Immobilized Copper(II) Diisatin-Schiff Base Complex on AgCo3O4 Nanoparticles as Efficient Catalysts for Styrene Oxidation.

Abstract

To advance the industrialization of the chemical productions, i.e., the organo-oxidizing reactions, a mono-organometallic Cu(II) diisatin-Schiff base complex (Cu(HmeL)₂Cl₂) is constructed from the complexing action of isatin-Schiff base ligand (HmeL) with half the amount of copper(II) chloride. The chemical structure of HmeL and Cu(HmeL)₂Cl₂ was established with many spectroscopic methods. The heterogeneity of Cu(HmeL)₂Cl₂ was accomplished within a processive coating of the AgCo₃O₄ nanoparticles (as Cu(HmeL)₂Cl₂@AgCo₃O₄). The internal structure, the elemental composition, and the surface morphology of nano-Cu(HmeL)₂Cl₂@AgCo₃O₄ composite were examined using different spectroscopic-microscopic techniques. The micrographs showed a nanocluster-shaped formation of Cu(HmeL)₂Cl₂@AgCo₃O₄ nanocomposite. The catalytic productivity of Cu(HmeL)₂Cl₂ (as a homogeneous catalyst) and Cu(HmeL)₂Cl₂@AgCo₃O₄ nanocomposite (as a nanocatalyst) was studied for the optimization in the redox productivity of styrene, as a representative example of olefins, to the corresponded epoxide (2-phenyloxirane) using an aqueous H₂O₂ under the control of temperature, time, and solvent (in an aerobic environment). For the optimized environment, the monooxygenation achievement of the homogeneous catalyst (Cu(HmeL)₂Cl₂) was adjusted with a lower temperature (80 °C after 5 h) with yielding 87% compared to the heterogenized phase (nano-Cu(HmeL)₂Cl₂@AgCo₃O₄ composite precatalyst (90 °C after 5 h), with 90%. The coated AgCo₃O₄ nanoparticles improved the catalytic potential of Cu(HmeL)₂Cl₂ complex in the yield of the selective product. The heterogeneity of Cu(HmeL)₂Cl₂ complex modified its reusing ability with 7 successful trials over that of the homogenous phase of Cu(HmeL)₂Cl₂ complex catalyst in the oxygenation system of styrene (three successful trials only).