Mn(III) complexes of the monoprotic tridentate ONN donor 2-[2-(1H-(benzo[d]imidazol-2-yl)ethylimino)methyl]phenol as a functional mimic of haloperoxidase

The reaction of MnII(ClO4)2 with 2-[2-(1H-(benzo[d]imidazol-2-yl)ethylimino)methyl]phenol (Hsal-aebmz, I) under aerobic conditions results in the formation of [MnIII(sal-aebmz)2]·ClO4 (1). In the presence of triethylamine and using MnCl2 under aerobic conditions, I forms [MnIII(sal-aebmz-H)(sal-aebmz)] (2). These complexes are characterised on the basis of elemental and electrochemical analyses, spectroscopic (IR and UV–Vis) data and thermogravimetric studies. Single crystal X-ray analysis of 2 shows that it is stabilized in the solid state through intermolecular hydrogen bonding between the NH groups of the two benzimidazole moieties after losing one of the hydrogen atoms; the coordination sites of the ligand are the imine nitrogen of the benzimidazole ring, the azomethine nitrogen and the deprotonated phenolic oxygen. Complex 2 catalyses the oxidative bromination of styrene by H2O2, yielding 1,2-dibromo-1-phenylethane, 1-phenylethane-1,2-diol and 2-bromo-1-phenylethane-1-ol, acting as a functional mimic of haloperoxidases.

Graphical abstractManganese(III) complexes with a monobasic tridentate ligand have been isolated, characterised and used as catalysts for the oxidative bromination of styrene by H2O2 in the presence of KBr and HClO4, acting as a functional mimic of haloperoxidases.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Manganese(III) complexes of an ONN donor ligand are reported. ► Deprotonation of one of the benzimidazole nitrogens occurs in [MnIII(sal-aebmz-H)(sal-aebmz)] (2). ► The molecular packing in 2 is controlled by intermolecular hydrogen bonding. ► Complex 2 catalyses oxidative bromination, a functional mimic of the haloperoxidases.