New carbazole derivatives including coumarin moiety for blue emitting materials

Article abstract of DOI:10.1080/15421406.2017.1355197

New carbazole derivatives including coumarin moiety, 7-(3-Carbazol-9-yl-phenyl)-chromen-2-one (C-PCa), 7-(9-Phenyl-9H-carbazol-3-yl)-chromen-2-one (PCa-C), 7-[9-(3-Carbazol-9-yl-phenyl)-9H-carbazol-3-yl]-chromen-2-one (PDCa-C) were synthesized by Suzuki reaction. A non-doped OLED was fabricated using the synthesized material as emitting materials. Among the three synthesized compounds, PDCa-C showed the highest efficiency with current efficiency of 1.34 cd/A and C.I.E of (0.18, 0.23) in the current density 10?mA/cm².

Full text of DOI:10.1080/15421406.2017.1355197

Molecular Crystals and Liquid Crystals
ISSN: 1542-1406 (Print) 1563-5287 (Online) Journal homepage: http://www.tandfonline.com/loi/gmcl20
New carbazole derivatives including coumarin
moiety for blue emitting materials
Hayoon Lee, Hyocheol Jung, Minjin Jo, Dong-Hee Shin, Kwang-Yol Kay &
Jongwook Park
To cite this article: Hayoon Lee, Hyocheol Jung, Minjin Jo, Dong-Hee Shin, Kwang-
Yol Kay & Jongwook Park (2017) New carbazole derivatives including coumarin moiety
for blue emitting materials, Molecular Crystals and Liquid Crystals, 654:1, 34-39, DOI:
10.1080/15421406.2017.1355197
To link to this article: https://doi.org/10.1080/15421406.2017.1355197
Published online: 22 Nov 2017.
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Date: 24 November 2017, At: 19:55

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
, VOL. , –
https://doi.org/./..
New carbazole derivatives including coumarin moiety for blue
emitting materials
Hayoon Leea, Hyocheol Junga, Minjin Job, Dong-hee Shinc, Kwang-Yol Kayc,d
and Jongwook Parka
,
aDepartment of Chemical Engineering, Kyung Hee University, Gyeonggi-do, Korea; bDepartment of Chemistry,
The Catholic University of Korea, Bucheon, Korea; cR&D Center, G-OLED Co., Ltd., Yeongtong-gu, Suwon, Korea;
dDepartment of Molecular Science and Technology, Ajou University, Suwon, Korea
ABSTRACT
KEYWORDS
Blue emitting materials;
carbazole; coumarin;
fluorescence; OLEDs
New carbazole derivatives including coumarin moiety, 7-(3-Carbazol-
9-yl-phenyl)-chromen-2-one (C-PCa), 7-(9-Phenyl-9H-carbazol-3-yl)-
chromen-2-one (PCa-C), 7-[9-(3-Carbazol-9-yl-phenyl)-9H-carbazol-3
-yl]-chromen-2-one (PDCa-C) were synthesized by Suzuki reaction. A
non-doped OLED was fabricated using the synthesized material as
emitting materials. Among the three synthesized compounds, PDCa-C
showed the highest efficiency with current efficiency of 1.34 cd/A and
C.I.E of (0.18, 0.23) in the current density 10 mA/cm2.
Introduction
Organic lighting emitting diodes (OLEDs) have received much attention because of its
advantages such as lower current drive voltage, less power consumption, and full-color
display [1, 2]. In order to fabricate full-color OLED display, red, green, and blue emitters
with high-efficiency, good thermal property and pure color coordinate are necessary [3–5].
Especially, blue emitter requires a wide band gap compared to red, green emitters, so, it
is very difficult to be well-matched with highest occupied molecular orbital (HOMO) and
lowest unoccupied molecular orbital (LUMO) levels of blue emitter and the other layer such
as hole transporting layer (HTL) and electron transporting layer (ETL). Thus, development
of blue emitting materials with a pure color and high efficiency is still required.
The emitting materials can be divided into fluorescent materials and phosphorescent mate-
rials. In the case of a blue-emitting material, many fluorescent materials have been synthesized
to improve the efficiency and the long lifetime [6]. The phosphorescent blue-emitting material
should use a lower triplet energy level (T1) than the singlet energy level (S1) of the fluorescent
material, and it is difficult to develop a phosphorescent blue emitting material because of the
limits in achieving a molecular structure with a high T1 level.
Most fluorescent material studies have tested using anthracene, pyrene, carbazole, which
are blue emitters with high luminous efficiency [7–9]. Also, coumarin has been used in various
areas such as fluorescence probe, charge-transfer agents due to its characteristics such as high
photo-stability and good solubility [10].
CONTACT Prof. Jongwook Park
jongpark@khu.ac.kr
Department of Chemical Engineering, Kyung Hee University, ,
Deogyeong-daero, Giheung-gu, Yongin-si, Gyeonggi-do, , Korea(ROK); Kwang-Yol Kay
ment of Molecular Science and Technology, Ajou University, Suwon , Korea.
kykay@ajou.ac.kr
Depart-
©  Taylor & Francis Group, LLC

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
[309]/35
In this study, coumarin was substituted in carbazole, which shows high luminous efficiency,
and 7-(3-Carbazol-9-yl-phenyl)-chromen-2-one (C-PCa), 7-(9-Phenyl-9H-carbazol-3-yl)-
chromen-2-one (PCa-C), and 7-[9-(3-Carbazol-9-yl-phenyl)-9H-carbazol-3-yl]-chromen-
2-one (PDCa-C) were synthesized. The three synthesized compounds were applied to OLED
devices as emitting layers and EL performance of devices were measured.
Experimental
Measurements
The 1H NMR spectra were recorded on Bruker Avance 400. The optical absorption spectra
were obtained by HP 8453 UV-VIS-NIR spectrometer. Perkin Elmer luminescence spec-
trometer LS50 (Xenon flash tube) was used for photo-luminescence (PL) spectroscopy. The
current–voltage-luminance (I-V-L) characteristics of the fabricated EL devices were obtained
by Keithley 2400 electrometer, and light intensity was obtained by Minolta CS-1000A.
Synthesis
Synthesis of -oxo-H-chromen--yl trifluoromethanesulfonate ()
Trifluoromethanesulfonic anhydride (20 ml, 119 mmol) was added to a solution of umbellif-
eron (21.35 g, 132 mmol) in pyridine (500 ml) at 0 °C. The mixture was stirred at 0 °C for
5 minutes and then at room temperature for 24 hours. The reaction mixture was poured into
water (400 ml) and extracted with toluene (400 ml). The organic extracts were washed with
10% HCl solution (100 ml) and then with saturated NaCl solution (100 ml). The organic layer
was dried over Na2SO4, filtered and evaporated to dryness to give 33.8 g (96%) in a white
solid.
1H NMR (400 MHz, CDCl3): δ 7.73 – 7.71 (d, 1H), 7.60 – 7.58 (d, 1H), 7.27 – 7.20 (m,
2H), 6.48 (d, 1H). Anal. Calcd. for C10H5F3O5S (294.2 g/mol): C, 40.82%; H, 1.71%. Found:
C, 40.74%; H, 1.82%.
Synthesis of -(,,,-tetramethyl-,,-dioxaborolan--yl)-H-chromen--one ()
A mixture of 2-oxo-2H-chromen-7-yl-trifluoromethanesulfonate (I) (2.13 g, 7.24 mmol),
bis(pinacolato)diboron (2.22 g, 8.74 mmol), [1,1’-bis(diphenylphosphino)ferrocene]
dichloropalladium(II) (0.18 g, 0.22 mmol), 1,1’-bis(diphenylphosphino)ferrocene (0.13 g,
0.23 mmol) and potassium acetate (2,2 g 22.4 mmol) in 1,4-dioxane (80 ml) was stirred at 80
°C for 18 hours. The reaction mixture was cooled to room temperature, reduced to a small
volume and extracted with dichloromethane (500 ml). The organic extracts were dried over
Na2SO4, filtered and evaporated to dryness. The crude product was then chromatographed
on silica gel with ethanol/hexane (1:9) to produce 1.0 g (61%) in a white solid.
1H NMR (400 MHz, CDCl3): δ 7.73 – 7.67 (m, 3H), 7.47 (d, 1H), 6.45 (d, 1H), 1.36 (s,
12H). Anal. Calcd. for C15H17BO4 (272.1 g/mol): C, 66.21%; H, 6.30%. Found: C, 65.98%; H,
6.46%.
Synthesis of -(-(H-carbazol--yl)phenyl)-H-chromen--one (C-PCa)
9-(3-Bromophenyl)-9H-carbazole(0.59 g, 1.83 mmol), 7-(4,4,5,5-tetramethyl-1,3,2-
dioxaborolan-2-yl)-2H-chromen-2-one (0.57 g, 2.09 mmol), tetrakis(triphenylphosphine)
palladium(0) (0.11 g, 0.09 mmol) and potassium carbonate (0.76 g, 5.49 mmol) were added
to a solution of toluene (40 ml), ethanol (15 ml) and water (15 ml). The reaction mixture

36/[310]
H. LEE ET AL.
was refluxed for 18 hours and then cooled to room temperature, reduced to a small volume
and extracted with dichloromethane (600 ml). The organic extracts were dried over Na2SO4,
filtered and evaporated to dryness. The crude product was then chromatographed on silica
gel with dichloromethane to afford 0.4 g (56%) in a white solid.
1H NMR (400 MHz, CDCl3): δ 8.16 (d, 2H), 7.84 (s, 1H), 7.75 – 7.72 (m, 3H), 7.62
– 7.56 (m, 4H), 7.48 – 7.42 (m, 4H), 7.33 – 7.31 (m, 2H), 6.45 (d, 1H). Anal. Calcd. for
C27H17NO2 (387.43 g/mol): C, 83.70%; H, 4.42%; N, 3.62%. Found: C, 83.47%; H, 4.60%; N,
3.51%.
Synthesis of -(-phenyl-H-carbazol--yl)-H-chromen--one (PCa-C)
3-Bromo-9-phenyl-9H-carbazole (0.44 g, 1.38 mmol), 7-(4,4,5,5-tetramethyl-1,3,2-
dioxaborolan-2-yl)-2H-chromen-2-one (0.38 g, 1.38 mmol), tetrakis(triphenylphosphine)
palladium(0) (0.08 g, 0.07 mmol) and potassium carbonate (0.57 g, 4.12 mmol) were added
to a solution of toluene (40 ml), ethanol (15 ml) and water (15 ml). The reaction mixture was
refluxed for 18 hours, cooled to room temperature, reduced to a small volume and extracted
with dichloromethane (600 ml). The organic extracts were dried over Na2SO4, filtered and
evaporated to dryness. The crude product was then chromatographed on silica gel with
dichloromethane to give 0.21 g (40%) in a yellow solid.
1H NMR (400 MHz, CDCl3): δ 8.39 (s, 1H), 8.20 (d, 1H), 7.75 – 7.73 (d, 2H), 7.66 – 7.61
(m, 4H), 7.58 – 7.54 (m, 3H), 7.49 – 7.43 (m, 3H), 7.35 – 7.33 (m, 2H), 6.41 (d, 1H). Anal.
Calcd. for C27H17NO2 (387.43 g/mol): C, 83.70%; H, 4.42%; N, 3.62%. Found: C, 83.54; H,
4.64%; N, 3.58.
Synthesis of -(-(-(H-carbazol--yl)phenyl)-H-carbazol--yl)-H-chromen--one
(PDCa-C)
9-(3-(9H-carbazol-9-yl)phenyl)-3-bromo-9H-carbazole (1.43 g, 2.93 mmol), 7-(4,4,5,5-
tetramethyl-1,3,2-dioxaborolan-2-yl)-2H-chromen-2-one (1.20 g, 4.41 mmol), tetrakis
(triphenylphosphine)palladium(0) (0.17 g, 0.15 mmol) and potassium carbonate (1.21 g,
8.75 mmol) were added to a solution of toluene (40 ml), ethanol (15 ml) and water (15 ml). The
reaction mixture was refluxed for 18 hours, cooled to room temperature, reduced to a small
volume and extracted with dichloromethane (600 ml). The organic extracts were dried over
Na2SO4, filtered and evaporated to dryness. The crude product was then chromatographed
on silica gel with dichloromethane to give 0.75 g (46.3%) in a yellow solid.
1H NMR (400 MHz, CDCl3): δ 8.40 (s, 1H), 8.16 (d, 3H), 7.88 (s, 1H), 7.73 – 7.71 (m,
4H), 7.69 – 7.63 (m, 4H), 7.58 – 7.53 (m, 4H), 7.48 – 7.43 (m, 4H), 7.33 – 7.31 (m, 2H), 6.45
(d, 1H). Anal. Calcd. for C39H24N2O2 (552.62 g/mol: C, 84.76%; H, 4.38%; N, 5.07%. Found:
C, 84.62%; H, 4.51%; N, 5.26%.
Results and discussion
The chemical structures and synthetic routes of compounds are shown in Scheme 1 and 2.
Compounds (3), (4) and (5) were synthesized according to the literature [11]. In film state,
maximum UV-Vis absorption (UVmax) of three synthesized compounds, C-PCa, PCa-C and
PDCa-C appeared in the range 331 to 345 nm. As observed for maximum photoluminescence
(PLmax), C-PCa, PCa-C and PDCa-C showed 449, 467 and 467 nm, respectively. (Figure. 1)
The UVmax values of PCa-C and PDCa-C were red-shifted about 20 nm compared to that
of C-PCa. This trend was similar to that seen in the PLmax values of PCa-C and PDCa-C
because PCa-C and PDCa-C had coumarin substituted para position in carbazole, increasing

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
[311]/37
Scheme . Chemical structures of the synthesized compounds.
Scheme . Synthetic routes of the synthesized compounds.
conjugation length [12, 13]. In contrast, C-PCa had coumarin substituted in meta position
to prevent conjugation length from increasing. In the case of PDCa-C, UVmax and PLmax
were observed in the region similar to PCa-C, and this is also because the two carbazoles
substituted in phenyl were connected in meta position. This connection does not affect the
conjugation length [13].
The three synthesized compounds were used as the emitting layer (EML), and non-
doped OLED was fabricated with the following structure: ITO/2-TNATA (60 nm)/NPB
(15 nm)/synthesized compounds (35nm) /TPBi (20 nm)/LiF (1 nm)/Al(200 nm). Here, 2-
TNATA was used as the hole injection layer (HIL), and NPB was used as the hole transport-
ing layer (HTL). TPBi was used as the electron transporting layer (ETL), LiF as the electron
Figure . UV&PL spectra of C-PCa, PCa-C, and PDCa-C in film state.

38/[312]
H. LEE ET AL.
Table . EL performances of multilayered devices with the synthesized compound at  mA/cm.
Volt[a]
(V)
C.E.[b]
(cd/A)
P. E. [c]
(lm/W)
C.I.E.[d]
(x, y)
EML
C-PCa
PCa-C
PDCa-C
.
.
.
.
.
.
.
.
.
(., .)
(., .)
(., .)
[a]: turn on voltage,
[b]: current efficiency,
[c]: power efficiency,
[d]: Commission International de l’Eclairage.
injection layer (EIL), and ITO and Al were respectively used as anode and cathode. The EL
performance is summarized in Table 1 and Figure 2 at 10mA/cm2.
C-PCa showed white emission of current efficiency of 1.16 cd/A and C.I.E of (0.26, 0.33).
(Figure. 3) The original emission peak of C-PCa showed at 466 nm in film state. However,
as shown EL spectrum of C-PCa, it can be seen that new emission peak has occurred about
520 nm. It probably means that exciplex has occurred within the device so, non-doped OLED
using C-PCa as EML exhibited white emission. C-PCa showed power efficiency of 0.59 lm/W,
which is the lowest power efficiency among three synthesized compounds because C-PCa had
the highest turn on voltage for 7.13 V.
Figure . EL characteristics of devices: (a) I-V-L curve (b) Current efficiency and power efficiency versus cur-
rent density.
Figure . Normalized EL spectra of C-PCa, PCa-C, and PDCa-C.

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
[313]/39
PCa-C showed current efficiency of 1.13 cd/A, power efficiency of 0.62 lm/W and C.I.E
of (0.19, 0.27). PDCa-C showed the highest current efficiency of 1.34 cd/A, power efficiency
of 0.62 and C.I.E of (0.18, 0.23). PCa-C and PDCa-C have emission in the blue region as in
film state. PDCa-C showed the highest current efficiency because carbazole, which is a chro-
mophore with high luminous efficiency, was substituted one more than C-PCa and PCa-C. In
other words, efficiency of final emitter might be found to increase with increasing efficiency
of the substituted group [14, 15].
Conclusion
Using coumrain and carbazole, chromophores with high luminous efficiency, new blue flu-
orescent compounds of C-PCa, PCa-C and PDCa-C were synthesized. This was applied to
non-doped OLED as the emitting layer, showing current efficiency of 1.16, 1.13 and 1.34 cd/A,
respectively. Among the three synthesized compounds, PDCa-C showed the highest efficiency
maintaining emission in blue region. This is because the substituent was maintained at meta-
position to avoid conjugation length from increasing, and a lot of chromophores with high
luminous efficiency were substituted.
Funding
This research was supported by a grant from the Technology Development Program for Strategic
Core Materials funded by the Ministry of Trade, Industry & Energy, Republic of Korea (Project No.
10047758). This research was also supported by National R&D Program through the National Research
Foundation of Korea(NRF) funded by the Ministry of Science & ICT (No. 2017M3A7B4041699).
References
[1] Tang, C. W., & Vanslyke, S. A. (1987). Appl. Phys. Lett., 51, 913.
[2] Zhao, Z., Deng, C., Chen, S., Lam, J. W. Y., Qin, W., Lu, P., Wang, Z., Kwok, H. S., Ma, Y., Qiu, H.,
& Tang, B. Z. (2011). Chem. Commun., 47, 8847.
[3] Giridhar, T., Han, T. H., Cho, W., Saravanan, C., Lee, T. W., & Jin, S. H. (2014). Chem. Eur. J., 20,
8260.
[4] Uoyama, H., Goushi, K., Shizu, K., Nomura, H., & Adachi, C. (2012). Nature, 492, 234.
[5] Yu, Y., Wu, Z., Li, Z., Jiao, B., Li, L., Ma, L., Wang, D., Zhou, G., & Hou, X. (2013). J. Mater. Chem.
C, 1, 8117.
[6] Kuma, H., & Hosokawa, C. (2014). Sci. Techol. Adv. Mater., 15, 034201.
[7] Hu, J. Y., Pu, Y. J., Satoh, F., Kawata, S., Katagiri, H., Sasabe, H., & Kido, J. (2014). Adv. Funct.
Mater., 24, 2064.
[8] Zhang, R., Zhao, Y., Zhang, T., Xu, L., & Ni, Z. (2016). Dyes and Pigments, 130, 106.
[9] Uoyama, H., Goushi, K., Shizu, K., Nomura, H., & Adachi, C. (2012). Nature, 492, 234.
[10] Zhang, H., Chai, H., Yu, T., Zhao, Y., & Fan, D. (2012). J. Fluoresc., 22, 1509.
[11] Jeon, S. O., & Lee, J. Y. (2012). J. Mater. Chem., 22, 7239.
[12] Yan, M. K., Tao, Y., Chen, R. F., Zheng, C., An, Z. F., & Huang, W. (2012). RSC Adv., 2, 7860.
[13] Wagner, D., Hoffmann, S. T., Heinemeyer, U., Münster, I., Köhler, A., & Strohriegl, P. (2013).
Chem. Mater., 25, 3758.
[14] Lee, H., Park, Y. I., Kim, B., Lee, J. H., & Park, J. (2014). Optical. Mater. Express., 4, 924.
[15] Niko, Y., Kawauchi, S., Otsu, S., Tokumaru, K., & Konishi, G. I. (2013). J. Org. Chem., 78, 3196.