3-Amino-5-mercapto-1,2,4-triazole-functionalized Fe3O4 magnetic nanocomposite as a green and efficient catalyst for synthesis of bis(indolyl)methane derivatives

Article abstract of DOI:10.1002/aoc.5641

A core–shell Fe₃O₄?silica magnetic nanocomposite functionalized with 3-amino-5-mercapto-1,2,4-triazole (Fe₃O₄/SiO₂/PTS/AMTA) was prepared using Fe₃O₄ with silica layer, and its s

Full text of DOI:10.1002/aoc.5641

Received: 2 October 2019
DOI: 10.1002/aoc.5641
Revised: 5 February 2020
Accepted: 7 February 2020
F U L L P A P E R
3-Amino-5-mercapto-1,2,4-triazole-functionalized Fe3O4
magnetic nanocomposite as a green and efficient catalyst
for synthesis of bis(indolyl)methane derivatives
Maryam Hajibabaei
| Masumeh Abdoli Senejani
| Fatemeh Shafiei
Department of Chemistry, Arak Branch,
Islamic Azad University, Arak, Iran
A core–shell Fe3O4@silica magnetic nanocomposite functionalized with
3-amino-5-mercapto-1,2,4-triazole (Fe3O4/SiO2/PTS/AMTA) was prepared
using Fe3O4 with silica layer, and its surface was modified with 3-amino-
5-mercapto-1,2,4-triazole. The novel synthesized magnetite nanocomposite
was characterized using various techniques. The catalytic activity of Fe3O4/
SiO2/PTS/AMTA was demonstrated in the synthesis of bis(indolyl)methane
derivatives under solvent-free conditions. Some of the bis(indolyl)methane
derivatives were synthesized through one-pot, three-component reaction of
1 mol of various benzaldehydes or ketones with 2 mol of indole in the presence
of Fe3O4/SiO2/PTS/AMTA in good to excellent isolated yields. In addition, the
catalyst could be recovered and used for several reaction runs without loss of
catalytic activity. The stability of recycled catalyst was investigated. This
method has some advantages including experimental simplicity, good to excel-
lent yields, solvent-free conditions and stability and reusability of the catalyst.
Correspondence
Masumeh Abdoli-Senejani, Department of
Chemistry, Arak Branch, Islamic Azad
University, Arak, Iran.
Email: mabdoli@iau-arak.ac.ir
K E Y W O R D S
bis(indolyl)methanes, green chemistry, heterogeneous catalyst, magnetic nanocatalyst, solvent
free
1 | INTRODUCTION
the magnetic properties of Fe3O4.[18] The surface of Fe3O4
often releases toxic Fe2+ ions and is oxidized by the air.
In the recent years, magnetic nanoparticles (MNPs) have
been employed in various scientific fields including
Hence, various procedures have been developed to mod-
ify and coat the surface of the particles. Magnetic core–
shell Fe3O4@SiO2 with hydroxyl groups can be
coupled with functional groups such as amines, carboxyl-
ates and thiols using appropriate organosilicon precur-
sors.[19, 20] Therefore, surface-functionalized Fe3O4@SiO2
nanocomposites can be applied as convenient
nanomagnetic catalysts, which can be separated using an
external magnet.
3-Amino-5-mercapto-1,2,4-triazole (AMTA) with sul-
fur and nitrogen atoms is an interesting compound com-
monly used in the processing of silver halide
photographic material, in the synthesis of organic com-
pounds, as a modifier of Au and Ag electrodes, as an
2]
catalysis,[1,
semiconductors,[3] sensors,[4] pigments,
wastewater treatments,[5, 6] adsorbents,[7] magnetic reso-
nance imaging,[8] magnetic data storage devices,[9] bio-
separations[10] and medicines.[11,
Recently, some
12]
MNPs have been used as highly useful supports for
immobilization of homogeneous catalysts in order to
obtain heterogeneous catalysts and enable them to be
recovered using an external magnet.[13–15] Among MNP
materials, magnetite (Fe3O4) has received more attention
in biomedical and chemical fields because of its unique
physical and chemical properties.[16, 17] Hopping of elec-
trons between Fe2+ and Fe3+ results in development of
Appl Organometal Chem. 2020;e5641.
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© 2020 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.5641

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HAJIBABAEI ET AL.
antioxidant and as a viscosity index improver.[21–23] As a
base group, AMTA can be applied successfully for the
functionalization of silica-coated Fe3O4 nanoparticles. In
the work reported herein, Fe3O4/SiO2/PTS/AMTA, as a
novel magnetically reusable catalyst, was prepared and
used for the synthesis of bis(indolyl)methane derivatives
under solvent-free conditions.
Figure 1 shows the powder XRD patterns of Fe3O4,
Fe3O4/SiO2, Fe3O4/SiO2/PTS and Fe3O4/SiO2/PTS/AMTA
in the range 10–80ꢀ. Peaks observed at 30.1ꢀ, 35.5ꢀ, 43.1ꢀ,
53.4ꢀ, 57.0ꢀ and 62.6ꢀ in the patterns of all
nanocomposites corresponded to the crystalline state of
cubic Fe3O4 MNPs. Results indicated that the Fe3O4
structure remained unchanged after modification and
attachment of AMTA.
Figure 2 shows the FT-IR spectra of Fe3O4, Fe3O4/
SiO2, Fe3O4/SiO2/PTS, AMTA and Fe3O4/SiO2/
PTS/AMTA. Comparison of the spectra indicated that
peaks at 570 cm−1 were attributed to Fe&bond;O
stretching vibration of Fe3O4. The peak at 1080 cm−1 was
assigned to Si&bond;O bond of the silica layer (Figure 2b,
c,e).[14] Comparison of FT-IR spectra presented in
Figure 2d,e showed that the peaks at 1594 and 1395 cm−1
corresponded to C&dbond;N and C&bond;N stretching
vibrations of AMTA heterocyclic ring of Fe3O4/SiO2/
PTS/AMTA, respectively, while the absorption peak of
S&bond;H at 2614 cm−1 disappeared in the spectrum of
Fe3O4/SiO2/PTS/AMTA showing a nucleophilic substitu-
tion of Cl by SH group of AMTA.[45]
Recently, bis(indolyl)alkanes have attracted a great
deal of interest due to their synthetic as well as biological
applications as
a
result of their antitumor,[24]
antileishmanial,[25] antihyperlipidemic[26] and anticancer
activities.[27] Several products containing bis(indolyl)
alkane derivatives have been separated previously from
29]
marine sources.[28,
In this regard, various methods
have been reported for the synthesis of bis(indolyl)alkane
derivatives, especially bis(indolyl)methanes, through
electrophilic substitution of indole with carbonyl com-
pounds in the presence of various acid or base catalytic
reagents such as ZrO2–MgO,[30] tetrabutylammonium
hydrogen sulfate,[31] montmorillonite K-10,[32] zeolite,[33]
ammonium
chloride,[34]
tungstophosphoric
acid
supported on zirconia,[35] Fe3O4@silica sulfuric
acid,[36]
H5PW10V2O40/pyridino-Fe3O4,[37]
nano-
Morphology and particle size of synthesized Fe3O4/
SiO2/PTS/AMTA were evaluated using SEM. As shown
in Figure 3, Fe3O4/SiO2/PTS/AMTA exhibited a uniform
and spherical morphology with an average particle size
of about 17 nm. Furthermore, energy-dispersive X-ray
(EDX) analysis showed characteristic peaks of Fe, Si, O,
C, N and S atoms confirming that Fe3O4 was coated with
SiO2 and functionalized with AMTA (Figure 4).
Fe3O4,[38] ZrO2–Al2O3–Fe3O4,[39] and [{Ti(salophen)
H2O}2O][OSO2C8F17]2.[40] Although these procedures are
valuable, some of them have disadvantages.
2 | RESULTS AND DISCUSSION
Following increasing interest in the green and efficient
synthesis of heterocyclic compounds,[41–44] in the study
presented here a convenient method was introduced for
the synthesis of bis(indolyl)methane derivatives in the
presence of Fe3O4/SiO2/PTS/AMTA as a novel magnetic
catalyst (Scheme 1).
First, the catalyst was synthesized by coating Fe3O4
with a layer of silica, followed by condensation with
chloropropyltrimethoxysilane (CPTMS) and substitution
of chlorine atom with AMTA as described in Section 3
(Scheme 2).
Subsequently, the obtained nanocatalyst was charac-
terized using Fourier transform infrared (FT-IR) spectros-
copy, field emission scanning electron microscopy (SEM),
powder X-ray diffraction (XRD) and vibrating sample
magnetometry (VSM).
Figure 5 shows field-dependent magnetization curves
of uncoated Fe3O4 powder, Fe3O4/SiO2 powder, Fe3O4/
SiO2/PTS powder and Fe3O4/SiO2/PTS/AMTA powder at
ambient temperature. All samples were super-
paramagnetic with saturation magnetizations of 63.7,
56.6, 53.19 and 49.60 emu g−1, respectively. The results
showed a reduction of saturation magnetization for
Fe3O4/SiO2, Fe3O4/SiO2/PTS and Fe3O4/SiO2/PTS/AMTA
in comparison with Fe3O4, attributed to the diamagnetic
contribution of SiO2 and organic group on the surface of
Fe3O4 nanoparticles. However, Fe3O4/SiO2/PTS/AMTA
still had sufficient magnetic properties and could be sepa-
rated from a reaction mixture using an external magnet.
Thermogravimetric analysis (TGA) was used to inves-
tigate the thermal stability of the synthesized Fe3O4/
SiO2/PTS/AMTA from room temperature to 800ꢀC under
a nitrogen atmosphere (Figure 6). Weight loss (14.1%)
was observed attributed to loss of adsorbed water and
decomposition of propyl and AMTA as organic functional
groups.
After the synthesis and characterization of Fe3O4/
SiO2/PTS/AMTA, its catalytic activity was investigated
for the preparation of bis(indolyl)methane derivatives. At
SCHEME 1 Synthesis of bis(indolyl)methanes catalyzed by
Fe3O4/SiO2/PTS/AMTA

3-AMINO-5-MERCAPTO-1,2,4-TRIAZOLE-FUNCTIONALIZED FE3O4 MAGNETIC
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SCHEME 2 Preparation of Fe3O4/SiO2/PTS/AMTA
FIGURE 1 XRD patterns of Fe3O4 (a), Fe3O4/SiO2 (b), Fe3O4/
SiO2/PTS (c) and Fe3O4/SiO2/PTS/AMTA (d)
FIGURE 2 FT-IR spectra of Fe3O4 (a), Fe3O4/SiO2 (b), Fe3O4/
SiO2/PTS (c), AMTA (d) and Fe3O4/SiO2/PTS/AMTA (e)
first, a mixture of benzaldehyde (1 mmol) and indole
(2 mmol) was stirred as a model reaction in the presence
of various amounts of the catalyst under different condi-
tions, and the results are presented in Table 1. According
to Table 1, the presence of catalyst was essential for the
reaction (entry 1) and an amount of more than 10 mg of
Fe3O4/SiO2/PTS/AMTA did not have much effect on
yield and reaction time (entry 10). In addition, the pres-
ence of solvent reduced the completion of the reaction.
Consequently, it was found that an amount of 10 mg of
Fe3O4/SiO2/PTS/AMTA at 80ꢀC under solvent-free condi-
tions were optimal for the preparation of bis(indolyl)
methanes (entry 8). When the reaction was carried out in
the presence of Fe3O4 MNPs or AMTA instead of Fe3O4/
SiO2/PTS/AMTA under identical conditions (entries
13 and 14), yields of reaction were approximately the
same. In this study, AMTA played the primary role as a
catalyst in Fe3O4/SiO2/PTS/AMTA and was supported on
Fe3O4 MNPs, which can be easily separated using an
external magnet.
Optimized reaction conditions were used for synthesis
of some bis(indolyl)methane derivatives by the three-
component reaction between various aldehydes and
ketones with indole to investigate the generality of this
procedure (Table 2). As evident from Table 2, this
method is useful for the reaction of indole with various
aromatic aldehydes bearing electron-withdrawing or
electron-donating groups to afford corresponding

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HAJIBABAEI ET AL.
FIGURE 3 SEM images of Fe3O4/SiO2/PTS/AMTA
FIGURE 6 TGA of Fe3O4/SiO2/PTS/AMTA
FIGURE 4 EDX analysis of Fe3O4/SiO2/PTS/AMTA
bis(indolyl)methane derivatives. Furthermore, the reac-
tion of isatin and cyclohexane with indole was carried
out under optimum conditions, which resulted in the
generation of corresponding products in good to excellent
yields.
Scheme 3 shows a plausible mechanism for the syn-
thesis of bis(indolyl)methane derivatives catalyzed by
Fe3O4/SiO2/PTS/AMTA. It is believed that Fe3O4/SiO2/
PTS/AMTA acts as an efficient base catalyst with nitro-
gen atoms of AMTA. So that, first, indole reacts with the
carbonyl group of aldehyde or ketone, and generates
intermediate IV through abstraction of a proton using
the catalyst. Then, the catalyst helps in loss of H2O from
indolyl carbinol (IV) and forms 3-arylidene-3H-indole
(V). Finally, the nucleophilic attack of the second mole
of indole to intermediate V and abstraction of a proton
from intermediate VII result in the production of
corresponding bis(indolyl)methane. The catalyst is reused
FIGURE 5 VSM analyses of Fe3O4 (a), Fe3O4/SiO2 (b), Fe3O4/
SiO2/PTS (c) and Fe3O4/SiO2/PTS/AMTA (d)

3-AMINO-5-MERCAPTO-1,2,4-TRIAZOLE-FUNCTIONALIZED FE3O4 MAGNETIC
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TABLE 1 Optimization of reaction conditions
Entry
Solvent
—
Temperature (ꢀC)
Catalyst (mg)
Time (h)
Yield (%)
1
r.t.
r.t.
r.t.
r.t.
60
60
80
80
100
80
60
80
80
80
Fe3O4/SiO2/PTS/AMTA (0)
Fe3O4/SiO2/PTS/AMTA (10)
Fe3O4/SiO2/PTS/AMTA(10)
Fe3O4/SiO2/PTS/AMTA (10)
Fe3O4/SiO2/PTS/AMTA (5)
Fe3O4/SiO2/PTS/AMTA (10)
Fe3O4/SiO2/PTS/AMTA (5)
Fe3O4/SiO2/PTS/AMTA (10)
Fe3O4/SiO2/PTS/AMTA (10)
Fe3O4/SiO2/PTS/AMTA (13)
Fe3O4/SiO2/PTS/AMTA (10)
Fe3O4/SiO2/PTS/AMTA (10)
Fe3O4 (10)
8
—
20
20
5
2
EtOH
MeOH
EtOAc
—
8
3
8
4
8
5
5
50
95
70
96
96
97
80
85
95
95
6
—
5
7
—
4
8
—
1.5
1.5
1.5
5
9
—
10
11
12
13
14
—
EtOH
EtOH
—
3
2
—
AMTA (10)
1.75
in the next reaction cycle, and increases the electrophilic-
ity of the carbonyl group with adsorbed hydrogen.[30, 50]
Reusability and recovery of Fe3O4/SiO2/PTS/AMTA
showed a preference for the current method due to it
being solvent-free and involving mild conditions, and
also its use of a small amount of nontoxic and recover-
able catalyst.
were
investigated
in
the
synthesis
of
4-chlorophenylmethane-3,30-bis(indolyl) (3f) under opti-
mized conditions. At the end of the reaction, the mixture
was diluted with ethanol, and the catalyst was magneti-
cally removed from the mixture using an external mag-
net, and then washed with ethanol and dried. Then, the
separated catalyst was used in a fresh reaction for five
runs without notable loss of activity (Figure 7).
The stability of the recycled catalyst was investigated
using SEM and TGA (Figures 8 and 9). Results of TGA
showed no change in the thermal stability of the catalyst
after five cycles. A comparison of the results obtained
from SEM analysis showed that the shape and size of
recycled catalyst particles and fresh catalyst particles
were identical.
A hot filtration test was also performed to investigate
the heterogeneity of the catalyst. In this regard, synthesis
of 4-chlorophenylmethane-3,30-bis (indolyl) (3f) was car-
ried out in the presence of Fe3O4/SiO2/PTS/AMTA under
optimized conditions for 1 hour. Then, the catalyst was
filtered off at the reaction temperature. The reaction pro-
gress was followed by GC, and the yield of 3f was equal
to 56%. The reaction with the filtrate was allowed to con-
tinue without using the catalyst for 2 hours, and no fur-
ther conversion was observed.
3 | EXPERIMENTAL
3.1 | General
All chemicals and reagents were purchased from
Sigma-Aldrich and were used without further purifica-
tion. The progress of the organic reactions was moni-
tored using TLC. Melting points were determined with
an Electrothermal digital melting point apparatus
(Bornstead). 1H NMR spectra were recorded using a
Bruker 400 MHz spectrometer in pure CDCl3. FT-IR
spectra were recorded with a Shimadzu IR-470 spec-
trometer using KBr disks. Powder XRD measurements
were made with an X’Pert Pro X-ray diffractometer
using a Cu tube over the 2θ range from 10ꢀ to 80ꢀ.
Elemental composition and surface morphology were
investigated using a field emission SEM instrument
(Tescan Mira III). Magnetization was assessed with a
vibrating sample magnetometer (MDK-VSM, model
MDKB).
Finally, the performance of this procedure regarding
the preparation of bis(indolyl)phenylmethane was com-
pared with that of various methods reported in the litera-
ture (Table 3). Results obtained from this comparison
3.2 | Synthesis of nanomagnetic Fe3O4
The Fe3O4 MNPs were prepared using a previously
reported chemical co-precipitation method with minor

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HAJIBABAEI ET AL.
TABLE 2 Synthesis of bis(indolyl)methane derivatives in presence of Fe3O4/SiO2/PTS/AMTA
M.p. (ꢀC)
Entry
Product
3a
Aldehyde/ketone
Time (h)
Yield (%)aa
Found
Reported
1
1.5
96
139–140
140–142[46]
2
3
4
3b
3c
3d
7.5
6.75
7
93
95
90
182–184
135–137
260–263
180–182[46]
134–135[47]
261–263[47]
5
6
7
3e
3f
6
2
1
83
90
98
217–219
76–79
218–220[47]
74–76[46]
73–75[46]
3g
73–75
8
3h
1.5
95
87–89
89–91[48]
9
3i
3j
5
8
85
70
112–114
340–343
110–112[47]
340–342[47]
10
11
3k
2.75
85
100–102
98–99[49]
(Continues)

3-AMINO-5-MERCAPTO-1,2,4-TRIAZOLE-FUNCTIONALIZED FE3O4 MAGNETIC
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TABLE 2 (Continued)
M.p. (ꢀC)
Entry
Product
3l
Aldehyde/ketone
Time (h)
Yield (%)aa
Found
Reported
12
6
75
318–320
320–322[48]
13
14
3m
3n
6
80
97
158–160
312–315
160–162[46]
2.75
312–314[31]
aIsolated yield.
FIGURE 7 Recyclability of Fe3O4/SiO2/PTS/AMTA in the
reaction between 4-chlorobenzaldehyde and indole under
optimized conditions
SCHEME 3 Plausible mechanism for synthesis of bis(indolyl)
methane derivatives catalyzed by Fe3O4/SiO2/PTS/AMTA
3.3 | Synthesis of Fe3O4/SiO2
nanocomposite
modifications.[55] First, 5.4 g of FeCl3ꢁ6H2O and 2.0 g
of FeCl2ꢁ4H2O were dissolved in 2 ml of concentrated
hydrochloric acid and 20 ml of double-distilled water.
The solution was stirred vigorously under a nitrogen
gas flow at 80ꢀC. Subsequently, a solution of ammo-
nium hydroxide (2 M) was added dropwise to the solu-
tion under vigorous stirring to adjust the pH value to
10 and a black precipitate was formed. The final prod-
uct was separated using an external magnet, was
washed several times using double distilled water and
was dried at room temperature to afford black
nanomagnetic Fe3O4.
SiO2 shells were coated on the prepared Fe3O4 MNPs
via condensation and hydrolysis of tetraethyl
orthosilicate (TEOS). Briefly, 2 g of synthesized Fe3O4
powder was added to 200 ml of a solution containing
water and ethanol (1:4), followed by ultrasonication for
30 minutes. Afterwards, TEOS (2.5 ml) and concen-
trated ammonia aqueous solution (10 ml) were added
to the mixture under continuous stirring at room tem-
perature for 12 hours. Finally, the product was col-
lected using an external magnet, was rinsed several
times using ethanol and double-distilled water and
then was dried.[56]

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HAJIBABAEI ET AL.
3.4 | Synthesis of chloropropyl-modified
Fe3O4/SiO2 nanocomposite (Fe3O4/SiO2/
PTS)
Chloropropyl-modified Fe3O4@SiO2 nanocomposite was
prepared according to a previously reported method.[57]
An amount of 2 g of synthesized silica-coated MNPs was
dispersed in 100 ml of toluene by ultrasonic treatment,
and then 2 ml of CPTMS was added dropwise to the mix-
ture. The mixture was refluxed under nitrogen atmo-
sphere for 2 hours. The resulting solid was separated
using an external magnet, was washed twice using
double-distilled water and ethanol and then was dried.
FIGURE 8 TGA of recycled Fe3O4/SiO2/PTS/AMTA
3.5 | Synthesis of Fe3O4/SiO2/PTS/AMTA
An amount of 0.1 g of AMTA was added to a suspension
containing 1.0 g of synthesized Fe3O4/SiO2/PTS in 70 ml
of dimethylformamide (DMF) and was refluxed under
nitrogen atmosphere at 60ꢀC for 6 hours. The magneti-
cally collected solid product then was washed with DMF
and was dried at room temperature to afford the Fe3O4/
SiO2/PTS/AMTA nanocatalyst.
3.6 | General procedure for synthesis of
bis(indolyl)methane derivatives using
Fe3O4/SiO2/PTS/AMTA
A
mixture containing indole (2 mmol), aldehyde
(1 mmol) and Fe3O4/SiO2/PTS/AMTA (0.01 g) was
stirred vigorously at 80ꢀC under solvent-free condi-
tions. The progress of reaction was followed by TLC
(n-hexane–ethyl acetate, 4/1). After complete conver-
sion, the reaction mixture was diluted with ethanol, an
FIGURE 9 SEM image of recycled Fe3O4/SiO2/PTS/AMTA
TABLE 3 Comparison of results with those reported in the literature regarding preparation of 1 mmol of bis(indolyl)methane
derivatives
Entry
Catalyst
Time
Yield (%)
70–98
Catalyst amount
10 mg
Condition
1
2
3
4
5
6
Fe3O4/SiO2/PTS/AMTA
Zeolite HY
1–8 h
Solvent free, 80ꢀC (this work)
CH2Cl2, r.t.[33]
[51]
1–1.5 h
0.5–5 h
10 min–6 h
15 h
65–85
50 mg
FeCl3ꢁ6H2O
Silica sulfuric acid (SSA)
78–98
5 mol%
[omim]PF6
67–95
50 mg
Solvent free, r.t.[52]
EtOH, r.t.[53]
Solvent free, r.t.[47]
Schiff base + CuSO4ꢁ5H2O
N,N,N,N-Tetrabromobenzene-1,
80–98
5 mol%
1 min–2 h
78–95
50 mg
3-disulfonamide (TBBDA)
7
ZrCl4
10 min–6 h
10–40 min
20 min
81–97
23 mg
CH3CN, r.t.[48]
8
Cellulose-supported perchloric acid (CSPA)
80–94
100 mg
100 mg
10 mol%
Solvent free, r.t.[54]
Solvent free, 70ꢀC[30]
Solvent free, r.t.[38]
9
ZrO2–MgO
94.5–99.2
40–99
10
Nano-Fe3O4
1 min–24 h

3-AMINO-5-MERCAPTO-1,2,4-TRIAZOLE-FUNCTIONALIZED FE3O4 MAGNETIC
9 of 12
external magnet was used to remove the catalyst and
crushed ice was added to the mixture. The precipitate
was filtered, was washed using distilled water and then
was dried at room temperature. The crude product
was purified by recrystallization from hexane and ethyl
acetate to afford a high-purity product.
3.7.4 | 4-Chlorophenylmethane-3,30-bis
(indolyl) (3f)
IR (KBr, νmax, cm−1): 3411 (N&bond;H), 3121 (aromatic
C&bond;H), 2932 (aliphatic C&bond;H), 1680 and 1487
(aromatic C&dbond;C), 1343 (C&bond;N). 1H NMR
(400 MHz, CDCl3, δ, ppm): 5.81 (1H, s, CH), 6.57 (2H, s,
ArH), 6.92 (2H, t, J = 7.6 Hz, ArH), 7.09 (2H, t,
J = 7.6 Hz, ArH), 7.13–7.32 (8H, m, ArH), 7.80 (2H, brs,
NH). Anal. Calcd for C23H17ClN2 (%): C, 77.41; H,
4.80; N, 7.85. Found (%): C, 77.45; H, 4.78; N, 7.90.
3.7 | Selected spectroscopic data
3.7.1 | 3,30-Bis(indolyl)phenylmethane
(3a)
IR (KBr, νmax
,
cm−1): 3400 (N&bond;H), 3100
3.7.5 | Cyclohexyl-3,30-bis(indolyl)
methane (3m)
(aromatic C&bond;H), 2932 (aliphatic C&bond;H),
1599 and 1493 (aromatic C&dbond;C), 1339 (C&bond;
N). 1H NMR (400 MHz, CDCl3, δ, ppm): 5.80 (1H,
s, C&bond;H), 6.55 (2H, s, Ar&bond;H), 6.95 (2H,
t, J = 7.4 Hz), 7.05–7.32 (11H, m, Ar&bond;H), 7.90
(2H, brs, NH). Anal. Calcd for C23H18N2 (%): C,
85.68; H, 5.63; N, 8.69. Found (%): C, 85.64; H,
5.66; N, 8.70.
IR (KBr, νmax, cm−1): 3409 (N&bond;H), 3100 (aromatic
C&bond;H), 2932 (aliphatic), 1600 and 1455 (aromatic
C&dbond;C), 1336 (C&bond;N). 1H NMR (400 MHz,
CDCl3, δ, ppm): 1.65 (6H, m, 3CH2), 2.58 (4H, t,
J = 5.4 Hz, 2CH2), 6.91(2H, t, J = 7.5 Hz, ArH), 7.12 (2H,
m, ArH), 7.32 (2H, d, J = 8.1 Hz, ArH), 7.59 (2H, d,
J = 8.1 Hz,Ar&bond;H), 7.92 (2H, brs, NH). Anal. Calcd
for C22H22N2 (%): C, 84.04; H, 7.05; N, 8.91. Found
(%): C, 84.16; H, 7.07; N, 8.77.
3.7.2 | 3,30-Bis(indolyl)-
4-methoxyphenylmethane (3b)
IR (KBr, νmax
,
cm−1): 3398 (N&bond;H), 3110
3.7.6 | 3-(1H-Indol-3-yl)-3,30-bis(10H-
indol)-2-one (3l)
(aromatic C&bond;H), 2927 (aliphatic C&bond;H), 1615
and 1490 (aromatic C&dbond;C), 1334 (C&bond;N),
1246 (C&bond;O). 1H NMR (400 MHz, CDCl3,
δ, ppm): 3.79 (3H, s, OCH3), 5.80 (1H, s, CH),
6.70 (2H, s, ArH), 6.84 (2H, d, J = 8.0 Hz, ArH), 7.00
(2H, t, J = 7.3 Hz, ArH), 7.17 (2H, t, J = 7.1 Hz,
ArH), 7.39–7.45 (4H, dd, J = 15.0, 8.0 Hz, ArH), 7.92
(2H, brs, NH). Anal. Calcd for C24H20N2O (%): C,
81.79; H, 5.72; N, 7.95. Found (%): C, 81.90; H,
5.76; N, 8.07.
IR (KBr, νmax, cm−1): 3427 (N&bond;H), 3067 (aromatic
C&bond;H), 1708 (C&dbond;O), 1613 and 1471 (aromatic
C&dbond;C), 1336 (C&bond;N). 1H NMR (400 MHz,
CDCl3, δ, ppm): 6.62–7.10 (m, 3H, ArH), 7.21–7.24 (m,
4H, ArH), 7.34 (d, J = 8.0 Hz, 2H, ArH), 10.54 (s, 1H,
NH), 10.95 (s, 2H, NH). Anal. Calcd for C24H17N3O
(%): C, 79.32; H, 4.72; N, 11.56. Found (%): C, 79.25; H,
4.79; N, 11.96.
3.7.3 | 3,30-Bis(indolyl)-
3-nitrophenylmethane (3d)
4 | CONCLUSIONS
An efficient and green protocol has been introduced for
the synthesis of bis(indolyl)alkane derivatives using
Fe3O4/SiO2/PTS/AMTA as a novel nanomagnetic catalyst
under solvent-free conditions. The Fe3O4/SiO2/
PTS/AMTA nanocomposite was prepared using Fe3O4
with a silica layer, and its surface was modified with
AMTA. The nanocatalyst was characterized using FT-IR,
SEM, XRD and VSM techniques. Following optimization
of the reaction conditions, several bis(indolyl)alkane
derivatives were synthesized by the three-component
reaction of various aldehydes and ketones with indole at
IR (KBr, νmax, cm−1): 3430 (N&bond;H), 3100 (aro-
matic C&bond;H), 2936 (aliphatic C&bond;H), 1526,
1347 (N&dbond;O), 1610, 1455 (aromatic C&dbond;C),
1245 (C&bond;N). 1H NMR (400 MHz, CDCl3, δ,
ppm): 6.00 (1H, s, CH), 6.70 (2H, s, ArH), 7.07 (2H, t,
J = 7.5 Hz, ArH), 7.23–7.49 (7H, m, ArH), 7.72 (1H,
d, J = 7.5, ArH), 8.01 (2H, brs, NH), 8.15 (1H, d,
J = 7.5, ArH), 8.25 (1H, s, ArH). Anal. Calcd for
C23H17N3O2 (%): C, 75.19; H, 4.66; N, 11.44. Found
(%): C, 75.20; H, 4.70; N, 11.37.

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HAJIBABAEI ET AL.
80ꢀC under solvent-free conditions. Experimental sim-
plicity, good to excellent yields, solvent-free conditions
and stability and recyclability of the catalyst are advan-
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ORCID
Maryam Hajibabaei https://orcid.org/0000-0002-9478-
1850
Masumeh Abdoli Senejani https://orcid.org/0000-0001-
8536-9218
Fatemeh Shafiei https://orcid.org/0000-0002-1169-4971
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How to cite this article: Hajibabaei M,
Senejani MA, Shafiei F. 3-Amino-5-mercapto-1,2,4-
triazole-functionalized Fe3O4 magnetic
nanocomposite as a green and efficient catalyst for
synthesis of bis(indolyl)methane derivatives. Appl
Organometal Chem. 2020;e5641. https://doi.org/10.
1002/aoc.5641
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