A Mixed-Valent Polyiron Oxo Complex that Models the Biomineralization of the Ferritin Core

Abstract

A novel polyiron oxo complex, [FeIII4FeII8(O)2(OCH3)18(O2CCH3)6(CH3OH) 4.67] (1), has been prepared from ferrous acetate and lithium methoxide in methanol by slow addition of dioxygen. The three-dimensional close-packed layered structure found in 1 closely mimics that proposed for the inorganic core in the iron storage protein ferritin. The Mössbauer spectra of 1 reveal superparamagnetic relaxation at temperatures below 15 K, a property characteristic of the ferritin core. The small size and mixed-valent nature of 1 suggest that it is a reasonable model for intermediates formed in the biomineralization of iron during ferritin core formation. A related compound, with the same iron-oxygen framework found in 1 but containing only two ferric ions, has also been structurally characterized. Because the clusters exhibit properties of both discrete molecules and extended solids, they are representative of a new class of nanometer-sized compounds that bridge the molecular solid-state boundary.

Iron Incorporation in Streptococcus suis Dps-like Peroxide Resistance Protein Dpr Requires Mobility in the Ferroxidase Center and Leads to the Formation of a Ferrihydrite-like Core

“…However, there is a debate on the structure of mineral ferrihydrite with mainly octahedral structures widely supported 44 , 45 according also to some ferritin model iron clusters. 34,46 In fact, the inorganic ferrihydrite seems to be a rather disordered mineral without the possibility to determine an unambiguous structure. 34 Thus, in the case of Dpr in vitro core, the Eggleton and Fitzpatrick type of ferrihydrite structure 43 appears the most plausible.…”

Large Clusters of Metal Ions: The Transition from Molecular to Bulk Magnets

“…the spectra of several polyiron 0x0 and thio clusters (1 6, 35,36) in the temperature range of 4 to 300 K and, in some cases, found a sextet spectrum in the absence of a n applied field. From comparison of the Mossbauer spectra recorded with and without a n external magnetic field, she concluded that some of them behave as superparamagnets and that, because the clusters showing this behavior have a pseudo threedimensional structure, it must be expected that bulk behavior shows up at a n earlier stage in pseudo three-dimensional than it does in pseudo one-and two-dimensional particles.…”

Water Oxidation Reaction Mediated by an Octanuclear Iron‐Oxo Cluster

“…In recognition of this, many groups have been using chelating ligands containing carboxylate functions and other functionalities in order to determine which parameters are important in controlling the speciation of iron. These studies have led to a wide variety of polyiron clusters containing bridging oxygen atoms and Fe 4 , Fe 6 , Fe 8 , Fe 10 , Fe 11 , Fe 12 , and Fe 16 centers . It has been demonstrated that the hydrolysis of iron salts can be controlled by organic ligands so as to yield soluble molecular aggregates with nanometer dimensions, which can often be isolated in crystalline form and structurally characterized.…”