References of "Grandjean, Fernande"
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See detailSynthesis, Magnetism, and 57Fe Mössbauer Spectroscopic Study of a Family of [Ln3Fe7] Coordination Clusters (Ln = Gd, Tb, and Er),”
Abbas, Ghulam; Lan, Yanhua; Mereacre, Valeriu et al

in Inorganic Chemistry (2013), 52

The reaction of N-methydiethanolamine (mdeaH2), benzoic acid, FeCl3, and Ln(NO3)3·6H2O or LnCl3·xH2O yields a series of decanuclear coordination clusters, [Ln3Fe7(μ4-O)2(μ3OH)2(mdea)7(μ-benzoate)4(N3)6 ... [more ▼]

The reaction of N-methydiethanolamine (mdeaH2), benzoic acid, FeCl3, and Ln(NO3)3·6H2O or LnCl3·xH2O yields a series of decanuclear coordination clusters, [Ln3Fe7(μ4-O)2(μ3OH)2(mdea)7(μ-benzoate)4(N3)6]·4MeCN·H2O, where Ln = Gd III (1)orTb III (2), and [Er 3Fe7(μ4-O)2(μ3-OH)2(mdea)7(μbenzoate)4(N3)5(MeOH)]Cl·7.5H2O·11.5MeOH (3). The isostructural compounds 1−3 all crystallize isotypically in the triclinic space group P1̅ with Z = 2, as does the previously reported dysprosium analogue 4. Six of the Fe III ions are pseudooctahedrally coordinated, whereas the seventh has a trigonal-bipyramidal coordination geometry. Temperature-dependent direct-current magnetic susceptibility studies indicate that intracluster antiferromagnetic interactions are dominant in 1−3. The frequency-dependent out-of-phase (χ′′) alternating-current susceptibility reveals that 2 undergoes a slow relaxation of its magnetization, presumably resulting from anisotropy of the Tb III ions. Between 30 and 295 K, the 57Fe Mö ssbauer spectra reveal paramagnetic behavior with six partially resolved quadrupole doublets, one for the trigonal-bipyramidal Fe III site and five for the six pseudooctahedral Fe III sites. The Mö ssbauer spectra of 2 and 3 obtained between 3 and 30 K are consistent with the presence of Fe III intracluster antiferromagnetic coupling with slow magnetic relaxation relative to the Larmor precession time. Further, the observed changes in the effective magnetic field values in the spectra measured at 3 K with increasing applied field are consistent with the effect of the local spin polarization along the applied magnetic field direction, a behavior reminiscent of antiparallel spin-coupled iron molecular paramagnetic systems. [less ▲]

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See detailSodium-Centered Dodecanuclear Co(II) and Ni(II) Complexes with 2‐(Phosphonomethylamino)succinic Acid: Studies of Spectroscopic, Structural, and Magnetic Properties
Gudima, Andryi; Shovkova, Ganna; Trunova, Olena et al

in Inorganic Chemistry (2013), 52

ABSTRACT: Two new isostructural cobalt(II) and nickel(II) polynuclear complexes with 2-(phosphonomethyl)aminosuccinic acid, H4PMAS, namely, N a [ C o 1 2 ( P M A S ) 6 ( H 2 O ) 1 7 ( O H ) ] · x 2 H 2 O ... [more ▼]

ABSTRACT: Two new isostructural cobalt(II) and nickel(II) polynuclear complexes with 2-(phosphonomethyl)aminosuccinic acid, H4PMAS, namely, N a [ C o 1 2 ( P M A S ) 6 ( H 2 O ) 1 7 ( O H ) ] · x 2 H 2 O , 1 · x 2 H 2 O , a n d N a - [Ni12(PMAS)6(H2O)17(OH)]·xH2O, 2·xH2O, have been synthesized for the fi rst time from aqueous solutions and studied by single crystal X-ray diffraction, infrared, and UV−visible diffuse reflectance spectroscopy; TG/DTA analysis; and magnetochemistry. Both 1 and 2 crystallize in the rhombohedral crystal system with the R3̅space group with 1/6 of the Co12(PMAS)6 or Ni12(PMAS)6 moieties in the asymmetric unit. The X-ray refinements reveal the presence of 18 water sites, but unit cell charge balance requires that one water molecule must be an OH− anion, an anion which is disordered over the 18 sites. The PMAS4− ligand forms two five-membered and one six-membered chelation ring. Both 1 and 2 contain 24-membered metallacycles as a result of the bridging nature of the PMAS4− ligands. The resulting three-dimensional structures have one-dimen- sional channels with a sodium cation at the center of symmetry. The temperature dependence of the magnetic susceptibility reveals the presence of weak antiferromagnetic exchange coupling interactions in both 1 and 2. Two exchange coupling constants, J1 = −15.3(7) cm−1 and J2 = −1.06(2) cm−1 with S1 = S2 = 3/2 for the Co(1)···Co(1) and Co(1)···Co(2) exchange pathways, respectively, are required for 1, and J1 = −1.17(6) cm−1 and J2 = −4.00(8) cm−1 with S1 = S2 = 1 for the Ni(1)···Ni(1) and Ni(1)···Ni(2) exchange pathways, respectively, are required for 2, in order to fit the temperature dependence of the observed magnetic susceptibilities. [less ▲]

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See detailRelationship between the Synthesis of Prussian Blue Pigments, Their Color, Physical Properties, and Their Behavior in Paint Layers
Samain, Louise ULg; Grandjean, Fernande ULg; Long, Gary J. et al

in Journal of Physical Chemistry C (2013), 117(19), 96939712

Prussian blue pigments, highly insoluble mixed-valence iron(III) hexacyanoferrate(II) complexes of typical stoichiometry Fe4III[FeII(CN)6]3·xH2O or KFeIII[FeII(CN)6]·xH2O, have been used as pigments in ... [more ▼]

Prussian blue pigments, highly insoluble mixed-valence iron(III) hexacyanoferrate(II) complexes of typical stoichiometry Fe4III[FeII(CN)6]3·xH2O or KFeIII[FeII(CN)6]·xH2O, have been used as pigments in oil paintings and watercolors for 300 years. For poorly understood reasons, these pigments often fade with time. Although the preparation methods have been recognized since the mid-eighteenth century as a contributory factor in the fading of the pigment, the spectral and physical properties of Prussian blue that vary with the type of synthesis were not precisely identified. Several Prussian blue pigments have been prepared by different methods and characterized by thermogravimetric analyses, high-energy powder X-ray diffraction, atomic absorption and flame emission, UV–visible, iron-57 Mössbauer, iron K-edge X-ray absorption, and Raman spectroscopy. The type of synthesis influences the hue, tinting strength, and hiding power properties of the Prussian blue pigments. Two major features appear to be strongly dependent on the preparative methods, the particle size and the local disorder. Both a nitrogen atmosphere and an intermediate aging step of the Berlin white, Fe2II[FeII(CN)6], during the synthesis are required to obtain a highly colored pigment through the optimization of particle size, minimization in the perturbations to the FeII–CN–FeIII intervalence electron transfer pathway, and the minimization of disordered vacancies. The potassium containing Prussian blue structure has been revisited. It can be described with the Pm3m space group, where approximately one-quarter of the [FeII(CN)6]4– sites are vacant and where the potassium cation is located at a zeolitic-like position inside the lattice cavities. The degree of ordering of the [FeII(CN)6]4– vacancies in all Prussian blues was quantified using atomic pair distribution analysis, an ordering that is consistent with the iron K-edge X-ray absorption spectra. The presence of strain in the crystals is observed by both powder X-ray diffraction and Mössbauer spectroscopy. The structural similarity between the alkali-free, improperly referred to as “insoluble”, and the alkali containing, “soluble”, Prussian blues may explain why the two varieties are almost undistinguishable by spectroscopic techniques. [less ▲]

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See detailRedox reactions in Prussian blue containing paint layers as a result of light exposure
Samain, Louise ULg; Gilbert, Bernard ULg; Grandjean, Fernande ULg et al

in Journal of Analytical Atomic Spectrometry [=JAAS] (2013)

Prussian blue, a mixed valence pigment, typically KFeIII[FeII(CN)6].xH2O, was the most widely used blue artistic pigment from ca. 1720 to the 1970's but, unfortunately, its paint layers, especially when ... [more ▼]

Prussian blue, a mixed valence pigment, typically KFeIII[FeII(CN)6].xH2O, was the most widely used blue artistic pigment from ca. 1720 to the 1970's but, unfortunately, its paint layers, especially when used in conjunction with a white pigment, tend to fade or turn green upon extended exposure to light. In order to identify the mechanism underlying these changes, paint layers have been prepared with differing amounts of these white pigments and subjected to accelerated light exposure fading. The resulting unfaded and faded paint layers as well as both the Berlin white pigment, Fe2II[FeII(CN)6], and the partially oxidized Berlin green pigment, {KFeIII[FeII(CN)6]}x{FeIII[FeIII(CN)6]}1–x, have been characterized by Raman and iron-57 Mössbauer spectroscopy. The results indicate that, upon fading, the Prussian blue pigment painted with a linseed oil binder and (PbCO3)2Pb(OH)2 or ZnO, and to a lesser extent with TiO2, undergoes a reduction at the exposed paint surface and an oxidation in the bulk of the paint layer. This combined reduction and oxidation disrupts, at least in part, the FeIII–N–C–FeII intervalent electron transfer pathways in Prussian blue thus leading to pigment fading through a reduction in the intervalent electron transfer absorbance at about 700 nm. [less ▲]

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See detailThe Pivotal Role of Mössbauer Spectroscopy in the Characterization of Prussian Blue and Related Iron Cyanide Complexes
Grandjean, Fernande ULg; Long, Gary J; Samain, Louise ULg

in Mössbauer Effect Reference and Data Journal (2012)

For 50 years, 57Fe Mössbauer spectroscopy has played a pivotal role in the characterization of Prussian blue complexes and many related iron cyanide complexes, a pivotal role that is extensively ... [more ▼]

For 50 years, 57Fe Mössbauer spectroscopy has played a pivotal role in the characterization of Prussian blue complexes and many related iron cyanide complexes, a pivotal role that is extensively illustrated in this paper. For the benefit of the young Mössbauer spectroscopists, the successes, the failures, and the pitfalls reported in the literature are discussed. The successes include the unquestionable distinction of iron oxidation and spin states in Prussian blue and the determination that Prussian blue and Turnbull's blue are the same. The failures include the distinction between low-spin FeII and high-spin FeIIIcations in Berlin green. The pitfalls include many, sometimes poorly determined, hyperfine parameters that have been reported for complexes whose stoichiometry is either unknown or unspecified and even sometimes incorrect. [less ▲]

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See detailStructural Chemistry and Spin-glass Behaviour of Nd18Li8Fe4TiO39
Thammajak, N; Battle, Peter D.; Grandjean, Fernande ULg et al

in Journal of Solid State Chemistry (2012), 187

Nd18Li8Fe4TiO39 has been synthesised and characterised by neutron powder diffraction, X-ray absorption spectroscopy, Mossbauer spectroscopy and magnetometry. The cubic structure (Pm3 n, a=411.97227(8) Å ... [more ▼]

Nd18Li8Fe4TiO39 has been synthesised and characterised by neutron powder diffraction, X-ray absorption spectroscopy, Mossbauer spectroscopy and magnetometry. The cubic structure (Pm3 n, a=411.97227(8) Å) is based on intersecting <1 1 1> chains comprised of alternating octahedral and trigonal-prismatic coordination sites. These chains lie within hexagonal-prismatic cavities formed by a Nd–O framework. The larger of the two crystallographically distinct octahedral sites, 8e, is occupied by iron, titanium and lithium in a ratio of 76:20:4; the smaller, 2a, is occupied by iron and titanium in a ratio of 79:21. The trigonal-prismatic site, 16i, is occupied by lithium and iron in a ratio of 98:2. The cations on the 2a sites are assigned as Ti4+and low-spin Fe4+, and those on the 16i sites as Li+ and Fe3+. The 8e sites are thought to be occupied by Li+, Fe3+ and Ti3+. Nd18Li8Fe4TiO39 undergoes a transition to a spin-glass state at 4.25(5) K. [less ▲]

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See detailMagnetic Properties of Fe2GeMo3N; an Experimental and Computational Study
Battle, Peter; Sviridov, L.A.; Woolley, R. J. et al

in Journal of Materials Chemistry (2012), 22

A polycrystalline sample of Fe2GeMo3N has been synthesized by the reductive nitridation of a mixture of binary oxides in a flow of 10% dihydrogen in dinitrogen. The reaction product has been studied by ... [more ▼]

A polycrystalline sample of Fe2GeMo3N has been synthesized by the reductive nitridation of a mixture of binary oxides in a flow of 10% dihydrogen in dinitrogen. The reaction product has been studied by magnetometry, neutron diffraction and M€ossbauer spectroscopy over the temperature range 1.8 # T/K # 700. The electronic properties have been modelled by DFT and Monte Carlo methods. Fe2GeMo3N adopts the cubic h-carbide structure with a ¼ 11.1630(1) at 300 K. The electrical conductivity was found to be 0.9 mU cm over the temperature range 80 # T/K # 300. On cooling below 455 K the compound undergoes a transition to an antiferromagnetic state. The magnetic unit cell contains an antiferromagnetic arrangement of eight ferromagnetic Fe4 tetrahedra; the ordered atomic magnetic moments, 1.90(4) mB per Fe atom at 1.8 K, align along a <111> direction. DFT predicts an ordered moment of 1.831 mB per Fe, albeit with a N eel temperature of >549 K. Monte Carlo calculations confirm that the experimentally determined magnetic structure is the lowest-energy antiferromagnetic structure. These results emphasise the potential of these computational methods in the search for new magnetic materials. [less ▲]

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See detailPyrazolyl methyls prescribe the electronic properties of iron(II) tetra(pyrazolyl)lutidine chloride complexes
Morin, Tyler J; Wanniarachchi, Sarath; Gwengo, Chengeto et al

in Journal of the Chemical Society. Dalton Transactions (2011), 40

A series of iron(II) chloride complexes of pentadentate ligands related to α,α,α’,α’-tetra(pyrazolyl)-2,6-lutidine, pz4lut, has been prepared to evaluate whether pyrazolyl substitution has any systematic ... [more ▼]

A series of iron(II) chloride complexes of pentadentate ligands related to α,α,α’,α’-tetra(pyrazolyl)-2,6-lutidine, pz4lut, has been prepared to evaluate whether pyrazolyl substitution has any systematic impact on the electronic properties of the complexes. For this purpose, the new tetrakis(3,4,5-trimethylpyrazolyl)lutidine ligand, pz**4lut, was prepared via a CoCl2-catalyzed rearrangement reaction. The equimolar combination of ligand and FeCl2 in methanol gives the appropriate 1:1 complexes [FeCl(pzR4lut)]Cl that are each isolated in the solid state as a hygroscopic solvate. In solution, the iron(II) complexes have been fully characterized by several spectroscopic methods and cyclic voltammetry. In the solid state, the complexes have been characterized by X-ray diffraction, magnetic measurements and, in some cases, by Mössbauer spectroscopy. The Mössbauer studies show that the complexes remain high spin to 4 K and exclude spin-state changes as the cause of the surprising solid-state thermochromic properties of the complexes. Counterintuitive results of spectroscopic and structural studies showed that methyl substitution at the 3- and 5- positions of the pyrazolyl rings reduces the ligand field strength through steric effects whereas methyl substitution at the 4-position of the pyrazolyl rings increases the ligand field strength through inductive effects. [less ▲]

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See detailSlow Magnetic Relaxation and Electron Delocalization in an S = 9/2 Iron(II/III) Complex Featuring Two Crystallographically Inequivalent Iron Sites
Hazra, Susanta; Sasmal, Sujit; Fleck, Michel et al

in Journal of Chemical Physics (2011), 134

The magnetic, electronic and Mössbauer spectral properties of [Fe2L(μ-OAc)2]ClO4, 1, where L is the dianion of the tetraimino-diphenolate macrocyclic ligand, H2L, indicate that 1 is a class III mixed ... [more ▼]

The magnetic, electronic and Mössbauer spectral properties of [Fe2L(μ-OAc)2]ClO4, 1, where L is the dianion of the tetraimino-diphenolate macrocyclic ligand, H2L, indicate that 1 is a class III mixed valence iron(II/III) complex with an electron that is fully delocalized between two crystallographically inequivalent iron sites to yield a [Fe2]V cationic configuration with a St = 9/2 ground state. Fits of the dc magnetic susceptibility between 2 and 300 K and of the isofield variable-temperature magnetization of 1 yield an isotropic magnetic exchange parameter, J, of –32(2) cm–1 for an electron transfer parameter, B, of 950 cm–1, a zero-field uniaxial D9/2 parameter of –0.9(1) cm–1, and g = 1.95(5). In agreement with the presence of uniaxial magnetic anisotropy, ac susceptibility measurements reveal that 1 is a single-molecule magnet at low temperature with a single molecule magnetic effective relaxation barrier, Ueff, of 9.8 cm–1. At 5.25 K the Mössbauer spectra of 1 exhibit two spectral components, assigned to the two crystallographically inequivalent iron sites with a static effective hyperfine field; as the temperature increases from 7 to 310 K the spectra exhibit increasingly rapid relaxation of the hyperfine field on the iron-57 Larmor precession time of 5 × 10–8 s. A fit of the temperature dependence of the average effective hyperfine field yields |D9/2| = 0.9 cm–1. An Arrhenius plot of the logarithm of the relaxation frequency between 5 and 85 K yields a relaxation barrier of 17 cm–1. [less ▲]

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See detailCaractérisation et vieillissement accéléré de pigments de bleu de Prusse synthétisés selon les méthodes de préparation anciennes et modernes
Samain, Louise ULg; Lauricella, Melina; Silversmit, Geert et al

Conference (2011, April 11)

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See detailA Seven-Coordinate Iron Platform and its Oxo and Nitrene Reactivity
Soo, Han Sen; Sougrati, Moulay T; Grandjean, Fernande ULg et al

in Inorganica Chimica Acta (2011), 369

We present a new structurally determined seven-coordinate iron platform supported by the tris(2picolyl)amine ligand 6,60 -(pyridin-2-ylmethylazanediyl)bis(methylene)bis(N-tert-butylpicolinamide) (TPA 2C(O ... [more ▼]

We present a new structurally determined seven-coordinate iron platform supported by the tris(2picolyl)amine ligand 6,60 -(pyridin-2-ylmethylazanediyl)bis(methylene)bis(N-tert-butylpicolinamide) (TPA 2C(O)NHtBu, 3) and its reactivity with oxo and nitrene transfer agents. Oxidation of the pentagonal bipyramidal, seven-coordinate iron(II)–triflate complex [TPA 2C(O)NHtBuFeII(OTf)][OTf] (4) with PhIO produces the corresponding diiron(III) l-oxo complex [(TPA 2C(O)NHtBuFeIII) 2(O)][OTf]4 (5). Mossbauer and magnetic measurements on 5 in the solid-state establish antiferromagnetic coupling between its two Fe(III) centers. Reactions of 4 with the nitrene transfer agents PhINTs (Ts = p-MeC6H4SO2) and PhINNs (Ns = p-NO2C6H4SO2) provide the corresponding iron(III)-amide congeners [TPA 2C(O)NHtBuFeIII(NHTs)][OTf]2 (6) and [TPA 2C(O)NHtBuFeIII(NHNs)][OTf] 2 (7), respectively, affording a rare pair of isolable Fe(III)-amide compounds formed from nitrene transfer. By characterizing well-defined products in the crystalline form, derived from atom and group transfer to seven-coordinate iron, the collective data provide a starting point for the exploration of high-valent and metal–ligand multiply bonded species supported by approximate pentagonal-type ligand fields. [less ▲]

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See detailHomochiral, Helical Supramolecular Metal-Organic Frameworks Organized by Strong π···π Stacking Interactions: Single-Crystal to Single-Crystal Transformations in Closely Packed Solids
Reger, Daniel L; Horger, Jacob J; Smith, Mark D et al

in Inorganic Chemistry (2011), 50

Enantiopure, trifunctional carboxylate ligands synthesized by linking the strong π3 3 3 π stacking 1,8-naphthalimide supramolecular synthon to three naturally occurring amino acids using the azide/alkyne ... [more ▼]

Enantiopure, trifunctional carboxylate ligands synthesized by linking the strong π3 3 3 π stacking 1,8-naphthalimide supramolecular synthon to three naturally occurring amino acids using the azide/alkyne click reaction have been prepared [amino acid = glycine (Lgly -), alanine (Lala -), and serine (Lser -)]. These ligands have been used to form complexes of the formula [M(Lamino acid)2(4,40-bipy)(H2O)2] 3 xH2O (M = Fe, Co,Ni, Cu, Zn; x = 4.25-5.52) when mixed with an appropriate metal salt and 4,40-bipyridine by layeringmethods. These complexes are isostructural, with the centralmetal atomcoordinated to two κ1-carboxylate ligands, two water molecules, and one end each of two 4,40-bipyridine ligands in a distorted octahedral environment. Each ligand is oriented in a trans arrangement. These complexes all have homochiral, helical, supramolecular, three-dimensional metal-organic framework structures, with the helical organization of the individual metallic units held together solely by strong, noncovalent π3 3 3 π stacking interactions of the naphthalimide; the other two dimensions are organized mainly by the bipyridine ligands. The helices are extremely large; one turn of the helix travels ∼60 and has a diameter of ca. 40 . For the achiral ligand Lgly -, the nickel complex forms two types of homochiral crystals in the same tube, a clear example of spontaneous resolution. Despite the large size of the individual helices, they are tightly interconnected and nestled closely together. Part of the interconnection comes from the interstitial watermolecules held inside the framework of the complexes in isolated pockets by hydrogen-bonding interactions. For both [Cu(Lala)2(4,40-bipy)(H2O)2] 3 4.25H2O and [Co(Lser)2(4,40-bipy)(H2O)2] 3 4.68H2O, the interstitial water molecules can be removed by placing the crystals under a vacuum for several hours, a process that can be reversed by exposure to atmospheric moisture. This removal/reintroduction of the interstitial water molecules takes place with no loss of crystallinity, representing dramatic examples of single-crystal to single-crystal transformations. The structures undergo little change other than the pockets holding the interstitial water molecules in the hydrated complexes become void spaces in the dehydrated complexes. The removal/reintroduction of the watermolecules in these closely packed solids is facilitated by the “soft”π3 3 3 πstacking interactions organizing one dimension of the structures. The observed magnetic and M€o ssbauer spectral properties are typical of isolated, magnetically dilute, paramagnetic pseudooctahedral divalent transition-metal complexes. [less ▲]

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See detailStructural and magnetic properties of Nd 18Li 8Co 4-xFe xO 39-y and Nd 18Li 8Co 4-xTi xO 39-y
Battle, Peter; Dutton, Sean E; Grandjean, Fernande ULg et al

in Journal of Solid State Chemistry (2011), 84

Nd18Li8Co3FeO39–y, Nd18Li8CoFe3O39–y and Nd18Li8Co3TiO39 39–y have been synthesisd and characterised by neutron powder diffraction, magnetometry and Mossbauer spectroscopy. Their cubic structure (Pm–3n, a ... [more ▼]

Nd18Li8Co3FeO39–y, Nd18Li8CoFe3O39–y and Nd18Li8Co3TiO39 39–y have been synthesisd and characterised by neutron powder diffraction, magnetometry and Mossbauer spectroscopy. Their cubic structure (Pm–3n, a~11.9 Å) is based on intersecting <1 1 1 > chains comprised of alternating octahedral and trigonal-prismatic coordination sites. These chains lie within hexagonal-prismatic cavities formed by a Nd–O framework. Each compound has an incomplete oxide sublattice (y~1), with vacancies located around the octahedral sites that lie at the points of chain intersection. These sites are fully occupied by a disordered arrangement of transition-metal ion-cations but only 75% of the remaining octahedral sites are occupied. The trigonal-prismatic sites are fully occupied by lithium except in the case of Nd18Li8CoFe3O39–y where some iron is present. Antiferromagnetic interactions are present on the Nd sublattice in each composition, but a spin glass forms below 5 K when a high concentration of spins is also present on the octahedral sites. [less ▲]

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See detailLattice dynamics in the FeSb3 skutterudite
Moechel, A.; Sergueev, I.; Long, Gary J. et al

in Physical Review (2011), 84(6),

Thin films of FeSb3 were characterized by electronic transport magnetometry, x-ray diffraction, Fe-57 and Sb-121 nuclear inelastic scattering, and Fe-57 Mossbauer spectroscopy. Resistivity and ... [more ▼]

Thin films of FeSb3 were characterized by electronic transport magnetometry, x-ray diffraction, Fe-57 and Sb-121 nuclear inelastic scattering, and Fe-57 Mossbauer spectroscopy. Resistivity and magnetometry measurements reveal semiconducting behavior with a 16.3(4) meV band gap and an effective paramagnetic moment of 0.57(6) mu(B) respectively. A systematic comparison of the lattice dynamics with CoSb3 and EuFe4Sb12 reveals that the Fe4Sb12 framework is softer than the Co4Sb12 framework, and that the observed softening and the associated lowering of the lattice thermal conductivity in the RFe4Sb12 filled skutterudites are not only related to the filler but also to the Fe4Sb12 framework. [less ▲]

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See detailSelective Binding of O2 over N2 in a Redox-Active Metal-Organic Framework with Open Iron(II) Coordination Sites
Bloch, Eric; Murray, Leslie; Queen, Wendy et al

in Journal of the American Chemical Society (2011), 133

The air-free reaction of FeCl2 and H4dobdc (dobdc4- = 2,5-dioxido-1,4- benzenedicarboxylate) in a mixture of DMF and methanol affords Fe2(dobdc), a metal-organic framework isostructural to M2(dobdc) (M ... [more ▼]

The air-free reaction of FeCl2 and H4dobdc (dobdc4- = 2,5-dioxido-1,4- benzenedicarboxylate) in a mixture of DMF and methanol affords Fe2(dobdc), a metal-organic framework isostructural to M2(dobdc) (M = Mg2+, Mn2+, Co2+, Ni2+, Zn2+). The desolvated form of this material has a BET surface area of 1360 m2/g and features 1-D hexagonal pores lined with coordinatively unsaturated Fe2+ cations. O2 adsorption isotherms indicate Fe2(dobdc) irreversibly binds oxygen at 298 K at a capacity over 0.10 mass fraction, corresponding to the adsorption of one O2 molecule per two framework Fe2+ cations. Remarkably, O2 uptake is reversible and the capacity increases two-fold to 0.19 mass fraction at 211 K. Powder neutron diffraction and IR spectroscopy indicate that in both scenarios O2 is coordinated side-on to the iron centers as superoxide at low temperatures and peroxide at room temperature, an observation that is confirmed by Mössbauer spectroscopy. Ideal adsorbed solution theory calculations reveal that Fe2(dobdc) is a promising material for the separation of O2 from air at temperatures well above those currently used in industrial settings. [less ▲]

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See detailFading of modern Prussian blue pigments in linseed oil medium
Samain, Louise ULg; Silversmit, Geert; Sanyova, Jana et al

in Journal of Analytical Atomic Spectrometry [=JAAS] (2011), 26(5), 930

The fading of modern laboratory-synthesized and commercial Prussian blue, iron(III) hexacyanoferrate(II), based pigments in a linseed oil medium during exposure to light has been investigated. The ... [more ▼]

The fading of modern laboratory-synthesized and commercial Prussian blue, iron(III) hexacyanoferrate(II), based pigments in a linseed oil medium during exposure to light has been investigated. The Prussian blue pigments were painted from linseed oil, as a pure pigment and mixed with white lead, (PbCO3)2Pb(OH)2, zinc white, ZnO, or titanium white, TiO2, pigment. The samples were subjected to accelerated ageing for 800 hours and the light fastness of the Prussian blue pigment was evaluated by reference to blue wool standards. Pure Prussian blue is extremely light fast whilst it strongly fades when mixed with a white pigment, especially with lead white or zinc oxide. The painted samples were studied by UV-visible, iron K-edge X-ray absorption, iron-57 transmission Mössbauer, and attenuated total reflectance infrared spectroscopy. X-ray absorption results reveal a decrease in the iron coordination number in aged samples in the presence of white pigment. The Mössbauer spectra of the pure Prussian blue and the unaged and aged mixtures of Prussian blue and lead white or zinc oxide at 1:100 and 1:10 dilution ratios, respectively, indicate the presence of iron(II) and iron(III) in a ratio close to one as expected for the bulk stoichiometric KFeIII[FeII(CN)6]; no change in the spectral parameters was observed upon ageing. Combined with the X-ray near edge absorption and infrared studies, these results suggest reduction of the surface iron ions in the Prussian blue with ageing upon exposure to light. [less ▲]

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See detailStructural, Electronic, and Magnetic Properties of UFeS3 and UFeSe3
Jin, G. B.; Ringe, Emilie; Long, Gary J. et al

in Inorganic Chemistry (2010), 49

Black prisms of UFeS3 and UFeSe3 have been synthesized by solid-state reactions of U, Fe, and S or Se with CsCl as a flux at 1173 K. The structure of these isostructural compounds consists of layers of ... [more ▼]

Black prisms of UFeS3 and UFeSe3 have been synthesized by solid-state reactions of U, Fe, and S or Se with CsCl as a flux at 1173 K. The structure of these isostructural compounds consists of layers of edge- and corner-sharing FeS6 or FeSe6 octahedra that are separated by layers of face- and edge-sharing US8 or USe8 bicapped trigonal prisms. The isomer shifts in the iron-57 Mössbauer spectra of both UFeS3 and UFeSe3 are consistent with the presence of high-spin iron(II) ions octahedrally coordinated to S or Se. The XANES spectra of UFeS3 and UFeSe3 are consistent with uranium(IV). Single-crystal magnetic susceptibility measurements along the three crystallographic axes of UFeSe3 reveal a substantial magnetic anisotropy with a change of easy axis from the a-axis above 40 K to the b-axis below 40 K, a change that results from competition between the iron(II) and uranium(IV) anisotropies. The temperature dependence of the magnetic susceptibility along the three axes is characteristic of two-dimensional magnetism. A small shoulder-like anomaly is observed in the magnetic susceptibilities along the a- and b-axes at 96 K and 107 K, respectively. Below 107 K, the iron-57 Mössbauer spectra of UFeS3 and UFeSe3 show that the iron nuclei experience a magnetic hyperfine field that results from long-range magnetic ordering of at least the iron(II) magnetic moments because the field exhibits Brillouin-like behavior. Below 40 K there is no significant change in the Mössbauer spectra as a result of change in magnetic anisotropy. The complexity of the iron-57 Mössbauer spectra and the temperature and field dependencies of the magnetic properties point towards a complex long-range magnetic structure of two independent iron(II) and uranium(IV) two-dimensional sublattices. The temperature dependence of the single-crystal resistivity of UFeSe3 measured along the a-axis reveals semiconducting behavior between 30 and 300 K with an energy gap of ca. 0.03 eV below the 53 K maximum in susceptibility, of ca. 0.05 eV between 50 and 107 K, and of 0.03 eV above 107 K; a negative magnetoresistance was observed below 60 K. [less ▲]

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See detailSlow Magnetic Relaxation in a Series of Non-Heme Trigonal Pyramidal Iron(II) Pyrrolide Complexes
Harmann, Hill E; Harris, T David; Freedman, Danna E et al

in Journal of the American Chemical Society (2010), 132

We present a family of novel non-heme trigonal pyramidal iron(II) complexes supported by tris(pyrrolyl-α-methyl)amine ligands of the form [M(solv)n][(tpaR)Fe] (M = Na, R = tert-butyl (1), phenyl (4); M ... [more ▼]

We present a family of novel non-heme trigonal pyramidal iron(II) complexes supported by tris(pyrrolyl-α-methyl)amine ligands of the form [M(solv)n][(tpaR)Fe] (M = Na, R = tert-butyl (1), phenyl (4); M = K, R = mesityl (2), 2,4,6-triisopropylphenyl (3), 2,6-difluorophenyl (5)) and their characterization by X-ray crystallography, cyclic voltammetry, and Mössbauer spectroscopy. Expanding on the initial discovery of slow magnetic relaxation in the recently reported mesityl derivative 2, we report the static and dynamic magnetic properties of a homologous series of high-spin mononuclear iron(II) complexes that exhibit this intriguing behavior. Magnetization experiments reveal large, negative zero-field splitting parameters of D = −48, −40, −36, −26 and −6.2 cm−1 for 1-5, respectively. In the case of 2,6-difluorophenyl 5, high-field EPR experiments provide an independent determination of the zero-field splitting parameters (D = −4.397(9)) that are in reasonable agreement with the magnetization data. Ac susceptibility measurements indicate field-dependent, thermally-activated spin reversal barriers in complexes 1, 2 and 4 of Ueff = 60, 42 and 25 cm−1, respectively. In the case of 1, this value constitutes the highest spin-reversal barrier observed for a mononuclear transition metal complex, a property that has broad implications for the design of molecules that can potentially store and process magnetic information. [less ▲]

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See detailHydrogen Storage and Carbon Dioxide Capture in an Iron-Based Sodalite-Type Metal-Organic Framework (Fe-BTT) Discovered via High-Throughput Methods
Sumida, Kenji; Horike, S; Kaye, S.S. et al

in Chemical Science (2010), 1

Using high-throughput instrumentation to screen conditions, the reaction between FeCl2 and H3BTT.2HCl(BTT3-=1,3,5-benzenetristetrazolate) in a mixture of DMF and DMSO was found to afford Fe3[(Fe4Cl)3(BTT ... [more ▼]

Using high-throughput instrumentation to screen conditions, the reaction between FeCl2 and H3BTT.2HCl(BTT3-=1,3,5-benzenetristetrazolate) in a mixture of DMF and DMSO was found to afford Fe3[(Fe4Cl)3(BTT)8]2.22DMF.32DMSO.11H2O. THis compound adopts a porous three-dimensional framework structure consisting of squre [Fe4CL]2+ units linked via triangulat BTT3- bridging ligands to give an anionic 3.8-net. Mossbauer spectroscopy carried out on a DMF-solvated version of the material indicated the framework to contain high-spin Fe2+ with a distribution of local environments and confirmed the presence of extra-framework iron cations. Upon soaking the compound in methanol and heating at 135 C for 24 h under dynamic vacuum, most of the solvent is removed to yield Fe3[(Fe4Cl)3(BTT)8(MeOH)4]2(Fe-BTT), a microporous solid with a BET surface area of 2010 m2g-1 and open Fe2+ coordination sites. Hydrogen adsorption data collected at 77 K show a steep rise in the isotherm, associated with an initial isosteric heat of adsorption of 11.9 kJ/mol, leading to a total storage capacity of 1.1 wt% and 8.4 g/L at 100 bar and 298 K. Powder neutron diffraction experiments performed at 4 K under various D2 loadings enabled identification of ten different adsorption sites. with the strongest binding site residing just 2.17(5) Å from the framework Fe2+ cation. Inelastic neutron scattering spectra are consistent with the strong rotational hindering of the H2 molecules at low loadings, and further reveal the catalytic conversion of ortho-H2 to para-H2 by the paramagnetic iron centers. The exposed Fe2+ cation sites within Fe-BTT also lead to the selective adsorption of CO2 over N2, with isotherms collected at 298 K indicating uptake ratios of 30.7 and 10.8 by weight at 0.1 and 1.0 bar, respectively. [less ▲]

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