Efficient second-order nonlinear optical chromophores based on dithienothiophene and thienothiophene bridges

Article abstract of DOI:10.1016/j.tet.2013.03.027

Two series of push-pull systems bearing dithienothiophene or thienothiophene as (part of) π-conjugated spacer have been synthesized. These compounds combine high second-order molecular nonlinearities with good thermal stabilities, showing one of the thienothiophene (TT) derivative the highest μβ₀ value found for a 4H-pyranylidene-containing merocyanine.

Full text of DOI:10.1016/j.tet.2013.03.027

Tetrahedron 69 (2013) 3919e3926
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journal homepage: www.elsevier.com/locate/tet
Efficient second-order nonlinear optical chromophores based
on dithienothiophene and thienothiophene bridges
a
a
,
a
a
a
*
ꢀ
ꢀ
A. Belen Marco , Raquel Andreu , Santiago Franco , Javier Garín , Jesus Orduna ,
b
b
ꢀ
Belen Villacampa , Raquel Alicante
Departamento de Química Organica, Facultad de Ciencias-ICMA, Universidad de Zaragoza-CSIC, Pedro Cerbuna 12, E-50009 Zaragoza, Spain
b Departamento de Física de la Materia Condensada, Facultad de Ciencias-ICMA, Universidad de Zaragoza-CSIC, 50009 Zaragoza, Spain
a
ꢀ
a r t i c l e i n f o
a b s t r a c t
Article history:
Two series of pushepull systems bearing dithienothiophene or thienothiophene as (part of)
p-conju-
Received 21 January 2013
Received in revised form 6 March 2013
Accepted 8 March 2013
gated spacer have been synthesized. These compounds combine high second-order molecular non-
linearities with good thermal stabilities, showing one of the thienothiophene (TT) derivative the highest
mb0 value found for a 4H-pyranylidene-containing merocyanine.
Available online 14 March 2013
Ó 2013 Elsevier Ltd. All rights reserved.
Dedicated to the memory of our colleague
Christian Claessens
Keywords:
Nonlinear optics
Dithienothiophene
Thienothiophene
4H-Pyranylidene
1. Introduction
a good balance between nonlinear optical response and thermal
stability.3 In this context, thiophenes are among the most studied
Over the last decades great efforts have been dedicated to
obtain materials exhibiting good second-order nonlinear optical
(NLO) properties due to their potential application in optical de-
vices.1 Following this trend, many high performing organic sys-
heterocyclic spacers for D-p
-A systems,3b,4 due to their relatively
low resonance energies, and have allowed the preparation of
chromophores with high stabilities and nonlinearities. On the
other hand, conjugated spacers based on fused thiophene rings
have been much less studied in this field, even though thieno[3,2-
b]thiophene (TT)5 and dithieno[3,2-b:20,30-d]thiophene (DTT)6
show a lower resonance energy per electron when compared to
thiophene7 and allow to increase conjugation, which typically
results in increased NLO responses. Just a few chromophores
bearing these fused heterocycles as (part of) the electron relay
have been reported.3a,8,9 Moreover, just one of the papers8a ap-
proaches these systems from the standpoint of the establishment
of structureeactivity relationships, and it is focused on the
comparison between thiophene and thieno[3,2-b]thiophene
moieties.
tems (specially donor-p-acceptor (D-p-A) type molecules) have
been synthesized, but the combination of high molecular hyper-
polarizabilities and good thermal stability in the same system is
still a subject of interest in materials science. Polyene-type
structures have often been included in the conjugated spacer
between the donor and the acceptor moieties because they pro-
vide the best conjugation pathway for the charge transfer, but
poor thermal stabilities are associated with the presence of these
olefinic fragments.2 The reverse situation is found for aryl-type
spacers. Then, the replacement of aryl rings by heteroaromatic
rings with lower resonance energies is the common way to obtain
In this work we focus our attention on the synthesis, character-
ization, and study of six new fused thiophene derivatives 1e4, which
are expected to be efficient NLO chromophores and to show high
* Corresponding author. Tel.: þ34 976762282; fax: þ34 976761194; e-mail ad-
dresses: bmarco@unizar.es (A.B. Marco), randreu@unizar.es (R. Andreu), sfranco@
unizar.es (S. Franco), jgarin@unizar.es (J. Garín), jorduna@unizar.es (J. Orduna),
bvillaca@unizar.es (B. Villacampa), raquela@unizar.es (R. Alicante).
thermal stability. New D-p-A molecules bear the proaromatic 4H-
pyran-4-ylidene unit as donor10 and two common strong organic
acceptors. To the best of our knowledge, no such merocyanines
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.03.027

3920
A.B. Marco et al. / Tetrahedron 69 (2013) 3919e3926
with a 4H-pyran-4-ylidene moiety and dithienothiophene or thie-
nothiophene relays in their structure have been previously reported.
The influence of these fused heterocycles on the optical and thermal
properties is discussed and compared with that exerted by a single
O
O
N
N
1a-b (79%; 76%)
3 (62%)
EtOH
8a-b, 9
S
11
thiophene unit in the p-spacer.
CHCl3, Et3N
8a, 9
2a (58%)
4 (37%)
Ph
O
Ph
S
Ph
O
Ph
S
CN
CN
CN
O
12
A
S
8b
EtOH
microwaves, 20 W
1a-b
2a-b
S
S
3, 4
2b (14%)
n
a: n = 0; b: n = 1
A
O
N
Scheme 2. Synthesis of chromophores 1e4.
CN
CN
CN
1, 3:
2, 4:
A =
A =
S
N
O
O
It is worth noting that the reaction of aldehyde 8b and acceptor
12 under the same conditions used for aldehydes 8a and 9 afforded
compound 2a instead of the expected 2b. This vinylene-shortening
reaction has already been reported for other Knoevenagel-type
reactions by us15 and other authors.16 Different reaction condi-
tions reported17 for Knoevenagel reactions involving acceptor 12
were tried with the same result. To overcome this drawback, the
reaction between aldehyde 8b and acceptor 12 was tested under
microwave conditions.18 In this approach the addition of a base is
not necessary, and therefore the aforementioned side-reaction is
less likely to happen. Using this procedure compound 2b was
eventually isolated in low yield.
2. Results and discussion
2.1. Synthesis
For the synthesis of the target systems 1e4, the previously un-
reported aldehydes 8a,b and 9 were chosen as precursors. Com-
pounds 8a, 9 were prepared by a Horner reaction between
pyranylphosphine oxide 711 and dicarbaldehydes 512 and 6,9b re-
spectively (Scheme 1). Reaction conditions were carefully tuned
(temperature, order of slow addition of reagents) in order to min-
imize the formation of pyranylidene-disubstituted derivatives as
by-products. Thus, a yield of 61% could be achieved for 8a, whereas
lower yields were obtained for 9 due to the insolubility of dicar-
baldehyde 6. Aldehyde 8b was obtained from reaction of 8a and
tributylphosphonium salt 1013 in the presence of sodium ethoxide
and a subsequent acid hydrolysis.
2.2. 1H NMR studies
Compounds 1b, 2a,b, and 4 have an all-trans geometry along the
spacer according to 3JHH coupling constant analysis. Whereas the s-
trans conformation for the bond linking the donor moiety to the
thieno[3,2-b]thiophene spacer is confirmed by selective ge-1D
NOESY experiments carried out on model compound 8a
(300 MHz, CDCl3, rt), the same conformation can be assumed for
NLO chromophores 1e4.
Ph
O
Ph
S
1H NMR data also provide valuable information about ground-
state polarization of the studied D-p-A systems. The chemical
(72%)
shifts of the H atoms along the polyenic spacer show the typical
S
8b
oscillatory behavior19 of a merocyanine-like compound, and the
CHO
3
high JHH values for the ]CHeCH] protons in the olefinic part of
O
O
Br
PBu3
1)
the spacer for compounds 1b and 2b (12.8 Hz for compound 1b
(CDCl3); 11.4 Hz for 2b (CD2Cl2)) show the contribution of their
zwitterionic form to their electronic ground states.
A slight downfield shift for the protons of the pyranylidene ring
of compound 2a when compared to 2b was observed (6.61 and
7.23 ppm for 2a and 6.56 and 7.20 ppm for 2b in CD2Cl2). This
finding indicates a higher contribution of the aromatic pyrylium
10
EtOH/EtONa
DMF, 90oC
2) HCl 1N
Ph
O
Ph
S
O
Ph
Ph
form for the shortest system, in agreement with other D-p-A sys-
H
P
tems with a 4H-pyran-4-ylidene unit previously described.10,15c,20
1H NMR spectra of DTT derivatives 3, 4 were recorded in dif-
ferent conditions as a result of their low solubility, leaving them out
of the comparison with 1e2.
S
CHO
OHC
OHC
Ph
O
7
Ph
S
S
CHO
S
(61%)
8a
5
n-BuLi, -30oC
Ph
O
Ph
S
THF
CHO
S
S
2.3. Calculated structures
S
6
CHO
(34%)
9
S
For a better understanding of the role of fused thiophene con-
jugated spacers in these chromophores, natural bond orbital (NBO)
atomic charge calculations for the target compounds and for
analogous systems bearing a single thiophene spacer 13, 1420
(Fig. 1) were carried out. The resulting charges for comparable
systems are shown in Fig. 2. It can be seen that part of the net
positive charge of the pushepull system is supported by the thio-
phene relays, in agreement with previously reported results.9d
Scheme 1. Synthesis of aldehyde precursors 8 and 9.
The Knoevenagel reaction between acceptors 11 and 12
(2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran,
TCF)14 and aldehydes 8a,b, 9 afforded the six new D-
pounds 1e4 (Scheme 2).
p-A com-

A.B. Marco et al. / Tetrahedron 69 (2013) 3919e3926
3921
For systems with the same conjugated spacer, there is a shift of
the jEredj values toward less cathodic potentials when changing the
acceptor from thiobarbiturate group to TCF, pointing to the superior
electron-withdrawing ability of the latter acceptor when compared
to the former. On the other hand, Eox values are not dramatically
influenced by the change of the electron-withdrawing group.
Concerning the number of fused thiophenes, comparison of TT
systems 1a and 2a with their thiophene analogues 13 and 1420
(Fig. 1) shows slightly increased potentials for the thienothio-
phene derivatives. This increase is in contrast to the effect of the
introduction of an additional fused thiophene ring in compounds 3,
4 (DTT derivatives), for which both Eox and jEredj are lower than
those of 1a, 2a, respectively.
O
Ph
S
Ph
A
13, 14
O
CN
N
N
14:
A =
13:
S
A =
CN
O
CN
O
Fig. 1. Structures of compounds 13 and 14.
π
Compd
Donor
-spacer
Acceptor
Ph
O
Finally, these observed trends in Eox(jEredj) are confirmed by the
calculated B3P86-6-31-G* HOMO (LUMO) energies (Table 1) except
for 13 and 14 when comparing with their TT analogues (1a and 2a).
Ph
A:
+0.196
+0.159
+0.146
+0.190
+0.177
+0.167
+0.082
+0.086
+0.094
+0.069
+0.070
+0.080
−0.276
−0.245
−0.240
−0.259
−0.247
−0.247
13
1a
3
π
-spacer
A
S
N
N
CN
O
14
2a
4
2.5. UVevis spectroscopy
CN
O
O
CN
Absorption spectra for compounds 1e4 afforded lmax data
recorded in Table 2 (see spectra in Supplementary data). All sys-
tems show broad, low energy absorption bands corresponding to
an intramolecular charge transfer (ICT).
Fig. 2. Calculated NBO charges from the optimized B3P86-6-31G* molecular
geometries.
Table 2
However, the portion of the positive charge located on the spacer is
highly dependent on the relative strength of the donor group.
While DTT relays linked to a relatively weak dialkylaminophenyl
donor bear a positive charge that can be even greater than that
supported by the donor itself,9d for the systems herein reported
most of the net positive charge (61e72%) is located on the strong
pyranylidene donor and the charge on the fused thiophene relay is
always below 0.1e.
Moreover, the charge on both the donor and acceptor ends of the
pushepull system decreases and the charge of the relay increases
on increasing the number of fused thiophenes (DTT>TT>thio-
phene). In other words, larger spacers have a stronger donor char-
acter and decrease the ground state charge transfer from the
pyranylidene to the acceptor.
UVevis dataa
Compd
lmax (log
1,4-Dioxane
3
)
lmax (log
CH2Cl2
3 )
lmax (log 3 )
DMF
1a
1b
3
2a
2b
4
625 (4.88)
642 (4.84)
636 (4.76)
656 (4.80)
660 (4.61)
658 (4.46)
611 (4.76)
665 (4.55)
653 (4.88)
677 (4.84)
659 (4.75)
711 (4.84)
708 (4.68)
708 (4.64)
644 (4.64)
708 (4.70)
638 (4.76)
669 (4.75)
642 (4.61)
681 (4.72)
668 (4.56)
675 (4.52)
d
13
14
d
a
All lmax data are in nm.
Comparison of compounds that only differ in the acceptor group
shows a bathochromic shift for TCF derivatives 2, 4, in agreement
with its higher electron-withdrawing ability, and in line with their
electrochemical properties.
2.4. Electrochemistry
For thieno[3,2-b]thiophene derivatives 1 and 2, lengthening the
spacer has a different effect on lmax values depending on the ac-
ceptor moiety. Systems 1a,b, containing thiobarbiturate acceptor,
show the expected bathochromic shift when conjugation is en-
larged. The same behavior was observed for the aldehyde pre-
cursors 8a,b (471 (467) nm for 8a and 499 (495) nm for 8b, in
CH2Cl2 (DMF)). For compounds 2a,b, with the stronger TCF accep-
tor, enlarging conjugation hardly affects maximum absorption
wavelength in solvents like dioxane and CH2Cl2, and results in
a slightly hypsochromic shift when solvent polarity is increased
(13 nm, 0.03 eV, DMF). This hypsochromic behavior with increasing
conjugation has been reported for other pushepull systems with
Electrochemical properties of compounds 1e4 were studied by
cyclic voltammetry (CV) in CH2Cl2. All compounds show irrevers-
ible waves corresponding to the oxidation of the pyranylidene
fragment and to the reduction of the corresponding acceptor
moieties (Table 1).
Table 1
Electrochemical data,a EHOMO, and ELUMO valuesb
Compd
Eox (V)
Ered (V)
EHOMO (eV)
ELUMO (eV)
1a
1b
3
2a
2b
4
þ0.72
þ0.59
þ0.55
þ0.69
þ0.55
þ0.54
þ0.67
þ0.67
ꢀ0.89
ꢀ0.72
ꢀ0.84
ꢀ0.71
ꢀ0.60
ꢀ0.63
ꢀ0.89
ꢀ0.69
ꢀ5.68
ꢀ5.62
ꢀ5.61
ꢀ5.84
ꢀ5.75
ꢀ5.75
ꢀ5.80
ꢀ5.91
ꢀ3.42
ꢀ3.55
ꢀ3.45
ꢀ3.85
ꢀ3.90
ꢀ3.87
ꢀ3.43
ꢀ3.85
different donors, acceptors, and p
-linkers,21,22 in some of which21f,g
a similar reliance of the shifts with the acceptor strength has been
established. Moreover, it has been found for a series of pushepull
substituted oligothiophenes that the blue shift becomes more
pronounced with increasing solvent polarity.22
13
14
a
10ꢀ3 M in CH2Cl2 versus Ag/AgCl (3 M KCl), glassy carbon working electrode, Pt
counter electrode, 20 ꢁC, 0.1 M NBu4PF6, 100 mV se1 scan rate. Ferrocene internal
reference E1/2¼þ0.43 V.
Meier explained this behavior21g,22 considering the ICT apart
from the extension of conjugation. If the decrease of the ICT effect
with increasing n prevails, the result is an overall hypsochromic
shift.
b
Calculated at the B3P86-6-31-G* level in the gas phase.
Concerning the number of fused thiophenes, the replacement of
thiophene by TT and subsequently by DTT also affects to the ICT
band position in a different way depending on the acceptor moiety.
Thus, for systems with thiobarbituric acid, there is a slight red shift
For a given acceptor, lengthening the conjugated spacer with
a vinylene unit leads to a decrease of Eox and jEredj values in all
cases, pointing to the weaker interaction between donor and ac-
ceptor groups.

3922
A.B. Marco et al. / Tetrahedron 69 (2013) 3919e3926
of lmax (in CH2Cl2 and dioxane) on going from 13 to 1a and 3, as
a result of the extended conjugation, and in agreement with the
behavior of the unsubstituted fused systems,23 and a previous
Moreover, for systems with thiobarbituric acid moiety,
lengthening conjugation with an additional thiophene ring (cf.
1a/3) leads to an increased mb0 value. In contrast, as regards TCF
acceptor derivatives, the dithienothiophene derivative 4 has
a lower NLO response than the shortest one 2a. This experimental
fact is also reproduced by calculated mb0 values (HF 6-31G*), that
predict an almost negligible difference between b0 values of
compounds 2a and 4, a lower dipole moment for 4 when com-
comparison between thiophene- and thieno[3,2-b]thiophene-D-p-
A systems.8a However, there is an almost negligible shift of lmax for
TCF derivatives (cf. 14/2a/4) in CH2Cl2, and for the non-polar di-
oxane a slight blue shift is encountered on passing from thiophene
to TT and DTT relay.
Concerning the dependence of the band position on solvent
polarity, positive solvatochromism for low polarity solvents (from
dioxane to CH2Cl2) that becomes negative when increasing solvent
polarity (from CH2Cl2 to DMF) was observed for compounds 1e4.
Nevertheless, the extended and broad shape of the bands precludes
an accurate identification of the longest wavelength absorption,
particularly for TCF derivatives 2, 4.
pared to 2a, and a larger angle between m and b vectors (q) for 4 (q
(2a)¼24.2ꢁ;
q
(4)¼28.0ꢁ). One of the possible explanations to this
fact could be the difference on the preferred conformation for
both types of compounds. Calculations suggest that while TT
derivatives show a ‘rod-type’ conformation, the presence of the
DTT relay induces a more ‘folded’ shape, thereby decreasing the
total polarity of the molecules. The longer resonance pathway is
not able therefore to compensate the important loss of dipole
moment with the strongest acceptor. Calculated values for mb0 are
in all cases overestimated but reproduce quite well the experi-
mental trends.
This solvatochromic behavior resembles that of other reported
dithienothiophene-9aeb or dithienylethylene-24containing systems.
Moreover, attempts to establish linear correlations of transition
energy with typical solvent parameters, such as Z-scale, ETN,
ET(30)25 failed.21f
*
p or
Measurements in DMSO were also performed to ascertain the
position of these chromophores on the Marder’s plot.27 For this
purpose, acceptor TCF derivatives 2(a,b), 4 were chosen. Compound
2.6. Nonlinear optical properties
3
was also measured to check the effect of the electron-
Second-order nonlinear optical properties of compounds 1e4
were measured by electric field-induced second harmonic gener-
ation at 1907 nm and the zero-frequency mb0 values were calcu-
lated by means of the two-level model26 using the lowest energy
absorption band for each compound (It should be noted that, for all
systems broad bands have been found.). For the sake of comparison,
Disperse Red 1, a common benchmark for organic NLO chromo-
phores shows a mb0 value of ca. 480ꢂ10ꢀ48 esu and 370ꢂ10ꢀ48 esu
in CH2Cl2 and DMSO, respectively, under the same experimental
conditions. Both the experimental and theoretical results (CPHF,
coupled perturbed HartreeeFock) are recorded in Table 3, where
data for compounds 13 and 1420 are also gathered.
withdrawing group. Results show a decline of mb0 in all cases
compared to those measured in dichloromethane, indicating that
our systems are left-hand chromophores and that the maximum of
the Marder’s plot has been exceeded. None of the values
approach zero or reach the negative zone, because the neutral form
predominates in this solvent polarity range. This fact contrasts with
other reported systems bearing dithienothiophene as electron re-
lay, which show similar solvatochromic behavior, but undergo sign
inversion in highly polar solvents.9b
Finally, it seems pertinent to point out that the mb0 values for
derivative 2b in CH2Cl2 is, to the best of our knowledge, the highest
one shown by a pyranylidene donor-based chromophore.
Table 3
Experimental and CPHF-calculated NLO properties
mba (10ꢀ48 esu)
(CH2Cl2)
mb0b (10ꢀ48 esu)
(CH2Cl2)
mbc (10ꢀ48 esu)
(DMSO)
mb0d (10ꢀ48 esu)
(DMSO)
mb0
b0 tote
mge (D)
e
Compd
(10ꢀ48 esu)
(10ꢀ30 esu)
1a
1b
3
2a
2b
4
2800
5400
4000
14,900
21,900
9200
1310
2340
1800
5670
8500
3500
665
d
d
2779
5876
3146
11,962
19,379
9987
213
417
273
545
831
572
94
13.6
14.6
11.6
24.1
25.1
19.8
13.0
23.4
d
d
2300
8000
9300
6200
d
1120
3300
4000
2650
d
13
14
1380
6790
1162
7165
2630
1400
d
328
a
mb values determined in CH2Cl2 at 1907 nm (experimental uncertainty better than ꢃ15% except for compounds 4 (w20%) and 3 (w30%) (see Section 4.2)).
Experimental mb0 values in CH2Cl2 calculated using the two-level model.
b
c
mb values determined in DMSO at 1907 nm (experimental uncertainty ꢃ15%).
d
e
Experimental mb0 values in DMSO calculated using the two-level model.
Calculated at the CPHF/6-31G*//B3P86/6-31G* level (gas phase).
mb values for TCF derivatives 2, 4 are remarkably superior to
2.7. Thermal stability
those of their thiobarbituric acid analogues 1, 3, respectively,
highlighting again the higher acceptor strength of the former.
For TT derivatives 1 and 2, the incorporation of a double bond in
the spacer leads to an important increase of the NLO response in
dichloromethane, as expected when conjugation is increased.
Comparison of systems 1a and 2a with previously reported
derivatives bearing a thiophene moiety 13 and 1420 could also be
useful to illustrate the features conferred by these fused hetero-
cycles. Measurements in dichloromethane show an increase of
around 50% in nonlinear optical response when a simple thiophene
is substituted by thieno[3,2-b]thiophene, (cf. 1a/13; 2a/14) as pre-
viously observed.8a
Thermal stabilities of compounds 1e4 were studied by
thermogravimetric analysis (TGA) (Table 4), estimating their
Table 4
Thermal stability
Compd
Td (ꢁC)
Compd
Td (ꢁC)
1a
1b
3
289
280
343
272
2a
2b
4
315
310
342
334
13
14

A.B. Marco et al. / Tetrahedron 69 (2013) 3919e3926
3923
decomposition temperatures (Td) as the intercept of the leading
edge of the weight loss with the baseline of the TGA scans.
All derivatives 1e4 are thermally stable with decomposition
temperatures above 280 ꢁC, in particular derivatives of acceptor
TCF, for which decomposition temperatures are higher than those
of their thiobarbiturate analogues, apart from compounds 3 and 4,
with Td values essentially identical. As expected, introduction of an
additional double bond in the spacer leads to a slight decrease of
thermal stability for both acceptors. With the exception of 2a,
thieno[3,2-b]thiophene derivatives are more stable than the thio-
phene systems (cf. 1a/13) in agreement with previous results.8a
Derivatives 3 and 4 show very high decomposition temperatures,
and are the most stable systems for a given acceptor.
Bu4NPF6 as supporting electrolyte (0.1 mol Le1). Scan rate was
100 mV se1. Thermogravimetric analysis (TGA) were carried out on
a TA Instruments TGA Q5000 at 10 ꢁC/min in nitrogen atmosphere
from 40 ꢁC to 600 ꢁC; from 600 ꢁC to 750 ꢁC heating was continued
in synthetic air atmosphere. Elemental analyses were carried out
with a PerkineElmer CHN2400 microanalyzer.
4.2. NLO measurements
Electric field-induced second harmonic generation (EFISH) mea-
surements have been performed using as the fundamental radiation
the 1.9 mm output of a H2 Raman shifter pumped by a Q-switched
Nd:YAG laser. This laser operates at 1064 nm, with a repetition rate of
10 Hz and pulse width of 8 ns. A computer controlled NLO spec-
3. Conclusions
trometer completes the SHG experimental set-up. The 1.9
cident light is split in two beams. The less intense one is directed to
a N-(4-nitrophenyl)-( )-prolinol (NPP) powder sample whose SH
signal is used as a reference in order to reduce the effects of laser
fluctuations. The other beam is passed through a linear polarizer and
focused into the EFISH wedge shaped liquid cell. Voltage pulses of
mm in-
Merocyanines 1e4, featuring fused thiophenes as electron relays
have been synthesized and studied, and their properties compared
to those of analogous systems bearing a thiophene spacer. The relay
L
supports part of the net positive charge of the D-p-A systems, in-
creasing with the number of fused thiophenes. EFISH measure-
ments reveal that 1e4 are located in the left-hand side of the
Marder’s plot, in region B, not reaching the cyanine limit region.
For a given acceptor, the best NLO response has been obtained for
compounds bearing a TT ring conjugated with a vinylene unit (1,2)b,
showing 2b the highest mb0 value reported for a pyranylidene donor-
based NLO chromophore, together with a decomposition tempera-
5 kV and 3 ms are applied across the cell (2 mm gap between the
electrodes) synchronously with the laser pulses. The harmonic sig-
nals from both the EFISH cell and the NPP reference are measured
with two photomultipliers. Interference filters are used to remove
the residual excitation light beyond the sample and the reference.
The molecular mb values have been determined in dichloro-
methane and DMSO for compounds 2e4 and in dichloromethane
for compounds 1. As a rule, several solutions of concentration in the
range (1e5)ꢂ10ꢀ4 M were measured. However, due to the low
solubility of compounds 3 and 4, the use of solutions below 10ꢀ4 M
(in dichloromethane) was required. The small difference between
the EFISH signals from these solutions and the pure solvent limited
the accuracy of mb values of these chromophores, especially in the
case of the thiobarbituric acid derivative 3.
ture above 300 ꢁC. Thus, D-
p-A compounds containing dithieno-
thiophene and thienothiophene as (part of) conjugated spacer
provide a good balance between NLO properties and thermal stability.
4. Experimental
4.1. General experimental methods
mb0 values were extrapolated using a two-level dispersion
model.26a Under the same experimental conditions mb0 deduced for
DR1 in dichloromethane was 480ꢂ10ꢀ48 esu, quite close to the
value reported in the same solvent by Dirk et al.28 mb0 value of the
same chromophore in DMSO was 370ꢂ10ꢀ48 esu.
Reactions under microwaves were carried out in a CEM Discover
reactor using sealed reaction vessels. Temperature was monitored
with an external surface sensor. Power was set to be 20 W and
maximum temperature was set to be 120 ꢁC. Infrared measure-
ments were carried out in KBr using a PerkineElmer Fourier
Transform Infrared 1600 spectrometer. Melting points were ob-
tained on a Gallenkamp apparatus in open capillaries and are un-
corrected. 1H and 13C NMR spectra were recorded on a Bruker
ARX300 or a Bruker AV400 at 300 or 400 MHz and 75 or 100 MHz,
4.3. Computational procedures
All theoretical calculations were performed by using the Gaussian
0929 program. The molecular geometries were optimized using the
B3P8630 functional and the 6-31G*31 basis set. Molecular hyper-
polarizabilities at zero-frequency were calculated by the coupled
perturbed HartreeeFock method (CPHF) using the HF/6-31G* model.
respectively;
d values are given in parts per million (ppm) (relative
to TMS) and J values in hertz (Hz). 1He1H COSY experiments were
recorded on a Bruker AV400 or a Bruker AV500 at 400 or 500 MHz
in order to establish peaks assignment and spatial relationships.
1He13C-HSQC and 1He13C-HMBC experiments were recorded on
a Bruker AV500 at 500 MHz in order to find some of the carbon
signals for compounds 1a and 2a. Selective ge-1D NOESY experi-
ments (mixing time: 0.95e3.17 s; selective 180 pulse: 40 ms) were
recorded on a Bruker ARX300 at 300 MHz for compound 8a, in
order to determine the conformation for the bond linking the donor
4.4. Synthesis and characterization
Compounds 5,12 6,9b 7,11 10,13 and 1214a were prepared as pre-
viously described.
4.4.1. 5-(2,6-Diphenyl-4H-pyran-4-ylidenemethyl)thieno[3,2-b]thio-
phen-2-carbaldehyde (8a). To a solution of 7 (0.55 g, 1.31 mmol) in
dry THF (20 mL) at ꢀ30 ꢁC, n-BuLi (0.85 mL, 1.36 mmol) 1.6 M in
hexanes was added under argon atmosphere. The solution turned to
dark green and was stirred at this temperature for 45 min. Then,
a suspension of 5 (0.28 g, 1.41 mmol) in dry THF (14 mL) was slowly
added via a syringe and the mixture was stirred for one further hour.
A solution of saturated NH4Cl (60 mL) was then added and the
aqueous phase was extracted with AcOEt (4ꢂ50 mL). The resulting
organic layer was dried over MgSO4 and evaporated. The crude
product was purified by flash column chromatography (silicagel)
using CH2Cl2 as eluent, affording 8a (0.33 g, 0.8 mmol, 61%) as a dark
red solid. Found: C 72.91, H 3.73. C25H16O2S2 requires C 72.79, H
moiety to the p-spacer. MALDI-ToF mass spectra were recorded on
a Bruker MicroFlex spectrometer with a nitrogen laser (3.68 eV)
using dithranol as matrix; accurate mass measurements were
achieved using PEG as external reference and calibrating with
[PEGþNa]þ. Electrospray mass spectra were recorded on a Bruker
Q-ToF spectrometer; accurate mass measurements were achieved
using sodium formate as external reference. Electronic spectra
were recorded with an UVeVis UNICAM UV4 spectrophotometer.
Cyclic voltammetry measurements were performed with a m-Au-
tolab ECO-Chemie potentiostat using a glassy carbon working
electrode, Pt counter electrode, and Ag/AgCl reference electrode.
The experiments were carried out under argon in CH2Cl2, with

3924
A.B. Marco et al. / Tetrahedron 69 (2013) 3919e3926
3.91%. Mp 213e217 ꢁC. IR (KBr, cmꢀ1): 1660 (C]O), 1581 (C]C, Ar),
1556 (C]C, Ar). 1H NMR (300 MHz, CDCl3):
9.91 (s, 1H, eCHO),
(8 mL), 1,3-diethyl-2-thiobarbituric acid (11) (0.048 g, 0.24 mmol) was
added in one portion under argon atmosphere and the mixture was
refluxed for 3 h. The reaction mixture was cooled to room tempera-
ture and then to 0 ꢁC. The resulting solid was isolated by filtration and
washed with cold ethanol, hexane, and pentane. Product 1a was
obtained as a dark green solid (0.11 g, 0.18 mmol, 79%). Found: C 66.87,
H 4.29, N 4.43. C33H26N2O3S3 requires C 66.64, H 4.41, N 4.71%. Mp
278e282 ꢁC. IR (KBr, cmꢀ1): 1644 (C]O), 1537 (C]C, Ar), 1101 (C]S).
d
7.92e7.83 (m, 3H, phenyleHþTTeH), 7.81e7.76 (m, 2H, phenyleH),
7.56e7.42 (m, 6H, phenyleH), 7.18 (d, J¼1.9 Hz,1H, pyranylideneeH),
7.13 (s, 1H, TTeH), 6.50 (d, J¼1.9 Hz,1H, pyranylideneeH), 6.15 (s,1H,
pyranylidene]CeH). 13C NMR (75 MHz, CDCl3):
d 182.6, 154.4, 152.1,
151.3, 147.0, 143.2, 136.9, 132.8, 132.6, 131.3, 130.0, 129.5, 129.0, 128.8,
128.7, 125.2, 124.6, 116.6, 108.4, 107.4, 102.6. HRMS (MALDIþ): found
412.0594 [Mþꢄ]. C25H16O2S2 requires 412.0586; found 413.0638
[MþH]þ. C25H17O2S2 requires 413.0665.
1H NMR (300 MHz, CDCl3):
d 8.65 (s, 1H, eTTeCH]A), 7.95 (s, 1H,
TTeH), 7.89e7.81 (m, 2H, phenyleH), 7.80e7.73 (m, 2H, phenyleH),
7.55e7.40 (m, 6H, phenyleH), 7.18 (s, 1H), 7,09 (s, 1H), 6.55 (br s, 1H,
pyranylideneeH), 6.21 (s, 1H, pyranylidene]CeH), 4.64e4.51(m, 4H,
eNCH2CH3), 1.39e1.25 (m, 6H, eNCH2CH3). 13C NMR (125 MHz,
4.4.2. (E)-3-(5-(2,6-Diphenyl-4H-pyran-4-ylidenemethyl)thieno[3,2-b]thi-
ophen-2-yl)acrylaldehyde (8b). To a mixture of 8a (0.18 g, 1.44 mmol)
and 1,3-dioxolan-2-ylmethyltributylphosphonium bromide (10)
(0.28 g, 0.75 mmol) in dry DMF (3 mL) a 0.48 M solution of sodium
ethoxide in ethanol (1.5 mL, 0.73 mmol) was added under argon
atmosphere. The mixture was stirred at 90 ꢁC for 22 h and then water
(75 mL) was added. The aqueous phase was extracted with AcOEt
(4ꢂ50 mL), and the resulting organic layer was washed with brine,
dried over MgSO4, and evaporated. To a solution of the crude residue
in THF (10 mL), an aqueous solution of HCl 1 N (40 mL) was added
and the mixture was stirred for 90 min at room temperature. Then,
water (50 mL) was added and the aqueous phase was extracted with
AcOEt (4ꢂ50 mL). The organic layer was dried over MgSO4 and
evaporated. The crude product was purified by flash column chro-
matography (silicagel) using CH2Cl2/hexane (9:1) as eluent, yielding
8b (0.14 g, 0.34 mmol, 72%) as a dark red solid. Found: C 73.55, H
3.90. C27H18O2S2 requires C 73.94, H 4.14%. Mp 220e222 ꢁC. IR (KBr,
cmꢀ1): 1651 (C]O), 1600 (C]C), 1552 (C]C). 1H NMR (300 MHz,
CDCl3): d 128.9, 125.2, 124.7, 119.9, 116.7, 108.8, 108.0, 46.6, 29.6. HRMS
(MALDIþ): found 594.1105 [Mþꢄ]. C33H26N2O3S3 requires 594.1100;
found: 595.1201 [MþH]þ. C33H27N2O3S3 requires 595.1178.
4.4.5. (E)-5-[3-(5-(2,6-Diphenyl-4H-pyran-4-ylidenemethyl)thieno
[3,2-b]thiophen-2-yl)alylidene]-1,3-diethyl-2-thioxodihydropyrimidin-
4,6-dione (1b). To a solution of 8b (0.048 g, 0.23 mmol) in absolute
ethanol (4 mL), 1,3-diethyl-2-thiobarbituric acid (11) (0.025 g,
0.13 mmol) was added in one portion under argon atmosphere and
the mixture was refluxed for 2 h. The reaction mixture was cooled to
room temperature and then to 0 ꢁC. The resulting solid was isolated
by filtration and washed with cold hexane and a cold mixture of
hexane/CH2Cl2 (9:1). Product 1b was obtained as a dark blue solid
(0.052 g, 0.083 mmol, 76%). Found: C 67.46, H 4.74, N 4.66.
C35H28N2O3S3 requires C 67.71, H 4.55, N 4.51%. Mp 285e287 ꢁC. IR
(KBr, cmꢀ1): 1649 (C]O),1542 (C]C, Ar).1H NMR (300 MHz, CDCl3):
CDCl3):
d
9.63 (d, J¼7.7 Hz, 1H, eCHO), 7.89e7.83 (m, 2H, phenyleH),
d
8.35 (dd, J1¼14.0 Hz, J2¼12.8 Hz, 1H, eTTeCH]CHeCH]A), 8.15 (d,
7.81e7.75 (m, 2H, phenyleH), 7.61 (d, J¼15.3 Hz, 1H, eCH]
CHeCHO), 7.54e7.40 (m, 7H, phenyleHþTTeH), 7.16 (d, J¼2.1 Hz,1H,
pyranylideneeH), 7.08 (br s,1H, pyranylideneeH), 6.48 (s,1H, TTeH),
6.47 (dd, J1¼15.3 Hz, J2¼7.7 Hz, 1H, eCH]CHeCHO), 6.14 (s, 1H,
J¼12.8 Hz, 1H, eTTeCH]CHeCH]A), 7.95e7.84 (m, 2H, phenyleH),
7.83e7.72 (m, 2H, phenyleH), 7.63 (d, J¼14.0 Hz, 1H, eTTeCH]
CHeCH]A), 7.58e7.38 (m, 7H, phenyleHþTTeH), 7.19 (s, 1H), 7.10
(s, 1H), 6.53 (s, 1H), 6.18 (s, 1H, pyranylidene]CeH), 4.65e4.50 (m,
4H, eNCH2CH3), 1.23e1.20 (m, 6H, eNCH2CH3). 13C NMR: not reg-
istered due to its low solubility. HRMS (MALDIþ): found 620.1212
[Mþꢄ]. C35H28N2O3S3 requires 620.1257; found 621.1328 [MþH]þ.
C35H29N2O3S3 requires 621.1335.
pyranylidene]CeH). 13C NMR (100 MHz, CDCl3):
d 192.5, 185.9,
154.2, 151.9, 148.7, 145.0, 139.5, 133.0, 132.8, 130.5, 129.9, 129.4, 128.8,
128.7, 125.7, 125.1, 125.0, 124.8, 124.6, 116.5, 108.5, 107.6, 102.7. HRMS
(ESIþ): found 439.0804 [MþH]þ. C27H19O2S2 requires 439.0821.
4.4.3. 6-(2,6-Diphenyl-4H-pyran-4-ylidenemethyl)dithieno[3,2-
b:20,30-d]thiophen-2-carbaldehyde (9). To a solution of 7 (0.33 g,
0.75 mmol) in dry THF (8 mL) at ꢀ30 ꢁC n-BuLi (0.55 mL, 0.88 mmol)
1.6 M in hexanes was added under argon atmosphere. The solution
turned to dark green and was stirred at this temperature for 15 min.
Then, this solution was slowly added with a cannula to a suspension
of 6 (0.19 g, 0.75 mmol) at ꢀ30 ꢁC in dry THF (12 mL) and the mixture
was stirred for further 30 min. A solution of saturated NH4Cl (50 mL)
was then added and the aqueous phase was extracted with AcOEt
(4ꢂ50 mL). The resulting organic layer was dried over MgSO4 and
evaporated. The crude product was purified by flash column chro-
matography (silicagel) using hexane/CH2Cl2 (1:1) as eluent, then
(3:7), affording 9 (0.12 g, 0.25 mmol, 34%) as a dark red solid. Found: C
69.46, H 3.35. C27H16O2S3 requires C 69.20, H 3.44%. Mp >280 ꢁC
(dec). IR (KBr, cmꢀ1): 1650 (C]O), 1580 (C]C, Ar). 1H NMR
4.4.6. (E)-5-[6-(2,6-Diphenyl-4H-pyran-4-ylidenemethyl)dithieno[3,2-
b:20,30-d]thiophen-2-yl-alylidene]-1,3-diethyl-2-thioxodihydropyrimidin-
4,6-dione (3). To a solution of 9 (0.050 g, 0.11 mmol) in absolute eth-
anol (4 mL), 1,3-diethyl-2-thiobarbituric acid (11) (0.023 g, 0.11 mmol)
was added in one portion under argon atmosphere and the mixture
was refluxed for 24 h. The reaction mixture was cooled to room
temperature and then to 0 ꢁC. The resulting solid was isolated by fil-
tration and washed with cold hexane and a cold mixture of hexane/
CH2Cl2 (9:1). Product 3 was obtained as a dark blue solid (0.044 g,
0.068 mmol, 62%). Found: C 64.41, H 4.17, N 4.11. C35H26N2O3S4 requires
C 64.59, H 4.03, N 4.30%. Mp 288e290 ꢁC. IR (KBr, cmꢀ1): 1651 (C]O),
1542 (C]C, Ar). 1H NMR (500 MHz, DMSO-d6, 90 ꢁC):
d 8.70 (s, 1H,
eDTTeCH]A), 8.58 (s, 1H, eDTTeH), 8.04e7.97 (m, 2H, phenyleH),
7.93e7.86 (m, 2H, phenyleH), 7.70e7.42 (m, 7H, phenyleHþDTTeH),
7.24 (s, 1H, pyranylideneeH), 6.93 (s, 1H, pyranylideneeH), 6.39 (s, 1H,
pyranylidene]CeH), 4.53 (q, J¼7.7 Hz, 4H, eNCH2CH3), 1.37e1.20 (m,
6H, eNCH2CH3). 13C NMR: not registered due to its low solubility.
HRMS (MALDIþ): found 650.0843 [Mþꢄ]. C35H26N2O3S4 requires
650.0821; found: 651.0866 [MþH]þ. C35H27N2O3S4 requires 651.0899.
(400 MHz, CDCl3):
d 9.93 (s, 1H, eCHO), 7.92 (s, 1H, DTTeH),
7.92e7.86 (m, 2H, phenyleH), 7.82e7.78 (m, 2H, phenyleH),
7.58e7.39 (m, 6H, phenyleH), 7.16 (dd, J1¼1.8 Hz, J2¼0.6 Hz, 1H,
pyranylideneeH), 7.14 (d, J¼0.6 Hz,1H, DTTeH), 6.48 (d, J¼1.8 Hz, 1H,
pyranylideneeH), 6.14 (s,1H, pyranylidene]CeH). 13C NMR (75 MHz,
CD2Cl2):
d
183.1, 154.8, 148.0, 143.4, 133.4, 133.2, 130.9, 130.8, 130.5,
4.4.7. (E)-2-(3-Cyano-4-(2-(5-(2,6-diphenyl-4H-pyran-4-ylidenem-
ethyl)thieno[3,2-b]thiophen-2-yl)vinyl)-5,5-dimethylfuran-2(5H)-yli-
dene)malononitrile (2a). To a solution of 8a (0.049 g, 0.12 mmol) and
acceptor TCF (12) (0.027 g, 0.13 mmol) in CHCl3 (2.5 mL), triethylamine
130.0, 129.4, 129.3, 125.7, 125.1, 118.1, 108.8, 107.8,102.9. HRMS (ESIþ):
found 469.0388 [MþH]þ. C27H17O2S3 requires 469.0385.
4.4.4. 5-[5-(2,6-Diphenyl-4H-pyran-4-ylidenemethyl)thieno[3,2-b]thi-
ophen-2-ylmethylen]-1,3-diethyl-2-thioxodihydropyrimidin-4,6-dione
(1a). To a solution of 8a (0.096 g, 0.23 mmol) in absolute ethanol
(17 mL, 0.12 mmol) was added via a syringe under argon atmosphere
and the mixture was refluxed for 24 h. The reaction mixture was
cooled to room temperature and then to 0 ꢁC. The resulting solid was

A.B. Marco et al. / Tetrahedron 69 (2013) 3919e3926
3925
isolated by filtration and washed with cold hexane. Product 2a was
obtained as a bright maroon solid (0.040 g, 0.067 mmol, 58%). Found:
C 72.61, H 3.75, N 7.24. C36H23N3O2S2 requires C 72.83, H 3.90, N 7.80%.
Mp 274e278 ꢁC. IR (KBr, cmꢀ1): 2223 (C^N), 1649 (C]C), 1538 (C]
Europeo (E39) is gratefully acknowledged. A predoctoral fellowship
to A.B.M. (FPI BES-2009-016966) is also acknowledged. We thank
Dr. E. Vispe (University of Zaragoza) for his help with microwave
reactions.
C). 1H NMR (400 MHz, DMSO-d6):
d
8.22 (d, J¼15.9 Hz, 1H, eTTeCH]
CHeA), 8.09 (s, 1H, eTTeH), 7.98 (d, J¼7.1 Hz, 2H, phenyleH), 7.91 (d,
J¼7.1 Hz, 2H, phenyleH), 7.64e7.46 (m, 7H, phenyleHþTTeH), 7.19 (s,
1H, pyranylideneeH), 7.06 (s, 1H, pyranylideneeH), 6.68 (d, J¼15.9 Hz,
1H, eTTeCH]CHeA), 6.38 (s, 1H, pyranylidene]CeH), 1.81 (s, 6H,
Supplementary data
NMR and UVevis spectra of new compounds, computed ener-
gies, and Cartesian coordinates of optimized geometries can be
found. Supplementary data associated with this article can be found
in the online version, at http://dx.doi.org/10.1016/j.tet.2013.03.027.
TCFeCH3). 13C NMR (75 MHz, DMSO-d6, 60 ꢁC):
d
173.8, 140.7, 131.8,
131.6, 130.1, 128.8, 128.6, 124.9, 124.3, 117.4, 111.0, 108.6, 108.0, 104.2,
98.0, 25.3. 13C NMR (125 MHz, CDCl3)
: 172.2,155.1,152.7,152.6,152.5,
d
147.0, 140.2, 138.9, 128.7, 128.6, 127.9, 125.1, 124.4, 116.6, 110.5, 108.5,
107.5, 102.7, 96.5, 26.4. HRMS (MALDIþ): found 593.1210 [Mþꢄ].
C36H23N3O2S2 requires 593.1226; found 594.1248 [MþH]þ.
C36H24N3O2S2 requires 594.1304.
References and notes
1. (a) Suponitsky, K. Yu; Timofeeva, T. V.; Antipin, M. Y. Russ. Chem. Rev. 2006, 75,
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Muller, T. J. J., Bunz, U. H. F., Eds.; Wiley-VCH: Weinheim, Germany, 2007;
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methyl)thieno[3,2-b]thiophen-2-yl)buta-1,3-dienyl)-5,5-dimethylfuran-
2(5H)-ylidene)malononitrile (2b). A suspension of 8b (0.056 g,
0.13 mmol) and acceptor TCF (12) (0.033 g, 0.17 mmol) in absolute
ethanol (5 mL) in a sealed tube under nitrogen atmosphere was ir-
radiated with microwaves (20 W) for 8 min. Then the tube was cooled
to 60 ꢁC and underwent the same procedure for six times. The re-
action mixture was cooled to room temperature and the solvent was
evaporated. The crude residue was purified by flash column chro-
matography (neutral alumina) using CH2Cl2/hexane (7:3) as eluent,
then CH2Cl2. Product 2b was obtained as a dark blue solid (0.011 g,
0.018 mmol, 14%). Found: C 73.85, H 4.21, N 6.61. C38H25N3O2S2 re-
quires C 73.64, H 4.07, N 6.78%. Mp >250 ꢁC (dec). IR (KBr, cmꢀ1):
2223 (C^N), 1650 (C]C), 1551 (C]C). 1H NMR (400 MHz, CD2Cl2):
pp 393e437; (c) Cho, M. J.; Choi, D. H.; Sullivan, P. A.; Akelaitis, A. J. P.; Dalton, L.
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Martín, N.; Sanchez, L.; Seoane, C.; Garín, J.; Orduna, J.; Alcala, R.; Villacampa, B.
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L. C.; Marques, M. A.; Hermstad, E. L.; Brichler, B. A. J. Org. Chem. 2004, 69,
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d
7.95e6.87 (m, 2H, phenyleH), 7.86e7.77 (m, 2H, phenyleH),
5. Litvinov, V. P. Adv. Heterocycl. Chem. 2006, 90, 125e203.
7.64e7.34 (m, 9H, phenyleHþTTeHþTTeCH]CHeCH]CHeA), 7.20
(d, J¼1.4 Hz, 1H, pyranylideneeH), 7.13 (s, 1H, TTeH), 6.82 (dd,
J1¼14.7 Hz, J2¼11.4 Hz, 1H, TTeCH]CHeCH]CHeA), 6.56 (d,
J¼1.4 Hz, 1H, pyranylideneeH), 6.49 (d, J¼15.2 Hz, 1H, TTeCH]
CHeCH]CHeA), 6.20 (s, 1H, pyranylidene]CeH), 1.72 (s, 6H,
TCFeCH3). 13C NMR: not registered due to its low solubility. HRMS
(ESIþ): found: 619.1377 [Mþꢄ]. C38H25N3O2S2 requires 619.1383; found
642.1278 [MþNa]þ. C38H25N3O2S2Na requires 642.1280.
6. Ozturk, T.; Ertas, E.; Mert, O. Tetrahedron 2005, 61, 11055e11077.
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€
1996, 1377e1384; (d) Boldt, P.; Bourhill, G.; Brauchle, C.; Jim, Y.; Kammler, R.;
€
Muller, C.; Rase, J.; Wichern, J. Chem. Commun. 1996, 793e795; (e) Beckmann,
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9. For DTT chromophores see: (a) Kim, O.-K.; Lehn, J.-M. Chem. Phys. Lett. 1996,
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4.4.9. (E)-2-(3-Cyano-4-(2-(6-(2,6-diphenyl-4H-pyran-4-ylidenem-
ethyl)dithieno[3,2-b:20,30-d]thiophen-2-yl)vinyl)-5,5-dimethylfuran-
2(5H)-ylidene)malononitrile (4). To
0.11 mmol) and acceptor TCF (12) (0.024 g, 0.12 mmol) in CHCl3
(3.5 mL), triethylamine (15 L, 0.11 mmol) was added under argon
a solution of 9 (0.050 g,
ꢀ
ꢀ
Hernandez, V.; Kim, O.-K.; Lehn, J.-M.; Lopez Navarrete, J. T.; Delgado Ledesma,
m
ꢀ
S.; Ponce Ortíz, R.; Ruiz Delgado, M. C.; Vida, Y.; Perez-Inestrosa, E. Chem.dEur.
J. 2004, 10, 3805e3816.
atmosphere and the mixture was refluxed for 24 h. The reaction
mixture was cooled to room temperature and then to 0 ꢁC. The
resulting solid was isolated by filtration and washed with cold
hexane and a cold mixture of hexane/CH2Cl2 (7:3). Product 4 was
obtained as a dark solid (0.026 g, 0.040 mmol, 37%). Found: C 70.42,
H 3.44, N 6.63. C38H23N3O2S3 requires C 70.24, H 3.57, N 6.47%. Mp
>300 ꢁC (dec). IR (KBr, cmꢀ1): 2223 (C^N),1652 (C]C),1540 (C]C).
10. Andreu, R.; Carrasquer, L.; Franco, S.; Garín, J.; Orduna, J.; Martínez de Baroja,
N.; Alicante, R.; Villacampa, B.; Allain, M. J. Org. Chem. 2009, 74, 6647e6657.
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F.-X.; Roncali, J.; Frere, P.; Skabara, P. J. J. Mater. Chem. 2003, 13, 1324e1332.
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1H NMR (500 MHz, DMSO-d6, 90 ꢁC):
d
8.19 (d, J¼15.8 Hz, 1H,
DTTeCH]CHeA), 8.18 (s, 1H, DTTeH), 8.01e7.94 (m, 2H, phenyleH),
7.92e7.85 (m, 2H, phenyleH), 7.64e7.45 (m, 7H, phenyleHþDTTeH),
7.20 (s, 1H, pyranylideneeH), 6.90 (s, 1H, pyranylideneeH), 6.80 (d,
J¼15.8 Hz, 1H, DTTeCH]CHeA), 6.35 (s, 1H, pyranylidene]CeH),
2.09 (s, 3H, TCFeCH3), 1.83 (s, 3H, TCFeCH3). 13C NMR: not registered
due to its low solubility. HRMS (MALDIþ): found: 649.0941 [Mþꢄ].
C38H23N3O2S3 requires 649.0947.
ꢀ
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Financial support from MICINN-FEDER (CTQ2011-22727, and
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W.; Hagan, D. J.; Bredas, J.-L.; Marder, S. R. J. Am. Chem. Soc. 2005, 127,
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