Design of novel iron compounds as potential therapeutic agents against tuberculosis

In the search for new therapeutic tools against tuberculosis two novel iron complexes, [Fe(L-H)3], with 3-aminoquinoxaline-2-carbonitrile N(1),N(4)-dioxide derivatives (L) as ligands, were synthesized, characterized by a combination of techniques, and in vitro evaluated. Results were compared with those previously reported for two analogous iron complexes of other ligands of the same family of quinoxaline derivatives. In addition, the complexes were studied by cyclic voltammetry and EPR spectroscopy. Cyclic voltammograms of the iron compounds showed several cathodic processes which were attributed to the reduction of the metal center (Fe(III)/Fe(II)) and the coordinated ligand. EPR signals were characteristic of magnetically isolated high-spin Fe(III) in a rhombic environment and arise from transitions between m(s) = +/- 1/2 (geff-9) or m(s) = +/- 3/2 (g(eff)similar to 4.3) states. Mossbauer experiments showed hyperfine parameters that are typical of high-spin Fe(III) ions in a not too distorted environment. The novel complexes showed in vitro growth inhibitory activity on Mycobacterium tuberculosis H(37)Rv (ATCC 27294), together with very low unspecific cytotoxicity on eukaryotic cells (cultured murine cell line J774). Both complexes showed higher inhibitory effects on M. tuberculosis than the "second-line" therapeutic drugs. (C) 2010 Elsevier B.V. All rights reserved.

Mössbauer spectroscopic study of the early crystallization stage of iron(III) hydroxide particles

Mössbauer spectroscopy was used to investigate the early aging stage of iron(III) hydroxide sols prepared by oxidation of Fe(CO)5 in ethanolic solution, followed by vacuum drying at room temperature. One sample was composed of amorphous particles, while two other samples were partially crystallized, either as a result of solvent change or of spontaneous aging. The main results of Mössbauer measurements in the 80-320 K temperature range are: (a) partially crystallized particles exhibit a strong, S-shaped temperature dependence of the quadrupole splitting, in contrast to a weak and linear variation for amorphous particles; (b) the recoilless fraction temperature dependence is affected by vibration of the particles as a whole, with an effective force constant which is smaller for crystallized particles than for amorphous ones. Furthermore, the former exhibit anf-factor discontinuity near 0°C, which is attributed to melting of a surface layer built up during the crystallization process. © 1986.

Magnetic properties of spindle-type iron fine particles obtained from hematite

Spindle-type iron fine particles have been prepared by reduction of silica-coated-hematite particles. Hydrogen reduction of the coated-hematite cores yielded uniform spindle-type iron particles, which were stabilized by surface oxidation. Narrow particle distributions are observed from TEM measurements. X-ray, Mössbauer and magnetization data are in agreement with the presence of nanosized α-Fe particles, having surface layer of spinel structure oxide. Mössbauer spectra show that the oxide surface is superparamagnetic at room temperature. © 2001 Elsevier Science B.V. All rights reserved.

Synthesis and spectroscopic characterization of new metal(II) complexes with methionine sulfoxide

Methionine sulfoxide complexes of iron(II) and copper(II) were synthesized and characterized by chemical and spectroscopic techniques. Elemental and atomic absorption analyses fit the compositions K2[Fe(metSO) 2]SO4 · H2O and [Cu(metSO)2] · H2O. Electronic absorption spectra of the complexes are typical of octahedral geometries. Infrared spectroscopy suggests coordination of the ligand to the metal through the carboxylate and sulfoxide groups. An EPR spectrum of the Cu(II) complex indicates tetragonal distortion of its octahedral symmetry. 57Fe Mössbauer parameters are also consistent with octahedral stereochemistry for the iron(II) complex. The complexes are very soluble in water.

A magnetically drivable nanovehicle for curcumin with antioxidant capacity and MRI relaxation properties

Curcumin possesses wide-ranging anti-inflammatory and anti-cancer properties and its biological activity can be linked to its potent antioxidant capacity. Superparamagnetic maghemite (gamma-Fe2O3), called surface-active maghemite nanoparticles (SAMNs) were surface-modified with curcumin molecules, due to the presence of under-coordinated Fe-III atoms on the nanoparticle surface. The so-obtained curcumin-modified SAMNs (SAMN@curcumin) had a mean size of 13 +/- 4 nm. SAMN@curcumin was characterized by transmission and scanning electron microscopy, UV/Vis, FTIR, and Mossbauer spectroscopy, X-ray powder diffraction, bulk susceptibility (SQUID), and relaxometry measurements (MRI imaging). The high negative contrast proclivity of SAMN@curcumin to act as potential contrast agent in MRI screenings was also tested. Moreover, the redox properties of bound curcumin were probed by electrochemistry. SAMN@curcumin was studied in the presence of different electroactive molecules, namely hydroquinone, NADH and ferrocyanide, to assess its redox behavior. Finally, SAMN@curcumin was electrochemically probed in the presence of hydrogen peroxide, demonstrating the stability and reactivity of bound curcumin.

Characterization of tetraethylene glycol passivated iron nanoparticles

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structural, morphological and magnetic characterization of electrodeposited Co-Fe-W alloys

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Análise estrutural e morfológica de ferrita NiFe2O4 dopada com cromo

This paper reports on the effect of the substitution of Fe3+ for Cr3+ ions in the spinel lattice of the powders was investigated. Nickel ferrite powders with a NiFe2-xCrxO4 nominal composition (x = 0.0; 0.5; 1.0 and 1.5 mol of the chromium) were synthesized by combustion reaction using urea as fuel. The powders resulting were characterized by XRD, nitrogen adsorption by BET, SEM and Mössbauer spectroscopy (57Fe Mössbauer spectra). The results show that the substitution of the Fe3+ for Cr3+ions increased the crystalline degree of the phase, reduced the superficial area and consequently increased the particle size. The Mössbauer spectra of the samples also confirm the distribution of the particles size by the magnetic properties. Analyze of the spectra Mössbauer gives an estimate of the superparamagnetic and ferromagnetic particles behavior in each sample for several chromium concentrations.

Magnetically drivable nano-bio-conjugate mimicking free curcumin redox behavior

Curcumin possesses wide-ranging anti-inflammatory and anti-cancer properties and its biological activity can be correlated to its potent antioxidant capacity. Novel maghemite (gamma-Fe3O4) nanoparticles, characterized by a diameter of about 10 nm and possessing peculiar colloidal properties and surface interactions, called Surface Active Maghemite Nanoparticles (SAMN), were superficially modified with curcumin by simple incubation, due to the presence of under-coordinated Fe(III) atoms on nanoparticle surface. The resulting curcumin-modified SAMNs (SAMN@curcumin) were characterized by transmission electron microscopy (TEM), FTIR, Mossbauer, EPR and UV-Vis spectroscopy. The redox properties of bound curcumin were tested by electrochemistry. Finally, SAMN@curcumin was studied in the presence of different electroactive substances, namely hydroquinone, NADH and ferrocyanide, in order to assess its electrochemical behavior. Moreover, SAMN@curcumin was electrochemically tested in the presence of one of the most diffuse reactive oxygen specie, such as hydrogen peroxide, demonstrating its stability. SAMN@curcumin in which curcumin is firmly bound, but still retaining its redox features represents a feasible adduct: a magnetically drivable nano-bio-conjugate mimicking free Curcumin redox behavior. The proposed nanostructured material could be exploited as magnetic drivable curcumin vehicle for biomedical applications.

Reaction of pentacarbonyliron with a nitrogen heterocycle. X-ray crystal structure of bis[(carbonyl)(quinoline-2-thiolate-N,S)]iron(II)

The monomeric compound bis[(carbonyl)(quinoline-2-thiolate-N,S)]iron(II) was synthesized and studied by IR and Mossbauer spectroscopy, cyclic voltammetry and X-ray diffraction. The molecule has two terminal carbonyl groups and two quinoline-2-thiolate anions coordinated as N,S-donor chelates, and the iron atom shows an octahedral coordination geometry.

Stabilization of polyaniline by the incorporation of magnetite nanoparticles

Nanocomposites obtained from the polymerization of aniline in the presence of nanoparticles of magnetite (Fe3O4) have been investigated in previous studies. However, there is a lack of information available on the redox interaction of the nanoparticle/conductive polymer couple and the stability that such an oxide can give to the organic phase. In this work, Fe3O4 nanoparticles were incorporated into a PANi matrix by the in-situ oxidative polymerization method. A combination of X-ray diffraction, Mossbauer spectroscopy, transmission electronic microscopy, UV-visible spectroscopy as well as the cyclic voltammetric and Raman spectroscopy techniques, was used to understand the redox effect that the partially oxidized nanoparticles produced on the polymer. It was found that magnetite greatly stabilised PANi, mainly by enhancing the Leucoemeraldine/Emeraldine redox couple and also by reducing the bipolaronic state. (C) 2011 Elsevier B.V. All rights reserved.

Magnetic and optical investigation of 40SiO(2)center dot 30Na(2)O center dot 1Al(2)O(3)center dot(29-x) B2O3 center dot xFe(2)O(3) glass matrix

Samples of 40SiO(2)center dot 30Na(2)O center dot 1Al(2)O(3)center dot(29 - x)B2O3 center dot xFe(2)O(3) (mol%), with 0.0 <= x <= 17.5, were prepared by the fusion method and investigated by electron paramagnetic resonance (EPR), optical absorption (OA) and Mossbauer spectroscopy (MS). The EPR spectra of the as-synthesized samples exhibit two well-defined EPR signals around g = 4.27 and g = 2.01 and a visible EPR shoulder around g = 6.4, assigned to isolated Fe3+ ion complexes (g = 4.27 and g = 6.4) and Fe3+-based clusters (g = 2.01). Analyses of both EPR line intensity and line width support the model picture of Fe3+-based clusters built in from two sources of isolated ions, namely Fe2+ and Fe3+; the ferrous ion being used to build in iron-based clusters at lower x-content (below about x = 2.5%) whereas the ferric ion is used to build in iron-based clusters at higher x-content (above about x = 2.5%). The presence of Fe2+ ions incorporated within the glass template is supported by OA data with a strong band around 1100 nm due to the spin-allowed E-5(g)-T-5(2g) transition in an octahedral coordination with oxygen. Additionally, Mossbauer data (isomer shift and quadrupole splitting) confirm incorporation of both Fe2+ and Fe3+ ions within the template, more likely in tetrahedral-like environments. We hypothesize that ferrous ions are incorporated within the glass template as FeO4 complex resulting from replacing silicon in non-bridging oxygen (SiO3O-) sites whereas ferric ions are incorporated as FeO4 complex resulting from replacing silicon in bridging-like oxygen silicate groups (SiO4). (C) 2012 Elsevier Masson SAS. All rights reserved.

Surface Segregation in Chromium-Doped Nanocrystalline Tin Dioxide Pigments

Surface properties play an important role in understanding and controlling nanocrystalline materials. The accumulation of dopants on the surface, caused by surface segregation, can therefore significantly affect nanomaterials properties at low doping levels, offering a way to intentionally control nanoparticles features. In this work, we studied the distribution of chromium ions in SnO2 nanoparticles prepared by a liquid precursor route at moderate temperatures (500 degrees C). The powders were characterized by infrared spectroscopy, X-ray diffraction, (scanning) transmission electron microscopy, Electron Energy Loss Spectroscopy, and Mossbauer spectroscopy. We showed that this synthesis method induces a limited solid solution of chromium into SnO2 and a segregation of chromium to the surface. The s-electron density and symmetry of Sn located on the surface were significantly affected by the doping, while Sn located in the bulk remained unchanged. Chromium ions located on the surface and in the bulk showed distinct oxidation states, giving rise to the intense violet color of the nanoparticles suitable for pigment application.

Synthesis and characterization of [Ru(eta(6)-C10H14)(dppf)X][PF6] (X = Cl, Br, I, SnF3) compounds: The X-ray structure of [Ru(eta(6)-C10H14)(dppf)Cl][SnCl3]center dot 0.45CH(2)Cl(2)

The arene-ruthenium complex [Ru(eta(6)-C10H14)(dppf)Cl]PF6 (1) was used as a precursor for the syntheses of the [Ru(eta(6)-C10H14)(dppf)Br]PF6 (2), [Ru(eta(6)-C10H14)(dppf)I]PF6 (3). [Ru(eta(6)-C10H14)(dppf)SnF3]PF6 (4) and [Ru(eta(6)-C10H14)(dppf)Cl][SnCl3]center dot 0.45CH(2)Cl(2) (5) complexes by its reactions with KBr, Kl, SnF2 and SnCl2. respectively. All of the compounds were characterized by NMR, IR, Fe-57 and Sn-119-Mossbauer spectroscopy, and cyclic voltammetry. The single-crystal X-ray structure analysis of the [Ru(eta(6)-C10H14)(dppf)Cl] [SnCl3]center dot 0.45CH(2)Cl(2) complex revealed the expected piano-stool geometry. Cyclic voltammograms of the complexes showed only one quasi-reversible electrochemical process, involving the oxidation of Fe(II) and Ru(II) at the same potential, which was confirmed by exhaustive electrolysis experiments. Fe-57-Mossbauer parameters obtained for the complexes (1-5) were fitted with one doublet corresponding to a site of one iron(II). The Sn-119-Mossbauer parameters of the complex (4) indicate that tin is tetra covalent. (c) 2012 Elsevier Ltd. All rights reserved.

Studio delle proprieta magnetiche del sistema nanogranulare magnetite/idrossiapatite per potenziali applicazioni in nanomedicina

Abbiamo sintetizzato un nuovo sistema nanogranulare consistente di nanoparticelle di magnetite inserite in idrossiapatite carbonata biomimetica per possibili future prospettive nell'ambito del tissue engineering osseo. Sono stati sintetizzati e studiati tre campioni nanogranulari, uno composto di nanoparticelle di magnetite e due composti di idrossiapatite contenenti magnetite per circa lo 0.8wt.% ed il 4wt.%. Le nanoparticelle di magnetite e il materiale composto sono stati analizzati tramite diffrazione a raggi X (XRD), spettroscopia all'infrarosso (FT-IR) e microscopia in trasmissione elettronica (TEM). Queste analisi hanno fornito informazioni sulla struttura delle nanoparticelle, come il size medio di circa 6 nm e hanno rivelato, sulla loro superficie, la presenza di gruppi idrossilici che incentivano la crescita successiva della fase di idrossiapatite, realizzando una struttura nanocristallina lamellare. I primi studi magnetici, condotti tramite un magnetometro SQUID, hanno mostrato che sia le nanoparticelle as-prepared sia quelle ricoperte di idrossiapatite sono superparamagnetiche a T=300K ma che il rilassamento della magnetizzazione è dominato da interazioni magnetiche dipolari di intensità confrontabile all'interno dei tre campioni. I valori di magnetizzazione più bassi di quelli tipici per la magnetite bulk ci hanno portato ad ipotizzare un possibile fenomeno di canting superficiale per gli spin delle nanoparticelle, fenomeno presente e documentato in letteratura. Nei tre campioni, quello di sole nanoparticelle di magnetite e quelli di idrossiapatite a diverso contenuto di magnetite, si forma uno stato collettivo bloccato a temperature inferiori a circa 20K. Questi risultati indicano che le nanoparticelle di magnetite tendono a formare agglomerati già nello stato as-prepared che sostanzialmente non vengono alterati con la crescita di idrossiapatite, coerentemente con la possibile formazione di legami idrogeno elettrostatici tra i gruppi idrossilici superficiali. L'analisi Mossbauer del campione di magnetite as-prepared ha mostrato un comportamento bimodale nelle distribuzioni dei campi iperfini presenti alle varie temperature. Passando dalle basse alle alte temperature lo spettro collassa in un doppietto, coerentemente con il passaggio dallo stato bloccato allo stato superparamagnetico per il sistema.