Abstract
This paper describes the synthesis of a novel Cu-Ni bimetallic system comprising of magnetic nanoparticles, as the core, and 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole (4-ABPT), as a conjugated bridge, between nickel and copper species. With low Cu and Ni loading (0.06 mol% Ni, 0.08 mol% Cu), the resulting Fe3O4@SiO2@4-ABPT/Cu-Ni showed to be a highly efficient catalyst for the Sonogashira and C-N cross-coupling reactions. The developed catalyst was well characterized by FT-IR, XRD, EDX-mapping, FE-SEM, TEM, ICP, VSM, TGA/DTG/DTA, LSV, and XPS techniques. Fe3O4@SiO2@4-ABPT/Cu-Ni nanocatalyst was compatible with a wide range of amines and aryl halides in the Sonogashira and C-N cross-coupling reactions and offered desired coupling products in high to excellent yields under palladium- and solvent-free conditions. Based on the XPS results, the 4-ABPT ligand can adjust electron transfer between Ni and Cu in Fe3O4@SiO2@4-ABPT/Cu-Ni, promoting the formation and stabilization of Cu+ and Ni3+ species. Electronic interactions and the synergistic effect between these metals increased the selectivity and activity of Fe3O4@SiO2@4-ABPT/Cu-Ni catalyst in the Sonogashira and C-N cross-coupling reactions compared with its monometallic counterparts. Additionally, the magnetic properties of Fe3O4@SiO2@4-ABPT/Cu-Ni facilitated its separation from the reaction mixture, promoting its reuse for several times with no significant loss in its catalytic activity or performance.