Functionalization of superparamagnetic Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub>nanoparticles with a Cu(II) binuclear Schiff base complex as an efficient and reusable nanomagnetic catalyst for<i>N</i>‐arylation of α‐amino acids and nitrogen‐containing heterocycles with aryl halides
Ali Reza Sardarian, Milad Kazemnejadi, Mohsen Esmaeilpour
Abstract
Fe 3 O 4 @SiO 2 nanoparticles was functionalized with a binuclear Schiff base Cu(II)‐complex (Fe 3 O 4 @SiO 2 /Schiff base‐Cu(II) NPs) and used as an effective magnetic hetereogeneous nanocatalyst for the N ‐arylation of α‐amino acids and nitrogen‐containig heterocycles. The catalyst, Fe 3 O 4 @SiO 2 /Schiff base‐Cu(II) NPs, was characterized by Fourier transform infrared (FTIR) and ultraviolet‐visible (UV‐vis) analyses step by step. Size, morphology, and size distribution of the nanocatalyst were studied by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and dynamic light scatterings (DLS) analyses, respectively. The structure of Fe 3 O 4 nanoparticles was checked by X‐ray diffraction (XRD) technique. Furthermore, the magnetic properties of the nanocatalyst were investigated by vibrating sample magnetometer (VSM) analysis. Loading content as well as leaching amounts of copper supported by the catalyst was measured by inductive coupled plasma (ICP) analysis. Also, thermal studies of the nanocatalyst was studied by thermal gravimetric analysis (TGA) instrument. X‐ray photoelectron spectroscopy (XPS) analysis of the catalyst revealed that the copper sites are in +2 oxidation state. The Fe 3 O 4 @SiO 2 /Schiff base‐Cu(II) complex was found to be an effective catalyst for C–N cross‐coupling reactions, which high to excellent yields were achieved for α‐amino acids as well as N ‐hetereocyclic compounds. Easy recoverability of the catalyst by an external magnet, reusability up to eight runs without significant loss of activity, and its well stability during the reaction are among the other highlights of this catalyst.