Synthesis and characterization of nanocrystalline In2O 3 and its efficacy as a catalyst for the one pot synthesis of amidoalkyl naphthols

Article abstract of DOI:10.1080/15533174.2012.740749

In₂O₃ nanopaticles were synthesized by glycine-nitrate combustion method. The synthesized In₂O₃ is characterized by the powder X-ray diffraction and transmission electron microscopy. The average crystallite size

Full text of DOI:10.1080/15533174.2012.740749

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Synthesis and Reactivity in Inorganic, Metal-Organic,
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Synthesis and Characterization of Nanocrystalline In2O3
and Its Efficacy as a Catalyst for the One Pot Synthesis
of Amidoalkyl Naphthols
Vishvanath D. Patil a , Jyotsna S. Thakur a , Shramesha Mhatre a , Medha Gole a & Aarti
Jaiswal a
a Department of Chemistry , C.K. Thakur College , New Panvel(w) , India
Accepted author version posted online: 10 Dec 2012.Published online: 26 Feb 2013.
To cite this article: Vishvanath D. Patil , Jyotsna S. Thakur , Shramesha Mhatre , Medha Gole & Aarti Jaiswal (2013)
Synthesis and Characterization of Nanocrystalline In2O3 and Its Efficacy as a Catalyst for the One Pot Synthesis of
Amidoalkyl Naphthols, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 43:4, 471-478, DOI:
10.1080/15533174.2012.740749
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 43:471–478, 2013
Copyright ꢀ Taylor & Francis Group, LLC
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ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2012.740749
Synthesis and Characterization of Nanocrystalline In2O3
and Its Efficacy as a Catalyst for the One Pot Synthesis
of Amidoalkyl Naphthols
Vishvanath D. Patil, Jyotsna S. Thakur, Shramesha Mhatre, Medha Gole,
and Aarti Jaiswal
Department of Chemistry, C.K. Thakur College, New Panvel(w), India
tential applications in solar cells,[6] PDP,[7] semiconductor gas
sensors,[8] and photocatalysts,[9] Pulse laser abalation,[10] spray
pyrolysis,[11] sol-gel method,[12] and hydrothermal synthesis[13]
are a few to mention that hich were commonly used for synthe-
sis of nanocrystalline In2O3. Recently Maensiri et al. reported
the environmentally benign method of synthesis of In2O3 using
indium acetylacetonate and aloe vera plant extract.[14] However,
many of these methods require either special equipments or ex-
pensive chemicals or they are time consuming as well as tedious.
The gel-combustion method[15] is now gaining lot of importance
due to its advantages such as fast kinetics of the process (instan-
taneous) and high purity, homogeneity, crystallinity, tunable and
fixed composition, and structure of products. Moreover, use of
nontoxic precursors (if at all possible), relatively few numbers of
reagents, and low temperature are plus points of the technique.
In this technique, stoichiometric amount of metal nitrates (oxi-
dizer) and fuel (reducing agent) are used. The combustion of the
aqueous mixture results into generation of high exothermicity
to obtain ultrafine particles of corresponding oxides.
Multicomponent reactions (MCRs) have attracted consider-
able attention because they are performed without isolating any
intermediate during their processes; this reduces time and saves
both energy and raw materials.[16] They have merits over two-
component reactions in several aspects including the simplicity
of a one-pot procedure, possible structural variations, and build-
ing up complex molecules.
Amidoalkyl naphthols can be prepared by MCR. It was re-
ported that 1- amidoalkyl-2-naphthols was prepared by mul-
ticomponent condensation of aryl aldehydes, 2-naphthol, and
acetonitrile or amide in the presence of Lewis or Brønsted
acid catalysts such as montmorillonite K10 clay,[17] HClO4-
SiO2,[18,19] iodine,[20,21] K5CoW12O40.3H2O,[22] p-TSA,[23] sul-
famic acid,[24,25] and cation-exchange resins.[26] The main draw-
back of many of these reactions is that they require high amount
of catalyst and due to this, they require large amount of organic
solvents which are volatile and toxic in nature. Ionic liquids
are one of the alternatives[27,28] to employ catalysts or catalytic
reagents as selective as possible and are superior to stoichiomet-
ric reagents.
In2O3 nanopaticles were synthesized by glycine-nitrate combus-
tion method. The synthesized In2O3 is characterized by the powder
X-ray diffraction and transmission electron microscopy. The av-
erage crystallite size, as determined by Scherrer’s formula, was
found to be about 48 nm. A catalytic amount of In2O3 nanopati-
cles, were used for an efficient synthesis of amidoalkyl naphthols
via multicomponent condensation of aryl aldehydes, β-naphthol,
and urea or acetamide. In2O3 nanopaticles were found to be highly
active for the transformation with excellent yield and purity of the
product in a short reaction time.
Keywords amidoalkyl naphthol, indium oxide, multicomponent con-
densation, nanocatalyst
INTRODUCTION
Over the past decade, research on nanocrystalline materials
has been greatly centered on manipulation of structures on the
molecular or atomic level. However, most of the studies have
been directed to the synthesis, characterization, and applica-
tions as structural and optical/electronic materials. As catalysts,
nanoclusters have been studied for a long time, but they are
mainly limited to supported metal systems.[1] Direct synthesis
and successful stabilization of nanocrystalline metallic and ce-
ramic materials have only recently been investigated in detail
for some catalytic applications.[2] Nanocrystalline metal oxides
as a catalyst in different areas of the organic chemistry have now
reached significant levels, not only for the possibility to perform
environmentally benign synthesis, but for the good yield.[3–5]
Indium oxide (In2O3) has been synthesized by various phys-
ical and chemical methods and studied for many of its po-
Received 19 March 2012; accepted 13 October 2012.
The support of this research by Dr. A. K. Tyagi, Head, Material
Chemistry Division, Bhabha Atomic Research Centre, Mumbai, and
Dr. Hemlata Bagla, Vice-Principal, K.C. College, Mumbai, is gratefully
acknowledged.
Address correspondence to Vishvanath D. Patil, Department
of Chemistry, C.K. Thakur College, Plot 3A, Sec. 10, Khanda
Colony, New Panvel (w), Raigad, Maharashtra, India 410206. E-mail:
patilvd148@yahoo.in
471

472
V. D. PATIL ET AL.
FIG. 2. TEM image of synthesized nanocrystalline In2O3.
FIG. 1. XRD pattern of synthesized nanocrystalline In2O3.
and its crystallite size was determined by Scherrer’s formula
and morphology was studied by TEM.
This study demonstrates synthesis of nanocrystalline In2O3
by gel-combustion method, characterization by powder X-ray
diffraction (XRD), and its scope as a catalyst in the novel and
rapid synthesis of various amidoalkyl napthols as compared to
the commercially available In2O3
Characterization of Nanocrystalline In2O3 Catalyst
X-ray diffraction measurements were carried for phase analy-
sis and crystallite size estimation, using monochromatized Cu-
Kα radiation on a Philips X-ray diffractometer, X’pert PRO
(Almelo, The Netherlands). Silicon was used as an external stan-
dard for correction due to instrumental broadening. The crys-
tallite size was calculated by Scherrer’s formula.[33] The TEM
micrographs were obtained with Phillips CM 200 transmission
electron microscope (TEM; Eindhoven, The Netherlands). The
preparation of samples for TEM analysis involved sonication
in isopropanol for 5 min and deposition on a carbon coated
copper grid. The accelerating voltage of the electron beam was
200 kV. The surface area analysis was carried out by the stan-
dard BET technique with N2 adsorption using a Quantachrome,
Autosorb-1 analyzer (Florida, USA).
EXPERIMENTAL
Synthesis of Nanocrystalline In2O3 Catalyst
Gel-combustion synthesis[29–31] is a soft chemical route used
to synthesize various nanocrystalline oxides. Stoichiometric
proportion of indium nitrate (oxidant) and glycine (fuel), calcu-
lated on the basis of propellant chemistry[32] is used to synthesize
indium oxide. Stoichiometric ratio of oxidant-to-fuel (1:1.66) is
dissolved in a minimum amount of deionized water to obtain
transparent aqueous solution. This solution is then heated at
about ∼100◦C on a hot plate to remove excess of solvent results
in highly viscous gel. On further heating at ∼300◦C, the gel
gets swelled and undergoes combustion with flame and rapid
evolution of gas to produce voluminous powder. The powder
obtained was then calcined at 600◦C for 1 h to remove carbona-
ceous impurities if any. The powder is then characterized by
One Pot Synthesis of Amidoalkyl Naphthols Derivatives
(General Procedure)
A mixture of 2-naphthol (2 mmol), m-nitrobenzaldehyde
powder XRD to confirm the formation of single-phasic In2O3 (2 mmol), acetamide or urea (2 mmol) and In2O3 bulk
SCH. 1. Synthesis of amidoalkyl naphthols.

NOVEL CATALYST SYNTHESIS OF AMIDOALKYL NAPHTHOL
473
TABLE 1
Synthesis of amidoalkyl naphthols by using catalyst as bulk and nanoparticles of In2O3
Bulk
Nanoparticles
Time
(min)
Yieldc
(%)
Time
(min)
Yieldd
(%)
Entry
1.
Aldehydesa
Acetamide/Urea
Productb
60
32
15
93
2.
70
35
10
95
3.
4.
5.
6.
70
90
38
43
44
33
15
15
15
15
95
89
87
85
90
120
(Continued on next page)

474
V. D. PATIL ET AL.
TABLE 1
Synthesis of amidoalkyl naphthols by using catalyst as bulk and nanoparticles of In2O3 (Continued)
Bulk
Nanoparticles
Time
(min)
Yieldc
(%)
Time
(min)
Yieldd
(%)
Entry
7.
Aldehydesa
Acetamide/Urea
Productb
120
34
46
45
15
15
15
88
90
90
8.
9.
90
60
10.
11.
70
80
48
47
10
15
96
95
12.
90
41
15
91

NOVEL CATALYST SYNTHESIS OF AMIDOALKYL NAPHTHOL
475
TABLE 1
Synthesis of amidoalkyl naphthols by using catalyst as bulk and nanoparticles of In2O3 (Continued)
Bulk
Nanoparticles
Time
(min)
Yieldc
(%)
Time
(min)
Yieldd
(%)
Entry
13.
Aldehydesa
Acetamide/Urea
Productb
90
120
120
90
43
36
38
47
50
30
15
15
15
15
15
15
90
87
90
89
92
70
14.
15.
16.
17.
18.
90
120
(Continued on next page)

476
V. D. PATIL ET AL.
TABLE 1
Synthesis of amidoalkyl naphthols by using catalyst as bulk and nanoparticles of In2O3 (Continued)
Bulk
Nanoparticles
Time
(min)
Yieldc
(%)
Time
(min)
Yieldd
(%)
Entry
19.
Aldehydesa
Acetamide/Urea
Productb
120
45
15
15
62
20.
120
25
65
aThe substrate(2-naphthol) was treated with benzaldehyde (2 mmol) and actamide or urea by using 5 mol% of In2O3 nanoparicles and bulk
in presence of hexane and at 60◦C.
bAll products were identified by their IR and NMR spectra.
cIsolated yields by using In2O3 bulk.
dIsolated yields by using In2O3 nanoparticles.
nanoparticles (5 mol%) was stirred magnetically at 60◦C in RESULTS AND DISCUSSION
the presence of hexane (1 mL) and the progress of the reaction
was monitored by thin-layer chromatography (TLC). The reac-
tion mixture was filtered and extracted with ethyl acetate (3 ×
30 mL) and water (10 mL). The combined extracts were dried
with Na2SO4 and concentrated under reduced pressure. In all
the cases, the product obtained after the usual work up gave
satisfactory spectral data.
Nanocrystalline In2O3 was successfully synthesized by sim-
ple and cost effective gel-combustion method. The powder XRD
pattern of as prepared In2O3 revealed that the product formed
is single-phasic and all diffraction peaks are in agreement
with the JCPDS card no. 06–0416 (Figure 1). The crystallite
size was estimated from broadening diffraction peak by us-
ing Scherrer’s equation,[19] which is found to be 48 nm. TEM
image (Figure 2) showed chains of irregularly shaped In2O3
nanoparticles. The grain size is in agreement with the XRD
results. The ultrafine grain size of the nanomaterials provides
high surface-to-volume ratio. The morphological features show
high population of atoms located at the edges, corners and
on the surfaces of nanocrystallites provides active sites for
catalyzing surface reactions.[34,35] Moreover, In(III) salts are
known as Lewis acids. Their stability to co-ordinating atoms
present in organic substrates makes them excellent catalysts.[36]
The specific surface area of the nanocrystalline In2O3 and
bulk In2O3 was measured and it was found that nanocrystalline
In2O3 has surface area 47.55 m2/g whereas bulk In2O3 has
surface area 1.02 m2/g. High specific surface area of nanocrys-
talline In2O3 attributes to enhanced surface chemical reactivity
than its bulk counterpart which in turn responsible for its high
catalytic activity.
For N-[(2-Hydroxy-naphthalen-1-yl)-(3-nitro-phenyl)-meth
yl]-acetamide (2b), pale yellow solid, IR (KBr): 712, 1348,
1
1412, 1522, 1655, 2973, 3086, 3395 cm–1. H NMR (DMSO-
d6): δ (ppm) = 2.03 (s, 3H), 7.25–8.11 (m, 11H), 8.64 (d,
J = 6.92 Hz, 1H), 10.15 (s, 1H). 13C NMR (DMSO-d6): δ
(ppm) = 23.6, 48.5, 118.5, 119.4, 121.1, 122.3, 123.7, 123.7,
127.7, 129.6, 129.6, 130.4, 130.5, 133.2, 133.5, 146.8, 148.6,
154.8, 170.2.
For N-[(2-Hydroxy-naphthalen-1-yl)-p-tolyl-methyl]-aceta
mide (4b), White solid, IR (KBr): 708, 1352, 1415, 1521, 1657,
2974, 3060, 3394 cm–1, 1H NMR (DMSO-d6): δ (ppm) = 2.00
(s, 3H), 2.20 (s, 3H), 7.10–7.32 (m, 8H), 7.70–7.82 (m,
3H), 8.40 (d, J = 8.12 Hz, 1H), 9.95 (s, 1H). 13C NMR
(DMSO-d6): δ (ppm) = 21.2, 23.8, 48.6, 119.9, 120.1, 123.3,
126.5, 127.6, 129.4, 129.7, 130.9, 133.4, 135.7, 140.6, 153.7,
170.3.

NOVEL CATALYST SYNTHESIS OF AMIDOALKYL NAPHTHOL
477
Here in this article we made an attempt to propose a novel
protocol for the rapid synthesis of a variety of amidoalkyl naph-
thols using a catalytic amount of In2O3 Nanopaticles under
extremely mild conditions (Scheme 1).
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Optimization of Reaction Condition
To optimize the conditions, the reaction of benzaldehyde, β-
naphthol, and acetamide was selected as a model to investigate
the effects of different amounts of catalyst on the yield. To
test the general scope and versatility of this procedure in the
synthesis of a variety of substituted amidoalkyl naphthols, we
examined a number of differently substituted aryl aldehydes,
β- naphthols, and acetamide. The best result was obtained by
carrying out the reaction with equal molar amounts of aldehyde,
β-naphthol, and acetamide. The reaction mixture was stirred
with 60◦C in the presence of 5 mol% of catalyst.
All aliphatic and aromatic aldehydes bearing electron-
donating or electron-withdrawing substituents gave correspond-
ing amidoalkyl naphthols. However, aromatic aldehydes were
more desirable in terms of yield. In case of aromatic aldehy-
des, it was observed that aldehydes with electron-withdrawing
groups (Table 1, entries 2, 3, 9–11) gave higher yields than
aldehydes with electron-donating groups (Table 1, entries 4–7,
12–17). Electronic and steric factors also decrease the yield of
the product (Table 1, entries 6–8, 14, 15, 17).
Synthesis of amidoalkyl naphthols was selectively carried
out by using In2O3 catalyst in the bulk form (commercially
available) as well as nanocrystalline form. It was found that
nanocrystalline In2O3 gave excellent yield in short period of
time while bulk In2O3 gave relatively poor yield. The plausible
reason behind this is the active surface, where the reaction takes
place. The active surface increases as the size of the catalyst
decreases, which ultimately results into the enhanced reaction
efficiency. Thus, nanocrystalline In2O3 is highly efficient as a
catalyst to obtain higher yield in the synthesis of amidoalkyl
naphthols.
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CONCLUSION
In conclusion, In2O3 nanoparticles synthesized by facile gel-
combustion method were found to catalyze synthesis of ami-
doalkyl naphthols derivatives with high efficacy. The salient
features of this method include a simple procedure, short reac-
tion time, mild conditions, easy purification, generality, and in
addition not cumbersome apparatus are needed. Nanostructured
catalysts have a significant influence on the conversion and se-
lectivity of the chemical reactions. Particle size and structure
of the catalytic active species is the most important factor in
understanding the difference between the catalytic properties of
nanostructured catalysts and its bulk counterpart.
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