Synthesis, optical, and electrochemical properties of 2,3-diphenyl-10H- indeno[1,2-g]quinoxaline, 15H-dibenzo[a,c]indeno[1,2-i]phenazine, and 15H-indeno[1,2-i]phenanthro[4,5-abc]phenazine derivatives

Article abstract of DOI:10.1016/j.dyepig.2014.04.042

A series of 2,3-diphenyl-10H-indeno[1,2-g]quinoxaline, 15H-dibenzo[a,c] indeno[1,2-i]phenazine, and 15H-indeno[1,2-i]phenanthro[4,5-abc]phenazine derivatives containing different terminal aromatic units such as phenyl, phenylethynyl, naphthyl, anthryl, pyrenyl, or 4-(diphenylamino)phenyl have been synthesized by employing palladium-catalyzed C-C cross-coupling reactions in good yields. All of the target compounds were characterized using ¹H NMR, ¹³C NMR, high resolution MS, optical absorption, and emission spectra. Even though the electronic absorption spectra of the compounds were influenced by the nature of the peripheral arenes, the emission spectra indicated close similarity for the excited states in the 15H-indeno[1,2-i] phenanthro[4,5-abc]phenazine series compounds. Most compounds possess a medium fluorescence-emitting ability with φ_FL values in the region of 0.40-0.71 and displayed blue, green, yellow, or red emission depending on the nature of the whole molecule. Structure-optical behavior characteristics and further details of the electronic properties from cyclic voltammetry measurements and theoretical calculations were discussed.

Full text of DOI:10.1016/j.dyepig.2014.04.042

Accepted Manuscript
Synthesis, optical and electrochemical properties of 2,3-diphenyl-10H-
indeno[1,2-g]quinoxaline, 15H-dibenzo[a,c]indeno[1,2-i]phenazine and 15H-
indeno[1,2-i]phenanthro[4,5-abc]phenazine derivatives
Zeng-Shuai Hao , Min-jie Li , Hai-Xia Lin , Ze-Bin Gu , Yong-Mei Cui
PII:
S0143-7208(14)00178-8
10.1016/j.dyepig.2014.04.042
DYPI 4370
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 27 December 2013
Revised Date: 26 April 2014
Accepted Date: 30 April 2014
Please cite this article as: Hao Z-S, Li M-j, Lin H-X, Gu Z-B, Cui Y-M, Synthesis, optical
and electrochemical properties of 2,3-diphenyl-10H-indeno[1,2-g]quinoxaline, 15H-
dibenzo[a,c]indeno[1,2-i]phenazine and 15H-indeno[1,2-i]phenanthro[4,5-abc]phenazine derivatives,
Dyes and Pigments (2014), doi: 10.1016/j.dyepig.2014.04.042.
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ACCEPTED MANUSCRIPT
Synthesis, optical and electrochemical properties of 2,3-diphenyl-10H-indeno[1,2-g]quinoxaline,
15H-dibenzo[a,c]indeno[1,2-i]phenazine and 15H-indeno[1,2-i]phenanthro[4,5-abc]phenazine derivatives
Zeng-Shuai Hao, Min-jie Li, Hai-Xia Lin , Ze-Bin Gu, Yong-Mei Cui
Department of Chemistry, College of Sciences, Shanghai University, 99 Shangda Road, Baoshan District,
Shanghai 200444, China
Abstract
A series of 2,3-diphenyl-10H-indeno[1,2-g]quinoxaline, 15H-dibenzo[a,c]indeno[1,2-i]phenazine and
15H-indeno[1,2-i]phenanthro[4,5-abc]phenazine derivatives containing different terminal aromatic units such
as phenyl, phenylethynyl, naphthyl, anthryl, pyrenyl, or 4-(diphenylamino)phenyl have been synthesized by
employing palladium-catalyzed C-C cross-coupling reactions in good yields. All of the target compounds were
1
13
characterized using H NMR, C NMR, high resolution MS, optical absorption and emission spectra. Even
though the electronic absorption spectra of the compounds were influenced by the nature of the peripheral
arenes, the emission spectra indicated close similarity for the excited states in the
15H-indeno[1,2-i]phenanthro[4,5-abc]phenazine series compounds. Most compounds possess a medium
fluorescence-emitting ability with φFL values in the region of 0.40-0.71 and displayed blue, green, yellow or
red emission depending on the nature of the whole molecule. Structure-optical behavior characteristics and
further details of the electronic properties from cyclic voltammetry measurements and theoretical calculations
were discussed.
Corresponding author. tel.: +86 21 66132190; fax: +86 21 66134594 (Y.-M.C.); Tel.: +86 21 66136050; fax: +86 21 66133039 (H.-X.L.); e-mail
addresses: ymcui@shu.edu.cn; haixialin@staff.shu.edu.cn
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Keywords: Synthesis; Fluorene; quinoxaline; phenazine; UV absorption; Fluorescence
Graphical Abstract
The molecular structures of the studied chromophores and fluorescence
colors in CH2Cl2 solutions (1×10-3 M) under UV light 365nm.
1. Introduction
Conjugated materials, which are one of the most investigated classes of advanced materials, have attracted
much attention in recent years because of their potential applications in electronics, photonics, and
optoelectronics [1-3]. Enormous efforts have been made toward the development of new high-performance
materials with desirable properties [4-21]. Due to their rigid planarized oligophenyl unit within the backbone
as well as the possibility of facile functionalization at the methylene bridge, fluorene-based derivatives,
including polymers and oligomers, exhibit unique photoluminescent properties and have been widely used as
luminescent materials [22-24], as well as carrier transport materials for FETs [25-28]. However,
small-molecule fluorene derivatives with good thermal stability and high photoluminescence (PL) efficiency
have been little reported [29-31]. Until now, there have only been a few linear fused-ring compounds with the
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introduction of the fluorene substructure, which may be due to the lack of efficient synthetic strategies [32-34].
Fluorescent heterocyclic compounds are of interest in many areas such as emitters for electroluminescence
devices, molecular probes for biochemical research, in traditional textile and polymer fields, fluorescent
whitening agents and photoconducting materials. Diazines which belong to the most important heterocycles
containing nitrogen are six-membered aromatics with two nitrogen atoms. Among which, pyrazine and
quinoxaline derivatives have been intensively studied not only for their medicinal uses, but also for their
technical applications as dyes, electroluminescent materials, organic semi-conductors and as suitable ligands
in coordination chemistry [35-38]. Fluorescent characteristics rely largely on molecular structure and
molecular assembly. Changes in the substitutional groups and substitution pattern, conjugation, and molecular
electronic structure can bring about very different optical and physical properties such as absorption, emission,
and thermal stability for such materials. There is presently great interest to increase the structural or spatial
dimensions of π-conjugated molecules in order to tune and acquire more favorable physical properties.
We recently presented detailed structure-property relationship investigations into new fluorene
derivatives
based
on
3,9-dihydro-9,9-dioctylfluoreno[3,2-d]imidazole
(DOFI)
and
10,10-dioctyl-3,6-dihydrofluoreno[2,3-d:6,7-d']diimidazoles (DOFDIs) [39, 40]. As an expanded continuation
of our studies related to the synthesis and optical properties of heterocycle-based chromophores, in this paper,
we present the initial synthesis and characterization of a series of asymmetrically substituted
2,3-diphenyl-10H-indeno[1,2-g]quinoxaline derivatives 3a-g, 15H-dibenzo[a,c]indeno[1,2-i]phenazine
derivatives 4a-g, and 15H-indeno[1,2-i]phenanthro[4,5-abc]phenazine derivatives 5a-g (Fig. 1), in which a
fluorene unit is fused with 2,3-diphenylpyrazine, dibenzo[f,h]quinoxaline or phenanthro[4,5-fgh]quinoxaline,
respectively. Extended conjugation is believed to result in intermolecular stacking interactions which are
detrimental to the emission characteristics. Therefore, two octyl groups were introduced to the C-9 position of
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the fluorene moiety to increase solubility as well as to release intermolecular π-π stacking. And we focused
our attention on different terminal aromatic units such as phenyl, phenylethynyl, naphthyl, anthryl, pyrenyl, or
4-(diphenylamino)phenyl to investigate their optical and electrochemical properties.
Fig. 1
2. Experimental
2.1. Reagents and instruments
Commercially available reagents were purchased and were used without further purification unless
1
otherwise mentioned. H NMR and 13C NMR spectra were recorded on a Bruker Avance (500MHz)
spectrometer in CDCl3 or DMSO-d6, unless otherwise noted. Chemical shifts are reported in parts per million
(ppm) and coupling constants (J) are reported in Hertz (Hz). Coupling patterns are described by abbreviations:
s (singlet), d (doublet), t (triplet), m (multiplet), br (broad). Chemical shifts were reported in the scale relative
1
to CHCl3 (7.26 ppm) or DMSO-d6 (2.50 ppm) for H NMR, and to CDCl3 (77.16 ppm) or DMSO-d6 (39.70
13
ppm) for C NMR, as internal references. The center line of the multiplets of DMSO-d6 was defined as 2.50
1
for H NMR. Silica gel plate GF254 was used for thin layer chromatography (TLC) and silica gel 300–400
mesh was used for flash column chromatography. Melting points were measured on a Digital Melting Point
Apparatus without correction. Yields are shown in terms of those isolated pure materials. The absorption and
fluorescence spectra were recorded using a UV-2501Pc spectrophotometer and a RF-5301 fluorescence
spectrophotometer. HR-MS were recorded on a Bruker Daltonics, Inc. APEXIII7.0 TESLA FTMS instrument.
The redox potentials of the compounds were determined with cyclic voltammetry (CV) using a Base 2000 CV
system. HOMO values were recalculated from reported literature values as HOMO = [Eonset]red/ox (vs SCE)
+ 4.6, Eg = 1240/UV(onset). Density functional theory (DFT) calculations have also been applied to
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characterize the three-dimensional geometries and the frontier molecular orbital energy levels of the
representative compounds at the B3LYP/6-31G* level by using the Gaussian 03 program.
2.2. Synthesis
2.2.1 . 2-Bromo-7-nitro-9H-fluorene (1b) [41]
To a stirred solution of 2-nitrofluorene (1a, 5 g, 23.67 mmol) in dry CH2Cl2 (30 mL) was added Br2 (47.34
mmol) slowly. The mixture was stirred for 5-6 h. The yellow precipitate was filtered off and washed with 5%
NaHSO3. The crude yellowish product was purified by recrystallization from DMF to afford 1b (5.5 g, 80%
1
yield) as light yellow powder. Mp 235-237 °C H NMR (500 MHz, DMSO-d6):
δ ppm 8.46 (s, 1H), 8.28 (m,
1H), 8.16 (m, 1H), 8.03 (m, 1H), 7.90 (s, 1H), 7.66 (m, 1H), 4.10 (s, 2H).
2.2.2. 2-Bromo-7-nitro-9,9-dioctyl-9H-fluorene (1c)
To a solution of compound 1b (5.5 g, 18.96 mmol) in DMSO (30 mL) were added KOH (4.25 g, 75.8
mmol) and the mixture was stirred at room temperature. After stirring for 30 min, n-C8H17Br (11 g, 56.87
mmol) was added slowly with the help of syringe. The resulting mixture was stirred continually for an
additional 5 hours. The reaction mixture was then extracted with ethyl acetate (30 mL×3), and the organic
layer was washed with saturated brine and dried over Na2SO4(S). After removing the solvent, the crude product
was purified by column chromatography on silica gel using ethyl acetate–hexane (1:30) as eluent to afford 1c
(9g, 92% yield) as a yellow-white powder. Mp 60-62°C 1H-NMR (500 MHz, CDCl3):
δ ppm 8.27-8.24 (dd, J1
= 7.0 Hz, J2 = 2.0 Hz, 1H), 8.18 (d, J = 1.9 Hz, 1H), 7.76 (d, J = 6.9 Hz, 1H), 7.65-7.62 (m, 1H), 7.54-7.51
(m, 2H), 2.06-1.93 (m, 4H), 7.65-7.62 (m, 1H), 1.23-1.02 (m, 20H), 0.81 (t, J = 7.1 Hz, 6H), 0.61-0.51 (m,
13
4H). C-NMR (125 MHz, CDCl3):
δ ppm 154.39, 151.62, 147.39, 146.45, 137.71, 130.72, 126.57, 123.69,
123.43, 122.48, 119.96, 118.29, 56.00, 39.94, 31.71, 29.76, 29.12, 23.69, 22.56, 14.03.
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2.2.3. 7-Bromo-9,9-dioctyl-9H-fluoren-2-amine (1d)
To a stirred solution of compound 1c (9 g, 16.5 mmol) in MeOH (30 mL) were added ferric chloride
hexahydrate (0.45 g, 1.65 mmol) and activated carbon (1.8 g). The mixture was heated to reflux with stirring
under nitrogen atmosphere. After refluxed for 10 min, hydrazine hydrate (9.7 g, 165 mmol) was added slowly
with a syringe. The resulting mixture was stirred continually for an additional 2 hours and cooled to room
temperature. The mixture was filtered and the filtrate was concentrated to the crude residue, which was
extracted with ethyl acetate (30 mL). The organic layer was washed with saturated brine and dried over
Na2SO4(S). The solvent was removed to give the final purified product 1d (7.9 g, 96% yield) as a white powder.
1H-NMR (500 MHz, CDCl3):
δ ppm 8.27-8.24 (dd, J1 = 7.0 Hz, J2 = 2.0 Hz, 1H), 8.18 (d, J = 1.9 Hz, 1H),
7.76 (d, J = 6.9 Hz, 1H), 7.65-7.62 (m, 1H), 7.54-7.51 (m, 2H), 2.06-1.93 (m, 4H), 1.23-1.02 (m, 20H), 0.81
(t, J = 7.1 Hz, 6H), 0.61-0.51 (m, 4H).
2.2.4. N-(7-Bromo-9,9-dioctyl-9H-fluoren-2-yl)acetamide (1e)
To a solution of compound 1d (6.8 g, 14 mmol) in AcOH (30 mL) were added acetic anhydride (5.8 g, 56
mmol). The resulting mixture was stirred at room temperature for 4 hours. The reaction mixture was then
extracted with ethyl acetate (30 mL×3), the organic layer was washed with saturated brine and dried over
Na2SO4(S). After removing the solvent, the crude product was purified by column chromatography on silica gel
using ethyl acetate–hexane (1: 5) as eluent to afford 1e (6.8 g, 92% yield) as a white powder. Mp 161-164°C
1H-NMR (500 MHz, CDCl3):
δ
ppm 7.60-7.55 (m, 2H), 7.49-7.46 (m, 1H), 7.45-7.41 (m, 3H), 7.38 (s, 1H),
13
2.21 (s, 3H), 1.93-1.88 (m, 4H), 1.17-1.00 (m, 20H), 0.81 (t, J = 7.0 Hz, 6H), 0.62-0.55 (m, 4H). C-NMR
(125 MHz, CDCl3):
δ ppm 168.15, 152.86, 151.53, 139.73, 137.57, 136.27, 129.91, 126.05, 120.63, 120.53,
120.14, 118.50, 114.23, 55.54, 40.29, 31.76, 29.95, 29.22, 24.78, 23.69, 22.59, 14.07.
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2.2.5. N-(7-Bromo-9,9-dioctyl-3-nitro-9H-fluoren-2-yl)acetamide (1f)
To a solution of compound 1e (6 g, 11.4 mmol) in AcOH (30 mL) was added fuming HNO3 (1.44 g, 22.8
mmol) dropwise. The resulting mixture was stirred at 0 °C for 30 min. The reaction mixture was then
extracted with ethyl acetate (30 mL×3), the organic layer was washed with saturated brine and dried over
Na2SO4(S). After removing the solvent, the crude product was purified by column chromatography on silica gel
using ethyl acetate–hexane (1: 30) as eluent to afford 1f (5.8 g, 90% yield) as a yellow powder. Mp 112-114°C
1H-NMR (500 MHz, CDCl3):
2H), 2.02-1.90 (m, 4H), 1.19-1.00 (m, 20H), 0.81 (t, J = 7.0 Hz, 6H), 0.61-0.52 (m, 4H). 13C-NMR (125 MHz,
CDCl3): ppm 169.04, 159.42, 152.76, 137.55, 135.75, 135.65, 134.73, 130.61, 126.41, 122.41, 121.40,
δ ppm 10.60 (s, 1H), 8.80 (s, 1H), 8.46 (s, 1H), 7.59-7.55 (m, 1H), 7.51-7.46 (m,
δ
116.63, 116.15, 56.56, 40.13, 31.72, 29.78, 29.13, 25.82, 23.77, 22.57, 14.07.
2.2.6. 7-Bromo-9,9-dioctyl-3-nitro-9H-fluoren-2-amine (1g)
To a solution of compound 1f (5.5 g, 9.62 mmol) in 80% sulfuric acid (20 mL) was added ethanol (2 mL)
and the resulting mixture was stirred at 80 °C for 2 hours. The reaction mixture was cooled down then
extracted with ethyl acetate (30 mL×3), the organic layer was washed with saturated brine and dried over
Na2SO4(S). After removing the solvent, the crude product was purified by column chromatography on silica gel
using ethyl acetate–hexane (1: 30) as the eluent and then recrystallized from MeOH to afford 1g (5.1 g, 93%
1
yield) as a red powder. Mp 92-94°C H-NMR (500 MHz, CDCl3):
δ ppm 8.38 (s, 1H), 7.51-7.43 (m, 2H),
7.38 (m, 1H), 6.72 (s, 1H), 6.27 (br, 2H),1.92-1.83 (m, 4H), 1.22-1.03 (m, 20H), 0.82 (t, J = 7.0 Hz, 6H),
0.65-0.57 (m, 4H). 13C-NMR (125 MHz, CDCl3):
ppm 159.57, 151.45, 144.95, 138.36, 131.86, 130.89,
δ
130.49, 126.07, 121.07, 120.79, 116.86, 112.31, 56.67, 40.80, 31.75, 29.88, 29.17, 23.76, 22.58, 14.06.
2.2.7. 7-Bromo-9,9-dioctyl-9H-fluorene-2,3-diamine (2)
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To a solution of compound 1g (5.1 g, 9.63 mmol) in MeOH (30 mL) were added ferric chloride hexahydrate
(0.26 g, 0.96 mmol) and activated carbon (1 g). The mixture was heated to reflux with stirring under nitrogen
atmosphere. After refluxed for 10 min, hydrazine hydrate (5.6 g, 96 mmol) was added slowly with a syringe.
The resulting mixture was stirred continually for an additional 2 hours and cooled to room temperature. The
mixture was filtered and the filtrate was concentrated to the crude residue, which was extracted by ethyl
acetate (30 mL). The organic layer was washed with saturated brine and dried over Na2SO4(S). The solvent was
removed to afford 2 (4.6 g, 96% yield) as a white powder. 1H-NMR (500 MHz, CDCl3):
δ ppm 7.37-7.31 (m,
3H), 7.00 (s, 1H), 6.63 (s, 1H), 1.86-1.81 (m, 4H), 1.19-1.03 (m, 20H), 0.83 (t, J = 7.0 Hz, 6H), 0.61-0.56 (m,
4H).
2.2.8. General procedure for synthesis of 3-5, 3a, 4a and 5a.
To
a
solution
of
7-bromo-9,9-dioctyl-9H-fluorene-2,3-diamine
(2,
2.4
mmol)
or
9,9-dioctyl-9H-fluorene-2,3-diamine (2a, 2.4 mmol) in deoxygenated AcOH (20 mL) were added the
corresponding dione (2.4 mmol) and potassium carbonate (0.17 g, 1.2 mmol). The mixture was heated to
reflux under nitrogen for 2-5 h. After cooling down, the mixture was extracted with ethyl acetate (20 mL) and
water (50 mL), the organic layer was washed with saturated brine and dried over Na2SO4(S). After removing
the solvent, the crude product was purified by column chromatography on silica gel using ethyl acetate–
hexane as eluent or recrystallized from dichloromethane (DCM)/MeOH to yield the desired compounds.
2.2.8.1. 8-Bromo-10,10-dioctyl-2,3-diphenyl-10H-indeno[1,2-g]quinoxaline (3).Colorless oil, yield 88%.
1H-NMR (500MHz, CDCl3):
6H),7.37-7.34 (m, 6H), 2.14-2.08 (m, 2H), 2.06-1.99 (m, 2H), 1.16-1.00 (m, 20H), 0.79 (t, J = 7.1 Hz, 6H),
0.70-0.62 (m, 4H). 13C-NMR(125 MHz, CDCl3):
ppm 153.53, 153.22, 152.88, 152.42, 143.13, 141.35,
δ ppm 8.39 (s, 1H), 8.07 (s, 1H), 7.76 (d, J = 7.7 Hz, 1H), 7.56-7.53 (m,
δ
141.32, 139.20, 139.17, 138.47, 130.62, 128.68, 128.24, 128.23, 126.50, 123.23, 122.48, 118.47, 55.46, 41.12,
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31.68, 29.90, 29.15, 29.13, 23.87, 22.51, 14.00.
2.2.8.2.13-Bromo-15,15-dioctyl-15H-dibenzo[a,c]indeno[1,2-i]phenazine (4).Yellow powder, yield 85%. Mp
1
157-159 °C H-NMR (500 MHz, CDCl3):
δ ppm 9.43-9.37 (m, 2H), 8.57 (d, J = 8.0 Hz, 2H), 8.52 (s, 1H),
8.21 (s, 1H), 7.80 (d, J = 8.0 Hz, 1H), 7.81-7.73 (m, 4H), 7.60-7.56 (m, 2H), 2.22-2.15 (m, 2H), 2.11-2.05 (m,
2H), 1.18-1.0 2 (m, 20H), 0.77 (t, J = 7.0 Hz, 6H), 0.74-0.67 (m, 4H).
2.2.8.3.13-Bromo-15,15-dioctyl-15H-indeno[1,2-i]phenanthro[4,5-abc]phenazine (5).Yellow powder, yield
1
90%. Mp 194-196°C H-NMR (500 MHz, CDCl3):
δ ppm 9.50-9.45(m, 2H), 8.53(s, 1H), 8.26 (s, 1H),
8.25-8.22 (m, 2H), 8.08-8.03 (m, 2H), 7.99 (s, 2H), 7.84 (d, J = 8.4 Hz, 1H), 7.60-7.57 (m, 2H), 2.26-2.18 (m,
2H), 2.14-2.07 (m, 2H), 1.18-1.04 (m, 20H), 0.79-0.72 (m, 10H). 13C-NMR (125 MHz, CDCl3):
ppm
δ
153.58, 153.34, 143,15, 142.60, 142.56, 142.51, 142.19, 131.24, 131.19, 130.71, 128.79, 128.76, 127.03,
126.98, 126.60, 126.58, 125.77, 123.54, 123.42, 123.39, 122.62, 122.48, 118.59, 55.47, 41.36, 31.71, 30.00,
29.24, 29.18, 22.52, 13.99.
1
2.2.8.4. 10,10-Dioctyl-2,3-diphenyl-10H-indeno[1,2-g]quinoxaline (3a). Colorless oil, yield 93%. H-NMR
(500 MHz, CDCl3):
3H), 7.40-7.35 (m, 6H), 2.18-2.06 (m, 4H), 1.22-1.02 (m, 20H), 0.81 (t, J = 7.0 Hz, 6H), 0.73-0.66 (m, 4H).
13C-NMR (125 MHz, CDCl3):
ppm 153.92, 152.65, 152.14, 151.39, 144.41, 141.39, 141.28, 139.43, 139.32,
δ ppm 8.44 (s, 1H), 8.11 (s, 1H), 7.96-7.92 (m, 1H), 7.60-7.56 (m, 4H), 7.47-7.43 (m,
δ
139.29, 129.82, 129.06, 128.60, 128.24, 128.22, 128.32, 123.20, 122.31, 121.16, 118.13, 55.16, 41.22, 31.70,
29.98, 29.18, 29.15, 23.92, 22.51, 14.00. HR-MS: calcd for C43H50N2 ([M+H]+), 595.4054; found, 595.4043.
2.2.8.5.15,15-Dioctyl-15H-dibenzo[a,c]indeno[1,2-i]phenazine (4a). Yellow powder, yield 85%. Mp 98-101
1
°C H-NMR (500 MHz, CDCl3):
δ ppm 9.49-9.42 (m, 2H), 8.61 (d, J = 7.5 Hz, 2H), 8.58 (s, 1H), 8.26 (s,
1H), 8.05-8.01 (m, 1H), 7.84-7.76 (m, 4H), 7.51-7.45 (m, 3H), 2.26-2.11 (m, 4H), 1.22-1.02 (m, 20H), 0.80 (t,
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J = 7.0 Hz, 6H), 0.77-0.70 (m, 4H). 13C-NMR (125 MHz, CDCl3):
δ ppm 154.08, 151.46, 144.53, 142.54,
142.44, 141.80, 141.32, 139.53, 131.84, 130.47, 130.43, 129.95, 129.25, 127.84, 127.40, 126.03, 125.88,
123.29, 122.94, 122.88, 122.28, 121.32, 118.17, 55.16, 41.46, 31.70, 30.02, 29.21, 29.16, 23.98, 22.51, 14.00.
HR-MS: calcd for C43H48N2 ([M+H]+), 593.3897; found, 593.3923.
2.2.8.6.15,15-Dioctyl-15H-indeno[1,2-i]phenanthro[4,5-abc]phenazine(5a). Yellow powder, yield 91%. Mp
1
101-104 °C H-NMR (500 MHz, CDCl3):
δ ppm 9.60-9.54 (m, 2H), 8.59 (s, 1H), 8.28 (s, 1H), 8.27-8.24 (m,
2H), 8.11-8.06 (m, 2H), 8.04-8.01 (m, 3H), 7.50-7.45 (m, 3H), 2.25-2.11 (m, 4H), 1.18-1.02 (m, 20H),
0.79-0.71 (m, 10H). 13C-NMR (125 MHz, CDCl3):
ppm 154.13, 151.48, 144.55, 142.71, 142.61, 142.49,
δ
142.03, 139.57, 131.31, 131.26, 129.58, 129.25, 128.71, 127.42, 127.10, 127.05, 126.66. 126.63, 125.81,
123.56, 123.40, 123.30, 122.34, 121.35, 118.24, 55.20, 41.49, 31.72, 30.07, 29.25, 29.18, 24.05, 22.52, 14.00.
HR-MS: calcd for C45H48N2 ([M+H]+), 617.3897; found, 617.3893.
2.2.9. General Procedure for synthesis of compounds 3b,3d-g, 4b,4d-g and 5b,5d-g.
To a mixture of compound 3, 4 or 5 (0.5 mmol), aryl boric acid pinacol ester (0.75 mmol, 1.5 equiv),
potassium carbonate (1 mmol, 2 equiv), PdCl2(PPh3)2 (0.05 mmol, 0.1 equiv) was added toluene (9 mL) and
water (1 mL) at room temperature. The reaction was heated to 90 oC under nitrogen atmosphere for 24h. After
cooling down, the mixture was then extracted with ethyl acetate (10 mL) and water (10 mL), the organic layer
was washed with saturated brine and dried over Na2SO4(S). After removing the solvent, the crude product was
purified by column chromatography on silica gel using ethyl acetate–hexane (1: 30) as eluent to afford the
final purified products in 44-91% yields.
1
2.2.9.1.10,10-Dioctyl-2,3,8-triphenyl-10H-indeno[1,2-g]quinoxaline (3b). Colorless oil, yield 91%. H-NMR
(500 MHz, CDCl3):
δ
ppm 8.45 (s, 1H), 8.11 (s, 1H), 7.98 (d, J = 7.5 Hz, 1H), 7.73-7.67 (m, 3H), 7.63 (m,
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1H), 7.59-7.56 (m, 4H), 7.52-7.48 (m, 2H), 7.42-7.35 (m, 7H), 2.20-2.09 (m, 4H), 1.19-1.03 (m, 20H),
0.81-0.71 (m, 10H). 13C-NMR (125 MHz, CDCl3):
δ ppm 154.21, 152.76, 152.19, 152.16, 144.09, 142.19,
141.53, 141.38,141.31, 139.40, 139.36, 138.74, 129.89, 128.89, 128.66, 128.30, 128.28, 127.54, 127.29,
126.67, 122.43, 121.81, 121.53, 118.22, 55.32, 41.30, 31.75, 30.03, 29.22, 29.21, 24.01, 22.57, 14.05.
HR-MS: calcd for C49H54N2 ([M+H]+), 671.4367; found, 671.4334.
2.2.9.2.8-(Naphthalen-1-yl)-10,10-dioctyl-2,3-diphenyl-10H-indeno[1,2-g]quinoxaline (3d). Colorless oil,
1
yield 70%. H-NMR (500 MHz, CDCl3):
δ ppm 8.49 (s, 1H), 8.13 (s, 1H), 8.03 (d, J = 7.6 Hz, 1H),
7.98-7.94 (m, 2H), 7.91 (d, J = 8.3 Hz, 1H), 7.61-7.51 (m, 9H), 7.48-7.43 (m, 1H), 7.40-7.34 (m, 6H),
13
2.20-2.07 (m, 4H), 1.21-1.03 (m, 20H), 0.85-0.76 (m, 10H). C-NMR (125 MHz, CDCl3):
δ ppm 154.18,
152.73, 152.19, 151.47, 144.16, 141.61, 141.36, 140.31, 139.32, 139.29, 138.58, 133.89, 131.65, 129.84,
129.39, 128.64, 128.38, 128.27, 128.25, 127.83, 126.92, 126.10, 125.88, 125.83, 125.38, 125.08, 122.42,
118.21, 55.28, 41.19, 31.71, 29.99, 29.23, 29.18, 24.09, 22.53, 14.01. HR-MS: calcd for C53H56N2 ([M+H]+),
721.4523; found, 721.4522.
2.2.9.3. 8-(Anthracen-9-yl)-10,10-dioctyl-2,3-diphenyl-10H-indeno[1,2-g]quinoxaline (3e). Colorless oil,
1
yield 52%. H-NMR (500 MHz, CDCl3):
δ ppm 8.55-8.53 (m, 2H), 8.14 (s, 1H), 8.12 (d, J = 7.7 Hz, 1H),
8.09(d, J = 8.6 Hz, 1H), 7.77-7.73 (m, 2H), 7.61-7.57 (m, 4H), 7.52-7.47 (m, 4H), 7.39-7.34 (m, 8H),
13
2.20-2.04 (m, 4H), 1.19-1.06 (m, 20H), 0.89-0.76 (m, 10H). C-NMR (125 MHz, CDCl3):
δ ppm 154.17,
152.80, 152.26, 151.60, 144.23, 141.59 141.43, 139.70, 139.36, 139.31, 138.88, 137.01, 131.40, 13.53,
130.21, 129.86, 128.66, 128.44, 128.30, 128.27, 126.73, 126.65, 126.45, 125.47, 125.14, 122.47, 121.18,
118.32, 55.37, 41.26, 31.74, 30.00, 29.31, 29.16, 24.20, 22.54, 14.03. HR-MS: calcd for C57H58N2 ([M+H]+),
771.4680; found, 771.4681.
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2.2.9.4.8-(Pyren-1-yl)-10,10-dioctyl-2,3-diphenyl-10H-indeno[1,2-g]quinoxaline (3f). Pale yellow solid, yield
58%. Mp 98-100 °C 1H-NMR (500 MHz, CDCl3):
8.15-8.09 (m, 4H), 8.07-8.02 (m, 2H), 7.72 (d, J = 7.9 Hz, 1H), 7.69 (s, 1H), 7.62-7.57 (m, 4H), 7.41-7.36 (m,
6H), 2.24-2.12 (m, 4H), 1.22-1.08 (m, 20H), 0.93-0.78 (m,10H). 13C-NMR (125 MHz, CDCl3):
ppm
δ ppm 8.54 (s, 1H), 8.30-8.22 (m, 3H), 8.21-8.16 (m, 2H),
δ
154.21, 152.77, 152.22, 151.61, 144.13, 142.06, 141.52, 141.40, 139.34, 139.30, 138.60, 137.76, 131.49,
130.94, 130.72, 129.95, 129.85, 128.65, 128.57, 128.28, 128.25, 127.58, 127.54, 127.52, 127.41, 126.08,
125.60, 125.22, 125.11, 125.06, 124.90, 124.86, 124.66, 122.47, 121.18, 118.32, 55.35, 41.21, 31.75, 30.03,
29.26, 29.21, 24.15, 22.56, 14.03. HR-MS: calcd for C59H60N2 ([M+H]+), 797.4836; found, 797.4750.
2.2.9.5. 4-(10,10-Dioctyl-2,3-diphenyl-10H-indeno[1,2-g]quinoxalin-8-yl)-N,N-diphenylaniline (3g). Yellow
1
solid, yield 44%. Mp 112-114 °C H-NMR (500 MHz, CDCl3):
δ ppm 8.41 (s, 1H), 8.09 (s, 1H), 7.94 (d, J =
7.8 Hz, 1H), 7.67-7.64 (m, 1H), 7.60-7.54 (m, 7H), 7.38-7.33 (m, 6H), 7.31-7.27 (m, 4H), 7.20-7.15 (m, 6H),
7.08-7.04 (m, 2H), 2.18-2.07 (m, 4H), 1.18-1.01 (m, 20H), 0.80-0.68 (m, 10H). 13C-NMR (125 MHz, CDCl3):
δ
ppm 154.21, 152.68, 152.12, 152.06, 147.58, 147.45, 144.17, 141.56, 141,51, 141.29, 139.36, 139.32,
138.24, 134.95, 129.84, 129.30, 128.61, 128.26, 128.24, 127.84, 126.07, 124.49, 123.77, 123.06, 122.31,
121.49, 121.08, 117.96, 55.24, 41.28, 31.71, 30.00, 29.19, 29.18, 23.97, 22.53, 14.01. HR-MS: calcd for
C61H63N3 ([M+H]+), 838.5102; found, 838.5109.
2.2.9.6. 13-Phenyl-15,15-dioctyl-15H-dibenzo[a,c]indeno[1,2-i]phenazine (4b). Yellow solid, yield 90%. Mp
101-103 °C 1H-NMR (500 MHz, CDCl3):
J = 7.5 Hz, 1H), 7.86-7.78 (m, 4H), 7.77-7.72 (m, 3H), 7.67 (s, 1H), 7.56-7.52 (m, 2H), 7.46-7.42 (m, 1H),
2.30-2.15 (m, 4H), 1.21-1.03 (m, 20H), 0.82-0.75 (m, 10H). 13C-NMR (125 MHz, CDCl3):
ppm 154.33,
δ ppm 9.50-9.44 (m, 2H), 8.64-8.59 (m, 3H), 8.27 (s, 1H), 8.08 (d,
δ
152.20, 144.16, 142.63, 142.50, 141.85, 141.34, 141.32, 138.84, 131.86, 130.49, 130.47, 129.96, 129.95,
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128.90, 127.84, 127.56, 127.31, 126.75, 126.06, 125.92, 122.95, 122. 37, 121.86, 121.67, 118.26, 55.31,
41.52, 31.75, 30.07, 29.25, 29.21, 24.08, 22.56, 14.03. HR-MS: calcd for C49H52N2 ([M+H]+), 669.4210;
found, 669.4202.
2.2.9.7. 13-(Naphthalen-1-yl)-15,15-dioctyl-15H-dibenzo[a,c]indeno[1,2-i]phenazine (4d). Yellow solid, yield
1
81%. Mp 129-131 °C H-NMR (500 MHz, CDCl3):
δ ppm 9.48-9.41 (m, 2H), 8.62 (s, 1H), 8.56 (d, J = 7.7
Hz, 2H), 8.30 (s, 1H), 8.12 (d, J = 7.6 Hz, 1H), 8.08-7.92 (m, 3H), 7.81-7.74 (m, 4H), 7.64-7.54 (m, 5H),
7.51-7.47 (m, 1H), 2.30-2.15 (m, 4H), 1.21-1.08 (m, 20H), 0.92-0.84 (m, 4H), 0.79 (t, J = 7. 0 Hz, 6H).
13C-NMR (125 MHz, CDCl3):
δ ppm 154.31, 151.53, 144.25, 142.63, 142.50, 141.86, 141.79, 141.37, 140.33,
138.69, 133.91, 131.86, 131.67, 130.46, 130.44, 129.98, 129.96, 129.48, 128.41, 127.85, 126.95, 126.12, 126.
05, 125.91, 125.85, 125.41, 125.16, 122.95, 122.89, 122.39, 121.21, 118.26, 55.27, 41.42, 31.73, 30.03, 29.26,
29.18, 24.15, 22.53, 14.00. HR-MS: calcd for C53H54N2 ([M+H]+), 719.4367; found, 719.4405.
2.2.9.8. 13-(Anthracen-9-yl)-15,15-dioctyl-15H-dibenzo[a,c]indeno[1,2-i]phenazine (4e).Yellow solid, yield
1
47%. Mp 129-131 °C H-NMR (500 MHz, CDCl3):
δ ppm 9.50-9.43 (m, 2H), 8.68 (s, 1H), 8.60-8.55 (m,
3H), 8.32 (s, 1H), 8.22 (d, J = 7.6 Hz, 1H), 8.10 (d, J = 8.9 Hz, 2H), 7.82-7.76 (m, 6H), 7.57-7.49 (m, 4H),
7.52-7.47 (m,4H), 7.42-7.37 (m, 2H), 2.30-2.12 (m, 4H), 1.21-1.08 (m, 20H), 0.97-0.87 (m, 4H), 0.78 (t, J =
13
7.0 Hz, 6H). C-NMR (125 MHz, CDCl3) :
δ ppm 154.28, 151.65, 144.32, 142.65, 142.55, 141.89, 141.41,
139.88, 138.96, 137.02, 131.87, 131.41, 130.61, 130.46, 130.44, 130.22, 129.99, 129.97, 128.45, 127.85,
126.75, 126.65, 126.52, 126.07, 125.91, 125.49, 125.15, 122.95, 122.89, 122.43, 121.32, 118.36, 55.35, 41.48,
31.74, 30.02, 29.33, 29.16, 24.27, 22.52, 14.01. HR-MS: calcd for C57H56N2 ([M+H]+), 769.4523; found,
769.4567.
2.2.9.9.13-(Pyren-1-yl)-15,15-dioctyl-15H-dibenzo[a,c]indeno[1,2-i]phenazine (4f). Yellow solid, yield 72%.
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1
Mp 129-130 °C H-NMR (500 MHz, CDCl3):
δ ppm 9.49-9.43 (m, 2H), 8.66 (s, 1H), 8.61-8.57 (m, 2H),
8.32-8.2 (m, 3H), 8.25-8.17 (m, 3H), 8.15-8.10 (m, 3H), 8.08-8.04 (m, 2H), 7.83-7.74 (m, 5H), 7.72 (s, 1H),
2.31-2.18 (m, 4H), 1.21-1.09 (m, 20H), 0.97-0.85 (m, 4H), 0.78 (t, J = 7.0 Hz, 6H). 13C-NMR (125 MHz,
CDCl3):
δ ppm 154.29, 151.63, 144.16, 142.61, 142.51, 142.20, 141.83, 141.34, 138.69, 137.75, 131.82,
131.80, 131.48, 130.93, 130.71, 130.41, 130.40, 130.03, 129.91, 128.55, 127.79, 127.58, 127.53, 127.51,
127.40, 126.06, 126.02,125.88, 125.67, 125.21, 125.11, 125.06, 124.89, 124.86, 124.66, 122.90, 122.82,
122.43, 121.33, 118.37, 55.32, 41.44, 31.76, 30.07, 29.31, 29.23, 24.23, 22.55, 14.03. HR-MS: calcd for
C59H58N2 ([M+H]+), 795.4680; found, 795.4615.
2.2.9.10. 4-(15,15-Dioctyl-15H-dibenzo[a,c]indeno[1,2-i]phenazin-13-yl)-N,N-diphenylaniline (4g). Yellow
solid, yield 64%. Mp 101-103 °C 1H-NMR (500 MHz, CDCl3):
δ ppm 9.46-9.41 (m, 2H), 8.58 (d, J = 7.5 Hz,
2H), 8.55 (s, 1H), 8.24 (s, 1H), 8.03 (d, J = 7.9 Hz, 1H), 7.82-7.74 (m, 4H), 7.70-7.67 (m, 1H), 7.64-7.60 (m,
3H), 7.33-7.28 (m, 4H), 7.23-7.17 (m, 6H), 7.09-7.05 (m, 2H), 2.27-2.13 (m, 4H), 1.18-1.01 (m, 20H),
0.81-0.73 (m, 10H). 13C-NMR (125 MHz, CDCl3):
δ ppm 154.31, 152.16, 147.57, 147.46, 144.21, 142.61,
142.41, 141.20, 138.33, 134.93, 131.78, 131.77, 130.44, 130.42, 129.88, 129.85, 129.30, 127.85, 127.77,
126.14, 126.00, 125.84, 124.50, 123.76, 123.07, 122.88, 122.81, 122.26, 121.64, 121.09,118.00, 55.21, 41.50,
31.70, 30.04, 29.21, 24.03, 22.51, 13.99. HR-MS: calcd for C61H61N3 ([M+H]+), 836.4945; found, 836.4964.
2.2.9.11. 13-Phenyl-15,15-dioctyl-15H-indeno[1,2-i]phenanthro[4,5-abc]phenazine (5b).Yellow solid, yield
90%. Mp 95-98 °C 1H-NMR (500 MHz, CDCl3):
δ ppm 9.70-9.58 (m, 2H), 8.66-8.61 (m, 1H), 8.36-8.26 (m,
3H), 8.19-8.04 (m, 5H), 7.80-7.72 (m, 3H), 7.68 (s, 1H), 7.58-7.52 (m, 2H), 7.47-7.41 (m, 1H), 2.30-2.15 (m,
13
4H), 1.20-1.03 (m, 20H), 0.86-0.75 (m, 10H). C-NMR (125 MHz, CDCl3):
δ ppm 154.42, 152.22, 144.22,
142.83, 142.69, 142.60, 142.34, 142.08, 141.33, 138.85, 131.37, 131.32, 129.64, 128.91, 128.77, 127.57,
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127.32, 127.14, 127.10, 126.76, 126.76, 126.69, 125.88, 123.62, 123.48, 122.43, 121.87, 121.70, 118.31 ,
55.35, 41.55, 31.76, 30.10, 29.27, 29.23, 24.13,22.56,14.03. HR-MS: calcd for C51H52N2 ([M+H]+), 693.4210;
found, 743.4216.
2.2.9.12. 13-(Naphthalen-1-yl)-15,15-dioctyl-15H-indeno[1,2-i]phenanthro[4,5-abc]phenazine (5d).Yellow
solid, yield 83%. Mp 99-101 °C 1H-NMR (500 MHz, CDCl3):
δ ppm 9.49-9.45 (m, 2H), 8.62 (s, 1H), 8.36 (s,
1H), 8.16-8.13 (m, 3H), 8.06 (d, J = 8.5 Hz, 1H), 8.02-7.98 (m, 3H), 7.97-7.93 (m, 1H), 7.91 (s, 2H),
7.66-7.55 (m, 5H), 7.54-7.49 (m, 1H), 2.36-2.20 (m, 4H), 1.24-1.13 (m, 20H), 1.01-0.94 (m, 4H), 0.81 (t, J =
13
7.0 Hz, 6H). C-NMR (125 MHz, CDCl3):
δ ppm 154.41, 151.55, 144.31, 142.83, 142.70, 142.61, 142.11,
141.81, 140.34, 138.71, 133.93, 131.67, 131.37, 131.32, 129.63, 129.51, 128.79, 128.42, 127.86, 127.15,
127.11, 126.96, 126.73, 126.70, 126.13, 125.91, 125.88, 125.86, 125.41, 125.18, 123.63, 123.47, 121.25,
118.33, 55.31, 41.45, 31.74, 30.07, 29.29, 29.21, 14.01. HR-MS: calcd for C55H54N2 ([M+H]+), 743.4367;
found, 743.4373.
2.2.9.13. 13-(Anthracen-9-yl)-15,15-dioctyl-15H-indeno[1,2-i]phenanthro[4,5-abc]phenazine (5e).Yellow
1
solid, yield 43%. Mp 91-93 °C H-NMR (500 MHz, CDCl3):
δ ppm 9.66-9.59 (m, 2H), 8.72 (s, 1H), 8.56 (s,
1H), 8.36 (s, 1H), 8.30-8.27 (m, 2H), 8.24 (d, J = 7.6 Hz, 1H), 8.13-8.08 (m, 4H), 8.05 (s, 2H), 7.80(d, J = 8.9
Hz, 2H), 7.58-7.54 (m, 2H), 7.53-7.48 (m, 2H), 7.41-7.37 (m, 2H), 2.31-2.24 (m, 2H), 2.20-2.13 (m, 2H),
1.17-1.08 (m, 20H), 0.96-0.86 (m, 4H), 0.77 (t, J = 7.1 Hz, 6H). HR-MS: calcd for C59H56N2 ([M+H]+),
793.4523; found, 793.4510.
2.2.9.14. 13-(Pyren-1-yl)-15,15-dioctyl-15H-indeno[1,2-i]phenanthro[4,5-abc]phenazine (5f).Yellow solid,
yield 77%. Mp 115-117 °C 1H-NMR (500 MHz, CDCl3):
δ ppm 9.66-9.60 (m, 2H), 8.71 (s, 1H), 8.38 (s, 1H),
8.32-8.28 (m, 4H), 8.26-8.20 (m, 3H), 8.17-8.11 (m, 5H), 8.10-8.05 (m, 4H), 7.80-7.74 (m, 2H), 7.83-7.74 (m,
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5H), 7.72 (s, 1H), 2.36-2.22 (m, 4H), 1.24-1.12 (m, 20H), 1.01-0.93 (m, 4H), 0.80 (t, J = 7.0 Hz, 6H).
13C-NMR (125 MHz, CDCl3):
δ ppm 154.45, 151.68, 144.32, 142.87, 142.75, 142.67, 142.25, 142.17, 138.70,
137.76, 131.49, 131.40, 131.36, 130.94, 130.73, 130.06, 129.67, 128.83, 128.57, 127.59, 127.55, 127.52,
127.41, 127.18, 127.14, 126.76, 126.74, 126.07, 125.94, 125.92, 125.69, 125.22, 125.12, 125.06,
124.90,124.87, 124.67, 123.66, 123.51, 122.49, 121.36, 118.40, 55.37, 41.46, 31.75, 30.08, 29.31, 29.23,
24.25, 22.55, 14.02. HR-MS: calcd for C61H58N2 ([M+H]+), 819.4680; found, 819.4587.
2.2.9.15.
4-(15,15-Dioctyl-15H-indeno[1,2-i]phenanthro[4,5-abc]phenazin-13-yl)-N,N-diphenylaniline
1
(5g).Yellow solid, yield 69%. Mp 131-133 °C H-NMR (500 MHz, CDCl3):
δ ppm 9.61-9.56 (m, 2H), 8.58
(s, 1H), 8.29 (s, 1H), 8.28-8.24 (m, 2H), 8.12-8.07 (m, 2H), 8.06-8.02 (m, 3H), 7.71-7.68 (m, 1H), 7.65-7.61
(m, 3H), 7.33-7.28 (m, 4H), 7.23-7.17 (m, 6H), 7.09-7.05 (m, 2H), 2.29-2.16 (m, 4H), 1.17-1.04 (m, 20H),
0.83-0.73 (m, 10H). 13C-NMR (125 MHz, CDCl3):
δ ppm 154.44, 152.19, 147.58, 147.48, 144.30, 142.83,
142.63, 142.53, 141.96, 141.72, 138.35, 134.94, 131.33, 131.29, 129.63, 128.31, 128.71, 127.86, 127.11,
127.07, 126.68, 126.66, 126.17, 125.86, 125.83, 124.52, 123.75, 123.58, 123.41, 123.08, 122.32, 121.76,
121.67, 121.11, 118.06, 55.26, 31.71, 30.06, 29.24, 29.19, 24.08, 22.51, 13.99. HR-MS: calcd for C63H61N3
([M+H]+), 860.4945; found, 860.4949.
2.2.10. General procedure for synthesis of compounds 3c, 4c and 5c.
To a mixture of compound 3, 4 or 5 (0.5 mmol), phenylacetylene (1 mmol, 2 equiv), CuI (0.05 mmol, 0.1
equiv), PdCl2(PPh3)2 (0.025 mmol, 0.05 equiv) was added dry triethylamine (10 mL) at room temperature. The
mixture was heated to reflux under nitrogen atmosphere for 24h. After cooling down, the mixture was then
extracted with ethyl acetate (15 mL) and water (10 mL), the organic layer was washed with saturated brine and
dried over Na2SO4(S). After removing the solvent, the crude product was purified by column chromatography
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on silica gel using ethyl acetate–hexane (1:30) as eluent to afford the final purified product in 75-84% yields.
2.2.10.1. 10,10-Dioctyl-2,3-diphenyl-8-(phenylethynyl)-10H-indeno[1,2-g]quinoxaline (3c). Pale yellow oil,
yield 77%. 1H-NMR (500 MHz, CDCl3):
δ ppm 8.42 (s, 1H), 8.09 (s, 1H), 7.88 (d, J = 7.9 Hz, 1H), 7.62-7.54
(m, 8H), 7.40-7.33 (m, 9H), 2.17-2.04 (m, 4H), 1.19-1.02 (m, 20H), 0.78 (t, J = 7.1 Hz, 6H), 0.73-0.64 (m,
13
4H). C-NMR (125 MHz, CDCl3):
δ ppm 153.89, 152.85, 152.39, 151.48, 143.58, 141.43, 141.37, 139.61,
139.26, 139.22, 131.62, 139.22, 131.62, 131.09, 129.82, 128.68, 128.39, 128.37, 128.27, 128.25, 126.26,
123.63, 123.16, 122.43, 121.13, 118.65, 90.41,90.14, 55.25, 41.23, 31.71, 29.99, 29.21, 29.18, 23.93, 22.53,
14.01. HR-MS: calcd for C51H54N2 ([M+H]+), 695.4367; found, 695.4368.
2.2.10.2. 13-Phenylethynyl-15,15-dioctyl-15H-dibenzo[a,c]indeno[1,2-i]phenazine (4c).Yellow solid, Mp
131-133 °C 1H-NMR (500 MHz, CDCl3):
J = 7.9 Hz, 1H), 7.74-7.70 (m, 4H), 7.67-7.63 (m, 4H), 7.43-7.37 (m, 3H), 2.26-2.14 (m, 4H), 1.20-1.05 (m,
20H), 0.82-0.75 (m,10H). 13C-NMR (125 MHz, CDCl3):
ppm 153.86, 151.50, 143.52, 142.46, 142.37,
δ ppm 9.38-9.35 (m, 2H), 8.51-8.47 (m, 3H), 8.25 (s, 1H), 7.95 (d,
δ
141.82, 141.40, 139.70, 131.79, 131.74, 131.62, 131.16, 130.29, 129.90, 128.38, 127.72, 126.29, 125.97,
125.86, 123.75, 123.18, 122.83, 122.75, 122.35, 121.26, 118.73, 90.52, 90.21, 55.21, 41.45, 31.71, 30.04,
29.25, 29.19, 24.02, 22.51, 13.98. HR-MS: calcd for C51H52N2 ([M+H]+), 693.4210; found, 693.4226.
2.2.10.3. 13-Phenylethynyl-15,15-dioctyl-15H-indeno[1,2-i]phenanthro[4,5-abc]phenazine (5c). Yellow solid,
yield 84%. Mp 138-141 °C 1H-NMR (500 MHz, CDCl3):
δ ppm 9.56-9.52 (m, 2H), 8.55 (s, 1H), 8.28 (s, 1H),
8.26-8.22 (m, 2H), 8.09-8.05 (m, 2H), 8.01-7.96 (m, 3H), 7.66-7.61 (m, 4H), 7.42-7.37 (m, 3H), 2.29-2.16 (m,
13
4H), 1.19-1.04 (m, 20H), 0.81-0.73 (m, 10H). C-NMR (125 MHz, CDCl3):
δ ppm 153.99, 151.53, 143.63,
142.67, 142.66, 142.17, 139.72, 131.63, 131.27, 131.22, 131.19, 129.47, 129.56, 128.78, 128.75, 128.39,
128.37, 127.05, 127.00, 126.63, 126.60, 126.31, 125.80, 125.79, 123.78, 123.57, 123.44, 123.19, 122.41,
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121.29, 118.77, 90.52, 90.21, 55.26, 41.48, 31.71, 30.06, 29.27, 29.20, 24.06, 22.51, 13.97. HR-MS: calcd for
C53H52N2 ([M+H]+), 717.4210; found, 717.4196.
2.3 Determination of crystal structure of 4
Suitable single crystals of 4 for X-ray structural analysis were obtained by slow evaporation of a solution
of the solid in chloroform at room temperature. The selected crystal with approximate dimensions of 0.20 x
0.14 x 0.08 mm for 4 was mounted on a four-circle single crystal X-ray diffractometer (CAD4 DIFFACTIS
586) using a graphite monochromated MoKα radiation (λ= 0.071073 nm ) and the data were collected at
296(2) K. The structure was solved by direct methods and refined by full-matrix least-squares method on F2
obs
by using the SHELXTL 97 software package. The non-hydrogen atoms were refined anisotropically. The
hydrogen atoms bound to carbon were located by geometrical calculations, with their position and thermal
parameters being fixed during the structure refinement. The final refinement converged at R1 = 0.0449, wR2 =
0.1036 for 4. A summary of the crystallographic data and structure refinement details is given in Table 1. The
crystal structure and cell structure of 4 are shown in Fig. 4.
Table 1
3. Result and discussion
3.1. Synthesis
The chemical structures of the studied compounds in the present work are illustrated in Fig. 1. The
synthetic strategy employed involved the efficient preparation of the key intermediate
7-bromo-9,9-dioctyl-9H-fluorene-2,3-diamine (2) from fluorene. A systematic synthetic route for similar
intermediate was reported by Lin’s group [38]. As shown in Fig. 2, 2 was successfully synthesized via a 7-step
procedure. 2-Bromo-7-nitro-9H-fluorene (1b) was synthesized by bromination of 2-nitrofluorene (1a) in 80%
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yield at room temperature according to the literature [41]. Dialkylation of 1b was accomplished by generation
of the substituted fluorenyl anion with KOH in DMSO and subsequent dioctylation with 1-bromooctane at
room temperature. Hydrogenation of 1c with hydrazine hydrate, activated carbon and ferric chloride
hexahydrate in MeOH under reflux afforded 7-bromo-9,9-dioctyl-9H-fluoren-2-amine (1d) as a white powder
in 96% yield [42]. Protection of the amine group of 1d with Ac2O/AcOH, followed by regiospecific nitration
with fuming nitric acid in AcOH, gave N-(7-bromo-9,9-dioctyl-3-nitro-9H-fluoren-2-yl)acetamide (1f) as a
yellow powder after column chromatographic purification in total 90% yield by two steps. Removal of acetyl
group of 1f, followed by hydrogenation with hydrazine hydrate, activated carbon and ferric chloride
hexahydrate
in
MeOH
under
reflux
afforded
the
key
intermediate7-bromo-9,9-dioctyl-9H-fluorene-2,3-diamine (2) in 84% yield (for two steps) as a white powder.
The alternate intermediate 9,9-dioctyl-9H-fluorene-2,3-diamine (2a) was synthesized as reported in our earlier
publication [39].
Condensation of 2 or 2a with the corresponding diones in deoxygenated AcOH under reflux for 2-5 h
afforded compounds 3-5, 3a, 4a and 5a in 85-93% yields [43] (Fig. 3). The bromo precursors 3-5 were
conveniently converted to the arylated derivatives 3b, 3d-g, 4b, 4d-g, 5b and 5d-g by treating them with the
corresponding boric acids in the presence of PdCl2(PPh3)2 and K2CO3 under the Suzuki reaction conditions
[44]. The compounds 3c, 4c and 5c containing phenylethynyl substituents were easily obtained by following
the Sonagashira coupling reaction between the suitable bromo precursors 3-5 and phenylethyne [44]. All target
compounds were isolated and purified by column chromatography on silica gel with high purity and their
1
13
molecular structures were confirmed by H NMR spectroscopy, C NMR spectroscopy, and high resolution
MS, which were shown detailed in experiment section.
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Fig. 2
Fig. 3
3.2. X-ray crystallography analysis
The spatial structure of compound 4 was determined by using X-ray diffraction analysis. The ORTEP view
of the structure of 4 (Fig. 4a) showed the almost planar arrangement of the dibenzo[a,c]indeno[1,2-i]phenazine
ring. The fluorene moiety ii forms dihedral angle of 1.865° with adjacent diazines ring iii and the adjacent
phenyl ring iv takes a torsion angle of 2.292° with the diazines ring iii. In the crystal lattice (Fig. 4b), the
molecule packing structure is mainly caused by π-π intermolecular Van der Waals force.
Fig. 4
3.3. Spectral properties
The photophysical properties of the compounds were examined by UV–vis and photoluminescent (PL)
spectra in dilute solutions and in the solid films, as shown in Figs. 5 and 6. The absorption peak wavelengths
(λabs), PL peak wavelengths (λex, λem) in solution and the solid-state, and quantum yields (φFL) in solution are
collected in Table 2. The UV-vis and PL spectra in the solid state were carried out on films spin-coated onto
quartz from chloroform solution. In the CH2Cl2 solutions, all compounds exhibit strong absorptions with their
absorption maxima in the range of 385-464 nm that can be attributed to the π-π* transitions. As it can be
observed in Fig. 5a, compound 3a bearing no aryl group at the terminal exhibited the absorption maximum at
385 nm in CH2Cl2.With the change of the substituents at the terminal position from the phenyl (3b) to other
aryl groups such as phenylethynyl (3c), naphthalen-1-yl (3d), anthracen-9-yl (3e), pyren-1-yl (3f) and
4-(diphenylamino)phenyl (3g), the UV-vis absorption maxima were all red-shifted. And a red shift of 23 nm
was observed at 408 nm for compound 3g, which possesses the longer conjugation length and stronger
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electron-donating groups, relative to those of the other compounds. By inserting triple bonds between the
fluorene ring and the phenyl substituents to overcome the twisted structure, compound 3c exhibited only small
longer absorption (398 nm) than that of 3b (394 nm). The naphthalene and anthracene substituted derivatives
(3d and 3e) exhibited shorter absorption wavelengths (391 and 392 nm, respectively) by comparison with 3b,
as a result of the larger restricted rotation around the single bond between the naphthalene (anthracene) and the
fluorene. However, in the case of pyrene substituents (3f), the absorption red shifted even though the existence
of
restricted
rotation
could
not
be
avoided.
The
absorption
spectra
of
all
15H-dibenzo[a,c]indeno[1,2-i]phenazine derivatives 4a-g were red-shifted relative to the corresponding
compounds 3a-g, and their relative order of the values of absorption maxima (λmax) retained the same as
observed in the series of 3a-g. Similarly, the largest red-shift was observed at 438 nm for compound 4g. And
new slightly intense absorption bands at 389, 403, 407, 401, 398, 411 nm for compounds 4a-f were observed,
respectively, presumably due to the n-π* transitions. The absorption spectra of compounds 5a-g were all
red-shifted almost 30 nm compared with compounds 4a-g, showing two characteristic absorption peaks in the
wave range from 424 to 464 nm, and the largest red-shift was observed at 464 nm for compound 5g. As shown
in Fig. 5b, the UV-vis absorption spectra measured in DMSO solutions indicated that all compounds showed
small red shifts no more than 4 nm, compared with the corresponding spectra in CH2Cl2, suggesting that the
ground states of all these compounds are rather nonpolar in nature.
Fig. 5
Table 2
All the compounds 3a-g, 4a-g, 5a-g displayed blue, green, yellow or red emission depending on the
nature of the whole molecule in CH2Cl2 solution (1×10-3 M) under UV light 365nm. Fig. 6 shows the
photoluminescence (PL) spectra recorded upon excitation at each excitation wavelength (λex) at room
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temperature. In dilute CH2Cl2 solution, compound 3a showed emission peak at 408 nm (Fig. 6a) and the
fluorescence quantum yield is 0.54, which is almost equal to quinine sulfate (φFL=0.55). The fluorescence
spectra of compounds 3b-d with emission peaks at 422 nm, 423 nm, 428 nm, respectively, were all red-shifted
relative to that of 3a. The fluorescence maxima of compound 3e, 3f and 3g, were red-shifted by 89 nm, 75 nm,
153 nm, respectively, due to the elongation of the conjugation length. It is interesting to note that compound
3g fluoresced in dichloromethane with yellow emission peaks at ca. 561 nm. The fluorescence spectra of 4a
showed a red shift of 21 nm by comparison with that of 3a. Similarly, compounds 4b-f exhibited different
extent of red shifts relative to 4a, showing emission peaks at 447 nm, 447 nm, 453 nm, 542 nm and 524 nm,
respectively. The largest red shift was observed for 4g, which showed two emission peaks at 613 and 642 nm.
Comparing compounds 3e and 3f, 4e and 4f, the replacement of the anthracene group by the pyrene group
resulted in slightly longer absorption wavelengths but much shorter emission wavelengths. Compared with 4a,
the emission maxima of compound 5a (λem = 473 nm) red-shifted by 44 nm. However, the emission peak of
the derivatives 5a-f was in the range of 473-478 nm, less sensitive to the terminal aryl group tethered to the
fluorene nucleus, indicating that the emission may be dominated by the state localized on the
15H-indeno[1,2-i]phenanthro[4,5-abc]phenazine chromophore. For the amine derivative 5g, an enormous
red shift was observed with two emission peaks at 615 and 640 nm. Except compounds 3g, 4g and 5g, all the
other compounds synthesized were moderate to high fluorescent in CH2Cl2 solution with fluorescence
quantum yields φFL in the range of 0.40-0.71. The relatively low quantum yields observed for the amine
compounds 3g, 4g and 5g suggest a prominent nonradiative deactivation pathway for the excited state.
Fig. 6
By comparison with the dilute CH2Cl2 solutions, the emission spectra of most compounds in solid states
showed red-shifts to longer wavelengths by 5-36 nm (Fig. 6b). The red-shifts of the emission observed in the
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solid state were probably due to the rigid parent diazines and its strong intermolecular forces, which drove the
molecules to pack at high density and formed J-aggregates, restricted the molecular rotation and increased the
π-conjugation significantly, in turn resulting in the red-shifts [45]. However, several compounds 3e-g, 4-g, 5g
showed blue-shifts to shorter wavelengths by 25-114 nm. These compounds probably drove the molecules to
form H-aggregates, which decreased the π-conjugation significantly, in turn resulting in the blue-shifts [46].
3.4. Electrochemical properties
The redox potentials of all the compounds were determined by cyclic voltammetry (CV) measurements
which were carried out in a three-electrode cell setup with 0.1 M tetrabutyl-ammonium perchlorate (Bu4NClO4)
as a supporting electrolyte in anhydrous CH2Cl2 to probe the electrochemical behavior of the materials. The
electrochemical properties are shown in Table 2. HOMO values were calculated from as HOMO = [Eonset red/ox
]
(vs SCE) + 4.6, Eg = 1240/UV(onset) [35, 36]. As seen from Table 2, it is clearly evident that the nature of the
aryl substituents and the π-acceptor units significantly alters the HOMO/LUMO energies. The HOMO
energies of all the compounds were at about 5.09-5.47 eV, which exhibited more properties of aryl when
introducing the relatively lager aryl substituent on the same π-acceptor units. The band gaps (Eg) of about
2.50-3.06 eV were estimated from the optical edge. Compounds 3a-g exhibited a relatively larger band gap by
comparison with those of compounds 4a-g, 5a-g, which derived from the more distorted π-conjugation
structures. The LUMO energy levels for compounds were determined to be around 2.14-2.87 eV by
combining the HOMO energy levels together with the band gaps. It was found that compounds 3d-f, 4d-f,
5d-f showed relatively lower HOMOs and LUMOs, which probably due to relatively good π-π* transition and
π-accepting ability of the naphthyl, anthryl, pyrenyl substituents [47].
Fig. 7
Density functional theory (DFT) calculations have also been applied to characterize the
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three-dimensional geometries and the frontier molecular orbital energy levels of the representative compounds
3e, 4e, 5e and 3g, 4g, 5g at the B3LYP/6-31G* level by using the Gaussian 03 program[35,36]. The orbital
plots of the HOMO-LOMOs are illustrated in Fig. 7. In all of the above compounds, the HOMO and LUMO
were mainly constituted by the aryl substituents and the indenoquinoxaline segments. In the case of the
compound 3e, the HOMO and LUMO were localized mainly on the anthracene unit, indicating that the
absorption and emission process were mostly attributed to the π-π* transition centered at the anthracene
moiety. And compound 5e spread the HOMO and LUMO through the fluorene moiety, which could explain
the relatively lower energy level by comparison of other substituents. The 4-(diphenylamino)phenyl
substituted compounds 3g, 4g, 5g exhibited fairly distorted structures, which could lead quick electronic
transition from the tribenzylamine group to the π-accepting moiety and this probably accounted for the poor
quantum yields.
4. Conclusion
In summary, 7-bromo-9,9-dioctyl-9H-fluorene-2,3-diamine, as a new multifunctional intermediate for π
conjugated molecules, was efficiently synthesized. A series of 2,3-diphenyl-10H-indeno[1,2-g]quinoxaline,
15H-dibenzo[a,c]indeno[1,2-i]phenazine and 15H-indeno[1,2-i]phenanthro[4,5-abc]phenazine derivatives
containing different terminal aromatic units such as phenyl, phenylethynyl, naphthyl, anthryl, pyrenyl, or
4-(diphenylamino)phenyl were synthesized via palladium-catalyzed C-C cross-coupling reactions in good
yields. The new target compounds were thoroughly analyzed by routine spectral methods and the absorption
spectra and fluorescence characteristics show dependence on their molecular structure. Most compounds
possess a medium fluorescence-emitting ability with φFL values in the region of 0.40-0.71 and displayed blue,
green, yellow or red emission depending on the nature of the whole molecule. The HOMO energy levels of
about 5.09-5.47 eV and the LUMO energy levels of about 2.14-2.87 eV were determined by the aryl
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substituents and the π-acceptor units significantly. Further research regarding the incorporation of these
systems usable both as organic light-emitting diodes and as fluorescent probes is under way in our laboratory.
Acknowledgements
The authors are grateful for supports from the National Natural Science Foundation of China (Project No. 81202402
and 21272154). The authors also thank Drs. H. Deng and M. Shao, The Instrumental Analysis & Research Center of
Shanghai University, for structural analysis.
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