Strong Second Harmonic Generation (SHG) Originating from Combined Second-Order Jahn–Teller (SOJT) Distortive Cations in a New Noncentrosymmetric Tellurite, InNb(TeO4)2

Chiral cadmium-amine complexes for stimulating non-linear optical activity and photoluminescence in solids based on aurophilic stacks

The design of high-performance optical materials can be realized using coordination polymers (CPs) often supported by non-covalent interactions, such as metallophilicity. The challenge is to control two or more optical effects, e.g., non-linear optics (NLO) and photoluminescence (PL). We present a new strategy for the combination of the NLO effect of second-harmonic generation (SHG) and the visible PL achieved by linking dicyanidoaurate(i) ions, which form luminescent metallophilic stacks, with cadmium(ii) complexes bearing chiral amine ligands, used to break the crystal's symmetry. We report a family of NLO- and PL-active materials based on heterometallic Cd(ii)-Au(i) coordination systems incorporating enantiopure propane-1,2-diamine (pda) ligands (1-S, 1-R), their racemate (2), and enantiopure trans-cyclopentane-1,2-diamine (cpda) ligands (3-S, 3-R). Due to acentric space groups, they exhibit the SHG signal, tunable within the range of 11-24% of the KDP reference, which was correlated with the dipole moments of Cd(ii) units. They show efficient blue PL whose energy and quantum yield, the latter ranging from 0.40 to 0.83, are controlled by Cd(ii) complexes affecting the Au-Au distances and vibrational modes. We prove that chiral Cd(ii)-amine complexes play the role of molecular agents for the stimulation of both the NLO and PL of the materials based on aurophilic stacks.

Rb8Nb10Ge6O41: a new niobium-germanate crystal featuring unique one-dimensional [Nb7O30]∞ chains and wide mid-IR transparency

Germanate oxides have garnered considerable interest owing to their diverse structural configuration and intriguing properties. Herein, we present a novel niobium germanate crystal, Rb8Nb10Ge6O41, extracted through the process of spontaneous crystallization. It showcases a unique three-dimensional (3D) structural framework composed of one-dimensional (1D) twisted [Nb7O30]∞ chains and isolated [Ge3O9] rings, arising from the divergent polymerized manifestations of [NbO6] and [GeO4] basic building blocks, respectively, marking the first instance of such a topography in germanate materials. Notably, the title compound exhibits exceptional thermal stability up to 1250 °C with a good congruent melting nature. Moreover, it achieves a short ultraviolet edge at 306 nm and a favorable infrared edge cutoff exceeding 6.2 μm, thus indicating a wide transparency window. Additionally, this study elucidates the microscopic birefringence of Rb8Nb10Ge6O41 and clarifies the intricate relationship between its structure and properties. Our findings suggest that the polymerization of distinct structural motifs within a single compound is an effective strategy for exploring novel inorganic materials.

Rational Design of a Niobium Tellurite Crystal Nb2Te3O11 Exhibiting Good Overall Infrared NLO Performance by Structural Genetic Engineering

Nonlinear optical (NLO) materials have aroused increasing interest owing to their promising applications in optoelectronic technologies. Herein, we present the synthesis of an acentric niobium tellurite crystal, Nb2Te3O11, extracted via a spontaneous crystallization approach. It adopts a unique three-dimensional (3D) structure constructed by the distorted [TeO3], [TeO4], and [NbO6] fundamental building units. The title compound undergoes incongruent melting at approximately 807 °C. Optical characterizations demonstrate that Nb2Te3O11 possesses an extended transparency window beyond 5 μm, along with a large band gap value of 3.1 eV. Moreover, the as-synthesized Nb2Te3O11 displays an appreciable second-harmonic generation (SHG) response of 2 × KDP and a notable birefringence of 0.11 under 1064 nm for achieving phase-matching. In addition, theoretical calculation investigations suggest that the intriguing optical properties are ascribed to the cooperative effect of three types of NLO-active motifs: [TeO3] pyramids, [TeO4] seesaws, and [NbO6] octahedra. These attributes provide new functional insights into Nb2Te3O11 and enrich the family of NLO crystals in the mid-infrared region.

Understanding of the structural chemistry in the uranium oxo-tellurium system under HT/HP conditions

The study of phase formation in the U-Te-O systems with mono and divalent cations under high-temperature high-pressure (HT/HP) conditions has resulted in four new inorganic compounds: K2 [(UO2) (Te2O7)], Mg [(UO2) (TeO3)2], Sr [(UO2) (TeO3)2] and Sr [(UO2) (TeO5)]. Tellurium occurs as TeIV, TeV, and TeVI in these phases which demonstrate the high chemical flexibility of the system. Uranium VI) adopts a variety of coordinations, namely, UO6 in K2 [(UO2) (Te2O7), UO7 in Mg [(UO2) (TeO3)2] and Sr [(UO2) (TeO3)2], and UO8 in Sr [(UO2) (TeO5)]. The structure of K2 [(UO2) (Te2O7)] is featured with one dimensional (1D) [Te2O7]4- chains along the c-axis. The Te2O7 chains are further linked by UO6 polyhedra, forming the 3D [(UO2) (Te2O7)]2- anionic frameworks. In Mg [(UO2) (TeO3)2], TeO4 disphenoids share common corners with each other resulting in infinite 1D chains of [(TeO3)2]4- propagating along the a-axis. These chains link the uranyl bipyramids by edge sharing along two edges of the disphenoids, resulting in the 2D layered structure of [(UO2) (Te2O6)]2-. The structure of Sr [(UO2) (TeO3)2] is based on 1D chains of [(UO2) (TeO3)2]∞2− propagating into the c-axis. These chains are formed by edge-sharing uranyl bipyramids which are additionally fused together by two TeO4 disphenoids, which also share two edges. The 3D framework structure of Sr [(UO2) (TeO5)] is composed of 1D [TeO5]4− chains sharing edges with UO7 bipyramids. Three tunnels based on 6-Membered rings (MRs) are propagating along [001] [010] and [100] directions. The HT/HP synthetic conditions for the preparation of single crystalline samples and their structural aspects are discussed in this work.

Two New Tellurite Halides with Cationic Layers: Syntheses, Structures, and Characterizations of CdPb2Te3O8Cl2 and Cd13Pb8Te14O42Cl14

Two new tellurite halides, CdPb2Te3O8Cl2 and Cd13Pb8Te14O42Cl14 with mixed cationic layered structures, have been synthesized by high-temperature solution method. CdPb2Te3O8Cl2 crystallizes in the noncentrosymmetric Aba2 space group, built by [CdPb2Te3O8]...

Single crystals of SnTe3O8 in the millimetre range grown by chemical vapor transport reactions

Tin(IV) trioxidotellurate(IV), SnTe3O8, is a member of the isotypic M IVTeIV 3O8 (M = Ti, Zr, Hf, Sn) series crystallizing with eight formula units per unit cell in space group Ia . In comparison with the previous crystal structure model of SnTe3O8 based on powder X-ray diffraction data [Meunier & Galy (1971 ▸). Acta Cryst. B27, 602-608], the current model based on single-crystal X-ray data is improved in terms of precision and accuracy. Nearly regular [SnO6] octa-hedra (Sn site symmetry ..) are situated in the voids of an oxidotellurate(IV) framework built up by corner-sharing [TeO4] bis-phenoids (Te site symmetry 2..). A qu-anti-tative structural comparison revealed a very high degree of similarity for the structures with M = Ti, Zr, Sn in the M IVTe3O8 series.

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.

New polymorphism for BaTi(IO3)6 with two polymorphs crystallizing in the same space group

Polymorphic α- and β-BaTi(IO₃)₆ have been synthesized. They crystallize in the same space group and exhibit highly similar structures. But the different powder X-ray patterns and crystal morphologies indicate that they belong to different phases, which represents the first phase transitions with two polymorphs possessing the same space group and similar cells.

The crystal structure of the first synthetic copper(II) tellurite arsenate, CuII5(TeIVO3)2(AsVO4)2

Crystals of the first synthetic copper tellurite arsenate, Cu^II₅(Te^IVO₃)₂(As^VO₄)₂ [systematic name pentacopper(II) bis-oxotellurate(IV) bis-oxoarsenate(V)], were grown by the chemical vapour transport method and structurally determined using single-crystal X-ray diffraction. Cu^II₅(Te^IVO₃)₂(As^VO₄)₂ possesses a novel structure type including a new topological arrangement of Cu^II and O atoms. Cu^II₅(Te^IVO₃)₂(As^VO₄)₂ is formed from a framework of two types of Jahn-Teller distorted [Cu^IIO₆] octahedra (one of which is considerably elongated) and [Cu^IIO₅] square pyramids, which are linked by edge-sharing to form chains and dimers and by corner-sharing to complete a three-dimensional framework. [As^VO₄] tetrahedra and [Te^IVO₅] polyhedra bridge the edges of channels along the a-axis direction, with void space remaining for the Te^IV stereoactive 5s² lone pairs. A comparison is made between the crystal structure of Cu^II₅(Te^IVO₃)₂(As^VO₄)₂ and those of known compounds and minerals, in particular fumarolitic Cu minerals.

Recent progress in selenite and tellurite based SHG materials

Fluorination and bandgaps have attracted more attention than d⁰ TM and SHG efficiency recently in metal selenites and tellurites.

Synthesis and characterization of a series of transition metal oxychlorides: MBi(SeO3)2(H2O)Cl (M = Co, Ni, Cu)

Three new transition metal oxychlorides MBi(SeO3)2(H2O)Cl (M = Co, Ni, Cu) have been firstly synthesized through a hydrothermal reaction method at 200 °C. They were structurally determined to be isostructural with the Pbca space group of the orthorhombic system. They feature a 3D framework topology with two-dimensional tunnels intersected and filled with Cl anions parallel to the crystallographic bc-plane. Two neighboring MO5Cl octahedra are connected by a sharing edge into a M2O8Cl2 dimer which serves as the structural knots to knit the 2D [Bi(SeO3)2]∞ layers in the ab-plane together into the total 3D crystal architecture. The optical band gaps of CoBi(SeO3)2(H2O)Cl (1), NiBi(SeO3)2(H2O)Cl (2) and CuBi(SeO3)2(H2O)Cl (3) were evaluated to be 3.7 eV, 3.5 eV and 3.2 eV, respectively, through extrapolating the UV-vis-NIR optical absorption spectra. Besides, the spin-allowed d-d transition absorption spectra of the transition ion centers are observed in three compounds exhibiting different colors. Compounds 1, 2 and 3 can stay thermally stable below 370 °C, 400 °C and 300 °C, respectively, as found from the results of thermal analysis based on the simultaneous thermogravimetry and differential scanning calorimetry techniques. 1, 2 and 3 exhibit antiferromagnetic properties below Néel temperatures 6 K, 18 K and 52 K, respectively. Above the Néel temperatures, Curie-Weiss behavior dominates in the M-T process for the three compounds. The cell parameters are listed: a = 14.056 Å, b = 7.582 Å, c = 14.996 Å, and Z = 8 for 1, a = 14.083 Å, b = 7.575 Å, c = 14.860 Å, and Z = 8 for 2, and a = 14.576 Å, b = 7.371 Å, c = 14.656 Å, and Z = 8 for 3.

PbTeGeO6: polar rosiaite-type germanate featuring a two dimensional layered structure

Polar rosiaite-type germanate PbTeGeO₆ with a layered structure shows a moderate second harmonic generation response.

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.

YCu(TeO3)2(NO3)(H2O)3: a novel layered tellurite

A new hydrated yttrium copper tellurite nitrate, yttrium(III) copper(II) bis-[trioxidotellurate(IV)] nitrate trihydrate, has been synthesized hydro-thermally in a Teflon-lined autoclave and structurally determined using synchrotron radiation. The new phase is the first example containing yttrium, copper and tellurium in one structure. Its crystal structure is unique, with relatively strongly bound layers extending parallel to (020), defined by YO8, CuO4 and TeO3 polyhedra, while the NO3 (-) anions and one third of the water mol-ecules lie between those layers. The structural unit consists of [Cu2(TeO3)4](4-) loop-branched chains of {Cu⋯Te⋯Cu⋯Te} squares running parallel to [001], which are linked further into layers only through Y(O,H2O)8 polyhedra. Weak 'secondary' Te bonds and O-H⋯O hydrogen-bonding inter-actions, involving water mol-ecules and layer O atoms, link the layers and inter-layer species. IR spectroscopic data are also presented.

A series of new silver selenites with d0-TM cations

Four silver selenites containing d⁰-TM cations have been reported, one of them displays a moderately strong SHG response.

Explorations of New SHG Materials in the Alkali-Metal-Nb(5+)-Selenite System

Standard high-temperature solid-state reactions of NaCl, Nb2O5, and SeO2 resulted in two new sodium selenites containing a second-order Jahn-Teller (SOJT) distorted Nb(5+) cation, namely, Na2Nb4O7(SeO3)4 (P1̅; 1) and NaNbO(SeO3)2 (Cmc21; 2). Compound 1 exhibits an unusual 3D [Nb4O7(SeO3)4](2-) anionic network composed of 2D [Nb4O11(SeO3)2](6-) layers which are further bridged by additional SeO3(2-) anions via corner sharing; the 2D [Nb4O11(SeO3)2](6-) layer is formed by unusual quadruple [Nb4O17](14-) niobium oxide chains of corner-sharing NbO6 octahedra being further interconnected by selenite anions via Nb-O-Se bridges. The polar compound 2 features a 1D [NbO(SeO3)2](-) anionic chain in which two neighboring Nb(5+) cations are bridged by one oxo and two selenite anions. The alignments of the polarizations from the NbO6 octahedra in 2 led to a strong SHG response of ∼7.8 × KDP (∼360 × α-SiO2), which is the largest among all phases found in metal-Nb(5+)-Se(4+)/metal-Nb(5+)-Te(4+)-O systems. Furthermore, the material is also type I phase matchable. The above experimental results are consistent with those based on DFT theoretical calculations. Thermal stabilities and optical properties for both compounds are also reported.