A luminescent inorganic-organic hybrid, [Cd(C16H10N2O8S)(H2O)], for the selective and recyclable detection of chromates and dichromates in aqueous solution

Article abstract of DOI:10.1039/c9nj03224j

A new inorganic-organic hybrid compound [Cd(H₂L)(H₂O)], 1, {where, H₂L^2- = 4,4′-sulfonylbis(phenylene)bis(oxamate)} has been prepared under solvothermal conditions. The compound has a three-dimensional structure

Full text of DOI:10.1039/c9nj03224j

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Yellowish and blue luminescent graphene oxide quantum dots
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A Luminescent Inorganic-Organic hybrid,
[Cd(C16H10N2O8S)(H2O)], for the Selective and Recyclable
Detection of Chromates and Dichromates in Aqueous
Solution
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Tanaya Kundu,a Krishna Manna,a Ajay K. Janaa and Srinivasan Natarajan*a,b
A
new inorganic organic hybrid compound [Cd(H2L)(H2O)], 1, {where, H2L2-
= 4,4ʹ-
sulfonylbis(phenylene)bis(oxamate)} has been prepared under solvothermal conditions. The
compound has a three dimensional structure. The compound exhibits strong luminescent behavior,
which was used for the detection of chromate and dichromate anions in aqueous media at low
concentrations. The compound exhibited high selectivity and recyclablity for the detection of low
concentrations (ppm levels) of chromate and dichromate ions. Compound 1 was also found to be
an effective catalyst for the Knoevenagel condensation involving aromatic aldehyde and
malononitrile under green solvent free conditions with high yield and recyclability.
over many decades resulted in a large library of compounds
(ligands) many of which can be employed as useful ligands in
binding with metal ions. This provides an excellent basis to
Introduction:
Inorganic–organic hybrid, metal-organic framework
(MOFs) or inorganic coordination polymer (CPs) compounds
have been investigated with much interest over the past two
decades. The intense research activity yielded many new
compounds that exhibit promise in the areas of sorption,
separation, sensing, heterogeneous catalysis, magnetism etc.
Many review articles, books and special issues of journals
were published highlighting the importance of these class of
compounds.1–10 From the available literature, it is becoming
clear that new compounds can be prepared by employing (i)
new synthetic protocols or (ii) employing new organic
functional ligands. The developments of organic chemistry
explore the preparation of CPs by employing new organic
ligands. There have been efforts towards the synthesis of new
organic ligands and their utilization in the preparation of new
and interesting hybrid framework compounds.11–13 One such
organic ligand is bis–oxamato ligand, which has been
employed in the preparation of complexes towards molecular
magnetism.14 The bis-oxamato ligand was used with copper
and many copper(II) complexes have been synthesized and
their magnetic properties evaluated. In addition, the
copper(II) complexes have also been employed to prepare a
number of heterometallic complexes that included higher
dimensional coordination polymers.15 Preparation of homo-
metallic complexes using bis-oxamate provides considerable
challenges as the bis-oxamate forms an anionic complex
immediately with metal ions. A modified synthetic approach
where the bis-oxamate are separated by an organic linker was
employed recently to prepare both hetero-metallic16 as well
as homo-metallic17 coordination polymer compounds. The
ligand, 4,4ʹ–sulfonylbis(phenylene)bis(oxamate), has an
angular V-shape, which might be useful in the preparation of
new and unusual structures.
a Framework Solids Laboratory, Solid State and Structural Chemistry Laboratory,
Indian Institute of Science, Bangalore 560 012, INDIA. Email:
snatarajan@iisc.ac.in
b Division of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-
Oiwakecho, Sakyo-Ku, Kyoto 606-8502, Japan.
ORCID (Srinivasan Natarajan): 0000-0002-4942-0968
Electronic Supplementary Information (ESI) available: [Bond distances and angles
(Tables S1 and S2), Scheme-1, PXRD patterns (Fig. S1, S4 and S18), IR (Fig. S2), TGA
(Fig. S3), UV-Vis spectra (Fig. S5), PL spectra (Fig. S6), Structure Figures (Figs. S7 –
S10) Sensing studies (Figs. S11 – S16), Scheme-2, NMR (Figs. S19 – S24]. See
DOI: 10.1039/x0xx00000x
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One of the recent interests in the study of MOFs as well as
CPs is to investigate their luminescence based properties. The
luminescence behaviour of the MOFs and CPs were exploited
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N,N-dimethylformamide,
tetrahydrofuran, View AreticthleaOnnloinle,
DOI: 10.1039a/Cc9idNJ0w32e2r4eJ
methanol, sodium hydroxide, hydrochloric
purchased from SDfine (India). Ethyl oxalyl chloride was
purchased from Spectrochem (India). The water used was
double distilled through a Millipore membrane. All the
chemicals were used as purchased without further
purification.
in the detection of harmful organics and other polluting
18–22
inorganics.
There have been efforts towards the
detection of metal ions as well.23–26 One of the major
industrial pollutant is chromium in +6 oxidation state,
especially the chromate (CrO4)2–, and dichromate (Cr2O7)2–
ions. The Cr6+ ions are generated from many industrial
processes related to leather tanneries, wood preservation,
chromium plating, pigments / paint / paper industries etc.27–
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Synthesis and initial characterization
H2Et2L was synthesized employing a reported procedure
by refluxing 4,4ʹ-diaminodiphenyl sulfone and ethyl oxalyl
chloride in THF (Scheme1, ESI).41 The desired ligand H4L, was
obtained by suitable hydrolysis of H2Et2L. 1H NMR (500 MHz,
) δ 11.14 (s,2H), 7.94 – 7.89 (m, 8H), 4.26 (t, J = 7.1 Hz, 4H),
1.26 (t, J = 7.1 Hz, 6H). 13C NMR (126 MHz) δ 160.52, 151,
142.48, 137.61, 128.80, 121.36, 63.27, 14.80. 1H NMR (DMSO-
d6), H2Et2L: δ 1.30(t, 6H, J = 8.0 Hz, J = 4.0 Hz), 4.30(q, 4H, J =
8.0 Hz), 7.96(m, 8H), 11.17(s, 2H). H4L: δ 7.95(m, 8H), 11.09(s,
2H).
Compound, 1, was prepared under mild reaction
conditions. The ligand H4L (0.0196 g, 0.05 mmol) was
dissolved in 0.5 mL of N,N-dimethylformamide and 1.5 mL of
ethanol mixture (Solution A). Cd(ClO4)2.H2O (0.0187 g, 0.06
mmol) was dissolved in 2 mL water (solution B). In a test tube,
2 mL of solution A was carefully layered on top of 2 mL of
solution B. The test tube was capped and kept undisturbed at
60 °C for 7 days, which resulted in large quantity of
needle-shaped crystals of 1. The crystals were carefully
filtered and washed with H2O and dried under vacuum.
Elemental analysis: Calcd (%): C 36.90, H 2. 32, N 5.38, S 6.16;
found: C 31.24, H 2.62, N 5.72, S 6.37.
30
The chromate and dichromates are known to be health
hazards and exposure to these ions would lead to nasal
epithelia, skin and other cancers.31–34 It is necessary to detect
and eliminate these ions from the industrial effluents through
a sensitive/ fast/ selective approach. One such technique is
the fluorometric detection, which is cheap, easy to detect and
2–
quick. The main drawback in the detection of CrO42– / Cr2O7
ions in aqueous solutions would be the stability of the
prepared MOFs or CPs. There have been attempts to detect
these ions employing luminescent inorganic-organic hybrid
compounds.35,36
Over the years, we have employed many different
aromatic carboxylates for the preparation of new and
interesting hybrid compounds. Of these, the aromatic
carboxylates where the benzene rings are separated by –O– ,
–SO2–, etc. are interesting as they have similar functionality
along with structural flexibility, which would lead to
compounds with unusual structures. We have so far explored
oxy-bis benzoic acid (HOOC-C6H4 – O – C6H4 – COOH),37,38
sulpho bis benzoic acid (HOOC-C6H4 – SO2 – C6H4 – COOH)39,40
as a ligand in the preparation of new hybrid compounds with
interesting structure as well as properties. In addition, we
have also been interested in utilizing the luminescence
behaviour of such compounds towards the detection of
pollutants, both organic as well as inorganic. The ligand, 4,4ʹ–
sulfonylbis(phenylene)bis(oxamate), has been shown to be a
useful ligand in the preparation of CPs.[16,17] We desired to
explore the reactivity of this ligand towards the formation of
newer frameworks. To this end, we have prepared the 4,4ʹ–
sulfonylbis(phenylene)bis(oxamate) and explored the
reactivity under mild reaction conditions employing cadmium
salts. Our synthesis was successful and we have now prepared
a new three dimensional compound, [Cd(H2L)(H2O)], 1. The
compound was found to exhibit good luminescence behaviour
and also found to be a selective sensor for chromates and
dichromates in aqueous medium. In this paper, we present
the synthesis, structure, sensing and heterogeneous catalytic
behaviour of this compound.
Initial characterizations were carried out by powder X-ray
diffraction (PXRD), infrared spectroscopy (IR), UV-Vis
spectroscopy, photoluminescence studies (PL), and
thermogravimetric analysis (TGA). The PXRD data were
recorded in the 2θ range 5-50° using CuKα radiation (Philips
X’pert). The observed PXRD pattern was found to be
consistent with the PXRD pattern simulated from the single
crystal structure study (Supporting Information, Figure S1).
UV−Vis and photoluminescence spectra were recorded at
room temperature using a Perkin Elmer (Lambda 35 and LS 55)
spectrophotometer, respectively. Thermogravimetric analysis
(Metler-Toledo) was carried out in oxygen atmosphere (flow
rate = 40 mL/min) in the temperature range 30−800°C
(heating rate = 10°C/min). 1H NMR data for the ligand was
collected using Bruker 400 MHz spectrometer. Chemical shifts
are reported in ppm using tetramethylsilane as the internal
reference. Elemental analyses (carbon, hydrogen, nitrogen
and sulfur) were performed in a Thermo Finnigan EA Flash
1112 Series. IR spectra were recorded as KBr pellets (Perkin
Elmer Frontier FTIR spectrometer, model no: L125000P,
Supporting Information, Figure S2). The strong IR band at ~
3465 cm-1 corresponds to the O–H stretching frequency of the
coordinated water. The bands around ~ 3360 cm-1 and 3315
cm-1 were due to the N–H stretching frequencies. The bands
Experimental:
Materials
The chemicals, Cd(ClO4)2.3H2O and 4,4ʹ-diaminodiphenyl
sulfone
were
acquired
from
Sigma-Aldrich.
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at ~1308 cm-1 and 1150 cm-1 corresponds to the S=O stretching R1 = Σ||Fo| − |Fc||/Σ|Fo|; wR2 = {Σ|w(Fo2 − Fc2)]/Σ
View Article Online
DOI: 10.1039/C9NJ03224J
2 2
,
[w(Fo ) ]}1/2. w = 1/[ρ2(Fo)2 + (aP)2 + bP]. P = [max (Fo O) +
frequencies. The aromatic C=C stretching and C=O stretching
were observed at ~ 3068–3105 cm−1, ~1590 cm−1 and ~1650
cm−1, respectively.42
2(Fc)2]/3, where a = 0.0353 and b = 0.0000 for 1
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Single Crystal Structure Determination
Thermogravimetric Analysis
Single crystal diffraction data for the compound 1 was
collected using a Bruker SMART APEX CCD diffractometer. The
X-ray generator was operated at 50 kV and 35 mA using Mo–
Kα (λ=0.71073 Å) radiation. The data reduction was carried out
9
The thermogravimetric analysis (TGA) of compound 1
indicated a initial weight loss of ∼3.5% in the temperature
range of 210−280 °C, which corresponds to the loss of the
coordinated water molecule (calc. 3.46%). Compound 1 starts
to decompose after 280 °C, (Supporting Information, Figure
S3). The final products after the TGA analysis was found to be
CdO (JCPDS: 75-0592) mixed with small amount of Cd3O2SO4
(JCPDS: 32-0140) (Supporting Information, Figure S4).
The UV-Vis absorption spectra of the compound as well as
the free ligand (H4L) were recorded in the solid state at room
temperature. The compound exhibited absorption bands in
the region of 200-400 nm, which are assigned to the intra-
ligand transitions. Similar absorption behavior had been
observed for the many aromatic ligands.47,48 (Supporting
Information, Figure S5)
The solid state luminescence behaviors of the compound
as well as the free ligand (H4L) were recorded at room
temperature. Compound 1 exhibited a strong emission band
at 430 nm, ( λex= 320nm, Supporting Information, Figure S6).
The observed emission band can be assigned to the
ligand-centered luminescence. Similar emission band was
also observed for free ligand at 400 nm (Supporting
Information, Figure S6). The observed red shift is due to the
binding of the ligand to the metal center, which has been
observed in many hybrid compounds before.49
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using SAINTPLUS and an empirical absorption correction
was applied using the SADABS program.44 The structure was
solved and refined using SHELXL97, present in the WINGX
package of programs (Version1.63.04a).45 The hydrogen
atoms of water and aromatic C-H hydrogen atoms were
initially located from the difference Fourier map, and latter
placed in geometrically ideal positions and refined in the
riding mode. The N-H hydrogen atoms were assigned from
the difference Fourier map using the SHELX97 program. The
full matrix least-squares refinement against |F2| was
performed using WinGx package of programs.46 The final
refinements included atomic positions for all the atoms,
anisotropic thermal parameters for all the non-hydrogen
atoms, and isotropic thermal parameters for all the hydrogen
atoms. The details of the structure solution and final
refinement parameters are listed in Table 1. The CCDC
numbers for the compound 1 is 1920748. These data can be
obtained free of charge from The Cambridge Crystallographic
Data
Center
(CCDC)
via
www.ccdc.cam.ac.uk/data_request/cif.
Table 1: Crystal Data and Structure Refinement Parameters
for Compound 1
Catalytic Studies:
Knoevenagal condensation reactions were carried out
under solvent free conditions. Typically, a mixture of the
aldehyde (1 mmol), malononitrile (2 mmol) and 1 (0.05 mmol)
were taken in a 10 mL round bottomed flask, and the reaction
mixture was heated at 60°C for 4h under constant stirring.
After 4h, 5mL dichloromethane was added and the reaction
mixture was filtered to separate the catalyst. The filtrate was
concentrated employing the rotary evaporator, and the
residue was washed with hot water and dried under vacuum.
Empirical formula
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
α (deg)
C16H12N2O9SCd
520.74
orthorhombic
P212121
4.9378(3)
10.8625(6)
31.1686(18)
90
β (deg)
90
Results and Discussion:
Structure of [Cd(C16H10N2O8S)(H2O)] (1)
γ (deg)
90
Volume (Å3)
Z
1671.79(17)
4
The asymmetric unit of compound 1 contains one Cd2+,
one H2L2- ligand and one coordinated water molecule
(Supporting Information, Figure S7). The Cd2+ ion has a
distorted octahedral coordination environment bonded with
five oxygen atoms of oxamato groups from four H2L2- ligands
(O2–O6) and one water molecule (O9) (Supporting
Information, Figure S8). The Cd–O distances are in the range
of 2.229(3) –2.400(3) Å (av. 2.311 Å) (Supporting Information,
Table S1). Of the two oxamato groups, one connects with two
Cd2+ ions through two oxygen atoms (O2, O3), while the other
Temperature (K)
293(2)
2.069
1.492
ρc (g cm-3)
μ (mm-1)
Wavelength (Å)
θ range (deg)
Reflns collected
Unique reflns
R1, wR2 [I>2σ(I)]
R1, wR2 (all data)
0.71073
3.22 to 25.00
36947
2930
0.0304, 0.0598
0.0435, 0.0627
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connects with two Cd2+ ions through three oxygen atoms (O4,
O5, O6) (Supporting Information, Figure S9).
View Article Online
DOI: 10.1039/C9NJ03224J
.
The structure of 1 can be described in simpler building
units. The Cd centers are bonded through the oxamate units
forming a two dimensional layer, which is corrugated (Figure
1 and 2). The cadmium oxamato layers are cross linked
through the H2L2- ligands forming the three dimensional
structure (Figure 3). Within the cadmium oxamato ligands, the
cadmium centers are separated with distances in the range of
4.94 – 5.93 Å. The close proximity of the N-H protons with the
coordinated water molecules as well as the oxamato oxygens
give rise to hydrogen bond interactions (Supporting
information, Figure: S10)
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Figure 3. The three dimensional structure of 1 showing the
connectivity between the corrugated layers through H2L2-
ligands.
(CrO4)2– and (Cr2O7)2– ion sensing
As mentioned before, compound 1 exhibits intense
emission at ~430 nm. We explored the utility of the emission
of 1 to detect harmful pollutants such as chromates and
dichromates. The luminescence based detection would be a
quick and reliable option. The detection of [CrO4]2– / [Cr2O7]2–
ions from aqueous solutions have been demonstrated before
using
luminescent
inorganic-organic
hybrid
compounds.[35,36,50] One of the drawbacks in employing the
inorganic-organic hybrid compounds for luminescence based
sensing is their lack of stability in the aqueous solution,
especially during the recyclability studies. Compound 1 has a
stable framework (stable up to 250 °C) and also exhibits good
luminescence behaviour, which we utilized in the detection of
chromate and dichromate oxoanions in aqueous solution.
It is important to establish that the compound not only is
useful in detecting chromate and dichromate anions in
solution, but also selective in the presence of other possible
competing ions. For the sensing selectivity, we initially
Figure 1. View of the two dimensional layer formed by the
connectivity involving the oxamato groups.
–
examined a number of anions ( F– , Cl–, Br–, I–, SCN–, NO3 , AcO–
–
–
–
–
, SO42–, ClO4 , BF4 , MoO4 , WO4 , CrO42–) independently in
aqueous solutions using fluorescence spectroscopy
(Supporting information, Figure S11). In a typical experiment,
the aqueous anion solutions were added to a aqueous
dispersion of 1 and the interaction between the anions and 1
were examined by following the changes in the florescence
intensity of 1. The studies reveal that the luminescent
intensity of 1 (426 nm; λex = 320 nm) appears to the strongly
affected (quenched) in the presence of [CrO4]2– and [Cr2O7]2–
ions only (Figure 4). The other anions that were examined
during the study appears to have negligible effect in reducing
Figure 2. View of the two-dimensional structure showing the
corrugated nature
the overall luminescence intensity of
1 (supporting
information, Figure: S11). Once we established the sensing
behaviour of 1 towards the [CrO4]2– and [Cr2O7]2–, we
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examined the selectivity for the chromate and dichromate ions. To this end, the luminescence spectra were recorded as
View Article Online
DOI: 10.1039/C9NJ03224J
ions in presence of other similar ions. Thus, the detection of a function of the addition of different concentrations of the
chromate and dichromate ions were examined in the anions [CrO4]2– and [Cr2O7]2– to 1 (Figure 4). As can be noted,
presence of other ions for possible competition in the the luminescence intensity decreases gradually with
detection (supporting information, Figure: S12). The studies increasing concentration of the ions. Both the ions appeared
indicated that compound 1 is highly selective for [CrO4]2– and to quench the luminescence intensity completely at a
[Cr2O7]2– ions only.
concentration of 10-3 M. In the case of [CrO4]2– ions a small
red shift of the luminescence band was noted. We evaluated
the quenching efficiency (%) for both the ions employing the
formula,
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-
Blank
1 + Cr2O72
(a)
25x10-6M
50x10-6M
75x10-6M
10x10-5M
15x10-5M
20x10-5M
25x10-5M
30x10-5M
40x10-5M
50x10-5M
70x10-5M
80x10-5M
10x10-4M
(Io-I/Io) X 100
800
Where Io is the initial emission intensity and I is the observed
intensity after the addition of the analyte (anions). From this,
the quenching efficiencies were observed to be 97% and 87%,
respectively, for 10-3 M solutions of [Cr2O7]2– and [CrO4]2– ions.
The limit of detection (LOD) was calculated employing the
equation, LOD = 3σ/m ; where σ is the standard deviation of
the blank measurement and m is the slope of the linear
change of the luminescent intensity vs. analyte concentration
(supporting information, Figure S15, Table S3, S4). The limit of
detection was found to be 0.45 ppm (1.53 μM) and 0.70 ppm
(3.64 μM), respectively of dichromate and chromate ions.
From the LOD, it appears that compound 1 exhibits good
detection limits compared to some of the earlier reported
values in the literature.35,36,50 A PXRD study was carried out
after the sensing studies, which indicated structural integrity
600
400
200
0
400
500
Wavelength (nm)
600
of compound 1 (supporting information, Figure: S1). The
2–
The selective quenching of chromate and dichromate in recyclability of compound 1 for the sensing of CrO4 and
the presence of other ions in aqueous medium holds much Cr2O72– ions was also examined, which revealed that 1 retains
promise. As the selectivity of [CrO4]2– and [Cr2O7]2– ions have the sensing activity for at least 4 cycles (supporting
been established, we investigated the limits of the detection information, Figure: S14). The quenching of the luminescence
for these
was also examined using Stern-Volmer equation,
I0/I = 1+ KSV[Q],
where I0 and I are the emission intensities before and after the
addition of analyte, [Q] is the concentration of the analyte and
K
Blank
50x10-6M
10x10-5M
15x10-5M
20x10-5M
30x10-5M
40x10-5M
50x10-5M
70x10-5M
90x10-5M
10x10-4M
12.5x10-4M
15x10-4M
17.5x10-4M
20x10-4M
22.5x10-4M
25x10-4M
-
1 + CrO42
(b)
800
SV is the Stern-Volmer constant. For [CrO4]2– and [Cr2O7]2– at
low concentrations the Stern−Volmer plots exhibits a linear
behavior, deviation from linearity was observed at higher
concentrations (Supporting Information, Figure S15). The
linear part is due to the static quenching which can be
attributed to the formation of a non–emissive ground state
complex between the analyte and 1. The nonlinearity could be
due to the self–adsorption or excited state energy transfer.
The Stern-Volmer quenching constants (KSV) calculated by
fitting the linear part in the Stern-Volmer plots (Figure 5),
gave values of 7.8 × 103 M−1 and 3.1 × 103 M−1 for [Cr2O7]2– and
[CrO4]2–, respectively. This suggests a strong quenching effect
for 1 by [Cr2O7]2–/[CrO4]2− ions in the aqueous medium.
600
400
200
0
400
500
Wavelength (nm)
600
Figure 4. The change in photoluminescence intensity of 1 in
aqueous solution at different concentrations of (a) Cr2O72− and
2−
(b) CrO4
.
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[Cr2O7]2−/[CrO4]2− and the N−H group present in the
framework. The hydrogen bond interactions may reduce the
electron density on the organic ligand of 1 and lead to the
reduction in the ligand electronic transition resulting in
View Article Online
DOI: 10.1039/C9NJ03224J
2.7
2.4
2.1
1.8
1.5
1.2
0.9
1
2
Cr
O
,
K
= 7800 M
2
7
sv
, K = 3140 M
sv
1
2
4
CrO
possible quenching of the luminescence intensity.
A
combination of resonance energy transfer from 1 to the
[Cr2O7]2−/[CrO4]2−, absorption of excitation energy by
[Cr2O7]2−/[CrO4]2−, as well as possible hydrogen bonding
interactions between the anions and 1 would be responsible
for the observed quenching behaviour.
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Knoevenagel Condensation Reaction
0.00
0.05
0.10
0.15
0.20
Knoevenagel condensation reaction involves the reaction
between the carbonyl compounds and activated methylene
compounds in the presence of a weak base as a catalyst (
Concentration (mM)
Figure 5. Stern−Volmer plots for 1 with Cr2O72− and CrO42− at Supporting information, Figure S17). It is known that,
low concentrations. The solid lines represent the linear fits Knoevenagel condensation reaction is facilitated by base
into the Stern−Volmer equation.
catalysts.51–63 The catalyst generally used in this reaction is a
mixture of amine (primary or secondary) and their ammonium
The observed quenching effect was rationalized by salt52 (base catalysed) and Al(III),57 Ga(III),58 In(III),59 Ni(II),60
investigating the UV–Vis spectra of the anions and 1. It is clear Cu(II),61 Zn(II)62 and lanthanide63 centers. Many metal-organic
that, [CrO4]2– and [Cr2O7]2– ions have a significant overlap framework compounds (MOFs) have been employed as a
between the absorption bands of the ions with the emission catalyst for the Knoevenagel condensation reaction.57-63 In the
spectra of compound 1 (Figure 6). The overlap indicates a present study, the presence of Cd(II) as well as the –NH group
possible route for the resonance energy transfer from 1 to the from the oxamato unit of the ligand would help in the
anions, which would be responsible for the quenching of the Knoevenagal condensation reaction.
luminescence intensity.
Our catalytic studies indicate a near quantitative yield for
the different derivatives employed in the present study (Table
1
2). The products are characterized by H NMR spectroscopy
(Supporting information, Figure: S19, S20, S21, S22, S23, S24).
A blank reaction (without 1) carried out under identical
conditions did not give the desired product, suggesting that
the formation of benzilidine derivative is due to the presence
of 1. In addition, two sets of reaction were also carried out
under the same condition employing Cd(NO3)2.4H2O and the
ligand, H4L, using benzaldehyde as the substrate. A yield of ~
64% and ~ 12% were observed for Cd(NO3)2.4H2O and H4L,
respectively. This study suggests that the Cd2+ ion along with
the presence of -NH groups would be catalysing the reaction.
The observed higher yield of the product obtained with 1 as
the catalyst suggests that the -NH group of the oxamate may
be important in the Knovenegal condensation reaction. A Cd
0.8
1
2-
CrO4
2-
Cr2O7
0.6
0.4
0.2
300
400
500
600
Wavelength (nm)
Figure 6. Figure shows the absorption bands of [Cr2O7]2- along based MOF, exhibiting good catalytic activity for the
with the emission spectra of 1. Note the considerable overlap Knoevenagel condensation involving the amide group has also
(see text).
been known.64,65 It has been suggested that the –NH moiety
of the amide group could act as a hydrogen donor and C=O
The [Cr2O7]2– and [CrO4]2– ions exhibit a wide absorption in moiety of the amide group could act as an electron donor for
the range of 230 to 440 nm, which overlaps the absorption the base catalytic interaction.66-68 In 1, we have the –NH group
band of 1 (320 nm) (Supporting Information, Figure S16). The of the oxamate group as the hydrogen donor and the oxygen
[Cr2O7]2−/[CrO4]2− ions may also compete with 1 for the of the –C=O group (electron donor) can interact with the
absorption of the excitation energy which would also reduce methylene proton enhancing the catalytic activity. The
the intensity of absorption of 1. This would result in the possible mechanism of Knoevenegal condensation reaction
quenching of the luminescence of 1. In addition to these two involving Cd metal centers in framework compounds has been
observations, the quenching behaviour can also be attributed well understood and established.69 We believe that the same
to the possible hydrogen bond interactions between mechanism would be applicable in this case as well. Thus, the
6 | J. Name., 2012, 00, 1-3
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In conclusion, a new three-dimensionally extended
Table 2. The products of the Knoevenagel condensation Cd(II) based inorganic-organic hybrid, [Cd(H2L)(H2O)] {where,
View Article Online
DOI: 10.1039/C9NJ03224J
reaction between malononitrile and various derivatives of H2L
aromatic aldehydes.
=
4,4ʹ-sulfonylbis(phenyl)bis(oxamate)} has been
prepared and its structure determined by single crystal
methods. The strong luminescence exhibited by the
compound was exploited for the detection of highly toxic
chromate and dichromate anions in aqueous medium with
good selectivity, recyclability and sensitivity under low
concentrations (in ppm level). Compound 1 was found to be
H
H
Catalyst
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59
60
NC
CN
+
R
O
Neat, 60°C
R
NC
% Yield
a
good catalyst for the base catalysed Knoevenagel
condensation reactions with good yields and recyclability.
S.
Reactant
Product
No.
1
H
H
O
97
CN
NC
Conflicts of Interest
“The authors declare no conflicts of interest to declare”.
NO2
H
NO2
2
3
99
98
H
O
CN
NC
Acknowledgements
H
H
O
CN
NC
NC
SN thanks the Science and Engineering Research Board
(SERB), Government of India for award of the J. C. Bose
national fellowship. SN also thanks Council of Scientific and
Industrial Research (CSIR) for a research grant. TK thanks
Government of India for the award of D. S. Kothari
postdoctoral fellowship. AKJ thanks Indian institute of
Science, Bangalore for the award of a post–doctoral
fellowship. SN also thanks the JSPS for a visiting fellowship.
NC
H
4
5
6
H
O
> 99
98
O2N
O2N
CN
NC
H
O
H
Cl
Cl
CN
NC
Notes and references
H
H
98
Br
Br
1. Metal Organic Frameworks: Design and Applications,
Ed. L.R. MacGillvray, 2010, Wiley.
2. Metal-Organic Frameworks as Heterogeneous
Catalysts: Eds. F.X. Llabres, I. Xamena and J. Gascon,
2013, RSC Publishing.
O
CN
NC
metal ion (Cd2+) would interact with the carbonyl group of the
aldehyde enhancing the electrophilic character of the
carbonylic carbon favouring the attack from the
malononitrile. Similarly, the cyano group of malononitrile can
also interact with the metal center enhancing the acidity of
the methylene protons. In addition, the presence of oxamato
group (basic site) can help in the abstraction of the methylenic
proton from malononitrile generating the nucleophile
(Supporting information, Figure S17), which would react with
the carbonyl group of the aldehyde forming the C–C bond. The
powder X-ray diffraction pattern after three cycles of the
catalytic study indicated that the compound retains the
crystallinity (Supporting Information, Figure S18a). The
recyclability studies also indicated considerable yield of > 90%
even after the 4th cycle (Supporting Information, Figure S18b).
3. Metal-Organic
Frameworks
(MOFs)
for
Environmental Applications, Ed. S. Ghosh, 2019,
Elsevier.
4. Metal-Organic Frameworks, Chem. Rev., 2012, 112,
673 – 1268.
5. Metal-Organic Frameworks – Promising Solid State
Porous Materials in 21st Century, J. Solid State Chem.,
2015, 223, 1-156.
6. New Generations of Porous Metal-Organic
Frameworks, Eds. S. Kaskal, R. Fischer and S.
Kitagawa, Microporous and Mesoporous Mater.,
2015, 216, 1 – 224.
7. The new age MOFs and of their porous related solids,
Eds. G. Maurin, C. Serre, A. Coper and G. Ferey,
Chem. Soc. Rev., 2017, 46, 3104 – 3356.
8. Metal-Organic Frameworks, Adv. Mater., 2018, 30.
9. Metal-Organic Frameworks heading towards
Applications, Eur. J. Inorg. Chem., 2016, 27, 4265 –
4529.
Conclusions:
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Page 8 of 10
ARTICLE
10. C.H. Hendon, A.J. Reith, A.D. Korzynshi and M. Dinca,
Journal Name
1
2
3
4
5
6
7
8
34. S. Sahu, U.K. Sahu, R.K. Patel, J. Chem. Eng. Data,
View Article Online
DOI: 10.1039/C9NJ03224J
ACS Central Sci., 2017, 3, 554 – 563.
11. X.J. Kong, T. He, Y.Z. Zhang, X.Q. Wu, S.N. Wang,
M.M.Xu, G.R. Si and J.R. Li, Chem. Sci., 2019, 10, 3949
– 3955.
12. Q. Li, M.H. Yu, J. Xu, A.L. Li, T.L. Hu, X.H. Bu, Dalton
Trans., 2017, 46, 3223 – 3228.
13. F.A.A. Paz, J. Klinowski, S.M.F. Vilela, J.P.C. Tome,
Chem. Soc. Rev., 2011, 41, 1088 – 1110.
14. O. Kahn, Acc. Chem. Res., 2000 33, 647 – 657 and the
references therein.
15. C.Q. Wan, T.C.W. Mak, New. J. Chem., 2011, 35, 319.
16. R.A.A. Cassaro, S. Ciatinni, S. Soriano, H.S. Amorium,
N.L. Speziali, M. Andruh and M.G.F. Vaz, Cryst.
Growth Des., 2013, 13, 2711 – 2715.
17. R.A.A. Cassaro, J.A.L.C. Resende, S. Santos Jr., L.
Sorace, M. Andrih and M.G.F. Vaz, CrystEnggComm.,
2013, 15, 8422 – 8425.
18. R.J. Brout, L. Robison, Z. Chen, T. Islamoglu and O.M.
Farha, Trends in Cgem., 2019, 1, 304 – 317.
19. L. Wang, G. Fan, X. Xu, D. Chen, L. Wang, W. Shi and
P. Cheng, J. Mater. Chem. A, 2017, 5, 5541 – 5549.
20. P. Yunhong, X. Li, Q. Xia and J. Wu, The Chem. Engn.
J., 2018, 337, 351 – 371.
21. S. Dhaka, R. Kumar, A. Deep, M.B. Kurade, S.-W. Ji
and B.-H. Jeon, Coord. Chem. Rev., 2019, 380, 330 –
352.
22. K. Vellingiri, J.E. Szulejko, P. Kumar, E.E. Kwon, K.-H.
Kim, A. Deep, D.W. Boukhvalov and R.J.C. Brown, Sci.
Rep., 2016, 6, Art. No. 27813.
2019, 64, 1294–1304.
35. A.K. Jana, T. Kundu, S. Natarajan, Crystal Growth and
Design, 2016, 16, 3497-3509.
36. S-N. Zhao, G. Wang; D. Poelman, P. V. D. Voort, Materials
(Basel), 2018, 11, Art No. 572.
37. P. Mahata, A. Sundaresan and S. Natarajan, Chem.
9
Commun., 2007, 4471 – 4473.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
38. P. Mahata, S. Natarajan, P. Panissod and M. Drillon,
J. Am. Chem. Soc., 2009, 131, 10140 – 10150.
39. S. Bhattacharya, M. Gnanavel, A. J. Bhattacharyya
and S. Natarajan, Crystal Growth & Design, 2014, 14,
310 – 325.
40. S. Bhattacharya, A.J. Bhattacharyya and S. Natarajan,
Inorg. Chem., 2015, 54, 1254 – 1271.
41. C.L. Muenchenstein, H.R.B. Gelterkinden and M.D.
Frenkendorf, FR 1567434, 1969; US 3639249, 1972.
42. Nakamoto, K. Infrared and Raman Spectra of
Inorganic and Coordination Compounds: Applications
in Coordination, Organometallic, and Bioinorganic
Chemistry; Wiley: New York, 2009.
43. SMART (V 5.628), SAINT (V 6.45a), XPREP, SHELXTL; Bruker
AXS Inc.: Madison, Wisconsin, USA, 2004.
44. G. M. Sheldrick, Siemens Area Correction Absorption
Correction Program; University of Göttingen: Göttingen,
Germany, 1994.
45. G. M. Sheldrick, SHELXS-97, Program for Crystal Structure
Solution and Refinement; University of Göttingen:
Göttingen, Germany, 1997.Å
46. L. J. Farrugia, J. Appl. Crystallogr., 1999, 32, 837−838.
47. C. B. Johanna, J. I. Kim Amy, E. deVries, S. E. Shaner, B.-M.
Lovaasen, Inorg. Chem., 2017, 56, 8212-8222.
23. C.-H. Chen, X.-S. Wng, L. Li, Y.-B. Huang and R. Cao,
Dalton Trans., 2018, 47, 3452 – 3458.
24. Q. Tang, L. Liu, Y. Liu, S. Li, L. Zhang, Z. Shi and Z.
Zheng, Inorg. Chem., 2013, 52, 2799 – 2801.
25. D.T. Sun, L. Peng, W.S. Reeder, S.M. Moosavi, D.
Tiana, D.K. Britt, E. Oveisi and W.L. Queen, ACS Cent.
Sci., 2018, 4, 349 – 356.
26. N. Rudd, H. Wang, E. Fuentes-Fernandez and S.J.
Teat, ACS Appl. Mater. & Interfaces, 2016, 8, 30294 –
30303.
48. L. Liu, J. Wang, C. Xu, Y. Zhang, Y. Li, C. Li, J. Wang, Y. Zhang,
J. Mol. Struc., 2019, 11, 7-14.
49. A. Majumder, G. M. Rosair, A. Mallick, N. Chattopadhyay,
S. Mitra, Polyhedron, 2006, 25, 1753–1762.
50. A.K. Jana, T. Kundu, S. Natarajan, Crystal Growth and
Design, 2016, 16, 3497-3509.
51. L. Zhu, X-Q. Liu, H-L. Jiang and L-B. Sun, Chem. Rev., 2017,
117, 8129 – 8176.
52. B. List, Angew. Chem. Int. Ed. 2010, 49, 1730 – 1734.
53. E.V. Delessandro, H.P. Colin, L.G.L. Guimaraes, M.S. Valle
and J.P. Pliego Jr., J. Phys. Chem. B., 2017, 121, 5300 – 5307.
54. H. Ishitni, Y. Saito, Y.Nakamura, W-J. Yoo and S. Kobayashi,
Asian J. Org. Chem., 2018, 7, 2061 – 2064.
55. P-Q. Huang, W. Ou, K-J. Xiao and A-E. Wang, Chem.
Commun., 2014, 50, 8761 – 8763.
56. A. Karmakar, G. M. D. M Rúbio, F. M. C. Guedes da Silva, A.
J. L. Pombeiro, ChemistryOpen. 2018, 7, 865–877.
57. A. Dhakshinamoorthy, N. Heidenreich, D. Lenzenb, N.
Stock, CrystEngComm. 2017, 19, 4187–4193.
27. M. Huang, S.B. Mishra, S. Liu, ACS Sustainable Chem.
Eng., 2017, 5, 8127–8136.
28. D. Park, S.-Y. Yun, J.H. Jo, J.M. Park, Ind. Eng. Chem.
Res., 2006, 45, 5059–5065.
29. K. Gong, Q. Hu, L. Yao, M. Li, D. Sun, Q. Shao, B. Qiu
and Z. Guo, ACS Sustainable Chem. Eng., 2018, 6,
7283–7291.
30. D. Wang, G. Zhang, Z. Dai, L. Zhou, P. Bian, K. Zheng,
Z. Wu and D. Cai, ACS Appl. Mater. Interfaces, 2018,
10, 18316–18326.
31. K. Salnikow and A. Zhitkovich, Chem. Res. Toxicol.,
2008, 21, 28–44
32. R. Codd, P.A. Lay, Chem. Res. Toxicol., 2003, 16, 881–
892.
58. Y. Ogiwara, K. Takahashi, T. Kitazawa, N. Sakai, J. Org.
Chem., 2015, 80, 3101−3110.
59. S. Hasegawa, S. Horike, R. Matsuda, S. Furukawa, K.
Mochizuki, Y. Kinoshita, S. Kitagawa, J. Am. Chem. Soc.,
2007, 129, 2607−2614.
60. S. Aryanejad, G. Bagherzade and A. Farrokhi, App.
Organometal. Chem., 2018, 32, e3995.
33. J. Tan, Y. Song X. Huang, L. Zhou, ACS Omega, 2018,
3, 17309–17318.
8 | J. Name., 2012, 00, 1-3
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61. A. Karmakar, A. Paul, K. M. Mahmudov, M. F. C. Silva, A. J.
ARTICLE
1
2
3
4
5
6
7
8
View Article Online
DOI: 10.1039/C9NJ03224J
L. Pombeiro, New J. Chem., 2016, 40, 1535−1546.
62. H. He, Q-Q. Zhu, F. Sun and G. Zhu, Crystal Growth &
Design., 2018, 18, 5573 – 5581.
63. Y. Zhang, Y. Wang, L. Liu, N. Wei, M-L. Gao, D. Zhao and Z-
B. Han, Inorg. Chem., 2018, 57, 2193 – 2198.
64. H-C. Kim, S. Huh, S-J. Kim, Y. Kim, Sci Rep, 2017, 7, 17185.
65. A. Karmakar, G. M. D. M Rúbio, F. M. C. Guedes da Silva, A.
J. L. Pombeiro, ChemistryOpen. 2018, 7, 865–877.
66. C. M. Lee, W. D. Kumler, J. Am. Chem. Soc., 1962, 84,
571−578.
67. H. A. Bent, Chem. Rev., 1968, 68, 587−648.
68. P. L. Huyskens, J. Am. Chem. Soc., 1977, 99, 2578−2582.
69. H-C. Kim, S. Huh, S-J. Kim, Y. Kim, Sci Rep, 2017, 7, 17185.
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Table of Content Entry
5
6
7
8
9
Blank
1 + Cr2O72
(a)
25x10-6
50x10-6
75x10-6
10x10-5
15x10-5
20x10-5
25x10-5
30x10-5
40x10-5
50x10-5
70x10-5
80x10-5
M
M
M
M
M
M
M
M
M
M
M
M
800
600
400
200
0
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
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51
52
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55
56
57
58
59
60
10x10-4
M
400
500
600
Wavelength (nm)
A three-dimensional inorganic-organic hybrid, Cd(H2L)(H2O)], was shown to detect highly toxic chromate and
dichromate anions in aqueous medium with good selectivity, recyclability and sensitivity under low
concentrations (in ppm level). The compound was also a good catalyst for the base catalysed Knoevenagel
reactions with good yields and recyclability.