Preparation and luminescence properties of isoquinoline-nucleated polycyclic aromatics

Article abstract of DOI:10.1016/j.dyepig.2019.107803

Two isoquinoline-nucleated polycyclic aromatic compounds, 4,5-diphenyl-7H-dibenzo[de,g]quinolin-7-one (A) and 3,4-diphenyl-6H-phenanthro[3,4,5-defg]quinolin-6-one (B), were synthesized in high yields through three-component reaction of phenanthrene diketone or pyrene diketone, ammonium acetate and 1,2-diphenylethyne in one-pot. Their structures, thermal stabilities, photophysical properties and energy levels are investigated systematically. Both compounds emit very weak fluorescence in acetone, but their luminescence intensity increased significantly when the water content reaches 50% for A and 40% for B, exhibiting aggregation-induced emission (AIE) characteristics, and showing that the AIE effect of the compound A is stronger than that of the compound B. The vacuum-processed doped devices based on the compound B showed green emission with a maximum brightness of 2162 cd/m², a maximum current efficiency of 2.97 cd/A and a maximum external quantum efficiency (EQE) of 2.23%.

Full text of DOI:10.1016/j.dyepig.2019.107803

Journal Pre-proof
Preparation and luminescence properties of isoquinoline-nucleated polycyclic
aromatics
Yanmei Li, Xinyu Li, Tianzhi Yu, Wenming Su, Youjia Wang, Yuling Zhao, Hui Zhang
PII:
S0143-7208(19)31498-6
DOI:
https://doi.org/10.1016/j.dyepig.2019.107803
DYPI 107803
Reference:
To appear in: Dyes and Pigments
Received Date: 30 June 2019
Revised Date: 7 August 2019
Accepted Date: 15 August 2019
Please cite this article as: Li Y, Li X, Yu T, Su W, Wang Y, Zhao Y, Zhang H, Preparation and
luminescence properties of isoquinoline-nucleated polycyclic aromatics, Dyes and Pigments (2019), doi:
https://doi.org/10.1016/j.dyepig.2019.107803.
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Graphical Abstract:
N
O
B

Preparation and luminescence properties of isoquinoline-nucleated
polycyclic aromatics
Yanmei Li‡1, Xinyu Li‡1, Tianzhi Yu1,*, Wenming Su2,*, Youjia Wang1, Yuling Zhao3, Hui
Zhang1
1Key Laboratory of Opto-Electronic Technology and Intelligent Control (Ministry of Education),
Lanzhou Jiaotong University, Lanzhou 730070, China
2Printable electronics research center, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese
Academy of Sciences, Suzhou 215123, China
3School of Chemical and Biological Engineering, Lanzhou Jiaotong University, Lanzhou 730070,
China
Abstract:
Two
isoquinoline-nucleated
polycyclic
aromatic
(A)
compounds,
and
4,5-diphenyl-7H-dibenzo[de,g]quinolin-7-one
3,4-diphenyl-6H-phenanthro[3,4,5-defg]quinolin-6-one (B), were synthesized in high yields
through three-component reaction of phenanthrene diketone or pyrene diketone, ammonium
acetate and 1,2-diphenylethyne in one-pot. Their structures, thermal stabilities, photophysical
properties and energy levels are investigated systematically. Both compounds emit very weak
fluorescence in acetone, but their luminescence intensity increased significantly when the water
content reaches 50% for A and 40% for B, exhibiting aggregation-induced emission (AIE)
characteristics, and showing that the AIE effect of the compound A is stronger than that of the
compound B. The vacuum-processed doped devices based on the compound B showed green
* Corresponding Authors.
Tianzhi Yu, E-mail: yutzh@mail.lzjtu.cn; Wenming Su, E-mail: wmsu2008@sinano.ac.cn
‡
These authors are contributed equally
1

emission with a maximum brightness of 2162 cd/m2, a maximum current efficiency of 2.97 cd/A
and a maximum external quantum efficiency (EQE) of 2.23%.
Key words: Polycyclic aromatic compound; Alkyne annulation; Aggregation-induced emission
(AIE); Photoluminescence; Electroluminescence
1. Introduction
Polycyclic aromatic hydrocarbons (PAHs), such as anthracen, pyrene and perylene, have been
used widespreadly in molecular electronics, optoelectronics, energy conversion devices and
various other forms of nanotechnology due to their chemical stabilities and photochemical
properties [1-6]. Due to the high abilities of fluorescence and charge-transport, PAHs are widely
used as the building blocks for molecular materials for organic electronics [7-11]. Recently,
numerous heteroaromatic ring fused PAHs exhibit fundamentally interesting and even practically
useful electrochemical and photophysical properties as the components of organic electronic
devises [12-16]. Therefore, the synthesis and structural elucidation of heteroaromatic ring fused
PAHs are of high interest [17-22]
.
Transition metal-catalyzed activation and functionalization of normally unreactive C–H
bonds have become an increasingly efficient and reliable approach for new carbon–carbon and
carbon–heteroatom bond formations [23-26], which allows the use of less expensive and more
readily available starting materials to obtain complex compounds in an atom- and step-economic
way. Since Murai and coworkers first reported on ruthenium(0)-catalyzed addition of aromatic C–
H bonds to alkenes [27], various transition metal complexes have been employed as catalysts for C–
H bond functionalization to produce a variety of heterocycles over the past decades. Among the
2

transition metal catalysts, the oxidative cyclization reactions of the alkenes and alkynes by
utilizing the less expensive and stable rhodium (III) complex [Cp*RhCl2]2 were proved to be a fast
access to heterocycles due to the high efficiency, selectivity and functional group tolerance [25]. In
the past few years, the [Cp*RhCl2]2-catalyzed annulation of various aromatic substrates with
alkynes using Cu(OAc)2·H2O as the oxidant was extensively used in the synthesis of heterocyclic
compounds. For example, the treatment of the substituted aromatic acids with alkynes using
[Cp*RhCl2]2 and Cu(OAc)2·H2O in o-xylene or DMF under N2 can afford various isocoumarin
[29]
products in good yields [28]. In the presence of Co(OAc)2·4H2O as the co-catalyst, Wang et al.
synthesized
a
series
of
naphtho[1′,2′:4,5]imidazo[1,2-a]pyridines
from
2-arylimidazo[1,2-a]pyridines and alkynes via Rh-catalyzed ([Cp*RhCl2]2) double C-H activation,
in which some products exhibited deep blue emissions. The Hua group reported an efficient
method for the synthesis of ring-fused and π-extended phenanthroimidazoles from one-pot
four-component reaction of 9,10-phenanthraquinone, ammonium acetate, aldehydes and alkynes
using [Cp*RhCl2]2 catalyst associated with the oxidant Cu(OAc)2·H2O in trifluoroethanol (TFE)
[30]. Recently, our group also reported two luminescent phenanthroimidazoisoquinoline derivatives
via facile multicomponent reaction in one-pot [12]
.
For some π‒conjugated planar organic compounds, they exhibit strong emission in the dilute
solutions, but their fluorescence is weakened or even quenched in the concentrated solution and
solid state due to the concentration-quenching effect (CQE) or the aggregation-caused quenching
(ACQ) caused by the strong intermolecular π‒π stacking interactions between neighboring
fluorophores [31,32]. The CQE and ACQ phenomena of luminophores in the concentrated solutions
and solid states drastically limit their practical applications as fluorescence sensors, biological
3

probes, polarized light emitters, emitting materials in organic light-emitting diodes (OLEDs), etc.
Although introduction of bulky substituents into molecular structures of the luminophores can
help change luminophores from being weakly luminescent to strongly emissive in the solid state
[33-35], this strategy can not fundamentally solve the CQE and ACQ effects because the aggregate
formation is an intrinsic process for luminogenic molecules in the condensed phase. In 2001, Tang
group first discovered the aggregation-induced emission (AIE) phenomenon that some
fluorophores were non-emissive in dilute solutions but became highly luminescent in concentrated
solutions or in solid films [36,37]. So far several kinds of luminescent materials with AIE effect have
been synthesized and successfully applied in OLEDs, probes and optical memory materials [38-43]
.
As a part of our continuous researches in developing new luminescent polycyclic aromatic
hydrocarbons (PAHs) for OLEDs, in this study, two new isoquinoline-nucleated polycyclic
aromatics with AIE effect were synthesized by one-pot method. Their photophysical and AIE
properties and thermal stability of the compounds were investigated. In addition, the investigation
of the vacuum-processed OLED devices and performances using the compounds as emitting
materials were also reported.
2. Experimental
2.1 Materials and methods
Phenanthrene-9,10-dione, pyrene, N-methylimidazole (NMI), NaIO3, RuCl3•3H2O,
1,2-diphenylacetylene and 2,2,2-trifluoroethanol (TFE) were obtained from Energy Chemical
(China). Bis[(pentamethylcyclopentadienyl)dichloro-rhodium] ([Cp*RhCl2]2) was purchased from
Beijing HWRK Chem. Co. LTD (China). All the other chemicals were analytical grade reagent.
4

Toluene was dried over sodium and freshly distilled prior in the related reaction.
13
1H and C NMR spectra were recorded on Bruker 500, AVANCE NEO. Mass spectra were
recorded using a Thermo Scientific Orbitrap Elite mass spectrometer. C, H, and N analyses were
obtained using an Elemental Vario-EL automatic elemental analysis instrument.
Thermogravimetric analysis (TGA) was performed on a PerkinElmer Pyris system. UV-vis
absorption spectra were recorded on a Shimadzu UV-2550 spectrometer. The cyclic
voltammograms were performed on a electrochemical analyzer (CHI Instruments 760 B). The
photoluminescence quantum yield was measured by an absolute method using the Edinburgh
Instruments FLS920 integrating sphere with the Xe lamp at room temperature. The
photoluminescence decay lifetime was measured by a time-correlated single photon counting
spectrometer using Edinburgh Instruments FLS920 with a microsecond flashlamp as the excitation
source (repetition rate 90 Hz) at room temperature.
2.2 Synthesis and characterization of the 4,5-diphenyl-7H-dibenzo[de,g]quinolin-7-one (A)
and 3,4-diphenyl-6H-phenanthro[3,4,5-defg]quinolin-6-one (B)
Pyrene-4,5-dione: The intermediate pyrene-4,5-dione was prepared according to the
literature [44]. Pyrene (5.00 g, 24.72 mmol), NMI (0.10 g, 1.22 mmol) and RuCl3•3H2O (0.65 g,
2.49 mmol) were dissolved in the mixed solvent of DCM (100 mL), THF (100 mL) and H2O (125
mL). Then, NaIO4 (23.80 g, 111.27 mmol) was added in small portions over 5 min. The reaction
mixture was stirred for 2 h under a nitrogen atmosphere. The resulting mixture was poured into
200 mL of water and extracted with dichloromethane (3 × 100 mL). The organic phase was
washed with water (2 × 100mL) and dried over anhydrous Na2SO4. After filtration and
evaporation of the solvent in vacuum, the crude was purified by chromatography on silica gel
5

using dichloromethane/petroleum ether (1:5, v/v) as the eluent to obtain pyrene-4,5-dione (2.81 g,
48.95%). 1H NMR (500 MHz, CDCl3, δ): 8.50 (d, J = 7.4 Hz, 2H), 8.19 (d, J = 8.0 Hz, 2H), 7.86
(s, 2H), 7.79 (t, J = 7.7 Hz, 2H).
4,5-diphenyl-7H-dibenzo[de,g]quinolin-7-one (A): Phenanthrene-9,10-dione (1.00 g, 4.80
mmol), NH4OAc (1.08 g, 14.01 mmol), [Cp*RhCl2]2 (0.30 g, 0.48 mmol), Cu(OAc)2·H2O (4.80 g,
23.08 mmol) and 1,2-diphenylacetylene (2.22 g, 23.62 mmol) were dissolved in 120 mL of TFE.
o
The reaction mixture was refluxed at 120 C for 24 h under a nitrogen atmosphere. After solvent
was evaporated in vacuum, the mixture was dissolved in dichloromethane, washed with water (3 ×
100 mL). The organic layer was dried over anhydrous Na2SO4 and concentrated in vacuum. The
residue was chromatographed on silica using dichloromethane/petroleum ether (1:50, v/v) as the
eluent to form faint yellow solid (1.50 g, 81.43%). m.p.: > 260 . 1H NMR (500 MHz, CDCl3, δ):
8.56 (d, J = 7.8 Hz, 1H), 8.41 (d, J = 7.0 Hz, 1H), 8.31 (d, J = 8.0 Hz, 1H), 7.83-7.73 (m, 3H),
7.60 (t, J = 8.0 Hz, 1H), 7.47-7.45 (m, 2H), 7.41-7.39 (m, 3H), 7.30-7.28 (m, 2H), 7.25-7.21 (m,
3H). 13C NMR (126 MHz, CDCl3, δ): 182.40, 153.48, 145.63, 139.88, 136.98, 136.61, 135.69,
135.01, 133.84, 131.70, 131.12, 130.64, 130.61, 129.10, 128.94, 128.49, 128.31, 127.92, 127.86,
127.67, 127.56, 123.95, 123.43, 123.15. HRMS: Calcd. for C28H17NO, 384.1310 [M+1]; Found:
384.1387. Anal. Calcd. for C28H17NO: C, 87.71; H, 4.47; N, 3.65. Found: C, 87.63; H, 4.49; N,
3.68.
3,4-diphenyl-6H-phenanthro[3,4,5-defg]quinolin-6-one (B): The preparation of the
compound B was similar to the compound A, which was obtained from the reaction between
pyrene-4,5-dione (1.50 g, 6.46 mmol) and 1,2-diphenylacetylene (0.73 g, 7.77 mmol) in the
presence of NH4OAc (1.50 g, 19.46 mmol), Cu(OAc)2·H2O (3.22 g, 14.58 mmol) and
6

[Cp*RhCl2]2 (0.11g, 0.18mmol). The crude was chromatographed on silica, eluting with
dichloromethane/petroleum ether (1:50, v/v) to form faint yellow solid (2.00 g, 75.99%). m.p.: >
260 . 1H NMR (500 MHz, CDCl3, δ): 8.95 (d, J = 7.2 Hz, 1H), 8.36 (d, J = 8.0 Hz, 1H), 8.18 (d,
J = 8.8 Hz, 1H), 8.06 (d, J =8.8 Hz, 1H), 8.01 (d, J =8.5 Hz, 1H), 7.94 (d, J = 7.5 Hz, 1H), 7.91 (d,
J = 9.5 Hz, 1H), 7.50 (t, J = 7.5 Hz, 2H), 7.44 (d, J = 4.9 Hz, 3H), 7.35 (t, J = 5.2 Hz, 2H), 7.25 (t,
J = 4.6 Hz, 3H). 13C NMR (126 MHz, CDCl3, δ): 182.90, 154.77, 146.30, 140.22, 136.72, 136.12,
135.69, 134.96, 131.56, 131.44, 131.35, 131.24, 130.73, 130.50, 130.46, 129.47, 128.38, 127.96,
127.73, 127.62, 127.47, 126.75, 126.09, 123.66, 121.50. HRMS: Calcd. for C30H17NO, 408.1310
[M+1]; Found: 408.1367. Anal. Calcd. for C30H17NO: C, 88.43; H, 4.21; N, 3.44. Found: C, 88.50;
H, 4.19; N, 3.46.
2.3 Crystallography
Suitable single crystal of the compound A obtained from its ethyl acetate solution was
selected for data collection that was performed on Bruker Smart Apex CCD diffractometer
equipped with graphite-monochromatic Mo Kα radiation (λ = 0.71073 Å) at 298 (2) K. Its
structures were solved by direct methods and refined by full-matrix least-squares method on F2
using SHELXL.
3. Results and discussion
3.1 Synthesis and characterization
The compound A and B were synthesized from one-pot three-component reaction of the
corresponding diketone (phenanthrene-9,10-dione or pyrene-4,5-dione), ammonium acetate and
1,2-diphenylacetylene using [Cp*RhCl2]2 catalyst associated with the oxidant Cu(OAc)2·H2O in
7

trifluoroethanol (TFE), as shown in Scheme 1.
Scheme 1. Synthetic routes to the compounds A and B.
Scheme 2. The supposed reaction mechanism for the compound A.
Based on the previous report [45], we herein propose the rhodium (III)-catalyzed annulation
mechanism depicted in Scheme 2. Phenanthrene-9,10-dione is transferred into imine I readily.
Initially, the reactive Cp*Rh(OAc)2 II is in situ generated from [Cp*RhCl2]2 and Cu(OAc)2 via
acetate-Cl exchange. While treated with the catalyst II, the imine I undergoes the C-H and N-H
cleavages and produces five-membered cyclic Rh-intermediate III. Then, the intermolecular
8

insertion of the alkyne into the Rh-C bond of III affords the seven-membered rhodiumcyclic
intermediate IV. Subsequently, the intramolecular oxidative coupling of the C-N bond of IV and
simultaneous reductive elimination of L-Rh V from Rh(III) to Rh(0) releases the
isoquinoline-nucleated aromatic cyclic product. Finally, the catalyst Cp*Rh(OAc)2 II is
regenerated via re-oxidation of Rh(0) intermediate V by Cu(OAc)2.
The compound A and B were purified by chromatography to yield pure solid products, and
1
characterized using H NMR, 13C NMR and high resolution mass spectra. In addition, the
molecular structure of the compound A was further confirmed by X-ray crystallography.
The crystal structure of the compound A is shown in Fig. 1. The crystal of the compound I
belongs to the monoclinic space group P2(1)/c, a = 13.2489(11) Å, b = 8.4596(8) Å, c =
18.1875(15) Å, α = γ = 90o, β = 103.057(2)o, U = 1985.8(3) Å3, Z = 4, Dc = 1.283 g cm-3, µ =
0.077 mm-1. As shown in Fig. 1, the dibenzo[de,g]quinolin-7-one framework is nearly on a plane,
and the dihedral angles between dibenzo[de,g]quinolin-7-one skeleton and the two propeller-like
benzene rings are 51.94o and 60.71o, respectively. The dihedral angle between the two benzene
rings in the propeller-like diphenylethylene moiety is 49.97o.
Fig. 1. Crystal structure of the compound A.
3.2 Thermal properties of the compounds
The thermal stabilities of the compound A and B were investigated by thermal gravimetric
9

analysis (TGA) measurements in nitrogen atmosphere, and the TGA curves of the compounds are
o
given in Fig. 2. The compounds showed good thermal stability up to 360 C (˂ 2% weight loss),
and the thermal decomposition temperature of the compound B (396 oC) is higher than that of the
compound A (369 oC). From their molecular structures, the conjugation and size of the polycyclic
aromatic skeleton of the compound B is larger than that of the compound A, the π-π interaction of
the polycyclic aromatic skeleton between the compound B molecules should be stronger, thus the
thermal stability of the compound B is better than that of the compound A. Their thermal
decomposition temperatures are over than 360 °C, these compounds are suitable for the fabrication
of OLED devices by evaporation.
Compound A
Compound B
100
90
80
70
60
50
0
100 200 300 400 500 600 700 800
Temperature (oC)
Fig. 2. Thermogravimetric analyses (TGA) of the compound A and B in
nitrogen atmosphere (heating rate: 10 °C/min).
3.3 Photophysical and electrochemical properties of the compounds
The UV–vis absorption and photoluminescence (PL) spectra of the compounds in
dichloromethane solutions are shown in Fig. 3, and their photophysical data are summarized in
Table 1.
As shown in Fig. 3, the compound A exhibited three absorption bands at 253, 324 and 418
nm, respectively, which could be attributed to π→π* transition of the polycyclic aromatic skeleton.
10

Compound with the compound A, the absorption bands of the compound B were red-shifted and
three absorption bands were located at 257, 325 and 427 nm due to the extended π-conjugation
caused by the aromatic ring expansion of the polycyclic aromatic skeleton. This spectral redshift
also occurs in their photoluminescence spectra, it is found that the compound A and B exhibited
green emission with peaks at 510 and 537 nm, respectively. The absolute photoluminescence
quantum yields (Φf) of the compound A and B in dichloromethane solutions (ca. 10−6 mol/L) were
measured to be 5.30% and 6.20% at room temperature, and their photoluminescence decay
lifetimes were measured to be 23.44 and 9.75 ns. The decay profiles monitored at the respective
emission maximum wavelengths are given in Fig. 4.
Compound A
Compound B
Compound A
Compound B
1.0
0.8
0.6
0.4
0.2
0.0
1.0
0.8
0.6
0.4
0.2
0.0
300
400
500
600
700
Wavelength (nm)
Fig. 3. UV–vis absorption and photoluminescence spectra of the compound A
and B in dichloromethane solutions (C = 1.0 × 10−5 mol/L).
From the photoluminescence quantum yields (Φf) and the photoluminescence decay lifetimes
(τ) of the compound A and B, the radiative rate constants (kr) and nonradiative rate constants (knr)
of the compound A and B were approximately calculated according to the equations [46]: kr = Φf/τ
and knr = (1-Φf)/τ, assuming that ΦISC = 1 (ISC = intersystem crossing). The radiative rate
constants of the compound A and B were calculated to be 2.26 × 106 and 6.36 × 106 s-1, and their
nonradiative rate constants were calculated to be 4.04 × 107 and 9.62 × 107 s-1, respectively.
11

Compound B
Compound A
5000
4000
3000
2000
1000
0
0
20
40
60
80
100
Time (ns)
Fig. 4. Photoluminescence decay lifetimes of the compounds in
dichloromethane solutions at room temperature (C = 1.0 × 10−6 mol/L).
Compound A (solution)
Compound B (solution)
1.0
Compound A (film)
Compound B (film)
0.8
0.6
0.4
0.2
a
0.0
250
300
350
400
450
500
550
Wavelength (nm)
250
Compound A (solution)
Compound B (solution)
Compound A (film)
Compound B (film)
200
150
100
50
30 times
b
0
450
500
550
600
650
Wavelength (nm)
Fig. 5. The contrast diagrams of UV–vis absorption (a) and photoluminescence
spectra (b) of the compound A and B in dichloromethane solutions (C = 1.0 ×
10−5 mol/L) and in the solid films.
12

In order to compare the UV-vis absorption and photoluminescence spectra of the compounds
in the solutions and solid films, Fig. 5 shows the constrast diagrams of UV–vis absorption and
photoluminescence spectra of the compounds in two states of existence. From Fig. 5(a), the
absorption spectra of the compounds in the solid films are similar to those in the solutions, but
their absorption spectra in the solid films shift red. However, the fluorescence quenching of the
compounds is very serious in the solid films, and the emissions of the compounds in the solid
films are very weak (Fig. 5(b)). When the PL intensities were magnified 30 times, their emission
bands in the solid films could be observed (emission peaks at 511 and 538 nm), which strongly
resemble those in the solutions.
Additionally, it was found that these two compounds exhibited a certain aggregation-induced
emission (AIE) phenomenon. Both compounds are soluble in many common organic solvents such
as tetrahydrofuran, chloroform, toluene, acetonitrile and acetone, slightly soluble in methanol, and
insoluble in water. To determine whether the compound A and B possess AIE behaviors, their
fluorescent behaviors were investigated in acetone/water mixture solvent with different water
fractions (fw, vol%) (C = 1.0 × 10-4 mol/L). As shown in Fig. 6(a), in dilute acetone solution, the
compound A was almost non-emissive under excitation at 418 nm. Afterwards, the
photoluminescence intensity of the compound A gradually increased with increasing the content
of water, and its emission spectrum also shifted slightly to longer wavelength region. When the
content of water (fw) reached to 50% in acetone/water, the photoluminescence intensity of the
compound A reached the maximum value (ca. 1192), which was about 80-fold higher than that in
acetone. When fw was over 50%, the fluorescence intensity tended to decrease gradually. The
emission intensity of the compound A in acetone/water with fw of 90% was about 15.8-fold higher
13

than that in acetone. The compound B also exhibited a fluorescent behavior similar to that of the
compound A with the increase of the content of water in acetone/water mixed solvent, but its
fluorescent change was not as obvious as that of the compound A. As shown in Fig. 6(b), the
compound B displayed weak blue emission with peak at 470 nm in dilute acetone solution, and
with increasing the content of water, its photoluminescence intensity gradually increased and its
emission spectrum obviously red-shifted. As fw is 40%, the acetone-water mixture’s
photoluminescence of the compound B enhanced the maximum value and the PL intensity was
approximately 3 times higher than that in acetone, and its emission peak was shifted to 508 nm.
When fw was over 40%, the PL intensity of the compound B gradually decreased, and even when
fw was over 70%, its PL intensity was weaker than that in acetone.
In dilute acetone solutions, two phenyl blades on the polycyclic aromatic skeletons of the
compound A and B rotate around the single-bond axles linking the peripheral aryl rotors, and the
intramolecular rotation converts photonic energy to heat and deactivates the excited states
non-radiatively, leading to the molecules non-emissive or weak emissive [33]. When the poor
solvent water was added, the solutions of the compounds gradually changed viscous, and the
intramolecular rotations of the compounds were restricted and the non-radiative relaxation channel
was obstructed, leading to the PL enhancement of the compounds. However, fw was over 50% for
the compound A and 40% for the compound B, the π‒π stacking interaction in the viscous
solutions of the compounds increased, which caused the formation of aggregates and leaded PL
quenching of the compounds. The photoluminescence of the compound A and B in solid states
were checked with a hand-held UV lamp, both of them really exhibited very weak blue-green
emission. It is indicated that the compound A and B have aggregation-caused quenching
14

characteristics.
300
250
200
150
100
50
300
200
100
1200
1000
800
600
400
200
0
1200
1000
800
600
400
200
0
a
b
fw
0%
fw
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
10%
20%
30%
40%
50%
60%
70%
80%
90%
0
10 20 30 40 50 60 70 80 90
fw (%)
0
10 20 30 40 50 60 70 80 90
fw (%)
0
450
500
550
600
650
700
750
450
500
550
600
650
700
750
Wavelength (nm)
Wavelength (nm)
Fig. 6. PL spectra and intensities (inset) of the compound A (a) and B (b) in acetone/water
with different water fraction fw. (C = 1.0 × 10−4 mol/L).
From the structures of the compound A and B, as the central stators, the conjugated degree of
7H-dibenzo[de,g]quinolin-7-one core in the compound
A
is less than that of
6H-phenanthro[3,4,5-defg]quinolin-6-one core in the compound B. The energy change of
7H-dibenzo[de,g]quinolin-7-one core caused by the rotations of two phenyl rotors in the
compound A is larger than that of 6H-phenanthro[3,4,5-defg]quinolin-6-one core by the rotations
of two phenyl rotors in the compound B. Thus, the fluorescent change of the compound A is more
obvious with the increase of the content of water in acetone/water mixed solvent.
The electrochemical properties of the compounds were investigated by cyclic voltammetry
(CV). The cyclic voltammograms of the compound A and B are shown in Fig. 7, the first
oxidation potentials of the compound A and B were located at 1.23 and 0.98 V, respectively. At the
same condition, the Fc/Fc+ potential was measured to be 0.54 V. The HOMO energy levels of the
compound A and B were found to be -5.49 and -5.24 eV as calculated from their initial oxidation
potentials [47]. From the absorption spectra in in dichloromethane solutions, the optical band edges
of the compound A and B were estimated to be at ca. 457 nm, the optical bandgaps of these
15

compounds were calculated to be 2.72 eV. Thus, the LUMO energy levels of the compound A and
B were calculated to be -2.77 and -2.52 eV, respectively.
The photophysical, electrochemical and thermal properties of the compound A and B are
summarized in Table 1.
2
1
Ferrocene
Compound A
Compound B
0
-1
-2
-2
-1
0
1
2
Potential (V, vs. Ag/Ag+)
Fig. 7. Cyclic voltammograms of ferrocene and the compound A and B
(scan rate: 10 mV/s; solvent: dichloromethane).
Table 1. Photophysical, thermal and electrochemical properties of the compound A and B
Compound
UV-vis
(nm)
PL
Td
Φf
τ
kr/knr
(ns) (× 106 s-1)a (V)b (eV)c
369 5.30 23.44 2.26/40.40 1.23 2.72
EOX Eopt
HOMO LUMO
(nm) (oC) (%)
(eV)d
(eV)e
253,
510
537
-5.49
-2.77
A
B
324, 418
257,
396 6.20
9.75 6.36/96.21 0.98 2.72
-5.24
-2.52
325, 427
akr and knr calculated by using the equations: kr = Φf/τ and knr = (1-Φf)/τ, assuming that ΦISC = 1
(ISC = intersystem crossing);
bAll the values are referred to Ag/AgCl and calibrated by Fc/Fc+;
e
cEopt ≈ 1241/λonset
;
dEHOMO = -e(EOX - 0.51 + 4.8) (eV); ELUMO = Eopt + EHOMO
Based on the X-ray data of the compound A, the structures of the compounds were optimized
by density functional theory (DFT) using a CAM-B3LYP/6-31+G* basis set to calculate the
frontier molecular orbitals of the compounds. The electronic distributions of the HOMO and
16

LUMO orbitals for the compounds obtained from time-dependent DFT (TD-DFT) calculation are
depicted in Fig. 8. In the HOMO orbitals of the compound A and B, the electron densities
distribute not only on the isoquinoline-nucleated polycyclic aromatic skeletons, but also on two
propeller-like benzene rings. However, in the LUMO orbitals of the compound A and B, all the
electron densities completely locate on the isoquinoline-nucleated polycyclic aromatic skeletons,
and there are no electron densities on two propeller-like benzene rings. From the electronic
distributions of HOMO and LUMO orbitals of the compound A and B, their UV-vis absorption
bands can be attributed to the charge transfer type π‒π* transitions from the HOMO located at two
propeller-like benzene rings to the LUMO located at the isoquinoline-nucleated polycyclic
aromatic moieties.
LUMO (-1.924 eV)
LUMO (-2.027 eV)
HOMO (-6.466 eV)
HOMO (-6.767 eV)
Compound B
Compound A
Fig. 8 Frontier orbitals of the compound A and B calculated at the DFT
CAM-B3LYP/6-31+G* level of theory.
3.4 Electroluminescence properties of the compounds
The multilayer OLEDs with a device structure of ITO/TAPC (30 nm)/TBADN:Dopant (x
17

wt%, 30 nm)/TPBi (30 nm)/Liq (2 nm)/Al (100 nm) were fabricated by vacuum-processed method
as previously described [41], in which the compound A and B were the dopants. The device
configuration and the energy level diagrams of the materials used in the work are shown in Fig. 9.
The device performances (EL spectra, J-V curves, EQE values ) were recorded with a Spectra
Scan PR655 and a computer controlled Keithley 2400 Sourcemeter.
TBADN
Fig. 9. Schematic diagram of the OLED device configuration (upper left), the
relative HOMO/LUMO energy levels of the materials investigated in this work
(upper right) and structures of TAPC, TBADN and TPBi (bottom).
The current density-voltage-luminance (J‒V‒L) curves and the current efficiency-power
efficiency-luminance (CE‒L‒PE) curves of the devices based on the compound A and B are
illustrated in Fig. 10 and Fig. 11, and their EL performances are summarized in Table 2. It was
shown that obvious concentration quenching effects was found with increasing from 7 wt% to 13
wt% for the compound A and from 4 wt% to 13 wt% for the compound B. The devices fabricated
from the compound A at 7 wt% doping concentration can approach maximum brightness of 1035
cd/m2 at 13 V and a maximum current efficiency of 1.20 cd/A, and corresponding to a power
18

efficiency of 0.47 lm/W and a maximum external quantum efficiency (EQE) of 0.89% were
obtained. For the compound B, the device with 4 wt% doping concentration exhibited maximum
brightness of 2162 cd/m2 at 12 V, but the device with 7 wt% doping concentration showed a
maximum current efficiency of 2.97 cd/A, maximum power efficiency of 1.40 lm/W and
maximum EQE of 2.23%. By comparing the device performances of the compounds, it can be
seen that the compound B exhibited better EL performances than the compound A, which could be
attributed to its higher photoluminescence quantum yield, consistent with the results of the
experiments.
100
800
600
400
200
0
4 wt%
7 wt%
10 wt%
13 wt%
4 wt%
7 wt%
10 wt%
13 wt%
1000
100
10
1
0.1
10
1
0.01
1E-3
0.1
0.01
1
a
b
0.1
4
6
8
10
12
14
1
10
100
1000
Luminance (cd/m2)
Voltage (V)
Fig. 10. L‒I‒V characteristics (a) and CE‒L‒PE curves (b) of the devices based on the
compound A with different dopant concentrations.
600
500
4 wt%
7 wt%
10 wt%
13 wt%
1000
100
10
10
1
1
0.1
400
300
200
100
0
4 wt%
7 wt%
10 wt%
13 wt%
1
a
b
0.1
0.01
0.1
4
6
8
10
12
1
10
100
1000
Luminance (cd/m2)
Voltage (V)
Fig. 11. L‒I‒V characteristics (a) and CE‒L‒PE curves (b) of the devices based on the
compound B with different dopant concentrations.
19

Table 2. EL performances of the compound A and B
Compound
Concentration ELmax
(nm)
Lmax
(cd/m2)
873
LEmax
(cd/A)
1.06
1.20
0.36
0.24
2.39
2.97
2.72
2.70
PEmax
(lm/W)
0.44
EQEmax
(%)
4 wt%
7 wt%
510
510
510
511
537
537
538
538
0.79
0.89
0.27
0.17
1.93
2.23
1.70
1.53
A
1035
899
0.47
10 wt%
13 wt%
4 wt%
0.11
353
0.09
2162
1664
901
1.07
B
7 wt%
1.40
10 wt%
13 wt%
1.20
364
1.16
4. Conclusions
Two new isoquinoline-nucleated polycyclic aromatics (compound A and B) were synthesized
via one-pot three-component reaction of the corresponding diketone (phenanthrene-9,10-dione or
pyrene-4,5-dione), ammonium acetate and 1,2-diphenylacetylene using [Cp*RhCl2]2 catalyst
associated with the oxidant Cu(OAc)2·H2O. Both compounds emit very weak fluorescence in
acetone, but their luminescence intensity increased gradually when the water content (fw) was
from 0 to 50%, exhibiting aggregation-induced emission (AIE) characteristics. However, fw was
over 50% for the compound A and 40% for the compound B, their PL intensities decreased due to
the formation of aggregates by π‒π stacking interaction in the viscous solutions of the compounds.
These compounds have good thermal stability, and the vacuum-processed doped devices were
fabricated. The EL performance of devices based on the compound B was higher than that of the
devices fabricated from the compound A, which could be attributed to its higher
photoluminescence quantum yield. The device with the compound B (4 wt%) exhibited a
maximum brightness of 2162 cd/m2, and the device with 7 wt% of the compound B showed a
maximum current efficiency of 2.97 cd/A and a maximum external quantum efficiency (EQE) of
20

2.23%.
Acknowledgements
This work was supported by the National Natural Science Foundation of China (Grant
51563014). We also thank to the Instrument Analysis Center of Lanzhou Jiaotong University.
Supplementary material
CCDC 1936905 contains the supplementary crystallographic data for the compound A in this
paper. The data can be obtained free of charge via http:www.ccdc.cam.ac.uk/conts/retrieving.html,
or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK;
fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
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26

Research Highlights
1. Two isoquinoline-nucleated polycyclic aromatic compounds were synthesized via one-pot
three-component reaction.
2. They exhibited aggregation-induced emission (AIE) characteristics when the water content (fw)
was from 0 to 50%.
3. The device based on 3,4-diphenyl-6H-phenanthro[3,4,5-defg]quinolin-6-one displayed the
brightness of 2162 cd/m2 and luminous efficiencies of 2.97 cd/A, and EQE of 2.23%.