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.