Synthesis, crystal and band structures, and optical properties of a new lanthanide–alkaline earth tellurium(IV) oxide: La2Ba(Te3O8)(TeO3)2

Thorium Chemistry in Oxo-Tellurium System under Extreme Conditions

Through the use of a high-temperature/high-pressure synthesis method, four thorium oxo-tellurium compounds with different tellurium valence states were isolated. The novel inorganic phases illustrate the intrinsic complexity of the actinide tellurium chemistry under extreme conditions of pressure and temperature. Th₂Te₃O₁₁ is the first instance of a mixed-valent oxo-tellurium compound, and at the same time, Te exhibits three different coordination environments (Te^IVO₃, Te^IVO₄, and Te^VIO₆) within a single structure. These three types of Te polyhedra are further fused together, resulting in a [Te₃O₁₁]^8- fragment. Na₄Th₂(Te^VI₃O₁₅) and K₂Th(Te^VIO₄)₃ are the first alkaline thorium tellurates described in the literature. Both compounds are constructed from ThO₉ tricapped trigonal prisms and Te^VIO₆ octahedra. Na₄Th₂(Te^VI₃O₁₅) is a three-dimensional framework based on Th₂O₁₅ and Te₂O₁₀ dimers, while K₂Th(Te^VIO₄)₃ contains tungsten oxide bronze like Te layers linked by ThO₉ polyhedra. The structure of β-Th(Te^IVO₃)(SO₄) is built from infinite thorium chains cross-linked by Te^IVO₃^2- and SO₄^2- anions. Close structural analysis suggests that β-Th(Te^IVO₃)(SO₄) is highly related to the structure of α-Th(SeO₄)₂. Additionally, the Raman spectra are recorded and the characteristic peaks are assigned based on a comparison of reported tellurites or tellurates.

Structural and magnetic studies on three new mixed metal copper(II) selenites and tellurites

Three new transition metal copper(II) selenites or tellurites, namely, CdCu(SeO3)2 (1), HgCu(SeO3)2 ()2, and Hg2Cu3(Te3O8)2 (3), have been obtained by conventional hydrothermal reactions of CdO (or Hg2Cl2), CuO and SeO2 (or TeO2). Compounds 1 and 2 are isostructural and crystallize in P2(1)/c. Their structures feature a 3D anionic framework of Cu(SeO3)2(2-) with 1D channels of eight-membered rings (MRs) along the c-axis and a-axis, respectively, which are filled by Cd(2+) or Hg(2+) cations. Compound 3 crystallizes in a tetragonal system of space group P42(1)2. Its structure is characterized by a [Cu3(Te3O8)2](2-) honeycomb layer composed of [Te3O8](4-) anions interconnected by Cu(2+) ions with 1D channels of 8-MRs along the c-axis. TOPOS analysis indicates that the copper(ii) tellurite layer exhibits a new topological structure with a Schläfli symbol of {4(6)·8(9)}(2){4(6)}(3). The above anionic copper(II) tellurite layers are further linked by dumbbell Hg2(2+) cations to form a novel 3D framework. Magnetic measurements based on magnetic susceptibility and heat capacity indicate that compounds 1 and 2 show a spin-singlet ground state with a spin gap based on the [Cu2O8](12-) dimeric model, whereas compound e3 xhibits a 2D spin-system with an antiferromagnetic ordering around 25 K correlated with its honeycomb [Cu3(Te3O8)2](2-) layer. Furthermore, crystalline structures, thermal stabilities, IR spectra and UV-Vis diffuse reflectance spectra have also been studied.

A series of new phases in the alkali metal-Nb(V)/Ta(V)-Se(IV)/Te(IV)-O systems

Six new phases in the alkali metal-Nb(V)/Ta(V)-Se(IV)/Te(IV)-O systems have been prepared by solid-state reactions at high-temperatures. Their structures were determined by single-crystal X-ray diffraction studies. AM(3)O(6)(QO(3))(2) (A = K, Rb, M = Nb, Ta, Q = Te; A = K, M = Nb, Q = Se) are isomorphous and their structures feature a 3D network with 1D 4- and 6-MRs tunnels along the a-axis which is composed of 2D layers of corner-sharing MO(6) octahedra bridged by QO(3) groups. The alkali metal ions are located at the above 1D tunnels of 6-MRs. The structure of Cs(3)Nb(9)O(18)(TeO(3))(2)(TeO(4))(2) features a thick Nb-Te-O layer built of corner-sharing NbO(6) octahedra, TeO(3) and TeO(4) groups. The 2D layer of the NbO(6) octahedra with 1D tunnels of 6-MRs along the c-axis are formed by 1D chains of NbO(6) chains along the c-axis and linear Nb(4)O(21) tetramers by corner-sharing. The TeO(3) and TeO(4) groups are grafted on both sides of the niobium-oxide layer via Nb-O-Te or/and Te-O-Te bridges. The caesium(i) ions are located at the above 1D tunnels of 6-MRs. TGA, UV-vis and infrared spectral measurements as well as electronic structure calculations have also been performed.