Journal of the Iranian Chemical Society
magnetic stirring. The sustained silica-coated magnetic
nanoparticles (SCMNPs) was separated from the solution
by use of a permanent magnet and washed several times
with distilled water and methanol, being dried at 25 °C
under vacuum. For the next step, the prepared SCMNPs
Results and discussion
Preparation and characterization
of the nanocatalyst
(
2.0 g) were suspended in toluene (100 ml) via sonica-
In this research, NHPI was successfully immobilized on silica-
coated magnetite nanoparticles including aminopropyl groups
via amide bonds. NHPI was appended on modiꢀed magnetic
support as illustrated in Scheme 2. At ꢀrst, silica-coated nano-
magnetite (Nano Fe O @SiO ) was prepared from Fe O
tion and then 3-aminopropyl triethoxysilane (2.0 ml) was
added to reaction mixture under argon atmosphere. The
reaction progressed under reꢃux condition for 12 h. Then,
the ꢀnal attained solid was readily separated by external
magnet and after washing with ethanol and acetone was
dried under vacuum at 80 °C.
3
4
2
3
4
and tetraethoxysilane (TEOS) in the presence of ammonium
hydroxide solution 28%. After that, this core–shell nanoparti-
cle system was modiꢀed with 3-aminopropyl triethoxysilane
(
APTES). Then, the interaction between trimellitic anhydride
Preparation of silica‑coated magnetic
nanoparticle‑supported NHPI
chloride (TAC) and amino-functionalized SiO —through
2
amide bond—lead to the formation of immobilized TAC prod-
uct. Eventually, this nanoparticle successfully converted to the
ꢀnal catalyst using hydroxylamine hydrochloride and pyridine.
Obtained ASCMNPs (2.0 g) was suspended in 30 ml of
CH Cl with sonication, and then, trimellitic anhydride
2
2
chloride (TAC) was added. After addition of triethylamine
Fourier transform infrared (FT‑IR) analysis
(
Et N) dropwise over 1 h via syringe, the reaction mixture
3
was allowed to stir for 24 h at room temperature and the
resulting anhydride was magnetically separated, washed
with ethanol and CH Cl and dried under vacuum. The
FT-IR measurements were carried out in order to conꢀrm
the presence of characteristic peaks of prepared compounds,
−
1
2
2
as shown in Fig. 1. Strong bands at 636 and 581 cm , as
−
1
resulting product was added to 30 ml pyridine along with
addition of hydroxylamine hydrochloride (0.2 g), and after
that, the reaction mixture was stirred for 16 h at 90 °C. The
product was magnetically separated, washed several times
with methanol, ethanol and distilled water and ꢀnally was
dried in an oven at 80 °C. The immobilized NHPI was
characterized with FT-IR spectroscopy, X-ray diꢂraction,
scanning and transmission electron microscopies and
vibrating sample magnetometry.
well as, an absorption band at around 462 cm (Fig. 1a) per-
tain to the Fe–O bond of magnetite. Furthermore, the drastic
−1
Si–O–Si stretching vibrations at the range of 1000–1100 cm
obviously represent the silica shell around Fe O . The FT-IR
3
4
spectrum of ASCMNPs (Fig. 1b) exhibited several signals
−
1
in the area of 1450–1550 and 2850–2925 cm , attributed to
C–H stretching vibrations which arise from the presence of
the propyl group. Moreover, two broad signals at 3445 and
−1
1629 cm are related to N–H group. In the FT-IR analysis of
immobilized TAC (Fig. 1c) appeared new peaks at 1852 and
−1
1
777 cm —relevant to carbonyl groups of anhydride. Addi-
−
1
Catalytic oxidation of benzyl alcohols and hydrocarbons
in the presence of silica‑coated magnetic
nanoparticle‑supported NHPI
tionally, absorption band emerged at 1632 cm , evidently
indicates the formation of amide bond between TAC moiety
and ASCMNPs. As displayed in Fig. 1d, FT-IR spectrum of
the ꢀnal NHPI-based catalyst unveiled the disappearance of
−1
Oxidation of benzyl alcohols and hydrocarbons was car-
ried out in a 50-ml round-bottomed ꢃask equipped with
a condenser and a mechanical stirrer. Hydrogen perox-
ide (aqueous solution 30% (w/w) of H O ) was used as
representative signal of anhydride group at 1852 cm , along
−1
with shifting the frequencies of carbonyl bond at 1777 cm
−
1
(related to O=C(O)) to 1785 cm (ascribed to O=C(N))
in which these results are in accordance with the formation
of corresponding product. Nevertheless, distinguishing of
N-hydroxyl group peak was diꢁcult owing to overlapping with
2
2
oxidant. In a typical procedure, to a mixture acetoni-
trile (5.0 ml) solution of benzyl alcohol (1 mmol) was
−
1
added catalyst (10 mg), o-phenanthroline (2.5 mol%), Br
N–H stretching vibration at 3445 cm .
2
(
3 mol%) and the H O (2 mmol). Then, the reaction mix-
2
2
ture was heated at reꢃux temperature. After completion of
the reaction, the catalyst was magnetically separated and
the products were analysed using GC–MS measurements.
Additionally, under the same reaction conditions, reac-
tivity of tetralin and indane was examined and excellent
conversion with high selectivity was observed.
X‑ray diꢀraction (XRD) analysis
In order to investigate the crystalline structure of obtained
products, X-ray diꢂraction (XRD) technique was utilized. As
depicted in Fig. 2, all the samples displayed characteristic
1
3