Rapid syntheses of oligo(p-phenyleneethynylene)s via iterative convergent approach

Article abstract of DOI:10.1016/j.tet.2004.05.085

A general and controlled bidirectional growth strategy enable a very rapid and efficient construction of oligo(phenyleneethynylene)s possessing functional groups such as methylthio and thioacetate groups at both ends. The strategy employs only one reactio

Full text of DOI:10.1016/j.tet.2004.05.085

Tetrahedron 60 (2004) 6285–6294
Rapid syntheses of oligo(p-phenyleneethynylene)s via iterative
convergent approach
Cuihua Xuea,b and Fen-Tair Luoa
,
*
aInstitute of Chemistry, Academia Sinica, 128, Academia Road, Sec. 2, Nankang, Taipei 11529, Taiwan
bDepartment of Chemistry, Sichuan University, Chengdu 610064, China
Received 11 May 2004; revised 26 May 2004; accepted 26 May 2004
Available online 19 June 2004
Abstract—A general and controlled bidirectional growth strategy enable a very rapid and efficient construction of oligo(phenylene-
ethynylene)s possessing functional groups such as methylthio and thioacetate groups at both ends. The strategy employs only one reaction
type with good to moderate yields to grow the conjugated chains. The synthesis is efficient and can give 23 benzene rings and 22 carbon–
1
carbon triple bonds in the conjugated chains. The compounds are fully characterized by H and 13C NMR and UV/vis and fluorescence
spectroscopy.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
reaction type with high yields and stereoselectivities to grow
the conjugated chains. In this paper, we report the similar
rapid synthesis of oligo(p-phenyleneethynylene)s (OPE)
derivatives with thiomethyl (SMe) or thioacetyl (SAc) end
groups from the repeating one building block molecule with
three benzene rings and four carbon–carbon triple bonds
and a series of Sonogashira and desilylation reactions to
build one OPE with 23 benzene rings and 22 triple bonds in
its conjugation system. Similar oligomer with 23 aromatic
rings and 22 carbon–carbon triple bonds in its conjugation
system has been reported by Tour and his co-worker.17
Recently, conjugated oligomers of precise length have
drawn much attention due to their interesting optical,
electrical, optoelectronic properties, and their applications
in optoelectronic devices such as molecular wires, molecu-
lar-scale electronic devices, solar cells, light-emitting
diodes, and field-effect transistors.1–13 Furthermore, since
the oligomers of the repeating unit of a polymer are often
useful in understanding the properties of a polymer system,
this is due to the close analogy of their physical properties,
as well as the ease of characterization of the oligomeric
system. These compounds can be served as models for
analogous polymers and they can also be used for the
construction of nanoarchitectures such as molecular wires in
molecular scale electronic devices.1 The precise length and
well-defined conjugated oligomers can play an important
role because their precise chemical structure and conju-
gation length may lead to define functionality and facilitate
control over their supramolecular structures in the
preparation of organic thin films.14 As to our knowledge,
Tour and his co-workers have reported the synthesis of the
longest OPE containing 16 benzene rings and 16 carbon–
carbon triple bonds so far.15 Recently, we have reported a
very rapid and efficient construction of oligo(p-phenylene-
vinylene)s (OPV) compounds with precise length and
possessing functional groups such as aldehyde and mercapto
groups at both ends.16 That strategy employed only one
2. Results and discussion
Our strategy in synthesizing the OPEs was shown in
Scheme 1. The key to the overall strategy is the synthesis of
building block molecule 1 with three benzene rings and
three carbon–carbon triple bonds. In order to control the
growth of the OPE chain, it is necessary to effectively block
one terminus of the growing OPE chain which was
successfully accomplished with monomer 1. Thus,
monomer 1 possesses an iodo group at one end and a
trimethylsilylacetylenyl group at the other end. The iodo
terminus of monomer 1 can couple with the terminal
acetylenes under the Sonogashira reaction condition while
the other terminal trimethylsilylacetylenyl group of
monomer 1 can be tolerated under this reaction condition.
Therefore, 2 equiv. of monomer 1 can couple with 1 equiv.
of compound 2 under the Sonogashira reaction conditions
and give oligomer 3 in 59% yield. The following
desilylation under basic condition afford oligomer 4 in
Keywords: Oligo(phenyleneethynylene)s; OPEs; Sonogashira reaction;
Desilylation.
*
Corresponding author. Tel.: þ886-2-27898576; fax: þ886-2-27888199;
e-mail address: luoft@chem.sinica.edu.tw
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.05.085

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C. Xue, F.-T. Luo / Tetrahedron 60 (2004) 6285–6294
Scheme 1. Iterative coupling reaction for the synthesis of OPEs.
94% yield. Similar coupling of 1 equiv. of oligomer 4 with
3 equiv. of monomer 1 under Sonogashira reaction
conditions and followed by basic desilylation successfully
afford oligomer 5 and 6, in 48 and 90% yields, respectively.
Iterative coupling of 1 equiv. of oligomer 6 with 2 equiv. of
monomer 1 under Sonogashira reaction conditions and
followed by basic desilylation can give oligomer 7 and 8, in
33 and 85% yields, respectively. Accordingly, the growth of
OPE chain commences with compound 2 and thereafter
monomer 1 is added in a repetitive stepwise fashion to add
six benzene rings and six carbon–carbon triple bonds at one
time. The process could be repeated to quickly build up
longer OPE molecules possessing terminal acetylene groups
as the functionalized termini. Oligomers 2, 4, 6, and 8 with
two terminal acetylene groups at the termini can further
undergo Sonogashira reaction with 2 equiv. of 1-iodo-4-
methylthiobenzene to form 9–12 in 62, 52, 31, and 24%
yields, respectively (Scheme 2). It is needed to know that
the introduction of masked thiol (mercapto) end-groups at
the terminal positions of the oligomers can serve as an
anchor groups for attachment to the gold electrode
surface.18,19 The single crystal X-ray analysis of oligomer
9 shows that the distance between the two sulfur atoms is
20
˚
33.635 A (Fig. 1). In addition, when oligomers 2 and 4
were treated with 2 equiv. of p-iodophenylthioacetate under
the Sonogashira reaction conditions, oligomers 13 and 14
Scheme 2. Preparation of OPEs with methylsulfide as the terminal groups.

C. Xue, F.-T. Luo / Tetrahedron 60 (2004) 6285–6294
6287
Figure 1. X-ray of compound 9.
could be isolated in 52 and 45% yields, respectively
(Scheme 3). The lower yields for the preparation of longer
OPEs may due to their lower solubilities under the reaction
conditions and some unknown by-products with lower Rf
values on thin layer chromatography analysis using a
mixture of hexane and chloroform as the mobile phase. The
transformation of the terminal methylsulfide groups on 9 to
the two terminal mercapto groups in good yield (.90%
yield) can be done by treating 9 with 5 equiv. of sodium
2-methyl-2-propanethiolate in very dry DMF.21 Reduced
solubility of the longer oligomers poses a problem in the
purification of these compounds, but analytically pure
samples could be obtained through careful flash column
chromatography using mixtures of chloroform and hexane
as the mobile phase. Yields for each of the steps are fair to
moderate with decreased solubility of the longer OPEs
limiting the yields somewhat. Presently, we have succeeded
in the synthesis and purification of oligomer 12, which has
23 benzene rings and 22 triple bonds in its conjugation
pathway, and a molecular weight of 3775.2238. Our success
Scheme 3. Preparation of OPEs with thioacetate as the terminal groups.
Scheme 4. Synthesis of building block molecules 1 and 2.

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C. Xue, F.-T. Luo / Tetrahedron 60 (2004) 6285–6294
Figure 2. UV and Em of OPE oligomers 9 (5.32£1026 M), 10 (4.06£1026 M), 11 (3.33£1026 M), and 12 (2.04£1026 M) in CHCl3 at 25 8C.
of preparing such a longer OPE may be due to its better
solubility in the reaction solvents than most reported OPEs
in their reaction solvents. The presence of the 2,5-alkoxyl
groups in every three benzene rings of these OPEs may also
increase their solubilities in the reaction solvents.16
Synthesis of longer oligomers is still in progress. All of
the spectroscopic studies and elemental analysis results are
consistent with the proposed molecular structures.
oligomers.23 Thus, the effective conjugation length in this
series of oligomers is reached at oligomer 10. All the four
OPEs 9–12 showed a shorter absorption wavelength
maximum at 340 nm. Elongation of the conjugation length
from 9 to 12 results in a red shift of 9 nm in the emission
spectra, while a red shift of 7 nm from 9 to 10 and a red shift
of 2 nm from 10 to 11 and the same lmax for 11 and 12 in the
emission spectra. The extinction coefficients based on the
oligomer molecules OPEs 9–12 are 1.00£105, 1.91£105,
3.07£105, and 4.88£105, respectively. It indicates that
increasing the conjugation length of OPE may also increase
the transition probability of electrons from their ground
states to the excited states. There is a major band with a
shoulder to the red of moderate intensity in the emission
spectrum of OPEs 9–12. It is noteworthy that the half band-
widths of the emission spectra of OPEs 9–12 are much
narrow as compared with that of OPVs.16 At present, it is
not clear why this should be the case. No change in any of
the emission spectra was observed when fluorescence
measurements were made over a wide range of concen-
trations (2£102525£1028 M), suggesting that excimer
formation does not occur. The fluorescence quantum yields
of the OPEs 9 to 12 in dichloromethane are 80, 77, 77, and
63%, respectively (Table 1). It is interesting to note that the
quantum yields are decreased as the conjugation length
increases.
The strategy in synthesizing the building block molecules
for OPEs was shown in Scheme 4. Thus, 1,4-diiodo-2,5-
dihexyloxybenzene22 was reacted with 2 equiv. of tri-
methylsilylacetylene under Sonogashira reaction conditions
could afford compound 15 (91% yield), which was
desilylated under basic reaction conditions to give com-
pound 16 in 97% yield. Dibromo compound 17 was
prepared in 81% yield by Sonogashira coupling reaction
from 1 equiv. of compound 16 and 2 equiv. of 4-bromo-1-
iodobenzene in highly regioselective manner. Lithium-
halogen exchange reaction followed by iodination with
1,2-diiodoethane could give diiodo compound 18 in 57%
yield. Sonogashira reaction of 1 equiv. of diiodo compound
18 with 1 equiv. of trimethylsilylacetylene could afford
compound 1 and compound 19 in 52 and 24% yields,
respectively. The two products could be separated from the
reaction mixture by flash column chromatography using a
mixture of hexane and ethyl acetate as the mobile phase. An
alternative approach and high yield (.93%) to the rapid
synthesis of OPE molecule 19 is to react 2.2 equiv. of
trimethylsilylethynyl with 1 equiv. of diiodo compound 18
under the Sonogashira reaction conditions.
Table 1. The absorption lmax (in CHCl3), extinction co-efficiency, emission
lmax (in CHCl3), and fluorescent quantum yield of OPEs
a
FF
Oligomer
UV lmax (nm)
1£1025
Em lmax (nm)
9
389
405
407
411
1.00
1.91
3.07
4.88
431
438
440
440
0.80
0.77
0.77
0.63
10
11
12
The absorption and emission spectra for the series of OPEs
that possess the methylthio end groups are shown in
Figure 2. All of the oligomers show strong and broad
absorption in the visible region. Elongation of the
conjugation length from oligomer 9 to oligomer 10 results
in a red shift of 16 nm (Table 1). However, only little red
shift is noticed after the conjugation length reaches 11
benzene rings and 10 triple bonds. The saturation in lmax
has been observed previously and arises because of
the limitations to electron delocalization in the longer
a
Use p-distyrylbenzene (FFø0.9) to compare with in dichloromethane.24
It should be pointed out that various syntheses of different
OPEs have been reported in the past.25–28 Tour et al. have
reported the improved and new synthesis of OPE molecules
with nitro groups and with nitrile group as the alligator clip
to a metal surface as the potential molecular electronic

C. Xue, F.-T. Luo / Tetrahedron 60 (2004) 6285–6294
6289
devices.25 Their rapid bi-directional synthesis of OPEs
containing with or without thienyl rings or the solid phase
synthesis of OPEs are also noteworthy.1,26 Godt et al. have
applied the iterative convergent/divergent strategy based on
the bromine–iodine selectivity of the palladium-catalyzed
alkyne-aryl coupling reactions to form OPEs with 9 mer.27
Meier et al. have investigated the non-linear optics of
monodisperse OPEs with up to 6 mer.28 The work presented
in this paper is distinct from others in that our approach is
open ended and very versatile, and it enables us to
synthesize longer oligomers that more closely resemble
organic polymeric conducting materials. Due to the fact that
the Sonogashira reaction tolerates a wide variety of
functional groups,18,19 it should be possible to synthesize
many different OPE molecules of various lengths and
structures. This is useful for fine-tuning the band gap in
emissive organic materials. Also noteworthy is the use of
only one reaction type to construct the whole molecules.
The use of building blocks with three benzene rings allows
for efficient and fast construction of the OPE chain. After
desilylation steps, two terminal acetylene functional groups
are left for further chemical manipulation which may
include either continued elongation or reaction with an end-
functionalized polymer to form novel diblock copolymers
or with an end-capped monomer to form longer oligomers.
Controlled bidirectional growth is also possible, enabling a
very rapid construction of OPEs possessing various
functional groups at both ends. Thus, we can use the
iterative coherent approach to effectively and rapidly
synthesize longer OPEs.
valley definition), and fitted with a magnet bypass flight
tube. MALDI-MS spectra were collected on spectrometer
equipped with a nitrogen laser (337 nm) and operated in the
delayed extraction reflector mode. MS spectra were
determined on a Shimadzu QP-1000 spectrometer or Fisons
MD800 GC/MS or VG 70-250S spectrometer. UV and
fluorescent spectra were recorded in CHCl3 solution unless
otherwise stated.
3.1.1. 1,4-Bis-hexyloxy-2,5-bis-trimethylsilylethynyl-
benzene 15. To a dried round-bottomed flask were added
1,4-bis-hexyloxy-2,5-diiodobenzene22 (10.0 g, 18.87 mmol),
bis(triphenylphosphine)palladium
dichloride
(0.52 g,
0.74 mmol), copper(I) iodide (0.28 g, 1.47 mmol), tri-
phenylphosphine (0.77 g, 2.94 mmol). The system was
evacuated and flushed with nitrogen (3£) and the dry
piperidine (50 mL) was degassed with nitrogen and then
added. Under stirring, trimethylsilylacetylene (3.71 g,
37.85 mmol) was added to solution. The mixture was stirred
at rt for 6 h. The solvent was evaporated, and chloroform
was added. The organic phase was washed with saturated
solution of NH4Cl (3£50 mL), solution of NaCl (3£50 mL),
and dried over anhydrous MgSO4. The solvent was removed
in vacuum, and residue was purified by column chroma-
tography (silica gel, hexane/chloroform, 10:0.5) to give the
compound 15 as white solid (8.09 g, 91% yield). Mp 75–
76 8C. 1H NMR (300 MHz, CDCl3) d 0.25 (s, 18H), 0.90 (t,
J¼7 Hz, 6H), 1.30–1.35 (m, 8H), 1.47–1.52 (m, 4H),
1.75–1.80 (m, 4H), 3.94 (t, J¼7 Hz, 4H), 6.88 (s, 2H) ppm;
13C NMR (75 MHz, CDCl3) d 0.03, 14.17, 22.72, 25.77,
29.37, 31.69, 69.49, 100.15, 101.13, 113.98, 117.23,
154.07 ppm; IR (CHCl3) n 2137, 1269, 1015 cm21; MS
(m/z) 470.2 (Mþ); HRMS calcd for C28H46O2Si2 470.3036,
found 470.3032.
In summary, our general and controlled bidirectional growth
strategy enables a very rapid and efficient construction of
OPEs possessing functional groups at both ends. So far, we
can prepare oligomer 12, which has 23 benzene rings and 22
triple bonds in its conjugation system. The strategy employs
only one reaction type to grow the conjugated chains. We
intend to use these molecules in the production of novel
molecular wires.
3.1.2. 1,4-Diethynyl-2,5-bis-hexyloxybenzene 16. Com-
pound 15 (8.0 g, 16.98 mmol) was dissolved in CHCl3
(50 mL), CH3OH (10 mL) and solution of NaOH (2.7 g,
67.5 mol) in 10 mL of water were added. The mixture was
stirred at rt for 12 h, and then washed with saturated
solution of NaCl (3£50 mL), and dried over anhydrous
MgSO4. The solvent was removed in vacuum, and residue
was recrystallized from CHCl3/hexane to provide pure
compound 16 as white solid (5.32 g, 97% yield). Mp 70–
71 8C. 1H NMR (300 MHz, CDCl3) d 0.90 (t, J¼7 Hz, 6H),
1.33–1.35 (m, 8H), 1.42–1.47 (m, 4H), 1.75–1.84 (m, 4H),
3.34 (s, 2H), 3.97 (t, J¼7 Hz, 4H), 6.95 (s, 2H) ppm; 13C
NMR (75 MHz, CDCl3) d 13.93, 22.50, 25.50, 29.00, 31.44,
69.52, 79.70, 82.37, 113.16, 117.60, 153.89 ppm; IR
(CHCl3) n 2106, 1269, 1015 cm21. MS (m/z) 326.3 (Mþ);
HRMS calcd for C22H30O2 326.2246, found 326.2254.
3. Experimental
3.1. General
All reactions were carried out under an atmosphere of
nitrogen. Tetrahydrofuran (THF) was dealt with dried NaH
and then distilled over sodium/benzophenone ketyl when-
ever needed. All organic extracts were dried over anhydrous
magnesium sulfate. TLC was done on aluminum sheets with
precoated silica gel 60 F254 (40£80 mm) from Merck.
Purification by column chromatography was carried out
with neutral silica gel 60 (70–230 mesh ASTM). The purity
of each compound was judged to be .95% by 1H NMR or
13C NMR spectral analyses. Melting points (Mps) were
taken on a MEL-TEMP capillary tube apparatus and are
uncorrected. IR spectra were recorded as either Nujol mulls
or in the solution form as denoted. 1H NMR and 13C NMR
spectra were recorded in CDCl3 solution on either a 300,
400 or 500 MHz instrument using TMS (0 ppm) and CDCl3
(77.0 ppm) as internal standards. HRMS spectra were
collected on an Autospec orthogonal acceleration-time of
flight mass spectrometer with a resolution of 6000 (5%
3.1.3. 1,4-Bis-(4-bromo-phenylethynyl)-2,5-bis-hexyl-
oxybenzene 17. To a dried round-bottomed flask were
added compound 16 (5.0 g, 15.31 mmol), 1-bromo-4-iodo-
benzene (8.67 g, 30.64 mmol), bis(triphenylphosphine)-
palladium dichloride (0.43 g, 0.61 mmol), copper(I) iodide
(0.23 g,
1.21 mmol),
triphenylphosphine
(0.63 g,
2.40 mmol). The system was evacuated and flushed with
nitrogen (3£), the dry piperidine (60 mL) was degassed with
nitrogen and then added into the reaction mixture. The
mixture was stirred at rt for 8 h. The solvent was evaporated,
and chloroform was added. The organic phase was washed

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C. Xue, F.-T. Luo / Tetrahedron 60 (2004) 6285–6294
with saturated solution of NH4Cl (3£50 mL), solution of
NaCl (3£50 mL), and dried over anhydrous MgSO4. The
solvent was removed in vacuum, and residue was purified
by column chromatography (silica gel, hexane/chloroform,
10:0.5) to give compound 17 as faint yellow solid (7.89 g,
81% yield). Mp 112–113 8C. 1H NMR (300 MHz, CDCl3) d
0.89 (t, J¼7 Hz, 6H), 1.33–1.37 (m, 8H), 1.51–1.56 (m,
4H), 1.79–1.86 (m, 4H), 4.02 (t, J¼7 Hz, 4H), 6.70 (s, 2H),
7.39 (d, J¼8 Hz, 4H), 7.49 (d, J¼8 Hz, 4H) ppm; 13C NMR
(75 MHz, CDCl3) d 14.02, 22.62, 25.70, 29.24, 31.56,
69.54, 87.05, 93.82, 113.78, 116.72, 122.35, 122.49, 131.57,
132.92, 153.60 ppm; IR (CHCl3) n 2209, 1274, 1186,
1067 cm21; MS (m/z) 634 (Mþ); HRMS calcd for
C34H36O2Br2 634.1082, found 634.1096.
J¼7 Hz, 6H), 1.30–1.35 (m, 8H), 1.51–1.56 (m, 4H),
1.79–1.86 (m, 4H), 4.02 (t, J¼7 Hz, 4H), 6.99 (s, 2H), 7.24
(d, J¼8 Hz, 4H), 7.45 (s, 4H), 7.68 (d, J¼8 Hz, 4H) ppm;
13C NMR (125 MHz, CDCl3) d 0.10, 14.03, 22.62, 25.71,
29.25, 31.56, 69.55, 69.58, 87.38, 87.88, 93.97, 94.12,
94.61, 96.31, 104.65, 113.75, 113.93, 116.76, 122.87,
122.94, 123.45, 131.31, 131.85, 133.00, 137.48,
153.62 ppm; IR (CHCl3) n 2147, 1274, 1248, 1191 cm21
;
MS (m/z) 700 (Mþ); HRMS calcd for C39H45O2SiI
700.2234, found 700.2227.
Compound 19. Yellow solid (1.10 g, 24% yield). Mp 156–
157 8C. 1H NMR (300 MHz, CDCl3) d 0.26 (s, 18H), 0.90 (t,
J¼7 Hz, 6H), 1.34–1.38 (m, 8H), 1.52–1.54 (m, 4H),
1.82–1.87 (m, 4H), 4.02 (t, J¼7 Hz, 4H), 7.00 (s, 2H), 7.45
(s, 8H) ppm; 13C NMR (75 MHz, CDCl3) d 20.10, 14.03,
22.63, 25.73, 29.26, 31.58, 59.57, 87.91, 94.60, 96.29,
104.66, 113.87, 116.77, 122.85, 123.47, 131.31, 131.85,
3.1.4. 1,4-Bis-hexyloxy-2,5-bis(4-iodo-phenylethynyl)-
benzene 18. To a dried two-neck round-bottomed flask
was added compound 17 (10 g, 15.72 mmol), the system
was evacuated and flushed with nitrogen. Dry ether
(200 mL) was added, and solution of n-BuLi (2.5 M,
12.6 mL) in ether (100 mL) was then added dropwise at
0 8C. After stirring at 0 8C for 3 h, the solution of 1,2-
diiodoethane (8.90 g, 31.56 mmol) in 20 mL of ether was
added, the reaction mixture was stirred at rt for 12 h. The
solution was then washed with saturated solution of
Na2S2O3 (2£50 mL), solution of NaCl (3£50 mL), and
dried over anhydrous MgSO4. The solvent was removed
under vacuum, the crude product was purified by column
chromatography (silica gel, hexane/CHCl3¼5:0.5) to give
compound 18 as a light yellow solid (6.5 g, 57% yield). Mp
110–111 8C. 1H NMR (300 MHz, CDCl3) d 0.88 (t,
J¼7 Hz, 6H), 1.29–1.36 (m, 8H), 1.47–1.54 (m, 4H),
1.78–1.97 (m, 4H), 4.01 (t, J¼7 Hz, 4H), 6.98 (s, 2H), 7.24
(d, J¼8 Hz, 4H), 7.67 (d, J¼8 Hz, 4H) ppm; 13C NMR
(75 MHz, CDCl3) d 14.05, 22.63, 25.72, 29.25, 31.57,
69.56, 87.35, 94.00, 94.16, 113.80, 116.74, 122.92, 133.01,
137.49, 153.61 ppm; IR (CHCl3) n 2199, 1274, 1212,
1051 cm21; MS (m/z) 730 (Mþ); HRMS calcd for
C34H36O2I2 730.0805, found 730.0811.
153.63 ppm; IR (CHCl3) n 2147, 1409, 1378, 1020 cm21
;
MS (m/z) 670.4 (Mþ); HRMS calcd for C44H54O2Si2
670.3662, found 670.3652.
The compound 19 can also be obtained in 96% yield by
reaction of compound 18 and 2.0 equiv. of
trimethylsilylacetylene.
3.1.6. 1,4-Bis-(4-ethynyl-phenylethynyl)-2,5-bis-hexyl-
oxy-benzene 2. Compound 19 (2.0 g, 2.98 mmol) was
dissolved in CHCl3 (50 mL), CH3OH (10 mL) and solution
of NaOH (0.96 g, 24.0 mol) in 10 mL of water were added.
The mixture was stirred at rt for 12 h, and then washed with
saturated solution of NaCl (3£50 mL), and dried over
anhydrous MgSO4. The solvent was removed in vacuum,
and residue was recrystallized from CHCl3/hexane to
provide pure compound 2 as yellow solid (1.50 g, 96%
yield). Mp 112–114 8C. 1H NMR (300 MHz, CDCl3) d 0.90
(t, J¼7 Hz, 6H), 1.31–1.36 (m, 8H), 1.50–1.58 (m, 4H),
1.80–1.87 (m, 4H), 3.18 (s, 2H), 4.03 (t, J¼7 Hz, 4H), 7.01
(s, 2H), 7.47 (s, 8H) ppm; 13C NMR (75 MHz, CDCl3) d
14.01, 22.62, 25.72, 29.25, 31.57, 69.55, 78.93, 83.28,
87.97, 94.39, 113.84, 116.76, 121.83, 123.89, 131.38,
3.1.5. {4-[2,5-Bis-hexyloxy-4-(4-iodo-phenylethynyl)-
phenylethynyl]phenylethynyl}-tri-methylsilane 1 and
1,4-bis-hexyloxy-2,5-bis(4-trimethylsilanylethynyl-
phenyl-ethynyl)benzene 19. To a dried round-bottomed
flask were added compound 18 (5.0 g, 6.85 mmol),
132.01, 153.65 ppm; IR (CHCl3)
n
2099, 1284,
1017 cm21; MS (m/z) 526 (Mþ); HRMS calcd for
C38H38O2 526.2872, found 526.2866.
bis(triphenylphosphine)palladium
dichloride
(0.11 g,
Oligomer 3. To a dried round-bottomed flask were added
compound 1 (1.73 g, 2.47 mmol), compound 2 (0.65 g,
1.23 mmol), bis(triphenylphosphine)palladium dichloride
(0.04 g, 0.06 mmol), copper(I) iodide (0.02 g, 0.11 mmol),
triphenylphosphine (0.06 g, 0.23 mmol). The system was
evacuated and flushed with nitrogen (3£), the dry piperidine
(50 mL) was degassed with nitrogen and then added. The
mixture was stirred at rt for 12 h. The solvent was
evaporated, and chloroform was added. The organic phase
was washed with saturated solution of NH4Cl (3£50 mL),
solution of NaCl (3£50 mL), and dried over anhydrous
MgSO4. The solvent was removed in vacuum, and residue
was purified by column chromatography (silica gel, hexane/
chloroform, 10:6) to give the oligomer 3 as yellow solid
0.16 mmol), copper(I) iodide (0.06 g, 0.32 mmol), tri-
phenylphosphine (0.16 g, 0.61 mmol). The system was
evacuated and flushed with nitrogen (3£), the dry piperidine
(30 mL) was degassed with nitrogen and then added into the
reaction mixture. Under stirring, trimethylsilylacetylene
(0.68 g, 6.94 mmol) was added to the solution. The mixture
was stirred at rt for 3 h. The solvent was evaporated, and
chloroform was added. The organic phase was washed with
saturated solution of NH4Cl (3£50 mL), solution of NaCl
(3£50 mL), and dried over anhydrous MgSO4. The solvent
was removed in vacuum, and residue was separated by
column chromatography (silica gel, hexane/chloroform,
10:0.5–1) to give the unreacted compound 18 (1.2 g),
compound 1 (2.51 g), and compound 19 (1.1 g).
1
(1.22 g, 59% yield). Mp 146–147 8C. H NMR (300 MHz,
CDCl3) d 0.26 (s, 18H), 0.85–0.92 (t, J¼7 Hz, 18H), 1.30–
1.37 (m, 24H), 1.55–1.58 (m, 12H), 1.83–1.87 (m, 12H),
4.03 (t, J¼7 Hz, 12H), 7.02 (s, 6H), 7.45 (s, 8H), 7.52 (s,
Compound 1. Yellow solid (2.51 g, 52% yield). Mp 98–
1
99 8C. H NMR (300 MHz, CDCl3) d 0.26 (s, 9H), 0.90 (t,

C. Xue, F.-T. Luo / Tetrahedron 60 (2004) 6285–6294
6291
16H) ppm; 13C NMR (125 MHz, CDCl3) d 20.09, 14.04,
22.64, 25.75, 29.29, 31.60, 69.61, 87.92, 88.06, 91.08,
94.67, 96.31, 104.68, 113.93, 116.81, 122.82, 123.48,
131.33, 131.52, 131.87, 132.41, 153.67 ppm; IR (CHCl3)
n 2135, 1277, 1019 cm21; MS (m/z) 1670.5 (Mþ); HRMS
calcd for C116H126O6Si2 1670.9093, found 1670.9072.
(m, 40H), 1.53–1.57 (m, 20H), 1.84–1.91 (m, 20H), 3.18 (s,
2H), 4.02–4.07 (m, 20H), 7.02 (s, 10H), 7.47 (s, 8H), 7.52
(s, 32H) ppm; 13C NMR (100 MHz, CDCl3) d 14.16, 22.76,
25.87, 29.42, 31.72, 69.76, 79.02, 83.43, 88.20, 91.21,
94.53, 94.81, 114.08, 116.97, 121.97, 122.95, 123.61,
124.06, 131.53, 131.64, 132.16, 153.82 ppm; IR (CHCl3)
n 2101, 1282, 1017 cm21; MS (m/z) 2527.5 (Mþ); HRMS
calcd for C182H182O10 2527.3733, found 2527.3742.
Oligomer 4. Oligomer 3 (1.0 g, 0.60 mmol) was dissolved in
CHCl3 (60 mL), CH3OH (10 mL) and solution of NaOH
(0.3 g, 7.5 mol) in 10 mL of water were added. The mixture
was stirred at 50 8C for 15 h, and then washed with saturated
solution of NaCl (3£50 mL), and dried over anhydrous
MgSO4. The solvent was removed in vacuum, and residue
was recrystallized from CHCl3/hexane to provide pure
oligomer 4 as yellow solid (0.86 g, 94% yield). Mp 117–
119 8C. 1H NMR (300 MHz, CDCl3) d 0.86–0.93 (m, 18H),
1.30–1.37 (m, 24H), 1.52–1.55 (m, 12H), 1.84–1.88 (m,
12H), 3.18 (s, 2H), 4.04 (m, 12H), 7.02 (s, 6H), 7.47 (s, 8H),
7.52 (s, 16H) ppm; 13C NMR (125 MHz, CDCl3) d 14.05,
22.65, 25.75, 29.30, 31.60, 69.62, 78.92, 83.32, 88.06,
91.09, 94.42, 94.70, 113.97, 116.86, 121.85, 122.83, 123.48,
123.93, 131.41, 131.53, 132.05, 153.69 ppm; IR (CHCl3) n
2099, 1280, 1015 cm21; MS (m/z) 1527.1 (Mþ); HRMS
calcd for C110H110O6 1526.8302, found 1526.8350.
Oligomer 7. To a dried round-bottomed flask were added
compound 1 (0.36 g, 0.51 mmol), bis(triphenylphosphine)-
palladium dichloride (0.02 g, 0.03 mmol), copper(I) iodide
(0.01 g, 0.05 mmol), triphenylphosphine (0.03 g,
0.11 mmol). The system was evacuated and flushed with
nitrogen (3£), THF (20 mL) and DIEA (20 mL) were
degassed with nitrogen and then added. Compound 6
(0.65 g, 0.26 mmol) was evacuated and flushed with
nitrogen (3£) in another dried round-bottomed flask, and
dissolved in degassed THF (35 mL), and then added above
system. The mixture was stirred at 50 8C for 24 h. The
solvent was evaporated, and chloroform was added. The
organic phase was washed with saturated solution of NH4Cl
(3£50 mL), solution of NaCl (3£50 mL), and dried over
anhydrous MgSO4. The solvent was removed in vacuum,
and residue was purified by column chromatography (silica
gel, hexane/chloroform, 10:6) to give the oligomer 7 as
yellow solid (0.31 g, 33% yield). Mp 176–177 8C. 1H NMR
(300 MHz, CDCl3) d 0.26 (s, 18H), 0.83–0.97 (m, 42H),
1.35–1.43 (m, 56H), 1.53–1.58 (m, 28H), 1.84–1.91 (m,
28H), 4.03–4.07 (m, 28H), 7.02 (s, 14H), 7.45 (s, 8H), 7.52
(s, 48H) ppm; 13C NMR (125 MHz, CDCl3) d 20.10, 14.05,
22.65, 25.75, 29.29, 31.60, 69.60, 88.06, 91.08, 94.68,
96.30, 104.65, 113.91, 116.79, 122.81, 123.47, 131.32,
131.51, 131.86, 153.67 ppm; IR (CHCl3) n 2145, 1278,
1019 cm21; MS (m/z) 3671.5 (Mþ); HRMS calcd for
C260H270O14Si2 3671.9954, found 3671.9962.
Oligomer 5. To a dried round-bottomed flask were added
compound 1 (0.80 g, 1.14 mmol), bis(triphenylphosphine)-
palladium dichloride (0.04 g, 0.06 mmol), copper(I) iodide
(0.02 g, 0.11 mmol), triphenylphosphine (0.06 g,
0.23 mmol). The system was evacuated and flushed with
nitrogen (3£), THF (20 mL) and DIEA (20 mL) were
degassed with nitrogen and then added. Compound 4
(0.95 g, 0.57 mmol) was evacuated and flushed with
nitrogen (3£) in another dried round-bottomed flask, and
dissolved in degassed THF (25 mL), and then added above
system. The mixture was stirred at rt for 12 h and then at
50 8C for 8 h. The solvent was evaporated, and chloroform
was added. The organic phase was washed with saturated
solution of NH4Cl (3£50 mL), solution of NaCl (3£50 mL),
and dried over anhydrous MgSO4. The solvent was removed
in vacuum, and residue was purified by column chroma-
tography (silica gel, hexane/chloroform, 10:6) to give the
oligomer 5 as yellow solid (0.73 g, 48% yield). Mp
Oligomer 8. Oligomer 7 (0.60 g, 0.16 mmol) was dissolved
in CHCl3 (80 mL), CH3OH (10 mL) and solution of NaOH
(0.15 g, 3.75 mol) in 10 mL of water were added. The
mixture was stirred at 75 8C for 35 h, and then washed with
saturated solution of NaCl (3£50 mL), dried over anhydrous
MgSO4. The solvent was removed in vacuum, and residue
was recrystallized from CHCl3/hexane to provide pure
oligomer 8 as yellow solid (0.49 g, 85% yield). Mp 155–
156 8C. 1H NMR (300 MHz, CDCl3) d 0.89–0.93 (m, 42H),
1.35–1.43 (m, 56H), 1.54–1.59 (m, 28H), 1.82–1.91 (m,
28H), 3.18 (s, 2H), 4.03–4.07 (m, 28H), 7.02 (s, 14H), 7.47
(s, 8H), 7.52 (s, 48H) ppm; 13C NMR (75 MHz, CDCl3) d
14.16, 22.76, 25.87, 29.42, 31.72, 69.75, 79.01, 83.42,
88.19, 91.21, 94.53, 94.81, 114.06, 116.96, 121.96, 122.94,
123.61, 124.05, 131.52, 131.64, 132.16, 153.81 ppm; IR
(CHCl3) n 2101, 1280, 1015 cm21; MS (m/z) 3527.7 (Mþ);
HRMS calcd for C254H254O14 3527.9164, found 3527.9172.
1
188–189 8C. H NMR (300 MHz, CDCl3) d 0.26 (s, 18H),
0.89–0.94 (m, 30H), 1.35–1.39 (m, 40H), 1.53–1.56 (m,
20H), 1.84–1.89 (m, 20H), 4.01–4.07 (m, 20H), 7.01–7.02
(m, 10H), 7.45 (s, 8H), 7.52 (s, 32H) ppm; 13C NMR
(125 MHz, CDCl3) d 20.10, 14.05, 22.65, 25.75, 29.29,
31.60, 69.61, 87.93, 88.07, 91.08, 94.68, 96.31, 104.67,
113.93, 116.80, 122.82, 123.48, 131.32, 131.52, 131.86,
153.68 ppm; IR (CHCl3) n 2145, 1279, 1020 cm21; MS
(m/z) 2671.8 (Mþ); HRMS calcd for C188H198O10Si2
2671.4524, found 2671.4532.
Oligomer 6. Oligomer 5 (0.80 g, 0.30 mmol) was dissolved
in CHCl3 (70 mL), CH3OH (10 mL) and solution of NaOH
(0.3 g, 7.5 mol) in 10 mL of water were added. The mixture
was stirred at 75 8C for 24 h, and then washed with saturated
solution of NaCl (3£50 mL), dried over anhydrous MgSO4.
The solvent was removed in vacuum, and residue was
recrystallized from CHCl3/hexane to provide pure oligomer
3.1.7. 1,4-Bis-hexyloxy-2,5-bis-[4-(4-methylsulfanyl-
phenylethynyl)-phenylethynyl]-benzene 9. To a dried
round-bottomed flask were added compound 2 (0.50 g,
0.95 mmol), 1-iodo-4-methylsulfanyl-benzene (0.48 g,
1.92 mmol), bis(triphenylphosphine)-palladium dichloride
(0.03 g, 0.04 mmol), copper(I) iodide (0.02 g, 0.11 mmol),
triphenylphosphine (0.06 g, 0.23 mmol). The system was
evacuated and flushed with nitrogen (3£), the dry piperidine
1
6 as yellow solid (0.68 g, 90% yield). Mp 146–147 8C. H
NMR (300 MHz, CDCl3) d 0.83–0.97 (m, 30H), 1.35–1.42

6292
C. Xue, F.-T. Luo / Tetrahedron 60 (2004) 6285–6294
(30 mL) was degassed with nitrogen and then added. The
mixture was stirred at rt for 10 h. The solvent was
evaporated, and chloroform was added. The organic phase
was washed with saturated solution of NH4Cl (3£50 mL),
solution of NaCl (3£50 mL), and dried over anhydrous
MgSO4. The solvent was removed in vacuum, and residue
was purified by column chromatography (silica gel, hexane/
chloroform, 10:4) to give the oligomer 9 as yellow solid
(0.45 g, 62% yield). This oligomer 9 can be further purified
by recrystallization from CHCl3 to give crystals for X-ray
and at 50 8C for another 6 h. The solvent was evaporated,
and chloroform was added. The organic phase was washed
with saturated solution of NH4Cl (3£50 mL), solution of
NaCl (3£50 mL), and dried over anhydrous MgSO4. The
solvent was removed in vacuum, and residue was purified
by column chromatography (silica gel, hexane/chloroform,
10:8) to give the oligomer 11 as yellow solid (0.17 g, 31%
yield). Mp 167–168 8C. 1H NMR (300 MHz, CDCl3) d
0.83–0.95 (m, 30H), 1.32–1.38 (m, 40H), 1.51–1.58 (m,
20H), 1.82–1.91 (m, 20H), 2.51 (s, 6H), 4.05 (t, J¼7 Hz,
20H), 7.02 (s, 10H), 7.22 (d, J¼8 Hz, 4H), 7.44 (d, J¼8 Hz,
4H), 7.50 (s, 8H), 7.52 (s, 32H) ppm; 13C NMR (125 MHz,
CDCl3) d 14.03, 15.31, 22.63, 25.73, 29.28, 31.58, 69.60,
87.86, 88.05, 89.25, 91.07, 94.67, 113.90, 116.78, 119.23,
122.80, 123.12, 123.46, 125.80, 131.40, 131.50, 131.85,
139.63, 153.66 ppm; IR (CHCl3) n 2210, 1276, 1089,
1010 cm21; MS (m/z) 2771.7 (Mþ); HRMS calcd for
C196H194O10S2 2771.4113, found 2771.4122.
1
analysis. Mp 187–188 8C. H NMR (300 MHz, CDCl3) d
0.91 (t, J¼7 Hz, 6H), 1.35–1.39 (m, 8H), 1.53–1.58 (m,
4H), 1.84–1.88 (m, 4H), 2.51 (s, 6H), 4.04 (t, J¼7 Hz, 4H),
7.02 (s, 2H), 7.22 (d, J¼8 Hz, 4H), 7.45 (d, J¼8 Hz, 4H),
7.50 (s, 8H) ppm; 13C NMR (125 MHz, CDCl3) d 14.05,
15.32, 22.65, 25.75, 29.29, 31.60, 69.60, 87.88, 89.27,
91.17, 94.73, 113.91, 116.80, 119.24, 123.11, 123.15,
125.81, 131.42, 131.48, 131.87, 139.64, 153.65 ppm; IR
(CHCl3) n 2212, 1275, 1089, 1011 cm21; MS (m/z): 770
(Mþ); HRMS calcd for C52H50O2S2 770.3252, found
770.3251.
Oligomer 12. To a dried round-bottomed flask were
added
1-iodo-4-methylsulfanyl-benzene
(0.05 g,
0.20 mmol), bis(triphenyl-phosphine)palladium dichloride
(0.02 g, 0.03 mmol), copper(I) iodide (0.01 g, 0.05 mmol),
triphenylphosphine (0.03 g, 0.11 mmol). The system was
evacuated and flushed with nitrogen (3£), THF (10 mL) and
DIEA (15 mL) were degassed with nitrogen and then added.
Compound 8 (0.35 g, 0.10 mmol) was evacuated and
flushed with nitrogen (3£) in another dried round-bottomed
flask, and dissolved in degassed THF (20 mL), and then
added above system. The mixture was stirred at 50 8C for
30 h. The solvent was evaporated, and chloroform was
added. The organic phase was washed with saturated
solution of NH4Cl (3£50 mL), solution of NaCl
(3£50 mL), and dried over anhydrous MgSO4. The solvent
was removed in vacuum, and residue was purified by
column chromatography (silica gel, hexane/chloroform,
10:6) to give the oligomer 12 as yellow solid (0.09 g, 24%
yield). Mp 175–176 8C. 1H NMR (300 MHz, CDCl3) d
0.83–0.95 (m, 42H), 1.32–1.38 (m, 56H), 1.51–1.58 (m,
28H), 1.82–1.91 (m, 28H), 2.51 (s, 6H), 4.05 (t, J¼7 Hz,
28H), 7.02 (s, 14H), 7.22 (d, J¼8 Hz, 4H), 7.44 (d, J¼8 Hz,
4H), 7.50 (s, 8H), 7.52 (s, 48H) ppm; 13C NMR (125 MHz,
CDCl3) d 14.04, 15.31, 22.64, 25.74, 29.28, 31.59, 69.59,
88.05, 91.07, 94.67, 113.90, 116.79, 122.80, 123.11, 123.46,
125.80, 131.51, 131.85, 139.63, 153.66 ppm; IR (CHCl3) n
2210, 1082, 1012 cm21; MS (m/z) 3772 (Mþ); HRMS calcd
for C268H266O14S2 3771.9544, found 3771.9552.
Oligomer 10. To a dried round-bottomed flask were
(0.13 g,
added
1-iodo-4-methylsulfanyl-benzene
0.52 mmol), bis(triphenyl-phosphine)palladium dichloride
(0.02 g, 0.03 mmol), copper(I) iodide (0.01 g, 0.05 mmol),
triphenylphosphine (0.03 g, 0.11 mmol). The system was
evacuated and flushed with nitrogen (3£), THF (10 mL) and
DIEA (15 mL) were degassed with nitrogen and then added.
Compound 4 (0.40 g, 0.26 mmol) was evacuated and
flushed with nitrogen (3£) in another dried round-bottomed
flask, and dissolved in degassed THF (20 mL), and then
added above system. The mixture was stirred at rt 8 h and at
50 8C for 6 h. The solvent was evaporated, and chloroform
was added. The organic phase was washed with saturated
solution of NH4Cl (3£50 mL), solution of NaCl (3£50 mL),
and dried over anhydrous MgSO4. The solvent was removed
in vacuum, and residue was purified by column chroma-
tography (silica gel, hexane/chloroform, 10:6) to give the
oligomer 10 as yellow solid (0.24 g, 52% yield). Mp 179–
1
180 8C. H NMR (300 MHz, CDCl3) d 0.91 (t, J¼7 Hz,
18H), 1.26–1.38 (m, 24H), 1.51–1.63 (m, 12H), 1.82–1.91
(m, 12H), 2.51 (s, 6H), 4.05 (t, J¼7 Hz, 12H), 7.02 (s, 6H),
7.22 (d, J¼8 Hz, 4H), 7.44 (d, J¼8 Hz, 4H), 7.50 (s, 8H),
7.52 (s, 16H) ppm; 13C NMR (75 MHz, CDCl3) d 14.05,
15.32, 22.65, 25.75, 29.29, 31.60, 69.61, 87.88, 88.07,
89.27, 91.09, 91.18, 94.67, 94.77, 113.86, 113.92, 113.98,
116.81, 119.24, 122.82, 123.14, 123.48, 125.82, 131.42,
131.48, 131.52, 131.87, 139.65, 153.68 ppm; IR (CHCl3) n
2210, 1276, 1088, 1011 cm21; MS (m/z) 1771 (Mþ); HRMS
calcd for C124H122O6S21770.8682, found 1770.8695.
3.1.8. Thioacetic acid S-[4-(4-{4-[4-(4-acetylsulfanyl-
phenylethynyl)-phenylethynyl]-2,5-bis-hexyloxyl-
phenylethynyl}phenylethynyl)phenyl]ester 13. To
a
dried round-bottomed flask were added 1-(4-iodo-
phenylthio)ethan-1-one (0.42 g, 1.51 mmol), bis(triphenyl-
phosphine)palladium dichloride (0.05 g, 0.07 mmol),
copper(I) iodide (0.03 g, 0.16 mmol), triphenylphosphine
(0.08 g, 0.31 mmol). The system was evacuated and flushed
with nitrogen (3£), THF (10 mL) and DIEA (10 mL) were
degassed with nitrogen and then added. Compound 2
(0.40 g, 0.76 mmol) was evacuated and flushed with
nitrogen (3£) in another dried round-bottomed flask, and
dissolved in degassed THF (10 mL), and then added above
system. The mixture was stirred at rt for 12 h. The solvent
was evaporated, and chloroform was added. The organic
Oligomer 11. To a dried round-bottomed flask were
added
1-iodo-4-methylsulfanyl-benzene
(0.10 g,
0.40 mmol), bis(triphenylphosphine)palladium dichloride
(0.02 g, 0.03 mmol), copper(I) iodide (0.01 g, 0.05 mmol),
triphenylphosphine (0.03 g, 0.11 mmol). The system was
evacuated and flushed with nitrogen (3£), THF (10 mL) and
DIEA (15 mL) were degassed with nitrogen and then added.
Compound 6 (0.50 g, 0.20 mmol) was evacuated and
flushed with nitrogen (3£) in another dried round-bottomed
flask, and dissolved in degassed THF (20 mL), and then
added above system. The mixture was stirred at rt for 8 h

C. Xue, F.-T. Luo / Tetrahedron 60 (2004) 6285–6294
6293
II; Tour, J. M. Appl. Phys. Lett. 1997, 71, 611. (e) Reinerth,
W. A.; Jones, L., II; Burgin, T. P.; Zhou, C.-W.; Muller, C. J.;
Deshpande, M. R.; Reed, M. A.; Tour, J. M. Nanotechnology
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phase was washed with saturated solution of NH4Cl
(3£50 mL), solution of NaCl (3£50 mL), and dried over
anhydrous MgSO4. The solvent was removed in vacuum,
and residue was purified by column chromatography (silica
gel, hexane/chloroform, 10:4) to give the oligomer 13 as
yellow solid (0.33 g, 52% yield). Mp 165–166 8C. 1H NMR
(300 MHz, CDCl3) d 0.91 (t, J¼7 Hz, 6H), 1.35–1.40 (m,
8H), 1.53–1.56 (m, 4H), 1.81–1.88 (m, 4H), 2.44 (s, 6H),
4.04 (t, J¼7 Hz, 4H), 7.02 (s, 2H), 7.40 (d, J¼8 Hz, 4H),
7.51 (s, 8H), 7.55 (d, J¼8 Hz, 4H) ppm; 13C NMR
(75 MHz, CDCl3) d 14.04, 22.64, 25.74, 29.29, 30.27,
31.59, 69.62, 88.09, 90.49, 90.79, 94.66, 113.94, 116.83,
122.67, 123.58, 124.28, 128.28, 131.50, 131.58, 132.16,
134.22, 153.69, 193.38 ppm; IR (CHCl3) n 2201, 1701,
1213, 1120, 1016 cm21; MS (m/z) 826 (Mþ); HRMS calcd
for C54H50O4S2 826.3151, found 826.3157.
2. Greenham, N. C.; Moratti, S. C.; Bradley, D. D. C.; Friend,
R. H.; Holmes, A. B. Nature 1993, 365, 628.
3. Katz, H. E.; Bent, S. F.; Wilson, W. L.; Schilling, M. L.;
Ungashe, S. B. J. Am. Chem. Soc. 1994, 116, 6631.
4. (a) Oelkrug, D.; Tompert, A.; Gierschner, J.; Egelhaaf, H. J.;
Hanack, M.; Hohloch, M.; Steinhuber, E. J. Phys. Chem. B
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5. Dottinger, S. E.; Hohloch, M.; Hohnholz, D.; Segura, J. L.;
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Oligomer 14. To a dried round-bottomed flask were added
1-(4-iodophenylthio)-ethan-1-one (0.21 g, 0.76 mmol),
bis(triphenylphosphine)palladium dichloride (0.03 g,
0.04 mmol), copper(I) iodide (0.02 g, 0.11 mmol), tri-
phenylphosphine (0.08 g, 0.15 mmol). The system was
evacuated and flushed with nitrogen (3£), THF (10 mL)
and DIEA (15 mL) were degassed with nitrogen and then
added. Compound 4 (0.58 g, 0.38 mmol) was evacuated and
flushed with nitrogen (3£) in another dried round-bottomed
flask, and dissolved in degassed THF (20 mL), and then
added above system. The mixture was stirred at rt for 12 h.
The solvent was evaporated, and chloroform was added.
The organic phase was washed with saturated solution of
NH4Cl (3£50 mL), solution of NaCl (3£50 mL), and dried
over anhydrous MgSO4. The solvent was removed in
vacuum, and residue was purified by column chromato-
graphy (silica gel, hexane/chloroform, 10:4) to give the
oligomer 14 as yellow solid (0.31 g, 45% yield). Mp 167–
168 8C. 1H NMR (300 MHz, CDCl3) d 0.88–0.93 (m, 18H),
1.32–1.38 (m, 24H), 1.54–1.56 (m, 12H), 1.82–1.91 (m,
12H), 2.44 (s, 6H), 4.05 (m, 12H), 7.02 (s, 6H), 7.41 (d,
J¼8 Hz, 4H), 7.52 (s, 24H), 7.56 (d, J¼8 Hz, 4H) ppm; 13C
NMR (75 MHz, CDCl3) d 14.05, 22.65, 25.75, 29.29, 30.29,
31.60, 69.61, 88.07, 90.48, 90.79, 91.08, 94.69, 113.92,
116.80, 122.67, 122.82, 123.47, 123.57, 124.28, 128.26,
131.52, 131.59, 132.17, 134.24, 153.68, 193.46 ppm; IR
(CHCl3) n 2201, 1705, 1212, 1016 cm21; MS (m/z) 1827
(Mþ); HRMS calcd for C126H122O8S2 1826.8581, found
1826.8589.
´
7. Cornil, J.; dos Santos, D. A.; Beljoune, D.; Bredas, J. L.
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Metals 1996, 83, 231.
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and Polymers; Nalwa, H. S., Ed.; Wiley: Chichester, UK,
¨
1997; Vol. 3. Chapter 13. (b) Bauerle, P.; Fischer, T.;
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Ed. Engl. 1995, 34, 303. (c) Martin, R. E.; Diederich, F.
Angew. Chem., Int. Ed. 1999, 38, 1350. (d) Zhou, C. Z.; Liu,
T. X.; Xu, J. M.; Chen, Z. K. Macromolecules 2003, 36, 1457.
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Ed. Engl. 1994, 33, 1360.
16. Xue, C.; Luo, F.-T. J. Org. Chem. 2003, 68, 4417.
17. Huang, S.; Tour, J. M. The similar oligomer with 23 aromatic
rings and 22 carbon–carbon triple bonds in its conjugation
system involving thienyl rings so that its bent shape shall have
different physical properties from that of our nearly linear type
OPEs. J. Org. Chem. 1999, 64, 8898.
Acknowledgements
18. Pearson, D. L.; Tour, J. M. J. Org. Chem. 1997, 62, 1388.
19. Hsung, R. P.; Babcock, J. R.; Chidsey, C. E. D.; Sita, L. R.
Tetrahedron Lett. 1995, 36, 4525.
We thank the National Science Council and Academia
Sinica for financial support.
20. Calculations from molecular modeling (Spartan ’04) showed
that the distance between the two sulfur atoms in oligomer 9
˚
˚
˚
are 33.495 A (AM1), 33.567 A (PM3), and 33.695 A
(Hartree–Fock//3-21G*). The structure of the oligomer 9
was confirmed by X-ray crystallography. Crystallographic
data (excluding structure factors) for the structures in this
paper have been deposited with the Cambridge Crystal-
lographic Data Centre as supplementary publication numbers
CCDC 239770. Copies of the data can be obtained, free of
charge, on application to CCDC, 12 Union Road, Cambridge
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