Fluorinated 1,8-naphthalimides: Synthesis, solid structure and properties

Article abstract of DOI:10.1016/j.cclet.2014.04.017

Three fluorinated 1,8-napthalimides were synthesized from acenaphthene. Their structures were characterized by NMR and EI-MS analyses. The structures of compounds 1b and 1c were also confirmed by X-ray diffraction analysis, which showed that they possessed different packing models. Their optoelectronic properties were investigated. The results indicated that all of the naphthalimides possess good solubility and low LUMO energy level, which make them good solution processing candidates in n-type semiconductor.

Full text of DOI:10.1016/j.cclet.2014.04.017

G Model
CCLET 2961 1–4
Chinese Chemical Letters xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Chinese Chemical Letters
journal homepage: www.elsevier.com/locate/cclet
1
2
Original article
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Fluorinated 1,8-naphthalimides: Synthesis, solid structure and
properties
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1
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Q1 Jie Huang , Di Wu , Hao-Jie Ge, Sheng-Hua Liu, Jun Yin *
Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079, China
A R T I C L E I N F O
A B S T R A C T
Article history:
Three fluorinated 1,8-napthalimides were synthesized from acenaphthene. Their structures were
characterized by NMR and EI-MS analyses. The structures of compounds 1b and 1c were also confirmed
by X-ray diffraction analysis, which showed that they possessed different packing models. Their
optoelectronic properties were investigated. The results indicated that all of the naphthalimides possess
good solubility and low LUMO energy level, which make them good solution processing candidates in
n-type semiconductor.
Received 28 January 2014
Received in revised form 11 April 2014
Accepted 11 April 2014
Available online xxx
Keywords:
ß 2014 Jun Yin. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Napthalimide
n-Type semiconductor
Optoelectronic properties
7
8
1. Introduction
electron-withdrawing groups to a conjugated system, such as 31
cyano, imide or fluorine groups [8,9]. Among all kinds of n-type 32
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
In recent years, organic semiconductors have drawn signifi-
cantly more attention, compared to the traditional inorganic
materials such as amorphous or crystalline silicon. They displayed
several advantages such as their adaptability to low-temperature
processing on flexible substrates, low cost, amenability to high-
speed fabrication, and tunable electronic properties [1–3]. Organic
semiconductors become a promising technology for large-area
electronic applications including electronic paper displays, radio
frequency identification tags, smart cards, and large-area sensors
[4,5]. Organic semiconducting materials are commonly classified
as p-type (hole-conducting) or n-type (electron-conducting),
depending on which type of charge carrier is more efficiently
transported through the material. So far, a large number of high
performance p-type organic semiconductors have been studied,
and stable organic p-type semiconductors have fulfilled many of
the requirements in diverse applications. However, high perfor-
mance n-type organic semiconductors are relatively rare, mainly
owing to synthetic difficulties and poor air stability [6].
organic semiconductors, naphthalene diimide (NDI) was consid- 33
ered one of the most promising candidates due to its good air- 34
stability and film-forming ability [10]. Fluorine atoms can lower 35
both the HOMO and LUMO energy levels to facilitate the electron 36
injection and stabilize the materials to display a greater resistance 37
against the degradative oxidation processes [11]. Moreover, the 38
C–Hꢀ ꢀ ꢀF interactions play an important role in the solid state 39
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
supramolecular organization, originating a typical
p-stack ar- 40
rangement that enhances the charge carrier mobility [12]. Herein, 41
we report three fluorinated 1,8-napthalimides. Their structures 42
were characterized and their optoelectronic properties were 43
investigated.
44
2. Experimental
45
Compounds 3, 4, 5 and 6a have been reported in the literature 46
13,14]. Unless otherwise mentioned, all commercially available 47
starting materials were used as received without further purifica- 48
tion. DMSO was dried with CaH and then distilled under reduced 49
[
In view of the requirements for the fabrication of organic
complementary circuits, n-type organic semiconductor has evoked
increasing interest recently [7]. To afford air stable n-type organic
semiconductors, the common strategy is to introduce strong
2
1
13
pressure. H NMR and C NMR spectra were collected on an 50
American Varian Mercury Plus at 400 spectrometer 400 MHz or 51
600 MHz. Chemical shifts (d) are reported in ppm, using TMS as an 52
internal standard. MS spectra were collected on a Thermo DSQ II. 53
UV–vis spectra were obtained on a U-3310 UV Spectrophotometer. 54
Fluorescence spectra were obtained on a FluoroMax-P. The crystal 55
structure was recorded on a Bruker SMART CCD area-detector 56
*
Corresponding author.
E-mail address: yinj@mail.ccnu.edu.cn (J. Yin).
These authors contributed equally to this work.
1
X-ray diffraction spectrometer.
57
http://dx.doi.org/10.1016/j.cclet.2014.04.017
001-8417/ß 2014 Jun Yin. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
1
Please cite this article in press as: J. Huang, et al., Fluorinated 1,8-naphthalimides: Synthesis, solid structure and properties, Chin. Chem.
Lett. (2014), http://dx.doi.org/10.1016/j.cclet.2014.04.017

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J. Huang et al. / Chinese Chemical Letters xxx (2014) xxx–xxx
Scheme 1. Synthesis of compounds 1a–c.
58
2.1. General synthetic procedures for 6b and 6c
2.2. General synthetic procedures for 1a–c
78
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60
61
62
63
64
65
66
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70
71
72
73
74
75
76
77
A
mixture of 4,5-dibromo-1,8-naphthoic anhydride
5
A mixture of 4,5-dibromo-1, 8-naphthalimide (0.5 mmol),
anhydrous powered CsF (3.3 mmol) in dry DMSO (50 mL) was
stirred for 1 h under nitrogen at 95 8C. The reaction mixture was
then cooled and poured into ice and the yellow solid was collected
by filtration. The residue was purified by column chromatography
using dichloromethane/petroleum ether (1:3, v/v) as an eluent to
afford the pure product.
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80
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84
85
86
87
88
89
90
91
92
93
94
95
96
97
(2.8 mmol), amine (2.8 mmol) in ethanol (50 mL) was stirred
overnight under nitrogen at 78 8C. The reaction mixture was then
cooled and the solvent was removed under vacuum. The residue
was purified by column chromatography using dichloromethane/
petroleum ether (1:3, v/v) as an eluent to afford pure product as a
yellow solid.
1
1
Compound 6b. Yield: 0.49 g, 40%. H NMR (400 MHz, CDCl
8.40 (d, 2H, J = 5.6 Hz), 8.21 (d, 2H, J = 8 Hz), 4.14 (t, 2H, J = 7.6 Hz),
3
):
d
Compound 1a. Yellow solid; yield: 36 mg, 25%. H NMR
(400 MHz, CDCl
3
): d 8.63 (d, 2H, J = 8.4 Hz), 7.45–7.28 (m, 2H),
1
3
1.73–1.68 (m, 2H), 1.41–1.25 (m, 6H), 0.89 (t, 3H, J = 4 Hz).
NMR (100 MHz, CDCl ): 163.00, 136.04, 131.36, 131.02, 127.97,
127.52, 123.01, 40.71, 31.46, 27.85, 26.71, 22.52, 14.02. EI-MS: m/z
439.00; calcd. for C18 NO : 439.14.
Compound 6c. Yield: 0.42 g, 35%. H NMR (600 MHz, CDCl
8.38 (d, 2H, J = 7.8 Hz), 8.21 (d, 2H, J = 8.4 Hz), 5.01–4.96 (m, 1H),
2.24–2.17 (m, 2H), 1.93–1.87 (m, 2H), 0.89 (t, 6H, J = 7.8 Hz).
NMR (100 MHz, CDCl ): 158.50, 136.20, 131.37, 131.00, 128.02,
127.75, 127.55, 57.55, 24.10, 10.90. EI-MS: m/z 424.82; calcd. for
C
4.16 (t, 2H, J = 7.6 Hz), 1.72–1.68 (m, 2H), 1.25–1.46 (m, 2H), 0.97
1
3
3
d
(t, 3H, J = 7.2 Hz). C NMR (100 MHz, CDCl
3
): d 162.86, 162.59,
162.48, 159.76, 159.65, 133.68, 131.41, 118.79, 112.88, 40.23,
H
17Br
2
2
13 2 2
30.00, 20.26, 13.75. EI-MS: m/z 289.03; calcd. for C16H F NO :
1
3
):
d
289.09.
1
Compound 1b. Yellow solid; yield: 33 mg, 21%. H NMR
(400 MHz, CDCl ): 8.63 (d, 2H, J = 7.6 Hz), 7.49–7.42 (m, 2H),
4.14 (t, 2H, J = 7.6 Hz), 1.75–1.67 (m, 2H), 1.41–1.33 (m, 6H), 0.89
1
3
C
3
d
3
d
1
3
3
(t, 3H, J = 6.6 Hz). C NMR (100 MHz, CDCl ): d 162.96, 162.71,
C
17
H
15Br
2
NO
2
: 424.94.
162.60, 159.89, 159.78, 133.75, 131.91, 131.56, 127.11, 126.78,
UV-vis (solution)
b
a
UV-vis (solution)
UV-vis (film)
PL (solution)
PL (film)
UV-vis (film)
1.0
1.0
0.8
0.6
0.4
0.2
0.0
PL (solution)
PL (film)
0
.8
.6
0
0.4
0.2
0.0
350
400
450
500
550
600
350
400
450
500
550
600
Wavelength (nm)
Wavelength (nm)
c
!
UV-vis (solution)
UV-vis (film)
PL (solution)
PL (film)
d
1.0
0.8
0.6
0.4
0.2
0.0
0.0
0.5
1.0
1
1
1
a
b
c
-
-
350
400
450
500
550
600
-2.0
-1.5
-1.0
-0.5
0.0
Wavelength (nm)
Potential (V)
ꢂ5
ꢂ1
ꢂ5
ꢂ1
Fig. 1. (a) Normalized UV–vis absorption and photoluminescence spectra of 1a in CH
2
Cl
2
(1.0 ꢁ 10 mol L ) and in thin film; (b) 1b in CH
2
Cl
2
(1.0 ꢁ 10 mol L ) and in
6
as supporting electrolyte.
(1.0 ꢁ 10ꢂ5 mol L ) and in thin film; (d) Cyclic voltammogram (CV) of 1a–c in dry DCM with 0.1 mol L Bu
ꢂ1
ꢂ1
NPF
thin film; (c) 1c in CH
2
Cl
2
4
Please cite this article in press as: J. Huang, et al., Fluorinated 1,8-naphthalimides: Synthesis, solid structure and properties, Chin. Chem.
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J. Huang et al. / Chinese Chemical Letters xxx (2014) xxx–xxx
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Table 1
Optical and electrochemical data of 1a–c.
a
a
b
ꢂ1
ꢂ1
1
r
onset
c
d
e
Compd.
l
Abs (nm)
l
max (PL) (nm)
e
max (L mol cm
)
E
(V)
E
r
(V)
LUMO (eV)
HOMO (eV)
g
E (eV)
1
1
1
a
b
c
338, 353 (solution); 350, 365 (film)
338, 352 (solution); 341, 358 (film)
338, 352 (solution); 340, 359 (film)
388 (solution); 419 (film)
388 (solution); 421 (film)
388 (solution); 436 (film)
26,000
14,400
22,800
ꢂ1.67
ꢂ1.66
ꢂ1.73
ꢂ1.63
ꢂ1.62
ꢂ1.69
ꢂ3.17
ꢂ3.18
ꢂ3.11
ꢂ6.52
ꢂ6.53
ꢂ6.49
3.35
3.35
3.38
a
b
c
(1.0 ꢁ 10ꢂ5 mol Lꢂ1).
The wavelength of absorption and photoluminescence in CH
2 2
Cl
The molar extinction coefficient.
onset
LUMO energy levels was calculated from the onset of the first reduction according to equation: LUMO = ꢂ(4.8 + E
r
) eV.
d
e
HOMO =LUMO ꢂ E
g
.
E
g
was calculated from the low-energy absorption onset in the absorption spectra according to equations: E
g
= 1240/
l
onset [15].
9
9
1
1
1
1
1
1
8
9
118.93, 112.93, 112.19, 40.52, 31.46, 27.93, 26.70, 22.50, 13.98. EI-
MS: m/z 317.18; calcd. for C18 NO : 317.12.
Compound 1c. White solid; yield: 22 mg, 15%. H NMR
(400 MHz, CDCl ): 8.61 (d, 2H, J = 9.3 Hz), 7.46–7.41 (m, 2H),
5.15–4.87 (m, 1H), 2.25–2.18 (m, 2H), 1.98–1.92 (m, 2H), 0.88 (t,
solution in Fig. 1a and Table 1, which represented a 50 nm Stokes 125
shift (excited at 338 nm). 126
H
17
F
2
2
1
00
01
02
03
04
05
The UV–vis absorption and fluorescence spectra of 1a were also 127
measured in the thin-film state as shown in Fig. 1a. The UV–vis 128
absorption spectra and fluorescence spectra collected in the thin 129
films were broader than those spectra collected in solutions and 130
showed a large bathochromic shift, indicating that the chromo- 131
3
d
1
3
3
6H, J = 7.4 Hz). C NMR (100 MHz, CDCl ): d 162.56, 162.43,
133.85, 131.74, 119.21, 119.03, 113.02, 112.91, 112.81, 57.48,
24.52, 10.82. EI-MS: m/z 303.09; calcd. for C17
H
15
F
2
2
NO : 303.10.
phore had a strong tendency to aggregate in the solid state.
132
As can be seen in Fig. 1b and c and Table 1, similar phenomena 133
were also observed on the absorption and emission spectra of 1b 134
and 1c in the solution and in the film state, indicated that the 135
different alkyl chain had little effects on their optical properties. 136
1
06
3. Results and discussion
107
108
109
110
111
112
113
114
115
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117
118
119
120
121
122
123
124
The synthesis of 1a–c was outlined in Scheme 1. Acenaphthene
was bromated using NBS to give 3. Subsequently, a two-step
oxidation reaction was performed to afford 5. Then naphthoic
anhydride was treated with different amine in ethanol to afford the
corresponding bromo-1,8-naphthalimide. The targeted com-
pounds were prepared from bromo-1,8-naphthalimide in dry
DMSO using CsF. These compounds showed very good solubility in
common solvents, such as dichloromethane, chloroform and
acetone. This good solubility allowed them to be processed in
solution and allowed the formation of thin films. The optical
properties were investigated by UV–vis absorption and fluores-
cence spectrometry. Fig. 1a showed the UV–vis absorption and
The values of optical energy gaps (E
calculated from the low-energy absorption onset in the absorption 138
spectra, as shown in Table 1. 139
g
) (ꢃ3.35–3.38 eV) were 137
Subsequently, the electrochemical properties of these naphtha- 140
limides were investigated by cyclic voltammetry (CV). The 141
measurements were carried out in dry dichloromethane at room 142
temperature under nitrogen atmosphere. As shown in Fig. 1d, one 143
pair of irreversible reduction waves were observed. For example, 144
compound 1a showed a reduction wave at ꢂ1.67 V and no obvious 145
oxidation waves were observed. The LUMO energy level of ꢂ3.17, 146
ꢂ3.18, ꢂ3.11 eV were estimated for 1a–c based on the onset 147
potential of the first reduction wave. The HOMO energy levels of 148
1a–c were also calculated based on the equation described in 149
Table 1. From these calculations, we found that these compounds 150
had similar HOMO and LUMO energy levels. The HOMO and LUMO 151
energy levels of 1a–c were much lower, in comparison with those 152
of non-substituted 1,8-naphthalimide. These data demonstrated 153
that fluorine atoms lowered not only the LUMO energy level but 154
2 2
fluorescence spectra of 1a in CH Cl . Two characteristic absorption
peaks at 338 nm and 353 nm were observed, compared with the
absorption bands at 334 nm and 344 nm of non-substituted 1,8-
naphthalimide [16], which suggested that the introduction of the
two fluorine atoms led to a slight red shift. Compound 1a had a
wavelength of 388 nm for the maximum fluorescence emission in
Fig. 2. The single crystal structures and packing views of 1b (a), 1c (b). (Top, side, and packing view from left to right. Hydrogen atoms have been omitted in packing views.).
Please cite this article in press as: J. Huang, et al., Fluorinated 1,8-naphthalimides: Synthesis, solid structure and properties, Chin. Chem.
Lett. (2014), http://dx.doi.org/10.1016/j.cclet.2014.04.017

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also the HOMO energy level, which was significant to afford air
stable n-type organic semiconductors.
cultivation grant from Central China Normal University (No.
2013YBYB60).
188
189
Single crystals of 1b and 1c suitable for crystallographic
analysis were grown by slow diffusion of n-hexane to their
dichloromethane solutions. As depicted in Fig. 2, C–Hꢀ ꢀ ꢀO
hydrogen bonds made 1b pack into one-dimensional planar
structures. Compound 1c displayed lamellar packing promoted
by the C–Hꢀ ꢀ ꢀO hydrogen bonds and C–Hꢀ ꢀ ꢀF hydrogen bonds. The
slight structural change induced by alkyl chain resulted in an
obvious change of packing form. It is well-known that molecular
stacking is very important for the properties of a material [17].
Hence, these results afforded an alternative approach to explore
organic optoelectronic materials by decorating of their structures.
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Please cite this article in press as: J. Huang, et al., Fluorinated 1,8-naphthalimides: Synthesis, solid structure and properties, Chin. Chem.
Lett. (2014), http://dx.doi.org/10.1016/j.cclet.2014.04.017