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

Abstract

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 is 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.

Cu(II) and Mn(II) Anchored on Functionalized Mesoporous Silica with Schiff Bases: Effects of Supports and Metal–Ligand Interactions on Catalytic Activity

“…The EPR spectra of the immobilized Mn(II) complexes ( Figure 9 B) show six hyperfine lines, with g values very close to that of the free electron, characteristic of oxygen-coordinated Mn(II) ion in disordered systems [ 67 ]. The simulation of the EPR spectra recorded for solid Mn complexes indicated an anisotropy of the hyperfine splitting characteristic of a 5/2 spin state.…”