Nanocasting, Template Synthesis, and Structural Studies on Cesium Salt of Phosphotungstic Acid for the Synthesis of Novel 1,3,5-Triaryl-pyrazoline Derivatives

Article abstract of DOI:10.1016/S1872-2067(11)60330-6

The elimination of the silica matrix of composites by HF occurred by a two-step reaction deposition of a Cs_2.5H_0.5PW₁₂O₄₀ (CsHPW) salt nanocrystal. We used 2D hexagonal SBA-15 silica as a template for the nanofabrication of CsHPW nanoparticles. Nanocast CsHPW materials are stable against leaching and colloidization in polar solvents. The catalytic performance of the nanocast CsHPW materials exceeded that of bulk Cs_2.5H_0.5PW₁₂O₄₀, which is the most active among the acidic HPW salts. A series of novel 1,3,5-triaryl-pyrazoline derivatives were synthesized by the reaction between chalcone and phenylhydrazine in high yield in the presence of CsHPW salt nanocrystals.

Full text of DOI:10.1016/S1872-2067(11)60330-6

CHINESE JOURNAL OF CATALYSIS
Volume 33, Issue 2, 2012
Online English edition of the Chinese language journal
Cite this article as: Chin. J. Catal., 2012, 33: 237–246.
ARTICLE
Nanocasting, Template Synthesis, and Structural Studies
on Cesium Salt of Phosphotungstic Acid for the Synthesis of
Novel 1,3,5-Triaryl-pyrazoline Derivatives
Razieh FAZAELI1,*, Hamid ALIYAN2, Shahram TANGESTANINEJAD1, Esmaeel MOHAMMADI1,
Maryam BORDBAR3
1Department of Chemistry, Shahreza Branch, Islamic Azad University, 86145-311, Iran
2Department of Chemistry, Mobarakeh Branch, Islamic Azad University, 84815-119, Iran
3Department of Chemistry, Faculty of Science, The University of Qom, 37185-359, Qom, Iran
Abstract: The elimination of the silica matrix of composites by HF occurred by a two-step reaction deposition of a Cs2.5H0.5PW12O40
(CsHPW) salt nanocrystal. We used 2D hexagonal SBA-15 silica as a template for the nanofabrication of CsHPW nanoparticles. Nanocast
CsHPW materials are stable against leaching and colloidization in polar solvents. The catalytic performance of the nanocast CsHPW ma-
terials exceeded that of bulk Cs2.5H0.5PW12O40, which is the most active among the acidic HPW salts. A series of novel
1,3,5-triaryl-pyrazoline derivatives were synthesized by the reaction between chalcone and phenylhydrazine in high yield in the presence of
CsHPW salt nanocrystals.
Key words: nanocasting; nanoparticle; green chemistry; 1,3,5-triaryl-2-pyrazoline; polyoxometalate
High-surface area inorganic materials have attracted wide-
spread attention in diverse areas such as heterogeneous ca-
talysis [1], adsorption [2–5], gas sensing [6,7], energy storage
[8], drug delivery [9,10] biomedical applications [11], and
electrochemistry [12–14] etc. Because of this broad range of
applications much effort has been put into reviewing and up-
dating the material's preparation methods [15–17]. The appli-
cation of the nanocasting technique to the fabrication of inor-
ganic compounds implies that the fabrication of these products
takes place in the nanospaces provided by the pores of a porous
solid (hard template). After the synthesis of the material, the
template framework is selectively removed and an inorganic
product is obtained.
Basically, the nanocasting route comprises three steps: (i)
infiltration of the porous the template (i.e. SiO2-SBA-15) with
a solution containing the precursors of the inorganic com-
pound; (ii) heat treatment under a controlled atmosphere of the
impregnated template to convert the infiltrated precursor into
an inorganic material and (iii) the removal of the template
framework by dissolution (i.e. silica) or by oxidation under
high temperatures (i.e. carbon) (Fig. 1). Because the synthesis
takes place in a confined nanospace sintering of the particles is
Fig. 1. Illustration of the nanocasting pathway.
Received 25 May 2011. Accepted 17 June 2011.
*Corresponding author. Tel: +98-321-3232706-7; Fax: +98-321-3232701-2; E-mail: fazaeli@iaush.ac.ir
This work was supported by Islamic Azad University, Shahreza Branch.
Copyright © 2012, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier BV. All rights reserved.
DOI: 10.1016/S1872-2067(11)60330-6

Razieh FAZAELI et al. / Chinese Journal of Catalysis, 2012, 33: 237–246
restricted and the preparation of high surface area materials
fluorescence quantum yield [33] and a high electrolumines-
cence yield [34]. Among the various pyrazoline derivatives,
1,3,5-triaryl-2-pyrazolines (TAP) seem to be the most fre-
quently studied pyrazoline-type compounds. Several catalysts
have been developed for the preparation of these heterocycles
including sodium acetate-acetic acid aqueous solution under
ultrasound irradiation [35], hot acetic acid solution [36],
K2CO3-mediated microwave irradiation [37], H3PW12O40 [38],
and tungstophosphoric acid supported on highly organosoluble
polyamide (PW12/PA) [39].
As a part of our continuing effort to understand the catalytic
properties of heteropoly acids (HPAs) [40–42], we report on
the use of a nanoparticle catalyst for the synthesis of TAP
derivatives (Scheme 1) and the introduction of a good appli-
cation for Cs2.5H0.5PW12O40 (CsHPW).
(nanostructures or nanoparticles) is achieved. In this way, even
though high (temperature) is required, numerous inorganic
compounds with high surface areas can be obtained. Moreover,
this synthetic strategy clearly suggests that the structure of the
synthesized inorganic compounds can be tailored depending on
the pore characteristics of the selected template [18].
Catalysis by polyoxometalates has attracted much attention
because of their strong acidity and redox properties. An addi-
tional attractive aspect of polyoxometalates in catalysis is their
inherent stability toward oxygen donors [19]. The practical
application of the cesium salts of CsPW12O40 (denoted CsPW
hereafter) have been limited by two factors: first is formation of
milky suspensions in the polar substrates, which causes filtra-
tion problems for the liquid phase reactions and the second is a
pressure drop in the fixed bed reactors [20]. Stabilizing them in
a mesoporous matrix can help to overcome the drawbacks.
Basically, they can support the catalytic phase and then be
liberated from the matrix to form a nanocast. Reaction deposi-
tion is used to nanocoat the materials at different stages during
the preparation of the CsHPW [21].
The real chemical composition of the CsHPW phase and its
accessible surface within the supporting composite materials
that determines the potential performance of the catalytic phase
remains unknown. All the existing protons in bulk microporous
CsHPW with a crystal size of 12 nm and a Cs/W12 ratio of 2.5
are available for the adsorption of NH3 [22] and pyridine [23].
Therefore, a further increase in the acidity and catalytic activity
can be expected by decreasing the crystal sizes to less than 10
nm. Also, diminishing the diffusion limitations of the re-
agents/products can increase the catalytic reaction rates be-
cause the diffusion limitations in microporous materials like
zeolites are insignificant in this range of crystal sizes [24].
Recently, it was shown that the insertion of CsHPW into
SBA-15 increases the absorbed ammonia more than 3 fold per
gram of CsHPW phase [25].
1 Experimental
All materials were commercial reagent grade. Aldehydes,
phenylhydrazine, acetophenone, and H3PW12O40 (HPW) were
purchased from Merck or Aldrich.ꢀInfrared spectra (FT-IR)
(400–4000 cm–1) were recorded using KBr pellets on a Nicolet
1
Impact 400 D spectrometer. H NMR spectra were obtained
using a 300 MHz Bruker-Avance AQS. Melting points were
determined using an electrothermal digital melting point ap-
paratus and are uncorrected. Reaction courses and product
mixtures were monitored by thin layer chromatography. X-ray
powdered diffraction (XRD) patterns were obtained using a
Bruker-D8 advance with automatic control. The patterns were
run with monochromatic Cu Kꢀ (ꢀ = 0.15406 nm) radiation at a
scan rate of 2°/min. Micrographs were recorded using a scan-
ning electron microscope (SEM, HITACHI COM-S-4200)
operated at an accelerating voltage of 30 kV. Thermogravim-
etric (TG) analyses were carried out on a Labsys-Setaram
TGA-DSC instrument in flowing N2 at a heating rate of 20
°C/min up to 1000 °C.
Pyrazolines are well known and important nitro-
gen-containing five-membered heterocyclic compounds and
various methods have been used for their synthesis [26].
Pyrazoline derivatives are attracting an increasing amount of
interest in medicinal chemistry because of their bioactivity
such as antimicrobial [27], antiamoebic [28], antinociceptive
1.1 Materials
1.1.1 SBA-15
SBA-15 was first synthesized by Sun et al. [43] in 1998
using the amphiphilic triblock copolymers, EO20PO70EO20
(Pluronic P123), as a template. In a typical synthesis, 1.00 g of
P123 was dissolved in a mixture of HCl/H2O (30.00 g of 2
[29],
anticancer
[30],
antidepressant
[31],
and
anti-inflammatory [32] activity and also their use in conjugated
fluorescent dyes as blue fluorescence emitters with a high
O
H
H
Ph
NH2
R1
R1
R2
N
H
5
CsHPW-Nanocrystals
EtOH
3
R2
4
+
N
2
N
1
1
2
Ph
3
Scheme 1. Synthesis of 1,3,5-triaryl-2-pyrazolines.

Razieh FAZAELI et al. / Chinese Journal of Catalysis, 2012, 33: 237–246
O
mol/L HCl to 7.50 g H2O). After dissolution 2.08 g of tetraethyl
CHO
orthosilicate (TEOS) or 1.96 g of sodium silicate was added.
The slurry was hydrothermally treated at 100 °C for 48 h after
stirring at 40 °C for 16 h. The product was filtered and dried at
800 °C for 10 h.
NaOH
+
Scheme 2 Synthesis of chalcone.
of sodium hydroxide in 200 ml of water and 100.00 g (122.5
ml) of rectified spirit was added. To this mixture freshly dis-
tilled acetophenone (52.00 g, 0.43 mol ) was added at 0 °C.
After stirring for 5 min, 46.00 g (44 ml, 0.43 mol) of pure
benzaldehyde was added. The temperature of the mixture was
kept at about 25 °C (the requirement is 15–30 °C) and it was
stirred vigorously until the mixture was thick enough for stir-
ring to no longer be effective (2–3 h). The stirrer was removed
and the reaction mixture was placed in an ice chest or refrig-
erator overnight. The product was filtered by suction using a
Buchner funnel or a sintered glass funnel, washed with cold
water until neutral to litmus followed by washing with 20 ml of
ice-cold rectified spirit. The crude chalcone, after drying in air,
weighed 88 g and melted at 50–54 °C. The chalcone was re-
crystallized from rectified spirit that was warmed to 50 °C
(about 5 ml per gram) (Scheme 2) [44].
1.1.2 CsHPW/SBA
CsHPW was inserted into the SBA-15 silica matrix by the
two-step reaction deposition method. The parent CsHPW/SBA
sample was obtained by dispersing surfactant-free SBA-15 (0.5
g) into 10 ml of n-propanol followed by the addition of 0.20 g
of cesium carbonate. The contents were stirred for 4 h, filtered
and dried under vacuum. The dry solids were treated for 12 h
with a solution containing excess HPW dissolved in n-propanol
under continuous stirring after which they were filtered and
washed with excess n-propanol. The resulting solids were dried
at 383 K for 2 h and calcined at 573 K for 2 h [21] (Fig. 2).
1.1.3 CsHPW nanoparticles
The silica matrix was gradually removed from the
CsHPW/SBA materials by treatment with HF. The CsHPW/
SBA composite 0.50 g was continuously stirred in 20 ml of an
aqueous HF solution for 3 h at room temperature (Fig. 3). The
solid was recovered by decantation after centrifugation (7000
r/min). The water addition/centrifugation sequence was re-
peated three times and finally the material was evacuated at
333 K [21].
1.3 Typical procedure for the synthesis of 1,3,5-triaryl
pyrazoline
The following components were added to the reaction ves-
sels: chalcone (1 mmol), phenylhydrazine (1 mmol), and
CsHPW nanocrystals (0.03 mmol). Reaction progress was
monitored by chin layer chromatography. At the end of the
reaction the produced mixture was washed off the vessel using
EtOAc (20 ml) and then it was filtered. The filtrate was dried
(MgSO4) and evaporated. The crude product was purified by
column chromatography to provide 1,3,5-triaryl pyrazoline.
1.2 General procedure for the synthesis of chalcone
(benzylideneacetophenone)
To a 500 ml bolt-head flask with a mechanical stirrer 22.00 g
1.4 Selected spectroscopic data
5-(4-Methylphenyl)-1,3-diphenyl-2-pyrazoline (3c). 1H
NMR (CDCl3): ꢁ 2.34 (s, 3H, CH3), 3.14 (dd, J = 7.1 Hz, 17.0
Hz, 1H), 3.85 (dd, J = 12.1, 17.0 Hz, 1H), 5.27 (dd, J = 6.9, 12
Hz, 1H) 6.77–7.75 (m, 14H). Anal. calcd. for C22H20N2: C,
84.62; H, 6.41; N 8.97; found C, 84.61; H, 6.43; N, 9.00. 13C
NMR (CDCl3): ꢁ 21.68, 44.09, 64.73, 113.69, 119.47, 126.23,
128.43, 128.88, 129.34, 129.57, 130.19, 133.07, 137.67,
141.53, 145.43, 147.17. IR (KBr) ꢂmax = 1117, 1499, 1593
cm–1.
Fig. 2. Preparation of CsHPW/SBA.
5-(4-Chlorophenyl)-1,3-diphenyl-2-pyrazoline
(3d).
1H-NMR (CDCl3): ꢁ 3.04 (dd, J = 7.4 Hz, 17.6 Hz, 1H), 3.77
(dd, J = 11.6 Hz, 17.6 Hz, 1H), 5.67 (dd, J = 7.4 Hz, 11.6 Hz,
1H), 6.71–7.64 (m, 14H); Anal. Calcd. for C21H17ClN2: C,
75.78; H, 5.15; N, 8.41. Found: C, 75.69; H; 5.10; N, 8.49%.
13CNMR (CDCl3): ꢁ 43.4, 63.8, 113.4, 119.4, 125.7, 127.3,
128.5, 128.7, 128.9, 129.3, 129.9, 132.5, 133.3, 141.1, 144.6,
Fig. 3. Preparation of the CsHPW nanoparticles.

Razieh FAZAELI et al. / Chinese Journal of Catalysis, 2012, 33: 237–246
146.7. IR (KBr) ꢂmax = 1123, 1495, 1598 cm–1.
2 Results and discussion
5-(3-Chlorophenyl)-1,3-diphenyl-2-pyrazoline (3e). 1H
NMR (CDCl3): ꢁ 3.08 (dd, J = 6.8 Hz, 17.0 Hz, 1H), 3.43 (dd, J
= 12.2 Hz, 17.2 Hz, 1H), 5.63 (dd, J = 6.9 Hz, 12.4 Hz, 1H)
6.85–7.81 (m, 14H). Anal. calcd. for C21H17N2Cl: C, 85.85; H,
5.72; N, 9.43; found C, 85.79; H, 5.70; N, 9.41. 13C NMR
(CDCl3): ꢁ 42.37, 61.54, 113.58, 119.60, 124.44, 127.79,
128.07, 128.92, 129.18, 129.48, 130.67, 132.53, 133.04,
135.04, 139.67, 144.84, 147.53. IR (KBr) ꢂmax = 1127, 1501,
1593 cm–1.
2.1 Characterization of the CsHPW
FT-IR spectroscopy is a convenient method for the charac-
terization of the Keggin structure of heteropolyanions. The
infrared spectrum of the Cs2.5H0.5PW12O40 nanocasts (Fig. 4(c))
gave strong vibrations at 1081 (ꢁas(P–Oa)), 986 (ꢁas(W–Oa)),
892 (ꢁas(W–O–W)), and 800 cmꢀ1 (ꢁas(W–Oc–W)) while
bulk-Cs2.5H0.5PW12O40 gave vibrations at 1080, 986, 891, and
801 cm–1 (Fig. 4(a)). In addition, the observed band at 523 cmꢀ1
may be attributed to the ꢂ(P–O) vibration [45]. Moreover, the
band located at 1622 cmꢀ1 may be characteristic of the O–H
stretching vibration (Fig. 4(c)).
The chemical composition of the bulk CsHPW samples and
their nanocasts were estimated by averaging the results of
energy dispersive X-ray spectroscopy (EDS) experiments at
five different positions in the samples. EDS results indicate that
the as-prepared CsHPW nanocast samples contain Cs, W, P,
and O (Fig. 5 and Table 1). The percentage of silica matrix
removed from the CsHPW/SBA composite was about 99%.
The Cs content in the CsHPW materials was characterized by
Cs/W12 further defined as the Cs/W12 ratio and this was calcu-
lated from the atomic percentages of Cs and W in the samples
5-(2-Chlorophenyl)-1,3-diphenyl-2-pyrazoline (3f). 1H
NMR (CDCl3): ꢁ 3.06 (dd, J = 4.8 Hz, 17.6 Hz, 1H), 3.96 (dd, J
= 11.2 Hz, 17.7 Hz, 1H), 5.64 (dd, J = 4.7 Hz, 11.0 Hz, 1H),
6.76–7.74 (m, 14H); Anal. Calcd. for C21H17ClN2: C, 75.78; H,
5.15; N, 8.41. Found: C, 75.83; H, 5.23; N, 8.38%.13C NMR
(CDCl3): ꢁ 41.9, 61.5, 113.3, 119.2, 125.9, 127.5, 127.9, 128.3,
128.5, 128.8, 129.3. 129.8, 131.4, 132.2, 139.5, 144.6, 147.4.
IR (KBr) ꢂmax = 1120, 1497, 1595 cm–1.
5-(2,4-Dichlorophenyl)-1,3-diphenyl-2-pyrazoline (3g).
1H NMR (CDCl3): ꢁ 3.02 (dd, J = 6.6 Hz, 17.6 Hz, 1H), 3.97
(dd, J = 12.5 Hz, 17.5 Hz, 1H), 5.59 (dd, J = 6.6 Hz, 12.2 Hz,
1H), 6.69–7.71 (m, 13H); Anal. Calcd. for C21H16Cl2N2: C,
68.67; H, 4.39; N, 7.62. Found: C, 68.73; H, 4.39; N, 7.71%.
13CNMR (CDCl3): ꢁ 41.5, 60.9, 113.5, 119.5, 124.3, 125.6,
127.4, 127.7, 128.6, 128.5, 128.5, 129.2, 129.5, 132.1, 133.9,
137.7, 144.4, 147.5. IR (KBr) ꢂmax = 1118, 1503, 1589 cm–1.
5-(3-Bromophenyl)-1,3-diphenyl-2-pyrazoline (3h). 1H
NMR (CDCl3): ꢁ 3.08 (dd, J = 7.1 Hz, 17.0 Hz, 1H), 3.35 (dd, J
= 12.1 Hz, 16.9 Hz, 1H), 5.68 (dd, J = 6.9 Hz, 12.7 Hz, 1H)
6.80–7.75 (m, 14H). Anal. calcd. for C21H17N2Br: C, 85.85; H,
5.72; N, 9.43; found C, 85.78; H, 5.69; N 9.43. 13C NMR
(CDCl3): ꢁ 42.35, 60.47, 113.35, 119.50, 124.23, 127.94,
128.05, 129.06, 129.16, 129.35, 130.59, 132.41, 133.18,
139.66, 145.25, 147.14. IR (KBr) ꢂmax = 1126, 1502, 1598
cm–1.
(a)
100
80
60
40
120
(b)
100
1
80
60
40
20
0
5-(4-Methoxyphenyl)-1,3-diphenyl-2-pyrazoline (3i). H
NMR (CDCl3): ꢁ 3.12 (dd, J = 7.1 Hz, 17.1 Hz, 1H), 3.82 (s,
3H, OCH3), 3.87 (dd, J = 12.1 Hz, 16.9 Hz, 1H), 5.24 (dd, J =
7.2 Hz, 12 Hz, 1H) 6.75–7.85 (m, 14H). Anal. calcd. for
C22H20N2O: C, 84.62; H, 6.41; N, 8.97; found C, 84.56; H,
6.40; N, 8.93. 13C NMR (CDCl3): ꢁ 44.08, 55.64, 64.14,
113.72, 114.46, 119.54, 126.42, 127.91, 128.47, 128.89,
129.19, 130.56, 133.21, 135.03, 145.34, 147.17. FT-IR (KBr)
ꢂmax = 1120, 1261, 1512, 1597 cm–1.
-20
(c)
100
80
60
40
3-(4-Chlorophenyl)-1,5-diphenyl-2-pyrazoline (3j). 1H
NMR (DMSO): ꢁ 3.15 (dd, J = 7.1 Hz, 17.0 Hz, 1H), 3.87 (dd,
J = 12.2 Hz, 17.1 Hz, 1H), 5.33 (dd, J = 7.3 Hz, 12.4 Hz, 1H)
6.83–7.67 (m, 14H). Anal. calcd. for C21H17N2Cl: C, 84.85; H,
5.72; N, 9.43; found C, 84.81; H, 5.77; N, 9.47. 13C NMR
(DMSO): ꢁ 42.39, 61.31, 113.53, 117.26, 126.83, 126.94,
128.64, 129.16, 129.39, 130.55, 132.17, 132.19, 136.05,
139.61, 143.73, 147.39. IR (KBr) ꢂmax = 1121, 1509, 1599
cm–1.
20
4000 3500 3000 2500 2000 1500 1000 500
Wavenumber (cmꢃ1)
Fig. 4. FT-IR spectra of Bulk-CsHPW (a), CsHPW/SBA-15 (b), and
CsHPW nanocrystals (c).

Razieh FAZAELI et al. / Chinese Journal of Catalysis, 2012, 33: 237–246
of about 43 nm. Isolated primary 10–20 nm nanoparticles of
CsHPW were also present in the TEM micrographs (Fig. 7).
However, isolated 5–9 nm nanoparticles of CsHPW were
clearly observed by HRTEM in the curved nanotubular chan-
nels within the silica microfibers [21].
The thermal stability of Cs2.5H0.5PW12O40 was investigated
for the crystalline samples under a N2 atmosphere from 50 to
700 °C (Fig. 8). The TGA curve indicates that the weight loss
of CsHPW can be divided into two steps. The first weight loss
of 1.701% from 48 to 84 °C involves the release of three lattice
water molecules. The second step beginning at about 465–518
°C (6.333%) is because of the decomposition of POM and the
release of WO3.
XRD analysis is widely used to study the structure of het-
eropoly complexes. XRD patterns of the as-prepared
CsHPW/SBA-15 composite and the CsHPW nanocasts are
shown in Fig. 9. The XRD peaks for the CsHPW phase within
the CsHPW/SBA-15 composites (Fig. 9(1)), the bulk-CsHPW
[21] and the CsHPW nanocasts (Fig. 9(2)) can be attributed to
their bcc cubic structure, which is commonly associated with
pure alkaline heteropoly salts [44]. Therefore, the removal of
the silica matrix does not affect the crystal structure. The wide
amorphous halo centered at 2ꢅ = 23° in the spectrum of
SBA-15 silica in the as-prepared composites completely dis-
appeared for the nanocasted materials.
The UV-Vis spectrum of the CsHPW nanocast is shown in
Fig. 10. The two bands near 208 and 266 nm are attributed to
OtꢆW and μ2-OꢆW ligand-to-metal charge transfer, respec-
tively. Electrons are promoted from the low energy electronic
states that are mainly composed of oxygen 2p orbitals to
high-energy states that are mainly composed of metal d orbi-
tals.
Fig. 5. EDS profile of CsHPW nanocast sample.
Table 1 EDS measurements carried out during the SEM observations
Element
Line
Ka
Ka
Ka
La
Intensity (c/s)
32.54
Conc (wt%)
1.788
0.954
1.177
12.525
83.556
O
Si
P
Cs
W
26.28
24.71
38.85
170.03
La
according to the EDS data. The good distribution of all the
analyzed elements is in agreement with the atomic adsorption
analysis, the neutron activation analysis (NAA) and ICP results
with deviations of ꢄ0.09. During the removal of silica the
excess cesium located within the micropores transfers to the
solution as it is dissolved in aqueous HF together with the silica
matrix. Cesium was indeed found in the filtrate of this solution
by atomic adsorption analysis. A SEM micrograph of CsHPW
is shown in Fig. 6. No defined morphology is apparent for the
particles but their edges appear to be spherical with diameters
N2 adsorption-desorption isotherms and the corresponding
BJH pore size distribution curves for bulk-CsHPW,
Fig. 6. SEM micrographs of the CsHPW nanoparticles.

Razieh FAZAELI et al. / Chinese Journal of Catalysis, 2012, 33: 237–246
Fig. 7. TEM micrographs of the CsHPW nanocast.
CsHPW/SBA-15 and nanocast CsHPW materials are shown in
than that of silica channels. After the removal of the silica
matrix the nitrogen sorption isotherms of the CsHPW nanocast
changed to a type I shape with small slopes for the plateau and
a H4 hysteresis loop, as shown in Fig. 11.
Fig. 11. The isotherms for the CsHPW/SBA-15 exhibit type IV
isotherm according to the IUPAC nomenclature [46] and this is
a typical characteristic of mesoporous materials [47,48]. The
physical properties of SBA-15, bulk-CsPW, CsPW/SBA-15,
and CsPW nanocast are listed in Table 2. As expected, the BET
surface areas, total pore volumes, and mesopore sizes of the
SBA-15 [21] material decrease from 873 to 439 m2/g, 1.4 to
0.74 cm3/g and 6.4 to 5.8 nm, respectively, after functionaliza-
tion with CsHPW. These changes reflect the part of the
mesopore volume in the SBA-15 matrix that is filled with
CsHPW nanocrystals resulting in pore diameters that are less
2.2 Choice of reaction media and effect of the catalyst on
the synthesis of TAP derivatives
Initially, the condensation reaction between chalcone and
phenylhydrazine was performed in the presence of a catalytic
amount of two polyoxometalate (POM) Cs salts (Table 3,
entries 1,2). The synthesis was not successful in the absence of
the catalyst. The performance of the CsHPW/SBA-15 com-
posite is shown in Table 3. Critically, the removal of silica
caused an increase in reactivity (Table 3, entries 4–6). To de-
termine the most appropriate medium for this heterocyclization
reaction, the synthesis of TAP from the condensation between
100
98
96
94
92
4
3
2
1
0
100
200
300
400
500
600
Temperature (oC)
Fig. 8. TG analysis of the Cs2.5H0.5PW12O40 nanoparticles.
200
300
400
500
600
700
Wavelength (nm)
Fig. 10. UV-Vis spectrum of the CsHPW nanocasts.
Table 2 Texture parameters of the parent CsHPW/SBA-15 and CsHPW
nanocasts and a comparison with bulk CsHPW materials
(1)
(2)
Surface areaa Pore volumea Pore diameter
Material
(m2/g)
873
(cm3/g)
1.4
(nm)
6.4
SBA-15 [21]
Bulk-CsHPW
CsHPW/SBA-15
CsHPW nanocast
19.336
439.29
83.825
0.3211
0.7415
0.2180
3.7672
5.8337
3.89
10
20
30
40
50
60
70
2ꢅ/(o )
aTotal pore volume measured at p/p0 = 0.99.
Fig. 9. XRD patterns of CsHPW/SBA-15 (a) and the Cs2.5H0.5PW12O40
(b) nanoparticles.

Razieh FAZAELI et al. / Chinese Journal of Catalysis, 2012, 33: 237–246
0.012
0.008
0.004
0.000
(a)
(b)
24
12
0
0.00
0.25
0.50
0.75
1.00
1
10
100
rp/nm
p/p0
600
400
200
0
(d)
(c)
0.6
0.3
0.0
0.00
0.25
0.25
0.50
p/p0
0.75
0.75
1.00
1.00
1
1
10
100
rp/nm
0.03
0.02
0.01
0.00
160
120
80
40
0
(f)
(e)
0.00
0.50
p/p0
10
rp/nm
100
Fig. 11. N2 adsorption-desorption isotherms and BJH pore sizes obtained from the adsorption branches recorded with bulk-CsPW (a, b), CsPW/SBA-15
(c, d), and CsPW nanocast (e, f).
chalcone and phenylhydrazine in the presence of a catalytic
amount of CsHPW nanoparticles was selected as a model re-
action. Alcoholic solvents (methanol and ethanol), CH2Cl2,
CH3CN, and CHCl3 gave good conversions (Fig. 11). Clearly,
ethanol stands out as the solvent of choice with its fast con-
version, high yield, and easy removal. To establish the optimal
conditions, a set of experiments was carried out by varying the
amount of catalyst (Table 3, entries 3–5). The feed ratios of the
reaction (Table 3, entries 4,7,8) and (Fig. 11 and Table 3) were
varied as well. The best conditions for the preparation of TAP
derivatives were achieved when 1 mol chalcone, 1 mol
phenylhydrazine, and 0.03 mol CsHPW nanoparticles were
used. These conditions were applied to a series of substituted
aromatic aldehydes.
On the basis of the above results, to extend the scope and
generality of this method several structurally diverse chalcones
and phenylhydrazines were cyclized to give TAP using
CsHPW nanocrystals. The results are listed in Table 4 and the
reactions proceeded well with all the substrates but the sub-
strates with electron-donating groups were generally more
reactive than those with electron-withdrawing groups.
synthesis of the 1,3,5-triarylpyrazoline derivatives that were
catalyzed by the CsHPW nanocrystals were higher than that of
PW12 and PW12/PA. One explanation for this behavior is that
the CsHPW nanocrystals have high specific structure areas.
We then attempted to prepare other types of 2-pyrazolines
using the above-mentioned optimum conditions. When alde-
hyde 4, methyl acetoacetate 5, phenylhydrazine 2, and
Table 3 Effect of different conditions on the reaction between chalcone
and phenylhydrazine at 45 °C
Ph
O
CsHPW, nanocrystals
EtOH
Ph
NH2
Ph
N
H
+
N
Ph
Ph
N
Ph
Catalyst amount
Isolated yield
Entry
Catalyst
(mol%)
(%)
68
45
86
92
78
92
82
80
1
2
3
4
5
6
7
8
Bulk-CsHPW
Bulk-CsHPMo
CsHPW/SBA-15
CsHPW-nanocrystals
CsHPW-nanocrystals
CsHPW-nanocrystals
CsHPW-nanocrystalsa
CsHPW-nanocrystalsb
3
3
4
3
2
4
3
3
To show the effect of CsHPW nanocrystal catalytic activity
on the synthesis of TAP derivatives, all the reactions were
repeated using the same reaction conditions in the presence of
H3PW12O40 [38] and PW12/PA [39] as catalysts. The obtained
results showed that the turnover frequencies (TOF) for the
Reaction conditions: chalcone (1 mmol), phenylhydrazine (1 mmol), and
catalyst (0.03 mmol) in EtOH (5 ml) over 2 h at 45 °C.
aChalcone/phenylhydrazine: 1/2.
bChalcone/phenylhydrazine: 1/3.

Razieh FAZAELI et al. / Chinese Journal of Catalysis, 2012, 33: 237–246
Table 4 Synthesis of TAP derivatives in the presence of CsHPW nanocrystals
Isolated yield
Melting point (oC)
Reported
TAP
R1
R2
TON
TOF
(%)b
95
Found
3a
3b
3c
3d
3e
3f
H
H
H
H
H
H
4-NO2
4-Me
4-Cl
3-Cl
2-Cl
2,4-Cl2
3-Br
4-MeO
H
3.135
2.970
3.234
2.970
2.805
2.871
2.97
3.036
3.234
3.036
2.805
9.5
9.0
9.8
9.0
8.5
8.7
9.0
9.2
9.8
9.2
8.5
130–132
136–138
128–130
136–137
131–133
131–133
136–138
139–141
109–111
143–145
144–147
134–135 [37]
—
90
98
90
85
87
90
92
>98
92
128–130 [35]
133–134 [36]
134–136 [35]
134–135 [36]
—
141–143 [35]
110–112 [35]
143–145 [35]
—
H
3g
3h
3i
H
H
H
3j
3k
4-Cl
4-Br
H
85
Reaction conditions: chalcone (1 mmol), phenylhydrazine (1 mmol) and CsHPW (0.03 mol) in EtOH over 20 min.
Ar3
N
N
6a (68% - 15 h)
Bulk-CsHPW
R
COOMe
O
Ar3
N
Ar3
NH2
COOMe
(a)
N
H
2
RCHO
4
+
+
N
6b (95% - 20 min)
5
R
CsHPW-nano particles
Bulk-CsHPW
COOMe
8a (57% - 15 h)
N
Ph
N
H
Ar3
NH2
O
O
N
H
(b)
+
2
8b (92% - 20 min)
7
N
CsHPW-nano particles
Ph
N
H
Scheme 3. Preparation of 2-pyrazolines using CsHPW.
bulk-CsHPW (Scheme 3) or acethyl acetonate 7 (1,3-diketone),
phenylhydrazine, and bulk-CsHPW were used the corre-
sponding 2-pyrazolines (6a, 8a) were obtained in 68% and
57% yields, respectively (Scheme 2). However, in the presence
of catalytic amounts of CsHPW nanocrystals the corresponding
2-pyrazolines (6b, 8b) were obtained in EtOH as solvent in
95% and 92% yields after 20 min, respectively.
3 Conclusions
90
80
EtOH
The preparation of CsHPW salts, supported on mesostruc-
tured SBA-15 silica, by the reaction deposition strategy causes
the formation of isolated CsHPW nanocrystals within the
nanotubular channels. A remarkable characteristic of the
SBA-15 structure is that all the cylindrical pores are connected
MeOH
70
60
50
40
30
20
10
0
CH3CN
CH2Cl2
CH3Cl
by small channels. This results in
a
completely
three-dimensional SBA-15 pore system. We have developed an
efficient strategy for the synthesis of 1,3,5-triaryl pyrazoline
and 2-pyrazolines using CsHPW nanoparticles as an
eco-friendly, inexpensive and efficient catalyst. The advan-
tages of this catalytic system are mild reaction conditions, short
reaction times, high product yields, easy catalyst preparation,
non-toxicity of the catalysts, and a simple and clean work-up of
the desired products.
1.0
1.5
2.0
2.5
Time (h)
3.0
3.5
4.0
Fig. 12. Effect of various solvents in the reaction between chalcone
with phenylhydrazine at room temperature. Reaction conditions: chal-
cone (1 mmol), phenylhydrazine (1 mmol) and catalyst (0.03 mmol) in
solvent (5 ml) over 4 h.

Razieh FAZAELI et al. / Chinese Journal of Catalysis, 2012, 33: 237–246
Talianker M. Ind Eng Chem Res, 2003, 42: 2773
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