The Hydrolytic Polymerization of Iron(III)

Spiro, Thomas G.; Allerton, Samuel E.; Renner, John W.; Terzis, A.; Bils, Robert; Saltman, Paul

doi:10.1021/ja00964a020

Cited by 258 publications

(88 citation statements)

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“…We have used different reaction conditions but still did not achieve pillaring. The difference in behaviour between hydroxy-Fe polycations and hydroxy-A1 polycations may well be related to their different morphologies as A1 polycations form sheets, whereas Fe polycations form discrete spheres (Spiro et al, 1966;Oades, 1984). The result from experiment 3 suggests that the presence of Fe 3+ ions in some way destabilizes the Keggin structure and no PILC is formed.…”

Section: Discussionmentioning

confidence: 94%

Preparation and characterization of iron oxide pillared montmorillonite

et al. 1988

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A B S T RA C T : Pillared smectites in which the pillars consist of iron oxide are expected to have interesting and unusual magnetic properties. Several possible routes by which such materials might be made have been investigated, namely intercalation of hydroxy-Fe(III) polycations, mixed hydroxy-Fe(III)/Al polycations, phenanthroline-Fe(II) cations, and trinuclear Fe(III) acetato cations into Na-montmorillonite. Only the last of these yielded a pillared clay (PILC) on calcination. The products have been characterized using X-ray powder diffraction and 57Fe M6ssbauer spectroscopy. The precursor Fe-PILC has a d-spacing of 21 A and expands to 23 A on solvation with glycol. The calcined Fe-PILC has a d-spacing of 19 A (gallery height 9.4 A) and does not expand with glycol, confirming cross-linking of the layers. From M6ssbauer spectra at 4.2 K it is estimated that there are of the order of some hundred Fe atoms per pillar.Pillared or cross-linked smectites, in which the interlayer is converted into a two dimensional zeolite-like structure, have recently attracted much interest because of their catalytic and molecular sieving properties (Pinnavaia, 1983;Barrer, 1986). The best understood pillared clays (PILCs) are those in which Al oxide pillars act as molecular-sized props permanently separating the silicate layers of the clay, and the structure of these materials has been investigated using 27A1 and 29Si solid state MAS NMR (Tennakoon et al., 1986;Plee et al., 1985Plee et al., , 1987. If, however, the pillars are formed of Fe oxide instead of A1 oxide, interesting and novel magnetic properties may be expected (Gangas et al., 1985) and M6ssbauer spectroscopy can be utilized to obtain structural information.Metal oxide pillared clays are normally the product of a two step process. The first step is one of cation exchange in which the simple interlayer cation of a smectite (usually Na +) is replaced by a large complex cation. The second step consists of a heat treatment which crosslinks the silicate layers. In this paper, the terms precursor-PILC and calcined-PILC are used in order to make a clear distinction between the products obtained after each step.The complex cation which is used in the preparation of A1-PILCs is the Keggin-like ion [AllaO4(OH)24(H20)12] 7+ (Baes & Mesmer, 1976). In this study we have investigated the PILC-forming potential of a number of large Fe cations which can occupy the exchange sites in smectite interlayers. These are hydroxy-Fe(III) polycations, mixed hydroxy-Fe(III)/Al cations, phenanthroline-Fe(II) complexes and trinuclear Fe(III) carboxylate complexes. CHARACTERISTICS OF METAL OXIDE PILLARED CLAYSIntercalation of complex cations into a smectite followed by heat treatment may, or may not, result in the formation of a PILC. The following three criteria have been used to identify 9 1988 The Mineralogical Society

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Section: Discussionmentioning

confidence: 94%

Preparation and characterization of iron oxide pillared montmorillonite

et al. 1988

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“…Heald et al (1979) used the extended X-ray absorption fine structure (EXAFS) technique to assess the coordination of iron in ferritin and in hydrolyzed Fe 3+ polymers. They distinguished two varieties of polymer: a soluble, spherical polymer (type A) identical with that described by Spiro et al (1966) and an insoluble polymer (type B). Their results indicate that the coordination number of iron in the soluble spherical polymer is 3.6, and in the insoluble polymer, 5.4.…”

Section: Review Of Previous Workmentioning

confidence: 99%

New Data and a Revised Structural Model for Ferrihydrite

Eggleton

Fitzpatrick

1988

Clays and clay miner.

293

208

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Abstract--Synthetic 2-line and 6-line ferrihydrite samples prepared from ferric nitrate solutions have the bulk compositions Fe4(O,OH,H20)12 and Fe4.6(O,OH,H20)lZ, respectively. The composition depends on crystal size, which averages 20/~ for 2-line and 35/k for 6-line ferrihydrite. X-ray absorption edge spectra indicate the presence of tetrahedral Fe 3+, a conclusion supported by heating experiments which show the development of maghemite after heating to 300~ in the presence of N2, followed by the formation of hematite at higher temperatures. These two reactions are recorded on differential thermal analysis traces by exotherms at 350 ~ and 450~ Transmission electron microscopy shows that 2-line ferrihydrite has no Z-axis regularity but does show hexagonal 2.54-/~ lattice fringes. Six-line ferrihydrite forms faceted crystals having 9.4-/~ c-parameter only detectable in dark field. In bright field, 2.54-/~ lattice fringes indicate greater atomic regularity than in 2-line ferrihydrite. Analysis of the X-ray powder diffraction pattern of 6-line ferrihydrite suggests a structure based on double-hexagonal close-packed oxygens, containing 36% Fe in tetrahedral sites. Selective chemical dissolution, surface area measurements, and magnetic susceptibility are consistent with the recorded properties of ferrihydrite.

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“…Although iron is the fourth-most-abundant element on earth, at neutral-to-alkaline pH and in the presence of oxygen, iron spontaneously assembles into ferric oxyhydroxide complexes (44). The solubility of these ferric polymers in water is extremely low, and therefore this nutrient is not readily bioavailable.…”

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confidence: 99%

Analysis of Achromobactin Biosynthesis byPseudomonas syringaepv. syringae B728a

Berti

Thomas

2009

J Bacteriol

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Pseudomonas syringae pv. syringae B728a is known to produce the siderophore pyoverdine under iron-limited conditions. It has also been proposed that this pathovar has the ability to produce a second siderophore, achromobactin. Here we present genetic and biochemical evidence supporting the hypothesis that P. syringae pv. syringae B728a produces both of these siderophores. We show that strains unable to synthesize either pyoverdine or achromobactin are unable to grow under iron-limiting conditions, which is consistent with these two molecules being the only siderophores synthesized by P. syringae pv. syringae B728a. Enzymes associated with achromobactin biosynthesis were purified and analyzed for substrate recognition. We showed that AcsD, AcsA, and AcsC together are able to condense citrate, ethanolamine, 2,4-diaminobutyrate, and ␣-ketoglutarate into achromobactin. Replacement of ethanolamine with ethylene diamine or 1,3-diaminopropane in these reactions resulted in the formation of achromobactin analogs that were biologically active. This work provides insights into the biosynthetic steps in the formation of achromobactin and is the first in vitro reconstitution of achromobactin biosynthesis.

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The Hydrolytic Polymerization of Iron(III)

Cited by 258 publications

References 0 publications

Preparation and characterization of iron oxide pillared montmorillonite

Preparation and characterization of iron oxide pillared montmorillonite

New Data and a Revised Structural Model for Ferrihydrite

Analysis of Achromobactin Biosynthesis byPseudomonas syringaepv. syringae B728a

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