Yu. D. Perfiliev

Spectroscopic investigation of indole-3-acetic acid interaction with iron(III)

Abstract FeIII was found to be gradually reduced by indole-3-acetic acid (IAA) in slightly acidic nitrate solution with further re-oxidation of the resulting FeII upon drying in air, which is reasoned to be of ecological significance considering IAA excretion by many soil micro-organisms. FeIII–IAA complex was isolated; its composition, some physicochemical properties and structural aspects were studied using Mossbauer, FTIR spectroscopic and other techniques. Possible influence of FeIII coordination on the redox properties of the ligand is also considered from the viewpoint of the nature of the bonding system which involves the conjugated π-electronic system of the pyrrole cycle along with the carboxylic O-donor atom.

Mössbauer study of sodium ferrates(IV) and (VI)

Sodium ferrates(IV) and (VI) were synthesized by the reaction between Fe2O3 and Na2O2 in a dry oxygen stream. The Mössbauer data for the obtained samples are presented (for Na2FeO3−δ=0.18(2) mm/s; for Na4FeO5−δ=−0.54(2) mm/s). It was shown that pure K2FeO4 and Cs2FeO4 can be obtained by heating Fe2O3 with apropriate alkali metal peroxides.

Mössbauer and FTIR spectroscopic studies of iron anthranilates: coordination, structure and some ecological aspects of iron complexation

Abstract The data on the coordination and structure of iron(II) and iron(III) anthranilates in the solid state and in aqueous medium are presented and discussed, as studied using Mossbauer (for solid products and frozen solutions) and FTIR spectroscopy (for solid samples). Whereas, in slightly acidic nitrate solutions under aerobic conditions ferric ions can still be gradually reduced by anthranilic ( o -aminobenzoic) acid, which may have some ecological significance, in circumneutral media this process is retarded. Mossbauer parameters calculated for iron(II) and iron(III) anthranilates, as well as characteristic vibration modes of certain functional groups involved in coordination with iron cations are discussed. The FTIR data obtained for ferrous anthranilates, as compared to anthranilic acid, definitely exhibit the direct involvement of both the carboxylic and the amino groups of anthranilic acid in coordination with iron.

Mössbauer spectroscopy of iron oxocompounds in higher oxidation states

Alkaline solutions of iron compounds synthesized by anodic dissolution of metallic iron in NaOH media have been studied by Mössbauer spectroscopy. The values of the isomer shift on iron in higher oxidation states are presented. The formation of the peroxoderivatives of iron in the solutions were not fixed.

Mössbauer Study of Hexavalent Iron Compounds

Six crystalline ferrates(VI): K3Na(FeO4)2, K2FeO4, Rb2FeO4, Cs2FeO4, K2Sr(FeO4)2 and BaFeO4, were studied by Mössbauer spectroscopy. Room-temperature spectra of potassium, rubidium and cesium ferrates are single lines, but spectra of barium, potassium–strontium and potassium–sodium ferrates show a presence of quadrupole interactions. Most of these salts display an antiferromagnetic transition with a Néel temperature within 2 to 8 K range.

X-Ray and Mössbauer Study of Mixed Potassium-Sodium Ferrate (VI)

Mixed potassium-sodium ferrate(VI), K3Na(FeO4)2 has been sytithesised by precipitation from alkaline solution. It crystallise in a hexagonal system with lattice parameters a=5.8273±0.0018 A, c=7.5415±0.0032 A and belongs to glaserite-like structures (space group P/3ml). Iron is present in oxidation state +6: room temperature Mossbauer spectrum is a doublet with isomer shift δ=∓0.89±0.01 mm·s−1 (relative to α-iron), quadrupole splitting Δ=0.21±0.01 mm·s−1 and full width at half-height Γ=0.22±0.01 mm·s−1.

Composite Ferric Oxyhydroxide-Containing Phases Formed in Neutral Aqueous Solutions of Tryptophan and Indole-3-Acetic Acid

Mössbauer, FTIR and XRD analyses showed that in aqueous medium in air in the presence of L-tryptophan (Trp) or indole-3-acetic acid (IAA) the ambient-temperature ageing of the precipitates formed from ferrous sulphate at pH∼7 gave composite phases with varying proportions of γ-FeOOH (a dominating crystalline phase), α-FeOOH (both fine-grained, showing superparamagnetic behaviour at 298 K, and relatively better crystallized) and amorphous ferric hydroxide. The experimental data suggested a competition for adsorption sites at the oxyhydroxide surface in the suspension during phase transformations, as well as the transformation of γ-FeOOH (and/or amorphous ferric hydroxide) to α-FeOOH via the dissolution-reprecipitation mechanism. The formation of certain ferric oxyhydroxide phases in the presence of Trp and IAA — released e.g., in the course of bacterial and plant metabolism — can contribute to the regulation of soil mineral composition.

Premelting as studied by positron annihilation and emission Mössbauer spectroscopies

We have estimated a local heating which takes place owing to the ionization energy losses at the terminal part of a fast positron track and at nano-vicinities of the 57Fe Mossbauer nuclei in case of the emission Mossbauer spectroscopy. It is shown that in experiments close to the melting point one may expect local melting near the probe species.

Prospects for emission Mössbauer spectroscopy in chemical investigations

Emission Mössbauer spectroscopy is a radiochemical method for investigating materials and the consequences of nuclear transformations taking place in them. Isotopes are traditionally used as structural probes, and the sensitivity of the method is 2–3 orders of magnitude higher than that of absorption Mössbauer spectroscopy. The elements of Mössbauer isotopes with parent nuclei that undergo electron capture or a converted isomeric transition (i.e., lead to high Auger ionization) are the best-studied elements. The electron processes that accompany ionization and their effect on the state of daughter Mössbauer atoms in qualitatively different compounds, from elementary oxides, superconductors, insulators and magnetics to sophisticated bioorganic complexes, are considered.

Chemical consequences of nuclear transformations /E. C., CIT/ and stabilizing electron chemistry

The mechanism of chemical transformations after57Co/119mSn/ decay in solids is discussed on the basis of recent results. The study of the effect of electron acceptor concentration indicates a significant role of mobile electrons during the stabilization process.