Synthesis, Fluorescence, and Two-Photon Absorption Properties of Push–Pull 5-Arylthieno[3,2-b]thiophene Derivatives

Article abstract of DOI:10.1002/ejoc.201600806

Three series of novel push–pull 5-arylthieno[3,2-b]thiophene derivatives functionalized with potent electron-withdrawing terminal moieties have been synthesized in moderate to excellent yields by Suzuki coupling followed by Knoevenagel condensation. These novel chromophores show intense absorption in the near-UV region through to the orange visible region, related to a strong intramolecular charge-transfer transition. By combining a strong donor and acceptor, large fluorescence quantum yields were achieved as well as large two-photon absorption responses. Interestingly, due to the improved rigidity and electronic delocalization provided by the thienothiophene moiety (as compared with the bithiophene unit), higher one- and two-photon brightness values have been achieved. As a result, several new fluorescent dyes showing enhanced brightness and tunable fluorescence (ranging from the blue to the NIR region) have been obtained that have potential for bioimaging applications.

Full text of DOI:10.1002/ejoc.201600806

A Journal of
Accepted Article
Title: Synthesis, fluorescence and two-photon absorption properties of novel push-
pull 5-aryl[3,2-b]thienothiophene derivatives
Authors: M. Manuela M. Raposo; Cyril Herbivo; Vincent Hugues; Guillaume Cler-
´
mont; M. Cidalia R Castro; Mireille Blanchard-Desce; Alain Comel
This manuscript has been accepted after peer review and the authors have elected
to post their Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by using the Digital
Object Identifier (DOI) given below. The VoR will be published online in Early View as
soon as possible and may be different to this Accepted Article as a result of editing.
Readers should obtain the VoR from the journal website shown below when it is pu-
blished to ensure accuracy of information. The authors are responsible for the content
of this Accepted Article.
To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201600806
Link to VoR: http://dx.doi.org/10.1002/ejoc.201600806
Supported by

European Journal of Organic Chemistry
10.1002/ejoc.201600806
FULL PAPER
Synthesis, fluorescence and two-photon absorption properties of
novel push-pull 5-aryl[3,2-b]thienothiophene derivatives
M. Manuela M. Raposo,*[a] Cyril Herbivo,[a] Vincent Hugues,[b] Guillaume Clermont,[b] M. Cidália R.
Castro,[a] Alain Comel,[c] Mireille Blanchard-Desce*[b]
Dedication:
Abstract: Three series of novel push-pull 5-aryl[3,2-
b]thienothiophene derivatives functionalized with potent electron-
withdrawing terminal moieties) were synthesized in moderate to
excellent yields through Suzuki coupling followed by Knoevenagel
condensation. These novel chromophores combine intense
absorption in the near-UV down to the orange visible region in
relation with a strong intramolecular charge transfer transition. By
combining strong donor and acceptor, large fluorescence quantum
Large two-photon absorption is often correlated with
significant intermolecular charge transfer (ICT) processes.
Hence a standard strategy for designing molecules with large
TPA cross-sections is based on connecting electron rich donor
entities (D) with electron deficient acceptors (A) through -
electron conjugated bridges within conjugated structures of
various topologies. Different factors influence the TPA, including
the conjugation length and its modulation, the molecular
yield are achieved as well as large two-photon absorption responses. planarity, the dimensionality of the charge-transfer network and
Interestingly, due to the improved rigidity and electronic
delocalization provided by the thienothiophene moiety (compared to
the bis-thiophene one) larger one- and two-photon brightness values
are achieved. As a result, several new fluorescent dyes showing
enhanced brightness and tunable fluorescence (ranging from the
blue to the NIR region) has been obtained which offer interesting
promises for bioimaging applications.
the donating and withdrawing abilities of the electron donor and
acceptor moieties. Different structural motifs have been
employed in an attempt to optimize the TPA properties including
dipolar, quadrupolar, octupolar stuctures where ICT plays a
major role, as well as conjugated branched or dendritic
structures and macrocycles.[1-9] Although significant advances in
the design of these materials have been made in recent years,
there is still need for improvement, in particular when large TPA
responses in the biological spectral window have to be
combined with large fluorescence quantum yield, tunable
fluorescence (in particular towards red and NIR-emitting
fluorophores) and photostability for imaging purposes. In that
perspective, a promising direction is the replacement of aromatic
systems with more easily delocalizable -excessive or -
deficient heteroaromatics which has been shown to result in an
increased ICT as well as an enhanced TPA, while preserving in
many cases the chemical and photochemical stability of these
systems. Moreover, modification of the structure by
incorporation of heterocycles into more complex -conjugated
systems allows to fine-tune the electronic and optical properties
and often results in strong fluorescence emission, which is an
essential prerequisite for certain TPA-based applications.[10] In
this context fused thienothiophene (TT) heterocyclic systems,
are expected to exhibit interesting TPA properties due to their
lower resonance energy per electron when compared to
thiophene as well as a their greater electronic relay role and
planarity compared the bithiophene counterpart. Those features
would also allow the increase of conjugation between the donor
(D) and the acceptor (A), which typically results in increased
NLO responses and improved thermal stability and a good
transparency–nonlinearity trade-off.[11,12]
Introduction
Organic materials displaying strong two-photon absorption
(TPA)[1-3] have attracted large interest due to a variety of
potential applications in photonics and optoelectronics, including
three-dimensional optical data storage,[4] three-dimensional
[5]
microfabrication,
optical limitation[6] and two-photon
microscopy (TPM).[7] For microscopic imaging, in particular for in
vivo imaging, the two-photon excitation process presents several
advantages as it provides intrinsic three-dimensional resolution
and improved in-depth tissue penetration.[7] Furthermore, the
combination of the two-photon absorbers with efficient singlet
oxygen generation offers the potential for further development of
photodynamic cancer therapy (PDT) methods.[8] While much
effort has been devoted to developing TPA dyes, fluorescent
quantum yields are often lower than desired, while photo-
bleaching can be a shortcoming for real applications. In addition
to large two-photon absorption, high two-photon excited
fluorescence (TPEF) cross-sections (i.e. two-photon brightness),
good photostability and appreciable solubility are also required
for practical applications.[1]
In the last 30 years, several investigators reported the
synthesis and characterization of functionalized thienothiophene
(TT) derivatives having in mind primarily their application in
materials and medicinal chemistry due to their interesting
optoelectronic properties and high thermal and chemical
stabilities as well as their wide range of biological activities.[13] In
materials chemistry these derivatives have found application in
several areas such as nonlinear optics (NLO),[11] dye sensitized
solar cells (DSSCs),[14] liquid crystals,[15] organic light emitting
diodes (OLEDs),[16] organic semiconductors, field-effect
transistors, conducting polymers, etc..[17] Despite their diverse
[a]
[b]
[c]
Center of Chemistry, University of Minho, Campus of Gualtar, 4710-
057 Braga, Portugal. Phone: +351 253 604381, E-mail:
mfox@quimica.uminho.pt
Univ. Bordeaux, Institut des Sciences Moléculaires (UMR 5255
CNRS), F-33405 Talence, France. Phone: +33 (5) 4000 6732, E-
mail: mireille.blanchard-desce@u-bordeaux.fr
Université de Lorraine, Institut Jean Barriol, Laboratoire de Chimie
et Physique - Analyse Multi-échelles des Milieux Complexes, F-
57048, Metz Cedex, France
This article is protected by copyright. All rights reserved

European Journal of Organic Chemistry
10.1002/ejoc.201600806
FULL PAPER
and interesting applications, the synthesis and reactivity studies
of thienothiophene derivatives are less developed compared to
other thiophene derivatives probably due to synthetic
difficulties.[13]
b]thiophene derivative. The synthetic method reported in this
paper is especially original, based on
a
domino
thiolation/cyclization reaction which can be applied for the
synthesis of benzo[b]thiophenes and thieno[3,2-b]thiophenes as
well. An earlier work report the synthesis of 2-aryl-thieno[3,2-
b]thiophenes functionalized with acceptor groups (NO2, CN,
CO2Me, SO2Me) in para position of the phenyl ring through
palladium catalysed arylation of thieno[3,2-b]thiophene or
In recent years we have been engaged on the synthesis of
novel
oligothiophenes, aryl(bi)thiophenes, (thienyl)pyrroles)[18] through
different synthetic methodologies. These heterocyclic
formyl-heterocyclic
systems,
(bithiophenes,
carbaldehydes reveal to be versatile precursors for the synthesis
of dicyanovinyl- and thiobarbituric acid derivatives with
interesting second order nonlinear optical properties.[18a,b,f, 19] We
report also the synthesis, the photophysical and TPA properties
of a series of push-pull aryl-bithiophene chromophores bearing
alkoxyl and N,N-dialkylamino electron-donating (D) groups and
formyl, dicyanovinyl and 1,3-diethyl-2-thioxodihydropyrimidine-
4,6-dione electron-withdrawing (A) end-groups.[18e, 20] In contrast
with corresponding push-pull polyenes,[21] these chromophores
bearing a phenyl-bithienyl conjugated path exhibited a significant
increase in fluorescence. Additionally, some of these
chromophores combine very large one and two-photon
brightness as well as sizeable emission in the red/NIR region,
being therefore promising biphotonic fluorescent probes for
bioimaging. [20b]
through
thiophenes.[23] On the other hand, the synthesis of 5-
triphenylamino-substituted thieno[3,2-b]thiophene-2-
intramolecular
cyclisation
of
2,3-disubstituted
carbaldehydes or carboxylates is more documented.[14] These
compounds are generally the starting points of structurally more
complex organic sensitizers designed for DSSCs application.
Two different synthetic ways are generally reported, using both
classical coupling reactions under mainly Suzuki, Suzuki-
Miyaura and Stille conditions.[14]
A
firstly prepared or
commercially available 2-thieno[3,2-b]thiophenyl-boronic acid or
2-thieno[3,2-b]thiophenyl-stannane can react with the suitable
aryl bromide or an aryl-stannane can be coupled to 5-substituted
or not 2-bromo(or iodo) thieno[3,2-b]thiophene. The 5-
triphenylamino-thieno[3,2-b]thiophene
can
be
further
functionalized[14g] or deprotected[14c,h] depending on the
thienothiophene derivative used.
Moreover, despite the large number of donor-acceptor
heterocyclic systems showing TPA properties reported in the
literature, the present concept of combining the 4-alkoxyl and 4-
N,N-dialkyl groups linked to an aryl[3,2-b]thienothiophene bridge
Synthesis of aldehydes 8 through Suzuki coupling
In order to prepare carbaldehydes 8 we synthesize in first
place the thieno[3,2-b]thiophene-2-carbaldehyde precursor 5
through the combination of two synthetic methodologies
described earlier by Fuller[24] and Prugh et al.[25] Therefore,
methyl thieno[3,2-b]thiophene-2-carboxylate 3 was synthesized
through Fuller´s method, followed by reduction of esther 3 with
lithium aluminium hydride to give alcohol 4 which was reoxidized
functionalized
with
dicyanovinyl
and
1,3-diethyl-2-
thioxodihydropyrimidine-4,6-dione strong acceptor groups has
not, to the best of our knowledge, been previously
communicated in the literature. Additionally, only scarce
examples of thienothiophenes have been investigated for
nonlinear optical applications and only as NLO-phores for
second-harmonic generation.[11]
We were therefore motivated to extend our previous
studies in order to explore the potential of three new series of
push-pull arylthienothiophene heterocyclic systems 8-10.
Consequently, we report herein the synthesis and a detailed
study of the fluorescence and TPA properties of three novel
with pyridinium chlorochromate (PCC) to the
b]thiophene-2-carboxaldehyde 5.[25] Reaction of 5 with bromine
in chloroform at 0o till room temperature gave
5-
thieno[3,2-
bromothieno[3,2-b]thiophene-2-carbaldehyde 6 as a pale yellow
solid in 88% yield (Scheme 1). The synthesis of compound 6
was only reported recently through two different methods which
consists in the lithiation of 2,5-dibromothieno[3,2-b]thiophene
followed by reaction with DMF[14b] or formylation of thieno[3,2-
b]thiophene followed by bromination with NBS.[26] Nevertheless
series of
arylthienothiophene derivatives bearing various
electron-donating (OR, NR2) groups and electron-withdrawing
(formyl, dicyanovinyl and barbiturate) end-groups (EWG) and a
aryl[3,2-b]thienothiophene conjugated bridge.
in both cases the characterization of compound
incomplete.
6 was
Results and Discussion
Synthesis
Due to the reasons described above we decided to focus
on the synthesis and characterization of the optical and thermal
properties of p-alkoxy and p-dialkylamino-substituted 5-aryl-
thieno[3,2-b]thiophene-2-carbaldehydes
8
and
the
corresponding dicyanovinyl 9 and barbiturate 10 derivatives
easily obtained through Knoevenagel condensation reactions.
Surprisingly, only a few works report the synthesis of 5-
aryl-thieno[3,2-b]thiophene derivatives. A recent reference[22]
described the preparation of a 2-(p-alkoxyphenylthieno[3,2-
Scheme 1. Synthesis of precursor 6.
This article is protected by copyright. All rights reserved

European Journal of Organic Chemistry
10.1002/ejoc.201600806
FULL PAPER
Aldehydes 8 were prepared through a Suzuki reaction of
commercially available arylboronic acids 7a-e with 5-
bromothieno[3,2-b]thiophene-2-carbaldehyde 6. The Suzuki
cross-coupling reactions were performed under a nitrogen
atmosphere through two different reaction conditions: Method A
using 1,2-dimethoxyethane (DME) at 80 °C, Pd(PPh3)4 (6%),
Na2CO3, H2O[18e,f] or
Method B using toluene at reflux,
Pd(PPh3)4 (10%), K2CO3, H2O, EtOH[27] (Scheme 2). In general,
formyl derivatives 8 were obtained in better yields (72-84%) and
shorter reactions times through Method B (Table 1).
Scheme 2. Synthesis of aldehydes 8 through Suzuki coupling and synthesis of
dicyanovinyl- 9 and thiobarbituric acid thienothiophene derivatives 10 through
Knoevenagel condensation of the corresponding aldehyde precursors 8 with
malononitrile or thiobarbituric acid.
Table 1. Synthesis of aldehydes 8a-e.
H
IR 
(cm-1)d
Reaction time (h)
Method A a
Yield (%)
Method A
Reaction time (h)
Method B b
Yield (%)
Method B
Comp.
R
(ppm)c
8a
8b
8c
8d
8e
H
MeO
24
4
35
50
85
36
30
1
1
1
2
2
80
72
79
84
70
9.97
9.94
9.94
9.91
9.90
1662
1660
1650
1655
1657
EtO
4
NEt2
4
Pyrrolidino
4
[a] Method A: DME, Pd(PPh3)4 (6%), Na2CO3, H2O / 80o.
[b] Method B: toluene, Pd(PPh3)4 (10%), K2CO3, H2O, EtOH, reflux.
[c] For the CHO proton for formyl-arylthienothiophenes 8 (300 MHz, CDCl3).
[d] All the spectra were recorded in nujol.
d
NEt2
d
81
8.63b
2214
412
Synthesis of dicyanovinyl-
9 and thiobarbituric acid
[a] For the CH=(CN)2 proton for dicyanovinyl-arylthienothiophenes 9 (300
MHz, DMSO-d6).
thieno[3,2-b]thiophene 10 derivatives through Knoevenagel
condensation
[b] For the CH=(CN)2 proton for dicyanovinyl-arylthienothiophenes 9 (400
MHz, DMSO-d6).
Knoevenagel condensation of carbaldehydes
8 with
[c] All the spectra were recorded in nujol.
malononitrile in dichloromethane at room temperature, or with
thiobarbituric acid in acetonitrile at reflux, in the presence of a
catalytical amount of piperidine, gave respectively, dicyanovinyl-
derivatives 9 (Table 2, 49-81%) and thiobarbituric acids 10
(Table 3, 42-82%), in moderate to good yields (Scheme 2).
[d] Decomposition temperature (Td) measured at a heating rate of 20 ºC min–1
under a nitrogen atmosphere, obtained by thermogravimetric analysis (TGA).
Table 3. Yields, 1H NMR, IR and Td data of thiobarbituric acid thienothiophene
derivatives 10.
Table 2. Yields, 1H NMR, IR and Td data of dicyanovinyl-arylthienothiophene
derivatives 9.
d
Td
H
Thiobarbituric-
arylthienothiophene
10
Yield
(%)
(oC)
Aldehyde
IR 
(cm-1)c
(ppm)a
R
8
d
Td
H
Dicyanovinyl-
arylthienothiophene
9
Yield
(%)
(oC)
Aldehyde
IR 
(cm-1)c
(ppm)a
R
8
1682,
1654
a
b
d
H
a
b
d
42
74
82
8.75
8.74
8.67b
333
335
253
a
b
c
H
a
b
c
54
49
74
8.76
8.72
8.71
2216
2219
2221
366
390
391
1682,
1653
MeO
NEt2
MeO
EtO
1681,
1655
This article is protected by copyright. All rights reserved

European Journal of Organic Chemistry
10.1002/ejoc.201600806
FULL PAPER
[a] For the C= CH proton for thiobarbituric-arylthienothiophenes 10 (400 MHz,
DMSO-d6).
IR spectroscopy was also used in order to identify the typical
absorption bands of the carbonyl group in aldehydes 8 (1650-1662
cm-1), carbonyl (1653-1655 cm-1) and thiocarbonyl groups (1683-
1685 cm-1) in thiobarbituric compounds 10 and the nitrile groups in
dicyanovinyl derivatives 9 (2214-2221 cm-1).
[b] For the C= CH proton for dicyanovinyl-arylthienothiophenes 10 (300 MHz,
CDCl3).
[c] All the spectra were recorded in nujol.
[d] Decomposition temperature (Td) measured at a heating rate of 20 ºC min–1
under a nitrogen atmosphere, obtained by thermogravimetric analysis (TGA).
Thermal stability studies
The structures of novel TT derivatives 8-10 were clearly
confirmed by their analytical and spectral data. The most
characteristic signals in the 1H NMR spectra for aldehydes 8
were those corresponding to the CHO protons at about 9.90-
9.97 ppm. For dicyanovinyl derivatives 9a-d as well for
thiobarbituric acid derivatives 10a, b and d a singlet at about
8.63-8.76 ppm or 8.67-8.75 ppm, respectively, were also
observed corresponding to the vinylic proton of the ethylenic
bridge (C=CH) linked to the dicyanovinyl or thiobarbituric acid
acceptor moieties (Tables 1-3). The analysis of the 1H NMR
spectra for push-pull systems 8-10 showed that the chemical
shifts of the CHO proton in compounds 8b-d as well as the
chemical shifts of protons of the ethylenic bridge (C=CH) linked
to the acceptor moieties in derivatives 9b-d and 10, b and d
exhibit signals that are shifted up-field relative to the
corresponding unsubstituted derivatives 8a, 9a and 10a, due to
the stronger mesomeric donor effect of the alkoxy and N,N-
dialkylamino groups substituted in para position of the aryl rings
linked to the TT spacer. Moreover, a gradual slight up-field shift
is observed with increasing donor strength.
It is well known that a good thermal stability is critical for
practical application of optical organic materials. Therefore, the
thermal stability of push-pull arylthienothiophene derivatives 9-
10 was determined by thermogravimetric analysis (TGA),
measured at a heating rate of 20 ºC min–1 under a nitrogen
atmosphere. The results obtained revealed the exceptional
thermal stability for dicyanovinyl push-pull derivatives 9 which
could be heated up to Td = 366–412 ºC. Substitution of the
dicyanovinyl acceptor group 9 by the thiobarbituric moiety 10
leads to lower decomposition temperatures (Td= 253 – 355 ºC).
These results are in agreement with earlier reports in which
good to excellent thermal stabilities were communicated for
other nonlinear optical thienothiophene derivatives.[11a, c, d, e]
Photophysical properties
Photophysical properties of all push-pull derivatives have been
investigated in chloroform. The experimental data are gathered
in Table 4.
Table 4. Photophysical and two-photon absorption properties of TT derivatives 8a-e, 9a-d, and 10a-d in chloroform .
f b)
Stokes
max
max
g)
max
max1
max1
max
em
maxf
 f  h)

abs
[nm]
TPA
[nm]
2max1 Фf
2
FWHM
abs
cpd
8a
shift
[cm-1]
3720
[cm-1] a)
[nm]
[M-1.cm-1]
[nm]
[M-1.cm-1]
7.2 102
[ns]
[GM] i)
[GM] j)
358
3.6 104
4.5 103
413
0.02 c-e)
0.12
716
/
/
/
0.58 c)
8b
8c
372
374
3.5 104
4.5 103
447
453
4510
4660
2.1 104
2.4 104
1.26
744
750
750
50
82
88
0.64 d-e)
0.65 c)
3.5 104
4.4 103
1.44
748
60
0.71 d-e)
8d
8e
9a
9b
428
428
436
455
3.9 104
2.8 104
5.3 104
3.9 104
4.2 103
4.2 103
3.4 103
3.6 103
543
545
491
531
4950
5020
2570
3150
0.87 d-e)
0.86 d-e)
0.002 d-f)
0.006 d-f)
3.4 104
2.4 104
106
2.45
2.44
0.3
856
856
872
910
850
850
890
940
240
180
0.2
1.4
276
209
100
233
234
0.2
0.007 d
9c
457
5.1 104
3.6 103
532
3080
331
0.1
914
960
2.4
369
0.006 e-f)
9d
10a
10b
534
495
514
5.4 104
7.2 104
7.7 104
3.5 103
2.8 103
2.9 103
652
548
579
3390
1950
2180
0.61 e-f)
3.3 104
216
462
2.2
0.84
0.13
1068
990
1028
1080
/
1050
510
/
2.4
836
/
400
0.003 e-f)
0.006 e-f)
0.20 e)
10d
595
7.6 104
3.0 103
710
2720
1.5 104
0.78
1190
≥1160
≥150
≥750
0.19 f)
a) Full width at half-maximum ; b) fluorescence quantum yield ; c) standard : quinine in 0.5M H2SO4 (f=0.546 d) standard : fluorescein in 0.1 M aq. NaOH
(f =0.90);e) standard : Rhodamine 6G in EtOH (f =0.94) ; f) standard : cresyl violet in methanol (f =0.54) ; g) brightness; h) experimental fluorescence lifetime ;
i) Molecular TPEF action cross section (i.e., two-photon brightness) at TPAmax;j) Molecular TPA cross section at TPAmax. 1 GM = 10 -50 cm4.s.photon -1
nature of the donor and acceptor end-groups significantly
Absorption
influences the position of this low-energy absorption band.
Increasing the donor strength is inducing progressive
a
As shown in Table 4, all compounds show an intense absorption
band in the near UV or visible region which can be ascribed to
intramolecular charge transfer transition (ICT). As expected, the
bathochromic shift as illustrated in Figure 1 for series 8a-e and
observed also for series 9a-d and 10a-d (see Table 4).
This article is protected by copyright. All rights reserved

European Journal of Organic Chemistry
10.1002/ejoc.201600806
FULL PAPER
(whose band is hidden by the more intense ICT one). In the
case of compounds of series 9 and 10 having weaker donors
(OMe, OEt), the n-* transition is most probably found at slightly
lower energy and thus responsible for only weak fluorescence
(due to reduced transition dipole). We note that compound 9d
and 10d show increased fluorescence quantum yield as
compared to their homologues having one or two thiophene
instead of a TT connecting unit (f=0.61 for 9d instead of 0.13
and 0.34 and (f=0.20 for 10d instead of 0.09 and 0.06). This
enhanced fluorescence can be ascribed to both larger radiative
rate and lower non-radiative rates. Hence the planarization
induced by the TT unit induces both higher transition dipoles and
increase rigidity, both responsible for improved fluorescence
efficiency. As a result compound 9d and 10d show much larger
brightness than their homologues having a thiophene or bis-
thiophene instead of TT (maxf = 3.3 104 M-1.cm-1 for dye 9d
compared to 1.3 104 M-1.cm-1 for its bis-thiophene homologue[20b]
and maxf = 1.5 104 M-1.cm-1 for the dye 10d compared to 2.6 103
M-1.cm-1) while their emission maximum is located in between
those of the two homologues (i.e. red-shifted compared to the
homologue having one thiophene in the -system and blue-
shifted compared to that of that of the homologue having two
thiophene).
8a
8b
8c
8d
8e
30x103
20
10
0
250
300
350
400
450
500
550
nm
Figure 1. Absorption spectra of compounds 8a-e in chloroform.
A marked bathochromic and hyperchromic shift as well as
narrowing of the main absorption band (Table 4) is observed
when increasing the electron-withdrawing strength of the
acceptor as indicated by comparison of compounds 8-10d (see
Figure 2) and compounds 8-10b (see Figure S1). These
combined effects points to an increased polarization of the
ground-state (in relation with larger contribution of the ICT
mesomeric form in the description of the electronic structure)
shifting the electronic structure towards a more “cyanine-like”
structure.[28]
The nature of the donor and acceptor end-groups also
significantly influences the fluorescence spectra. In all series,
increasing the strength of the donor end-groups induces a
progressive red-shift of the emission spectrum as illustrated in
Figure 3 for series 8a-e. In all cases an increase of the Stokes
shift value is also observed (see Table 4) indicating a more
pronounced photo-induced ICT.
8d
9d
10d
60x103
40
20
0
1.0
8a
8b
8c
0.8
8d
8e
0.6
300
400
500
nm
600
700
0.4
0.2
0.0
Figure 2. Absorption spectra of compounds 8-10d in chloroform
Fluorescence
400
500
600
700
As noted from Table 4, a number of the push-pull derivatives
built from a TT -connector investigated in the present work
show significant fluorescence. The fluorescence quantum yield
is found to depend drastically on the nature of the acceptor and
donor end-groups. Indeed all derivatives of series 8 (i.e. push-
pull derivatives bearing an aldehyde as acceptor) but 8a (lacking
the presence of a donor) show significant fluorescence quantum
yield. In contrast, for derivatives bearing strong acceptor end-
groups (i.e. dicyano or diethylthiobarbiturate) of series 9 and 10,
only compounds 9d and 10d bearing the strongest donor (i.e.
diakylamino) show sizeable. Such behavior was observed earlier
in related homologous compounds having a thiophene or bis-
thiophene unit instead of TT.[20b] This behavior can be related to
the nature of the lowest-energy excited state (responsible for
emission): for stronger donor and acceptor end-groups the ICT
* transition shifts to lower energy and the corresponding
excited state is thus located below that of the n-* transition
nm
Figure 3. Emission spectra of compounds 8a-e in chloroform
Increasing the strength of the acceptor end-group also induces a
red-shift of the emission as shown in Figure 4 for series 8-10b
(and illustrated in Fig.S2 for series 8-10d). In both cases
however, we note a reduction of the Stokes shift values (Table
4). This effect concomitant with a narrowing of the ICT
absorption band and red shifts of both the emission and
absorption bands points to a shift of the electronic structure of
the dye towards the cyanine limit (with increasing contribution of
the zwitterionic mesomeric form to the description of the ground-
state structure). Compound 10d which has the larger extinction
coefficient, narrowest absorption band, smallest Stokes’ shift
value and the most red-shifted absorption and emission (with
maximum located in the NIR region) is the closest to the
cyanine-dye like structure.
This article is protected by copyright. All rights reserved

European Journal of Organic Chemistry
10.1002/ejoc.201600806
FULL PAPER
brightness; respectively 240 GM for green-yellow emitter 8d,
510 GM for red emitter 9d, and 150 GM for NIR emitter 10d.
1.0
0.8
0.6
0.4
0.2
0.0
8b
9b
10b
8b
500
400
300
200
100
0
9b
10b
400
450
500
550
nm
600
650
700
750
Figure 4. Emission spectra of compounds 8-10b in chloroform
700
800
900
TPA / nm
1000
1100
Finally, we note that whereas dye 8b-d are either blue-(8b-c) or
green (8d-e) bright emitters (with brightness values ranging
between 2.1 104 M-1.cm-1 and 3.4 104 M-1) dyes 9d and 10d are
complementary bright red and NIR emitters.

Figure 6. Two-photon absorption spectra of compounds 8-10b in chloroform
Increasing the strength of the acceptor end-group also induces
a red-shift of the TPA band as illustrated in Figure 6 for series 8-
10b and Figure 7 for series 8-10d. In the case of the series
bearing a MeO donor end-group (8-10b) the stronger acceptor
(diethylthiobarbiturate) leads to the largest maximum TPA cross-
section while in the case of the series bearing a NEt2 donor end-
group (8-10d), the maximum TPA cross-section is attained with
the push-pull derivative bearing a dicyano acceptor (836 GM).
This may be related to the electronic structure of dye 10d which
is much closer to the cyanine limit than 9d thus leading to lower
TPA response.[29] In addition, we note that in the case of the
diethylthiobarbiturate acceptor, steric hindrance due to the
repulsion and repulsion between the lone pairs of the sulfur of
the thiophene ring and the oxygen atoms of the acceptor may
cause deviation from planarity which may also influence the TPA
properties.
Two-photon absorption
Thanks to their fluorescence properties, the TPA of most push-
pull derivatives could be determined by investigating their two-
photon induced fluorescence in solution. TPA spectra were
obtained in the 700-1200 nm spectral range through
femtosecond two-photon excited fluorescence experiments and
by following the methodology described by Webb and
collaborators.[28] The corresponding data are gathered in Table 4.
All compounds show a broad TPA band (Figures 5-7) whose
maximum is located at about twice the wavelength of the one-
photon absorption (OPA) band, which indicates that the lowest
excited state is both one and two-photon allowed as expected
for push-pull derivatives (see Fig. S3-S5 in SI). We stress that
most probably, the TPA properties of these dipolar derivatives
are influenced by the solvent polarity as reported recently for
other dipolar heterocyclic derivatives.[10p] Here we chose a
solvent of medium polarity to conduct experiments.
800
8d
9d
10d
600
800
9a
9b
9c
9d
400
200
600
400
200
0
700
800
900
TPA / nm
1000
1100

Figure 7. Two-photon absorption spectra of compounds 8-10d in chloroform
700
800
900
TPA / nm
1000
1100

Finally, it is of interest to compare the two-photon absorption
response of the brightest two-photon dyes (i.e. 8d, 9d and 10d)
to that of their homologue having a bis-thiophene -connector
instead of TT -connector in the conjugated path.[20b] The
aldehyde derivative 8d show slightly larger TPA maximum
cross-section (276 GM compared to 253 GM), whereas the
dicyanovinyl derivative 9d show much larger TPA maximum
cross-section (369 GM compared to 115 GM), while the
thiobarbituric acid derivative 10d show smaller response TPA
maximum cross-section (750 GM compared to 1600 GM).
Figure 5. Two-photon absorption spectra of compounds 8a-e in chloroform
As illustrated in Figure 5, for series 9a-d increasing the strength
of the donating end-groups induces both a red-shift of the TPA
band in the NIR region and pronounced enhancement of the
maximum TPA cross-section. Such effect is also observed in the
case of series 8b-d and 10b-d (see Table 4 and SI). As the
fluorescence quantum yield values also increase, the push-pull
compounds bearing the strongest donating end-group (i.e.,
dialkylamino moiety) are found to lead to the largest two-photon
This article is protected by copyright. All rights reserved

European Journal of Organic Chemistry
10.1002/ejoc.201600806
FULL PAPER
This trend can be interpreted by the different polarization of the
derivatives bearing the different acceptor end-groups. Increasing
the acceptor strength leads to increased polarization as
mentioned above. Replacing the bis-thiophene -connector by
the TT -connector also increases the polarization and shifts the
electronic structure closer to the cyanine limit. This is due to the
reduced aromaticity of the TT unit compared to that of the bis-
thiophene (leading to lower gap V[29]). In addition, the planarity of
the TT moiety (as compared to the free rotation of the single
bond linking the two thiophene rings in the bis-thiophene -
connector) favor coupling and thus also shifts the structure
closer to the cyanine limit. The narrower ICT absorption bands
combining
a
strong acceptor (i.e., dicyanonvinyl or
diethylthiobarbiturate) and stronger donor (dialkylamino) show
sizeable fluorescence. In addition, these derivatives are found to
show both improved fluorescence quantum yield as compared to
their homologues having a bis-thiophene instead of TT in the
conjugated -system as well as larger TPA response. As a result,
by using the fused thiophene conjugating system, several new
fluorescent dyes showing enhanced one- and two-photon
brightness and tunable emission (i.e. blue, green, red and NIR)
has been obtained. These dyes hold promise as new fluorescent
probes for bioimaging purposes.
of the compounds 8d, 9d and 10d as compared to those of their
[20b]
analogues having a bis-thiophene -connector
provides a
Experimental Section
clear evidence of this effect. Since there is an optimum
electronic distribution (positioned in between the neutral form
and the cyanine limit) which maximizes the TPA response of
push-pull derivatives, the effect of increased polarization
depends on the initial polarization.[29] Due the low initial
polarization in aldehyde derivatives (i.e., derivatives 8), the
effect of TT is favorable as it increases the polarization and
shifts the structure closer to optimum polarization. This effect is
even more pronounced for the dicyanovinyl derivative which is
most probably very close to the optimum polarization leading to
maximum TPA response for compound 9d. In contrast, due to
Synthesis
Thin layer chromatography was carried out on 0.25 mm thick precoated
silica plates (Merck Fertigplatten Kieselgel 60F254). Melting points were
measured on a Gallenkamp melting point apparatus. NMR spectra were
obtained on a Varian Unity Plus Spectrometer at an operating frequency
of 300 MHz for H NMR and 75.4 MHz for 13C NMR or a Bruker Avance
1
III 400 at an operating frequency of 400 MHz for 1H NMR and 100.6 MHz
for 13C NMR using the solvent peak as internal reference at 25 ºC. All
chemical shifts are given in ppm using δHMe4Si = 0 ppm as reference
and J values are given in Hz. Assignments were made by comparison of
chemical shifts, peak multiplicities and J values and were supported by
spin decoupling-double resonance and bidimensional heteronuclear
HMBC and HMQC correlation techniques. IR spectra were run on a FTIR
Perkin-Elmer 1600 spectrophotometer in nujol or in KBr. Elemental
analyses were carried out on a Leco CHNS 932 instrument. Low and
high resolution mass spectrometry analyses were performed at the
“C.A.C.T.I. - Unidad de Espectrometria de Masas”, at University of Vigo,
Spain.
the
strong
electron-withdrawing
strength
of
the
diethylthiobarbiturate, its electronic distribution is close to the
cyanine limit (i.e. past the optimum polarization), thus leading to
a
decrease of the TPA response when increasing the
polarization.
In any case, thanks to the much larger fluorescence quantum
yield, both 8d, 9d and 10d show improved two-photon
brightness values as compared to their homologues having bis-
thiophene instead of TT in the conjugated system. This
demonstrates that the implemented strategy is of major interest
to yield a series of bright fluorescent dyes showing tunable
emission in the visible region down to the NIR region and large
two-photon brightness. In particular fluorescent dye 10d offers
major promises as it can be both two-photon excited in the NIR
region (close to 1.2 m) and emits in the NIR region. As such it
holds promise as novel fluorochromes for biological imaging.
All Suzuki couplings were carried out under an argon atmosphere and all
commercially available reagents and solvents were used as received.
Synthesis of 3-bromothiophene-2-carbaldehyde 2
3-Bromothiophene 1 (29.35 g, 180 mmol) was added dropwise to a
stirred solution of lithium diisopropylamide (LDA) [prepared by addition of
butyllithium (2.5 mol.l-1 in hexane; 80 mL, 200 mmol) to diisopropylamine
(22.24 g, 220 mmol)] in dry tetrahydrofuran (300 mL) at 0 °C and the
resulting mixture was stirred for a further 30 min at this temperature prior
to addition of dimethylformamide (16.3 ml, 15.3 g, 210 mmol). The
mixture was stirred during 3 hours when an excess of 20% aqueous
ammonium chloride was added to it. The product was extracted with
diethyl ether 3x250 mL), washed three times with water (300 mL) and
dried with magnesium sulfate. Evaporation of the organic solvent gave
(34.4 g, 180 mmol) of 3-bromothiophene-2-carbaldehyde 2[24] in
quantitative yield as a brown oil. 1H NMR (CDCl3)  7.13 (d, 1H, J=
5.1Hz), 7.70 (dd, 1H, J= 5.1Hz, J= 1.4Hz), 9.95 (d, 1H, J= 1.4 Hz, CHO).
Conclusions
5-Arylthieno[3,2-b]thiophene aldehydes
8 were synthesized
through Suzuki coupling reaction of functionalized aryl boronic
acids with 5-bromothieno[3,2-b]thiophene-2-carbaldehyde 6.
Donor-acceptor substituted thieno[3,2-b]thiophenes 9-10 have
been prepared, in moderate to good yields from the formyl-
substituted derivatives 8 and low cost commercially available
reagents, using simple and convenient synthetic methodologies.
These new derivatives are found to show intense absorption in
the near UV down to the orange visible region depending on the
nature of the donor or acceptor end-groups, in relation with an
strong ICT transition. Whereas all push-pull aldehydes show
good fluorescence properties, only the push-pull derivatives
Synthesis of methyl thieno[3,2-b]thiophene-2-carboxylate 3
3-Bromothiophene-2-carbaldehyde 2 (34.4 g, 180 mmol) was added to a
stirred mixture of methyl 2-sulfanylacetate (16.1 ml, 19.10 g, 180.0 mmol),
potassium carbonate (37.3 g) and N,N-dimethylformamide (140 ml) at
room temperature and the resulting mixture was stirred during 72 h at
60°C. Then it was poured into water (600 ml) and the precipitate was
This article is protected by copyright. All rights reserved

European Journal of Organic Chemistry
10.1002/ejoc.201600806
FULL PAPER
filtered to give 21.4 g of methyl thieno[3,2-b]thiophene-2-carboxylate 3[24]
as an yellow solid in 60% yield, mp: 95-96°. H NMR (CDCl3)  3.91 (s,
Method A:
1
3H), 7.27 (d, 1H, J= 5.3 Hz), 7.58 (d, 1H, J= 5.3Hz), 7.99 (s, 1H).
5-Bromothieno[3,2-b]thiophene-2-carbaldehyde 6 (0.25 mmol, 100 mg)
was coupled to boronic acids 7a-e (0.33 mmol) in a mixture of DME (6
mL), aqueous solution of Na2CO3 (0.4 mL, 2 M) and Pd(PPh3)4 (6 mol%)
at 80°C under nitrogen. The reactions were monitored by TLC which
determined the different reaction times (4-24 h). After cooling, the mixture
was filtered and ethyl acetate and a saturated solution of NaCl were
added and the phases were separated. The organic phase was washed
with water (3 x 10 mL) and with a solution of NaOH (10%) (1 x 10 mL).
The organic phase obtained was dried using MgSO4, filtered and the
solvent was removed under vacuum to give the crude mixture products
which were submitted to column chromatography on silica with
increasing amounts of ether in light petroleum as eluent to afford the pure
products 8a-e.
Synthesis of 2-(hydroxymethyl)thieno[3,2-b]thiophene 4
A solution of methyl thieno[3,2-b]thiophene-2-carboxylate 3 (15 g, 75.7
mmol) in dry dimethyl ether (350 mL) was added during 2 h to a
suspension of lithium aluminum hydride (5.75 g, 151.5 mmol) in dry
dimetylether (200 mL) which had been cooled in an ice-water bath. After
the addition was completed, the mixture was stirred at room temperature
for 3 h. The reaction was worked up by cooling in an ice-water bath with
successive dropwise addition of water (5.7 ml), 15% aqueous sodium
hydroxide (6 mL), and water (18 mL) with vigorous stirring. Vigorous
stirring was continued until the salts were well granulated. The ether
solution of the product was decanted and the salts washed further with
ether. The combined ether solutions were dried with MgSO4 and filtered,
and the solvent was evaporated under vacuum to give 11.6 g of product
4 as a white solid[25] in 90% yield. 1H NMR (CDCl3)  4.87 (s, 2H), 7.19 (s,
1H), 7.22 (d, 1H, J= 5.2 Hz), 7.34 (d, 1H, J= 5.2 Hz). 13C NMR (CDCl3) 
61.0, 117.8, 119.6, 127.0, 139.2, 146.1.
Method B:
5-Bromothieno[3,2-b]thiophene-2-carbaldehyde 6 (0.25 mmol, 100 mg)
was coupled to boronic acids 7a-e (0.33 mmol) in a mixture of toluene (6
mL), K2CO3 (2,5 mmol, 0.64g, 10 eq.), ethanol (3.2 mL), 1 mL of water
and Pd(PPh3)4 (10 mol%) at reflux under nitrogen. The reactions were
monitored by TLC which determined the different reaction times (1-2 h).
After cooling, the mixture was filtered and the solid was washed with
CH2Cl2. The organic phase obtained was washed with water (3x10 mL),
dried with MgSO4 filtered and the solvent was removed under vacuum to
give the crude products which were submitted to column chromatography
on silica with dichloromethane as eluent to afford the coupled products
8a-e. Recrystallization from dichloromethane/petroleum ether gave the
pure compounds.
Synthesis of thieno[3,2-b]thiophene-2-carboxaldehyde 5
A solution of 2-(hydroxymethyl)thieno[3,2-b]thiophene 4 (11.6 g, 68.3
mmol) in methylene chloride (160 mL) was added all at once to a stirred
suspension of pyridinium chlorochromate (22.1 g, 102.4 mmol) which had
been ground in a mortar and pestle and partially dissolved in methylene
chloride with vigorous stirring. Stirring was continued for 2 h. Pyridinium
chlorochromate (5.9 g, 27.3 mmol) was added, and the mixture was
stirred vigorously for 30 min. The solution was worked up by adding
dimethylether (1 L) and then filtering through a column of silica gel. The
gum in the flask was washed with ether (3 x 1500 mL) and these
washings were passed through the column. The solvents were
evaporated under vacuum to give 8.37 g of crude dark purple crude
product which was recristalised from cyclohexane to give the pure
compound as a pale gray solid, mp: 51-52°C [lit.[25] 53-54]. 1H NMR
(CDCl3)  7.33 (d, 1H, J= 5.2 Hz), 7.47 (d, 1H, J= 5.2 Hz), 7.92 (s, 1H),
9.98 (s, 1H, CHO).
5-Phenylthieno[3,2-b]thiophene-2-carbaldehyde (8a): Yellow solid
1
(Method A, 35% yield; Method B, 80% yield ), m.p. 165-166°C. H NMR
(300 MHz, CDCl3) :  7.39-7.49 (m, 3H, H4’, H3’ and H5’), 7.55 (s, 1H,
H6), 7.67-7.69 (m, 2H, H2’and H6’), 7.93 (s, 1H, H3), 9.97 (s, 1H, CHO)
ppm. 13C NMR (75.4 MHz, CDCl3) :  115.8, 126.2 129.0, 129.2, 133.7,
138.2, 144.5, 146.7, 152.9, 181.2 ppm. IR (nujol): ῡ = 3094, 3059, 2851,
1662, 1625, 1513, 1498, 1259, 1021 cm-1. MS (EI): m/z (%) = 245 (M++1,
15), 244 (M+, 100), 243 (61), 216 (14), 215 (17), 171 (33), 145 (12), 93
(17). HRMS (EI) : calcd. for [C13H8OS2] + 244.0017 : found 244.0021.
Synthesis of 5-bromothieno[3,2-b]thiophene-2-carbaldehyde 6
5-(4-Methoxyphenyl)thieno[3,2-b]thiophene-2-carbaldehyde
(8b):
Yellow solid (Method A, 50% yield; Method B, 72% yield ), m.p. 169-
170°C. 1H NMR (300 MHz, CDCl3) :  3.87 (s, 3H, OCH3), 6.96 (d, 2H,
J=6.9 Hz, H3’ and H5’), 7.41 (d, 1H, J=0.6 Hz, H6), 7.59 (d, 2H, J=6.9
Hz, H2’ and H6’), 7.88 (d, 1H, J=0.6 Hz, H3), 9.94 (s, 1H, CHO) ppm.
13C NMR (75.4 MHz, CDCl3) :  55.4, 114.6, 126.5, 127.6, 129.3, 137.5,
144.0, 147.0, 153.1, 160.4, 183.1 ppm. IR (nujol): ῡ = 3091, 3047, 2980,
2851, 1660, 1603, 1523, 1462, 1262, 1024 cm-1. MS (EI): m/z (%) = 275
(M++1, 11), 274 (M+, 60), 259 (47), 231 (8), 203 (14), 149 (9), 137 (20),
123 (14), 121 (17), 109 (12), 95 (21), 93 (7), 81 (63), 69 (100). HRMS
(EI) : calcd. for [C14H10O2S2] 274.0122 : found 274.0122.
Thieno[3,2-b]thiophene-2-carboxaldehyde 5 (8.37 g, 49.8 mmol) was
dissolved in 150 mL of chloroform. 4.6 g of sodium hydrogenocarbonate
were added to the solution and cooled at 0°C. Bromine (2.56 mL, 8,0 g,
49.8 mmol) was added dropwise and the mixture was stirred at room
temperature during 2 hours. The organic layer was extracted with 200 mL
of water, and the aqueous phase was extracted (3x150 mL) with
methylene chloride. The organic solutions were combined, dried with
magnesium sulfate and evaporated under vacuum to leave a dark solid
which was recristalised from cyclohexane to give (9.4 g, 88%) of 5-
bromothieno[3,2-b]thiophene-2-carbaldehyde 6[14b,26], as a gray solid mp:
142-143°C. IR (Nujol) : 1660, 1409, 1336, 1301, 1280, 1264, 1225, 1148,
1122, 990, 977, 853, 829, 807, 790, 738, 722, 694, 658, 630 cm-1 1H
NMR (CDCl3)  7.34 (s, 1H), 7.83 (s, 1H), 9.96 (s, 1H, CHO). 13C NMR
(CDCl3)  120.9, 122.9, 128.2, 139.3, 144.5, 144.7, 183.3. MS (EI) m/z
(%) : 247 (M+ 81Br, 63), 245 (M+ 79Br, 66), 219 (6), 218 (13), 217 (7), 216
(11), 139 (13), 138 (20), 95 (9), 93 (16), 81 (4), 69 (100). HRMS : m/z
(EI) for C7H379BrOS2 calcd: 245,8809; found: 245,8810; for C7H381BrOS2
calcd: 247,8788; found 247,8790.
5-(4-Ethoxyphenyl)thieno[3,2-b]thiophene-2-carbaldehyde
(8c):
Yellow solid (Method A, 85% yield; Method B, 79% yield ), m.p. 175-
1
176°C. H NMR (250 MHz, CDCl3) :  1.37 (t, 3H, J=7.0 Hz, OCH2CH3),
4.09 (q, 2H, J=7.0 Hz, OCH2CH3), 6.95 (d, 2H, J=8.8 Hz, H3’ and H5’),
7.42 (s, 1H, H6), 7.58 (d, 2H, J=8.8 Hz, H2’and H6’), 7.90 (s, 1H, H3),
9.94 (s, 1H, CHO) ppm. 13C NMR (62.9 MHz, CDCl3) :  14.8, 63.7, 115.1,
126.3, 127.6, 129.3, 137.5, 144.0, 147.1, 153.3, 159.8 , 183.1 ppm. IR
(nujol): ῡ = 3091, 3050, 2978, 2850, 1650, 1605, 1523, 1469, 1259, 1044
cm-1. MS (EI): m/z (%) = 289 (M++1, 15), 288 (M+, 98), 262 (11), 261 (22),
General procedures for Suzuki coupling
This article is protected by copyright. All rights reserved

European Journal of Organic Chemistry
10.1002/ejoc.201600806
FULL PAPER
260 (88), 259 (100), 233 (6), 232 (14), 203 (19), 187 (11), 171 (12), 158
(9). HRMS (EI) : calcd. for [C15H12O2S2] 288.0279 : found 288.0285.
298 (23), 209 (15). HRMS (EI) : calcd. for [C17H10N2OS2] + 322.0229 :
found 322.0228.
5-(4-Diethylaminophenyl)thieno[3,2-b]thiophene-2-carbaldehyde
(8d): Orange solid (Method A, 36% yield; Method B, 84% yield ), m.p.
202-203°C. 1H NMR (300 MHz, DMSO-d6) :  1.13 (t, 6H, J=6.9 Hz,
N(CH2CH3)2), 3.40 (q, 4H, J=6.9 Hz, N(CH2CH3)2), 6.74 (d, 2H, J=9.0 Hz,
H3’ and H5’), 7.52 (d, 2H, J=9.0 Hz, H2’ and H6’), 7.65 (s, 1H, H6), 8.25
(s, 1H, H3), 9.91 (s, 1H, CHO) ppm. 13C NMR (75.4 MHz, DMSO-d6) : 
12.1, 43.4, 111.6, 112.8, 119.8, 126.8, 130.5, 135.8, 142.5, 146.3, 147.9,
153.6, 183.3 ppm. IR (nujol): ῡ = 3089, 2892, 2803, 1655, 1602, 1552,
1430, 1355 cm-1. MS (EI): m/z (%) = 316 (M++1, 7), 315 (M+, 39), 300
(100), 271 (28), 243 (7), 171 (8), 150 (4). HRMS (EI) : calcd. for
[C17H17NOS2] 315.0752 : found 315.0750.
2-((2-(4-Ethoxyphenyl)thieno[3,2-b]thiophen-5-
yl)methylene)malononitrile (9c): Red solid (231 mg, 74%). M.p. 236-
237°C. 1H NMR (300 MHz, DMSO-d6) :  1.35 (t, 3 H, J=7.2 Hz,
OCH2CH3), 4.09 (q, 2H, J=7.2 Hz, OCH2CH3), 7.04 (d, 2 H, J=7.2 Hz, H3’
and H5’), 7.68 (d, 2 H, J=7.2 Hz, H2’and H6’), 7.89 (s, 1 H, H6), 8.22 (s,
1 H, H6), 8.71 (s, 1 H, CH=C(CN)2) ppm. 13C NMR (75.4 MHz, DMSO-
d6) :  14.2, 63.2, 73.3, 113.8, 114.5, 115.2, 125.4, 127.3, 133.1, 135.5,
137.5, 148.6, 152.9, 159.5 ppm. IR (nujol): ῡ = 3021, 2971, 2221, 1609,
1485, 1414, 1259, 1051, cm-1. MS (EI): m/z (%) = 336 (M+, 100), 274 (10),
209 (11). HRMS (EI) : calcd. for [C18H12N2OS2]
336.0385.
+
336.0386 : found
5-(4-Pyrrolidin-1-ylphenyl)thieno[3,2-b]thiophene-2-carbaldehyde
(8e): Orange solid (Method A, 30% yield; Method B, 70% yield ), m.p.
over 250°C. 1H NMR (300 MHz, DMSO-d6) :  1.94-1.99 (m, 4H,
N(CH2CH2)2), 3.26-3.28 (m, 4H, N(CH2CH2)2), 6.61 (d, 2H, J=8.7 Hz, H3’
and H5’), 7.55 (d, 2H, J=8.7 Hz, H2’ and H6’), 7.73 (s, 1H, H6), 8.31 (s,
1H, H3), 9.90 (s, 1H, CHO). 13C NMR (100 MHz, DMSO-d6) :  24.9
(N(CH2CH2)2), 47.3 (N(CH2CH2)2), 112.0 (C6), 113.1 (C3’ and C5’), 120.1
(C1’), 127.0 (C2’ and C6’), 131.4 (C3), 136.0 (C5), 142.6 (C3a ou C6a),
146.7 (C6a or C3a), 148.2 (C2), 154.1 (C4’), 184.0 (CHO) ppm. IR
2-((2-(4-(Diethylamino)phenyl)thieno[3,2-b]thiophen-5-
yl)methylene)malononitrile (9d): Violet solid (154 mg, 49%). M.p. 220-
221°C. 1H NMR (400 MHz, DMSO-d6) :  1.11 (t, 6H, J=7.0 Hz,
N(CH2CH3)2), 3.40 (q, 4H, J=7.0 Hz, N(CH2CH3)2), 6.73 (d, 2H, J=8.8 Hz,
H3’ and H5’), 7.55 (d, 2H, J=8.8 Hz, H2’and H6’), 7.79 (s, 1H, H6), 8.17
(s, 1H, H3), 8.63 (s, 1 H, CH=C(CN)2) ppm. 13C NMR (100 MHz, DMSO-
d6) :  12.4, 43.8, 71.5, 111.6, 113.1, 115.2, 119.4, 127.5, 133.8, 134.8,
136.5, 148.5, 149.9, 152.9 ppm. IR (nujol): ῡ = 3025, 2978, 2214, 1606,
1534, 1403, 1355 cm-1. MS (EI): m/z (%) = 363 (M+, 100), 165 (5). HRMS
(EI) : calcd. for [C20H17N3S2] + 363.0858 : found 363.0855.
(nujol): ῡ
-
-
-Ald), 1657
-N) cm-1. MS
(EI): m/z (%) = 314 (M++1, 25), 313 (M+, 100), 309 (61), 285 (5), 280 (13),
270 (9), 257 (21), 171 (14), 93 (10), 84 (5). HRMS (EI) : calcd. for
[C17H15NOS2] 313.0595 : found 313.0599.
General procedure for the synthesis of arylthienothiophene
thiobarbituric acid derivatives 10a-c from the corresponding formyl
precursors 8 by Knoevenagel condensation with thiobarbituric acid
General
procedure
for
the synthesis
of
dicyanovinyl-
To a solution of 1,3-diethyl-2-thiobarbituric acid (80 mg, 0.38 mmol, 1.2
equiv) and aldehydes 8 (0.32 mmol, 1.0 equiv) in acetonitrile (20 mL)
was added piperidine (1 drop). The solution was refluxed for 2 to 3 h,
then cooled to 0°C. Compounds 8 precipitate, were filtrated, washed with
15 mL of diethyl ether and collected. Recrystallization from
dichloromethane/petroleum ether gave the pure compounds.
arylthienothiophene derivatives 9 from the corresponding formyl
precursors 8 by Knoevenagel condensation with malononitrile
To a solution of malononitrile (0.08 g, 1.2 mmol) and aldehydes 8 (1.0
mmol) in dichloromethane (25 mL) was added piperidine (1 drop). The
solution was stirred at room temperature during different reaction times
(15 min.- 3 h), then petroleum ether (200 mL) was added and the
dicyanovinyl- derivatives 9 precipitate and were filtrated. The crude
compounds were submitted to silica gel column chromatography using
mixtures of chloroform and light petroleum of increasing polarity. The
fraction containing the purified product were collected and evaporated
under vacuum. Recrystallization from dichloromethane/petroleum ether
gave the pure compounds.
1,3-Diethyl-dihydro-5-((2-phenylthieno[3,2-b]thiophen-5-
yl)methylene)-2-thioxopyrimidine-4,6(1H,5H)-dione (10a): Red solid
1
(33 mg, 42%). M.p. 227-228 °C. H NMR (400 MHz, DMSO-d6) :  1.32-
1.39 (m, 6H, N(CH2CH3)2), 4.57-4.66 (m, 4H, N(CH2CH3)2), 7.40-7.49 (m,
3H, H3’, H’4’and H5’), 7.56 (s, 1H, H6), 7.71 (d, 2H, J=6.8 Hz, H2’and
H6’), 8.08 (s, 1H, H3), 8.75 (s, 1 H, C=CH) ppm. 13C NMR (75.4 MHz,
DMSO-d6) :  12.4, 12.5, 43.3, 44.0, 110.5, 115.8, 126.5, 129.3, 129.6,
133.6, 137.4, 139.3, 150.2, 155.2, 155.8, 159.8, 161.0, 178.6 ppm. IR
(nujol): ῡ = 3088, 1682, 1654, 1549, 1511, 1416, 1345 cm-1. MS (EI): m/z
(%) = 427 (M+1, 5), 391 (7), 364 (16), 339 (19), 310 (100), 279 (7), 192
(5), 153 (2). HRMS (EI) : calcd. for [C21H18N2O2S3 + H]+ 427.0603 : found
427.0602.
2-((2-Phenylthieno[3,2-b]thiophen-5-yl)methylene)malononitrile (9a):
Orange solid (132 mg, 54%). M.p. 245-246°C. as an 1H NMR (300 MHz,
DMSO-d6) :  7.41-7.53 (m, 3H, H3’, H4’and H5’), 7.77 (d, 2H, J=6.9 Hz,
H2’and H6’), 8.08 (s, 1H, H6), 8.27 (s, 1H, H3), 8.76 (s, 1 H, CH=C(CN)2)
ppm. 13C NMR (75.4 MHz, DMSO-d6) :  74.2, 114.0, 114.7, 117.1,
126.0, 129.5, 129.6, 133.1, 133.8, 136.4, 138.4, 148.4, 153.6 ppm. IR
(nujol): ῡ = 3020, 2948, 2216, 1606, 1509, 1413 cm-1. MS (EI): m/z (%) =
293 (M+, 100), 277 (32), 263 (30), 237 (31), 226 (56), 203 (11). HRMS
(EI) : calcd. for [C16H9N2S2] + 293.0202 : found 293.0203.
1,3-Diethyl-dihydro-5-((2-(4-methoxyphenyl)thieno[3,2-b]thiophen-5-
yl)methylene)-2-thioxopyrimidine-4,6(1H,5H)-dione (10b) : Red solid
(65 mg, 74%). M.p. 249-250 °C. 1H NMR (400 MHz, CDCl3) :  1.33-1.37
(m, 6H, N(CH2CH3)2), 3.88 (s,
3 H, OCH3), 4.59-4.64 (m, 4H,
N(CH2CH3)2), 6.98 (d, 2 H, J=8.8 Hz, H3’ and H5’), 7.44 (s, 1 H, H6),
7.66 (d, 2 H, J=8.8 Hz, H2’and H6’), 8.06 (s, 1H, H3), 8.74 (s, 1 H,
C=CH) ppm. 13C NMR (100 MHz, CDCl3) :  12.4, 12.5, 43.2, 44.0, 55.5,
109.9, 114.7, 126.3, 127.9, 137.5, 138.6, 138.9, 150.1, 155.9, 156.3,
159.8, 160.9 161.1, 178.6 ppm. IR (nujol): ῡ = 3089, 2978, 1682, 1653,
1606, 1479, 1416, 1330, 1262, 1063 cm-1. MS (EI): m/z (%) = 457 (M+1,
6), 401 (11), 371 (100), 299 (56), 223 (12). HRMS (EI) : calcd. for
[C22H20N2O3S3 + H]+ 457.0708 : found 457.0709.
2-((2-(4-Methoxyphenyl)thieno[3,2-b]thiophen-5-
yl)methylene)malononitrile (9b): Red solid (134 mg, 49%). M.p. 212-
213°C. 1H NMR (300 MHz, DMSO-d6) :  3.82 (s, 3 H, OCH3), 7.06 (d, 2
H, J=8.8 Hz, H3’ and H5’), 7.71 (d, 2 H, J=6.8 Hz, H2’and H6’), 7.95 (s, 1
H, H6), 8.24 (s, 1H, H3), 8.72 (s, 1 H, CH=C(CN)2) ppm. 13C NMR (75.4
MHz, DMSO-d6) :  55.4, 73.4, 114.1, 114.8 , 115.6, 125.7, 127.6, 133.8,
135.8, 137.7, 148.9, 153.4, 160.4 ppm. IR (nujol): ῡ = 3024, 2984, 2219,
1606, 1523, 1412, 1257, 1033 cm-1. MS (EI): m/z (%) = 322 (M+, 100),
This article is protected by copyright. All rights reserved

European Journal of Organic Chemistry
10.1002/ejoc.201600806
FULL PAPER
1,3-Diethyl-dihydro-5-((2-(4-(diethylamino)phenyl)thieno[3,2-
b]thiophen-5-yl)methylene)-2-thioxopyrimidine-4,6(1H,5H)-dione
(10d): Green solid (83 mg, 82%). M.p. 238-239°C. 1H NMR (300 MHz,
Acknowledgements
MMMR thanks the Fundação para a Ciência e Tecnologia
(Portugal) for financial support to the Portuguese NMR network
(PTNMR, Bruker Avance III 400-Univ. Minho), FCT and FEDER
(European Fund for Regional Development)-COMPETEQREN-
EU for financial support to the research centre CQ/UM [PEst-
C/QUI/UI0686/2013 (FCOMP-01-0124-FEDER-037302] and a
PhD grant to M.C.R. Castro (SFRH/BD/78037/2011). M.B.-D.
acknowledges financial support from the Conseil Régional
d’Aquitaine (Chair of Excellence to M.B.-D. and fellowship to
V.H.). This study has been carried out with financial support
from the French State, managed by the French National
Research Agency (ANR) in the frame of “the Investments for the
future” Programme IdEx Bordeaux – LAPHIA (ANR-10-IDEX-03-
02).
CDCl3)
:  1.25-1.28 (m, 6H, N(CH2CH3)2), 1.31-1.39 (m, 6H,
N(CH2CH3)2), 3.46-3.51 (m, 4H, N(CH2CH3)2), 4.57-4.66 (m, 4H,
N(CH2CH3)2), 6.44 (d, 2H, J=8.7 Hz, H3’ and H5’), 7.66 (d, 2H, J=8.7 Hz,
H2’and H6’), 8.04 (s, 1H, H6), 8.54 (s, 1H, H3), 8.67 (s, 1 H, C=CH) ppm.
IR (nujol): ῡ = 3073, 2931, 1681, 1655, 1602, 1545, 1405, 1351, 1328
cm-1. MS (EI): m/z (%) = 497 (M+, 100). HRMS (EI) : calcd. for
[C25H27N3O2S3 ]+ 497.1260 : found 497.1258. C25H27N3O2S3 (497.70) :
calcd. C 60.33, H 5.47, N 8.44, S 19.33; found C 60.06, H 5.58, N 8.16, S
19.23.
Photophysical study
All photophysical properties were analyzed with freshly prepared air
equilibrated solutions at room temperature (293 K). UV/Vis absorption
spectra were recorded using a Jasco V-570 spectrophotometer. Steady-
state fluorescence measurements were performed on dilute solutions
(optical density < 0.1) contained in standard 1 cm quartz cuvettes using a
Horiba (FluoroLog or FluoroMax) spectrometer in photon-counting mode.
Keywords: Aldehydes • Suzuki coupling • push-pull
thienothiophenes • Fluorescence •Two-photon absorption
Fully corrected emission spectra were obtained for each compound at ex
max
= abs
with an optical density at ex ≤ 0.1 to minimize internal
absorption. Fluorescence quantum yields were measured according to
literature procedures,[30] using fluorescein in 0.1 M NaOH (f = 0.9),
quinine bisulfate in 0.5 M H2SO4 (f = 0.546), Rhodamine 6G in EtOH (f
=0.94) or cresyl violet in MeOH (f = 0.54). Fluorescence decays were
References
[1]
M. Pawlicki, H. A. Collins, R. G. Denning, H.L. Anderson, Angew. Chem
Int. Ed. 2009, 48, 3244–3266; F. Terenziani, C. Katan, E. Badaeva, E.
Tretiak, M. Blanchard-Desce, Adv. Mater. 2008, 20, 4641–4678; G.S.
He, L.-S. Tan, Q. Zheng, P. N. Prasad, Chem Rev. 2008, 108, 1245–
1330.
measured in
a time-correlated single photon counting (TCSPC)
configuration, under excitation from selected nanoLED (370, 455 or 570
nm). The instrument response was determined by measuring the light
scattered by a Ludox suspension. The lifetime values were obtained from
the reconvolution fit analysis of the decay profiles; the quality of the fits
was judged by the reduced 2 value (2 <1.1). The reported lifetimes are
within ±0.1 ns.
[2]
[3]
H. M. Kim, B. R. Cho, Chem. Commun., 2009, 1539.
D. Kim, H. G. Ryu, K. H. Ahn, Org. Biomol. Chem., 2014, 12, 4550-
4566
[4]
[5]
A. S. Dvornikov, E. P. Walker, P. M. Rentzepis, J. Phys. Chem. A 2009,
113, 13633–13644; C. C. Corredor, Z.-L. Huang, K. D. Belfield, A. R.
Morales, M. V. Bondar, Chem. Mater., 2007, 19, 5165-5173.
S. Kawata, H.-B. Sun, T. Tanaka and K. Takada, Nature, 2001, 412,
697-698; I. Sakellari, E. Kabouraki, D. Gray, V. Purlys, C. Fotakis, A.
Pikulin, N. Bityurin, M. Vamvakaki, M. Farsari, ACS Nano, 2012, 6,
2302-2311.
Two-photon absorption
TPA cross-sections (2) were determined from the two-photon excited
fluorescence (TPEF) cross sections (2f) and the fluorescence emission
quantum yield (f). TPEF cross sections of 10-4 M chloroform solutions
were measured relative to fluorescein in 0.01M aqueous NaOH for 715-
980 nm, using the well-established method described by Xu and Webb
and the appropriate solvent-related refractive index corrections.[31] The
quadratic dependence of the fluorescence intensity on the excitation
power was checked for each sample and all wavelengths, indicating that
the measurements were carried out in intensity regimes where saturation
or photodegradation did not occur.
[6]
[7]
Q. Zheng, G. S. He, P. N. Prasad, Chem. Phys. Lett., 2009, 475, 250-
255.
W. Denk, J. H. Strickler, W. W. Webb, Science, 1990, 248, 73-76; b) K.
Svoboda, W. Denk, D. Kleinfeld, D. W. Tank, Nature, 1997, 385, 161-
165; M. Blanchard-Desce, C. R. Physique, 2002, 3, 439-448; H. M. Kim,
B. R. Cho, Chem. Commun. 2009, 153–164; H. M. Kim, B. R. Cho,
Chem. Asian J. 2011, 6, 58-69.
[8]
[9]
K. Ogawa, Y. Kobuke, Org. Biomol. Chem. 2009, 7, 2241–2246; J. R.
Starkey, A. K. Rebane, M. A. Drobizhev, F. Meng, A. Gong, A. Elliott, K.
McInnerney, C. W. Spangler, Clin. Cancer Res., 2008, 14, 6564-6573;
H. A. Collins, M. Khurana, E. H. Moriyama, A. Mariampillai, E.
Dahlstedt, M. Balaz, M. K. Kuimova, M. Drobizhev, V. X. D. Yang, D.
Phillips, A. Rebane, B. C. Wilson, H. L. Anderson, Nat. Photonics, 2008,
2, 420-424.
Measurements were conducted using excitation sources delivering fs
pulses. This is preferred in order to avoid excited state absorption during
the pulse duration, a phenomenon which has been shown to lead to
overestimated TPA cross-section values. To span the 700-980 nm range,
a Nd:YLF-pumped Ti:sapphire oscillator was used generating 150 fs
pulses at a 76 MHz rate. To span the 1000-1400 nm range, an OPO (PP-
BBO) was added to the setup to collect and modulate the output signal of
the Ti:sapphire oscillator. The excitation was focused into the cuvette
through a microscope objective (10X, NA 0.25). The fluorescence was
M. Albota, D. Beljonne, J. L. Bredas, J. E. Ehrlich, J. Y. Fu, A. A. Heikal,
S. E. Hess, T. Kogej, M. D. Levin, S. R. Marder, D. McCord-Maughon, J.
W. Perry, H. Rockel, M. Rumi, C. Subramaniam, W. W. Webb, X. L. Wu,
C. Xu, Science 1998, 281, 1653–1656.
detected in epifluorescence mode via
a dichroic mirror (Chroma
[10] a) V. Parthasarathy, S. Fery-Forgues, E. Campioli, G. Recher, F.
Terenziani, M. Blanchard-Desce, Small, 2011, 7, 3219–3229; b) Y.
Jiang, Y. Wang, J. Hua, S. Qu, S. Qian, H. Tian, Chem. Phys. Phys.
Chem. 2011, 13, 8838-8846; c) M. Zhang, M. Li, F. Li, D. Zhang, J.
Zhang, F. Yi, C. Huang, Tetrahedron Lett. 2007, 48, 2329-2333; d) Q.
Li, J. Huang, A. Zhong, C. Zhong, M. Peng, J. Liu, Z. Pei, Z. Huang, J.
675dcxru) and a barrier filter (Chroma e650sp-2p) by a compact CCD
spectrometer module BWTek BTC112E. Total fluorescence intensities
were obtained by integrating the corrected emission. The experimental
uncertainty of the action cross-section values determined by this method
has been estimated to be ±10%.
This article is protected by copyright. All rights reserved

European Journal of Organic Chemistry
10.1002/ejoc.201600806
FULL PAPER
Qin, Z. J. Li, J. Phys. Chem. 2011, 115, 4279-4285; e) V. Hrobáriková,
P. Hrobárik, P. Gajdoš, I. Fitilis, M. Fakis, P. Persephonis, P. Zahradník,
J. Org. Chem. 2010, 75, 3053-3068; f) H. Zhou, F. Zhou, S. Tang, P.
Wu, Y. Chen, Y. Tu, J. Wu, Y. Tian, Dyes Pigments 2011, 92, 633-641;
g) P. Lind, M. Carlsson, B. Eliasson, E. Glimsdal, M. Lindgren, C.
Lopes, L. Boman, P. Norman, Molecular Phys. 2009, 107, 629-641; h)
P Hrobárik, V. Hrobáriková, I. Sigmundová, P. Zahradník, M. Fakis, I.
Polyzos, P. Persephonis, J. Org. Chem. 2011, 76, 8726-8736; i) Y. M.
Poronik, V. Hugues, M. Blanchard-Desce, D. T. Gryko, Chem. Eur. J.
2012, 18, 9258-9266; j) G. Argouarch, R. Veillard, T. Roisnel, A. Amar,
H. Meghezzi, A. Boucekkine,* V. Hugues, O. Mongin, M. Blanchard-
Desce, F. Paul, Chem. Eur. J., 2012, 18, 11811–11827; k)K. Amro, J.
Daniel, G. Clermont, T. Bsaibess, M. Pucheault, E. Genin, M. Vaultier,
M. Blanchard-Desce, Tetrahedron, 2014, 70, 1903-1909; l) A. I. Ciuciu,
D. Firmansyah, V. Hugues, M. Blanchard-Desce, D. T. Gryko, L.
Flamigni, J. Mater. Chem. C, 2014, 2, 4552-4565; m) M. Grzybowski, V.
Hugues, M. Blanchard-Desce, D. T. Gryko, Chem. Eur. J., 2014, 20,
12493-12501; n) P. Hrobárik, V. Hrobáriková, V. Semak, P. Kasák, E.
Rakovský, I. Polyzos, M. Fakis, P. Persephonis, Org. Lett., 2014, 16,
6358–6361; o) M. Grzybowski, E. Glodkowska-Mrowka, V. Hugues, M.
Blanchard-Desce, D. T. Gryko, Chem. Eur. J. 2015, 21, 9101-9110; p)
R. Orłowski, M. Banasiewicz, G. Clermont, F. Castet, R. Nazir, M.
Blanchard-Desce, D. T. Gryko, Phys. Chem. Chem. Phys., 2015, 17,
23724-23731.
2009, WO 2009051390 A2 20090423; i) A. Mishra, M. K. R. Fischer, P.
Bäuerle, Angew. Chem. Int. Ed. 2009, 48, 2474-2499.
[15] a) J. I. Tietz, J. R. Mastriana, P. Sampson, A. J. Seed, Liquid Crystals
2012, 39, 515–530. b) R. M. Gipson, P. Sampson, A. J. Seed, Liquid
Crystals 2010, 37, 101-108.
[16] M. C. G. M. Heeney, W. Zhang, K. S. Whitehead, D. D. C. Bradley, I.
McCullochd, A. J. Campbell, Chem. Commun. 2008, 1079–1081.
[17] a) C. B. Nielsen, I. McCulloch, Progress in Polymer Science 2013, 38,
2053–2069; b) A. Capan, H. Veisi, A. C. Goren, T. Ozturk,
Macromolecules 2012, 45, 8228-8236; c) N. Hergué, P. Frère, J.
Roncali, Org. Biomol. Chem. 2011, 9, 588-595; d) K. Nakayama, Y.
Hirose, J. Soeda, M. Yoshizumi, T. Uemura, M. Uno, W. Li, M. J. Kang,
M. Yamagishi, Y. Okada, E. Miyazaki, Y. Nakazawa, A. Nakao, K.
Takimiya, J. Takeya, Adv. Mater. 2011, 23, 1626–1629; e) K. Niimi, S.
Shinamura, I. Osaka, E. Miyazaki, K. Takimiya, J. Am. Chem. Soc.
2011, 133, 8732–8739.
[18] a) M. M. M. Raposo, G. Kirsch, Tetrahedron 2003, 59, 4891-4899; b) M.
M. M. Raposo, A. M. C. Fonseca, G. Kirsch, Tetrahedron 2004, 60,
4071-4078; c) S. P. G. Costa, R. M. F. Batista, P. Cardoso, M. Belsey,
M. M. M. Raposo, Eur. J. Org. Chem. 2006, 17, 3938-3946; d) M. M. M.
Raposo, A. M. R. C. Sousa, A. M. C. Fonseca, G. Kirsch Tetrahedron
2006, 62, 3493-3501; e) C. Herbivo, A. Comel, G. Kirsch, M. M. M.
Raposo, Tetrahedron 2009, 65, 2079-2086; f) M. C. R. Castro, M.
Belsley, A. M. C. Fonseca, M. M. M. Raposo, Tetrahedron 2012, 68,
8147-8155.
[11] a) V. P. Rao, K. Y. Wong, A. K.-Y. Jean and K. J. Drost, Chem. Mater.
1994, 6, 2210–2212; b) M. Blenkle, P. Boldt, C. Bräuchle, W. Grahn, I.
Ledoux, H. Nerenz, S. Stadler, J. Wichern, J. Zyss, J. Chem. Soc.
Perkin Trans. 2 1996, 1377-1384; c) P. Boldt, G. Bourhill, C. Bräuchle,
Y. Jim, R Kammler, C. Müller, J. Rase, J. Wichern, Chem. Commun.
1996, 793-795; d) I. Cazenobe, I. Ledoux, J. Zyss, P. Boldt, J. Wichern,
T. H. Kirchberger, J. Rase, Opt. Mater. 1998, 9, 280-285; e) A. B.
Marco, R. Andreu, S. Franco, J. Garín, J. Orduna, B. Villacampa, R.
Alicante, Tetrahedron 2013, 69, 3919–3926; f) A. B. Marco, R. Andreu,
S. Franco, J. Garín, J. Orduna, B. Villacampa, B. E. Diosdado, J. L.
Navarrete, J. Casado, Org. Biomol. Chem. 2013, 11, 6338–6349.
[12] a) O-K. Kim, A. Fort, M. Barzoukas, M. Blanchard-Desce, J-M. Lehn, J.
Mater. Chem. 1999, 9, 2227–2232. b) P. J. Skabara, In Handbook of
Thiophene-based Materials, Vol.1 (Eds.: I. F. Perepichka, D. F.
Perepichka), John Wiley & Sons, Chichester, 2009, Chapter 3.
[19] a) M. M .M. Raposo, A. M. R. C. Sousa, G. Kirsch, P. Cardoso, M.
Belsey, E. M. Gomes, A. M. C. Fonseca, Org. Lett. 2006, 8, 3681-3684;
b) A. Wojciechowski, M. M. M. Raposo, M. C. R. Castro, W. Kuznik, I.
Fuks-Janczrek, F. Bureš, I. V. Kityk, J. Mater. Sci: Mater. Electron.
2014, 25, 1745-1750.
[20] a) C. Herbivo, A. Comel, G. Kirsch, A. M. C. Fonseca, M. Belsley, M. M.
M. Raposo, Dyes Pigm. 2010, 86, 217-226; b) E. Genin, V. Hugues, G.
Clermont, C. Herbivo, A. Comel, M. C. R. Castro, M. M. M. Raposo, M.
Blanchard-Desce, Photochem. Photobiol. Sci. 2012, 11, 1756-1766.
[21] a) M. Blanchard-Desce, V. Alain, P. V. Bedworth, S. R. Marder, A. Fort,
C. Runser, M. Barzoukas, S. Lebus, R. Wortmann, Chem. Eur. J. 1997,
3, 1091-1104; b) V. Alain, L. Thouin, M. Blanchard-Desce, U. Gubler, C.
Bosshard, P. Günter, J. Muller, A. Fort, M. Barzoukas, Adv. Mater.,
1999, 11, 1210-1214.
[13] For reviews see: a) V. P. Litvinov, Y.aL. Gol’dfarb, Adv. Heterocycl.
Chem. 1976, 19, 123–214; b) A. Comel, G. Sommen, G. Kirsch, Mini-
Rev. Org. Chem. 2004, 1, 367–374; c) V. P. Litvinov, Russ. Chem. Rev.
2005, 74, 217-248; d) V. P. Litvinov, Adv. Heterocycl. Chem. 2006, 90,
125–203; e) M. E. Cinar, T. Ozturk, Chem. Rev. 2015, 115, 3036−3140.
[14] For some selected examples see: a) J. Zhang, H.-B. Li, S.-L. Sun, Y.
Geng, Y. Wu, Z.-M. Su, J. Mater. Chem. 2012, 22, 568-576, b) B.-G.
Kim , C.-G. Zhen , E. J. Jeong , J. Kieffer , J. Kim, Adv. Funct. Mater.
2012, 22, 1606–1612; c) X. Zong, M. Liang, T. Chen, J. Jia, L. Wang, Z.
Sun, S. Xue, Chem. Commun. 2012, 48, 6645–6647; d) H. Choi, I.
Raabe, D. Kim, F. Teocoli, C. Kim, K. Song, J.-H. Yum, J. Ko, M. K.
Nazeeruddin, M. Gratzel, Chem. Eur. J. 2010, 16, 1193–1201, e) G.
Zhang, Y. Bai, R. Li, D. Shi, S. Wenger, S. M. Zakeeruddin, M. Grätzel,
P. Wang, Energy Environ. Sci. 2009, 2, 92-95; f) D. Kim, C. Kim, H.
Choi, K. Song, M.-S. Kang, J. Ko, J. Photochem. Photobiol. A:
Chem. 2011, 219, 122–131; g) M. Xu, R. Li, N. Pootrakulchote, D. Shi,
J. Guo, Z. Yi, S. M. Zakeeruddin, M. Grätzel, P. Wang, J. Phys. Chem.
C 2008, 112, 19770-19776; h) H.-G. Bae, C.-C Lee, J.-B. Kim, H.-D.
Moon, T.-J. Park, J.-H. Baek, H.-T. Yang, H.-C. An., PCT Int. Appl.
[22] M. Kuhn, F. C. Falk, J. Paradies, Org. Lett. 2011, 13, 4100-4103.
[23] D. Prim, G. Kirsch, J. Chem. Soc. Perkin Trans. 1 1994, 18, 2603.
[24] L. S. Fuller, B. Iddon, K. A. Smith, J. Chem. Soc. Perkin Trans. 1
1997, 22, 3465.
[25] J. D. Prugh, G.D. Hartman, P. J. Mallorga, B. M. McKeever, S. R.
Michelson, M. A. Murcko, H. Schwam, R. L. Smith, J. M. Sondey, J.
Med. Chem. 1991, 34, 1805-1818.
[26] S. Cai, G. Tian, X. Li, J. Su, H. Tian, J. Mater. Chem. A 2013, 1, 11295-
11305.
[27] F. Quist, C. M. L. Van de Velve, D. Didier, A. Teshome, K. Clays, S.
Sergeyev, Dyes Pigments 2009, 81, 203-210.
[28] a) C. Xu, W. W. Webb, J. Opt. Soc. Am. B, 1996, 13, 481-491; b) M. A.
Albota, C. Xu, W. W. Webb, Appl. Opt., 1998, 37, 7352-7356.]
[29] M. Barzoukas, M. Blanchard-Desce, J. Chem. Phys., 2000, 113, 3951-
3959.
[30] D. F. Eaton, Pure & Appl. Chem. 1988, 60, 1107-1114; b) G. A. Crosby,
J. N. Demas, J. Phys. Chem. 1971, 75, 991-1024.
[31] M. H. V. Werts, N. Nerambourg, D. Pelegry, Y. L. Grand, M. Blanchard-
Desce, Photochem. Photobiol. Sci. 2005, 4, 531- 538.
This article is protected by copyright. All rights reserved

European Journal of Organic Chemistry
10.1002/ejoc.201600806
FULL PAPER
Entry for the Table of Contents (Please choose one layout)
Layout 2:
FULL PAPER
M. Manuela M. Raposo*, Cyril Herbivo,
Vincent Hugues, Guillaume Clermont,
M. Cidália R. Castro, Alain Comel,
Mireille Blanchard-Desce*
Page No. – Page No.
Synthesis, fluorescence and two-
photon absorption properties of
novel push-pull 5-aryl[3,2-
Fusion makes it better!
b]thienothiophene derivatives
Fusion makes it better! Push-pull compounds built from a thienothiophene -connector were
synthesized. Due to improved rigidity and conjugation, derivatives having strong donor end-groups
were shown to combine strong and tunable fluorescence as well as large two-photon absorption in the
NIR region. These series of dyes provides a route towards bright fluorophores spanning the visible
region to the NIR.
This article is protected by copyright. All rights reserved