A novel Cu(II) nanoparticles anchored on cyanuric chloride-attached magnetic nanocatalyst: A highly stable, recyclable and efficient nanocatalyst for the synthesis of chromene derivatives

Abstract

As a novel core-shell magnetic nanocatalyst, a copper nanocatalyst, Cu(II)-Schiff base-TCT-APTES@SiO2@Fe3O4 was successfully synthesized through the reaction of the cyanuric chloride grafted onto the core-shell magnetic nanocatalyst with Schiff base complex and finally treated with Cu(NO3)2·3H2O The noteworthy point is that the novel Schiff base separated by employing hydrazine with 2-pyridinecarboxaldehyde was synthesized and purified by a simple washing and identified by FT-IR, 1HNMR and 13CNMR spectrums. The catalyst was studied relying on various techniques and spectroscopic procedures including FT-IR, SEM, TEM, XPS, XRD, VSM, BET, TGA, and ICP analyses. The TEM images indicated that the catalyst was synthesized with an average size of 37–47 nm and a spherical shape. BET analysis showed that our catalyst has been synthesized with mesoporous structure and high surface area (52.55 m2/g). Moreover, the XPS results clearly demonstrated the peak at 937.2 eV and 949.2 eV that was related to the presence of Cu(II) in structure of catalyst. Then, copper nanocatalyst was successfully tested for the one-pot three component reaction of chromene derivatives of various aldehydes, phenols (2-hydroxynaphthalene-1,4-dione, resorcinol and β-naphthol) and malononitrile in ethanol under reflux conditions. All products were obtained in excellent yields for a diverse range of aromatic aldehydes. TON and TOF numbers for the compound 4j with the highest yield were found to be 192 and 581.8 h−1, respectively. Further, the copper catalyst can be reused by external magnetic field over eight times with a negligible loss in activity, showing 0.08 % leaching of Cu after 7 times recycling. Also, Density Functional Theory (DFT) calculations were carried out to investigate the electrostatic potential (ESP), natural bond orbital (NBO), images of HOMO and LUMO orbitals and drawing the reaction mechanism using total energy of reactant and product.