A copper(ii) complex containing pyridine-2-carbaldehyde and its direct binding onto ethylenediamine functionalized with Fe3O4@SiO2 nanoparticles for catalytic applications

Abstract

In the present study, a copper(II) complex containing a pyridine-2-carbaldehyde ligand and its direct binding onto ethylenediamine functionalized with Fe₃O₄@SiO₂ nanoparticles [Cu(II)-Schiff base-(CH₂)₃-SiO₂@Fe₃O₄] as a heterogeneous magnetic nanocatalyst can be easily prepared using a multi-step method. Next, the structural and magnetic properties of the synthesized nanoparticles were identified using Fourier-transform infrared spectroscopy (FT-IR), inductively coupled plasma (ICP), vibrating-sample magnetometry (VSM), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA), PXRD (Powder X-ray diffraction), Brunauer–Emmett–Teller (BET), and energy-dispersive X-ray spectrometry (EDX) techniques. TEM images reveal that the average particle size distribution was found to be in the range of 45–55 nm with spherical shape. The PXRD analysis indicated that the crystallite size was found to be 35.2 nm. The synthesized nanocatalyst exhibited a very good catalytic ability in the synthesis reaction of pyran derivatives and 2-benzylidenemalononitrile derivatives. Product 2-amino-7,7-dimethyl-4-(4-nitrophenyl)-5-oxo-5,6,7,8-tetrahydrobenzo[b]pyran 4e was achieved in 97% yield with a TON of 129.3 and a TOF of 646.6 h⁻¹ and product 2-(4-cyanobenzylidene)malononitrile 3j was achieved in 96% yield with a TON of 128 and a TOF of 984.6 h⁻¹. In addition, the synthesized nanocatalyst was easily separated from the reaction mixture by a magnet and used 7 consecutive times without significant loss of catalytic activity. Also, leaching of copper metal from the synthesized nanocatalyst was very insignificant for this reaction.