Nanomagnetic tetraaza (N4 donor) macrocyclic Schiff base complex of copper(ii): synthesis, characterizations, and its catalytic application in Click reactions

Abstract

In this research, a novel nanomagnetic tetra-azamacrocyclic Schiff base complex of copper(II) was produced via a post-synthetic surface modification of an Fe₃O₄ surface by a silane-coupling agent that contains acetylacetone functionalities at the end of its chain. Moreover, the target Cu complex that involves a tetradentate Schiff base ligand was obtained from a template reaction with o-phenylenediamine and Cu(NO₃)₂·3H₂O. Furthermore, the prepared complex was nominated as [Fe₃O₄@TAM-Schiff-base-Cu^(II)]. The Fourier-transform infrared (FT-IR) analysis indicates the presence of a Schiff-base-Cu complex in the catalyst. X-ray spectroscopy (EDS) and TGA analysis reveal that approximately 6–7% of the target catalyst comprises hydrocarbon moieties. The scanning electron microscope (SEM) and transmission electron microscopy (TEM) images demonstrate the presence of uniformly shaped particles, nearly spherical in nature, with sizes ranging from 9 to 18 nm. [Fe₃O₄@TAM-Schiff-base-Cu^(II)] was applied as a catalyst for the click synthesis of a diverse range of 5-substituted-1H-tetrazoles in PEG-400 as a green medium. Regarding the electrical properties of the Cu(II) complex, the presence of a tetra-aza (N₄ donor) macrocyclic Schiff base as an N-rich ligand was reasonable – leading to its excellent capacity to catalyze these organic transformations. Finally, the high magnetization value (44.92 emu g⁻¹) of [Fe₃O₄@TAM-Schiff-base-Cu^(II)] enables its recycling at least four times without compromising the catalytic efficiency.