New Cu(II) Schiff-base complex modified on magnetic nanoparticles: Oxidation and DFT investigation

Abstract

A copper magnetic nanocatalyst was facilely synthesized by surface modification of silica magnetic nanoparticles (Fe3O4@SiO2) via reaction with 3-aminopropyltrimethoxysilane (Fe3O4@SiO2@APTMS), followed by a subsequent reaction with thiophene-2-carbaldehyde to form a Schiff base (Fe3O4@SiO2@SB). Sequentially, reaction with Cu(CH3COO)2·H2O in ethanol yielded Fe3O4@SiO2@[SB@Cu] (CH3COO)2. This nanomagnetic catalyst was comprehensively characterized using Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Thermogravimetric Analysis (TGA), and Vibrating Sample Magnetometry (VSM) techniques. The catalytic proficiency of these nanoparticles was evaluated through alkene and alcohol oxidation reactions. Under optimized conditions, the nanocatalyst exhibited significant efficacy in oxidizing styrene, cyclohexene, and benzyl alcohol, with notable selectivity values of 88 %, 100 %, and 100 % for the respective formation of styrene epoxide, 2-cyclohexene-1-one, and benzoic acid. The heterogeneous copper nanocatalyst offers advantages, including high conversion rates, facile separation, and exceptional selectivity in alkene and alcohol oxidation. Additionally, this study investigated density functional theory (DFT) methods, encompassing geometric optimization, natural charge analysis, molecular electrostatic potential maps, and vibrational normal modes of the chelating ligands.