Synthesis and properties of a thiophene-substituted diaza[7]helicene for application as a blue emitter in organic light-emitting diodes

Article abstract of DOI:10.1016/j.tetlet.2016.12.069

Carbazole-based diaza[7]helicene substituted by thiophene groups, 2,12-dithiophene-5,15-dihexyl-5,15-diaza[7]helicene (6), was synthesised successfully and confirmed by¹H NMR,¹³C NMR, High Resolution Mass Spectrometry, Time of Flight Mass Spectrometry. Compound 6 exhibited good solubility and excellent thermal stability with no melting point and a high decomposition temperature of 453.64?°C. A doped device with a structure of ITO/NPB (50?nm)/CBP: 10% 6 (30?nm)/Bphen (20?nm)/Mg:Ag (150?nm)/Ag (50?nm) emitted the blue light at 460?nm with Commission Internationale de LEclairage (CIE) coordinate of (0.176, 0.26). The maximum brightness and external quantum efficiency (EQE) were 2306?cd?m^?2and 0.41%, respectively.

Full text of DOI:10.1016/j.tetlet.2016.12.069

Accepted Manuscript
Synthesis and properties of a thiophene-substituted diaza[7]helicene for appli-
cation as a blue emitter in organic light-emitting diodes
Ting Chen, Baojie Zhang, Zhi Liu, Lian Duan, Guifang Dong, Ying Feng, Xinyu
Luo, Deliang Cui
PII:
S0040-4039(16)31724-5
DOI:
http://dx.doi.org/10.1016/j.tetlet.2016.12.069
TETL 48481
Reference:
Tetrahedron Letters
To appear in:
Received Date:
Revised Date:
Accepted Date:
2 December 2016
20 December 2016
23 December 2016
Please cite this article as: Chen, T., Zhang, B., Liu, Z., Duan, L., Dong, G., Feng, Y., Luo, X., Cui, D., Synthesis
and properties of a thiophene-substituted diaza[7]helicene for application as a blue emitter in organic light-emitting
diodes, Tetrahedron Letters (2016), doi: http://dx.doi.org/10.1016/j.tetlet.2016.12.069
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Graphical Abstract
To create your abstract, type over the instructions in the template box below.
Fonts or abstract dimensions should not be changed or altered.
Synthesis and properties of a thiophene-
substituted diaza[7]helicene for application
as a blue emitter in organic light-emitting
diodes
Leave this area blank for abstract info.
Ting Chena, Baojie Zhanga, Zhi Liua, , Lian Duanb, Guifang Dongb, Ying Fenga, Xinyu Luoa, and Deliang Cuia
aState Key Laboratory of Crystal Materials, Shandong University, Jinan, 250100 (China).
bKey Lab of Organic Optoelectronics & Molecular Engineering of Ministry of Education, Department of
Chemistry, Tsinghua University, Beijing 100084 (China)

1
Tetrahedron Letters
Synthesis and properties of a thiophene-substituted diaza[7]helicene for application as
a blue emitter in organic light-emitting diodes
Ting Chena, Baojie Zhanga, Zhi Liua, , Lian Duanb, Guifang Dongb, Ying Fenga, Xinyu Luoa, and Deliang
Cuia
aState Key Laboratory of Crystal Materials, Shandong University, Jinan, 250100 (China).
bKey Lab of Organic Optoelectronics & Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing 100084
(China)
ARTICLE INFO
ABSTRACT
Article history:
Received
Carbazole-based diaza[7]helicene substituted by thiophene groups, 2,12-dithiophene-5,15-
dihexyl-5,15-diaza[7]helicene (6), was synthesized successfully and confirmed by 1H NMR, 13
C
Received in revised form
Accepted
Available online
NMR, High Resolution Mass Spectrometry, Time of Flight Mass Spectrometry. Compound 6
exhibited good solubility and excellent thermal stability with no melting point and a high
decomposition temperature of 453.64 ℃. A doped device with a structure of ITO/NPB (50
nm)/CBP: 10% 6 (30 nm)/Bphen (20 nm)/Mg:Ag (150 nm)/Ag (50 nm) emitted the blue light at
460 nm with Commission Internationale de LEclairage (CIE) coordinate of (0.176, 0.26). The
maximum brightness and external quantum efficiency (EQE) were 2306 cd m-2 and 0.41%,
respectively.
Keywords:
Thiophene-substituted Diaza[7]helicene
fluorescence
Blue-emitting material
OLED
2009 Elsevier Ltd. All rights reserved.
materials,11 biomedicine,12 light-emitting materials on OLEDs,13-
15 and so on.
Introduction
It is well known that three kinds of RGB (red, green, blue)
emitting materials are required to meet demands of a full-color
display and white solid-state lighting. The red and green emitters
have a good development while the suitable blue-light-emitting
materials are still needed to develop and are ongoing towards
commercialization.1-6
A
carbazole-based diaza[7]-helicene, 2,12-dihexyl-2,12-
diaza[7]helicene (Compound 7) exhibited excellent thermal
stability with a high decomposition temperature (Td) of 372.1 ℃
and a high glass transition temperature (Tg) up to 203.0 ℃,
which is beneficial to the stability of device performance at high
temperature. However, the imbalanced charge injection of OLED
based on compound 7 brought damage to the performance since
the electron-injection barrier between ETL and EML was 0.93
eV while the potential barrier of the hole-injection between HTL
and EML was 0.37 eV.7 It is well known that balanced charge
injection have a positive effect on the OLED performance.
Thiophene is an electron-rich ring group and can be used to
increase the intermolecular force as a substituent attached to the
helicene core and facilitate charge transfer. Therefore, in this
paper, we introduced thiophene into the helicene to decrease the
electron-injection barrier and optimize the fluorescent properties.
2,12-dithiophene-5,15-dihexyl-diaza[7]helicene(6), was designed
and synthesized through Suzuki reaction, Mcmurry reaction and
photocyclization reaction. Compound 6 exhibited good solubility
and excellent thermal stability with a high Td of 453.64 ℃. In
differential scanning calorimetry measurement, the heating
temperature rose from room temperature to 600 ℃ and the
melting point had not appeared. This suggested that compound 6
was amorphous material, which was also proved in the fact that it
is difficult to grow single crystals. A doped device with a
Helicenes have a twisted and non-coplanar screw-shaped
configuration, which can effectively prevent close-packing effect
and decrease excited-state quenching. What’s more, their highly
twisted geometry could shorten the π-system. This characteristic
makes helicenes to be utilized in Blue-Emitting OLEDs.7,8
The group thiophene enhances the molecular fluorescence,
which is called fluorescence auxochrome. Thiophene has a
conjugated structure and the capability to donate electrons.
Therefore, it increases the conjugated system HOMO energy
level and enhances the ability to donate π electrons. At the same
time, the energy gap between HOMO and LUMO energy levels
is decreased, reducing the energy required for electrons from the
ground state to the excited state transition and facilitating the
corresponding transition. Easier electron transition is conducive
to the generation of fluorescence. Thiophene can occur
electrophilic substitution reaction on α or β position. As a
functional group attached to the core rings, it has been widely
in organic photovoltaic materials,9,10 thermoelectric
u—se—d —
 Corresponding author. Tel.: + 86-531-88362135; fax: + 86-531-88362135; E-mail: lz@sdu.edu.cn

2
Tetrahedron
structure of ITO/NPB (50 nm)/CBP: 10% 6 (30 nm)/Bphen (20
coplanar spiral structure also had a significant contribution. Such
good solubility not only overcame the formidable insolubility
problem of long helicenes, which typically form highly rigid and
annulated structures,16 but also made it possible for us to afford
homogeneous films17 and the fabrication of devices in
solution.18,19
nm)/Mg:Ag (150 nm)/Ag (50 nm) emitted blue light at 460 nm
with Commission Internationale de LEclairage (CIE) coordinates
of (0.176,0.26). The maximum luminance efficiency and
brightness were 0.70 cd A-1 (0.15 Lm W-1) and 2306 cd m-2 and
EQE was 0.41%. Compared with diaza[7]-helicene-based OLED,
compound 6-based OLED exhibited better electroluminescent
properties. The way to modify the existing helicenes through the
substitution reactions opens a new door to taking advantage of
helicenes as light emitters in OLEDs.
The thermal properties of compound 6 were investigated by
differential scanning calorimetry (DSC) and thermogravimetric
analysis (TGA) under N2. As shown in Fig. 2, the TGA was
measured from room temperature to 600 ℃. There was a weight
loss of 7.045% within 100 and 276.92 ℃, which was similar to
that of the compound 7.7 We speculated that this was caused by
the solvent absorbed in the clathrate.7 Decomposition
temperature (Td) was about 453.64 ℃, which was higher than
that of compound 7 because of the higher molecular weight.20
High Td could meet requirements of the fabricating device. The
DSC was also measured from room temperature to 600 ℃. No
melting point was found, which indicated that compound 6 might
be amorphous.
Fig. 1 Compound 6, compound 7 and thiophene
Results and discussion
The synthetic process for compound 6 was showed in Scheme
1. Compound 1 was synthesised by using phase transfer catalyst.
The hexyl could increase the solubleness of compound 6. Then,
compound 1 with DMF and POCl3 underwent Vilsmeier-Hack
reaction to afford compound 2, and NBS reacted with compound
2 to obtain compound 3. Using Suzuki reaction, compound 3
reacted with 2-thiophene boric acid to achieve compound 4.
Compound 5 was synthesised by utilizing Mcmurry reaction.
Finally, under the high pressure mercury lamp’s illumination, the
2,12-dithiophene-5,15-dihexyl-diaza[7]helicene(6) was achieved.
1
These compounds were verified by H NMR, 13C NMR, High
Resolution Mass Spectrometry, Time of Flight Mass
Spectrometry. Experimental section including materials and
instruments, device fabrication and measurement, and synthesis
was in the supplementary data.
Fig. 2 TG and DSC curves of compound 6 recorded under nitrogen at heating
rates of 10℃ min-1.
The optical properties of compound 6 were investigated by
UV-vis spectra and fluorescence-emission spectra in different
solvent and film state. As shown in Fig. 3, we measured the UV-
vis and fluorescene-emission in dichloromethane, tetrahydrofuran,
ethyl acetate, trichloromethane, N,N-dimethyl formamide. The
test concentration was 10-5 mol L-1. In the UV-vis spectra,
compound 6 had an absorption maximum peak at 310 nm, a
secondary maximum peak at 347 nm, two shoulders at 368 and
376 nm, and some small peaks at nearby 420 nm, 441 nm in
dichloromethane. When the polarity of solvents changed, a very
small red-shift or blue-shift phenomenon occurred. This indicated
that the compound 6 had a good solvent independence of UV/Vis
absorption spectra. In the film state, there was about 5 nm red-
shifted in absorption spectrum compared with those in solvents
and a new peak at 325 nm appeared. Furthermore, the main peaks
were broadened than those in the dilute solutions.21 These
phenomena could be explained by the formation of weak J-
aggregated molecules22,23 in the ground state of the thin film. In
the fluorescence emission measurement, the excitation
wavelength was 310 nm. Compound 6 emitted blue light with the
peaks at 456 and 490 nm. The shape of film spectrum was similar
to those in solvents. There was a red-shift of about 2 nm in the
emission of the thin film, which indicated that the screw and non-
coplanar molecular structure and a long hexyl substitution
attached to the helical core could effectively decrease close-
Scheme 1. Synthesis of compound 6.
Simple and convenient synthetic process and satisfactory
product yields made 6 to be gained on a large scale. Particularly,
compound 6 was achieved in a short reaction time (about 20 min)
and high productivity (71%), which gave an efficient and
convenient strategy to us to synthesize helicene derivative or
modify helicene. Compound 6 had good solubleness in common
organic solvents, because of its hexyl substituents. The non-

3
packing in the solid state. Compared with the compound 7,7 there
was a red-shift of ca. 10 nm in absorption and emission spectrum
of compound 6 due to the π-conjugation increase. Thiophene is
an electron-rich group and the delocalization of the π-electron
system along the backbone is extended by introducing thiophene
groups into the helical core. Therefore, the HOMO-LUMO
energy gap was decreased24 and the fluorescence quantum yield
was increased.25-29 Based on the UV absorption edge at 471 nm,
the band gap was calculated to be 2.32 eV, which was lower than
that of compound 7 (2.79 eV). The fluorescence quantum yields
of compound 6 in different solvents were also measured with 10-5
M Quinine sulfate aqueous solution used as a reference, whose
values were from 13% to 32% (summarized in Table 1). The
value up to 32% in ethyl acetate was the best, which increased by
more than two-fold compared with fluorescence quantum yields
from 9% to 10% of the compound 7.
Fig. 4 was the curve of electrochemical properties. The
oxidation peaks were at 1.03 V and 1.98 V, and its onset
oxidation potential was determined to be 0.80 V. According to
the equation HOMO = -[Eonset(ox)-E1/2,Fc/Fc++4.8] eV,31 the HOMO
energy level was calculated to be -4.95 eV. Correspondingly, the
LUMO energy level was located at -2.63 eV.
Fig. 4 CV of compound 6 in CH2Cl2 (0.1 mol L-1 Bu4NClO4) at a scanning
rate of 200 mV s-1.
Electroluminescence properties of compound
6
were
examined by using the configuration of ITO/NPB (50
nm)/Emitter (30 nm)/Bphen (20 nm)/Mg:Ag (150 nm)/Ag (50
nm). Layers of the device A based on compound 6 were
fabricated by vacuum evaporation. The device configuration and
the energy diagram were shown in Fig. 5. The EL properties of
compound 6 and 7 were summarized in Table 2.
Fig. 3 UV-vis and fluorescence-emission normalized spectra of compound 6
at different solvent and film.
Table 1. The maximum absorption wavelength, maximum
emission wavelength and corresponding fluorescence
quantum yield of compound 6 at different solvent.
e
a
Solvent
max [a](nm)
[b](nm)
Фf[c](%)
max
Dichloromethane
Tetrahydrofuran
Ethyl acetate
310
308
306
307
456
23
17
32
13
453
452
456
Fig. 5 (a) The configuration of device A: ITO/NPB (50 nm)/Emitter (30
nm)/Bphen (20 nm)/Mg:Ag (150 nm)/Ag (50 nm). (b) Energy-level diagram
of device A (relative to the vacuum energy level).
Trichloromethane
N,N-
309
456
19
Dimethylformamide
maax
max
a
b
c
maximum absorption wavelength.
maximum emission wavelength excited at 313 nm.
e
Фf
PL quantum yields calculated using a quinine sulfates in 0.1 mol L-1
H2SO4. .
The electrochemical properties were identified by cyclic
voltammetry under N2. A three-electrode cell with a Pt working
electrode, a glassy carbon assistant electrode, a saturated
Ag/AgCl reference electrode was utilized. The potential of a
saturated Ag/AgCl reference electrode in the purified
dichloromethane (0.1 M tetrabutylammonium perchlorate) was
calibrated by using ferrocene (Fc/Fc+) redox system.30 In this
measurement, the half-wave potential of Fc/Fc+ was 0.65 eV
versus Ag/AgCl.
Fig. 6 The normalized emission spectra of compound 6 in dichloromethane,
thin-film and device A.

4
Tetrahedron
Fig. 6 depicted EL spectrum of device A at the driving
improve the PL and EL performance, especially fluorescence
quantum yield and the external quantum efficiency.
voltage of 8 V and PL spectra of compound 6 in dichlormethane
and solid state film. Device A emitted blue light with two peaks
at 460 and 488 nm with the CIE coordinate of (0.176, 0.260). The
maximum peak of the device had a slight red-shift of about 4 nm
compared to that at 456 nm in dichloromethane. EL spectrum of
device A was almost consistent with the PL spectra of compound
6 in thin-film and dichlormethane (Fig. 6). This suggested that
the EL of device A originated from compound 6 and compound 6
in the emitting layer was maintained in a good amorphous state.
According to the energy level diagram presented in Fig. 5, there
were energy barriers of 0.73 eV for ITO/NPB junction and 0.77
eV for the NPB/CBP junction. Since HOMO energy level of
compound 6 was higher than those of NPB and CBP, hole-
accumulation occurred at the interface between NPB and the
emitting layer. The electron-injection barriers ranged from 0.4 eV
to 0.8 eV. Similarly, the electrons appeared at the interface of the
blue-emitting layer and Bphen layer. These injection barriers
were responsible for the slightly high turn-on voltage of 5.2 V
(Table 2).
Fig.7(a) The power efficiency and current efficiency of device A.
The power efficiency, current efficiency and current density–
voltage–luminance (J–V–L) characteristics of device A were
shown in Fig. 7. Introducing thiophene into compound 7 resulted
in the decrease of the LUMO energy level and the increase of the
HOMO energy level relative to those of compound 7. Therefore,
the band gap was reduced and corresponding spectra were red-
shifted. The device achieved maximum brightness of 2302 cd m-2,
maximum current efficiency of 0.70 cd A-1, maximum power
efficiency of 0.15 lm W-1. The maximum external quantum
efficiency of 0.41% was almost twice as much as that of device 1
based on compound 7.
The maximum external quantum efficiency of the device was
attributed to the following factors: 1) Fluorescence quantum
yields of compound 6 in solvents were increased. 2) Introducing
thiophene into compound 7 decreased the electronic injection
barrier of device A, whose value was 1.2 eV. In contrast, that of
the device 1 based on compound 7 was 1.43 eV. 3) The ability of
hole transport and injection by introduction thiophene into
compound 7 was enhanced. Generally, the EL performance of the
device A was superior to that of the device 1. These results
manifested that introduction thiophene into compound 7 could
Fig.7(b) The Current density (J)-voltage (V)-brightness (B) curve of device A.
Table 2. The properties of devices based on compound 6 and compound 7.
Device
V
onseta［V］
B
maxb［cd m-2］
η
c, maxc［cd A-1］
ηp, maxd［lm W-1］
CIE e［x,y］
λ
maxe［nm］
η
ext, maxf［%］
A
5.2
2302
0.70
0.15
(0.176,0.260)
460
0.41
based
on 6
1 based
on 77
5.3
2365
0.22
0.09
(0.150,0.100)
446
0.23
aVonset: The turn-on voltage was measured at the brightness of 1 cd m-2.
bBmax: The maximum brightness was measured at 18 V and 14.6 V, respectively.
cηc, max: The maximum current efficiency was measured at 14.6 V and 11.8V, respectively.
dηp, max: The maximum power efficiency was measured at 14.6 V and 7.1 V, respectively.
eThe CIE coordinate and emission peak was measured at 10 V and 8 V, respectively.
fηext
, max: The external quantum efficiency was calculated by using relevant current efficiency.

5
7. Shi, L.; Liu, Z.; Dong, G.; Duan, L.; Qiu, Y.; Jia, J.; Guo,W.;
Zhao, D.; Cui, D.; Tao, X. Chem-Eur. J. 2012, 18, 8092-8099.
8. Hua,W.; Liu, Z.; Duan,L.; Dong, G.; Qiu, Y.; Zhang, B.; Cui, D.;
Tao, X.; Cheng, N.; Liu, Y. RSC Adv. 2015, 5, 75-84.
9. Stylianakis, M. M.; Mikroyannidis, J. A.; Kymakis, E. Sol. Energ.
Mat. Sol. C. 2010, 94, 267–274.
Conclusion
A
thiophene modified carbazole-based diaza[7]helicene,
namely, 2,12-dithiophene-5,15-dihexyl-diaza[7]helicene(6), was
synthesised by a photochemical synthesis and characterized by
1H NMR, 13C NMR, HRMS, MS (MALDI-TOF). Its thermal,
10. Bronstein, H.; Chen, Zh. Y.; Ashraf, R. Sh.; Zhang, W. M.; Du, J.
photophysical,
electrochemical,
and
electroluminescent
P.; Durrant, J. R.; Tuladhar, P. S.; Song, K.; Watkins, S. E.; Geerts,
Y.; Wienk, M. M.; Janssen, R. A. J.; Anthopoulos, T.; Sirringhaus,
H.; Heeney, M.; McCulloch, I. J. Am. Chem. Soc. 2011, 133, 3272–
3275.
properties were investigated. The study indicated that the
compound 6 owned good solubility and high thermal stability
and exhibited better photophysical, electrochemical, and
electroluminescent properties compared with the compound 7
and showed that the introduced thiophene could optimize the
structure and improve the performance and have the potential to
use in other organic light-emitting material. An OLED that
included compound 6 as the guest emitter with the configuration
ITO/NPB (50 nm)/Emitter (30 nm)/Bphen (20 nm)/Mg:Ag (150
nm)/Ag (50 nm) emitted blue light at 460 and 488 nm with the
CIE coordinate of (0.176, 0.260). The device achieved maximum
brightness of 2302 cd m-2, maximum current efficiency of 0.70
cd A-1, maximum power efficiency of 0.15 lm W-1, the maximum
external quantum efficiency of 0.41%. It was worth noting that
introducing thiophene into diaza[7]helicene could improve the
PL and EL performance, especially fluorescence quantum yield
and the external quantum efficiency, whose values were nearly a
two-fold increase.
11. Liu, C.; Jiang, F.; Huang, M.; Yue, R.; Lu, B.; Xu, J.; Liu, G. J.
Electron. Mater. 2011, 40(5), 648-651.
12. Rozlosnik, N. Anal. Bioana. Chem. 2009, 395, 637-645.
13. Park, S. M.; Ebihara, K. J.; Ikegami, T.; Lee, B. J.; Lim, K. B.; Shin,
P. K. Curr. Appl. Phys. 2007, 7, 474-479.
14. Kumar, N. S.; Clement, J. A.; Mohanakrishnan, A. K. Tetrahedron.
2009, 65, 822-830.
15. Panchamukhi, S. I.; Belavagi, N.; Rabinal, M. H.; Khazi, I. A. J.
Fluoresc. 2011, 21, 1515-1519.
16. Rajca, A.; Pink, M.; Xiao, S.; Miyasaka, M.; Rajca, S.; Das, K.;
Plessel, K. J. Org. Chem. 2009, 74, 7504 –7513.
17. Zhu, M.; Ye, T.; Li, C.; Cao, X.; Zhong, C.; Ma, D.; Qin, J.; Yang,
C. J. Phys. Chem. C. 2011, 115, 17965–17972.
18. Sonar, P.; Soh, M. S.; Cheng, Y. H.; Henssler, J. T.; Sellinger, A.
Org. Lett. 2010, 12(15), 3292 –3295.
19. Zhang, M.; Xue, S.; Dong, W.; Wang, Q.; Fei, T.; Gu, C.; Ma, Y.
Chem. Commun. 2010, 46, 3923–3925.
20. Tang, C.; Liu, F.; Xia, Y. J.; Lin, J.; Xie, L. H.; Zhong, G. Y.; Fan,
Q. L.; Huang, W. Org. Electron. 2006, 7, 155-162.
21. An, T. K.; Hahn, S. H.; Nam, S.; Cha, H.; Rho, Y.; Chung, D. S.;
Ree, M.; Kang, M. S.; Kwon, S. K.; Kim, Y. H.; Park, C. E. Dyes
Pigm. 2013, 96, 756-762.
22. Spano, F. C. Annu. Rev. Phys. Chem. 2006, 57, 217-243.
23. Spano, F. C. Accounts. Chem. Res. 2010, 43(3), 429-439.
24. Promarak, V.; Saengsuwan, S.; Jungsuttiwong, S.; Sudyoadsuk, T.;
Keawin, T. Tetrahedron Lett. 2007, 48, 89–93.
25. Chavez, R.; Cai, M.; Tlach, B.; Wheeler, D. L.; Kaudal, R.;
Tsyrenova, A.; Tomlinson, A. L.; Shinar, R.; Shinar, J.; Jeffries-El,
M. J. Mater. Chem. C, 2016, 4, 3765–3773.
26. Data, P.; Kurowska, A.; Pluczyk, S.; Zassowski, P.; Pander, P.;
Jedrysiak, R.; Czwartosz, M.; Otulakowski, L.; Suwinski, J.;
Lapkowski, M.; Monkman, A. P. J. Phys. Chem. C. 2016, 120,
2070–2078.
27. Kim, S. K.; Yang, B.; Ma, Y.; Lee, J. H.; Park, J. W. J. Mater.
Chem. 2008, 18, 3376–3384.
28. Huang, J.; Su, J. H.; Li, X.; Lam, M. K.; Fung, K. M.; Fan, H. H.;
Cheah, K. W.; Chen, C. H.; Tian, H. J. Mater. Chem. 2011, 21,
2957–2964.
29. Tao, S.; Zhou, Y.; Lee, C. S.; Lee, S. T.; Huang, D.; Zhang, X. J.
Phys. Chem. C. 2008, 112, 14603–14606.
30. Connelly, N. G.; Geiger, W. E. Chem. Rev. 1996, 96, 877–910.
31. Michinobu, T.; Osako, H.; Shigehara, K. Macromolecules. 2009,
42, 8172–8180.
Acknowledgements
The research was supported by the Natural Science
Foundation of Shandong Province [grant number ZR2015EM006]
and the National Natural Science Foundation of China [grant
number 51372143].
Supplementary data
1
Supplementary data (experimental section, and H NMR，
13C NMR, HRMS, MALDI-TOF spectra of compounds 1-6)
associated with this article can be found, in the online version, at
http://dx.doi.org/10.1016/
.
References
1. Wang, P.; Hong, Z.; Xie, Z.; Tong, S.; Wong, O.; Lee, C. S.; Wong,
N.; Hung, L.; Lee, S. Chem. Commun. 2003, 1664–1665.
2. Tsuzuki, T.; Tokito, S. Adv. Mater. 2007, 19, 276–280.
3. Cocchi, M.; Virgili, D.; Fattori, V.; Rochester, D. L.; Williams, J. A.
G. Adv. Funct. Mater. 2007, 17, 285–289.
4. Zhu, M.; Yang, C. Chem. Soc. Rev. 2013, 42, 4963–4976.
5. Liu, C.; Fu, Q.; Zou, Y.; Yang, C.; Ma, D.; Qin, J. Chem. Mater.
2014, 26, 3074–3083.
6. Hancock, J. M.; Gifford, A. P.; Tonzola, C. J.; Jenekhe, S. A. J.
Phys. Chem. C. 2007, 111, 6875–6882.

7
Highlights



A synthetic route to a thiophene-
substituted diaza[7]helicene was
demonstrated.
Fluorescence quantum yield up to 32%
of this compound in acetidin was
reported.
Great improvement of EQE of 0.41% of
a doped OLED based on this compound
was made.