 127.7, 127.6, 125.4, 119.6 ppm;
d=8.30 (d, J=8.9 Hz, 1H), 8.21–8.16 (m, 3H), 7.82 (d, J=8.9 Hz,
1H), 7.76 (dd, J=8.5, 7.5 Hz, 1H), 7.56–7.44 ppm (m, 9H); 13C NMR
(125 MHz, CDCl3): d=157.4, 148.8, 140.5, 139.8, 135.3, 130.3, 129.6,
129.5, 129.4, 129.1, 128.7, 127.9, 127.8, 127.7, 127.2, 125.8,
119.2 ppm; FTIR (ATR): n˜ =2970, 1738, 1366, 1216, 822, 780,
702 cmÀ1; MS (EI): m/z: 281 [M+]; HRMS (EI+): m/z calcd for
C21H15N: 281.1204; found: 281.1205.
FTIR (ATR): n˜ =3028, 2970, 1738, 1595, 1366, 1216, 764, 677 cmÀ1
MS (EI): m/z: 281 [M+]; HRMS (EI+): m/z calcd for C21H15N:
;
281.1204; found: 281.1203.
5-Fluoro-2-phenylquinoline (L2): Yield: 87%; 1H NMR (300 MHz,
CDCl3): d=8.50 (d, J=8.8 Hz, 1H), 8.19–8.16 (m, 2H), 7.98 (d, J=
8.6 Hz, 1H), 7.94 (d, J=8.8 Hz, 1H), 7.68–7.61 (m, 1H), 7.57–7.48
(m, 3H), 7.19 ppm (d, J=8.7 Hz, 1H); 13C NMR (125 MHz, CDCl3):
d=158.4, 158.2 (d, J(F,C)=254.3 Hz), 149.4 (d, J(F,C)=2.8 Hz), 139.5,
130.3 (d, J(F,C)=3.9 Hz), 129.1, 129.8, 125.8 (d, J(F,C)=3.9 Hz), 119.3
(d, J(F,C)=2.8 Hz), 118.1 (d, J(F,C)=16.6 Hz), 110.1 ppm (d, J(F,C)=
19.4 Hz); FTIR (ATR): n˜ =3016, 2970, 1738, 1441, 1366, 1216, 771,
691 cmÀ1; MS (EI): m/z: 223 [M+]; HRMS (EI+): m/z calcd for
C15H10FN: 223.0797; found: 223.0798.
6-(4-Fluorophenyl)-2-phenylquinoline (L8): Yield: 82%; 1H NMR
(300 MHz, CDCl3): d=8.25 (t, J=8.7 Hz, 2H), 8.21–8.17 (m, 2H),
7.95 (s, 1H), 7.91 (d, J=8.7 Hz, 2H), 7.69 (dd, J=5.3, 8.8 Hz, 2H),
7.57–7.47 (m, 3H), 7.19 ppm (t, J=8.7 Hz, 2H); FTIR (ATR): n˜ =3016,
2970, 1738, 1366, 1217, 762, 655 cmÀ1; MS (EI): m/z: 299 [M+];
HRMS (EI+): m/z calcd for C21H14FN: 299.1110; found: 299.1107.
2,4,6-Triphenylquinoline (L9): Yield: 59%; 1H NMR (300 MHz,
CDCl3): d=8.30 (d, J=8.7 Hz, 1H), 8.20 (d, J=7.0 Hz, 2H), 8.09 (d,
J=1.9 Hz, 1H), 7.98 (dd, J=1.9, 8.7 Hz, 1H), 7.83 (s, 1H), 7.62–7.57
(m, 5H), 7.55–7.50 (m, 4H), 7.48–7.40 (m, 3H), 7.34 ppm (d, J=
7.2 Hz, 1H); 13C NMR (125 MHz, CDCl3): d=157.1, 149.6, 148.5,
140.9, 139.9, 139.3, 138.7, 130.8, 129.8, 129.6, 129.5, 129.1, 129.0,
129.9, 128.7, 127.8, 127.6, 126.2, 123.6, 120.0 ppm; FTIR (ATR): n˜ =
3016, 2970, 1738, 1366, 1216, 761, 697 cmÀ1; MS (EI): m/z: 357 [M+
]; HRMS (EI+): m/z calcd for C27H19N 357.1517; found: 357.1516.
5-(4-Fluorophenyl)-2-phenylquinoline (L3): Yield: 82%; 1H NMR
(300 MHz, CDCl3): d=8.24 (dd, J=0.8, 8.9 Hz, 1H), 8.21–8.15 (m,
2H), 7.83 (d, J=8.9 Hz, 1H), 7.75 (dd, J=7.1, 8.5 Hz, 1H), 7.56–7.51
(m, 3H), 7.50–7.44 (m, 4H), 7.21 ppm (t, J=8.8 Hz, 2H); 13C NMR
(125 MHz, CDCl3): d=162.7 (d, J(F,C)=247.1 Hz), 157.5, 148.8,
139.7, 139.4, 135.7 (d, J(F,C)=3.3 Hz), 135.1, 131.8 (d, J(F,C)=
7.7 Hz), 129.7, 129.6, 129.4, 129.2, 127.8, 127.3, 125.8, 119.3,
115.7 ppm (d, J(F,C)=21.6 Hz); MS (EI): m/z: 299 [M+]; HRMS (EI+):
m/z calcd for C21H14FN: 299.1110; found: 299.1111.
2-Chloro-5-phenylquinoline (12): To a mixture of 5-phenylquino-
line (1.0 g, 4.28 mmol) in anhydrous CHCl3 (20 mL) at 08C was
added dropwise peracetic acid (32%) (30.0 mmol) in CHCl3 (10 mL)
under a N2 atmosphere. The reaction mixture was heated to re-
fluxed at 708C for 4 h. Subsequently, the solution was stirred at
room temperature for 4 h. A solution of anhydrous quinoline N-
oxide in phosphoryl trichloride (10 mL, 34.0 mmol) was prepared
by slow addition at À58C. The mixture was heated to reflux for 3 h
and then poured on ice, neutralized with aqueous sodium hydrox-
ide, and extracted with dichloromethane. The extracts were dried
over sodium sulfate, filtered, and evaporated under reduced pres-
sure. The crude product was purified by silica gel column chroma-
tography (ethyl acetate/hexane, 1:4), giving 2-chloro-5-phenylqui-
noline (12) (0.55 g, 60%) as a white solid. 1H NMR (300 MHz,
CDCl3): d=8.23 (d, J=8.8 Hz, 1H), 8.09 (d, J=8.5 Hz, 1H), 7.83 (t,
J=8.5 Hz, 1H), 7.58–7.47 (m, 6H), 7.38 ppm (d, J=8.8 Hz, 1H);
13C NMR (75 MHz, CDCl3): d=150.9, 148.5, 140.8, 139.2, 137.6,
130.3, 130.1, 128.8, 128.2, 128.1, 127.9, 125.6, 122.5 ppm; MS (EI):
m/z: 240 [M++H]; HRMS (EI+): m/z calcd for C15H11ClN: 240.0580;
found: 240.0579.
2-Chloro-5-(4-fluorophenyl)quinoline (14): Yield: 60%; 1H NMR
(300 MHz, CDCl3): d=8.12 (d, J=8.8 Hz, 1H), 8.05 (d, J=8.5 Hz,
1H), 7.77 (t, J=7.2 Hz, 1H), 7.49 (dd, J=0.9, 7.2 Hz, 1H), 7.41 (dd,
J=5.4, 8.5 Hz, 2H), 7.34 (d, J=8.8 Hz, 1H), 7.21 ppm (t, J=8.6 Hz,
2H); 13C NMR (75 MHz, CDCl3): d=162.9 (d, J(F,C)=247.7 Hz),
151.0, 148.5, 139.7, 137.3, 135.1 (d, J(F,C)=3.3 Hz), 131.7 (d, J(F,C)=
8.3 Hz), 130.3, 128.5, 128.0, 125.6, 122.6, 115.8 ppm (d, J(F,C)=
21.6 Hz); FTIR (ATR): n˜ =3017, 2970, 1739, 1509, 1366, 1224, 1218,
845, 805 cmÀ1; MS (EI): m/z: 257 [M+]; HRMS (EI+): m/z calcd for
C15H9NClF: 257.0407; found: 257.0410.
2-(9,9-Dimethyl-9H-fluoren-2-yl)-5-phenylquinoline (L4): Yield:
76%; 1H NMR (300 MHz, CDCl3): d=8.31 (d, J=8.6 Hz, 2H), 8.14
(dd, J=1.8, 8.4 Hz, 1H), 7.88 (t, J=8.1 Hz, 3H), 7.81–7.75 (m, 3H),
7.54–7.45 (m, 5H), 7.40–7.33 (m, 3H), 1.60 ppm (s, 6H);13C NMR
(125 MHz, CDCl3): d=157.6, 154.6, 154.5, 148.9, 140.8, 140.5, 139.9,
138.9, 138.8, 135.2, 130.3, 129.5, 129.3, 128.7, 127.9, 127.8, 127.3,
127.1, 127.0, 125.7, 122.9, 122.1, 120.6, 120.5, 119.4, 47.3, 27.5 ppm;
FTIR (ATR): n˜ =3016, 2970, 1738, 1444, 1366, 1216, 762, 739 cmÀ1
;
MS (EI): m/z: 397 [M+]; HRMS (EI+): m/z calcd for C21H15N:
281.1204; found: 281.1203.
2-(9,9-Dimethyl-9H-fluoren-2-yl)-5-fluoroquinoline (L5): Yield:
77%; 1H NMR (300 MHz, CDCl3): d=8.50 (dd, J=0.7, 8.8 Hz, 1H),
8.29 (d, J=1.1 Hz, 1H), 8.15 (dd, J=1.7, 8.0 Hz, 1H), 8.01 (d, J=
8.8 Hz, 2H), 7.87 (d, J=8.0 Hz, 1H), 7.81–7.74 (m, 1H), 7.69–7.62
(m, 1H), 7.50–7.47 (m, 1H), 7.39–7.34 (m, 2H), 7.22–7.16 (m, 1H),
1.60 ppm (s, 6H); 13C NMR (125 MHz, CDCl3): d=158.7, 158.2 (d,
J(F,C)=254.8 Hz), 154.6, 154.5, 149.6 (d, J(F,C)=2.8 Hz), 141.1,
138.8, 138.5, 130.2 (d, J(F,C)=4.4 Hz), 129.3 (d, J(F,C)=9.4 Hz),
128.0, 127.4, 127.8, 125.8 (d, J(F,C)=3.9 Hz), 122.9, 122.2, 120.7,
120.6, 119.5 (d, J(F,C)=2.8 Hz), 117.9 (d, J(F,C)=16.6 Hz), 109.9 (d,
J(F,C)=19.4 Hz), 47.3, 27.5 ppm; FTIR (ATR): n˜ =3016, 2970, 1738,
1366, 1216, 834, 737 cmÀ1; MS (EI): m/z: 339 [M+]; HRMS (EI+): m/z
calcd for C24H18FN: 339.1423; found: 339.1421.
2-(9,9-Dimethyl-9H-fluoren-2-yl)-5-(4-fluorophenyl)quinoline
1
(L6): Yield: 83%; H NMR (300 MHz, CDCl3): d=8.28 (d, J=1.5 Hz,
1H), 8.24 (t, J=8.8 Hz, 2H), 8.13 (dd, J=1.8, 7.8 Hz, 1H), 7.90 (d,
J=8.8 Hz, 1H), 7.86 (d, J=7.9 Hz, 1H), 7.81–7.76 (m, 2H), 7.50–7.44
(m, 4H), 7.39–7.35 (m, 2H), 7.26–7.19 (m, 2H), 1.59 ppm (s, 6H);
13C NMR (125 MHz, CDCl3): d=162.7 (d, J(F,C)=245.8 Hz), 157.2,
154.6, 154.5, 148.9, 140.8, 139.4, 138.8, 138.6, 135.7 (d, J(F,C)=
2.8 Hz), 134.9, 131.9 (d, J(F,C)=7.8 Hz), 129.4, 129.3, 127.9, 127.3,
127.1, 126.8, 125.7, 122.9, 121.9, 120.6, 120.4, 119.1, 115.5 (d,
J(F,C)=21.6 Hz), 47.3, 27.2 ppm; FTIR (ATR): n˜ =3016, 2970, 1738,
1366, 1217, 901, 764, 740 cmÀ1; MS (EI): m/z: 415 [M+]; HRMS (EI+):
m/z calcd for C30H22FN: 415.1736; found: 415.1737.
6-Bromo-2-phenylquinoline (15): 5-Bromo-2-aminobenzo-phe-
none (0.4 g, 1.99 mmol) and acetophenone (0.25 g, 2.02 mmol)
were dissolved in acetic acid (8 mL) and then concentrated H2SO4
(0.13 mL) was added. After heating to reflux for 12 h under an
argon atmosphere, the solution was poured into a mixture of con-
centrated NH3·H2O (30 mL) and ice water (30 g). The resulting pre-
cipitate was filtered and washed with water. The pure compounds
were recrystallized from THF/ethanol. Compound 15 was obtained
1
as pale yellow crystals (0.26 g, 46%). H NMR (300 MHz, CDCl3): d=
Chem. Eur. J. 2016, 22, 4036 – 4045
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8.17–8.13 (m, 3H), 8.04 (d, J=9.0 Hz, 1H), 8.00 (d, J=2.1 Hz, 1H),
7.91 (d, J=8.7 Hz, 1H), 7.79 (dd, J=2.1, 9.0 Hz, 1H), 7.54–7.48 ppm
(m, 3H); 13C NMR (75 MHz, CDCl3): d=157.9, 147.1, 139.4, 136.1,
133.4, 131.7, 129.8, 129.7, 129.2, 128.5, 127.8, 120.3, 120.1 ppm; MS
(EI): m/z: 283 [M+]; HRMS (EI+): m/z calcd for C15H10BrN: 282.9996;
found: 282.9995.
C47H33F2IrN2O2 (Mw =888): C 63.57, H 3.75, N 3.81; found: C 63.47, H
3.78, N 3.78.
Complex 4: Red solid; yield: 26%; 1H NMR (300 MHz, CDCl3): d=
8.60 (d, J=8.1 Hz, 1H), 8.41 (d, J=9.0 Hz, 1H), 8.33 (d, J=9.9 Hz,
1H), 8.12 (dd, J=4.5, 4.8 Hz, 2H), 7.85 (s, 2H), 7.62–7.58 (m, 7H),
7.55–7.52 (m, 3H), 7.48–7.41 (m, 4H), 7.30 (d, J=7.8 Hz, 3H), 6.93
(s, 1H), 6.75 (s, 1H), 2.16 (s, 6H), 1.49 ppm (s, 6H); 13C NMR
(125 MHz, CDCl3): d=154.9, 136.7, 136.0, 130.5, 129.9, 128.7, 127.9,
127.5, 127.1, 126.8, 126.5, 122.6, 120.5, 116.9, 89.9, 86.5, 78.7, 46.3,
31.2, 28.6, 27.9, 27.7, 27.5 ppm; FTIR (ATR): n˜ =3016, 2970, 1738,
1599, 1519, 1366, 875, 760, 740 cmÀ1; MS (FAB): m/z: 1084 [M+];
HRMS (FAB+): m/z calcd for C65H51IrN2O2: 1084.3580; found:
1084.3577; elemental analysis calcd (%) for C65H51IrN2O2 (Mw =
1084): C 72.00, H 4.74, N 2.58; found: C 71.74, H 4.69, N 2.55.
Complex 5: Red solid; yield: 57%; 1H NMR (300 MHz, CDCl3): d=
8.50 (d, J=9.0 Hz, 2H), 8.29 (d, J=8.8 Hz, 2H), 8.23 (d, J=9.0 Hz,
2H), 7.89 (s, 2H), 7.38–7.29 (m, 4H), 7.14 (d, J=8.4 Hz, 4H), 7.06–
7.03 (m, 4H), 6.85 (s, 2H), 4.70 (s, 1H), 1.55 (s, 6H), 1.52 (s, 6H),
1.46 ppm (s, 6H); 13C NMR (125 MHz, CDCl3): d=186.2, 171.5,
158.2 (d, J(F,C)=251.8 Hz), 155.1, 150.0 (d, J(F,C)=3.6 Hz), 149.5,
147.2, 145.9, 140.9, 138.5, 131.1 (d, J(F,C)=6.2 Hz), 130.3 (d, J(F,C)=
9.1 Hz), 127.8, 127.0, 126.7, 122.6, 122.3 (d, J(F,C)=3.9 Hz), 121.2,
120.6, 117.9 (d, J(F,C)=18.0 Hz), 117.3, 109.8 (d, J(F,C)=19.2 Hz),
100.5, 46.4, 28.1 ppm; FTIR (ATR): n˜ =3004, 2970, 1738, 1584, 1518,
1364, 1020, 920, 763, 738 cmÀ1;MS (FAB) (m/z): 968 [M+];HRMS (EI+
) calcd for C53H41F2IrN2O2: 968.2765 found: 968.2760; elemental
analysis calcd (%) for C53H41F2IrN2O2 (Mw =968): C 65.75, H 4.27, N
2.89; found: C 64.98, H 4.24, N 2.84.
Complex 6: Red solid; yield: 50%; 1H NMR (300 MHz, CDCl3): d=
8.54 (d, J=8.7 Hz, 2H), 8.26 (d, J=9.1 Hz, 2H), 8.12 (d, J=9.2 Hz,
2H), 7.85 (s, 2H), 7.59–7.56 (m, 4H), 7.44 (d, J=6.9 Hz, 2H), 7.39 (d,
J=6.6 Hz, 2H), 7.32–7.25 (m, 8H), 7.13–7.03 (m, 4H), 6.92 (s, 2H),
4.73 (s, 1H), 1.55 (s, 6H), 1.54 (s, 6H), 1.45 ppm (s, 6H); 13C NMR
(125 MHz, CDCl3): d=186.5, 170.3, 162.9 (d, J(F,C)=246.6), 155.1,
149.9, 148.9, 147.1, 146.4, 140.6, 139.7, 138.8, 136.3, 135.8 (d,
J(F,C)=3.3 Hz), 132.2 (d, J(F,C)=8.1 Hz), 130.0, 127.6, 127.1, 126.6,
126.1, 125.7, 122.6, 120.8, 120.5, 117.1, 115.6 (d, J(F,C)=21.6 Hz),
100.4, 46.4, 28.2, 27.5, 27.4 ppm; FTIR (ATR): n˜ =3050, 2961, 1690,
1599, 1521, 1358, 975, 769, 740 cmÀ1; MS (FAB): m/z: 1120 [M+];
HRMS (FAB+): m/z calcd for C65H49F2IrN2O2: 1120.3391; found:
1120.3387; elemental analysis calcd (%) for C65H49F2IrN2O2 (Mw =
1120): C 69.69, H 4.41, N 2.50; found: C 68.85, H 4.39, N 2.49.
Complex 7: Red solid; yield: 41%; 1H NMR (300 MHz, CDCl3): d=
8.56 (d, J=9.2 Hz, 2H), 8.24 (d, J=8.6 Hz, 2H), 8.11 (d, J=8.8 Hz,
2H), 8.00 (d, J=1.9 Hz, 2H), 7.85 (d, J=7.6 Hz, 2H), 7.71 (d, J=
8.2 Hz, 6H), 7.49 (t, J=7.4 Hz, 4H), 7.40 (d, J=7.2 Hz, 2H), 6.96 (t,
J=6.7 Hz, 2H), 6.67–6.56 (m, 4H), 4.69 (s, 1H), 1.54 ppm (s, 6H);
13C NMR (125 MHz, CDCl3): d=185.8, 170.6, 151.4, 149.1, 147.3,
140.2, 138.6, 138.3, 136.4, 130.1, 129.2, 128.9, 127.9, 127.7, 127.5,
127.4, 126.1, 125.6, 121.2, 117.3, 100.5, 28.5 ppm; FTIR (ATR): n˜ =
3057, 2979, 1684, 1579, 1516, 1342, 965, 760, 734 cmÀ1; MS (FAB):
m/z: 852 [M+]; HRMS (FAB+): m/z calcd for C47H35IrN2O2: 852.2328;
found: 852.2319; elemental analysis calcd (%) for C47H35IrN2O2
(Mw =852): C 66.26, H 4.14, N 3.29; found: C 65.87, H 4.10, N 3.25.
General procedure of the [(CN)2Ir(acac)] complexes: The corre-
sponding ligand (4.46 mmol) was dissolved in 2-ethoxyethanol
(18.0 mL) in a 50 mL round-bottom flask. IrCl3·3H2O (2.01 mmol)
and water (6.0 mL) were then added to the flask. The mixture was
stirred under nitrogen at 1208C for 24 h and cooled to room tem-
perature. The precipitate formed in the mixture was collected and
washed with methanol and hexane, and dried in a vacuum to give
the corresponding cyclometalated IrIII-m-chloro-bridged dimer. In
a 50 mL flask, the dimmer complex, acetylacetone (3.02 mmol) and
Na2CO3 (6.03 mmol) were mixed with 2-ethoxyethanol (20 mL), and
the mixture was heated to 1008C for 6 h. After cooling to room
temperature, the precipitated solid was collected by filtration and
washed with ethanol and hexane. The residue was dissolved in di-
chloromethane and the solid was filtered. The solution was con-
centrated in vacuo and the residue was purified on a silica gel
column by using dichloromethane and methanol as the eluent.
The product was obtained after recrystallization from dichlorome-
thane/ethanol. Similar procedures were also used to synthesize the
other iridium(III) complexes. The yields and spectral data of all iridi-
um complexes are as follows.
Complex 1: Red solid; yield: 48%; 1H NMR (300 MHz, CDCl3): d=
8.53 (dd, J=1.1, 8.1 Hz, 2H), 8.26 (d, J=9.0 Hz, 2H), 7.99 (d, J=
9.2 Hz, 2H), 7.80 (d, J=7.9 Hz, 2H), 7.56–7.41 (m, 14H), 6.91 (td, J=
1.5, 7.3 Hz, 2H), 6.65–6.58 (m, 4H), 4.72 (s, 1H), 1.53 ppm (s, 6H);
13C NMR (125 MHz, CDCl3): d=186.2, 169.8, 150.8, 150.4, 149.8,
147.7, 138.0, 136.1, 130.6, 130.0, 129.1, 129.0, 128.9, 128.8, 126.9,
126.5, 126.3, 126.2, 121.3, 117.4, 100.4, 28.3 ppm; FTIR (ATR): n˜ =
3028, 2970, 1739, 1578, 1518, 1365, 926, 762, 738 cmÀ1; MS (FAB):
m/z: 852 [M+]; HRMS (FAB+): m/z calcd for C47H35IrN2O2: 852.2328;
found: 852.2321; elemental analysis calcd (%) for C47H35IrN2O2
(Mw =852): C 66.26, H 4.14, N 3.29; found: C 66.03, H 4.11, N 3.26.
Complex 2: Red solid; yield: 34%; 1H NMR (300 MHz, CDCl3): d=
8.46 (d, J=8.9 Hz, 2H), 8.25 (d, J=9.0 Hz, 2H), 8.11 (d, J=9.0 Hz,
2H), 7.84 (d, J=7.0 Hz, 2H), 7.39–7.31 (m, 2H), 7.15 (dd, J=1.6,
8.6 Hz, 2H), 6.95 (dd, J=1.2, 7.5 Hz, 2H), 6.62 (td, J=1.3, 7.4 Hz,
2H), 6.50 (dd, J=1.1, 7.7 Hz, 2H), 4.66 (s, 1H), 1.50 ppm (s, 6H);
13C NMR (125 MHz, CDCl3): d=186.2, 171.5, 158.2 (d, J(F,C)=
252.5 Hz), 150.9, 150.0 (d, J(F,C)=3.9 Hz), 147.0, 136.1, 131.4 (d,
J(F,C)=6.1 Hz), 130.4 (d, J(F,C)=9.4 Hz), 129.4, 126.8, 122.4 (d,
J(F,C)=3.9 Hz), 121.5, 118.1 (d, J(F,C)=18.3 Hz), 117.1, 110.0 (d,
J(F,C)=18.9 Hz), 100.4, 28.1 ppm; FTIR (ATR): n˜ =3015, 2970, 1738,
1578, 1366, 1216, 1046, 912, 722, 738 cmÀ1; MS (FAB): (m/z: 736
[M+]; HRMS (FAB+): m/z calcd for C35H25F2IrN2O2: 736.1513; found:
736.1512; elemental analysis calcd (%) for C35H25F2IrN2O2 (Mw =
736): C 57.13, H 3.42, N 3.81; found: C 56.97, H 3.38, N 3.79.
Complex 3: Red solid; yield: 42%; 1H NMR (300 MHz, CDCl3): d=
8.53 (dd, J=0.9, 8.6 Hz, 2H), 8.21 (d, J=9.0 Hz, 2H), 8.01 (d, J=
9.2 Hz, 2H), 7.81 (d, J=7.8 Hz, 2H), 7.51 (dd, J=5.4, 8.7 Hz, 4H),
7.48–7.38 (m, 4H), 7.27–7.22 (m, 4H), 6.95 (td, J=1.3, 7.8 Hz, 2H),
6.68–6.57 (m, 4H), 4.72 (s, 1H), 1.53 ppm (s, 6H); 13C NMR
(125 MHz, CDCl3): d=186.2, 170.3, 162.9 (d, J(F,C)=246.9 Hz),
150.4, 149.8, 147.4, 139.8, 136.5, 136.1, 135.6 (d, J(F,C)=3.3 Hz),
132.1 (d, J(F,C)=7.7 Hz), 130.1, 129.0, 127.2, 126.4, 126.2, 125.9,
121.3, 116.9, 115.7 (d, J(F,C)=21.6 Hz), 100.4, 28.2 ppm; FTIR (ATR):
Complex 8: Red solid; yield: 36%; 1H NMR (300 MHz, CDCl3): d=
8.55 (d, J=9.2 Hz, 2H), 8.19 (d, J=8.6 Hz, 2H), 8.09 (d, J=8.8 Hz,
2H), 7.92 (s, 2H), 7.83 (d, J=7.9 Hz, 2H), 7.66–7.61 (m, 6H), 7.15 (t,
J=8.6 Hz, 4H), 6.95 (t, J=7.3 Hz, 2H), 6.63 (d, J=7.5 Hz, 2H), 6.56
(d, J=7.5 Hz, 2H), 4.69 (s, 1H), 1.52 ppm (s, 6H); 13C NMR (75 MHz,
CDCl3): d=185.8, 170.6, 151.3, 148.9, 147.2, 145.1 (d, J(F,C)=
281.4 Hz), 138.3, 137.6, 136.3, 129.9, 129.2 (d, J(F,C)=7.2 Hz), 128.9
(d, J(F,C)=3.9 Hz), 127.7, 127.4, 126.1, 125.4, 124.2, 121.2, 117.4,
116.1 (d, J(F,C)=21.5 Hz), 100.5, 28.5 ppm; FTIR (ATR): n˜ =3062,
n˜ =3006, 2970, 1738, 1578, 1521, 1365, 1014, 978, 777, 739 cmÀ1
;
MS (FAB): m/z: 888 [M+]; HRMS (EI+): m/z calcd for C47H33F2IrN2O2:
888.2139; found: 888.2130; elemental analysis calcd (%) for
Chem. Eur. J. 2016, 22, 4036 – 4045
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ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
1689, 1578, 1517, 1344, 964, 749, 737 cmÀ1; MS (FAB): m/z: 888 [M+
]; HRMS (EI+): m/z calcd for C47H33F2IrN2O2: 888.2139; found:
888.2135; elemental analysis calcd (%) for C47H33F2IrN2O2 (Mw =
888): C 63.57, H 3.75, N 3.15; found: C 62.96, H 3.71, N 3.12.
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Complex 9: Red solid; yield: 62%; 1H NMR (500 MHz, CDCl3): d=
8.68 (d, J=9.2 Hz, 2H), 8.06 (d, J=2.0 Hz, 2H), 8.04 (s, 2H), 7.85 (d,
J=8.1 Hz, 2H), 7.74–7.70 (m, 6H), 7.64 (t, J=7.5 Hz, 4H), 7.59–7.57
(m, 6H), 7.41 (t, J=7.6 Hz, 4H), 7.33 (t, J=7.4 Hz, 2H), 6.97–6.94
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(125 MHz, CDCl3): d=185.9, 169.9, 151.3, 150.4, 149.4, 147.5, 140.5,
138.6, 138.3, 136.5, 130.1, 129.9, 129.1, 129.0, 128.9, 127.8, 127.5,
126.3, 126.1, 123.9, 121.2, 117.8, 100.6, 28.7 ppm; FTIR (ATR): n˜ =
3026, 1738, 1579, 1366, 878, 760, 738 cmÀ1; MS (FAB): m/z: 1004
[M+]; HRMS (FAB+): m/z calcd for C59H43IrN2O2: 1004.2954;
found:1004.2953; elemental analysis calcd (%) for C59H43IrN2O2
(Mw =1004): C 70.57, H 4.32, N 2.79; found: C 69.97, H 4.30, N 2.72.
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Fabrication and characterization of the devices: For the OLED
fabrication, indium tin oxide (ITO) thin films coated on glass sub-
strates were used, which were 12 WsquareÀ1 of the sheet resistivity
with 1000 Š of thickness. The ITO-coated glass was cleaned in an
ultrasonic bath by the following sequence: acetone, methyl alco-
hol, distilled water, followed by storage in isopropyl alcohol for
20 min and drying with a N2 gas gun. The substrates were treated
with O2 plasma argon environment. Organic layers were deposited
by thermal evaporation from resistively heated alumina crucibles
onto the substrate at a rate of 1.0 ŠsÀ1. All organic materials and
the metal were deposited under high vacuum (5.0”10À7 Torr). De-
vices were fabricated in the following structure: ITO/4,4’,4’’-tris[2-
naphthyl(phenyl)amino]triphenylamine (2-TNATA) (60 nm)/4,4’-
bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) (20 nm)/CBP: 8%
iridium(III) complexes (30 nm)/BCP (10 nm)/Alq3 (20 nm)/8-hydroxy-
quinoline lithium (Liq) (2 nm)/Al (100 nm). The current density J,
the luminance L, the luminous efficiency LE, and the CIE chromatic-
ity coordinates of the OLEDs were measured with a Keithly 2400,
Chroma meter CS-1000A. The electroluminance (EL) was measured
by using a Roper Scientific Pro 300i.
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Acknowledgements
This research was supported by the Basic Science Research
Program through the NRF funded by the Ministry of Education,
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2013R1A1A2A10008105).
Keywords: 2-arylquinoline ligands
phosphorescence · red electroluminescence
·
iridium
·
OLEDs
·
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Received: November 2, 2015
Published online on February 16, 2016
Chem. Eur. J. 2016, 22, 4036 – 4045
www.chemeurj.org
4045
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim