Rich Structural Chemistry in New Alkali Metal Yttrium Tellurites: Three-Dimensional Frameworks of NaYTe4O10, KY(TeO3)2, RbY(TeO3)2, and a Novel Variant of Hexagonal Tungsten Bronze, CsYTe3O8

KIn0.33IIITe0.67VITe2IVO7: Zirconolite-like Mixed-Valent Metal Oxide with a 3D Framework

We provide the material synthesis method, crystal structure information, and characterization of a novel mixed-valent metal oxide KIn_0.33^IIITe_0.67^VITe₂^IVO₇, closely related to zirconolite (CaZrTi₂O₇), a radioactive waste immobilized material, having a 3D framework. The reported metal oxide containing an alkali-metal cation (K⁺), main-group cation (In³⁺), tellurate, and tellurite has been synthesized as both single crystals and a pure polycrystalline phase through a hydrothermal synthesis method. Single-crystal X-ray diffraction indicates that KIn_0.33Te_2.67O₇ crystallizing in the orthorhombic space group Cmcm (No. 63) reveals a 3D framework structure with a 1D channel consisting of Te/InO₆ octahedra and TeO₄ polyhedra. An interesting transition reaction from KIn_0.33Te_2.67O₇ to KIn(TeO₃)₂ under hydrothermal conditions at 230 °C is discussed.

Hydrothermal synthesis, crystal structures, and X-ray photoelectron spectroscopy of lead tellurium(IV) and tellurium(VI) oxycompounds: Ba3PbTe6O16 and Na2Pb9(μ6-O)2(Te2O10)2

An exploratory study of the lead-tellurium-oxygen phase space led to two new compounds, Ba3PbTe6O16 (BPTO) and Na2Pb9(μ6-O)2(Te2O10)2 (NPTO), which were synthesized under hydrothermal conditions at 550 °C and 210 °C, respectively, and characterized by single-crystal X-ray diffraction, infrared and X-ray photoelectron spectroscopy. BPTO adopts a layer structure. The Te4+ cation in BPTO is bonded to four oxygen atoms at about 2.0 Å with two more oxygens at about 3.0 Å. The seesaw-shaped TeO4 units share corners to form 2D layers containing six-membered rings and the Ba2+ and Pb2+ cations are situated in the interlayer region. The structure of NPTO contains dimers of edge-sharing Te6+O6 octahedra, which are connected through five-coordinate Pb2+ cations. A unique six-coordinate O atom is at the center of the octahedron formed by five Pb2+ and one Na+ cations. BPTO is one of the few metal tellurites which were synthesized under supercritical hydrothermal reaction conditions. The Pb2+ cation in NPTO shows pronounced stereochemical effects of the lone electron pair. In contrast, BPTO shows no stereochemical evidence of the inert pair.

The complete series of sodium rare-earth metal(III) chloride oxotellurates(IV) Na2 RE 3Cl3[TeO3]4 (RE = Y, La–Nd, Sm–Lu)

The complete series of sodium rare-earth metal(III) chloride oxotellurates(IV) with the composition Na2 RE 3Cl3[TeO3]4 (RE = Y, La–Nd, Sm–Lu) has been synthesized via solid-state reactions. For these conversions mixtures of the respective rare-earth metal(III) oxides, tellurium dioxide and sodium chloride as flux and reactant were prepared, intimately ground and heated for 5 days at 1225 K. The almost colorless single crystals were characterized via single-crystal X-ray diffractometry. In the monoclinic crystal structure of these compounds two crystallographically different rare-earth metal(III), but only one sodium cation sites occur. [REO8]13− polyhedra around both RE 3+ positions as well as sodium-centered polyhedra [NaO4Cl4]8− form layers via different connectivity modes. These layers spread out parallel to the (001) plane and arrange alternatingly resulting in the three-dimensional network of the Na2 RE 3Cl3[TeO3]4 structure, where the Te4+ lone-pair cations at two different sites work as linkers by forming isolated ψ 1-tetrahedra [TeO3]2−. Some of these compounds were represented before in different settings of space group C2/c. Now the complete series of the Na2 RE 3Cl3[TeO3]4 representatives with RE = Y, La–Nd, Sm–Lu is described consistently for a better comparison and understanding. Additionally, a single crystal of Na2Pr3Cl3[TeO3]4 was measured via energy dispersive X-ray analysis to verify the included elements, powder samples of Na2Nd3Cl3[TeO3]4 were characterized by X-ray diffractometer data for a phase-purity check and a single-crystal Raman spectrum of Na2Yb3Cl3[TeO3]4 served for proving the signature of discrete [TeO3]2− anions.

Synthesis, crystal structures, and magnetic properties of one-dimensional alkali metal copper chlor-tellurites A(NH4)Cu4Te2O6Cl6 (A = K, Cs), NaCu4Te2Cl5O6 and Rb3(NH4)2Cu12Te6Cl16.5O18(OH)0.5

Four new alkali metal copper chlor-tellurites, [Cs(NH4)]layer[Cu4Te2O6Cl6]layer (I), [Rb3(NH4)2(OH)0.5]layer[Cu12Te6Cl16.5O18]layer (II), [K(NH4)]layer[Cu4Te2O6Cl6]layer (III) and [NaCl]layer[Cu4Te2O6Cl4]layer (IV), have been synthesized via hydrothermal reactions using mixtures of AF (A = Cs, Rb, K, Na), CuCl2·2H2O, TeO2, and hydrazine monohydrate. They have two-dimensional (2D)-layered [Cu4Te2Cl5+x-yO6]∞ (x = 0, 2/3, 1; y = 0, 1/6) structures that are separated by different layers comprised of various cations and anions, including A+, NH4+ Cl- OH-, etc. The blocks feature S-shaped ∞[Cu2O3Cl3-x] chains linked by TeO3 trigonal pyramids. The magnetic susceptibility shows a broad maximum at 220 K for I and 240 K for III, which is well simulated by using an alternating antiferromagnetic chain model. The J2/J1 ratio within the alternating chain is estimated to be 0.60(1), and the spin gaps are refined to be 152 K for I and 136 K for III.

Unexpected Roles of Alkali-Metal Cations in the Assembly of Low-Valent Uranium Sulfate Molecular Complexes

The directing effect of coordinating ligands in the formation of uranium molecular complexes has been well established, but the role of counterions in metal-ligand interactions remains ambiguous and requires further investigation. In this work, we describe the targeted isolation, through the choice of alkali-metal ions, of a family of tetravalent uranium sulfates, showing the influence of the overall topology and, unexpectedly, the U^IV nuclearity upon the inclusion of such countercations. Analyses of the structures of uranium(IV) oxo/hydroxosulfate oligomeric species isolated from consistent synthetic conditions reveal that the incorporation of Na⁺ and Rb⁺ promotes the crystallization of 0D discrete clusters with a hexanuclear [U₆O₄(OH)₄(H₂O)₄]¹²⁺ core, whereas the larger Cs⁺ ion allows for the isolation of a 2D-layered oligomer with a less condensed trinuclear [U₃(O)]¹⁰⁺ center. This finding expands the prevalent view that counterions play an innocent role in molecular complex synthesis, affecting only the overall packing but not the local oligomerization. Interestingly, trends in nuclearity appear to correlate with the hydration enthalpies of alkali-metal cations, such that the alkali-metal cations with larger hydration enthalpies correspond to more hydrated complexes and cluster cores. These findings afford new insights into the mechanism of nucleation of U^IV, and they also open a new path for the rational design and synthesis of targeted molecular complexes.

Lone-pair self-containment in pyritohedron-shaped closed cavities: optimized hydrothermal synthesis, structure, magnetism and lattice thermal conductivity of Co15F2(TeO3)14

Co₁₅F₂(TeO₃)₁₄ features an extremely rare example of the Te(iv) lone pairs self-containment in pyritohedron-shaped [(TeO₃)₁₄]²⁸⁻ units, which allows Te atom to vibrate with large amplitude, leading to extremely low lattice thermal conductivity.

Hexagonal tungsten oxides with large bandgaps synthesized by a chemical substitution method

A novel hexagonal tungsten oxide designed by a chemical substitution method, NH₄(GaF₂)₃(SeO₃)₂, exhibits the largest bandgap among all known phase-matchable NLO selenite compounds.

BaLiTe2O5X (X = Cl, Br): mixed alkali/alkaline-earth metal tellurite halides with [Te2O5]∞ chains

Isostructural BaLiTe₂O₅X (X = Cl, Br) feature [BaLiTe₂O₅]_∞ double layers, demonstrating wide optical bandgaps and large birefringence.

Functional layered materials with heavy metal lone pair cations, Pb2+, Bi3+, and Te4+

Syntheses, structures, representative properties, and the structure–property relationships for a series of functional layered materials are presented.

Noncentrosymmetric (NCS) solid solutions: elucidating the structure-nonlinear optical (NLO) property relationship and beyond

A systematic approach toward the discovering of novel functional noncentrosymmetric (NCS) materials revealing technologically useful applications is an ongoing challenge. This Frontiers article investigates a series of NCS solid solutions with respect to their crystal structure and second-harmonic generation (SHG) response. The solid solutions include NCS polar aluminoborates, Al_5-xGa_xBO₉ (0.0 ≤ x ≤ 0.5), rare earth element-doped bismuth tellurites, Bi_2-xRE_xTeO₅ (RE = Y, Ce, and Eu; 0.0 ≤ x ≤ 0.2), layered perovskites, Bi_4-xLa_xTi₃O₁₂ (0.0 ≤ x ≤ 0.75: Aurivillius phases) and CsBi_1-xEu_xNb₂O₇ (0.0 ≤ x ≤ 0.2: Dion-Jacobson phases), calcium bismuth oxides, Ca₄Bi_6-xLn_xO₁₃ (Ln = La and Eu; x = 0, 0.06 and 0.12), and sodium lanthanide iodates, NaLa_1-xLn_x(IO₃)₄ (Ln = Sm and Eu; 0 ≤ x ≤ 1). The origin of SHG for all the NCS solid solutions is discussed and the detailed structure-nonlinear optical (NLO) property relationships are elucidated. In addition, photoluminescence (PL) properties and subsequent energy transfer mechanisms for NCS solid solutions are provided.

125Te NMR Probes of Tellurium Oxide Crystals: Shielding-Structure Correlations

The local environments around tellurium atoms in a series of tellurium oxide crystals were probed by ¹²⁵Te solid-state NMR spectroscopy. Crystals with distinct TeO_n units (n from 3 to 6), including Na₂TeO₃, α-TeO₂ and γ-TeO₂, Te₂O(PO₄)₂, K₃LaTe₂O₉, BaZnTe₂O₇, and CsYTe₃O₈ were studied. The latter four were synthesized through a solid-state process. X-ray diffraction was used to confirm the successful syntheses. The ¹²⁵Te chemical shift was found to exhibit a strong linear correlation with the Te coordination number. The ¹²⁵Te chemical-shift components (δ₁₁, δ₂₂, and δ₃₃) of the TeO₄ units were further correlated to the O-Te-O-bond angles. With the aid of ¹²⁵Te NMR, it is likely that these relations can be used to estimate the coordination states of Te atoms in unknown Te crystals and glasses.

Toward the Rational Design of Novel Noncentrosymmetric Materials: Factors Influencing the Framework Structures

Solid-state materials with extended structures have revealed many interesting structure-related characteristics. Among many, materials crystallizing in noncentrosymmetric (NCS) space groups have attracted massive attention attributable to a variety of superb functional properties such as ferroelectricity, pyroelectricity, piezoelectricity, and nonlinear optical (NLO) properties. In fact, the characteristics are pivotal to many industrial applications such as laser systems, optical communications, photolithography, energy harvesting, detectors, and memories. Thus, for the past several decades, a great deal of synthetic effort has been vigorously made to realize these technologically important properties by improving the occurrence of macroscopic NCS space groups. A bright approach to increase the incidence of NCS structures was combining local asymmetric units during the initial synthesis process. Although a significant improvement has been achieved in obtaining new NCS materials using this strategy, the majority of solid-state materials still crystallize in centrosymmetric (CS) structures as the locally unsymmetrical units are easily lined up in an antiparallel manner. Therefore, discovering an effective method to control the framework structure and the macroscopic symmetry is an imminent ongoing challenge. In order to more effectively control the overall symmetry of solid-state compounds, it is critical to understand how the backbone and the subsequent centricity are affected during the crystallization. In this Account, several factors influencing the framework structure and centricity of solid-state materials are described in order to more systematically discover novel NCS materials. Recent studies on crystalline solid-state materials suggest three factors affecting the local coordination environment as well as the overall symmetry of the framework structure: (1) size variations of the various template cations, (2) a variable backbone arrangement occurring from the hydrogen-bonding interactions, and (3) the presence of framework flexibility. With regard to the first factor, the impact of size of the various metal cations and coordination numbers on the alignment of other adjacent polyhedra, linkers, and lone pairs determining the framework geometries of mixed metal oxides is analyzed. The second factor considers the regulation of crystallographic centricity determined by the availability of hydrogen-bonding interactions between anionic frameworks containing local asymmetric polyhedra and organic cations. Finally, the third factor explores the framework architecture and the space group symmetry influenced by the flexibility of polyhedra revealing variable coordination numbers. The centricity and framework of new solid-state materials might be controlled by using a variety of synthetically controllable asymmetric units such as organic structure-directing cations and linkers with different sizes and functional groups.