2
of 10
HABIBI ET AL.
−
2
cm . At the end of the electrolysis, which was monitored
with TLC, the cell was placed in a fridge overnight. The
product was collected by filtration, washed with copious
amounts of distilled water and characterized using FT‐
IR, NMR and MS.
SCHEME
Fe O @Quindiol@Cu nanocatalyst.
3 4
1
Synthesis
of
tetrazoles
catalysed
by
potentials measured versus Ag/AgCl. The anode used in
constant‐current bulk electrolysis was an assembly of four
graphite rods (6 mm in diameter and 6 cm in length) and
a large stainless steel cylinder was used as the cathode.
Electrochemical synthesis was performed under con-
stant‐current electrolysis in an undivided cell with a mag-
netic stirrer.
Isolated yield 65%; m.p. > 300°C (dec.). FT‐IR (KBr,
cm ): 3371, 1622, 1531, 1222, 1054, 768. H NMR (400
−
1
1
MHz, DMSO‐d , δ, ppm): 6.67–8.02 (m, 5H Ar, 2H amine,
6
13
2H phenols). C NMR (100 MHz, DMSO‐d , δ, ppm):
6
113.19, 114.16, 129.51, 130.46, 131.26, 134.36, 161.55. MS
+
m/e (relative intensity): 215 (M , 10), 104 (10), 91 (15),
77 (20), 43 (100).
Fourier transform infrared (FT‐IR) spectra (KBr) were
recorded with a PerkinElmer GX FT‐IR spectrometer.
NMR spectra were recorded with a Bruker Ultra‐Shield
1
.3 | Surface Modification of Fe O MNPs
3 4
4
00 spectrometer. Mass spectra were recorded with an
with Quindiol (Fe O @Quindiol)
3
4
HP 5973 GC‐MS instrument operating at an ionization
potential of 70 eV. Transmission electron microscopy
Fe O MNPs (1.0 g) were dispersed in water (20 ml) and
3 4
(
TEM) images were recorded with a Zeiss‐EM10C 80 kV
methanol (10 ml) by sonication for 20 min at room tem-
perature. Then, Quindiol (1.0 g, 4.65 mmol) in methanol
(5 ml) was added and subjected to under ultrasound for
2 h. The obtained Fe O @Quindiol was separated using
an external magnet and dried under vacuum at 50°C for
2 h.
microscope and scanning electron microscopy (SEM)
images were recorded with a Philips XL‐30 microscope.
X‐ray diffraction (XRD) measurements were conducted
with a Bruker D8 Advance powder diffractometer, using
Cu Kα (λ = 1.54 Å) as the incident radiation. Metal con-
centrations were determined with a Contra AA 700
3
4
(Analytik Jena AG). Magnetic measurements were carried
out at room temperature using a vibrating sample magne-
tometry (VSM) instrument (Meghnatis Daghigh Kavir
Co., Iran).
1
.4 | Preparation of Cu(II) Complex of
Fe O @Quindiol (Fe O @Quindiol@Cu)
3
4
3 4
Chemicals and solvents were purchased from Merck
and Aldrich and used without further purification.
Fe O @Quindiol (0.5 g) was dispersed in a water–metha-
nol solution (30 ml, 1:1) by sonication for 20 min at room
3
4
temperature. Then, CuCl ⋅2H O (100 mg) dissolved in
2
2
water (20 ml) was added and the reaction mixture
1
.1 | Preparation of Fe O MNPs
3 4
refluxed for 6 h. The resulting Fe O @Quindiol@Cu
3
4
A mixture of FeCl ⋅6H O (3.0 g) and FeSO ⋅4H O (2.0 g)
nanocatalyst was separated with an external magnet,
washed with water–ethanol solution, dried in vacuum at
70°C for 6 h and kept in a desiccator.
3
2
4
2
was dissolved in water (100 ml), and the solution stirred
for 0.5 h at 80°C. A solution of 37% ammonia was then
added dropwise with vigorous stirring which afforded a
black solid product obtained when the reaction medium
reached a pH of 10. The mixture was heated for 0.5 h at
1
.5 | Preparation of 1‐Substituted‐1H‐
7
0°C and the black magnetite solid product was filtered,
washed with methanol (3 × 20 ml) and dried at 80°C for
2 h.
tetrazole Derivatives
1
A mixture of amine (1.0 mmol), sodium azide (1.0 mmol),
triethyl
orthoformate
(1.2
mmol)
and
the
Fe O @Quindiol@Cu nanocatalyst (0.01 g) was stirred
3
4
1
.2 | Electrochemical Synthesis of
at 100°C until monitoring with TLC showed no further
progress in the conversion. When the reaction mixture
came to ambient temperature, it was washed with ethyl
acetate (2 × 20 ml) and the catalyst separated using an
external magnet. The resulting solution was then treated
Quindiol Ligand
A phosphate buffer (0.2 M, pH = 6.4)–ethanol solution
mixture (90:10 v/v) containing catechol (1a; 55 mg, 0.5
mmol) and 2,3‐diaminopyridine (2a; 53 mg, 0.5 mmol)
was electrolysed in an undivided cell equipped with four
graphite rods as an anode and a large stainless steel cylin-
der as a cathode at 25°C at a current density of 1.35 mA
with water (20 ml), dried over anhydrous MgSO and
4
evaporated. The residue was concentrated and recrystal-
lized from EtOAc–hexane mixture (1:10).