Access to the structures of fluoromagnesium compounds: synthesis and structural characterization of the β-diketiminato magnesium fluoride [{CH(CMeNAr)2}Mg(μ-F)(THF)]2·toluene

β-Diketiminato magnesium fluoride [{CH(CMeNAr)₂}Mg(μ-F)(THF)]₂·toluene (Ar=2,6-i-Pr₂C₆H₃, 2·toluene) was synthesized. The molecular structure of 2 revealed for the first time, the double fluoro bridge feature between the two magnesium atoms with a typical MgF bond length (average 1.95 Å).     

Crystal Structure of Cesium Dihydrotrifluoride,CsH2F3. Refinement of the Crystal Structures of NMe4HF2 and NMe4H2F3

Single crystals of (NMe₄)(HF₂) were obtained during attempted recrystallization of NMe₄F from fluoroolefin. X‐ray diffraction data show that (NMe₄)(HF₂) crystallizes in the orthorhombic space group Pmmn with unit cell dimensions a = 6.535(2), b = 8.688(3), and c = 5.333(2) Å. The symmetric and virtually linear HF₂ anions exhibit a short F···F distance of 2.256(2) Å. The both crystal structures of (NMe₄)(H₂F₃) (orthorhombic, Pbca, a = 8.509(1), b = 11.273(2), and c = 14.880(2) Å) and CsH₂F₃ (orthorhombic, P2₁2₁2₁, a = 7.345(3), b = 9.126(4), and c = 11.444(4) Å) contain dihydrogentrifluoride anions, H₂F₃^?, which have a bent shape and F···F distances of 2.30‐2.34Å.     

Struktur‐ und magnetochemische Untersuchungen an KCuGaF6

Structural and Magnetochemical Studies on KCuGaF₆ The crystal structure of KCuGaF₆ was determined on the base of X‐ray single crystal data (wR₂ = 0.084 for 2476 independent reflections). The compound crystallizes with a = 728.56(4), b = 989.51(6), c = 676.27(3) pm, β = 93.120(5)°, Z = 4 in space group P2₁/c of the pyrochlore related KCuCrF₆ type. The octahedral coordinations [GaF₆] and [CuF₆] are slightly resp. strongly distorted (mean values Ga‐F: 188.2 pm resp. Cu‐F: 188.2/200.1/227.6 pm). The longest distances Ga‐F and the shortest ones Cu‐F are found within octahedral chains of these two kinds of atoms, running along [100] and [001], resp., and being mutually bridged as well (M‐F‐M in between 114 and 145°). The magnetic mole susceptibilities measured at powders and at a single crystal follow the isotropic Heisenberg model for S = ¹/₂, if effects of chain disrupture are considered in the form of some paramagnetic portion. No indication of threedimensional magnetic order is observed down to T = 2 K and low magnetic fields H < 100 G. KCuGaF₆ (J/k = —71 K for the powder) is distinguished this way from the chain structure compounds KCuAlF₆ und Na₂CuScF₇ (J/k = —76 resp. —59 K) which were also magnetically studied and yield similar antiferromagnetic exchange constants J/k.     

Advances in the TBAF-induced aldol-type addition of α-trialkylsilyl-α-diazoacetones: TIPS versus TES

α-Triisopropylsilyl-α-diazoacetone (TIPS-diazoacetone) underwent high-yielding “diazo-side” Mukaiyama aldol-type addition with a range of aryl and alkyl aldehydes when subjected to stoichiometric amount of tetrabutylammonium fluoride at −16 °C, in Et₂O. Robustness of the TIPS group makes TIPS-diazoacetone a stable surrogate for α-triethylsilyl-α-diazoacetone, on which generation of the corresponding carbanion can still be efficiently achieved under nucleophilic, weakly basic and practical conditions. These results highlight the synthetic potential that can be expected from TIPS-diazoacetone, promising building block for the convergent elaboration of highly functionalised versatile diazocarbonyl compounds.     

The Novel Method of Synthesis of Solid Solutions LnxCa1-xF2+x (Ln=Yb,Nd) Using Beta-cyclodextrin

In this study we propose the novel method of synthesis of solid solutions Ln_xCa_1-xF_2+x (Ln = Yb, Nd) by decomposition of metal trifluoroacetate hydrates with beta-cyclodextrin. It is important to mention that the decomposition of the similar reaction mixture without beta-cyclodextrin does not induce the formation of such compounds. In this case, the formation of individual fluorides takes place. The metal fluorides were studied by XRD and X-ray fluorescence. The advantages of the method proposed are as follows: relatively low temperature of the synthesis, simplicity of a change in the composition of the prepared compounds, and a homogeneous distribution of the elements in products.     

A near-infrared phosphor doped with Cr3+ towards zero-thermal-quenching for high-power LEDs

Cr³⁺-doped phosphors show significant application potential in near-infrared (NIR) light-emitting diodes (LEDs). However, the development of thermally stable and efficient NIR phosphors still faces enormous challenges. Herein, NIR phosphors K₂NaMF₆:Cr³⁺ (M³⁺ = Al³⁺, Ga³⁺, and In³⁺) were synthesized by the hydrothermal method. The represented K₂NaAlF₆:Cr³⁺ phosphor can be effectively excited by blue light (～430 nm) to present broadband emission at half a maximum of 96 nm peaking at ～ 728 nm. Meanwhile, the K₂NaAlF₆:Cr³⁺ phosphor exhibits excellent internal quantum efficiency (IQE = 68.08%) and nearly zero-thermal-quenching behavior, which is able to maintain 96.5% emission intensity at 150 °C of the initial value at 25 °C. The NIR phosphor-converted LED was fabricated based on K₂NaAlF₆:Cr³⁺ phosphor and a blue LED chip, showing a NIR output power of 394.39 mW at 300 mA with a high photoelectric conversion efficiency of 10.9% at 20 mA. Using the high-power NIR LED as a lighting source, transparent and quick veins imaging as well as non-destructive testing were demonstrated, suggesting the NIR phosphor has a wide range of practical applications.     

Electrical investigation of some fluorides of composition A2MII+MIII+F9 by impedance spectroscopy

The ac conductivity of three fluorides of A₂M^II+ M^{III +} F₉ type, Sr₂NiAlF₉, Sr₂ZnGaF₉ and Ba₂MnCrF₉, between 293 and 773K, has been analyzed within a combined complex impedance and modulus formalism. The antiferroelectric-paraelectric phase transition of Sr₂ZnGaF₉ has been characterized. A hopping mechanism for charge carriers is suggested for the three materials; their electrical performance are relatively weak. Sr₂NiAlF₉ and Sr₂ZnGaF₉ can be considered as ionic conductors of the F- ion. On the contrary, the conductivity in Ba₂MnCrF₉ is rather of an electronic nature.     

Synthesis and photoluminescent properties of silica-coated LaCeF<Subscript>3</Subscript>:Tb nanocrystals

La_0.45Ce_0.45F₃:Tb (10 mol% Tb) nanoparticles was synthesized via sonochemical method and then coated with silica (SiO₂) shells through a microemulsion process, resulting in the formation of core/shell structured LaCeF₃:Tb/SiO₂ nanoparticles. The obtained core/shell LaCeF₃:Tb/SiO₂ nanoparticles are spherical and uniform in size (average size about 60 nm), strongly fluorescent, and long fluorescence lifetime (1.87 ms). This kind of nanoparticles was water-soluble, which could be applied in biological labeling and other fields.     

CsSc3F6[SeO3]2: A New Rare‐Earth Metal(III) Fluoride Oxoselenate(IV) With Sections Of The ReO3‐Type Structure

A new representative of rare‐earth metal(III) fluoride oxoselenates(IV) derivatized with alkali metals could be synthesized via solid‐state reactions. Colorless single crystals of CsSc₃F₆[SeO₃]₂ were obtained through the reaction of Sc₂O₃, ScF₃, and SeO₂ (molar ratio 1:1:3) with CsBr as reactant and fluxing agent. For this purpose, corundum crucibles embedded as liners into evacuated silica ampoules were applied as containers for these reactions at 700 °C for seven days. The new quintenary compound crystallizes in the trigonal space group P3m1 with a = 565.34(4) and c = 1069.87(8) pm (c/a = 1.892) for Z = 1. The crystal structure of CsSc₃F₆[SeO₃]₂ contains two crystallographically different Sc³⁺ cations. Each (Sc1)³⁺ is surrounded by six fluoride anions as octahedron, while the octahedra about (Sc2)³⁺ are formed by three fluoride anions and three oxygen atoms from three terminal [SeO₃]^2– anions. The [(Sc1)F₆]^3– octahedra link via common F^– vertices to six fac‐[(Sc2)F₃O₃]^6– octahedra forming ²_∞{[Sc₃F₆O₆]^9–} layers parallel to (001). These layers are separated by oxygen‐coordinated Cs⁺ cations (C.N. = 12), arranging for the charge compensation, while Se⁴⁺ cations within the layers surrounded by three oxygen atoms as ψ¹‐tetrahedral [SeO₃]^2– units complete the structure. EDX measurements confirmed the composition of the title compound and single‐crystal Raman studies showed the typical vibrational modes of isolated [SeO₃]^2– anions with ideal C_3v symmetry.