Synthesis and structural investigation of the compounds containing HF2 anions: Ca(HF2)2, Ba4F4(HF2)(PF6)3 and Pb2F2(HF2)(PF6)

Three new compounds Ca(HF₂)₂, Ba₄F₄(HF₂)(PF₆)₃ and Pb₂F₂(HF₂)(PF₆) were obtained in the system metal(II) fluoride and anhydrous HF (aHF) acidified with excessive PF₅. The obtained polymeric solids are slightly soluble in aHF and they crystallize out of their aHF solutions. Ca(HF₂)₂ was prepared by simply dissolving CaF₂ in a neutral aHF. It represents the second known compound with homoleptic HF environment of the central atom besides Ba(H₃F₄)₂. The compounds Ba₄F₄(HF₂)(PF₆)₃ and Pb₂F₂(HF₂)(PF₆) represent two additional examples of the formation of a polymeric zigzag ladder or ribbon composed of metal cation and fluoride anion (MF⁺)_n besides PbF(AsF₆), the first isolated compound with such zigzag ladder. The obtained new compounds were characterized by X-ray single crystal diffraction method and partly by Raman spectroscopy. Ba₄F₄(HF₂)(PF₆)₃ crystallizes in a triclinic space group P1¯ with a=4.5870(2) Å, b=8.8327(3) Å, c=11.2489(3) Å, α=67.758(9)°, β=84.722(12), γ=78.283(12)°, V=413.00(3) Å³ at 200 K, Z=1 and R=0.0588. Pb₂F₂(HF₂)(PF₆) at 200 K: space group P1¯, a=4.5722(19) Å, b=4.763(2) Å, c=8.818(4) Å, α=86.967(10)°, β=76.774(10)°, γ=83.230(12)°, V=185.55(14) ų, Z=1 and R=0.0937. Pb₂F₂(HF₂)(PF₆) at 293 K: space group P1¯, a=4.586(2) Å, b=4.781(3) Å, c=8.831(5) Å, α=87.106(13)°, β=76.830(13)°, γ=83.531(11)°, V=187.27(18) Å³, Z=1 and R=0.072. Ca(HF₂)₂ crystallizes in an orthorhombic Fddd space group with a=5.5709(6) Å, b=10.1111(9) Å, c=10.5945(10) Å, V=596.77(10) Å³ at 200 K, Z=8 and R=0.028.     

High-pressure high-temperature synthesis and crystal structure of the isotypic rare earth (RE)-thioborate-sulfides RE9[BS3]2[BS4]3S3, (RE=Dy-Lu)

Application of high-pressure high-temperature conditions (3.5 GPa at 1673 K for 5 h) to mixtures of the elements (RE:B:S=1:3:6) yielded crystalline samples of the isotypic rare earth-thioborate-sulfides RE₉[BS₃]₂[BS₄]₃S₃, (RE=Dy-Lu), which crystallize in space group P6₃ (Z=2/3) and adopt the Ce₆Al_3.33S₁₄ structure type. The crystal structures were refined from X-ray powder diffraction data by applying the Rietveld method. Dy: a=9.4044(2) Å, c=5.8855(3) Å; Ho: a=9.3703(1) Å, c=5.8826(1) Å; Er: a=9.3279(12) Å, c=5.8793(8) Å; Tm: a=9.2869(3) Å, c=5.8781(3) Å; Yb: a=9.2514(5) Å, c=5.8805(6) Å; Lu: a=9.2162(3) Å, c=5.8911(3) Å. The crystal structure is characterized by the presence of two isolated complex ions [BS₃]^3- and [BS₄]^5- as well as [□(S^2-)₃] units.     

Two new octahedral/pyramidal frameworks containing both cation channels and lone-pair channels: syntheses and structures of Ba2MnMn2(SeO3)6 and PbFe2(SeO3)4

The hydrothermal syntheses, single crystal structures, and some properties of Ba₂Mn^IIMn₂^III(SeO₃)₆ and PbFe₂(SeO₃)₄ are reported. These related phases contain three-dimensional frameworks of vertex (FeO₆) and vertex/edge linked (MnO₆) octahedra and SeO₃ pyramids. In each case, the MO₆/SeO₃ framework encloses two types of 8 ring channels, one of which encapsulates the extra-framework cations and one of which provides space for the Se^IV lone pairs. Crystal data: Ba₂Mn₃(SeO₃)₆, M_r=1201.22, monoclinic, P2₁/c (No. 14), a=5.4717 (3) Å, b=9.0636 (4) Å, c=17.6586 (9) Å, β=94.519 (1)°, V=873.03 (8) Å³, Z=2, R(F)=0.031, wR(F²)=0.070; PbFe₂(SeO₃)₄, M_r=826.73, triclinic, (No. 2), a=5.2318 (5) Å, b=6.7925 (6) Å, c=7.6445 (7) Å, α=94.300 (2)°, β=90.613 (2)°, γ=95.224 (2)°, V=269.73 (4) Å³, Z=1, R(F)=0.051, wR(F²)=0.131.     

Syntheses, structures, and vibrational spectroscopy of the two-dimensional iodates Ln(IO3)3 and Ln(IO3)3(H2O) (LnYb, Lu)

The reaction of Lu³⁺ or Yb³⁺ and H₅IO₆ in aqueous media at 180 °C leads to the formation of Yb(IO₃)₃(H₂O) or Lu(IO₃)₃(H₂O), respectively, while the reaction of Yb metal with H₅IO₆ under similar reaction conditions gives rise to the anhydrous iodate, Yb(IO₃)₃. Under supercritical conditions Lu³⁺ reacts with HIO₃ and KIO₄ to yield the isostructural Lu(IO₃)₃. The structures have been determined by single-crystal X-ray diffraction. Crystallographic data are (MoKα, λ=0.71073 Å): Yb(IO₃)₃, monoclinic, space group P2₁/n, a=8.6664(9) Å, b=5.9904(6) Å, c=14.8826(15) Å, β=96.931(2)°, V=766.99(13), Z=4, R(F)=4.23% for 114 parameters with 1880 reflections with I>2σ(I); Lu(IO₃)₃, monoclinic, space group P2₁/n, a=8.6410(9), b=5.9961(6), c=14.8782(16) Å, β=97.028(2)°, V=765.08(14), Z=4, R(F)=2.65% for 119 parameters with 1756 reflections with I>2σ(I); Yb(IO₃)₃(H₂O), monoclinic, space group C2/c, a=27.2476(15), b=5.6296(3), c=12.0157(7) Å, β=98.636(1)°, V=1822.2(2), Z=8, R(F)=1.51% for 128 parameters with 2250 reflections with I>2σ(I); Lu(IO₃)₃(H₂O), monoclinic, space group C2/c, a=27.258(4), b=5.6251(7), c=12.0006(16) Å, β=98.704(2)°, V=1818.8(4), Z=8, R(F)=1.98% for 128 parameters with 2242 reflections with I>2σ(I). The f elements in all of the compounds are found in seven-coordinate environments and bridged with monodentate, bidentate, or tridentate iodate anions. Both Lu(IO₃)₃(H₂O) and Yb(IO₃)₃(H₂O) display distinctively different vibrational profiles from their respective anhydrous analogs. Hence, the Raman profile can be used as a complementary diagnostic tool to discern the different structural motifs of the compounds.     

(C6H17N3)[Zn4(PO4)2(HPO3)2]: a new layered zinc phosphate-phosphite templated by 1-(2-Aminoethyl) piperazine

Employing 1-(2-Aminoethyl) piperazine as a template, a new organically templated layered zinc phosphate-phosphite (C₆H₁₇N₃)[Zn₄(PO₄)₂(HPO₃)₂] has been prepared hydrothermally. Single-crystal X-ray diffraction analysis shows that it crystallizes in the monoclinic space group Cc with a=5.3272(11) Å, b=17.146(3) Å, c=22.071(4) Å, β=94.58(3)°, V=2009.5(7) Å³, Z=4, R₁=0.0201 (I>2σ(I)) and wR₂=0.0812 (all data). The inorganic network is based on strictly alternating ZnO₄ tetrahedral units and P-centered units including PO₄ tetrahedra and HPO₃ pseudo-pyramids forming a double layered structure that contains columns of double six-membered rings. The diprotonated 1-(2-Aminoethyl) piperazine molecules reside in the interlayer region and interact with the inorganic network through H-bonds.     

Ternary rare-earth titanium antimonides: Phase equilibria in the RE-Ti-Sb (RE=La, Er) systems and crystal structures of RE2Ti7Sb12 (RE=La, Ce, Pr, Nd) and RETi3(SnxSb1-x)4 (RE=Nd, Sm)

Investigations on phase relationships and crystal structures have been conducted on several ternary rare-earth titanium antimonide systems. The isothermal cross-sections of the ternary RE-Ti-Sb systems containing a representative early (RE=La) and late rare-earth element (RE=Er) have been constructed at 800 °C. In the La-Ti-Sb system, the previously known compound La₃TiSb₅ was confirmed and the new compound La₂Ti₇Sb₁₂ (own type, Cmmm, Z=2, a=10.5446(10) Å, b=20.768(2) Å, and c=4.4344(4) Å) was discovered. In the Er-Ti-Sb system, no ternary compounds were found. The structure of La₂Ti₇Sb₁₂ consists of a complex arrangement of TiSb₆ octahedra and disordered fragments of homoatomic Sb assemblies, generating a three-dimensional framework in which La atoms reside. Other early rare-earth elements (RE=Ce, Pr, Nd) can be substituted in this structure type. Attempts to prepare crystals in these systems through use of a tin flux resulted in the discovery of a new Sn-containing pseudoternary phase RETi₃(Sn_xSb_1−x)₄ for RE=Nd, Sm (own type, Fmmm, Z=8; a=5.7806(4) Å, b=10.0846(7) Å, and c=24.2260(16) Å for NdTi₃(Sn_0.1Sb_0.9)₄; a=5.7590(4) Å, b=10.0686(6) Å, and c=24.1167(14) Å for SmTi₃(Sn_0.1Sb_0.9)₄). Its structure consists of double-layer slabs of Ti-centred octahedra stacked alternately with nets of the RE atoms; the Ti atoms are arranged in kagome nets.     

Crystal structures of lanthanide and zirconium phosphates with general formula Ln0.33Zr2(PO4)3, where Ln=Ce, Eu, Yb

Crystal structures of synthetic phosphates Ce_0.33Zr₂(PO₄)₃, Eu_0.33Zr₂(PO₄)₃ and Yb_0.33Zr₂(PO₄)₃ have been refined by Rietveld method using powder diffraction data. Unit cell parameters: a=8.7419 (4), c=23.128 (2) Å; a=8.7659 (1), c=22.822 (1) Å; a=8.8078 (4), c=22.485 (3) Å, respectively; Z=6. Values of final R-factors in isotropic approximation: R_wp=4.00, R_wp=3.33, R_wp=4.12%, respectively. New space group P3¯c has been established for the compounds with general formula Ln_0.33Zr₂(PO₄)₃, where Ln=Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y. It has been confirmed that the synthetic phosphates with general formula Ln_0.33Zr₂(PO₄)₃ belong to the NZP (sodium zirconium phosphate) structure type.     

New one-dimensional uranyl and neptunyl iodates: crystal structures of K3[(UO2)2(IO3)6](IO3)·H2O and K[NpO2(IO3)3]·1.5H2O

The uranyl and neptunyl(VI) iodates, K₃[(UO₂)₂(IO₃)₆](IO₃)·H₂O (1) and K[NpO₂(IO₃)₃]·1.5H₂O (2), have been prepared and crystallized under mild hydrothermal conditions. The structures of 1 and 2 both contain one-dimensional _∞¹[AnO₂(IO₃)₃]¹⁻(An=U,Np) ribbons that consist of approximately linear actinyl(VI) cations bound by iodate anions to yield AnO₇ pentagonal bipyramids. The AnO₇ units are linked by bridging iodate anions to yield chains that are in turn coupled by additional iodate anions to yield ribbons. The edges of the ribbons are terminated by monodentate iodate anions. For 1 and 2, K⁺ cations and water molecules separate the ribbons from one another. In addition, isolated iodate anions are also found between _∞¹[UO₂(IO₃)₃]¹⁻ ribbons in 1. In order to aid in the assignment of oxidation states in neptunyl containing compounds, a bond-valence sum parameter of 2.018 Å for Np(VI) bound exclusively to oxygen has been developed with b=0.37 Å. Crystallographic data (193 K, MoKα, λ=0.71073): 1, triclinic, , a=7.0609(4) Å, b=14.5686(8)  Å, c=14.7047(8)  Å, α=119.547(1)°, β=95.256(1)°, γ=93.206(1)°, Z=2, R(F)=2.49% for 353 parameters with 6414 reflections with I>2σ(I); (203 K, MoKα, λ=0.71073): 2, monoclinic, P2₁/c, a=7.796(4)  Å, b=7.151(3)  Å, c=21.79(1)  Å, β=97.399(7)°, Z=4, R(F)=6.33% for 183 parameters with 2451 reflections with I>2σ(I).     

[Co(en)3][In3(H2PO4)6(HPO4)3]·H2O: A new layered indium phosphate templated by cobalt complex

A new layered indium phosphate [Co(en)₃][In₃(H₂PO₄)₆(HPO₄)₃]·H₂O (1) has been synthesized solvothermally by using a racemic mix of chiral metal complex Co(en)₃Cl₃ as a template. Its structure is determined by single-crystal X-ray diffraction analysis and further characterized by X-ray powder diffraction, ICP, NMR and TG analyses. The inorganic layer is built up by alternation of In-centred octahedra (InO₆) and P-centered tetrahedra (PO₃(OH), PO₂(OH)₂, PO₂(=O)(OH) and PO(=O)(OH)₂) forming a 4.12-net. The metal complex cations locate in the interlayer region and interact with the host network through H-bonds. It is the first indium phosphate compound templated by a transition-metal complex and is isostructural with GaPO-CJ14. Crystal data: 1, monoclinic, space group P2₁/m (No. 11), a=9.1700(18) Å, b=22.6923(5) Å, c=9.9116(2) Å, β=107.87(3)°, Z=4, R_1[I>2σ(I)]=0.0287 and wR_{2(all data)}=0.0939.     

Synthesis, crystal structures and photoluminescence properties of new oxyborates, Mg5NbO3(BO3)3 and Mg5TaO3(BO3)3, with novel warwickite-type superstructures

Single crystals of new oxyborates, Mg₅NbO₃(BO₃)₃ and Mg₅TaO₃(BO₃)₃, were prepared at 1370 °C in air using B₂O₃ as a flux. They were colorless and transparent with block shapes. X-ray diffraction analysis of the single crystals revealed Mg₅NbO₃(BO₃)₃ and Mg₅TaO₃(BO₃)₃ to be isostructural. The X-ray diffraction reflections were indexed to the orthorhombic Pnma (No. 62) system with a=9.3682(3) Å, b=9.4344(2) Å, c=9.3379(3) Å and Z=4 for Mg₅NbO₃(BO₃)₃ and a=9.3702(3) Å, b=9.4415(3) Å, c=9.3301(2) Å and Z=4 for Mg₅TaO₃(BO₃)₃. The crystal structures of Mg₅NbO₃(BO₃)₃ and Mg₅TaO₃(BO₃)₃ are novel warwickite-type superstructures having ordered arrangements of Mg and Nb/Ta atoms. Polycrystals of Mg₅NbO₃(BO₃)₃ prepared by solid state reaction at 1200 °C in air showed broad blue-to-green emission with a peak wavelength of 470 nm under 270 nm ultraviolet excitation at room temperature.     

Crystal structures of lazulite-type oxidephosphates TiTi3O3(PO4)3 and M4Ti27O24(PO4)24 (M=Ti, Cr, Fe)

Single crystals of the oxidephosphates Ti^IIITi^IV₃O₃(PO₄)₃ (black), Cr^III₄Ti^IV₂₇O₂₄(PO₄)₂₄ (red-brown, transparent), and Fe^III₄Ti^IV₂₇O₂₄(PO₄)₂₄ (brown) with edge-lengths up to 0.3 mm were grown by chemical vapour transport. The crystal structures of these orthorhombic members (space group F2dd ) of the lazulite/lipscombite structure family were refined from single-crystal data [Ti^IIITi^IV₃O₃(PO₄)₃: Z=24, a=7.3261(9) Å, b=22.166(5) Å, c=39.239(8) Å, R₁=0.029, wR₂=0.084, 6055 independent reflections, 301 variables; Cr^III₄Ti^IV₂₇O₂₄(PO₄)₂₄: Z=1, a=7.419(3) Å, b=21.640(5) Å, c=13.057(4) Å, R₁=0.037, wR₂=0.097, 1524 independent reflections, 111 variables; Fe^III₄Ti^IV₂₇O₂₄(PO₄)₂₄: Z=1, a=7.4001(9) Å, b=21.7503(2) Å, c=12.775(3) Å, R₁=0.049, wR₂=0.140, 1240 independent reflections, 112 variables). For Ti^IIITi^IVO₃(PO₄)₃ a well-ordered structure built from dimers [Ti^III,IV₂O₉] and [Ti^IV,IV₂O₉] and phosphate tetrahedra is found. The metal sites in the crystal structures of Cr₄Ti₂₇O₂₄(PO₄)₂₄ and Fe₄Ti₂₇O₂₄(PO₄)₂₄, consisting of dimers [M^IIITi^IVO₉] and [Ti^IV,IV₂O₉], monomeric [Ti^IVO₆] octahedra, and phosphate tetrahedra, are heavily disordered. Site disorder, leading to partial occupancy of all octahedral voids of the parent lipscombite/lazulite structure, as well as splitting of the metal positions is observed. According to Guinier photographs Ti^III₄Ti^IV₂₇O₂₄(PO₄)₂₄ (a=7.418(2) Å, b=21.933(6) Å, c=12.948(7) Å) is isotypic to the oxidephosphates M^III₄Ti^IV₂₇O₂₄(PO₄)₂₄ (M^III: Cr, Fe). The UV/vis spectrum of Cr₄Ti₂₇O₂₄(PO₄)₂₄ reveals a rather small ligand-field splitting Δ_o=14,370 cm⁻¹ and a very low nephelauxetic ratio β=0.72 for the chromophores [Cr^IIIO₆] within the dimers [Cr^IIITi^IVO₉].     

Synthesis and characterization of a new layered gallium phosphate [Co(en)3][Ga3(H2PO4)6(HPO4)3] templated by cobalt complex

A new layered gallium phosphate [Co(en)₃][Ga₃(H₂PO₄)₆(HPO₄)₃], denoted as GaPO-CJ14, has been synthesized solvothermally by using a racemic mix of chiral metal complex Co(en)₃Cl₃ as a template. Its structure was determined by single-crystal X-ray diffraction analysis and further characterized by X-ray powder diffraction, ICP, and TG analyses. The compound crystallizes in the monoclinic space group P2₁/m (No. 11) with a=9.2103(3), b=22.0936(8), c=9.5458(4) Å, β=108.278(2)°, Z=2, R₁=0.0497 and wR₂=0.1122 for all data. The inorganic layer is built up by alternation of Ga-centered octahedra (GaO₆) and P-centered tetrahedra (PO₃(OH), PO₂(OH)₂ , PO₂(O)(OH) and PO(O)(OH)₂) forming a 4.12-net. The sheet structure is featured by a series of structural units composed of two centrosymmetrically related [3.3.3] propellane-like chiral motifs. The metal complex cations locate in the interlayer region and interact with the host network through H-bonds.     

Non-centrosymmetric Ba3Ti3O6(BO3)2

The compound previously reported as Ba₂Ti₂B₂O₉ has been reformulated as Ba₃Ti₃B₂O₁₂, or Ba₃Ti₃O₆(BO₃)₂, a new barium titanium oxoborate. Small single crystals have been recovered from a melt with a composition of BaTiO₃:BaTiB₂O₆ (molar ratio) cooled between 1100°C and 850°C. The crystal structure has been determined by X-ray diffraction: hexagonal system, non-centrosymmetric space group, a=8.7377(11) Å, c=3.9147(8) Å, Z=1, wR(F²)=0.039 for 504 unique reflections. Ba₃Ti₃O₆(BO₃)₂ is isostructural with K₃Ta₃O₆(BO₃)₂. Preliminary measurements of nonlinear optical properties on microcrystalline samples show that the second harmonic generation efficiency of Ba₃Ti₃O₆(BO₃)₂ is equal to 95% of that of LiNbO₃.     

Synthesis, crystal structure and electrical characterization of two new potassium uranyl molybdates K2(UO2)2(MoO4)O2 and K8(UO2)8(MoO5)3O6

Two new potassium uranyl molybdates K₂(UO₂)₂(MoO₄)O₂ and K₈(UO₂)₈(MoO₅)₃O₆ have been obtained by solid state chemistry . The crystal structures were determined by single crystal X-ray diffraction data, collected with MoKα radiation and a charge coupled device (CCD) detector. Their structures were solved using direct methods and Fourier difference techniques and refined by a least square method on the basis of F² for all unique reflections, with R₁=0.046 for 136 parameters and 1412 reflections with I?2σ(I) for K₂(UO₂)₂(MoO₄)O₂ and R₁=0.055 for 257 parameters and 2585 reflections with I?2σ(I) for K₈(UO₂)₈(MoO₅)₃O₆. The first compound crystallizes in the monoclinic symmetry, space group P2₁/c with a=8.250(1) Å, b=15.337(2) Å, c=8.351(1) Å, β=104.75(1)°, ρ_mes=5.22(2) g/cm³, ρ_cal=5.27(2) g/cm³ and Z=4. The second material adopts a tetragonal unit cell with a=b=23.488(3) Å, c=6.7857(11) Å, ρ_mes=5.44(3) g/cm³, ρ_cal=5.49(2) g/cm³, Z=4 and space group P4/n.In both structures, the uranium atoms adopt a UO₇ pentagonal bipyramid environment, molybdenum atoms are in a MoO₄ tetrahedral environment for K₂(UO₂)₂(MoO₄)O₂ and MoO₅ square pyramid coordination in K₈(UO₂)₈(MoO₅)₃O₆. These compounds are characterized by layered structures. The association of uranyl ions (UO₇) and molybdate oxoanions MoO₄ or MoO₅, give infinite layers [(UO₂)₂(MoO₄)O₂]²⁻ and [(UO₂)₈(MoO₅)₃O₆]⁸⁻ in K₂(UO₂)₂(MoO₄)O₂ and K₈(UO₂)₈(MoO₅)₃O₆, respectively. Conductivity properties of alkali metal within the interlayer spaces have been measured and show an Arrhenius type evolution.     

Magnetism and Raman spectroscopy of the dimeric lanthanide iodates Ln(IO3)3 (Ln=Gd, Er) and magnetism of Yb(IO3)3

Colorless single crystals of Gd(IO₃)₃ or pale pink single crystals of Er(IO₃)₃ have been formed from the reaction of Gd metal with H₅IO₆ or Er metal with H₅IO₆ under hydrothermal reaction conditions at 180 °C. The structures of both materials adopt the Bi(IO₃)₃ structure type. Crystallographic data are (MoKα, λ=0.71073 Å): Gd(IO₃)₃, monoclinic, space group P2₁/n, a=8.7615(3) Å, b=5.9081(2) Å, c=15.1232(6) Å, β=96.980(1)°, V=777.03(5) Z=4, R(F)=1.68% for 119 parameters with 1930 reflections with I>2σ(I); Er(IO₃)₃, monoclinic, space group P2₁/n, a=8.6885(7) Å, b=5.9538(5) Å, c=14.9664(12) Å, β=97.054(1)°, V=768.4(1) Z=4, R(F)=2.26% for 119 parameters with 1894 reflections with I>2σ(I). In addition to structural studies, Gd(IO₃)₃, Er(IO₃)₃, and the isostructural Yb(IO₃)₃ were also characterized by Raman spectroscopy and magnetic property measurements. The results of the Raman studies indicated that the vibrational profiles are adequately sensitive to distinguish between the structures of the iodates reported here and other lanthanide iodate systems. The magnetic measurements indicate that only in Gd(IO₃)₃ did the 3+ lanthanide ion exhibit its full 7.9 μ_B Hund's rule moment; Er³⁺ and Yb³⁺ exhibited ground state moments and gap energy scales of 8.3 μ_B/70 K and 3.8 μ_B/160 K, respectively. Er(IO₃)₃ exhibited extremely weak ferromagnetic correlations (+0.4 K), while the magnetic ions in Gd(IO₃)₃ and Yb(IO₃)₃ were fully non-interacting within the resolution of our measurements (∼0.2 K).     

New Gallium Phosphate Frameworks Containing 1,4-Diaminobutane and 1,5-Diaminopentane: [NH3(CH2)xNH3][Ga4(PO4)4(HPO4)] and [NH3(CH2)xNH3][Ga(PO4)(HPO4)] (x=4 and 5)

Two new gallium phosphates, [NH₃(CH₂)₄NH₃][Ga₄(PO₄)₄ (HPO₄)] (I) and [NH₃(CH₂)₄NH₃][Ga(PO₄)(HPO₄)] (II), have been synthesized under solvothermal conditions in the presence of 1,4-diaminobutane and their structures determined using room-temperature single-crystal X-ray diffraction data. Compound (I) (M_r=844.90, triclinic, space group P-1, a=9.3619(3), b=10.1158(3) and c=12.6456(5) Å, α=98.485(1), β=107.018(2) and γ=105.424(1)°; V=1070.39 ų, Z=2, R=3.68% and R_w=4.40% for 2918 observed data [I>3(σ(I))]) consists of GaO₄ and PO₄ tetrahedra and GaO₅ trigonal bipyramids linked to generate an open three-dimensional framework containing 4-, 6-, 8-, and 12-membered rings of alternating Ga- and P-based polyhedra. 1,4-Diaminobutane dications are located in channels bounded by the 12-membered rings in the two-dimensional pore network and are held to the framework by hydrogen bonding. Compound (II) (M_r=350.84, monoclinic, space group P2₁/c, a=4.8922(1), b=18.3638(6) and c=13.7468(5) Å, β=94.581(1)°; V=1227.76 ų, Z=4, R=2.95% and R_w=3.37% for 2050 observed data [I>3(σ(I))]) contains chains of edge-sharing 4-membered rings of alternating GaO₄ and PO₄ tetrahedra constituting a backbone from which hang ‘pendant’ PO₃(OH) groups. Hydrogen bonding between the GaPO framework and the diamine dications holds the structure together. A previously reported phase, [NH₃(CH₂)₄NH₃][Ga₄(PO₄)₄(HPO₄)] (V), structurally related but distinct from its stoichiometric equivalent, (I), has been prepared as a pure phase by this method. Two further materials, [NH₃(CH₂)₅NH₃][Ga₄(PO₄)₄(HPO₄)] (III) (tricli- nic, lattice parameters from PXD: a=9.3565(4), b=5.0156(2) and c=12.7065(4) Å, α=96.612(3), β=102.747(4) and γ=105.277(3)°) and [NH₃(CH₂)₅NH₃][Ga(PO₄)(HPO₄)] (IV) (M_r=364.86, monoclinic, space group P2₁/n, a=4.9239(2), b=13.2843(4) and c=19.5339(7) Å, β=96.858(1)°; V=1268.58 ų, Z=4, R=3.74% and R_w=4.44% for 2224 observed room-temperature data [I>3(σ(I))]), were also prepared under similar conditions in the presence of 1,5-diaminopentane. (III) and (IV) are structurally related to, yet distinct from (I) and (II) respectively.     

Syntheses, structures, and properties of Ag4(Mo2O5)(SeO4)2(SeO3) and Ag2(MoO3)3SeO3

Ag₄(Mo₂O₅)(SeO₄)₂(SeO₃) has been synthesized by reacting AgNO₃, MoO₃, and selenic acid under mild hydrothermal conditions. The structure of this compound consists of cis-MoO₂²⁺ molybdenyl units that are bridged to neighboring molybdenyl moieties by selenate anions and by a bridging oxo anion. These dimeric units are joined by selenite anions to yield zigzag one-dimensional chains that extended down the c-axis. Individual chains are polar with the C₂ distortion of the Mo(VI) octahedra aligning on one side of each chain. However, the overall structure is centrosymmetric because neighboring chains have opposite alignment of the C₂ distortion. Upon heating Ag₄(Mo₂O₅)(SeO₄)₂(SeO₃) looses SeO₂ in two distinct steps to yield Ag₂MoO₄. Crystallographic data: (193 K; MoKα, λ=0.71073 Å): orthorhombic, space group Pbcm, a=5.6557(3), b=15.8904(7), c=15.7938(7) Å, V=1419.41(12), Z=4, R(F)=2.72% for 121 parameters with 1829 reflections with I>2σ(I). Ag₂(MoO₃)₃SeO₃ was synthesized by reacting AgNO₃ with MoO₃, SeO₂, and HF under hydrothermal conditions. The structure of Ag₂(MoO₃)₃SeO₃ consists of three crystallographically unique Mo(VI) centers that are in 2+2+2 coordination environments with two long, two intermediate, and two short bonds. These MoO₆ units are connected to form a molybdenyl ribbon that extends along the c-axis. These ribbons are further connected together through tridentate selenite anions to form two-dimensional layers in the [bc] plane. Crystallographic data: (193 K; MoKα, λ=0.71073 Å): monoclinic, space group P2₁/n, a=7.7034(5), b=11.1485(8), c=12.7500(9) Å, β=105.018(1) V=1002.7(2), Z=4, R(F)=3.45% for 164 parameters with 2454 reflections with I>2σ(I). Ag₂(MoO₃)₃SeO₃ decomposes to Ag₂Mo₃O₁₀ on heating above 550 °C.     

3D [Ag-Mg] polyanionic frameworks in the La4Ag10Mg3 and La4Ag10.3Mg12 new ternary compounds

The crystal structures of two new ternary phases, La₄Ag₁₀Mg₃ and La₄Ag_10.3Mg₁₂, were refined from X-ray single crystal diffraction data. La₄Ag₁₀Mg₃ crystallizes in the Ca₄Au₁₀In₃ structure type, an ordered variant of the binary Zr₇Ni₁₀ compound: orthorhombic, Cmce, oS68, a=14.173(5), b=10.266(3), c=10.354(3) Å, Z=4, wR₂=0.0826, 676 F² values, 50 variables. La₄Ag_10.3Mg₁₂ represents a new structure type: orthorhombic, Cmmm, oS116-10.32, a=9.6130(3), b=24.9663(8), c=9.6333(2) Å, Z=4, wR₂=0.0403, 1185 F² values, 101 variables. The structural analysis of both compounds, highlighting a significant contraction of the Ag-Mg distances, suggests the existence of three-dimensional [Ag-Mg] networks hosting La atoms. LMTO calculations applied to La₄Ag₁₀Mg₃ indicate that the strongest bonds occur for Ag-Ag and Ag-Mg interactions, and confirm the presence of a 3D_∞[Ag₁₀Mg₃]^δ− polyanionic framework balanced by positively charged La atoms.     

Structure of two new borates YCa3(AlO)3(BO3)4 and YCa3(GaO)3(BO3)4

By replacing Mn in YCa₃(MnO)₃(BO₃)₄ with trivalent Al and Ga, two new borates with the compositions of YCa₃(MO)₃(BO₃)₄ (M=Al, Ga) were prepared by solid-state reaction. Structure refinements from X-ray powder diffraction data revealed that both of them are isostructural to gaudefroyite with a hexagonal space group P6₃/m. Cell parameters of a=10.38775(13)Å, c=5.69198(10)Å for the Al-containing compound and a=10.5167(3)Å, c=5.8146(2)Å for the Ga analog were obtained from the refinements. The structure is constituted of AlO₆ or GaO₆ octahedral chains interconnected by BO₃ groups in the ab plane to form a Kagomé-type lattice, leaving trigonal and apatite-like tunnels. It is found that most rare-earth and Cr, Mn ions can be substituted into the Y³⁺ and M³⁺ sites, respectively, and the preference of rare-earth ions to locate in the trigonal tunnel is correlated to the sizes of the M³⁺ ions.     

Syntheses, crystal structures and optical spectroscopy of Ln2(SO4)3·8H2O (Ln=Ho, Tm) and Pr2(SO4)3·4H2O

The lanthanide sulphate octahydrates Ln₂(SO₄)₃·8H₂O (Ln=Ho, Tm) and the respective tetrahydrate Pr₂(SO₄)₃·4H₂O were obtained by evaporation of aqueous reaction mixtures of trivalent rare earth oxides and sulphuric acid at 300 K. Ln₂(SO₄)₃·8H₂O (Ln=Ho, Tm) crystallise in space group C2/c (Z=4, a_Ho=13.4421(4) Å, b_Ho=6.6745(2) Å, c_Ho=18.1642(5) Å, β_Ho=102.006(1) Å³ and a_Tm=13.4118(14) Å, b_Tm=6.6402(6) Å, c_Tm=18.1040(16) Å, β_Tm=101.980(8) Å³), Pr₂(SO₄)₃·4H₂O adopts space group P2₁/n (a=13.051(3) Å, b=7.2047(14) Å, c=13.316(3) Å, β=92.55(3) Å³). The vibrational and optical spectra of Ho₂(SO₄)₃·8H₂O and Pr₂(SO₄)₃·4H₂O are also reported.