Synthesis, structural characterisation, and catalytic activity of Mn(II)–protected amino acid complexes covalently immobilised on chloropropylated silica gel

• Building biomimetic Mn(II)–amino acid complexes over silica gel via covalent grafting.
• Structural characterisation of the silica-anchored complexes with a variety of methods.
• Testing with a superoxide dismutase biochemical test reaction.
• Oxidation of cyclohexane with high epoxide selectivity.

In this work the syntheses, structure, superoxide dismutase (SOD) activity and the catalytic use in the oxidative transformations of cyclohexene of covalently grafted Mn(II)–complexes formed with various C-protected amino acid (l-histidine, l-cysteine and l-cystine) ligands are presented. The structural features of the surface complexes were studied by EPR, X-ray absorption, and mid/far IR spectroscopies. The superoxide dismutase activities of the materials were determined in a biochemical test reaction. The obtained materials were used as catalysts for the oxidation of cyclohexene with peracetic acid in acetone. Covalent grafting and building the complex onto the surface of the chloropropylated silica gel were successful in all cases. It was found that in many instances the structures obtained and the coordinating groups substantially varied upon changing the conditions of the syntheses. All the covalently immobilised Mn(II)–complexes displayed superoxide dismutase activity and could catalyse the oxidation of cyclohexene.

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