Mn-[4-Chlorophenyl-Salicylaldimine-Methylpyranopyrazole]Cl2 as a Novel Nanostructured Schiff Base Complex and Catalyst

Article abstract of DOI:10.1002/jccs.201600890

Mn-[4-chlorophenyl-salicylaldimine-methylpyranopyrazole]Cl₂ ([Mn-4CSMP]Cl₂) as nano-Schiff base complex was prepared and fully characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermal gravimetric analysis,

Full text of DOI:10.1002/jccs.201600890

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Mn-[4-Chlorophenyl-Salicylaldimine-Methylpyranopyrazole]Cl2 as a Novel
Nanostructured Schiff Base Complex and Catalyst
*
Ahmad Reza Moosavi-Zare , Hamid Goudarziafshar and Sharmin Dastbaz
Sayyed Jamaleddin Asadabadi University, Asadabad 6541835583, I. R. Iran
(Received: December 30, 2016; Accepted: May 14, 2017; DOI: 10.1002/jccs.201600890)
Mn-[4-chlorophenyl-salicylaldimine-methylpyranopyrazole]Cl2 ([Mn-4CSMP]Cl2) as nano-Schiff
base complex was prepared and fully characterized by Fourier transform infrared spectroscopy,
X-ray diffraction, thermal gravimetric analysis, derivative thermogravimetry, scanning electron
microscopy, energy-dispersive X-ray analysis, and UV–vis spectroscopy. The reactivity of nano-
[Mn-4CSMP]Cl2 as a catalyst was tested on the tandem cyclocondensation–Knoevenagel
condensation–Michael reaction between phenylhydrazine and ethyl acetoacetate with various aro-
matic aldehydes to give 4,40-(arylmethylene)-bis-(3-methyl-1-phenyl-1H-pyrazol-5-ol)s derivatives.
Keywords: Schiff base complex; Pyranopyrazole; Bis(pyrazolyl)methane; Tandem reaction.
INTRODUCTION
Recently, because of the presence of heterocyclic
RESULTS AND DISCUSSION
Nano-[Mn-4CSMP]Cl2 was prepared by the reac-
tion of 4-chlorobenzaldehyde with ethyl acetoacetate,
malononitrile, and hydrazine hydrate to obtain the
related pyranopyrazole according to previous
literature,17 which was then reacted with salicylalde-
hyde and MnCl2.4H2O in ethanol to afford nano-[Mn-
4CSMP]Cl2 as a nano-Schiff base complex (Scheme 2).
The structure of nano-[Mn-4CSMP]Cl2 was confirmed
by infrared (IR) spectroscopy, X-ray diffraction
(XRD), energy-dispersive X-ray (EDX) analysis, ther-
mogravimetric analysis (TGA), derivative thermogravi-
metry (DTG), UV–vis spectroscopy, and elemental
analysis (CHN).
compounds in many natural products and their applica-
tions in pharmacological chemistry, researchers have been
devoting much effort to the synthesis of similar com-
pounds and their derivatives using multicomponent reac-
tions (MCRs). MCRs are characterized by clean reaction
conditions, high atom economy, and the combining of
many complex reactions in effectively one step.1–8
Schiff base compounds are widely studied as an
important class of ligands due to their easy and conven-
ient protocols of preparation and their interesting coor-
dination chemistry.9 Schiff base or azomethine ligands
are among the principal chelating systems in bioinor-
ganic and various related natural biological processes,
and often the coordination chemistry of several forms of
Schiff bases is studied extensively. Schiff bases are intro-
duced as ligands to prepare coordination complexes with
metal ions and used to prepare catalysts.10–16
The IR spectrum of the catalyst showed a broad
peak at 2100–3500 cm−1, which could be related to the
O–H stretching of OH group, and the peak observed at
1670 cm−1 corresponds to the stretching mode of C N
bond of azomethine.
In the presented work, we have prepared and charac-
terized nano-Mn-[4-chlorophenyl-salicylaldimine-methyl-
As shown in Figure 2, the XRD patterns of nano-
[Mn-4CSMP]Cl2 has diffraction peaks corresponding to
a highly crystalline nature at about 2θ ≈ 11.3ꢀ, 17.0ꢀ,
21.4ꢀ, and 26.8ꢀ. The crystallite size was obtained by the
Debye–Scherrer formula D = Kλ/(βcos θ). The crystal-
lite size obtained using this formula was at about
23.35 nm (for the highest diffraction line at 26.8ꢀ), and
inter-planar distance was calculated via the Bragg equa-
pyranopyrazole]Cl2
(nano-[Mn-4CSMP]Cl2),
whose
proposed structure is shown in Figure 1. Nano-[Mn-
4CSMP]Cl2 was successfully used as an efficient catalyst
for
the
tandem
cyclocondensation–Knoevenagel
condensation–Michael reaction of phenyl hydrazine, ethyl
acetoacetate, and aryl aldehydes to give bis(pyrazolyl)
methanes (Scheme 1).
tion: d(hkl) = λ/(2sin θ), which gave
a
value of
*Corresponding author. Email: moosavizare@yahoo.com
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Moosavi-Zare et al.
Fig. 1. Proposed structures of nano-[Mn-4CSMP]Cl2.
Fig. 2. XRD result of nano-[Mn-4CSMP]Cl2.
Table 1. XRD data for the catalyst
Peak
width
Size
Inter-planar
Entry
2θ
(FWHM)
(nm)
distance (nm)
1
2
3
4
11.3
17.0
21.4
26.8
0.0034
0.0034
0.0043
0.0061
40.90
41.21
32.80
23.35
0.7825
0.5209
0.4148
0.3323
Scheme 1. Preparation of 4,40-(arylmethylene)-bis
(3-methyl-1-phenylpyrazol-5-ol)s using
nano-[Mn-4CSMP]Cl2.
Scheme 2. Preparation of nano-[Mn-4CSMP]Cl2.
0.3323 nm (λ:Cu radiation 0.154178 nm). The peak
width (full width at half-maximum; FWHM), size, and
inter-planar spacing of the catalyst are given in Table 1.
SEM micrographs of the catalyst were also stud-
ied, which showed that the particles of the catalyst were
in the nano-size range, being in good agreement with
calculated size through the Debye–Scherrer equation
(Figure 3).
Fig. 3. SEM micrograph of nano-[Mn-4CSMP]Cl2.
structure of nano-[Mn-4CSMP]Cl2, namely carbon,
oxygen, nitrogen, manganese, and chlorine (Figure 4).
Therefore, the structure of the catalyst was completely
confirmed by EDX analysis.
EDX spectra of the prepared nanoparticles
showed the presence of the expected elements in the
2
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Nano-[Mn-4CSMP]Cl2 as a New Schiff Base
500
C
400
300
O
200
Mn
100
Cl
Cl
N
Mn
Mn
keV
0
0
5
10
Fig. 6. UV spectra of amine, Schiff base,
MnCl2.4H2O, and nano-[Mn-4CSMP]Cl2
in DMSO.
Fig. 4. Energy-dispersive X-ray (EDX) spectrum of
nano-[Mn-4CSMP]Cl2.
TGA of the nano-[Mn-4CSMP]Cl2 was also car-
for the preparation of 4,40-(arylmethylene)-bis(3-methyl-
1-phenyl-1H-pyrazol-5-ol)s. For this, the reaction of
ethyl acetoacetate (2 mmol) and phenyl hydrazine
(2 mmol) with 4-chlorobenzaldehyde (1 mmol) was
selected as a model reaction and tested in the presence
of different quantities of the nano-[Mn-4CSMP]Cl2 in
the temperature range 60–100ꢀC under solvent-free con-
ditions. Higher yield and shorter reaction time were
obtained using 10 mol% of catalyst at 100ꢀC under
solvent-free conditions.
Then, to explore the efficiency and the scope of
the presented protocol, ethyl acetoacetate (2 mmol) and
phenyl hydrazine (2 mmol) were treated with various
aromatic aldehydes (1 mmol) using nano-[Mn-4CSMP]
Cl2 as catalyst. The corresponding results are summar-
ized in Table 2. As the table shows, all corresponding
4,40-(arylmethylene)-bis (3-methyl-1-phenylpyrazol-5-ol)
derivatives were obtained in good to excellent yields
and in relatively short reaction times.
ried out. The corresponding results are shown in
Figures 5. TG and DTG results of nano-[Mn-4CSMP]
Cl2 showed that it decomposed after 200ꢀC.
The UV spectra also evidenced the production of
nano-[Mn-4CSMP]Cl2. UV studies were carried out in
DMSO as solvent. The maximum of absorption for
amine, Schiff base (4CSMP), nano-[Mn-4CSMP]Cl2,
and MnCl2.4H2O appeared at 263, 261, 257 and
259 nm, respectively (Figure 6). Therefore, λmax of the
complex is different from that of the species used for
the synthesis of Nano-[Mn-4CSMP]Cl2.
After full characterization of nano-[Mn-4CSMP]
Cl2, we examined the catalytic activity of the catalyst
EXPERIMENTAL
General
All chemicals were purchased from Merck or
Fluka. The known products were identified by compari-
son of their melting points and spectral data with those
reported in the literature.
Fig. 5. Thermogravimetric (TG) and differential
thermogravimetry (DTG) analysis of nano-
[Mn-4CSMP]Cl2 in the range 0–600ꢀC, at
the temperature increase rate of 10ꢀC.
Procedure for the synthesis of nano-[Mn-4CSMP]Cl2)
A mixture of 4-chlorobenzaldehyde (1 mmol),
malononitrile (0.066 g, 1 mmol), ethyl acetoacetate
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Communication
Moosavi-Zare et al.
Table 2. Preparation of bis(pyrazolyl)methanes using nano-
[Mn-4CSMP]Cl2
Table 2. Continued
65/60
93/50
157–159 (157–159)5
176–180 (175–177)19
Product
Yielda/time (min)
60/45
mp. ꢀC (lit.)
160–163 (160–162)5
Ar
Yielda/time (min)
83/30
mp. ꢀC (lit.)
225–228 (232–235)5
90/30
200–204 (209–210)5
85/40
59/50
216–220 (214–219)20
160–163 (151–152)21
73/60
63/50
155–160 (153–154)5
240–243 (235–236)5
a Isolated yield.
80/80
95/30
216–220 (219–221)5
224–227 (228–230)5
reflux condenser and stirred at 85ꢀC. After the comple-
tion of the reaction, as monitored by TLC, the reac-
tion mixture was cooled to room temperature. Water
was added to the reaction mixture to dissolve isonico-
tinic acid, and the aqueous layer was separated from
the mixture. Afterwards, the solid residue (crude prod-
uct) was tritrated by a mixture of ethanol/water (9:1)
to afford 6-amino-3-methyl-4-(4-chlorophenyl)-2,4-
dihydropyrano [2,3-c]pyrazole-5-carbonitrile as an
68/60
70/20
217–219 (217–218)5
165–168 (173–175)18
amine end product.17
A mixture of the amine
(1 mmol) and ethanol (5 mL) was added dropwise to a
25-mL round-bottomed flask containing ethanol
(10 mL), salicylaldehyde (1.5 mmol), and MnCl2.4H2O
(1 mmol) connected to a reflux condenser for 1 h and
then stirred for 24 h under reflux conditions. After this
time, ethanol was removed and the reaction mixture
was washed by ethyl acetate/ hexane (9:1) three times
to purify nano-[Mn-4CSMP]Cl2 from the excess
salicylaldehyde.
(0.13 g, 1 mmol) hydrazine hydrate (1.25 mmol), and
isonicotinic acid (0.1 mmol) (0.0123 g, 10 mol%) was
taken in a 10-mL round-bottomed flask connected to a
4
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Nano-[Mn-4CSMP]Cl2 as a New Schiff Base
6. A. R. Moosavi-Zare, M. A. Zolfigol, Z. Rezanejad, Can.
J. Chem. 2016, 94, 626.
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Moratab, E. Noroozizadeh, J. Mol. Catal. A Chem.
2016, 415, 144.
General procedure for the synthesis of bis(pyrazolyl)
methanes
A mixture of ethyl acetoacetate (2 mmol), phenyl
hydrazine (2 mmol), and nano-[Mn-4CSMP]Cl2 (10 mol
%) was taken in a 10-mL round-bottomed flask connected
to a reflux condenser and was stirred at 100ꢀC for 5 min.
Then aromatic aldehyde (1 mmol) was added to the reac-
tion mixture and continued stirring for an appropriate
time. After completion of the reaction, as monitored by
TLC, the reaction mixture was cooled to room tempera-
ture and recrystallized from ethanol (95%) The spectra of
compounds have been reported in supporting information.
8. (a) A. R. Moosavi-Zare, M. A. Zolfigol, V. Khakyzadeh,
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(c)
A.
R.
Moosavi-Zare,
M.
A.
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E. Noroozizadeh, M. Tavasoli, V. Khakyzadeh, A. Zare,
New J. Chem. 2013, 37, 4089; (d) A. R. Moosavi-Zare,
M. A. Zolfigol, M. Daraei, Synlett 2014, 25, 1173;
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A. Zare, A. R. Pourali, R. Ayazi-Nasrabadi, Synlett
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CONCLUSIONS
In summary, we have prepared and characterized
nano-[Mn-4CSMP]Cl2 as a Schiff base complex in
nano-size, based on 6-amino-3-methyl-4-(4-chlorophe-
nyl)-2,4-dihydropyrano[2,3-c] pyrazole-5-carbonitrile as
a biological compound for the first time. Nano-[Mn-
4CSMP]Cl2 was successfully applied as an efficient and
catalyst for tandem cyclocondensation–Knoevenagel–
Michael reaction of phenylhydrazine, ethyl acetoacetate
arylaldehydes, and malononitrile to give 4,40-(aryl-
methylene)-bis(3-methyl-1-phenyl-1H-pyrazol-5-ol)s.
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ACKNOWLEDGMENT
This work was supported by the Sayyed Jamaled-
din Asadabadi University.
Supporting information
Additional supporting information is available in
the online version of this article.
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