Mononuclear Mn(III) complex with sterically constrained phenol-based ligand: Synthesis, structure and catecholase activity

Abstract A mononuclear Mn(III) complex of a sterically constrained phenol-based tetradentate N2O2 ligand N,Nʹ-dimethyl-N,Nʹ-bi(2-hydroxy-3,5-dichlorobenzyl)-ethylenediamine (H2L) have been reported. Benzoylacetone (bzac) has been used as an ancillary ligands to obtain the mixed ligand mononuclear complex [MnIIIL(bzac)] 1. The syntheses, molecular and supra molecular structure, spectroscopic studies and catecholase activity of the complex are described. Complex 1 crystallizes in orthorhombic space group P212121 with a = 12.935(4) A, b = 13.536(4) A and c = 16.804(5) A. Mn(III) complex acts as an effective catalyst towards the oxidation of 3,5-di-tert-butylcatechol in methanol solvent. The kinetic studies confirm the Kcat value for the oxidation reaction is 2.086 × 103 h−1. Mechanistic study of the catalytic behavior by ESI-MS spectra and estimation of hydrogen peroxide formation suggest that the catalytic process takes place through the reduction of Mn(III) to Mn(II).