Nitrochalcones as organogelators: Evidence of the involvement of nitro groups and solvent in gel formation

Article abstract of DOI:10.1039/b902444a

New 4-alkoxynitrochalcones have been synthesized and shown to be organogelators; dodecyloxy/benzyl alcohol gels have been studied by freeze-fracture electron microscopy, DSC and FTIR. We show that the nitro group is involved in the formation of the gel an

Full text of DOI:10.1039/b902444a

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www.rsc.org/njc | New Journal of Chemistry
Nitrochalcones as organogelators: evidence of the involvement of nitro
groups and solvent in gel formationw
Franc
Jean-Franc
¸
ois-Xavier Simon,a Thi-Thanh-Tam Nguyen,a Marc Schmutz,a Gero Decher,a
b
a
´
ois Nicoud* and Philippe J. Mesini*
¸
Received (in Montpellier, France) 5th February 2009, Accepted 21st April 2009
First published as an Advance Article on the web 26th May 2009
DOI: 10.1039/b902444a
New 4-alkoxynitrochalcones have been synthesized and shown to be organogelators;
dodecyloxy/benzyl alcohol gels have been studied by freeze-fracture electron microscopy,
DSC and FTIR. We show that the nitro group is involved in the formation of the gel
and that the gelator co-assembles with solvent molecules.
solvents. We explore the structure of the formed gels by
Introduction
electron microscopy. FT-IR measurements have been
performed to examine the role of the nitro group in the
self-association of the gelator.
Low mass organogelators1–5 (LMOGs) are a growing class of
compounds able to form gels with organic solvents at
low concentrations (typically a few % per weight). This
macroscopic property expresses the ability at the microscopic
level to self-assemble into three-dimensional fibrillar networks.
Besides the fundamental aspects, these gels have received
increasing attention due to their potential applications in
photovoltaics,6 pollution control, as oil spill recovery7 or
toxicity remediation devices,8 biomedical fields, as scaffolds
for tissue repair9,10 or drug-delivery systems,11,12 mesoporous
materials, as templates for silica nanotubes13 or polymeric
mesoporous materials.14–16
Results and discussion
New compounds incorporating the chalcone unit were
synthesized (Scheme 1). Cn-Ch-NO2 denotes 40-alkoxy-4-
nitrochalcones with different alkyl chain lengths (Scheme 1).
For the sake of comparison, compounds O2N-Ch-C12, where
the location of the nitro and alkyl groups are inverted, and
di-C18-Ch-NO2, which bears two side chains, were also
synthesized.
The self-association of gelators is achieved by a combination
of non-covalent interactions, including H-bonds, p–p stacking,
metal coordination and van der Waals interactions. Most
known gelators possess H-bonding groups. Gelators that
are able to self-assemble without H-bonds and only by
weaker interactions are rare. Among them, one can find
alkoxyaromatic17,18 compounds, azobenzene derivatives,19
semifluoroalkanes20 and even simple alkanes.21 Ajayaghosh
and Praveen22 have extensively studied oligophenylvinylidenes
as gelators and have shown that these compounds form gels
only if they bear either a H-bonding group, such as hydroxyl,
or a polar group, such as nitrile or nitro. Derivatives lacking
these groups provided only limited aggregation. Herein, we
report the synthesis of new compounds based on the chalcone
unit. Chalcone itself comprises of two benzene rings linked
together by a conjugated enone and does not show any
aggregation. We will demonstrate that the introduction of a
nitro group on one side and an alkoxy group on the opposite
leads to the aggregation of the resulting molecules in various
The synthesis described in Scheme 1 proceeds through the
condensation of alkoxyacetophenone with 4-nitrobenzaldehyde
in ethanol (Cn-Ch-NO2) or the condensation of 4-nitro-
acetophenone with 4-dodecyloxybenzaldehyde (O2N-Ch-C12),
with NaOH as a catalyst, according to a previously described
method.23 The pure compounds were obtained with yields
a Institut Charles Sadron, CNRS, 23 rue du Loess, BP 84047,
67034 Strasbourg Cedex 2, France. E-mail: mesini@ics.u-strasbg.fr;
Fax: +33 (0)388 41 40 99; Tel: +33 (0)388 41 40 70
b Laboratoire de Biophotonique et Pharmacologie, CNRS UMR 7213,
´
Faculte de Pharmacie, 74 route du Rhin, BP 60024, 67401 Illkirch
Cedex, France. E-mail: Jean-Francois.Nicoud@pharma.u-strasbg.fr;
Tel: +33 (0)390 24 42 76
w Electronic supplementary information (ESI) available: FTIR spectra
of C12-Ch-NO2 gels in tert-butyl acetate and CCl4, and C12-Ch-NO2
solid. See DOI: 10.1039/b902444a
Scheme 1 Synthesis and structure of the studied compounds.
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Table 1 Gelation properties of the nitrochalcones with various solventsa
Solvent
C4-Ch-NO2
C8-Ch-NO2
C12-Ch-NO2
Di-C18-Ch-NO2
O2N-Ch-C12
C6H6
Et2O
CCl4
P
P
P
S
P
S
P
S
S
P
P
P
P
P
S
/
G (4)
G (2)
S
S
P
G (2)
G (2)
S
P
P
S
/
P
P
S
/
CHCl3
CH2Cl2
MeOH
BuOH
BnOH
Toluene
EtOAc
nBuOAc
tBuOAc
S
P
G (4)b
I
G (4)
G (2)
P
S
P
P
P
S
S
S
S
G (4)
P
Visc. S
S
S
S
/
P
P
S
G (2)
G (2)
G (2)
a
b
P: precipitates, I: insoluble in boiling solvent, G: gel (minimal gel concentration in wt%), Visc. S: viscous solution. Opaque gel.
between 66 and 82%. They all are solids at room temperature
and are soluble in CH2Cl2, CHCl3, toluene and EtOAc
(Table 1). In alcohols, their solubility properties depend on
the alkyl chain length. In MeOH C4-Ch-NO2 forms a gel,
whereas longer chain analogues precipitate. In BuOH, the
trend is the opposite: compounds C4-Ch-NO2 and C8-Ch-NO2
precipitate, whereas C12-Ch-NO2 and di-C18-Ch-NO2 form
gels. In BnOH, the C4 and C8 analogues are soluble
but longer chain analogues form gels. The reverse analogue,
O2N-Ch-C12, differs from the other analogues since it
precipitates in BuOH and is soluble in BnOH. This result
suggests that the orientation of the chalcone with respect to
the alkyl chain is decisive in the packing of the molecules to
form gels.
axis of the fibers. In the gels, the ordered fibers are surrounded
by disordered and shorter arrays (Fig. 1A and 1B, arrowhead).
In close vicinity to the main bundles, these shorter structures
are arranged parallel to the fibers, but the alignment decreases
when their distance from the bundles increases.
The gel-to-sol transition was studied by DSC (Fig. 2). The
thermograms clearly showed a first order and endothermic
transition upon melting. The transition was very broad, with
an onset as low as 6 1C and a maximum at 45 1C. The enthalpy
value was found to be 48 kJ molꢂ1. When the mixture
was cooled back down, a sharp exothermic transition was
observed. Both endothermic and exothermic peaks yielded the
same absolute value of heat within 2% of experimental
uncertainty.
The structures of the gels have been explored by electron
microscopy. The studies were performed by freeze-fracture.
This technique consists of rapid freezing of the gel, which
preserves the self-assemblies in an amorphous solvent
surrounding. This method, which is well-known for aqueous
media, has been implemented successfully for organic
solutions and gels, and has proved to be efficient for the direct
observation of self-assembled structures.16,24,25 The success of
the technique depends on the ability of the solvent to remain
amorphous when the sample is frozen. In our hands, only
BnOH gave satisfactory results with the selected gelators; in
the other systems, either the solvent crystallized during the
freeze, which prevented the observation of structures, or the
fracture planes displayed no objects.
The transition was also studied by FTIR at different
temperatures. Most of the bands of the spectra showed little
or no evolution. The strongest evolution was found for the
bands between 1510 and 1540 cmꢂ1. These signals comprised
of one peak at 1521 cmꢂ1, and a set of two overlapping peaks
at 1538 and 1534 cmꢂ1
.
At lower temperatures, the bands at 1538 and 1534 cmꢂ1
were the dominant ones. When the temperature was increased,
their intensities decreased, while the peak at 1521 cmꢂ1
increased and became the major one. All of these peaks could
be assigned to antisymmetric NO2 stretching (nas(NO2)).26
This strong change in the FTIR spectrum during the transition
shows that the NO2 group is involved in the self-assembly and
packing of C12-Ch-NO2 during gel formation. In chloroform,
C12-Ch-NO2 did not form a gel, and its IR spectrum was
similar to that in BnOH at a higher temperature: only a major
peak at 1523 cmꢂ1 (Fig. 3A) being observed.
For the gel from C12-Ch-NO2 in BnOH, the fractures
showed oblong structures (Fig. 1A, arrows). Higher magnifi-
cations (Fig. 1B) showed that these objects are made from an
assembly of fibrillar structures that are ordered into bundles.
Solutions of the same compounds (conc. 1.9 wt%) have been
studied after deposition on carbon-coated grids and rotary
shadowing (Fig. 1C). They showed the same fibrils as the
ones observed in the gels, but less associated (arrows). The
characteristic sizes of the hundreds of fibrils were measured
and averaged, both in gels and solutions, and were found to be
identical in both states. The fibrils have a width of 25 ꢁ 3 nm
and exhibit a periodic structure with alternate shadowed and
clear strips (Fig. 1D). The widths of the shadowed strips are
10 ꢁ 2 nm and the periodic distance between two consecutive
strips is 17 ꢁ 2 nm. They form an angle of 501 with the main
The evolution of the intensity of the band at 1521 cmꢂ1 with
temperature was very slow, and half of the maximum intensity
was reached at 50 1C (Fig. 3B). For gels in tert-butyl acetate
and CCl4, the same complex bands could be observed
(see ESIw) in the ns(NO2) region (tBuOAc: 1538, 1534 and
1526 cmꢂ1; CCl4: 1536 and 1526 cmꢂ1). The intensity of the
band at 1526 cmꢂ1 increased with increasing temperature, like
the band at 1521 cmꢂ1 in BnOH. For the neat solid, only one
peak at 1536 cmꢂ1 was observed. These results show that the
splitting of the nas(NO2) band is characteristic of the gel state.
For the gels in BnOH, the spectral region between 3700 and
3500 cmꢂ1 exhibited two peaks after subtracting the signal of
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Fig. 2 The thermogram of the C12-Ch-NO2/BnOH gel (2 wt%).
The measured enthalpy for the gel-to-sol transition was DH =
48 kJ molꢂ1
.
Fig. 3 FTIR spectra of the C12-Ch-NO2/BnOH gel (2 wt%) in the
nas(NO2) region for temperatures varying from 32 to 65 1C (plain lines)
(dotted line: C12-Ch-NO2/CHCl3 solution). (B) Amplitude of the band
at 1521 cmꢂ1 (J) and sum of the amplitudes of the bands at 1334 and
1338 cmꢂ1 (n).
Fig.
1 A: TEM of C12-Ch-NO2/BnOH gels (2 wt%) after
freeze-fracture. Arrows: periodic structures. Arrowhead: disordered
structures. B: The same objects with a higher magnification. C: TEM
of a solution of C12-Ch-NO2 in BnOH (1.9 wt%) after adsorption onto
carbon grids. Short arrow: single fibril. Long arrow: double fibers.
D: Scheme of the characteristic distances measured in the fibers (ꢁ 2 nm).
structure of the gel. It is possible that the hydroxyl groups
interact directly with the gelator, either by an H-bond with the
nitro group, as observed in solid state,27–29 or by the formation
of a p-adduct between the OH and the gelator.30,31 It is also
possible that these BnOH molecules are associated with the
gelator through van der Waals interactions, and that this
association weakens their H-bonds with the rest of the solvent.
The presence of isosbestic points proves that the system
evolves through a two-state equilibrium, which corroborates
the calorimetric data and indicates that the transition is a
first-order one. The intensity of the peak at 1521 cmꢂ1 evolves
slowly over a large temperature range, in the same way as the
the pure solvent. This spectral window does not comprise any
bands for the gelator molecules and corresponded only to OH
stretching bands of the benzyl alcohol. In the gel state, these
bands were clearly shifted towards higher frequencies than in
the pure solvent (Fig. 4). Hence, for a small proportion of the
benzyl alcohol molecules in the gel, the hydroxyl groups lead
to H-bonds different from those in the pure solvent. These
bands also change when the gel melts, which shows
the involvement of this fraction of BnOH molecules in the
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the spectra. The amplitudes and widths of the peaks were fitted
with Gaussian curves using the built-in Igor algorithm. The
spectra of the pure solids were measured by attenuated total
reflection (ATR) over a diamond crystal.
DSC
Thermograms were recorded using a microcalorimeter DSC III
from Setaram. A first heating cycle was performed between
6 and 85 1C at a rate of 1 1C minꢂ1. The heat was measured in
the second and third scan at a rate of 0.1 1C minꢂ1. No
differences were observed between the second and third scan.
Freeze-fracture electron microscopy
Fig. 4 Solid lines: FTIR spectra of the C12-Ch-NO2/BnOH gel
(2 wt%) in the OH stretching region for temperatures varying from
32 to 65 1C. Dotted line: IR spectrum of pure BnOH.
Transmission electron microscopy (TEM) was performed
using a Philips CM12 microscope operating at 120 kV. The
gel samples were placed between two copper holders and
rapidly frozen in liquid nitrogen. The sample was kept frozen
and transferred into a freeze-fracture apparatus (developed by
Dr J.-C. Homo), where the sample was cleaved. Pt was
evaporated onto the sample under a 451 angle, and then
carbon under a 901 angle with respect to the surface. The
sample was warmed to room temperature, and the replica was
rinsed with chloroform and deposited on a 400 mesh grid.
transition proceeds. The other bands in the spectrum vary only
slightly, which shows that the other parts of the molecule play
only a minor role compared to the nitro group. For instance,
the symmetric vibration of the CH2 groups show a very weak
increase from 2848 to 2849.5 cmꢂ1 in parallel to the evolution
of the NO2 bands. The range of values indicates that the alkyl
chains remain relatively well ordered and in an extended
conformation in the sol phase.
Synthesis
The compounds were synthesized by the method of Wattanasin
and Murphy.23 A typical procedure is described for the
example below.
Conclusions
Several new 4-alkoxynitrochalcones have been synthesized.
These molecules were able to form gels in tert-butyl acetate
at a few wt%. The dodecyl derivative was also able to gel in
BuOH, BnOH, diethyl ether and CCl4. The introduction of the
polar nitro group into soluble chalcones transforms them into
self-associating compounds. Freeze-fracture TEM allowed the
visualization of the fibrillar structure formed by self-association.
An FTIR study in BnOH confirmed the strong implication of
the nitro group in the formation of the gel. The same studies
also showed the involvement of solvent molecules in the
structure of the gel. This phenomenon is very rarely observed
in organogels, and can be considered as an extension of the
case of two-component gelators32 such as AOT/phenol.32–35
In those cases, a mixture of two molecules is required to form
the gel. Therefore, despite their modest gel concentration, this
new family of gelators has an original structure. Further
structural studies are in progress to gain new insights into
these self-assemblies and to increase their gelation abilities.
40-Dodecyloxy-4-nitrochalcone (C12-Ch-NO2). 4-Nitro-
benzaldehyde (100.2 mg, 0.66 mmol) and 4-dodecyloxyaceto-
phenone (201.6 mg, 0.66 mmol, 1 equiv.) were added to a
solution of NaOH in EtOH (0.1 M, 10 mL). The reaction
mixture was stirred at 25 1C for 24 h. Water (150 mL) was
added and the resulting precipitate separated by centrifugation,
re-suspended in fresh water and centrifuged twice more. The
dried precipitate was recrystallized from cyclohexane to yield
the pure compound as a yellow powder (191 mg, 66% yield).
M.p. 103.5 1C. Found: C, 73.88; H, 8.30; N, 3.22. Calc. for
C27H35NO4: C, 74.11; H, 8.06; N, 3.20%. dH(400 MHz,
CDCl3): 8.28 (2H, d, ArNO2 C3–H), 8.04 (2H, d, J =
8.9 Hz, ArNO2 C2–H), 7.83–7.77 (3H, m, CHQCH–CO and
ArOR-C2–H), 7.66 (1H, d, J = 15.7 Hz, CHQCH–CO),
7.00–6.98 (2H, m, ArOR-C4–H), 4.05 (2H, t, J = 6.5 Hz,
ArOCH2), 1.82 (2H, p, J = 7.0 Hz, ArOCH2CH2), 1.48
(2H, p,
J
=
7.0 Hz, ArOCH2CH2CH2), 1.38–1.24
Experimental
(16H, m, CH2) and 0.88 (3H, t, J = 7.0 Hz, CH3).
dC(100 MHz, CDCl3): 187.7 (CO), 163.5 (C4–O), 148.4
(C–NO2), 141.3 (CQC–CO), 140.5 (C1-ArNO2), 131.0 and
130.2 (C1-ArOR), 128.8 (C2-ArNO2), 125.7 (CO–CHQCH),
124.2 (C2-ArNO2), 114.5 (C3-ArOR), 68.4 (ArOCH2), 31.9
(CH2CH2CH3), 29.63, 29.60, 29.56, 29.53, 29.32, 29.1, 26.0
(ArOCH2CH2CH2), 22.7 (CH2CH3) and 14.1 (CH3).
FTIR
Spectra were recorded on a Bruker Vertex 70 spectro-
photometer equipped with a thermostatic cell holder and a
temperature-controlling unit (Specac West 6100+). The gels
were placed in an NaCl cell with an optical path of 0.1 mm.
The samples were visually checked after a heating period to
ensure that no loss of solvent occurred. The curves were
processed and fitted using Igor (Wavemetrics, Inc.). The
complex signals were deconvoluted as follows: the maxima
of the peaks were found with the second or forth derivatives of
l
max(CHCl3/nm): 314 (e/dm3 molꢂ1 cmꢂ1: 12 900). n(gel in
BnOH/cmꢂ1): 2957, 2939, 2939, 2918, 2947, 1656 (n(CO)),
1610, 1600, 1538 (nas(NO2)), 1534 (nas(NO2)), 1521 (ns(NO2)),
1344, 1320 (ns(NO2)), 1310 (ns(NO2)), 1262, 1225, 1179, 855,
831 and 816.
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40-Butyloxy-4-nitrochalcone (C4-Ch-NO2). M.p. 125 1C.
Found: C, 69.95; H, 6.05; N, 4.12. Calc. for C19H19NO4: C,
70.14; H, 5.89; N, 4.31%. dH(400 MHz, CDCl3): 8.29 (2H, d,
J = 8.2 Hz, ArNO2-C3–H), 8.06 (2H, d, J = 8.4 Hz,
ArNO2-C2–H), 7.84–7.79 (3H, m, CHQCH–CO and
ArOR-C2–H), 7.67 (1H, d, J = 15.5 Hz, CHQCH–CO),
7.02 (2H, d, 8.5, ArOR-C4–H), 4.08 (2H, t, J = 6.6 Hz,
ArOCH2), 1.83 (2H, p, J = 6.6 Hz, ArOCH2CH2), 1.55
(2H, m, ArOCH2CH2CH2) and 0.88 (3H, t, J = 7.2 Hz,
CH3). dC (100 MHz, CDCl3): 187.7 (CO), 163.6 (C4–O),
148.4 (C–NO2), 141.3 (CHQCH–CO), 140.5 (C1-ArNO2),
131.2 (C2-ArOR), 130.2 (C1-ArOR), 128.8 (C2-ArOR),
125.7 (CHQCH–CO), 124.2 (C3-ArNO2), 114.5 (C3-ArOR),
68.1 (ArOCH2), 31.1 (CH2CH2CH3), 19.2 (CH2CH3) and 14.1
(CH3). n(ATR, solid/cmꢂ1): 3079.4, 1657 (n(CO)), 1607, 1598,
1586, 1510 (s, nas(NO2)), 1473, 1339 (s, ns(NO2)), 1228, 1123,
1169 (s, n(CN)), 1000, 833, 825 and 760.
2849 (ns(CH2)), 1655 (n(CO)), 1578 (n(CQCenone)), 1525
(s, nas(NO2)), 1514, 1467, 1434 (n(CHvinyl)), 1343 (s, ns(NO2)),
1278, 1267 (s, nas(QC–O–C)), 1217, 1177, 1153 (s, n(CN)),
1069 (s, ns(QC–O)), 995 (n(C–N) stretch), 840, 813, 754, 721,
675 and 630.
4-Dodecyloxy-40-nitrochalcone (O2N-Ch-C12). M.p. 108 1C.
Found: C, 73.92; H, 8.24; N, 3.25. Calc. for C27H35NO4: C,
74.11; H, 8.06; N, 3.20%. dH(400 MHz, CDCl3): 8.34 (2H, d,
J = 8.4 Hz, ArNO2-C3–H and -C5–H), 8.12 (2H, d, J =
8.2 Hz, ArNO2-C2–H and -C6–H), 7.81 (1H, d, J = 15.2 Hz,
CHQCH–CO), 7.60 (2H, d, J = 8.4 Hz, ArOR-C2–H
and -C6–H), 7.35 (1H, d, J = 15.4 Hz, CHQCH–CO), 6.94
(2H, d, J = 8.0 Hz, ArOR-C3–H and C5–H), 4.02 (2H, t, J =
6.3 Hz, ArOCH2), 1.81 (2H, p, J = 6.6 Hz, ArOCH2CH2),
1.54–1.21 (18H, CH2) and 0.89 (3H, t, J = 7.2 Hz, CH3). dC
(100 MHz, CDCl3): 189.4 (CO), 162.3 (C4–O), 162.25
(C–NO2), 147.2 (C1-ArNO2), 143.9 (CHQCH–CO), 131.0
(C2-ArNO2), 129.7 (C2- and C6-ArOR), 127.1 (C1-ArOR),
124.2 (C3- and C5-ArNO2), 119.1 (CHQCH–CO), 115.4
(C5- and C3-ArOR), 68.7 (ArOCH2), 32.3 (CH2CH2CH3),
26.3 (ArOCH2CH2CH2), 23.0 (CH2CH3) and 14.5 (CH3).
n(ATR/cmꢂ1): 2946 (nas(CH3)), 2916 (nas(CH2)), 2871
(ns(CH3)), 2849 (ns(CH2)), 1657 (n(CO)), 1587 (n(CQCenone)),
1567, 1512 (s, nas(NO2)), 1476, 1463, 1425, 1340 (s, ns(NO2)),
1295, 1256 (s, nas(QC–O–C)), 1217, 1173 (s, n(CN)), 1061
(s, ns(QC–O)), 989 (n(C–N) stretch), 832, 826, 767, 727, 703
and 638.
40-Octyloxy-4-nitrochalcone (C8-Ch-NO2). M.p. 106 1C.
Found: C, 72.22; H, 7.31; N, 3.82. Calc. for C27H35NO4: C,
72.42; H, 7.13; N, 3.67%. dH(400 MHz, CDCl3): 8.27 (2H, d,
J = 8.53 Hz, ArNO2-C3–H and -C5–H), 8.03 (2H, d, J =
8.7 Hz, ArNO2-C2–H and -C6–H), 7.82–7.79 (3H, m,
CHQCH–CO and ArOR-C2–H and -C6–H), 7.65 (1H, d,
J = 15.7 Hz, CHQCH–CO), 6.99 (2H, d, J = 8.7 Hz,
ArOR-C30–H and -C50–H), 4.04 (2H, t, J = 6.3 Hz,
ArOCH2), 1.82 (2H, p, J = 6.6 Hz, ArOCH2CH2), 1.59
(2H, m, ArOCH2CH2CH2), 1.47–1.20 (8H, CH2) and 0.89
(3H, t, J = 7.2 Hz, CH3). dC (100 MHz, CDCl3): 188.1 (CO),
163.9 (C4–O), 148.8 (C–NO2), 141.7 (CHQCH–CO), 140.9
(C1-ArNO2), 131.3 (C20-ArOR), 130.6 (C10-ArOR), 129.2
(C2- and C6-ArNO2), 126.0 (CHQCH–CO), 124.5 (C3- and
C5-ArNO2), 114.8 (C30- and C50-ArOR), 68.7 (ArOCH2), 32.1
(CH2CH2CH3), 29.7 (ArOCH2CH2), 29.5 (ArO(CH2)3CH2),
29.4 (ArO(CH2)4CH2), 26.3 (ArO(CH2)2CH2), 23.0 (CH2CH3)
and 14.4 (CH3). n(ATR, solid/cmꢂ1): 2955 (nas(CH3)), 2919
(nas(CH2)), 2874 (ns(CH3)), 2850 (ns(CH2)), 1656 (n(CO)), 1610
(n(CCAr)), 1593 (n(CQCenone)), 1534 (s, nas(NO2)), 1511, 1467,
1342 (s, ns(NO2)), 1259 (s, nas(QC–O–C)), 1221, 1178
(s, n(CN)), 1070 (s, ns(QC–O)), 1033, 988 (n(C–N)), 980,
780, 760, 733, 655 and 631.
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C27H35NO4: C, 77.52; H, 10.59; N, 1.77%. dH(400 MHz,
CDCl3): 8.27 (2H, d, J = 8.72 Hz, ArNO2-C3–H), 7.82–7.77
(3H, m, ArNO2-C2–H and CHQCH–CO), 7.67–7.61 (3H, m,
ArOR-C6–H and CHQCH–CO), 6.92 (1H, d, J = 8.52 Hz,
ArOR-C5–H), 4.09 (4H, t, J = 6.48 Hz, ArOCH2), 1.86
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(4H, p,
J = 6.48 Hz, ArOCH2CH2), 1.57 (4H, m,
ArOCH2CH2CH2), 1.48 (4H, m, CH2CH3), 1.25 (52H, CH2)
and 0.88 (6H, t, J = 7.0 Hz, CH3). dC (100 MHz, CDCl3):
188.1 (CO), 154.4 (C4-OR), 149.7 (C–NO2), 148.8
(CHQCH–CO), 140.8 (C1-ArNO2), 130.8 (C1-ArOR), 129.2
(C2-ArNO2), 126.0 (CHQCH–CO), 124.5 (C3-ArNO2), 123.7
(C6-ArOR), 113.3 (C2-ArOR), 111.9 (C5-ArOR), 69.7
(ArOCH2–R0), 69.5 (ArOCH2–R), 32.3 (CH2CH2CH3), 27.3
(ArOCH2CH2CH2), 23.0 (CH2CH3) and 14.5 (CH3). n(ATR,
solid/cmꢂ1): 2956 (nas(CH3)), 2916 (nas(CH2)), 2873 (ns(CH3)),
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2032 | New J. Chem., 2009, 33, 2028–2033

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