K2M(III)2(M(VI)O4)(PO4)2 (M(III) = Fe, Sc; M(VI) = Mo, W), novel members of the lagbeinite-related family: synthesis, structure, and magnetic properties.

The possibility of PO(4)(3-) for MoO(4)(2-) partial substitution in the langbeinite framework has been studied by exploration of the K-Fe(Sc)-Mo(W)-P-O systems using the high-temperature solution method. It was shown that 1/3PO(4)(3-) for MoO(4)(2-) substitution leads to formation of three novel compounds K(2)Fe(MoO(4))(PO(4))(2), K(2)Sc(MoO(4))(PO(4))(2), and K(2)Sc(WO(4))(PO(4))(2) with slightly increased lattice parameters and significant distortion of the anion tetrahedra without structure changes. In contrast, the antiferromagnetic structure is modified by substitution in the low-temperature region. The structural peculiarities are discussed in light of bond-valence sums calculations.

Crystal growth, layered structure and luminescence properties of K2Eu(PO4)(WO4).

K2Eu(PO4)(WO4) has been prepared via the high-temperature solution growth (HTSG) method using K2WO4-KPO3 molten salts as a self-flux and characterized by single-crystal X-ray diffraction analysis, IR and luminescence spectroscopy. The structure of this new compound features a 2D framework containing [EuPO6]4- layers, which are composed of zigzag chains of [EuO8]n interlinked by slightly distorted PO4 tetrahedra. Isolated WO4 tetrahedra are attached above and below these layers, leaving space for the K+ counter-cations. The photoluminescence (PL) characteristics (spectra, line intensity distribution and decay kinetics) confirm structural data concerning one distinct position for europium ions. The luminescence color coordinates suggest K2Eu(PO4)(WO4) as an efficient red phosphor for lighting applications.

Structural and optical properties of langbeinite-related red-emitting K2Sc2(MoO4)(PO4)2:Eu phosphors.

The concentration series of langbeinite-related solid solutions K2Sc2(MoO4)(PO4)2:xEu (x = 0.1, 0.2, 0.6, 0.8, and 1.0 mol%) has been prepared via a solid state route and the effects of europium content on the phase composition, morphology, crystal structure and luminescence properties have been studied by scanning electron microscopy, X-ray powder diffraction, UV-vis, IR and luminescence spectroscopy. The band gap values have been estimated from UV-vis spectra and are in the range of 3.7-3.8 eV for all concentrations studied. The electronic band structure calculations have shown that Sc d, Mo d and Ophos p states dominate in the band edge region and determine the optical transitions in the K2Sc2(MoO4)(PO4)2 host. The photoluminescence (PL) spectra, intensity and decay time dependences on the Eu3+ concentration revealed complex behavior of europium-containing emitting centers. The PL characteristics indicated the presence of at least two types of luminescence centers. One of them (EuK) is shown to be formed by the Eu3+ ion located within K sites, while the other one is formed by the Eu3+ ions that reside in Sc sites (EuSc). The luminescence color coordinates calculated for K2Sc2(MoO4)(PO4)2:xEu indicated that these ceramics can be potential candidates for UV-based lighting applications as efficient red phosphors.

Scheelite-related MBi1-xV1-xMoxO4 (MII- Ca, Sr) solid solution-based photoanodes for enhanced photoelectrochemical water oxidation.

The photoelectrochemical properties of scheelite-related MBi1-xV1-xMoxO4 (MII = Ca, Sr, x = 0.1 to 0.9) solid solutions deposited on conductive glass (coated with SnO2, F-doped) have been investigated as photoanodes in photoelectrochemical (PEC) water splitting. The variation of the final annealing temperature during the preparation of the conduction electrodes as well as the value of substitution x have been shown to affect the PEC performance. The micropowders of MBi1-xV1-xMoxO4 (MII = Ca, Sr, x = 0.1 to 0.9) samples were first fabricated vi a solid-state method; they were characterised by SEM microscopy and powder and single crystal X-ray diffraction, and the band gap values were estimated using diffusive reflectance data. The value of substitution x = 0.1 in the cases of samples containing calcium and strontium affords the highest PEC performance reported for the whole range of substitution. These results demonstrate a promising approach for the beneficial utilization of BiVO4-substituted scheelite-related solid solutions in photo-electrochemical cells towards efficient and inexpensive photoanodes.

Cs(2)Bi(PO(4))(WO(4)).

Dicaesium bis-muth(III) phosphate(V) tungstate(VI), Cs(2)Bi(PO(4))(WO(4)), has been synthesized during complex investigation in a molten pseudo-quaternary Cs(2)O-Bi(2)O(3)-P(2)O(5)-WO(3) system. It is isotypic with K(2)Bi(PO(4))(WO(4)). The three-dimensional framework is built up from [Bi(PO(4))(WO(4))] nets, which are organized by adhesion of [BiPO(4)] layers and [WO(4)] tetra-hedra above and below of those layers. The inter-stitial space is occupied by Cs atoms. Bi, W and P atoms lie on crystallographic twofold axes.

Crystal structure of poly[[di-aqua-tetra-µ2-cyanido-iron(II)platinum(II)] acetone disolvate].

In the title polymeric complex, {[FePt(CN)4(H2O)2]·2C3H6O} n , the FeII cation has an octa-hedral [FeN4O2] geometry being coordinated by two water mol-ecules and four cyanide anions. The Pt cation is located on an inversion centre and has a square-planar coordination environment formed by four cyanide groups. The tetra-cyano-platinate anions bridge the FeII cations to form infinite two-dimensional layers that propagate in the bc plane. Two guest mol-ecules of acetone per FeII are located between the layers. These guest acetone mol-ecules inter-act with the coordinated water mol-ecules by O-H⋯O hydrogen bonds.

Crystal structure of catena-poly[[[(2-eth-oxy-pyrazine-κN)copper(I)]-di-µ2-cyanido] [copper(I)-µ2-cyanido]].

In the asymmetric unit of the title coordination compound, {[Cu(CN)(C4H3OC2H5N2)][Cu(CN)]} n , there are two Cu atoms with different coordination environments. One CuI ion is coordinated in a triangular coordination geometry by the N atom of the 2-eth-oxy-pyrazine mol-ecule and by two bridging cyanide ligands, equally disordered over two sites exchanging C and N atoms, thus forming polymeric chains parallel to the c axis. The other Cu atom is connected to two bridging cyanide groups disordered over two sites with an occupancy of 0.5 for each C and N atom, and forming an almost linear polymeric chain parallel to the b axis. In the crystal, the two types of chain, which are orthogonal to each other, are connected by cuprophilic Cu⋯Cu inter-actions [2.7958 (13) Å], forming two-dimensional metal-organic coordination layers parallel to the bc plane. The coordination framework is further stabilized by weak long-range (electrostatic type) C-H⋯π inter-actions between cyano groups and 2-eth-oxy-pyrazine rings.

Crystal structure of poly[tetra-µ-cyanido-ethanol-bis(2-iodo-pyrazine)-digold(I)iron(II)].

In the title polymeric complex, [Au2Fe(CN)4(C4H3IN2)2(C2H6O)] n , the FeII cation is coordinated by two iodo-pyrazine mol-ecules, one ethanol mol-ecule and three di-cyano-aurate anions in a distorted N5O octa-hedral geometry. In the crystal, the di-cyano-aurate anions bridge the FeII cations to form polymeric chains propagating along the b-axis direction. Stabilization of the crystal structure is provided by O-H⋯N hydrogen bonds and π-π stacking between parallel iodo-pyrazine rings of neighbouring chains, the centroid-centroid distances being 3.654 (10) and 3.658 (9) Å.

Crystal structure of poly[tetra-µ2-cyanido-1:2κ8N:C-bis-(dimethyl sulfoxide-1κO)diargentate(I)iron(II)].

In the title polymeric complex, [Fe{OS(CH3)2}2{Ag(CN)2}2], the FeII cation is located at an inversion centre and is coordinated by four cyanide (CN-) anions and two dimethyl sulfoxide mol-ecules in a slightly compressed N4O2 octa-hedral geometry, the AgI cation is C-coordinated by two CN- anions in a nearly linear geometry. The CN- anions bridge the FeII and AgI cations to form a two-dimensional polymeric structure extending parallel to (102). In the crystal, the nearest Ag⋯Ag distance between polymeric sheets is 3.8122 (12) Å. The crystal studied was a twin with a contribution of 0.2108 (12) for the minor component.

Structural transformation of Bi1-x/3V1-xMoxO4 solid solutions for light-driven water oxidation.

The influence of molybdenum content in the solid solutions of Bi1-x/3V1-xMoxO4 (x = 0.05-0.20) on the morphology, band gap, structure and light-driven water oxidation properties has been studied by scanning electron microscopy, X-ray powder diffraction and vibrational spectroscopy (Raman and infrared). To find out the peculiarities of structural changes for bismuth scheelite-related oxides containing both vanadium and molybdenum crystals of Bi0.98V0.93Mo0.07O4 have been grown from a K-Bi-V-Mo-O high-temperature melt and characterized by single crystal X-ray diffraction. For the scheelite-related framework both V and Mo were found to occupy the same positions lowering the point group symmetry of tetrahedra from 4/m to 2/m giving monoclinic distortion for solid solutions with x = 0.05-0.10. The most promising photocatalytic performance was obtained for Bi0.96Mo0.10V0.90O4, in which the oxygen evolution could reach 21 µM in 50 s under visible light of LEDs, λ = 470 ± 10 nm, and 820 µE cm(-2) s(-1). The changes in catalytic properties are shown to be governed by a crystal structure strain with a maximum obtained for the boundary sample between the monoclinic and tetragonal phase.