Isomer Shift Research Articles

Characterizing the Biosynthesis of the [Fe(II)(CN)(CO)2(cysteinate)]- Organometallic Product of the Radical-SAM Enzyme HydG by EPR and Mössbauer Spectroscopy.

[FeFe]-hydrogenases employ a catalytic H-cluster, consisting of a [4Fe-4S]H cluster linked to a [2Fe]H subcluster with CO, CN- ligands, and an azadithiolate bridge, which mediates the rapid redox interconversion of H+ and H2. In the biosynthesis of this H-cluster active site, the radical S-adenosyl-l-methionine (radical SAM, RS) enzyme HydG plays the crucial role of generating an organometallic [Fe(II)(CN)(CO)2(cysteinate)]- product that is en route to forming the H-cluster. Here, we report direct observation of this diamagnetic organometallic Fe(II) complex through Mössbauer spectroscopy, revealing an isomer shift of δ = 0.10 mm s-1 and quadrupole splitting of ΔEQ = 0.66 mm s-1. These Mössbauer values are a change from the starting values of δ = 1.15 mm s-1 and ΔEQ = 3.23 mm s-1 for the ferrous "dangler" Fe in HydG. These values of the observed product complex B are in good agreement with Mössbauer parameters for the low-spin Fe2+ ions in synthetic analogues, such as 57Fe Syn-B, which we report here. These results highlight the essential role that HydG plays in converting a resting-state high-spin Fe(II) to a low-spin organometallic Fe(II) product that can be transferred to the downstream maturase enzymes.

Mullite‐type EMBO4: synthesis, structural, optical, and vibrational properties of rare tin(II) borates with M = Al and Ga

AbstractMetal tin‐(II)‐borates are rarely studied mainly due to the susceptibility of either oxidation into tin(IV) or disproportionation into elemental tin(0) and tin(IV). We report mullite‐type SnAlBO4 and SnGaBO4 ceramics produced by conventional solid‐state synthesis in sealed quartz tubes at low pressure of 10–7 MPa. Both compounds are isostructural to PbAlBO4 as confirmed by Rietveld refinements of powder X‐ray data. The crystal structures are highly influenced by the stereochemical activity of the 5s2 lone electron pair of the Sn2+ cation measured by the Wang–Liebau eccentricity parameter. To further consolidate the structural features 119Sn Mössbauer, solid state NMR, Raman, IR and UV/vis spectroscopic measurements are performed. The 119Sn Mössbauer isomer shifts and the quadrupole splitting values confirm the SnO4 coordination and Sn(II) valence states. Solid state 11B, 27Al and 119Sn NMR spectra provided insights into the local crystal‐chemical environment. The vibrational properties are discussed from group theoretical analysis to mode assignments. SnAlBO4 and SnGaBO4, respectively, possess an electronic band gap of 3.73(9) and 3.21(4) eV calculated from the diffuse reflectance UV/Vis spectra.

Modifications in structure dependent magnetic parameters of Nd-doped Ba–Ca hexaferrites synthesized by sol gel using lemon extract as a fuel

The Nd doped Ba–Ca ferrites, Ba0.5Ca0.5NdXFe12-XO19 (x = 0 to 0.2, Δx = 0.05) are synthetically prepared by sol gel auto-ignition method using lemon extract as the fuel. Differential thermal analysis of the thermogravimetric spectrum clearly exhibits the thermal decomposition till 1050 °C. The powder X-ray diffraction (XRD) patterns of the hexaferrites sintered at 1050 °C reveals the single-phase M-type hexaferrites possessing nano dimensions. The lattice parameters, unit cell volumes, densities, and porosities of the hexaferrites were computed from the XRD patterns. The morphology of the synthesized hexaferrites is analyzed from the digital images of the powder samples obtained by utilizing Field Emission Scanning Electron Microscope (FESEM). The relative abundance of the elements within the hexaferrites was studied by means of Energy Dispersive X-Ray Analysis (EDAX). The oxidation states and valence of the metal elements within the hexaferrites are confirmed by means of the X-ray photoelectron spectroscopy (XPS). Magnetic parameters such as coercivity, saturation magnetization, and remanence are measured by using Vibrating-Sample Magnetometer (VSM). The Mössbauer spectra of the hexaferrites are obtained to analyze the hyperfine interactions by measuring the parameters such as hyperfine field, isomer shift, quadrupole splitting, relative area, and outer line width. The varying Nd doping concentrations have modulated the magnetic parameters of Ba–Ca hexaferrites showing the control of Nd doping on magnetic behavior of the hexaferrite. The moderate saturation magnetization and high coercivity values suggest the possible use of the hexaferrites as the permanent magnets.

A switch from ferro- to antiferromagnetic ordering in the solid solutions CeAuGe1−x Sn x

Abstract CeAuGe and CeAuSn (both NdPtSb type, space group P63 mc) form a complete solid solution CeAuGe1−x Sn x with Vegard-type behavior of the cell volume. Samples with steps of x = 0.1 were synthesized from the pure elements by arc-melting. The structure of CeAuGe0.13(2)Sn0.87(2) was refined from single-crystal X-ray diffractometer data: a = 469.10(6), c = 773.90(10) pm, wR 2 = 0.0359, 251 F 2 values and 12 variables. The induced structural disorder caused by the Ge/Sn mixing affects the magnetic ground state of the cerium ions. From the germanium-rich side, the Curie temperature of CeAuGe (10.0 K) decreases towards CeAuGe0.6Sn0.4, while the Néel temperature of CeAuSn (4.4 K) decreases at the tin-rich side toward CeAuGe0.4Sn0.6. The switch of the magnetic ground state occurs approximately around the Ge/Sn ratio of 1:1. 119Sn Mössbauer spectra of CeAuGe0.1Sn0.9 and CeAuGe0.7Sn0.3 confirm the presence of single crystallographic tin sites in both cases, and the isomer shifts are comparable to that of pure CeAuSn, indicating similar electron density distribution at the tin nuclei.

Ultrathin Fe Films Sandwiched Between Au Layers: CEMS- study

The STM studies of Fe films with thickness above 0.6 ML do not contribute significantly to the solution of the structural problems, because of the Au surface layer, which hinders details of the Fe sub-surface layers. The Mossbauer spectroscopy appears in this case as an exceptional method, which has the ability to solve structural and magnetic problems. Our discussion is based on a simplified spectrum analysis, assuming a discrete character of the spectral components. In reality, a distribution of the hyperfine magnetic field, as well as isomer shift and the quadrupole splitting is an obvious and natural consequence of the finite size system 'presented by the monolayer film. The exact fitting of all hyperfine parameters distribution is too difficult. Most of the fitting procedures treat the distributions of IS vs. Bhf and QS vs. Bhf as linearly dependent as described using the well-known Voigt-based method.

Mössbauer analysis, structural parameter studies and magnetic properties of LiCoxFe5-xO8 (x= 0, 0.025, 0.05, 0.075, 0.1) nanoparticles

We report on detailed structural parameter analysis, Mössbauer spectra and magnetic properties of LiCoxFe5-xO8 (x = 0, 0.025, 0.05, 0.075, 0.1) nanoparticles prepared by sol-gel method. Prepared LiCoxFe5-xO8 nanoparticles crystalizes in inverse spinel structure with the crystallite size ranging from 23.7 to 29.8 nm. Hopping length, radii of tetrahedral and octahedral sites (rA and rB), tetrahedral bond length (dAx), octahedral bond lengths (dBx), tetrahedral and octahedral shared edges (dAxE, dBxE), unshared octahedral edges (dBxEU) values and oxygen positional parameter (u) are seen to increase with increasing Co concentration. Chemical state of all the elements are confirmed by X-ray photoelectron spectroscopy technique. The hyperfine field, isomer shift, quadrupole shift and line width parameters calculated from the Mössbauer spectra confirms the Co2+ substitution in LiFe5O8. The saturation magnetization value decreases from 59.2 to 54.1 emu/g with increasing Co concentration, which is examined by three sublattice model derived by Yafet and Kittel (Y-K model). Y-K angles increases with Co concentration from 16.46 to 19.98°. Curie temperature of LiFe5O8 decreases from 865 K to 858 K with increasing Co concentration to x = 0.1.

Photocatalytic and Cathode Active Abilities of Ni-Substituted α-FeOOH Nanoparticles.

The present study investigates the relationship between the local structure, photocatalytic ability, and cathode performances in sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs) using Ni-substituted goethite nanoparticles (NixFe1-xOOH NPs) with a range of 'x' values from 0 to 0.5. The structural characterization was performed applying various techniques, including X-ray diffractometry (XRD); thermogravimetry differential thermal analysis (TG-DTA); Fourier transform infrared spectroscopy (FT-IR); X-ray absorption spectroscopy (XANES/EXAFS), both measured at room temperature (RT); 57Fe Mössbauer spectroscopy recorded at RT and low temperatures (LT) from 20 K to 300 K; Brunauer-Emmett-Teller surface area measurement (BET), and diffuse reflectance spectroscopy (DRS). In addition, the electrical properties of NixFe1-xOOH NPs were evaluated by solid-state impedance spectroscopy (SS-IS). XRD showed the presence of goethite as the only crystalline phase in prepared samples with x ≤ 0.20, and goethite and α-Ni(OH)2 in the samples with x > 0.20. The sample with x = 0.10 (Ni10) showed the highest photo-Fenton ability with a first-order rate constant value (k) of 15.8 × 10-3 min-1. The 57Fe Mössbauer spectrum of Ni0, measured at RT, displayed a sextet corresponding to goethite, with an isomer shift (δ) of 0.36 mm s-1 and a hyperfine magnetic distribution (Bhf) of 32.95 T. Moreover, the DC conductivity decreased from 5.52 × 10-10 to 5.30 × 10-12 (Ω cm)-1 with 'x' increasing from 0.10 to 0.50. Ni20 showed the highest initial discharge capacity of 223 mAh g-1, attributed to its largest specific surface area of 174.0 m2 g-1. In conclusion, NixFe1-xOOH NPs can be effectively utilized as visible-light-activated catalysts and active cathode materials in secondary batteries.

Mineral and crystal chemical study of pseudo-C2/mnon-metamict chevkinite-(Ce): An investigation into the intracrystalline distribution of LREE, HREE, and octahedral cations in samples from the Azores and Pakistan

AbstractThe cation distribution among the A, B, C, and D sites of 13 crystals of chevkinite-(Ce) by X-ray single-crystal diffraction and electron microprobe analyses is reported in this article. The general formula of chevkinite-(Ce) is A4BC2D2O8(Si2O7)2, where A = REE, Ca, Th, Sr; B = Fe, Mn, Mg; C = Fe, Ti, Nb, Zr, Mg, Al; and D = Ti. Ten crystals come from quartz-bearing syenite samples of Agua de Pau (Azores Islands), and three are euhedral chevkinite crystals of a quartz-bearing pegmatite from Tangir Valley, northwestern Pakistan. The real space group for these samples is P21/a, but the average structure in space group C2/m was used for structural refinement and further interpretation. Cation distribution was determined by minimization of the function fΣNσ2 that represents the sum of the squared numbers of standard deviation by which each expected quantity differs from the calculated one. Both X-ray diffraction and electron microprobe data were considered in minimization. Our results show that the two non-equivalent A sites are occupied dominantly by REE and Ca, distributed mainly as a function of their ionic size. Lanthanum enters only the 10-coordinated A2 site, whereas heavier and smaller REE enter only the 8-coordinated A1. Furthermore, comparison between bond valence sum and formal charge revealed highly stretched bonds for the A1 polyhedron, suggesting that bond lengths are too long for HREE. These findings can help better characterize the well-known ability of chevkinite to fractionate LREE from HREE. The Azores chevkinite is particularly enriched in Nb relative to its host rock. Our results show that Ti occupancy in the D sites can be as low as ca. 50% due to the presence of significant amounts of Nb, besides Fe and Zr. For two Azores crystals showing patchy zoning, a complex history of late-stage crystallization is inferred, with multiple events of Ca and REE enrichments. One of these crystals showed the best structure refinement, implying that late-magmatic to deuteric alteration stages did not affect its crystallinity. The CaO content of Azores chevkinites practically spans the entire chevkinite field in the chevkinite/perrierite CaO vs. FeO discrimination diagram. In addition, we identified possible structural stability limits that can be linked to the occupancy of the B site at high CaO, and of the C sites at high-FeO contents. The Pakistan chevkinites were also analyzed by Mössbauer spectroscopy. Only one Fe3+ component was identified, which occupies the C sites. Among the two ferrous doublets, the component with the highest isomeric shift value is Fe2+ entering the most distorted crystallographic site B, while the other, representative of a less distorted octahedral site, corresponds to Fe2+ entering the D sites.

[formula omitted] Mössbauer, optical and structural properties with ligand field effects of borosilicate glass doped with iron oxide

Here, an investigation of borosilicate glass doped with iron oxide and prepared by classical melt-quenching method. The internal macrostructure, optical absorbance, ligand field parameters, and Mössbauer spectra were studied. The density increased with increasing SiO2 content, while Fourier-transform infrared (FTIR) analysis reported that BO4 and SiO4 content increase with a decrease in NBO content. Optical electronic transitions through wavelength (402–948 nm) confirmed the existence of Fe3+ state, while the Fe2+ is not observed in optical absorbance because of its inane electronic transition at 2222 nm. The electronic transitions at (402, 452, 513, 602, and 701 nm) are assigned to Fe3+ in tetrahedral coordination (FeO4), while the electronic transitions at (795 and 948 nm) are related to Fe3+ in octahedral coordination (FeO6). Astonishingly, the ligand field parameters of Fe ions were studied. The crystal field splitting exhibits increasing values, while Racah parameters exhibit decreasing values. Moreover, nephelauxetic parameters reflect the propensity of the bonding nature between the Fe cations and their ligands towards a higher covalent nature with SiO2 additives. Further, a scant decrease in the optical band gap was explained based on the mixed former effect. Moreover, non-linear refractive indices augment with SiO2 addition. The decrease in the optical gap energy justified such a trend. Bewitchingly, Mössbauer spectra reported the existence ofFe3+ ions with isomer shift (0.285–0.314) mm s−1 in tetrahedral sites, while Fe3+ ions with isomer shift (0.339–0.425) mm s−1 in octahedral sites, agreeing with optical data. Surprisingly, Fe2+ ions with isomer shift at about 0.905 mm s−1 in tetrahedral sites was observed. The observed decrease in isomer shift of all phases is due to the decrease in electronegativity of formers. Furthermore, the decrease in quadrable splitting is attributed to the decline in the polarization power of the glass former cations with SiO2 addition.

A DFT and Mössbauer spectroscopy investigation of spin‐crossover iron(II) complexes with 2,6‐bis(1H‐imidazol‐2‐yl)pyridines

AbstractA quantum chemical study was carried out for a number of iron(II) complexes [FeL2]Ai·nH2O (L = 2,6‐bis(1H‐imidazole‐2‐yl)pyridine (L1); 2,6‐(4,5‐dimethyl‐1H‐imidazole‐2‐yl)pyridine (L2); 2,6‐bis(1H‐benzimidazole‐2‐yl)pyridine (L3); A = ReO4−, B10H102−, B12H122−; n = 0–2). These complexes exist in the low spin (LS) form 1A1 (total electron spin S = 0) at room temperature and switch to the high spin (HS) form 5T2 (S = 2) upon heating. The experimental isomeric shift and quadrupole splitting values for compounds with L2 exceed those for compounds with L1 and L3 by <0.02> mm/s and <0.1> mm/s, respectively (for LS forms). Such a discrepancy between MS parameters can be explained by the assumption that chemical bonding between the iron ion and the surrounding nitrogen atoms in the compounds with L2 may be more ionic in character than that in the compounds with L1 and L3. At the same time, the results obtained with the TPSSh hybrid meta‐GGA functional gave a better agreement with the experimental data than those obtained with the B3LYP exchange‐correlation functional.

Predicting Mössbauer Parameters of Nonheme Diiron Complexes with Density Functional Theory.

Mössbauer spectroscopy provides significant insights into the electronic structure and environment of the metal centers. Herein, we investigate the electronic structures of a set of nonheme diiron complexes by evaluating two key parameters pertaining to Mössbauer spectroscopy, namely, the isomer shift (δ) and quadrupole splitting (|ΔEQ|), using different levels of density functional theory (DFT). The diiron systems investigated here span diverse oxidation states, bridging motifs, and spin coupling patterns, which present a challenging case for theoretical predictions. We demonstrate that the combination of B97-D3/def2-TZVP is an efficient approach in modeling both the δ and |ΔEQ| values with high accuracy for the representative nonheme diiron complexes. We also show that δ is accurately predicted irrespective of the choice of approximate density functional while the |ΔEQ| is sensitive to the level of theory employed. Further investigation shows that the present methodology assessed using synthetic nonheme diiron complexes could be extended to nonheme diiron enzyme active sites, featuring both ferromagnetic and antiferromagnetic coupling between the iron centers.

Structural transformations of low-nickel Fe-Ni alloys probed by Mössbauer spectroscopy

The structure and magnetic state of Fe100-xNix alloys (x ≤ 20) quenched from 1100 °С have been studied by means of Mössbauer spectroscopy, X-ray diffraction, transmission electron microscopy, and magnetization measurements. The concentration dependences of the lattice parameter of bcc structure and of spontaneous magnetic moment were measured at room temperature. From the analysis of Mössbauer spectra, concentration dependences of average hyperfine parameters have been determined. Both isomer shift and hyperfine field increase with increasing Ni content in the alloy. Fitting of the spectra with a set of subspectra gives grounds to conclude that the structure of quenched Fe-Ni samples represents a system of bcc regions of varying content, which is formed as a result of separation of the alloy composition. This conclusion is supported by the data of transmission electron microscopy.

Crystal structure and hyperfine fields in Mn1-xCoFexGe magnetocaloric alloys

The phase analysis, site occupancy, and hyperfine fields of Mn1-xCoFexGe alloys (x = 0.01, 0.02, 0.05, 0.10) after annealing procedure are presented. Mössbauer spectroscopy was performed with and without an external magnetic field of B = 1.3 T parallel to the beam direction at room temperature. RT X-ray diffraction shows that Mn1-xCoFexGe compound is two phases of Ni2In type hexagonal structure and TiNiSi type orthorhombic structure. Samples with × = 0.01, 0.02 and 0.05 exhibit (pre)dominant contribution of the orthorhombic structure while for × = 0.10 the amount of hexagonal phase increases significantly. In the series of alloys, the lattice parameters and the unit cell volume remain weakly sensitive to Fe concentration at both phases. The measured Mössbauer spectra are superpositions of two doublets which come from the Fe atoms located in hexagonal structure and two broad sextets of Fe orthorhombic structure origin. The values of isomer shift and quadrupole splitting do not change with increasing iron content. Using information about the composition of local environment and measured values of isomer shift, we identify the origin of individual subspectra, and site occupation of Fe atoms in the alloy. The Mössbauer measurements carried out in external magnetic field shows that induced hyperfine magnetic field in the hexagonal structure is much higher for Fe at Mn sites than the observed for Fe at Co sites. Analysis of sextets shows that magnetic moments of Fe tend to arrange along the external field direction with almost the same values of about 0.87 µB.

On the interpretation of Mössbauer isomer shifts of iron-organic compounds

On the interpretation of Mössbauer isomer shifts of iron-organic compounds

Kinetics of Transformation, Border of Metastable Miscibility Gap in Fe–Cr Alloy and Limit of Cr Solubility in Iron at 858 K

The study was aimed at determination of the position of the Fe-rich border of the metastable miscibility gap (MMG) and of the solubility limit of Cr in iron at 858 K. Towards this end, a Fe73.7Cr26.3 alloy was isothermally annealed at 858 K in vacuum up to 8144 hours and Mössbauer spectra were recorded at room temperature after every step of the annealing. Three spectral parameters viz. the average hyperfine field, 〈B〉, the average isomer shift, 〈IS〉, and the probability of the atomic configuration with no Cr atoms in the two-shell vicinity of the probe Fe atoms, P(0,0), gave evidence that the transformation process took place in two stages. All three parameters could have been well described in terms of the Johnson–Mehl–Avrami–Kolmogorov equation, yielding kinetics parameters. The first stage, associated with the phase decomposition, proceeded much faster than the second stage, associated with the alpha-to-sigma phase transformation. The most reliable estimation of the position of the MMG and that of the value of the Cr solubility limit was obtained from the annealing time dependence of 〈B〉, namely 24.5 at. pct Cr for the former and 20.3 at. pct Cr for the latter. A comparison of these figures with the recent phase diagrams pertinent to Fe–Cr system was done.

Structural and Electrical Properties of Novel Cr/Fe Mixed Transition-Metal Phosphates.

The phosphate KCoCr(PO4)2 and iron-substituted variants KCoCr1-xFex(PO4)2 (x = 0.25, 0.5, and 0.75) were synthesized by a solid-state reaction route, while a high substitution level of Fe was achieved. Their structures were refined using powder X-ray diffraction and indexed in a monoclinic system with a P21/n space group. A 3D framework with six-sided tunnels parallel to the [101] direction was formed in which the K atoms are located. Mössbauer spectroscopy confirms the exclusive presence of octahedral paramagnetic Fe3+ ions, with isomer shifts increasing slightly with x substitution. Electron paramagnetic resonance spectroscopy confirmed the presence of paramagnetic Cr3+ ions. The activation energy, determined by dielectric measurements, shows that the iron-containing samples present higher ionic activity. Relative to the electrochemical activity of K, these materials could be good candidates for positive and/or negative electrode materials for energy storage applications.

Mössbauer and Structure-Magnetic Properties Analysis of AyB1-yCxFe2-xO4 (C=Ho,Gd,Al) Ferrite Nanoparticles Optimized by Doping.

AyB1-yCxFe2-xO4 (C=Ho,Gd,Al) ferrite powders have been synthesized by the sol-gel combustion route. The X-ray diffraction of the CoHoxFe2-xO4 (x = 0~0.08) results indicated the compositions of single-phase cubic ferrites. The saturation magnetisation of CoHoxFe2-xO4 decreased by the Ho3+ ions, and the coercivity increased initially and then decreased with the increase of the calcination temperature. The Mössbauer spectra indicated that CoHoxFe2-xO4 displays a ferrimagnetic behaviour with two normal split Zeeman sextets. The magnetic hyperfine field tends to decrease by Ho3+ substitution owing to the decrease of the A-B super-exchange by the paramagnetic rare earth Ho3+ ions. The value of the quadrupole shift was very small in the CoHoxFe2-xO4 specimens, indicating that the symmetry of the electric field around the nucleus is good in the cobalt ferrites. The absorption area of the Mössbauer spectra changed with increasing Ho3+ substitution, indicating that the substitution influences the fraction of iron ions at tetrahedral A and octahedral B sites. The X-ray diffraction of Mg0.5Zn0.5CxFe2-xO4(C=Gd,Al) results confirmed the compositions of single-phase cubic ferrites. The variation of the average crystalline size and lattice constant are related to the doping of gadolinium ions and aluminum ions. With increasing gadolinium ions and aluminum ions, the coercivity increased and the saturation magnetization underwent a significant change. The saturation magnetization of AlMg0.5Zn0.5FeO4 ferrite reached a minimum value (MS= 1.94 mu/g). The sample exhibited ferrimagnetic and paramagnetic character with the replacement with Gd3+ ions, that sample exhibited paramagnetic character with the replacement with Al3+ ions, and the isomer shift values indicated that iron is in the form of Fe3+ ions.

Mössbauer and X-ray Studies of Radiation-Induced Processes in Nb-Zr Alloys Implanted with 57Fe Ions.

The effect of implanting 57Fe ions on the crystal structure of Nb-Zr alloys has been studied using Mössbauer spectroscopy on 57Fe nuclei and X-ray diffraction. As a result of implantation, a metastable structure was formed in the Nb-Zr alloy. The XRD data indicated a decrease in the crystal lattice parameter of niobium; that is, there was a compression of the niobium planes when implanted with iron ions. Mössbauer spectroscopy revealed three states of iron. The singlet indicated a supersaturated Nb(Fe) solid solution; the doublets characterized the diffusion migration of atomic planes and crystallization of voids. It was shown that the values of the isomer shifts in all three states did not depend on the implantation energy, which indicates the invariance of the electron density on the 57Fe nuclei in the studied samples. The resonance lines of the Mössbauer spectra were significantly broadened, which is typical for materials with low crystallinity and a metastable structure that is stable at room temperature. The paper discusses the mechanism of radiation-induced and thermal transformations in the Nb-Zr alloy, which leads to the formation of a stable well-crystallized structure. A Fe2Nb intermetallic compound and the Nb(Fe) solid solution formed in its near-surface layer, while Nb(Zr) remained in the bulk.

Mössbauer-spectroscopic characterization of the stannides Sr2Pd2Sn and Eu2Pd2Sn

Abstract The Ca2Pd2Ge-type stannides Sr2Pd2Sn and Eu2Pd2Sn were synthesized by reaction of the elements in sealed tantalum ampoules in a high-frequency furnace and characterized by powder X-ray diffraction. The structure of Sr2Pd2Sn (Fdd2, a = 1063.95(5), b = 1623.22(9), c = 594.63(14) pm, wR2 = 0.0472, 972 F 2 values and 26 variables) was refined from single-crystal X-ray diffractometer data. The striking structural motif features equidistant chains formed by the palladium atoms (304.7 pm Pd–Pd), which are interlinked by the tin atoms (266.9 and 268.7 pm Pd–Sn). Together, the palladium and tin atoms form a three-dimensional [Pd2Sn] δ– polyanionic network in which the strontium atoms reside in larger cavities. The divalent character of europium in Eu2Pd2Sn was manifested by 151Eu Mössbauer spectroscopy. The isomer shift is δ = −9.48(1) mm s−1 at room temperature. The results of 119Sn Mössbauer-spectroscopic experiments have confirmed the tin site determined by the single-crystal study, the isomer shifts being δ = 1.71(1) mm s−1 for Eu2Pd2Sn and δ = 1.73(1) mm s−1 for Sr2Pd2Sn. Sr2Pd2Sn is a Pauli paramagnet with a susceptibility of 2.2(1) × 10−5 emu mol−1 at room temperature. Eu2Pd2Sn shows Curie-Weiss paramagnetism with an experimental magnetic moment of 7.85(1) µB per Eu atom, confirming divalent europium. The europium magnetic moments order antiferromagnetically at T N = 14 K.

Two Shared Icosahedral Metallacarboranes through Iron: A Joint Experimental and Theoretical Refinement of Mössbauer Spectrum in [Fe(1,2-C2B9H11)2]Cs.

Mössbauer and X-ray photoelectron spectroscopies (XPS) are complemented with high-level quantum-chemical computations in the study of the geometric and electronic structure of the paramagnetic salt of the metallacarborane sandwich complex [Fe(1,2-C2B9H11)2]Cs = FeSanCs. Experimental 57Fe isomer shifts and quadrupole splitting parameters are compared with the theoretical prediction, with good agreement. The appearance of two sets of Cs(3d) doublets in the XPS spectrum, separated by 2 eV, indicates that Cs has two different chemical environments due to ease of the Cs(+) cation moving around the sandwich complex with low-energy barriers, as confirmed by quantum-chemical computations. Several minimum-energy geometries of the FeSanCs structure with the corresponding energies and Mössbauer parameters are discussed, in particular the atomic charges and spin population and the surroundings of the Fe atom in the complex. The Mössbauer spectra were taken at different temperatures showing the presence of a low-spin Fe atom with S = 1/2 and thus confirming a paramagnetic FeIII species.