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Iron
Kinds of Iron Terms modified by Iron Selected AbstractsGRAPE SEED PROANTHOCYANIDIN EXTRACT CHELATES IRON AND ATTENUATES THE TOXIC EFFECTS OF 6-HYDROXYDOPAMINE: IMPLICATIONS FOR PARKINSON'S DISEASEJOURNAL OF FOOD BIOCHEMISTRY, Issue 2 2010TZU-HUA WU ABSTRACT Proanthocyanidins are potent antioxidants associated with protection against diseases. We tested the reducing capacity, iron chelating activity, and anti-auto-oxidation ability of grape seed proanthocyanidin extract (GSPE). The mechanisms underlying GSPE attenuation of oxidative processes induced by 6-hydroxydopamine (6-OHDA), a neurotoxin used to induce Parkinson's disease, were investigated in cell-based systems. At high concentrations, GSPE (50 µg/µL) was a mild pro-oxidant in a Fenton-type reaction. GSPE (300 µg/mL) was as potent as 30 µM deferoxamine in its iron-chelating capacity, and as efficient as 5 mM ascorbic acid in delaying 6-OHDA auto-oxidation. In PC-12 cell cultures, 100 and 300 µg/mL GSPE significantly protected (P < 0.05) cells from 6-OHDA-induced (400 µM) toxicity. GSPE-induced cytoprotection is enhanced by a nitric oxide synthase inhibitor (NOSI), implying that the cytoprotective effect of GSPE does not require NOS activation. In conclusion, the iron-chelating activity of GSPE minimizes its pro-oxidant activity and delays 6-OHDA auto-oxidation to provide cytoprotection. PRACTICAL APPLICATIONS Parkinson's disease is a neurodegenerative disorder characterized by the degeneration of dopaminergic neurons. The recognized pharmacological strategies to prevent or treat Parkinson's disease include the minimization of oxidative stress, iron release and excitotoxicity resulting from excess nitric oxide formation. One of the best ways to delay or prevent the onset of the disease is to improve the biological antioxidant status by providing additional radical scavengers that are not pro-oxidants. The pro-oxidant activity, such as that of the antioxidant ascorbic acid, enhances radical cycling under certain conditions, and therefore may be detrimental. Grape seed proanthocyanidin extracts (GSPEs) are used as a dietary supplement in food products in several countries. Our current report provides evidence that GSPE has limited pro-oxidant activity, presumably because of its iron-chelating abilities, and protects cells from neurotoxic insults. GSPE may be effective as a dietary supplement for prophylactic use against the progressive neurodegeneration seen in Parkinson's disease. [source] INTRAVENOUS IRON IN CHRONIC KIDNEY DISEASE: HAEMOGLOBIN CHANGE SHORTLY AFTER TREATMENT OF PATIENTS NEITHER ON DIALYSIS NOR ON ERYTHROPOIETINJOURNAL OF RENAL CARE, Issue 3 2008Senyo Tagboto SUMMARY Anaemia is a common in chronic kidney disease. Although erythropoietin and iron supplementation are established treatments, knowledge on the use of IV iron alone in patients not on dialysis or erythropoietin is incomplete. The responses of 82 patients referred to the renal anaemia service with haemoglobin of 11.5 g/dl or less were assessed 1 week after completing four once weekly doses of 200 mg of venofer. No patients were on dialysis or erythropoietin. The haemoglobin rise 1 week after treatment was 0.53 g/dl. Ferritin levels improved from 110.8 to 410.2 ng/l and transferrin saturation from 17.7 to 27.3%. Ferritin levels remained below our target range (200,500 ng/l) in 7.7% while 25.6% had levels above this. Ferritin levels remained less than 800 ng/l in nearly all patients. Intravenous iron is cost effective and should be considered for use in patients with renal anaemia. Patients with CKD stage 5 appeared to respond less well. [source] Serum Iron and Matrix Metalloproteinase-9 Variations in Limbs Affected by Chronic Venous Disease and Venous Leg UlcersDERMATOLOGIC SURGERY, Issue 6 2005Paolo Zamboni MD Background. Severe chronic venous disease (CVD) is characterized by both dermal hemosiderin accumulation and matrix metalloproteinase (MMP) hyperactivation. The iron-driven pathway is one of the recognized mechanisms of MMP hyperactivation. Objective. To investigate the potential consequences of leg hemosiderin deposits on both iron metabolism and activation of MMPs. Methods. We contemporaneously assessed the following in the serum of the arm and ankle veins of 30 patients (C4,6) with CVD and 14 normal subjects: ferritin, transferrin, iron, percentage of transferrin iron binding capacity (%TIBC), and MMP-9. Optical microscopy examinations with Perls' staining of chronic wounds were also performed. Results. Histology consistently revealed iron deposits. Serum ferritin, iron, and %TIBC were significantly increased in the legs affected by severe CVD compared with the arm of the same subjects or the controls. In addition, iron and %TIBC were significantly elevated in the legs of ulcer patients. The rate of activation of MMP-9 was significantly elevated in CVD. Conclusions. The increased iron deposition in legs affected by CVD seems to be more instable in ulcer patients, leading to iron release in the serum of the affected leg. Our data suggest the iron-driven pathway as a further mechanism for MMP hyperexpression leading to tissue lesion. [source] Heterogeneous Electron Transfer and Oxygen Reduction Reaction at Nanostructured Iron(II) Phthalocyanine and Its MWCNTs NanocompositesELECTROANALYSIS, Issue 9 2010Solomon Abstract Electron transfer and oxygen reduction dynamics at nanostructured iron(II) phthalocyanine/multi-walled carbon nanotubes composite supported on an edge plane pyrolytic graphite electrode (EPPGE-MWCNT-nanoFePc) platform have been reported. All the electrodes showed the category 3 diffusional behaviour according to the Davies,Compton theoretical framework. Both MWCNTs and MWCNT-nanoFePc showed huge current responses compared to the other electrodes, suggesting the redox processes of trapped redox species within the porous layers of MWCNTs. Electron transfer process is much easier at the EPPGE-MWCNT and EPPGE-MWCNT-nanoFePc compared to the other electrodes. The best response for oxygen reduction reaction was at the EPPGE-MWCNT-nanoFePc, yielding a 4-electron process. [source] Heavy Metals in Matrices of Food Interest: Sequential Voltammetric Determination at Trace and Ultratrace Level of Copper, Lead, Cadmium, Zinc, Arsenic, Selenium, Manganese and Iron in MealsELECTROANALYSIS, Issue 18 2004Clinio Locatelli Abstract The voltammetric methods are very suitable and versatile techniques for the simultaneous metal determination in complex matrices. The present work, regarding the sequential determination of Cu(II), Pb(II), Cd(II), Zn(II) by square-wave anodic stripping voltammetry (SWASV), As(III), Se(IV) by square-wave cathodic stripping voltammetry (SWCSV) and Mn(II), Fe(III) by square-wave voltammetry (SWV) in matrices involved in foods and food chain as wholemeal, wheat and maize meal, are an interesting example of the possibility to sequentially determine each single element in real samples. Besides the set up of the analytical method, particular attention is aimed either at the problem of possible signal interference or to show that, using the peak area Ap as instrumental datum, it is possible to achieve lower limits of detection. The analytical procedure was verified by the analysis of the standard reference materials: Wholemeal BCR-CRM 189, Wheat Flour NIST-SRM 1567a and Rice Flour NIST-SRM 1568a. Precision, as repeatability, and accuracy, expressed as relative standard deviation and relative error, respectively, were lower than 6% in all cases. In the presence of reciprocal interference, the standard addition method considerably improved the resolution of the voltammetric technique. Once set up on the standard reference materials, the analytical procedure was transferred and applied to commercial meals sampled on market for sale. A critical comparison with spectroscopic measurements is also discussed. [source] Electrochemical Behavior and Detection of Dopamine and Ascorbic Acid at an Iron(II)tetrasulfophthalocyanine Modified Carbon Paste MicroelectrodeELECTROANALYSIS, Issue 10 2003Joshua Oni Abstract In this article the electrocatalytic behavior of an iron(II)tetrasulfophthalocyanine modified carbon paste microelectrode for the oxidation of dopamine (DA) and ascorbic acid (AA) is described. Although the oxidation potential of ascorbic acid is shifted by over 100,mV to more positive potentials, no peak separation could be obtained. This can be explained by the immediate homogeneous reduction of the oxidation product of dopamine by ascorbic acid in solution. However, this reaction induces a shift of the half-wave potential as a function of ratio of concentration of dopamine to ascorbic acid (cDA/cAA). Therefore it was possible to determine the cAA and cDA from this potential shift and the experimental peak current. Detection limits of 4.5±0.2×10,7 and 7.5±0.5×10,7,mol,L,1 were obtained respectively for dopamine and ascorbic acid for cDA/cAA>0.01. [source] Enhancement of Anodic Response for DMSO at Ruthenium Oxide Film Electrodes as a Result of Doping with Iron(III)ELECTROANALYSIS, Issue 2 2003Brett Abstract The oxidation of dimethyl sulfoxide (DMSO) to dimethyl sulfone (DMSO2) is representative of numerous anodic oxygen-transfer reactions of organosulfur compounds that suffer from slow kinetics at noble metal electrodes. Anodic voltammetric data for DMSO are examined at various RuO2 -film electrodes prepared by thermal deposition on titanium substrates. The response for DMSO is slightly larger at RuO2 films prepared in a flame as compared with films prepared in a furnace; however, temperature is more easily controlled in the furnace. Doping of the RuO2 films with Fe(III) further improves the sensitivity of anodic response for DMSO. Optimal response is obtained at an Fe(III)-doped RuO2 -film electrode prepared using a deposition solution of 50,mM RuCl3 and 10,mM FeCl3 in a 1,:,1 mixture of isopropanol and 12,M HCl at an annealing temperature of 450,°C. The Levich plot (i vs. ,1/2) and Koutecky-Levich plot (1/i vs. 1/,1/2) of amperometric data for the oxidation of DMSO at an Fe(III)-doped RuO2 -film electrode configured as a rotated disk are consistent with an anodic response controlled by mass-transport processes at low rotational velocities. Flow injection data demonstrate that Fe(III)-doped RuO2 -film electrodes exhibit detection capability for methionine and cysteine in addition to DMSO. Detection limits for 100-,L injections of the three compounds are ca. 3.2×10,4,mM, i.e., ca. 32,pmol. [source] Comparative mutagenic effects of structurally similar flavonoids quercetin and taxifolin on tester strains Salmonella typhimurium TA102 and Escherichia coli WP-2 uvrAENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 6 2009Patrudu S. Makena Abstract Quercetin (QT) and Taxifolin (TF) are structurally similar plant polyphenols. Both have been reported to have therapeutic potential as anti-cancer drugs and antioxidants. Mutagenic effects of QT and TF were evaluated using Salmonella typhimurium TA102 and Escherichia coli WP-2 uvrA tester strains. Either in the presence or absence of S9 mix, QT was mutagenic to TA102 and WP2 uvrA. However, the mutagenicity of QT was significantly enhanced in the presence of S9 mix. Likewise, in the presence of Iron (Fe2+) and NADPH generating system (NGS) and absence of S9 mix, QT induced significantly high mutations in both TA102 and WP-2 uvrA. Mutagenicity of QT decreased in both strains in the presence of Iron (Fe2+) or NGS alone. TF was not mutagenic in the presence or absence of S9 mix in both TA102 and WP-2 uvrA 2, regardless of the presence of iron or NGS. Incorporation of antioxidants (ascorbate, superoxide dismutase (SOD), catalase (CAT)) and/or iron chelators (desferroxamine (DF) and ethylenediamine-tetraacetate (EDTA)) in the test systems markedly decreased QT-induced mutations in both tester strains. These results suggest that QT but not TF, could induce mutations in the presence or absence of rat liver S9 or Iron (Fe2+) and NGS in both tester strains by redox cycling and Fenton reactions to produce oxygen free radicals. Our results indicate that a minor structural variation between the two plant polyphenols could elicit a marked difference in their genotoxicities. These results provide a basis for further study into the potential use of QT in combination with iron supplements. Environ. Mol. Mutagen. 2009. © 2009 Wiley-Liss, Inc. [source] Arsenic Binding to Iron(II) Minerals Produced by An Iron(III)-Reducing Aeromonas Strain Isolated from Paddy SoilENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2009Xin-Jun Wang Abstract An iron-reducing bacterial strain was isolated from a paddy soil and identified as a member of the Aeromonas group by 16S rRNA gene sequence analysis. When the cells were growing with dissolved Fe(III) as the electron acceptor in the presence of As(V), Fe(II) minerals (siderite and vivianite) were formed and dissolved. As was removed efficiently from solution. When the cells were growing with the Fe(III) hydroxide mineral (ferrihydrite) as the electron acceptor in the presence of As(V), ferrihydrite was reduced and dissolved As(V) concentrations decreased sharply. The present study results demonstrated first that members of the Aeromonas group can reduce Fe(III) in paddy soils and second that iron reduction does not necessarily lead to arsenic mobilization. However, As immobilization can occur in environments that contain significant concentrations of counterions such as bicarbonate and phosphate. [source] Iron enhances endothelial cell activation in response to Cytomegalovirus or Chlamydia pneumoniae infectionEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 10 2006A. E. R. Kartikasari Abstract Background, Chronic inflammation has been implemented in the pathogenesis of inflammatory diseases like atherosclerosis. Several pathogens like Chlamydia pneumoniae (Cp) and cytomegalovirus (CMV) result in inflammation and thereby are potentially artherogenic. Those infections could trigger endothelial activation, the starting point of the atherogenic inflammatory cascade. Considering the role of iron in a wide range of infection processes, the presence of iron may complicate infection-mediated endothelial activation. Materials and methods, Endothelial intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and endothelial selectin (E-selectin) expression were measured using flow cytometry, as an indication of endothelial activation. Cytotoxicity was monitored using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Immunostaining was applied to measure Cp and CMV infectivity to endothelial cells. Results, An increased number of infected endothelial cells in a monolayer population leads to a raised expression of adhesion molecules of the whole cell population, suggesting paracrine interactions. Iron additively up-regulated Cp-induced VCAM-1 expression, whereas synergistically potentiated Cp-induced ICAM-1 expression. Together with CMV, iron also enhanced ICAM-1 and VCAM-1 expression. These iron effects were observed without modulation of the initial infectivity of both microorganisms. Moreover, the effects of iron could be reversed by intracellular iron chelation or radical scavenging, conforming modulating effects of iron on endothelial activation after infections. Conclusions, Endothelial response towards chronic infections depends on intracellular iron levels. Iron status in populations positive for Cp or CMV infections should be considered as a potential determinant for the development of atherosclerosis. [source] Serum transferrin receptor, ferritin, and reticulocyte maturity indices during the first year of life in ,large' preterm infantsEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 5 2007Vassiliki Schiza Abstract Background:, Preterm infants are at risk of developing iron deficiency; among the iron status and hemopoiesis indices the serum transferrin receptor (sTfr) has been shown to be a useful indicator in assessing iron status, while immature reticulocyte production is regarded as an estimator of erythropoiesis. Objective:, To investigate age-related changes in iron status infants born ,moderately' preterm, with a gestational age (GA) of 32,36 wk, and identify associations between sTfr and other hematological and biochemical iron indices. Design:, Hospital-based prospective, longitudinal study in preterm infants. Methods:, Iron and erythropoiesis parameters were evaluated in 181 formula-fed preterm infants at 2 and 6 wk and 3, 6, 9, and 12 months chronological age. Hemoglobulin (Hb), hematocrit (Hct), mean corpuscular volume (MCV), reticulocytes, serum iron (sFe), serum ferritin (sFer), sTfr, and reticulocyte subpopulations were measured. Results:, A total of 756 measurements were performed. After an initial decline, Hb rose from month 3 to 12 of life. SFe and sFer and immature reticulocyte count decreased from the second week to the third month and remained stable thereafter. STfr was lower up to 6 wk and stable from month 3 to 12. Iron deficiency anemia (IDA) was found in 5.5% of infants. In 76 measurements sFer was <12 ,g/L, implying storage iron deficiency (SID). A negative correlation was observed between sTfr and other indices of iron status such as Hb, Hct, MCV, sFe, and sFer. Infants with sFer <12 ,g/L had lower sTfr than those with sFer >12 ,g/L. Reticulocyte production was positively associated with STfr, but this association was dependent on the chronological age of the infant. Conclusion:, Iron depletion is common in formula-fed preterm (32,36 wk GA) infants between month 3 and 12 of life. STfr appears to be an indicator of iron status in preterm infants during the first year of life. [source] The Effect of Surface Area and Crystal Structure on the Catalytic Efficiency of Iron(III) Oxide Nanoparticles in Hydrogen Peroxide DecompositionEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2010Cenek Gregor Abstract Iron(II) oxalate dihydrate has been used as a readily decomposable substance for the controlled synthesis of nanosized iron(III) oxides. The polymorphous composition, particle size and surface area of these iron oxide nanoparticles were controlled by varying the reaction temperature between 185 and 500 °C. As-prepared samples were characterized by XRD, low-temperature and in-field Mössbauer spectroscopy, BET surface area and the TEM technique. They were also tested as heterogeneous catalysts in hydrogen peroxide decomposition. At the selected temperatures, the formed nanomaterials did not contain any traces of amorphous phase, which is known to considerably reduce the catalytic efficiency of iron(III) oxide catalysts. As the thickness of the sample (, 2 mm) was above the critical value, a temporary temperature increase ("exo effect") was observed during all quasi-isothermal decompositions studied, irrespective of the reaction temperature. Increasing the reaction temperature resulted in a shift of the exo effect towards shorter times and an increased content of maghemite phase. The maghemite content decreases above 350 °C as a result of a thermally induced polymorphous transition into hematite. The catalytic data demonstrate that the crystal structure of iron(III) oxide (i.e. the relative contents of maghemite and hematite) does not influence the rate of hydrogen peroxide decomposition. However, the rate constant increases monotonously with increasing sample surface area (and decreasing thermolysis temperature), reaching a maximum of 27,×,10,3 min,1(g/L),1 for the sample with a surface area of 285 m2,g,1. This rate constant is currently the highest reported value of all known iron oxide catalytic systems and is even slightly higher than that observed for the most efficient catalyst reported to date, which has a significantly larger surface area of 337 m2,g,1. This surprisingly high catalytic activity at relatively low surface area can be ascribed to the absence of a amorphous phase in the samples prepared in this study. Taking into account these new findings, the contributions of the key factors highlighted above (surface area, particle size, crystal structure, crystallinity) to the overall activity of iron oxides forhydrogen peroxide decomposition are discussed. [source] Synthesis, Structures, and Magnetic Properties of N -Trialkylsilyl-8-amidoquinoline Complexes of Chromium, Manganese, Iron, and Cobalt as well as of Wheel-Like Hexanuclear Iron(II) and Manganese(II) Bis(8-amidoquinoline)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2010Astrid Malassa Abstract The transamination of 8-(tert -butyldimethylsilylamino)quinoline with (thf)2Cr[N(SiMe3)2]2 yields monomeric bis[8-(tert -butyldimethylsilylamido)quinoline]chromium(II) (1). Similar reactions of M[N(SiMe3)2]2 (M = Mn, Fe, Co) with 8-(trialkylsilylamino)quinoline lead to the formation of monomeric bis[8-(trialkylsilylamido)quinoline]metal(II) [M = Mn, SiR3 = SiMe2tBu (2a), SiiPr3 (2b); M = Fe, SiR3 = SiMe2tBu (3a),SiiPr3 (3b); M = Co, SiR3 = SiMe2tBu (4a), SiiPr3 (4b)]. The transamination of 8-aminoquinoline with M[N(SiMe3)2]2 (M = Mn, Fe, Co) allows the isolation of the heteroleptic 1:1 and homoleptic 2:1 products. The 1:1 complexes bis[8-amidoquinoline metal(II)bis(trimethylsilyl)amide] [M = Mn (5), Fe (6), Co (7)] are dimeric with bridging 8-amidoquinoline moieties. The 2:1 complexes of Mn and Fe, bis(8-amidoquinoline)manganese(II) (8) and bis(8-amidoquinoline)iron(II) (9), form hexamers with wheel-like molecular structures consisting of metal-centered nitrogen octahedra interconnected by common N···N edges. The cobalt complex, bis(8-amidoquinoline)cobalt(II) (10), precipitates as a microcrystalline powder. Investigations of the magnetic properties by DFT corroborate the experimental data for the Mn derivative 8, where an antiferomagnetic coupling is observed. By contrast, calculations on the Fe6 -wheel 9 yield very close-lying ferromagnetically and antiferromagnetically coupled states. [source] Comparative Solution Equilibrium Study of the Interactions of Copper(II), Iron(II) and Zinc(II) with Triapine (3-Aminopyridine-2-carbaldehyde Thiosemicarbazone) and Related LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2010Éva A. Enyedy Abstract The interactions of CuII, ZnII and FeII with Triapine (3-aminopyridine-2-carbaldehyde thiosemicarbazone), which is currently undergoing phase II clinical trials as a chemotherapeutic antitumour agent, were investigated in a water/DMSO mixture. The proton-dissociation constants of the ligands, the stability constants and the coordination modes of the metal complexes formed were determined by pH-potentiometric, UV/Vis spectrophotometric, EPR, 1H NMR spectroscopic and ESI-MS methods. Two N-terminally dimethylated derivatives of Triapine were also studied. Mono- and bis-ligand complexes in different protonation states were identified. Furthermore, the formation of the dinuclear species [Cu2L3]+ was confirmed for all ligands by EPR spectroscopy and ESI-MS measurements. The results showed that the N-terminally dimethylated ligands are much more potent chelators than Triapine for the divalent metal ions studied. All three ligands formed the least stable complexes with ZnII, whereas the FeII complexes were somewhat more stable than the corresponding CuII species. [source] Two New Iron(II) Spin-Crossover Complexes with N4O2 Coordination Sphere and Spin Transition around Room TemperatureEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 36 2009Birgit Weber Abstract The reaction of iron(II) acetate with the tetradentate Schiff base like ligand H2L1 {[3,3,]-[4,5-dihydroxy-1,2-phenylenebis(iminomethylidyne)bis(2,4-pentanedion)]} leads to the formation of the complex [FeL1(MeOH)]. Reaction of this complex with pyridine (py) or N,N,-dimethylaminopyridine (dmap) leads to the two N4O2 -coordinated complexes [FeL1(py)2]·py (1) and [FeL1(dmap)2]·MeOH·0.5dmap (2). Both complexes are spin-crossover compounds that were characterised by using magnetic measurements, X-ray crystallography and temperature-dependent 1H NMR spectroscopy. Special attention was given to the role of the two hydroxy groups on the phenyl ring in the formation of a hydrogen-bonding network and the influence of this network on the spin-transition properties. Although only a gradual spin crossover was observed for both complexes, the transition temperature was shifted to higher temperatures relative to that of the complexes with no additional hydroxy groups at the Schiff base like ligand. The hydrogen-bonding network was responsible for this effect.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Unconventional Spin Crossover in Dinuclear and Trinuclear Iron(III) Complexes with Cyanido and Metallacyanido BridgesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 21 2009alitro Abstract A nonsymmetrical triamine, 1,6-diamino-4-azahexane, was Schiff-condensed with (X-substituted) o -salicylaldehyde to yield pentadentate ligands X-L5: salpet and MeBu-salpet. These ligands form mononuclear, dinuclear, and trinuclear FeIII complexes, whose structures were determined by single-crystal X-ray analysis. Of the mononuclear complexes, [FeIII(salpet)Cl] and [FeIII(MeBu-salpet)Cl] are high spin (S = 5/2), whereas [FeIII(salpet)CN]·MeOH is low spin (S = 1/2). The dinuclear and trinuclear complexes show a kind ofthermally induced spin crossover. The dinuclear complex [L5FeIII(CN)FeIIIL5](ClO4)·2H2O (L5 = salpet) is a mixed-spin assembly: the C -coordinated FeIII center is low spin (L) and the N -coordinated FeIII center is high spin (H) at low temperature; an antiferromagnetic interaction occurs between them. This LH reference state is mixed with the LL one. Upon heating, the system shows an increasing content of the HH state. Also, the dinuclear complex [L5FeIII(CN)FeIIIL5](BPh4)·2MeCN (L5 = MeBu-salpet) exhibits a spin transition between LH and HH spin pairs. The mixed-valence trinuclear complex [L5FeIII{FeII(CN)5(NO)}FeIIIL5]·0.5MeOH·3.75H2O (L5 = salpet) shows spin crossover with a residual high-spin fraction at liquid He temperature owing to the LL + LH ground state. The metallacyanido-bridged complex [L5FeIII{Ni(CN)4}FeIIIL5]·2MeOH (L5 = MeBu-salpet) contains a high-spin pair, HH, over the whole temperature interval with a ferromagnetic exchange interaction. A theoretical model was outlined that allows simultaneous fitting of all available experimental data (magnetic susceptibility, magnetization, high-spin mole fraction obtained from the Mössbauer spectra) on a common set of parameters. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Quenching the Hysteresis in Single Crystals of a 1D Chain Iron(II) Spin Crossover ComplexEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2008Birgit Weber Abstract The unusual grinding effects observed in the 1D spin crossover polymer [FeL(bipy)]n (1), with L being a tetradentate N2O22, coordinating Schiff base type ligand {(3,3,)-[1,2-phenylenebis(iminomethylidyne)]bis(2,4-pentanedionato)(2,)- N,N,,O2,O2,} and bipy = 4,4,-bipyridine, are investigated using magnetic measurements, X-ray powder diffraction and optical reflectivity studies. The observed behaviour can be explained when solvent effects are taken into account. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Amphiphilic Iron(II) and Nickel(II) Complexes Based on Alkylated Diazaoxa- and TriazacyclononaneEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2008David Domķnguez-Gutiérrez Abstract It is known that including a metal into a micellar solution enhances both the colour and catalytic potential of such systems. This fact is well exemplified by the broad use of surfactant species as phase-transfer catalysts. In the present work, we report our studies concerning the aggregation properties of a series of iron and nickel-based triazacyclononane metalloamphiphiles. Upon multiple alkylation of the triazamacrocycle, we were able to obtain amphiphilic complexes that aggregate in toluene. We characterised the sizes and shapes of the aggregates by dynamic light scattering while their nature was assessed by atomic force microscopy.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Using Chiral Ligand Substituents To Promote the Formation of Dinuclear, Double-Stranded Iron, Manganese, and Zinc MesocatesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 33 2007Stuart D. Reid Abstract The synthesis and structures of dinuclear manganese, iron, and zinc complexes of chiral di-iminodipyrromethane ligands (L) are reported. Schiff base condensation reactions between 5,5,-diformyl-2,2,-dipyrromethane and the chiral amines (,)-(R)-CH(Me)tBu and (+)-(R)-CH(Me)Ph result in the straightforward synthesis of the new, chiral ligands H2L2 and H2L3, respectively. Salt elimination reactions between K2L and divalent Mn and Fe halides, and protonolysis reactions between ZnMe2 and H2L result in the formation of the new dinuclear complexes [M2(L)2]. Investigation of the structures of these compounds in solution and in the solid state reveal that chiral mesocates are formed for L = L2, whereas for L = L3, a racemic mixture of helicates is present.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Coordination Chemistry of 3-Mercapto-2-(mercaptomethyl)propanoic Acid (Dihydroasparagusic Acid) with Iron and NickelEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2006Phillip I. Volkers Abstract The first transition-metal complexes bearing the natural product dihydroasparagusic acid, (HSCH2)2CHCO2H, as a ligand are reported. Various coordination modes and nuclearities are demonstrated for the chelating ligand by a series of iron and nickel complexes. Fe2[(SCH2)2CHCO2H](CO)6 retains carbonyl substitution reactivity typical of Fe2(SR)2(CO)6 complexes, yet carboxy coordination to FeI was unobserved. Coupling of the carboxylic acid with amines yields the corresponding amides Fe2[(SCH2)2CHC(O)NHR](CO)6 (R = Et, gly,O,tBu). Fe2[(SCH2)2CHCO2H](CO)4(PMe3)2 catalyzes H2 production, but no better than unfunctionalized alkyl dithiolate analogs. Reactions of the ligand with NiCl2(dppe) afforded mono-, di-, and trinuclear complexes. Noteworthy is Ni3[(SCH2)2CHCO2]2(dppe)2, which features an octahedrally coordinated NiII center linked to a pair of square-planar NiII centers. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Mössbauer Investigation of Peroxo Species in the Iron(III),EDTA,H2O2 SystemEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 21 2005Virender K. Sharma Abstract The reaction of a diiron(III),EDTA complex with H2O2 in alkaline medium is studied by Mössbauer spectroscopy in conjunction with the rapid-freeze/quench technique in order to identify possible intermediate species during the formation and decomposition of the purple (EDTA)FeIII(,2 -O2)3, complex ion. Starting from the six-coordinate [FeIIIEDTA], species at acidic pH, it is demonstrated that mononuclear complexes formed at a pH of about 1 are convert into the diiron(III),EDTA complex [(EDTA)FeIII -O-FeIII(EDTA)]4, upon raising the pH to around 10.4. H2O2 reacts with the diiron(III) complex to give peroxide/hydroperoxide related adducts. Initially, the reaction tears apart the dimers to form a peroxo adduct, namely the seven-coordinate mononuclear [(EDTA)FeIII(,2 -O2)]3,, which is stable only at very high pH. The decomposition of this peroxo adduct gives two new species, which are reported for the first time. The Mössbauer parameters of these species suggest a six-coordinate ,-peroxodiiron(III) complex [(EDTA)FeIII -(OO)-FeIII(EDTA)]4, and a seven-coordinate ,-hydroxo-,-peroxodiiron(III) complex [(EDTA)FeIII -(OO)(OH)-FeIII(EDTA)]5,. A badly resolved, extremely broad component is observed in the Mössbauer spectra during the conversion of the monomer to dimeric peroxo species, which may be attributed to the short-lived [(EDTA)FeIII -OO]3, or [(EDTA)FeIII -OOH]2, intermediate species. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Incorporation of Aluminium and Iron into the Zeolite MCM-58EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2005Gabriela Ko Abstract The hydrothermal synthesis of zeolite MCM-58 is investigated with N -benzylquinuclidinium bromide as a structure-directing agent in order to isomorphously substitute aluminium or iron for silicon. Al-MCM-58 was synthesised in a wide range of nSi/nAl ratios (from 19 to 56), and Fe-MCM-58 was successfully prepared in a narrower range of nSi/nFe ratios (from 18 to 36). The obtained products were characterised by XRD, SEM, 27Al MAS NMR, 29Si MAS NMR, FTIR, and ESR spectroscopy. Two different calcination procedures, viz. in a stream of nitrogen and air or in a stream of ammonia, were used in order to modify the acid sites in the zeolite. FTIR spectroscopy before and after the adsorption of [D3]acetonitrile and pyridine was employed to determine the concentration and type of the acid sites. The acid forms of Al(Fe)-MCM-58 are characterised by the vibrations of bridging Si,OH,Al(Fe) groups at 3628 cm,1 and 3564 cm,1 (Al-MCM-58) or 3646 cm,1 and 3520 cm,1 (Fe-MCM-58). The acid sites of both zeolites Al-MCM-58 and Fe-MCM-58 are accessible for [D3]acetonitrile and pyridine, and all materials contain substantial numbers of Lewis sites (Al-MCM-58: 50,% of the total acid sites; Fe-MCM-58: 90,%) over the whole range of nSi/nAl (nSi/nFe) ratios studied. Only a small increase in the concentration of Brųnsted acid sites was achieved after calcination of the as-synthesised samples in a flow of ammonia. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Iron(III) Chelation: Tuning of the pH Dependence by Mixed LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2003Anne-Marie Albrecht-Gary Abstract The iron(III) chelating properties of two heteropodands with 8-hydroxyquinoline and catechol binding groups were examined and compared to those of the corresponding homopodal analogues, O-TRENSOX and TRENCAMS. Like the parent homopodands, the two heteropodands are based on the TREN scaffold and the chelating units are connected by amide groups, TRENSOX2CAMS having two 8-hydroxyquinoline and one catechol arms and TRENSOXCAMS2 one 8-hydroxyquinoline and two catechol moieties. The aqueous coordination chemistry of these ligands was examined by potentiometric and spectrophotometric methods in combination with 1H NMR spectroscopy. The respective pFeIII values showed a cooperative effect of the mixed chelating units. Moreover, the pFeIII dependence on pH showed that the mixed ligands exhibit a higher complexing ability than the parent ligands over the pH range 5,9 which is of biological relevance. This result could be of great interest for medical applications. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Magnetic, 57Fe Mössbauer, and IR Monitoring of the Thermal Spin Transition in a New Family of Iron(II) Spin-Transition ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2003Arno F. Stassen Abstract A new family of iron(II) tetrafluoroborate and perchlorate spin-crossover compounds has been synthesised and is discussed. The iron(II) ion is surrounded by six 1-ethyltetrazole ligands, which are halogen-substituted on the C2 atom of the ethyl group. The spin-crossover temperatures T1/2 are high compared to the unsubstituted (1-alkyltetrazole)iron(II) complexes. The shape of the spin-transition curve (i.e. ,HS vs. T) varies largely over the different complexes and appears to be influenced neither by the crystal packing, nor by the electronic effects. The temperature-dependent spin-transition behaviour has been studied by magnetic susceptibility and by 57Fe-Mössbauer spectroscopy. These data have been supported by temperature-dependent mid-range infrared spectroscopy: the thermally induced spin transition has been observed by direct monitoring of the aromatic C,H stretching frequency. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Broadening the Synthetic Scope of the Iron(III)-Catalyzed Aza-Prins CyclizationEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 12 2010Rubén M. Carballo Abstract The nature and influence of the N -sulfonyl group in aza-Prins cyclization and the reactivity of the six-membered aza-cycle generated has been studied. The aza-Prins cyclization of ,,,-unsaturated amines with a tosyl group at the nitrogen atom produces 2-alkyl-4-halo-1-tosyl-1,2,5,6-tetrahydropyridines with a halovinyl function, extraordinarily stable to further derivatization and detosylation conditions. To modulate the reactivity of such aza-cycles, a general study of the aza-Prins cyclization reaction was performed with several sulfonamides. Ring formation occurs satisfactorily with both N -nosyl and N -mesylamines providing optimal conditions for further synthetic transformations. To exemplify the scope of this methodology, a short synthesis of the alkaloid coniine was successfully carried out. [source] Iron,Palladium Association in the Preparation of Indoles and One-Pot Synthesis of Bis(indolyl)methanesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 32 2007Vincent Terrasson Abstract Indoles were prepared by annulation of the parent alkynylanilines with the use of a new FeCl3,PdCl2 catalytic combination. High yields were obtained by using low loadings of the transition-metal complex (FeCl3,PdCl2: 2 and 1 mol-%, respectively). One-pot accesses to bis(indolyl)methanes and trisubstituted indoles through annulation/Friedel,Crafts alkylation and annulation/1,4-Michael addition sequences, in which FeCl3 acts both as a cooxidant and a Lewis acid are described.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Joining Strategies for Open Porous Metallic Foams on Iron and Nickel Base Materials,ADVANCED ENGINEERING MATERIALS, Issue 8 2007S. Longerich Within the Collaborative Research Centre (SFB) 561 "Thermally highly loaded, porous and cooled multilayer systems for combined cycle power plants" open porous Ni-based structures are developed for the requirements of an effusion cooling. A two-dimensional cooling strategy for the walls of combustion chambers, that allows the outflow of the cooling medium over the complete wall area of the combustion chamber, could be realized by an open porous metallic foam structure. The challenge is to join the porous foam structure with the solid substrate material. Capacitor discharge welding and laser beam welding/-brazing methods seems to be promising methods due to a minimum input of energy and, connected with this, a small joining zone. [source] Bacterial IscU is a well folded and functional single domain proteinFEBS JOURNAL, Issue 11 2004Salvatore Adinolfi Iron,sulfur clusters are widely represented in most organisms, but the mechanism of their formation is not fully understood. Of the two main proteins involved in cluster formation, NifS/IscS and NifU/IscU, only the former has been well studied from a structural point of view. Here we report an extensive structural characterization of Escherichia coli IscU. We show by a variety of physico-chemical techniques that E. coli IscU construct can be expressed to high purity as a monomeric protein, characterized by an ,, fold with high ,-helix content. The high melting temperature and the reversibility of the thermal unfolding curve (as measured by CD spectroscopy) hint at a well ordered stable fold. The excellent dispersion of cross peaks in the 1H- 15N correlation spectrum is consistent with these observations. Monomeric E. coli IscU is able to provide a scaffold for Iron,sulfur cluster assembly, but has no direct interaction with either Fe(II) or Fe(III) ions, suggesting the need of further partners to achieve a stable interaction. [source] Iron limits primary productivity during spring bloom development in the central North AtlanticGLOBAL CHANGE BIOLOGY, Issue 4 2006C. MARK MOORE Abstract We present in situ biophysical measurements and bioassay experiments that demonstrate iron limitation of primary productivity during the spring bloom in the central North Atlantic. Mass balance calculations indicate that nitrate drawdown is iron (Fe)-limited and that aeolian Fe supply to this region cannot support maximal phytoplankton growth during the bloom. Using a simple simulation model, we show that relief of Fe limitation during the spring bloom can increase nitrate drawdown and, hence, new primary production, by 70%. We conclude that the episodic nature of iron supplied by dust deposition is an important factor controlling the dynamics of the spring bloom. From this, we hypothesize that variability in the timing and magnitude of the spring bloom in response to aeolian Fe supply will affect carbon drawdown and food web dynamics in the central North Atlantic. [source] Geochemistry of Extremely Alkaline (pH > 12) Ground Water in Slag-Fill AquifersGROUND WATER, Issue 6 2005George S. Roadcap Extremely alkaline ground water has been found underneath many shuttered steel mills and slag dumps and has been an impediment to the cleanup and economic redevelopment of these sites because little is known about the geochemistry. A large number of these sites occur in the Lake Calumet region of Chicago, Illinois, where large-scale infilling of the wetlands with steel slag has created an aquifer with pH values as high as 12.8. To understand the geochemistry of the alkaline ground water system, we analyzed samples of ground water and the associated slag and weathering products from four sites. We also considered several potential remediation schemes to lower the pH and toxicity of the water. The principal cause of the alkaline conditions is the weathering of calcium silicates within the slag. The resulting ground water at most of the sites is dominated by Ca2+ and OH, in equilibrium with Ca(OH)2. Where the alkaline ground water discharges in springs, atmospheric CO2 dissolves into the water and thick layers of calcite form. Iron, manganese, and other metals in the metallic portion of the slag have corroded to form more stable low-temperature oxides and sulfides and have not accumulated in large concentrations in the ground water. Calcite precipitated at the springs is rich in a number of heavy metals, suggesting that metals can move through the system as particulate matter. Air sparging appears to be an effective remediation strategy for reducing the toxicity of discharging alkaline water. [source] | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||