La3 B6 O13 (OH): The First Acentric High-Pressure Borate Displaying Edge-Sharing BO4 Tetrahedra

La₃B₆O₁₃(OH) was obtained by a high‐pressure/high‐temperature experiment at 6 GPa and 1673 K. The compound crystallizes in the space group P2₁ (no. 4) with the lattice parameters a=4.785(2), b=12.880(4), c=7.433(3) Å, and β=90.36(10)°, and is built up of corner‐ as well as edge‐sharing BO₄ tetrahedra. It represents the first acentric high‐pressure borate containing these B₂O₆ entities. The compound develops borate layers of „sechser“‐rings with the La³⁺ cations positioned between the layers. Single‐crystal and powder X‐ray diffraction, vibrational and MAS NMR spectroscopy, second‐harmonic generation (SHG) and thermoanalytical measurements, as well as computational methods were used to affirm the proposed structure and the B₂O₆ entities.

Elucidating the physical properties of the molybdenum oxide Mo4O11 and its tantalum substituted variant Mo2Ta2O11

Although γ/η-Mo4O11 and Mo2Ta2O11 are used in a variety of industrial applications and can easily be synthesized in a chemical vapour transport (CVT) process or reactions in silica ampoules, respectively, only few data are available concerning their physical properties. In this paper, we further explore the properties of the three compounds with respect to their thermal and magnetic behavior, surface composition, and Raman spectroscopic properties.

Synthesis and crystal structures of two 1,3-di(alk-yloxy)-2-(methyl-sulfan-yl)imidazolium tetra-fluorido-borates

In both structures, the alk­yloxy and methyl­sulfanyl groups are rotated out of the plane of the respective heterocyclic ring.

Two salts were prepared by methyl­ation of the respective imidazoline-2-thione at the sulfur atom, using Meerwein’s salt (tri­methyl­oxonium tetra­fluorido­borate) in CH₂Cl₂. 1,3-Dimeth­oxy-2-(methyl­sulfan­yl)imidazolium tetra­fluorido­borate (1), C₆H₁₁N₂O₂S⁺·BF₄⁻, displays a syn conformation of its two meth­oxy groups relative to each other whereas the two benz­yloxy groups present in 1,3-dibenz­yloxy-2-(methyl­sulfan­yl)imidazolium tetra­fluorido­borate (2), C₁₈H₁₉N₂O₂S⁺·BF₄⁻, adopt an anti conformation. In the mol­ecules of 1 and 2, the methyl­sulfanyl group is rotated out of the plane of the respective heterocyclic ring. In both crystal structures, inter­molecular inter­actions are dominated by C—H⋯F—B contacts, leading to three-dimensional networks. The tetra­fluorido­borate counter-ion of 2 is disordered over three orientations (occupancy ratio 0.42:0.34:0.24), which are related by rotation about one of the B—F bonds.

Serendipitous formation of K15NaSn5F36

K15NaSn5F36 crystallizes in the hexagonal crystal system with space group P63/m and lattice parameters of a = 1060.3(2) and c = 2011.9(4) pm. The unit-cell volume amounts to 1.9588(7) nm3. Its fundamental building blocks are quasi-isolated [SnF6]2− and [NaF6]5− octahedra, which are imbedded into a matrix of potassium cations. Within the structure, these units form a layer-like arrangement consisting either of mixed [SnF6]2−/[NaF6]5− or pure [SnF6]2− layers. The structural model was further confirmed by BLBS and CHARDI calculations.

A Double-Band Emitter with Ultranarrow-Band Blue and Narrow-Band Green Luminescence

Understanding the origin and mechanisms of luminescence is a crucial point when it comes to the development of new phosphors with targeted luminescence properties. Herein, a new phosphor belonging to the substance class of alkali metal lithosilicates with the generalized sum formula Cs4-x-y-z Rbx Nay Liz [Li3 SiO4 ]4 :Eu2+ is reported. Single crystals of the cyan-emitting UCr4 C4 -type phosphor show a peculiar double-band luminescence with one ultranarrow emission band at 473 nm and a narrow emission band at 531 nm under excitation with UV light (λexc =408 nm). Regarding occupation of the channels by the light metal ions, investigations of single-crystal XRD data led to the assumption that domain formation with distinct lithium- and sodium-filled channels occurs. Depending on which of these channels hosts the activator ion Eu2+ , a green or blue emission results. The herein-presented results shed new light on the luminescence process in the well-studied UCr4 C4 -type alkali metal lithosilicate phosphors.

High fatigue resistance of a photochromic dithienylethene embedded into the pores of a metal–organic framework (MOF)

The incorporation of photochromic dyes into porous metal–organic frameworks (MOFs) is an attractive way to transfer the photochromic properties of the dye to a solid crystalline material.

Synthesis and characterization of K5Sn2OF11

The potassium oxidofluoridostannate(IV) fluoride K5Sn2OF11 was synthesized via a solid-state route at T = 300°C in arc-weldeded copper ampoules. It crystallizes in the orthorhombic system in the acentric space group Ama2 (no. 40) with a unit cell volume of V = 2.5727(4) nm3. The cell parameters are a = 1758.3(2), b = 2452.3(2) and c = 596.7(1) pm. As a main structural motif, K5Sn2OF11 exhibits two different kinds of dinuclear [Sn2OF11]5‒ units, which are embedded into a matrix consisting of potassium cations and fluoride anions. The substance was characterized by single-crystal and powder X-ray diffraction, as well as by FT-IR spectroscopy.

SrAl2-xLi2+xO2+2xN2-2x:Eu2+ (0.12 ≤ x ≤ 0.66)-Tunable Luminescence in an Oxonitride Phosphor

Starting from the recently published narrow band red phosphor SALON, a tunable oxonitride-phosphor can be derived by introducing disorder into the structure. To achieve this, the oxygen content of the reaction mixture is increased, thereby prohibiting the oxygen/nitrogen ordering observed in SALON. The resulting compound is isotypic to UCr₄C₄ and exhibits mixed oxygen/nitrogen and lithium/aluminum sites. Further variation of the oxygen/nitrogen ratio revealed that the structure remains stable over a wide range of compositions. The compound can therefore be described by the general sum formula SrAl_2-xLi_2+xO_2+2xN_2-2x with x ranging between 0.12 and 0.66. When doped with Eu²⁺, the title compound exhibits an intense luminescence upon excitation with blue light. The maximum of this emission varies depending on the oxygen content and can be tuned to values between 581 nm (x = 0.66) and 672 nm (x = 0.12).

Polymorphs and derivates of Sr2LiAlO4:Eu2+

Recently, Wang et al. (Z. Wang, J. Ha, Y. H. Kim, W. B. Im, J. McKittrick, S. P. Ong, Joule 2018, 2, 914–926) predicted and discovered Sr2LiAlO4, a quaternary compound with a layered structure crystallizing in the monoclinic space group P21/m, and they refined the structure from PXRD data. Upon partially substituting strontium with europium, the substance exhibits a yellow broadband luminescence consisting of two overlapping emission bands. In this paper, the crystal structure of Sr2LiAlO4 is confirmed by additional SC-XRD measurements and a newly discovered polymorph of Sr2LiAlO4 is presented crystallizing in the orthorhombic space group Cmcm. When Eu2+ is incorporated, this polymorph exhibits only one of the emission bands present in the P21/m-polymorph. Additionally, two substitutional variants of Sr2LiAlO4 are presented along with their luminescence properties upon incorporating Eu2+. One with a partial substitution of strontium for barium, leading to a structure in space group Pnma, and one with a partial substitution of oxygen for nitrogen, exhibiting the structure in space group Cmcm. The structure-property relationships in the above mentioned compounds are discussed with regard to their luminescence performance.

Synthesis of the first nickel borate nitrate K7Ni[B18O24(OH)9](NO3)6· (H3BO3)

The novel potassium nickel borate nitrate K7Ni[B18O24(OH)9](NO3)6 ·(H3BO3) was obtained from a simple hydrothermal synthesis in a stainless-steel autoclave at T = 513 K starting with nickel dichloride hexahydrate, and boric and nitric acid with the pH adjusted to 8 by KOH. Single-crystal X-ray diffraction data provided the basis for the structure analysis and refinement. The compound crystallizes in the trigonal space group R3̅ (no. 148) with the lattice parameters a = 1222.29(8) and c = 5478.4(4) pm. Generally, K7Ni[B18O24(OH)9](NO3)6 ·(H3BO3) is comprised of nitrate layers and complex nickel borate layers surrounded by boric acid, nitrate anions, and potassium cations.

RbKLi2[Li3SiO4]4:Eu2+ an ultra narrow-band phosphor

The new phosphor RbKLi2[Li3SiO4]4:Eu2+ was synthesized by different high-temperature solid-state reactions. It is accessible from the alkali metal carbonates, SiO2, and Eu2+ as a luminous active cation either in closed tantalum ampoules or by conventional solid-state reaction in nickel crucibles, under a constant flow of forming gas. The structure of the thereby received rod-shaped crystals was solved and refined on the basis of single crystal X-ray diffraction data. The compound crystallizes isostructurally to CsKNa2[Li3SiO4]4 and forms a highly condensed network of LiO4 and SiO4 tetrahedra [I4/m (no. 87), Z = 2, a = 10.9508(6) and c = 6.3334(3) Å]. It is a new member of the recently discovered family of alkali lithosilicate phosphors. Under excitation with UV to blue light, the compound exhibits interesting luminescence properties. Depending on the mode of synthesis, either green or blue luminescence of the samples is observed. Both emission profiles can be described as ultra-narrow-banded, since the full width at half maximum (fwhm) is below 0.2 eV. The green phosphor shows an emission maximum at 532 nm with a fwhm of 43.5 nm (0.193 eV) and the blue one at 474 nm with a fwhm of 24.8 nm (0.137 eV). Furthermore, the material presented here allows a more detailed localization of the luminescence center inside the structure, which may allow a better understanding of the luminescence properties of many other alkali lithosilicate phosphors.

Serendipitous formation and characterization of K2[Pd(NO3)4]·2HNO3

A potassium tetranitratopalladate(II) with the composition K2[Pd(NO3)4] · 2HNO3 was synthesized by a simple solvothermal process in a glass ampoule. The new compound crystallizes in the monoclinic space group P21 /c (no. 14) with the lattice parameters a = 1017.15(4), b = 892.94(3), c = 880.55(3) Å, and β = 98.13(1)° (Z = 2). The crystal structure of K2[Pd(NO3)4] · 2HNO3 reveals isolated complex [Pd(NO3)4]2− anions, which are surrounded by eight potassium cations and four HNO3 molecules. The complex anions and the cations are associated in layers which are separated by HNO3 molecules. K2[Pd(NO3)4] · 2HNO3 can thus be regarded as a HNO3 intercalation variant of β-K2[Pd(NO3)4]. The characterization is based on single-crystal X-ray and powder X-ray diffraction.