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

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.

BaBOF3: a new aurivillius-like borate containing two types of F atoms

A new Aurivillius-like fluorine-containing borate, BaBOF₃, featuring both structural characteristics of borate fluorides and fluorooxoborates has been synthesized.

BaLiZn3(BO3)3: a new member of the KBe2BO3F2family possessing dense BO3triangles and the smallest interlayer distance

A new beryllium-free borate, BaLiZn₃(BO₃)₃, featuring dense BO₃triangles and the smallest interlayer distance among KBe₂BO₃F₂derivatives is developed.

A(VO2F)(SeO3) (A = Sr, Ba) and Ba(MOF2)(TeO4) (M = Mo, W): first examples of alkali-earth selenites/tellurites with a fluorinated d0-TM octahedron

First examples of alkali-earth selenites/tellurites with a fluorinated d⁰-TM octahedron, namely, A(VO₂F)(SeO₃) (A = Sr 1, Ba 2) and Ba(MOF₂)(TeO₄) (M = Mo 3, W 4), were synthesized successfully by hydrothermal reactions.

Four new quaternary chalcogenides A2Ba7Sn4Q16 (A = Li, Na; Q = S, Se): syntheses, crystal structures determination, nonlinear optical performances investigation

Four new quaternary chalcogenides with interesting structures and potential nonlinear optical performances were synthesized for the first time.

Remarkable multimember-ring configurations in a new family of Na7MIISb5S12 (MII = Zn, Cd, Hg) exhibiting various three-dimensional tunnel structures

A new series of thioantimonates featuring the newly discovered trimer (M^II/Sb)₃S₉ and 12 + 12-MR configurations are verified as potential IR birefringent materials.

Ion-induced structural and optical performance evolution in LBO-like crystals: experimental and theoretical investigation

A new alkali metal borate fluoride Li₃KB₉O₁₅F has been obtained for the first time with a UV cut-off edge below 175 nm.

Cation-tuned synthesis of the A2SO4·SbF3 (A = Na+, NH4+, K+, Rb+) family with nonlinear optical properties

Four stoichiometrically equivalent compounds have been successfully synthesized through A⁺ cations by tuning the framework structures and macroscopic centricities.

K11RbB28O48: a new triple-layered borate with an unprecedented [B28O57] fundamental building block

A new borate, K₁₁RbB₂₈O₄₈, featuring an unprecedented [B₂₈O₅₇] fundamental building block and an unusual triple-layered anionic group, has been synthesized.

Na6Zn3MIII2Q9 (MIII = Ga, In; Q = S, Se): four new supertetrahedron-layered chalcogenides with unprecedented vertex-sharing T3-clusters and desirable photoluminescence performances

Four new supertetrahedron-layered chalcogenides as the first example of exhibiting vertex-sharing T₃-clusters in the known quaternary chalcogenides were discovered.

NaBaMIIIQ3 (MIII = Al, Ga; Q = S, Se): first quaternary chalcogenides with isolated edge-sharing (MIII2Q6)6− dimers

New series of quaternary chalcogenides with firstly discovered isolated edge-sharing (MIII2Q₆)⁶⁻ dimers showing obvious optical anisotropy were reported.

Ba2ZnSc(BO3)3and Ba4Zn5Sc2(BO3)8: first examples of borates in the Zn–Sc–B–O system featuring special structure configurations

First examples in the Zn–Sc–B–O system featuring a special Zn/Sc–O configuration ([Zn₂(BO₃)₆]¹⁴⁻cluster, lowest-coordinated ScO₅polyhedra, and coexistence of ZnO₄and ZnO₆units).

Structural diversities induced by cation sizes in a series of fluorogermanophosphates: A2[GeF2(HPO4)2] (A = Na, K, Rb, NH4, and Cs)

Germanophosphates, in comparison with other metal phosphates, have been less studied but potentially exhibit more diverse structural chemistry with wide applications. Herein we applied a hydro-/solvo-fluorothermal route to make use of both the "tailor effect" of fluoride for the formation of low dimensional anionic clusters and the presence of alkali cations of different sizes to align the anionic clusters to control the overall crystal symmetries of germanophosphates. The synergetic effects of fluoride and alkali cations led to structural changes from chain-like structures to layered structures in a series of five novel fluorogermanophosphates: A₂[GeF₂(HPO₄)₂] (A = Na, K, Rb, NH₄, and Cs, denoted as Na, K, Rb, NH4, and Cs). Although these fluorogermanophosphates have stoichiometrically equivalent formulas, they feature different anionic clusters, diverse structural dimensionalities, and contrasting crystal symmetries. Chain-like structures were observed for the compounds with the smaller sized alkali ions (Na⁺, K⁺, and Rb⁺), whereas layered structures were found for those containing the larger sized cations ((NH₄)⁺ and Cs⁺). Specifically, monoclinic space groups were observed for the Na, K, Rb, and NH4 compounds, whereas a tetragonal space group P4/mbm was found for the Cs compound. These compounds provide new insights into the effects of cation sizes on the anionic clusters built from GeO₄F₂ octahedra and HPO₄ tetrahedra as well as their influences on the overall structural symmetries in germanophosphates. Further characterization including IR spectroscopy and thermal analyses for all five compounds is also presented.

Two Barium Gold Iodates: Syntheses, Structures, and Properties of Polar BaAu(IO3)5 and Nonpolar HBa4Au(IO3)12 Materials

Two new barium gold iodates, namely, BaAu(IO₃)₅ and HBa₄Au(IO₃)₁₂, have been prepared. BaAu(IO₃)₅ crystallizes in the polar space group Pca2₁, whereas HBa₄Au(IO₃)₁₂ crystallizes in the centrosymmetric space group P2₁/c. BaAu(IO₃)₅ consists of unique polar [Au(IO₃)₄]^- anions whose four iodate groups are located at both sides of the AuO₄ plane and the polarity points in the [001̅] direction. BaAu(IO₃)₅ displays strong second-harmonic-generation (SHG) effects about 0.6KTiOPO₄ (KTP) and is phase-matchable. Thermal properties, optical spectra analyses, and theoretical calculations are also reported.

Two tartratoborates with hybrid anionic groups from unusual condensation reactions

Two novel tartratoborates, namely, K₂[(C₄H₂O₆)(B₃O₄H)](H₂O) (1) and KCu₂[(C₄H₂O₆)₂B](H₂O)_2.5 (2), have been successfully synthesized by solvothermal reactions. They feature different kinds of structural types based on hybrid borate-tartrate motifs. The structure of compound 1 features a 3D network composed of novel [(C₄H₂O₆)₂(B₃O₄H)₂]^4- anionic groups interconnected by K⁺ cations. The [(C₄H₂O₆)₂(B₃O₄H)₂]^4- anion was formed by the condensation of two (B₃O₈H)^6- groups and two tartrate anions, and such condensation reaction has never been reported previously. Compound 2 exhibits a novel 3D network structure in which 2D {Cu₂[(C₄H₂O₆)₂B](H₂O)₂}^- layers are further interconnected via K⁺ ions. The [(C₄H₂O₆)₂B]^5- anion was formed by the condensation of two tartrate anions with a B(OH)₄^- unit. Magnetic measurements reveal a dominant antiferromagnetic interaction between neighboring Cu²⁺ ions in compound 2. Furthermore, UV-vis and infrared spectra and thermal analyses were also performed.

Chemistry-Inspired Adaptable Framework Structures

Adaptable crystalline frameworks are important in modern solid-state chemistry as they are able to accommodate a wide range of elements, oxidation states, and stoichiometries. Owing to this ability, such adaptable framework structures are emerging as the prototypes for technologically important advanced functional materials. In this Account, the idea of cosubstitution is explored as a useful "pairing" concept that can potentially lead to the creation of many new members of one particular framework structure. Cosubstitution as practiced is the simultaneous replacement of two or more cations, anions, complex anions, other fundamental building units, or vacancies. Although the overall sum of the oxidation states is constant, each component is not necessarily isovalent. This methodology is typically inspired by either mineral-type structural prototypes found in nature or those discovered in the laboratory. Either path leads to the appearance of new phases and the discovery of new materials. In addition, the chemical cosubstitution approach can be successfully adopted to improve physical properties associated with structures. This Account is structured as follows: first, we illustrate the significance and background of chemical cosubstitution by reviewing mineral-inspired structures, such as perovskite and lyonsite, and the structural unit discovered in some selected solid state compounds. With time, the number of lyonsite related phases should rival or even surpass the perovskite family. Several members of the lyonsite-type have been identified as Li-ion conductors and photocatalysts. There is also a noncentrosymmetric structure-type, and therefore the other properties associated with the loss of inversion symmetry should be anticipated. Next, we illustrate recent advances in the synthesis of the new cosubstituted solid state materials from our two groups including (1) nonlinear optical materials, (2) luminescent materials, (3) transparent conducting oxides, and (4) photocatalyst and photovoltaic materials. We emphasize that a concerted and rigorous theoretical and experimental approach will be required to define thermodynamic stability of the complex cosubstitution chemistries, structures, and properties that are yet unknown. We conclude by summarizing the topic and suggesting other possible adaptable framework structures where cosubstitution can be expected.

Ag3I[(MoO3)2(IO3)2]: a new polar material synthesized from the structural modulation of molybdenyl iodate architectures by polarizable cation (Ag+) and anion (I−)

A new noncentrosymmetric compound Ag₃I[(MoO₃)₂(IO₃)₂] has been hydrothermally synthesized and characterized.

LiMCO3 (M = K, Rb, Cs): a series of mixed alkali carbonates with large birefringence

We report a series of mixed alkali carbonates LiACO₃ (A = K, Rb, Cs) which have a wave like structure and large birefringence.