Diaminomalenonitrile-decorated cholesterol-based supramolecular gelator: aggregation, multiple analyte (hydrazine, Hg2+ and Cu2+) detection and dye adsorption

Article abstract of DOI:10.1039/c8nj02426j

A low molecular weight gelator (LMWG) containing a diaminomalenonitrile functional group 1 has been designed and synthesized. The compound forms supramolecular gels from DMF-H₂O and 1,2-dichlorobenzene. The morphology of the gels reveals fibrous networks. The rheological study demonstrates that the DMF-H₂O gel is stable and robust than the gel obtained from 1,2-dichlorobenzene, which is due to the existence of strong intermolecular forces among the gelators in DMF-H₂O. The analysis of tan?δ values from the frequency sweep (tan?δ = G′′_av/G′_av) indicates that the DMF-H₂O gel exhibits higher mechanical strength (lower tan?δ) than the 1,2-dichlorobenzene gel. The DMF-H₂O gel has been explored for sensing and dye adsorption. The gel is established to be selective for visual recognition of hydrazine, Hg²⁺ and Cu²⁺ ions. Moreover, the gel exhibits excellent efficacy towards rapid and selective adsorption of cationic dyes from water (<1 min).

Full text of DOI:10.1039/c8nj02426j

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ISSN 1144-0546
PAPER
Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
diarylethene-based metal–organic frameworks
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JOURNAL NAME
ARTICLE
Diaminomalenonitrile
decorated
cholesterol-based
supramolecular gelator: Aggregation, multiple analytes
2
+
2+
Received 00th January 20xx,
Accepted 00th January 20xx
(
hydrazine, Hg and Cu ) detection and dye adsorption
DOI: 10.1039/x0xx00000x
www.rsc.org/
*
Atanu Panja and Kumaresh Ghosh
Abstract: Diaminomalenonitrile functional group containing low molecular weight gelator (LMWG) 1 has been designed
and synthesized. The compound forms supramolecular gels from DMF-H
the gels reveals the fibrous networks. The rheological study demonstrates that DMF-H
of the gel obtained from 1,2-dichlorobenzene. This is attributed to the existence of strong intermolecular forces among
the gelators in DMF-H O. Analysis of tan δ values from frequency sweep (tan δ = G′′av/ G′av, ) indicates that the DMF-H
gel exhibits higher mechanical strength (lower tan δ) than the 1,2-dichlorobenzene gel. The DMF-H gel has been
explored in sensing and dye adsorption. The gel is established to be selective for visual recognition of hydrazine, Hg and
2
O and 1,2-dichlorobenzene. The morphology of
2
O gel is stable and robust than that
2
2
O
2
O
2
+
2
+
Cu ions. Moreover, the gel exhibits excellent efficacy towards rapid and selective adsorption of cationic dyes from water
in almost no time (˂ 1 min).
different conditions. Utility of such kind of molecular structure
is appealing in supramolecular chemistry. Although some
fluorescence signalling probes for multiple ion detection are
Introduction
During the last few decades, the design and synthesis of low
molecular weight supramolecular gelators have attracted
attention in the area of supramolecular chemistry owing to
their broad applications in material science, catalysis, sensing,
5
a,b
5c-f
known, LMWGs, capable of showing the same are rare.
In order to design the molecular frameworks of these LMWGs,
choice of binding site and maintenance of hydrophobic and
hydrophilic parts in the structure are considered to be
1
medicine, water purification and pollutant removal etc.
important. In the present structure
components are highlighted
1
, the different structural
Supramolecular gel formation occurs due to the involvement
of several weak non-covalent forces that encourage the linking
of small gelator molecules to establish a three dimensional
in Fig. 1. While
6
diaminomalenonitrile has been used as the site for interaction
with the analytes (cations and hydrazine), the cholesterol
motif is employed to provide the large hydrophobic surface for
assisting self-association of the molecules through
2
network for solvent trapping. Exposure of these gels to
physical stimuli or chemical analytes causes gel-to-sol
transition by disturbing the weak forces. Thus gelators of this
class are called the stimuli responsive low molecular weight
3
c
hydrophobic interaction. It is further mentionable that use of
large hydrophobic surface in the design has significant impact
3
gelators (LMWGs). Stimuli responsive gelators are always
4
f
in dye adsorption in the aggregated state.
unique as they provide rapid naked eye detection applicability
1
with improve selectivity and operational simplicity.
-4
Our ongoing interest in ion sensing by designed structures in
4
solution and gel states has prompted us to explore new
structural scaffold
1 that acts as multi analyte sensor for a
2
+
number of species such as Hg , Cu and hydrazine under
2+
Department of Chemistry, University of Kalyani, Kalyani-741235, India. Email:
ghosh_k2003@yahoo.co.in, Fax: +913325828282; Tel: +913325828750.
†
Electronic Supplementary Information (ESI) available: Gelation tests, gel pics,
Figure 1. Design, concept and structure of gelator 1.
1 13
binding curves, detection limit, comparative tables, H, C NMR and HRMS are
available. See http://dx.doi.org/10.1039/b000000x/
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As anticipated the gelator
1
responds in gelation from DMF- with its amorphous state and thereby supported the hydrogen
O gel of exhibited bond-mediated aggregation of the gelators (Fig. 2S).
H
2
O and 1,2-dichlorobenzene. The DMF-H
2
1
sharp and selective response towards hydrazine, causing rapid The morphologies of the gels were realized from the SEM
gel-to-sol conversion. Similar phase transition was observed images (Fig. 2), which revealed the presence of fibrillar
2
+
2+
selectively in the presence of Cu and Hg ions. Moreover, networks. The fibers are densely packed in DMF-H
2
O gel in
DMF-H O gel of
2
1
was extremely convincing in rapid (˂ 1 min) comparison to the gel obtained from 1,2-dichlorobenzene. This
and successful removal of toxic dyes especially the cationic may be the result of a greater degree of fibre-fibre interaction.
dyes from a mixture of cationic and anionic dyes in waste This is in concurrent with their different thermal behaviors.
water. To the best of our knowledge, the example in this
manuscript is the first report of a LMWG that acts as hydrazine
selective chemodosimeter, single molecular multi analyte
2
+
2+
sensor for different cations such as Hg and Cu and a useful
material with practical application involving fastest dye
adsorption from water in almost no time.
Results and discussion
Synthesis
Figure 2. SEM images of the xerogels of
(scale bar 2 μm) and (b) 1,2-dichlorobenzene (scale bar 1 μm).
2
1 in (a) DMF-H O (1:1, v/v)
Compound
Initially, cholesterol was converted to the chloro ester
on reflux with 4-hydroxybenzaldehyde in the presence of
1
was synthesized according to the Scheme 1.
2
which
4
i
Mechanical behavior of the gels
K
2
CO
Reaction of the aldehyde
the Schiff base with appreciable yield. All the compounds
3
gave the corresponding cholesteryl aldehyde
3.
To analyse the mechanical property of the gels, their
oscillatory rheological behaviours were studied. Both
amplitude and frequency sweep rheology, as shown in Fig. 3a
and 3b, respectively, provide information on the deformation
3
with diaminomalenonitrile afforded
1
were fully characterized by usual spectroscopic methods.
and flow characteristics of the gels of
1 prepared from DMF-
H
2
O and 1,2-dichlorobenzene at the concentration slightly
CHO
higher than their respective mgc values (i.e., 1.2 wt% of mgc of
the gels). The amplitude sweep of the dynamic viscous/loss
modulus (G′′) and elastic/storage modulus (G′) of different gels
at a fixed angular frequency of 1 Hz is shown in Fig. 3a. Both
the gels were mechanically strong (G′ >> G′′) over a wide range
of applied strain. The crossover points as detected at the yield
stresses of 8.04% and 40.16% strain for the 1,2-
O
(
i)
(ii)
(iii)
R
OH
R =
Cl
1
R
H
9
6%
O
78%
76%
O
O
2
3
R
O
H
H
dichlorobenzene and DMF-H
2
O gels of 1, respectively indicated
the lower elasticity of 1,2-dichlorobenzene gel.
Scheme 1. (i) Chloroacetyl chloride, pyridine, dry CHCl
hydroxybenzaldehyde, K CO , CH CN, 5h; (iii) diaminomalenonitrile,
dry benzene, reflux, 3 days.
3
, rt, 10h; (ii) 4-
2
3
3
Gelation test, morphological study and thermal stability of
the gels of 1
The gelation propensity of
combinations, following the usual inversion of vial method was
conducted carefully (Table 1S). Compound formed stable
thermoreversible gels from 1,2-dichlorobenzene and DMF-H
1:1, v/v) solvents (Fig. 1S). The DMF-H O (1:1, v/v) gel exhibits
1 in different solvents and solvent
1
2
O
(
2
Figure
3
.
Rheology experiment of the DMF-H
2
O
and 1,2-
lower critical gelator concentration and higher gel melting
0
temperature (10 mg/ml and 58 C) compared to the gel
0
obtained from 1,2-dichlorobenzene (42 mg/ml and 44 C). This
dichlorobenzene gels of
1
.
In frequency sweep experiment of both the gels, at a constant
strain of 0.5%, both G′ and G′′ were frequency invariant and
the values of G′ were always higher than that of G′′ at any
frequency over the entire range studied. This corroborated the
elastic semisolid nature of both the gels. Despite of the
is presumably due to the role of water that participates in
establishing strong intermolecular hydrogen bonding among
the gelator molecules of
1 in semi-aqueous medium.
In FTIR, there was broadening and large shifting of the signals
-1
-
1
-1
2
at 3430 cm (-NH ), 2115 cm (-CN), 1655 cm (-C=N) and
significant difference in concentration of the two gels (the
th
O was less than 1/4 of the
-1
1
391 cm (-C-N) for the semi-aqueous gel while compared
gelator concentration in DMF-H
2
2
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gelator concentration in 1,2-dichlorobenzene), the higher hydrazine; but it occurred slowly and took couple of hours
values of G′ of the DMF-H O gel compared to that of the 1,2- (almost 1.5-2h) to complete the phase change. Mere
dichlorobenzene gel (Table 1) suggested its stable and robust interaction of other amines with the compound was
2
1
1
i
nature. This is presumably due to the role of water in DMF presumed to be due to their weak nucleophilicities.
that encourages to build up strong intermolecular forces. However, to be acquainted with the solution phase
Moreover, analysis of tan δ values from frequency sweep (tan interaction, UV-vis titration experiments were conducted in
δ = G′′av/ G′av; Table 1) indicated that the DMF-H
higher mechanical strength (lower tan δ) than the 1,2- from Figs 4a and 4b, compound
dichlorobenzene gel. Trend of these data are in good only with hydrazine. Successive addition of equiv. amount of
2
O gel exhibits DMF-H
2
O (1:1, v/v) with the amines examined. As can be seen
1
shows significant interaction
agreement with their thermal stabilities.
hydrazine decreased the absorbance of the bands positioned
at 323 nm and 280 nm, corresponding to n-π* and π-π*
Table 1. Summary of the rheological properties of the gels of
1
transitions, respectively (Fig. 4a). The selectivity of
hydrazine was also investigated both in gel (in presence of
ethylenediamine and NH OH) and solution phases (in presence
1 toward
in different solvents.
2
Solvent
Yield
stress (%)
40.16
G′av (Pa)
G′′av (Pa)
tan δ
(G′′av/ G′av
all amines tested) (Fig. 5). The observation as cited in Fig. 5
highlighted a clear cut selectivity of the probe for hydrazine.
)
DMFꢀH
,2ꢀ
dichlorobenzene
2
O
14807.86
345.50
2547.50
124.08
0.17
1
8.04
0.36
Stimuli responsive behaviors of the DMF-H
2
O gel of 1:
O gel of 1 was
Hydrazine sensing
The stimuli responsive nature of the DMF-H
2
investigated in the presence of a series of aliphatic and
aromatic amines. This study was undertaken due to the
presence of the activated olefinic moiety in the probe (Fig. 1)
which may be attacked by different amines of varying
nucleophilicities. Of the different amines, hydrazine (taken as
hydrazine hydrate) brought a rapid gel-to-sol transition while Figure 5. Selectivity experiment of the probe
phase and solution state.
1
toward hydrazine in gel
added in equivalent amount to the gel. The gel was completely
1
The mechanism of interaction was understood from H NMR,
1
HRMS and FTIR analysis. In H NMR, addition of hydrazine to
the solution of
spectrum. The amine proton (H
invisible with the appearance of a new peak at 6.59 ppm which
corresponds to the H proton of the adduct (Fig. 6, top).
Moreover, an upfield chemical shift of the imine proton (H
from 8.27 ppm to 7.76 ppm was observed. The protons of
types H and H of phenyl ring also showed upfield chemical
1
in d
6
-DMSO brought a marked change in the
b
) of at 7.84 ppm became
1
e
a
)
c
d
shifts possibly due to increase in electron density in the ring for
nucleophilic attack of hydrazine at the malenonitrile segment.
These observations altogether suggested that the mechanism
of interaction did not follow the usual nucleophilic addition
reaction; rather it involved the addition-eliminitation pathway,
as shown in Fig. 6.
In mass spectrum of the hydrazine adduct, the important peak
+
at 655.33 for the formula (M+H+1) enabled us to be familiar
with the suggested mechanism (Fig. 6).
Figure 4. Photograph showing the changes in gel states of
1 (c = 10
mg/mL) upon addition of equiv. amount of different amines (c = 0.2M) Importantly, during gel-to-sol transition in presence of
after 30 min [from left to right: (a) hydrazine, (b) ethylenediamine, (c)
hydrazine the FTIR spectral analysis were done. As we move
2 3
NH OH, (d) ethanolamine, (e) Et N, (f) n-propylamine, (g) n-butylamine
from gel to sol, the characteristic stretching frequencies of
some functional groups are changed. In presence of hydrazine
2
O (1:1, there was lowering of stretching frequencies of the C=C bond
,
(h) ethylamine and (i) aniline] (top) and change in absorbance of
1
(c
-
5
=
hydrazine and (b) different amines (c = 1.0 x 10 M) in DMF-H
2.50 x 10 M) upon successive addition of 1 equiv. amount of (a)
-
3
-
1
-1
v/v) (bottom).
(
from 1618 cm to 1609 cm ) and increasing of stretching for
-1
-1
the C=N bond (1643 cm to 1656 cm ) (Fig. 3S).
converted to the sol within 15 min (Fig. 4). The same gel-to-sol
transition was possible in the presence of 0.5 equiv. amount of
The kinetics of interaction of hydrazine in solution was
understood by recording the absorbance of 1 with time. As can
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1
0
be seen from Fig. 4S, the change in absorbance is rapid and damages and even can lead to gene mutation and cancer. As
becomes constant within mins which explains the a consequence, development of an easy and efficient method
5
completion of reaction as corroborated in Fig. 6. The linear of detection for hydrazine is of great importance and attracts
7
nature of the Benesi-Hildebrand plot corresponded 1:1 attention. In the literature, although a reasonable number of
8
stoichiometric interaction and the detection limit was fluorogenic and chromogenic sensors for hydrazine are
-
6
11
known, to date an approach towards designing of hydrazine-
determined to be as low as 2.54 x 10 M (Fig. 5S,6S).
responsive LMWG is unexplored (Table 2S).
Cation sensing
Owing to the presence of amine groups in the malenonitrile
motif, we also investigated the interaction of
1 with different
metal ions (taken as perchlorate salts) in both gel and sol
states. Use of malenonitrile in different structures as metal
6
chelator is known, but its use in the development of
supramolecular gelators for metal ion sensing is unknown.
Therefore, in the present study, the effect of different metal
ions was studied upon addition of them in equiv. amounts to
2
+
2+
the gel of
2
1 in DMF/H O (1:1 v/v). Only Hg and Cu ions
2
+
disrupted the gel into sol (Fig. 7, top). While Hg ions showed
measurable interaction and ruptured the gel completely within
2
0 min, Cu ions took almost 30 min for the same observation.
+
2
2
+
2+
In order to discriminate Hg from Cu , the gels of 1 were tried
to be prepared in the presence of the metal ions and chelating
agents. Interestingly, although, in both cases, 1-dodecanethiol
and EDTA were capable to recover the gels; successful
-
-
discrimination was possible using CN ion (Fig. 8, bottom). CN
2
+
ion on complexing Cu caused demetallation and enforced
gelation.
CN
NH
2
NC
N
H
N
R =
H
H
O
H
R
O
O
+
calcd. 655.43 (M + H + 1)
+
found. 655.33 (M + H + 1)
1
Figure 6. Partial H NMR spectra of
presence of equiv. amount of hydrazine in d
mass spectra of the product from the reaction of
bottom).
1
(c = 0.02 M) (a) in absence and (b)
-DMSO (top) and the
with hydrazine Figure 7. Photograph showing the changes in gel states of
upon addition of equiv. amount of different metal ions (c = 0.2M in
6
1
1 (at mgc)
(
2
+
2+
+
2+
water) after 1h [from left to right: (a) Cu , (b)Hg , (c) Ag , (d) Zn , (e)
2
+
2+
2+
2+
2+
3+
3+
2+
Cd , (f) Pb , (g) Ni , (h) Co , (i) Fe , (j) Fe , (k) Al and (l) Mg ] in
DMF-H O (1:1, v/v) (top) and chemical reversibility of the metal ion
Of the different amines in the study, hydrazine draws
attention. As an important chemical, it is widely used in
2
2+
2+
induced sols and discrimination of Hg and Cu ions (bottom).
various fields, such as pharmaceutical, chemical, involving
9
2+
2+
catalysts and agricultural industries. Because of its extreme Similar to the observations in gel state, both Hg and Cu ions
explosive nature; it is often used as high energy fuel in missile over the other metal ions in solution brought about drastic
and rocket-propulsion systems. However, despite of its wide change in the absorption spectrum of
1 (Fig. 8). Addition of
2
+
industrial usages, it is considered as a carcinogenic and toxic equiv. amount of Hg ion induced ratiometric spectral change,
environmental pollutant as its intake into the human body by where the absorption bands at 323 nm and 280 nm were
orally or through skin penetration may cause serious health gradually decreased with the formation of weak absorption
4
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band at 430 nm resulting in an isosbestic point at 398 nm (Fig. Dye adsorption
a). In comparison, weak ratiometric response with isosbestic Due to the presence of large hydrophobic surface together
8
2
+
point at 425 nm was noted with Cu ions (Fig. 8b). Indeed, the with the ion binding motif in
1
, we became, further, interested
in presence of Hg and to apply the semi-aqueous gel of for dye adsorption from
Cu ions was further rationalized and distinguished by water. Dyes are widely used as coloring agents in many
2
+
almost identical spectral changes of
1
1
2
+
-
performing the demetallation reactions using CN (Fig. 8c). As industries
including
food,
textile,
lather,
paper,
can be seen from Fig. 8c, the recovery of the absorbance of pharmaceuticals etc.; however, they are toxic, and their direct
2
+
compound
extent than the Hg -complex. Other metal ions exhibited aquatic lives. So, a good dye adsorbent, with high adsorption
negligible change in the absorption spectra of (Fig. 8d). capacity as well as easy and simple recycle ability is
revealed metal (Hg /Cu )-induced demanding. In this context, DMF-H O gel of system has been
small downfield chemical shifts of the –NH (H ) and imine (H established to be unique. Suitable hydrophilic (-NH group) and
protons of by 0.01 ppm. This small change in chemical shift hydrophobic (cholesterol unit) balance within the gelator and a
suggested weak interaction involving the –NH and imine N- cross-linked porous gel network are expected to adsorb the
1 from Cu -complex is significantly to the greater discharge to the environment is a threat to both human and
2
+
14
1
2+
1
2+
H NMR study in CDCl
3
2
1
2
b
a
)
2
1
2
6
1h,4f,15
atoms (Fig. 7S). The linear nature of the Benesi-Hildebrand dyes efficiently.
7
plots interpreted 1:1 binding stoichiometry of
2+
with Hg and
1
2
Cu ions (Fig. 8S). The detection limits were calculated to be as
+
-6
-6
2+
2+
.61 x 10 M and 1.59 x 10 M for Hg and Cu ions,
2
respectively(Fig. 9S).
-
(c = 2.50 x 10 M) upon addition of
5
Figure 8. Change in absorbance of
1
1
2
+
2+
-3
equiv. amount of (a) Hg and (b) Cu ion (c = 1.0 x 10 M) in DMF-
2
O (1:1, v/v); (c) comparative plot showing the demetallation of the
H
metal ion ensembles of
-
-3
1
d) change in absorbance of
in the presence of CN ion (c = 1.0 x 10 M);
in presence of 1 equiv. amount of
(
1
-3
different metal ions (c = 1.0 x 10 M) in DMF-H
2
O (1:1, v/v).
2
+
2+
Hg and Cu ions are some important metal ions that have
Figure 9. Photograph showing the dye adsorption of Crystal Violet
biological and physiological relevance. These metal ions, (A→A'), Malachite Green (B→B'), Uranine (C→C'), Crystal Violet +
-
though serve as a catalytic cofactor for a variety of Malachite Green (D→D') and Crystal Violet + Uranine (E→E') (c= 2 x 10
5
1
2
M) dyes, respectively on keeping in contact with the gel of
mg/ml in 1:1 DMF–H O (v/v)] and the bar plot shows the respective
1
[20
metalloenzymes, can cause environmental pollution. Excess
influx of them leads to toxicity and serious health deceases,
2
adsorption data.
1
especially neurological disorders. Therefore, the selective
3
recognition and sensing of these ions is desirable. In this To perform the dye adsorption experiment, the DMF-H O gel
2
capacity, there are various reports on receptor structures, built of
1 was added to the vial containing the aqueous dye solution
on malenonitrile motif, which respond in solution towards (3 ml), just inverted the vial slowly, and then immediately
various metal ions either colorimetrically or fluorimetrically. filtered to separate the dye adsorbed gel from aqueous part.
But the visual sensing of these ions using LMWGs comprised of The total experiment was carried out in minimum time (˂ 1
malenonitrile is unknown in the literature (Table 3S).
min). The efficiency of the gel as dye adsorbent was measured
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by recording the change in absorption of the dye solution characteristics (Fig. 10C) than the inherent net-like fibrous
before and after the addition of gel. The response time was so network (Fig. 2a). Importantly, the used adsorbent was
first, that we were unable to record the time dependent UV– recovered (~96%), by washing the dye adsorbed gel with
vis spectra during the dye adsorption process.
aqueous MeOH (1:1 v/v), with minimum weight loss, and
The details of the experiment are represented in Figure 9. As thereby demonstrated the recyclability of the process (Fig.
can be seen from Fig. 9, the gel is excellent in adsorbing Crystal 10D).
Violet, an example of cationic dye. In the study, almost More interestingly, although the gel showed almost similar
4
f
7.06% of the dye was removed, and the dye solution efficacy towards another cationic dye such as Malachite green
9
became almost colorless in ˂ 1 min (Figs. 9 and 10A).
Table 2. Adsorption data of gel using various dye
(96.4%), it was unable to remove the anionic dye such as
Uranine (5.67%). Figures 9 and 11 and Table 2, in this regard,
represent the details along this direction. The gel was also
capable of removing the mixture of cationic dyes (Crystal
Violet and Malachite green, 1:1, 97.39%) from aqueous
solution (Fig. 10,11c). Not only that, the gel could efficiently
adsorb almost all the Crystal Violet from the mixture of
cationic and anionic dyes (Crystal Violet and Uranine, 1:1,
99.08%) (Figs. 10 and 11d). The selective removal of the
cationic dyes by the gel is certainly due to the
aminomalenonitrile part that exerts a nucleophilic interaction.
1
Dye
max in nm)
Initial conc.
of the dye
Equilibrium
conc. of the
Quantity of the
(
λ
adsorbed dye
(mg per gram of
the gelator)
(
C
i
) [mM]
f
dye (C ) [mM]
ꢀ1
ꢀ1
(
mgL )
(mgL )
ꢀ
2
ꢀ4
ꢀ4
ꢀ2
Crystal Violet
590)
2 x 10 (8.15)
5.87 x 10
(0.24)
7.23 x 10
1182
1053
63
(
ꢀ2
Malachite
Green (617)
2 x 10 (7.28)
(
0.26)
1.88 x 10
7.10)
ꢀ2
Uranine (490)
2 x 10 (7.52)
(
Figure 11. UV–vis spectra of the dye solution of (a) Malachite green,
(b) Uranine, (c) Crystal Violet and Malachite green (1:1) and (d) Crystal
Violet and Uranine (1:1) before and after dye adsorption.
Figure 10. (A) UV–vis spectra of the dye solution of Crystal Violet (c =
-
.0 x 10 M) before and after dye adsorption, (B) comparision of
5
2
normalized UV-vis spectra of DMF-H O gel of before and after
This observation has strong relevance in real life as the
response time is too short compared to other reported gels
that take couple of minutes (very few report) and even hours
to perform the process.
2
1
adsorption of crystal violet, (C) SEM image of the Crystal Violet
adsorbed gel and (D) the recyclability of the Crystal Violet adsorption
process.
1
6
To be confirmed with the adsorption, we compared the FTIR,
UV-vis spectra and the SEM image of the dye adsorbed gel
with the original one. The adsorbed gel had both the
Conclusions
In conclusion, we have designed and synthesized a simple
cholesterol coupled diaminomalenonitrile-based LMWG
1,
characteristics stretching signals of
some variations in peak positions (Fig. 10S). Furthermore, UV-
vis spectra of the gel of itself and after adsorption of crystal
1 and crystal violet with
which successfully acts as single molecular multi analyte
2
+
2+
(
hydrazine, Hg and Cu ) sensor. The gelator forms a stable
and robust gel in DMF-H O as confirmed by detailed
rheological study. The morphology of the gel exhibits fibrillar
network. The DMF-H O gel of has been noted to be stimuli
1
2
violet were compared (Fig. 10B). The strong absorption at 597
nm for crystal violet clearly indicated the adsorption
phenomena. During adsorption, the morphology of the dye-
adsorbed gel showed more compact and aggregated spongy
2
1
responsive. Selective dosimetric interaction of the
6
| J. Name., 2012, 00, 1-3
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ARTICLE
malenonitrile motif with hydrazine brings gel to sol conversion 7.85 (d, 2H, J = 8 Hz), 7.01 (d, 2H, J = 8 Hz), 5.38 (d, 1H, J = 4 Hz),
1
3
and reports the visual sensing of hydrazine. As per our 4.75 (m, 1H), 4.68 (s, 2H ), 2.35–0.67 ( 43H, cholesteryl protons);
C
knowledge goes, this is a first time report of hydrazine sensing NMR (CDCl , 100 MHz): δ 190.7, 167.5, 162.6, 139.0, 131.9, 130.6,
3
in gel phase.
123.2, 114.9, 75.6, 65.3, 56.6, 56.1, 49.9, 42.3, 39.6, 39.5, 37.9,
In addition, compound
1
shows the metal ion interaction 36.8, 36.5, 36.1, 35.7, 31.89, 31.82, 29.7, 28.2, 28.0, 27.6, 24.2,
-1
involving the malenonitrile motif and successfully reports the 23.8, 22.8, 22.5, 21.0, 19.2, 18.7, 11.8; FTIR (KBr, cm ): 2945, 1775,
2
visual sensing of Cu and Hg ions through gel to sol 1701, 1606, 1468, 1212; HRMS (TOF MS ES+): calcd. 549.3866
+
2+
+
+
conversion. Moreover, the gel exhibits excellent efficacy (M+1) , found 549.3890 (M+1) .
towards rapid and selective adsorption of cationic dyes from
water in almost no time (˂ 1 min).
Compound 1:
Compound 3 (1.0 g, 1.82 mmol) and diaminomalenonitrile (0.78 g,
7
.28 mmol) were taken in 20 ml of dry benzene and the mixture
was refluxed for 3 days. Progress of the reaction was monitored by
checking TLC. After completion of the reaction, benzene was
evaporated and the reaction mixture was repeatedly washed with
MeOH to have the pure compound 1 in appreciable yield (0.88 g,
Experimental
Materials and methods
All the chemicals and reagents were purchased from Spectrochem,
India. Perchlorate salts of the metal ions were purchased from
Sigma-Aldrich and were carefully handled. All solvents used in the
synthesis were purified, dried and distilled as required. Solvents
used in NMR experiments were obtained from Aldrich. Thin layer
chromatography was performed on Merck precoated silica gel 60-
o
1
yield 76%, mp 214 C). H NMR (400 MHz, CDCl
.71 (d, 2H, J = 8.4 Hz), 6.89 (d, 2H, J = 8.4 Hz), 5.32 (d, 1H, J = 3.6
Hz), 5.06 (s, 2H ), 4.75 (m, 1H), 4.60 (s, 2H), 2.28–0.79 (43H,
3
): δ 8.28 (s, 1H),
7
1
3
cholesteryl protons); C NMR (100 MHz, CDCl
3
): δ 167.6, 161.2,
1
7
3
1
1
C
8
58.2, 139.0, 131.9, 131.1, 128.6, 123.2, 115.1, 114.9, 113.6, 112.4,
1
13
5.6, 65.3, 56.6, 56.1, 49.9, 42.3, 39.6, 39.5, 37.9, 36.8, 36.5, 36.1,
5.7, 31.89, 31.82, 28.2, 28.0, 27.6, 24.2, 23.8, 22.8, 22.5, 21.0,
F
254 plates. H and C NMR spectra were recorded using Bruker 400
MHz instrument using TMS as internal standard. FTIR
measurements of the compounds were carried out using a Perkin-
-1
9.2, 18.7, 11.8; FTIR (KBr, cm ): 3450, 2936, 2234, 2204, 1739,
+
-
1
643, 1618, 1430, 1380; mass m/z: 637.41 [M − 1] ; Anal Calcd for
Elmer L120-00A spectrometer (
ν
max in cm ) using KBr pellet. UV-vis
40 54 4 3
H N O : C, 75.20; H, 8.52; N, 8.77, Found: C, 75.45; H, 8.59; N,
studies were performed
using Shimadzu UV-2450
.91.
spectrophotometer.
Synthesis
General procedure for gelation test
Chloro-acetic
acid
17-(1,5-dimethyl-hexyl)-10,13-dimethyl-
The requisite amount of compound was taken in desired solvent (1
mL), slightly warmed to form a homogeneous solution and then
allowed to cool to room temperature to form a gel. Stimuli
responsive behavior of the gel was investigated in presence of
different analytes in the same way. The gel formation was tested
via the usual inversion of vial method. Samples of gels for SEM
imaging were dried under vacuum and then coated with a thin layer
2
,3,4,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-
4
i
cyclopenta[a]phenanthren-3-yl ester (2):
To a stirred solution of cholesterol (0.5 g, 1.29 mmol) in 20 mL dry
CHCl was added chloroacetyl chloride (0.16 mL, 1.93mmol) and
3
pyridine (0.05 mL, 0.65 mmol) under nitrogen atmosphere. The
mixture was allowed to stir for 10 h at room temperature. After
completion of reaction, the reaction mixture was neutralized with
of gold metal. The gel-to-sol transition temperature (T
measured by the dropping ball method.
g
) was
NaHCO
The organic layer was washed several times with water and
separated and dried over Na SO . Evaporation of the solvent gave
white solid compound. Recrystallization from CH OH afforded pure
product 2 (0.58 g, yield 96%, mp 148 °C). H NMR (400 MHz, CDCl ):
δ 5.37 (m, 1H), 4.72 (m, 1H), 4.03 (s, 2H), 2.36 (m, 2H), 2.02–0.85
3 3
solution, and then was extracted with CHCl (3 × 30 mL).
2
4
General procedures for UV-vis titrations
3
1
Stock solutions of the compounds were prepared in required
3
-5
solvents in the concentration range of 10 M. Stock solutions of
metal ions and hydrazine were prepared in the same solvent in the
−1
(m, 38H, cholesteryl protons), 0.67 (s, 3H); FTIR (KBr, cm ): 2939,
-3
concentration range of 10 M. Solutions of the compound (2 mL)
were taken in the cuvette and to the solution different analytes
were individually added in different amounts. Upon addition of
analytes, the changes in absorbance of the compound were
recorded.
2
907, 2821, 1753, 1620, 1195.
4
i
Compound 3:
A mixture of 4-hydroxybenzaldehyde (1g, 8.19 mmol) and K
2 3
CO
(2.26 g, 16.38 mmol) was refluxed in dry CH CN for 2 h and then
3
compound 2 (4.55 g, 9.82 mmol) was added to it. The reaction
mixture was refluxed for 5 h. Then the organic solvent was
evaporated under reduced pressure and water was added to the
7
Binding constant determination
Benesi-Hildebrand plot was adopted to determine the binding
-
0 0 M M C a
constant value using the expression: A /(A-A ) = [ε /(ε – ε )](K
crude mass. Then reaction mixture was extracted with 2% CH
3
OH in
1
-1
g
C
+1), where ε
the receptor and the complex, respectively, at
wavelength, A denotes the absorbance of free receptor at that
specific wavelength and C
M
and ε
C
represent molar extinction coefficients for
CHCl . Evaporation of the solvent gave the crude product which was
3
a
selected
purified by column chromatography using 10% ethyl acetate in
petroleum ether as eluent to afford the pure compound 3 in 78 %
0
0
1
yield (3.50 g, mp 114 C). H NMR (CDCl , 400 MHz): δ 9.90 (s, 1H),
3
g
is the concentration of the guest. The
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measured absorbance A
0
/(A-A
0
) as a function of the inverse of the
Chem. Phys., 2014, 16, 8346; (c) H. Svobodova, V. Noponen,
E. Kolehmainen and E. Sievanen, RSC Adv., 2012, , 4985; (d)
S. –M. Lu, J. –C. Huang, G. –T. Liu, Z. –W. Lin, Y. –T. Li, X. –H.
Huang, C. –C. Huanga and S. –T. Wu, RSC Adv., 2017,
0979; (e) H. Maeda, Chem. Eur. J., 2008, 14, 11274. (f) M. –
2
guest concentration fits a linear relationship, indicating 1:1
stoichiometry of the receptor guest complex. The ratio of the
intercept to the slope was used to determine the binding constant
7
,
3
K
a
. Instead of fluorescence intensities, respective absorbance of the
O. M. Piepenbrock, G. O. Lioyd, N. Clarke and J. W. Steed,
Chem. Rev., 2010, 110, 1960.
(a) K. Ghosh and S. Panja, Supramol. Chem., 2017, 29, 350;
receptor was also used to get the binding constant values.
4
8
(b) K. Ghosh, A. Panja and S. Panja, New. J. Chem. 2016, 40,
Calculation of detection limit
3
2
476; (c) K. Ghosh, S. Panja and S. Bhattacharya, RSC. Adv.,
015, , 72772; (d) K. Ghosh and S. Panja, ChemistrySelect,
, 3667; (e) K. Ghosh and S. Panja, RSC. Adv., 2015,
12094; (f) S. Panja, S. Bhattacharya and K. Ghosh, Langmuir,
Detection limit was calculated using the UV-vis titration data. The
absorbance of 3 was measured 5 times, and the standard deviation
of blank measurement was achieved. To have the slope, absorbance
values were plotted against concentrations of analyte. The
detection limit were calculated using the equation: Detection limit =
5
1
2016,
5,
2
2
017, 33, 8277; (g) K. Ghosh and S. Panja, ChemistrySelect,
017, , 959; (h) S. Panja, S. Bhattacharya and K. Ghosh,
, 385; (i) A. Panja and K. Ghosh,
2018, DOI:
2
Mater. Chem. Front., 2018,
Supramol. Chem.,
2
3
σ/k , where σ is the standard deviation of blank measurement, and
k is the slope.
10.1080/10610278.2018.1461219; (j) S. Panja, S. Ghosh and
K. Ghosh, New J. Chem., 2018, 42, 6488.
4
f
Dye adsorption experiment
5
(a) X. X. He, J. Zhang, X. G. Liu, L. Dong, D. Li, H. Y. Qiu and S.
C. Yin, Sens. Actuators, B, 2014, 192, 29; (b) T. He, C. L. Lin, Z.
Y. Gu, L. N. Xu, A. L. Yang, Y. Y. Liu, H. J. Fang, H. Y. Qiu, J.
Zhang, S. C. Yin, Spectrochim. Acta A, 2016, 167, 66; (c) K.
Fan, J. Yang, X. Wang and J. Song, Soft Matter, 2014, 10,
8370; (d) H. Komatsu, S. Matsumoto, S. -i. Tamaru, K.
For this study, the gel of 1 [20 mg/ml] was prepared in 1:1 DMF–
O (v/v) solvent. Dye solutions were prepared in the concentration
H
2
-5
of c = 2 x 10 M in water. The dye removal efficiency (RE) of the gel
phase from its aqueous solution (2 mL) was estimated using UV-vis
spectroscopy. The final concentration of the dye in solution was
calculated according to the Beer-Lambert law (A = εcl, A is the
absorbance of the dye at a certain absorption wavelength in
solution, ε is the molar extinction coefficient and l is the path length
of the incident light). The final concentration of the dye in solution
could be obtained by the Beer-Lambert equation, which ultimately
determined the removal efficiency of the dye via the equation as:
Kaneko, M. Ikeda and I. Hamachi, J. Am. Chem. Soc., 2009,
1
31, 5580; (e) P. Xue, R. Lu, J. Jia, M. Takafuji and H. Ihara,
Chem.–Eur. J., 2012, 18, 3549; (f) X. Y. Yang, G. X. Zhang and
D. Q. Zhang, J. Mater. Chem., 2012, 22, 38.
6
(a) T. G. Jo, Y. J. Na, J. J. Lee, M. M. Lee, S. Y. Lee and C. Kim,
New J. Chem., 2015, 39, 2580; (b) S. Goswami, S. Das and K.
Aich, Tetrahedron Lett., 2013, 56, 4620; (c) K. M. Vengaian,
D. Britto, K. Sekar, G. Sivaraman and S. Singaravadivel, Sens.
Actuators, B, 2016, 235, 232, (d) S. –P. Wu, T. –H. Wang and
S. –R. Liu, Tetrahedron, 2010, 66, 9655.
RE = (C
i
– C
f
)/C
i
i
, in which C represents the initial concentration of
the dye in solution; C
f
is the final concentration of the dye in the
presence of adsorbing gel.
7
8
9
P. T. Chou, G. R. Wu, C. Y. Wei, C. C. Cheng, C. P. Chang and F.
T. Hung, J. Phys. Chem. B, 2000, 104, 7818.
A. R.Sarkar, C. H. Heo, M. Y. Park, H. W. Lee, H. M. Kim,
Chem.Commun. 2014, 50, 1309.
(a) U. Ragnarsson, Chem. Soc. Rev., 2001, 30, 205; (b) S. D.
Zelnick, D. R. Mattie and P. C. Stepaniak, Aviat. Space
Environ. Med., 2003, 74, 1285.
Acknowledgements
We AP thanks CSIR, New Delhi, India for a fellowship. KG
thanks SERB, DST, New Delhi, for financial support (File No.
EMR/2016/008005/OC).
1
0 (a) C. A. Reilly and S. D. Aust, Chem. Res. Toxicol., 1997, 10,
28; (b) International Agency for Research on Cancer. Re-
3
evaluation of some organic chemicals, hydrazine, and
hydrogen peroxide. IARC Monographs on the Evaluation of
Carcinogenic Risk of Chemicals to Humans; IARC: Lyon, 1999;
References
Vol.
iarc.fr/ENG/Monographs/vol71/mono71-43.pdf.
1 (a) Y. Tang, D. Lee, J. Wang, G. Li, J. Yu, W. Lin and J. Yoon,
Chem. Soc. Rev., 2015, 44, 5003; (b) M. G. Choi, J. O. Moon, J.
Bae, J. W. Lee and S. –K. Chang, Org. Biomol. Chem., 2013,
71,
pp
991-1013;
http://monographs.
1
(a) J. W. Steed, Chem. Soc. Rev., 2010, 39, 3686; (b)
Functional Molecular Gels, in soft matter, ed. B. Escuder and
J. F. Miravet, The Royal Society of Chemistry, Cambridge, UK,
1
2
2
014; (c) G. Yu, X. Yan, C. Han and F. Huang, Chem. Soc. Rev.,
013, 42, 6697; (d) D. B. Amabilino, D. K. Smith and J. W.
1
1
, 2961.
2 E. L. Que, D. W. Domaille and C. J. Chang, Chem. Rev., 2008,
08, 1517.
Steed, Chem. Soc. Rev. 2017, 46, 2404; (e) M. J. Webber, and
R. Langer, Chem. Soc. Rev. 2017, 46, 6600; (f) N. M.
Sangeetha and U. Maitra, Chem. Soc. Rev., 2005, 34, 821; (g)
1
1
1
3 (a) B. Sarkar, In Metal Ions in Biological Systems, H. Siegel, A.
Siegel, Eds.; Marcel Dekker: New York, 1981; Vol. 12, pp 233-
S. Datta and S. Bhattacharya, Chem. Soc. Rev., 2015, 44
,
5
2
596; (h) B. O. Okesola and David K. Smith, Chem. Soc. Rev.,
016, 45, 4226; (i) J. Bachl, J. Mayr, F. J. Sayago, C. Cativiela
2
82; (b) H. T. Ratte, Environ. Toxicol. Chem. 1999, 18, 89.
4 (a) B. Adhikari, G. Palui and A. Banerjee, Soft Matter, 2009,
452; (b) P. Chakraborty, B. Roy, P. Bairi and A. K. Nandi, J.
1
5,
and D. D. Diaz, Chem. Commun., 2015, 51, 5294.
3
2
(a) R. G. Weiss and P. Terech, Molecular Gels, Springer,
Dordrecht, 2006, pp. 978; (b) F. Fages, Low Molecular Mass
Gelators, Topics in Current Chemistry, Springer-Verlag, Berlin,
Mater. Chem., 2012, 22, 20291.
5 S. Samai and K. Biradha, Chem. Mater., 2012, 24, 1165.
6 Y.-T. Tang, X.-Q. Dou, Z.-A. Ji, P. Li, S.-M. Zhu, J.-J. Gu, C.-L.
Feng and D. Zhang, J. Mol. Liq., 2013, 177, 167.
1
1
2
005, 256, 283; (c) S. S. Babu, V. K. Praveen and A.
Ajayaghosh, Chem. Rev. 2014, 114, 1973; (d) P. A. Gale, N.
Busschaert, C. J. E. Haynes, L. E. Karagiannidis and I. L. Kirby,
Chem. Soc. Rev., 2014, 43, 205.
3
(a) C. D. Jones and J. W. Steed, Chem. Soc. Rev., 2016, 45,
6546; (b) P. Xing, X. Chu, M. Ma, S. Li and A. Hao, Phys. Chem.
8
| J. Name., 2012, 00, 1-3
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New Journal of Chemistry
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DOI: 10.1039/C8NJ02426J
GRAPHICAL ABSTRACT
Diaminomalenonitrile decorated cholesterol-based supramolecular gelator:
2+
2+
Aggregation, multiple analytes (hydrazine, Hg and Cu ) detection and dye
adsorption
Atanu Panja and Kumaresh Ghosh*
Diaminomalenonitrile functional group containing low molecular weight gelator (LMWG) 1 has been designed and
synthesized. The compound forms supramolecular gels from DMF-H O and 1,2-dichlorobenzene. The DMF/H O
2
2
2
+
2+
gel is multi analyte responsive (Hg , Cu and hydrazine) and acts as useful material with practical application
involving fastest dye adsorption from water in almost no time.
.
_
____________________________________________________________________________________