Synthesis and characterization of magnetic bromochromate hybrid nanomaterials with triphenylphosphine surface-modified iron oxide nanoparticles and their catalytic application in multicomponent reactions

Abstract

In this work, the preparation of a new magnetic hybrid core–shell nanomaterial is reported in four steps. The magnetic Fe₃O₄ nanoparticles were synthesized via a simple hydrothermal system. Tetraethyl orthosilicate was used as a source of SiO₂ for the creation of Fe₃O₄@SiO₂ core–shell nanoparticles. The subsequent functionalization of Fe₃O₄@SiO₂ was achieved by using (3-chloropropyl)trimethoxysilane and triphenylphosphine. Finally, immobilization of the anionic part including the [CrO₃Br]⁻ was carried out to obtain Fe₃O₄@SiO₂@PPh₃@[CrO₃Br]. The structure and morphology of the prepared nanocatalyst was characterized by using elemental analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and a vibrating sample magnetometer (VSM). The prepared catalyst showed efficient activity as an heterogeneous catalyst in the synthesis of 1,4-dihydropyridine derivatives at room temperature. Moreover, the catalyst can be readily recovered by simple magnetic decantation and can be recycled several times with no significant loss of catalytic activity.