Organogels from unsymmetrical π-conjugated 1,3,4-oxadiazole derivatives

Article abstract of DOI:10.1039/c3nj40648b

In this study, the unsymmetrical π-conjugated gelators, 2-(3,4-bis(alkoxy)phenyl)-5-(pyridine-4-yl)-1,3,4-oxadiazole [4-POXD-Bn (n = 4, 8, 12)], were synthesized and screened for gelation in various solvents. The tendencies of the critical gelation concen

Full text of DOI:10.1039/c3nj40648b

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Organogels from unsymmetrical p-conjugated
1,3,4-oxadiazole derivatives†
Cite this: DOI: 10.1039/c3nj40648b
Chengxiao Zhao,a Haitao Wang,a Binglian Bai,b Songnan Qu,c Jianxi Song,a
Xia Ran,a Yan Zhanga and Min Li*a
In this study, the unsymmetrical p-conjugated gelators, 2-(3,4-bis(alkoxy)phenyl)-5-(pyridine-4-yl)-1,3,4-
oxadiazole [4-POXD-Bn (n = 4, 8, 12)], were synthesized and screened for gelation in various solvents.
The tendencies of the critical gelation concentration (CGC) and the gel–sol phase transition
temperatures (Tgel) of the 4-POXD-B8 gels, as well as the relationship between the end-chain length of
gelator and gelation ability, indicated that the solvophobic effect has a critical role in gelation. For the
specific gelator that we studied, we observed that the strength of the solvophobic force was related to
the solvent properties. The solvent effect on gelation was studied quantitatively using the solvent
polarity parameters: polar solubility parameter (da), dielectric constant (e), and polarity parameter
(ET(30)). The results revealed that the favorable da domain and ET(30) domain for the gelation of
Received (in Montpellier, France)
25th July 2012,
4-POXD-B8 was in the range of 8.1–12.6 (cal cmꢀ3 1/2 and 43.3–55.7 kcal molꢀ1
, respectively.
)
Accepted 13th February 2013
Meanwhile, a decrease of da and ET(30) in the solvents is unfavorable for gelation. Furthermore, the
solvent effect on the microstructure of the gels was studied via scanning electron microscopy (SEM). The
SEM images revealed that the gels from 4-POXD-B8 in DMSO and DMF were composed of helical
ribbons, whereas those formed in other solvents consisted of flat ribbons.
DOI: 10.1039/c3nj40648b
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gelator can be synthesized by introducing n-alkyl chains,
amide, or urea groups into the central p-conjugated cores, such
Introduction
as phthalocyanine,4 acene,5,6 anthracene,6 perylene,7,10 hexan-
benzocoronene,8 bisphenazine,9 etc. The n-alkyl chains, amide,
and urea groups direct the self-assembly and gelation of
p-conjugated molecules through van deer Walls and hydrogen
bonding interactions.2,3 Hopf and co-workers have reported
on the p-conjugated organogelator, 2,3-di-alkoxytetracenes, in
which the p–p stacking and van der Waals interactions are the
driving forces for the gelation.6 Wu¨rthner et al. synthesized a
urea-containing tetraphenoxy-substituted perylene bisimide
gelator, forming a gel in toluene via self-assembly through
hydrogen bonding and p–p stacking interactions.10
Recent studies have shown that solvents have an important
role in the delicate equilibrium for gelation, aside from the
influence of the gelator structure.11,17 The simplest approach to
quantifying solvent effects is to use solvent parameters, such
as the dielectric constant (e), Kamlet–Taft,12 Hildebrand (d),
Reichardt’s (ET(30)),13 and Hansen parameters (dd, dp, dh).11
Hanabusa and co-workers have reported that the minimum
gelation concentration of cyclo(dipeptide) gelators is depen-
dent on the Hildebrand parameters of solvents.14 Tritt-Goc and
co-workers correlated the thermal gelation properties of the gels
with different solvent parameters.15 Furthermore, Smith and
Low-molecular-mass organogels (LMOGs) are a new class of
materials in supramolecular chemistry, in which organo-
gelators spontaneously self-assemble through noncovalent
interactions to create three-dimensional networks capable of
entrapping solvents therein.1 Different kinds of non-covalent
interactions, such as hydrogen bonds, p-stacking, van der
Waals, and the solvophobic effect, etc., are involved in such
supramolecular building.2 Among the reported LMOGs, the
p-conjugated LMOGs have drawn significant attention because
of their potential application in optoelectronics.3 At present,
the structure–activity relationships that underpin self-assembly
into gels are not fully understood. However, a new p-conjugated
a Key Laboratory of Automobile Materials (Jilin University), Ministry of Education,
Institute of Materials Science and Engineering, Jilin University,
Changchun 130012, PR China. E-mail: minli@jlu.edu.cn
b College of Physics, Jilin University, Changchun 130012, PR China
c Key Laboratory of Excited State Processes, Changchun Institute of Optics,
Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033,
PR China
† Electronic supplementary information (ESI) available: SEM images, gel photo-
graphs, solvent parameters, XRD and UV-vis spectra. See DOI: 10.1039/
c3nj40648b
c
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Table 1 Gelation properties of 4-POXD-Bn (n = 4, 8, 12) in different solventsa
Solvents
4-POXD-B4
4-POXD-B8
4-POXD-B12
Methyl cyclohexane
Methanol
Ethanol
n-Propanol
n-Butanol
Acetonitrile
Dimethylformamide
Dimethyl sulfoxide
Sb
Gb
Gb
WGb
WGb
Sb
G(5.01)
G(6.12)b
G(6.49)b
G(12.4)b
G(4.95)
G(29.4)
G(3.34)
Pb
Pb
Pb
Sb
S
S
S
G(9.79)b
G(4.09)
G(16.3)
G(2.16)
Scheme 1 Molecular structures of 4-POXD-Bn (n = 4, 8, 12).
co-workers noticed that the Kamlet–Taft parameters, in parti-
a
G = opaque gel; WG = weak gel that can change into a solution at room
temperature at a concentration of 5.5 ꢁ 10ꢀ2 mol Lꢀ1; P = precipitation;
S = solution; the values in the brackets denote the CGC (10ꢀ3 mol Lꢀ1).
Gel or precipitation formed at ꢀ20 1C.
cular a, can have a degree of predictive power for the gelation
processes.16 Jamart-Gregoire and co-workers established the
´
b
relationship between the gel behavior of amino acid gelators
and the hydrogen-bonding Hansen parameters.17 These studied
gelators have a common denominator, i.e., gelator–gelator
hydrogen bonding, indicating that the solvents can easily affect
the gelation through solvent–geltor hydrogen bonding. The
existence of solvent–gelator interactions has also been demon-
strated for the gelator without hydrogen bonding. However,
only a few studies have focused specifically on the influence of
solvents on gelation. Thus, the current study investigates the
influence of solvents on the gelation of p-conjugated gelators
without gelator–gelator hydrogen bonding.
1,3,4-Oxadiazole derivatives (OXD) have gained widespread
use as electron-transporting/hole-blocking materials, emitting
layers in electroluminescent diodes and nonlinear optical materials
because of the electron-deficient nature of their heterocycle,
high photoluminescence quantum yield, and good thermal and
chemical stabilities. In our previous study, we have reported a
series of twin-tapered p-conjugated molecules, bi-1,3,4-oxadiazole
derivatives (BOXD), and found that the 1,3,4-oxadiazole ring was
fully conjugated with the adjacent phenylene groups and the
face-to-face donor–acceptor interactions were beneficial to
p-stacking.18,19 In this context, we have designed and synthesized
a series of unsymmetrical p-conjugated 1,3,4-oxadiazole gelators,
2-(3,4-bis(alkoxy)phenyl)-5-(pyridine-4-yl)-1,3,4-oxadiazole (4-POXD-Bn
(n = 4, 8, 12); in Scheme 1), which consisted of a rigid part
and two flexible terminal alkoxyl chains. The p–p stacking,
van der Waals interactions, and solvophobic effect are expected
to be the driving forces for gelation. Moreover, a relationship
between the gelation properties of the p-conjugated 1,3,4-
oxadiazole gelators and solvents was established to better
understand the solvent effect.
The data shows that 4-POXD-B8 can dissolve in esters,
ethers, aromatic, as well as chlorinated solvents and gel DMSO,
DMF, acetonitrile, and alcohols. Most of the gelified solvents
are polar solvents, indicating the importance of solvophobic
interactions between the gelator and solvent. The only exception
to this trend is methyl cyclohexane (MCH), which might involve
strong p–p stacking interactions due to MCH being benign for p
systems.20 Furthermore, the critical gelation concentration
(CGC) value of 4-POXD-B8 declined from 2.94 ꢁ 10ꢀ2 mol Lꢀ1
(DMF) to 4.95 ꢁ 10ꢀ3 mol Lꢀ1 (acetonitrile), and then to 3.34 ꢁ
10ꢀ3 mol Lꢀ1 (DMSO), as the solvent polarity varied. Fig. 1 shows
the gel–sol phase transition temperatures (Tgel) plotted against the
concentration of 4-POXD-B8. Tgel increased until a plateau region
was reached (denoted by a concentration-independent Tgel) as the
concentration increased. After changing the solvent, the value of
the Tgel in the ‘‘plateau region’’ decreased from 44 1C (DMSO) to
39 1C (methanol), and then to 28.6 1C (ethanol). The tendencies
of the CGC and Tgel in the ‘‘plateau region’’, which were in
agreement with the compatibility of alkanes with the solvents,21
indicated that the solvophobic effect was the main driving force
for gelation.
4-POXD-B4 and 4-POXD-B12, with shorter alkoxyl chains and
longer alkoxyl chains, respectively, compared to 4-POXD-B8,
Results and disscusion
Gel properties of 4-POXD-Bn
A certain solubility of a gelator in solvents is a prerequisite for
gelation, whereas microphase segregation from dissolved sol-
vents induces gelation, in which different types of intermole-
cular interactions underpin the self-assembly of the gelators.
The new gelators (4-POXD-Bn, n = 4, 8, 12) were screened for
their gelation ability in different types of solvents, such as
aromatic solvents, alkanes, chlorinated solvents, esters, ethers,
ketones, alcohols, and other polar solvents (Table S1, ESI†). The
results are listed in Table 1 and Table S1 (ESI†).
Fig. 1 Gel–sol phase-transition curves of 4-POXD-B8 in DMSO, acetonitrile,
methanol, and ethanol.
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were screened for gelation in these solvents to confirm the
significance of the solvophobic effect in gelation (Table 1).
4-POXD-B4 formed weak gels in methanol and ethanol, and
dissolved in DMSO and acetonitrile. Meanwhile, 4-POXD-B12
precipitated from methanol, ethanol, and n-propanol (Table 1),
suggesting that the compatibility of the gelator with the
solvents was weakened by lengthening the alkoxyl chains of
the gelator; the length of the alkoxyl chains in 4-POXD-B8 was
suitable for gelation.
Influence of the solvent on gelation
Based on the Gibbs energies of the solvation of alkanes in
various solvents (Table S3, ESI†) reported by Solomonov et al.,21
the strength of the solvophobic effects of the alkoxyl chains
towards the solvents increased as the polarity of the solvents
increased, such that solvents with a high polarity interacted
with the alkoxyl chains weakly. Thus, the bulk polarity para-
meters of the solvents, such as the polar solubility parameter
(da),22 dielectric constant (e), and polarity parameter (ET(30)),
were chosen to investigate the solvent effect on gelation of
4-POXD-Bn quantitatively. Table S2 (ESI†) summarizes the
values of these parameters for the studied solvents.
First, the gel behaviors of 4-POXD-Bn (n = 8, 12) were
correlated with the solvent parameters. The behavior of
4-POXD-B8 defines a wide, favorable da domain for gelation
between 8.1 and 12.6 (cal cm
viors are observed, as shown in Fig. 2a. The ‘‘precipitation’’ or
‘‘insoluble’’ behaviors were observed above 12.6 (cal cmꢀ3 1/2
whereas the ‘‘solution’’ behaviors were noticeable below
8.1 (cal cm
ꢀ3 1/2, indicating that a moderate strength of
)
ꢀ3 1/2, at which only ‘‘gel’’ beha-
)
,
Fig. 2 Effect of the combined (a) polar solubility parameter da and (b) polarity
parameter ET(30) of the studied solvents on the gelation behaviors of 4-POXD-Bn
(n = 8, 12). G = gel; P = precipitation; S = solution; IS = insolubility.
)
the solvophobic effect is favorable for gelation. Similarily,
4-POXD-B12 defines a narrow da domain for gelation between
8.1 and 9.6 (cal cm )
ꢀ3 1/2, except for n-propanol. Fig. 2b shows
the gelation behaviors versus the ET(30) graph. The ET(30)
Table 2 Bulk solvent parameters of the selected solvents: e = dielectric constant,
da = polar solubility parameters, and ET(30) = polarity parameter. The Tgel is the
domains for the gelation of 4-POXD-B8 and 4-POXD-B12 were
43.3–55.7 kcal molꢀ1 and 43.3–50.4 kcal molꢀ1, respectively. gel–sol temperature for the studied gels with concentration of 1.32 ꢁ 10ꢀ2 mol Lꢀ1
Further, the strength of the gels were correlated with the
GN
Tgel/1C
solvent parameters. The gelation number (GN), which gives
the number of solvent molecules gelified per molecule of
gelator,23 is one of the most common criteria to evaluate the
strength of a gel as well as the gel–sol phase transition
temperature. Within each solvent class, the GN and Tgel values
ET(30)/
kcal
4-POXD- 4-POXD- 4-POXD- 4-POXD-
B8
da/(cal
cmꢀ3 1/2
)
e
molꢀ1
B12
B8
B12
DMSO
9.43
Acetonitrile 9.3
DMF 8.67
48.9 45.1 4219
38.8 45.6 3859
6523
4675
795
—
—
—
43
34
18
37
26
17
16
64
48
19
—
—
—
—
37.6 43.8
441
of the 4-POXD-B8 gels increased with an increase of da in each Methanol 12.44
solvent class (Table 2 and Fig. S4, ESI†).
33.62 55.4 4934
25.07 51.6 2799
20.8 50.7 2056
Ethanol
n-Propranol 9.12
n-Butanol 8.19
10.43
17.84 50.2
882
1121
Organogel structure
The xerogels were subjected to scanning electron microscopy
(SEM) to examine the solvent effect on gel the microstructure. helical ribbons were composed of several narrow ribbons.
Fig. 3 shows the SEM images of the 4-POXD-B8 xerogels from The helical pitches were non-uniform and both straight and
different solvents. Flat and broad ribbons with a width of flexible ribbons were observed, indicating that the helical
ca. 2 mm to 5 mm were observed in the 4-POXD-B8 xerogels structures did not come from the molecular chirality. The
from acetonitrile (Fig. 3a) and methanol (Fig. 3b). The xerogel helical structures were also observed under an optical micro-
from ethanol showed straight ribbons of 0.1 mm to 0.5 mm scopic (OM), in which the ribbons exhibited periodical repeti-
width (Fig. 3c). Interestingly, the 4-POXD-B8 xerogel from tions of bright and dark regions (Fig. 3f). Similar helical
DMSO consisted of right- and left-handed helical ribbons with structures were also found in 4-POXD-B8 xerogels from DMF
a width of 0.5 mm to 3 mm (Fig. 3d). In some cases, the wide (Fig. 3e). The results clearly indicated that the solvent significantly
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Fig. 3 SEM images of the 4-POXD-B8 xerogels from (a) acetonitrile, (b) methanol, (c) ethanol, (d) DMSO, and (e) DMF. (f) Optical microscopic image of the
xerogel from DMSO.
affects the microstructure of the 4-POXD-B8 gels. The 4-POXD-B8
film casted from the dilute DMSO solution consisted of flat and
flexible ribbons (Fig. S6, ESI†), whereas more ribbons, twisted
nodes, and helical ribbons appeared with the increase in
concentration. A similar phenomenon could be observed in
the concentration-dependent DMF solutions of 4-POXD-B8
(Fig. S7, ESI†). This phenomenon indicates that the entangle-
ment of ribbons may be one of the factors that cause the
helical structure. The twisted fibers, which are much finer
and denser, can be observed in the 4-POXD-B12 xerogel from
DMSO (Fig. S8, ESI†).
The X-ray diffraction (XRD) patterns of the 4-POXD-B8
xerogels from different solvents exhibited several sharp diffrac-
tion peaks in the small- and high-angle regions, suggesting
their crystalline features (Fig. 4). The slow evaporation of
ethanol gave a precipitate showing a series of strong diffrac-
tions with d-spacings of 16.5 (11), 15.8 (20), and 12.8 Å (21)
in the small-angle region, corresponding to the rectangular
columnar structure with a = 31.7 Å and b = 19.4 Å. The XRD
pattern of the 4-POXD-B8 xerogel from methanol shows two
sets of diffractions; one set is similar to that of the precipitate
from ethanol and the other set corresponds to the d-spacings of
39.4, 19.1, and 13.1 Å in the small-angle region. The d-spacing
of 39.4 Å is nearly twice of the calculated full extended mole-
cular length (ca. 20.5 Å) of 4-POXD-B8, indicating a bilayer
structure. Similar structures were observed in the xerogels from
DMSO and DMF (Fig. S9, ESI†). The 4-POXD-B8 xerogel form
acetonitrile showed the first diffraction peak at a d-spacing of
Fig. 4 X-Ray diffraction (XRD) spectra of the 4-POXD-B8 xerogels from DMSO,
methanol, and acetonitrile.
Moreover, a bilayer structure was also observed in the 4-POXD-B12
xerogels (Fig. S10, ESI†).
Solvent-dependent optical properties of 4-POXD-B8
27.1 Å (20.5 Å o d o 41 Å), indicating that the 4-POXD-B8 The optical properties of 4-POXD-B8 in various solvents are shown
molecules may have a large angle tilt in the bilayers (about 421). in Table 3. The shape (Fig. S11, ESI†) and position (Table 3) of the
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Table
3
Photophysical properties of 4-POXD-B8 in various solvents (1
ꢁ
X-ray diffraction was carried out with a Bruker Avance D8 X-ray
diffractometer. Fourier transform infrared (FTIR) spectra were
recorded with a Perkin-Elmer spectrometer (Spectrum One B).
The sample was pressed into KBr pellets. The FTIR spectra of
the xerogel samples were measured on a silicon wafer. Photo-
luminescence was measured on a Perkin-Elmer LS 55 spectro-
meter and the absorption measurements were recorded using a
UV-2550 spectrometer. The UV-vis absorption spectrum in the
gel state measured by casting a drop of concentrated solutions
of 4-POXD-B8 on quartz. SEM observations were taken with a
JSM-6700F apparatus. OM observation was conducted on a
Leica DMLP optical microscope. The xerogel samples for SEM
10ꢀ5 mol Lꢀ1) at room temperature
Solvent
lem/nm
labs/nm
FF/%
Cyclohexane
Toluene
THF
DMF
DMSO
1-Butanol
1-Propanol
Ethanol
Methanol
351, 369, 384
315
319
318
317
319
321
320
319
318
80.7
81.6
64.9
73.3
38.5
11.2
6.0
394
425
458
465
460
466
472
479
4.1
0.5
absorbance maxima of 4-POXD-B8 are dependent on the solvent, and OM measurements were prepared by dropping a small
indicating that the conjugation-structure of the 4-POXD-B8 mole- amount of gel on a silicon and glass wafer respectively, followed
cule in its ground state changed with solvents.24 In protic solvents, by lyophilization. The molecular length was calculated by MM2.
however, the absorbance maxima of 4-POXD-B8 blue-shifted from The gel–sol phase transition temperatures were determined by
321 nm (n-butanol) to 318 nm (methanol), suggesting the for- the ‘‘falling drop’’ method.25
mation of solvent–solute hydrogen bonds. On the other hand,
Syntheses
4-POXD-B8 exhibited strong fluorescence with a vibronic structure
in the apolar solvent cyclohexane and a weak broad fluorescence
in polar solvents (Fig. S13, ESI†). The emission maxima red-
shifted from 369 nm (in cyclohexane) to 465 nm (in DMSO) when
the polarity of the solvent increased, and its fluorescence quan-
tum yield (FF) decreased from 80.7% (in cyclohexane) to 38.5%
(in DMSO). This suggested the existence of intramolecular charge-
transfer. The fluorescence quantum yields of 4-POXD-B8 in the
aprotic solvents were markedly higher than that in the protic
solvents, which may be due to solvent–solute hydrogen bonding.
The synthesis of 4-POXD-Bn (n = 4, 8, 12,) is outlined in
Scheme 2. 3,4-Bis(alkoxy)benzoic acids (1) were prepared
according to the literature26 and the corresponding chlorides
(2) were obtained by refluxing 1 with SOCl2 for 8 h.27 Com-
pounds 2 were employed to react with equimolar isonicotino-
hydrazide in a 100 mL mixture of 1-methyl-2-pyrrolidinone
(NMP) and THF at room temperature for 12 h. The solution
was poured into 1000 mL distilled water and filtrated to obtain
the white solid. The pure compounds of 4-PHP-Bn recrystallized
from ethanol were refluxed in POCl3 for 30 h for the synthesis
of 4-POXD-Bn (n = 4, 8, 12).28 The reaction mixtures were
Conclusion
This study reports the synthesis and gelation behaviors of a series
of unsymmetrical p-conjugated gelators, 4-POXD-Bn (n = 4, 8, 12).
The 4-POXD-B8, with a moderate length of end-chains, can gel
polar solvents, such as DMSO, acetonitrile, DMF, and alcohols. The
tendencies of the CGC and Tgel indicate that the solvophobic effect
is the driving force for gelation. Changing the length of the oxyalkyl
chains in the gelators can induce a drastic change in the gelation
properties, confirming that the solvophobic effect of the alkyoxyl
chains towards the solvent dominates the gelation. The correlations
between the gelation of 4-POXD-Bn and the solvents were estab-
lished using the solvent polarity parameters (da, e and ET(30)). The
favorable da domain and ET(30) domain for the gelation of 4-POXD-B8
was in the range of 8.1–12.6 (cal cm ) ,
ꢀ3 1/2 and 43.3–55.7 kcal molꢀ1
respectively. Thus, the capacity of a solvent to form a gel with our
compounds can be predicted by the da and ET(30) values. The GN
and Tgel values of the gels increased with the increase of da, e, and
ET(30). The SEM images revealed that the gels prepared from
4-POXD-B8 in DMSO and DMF are composed of helical ribbons,
whereas those formed in other solvents consist of flat ribbons.
Experimental section
Characterization
1H NMR and 13C NMR spectra were recorded with a Mercury-300BB
spectrometer, using tetramethylsilane (TMS) as an internal standard. Scheme 2 Synthetic routes of 4-POXD-Bn (n = 4, 8, 12).
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gradually poured into 1000 mL distilled water and filtrated to 831, 802, 739, 722, 702; Anal. For C29H41N3O3, Found: C, 72.62;
obtain the yellow solid. The yellow solid was dried under H, 8.62; N, 8.76. Calcd: C, 72.79; H, 8.78; N, 8.84.
vacuum and recrystallized from ethanol three times to give
pure 4-POXD-Bn gelators with a yield of more than 60%.
2-(3,4-Bis(dodecyloxy)phenyl)-5-(pyridine-4-yl)-1,3,4-oxadiazole
(4-POXD-B12). H NMR (300 MHz, CDCl3): d ppm 8.85 (dd, J =
1
N0-(3,4-Bis(butoxy)benzoyl)isonicotinohydrazide (4-PHP-B4). 4.6, 1.6 Hz, 2H), 8.07 (dd, J = 4.6, 1.6 Hz, 2H), 7.70 (d, J = 2.1 Hz,
1H NMR (300 MHz, CDCl3): d ppm 10.23 (s, 1H), 9.43 (s, 1H), 1H), 7.66 (dd, J = 6.6, 2.0 Hz, 1H), 6.99 (d, J = 8.4 Hz, 1H),
8.78 (s, 2H), 7.80 (s, 2H), 7.43 (s, 1H), 7.40 (s, 1H), 6.84 (d, J = 4.10 (q, J = 6.5 Hz, 4H), 1.87 (m, 4H), 1.42 (m, 36H), 0.88 (t, J =
8.1 Hz, 1H), 4.01 (m, 4H), 1.82 (m, 4H), 1.50 (m, 4H), 0.97 6.7 Hz, 6H); 13C NMR (75 MHz, CDCl3): d ppm 165.8, 162.2,
(m, 6H); FT-IR (KBr, pellet, cmꢀ1) n: 3250, 3128, 3049, 3028, 153.0, 150.3, 149.6, 131.7, 120.9, 120.4, 115.6, 113.2, 112.1, 69.6,
2958, 2936, 2874, 2850, 1691, 1644, 1601, 1583, 1557, 1523, 69.3, 31.9, 29.7, 29.6, 29.4, 29.3, 29.2, 29.1, 26.1, 26.0, 14.1;
1511, 1473, 1428, 1408, 1394, 1339, 1304, 1275, 1235, 1217, FT-IR (KBr, pellet, cmꢀ1) n: 3086, 2954, 2919, 2865, 2849, 1602,
1191, 1159, 1134, 1111, 1066, 1024, 1007, 968, 908, 873, 845, 1572, 1555, 1537, 1508, 1498, 1466, 1446, 1410, 1391, 1377,
813, 795, 749, 690, 615.
1336, 1277, 1252, 1221, 1139, 1111, 1066, 1030, 993, 977, 923,
N0-(3,4-Bis(octyloxy)benzoyl)isonicotinohydrazide (4-PHP-B8). 856, 824, 809, 739, 723, 700; Anal. For C37H57N3O3, Found:
1H NMR (300 MHz, CDCl3): d ppm 9.67 (d, J = 6.3 Hz, 1H), 9.14 C, 75.08; H, 9.71; N, 7.10. Calcd: C, 75.14; H, 9.77; N, 6.99.
(d, J = 5.1 Hz, 1H), 8.78 (dd, J = 4.5, 1.6 Hz, 2H), 7.70 (dd, J =
4.5, 1.6 Hz, 2H), 7.43 (d, J = 2.0 Hz, 1H), 7.39 (d, J = 2.0 Hz, 1H),
Acknowledgements
6.89 (d, J = 8.1 Hz, 1H), 4.04 (q, J = 6.7 Hz, 4H), 1.84 (m, 4H),
1.40 (m, 20H), 0.89 (m, 6H); FT-IR (KBr, pellet, cmꢀ1) n: 3245,
The authors are grateful to the National Science Foundation
Committee of China (project no. 51073071, 51103057, 21072076),
and Project 985-Automotive Engineering of Jilin University for
their financial support of this work.
3127, 3049, 3027, 2956, 2922, 2873, 2852, 1691, 1642, 1601,
1583, 1557, 1523, 1510, 1470, 1428, 1406, 1392, 1305, 1274,
1232, 1215, 1190, 1159, 1110, 1065, 1018, 999, 962, 908, 870,
844, 813, 748, 721, 690, 614.
N0-(3,4-Bis(dodecyloxy)benzoyl)isonicotinohydrazide (4-PHP-B12).
1H NMR (300 MHz, CDCl3): d ppm 9.68 (d, J = 6.4 Hz, 1H), 9.13
(d, J = 5.1 Hz, 1H), 8.78 (dd, J = 4.7, 1.6 Hz, 2H), 7.70 (dd, J =
4.6, 1.7 Hz, 2H), 7.43 (d, J = 2.1 Hz, 1H), 7.39 (d, J = 2.1 Hz, 1H),
6.88 (d, J = 8.2 Hz, 1H), 4.03 (q, J = 6.7 Hz, 4H), 1.84 (m, 4H),
1.39 (m, 36H), 0.88 (m, 6H); FT-IR (KBr, pellet, cmꢀ1) n: 3243,
3130, 3050, 2954, 2920, 2870, 2849, 1689, 1642, 1602, 1583,
1557, 1520, 1511, 1470, 1429, 1406, 1393, 1379, 1305, 1274,
1233, 1215, 1191, 1160, 1110, 1065, 1018, 1000, 962, 910, 870,
844, 831, 813, 748, 722, 690, 652.
Notes and references
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2-(3,4-Bis(butoxy)phenyl)-5-(pyridine-4-yl)-1,3,4-oxadiazole
1
(4-POXD-B4). H NMR (300 MHz, CDCl3): d ppm 8.86 (s, 2H),
8.04 (d, J = 4.8 Hz, 2H), 7.70 (d, J = 2.1 Hz, 1H), 7.66 (dd, J =
5.2, 2.0 Hz, 1H), 6.99 (d, J = 8.4 Hz, 1H), 4.11 (q, J = 6.5 Hz, 4H),
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(4-POXD-B8). 1H NMR (300 MHz, CDCl3): d ppm 8.85 (d, J =
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6.5 Hz, 4H), 1.88 (m, 4H), 1.43 (m, 20H), 0.89 (t, J = 6.8 Hz, 6H);
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149.6, 131.4, 120.8, 120.3, 115.7, 113.2, 112.1, 69.6, 69.3, 31.8,
29.4, 29.3, 29.2, 29.1, 26.1, 26.0, 22.6, 14.1; FT-IR (KBr, pellet,
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1556, 1539, 1509, 1478, 1410, 1398, 1378, 1334, 1318, 1276,
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