Mössbauer spectroscopic study of Prussian Blue from different provenances

Ferric ferrocyanides synthesized from different sources of ferric cations and ferrocyanide anions and those derived from ferrous ferricyanide, ferrous ferrocyanide and ferric ferricyanide have been studied using Mössbauer and XRD techniques. Structural information of the effect of the provenance on the properties of the final compound is obtained. Significant correlations between isomer shift and quadrupole splitting of inner and outer iron cations have been observed.     

Mössbauer and infrared spectroscopic studies of novel mixed valence states in cobaltous ferrocyanides and ferricyanides

Novel mixed valence states have been obtained by the treatment of cobaltous ferrocyanides (Co⁺²Fe^II) and ferricyanides (Co⁺²Fe^III) in an ozone flow. The CN stretching bands occur at 2085 cm^–1 for Co⁺²Fe^II and at 2160 cm^–1 for Co⁺²Fe^III. After the ozonization process of Co⁺²Fe^II, an intense band approximately at 2125 cm^–1 is detected. This intermediate band must correspond to a mixed valence state of the type: Fe^II–CN–Co²⁺–NC–Fe^III Mössbauer spectra recorded in situ during the ozonization of Co⁺²Fe^II show the presence of two components: a doublet with isomer shift and quadrupole splitting values close to the cobalti ferricyanide and a very broad line for the mixed valence state. From the Mössbauer and infrared spectra of the aged samples of the Co⁺²Fe^II after ozonization, a relaxation process to the initial state of the samples is observed but the mixed valence state is stable.     

The existence of ferrous ferricyanide

Evidence in the literature on the synthesis of ferrous ferricyanide is critically discussed. Pyrolysis and pressure effects on Prussian Blue lead to ferrous ferrocyanide together with decomposition by-products, and not to ferrous ferricyanide. The latter compound could be a precursor in the formation of Turnbull's Blue or an excited state of Prussian Blue, but it is not a stable chemical species.     

Complex Formation of Ferric Protoporphyrin IX From the Reaction of Hemin with Ammonia and Small Aliphatic Amines

Complexes of Fe^III protoporphyrin IX (Fe^IIIPPIX) with the amido anion were obtained from the reaction of Fe^IIIPPIX chloride (hemin) with ammonia and small aliphatic amines under solvent free conditions. The reaction of hemin with gaseous ammonia leads to a pentacoordinated complex at the iron site, PPIX–Fe–NH₂, plus NH₄Cl, while at the peripheral propionic acidic groups ammonium carboxylate is formed. The corresponding stoichiometry (1:4 molar ratio of hemin to ammonia) was confirmed by the adsorption isotherm. Analogous reactions and complex formation were observed with EtNH₂ and Et₂NH. These reactions were monitored using X-ray diffraction (XRD), and i.r. and Mössbauer spectroscopies. The isomer shift and quadrupole splitting values of the resulting complexes are in correspondence with the strong -donor character of the amido anion linked to the iron atom. For comparison, the Mössbauer parameters for hemin complexes with arginine and 2-aminoguanidine, which also have pure interaction with the porphyrin iron, were included and discussed.     

Mössbauer spectra of ferrous salts of transition metal cyano complexes. A survey

Ferrous salts of ten hexacyanometallates and three tetracyanometallates were obtained and their Mössbauer spectra interpreted according to recent structural models for these families of compounds. Ferrous ferrocyanide (Williamson White) and its ruthenium and osmium analogs prepared mechanochemically are stable for hours, allowing their study by Mössbauer spectroscopy and other related techniques. For ferrous salts of trivalent hexacyanometallate anions, the random distribution of anion vacancies is discarded and a model of two well defined relative positions of CN and H2O ligands around the Fe2+ is suggested. Iron was found octahedrally coordinated in tetracyanometallates.     

Poincaré series of resolutions of surface singularities

Let be a resolution of singularities of a normal surface singularity , with integral exceptional divisors . We consider the Poincaré series

where

We show that if has characteristic zero and is a semi-abelian variety, then the Poincaré series is rational. However, we give examples to show that this series can be irrational if either of these conditions fails.

     

Solid State Reactions of Hemin with Basic Substances: Formation of bis and Mixed Complexes

The solid state reactions of hemin with KCN, Na₂SxH₂O, arginine, imidazole, 1-methylimidazole, 2-methylimidazole, benzimidazole, and mixtures of these basic reagents were monitored using IR, Mössbauer, and XRD techniques. All these basic substances react at the peripheral propionic acid group of hemin-forming salts. Binary mixtures of KCN, arginine, imidazole, 1-methylimidazole, 2-methylimidazole, and benzimidazole were found to form complexes with mixed ligands at the iron site of hemin. According to the structural information obtained for these mixed complexes, mechanisms for their formation are proposed. The solid state synthesis and the properties of the obtained products reveal the specifities of the involved ligands.     

The first total synthesis of the (±)-17-methyl-trans-4,5-methyleneoctadecanoic acid and related analogs with antileishmanial activity

The first total synthesis of the marine cyclopropane fatty acid (±)-17-methyl-trans-4,5-methyleneoctadecanoic acid was accomplished in eight steps and in 9.1% overall yield starting from 1-bromo-12-methyltridecane. The cis analog (±)-17-methyl-cis-4,5-methyleneoctadecanoic acid was also synthesized but in seven steps and in 16.4% overall yield. With the two isomeric cyclopropane fatty acids at hand it was possible to unequivocally corroborate the trans relative configuration of the naturally occurring fatty acid by gas chromatographic co-elution of the corresponding methyl esters. The cis isomer was cytotoxic to Leishmania donovani promastigotes with an IC₅₀ of 300.2 ± 4.2 μM.     

Mechanochemical Synthesis of Urea Adducts with Long Chain Alkyl Derivatives

The adducts of urea and solid alkyl derivatives can beobtained mechanochemically in good yields. Theproducts synthesized by grinding the solid reagentshave identical IR spectra and XRD powder patterns tothose obtained by crystallization from ethanolicsolutions.