Synthesis and Characterization of Silica-Supported Schiff Base Ligands and Their Metal Complexes: Applications as Catalysts for the Oxidation of Alkanes

GRAPHICAL ABSTRACT

Abstract

Copper and cobalt metal complexes of novel ligands, immobilized on 3-aminopropyl functionalized silica, were used as catalysts for the oxidation of cyclohexane and cyclooctane by H₂O₂ under moderate reaction conditions. The complexes of the Schiff bases are formed by coordination of N, O atoms of the ligands. The proposed structures were confirmed by elemental analyses, Fourier transform infrared (FTIR), inductively coupled plasma optical emission spectrometry (ICP-OES), thermal, and scanning electron microscope (SEM) analyses. Thermal gravimetric analysis (TGA) shows that supported complexes are stable up to ca. 200°C. Catalytic properties of the complexes were investigated for the selective oxidation of cyclohexane and cyclooctane and found that Cu(II) complexes showed well-selective catalytic activity with 91% and 77% conversation.

Keywords:

• Metal complexes
• immobilization
• oxidation catalyst
• cycloalkanes
• SEM