(Super)gelators derived from push-pull chromophores: Synthesis, gelling properties and second harmonic generation

Article abstract of DOI:10.1039/c8ob00251g

The present work takes advantage of the self-assembly process occurring along organogelation, to organize Second Harmonic Generation (SHG) active chromophores. To do so, three push-pull chromophores endowed with a dodecyl urea chain were synthesized and characterized. Their organogelating properties were studied in a wide range of solvents. Despite similar architectures, these derivatives exhibit very different gelling properties, from supergelation to the absence of gelling ability. The utilization of the Hansen solubility parameters allows for observing clear relationships between the gelled solvents and critical gelation concentrations. By evaporating the solvents from the organogels, xerogel materials were prepared and systematically studied by means of optical and electron microscopy as well as SHG microscopy. These studies demonstrate the critical role of the solvent over material structuring and allow generalizing the approach exploiting organogelation as a structuring tool to spontaneously organize push-pull chromophores into SHG-active materials.

Full text of DOI:10.1039/c8ob00251g

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Takeharu Haino et al.
Solvent-induced emission of organogels based on tris(phenylisoxazolyl)
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PAPER
(Super)Gelators derived from push-pull chromophores:
Synthesis, gelling properties and second harmonic generation
Received 00th January 20xx,
Accepted 00th January 20xx
a
b
b
a
,a
A.Belén Marco, Denis Gindre, Konstantinos Iliopoulos, Santiago Franco, Raquel Andreu,*
,
b
,b
David Canevet,* Marc Sallé*
DOI: 10.1039/x0xx00000x
The present work takes advantage of the self-assembly process occuring along organogelation, to organize Second
Harmonic Generation (SHG) active chromophores. To do so, three push-pull chromophores endowed with a dodecyl urea
chain were synthesized and characterized. Their organogelating properties were studied in a wide range of solvents.
Despite similar architectures, these derivatives exhibit very different gelling properties, from supergelation to absence of
gelling ability. The utilization of the Hansen solubility parameters allows for observing clear relationships between the
gelled solvents and critical gelation concentrations. By evaporating the solvents from the organogels, xerogel materials
were prepared and systematically studied by means of optical and electron microscopies as well as SHG microscopy. These
studies demonstrate the critical role of the solvent over materials structuring and allow generalizing the approach
exploiting organogelation as a structuring tool to spontaneously organize push-pull chromophores into SHG-active
materials.
www.rsc.org/
exciting results in the context of organic photonics. For
instance, various photostimulable organogels proved to show
Introduction
1
7
gel-sol transitions upon irradiation. The gel state also allowed
preparing materials with increased quantum yields of emission
Low molecular weight organogelators (LMWGs) have
increasingly focused attention over the last two decades given
1
through aggregation-induced emission, improved efficiencies
3
1
–5
their specific and appealing features.
6
interest in drug delivery, crystallization engineering,
They notably show
7
1
8
in upconversion processes, or endowed with wave guiding
1
9
8
9,10
properties. Still in the context of photonics, we recently
described gel-based materials derived from and , which
display a Second Harmonic Generation (SHG) response.
pollutant removal,
1
self-healing materials,
12
tissue
1
13
A
,
B
C
regeneration, or organic electronics and photonics. In the
latter fields, their strong potential mainly lies on their ability to
2
0,21
To
1
4
generate a second harmonic with such chromophores, it is
generally necessary to process the materials with sophisticated
techniques to reach a non-centrosymmetric state, which is
form supramolecular polymers during the gelation process.
Once the solvent evaporated, the as-prepared organic
material, i.e. a xerogel, basically consists of intertwined nano-
and microfibers, which display a well-defined organization at
the supramolecular scale. Therefore, preparing an
22
requisite to observe the phenomenon. In previous studies
based on Disperse Red 1 (DR1) derivatives, we demonstrated
that such heavy processes can be avoided by designing
suitable organogelators, which were able to spontaneously
self-assemble into SHG-active xerogels after a simple drop
organogelator endowed with
a given functional unit
constitutes a way to organize these molecular fragments in an
anisotropic manner and reach a desired arrangement. This
singular aspect allowed for major breakthroughs in organic
electronics with a whole generation of semiconducting and
casting and evaporation sequence. Compound
A, which
includes a push-pull azobenzene chromophore derived from
1
2
metallic nano- and microwires, which find application in the
16
1
5
O
fields of photovoltaics or sensors for example.
As far as organizing -functional units into unidimensional
N
π
structures is concerned, organogelators are also associated to
N
H
N
H
9 19
C H
N
N
N
A
O
O
2
N
O
N
OC12
H
25
25
X
N
OC12
25
0,21
H
B: X = NH
C: X = O
OC12
H
2
N
2
Scheme 1 Chemical structures of previously reported gelators A-C.
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1
2
3
CN
S
CN
CN
S
CN
CN
CN
CN
S
O
5
11
12
O
N
C9H19
N
H
N
H
O
7
Scheme 4 Alternative retrosynthesis involving intermediate 7.
characterization.Therefore, attempts were performed to
synthesize by addition of dodecyl isocyanate in dry
1
dichloromethane over this solid, but this approach proved to
be unsuccessful. To circumvent this issue and be able to
characterize the different intermediates, an alternative
retrosynthesis, which lies on the formation of the push-pull
system in the last step (Scheme 4), was considered with a main
Scheme 2 Chemical structures of targeted compounds 1-3.
DR1 and a urea-dodecyl gelling fragment, allowed us to deliver
2
a proof of principle. This strategy was subsequently extended
0
to DR1 derivatives and , which include other gelling
B
C
2
1
advantage: aldehyde
to prepare all target derivatives 1-3 in a single step. The
aldehyde function of was first protected in the presence of
glycol and p-toluene sulfonic acid (PTSA) monohydrate in a
spacers promote efficient intramolecular charge transfers, Dean-Stark apparatus ( , 88 %) (Scheme 5). The subsequent
bathochromically shifted absorption in the UV-visible region reduction of under standard conditions allowed the isolation
with 78 % yield. Then, the urea moiety was
7 constitutes a common key intermediate
moieties. The results presented herein show that the scope
of our approach can be extended to other push-pull systems
4
displaying a non-character (
1 and 2) appeared a as particularly
relevant choice since previous studies showed that quinoid
8
8
23,25
and higher nonlinear optical responses.
of amine 9
generated through nucleophilic addition over dodecyl
isocyanate in dry dichloromethane, to afford 10 with a good
28
yield (76 %). Its aldehyde function was subsequently
Results and discussion
2
7 (30%). The latter was
9
Synthesis
deprotected to yield key intermediate
2
successfully reacted with 2-dicyanomethylthiophene 11 in
7
By analogy with the synthesis of compounds
considered retrosynthesis to prepare urea-based derivatives
-3 lied on final addition reaction involving dodecyl
isocyanate and the corresponding amines. This strategy was
tested to prepare according to Scheme 3. The initial step
consisted in a condensation reaction between azide
A-C, the first
3
absolute ethanol (63 %) and acceptor 12 was condensed in
0
1
a
1
2
4
6
and
in acetic anhydride,
with a moderate yield (24 %). The reduction of the
2
5
7
dicyanomethylthienothiophene
affording
6
azide function was subsequently tried through Staudinger
reaction to obtain the corresponding amine. The complete
insolubility of the isolated solid prevented any
Scheme 3 First strategy followed to prepare chromophore 1.
Scheme 5 Synthetic scheme followed to prepare 1-3.
2
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the same solvent in the presence of acetic acid and pyridine Table 1 Phase behaviour of compounds 1’-3. NS indicates that the powder did not
dissolve at high temperatures. G stands for gel (the critical gelation concentrations
(
77 %). As for chromophore 1, we were not able to detect its
-
1
(
CGCs) are given between brackets in g.L ), P for precipitate and S for soluble (no
formation despite several attempts summed up in Table S1.
One will note that the conditions reported to synthesize an
2
analogous chromophore devoid of urea-dodecyl moiety did
-1
gelation was observed up to 50 mg.mL ).
Solvents
1’
2
3
3
Hexane
NS
NS
NS
NS
P
P
S
not allow obtaining target compound 1. Moreover, in the
Cyclohexane
Toluene
NS
NS
mildest conditions, i.e. in absolute ethanol at room
G (3.3)
P
temperature, or in chloroform in the presence of silica under
p-Xylene
P
P
microwave heating, a regioisomer of compound
1 (see Scheme
Chlorobenzene
o-Dichlorobenzene
G (1.1)
P
1
S1) was detected by H NMR spectroscopy. To prevent the
formation of this isomer and favour the grafting at the desired
position, thienothiophene-based reagent 15, endowed with
methyl blocking groups on the 3- and 6-positions, was
synthesized according to Scheme 6. In an autoclave, 2,5-
G (0.6)
G (10.6)
P
P
S
1
,2,4-Trichlorobenzene
G (0.9)
G (17.7)
Chloroform
G (5.8)
P
Carbon tetrachloride
G (1.3)
P
S
1
,1,2,2-Tetrachloroethane
P
P
S
dimethylhex-3-yn-2,5-diol was heated in the presence of Acetonitrile
P
G (6.8)
P
P
P
S
elemental sulfur and benzene at 200°C to yield 3,6- Acetone
P
G (13.3)
3
dimethylthieno[3,2-b]thiophene 13 (13 %). Following
1
a
Ethyl acetate
P
P
procedure reported by Seed and coworkers with analogous 1,4-Dioxane
P
P
3
2
derivatives, the action of N-iodosuccinimide (NIS) over 13 in a Tetrahydrofuran
Methanol
G (8.0)
S
S
P
P
P
P
G (13.0)
S
mixture of chloroform and acetic acid allowed isolating 14 with
Ethanol
P
P
P
S
a 75 % yield. The dicyanomethyl moiety was subsequently
Propan-2-ol
P
P
introduced in the presence of sodium hydride, malononitrile
2
7
Octan-1-ol
and bis(triphenylphosphine) palladium (II) chloride (17 %).
The last step consisted in performing the condensation
reaction of 15 on aldehyde in conditions that had allowed for
detecting the regioisomer of target compound (Table S1).
gelation was observed, the corresponding critical gelation
concentration was systematically determined through the
inverted vial method (Table 1). At first glance, it appears that
7
1
This strategy proved to be valuable since mixing both reagents
in refluxing absolute ethanol allowed for isolating target
compound 1’ (51 %). The chemical structures of intermediates
and target derivatives were confirmed through standard
analytical techniques (see Experimental section).
derivative 3 does not form any gel, despite the fact that
-1
concentrations as high as 80 mg.mL (chloroform or dioxane),
-1
or 100 mg.mL (tetrahydrofuran or carbon tetrachloride) were
tested. A main structural difference exists between 1’
, 2 and 3
since push-pull systems in gelators 1’ and 2 display a quinoidal
structure and are planar. Regarding the latter, such a planarity
Phase behaviour in solvents
is likely to favour intermolecular interactions through π−π
Both the chemical structures and the methods used to process stacking while two methyl groups can impede such contacts in
3
4,35
the corresponding materials must be tuned to reach specific the case of
3.
In any case, the absence of quinoidal
properties. On this basis, we explored the phase behaviours character does not explain the absence of gelling properties on
of compounds 1’ and in a wide variety of solvents. When
its own since non-quinoidal push-pull system did form gels.
Organogelators 1’ and proved to be soluble at high
3
3
,
2
3
A
2
temperatures in all solvents but alkanes, and displayed very
different gelling properties. Gelator 1’ had a clear tendency to
gel chlorinated solvents, while
2 afforded gels in miscellaneous
solvents, without obvious correlation. Over the last years,
Bouteiller and coworkers have extended the use of Hansen
solubility parameters to understand the gelling properties of
3
6,37
LMWGs.
Therefore, we tried to rationalize our
observations in light of this theory by plotting the solubility
data in the Hansen space (Table S2 and Figure S1). To do so,
we plotted the tested solvents in a three-dimensional graph,
H p d
where the coordinates are δ , δ and δ , i.e. Hansen solubility
parameters. The latter respectively translate the ability of a
given solvent to interact through hydrogen bonding, polar
interactions and dispersion forces. For both organogelators,
some tendencies were observable since, in each case, all gelled
solvents belong to the same region of the Hansen space.
Gelator 1’ tended to gel solvents displaying a low ability to
Scheme 6. Synthetic scheme followed to prepare chromophore 1’
.
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interact through hydrogen bonds, with maximum
δ
H
values of
.0155 and 5.7195 MPa for tetrahydrofuran and chloroform,
i.e. the solvents that showed the largest critical gelation
1
/2
8
-1
concentrations (8 and 5.8 mg.mL , respectively). Conversely,
when considering the and solubility parameters for gelled
δ
d
δ
p
solvents, one will observe they are relatively high in
comparison to non-gelled solvents. Altogether, these
observations underline the need for both an efficient solvation
of the gelling molecule and the preservation of the hydrogen
bonding ability of 1’. Organogelator
2 exhibited an unexpected
behaviour since it gels solvents that do not belong to the same
sphere in the Hansen space. Interestingly, plotting a projection
of the same graph according to the δd axis (Fig. S2) suggests
that a frontier exists between the gelled solvents and the
others and hence, that
a correlation between solvent
properties and gelling ability exists.
To quantitatively assess the respective gelling abilities of 1’
and
2 in the different solvents, the required weight
percentages of gelators as well as their gelation numbers
3
8
(GN)
were calculated (Table 2). Exceptional gelating Fig. 1 Optical micrographs of 1’-based xerogels prepared from chlorobenzene (CB) and
properties are found for 1’. In particular, the latter is able to toluene under non-polarized (NPL) and polarized (PL) light.
3
9
gel several solvents with a weight percentage below 0.1 %
carbon tetrachloride, 1,2,4-trichlorobenzene (TCB) and 1,2- structures that are locally collinear one to each other, could be
dichlorobenzene (o-DCB)), therefore classifying this compound observed. The birefringence of these structures demonstrates
(
in the supergelator family. One will also note that the gelation their anisotropy couple under consideration (Fig. S3 and S4). In
number for compound 2 increases with the Hansen solubility chlorobenzene and toluene, organogelator 1’ was prone to
parameter δp, which illustrates the solvent ability to interact form films, which did not display any defined structure under
with a solute through dipolar forces.
non-polarized light (Fig. 1a-b). Under polarized one (Fig. 1c-d),
the observation was and hence, their organized character. In
o-dichlorobenzene, chloroform and carbon tetrachloride,
heterogeneous films were obtained. While fibrillary structures
were clearly observed in the case of carbon tetrachloride, the
structures obtained from o-dichlorobenzene and chloroform
did not seem fibrillary at first glance. In this regard, scanning
electron microscopy (SEM) (Fig. S5) proved to be valuable
since it allowed the imaging of the thin films that could not be
observed by optical microscopy and which are located
between larger objects. As for the microstructures prepared
from 1,2,4-trichlorobenzene and tetrahydrofuran, these
appeared spread and well dispersed over the glass slide,
weaving a dense network of fibres. In the former case, the
material was composed of two types of structures, i.e. small
particles displaying a diameter about 10 µm and microwires
between the particles (length ≈ 20 µm; diameter ≈ 2 µm) (Fig.
S6). Both types proved to be visible through polarized light
optical microscopy, confirming their short scale ordering (Fig.
S6).
Table 2 Weight percentages required to gel solvents with derivative 1’ and 2 and the
a
corresponding gelation numbers.
1
’
2
δ
p
a
a
Solvent
THF
%w
GN
Solvent
%w
GN
1/2
(
MPa
)
0.89
931
TCB
1.61
0.81
235
434
531
988
6
CHCl
3
0.39 1291
o-DCB
6.31
10.4
Toluene 0.38 1721
Acetone 1.66
MeOH 1.61
CH CN
CCl
4
0.08 4802
0.06 5362
12.32
18.04
TCB
b
CB
3
0.86 1463
0.1
5413
o-DCB
0.05 8900
a
The gelation number corresponds to the number of solvent molecules gelled by
a single gelator molecule.
b
CB stands for chlorobenzene
Xerogels and their microscopic characterizations
As mentioned before, the solvent may have a dramatical
4
0
Regarding compound 2, the solvent also strongly affected the
impact on the obtained xerogels structures. To evaluate the
influence of this parameter, optical microscopy constitutes a
first valuable tool (Fig. 1, S3 and S4). To perform these
measurements, samples were systematically prepared by drop
materials structuring (Fig. S4). For instance, in o-
dichlorobenzene and acetone, fibrillary structures were easily
observed by optical microscopy (for SEM micrographs, see Fig.
2
), while hardly observable with other solvents. The
casting
a warm solution of gelator (C = Critical Gel
evaporation of 1,2,4-trichlorobenzene and acetonitrile from
the gels afforded structures which were hardly imaged by
optical microscopy given their thicknesses. However, thin
purple fibres could be observed at the periphery of larger
objects in the former solvent and monodimensional
Concentration) over a glass slide. A first assessment lies on the
radically different microstructures obtained depending on the
solvent/gelator quite different since clear monodimensional
4
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that are responsible for gelation and motivated us to record the
corresponding SEM micrograph (Fig. 2b), which also shows a
fibrillary microstructure.
Second Harmonic Generation (SHG) properties
2
0
The previously described experimental setup was modified
as specified in the experimental part (see also Fig. S8) to
record SHG micrographs of the different xerogels. A major
difference with our previous SHG studies, lies on the fact that
the second harmonic generation response is no longer
recorded in a transmission mode. Studying the SHG activity of
thick materials, which may absorb or scatter the second
harmonic, was consequently facilitated. The xerogels were
studied through this technique and the corresponding optical
and SHG micrographs are presented in Fig. 3 and Tables S3-4.
Despite the casting of a warm solution of gelator and
subsequent evaporation of the solvent, a SHG response could
be observed with all xerogels (Figure 3). Given that non-
centrosymmetry constitutes a sine qua non condition to detect
a SHG response, the interactions driving the supramolecular
polymerization and the gelation phenomenon, definitely lead
to a non-centrosymmetric character and hence, SHG-active
Fig. 2 SEM micrographs of 2-based xerogels obtained from acetonitrile (a), methanol
(
b), o-dichlorobenzene (c) and acetone (d).
materials.
Such
feature,
already
41
observed
with
structures could be distinguished in the case acetonitrile when
studying these samples under polarized light (Fig. S7). To confirm
this last assertion, SEM micrographs were recorded and did
demonstrate the occurrence of a dense network of micro and
nanofibers in acetonitrile (Fig. 2). Eventually, the sample prepared
with methanol turned out to be a particular case. Indeed, a very
smooth film was obtained when drop casting a warm solution of
gelator 2 in this solvent. The specific interaction between the latter
and glass provoked a fast spread of the solution over the substrate
in comparison to other solvents. This could explain why such a thin
and smooth material was produced. Consequently, optical
microscopy could not help imaging the fibres
bis(diarylamine)-based chromophores or Disperse Red-based
20,21
xerogels,
demonstrates that our approach, which consists
in grafting a gelling fragment to SHG active chromophores,
constitutes a relevant strategy for promoting spontaneous
SHG through organogelation. Moreover, these results show
that such a concept can be extended to various classes of
chromophores. Finally, it has to be noted that though certain
microstructures could not be observed by SHG microscopy,
optical and SHG micrographs match whatever the solvent
under consideration. This results from the fact that second
harmonic generation is
a
polarization dependent
phenomenon. Hence, it was possible to tune the SHG response
of a given microstructure by simply rotating the polarization of
the incident laser (Fig. S9).
Conclusions
We successfully synthesized and characterized three new
push-pull chromophores endowed with urea-dodecyl moieties,
1
’
,
2
and
3
.
The difficulties encountered to prepare
were circumvented by
thienothiophene-based gelator
1
blocking the 3- and 6-positions of the thienothiophene unit. In
this manner, we were able to orient its reactivity and obtain
the desired regioisomer 1’. Targets 1’ and
2 proved to gel a
wide range of solvents, with a peculiar emphasis for 1’, which
constitutes a supergelator. By comparing their gelling abilities
and plotting the solvents under consideration in the Hansen
space, we could establish relevant relationships to rationalize
the gelling properties and tendencies regarding the critical
gelation concentrations. The critical role of the solvent
regarding materials processing and structuring could be
evidenced. Eventually, nonlinear optical properties could be
shown from the corresponding materials through SHG
microscopy, demonstrating that designing appropriate SHG
Fig. 3 Optical (left) and SHG (right) micrographs of xerogels prepared from 1’ (top) and
2
(bottom) (same zone) after evaporation of o-dichlorobenzene. These images have the
same scale and are 360 µm wide.
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active organogelators constitutes an efficient strategy to The solution was refluxed for 19 hours and concentrated in
afford materials that can spontaneously generate a second vacuo. Target compound 1’ was isolated by silica gel
harmonic, without need for sophisticated techniques.
chromatography (eluent: CHCl /MeOH 99/1) as a green solid
3
displaying a metallic sheen with a 51 % yield (67 mg).
–
1
1
m.p. 198–200
MHz, CDCl , 343 K)
1H), 6.83 (d, J = 8.9 Hz, 2H), 4.58–4.49 (m, 1H), 4.32–4.23 (m,
º
C. IR (ATR) cm : 2194 (C≡N). H–NMR (300
Experimental
3
δ
(ppm): 7.53 (d, J = 8.9 Hz, 2H), 7.03 (s,
Materials and methods
1
5
H), 3.62 (t, J = 5.7 Hz, 2H), 3.50–3.40 (m, 2H), 3.18–3.06 (m,
Starting materials were purchased and used without further
purification. Thin-layer chromatography (TLC) was performed
H), 2.37 (s, 3H), 2.32 (s, 3H), 1.36–1.21 (m, 20H), 0.94–0.83
1
3
on aluminium plates coated with MerckSilica gel 60 F254. (m, 3H). C–NMR (75 MHz, DMSO–d
6
) δ (ppm): 158.0; 151.5.
When necessary, silica gel 60 (35–70 mesh, SDS) was used to 142.8, 132.9, 131.5. 121.3, 112.3, 83.1, 59.4, 54.8, 38.0. 31.3,
1
13
isolate the desired derivatives. H and C NMR spectra were 31.2, 29.9, 29.1, 29.0. 28.9, 28.7, 28.6, 26.4, 26.1, 22.0. 21.9,
+
+
[M+H] :
recorded using deuterated solvents as internal references on a 13.9, 13.5. HRMS (ESI ) m/z: calc. for C34
H
46
N
5
OS
2
BRUKER Advance DRX 300 or a BRUKER AV400 spectrometer. 604.3144, found: 604.3131.
Multiplicities are denoted as follows: s = singlet, d = doublet, t
Organogelator 2. Aldehyde 7 (90 mg, 0.23 mmol) was added to
=
triplet, m = multiplet, br = broad. The mass spectra were
to a solution of compound 11 (38 mg, 0.25 mmol) in absolute
ethanol (20 mL) under argon atmosphere. The medium was
maintained at room temperature for 18 hours and
concentrated in vacuo. A silica gel chromatography (eluent:
recorded on a Q-ToF spectrometer (accurate mass
measurements were achieved using sodium formate as
internal reference), a Jeol JMS 700 (high-resolution mass
spectra (HRMS) or a Bruker Biflex III spectrometer (MALDI-
TOF). The infrared absorption spectra were recorded on an
FTIR BRUKER VERTEX 70. Optical microscopy was performed by
employing a Leica DM 2500P microscope. SEM micrographs
were recorded by scanning electron microscopy (SEM) with a
JEOL JSM 6301F operating at tensions of 3 kV.
chloroform/methanol 99/1) allowed isolating organogelator
2
as a purple solid (70 mg, 63 %).
–1
m.p. 164–166ºC. IR (ATR) cm : 2201 (C≡N), 1686 (C=O).
1
3
H–NMR (300 MHz, CDCl ) δ (ppm): 7.50 (d, J = 9.1 Hz, 2H),
7
6
3
1
.33 (d, J = 5.4 Hz, 1H), 7.22 (s, 1H), 7.01 (d, J = 5.4 Hz, 1H),
.82 (d, J = 9.1 Hz, 2H), 4.39–4.29 (m, 1H), 4.24–4.14 (m, 1H),
.66–3.59 (m, 2H), 3.46–3.38 (m, 2H), 3.13–3.07 (m, 5H), 1.49–
Second Harmonic Generation (SHG) microscopy
1
3
.38 (m, 2H), 3.31–3.20 (m, 18H), 0.88 (t, J = 6.8 Hz, 3H). C–
(ppm): 147.8, 136.6, 133.3, 129.7,
25.6, 112.5. 52.2, 45.0. 40.8, 38.8, 38.0. 37.9, 31.9, 30.1, 29.7,
9.6, 29.6, 29.5. 29.5. 29.4, 29.3, 29.2, 26.9, 22.7, 14.1. HRMS
The microscope used to record SHG micrographs corresponds
2
to a previously reported setup which was modified.
0
3
NMR (75 MHz, CDCl ) δ
1
Given the thickness and opaque character of certain samples,
the setup was modified in order to allow the detection of the
reflected SHG signal. To do so, a removable dichroic mirror
was implanted on the commercial microscope (IX 71, Olympus)
2
+
+•
(ESI ) m/z: calc. for C30
41 5
H N OS [M ]: 519.3032, found:
5
19.3042.
using specific parts 3D printed (Fig. S8). A 3D-printed optical Compound 3. Pyridine (560 µL, 7 mmol) and acetic acid (280
block was also inserted between the microscope and the µL, 4.9 mmol) were added to a solution of aldehyde
(200 mg,
photomultiplier (Fig. S8). It supports low pass filter 0.5 mmol and acceptor
(120 mg, 0.6 mmol) in absolute
FESH0450, Thorlabs), a 400 nm bandpass filter (FB400-40, ethanol (25 mL). The medium was heated to reflux under
7
a
2
(
Thorlabs) and a lens that focuses the beam on the cathode argon atmosphere for 18 hours. The solvent was evaporated
photomultiplier. Aiming at constructing multi-pass images under reduced pressure and the residue was dissolved in a
through the pixel-by-pixel addition of each scan, the minimum of dichloromethane. Hexane was added to provoke
acquisition program was modified. It should be noted that an precipitation and the suspension was filtered. The solid was
image obtained from only one scan does not display a rinsed with hexane to obtain pure
sufficient contrast. On the contrary, performing multi-pass 77 %).
3
as a purple solid (225 mg,
–
1
1
C. IR (ATR) cm : 2224 (C≡N). H–NMR (300
imaging, one can obtain very well contrasted micrographs. This m.p. 128–130
technique permits to obtain SHG images in specific conditions: MHz, CDCl3)
º
δ
(ppm): 7.60 (d, J = 15.1 Hz, 1H), 7.53 (d, J = 9.0
in the presence of very low excitation intensities, with Hz, 2H), 6.81 (d, J = 9.0 Hz, 2H), 6.72 (d, J = 15.1 Hz, 1H), 4.47–
materials displaying weak nonlinear responses, or with 4.39 (m, 1H), 4.27–4.19 (m, 1H), 3.69–3.58 (m, 2H), 3.48–3.36
unstable materials. The images presented in this study were (m, 2H), 3.14 (s, 3H), 3.12–3.05 (m, 2H), 1.75 (s, 6H), 1.34–1.17
1
3
built from 100 successive scans of the area of interest.
(m, 20H), 0.88 (t, J = 6.8 Hz, 3H). C–NMR (75MHz, CDCl3) δ
(
ppm): 176.3, 174.2, 158.1, 153.4, 148.4, 132.4, 124.9, 122.0.
Synthetic procedures.
1
3
1
12.4, 112.0. 111.5. 108.6, 96.9, 93.9, 52.3, 40.7, 38.9, 37.9,
6.5. 31.9, 30.9, 30.2, 29.7, 29.6, 29.5. 29.3, 26.9, 26.7, 22.7,
Organogelator 1’. Absolute ethanol (3 mL) was added at room
+
+
temperature under argon atmosphere to
a mixture of
47 6 2
4.1. HRMS (ESI ) m/z: calc. for C34H N O [M+H] : 571.3760,
aldehyde 7 (85 mg, 0.22 mmol) and 15 (51 mg, 0.22 mmol).
6
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Paper
+
found: 571.3754; calc. for C H N NaO [M+Na] : 593.3580, Compound 9. To a solution of azide
8
(1.033 g, 4.2 mmol) in
3
4
46
6
2
found : 593.3770.
Azide 6. To a mixture of aldehyde
dicyanomethylthieno[3,2-b]thiophene
absolute ethanol, palladium over chacoal 10 % was added
1.04 g) at room temperature under hydrogen atmosphere.
(
4
(50 mg, 0.25 mmol) and 2-
(50 mg, 0.248 mmol)
The mixture was stirred for 10 hours and filtered through
celite and concentrated in vacuo. The desired compound (722
mg, 78 %) was used in the next without further purification as
a light brown oil.
5
under an argon atmosphere, acetic anhydride (1.5 mL) was
added. The mixture was heated to reflux and stirred for 1 hour
and then slowly cooled to room temperature. Hexane was
added and the resulting solid was filtered off and washed with
hexane. The crude product was purified by flash column
-1
IR cm : 3361 (–NH), 3299 (–NH), 1614 (C=C Ar), 1178 (C=O).
1
H–NMR (400 MHz, CDCl
.71 (d, J = 8.8 Hz, 2H), 5.72 (s, 1H), 4.15–4.09 (m, 2H), 4.03–
3.96 (m, 2H), 3.81–3.63 (m, 2H), 3.43 (t, J = 6.5 Hz, 2H), 2.91 (s,
3
) δ (ppm): 7.32 (d, J = 8.8 Hz, 2H),
6
chromatography (silica gel) using hexane/CH
eluent to afford azide (23 mg, 24 %) as a blue solid. H NMR
300 MHz, CDCl ): 8.34 (s, 1H), 7.74–7.71 (m, 2H), 7.20 (s, 1H),
.00 (s, 1H), 6.81–6.78 (m, 2H), 3.68 (t, J = 5.9 Hz, 2H), 3.56 (t,
2 2
Cl 2:8 as the
1
6
1
3
3
H), 2.83 (t, J = 6.5 Hz, 2H). C–NMR (100 MHz, CDCl3)
δ
ppm): 150.3, 127.6, 125.2, 111.9, 104.2, 65.1, 52.9, 47.2, 38.7.
(
3
(
7
+
MS (ESI ) m/z: 223.0 [M+H] .
+
J = 5.9 Hz, 2H), 3.18 (s, 3H).
Compound 10. Compound
9 (722 mg, 3.25 mmol) was
Aldehyde 7. Compound 10 (794 mg, 1.8 mmol) was dissolved
in tetrahydrofuran (10 mL) and anhydrous Amberlyst 15 was
added at room temperature. The mixture was stirred for 15
minutes before filtration. The resin was rinsed with
dichloromethane (50 mL) and the filtrate was concentrated in
dissolved in dry dichloromethane (15 mL) and dodecyl
isocyanate (0.9 mL, 3.6 mmol) was added at room
temperature under inert atmosphere. The mixture was stirred
for 14 hours and concentrated in vacuo. The residue was
dispersed in pentane and isolated by filtration as a white solid
vacuo. Aldehyde
eluent: 1) CHCl , 2) CHCl
a 30 % yield (211 mg).
m.p. 72–74 C. IR (KBr) cm : 3334 (–NH), 1678, 1661 (C=O).
H–NMR (400 MHz, CDCl (ppm): 9.70 (s, 1H), 7.69 (d, J = 9.0
Hz, 2H), 6.75 (d, J = 9.0 Hz, 2H), 4.59 (t, J = 5.9 Hz, 1H), 4.38 (t, J
7
was isolated by silica gel chromatography
(1.072 g, 76 %).
1
(
3
3
/MeOH 99/1) as a white powder with
3
H–NMR (400 MHz, CDCl ) δ (ppm): 7.34 (d, J = 8.8 Hz, 2H),
–
1
6.68 (d, J = 8.8 Hz, 2H), 5.72 (s, 1H), 4.16–4.10 (m, 2H), 4.04–
3.97 (m, 2H), 3.53–3.44 (m, 2H), 3.43–3.32 (m, 2H), 3.08–2.98
º
1
3
) δ
(
m, 2H), 2.93 (s, 3H), 1.34–1.11 (m, 20H), 0.88 (t, J = 6.8 Hz,
+
H). MS (ESI ) m/z: 434.2 [M+H] .
+
3
=
3
1
5.5 Hz, 1H), 3.59 (t, J = 6.4 Hz, 2H), 3.44–3.37 (m, 2H), 3.14–
.08 (m, 2H), 3.07 (s, 3H), 1.48–1.39 (m, 2H), 1.29–1.22 (m, Compound 13. In an autoclave, 2,5–dimethylhex-3-yn–2,5–diol
1
3
8H), 0.87 (t, J = 6.9 Hz, 3H). C–NMR (100 MHz, CDCl )
δ
(4.26 g, 30 mmol) and sulfur (2.38 g, 74 mmol) were dispersed
3
(ppm): 190.3, 158.1, 153.8, 132.2, 125.3, 111.0. 52.1, 40.7, in benzene (25 mL) and heated at 190°C for 12 hours. Benzene
3
8.7, 38.0. 31.9, 30.2, 29.7, 29.6, 29.4, 26.9, 22.7, 14.2. HRMS was evaporated under reduced pressure and compound 13
+
ESI ) m/z: calc. for C H N O [M+H] : 390.3115, found: was purified by silica gel chromatography (eluent: hexane).
+
(
2
3 40 3 2
+
[M+Na] : 412.2934, found: When necessary, the traces of elemental sulfur were
3
90.3096; calc. for C23
12.2916.
H39NaN
3
O
2
4
eliminated through precipitation in hexane. This method
allowed for the isolation of compound 13 as a white solid with
Compound 8. A solution of aldehyde
4 (0.97 g, 4.75 mmol),
a 13 % yield (0.65 g).
1
m.p. 90–92°C. H–NMR (300 MHz, CDCl )
ethylene glycol (0.73 g, 11.85 mmol) and p–toluene sulfonic
acid monohydrate (0.154 g, 0.81 mmol) in toluene (35 mL) was
refluxed under inert atmosphere for 17 hours. After cooling
down to room temperature, a saturated solution of sodium
δ
(ppm): 6.96 (s, 2H),
3
1
.36 (s, 6H). C–NMR (75 MHz, CDCl
3
2
3
)
δ
(ppm): 140.1, 130.4,
1
21.8, 14.7.
hydrogenocarbonate (60 mL) was added. The aqueous phase Compound 14. Compound 13 (0.4 g, 2.4 mmol) and N–
was extracted three times with ethyl acetate (50 mL). The iodosuccinimide (0.6 g, 2.6 mmol) were introduced in a three-
combine organic layers were washed with water (3 x 50 mL), necked flask under inert atmosphere. A mixture of chloroform
dried over magnesium sulfate and concentrated in vacuo. In (10 mL) and acetic acid (10 mL) was added and the medium
this manner, the relatively unstable compound
with a 88 % yield (1.03 g).
8
was obtained was stirred for 18 hours. Ether (50 mL) was added and the
organic phase was washed with a saturated solution of sodium
–1
IR cm : 2097 (–N
1
3
), 1616 (C=C, Ar), 1520 (C=C, Ar), 1178 (C–O). hydrogenocarbonate (3 x 50 mL), a saturated solution of
H–NMR (400 MHz, CDCl3) (ppm): 7.35 (d, J = 8.7 Hz, 2H), sodium thiosulfate (3 × 50 mL) and brine (3 × 50 mL). The
δ
6
3
3
1
,71 (d, J = 8.7 Hz, 2H), 5.73 (s, 1H), 4.16–4.10 (m, 2H), 4.04– organic phase was dried over magnesium sulfate, filtered and
.98 (m, 2H), 3.55 (t, J = 6.0 Hz, 2H), 3.44 (t, J = 6.0 Hz, 2H), concentrated in vacuo. In this manner, compound 14 (524 mg)
1
3
.02 (s, 3H). C–NMR (100 MHz, CDCl
3
) δ (ppm): 149.2, 127.7, was isolated with a 75 % yield.
+
1
25.8, 111.8, 104.1, 65.2, 51.9, 48.7, 38.9. HRMS (ESI ) m/z: m.p. 88–90°C. H–NMR (300 MHz, CDCl3)
δ
13
(ppm): 7.01–6.98
+
[M+H] : 249.1346, found: 249.1354.
calculated for C12
H
17
N
4
O
2
(m, 1H), 2.33–2.32 (m, 3H), 2.31 (s, 3H). C–NMR (75 MHz,
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Paper
CDCl
Organic & Biomolecular Chemistry
) δ
(ppm): 134.7, 129.9, 124.1, 121.5. 75.1, 16.9, 14.6. MS 9 Z. Wei, J. H. Yang, J. Zhou, F. Xu, M. Zrínyi, P. H. Dussault, Y. Osada
3
+
+•
and Y. M. Chen, Chem. Soc. Rev., 2014, 43, 8114.
0 X. Yu, L. Chen, M. Zhang and T. Yi, Chem. Soc. Rev., 2014, 43
5346.
(ESI ) m/z: 294.2 [M ].
1
,
Compound 15. Under argon atmosphere,
a
solution of
malononitrile (375 mg, 5.7 mmol) in dry tetrahydrofuran (2 11 J. Yan, B. S. Wong and L. Kang, in Soft Fibrillar Materials, Wiley-
VCH Verlag GmbH & Co. KGaA, 2013, pp. 129.
2 S. S. Babu, V. K. Praveen and A. Ajayaghosh, Chem. Rev., 2014,
mL) was added dropwise at 0°C to a suspension of sodium
hydride (60 % in mineral oil, 333 mg, 35 mmol) in dry
tetrahydrofuran (4 mL). After the addition, the mixture was
1
1
14, 1973.
1
1
3 Z. Zhao, J. W. Y. Lam and B. Z. Tang, Soft Matter, 2013, 9, 4564.
4 R. G. Weiss and P. Terech, Eds., Molecular gels: materials with
self-assembled fibrillar networks, Springer, Dordrecht, 2006.
allowed
to
warm
at
room
temperature
and
bis(triphenylphosphine)palladium (II) chloride (199 mg, 0.3
mmol) as well as a solution of 2-iodo-3,6-dimethylthieno[3,2- 15 R. J. Kumar, J. M. MacDonald, T. B. Singh, L. J. Waddington and
b]thiophene 14 (238 mg, 0.8 mmol) in dry tetrahydrofuran (2
mL). After 60 hours refluxing and cooling to room
temperature, chlorhydric acid (1 M, 50 mL) was added. The
aqueous layer was extracted with dichloromethane (3 x 50
mL). The combined organic phases were washed with water (2
x 50 mL) and brine (50 mL), dried over magnesium sulfate,
filtered and concentrated in vacuo. The desired compound was
A. B. Holmes, J. Am. Chem. Soc., 2011, 133, 8564.
1
1
6 T. Tu, W. Fang and Z. Sun, Adv. Mater., 2013, 25, 5304.
7 M. Morimoto, S. Kobatake, M. Irie, H. K. Bisoyi, Q. Li, S. Wang
and H. Tian, in Photochromic Materials, Preparation, Properties
and Applications, Wiley-VCH, He Tian and Junji Zhang., pp. 281.
8 K. Sripathy, R. W. MacQueen, J. R. Peterson, Y. Y. Cheng, M.
Dvořák, D. R. McCamey, N. D. Treat, N. Stingelin and T. W.
1
Schmidt, J. Mater. Chem. C, 2015, 3, 616.
isolated
by
silica
gel
chromatography
(eluent: 19 S. Qu, H. Wang, W. Zhu, J. Luo, Y. Fan, L. Song, H.-X. Zhang and
X. Liu, J. Mater. Chem., 2012, 22, 3875.
dichloromethane) as a brown solid with a 27 % yield (51 mg).
1
20 A. B. Marco, F. Aparicio, L. Faour, K. Iliopoulos, Y. Morille, M.
Allain, S. Franco, R. Andreu, B. Sahraoui, D. Gindre, D. Canevet
and M. Sallé, J. Am. Chem. Soc., 2016, 138, 9025.
1 F. Aparicio, L. Faour, D. Gindre, D. Canevet and M. Sallé, Soft
Matter, 2016, 12, 8480.
2 G. Zerbi, Organic Materials for Photonicsꢀ: Science and
Technology, Elsevier, 1993.
3 A. B. Marco, R. Andreu, S. Franco, J. Garín, J. Orduna, B.
Villacampa, B. E. Diosdado, J. T. López Navarrete and J. Casado,
Org. Biomol. Chem., 2013, 11, 6338.
H–NMR (300 MHz, CDCl
3
) δ (ppm): 7.09 (br s, 1H), 5.22 (br s,
1H), 2.46 (d, J = 0.4 Hz, 3H), 2.38–2.36 (m, 3H). MS (MALDI)
m/z: 231.3.
2
2
2
Conflicts of interest
There are no conflicts to declare.
2
2
4 X. Tang, L. Pan, K. Jia and X. Tang, Chem. Phys. Lett., 2016, 648,
Acknowledgements
1
14.
5 A. B. Marco, P. M. Burrezo, L. Mosteo, S. Franco, J. Garín, J.
Orduna, B. E. Diosdado, B. Villacampa, J. T. López Navarrete, J.
The authors are grateful to the University of Angers for its
support through an Arianes Fellowship as well as the Region
Pays de la Loire and Angers Loire Metropole for funding a
postdoctoral fellowship through the LUMOMAT program. The
authors also acknowledge the PIAM and the SCIAM platforms
of the University of Angers for their help. The authors also
thank the Agence Nationale de la Recherche for granting the
FOGEL project and DC is grateful to the Centre National de la
Recherche Scientifique (CNRS) for a Délégation period.
Casado and R. Andreu, RSC Adv., 2015,
6 H.-C. Peng, C.-C. Kang, M.-R. Liang, C.-Y. Chen, A. Demchenko,
C.-T. Chen and P.-T. Chou, ACS Appl. Mater. Interfaces, 2011,
713.
7 K. Takahashi and S. Tarutani, Heterocycles, 1996, 43, 1927.
5, 231.
2
3
,
1
2
2
8 T.-L. Lai, D. Canevet, Y. Almohamed, J.-Y. Mévellec, R. Barillé, N.
Avarvari and M. Sallé, New J. Chem., 2014, 38, 4448.
29 R. Pal, T. Sarkar and S. Khasnobis, Ark. Online J. Org. Chem.
The research led in the Universidad de Zaragoza was financed 30 G. Melikian, F. P. Rouessac and C. Alexandre, Synth. Commun.,
by MINECO (CTQ2014-52331R) and the Gobierno de Aragon-
Fondo Social Europeo (E39). A predoctoral fellowship (FPI
1995, 25, 3045.
3
3
3
3
1 K. S. Choi, K. Sawada, H. Dong, M. Hoshino and J. Nakayama,
Heterocycles, 1994, 38, 143.
2 J. I. Tietz, J. R. Mastriana, P. Sampson and A. J. Seed, Liq. Cryst.,
́
BES2009-016966), with EEBB FPI 2012 and 2013, is also
acknowledged.
2
012, 39, 515.
3 P. A. Korevaar, C. Schaefer, T. F. A. de Greef and E. W. Meijer, J.
Am. Chem. Soc., 2012, 134, 13482.
4 For a X-ray crystal structure showing the hindrance resulting
from both methyl groups, see: P.-A. Bouit, G. Wetzel, G. Berginc,
B. Loiseaux, L. Toupet, P. Feneyrou, Y. Bretonnière, K. Kamada, O.
Maury and C. Andraud, Chem. Mater., 2007, 19, 5325.
References
1
2
P. Terech and R. G. Weiss, Chem. Rev., 1997, 97, 3133–3159.
A. R. Hirst, B. Escuder, J. F. Miravet and D. K. Smith, Angew. Chem.
Int. Ed., 2008, 47, 8002.
3
4
5
6
7
8
L. E. Buerkle and S. J. Rowan, Chem. Soc. Rev., 2012, 41, 6089.
P. Dastidar, Chem. Soc. Rev., 2008, 37, 2699.
N. M. Sangeetha and U. Maitra, Chem. Soc. Rev., 2005, 34, 821.
A. Vintiloiu and J.-C. Leroux, J. Controlled Release, 2008, 125, 179.
D. K. Kumar and J. W. Steed, Chem. Soc. Rev., 2014, 43, 2080.
B. O. Okesola and D. K. Smith, Chem. Soc. Rev., 2016, 45, 4226.
35 P. A. Bouit, E. Di Piazza, S. Rigaut, B. Le Guennic, C. Aronica, L.
Toupet, C. Andraud and O. Maury, Org. Lett., 2008, 10, 4159.
36 M. Raynal and L. Bouteiller, Chem. Commun., 2011, 47, 8271.
37 J. Bonnet, G. Suissa, M. Raynal and L. Bouteiller, Soft Matter,
2014, 10, 3154.
8
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Paper
3
3
4
4
8 Y. Lan, M. G. Corradini, R. G. Weiss, S. R. Raghavan and M. A.
Rogers, Chem. Soc. Rev., 2015, 44, 6035.
9 K. Tiefenbacher, H. Dube, D. Ajami and J. Rebek, Chem.
Commun., 2011, 47, 7341.
0 D. Canevet, A. Pérez Del Pino, D. B. Amabilino and M. Sallé, J.
Mater. Chem., 2011, 21, 1428.
1 Y. Jiang, M. Allain, D. Gindre, S. Dabos-Seignon, P. Blanchard, C.
Cabanetos and J. Roncali, Sci. Rep., 2017, 7, 8317.
This journal is © The Royal Society of Chemistry 2018
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