Copper(II) complex intercalated graphene oxide nanocomposites as versatile, reusable catalysts for click reaction

Article abstract of DOI:10.1002/aoc.6017

In this work, we report the efficient, high stable copper(II) complexes intercalated graphene oxide (GO) used as green catalysts for copper(II) complex mediated click reaction. Copper(II) Bis(2,2′-bipyridine) [Cu^II (bpy)₂] (C1) and C

Full text of DOI:10.1002/aoc.6017

Received: 11 March 2020
DOI: 10.1002/aoc.6017
Revised: 29 July 2020
Accepted: 27 August 2020
F U L L P A P E R
Copper(II) complex intercalated graphene oxide
nanocomposites as versatile, reusable catalysts for click
reaction
1
1,4
1
Angel Green Samuel | Karthikeyan Nagarajan
| Karthick Cidhuraj
|
2
2
3
Bhalerao Gopal | Sujay Chakravarty | Varadharajaperumal Selvaraj
|
1
1
Emmanuvel Lourdusamy | Jebasingh Bhagavathsingh
1
Department of Chemistry, Karunya
In this work, we report the efficient, high stable copper(II) complexes interca-
lated graphene oxide (GO) used as green catalysts for copper(II) complex medi-
Institute of Technology and Sciences,
Coimbatore, Tamilnadu, India
2
Material Characterization Division,
0
II
ated click reaction. Copper(II) Bis(2,2 -bipyridine) [Cu (bpy) ] (C1) and
2
UGC-DAE-Consortium for Research,
IGCAR-Kalpakkam Node, Kalpakkam,
Chennai, India
II
Copper(II) Bis(1,10-phenanthroline) [Cu (phen) ] (C2) have synthesized for
2
II
the intercalation of corresponding nanocomposites with GO, [GO@Cu
3
II
Centre for Nanoscience and Engineering
(bpy) ] (GO-C1) and [GO@Cu (phen) ] (GO-C2). The noncovalent interac-
2
2
(
CeNSE), Indian Institute of Science,
tion of complexes supported on the surface of the GO nanosheets proves as an
evident active site to facilitate the enhanced catalytic activity of copper-
Bengaluru, India
4
Quality Control Lab, GVK Biosciences
II
Pvt. Ltd., Jigani, Karnataka, India
catalyzed alkyne azide cycloaddition (Cu AAC) reaction for the isolation of
1
8
,4-disubstituted-1,2,3-triazoles as click products in shorter reaction time with
Correspondence
0%–91% yield (five examples). The X-ray diffraction (XRD) pattern of these
Jebasingh Bhagavathsingh, Department of
Chemistry, Karunya Institute of
Technology and Sciences, Coimbatore
composites shows the enhanced interlayers d-spacing range of 1.01–1.12 nm
due to the intercalation of copper(II) complexes in between the GO basal
planes and characterized by X-ray photoelectron spectroscopy (XPS), Fourier-
transform infrared spectroscopy (FT-IR), Raman, UV, scanning electron micro-
scope (SEM), and thermogravimetric analysis (TGA). The as-prepared
nanocomposites were employed for the typical click reactions using the sub-
strates of azide and acetylene. These classes of composite materials can be
referred to recyclable, heterogeneous, green catalysts with high atom economy
and could also be used for the isolation of click products in biomolecules.
641114. Tamilnadu, India.
Email: jebasinghb@karunya.edu
Funding information
UGC DAE Consortium Scientific
Research, IGCAR-Kalpakkam, Grant/
Award Number:
CSR/Acctts/2016-17/1347; Department of
Science and Technology, DST-DPRP,
Grant/Award Number: VI-
D&P/562/2016-17/TDT(C)
K E Y W O R D S
1
,2,3-triazoles, bipyridine ligands, click catalyst, Cu(II) complexes, intercalated graphene oxide
1
| INTRODUCTION
sustainable developments with process of green technolo-
[6,7]
[8,9]
gies
and clean energy materials.
GO is a two-
Over a few decades, among the various allotropes of car-
bon, graphene oxide (GO) has emerged as one of the most
encouraging material because of its marvelous electronic,
dimensional carbon network with single-atom-thick
2
3
lattice of honeycomb-like sp - and sp -bonded carbon
atoms, bearing oxygen-containing functional groups
(i.e., OH, C O C-epoxide, terminal COOH) on the
surface, which are able to enhance the electron transfer
[1–5]
optical, thermal, and mechanical properties.
Due to its
myriad properties, GO has also been incorporated in
Appl Organomet Chem. 2020;e6017.
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© 2020 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.6017

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SAMUEL ET AL.
rate, water dispersibility, and biocompatibility. 10–14] The
presence of various functional groups in the basal and edge
planes of the GO make it an ideal support for surface-
[
in 30 ml of methanol, copper(II) perchlorate hexahydrate
(0.5 equiv.) in 20 ml of methanol was added dropwise over
the period of 1 h under argon atmosphere. The resulting
solution was refluxed for overnight. Then, the reaction mix-
ture was cooled, and the solvent was removed by rotary
evaporator. The blue colored solid was washed with diethyl
ether to get the respective powdered Cu(II) complexes and
stored in vacuum desiccators.
[15,16]
engineering.
GO has been considered as an interesting
surface support due to easy functionalization, high surface
area, good thermal stability, and better dispersion in water
[17,18]
and other organic solvents.
The strategy of func-
tionalization on the GO sheets include two approaches
such as (a) covalent functionalization of the intercalant by
the ring opening of epoxides or chemical conjugation on
the secondary OH moieties or coupling on the terminal
and (b) noncovalent interactions on the
surface of GO through van der Waals interactions using
Spyrou et al. have demonstrated
the intercalation of organic polycyclic aromatic amines in
the GO planes and proved that its interaction with GO
Teo et al. have
reported the non-covalent interaction of aminopyrene with
II
2.2 | Intercalation of (Cu (bpy) ) C1 and
2
[19–22]
II
acid moieties
(Cu (phen) ) C2 onto the GO planes
2
[23–26]
[37]
aromatic substrates.
GO was synthesized by the reported method.
The
II
intercalation of Cu complexes into the GO sheets was
performed by the dropwise addition of C1 or C2 to the
well-dispersed solution of GO under high dilution condi-
tion. In the typical procedure, GO (1 g) was dispersed in
200 ml of distilled water and sonicated for one hour. To
the dispersed GO solution, corresponding copper(II)
complex C1 or C2 (1 g) in 50 ml of ethanol was added
dropwise and stirred for about 12 h. Upon the intercala-
tion, the brown dispersed solution was changed to black
color. The black solid was centrifuged and washed with
[27]
differs with the size of the intercalants.
[28]
reduced GO as a supercapacitor electrode.
Ajay Gupta
et al. have developed an easy and efficient click method for
the synthesis of flavanone-containing triazole moiety
[29]
catalyzed by CuO/rGO nanocomposite.
The catalytic
activity of GO supported copper oxide (CuO–GO) has been
investigated in click synthesis of 1,2,3-triazole derivatives
under green reaction conditions by Reddy et al.
[30]
II
Zhao
water and ethanol to remove the excess of Cu
et al. studied the immobilized copper (salen) complex on
complexes. Diethyl ether was added to remove all the
residual solvents and dried at RT to isolate the free-flow
black solid.
[31]
GO for the epoxidation of olefins.
We have proved in
our previous work, the enhanced interlayer d-spacing of
GO sheets due to covalent intercalation of phthalimide
[32]
protected DETA.
Epoxidation of olefins was performed
by Masteri-Farahani et al. using peroxophosphotungstate
2.3 | General procedure for CuAAC
reaction
[33]
anion in the GO basal planes.
Gorji et al. reported the
synthesis of Cu(II) Schiff base complex immobilized on
GO/α-Fe O3 as heterogeneous catalyst for the three-
In a round bottom flask fitted with stopper, phenyl acety-
lene (1.0 mmol), an organic azide (1.0 mmol), GO-C1 or
GO-C2 (50 mg) were added in 2 ml of t-butanol followed
by the addition of sodium ascorbate (10 mg) dissolved in
3 ml of water. The reaction mixture was stirred at room
temperature for about 60 min. The GO-based catalyst
was filtered and the resulting reaction mixture was
diluted with ethyl acetate (50 ml) and water (5 ml) to get
biphasic layer. The organic layer was separated and dried
over anhydrous sodium sulfate and concentrated under
reduced pressure. The crude product was purified using
silica gel column chromatography (Eluents: Hexane-
Ethyl acetate, 6:4 v/v) to isolate the corresponding
2
component
synthesis
of
2-Amino-4H-Chromenes
[34]
derivatives. Therefore, it is of our interest to prepare the
versatile GO nanocomposites through the intercalation of
high stable Cu complexes in the GO basal planes and to
II
demonstrate its catalytic activity towards the click
reaction. In this work, we report the noncovalent
II
interaction of Cu
complexes of bipyridine and
phenanthroline Ligands on GO nanocomposites as efficient
catalysts for click reaction.
2
2
| EXPERIMENTAL METHODS
.1 | Synthesis of copper(II) complexes
1,4-disubstitued-1,2,3-triazole (1c-5c) in good yield.
(
C1 and C2)
2
.4 | Characterization
The copper(II) complexes of bipyridine and phenanthroline
were prepared by the modified method.
tion of the ligands, bipyridine, or phenanthroline (1 equiv.)
[35,36]
To the solu-
The absorbance was recorded at 200–800 nm using
Perkin Elmer Lambda 35 UV–Vis spectrophotometer.

SAMUEL ET AL.
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FIGURE 1 (a) Powder X-ray diffraction (XRD) spectra of graphene oxide (GO), GO-C1, and GO-C2; (b) Fourier-transform infrared
spectroscopy (FT-IR) spectra of GO, GO-C1, and GO-C2
Fourier-transform infrared spectroscopy (FT-IR) analysis
3 | RESULTS AND DISCUSSION
was carried out with the spectral range of
1
4
00–4,000 cm− using IR-Prestise-21 Shimadzu instru-
The powder XRD patterns of GO-C1 and GO-C2
ment. The crystalline structure of the GO, GO-C1, and
GO-C2 nanocomposites were studied using X-ray
diffraction (XRD) technique. The XRD patterns were
recorded on a Shimadzu XRD-6000 Powder X-Ray dif-
fractometer at 40 kV voltages and 30 mA current. All the
spectra were acquired at a pressure using ultra high vac-
uum with Al Kα excitation at 250 W. Scanning electron
microscope (SEM) images were measured by Hitachi
S4800 field emission SEM system. X-ray photoelectron
spectroscopic (XPS) analysis was carried out in axis ultra
multitechnique XPS. All the spectra were acquired at a
pressure using ultra high vacuum with Al Kα
excitation at 250 W. Raman spectra were recorded on a
Horiba-Jobin Raman spectrometer with a 514 nm laser
power. Thermogravimetric analysis (TGA) measurements
nanomaterials show the diffraction peaks at 2θ value
ꢀ
ꢀ
of 8.77 and 9.06 with the enhanced interlayer d-spacing
of 1.12 and 1.01 nm, respectively, due to the intercalation
of C1 and C2 complexes into the basal planes of GO
(Figure 1a). In addition, the notable diffraction peaks at
ꢀ
ꢀ
37.90 and 39.50 correspond to (111) plane of mono-
ꢀ
ꢀ
clinic CuO (JCPDS 80-1917) and at 42.40 , 49.90 and
ꢀ
ꢀ
42.60 , 48.00 were indexed to (111) and (200) planes of
metallic Cu particles (JCPDS 04-0836) exist in the GO-C1
[
39–41]
and GO-C2 nanocomposites, respectively.
The as-
prepared composites were also characterized by FT-IR,
XPS, Raman, and UV spectroscopic techniques. FT-IR
spectra of GO-C1 and GO-C2 material (Figure 1b) show
−
1
the characteristic peaks at 3,614, 3,414 cm and 3,654,
3,447 cm− correspond to NHstr and OH vibrations,
1
str
−
1
were carried out under a N atmosphere using NETZSCH
respectively. The peaks at 1,648, 1,617 cm and 1,516,
1,592 cm− correspond to C O and C Cstr vibrations of
GO-C1 and GO-C2 respectively. The peak at 1383 and
1,039 cm− corresponds to C N (amine) stretching
vibrations and C O Cstr vibrations of GO-C1 and
GO-C2, respectively.
2
1
STA 449 F3 Jupiter. Transmission electron microscopic
(TEM) images were recorded using a JEOL JEM-2100
1
transmission electron microscope operating at 200 kV.
The loading content of copper of the GO-C1 and GO-C2
was determined by inductively coupled plasma optical
emission spectroscopy (Vista-MPX, Perkin Elmer
XPS analysis was performed to understand the effect
of intercalation and evaluate the oxidation state of copper
metal, binding energies, and elemental composition of
as-prepared materials. In our previous work, we have
reported the XPS spectra of the GO which shows the two
characteristic peaks at 284 and 532 eV corresponding to
1
13
ICPOES, Model 5300 DV). H and C-NMR spectra of
click products were recorded with a Bruker Avance III
HD Nanobay 400 MHz FT-NMR Spectrometer. Mass
spectrum of the Cu(II) complexes and triazole com-
pounds were recorded in Agilent mass spectrometer
LCMS-1260 INFINITY II under nitrogen atmosphere.
The azides were prepared from the corresponding halides
[37]
the C1s and O1s binding energies, respectively.
The
XPS survey spectrum of GO-C1 and GO-C2 (Figure 2a)
shows the significant binding energy at 399–405 eV for
[38]
treated with sodium azide in dry acetone.

4
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SAMUEL ET AL.
FIGURE 2 (a) X-ray photoelectron spectroscopy (XPS) survey spectrum of graphene oxide (GO), GO-C1, and GO-C2; (b) Deconvoluted
C1s of GO-C1 and GO-C2; (c) Deconvoluted N1s of GO-C1 and GO-C2; (d) Deconvoluted O1s of GO-C1 and GO-C2; (e) Core level spectrum
of Cu 2p of GO-C1 and GO-C2
N1s and 931–952 eV for core-level spectrum of Cu 2p,
which confirms the intercalation of Cu(II) tetraaza
complexes in between the GO planes. The deconvoluted
XPS spectra of C1s spectra (Figure 2b) of GO-C1 and
GO-C2 shows the deconvoluted bands at 284.5, 286.4,
and 288.4 eV which correspond to C C/C C, C OH
and COOH, respectively. The N1s spectra (Figure 2c) of
GO-C1 and GO-C2 show two deconvoluted bands at
The Raman spectra of GO shows two bands at 1,349
and 1,592 cm corresponds to the D and G bands respec-
−1
[
32]
tively
and in the case of as-prepared catalysts also
−
1
show two bands each at 1,322.78 and 1,520.28 cm for
GO-C1 and 1,326.54 and 1,516.73 cm− for GO-C2, which
are assigned to D band and G band, respectively
1
(Figure 3a). The I /IG value is found to be 0.87 for
D
[
45,46]
GO-C1 and 0.88 for GO-C2 composite.
The UV
3
99.3 and 401.3 eV were assigned to the N H of amine
and protonated N-atoms, respectively. The O1s spectra
Figure 2d) shows two deconvoluted bands at 531 and
32.5 eV correspond to OH of primary alcohol and
absorbance of GO-C1 shows the shifted peaks at 248 and
307 nm were assigned to π-π* transitions of C C, n-π*
transitions of C N bonds, respectively. In the case of
GO-C2 composite, the absorbance bands at 206, 229,
265, and 300 nm correspond to π-π* transitions of C C,
(
5
C O of carboxylic acid, respectively. Moreover, the bind-
ing energy peaks at 952.4 and 932.3 eV correspond to the
spin-orbit splitting components of Cu 2p and Cu 2p3/2
II
π-π* transitions in Cu tetraaza complex and n-π* transi-
[
47]
tions of C N, respectively (Figure 3b).
The GO-C1
1/2
+
2+
of Cu and Cu
species of GO-C1 and GO-C2
and GO-C2 nanocomposites show the redshift indicates
II
(Figure 2e). The further satellite peaks for Cu 2p3/2 and
the π electrons interaction with GO and Cu complexes.
Cu 2p1/2 were observed at 944 and 962 eV that indicates
the +2 oxidation state of copper metal in the GO-C1and
GO-C2 composite.
The thermal stability of intercalated GO-C1 and GO-C2
nanocomposites were investigated by TGA analysis and
shown in Figure 3c. These composites show the initial
[42–44]

SAMUEL ET AL.
5 of 10
FIGURE 3 (a) Raman spectrum; (b) UV Spectrum; (c) thermogravimetric analysis (TGA) analysis of graphene oxide (GO), GO-C1, and
GO-C2; (d) scanning electron microscope (SEM) image of GO-C1; (e) SEM image of GO-C2
ꢀ
weight loss of around 21% at 100 C which attributes the
removal of intercalated water. The significant weight loss
of GO-C1 and GO-C2 show the significant irregular
stacked layered structure and dark zones even at
wrinkled edges which clearly shows that the layered
structure associated with the dispersed C1 and C2 on the
surface as depicted in Figure 4b,c,f,g. The appearance of
the selected area electron diffraction (SAED) pattern
images of GO-C1 and GO-C2 indicates multilayered
crystalline structure (Figure 4d,h). A typical sharp, poly-
crystalline ring pattern was observed. The first ring corre-
sponds to the (1100) plane and the second ring attributed
ꢀ
ꢀ
was shown at 150 C–190 C (17%) attributed to the
thermal decomposition of unutilized oxygen-containing
functionalities. The maximum weight loss observed in
ꢀ
ꢀ
the temperature was from 350 C to 700 C due to
II
the slow decomposition of intercalated Cu tetraaza
[48,49]
complexes.
The SEM and high-resolution transmission electron
microscopy (HR-TEM) analysis were performed to inves-
tigate the microstructure and morphology of GO upon
the functionalization of C1 and C2. The SEM images of
GO-C1 and GO-C2 were shown in Figure 3d,e. The SEM
images show the sheet-like structure with the wrinkled
surface due to the intercalation whereas the GO sheets
present the granulate surface textures with spherical
[
53]
to the (1120) of GO basal planes.
The unequal inten-
sity of the diffraction spots in the SAED pattern might be
due to the adsorption of intercalants (C1 or C2) on the
surface of GO. The quantitative analysis of the copper
content in the catalyst was determined by inductively
coupled plasma optical emission spectroscopy (ICP-OES),
and the copper content of 3.40% and 3.22% (w/w) were
detected for GO-C1 and GO-C2, respectively (Table S2).
The existing Van der Waals interaction of the copper
complexes (C1 and C2) on the GO basal planes in the
layered structures facilitates the heterogeneous catalyst to
immobilize on the GO planes due to the availability of
the surface functionalities. The significant catalytic activ-
ity was not only due to the good dispersion of GO-C1 and
[50–52]
edges.
In TEM analysis at different-magnification,
GO-C1 and GO-C2 shows typical rippled and crumpled
morphology in which the nanosheet contains many
wrinkles throughout the surface respectively as seen in
SEM images (Figure 4a,e). Such characteristic surface
wrinkling would be an important advantage for applica-
tions in catalytic reactions, due to the higher accessibility
of the catalytic sites. While high resolution TEM images

6
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SAMUEL ET AL.
FIGURE 4 Transmission electron microscopic (TEM) image and a typical selected area electron diffraction (SAED) pattern of the
graphene oxide (GO)-C1 (a–d) and GO-C2 (e–h)
GO-C2 nanosheets in the heterogeneous mixture but also
facilitate the mass transfer of organic precursors into
products under the reaction condition.
isolated as 91% and 88% yield using GO-C1 and GO-C2
catalysts, respectively (Scheme 1).
To demonstrate the scope of the click protocol using
GO-C1, we have chosen the series of azides containing
an electron-donating and electron-withdrawing group to
perform click reaction with phenyl acetylene under
optimized conditions to achieve their corresponding
3.1 | Click reaction using GO-C1 and GO-
C2 nanocomposites
1,4-disubstituted-1,2,3-triazoles and the results are
It is of our interest to explore the catalytic properties of
tabulated in Table 1. It is noteworthy to report that the
intercalated nanocomposites are convenient, reproduc-
ible, and reusable as click catalysts for alkyl and aryl
azide substrates.
II
GO-C1 and GO-C2 composites for Cu AAC alkyne-azide
[54–56]
coupling reaction in green solvents.
The typical
click reaction of phenyl acetylene with benzyl azide was
performed by the catalysts (50 mg) and sodium ascorbate
The high catalytic activity of GO-C1 is attributed due
to the hydrophilic nature of GO surface and also due to
(
10 mg) at RT using t-butanol/H O as a solvent. The
2
[
57,58]
desired product, 1,4-disubstituted-1,2,3 triazole was
the “Breslow effect.”
According to the “Breslow

SAMUEL ET AL.
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SCHEME 1 Optimization of the synthesis of triazole using GO-Cu(II)L catalyst
TABLE 1 Table of optimization of GO-Cu(II)L catalyst with
time and isolated yield
effect” during the reaction, the well dispersed
functionalized GO catalyst (GO-C1 or GO-C2) in
organic/aqueous solvent mixture facilitates the cycloaddi-
tion of phenyl acetylene and aryl azide using copper com-
plex (C1 or C2) supported on the surface of GO as an
active sites within the nanocomposites and thereby
increasing the yields of 1,2,3-triazoles. The addition of
GO-Cu(II)L Catalyst
GO-C1
Time (min)
Yield (%)
60
80
91
88
GO-C2
Abbreviation: GO, graphene oxide.
TABLE 2 Various azides utilized and the respective triazole products with time and isolated yield
Entry
1
R-N
3
(1b-5b)
Time (min)
Isolated product (1c-5c)
Yield (%)
Yield (g)
60
91
0.213
2
70
89
0.231
3
4
65
75
83
80
0.183
0.239
5
80
81
0.181

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SAMUEL ET AL.
TABLE 4 Various solvent effects for the isolation of better
yields
GO-C1 catalyst
Entry (mg)
Yield
(%)
[a]
[b]
Solvent
1
2
3
4
-
t-Butanol/H
(2:3 v/v)
2
2
2
2
O
O
O
O
0
II
SCHEME 2 General scheme of the Cu AAC reaction using
GO-C1
10
25
50
t-Butanol/H
50
76
91
(
2:3 v/v)
t-Butanol/H
2:3 v/v)
t-Butanol/H
2:3 v/v)
(
catalytic amount of the sodium ascorbate during the
reaction involves in the initiation of the reduction of
Cu(II)L supported on the GO, which promotes product
formation by accelerating the electron transfer process.
Hence, the heterogeneous GO support is required for
the cycloaddition of various acetylene-azide organic
precursors resulting in high yields with enhanced
catalytic activity of GO-C1 catalyst (Table 2) (Scheme 2).
(
5
6
7
8
9
50
50
50
50
50
t-Butanol
80
67
77
64
51
Ethanol
CH
3
CN
2
H O
DMSO
a
Reaction conditions: Phenyl acetylene (1 mmol), benzyl azide
(
1 mmol), and sodium ascorbate (10 mg) were reacted at RT.
Isolated yield of 1-benzyl-4-phenyl-1H-1,2,3-triazole.
3.2 | Reusability study of GO-C1
b
After completion of the click reaction of first cycle, the
heterogeneous catalyst GO-C1 was filtered and washed
with ethyl acetate followed by acetone and water thrice
and was rinsed with diethyl ether in the end. The solid
GO-C1 catalyst was dried at room temperature for about
best yield was obtained in t-Butanol/H O (2:3 v/v) solvent
mixture for the CuAAC reaction (Table 4).
2
1
2 h and used for the next two batches of click reaction
4 | CONCLUSION
of phenyl acetylene and benzyl azide to get the triazole
product in considerable moderate yield (Table 3).
The new class of GO composite materials was success-
fully prepared by the intercalation of Cu(II) tetraaza com-
plexes into the GO layers and thereby the enhanced
interlayer d-spacing was achieved. The noncovalent inter-
3.3 | Optimization of reaction conditions
II
of click reaction catalyzed by GO-C1
calation of Cu complexes on the GO sheets was
confirmed by spectroscopic and microscopic analysis.
The XPS survey spectra confirms the intercalation of C1
and C2 in between the GO planes by showing significant
binding energy of 399–405 eV for N1s and 932.3 eV for
Cu. These composites were used as efficient, green, click
The effect of catalyst dosage and solvent were studied in
optimizing the reaction conditions of click reaction of
phenyl acetylene and benzyl azide catalyzed by GO-C1.
From the below table, it was inferred that 50 mg of
GO-C1 was the most effective catalytic amount and the
II
catalysts for alkyne-azide cycloaddition (Cu AAC) reac-
tion and could facilitate the electron transfer rate by
stabilizing Cu(I) intermediates in the catalytic cycle in
the click mechanism. The as-prepared click catalysts
could be used for the development of click products from
proteins, peptides and amino acids in green solvents.
TABLE 3 Recyclability of GO-C1 nanocomposite materials
and its yield
[
a]
[b]
Entry
GO-C1 catalyst
Click reaction
Recycle 1
Yield (%)
1
2
3
91
69
60
ACKNOWLEDGMENTS
The authors sincerely thank UGC DAE Consortium
Scientific Research, IGCAR-Kalpakkam, for the grant
Recycle 2
(
no.: CSR/Acctts/2016-17/1347) and Department of
a
Reaction conditions: Phenyl acetylene (1 mmol), Benzyl azide
Science and Technology, DST-DPRP division (no.:
VI-D&P/562/2016-17/TDT(C)) for their research grant to
carry out this research.
(
1 mmol) GO-C1 catalyst (50 mg) and Sodium ascorbate (10 mg)
O at RT.
Isolated yield of 1-benzyl-4-phenyl-1H-1,2,3-triazole.
were reacted in 2:3 t-butanol/H
2
b

SAMUEL ET AL.
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AUTHOR CONTRIBUTIONS
[20] R. K. Singh, R. Kumar, D. P. Singh, RSC Adv. 2016, 6, 64993.
[21] A. M. Shanmugharaj, J. H. Yoon, W. J. Yang, S. H. Ryu,
Angel Green Samuel: Formal analysis; investigation;
visualization. Karthikeyan Nagarajan: Formal analysis;
software; validation; visualization. Karthick Cidhuraj:
Formal analysis; software; validation. Bhalerao Gopal:
Formal analysis; methodology; resources; validation.
Sujay Chakravarty: Formal analysis; methodology;
resources; validation. Varadharajaperumal Selvaraj:
Formal analysis; methodology; software; validation.
Emmanuvel Lourdusamy: Formal analysis; methodol-
ogy; software; validation. JEBASINGH Bhagavathsingh:
Conceptualization; formal analysis; investigation; method-
ology; project administration; resources; software; supervi-
sion; validation.
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CONFLICT OF INTEREST
Authors declare no conflict of interest.
ORCID
Jebasingh Bhagavathsingh https://orcid.org/0000-0003-
[
[
3
405-6208
2
017, e4142.
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How to cite this article: Samuel AG,
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