Preparation of trifluoroacetic acid-immobilized Fe3O4@SiO2-APTES nanocatalyst for synthesis of quinolines

Article abstract of DOI:10.1016/j.jfluchem.2015.08.007

A specific task magnetically recoverable trifluoroacetic acid-immobilized Fe₃O₄@SiO₂-APTES core-shell nanocatalyst was prepared and characterized by FTIR, XRD, TGA, CHN, TEM and DLS. This super Br?nsted acid supported cata

Full text of DOI:10.1016/j.jfluchem.2015.08.007

Accepted Manuscript
Title: Preparation of trifluoroacetic acid-immobilized
Fe3O4@SiO2–APTES nanocatalyst for synthesis of quinolines
Author: Mohammad Jafarzadeh Ebrahim Soleimani Parastoo
Norouzi Rohana Adnan Heshmatollah Sepahvand
PII:
S0022-1139(15)00251-1
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.jfluchem.2015.08.007
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Revised date:
Accepted date:
28-5-2015
1-8-2015
8-8-2015
Please cite this article as: M. Jafarzadeh, E. Soleimani, P. Norouzi, R. Adnan, H.
Sepahvand, Preparation of trifluoroacetic acid-immobilized Fe3O4@SiO2ndashAPTES
nanocatalyst for synthesis of quinolines, Journal of Fluorine Chemistry (2015),
http://dx.doi.org/10.1016/j.jfluchem.2015.08.007
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*Graphical Abstract - Pictogram
Graphical abstract
Page 1 of 20

*Graphical Abstract - Synopsis
Graphical abstract text
Trifluoroacetic acid is attached electrostatically to the aminopropyl groups of
modified silica. The ionic interactions between ammonium and trifluoroactate led to
the formation of ion pair on the surface. This bifunctional nanocatalyst, super acid/ion
pair, exhibited catalytic activity for the Friedländer annulation-based synthesis of
quinolines.
Page 2 of 20

*Highlights (for review)
Highlights
 Immobilization of trifluoroacetic acid on the core-shell particles
 Catalytic activity of super acid/ionic liquid-supported nanocatalyst
 Supported organocatalysis for Friedländer synthesis of quinolines
 Simple recoverability and reusability of magnetic heterogeneous acid
1
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*Manuscript
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Preparation of trifluoroacetic acid-immobilized Fe3O4@SiO2–APTES
nanocatalyst for synthesis of quinolines
Mohammad Jafarzadeha*, Ebrahim Soleimania,b*, Parastoo Norouzia, Rohana Adnanc, Heshmatollah
Sepahvanda
aFaculty of Chemistry, Razi University, Kermanshah 67149-67346, Iran
bDepartment of Chemistry, College of Sciences, Kermanshah Branch, Islamic Azad University,
Kermanshah, Iran
cSchool of Chemical Sciences, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia
*Corresponding author (M. Jafarzadeh): Email: mjafarzadeh1027@yahoo.com
(E. Soleimani): E_Soleimanirazi@yahoo.com
Page 4 of 20

Abstract
A specific task magnetically recoverable trifluoroacetic acid-immobilized Fe3O4@SiO2–
APTES core-shell nanocatalyst was prepared and characterized by FTIR, XRD, TGA, CHN,
TEM and DLS. This super Brönsted acid supported catalyst exhibited catalytic activity for
the Friedländer synthesis of quinolines using various cyclic and acyclic dicarbonyl
compounds under solvent-free condition.
Keywords: Trifluoroacetic acid, Silica, Magnetic nanocatalyst, Quinoline
1 Introduction
There are many efforts for the synthesis of heterocyclic compounds, quinolines and their
derivatives, in the literature due to their biological activities and medicinal properties [1].
They found pharmaceutical application as anti-malarial, anti-asthmatic, anti-inflammatory,
anti-bacterial, and anti-hypertensive [2]. Polyquinoline also developed in electronic and non-
linear photonic-based devices [3]. Friedländer reaction is one of the classic reactions in the
synthesis of quinolines, which involve a reaction of 2-aminoaryl aldehydes or ketones with
enolizable carbonyl compounds in acidic conditions [4,5]. In view point of Friedländer
reaction mechanism, two different mechanisms are proposed in literature [4]: (1) initial
formation of a Schiff base via a reaction between 2-aminoaryl carbonyls and enolized
compounds, followed with an intra-molecular aldol/cyclization reaction and aromatization
through dehydration reaction, (2) initial inter-molecular aldol reaction between the precursors
and followed by cyclization to form nitrogen-containing heterocyclic rings. Friedländer
annulations are generally required refluxing condition in aqueous or alcoholic medium and/or
elevated temperature (e.g. 150-220 ºC) in catalyst-free condition [4]. Wide varieties of solid
Brönsted acids, inorganic and polymeric supported Brönsted acids, acidic organocatalysis,
acidic ionic liquids such as H2SO4 [6a], zeolite [6b], H3PW12O40 [6c], HO3SO-SiO2 [6d,e],
HClO4-SiO2 [6f], NaHSO4/silica-gel [6g], SBA-15/propyl-SO3H [6h], PEG-OSO3H [6i],
chitosan-SO3H [6j], CF3COOH [6k], I2 [6l], p-toluenesulphonic acid [6m],
dodecylphosphonic acid [6n], L-(+)-tartaric acid/urea [6o], TsOH/ionic liquid [6p],
[Hbim]BF4 [6q] were used for the synthesis of quinolines and their derivatives. Furthermore,
various Lewis acids have been employed for milder reaction condition such as Y(OTf)3 [7a],
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Cu(OTf)2 [7b], zirconium dodecyl sulfates [7c]. Recently, nanomaterials such as ZnO nano-
flake [8a] and TiO2 nanoparticles (NPs) [8b] received much attention for catalyzing the
Friedländer based reactions due to their large surface area and high number of active sites.
Some limitations can be found for the above catalytic systems, for example require strong
and corrosive acid, difficult catalyst isolation, catalyst non-recyclability, harmful solvents
(CH3CN) and microwave irradiation. As an alternative heterogeneous supported catalyst and
magnetically recyclable catalyst were introduced. Nanomaterials are suitable candidates to
reduce the drawbacks of heterogeneous and homogeneous catalysts as they exhibit new
properties possessing the advantageous of both catalytic systems. Reducing the time, energy
and solvent usage in purification of products, recoverability and reusability of the catalyst,
and also increasing the contact site between the catalyst and reactants can be achieved by
employing nanocatalysts [9].
Silica is an inexpensive, widely abundant, non-toxic, biocompatible, and thermally and
chemically stable material [10]. Silica in nano-size provides high surface area and porosity
with high amount of silanol (Si–OH) groups on the surface which can be tailored by various
kind of organic compounds for different purposes, e.g. catalysis, separation, coating, etc.
[11]. Organic moieties can be directly attached to the silica nanomaterials or through
organosilane coupling agents, for example γ-aminopropylalkoxysilanes (APTES). Coating of
silica on the surface of magnetic nanoparticles can efficiently improve the separation of the
nanocatalyst after completion of the reaction [12]. In this research, trifluoroacetic acid (TFA)
was immobilized on the surface of organo-modified Fe3O4@SiO2 core-shell nanoparticles,
and then used for the synthesis of quinolines via Friedländer annulation reaction under
solvent-free conditions. TFA is inexpensive, readily available, less-toxic [13], and soluble in
organic and aqueous solvents [14] that could be applied for organic synthesis as a solvent,
catalyst and reagent [15]. The role of TFA in various organic reactions such as organic
rearrangements, functional group deprotections, oxidations, reductions, condensations,
hydroarylations and trifluoromethylations was observed [15]. In our system, TFA was
attached electrostatically to the amine groups of aminopropyl (APTES) and formed ion-pair
on the surface. By employing triple-fluorinated acetic acid with pKa 0.23 at 25 °C in H2O
(cf., pKa= 4.76 for acetic acid) [15], the formation of Schiff base (initial stage in quinoline
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synthesis) is expected to further accelerate via effective protonation of oxygen of carbonyl
compounds. This work is a first report using magnetically supported ion-pair nanocatalyst for
synthesis of quinolines by Friedländer reaction.
2 Experimental
All chemicals were purchased from Fluka and Merck. Yields refer to isolated product. The
known products were identified by comparison of their spectral data and physical properties
with data reported in the literature. Progress of the reaction was monitored by TLC (Thin
Layer Chromatography) using silica gel polygrams SIL G/UV 245 plates.
2.1 Typical procedure for the preparation of Fe3O4 nanoparticles
In brief, 0.036 mol of FeCl3.6H2O and 0.018 mol of FeCl2.4H2O were dissolved in 20 mL
deionized water under nitrogen gas with vigorous stirring [16]. Then, NH3 (25%) was added
into the solution until the pH of the solution reached 11 and the stirring was continued for 1 h
at 60 ºC. The color of bulk solution turned from orange to black immediately. The magnetite
precipitate was separated from the solution using magnet and washed several times with
deionized water and ethanol, and left to dry in air.
2.2 Typical procedure for the synthesis of Fe3O4@SiO2–APTES
Approximately 45 mg of the as-prepared hydrophilic Fe3O4 NPs were dispersed in 16 mL
deionized water under vigorous stirring and then mixed with 2 mL of aqueous ammonia
solution (25 wt.%) and 80 mL ethanol. Next, 0.8 mL TEOS was added dropwise into the
above solution under vigorous stirring at room temperature for 24 h. The products were
separated using an external magnet and washed several times with water. The final product
(Fe3O4@SiO2) was collected and dried at 50 ºC. In next step, 0.2 g of Fe3O4@SiO2 was
dispersed in 2.5 mL APTES solution (4% v/v in dry toluene). The mixture was stirred under
reflux condition at 110 ºC for 24 h. After it is cooled to room temperature, the sample was
separated from the solution by an external magnet, and washed thoroughly twice with toluene
and once with distilled water to remove un-reacted APTES. The samples were dried in an
oven at 80 ºC for 24 h.
2.3 Typical procedure for the synthesis of Fe3O4@SiO2–APTES-TFA
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In a round-bottomed flask (25 mL), 0.5 g Fe3O4@SiO2–APTES core-shell particles and 1 mL
dry dichloromethane were added into the flask. 1 mL trifluoroacetic acid (TFA) was then
added dropwise into the mixture under continuous stirring for 3 h. The product was separated
using an external magnet and washed twice with dry toluene and once with anhydrous diethyl
ether, and left to dry in air.
2.4 Synthesis of quinolines using the nanocatalyst
1.0 mmol of 2-aminoarylketone, 1.2 mmol of 1,3-dicarbonyl compound, and 0.2 g of the
catalyst were added into a round-bottomed flask (25 mL) and heated under continuous
stirring at 100 ºC for 5 h under solvent-free condition. After completion of the reaction, the
reaction mixture was diluted with ethanol and the catalyst was separated using an external
magnet. Then, the catalyst was recycled and reused for subsequent runs under the same
reaction conditions.
2.5 Characterization techniques
Melting points were determined in open capillaries with a Gallen-Kamp melting point
apparatus. Infrared spectra were obtained by using a Ray Leigh Wqf-510 FT-IR
spectrophotometer. X-ray diffraction was conducted using Philips X’pert Pro X-ray
diffractometer (PW 3040), with monochromatic high-intensity Cu-Kα radiation (k = 1.54056
Å, 40 kV, 30 mA) at room temperature. Particle size and particle size distribution were
determined by Zetasizer nanoparticle analyzer, Malvern Nano ZS series (Model: ZEN3600)
at room temperature. The morphological studies were performed using a TEM (Transmission
Electron Microscopy), Philips CM10 operated at 80 kV electron beams accelerating voltage
and equipped with a CCD camera. Thermogravimetric analysis (TGA) was performed by a
TGA6 instrument (Perkin–Elmer) with heating rate of 20 ºC min-1 under N2 flow. Elemental
analysis was performed with a CHN machine (Perkin Elmer Series II, 2400).
3 Results and Discussion
3.1 Synthesis and characterization of Fe3O4@SiO2–APTES-TFA
The schematic pathways for preparation of TFA-modified silica-coated magnetite NPs are
depicted in Scheme 1. Fe3O4 NPs were prepared via chemical co-precipitation method [16]
and used as a support for coating by silica via a modified Stöber method [17]. The ferric
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hydroxides on the Fe3O4 NPs surface make ether bonds with OH groups of hydrolyzed TEOS
(silica precursor) [16]. Post-modification technique was employed to introduce organosilanes
to the silica layer via a reaction between silanol groups of silica surface and hydroxyl groups
of hydrolyzed APTES [18]. Parts of silanol groups could be replaced with aminopropyl
groups depending on surface modification efficiency. Consequently, the hydrophilic nature of
silica surface transformed to slightly hydrophobic upon organo-functionalization [18].
Although the specific surface area of silica is generally decreased upon post-modification
reaction with APTES [19], but the NH2 groups of APTES on the surface of Fe3O4@SiO2–
APTES are able to serve as a linker for organic moieties. Triflouroacetic acid was anchored
to the surface of the amino-functionalized nanocatalysts via electrostatic forces arising from
acid-base reaction. Strong ionic interactions between quaternary ammonium and
+-
trifluoroacetate groups in Fe3O4@SiO2–CH2CH2CH2NH3 OOCCF3 can provide an ion-pair
with unique behavior similar to ionic liquids. Therefore, the formation of thin layer ion-pair
on the surface of solid particles is expected to promote an efficient, facile and close contact
between organic reactants with active sites of the catalyst in catalytic organic reactions. This
solid supported ion-pair generally is able to act as host for both organic reactants and
inorganic reagents. The advantages of heterogeneous ion-pair compared to their
corresponding homogeneous can be easy separation.
Scheme 1. Preparation of Fe3O4@SiO2-CH2CH2CH2NH2-TFA nanocatalyst.
Since silica has large number of silanol groups on the surface, esterification reaction between
the silanol groups and carboxylic groups of trifluoroacetic acid is strongly possible.
Moreover, the strong hydrogen bonding between TFA and silanol groups is another inter-
molecular interaction possibility. It is expected that large amount of TFA adsorb to the
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Fe3O4@SiO2–APTES surface via covalently bound with silanol groups and strong interaction
with amine and silanol groups.
Figure 1 shows the XRD pattern of the materials involve in the preparation of Fe3O4@SiO2–
APTES-TFA nanocatalyst. Crystalline diffraction peaks with 2θ at 30º, 35.5º, 43º, 53.8º,
56.9º and 62.5º correspond to the characteristic planes of cubic spinel Fe3O4, respectively
[20]. No significant change was observed in the XRD pattern of the Fe3O4 core upon
modification and immobilization of the magnetite surface by APTES and TFA, respectively
(Figure 1 b, c). The calculated mean crystallite size was about 27 nm according to the
Scherrer’s formula using (311) plane.
Figure 1. XRD patterns of (a) Fe3O4, (b) Fe3O4@SiO2–APTES and (c) Fe3O4@SiO2–
APTES-TFA.
The Fourier Transform Infrared (FTIR) spectrum of Fe3O4@SiO2–APTES-TFA NPs is given
in Supplementary Information (S1). An absorption peak at 1703 cm-1 is assigned to the
vibrational mode of the carbonyl groups in trifluoroactate. The shift of the carbonyl peak
compared to the common saturated aliphatic carboxylic acid (1760 cm-1), esters (1750-1735
cm-1) and carboxylate (1650-1550 cm-1) may be also attributed to the existence of ionic
interaction and esterification reaction between TFA and Fe3O4@SiO2–APTES. Weak
vibrations in the range of 2850–2950 cm-1 and at 1384 cm-1 are due to the symmetric
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vibration of the C–H groups and bending mode of Si–CH2, respectively [18]. The stretching
and bending vibrations of aliphatic amine (N–H) groups at 3400 and 1616 cm-1 overlapped
with the vibration of siloxane (Si–O–Si) and silanol (Si–OH) groups. A shoulder in the range
of 500-600 cm-1 is attributed to the characteristic bands of Fe3O4 NPs [16]. Other peaks are
characteristic absorption bands of silanol and siloxane groups, and the adsorbed water on the
silica surface [18].
Thermogravimetric analysis results of Fe3O4@SiO2–APTES-TFA and Fe3O4@SiO2–APTES
are shown in Figure 2. The DTG thermograms make a correlation between temperature and
mass loss of the immobilized organic species on the surface of Fe3O4@SiO2. Three stages of
mass loss were observed in Fe3O4@SiO2–APTES-TFA thermogram. The initial loss in the
range of 30-180 ºC is related to the adsorbed water on the surface [18], and trapped residual
and loosely-bound TFA. The second mass loss occurred between 330 and 410 ºC, which
could correspond to the release of TFA upon breaking the ionic bonds, and the initial
decomposition of the aminopropyl groups [18]. In third stage, the degradation of organic
species and dehydroxylation of silanol groups [18] were main reasons for the mass losses in
temperature range of 400-570 ºC. Higher mass losses in Fe3O4@SiO2–APTES-TFA rather
than Fe3O4@SiO2–APTES were concluded to be due to the hydrophilic behavior of the shell
surface, adsorption of high amount of water and also higher content of immobilized TFA via
strong electrostatic interactions (ionic forces) and esterification reactions.
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Figure 2. DTG thermograms of Fe3O4@SiO2–APTES (dash line) and Fe3O4@SiO2–APTES-
TFA (solid line).
CHN analysis was confirmed the immobilization process of TFA on the surface of
Fe3O4@SiO2–APTES. The results showed 65.7, 13.4, and 7.0 mg g-1 of carbon, hydrogen and
nitrogen, respectively for Fe3O4@SiO2–APTES-TFA rather than 34.1, 7.4, and 7.1 mg g-1 of
carbon, hydrogen and nitrogen, respectively for Fe3O4@SiO2–APTES. The quantity of NH2
on the surface of Fe3O4@SiO2–APTES is estimated to be roughly 0.5 mmol. It is expected
that majority of this amount neutralize by TFA.
Figure 3 shows TEM images of Fe3O4@SiO2–APTES and Fe3O4@SiO2–APTES-TFA NPs.
The images obviously show that the roughly nanospherical Fe3O4 cores were coated by silica,
and subsequently immobilized by APTES and TFA. Subsequent immobilization on the
surface of silica shells by APTES and TFA did not affect the morphology of Fe3O4@SiO2
core-shell particle. The average size of the cores is less than 50 nm, consistent with the XRD
results for Fe3O4. Moreover, the thickness of the silica shell estimates less than 50 nm. The
organo-modified core-shell magnetic particles also showed reasonable response to applied
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external magnetic field even after silica coating and organo-functionalization. It might be
related to the encapsulation of few magnetic cores inside each core-shell particle. Thus, it is
promising for this new designed catalyst in magnetically separation from an organic reactions
medium.
(a)
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(b)
Figure 3. TEM images of (a) Fe3O4@SiO2–APTES and (b) Fe3O4@SiO2–APTES-TFA.
Dynamic light scattering (DLS) technique was applied to determine the particle size
distribution of Fe3O4@SiO2–APTES-TFA NPs (Supplementary Information, S2). The Z-
average particle size of ~384 nm (PDI= 0.447) in radius was found for colloidal core-shell
particles in ethanol. The DLS generally shows larger particle size compared to that in XRD
and TEM, because the particle size is attributed to an average hydrodynamic size of
agglomerated nanoparticles. The surface charge of the nanoparticles was inferred to affect the
hydrodynamic size measuring of the sample in colloidal form, while dried samples is
generally used for TEM analysis [21]. On the other hand, by increasing the number of
hydrophilic groups on the surface the probability of undesirable agglomeration among
nanoparticles increase. In addition, the existence of ionic bonds between ammonium and
trifluoroacetate group in Fe3O4@SiO2–APTES-TFA further enhance the polarity of the shell.
3.2 Catalytic activity of Fe3O4@SiO2–APTES-TFA
Catalytic activity of the nanocatalyst was evaluated for the reaction involving 2-
aminobenzophenone (1 mmol) with acetylacetone (1.2 mmol) as a model. The best result was
obtained with 0.2 g of the catalyst (equal to 0.1 mmol NH2) (Table 1, entry 3). Higher
amounts of catalyst did not enhance the yield (Table 1, entry 4) as by increasing the amount
of the catalyst the chance of undesirable agglomeration increases, thus the total number of
active sites decreases. Furthermore, no product was observed under similar reaction
conditions in the absence of catalyst after 24 h. The process was further extended to various
cyclic and acyclic β-dicarbonyl compounds (e.g. ketones and esters), and cyclic ketones and
the results are listed in Table 2. It is expected that the supported ion-pair on the surface of the
catalyst can promote the contact with various kind of the reactants. It can be seen from the
results; both aliphatic and aromatic ketones gave the corresponding quinoline products in
almost same yields. Higher yield was obtained for 2-aminoaromatic ketones with electron-
withdrawing group (e.g. Cl) on the ring. Moreover, cyclohexanone was used as an enolizable
compound with lower yield compared to using dicarbonyl compounds. The more acidity of α-
hydrogen induced by two carbonyl groups in β-dicarbonyls could accelerate the formation of
enolate. Based on the reported mechanism [4], the presence of fluorine in TFA could induce
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the protonation of β-dicarbonyl compounds in formation of Schiff base (initial stage) and
follow the cyclization reaction. Our preliminary test showed that acetic acid, a weak organic
acid, was not as successful as TFA in synthesis of quinolines even in longer period of time.
Table 1. Optimization of the Friedlander reaction condition by using different amount of the
catalyst.a
Entry
Reaction condition
Yield (%)b
1
2
3
4
Fe3O4@SiO2-APTES-TFA (0.05g) 100 ˚C
Fe3O4@SiO2-APTES-TFA (0.1g) 100 ˚C
Fe3O4@SiO2-APTES-TFA (0.2g) 100 ˚C
Fe3O4@SiO2-APTES-TFA (0.3g) 100 ˚C
78
85
98
92
a Reaction conditions: 2-aminobenzophenone (1 mmol), acetylacetone (1.2 mmol), catalyst, solvent-
free, 100 ºC
b Isolated yields
Table 2. Synthesis of the quinolines in the presence of a catalytic amount of Fe3O4@SiO2-
APTES-TFA under solvent-free condition.a
Ph
Ph
O
R2
R1
Catalyst
O
R2
+
R1
1000C, solvent-free
NH2
N
Entry
Aminoaryl
ketones
CH acid
Product
Yield
(%)b
mp (ºC)
Found Reportedc
Ph
O
Ph O
O
O
O
O
98
96
87
110
150
106
(112-
1
113)6h
N
NH2
Ph
Ph O
Cl
Cl
(151-
O
2
3
153)6h
N
NH2
Ph
O
O
Ph O
(107)6q
OMe
OMe
O
N
NH2
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Ph
O
O
Ph O
Cl
Cl
OMe
OMe
O
90
91
92
133
(133-
4
135)6b
N
NH2
Ph
O
O
Ph O
(98)6n
100-
101
OEt
OEt
OEt
O
5
6
7
N
NH2
Ph
O
O
Ph O
(108)6l
Cl
Cl
110
OEt
O
N
NH2
Ph
Ph O
N
O
NH2
Ph
93
96
187-
190
(191-
192)6l
O
O
O
Ph O
Cl
Cl
O
(208-
204
8
210)6h
O
NH2
Ph
N
Ph
O
O
NH2
Ph
68
75
140
162
(139-
9
141)6h
N
O
Ph
Cl
Cl
(161-
O
10
163)6c
N
NH2
a Reaction conditions: 2-aminobenzophenone (1 mmol), 1,3-dicarbonyl compounds (1.5 mmol),
Fe3O4@SiO2-APTES-TFA (0.2 g).
b Isolated yield.
c Data from literature [6b,6c,6h,6l,6n,6q].
The recyclability and reusability of the catalyst was investigated by using a model reaction of
2-aminobenzophenone and acetylacetone. This heterogeneous catalyst could be easily
recovered with an external magnet and reused for at least four runs without significant
decrease in the catalytic activity and performance (Table 3).
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Table 3. Reusability of the catalyst in the reaction of 2-aminobenzophenone with
acetylacetone.
Run
1st
98
2nd
88
3rd
85
4th
78
Yield (%)
4 Conclusions
The immobilization of homogeneous acids on the surface of organo-functionalized magnetic
nanoparticles can be promising for a clean and economic synthesis of organic compounds.
The non-toxic and inexpensive Fe3O4@SiO2-APTES-TFA nanoparticle has been prepared
through simple synthetic procedures. This bifunctional and recyclable catalyst was
successfully utilized for the Friedländer annulation reaction in absence of solvent. The
fluorinated acetic acid as a highly strong acid was efficiently promoted the quinoline
formation reaction. The advantage of this approach was facile magnetic-assisted recovery of
the solid catalyst and several times reusability.
Acknowledgment
The authors gratefully acknowledge the financial support and technical support from Razi
University and Universiti Sains Malaysia (through the USM Short Term Grant no
304/PKIMIA/6312088).
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