Synthesis and optical and electronic properties of thiophene derivatives

Article abstract of DOI:10.1002/ejoc.200900850

Using the Hinsberg synthesis of thiophenes, a versatile method to prepare fully derivatized, π-extended thiophenes is reported. Functionalized thiophenes were divergently synthesized to create three classes of compounds - electron-deficient, extended conj

Full text of DOI:10.1002/ejoc.200900850

FULL PAPER
DOI: 10.1002/ejoc.200900850
Synthesis and Optical and Electronic Properties of Thiophene Derivatives
Raphael P. Jimenez,[a] Masood Parvez,[a] Todd C. Sutherland,*[a] and Joel Viccars[a]
Keywords: Structure-activity relationships / Heterocycles / Chromophores / Electrochemistry / Density functional calculations
Using the Hinsberg synthesis of thiophenes, a versatile
method to prepare fully derivatized, π-extended thiophenes
is reported. Functionalized thiophenes were divergently syn-
thesized to create three classes of compounds – electron-de-
ficient, extended conjugation and electron-rich – to assess
substituent effects on optical and electrochemical properties.
Properties were assessed by solution absorption spec-
troscopy, solution- and solid-state fluorescence spectroscopy,
on the optical and electrochemical properties was investi-
gated by the installation of bis(2-thienylacryoni-
trile) groups onto three thiophene cores. The extended conju-
gation led to compounds that demonstrated both solution-
and solid-state fluorescence and moderate, irreversible re-
duction potentials (–1.2 V versus Fc/Fc+). The Lewis-acid-
catalyzed coupling of four indoles to thiophene-2,5-dicarbal-
dehydes was studied to assess the effects of both electron-
cyclic voltammetry and density functional theory calcula- donating substituents and a quinoidal thiophene. The tetra-
tions. Tetracyano derivatives, prepared through Knoevena-
gel condensations of malononitrile with thiophene-2,5-dicar-
indolic thiophenes possessed low HOMO–LUMO energy
gaps of 1.91 eV, high-lying HOMO energy levels and tunable
baldehydes, were used as electron-poor analogs. These de- LUMO energy levels, attributed to the thiophene quinoidal
rivatives showed quasireversible reduction reactions and
very low-lying calculated LUMO energies (–0.55 V reduction
potentials vs. Fc/Fc+). The effect of extending π conjugation
ground-state structure.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
gies are generally employed to decrease the HOMO–
LUMO energy gap. The first strategy involves increasing
the degree of conjugation by the introduction of more
double bonds. The second strategy involves the incorpora-
tion of both an electron-donating group (EDG) and elec-
tron-withdrawing group (EWG) within the same mole-
cule.[29] Small-molecule tuning, as opposed to a polymeric
approach, permits well-defined structure-property relation-
ships to be built in the absence of aggregate or supramolec-
ular structures. Low-band-gap organics have been synthe-
sized by Osuka and co-workers[30,31] using fused porphyrin
tapes that demonstrate electronic transitions at energies as
low as 0.45 eV. Unfortunately, due to low yields and poor
solubility, these materials do not lend themselves to practi-
cal materials applications. Roncali and co-workers have syn-
thesized a wide variety of thiophenes for use as organic
semiconductors with tunable HOMO–LUMO ener-
gies.[32–34] Molecules with small HOMO–LUMO energy dif-
ferences can also be obtained by the installation of an elec-
tron-donating (increasing the HOMO energy) moiety and
an electron-accepting (lowering the LUMO energy) moiety
into a single molecule.[29] However, the frontier molecular
orbitals (FMOs) of these donor-acceptor (D-A) dyads are
localized on the respective electron-rich and electron-poor
regions of the molecule, often resulting in poor overlap and
weaker electronic transitions. Nevertheless, small molecules
with low HOMO–LUMO energy differences have been syn-
thesized using the D-A approach.[35]
Introduction
Interest in organic electronics has grown significantly
over the past several decades. Research has focused on im-
proving material processability, stability and perform-
ance.[1–7] Today, thiophene-based materials show applica-
tions in organic field-effect transistors (OFETs),[8–12] or-
ganic light-emitting diodes (OLEDs),[13,14] conducting poly-
mers[15–17] and organic photovoltaic devices.[18–20] More re-
cently, efforts in developing and optimizing materials useful
for optoelectronics has increased due to the need for solar
energy conversion materials.[21] Near-IR absorption[22,23] as
well as band-gap tunability[6,19,24–28] are key features needed
for such materials. The ubiquitous use of thiophene in or-
ganic materials is in part due to its electronic properties,
ease of derivatisation and commercial availability.
The synthesis of new molecules that have small HOMO–
LUMO energy differences is paramount to advancing or-
ganic materials applications. Moreover, the synthesis should
also be scalable, efficient, modular and divergent to allow
tuning of the electronic structure and solubility characteris-
tics required for different materials applications. Two strate-
[a] Department of Chemistry, University of Calgary,
2500 University Drive NW, Canada
Fax: +1-403-289-9488
E-mail: todd.sutherland@ucalgary.ca
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.200900850 or from
the author.
Eur. J. Org. Chem. 2009, 5635–5646
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
5635

R. P. Jimenez, M. Parvez, T. C. Sutherland, J. Viccars
FULL PAPER
There is a clear need for new organic compounds that aldehyde functionality is a reactive handle for a variety of
have tunable electronic and optical properties. This contri- coupling reactions, such as acid-catalyzed aromatic substi-
bution explores an efficient route to synthesize thiophenes tution or a variety of carbanion couplings, which are dem-
with the potential for different functionalities at the ring onstrated later in this contribution.
positions, as shown in Scheme 1. This contribution is di-
Symmetric α-diketones were used to furnish the 3,4-thio-
vided into two parts: first, the synthesis and optical and phene substituents. We investigated a family of diketones to
electronic characterisation of a series of thiophene cores cover a range of electronic tuning from alkyl (a) to phenyl
and second, the divergent modification of those thiophene (b) to fused naphthyl (c). In order to develop structure-
cores into classes of electronically diverse derivatives. For function relationships, we needed a thorough understand-
the first part, the Hinsberg thiophene synthesis was em- ing of the electronic properties of 1a–c (thiophene-diols)
ployed, which resulted in three fully derivatised thiophene and 2a–c (thiophene-dicarbaldehydes) before synthetically
structures in moderate yields after a simple purification. modifying the core thiophene structure. We examined both
For the second part, the three thiophene cores were modi- series 1 and 2 by cyclic voltammetry (CV), UV/Vis and den-
fied by the installation of either EWGs, π-extension groups sity functional theory (DFT) calculations to provide the ba-
or EDGs to create a tunable family of thiophene deriva- sis for comparison with further derivatisation.
tives.
We crystallised the three thiophene-dicarbaldehydes
(series 2) as well as thiophene-dimethanol 1b from a ternary
solvent of methanol, dichloromethane and toluene
(10:10:1), yielding crystals of X-ray quality. ORTEP images
(at 50% probability) of each are shown in Figure 1. Com-
parisons with available crystal data (CCDC) of neutral
tetrasubstituted thiophenes show typical bond lengths and
angles, which are included in the Supporting Information.
Scheme 1. Hinsberg synthesis of 1a–c and 2a–c with a thiophene
core.
Results and Discussion
The Hinsberg thiophene synthesis[36] starts with the con-
densation of dimethyl 2,2Ј-thiodiacetate with an α-diketone
in the presence of base to produce thiophene,[37] as shown
in Scheme 1. During the Hinsberg reaction, the 2- and 5-
positions of thiophene become differentiated resulting in an
asymmetrical, substituted thiophene (2-acid-5-ester) from
symmetric starting materials. We did not exploit the asym-
metry. Instead, we reduced the 2-acid-5-ester-thiophenes to
the symmetric thiophene-2,5-dimethanols, shown as series
1. Related thiophene-2,5-dimethanols have been synthe-
sized previously,[38–40] and the synthesis of 1b has been re-
Figure 1. ORTEP represenatations of 1b and 2a–c at 50% probabli-
ties.
We used the single-crystal-determined geometries (for 1b
ported by Nakayama[41] and Chandra.[42] We gently oxid- and 2a–c) as the geometry input files for DFT calculations.
ized series 1 using MnO2[43] to yield thiophene-2,5-dicarbal- A comparison of crystal geometries with optimized DFT
dehydes, series 2, in nearly quantitative yields. Several thio- structures [using the B3LYP functional with the 6-
phene-2,5-dicarbaldehyde examples[39,44–50] have been syn- 31+G(d,p) basis set] revealed very good agreement, with
thesized over the last twenty years, including fused aro- the exception of 2a, where the crystal structure had both
matics thiophenes. Specifically, the synthesis of 2b has been 3,4-ethyl pendant groups in a cis orientation, which we at-
previously reported.[41,42] The conversion of the thiophene- tributed to a solid-state packing phenomena. The agree-
dimethanol derivatives to their corresponding dicarbal- ment of the crystal data with optimized structures gave
dehydes (series 2) explores the electronic effects of EDGs credibility to the optimized structures where crystal data is
and EWGs at the 2,5-loci of thiophene. In addition, the not available.
5636
www.eurjoc.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 5635–5646

Synthesis and Properties of Thiophene Derivatives
We carried out nucleus-independent chemical shift
The CV results are compiled in Table 1. Generally, series
(NICS) calculations[51,52] to assess the aromaticity of the 1 showed two irreversible oxidation waves. The first oxi-
thiophene ring using GIAO-SCF at the HF/6-31G+(d,p) dation wave we attributed to the one-electron oxidation of
level with the GAUSSIAN 03 software package[53] (see the thiophene (1.0 V to 1.2 V) to the radical cation, which be-
Supporting Information). The objective of the NICS(1) cal- comes less energetic with increased conjugation.[55,56] The
culations was to correlate the effects of aromaticity of the oxidation of thiophenes is known to be irreversible and fall
thiophene core on its optical and redox properties. The within the reported potential region.[57] The second irrevers-
NICS(1) values of series 1 showed decreasing aromatic ible oxidation wave, which was at similar potentials
character from –11.5 to –8.34 to –7.61 for 1a to 1c, respec- throughout series 1, we attributed to the alcohol oxidation
tively. We observed a similar decreasing aromatic trend for (about 1.5 V).
series 2 with NICS(1) values of –10.26, –9.04 and –8.56 for
Compounds 1a and 1b did not show reduction peaks
2a to 2c, respectively. The decrease in aromaticity for both within the solvent stability window, whereas 1c showed two
series, from the diethyl-thiophene to the acenaphthyl quasireversible reduction waves at –1.43 V (∆Ep = 110 mV)
(AcNp)-thiophene derivatives, was consistent with the thio- and –1.89 V (∆Ep = 110 mV). The two quasireversible re-
phene ring delocalizing its π-system to the 3,4 aromatic sub- duction waves we tentatively assigned to the radical anion
stituents (extension of the αC–S bonds and contraction of and dianion delocalized over the entire molecule,[58,59] as sug-
the fused aromatic σ bonds). The solid-state packing dia- gested by the LUMO of 1c. Spectroelectrochemical experi-
grams of 1b and 2a–c are included in the Supporting Infor- ments are ongoing to determine the identity of the reduced
mation.
species. A trend in series 1 of decreasing oxidation potential
The UV/Vis absorption spectra of series 2 are shown in (from 1a to 1c) was consistent with optical measurements and
Figure 2, and as expected, the more π-delocalized thio- DFT calculations. The thiophene-dicarbaldehydes (series 2)
phene structures showed red-shifted absorptions.[29,54] The did not exhibit a second oxidation wave, which supports the
onset of the absorption, used to determine the HOMO– alcohol oxidation assignment made for series 1. The first
LUMO energy gap, of the molecule is included in Table 1. irreversible oxidation waves of 2a–c occurred at similar or
Within both series 1 and 2, the HOMO–LUMO energy gap lower values than those of series 1, suggesting the small effect
decreased progressing from the diethyl (a) to diphenyl (b) to that EDGs or EWGs in the thiophene α-positions have on
AcNp (c) thiophenes. The decrease in the HOMO–LUMO the HOMO levels of thiophenes. All of series 2 showed two
energy gap we attributed to increased conjugation, which quasireversible reduction waves. Compound 2a had the high-
was supported by DFT calculations. The UV/Vis absorp- est reduction potential at –1.75 V (∆Ep = 700 mV) and –2.5 V
tion spectra also showed series 2 had a consistently lower (∆Ep = 650 mV), whereas 2b (∆Ep = 250 mV) and 2c (∆Ep =
HOMO–LUMO gap than its thiophene-2,5-dimethanol 560 mV) had their first reduction potentials at –1.5 V. The
precursor. We note the calculated HOMO–LUMO energies two reduction waves of series 2 we attributed to the radical
are gas-phase calculations and should be considered as ver- anion and dianion species.
ifying a trend in energies rather than matching experimental
The energy levels of the FMOs for series 1 and 2 are
values. Neither series 1 nor 2 were fluorescent in solution shown in Figure 3. Two trends are apparent. First, the
(THF) or the solid state.
HOMO energy levels increased from a to c in both series 1
and 2. Second, the electron-rich 2,5-dimethanol derivatives
(1) had higher energy lying HOMO and LUMO levels than
does series 2. Both 3,4-diethylthiophenes (1a and 2a) had
HOMOs confined to the thiophene ring, whereas the 3,4-
diphenylthiophenes and AcNp-thiophene (1b, 1c, 2b and
2c) showed π-delocalization onto the 3,4-thiophene substit-
uents, suggesting potential tuning. All FMO images are
available in the Supporting Information. The HOMO en-
ergy level changes for both series 1 and 2 were consistent
with the observed first oxidation wave measured by CV.
Figure 2. UV/Vis spectra of 2a–c in THF.
Table 1. Electrochemical and optical data of 1a–c and 2a–c.
Entry
Compound
Absorbance onset [nm] (eV)
Eox1 [V]
Eox2 [V]
Ered1V
Ered2 [V]
Calculated HOMO–LUMO [eV][c]
[d]
[d]
1
2
3
4
5
6
1a[a]
1b[a]
1c[a]
2a[b]
2b[b]
2c[b]
309 (4.01)
294 (4.21)
399 (3.11)
354 (3.50)
398 (3.11)
423 (2.93)
1.13
1.19
1.01
1.13
1.15
0.85
1.50
1.56
1.44
–
–
–
–
–
5.95
5.08
4.03
5.25
3.90
3.44
[d]
[d]
–
–
–1.43
–1.75
–1.54
–1.59
–1.89
–2.47
–2.02
–2.17
[a] Measurements were conducted in CH3CN. [b] Measurements in THF; scan rate of 0.1 Vs–1; concentration of 1.0 m; tetrabutylammo-
nium hexafluorophosphate (0.1 ) was the supporting electrolyte vs. an Fc/Fc+ reference. [c] Calculated by the DFT B3LYP functional
with the 6-31+G(d,p) basis set. [d] Not observed within the potential window of the solvent.
Eur. J. Org. Chem. 2009, 5635–5646
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5637

R. P. Jimenez, M. Parvez, T. C. Sutherland, J. Viccars
FULL PAPER
Figure 3. FMO energy levels calculations [DFT B3LYP functional
and 6-31G+(d,p) basis set] for series 1 and 2. Quinoidal-shaped
LUMO orbitals are indicated by the dashed line.
Scheme 2. Synthesis of tetracyano-thiophene (3), dithienyldicyano-
thiophene (4) and tetraindole-thiophene (5).
The LUMOs of all compounds except for 1c had the ex- phenyl groups did not impact the HOMO–LUMO energy
pected quinoidal thiophene shape[60] with density on the gap. DFT calculations resulted in a HOMO–LUMO energy
thiophene ring, as exemplified by 2c-LUMO in Figure 3. gap of 2.93 eV and 2.95 eV for 3a and 3b, respectively,
The energy levels of the quinoidal LUMOs changed slightly which was consistent with the optically determined
for 2a–2c, which was consistent with the small changes ob- HOMO–LUMO energy gap. As expected, the strong EWGs
served in the first reduction. Interestingly, the LUMO+1 of had lowered the LUMO energy level by about 1.1 eV com-
2c did show a significant decrease in energy compared to pared to that of series 2. The large change observed in the
the LUMO+1 of both 2a and 2b. This drop in energy is LUMO energy level resulted in a modest (0–0.3 eV) de-
critical for the tunability of these fused aromatic com- crease in the HOMO energy level. Compound 3c exhibited
pounds. However, in the AcNp-thiophene (1c) case, the a larger 100 nm bathochromic shift in its absorption onset
LUMO energy dropped below the quinoidal orbital (now (525 nm) compared to that of its series 2 parent. The ace-
LUMO+1), showing the potential for extensive LUMO tun- naphtho-fused aromatic thiophene (3c) exhibited delocal-
ability using fused aromatic thiophenes. The DFT calcula- ization of the π-system through the 3,4-positions, which did
tions indicated the installation of EDGs at the 2,5-loci of not occur in either the diethyl (3a) or diphenyl (3b) cases.
thiophene allow for LUMO energy-level tuning, and the A similar compound (R = H in Scheme 2), was first re-
fused aromatics at the 3,4-loci permit HOMO energy level ported by Sone[61] and was later investigated as an electron-
tuning.
acceptor material.[62] In addition, a 3,4-benzannulated ana-
With a thorough characterisation of the optical and elec- logue of 3a was synthesized previously[62] and showed two
tronic properties of the thiophene core, we synthesized three reversible reduction waves at –0.25 V and –0.62 V (vs.
divergent families of compounds from series 2. Scheme 2 Ag|AgCl).[62] The addition of the four cyano groups in
illustrates the synthetic versatility of the thiophene core, series 3 resulted in bathochromic shifts, and we observed
which is conducive to the addition of electron-withdrawing insignificant changes in molar absorptivity, suggesting the
cyano groups by Knoevenagel condensations (series 3), the cyano groups did not extend the π-conjugation but rather
extension of conjugation via bis(2-thienylacrylonitrile)-thio- lowered the LUMO energy level inductively. Only 3c pos-
phene derivatives (series 4) and the formation of a tetra- sessed weakly emissive properties in THF with a λem maxi-
indolic thiophenes (series 5).
mum at 544 nm (λex = 490 nm). The excitation spectrum
We carried out the Knoevenagel condensations of thio- peaked at 490 nm, consistent with the absorption spectrum,
phene-2,5-dicarbaldehydes 2 with malononitrile in EtOH/ corresponding to a moderate Stokes shift of 53 nm.
THF with gentle heating, resulting in 67–72% conversions NICS(1) calculations for 3a–c showed a decrease in thio-
to the tetracyano-thiophenes (series 3) within 25 min. We phene aromatic character with values of –9.98, –9.85 and
purified each of the series 3 compounds by crystallisation, –7.86, respectively, consistent with the trends observed for
and their UV/Vis absorption spectra are included in the series 2. NICS(1) results indicated that better chromophores
Supporting Information. The installation of the four cyano based on thiophene cores should possess less aromatic thio-
groups onto the divinyl thiophene core resulted in a ba- phenes. Interestingly, both 3a and 3b were weakly emissive
thochromic absorption relative to series 2. Both structures in the solid state. Single crystal X-ray structures of 3a and
3a and 3b had absorption onsets of about 450 nm, which 3b showed antiparallel stacking of the thiophene groups
were shifted 100 nm from 2a and 50 nm from 2b. Clearly, with little π-overlap (see the Supporting Information). The
the replacement of the 3,4-diethyl groups with the 3,4-di- solid-state excitation spectra of 3a and 3b overlapped with
5638
www.eurjoc.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 5635–5646

Synthesis and Properties of Thiophene Derivatives
their absorption spectra, suggesting the solid-state packing Table 2. Summary of electrochemical[a] and optical[b] data for series
3–5.
did not involve donor-acceptor orbital mixing. Instead, the
solid-state packing confined the thiophene and limited
other relaxation pathways, resulting in a weakly emissive
solid at similar energy to solution fluorescence.
Entry
Ered2 [V] Ered1 [V] Eox1 [V] Eox2 [V] Optical Eg [eV][b]
1
2
3
4
5
6
7
8
9
3a
3b
3c
4a
4b
4c
5a
5b
5c
–1.22
–1.11
–0.99
–1.84
NA
–0.59
–0.54
–0.69
–1.29
–1.26
–1.10
NA
NA
NA
NA
NA
NA
NA
NA
NA
1.63
NA
NA
NA
NA
NA
NA
NA
NA
NA
2.58
2.61
2.36
2.36
2.36
2.25
2.07
2.07
1.91
The CVs of series 3 are included in the Supporting Infor-
mation. Generally, we reduced the tetracyano-thiophene de-
rivatives easily at moderate potentials (–0.55 V vs. Fc/Fc+,
see Table 2.) Compound 3a showed irreversible reduction,
whereas both 3b and 3c showed quasireversible behaviour
under the same conditions, as shown in Figure 4. The qua-
sireversible CV peaks were most likely the radical anion
that has been observed previously.[63] We note that we did
not observe quasireversible behaviour when the reversal po-
tential was more negative than –0.6 V (–1.1 V vs. Fc/Fc+)
because further reduction created a new, coloured species,
which we observed diffusing from the electrode surface. At
this time, the identity of the reactive species in unknown,
but we observed the subsequent oxidation of the new spe-
cies in the return wave at potentials near 0 V. We did not
observe the oxidation peak above 0 V in the first anodic
scan, and it only appeared on subsequent scans after we
applied reduction potentials more negative than –0.6 V. In
a cathodic potential sweep experiment, the potential where
the current begins to increase is termed the onset of re-
duction and provides an estimate of the LUMO energy
level. Based on the CV data, we observed no discernible
differences in LUMO energy levels for series 3, which was
supported by DFT calculations (discussed below). Simi-
larly, the HOMO energy levels can be evaluated electro-
chemically by the onset of oxidation, but in the tetracyano
derivatives, this oxidation potential resided outside the sol-
vent stability window. The low reduction potentials of 3b
and 3c indicated the possible use of this class of thiophene
as n-type organic materials. The quasireversible CVs of 3b
and 3c, shown in Figure 4, suggested the stability of the
reduced species was enhanced by the introduction of the
four cyano groups and could play a role in eventual device
longevity. Moreover, the kinetics of the electron-transfer re-
NA
NA
NA
NA
NA
NA
[a] All electrochemical measurements were conducted in 0.1 
NBu4PF6 as the supporting electrolyte in THF at a scan rate of
0.1 Vs–1, using a Pt wire working electrode vs. A Fc/Fc+ reference.
[b] The optical band gap was determined from the onset of absorp-
tion in 1ϫ 10–5  THF solutions.
Figure 4. CVs of 3b (solid line) and 3c (dashed line) in THF at
room temperature; scan rate of 0.1 Vs–1; concentration of 1.0 m;
tetrabutylammonium hexafluorophosphate (0.1 ) was the sup-
porting electrolyte; reference electrode of Ag|AgCl|KCl3M; a Pt wire
as the working electrode and a Pt mesh as the counter electrode.
actions, as assessed by the oxidation and reduction peak band-gap of 1.6 eV. The UV/Vis spectra of series 4 are in-
separation, indicated 3c (∆Ep = 80 mV) was operating near cluded in the Supporting Information. Series 4 showed ba-
diffusion-controlled limits, in contrast to 3b (∆Ep
260 mV), and could lead to materials with superior charge- The absorption onsets for 4a, 4b and 4c were 525, 525 and
transfer rates. 550 nm, respectively. In addition, the absorption profiles of
=
thochromic absorptions compared to its parent dialdehyde.
We synthesized series 4 from the condensation of 2-thien- 4a and 4b in the low-energy region were nearly superimpos-
ylacetonitrile with series 2 in the presence of tert-butoxide. able, indicating little electronic tuning of the HOMO or
The conversion to the bis(2-thienylacrylonitrile)-thiophene LUMO occurred due to substitution at the 3,4-positions of
was nearly quantitative with yields ranging from 91–97% in phenyl for ethyl. Fusion of an acenaphthylene ring to the
a 30 min reaction. Both Roncali et al.[64] and Hanack et thiophene core allowed the 3,4-loci to participate in π-delo-
al.[65] have synthesized the 3,4-proton version of 4a, which calization, resulting in lower-energy electronic transitions.
showed a λmax value at 480 nm in CH2Cl2 and reversible The lower-energy absorption onset of series 4 compared to
oxidation and reduction waves. In addition, electrochemical series 3 was due to the additional conjugation length, con-
anodic polymerization of the protonated derivative pro- sistent with the increase in molar absorptivity from 2ϫ104
duced a polymer film with a band-gap of 0.65 eV. A related, to 3ϫ104 –1 cm–1. DFT calculations of series 4 indicated
conjugated, donor-acceptor derivative[66] of bis(2-pyrrol-ac- the HOMO–LUMO energy gaps were mainly dependent on
ryolnitrile)-thiophene showed oxidation at 0.48 V (vs. HOMO-level tuning. The LUMO energy levels of series 4
Ag|0.1  AgClO4, CH3CN) and λmax at 490 nm, which was were similar in energy to those of its parent series 2 dialde-
also electropolymerised and produced a polymer with a hydes, despite the introduction of the acrylonitrile group.
Eur. J. Org. Chem. 2009, 5635–5646
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5639

R. P. Jimenez, M. Parvez, T. C. Sutherland, J. Viccars
FULL PAPER
The electron-withdrawing cyano groups did not alter the
LUMO energy level because the electronics were compen-
sated by the electron-rich thienyl groups. However, the thi-
enyl substituents, due to extended π-conjugation, increased
the HOMO energy level by 0.9–1.3 eV. The results of the
DFT calculations on series 4 clearly indicated the thienyl
groups donated significant electron density into the conju-
gated π-backbone. NICS(1) calculations resulted in less
thiophene aromatic character than series 3 with 4a–c having
values of –9.82, –8.22 and –7.32, respectively, which was
consistent with the notion of extended conjugation.
Both 4b and 4c were fluorescent as dilute THF solutions
with emission peaks at 520 and 540 nm, respectively, and
small Stokes shifts of 25 and 20 nm, respectively. All of
series 4 exhibited solid-state fluorescence. Notably, 4b
showed a solid-state fluorescence that was red-shifted com-
pared to its solution-based fluorescence. The solid-state
emission maxima for 4a and 4b were 580 and 675 nm,
respectively. An X-ray structure for 4a (Figure 5) showed
stacking of the π-extended thiophenes with a distance be-
tween thiophene ring planes of 3.47 Å, which could lead to
intermolecular π-π interactions and orbital mixing, re-
sulting in lower energy electronic transitions. A similar
structure and packing motif was reported by Wagner et
al.[67] Presumably, similar packing could explain the ba-
thochromic solid-state emission spectrum of 4b, but a single
Figure 5. a) Ortep representation of 4a shown at the 50% prob-
ability level. b) side view of solid-state packing; c) top view of solid-
crystal is not yet available. The overlap of π-orbitals in the state packing.
solid-state packing of 4a is clearly visible in parts b and c
of Figure 5, in contrast to the limited degree of π-orbital
overlap seen in the solid-state packing of 3a or 3b (see the
We synthesized series 5 using the Lewis-acid-catalyzed
Supporting Information). The solid-state emission spec- reaction of the dialdehyde (series 2) with indole, resulting
trum of 4c did not follow the solution-based absorption and in moderate yields of 41–49%. The conversion took longer
emission trend with an emissive peak at 590 nm. Most than for either series 3 or 4, and column chromatography
1
likely, the solid-state structure of 4c did not provide effec- was required to purify the final products. The H NMR of
tive intermolecular overlap of the π-systems, resulting in an 5a was unique because it showed two conformations of the
emissive peak that was only 40 nm red-shifted compared to 3,4-diethyl groups – syn and anti – at room temperature.
1
its solution fluorescent peak.
Variable-temperature H NMR spectra (see the Supporting
The CVs of series 4 are included in the Supporting Infor- Information) showed the convergence of the C2-symmetric
mation. None of series 4 showed reversible redox behaviour, anti conformer into the thermodynamically preferred,
and the onsets of reduction were shifted cathodically com- asymmetric syn conformer. We established the assignment
pared to series 3, due to the two electron-rich thienyl sub- of the two conformers using COSY and NOESY experi-
stituents. The addition of electron density to the system re- ments (see the Supporting Information) and DFT calcula-
sulted in an increase in LUMO energy. Both 4a and 4b tions. The asymmetric syn diethyl conformer was more
showed the same reduction onset potentials, which were in stable than the anti diethyl conformer by 5 kJmol–1 [calcu-
agreement with the DFT-determined LUMO energy levels, lated value using the B3LYP functional with the 6-31
1
and 4c was slightly easier to reduce, which was also consis- G+(d,p) basis set]. The two diethyl conformations and H
tent with DFT calculations. The oxidation peaks of the first NMR assignments are available in the Supporting Infor-
anodic scan, to determine HOMO energy levels, were out- mation. The UV/Vis spectra of series 5 are shown in Fig-
side the stability window of the solvent. However, upon ure 6. We observed the same overall trends as we did for
subsequent CV scans, we observed two oxidation peaks in series 3 and 4, with the diethyl and diphenyl derivatives hav-
the CV between 0 V and 1 V that we attributed to a highly ing nearly overlapping spectral features in the low-energy
coloured, oligomeric species observed with related bis- region. The absorption spectrum of 5c was unique because
(thienylvinyl)thiophenes formed during the reductive of its lower molar absorptivity and broad transitions, which
cycle.[59,65] On the first anodic scan of a clean electrode, the could be attributed to the different conformations present
oxidation peaks between 0 and 1 V were absent, and after at room temperature. However, series 5 did exhibit the
several cycles, we did not observe any visible film on the largest bathochromic shifts of all the series, which we as-
electrode surface owing to the solubility of the oligomeric cribed to the extensive delocalization of the π-system and
species in THF.
the quinoidal thiophene ground-state structure. The ab-
5640
www.eurjoc.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 5635–5646

Synthesis and Properties of Thiophene Derivatives
sorption onsets of 5a–c were 600, 600 and 650 nm, respec-
The cumulative results of the DFT gas-phase calcula-
tively. For comparison, quinoidal thiophenes synthesized by tions with the B3LYP/6-31G+(d,p) basis set are shown in
Hanack et al.[65,68–71] bearing bis(2-thienyl)thiophene with Figure 7. Series 3, with the four cyano groups, possessed
3,4-annulated phenyl and thiophene groups showed ab- the lowest energy LUMOs and highest energy HOMOs and
sorbance maxima at 432 and 405 nm, respectively. Ad- was the easiest to reduce. Series 4, with the added electron
ditionally, non-annulated, quinoidal, terthiophenes showed density of the pendant thienyl groups, had both a higher
an absorbance maximum at 554 nm.[70] Lorcy et al. synthe- energy HOMO and LUMO than those of series 3. Series 5
sized tetracyano, benzannulated, quinoidal thiophenes, showed an increase in HOMO energy over that of series 4,
which gave an absorption maximum at 408 nm.[62] Ishii et concurrent with an increase in LUMO energy. Within series
al. synthesized several 2,5-bis(diarylmethylene)thiophenes 3, it was clear that the LUMO energy was not altered or
that exhibited absorbance maxima from 414 to 527 nm in tunable by changes to the 3,4-loci of the thiophene.
CH3CN.[72] An interesting set of quinoidal tetraazulene-
thiophenes by Ito et al.[73] and Takekuma et al.[74] had ab-
sorbance peaks at 530 and 550 nm, respectively.
Figure 6. UV/Vis spectra of series 5 in THF.
Figure 7. FMOs of series 3–5, determined with the DFT B3LYP
functional and the 6-31G+(d,p) basis set. Quinoidal-shaped orbit-
DFT calculations revealed that the HOMO energy levels als are indicated by the dashed line.
for series 5 increased substantially (2.2–2.8 eV) from those
of the parent dialdehydes, series 2. We observed a concur-
rent increase in LUMO energy level (compared to series 2),
However, the HOMO energy of the fused acenaphtho de-
but at a much smaller magnitude (0.8–1.3 eV), resulting in rivative, 3c, did show tunability potential, as seen by the 3c-
an overall smaller energy gap. NICS(1) calculations clearly HOMO surface shown in Figure 8. The 3c HOMO surface
demonstrated a quinoidal (nonaromatic) form of thiophene did indicate much electron density was delocalized over the
with values of –2.97, –1.47 and –1.50 for 5a–c, respectively. naphthalene ring, an effect not repeated with either the di-
Only 5b and 5c displayed fluorescent behaviour as dilute phenyl (3b) or diethyl (3a) derivatives (see the Supporting
THF solutions, and these data are included in the Support- Information for FMOs). Within series 4, only moderate
ing Information. The excitation spectrum of 5b aligned with changes of either the HOMO or LUMO energy levels were
the absorption spectrum shown in Figure 6 and had an apparent. The largest changes in series 4 stemmed from the
emission peak at 570 nm. The excitation spectrum of 5c was LUMO lowering of the fused acenaphtho derivative, 4c, at-
very different from the 5c absorption spectrum shown in tributed to the small delocalization onto the naphthalene
Figure 6. The 5c excitation spectrum peaked at 340 nm and ring in the LUMO surface. Within series 5, the HOMO en-
emitted at 415 nm, clearly blue-shifted from the absorption ergy level remained constant. Importantly, the HOMO sur-
spectrum. Excitations at the absorption shoulders of face for all of series 5 changed to a quinoidal shape, as
600 nm or 460 nm for 5c did not result in emissive transi- shown in Figure 8, with the majority of electron density
tions, whereas photoexcitation of the shoulder at 340 nm residing on the thiophene ring and limited density spread
resulted in emission at 415 nm. This blue-shifted emission over the heterocycle of the indole. The quinoidal HOMO
we attributed to one of the indoles relaxing. Due to lack of orbital did not include contributions from the 3,4-loci and,
solubility, the CVs of series 5 were not informative. The therefore, the energy remained constant across the series.
DFT-determined LUMO energy levels for the tetraindoles However, the LUMO energy of series 5 was highly tunable
showed a decreasing energy trend across the diethyl (5a) to by the 3,4-loci of thiophene. The LUMO of the diethyl de-
diphenyl (5b) to acenaphtho-fused (5c) derivatives.
rivative, 5a, showed no contribution on the ethyl pendants,
Eur. J. Org. Chem. 2009, 5635–5646
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5641

R. P. Jimenez, M. Parvez, T. C. Sutherland, J. Viccars
FULL PAPER
whereas both the diphenyl (5b) and fused acenaphtho (5c) tions of the thiophene causes large changes in both the
derivatives showed delocalization through the 3,4-thiophene HOMO and LUMO energy levels. Conversely, the derivatis-
positions, concurrent with a stepwise reduction in LUMO ation of the 3,4-positions of thiophene causes minor
energy level.
changes in the electronic structure. The results clearly indi-
cate that the fused acenaphtho-thiophene has the smallest
HOMO–LUMO energy gap, and quinoidal-shaped thio-
phene ground states are attractive targets for low-band-gap
organic materials. A major limitation is poor solubility;
however, employing the Hinsberg synthesis allows a modu-
lar approach to the installation of solubilising groups at the
α-diketone stage while maintaining the desired electronic
structure. We envisage a combination of structures 3c and
5c into a new material that could produce a theoretical
band gap of 0.1 eV. The major findings of this paper are
threefold: 1) the Hinsberg thiophene synthesis is a versatile,
efficient method for incorporating different functionality
into the 3,4-positions and provides a path to fused aromatic
structures, 2) the Knoevenagel condensations of thiophene-
2,5-dicarbaldehydes, to extend conjugation, can alter the
electronic structure dramatically, depending on the number
of EWGs and length of conjugation, and 3) the formation
of a quinoidal-shaped ground-state thiophene structure is
advantageous to designing molecules with small HOMO–
LUMO energy gaps.
Experimental Section
Figure 8. DFT-calculated HOMO–LUMO surfaces for 3c, 4c and
5c.
General Methods: All chemical reagents were obtained from Ald-
rich and used without further purification, except deuterated sol-
vents for NMR spectra, which were from Cambridge Isotope
Laboratories. High-resolution mass spectra (HR-MS) were col-
lected using a Waters GCT Premier instrument. H and 13C NMR
1
Conclusions
spectra were recorded with a Bruker DMX-300 MHz or a DRY-
400 MHz spectrometer. Proton spectra were referenced to CHCl3
(δ = 7.27 ppm) or DMSO (δ = 2.50 ppm) as an internal standard.
All carbon NMR samples were proton-decoupled and referenced
to CDCl3 (δ = 77.00 ppm) or DMSO (δ = 39.51 ppm). The UV/
Vis/NIR spectra were recorded with a Varian Cary 5000 photospec-
trometer in CH3CN at room temperature using a quartz 1 cm path
length microcell. Infrared spectra were recorded with a Varian
FTS-7000 FT-IR spectrometer in a KBr suspension operating in
diffuse reflectance mode at room temperature. CVs were recorded
in CH3CN or THF at room temperature: scan rate of 0.1 Vs–1;
concentration of 1.0 m; tetrabutylammonium hexafluorophos-
In summary, this contribution details a facile Hinsberg
synthesis of thiophene-2,5-dicarbaldehyde with ethyl,
phenyl and naphthaleno-bridge substituents at the 3,4-thio-
phene positions. These thiophene-dialdehydes were sub-
jected to three reactions to illustrate the tunability of the
electronic energy levels. The Knoevenagel condensation
with malononitrile resulted in high conversions into very
electron-deficient thiophenes, which were reduced readily
and exhibited weak solid-state emissions. The addition of
two thienyl substituents and two cyano groups resulted in
extended conjugation with little change in the HOMO en-
ergy level compared to that of its parent dialdehyde. How-
ever, the enhanced conjugation led to a large bathochromic
shift and a solid-state fluorescence. The final series of syn-
theses was accomplished by the Lewis-acid-catalyzed reac-
tion of indole with the parent dialdehyde resulting in a tet-
raindolic thiophene species. The tetraindolic species was
more electron-rich than the other series studied and exhib-
ited the lowest HOMO–LUMO gap. In addition, the tetra-
indolic compounds possessed a quinoidal thiophene core.
Each compound was subjected to DFT calculations with
the B3LYP functional and 6-31G+(d,p) basis set, and the
calculations support both the electrochemical and photo-
physical measurements. The experimental and theoretical
+
–
phate (NBu4 PF6 , 0.1 ) as the supporting electrolyte; reference
of Ag|AgCl|KCl3M using a Pt wire as the working electrode and a
Pt mesh as the counter electrode. Fluorescence spectra were re-
corded with a Jasco FP6600 Spectrofluorimeter in THF at room
temperature using a quartz 1 cm path length cell. Solid-state fluo-
rescence samples were prepared by drop casting the compound
from 10–5  THF solutions onto a quartz window fixed at a 30°
incident angle.
1a: 3,4-Diethyl-5-(methoxycarbonyl)thiophene-2-carboxylic acid
(0.45 g, 1.87 mmol) was added to a solution of lithium aluminium
hydride (0.18 g, 4.76 mmol) in THF (20 mL) at –78 °C. The grey
solution was slowly warmed to room temperature and stirred over-
night, at which point the solution was cooled to 0 °C, and water
(0.5 mL) and aqueous NaOH (0.5 mL, 10%) were added slowly
with frequent venting. The solution was then filtered to remove
calculations indicate that the derivatisation of the 2,5-posi- salts and insoluble particles. After recrystallisation from dichloro-
5642 Eur. J. Org. Chem. 2009, 5635–5646
www.eurjoc.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Synthesis and Properties of Thiophene Derivatives
methane, colourless crystals weighing 0.083 g (21.0%) were ob-
J = 7.6 Hz, 3 H, CH2CH3) ppm. 13C NMR (75 MHz, CDCl3): δ =
tained; m.p. 139–141 °C. 1H NMR (300 MHz, [D6]DMSO): δ = 183.2, 152.1, 143.5, 19.8, 16.6 ppm. UV/Vis: λ (ε, –1 cm–1) = 325
5.20 (t, J = 5.47 Hz, 1 H, OH), 4.55 (d, J = 5.46 Hz, 2 H, CH2OH), (5300) sh, 305 (7500), 230 (6300), 207 (18000) nm. IR: ν 2973 (CH),
˜
2.49 (q, J = 7.5 Hz, 2 H, CH2CH3), 1.02 (t, J = 7.53 Hz, 3 H, 2935 (CH), 2866 (CH), 2357 (CH), 1651 (CO), 702 (CS) cm–1.
CH2CH3) ppm. 13C NMR (101 MHz, [D6]DMSO): δ = 139.1, LRMS (EI, 70 eV, m/z): 196.1 [M]+. C10H12O2S (196.3): calcd. C
137.3, 56.9, 20.0, 16.2 ppm. UV/Vis: λ (ε, –1 cm–1) = 285 (210),
61.20, H 6.16; found C 60.93, H 6.45.
252 (4400) sh, 248 (4700) nm. IR: ν = 3340, 3267, 2742, 1990, 1442
˜
2b: Compound 1b (0.3864 g, 1.3 mmol) was dissolved in chloro-
form (200 mL), and MnO2 (1.700 g, 19.6 mmol) was then added.
The dark black solution was stirred for 90 min and filtered through
Celite. Slow evaporation of the solvent yielded colourless crystals
weighing 0.3811 g (99%); m.p. 134–137 °C. 1H NMR (300 MHz,
CDCl3): δ = 9.79 (s, 1 H, CHO), 7.38–7.28 (m, 3 H), 7.16–7.09 (m,
2 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 185.2, 150.8, 144.1,
131.7, 130.5, 128.9, 128.5 ppm. UV/Vis: λ (ε, –1 cm–1) = 348 (1900)
cm–1. LRMS (EI, 70 eV, m/z): 200 [M]+. C10H16O2S (200.3): calcd.
C 59.96, H 8.05; found C 59.60, H 8.02.
1b: 5-(Methoxycarbonyl)-3,4-diphenylthiophene-2-carboxylic acid
(9.99 g, 28.3 mmol) was added to a solution of lithium aluminium
hydride (2.61 g, 68.6 mmol) in THF (100 mL) at –78 °C. The grey
solution was slowly warmed to room temperature and stirred over-
night, at which point the solution was cooled to 0 °C, and water
(1.0 mL) and aqueous NaOH (2 mL, 10%) were added slowly with
frequent venting. The solution was then filtered to remove salts and
insoluble particles. After recrystallisation from dichloromethane, a
white solid was obtained, weighing 7.38 g (88%); m.p. 169–172 °C.
1H NMR (300 MHz, [D6]DMSO): δ = 7.18 (m, 3 H), 6.96 (m, 2
H), 5.41 (t, J = 5.40 Hz, 1 H, OH), 4.45 (d, J = 5.41 Hz, 2 H,
CH2OH) ppm. 13C NMR (75 MHz, [D6]DMSO): δ = 150.9, 143.2,
140.7, 136.1, 130.3, 128.3, 127.1, 57.6 ppm. UV/Vis: λ (ε, –1 cm–1)
= 275 (20400) sh, 266 (29300), 237 (61100), 212 (235000) nm. IR:
sh, 315 (4000), 247 (6500), 208 (18000) nm. IR: ν = 3082 (CH),
˜
3024 (CH), 2923 (CH), 1668 (CO), 1157 (CH), 697 (CS) cm–1.
LRMS (EI, 70 eV, m/z): 292.1 [M]+. C18H12O2S (292.1): calcd. C
73.95, H 4.14; found C 73.55, H 4.10.
2c: Compound 1c (0.0068 g, 0.025 mmol) was dissolved in THF
(200 mL), and MnO2 (0.033 g, 0.38 mmol) was then added. The
dark black solution was stirred for 90 min and filtered through Ce-
lite. Slow evaporation of the solvent yielded red crystals weighing
1
0.0064 g (96%); m.p. 121–125 °C. H NMR (400 MHz, CDCl3): δ
ν = 3317, 3055, 2937, 1600, 1471 cm–1. LRMS (EI, 70 eV, m/z): 296
˜
= 10.35 (s, 1 H, CHO), 8.46 (d, J = 7.1 Hz, 1 H, ArH), 8.02 (d, J
= 8.2 Hz, 1 H, ArH), 7.74 (dd, J = 7.2, 8.2 Hz, 1 H, ArH) ppm.
13C NMR (101 MHz, CDCl3): δ = 182.0, 149.5, 136.3, 130.8, 130.6,
129.0, 128.3, 125.3 ppm. UV/Vis: λ (ε, –1 cm–1) = 378 (8700), 331
[M]+. C18H16O2S (296.4): calcd. C 72.94, H 5.44; found C 72.44,
H 5.59.
1c: Acenaphthenequinone (6.0 g, 0.033 mol) and dimethyl 2,2Ј-
thiodiacetate (6.74 g, 0.0378 mol) were dissolved in dry THF
(175 mL) by warming the mixture to reflux. Sodium methoxide
(4.085 g, 0.0756 mol) was added, and the solution was stirred under
a N2 atmosphere overnight. Aqueous HCl (0.1 , 100 mL) was
added to the dark red solution, and the mixture was stirred for an
additional 30 min. The organic layer was extracted repeatedly with
aqueous ammonium hydroxide (25%, 50 mL) until a sample of the
aqueous layer gave no precipitate upon acidification. The combined
aqueous layers were heated briefly to remove dissolved ether and
acidified with concentrated HCl, yielding a crude brown solid,
weighing 5.72 g. The crude acenaphtho[1,2-c]thiophene-7,9-dicar-
boxylic acid (5.55 g, 16.3 mmol) was added to a solution of lithium
aluminium hydride (1.53 g, 40.2 mmol) in dry THF (100 mL) at
–78 °C. The grey solution was slowly warmed to room temperature
and stirred overnight, at which point the solution was cooled to
0 °C, and water (1.0 mL) and aqueous NaOH (2 mL, 10%) were
added slowly with frequent venting. The solution was then filtered
to remove salts and insoluble particles. After crystallisation from
dichloromethane, a tan solid was obtained, weighing 3.24 g (37%);
(61000), 318 (39000) sh, 285 (15000), 238 (91000) nm. IR: ν = 3049
˜
(CH), 2921 (CH), 2859 (CH), 1940 (CH), 1880 (CH), 1819 (CH),
1674 (CO), 770 (CS) cm–1. LRMS (EI, 70 eV, m/z): 264.1 [M]+.
HRMS (EI, 70 eV, m/z): calcd. for C15H8OS 236.0296 [M + OCH
+ H]+; found 236.0296.
3a: Compound 2a (0.100g, 0.51 mmol) was dissolved in absolute
ethanol/THF (25 mL, 1:5), malononitrile (0.0741 g, 1.12 mmol)
was added, and the mixture was gently heated to produce a yellow
precipitate within 3 min. The solution was allowed to stir for an
additional 20 min, and the precipitate was collected by vacuum fil-
tration and washed with ethanol. Orange crystals were formed by
recrystallisation from methanol/dichloromethane/toluene (10:10:1);
yield 0.108 g, 72%; m.p. 231–233 °C. 1H NMR (400 MHz, CDCl3):
δ = 7.96 (s, 1 H, vinylCH), 2.81 (q, J = 7.7 Hz, 2 H, CH2CH3),
1.24 (t, J = 7.7 Hz, 3 H, CH2CH3) ppm. 13C NMR (101 MHz,
CDCl3): δ = 154.0, 147.1, 136.3, 113.5, 112.2, 82.5, 20.7, 16.4 ppm.
UV/Vis: λ (ε, –1 cm–1) = 438 (17000), 416 (19000), 392 (15000) sh,
372 (12000) sh, 284 (18000), 276 (16000), 210 (37000) nm. IR: ν =
˜
3132, 3039, 2985, 2929, 2897, 2360, 2322, 2227 cm–1. HRMS (EI,
1
70 eV, m/z): calcd. for C16H12N4S 292.0783 [M]+; found 292.0791.
m.p. 101–103 °C. H NMR (300 MHz, [D6]DMSO): δ = 7.77 (dd,
J = 7.5, 4.7 Hz, 2 H, ArH), 7.59 (m, 1 H), 5.72 (t, J = 5.5 Hz, 1
H, OH), 4.91 (d, J = 5.2 Hz, 2 H, CH2OH) ppm. 13C NMR (75
MHz, [D6]DMSO): δ = 139.3, 139.2, 136.4, 133.2, 131.2, 128.4,
125.4, 120.7, 57.7 ppm. UV/Vis: λ (ε, –1 cm–1) = 369 (3400), 352
(3800), 334 (2200) sh, 321 (1200) sh, 285 (5700), 275 (14000), 268
3b: Compound 2b (0.100 g, 0.34 mmol) was dissolved in absolute
ethanol/THF (25 mL, 1:5), and malononitrile (0.04971 g,
0.753 mmol) was added. The colourless solution was gently
warmed to produce a bright yellow precipitate within 30 min. The
precipitate was collected by vacuum filtration and washed with eth-
anol. Yellow crystals were formed by recrystallisation from meth-
anol/dichloromethane/toluene (10:10:1); yield 0.089 g, 67%; m.p.
(13000) sh, 246 (14000), 239 (12000) nm. IR: ν = 3327, 3045, 2922,
˜
1724, 1608 cm–1. LRMS (EI, 70 eV, m/z): 268 [M]+.
C16H12O2S·H2O (286.3): calcd. C 67.11, H 4.93; found C 67.56, H
4.55.
1
309–311 °C. H NMR (400 MHz, CDCl3): δ = 7.70 (d, J = 6.7 Hz,
1 H, vinylCH), 7.47–7.34 (m, 3 H), 7.00 (dd, J = 1.3, 8.1 Hz, 2 H,
ArH) ppm. 13C NMR (101 MHz, [D8]THF): δ = 149.8, 147.3,
130.5, 128.8, 127.1, 126.6, 111.4, 110.6, 81.4 ppm. UV/Vis: λ (ε,
2a: Compound 1a (0.05 g, 0.25 mmol) was dissolved in chloroform
(20 mL), and MnO2 (0.325 g, 3.74 mmol) was then added. The dark
black solution was stirred for 90 min and filtered through Celite.
Slow evaporation of the solvent yielded colourless crystals weighing

–1 cm–1) = 434 (14248), 412 (16983), 391 (14649) sh, 305 (13266),
274 (19002), 237 (27506) sh, 209 (72269) nm. IR: ν = 3124, 3061,
˜
1
0.049 g (99%); m.p. 132–134 °C. H NMR (300 MHz, CDCl3): δ =
3028, 2954, 2223 cm–1. HRMS (EI, 70 eV, m/z): calcd. for
10.10 (s, 1 H, CHO), 2.94 (q, J = 7.5 Hz, 2 H, CH2CH3), 1.25 (t, C24H12N4S 388.0783 [M]+; found 388.0784.
Eur. J. Org. Chem. 2009, 5635–5646
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5643

R. P. Jimenez, M. Parvez, T. C. Sutherland, J. Viccars
FULL PAPER
3c: Compound 2c (0.05 g, 0.189 mmol) was dissolved in absolute
ethanol/THF (25 mL, 1:5), and malononitrile (0.0275 g,
0.416 mmol) was added. The colourless solution was warmed and
produced a dark red precipitate after 20 min, which was collected
by vacuum filtration and washed with ethanol. The product was
crystallised from methanol/dichloromethane/toluene (10:10:1);
ethanol. Red crystals were grown from methanol/dichloromethane/
toluene (10:10:1); yield 0.0817 g, (91%); m.p. 342–344 °C. 1H NMR
(399 MHz, [D6]DMSO, 345 K): δ = 8.25 (s, 1 H, vinylCH), 8.15 (d,
J = 7.0 Hz, 1 H, ArH), 8.03 (d, J = 8.2 Hz, 1 H, ArH), 7.82–7.75
(m, 2 H), 7.65 (d, J = 3.7 Hz, 1 H, ArH), 7.25 (t, J = 4.4 Hz, 1 H,
ArH) ppm. 13C NMR: the material was not soluble enough to ac-
yield 0.0462 g, 68%; m.p. Ͼ 350 °C. 1H NMR (399 MHz, [D6]- quire a spectrum. UV/Vis: λ (ε, –1 cm–1) = 513 (17000), 479
DMSO, 300 K): δ = 10.53 (s, 1 H, vinylCH), 9.18 (s, 1 H, vinylCH), (20000), 451 (14000) sh, 383 (22000), 368 (21000), 289 (8000), 254
8.67 (d, J = 7.2 Hz, 1 H, ArH), 8.56 (d, J = 7.0 Hz, 1 H, ArH),
8.17 (d, J = 8.2 Hz, 2 H, ArH), 7.86–7.80 (m, 2 H) ppm. 13C NMR:
the material was insufficiently soluble to acquire a spectrum. UV/
Vis: λ (ε, –1 cm–1) = 491 (7600), 453 (10000), 381 (20000) sh, 358
(23000), 276 (11000), 251 (33000) sh, 244 (40000), 209 (103000) nm.
(14000), 213 (37000) nm. IR: ν = 3427, 3109, 3068, 3028, 2926,
˜
2852, 2212 cm–1. HRMS (EI, 70 eV, m/z): calcd. for C28H14N2S3
474.0319 [M]+; found 474.0300.
5a: Compound 2a (0.105 g, 0.534 mmol) was dissolved in dry
dichloromethane (20 mL), and indole (0.263 g, 2.14 mmol) was
added, followed by the quick addition of borontrifluoride–diethyl
ether (0.0539 mL, 0.428 mmol). The flask was shielded from the
light and stirred under an atmosphere of N2. After 2 h, the solvent
was removed in vacuo, and the residue was purified by column
chromatography (silica gel, dichloromethane/methanol, 20:1), af-
IR: ν = 3082, 3034, 2900, 2831, 2229 cm–1. HRMS (EI, 70 eV, m/z):
˜
calcd. for C22H8N4S 360.047 [M]+; found 360.0473.
4a: Potassium tert-butoxide (0.0114 g, 0.102 mmol) was dissolved
in absolute ethanol (3 mL). 2-Thiopheneacetonitrile (0.0628 g,
0.510 mmol) was added to the solution, and the mixture was al-
lowed to stir at room temperature for an additional 30 min. In a
separate flask, 2a (0.05 g, 0.255 mmol) was dissolved in absolute
ethanol/THF (4 mL, 3:1). The solution of 2a was then added to
the 2-thiopheneacetonitrile solution, and the mixture gave a red
precipitate after 30 min of stirring at room temperature. The pre-
cipitate was collected by vacuum filtration and washed with etha-
nol. Red crystals were formed by recrystallisation from methanol/
dichloromethane/toluene (10:10:1); yield 0.1005 g (97%); m.p. 241–
1
fording a dark red solid; yield 0.157 g, 47%; m.p. 191–193 °C. H
NMR (399 MHz, [D6]DMSO, 355 K): δ = 10.70 (s, 2 H, NH), 8.31
(s, 2 H, NH), 7.69–6.86 (m, 19 H), 6.33 (s, 1 H), 2.76 (q, J = 7.4 Hz,
2 H, CH2CH3), 2.33 (q, J = 7.5 Hz, 2 H, CH2CH3), 1.09 (t, J =
7.4 Hz, 3 H, CH2CH3), 0.90 (t, J = 7.5 Hz, 3 H, CH2CH3) ppm.
13C NMR (100 MHz, [D6]DMSO, 355 K): δ = 137.2, 131.9, 128.4,
126.9, 126.0, 125.3, 124.4, 122.9, 122.0, 121.6, 121.3, 120.99, 119.2,
119.1, 117.8, 117.4, 112.3, 112.1, 67.5, 31.0, 25.6 ppm. UV/Vis: λ
(ε, –1 cm–1) 508 (17000), 458 (19000), 388 (10000) sh, 290 (23000)
1
242 °C. H NMR (400 MHz, CDCl3): δ = 7.51 (s, 1 H, vinylCH),
7.38 (dd, J = 1.0, 3.7 Hz, 1 H, ArH), 7.30 (dd, J = 1.0, 5.1 Hz, 1
H, ArH), 7.08 (dd, J = 3.7, 5.1 Hz, 1 H, ArH), 2.75 (q, J = 7.6 Hz,
2 H, CH2CH3), 1.21 (t, J = 7.6 Hz, 3 H, CH2CH3) ppm. 13C NMR
(100 MHz, CDCl3): δ = 148.1, 139.5, 134.6, 129.0, 128.4, 127.5,
126.3, 116.6, 104.3, 20.5, 16.1 ppm. UV/Vis: λ (ε, –1 cm–1) = 491
(17400) sh, 458 (32000), 438 (30400) sh, 320 (10000), 317 (10200),
sh, 282 (26000), 250 (29000), 229 (57000) nm. IR: ν = 3633, 3412,
˜
3059, 2966, 2929, 2872 cm–1. HRMS (TOF-MS, m/z): calcd. for
C42H34N4S 627.2522 [M + H]+; found 627.2546.
5b: Compound 2b (0.100 g, 0.345 mmol) was dissolved in dry
dichloromethane (20 mL), and indole (0.194 g, 1.66 mmol) was
added, followed by the quick addition of borontrifluoride–diethyl
ether (0.1824 mL, 1.45 mmol). The flask was shielded from the
light and stirred under an atmosphere of N2. After 2 h, the solvent
was removed in vacuo, and the residue was purified by column
chromatography (silica gel, dichloromethane/methanol, 20:1) af-
fording a dark red solid; yield 0.122 g, 49%; m.p. Ͼ 350 °C. 1H
NMR (399 MHz, [D6]DMSO): δ = 10.95 (s, 1 H), 8.24 (s, 1 H),
7.58–6.57 (m, 31 H), 6.04 (s, 1 H) ppm. 13C NMR (101 MHz, [D6]-
DMSO): δ = 141.2, 137.1, 135.6, 135.1, 134.6, 130.3, 130.0, 129.9,
128.7, 127.9, 127.7, 127.4, 127.0, 126.4, 125.7, 124.3, 124.0, 123.6,
121.7, 121.2, 119.1, 119.1, 117.5, 115.3, 115.3 ppm. UV/Vis: λ (ε,
291 (7900) sh, 274 (4700) nm. IR: ν = 3448, 3080, 3030, 2974, 2935,
˜
2877, 2210 cm–1. LRMS (EI, 70 eV, m/z): C22H18N2S3 [M]+ 406.0.
C22H18N2S3 (406.1): calcd. C 64.99, H 4.46, N 6.89; found C 64.83,
H 4.09, N 6.83.
4b: Potassium tert-butoxide (0.0077 g, 0.068 mmol) and 2-thio-
pheneacetonitrile (0.0438 g, 0.342 mmol) were dissolved in absolute
ethanol (3 mL) and stirred for 15 min. In a separate flask, 2b
(0.050 g, 0.171 mmol) was dissolved in absolute ethanol/THF
(4 mL, 2.5:1.5). The solution of 2b was then added to the thio-
pheneacetonitrile mixture, and after 20 min, a reddish-orange pre-
cipitate was collected by vacuum filtration and washed with etha-
nol. Red crystals formed from methanol/dichloromethane/toluene
(10:10:1); yield 0.081 g, 94%; m.p. 271–275 °C. 1H NMR
(400 MHz, CDCl3): δ = 7.35 (dd, J = 0.9, 3.7 Hz, 1 H, ArH), 7.34
(s, J = 1.0 Hz, 1 H, vinylCH), 7.32 (m, 3 H), 7.25 (dd, J = 1.0,
5.0 Hz, 1 H, ArH), 7.06 (m, 3 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 146.9, 139.2, 135.6, 133.8, 130.7, 130.6, 128.3, 128.2,
128.2, 127.6, 126.6, 116.5, 105.4 ppm. UV/Vis: λ (ε, –1 cm–1) = 487
(20000) sh, 458 (32000), 437 (28000), 405 (15000), 343 (16000), 332

–1 cm–1) = 522 (11000), 458 (14000), 340 (6000), 281 (24000), 242
(28000) nm. IR: ν = 3635, 3417, 3057, 2926, 1409 cm–1. HRMS (EI,
˜
70 eV, m/z): calcd. for C50H34N4S 722.2504 [M]+; found 722.2485.
5c: Compound 2c (0.016 g, 0.061 mmol) was dissolved in dry
dichloromethane (8 mL), and indole (0.030 g, 0.254 mmol) was
added, followed by the quick addition of borontrifluoride–diethyl
ether (0.0345 mL, 0.243 mmol). The flask was shielded from the
light and stirred under an atmosphere of N2. After 2 h, the solvent
was removed in vacuo, and the residue was directly purified by
column chromatography [silica gel, dichloromethane/methanol
(20:1)] affording a dark purple solid; yield 0.017 g, 41%; m.p. Ͼ
350 °C. 1H NMR (399 MHz, [D6]DMSO, 370 K): δ = 8.34 (s, 1 H),
8.00–6.80 (m, 14 H) ppm. 13C NMR: the material was not soluble
enough to acquire a spectrum. UV/Vis: λ (ε, –1 cm–1) = 602 (1500),
(16000), 286 (7600) nm. IR: ν = 3358, 3105, 3059, 3026, 2924, 2212
˜
cm–1. HRMS (EI, 70 eV, m/z): calcd. for C30H18N2S3 502.0632
[M]+; found 502.6723.
4c: Potassium tert-butoxide (0.0849 g, 0.757 mmol) and 2-thio-
pheneacetonitrile (0.0466 g, 0.378 mmol) were dissolved in absolute
ethanol (3 mL) and stirred for 15 min. In a separate flask, 2c
(0.050 g, 0.189 mmol) was dissolved in absolute ethanol/THF 539 (4000) sh, 462 (9000), 385 (12000), 324 (17000), 277 (33000)
(4 mL, 2.5:1.5). The solution of 2c was then added to the thio-
pheneacetonitrile solution. Within 15 min, a dark red precipitate
formed, which was collected by vacuum filtration and washed with
sh, 245 (46000) nm. IR: ν = 3404, 3109, 3057, 2924, 2870, 1483,
˜
1415 cm–1. HRMS (TOF-MS, m/z): calcd. for C48H30N4S 695.2269
[M + H]+; found 695.2237.
5644
www.eurjoc.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 5635–5646

Synthesis and Properties of Thiophene Derivatives
[23] A. Dhanabalan, J. K. J. Van Duren, P. A. Van Hal, J. L. J.
Van Dongen, R. A. J. Janssen, Adv. Funct. Mater. 2001, 11,
255–262.
[24] P.-T. Wu, F. S. Kim, R. D. Champion, S. A. Jenekhe, Macro-
molecules 2008, 41, 7021–7028.
[25] L. R. Dalton, Handbook of Conducting Polymers (3rd Edition)
2007, vol. 2, p. 6/1–6/39.
Supporting Information (see also the footnote on the first page of
1
this article): H and 13C NMR spectra for 1–5, a crystal compari-
son Table for 1b and 2a–c, the crystallographic packing for 1b, 2a–
c, and 3a,b, the computational data for 1–5, the FMOs of 1–5, UV/
Vis spectra of 1a–c, 3 and 4, cyclic voltammetry of 1–4, solution
fluorescence spectra of 3c, 4b, 4c, 5b and 5c, and solid-state fluores-
cence of 3a, 3b and 4.
[26] J. Gierschner, J. Cornil, H.-J. Egelhaaf, Adv. Mater. 2007, 19,
173–191.
CCDC-695325 (for 1b), -695326 (for 2a), -695327 (for 2b), -695328
(for 2c), -735357 (for 3a), -735358 (for 3b) and -735359 (for 4a)
contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge via www.ccdc.cam.ac.uk/
data_request/cif.
[27] A. Kohler, J. S. Wilson, R. H. Friend, Adv. Mater. 2002, 14,
701–707.
[28] U. Mitschke, P. Bauerle, J. Mater. Chem. 2000, 10, 1471–1507.
[29] D. F. Perepichka, M. R. Bryce, Angew. Chem. Int. Ed. 2005, 44,
5370–5373.
[30] H. S. Cho, D. H. Jeong, S. Cho, D. Kim, Y. Matsuzaki, K.
Tanaka, A. Tsuda, A. Osuka, J. Am. Chem. Soc. 2002, 124,
14642–14654.
Acknowledgments
[31] A. Tsuda, H. Furuta, A. Osuka, J. Am. Chem. Soc. 2001, 123,
The authors thank the Natural Sciences and Engineering Research
Council of Canada, the Alberta Government and the Canadian
Foundation for Innovation for funding.
10304–10321.
[32] M. Ocafrain, T. K. Tran, P. Blanchard, S. Lenfant, S. Godey,
D. Vuillaume, J. Roncali, Adv. Funct. Mater. 2008, 18, 2163–
2171.
[33] F. Moggia, F. Fages, H. Brisset, C. Chaix, B. Mandrand, E.
Levillain, J. Roncali, J. Electroanal. Chem. 2009, 626, 42–46.
[34] L. Pouchain, O. Aleveque, Y. Nicolas, A. Oger, C.-H. Le Re-
gent, M. Allain, P. Blanchard, J. Roncali, J. Org. Chem. 2009,
74, 1054–1064.
[1] M.-C. Chen, Y.-J. Chiang, C. Kim, Y.-J. Guo, S.-Y. Chen, Y.-J.
Liang, Y.-W. Huang, T.-S. Hu, G.-H. Lee, A. Facchetti, T. J.
Marks, Chem. Commun. 2009, 1846–1848.
[2] R. P. Ortiz, J. Casado, V. Hernandez, J. T. L. Navarrete, J. A.
Letizia, M. A. Ratner, A. Facchetti, T. J. Marks, Chem. Eur. J.
2009, 15, 5023–5039.
[35] M. Bendikov, F. Wudl, D. F. Perepichka, Chem. Rev. 2004, 104,
4891–4946.
[3] H. Usta, A. Facchetti, T. J. Marks, J. Am. Chem. Soc. 2008,
[36] R. J. Mullins, D. R. Williams, Name React. Heterocycl. Chem.
2005, 199–206.
130, 8580–8581.
[4] H. Usta, C. Risko, Z. Wang, H. Huang, M. K. Deliomeroglu,
A. Zhukhovitskiy, A. Facchetti, T. J. Marks, J. Am. Chem. Soc.
2009, 131, 5586–5608.
[5] M.-H. Yoon, S. A. DiBenedetto, A. Facchetti, T. J. Marks, J.
Am. Chem. Soc. 2005, 127, 1348–1349.
[6] J. L. Segura, N. Martin, J. Mater. Chem. 2000, 10, 2403–2435.
[7] M. Muccini, Nat. Mater. 2006, 5, 605–613.
[8] H. Usta, A. Facchetti, T. J. Marks, Org. Lett. 2008, 10, 1385–
1388.
[9] C. Kim, A. Facchetti, T. J. Marks, Science 2007, 318, 76–80.
[10] P. Gao, D. Beckmann, H. N. Tsao, X. Feng, V. Enkelmann, M.
Baumgarten, W. Pisula, K. Muellen, Adv. Mater. 2009, 21, 213–
216.
[11] M. Surin, P. Sonar, A. C. Grimsdale, K. Muellen, S. De Feyter,
S. Habuchi, S. Sarzi, E. Braeken, A. Ver Heyen, M.
Van der Auweraer, F. C. De Schryver, M. Cavallini, J.-F. Mou-
lin, F. Biscarini, C. Femoni, R. Lazzaroni, P. Leclere, J. Mater.
Chem. 2007, 17, 728–735.
[12] P. Gao, X. Feng, X. Yang, V. Enkelmann, M. Baumgarten, K.
Muellen, J. Org. Chem. 2008, 73, 9207–9213.
[13] M. Segal, M. Singh, K. Rivoire, S. Difley, T. Van Voorhis,
M. A. Baldo, Nat. Mater. 2007, 6, 374–378.
[14] I. F. Perepichka, D. F. Perepichka, H. Meng, F. Wudl, Adv.
Mater. 2005, 17, 2281–2305.
[37] H. Wynberg, D. J. Zwanenburg, J. Org. Chem. 1964, 29, 1919–
1922.
[38] R. A. Aitken, A. N. Garnett, J. Chem. Soc. Perkin Trans. 1
2000, 3020–3021.
[39] F. Banishoeib, A. Henckens, S. Fourier, G. Vanhooyland, M.
Breselge, J. Manca, T. J. Cleij, L. Lutsen, D. Vanderzande,
L. H. Nguyen, H. Neugebauer, N. S. Sariciftci, Thin Solid Films
2008, 516, 3978–3988.
[40] G. Trippe, D. Canevet, F. Le Derf, P. Frere, M. Salle, Tetrahe-
dron Lett. 2008, 49, 5452–5454.
[41] J. Nakayama, Y. Hasegawa, Y. Sugihara, A. Ishii, Sulfur Lett.
1999, 22, 131–140.
[42] R. Chandra, A. Sarkar, N. Biswas, Proc. Indian Natl. Sci. Acad.
Part A 1994, 60, 465–470.
[43] S. V. Ley, S. C. Smith, P. R. Woodward, Tetrahedron 1992, 48,
1145–1174.
[44]
[45]
[46]
[47]
[48]
[49]
[50]
[51]
[52]
[53]
M. Bourgeaux, W. G. Skene, J. Org. Chem. 2007, 72, 8882–
8892.
S. Destri, M. Pasini, C. Pelizzi, W. Porzio, G. Predieri, C. Vig-
nali, Macromolecules 1999, 32, 353–360.
E. H. Elandaloussi, P. Frere, P. Richomme, J. Orduna, J. Garin,
J. Roncali, J. Am. Chem. Soc. 1997, 119, 10774–10784.
A. K. Mohanakrishnan, M. V. Lakshmikantham, M. P. Cava,
R. D. Rogers, L. M. Rogers, Tetrahedron 1998, 54, 7075–7080.
Y. Shimizu, Z. Shen, S. Ito, H. Uno, J. Daub, N. Ono, Tetrahe-
dron Lett. 2002, 43, 8485–8488.
Y. Shimizu, Z. Shen, T. Okujima, H. Uno, N. Ono, Chem.
Commun. 2004, 374–375.
H. Uoyama, K. Nakamura, M. Tukiji, M. Furukawa, H. Uno,
Heterocycles 2007, 73, 673–688.
P. v. R. Schleyer, C. Maerker, A. Dransfeld, H. Jiao, N. J. R.
v. E. Hommes, J. Am. Chem. Soc. 1996, 118, 6317–6318.
L. Wang, H. J. Wang, W. B. Dong, Q. Y. Ge, L. Lin, Struct.
Chem. 2007, 18, 25–31.
M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, J. A. Montgomery, T. V. K. N.
Kudin Jr., J. C. Burant, J. M. Millam, S. S. Iyengar, J. Tomasi,
V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G. A.
Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R.
[15] S. Cho, J. Yuen, J. Y. Kim, K. Lee, A. J. Heeger, Appl. Phys.
Lett. 2006, 89, 153505/153501–153505/153503.
[16] C. Yang, S. Cho, R. C. Chiechi, W. Walker, N. E. Coates, D.
Moses, A. J. Heeger, F. Wudl, J. Am. Chem. Soc. 2008, 130,
16524–16526.
[17] J. Pei, W.-L. Yu, W. Huang, A. J. Heeger, Macromolecules 2000,
33, 2462–2471.
[18] A. G. MacDiarmid, Synth. Met. 2001, 125, 11–22.
[19] Y. Shirota, J. Mater. Chem. 2000, 10, 1–25.
[20] L. M. Campos, A. Tontcheva, S. Guenes, G. Sonmez, H. Neug-
ebauer, N. S. Sariciftci, F. Wudl, Chem. Mater. 2005, 17, 4031–
4033.
[21] N. Armaroli, V. Balzani, Angew. Chem. Int. Ed. 2007, 46, 52–
66.
[22] J. Dai, X. Jiang, H. Wang, D. Yan, Appl. Phys. Lett. 2007, 91,
253503/253501–253503/253503.
Eur. J. Org. Chem. 2009, 5635–5646
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5645

R. P. Jimenez, M. Parvez, T. C. Sutherland, J. Viccars
Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. [61] T. Sone, Bull. Chem. Soc. Jpn. 1964, 37, 1197–1200.
FULL PAPER
Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian,
J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts,
R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pom-
elli, J. W. Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth, P.
Salvador, J. J. Dannenberg, V. G. Zakrzewski, S. Dapprich,
A. D. Daniels, M. C. Strain, O. Farkas, D. K. Malick, A. D.
[62] D. Lorcy, K. D. Robinson, Y. Okuda, J. L. Atwood, M. P.
Cava, J. Chem. Soc., Chem. Commun. 1993, 345–347.
[63] M. Scholz, G. Gescheidt, U. Schoeberl, J. Daub, J. Chem. Soc.
Perkin Trans. 2 1992, 2137–2143.
[64] H. A. Ho, H. Brisset, E. H. Elandaloussi, P. Frere, J. Roncali,
Adv. Mater. 1996, 8, 990–994.
Rabuck, K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui, [65] U. Schlick, F. Teichert, M. Hanack, Synth. Met. 1998, 92, 75–
A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov, G. Liu,
A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J.
Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara,
M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W.
Wong, C. Gonzalez, J. A. Pople, Gaussian 03, Revision E.01,
Gaussian, Inc., Wallingford, CT, 2004.
85.
[66] G. Zotti, S. Zecchin, G. Schiavon, A. Berlin, G. Pagani, M.
Borgonovo, R. Lazzaroni, Chem. Mater. 1997, 9, 2876–2886.
[67] P. Wagner, D. L. Officer, M. Kubicki, Acta Crystallogr., Sect.
E: Struct. Rep. Online 2006, 62, o5931–o5932.
[68] S. Echinger, U. Schmid, F. Teichert, J. Hieber, H. Ritter, M.
Hanack, Synth. Met. 1993, 61, 163–165.
[54] T. M. Pappenfus, B. J. Hermanson, T. J. Helland, G. G. W. Lee,
S. M. Drew, K. R. Mann, K. A. McGee, S. C. Rasmussen, Org.
Lett. 2008, 10, 1553–1556.
[69] M. Hanack, G. Hieber, K. M. Mangold, H. Ritter, U. Roehrig,
U. Schmid, Synth. Met. 1993, 55, 827–832.
[55] P. Leriche, P. Frere, A. Cravino, O. Aleveque, J. Roncali, J. Org.
Chem. 2007, 72, 8332–8336.
[56] H. Zimmer, K. Sudsuansri, H. B. Mark, B. Ziegler, Phosphorus
Sulfur Silicon Relat. Elements 1997, 122, 269–286.
[70] M. Hanack, K.-M. Mangold, U. Roehrig, C. Maichle-
Moessmer, Synth. Met. 1993, 60, 199–210.
[71] H. Ritter, K. M. Mangold, U. Roehrig, U. Schmid, M. Han-
ack, Synth. Met. 1993, 55, 1193–1197.
[57] A. F. Diaz, J. Crowley, J. Bargon, G. P. Gardini, J. B. Torrance, [72] A. Ishii, Y. Horikawa, I. Takaki, J. Shibata, J. Nakayama, M.
J. Electroanal. Chem. Interfacial. Electrochem. 1981, 121, 355–
Hoshino, Tetrahedron Lett. 1991, 32, 4313–4316.
[73] S. Ito, S. Kikuchi, T. Okujima, N. Morita, T. Asao, J. Org.
Chem. 2001, 66, 2470–2479.
[74] S.-i. Takekuma, K. Sonoda, T. Minematsu, H. Takekuma, Tet-
rahedron 2008, 64, 3802–3812.
361.
[58] D. Jones, M. Guerra, L. Favaretto, A. Modelli, M. Fabrizio,
G. Distefano, J. Phys. Chem. 1990, 94, 5761–5766.
[59] H. A. Ho, H. Brisset, E. H. Elandaloussi, P. Frère, J. Roncali,
Adv. Mater. 1996, 8, 990–994.
Received: July 27, 2009
Published Online: September 21, 2009
[60] J. Roncali, Macromol. Rapid Commun. 2007, 28, 1761–1775.
5646
www.eurjoc.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 5635–5646