Syntheses, Structure, and 2/5 Magnetization Plateau of a 2D Layered Fluorophosphate Na3Cu5(PO4)4F·4H2O

A Novel Mineral-like Copper Phosphate Chloride with a Disordered Guest Structure: Crystal Chemistry and Magnetic Properties

Novel copper phosphate chloride has been obtained under middle-temperature hydrothermal conditions. Its crystal structure was established based on the low-temperature X-ray diffraction data: Na₂Li_0.75(Cs,K)_0.5[Cu₅(PO₄)₄Cl]·3.5(H₂O,OH), sp. gr. C2/m, a = 19.3951(8) Å, b = 9.7627(3) Å, c = 9.7383(4) Å, β = 99.329(4)°, T = 150 K, MoK_α (λ = 0.71073 Å), R = 0.049. The crystal structure includes tetrameric copper clusters as the main building blocks, which are built of four CuO₄Cl pyramids sharing apical Cl vertices. The clusters are combined through phosphate groups and additional copper-centered polyhedra to form two mostly ordered periodic layers. Between the layers and inside the framework channels, alkali ions, H₂O molecules, or OH groups are statistically distributed. Na₂Li_0.75(Cs,K)_0.5[Cu₅(PO₄)₄Cl]·3.5(H₂O,OH) is a synthetic modification of a sampleite-polymorph of the lavendulan mineral group and represents a new member in a mero-plesiotype series of copper phosphates and arsenates, for which the crystal structures contain two-periodic [Cu₄X(TO₄)₄]_∞ modules (T = As, P; X = Cl, O). Magnetically, this phase exhibits the phase transition at T_C = 6.5 K, below which it possesses a weak ferromagnetic moment.

A cobalt(ii) chain based on pymca generated in situ from the hydrolysis of 2-cyanopyrimidine: spin canting and magnetic relaxation

A one-dimensional (1D) coordination polymer, [{Co2(pymca)2·(H2O)4}SO4·2H2O] n (1) (pymca = 2-carboxypyrimidine), was solvothermally synthesized via the reaction of 2-cyanopyrimidine and Co(SCN)2. A bidentate pymca ligand was formed in situ by the hydrolysis of 2-cyanopyrimidine. Furthermore, in this study, the magnetic properties of complex 1 were investigated in detail. The results indicated that complex 1 showed a single-chain magnet (SCM) behavior below ca. 3 K. The energy barrier (Δτ 1/k B) and preexponential factor (τ 0) of SCM were 31.2 K and 5.4 × 10-9 s, respectively.

Novel tantalum phosphate Na13Sr2Ta2(PO4)9: synthesis, crystal structure, DFT calculations and Dy3+-activated fluorescence performance

A new tantalum phosphate, tridecasodium distrontium ditantalum nonaphosphate, Na13Sr2Ta2(PO4)9, was prepared using the high-temperature flux method. The structure can be described as a three-dimensional open framework containing isolated [TaV2(PO4)9]17−units that are interlocked by Na and Sr ions. Band structure studies by the first-principles method revealed that Na13Sr2Ta2(PO4)9is an insulator with an indirect band gap of 4.78 eV, which makes it suitable as a luminescent host matrix. A series of solid solutions,i.e.Na13Sr2–xTa2(PO4)9:xDy3+(x= 0.01, 0.02, 0.04, 0.06, 0.08, 0.1, 0.12 and 0.14), were prepared and their photoluminescence properties studied. Under 350 nm light excitation, these emit two typical emissions of the Dy3+ion,i.e.the4F9/2→6H15/2transition centred at 476 nm and the4F9/2→6H13/2transition centred at 570 nm.

PbFePO4F2 with a 1/6th bond depleted triangular lattice

A 1/6th bond depleted triangular lattice has been experimentally realized in the novel compound PbFePO₄F₂ with moderately strong frustration.