New red phosphorescent iridium(III) complex with 4-tert-Butylphenyl-boronic acid of organic borane

Article abstract of DOI:10.1080/15421406.2016.1200946

A new phosphorescent (CQ-BP)₂Ir(acac), (CMQ-BP)₂Ir(acac), (BQ-BP)₂Ir(acac) was synthesized for organic light-emitting diodes (OLEDs). OLEDs using phosphorescent iridium(III) complexes attract enormous attention because they allow highly efficient electro phosphorescence. The donor-acceptor type ligands for the Iridium(III) complexes were synthesized by Suzuki coupling reaction. The ligands through changes in oxidative addition materials (electron-acceptor) and organic borane (electron-donor) to get the red color were to study the appropriate Iridium(III) complexes. Oxidative addition materials were used such as 2-chloro-4-methylquinoline, 1-chloroisoquinoline and 2-bromoquinoline. 4-tert-Butylphenyl-boronic acid was used as organic borane. The dopant was synthesized by Nonoyama reaction. Red dopants were observed with an emission peak at approximately 600?nm. Iridium(III) complexes were measured by nuclear magnetic resonance (NMR), UV-visible spectroscopy and photoluminescence (PL). The phosphorescence emission maxima were dependent on the electron density of donor and acceptor moiety of the ligands.

Full text of DOI:10.1080/15421406.2016.1200946

Molecular Crystals and Liquid Crystals
ISSN: 1542-1406 (Print) 1563-5287 (Online) Journal homepage: http://www.tandfonline.com/loi/gmcl20
New red phosphorescent iridium(III) complex with
4-tert-Butylphenyl-boronic acid of organic borane
Sang-Wook Lee & Dong-Myung Shin
To cite this article: Sang-Wook Lee & Dong-Myung Shin (2016) New red phosphorescent
iridium(III) complex with 4-tert-Butylphenyl-boronic acid of organic borane, Molecular Crystals
and Liquid Crystals, 636:1, 67-72, DOI: 10.1080/15421406.2016.1200946
To link to this article: http://dx.doi.org/10.1080/15421406.2016.1200946
Published online: 01 Nov 2016.
Submit your article to this journal
Article views: 12
View related articles
View Crossmark data
Full Terms & Conditions of access and use can be found at
http://www.tandfonline.com/action/journalInformation?journalCode=gmcl20
Download by: [The UC San Diego Library]
Date: 12 January 2017, At: 11:55

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
, VOL. , –
http://dx.doi.org/./..
New red phosphorescent iridium(III) complex with
-tert-Butylphenyl-boronic acid of organic borane
Sang-Wook Lee∗ and Dong-Myung Shin
Department of Chemical Engineering, Hong-ik University, Seoul, Korea
ABSTRACT
KEYWORDS
red dopant; iridium(III)
complex; OLED;
phosphorescent
A
new phosphorescent (CQ-BP)2Ir(acac), (CMQ-BP)2Ir(acac), (BQ-
BP)2Ir(acac) was synthesized for organic light-emitting diodes (OLEDs).
OLEDs using phosphorescent iridium(III) complexes attract enormous
attention because they allow highly efficient electro phosphores-
cence. The donor-acceptor type ligands for the Iridium(III) complexes
were synthesized by Suzuki coupling reaction. The ligands through
changes in oxidative addition materials (electron-acceptor) and
organic borane (electron-donor) to get the red color were to study
the appropriate Iridium(III) complexes. Oxidative addition materials
were used such as 2-chloro-4-methylquinoline, 1-chloroisoquinoline
and 2-bromoquinoline. 4-tert-Butylphenyl-boronic acid was used as
organic borane. The dopant was synthesized by Nonoyama reaction.
Red dopants were observed with an emission peak at approximately
600 nm. Iridium(III) complexes were measured by nuclear magnetic
resonance (NMR), UV-visible spectroscopy and photoluminescence
(PL). The phosphorescence emission maxima were dependent on the
electron density of donor and acceptor moiety of the ligands.
1. Introduction
Organic light-emitting diodes (OLEDs) have attracted considerable attention in scientific
and industrial utilization due to their merits in low operating voltage, wide range of self-
emissive materials, high contrast, fast response time, wide-viewing angle, ultrathin structure
and light weight [1–10]. In particular, heavy metal ions, such as Pt(III), Ru(III), and Ir(III)
have been employed for the synthesis of high emission phosphorescent materials to utilize for
the solar-cells and the OLEDs. OLEDs composed of glass substrate, transparent conductor
(ITO), electron injection layer (EIL), electron transfer layer (ETL), emission material layer
(EML), hole transfer layer (HTL), hole injection layer (HJL) and metal cathode [11–14]. We
has been studying phosphorescent iridium(III)complex dopants for the EML layer. The exci-
tons formed in EML are composed of 25% singlet and 75% triplets [15]. Which enable both
nearly 100%internal device quantum efficiency. Such promising features prompted the devel-
opment of a number of novel phosphorescent Iridium(III) complexes. In this paper, we report
synthesis and emission properties of novel red-emitting iridium complexes through changed
CONTACT Dong-Myung Shin
shindm@hongik.ac.kr
Department of Chemical Engineering, Hong-ik University, ,
Wausan-ro, Mapo-gu, Seoul, Korea.
∗Present address: Hong-ik University, , Wausan-ro, Mapo-gu, Seoul, Korea.
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/gmcl.
©  Taylor & Francis Group, LLC

68/[258]
S. -W. LEE AND D. -M. SHIN
electron-donor and electron-acceptor of ligand and measure characteristic respectively
[16–18].
2. Experimental
2.1. General information
All reactions and manipulation were carried out under N2 with the use of standard inert
atmosphere. Solvents were dried by standard procedures. All column chromatography was
performed under standard atmosphere with the use of silica gel (230–400 mesh, Sigma-
Aldrich) as the stationary phase in a column of 30 cm long and 2.0 cm diameter. The 1H
NMR spectra were measured by using a Bruker DRX 400 spectrometer in deuterated chlo-
roform solution. 500 MHz UV-visible absorption spectra were recorded on an Agilent8453
UV-Vis spectrophotometer. All measurements were carried out room temperature. For expect
phosphorescent emission energy and electronic state of newly designed iridium complex, we
used Gaussian 08 program. Gaussian 08 program performs structure optimization and time-
dependent density functional theory (TD-DFT) calculations HF and DFT.
2.2. Synthesis of ligand
-(-(tert-butyl)phenyl)isoquinoline
A mixture of 4-tert-Butylphenylboronic acid (2.00 g, 11.234 mmol), 1-Chloroisoquinoline
(2.02 g, 12.357 mmol), Pd(PPh3)4 (0.13 g, 0.112 mmol, 1 mol%), Potassium carbonate
(33.17 g, 240 mmol), tetrahydrofuran (120 mL), water (60 mL) was headed under nitro-
gen atmosphere at 80°C for 24-hour(This reaction is Suzuki coupling reaction). After cool-
ing to room temperature, the crude reaction product was poured into water, extracted with
dichloromethane. And extract is concentrated under vacuum. The product was purified by
column chromatography to obtain a dark-red powder with yield of 61.2% and dried in vac-
uum to yield light-green solid product with 79.4% yield.
H NMR (CDCl3, 500MHz): δH(ppm) 8.42(d, 1H), 8.22(d, 2H), 7.92(d, 1H), 7.63(d, 1H),
7.49(d, 1H), 7.42(d, 1H), 7.41(d, 1H), 7.10(d, 1H), 1.35(s, 1H)
-(-(tert-butyl)phenyl)--methylquinoline
A mixture of 4-tert-Butylphenylboronic acid (2.00 g, 11.234 mmol), 2-chloro-4-
methylquinoline (2.19 g, 12.357 mmol), Pd(PPh3)4 (0.13 g, 0.112 mmol, 1 mol%), Potassium
carbonate (33.17 g, 240 mmol), tetrahydrofuran (120 mL), water (60 mL) was headed under
nitrogen atmosphere at 80°C for 24 h. hours(This reaction is Suzuki coupling reaction).
The abstraction and purification process are the same as the method described above. Yield:
87.3%.
H NMR (CDCl3, 500MHz): δH(ppm) 8.22(d, 2H), 8.16(d, 1H), 7.95(d, 1H), 7.75(t, 1H),
7.59(t, 1H), 7.41(d, 1H), 7.00(s, 1H), 2.61(s, 1H), 1.35(s, 3H),
-(-(tert-butyl)phenyl)quinolone
A mixture of 4-tert-Butylphenylboronic acid (2.00 g, 11.234 mmol), 2-bromoquinoline
(2.57 g, 12.357 mmol), Pd(PPh3)4 (0.13 g, 0.112 mmol, 1 mol%), Potassium carbonate
(33.17 g, 240 mmol), tetrahydrofuran (120 mL), water (60 mL) was headed under nitrogen
atmosphere at 80°C for 24 h. hours(This reaction is Suzuki coupling reaction). The abstrac-
tion and purification process are the same as the method described above. Yield: 83.4%.

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
[259]/69
H NMR (CDCl3, 500MHz): δH(ppm) 8.22(d, 2H), 8.10(s, 1H), 8.06(t, 1H), 7.98(d, 1H),
7.78(t, 1H), 7.6(t, 1H), 7.41(t, 2H), 7.35(d, 1H), 1.35(d, 3H)
2.3. Synthesis of dimer
Dimer [(CQ-BP)IrCl] diiridium(III)
The cyclometalated iridium (III) μ-chloride-bridged dimer, [CQ-BP)2Ir(μ-Cl)]2 (II) was pre-
pared using a slight modification of the Nonoyama reaction step 1. Iridium (III) chloride
hydrate (1.331 g, 4.457 mmol) and Ligand (2.330 g, 8.915 mmol) was added a 3:1 in mixture
of 2-ethoxyethanol and water. The reaction is required under nitrogen atmosphere. The mix-
ture was heated to reflux for 27-hour at 135 C. The solution was cooled to room temperature,
and leaves the flask in ice bath 2 hours. The crude reaction product was poured into water,
extracted with dichloromethane. And extract is concentrated under vacuum. yield: 95.7%.
Dimer [(CMQ-BP)IrCl] diiridium(III)
The cyclometalated iridium (III) μ-chloride-bridged dimer, [CMQ-BP)2Ir(μ-Cl)]2 (II) was
prepared using a slight modification of the Nonoyama reaction step 1. Iridium (III) chloride
hydrate (1.464 g, 4.902 mmol) and Ligand (2.7 g, 9.804 mmol) was added a 3:1 in mixture of
2-ethoxyethanol and water. The reaction is required under nitrogen atmosphere. The mixture
was heated to reflux for 27-hour at 135 C. The purification process is the same as the method
described above. yield: 89.1%.
Dimer [(BQ-BP)IrCl] diiridium(III)
The cyclometalated iridium (III) μ-chloride-bridged dimer, [BQ-BP)2Ir(μ-Cl)]2 (II) was pre-
pared using a slight modification of the Nonoyama reaction step 1. Iridium (III) chloride
hydrate (1.399 g, 4.687 mmol) and Ligand (2.45 g, 9.374 mmol) was added a 3:1 in mixture of
2-ethoxyethanol and water. The reaction is required under nitrogen atmosphere. The mixture
was heated to reflux for 27-hour at 135 C. The purification process is the same as the method
described above. yield: 96.7%.
2.4. Synthesis of iridium(III) complexes
(CQ-BP)Ir(acac)
Dimer (3.11 g, 2.072 mmol) were dissolved in 2-ethoxyethanol (124.40 mL). 5 equivalent
acetylacetone (1.037 g, 10.361 mmol) and sodium carbonate (2.864 g, 20.722 mmol) is placed.
Reactants refluxed under nitrogen atmosphere for 21-hour at 130°C (Fig. 1). After cool-
ing to room temperature, the crude reaction product was poured into water, extracted with
Figure . Synthetic route of (CQ-BP)Ir(acac).

70/[260]
S. -W. LEE AND D. -M. SHIN
Figure . Synthetic route of (CMQ-BP)Ir(acac).
dichloromethane. And extract is concentrated under vacuum. The product was purified by
column chromatography to obtain a red powder with yield of 74.3%.
1H NMR (CDCl3, 500MHz): δH(ppm) 8.22(d, 1H), 8.10(d, 2H), 8.06(d, 2H), 7.98(d, 1H),
7.78(t, 2H), 7.60(d, 2H), 7.56(s, 2H), 7.41(d, 2H), 7.35(d, 2H), 2.24(s, 1H), 1.35(s, 6H), 1.27
(d, 1H)
(CMQ-BP)Ir(acac)
Dimer (3.4 g, 2.184 mmol) were dissolved in 2-ethoxyethanol (136 mL). 5.0 equivalent acety-
lacetone (1.093 g, 10.922 mmol) and sodium carbonate (3.019 g, 21.844 mmol) is placed.
Reactants refluxed under nitrogen atmosphere for 21-hour at 135°C (Fig. 2). The abstraction
and purification process are the same as the method described above. Yield: 67.4%.
1H NMR (CDCl3, 500MHz): δH(ppm) 8.22(d, 2H), 8.16(d, 2H), 7.95(d, 2H), 7.75(t, 2H),
7.59(s, 2H), 7.56(d, 2H), 7.41(d, 2H), 7.0(s, 2H), (d, 1H), 5.75(d, 1H), 2.61(s, 2H), 2.24(s, 1H),
1.35(s, 6H), 1.27(d, 1H)
(BQ-BP)Ir(acac)
Dimer (3.4 g, 2.265 mmol) were dissolved in 2-ethoxyethanol (136 mL). 5.0 equivalent acety-
lacetone (1.134 g, 11.327 mmol) and sodium carbonate (3.131 g, 22.654 mmol) is placed.
Reactants refluxed under nitrogen atmosphere for 21-hour at 135°C (Fig. 3). The abstraction
and purification process are the same as the method described above. Yield: 46.8%.
1H NMR (CDCl3, 500MHz): δH(ppm) 8.22(d, 2H), 8.18(d, 2H), 7.92(d, 2H), 7.63(d, 2H),
7.56(s, 2H), 7.49(t, 2H), 7.42(t, 2H), 7.41(s, 2H), 7.02(d, 2H), 5.75(d, 1H), 4.08(t, 1H), 2.24(s,
1H), 1.35(s, 6H), 1.27(d, 1H),
3. Results and discussion
The maximum PL emission of (CMQ-BP)2Ir(acac), (BQ-BP)2Ir(acac) and (CQ-BP)2Ir(acac)
were observed at 591 nm 596.5 nm, 623.5 nm respectively (Fig. 4 and Table 1).
Figure . Synthetic route of (BQ-BP)Ir(acac).

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
[261]/71
Figure . UV–visible absorption, and photoluminescence spectrum of Iridium(III) complexes in CHCl solu-
tion. (A) (CQ-BP)Ir(acac),(B) (CMQ-BP)Ir(acac), (C) (BQ-BP)Ir(acac).
Table . UV–visible absorption, and photoluminescence spectrum peaks of Iridium(III) complexes.
UV absorption spectrum
Second peak
PL emission spectrum
Maximum peak
Iridium complex
Firs peak
(CQ-BP)Ir(acac)
(CMQ-BP)Ir(acac)
(BQ-BP)Ir(acac)
nm
nm
nm
nm
nm
nm
nm
nm
.nm
The methyl group is electron donating group. The electron density of 2-chloro-4-
methylquinoline is higher than 2-bromoquinoline in the pyridine ring. Therefore, the electron
density in the pyridine ring is increased and the lowest unoccupied molecular orbital (LUMO)
energy level is increased. Therefore, the HOMO-LUMO energy gap of (CMQ-BP)2Ir(acac) is
increased and the emission wavelength is decreased. So wavelength of (CMQ-BP)2Ir(acac)
is lower than (BQ-BP)2Ir(acac). At the same results, 1-chloroisoquinoline is more electron
donating role than 2-bromoquinoline in the pyridine ring. So wavelength of (CQ-BP)2Ir(acac)
is higher than (BQ-BP)2Ir(acac).[19]
4. Conclusion
As a result of a simulation using the Gaussian 09Wprogram, (CQ-BP)2Ir(acac), (CMQ-
BP)2Ir(acac), (BQ-BP)2Ir(acac) were predicted to emit luminance at 620nm, 598nm,
604.5 nm respectively. When Iridium(III) complexes were synthesized and had the maximum
PL of (CQ-BP)2Ir(acac), (CMQ-BP)2Ir(acac), (BQ-BP)2Ir(acac) was observed at 623nm,
591nm, 596.5 nm at room temperature respectively. As a result, it was confirmed that
(CQ-BP)2Ir(acac), (CMQ-BP)2Ir(acac), (BQ-BP)2Ir(acac) are suitable for red-emitting Irid-
ium(III)complex.

72/[262]
S. -W. LEE AND D. -M. SHIN
Acknowledgment
This work was supported by the Technology Innovation Program (201210940003, Materials Develop-
ment for 50-inches UD OLED TV Using Super Hybrid Process) funded by the Ministry of Knowledge
Economy (MKE, Korea).
References
[1] You, Y. M., & Park, S. Y. (2009). Dalton Trans., 8, 1267.
[2] Kim, J., Kato, H., & Kakihana, (2012). J. Inf. Disp., 13, 97–100.
[3] Yu, S., Kim, D., Choi, Y., & Kim, H. (2009). J. Inf. Disp., 10, 49–53.
[4] Mativenga, M., Choi, J. W., Hur, J. H., Kim, H. J., & Jang, J. (2011). J. Inf. Disp., 12, 47–50
[5] Brown, J. el al. (2012). Article first published online. 10, 1889.
[6] D’Andrade, B. W., & Forrest, S. R. (2004). Adv. Mater., 16, 1585.
[7] Lim, S. H. el al. (2008). Mol. Cryst. Liq. Cryst., 491, 40.
[8] Ryu, G. Y. el al. (2009). Mol. Cryst. Liq. Cryst., 499, 75.
[9] Park, N. R. el al. (2011). Mol. Cryst. Liq. Cryst., 538, 75.
[10] Lee, S. N. el al. (2013). Mol. Cryst. Liq. Cryst., 587, 59.
[11] Lee, S. N. el al. (2014). J. Nanosci. Nanotechnol., 14, 6185.
[12] Geffroy, B. el al. (2006). Article first published online. 10, 1002.
[13] Liang, B. el al. (2006). J. Mater. Chem., 16, 1281.
[14] Marin, V. el al. (2007). Chem. Soc.Rev., 36, 618.
[15] Chou, P. T., & Chi, Y. (2007). Chem.–Eur. J., 13, 380.
[16] Rehmann, N. el al. (2007). Appl. Phys. Lett., 91, 103507.
[17] Schwartz, G. el al. (2009). Adv. Funct. Mater., 19, 1319.
[18] Q. Wang, J. Ding, D. Ma, Y. Cheng, L. Wang, X. Jing, & F. Wang (2009). Adv. Funct. Mater., 19, 84.
[19] X.M. Yu, G.J. Zhou, C.S. Lam, W.Y. Wong, X.L. Zhu, J.X. Sun, M. Wong, & H.S. Kwonk (2008). J
Organomet. Chem., 693, 1518.