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Despite considerable interest in heteroatom-containing conjugated polymers, there are only few examples with heavier p-block elements in the conjugation path. The recently reported heavier acyclic diene metathesis (HADMET) allowed for the synthesis of a polymer containing Ge=Ge double bonds - albeit insoluble and with limited degree of polymerization. By incorporation of long alkyl chains, we now obtained soluble representatives, which exhibit degrees of polymerization near infinity according to diffusion-ordered NMR spectroscopy (DOSY) and dynamic light scattering (DLS). Analyses of the UV/Vis absorption and the NMR spectroscopic data confirm the presence of σ,π-conjugation across the silylene-phenylene linkers between the Ge=Ge double bonds. Favorable intermolecular dispersion interactions lead to ladder-like cylindrical supramolecular assemblies as confirmed by X-ray diffraction (XRD), small angle X-ray scattering (SAXS) and DLS. AFM and TEM images of deposited thin films reveal lamellar ordering of extended polymer bundles., (© 2024 Wiley‐VCH GmbH.)

Porous organic cobaltocenium-containing particles are scarce in literature but highly interesting for their electrochemical properties and reusability in, for example, catalysis or magnetic systems. In this work, we present a scalable one-pot strategy to introduce tailorable amounts of cobaltocenium on a porous substrate, adjusting the electrochemical switching capability. For this purpose, 3-(triethoxysilyl)propan-1-amine (APTES) and ethynyl cobaltocenium hexafluorophosphate is used as functionalization agents for in-situ catalyst-free hydroamination, followed by silane condensation at the particles' surface. Functionalized particles are characterized by attenuated total reflection infrared spectroscopy (ATR-IR), thermogravimetric analysis (TGA), laser scanning confocal microscopy (LSCM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), inductively coupled plasma mass spectrometry (ICP-MS), powder X-ray diffraction (PXRD) and cyclic voltammetry (CV) showing excellent control over the degree of functionalization, i. e., the added cobaltocenium reagents. The electrochemical stability and good addressability while preserving the porous structure are shown. By utilizing higher amounts of APTES, the overall cobaltocenium amount can be reduced in favor of additional amine groups, strongly affecting the electrochemical behavior, making this functionalization strategy a good platform for metallopolymer immobilization and tailored functionalization. Additionally, thermal treatment of the synthesized metallopolymer microparticles paves the way to magnetic properties with tailorable microporous architectures for end-of-life and upcycling aspects., (© 2024 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH.)

Gd 2 Al 3 Rh was synthesized from the elements using arc-melting techniques, along with subsequent annealing. The title compound adopts the hexagonal MgZn 2 type structure (space group P 6 3 / mmc , hP 12, Wyckoff sequence hfa ) with the Gd atoms found on the Mg positions (4 f ), the Rh (2 a ) and Al (6 h ) atoms occupying the two Zn sites of the prototype. In addition, mixing of Rh and Al on both crystallographic positions is observed. The magnetic susceptibility and magnetization experiments were conducted indicating ferromagnetic ordering below the Curie temperature of T C = 51.3(1) K and very high magnetization of 6.96(1) μ B at 3 K and 70 kOe. In addition, heat capacity and electrical resistivity measurements were conducted. The magnetocaloric properties of ferromagnetic Gd 2 Al 3 Rh have been determined by means of magnetization measurements. For a field change of Δ H = 0 → 50 kOe the magnetic entropy change equals Δ S M max = -4.8 J kg -1 K -1 , leading to a relative cooling power of RCP = 283 J kg -1 for the same field change. The adiabatic temperature change was estimated to be Δ T ad max = 2.1 K using the heat capacity data.

In the pursuit of fabricating functional ceramic nanostructures, the design of preceramic functional polymers has garnered significant interest. With their easily adaptable chemical composition, molecular structure, and processing versatility, these polymers hold immense potential in this field. Our study succeeded in focusing on synthesizing ferrocene-containing block copolymers (BCPs) based on polyacrylonitrile (PAN). The synthesis is accomplished via different poly(acrylonitrile- block -methacrylate)s via atom transfer radical polymerization (ATRP) and activators regenerated by electron transfer ATRP (ARGET ATRP) for the PAN macroinitiators. The molecular weights of the BCPs range from 44 to 82 kDa with dispersities between 1.19 and 1.5 as determined by SEC measurements. The volume fraction of the PMMA block ranges from 0.16 to 0.75 as determined by NMR. The post-modification of the BCPs using 3-ferrocenyl propylamine has led to the creation of redox-responsive preceramic polymers. The thermal stabilization of the polymer film has resulted in stabilized morphologies based on the oxidative PAN chemistry. The final pyrolysis of the sacrificial block segment and conversion of the metallopolymer has led to the formation of a porous carbon network with an iron oxide functionalized surface, investigated by scanning electron microscopy (SEM), energy dispersive X-ray mapping (EDX), and powder X-ray diffraction (PXRD). These findings could have significant implications in various applications, demonstrating the practical value of our research in convenient ceramic material design.

Following recent investigation in the ternary system Sr-Al-Pt led to the discovery of SrAl 5 Pt 3 which crystallizes in the orthorhombic YNi 5 Si 3 type ( Pnma ) structure. Interestingly, only two more aluminum representatives, CeAl 5 Pt 3 and EuAl 5 Pt 3 , have been reported to adopt this structure type. Therefore, we decided to investigate the existence range of compounds adopting the YNi 5 Si 3 type structure. Besides the already known Sr, Ce and Eu members, the series could be extended to Ca, Y and La-Nd as well as Sm-Er. All compounds were synthesized from the elements and characterized by powder X-ray diffraction. While for CaAl 5 Pt 3 and LaAl 5 Pt 3 also the respective M 2 Al 16 Pt 9 members were observed, the other compounds could be obtained either as X-ray pure materials or with small amounts of Al 3 Pt 2 as a side phase. The structure of ErAl 5 Pt 3 could be refined from single crystal data, verifying that also the small rare-earth elements adopt the YNi 5 Si 3 type structure. Selected members of the series were furthermore characterized by magnetization and susceptibility measurements. Since YAl 5 Pt 3 could be obtained as a phase pure material and exhibits no paramagnetic behaviour it was investigated by 27 Al MAS NMR investigations. Also, XPS measurements were conducted on this compound to gain an insight into the charge distribution. Finally, quantum-chemical calculations supported the NMR measurements and gave an insight into the chemical bonding and the charge distribution.

Laves phases exhibit a plethora of different structures and a multitude of physical properties. Investigations in the ternary system Hf-V-Al led to the discovery of numerous members of the solid solution Hf(V 1- x Al x ) 2 , which adopt the hexagonal MgZn 2 type (C14) for medium to high amounts of Al ( x = 0.2-1) and the cubic MgCu 2 type (C15) for small Al amounts ( x = 0.05-0.1). While all members exhibit Pauli-paramagnetic behavior due to the absence of localized magnetic moments, the V-rich cubic member Hf(V 0.95 Al 0.05 ) 2 additionally exhibits a superconducting state below T C = 7.6(1) K. All synthesized compounds were characterized by powder X-ray diffraction, and selected samples were furthermore investigated by 27 Al solid-state magic-angle spinning (MAS) NMR. HfAl 2 exhibits two Al resonances, one rather sharp and one significantly broadened signal, in line with the crystal structure and respective coordination environments. The members of the solid solution exhibit extremely broadened resonances due to the mixing of V and Al on the same crystallographic sites. For nominal Hf(V 0.125 Al 0.875 ) 2 , however, two distinct sharp NMR signals were observed. This contrasts with the description of a solid solution. Therefore, single-crystal X-ray studies were conducted, showing that Hf(V 0.125 Al 0.875 ) 2 really is an ordered compound with the sum formula Hf 4 VAl 7 ( P 3̅ m 1), which exhibits an, thus far, unknown superstructure of MgZn 2 .

Oligo- and polysiloxanes are usually prepared by condensation reactions in solvents without control of stereochemistry. Here we present a solventless thermal condensation of stable organosilanols. We investigated the condensation reactions of organosilanediols with different organic substituents, having in common at least one aromatic group. The condensation kinetics of the precursors observed by NMR spectroscopy revealed a strong dependence on temperature, time, and substitution pattern at the silicon atom. SEC measurements showed that chain length increases with increasing condensation temperature and time and lower steric demand of the substituents, which also influences the glass transition temperatures (T g ) of the resulting oligo- or polymers. X-ray diffraction studies of the crystalline silanediols and their condensation products revealed a structural correlation between the substituent location in the crystalline precursors and the formed macromolecules induced by the hydrogen bonding pattern. In certain cases, it is possible to carry out topotactic polymerization in the solid-state, which has its origin in the crystal structure., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The present review summarizes important aspects of the crystal chemistry of ytterbium-based intermetallic compounds along with a selection of their outstanding physical properties. These originate in many cases from the ytterbium valence. Different valence states are possible here, divalent (4f 14 ), intermediate-valent, or trivalent (4f 13 ) ytterbium, resulting in simple diamagnetic, Pauli or Curie-Weiss paramagnetic, or valence fluctuating behavior. Especially, some of the Yb 3+ intermetallics have gained deep interest due to their Kondo or heavy Fermion ground states. We have summarized their property investigations using magnetic and transport measurements, specific heat data, NMR, ESR, and Mössbauer spectroscopy, elastic and inelastic neutron scattering, and XAS data as well as detailed thermoelectric measurements., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

The synthesis of a water-soluble polycobaltoceniumylmethylene chloride (PCM-Cl) via ring-opening transmetalation polymerization is presented. Starting from a carba[1]magnesocenophane and cobalt(II) chloride, this route gives access to a polymer with methylene-bridged cobaltocenium moieties within the polymers' main-chain. The polymer was characterized by NMR spectroscopy, elemental analysis, TGA, DSC, XRD, and CV measurements, as well as UV-vis spectroscopy. Furthermore, GPC measurements in an aqueous eluent versus pullulan standards were conducted to gain insight into the obtained molar masses and distributions. In addition, the ion-dependent solubility was demonstrated by anion exchange, tuning the hydrophobic/hydrophilic properties of this redox-responsive material.

The fabrication of nanocomposites containing magnetic nanoparticles is gaining interest as a model for application in small electronic devices. The self-assembly of block copolymers (BCPs) makes these materials ideal for use as a soft matrix to support the structural ordering of the nanoparticles. In this work, a high-molecular-weight polystyrene- b -poly(methyl methacrylate) block copolymer (PS- b -PMMA) was synthesized through anionic polymerization. The influence of the addition of different ratios of PMMA-coated FePt nanoparticles (NPs) on the self-assembled morphology was investigated using transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). The self-assembly of the NPs inside the PMMA phase at low particle concentrations was analyzed statistically, and the negative effect of higher particle ratios on the lamellar BCP morphology became visible. The placement of the NPs inside the PMMA phase was also compared to theoretical descriptions. The magnetic addressability of the FePt nanoparticles inside the nanocomposite films was finally analyzed using bimodal magnetic force microscopy and proved the magnetic nature of the nanoparticles inside the microphase-separated BCP films.

During attempts to synthesize Sc 4 AuAl in the cubic Gd 4 RhIn-type structure, the solid solution Sc 2 Au 0.5 Al 0.5 in the PbCl 2 -type structure formed instead. Subsequently, the solid solution Sc 2 Au 1- x Al x was investigated with respect to its existence range along with the structure types formed for different compositions with x = 0, 0.25, 0.5, 0.75, and 1. According to X-ray powder diffraction studies, Sc 2 Al and nominal Sc 2 Au 0.25 Al 0.75 crystallized in the hexagonal Ni 2 In-type structure ( P 6 3 / mmc ), while Sc 2 Au 0.5 Al 0.5 , Sc 2 Au 0.75 Al 0.25 , and Sc 2 Au were found to crystallize in the orthorhombic PbCl 2 -type structure ( Pnma ). The crystal structures of Sc 2 Au and Sc 2 Au 0.59(1) Al 0.41(1) were refined from single-crystal data (Sc 2 Au: a = 648.0(1), b = 467.2(1), c = 835.2(2) pm, wR 2 = 0.0382, 535 F 2 values, 25 variables; Sc 2 Au 0.59(1) Al 0.41(1) : a = 632.48(5), b = 472.16(3), c = 848.67(6) pm, wR 2 = 0.0484, 540 F 2 values, 21 variables). Contamination with air during the synthesis of Sc 2 Au led to the discovery of a compound adopting the cubic W 4 Co 2 O 2 Ni type). Using Sc 2 O 3 O 4 Au 2 O 1- x . All intermetallic compounds exhibited Pauli paramagnetic behavior in the investigated temperature range of 2.1 to 300 K, and no superconductivity was observed at low temperatures and low fields. Sc 2 Au and Sc 2 Al were investigated by 27 Al and 45 Sc solid-state NMR investigations. For Sc 2 Al, one signal was found in the 27 Al NMR spectra in line with the crystal structure; however, an extremely negative resonance shift of δ = -673 ppm was observed. In both compounds, two Sc resonances were observed, in line with the proposed crystal structure. Finally, it was observed that the stability of Sc 2 Au in air is limited. This was investigated via thermal analysis and (temperature-dependent) powder X-ray diffraction. DFT calculations helped in assessing charge analysis, electronic properties, and chemical bonding.

Partially or fully reduced transition metal oxides show extraordinary electronic and catalytic properties but are usually prepared by high temperature reduction reactions. This study reports the systematic investigation of the fast mechanochemical reduction of rutile-type TiO 2 and H-Nb 2 O 5 to their partially reduced black counterparts applying NaH and LiH as reducing agents. Milling time and oxide to reducing agent ratio show a large influence on the final amount of reduced metal ions in the materials. For both oxides LiH shows a higher reducing potential than NaH. An intercalation of Li + into the structure of the oxides was proven by PXRD and subsequent Rietveld refinements as well as 6 Li solid-state NMR spectroscopy. The products showed a decreased band gap and the presence of unpaired electrons as observed by EPR spectroscopy, proving the successful reduction of Ti 4+ and Nb 5+ . Furthermore, the developed material exhibits a significantly enhanced photocatalytic performance towards the degradation of methylene blue compared to the pristine oxides. The presented method is a general, time efficient and simple method to obtain reduced transition metal oxides., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Inorganic-organic hybrid materials with redox-active components were prepared by an aqueous precipitation reaction of ammonium heptamolybdate (AHM) with para-phenylenediamine (PPD). A scalable and low-energy continuous wet chemical synthesis process, known as the microjet process, was used to prepare particles with large surface area in the submicrometer range with high purity and reproducibility on a large scale. Two different crystalline hybrid products were formed depending on the ratio of molybdate to organic ligand and pH. A ratio of para-phenylenediamine to ammonium heptamolybdate from 1 : 1 to 5 : 1 resulted in the compound [C 6 H 10 N 2 ] 2 [Mo 8 O 26 ] ⋅ 6 H 2 O, while higher PPD ratios from 9 : 1 to 30 : 1 yielded a composition of [C 6 H 9 N 2 ] 4 [NH 4 ] 2 [Mo 7 O 24 ] ⋅ 3 H 2 O. The electrochemical behavior of the two products was tested in a battery cell environment. Only the second of the two hybrid materials showed an exceptionally high capacity of 1084 mAh g -1 at 100 mA g -1 after 150 cycles. The maximum capacity was reached after an induction phase, which can be explained by a combination of a conversion reaction with lithium to Li 2 MoO 4 and an additional in situ polymerization of PPD. The final hybrid material is a promising material for lithium-ion battery (LIB) applications., (© 2022 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

The cubic Laves-phase aluminides REAl 2 with RE = Sc, Y, La, Yb and Lu were prepared from the elements by arc-melting or using refractory metal ampoules and induction heating. They all crystallize in the cubic crystal system with space group Fd 3̄ m and adopt the MgCu 2 type structure. The title compounds were characterized by powder X-ray diffraction and spectroscopically investigated using Raman and 27 Al and in the case of ScAl 2 by 45 Sc solid-state MAS NMR. In both, the Raman and NMR spectra, the aluminides exhibit only one signal due to the crystal structure. DFT calculations were used to calculate Bader charges illustrating the charge transfer in these compounds along with NMR parameters and densities of states. Finally, the bonding situation was assessed by means of ELF calculations rendering these compounds aluminides with positively charged RE δ + cations embedded in an [Al 2 ] δ - polyanion.

The binary alkaline-earth aluminides AE Al 2 ( AE = Ca and Sr) and AE Al 4 ( AE = Ca-Ba) have been synthesized from the elements and investigated via powder X-ray diffraction experiments. CaAl 2 adopts the cubic MgCu 2 -type structure ( Fd 3̅ m ), while SrAl 2 crystallizes in the orthorhombic KHg 2 -type ( Imma ). LT-CaAl 4 crystallizes with the monoclinic CaGa 4 -type ( C 2/ m ), while HT-CaAl 4 , SrAl 4 , and BaAl 4 adopt the tetragonal BaAl 4 -type structure ( I 4/ mmm ). The close structural relation of the two CaAl 4 polymorphs was established using a group-subgroup relation in the Bärnighausen formalism. In addition to the room-temperature and normal pressure phase of SrAl 2 , a high-pressure/high-temperature phase has been prepared using multianvil techniques, and its structural and spectroscopic parameters were determined. Elemental analysis by inductively coupled plasma mass spectrometry showed that no significant impurities with other elements besides the weighed ones are present and the chemical compositions match the synthesized ones. The title compounds have been furthermore investigated by 27 Al solid-state magic angle spinning NMR experiments to validate the crystal structure and to gain information about the influence of the composition on the electron transfer and the NMR characteristics. This has also been investigated from a quantum chemical point of view using Bader charges, while the stabilities of the binary compounds in the three phase diagrams (Ca-Al, Sr-Al and Ba-Al) have been studied by calculations of formation energies per atom.

The silanide [Si 4 {N(SiMe 3 )Dipp} 3 ] - (1) transforms into the anionic siliconoid cluster [Si 7 {N(SiMe 3 )Dipp} 3 ] - (2) with four unsubstituted silicon atoms as a contact ion pair with [K([18]crown-6)] in C 6 D 6 at room temperature within five weeks. Anion 2 was investigated by natural population analysis and visualization of intrinsic atomic orbitals. Magnetically induced current-density calculations of 2 revealed two distinct strong diatropic vortices that sum up in one direction and create a strongly shielded apical silicon atom in 2., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Transition-metal borides (TMBs) containing B n -fragment (n>3) have recently gained interest for their ability to enable exciting magnetic materials. Herein, we show that the B 4 -containing TiFe 0.64(1) Os 2.36(1) B 2 is a new ferromagnetic TMB with a Curie temperature of 523(2) K and a Weiss constant of 554(3) K, originating from the chain of M 3 -triangles (M=64 %Fe+36 %Os). The new phase was synthesized from the elements by arc-melting, and its structure was elucidated by single-crystal X-ray diffraction. It belongs to the Ti 1+x Os 2-x RuB 2 -type structure (space group P 6 ‾ 2 m, no. 189) and contains trigonal-planar B 4 boron fragments [B-B distance of 1.87(4) Å] interacting with M 3 -triangles [M-M distances of 2.637(8) Å and 3.0199(2) Å]. The experimental results were supported by computational calculations based on the ideal TiFeOs 2 B 2 composition, which revealed strong ferromagnetic interactions within and between the Fe 3 -triangles. This discovery represents the first magnetically ordered Os-rich TMB, thus it will help expand our knowledge of the role of Os in low-dimensional magnetism of intermetallics and enable the design of such materials in the future., (© 2022 Wiley-VCH GmbH.)

Two polymorphs of the borosulfate Cu[B 2 (SO 4 ) 4 ] can be selectively prepared by solvothermal syntheses. The crystal structures of inosilicate-analogous α-Cu[B 2 (SO 4 ) 4 ] ( P 1̄, no. 2, a = 5.2636(2), b = 7.1449(2), c = 7.9352(2) Å, α = 73.698(2)°, β = 70.737(2)°, γ = 86.677(2)°, 65 parameters, R Bragg = 0.0052) and the new phyllosilicate-analogous polymorph β-Cu[B 2 (SO 4 ) 4 ] ( P 2 1 / n , no. 14, a = 7.712(3), b = 8.149(3), c = 9.092(3) Å, β = 111.22(1)°, 3829 independent reflections, 106 parameters, wR 2 = 0.054) are discussed. Further, the optical, magnetic and thermal properties of both polymorphs are investigated with focus on the role of the Cu 2+ cation and its Jahn-Teller effect. The findings are confirmed by DFT calculations yielding insights in the stability of the synthesised polymorphs as well as a predicted γ-modification. Additionally, the crystal structures of two polymorphs of copper hydrogensulfate Cu(HSO 4 ) 2 -I ( P 2 1 / n , no. 14, a = 4.7530(2), b = 8.5325(4), c = 7.3719(3) Å, β = 100.063(1)°, 1063 independent reflections, 55 parameters, wR 2 = 0.052) and Cu(HSO 4 ) 2 -II ( P 1̄, no. 2, a = 4.79.88(8), b = 7.857(1), c = 8.057(1) Å, α = 77.86(1)°, β O γ = 89.82(1)°, 1044 independent reflections, 109 parameters, wR 2 = 0.132) as well as that of Cu[S 2 O 7 ] ( C 2/ c , no. 15, a = 6.6341(4), b = 8.7302(5), c = 9.0555(8) Å, β = 104.763(3)°, 1117 independent reflections, 48 parameters, wR 2 = 0.049) are presented and the cyclosilicate-analogous borosulfate Cu[B(SO 4 ) 2 (HSO 4 )] is fully characterised with respect to its optical and thermal properties.

Due to their various applications, metal oxides are of high interest for fundamental research and commercial usage. Per applications as catalysts or electrochemical devices, the tailored design of metal oxides featuring a high specific surface area and additional functionalities is of the utmost importance for the performance of the resulting materials. We report a new method for preparing free-standing films consisting of hierarchically porous metal oxides (titanium and niobium based) by combining emulsion polymerization and shear-induced monodisperse particle self-assembly in the presence of sol-gel precursors. After thermal treatment, the resulting porous materials can be used as electrodes in Li-ion batteries. The titanium and niobium sol-gel precursors were partially immobilized to the surface of organic core-interlayer particles featuring hydroxyl groups to obtain hybrid organic-inorganic particles through the melt-shear organization process. Free-standing particle-based films, in analogy to elastomeric opal films and colloidal crystals, can be prepared in a convenient one-step preparation process. After thermal treatment, ordered pores are obtained, while the pristine metal oxide precursor shell can be converted to the (mixed) metal oxide matrix. Heat treatment under CO 2 leads to mixed-TiNb oxide/carbon hybrid materials. The highly porous derivative structure enhances electrolyte permeation. When tested as Li-ion battery electrodes, it shows a specific capacity of 335 mAh·g -1 at a rate of 10 mA·g -1 . After 1000 cycles at 250 mA·g -1 , the electrodes still provided a specific capacity of 191 mAh·g -1 .

Designing new rare-earth-free (REF) permanent magnetic materials (PMM) to replace the high performing but critically restrained rare-earth-based PMM remains a great challenge to the scientific community. Here, we report on the rational design of new REF PMM, Hf 2 M Ir 5 B 2 ( M = Fe, Mn) via a theory-experiment combined approach. Density functional theory (DFT) predicted strong interchain M - M spin-exchange coupling and large magnetocrystalline anisotropy energies ( E MAE ) for the new compounds, suggesting potential intrinsic PMM properties. Subsequent experimental bulk syntheses and magnetic characterizations established the highest ordering temperature ( T C ∼ 900 K) for Hf 2 FeIr 5 B 2 and the highest intrinsic coercivity ( H C ) value for Hf 2 MnIr 5 B 2 ( H C = 62.1 kA/m) reported to date for Ti 3 Co 5 B 2 -type compounds. Importantly, at room temperature both phases show significant coercivities due to intrinsic factors only, hinting at their huge potential to create REF PMM by improving extrinsic factors such as controlling the microstructure and the domain orientation.

A new member to the A 2 I B II C IV X 4 compound family, Cu 2 ZnSbS 4 , was synthesized successfully using ball milling and postannealing in H 2 S-atmosphere. For comparative purposes, Cu 3 SbS 4 was additionally prepared using the same synthetic approach. As is common for A 2 I B II C IV X 4 compounds, Cu 2 ZnSbS 4 crystallizes isostructural to Cu 3 SbS 4 in the stannite-type structure in space group I 42 m . Both antimony sulfides contain monovalent diamagnetic copper and are characterized by substantial covalent bonding. This is consistent with the 121 Sb isomer shifts occurring for the Mössbauer spectra of Cu 2 ZnSbS 4 (-7.71 mm s -1 ) and Cu 3 SbS 4 (-7.68 mm s -1 ) which fall in the region of covalently bonded Sb(V) compounds. These spectroscopic results are supported by electronic structure calculations.

Borosulfates are compounds analogous to silicates, with heteropolyanionic subunits of vertex-linked (SO 4 )- and (BO 4 )-tetrahedra. In contrast to the immense structural diversity of silicates, the number of borosulfates is yet very limited and the extent of their properties is still unknown. This is particularly true for representatives with phyllosilicate and tectosilicate analogue anionic substructures. Herein, we present Ni[B 2 (SO 4 ) 4 ] and Co[B 2 (SO 4 ) 4 ], two new borosulfates with phyllosilicate analogue topology. While the anionic subunits of both structures are homeotypic, the positions of the charge compensating cations differ significantly: Ni II is located between the borosulfate layers, while Co II -in contrast-is embedded within the layer. Detailed analysis of these two structures based on single-crystal X-ray diffraction, magnetochemical investigations, X-ray photoelectron spectroscopy, and quantum chemical calculations, unveiled the reasons for this finding. By in silico comparison with other divalent borosulfates, we uncovered systematic trends for phyllosilicate analogues leading to the prediction of new species., (© 2020 The Authors. Published by Wiley-VCH GmbH.)

The pentasodium rare-earth tungstates Na5M(WO4)4 are closely related to the sodium rare-earth double tungstates Na5M(WO4)2 both adopting the scheelite structure type (space group I41/a, no. 88). After the preparation of polycrystalline powders via flux syntheses improving the phase purity significantly, the crystal structures of Na5M(WO4)4 (M = Y, La-Nd, Sm-Lu, Bi) were determined by single crystal XRD and Rietveld analysis. Na5M(WO4)4 is a promising phosphor material both as a host and as a 100% phosphor due to the possible charge transfer of the tungstate group and the absence of any concentration quenching. Na5M(WO4)4 incongruently melts to Na5M(WO4)2 and Na2WO4. After the clarification of the crystallographic relationship of Na5M(WO4)4 and Na5M(WO4)2 based on a rare isomorphic transition of index 5 (i5) the non-linear trend of the decomposition temperature within the row of rare earth ions is explained systematically taking into account the existence of domains within the crystal structure predetermining the posterior decomposition. A miscibility gap for solid solutions of Na5Y(WO4)4 and Na5Eu(WO4)4 or Na5Tb(WO4)4 is identified and its temperature dependence is investigated. Furthermore, the investigation of the fluorescent properties of Na5M(WO4)4 (M = Pr, Sm, Eu, Tb, Tm, Bi), Na5Y1-xEux(WO4)4 and Na5Y1-yTby(WO4)4 provided insights into the weak ligand field and the energy transfer from WO42- to M3+ governed by the emission of the sensitiser within Na5M(WO4)4. Additionally, the compounds were characterised by magnetic measurements and vibrational, UV/Vis and 151Eu Mössbauer spectroscopy.

The new Y2Co3Ga9 and Gd3Ru4Al12 type representatives M2T3Al9 (M = Ca, Sr, Eu; T = Ir, Pt) and M3Rh4Al12 (M = Ca, Eu) have been synthesized from the elements by heating the respective elemental compositions in sealed tantalum tubes. The samples were analysed by powder X-ray diffraction to check their purity. By applying different temperature treatments, their phase purity and crystallinity were enhanced. The crystal structures of Ca3Rh4Al12 and Eu3Rh4Al12 (hexagonal Gd3Ru4Al12 type, P63/mmc) as well as Ca2Ir3Al9 and Ca2Pt3Al9 (orthorhombic Y2Co3Ga3 type, Cmcm) were refined from single-crystal X-ray diffraction data. All structures can be described based on distorted cube-like T@Al8 units that are connected to form strands. Additionally, an Al11 supertetrahedral building block can be identified within the structures. While the trigonal bipyramidal core of the cluster contains substantial bonding interactions in the case of the M3Rh4Al12 members, the connection via common edges in the case of the M2Ir3Al9 compounds seems to weaken these interactions. The differences in the bonding situation and the question why these different structure types are formed for the different transition metals has been targeted by quantum-chemical calculations. The calculated formation energy using three different reaction paths suggests that the stability of these phases is highly dependent on the side phases involved, even though Ca3T4Al12 phases are in general thermodynamically more favourable. According to the Bader analysis of the two polyanions, an improved covalent bonding can be observed in the [T4Al12]δ- over the [T3Al9]δ- framework.

TbPdAl 2 and the solid solution Tb 1- x Lu x PdAl 2 ( x = 0.1-1) have been synthesized via arc-melting techniques using the elements as starting materials and crystallize in the orthorhombic MgCuAl 2 -type structure ( Cmcm ). As expected, the unit cell volumes decrease due to the lanthanide contraction from the Tb to Lu compounds, thus showing Vegard behavior because of the differences of the ionic radii of the trivalent rare-earth cations. TbPdAl 2 orders ferromagnetically below T C = 85.5(5) K and shows partial magnetic saturation already at low fields. The magnetic phase transition has been additionally investigated by heat capacity measurements, showing a broadened λ anomaly at T HC = 83.2(1) K. The electrical resistivity is almost linear above T C , indicating dominant electron-phonon interactions. Below the ordering temperature, electron-spin wave scattering with a ρ ∼ T 2 behavior is evident. In the solid solution Tb 1- x Lu x PdAl 2 ( x = 0-1), the ferromagnetic Curie temperatures decrease in a linear fashion with increasing Lu content. Investigations of the magnetocaloric properties of TbPdAl 2 obtained a maximum magnetic entropy change of -Δ S M max = 1.2, 2.2, 3.1, and 3.6 J kg -1 K -1 for the field changes of Δ H = 10, 20, 50, and 70 kOe, respectively. The rather low values are caused by entropy losses due to hysteresis behavior. The relative cooling power for TbPdAl 2 , therefore, also exhibits comparably low values of 32, 81, 142, and 178 J kg -1 .

Over 20 new compounds of the RE 6 T 5 Al 7 series (RE = Sc, Y, Ce-Nd, Sm, Gd-Lu; T = Ru, Ir; Yb 6 Ir 5 Ga 7 type structure; superstructure of MgZn 2 ; fully ordered Nb 6.4 Ir 4 Al 7.6 type) have been synthesized. They crystallize in the hexagonal crystal system with space group P 6 3 / mcm . Their lattice parameters are in the ranges of a = 935-963 and c = 851-874 pm for the RE 6 Ru 5 Al 7 and a = 913-966 and c = 825-865 pm for the RE 6 Ir 5 Al 7 series. Four structures (Ho 6 Ru 5 Al 7 , Yb 6 Ru 4.68(1) Al 7.32(1) , Sc 6 Ir 5 Al 7 , and Ho 6 Ir 4.53(1) Al 7.47(1) ) have been refined from single-crystal data, indicating fully ordered structures for Ho 6 Ru 5 Al 7 and Sc 6 Ir 5 Al 7 ; however, T/Al mixing was observed on one crystallographic site for Ho 6 Ir 4.53(1) Al 7.47(1) and on two sites for Yb 6 Ru 4.68(1) Al 7.32(1) . The Sc-, Y-, and Lu-containing compounds exhibit Pauli paramagnetism in line with a filled d band for Ru and Ir. Ce 6 Ru 5 Al 7 exhibits mixed-valent behavior, while Yb 6 Ru 5 Al 7 is solely trivalent. The other compounds exhibit paramagnetism and ferromagnetic phase transitions up to temperatures of T C = 83.4(1) K for Gd 6 Ru 5 Al 7 . In addition to the basic magnetic characterizations and studies of the electrical resistivity and heat capacity, the magnetocaloric properties of Gd 6 Ru 5 Al 7 , Tb 6 Ru 5 Al 7 , and Dy 6 Ru 5 Al 7 have been investigated, revealing magnetic entropy changes of -Δ S M max = 6.2(1), 7.7(1), and 5.4(1) J kg -1 K -1 (0 → 5 T) and relative cooling powers RCP = 242, 207, and 135 J kg -1 , respectively. For a deeper insight into the second-order magnetic phase transitions, the critical behavior was investigated according to the scaling hypothesis. The critical behavior of Gd 6 Ru 5 Al 7 is in accordance with the mean-field theory; the critical exponents of Tb 6 Ru 5 Al 7 and Dy 6 Ru 5 Al 7 , however, deviate strongly from this universality class. For comparison of the structural and magnetic properties, the thus far unstudied members of the RERuAl series (RE = Sc, Y, Sm, Gd-Lu; MgZn 2 type) have additionally been prepared and characterized.

A temperature induced valence phase transition from Yb 3+ at higher temperatures to Yb 2+ at lower temperatures was observed at T = 110(1) K for intermetallic YbPd 2 Al 3 . The title compound has been prepared from the elements in sealed tantalum ampoules. The structure was refined from single-crystal data and the title compound was found to crystallize in the hexagonal YNi 2 Al 3 type structure with space group P 6/ mmm and lattice parameters of a = 929.56(7) and c = 420.16(3) pm (300 K data). Full ordering of the Pd and Al atoms within the [Pd 2 Al 3 ] δ - polyanion was observed. Magnetic measurements revealed an anomaly in the dc susceptibility data and intermediate valent Yb at higher temperature, as observed from the effective magnetic moment. The proposed valence phase transition was also observed as a λ -type anomaly in heat capacity measurements ( T = 108.4(1) K), however, no systematic shift of the λ -peak was observed in field dependent heat capacity measurements. An antiferromagnetic ordering at this temperature, however, could be excluded, based on field-dependent susceptibility measurements and magnetization isotherms. No dynamic phenomenon was observed in ac susceptibility measurements, excluding e.g. spin-glass behavior. Subsequent temperature dependent single-crystal and powder X-ray diffraction experiments indicated a steep increase in the length of the c axis around T = 110 K upon cooling. However, no structural phase transition was found via single-crystal diffraction experiments conducted at 90 K. The anomaly was also observed in other physical measurements of e.g. the electrical resistivity, indicating a clear change in the electronic structure of the material. X-ray photoelectron spectroscopy conducted at room temperature shows the presence of both, Yb 2+ and Yb 3+ , underlining the mixed-valent state. Members of the solid solution Yb 1- x Ca x Pd 2 Al 3 ( x = 0.33, 0.67, 1) were finally used to further study the charge ordering and the present temperature induced valence phase transition., (This journal is © The Royal Society of Chemistry 2019.)

The new intermetallic compound Ba 6 Pt 22 Al 53 was obtained from reaction of the elements. The title compound crystallizes in the hexagonal crystal system with lattice parameters of a = 1427.5(3) and c = 1614.3(4) pm and space group P6 3 /mcm (Z = 2) and adopts a new structure type (Pearson code hP162, Wyckoff sequence l 2 k 3 j 2 i 2 hg 2 ecb). In the structure, the Pt and Al atoms form a complex polyanionic [Pt 22 Al 53 ] δ- network, while the Ba cations reside in cavities. The structure can be described as a packing of layers, formed by the Pt@Al n polyhedra parallel to (001). The layers are stacked in an ABCB fashion. Within the [Pt 22 Al 53 ] framework, one of the shortest Pt-Al distances (239 pm) reported is found, suggesting extremely strong covalent bonding interactions. Due to slightly enhanced displacement parameters of the Al9 site, temperature dependent single-crystal X-ray diffraction (285 and 90 K) and low-temperature heat capacity experiments were conducted. However, no structural phase transition was observed down to 2 K. With the help of DFT calculations, the bonding situation was elucidated in detail, verifying the strong heteroatomic bonding and the destabilization of the structure upon in silico distortions. Mulliken charge calculations confirm the picture of the polyanionic framework and cationic Ba atoms within the cavities.

The synthesis of zero-valent iron (Fe(0)) nanoparticles in pyridine using lithium bipyridinyl ([LiBipy]) or lithium pyridinyl ([LiPy]) is presented. FeCl 3 is used as the most simple starting material and reduced either in a [LiBipy]-driven two-step approach or in a [LiPy]-driven one-pot synthesis. High-quality nanoparticles are obtained with uniform, spherical shape, and mean diameters of 2.9 ± 0.5 nm ([LiBipy]) or 4.1 ± 0.7 nm ([LiPy]). The as-prepared, high purity Fe(0) nanoparticles are monocrystalline. In addition to particle characterization (high-resolution transmission electron microscopy, scanning transmission electron microscopy, dynamic light scattering), composition and purity are examined in detail based on electron diffraction, X-ray powder diffraction, elemental analysis, infrared spectroscopy, 57 Fe Mössbauer spectroscopy, and magnetic measurements. Due to their small size and high purity, the Fe(0) nanoparticles are highly reactive. They can be used in follow-up reactions to obtain a variety of iron compounds, which is exemplarily shown for the transformation to iron carbide (Fe 3 C) nanoparticles, the reaction with sulfur to obtain FeS nanoparticles, or the direct reaction with pentamethylcyclopentadiene to FeCp* 2 (Cp*: pentamethylcyclopentadienyl)., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Four new MPtAl 2 (M=Ca, Sr, Ba, Eu) compounds, adopting the orthorhombic MgCuAl 2 -type structure, have been synthesized from the elements using tantalum ampoules. All compounds are obtained as platelet-shaped crystallites and exhibit an increasing moisture sensitivity with increasing size of the formal M cation. Structural investigations indicate a pronounced elongation of the crystallographic b-axis, which results in a significant distortion of the [PtAl 2 ] δ- polyanion. Within the polyanion, layer-like arrangements can be found with bonding Pt-Al interactions within the slab; the increase of the b-axis can be attributed to increasing Al-Al distances and therefore decreasing interactions between the slabs, caused by the differently-sized formal M cations. While the alkaline earth (M=Ca, Sr) representatives exhibit Pauli paramagnetism, BaPtAl 2 shows diamagnetic behavior, finally EuPtAl 2 is ferromagnetic with T C =54.0(5) K. The effective magnetic moment indicates that the Eu atoms are in a divalent oxidation state, which is confirmed by 151 Eu Mössbauer spectroscopic investigations. Measurements below the Curie-temperature show a full magnetic hyperfine field splitting with B hf =21.7(1) T. 27 Al and 195 Pt magic-angle spinning NMR spectroscopy corroborates the presence of single crystallographic sites for the Pt and Al atoms. The large 27 Al nuclear electric quadrupolar coupling constants confirm unusually strong electric field gradients, in agreement with the structural distortions and the respective theoretical calculations. X-ray photoelectron spectroscopy has been utilized to investigate the charge transfer within the polyanion. The Pt 4f binding energy decreases with decreasing electronegativity / ionization energy of the alkaline earth elements, suggesting an increasing electron density at the Pt atoms. Theoretical investigations underline the platinide character of the investigated compounds by Bader charge calculations. The analysis of the integrated crystal orbital Hamilton population (ICOHP) values, electron localization function (ELF) and isosurface analyses lead to a consistent structural picture, indicating stable layer-like arrangements of the [PtAl 2 ] δ- polyanion., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A total of 35 intermetallic aluminum compounds have been synthesized from the elements via arc melting and characterized by powder X-ray diffraction. A total of 15 of them have been previously reported; however, detailed property investigations were missing. Compounds of the RETMAl 2 (rare earth metal RE = Sc, Y, La-Nd, Sm, Gd-Tm, Lu) series with transition metal TM = Ni, Pd, and Pt crystallize isostructurally in the orthorhombic MgCuAl 2 type structure ( Cmcm, oC16, fc 2 ). Single-crystal X-ray diffraction investigations were conducted on YNiAl 2 , LaNiAl 2 , YPdAl 2 , ScPtAl 2 , and YPtAl 2 . The TM and Al atoms form a [TMAl 2 ] δ- polyanion, the RE atoms reside in cavities within the framework. While the Sc, Y, La, and Lu compounds exhibit Pauli-paramagnetic behavior, consistent with all atoms being closed shell, the other RETMAl 2 compounds show paramagnetism along with magnetic ordering at low temperatures, in line with an open-shell trivalent oxidation state for the RE atoms. Solid-state 27 Al NMR investigations were carried out on the Pauli-paramagnetic samples, all showing only a single central transition, in line with one crystallographic site for the respective atoms. The observed quadrupolar coupling constants and electric-field-gradient asymmetry parameters were found to be in good agreement with the density-functional-theory-calculated values. Isotropic resonance shifts are dominated by the Fermi-contact interactions with s-conduction electron densities at the Fermi edge (Knight shifts). The bonding characteristics mirror the electronic density of states and crystal chemistry of the family of intermetallic compounds under consideration. Both the Knight shifts and quadrupolar coupling constants can be predicted based on element-specific increments.

3d transition metal nitridophosphates M II P 8 N 14 (M II =Fe, Co, Ni) were prepared by high-pressure metathesis indicating that this route might give a systematic access to a structurally rich family of M-P-N compounds. Their structures, which are stable in air up to at least 1273 K, were determined through powder X-ray diffraction and consist of highly condensed tetra-layers of PN 4 tetrahedra and MN 6 octahedra. Magnetic measurements revealed paramagnetic behavior of CoP 8 N 14 and NiP 8 N 14 down to low temperatures while, FeP 8 N 14 exhibits an antiferromagnetic transition at T N =3.5(1) K. Curie-Weiss fits of the paramagnetic regime indicate that the transition metal cations are in a oxidation state +II, which was corroborated by Mössbauer spectroscopy for FeP 8 N 14 . The ligand field exerted by the nitride ions in CoP 8 N 14 and NiP 8 N 14 was determined from UV/Vis/NIR data and is comparable to that of aqua-ligands and oxophosphates., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Eu 2 Ir 3 Al 9 , synthesized from the elements in tantalum tubes, is one of the rare examples for trivalent europium in the field of intermetallic compounds. The compound crystallizes in the Y 2 Co 3 Ga 9 -type structure (space group Cmcm), with lattice parameters fitting in between the isostructural samarium and gadolinium compounds. In the crystal structure, the Eu atoms form Al 3 -triangle-centered honeycomb layers and exhibit a coordination number of 17 in the shape of a fivefold-capped hexagonal prism (Eu@Ir 6 Al 6 +Al 5 ). Magnetic measurements indicate an overall low susceptibility, in line with van Vleck paramagnetism caused by the Eu 3+ cations. Fits of the susceptibility yield a coupling constant of λ=290(10) K and an effective magnetic moment of μ eff =4.56(1) μ B , in line with a slight hybridization of the 7 F 0 and 7 F 1 state. 151 Eu Mössbauer spectroscopic investigations unambiguously prove the presence of solely Eu 3+ in the bulk material., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Antiferromagnetic coupling in TEMPO-based radicals can be enhanced via self-assembly through London dispersion interactions in amphiphilic solids. The synthesis, magnetic characterization, and three crystal structures of the solid radical ion salts (R-DMAT-n)X with various counterions X and alkyl chain lengths n are reported. Magnetic susceptibility and absolute EPR signal intensity measurements show singlet-triplet transitions in a number of cases, which is discussed in relation to the crystal structures. Antiferromagnetic ordering effects are sensitive to both the length of the alkyl chain and the counter anion.

K 2 Cu 3 Ge 4 O 12 was synthesized via a solid-state reaction in a high-temperature experiment at 1073 K. Crystal structure analysis provided the following data: space group Cmcm (no. 63), a = 1407.9(2), b = 578.0(1), c = 1389.2(1) pm, V = 1.1305 nm 3 , and Z = 4. The structure consists of alternating layers of netlike arranged trimeric [Cu 3 O 8 ] 10- units and layers of four-membered rings of GeO 4 tetrahedra. The potassium cations connect the different structural moieties. Although both structural motifs are well-known, the way they are connected in K 2 Cu 3 Ge 4 O 12 is unique. K 2 Cu 3 Ge 4 O 12 was further characterized via vibrational spectroscopy and SEM-EDX measurements. Magnetic measurements exhibit an antiferromagnetic behavior at low temperatures along with an unusual pseudo-2D coupling.

In this article, the first thoroughly characterized mixed-valent binary rare earth oxide synthesized under high-pressure/high-temperature conditions, and its low-temperature polymorph are reported. Crystalline HT-HP-Tb 3 O 5 has been prepared from an equimolar mixture of Tb 4 O 7 and Tb 2 O 3 under reaction conditions of 8 GPa and 1323 K. Single-crystal X-ray structure determination showed that HT-HP-Tb 3 O 5 crystallizes in the orthorhombic space group Pnma, isopointal to the β-Yb 5 Sb 3 -type structure. Temperature-dependent measurements of the magnetic susceptibility showed that HT-HP-Tb 3 O 5 is a Curie-Weiss paramagnet. The observed effective magnetic moment of μ eff =9.21(2) μ B per formula unit fits well to the calculated moment of μ calc =9.17 μ B . Low-field measurements revealed antiferromagnetic ordering at T N =3.6(1) K. Heat capacity measurements indicated an intrinsic structural phase transition of HT-HP-Tb 3 O 5 at low temperature, which was confirmed by synchrotron X-ray powder diffraction data recorded at 2 K. The metastable high-pressure modification HT-HP-Tb 3 O 5 undergoes a translationengleiche transition from space group Pnma to Pn2 1 a (non-standard setting of Pna2 1 ), leading to the low-temperature polymorph LT-HP-Tb 3 O 5 by loss of a mirror plane (displacive phase transition)., (© 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

In this study, we address the question of the origin of ferromagnetic or antiferromagnetic interactions in alkynyl-substituted 1,5-diphenyl-6-oxo verdazyl radicals. While a TMS-alkynyl derivative (3) shows antiferromagnetic ordering at low temperatures, the corresponding deprotected alkynyl verdazyl (4) shows ferromagnetic interactions. For both compounds, magnetic Heisenberg chains are characteristic, which were studied systematically by means of X-ray crystallography and quantum chemical calculations. Ferromagnetic interactions are rarely found in such radicals. Therefore, uncovering such structure-property relationships is of crucial importance in order to understand and design promising ferromagnetic networks. Using this knowledge, we were able to design and crystallize diyne derivatives showing comparable solid state characteristics and therefore antiferro- and ferromagnetic Heisenberg chain structures. We show that the understanding of such property-structure relationships is adequate for the design of organic-magnetic materials with defined cooperative effects within the class of verdazyl radicals.

Trinuclear titanium complexes coordinated by one ligand with three coordination sites have shown properties of mixed valency and a high number of reversible redox steps. Herein we report on the hexaphenyl-substituted derivative (Cp 2 Ti) 3 (μ 3 -HATNPh 6 ) (2). On reaction of 2 with the ferrocenium salt [Cp 2 Fe]BF 4 , the cationic complexes [(Cp 2 Ti) 3 (μ 3 -HATNPh 6 )] n+ ( n = 1-3; 3-5) become available in a selective way. Cyclic voltammograms show 10 reversible redox states of the trinuclear species 2 without decomposition. In order to classify the degree of electronic communication between the titanium centers, comproportionation constants K c , IVCT bands in NIR spectra, and magnetic measurements were analyzed. These parameters show strong coupling effects between the titanium centers but no full delocalization. In addition, single-crystal X-ray analysis of the neutral complex 2 and its oxidation products (1+ (3), 2+ (4), and 3+ (5)) revealed the geometric structure of the molecule in the solid state. For the cationic species anion-π interactions between the electron-deficient central ring of the HATNPh 6 ligand and BF 4 - counterions were found.

Borosulfates are an ever-expanding class of compounds and the extent of their properties is still elusive. Herein, the first two copper borosulfates Cu[B 2 (SO 4 ) 4 ] and Cu[B(SO 4 ) 2 (HSO 4 )] are presented, which are structurally related but show different dimensionalities in their substructure: While Cu[B 2 (SO 4 ) 4 ] reveals an anionic chain, ∞1 [B(SO 4 ) 4/2 ] - , with both a twisted and a unique chair conformation of the B(SO 4 ) 2 B subunits, Cu[B(SO 4 ) 2 (HSO 4 )] reveals isolated [B 2 (SO 4 ) 4 (HSO 4 ) 2 ] 4- anions showing exclusively a twisted conformation. The complex anion can figuratively be obtained as a cut-out from the anionic chain by protons. Comparative DFT calculations based on magnetochemical measurements complement the experimental studies. Calculation of the pK a  values of the two conformers of the [B 2 (SO 4 ) 4 (HSO 4 ) 2 ] 4- anion revealed them to be more similar to silicic than to sulfuric acid, highlighting the close relationship to silicates., (© 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Eu 2 Pt 6 Al 15 has been prepared from the elements via arc-melting and subsequent temperature treatment; the structure was refined from single crystal X-ray diffraction data. The compound crystallizes in an orthorhombic (3 + 1)D commensurately modulated structure (Sc 2 Pt 6 Al 15 type) with space group Cmcm(α,0,0)0 s0 (α = 2/3). Full ordering of the Pt and Al atoms within the [Pt 6 Al 15 ] δ- polyanion was observed. Magnetic measurements revealed an anomaly in the susceptibility data at T = 41.6(1) K, which was also observed as λ-type anomaly in heat capacity measurements ( T = 40.7(1) K). Temperature dependent powder X-ray diffraction experiments indicated a drastic shortening of the c axis (-18 pm, -1.1%) around 45 K, while the a axis nearly remains the same (-1 pm, -0.2%). Measurements of the electrical resistivity verified the anomaly, indicating a clear change in the electronic structure of the material. The observed anomalies in the physical measurements can be explained by a temperature driven first order valence change from Eu 2+ at higher temperatures (>55 K) to Eu 3+ at low temperatures. This valence change was proven by temperature dependent 151 Eu Mössbauer spectroscopic investigations. Isostructural Eu 2 Pt 6 Ga 15 was prepared in comparison, and it shows divalent Eu atoms down to 2.5 K along with antiferromagnetic ordering at T N = 13.1(1) K.

Dimeric germole dianion bridged Ti III and Zr IV complexes have been synthesized. In these complexes, the germole dianion adopts a formal η 1 ,η 5 coordination to the two metal centers. The bonding situation in these bridged dimers is dominated by a covalent Ge-Ge interaction that results, for example, in a strong antiferromagnetic coupling of the d 1 Ti centers., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The germanides YPtGe2 and GdPtGe2 were synthesized from REGe2 precursor compounds and platinum by arc-melting and their structures were studied on the basis of temperature-dependent single crystal X-ray diffraction data. At room temperature both germanides adopt the orthorhombic YIrGe2 type structure, space group Immm, with enhanced U11 displacement parameters for the Ge1 atoms. Below 174 and 145 K, respectively, satellite reflections emerge in the diffraction patterns, giving rise to modulations. The low-temperature structures were refined in the superspace group Pnnn(1/2,1/2,γ)qq0 (48.1.11.3). The structural phase transition is also evident in the magnetic susceptibility, specific heat and resistivity data. The high- and low-temperature modifications are discussed on the basis of a group-subgroup scheme.

Highly condensed nitridosilicates doped with Eu 2+ or Ce 3+ play an important role in saving energy by converting the blue light of (In,Ga)N-LEDs. Although nitridosilicates are known for great structural variety based on covalent anionic Si-N networks, elemental variety is restricted. Presenting a significant extension of the latter, this work describes a general access to open-shell transition-metal nitridosilicates. As a proof-of-principle, the first iron nitridosilicate, namely Fe 2 Si 5 N 8 , was prepared by exchanging Ca 2+ in α-Ca 2 Si 5 N 8 applying a FeCl 2 melt (salt metathesis). The title compound was analyzed by powder X-ray diffraction, EDX, ICP-OES, combustion analysis, TG/DSC, Mössbauer spectroscopy and magnetic susceptibility measurements. Furthermore, the structure of α-Ca 2 Si 5 N 8 was determined at 1073 and 1173 K confirming the anionic network of α-Ca 2 Si 5 N 8 providing possible migration pathways for the ion-exchange reaction., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Recently, we reported the synthesis and investigations of EuSr 2 Bi 2 S 4 F 4 and Eu 2 SrBi 2 S 4 F 4 . We have now been able to induce superconductivity in EuSr 2 Bi 2 S 4 F 4 by Se substitution at the S site (isovalent substitution) with T c = 2.9 K in EuSr 2 Bi 2 S 2 Se 2 F 4 . The other compound, Eu 2 SrBi 2 S 4 F 4 , shows a significant enhancement of T c . In Se-substituted Eu 2 SrBi 2 S 4-x Se x F 4 , we find T c = 2.6 K for x = 1.5 and T c = 2.8 K for x = 2, whereas T c = 0.4 K in the Se-free sample. In addition to superconductivity, an important effect associated with Se substitution is that it gives rise to remarkable changes in the Eu valence. Our 151 Eu Mössbauer and X-ray photoemission spectroscopic measurements show that Se substitution in both of the compounds Eu 2 SrBi 2 S 4 F 4 and EuSr 2 Bi 2 S 4 F 4 gives rise to an increase in the Eu 2+ component in the mixed-valence state of Eu.