Bridged 3,3″′-didodecylquaterthiophene-based dimers: Design, synthesis, and optoelectronic properties

Article abstract of DOI:10.1016/j.tet.2012.04.072

Five functionalized quaterthiophene dimers including a non-conjugated bridge have been designed and efficiently synthesized. The synthetic pathways explored toward these dimers revealed unexpected features, such as the direct formation of secondary and tertiary quaterthiophene amines through a procedure initially developed for the preparation of primary amine exclusively. All these dimers possess a promising potential for the elaboration of semiconducting materials with a charge transport of higher dimensionality compared to quaterthiophene.

Full text of DOI:10.1016/j.tet.2012.04.072

Tetrahedron 68 (2012) 5599e5605
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Bridged 3,3000-didodecylquaterthiophene-based dimers: design, synthesis,
and optoelectronic properties
,
a
b
a
Claude Niebel a , Maud Jenart , Christelle Gautier , Yves Henri Geerts
*
a
ꢀ
Universite Libre de Bruxelles (ULB), Laboratory of Polymer Chemistry, C.P. 206/01, Boulevard du Triomphe, 1050 Brussels, Belgium
Universite d’Angers, Laboratoire MOLTECH-Anjou, CNRS UMR 6200, 2 boulevard Lavoisier, 49045 Angers, France
b
ꢀ
a r t i c l e i n f o
a b s t r a c t
Article history:
Five functionalized quaterthiophene dimers including a non-conjugated bridge have been designed and
efficiently synthesized. The synthetic pathways explored toward these dimers revealed unexpected
features, such as the direct formation of secondary and tertiary quaterthiophene amines through
a procedure initially developed for the preparation of primary amine exclusively. All these dimers
possess a promising potential for the elaboration of semiconducting materials with a charge transport of
higher dimensionality compared to quaterthiophene.
Received 29 February 2012
Received in revised form 13 April 2012
Accepted 19 April 2012
Available online 26 April 2012
Keywords:
Ó 2012 Elsevier Ltd. All rights reserved.
Oligothiophene synthesis
Organic electronics
Mitsunobu coupling
Reductive amination
Optoelectronic properties
1. Introduction
made on the superexchange charge transfer in organic and organo-
metallic donorebridgeeacceptor systems have involved the one-step
Charge transfer in
p
-conjugated oligomers is a crucial mechanism
tunneling through a uniform and rectangular barrier. Wenger et al.
have extended this study using metal complex based dyads with
a molecular bridge composed of p-dimethoxybenzene, which im-
poses a so called double barrier to hole transfer.11 In this particular
donorebridgeeacceptor system, the photoinduced hole transfer has
been measured to be one order of magnitude more rapid than hole
transfer across a comparable uniform barrier, emphasizing even fur-
in the field of organic electronics.1e3 Numerous studies have been
made on organic and organometallic donorebridgeeacceptor sys-
tems to determine the parameters influencing the charge transfer.4e6
These fundamental understandings have also lead to the distinction
between two intramolecular charge transfer mechanisms: the
superexchange, also named charge-tunneling, and the hopping
mechanism.4,6,7 The charge-tunneling is predominant when the
transient reduction of the bridging moiety is thermodynamically
ther the importance of the tunneling-energy gap
D 3 .
Besides, dyads composed of two identical organic redox centers
separated by a bridging unit have also been studied for charge
delocalization purposes.12,13 If most of these investigations have
impossible. The distance decayconstant (
b) and tunneling-energy gap
(
D 3
) appear of pivotal importance for superexchange charge transfer.8
Indeed, in their study of the photoinduced charge transfer in synthetic
DNA hairpin, Wasiliewski et al. have shown the exponential decrease
of its rate constant with increasing the distance between
donoreacceptor, made of guanine and stilbene, respectively.9 Beratan
et al. have also investigated the electron transfer in synthetic DNA
hairpin with an additional focus on the influence of donoreacceptor
energetics relative to the bridge separating both redox centers. Their
results show the strong dependence of DNA electron superexchange
not on the donoreacceptor distance but rather on the tunneling-
energy gap.10 In addition, most of the numerous investigations
been made on systems with a p-conjugated bridge, some attention
has also been paid on dyads incorporating a non-conjugated spacer.
€
For instance, Mullen et al. have shown that the mode of linking two
anthryl electrophores through a non-conjugated bridge drastically
affects the rate of the intramolecular electron transfer.14 Our group
has recently reported on the interest of introducing a non-
conjugated ethylene bridge between two 3,3000-didodecylquater-
thiophene cores (B1) to enhance the charge transport di-
mensionality in this type of semiconducting materials (Fig. 1).15
Indeed, 3,3000-didodecylquaterthiophene (1) is known to form
a lamellar-type structure with a one-dimensional charge transport
ability.16 The ethylene bridge in B1 allows an additional electronic
coupling between the two oligothiophenes cores, pushing the solid
state charge transport dimensionality from 1D to 2D.15
* Corresponding author. Tel.: þ32 2650 5390; fax: þ32 2650 5410; e-mail
address: claude.niebel@ulb.ac.be (C. Niebel).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2012.04.072

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C. Niebel et al. / Tetrahedron 68 (2012) 5599e5605
Fig. 1. Bridged didodecylquaterthiophene dimers B1eB6.
The derivatization of the non-conjugated spacer in B1 is thought
to analogously affect the charge transport properties of this type of
semiconducting materials. The presence of an additional organic
moiety within the bridge will provide the quaterthiophene dimer
with a supplementary functional group together with modifying
Scheme 1. Explored synthetic pathways toward quaterthiophene dimer B2.
The diol intermediate 4 was finally prepared by the dinucleophilic
attack of mono-lithiated quaterthiophene on terephthaldicarbox-
aldehyde. The low yield of this reaction (12%) can be explained by the
relatively low reactivity of 1 mono-lithiated intermediate. This low
reactivity is also illustrated by the poor yield obtained for the prep-
aration of the mono-aldehyde 3 followinga conventional n-BuLi/DMF
procedure.15 The subsequent reductive deoxygenation of diol 4 to-
ward B2 was carried out using the convenient and efficient
ZnI2eNaCNBH3 procedure described by Lau et al.19
the
b and D 3 of the system. The dimers B2, B3/B4 and B5 in-
corporate, respectively a phenylene, diamino phenylene, and
pyromellitic diimine units within the bridge (Fig. 1), which obvi-
ously enlarge the distance between the two oligothiophene cores
and thus increase the
b coefficient compared to the reference B1.
The introduction of a heteroatom, such as nitrogen in the non-
conjugated spacer is however thought to conduct to an energetic
double barrier, potentially shifting the tunneling-energy gap
D 3 in
favor of a promoted intramolecular charge transfer comparable to
the one observed by Wenger et al.11 (See Fig. S12 in Supplementary
data). This feature would also allow an enhancement of the charge
transport dimensionality from 1D to 2D in such materials. Qua-
terthiophene dimers B6 and B3/B4 present such an amino-
functionalization within the bridge compared to B1 and B2, re-
spectively. The dimers B2eB6, in addition to B1, therefore represent
some valuable oligothiophenes for the production of functionalized
semiconducting materials with a higher charge transport di-
mensionality compared to quaterthiophene 1. In this purpose, we
have decided to prepare the 3,3000-didodecylquaterthiophene-based
dimers B2eB6.
Concerning the preparation of the phenylenediamine de-
rivatives B3 and B4, synthetic investigations were firstly tried on
simple aniline (Scheme 2). The condensation of aniline with the
mono-quaterthiophene aldehyde 3 went smoothly, even without
the use of a Dean Stark apparatus to remove the water formed
during the reaction. The reduction of the imine 5 needed hard
conditions. Indeed, 20 h of reflux in the presence of about 5 equiv of
sodium borohydride were not sufficient to totally reduce 5, and the
addition of a new portion of sodium borohydride (w5 equiv) was
necessary to complete the reaction. The commonly extracted crude
product appeared to be almost pure looking at its 1H NMR, and is
obtained in nearly quantitative yield. Nevertheless, its further pu-
rification by chromatography resulted in partial decomposition of
the target amine 6 on silica gel, which explains its isolated yield of
only 54%. As for the aniline, the condensations of para- and meta-
penylenediamine with mono-aldehyde 3 allowed the preparation
of imines 7 and 8, respectively in quantitative yield. The same
In this synthetic paper, we report on the synthetic pathways
explored for the preparation of quaterthiophene bridged dimers
B2eB6. The optoelectronic properties of all these dimers will then
be discussed, together with the references 1 and B1 ones.
2. Synthesis
The bridged quaterthiophene reference B1 was prepared from
the mono-formylated derivative 3 in two steps.15 Several differ-
ent synthetic pathways were investigated to produce the phe-
nylene derivative B2. First of all, a typical AlCl3 or SnCl4 mediated
Friedel and Crafts acylation was tried using terephthaloyl
dichloride as acylating agent.17 The aim was to produce the in-
termediate 2, which could further be reduced into target B2
(Scheme 1). This acylation was however unsuccessful and led to
the complete recovery of unreacted quaterthiophene 1. The at-
tempt
of
direct
dinucleophilic
substitution
of
1,4-
bis(bromomethyl)benzene by a mono-lithiated thiophene in-
termediate also resulted in the complete recovery of starting
quaterthiophene 1. Moreover, the addition of para-bis-lithiated
benzene, prepared from para-dibromobenzene,18 to a solution of
quaterthiophene mono-aldehyde
3 engendered the partial
decompostion of the starting aldehyde without any traces of the
expected diol 4 (Scheme 1).
Scheme 2. Synthesis of quaterthiophene derivatives 6, B3 and B4.

C. Niebel et al. / Tetrahedron 68 (2012) 5599e5605
5601
procedure was also applied to ortho-phenylenediamine, but in this
case the reaction didn’t proceed to the formation of the expected
diimine. This feature is certainly explained by sterical hindrance
effects due to the spatial proximity of the two amino functions in
ortho-phenylenediamine. It is also worth to notice that both dii-
mine derivatives 7 and 8 are used further without any additional
purification. Indeed, an attempt of purification by chromatography
shows, in both cases, the partial hydrolysis of the diimine on silica
gel, even after neutralization of silica gel acidity with triethylamine.
The reduction of both diimines required even stronger conditions
than the one used for 5. The crude product obtained after a 24 h
reflux of 7 and 8, respectively, in the presence of 10 equiv of sodium
borohydride was actually composed of a mixture of mono- and
direduced species. The use of lithium borohydride in large excess
(30 equiv) was finally sufficient to get a complete reduction leading
to target B3 and B4. As in the case of 6, both bridged dimers B3 and
B4 were collected nearly quantitatively as crude products. How-
ever, their purification by chromatography on silica gel again in-
duced a loss of isolated compounds due to partial decomposition.
The bridged quaterthiophene derivative B5 was thought to be
produced through a Mitsunobu coupling involving the quaterthio-
phene primary alcohol 9 (Scheme 3). 9 was nearly quantitatively
obtained by a simple reduction of the corresponding aldehyde 3
using sodium borohydride. Concerning the coupling step, synthetic
investigations were firstly tried on phthalimide before going to its
pyromellitic analog. Typical Mitsunobu conditions,20 including the
slow addition of diisopropyl azodicarboxylate to a mixture of the
other reagents, allowed the synthesis of the imide 10 in an accept-
able yield of 58%. The same synthetic procedure was then used to
prepare the target bridged derivative B5 in 34% yield using pyro-
mellitic diimide as nucleophilic agent.
Scheme 4. Reductive amination of quaterthiophene aldehyde
ammonia.
3
using aqueous
3. Optoelectronic properties in dilute solution
The absorption and fluorescence properties of quaterthiophene
1 and its the six bridged derivatives B1eB6 were recorded in THF
solutions (See Fig. S9 and S10 in Supplementary data). All the ab-
sorption spectra present an analog predominant absorption band,
which is known to correspond to the quaterthiophene HOMO-
eLUMO transition.22,23 The structureless feature of all these ab-
sorption bands shows the flexibility of the two oligothiophene
cores in the ground state. A small red shift of the lmax(abs) is ob-
served when going from the quaterthiophene 1 to its bridged de-
rivatives B1eB6, which is certainly due to inductive effect of the
bridge. Moreover, the lmax(abs) of each bridged dimers are closely
the same indicating that the nature of the non-conjugated bridge
has no influence on the quaterthiophene electronic transitions. The
extinction coefficients of the dimers B1eB6 are of the same order of
magnitude and correspond to the double of their precursor 1 one,
as expected (Table 1). Besides, all the fluorescence spectra of these
compounds show vibrational structure due to the known rigid
quinoid form adopted by oligothiophenes in S1 excited state.24e26
A
light bathochromic shift is again observed when going from
lmax(em) of 1 to the dimers B1eB6. As it is the case for the UVevis
absorption, the lmax(em) of the derivatives B1eB6 are almost equal,
which confirms the absence of influence of the bridge on the
quaterthiophene electronic transition (Table 1).
Table 1
Molar extinction coefficients
lmax(em)) maximum of quaterthiophene 1 and its bridged derivatives B1eB6 in
10ꢀ5 M solution in THF
3
, absorption (lmax(abs)) and fluorescence
max
(
3
(Mꢀ1 cmꢀ1
)
lmax(abs) (nm/eV)
lmax(em) (nm/eV)
max
1
30,000
61,000
59,000
64,000
63,000
64,000
59,000
376/3.30
384/3.23
383/3.24
384/3.23
386/3.22
382/3.25
384/3.23
453/2.74
458/2.71
460/2.70
459/2.70
460/2.70
458/2.71
459/2.70
B1
B2
B3
B4
B5
B6
Scheme 3. Synthesis of quaterthiophene derivatives 10 and B5.
Noteworthy, the electrochemical properties of 1 and its de-
rivatives B1eB6 were investigated by cyclic voltammetry (CV). CVs
were achieved in 0.1 M Bu4NPF6/CH2Cl2 solutions containing 1 mM
of compounds. The CV of 1 shows an expected fast electro-
polymerization initiated by the oxidation of the quaterthiophene
core. Unfortunately, all the bridge derivatives B1eB6 follow the
same oxidative polymerization, even after only one cycle, which
makes the calculation and comparison of their oxydation potentials
unfeasable (See Fig. S11 in Supplementary data).
Finally, the bridged amino-derivative B6 was surprisingly
obtained through a direct reductive amination of the mono-aldehyde
3 using aqueous ammonia (Scheme 4). The reaction conditions used
here were the same as the one described by Dangerfield et al. for the
synthesisof primaryaminesfromfuranosideand analogs.21 However,
in our case, the reductive amination didn’t stop to the primary amine
and proceeded to the secondary (B2) and also tertiary amine 11. This
feature can be explained by the formation of aldehyde 3 p-stacks or
aggregates, which would therefore promote the subsequent reaction
of the amine just formed with neighboring aldehyde. The conversion
was nearly quantitative looking at the crude product 1H NMR, but the
yield of the isolated compounds decreased significantly due to their
partial decomposition on silica gel during the purification step, even
after neutralization of silica gel acidity.
4. Conclusion
In conclusion, we successfully synthesized the target bridged
quaterthiophene dimers B2eB6 starting from easily available 3,3000
-
didodecylquaterthiophene 1. The synthetic pathways explored to-
ward these dimers revealed some unexpected features, such as the

5602
C. Niebel et al. / Tetrahedron 68 (2012) 5599e5605
14.3; HRMS (MALDI-ToF): [Mþ
1466.7211, found 1466.7186.
] calcd for C88H122O2S8 m/z
ꢂ
low reactivity of 1 mono-lithiated intermediate or the direct for-
mation of secondary (B6) and tertiary amine (11) through a pro-
cedure initially developed for the preparation of primary amine
exclusively. The synthetic procedure developed for the preparation
of B3, B4, and B6 is easily adaptable to scale up the production of
large amounts of materials, however those three dimers appeared
to be quite unstable on silica gel. All the synthesized dimers B2eB6
possess a high potential for the elaboration of semiconducting
materials with a charge transport of higher dimensionality com-
pared to 1. The next steps beyond the scope of this synthetic paper
involve the fabrication and characterization of thin films made of
these dimers, to measure and compare the charge carrier mobility
in field-effect transistors.
5.2.2. 1,4-Bis((3,3000-didodecyl-[2,20:50,200:500,2000-quaterthiophen]-5-
yl)methyl)benzene (B2). Sodium cyanoborohydride (0.042 g,
0.67 mmol) was added at room temperature to a suspension of zinc
iodide (0.043 g, 0.14 mmol) and 4 (0.066 g, 0.05 mmol) in 1,2-
dichloroethane (10 mL). The reaction mixture was stirred overnight
at room temperature. It was then filtered over silica gel using
dichloromethane as eluant to give B2 (0.059 g, 0.04 mmol, 91%) as
a yellow waxy solid. Rf (petroleum ether/dichloromethane 4/1 v/v):
0.60; 1H NMR (CDCl3, 300 MHz)
d: 7.25 (s, 4H, eC6H4e), 7.17 (d, 2H,
J¼5.2 Hz, H5000), 7.10 (d, 2H, J¼3.6 Hz, H300 orH40), 7.09 (d, 2H, J¼3.6 Hz,
H40 or H300), 7.01 (d, 2H, J¼3.8 Hz, H400), 6.96e6.92 (m, 4H, H30, H4000),
6.66 (s, 2H, H4), 4.08 (s, 4H, CthiopheneeCH2eC6H4), 2.82e2.66 (m, 8H,
5. Experimental section
C
thiopheneeCH2e),1.71e1.55 (m, 8H, CthiopheneeCH2eCH2e),1.42e1.20
(m, 72H, e(CH2)9eCH3), 0.92e0.83 (m, 12H, eCH3); 13C NMR (CDCl3,
75 MHz) : 142.6, 140.0, 139.8, 138.4, 137.0, 136.5, 135.7, 135.3, 130.5,
5.1. Materials and methods
d
130.2, 129.0, 128.5, 126.6, 126.1, 123.93, 123.88, 123.8, 77.6, 77.2, 76.7,
36.0, 32.1, 30.81, 30.75, 29.82, 29.76, 29.7, 29.6, 29.5, 29.4, 22.9, 14.3;
HRMS (MALDI-ToF): [Mþꢂ] calcd for C88H122S8 m/z 1434.7312, found
1434.7319.
Unless otherwise noted, all chemicals were purchased from
Aldrich or Acros and used without further purification. THF was
dried by conventional method (Na/benzophenone distillation pro-
cedure under argon) and collected with glass syringes. TLC: SiO2
Silica gel 60F254 on aluminum sheet (Merck). Column chromatog-
raphy: Silica gel 60 (particle size 0.063e0.200 mm, Merck). 1H NMR
(300 MHz) and 13C NMR (75 MHz) were recorded on Bruker Avance
300 at room temperature. Chemical shifts are given in parts per
million and coupling constants J in Hertz. The residual signal of the
solvent was taken as internal reference standard. EI-HRMS mea-
surements were made on a Waters AutoSpec 6 and MALDI-ToF
experiments on a Waters QToF Premier. Absorption spectra were
recorded on an Agilent 8453 spectrophotometer in a quartz cell
(optical path of 1 cm) in tetrahydrofuran (concentration solutions
of 10ꢀ5 M were used). Emission spectra were measured on an
Aminco Bowman series 2 luminescence spectrophotometer.
5.3. Synthetic procedures for the preparation of 6, B3, and B4
5.3.1. N-((3,3000-Didodecyl-[2,20:50,200:500,2000-quaterthiophen]-5-yl)
methylene)aniline (5). A solution of quaterthiophene aldehyde 3
(0.100 g, 0.14 mmol) and aniline (0.013 g, 0.14 mmol) in an equi-
volume mixture (4 ml) of chloroform and absolute ethanol was
gently refluxed for 20 h under inert atmosphere. The reaction
mixture was then cooled down to room temperature and concen-
trated under reduced pressure. The residue was washed several
times with methanol to afford the expected imine 5 (0.011 g,
0.14 mmol, quantitative) as a dark red oil. This crude product was
used directly in the next step without further purification. Rf (tol-
uene): 0.90; 1H NMR (CDCl3, 300 MHz)
d: 8.48 (s, 1H, eCH]Ne),
7.42e7.35 (m, 2H, eCH]CHeCH]), 7.31 (s, 1H, H4), 7.25e7.14 (m,
7H, H300, H40, H5000, eCH]CHeCeN], eCH]CHeCH]), 7.03 (d, 1H,
J¼3.8 Hz, H30), 6.95 (d, 1H, J¼5.2 Hz, H4000), 2.86e2.75 (m, 4H,
5.2. Synthetic procedures for the preparation of B2
5.2.1. 1,4-Phenylenebis((3,3000-didodecyl-[2,20:50,200:500,2000-quaterthio-
phen]-5-yl)methanol) (4). To a solution of quaterthiophene
CthiopheneeCH2e), 1.76e1.59 (m, 4H,
CthiopheneeCH2eCH2e),
1
1.44e1.22 (m, 36H, e(CH2)9eCH3), 0.88 (t, 7H, J¼6.7 Hz, eCH3); 13
C
(0.170 g, 0.25 mmol) in dry THF (15 mL) was added dropwise a 1.6 M
solution of n-butyllithium in hexanes (0.19 ml, 0.31 mmol) at
ꢀ30 ꢁC under an argon atmosphere. The reaction mixture was
warmed to 0 ꢁC and stirred at this temperature for 1 h. It was then
cooled down to ꢀ78 ꢁC, and a solution of terephthaldicarbox-
aldehyde in dry THF (3 mL) was added in one portion. The reaction
mixture was allowed to warm up slowly to room temperature
overnight. The reaction was then quenched by the addition of water
(10 mL). The mixture was extracted with dichoromethane
(2*50 mL). The combined organic layers were washed with water
and brine, dried over MgSO4 and concentrated under reduced
pressure. The crude product was purified by column chromatog-
raphy on silica gel (eluant: petroleum ether/ethyl acetate 8/2 v/v)
NMR (CDCl3, 75 MHz) d: 152.5, 151.5, 140.1, 140.02, 139.97, 138.0,
136.5, 135.9, 135.8, 135.2, 134.8, 130.3, 130.2, 129.4, 129.2, 127.4,
126.6, 126.1, 124.3, 124.1, 124.0, 121.2, 115.2, 32.1, 30.8, 30.4, 29.8,
29.7, 29.6, 29.5, 29.4, 22.8, 14.3.
5.3.2. N-((3,3000-Didodecyl-[2,20:50,200:500,2000-quaterthiophen]-5-yl)
methyl)aniline (6). To a solution of quaterthiophene imine 5
(0.100 g, 0.13 mmol) in a mixture of toluene (5 ml) and methanol
(10 ml) was added sodium borohydride (0.025 g, 0.65 mmol) at
room temperature. The reaction mixture was refluxed for 20 h
under an inert atmosphere. A TLC of the reaction medium showed
the presence of the expected aniline 6 together with unreacted
starting imine 5. A new portion of sodium borohydride (0.025 g,
0.65 mmol) was then added to the reaction mixture and 4 addi-
tional hours of reflux were necessary to complete the reduction.
The mixture was then cooled down to room temperature, poured
into ice/water and extracted with dichloromethane (2*50 mL). The
combined organic layers were washed with water and brine, dried
over MgSO4 and concentrated under reduced pressure. The crude
product was purified by column chromatography on silica gel (el-
uant: toluene/petroleum ether 1/1 v/v) affording the target qua-
terthiophene aniline 6 (0.054 g, 0.07 mmol, 54%) as a yellowish oil,
which solidifies upon cooling. Rf (toluene/petroleum ether 1/1 v/v):
affording the target bridged quaterthiophene
0.04 mmol,12%) as a yellowish oil. Rf (petroleum ether/ethyl acetate
4/1 v/v): 0.57; 1H NMR (CDCl3, 300 MHz)
: 7.50 (s, 4H, eC6H4e),
4 (0.066 g,
d
7.17 (d, 2H, J¼5.2 Hz, H5000), 7.10 (d, 2H, J¼3.7 Hz, H300 or H40), 7.09 (d,
2H, J¼3.7 Hz, H40 or H300), 7.00 (d, 2H, J¼3.8 Hz, H400), 6.97 (d, 2H,
J¼3.8 Hz, H30), 6.93 (d, 2H, J¼5.2 Hz, H4000), 6.76 (s, 2H, H4), 5.99 (s,
2H, eCHOHe), 2.81e2.65 (m, 8H, CthiopheneeCH2e), 2.65 (br s, 2H,
-OH), 1.70e1.55 (m, 8H, CthiopheneeCH2eCH2e), 1.42e1.20 (m, 72H,
e(CH2)9eCH3), 0.92e0.83 (m, 12H, eCH3); 13C NMR (CDCl3,
75 MHz) d: 145.9, 142.8, 140.0, 139.6, 137.0, 136.9, 135.5, 135.2, 130.6,
130.4, 130.2, 128.1, 126.7, 126.62, 126.56, 124.0, 123.9, 72.4, 32.1,
30.8, 30.7, 29.82, 29.76, 29.75, 29.7, 29.61, 29.59, 29.5, 29.4, 22.9,
0.57; mp: 49.1e52.9 ꢁC; 1H NMR (CDCl3, 300 MHz)
d: 7.24e7.15 (m,
3H, H5000, eCH]CHeCH]), 7.11 (d, 2H, J¼3.7, H300 or H40), 7.10 (d,

C. Niebel et al. / Tetrahedron 68 (2012) 5599e5605
5603
2H, J¼3.7, H40 or H300), 7.01 (d, 1H, J¼3.8 Hz, H400), 6.97 (d, 1H,
J¼3.8 Hz, H30), 6.94 (d, 1H, J¼5.2 Hz, H4000), 6.85 (s, 1H, H4), 6.76 (t,
1H, J¼7.3 Hz, eCH]CHeCH]), 6.72e6.67 (m, 2H, eCH]
CHeCeN]), 4.46 (s, 2H, eCH2eNHe), 4.07 (br s, 1H, eNHe),
solution in THF (3.19 ml, 6.38 mmol). B3 (0.165 g, 0.11 mmol, 53%)
was isolated as a yellow solid. Rf (toluene): 0.51; mp: 67.7e71.2 ꢁC;
1H NMR (CDCl3, 300 MHz)
d
: 7.17 (d, 2H, J¼5.2 Hz, H5000), 7.12e7.08
(m, 4H, H300, H40), 7.01 (d, 2H, J¼3.8 Hz, H40000), 6.97 (d, 2H, J¼3.8 Hz,
H30), 6.94 (d, 2H, J¼5.2 Hz, H4000), 6.84 (s, 2H, H4), 6.66 (s, 4H,
eC6H4e), 4.40 (s, 4H, eCH2eNHe), 2.82e2.67 (m, 8H,
2.82e2.68 (m, 4H,
CthiopheneeCH2e), 1.70e1.56 (m, 4H,
C
thiopheneeCH2eCH2e), 1.41e1.19 (m, 36H, e(CH2)9eCH3), 0.87 (t,
6H, J¼6.7 Hz, eCH3); 13C NMR (CDCl3, 75 MHz)
d
: 147.7, 141.4, 140.0,
C
thiopheneeCH2e), 1.70e1.55 (m, 8H,
CthiopheneeCH2eCH2e),
139.8, 136.9, 136.8, 135.5, 135.4, 130.5, 130.2, 129.6, 129.5, 128.2,
126.7, 126.4, 124.0, 123.9, 118.3, 113.3, 43.9, 32.1, 30.82, 30.75, 29.82,
29.76, 29.7, 29.62, 29.58, 29.5, 29.4, 22.9, 14.3; HRMS (MALDI-ToF):
[Mþꢂ] calcd for C47H65NS4 m/z 771.4000, found 771.3996.
1.43e1.18 (m, 72H, e(CH2)9eCH3), 0.87 (t, 12H, J¼6.5 Hz, eCH3); 13
C
NMR (CDCl3, 75 MHz) d: 142.0, 140.7, 140.0, 139.7, 137.0, 136.7, 135.6,
135.4, 130.5, 130.2, 129.4, 129.2, 128.4, 128.0, 126.7, 126.4, 125.5,
124.0, 123.93, 123.90, 115.3, 45.1, 32.1, 30.82, 30.76, 29.84, 29.82,
29.76, 29.71, 29.68, 29.6, 29.5, 29.4, 22.9, 14.3; HRMS (MALDI-ToF):
[Mþꢂ] calcd for C88H124N2S8 m/z 1464.7530, found 1464.7521.
5.3.3. General procedure for the preparation of the diimine de-
rivatives 7 and 8. A solution of quaterthiophene aldehyde 3
(1 equiv) and phenylenediamine (2 equiv) in an equivolume mix-
ture (6 ml) of chloroform and absolute ethanol was gently refluxed
for 20 h under inert atmosphere. The reaction mixture was cooled
down to room temperature and concentrated under reduced
pressure. The residue was then washed several times with meth-
anol (3*5 ml) to afford the expected crude diimine as a red oil,
which solidifies upon cooling. This crude product was used directly
in the next step without further purification.
5.3.4.2. N1,N3-Bis((3,3000-didodecyl-[2,20:50,200:50000,2000-quaterthio-
phen]-5-yl)methyl)benzene-1,3-diamine (B4). This compound was
prepared starting from 8 (0.150 g, 0.10 mmol) and a 2 M LiBH4
solution in THF (1.54 ml, 3.08 mmol). B4 (0.086 g, 0.06 mmol, 57%)
was isolated as a yellow oil. Rf (toluene): 0.68; 1H NMR (CDCl3,
300 MHz)
d
: 7.18 (d, 2H, J¼5.2 Hz, H5000), 7.12e7.09 (m, 4H, H300, H40),
7.04 (t, 1H, J¼8.0 Hz, eCH]CHeCH]), 7.01 (d, 2H, J¼3.8 Hz, H400),
6.97 (d, 2H, J¼3.8 Hz, H30), 6.94 (d, 2H, J¼5.2 Hz, H4000), 6.84 (s, 2H,
H4), 6.15 (dd, 2H, J¼8.0 and 2.0 Hz, eCH]CHeCH]), 6.04 (t, 1H,
J¼2.0 Hz, ]NeC]CHeCeN]), 4.43 (s, 4H, ]CH2eNHe), 4.00 (br s,
2H, eNHe), 2.83e2.67 (m, 8H, CthiopheneeCH2e), 1.72e1.56 (m, 8H,
5.3.3.1. N1,N4-Bis((3,3000-didodecyl-[2,20:50,200:500,2000-quaterthio-
phen]-5-yl)methylene)benzene-1,4-diamine (7). This compound was
prepared starting from 3 (0.310 g, 0.45 mmol) and para-phenyl-
enediamine (0.024 g, 0.22 mmol). 7 (0.321 g, 0.22 mmol, quantita-
tive) was isolated as a red solid. Rf (toluene): 0.71; mp: 92.2e95.9 ꢁC;
C
thiopheneeCH2eCH2e), 1.45e1.19 (m, 72H, e(CH2)9eCH3),
0.93e0.83 (m, 12H, eCH3); 13C NMR (CDCl3, 75 MHz)
d: 148.9, 141.6,
140.0, 139.7, 137.0, 136.7, 135.5, 135.4, 130.5, 130.3, 130.2, 129.5,
128.1, 126.6, 126.4, 123.94, 123.90, 104.0, 98.0, 43.9, 32.1, 30.8, 29.84,
29.82, 29.78, 29.75, 29.72, 29.68, 29.6, 29.5, 29.4, 22.9, 14.3; HRMS
(MALDI-ToF): [Mþꢂ] calcd for C88H124N2S8 m/z 1464.7530, found
1464.7507.
1H NMR (CDCl3, 300 MHz)
d: 8.52 (s, 2H, eCH]Ne), 7.31 (s, 2H, H4),
7.28 (s, 4H, eC6H4e), 7.20e7.14 (m, 8H, H5000, H300, H40, H400), 7.03 (d,
2H, J¼3.8 Hz, H30), 6.95 (d, 2H, J¼5.2 Hz, H4000), 2.86e2.75 (m, 8H,
C
thiopheneeCH2e), 1.76e1.59 (m, 8H,
CthiopheneeCH2eCH2e),
1.44e1.20 (m, 72H, e(CH2)9eCH3), 0.91e0.84 (m, 12H, eCH3); 13C
NMR (CDCl3, 75 MHz) : 151.8, 149.5,140.1,138.0,136.6, 135.9, 135.8,
d
5.4. Synthetic procedures for the preparation of 10 and B5
135.2, 134.9, 130.4, 130.3, 127.4, 126.7, 124.3, 124.2, 124.1, 122.2, 32.1,
30.8, 30.5, 29.82, 29.76, 29.7, 29.6, 29.5, 29.4, 22.9, 14.3.
5.4.1. (3,3000-Didodecyl-[2,20:50,200:50000,2000-quaterthiophen]-5-yl)
methanol (9). To a solution of quaterthiophene aldehyde 3 (0.710 g,
1.02 mmol) in MeOH/Tol (2/1 v/v, 60 ml) was added sodium bo-
rohydride (0.077 g, 2.04 mmol). The reaction mixture was stirred
under reflux for 2 h. It was then cooled down to room temperature,
poured into water/ice and extracted with toluene (2*100 ml). The
combined organic layers are washed with water and brine, dried
over MgSO4 and concentrated under reduced pressure. The crude
product obtained was purified by recrystallization in n-hexane to
give 9 (0.690 g, 0.99 mmol, 97%) as an orange solid. Rf (toluene):
5.3.3.2. N1,N3-Bis((3,3000-didodecyl-[2,20:50,200:500,2000-quaterthio-
phen]-5-yl)methylene)benzene-1,3-diamine (8). This compound was
prepared starting from 3 (0.200 g, 0.29 mmol) and meta-phenyl-
enediamine (0.015 g, 0.14 mmol). 8 (0.199 g, 0.14 mmol, quantitative)
was isolated as a red oil. Rf (toluene/petroleum ether 8/2 v/v): 0.83;
1H NMR (CDCl3, 300 MHz)
d: 8.53 (s, 2H, eCH]Ne), 7.42e7.35 (m,
1H, eCH]CHeCH]), 7.32 (s, 2H, H4), 7.21e7.14 (m, 8H, H5000, H300,
H40, H400), 7.13e7.07 (m, 3H, eCH]CHeCH], ]NeC]CHeCeN]),
7.03 (d, 2H, J¼3.8 Hz, H30), 6.95 (d, 2H, J¼5.2 Hz, H4000), 2.86e2.75 (m,
8H, CthiopheneeCH2e), 1.76e1.59 (m, 8H, CthiopheneeCH2eCH2e),
1.44e1.20 (m, 72H, e(CH2)9eCH3), 0.91e0.84 (m, 12H, eCH3); 13C
0.18; mp: 54.5e56.7 ꢁC; 1H NMR (CDCl3, 300 MHz)
d: 7.18 (d, 1H,
J¼5.2 Hz, H5000), 7.13 (d, 1H, J¼3.7 Hz, H300 or H40), 7.12 (d, 1H,
J¼3.7 Hz, H40 or H300), 7.02 (d, 1H, J¼3.8 Hz, H400), 7.01 (d, 1H,
J¼3.8 Hz, H30), 6.94 (d, 1H, J¼5.2 Hz, H4000), 6.86 (s, 1H, H4), 4.77 (s,
2H, eCH2eOH), 2.83e2.69 (m, 4H, CthiopheneeCH2e), 1.85 (br s, 1H,
eOH), 1.71e1.58 (m, 4H, CthiopheneeCH2eCH2e), 1.43e1.20 (m, 36H,
e(CH2)9eCH3), 0.88 (t, 6H, J¼6.6 Hz, eCH3); 13C NMR (CDCl3,
NMR (CDCl3, 75 MHz) d: 153.0, 152.5, 140.2, 139.9, 138.1, 136.6,
136.00, 135.95, 135.5, 134.8, 130.34, 130.27, 127.5, 126.7, 124.4, 124.2,
124.1, 32.1, 30.8, 30.5, 29.82, 29.76, 29.7, 29.6, 29.5, 29.4, 22.9, 14.3.
5.3.4. General procedure for the reduction of the diimine derivatives
B3 and B4. A 2 M LiBH4 solution (30 equiv) inTHF was added at room
temperature to a solution of quaterthiophene diimine 7 or 8 (1 equiv)
in THF (10 ml), under inert atmosphere. The reaction mixture was
refluxed for 24 h. It was then cooled down to room temperature,
poured into ice/waterand extractedtwicewithdichloromethane. The
combined organic layers were washed with water and brine, dried
over MgSO4 and concentrated under reduced pressure affording the
expected crude diamine. This crude product was purified by column
chromatography on silica gel (eluant: toluene).
75 MHz) d: 142.2, 140.0, 139.8, 137.0, 136.8, 135.5, 135.3, 130.6, 130.4,
130.2, 128.6, 126.6, 124.0, 123.9, 60.3, 32.1, 30.81, 30.76, 29.84, 29.81,
29.75, 29.7, 29.6, 29.5, 29.4, 22.8, 14.3; HRMS (MALDI-ToF): [Mþ
]
ꢂ
calcd for C41H60OS4 m/z 696.3527, found 696.3524.
5.4.2. 2-((3,3000-Didodecyl-[2,20:50,200:500,2000-quaterthiophen]-5-yl)
methyl)isoindoline-1,3-dione (10). To a solution of quaterthiophene
alcohol 9 (0.350 g, 0.50 mmol), triphenylphosphine (0.171 g,
0.65 mmol) and phthalimide (0.096 g, 0.65 mmol) in dry THF
(25 ml) was added diisopropyl azodicarboxylate (0.132 g,
0.65 mmol) at 0 ꢁC and under inert atmosphere. The reaction
mixture was then allowed to warm up to room temperature and
was stirred further for 24 h. The mixture was concentrated under
reduced pressure and directly purified by column chromatography
5.3.4.1. N1,N4-Bis((3,3000-didodecyl-[2,20:50,200:500,2000-quaterthio-
phen]-5-yl)methyl)benzene-1,4-diamine (B3). This compound was
prepared starting from 7 (0.311 g, 0.21 mmol) and a 2 M LiBH4

5604
C. Niebel et al. / Tetrahedron 68 (2012) 5599e5605
on silica gel (eluant: toluene/dichloromethane 9/1 v/v) to give 10
(0.240 g, 0.29 mmol, 58%) as a yellow solid. Rf (toluene): 0.53; mp:
HRMS (MALDI-ToF): [Mþꢂ] calcd for C82H119NS8 m/z 1373.7108,
found 1373.7073.
50.1e52.3 ꢁC; 1H NMR (CDCl3, 300 MHz)
d 7.90e7.83 (m, 2H,
eCOeCeCH]CHe), 7.75e7.68 (m, 2H, eCOeCeCH]CHe), 7.17 (d,
2H, J¼5.2 Hz, H5000), 7.11e7.07 (m, 4H, H300, H40), 7.01 (d, 2H,
J¼3.8 Hz, H400), 6.98 (s, 1H, H4), 6.97 (d, 1H, J¼3.8 Hz, H30), 6.93 (d,
2H, J¼5.2 Hz, H4000), 4.95 (s, 2H, eCH2eNe), 2.82e2.65 (m, 4H,
5.5.2. Tris((3,3000-didodecyl-[2,20:50,200:500,2000-quaterthiophen]-5-yl)
methyl)amine (11). Rf (toluene/petroleum ether 1/1 v/v): 1.0; 1H
NMR (CDCl3, 300 MHz)
d
: 7.17 (d, 3H, J¼5.1 Hz, H5000), 7.15e7.08 (m,
6H, H300, H40), 7.06e6.98 (m, 6H, H400, H30), 6.94 (d, 3H, J¼5.1 Hz,
H4000), 6.82 (s, 3H, H4), 3.89 (s, 6H, eCH2eNHe), 2.83e2.68 (m,
12H, CthiopheneeCH2e), 1.72e1.59 (m, 12H, CthiopheneeCH2eCH2e),
1.41e1.20 (m, 108H, e(CH2)9eCH3), 0.92e0.82 (m, 18H, eCH3); 13C
C
thiopheneeCH2e), 1.70e1.55 (m, 4H,
CthiopheneeCH2eCH2e),
1.41e1.19 (m, 36H, e(CH2)9eCH3), 0.92e0.83 (m, 6H, eCH3); 13C
NMR (CDCl3, 75 MHz) : 167.7, 140.0, 139.7, 137.0, 136.9, 136.3, 135.5,
d
135.0, 134.2, 132.2, 130.94, 130.87, 130.4, 130.2, 126.7, 126.6, 123.94,
123.88, 123.6, 36.0, 32.1, 30.8, 30.7, 29.8, 29.74, 29.72, 29.66, 29.60,
29.57, 29.5, 29.4, 22.8, 14.3; HRMS (MALDI-ToF): [Mþꢂ] calcd for
C49H63NO2S4 m/z 825.3742, found 825.3759.
NMR (CDCl3, 75 MHz) d: 140.6, 140.0, 139.4, 137.1, 136.7, 135.8,
135.3, 130.5, 130.2, 130.1, 129.3, 126.6, 126.4, 123.93, 123.86, 51.9,
32.1, 30.8, 29.83, 29.75, 29.7, 29.6, 29.5, 29.4, 22.9, 14.3; HRMS
(MALDI-ToF): [Mþꢂ] calcd for C123H177NS12 m/z 2052.0530, found
2052.0588.
5.4.3. 2,6-Bis((3,3000-didodecyl-[2,20:50,200:500,2000-quaterthiophen]-5-
yl)methyl)pyrrolo[3,4-f]isoindole-1,3,5,7(2H,6H)-tetraone
(B5). To
Acknowledgements
a solution of quaterthiophene alcohol 9 (0.464 g, 0.67 mmol),
triphenylphosphine (0.192 g, 0.73 mmol) and pyromellitic diimide
(0.072 g, 0.33 mmol) in dry THF (25 ml) was added diisopropyl
azodicarboxylate (0.148 g, 0.73 mmol) at 0 ꢁC and under inert
atmosphere. The reaction mixture then allowed to warm up to
room temperature and was stirred further for 24 h. The mixture
was then concentrated under reduced pressure and directly pu-
rified by column chromatography on silica gel (eluant: toluene/
dichloromethane 9/1 v/v) to give B5 (0.198 g, 0.13 mmol, 38%) as
a yellow solid. Rf (toluene): 0.20; mp: 96.4e101.9 ꢁC; 1H NMR
This work has been financially supported by the Belgian Federal
Science Policy Office (PAI SF2), by a concerted research action of the
French Community of Belgian (ARC Nꢁ 20061), and by the Belgian
National Fund for Scientific Research (FNRS). The authors also
would like to thank Pr. Pascal Gerbaux for his help with the mass
spectrometry.
Supplementary data
(CDCl3, 300 MHz)
d 8.30 (s, 2H, eCOeCeCH]Ce), 7.17 (d, 2H,
1H and 13C spectra of quaterthiophene derivatives 6, 10 and
the bridged compounds B2eB6 are shown in Supplementary
data. Absorption and fluorescence spectra of 1 and its bridged
derivatives B1eB6 as well as CVs of B4 are also depicted in
Supplementary data. Supplementary data associated with this
article can be found in online version. Supplementary data re-
lated to this article can be found online at doi:10.1016/
j.tet.2012.04.072.
J¼5.2 Hz, H5000), 7.11e7.06 (m, 4H, H300, H40), 7.02e6.98 (m, 4H,
H400, H4), 6.96 (d, 2H, J¼3.8 Hz, H30), 6.93 (d, 2H, J¼5.2 Hz, H4000),
4.99 (s, 4H, eCH2eNe), 2.80e2.65 (m, 8H, CthiopheneeCH2e),
1.70e1.53 (m, 8H,
CthiopheneeCH2eCH2e), 1.41e1.17 (m, 72H,
e(CH2)9eCH3), 0.92e0.82 (m, 12H, eCH3); 13C NMR (CDCl3,
75 MHz) 165.5, 140.0, 139.8, 137.4, 137.2, 136.7, 135.6, 135.1, 134.7,
131.5, 131.4, 130.4, 130.2, 126.8, 126.6, 124.04, 123.9, 118.8, 36.6,
32.1, 30.8, 30.7, 29.8, 29.74, 29.71, 29.66, 29.60, 29.56, 29.5, 29.4,
22.8, 14.3; HRMS (MALDI-ToF): [Mþꢂ] calcd for C92H120N2O4S8 m/z
1572.7014, found 1572.7003.
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