Synthesis, characterization and catalase-like activity of the tetranuclear iron(III) complex involving a (μ-oxo)(μ-hydroxo)bis(μ-alkoxo)tetra(μ-carboxylato)tetrairon core

• A tetrairon complex, which is a dimer of dimer, presents a catalase-like behavior.
• The chemical environment for the four iron atoms is the same.
• The complex presents two (μ-oxo) bridges with a H between them.
• The catalase-like activity presents the order: water < TRIS buffer < acetonitrile.
• The catalase-like activity was followed by UV–Vis, ESI-MS/Q-TOF and EPR.

The synthesis, characterization and catalase-like activity of the tetranuclear complex [Fe4(μ-O)(μ-OH)(μ-OAc)4(L)2](ClO4)3 (HL is the ligand 1,3-bis[(2-aminoethyl)amino]-2-propanol) is described herein. The complex was obtained from the self-assembly of Fe(ClO4)3·xH2O, NaOAc·3H2O and HL. The X-ray structural elucidation, together with spectroscopic and ESI-MS data, disclosed a (μ-oxo)(μ-hydroxo)bis(μ-alkoxo)tetra(μ-carboxylato)tetrairon core structure that can be described as a dimer of dimer, where the four metallic centers are embedded in the same chemical environment. The kinetics of the catalase-like activity was investigated in water, TRIS buffer and acetonitrile, and it revealed a Michaelis–Menten behavior. The progress of H2O2 disproportionation reactions was followed by UV–Vis, ESI-MS/Q-TOF and EPR, indicating the disruption of the tetranuclear core, which was accelerated at higher proton concentration. The rate constant was higher in CH3CN than in aqueous solution (kobs(CH3CN) > kobs(buffer) > kobs(H2O)).

The catalase-like activity of [Fe4(μ-O)(μ-OH)(μ-OAc)4(L)2](ClO4)3 was investigated in water, buffer and acetonitrile. Kinetic studies revealed a Michaelis–Menten behavior, with kobs(CH3CN) > kobs(buffer) > kobs(H2O). The progress of H2O2 disproportionation was followed by UV–Vis and ESI-MS/Q-TOF, indicating disruption of the tetranuclear core, which was accelerated at lower pH.Figure optionsDownload as PowerPoint slide