Synthesis of tetra-oligothiophene-substituted calix[4]arenes and their optical and electrochemical properties

Article abstract of DOI:10.1016/j.tet.2006.05.050

A facile and efficient approach to synthesize tetra-oligothiophene-substituted calix[4]arenes, Calix-OT(n) with n up to 4 using palladium-catalyzed Kumada coupling of thienylmagnesium bromide and bromo-substituted calix[4]arene as a key step has been deve

Full text of DOI:10.1016/j.tet.2006.05.050

Tetrahedron 62 (2006) 7846–7853
Synthesis of tetra-oligothiophene-substituted calix[4]arenes
and their optical and electrochemical properties
*
Xiao Hua Sun, Chi Shing Chan, Man Shing Wong and Wai Yeung Wong
Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong, China
Received 3 April 2006; revised 17 May 2006; accepted 18 May 2006
Available online 9 June 2006
Abstract—A facile and efficient approach to synthesize tetra-oligothiophene-substituted calix[4]arenes, Calix-OT(n) with n up to 4 using
palladium-catalyzed Kumada coupling of thienylmagnesium bromide and bromo-substituted calix[4]arene as a key step has been developed.
The close proximity of the tetra-oligothiophenes constructed within a calix[4]arene assembly leads to peak/band broadening, spectral shifting,
i.e., blue-shift in absorption and red-shift in emission spectra as well as fluorescence quantum yield quenching as compared to those of mono-
mers indicating the existence of chromophoric interaction. We have shown that the intra-chromophoric interaction lowers the first ionization
(raises HOMO level) of an oligothiophene within an assembly. It also stabilizes the formation of a radical cation, which results in an increase
in the subsequent voltammetric oxidation and the occurrence of the higher oxidation states as compared to the monomeric counterparts. This
assembly can serve as a model for the investigation of molecular interaction of p-conjugated systems.
Ó 2006 Elsevier Ltd. All rights reserved.
1. Introduction
for p-stacking effects.6 In addition, the intramolecular inter-
action and corporation effect of the proximate chromophores
could give rise to novel or enhanced functional and struc-
tural/morphological properties of resulting materials.7
Oligothiophenes are an important class of p-conjugated
organic materials that have been extensively investigated
and explored as active materials for (opto)electronic device
applications such as field-effect transistors, light emitting
diodes, photovoltaic cells, and sensors in the last few years.1
Tuning the molecular properties of oligothiophenes by
means of chemical and structural modifications has been
successfully much achieved in recent years.2 However, the
ultimate bulk performance of an oligothiophene-based mate-
rial relies greatly on the molecular/chain arrangement in the
solid-state and/or morphology of the material.3 For example,
ordered close packing of sexithiophenes in the solid-state
leads to low photoluminescence efficiency due to excitonic
coupling of proximate oligomers.4 On the other hand, proper
molecular alignment results in better charge transport and
lowers operating voltages in field-effect transistor applica-
tions.5 As a result, structural studies of oligothiophenes and
morphological investigations of these materials are impor-
tant issues related to their applications. Toward this end, it
is of great interest to investigate well-defined multi-oligo-
thiophene-based molecular assemblies, in which thiophene
oligomers are preorganized and preoriented within a molec-
ular framework, within which studies would provide insight
into the effect of through-space interactions of oligomeric
and polymeric chains. Several cyclophane-based oligothio-
phene assemblies have been synthesized and investigated
Calixarenes are one of the most useful building platforms for
constructing supramolecular systems and have been widely
used in the preparation of artificial receptors for neutral
and ionic molecules.8 One of the unique features of these
calix[4]arene derivatives is that they can exist in a relatively
rigid and stable cone structure, in which four functionalized
phenolic units, oriented in the same direction are linked at
their ortho-positions by methylene bridges. With oligothio-
phenes built onto such frameworks, the arrangement and
orientation of oligothiophenes will be predefined and pre-
organized with the oligothiophene units close enough to
interact. Thus, the effect of coupling interactions on various
functional properties of such assemblies could readily be
probed. We herein report the facile and efficient synthesis
and optical and electrochemical properties of a novel series
H
H
S
H
S
H
H
S
S
S
O
R
O
R
O
R
O
R
O
R
Keywords: Tetra-oligothiophene-substituted calix[4]arene; Intra-chromo-
phoric interaction; Kumada coupling.
* Corresponding author. E-mail: mswong@hkbu.edu.hk
Calix-OT(n), n = 1-4
M-OT(n), n = 1-4
0040–4020/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2006.05.050

X. H. Sun et al. / Tetrahedron 62 (2006) 7846–7853
7847
of monodisperse and well-defined p-conjugated tetra-oligo-
thiophene-substituted calix[4]arene assemblies, Calix-
OT(n) where n¼1–4.
prepared thienylmagnesium bromide and 2 in the presence
of PdCl2(dppf) as a catalyst afforded tetrathienylcalix[4]-
arene, Calix-OT(1) in a good yield (85–87%). Bromination
of tetrathienylcalix[4]arene with NBS in refluxing CH2Cl2
gave tetrabromothienylcalix[4]arene, Calix-OT(1)-Br in an
excellent yield (90–93%). Subsequent cross-coupling reac-
tion of Calix-OT(1)-Br with thienylmagnesium bromide
afforded tetrakis-(bithienyl)calix[4]arene, Calix-OT(2) in
83–87% yield. By repeating such a sequence of bromina-
tion and cross-coupling reactions, a higher homologue
series of oligothiophene-substituted calix[4]arenes includ-
ing Calix-OT(3) and Calix-OT(4) were readily synthe-
sized. The MALDI-TOF mass spectra of Calix-OT(3) and
Calix-OT(4) showed a base peak at m/z 1970.6421 and
2299.6157, corresponding to [M+] and [M++H], respec-
tively. In addition to low/high-resolution mass spectros-
copy, all the newly synthesized oligothiophene-substituted
2. Results and discussion
Recently, various oligophenylene-substituted calix[4]arenes
have been efficiently synthesized by palladium-catalyzed
Suzuki cross-coupling reactions;7b,c however, such protocols
were found to be not useful for the synthesis of tetra-oligo-
thiophene-substituted calix[4]arenes, Calix-OT(n). Even
though bis(dithienyl)-substituted calix[4]arenes were previ-
ously prepared by Stille cross-coupling reaction,1e we find
that palladium-catalyzed Kumada cross-coupling is more
efficient and useful for the synthesis of tetra-oligothio-
phene-substituted calix[4]arenes. Since the preparations of
oligothienylmagnesium bromides were non-trivial and in-
efficient, the use of convergent approach to synthesize the
higher homologous was not practical. As a result, the tetra-
oligothienyl chains were constructed onto the calix[4]arene
framework by a divergent approach using palladium-cata-
lyzed Kumada cross-coupling of thienylmagnesium bromide
and tetrabromo(oligothienyl)-calix[4]arene as a key step for
chain length extension. The synthetic route is outlined in
Scheme 1. To stabilize the cone conformation, calix[4]arene
1 was alkylated with either bromopropane or bromodecane
using NaH as a base in DMF.9 Bromination of tetraalk-
oxycalix[4]arene with NBS in refluxing CHCl3 afforded
the tetrabromocalix[4]arene 2.7a Cross-coupling of freshly
1
calix[4]arenes were fully characterized by H NMR, 13C
NMR, and/or elemental analyses and found to be in good
agreement with the expected structures. For properties com-
parison, their corresponding monomers oligothiophene-
substituted 4-alkyoxy-3,5-dimethylbenzenes, M-OT(n) with
n up to 4 were also synthesized using the same strategy as
shown in Scheme 2.
Figure 1 shows the single crystal X-ray structure of Calix-
OT(2), which adopts a pinched cone structure similar to
other arylene-substituted calix[4]arenes.10 In contrast to
the biphenylene counterparts, all the bithiophene units are
in an anti coplanar conformation except there is a twist
H
H
S
H
H
Br
Br
Br
Br
S
S
S
(i), (ii)
(iii)
O
O
H
O
O
O
H
O
R
O
O
H
R
R
H
O
O
R
R
O
R
O
R
1
2
R = C3H7 or
R
C
10H21
Calix-OT(1)
85-87%
H
H
S
H
S
H
Br
Br
S
Br
Br
S
S
S
S
S
(ii)
(iii)
S
S
S
S
O
O
O
R
O
R
R
R
O
O
R
O
R
O
R
R
Calix-OT(1)-Br
97-99 %
m = 1: Calix-OT(2) 83-87 %
(ii), (iii)
m = 2: Calix-OT(3) 69-77 %
(ii), (iii)
m = 3: Calix-OT(4) 67-70 %
Scheme 1. Synthesis of oligothiophene-substituted calix[4]arene assemblies, Calix-OT(n), n¼1–4. Reagents and conditions: (i) NaH, C3H7Br or C10H21Br,
DMF, 50 ꢀC; (ii) NBS, CHCl3 or CH2Cl2, reflux; (iii) (a) 2-bromothiophene, Mg, THF, reflux and (b) PdCl2(dppf), reflux.

7848
X. H. Sun et al. / Tetrahedron 62 (2006) 7846–7853
H
S
Br
Br
(ii)
(i)
OH
OC10H21
OC10H21
H
M-OT(1) 87%
Br
S
S
(ii)
(iii)
S
OC10H21
OC10H21
Figure 1. ORTEP drawings of Calix-OT(2) (25% probability). All hydro-
gen atoms are omitted for clarity.
M-OT(1)-Br
98 %
m = 1: M-OT(2) 92 %
calix[4]arenes are highly soluble in common organic sol-
vents except Calix-OT(4).
(iii), (ii)
m = 2: M-OT(3) 81 %
The electronic absorption and emission spectra of all the
oligomers, M-OT(n) and assemblies, Calix-OT(n) were
recorded in chloroform and their results are summarized in
Table 1. In general, there is a sequential increase in the
absorption maxima with a concomitant increase in molar
absorptivity and the emission maxima in both series as the
thienyl unit increases. However, in addition to the peak
broadening, the absorption spectra of oligothiophene-substi-
tuted calix[4]arenes are relatively blue-shifted (D¼3–8 nm)
whereas their emission spectra are shifted to the longer wave-
lengths (D¼12–14 nm) as compared to those of correspond-
ing monomer (Fig. 2). In contrast to the monomeric series,
the moderate increase in the fluorescence quantum yield as
the chain length extends was not observed in oligothio-
phene-substituted calix[4]arene series. All these phenomena
suggest the occurrence of the chromophoric interaction of
proximate tetra-thiophene oligomers constructed within the
calix[4]arene framework. The blue-shift in absorption spec-
tra can be explained in terms of the excited state splitting due
to the exciton coupling of the proximate chromophores
within the assembly in which the singlet–singlet transitions
(iii), (ii)
m = 3: M-OT(4) 83 %
Scheme 2. Synthesis of monomeric oligothiophenes, M-OT(n), n¼1–4.
Reagents and conditions: (i) NaH, C10H21Br, DMF, 50 ꢀC; (ii) (a) 2-bromo-
thiophene, Mg, THF, reflux and (b) PdCl2(dppf), reflux; (iii) NBS, CHCl3 or
CH2Cl2, reflux.
between the aryl ring of calix[4]arene skeleton and bithio-
phene. Although the two parallel bithiophene units are
leaned toward each other, the distal terminal thiophene rings
do not pack in a co-facial arrangement owing to the anti con-
formation of bithiophene.
The thermal behavior and stability of these oligothiophene-
substituted calix[4]arenes were investigated by DSC and
TGA analyses, respectively. The results are summarized in
Table 1. In general, Calix-OT(n) shows an excellent and en-
hanced thermal stability with Td>400 ꢀC than that of the
corresponding M-OT(n). All the oligothiophene-substituted
Table 1. Summaries of physical measurements of Calix-OT(n) and M-OT(n) series
a,c
f
g
lambasxa/nm
lemmaxa,b/nm
FFL
FL lifetime in
solution/nsa,d
Eoxe/V
Tm (Td )/ꢀC
(3maxꢁ104/Mꢂ1 cmꢂ1
)
h
M-OT(1)
M-OT(2)
M-OT(3)
M-OT(4)
Calix-OT(1)
Calix-OT(2)
Calix-OT(3)
Calix-OT(4)
286 (1.97)
348 (2.71)
384 (3.54)
414 (4.64)
288 (8.02)
342 (8.80)
381 (12.9)
406 (14.8)
385, 402
396, 414
442, 469
477, 510
402, 425
427
1.03
1.19
1.17
1.36
1.20
1.87
1.77
1.50
0.87 (ir, 1e)
0.63 (ir, 1e)
0.47 (r, 1e), 0.76 (q, 1e)
0.37 (r, 1e), 0.67 (r, 1e)
0.75 (ir, 1e)
0.47 (ir, 1e), 0.61 (ir, 1e)
0.44 (ir, 1e). 0.87 (q, 2e)
0.38 (q, 1e), 0.73 (q, 2e)
(292)
63 (352)
0.07
0.15
0.31
112 (396)
177 (427)
239 (412)
241 (409)
200 (431)
227 (421)
h
0.08
0.11
0.11
454, 482
489, 524
a
Measured in CHCl3.
Excited at the absorption maxima.
b
c
d
e
Using quinine in 0.1 M H2SO4 (F365¼0.54) as a standard.
Estimated using an iterative fitting procedure from the measured fluorescence decayed excited by nitrogen laser.
Eox estimated by CV method using platinum disc electrode as a working electrode, platinum wire as a counter electrode, and SCE as a reference electrode with
an agar salt bridge connecting to the oligomer solution and all the potentials were calibrated with ferrocene, which was also used as an internal standard, E1/2
(Fc/Fc+)¼0.49 V versus SCE with a scan rate of 100 mV/s.
f
Determined by differential scanning calorimeter with a heating rate of 10 ꢀC/min under N2.
Determined by thermal gravimetric analyzer with a heating rate of 10 ꢀC/min under N2.
Less than 0.01.
g
h

X. H. Sun et al. / Tetrahedron 62 (2006) 7846–7853
7849
200000
180000
160000
140000
120000
100000
80000
60000
40000
20000
0
1.0
0.8
0.6
0.4
0.2
0.0
(a)
Calix-OT(1)
Calix-OT(2)
Calix-OT(3)
Calix-OT(4)
300
350
400
450
500
550
600
650
700
Wavelength/nm
60000
55000
50000
45000
40000
35000
30000
25000
20000
15000
10000
5000
1.0
(b)
M-OT(1)
M-OT(2)
M-OT(3)
M-OT(4)
0.8
0.6
0.4
0.2
0.0
0
300
350
400
450
500
550
600
650
700
Wavelength/nm
Figure 2. Absorption and emission spectra of (a) Calix-OT(n) and (b) M-OT(n) series.
from the ground state to the lowest coupled excited state are
forbidden but to the second excited state are allowed.11 Be-
cause of the through-space interaction and/or the steric
shielding imposed by proximate oligomers, the oligothio-
phene-substituted calix[4]arenes exhibit slightly longer fluo-
rescence lifetimes (1.20–1.87 ns) than the corresponding
monomeric counterparts (1.03–1.36 ns).
to M-OT(1) and M-OT(2), the voltammetric wave of
M-OT(3) and M-OT(4) also exhibits two one-electron
oxidation waves corresponding to the sequential formation
of monocation and dication. The second oxidation potential
also decreases with an increase in thienyl unit. All these
evolution/changes are attributed to the stabilizing effect of
the enhanced p-conjugation of the longer homologues.
The redox properties of M-OT(n) and Calix-OT(n) were
studied by cyclic voltammetry, which was carried out in
a three-electrode cell set-up with 0.1 M of Bu4NPF6 as sup-
porting electrolyte in CHCl3. All the potentials reported are
internally referenced to Fc/Fc+ standard and the results are
tabulated in Table 1. M-OT(1) exhibits an irreversible one-
electron oxidation with Epa at 0.87 V in CHCl3 correspond-
ing to the formation of monocation. When repeated cycling
of the electrode between 0 and 1.8 V, an appearance of
solid films on the electrode surface and a growing broad
wave at a lower potential associated with an increased
peak current were observed indicating the occurrence of
electrochemical dimerization/polymerization. As the thienyl
unit increases, the first oxidation potential decreases progres-
sively. Furthermore, there is an improvement in reversibility
of the voltammetric wave and instability toward electro-
chemical reactions as the chain length increases. In contrast
Even though there were several reports on the electrochemi-
calstudiesofpolythiophene–calixarenehybridmaterials,1e,12
the electrochemical properties of tetra-oligothiophene–
calixarene molecules are not known. The influence of intra-
molecular chromophoric interaction on the electrochemical
properties of Calix-OT(n) is profound. Even though Calix-
OT(1) exhibits an irreversible one-electron oxidation similar
to M-OT(1), its oxidation potential (Epa¼0.75 V) is substan-
tially lower than that of M-OT(1) (Epa¼0.87 V). The lower-
ing of the first oxidation potential of Calix-OT(n)s relative to
M-OT(n)s is consistently observed throughout the series.
This phenomenon suggests that the cation formed is stabi-
lized by the proximate thiophene oligomers within the as-
sembly. In addition, the intra-chromophoric stabilization
leads to the exhibition of two well-resolved one-electron
oxidation waves of Calix-OT(2) corresponding to the se-
quential formation of monocation and dication whereas

7850
(a)
X. H. Sun et al. / Tetrahedron 62 (2006) 7846–7853
(b)
10
10
8
8
Calix-OT(1)
M-OT(1)
6
6
M-OT(2)
M-OT(3)
M-OT(4)
Calix-OT(2)
4
4
Calix-OT(3)
2
2
Calix-OT(4)
0
0
0
500
1000
1500
2000
2500
3000
0
500
1000
1500
2000
2500
3000
Potential mV
Voltage mV
Figure 3. CV traces of (a) Calix-OT(n) and (b) M-OT(n) series with ferrocene were used as an internal standard, E1/2 (Fc/Fc+)¼0.49 V versus SCE with a scan
rate of 100 mV/s.
M-OT(2) only exhibits a single one-electron oxidation
(Fig. 3). The stabilizing effect imposed by proximate oligo-
mers and chain length extension also leads to the exhibition
of the higher oxidation states in Calix-OT(3) and Calix-
OT(4). There are small steps appearing in the oxidation
waves of the higher homologues, which are attributed to
the micro-environment difference for each thiophene oligo-
mer within an assembly. Such a difference is likely created
by the relatively slow interconversion of two conformation-
ally mobile C2v ‘pinched or flattened’ cone conformers in
solution for the higher homologues within CV time scale.
On the other hand, Calix-OT(3) appears to have a higher
second oxidation potential than that of Calix-OT(2), which
is attributed to one more electron involved in the second
oxidation of Calix-OT(3). For Calix-OT(4), the second
oxidation potential drops again. Since the number of elec-
trons involved in the second oxidation of Calix-OT(3) and
Calix-OT(4) is more, their second oxidation generally
occurs at a higher potential than that of the corresponding
M-OT(n). Electro-polymerization also occurs readily for
the Calix-OT(n) series upon repeated anodic scans.
4. Experimental
4.1. General
All the solvents were dried by the standard methods wherever
needed. H NMR spectra were recorded using a 270 MHz
1
or 400 MHz FT-NMR spectrometer and are referenced to
the residual CHCl3 7.24 ppm. 13C NMR spectra were re-
corded using a 270 MHz or 400 MHz FT-NMR spectrometer
and are referenced to the CDCl3 77 ppm. High-resolution
mass spectroscopy (HRMS) measurement was carried using
MALDI-TOF method. The fluorescence decay curves were
recorded on PTI fluorescence Master 2M1 Luminescence
Spectrophotometer using PTI G2-3300 Nitrogen Laser as
excitation. The lifetimes were estimated from the measured
fluorescence decay using iterative fitting procedure. E1/2
(Epa) versus Fc+/Fc was estimated by cyclic voltammetric
method using platinum disc electrode as a working elec-
trode, platinum wire as a counter electrode, and SCE as a ref-
erence electrode with an agar salt bridge connecting to the
oligomer solution (1 mM) dissolved in CHCl3 using 0.1 M
of Bu4NPF6 as a supporting electrolyte with a scan rate of
100 mV/s and all the potentials were calibrated and refer-
enced with ferrocene (E1/2 (Fc/Fc+)¼0.49 V vs SCE) as an
internal standard.
3. Conclusions
In summary, we have developed a divergent approach to syn-
thesize a novel series of tetra-oligothiophene-substituted
calix[4]arenes, Calix-OT(n) with n up to 4 by means of
a facile and efficient palladium-catalyzed Kumada coupling
of thienylmagnesium bromide and bromo-substituted calix-
[4]arene as the key step. In addition to the spectral widen-
ing, blue-shift of absorption spectra, red-shift of emission
spectra, and increased quenching in fluorescence quantum
yields, the intramolecular coupling/interaction leads to low-
ering of the first oxidation potential of an oligothiophene
stabilizing the formation of radical cation and exhibiting
higher oxidation states in higher homologues of the tetra-
oligothiophene-substituted calix[4]arenes assembly. These
assemblies can serve as a model in the intermolecular inter-
action of p-conjugated molecules/polymers. Our studies
also provide an insight into the influence of intermolecular
interaction on the positive charge in the condensed phase.
4.1.1. 5,11,17,23-Tetrakis(thienyl)-25,26,27,28-tetraprop-
oxycalix[4]arene Calix-OT(1). To a flame dried 100-mL
two-necked flask containing 2-bromothiophene (0.7 g,
4.3 mmol) in 20 mL anhydrous THF were added Mg turn-
ings (0.12 g, 5 mmol) at room temperature under N2. The
solution mixture was stirred vigorously. After the boiling
had stopped, the reaction mixture was heated to reflux
for 3 h. After cooling to room temperature, tetrabromo-
calix[4]arene 2 (0.2 g, 0.22 mmol) and PdCl2(dppf) (9 mg,
5 mmol %) were added and allowed to reflux overnight.
After cooling, the reaction mixture was quenched with
50 mL of water, acidified with 6 M HCl to pH 4–5 and then
extracted with DCM (3ꢁ20 mL). The combined organic sol-
vent was washed with brine and dried over Na2SO4 and
evaporated to dryness. The crude product was purified by
flash silica gel column chromatography using petroleum

X. H. Sun et al. / Tetrahedron 62 (2006) 7846–7853
7851
ether as eluent affording the title compound as a white solid
(0.17 g, 85% yield). 1H NMR (270 MHz, CDCl3, d) 6.98 (t,
J¼3.2 Hz, 4H), 6.92 (s, 8H), 6.78 (d, J¼3.5 Hz, 8H), 4.47 (d,
J¼13.2 Hz, 4H), 3.89 (t, J¼7.6 Hz, 8H), 3.20 (d, J¼13.2 Hz,
4H), 1.96–1.94 (m, 8H), 1.00 (t, J¼4.9 Hz, 12H). 13C NMR
(67.5 MHz, CDCl3, d) 156.1, 144.4, 135.0, 128.5, 127.5,
125.9, 123.4, 121.8, 76.9, 31.1, 23.3, 10.5. MS (FAB) m/z
920.6 [M+]. Anal. Calcd for C56H56O4S4: C, 73.01; H,
6.13. Found: C, 72.89; H, 6.12.
4.1.5. 5,11,17,23-Tetrakis(terthienyl)-25,26,27,28-tetra-
decyloxycalix[4]arene Calix-OT(3). The coupling proce-
dure described above was followed using Calix-OT(2)-Br
(2 g, 1 mmol), 2-bromothiophene (3.26 g, 20 mmol), Mg
turnings (3.9 g, 0.16 mmol), and PdCl2(dppf) (16 mg,
2 mmol %) affording a dark yellow solid (1.54 g, 78%
1
yield). H NMR (400 MHz, CDCl3, d) 7.26 (d, J¼8 Hz,
4H), 7.15 (d, J¼4.8 Hz, 4H), 7.05–7.04 (m, 20H), 6.85 (s,
4H), 6.76 (s, 4H), 4.49 (d, J¼13.2 Hz, 4H), 3.94 (t,
J¼6.8 Hz, 8H), 3.23 (d, J¼13.2 Hz, 4H), 1.95 (s, 8H),
1.41–1.29 (m, 56H), 0.9 (t, J¼6.8 Hz, 12H). 13C NMR
(100 MHz, CDCl3, d) 156.5, 143.5, 137.3, 136.6, 135.5,
135.3, 135.1, 128.2, 127.8, 125.6, 124.4, 124.2, 124.0,
123.6, 123.4, 122.6, 75.5, 32.0, 31.1, 30.3, 30.0, 29.9,
29.8, 29.5, 26.4, 22.7, 14.1. MS (FAB) m/z 1969.7 [M+].
HRMS (MALDI-TOF) Calcd for C116H128O4S12:
1970.6484. Found: 1970.6421 [M+].
4.1.2. 5,11,17,23-Tetrakis(5-bromothienyl)-25,26,27,28-
tetrapropoxycalix[4]arene Calix-OT(1)-Br. To a stirred
solution of Calix-OT(1) (0.22 g, 0.24 mmol) in 30 mL
CH2Cl2 in a 100-mL round-bottomed flask was added
NBS (0.17 g, 0.96 mmol). The solution mixture was heated
to reflux overnight. After evaporating the solvent, the residue
was purified by flash silica gel column chromatography
using CH2Cl2 as eluent affording a white solid (0.27 g
1
90% yield). H NMR (270 MHz, CDCl3, d) 6.81–6.79 (m,
4.1.6. 5,11,17,23-Tetrakis(500-bromoterthienyl)-
25,26,27,28-tetradecyloxycalix[4]arene Calix-OT(3)-Br.
The bromination procedure described above was followed
using Calix-OT(3) (0.61 g, 0.3 mmol) and NBS (0.2 g,
1.2 mmol) affording a dark yellow solid (0.66 g, 96% yield).
1H NMR (270 MHz, CDCl3, d) 6.93 (s, 8H), 6.87–6.80 (m,
16H), 6.73 (d, J¼5.4 Hz, 8H), 4.47 (d, J¼13.2 Hz, 4H),
3.92 (t, J¼5.4 Hz, 8H), 3.21 (d, J¼13.2 Hz, 4H), 1.94 (s,
8H), 1.39–1.28 (m, 56H), 0.87 (t, J¼5.4 Hz, 12H). 13C
NMR (67.5 MHz, CDCl3, d) 156.4, 143.6, 138.6, 136.9,
135.2, 134.8, 134.2, 130.5, 128.0, 125.6, 124.4, 124.2,
123.4, 123.1, 122.5, 110.6, 75.4, 32.1, 31.1, 30.4, 30.09,
30.07, 29.9, 29.5, 26.5, 22.8, 14.2. HRMS (MALDI-TOF)
Calcd for C116H124Br4O4S12: 2286.2859. Found:
2286.2850 [M+].
12H), 6.55 (d, J¼3.8 Hz, 4H), 4.45 (d, J¼13.2 Hz, 4H),
3.86 (t, 8H), 3.16 (d, J¼13.2 Hz, 4H), 1.93–1.88 (m, 8H),
0.99 (t, 12H). 13C NMR (67.5 MHz, CDCl3, d) 156.4,
145.7, 135.2, 130.5, 127.7, 125.3, 121.9, 77.2, 31.1, 23.3,
10.4. MS (FAB) m/z 1236.2 [M+]. HRMS (MALDI-TOF)
Calcd for C56H53Br4O4S4: 1236.9527. Found: 1236.9569
[M++H].
4.1.3. 5,11,17,23-Tetrakis(dithienyl)-25,26,27,28-tetra-
propoxycalix[4]areneCalix-OT(2). Thecoupling procedure
described above was followed using 2-bromothiophene
(0.8 g, 4.9 mmol), Mg turnings (0.14 g, 5.8 mmol), Calix-
OT(1)-Br (0.3 g, 0.24 mmol), and PdCl2(dppf) (9 mg,
5 mmol %). The crude product was purified by flash silica
gel column chromatography using CH2Cl2/petroleum ether
(v/v¼1/3) as eluent affording a pale yellow solid (0.25 g,
4.1.7. 5,11,17,23-Tetrakis(quaterthienyl)-25,26,27,28-
tetradecyloxycalix[4]arene Calix-OT(4). The coupling
procedure described above was followed using Calix-
OT(3)-Br (0.63 g, 0.28 mmol), 2-bromothiophene (0.9 g,
5.6 mmol), Mg (0.16 g, 6.7 mmol), and PdCl2(dppf)
(11 mg, 5 mmol %) to afford a dark yellow solid (0.4 g,
63% yield). 1H NMR (400 MHz, CDCl3, d) 7.17 (d,
J¼5.2 Hz, 8H), 7.06 (d, J¼3.6 Hz, 8H), 6.96–6.86 (m,
20H), 6.79 (s, 8H), 4.49 (d, J¼13.2 Hz, 8H), 3.94 (s, 8H),
3.23 (d, J¼13.2 Hz, 8H), 1.96–1.94 (m, 8H), 1.41–1.25
(m, 56H), 0.89 (t, J¼6.0 Hz, 12H). 13C NMR (100 MHz,
CDCl3, d) 156.5, 143.6, 142.1, 136.55, 136.51, 136.4,
135.4, 135.2, 131.3, 128.7, 128.2, 125.7, 124.3, 124.2,
124.1, 123.7, 123.5, 122.6, 75.5, 32.0, 31.4, 30.4, 29.8,
29.5, 29.0, 28.6, 26.4, 22.7, 14.1. HRMS (MALDI-TOF)
Calcd for C132H137O4S16: 2299.6073. Found: 2299.6157
[M++H]. Anal. Calcd for C132H136O4S16: C, 68.95; H,
5.96. Found: C, 69.14; H, 5.93.
1
83%). H NMR (400 MHz, CDCl3, d) 7.10 (d, J¼1.2 Hz,
4H), 7.01 (d, J¼3.6 Hz, 4H), 6.93 (s, 8H), 6.92–6.89 (m,
4H), 6.80 (d, J¼3.6 Hz, 4H), 6.71 (d, J¼3.2 Hz, 4H), 4.49
(d, J¼13.6 Hz, 4H), 3.90 (t, J¼7.2 Hz, 8H), 3.22 (d,
J¼13.6 Hz, 8H), 1.99–1.93 (m, 8H), 1.02 (t, J¼7.2 Hz,
12H). 13C NMR (100 MHz, CDCl3, d) 156.4, 143.3, 137.8,
135.3, 135.2, 128.3, 127.6, 125.6, 124.4, 123.6, 123.0,
122.5, 76.9, 31.0, 23.2, 10.3. MS (FAB) m/z 1248.8 [M+].
Anal. Calcd for C72H64O4S8: C, 69.19; H, 5.16. Found: C,
69.08; H, 5.14.
4.1.4. 5,11,17,23-Tetrakis(50-bromodithienyl)-25,26,27,28-
tetradecyloxycalix[4]arene Calix-OT(2)-Br. The bro-
mination procedure described above was followed using
Calix-OT(2) (0.16 g, 0.1 mmol) and NBS (69.5 mg,
0.4 mmol). The crude product was purified by flash silica
gel column chromatography using CH2Cl2/petroleum ether
(v/v¼1/3) as eluent affording a white solid with a quantitative
1
yield. H NMR (400 MHz, CDCl3, d) 6.91 (s, 8H), 6.87 (d,
Crystal data for Calix-OT(2): C72H64O4S8, Mw¼1249.71,
crystal size¼0.34ꢁ0.22ꢁ0.20 mm3, monoclinic, spacegroup
J¼3.2 Hz, 4H), 6.77 (s, 4H), 6.74 (d, J¼3.6 Hz, 8H), 4.48
(d, J¼13.2 Hz, 4H), 3.93 (t, J¼7.2 Hz, 4H), 3.21 (d,
J¼13.2 Hz, 4H), 1.93–1.92 (m, 8H), 1.39–1.29 (m, 56H),
0.89 (t, J¼6.4 Hz, 12H). 13C NMR (100 MHz, CDCl3, d)
156.6, 143.8, 139.2, 135.3, 134.4, 130.4, 128.0, 125.6,
124.5, 122.9, 122.5, 110.2, 75.5, 32.0, 31.0, 30.3, 30.0,
29.9, 29.8, 29.5, 26.4, 22.7, 14.1. MS (FAB) m/z 1956.6
[M+]. HRMS (MALDI-TOF) Calcd for C100H117Br4O4S8:
1959.3425. Found: 1959.3488 [M++H].
˚
C2/c, a¼21.6040(14), b¼22.1252(15), c¼17.1240(11) A,
3
ꢀ
˚
b¼125.4460(10) , V¼6668.1(8) A , Z¼4, m(Mo Ka)¼
0.315 mmꢂ1. Intensity data were measured on a Bruker-
AXS CCD area-detector diffractometer with graphite
˚
monochromated Mo Ka (l¼0.71073 A) radiation, 15,702
reflections measured, 5670 unique, R(int)¼0.0252. Final
R¼0.0594 and wR2¼0.1568 for 3457 observed reflections
with I>2s(I) and GOF¼1.005.

7852
X. H. Sun et al. / Tetrahedron 62 (2006) 7846–7853
Crystallographic data (excluding structure factors) for the
structures in this paper have been deposited with the Cam-
bridge Crystallographic Data Centre with supplementary
publication no. CCDC 606338. Copies of the data can be
obtained, free of charge, on application to CCDC, 12 Union
Road, Cambridge CB2 1EZ, UK (fax: +44 1223 336033 or
e-mail: deposit@ccdc.cam.ac.uk).
CDCl3, d) 156.1, 143.8, 139.1, 134.9, 131.6, 130.6, 129.2,
126.1, 124.8, 123.4, 123.0, 110.6, 72.5, 31.9, 30.4, 29.6,
29.58, 29.55, 29.3, 26.1, 22.7, 16.4, 14.1. MS (FAB) m/z
506.1 [M+]. HRMS (MALDI-TOF) Calcd for C26H33BrOS2:
506.1132. Found: 506.1134 [M+].
4.1.12. 1-Decyloxy-2,6-dimethyl-4-terthienylbenzene M-
OT(3). The coupling procedure described in the paper was
followed using M-OT(2)-Br (0.47 g, 0.93 mmol), 2-bromo-
thiophene (0.76 g, 4.7 mmol), Mg (0.13 g, 5.6 mmol), and
PdCl2(dppf) (11 mg, 0.15 mmol %) affording a yellow solid
4.1.8. 1-Decyloxy-2,6-dimethyl-4-thienylbenzene M-
OT(1). The coupling procedure described in the paper was
followed using 1-decyloxy-2,6-dimethyl-4-bromobenzene
(1 g, 2.9 mmol), 2-bromothiophene (2.5 g, 0.015 mol), Mg
(0.45 g, 0.019 mol), and PdCl2(dppf) (10 mg, 0.5 mmol %)
1
(0.4 g, 85% yield). H NMR (400 MHz, CDCl3, d) 7.25
(s, 2H), 7.21 (dd, J¼5.2, 1.2 Hz, 1H), 7.17 (dd, J¼3.6,
1.2 Hz, 1H), 7.12 (dd, J¼6.4, 4 Hz, 2H), 7.08 (dd, J¼5.2,
3.6 Hz, 2H), 7.02 (dd, J¼4.8, 3.6 Hz, 1H), 3.77 (t,
J¼6.4 Hz, 2H), 2.31 (s, 6H), 1.85–1.78 (m, 2H), 1.54–1.49
(m, 2H), 1.34–1.28 (m, 12H), 0.89 (t, J¼6.8 Hz, 3H). 13C
NMR (100 MHz, CDCl3, d) 156.1, 143.4, 137.2, 136.4,
135.9, 135.7, 131.6, 129.3, 127.9, 126.1, 124.47, 124.43,
124.4, 123.9, 123.6, 123.1, 72.6, 31.9, 30.4, 29.6, 29.57,
29.56, 29.3, 26.1, 22.7, 16.4, 14.1. MS (FAB) m/z 508.3
[M+]. HRMS (MALDI-TOF) Calcd for C30H36OS3:
508.1928. Found: 508.1926.
1
affording a colorless liquid (0.88 g, 87% yield). H NMR
(400 MHz, CDCl3, d) 7.22–7.20 (m, 2H), 7.03 (dd, J¼4.8,
2.0 Hz, 1H), 3.76 (t, 2H), 2.30 (s, 6H), 1.84–1.77 (m, 2H),
1.52–1.48 (m, 2H), 1.38–1.28 (m, 12H), 0.89 (t, 3H). 13C
NMR (100 MHz, CDCl3, d) 155.8, 144.4, 131.4, 129.8,
127.8, 126.4, 124.1, 122.4, 72.5, 31.9, 30.4, 29.6, 29.57,
29.55, 29.3, 26.1, 22.7, 16.4, 14.1. MS (FAB) m/z 344.3
[M+]. HRMS (MALDI-TOF) Calcd for C22H32OS:
344.2173. Found: 344.2177.
4.1.9. 1-Decyloxy-2,6-dimethyl-4-(5-bromothienyl)benz-
ene M-OT(1)-Br. The bromination procedure described in
the paper was followed using M-OT(1) (1.17 g, 3.4 mmol)
and NBS (0.6 g, 3.4 mmol) affording a blue sticky solid
4.1.13. 1-Decyloxy-2,6-dimethyl-4-(500-bromoterthienyl)-
benzene M-OT(3)-Br. The bromination procedure de-
scribed in the paper was followed using M-OT(3) (0.3 g,
0.6 mmol) and NBS (0.11 g, 0.6 mmol) affording a yellow
1
(1.4 g, 98% yield). H NMR (400 MHz, CDCl3, d) 7.15 (s,
1
2H), 6.98 (d, J¼3.2 Hz, 1H), 6.93 (d, J¼3.2 Hz, 1H), 3.75
(t, 2H), 2.30 (s, 6H), 1.82–1.78 (m, 2H), 1.51–1.48 (m, 2H),
1.33–1.28 (m, 12H), 0.88 (t, 3H). 13C NMR (100 MHz,
CDCl3, d) 156.2, 145.9, 131.6, 130.6, 129.0, 126.1, 122.5,
110.4, 72.5, 31.9, 30.4, 29.61, 29.57, 26.1, 22.7, 16.4, 14.1.
MS (FAB) m/z 422.2 [M+]. HRMS (MALDI-TOF) Calcd
for C22H31BrOS: 424.1255. Found: 424.1253 [M+].
solid (0.34 g, 99% yield). H NMR (400 MHz, CDCl3, d)
7.24 (s, 2H), 7.11 (dd, J¼6.8, 4 Hz, 2H), 7.05 (d, J¼
3.6 Hz, 1H), 7.0 (d, J¼4 Hz, 1H), 6.97 (d, J¼3.6 Hz, 1H),
6.90 (d, J¼3.6 Hz, 1H), 3.77 (t, J¼6.8 Hz, 2H), 2.30 (s,
6H), 1.84–1.77 (m, 2H), 1.52–1.48 (m, 2H), 1.35–1.28 (m,
12H), 0.89 (t, J¼6.8 Hz, 3H). 13C NMR (66 MHz, CDCl3,
d) 155.9, 143.4, 138.5, 136.8, 135.2, 134.6, 131.4, 130.5,
129.1, 125.9, 124.5, 124.4, 123.7, 123.4, 123.0, 110.8, 72.5,
32.0, 30.5, 29.70, 29.67, 29.63, 29.40, 26.2, 22.8, 16.5,
14.2. MS (FAB) m/z 588.2 [M+]. HRMS (MALDI-TOF)
Calcd for C30H35BrOS3: 588.1009. Found: 588.1005 [M+].
4.1.10. 1-Decyloxy-2,6-dimethyl-4-dithienylbenzene M-
OT(2). The coupling procedure described in the paper was
followed using M-OT(1)-Br (0.57 g, 1.34 mmol), 2-bromo-
thiophene (1.1 g, 6.7 mmol), Mg (0.2 g, 8.3 mmol), and
PdCl2(dppf) (11 mg, 0.1 mmol %) affording a blue solid
4.1.14. 1-Decyloxy-2,6-dimethyl-4-quaterthienylbenzene
M-OT(4). The coupling procedure described in the paper
was followed using M-OT(3)-Br (0.4 g, 0.68 mmol), 2-
bromothiophene (0.55 g, 3.37 mmol), Mg (0.1 g, 4.2 mmol),
and PdCl2(dppf) (11 mg, 2 mmol %) affording a yellow
1
(0.53 g, 92% yield). H NMR (400 MHz, CDCl3, d) 7.24
(s, 2H), 7.20 (dd, J¼4.2, 1.2 Hz, 1H), 7.17 (dd, J¼4.2,
1.2 Hz, 1H), 7.12 (s, 2H), 7.02 (dd, J¼4.8, 3.2 Hz, 1H),
3.77 (t, J¼6.4 Hz, 2H), 2.31 (s, 6H), 1.83–1.77 (m, 2H),
1.52–1.48 (m, 2H), 1.38–1.24 (m, 12H), 0.89 (t, J¼6.8 Hz,
3H). 13C NMR (66 MHz, CDCl3, d) 155.8, 143.0, 137.5,
135.8, 131.4, 129.3, 127.7, 126.0, 124.4, 124.0, 123.2,
123.0, 72.5, 32.0, 30.5, 29.69, 29.66, 29.63, 29.4, 26.2,
22.8, 16.5, 14.2. MS (FAB) m/z 426.3 [M+]. HRMS
(MALDI-TOF) Calcd for C26H34OS2: 426.2051. Found:
426.2057.
1
solid (0.34 g, 84% yield). H NMR (400 MHz, CDCl3, d)
7.25 (s, 2H), 7.22 (d, J¼5.2 Hz, 1H), 7.18 (d, J¼3.6 Hz,
1H), 7.12, (dd, J¼6.0, 3.6 Hz, 2H), 7.08 (dd, J¼5.2, 4 Hz,
2H), 7.02 (dd, J¼4.8, 3.6 Hz, 1H), 3.77 (t, J¼6.4 Hz, 2H),
2.37 (s, 6H), 1.83–1.79 (m, 2H), 1.52–1.48 (m, 2H), 1.34–
1.28 (m, 12H), 0.89 (t, J¼6.8 Hz, 3H). 13C NMR
(100 MHz, CDCl3, d) 156.1, 143.5, 137.1, 136.6, 136.3,
135.9, 135.6, 131.6, 129.3, 127.9, 126.1, 124.5, 124.4,
124.3, 124.2, 123.9, 123.7, 123.2, 72.5, 31.9, 30.4, 29.6,
29.59, 29.56, 29.3, 26.2, 22.7, 16.4, 14.1. MS (FAB) m/z
590.3 [M+]. HRMS (MALDI-TOF) Calcd for C34H38OS4:
590.1805. Found: 590.1829.
4.1.11. 1-Decyloxy-2,6-dimethyl-4-(50-bromodithienyl)-
benzene M-OT(2)-Br. The bromination procedure de-
scribed in the paper was followed using M-OT(2) (0.53 g,
1.24 mmol) and NBS (0.22 g, 1.24 mmol) affording a yellow
solid (0.6 g, 95% yield). 1H NMR (400 MHz, CDCl3, d) 7.23
(s, 2H), 7.09 (dd, J¼3.6, 1.6 Hz, 1H), 7.03 (dd, J¼4.0,
1.6 Hz, 1H), 6.96 (dd, J¼3.6, 1.6 Hz, 1H), 6.90 (dd,
J¼3.6, 1.6 Hz, 1H), 3.76 (t, J¼6.8 Hz, 2H), 2.30 (s, 6H),
1.82–1.79 (m, 2H), 1.52–1.48 (m, 2H), 1.33–1.28 (m,
12H), 0.89 (t, J¼6.4 Hz, 3H). 13C NMR (100 MHz,
Acknowledgements
This work was supported by Earmarked Research Grant
(HKBU2019/02P) from Research Grants Council, Hong

X. H. Sun et al. / Tetrahedron 62 (2006) 7846–7853
7853
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advice on the electrochemical measurements.
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