AbstractAußergewöhnlich elektronenreiche, nahezu trigonal‐planare Tricyanidometallat‐Anionen [Fe(CN)3]7− und [Ru(CN)3]7− wurden in LiSr3[Fe(CN)3] und EA3.5[M(CN)3] (EA=Sr, Ba; M=Fe, Ru) stabilisiert. Es sind die ersten Beispiele für Metalle der Gruppe 8 in der Oxidationsstufe −IV. Mikrokristalline Pulver wurden über festkörperchemische Reaktionen erhalten, Einkristalle aus Alkalimetallschmelzen gezüchtet. Während LiSr3[Fe(CN)3] in P63/m kristallisiert, wird für EA3.5[M(CN)3] die polare Raumgruppe P63 mit dreifach vergrößertem Zellvolumen durch Frequenzverdopplung (SHG) bestätigt. Röntgenbeugung, IR‐ und Raman‐Spektroskopie zeigen größere C‐N‐Abstände (124–128 pm) und deutlich geringere Valenzschwingungsfrequenzen (1484–1634 cm−1) als in klassischen Cyanidometallaten. Das Bindungsschema aus schwachen C‐N‐Bindungen in Kombination mit starken M‐C‐π‐Bindungen erinnert an Carbonylmetallate. Abweichend von der rein formalen Notation [Fe−IV(CN−)3]7− führen quantenchemische Rechnungen zu redox‐aktiven, zwischenvalenten CN1.67− Liganden und einer geschlossenschaligen Fe d10‐Konfiguration, also Fe2−.

Exceptionally electron-rich, nearly trigonal-planar tricyanidometalate anions [Fe(CN)3 ]7- and [Ru(CN)3 ]7- were stabilized in LiSr3 [Fe(CN)3 ] and AE3.5 [M(CN)3 ] (AE=Sr, Ba; M=Fe, Ru). They are the first examples of group 8 elements with the oxidation state of -IV. Microcrystalline powders were obtained by a solid-state route, single crystals from alkali metal flux. While LiSr3 [Fe(CN)3 ] crystallizes in P63 /m, the polar space group P63 with three-fold cell volume for AE3.5 [M(CN)3 ] is confirmed by second harmonic generation. X-ray diffraction, IR and Raman spectroscopy reveal longer C-N distances (124-128 pm) and much lower stretching frequencies (1484-1634 cm-1 ) than in classical cyanidometalates. Weak C-N bonds in combination with strong M-C π-bonding is a scheme also known for carbonylmetalates. Instead of the formal notation [Fe-IV (CN- )3 ]7- , quantum chemical calculations reveal non-innocent intermediate-valent CN1.67- ligands and a closed-shell d10 configuration for Fe, that is, Fe2- .

Research on topological insulators (TIs) has rapidly progressed, notably owing to their intriguing physical properties. These materials are bulk semiconductors but host protected metallic surface states. As shown in the cover artwork, the spins of the electrons in these states are locked orthogonally to their propagation direction. Specific symmetries of the electronic band structure allow dissipation-free electron and information transport. Therefore, they are envisioned as promising candidates in the development of high-performance spin field-effect transistors and quantum bits. More information can be found in the Full Paper by M. Ruck et al. on page 15549.

Topological insulators (TIs) gained high interest due to their protected electronic surface states that allow dissipation-free electron and information transport. In consequence, TIs are recommended as materials for spintronics and quantum computing. Yet, the number of well-characterized TIs is rather limited. To contribute to this field of research, we focused on new bismuth-based subiodides and recently succeeded in synthesizing a new compound Bi12 Rh3 Sn3 I9 , which is structurally closely related to Bi14 Rh3 I9 - a stable, layered material. In fact, Bi14 Rh3 I9 is the first experimentally supported weak 3D TI. Both structures are composed of well-defined intermetallic layers of ∞ 2 [(Bi4 Rh)3 I]2+ with topologically protected electronic edge-states. The fundamental difference between Bi14 Rh3 I9 and Bi12 Rh3 Sn3 I9 lies in the composition and the arrangement of the anionic spacer. While the intermetallic 2D TI layers in Bi14 Rh3 I9 are isolated by ∞ 1 [Bi2 I8 ]2- chains, the isoelectronic substitution of bismuth(III) with tin(II) leads to ∞ 2 [Sn3 I8 ]2- layers as anionic spacers. First transport experiments support the 2D character of this material class and revealed metallic conductivity.

The influence of the growth temperature on the phase stability and composition of single-phase In1-xGaxN epilayers has been studied. The In1-xGaxN epilayers were grown by high-pressure Chemical Vapor Deposition with nominally composition of x = 0.6 at a reactor pressure of 15 bar at various growth temperatures. The layers were analyzed by x-ray diffraction, optical transmission spectroscopy, atomic force microscopy, and Raman spectroscopy. The results showed that a growth temperature of 925°C led to the best single phase InGaN layers with the smoothest surface and smallest grain areas

The reaction of Bi, BiCl3, and TlCl in the ionic liquid [BMIm]Cl·4AlCl3 (BMIm = 1-n-butyl-3-methylimidazolium) at 180 °C yielded air-sensitive black crystals of (Bi8)Tl[AlCl4]3. X-ray diffraction on single crystals at room temperature revealed a structure containing [ Tl ( AlCl 4 ) 3 ] ∞ 1 2 − strands separated by isolated Bi82+ square antiprisms. The thallium(I) ion is coordinated by twelve Cl− ions of six [AlCl4]− groups, resulting in a chain of face-sharing [TlCl12]11− icosahedra. The Bi82+ polycation is disordered, simulating a threefold axis through its center and overall hexagonal symmetry (space group P63/m). Slowly cooling the crystals to 170 K resulted in increased order in the Bi8 cluster orientations. An ordered structure model in a supercell with a’ = 2a, b’ = 2b, c’ = 3c and the space group P65 was refined. The structure resembles a hexagonal perovskite, with complex groups in place of simple ions.

High-quality single crystals of MnBi2Te4 are grown for the first time by slow cooling within a narrow range between the melting points of Bi2Te3 (586 degrees C) and MnBi2Te4 (600 degrees C). Single-crystal X-ray diffraction and electron microscopy reveal ubiquitous antisite defects in both cation sites and, possibly, Mn vacancies (Mn0.85(3)Bi2.10(3)Te4). Thermochemical studies complemented with high-temperature X-ray diffraction establish a limited high temperature range of phase stability and metastability at room temperature. Nevertheless, the synthesis of MnBi2Te4 can be scaled-up as powders can be obtained at subsolidus temperatures and quenched at room temperature. Bulk samples exhibit long-range antiferromagnetic ordering below 24 K. The Mn(II) out-of-plane magnetic state is confirmed by the magnetization, X-ray photoemission, X-ray absorption, and linear dichroism measurements. The compound shows a metallic type of resistivity in the range 4.5-300 K and is an n-type conductor that reaches a thermoelectric figure of merit up to ZT = 0.17. Angle-resolved photoemission experiments show a surface state forming a gapped Dirac cone, thus strengthening MnBi2Te4 as a promising candidate for the intrinsic magnetic topological insulator, in accordance with theoretical predictions. The developed synthetic protocols enable further experimental studies of a crossover between magnetic ordering and nontrivial topology in bulk MnBi2Te4.

The crystal structure of the important industrial orange pigment PO82, major part of the BASF Colors & Effects® product Sicopal® Orange K/L 2430, was solved from combined X‐ray single crystal, X‐ray and neutron powder diffraction, 119Sn Mössbauer spectroscopy, transmission electron microscopy, electron diffraction, and chemical analyses. The structure contains Keggin type clusters composed of four [M3O13] trimers consisting each of three MO6 octahedra that share edges and one common oxygen atom connecting the trimers to the central ZnO4 tetrahedron. The octahedrally coordinated metal atom position is mixed occupied by Ti4+, Sn4+, and Zn2+. Adjacent Keggin clusters share vertices and are further interconnected to four ZnO4 tetrahedra. This framework of interconnected MO6 octahedra and ZnO4 tetrahedra contains channels along [110], in which the Sn2+ cations are located.

We assessed the influence of Yb3+ and Er3+ dopant concentration on the relative spectral distribution, quantum yield (ΦUC), and decay kinetics of the upconversion luminescence (UCL) and particle brightness (BUC) for similarly sized (33 nm) oleate-capped β-NaYF4:Yb3+,Er3+ upconversion (UC) nanoparticles (UCNPs) in toluene at broadly varied excitation power densities (P). This included an Yb3+ series where the Yb3+ concentration was varied between 11%-21% for a constant Er3+ concentration of 3%, and an Er3+ series, where the Er3+ concentration was varied between 1%-4% for a constant Yb3+ concentration of 14%. The results were fitted with a coupled rate equation model utilizing the UCL data and decay kinetics of the green and red Er3+ emission and the Yb3+ luminescence at 980 nm. An increasing Yb3+ concentration favors a pronounced triphotonic population of 4F9/2 at high P by an enhanced back energy transfer (BET) from the 4G11/2 level. Simultaneously, the Yb3+-controlled UCNPs absorption cross section overcompensates for the reduction in ΦUC with increasing Yb3+ concentration at high P, resulting in an increase in BUC. Additionally, our results show that an increase in Yb3+ and a decrease in Er3+ concentration enhance the color tuning range by P. These findings will pave the road to a deeper understanding of the energy transfer processes and their contribution to efficient UCL, as well as still debated trends in green-to-red intensity ratios of UCNPs at different P.

An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the joint CCDC and FIZ Karlsruhe Access Structures service and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The reaction of Bi, BiCl3 , and CuCl in the ionic liquid [BMIm]Cl⋅4 AlCl3 (BMIm=1-n-butyl-3-methylimidazolium) at 180 °C yielded air-sensitive shiny black crystals of (CuBi8 )[AlCl4 ]2 [Al2 Cl7 ] and (CuBi8 )[AlCl4 ]3 . For both compounds X-ray diffraction on single crystals revealed monoclinic structures that contain the intermetalloid cluster (CuBi8 )3+ . It is the first pure bismuth cluster with a 3d metal and the first with a metal that does not form binary intermetallics with bismuth under ambient pressure. The cluster can be interpreted either as a copper(I) cation, η4 -coordinated by a square-antiprismatic Bi82+ polycation (Bi-Cu 267 pm), or as a nine-atomic intermetalloid nido-cluster with 22 skeletal electrons and the C4v symmetry. One of the chloride ions of a tetrahedral [AlCl4 ]- group coordinates the copper atom (Cu-Cl 228 pm) and thereby completes its 18 electron count. DFT-based calculations, followed by real-space bonding analysis, revealed a multicenter bonding situation between copper and bismuth atoms with about seven shared electrons.

Crystal growth of MnBi$_{2}$Te$_{4}$ has delivered the first experimental corroboration of the 3D antiferromagnetic topological insulator state. Our present results confirm that the synthesis of MnBi$_{2}$Te$_{4}$ can be scaled-up and strengthen it as a promising experimental platform for studies of a crossover between magnetic ordering and non-trivial topology. High-quality single crystals of MnBi$_{2}$Te$_{4}$ are grown by slow cooling within a narrow range between the melting points of Bi$_{2}$Te$_{3}$ (586 {deg}C) and MnBi$_{2}$Te$_{4}$ (600 {deg}C). Single crystal X-ray diffraction and electron microscopy reveal ubiquitous antisite defects in both cation sites and, possibly, Mn vacancies. Powders of MnBi$_{2}$Te$_{4}$ can be obtained at subsolidus temperatures, and a complementary thermochemical study establishes a limited high-temperature range of phase stability. Nevertheless, quenched powders are stable at room temperature and exhibit long-range antiferromagnetic ordering below 24 K. The expected Mn(II) out-of-plane magnetic state is confirmed by the magnetization, X-ray photoemission, X-ray absorption and linear dichroism data. MnBi$_{2}$Te$_{4}$ exhibits a metallic type of resistivity in the range 4.5-300 K. The compound is an n-type conductor that reaches a thermoelectric figure of merit up to ZT = 0.17. Angle-resolved photoemission experiments provide evidence for a surface state forming a gapped Dirac cone.

Halogen substitution, that is, bromine for iodine, in the series of topological BinTeI (n = 1, 2, 3) materials was conducted in order to explore the impact of anion exchange on topological electronic structure. In this proof-of-conceptstudy, we demonstrate the applicability of the modular view on crystal and electronic structures of new Bi2TeBr and Bi3TeBr compounds. Along with the isostructural telluroiodides, they constitute a family of layered structures that are stacked from two basic building modules, (2)(infinity)[Bi-2] and (2)(infinity)[BiTeX] (X = I, Br). We present solid-state synthesis, thermochemical studies, crystal growth, and crystal-structure elucidation of Bi2TeBr [space group R (3) over barm (no. 166), a = 433.04(2) pm, c = 5081.6(3) pm] and Bi3TeBr [space group R3m (no. 160), a = 437.68(3) pm, c = 3122.9(3) pm]. First-principles calculations establish the topological nature of Bi2TeBr and Bi3TeBr. General aspects of chemical bonding appear to be similar for BiTeX (X = I, Br) with the same n, so that alternation of the global gap size upon substitution is insignificant. The complex topological inversion proceeds between the states of two distinct modules, (2)(infinity)[Bi-2] and 203[BinTeBr]; thus, the title compounds can be seen as heterostructures built via a modular principle. Furthermore, highly disordered as well as incommensurately modulated ternary phase(s) are documented near the Bi2TeBr composition. Single crystal X-ray diffraction experiments on BiTeBr and Bi2TeI resolve some discrepancies in prior published work.

A convenient approach for a controlled and high-yield synthesis of copper-deficient Cu3-xP (0.1 < x < 0.7) is reported that makes use of ionic liquids with highly nucleophilic "naked" halide anions. Halide anions drastically enhance the reactivity of the white phosphorus precursor and kinetically disfavor the formation of phosphorus-rich side products. Cu3-xP shows a high degree of tolerance for cation vacancies without major structural reorganization, as evidenced by X-ray diffraction and solid-state nuclear magnetic resonance spectroscopy. Measurements of the electric properties reveal that Cu3-xP is a bad metallic p-type conductor. The resistivity is composition-dependent and displays a distinct anomaly from a phase transition, leading to the discovery and structural characterization of two hitherto unknown low temperature polymorphs. Electrochemical evaluation of copper-deficient Cu3-xP as anode material for lithium ion batteries reveals a drastic change in the cycling mechanism leading to an increase of the initial capacities by about 70%. This work gives a comprehensive insight into the chemical and structural features of copper-deficient Cu3-xP and should lead to an improved understanding of its properties, not just for battery applications.

We optimized the syntheses of α‐ and β‐Bi4I4 and transferred the method to the very bismuth‐rich iodides Bi14I4, Bi16I4, and Bi18I4. Phase‐pure, microcrystalline powders of BimI4 (m = 4, 14, 18) can now by synthesized on a multigram scale. Conditions for the growth of single crystals of Bi16I4 and Bi18I4 were determined. The redetermination of the crystal structure of Bi16I4 hints at a stacking disorder or the presence of 1∞[BimI4] ribbons with m = 14 and 18 among the dominant type along with m = 16. The electronic band structures for m = 14, 16, and 18 were calculated including spin‐orbit coupling. They vary markedly with m and show numerous bands crossing the Fermi level, predicting a 3D‐metallic behavior. Measurements of the electrical resistivity of a polycrystalline sample of Bi14I4 as well as polycrystalline and single‐crystalline samples of Bi18I4 confirmed their metallic nature over the temperature range 300 K to 2 K. For Bi18I4, a positive and strictly linear magnetoresistance at 2 K in static magnetic fields up to 14 T was observed, which could indicate a topologically nontrivial electronic state.

In article 1701635, by Ute Resch-Genger, Artur Bednarkiewicz, and co-workers, Yb3+ and Ho3+ co-doped core–shell colloidal nanoparticles are synthesized and studied. The obtained nanocrystals were designed to have the same chemical composition, but diverse spatial distribution of dopants. The observed differences shine new light on the photo-physical behavior of luminescent nanoparticles with tailored chemical architecture for numerous potential applications.

Structural engineering of topological bulk materials is systematically explored with regard to the incorporation of the buckled bismuth layer [Bi-2], which is a 2D topological insulator per se, into the layered BiTeI host structure. The previously known bismuth telluride iodides, BiTeI and Bi2TeI, offer physical properties relevant for spintronics. Herewith a new cousin, Bi3TeI (sp.gr. R3m, a = 440.12(2) pm, c = 3223.1(2) pm), joins the ranks and expands this structural family. Bi3TeI = [Bi-2] [BiTeI] represents a stack with strictly alternating building blocks. Conditions for reproducible synthesis and crystal-growth of Bi2TeI and Bi3TeI are ascertained, thus yielding platelet-like crystals on the millimeter size scale and enabling direct measurements. The crystal structures of Bi2TeI and Bi3TeI are examined by X-ray diffraction and electron microscopy. DFT calculations predict metallic properties of Bi3TeI and an unconventional surface state residing on various surface terminations. This state emerges as a result of complex hybridization of atomic states due to their strong intermixing. Our study does not support the existence of new stacking variants BixTeI with x > 3; instead, it indicates a possible homogeneity range of Bi3TeI. The series BiTeI-Bi2TeI-Bi3TeI illustrates the influence of structural modifications on topological properties.

The rational design of brighter upconversion nanoparticles (UCNPs) requires a better understanding of the radiationless deactivation pathways in these materials. Here, we demonstrate the potential of excitation power density (P)-dependent studies of upconversion (UC) luminescence intensities, slope factors, and absolute quantum yields (ΦUC) of popular β-NaYF4:20% Yb3+,2% Er3+ UCNPs of different surface chemistries in organic solvents, D2O, and water as a tool to gain deeper insight into the UC mechanism including population and deactivation pathways particularly of the red emission. Our measurements, covering a P regime of three orders of magnitude, reveal a strong difference of the P-dependence of the ratio of the green and red luminescence bands (Ig/r) in water and organic solvents and P-dependent population pathways of the different emissive energy levels of Er3+. In summary, we provide experimental evidence for three photon processes in UCNPs, particularly for the red emission. Moreover, we demonstrate changes in the excited population dynamics via bi- and triphotonic processes dependent on the environment, surface chemistry, and P, and validate our findings theoretically.