Phenoxazinone synthase activity of two iron(III) complexes comprising the same Schiff base ligand: Biomimetic functional model and mechanistic investigation

Abstract A new 4,4′-bipyridine (4,4′-byp) mediated 1D- polymeric Fe III complex (complex 1 ) of Schiff base ligand H 2 L, a 1:2 condensation product of 1,2-diaminopropane and salicylaldehyde, has been synthesized. Complex 1 is structurally characterized by single crystal X-ray diffraction. A phenoxo bridged dinuclear Fe III complex (complex 2 ) of analogous ligand has been synthesized also. Dioxygen activation in terms of Phenoxazinone synthase activity using o -aminophenol (OAPH) as a model substrate catalyzed by both the complexes are thoroughly investigated here. ESI-MS spectral study reveals that polynuclear complex 1 dissociates into mononuclear units while dissolve in methanol during catalytic study. The kinetic study illustrates that both the complexes have well competence towards o -aminophenol oxidation where dinuclear Fe III species demonstrate higher activity than mononuclear intermediate species. Important finding from the mass spectral and electrochemical study provide significant information of the mechanistic pathway of the functioning phenoxazinone synthase like activity of synthesized iron complexes.