Ferryl and Ferrate Species: Mössbauer Spectroscopy Investigation

Abstract

High-valent iron species of oxidation states +4, +5, and +6, have been involved as intermediates in enzymatic reactions, in green organic synthesis, and in purification and disinfection of water. Many of these species have been synthesized to understand their role in different systems, which include ferryl complexes (oxoiron(IV) (Fe IV =O), oxoiron(V) (Fe V =O)), iron(IV / V / VI)-nitride complexes, and ferrates ((Fe VI O4 2-, Fe(VI), Fe V O4 3-, Fe(V), and Fe IV O4 4-, Fe(IV)). Ferryl and iron-nitride complexes have organic ligands surrounded at the iron center and are soluble in non-aqueous solvent. Comparatively, ferrate species are tetraoxyanions and are soluble in water. This paper presents Mössbauer spectroscopy as a tool to distinguish different oxidation states of iron and to gain information on the geometry and structure of high-valent iron complexes. Examples are given to demonstrate the application of Mössbauer spectroscopy in learning mechanisms of thermal decomposition of ferrates, encapsulation of heavy metals by ferrates, and oxidation of thiols by ferrates.

Structural, magnetic and quantum-chemical study of dinuclear copper(II) thiophenecarboxylate and furancarboxylate complexes

“…It has been found that the biological activities of the discussed compounds are considerably increased when they are bonded into metal complex molecules. For example, such effects have been observed for Co(II), Ni(II), Cu(II) and Zn(II) chelates with several ligands, including 2-thiophenecarboxylic acid tested, on some selected fungi [5]. In addition, the Co(II), Ni(II) and Cu(II) complexes with 2-thiophenecarboxylic acid have received increasing attention as potential anticancer drugs [6].…”

On the Origins of Some Spectroscopic Properties of “Purple Iron” (the Tetraoxoferrate(VI) Ion) and Its Pourbaix Safe-Space

“…Using Density Function Theory (DFT) calculations, Poleshchuk et al estimated the chemical shift of “Fe VIII O 4 ” to be δ = −1.40 mm s −1 (with respect to α-iron) and that the Fe-O bond was calculated to be 1.586 Å, assuming all Fe-O bonds are identical [ 97 ]. Sharma & Zboril (2015) produced a linear correlation equation between chemical shift and oxidations state of iron [ 98 ], therefore: δ (mm s −1 ) = 1.084 − 0.326 × (oxidation state) …”

Epoxidation of propylene by hydrogen peroxide catalyzed by the silanol‐functionalized polyoxometalates‐supported ferrate: Electronic structure, bonding feature, and reaction mechanism

“…The instability of FeO 4 2− severely limits its large‐scale application and becomes a bottleneck for further development. [ 38–39 ] On the other hand, such a reaction system is completely against the objective of the green chemical production technology advocated today because a large mass of FeO 4 2− has been consumed to form inorganic waste contaminated by organic tars. [ 40–43 ] Therefore, it is very important to establish a new catalytic system to effectively utilize FeO 4 2− .…”