Pressure effect on temperature induced high-spin–low-spin phase transitions

The effect of hydrostatic pressure on the transition temperature and the hysteresis widths of first-order spin crossover phase transitions is considered in the frame of the mean field theory and on the basis of the scope of recent pressure experiments. Relevant parameters for a qualitative description of the behaviour of spin transition compounds under pressure are derived and analysed.

A Novel Dinuclear Fe II Spin‐Crossover Complex Based on a 2,2‐Bipyrimidine Bridge Ligand: [Fe(CH 3 bipy)(NCS) 2 ] 2 bpym

The dinuclear iron(II) complex {[Fe(CH3bipy)(NCS)2]2bpym} has been synthesised and its crystal structure determined at 293 K. The magnetic properties display intramolecular antiferromagnetic coupling at 1 bar (J = −4.2 cm−1), and the onset of a pressure-induced spin conversion is observed at 11 kbar. Magnetic field Mossbauer measurements have been carried out at 4.2 K, and indicate that the HS species correspond to [HS-HS] pairs. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Interplay of Antiferromagnetic Coupling and Spin Crossover in Dinuclear Iron(II) Complexes

This article reports on the study of the interplay between magnetic coupling and spin transition in 2,2′-bipyrimidine (bpym)-bridged iron(II) dinuclear compounds. Coexistence of both phenomena has been observed in [Fe(bpym)(NCS)2]2bpym, [Fe(bpym)(NCSe)2]2bpym and [Fe(bt)(NCS)2]2bpym (bpym = 2,2′-bipyrimidine, bt = 2,2′-bithiazoline) by the action of external physical factors namely pressure or electromagnetic radiation. Competition between magnetic exchange and spin crossover has been studied in [Fe(bpym)(NCS)2]2bpym at 6.3 kbar. LIESST experiments carried out in [Fe(bpym)(NCSe)2]2bpym and [Fe(bt)(NCS)2]2bpym at 4.2 K have shown that is possible to achieve dinuclear molecules with different…

Pyridazine-Supported Polymeric Cyanometallates with Spin Transitions

Heterometallic cyano-bridged spin-crossover complexes form a large family of switchable compounds with different structural motives and diverse transition characteristics. Here we report on the hysteretic water-dependent spin transitions found in the family of [Fe(pyridazine)2M(CN)4] frameworks (M = Ni, Pd, Pt). The structure of three new spin-crossover compounds is built of cyanometallic layers supported by pyridazine ligands. The frameworks contain water guest molecules that can be removed upon heating. Spin transition was found in both hydrated and dehydrated compounds, while the removal of water stimulated a complete spin state switch. Mössbauer spectroscopy revealed two different …

Half-metallic ferromagnetism with high magnetic moment and high Curie temperature in Co$_2$FeSi

Co$_2$FeSi crystallizes in the ordered L2$_1$ structure as proved by X-ray diffraction and M\"o\ss bauer spectroscopy. The magnetic moment of Co$_2$FeSi was measured to be about $6\mu_B$ at 5K. Magnetic circular dichroism spectra excited by soft X-rays (XMCD) were taken to determine the element specific magnetic moments of Co and Fe. The Curie temperature was measured with different methods to be ($1100\pm20$)K. Co$_2$FeSi was found to be the Heusler compound as well as the half-metallic ferromagnet with the highest magnetic moment and Curie temperature.

„Supramolekulare“ Festkörperchemie: einander durchdringende diamantartige Gerüststrukturen mit U4+-Ionen und zweizähnigen molekularen P2S62−-S,S′-„Stäben“ in UP4S12

One-Dimensional Iron(II) Compounds Exhibiting Spin Crossover and Liquid Crystalline Properties in the Room Temperature Region

A novel series of 1D Fe(II) metallomesogens have been synthesized using the ligand 5-bis(alkoxy)- N-(4 H-1,2,4-triazol-4-yl)benzamide (C n -tba) and the Fe(X) 2. sH 2O salts. The polymers obey the general formula [Fe(C n -tba) 3](X) 2. sH 2O [X = CF 3SO 3 (-), BF 4 (-); n = 4, 6, 8, 10, 12]. The derivatives with n = 4, 6 exhibit spin transition behavior like in crystalline compounds, whereas those with n = 8, 10, 12 present a spin transition coexisting with the mesomorphic behavior in the room-temperature region. A columnar mesophase has been found for the majority of the metallomesogens, but also a columnar lamellar mesophase was observed for other derivatives. [Fe(C 12-tba) 3](CF 3SO 3) 2…

Distinct microbial populations are tightly linked to the profile of dissolved iron in the methanic sediments of the Helgoland mud area, North Sea

Iron reduction in subseafloor sulfate-depleted and methane-rich marine sediments is currently a subject of interest in subsurface geomicrobiology. While iron reduction and microorganisms involved have been well studied in marine surface sediments, little is known about microorganisms responsible for iron reduction in deep methanic sediments. Here, we used quantitative PCR-based 16S rRNA gene copy numbers and pyrosequencing-based relative abundances of bacteria and archaea to investigate covariance between distinct microbial populations and specific geochemical profiles in the top 5 m of sediment cores from the Helgoland mud area, North Sea. We found that gene copy numbers of bacteria and ar…

Spin-crossover nanocrystals with magnetic, optical, and structural bistability near room temperature.

Spin crossover behavior under pressure of Fe(PM-L)2(NCS)2 compounds with substituted 2′-pyridylmethylene 4-anilino ligands

Abstract New iron(II) spin crossover systems with large aromatic ligands, based on 2′-pyridylmethylene 4-anilino units, have been synthesized and studied. The whole range of spin crossover behavior has been observed, starting from pure high-spin to more or less complete gradual transitions and finally to discontinuous type transitions with both small and large hysteresis. Magnetic measurements under pressure have revealed that two of the compounds exhibit pressure-induced new phases with larger hysteresis than at atmospheric pressure. For one of the compounds the formation of this new phase is irreversible and the hysteresis width is ∼100 K, as compared to 37 K before applying pressure.

Enhanced thermoelectric performance of chalcopyrite nanocomposite via co-milling of synthetic and natural minerals

Chalcopyrite CuFeS2 was shown to be a promising thermoelectric material. Considering thermoelectric efficiency, its relatively high and temperature weakly dependent power factor, economic affordability and ecological benignity is counterbalanced by a high lattice thermal conductivity. Thus it is highly desirable to lower the thermal conductivity of chalcopyrite thermoelectric material without deterioration of other thermoelectric characteristics. In our study, we demonstrate that mechanosynthesis followed by appropriate sintering enables to prepare such nanostructured ceramics with a favourable thermoelectric response. Our study shows that mechanosynthesis is a low-cost technological route …

Superparamagnetic γ-Fe2O3 nanoparticles with tailored functionality for protein separation

Polymer coated superparamagnetic gamma-Fe(2)O(3) nanoparticles were derivatized with a synthetic double-stranded RNA [poly(IC)], a known allosteric activator of the latent (2-5)A synthetase, to separate a single 35 kDa protein from a crude extract which cross reacted with antibodies raised against the sponge enzyme.

Novel Iron(II) Microporous Spin-Crossover Coordination Polymers with Enhanced Pore Size

In this Communication, we report the synthesis and characterization of novel Hofmann-like spin-crossover porous coordination polymers of composition {Fe(L)[M(CN)4]}·G [L = 1,4-bis(4-pyridylethynyl)- benzene and MII = Ni, Pd, and Pt]. The spin-crossover properties of the framework are closely related to the number and nature of the guest molecules included in the pores.

Pressure-induced hysteresis in the high spin \leftrightarrow low spin transition in bis(2,4-bis(pyridin-2-yl)thiazole) iron(II) tetrafluoroborate

Studies of the spin transition behavior of the mononuclear compound [Fe(pythiaz)2](BF4)2 have been carried out under hydrostatic pressures up to 9.13 kbar in the 5–300 K temperature range. Under ambient pressure this compound exhibits an approximately half-step (incomplete) HS ↔ LS transition with T1/2 = 146 K without any thermal hysteresis. At pressures up to 4.5 kbar the behavior remains similar but with an upward displacement of T1/2 and a slight decrease in the residual high spin fraction at low T . Application of higher pressures resulted in an almost complete two-step spin transition with several unusual pressure effects. Along with the expected pressure dependence of T1/2 the surpris…

Magnetic transitions in double perovskiteSr2FeRe1−xSbxO6(0⩽x⩽0.9)

The double perovskites ${\mathrm{Sr}}_{2}\mathrm{Fe}M{\mathrm{O}}_{6}$ $(M=\mathrm{Re},\mathrm{Mo})$ belong to the important class of half-metallic magnetic materials. In this study we explore the effect of replacing the electronic $5d$ buffer element Re with variable valency by the main group element Sb with fixed valency. X-ray diffraction reveals ${\mathrm{Sr}}_{2}{\mathrm{FeRe}}_{1\ensuremath{-}x}{\mathrm{Sb}}_{x}{\mathrm{O}}_{6}$ $(0lxl0.9)$ to crystallize without antisite disorder in the tetragonally distorted perovskite structure (space group $I4∕mmm$). The ferrimagnetic behavior of the parent compound ${\mathrm{Sr}}_{2}{\mathrm{FeReO}}_{6}$ changes to antiferromagnetic upon Sb subst…

Multifunctional polymer-derivatized γ-Fe2O3 nanocrystals as a methodology for the biomagnetic separation of recombinant His-tagged proteins

Abstract Multifunctional polymer-derivatized superparamagnetic iron oxide (γ-Fe2O3) nanoparticles were prepared for biomagnetic separation of histidine-tagged recombinant proteins building up a faster and efficient method for protein separation by making use of their intrinsic magnetic properties. Using polymer bound γ-Fe2O3 nanocrystals, a 6× histidine-tagged recombinant protein (silicatein) with a molecular weight of 24 kDa has been isolated and purified. The supermagnetic iron oxide nanocrystals were characterized by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), SQUID and Mossbauer and the polymer functionalization of the γ-Fe2O3 nanocrystals was monitored by UV–vi…

Strong Field Iron(II) Complex Converted by Light into a Long-Lived High-Spin State

Structure and properties of CoMnSb in the context of half-metallic ferromagnetism

Although its X-ray powder diffraction patterns show a superstructure, the compound CoMnSb, like the well-known half-Heusler alloy NiMnSb, is often referred to the category of half-metallic ferromagnets with $C{1}_{b}$ structure. Our study assigns CoMnSb to space group $Fm\overline{3}m$. The crystal structure of CoMnSb can be represented as an alternation of ${\mathrm{Co}}_{2}\mathrm{Mn}\mathrm{Sb}$ and MnSb structural units, and, in contrast to NiMnSb, displays three Mn and two Sb positions in the elementary cell. The presence of nonequivalent antimony and manganese positions was verified using NMR and M\"ossbauer spectroscopic measurements. Band-structure calculations based on a proposed s…

Synthesis and immobilization of molecular switches onto titaniumdioxide nanowires

Abstract The precursor [Fe III (L)Cl (L =  N , N ′-bis(2′-hydroxy-3′-methyl-benzyliden)-1,7-diamino-4-azaheptane) is combined with [Mo(CN) 8 ] 4− yields a star shaped nona-nuclear cluster, [Mo IV {(CN)Fe III (L)} 8 ]Cl 4 . This Fe 8 Mo molecule is a high-spin system at room temperature. On cooling to 20 K some of the iron(III) centres in the molybdenum(IV)-star switch to the low-spin state as proven by Mossbauer spectroscopy. This molecule was deposited on TiO 2 nanowires by electrostatic interactions between the cluster cations and the surface functionalized titanium oxide nanowire. The synthesis and surface binding of the multistable molecular switch was demonstrated using IR and UV–Vis s…

X-ray powder diffraction and LIESST-effect of the spin transition material [Fe(bpp)2](NCS)2·2H2O

Abstract We have studied the X-ray powder diffraction of the spin transition material [Fe(bpp)2](NCS)2 · 2H2O (bpp: 2,6-bis(pyrazol-3-yl)pyridine) at room temperature. Two crystallographic phases have been observed depending on the sample history of this material. The results obtained corroborate the earlier observations from magnetic and calorimetric studies. Relatively prolonged exposure of the sample to X-rays caused a structural change. LIESST and Reverse-LIESST effects, characterised by 57Fe Mossbauer spectroscopy, have been observed in this material.

Pressure effect studies on spin crossover systems

Abstract In the present review article we discuss the results of investigations of the influence of hydrostatic pressure (up to 1.2 GPa) on the spin transition behaviour in coordination compounds of 3d transition metal ions. The systems under investigation are mononuclear spin crossover compounds of iron(II) and chromium(II), dinuclear complexes of iron(II) exhibiting coexistence of intramolecular anti-ferromagnetic coupling and thermal spin crossover, and 1D, 2D and 3D polynuclear spin crossover complexes of iron(II). It is demonstrated that the application of hydrostatic pressure serves as a tool for modifying the ligand field strength in a controlled manner.

Pressure Effect Studies on the Spin‐Transition Behavior of a Dinuclear Iron(II) Compound

Magnetic studies into the effect of different hydrostatic pressures between ambient and 1.03 GPa on the high-spin (HS) i low-spin (LS) transition behavior of the dinuclear iron(II) compound [Fe II 2(PMAT)2](BF4)4·DMF (1, PMAT = 4-amino3,5-bis{[(2-pyridylmethyl)amino]methyl}-4H-1,2,4-triazole, DMF = N,N-dimethylformamide) have been carried out at 2– 300 K. Under ambient pressure, the sample studied exhibits a [HS–HS] to [HS–LS] half spin transition (ST) at T½ = 208 K without any thermal hysteresis. Increasing the pressure above 0.2 GPa causes an increase (initially rapid but above 0.5 GPa more gradual) of T½ as well as a matching reduction in the residual high-spin fraction at room temperatu…

Verwey-type transition in EuNiP

High temperature 151Eu Mossbauer measurements provide proof for inhomogeneous mixed-valent behaviour in EuNiP. We observed that EuNiP undergoes a Verwey-type charge delocalisation transition when heated above 470 K prior to the structural γ-β phase transition at T ≈ 510 K. This finding confirms the results of photoemission spectroscopy in the isostructural compound EuPdP and of TB-LMTO-ASA band structure calculations. We discuss the role of a van Hove singularity associated with a high density of 4f states close to the Fermi energy in inhomogeneous mixed europium valency, and the microscopic mechanism of γ-β phase transition in compounds analogous to EuNiP.

Synthesis and magnetic properties of an iron 1,2-bisthienyl perfluorocyclopentene photochromic coordination compound

Abstract The coordination compound Fe(BM-4-PTP) 2 (NCS) 2 ⋅2MeOH ( 1 ) including the photoisomerizable ligand BM-4-PTP (1,2-bis(2′-methyl-5′-(pyrid-4″-yl)thien-3′-yl)perfluorocyclopentene) was obtained as an orange powder. The powder turns blue upon photocyclization of the 1,2-bisthienyl photochromic ligand induced by UV light irradiation at room temperature. Photocycloreversion is obtained by visible light irradiation of the material in the solid state. The orange and blue powders were investigated over the temperature range (5–293 K) and pressure range (1 bar–12 kbar) by magnetic susceptibility measurements and variable temperature 57 Fe Mossbauer spectroscopy. The photo-induced colour ch…

Crystalline Non‐Equilibrium Phase of a Cobalt(II) Complex with Tridentate Ligands

In six-coordinate complexes, flexible tridentate ligands enable mer, cis-fac, and trans-fac stereoisomers. With labile metal ions of the first transition metal series, typically only the final thermodynamic product is available because of the rapid isomerization processes. Here we report on the structural characterization of a so far elusive kinetic intermediate of [Co(ddpd)2](BF4)2 (1; ddpd = N,N′-dimethyl-N,N′-dipyridine-2-yl-pyridine-2,6-diamine). Microcrystals of the cis-fac isomer of 1 were obtained by rapid precipitation. The solid-state structure of cis-fac-1 was determined from electron diffraction data.

Chiral spin crossover nanoparticles and gels with switchable circular dichroism

Spin crossover complexes represent spectacular examples of molecular switchable materials. We describe a new approach towards homochiral coordination nanoparticles of [Fe(NH2trz)3](L-CSA)2 (NH2trz = 4-amino-1,2,4-triazole, L-CSA = L-camphorsulfonate) that display an abrupt switch of chiral properties associated with a cooperative spin transition. This is an original method that generates stable and additive-free colloidal solutions of nanoparticles with a spin transition around room temperature. The introduction of a chiral anion to the coordination framework makes these nanoparticles display specific chiro-optical (circular dichroism) properties that are different in high and low spin stat…

A Heteroleptic Push-Pull Substituted Iron(II) Bis(tridentate) Complex with Low-Energy Charge-Transfer States

A heteroleptic iron(II) complex [Fe(dcpp)(ddpd)](2+) with a strongly electron-withdrawing ligand (dcpp, 2,6-bis(2-carboxypyridyl)pyridine) and a strongly electron-donating tridentate tripyridine ligand (ddpd, N,N'-dimethyl-N,N'-dipyridine-2-yl-pyridine-2,6-diamine) is reported. Both ligands form six-membered chelate rings with the iron center, inducing a strong ligand field. This results in a high-energy, high-spin state ((5) T2 , (t2g )(4) (eg *)(2) ) and a low-spin ground state ((1) A1 , (t2g )(6) (eg *)(0) ). The intermediate triplet spin state ((3) T1 , (t2g )(5) (eg *)(1) ) is suggested to be between these states on the basis of the rapid dynamics after photoexcitation. The low-energy …

Magneto-structural correlations in self-assembled spin-transition nano-architectures of the [][2×2]-grid-type

Abstract The magnetism of a series of tetranuclear complexes of the [ Fe II 4 L 4 ]( BF 4 ) 8 [2×2] -grid-type was investigated, revealing the occurrence of spin-transition (ST) behavior within this class of compounds. The phenomenon depends directly on the nature of the substituent R1 of the ligand L . All FeII ions in compounds with R1 substituents favoring strong ligand fields ( R 1 = H ; OH ) remain completely in the diamagnetic low-spin state. Only the complex bearing R1=Ph exhibits thermally induced ST behavior.

On the Nature of the Plateau in Two-Step Dinuclear Spin-Crossover Complexes

A remarkable feature of the spin-crossover process in several dinuclear iron(II) compounds is a plateau in the two-step transition curve. Up to now, it has not been possible to analyse the spin state of dinuclear pairs that constitute such a plateau, due to the relative high temperatures at which the transition takes place in complexes investigated so far. We solved this problem by experimentally studying a novel dinuclear spin-crossover compound [[Fe(phdia)(NCS)(2)](2)(phdia)] (phdia: 4,7-phenanthroline-5,6-diamine). We report here on the synthesis and characterisation of this system, which exhibits a two-step spin transition at T(c1)=108 K and T(c2)=80 K, displaying 2 K and 7 K wide therm…

Pressure Effect on Spin Crossover in [Fe(phen)2(NCS)2] and [CrI2(depe)2]

In the present article, we discuss the results of investigations of the influence of hydrostatic pressure (up to 1.2 GPa) on the spin transition behavior in [Fe(phen)2(NCS)2] polymorph II and [CrI2(depe)2]. It is demonstrated that pressure effect studies are very helpful in elucidating the mechanism of cooperative dynamic electronic structure phenomena accompanied by significant volume changes. Application of hydrostatic pressure serves as a tool for modifying the ligand field strength in a controlled manner.

Supramolecular Spintronic Devices: Spin Transitions and Magnetostructural Correlations in[Fe4IIL4]8+[2×2]-Grid-Type Complexes

The magnetism of a series of tetranuclear complexes of the [Fe4IIL4]8+ [2x2]-grid-type was investigated, revealing the occurrence of spin transition behavior within this class of compounds. The phenomenon depends directly on the nature of the substituent R(1) in the 2-position on the central pyrimidine group of the ligand L. All Fe(II) ions in compounds with R(1) substituents favoring strong ligand fields (R(1)=H; OH) remain completely in the diamagnetic low-spin state. Only complexes bearing R(1) substituents attenuating the ligand field by steric (and to a lesser extent electronic) effects (R(1)=Me; Ph) exhibit spin transition behavior triggered by temperature. In general, gradual and inc…

Five-Coordinate Complexes [FeX(depe)2]BPh4, X = Cl, Br:  Electronic Structure and Spin-Forbidden Reaction with N2

The bonding of N(2) to the five-coordinate complexes [FeX(depe)(2)](+), X = Cl (1a) and Br (1b), has been investigated with the help of X-ray crystallography, spectroscopy, and quantum-chemical calculations. Complexes 1a and 1b are found to have an XP(4) coordination that is intermediate between square-pyramidal and trigonal-bipyramidal. Mössbauer and optical absorption spectroscopy coupled with angular overlap model (AOM) calculations reveal that 1a and 1b have (3)B(1) ground states deriving from a (xz)(1)(z(2))(1) configuration. The zero-field splitting for this state is found to be 30-35 cm(-1). In contrast, the analogous dinitrogen complexes [FeX(N(2))(depe)(2)](+), X = Cl (2a) and Br (…

High temperature spin crossover in [Fe(pyrazine){Ag(CN) 2 } 2 ] and its solvate

A high temperature spin crossover (Tup = 367 K) was detected in a metal–organic framework [Fe(pz){Ag(CN)2}2]·MeCN (pz = pyrazine). Upon heating, this solvate released acetonitrile guest molecules, which slightly shifted the transition temperature of the complex (Tup = 370 K and Tdown = 356 K).

Stark-Feld-Eisen(II)-Komplex konvertiert durch Licht in einen langlebigen High-Spin-Zustand

Gold(ii) in redox-switchable gold(i) catalysis

Chemical communications 55(32), 4615 - 4618 (2019). doi:10.1039/C9CC00283A

Pressure- and temperature-induced valence tautomeric interconversion in a o-dioxolene adduct of a cobalt-tetraazamacrocycle complex

An electronic switch at the molecular level has been realized by using a class of ionic compounds of the formula [Co(L)(diox)]Y (L = tetraazamacrocyclic ligand, Y = mononegative anion). Such compounds undergo temperature- and pressure-induced intramolecular one-electron transfer equilibria. The transition temperature of interconversion varies with the nature of the counterions Y (Y = PF6, BPh4, I). Surprisingly the effect of the anion on the transition temperature is not only governed by its volume but also by its coulombic interaction.

Geometric, electronic, and magnetic structure of Co$_2$FeSi: Curie temperature and magnetic moment measurements and calculations

In this work a simple concept was used for a systematic search for new materials with high spin polarization. It is based on two semi-empirical models. Firstly, the Slater-Pauling rule was used for estimation of the magnetic moment. This model is well supported by electronic structure calculations. The second model was found particularly for Co$_2$ based Heusler compounds when comparing their magnetic properties. It turned out that these compounds exhibit seemingly a linear dependence of the Curie temperature as function of the magnetic moment. Stimulated by these models, Co$_2$FeSi was revisited. The compound was investigated in detail concerning its geometrical and magnetic structure by m…

Hofmann-Like Frameworks Fe(2-methylpyrazine)n[M(CN)2]2 (M = Au, Ag) : Spin-Crossover Defined by the Precious Metal

Hofmann-like cyanometalates constitute a large class of spin-crossover iron(II) complexes with variable switching properties. However, it is not yet clearly understood how the temperature and cooperativity of a spin transition are influenced by their structure. In this paper, we report the synthesis and crystal structures of the metal–organic coordination polymers {FeII(Mepz)[AuI(CN)2]2} ([Au]) and {FeII(Mepz)2[AgI(CN)2]2} ([Ag]), where Mepz = 2-methylpyrazine, along with characterization of their spin-state behavior by variable-temperature SQUID magnetometry and Mössbauer spectroscopy. The compounds are built of cyanoheterometallic layers, which are pillared by the bridging Mepz…

Pressure-Induced Spin State Conversion in Antiferromagnetically Coupled Fe(II) Dinuclear Complexes

The effect of pressure on the thermal dependence of the magnetic susceptibility has been investigated in the 2,2‘-bipyrimidine (bpm)-bridged iron(II) complexes of formula {[Fe(L)(NCX)2]2bpm} (X = S...

Large orbital moments and internal magnetic fields in lithium nitridoferrate(I)

The iron nitridometalates Li2[(Li(1-x)Fe(I)(x))N] display ferromagnetic ordering and spin freezing. Large magnetic moments up to 5.0mu(B)/Fe are found in the magnetization. In Mössbauer effect studies huge hyperfine magnetic fields up to 696 kOe are observed at specific Fe sites. These extraordinary fields and moments originate in an unusual ligand field splitting for those Fe species leading [within local spin density approximation (LSDA)] to a localized orbitally degenerate doublet. Including spin-orbit interaction and strong intra-atomic electron correlation (LDA+SO+U) gives rise to a large orbital momentum.

Crystal growth, structure, magnetic properties and theoretical exchange interaction calculations of Cu2MnBO5

Single crystals of ludwigite Cu2MnBO5 were synthesized by flux growth technique. The detailed structural and magnetic characterizations of the synthesized samples have been carried out. The cations composition of the studied crystal was determined using X-ray diffraction and EXAFS technique, the resulting composition differ from the content of the initial Mn2O3–CuO components of the flux. Magnetic susceptibility measurements and the calculations of the exchange integrals in frameworks of indirect coupling model revealed that monoclinic distortions strongly affect exchange interactions and appearance of magnetic ordering phase at the temperature T=93 K. The hypothesis of the existence of sev…

Room temperature hysteretic spin crossover in a new cyanoheterometallic framework.

A new iron(II)-based spin-crossover compound with thermal hysteresis operating under ambient conditions is reported. This complex exhibits a high reproducibility of the spin transition in many successive thermal cycles, stability of both spin states at room temperature and an attractive operational temperature range.

Phase Trapping in Multistep Spin Crossover Compound

The dimeric motif is the smallest unit for two interacting spin centers allowing for systematic investigations of cooperative interactions. As spin transition compounds, dinuclear complexes are of particular interest, since they potentially reveal a two-step spin crossover (SCO), switching between the high spin-high spin [HS-HS], the high spin-low spin [HS-LS], and the low spin-low spin [LS-LS] states. Herein, we report the synthesis and characterization of six dinuclear iron(II) complexes [FeII2(μ2-L1)2](BF4)4 (C1), [FeII2(μ2-L1)2](ClO4)4 (C2), [FeII2(μ2-L1)2](F3CSO3)4 (C3), [FeII2(μ2-L2)2](BF4)4 (C4), [FeII2(μ2-L2)2](BF4)4 (C5), and [FeII2(μ2-L2)2](BF4)4 (C6), based on the 1,3,4-thiadiazo…

Synthesis of Nanocrystals and Particle Size Effects Studies on the Thermally Induced Spin Transition of the Model Spin Crossover Compound [Fe(phen)2(NCS)2].

Surfactant-free nanocrystals of the model spin-crossover compound [Fe(phen)2(NCS)2] (phen: 1,10-phenanthroline) have been synthesized applying the reverse micelle technique. The morphology of the nanocrystals, characterized by scanning electronic microscopy, corresponds to rhombohedric platelets with dimensions ranging from 203 × 203 × 106 nm to 142 × 142 × 74 nm. Variation of the concentration of the Fe(BF4)2·6H2O salt in the synthesis has been found to have little influence on the crystallite size. In contrast, the solvent-surfactant ratio (ω) is critical for a good particle growth. The spin transition of the nanocrystals has been characterized by magnetic susceptibility measurements and …

An Inorganic Double Helix Sheathing Alkali Metal Cations: ANb2P2S12(A=K, Rb, Cs), A Series of Thiophosphates Close to the Metal-Nonmetal Boundary-Chalcogenide Analogues of Transition-Metal Phosphate Bronzes?

The new quaternary niobium thiophosphates ANb 2 P 2 S 1 2 (A=K, Rb, Cs) have been prepared and characterized. The title compounds were synthesized by reacting Nb metal, A 2 S, P 2 S 5 , and S at 600-700°C in evacuated silica tubes. They crystallize as "stuffed" variants of the tetragonal TaPS 6 structure type in the tetragonal space group I42d with eight formula units per unit cell and lattice constants a=15.923(2) and c=13.238(3) A for CsNb 2 P 2 S 1 2 , a= 15.887(3) and c=13.132(3) A for RbNb 2 P 2 S 1 2 , and a=15.850(2) and c= 13.119(3) A for KNb 2 P 2 S 1 2 . Their structures are based on double helices formed from interpenetrating, noninteracting spiral chains of binuclear [Nb 2 S 1 2…

dsRNA-functionalized multifunctional gamma-Fe2O3 nanocrystals: a tool for targeting cell surface receptors.

Iron(II) Metallomesogens Exhibiting Coupled Spin State and Liquid Crystal Phase Transitions near Room Temperature

Reaction of the ligand 2,2,2-tris(2-aza-3-((5-akloxy)(6-methyl)(2-pyridyl))prop-2-enyl)ethane (C n -tameMe) with Fe(X) 2 . sH 2 O salts afforded a series of spin crossover metallomesogens with general formula [Fe(C n -tame)](X) 2 . sH 2 O (s ≥ 0), with n = 6, 10, 12, 14, 16, 17, 18, or 20 and X =ClO 4 - or BF 4 -. Single crystal X-ray measurements have been performed on the [Fe(C 6 -tameMe)](ClO 4 ) 2 (C 6 -1) derivative at 100 K. The complex C 6 -1 crystallizes in the triclinic system and adopts the Pbca space group. The iron(II) ion is in a distorted octahedral environment shaped by three imine and three pyridine nitrogen atoms of the C n -tameMe ligand. The average Fe-N im and Fe-N py bo…

Synthesis, characterization and functionalization of nearly mono-disperse copper ferrite CuxFe3−xO4 nanoparticles

Magnetic nanocrystals are of great interest for a fundamental understanding of nanomagnetism and for their technological applications. CuxFe3−xO4 nanocrystals (x ≈ 0.32) with sizes ranging between 5 and 7 nm were synthesized starting from Cu(HCOO)2 and Fe(CO)5 using oleic acid and oleylamine as surfactants. The nanocrystals were characterized by high-resolution transmission electron microscopy (HRTEM), electron diffraction (ED), magnetization studies and Mossbauer spectroscopy. The CuxFe3−xO4 particles are superparamagnetic at room temperature 300 K with a saturation magnetization of 30.5 emu g−1. Below their blocking temperature of 60 K, they become ferrimagnetic, and at 5 K they show a co…

Hysteresis in the spin transition regime of [Fe(NH2trz)3](NO3)2 as probed by ZF-μSR

The thermal spin transition which occurs in the polymeric chain compound [Fe(NH(2)trz)(3)](NO3)(2) above room temperature has been investigated by zero-field muon spin relaxation (mu SR) (similar to 8-402 K). The depolarization curves are best described by a Lorentzian and a Gaussian line that represent fast and slow components respectively. The spin transition is associated with a hysteresis loop of width Delta T = 34 K (T-1/2(up arrow) = 346 K and T-1/2(down arrow) = 312 K) that has been delineated by the temperature variation of the initial asymmetry parameter. Comparison of zero-field and transverse field (20 Oe) mu SR measurements shows that diamagnetic muon species occur over the enti…

Structure and Properties of GdAuSn and the GdAuSn/MnAuSn System

The crystal structure of GdAuSn was refined by means of single crystal X-ray diffraction. Band structure calculations based on the structural data confirmed the antiferromagnetic ground state and the metallic behaviour of GdAuSn. 119mSn, 155Gd and 197Au Mossbauer spectroscopic studies were used to verify the values of the hyperfine parameters that were given by the band structure calculations. Band structure calculations of MnAuSn confirmed that this half-Heusler compound belongs to the family of half-metallic ferromagnets. Magnetic susceptibility, conductivity and Mossbauer studies were used to characterize granular material based on the half-Heusler ferromagnet MnAuSn in the antiferromagn…

Pressure effect on a novel spin transition polymeric chain compound

[Fe(hyptrz)3]A2·H2O (hyptrz = 4-(3′-hydroxypropyl)-1,2,4-triazole and A = 4-chlorobenzenesulfonate) represents a novel iron(II) polymeric chain compound. A discontinuous spin transition has been observed by temperature dependent magnetic susceptibility measurements. The spin transition curves are shifted from 181 K to 324 K as the pressure varies from 1 bar to 5.9 kbar. The shapes of these curves are not strongly modified, and this is interpreted as being due to effective cooperative interactions along the chain. This behaviour under pressure can be extended to the family of iron(II)-1,2,4-triazole polymeric chain spin crossover materials.

Ni@Fe2O3 heterodimers: controlled synthesis and magnetically recyclable catalytic application for dehalogenation reactions

Ni@Fe2O3 heterodimer nanoparticles (NPs) were synthesized by thermal decomposition of organometallic reactants. After functionalization, these Ni@Fe2O3 heterodimers became water soluble. The pristine heterodimeric NPs were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Mossbauer spectroscopy and magnetic susceptibility measurements. A special advantage of the heterodimers lies in the fact that nanodomains of different composition can be used as catalysts for the removal of environmentally hazardous halogenated pollutants.

New polynuclear 4,4ˈ-bis-1,2,4-triazole Fe(II) spin crossover compounds

L'interet porte aux materiaux moleculaires du Fe(II) presentant une transition entre un etat haut-spin (HS, S = 2) et un etat bas-spin (LS, S = 0), sous l'effet d'une variation de temperature, de pression ou d'une irradiation lumineuse, n'a cesse de croitre au cours de ces dix dernieres annees [1-4]. La famille des composes du Fe(II) a base de derives du 1,2,4-triazole substitues par un groupe R sur l'azote 4 a ete tres etudiee pour ses proprietes de transition de spin (TS), qui pourraient permettre des applications en electronique moleculaire [5-15, 29, 32, 36, 37]. Nous avons recemment presente le premier compose a TS possedant une structure tridimensionnelle (figure 2). Ce compose de for…

Electronic Relaxation Phenomena Following 57Co(EC)57Fe Nuclear Decay in [MnII(terpy)2](ClO4)2·1/2H2O and in the Spin Crossover Complexes [CoII(terpy)2]X2·nH2O (X = Cl and ClO4):  A Mössbauer Emission Spectroscopic Study

The valence states of the nucleogenic 57Fe arising from the nuclear disintegration of radioactive 57Co by electron capture decay, 57Co(EC)57Fe, have been studied by Mossbauer emission spectroscopy (MES) in the 57Co-labeled systems:  [57Co/Co(terpy)2]Cl2·5H2O (1), [57Co/Co(terpy)2](ClO4)2·1/2H2O (2), and [57Co/Mn(terpy)2](ClO4)2· 1/2H2O (3) (terpy = 2,2‘:6‘,2‘ ‘-terpyridine). The compounds 1, 2, and 3 were labeled with ca. 1 mCi of 57Co and were used as the Mossbauer sources at variable temperatures between 300 K and ca. 4 K. [Fe(terpy)2]X2 is a diamagnetic low-spin (LS) complex, independent of the nature of the anion X, while [Co(terpy)2]X2 complexes show gradual spin transition as the temp…

Rapid cooling experiments and use of an anionic nuclear probe to sense the spin transition of the 1D coordination polymers [Fe(NH2trz)3]SnF6n x H2O (NH2trz=4-amino-1,2,4-triazole).

[Fe(NH(2)trz)(3)]SnF(6)n H(2)O (NH(2)trz=4-amino-1,2,4-triazole; n=1 (1), n=0.5 (2)) are new 1D spin-crossover coordination polymers. Compound 2 exhibits an incomplete spin transition centred at around 210 K with a thermal hysteresis loop approximately 16 K wide. The spin transition of 2 was detected by the Mossbauer resonance of the (119)Sn atom in the SnF(6) (2-) anion primarily on the basis of the evolution of its local distortion. Rapid-cooling (57)Fe Mossbauer and superconducting quantum interference device experiments allow dramatic widening of the hysteresis width of 2 from 16 K up to 82 K and also shift the spin-transition curve into the room temperature region. This unusual behavio…

Pressure effect studies in molecular magnetism

We report on temperature dependent magnetic susceptibility and Mossbauer effect studies of the influence of hydrostatic pressure (up to 1.2 GPa) on dynamic electronic structure phenomena in 3d transition metal coordination compounds. The systems under investigation are mononuclear spin crossover compounds of iron (II) and chromium (II), dinuclear complexes of iron (II) exhibiting coexistence of intramolecular antiferromagnetic coupling and thermal spin crossover, 1D, 2D and 3D polynuclear spin crossover complexes of iron (II), a valence tautomeric system of cobalt (II) showing a thermal transition from a high spin [CoII (semiquinone)] to a low spin [CoII (catecholate)] species on lowering t…

Hierarchical Self-Assembly of Supramolecular Spintronic Modules into 1D- and 2D-Architectures with Emergence of Magnetic Properties

Hierarchical self-assembly of complex supramolecular architectures allows for the emergence of novel properties at each level of complexity. The reaction of the ligand components A and B with Fe II cations generates the (2 K 2) grid-type functional building modules 1 and 2, presenting spin-tran- sition properties and preorganizing an array of coordination sites that sets the stage for a second assembly step. Indeed, binding of La III ions to 1 and of Ag I ions to 2 leads to a 1D columnar superstructure 3 and to a wall-like 2D layer 4, respectively, with concomitant modulation of the magnetic properties of 1 and 2. Thus, to each of the two levels of structural complexity generat- ed by the t…

Intercalation effect on hyperfine parameters of Fe in FeSe superconductor with Tc = 42 K

57Fe-Mossbauer spectra of superconducting beta-FeSe, the Li/NH3 intercalate product and a subsequent sample of this intercalate treated with moist He gas have been measured in temperature range 4.7 - 290 K. A correlation is established between hyperfine parameters and critical temperature Tc in these phases. A strong increase of isomer shift upon intercalation is explained by a charge transfer from the Li/NH3 intercalate to the FeSe layers resulting in an increase of Tc up to 42 K. A significant decrease of the quadrupole splitting above 240 K has been attributed to diffusive motion of Li+ ions within the interlamellar space.

Investigation of Co$_2$FeSi: The Heusler compound with Highest Curie Temperature and Magnetic Moment

This work reports on structural and magnetic investigations of the Heusler compound Co$_2$FeSi. X-Ray diffraction and M\"o\ss bauer spectrometry indicate an ordered $L2_1$ structure. Magnetic measurements by means of X-ray magnetic circular dichroism and magnetometry revealed that this compound is, currently, the material with the highest magnetic moment ($6 \mu_B$) and Curie-temperature (1100K) in the classes of Heusler compounds as well as half-metallic ferromagnets.

ChemInform Abstract: Ln2Ti2S2O5 (Ln: Nd, Pr, Sm): A Novel Series of Defective Ruddlesden-Popper Phases.

ChemInform Abstract: K3Cr2(PS4)3: A New Chromium Thiophosphate with a One-Dimensional [Cr2(PS4)3]3- Anion Chain.

Synthesis, crystal structure and magnetic properties of bis[μ-bis(3-(pyridin-2-yl)-1,2,4-triazole-N′,N1,N2)] bis[triaqua nickel(II)] tetranitrate

Abstract A new dinuclear nickel(II) coordination compound of formula Ni2(Hpt)2(H2O)6(NO3)4 (Hpt=3-(pyridin-2-yl)-1,2,4-triazole) was synthesized. The structure was solved at 298 K by single-crystal X-ray analysis. Bisμ-bis(3-(pyridin-2-yl)-1,2,4-triazole-N′,N1,N2) bistriaqua nickel(II) tetranitrate (C14H24N12O18Ni2) crystallizes in the triclinic space group P-1, a=7.2266(1), b=9.9144(1), c=11.2647(1) A, α=66.854(1)°, β=74.000(1)°, γ=86.400(2)°, V=712.42(1) A3, Z=1 (dinuclear units), 2823 reflections (1 > 2σ(I)), R1=0.0442, wR2=0.1197. The Ni(II) ions are bridged by two neutral Hpt ligands coordinating via N1 and N2 in the equatorial plane, Ni(1)-Ni(1)′=4.098(1) A. The Hpt bridging mode is a…

The influence of hydrostatic pressure on hysteresis phase transition in spin crossover compounds

Abstract The effect of hydrostatic pressure on the transition temperature and the hysteresis widths of first order spin crossover phase transitions has been studied. A decrease as well as an increase of the hysteresis width with increasing pressure was reported in the literature. The increase of width with increasing pressure contradicts the expectation derived from mean field theory. We remeasured the pressure dependence of the temperature hysteresis of the compound [Fe(phy)2](BF4)2 (phy=1, 10-phenanthroline-2-carbaldehydephenylhydrazone). The spin transition temperatures at ambient temperature are T ↑ 1/2 =289±1 K, T ↓ 1/2 =283±1 K . An increase of the hysteresis width of d Δ T 1/2 / d p=…

Durch Temperatur, Druck oder Licht induzierter Spinübergang in einer supramolekularen Fe‐[2×2]‐Gitterverbindung

Proton-Coupled Electron Transfer in Ferrocenium–Phenolate Radicals

Electron and proton transfer (ET, PT) can be intimately coupled, provided suitable redox and acid/base sites are available. The amide-linked ferrocene–phenol H-1 is deprotonated to the phenolate [1]– by phosphazene bases and oxidized to the ferrocenium ion [H-1]+ by silver hexafluoroantimonate. Concomitant oxidation and deprotonation yields the radical [1]•, featuring a characteristic near-IR absorption band. The ground state of [1]• is best described as the ferrocenium–phenolate zwitterion [1b]• with a dynamic dissymmetric N···H···O hydrogen bond (PT). The ferrocenium–iminolate N···H–O tautomer [1b]•-NHO′ can undergo a thermal structural rearrangement to the high-energy OH···O tautomer [1b…

Superconductivity and magnetism in Rb0.8Fe1.6Se2under pressure

High-pressure magnetization, structural and 57Fe M\"ossbauer studies were performed on superconducting Rb0.8Fe1.6Se2.0 with Tc = 32.4 K. The superconducting transition temperature gradually decreases on increasing pressure up to 5.0 GPa followed by a marked step-like suppression of superconductivity near 6 GPa. No structural phase transition in the Fe vacancy-ordered superstructure is observed in synchrotron XRD studies up to 15.6 GPa, while the M\"ossbauer spectra above 5 GPa reveal the appearance of a new paramagnetic phase and significant changes in the magnetic and electronic properties of the dominant antiferromagnetic phase, coinciding with the disappearance of superconductivity. Thes…

Maghemite polymer nanocomposites with modulated magnetic properties

A method is presented for the production of maghemite polymer nanocomposites with modulated magnetic properties. Magnetic nanocomposites prepared using this method show regular variation in the magnetic blocking temperature from 2 K to 300 K, and variation in the saturation magnetization from 0 to 50 emu g � 1 (Fe2O3). The method is based on the in situ formation of maghemite nanoparticles in nitrogen-base polymer matrixes. The particle size can be varied regularly from 1.5 nm to 16 nm by changing the ratio of iron loading in the polymer and/or the Fe(II)/Fe(III) ratios. The particles are isolated and uniformly distributed within the matrix. The mate

Pressure effect on the magnetism of layered copper(II) compounds with interlayer spacing up to 40.7 Å: Nature of the magnetic ordering

The influence of pressure on the structure and magnetic properties of the layered hybrid compounds Cu 2 (OH) 3 (n-C m H 2 m + 1 CO 2 ), zH 2 O is investigated for m = 10 and 12. It is shown that the distance between magnetic copper(II) layers, up to 40.7 A, is not significantly modified and that the temperature of the ferromagnetic ordering decreases linearly with pressure increase. We present a new analysis of the susceptibility data, based on the scaling theory of phase transitions, which clearly shows up a crossover from a high-temperature two-dimensional (2D) behavior to a 3D regime at about 30 K, around 10 K above the long-range ordering temperature. A model of quantum ferromagnetic la…

Phosphoraneiminato complexes of manganese and cobalt with heterocubane structure

The phosphoraneiminato complexes [MnBr(NPEt3)]4 (1) and [M4Br5{NP(NMe2)3}3] with M = Mn (2) and M = Co (3) are prepared by melting reactions from the anhydrous metal dibromides with the silylated phosphaneimines Me3SiNPR3 (R = Et, NMe2) in the presence of potassium fluoride. All complexes are characterized by crystal structure analyses. 1 forms an only slightly distorted Mn4N4 heterocubane skeleton with an approximate Td symmetry and short Mn…Mn distances of average 295.7 pm. In the structures of 2 and 3 one μ3-NPEt3 ligand of 1 is replaced by one bromine atom with μ3-function. This leads to the novel heterocubane type M4N3Br with approximate C3 symmetry. The deformation of the cubic skelet…

First Example of Coexistence of Thermal Spin Transition and Liquid-Crystal Properties.

The rodlike FeIII complex of an N-alkyloxysalicylidenyl-N'-ethyl-N-ethylenediamine ligand, shown as a computer model in the picture, is the first compound in which spin-crossover (SC) and liquid-crystalline (LC) properties coexist. This synergy should allow the magnetic and optical properties of SC compounds to be combined with the sensitivity of the LC state to electromagnetic fields.

Thermal- and light-induced spin crossover in novel 2D Fe(II) metalorganic frameworks {Fe(4-PhPy)(2)[M(II)(CN)(x)](y)}.sH(2)O: spectroscopic, structural, and magnetic studies.

Five novel two-dimensional coordination polymers {Fe(4PhPy)(2)[M(II)(CN)(4)]}.sH(2)O (4PhyPy = 4-phenylpyridine; 1: M(II) = Pd, s = 0; 2: M(II) = Ni, s = 0; 3: M(II) = Pt, s = 1) and {Fe(4PhPy)(2)[M(I)(CN)(2)](2)}.sH(2)O (4: M(I) = Ag, s = 1; 5: M(I) = Au, s = 0.5) exhibiting spin-crossover properties have been synthesized. They were characterized at various temperatures using X-ray absorption spectroscopy (XAS), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), and magnetic susceptibility measurements. The occurrence of a cooperative thermal spin transition detected by the magnetic method is located at critical temperatures T(c)( downward arrow)/T(c)( upward arrow) …

Spin-Crossover and Liquid Crystal Properties in 2D Cyanide-Bridged FeII−MI/II Metalorganic Frameworks

Novel two-dimensional heterometallic Fe(II)-M(Ni(II), Pd(II), Pt(II), Ag(I), and Au(I)) cyanide-bridged metalorganic frameworks exhibiting spin-crossover and liquid crystal properties, formulated as {FeL(2)[M(I/II)(CN)(x)](y)}·sH(2)O, where L are the ligands 4-(4-alkoxyphenyl)pyridine, 4-(3,4-dialkoxyphenyl)pyridine, and 4-(3,4,5-trisalkoxyphenyl)pyridine, have been synthesized and characterized. The physical characterization has been carried out by means of EXAFS, X-ray powder diffraction, magnetic susceptibility, differential scanning measurements, and Mössbauer spectroscopy. The 2D Fe(II) metallomesogens undergo incomplete and continuous thermally induced spin transition at T(1/2) ≈ 170 …

Synthesis, crystal structure, magnetic properties and 57Fe Mossbauer spectroscopy of the new trinuclear [Fe3(4-(2'-hydroxyethyl)-1,2,4- triazole)6(H2O)6](CF3SO3)6 spin crossover compound

Hyetrz = 4-(2prime-hydroxyethyl)-1,2,4-triazole represents the first structurally characterized iron(II) spin crossover compound for which the structure has been solved above and below room temperature in both spin states. The compound crystallizes in the trigonal system, space group R3, a = 12.763(1) b= 67.144(1), V = 1684.3(1) 3, Z = 6 at 120K. At 330K the space group is retained and a = 13.0183(3) b=67.376(3), V = 1805.8(1) 3. The molecular structure consists of trinuclear FeII entities linked together by an unprecedented three-dimensional network of hydrogen bonds. This compound shows a gradual spin crossover behavior centered around room temperature, which has been followed by temperat…

Iron-based Heusler compounds Fe2YZ: Comparison with theoretical predictions of the crystal structure and magnetic properties

The present work reports on the new soft ferromagnetic Heusler phases Fe${}_{2}$NiGe, Fe${}_{2}$CuGa, and Fe${}_{2}$CuAl, which in previous theoretical studies have been predicted to exist in a tetragonal Heusler structure. Together with the known phases Fe${}_{2}$CoGe and Fe${}_{2}$NiGa these materials have been synthesized and characterized by powder x-ray diffraction, ${}^{57}$Fe M\"ossbauer spectroscopy, superconducting quantum interference device, and energy-dispersive x-ray measurements. In particular M\"ossbauer spectroscopy was used to monitor the degree of local atomic order/disorder and to estimate magnetic moments at the Fe sites from the hyperfine fields. It is shown that in con…

Iron Oxide Superparticles with Enhanced MRI Performance by Solution Phase Epitaxial Growth

Organized three-dimensional (3D) nanomaterial architectures are promising candidates for applications in optoelectronics, catalysis, or theranostics owing to their anisotropy and advanced structural features that allow tailoring their physical and chemical properties. The synthesis of such complex but well-organized nanomaterials is difficult because the interplay of interfacial strain and facet-specific reactivity must be considered. Especially the magnetic anisotropy with controlled size and morphology plays a decisive role for applications like magnetic resonance imaging (MRI) and advanced data storage. We present a solution phase seed mediated synthesis of colloidal, well dispersible ir…

Lattice Instability and Competing Spin Structures in the Double Perovskite InsulatorSr2FeOsO6

The semiconductor Sr2FeOsO6, depending on temperature, adopts two types of spin structures that differ in the spin sequence of ferrimagnetic iron-osmium layers along the tetragonal c axis. Neutron powder diffraction experiments, 57Fe Mossbauer spectra, and density functional theory calculations suggest that this behavior arises because a lattice instability resulting in alternating iron-osmium distances fine-tunes the balance of competing exchange interactions. Thus, Sr2FeOsO6 is an example of a double perovskite, in which the electronic phases are controlled by the interplay of spin, orbital, and lattice degrees of freedom.

ChemInform Abstract: Synthesis, Structure and Properties of [Cr2(PS4)4]6-; the First Discrete Transition Metal Cluster from Thiophosphate Flux Reactions.

Canted Antiferromagnetism on Rectangular Layers of Fe2+ in Polymorphic CaFeSeO

From stoichiometric amounts of CaO, Fe, and Se, pure powders and single crystals of quaternary Ca[FeSe2/2O2/2]∞2 can be obtained by solid-state reaction and self-flux growth, respectively. The as-synthesized compound exhibits a polymorphic crystal structure, where the two modifications have different stacking sequences of [FeSe2/2O2/2]2−∞2 layers. The two polymorphs have similar unit cells but different crystal symmetries (Cmc21 and Pnma), of which the former is non-centrosymmetric. Fe is divalent (d6) and high-spin, as proven by X-ray spectroscopy, Mossbauer spectroscopy, and powder neutron diffraction data. The latter two, in combination with magnetic susceptibility and specific heat data…

Synthesis, Structure and Properties of a Mixed Mononuclear/Dinuclear Iron(II) Spin-Crossover Compound with the Ligand 4-(p-Tolyl)-1,2,4-triazole

A new iron(II) compound with the formula [Fe2(L)5(NCS)4]2[Fe(L)2(NCS)2(H2O)2] (I) [where L = 4-(p-tolyl)-1,2,4-triazole] has been synthesized and subjected to X-ray structure determination. Compound I crystallizes in the triclinic space group P–1 (no. 2) with a = 14.5785(11), b = 16.1253(11), c = 16.1963(8) A, α = 80.930(5), β = 85.796(5), γ = 78.132(6)°, V = 3676.2(4) A3. The structure refinement converged to wR2 = 0.172, RF = 0.084. The structure was found to consist of two types of iron-containing structural units, a mononuclear unit and a dinuclear one. The mononuclear unit has a crystallographic inversion centre, and is coordinated by two NCS anions, two triazole N1 nitrogen atoms, and…

A spin transition molecular material with a wide bistability domain.

International audience; [Fe(hyptrz)3](4-chloro-3-nitrophenylsulfonate)22 H2O (1; hyptrz=4-(3-hydroxypropyl)-1,2,4-triazole) has been synthesized and its physical properties have been investigated by several physical techniques including magnetic susceptibility measurements, calorimetry, and Mössbauer, optical, and EXAFS spectroscopy. Compound 1 exhibits a spin transition below room temperature, together with a very wide thermal hysteresis of about 50 K. This represents the widest hysteresis loop ever observed for an FeII-1,2,4-triazole spin transition material. The cooperativity is discussed on the basis of temperature-dependent EXAFS studies and of the structural features of a CuII analogu…

Spin Crossover Phenomenon in Nanocrystals and Nanoparticles of [Fe(3-Fpy)2M(CN)4] (MII = Ni, Pd, Pt) Two-Dimensional Coordination Polymers

The two-dimensional spin crossover (SCO) polymers [Fe(3-Fpy)2M(CN)4] (MII = Ni(1), Pd(2), Pt(3)) were nanostructured in the form of nanocrystals and nanoparticles, and their chemical, structural, and physical characterization was carried out using different experimental methods (powder X-ray diffraction, magnetic susceptibility measurements, Mossbauer and infrared spectroscopy, transmission and scanning electronic microscopy, etc.). Surfactant-free nanocrystals of average dimensions 400 × 400 × 30 nm (1a, 1a*, 2a, 3a) were synthesized from water in oil microemulsions (w/o) while nanoparticles of average size 200 × 100, 100 × 60, and 70 × 30 nm were obtained in poly(vinylpyrrolidone) (PVP) c…

From Single Molecules to Nanostructured Functional Materials: Formation of a Magnetic Foam Catalyzed by Pd@FexO Heterodimers

Multicomponent nanostructures containing purely organic or inorganic as well as hybrid organic–inorganic components connected through a solid interface are, unlike conventional spherical particles, able to combine different or even incompatible properties within a single entity. They are multifunctional and resemble molecular amphiphiles, like surfactants or block copolymers, which makes them attractive for the self-assembly of complex structures, drug delivery, bioimaging, or catalysis. We have synthesized Pd@FexO heterodimer nanoparticles (NPs) to fabricate a macroporous, hydrophobic, magnetically active, three-dimensional (3D), and template-free hybrid foam capable of repeatedly separati…

Structural and magnetic properties of the solid solution series Sr2Fe1–xMxReO6(M = Cr, Zn)

Strong correlations between the electronic, structural and magnetic properties have been found during the study of doped double perovskites Sr2Fe1−xMxReO6 (0 ≤ x ≤ 1, M = Zn, Cr). The interplay between the van Hove singularity and the Fermi level plays a crucial role for the magnetic properties. Cr doping of the parent compound Sr2FeReO6 leads to a non-monotonic behaviour of the saturation magnetization and an enhancement for doping levels up to 10%. The Curie temperatures monotonically increase from 401 to 616 K. In contrast, Zn doping leads to a continuous decrease in the saturation magnetization and the Curie temperatures. Superimposed on the electronic effects is the structural influenc…

Hierachical Ni@Fe2O3superparticles through epitaxial growth of γ-Fe2O3nanorods on: In situ formed Ni nanoplates

One endeavour of nanochemistry is the bottom-up synthesis of functional mesoscale structures from basic building blocks. We report a one-pot wet chemical synthesis of Ni@γ-Fe2O3 superparticles containing Ni cores densely covered with highly oriented γ-Fe2O3 (maghemite) nanorods (NRs) by controlled reduction/decomposition of nickel acetate (Ni(ac)2) and Fe(CO)5. Automated diffraction tomography (ADT) of the Ni-Fe2O3 interface in combination with Mossbauer spectroscopy showed that selective and oriented growth of the γ-Fe2O3 nanorods on the Ni core is facilitated through the formation of a Fe0.05Ni0.95 alloy and the appearance of superstructure features that may reduce strain at the Ni-Fe2O3 …

The effect of Fe doping on superconductivity in ZrRuP

Abstract This work reports the structure and superconducting properties of the superconductor ZrRuP doped with Fe; the ZrRu 1− x Fe x P solid solution was investigated by means of X-ray powder diffraction, SQUID magnetometry and Mosbauer spectroscopy. It is shown that the modification of the superconducting properties by doping with Fe is similar to the effect of chemical pressure and that the Fe doped compounds do not show any magnetic ordering.

Anomalous Spin Transition Observed in Bis(2,6-bis(pyrazol-3-yl)pyridine)iron(II) Thiocyanate Dihydrate

Bis(2,6-bis(pyrazol-3-yl)pyridine)iron(II) thiocyanate dihydrate undergoes a two-step singlet (1A1) ⇄ quintet (5T2) transition in which both steps are associated with thermal hysteresis. Thermal cycling of the sample results in its conversion to a second phase which displays a single-step transition with a very narrow hysteresis loop. This second phase slowly reverts to the initial phase on standing at 300 K. The interconversions are completely reversible. The spin state changes have been monitored by measurement of magnetism and Mossbauer spectra and by differential scanning calorimetry (DSC) studies.

Stoichiometry of LiNiO2 Studied by Mössbauer Spectroscopy

From the 61Ni and 57Fe Mossbauer spectroscopy data follows the cationic site assignment in Li1−x Ni1+x O2. Our data explain the ferromagnetic properties of this material because of the appearance of Ni2+ (S = 1) among Ni3+ (S = 1/2) in Ni3+O2 hexagonal planes. We have no evidence for the ferromagnetic interaction between the NiO2 layers through the excess Ni2+ ions substituting the Li+ ions. The presence of Ni2+ found in the Ni3+O2 planes explains the absence of the Jahn-Teller distortions probably because of the electronic transfer between the Ni3+ and Ni2+ ions.

NQR/NMR and Mössbauer spectroscopy of sulfides: potential and versatility

Nuclear quadrupole resonance (NQR), nuclear magnetic resonance (NMR) and nuclear gamma-resonance (NGR or Mossbauer Effect) methods are generally described as highly sensitive tools in studies of local electronic structure and symmetry in solid-state materials. This is due to high informativity in electronic structure investigations, high resolution in phase-structural diagnostics (down to nano-scale), possibility to study polycrystalline and complex compounds, and to the non-destructive character of these methods. As applied to Earth sciences, both NQR/NMR and Mossbauer spectroscopy methods contribute to mineralogical material science and mineral physics. Another important aspect is the fac…

Strukturaufklärung der Halb-Heusler-Verbindung CoMnSb mit Hilfe von121Sb-Mößbauer-Spektroskopie

The surface chemistry of iron oxide nanocrystals: surface reduction of γ-Fe2O3 to Fe3O4 by redox-active catechol surface ligands

The effect of surface functionalization on the structural and magnetic properties of catechol-functionalized iron oxide magnetic (γ-Fe2O3) nanocrystals was investigated. γ-Fe2O3 nanocrystals (NCs) were synthesized from iron acetyl acetonate in phenyl ether with 1,2-tetradecanediol, oleic acid, and oleylamine. X-ray powder diffraction in combination with Mossbauer spectroscopy revealed the presence of γ-Fe2O3 (maghemite) particles only. Replacement of oleic acid (OA) with catechol-type 3,4-dihydroxyhydrocinnamic acid (DHCA) or polydentate polydopamine acrylate (PDAm) surface ligands leads to a pronounced change of the magnetic behavior of the γ-Fe2O3 nanocrystals and separated them into two …

Tetragonal-to-orthorhombic structural phase transition at 90 K in the superconductor Fe(1.01)Se.

In this Letter we show that superconducting ${\mathrm{Fe}}_{1.01}\mathrm{Se}$ undergoes a structural transition at 90 K from a tetragonal to an orthorhombic phase but that nonsuperconducting ${\mathrm{Fe}}_{1.03}\mathrm{Se}$ does not. High resolution electron microscopy at low temperatures further reveals an unexpected additional modulation of the crystal structure of the superconducting phase that involves displacements of the Fe atoms, and that the nonsuperconducting composition shows a different, complex nanometer-scale structural modulation. Finally, we show that magnetism is not the driving force for the phase transition in the superconducting phase.

Substitution Effects in Double Perovskites: How the Crystal Structure Influences the Electronic Properties

We systematically studied substituted Sr2FeReO6 with respect to experimental characterization and theoretical band structure calculations. In the framework of the tight-binding approach, hole- or electron-doping of Sr2MM’O6 were performed at the M or M’ positions either by transition or main group metals. Hole-doping, rather than electron-doping, has a favorable effect to improve the half-metallicity (Curie temperature and saturation magnetization) of the parent compound. When M is substituted by another metal, the original M’ metal will serve as a redox buffer (and vice versa). Substituting M by another metal with a size similar to that of the metal at M’ position causes disorder, which ha…

Structural and magnetic properties of Fe2CoGa Heusler nanoparticles

Abstract Fe2CoGa Heusler nanoparticles are synthesized by a chemical method. The structure and magnetic properties of Fe2CoGa Heusler nanoparticles are investigated by x-ray diffraction, extended x-ray absorption fine structure and Mössbauer spectroscopy. The crystal structure of Fe2CoGa nanoparticles is described by the X-type structure (prototype: Li2AgSb). Magnetic measurements reveal the presence of small Fe2CoGa nanoparticles and lower magnetic moments compared with the theoretically predicted values.

Determining Magnetite/Maghemite Composition and Core–Shell Nanostructure from Magnetization Curve for Iron Oxide Nanoparticles

Iron oxide magnetic nanoparticles produced by chemical synthesis are usually composed of both magnetite and maghemite phases. Information about the phase composition is typically obtained using Mos...

dsRNA-funktionalisierte γ-Fe2O3-Nanokristalle: ein Instrument zur gezielten Adressierung von Rezeptoren an der Zelloberfläche

Pressure-induced electron transfer in ferrimagnetic Prussian blue analogs

M\"ossbauer and magnetic susceptibility measurements were performed under pressure on three Prussian blue analogs, ${\mathrm{K}}_{0.1}{\mathrm{Co}}_{4}[{\mathrm{Fe}(\mathrm{CN})}_{6}{]}_{2.7}\ensuremath{\cdot}18{\mathrm{H}}_{2}\mathrm{O},$ ${\mathrm{K}}_{0.28}{\mathrm{Co}}_{4}[{\mathrm{Fe}(\mathrm{CN})}_{6}{]}_{2.76}\ensuremath{\cdot}18{\mathrm{H}}_{2}\mathrm{O},$ and ${\mathrm{Cs}}_{0.7}{\mathrm{Co}}_{4}[{\mathrm{Fe}(\mathrm{CN})}_{6}{]}_{2.9}\ensuremath{\cdot}16{\mathrm{H}}_{2}\mathrm{O}.$ A pressure-induced electron transfer ${\mathrm{Co}}^{2+}(S=\frac{3}{2})\ensuremath{-}{\mathrm{Fe}}^{3+}(S=\frac{1}{2})\ensuremath{\rightarrow}{\mathrm{Co}}^{3+}(S=0)\ensuremath{-}{\mathrm{Fe}}^{2+}(S=0)…

Density of Phonon States in Superconducting FeSe as a Function of Temperature and Pressure

The temperature and pressure dependence of the partial density of phonon states (phonon-DOS) of iron atoms in superconducting ${\text{Fe}}_{1.01}\text{Se}$ was studied by $^{57}\text{F}\text{e}$ nuclear inelastic scattering. The high-energy resolution allows for a detailed observation of spectral properties. A sharpening of the optical phonon modes and shift of all spectral features toward higher energies by $\ensuremath{\sim}4\mathrm{%}$ with decreasing temperature from 296 to 10 K was found. However, no detectable change at the tetragonal--orthorhombic phase transition around 100 K was observed. Application of a pressure of 6.7 GPa, connected with an increase in the superconducting temper…

Understanding the Stability and Recrystallization Behavior of Amorphous Zinc Phosphate

Zinc phosphate, an important pigment in phosphate conversion coatings, forms protective films on rubbing surfaces. We have simulated the underlying reactions under shear by ball-milling zinc phosphate and monitored the reaction of hopeite (Zn3(PO4)2·4H2O) and the retarded recrystallization of the amorphous reaction product by powder X-ray diffraction (PXRD) and quantitative infrared (IR) spectroscopy. Abrasion of stainless steel was simulated by addition of pure 57Fe. The results provide insight into the chemistry of phosphate conversion coatings or during battery cycling of metal phosphates and give theoretical guidance for the preparation of amorphous phosphates. Thermal analysis revealed…

Indefinitely stable iron(IV) cage complexes formed in water by air oxidation

In nature, iron, the fourth most abundant element of the Earth's crust, occurs in its stable forms either as the native metal or in its compounds in the +2 or +3 (low-valent) oxidation states. High-valent iron (+4, +5, +6) compounds are not formed spontaneously at ambient conditions, and the ones obtained synthetically appear to be unstable in polar organic solvents, especially aqueous solutions, and this is what limits their studies and use. Here we describe unprecedented iron(IV) hexahydrazide clathrochelate complexes that are assembled in alkaline aqueous media from iron(III) salts, oxalodihydrazide and formaldehyde in the course of a metal-templated reaction accompanied by air oxidation…

Effect of cation disorder on the magnetic properties ofSr2Fe1−xGaxReO6(0<x<0.7)double perovskites

The effect of diamagnetic dilution of the Fe sublattice on the structural and magnetic properties of the double perovskite Sr{sub 2}Fe{sub 1-x}Ga{sub x}ReO{sub 6} (0 =}0.4 is detected by x-ray structural analysis accompanied by the observation of a magnetically ordered and a paramagnetic phase in the corresponding Moessbauer spectra. Below 20% Ga content, Ga statistically dilutes the -Fe-O-Re-O-Fe- double-exchange pathways. Phase separation begins at 20% Ga substitution; between 20% and 40% ofmore » Ga content, the paramagnetic Ga-based phase does not contain any Fe. The Fe-containing, paramagnetic cubic phases which can be detected by Moessbauer spectroscopy first appear for x=0.4.« less

Cooperative High-Temperature Spin Crossover Accompanied by a Highly Anisotropic Structural Distortion

Spin transitions are a spectacular example of molecular switching that can provoke extreme electronic and structural reorganizations in coordination compounds. A new 3D cyanoheterometallic framework, [Fe(pz)(Au(CN)2)2], has been synthesized in which a highly cooperative spin crossover has been observed at 367 and 349 K in heating and cooling modes, respectively. Mössbauer spectroscopy revealed a complete transition between the diamagnetic and paramagnetic states of the iron centres. The low-spin-to-high-spin transition induced a drastic structural distortion involving a large one-directional expansion (ca. 10.6%) and contraction (ca. 9.6%) of the lattice. Negative thermal expansion along th…

Controlling phase formation in solids: rational synthesis of phase separated Co@Fe2O3 heteroparticles and CoFe2O4 nanoparticles

A wet chemical approach from organometallic reactants allowed the targeted synthesis of Co@Fe(2)O(3) heterodimer and CoFe(2)O(4) ferrite nanoparticles. They display magnetic properties that are useful for magnetic MRI detection.

“Supramolecular” Solid-State Chemistry: Interpenetrating Diamond-Type Frameworks of U4+ Ions Linked byS,S′-Bidentate P2S62− Molecular Rods in UP4S12

Inseparably interwoven are three independent polymeric diamond-type U(P2 S6 )2 frameworks in the structure of the title compound. The linear P2 S6 units act as molecular rods linking the pseudotetrahedral U4+ centers. U(P2 S6 )2 may be viewed as a coordination polymer which is formed from U/P/S melts by the solid-state equivalent of the self-assembly reactions in solution.

Lattice Instability and Competing Spin Structures in the Double Perovskite Insulator Sr2FeOsO6

The semiconductor Sr2FeOsO6, depending on temperature, adopts two types of spin structures that differ in the spin sequence of ferrimagnetic iron - osmium layers along the tetragonal c-axis. Neutron powder diffraction experiments, 57Fe M\"ossbauer spectra, and density-functional theory calculations suggest that this behavior arises because a lattice instability resulting in alternating iron-osmium distances fine-tunes the balance of competing exchange interactions. Thus, Sr2FeOsO6 is an example for a double perovskite, in which the electronic phases are controlled by the interplay of spin, orbital, and lattice degrees of freedom.

Enantioselective Guest Effect on the Spin State of a Chiral Coordination Framework

The diversity of spin crossover (SCO) complexes that, on the one hand, display variable temperature, abruptness and hysteresis of the spin transition, and on the other hand, are spin-sensitive to the various guest molecules, makes these materials unique for the detection of different organic and inorganic compounds. We have developed a homochiral SCO coordination polymer with a spin transition sensitive to the inclusion of the guest 2-butanol, and these solvates with (R)- and (S)-alcohols demonstrate different SCO behaviours depending on the chirality of the organic analyte. A stereoselective response to the guest inclusion is detected as a shift in the temperature of the transition both fr…

Diferrocenyl tosyl hydrazone with an ultrastrong NHFe hydrogen bond as double click switch.

The intramolecular NH⋯Fe hydrogen bond in diferrocenyl hydrazone 2 raises the barrier for intramolecular electron transfer in its mixed-valent cation 2+ and is only disrupted by double oxidation to 22+.

Spin Crossover in a Supramolecular Fe4II [2×2] Grid Triggered by Temperature, Pressure, and Light

A multiplex electronic switch on the molecular level has been realized by using a tetranuclear FeII complex of the [2×2] grid type. The four metal ions can be switched stepwise between their high-spin and low-spin states by temperature, pressure, and light, thus representing a triple level, triple switch system as illustrated in the picture.

Phase separation in superconducting and antiferromagneticRb0.8Fe1.6Se2probed by Mössbauer spectroscopy

${}^{57}$Fe-M\"ossbauer studies of superconducting Rb${}_{0.8}$Fe${}_{1.6}$Se${}_{2.0}$ with ${T}_{C}$ $=$ 32.4 K were performed on single-crystalline and polycrystalline samples in the temperature range 4.2--295 K. They reveal the presence of 88% magnetic and 12% nonmagnetic Fe${}^{2+}$ species with the same polarization dependence of their hyperfine spectra. The magnetic species are attributed to the 16$i$ sites of the $\sqrt{5}\ifmmode\times\else\texttimes\fi{}\sqrt{5}\ifmmode\times\else\texttimes\fi{}1$ superstructure and the nonmagnetic Fe species to a nanosized phase observed in recent structural studies of superconducting K${}_{x}$Fe${}_{2\ensuremath{-}}$${}_{y}$Se${}_{2}$ systems ra…

Metal-to-metal electron transfer and magnetic interactions in a mixed-valence Prussian Blue analogue

Abstract In search of a new Prussian Blue analogue exhibiting fascinating magnetic properties, potassium manganese hexacyanoferrate, K 0.2 Mn 0 . 66 II Mn 1.44 III [ Fe 0.2 II Fe 0.8 III ( CN ) 6 ] O 0.66 ( CH 3 COO ) 1.32 ] , 7.6H2O, has been synthesized. This compound undergoes a paramagnetic to ferrimagnetic transition at 10 K. Temperature and magnetic field-dependent magnetization studies of this compound have revealed different spin alignments below and above 3 K. The nature of possible magnetic interactions between the nearest neighbor magnetic centers has been discussed in order to explore the origin of the observed magnetic interactions. Mossbauer spectroscopic study at different te…

Weak itinerant ferromagnetism and electronic and crystal structures of alkali-metal iron antimonides: NaFe4Sb12andKFe4Sb12

The synthesis, chemical, structural, and magnetic properties of alkali-metal compounds with filled-skutterudite structure, $\mathrm{Na}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$ and $\mathrm{K}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$, are described. X-ray and neutron diffraction and elemental analysis established the crystal structure without defects and disorder on the cation site. The temperature and pressure dependence of the cubic unit cell of $\mathrm{Na}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$ and the displacement parameter of Na are investigated. The electronic structure is calculated by density functional methods (LMTO, FPLO). Quantum chemical calculations (electron localization function) reveal …

Spin transition in [Fe(phen)2(NCS)2] - �SR study

The reversible thermal spin transition which occurs in [Fe(phen)(2)(NCS)(2)] around T-1/2 similar to 177 K has been investigated by muon spin relaxation (muSR) (similar to10-280 K). The depolarisation curves are well described by two Lorentzian lines represent fast and slow components in the decay curves, with the initial asymmetry parameter of the fast component found to track the spin transition in [Fe(phen)2(NCS),]. Comparison of zero-field and transverse field (20 Oe) muSR measurements shows that diamagnetic muonic species occur over the entire temperature range.

Pressure effect on superconductivity in FeSe0.5Te0.5

Due to the simple layered structure, isostructural FeSe and FeSe0.5Te0.5 are clue compounds for understanding the principal mechanisms of superconductivity in the family of Fe-based superconductors. High-pressure magnetic, structural and Mossbauer studies have been performed on single-crystalline samples of superconducting FeSe0.5Te0.5 with Tc = 13.5 K. Susceptibility data have revealed a strong increase of Tc up to 19.5 K for pressures up to 1.3 GPa, followed by a plateau in the Tc(p) dependence up to 5.0 GPa. Further pressure increase leads to a disappearance of the superconducting state around 7.0 GPa. X-ray diffraction and Mossbauer studies explain this fact by a tetragonal-to-hexagonal…

Pressure-Induced High Spin State in [Fe(btr)2(NCS)2]·H2O (btr = 4,4′-bis-1,2,4-triazole)

Application of hydrostatic pressure (≤ 10.5 kbar) on the two-dimensional spin transition compound [Fe(btr)2(NCS)2]·H2O (btr = 4,4‘-bis-1,2,4-triazole) results in an unexpected stabilization of the HS state. On release of the pressure, the HS state is found to be partially trapped. After thermal relaxation of the metastable HS state obtained by the LIESST effect (light-induced excited spin state trapping), a pure LS state is obtained in contrast to the pressure experiments. This different behavior supports a structural phase transition as the likely basis of the pressure-induced HS state.

Off-stoichiometry in Co2FeSi thin films sputtered from stoichiometric targets revealed by nuclear magnetic resonance

Co2FeSi is predicted to be a half-metallic ferromagnet with an extraordinary high magnetic moment and Curie temperature. However, a low tunnel magneto-resistance ratio, a lower spin polarization and a lower magnetic moment were experimentally observed in thin film samples. Consequently, thin Co2FeSi films of different groups were studied using spin-echo nuclear magnetic resonance (NMR). NMR probes the local hyperfine fields of the active atoms, which strongly depend on the local environment. NMR is thus able to reveal the next neighbouring shells of the Co-59 nuclei in the Co2FeSi thin films. As expected, our NMR study shows the main resonance line corresponding to Co-59 nuclei in the L2(1)…

Co–Co and Co–Fe cyano-bridged pentanuclear clusters based on a methylpyrazinyl-diamine tetradentate ligand: spin crossover and metal substitution effects

A pentanuclear [CoII3CoIII2] cluster complex has been developed by a solvothermal synthesis. Its highly stable metal-mixed Fe–Co derivatives display robust spin crossover (T1/2 = 268 K) controlled by the degree of substitution.

Fabrication of a Silica Coating on Magnetic γ-Fe2O3 Nanoparticles by an Immobilized Enzyme

Silicatein, a hydrolytic protein encountered in marine sponges, was immobilized on maghemite (γ-Fe2O3) nanoparticles that were surface functionalized with a reactive mulfunctional polymer. This polymer carries an anchor group based on dopamine which is capable of binding to the γ-Fe2O3 surface and a reactive functional group which allows binding of various biomolecules onto inorganic nanoparticles. This functional nitrilotriacetic acid (NTA) group allows immobilization of His-tagged silicatein on the surface of the γ-Fe2O3 nanoparticles. The surface-bound protein retains its native hydrolytic activity to catalyze formation of silica through copolymerization of alkoxysilanes Si(OR)4. Functio…

Magnetic polyorganosiloxane core–shell nanoparticles: Synthesis, characterization and magnetic fractionation

Abstact Here, we present the synthesis, characterization and magnetic separation of magnetic polyorganosiloxane nanoparticles. Magnetic iron oxide nanoparticles with average particle radii of 3.2 nm had been synthesized by a simple coprecipitation process of iron(II) and iron(III) salt in basic solution. Afterwards, the particles were successfully incorporated into a polyorganosiloxane network via a polycondensation reaction of trimethoxymethylsilane (T), diethoxydimethylsilane (D) and the functional monomer (chloromethylphenyl)trimethoxysilane (ClBz-T) in aqueous dispersion. A core–shell system was chosen to increase the flexibility of the system concerning size, composition and functional…

Direct monitoring of spin state in dinuclear iron(II) coordination compounds

So far there has been no direct method to determine the spin state of molecules in dinuclear iron(II) compounds. The molecular fractions of high-spin (HS) and low-spin (LS) species have been deduced from magnetic susceptibility and zero-field Mossbauer spectroscopy data irrespective of whether they belong to LS–LS, LS–HS and HS–HS pairs. However, the distinction of pairs becomes possible if Mossbauer measurements are carried out in an external magnetic field. The proposed method opens new possibilities in the study of spin crossover phenomena in dinuclear compounds.

Spin crossover star-shaped metallomesogens of iron(II).

Three new types of spin crossover (SCO) metallomesogens of Fe-II based on symmetric tripod ligands and their magnetic and structural properties are reported here. These were obtained by condensation of tris(2-aminoethyl)-amin (tren) with the aldehyde derived from 3-alkoxy-6-methylpyridine (mpyN, N (number of carbon atoms in n-alkyl chains) = 8, 18), 1-alkyl-1H-imidazole (imN, N = 4, 16, 18, 20, 22), or 1-alkyl-1H-benzimidazole (bimN, N = 6, 14, 16, 18, 20). A complex derived from 1-octadecyl-1H-naphtho[2,3-d]imidazole (nim18) retains the high spin state at any temperature. Single crystals of the short-chain complexes were investigated by a combination of X-ray crystallography, magnetic meas…

Spin-State-Dependent Redox-Catalytic Activity of a Switchable Iron(II) Complex

The spin state of catalytically active 3d metal centers plays a significant role for their activity in enzymatic processes and organometallic catalysis. Here we report on the catalytic activity of a Fe(II) coordination compound that can undergo a cooperative switch between low-spin (LS) and high-spin (HS) states. Catalytic measurements within 291 - 318 K temperature region reveal a drastic drop of the catalytic activity upon conversion of metallic centers from the LS to the HS form. For a thermoswitchable [Fe(NH2trz)3]Br2 complex (Tup = 305 K), an activation energy is found to be considerably lower for the LS state (158 kJ mol-1) comparing to the HS state (305 kJ mol-1). Mossbauer analysis …

Coexistence of spin-crossover and antiferromagnetic coupling phenomena in the novel dinuclear Fe(II) complex [Fe(dpa)(NCS)2]2bpym

Abstract The iron(II) spin crossover dinuclear compound [Fe(dpa)(NCS) 2 ] 2 bpym where dpa = 2,2 ′ -dipyridylamine and bpym = 2,2 ′ -bipyrimidine has been synthesized and characterized. Variable-temperature magnetic susceptibility and 57 Fe Mossbauer spectroscopy data provide evidence for a rather complete and continuous S=2 ( HS )↔S=0 (LS) spin-crossover behavior taking place in the temperature range 400–50 K (T 1/2 =245 K ) without the presence of a plateau at 50% of conversion. The absence of such plateau, which is characteristic of all dinuclear compounds so far studied, is interpreted in terms of synergetic effect between intramolecular and intermolecular interactions.

Polymorphism and Pressure Driven Thermal Spin Crossover Phenomenon in [Fe(abpt)2(NCX)2] (X=S, and Se): Synthesis,Structure and Magnetic Properties

The monomeric compounds [Fe(abpt 2(NCX)2(X = S (1), Se (2) and abpt = 4-amino- 3,5-bis(pyridin-2-yl)-1,2,4-triazole) have been synthesized and characterized. They crystallize in the monoclinic P21/n space group with a = 11.637(2) A, b = 9.8021(14) A, c = 12.9838(12) A, β = 101.126(14)°, and Z=2 for 1, and a= 11.601(2) A, b = 9.6666(14) A, c = 12.883(2) A, β = 101.449(10)°, and Z = 2 for 2. The unit cell contains a pair mononuclear [Fe(abpt)2(NCX)21 units related by a center of symmetry. Each iron atom, located at a molecular inversion center, is in a distorted octahedral environment. Four of the six nitrogen atoms coordinated to the Fe(II) ion belong to the pyridine-N(1) and triazole-N(2) r…

Pressure effect on superconductivity in FeSe0.5Te0.5

Due to the simple layered structure, isostructural FeSe and FeSe0.5Te0.5 are clue compounds for understanding the principal mechanisms of superconductivity in the family of Fe-based superconductors. High-pressure magnetic, structural and M\"ossbauer studies have been performed on single-crystalline samples of superconducting FeSe0.5Te0.5 with Tc = 13.5 K. Susceptibility data have revealed a strong increase of Tc up to 19.5 K for pressures up to 1.3 GPa, followed by a plateau in the Tc(p) dependence up to 5.0 GPa. Further pressure increase leads to a disappearance of the superconducting state around 7.0 GPa. X-ray diffraction and M\"ossbauer studies explain this fact by a tetragonal-to-hexag…

Probing the Size Effect of Co2FeGa-SiO2@C Nanocomposite Particles Prepared by a Chemical Approach

In this contribution, we report the chemical synthesis of carbon coated, silica supported Co2FeGa (Co2FeGa-SiO2@C) nanocomposite particles. The particle size of Co2FeGa particles can be tuned by varying the amount of silica supports. The dependences of the crystal structure and magnetic properties on particle size have been investigated by synchrotron radiation based X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) spectroscopy, transmission electron microscope (TEM), 57Fe Mossbauer spectroscopy, and superconducting quantum interference device (SQUID). The superparamagnetic critical size of Co2FeGa Heusler nanoparticles is found to be ∼17 nm by correlating the TEM derived par…

Geometric, electronic, and magnetic structure ofCo2FeSi: Curie temperature and magnetic moment measurements and calculations

In this work a simple concept was used for a systematic search for materials with high spin polarization. It is based on two semiempirical models. First, the Slater-Pauling rule was used for estimation of the magnetic moment. This model is well supported by electronic structure calculations. The second model was found particularly for ${\mathrm{Co}}_{2}$ based Heusler compounds when comparing their magnetic properties. It turned out that these compounds exhibit seemingly a linear dependence of the Curie temperature as function of the magnetic moment. Stimulated by these models, ${\mathrm{Co}}_{2}\mathrm{FeSi}$ was revisited. The compound was investigated in detail concerning its geometrical…

Pressure induced increase in Tc for the organic-based magnet FeII(TCNE)2 (TCNE=tetracyanoethylene)

Abstract Pressure dependent magnetization and 57Fe Mossbauer studies were performed on Fe(TCNE)[C4(CN)8]1/2·zCH2Cl2 (TCNE = tetracyanoethylene). Pressure did not influence the Mossbauer parameters in paramagnetic state. Mossbauer data reveals the onset of magnetic ordering at 130 K and significant enhancement of the magnetic ordering temperature from 100 to 150 K accompanied by an increase of the spontaneous magnetization, which is higher than reported from the magnetic data, and application of pressure induces the reversible formation of a new, metastable magnetic species. These changes suggest an increase of the dimensionality of magnetic interaction, i.e., stronger interlayer coupling. A…

Einfluss des Sauerstoffgehalts auf die physikalischen Eigenschaften von Sr2MO3Cl (M = Fe, Co)

Spin Crossover in Fe(II)–M(II) Cyanoheterobimetallic Frameworks (M = Ni, Pd, Pt) with 2-Substituted Pyrazines

Discovery of spin-crossover (SCO) behavior in the family of Fe(II)-based Hofmann clathrates has led to a "new rush" in the field of bistable molecular materials. To date this class of SCO complexes is represented by several dozens of individual compounds, and areas of their potential application steadily increase. Starting from Fe(2+), square planar tetracyanometalates M(II)(CN)4(2-) (M(II) = Ni, Pd, Pt) and 2-substituted pyrazines Xpz (X = Cl, Me, I) as coligands we obtained a series of nine new Hofmann clathrate-like coordination frameworks. X-ray diffraction reveals that in these complexes Fe(II) ion has a pseudo-octahedral coordination environment supported by four μ4-tetracyanometallat…

ChemInform Abstract: “Supramolecular” Solid-State Chemistry: Interpenetrating Diamond-Type Frameworks of U4+ Ions Linked by S,S′-Bidentate P2S2-6 Molecular Rods in UP4S12.

Pressure-induced magnetic collapse and metallization of TlFe1.6Se2

The crystal structure, magnetic ordering, and electrical resistivity of $\mathrm{TlF}{\mathrm{e}}_{1.6}\mathrm{S}{\mathrm{e}}_{2}$ were studied at high pressures. Below $\ensuremath{\sim}7\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$, $\mathrm{TlF}{\mathrm{e}}_{1.6}\mathrm{S}{\mathrm{e}}_{2}$ is an antiferromagnetically ordered semiconductor with a $\mathrm{ThC}{\mathrm{r}}_{2}\mathrm{S}{\mathrm{i}}_{2}$-type structure. The insulator-to-metal transformation observed at a pressure of $\ensuremath{\sim}7\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ is accompanied by a loss of magnetic ordering and an isostructural phase transition. In the pressure range $\ensuremath{\sim}7.5\text{--}11\phantom{\rule{…

Pressure-restored superconductivity in Cu-substituted FeSe

Copper doping of FeSe destroys its superconductivity at ambient pressure, even at low doping levels. Here we report the pressure-dependent transport and structural properties of Fe${}_{1.01\ensuremath{-}x}$Cu${}_{x}$Se with 3$%$ and 4$%$ Cu doping and find that the superconductivity is restored. Metallic resistivity behavior, absent in Cu-doped FeSe, is also restored. At the low pressure of 1.5 GPa, superconductivity is seen at 6 K for 4$%$ Cu doping, somewhat lower than the 8 K ${T}_{c}$ of undoped FeSe. ${T}_{c}$ reaches its maximum of 31.3 K at 7.8 GPa, lower than the maximum superconducting temperature in the undoped material under pressure (${T}_{c}$ max of 37 K) but still very high. X…

Mössbauer investigation of the photoexcited spin states and crystal structure analysis of the spin-crossover dinuclear complex [{Fe(bt)(NCS)(2)}(2)bpym] (bt=2,2'-bithiazoline, bpym=2,2'-bipyrimidine).

The crystal structure of the complex [{Fe(bt)(NCS)(2)}(2)bpym] (1) (bt=2,2'-bithiazoline, bpym=2,2'-bipyrimidine) has been solved at 293, 240, 175 and 30 K. At all four temperatures the crystal remains in the P space group with a=8.7601(17), b=9.450(2), c=12.089(3) A, alpha=72.77(2), beta=79.150(19), gamma=66.392(18) degrees , V=873.1(4) Angstrom(3) (data for 293 K structure). The structure consists of centrosymmetric dinuclear units in which each iron(II) atom is coordinated by two NCS(-) ions in the cis position and two nitrogen atoms of the bridging bpym ligand, with the remaining positions occupied by the peripheral bt ligand. The iron atom is in a severely distorted octahedral FeN(6) e…

Spin Crossover in Fe(II) Molecular Compounds — Mössbauer and µSR Investigations

The compound [Fe(ptz)6](C104)2 (ptz = 1-propyl-tetrazole) displays a complete and gradual spin crossover centred around 125 K as evidenced by magnetic and muon measurements over the temperature range ∼ 4.2–300 K. Although the crystal structure reveals only one crystallographic site, line broadening is observed in the Mossbauer spectra in the vicinity of the spin transition. The muon spin relaxation behaviour of this compound indicates that a structural transformation rather than dynamic processes may account for the observed spectral features. Both the Mossbauer and muon measurements are consistent with a mixture of high and low spin Fe ions in the transition region.

Self‐Organized Arrays of SnO 2 Microplates with Photocatalytic and Antimicrobial Properties

Coordination of expanded terpyridine ligands to cobalt

Abstract The tridentate expanded terpyridine-like ligand N,N′-dimethyl-N,N′-dipyridin-2-yl-pyridin-2,6-diamine (ddpd) and [Co(H2O)6](BF4)2 give the high-spin complex mer-[Co(ddpd)2](BF4)2 with a tetragonally compressed CoN6 coordination geometry according to X-ray diffraction and SQUID measurements. UV–Vis–NIR spectra indicate a large ligand field splitting close to the high-spin/low-spin crossover point. Oxidation of the CoII complex to CoIII is achieved with silver triflate. The self exchange between high-spin CoII and low-spin CoIII is slow on the NMR time scale.

Heusler compounds as ternary intermetallic nanoparticles: Co2FeGa

This work describes the preparation of ternary nanoparticles based on the Heusler compound Co2FeGa. Nanoparticles with sizes of about 20?nm were synthesized by reducing a methanol impregnated mixture of CoCl2 ? 6H2O, Fe(NO3)3 ? 9H2O and Ga(NO3)3 ? xH2O after loading on fumed silica. The dried samples were heated under pure H2 gas at 900??C. The obtained nanoparticles?embedded in silica?were investigated by means of x-ray diffraction (XRD), transmission electron microscopy, temperature dependent magnetometry and M??bauer spectroscopy. All methods clearly revealed the Heusler-type L21 structure of the nanoparticles. In particular, anomalous XRD data demonstrate the correct composition in addi…

Extreme sensitivity of superconductivity to stoichiometry in Fe1+?Se

The recently discovered iron arsenide superconductors appear to display a universal set of characteristic features, including proximity to a magnetically ordered state and robustness of the superconductivity in the presence of disorder. Here we show that superconductivity in Fe1+?Se, which can be considered the parent compound of the superconducting arsenide family, is destroyed by very small changes in stoichiometry. Further, we show that nonsuperconducting Fe1+?Se is not magnetically ordered down to 5 K. These results suggest that robust superconductivity and immediate instability against an ordered magnetic state should not be considered as intrinsic characteristics of iron-based superco…

Effect of pressure on superconductivity in NaAlSi

The ternary superconductor NaAlSi, isostructural with LiFeAs, the ``111'' iron pnictide superconductor, is investigated under pressure. The structure remains stable up to 15 GPa. Resistivity and susceptibility measurements show an increase of ${T}_{c}$ up to 2 GPa, followed by a decrease until superconductivity disappears at 4.8 GPa. Band structure calculations show that pressure should have a negligible effect on the electronic structure and the Fermi surface and thus the disappearance of superconductivity under pressure must have a different origin. We compare the electronic structure of NaAlSi under pressure with that of nonsuperconducting isostructural NaAlGe.

Electroless synthesis of lepidocrocite (γ-FeOOH) nanotubes in ion track etched polycarbonate templates

In this study, we describe the electroless synthesis of lepidocrocite (γ-FeOOH) nanotubes produced in ion track etched polycarbonate foils. The foils act as templates after they had been irradiated with heavy ions to produce latent tracks that were etched with a desired diameter. Templates are used to fabricate shape formed 1D nanostructures in general. The synthesis of lepidocrocite nanotubes was carried out in a simple two-step method: firstly, particles were formed by precipitation in aqueous solution; secondly, nanotubes were produced by the deposition of the particles inside the nanochannels of the polycarbonate template. Solvent effects were considered to achieve homogeneous growth re…

Multiple spin phases in a switchable Fe(ii) complex: polymorphism and symmetry breaking effects

Polymorphism in spin-crossover (SCO) compounds allows accessing additional forms of switchable materials with diverse transition properties. We have prepared three polymorphs of a new complex [FeLBr(dca)2], where LBr is N,N′-bis[(5-bromo-2-pyridyl)methyl]ethane-1,2-diamine and dca is dicyanamide. They display different SCO properties: the α-form displays a hysteretic one-step switch centered at 134 K, the β-form undergoes hysteretic two-step spin transition with a plateau (T1/2 = 153 and 144 K) and the γ-form remains high spin (HS) over the whole temperature region. The kinetic origin of the hysteresis loop was demonstrated in temperature rate dependent magnetic measurements. Spin transitio…

Structural properties of the quaternary Heusler alloy Co2Cr1−xFexAl

The quarternary substitutional series Co2Cr1?xFexAl was investigated by means of surface and bulk sensitive techniques in order to exploit its structural and compositional properties. Both bulk and powder samples of the alloy series were investigated to obtain specific information about this material.The long range order was determined by means of x-ray diffraction and neutron diffraction, while the site specific (short range) order was proved by extended x-ray absorption fine structure spectroscopy. The magnetic structure was investigated by M?ssbauer spectroscopy in transmission and scattering modes in order to compare and separate powder and bulk properties. The chemical composition was …

Spin Transition Molecular Materials: New Sensors

This short review article concerns a new family of iron(II) spin transition chain compounds containing 4-R-1,2,4-triazole derivatives whose properties have been followed by several physical techniques. A clear evidence of the LIESST effect at 20 K has been found for one of these materials by 57Fe Mossbauer spectroscopy. Potential applications in terms of pressure and thermal sensors are discussed.

Pd@Fe2O3 Superparticles with Enhanced Peroxidase Activity by Solution Phase Epitaxial Growth

Compared to conventional deposition techniques for the epitaxial growth of metal oxide structures on a bulk metal substrate, wet-chemical synthesis based on a dispersible template offers advantages such as low cost, high throughput, and the capability to prepare metal/metal oxide nanostructures with controllable size and morphology. However, the synthesis of such organized multicomponent architectures is difficult because the size and morphology of the components are dictated by the interplay of interfacial strain and facet-specific reactivity. Here we show that solution-processable two-dimensional Pd nanotetrahedra and nanoplates can be used to direct the epitaxial growth of γ-Fe2O3 nanoro…

Structural transitions under high-pressure in a langasite-type multiferroic Ba3TaFe3Si2O14

Abstract The iron containing langasite family compound Ba3Ta57Fe3Si2O14 was studied at high pressure up to 30 GPa at room temperature by means of in situ X-ray diffraction, Raman and Mossbauer spectroscopies in diamond anvil cell. Two structural transitions at pressures ∼5 and ∼20 GPa are observed. At ∼5 GPa, the low-pressure trigonal P321 phase undergoes phase transition to the most likely P3 structure as manifested by slight increase in the c/a ratio and by anomalies of the Mossbauer and Raman spectra parameters. At ∼20 GPa, the first order phase transition to monoclinic structure occurred with a drop of unit cell volume by 9%. The appearance of the ferroelectric state at such transitions…

FeMoO4 Revisited: Crosslike 90° Noncollinear Antiferromagnetic Structure Caused by Dzyaloshinskii–Moriya Interaction

The ground state of Fe2+ (S = 2) in α- and β-FeMoO4 is investigated by experiments including X-ray diffraction, Raman scattering, and 57Fe–Mossbauer spectroscopy below 300 K and evaluated by theore...

Haloperoxidase Mimicry by CeO2−xNanorods Combats Biofouling

CeO2-x nanorods are functional mimics of natural haloperoxidases. They catalyze the oxidative bromination of phenol red to bromophenol blue and of natural signaling molecules involved in bacterial quorum sensing. Laboratory and field tests with paint formulations containing 2 wt% of CeO2-x nanorods show a reduction in biofouling comparable to Cu2 O, the most typical biocidal pigment.

Conventional superconductivity at 203 kelvin at high pressures in the sulfur hydride system.

A superconductor is a material that can conduct electricity without resistance below a superconducting transition temperature, Tc. The highest Tc that has been achieved to date is in the copper oxide system: 133 kelvin at ambient pressure and 164 kelvin at high pressures. As the nature of superconductivity in these materials is still not fully understood (they are not conventional superconductors), the prospects for achieving still higher transition temperatures by this route are not clear. In contrast, the Bardeen-Cooper-Schrieffer theory of conventional superconductivity gives a guide for achieving high Tc with no theoretical upper bound--all that is needed is a favourable combination of …

Reactivity and Structural Defects in Glaserite-Type Iron-Vanadates

In situ— High Temperature Mössbauer Spectroscopy of Iron Nitrides and Nitridoferrates

The stoichiometric iron nitrides γ′-Fe4N, e-Fe3N and ζ-Fe2N were characterized by Mossbauer spectroscopy. The thermal decomposition of e-Fe3N was studied in-situ by means of a specially developed Mossbauer furnace. We found e-Fe3N to γ′-Fe4N and e-Fe3Nx (x ≥ 1.3) as decomposition products and determined the border of γ′/e transformation at T ≅ 930 K. Mossbauer spectroscopy was applied to study in-situ the thermal decomposition of the nitridometalate Li3[FeIIIN2] and the formation of Li2[(Li1-xFeIx)N], the compound with the largest local magnetic field ever observed in an iron containing material. The kinetics of formation and the stability of Li2[(Li1-xFeIx)N] was of particular interest in …

Multifunctionality in spin crossover materials

Abstract One of the most important trends in the spin crossover (SCO) field is focused on the synthesis of new molecule-based functional materials in which the SCO properties may be combined with other physical or chemical properties in a synergic fashion. The current stage of investigations regarding interplay and synergic effects between SCO, magnetic coupling, liquid crystalline properties, host–guest interactions, non-linear optical properties, electrical conductivity, and ligand isomerization is highlighted and discussed.

Magnetic properties of GdPdSb and GdNiSb studied by 155Gd-Mössbauer spectroscopy

Abstract 155 Gd-Mossbauer spectroscopy was applied to study the magnetic properties of GdPdSb with hexagonal LiGaGe structure and of GdNiSb in the cubic MgAgAs-type structure as well as in the hexagonal AlB 2 -type structure. In GdPdSb magnetic ordering is observed at 13.0 K with indications of a tilted spin structure at lower temperatures. In the cubic phase of GdNiSb magnetic ordering is observed at 9.5 K and in the hexagonal phase around 3.5 K. These results are discussed in conjunction with previous investigations of these samples.

Structure and electrical resistivity of mixed-valent EuNi2P2 at high pressure.

The structural properties and electrical resistivity of homogeneous mixed-valent EuNi2P2 are studied at pressures up to 45 GPa. No structural phase transition is observed in the whole pressure range and the overall pressure behavior of the structural parameters is similar to that of related compounds in the collapsed tetragonal ThCr2Si2-type structure. Electrical resistivity measured up to 31 GPa at temperatures between 4 and 300 K exhibits continuous changes from the behavior typical for a mixed-valent Eu system to that of a normal metallic system at pressures above 20 GPa, indicating a transition of the strongly mixed-valent Eu atoms with a valence ~2.5 towards a pure trivalent state. No …

Double-stranded RNA polyinosinic-polycytidylic acid immobilized onto gamma-Fe2O3 nanoparticles by using a multifunctional polymeric linker.

Electronic, magnetic, and structural properties of the ferrimagnet Mn2CoSn

The magnetic ground state of the Heusler compound Mn${}_{2}$CoSn was predicted to be nearly half-metallic ferrimagnetic with a high spin polarization by ab initio electronic structure calculations. Mn${}_{2}$CoSn was synthesized, and the magnetic behavior of the compound was studied using a superconducting quantum interference device and x-ray magnetic circular dichroism. The experimental values were found to be in fair accordance with the theoretical predictions. The electronic structure and the crystal structure of Mn${}_{2}$CoSn were characterized comprehensively using x-ray powder diffraction, $^{119}\mathrm{Sn}$ M\"ossbauer spectroscopy, nuclear magnetic resonance, and hard x-ray photo…

CCDC 1422402: Experimental Crystal Structure Determination

Related Article: Il'ya A. Gural'skiy, Bohdan O. Golub, Sergii I. Shylin, Vadim Ksenofontov, Helena J. Shepherd, Paul R. Raithby, Wolfgang Tremel and Igor O. Fritsky|2016|Eur.J.Inorg.Chem.||3191|doi:10.1002/ejic.201600406

CCDC 1422398: Experimental Crystal Structure Determination

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CCDC 1422396: Experimental Crystal Structure Determination

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CCDC 1949845: Experimental Crystal Structure Determination

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CCDC 1422397: Experimental Crystal Structure Determination

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CCDC 1042437: Experimental Crystal Structure Determination

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CCDC 1480686: Experimental Crystal Structure Determination

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CSD 1784742: Experimental Crystal Structure Determination

Related Article: Leslie Schoop, Lukas Müchler, Jennifer Schmitt, Vadim Ksenofontov, Sergey Medvedev, Jürgen Nuss, Frederick Casper, Martin Jansen, R. J. Cava, Claudia Felser|2012|Phys.Rev.B|86|174522|doi:10.1103/PhysRevB.86.174522

CCDC 1949842: Experimental Crystal Structure Determination

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CCDC 1400635: Experimental Crystal Structure Determination

Related Article: Stefania Tomyn, Sergii I. Shylin, Dmytro Bykov, Vadim Ksenofontov, Elzbieta Gumienna-Kontecka, Volodymyr Bon, Igor O. Fritsky|2017|Nat.Commun.|8|14099|doi:10.1038/ncomms14099

CCDC 1986756: Experimental Crystal Structure Determination

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CCDC 1838583: Experimental Crystal Structure Determination

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CCDC 1480684: Experimental Crystal Structure Determination

Related Article: Olesia I. Kucheriv, Sergii I. Shylin, Vadim Ksenofontov, Sebastian Dechert, Matti Haukka, Igor O. Fritsky, and Il’ya A. Gural’skiy|2016|Inorg.Chem.|55|4906|doi:10.1021/acs.inorgchem.6b00446

CCDC 1582829: Experimental Crystal Structure Determination

Related Article: Hao Hang, Bin Fei, Xiu Qin Chen, Ming Liang Tong, Vadim Ksenofontov, Il’ya A. Gural'skiy, Xin Bao|2018|J.Mater.Chem.C|6|3352|doi:10.1039/C7TC05111E

CCDC 1422405: Experimental Crystal Structure Determination

Related Article: Il'ya A. Gural'skiy, Bohdan O. Golub, Sergii I. Shylin, Vadim Ksenofontov, Helena J. Shepherd, Paul R. Raithby, Wolfgang Tremel and Igor O. Fritsky|2016|Eur.J.Inorg.Chem.||3191|doi:10.1002/ejic.201600406

CCDC 1422399: Experimental Crystal Structure Determination

Related Article: Il'ya A. Gural'skiy, Bohdan O. Golub, Sergii I. Shylin, Vadim Ksenofontov, Helena J. Shepherd, Paul R. Raithby, Wolfgang Tremel and Igor O. Fritsky|2016|Eur.J.Inorg.Chem.||3191|doi:10.1002/ejic.201600406

CCDC 1569643: Experimental Crystal Structure Determination

Related Article: Bin Fei, Jian Zhou, Zheng Yan, Sergii I. Shylin, Vadim Ksenofontov, Il'ya A. Gural'skiy, Xin Bao|2017|CrystEngComm|19|7079|doi:10.1039/C7CE01826F

CCDC 1959867: Experimental Crystal Structure Determination

Related Article: Fabian Fürmeyer, Luca M. Carrella, Vadim Ksenofontov, Angela Möller, Eva Rentschler|2020|Inorg.Chem.|59|2843|doi:10.1021/acs.inorgchem.9b03170

CCDC 1480687: Experimental Crystal Structure Determination

Related Article: Olesia I. Kucheriv, Sergii I. Shylin, Vadim Ksenofontov, Sebastian Dechert, Matti Haukka, Igor O. Fritsky, and Il’ya A. Gural’skiy|2016|Inorg.Chem.|55|4906|doi:10.1021/acs.inorgchem.6b00446

CCDC 1422403: Experimental Crystal Structure Determination

Related Article: Il'ya A. Gural'skiy, Bohdan O. Golub, Sergii I. Shylin, Vadim Ksenofontov, Helena J. Shepherd, Paul R. Raithby, Wolfgang Tremel and Igor O. Fritsky|2016|Eur.J.Inorg.Chem.||3191|doi:10.1002/ejic.201600406

CCDC 1949843: Experimental Crystal Structure Determination

Related Article: Fabian Fürmeyer, Luca M. Carrella, Vadim Ksenofontov, Angela Möller, Eva Rentschler|2020|Inorg.Chem.|59|2843|doi:10.1021/acs.inorgchem.9b03170

CCDC 1838587: Experimental Crystal Structure Determination

Related Article: Il'ya A. Gural'skiy, Sergii I. Shylin, Vadim Ksenofontov, and Wolfgang Tremel|2019|Eur.J.Inorg.Chem.|2019|4532|doi:10.1002/ejic.201900782

CCDC 1478973: Experimental Crystal Structure Determination

Related Article: Il'ya A. Gural'skiy, Sergii I. Shylin, Bohdan O. Golub, Vadim Ksenofontov, Igor O. Fritsky, Wolfgang Tremel|2016|New J.Chem.|40|9012|doi:10.1039/C6NJ01472K

CCDC 1959865: Experimental Crystal Structure Determination

Related Article: Fabian Fürmeyer, Luca M. Carrella, Vadim Ksenofontov, Angela Möller, Eva Rentschler|2020|Inorg.Chem.|59|2843|doi:10.1021/acs.inorgchem.9b03170

CCDC 1838584: Experimental Crystal Structure Determination

Related Article: Il'ya A. Gural'skiy, Sergii I. Shylin, Vadim Ksenofontov, and Wolfgang Tremel|2019|Eur.J.Inorg.Chem.|2019|4532|doi:10.1002/ejic.201900782

CCDC 1400636: Experimental Crystal Structure Determination

Related Article: Stefania Tomyn, Sergii I. Shylin, Dmytro Bykov, Vadim Ksenofontov, Elzbieta Gumienna-Kontecka, Volodymyr Bon, Igor O. Fritsky|2017|Nat.Commun.|8|14099|doi:10.1038/ncomms14099

CCDC 1569642: Experimental Crystal Structure Determination

Related Article: Bin Fei, Jian Zhou, Zheng Yan, Sergii I. Shylin, Vadim Ksenofontov, Il'ya A. Gural'skiy, Xin Bao|2017|CrystEngComm|19|7079|doi:10.1039/C7CE01826F

CCDC 1838585: Experimental Crystal Structure Determination

Related Article: Il'ya A. Gural'skiy, Sergii I. Shylin, Vadim Ksenofontov, and Wolfgang Tremel|2019|Eur.J.Inorg.Chem.|2019|4532|doi:10.1002/ejic.201900782

CCDC 1949841: Experimental Crystal Structure Determination

Related Article: Fabian Fürmeyer, Luca M. Carrella, Vadim Ksenofontov, Angela Möller, Eva Rentschler|2020|Inorg.Chem.|59|2843|doi:10.1021/acs.inorgchem.9b03170

CCDC 1016554: Experimental Crystal Structure Determination

Related Article: Andreas K. C. Mengel, Christoph Förster, Aaron Breivogel, Katharina Mack, Julian R. Ochsmann, Frédéric Laquai, Vadim Ksenofontov, Katja Heinze|2015|Chem.-Eur.J.|21|704|doi:10.1002/chem.201404955

CCDC 975036: Experimental Crystal Structure Determination

Related Article: Maksym Seredyuk, M. Carmen Muñoz, Vadim Ksenofontov, Philipp Gütlich, Yury Galyametdinov, and Jose A. Real|2014|Inorg.Chem.|53|8442|doi:10.1021/ic5010159

CCDC 975041: Experimental Crystal Structure Determination

Related Article: Maksym Seredyuk, M. Carmen Muñoz, Vadim Ksenofontov, Philipp Gütlich, Yury Galyametdinov, and Jose A. Real|2014|Inorg.Chem.|53|8442|doi:10.1021/ic5010159

CCDC 1878182: Experimental Crystal Structure Determination

Related Article: Volodymyr M. Hiiuk, Sergiu Shova, Aurelian Rotaru, Vadim Ksenofontov, Igor O. Fritsky, Il'ya A. Gural'skiy|2019|Chem.Commun.|55|3359|doi:10.1039/C8CC10260K

CCDC 1838588: Experimental Crystal Structure Determination

Related Article: Il'ya A. Gural'skiy, Sergii I. Shylin, Vadim Ksenofontov, and Wolfgang Tremel|2019|Eur.J.Inorg.Chem.|2019|4532|doi:10.1002/ejic.201900782

CCDC 1422404: Experimental Crystal Structure Determination

Related Article: Il'ya A. Gural'skiy, Bohdan O. Golub, Sergii I. Shylin, Vadim Ksenofontov, Helena J. Shepherd, Paul R. Raithby, Wolfgang Tremel and Igor O. Fritsky|2016|Eur.J.Inorg.Chem.||3191|doi:10.1002/ejic.201600406

CCDC 1582828: Experimental Crystal Structure Determination

Related Article: Hao Hang, Bin Fei, Xiu Qin Chen, Ming Liang Tong, Vadim Ksenofontov, Il’ya A. Gural'skiy, Xin Bao|2018|J.Mater.Chem.C|6|3352|doi:10.1039/C7TC05111E

CCDC 1458636: Experimental Crystal Structure Determination

Related Article: Stefania Tomyn, Sergii I. Shylin, Dmytro Bykov, Vadim Ksenofontov, Elzbieta Gumienna-Kontecka, Volodymyr Bon, Igor O. Fritsky|2017|Nat.Commun.|8|14099|doi:10.1038/ncomms14099

CCDC 975039: Experimental Crystal Structure Determination

Related Article: Maksym Seredyuk, M. Carmen Muñoz, Vadim Ksenofontov, Philipp Gütlich, Yury Galyametdinov, and Jose A. Real|2014|Inorg.Chem.|53|8442|doi:10.1021/ic5010159

CCDC 1986758: Experimental Crystal Structure Determination

Related Article: Sergii I. Shylin, Olesia I. Kucheriv, Sergiu Shova, Vadim Ksenofontov, Wolfgang Tremel, Il’ya A. Gural’skiy|2020|Inorg.Chem.|59|6541|doi:10.1021/acs.inorgchem.0c00627

CCDC 1838586: Experimental Crystal Structure Determination

Related Article: Il'ya A. Gural'skiy, Sergii I. Shylin, Vadim Ksenofontov, and Wolfgang Tremel|2019|Eur.J.Inorg.Chem.|2019|4532|doi:10.1002/ejic.201900782

CCDC 1480685: Experimental Crystal Structure Determination

Related Article: Olesia I. Kucheriv, Sergii I. Shylin, Vadim Ksenofontov, Sebastian Dechert, Matti Haukka, Igor O. Fritsky, and Il’ya A. Gural’skiy|2016|Inorg.Chem.|55|4906|doi:10.1021/acs.inorgchem.6b00446

CCDC 1422400: Experimental Crystal Structure Determination

Related Article: Il'ya A. Gural'skiy, Bohdan O. Golub, Sergii I. Shylin, Vadim Ksenofontov, Helena J. Shepherd, Paul R. Raithby, Wolfgang Tremel and Igor O. Fritsky|2016|Eur.J.Inorg.Chem.||3191|doi:10.1002/ejic.201600406

CCDC 1480683: Experimental Crystal Structure Determination

Related Article: Olesia I. Kucheriv, Sergii I. Shylin, Vadim Ksenofontov, Sebastian Dechert, Matti Haukka, Igor O. Fritsky, and Il’ya A. Gural’skiy|2016|Inorg.Chem.|55|4906|doi:10.1021/acs.inorgchem.6b00446

CCDC 1582830: Experimental Crystal Structure Determination

Related Article: Hao Hang, Bin Fei, Xiu Qin Chen, Ming Liang Tong, Vadim Ksenofontov, Il’ya A. Gural'skiy, Xin Bao|2018|J.Mater.Chem.C|6|3352|doi:10.1039/C7TC05111E

CCDC 1582833: Experimental Crystal Structure Determination

Related Article: Hao Hang, Bin Fei, Xiu Qin Chen, Ming Liang Tong, Vadim Ksenofontov, Il’ya A. Gural'skiy, Xin Bao|2018|J.Mater.Chem.C|6|3352|doi:10.1039/C7TC05111E

CCDC 1569644: Experimental Crystal Structure Determination

Related Article: Bin Fei, Jian Zhou, Zheng Yan, Sergii I. Shylin, Vadim Ksenofontov, Il'ya A. Gural'skiy, Xin Bao|2017|CrystEngComm|19|7079|doi:10.1039/C7CE01826F

CCDC 975037: Experimental Crystal Structure Determination

Related Article: Maksym Seredyuk, M. Carmen Muñoz, Vadim Ksenofontov, Philipp Gütlich, Yury Galyametdinov, and Jose A. Real|2014|Inorg.Chem.|53|8442|doi:10.1021/ic5010159

CCDC 1959866: Experimental Crystal Structure Determination

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CCDC 1016552: Experimental Crystal Structure Determination

Related Article: Andreas K. C. Mengel, Christoph Förster, Aaron Breivogel, Katharina Mack, Julian R. Ochsmann, Frédéric Laquai, Vadim Ksenofontov, Katja Heinze|2015|Chem.-Eur.J.|21|704|doi:10.1002/chem.201404955

CCDC 1582832: Experimental Crystal Structure Determination

Related Article: Hao Hang, Bin Fei, Xiu Qin Chen, Ming Liang Tong, Vadim Ksenofontov, Il’ya A. Gural'skiy, Xin Bao|2018|J.Mater.Chem.C|6|3352|doi:10.1039/C7TC05111E

CCDC 1959864: Experimental Crystal Structure Determination

Related Article: Fabian Fürmeyer, Luca M. Carrella, Vadim Ksenofontov, Angela Möller, Eva Rentschler|2020|Inorg.Chem.|59|2843|doi:10.1021/acs.inorgchem.9b03170

CCDC 1816546: Experimental Crystal Structure Determination

Related Article: Hao Hang, Bin Fei, Xiu Qin Chen, Ming Liang Tong, Vadim Ksenofontov, Il’ya A. Gural'skiy, Xin Bao|2018|J.Mater.Chem.C|6|3352|doi:10.1039/C7TC05111E

CCDC 1031559: Experimental Crystal Structure Determination

Related Article: Christoph Förster, Philipp Veit, Vadim Ksenofontov, Katja Heinze|2015|Chem.Commun.|51|1514|doi:10.1039/C4CC08868A

CCDC 975038: Experimental Crystal Structure Determination

Related Article: Maksym Seredyuk, M. Carmen Muñoz, Vadim Ksenofontov, Philipp Gütlich, Yury Galyametdinov, and Jose A. Real|2014|Inorg.Chem.|53|8442|doi:10.1021/ic5010159

CCDC 975040: Experimental Crystal Structure Determination

Related Article: Maksym Seredyuk, M. Carmen Muñoz, Vadim Ksenofontov, Philipp Gütlich, Yury Galyametdinov, and Jose A. Real|2014|Inorg.Chem.|53|8442|doi:10.1021/ic5010159

CCDC 1582831: Experimental Crystal Structure Determination

Related Article: Hao Hang, Bin Fei, Xiu Qin Chen, Ming Liang Tong, Vadim Ksenofontov, Il’ya A. Gural'skiy, Xin Bao|2018|J.Mater.Chem.C|6|3352|doi:10.1039/C7TC05111E

CCDC 1878181: Experimental Crystal Structure Determination

Related Article: Volodymyr M. Hiiuk, Sergiu Shova, Aurelian Rotaru, Vadim Ksenofontov, Igor O. Fritsky, Il'ya A. Gural'skiy|2019|Chem.Commun.|55|3359|doi:10.1039/C8CC10260K

CCDC 1949844: Experimental Crystal Structure Determination

Related Article: Fabian Fürmeyer, Luca M. Carrella, Vadim Ksenofontov, Angela Möller, Eva Rentschler|2020|Inorg.Chem.|59|2843|doi:10.1021/acs.inorgchem.9b03170

CCDC 1016553: Experimental Crystal Structure Determination

Related Article: Andreas K. C. Mengel, Christoph Förster, Aaron Breivogel, Katharina Mack, Julian R. Ochsmann, Frédéric Laquai, Vadim Ksenofontov, Katja Heinze|2015|Chem.-Eur.J.|21|704|doi:10.1002/chem.201404955

CCDC 1016551: Experimental Crystal Structure Determination

Related Article: Andreas K. C. Mengel, Christoph Förster, Aaron Breivogel, Katharina Mack, Julian R. Ochsmann, Frédéric Laquai, Vadim Ksenofontov, Katja Heinze|2015|Chem.-Eur.J.|21|704|doi:10.1002/chem.201404955

CCDC 1480682: Experimental Crystal Structure Determination

Related Article: Olesia I. Kucheriv, Sergii I. Shylin, Vadim Ksenofontov, Sebastian Dechert, Matti Haukka, Igor O. Fritsky, and Il’ya A. Gural’skiy|2016|Inorg.Chem.|55|4906|doi:10.1021/acs.inorgchem.6b00446

CCDC 1422401: Experimental Crystal Structure Determination

Related Article: Il'ya A. Gural'skiy, Bohdan O. Golub, Sergii I. Shylin, Vadim Ksenofontov, Helena J. Shepherd, Paul R. Raithby, Wolfgang Tremel and Igor O. Fritsky|2016|Eur.J.Inorg.Chem.||3191|doi:10.1002/ejic.201600406