Common Corners Research Articles

Rb2Lu[Si4O10]F, a tubular chain silicate.

Single crystals of Rb2Lu[Si4O10]F (dirubidium lutetium tetra­silicate fluoride) were obtained in flux-synthesis experiments in the system SiO2–Lu2O3–RbF. The compound belongs to the group of tubular chain silicates, i.e. it is based on multiple chains of condensed [SiO4] tetra­hedra forming closed columns. The periodicity of the unbranched multiple chains is four and corresponds to the length of the b axis. Adjacent columns are connected by Lu3+ cations, which are coordinated by four oxide and two fluoride anions in the form of slightly distorted octa­hedra. By sharing common fluoride corners, the single octa­hedra are linked into chains running parallel to the silicate tubes. Electroneutrality is achieved by the incorporation of additional Rb+ cations. All four symmetrically independent rubidium ions, four out of twelve oxide as well as the two fluoride anions are located on mirror planes. The remaining atoms reside on general positions.

Synthesis, structure, and bonding of the hexagonal form of the oxide carbide ScAlOC

Red single crystals of a hexagonal form of ScAlOC were obtained as a by-product from the synthesis of ScAl3C3 by reacting scandium and carbon in an aluminium melt at 1820 °C. The crystal structure (hP8, space group P63mc, Z = 2, a = 3.24793(3) Å, c = 10.1739(1) Å, 629 refl., 15 param., R1(F) = 0.010, wR2(F2) = 0.023) can directly be derived from the binary nitrides AlN and ScN or the oxide carbides Sc(O,C) and Al(O,C), respectively. ScAlOC-II or h-ScAlOC represents a new structure type with simple closest packing of alternating layers of oxygen and carbon. The stacking sequence is ABAC (=(hc)2) with oxygen in a cubic and carbon in a hexagonal sequence. According to the difference in size Sc occupies octahedral voids between every second layer leading to layers of edge-sharing ScO3C3 octahedra. Aluminium is located in half of the tetrahedral voids. The AlOC3-tetrahedra are connected to layers by common corners of the carbon atoms. h-ScAlOC continues the row of the rare examples of oxide carbides with ordered anion distribution. Band structure calculations by FP-(L)APW methods revealed that ScAlOC is electron precise with a band gap of 1.2 eV. Calculations of charges by the Bader-method reveal values of Sc+1.87, Al+2.33, O−1.52 and C−2.67. Together with the charge densities and the values of the Laplacian this stands for a mainly ionic bonding containing significant covalent contributions, too. Despite the close similarity to rhombohedral ScAlOC (r-ScAlOC) there is a striking difference in colour, as r-ScAlOC is black. This is confirmed and explained by the results of the P-DOS, because the lowest states of the conduction band are determined by Sc-d-states. These are significantly lower in r-ScAlOC with ScC6 and ScO6 octahedra than in h-ScAlOC leading to a calculated band gap of 0.3 eV.

Magnesium Double Nitride Mg3GaN3 as New Host Lattice for Eu2+ Doping: Synthesis, Structural Studies, Luminescence, and Band-Gap Determination

The double nitride Mg3GaN3 and binary nitride Mg3N2 were synthesized from the elements by reaction with NaN3 in a sodium flux. Reactions were carried out at 760 °C in welded shut tantalum ampules. Mg3GaN3 was obtained as single crystals (space group R3m (No. 166), a = 3.3939(5) A and c = 25.854(5) A, Z = 3, R1 = 0.0252, wR2 = 0.0616 for 10 refined parameters, 264 diffraction data points). This double nitride consists of an uncharged three-dimensional network of MgN4 and mixed (Mg/Ga)N4 tetrahedra, which share common corners and edges. First-principles density functional theory (DFT) calculations predict Mg3GaN3 to have a direct band gap of 3.0 eV, a value supported by soft X-ray spectroscopy measurements at the N K-edge. Eu2+-doped samples show yellow luminescence when irradiated with UV to blue light (λmax = 578 nm, full width at half maximum (fwhm) = 132 nm). Eu2+-doped samples of Mg3N2 also show luminescence at room temperature when excited with ultraviolet (UV) to blue light. The maximum intensity of...

ChemInform Abstract: RbCuFe(PO4)2.

AbstractSingle crystals of RbCuFe(PO4)2 are grown from a Rb2Mo2O7 flux.

RbCuFe(PO4)2

A new iron phosphate, rubidium copper(II) iron(III) bis­(phosphate), RbCuFe(PO4)2, has been synthesized as single crystals by the flux method. This compound is isostructural with KCuFe(PO4)2 [Badri et al. (2011 ▶), J. Solid State Chem. 184, 937–944]. Its structure is built up from Cu2O8 units of edge-sharing CuO5 polyhedra, inter­connected by FeO6 octa­hedra through common corners to form undulating chains that extend infinitely along the [011] and [01-1] directions. The linkage of such chains is ensured by the PO4 tetra­edra and the resulting three-dimensional framework forms quasi-elliptic tunnels parallel to the [101] direction in which the Rb+ cations are located.

Lithium Mobility in the Stannides Li2CuSn2 and Li2AgSn2

AbstractThe stannides Li2CuSn2 and Li2AgSn2 were synthesized by induction‐melting (or in a muffle furnace) of the elements in sealed niobium ampoules. The new phases were characterized by powder X‐ray diffraction. The structures of both stannides were investigated by X‐ray diffraction on single crystals: Li2AuSn2 type, I41/amd, a = 442.6(1), c = 1940.9(8) pm, wR2 = 0.0742, 310 F2 values for Li2CuSn2 and a = 456.33(9) c = 2018.2(6) pm, wR2 = 0.0626, 339 F2 values for Li2AgSn2 with 10 variables for each refinement. The transition metal (T) atoms have tetrahedral tin coordination. The TSn4 tetrahedra are condensed via common corners forming layers that are further condensed by Sn–Sn bonding, leading to three‐dimensional [CuSn2] and [AgSn2] networks which leave distorted hexagonal channels for the lithium atoms. The lithium ions show considerable mobility, with activation energies of 0.29 and 0.47 eV extracted from variable temperature 7Li solid state NMR spectra. 119Sn Mössbauer spectra at 78 K show signals at isomer shifts of δ = 2.13(1) mm s–1 for Li2CuSn2 and δ = 2.07(1) mm s–1 for Li2AgSn2. The signals show electric quadrupolar splitting because of the non spherical environment of the tin nuclei. A minor impurity of β‐Sn could be identified in both spectra.

RE4B4O11F2 (RE = Pr, Nd): Two New Rare-earth Fluoride Borates Isotypic to Gd4B4O11F2

Abstract The rare-earth fluoride borates RE 4B4O11F2 (RE = Pr, Nd) were obtained in a Walker-type multianvil device from the corresponding rare-earth oxides and fluorides, and boron oxide. Pr4B4O11F2 was obtained under high-pressure/high-temperature conditions of 8.5 GPa=1150°C, and Nd4B4O11F2 at 8 GPa and 1300°C. The single-crystal structure determinations revealed that both compounds are isotypic to RE 4B4O11F2 (RE = Eu, Gd, Dy), crystallizing in the space group C2=c (Z = 4) with the parameters a = 1397.3(3), b = 472.78(9), c = 1400.2(3) pm, β = 91:1(1)°, V = 0.9248(3) nm3, R 1 = 0.0444, and wR 2 = 0.0539 (all data) for Pr4B4O11F2, and a = 1389.1(3), b = 471.2(1), c = 1394.4(3) pm, β = 91:1(1)°, V = 0.9125(3) nm3, R 1 = 0.0286, and wR 2 = 0.0601 (all data) for Nd4B4O11F2. The structure type of Gd4B4O11F2 contains BO4 tetrahedra as well as BO3 groups connected via common corners. Here, we report about the crystallographic characterization of both compounds in comparison to the isotypic phases and discuss their IR spectra.

Diethyl(μ3-2-methyl-4-oxo-4H-pyran-3-olato-κ4O3,O4:O3:O3)tris(μ2-2-methyl-4-oxo-4H-pyran-3-olato-κ3O3,O4:O3)trizinc toluene disolvate

The title compound, [Zn3(C2H5)2(C6H5O3)4]·2C7H8, crystallizes with one complex mol­ecule solvated by two mol­ecules of toluene in the asymmetric unit. The ZnII ions are coordinated by two terminal ethyl (Et) groups and four maltolate ligands, which act as μ3- and μ2-bridges. The metal atoms are arranged in an incomplete cubane Zn3O4 core structure, derived from one EtZnO3 tetra­hedron, one EtZnO4 bipyramid and one ZnO6 octa­hedron, sharing common corners. The structure is stabilized by weak C—H⋯O and C—H⋯π inter­actions.

Synthesis, Crystal Structures and Properties of the First Lanthanum Selenide Chlorides, LaSeCl and La3Se4Cl

AbstractThe first two lanthanum selenide chlorides, LaSeCl and La3Se4Cl, both crystallize orthorhombically in space group Pnma (no. 62). They emerged from reactions of LaCl3 with lanthanum and selenium in appropriate molar ratios at 800–900 °C. Single crystals of the yellow LaSeCl adopt the cotunnite‐type structure of PbCl2 with a = 760.63(5), b = 433.52(3) and c = 910.07(6) pm (Z = 4). The tricapped trigonal prisms [LaSe5Cl4]11– share their triangular faces to form chains that run parallel to the [010] direction and are condensed through caps and common edges to give a complete crystal structure in accord with ∞3{LaSe5/5Cl4/4}. Dark‐red La3Se4Cl exhibits the U3S5‐type structure with a = 1271.98(5), b = 855.84(3) and c = 795.05(2) pm (Z = 4). The chloride anions are located at the Wyckoff position 8d together with selenium showing site occupation factors of 0.5 for both anion types. Bicapped trigonal prisms [LaSe7Cl]12– with (La2)3+ are connected through common faces and corners to form a three‐dimensional framework suited to the embedding of chains of fused tricapped trigonal prisms [LaSe5+1Cl2]11– with (La1)3+ running parallel to [010]. The absorption edge energy of approximately 1.75 eV indicates a wide band‐gap semiconductor that is stable towards air, water and some aqueous bases at different concentrations.

Rare earth–zinc–germanides RE4Zn5Ge6 (RE = Y, Dy, Ho, Er) and RE5Zn4−xGe6 (RE = Er, Tm, Lu)

Phase analytical studies in the rare earth metal–zinc–germanium systems led to the synthesis of eight new ternary germanides. The compounds RE4Zn5Ge6 (RE = Y, Dy, Ho, Er) crystallize with the orthorhombic Gd4Zn5Ge6 type structure, space group Cmc21. Er5Zn4−xGe6 and the low-temperature modification of Tm5Zn4−xGe6 adopt the Eu5Cd4−xBi6 structure, while HT-Tm5Zn4−xGe6 and Lu5Zn4−xGe6 crystallize with a new type. All eight structures were refined on the basis of single crystal diffractometer data. The common structural motif is the distorted tetrahedral germanium coordination of the zinc atoms. The ZnGe4 tetrahedra are condensed via common edges and/or corners, leading to a two-dimensional polyanionic network in LT-Tm5Zn4−xGe6 and three-dimensional ones in HT-Tm5Zn4−xGe6 and Y4Zn5Ge6. In all three structure types part of the germanium atoms form dumb-bells with single bond character. The RE4Zn5Ge6 germanides are electron-precise Zintl phases with an electron partitioning (4RE3+)(5Zn2+)(Ge26−)(4Ge4−). This is different in the RE5Zn4−xGe6 phases. Both structure types of that composition show systematic defects on one zinc site. These zinc defects compensate the excess electron that would remain according to an electron partitioning (5RE3+)(4Zn2+)(Ge26−)(4Ge4−)·e−. These crystal chemical features are supported by electronic structure calculations that reveal optimization of Zn–Ge and Ge–Ge bonding through lowering the Fermi energy.

Solvothermal syntheses, crystal structures, and properties of new mercury(II)–thioantimonates(III) and a mixed-valent thioantimonate(III,V)

New heterometallic thioantimonates(III) [Co(dien)2]HgSb2S5 (1), [Ni(dien)2]HgSb2S5 (2) and [H2dien]HgSb8S14 (3), and a mixed-valent thioantimonate(III,V) [Co(dien)2]2Sb4S9 (4) were solvothermally prepared in diethylenetriamine (dien) solvent from Co(Ni)–Hg–Sb–S, Hg–Sb–S and Co–Sb–S systems, respectively. In 1 and 2, the bimeric subunit Sb2S5 condenses with HgS4 tetrahedron via sharing common S atoms to form an one-dimensional [HgSb2S5]n2n− chain, in which a new μ3-1κ2S1,S5:2κS2:3κS4 bridging mode of the Sb2S5 subunit is obtained. In 3, four SbS3 trigonal pyramids and a linear HgS2 unit condense via sharing S atoms to generate an one-dimensional double-lined [HgSb8S14] n2n− chain. In 4, three SbIIIS3 pyramids and a SbVS4 tetrahedron share common corners to form an one-dimensional mixed-valent [Sb4S9]n4n− anion. The syntheses of 1–4 demonstrated that the Hg2+ ion is easily incorporated into thioantimonate networks, and has a higher affinity to S than that of transition metals. 1–4 exhibit semiconducting properties with optical band gaps in 2.0–2.4eV.

The pyrochlore-type molybdate Pr2Mo1.73Sc0.27O7

Dipraseodymium molybdenum scandium hepta­oxide, Pr2Mo1.73Sc0.27O7, crystallizes in the cubic pyrochlore-type structure. In the crystal, (Mo,Sc)O6 octa­hedra are linked together by common corners, forming a three-dimensional [(Mo,Sc)2O6] framework. The Pr atom and another O atom atom are located in the voids of this framework. The Mo and the Sc atom are distributed statistically over the same 16d crystallographic position, with site-occupancy factors of 0.867 (3) and 0.133 (3), respectively. The Pr3+ ions are surrounded by six O atoms from the MoO6 octa­hedra and by two other O atoms, forming a ditrigonal scalenohedron. All atoms lie on special positions. The Pr and the statistically distributed (Mo,Sc) sites are in the 16c and 16d positions with .-3m symmetry, and two O atoms are in 48f and 8a positions with 2.mm and -43m site symmetry, respectively.

Two tetranuclear zinc clusters, [Zn4(μ3-OEt)2(μ2-MalO)4Et2] and [Zn4(μ3-GueO)2(μ2-GueO)2(μ2-MalO)2(MalO)2]·2C7H8, containing defective dicubane core geometries (MalOH is maltol and GueOH is guethol)

The zinc alkoxide molecules in di-μ(3)-ethanolato-diethyltetrakis(μ(2)-2-methyl-4-oxo-4H-pyran-3-olato-κ(3)O(3),O(4):O(3))tetrazinc(II), [Zn(4)(C(2)H(5))(2)(C(2)H(5)O)(2)(C(6)H(5)O(3))(4)], (I), and bis(μ(3)-2-ethoxyphenolato-κ(4)O(1),O(2):O(1):O(1))bis(μ(2)-2-ethoxyphenolato-κ(3)O(1),O(2):O(1))bis(μ(2)-2-methyl-4-oxo-4H-pyran-3-olato-κ(3)O(3),O(4):O(3))bis(2-methyl-4-oxo-4H-pyran-3-olato-κ(2)O(3),O(4))tetrazinc(II) toluene disolvate, [Zn(4)(C(6)H(5)O(3))(4)(C(8)H(9)O(2))(4)]·2C(7)H(8), (II), lie on crystallographic centres of inversion. The asymmetric units of (I) and (II) contain half of the tetrameric unit and additionally one molecule of toluene for (II). The Zn(II) atoms are four- and six-coordinated in distorted tetrahedral and octahedral geometries for (I), and six-coordinated in a distorted octahedral environment for (II). The Zn(II) atoms in both compounds are arranged in a defect dicubane Zn(4)O(6) core structure composed of two EtZnO(3) tetrahedra and ZnO(6) octahedra for (I), and of four ZnO(6) octahedra for (II), sharing common corners. The maltolate ligands exist mostly in a μ(2)-bridging mode, while the guetholate ligands prefer a higher coordination mode and act as μ(3)- and μ(2)-bridges.

Synthesis, structure, physical properties, and electronic structure of KGaSe2

The ternary gallium selenide KGaSe2 has been synthesized by solid-state reactions and good quality crystal has been obtained. KGaSe2 crystallizes in the monoclinic space group C2/c with cell dimensions of a = 10.878(2) Å, b = 10.872(2) Å, c = 15.380(3) Å, and β = 100.18(3)°. In the structure, adamantane like [Ga4Se10]8− units are connected by common corners forming two-dimensional [GaSe2]− layers which are separated by K+ cations. KGaSe2 exhibits congruent-melting behavior at around 965 °C. It is transparent in the range of 0.47–20.0 μm and has a band gap of 2.60(2) eV. From a band structure calculation, KGaSe2 is a direct-gap semiconductor. The band gap is mainly determined by the [GaSe2]− layer.

Li14Ln5[Si11N19O5]O2F2 with Ln = Ce, Nd—Representatives of a Family of Potential Lithium Ion Conductors

The isotypic layered oxonitridosilicates Li(14)Ln(5)[Si(11)N(19)O(5)]O(2)F(2) (Ln = Ce, Nd) have been synthesized using Li as fluxing agent and crystallize in the orthorhombic space group Pmmn (Z = 2, Li(14)Ce(5)[Si(11)N(19)O(5)]O(2)F(2): a = 17.178(3), b = 7.6500(15), c = 10.116(2) Å, R1 = 0.0409, wR2 = 0.0896; Li(14)Nd(5)[Si(11)N(19)O(5)]O(2)F(2): a = 17.126(2), b = 7.6155(15), c = 10.123(2) Å, R1 = 0.0419, wR2 = 0.0929). The silicate layers consist of dreier and sechser rings interconnected via common corners, yielding an unprecedented silicate substructure. A topostructural analysis indicates possible 1D ion migration pathways between five crystallographic independent Li positions. The specific Li-ionic conductivity and its temperature dependence were determined by impedance spectroscopy as well as DC polarization/depolarization measurements. The ionic conductivity is on the order of 5 × 10(-5) S/cm at 300 °C, while the activation energy is 0.69 eV. Further adjustments of the defect chemistry (e.g., through doping) can make these compounds interesting candidates for novel oxonitridosilicate based ion conductors.

Na7Mg13Nd(PO4)12

Investigations of the quasi-ternary system Na3PO4–Mg3(PO4)2–NdPO4 allowed us to obtain the new phosphate hepta­sodium trideca­magnesium neodymium dodeca­kis­phosphate, Na7Mg13Nd(PO4)12, by applying a flux method. The crystal structure is isotypic with that of the previously reported Na7Mg13 Ln(PO4)12 (Ln = Eu, La) compounds. It consists of a complex three-dimensional framework built up from an NdO8 polyhedron (m symmetry), an MO6 octa­hedron statistically occupied by M = Mg and Na, and eight MgOx (x = 5, 6) polyhedra (four with site symmetry m), linked either directely by sharing corners, edges and faces, or by one of the eight unique PO4 tetra­hedra through common corners. Two of the PO4 tetra­hedra are statisticaly disordered over a mirror plane. The whole structure can be described as resutling from an assembly of two types of structural units, viz [Mg4 MP4O22]∞ 2 layers extending parallel to (100) and stacked along [100], and [Mg4NdP4O36]∞ 1 undulating chains running along the [010] direction. The six different Na+ cations (five with site symmetry m and one with 0.5 occupancy) are situated in six distinct cavities delimited by the framework. The structure was refined from data of a racemic twin.

Wyllieite-type Ag1.09Mn3.46(AsO4)3

Single crystals of wyllieite-type silver(I) manganese(II) tris­orthoarsenate(V), Ag1.09Mn3.46(AsO4)3, were grown by a solid-state reaction. The three-dimensional framework is made up from four Mn2+/Mn3+ cations surrounded octa­hedrally by O atoms. The MnO6 octa­hedra are linked through edge- and corner-sharing. Three independent AsO4 tetra­hedra are linked to the framework through common corners, delimiting channels along [100] in which two partly occupied Ag+ sites reside, one on an inversion centre and with an occupancy of 0.631 (4), the other on a general site and with an occupancy of 0.774 (3), both within distorted tetra­hedral environments. One of the Mn sites is also located on an inversion centre and is partly occupied, with an occupancy of 0.916 (5). Related compounds with alluaudite-type or rosemaryite-type structures are compared and discussed.

Synthesis and structural characterization of the ternary Zintl phases AE3Al2Pn4 and AE3Ga2Pn4 (AE=Ca, Sr, Ba, Eu; Pn=P, As)

Ten new ternary phosphides and arsenides with empirical formulae AE3Al2Pn4 and AE3Ga2Pn4 (AE=Ca, Sr, Ba, Eu; Pn=P, As) have been synthesized using molten Ga, Al, and Pb fluxes. They have been structurally characterized by single-crystal and powder X-ray diffraction to form with two different structures—Ca3Al2P4, Sr3Al2As4, Eu3Al2P4, Eu3Al2As4, Ca3Ga2P4, Sr3Ga2P4, Sr3Ga2As4, and Eu3Ga2As4 crystallize with the Ca3Al2As4 structure type (space group C2/c, Z=4); Ba3Al2P4 and Ba3Al2As4 adopt the Na3Fe2S4 structure type (space group Pnma, Z=4). The polyanions in both structures are made up of TrPn4 tetrahedra, which share common corners and edges to form [TrPn2]3–∞2 layers in the phases with the Ca3Al2As4 structure, and [TrPn2]3–∞1 chains in Ba3Al2P4 and Ba3Al2As4 with the Na3Fe2S4 structure type. The valence electron count for all of these compounds follows the Zintl–Klemm rules. Electronic band structure calculations confirm them to be semiconductors.

Hydrothermal synthesis and electrochemical properties of α-MoO3 nanobelts used as cathode materials for Li-ion batteries

Uniform α-MoO3 nanobelts were successfully synthesized by the hydrothermal process at 180°C for 20 h of the acidic solutions with different pH values of 0–0.75, adjusted using HCl (conc.). XRD and SEM results revealed that the pH of the precursor solutions played an important role in the phase, impurities, and morphology of the products. At the pH=0, the perfect α-MoO3 nanobelts with a few tens of microns long were synthesized. By the TEM characterization, orthorhombic MoO3 has a distinctive layered structure along the [010] direction, consisting of distorted MoO6 octahedrons connected by common corners along the [100] direction and common edges along the [001] direction. The electrochemical measurement showed that the α-MoO3 nanobelts have high specific charge capacity.

PbCa2[Al8O15] with a novel three-dimensional aluminate anion

The asymmetric unit of the title compound, lead(II) dicalcium octaaluminate, contains one Pb, one Ca, four Al and eight O atoms, with the Pb atom and one O atom situated on mirror planes. Three Al atoms exhibit slightly distorted tetrahedral coordinations with a mean Al-O bond length of 1.76 Å. The fourth Al atom is in a considerably distorted trigonal-bipyramidal coordination with a mean Al-O bond length of 1.89 Å. One AlO(4) tetrahedron forms infinite chains parallel to [100] via corner-sharing. These chains are linked by parallel chains of edge-sharing AlO(5) trigonal bipyramids into layers A of six-membered double rings extending parallel to (010). The second layer B is made up of the remaining two AlO(4) tetrahedra. These tetrahedra share corners, resulting in likewise six-membered double rings. Finally, the parallel layers A and B are linked into a three-dimensional framework by common corners. Charge compensation is achieved by the Pb(2+) and Ca(2+) cations, which are situated in the cavities of the anionic framework, and which are surrounded by seven and six O atoms, respectively, both within highly irregular coordination polyhedra.