A New Three-Dimensional Vanadium Selenite, (VO)2(SeO3)3, with Isolated and Edge-Shared VO6 Octahedra

Theoretical investigations on the defect structures and g factors for V4+ in 30PbO-5Bi2 O3 -(65-x)SiO2 glasses at different concentrations

For 3d¹ (V⁴⁺ ) impurity in 30PbO-5Bi₂ O₃ -(65-x)SiO₂ glass systems with different concentrations x of V2O5, the defect structures and gyromagnetic factors are theoretically investigated by using the perturbation formulas of g factors for a tetragonally compressed octahedral 3d¹ group. The concentration dependences of d-d transition band and g factors are suitably explained from the Fourier type concentration functions of the cubic crystal field parameter Dq, covalency factor N and relative tetragonal compression ratio ρ. The above concentration dependences of these quantities are suitably illustrated by the modifications of the local crystal field strength and electron cloud distribution with increasing x. The concentration variations of the electrical conductivity and dielectric relaxation are further analyzed from the stability of the systems in view of two competitive factors (increasing network polymerization and bulk stability at low concentrations and decreasing former SiO₂ and stability at high concentrations).

Theoretical studies on the g factors, optical absorption, and their concentration variations for Mo5+ in 40PbO-(10 - x)Y2 O3 -50P2 O5 :xMoO3 glass

On the basis of the higher order perturbation formulas of g factors for a 4d¹ group in tetragonally compressed octahedra, the g factors, optical absorption, local structure, and their concentration dependences of pentavalent molybdenum in 40PbO-(10 - x)Y₂ O₃ -50P₂ O₅ :xMoO₃ (1 ≤ x ≤ 5 mol%) glass are uniformly investigated. The experimental optical absorption spectra and g factors for Mo⁵⁺ at various concentrations x are reasonably regenerated by using the reasonable exponential concentration functions of the cubic field parameter D_q , covalent factor N, and relative tetragonal compression ratio ρ. The tetragonal compression ratio ρ due to the Jahn-Teller effect was found in the range of 3.8% to 4.2%. The decreasing trend of D_q and N and the increasing trend of ρ with concentration can be interpreted as the fact that the variations of MoO₃ and Y₂ O₃ concentrations lead to the modulations of local structure and electron cloud distribution around Mo⁵⁺ , associated with the adjustment of the glass network. The concentration dependence of optical basicity is also analyzed for the above glass systems.

Theoretical studies of the concentration dependences of d-d transition band, g factors, and local distortion for V4+ in Li2 O-PbO-B2 O3 -P2 O5 glasses

In this work, the g factors, d-d transition band, local distortion, and their concentration dependences for impurity V⁴⁺ in 20Li₂ O-20PbO-45B₂ O₃ -(15 - x)P₂ O₅ :V₂ O₅ (0 ≤ x ≤ 2.5 mol%) glasses are theoretically investigated by using perturbation formulas of g factors for a tetragonally compressed octahedral 3d¹ cluster. In the light of the cubic polynomial concentration functions for cubic field parameter D_q , covalency factor N, and relative tetragonal compression ratio ρ, the calculated concentration dependences of d-d transition band and g factors for V⁴⁺ show good agreement with the experimental data. With increasing x, N (≈0.7682-0.8165) displays the monotonously increasing trend, whereas ρ (≈6.5-4.2%) and D_q (≈1504.9-1481.1 cm^-1 ) exhibit the decreasing tendencies. The above concentration dependences can be ascribed to the modifications of the V⁴⁺ -O^2- bonding and orbital admixtures around the impurity V⁴⁺ due to the effects of V₂ O₅ doping on the stability of the glass network, the strength of local crystal fields, and the electron cloud distribution.

Studies on the local structure and spin Hamiltonian parameters for V4+ in Na2 O-PbO-Bi2 O3 -SiO2 glass ceramics

The local structure, d-d transition band, and spin Hamiltonian parameters (SHPs) are theoretically studied for the V⁴⁺ probe in Na₂ O-PbO-Bi₂ O₃ -SiO₂ (NPBS) glass ceramics containing V₂ O₅ dopant with various concentration x (0 ≤ x ≤ 5 mol%) by using the perturbation formulas of the SHPs for tetragonally compressed octahedral 3d¹ clusters. The first decreasing (or increasing) and then increasing (or decreasing) d-d transition band (= 10 D_q ) and hyperfine structure constants A_// and A_⊥ (or g factors g_// and g_⊥ ) with x can be suitably simulated with the similarly varying Fourier type concentration functions of cubic field parameter D_q , covalence factor N, core polarization constant κ, and reduction factor H (or relative tetragonal compression ratio ρ), with the minima (or maxima) at the middle concentration x = 3 mol%, respectively. The above concentration variations of SHPs and the related quantities may originate from the modifications of local crystal field strength, tetragonal compression, and electron cloud distribution near the impurity V⁴⁺ with x, corresponding to the highest [V⁴⁺ ]/[V⁵⁺ ] ratio at 3 mol%. Present studies would be helpful to explore novel sodium lead bismuth silicate glass ceramics by modifying the concentration of V₂ O₅ dopant.

Selenite bromide nonlinear optical materials Pb2GaF2(SeO3)2Br and Pb2NbO2(SeO3)2Br: synthesis and characterization

Two new isomorphic selenite bromides, namely Pb2GaF2(SeO3)2Br (1) and Pb2NbO2(SeO3)2Br (2), were synthesized by mild hydrothermal reactions. These two compounds crystallize in the noncentrosymmertric space group P21 and feature 3D structures consisting of 1D (Pb2Br)3+ cationic chains and 2D [Ga2F4(SeO3)4]6-/[Nb2O4(SeO3)4]6- anonic chains. As measured, 1 and 2 are phase-matchable and exhibit excellent second harmonic generation (SHG) responses of 4.5 and 1.4 times that of KDP, respectively. Moreover, these two compounds possess wide bandgaps (>3.17 eV) and high thermal stabilities (>425 °C), indicating their suitable performances as potential nonlinear optical materials. First-principle density functional theory (DFT) calculations were also performed to explicate the structure-property relationship.

A Barium Vanadium(V) Selenite Hydrate, Ba(VO2)2(SeO3)2·H2O: A Novel 3D Polymer of Cross-Linked Sheets with Embedded ···V–O–V··· 21 Helices

The characterisation, by a single-crystal X-ray study at ~150 K, of brown acicular crystals of barium(ii) bis(dioxovanadium(v)) bis(selenite(iv)) monohydrate, BaSe2V2O10·H2O, obtained as a minor product of the synthesis of the previously reported ‘Ba(VO)2(SeO3)2(HSeO3)2’, is recorded. Crystals are monoclinic, P21/c, a = 10.803(2), b = 5.1126(8), c = 17.905(3) Å, β = 92.048(2)°, V = 988.3(3) Å3, 2456 independent diffractometer reflections refining to R1 = 0.032, wR2 = 0.084. A single BaV2Se2O11H2 formula unit, devoid of crystallographic symmetry, comprises the asymmetric unit of the structure, which is a three-dimensional polymer, with component sheets parallel to the crystallographic b axis, containing pentavalent vanadium atoms, one five-, the other six-coordinate, linked by selenite pyramids.

Salt-Inclusion Synthesis of Two New Polar Solids, Ba6Mn4Si12O34Cl3 and Ba6Fe5Si11O34Cl3

A new family of salt-containing, mixed-metal silicates (CU-14), Ba6Mn4Si12O34Cl3 (1) and Ba6Fe5Si11O34Cl3 (2), was synthesized via the BaCl2 salt-inclusion reaction. These compounds crystallize in the noncentrosymmetric (NCS) space group Pmc2(1) (No. 26), adopting 1 of the 10 NCS polar, nonchiral crystal classes, mm2 (C2v). The cell dimensions are a = 6.821(1) A, b = 9.620(2) A, c = 13.172(3) A, and V = 864.4(3) A3 for 1 and a = 6.878(1) A, b = 9.664(2) A, c = 13.098(3) A, and V = 870.6(3) A3 for 2. The structures form a composite framework made of the (M(4+x)Si(12-x)O34)9- (M = Mn, x = 0; M = Fe, x = 1) covalent oxide and (Ba6Cl3)9+ ionic chloride sublattices. The covalent framework exhibits a pseudo-one-dimensional channel where the extended barium chloride lattice (Ba3Cl1.5)(infinity) resides, and it consists of fused eight-membered meta-silicate rings propagating along [100] via sharing two opposite [Si2O7]6- units to form an acentric lattice. Single-crystal structure studies also reveal the ClBa4 unit adopting an interesting seesaw configuration, in which the lone pair electrons of chlorine preferentially face the oxide anions of the transition metal silicate channel, thus forming the observed polar frameworks. Similar to the synthesis of organic-inorganic hybrid materials, the salt-inclusion method facilitates a promising approach for the directed synthesis of special framework solids, including NCS compounds, via composite lattices.

Salt-inclusion synthesis of Ba2MnSi2O7Cl. A fresnoite-type polar framework containing the acentric [Si2O7]6 - polyanion in the anti-ReO3 type [(Ba2Mn)Cl]6+) cage

A novel non-centrosymmetric (NCS) solid, Ba(2)Mn(Si(2)O(7))Cl (CU-13), was isolated via high-temperature, salt-inclusion reactions. This manganese(III) silicate chloride adopts the fresnoite structure exhibiting pseudo-one-dimensional channels in which the Ba(2+) cations reside. The framework can be viewed alternatively as made of a fascinating anti-ReO(3) type (Ba(2)Mn)Cl lattice centered on the acentric Si(2)O(7) unit. This new compound crystallizes in one of the 10 NCS polar crystal classes, 4mm (C(4)(v)()), which is cooperatively attributed to the MnO(4)Cl(2) tetragonal distortion and the oriented Si(2)O(7) polyhedral unit. This discovery once again demonstrates the utility of salt inclusion with the formation of NCS frameworks.

Hydrothermal syntheses and crystal structures of complex-linked three-Dimensional coordination vanadium selenites: M(4,4'-bipy)(H(2)O)V(2)Se(2)O(10) (M = Co, Ni)

Two inorganic-organic hybrid compounds with the formula M(4,4'-bipy)(H(2)O)V(2)Se(2)O(10) (M = Co, Ni) were hydrothermally synthesized and characterized by single-crystal X-ray diffraction. Compounds Co(4,4'-bipy)(H(2)O)V(2)Se(2)O(10) (1) and Ni(4,4'-bipy)(H(2)O)V(2)Se(2)O(10) (2), which are structural analogues, crystallize in the triclinic space group Ponemacr; with crystal data a = 7.9665(3) A, b = 8.1974(3) A, c = 13.8096(4) A, alpha = 85.704(2) degrees, beta = 73.5180(10) degrees, gamma = 75.645(2) degrees, V = 837.76(5) A(3), and Z = 2 and a = 7.9489(19) A, b = 8.128(2) A, c = 13.709 A, alpha = 85.838(6) degrees, beta = 73.736(8) degrees, gamma = 75.594(9) degrees, V = 823.5(4) A(3), and Z = 2, respectively. [M(4,4'-bipy)(H(2)O)V(2)Se(2)O(10)] (M = Co, Ni) have a three-dimensional structure and consist of two subunits, [(VO(2))(SeO(3))](-) infinite chains and [M(4,4'-bipy)(H(2)O)](2+) fragments. The [(VO(2))(SeO(3))](-) chains are composed of [V(2)Se(4)O(14)](4)(-) clusters linked by VO(4)N triangular bipyramids. The 4,4'-bipy molecule as a bifunctional organic ligand is directly linked to Co or Ni and V atoms, affording the three-dimensionality. The compounds were characterized by infrared spectroscopy and differential thermal and thermogravimetric analyses.

Hydrothermal preparation, structures, and NLO properties of the rare earth molybdenyl iodates, RE(MoO2)(IO3)4(OH) [RE = Nd, Sm, Eu]

The reactions of RE(IO3)3 [RE = Nd, Sm, Eu] with I2O5 and MoO3 in a 1:2:2 molar ratio at 200 degrees C in aqueous media provide access to RE(MoO2)(IO3)4(OH) [RE = Nd (1), Sm (2), Eu (3)] as pure phases as determined from powder X-ray diffraction data. Single crystal X-ray diffraction experiments demonstrate that these compounds are isostructural and crystallize in the chiral and polar space group P2(1). The structures are composed of three-dimensional networks formed from eight-coordinate, square antiprismatic RE3+ cations and MoO2(OH)+ moieties that are bound by bridging iodate anions. The Mo(VI) centers are present in distorted octahedral environments composed of two cis-oxo atoms, a hydroxo group, and three bridging iodate anions arranged in a fac geometry. There are four crystallographically unique iodate anions in the structures of 1-3, one of these is actually present in the form of a IO3+1 polyhedron where a short interaction of 2.285(4) A is formed between the iodate anion and the hydroxo group bound to the Mo(VI) center. This interaction results in significant distortions of the iodate anion similar to those found in tellurites with TeO3+1 units. Two of the four iodate anions are aligned along the polar b-axis, imparting the required polarity to these compounds. Second-harmonic generation (SHG) measurements on sieved powders of 1 show a response of 350 x alpha-quartz. Crystallographic data: 1, monoclinic, space group P2(1), a = 6.9383(5) A, b = 14.0279(9) A, c = 7.0397(5) A, beta = 114.890(1) degrees, Z = 2; 2, monoclinic, space group P2(1), a = 6.9243(6) A, b = 13.963(1) A, c = 7.0229(6) A, beta = 114.681(1) degrees, Z = 2; 3, monoclinic, space group P2(1), a = 6.9169(6) A, b = 13.943(1) A, c = 7.0170(6) A, beta = 114.542(1) degrees, Z = 2.

Hydrothermal syntheses, structures, and properties of the new uranyl selenites Ag(2)(UO(2))(SeO(3))(2), M[(UO(2))(HSeO(3))(SeO(3))] (M = K, Rb, Cs, Tl), and Pb(UO(2))(SeO(3))(2)

The transition metal, alkali metal, and main group uranyl selenites, Ag(2)(UO(2))(SeO(3))(2) (1), K[(UO(2))(HSeO(3))(SeO(3))] (2), Rb[(UO(2))(HSeO(3))(SeO(3))] (3), Cs[(UO(2))(HSeO(3))(SeO(3))] (4), Tl[(UO(2))(HSeO(3))(SeO(3))] (5), and Pb(UO(2))(SeO(3))(2) (6), have been prepared from the hydrothermal reactions of AgNO(3), KCl, RbCl, CsCl, TlCl, or Pb(NO(3))(2) with UO(3) and SeO(2) at 180 degrees C for 3 d. The structures of 1-5 contain similar [(UO(2))(SeO(3))(2)](2-) sheets constructed from pentagonal bipyramidal UO(7) units that are joined by bridging SeO(3)(2-) anions. In 1, the selenite oxo ligands that are not utilized within the layers coordinate the Ag(+) cations to create a three-dimensional network structure. In 2-5, half of the selenite ligands are monoprotonated to yield a layer composition of [(UO(2))(HSeO(3))(SeO(3))](1-), and coordination of the K(+), Rb(+), Cs(+), and Tl(+) cations occurs through long ionic contacts. The structure of 6 contains a uranyl selenite layered substructure that differs substantially from those in 1-5 because the selenite anions adopt both bridging and chelating binding modes to the uranyl centers. Furthermore, the Pb(2+) cations form strong covalent bonds with these anions creating a three-dimensional framework. These cations occur as distorted square pyramidal PbO(5) units with stereochemically active lone pairs of electrons. These polyhedra align along the c-axis to create a polar structure. Second-harmonic generation (SHG) measurements revealed a response of 5x alpha-quartz for 6. The diffuse reflectance spectrum of 6 shows optical transitions at 330 and 440 nm. The trailing off of the 440 nm transition to longer wavelengths is responsible for the orange coloration of 6.

Structural modulation of molybdenyl iodate architectures by alkali metal cations in AMoO3(IO3) (A = K, Rb, Cs): a facile route to new polar materials with large SHG responses

Three new molybdenyl iodates, KMoO3(IO3) (1), RbMoO3(IO3) (2), and CsMoO3(IO3) (3), have been prepared through the hydrothermal reactions of MoO3 with AIO4 (A = K, Rb, or Cs) at 180 C. These compounds are isolated as nearly colorless, air-stable crystals. Single-crystal X-ray diffraction experiments reveal that 1 possesses a corrugated layered structure constructed from molybdenum oxide chains that are bridged by iodate anions. The puckering of the layers is caused by the alignment of bent molybdenyl (MoO2(2+)) groups along one side of the molybdenum oxide chains. The K+ cations separate these layers from one another and serve to balance charge. In contrast, compounds 2 and 3, which are isostructural, form three-dimensional structures with small cavities filled with Rb+ or Cs+ cations. The differences between the structures of 1 and those of 2 and 3 are due to rotation of the molybdenyl units as translation occurs down the molybdenum oxide chains in order to accommodate the increased size of the Rb+ and Cs+ cations. This rotation allows for the iodate anions to bridge the molybdenum oxide chains in an additional dimension, creating a three-dimensional network structure. Furthermore, while 1 crystallizes in a centrosymmetric space group, 2 and 3 crystallize in polar space groups. Second-harmonic generation measurements on 2 and 3 show large responses of 400x alpha-quartz. Differential scanning calorimetry measurements demonstrate that 2 and 3 are thermally stable to 494 and 486 C, respectively. UV-vis diffuse reflectance spectra of these compounds show a high degree of transparency from 1 to 3 eV and a band gap of 3.1 eV.

Synthesis and structural characterization of a new series of vanadoselenites, [Se(x)V(4-x)O(12-x)](4-x)- (x=1,2)

Two new vanadoselenites, [SeV(3)O(11)](3)(-) and [Se(2)V(2)O(10)](2)(-), were synthesized by reacting SeO(2) with VO(3)(-). Single-crystal X-ray structural analyses of [(n-C(4)H(9))(4)N](3)[SeV(3)O(11)].0.5H(2)O [orthorhombic, space group P2(1)2(1)2, a = 22.328(5) A, b = 44.099(9) A, c = 12.287(3) A, Z = 8] and [[(C(6)H(5))(3)P](2)N](2)[Se(2)V(2)O(10)] [monoclinic, space group P2(1)/n, a = 12.2931(3) A, b = 13.5101(3) A, c = 20.9793(5) A, beta = 106.307(1) degrees, Z = 2] revealed that both anions are composed of Se(x)()V(4)(-)(x)()O(4) rings. The (51)V, (77)Se, and (17)O NMR spectra established that both [SeV(3)O(11)](3)(-) and [Se(2)V(2)O(10)](2)(-) anions maintain this ring structure in solution.

Synthesis and characterization of non-centrosymmetric TeSeO4

The synthesis, crystal structure, and characterization of a non-centrosymmetric oxide, TeSeO4, are reported. The material was synthesized by combining TeO2 and SeO2 in a quartz tube and heating at 370 degrees C. TeSeO4 has a three-dimensional structure containing [SeO(3/2)](+) cations linked to [TeO(5/2)](-) anions. Both the Se(4+) and the Te(4+) atoms are in asymmetric environments owing to their nonbonded electron pair. The material is SHG active, with a SHG intensity of 400 times SiO(2). Crystal data: monoclinic, space group Ia (No. 9, cell choice 3), with a = 4.3568(8) A, b = 12.465(3) A, c = 6.7176(15) A, beta = 90.825(4) degrees, and Z = 4.