4
A. Zare et al. / Journal of Molecular Structure 1211 (2020) 128030
instrument, at 25e600 ꢁC, with temperature increase rate of
10 ꢁC.minꢀ1 in argon atmosphere.
2.2. Production of nano-[Fe3O4@-SiO2@R-NHMe2][H2PO4] (nano-
[FSRN][H2PO4])
Nano-Fe3O4 was prepared according to a reported method
[39,40]. A mixture of nano-Fe3O4 (0.50 g), Si(OEt)4 (1.5 ml), H2O
(10 ml), EtOH (40 ml) and ammonia (1.5 ml) was refluxed for 12 h to
give I. Then, a mixture of I and (3-chloropropyl)trimethoxysilane
(0.92 ml, 5 mmol) in dry toluene (40 ml) was refluxed under ni-
trogen gas for 12 h; the resulting mixture was centrifuged, dec-
anted, washed twice by dry toluene and anhydrous Et2O, and dried
under vacuum at 90 ꢁC to give II [40,41]. N,N,N0,N0-Tetramethyle-
thylenediamine (0.75 ml, 5 mmol) was added to II in toluene
(30 ml), and the resulting mixture was refluxed for 12 h. The ob-
tained solid was separated by centrifuging and decanting, and
washed by toluene and dried under vacuum at 90 ꢁC to furnish III.
Finally, H3PO4 (0.26 ml, 5 mmol) was added gradually to III at room
temperature, stirred for 5 h at the same temperature and 1 h at
60 ꢁC, and dried under vacuum at 90 ꢁC to afford nano-[FSRN]
[H2PO4].
Fig. 4. The VSM curve of nano-[FSRN][H2PO4].
2.3. General procedure for the synthesis of pyrimido[4,5-b]
quinolines
A mixture of 6-amino-1,3-dimethyluracil (0.155 g, 1 mmol),
aldehyde (1 mmol), dimedone (0.140 g, 1 mmol) and nano-[FSRN]
[H2PO4] (0.080 g) was stirred vigorously by a small rod at 120 ꢁC till
the starting materials were consumed (as monitored by TLC). Then,
the reaction mixture was cooled to room temperature, EtOAc
(40 ml) was added, stirred for 2 min under reflux conditions, and
the catalyst was separated magnetically (washed by EtOAc, and
dried). EtOAc of the retained solution was evaporated, and the
residue was recrystallized from EtOH (95%) to give the pure
product.
Note: Selected spectral data and original spectrums of the
synthesized pyrimido[4,5-b]quinolines have been presented in
supplementary data.
Fig. 5. The XRD diagram of the hybrid nanomaterial.
3. Results and discussion
3.1. The catalyst characterization
The novel organic-inorganic hybrid magnetic nanomaterial, i.e.
nano-[Fe3O4@-SiO2@R-NHMe2][H2PO4] (nano-[FSRN][H2PO4]), was
synthesized according to Scheme 1, and characterized by FT-IR,
EDS, FE-SEM, VSM, XRD and TGA methods.
The peaks related to the expected bonds and functional groups
in the structure of nano-[FSRN][H2PO4] were observed in the FT-IR
spectrum (Fig. 1). The obtained data are summarized in Table 1; the
literature confirmed these interpretations [40].
The EDS spectrum showed the presence of silicon, iron, oxygen,
carbon, nitrogen, chlorine and phosphorous elements in the
structure of nano-[FSRN][H2PO4] (as expected) (Fig. 2). No extra
peak related to any impurity was seen in the spectrum.
FE-SEM was used for determination of size and morphology of
the catalyst particles (Fig. 3). The micrograph showed that the
particles are in nano-size (below 100 nm) with different crystalline
shapes and also amorphous form [42].
Fig. 6. The TG, DTG and DTA curves of nano-[FSRN][H2PO4].
Magnetic measurement of nano-[Fe3O4@-SiO2@R-NHMe2]
[H2PO4] was achieved using a vibrating sample magnetometer at
room temperature; the respective curve is illustrated in Fig. 4. Ac-
cording to the VSM results, saturation magnetization of the catalyst
radiation (
l
¼ 1.5408, model: X’Pert PRO MPD, PANalytical, the
Netherlands). TGA was performed by Bahr STA 504 (Germany)
Dianat, Manije
