Synthesis and characterization of novel styryl-substituted oligothienylenevinylenes

Article abstract of DOI:10.1016/j.tet.2005.12.017

A number of 3-monosubstituted bis(thienylvinyl)thiophenes, suitable for the preparation of electronically-variable poly(thienylenevinylene)s have been synthesized for the first time. These materials have been characterized by both NMR spectroscopy and mas

Full text of DOI:10.1016/j.tet.2005.12.017

Tetrahedron 62 (2006) 2190–2199
Synthesis and characterization of novel
styryl-substituted oligothienylenevinylenes
*
Pawel Wagner, Amy M. Ballantyne, Kenneth W. Jolley and David L. Officer
Nanomaterials Research Centre and MacDiarmid Institute for Advanced Materials and Nanotechnology, Massey University,
Private Bag 11 222 Palmerston North, New Zealand
Received 11 October 2005; revised 15 November 2005; accepted 9 December 2005
Available online 10 January 2006
Abstract—A number of 3-monosubstituted bis(thienylvinyl)thiophenes, suitable for the preparation of electronically-variable
poly(thienylenevinylene)s have been synthesized for the first time. These materials have been characterized by both NMR spectroscopy
and mass spectrometry, and a single crystal X-ray structure analysis of (E,E)-3-(5,5-dimethyl[1,3]dioxin-2-yl)-2,5-bis(2-thien-
2-ylvinyl)thiophene has shown that the planarity of the terthienylenevinylene chain is maintained on substitution at the 3 position of
the central thiophene ring. UV/visible spectroscopy measurements are reported and cyclic voltammetric measurements show that, with the
exception of (E,E,E)-2,5-bis(2-thien-2-ylvinyl)-3-(2-(4-dimethylaminophenyl)vinyl)-thiophene, electroactive films are produced on
electrochemical oxidation of the monomers.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
used in the fabrication of LEDs operating in the infrared.
Furthermore, the increased electron affinity associated with
a low-lying LUMO level allows for the fabrication of LEDs
with stable metal electrodes.9
Since their discovery in 1977,1,2 conjugated polymers and
oligomers have been extensively investigated for use in
applications such as solar cells, actuators, light emitting
diodes and non-linear optical materials.3 Prominent among
the conjugated materials studied to date are the oligo- and
polythiophenes. These materials have good chemical
stability in both their oxidized and reduced states, and a
wide variety of functionality can be readily built onto the
monomers whether thiophene, bithiophene, or terthio-
phene.4–10
Another way in which the electronic properties of thiophene
oligomers and polymers may be tuned is to introduce
functionality to the polymer chain, typically in the form of
aromatic substituents. Thus, poly(3-arylthiophenes) have
improved doping capacity and cyclability compared with
polythiophene,21,22 and fusing benzene to thiophene leads to
poly(isothianaphthene), the prototypical small band gap
polymer.23 In contrast to the planar-fused benzene ring of
the isothianaphtene, the 3-aryl substituents are twisted out
of the plane of the polymer backbone, reducing their
electronic impact as well as disrupting the polymer
interchain interactions. The styryl group is an alternative
and readily accessible aromatic functionality, which should
not have these disadvantages and may enhance a planar
morphology. Attempts to polymerise styrylthiophenes,
however, have not been so successful. Electrochemical
homopolymerization of 3-styrylthiophene resulted in a
nonconductive material, presumably through side-chain
polymerization, and other styryl derivatives showed similar
behaviour.24 However, electrically conductive polymers
have been obtained by copolymerisation of styryl-sub-
stituted thiophenes with 3-methylthiophene,25 and an
improvement in the photoconductivity of polythiophene
was accomplished on copolymerisation of thiophene and 3-
(4-nitrostyryl)thiophene.26 Copolymers of bithiophene and
para-substituted (E)-3-styrylthiophenes have also been
The introduction of vinylene bridges between thiophene
moieties improves the electronic properties of the resulting
thienylenevinylene polymers11–16 by decreasing the aroma-
ticity and enhancing both the planarity17 and the effective
conjugation length.15,18,19 However, the introduction of
more that one vinylene bridge leads to a decrease in
chemical stability with no significant improvement in the
electronic properties,20 as does the introducion of an
acetylene bridge.14 The HOMO–LUMO gap in thienylene-
vinylene polymers decrease with increasing number of
carbons in the conjugated chain and large red shifts in lmax
are observed.18 This gives rise to the possible fabrication of
conjugated polymers that are transparent in the visible
region of the electromagnetic spectrum and which might be
Keywords: Oligothiophenes; Thienylenevinylenes; Conjugated polymers.
*
Corresponding author. Tel.: C64 6 350 5799x3525; fax: C64 6 350
5612; e-mail: p.wagner@massey.ac.nz
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.12.017

P. Wagner et al. / Tetrahedron 62 (2006) 2190–2199
2191
shown to produce photovoltaic responses in photoelec-
trochemical cells.27 Whilst these copolymerizations
undoubtedly lead to improvement in desirable polymer
properties, their irregular and random structure makes it
difficult to deconvolute the role of the substituent in these
improvements.
knowledge, no examples of 3-vinyl substituted bis(thienyl-
vinyl)thiophenes have been reported to date. The facile
synthesis of thienylenevinylene-3-carboxyaldehyde 5
reported here potentially provides access to a wide variety
of other bis(thienylvinyl)thiophene substituents.
An alternative approach to the formation of regioregular
styryl-functionalised oligo- and polythiophenes is to
polymerize styryl substituted terthiophene monomers and
towards this end we have reported the syntheses of a range
of terthiophenes functionalized at the 30-position with styryl
moieties.4,5,28–31 We have demonstrated that the styryl
functionality can control oligomer regioregularity and
provides advantages in some applications. However,
styrylterthiophenes largely form dimers on oxidative
polymerization as a result of ‘polaron trapping’.6 Given
the decreased aromaticity in thienylenevinylene polymers,17
this effect may not be so pronounced in styrylthienylene-
vinylenes and consequently polymers rather than dimers
may be produced.
2. Results and discussion
2.1. Synthesis
Several methods have been used to syntheses oligothienyl-
enevinylenes including the McMurry reaction,18,32–34
Wittig condensation,33,35,36 Wittig–Horner conden-
sation,18,19,37–39 and others11,12,16,40–42 Of these, the Wittig
condensation is economic and straightforward and allows
the ready introduction of a wide variety of donor/acceptor-
functionalized aromatic substituents.
The precursor to the bis(thienylvinyl)thiophene backbone,
protected trialdehyde 3 (Scheme 1), was synthesised in 80%
yield, by lithiation of the dibromo derivative 2 using a slight
excess of n-butyl lithium, followed by DMF formylation.
No monosubstituted product was observed and increasing
the lithiation time above 30 min did not improve the
reaction yield. The styryl functionality was introduced in
an analogous manner to that used for terthiophenes,5 with
With the eventual aim of producing conjugated styryl-
substituted oligo(thienylenevinylene)s we describe in this
paper the synthesis of six novel (E,E,E)-30-styrylbis(thienyl-
vinyl)thiophenes and report on their spectral and electro-
chemical properties. It should be noted that to the best of our
Scheme 1. (i) 2,2-Dimethyl-1,3-propanediol, PTSA, toluene, reflux, quantitative; (ii) n-BuLi, DMF, THF, K78 8C, 82%; (iii) thiophen-
2-ylmethyltriphenylphosphonium bromide, DBU, THF, reflux, 45%; (iv) TFAA, dichloromethane, rt, 83%; (v) phosphonium salt, DBU, THF, reflux,
23–73%; (vi) 1,3-indandione, piperidine, dichloromethane, rt, 53%.

2192
P. Wagner et al. / Tetrahedron 62 (2006) 2190–2199
Scheme 2. (i) Benzyltriphenylphosphonium chloride, THF, DBU, reflux, 85%; (ii) K78 8C, n-BuLi, THF, DMF, 80%; (iii) I2 3 equiv, dichloromethane, rt,
7 days, 74%; (iv) thiophen-2-ylmethyltriphenylphosphonium bromide, DBU, THF, reflux, 62%.
the key intermediate being aldehyde 5. A Wittig conden-
sation of 3 with thiophen-2-ylmethyltriphenylphosphonium
bromide gave 4 as a pure E,E isomer. Increasing the reaction
time decreased the product yield significantly. The products
of monodecarbonylation of the thiophene dicarbaldehyde
derivatives, observed previously in the presence of a strong
base,20 were not detected here. Deprotection of 4 by
trifluoroacetic acid in dichloromethane gave 5 in high yield
together with some traces of polymeric side products.
approach utilised for 6a was investigated as an alternative
pathway for the synthesis of 6b (Scheme 3). For these
electron donating materials, the styryl functionality was
introduced using diiodothiophene phosphonate 10, pre-
viously prepared for the first time in our laboratory.43 This
compound was condensed with the appropriate aldehyde,
under Horner–Emmons conditions, to give styryl derivative
11 as the E isomer with only minor traces of the Z isomer.
Treatment of 11 with n-butyl lithium and DMF gave the
dialdehyde 12 in high yield. Double Wittig condensation of
12 with thiophen-2-ylmethyltriphenylphosphonium
bromide gave 6b in high yield as the pure E,E,E isomer.
The yield by this route, after four steps, is 40%, which is
significantly better than that used in Scheme 1 (21%).
However, this approach is not suitable for compounds that
contain groups sensitive to n-butyl lithium.
The Wittig condensations between aldehyde 5 and the
appropriate phosphonium salts were carried out in boiling
THF with DBU as base to give the corresponding 3-styryl
derivatives 6a–e. While 6b–e were obtained as pure E
isomers, the phenyl derivative 6a was obtained as an
inseparable mixture of 1:1 E/Z isomers, which suggests
that the Z-isomer of an unsubstituted styryl derivative is more
stable than one with an electron withdrawing or donating
group. Compound 7 was synthesized, in high yield, by a
Knoevenagel condensation of aldehyde 5 with an equimolar
amount of 1,3-indandione in THF with piperidine as the base.
Since it proved impossible to separate the E and Z isomers
of 6a an alternative, but less general, synthetic path was
devised (Scheme 2). The styryl functionality was first
introduced through a condensation of aldehyde 1 with
benzyltriphenylphosphonium chloride to give 8 (85%) as an
inseparable E/Z 1:1 mixture. The conversion of 8 to an
isomeric mixture of the dialdehyde E/Z 9 was readily
achieved as described for 3 above. Isomerization of E/Z 9
was succesfully carried out in dichloromethane at room
temperature using iodine. After a reaction time of 7 days
less than 10% of the Z isomer was present, and this was
readily removed by chromatography to give pure E-9. This
material, in a Wittig reaction with thiophen-2-ylmethyl-
triphenylphosphonium bromide, gave 6a as the pure E,E,E
isomer.
Scheme 3. (i) 4-Methoxybenzaldehyde, t-BuOK, THF, rt, 76%; (ii) n-BuLi,
DMF, THF, K78 8C, 72%; (iii) thiophen-2-ylmethyltriphenylphosphonium
bromide, DBU, THF, reflux, 82%.
The yields of compounds 6b,c, that is, those containing
electron releasing groups, is only average to low, so the

P. Wagner et al. / Tetrahedron 62 (2006) 2190–2199
2193
2.2. NMR spectroscopy
2.3. Electronic absorption spectra
Analysis of the target compounds by NMR spectroscopy
reveals signals that are common to all compounds.
Molecules 6b–e all contain para-subs0tituted aromatic
rings, that give rise to characteristic AA BB0 or AA0XX0
spectra, according to the magnitude of the chemical shift
separation between the two types of protons. In cyano
derivative 6d, for example, this is only 0.07 ppm, whereas in
nitro derivative 6e it is 0.58 ppm as a result of the strong
deshielding effect of the nitro group on the adjacent protons.
The vinylic proton resonances appear as two doublets with a
coupling of approximately 16 Hz, typical of an E
configuration. The nature of the styryl substituent has little,
if any, effect on the chemical shifts of the 2- and 5-vinyl
protons (see Fig. 1) but there are larger variations in the
chemical shifts of the 3-vinyl protons of the styryl groups as
a result of shielding or deshielding effects induced by the
substituent on the benzene ring. The nature of the vinyl
substituent also has little effect on the H4 resonance of the
inner thiophene ring, which appears as a singlet over the
very narrow range of 7.17–7.19. The proton resonances of
the outer thiophene rings exhibit AMX spectra and the
assignments of the H3, H4, and H5 protons of each ring was
achieved with the aid of COSY experiments. This
established a coupling between the H4 proton and the
3-vinyl proton, and a further long range five-bond coupling
between the 3-vinyl proton and the 2-vinyl proton was
identified in compounds 6a, 6d and 6e. These correlations
allow for an unambiguous assignment of the outer thiophene
resonances to specific thiophene rings. It is inte0resting to
note that the chemical shifts of the thiophene H5 and H500
protons are identical in compounds 6a–c, and differ by only
0.02 ppm in compounds 6d and 6e. In the corresponding
terthiophene monomers the chemical shifts in these
positions differ by between 0.11 ppm (RZNMe2) and
0.15 ppm (RZCN).5
The electronic absorption spectra of compounds 6a, 6c, and
6e are shown in Figure 2. The spectra of compounds 6b and
6d are similar in appearance to that of 6a. All spectra are
characterised by an absorption band with a lmax in the range
422 nm (6d) to 436 nm (6c) indicating that, despite the
planarity and therefore increased conjugation of the styryl
group, the nature of the para substituent on the benzene ring
has little effect on the HOMO–LUMO gap in these
compounds. Previous work has shown that the position of
the absorption maximum of alkyl substituted thienylene-
vinylene oligomers is largely determined by the number of
carbon atoms in the conjugated chain,18 with lmax for (E,E)-
2,5-bis(20-thienylvinyl)-3,4-dibutylthiophene (16 carbon
atoms in the conjugated chain) in CH2Cl2 being 423 nm.
It is clear from the above that the molecular orbitals
contributing to this band must be primarily situated along
the thienylenevinylene backbone, as has been observed for
the corresponding terthiophenes.44
6c
6a
1
0.8
6e
0.6
0.4
0.2
0
300
400
500
l
/nm
Figure 2. The normalized absorption spectra of 6a, 6c and 6e in CH2Cl2
solvent.
Vibronic structure is present in all compounds 6a–e, as
previously reported for thienylenevinylene oligo-
mers,18,19,45 although it is much less resolved in 6c. In 6a,
for example, the 0–0 transition is at 452 nm with vibronic
side bands at 428 and 405 nm. The energy difference
between successive maxima is thus 0.15 eV, a value
5"
S
5
S
2
4
3
5'
S
consistent with a C]C stretching mode (w1200 cmK1
)
strongly coupled to the electronic structure.46 The
w0.15 eV separation between excited state vibrational
levels is common to all the styryl-substituted
thienylenevinylenes.
R
Figure 1. Generalized styryl-substituted bis(thienylvinyl)thiophene struc-
ture showing the numbering.
The band to lower wavelengths is due to transitions between
molecular orbitals associated with the styryl substituent as it
is absent in thienylenevinylene oligomers with no styryl
substituent. The variation in lmax for this band is much
greater than that for the high-wavelength band, ranging
from 337 nm for 6a to 379 nm for 6e, consistent with the
expected influence of the electron donating and with-
drawing groups. Vibronic structure is clearly observed in
this band in compounds 6a, 6b, and 6d, and less clearly in
6e. As in the high-wavelength band, the separation between
successive maxima corresponds to 0.15 eV and can be
associated with a C]C stretching mode.
The spectrum of 7 is similar to those of compounds 6a–e.
The main differences are shifts to low fields of the
resonances of both the 3-vinyl proton and the thiophene-
4H proton by 1 and 1.4 ppm, respectively, both as a result of
intramolecular hydrogen bonding between the respective
protons and the closest oxygen of the neighbouring
indandione ring. The 2-vinyl protons undergo a smaller
downfield shift of about 0.2 ppm whilst the chemical shifts
of the 5-vinyl protons are little affected, as are the chemical
shifts of the outer thiophene protons.

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P. Wagner et al. / Tetrahedron 62 (2006) 2190–2199
The spectrum of 7 exhibits two broad bands with lmax
values of 378 and 520 nm. The low wavelength band
has shoulders at 409 and 431 nm with a w0.15 eV
separation between excited state vibrational levels. The
band at 520 nm is most likely the result of intramolecular
charge transfer.47–49
2.5. Cyclic voltammetry
Cyclic voltammograms (CVs) for compounds 6a–e are
similar in appearance and those for 6e are shown in Figure 4.
The oxidation onset potential of 6a (0.56 V) is lower than
that measured for styrylterthiophene (0.74 V on a micro-
electrode), due to the greater stability of the bis(thienyl-
vinyl)thiophene radical cation as a result of the extra
conjugation introduced by the vinyl linkers. Oxidation onset
potentials of 0.56 V are also measured for the compounds
6d, and 6e indicating that the reactivity of the 50 and 500
positions are not significantly affected by electron-with-
drawing substituents at the para-position on the benzene
ring. In contrast, the oxidation onset potential for 6b is lower
at 0.44 V, due to a stabilization of the resulting radical
cation by the electron-donating substituent. Subsequent
cycles show two oxidation peaks, the peak at potentials less
than 0.5 V is the result of oxidation of the deposited
electroactive film, and the cathodic peaks are most likely
due to reduction of the oxidised film back to neutral
material.
2.4. X-ray structure analysis of 3-(5,5-dimethyl[1,3]-
dioxin-2-yl)-2,5-bis(2-thien-2-ylvinyl)
thiophene (4)
Attempts to grow single crystals of the target compounds
were unsuccessful. However, crystals of sufficient quality
for X-ray determination were obtained for compound 4.
The crystal structure of this compound (Fig. 3) illustrates
that the planarity of the conjugated terthienylenevinylene
chain is maintained on introduction of the b-substituent as
observed by Roncali et al.19 in the only comparable
crystal structure of tetra(thienylenevinylene). The dihedral
angles between the S(1) and S(2) rings, the S(2) and S(3)
rings, and the S(1) and S(3) rings are, respectively, 8.1(2),
7.2(2), and 8.5(2)8, and the thiophene rings are perfectly
planar.
(a) 15
0.4
0.2
10
0.0
–0.2
5
–0.5 –0.3 –0.1 0.1 0.3 0.5 0.7
+
Potential / V vs Ag/Ag
0
–5
–10
–0.5
–0.3
–0.1
0.1
0.3
0.5
0.7
+
Potential / V vs Ag/Ag
15
10
5
(b)
0
–5
–10
Figure 3. The crystal structure of 4. Displacement ellipsoids were set at
50% of probability.
–15
–0.5
–0.3
–0.1
0.1
0.3
0.5
0.7
+
Potential / V vs Ag/Ag
For terthiophene ring systems with substituents in the
b-position of the central ring, the rings are far from
coplanar. For example, in the case of 30-phenyl-2,20:50,200-
terthiophene,50 the two outer rings are twisted by K156 and
138.48 with respect to the central thiophene ring. With a
styryl group in the 3-position, the torsion angle between the
outer ring closest to the alkene linker on the central
thiophene ring is K148.68 and the corresponding angle on
the other side of the central thiophene ring is K151.28.5 This
steric interaction that leads to a distortion of the thiophene
rings has also been observed in other 3-substituted
terthiophenes.49 Thus, compared with terthiophene oligo-
mers, the addition of the alkene spacers between the rings
leads to an increase in the p-orbital overlap along the
oligomer backbone.
Figure 4. (a) Potentiodynamic growth of 6e on a Pt microelectrode.
Monomer concentration: 5 mM. Supporting electrolyte: 1:1 DCM–
acetonitrile/0.1 M TBAP. Scan rate: 100 mV sK1. The insert represents
the first three cycles. (b) Post growth cycling of 6e deposited on a Pt micro
electrode. Supporting electrolyte: acetonitrile/0.1 TBAP. Scan rate:
100 mV sK1
.
The growth cyclic voltammogram of 6c is different to that of
the other samples. A much lower oxidation onset potential
of 0.22 V is observed, and four oxidation and four reduction
peaks are produced on the first scan. Subsequent scans show
an increase in oxidation onset potential, and a decreasing
growth in current with each cycle, indicating the deposition
of poorly conducting material. These observations suggest
that processes other than polymerisation through the 50 and

P. Wagner et al. / Tetrahedron 62 (2006) 2190–2199
2195
500 positions are occurring, possibly involving the dimethyl-
amino substituent.51,52
Crystals for X-ray analysis were obtained by slow
evaporation of ethanol. Data were collected on a Siemens
SMART CCD diffractometer at 273 K with graphite-
˚
Post-growth CVs of the electrochemically deposited films
(see Fig. 4b for that of 6e) reveal a considerable variation in
the stability of the depositions. Those produced from 6b and
6e are quite stable, 6d gives rise to a film that exhibits a
gradual decrease in current with increasing cycle number,
and the fall in current is rapid on post cycling of the films
produced from 6a and 6c.
monochromated Mo Ka radiation (l 0.71073 A) using u/
2q scans. The structures were determined by means of direct
methods53 and refined by the full-matrix least squares
technique.54 All hydrogen atoms were obtained from the
electron differential Fourier map and refined using a riding-
˚
model (C–H bonds set to 0.93 A). Crystallographic data
(excluding structure factors) for the structure in this paper
has been deposited with the Cambridge Crystallographic
Data Centre as supplementary publication number CCDC
271152. Copies of the data can be obtained, free of charge,
on application to CCDC, 12 Union Road, Cambridge CB 2
1EZ, UK [fax: C44 1223 336033 or e-mail: deposit@ccdc.
cam.ac.uk].
3. Conclusions
Wittig chemistry provides a convenient and straightforward
method for the synthesis of b-styryl-functionalized bis(thie-
nylvinyl)thiophenes. The electronic absorption spectra of all
the molecules exhibit red shifts compared to those of the
corresponding oligothiophenes as a result of an enhanced
planarity, as confirmed by single crystal X-ray structural
analysis of (E,E)-3-(5,5-dimethyl[1,3]dioxin-2-yl)-2,5-
bis(2-thien-2-ylvinyl)thiophen, and the consequent increase
in the effective conjugation lengths. The lmax values fall in a
narrow range and are similar to those observed in
unsubstituted oligothienylenevinylenes showing that the
nature of the styryl substituent has little effect on the
HOMO–LUMO gap in these compounds. With the
exception of the dimethylamino derivative 6c, electroactive
films are produced on electrochemical oxidation of the
bis(thienylvinyl)thiophene monomers. A full investigation
into the polymerization of these materials is currently
underway.
2,5-Dibromo-3-thiophenylcarbaldehyde (1),5 5,5-dimethyl-2-
(2,5-dibromothiophen-3-yl)[1,3]dioxane (2)5 and thiophen-2-
ylmethyltriphenylphosphonium
bromide,55
were
synthesized according to literature procedures. Other reagents
used in the syntheses were obtained from commercial sources.
4.1.1. 3-(5,5-Dimethyl-[1,3]dioxan-2-yl)thiophene-2,5-
dicarbaldehyde (3). Dibromide 2 (5.10 g, 0.015 mol) was
dissolved in dry THF (75 mL), cooled to K78 8C, and a
solution of 2.5 mol LK1 n-butyl lithium in hexane (14 mL,
0.035 mol) was added dropwise by a syringe. The resulting
mixture was stirred at K78 8C for 30 min before a solution
of dry DMF (6.60 g, 0.09 mol) in THF (10 mL) was added.
The reaction mixture was left to reach room temperature,
stirred for 30 min, and poured into 1 mol LK1 hydrochloric
acid (150 mL) before being extracted twice with diethyl
ether. The organic layer was separated, dried over
magnesium sulphate and evaporated to dryness at 50 8C
under reduced pressure to give a brownish oil. After
purification on silica, using 30% ethyl acetate in hexane
as eluent, a colourless oil was obtained (3.11 g, 82%).
Recrystallization from hexane at K20 8C gave colourless
crystals: mp 69–70 8C; dH (400 MHz, CDCl3) 10.35 (1H, s,
2-CHO), 9.97 (1H, s, 5-CHO), 7.91 (1H, s, ThH4), 5.81 (1H,
s, diox-H2), 3.81 (2H, d, JZ11 Hz, CH2), 3.70 (2H, d, JZ
11 Hz, CH2), 1.29 (3H, s, Me), 0.84 (3H, s, Me); dC
(100.6 MHz, CDCl3) 184.3, 183.3, 147.1, 145.9, 135.4,
97.2, 77.7, 30.2, 23.1, 21.8; m/z (EI) 254 (39, MC), 185 (10),
168 (72), 139 (28), 70 (35), 56 (100), 41 (57), 39 (34%);
HRMS (EI): MC, found 254.06010. C12H14O2S requires
254.0613; nmax (KBr) 3320, 3110, 2960, 2865, 1675, 1665,
1545, 1465, 1380, 1365, 1335, 1310, 1225, 1205, 1150,
4. Experimental
4.1. General
NMR spectra were recorded on a Bruker Avance 400
spectrometer using TMS as the internal standard. In some
cases not all of the carbon resonances were resolved due to
the overlap of peaks. The UV spectra were recorded on a
Shimadzu UV3101PC spectrometer using dichloromethane
as the solvent. The melting points are uncorrected. All new
compounds were determined to be greater than 95% pure by
1H NMR spectroscopy.
Cyclic voltammograms were recorded in air using an
Autolab Potentiostat Galvanostat running Autolab GPES
software. A one compartment, three-electrode glass cell was
used for all measurements. The cell incorporated a platinum
mesh counter electrode, a silver/silver chloride reference
electrode, and the working electrode was a platinum
microelectrode with a 10 mm2 surface area. The scan rate
used was 100 mV sK1 and the scans were started from the
most negative potential. Films were grown using cyclic
voltammetry between the limits of K0.5 and 0.8 V in 5 mM
monomer solutions in 1:1 DCM–acetonitrile/0.1 M TBAP.
Post growth electrochemistry was performed in acetonitrile/
0.1 M TBAP monomer-free solutions. All solutions were
freshly prepared and solutions were degassed by ultra-
sonification immediately prior to measurement.
1110, 1020, 1010 cmK1
.
4.1.2. (E,E)-3-(5,5-Dimethyl[1,3]dioxin-2-yl)-2,5-bis(2-
thien-2-ylvinyl)thiophene (4). Dialdehyde 3 (2.54 g,
0.010 mol) and triphenylthiophen-2-ylmethylphosphonium
bromide (9.67 g, 0.022 mol) were dispersed in dry THF
(75 mL). DBU (7.5 g, 0.05 mol) was added and the resulting
mixture was refluxed under argon for 5 h. The reaction
mixture was poured into 1 mol LK1 hydrochloric acid
(300 mL) before being extracted twice with dichloro-
methane. The organic extracts were dried over magnesium
sulphate and evaporated to dryness at 50 8C under vacuum
to yield a dark-brown oil. Purification on silica, using 30%
ethyl acetate in hexane as eluent, and recrystallization from

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P. Wagner et al. / Tetrahedron 62 (2006) 2190–2199
a dichloromethane/methanol mixture gave fine yellow
prisms (1.86 g, 45%): mp 172–174 8C; dH (400 MHz,
CDCl3) 7.27 (d, 1H, JZ15.7 Hz, 5-vinyl-H), 7.19 (1H, dd,
JZ5.2, 1.0 Hz, Th-H50), 7.17 (1H, dd, JZ5.2, 1.0 Hz,
Th-H500), 7.08 (1H, s, Th-H4), 7.04 (1H, dd, JZ3.6, 1.0 Hz,
Th-H30), 7.03 (1H, dd, JZ3.6, 1.0 Hz, Th-H30), 7.02 (1H, d,
JZ15.7 Hz, 2-vinyl-H), 7.00 (1H, d, JZ15.8 Hz, 5-vinyl-
H), 6.99 (1H, dd, JZ5.2, 3.6 Hz, Th-H40), 6.98 (1H, dd. JZ
5.2, 3.6 Hz, Th-H400), 6.93 (1H, d, JZ15.8 Hz, 5-vinyl-H),
5.52 (1H, s, diox-H2), 7.79–3.77 (2H, m, CH2), 3.67–3.64
(2H, m, CH2), 1.35 (3H, s, CH3), 0.81 (3H, s, CH3); dC
(100.6 MHz, CDCl3) 142.5, 142.3, 139.8, 138.3, 137.0,
127.7, 126.8, 126.5, 126.2, 124.7, 124.5, 122.6, 121.8,
121.2, 119.5, 97.8, 77.7, 30.2, 23.2, 21.9; m/z (EI) 414 (100,
MC), 344 (15), 328 (24), 317 (14), 266 (12), 97 (10%);
HRMS (EI): MC found 414.0780. C22H22O2S3 requires
414.0782; nmax (KBr) 3105, 3015, 2950, 2860, 1461, 1430,
1400, 1375, 1354, 1330, 1310, 1280, 1235, 1210, 1155,
4.2.1. (E,E,E)-2,5-Bis(2-thien-2-ylvinyl)-3-(2-(4-methoxy-
phenyl)vinyl)thiophene (6b). Recrystallization from
dichloromethane/methanol yielded yellow needles (69%):
mp 171–172 8C; dH (400 MHz, CDCl3) 7.46 (2H, d, JZ
8.6 Hz, Ar-H), 7.24 (1H, d, JZ16.1 Hz, 2-vinyl-H), 7.21
(2H, dd, JZ5.5, 1.2 Hz, Th-H50, H500), 7.19 (1H, s, Th-H4),
7.09 (1H, d, JZ16.0 Hz, 3-vinyl-H), 7.06 (2H, dd, JZ5.5,
3.6 Hz, Th-H30, H300), 7.05 (1H, d, JZ16.0 Hz, 5-vinyl-
H),7.03 (1H, d, JZ16.1 Hz, 2-vinyl-H), 7.02 (1H, d, JZ
16.0 Hz, 5-vinyl-H), 7.01 (2H, dd, JZ3.6, 1.2 Hz, Th-H40,
H400), 6.92 (2H, d, JZ8.6 Hz, Ar-H), 6.84 (1H, d, JZ
16.0 Hz, 3-vinyl-H), 3.84 (3H, s, CH3); dC (100.6 MHz,
CDCl3) 142.7, 142.2, 139.9, 137.8, 136.3, 130.0, 129.5,
127.8, 127.7, 127.6, 126.4, 126.3, 125.0, 124.7, 124.6,
122.4, 121.9, 121.2, 119.1, 118.2, 55.3; m/z (EI) 432 (100,
MC), 335 (18), 311 (11), 121 (10%); HRMS (EI): MC
found 432.0673. C25H20OS3 requires 432.0676; lmax nm (3)
343 (48,500), 357 (49,500), 406 sh (28,500), 429 (33,000),
453 (24,000).
1105, 1040, 1015, 1000 cmK1
.
4.2.2. (E,E,E)-2,5-Bis(2-thien-2-ylvinyl)-3-(2-(4-dimethyl-
aminophenyl)vinyl)thiophene (6c). Recrystallization
from dichloromethane/methanol yielded fragile orange
plates (23%): mp 205–206 8C; dH (400 MHz, CDCl3) 7.42
(2H, d, JZ8.8 Hz, Ar-H); 7.25 (1H, d, JZ15.6 Hz, 2-vinyl-
H), 7.19 (2H, dd, JZ5.5, 1.2 Hz, Th-H50, H500)0, 7.18 (1H, s,
Th-H4), 7.05 (2H, dd, JZ5.5, 3.6 Hz, Th-H3 , H300), 7.04
(1H, d, JZ16.0 Hz, 3-vinyl-H), 7.02–6.98 (5H, m, Th-H40,
H400, 2!5-vinyl-H, 2-vinyl-H), 6.88 (1H, d, JZ15.6 Hz,
3-vinyl-H), 6.73 (2H, d, JZ8.8 Hz, Ar-H), 2.99 (6H, s,
NCH3); dC (100.6 MHz, CDCl3) 150.3, 142.7, 142.4, 139.8,
138.5, 135.4, 130.6, 127.8, 127.7, 127.6, 126.3, 126.0,
125.1, 124.6, 124.4, 122.2, 121.4, 121.3, 119.4, 116.1,
112.5, 40.4; m/z (EI) 445 (100, MC), 348 (19), 222 (10), 134
(52), 105 (24), 91 (33), 69 (22), 57 (31), 49 (44%); HRMS
(EI): MC found 445.0994. C26H23NS3 requires 445.0993;
lmax nm (3) 378 (60,000), 436 sh (33,500).
4.1.3. (E,E)-2,5-Bis(2-thien-2-ylvinyl)thiophene-3-carb-
aldehyde (5). Compound 4 (1.45 g, 3.5 mmol) was
dissolved in dichloromethane (15 mL), then trifluoroacetic
acid (15 mL) and water (5 mL) were added. The resulting
mixture was stirred at room temperature for 1.5 h, placed
into the separating funnel and the organic layer collected,
washed with water, then with a saturated solution of sodium
bicarbonate and dried over magnesium sulphate. The
solvent was removed under vacuum at 50 8C and the residue
was purified on silica using pure dichloromethane as eluent.
The red-orange solid on recrystallization from a dichloro-
methane–methanol mixture gave fine red needles (0.95 g,
83%): mp 115–116 8C; dH (400 MHz, CDCl3) 10.08 (1H, s,
CHO), 7.70 (1H, d, JZ16.0 Hz, 2-vinyl-H), 7.31 (1H, dd,
JZ5.0, 1.2 Hz, Th-H50), 7.26 (1H, s, Th-H4), 7.25 (1H, d,
JZ16.0 Hz, 2-vinyl-H), 7.23 (1H, dd, JZ5.0, 1.2 Hz, Th-
H500), 7.17 (1H, dd, JZ030 .6, 1.2 Hz, Th-H30), 7.07 (1H, dd,
JZ3.6, 1.2 Hz, Th-H3 ), 7.04 (1H, dd, JZ5.0, 3.6 Hz,
Th-H40), 7.01 (1H, dd, JZ5.0, 3.6 Hz, Th-H400) 7.00 (1H, d,
JZ16.0 Hz, 5-vinyl-H), 6.93 (1H, d, JZ16 Hz, 5-vinyl-H);
dC (100.6 MHz, CDCl3) 184.0, 149.8, 141.6, 141.5, 140.0,
136.9, 128.3, 128.0, 127.8, 127.0, 126.9, 126.6, 126.5,
125.3, 123.6, 120.2, 117.8; m/z (EI) 328 (100, MC), 295
(20), 266 (22), 134 (10), 156 (10%); HRMS (EI): MC found
328.0047. C17H12OS3 requires 328.0050; nmax (KBr) 3080,
1660, 1600, 1530, 1505, 1460, 1425, 1385, 1350, 1280,
4.2.3. (E,E,E)-2,5-Bis(2-thien-2-ylvinyl)-3-(2-(4-cyano-
phenyl)vinyl)thiophene (6d). Recrystallization from
dichloromethane/methanol yielded yellow prisms (73%):
mp 172–173 8C; dH (400 MHz, CDCl3) 7.63 (2H, d, JZ
8.4 Hz, Ar-H), 7.56 (2H, d, JZ8.4 Hz, Ar-H), 7.29 (1H, 0d,
JZ16.1 Hz, 3-vinyl-H), 7.24 (1H, d, JZ5.2 Hz, Th-H5 ),
7.22 (1H, d, JZ5.2 Hz, Th-H500), 7.19 (1H, d, JZ15.3 Hz,
2-vinyl-H), 7.17 (1H, s, Th-H4), 7.09 (1H, d, JZ3.6 Hz,
Th-H30), 7.08 (1H, d, JZ15.3 Hz, 2-vinyl-H), 7.06 (1H, 0d,
JZ3.6 Hz, Th-H300), 7.03 (1H, dd, JZ5.2, 3.6 Hz, Th-H4 ),
7.02 (1H, d, JZ16.0 Hz, 5-vinyl-H), 7.01 (1H, dd, JZ5.2,
3.6 Hz, Th-H400), 6.96 (1H, d, JZ16.0 Hz, 5-vinyl-H), 6.89
(1H, d, JZ16.1 Hz, 3-vinyl-H); dC (100.6 MHz, CDCl3)
142.2, 142.0, 141.8, 140.4, 138.9, 136.3, 132.5, 127.9,
127.8, 127.7, 126.9, 126.8, 126.7, 125.1, 125.0, 124.5,
123.5, 123.1, 122.9, 120.8, 118.4, 110.6; m/z (EI) 247 (100,
MC), 330 (18), 97 (15), 91 (12%); HRMS (EI): MC found
427.0526. C25H17NS3 requires 427.0523; lmax nm (3) 346
(49,500), 361 (49,500), 427 (39,000), 451 sh (32,000).
1195, 1145, 1045 cmK1
.
4.2. General procedure for preparation of styryl
derivatives 6b–e
Aldehyde 5 (104 mg, 0.32 mmol) and 1.2 equiv of
phosphonium salt were dispersed in THF (10 mL). To the
suspension DBU (1.0 g, 6.7 mmol) was added and the
mixture refluxed overnight under argon. The reaction
mixture was then diluted with dichloromethane and washed
with 1 mol LK1 hydrochloric acid. The organic layer was
separated, dried over magnesium sulphate and the solvents
were removed under vacuum at 50 8C. The residue was
purified on silica using pure dichloromethane as an eluent
and recrystallized.
4.2.4. (E,E,E)-2,5-Bis(2-thien-2-ylvinyl)-3-(2-(4-nitro-
phenyl)vinyl)thiophene (6e). Recrystallization from
dichloromethane/methanol yielded red plates and blocks
(70%): mp 185–186 8C; dH (400 MHz, CDCl3) 8.22 (2H, m,
Ar-H), 7.61 (2H, m, Ar-H), 7.64 (1H, d, JZ16.1 Hz,

P. Wagner et al. / Tetrahedron 62 (2006) 2190–2199
2197
3-vinyl-H), 7.25 (1H, d, JZ4.8 Hz, Th-H50), 7.23 (1H, d,
JZ4.8 Hz, Th-H500), 7.20 (1H, d, JZ16.0 Hz, 2-vinyl-H),
7.18 (1H, s, Th-H4), 7.10 (1H, d, JZ3.6 Hz, Th-H40), 7.07
(1H, d, JZ16.0 Hz, 2-vinyl-H), 7.06 (1H, d, JZ3.6 Hz,
Th-H300), 7.02 (1H, d, JZ15.6 Hz, 5-vinyl-H), 7.02 (1H, dd,
JZ4.8, 3.6 Hz, Th-40), 7.01 (1H, dd, JZ4.8, 3.6 Hz, Th-400),
6.96 (1H, d, JZ15.6 Hz, 5-vinyl-H), 6.94 (1H, d, JZ
16.1 Hz, 3-vinyl-H); dC (100.6 MHz, CDCl3) 146.7, 143.8,
142.2, 142.0, 140.4, 139.4, 136.2, 127.9, 127.8, 127.1,
127.0, 126.7, 125.2, 125.0, 124.4, 124.3, 124.2, 123.3,
123.0, 120.8, 118.3; m/z (EI) 447 (100, MC), 445 (22), 417
(48), 350 (13), 106 (27), 105 (14), 97 (12), 91 (18), 55 (17),
43 (19%); HRMS (EI): MC found 447.0414. C24H17NO2S3
requires 447.0421; lmax nm (3) 335 (23,500), 379 (39,500),
422 (39,500), 446 sh (32,000).
128.2, 127.8, 127.4, 126.6, 121.6, 120.0, 111.9, 111.6,
110.5, 110.1; m/z (EI) 346 (6, MC), 344 (12), 342 (7), 184
(100), 139 (11), 92 (12%); HRMS (EI): MC found
341.8710. C12H8Br2S requires 341.8713.
4.2.7. (E)-3-(2-Phenylvinyl)thiophene-2,5-dicarbaldehyde
(9). Compound 8 (1.65 g, 4.8 mmol) was dissolved in dry
THF (30 mL), cooled to K78 8C and a 2.5 mol LK1 solution
of n-butyl lithium in hexane (3.8 mL, 9.5 mmol) was added
dropwise with a syringe. The resulting mixture was stirred at
K78 8C for 15 min then dry DMF (6.6 g, 20 mmol)
dissolved in THF (5 mL) was added. The reaction mixture
was allowed to reach room temperature for 30 min before
being poured into 150 mL of 1 mol LK1 hydrochloric acid
and extracted twice with dichloromethane. The organic
layers were dried over magnesium sulphate and evaporated
to dryness under reduced pressure at 50 8C to yield a dark
oil. After purification on silica using dichloromethane as
eluent yellow crystals of E/Z 9 were obtained (0.92 g, 80%).
Isomerization procedure. Compound E/Z 9 (1.69 g,
7 mmol) was dissolved in dichloromethane (50 mL) and
iodine (5.33 g, 21 mmol) was added. The resulting mixture
was stirred at room temperature for 7 days then washed with
saturated solution of sodium thiosulphate and water. The
organic layer was dried over magnesium sulphate, evapo-
rated to dryness and the residue was purified on silica using
dichloromethane as eluent. Recrystallization from an
ethanol–water mixture yielded thin yellow needles of 9
(1.25 g, 74%): mp 133–134 8C; dH (400 MHz, CDCl3) 10.29
(1H, s, 2-CHO), 10.03 (1H, s, 5-CHO), 8.09 (1H, s, Th-H4),
7.69 (1H, d, JZ16.2 Hz, vinyl-H), 7.57–7.55 (2H, m,
Ph-H), 7.44–7.40 (3H, m, Ph-H), 7.24 (1H, d, JZ16.2 Hz,
vinyl-H); dC (100.6 MHz, CDCl3) 183.4, 182.8, 147.9,
146.1, 141.8, 135.9, 135.7, 133.5, 129.3, 129.0, 127.1,
118.4; m/z (EI) 242 (100, MC), 213 (22), 185 (62), 184 (37),
165 (11), 152 (20), 141 (16), 92 (10%); HRMS (EI): MC
found 242.0399. C14H10O2S requires 242.0402.
4.2.5. (E,E)-2,5-Bis(2-thien-2-ylvinyl)-3-(1,3-indandion-
2-ylmethylen)thiophene (7). Aldehyde
5 (77 mg,
0.23 mmol) and 1,3-indandione (0.034 g, 0.23 mmol) were
dissolved in dry THF (10 mL) and piperidine (1 mL,
10 mmol) was added. The colour of the reaction mixture
immediately turned to deep red. After stirring overnight at
room temperature the reaction mixture was diluted with
dichloromethane and washed with 1 mol LK1 hydrochloric
acid. The organic layer dried over magnesium sulphate and
the solvents were removed under vacuum at 50 8C. The
residue was purified on silica using pure dichloromethane as
an eluent and recrystallization from dichloromethane/
methanol yielded red irregular crystals (57 mg, 53%): mp
186 8C dec; dH (400 MHz, CDCl3) 8.60 (1H, s, Th-H4),
7.98–7.95 (2H, m, Ar-H), 7.96 (1H, s, 3-vinyl-H), 7.80–7.78
(2H, m, Ar-H), 7.42 (1H, d, JZ15.5 Hz, 2-vinyl-H), 7.32
(1H, d, JZ5.0 Hz, Th-H50), 7.26 (1H, d, JZ15.5 Hz,
2-vinyl-H), 7.22 (1H, d, Th-H500), 7.19 (1H, d, JZ3.6 Hz,
Th-H30), 7.09–7.03 (4H, m, Th-H300, 5-vinyl-H, Th-H40),
7.00 (1H, dd, JZ5.0, 3.6 Hz, Th-H400); dC (100.6 MHz,
CDCl3) 190.7, 189.3, 153.2, 142.6, 142.0, 141.6, 140.0,
139.4, 135.1, 135.0, 133.58, 133.55, 130.5, 128.5, 128.1,
127.7, 126.9, 126.8, 126.7, 126.6, 125.2, 123.3, 123.1,
123.0, 120.9, 117.6; m/z (EI) 456 (11, MC), 307 (24), 289
(12), 155 (26), 154 (100), 137 (57), 136 (67), 120 (12), 107
(24), 89 (22), 77 (23%); HRMS (EI): MC found 456.0313.
C26H16O2S3 requires 456.0313; lmax nm (3) 377 (48,500),
400 sh (40,000), 517 (18,000).
4.2.8. (E,E,E)-2,5-Bis(2-thien-2-ylvinyl)-3-(2-phenyl-
vinyl)thiophene (6a). Compound 9 (1.21 g, 5 mmol) and
thiophen-2-ylmethyltriphenylphosphonium
bromide
(4.83 g, 11 mmol) were dispersed in dry THF (30 mL).
DBU (3.00 g, 19.7 mmol) was added and the mixture was
refluxed under argon overnight. The resulting reaction
mixture was poured into of 1 mol LK1 hydrochloric acid
(100 mL) and extracted twice with dichloromethane. The
organic layers were dried over magnesium sulphate and
evaporated to dryness under reduced pressure at 50 8C. The
residue was purified on silica using 20% ethyl acetate in
hexane as eluent and recrystallized from dichloromethane–
methanol mixture to give irregular yellow-orange blocks
(1.24 g, 62%): mp 156–157 8C; dH (400 MHz, CDCl3) 7.52
(3H, m, Ph-H), 7.37 (1H, d, JZ15.9 Hz, 3-vinyl-H), 7.36
(2H, s, Ph-H), 7.27 (1H, d, JZ15.9 Hz, 3-vinyl-H), 7.29–20
(4H, m, Th-H50, H500, H30, H300), 7.22 (1H, d, JZ16.0 Hz,
2-vinyl-H), 7.20 (1H, d, JZ15.9 Hz, 5-vinyl-H), 7.19 (1H,
s, Th-H4), 7.06 (1H, dd, JZ5.2, 3.6 Hz, Th-H40), 7.02 (1H,
d, JZ16.0 Hz, 2-vinyl-H), 7.00 (11H, dd, JZ5.2, 3.6 Hz,
Th-H400), 6.93 (d, 1H, JZ15.9 Hz, 5-vinyl-H); dC
(100.6 MHz, CDCl3) 142.6, 142.2, 137.4, 127.3, 137.1,
129.9, 128.9, 128.7, 128.3, 127.8, 127.7, 126.5, 125.0,
124.7, 124.6, 122.5, 122.2, 121.1, 120.2, 118.9; m/z (EI) 402
(100, MC), 311 (12), 305 (21), 292 (10%); HRMS (EI): MC
4.2.6. 3-(2-Phenylvinyl)-2,5-dibromothiophene (8).
Dibromide 1 (9.67 g, 0.036 mol) and benzyltriphenyl-
phosphonium chloride (13.93 g, 0.036 mol) were dispersed
in THF (100 mL). To the resulting suspension DBU (10 g,
6.6 mmol) was added and the resulting mixture refluxed
overnight under argon. The resulting reaction mixture was
diluted with dichloromethane and washed with 1 mol LK1
hydrochloric acid. The organic layer was separated, dried
over magnesium sulphate and the solvents removed under
vacuum at 50 8C. The residue was purified on silica using
10% ethyl acetate in hexane as eluent to give a yellow oil
(10.5 g, 85%): dH (400 MHz, CDCl3) 7.51 (2H, m, E-Ph-H),
7.37–7.35 (3H, m, E-Ph-H), 7.29–7.23 (5H, m, Z-Ph-H),
7.23 (1H, s, Th-H4-E), 7.01 (1H, d, JZ12.8 Hz, vinyl-H-Z),
6.91 (1H, d, JZ12.8 Hz, vinyl-H-Z), 6.69 (1H, d, JZ
16.0 Hz, vinyl-H-E), 6.60 (1H, s, Th-H4-Z), 6.33 (1H, d, JZ
16.0 Hz, vinyl-H-E); dC (100.6 MHz, CDCl3) 139.1, 138.3,
136.6, 136.4, 132.2, 131.3, 130.2, 128.8, 128.7, 128.4,

2198
P. Wagner et al. / Tetrahedron 62 (2006) 2190–2199
found 402.0568. C24H18S3 requires 402.0571; lmax nm (3):
336 (39,500), 351 (38,500), 406 sh (25,000), 428 (31,000),
451 (24,500).
eluent and recrystallized from dichloromethane–methanol
mixture to give fine yellow needles of 6b. (0.35 g, 82%).
4.2.9. (E)-3-(2-(4-Methoxyphenyl)vinyl)-2,5-diiodothio-
phene (11). Compound 10 (4.86 g, 10 mmol) and
4-methoxybenzaldehyde (1.43 g, 11 mmol) were dissolved
in THF (50 mL) and cooled to 0 8C. To the resulting
solution potassium tert-butoxide (2.24 g, 20 mmol) was
added, the cooling bath was removed and the resulting
mixture stirred at room temperature overnight under argon.
The resulting reaction mixture was diluted with dichloro-
methane and washed with 1 mol LK1 hydrochloric acid. The
organic layer was dried over magnesium sulphate and the
solvents were removed under vacuum at 50 8C. The residue
was purified on silica using 30% dichloromethane in hexane
as eluent and recrystallized from ethanol to give fine white
needles (3.55 g, 76%): mp 99–100 8C; dH (400 MHz,
CDCl3) 7.45–7.43 (2H, m, Ar-H), 7.29 (1H, s, Th-H4),
6.91–6.89 (2H, m, Ar-H), 6.86 (1H, d, JZ16.2 Hz, vinyl-
H), 6.75 (1H, d, JZ16.2 Hz, vinyl-H), 3.83 (3H, s, OCH3);
dC (100.6 MHz, CDCl3) 159.7, 145.3, 134.4, 131.1, 129.3,
127.9, 114.2, 78.6, 77.2, 55.3; m/z (EI) 468 (73, MC), 342
(13), 214 (100), 199 (21), 171 (48), 107 (10%); HRMS (EI):
MC found 467.8543. C13H10I2OS requires 467.8542.
Acknowledgements
This work has been made possible by financial support from
the New Zealand Foundation for Research, Science and
Technology, New Economy Research Fund (MAUX0202
and MAUX0221) and the MacDiarmid Institute for
Advanced Materials and Nanotechnology. We would also
like to thank Dr. K. Wagner for assistance with electro-
chemical measurements.
References and notes
1. Chiang, C. K.; Fincher, C. R., Jr.; Park, Y. W.; Heeger, A. J.;
Shirakawa, H.; Louis, E. J.; Gau, S. C.; MacDiarmid, A. G.
Phys. Rev. Lett. 1977, 39, 1098.
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Heeger, A. J. J. Chem. Soc., Chem. Commun. 1977, 578.
3. Skotheim, T. A.; Elsenbaumer, R. L.; Reynolds J. R., Eds.,
Handbook of Conducting Polymers, 2nd ed.; Marcel Dekker:
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4. Collis, G. E.; Burrell, A. K.; Officer, D. L. Tetrahedron Lett.
2001, 42, 8733–8735.
4.2.10. (E)-3-(2-(4-Methoxyphenyl)vinyl)thiophene-2,5-
dicarbaldehyde (12). Compound 11 (2.43 g, 5 mmol) was
dissolved in dry THF (20 mL), cooled to K78 8C, and a
2.5 mol LK1 solution of n-butyl lithium in hexane (4 mL,
0.010 mol) was added dropwise with a syringe. The
resulting mixture was stirred at K78 8C for 15 min, after
which, a solution of dry DMF (2.19 g, 0.03 mol) in THF
(1 mL) was added. The reaction mixture was allowed to
reach room temperature before being poured into 1 mol LK1
hydrochloric acid (150 mL) and extracted twice with
dichloromethane. The organic layer was separated, dried
over magnesium sulphate and evaporated to dryness under
reduced pressure at 50 8C to give a brownish oil. Purification
on silica, using dichloromethane as eluent followed by
recrystallization from ethanol yielded yellow crystals
(0.98 g, 72%): mp 142–144 8C; dH (400 MHz, CDCl3)
10.26 (1H, s, 2-CHO), 10.01 (1H, s, 5-CHO); 8.05 (1H, s,
Th-H4), 7.54 (1H, d, JZ16 Hz, vinyl-H), 7.50–7.48 (2H, m,
Ar-H), 7.18 (1H, d, JZ16 Hz, vinyl-H), 6.95–6.92 (2H, m,
Ar-H), 3.85 (3H, s, OCH3); dC (100.6 MHz, CDCl3) 183.5,
182.8, 160.5, 147.8, 146.6, 141.0, 135.5, 133.4, 128.5,
128.3, 116.2, 114.4, 55.4; m/z (EI) 272 (100, MC), 215 (16),
200 (18), 184 (12), 108 (10%); HRMS (EI): MC found
272.0508. C15H12O3S requires 272.0507.
5. Collis, G. E.; Burrell, A. K.; Scott, S. M.; Officer, D. L. J. Org.
Chem. 2003, 68, 8974–8983.
6. Grant, D. K.; Jolley, K. W.; Officer, D. L.; Gordon, K. C.;
Clarke, T. M. Org. Biomol. Chem. 2005, 3, 2008–2015.
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8. Roncali, J. J. Mater. Chem. 1999, 9, 1875.
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