Magnetic Cu–Schiff base complex with an ionic tail as a recyclable bifunctional catalyst for base/Pd-free Sonogashira coupling reaction

Abstract

A Cu(II)–Schiff base complex containing imidazolium ionic phase was prepared and decorated on γ-Fe2O3 magnetic nanoparticles (γ-Fe2O3@Cu(II)IL-SB) and found to be an efficient catalyst for the Pd- and base-free Sonogashira coupling reaction. The heterogeneous catalyst was characterized by FTIR spectroscopy, UV–visible spectroscopy, FE-SEM, TEM, XRD spectroscopy, EDX spectroscopy, VSM, ICP spectroscopy, and atomic absorption spectroscopy. The coupling reactions were performed using the catalyst under mild and base-free conditions, and high-to-excellent yields were obtained for a variety of substrates. The catalyst demonstrates a dual-functionality arising from metal sites and imidazolium moieties and that the later plays a base role. Reusability and stability of γ-Fe2O3@Cu(II)IL-SB were studied several times, which can be reused up to eight consecutive runs with at least reduction in catalytic activity. Also, the mechanism of this bifunctional catalytic system was thoroughly investigated.