Crystal clear: unveiling giant birefringence in organic-inorganic cocrystals

Coplanar groups with large anisotropic polarizability are suitable as birefringence-active groups for investigating compounds with significant birefringence. In this study, the organic coplanar raw reagent, o-C5H5NO (4HP), was selected as an individual complement. Utilizing the cocrystal engineering strategy, we successfully designed two cocrystals: [LiNO3·H2O·4HP]·4HP (Li-4HP2) and [Mg(NO3)2·6H2O]·(4HP)2 (Mg-4HP), and one by-product: LiNO3·H2O·4HP (Li-4HP), which were grown using a mild aqua-solution method. The synergy of the coplanar groups of NO3 - and 4HP in the structures resulted in unexpectedly large birefringence values of 0.376-0.522@546 nm. Furthermore, the compounds exhibit large bandgaps (4.08-4.51 eV), short UV cutoff edges (275-278 nm), and favorable growth habits, suggesting their potential as short-wave UV birefringent materials.

α-LiMB9O15 (M = Sr, Pb): Flexible [B3O7] Units Leading to the Low Temperatures Phase of β-LiMB9O15 (M = Sr, Pb)

Polymorphism is a very important phenomenon in borates and is helpful to study the structure and properties. The low-temperature phase α-LiMB9O15 (M = Sr, Pb) crystallized in chiral space groups...

Pb2Al2B3O8F3: Structure and Properties of a New Fluoroaluminoborate with Non-traditional Chain-like B3O8 Group

A new fluoroaluminoborate, Pb2Al2B3O8F3, with a non-traditional chain [B3O8]7- was synthesized by high temperature reactions in closed systems for the first time. Different from the traditional [B3O8]7- ring [(3:Δ +...

NaRbB3 O4 F3 : A New Fluorooxoborate with a Short UV Cutoff Edge Enriching the Structural Chemistry of Borate

The combination of RbB₃ O₄ F₂ and NaF generates a new member of fluorooxoborates, NaRbB₃ O₄ F₃ , with a wide transparency range from the IR to DUV region. NaRbB₃ O₄ F₃ shows a three-dimensional (3D) structure composed of 1D [B₃ O₄ F₃ ]_∞ chains, [NaO₃ F₃ ] and [RbO₅ F₅ ] polyhedra. The structural evolution from NaRbB₃ O₄ F₃ to RbB₃ O₄ F₂ , as well as the structural comparison between NaRbB₃ O₄ F₃ and its identical stoichiometry compound, Li₂ B₃ O₄ F₃ were discussed in detail. The IR spectrum verifies its structural validity. The spectral measurement shows that the reflectance has no obvious change in the range of 175-300 nm, and its cutoff edge is below 175 nm. In addition, theoretical calculations are carried out to understand its electronic structure and optical properties.

BaZn3(BO3)2F2: a new beryllium-free zincoborate with a KBBF-type structure

A new beryllium-free zincoborate, BaZn₃(BO₃)₂F₂, with a KBBF-type structure has been synthesized for the first time. The electrostatic force of interaction in BaZn₃(BO₃)₂F₂ provides better linkage in neighboring [ZnBO₃F]_∞ single layers. BaZn₃(BO₃)₂F₂ is the first case of borates with both [ZnO₃F] tetrahedra and [ZnO₆] octahedra, enriching the structural chemistry of borate system. All the coplanar [BO₃] triangles align in the same direction with a high density, which endows BaZn₃(BO₃)₂F₂ with a large birefringence of cal. 0.076 at 1064 nm. This work is of great significance to design beryllium-free borates with a KBBF-type structure.

The First Mixed Calcium Zinc Borate with a Flexible [B8 O17 ] Fundamental Building Block and Short UV Cutoff Edge

The first mixed calcium zinc borate with a new fundamental building block (FBB) [B₈ O₁₇ ], Ca_1.13 Zn_0.87 B₈ O₁₄ has been successfully synthesized. It exhibits two independent interpenetrating three-dimensional B-O anion networks constructed by [B₈ O₁₇ ] groups, enriching the structural diversity of B-O configurations. In particular, the UV-Vis-NIR diffuse-reflectance spectrum shows that it has a short UV cutoff edge (<195 nm).

Large optical polarizability causing positive effects on the birefringence of planar-triangular BO3 groups in ternary borates

The structure-property relationship of photoelectric functional materials has been recognized as a hot topic. The study of the inner link between the band gaps and birefringence of optical materials is extremely crucial for the design and creation of novel optical devices, but still remains rather unexplored. In this work, taking a series of borates with only planar-triangular BO₃ groups, α-/β-TM₃(BO₃)₂ (TM = Zn, Cd), Cd₂B₂O₅, and M₃(BO₃)₂ (M = Hg, Mg, Ca, Sr) as the research subject, the comprehensive relationship between their electronic structures and linear optical properties has been systematically investigated. Through combining experimental measurements and theoretical calculations, the effect of optical polarizability on the birefringence of these borates was clarified. Based on the present discussion, the relationship between the O (2p) bandwidth of the highest valence band and the HSE06 band gaps is opposite. Meanwhile, a method involving the determination of so-called optical permittivity Δε to evaluate the magnitude of birefringence Δn is found to be feasible. A large Δε makes a positive contribution to Δn. In addition, the experimentally measured band gaps and IR vibrations are in good agreement with theoretical results for the compounds α-Cd₃(BO₃)₂ and Cd₂B₂O₅.

Al8(BO3)4(B2O5)F8: A F-Containing Aluminum Borate Featuring Two Types of Isolated B-O Groups

Al₈(BO₃)₄(B₂O₅)F₈, as a new aluminum borate fluoride, has been synthesized by the high-temperature reaction with the closed system for the first time. With respect to its structure, the isolated BO₃ and B₂O₅ groups reside in the center and edge of tunnels constructed by the AlO₄F₂ polyhedra. The AlO₄F₂ polyhedra play the vital role on the formation of isolated B-O groups. According to our investigation, Al₈(BO₃)₄(B₂O₅)F₈ is the first case, which features two types of independently isolated B-O groups in the aluminum borate fluorides. Its cutoff edge is up to deep ultraviolet (DUV) range. What is more, the energy dispersive spectroscopy (EDS), infrared (IR) spectrum, and the first-principles calculations of Al₈(BO₃)₄(B₂O₅)F₈ have been performed.

Pb3Ba3Zn6(BO3)8 and α-BaZn2(BO3)2: new members of the zincoborates containing two different dimensional Zn–O units

Two new zincoborates, namely, Pb₃Ba₃Zn₆(BO₃)₈ and α-BaZn₂(BO₃)₂, were synthesized by the high-temperature solution method and their structures were determined by single-crystal X-ray diffraction for the first time.

From BaAl2(BO3)2O to SnAl2(BO3)2F2: structure transformation based on ion regulation

Sn atoms reside in each Al–B–O–F channel consisting of Al₈B₈O₃₂F₁₂ cavities, which makes SnAl₂(BO₃)₂F₂ possess a special structure.

Research and Development of Zincoborates: Crystal Growth, Structural Chemistry and Physicochemical Properties

Borates have been regarded as a rich source of functional materials due to their diverse structures and wide applications. Therein, zincobrates have aroused intensive interest owing to the effective structural and functional regulation effects of the strong-bonded zinc cations. In recent decades, numerous zincoborates with special crystal structures were obtained, such as Cs₃Zn₆B₉O₂₁ and AZn₂BO₃X₂ (A = Na, K, Rb, NH₄; X = Cl, Br) series with KBe₂BO₃F₂-type layered structures were designed via substituting Be with Zn atoms, providing a feasible strategy to design promising non-linear optical materials; KZnB₃O₆ and Ba₄Na₂Zn₄(B₃O₆)₂(B₁₂O₂₄) with novel edge-sharing [BO₄]^5- tetrahedra were obtained under atmospheric pressure conditions, indicating that extreme conditions such as high pressure are not essential to obtain edge-sharing [BO₄]^5--containing borates; Ba₄K₂Zn₅(B₃O₆)₃(B₉O₁₉) and Ba₂KZn₃(B₃O₆)(B₆O₁₃) comprise two kinds of isolated polyborate anionic groups in one borate structure, which is rarely found in borates. Besides, many zincoborates emerged with particular physicochemical properties; for instance, Bi₂ZnOB₂O₆ and BaZnBO₃F are promising non-linear optical (NLO) materials; Zn₄B₆O₁₃ and KZnB₃O₆ possess anomalous thermal expansion properties, etc. In this review, the synthesis, crystal structure features and properties of representative zincoborates are summarized, which could provide significant guidance for the exploration and design of new zincoborates with special structures and excellent performance.

Li3Ba4Sc3(BO3)4(B2O5)2: featuring the coexistence of isolated BO3 and B2O5 units

A new mixed alkali/alkaline earth scandium borate Li₃Ba₄Sc₃(BO₃)₄(B₂O₅)₂ with isolated and almost co-planar BO₃ and B₂O₅ groups is reported.

Insights of BO3–PO4 replacement for the design and synthesis of a new borate–phosphate with unique 1∞[Zn4BO11] chains and two new phosphates

A borate–phosphate CsZn₄(BO₃)(PO₄)₂ and two phosphates CsZn₄(PO₄)₃ and RbZn₄(PO₄)₃ were obtained via BO₃–PO₄ replacement, and the substitution of BO₃–PO₄ is a feasible strategy for preparing new compounds.

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.

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.

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).

Li6Zn3(BO3)4: a new zincoborate featuring vertex-, edge- and face-sharing LiO4tetrahedra and exhibiting reversible phase transitions

A new zincoborate, Li₆Zn₃(BO₃)₄, was prepared, which exhibits two reversible phase transitions and contains a face-sharing LiO₄configuration.

The structural diversity of halogen-centered secondary building units: two new mixed-metal borate halides with deep-ultraviolet cut-off edges

Categories of halogen-centered SBUs were investigated among borates to elaborate the role of halogen to enrich the structural diversity of borates.