Biguanide-Functionalized Fe₃O₄/SiO₂Magnetic Nanoparticles: An Efficient Heterogeneous Organosuperbase Catalyst for Various Organic Transformations in Aqueous Media

Abstract

A novel biguanide-functionalized Fe 3 O 4 /SiO 2 magnetite nanoparticle with a core-shell structure was developed for utilization as a heterogeneous organosuperbase in chemical transformations. The structural, surface, and magnetic characteristics of the nanosized catalyst were investigated by various techniques such as transmission electron microscopy (TEM), powder X-ray diffraction (XRD), vibrating sample magnetometry (VSM), elemental analyzer (EA), thermogravimetric analysis (TGA), N 2 adsorption-desorption (BET and BJH) and FT-IR. The biguanide-functionalized Fe 3 O 4 /SiO 2 nanoparticles showed a superpara-magnetic property with a saturation magnetization value of 46.7 emu/g, indicating great potential for application in magnetically separation technologies. In application point of view, the prepared catalyst was found to act as an efficient recoverable nanocatalyst in nitroaldol and domino Knoevenagel condensation/Michael addition/cyclization reactions in aqueous media under mild condition. Additionally, the catalyst was reused six times without significant degradation in catalytic activity and performance.

Structure Analysis of Fe3O4@SiO2 Core Shells Prepared from Amorphous and Crystalline SiO2 Particles

“…On the other hand, the peaks at 468, 800, 950, and 1097 cm -1 present asymmetrical vibrations and symmetrical stretching of Si-O-Si siloxane and silanol bonds on silica. Therefore, it indicates that the Fe3O4 particles can succeed to form a core formation shell with SiO2 as a layer [1,18,40,41].The stretching and bending vibration of the H-O-H bond are found at wave numbers of 1641-3465 cm -1 . Such functional groups have almost similar characteristics with the Fe3O4@a-SiO2 particles obtained from the references [27], [28].…”

Synthesis and Characterization of Fe3O4@SiO2 NPs as an Effective Catalyst for the Synthesis of Tetrahydrobenzo[a]xanthen-11-ones

“…6,7 Recently, functionalized magnetite nanoparticles were used as efficient catalytic systems in many chemical transformations including synthesis of α-amino nitriles, 8 1,1-diacetates from aldehydes, 9 diazepine derivatives, 10 indazolo[2,1-b]phthalazine-triones and pyrazolo [1,2-b]phthalazine-diones, 11 3,4-dihydropyrimidin-2(1H)-ones, 12 2-amino-4H-chromen-4-yl phosphonates, 13 1,4-dihydropyridines 14 and pyrrole synthesis. 15 In addition, a series of organic reactions such as Knoevenagel condensation/Michael addition, 16 Suzuki/Heck cross-coupling, 17 asymmetric aldol reaction, 18 Suzuki coupling, 19 asymmetric hydrogenation of aromatic ketones, 20 acetalization reaction, 21 Ritter reaction, 22 23 Henry reaction, 24 enantioselective directaddition of terminal alkynes to imines 25 have been done using functionalized nanostructures.…”

Composites of Fe3O4/SiO2from Natural Material Synthesized by Co-Precipitation Method

“…This method can be utilized to prepare an inorganic compound based on the precipitation process of substances. The advantage of this method is having a relatively low temperature in a short process [12,13]. Interestingly, the method can prepare the Fe 3 O 4 /SiO 2 nanoparticle that was illustrated to form a composite formation, where the Fe 3 O 4 ferromagnetic particle is covered inside the hollow of SiO 2 particle [11,14].…”