Highly conjugated poly(thiophene)s - Synthesis of regioregular 3-alkylthiophene polymers and 3-alkylthiophene/thiophene copolymers

Article abstract of DOI:10.1002/1099-0690(200104)2001:7<1249::AID-EJOC1249>3.0.CO;2-F

Tributyltin derivatives of 2-bromo-3-octylthiophene and 5-bromo-4-octyl-2,2′-bi(thiophene) have been selectively prepared. Condensation reactions in the presence of Pd₂(dba)₃(CHCl₃)/4 PPh₃ led to high yields (ca. 90%) of regioregular poly(3-octylthiophene) (M_w = 21.4 × 10⁴, M_w/M_n = 1.48) and poly[4-octylbi(thiophene)] (M_w = 3.8 × 10⁴, M_w/M_n = 1.1). The regioregularity of the head-to-tail (HT) coupling has been determined by ¹H NMR, which showed HT > 95% for poly(3-octylthiophene) and HT > 90% for the new poly[4-octylbi(thiophene)]. The conjugation properties of these materials have been characterized by FT-IR and UV/Vis spectroscopy. Compared to the corresponding random polymers, the absorption maxima of the new regular polymers are shifted to higher wavelengths (λ_max = 448 and 466 nm, respectively). The mean conjugation length increases with increasing regioregularity of the coupling and with fewer substituents along the conjugated chain. The electroactive properties of the materials have also been studied. The new poly[4-octylbi(thiophene)] shows an oxidation peak at a low potential, and, compared to poly(3-octyl-thiophene), a reduction peak is also observed at a lower potential indicating a higher electron affinity. Both polymers exhibit reversible blue-red electrochromic behavior associated with the reversible redox properties.

Full text of DOI:10.1002/1099-0690(200104)2001:7<1249::AID-EJOC1249>3.0.CO;2-F

FULL PAPER
Highly Conjugated Poly(thiophene)s ؊ Synthesis of Regioregular
3-Alkylthiophene Polymers and 3-Alkylthiophene/Thiophene Copolymers
[a]
[a]
[a]
`
¨
Jean-Pierre Lere-Porte, Joel J. E. Moreau,* and Christophe Torreilles
Keywords: Conducting materials / Polythiophene / Palladium / Organometallic coupling
Tributyltin derivatives of 2-bromo-3-octylthiophene and 5-
bromo-4-octyl-2,2Ј-bi(thiophene) have been selectively pre- mers are shifted to higher wavelengths (λmax = 448 and
pared. Condensation reactions in the presence of 466 nm, respectively). The mean conjugation length in-
Pd2(dba)3(CHCl3)/4 PPh3 led to high yields (ca. 90%) of re- creases with increasing regioregularity of the coupling and
polymers, the absorption maxima of the new regular poly-
gioregular poly(3-octylthiophene) (Mw = 21.4 × 104, Mw/
Mn = 1.48) and poly[4-octylbi(thiophene)] (Mw = 3.8 × 104,
Mw/Mn = 1.1). The regioregularity of the head-to-tail (HT)
coupling has been determined by 1H NMR, which showed
HT Ͼ 95% for poly(3-octylthiophene) and HT Ͼ 90% for the
new poly[4-octylbi(thiophene)]. The conjugation properties
with fewer substituents along the conjugated chain. The
electroactive properties of the materials have also been
studied. The new poly[4-octylbi(thiophene)] shows an oxida-
tion peak at a low potential, and, compared to poly(3-octyl-
thiophene), a reduction peak is also observed at a lower po-
tential indicating a higher electron affinity. Both polymers ex-
of these materials have been characterized by FT-IR and UV/ hibit reversible blue-red electrochromic behavior associated
Vis spectroscopy. Compared to the corresponding random
with the reversible redox properties.
Introduction
coupling reaction[26] has also proved useful in polycondens-
ation reactions of arylene and vinylene units.[27Ϫ31] Re-
cently, we also reported the synthesis of conjugated poly-
mers with electrochromic or electroluminescent properties
using the tin route.[32] Our interest lies in the tuning of the
electrical and optical properties of processable polythio-
phene derivatives. To some extent, these can be controlled
by the nature and arrangement of the substituents on the
thiophene ring.[33] For example, control of the regiochemis-
try[34] of the alkyl-substituted polymer backbone or control
of the distribution of the alkyl substituent[35] along the con-
jugated chain can lead to material with enhanced conjuga-
tion properties. We wish to report herein on the selective
synthesis of well-defined regioregular alkylthiophene poly-
mers and thiopheneϪalkylthiophene copolymers, as well as
on the optical properties of the resulting materials. A por-
tion of this work has been presented as a communica-
tion.[36]
Since the initial discovery of organic conducting poly-
mers in the late 1970s, very diverse applications of these
materials have emerged owing to their remarkable electronic
and photonic properties.[1Ϫ3] The structure of the conjug-
ated chain is very important in determining the physical
properties of the material. Therefore, many efforts are being
made to control the macroscopic properties of the poly-
meric material by a design strategy based on molecular en-
gineering. Polythiophene and its derivatives have been the
subject of much attention in this field.[4Ϫ7] The difficulty
arising from the low processability of the polymers obtained
in the early syntheses[8Ϫ12] was overcome by the preparation
of soluble materials[13Ϫ17] using 3-substituted thiophene
monomers. The preparation of thiophene-based materials
with defined properties and functions requires a selective
synthesis as the first step. This involves control of the struc-
ture of the chain unit in the monomer and control of the
coupling of the chain units leading to the conjugated back-
bone of the polymer. Additionally, the arrangement of the
polymeric chain in the solid is also of great importance,
since interchain interactions and dimensionality also play a
role in determining the physical properties of the material.
Our ongoing interest in the development of organometal-
lic synthetic routes for controlling the structures of two-
and three-dimensional networks containing conjugated or-
ganic units[18Ϫ25] has led us to explore the use of tin-func-
tionalized monomers. The palladium-catalysed aryltin
Results and Discussion
Regioregular Poly(3-alkylthiophene) and Poly[4-alkyl-2,2Ј-
bi(thiophene)]
Several syntheses of regioregular head-to-tail (HT)
coupled poly(3-alkylthiophenes) have been reported. The
nickel-catalysed polycondensation of a 3-alkyl-5-bromothi-
enyl Grignard reagent[37] and the related cross-coupling re-
action of the corresponding zinc reagent[38] were first re-
ported to give 98Ϫ99% HT poly(3-alkylthiophene). The ox-
idative coupling of bulky or unsymmetrical thiophene de-
rivatives was also found to selectively afford HT
polymers.[39,40] We[36] and others[41,42] have recently shown
that HT coupling can also be achieved in the palladium-
[a]
´
Laboratoire de Chimie Organometallique, UMR CNRS 5076,
´
Ecole Nationale Superieure de Chimie,
8, rue de l’Ecole Normale, 34296 Montpellier Cedex 5, France
Fax: (internat.) ϩ 33-(0)4 67 14 72 12
E-mail: jmoreau@cit.enscm.fr
Eur. J. Org. Chem. 2001, 1249Ϫ1258
WILEY-VCH Verlag GmbH, 69451 Weinheim, 2001
1434Ϫ193X/01/0407Ϫ1249 $ 17.50ϩ.50/0
1249

´
J.-P. Lere-Porte, J. J. E. Moreau, C. Torreilles
FULL PAPER
catalysed coupling of tin or boron derivatives of halo-3-al- mol-% (entry 5), only oligomers were formed. Higher con-
kylthiophenes.
centrations, e.g. 1.75 mol-%, did not increase the molecular
weight (cf. entries 6 and 4).
High Molecular Weight Poly(3-alkylthiophene)
We also studied the influence of the nature of the cata-
lyst. The results are summarized in Table 2. The use of a
PdII catalyst precursor led only to oligomers (entry 2). The
palladium dibenzalacetone complex was rather unstable in
the absence of added ligand and gave only a low conversion
(entry 3). The effect of the phosphane ligand and of the
ligand-to-palladium ratio proved to be critical. This was
studied by preparing the catalytic species in situ by mixing
Pd2(dba)3(CHCl3) and the appropriate phosphane ligand.
A 1:2 Pd to PPh3 ratio (entry 4) led to a poor yield of
polymeric material. This is most likely attributable to in-
stability of the generated catalytic species. Interestingly,
with Pd to PPh3 ratios of 1:4 or greater, a high yield of very
high molecular weight poly(3-alkylthiophene) was pro-
duced (entries 5 and 6). It is worth noting that the catalytic
species generated under these conditions is much more act-
ive than Pd(PPh3)4 (entry 1). When ligands other than PPh3
were used, e.g. P(OPh)3, P(p-Tol)3, P(C6H11)3, or dppe, the
polymer produced had a comparatively low average molecu-
lar weight and was often obtained in lower yields (entries
7Ϫ10). The best conditions therefore appeared to be those
given in Equation (2), which led to a high yield of a high
molecular weight poly(3-alkylthiophene) (Mw ഠ 21 ϫ 104,
Mw/Mn ഠ 1.48).
Our approach based on the Stille coupling reaction in-
volved the self-condensation of the bromotributylstannyl
monomer 1, which was selectively prepared according to
Scheme 1. Its synthesis required selective bromination of 3-
alkylthiophene at the 2-position followed by lithiation and
stannylation at the 5-position. The monomer 1 was isolated
in very good yield.
Scheme 1. Preparation of 2-bromo-3-octyl-5-tributylstannylthio-
phene (1)
We then studied the polycondensation of 1 in the pres-
ence of a zerovalent palladium complex according to Equa-
tion (1). The reaction was studied as a function of the solv-
ent, and of the concentration, source, and ligation of the
catalyst. The poly(3-alkylthiophene) was isolated after pre-
cipitation by the addition of acetone to the reaction mix-
ture. Molecular weights were determined by means of gel
permeation chromatography, using THF as the eluent and
polystyrene samples as calibration standards.
(1)
The polymerization was first studied using (PPh3)4Pd (1
mol-%) at 80 °C for 72 h. The results are shown in Table 1.
The choice of solvent was important since it must keep the
growing polymer in solution as well as stabilize the zeroval-
ent catalytic species. The catalyst is stable in THF or diox-
ane, but the solubility of the polymer in these solvents is
low. A 1:1 mixture of THF and DMF was found to give phene) in solution can be determined by means of H and
poly(3-alkylthiophene) with the highest molecular weight 13C NMR analysis.[5] The coupling of 3-alkylthiophene un-
(entry 4). Interestingly, the polymer yield was also much its can occur with three possible regiochemistries corres-
higher than that achieved in a similar polycondensation of ponding to head-to-tail (HT), head-to-head (HH), and tail-
an iodo derivative.[41] The optimal catalyst concentration to-tail (TT) coupling. This leads to four chemically distinct
(2)
Regioregularity of Poly(3-alkylthiophene)
The structure and regiochemistry of poly(3-alkylthio-
1
1
appeared to be 1 mol-%. At a lower concentration, e.g. 0.2 triad regioisomers (Figure 1). Distinct H NMR chemical
Table 1. Pd(PPh3)4-catalysed polymerization of 2-bromo-3-octyl-5-tributylstannylthiophene 1
Entry[a]
Solvent
Catalyst (mol-%)
Polymer Yield[b] (%)
Mn
Mw
Mw/Mn
[c]
1
2
3
4
5
6
THF
1.0
1.0
1.0
1.0
0.2
1.75
88
80
90
84
88
80
4670
4440
8510
11640
2720
10610
8970
1.9
1.2
2.0
2.1
1.1
1.9
Dioxane
5160
DMF
16910
24610
3060
THF/DMF[d]
THF/DMF[d]
THF/DMF[d]
20800
[a]
[b]
[c]
Reactions performed at 80 °C for 72 h. Ϫ Isolated material by precipitation from THF solutions. Ϫ Determined by GPC using
[d]
polystyrene standards. Ϫ 1:1 mixtures were used.
1250
Eur. J. Org. Chem. 2001, 1249Ϫ1258

Highly Conjugated Poly(thiophene)s
FULL PAPER
Table 2. Influence of the nature of the catalyst in the polymerization of 2-bromo-3-octyl-5-tributylstannylthiophene 1
Entry[a]
Catalyst
Polymer Yield[b] (%)
Mn
Mw
Mw/Mn
[c]
1
2
3
4
5
6
7
8
9
10
Pd(PPh3)4
84%
84%
10%
10%
90%
83%
90%
60%
70%
70%
11640
2330
24610
5670
2.1
2.4
1.4
2.9
1.5
1.6
1.9
1.6
2.0
1.4
[d]
Pd(PPh3)2Cl2
Pd2(dba3)(CHCl3)
3240
4440
Pd2(dba3)(CHCl3), 4 PPh3
Pd2(dba3)(CHCl3), 8 PPh3
Pd2(dba3)(CHCl3), 12 PPh3
Pd2(dba3)(CHCl3), 8 P(OPh)3
Pd2(dba3)(CHCl3), 8 P(p-Tol)3
Pd2(dba3)(CHCl3), 8 P(C6H11)3
Pd2(dba3)(CHCl3), 4 dppe
6540
19210
210910
223940
10350
6440
15660
7520
142020
138240
5500
4010
7770
5260
[a]
[b]
The reaction was performed at 80 °C for 72 h in a THF/DMF mixture (1:1) using 1 mol-% of Pd catalyst. Ϫ Soluble fractions that
were isolated after precipitation with acetone. Ϫ [c]Determined by GPC using polystyrene standards. Ϫ
The oligomer obtained here
[d]
exhibited poor regioregularity. Head-to-head coupling probably occurs in the initial reduction of the PdII precursor to form the Pd0
active catalytic species.
shifts are observed for the protons at the 4-carbon atoms yield. Interestingly, the molecular weight determined for
on the central aromatic thiophene rings. Synthesis of the PAT1 was Mn ഠ 14 ϫ 104 with a polydispersity Mw/Mn ϭ
four isomeric trimers allowed unambiguous assignment of 1.48; these values compare favorably with those of related
the relative chemical shift of each triad,[43] thereby provid- materials reported previously.[5,37Ϫ42]
ing a means of evaluating the proportion of HT coupling
in a poly(3-alkylthiophene). Additionally, the relative ratio
of HTϪHT coupling to non-HTϪHT coupling can be de-
termined by an analysis of the signals of the α-CH2 protons
of the 3-substituent on the thiophene ring.[44Ϫ47]
Figure 2. Aromatic region (δ ϭ 6.9Ϫ7.1) of the 1H NMR spectrum
of PAT1
Poly[4-octyl-2,2Ј-bi(thiophene)]
We also studied the preparation of regioregular poly[alk-
ylbi(thiophene)] since, in addition to the regiochemistry of
the polymer chain, a reduction in the number of alkyl sub-
stituents can lead to an increase in the mean conjugation
length of the material.[35] 5-Bromo-4-octyl-5Ј-tributylstan-
nyl-2,2Ј-bi(thiophene) (2) was obtained according to
Scheme 2.
The synthesis involves silylation at the 2-position of 3-
alkylthiophene followed by coupling of the 5-lithio derivat-
ive with 2-bromothiophene. Despite the use of the silyl de-
rivative, the formation of the cross-coupling product 3-oc-
Figure 1. Four possible triad regioisomers in poly(3-octylthio-
phene) (see ref.[5]
)
The 1H NMR spectrum of poly(thiophene) PAT1 ob- tyl-2-trimethylsilylbi(thiophene) was accompanied by 30%
tained from the palladium-catalysed polycondensation of 1 formation of the homo-coupled bis(silyl)bi(thiophene). The
[Equation (2)] is shown in Figure 2. PAT1 was assigned as desired unsymmetrical bi(thiophene) could nevertheless be
having 95% head-to-tail (HT) linkages on the basis of the isolated in a pure state in about 40% yield. Bromination
relative integrals of the relevant resonances. The degree of occurred selectively at the 2-position after desilylation and
structural regularity of PAT1 is also apparent from its 13C was followed by lithiation and stannylation at the 5Ј-posi-
NMR spectrum, which shows only four resonances in the tion to give pure 2.
aromatic region (δ ϭ 128.6, 130.5, 133.7, and 139.9) (Fig-
The polymerization of 2 was then effected under the op-
ure 3). Therefore, the polymerization described by Equa- timal conditions established in the case of 1 [Equation (3)].
tion (2) led to regioregular poly(3-octylthiophene) in high The poly[alkylbi(thiophene)] PABT1 was isolated after pre-
Eur. J. Org. Chem. 2001, 1249Ϫ1258
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J.-P. Lere-Porte, J. J. E. Moreau, C. Torreilles
FULL PAPER
In order to evaluate the properties of PABT1, for compar-
ison purposes we also prepared a related polymer using the
classical chemical oxidation procedure.[39,40] 4-Octyl-2,2Ј-bi-
(thiophene) was treated with FeCl3 in CHCl3 to give poly-
[alkylbi(thiophene)] PABT2 [Equation (4)]. It was isolated in
60% yield upon precipitation with MeOH. Analytical data
for PABT2 were consistent with the structure depicted in
Equation (4).
(4)
Regioregularity of Poly[4-octyl-2,2Ј-bi(thiophene)]
The regiochemistry of the coupling of the bi(thiophene)
units was studied by NMR analysis of samples of the poly-
mer. The structures were analysed on a similar basis as that
discussed for poly(3-alkylthiophene).[34]
The three possible regiochemical couplings, HH, TT, and
HT, give rise to three chemically distinct substructures (Fig-
ure 4).
Figure 3. 13C NMR spectrum of PAT1 (in the region δ ϭ 125Ϫ145)
Figure 4. Three possible regioisomer substructures in poly[4-octyl-
2,2Ј-bi(thiophene)]
Scheme 2. Preparation of 5-bromo-4-octyl-5Ј-tributylstannyl-2,2Ј-
bi(thiophene) (2)
For a regioregular HT poly[alkylbi(thiophene)], three
aromatic proton signals can be expected in the H NMR
1
spectrum. In cases where HH and TT coupling occur, addi-
tional signals can be expected. The H NMR spectrum of
cipitation with acetone in 88% yield. A high molecular
weight material with a low polydispersity was obtained. Its
elemental analysis was consistent with the structure pre-
sented in Equation (3).
1
PABT2 shows five resonances of unequal intensity (δ ϭ
7.025, 7.07, 7.10, 7.16, 7.22), while that of PABT1 also
shows several lines with two major resonances at δ ϭ 7.025
and 7.10. However, firm conclusions regarding the regioch-
emistry could not be drawn from analysis of the aromatic
regions of the spectra. Examination of the δ ϭ 1.5Ϫ3.0 re-
gion was more helpful in this matter. Figure 5 shows the 1H
NMR spectra of PABT1 and PABT2 in this region. By ana-
logy to the resonances observed for poly(3-
alkylthiophene),[44Ϫ48] the signals at δ ϭ 2.54 and 2.77 can
(3) be assigned to the protons of the α-methylene group of the
1252
Eur. J. Org. Chem. 2001, 1249Ϫ1258

Highly Conjugated Poly(thiophene)s
FULL PAPER
n-octyl substituent, while those at δ ϭ 1.56 and 1.69 can be
attributed to the adjacent β-methylene protons. The two
sets of resonances correspond to the two different diads
arising from head-to-tail (HT) and head-to-head (HH)
coupling, respectively. The PABT2 produced by oxidative
coupling of 4-octyl-2,2Ј-bi(thiophene) [Equation (4)]
showed resonance lines with similar intensities (Figure 5).
The observed spectrum was consistent with a regiorandom
chain structure with an equal distribution of HT and HH
linkages, as was expected for FeCl3 oxidation of 4-octyl-
2,2Ј-bi(thiophene), which has similarly reactive 5- and 5Ј-
positions. Interestingly, the spectrum of PABT1 was quite
different, being dominated by major signals at δ ϭ 1.7 and
2.77. This is in agreement with predominantly HT coupling
in the polymerization of 2 [Equation (3)]. Integration of the
signals indicated in excess of 90% HT linkages in the chain
structure of PABT1. The 13C NMR spectra of the two
samples (Figure 6) were also consistent with a regioregular
chain structure for PABT1 and a regiorandom one for
PABT2.
Figure 6. 13C NMR spectra of regiorandom PABT2 (a) and regio-
regular PABT1 (b)
Poly(alkylthiophene) and Poly[4-alkylbi(thiophene)]
Infrared Characterization
Poly(thiophene)s can be compared in terms of conjuga-
tion length on the basis of the intensity of the infrared ab-
sorption associated with the carbonϪcarbon vibration
modes ν(CϭC) symmetric (1450 cmϪ1) and ν(CϭC) asym-
metric (1490 cmϪ1). The intensity ratio Iasym/Isym increases
with the mean conjugation length.[48]
The measured values for poly(3-alkylthiophene) and
poly[4-alkylbi(thiophene)] are shown in Table 3. The value
of the intensity ratio increases with the regioregularity of
the polymer (HT linkages). Thus, much higher values are
observed for poly[4-alkylbi(thiophene)]s than for poly(3-al-
kylthiophene)s. The conjugation length increases with an
increase in the degree of HT linkage and with a decrease in
the number of alkyl side chains.
Optical Properties
In the case of conjugated polymers, the position of the
absorption maximum (λmax) in the visible spectrum corre-
Table 3. Intensity ratios of the infrared asymmetric and symmetric
vibrations ν(CϭC) in poly(alkylthiophene), recorded in the solid
state with samples in KBr pellets
Poly(3-octylthiophene)
Iasym/Isym
Poly[4-alkyl-2,2Ј-bi(thiophene)]
Iasym/Isym
PAT1[a(]95% HT) 0.76
PABT1
PABT1
1.00
0.94
(90% HT)
(50% HT)
PAT
0.60
(70% HT)
[a]
This sample (with nonregioselective coupling) was prepared by
FeCl3 oxidation of 3-octylthiophene according to Sugimoto et
al.[53] for comparison.
Figure 5. 1H NMR spectra of PABT1 (a) and PABT2 (b) (in the
region δ ϭ 3Ϫ1.5)
Eur. J. Org. Chem. 2001, 1249Ϫ1258
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J.-P. Lere-Porte, J. J. E. Moreau, C. Torreilles
FULL PAPER
sponds to a π-π* electronic transition and depends on the
effective conjugation length in the polymeric material. The
absorption maximum of a solution of poly(3-alkythio-
phene) is related to the proportion to TT linkages in the
polymer backbone.[34,43] It has been shown that TT linkages
of two consecutive 3-alkylthiophene units cause conjuga-
tion defects arising from the torsion about the
carbonϪcarbon single bond. This results in a decrease in
the effective conjugation length and the absorption max-
imum (λmax) is shifted towards lower wavelengths. The vis-
ible absorption spectra of regioregular poly(alkylthio-
phene)s are shown in Figure 7.
Figure 8. UV/Vis spectra of thick films of PAT1 (a) and PABT1 (b)
deposited on glass
of 0.1 and 0.2% were found; a similar observation has been
made for poly(3-hexylthiophene).[54] The slightly higher
value in the case of poly[4-octylbi(thiophene)] may arise
from a greater planarity and rigidity of the conjugated π-
system. Polymers possessing a high degree of coplanarity
and rigidity are less susceptible to deactivation through tor-
sional vibrations.
Electrochemistry
The cyclic voltammetry of thin films of PAT1 and PABT1
on a platinum electrode was studied (Figure 9). In the case
of PAT1, the voltammogram showed two reversible oxida-
tion potentials. It exhibited two oxidation peaks at Epa
(1) ഠ 0.8 V (vs. SCE) and Epa (2) ഠ 1.05 V (vs. SCE). In
the case of irregular poly(3-alkylthiophene), a broad oxida-
tion peak was observed Epa ഠ 1.1 V (vs. SCE). These results
can be interpreted in terms of coplanarity of the adjacent
thiophene rings.[34] As the system moves towards coplanar-
ity, the increase in molecular orbital overlap will help to
stabilize both polaronic (radical cationic) and bipolaronic
(dicationic) states. Compared to the case of PAT1, the vol-
tammogram of PABT1 exhibits a single oxidation peak at a
low potential value (0.84 V vs. SCE). A reduction peak is
also observed at a lower potential (Ϫ1.84 V vs. SCE; Fig-
ure 9), thus indicating a higher electron affinity. A blue-red
electrochromism is associated with the redox transfer. Ab-
sorption spectra were recorded for films of PAT1 and
PABT1 deposited on an ITO (indium tin oxide) glass sup-
port at potential values ranging from 0.4 to 1.3 V vs. SCE.
The change in the absorption spectrum as a function of the
applied potential is shown in Figure 10. The spectra of
PAT1 and PABT1 in the neutral form (before oxidation)
show bands at 480 nm. Upon oxidation, the maxima are
shifted to 720 nm and 750 nm for PAT1 and PABT1, re-
spectively, owing to a π-π* interband transition and the ap-
pearance of localized states in the gap. The changes in the
spectra as a function of the applied potential are similar in
each case. PABT1 was found to exhibit a well-defined isos-
bestic point (Figure 10, b), which shows that only the two
absorption bands at 480 and 750 nm are involved.
Figure 7. UV/Vis spectra of CHCl3 solutions of PAT1 (a) and
PABT1 (b)
In CHCl3 solution, a λmax value of 448 nm is observed
for regioregular PAT1. This value is similar to those re-
ported for related regioregular poly(alkylthiophene)s[37Ϫ42]
and much higher than the λmax values of 428 and 436 nm
measured for irregular poly(alkylthiophene)s with 50% and
70% HT linkages of the alkylthiophene units, respect-
ively.[48,49] The λmax values observed for poly[4-alkylbi(thio-
phene)]s are also much higher in the case of the more re-
gioregular PABT1 (HT ϭ 90%, λmax ϭ 466 nm). A lower
value was found for PABT2 (HT ϭ 50%, λmax ϭ 458 nm).
On the basis of the much higher λmax value, the effective
conjugation length appeared to be greater in poly[4-alkylbi-
(thiophene)] PABT1 than that in poly(3-alkylthiophene)
PAT1. This arises because of the reduced number of alkyl
side chains in the polymer and may be attributed to a de-
crease in the steric interactions between the sulfur in one
thiophene ring and the alkyl substituent on the adjacent
ring. Such interactions have been proposed as being re-
sponsible for less conjugated conformations of the poly-
mer chain.[50]
When the UV/Vis spectra were recorded in the solid state
(Figure 8) using films of PAT1 and PABT1, significant ba-
thochromic shifts (67 nm and 109 nm, respectively) were
observed. The absorption maxima, λmax ϭ 515 nm and
575 nm, may be attributed to packing effects in the solid
state.[51] Better conjugated arrangements of the polymeric
chain can be obtained upon casting the material into films.
Absorption maximum of λmax ϭ 520Ϫ525 nm have been
reported for related materials,[49,52] although it is difficult to
compare these values since λmax is dependent on the film
preparation procedure and on the film thickness.[34]
Conclusion
The emission spectra of CHCl3 solutions of the regioreg-
ular PAT1 and PABT1 were also recorded (excitation wave-
Condensation reactions of tributyltin derivatives of 2-
length 450 nm). Emission maxima of λmax ϭ 574 and bromo-3-octylthiophene and 5-bromo-4-octyl-2,2Ј-bi(thio-
569 nm, respectively, were observed. Low quantum yields phene) in the presence of palladium catalysts have been
1254
Eur. J. Org. Chem. 2001, 1249Ϫ1258

Highly Conjugated Poly(thiophene)s
FULL PAPER
Figure 9. Cyclic voltammograms of PAT1 (a) and PABT1 (b) depos-
ited on a Pt electrode from chloroform solutions (scan rate 50 mV/
s, electrolytic medium: 0.1  Bu4NPF6 in MeCN)
Figure 10. Spectro-electrochemistry of PAT1 (a) and PABT1 (b);
each spectrum was recorded for E (vs. SCE) from 0.4 V to 1.3 V
with an increment of 0.02 V
shown to produce high yields (ca. 90%) of regioregular
poly(3-octylthiophene) (Mw ϭ 21.4 ϫ 104, Mw/Mn ϭ 1.48)
and of the new poly[4-octylbi(thiophene)] (Mw ϭ 3.8 ϫ 104, interactions between the octyl groups along the conjugated
Mw/Mn ϭ 1.1). The best catalyst precursor proved to be chain. The electroactive properties of the materials have
Pd2(dba)3(CHCl3)/4 PPh3, in a 1:1 mixture of THF and also been studied. Both polymers exhibit reversible blue-red
DMF as solvent. The average molecular weight of the re- electrochromic behavior associated with the reversible redox
sulting regioregular poly(3-octylthiophene) was found to be properties. The new poly[4-octylbi(thiophene)] shows an ox-
much higher than that of a similar polymer prepared using idation peak at a low potential, and, compared to poly(3-
an iodothiophene derivative.[41] The regioregularity of the octylthiophene), a reduction peak is also observed at a
head-to-tail coupling was assessed by 1H NMR, which lower potential, indicating a higher electron affinity.
showed HT Ͼ 95% for poly(3-octylthiophene) and HT Ͼ
90% for the new poly[4-octylbi(thiophene)]. The conjuga-
Experimental Section
tion properties of these materials have been characterized
by FT-IR and UV/Vis spectroscopy. Compared to regioran-
dom polymers, the absorption maxima of the new regioreg-
ular polymers are shifted to higher wavelengths (λmax ϭ 448
and 466 nm, respectively). Similarly, their emissions appear
at higher wavelengths (λmax ϭ 515 and 575 nm, respect-
ively). The mean conjugation length increases with an in-
crease in the regioregularity of the coupling and with a de-
crease in the number of octyl substituents along the conjug-
ated chain. This is associated with a reduction in the num-
General: All experiments were carried out under an inert N2 atmo-
sphere using Schlenk techniques. CHCl3, THF, DMF, toluene, and
hexane (SDS) were dried by distillation over phosphorus pentoxide,
sodium benzophenone ketyl, and CaH2 as appropriate. 2-Bromo-
thiophene, 1-bromooctane, and tributyltin chloride (Aldrich) were
used without further purification. Ni(dppp)Cl2 and n-butyllithium
(2.5  solution in hexanes) were purchased from Aldrich. The pal-
ladium complexes were prepared according to literature proced-
ures: Pd(PPh3)4,[55] Pd(PPh3)2Cl2,[56] Pd2(dba)3(CHCl3).[57] UV/Vis
ber of conjugation defects that arise because of steric spectra were recorded on an MC2 Safas spectrometer and emission
Eur. J. Org. Chem. 2001, 1249Ϫ1258 1255

´
J.-P. Lere-Porte, J. J. E. Moreau, C. Torreilles
FULL PAPER
spectra on an SLM-Aminco MC 200 spectrometer. Ϫ Fluorescence
3-Octyl-2-trimethylsilylthiophene: A solution of 2-bromo-3-octyl-
thiophene (30 g, 0.14 mol) in THF (150 mL) was added dropwise
to magnesium turnings (3.31 g, 0.14 mol) and THF (10 mL). The
resulting mixture was refluxed for 2 h and then cooled to room
quantum yields were measured by the standard procedure.[59]
Ϫ
GPC measurements were made on a Waters chromatograph
equipped with HR2 and HR3 Styragel columns using THF as the
eluent and polystyrene samples as calibration standards. Ϫ Cyclic temp., whereupon a solution of chlorotrimethylsilane (15 mL,
voltammetry was carried out on an EG & G potentiostat connected
to a Kipp & Zonen tracer. Ϫ Electrochromism measurements were
made using a three-electrode (ITO, Pt, Ag) spectroelectrochemical
cell connected to an EG & G 362 potentiostat.
0.12 mol) in THF (30 mL) was slowly added. After the addition
was complete, the mixture was refluxed for 6 h. It was then poured
into cold water. The mixture was extracted with diethyl ether, the
combined ethereal extracts were dried over MgSO4, and the solv-
ents were evaporated. Distillation of the residue afforded 28.6 g of
3-octyl-2-trimethylsilylthiophene (76%); b.p. 93 °C (0.5 Torr). Ϫ 1H
NMR (CDCl3): δ ϭ 0.39 (s, 9 H, SiMe3), 0.92 (t, 3 H, CH3), 1.32
(m, 10 H, 5 CH2), 1.64 (m, 2 H, β-CH2), 2.71 (t, 2 H, α-CH2), 7.05
(d, 1 H, 4-H, 1J ϭ 4.6 Hz), 7.45 (d, 1 H, 5-H, 1J ϭ 4.67 Hz). Ϫ
13C NMR (CDCl3): δ ϭ 0.4 (3 CH3, SiMe3), 14.1 (CH3, alkyl),
31.9, 31.9, 31.3, 29.8, 29.5, 29.3, 22.7 (7 CH2, alkyl), 129.3 (CH,
C-5), 130.3 (CH, C-4), 132.5 (C, C-2), 150.5 (C, C-3). Ϫ 29Si NMR
(CDCl3): δ ϭ Ϫ8.2 (SiMe3). Ϫ C15H28SSi (268.53): calcd. C 67.16,
H 10.44, S 11.94; found C 67.12, H 10.39, S 11.92.
3-Octylthiophene: This compound was prepared according to a lit-
erature procedure[59] as follows. Ni(dppp)Cl2 (0.8 g, 2 mmol) was
added to a solution of 3-bromothiophene (24.5 g, 0.15 mol) in THF
(200 mL) in a 1-dm3 flask. 1-Octylmagnesium bromide [prepared
from magnesium turnings (6.4 g, 0.26 mol) and 1-bromooctane
(38 mL, 0.22 mol) in THF (200 mL)] was then slowly added at
room temp. Following the addition, the mixture was stirred for 12 h
at room temp. Pentane (400 mL) was then added and the resulting
mixture was filtered. The filtrate was concentrated in vacuo and
distillation of the residue afforded 23 g of 3-octylthiophene (78%
1
4-Octyl-5-trimethylsilyl-2,2Ј-bi(thiophene): At 0 °C, nBuLi (1.6 
yield); b.p. 106 °C/4 Torr. Ϫ H NMR (CDCl3): δ ϭ 0.91 (t, 3 H,
solution in diethyl ether, 25.6 mL, 0.041 mol) was added dropwise
CH3), 1.30 (m, 10 H, 5 CH2), 1.64 (m, 2 H, β-CH2), 2.64 (t, 2 H,
α-CH2), 6.94 (m, 2 H, 2 CH), 7.24 (m, 1 H, CH). Ϫ 13C NMR
(CDCl3): δ ϭ 14.1 (CH3, alkyl), 31.9, 30.6, 30.3, 29.5, 29.4, 29.3,
22.7 (7 CH2, alkyl), 119.7 (CH, C-2), 125.0 (CH, C-5), 128.3 (CH,
C-4), 143.3 (C, C-3). Ϫ C12H20S (196.35): calcd. C 73.16, H 10.20,
S 16.42; found C 73.48, H 10.24, S 16.30.
to
a
solution of 3-octyl-2-trimethylsilylthiophene (11.0 g,
0.041 mol) in THF (40 mL). The resulting mixture was stirred for
1 h at this temp. and was then allowed to warm to room temp. It
was added to a solution of ZnCl2 (6.4 g, 0.041 mol) in THF
(40 mL). The resulting organozinc reagent solution was then slowly
added to a solution of 2-bromothiophene (6.68 g, 0.041 mol) and
Pd(PPh3)4 (0.46 g, 0.4 mmol) in THF (40 mL). After the addition
was complete, the mixture was heated at 50 °C for 12 h. The solv-
ents were then removed in vacuo and the residue was extracted
with hexane. Evaporation of the hexane from the extract and distil-
lation of the residue afforded 5.6 g of 4-octyl-5-trimethylsilyl-2,2Ј-
2-Bromo-3-octylthiophene: N-Bromosuccinimide (NBS) (5.34 g,
0.03 mol) was added to a solution of 3-octylthiophene (5.89 g,
0.03 mol) in CHCl3 (30 mL). The resulting yellow solution was
stirred at room temp. for 4 h. It was then refluxed for 4 h, allowed
to cool to room temp., and diluted with pentane (50 mL). The mix-
ture was filtered and the filtrate was concentrated in vacuo. The
yellow residue was distilled to give 7.4 g (90%) of 2-bromo-3-octyl-
1
bi(thiophene) (39%); b.p. 150 °C (0.3 Torr). Ϫ H NMR (CDCl3):
δ ϭ 0.38 (s, 9 H, SiMe3), 0.92 (t, 3 H, CH3), 1.32 (m, 10 H, 5 CH2),
1.62 (m, 2 H, β-CH2), 2.65 (t, 2 H, α-CH2), 7.01 (q, 1 H, 4Ј-H,
J4Ј3Ј ϭ 4.98 Hz, J4Ј5Ј ϭ 3.68 Hz), 7.14 (s, 1 H, 3-H), 7.18 (q, 1 H,
1
thiophene; b.p. 123 °C (1.1 Torr). Ϫ H NMR (CDCl3): δ ϭ 0.90
(t, 3 H, CH3), 1.30 (m, 10 H, 5 CH2), 1.59 (m, 2 H, β-CH2), 2.58
(t, 2 H, α-CH2), 2 aromatic H (νB ϭ 7.18, νA ϭ 6.80, J ϭ 5.59 Hz).
5Ј-H, J5Ј4Ј ϭ 3.68 Hz, J5Ј3Ј ϭ 1.16 Hz), 7.20 (q, 1 H, 3Ј-H, J3Ј4Ј
ϭ
Ϫ
13C NMR (CDCl3): δ ϭ 14.1 (CH3, alkyl), 31.9, 29.7, 29.4, 29.2,
4.98 Hz, J3Ј5Ј ϭ 1.16 Hz). Ϫ 13C NMR (CDCl3): δ ϭ 0.42 (3 CH3,
Me3Si), 14.15 (CH3, alkyl), 31.93, 31.78, 31.54, 29.78, 29.56, 29.31,
22.73 (7 CH2, alkyl), 123.52, 124.14, 127.22, 127.73 (4 CH, C-3, C-
3Ј, C-5Ј), 132.34, 137.67 (2 C, C-2, C-2Ј), 140.95 (C, C-5), 151.25
(C, C-4). Ϫ 29Si NMR (CDCl3): δ ϭ Ϫ8.26 (Me3Si). Ϫ C19H30S2Si
(350.65): calcd. C 65.08, H 8.62, S 18.29; found C 65.16, H 8.50,
S 18.31.
22.7 (7 CH2, alkyl), 108.8 (C, C-2), 125.1 (CH, C-5), 128.2 (CH,
C-4), 142.0 (C, C-3). Ϫ C12H19BrS (275.25): calcd. C 52.36, H 6.90,
S 11.63; found C 52.32, H 6.94, S 11.58.
2-Bromo-3-octyl-5-tributylstannylthiophene (1): A solution of 2-
bromo-3-octylthiophene (8.5 g, 0.03 mol) in THF (30 mL) was co-
oled to Ϫ40 °C, whereupon LDA (2  in THF, 15 mL, 0.03 mol.)
was added dropwise. The resulting mixture was stirred at Ϫ40 °C
4-Octyl-2,2Ј-bi(thiophene): To a solution of 4-octyl-5-trimethylsilyl-
for 30 min. Then, chlorotributylstannane (9.49 mL, 0.035 mol) was 2,2Ј-bi(thiophene) (1.75 g, 5 mmol) in THF (5 mL) was added 10%
slowly added at the same temperature. The mixture was allowed to
warm to room temperature and stirred for 12 h. It was then hydro-
lysed, the organic layer was extracted with diethyl ether, and the
combined ethereal extracts were dried over MgSO4. The solvents
were removed in vacuo and the residue was distilled to give crude
1. The product was further purified by column chromatography on
alumina (eluent: CHCl3) to give 13.4 g of pure 1 (yield 79%); b.p.
aqueous HCl solution (5 mL). The resulting mixture was stirred
vigorously for 1 h at room temp. and then extracted with diethyl
ether. The combined extracts were dried over MgSO4 and then con-
centrated in vacuo; distillation of the residue afforded 1.25 g of 4-
octyl-2,2Ј-bi(thiophene) (90% yield); b.p. 120 °C (0.3 Torr). Ϫ 1H
NMR (CDCl3): δ ϭ 0.90 (t, 3 H, CH3), 1.29 (m, 10 H, 5 CH2),
1.60 (m, 2 H, β-CH2), 2.59 (t, 2 H, α-CH2), 6.80 (d, 1 H, 5-H,
1
165 °C (1.5 ϫ 10Ϫ2 Torr). Ϫ H NMR (CDCl3): δ ϭ 0.91 (t, 9 H,
J53 ϭ 0.99 Hz), 7.01 (q, 1 H, 4Ј-H, J4Ј3Ј ϭ 5.06 Hz, J4Ј5Ј ϭ 3.59 Hz),
3 CH3), 1.09 (t, 3 H, CH3), 1.29 (m, 22 H, 11 CH2), 1.55 (m, 8 H, 7.03 (d, 1 H, 3-H, J3,5 ϭ 0.99 Hz), 7.15 (q, 1 H, 5Ј-H, J5Ј4Ј
ϭ
4 CH2), 2.58 (t, 2 H, α-CH2), 6.83 (t, 1 H, CH, JHϪSn ϭ 11.98 Hz). 3.59 Hz, J5Ј3Ј ϭ 1.13 Hz), 7.19 (q, 1 H, 3Ј-H, J3Ј4Ј ϭ 5.06 Hz,
Ϫ
13C NMR (CDCl3): δ ϭ 11.06 (3 CH3, Bu3Sn), 13.64, 26.94,
28.91 (9 CH2, Bu3Sn), 14.26 (CH3, alkyl), 31.91, 29.87, 29.34,
J3Ј5Ј ϭ 1.13 Hz). Ϫ 13C NMR (CDCl3): δ ϭ 14.20 (CH3, alkyl),
31.98, 30.59, 30.47, 29.52, 29.41, 29.36, 22.77 (7 CH2, alkyl), 119.01
29.23, 29.12, 27.24, 22.69 (7 CH2, alkyl), 113.20 (C, C-2), 136.56 (CH, C-5), 123.44, 124.08, 125.17, 127.74 (4 CH, C-3, C-3Ј, C-4Ј,
(CH, C-4), 137.00 (C, C-5), 142.92 (C, C-3). Ϫ C24H45BrSSn
(564.27): calcd. C 51.08, H 8.04, S 5.68; found C 51.10, H 8.07,
S 5.66.
C-5Ј), 137.04, 137.88 (2 C, C-2, C-2Ј), 144.08 (C, C-4). Ϫ C16H22S2
(278.47): calcd. C 69.00, H 7.96, S 23.03; found C 69.01, H 7.97,
S 23.01.
1256
Eur. J. Org. Chem. 2001, 1249Ϫ1258

Highly Conjugated Poly(thiophene)s
FULL PAPER
1
5-Bromo-4-octyl-2,2Ј-bi(thiophene): NBS (0.9 g, 5 mmol) was added
to a solution of 4-octyl-2,2Ј-bi(thiophene) (1.4 g, 5 mmol) in CHCl3
(5 mL). The resulting pale-yellow solution was stirred at room
temp. for 4 h. Hexane (20 mL) was then added and the mixture was
filtered. The filtrate was concentrated in vacuo and the yellow oily
residue was chromatographed on a silica column using hexane as
the eluent to furnish 1.43 g of 5-bromo-4-octyl-2,2Ј-bi(thiophene)
in 88% yield. Ϫ H NMR (CDCl3): δ ϭ 7.10 and 7.04 (2 H, thi-
ophene-H), 7.025 (s, 1 H, thiophene-H), 2.77 and 2.54 (m, 2 H,
CH2; HT and HH, respectively), 1.69 and 1.56 (m, 2 H, CH2; HT
and HH, respectively), 1.28 (m, 10 H, 5 CH2), 0.88 (t, 3 H, CH3);
90% HT. Ϫ 13C NMR (CDCl3): δ ϭ 140.6, 134.8, 137.2, 129.6,
126.6, 126.4, 123.9, 31.9, 30.5, 29.6, 29.4, 29.3, 22.7, 14.1. Ϫ IR
(KBr): ν˜ ϭ 3056 cmϪ1, 2953, 2922, 2852, 1495, 1457, 1435, 1374,
(80% yield). Ϫ 1H NMR (CDCl3): δ ϭ 0.91 (t, 3 H, CH3), 1.30 (m, 828, 790. Ϫ UV/Vis: solution λmax ϭ 466 nm, solid λmax ϭ 575 nm.
10 H, 5 CH2), 1.61 (m, 2 H, β-CH2), 2.55 (t, 2 H, α-CH2), 6.87 (s, Mw ϭ 37943, Mn ϭ 34027, Mw/Mn ϭ 1.11. Analysis calcd. for
3-H, CH), 7.00 (q, 1 H, 4Ј-H, J4Ј3Ј ϭ 5.07 Hz, J4Ј5Ј ϭ 3.57 Hz), (C16H20S2)n: C 69.51, H 7.29, S 23.19; found C 68.93, H 7.31, S
7.10 (q, 1 H, 5Ј-H, J5Ј4Ј ϭ 3.57 Hz, J5Ј3Ј ϭ 1.07 Hz), 7.21 (q, 1 H,
3Ј-H, J3Ј4Ј ϭ 5.07 Hz, J3Ј5Ј ϭ 1.07 Hz). Ϫ 13C NMR (CDCl3): δ ϭ
14.16 (CH3, alkyl), 31.92, 29.76, 29.70, 29.62, 29.42, 29.28, 22.72
(7 CH2, alkyl), 107.60 (C, C-5), 123.71, 124.52, 124.54, 127.82 (4
CH, C-3, C-3Ј, C-4Ј, C-5Ј), 136.84 (C, C-2), 142.89 (C, C-4), 142.98
(C, C-2Ј). Ϫ C16H21BrS2 (357.37): calcd. C 53.77, H 5.92, S 17.94;
found C 53.75, H 5.90, S 17.96.
22.85.
Poly[4-octyl-2,2Ј-bi(thiophene)] (PABT2): The nonregioregular
polymer PABT2 was obtained as follows. Over a period of 15 min,
a solution of 4-octyl-2,2Ј-bi(thiophene) (2.78 g, 0.01 mol) in CHCl3
(40 mL) was added to a solution of freshly sublimed FeCl3 (4.8 g,
0.03 mol) in CHCl3 (100 mL) in a Schlenk tube. The blue mixture
was stirred for 3 days at room temp. and then MeOH (200 mL)
was added. Filtration of the reaction mixture allowed the collection
of a solid, which was washed with MeOH for 24 h (soxhlet ex-
tractor). Thereafter, a red powder (1.68 g) was obtained (60%
5-Bromo-4-octyl-5Ј-tributylstannyl-2,2Ј-bi(thiophene) (2): LDA (2 
solution in THF, 1.89 mL, 3.7 mmol) was added dropwise to a so-
lution of 5-bromo-4-octyl-2,2Ј-bi(thiophene) (1.23 g, 3.4 mmol) in
THF (10 mL) at 40 °C. After stirring for 30 min, chlorotributyltin
(1.025 mL, 3.7 mmol) was added and the mixture was allowed to
warm to room temp. and stirred for 12 h. The solvent was then
evaporated and the residue was extracted with hexane. After evap-
oration of the hexane from the extract, the oily residue was purified
by column chromatography on a short alumina column using hex-
ane and CHCl3 as the eluents to furnish 1.98 g of 5-bromo-4-octyl-
5Ј-tributylstannyl-2,2Ј-bi(thiophene) 2 (90% yield). Ϫ 1H NMR
(CDCl3): δ ϭ 0.92 (t, 9 H, 3 CH3), 1.13 (t, 3 H, CH3), 1.31 (m, 22
1
yield). Ϫ H NMR (CDCl3): δ ϭ 7.10 and 7.07 (2 H, thiophene-
H), 7.025 (s, 1 H, thiophene-H), 2.77 and 2.54 (m, 2 H, CH2; HT
and HH, respectively), 1.69 and 1.56 (m, 2 H, CH2; HT and HH,
respectively), 1.28 (m, 10 H, 5 CH2), 0.88 (t, 3 H, CH3); 56% HT.
Ϫ UV/Vis: solution λmax ϭ 450 nm, solid λmax ϭ 596 nm. Mw
25326, Mn ϭ 14898, Mw/Mn ϭ 1.70. Analysis calcd. C 69.51, H
ϭ
7.29, S 23.19; found C 69.36, H 7.37, S 23.08.
H, 11 CH2), 1.60 (m, 8 H, 4 CH2), 2.54 (t, 2 H, α-CH2), 6.87 (s, 1 Acknowledgments
H, CH), 7.05 and 7.22 (J ϭ 3.38 Hz). Ϫ 13C NMR (CDCl3): δ ϭ
We are grateful to J.-P. Fluxench for help with the preparation of
some figures in the manuscript.
10.91 (3 CH3, Bu3Sn), 13.69, 27.28, 28.97 (9 CH2, Bu3Sn), 14.30
(CH3, alkyl), 31.93, 29.70, 29.62, 29.43, 29.28, 27.28, 22.72 (7 CH2,
alkyl), 107.23 (C, C-5), 124.21 (CH, C-3), 124.89 (CH, C-3Ј, 2 satel-
lites J ϭ 17.16 Hz) , 136.09 (CH, C-4Ј, 2 satellites J ϭ 10.87 Hz) ,
136.91, 137.11 (2 C, C-2, C-2Ј), 142.16 (C, C-5Ј), 142.79 (C, C-4).
Ϫ C28H47BrS2Sn (646.39): calcd. C 52.02, H 7.33, S 9.92; found C
52.04, H 7.37, S 9.90.
[1]
T. Skotheim, Handbook of Conducting Polymers, Marcel
Dekker, New York, 1986.
[2]
T. Skotheim, J. Reynolds, R. Elsenbaumer, Handbook of Con-
ducting Polymers, Marcel Dekker, New York, 1998.
[3]
H. S. Nalwa, Handbook of Organic Conductive Molecules and
Polymers, J. Wiley & Sons, New York, 1996.
[4]
Poly(3-octylthiophene)s: Palladium-catalysed polycondensation re-
actions of 1 were performed according to the same general proced-
ure. The results are given in Table 1. The preparation of PAT1 is
given as an example.
J. Roncali, Chem. Rev. 1992, 92, 711Ϫ738, and references
therein.
[5]
R. D. McCullough, Adv. Mater. 1998, 10, 93Ϫ116, and refer-
ences therein.
[6]
G. Schopf, A. Kossmehl, Adv. Poly. Sci. 1997, 129, 1Ϫ166.
J. Roncali, Chem. Rev. 1997, 97, 173Ϫ205.
[7]
A Schlenk tube was charged with Pd2(dba)3(CHCl3) (10.3 mg,
0.01 mmol) and PPh3 (21 mg, 0.08 mmol) and a 1:1 mixture of
THF and DMF (10 mL). After stirring at room temperature for
15 min, 2-bromo-3-octyl-5-tributylstannylthiophene (1) (0.564 g,
1 mmol) was added. The resulting mixture was stirred at 80 °C for
3 days. After cooling to room temperature, the addition of acetone
led to the precipitation of the polymer as a deep-red powder. After
filtration and washing, 0.17 g (90% yield) of PAT1 was isolated. Ϫ
1H NMR (CDCl3): δ ϭ 6.98 (s, 1 H, thiophene-H), 2.80 (t, 2 H,
CH2), 1.72 (m, 2 H, CH2), 1.28 (m, 10 H, 5 CH2), 0.88 (t, 3 H,
CH3). Ϫ 13C NMR (CDCl3): δ ϭ 139.9, 133.7, 130.5, 128.6, 31.9,
[8]
T. Yamamoto, K. Sanechika, A. Yamamoto, J. Polym. Sci.,
Polym. Lett. Ed. 1980, 18, 19Ϫ24.
[9]
J. W. P. Lin, L. P. Dudck, J. Polym. Sci., Polym. Lett. Ed. 1980,
18, 2869Ϫ2873.
[10]
G. Tourillon, F. Garnier, J. Electroanal. Chem. 1982, 135,
173Ϫ205.
M. Kobayashi, J. Chen, T.-C. Chung, F. Moraes, A. J. Heeger,
F. Wudl, Synth. Met. 1984, 9, 77Ϫ86.
K. Yoshino, S. Hayashi, R. Sugimoto, Jpn. J. Appl. Phys. 1984,
23, 899Ϫ900.
R. L. Elsenbaumer, K-Y. Jen, R. Oboodi, Synth. Met. 1986,
15, 169Ϫ174.
G. G. Miller, R. L. Elsenbaumer, J. Chem. Soc., Chem. Com-
mun. 1986, 1346Ϫ1347.
R. Sugimoto, S. Takeda, H. B. Gu, K. Yoshino, Chem. Express
1986, 1, 635Ϫ638.
M. Sato, S. Tanaka, K. Kaeriyama, J. Chem. Soc., Chem. Com-
mun. 1986, 873Ϫ874.
[11]
[12]
[13]
30.5, 29.6, 29.4, 29.3, 22.7, 14.1. Ϫ IR (KBr): ν˜ ϭ 3056 cmϪ1
,
[14]
2953, 2852, 1510, 1461, 1450, 1374, 824. Ϫ UV/Vis: solution λmax ϭ
448 nm, solid λmax ϭ 515 nm (555 nm, 602 nm). Ϫ Mw ϭ 210912,
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