Use of iron and manganese porphyrins in solution and immobilized on silica obtained by the sol–gel process as catalyst in the oxidation of organic substrates

The preparation and characterization of the metalloporphyrins [Fe(TAPP)]Cl, 5,10,15,20-tetrakis(acetalphenyl porphyrin) iron(III) chloride, and [Mn(TAPP)]Ac, 5,10,15,20-tetrakis (acetalphenyl porphyrin) manganese(III) acetate and of the solids obtained by their heterogenization in silica obtained by the sol–gel process in acidic and basic media are reported. The compounds were characterized by ultraviolet–visible absorption spectroscopy (UV–vis), X-ray diffraction (XRD), infrared spectroscopy (FTIR), electron paramagnetic resonance (EPR), and thermogravimetric analysis (TGA). The catalytic activity of the metalloporphyrins in solution and as heterogeneous catalysts concerning the oxidation of organic substrates like cyclooctene and cyclohexane was investigated. The catalysts employed here, which consist of reasonably low-cost metalloporphyrins with intermediate structure between first- and second-generation porphyrins, furnished promising results. These novel solid materials offered benefits such as higher product yields, compared to the first-generation catalysts, and inexpensive preparation routes, compared to the cost involved in the production of second-generation metalloporphyrins.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (31 K)Download as PowerPoint slideHighlights► Preparation of metalloporphyrins [Fe(TAPP)]Cl and [Mn(TAPP)]Ac. ► Low-cost porphyrins with intermediate structure between 1st and 2nd generation. ► Heterogenization of metalloporphyrins in silica obtained by the sol–gel process. ► Efficiency and selectivity in oxidation reaction. ► Catalyst for heterogeneous catalysis with reuse capacity.