Energy-level modulation of organic alkynes by click chemistry

Article abstract of DOI:10.1016/j.tet.2012.10.081

A series of novel donoreacceptor chromophores have been successfully synthesized in excellent yield by metal-free [2+2] click chemistry, which was effective in the energy-level modulation. Structures of the conjugated compounds were fully characterized by

Full text of DOI:10.1016/j.tet.2012.10.081

Tetrahedron 69 (2013) 895e901
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Energy-level modulation of organic alkynes by click chemistry
,
a,b
Dong Wang a, Wanshu Zhang a, Yan Xing b, Hong Gao b , Xiangke Wang
,
*
,
Yuzhen Zhao a, Huai Yang a
*
a University of Science and Technology Beijing, Beijing 100083, PR China
b China Academy of Space Technology, Beijing 100083, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of novel donoreacceptor chromophores have been successfully synthesized in excellent yield by
metal-free [2þ2] click chemistry, which was effective in the energy-level modulation. Structures of the
conjugated compounds were fully characterized by NMR, IR, and MS. By introducing TCNE, TCNQ, F4-
TCNQ click monomers, we obtained energy-level tunable materials in high solubility, which was bene-
ficial for processing. It has been demonstrated that the absorption characteristics of all the newly pre-
pared compounds have been strongly bathochromically shifted with an end-absorption far into the near
infrared region due to the efficient intramolecular charge-transfer (CT) interaction. The electrochemical
properties have been studied by cyclic voltammograms indicating good agreement between the elec-
trochemical and optical band gaps determined by the end absorption.
Received 8 June 2012
Received in revised form 26 September
2012
Accepted 9 October 2012
Available online 8 November 2012
Keywords:
Energy-level modulation
Click chemistry
Selective alkynes
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
cycloaddition followed by the ring opening reaction proceeds in the
quantitative yield under mild conditions (Scheme 1).11
Energy-level modulation of organic photoelectric materials has
received tremendous research attention in both academic interests
and commercial applications, such as solar cells and organic lighting
emitting display (OLED).1 Tuning of the electronic HOMO and LUMO
levels is crucial in improving the optoelectronic properties of or-
ganic materials. However, the use of organic photoelectric materials
with controllable charge transport is still in its infancy, and it re-
mains a major challenge to effectively tune the charge transport.
Scheme 1. Click chemistry-type addition reaction between TCNE and alkynes acti-
vated by electron-donating group (EDG).
Fortunately, design of new donoreacceptor type
p-conjugated
molecules is one solution,2 which can be achieved by the thermal
[2þ2] cycloaddition followed by the ring-opening of click chemistry.
Click chemistry provides efficient, reliable, and selective reactions
for synthesizing new compounds and to generate combinatorial li-
braries.3 Nowadays the most popular and well-studied click reaction
is the copper (I)-catalyzed azideealkyne cycloaddition reaction
(CuAAC), forming a triazole ring4 by Sharpless5 and Meldal,6 which
has been widely used for the preparation of functional materials.7
However, the development of other click-type reactions has simul-
taneously been pursued,8 typically thermal [2þ2] cycloadditions,
followed by retro-electrocyclization, of tetracyanoethene (TCNE),9
7,7,8,8-tetracyanoquiodimethane (TCNQ),10 and 2,3,5,6-tetrafluoro-
7,7,8,8-tetra cyanoquinodimethane (F4-TCNQ) to ‘electronically con-
fused’ alkynes. For example, when dialkylanilino groups are
The [2þ2] click reactions are with significant advantages that the
products feature strong charge-transfer (CT) interactions in the visible
absorption region, potent redox activities,12 and are useful for opti-
mization of the electronic states, thereby leading to the enhanced
performanceoftheoptoelectronicdevices,suchasphotovoltaiccells.13
In the present work, we designed and synthesized a family of or-
ganic conjugated molecules with great potential applications for
photoelectric materials. Meanwhile, the novel click chemistryallowed
us to efficientlymodulatetheHOMOeLUMO energy band gap, leading
to p-conjugatedmolecules withtunableelectrochemicalproperties as
well as excellent solubility, which was beneficial for processing.
2. Results and discussion
2.1. Synthesis
employed as the electron-donating group (EDG),
a
[2þ2]
The reacting aromalkyne molecules C1eC4 were shown in
Scheme 2. C1, C3, and C4 were synthesized according to the
* Corresponding authors. Tel./fax: þ8610 62333969; e-mail addresses: wangdong_
ustb@foxmail.com (D. Wang), yanghuai@mater.ustb.edu.cn (H. Yang).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.10.081

896
D. Wang et al. / Tetrahedron 69 (2013) 895e901
as TCNE, while the blue ones were alternative. The click reactions
required heating in dichlorobenzene up to 100 ꢀC for 1 h with
significantly high yields ranging from 89% to 94%. In fact, the re-
actions with click reagent TCNE could be fulfilled under ambient
temperature and enhancement of temperature to 100 ꢀC was just
for higher efficiency. All the newly prepared products were in high
purity, which was confirmed by NMR, IR, and MS spectra. Moreover,
they were stable at ambient temperature under air and reasonably
soluble in common organic solvents, such as CH2Cl2, acetone, and
acetonitrile, which was beneficial for processing. Furthermore, no
special purification process was necessary because of the absence
of byproducts. Therefore, this kind of reaction satisfied most of the
requirements of click chemistry, and it could be classified as a new
metal-free click chemistry that further improved optoelectronic
properties of organic materials.
2.2. UVevis spectroscopy
The normalized UVevis absorption spectra were shown in Fig. 1.
The spectral shapes and positions were very similar to the reported
click products.15 Most of the prepared products showed intense CT
bands with end-absorptions reaching into the near infrared region.
Aromoalkyne C1 reacting with different click reagents TCNE, TCNQ,
and F4-TCNQ yielded 1a, 3a, and 5a, respectively (Fig. 1(a)). The
electron-withdrawing groups tended to bathochromically shift the
spectra relative to C1, and the shift in the end absorption (lend) from
that of C1 (417 nm) was 128, 371, and 551 nm for 1a, 3a, and 5a,
respectively. Comparing 3a with 1a, the intensification of conju-
gation was much larger, and the intramolecular charge transferred
over a longer conjugation length along the molecular backbones, so
the CT bands were red shifted. Although the conjugation length of
3a and 5a was similar, the introduction of the strong electron-
withdrawing group F into 5a further lowered the LUMO energy
Scheme 2. Structures of C1eC4 and their synthesis routes: (a) ethynyl-
triisopropylsilane, Pd(PPh3)4, CuI, THF, diisopropylamine (i-Pr2NH), 80 ꢀC, 12 h.
literature methods,14 while C2 monomer was newly synthesized
and fully characterized by NMR, IR, and MS spectra from which the
chemical structures were verified. Compounds C1eC4 have good
solubility in common organic solvents.
Synthesis of donoreacceptor chromophores 1ae8a and 1be6b
was achieved through introducing in amine-substituted aromatic
precursors by the high-yielding [2þ2] click reactions using TCNE,
TCNQ, and F4-TCNQ as acceptor molecules. As it was shown in
Scheme 3, the click reaction was selective, namely, all the acetylenic
bonds with red high light reacted with the electron acceptor, such
Scheme 3. Synthesis of donoreacceptor chromophores: (a) dichlorobenzene, 100 ꢀC, 1 h.

D. Wang et al. / Tetrahedron 69 (2013) 895e901
897
27 nm more of redshifts than 4b which was the co-impact of the
conjugation length and the number of electron-withdrawing group
CN. Namely, although 4b had two more CN groups than 3b, which
benefited the diminution of the band gap, the triple bond reacting
with the second TCNQ decreased the conjugation length so that the
band gap decrease was inhibited.
Fig. 1(c) exhibited the absorption spectra of products of different
monomers C1eC4 reacting with the same click reagent (TCNE). The
extent of bathochromical shift depended not only on the conjuga-
tion length of the main chains but also the electron-withdrawing
ability of the substituents. As the electron-withdrawing ability in-
creased in the order of TIPS<OC16H33<Br<NO2, correspondingly,
the redshift increased in the sequence of 1b<8a<1a<7a. Thus,
electron-rich substituents shifted the CT bands bathochromically.
According to Fig. 2, the resulting donoreacceptor chromophores
featured well-defined CT bands in the visible region. Subsequently,
the reaction of C3 was initially investigated by UVevis spectro-
scopic titration experiments by adding acceptor molecule TCNE to
C3 in chlorinated solvents. When TCNE was selected as a compact
acceptor molecule, the reaction immediately proceeded at 100 ꢀC,
suggesting the occurrence of click functionalization. Thus, the ab-
sorption intensities of the precursor (C3) started to decrease and
a new CT band with a relatively weak peak at 599 nm shown due to
the occurrence of click product 7a. The peak position of the CT
bands was unchanged, while the intensities linearly increased with
the increasing amount of the added TCNE. The presence of the
isosbestic points at 354 and 493 nm for C3 indicated no side re-
actions. Similarly, the same titration experiments were carried out
for C4. Very interestingly, when the intense CT absorption was
noted, the peak top values shifted bathochromically with
increasing amount of TCNE addition. The possibility of the
intermolecular aggregation was ruled out.
Fig. 1. UVevis absorption spectra of (a) C1, 1a, 3a, and 5a; (b) C2, 3b, and 4b; (c) 1a, 1b,
7a, and 8a in CH2Cl2 at 298 K. The inset photographs showed the colors of the cor-
responding solutions.
Fig. 2. UVevis spectral changes of C3 upon titration with TCNE (0e1.0 equiv) in
chloroform at 20 ꢀC. Inset: zoom on the low energy CT band.
If the side-chain chromophores did not interact with each other,
the peak top values should be constant.16 This result suggested that
this click-type reaction could affect the electronic state of the whole
conjugated compounds14 thus could be employed for tuning the
energy levels of the conjugated materials.
level and band gap, and enhanced the electron affinity, so the
redshift was more significant. Thus, the extent of the shift increased
in the sequence of 1a<3a<5a.
The positions of lend also depended on the number of click re-
agents (Fig. 1(b)). Compounds 3b and 4b were synthesized by in-
troduction of one or two TCNQ in monomer C2, respectively. In
comparison with C2 (425 nm), 3b (736 nm) and 4b (709 nm) both
lowered the energy of the CT bands, which was due to the in-
troduction of the electron-withdrawing group CN, while the extent
of bathochromical shifts was similar. Compound 3b exhibited only
2.3. Electrochemistry
One of the most important features of donoreacceptor chro-
mophores was the oxidation/reduction activities. To clarify the
electrochemical properties, the electrochemical behavior of

898
D. Wang et al. / Tetrahedron 69 (2013) 895e901
products and reactants was examined by cyclic voltammetry (CV).
Cyclic voltammogram of 7a was shown in Fig. 4, and all the others
were set in the Supplementary data. The energy levels were calcu-
lated using the Ferrocene (Fc) value of ꢁ4.8 eV with respect to the
vacuum level, which was defined as zero. The measured oxidation
potential of Fc (vs Ag/AgCl) was 0.46 V. Therefore, the EHOMO levels of
the products could be calculated by the equation EHOMO¼ꢁe
[Uonset(ox)ꢁU1/2,Fcþ4.8 V] and the LUMO energy (ELUMO) levels could
be estimated by the equation ELUMO¼ꢁe[Uonset(red)ꢁU1/2,Fcþ4.8 V],
where U1/2,Fc standards for the half-wave potential of Fc/Fcþ.
compounds exhibited smaller electrochemical band gaps Ebg than
TCNE-products, which was probably caused by the expanded
conjugation of the acceptor moieties and strongly electron-
withdrawing ability.
p
-
3. Conclusions
A series of stable derivatives were prepared by the [2þ2] cy-
cloaddition of TCNE, TCNQ, and F4-TCNQ to donor-substituted al-
kynes in excellent yields, and fully characterized. The results
Fig. 3. HOMO and LUMO energy levels of C1, C2 and products 1e6a, 1e6b. On the right are the chemical structures of C1 and C2.
obtained by UVevis spectra of these pure compounds indicated
the efficient intramolecular charge-transfer (CT) interactions,
which was in result of the enlargement of the absorption spec-
trum and the corresponding CT bands strongly bathochromically
shifted with an end-absorption reaching far into the near infrared
region. Meanwhile, the energy level of the products was effec-
tively modulated by the novel metal-free [2þ2] click reaction
which further improved optoelectronic properties of organic ma-
terials. Moreover, all the newly prepared compounds were in high
solubility, which contributed greatly to the processability. There-
fore, the brand-new products synthesized in this paper have great
potential for the application as optoelectronic materials, and will
be worthwhile for future projects.
4. Experimental section
4.1. General
Fig. 4. Cyclic voltammogram of 7a in CH2Cl2/Bu4NPF6 at 20 ꢀC. Inset: HOMO and LUMO
of product 7a.
Reagents were purchased from commercial sources (Aldrich)
and used without further purification. Monomers C1, C3, and C4
were synthesized according to the literature methods.13 1H NMR
and 13C NMR spectra were measured on a Bruker AV300 NMR
spectrometer (300 MHz) at 20 ꢀC. Chemical shifts are reported in
parts per million downfield from SiMe4, using the solvent’s residual
signal as an internal reference. FT-IR was recorded on a Per-
kineElmer LR-64912C Fourier transform infrared spectrometer. All
MALDI-TOF-MS spectra were measured on a Shimadzu AXIMA-CFR
mass spectrometer. The operation was performed at an accelerating
For all the materials, multi-reversible oxidation potentials and
reduction potentials were observed in CH2Cl2. Onset oxidation/re-
duction potentials, band gaps, LUMO and HOMO levels were listed
in Table 1 and Fig. 3, respectively. Compared with the reactants, the
resulting compounds showed anodically shifted first reduction
potentials (Eroend). The anodic shift of Ered,1 could be explained by the
efficient interaction of aromatic precursors with the acceptors,
which made the reduction more easy. TCNQ and F4-TCNQ

D. Wang et al. / Tetrahedron 69 (2013) 895e901
899
Table 1
Electrochemical properties of the products 1e8a, 1e6b and reactants C1eC4
ox
a
red a
b
ox
a
red a
Materials
E
(eV)
E
(eV)
Eg (eV)
Energy level (eV)
Eg c (eV)
Materials
E
(eV)
E
on
(eV)
Eg b (eV)
Energy level (eV)
Eg c (eV)
on
on
on
HOMO
LUMO
HOMO
LUMO
1a
2a
3a
4a
5a
6a
7a
C1
C3
0.69
1.00
0.61
0.52
0.61
0.24
0.97
0.49
0.55
ꢁ0.48
ꢁ0.50
ꢁ0.27
ꢁ0.51
ꢁ0.62
ꢁ0.81
ꢁ0.45
ꢁ0.82
ꢁ1.11
1.17
1.50
0.88
1.03
1.23
1.05
1.42
1.31
1.66
ꢁ5.26
ꢁ5.57
ꢁ5.18
ꢁ5.09
ꢁ5.18
ꢁ4.81
ꢁ5.54
ꢁ5.06
ꢁ5.12
ꢁ4.09
ꢁ4.07
ꢁ4.30
ꢁ4.06
ꢁ3.95
ꢁ3.76
ꢁ4.12
ꢁ3.75
ꢁ3.46
1.51
1.47
1.17
1.17
1.02
0.96
1.53
2.73
2.32
1b
2b
3b
4b
5b
6b
8a
C2
C4
0.61
0.61
0.64
0.58
0.57
0.64
0.97
0.48
0.49
ꢁ0.48
ꢁ0.47
ꢁ0.43
ꢁ0.59
ꢁ0.65
ꢁ0.39
ꢁ0.48
ꢁ0.73
ꢁ0.99
1.09
1.08
1.07
1.17
1.22
1.03
1.45
1.21
1.48
ꢁ5.18
ꢁ5.18
ꢁ5.21
ꢁ5.15
ꢁ5.14
ꢁ5.21
ꢁ5.54
ꢁ5.05
ꢁ5.06
ꢁ4.09
ꢁ4.10
ꢁ4.14
ꢁ3.98
ꢁ3.92
ꢁ4.18
ꢁ4.09
ꢁ3.84
ꢁ3.58
1.72
2.08
1.24
1.24
1.11
1.01
1.50
2.62
2.77
a
Onset potentials determined from cyclic voltammograms in CH2Cl2/Bu4NPF6 at a scan rate of 40 mV/s.
Band gap calculated from the energy level of cyclic voltammograms.
b
c
Band gap estimated from the onset wavelength of optical absorption in CH2Cl2 solution.
potential of 20 kV by a linear positive ion mode with dithranol as
1144, 1060, 816, 720 cmꢁ1. MALDI-TOF-MS (dithranol): m/z: calcd
for C92H142Br2N6: 1488.97 g molꢁ1, found: 1489.8 g molꢁ1 [MH]þ;
elemental analysis calcd (%) for C92H142Br2N6 (1488.97): C 74.06, H
9.59, N 5.63; found: C 74.08, H 9.56, N 5.64.
a matrix. UVevis spectra were recorded in a quartz cuvette on
a JASCO V-570 spectrophotometer. Cyclic voltammetric measure-
ments were carried out in a conventional three-electrode cell using
Glassy Carbon working electrodes of 2 mm diameter, a platinum
wire counter electrode, and an Ag/AgCl reference electrode on
a computer-controlled CHI 660C instrument at rt.
4.1.3. 2-(4-(Dihexadecylamino)phenyl)-3-(4-((4-(dihexadecylamino)
phenyl)ethynyl)-2,5-bis((triisopropylsilyl)ethynyl)phenyl)buta-1,3-
diene-1,1,4,4-tetracarbonitrile (1b). The molar amount of the re-
actants, the reaction condition and the yield calculation method
were all the same as 1a. The crude product was purified by column
chromatography (SiO2, CH2Cl2) to give 1b (0.0763 g, 90%) as a dark
4.1.1. 4,40-((2,5-Bis((triisopropylsilyl)ethynyl)-1,4-phenylene)bis(ethyne-
2,1-diyl))bis(N,N-dihexadecylaniline) (C2). The monomer C1 (1.36 g,
1.00 mmol) cross-coupled with (triisopropylsilyl)acetylene (0.54 g,
3.00 mmol) was dissolved in i-Pr2NH/THF 1:1 (40 mL). After the
solution was purged with bubbling Ar for 30 min, Pd(PPh3)4 (70 mg,
0.06 mmol) and CuI (23 mg, 0.12 mmol) were added. The reaction
mixture was then stirred at rt for 12 h under Ar. The mixture was
concentrated, rediluted with CH2Cl2, and filtered through a plug of
silica gel. The solvent was removed in vacuo and the crude product
was purified by column chromatography (SiO2, hexane/CH2Cl2 10:1)
to give C2 (1.03 g, 66%) as a yellow solid. 1H NMR (CDCl3, 300 MHz):
red solid. 1H NMR (CDCl3, 300 MHz):
1.26 (s, 104H), 1.56 (m, 8H), 3.35 (m, 8H), 6.62 (d, J¼9.3 Hz, 4H), 7.58
d
¼0.88 (m,12H),1.20 (m, 42H),
(s, 2H), 7.83 (d, J¼9.2 Hz, 4H) ppm. FT-IR (KBr):
n
¼2925, 2855, 2216,
2191, 1604, 1579, 1523, 1483, 1466, 1417, 1367, 1243, 1211, 1183, 1103,
997, 883, 813, 720 cmꢁ1. MALDI-TOF-MS (dithranol): m/z: calcd for
C114H184N6Si2: 1693.41 g molꢁ1, found: 1694.3 g molꢁ1 [MH]þ; ele-
mental analysis calcd (%) for C114H184N6Si2 (1693.41): C 80.79, H
10.94, N 4.96; found: C 80.80, H 10.98, N 4.97.
d
¼0.89 (m, 12H), 1.16 (m, 42H), 1.28 (s, 104H), 1.56 (m, 8H), 3.28 (m,
8H), 6.55 (d, J¼8.4 Hz, 4H), 7.36 (d, J¼8.4 Hz, 4H), 7.59 (s, 2H) ppm.13C
4.1.4. 2-(2,5-Dibromo-4-(1,1,4,4-tetracyano-3-(4-(dihexadecyl
amino)phenyl)buta-1,3-dien-2-yl)phenyl)-3-(4-(dihexadecyl amino)
phenyl)buta-1,3-diene-1,1,4,4-tetracarbonitrile (2a). Except that the
click reagent molar amount was twice as that of the monomer, all
the other conditions were the same as 1a. The crude product was
purified by column chromatography (SiO2, CH2Cl2/ethyl
acetate¼20:1) to give 2a (0.146 g, 90%) as a light brown solid. 1H
NMR (CDCl3, 75 MHz):
29.6, 29.7, 31.9, 50.9, 85.7, 96.2, 96.6, 105.0, 108.5, 111.0, 124.5, 125.2,
d¼11.4, 14.1, 18.8, 22.7, 27.1, 27.2, 29.3, 29.5,
133.1, 136.0, 148.1 ppm. FT-IR (KBr):
n
¼2924, 2853, 2193, 1605, 1521,
1466, 1367, 1193, 1136, 882, 810 cmꢁ1. MALDI-TOF-MS (dithranol):
m/z: calcd for C108H184N2Si2: 1565.4 g molꢁ1, found: 1566.5 g molꢁ1
[MH]þ; elemental analysis calcd (%) for C108H184N2Si2 (1565.4): C
82.79, H 11.84, N 1.79, Si 3.59; found: C 82.80, H 11.86, N 1.78.
NMR (CDCl3, 300 MHz):
8H), 3.37 (m, 8H), 6.66 (d, J¼9.3 Hz, 4H), 7.64 (d, J¼9.0 Hz, 4H), 7.77
(s, 2H) ppm; 13C NMR (CDCl3, 75 MHz):
d
¼0.88 (m, 12H), 1.26 (s, 104H), 1.58 (m,
4.1.2. 2-(2,5-Dibromo-4-((4-(dihexadecylamino)phenyl)ethynyl)phe-
nyl)-3-(4-(dihexadecylamino)phenyl)buta-1,3-diene-1,1,4,4-
tetracarbonitrile (1a). The monomer C1 (0.136 g, 0.100 mmol) and
click reagent TCNE (0.128 g, 1.00 mmol) were dissolved in di-
chlorobenzene (1 mL). The reaction mixture was then stirred at
100 ꢀC for 1 h under Ar. The mixture was concentrated, rediluted
with CH2Cl2, and filtered through a plug of silica gel. The solvent
was removed in vacuo and the crude product was purified by col-
umn chromatography (SiO2, CH2Cl2) to give 1a (0.0822 g, 92%) (the
productivity was calculated by removing the amount of the
monomer that unreacted or reacted with two click reagents) as
d
¼14.1, 22.7, 27.0, 27.2, 29.3,
29.5, 29.6, 31.9, 51.4, 75.6, 85.6, 96.7, 110.1, 110.7, 112.2, 113.9, 117.3,
122.4, 133.1, 137.0, 137.7, 153.2, 160.4, 164.3 ppm. FT-IR (KBr):
n
¼2923, 2852, 2214, 1604, 1484, 1467, 1418, 1346, 1300, 1210, 1184,
822, 721 cmꢁ1
. MALDI-TOF-MS (dithranol): m/z: calcd for
C98H142Br2N10: 1616.98 g molꢁ1, found: 1617.9 g molꢁ1 [MH]þ; el-
emental analysis calcd (%) for C98H142Br2N10 (1616.98): C 72.66, H
8.83, N 8.56; found: C 72.68, H 8.86, N 8.58.
4.1.5. 3,30-(2,5-Bis((triisopropylsilyl)ethynyl)-1,4-phenylene)bis(2-(4-
(dihexadecylamino)phenyl)buta-1,3-diene-1,1,4,4-tetracarbonitrile)
(2b). Except for the reactant monomer, all the other experiment
conditions were the same as those of 2a. The crude product was
purified by column chromatography (SiO2, CH2Cl2/ethyl
acetate¼15:1) to give 2b (0.170 g, 93%) as a brown solid. 1H NMR
a brown solid. 1H NMR (CDCl3, 300 MHz):
d¼0.88 (m, 12H), 1.26 (s,
104H), 1.58 (m, 8H), 3.29 (m, 4H), 3.36 (m, 4H), 6.57 (d, J¼8.7 Hz,
2H), 6.64 (d, J¼8.7 Hz, 2H), 7.39 (d, J¼8.4 Hz, 2H), 7.63 (s, 1H), 7.65
(d, J¼9.3 Hz, 2H), 7.79 (s, 1H) ppm; 13C NMR (CDCl3, 75 MHz):
d
¼14.1, 22.7, 26.9, 27.0, 27.1, 27.2, 29.3, 29.4, 29.5, 29.6, 31.9, 51.0,
(CDCl3, 300 MHz):
d
¼0.88 (m, 12H), 1.20 (m, 42H), 1.26 (s, 104H),
51.4, 85.6, 94.5, 103.4, 106.5, 110.7, 111.1, 111.5, 111.9, 113.7, 114.7,
118.5, 121.3, 121.3, 124.1, 132.1, 132.6, 133.3, 133.7, 134.7, 137.4, 149.0,
1.56 (m, 8H), 3.35 (m, 8H), 6.62 (d, J¼9.3 Hz, 4H), 7.58 (s, 2H), 7.83 (d,
J¼9.2 Hz, 4H) ppm. FT-IR (KBr): ¼2924, 2853, 2213, 1604, 1483,
n
152.9, 162.1, 165.9 ppm; FT-IR (KBr):
1604, 1568, 1522, 1484, 1466, 1415, 1402, 1368, 1293, 1207, 1183,
n
¼2923, 2852, 2211, 2190,
1466, 1345, 1212, 1184, 995, 882, 800, 724 cmꢁ1. MALDI-TOF-MS
(dithranol): m/z: calcd for C120H184N10Si2: 1821.42 g molꢁ1, found:

900
D. Wang et al. / Tetrahedron 69 (2013) 895e901
1822.6
g
molꢁ1 [MH]þ; elemental analysis calcd (%) for
C120H184N10Si2 (1821.42): C 79.06, H 10.17, N 7.68; found: C 79.11, H
C120H184N10Si2 (1821.42): C 79.06, H 10.17, N 7.06; found: C 79.09, H
10.16, N 7.08.
10.18, N 7.68.
4.1.10. 2-(1-(2,5-Dibromo-4-((4-(dihexadecylamino)phenyl)ethynyl)
phenyl)-2-(4-(dicyanomethylene)-2,3,5,6-tetrafluorocyclohexa-2,5-
dienylidene)-2-(4-(dihexadecylamino)phenyl)ethylidene)malononi-
trile (5a). Except that the click reagent was F4-TCNQ, all the other
conditions were the same as 1a. The crude product was purified by
column chromatography (SiO2, petroleum ether/ethyl acetate¼1:4) to
give 5a (0.0604 g, 92%) as a green solid. 1H NMR (CDCl3, 300 MHz):
4.1.6. 2-(1-(2,5-Dibromo-4-((4-(dihexadecylamino)phenyl)ethynyl)
phenyl)-2-(4-(dicyanomethylene)cyclohexa-2,5-dienylidene)-2-(4-
(dihexadecylamino)phenyl)ethylidene)malononitrile
(3a). Except
that the click reagent was TCNQ, all the other conditions were the
same as 1a. The crude product was purified by column chroma-
tography (SiO2, CH2Cl2/ethyl acetate¼15:1) to give 3a (0.0729 g,
93%) as a brown solid. 1H NMR (CDCl3, 300 MHz):
d¼0.89 (m, 12H),
d
¼0.89 (m, 12H), 1.26 (s, 104H), 1.58 (m, 8H), 3.29 (m, 8H), 6.57 (d,
1.26 (s, 104H), 1.56 (m, 8H), 3.28 (m, 4H), 3.36 (m, 4H), 6.56 (d,
J¼9.1 Hz, 2H), 6.62 (d, J¼9.1 Hz, 2H), 7.37 (d, J¼9.0 Hz, 2H), 7.13 (d,
J¼8.9 Hz, 2H), 7.18 (d, J¼9.3 Hz, 2H), 7.23 (d, J¼9.7 Hz, 2H), 7.59 (s,
J¼9.1 Hz, 4H), 7.39 (d, J¼9.0 Hz, 8H), 7.70 (s, 2H) ppm. FT-IR (KBr):
n
¼2923, 2852, 2198, 1633, 1599, 1568, 1523, 1467, 1431, 1387, 1356,
1308,1190,1143,1066, 975, 851, 722 cmꢁ1. MALDI-TOF-MS(dithranol):
m/z: calcd for C98H142Br2F4N6: 1636.96 g molꢁ1, found: 1637.9 g molꢁ1
[MH]þ; elemental analysis calcd (%) for C98H142Br2F4N6 (1636.96): C
77.71, H 8.73, N 5.12; found: C 77.73, H 8.75, N 5.14.
1H), 7.69 (s, 1H) ppm. FT-IR (KBr):
n
¼2921, 2853, 2209, 1606, 1584,
1523, 1466, 1404, 1363, 1325, 1273, 1183, 1144, 1062, 959, 814,
722 cmꢁ1. MALDI-TOF-MS (dithranol): m/z: calcd for C98H146Br2N6:
1565.00 g molꢁ1, found: 1566.0 g molꢁ1 [MH]þ; elemental analysis
calcd (%) for C98H146Br2N6 (1565.00): C 75.06, H 9.38, N 5.36; found:
C 75.10, H 9.41, N 5.38.
4.1.11. 2-(4-(3,3-Dicyano-1-(4-(dihexadecylamino)phenyl)-2-(4-((4-
(dihexadecylamino)phenyl)ethynyl)-2,5-bis((triisopropylsilyl) ethy-
nyl)phenyl)allylidene)-2,3,5,6-tetrafluorocyclohexa-2,5-dienylidene)
malononitrile (5b). Except that the click reagent was F4-TCNQ, all
the other conditions were the same as 1b. The crude product was
purified by column chromatography (SiO2, petroleum ether/ethyl
acetate¼1:3) to give 5b (0.0578 g, 91%) as a blue solid. 1H NMR
4.1.7. 2-(4-(3,3-Dicyano-1-(4-(dihexadecylamino)phenyl)-2-(4-((4-
(dihexadecylamino)phenyl)ethynyl)-2,5-bis((triisopropylsilyl)ethy-
nyl)phenyl)allylidene)cyclohexa-2,5-dienylidene)
malononitrile
(3b). Except that the click reagent was TCNQ, all the other con-
ditions were the same as 1b. The crude product was purified by
column chromatography (SiO2, CH2Cl2/ethyl acetate¼10:1) to give
3b (0.0832 g, 94%) as a green solid. 1H NMR (CDCl3, 300 MHz):
(CDCl3, 300 MHz):
1.60 (m, 8H), 4.29 (m, 8H), 7.53 (d, J¼6.0 Hz, 4 H), 7.54 (d, J¼6.3 Hz,
4H), 7.71 (s, 2H) ppm. FT-IR (KBr):
¼2924, 2853, 2200, 1598, 1521,
1466, 1389, 1355, 1191, 1034, 970, 814, 679 cmꢁ1. MALDI-TOF-MS
d
¼0.87 (m, 12 H), 1.12 (m, 42H), 1.26 (s, 104H),
n
d
¼0.89 (m, 12H), 1.10 (m, 36H), 1.20 (m, 6H), 1.26 (s, 104H), 1.56
(m, 8H), 3.27 (m, 4H), 3.36 (m, 4H), 6.53 (d, J¼9.3 Hz, 2H), 6.64 (d,
J¼9.3 Hz, 2H), 7.07 (s, 2H), 7.33 (d, J¼9.0 Hz, 2H), 7.35 (d, J¼9.3 Hz,
(dithranol): m/z: calcd for C120H184F4N6Si2: 1841.41 g molꢁ1
,
found: 1842.5 g molꢁ1 [MH]þ; elemental analysis calcd (%) for
C120H184F4N6Si2 (1841.41): C 78.21, H 10.06, N 4.56; found: C 78.23,
H 10.07, N 4.55.
2H), 7.42 (d, J¼9.3 Hz, 2H), 7.74 (m, 2H) ppm. FT-IR (KBr): ¼2925,
n
2854, 2204, 1726, 1606, 1580, 1523, 1466, 1402, 1366, 1347, 1285,
1180, 1104, 996, 883, 810, 721 cmꢁ1. MALDI-TOF-MS (dithranol):
m/z: calcd for C120H188N6Si2: 1769.44
1770.3
g
molꢁ1
,
found:
4.1.12. 2,20-(1,10-(2,5-Dibromo-1,4-phenylene)bis(2-(4-(dicyano-
methylene)-2,3,5,6-tetrafluorocyclohexa-2,5-dienylidene)-2-(4-(di-
hexadecylamino)phenyl)ethan-1-yl-1-ylidene))dimalononitrile
(6a). Except that the click reagent was F4-TCNQ, all the other
conditions were the same as 2a. The crude product was purified by
column chromatography (SiO2, petroleum ether/ethyl acetate¼1:2)
to give 6a (0.174 g, 91%) as a red solid. 1H NMR (CDCl3, 300 MHz):
g
molꢁ1 [MH]þ; elemental analysis calcd (%) for
C120H188N6Si2 (1769.44): C 81.38, H 10.70, N 4.75; found: C 81.40,
H 10.75, N 4.76.
4.1.8. 2,20-(1,10-(2,5-Dibromo-1,4-phenylene)bis(2-(4-(dicyanom
ethylene)cyclohexa-2,5-dienylidene)-2-(4-(dihexadecylamino)phe-
nyl)ethan-1-yl-1-ylidene))dimalononitrile (4a). Except that the click
reagent was TCNQ, all the other conditions were the same as 2a.
The crude product was purified by column chromatography (SiO2,
petroleum ether/ethyl acetate¼1:3) to give 4a (0.159 g, 90%) as an
d
¼0.89 (m, 12H), 1.26 (s, 104H), 1.57 (m, 8H), 3.29 (m, 8H), 6.57 (d,
J¼9.2 Hz, 4H), 7.69 (s, 2H) ppm. FT-IR (KBr): ¼2924, 2853, 2198,
1633, 1598, 1526, 1484, 1389, 1356, 1192, 1039, 975, 822, 777 cmꢁ1
n
.
MALDI-TOF-MS (dithranol): m/z: calcd for C110H142Br2F8N10
:
orange solid. 1H NMR (CDCl3, 300 MHz):
d
¼0.89 (m, 12H), 1.26 (s,
104H), 1.58 (m, 8H), 3.35 (m, 8H), 6.62 (d, J¼9.2 Hz, 8H), 7.13 (d,
J¼9.1 Hz, 8H), 7.60 (s, 2H) ppm. FT-IR (KBr): ¼2924, 2852, 2205,
1581, 1522, 1466, 1399, 1349, 1181, 961, 862, 720 cmꢁ1. MALDI-TOF-
1912.97 g molꢁ1, found: 1913.8 g molꢁ1 [MH]þ; elemental analysis
calcd (%) for C110H142Br2F8N10 (1912.97): C 65.95, H 7.47, N 7.31;
found: C 66.98, H 7.47, N 7.32.
n
MS (dithranol): m/z: calcd for C110H50Br2N10: 1769.04 g molꢁ1
,
4.1.13. 2,20-(1,10-(2,5-Bis((triisopropylsilyl)ethynyl)-1,4-phenylene)
bis(2-(4-(dicyanomethylene)-2,3,5,6-tetra-fluorocyclohexa-2,5-
dienylidene)-2-(4-(dihexadecylamino)phenyl)ethan-1-yl-1-ylidene))
dimalononitrile (6b). Except that the click reagent was F4-TCNQ, all
the other conditions were the same as 2b. The crude product was
purified by column chromatography (SiO2, petroleum ether/ethyl
acetate¼1:2) to give 6b (0.195 g, 92%) as an orange solid. 1H NMR
found: 1770.1 g molꢁ1 [MH]þ; elemental analysis calcd (%) for
C110H50Br2N10 (1769.04): C 74.55, H 8.53, N 7.90; found: C 74.57, H
8.55, N 7.88.
4.1.9. 3,30-(2,5-Bis((triisopropylsilyl)ethynyl)-1,4-phenylene)bis(2-(4-
(dihexadecylamino)phenyl)buta-1,3-diene-1,1,4,4-tetracarbonitrile)
(4b). Except for the reactant monomer, all the other experiment
conditions were the same as those of 4a. The crude product was
purified by column chromatography (SiO2, petroleum ether/ethyl
acetate¼1:4) to give 4b (0.176 g, 89%) as a blue solid. 1H NMR (CDCl3,
(CDCl3, 300 MHz):
1.56 (m, 8H), 3.39 (m, 8H) ppm. FT-IR (KBr):
1635, 1599, 1533, 1483, 1389, 1352, 1311, 1192, 1038, 974, 882, 820,
d
¼0.87 (m, 12 H), 1.13 (m, 42H), 1.26 (s, 104H),
n
¼2925, 2853, 2200,
723 cmꢁ1
.
MALDI-TOF-MS (dithranol): m/z: calcd for
300 MHz):
d
¼0.87 (m,12H),1.13 (m, 42H),1.26 (s,104H),1.56 (m, 8H),
C132H184F8N10Si2: 2117.41 g molꢁ1, found: 2118.5 g molꢁ1 [MH]þ;
elemental analysis calcd (%) for C132H184F8N10Si2 (2117.41): C 74.82,
H 8.75, N 6.61; found: C 74.84, H 8.76, N 6.62.
3.39 (m, 8H), 6.70 (d, J¼9.6 Hz, 8H), 7.16 (s, 2H), 7.33 (d, 9.5 Hz, 4H),
7.42 (d, J¼9.6 Hz) ppm. FT-IR (KBr): ¼2925, 2854, 2361, 2206, 1583,
n
1542,1466,1405,1347,1182, 960, 861, 799, 722 cmꢁ1. MALDI-TOF-MS
(dithranol): m/z: calcd for C120H184N10Si2: 1821.42 g molꢁ1, found:
4.1.14. 2-(4-(Dihexadecylamino)phenyl)-3-(4-((4-nitrophenyl) ethy-
nyl)phenyl)buta-1,3-diene-1,1,4,4-tetracarbonitrile (7a). Except for
1822.5
g
molꢁ1 [MH]þ; elemental analysis calcd (%) for

D. Wang et al. / Tetrahedron 69 (2013) 895e901
901
the reactant monomer, all the other experiment conditions were
Supplementary data
the same as those of 1a. The crude product was purified by column
chromatography (SiO2, petroleum ether/ethyl acetate¼1:1) to give
7a (0.0976 g, 91%) as a purple solid. 1H NMR (CDCl3, 300 MHz):
Cyclic voltammograms and UVevis spectra of products 1ae8a,
1be6b and reactants C1eC4. Supplementary data related to this
article can be found online at http://dx.doi.org/10.1016/
j.tet.2012.10.081.
d
¼0.88 (m, 6H), 1.25 (s, 52H), 1.58 (m, 4H), 3.38 (m, 4H), 6.67 (d,
J¼9.6 Hz, 2H), 7.66 (d, J¼9.3 Hz, 2H), 7.71 (s, 1H), 7.74 (m, 2H), 7.92
(s, 1H), 8.26 (m, 2H) ppm. FT-IR (KBr):
n
¼2924, 2852, 2215, 1603,
1521, 1484, 1466, 1417, 1342, 1289, 1208, 1183, 1063, 856, 822,
749 cmꢁ1. MALDI-TOF-MS (dithranol): m/z: calcd for C60H78N6O2:
914.62 g molꢁ1, found: 915.6 g molꢁ1 [MH]þ; elemental analysis
calcd (%) for C60H78N6O2 (914.62): C 78.73, H 8.59, N 9.18; found: C
78.72, H 8.56, N 9.16.
References and notes
1. Sergeyev, S.; Pisula, W.; Geerts, Y. H. Chem. Soc. Rev. 2007, 36, 1902e1929.
2. Li, Y.; Tsuboi, K.; Michinobu, T. Macromolecules 2010, 43, 5277e5286.
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2004e2021.
4. Huisgen, R.; Szeimies, G.; Moebius, L. Chem. Ber. 1967, 100, 2494e2507.
5. Rostovtsev, V. V.; Green, L. G.; Fokin, V. V.; Sharpless, K. B. Angew. Chem., Int. Ed.
2002, 41, 2596e2599.
6. Tornoe, C. W.; Christensen, C.; Meldal, M. J. Org. Chem. 2002, 67, 3057e3064.
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130, 5062e5064; (d) Gacal, B.; Akat, H.; Balta, D. K.; Arsu, N.; Yagci, Y. Macro-
molecules 2008, 41, 2401e2405.
4.1.15. 2-(2,5-Dibromo-4-((4-(hexadecyloxy)phenyl)ethynyl)phenyl)-
3-(4-(dihexadecylamino)phenyl)buta-1,3-diene-1,1,4,4-tetracarboni-
trile (8a). Except for the reactant monomer, all the other experi-
ment conditions were the same as those of 1a. The crude product
was purified by column chromatography (SiO2, petroleum ether/
ethyl acetate¼1:1) to give 8a (0.114 g, 90%) as an orange solid. 1H
NMR (CDCl3, 300 MHz):
d¼0.88 (m, 9H), 1.25 (s, 78H), 1.62 (m, 4H),
1.79 (m, 2H), 3.37 (m, 4H), 3.98 (m, 2H), 6.65 (d, J¼9.6 Hz, 2H), 6.89
(m, 2H), 7.50 (m, 2H), 7.65 (d, J¼9.3 Hz, 2H), 7.754 (s, 1H), 7.84 (s,
1H) ppm. FT-IR (KBr):
n
¼2923, 2852, 2215, 1603, 1574, 1519, 1489,
1467, 1416, 1341, 1291, 1252, 1183, 1061, 832 cmꢁ1. MALDI-TOF-MS
(dithranol): m/z: calcd for C76H109Br2N5O: 1265.70
g ,
molꢁ1
9. Bruce, M. I.; Rodgers, J. R.; Snow, M. R.; Swincer, A. G. J. Chem. Soc., Chem.
Commun. 1981, 271e272.
10. Onuma, K. i.; Kai, Y.; Yasuoka, N.; Kasai, N. Bull. Chem. Soc. Jpn. 1975, 48,
1696e1700.
11. Kato, S. i.; Diederich, F. Chem. Commun. 2010, 1994e2006.
12. (a) Wu, X.; Wu, J.; Liu, Y.; Jen, A. K. Y. J. Am. Chem. Soc. 1999, 121, 472e473; (b)
found: 1266.8 g molꢁ1 [MH]þ; elemental analysis calcd (%) for
C76H109Br2N5O (1265.70): C 71.96, H 8.66, N 5.52; found: C 72.01, H
8.68, N 5.53.
€
€
Cai, C.; Liakatas, I.; Wong, M. S.; Bosch, M.; Bosshard, C.; Gunter, P.; Concilio, S.;
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Gisselbrecht, J. P.; Seiler, P.; Gross, M.; Diederich, F. Angew. Chem., Int. Ed. 2007,
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Acknowledgements
13. (a) Otsubo, T.; Aso, Y.; Takamiya, K. J. Mater. Chem. 2002, 12, 2565e2575; (b)
Tang, C.; Liu, F.; Xia, Y. J.; Lin, J.; Xie, L. H.; Zhong, G. Y.; Fan, Q. L.; Huang, W. Org.
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This work was supported by National Natural Science Fund for
Distinguished Young Scholar (Grant No. 51025313), National Nat-
ural Science Foundation (Grant No. 51103010, 50973010, 51173003),
Specialized Research Fund For Doctoral Program of Higher Educa-
tion of China (Grant No. 20110006120002).
14. Wang, D.; Michinobu, T. J. Polym. Sci., Part A: Polym. Chem. 2011, 49, 72e81.
€
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N.; Jarowski, P. D.; Gescheidt, G.; Diederich, F. Chem.dEur. J. 2009, 15,
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