Green synthesis and characterization of novel Mn-MOFs with catalytic and antibacterial potentials

Article abstract of DOI:10.1039/c9nj04977k

This study focused on the synthesis of a new manganese-based metal-organic framework and the investigation of its application aspects. A Mn-MOF nanostructure, namely UoB-4, was prepared using a Schiff base organic linker (H₂bbda: 4,4′-[benzene-

Full text of DOI:10.1039/c9nj04977k

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Green synthesis and characterization of
novel Mn-MOFs with catalytic and
Cite this:DOI: 10.1039/c9nj04977k
antibacterial potentials
a
Sima Aryanejad,
Ghodsieh Bagherzade*a and Maryam Moudib
This study focused on the synthesis of a new manganese-based metal–organic framework and the
investigation of its application aspects. A Mn-MOF nanostructure, namely UoB-4, was prepared using a
Schiff base organic linker (H2bbda: 4,40-[benzene-1,4-diylbis(methylylidenenitrilo)]dibenzoic acid) under
ultrasound irradiation. The structure of the as-synthesized UoB-4 was characterized via PXRD, TGA,
CHNO, ICP, TEM, BET, and FTIR techniques. The catalytic performance of UoB-4 was evaluated in the
reactions of Hantzsch for the synthesis of 1,4-dihydropyridines and alcohol oxidation. The products of
both reactions were obtained with high yields under green conditions. A recycling study of UoB-4
revealed that it can be used as a recoverable stable heterogeneous catalyst without significant loss in
performance. In the next step of this study, the efficiency of UoB-4 was evaluated, showing the
biological potential as an antibacterial agent. Its antibacterial activity was tested against Bacillus cereus
and Escherichia coli in vitro by determining the diameter of the inhibition zone in the disc diffusion method.
The results indicated the acceptable activity of UoB-4 against both Gram-positive and Gram-negative
bacteria. The antibacterial activity of UoB-4 was greater towards Gram-positive bacteria (B. cereus)
compared to that towards Gram-negative one (E. coli). These results open the mentality that there is the
synthesis possibility of Mn-based MOFs with various application aspects and high performance.
Received 2nd October 2019,
Accepted 16th December 2019
DOI: 10.1039/c9nj04977k
rsc.li/njc
different applications of MOFs, the catalytic activity is the most
rapidly growing one. The main reasons for this are the intrinsic
1 Introduction
Metal–organic frameworks, sometimes called multidimensional properties of MOFs such as high density, uniform dispersion of
porous coordination polymers, compose a large and successively active sites, and readily accessible active sites due to the highly
expanding group of micro- and mesoporous materials. In these porous structure that greatly facilitates the diffusion and transport
porous compounds, crystalline three-dimensional structures are of the substrates and products. Therefore, MOFs effectively
covalently formed by combining inorganic parts (metal ions) incorporate the advantages of both homogeneous and hetero-
with organic parts (linkers).1,2 The obvious feature of MOFs is geneous catalysts, with amazing reaction efficiency and
that they exhibit the greatest flexibility of structure and property recyclability.6
compared to other crystalline nanoporous materials such as
Multi-component reactions in one-pot syntheses play an
zeolites and mesoporous molecular sieves.3 The main reason is important role in modern synthetic chemistry since they not
that MOFs benefit from the combination of inorganic and only reveal a higher selectivity and atom economy, but also
organic structural building units and the feasibility of modifications allow the construction of molecules of more varieties and
(both before and after the synthesis). Actually, MOFs are the bridge complexities.7 Furthermore, multicomponent reactions are
of the gap between pure organic and inorganic materials; accompanied by many advantages such as the simple procedure,
hence, they are the interesting materials with numerous energy saving and reduced waste.8,9 Multicomponent reactions in
potential applications including gas adsorption/separation, making heterocyclic compounds are powerful tools in the drug-
sensing, biomedical applications, and catalysis.4,5 Among these discovery process as they can offer the suitable synthesis of
libraries of drug-like compounds in a single procedure.10 The
one-pot multicomponent condensation reaction between aldehyde
aromatic, b-ketoesters and ammonium acetate has been recog-
nised as a suitable synthesis method of 1,4-dihydropyridine
(1,4-DHP). They have attracted remarkable interest because of
their promising pharmacological and therapeutic activities
a Department of Chemistry, Faculty of Sciences, University of Birjand, Birjand,
97175-615, Iran. E-mail: gbagherzade@gmail.com, bagherzade@birjand.ac.ir;
Fax: +98 56 32345192; Tel: +98 56 32345192
b Department of Biology, Faculty of Sciences, University of Birjand, Birjand,
97175-615, Iran
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such as serving as integral backbones of several calcium UoB-4 exhibits a strong antibacterial activity against the growth
channel blockers, vasodilation, bronchodilation, and gero- of microorganisms.
protective, hepatoprotective, and antidiabetic functions.11,12
In addition, 1,4-DHPs are already commercial products and
among the most widely used drugs (e.g. amlodipine,13
isradipine,14 lacidipine,15 nitrendipine,16 nifedipine17 and
nimodipine B18). Due to the aforementioned advantages of
1,4-DHPs in the biological and chemical worlds, many efforts
have already been made toward the synthesis of these
compounds.19–21 Nevertheless, the optimization of 1,4-DHP
preparation can be important and should be predominantly
based on the development of more effective and selective
catalysts. According to the extraordinary properties of MOFs,
they can help a lot for the progress in the synthesis of useful
chemical compounds; however, there have been only a few
reports about the usage of MOFs as heterogeneous catalysts for
the preparation 1,4-DHPs. In 2014, Morsali and co-workers
reported the utilization of IRMOF-3 as a catalyst in the Hantzsch
condensation reaction for the synthesis of 1,4-DHPs.22 Recently,
the same research group has also presented their studies on the
use of Cd-MOFs as reusable catalysts.23 In another search,
Hajiashrafi et al. have developed a new catalytic system based
on Er-MOFs that displayed excellent selectivity and good yield for
this reaction.24 With respect to the significance of 1,4-DHPs as
pharmaceutical compounds and the few reports on MOFs that
have been used for their preparation, this research work aimed
at the introduction of a new MOF as a heterogeneous catalyst for
the improvement of 1,4-DHP synthesis methods. Therefore, we
have herein synthesized novel, flexible, microporous Mn-MOF
nanostructures (UoB-4) under ultrasound irradiation as a
procedure, which better meets the ecological requirements.
In addition, the results indicated that Mn-MOFs can be used
as suitable, efficient and green catalysts for the Hantzsch
condensation of aldehydes and b-ketoesters with ammonium
acetate without any solvent, salts and additives, with good to
excellent yields of DHPs.
2 Experimental
2.1 Materials and measurement
All the chemicals were obtained from a commercial source and
used without further purification. The ligand (H2bdda: 4,40-
[benzene-1,4-diylbis-(methylylidenenitrilo)]dibenzoic acid) was
synthesized according to our reported procedure.25 Elemental
analyses of C, H, N, and O were performed using a PerkinElmer
CHNS-O elemental analyzer. Inductively coupled plasma atomic
emission spectroscopic (ICP-AES) analysis was conducted using
an OPTIMA 7300DV. Thermogravimetric analysis (TGA) was
obtained using a Shimadzu Thermoanalyzer between 30 and
710 1C at a heating rate of 10 1C minꢀ1 in a nitrogen atmosphere.
Infrared (IR) samples were prepared as KBr pellets, and the
spectra were recorded in the range of 400–4000 cmꢀ1 using a
NICOLET system. Transmission electron microscopic (TEM)
analysis was performed using a Philips CM120 electron micro-
scope. The Brunauer–Emmett–Teller (BET) surface area and pore
sizes of the UoB-4 were measured using N2 adsorption/desorption
isotherms at 77 K using a Belsorp mini II instrument. Powder
X-ray diffraction (PXRD) was conducted using an X’Pert Pro
MPD diffractometer equipped with a Cu-Ka (l = 1.54060 Å)
radiation source between 2y = 21 and 2y = 50.01. The progress
of the reactions and purity of the products were analysed by
TLC on silica gel polygram SILG/UV254 plates. 1H-NMR (CDCl3)
spectra were recorded using a Bruker UltraShieldt spectrometer
at 400 MHz.
2.2 Synthesis of nanoscale Mn-MOFs (UoB-4)
At first, NaOH 10% (1 mL) was added to an H2bdda (0.372 g,
1 mmol) solution in deionized water (20 mL), whereupon the
system was stirred for 5 minutes at room temperature to obtain
a clear yellow solution. Then, a solution of Mn(acac)2 (0.704 g,
2 mmol) in deionized water (10 mL) was added dropwise to the
obtained mixture under ultrasonic irradiation at room tempera-
ture for 15 minutes and was kept under the same condition for
30 minutes. The resulting green precipitate was collected by
centrifugation and washed three times with ethanol. The obtained
products were dried in an oven at 100 1C and made Mn3(bdda)2
acac2ꢁ5H2O. Anal. calcd for: C: 54.22%; H: 4.8%; N: 4.68% and
Mn: 13.8%; found: C: 54.35%; H: 3.8%; N: 5.48% and Mn: 13.79%.
In the course of our continuing investigation on the catalytic
activity of MOFs, the successful use of different MOFs with a
Schiff base linker to catalyze alcohol oxidation reactions under
green conditions was reported.25–27 In this study, the catalytic
use of UoB-4 nanostructures has also been explored in the
catalytic oxidation of primary/secondary alcohols to afford
corresponding carbonyl compounds with a high percentage of
conversion and good selectivity. The obtained results exhibited
that UoB-4 nanostructures are high-efficiency recyclable versatile
heterogeneous catalysts for the Hantzsch and alcohol oxidation
reactions under mild and green conditions.
2.3 The general catalytic Hantzsch reaction procedure
As mentioned above, the excellent properties of MOFs
A mixture of aldehyde (1.0 mmol), ammonium acetate
enhance their application potentials in various fields. Our (1.2 mmol), 1,3-dicarbonyl (2.0 mmol), and UoB-4 (1.5 mol%)
interest in expanding the functional aspects of MOFs led to without any organic solvents as green conditions was stirred at
the investigation of UoB-4 efficiency in the biomedical field as 65 1C for an appropriate time. The reaction progress was
an anti-bacterial reagent. For this purpose, commercially avail- surveyed by thin-layer chromatography (TLC) using EtOAc/
able strains of Bacillus cereus (Gram-positive) and Escherichia n-hexane (1 : 3) as the eluent. After completion of the reaction,
coli (Gram-negative) were used, and the anti-bacterial perfor- the catalyst was removed by centrifugation. A pure product was
mance of UoB-4 nanostructures was investigated based on the obtained by recrystallization from alcohol–water. The products
standard zone of the inhabition test. The results indicated that were identified by comparing their melting points with those
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previously reported because the products are known compounds. nanostructures against Bacillus cereus (ATCC 13061) and Escherichia
The spectral data for the selected compounds are as follows:
coli (ATCC 25922DQ) as model Gram (+) and Gram (ꢀ) bacteria.
Diethyl 2,6-dimethyl-4-phenyl-1,4-dihydropyridine-3,5-dicarb- First, the bacterial strains were cultivated on nutrient agar plates at
oxylate. Pale yellow solid; IR (KBr, cmꢀ1) n: 3340 (N–H str), 3034 37 1C for 24 h and then stored at 4 1C for future use. Solid agar
(Ar–H), 2953 (C–H str of CH3), 1755 (CQO, ester), 802 (Ar–H). nutrient plates were prepared by dissolving 15.0 g Lꢀ1 agar powder,
1H NMR (400 MHz, CDCl3): d = 7.30–7.28 (2H, m, Ar–H), 7.23–7.19 5.0 g Lꢀ1 tryptone, 2.5 g Lꢀ1 yeast extract, and 1.0 g Lꢀ1 glucose in
(2H, m, Ar–H), 7.15–7.11 (1H, m, Ar–H), 5.58 (1H, brs, NH), 5.00 deionized water in a 500 mL capacity Erlenmeyer flask. The
(1H, s, aryl –CH), 4.15–4.03 (4H, m, –CH2CH3), 2.34 (6H, s, –CH3), obtained mixture was heated and stirred until the agar dissolved.
1.23 (t, J = 7.2 Hz, 6H, –CH2CH3); 13C NMR (100 MHz, CDCl3) d: For adjusting the pH of the solution to 7.0 ꢂ 0.1, sodium hydroxide
167.6, 147.7, 143.7, 128.0, 127.8, 126.1, 104.2, 59.7, 39.6, 19.6, 14.2. or hydrochloric acid was utilized. After that, the sterile nutrient agar
Diethyl-4-(4-methoxyphenyl)-2,6-dimethyl-1,4-dihydropyridine- was poured, cooled to room temperature, and then was autoclaved
3,5-dicarboxylate. Pale yellow solid; IR (KBr, cmꢀ1) n: 3352 (N–H str), at 121 1C under a pressure of 15 psi for 20 minutes.
3026 (Ar–H), 2961 (C–H str of CH3), 1742 (CQO, ester), 823 (Ar–H).
A fresh bacterial suspension of Bacillus cereus and Escherichia
1H NMR (400 MHz, CDCl3) d: 7.18 (2H, d, J = 8.4 Hz, Ar–H), 6.73 (2H, coli (200 mL, containing 5 ꢃ 107 colony-forming units (CFU) mLꢀ1
)
d, J = 8.4 Hz, Ar–H), 5.99 (1H, s, NH), 4.92 (1H, s, aryl –CH), 4.14–4.02 was spread on the prepared agar plates. The plates were dried, and
(4H, m, –CH2CH3), 3.73 (3H, s, –OCH3), 2.29 (6H, s, –CH3), 1.22 (6H, the holes (7 mm diameter) were punched with the sterile tip over
t, J = 7.2 Hz, –CH2CH3); 13C NMR (100 MHz, CDCl3) d: 167.7, 157.8, them. UoB-4 (1 mg) was directly disposed of onto the holes of agar
143.8, 140.3, 128.9, 113.1, 104.1, 59.6, 55.0, 38.6, 19.4, 14.2.
plates, after which the plates were incubated at 37 1C for 48 h. The
Diethyl-4-(4-chlorophenyl)-2,6-dimethyl-1,4-dihydropyridine- antibacterial activity was observed after incubating based on the
3,5-dicarboxylate. Pale yellow solid; IR (KBr, cmꢀ1) n: 3332 (N–H inhibition surrounding the spotted compound. The growth
str), 3074 (Ar–H), 2942 (C–H str of CH3), 1741 (CQO, ester), 837 inhibition zone was reported in centimeters, and the procedure
1
(C–Cl), 787 (Ar–H). H NMR (400 MHz, CDCl3) d: 7.21 (2H, d, J = was repeated two times.
8.4 Hz, Ar–H), 7.16 (2H, d, J = 8.4 Hz, Ar–H), 6.24 (1H, s, NH), 4.96
(1H, s, aryl –CH), 4.14–4.02 (4H, m, –CH2CH3), 2.28 (6H, s, –CH3),
3 Results and discussions
1.21 (6H, t, J = 7.2 Hz, –CH2CH3); 13C NMR (100 MHz, CDCl3) d:
3.1 Syntheses and characterization
167.5, 146.3, 144.3, 131.5, 129.3, 127.8, 103.4, 59.7, 39.1, 19.3, 14.1.
Ultrasound irradiation was used as a facile procedure for the
synthesis of UoB-4 nanostructures. The reaction of manganese(II)
acetylacetonate with H2bdda, which was synthesized according
to the procedure reported earlier, in the presence of water
and NaOH leads to the formation of [Mn3(bdda)2acac2ꢁ5H2O]
(Scheme 1).
Thermogravimetric analysis (Fig. 1a) indicated that dehydration
of UoB-4 nanostructures occurred at 300 1C with a weight loss of
6.66% (calcd: 6.53%). The weight loss has been followed by the
expulsion of organic components.
2.5 The general catalytic alcohol oxidation reaction procedure
In a typical experiment, UoB-4 nanostructures (3 mol%) and
TBHP (2 mmol) were placed in a vessel containing benzyl
alcohol (1 mmol) under solvent-free conditions. The reaction
mixture was vigorously stirred at 45 1C. Upon reaction comple-
tion, monitored by TLC, the catalyst was removed from the
mixture of reaction by centrifugation. The products were purified
on a silica gel plate to give pure products. For the identification
of the final products, their physical data were compared with
those of authentic samples, because all of them are known.
N2 adsorption–desorption measurement was performed to
evaluate the textural properties of UoB-4 nanostructures, and
the results are shown in Fig. 1b. The structure of UoB-4 exhibits
2.6 Anti-bacterial activity
The antibacterial test was conducted based on the disk diffusion the type IV isotherm with an H1 hysteresis loop, which is the
test28 to examine the antibacterial performance of UoB-4 typical characteristic of the material with cylindrical mesopores.
Scheme 1 Synthesis of UoB-4 nanostructures under ultrasonic irradiation in water as a solvent.
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Fig. 1 (a) TGA curve; (b) N2 adsorption–desorption isotherms; and (c) pore width of UoB-4 nanostructures.
Through the N2 isotherm, the specific surface area and pore
value were determined as 127 m2 gꢀ1 and 0.17 cm3 gꢀ1
,
respectively. Furthermore, the pore-size distribution, calculated
by Barret–Joyner–Halenda (BJH), revealed an approximately
narrow pore size distribution in the range of 2–10 nm with a
peak maximum of 8 nm (Fig. 1c).
The morphology of UoB-4 nanostructures was investigated
using the TEM images (Fig. 2a). The images exhibit that
nanoparticles are framework structures with uniform size and
morphology. Moreover, it can be obviously shown that the
UoB-4 nanostructures are monodispersed without any amorphous
components. The TEM images were used to draw the particle size
distribution, based on which the average diameter of nanostruc-
tures was obtained to be 59 nm (Fig. 2b).
The XRD pattern of UoB-4 nanostructures is illustrated
in Fig. 3. The sharp reflections appearing at the low angel
(2y o 10) confirmed a high degree of mesoscopic ordering. It is
Fig. 3 XRD pattern of UoB-4 nanostructures.
noteworthy that the XRD pattern of UoB-4 is similar to the for determining the coordination modes of carboxylate groups
reported simulated pattern of IRMOF-74.29 Therefore, it can be to metal.30 Thus, the carboxylate groups coordinated to Mn as
concluded that both the structures (UoB-4 & IRMOF-74) are a bridging mode based on the obtained Dn values. The O–H
isostructural.
vibration of adsorbed water and the C–O stretching appeared
More information about the structure of UoB-4 nanostruc- around 3350 and 1172 cmꢀ1, respectively.
tures was achieved using FT-IR spectra (Fig. 4). A broad and
strong peak at 3400 cmꢀ1 is attributed to the stretching vibra-
3.2 Catalytic activity
tions of the coordinated water molecules. Moreover, the band
3.2.1 Hantzsch reaction. The presence of azomethine
at 1690 cmꢀ1 established the presence of the coordinated group and metal–carboxylate in the UoB-4 nanostructure
acetylacetonate ligand. The asymmetric stretching of carboxylate caused to investigate its behavior as a catalyst in the synthesis
groups (–COO–) of UoB-4 appeared at 1595 and 1530 cmꢀ1 and of Hantzsch 1,4-dihydropyridines (Scheme 1). To optimize the
the symmetric stretching of carboxylate groups appeared at conditions of the catalytic reaction, benzaldehyde, ethyl aceto-
1399 cmꢀ1. The difference in the symmetric and asymmetric acetate and ammonium acetate were selected as model substrates.
stretching vibrations of carboxylate groups (Dn) can be applied Several parameters such as the nature of solvent, temperature and
the amount of catalyst were investigated and the obtained results
are presented in Table 1 (Scheme 2).
First, the effect of the nature of the solvent on the yield of
1,4-DHPs was studied in the presence of UoB-4 in various
solvents (entries 1–4). The model reaction occurred more
efficiently under solvent-free conditions with respect to the
solvent medium, as the catalysts and reagents are in more
significant proximity to each other when a solvent is not
employed. Consequently, performing the reaction under these
conditions is accompanied by advantages such as simple
reactors, and simple and efficient workup procedures that are
often more environmentally friendly. Next, the effect of the
Fig. 2 (a) TEM image of the 4UoB-4 nanostructures and (b) particle size
distribution histogram.
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Fig. 4 (a) FTIR spectrum of UoB-4 and (b) the suggested geometry around the Mn center.
Table
1
Screening of factors in the synthesis of 1,4-DHPs via the
(entries 10–13). The product yield increased from 40 to 97%
in the presence of UoB-4 when the temperature of the model
reaction changed from room temperature to 65 1C. However,
when the reaction temperature was further increased to over
85 1C, the reaction efficiency did not change significantly.
With the experimental results in hand, the scope of the
Hantzsch reaction was developed using different aldehydes
with electron-donating/withdrawing substituent groups and
b-ketoesters under optimized reaction conditions. All reactions
proceeded smoothly to afford the corresponding 1,4-DHPs
within the short reaction time in good to high yields (Table 2).
Hantzsch reaction by UoB-4 nanostructuresa
Entry
Solvent
Temp. (1C)
Catalyst (mol%)
Yieldb (%)
1
2
3
4
5
6
7
8
H2O
EtOH
EtOAc
—
—
—
—
—
—
—
65
65
65
65
65
65
65
65
65
r.t.
45
65
80
1.5
1.5
1.5
1.5
—
0.5
1
1.5
2
1.5
1.5
1.5
1.5
43
54
40
97
10
30
44
97
97
40
60
97
98
9
10
11
12
13
—
—
—
Table
2
Preparation of 1,4-DHPs via the Hantzsch reaction in the
presence of the UoB-4 nanocatalyst
a
Reaction conditions: benzaldehyde (1 mmol), ethyl acetoacetate
b
(2 mmol), urea (1.2 mmol), 30 min. Yields of product isolated.
M.p.b (1C)
Time (min) Yielda (%) Found
Reported
Entry R1
R2
Et
Scheme 2 Synthesis of 1,4-DHP by UoB-4 nanostructures.
1
2
H
30
20
20
30
40
35
25
40
97
96
94
85
90
93
91
81
95
97
96
84
81
90
157–158 157–159
134–136 135–136
165–166 165–167
139–141 139–140
143–145 145
144–145 144–146
168–170 169
156–158 142
195–197 196–197
168–169 168
4-NO2 Et
3
4
4-CN
4-Me
Et
Et
amount of catalysts on the yield of 1,4-DHPs was studied
(entries 5–9). Initially, when the model reaction was carried
out in the presence and absence of UoB-4 nanostructures, the
yield of product was 97% and 10%, respectively. The results
indicated that UoB-4 as a catalyst is very effective to promote
the given reaction. Upon increasing the amount of UoB-4 from
0.5 to 1.5 mol%, the yield of the product was improved, whereas
a further increase of up to 2 mol% had no impressive effect on
it. The effect of temperature on the reaction efficiency was
also investigated by carrying out the model Hantzsch reaction
5
6
4-OMe Et
4-Cl Et
7
8
2-NO2 Et
2-OMe Et
9
Ph Me 30
4-NO2 Me 25
Me 25
Me 35
4-OMe Me 35
10
11
12
13
14
4-CN
4-Me
226–227 225–227
172–174 175
186–188 188
4-Cl
Me 30
197–199 198
a
b
Isolated yields. The physical data of all products were compared
using optimal amounts of UoB-4 at different temperatures with those reported in the literature.24,31,32
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Table 4 Screening reaction conditionsa
It could be noticed that the aromatic aldehyde electron-
withdrawing substituent groups (NO2, CN) were fairly more
active than the electron-donor ones (OMe, Me) in terms of the
reaction time or the product yield. It is also notable that
the sterically demanding ortho-substituted aromatic aldehydes
afforded the corresponding products in high yields (entries 7
and 8). These observations strongly establish excellent efficiency
and powerful activity of the present catalyst for a broad range of
substrates to produce different derivatives of 1,4-DHPs, which
are applicable and important in drug chemistry.
The uniqueness of the UoB-4 nanostructures is rationalized
based on their selectivity in 1,4-DHP synthesis over the other
existing system, which is displayed by comparison with the
previously reported homogeneous and heterogeneous catalysts
(Table 3). The present catalyst exhibits a better catalytic activity
in the Hantzsch reaction in terms of catalyst load, reaction
time, temperature, and non-solvent conditions which afford
the favorable conditions for green chemistry. In analogy, UoB-4
nanostructures are highly stable, reusable, and scalable
catalysts for the synthesis of 1,4-DHPs.
Entry Solvent Temp. (1C) Catalyst (mol%) TBHP (mmol) Yieldb (%)
1
2
3
4
5
6
7
8
H2O
45
3
3
3
3
3
3
3
3
1
2
3
4
3
3
3
3
3
2
2
2
2
2
2
2
2
2
2
2
2
0.5
1
1.5
2
23
70
50
63
90
47
90
70
45
70
90
91
32
50
72
90
70
EtOH 45
EtOAc 45
CH3CN 45
—
—
—
—
—
—
—
—
—
—
—
—
—
45
r.t.
45
65
45
45
45
45
45
45
45
45
45
9
10
11
12
13
14
15
16
17
3
a
b
Reaction conditions: benzyl alcohol (1 mmol), 75 min. Yields of
product isolated.
3.2.2 Alcohol oxidation reaction. Our research group has
dedicated the past few years to some catalytic oxidation reactions,
particularly alcohol oxidation with MOF nanostructures as catalysts.
According to the previous reports, the manganese complexes were (entries 6–8). The product yield was increased up to 45 1C
proven to be efficient catalysts in alcohol oxidation.41–44 However, and was decreased significantly at 65 1C. The reduction in the
UoB-4 nanostructures, as MOFs synthesized based on Mn, exhibited product yield could be due to the decomposition of TBHP to
high catalytic activity. These findings indicated a possibility that molecular water and tert-butanol in the presence of UoB-4 at
UoB-4 could promote alcohol oxidation reactions. In an attempt evaluated temperatures. As a result, 45 1C was selected the as
to expand the application of MOFs, UoB-4 nanostructures were optimum reaction temperature. To determine the amount of
employed to the oxidation of a series of primary and secondary catalysts, the benzyl alcohol oxidation was performed with a
alcohols.
different amount of UoB-4 at 45 1C without any solvent. Increasing
First, benzyl alcohol was chosen as a model substrate the amount of the catalyst up to 3 mol% led to improved yields,
to screen the optimal conditions, and the main results are but the more increasing of it had no important effect on the
summarized in Table 4. It should be noted that no significant product yield (entries 9–12). Further investigation disclosed that
progress of reaction took place without the manganese catalyst the amount of oxidizing agents is crucial to the product yield
or in the presence of the precursor salt. Furthermore, benzyl (entries 13–17). When the oxidation of the model reaction was
alcohol oxidation was performed in various solvents under carried out using 0.5, 1, 1.5 and 2 mmol of tert-butyl hydro-
solvent-free conditions (entries 1–5). The best result based on peroxide, the yield of the product increased as the concentration
the product yield was obtained under solvent-free conditions, of tert-butyl hydroperoxide increased. However, using more than
which is in line with the green chemistry. The reason for this 3 mmol oxidizing agents had the opposite effect on the product
observation could be the exposed catalytic sites under solvent- yield that it could be due to over-oxidation.
free conditions. Then, the model reaction was carried out under
The ability of different single oxygen donors such as NaIO4,
solvent-free conditions at room temperature, 45 and 65 1C H2O2, oxone, and TBHP was examined in the oxidation of
Table 3 Comparison of the catalytic activity of UoB-4 with formerly reported catalysts
Entry
Catalyst
Time
Catalyst amount
Temperature
Solvent
Yield (%)
Ref.
1
2
3
4
5
Ce(SO4)2ꢁ4H2O
PdNiRu@GO
Zr-SBA-16
15 min
45 min
3 h
25 min
2.5 h
2.5 h
45 min
4 h
4 mol%
6 mg
R.T.
EtOH/H2O
DMF
EtOH
EtOH
H2O
EtOH
EtOH
EtOH
Solvent free
EtOH
60
93
77
86
95
96
94
92
90
99
97
33
34
35
36
37
38
39
24
70 1C
80 1C
R.T.
6 mmol%
10 mol%
10 mol%
0.1 mol%
10 mol%
40 mg
4 mol%
20 wt%
1.5 mol%
SBA-SO3H
Triton-X-100
Fe–C–O–Mo alloy
H5BW12O40
Er-MOF
IRMOF-3
MIL-101-SO3H
UoB-4
R.T.
Reflux
Reflux
70 1C
Reflux
60 1C
65 1C
6
7
8
9
5 min
8 h
30 min
22
40
10
Solvent free
This work
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Table 5 Screening the nature of oxidantsa
Table 6 Scope for substratesa
Entry
Oxidant
Time (min)
Yieldb (%)
1
2
3
4
H2O2
75
120
90
63
20
23
90
Oxone
NaIO4
TBHP
75
a
Reaction conditions: benzyl alcohol (1 mmol), oxidant (2 mmol), UoB-4
b
(3 mol%), S. F., 45 1C. Yields of product isolated.
Entry
1
Substrates
Time (min)
75
Yieldb (%)
90
benzyl alcohol in the presence of UoB-4 under solvent-free
conditions at 45 1C. The results indicated that TBHP is the best
oxygen source because of its good oxidation conversion (Table 5).
After the optimized conditions were established, this cata-
lytic system was applied for the oxidation of a wide variety of
primary and secondary alcohols to the corresponding carbonyl
compounds. As shown in Table 6, good to excellent yields were
accomplished in both primary and secondary alcohols. Clearly,
the electron nature of the substituents on the aromatic ring of
primary alcohols displayed no obvious effect on this trans-
formation, because the products were obtained in high yields.
3.2.3 Reusability. To further evaluate the potential for
industrial applications of UoB-4 nanostructures, their recycl-
ability was examined for use with successive batches of fresh
benzyl alcohol (for alcohol oxidation reaction)/benzaldehyde,
ammonium acetate and 1,3-dicarbonyl (for the Hantzsch
reaction). Both reactions were performed using optimized
conditions. After the reaction completion, the nanostructures
were recovered and then used as catalysts for the fresh batch of
substrates. This procedure was repeated for a total of five runs
using the same nanostructures, and the product yields
were obtained from each run. However, the reaction yields
progressively decreased, but they remained appropriate for
both reactions even after five reuse cycles of UoB-4 nanostruc-
tures. FT-IR analysis of reused UoB-4 indicated that there is no
significant change in terms of the internal structure (Fig. 5).
2
3
4
5
60
60
70
60
80
78
83
90
6
60
92
7
75
75
75
75
87
90
85
87
8
9
3.3 Antibacterial activity (performance)
10
In the last decades, antibacterial agents have attracted con-
siderable attention because of the appearance of contagious
diseases caused by pathogenic bacteria. Moreover, researchers
have recently increased their studies to find out new anti-
bacterial agents due to the increased resistance of bacteria to
old antibacterial compounds.45 Despite the widespread use of
MOFs in storage/adsorption gas and drug delivery, the usage of
them as antibacterial reagents has rarely been reported.46
MOFs, with unique properties such as long-term stability, and
high thermal and optical resistance, are very suitable candi-
dates for use as antibacterial compounds. Therefore, we
decided that the antibacterial efficiency of UoB-4 nanostruc-
tures should be investigated. As a proof of concept, Gram-
negative bacteria, Escherichia coli, and Gram-positive bacteria,
Bacillus cereus, were selected as model microorganisms at a
concentration of 80 mL by a disk diffusion susceptibility test.
The diameters of the inhibition zones against E. coli and
B. cereus were approximately 180 and 280 mm, in the presence
11
12
90
90
80
75
13
90
77
a
Reaction conditions: substrate (1 mmol), TBHP (2 mmol), UoB-4
b
(3 mol%), S. F., 45 1C. Yields of product isolated.
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Fig. 5 (left) Catalyst recyclability test for Hantzsch and alcohol oxidation reactions. (right) FTIR spectra of UoB-4: (a) fresh, (b) after Hantzsch reaction;
and (c) after alcohol oxidation.
as a nanocatalyst for the multi-component and oxidation reactions
as the two type of different them. It exhibited high catalytic activity
for the green synthesis of 1,4-DHPs under solvent free conditions via
the Hantzsch reaction. In addition, UoB-4 was demonstrated to be
an efficient catalyst for the various primary/secondary alcohol
oxidations when TBHP was used as an oxidant under solvent-free
conditions. The catalysis protocols displayed in this work offer
several advantages such as good to excellent yields, mild and green
reaction conditions, short reaction times, and eco-friendly synthesis.
Fig. 6 Agar plate diffusion experiment to estimate the antibacterial activity
on (right) B. cereus, and (left) E. coli with UoB-4 nanostructures.
These nanostructures showed suitable recyclability with no signifi-
cant yield decrease after five runs. The antibacterial activity of UoB-4
was also examined as another applied aspect of UoB-4, which
revealed a strong activity against both Gram-positive (B. cereus) and
-negative (E. coli) bacteria. Given its performance, UoB-4 nanostruc-
tures, as a substance that is easily synthesized, can be effective
materials for various applications.
of UoB-4 nanostructures, respectively (Fig. 6). This initial
experiment revealed that UoB-4 nanostructures can be effective
in this medium and can inhibit the growth of both used
microorganisms. UoB-4 was more effective at inhibiting the
growth of B. cereus compared to E. coli. It may be due to the
difference of Gram-positive and Gram-negative bacteria in
the susceptibility to UoB-4 nanostructures, because of their
Conflicts of interest
distinction in the cell structure, physiology, and metabolism.
There are no conflicts to declare.
4 Conclusion
Acknowledgements
In summary, new Mn-MOF, UoB-4, nanostructures have been This work was supported by Iran National Science Foundation
successfully prepared and characterized, and their application (Project No. 96008530). We also thank University of Birjand
aspects have been verified. UoB-4 demonstrated an excellent activity Research Council.
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25 S. Aryanejad, G. Bagherzade and A. Farrokhi, Inorg. Chem.
Commun., 2017, 81, 37–42.
26 S. Aryanejad, G. Bagherzade and A. Farrokhi, Appl. Organo-
met. Chem., 2018, 32, e3995.
27 S. Aryanejad, G. Bagherzade and M. Moudi, Appl. Organo-
met. Chem., 2019, 33, e4820.
28 A. W. Bauer, W. M. M. Kirby, J. C. Sherris and M. Turck, Am.
J. Clin. Pathol., 1966, 45, 493–496.
References
1 S. Kitagawa, Chem. Soc. Rev., 2014, 43, 5415–5418.
2 H. C. Zhou, J. R. Long and O. M. Yaghi, Chem. Rev., 2012,
112, 673.
3 D. Farrusseng, S. Aguado and C. Pinel, Angew. Chem., Int.
Ed., 2009, 48, 7502–7513.
ˇ
4 J. Cejka, Angew. Chem., Int. Ed., 2012, 51, 4782–4783.
5 H. Furukawa, K. E. Cordova, M. O’Keeffe and O. M. Yaghi,
Science, 2013, 341, 1230444.
6 Q. Yang, Q. Xu and H.-L. Jiang, Chem. Soc. Rev., 2017, 46,
4774–4808.
7 J. Zhu and H. Bienayme, Multicomponent reactions, John
Wiley & Sons, 2006.
29 H. Deng, S. Grunder, K. E. Cordova, C. Valente,
´
H. Furukawa, M. Hmadeh, F. Gandara, A. C. Whalley,
Z. Liu and S. Asahina, Science, 2012, 336, 1018–1023.
30 K. Nakamoto and K. Nakamoto, Infrared and Raman spectra
of inorganic and coordination compounds, Wiley, 1977.
31 N. Koukabi, E. Kolvari, A. Khazaei, M. A. Zolfigol,
B. Shirmardi-Shaghasemi and H. R. Khavasi, Chem. Com-
mun., 2011, 47, 9230–9232.
32 G. Sabitha, K. Arundhathi, K. Sudhakar, B. S. Sastry and
J. S. Yadav, Synth. Commun., 2009, 39, 2843–2851.
33 E. Mosaddegh and A. Hassankhani, Bull. Chem. Soc. Ethiop.,
2012, 26, 461–465.
´
8 S. Wu, X. Lei, E. Fan and Z. Sun, Org. Lett., 2018, 20, 522–525.
´
9 R. Echemendıa, G. P. da Silva, M. Y. Kawamura,
ˆ
F. Alexander, A. G. Correa, M. A. B. Ferreira, D. G. Rivera
and M. W. Paixao, Chem. Commun., 2019, 55, 286–289.
10 M. A. Zolfigol, S. Baghery, A. R. Moosavi-Zare, S. M. Vahdat,
H. Alinezhad and M. Norouzi, RSC Adv., 2014, 4, 57662–57670.
11 P. P. Ghosh, S. Paul and A. R. Das, Tetrahedron Lett., 2013,
54, 138–142.
˜
34 T. Demirci, B. Çelik, Y. Yıldız, S. Eris-, M. Arslan, F. Sen and
B. Kilbas, RSC Adv., 2016, 6, 76948–76956.
12 P. P. Mager, R. A. Coburn, A. J. Solo, D. J. Triggle and
H. Rothe, Drug Des. Discovery, 1992, 8, 273–289.
13 S. A. Khedkar and P. B. Auti, Mini-Rev. Med. Chem., 2014, 14,
282–290.
14 B. A. Johnson, N. Ait-Daoud and L. T. Wells, Neuropsycho-
pharmacology, 2000, 22, 504–512.
35 R. Maheswari, V. V. Srinivasan, A. Ramanathan, M. P.
Pachamuthu, R. Rajalakshmi and G. Imran, J. Porous Mater.,
2015, 22, 705–711.
36 E. Doustkhah, S. Rostamnia and A. Hassankhani, J. Porous
Mater., 2016, 23, 549–556.
´
37 P. PratimaGhosh, RSC Adv., 2013, 3, 8220–8226.
15 Y. Huai, H. Wang, L. Zhao, L. Zhao and J. Pei, Eur.
J. Pharmacol., 2013, 718, 441–447.
16 J. Y. Wu, L. Zhang, L. L. Cai and Y. Zhang, Advanced
Materials Research, Trans Tech Publications, 2012, vol.
518, pp. 3943–3946.
17 A. Colucci, R. Giunti, S. Senesi, F. L. Bygrave, A. Benedetti and
A. Gamberucci, Arch. Biochem. Biophys., 2009, 481, 80–85.
18 R. F. Affeldt, E. V. Benvenutti and D. Russowsky, New
J. Chem., 2012, 36, 1502–1511.
19 S. Ghosh, F. Saikh, J. Das and A. K. Pramanik, Tetrahedron
Lett., 2013, 54, 58–62.
38 P. Wu, L. Feng, Y. Liang, X. Zhang, B. Mahmoudi and
M. Kazemnejadi, Appl. Catal., A, 2019, 117301.
39 T. Momeni, M. M. Heravi, T. Hosseinnejad, M. Mirzaei and
V. Zadsirjan, J. Mol. Struct., 2020, 1199, 127011.
40 N. Devarajan and P. Suresh, New J. Chem., 2019, 43,
6806–6814.
41 I. Kani and S. Bolat, Appl. Organomet. Chem., 2016, 30,
713–721.
42 M. Kazemnejadi, M. Nikookar, M. Mohammadi, A. Shakeri
and M. Esmaeilpour, J. Colloid Interface Sci., 2018, 527,
298–314.
20 T. R. R. Naik and S. A. Shivashankar, Tetrahedron Lett., 2016,
57, 4046–4049.
43 V. Vermaak, D. A. Young and A. J. Swarts, Dalton Trans.,
2018, 47, 16534–16542.
21 B. Zeynizadeh, S. Rahmani and E. Eghbali, Polyhedron,
2019, 168, 57–66.
44 Z. Zhang, L. Khrouz, G. Yin and B. Andrioletti, Eur. J. Org.
Chem., 2019, 323–327.
22 S. Rostamnia and A. Morsali, RSC Adv., 2014, 4, 10514–10518.
23 F. Rouhani and A. Morsali, New J. Chem., 2017, 41, 15475–15484.
24 T. Hajiashrafi, M. Karimi, A. Heydari and A. A. Tehrani,
Catal. Lett., 2017, 147, 453–462.
45 X. Zhu, A. F. Radovic-Moreno, J. Wu, R. Langer and J. Shi,
Nano Today, 2014, 9, 478–498.
46 X. Lu, J. Ye, D. Zhang, R. Xie, R. F. Bogale, Y. Sun, L. Zhao,
Q. Zhao and G. Ning, J. Inorg. Biochem., 2014, 138, 114–121.
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