K2Sb(P2O7)F: Cairo Pentagonal Layer with Bifunctional Genes Reveal Optical Performance

Discovering new functional genes, designing perfect crystal structures, and developing high-performance materials are the goals being pursued by scientists. Herein, the first antimony pyrophosphate, K₂Sb(P₂O₇)F, possessing an optimal layered structure, is reported, where the perfect structural arrangement induces excellent optical properties. K₂Sb(P₂O₇)F not only displays a sharply enhanced birefringence (0.157@546 nm) compared to the existing phosphate optical materials, but also exhibits a strong second-harmonic generation response (4.0×KDP). Remarkably, a new bifunctional gene, the square-pyramidal SbO₄F group, was discovered, and a unique two-dimensional arrangement of Cairo pentagonal tiling units was observed in inorganic compounds for the first time.     

Rational Design of the Metal‐Free KBe2BO3F2⋅(KBBF) Family Member C(NH2)3SO3F with Ultraviolet Optical Nonlinearity

The first fluorosulfonic ultraviolet (UV) nonlinear optical (NLO) material, C(NH₂)₃SO₃F, is rationally designed by taking KBe₂BO₃F₂ (KBBF) as the parent compound. C(NH₂)₃SO₃F features similar topological layers as KBBF by replacing inorganic (BO₃)^3? with organic C(NH₂)₃⁺ trigonal units and BeO₃F with SO₃F^? tetrahedra. Therefore, C(NH₂)₃SO₃F is a metal‐free UV NLO crystal. Benefiting from the coplanar configuration of the C(NH₂)₃⁺ cationic groups, it possesses a large SHG response of 5×KDP and moderate birefringence of 0.133@1064 nm. Besides, it has a short UV cutoff edge of 200 nm. The calculated results reveal the shortest SHG phase‐matching wavelengths can reach 200 nm. These findings highlight the exploration of metal‐free compounds as nontoxic and low‐cost UV NLO materials as a new research area.     

Syntheses and Crystal Structures of Hydrated Ternary Cerium Sulfates: Mixed‐valence K5Ce2(SO4)6·H2O and K2Ce(SO4)3·H2O

A new chemical and structural interpretation of K₅Ce₂(SO₄)₆·H₂O ( I ) and a redetermination of the structure of K₂Ce(SO₄)₃·H₂O ( II ) is presented. The mixed‐valent compound I crystallizes in the space group C2/c with a = 17.7321(3), b = 7.0599(1), c = 19.4628(4) Å, β = 112.373(1)° and Z = 4. Compound I has been discussed earlier with space group Cc. In the structure of I , there are pairs of edge sharing cerium polyhedra connected by sulfate oxygen atoms in the μ₃ bonding mode. These cerium dimers are linked through edge and corner sharing sulfate bridges, forming layers. The layers are joined by potassium ions which together with the water molecules are placed between the layers. No irregularity in the distribution of the Ce^III and Ce^IV to cause the lost of a crystallographic center of symmetry was detected. We suggest that the charge exerted by the extra f¹ electron for every cerium dimer is delocalized over the Ce1–O₂–Ce2 moiety in a non‐bonding mode. As a result, the oxidations state of each cerium ion is a mean value between III and IV at each atomic position. Compound II crystallizes in the space group C2 with a = 20.6149(2), b = 7.0742(1), c = 17.8570(1) Å, β = 122.720(1)° and Z = 8. The hydrogen atoms have been located and the absolute structure has been established. Neither hydrogen atom positions nor anisotropic displacement parameters were given in the previous reports. In compound II , the cerium polyhedra are connected by edge and corner sharing sulfate groups forming a three‐dimensional network. This network contains Z‐shaped channels hosting the charge compensating potassium ions.     

Li7Cd4.5Ge4Se16 and Li6.4Cd4.8Sn4Se16: Strong Nonlinear Optical Response in Quaternary Diamond‐Like Selenide Networks

Two new selenides with diamond‐like structures, Li₇Cd_4.5Ge₄Se₁₆ and Li_6.4Cd_4.8Sn₄Se₁₆, were synthesized by using a conventional high‐temperature solid‐state reaction method. They crystallize in the space group Pna2₁ (no. 33) of the orthorhombic system. Their three‐dimensional frameworks consist of corner‐sharing LiSe₄, CdSe₄, and MSe₄ (M=Ge, Sn) tetrahedra. These two compounds exhibit strong powder second‐harmonic generation responses that are about 1.2 and 2.5 times that of the benchmark AgGaS₂ at a laser wavelength of λ=2.09 μm, and also demonstrate type I phase‐matchable behavior. The optical bandgaps were determined to be 2.18 and 1.95 eV for Li₇Cd_4.5Ge₄Se₁₆ and Li_6.4Cd_4.8Sn₄Se₁₆, respectively. Furthermore, these two materials exhibit congruent melting behavior at rather low temperatures of 985 and 1060 K, respectively, which makes bulk single crystal growth by using the Bridgman–Stockbarger method possible. Our study indicates that these two materials show advantages over the traditional IR NLO material CdSe and are promising for practical applications.     

Polar Fluorooxoborate,NaB4O6F: A Promising Material for Ionic Conduction and Nonlinear Optics

The search of new borates with improved functional properties has attracted considerable attention. Herein, a new polar fluorooxoborate, NaB₄O₆F (NBF) was prepared by high‐temperature solid‐state reaction. NBF belongs to the AB₄O₆F family (A=alkali metal or ammonium), a series of compounds that undergoes significant cation‐dependent structural changes. NBF is of particular interest owing to the special cation position. Temperature‐dependent ionic conductivity measurements show that NBF is a solid ionic conductor, and it has the lowest active energy of 32.5 kJ mol^?1 of fluorooxoborates. NBF also shows a second‐harmonic generation (SHG) response of 0.9×KH₂PO₄ and 0.2×β‐BaB₂O₄, at 1064 and 532 nm, respectively, and it has a short UV cutoff edge below 180 nm. Based on bond valence (BV) concepts, symmetry analysis, and the first principles calculation, the unique [B₄O₆F]_∞ layer can be regarded as the “multifunctional unit”, which is responsible for the observed properties of NBF.     

A Cationic Antimonite Chain Templated by Sulfate: [Sb(6)O(7)(4+)][(SO(4)(2-))(2)

An extended metal oxide possessing a cationic charge on the host has been synthesized by hydrothermal methods. The structure consists of 1D antimony oxide [Sb(6)O(7)](4+) chains with a new structural motif of four Sb atoms wide and unprotonated sulfate anions between the chains. The material was characterized by powder and single-crystal X-ray diffraction. Thermal behavior and chemical resistance in aqueous acidic conditions (pH ～2) indicate a highly stable cationic material. The stability is attributed to the entirely inorganic composition of the structure, where 1D covalently extended chains are electrostatically bound to divalent anions.     

Na6MQ4 (M=Zn,Cd; Q=S,Se): Promising New Ternary Infrared Nonlinear Optical Materials

Four sodium-based ternary IR nonlinear optical (NLO) materials, Na₆MQ₄ (M=Zn, Cd; Q=S, Se), were prepared through a high-temperature flux method. The crystal structure of the compounds is built up of isolated [MQ₄] tetrahedra and a 3D framework formed by the NaQ_n (n=4, 5) units. The two selenides, Na₆MSe₄ (M=Zn, Cd), as promising IR NLO materials, show moderate second-harmonic generation (SHG) responses (0.9 and 0.5×AgGaS₂) with good phase-matching behavior, as well as high laser damage thresholds (2 and 1.9×AgGaS₂). The two sulfides, Na₆MS₄ (M=Zn, Cd), exhibit higher laser damage thresholds (13 and 4×AgGaS₂), but smaller SHG responses (0.3 and 0.2×AgGaS₂). Theoretical calculations and statistical analyses indicate that the SHG effect and band gap in the compounds originate mainly from the distorted NaQ₄ NLO-active units with a short Na−S bond length, which provides a new insight into the design of novel IR NLO materials.     

Li2MnSnSe4: A New Quaternary Diamond‐Like Semiconductor with Nonlinear Optical Response and Antiferromagnetic Property

A new selenide with a diamond‐like structure, Li₂MnSnSe₄, was synthesized for the first time by using a conventional high‐temperature solid‐state reaction method. Li₂MnSnSe₄ crystallizes in the space group Pmn 2₁ (no. 31) of the orthorhombic system. Its three‐dimensional framework is constructed by corner‐sharing LiSe₄, MnSe₄, and SnSe₄ tetrahedra. The title compound has been discovered to have both type I phase‐matchable behavior and to exhibit moderate powder second‐harmonic generation intensity, about 0.5 times that of commercial AgGaS₂ in the particle size of 200–250 μm at a laser radiation of 2.09 μm. In addition, Li₂MnSnSe₄ exhibits congruent melting behavior, which makes the bulk single‐crystal growth by the Bridgman–Stockbarger method possible. The temperature‐dependent susceptibility measurement indicates an antiferromagnetic interaction with a Néel temperature (T _N) of 8.6 K for this compound.     

CsB4O6F: A Congruent‐Melting Deep‐Ultraviolet Nonlinear Optical Material by Combining Superior Functional Units

The discovery of new nonlinear optical (NLO) materials for coherent light generation in the deep‐ultraviolet (DUV, wavelength below 200 nm) region is essential for the development of laser technologies. Herein, we report a new material CsB₄O₆F (CBF), which combines the superior structural properties of two well‐known NLO materials, β‐BaB₂O₄ (BBO) and KBe₂BO₃F₂ (KBBF). CBF exhibits excellent DUV optical properties including a short cutoff edge (155 nm), a large SHG response (≈1.9×KDP), and a suitable birefringence that enables frequency doubling down to 171.6 nm. Remarkably, CBF melts congruently and shows an improved growth habit. In addition, our rational design strategy will contribute to the discovery of DUV NLO materials.     

Benzodithiazolium‐Chlorooxomolybdate(V): Darstellung und Kristallstruktur von (C6H4NS2)[MoOCl4] und (C6H4NS2)[MoOCl4·H2O]

Benzodithiazolium Chlorooxomolybdate(V): Preparation and Crystal Structure of (C₆H₄NS₂)[MoOCl₄] and (C₆H₄NS₂)[MoOCl₄·H₂O] Red benzo‐1,3,2‐dithiazolium‐chlorooxomolybdate(V) (C₆H₄NS₂)[MoOCl₄] ( 1 ) was obtained by the reaction of benzo‐1,3,2‐dithiazoliumchloride and molybdenum(V)chloride oxide in dichlormethane under solvothermal conditions at 70 °C. In the presence of small amounts of concentrated hydrochloric acid the yellow compound (C₆H₄NS₂)[MoOCl₄·H₂O] ( 2 ) is formed under analogue conditions. Both crystal structures ( 1 : monoclinic, C2/c, a = 799.2(1), b = 2091.5(2), c = 791.5(1) pm, β = 102.2(1)°, Z = 4; 2 : monoclinic, Cc, a = 953.7(1), b = 2468.9(3), c = 608.1(1) pm, β = 112.5(1)°, Z = 4) contain the planar benzo‐1,3,2‐dithiazolium ion. Within the structure of 1 the molybdenum atoms in the [MoOCl₄]^? ions are coordinated in a square pyramidal fashion with an oxygen atom in apical position and the basal plane formed by chlorine atoms. The nitrogen atom of the cation, which bears a partial negativ charge, expands the coordination to a distorted octahedron. The structure therefore is made up of ionic pairs {(C₆H₄NS₂)⁺ [MoOCl₄]^?} with a Mo–N distance of 266 pm. 1 is paramagnetic with a magnetic moment of 1.7 B.M. corresponding to one unpaired electron per formula unit. In the structure of 2 the coordination of the [MoOCl₄]^? ion is expanded by the oxygen atom of a coordinating water molecule. The structure is dominated by hydrogen bonds between the oxygen atoms of the [MoOCl₄·H₂O]^? ions which cause the concatenation of the anions to infinite chains.     

CsSbF2SO4: An Excellent Ultraviolet Nonlinear Optical Sulfate with a KTiOPO4 (KTP)‐type Structure

A novel noncentrosymmetric (NCS) polar fluoride sulfate, CsSbF₂SO₄, was obtained by ionothermal synthesis. A meticulously designed co‐substitution approach was used to successfully replace the [TiO₆]^8? and [PO₄]^3? functional groups in KTiOPO₄ (KTP) with [SbO₄F₂]^7? and [SO₄]^2? units, respectively. The structure of CsSbF₂SO₄ features a pseudo‐3D framework consisting of interconnected 1D [SbF₂O₂SO₄]^5? chains of corner‐sharing [SbO₄F₂]^7? octahedra and [SO₄]^2? tetrahedra. The title compound exhibits a sharply enlarged band gap compared to its parent compound, KTP, benefitting from the introduction of F^? ions and the displacement of Sb³⁺ cations. Second harmonic generation (SHG) measurements manifested that CsSbF₂SO₄ is phase‐matchable and revealed a strong SHG response of about 3.0 KH₂PO₄ (KDP), which is the highest value reported for any metal sulfate reported to date. The reported fluoride sulfate is a promising near ultraviolet (UV) nonlinear optical (NLO) material.     

Reaction with SO3 in Ionic Liquids: The Example of K2(S2O7)­(H2SO4)

The ionic liquid 1‐butyl‐3‐methylimidazolium hydrogensulfate, [bmim]HSO₄, turned out to be resistant even to strong oxidizers like SO₃. Thus, it should be a suitable solvent for the preparation of polysulfates at low temperatures. As a proof of principle we here present the synthesis and crystal structure of K₂(S₂O₇)(H₂SO₄), which has been obtained from the reaction of K₂SO₄ and SO₃ in [bmim]HSO₄. In the crystal structure of K₂(S₂O₇)(H₂SO₄) (orthorhombic, Pbca, Z = 8, a = 810.64(2) pm, b = 1047.90(2) pm, c = 2328.86(6) pm, V = 1978.30(8) ų) two crystallographically unique potassium cations are coordinated by a different number of monodentate and bidentate‐chelating disulfate anions as well as by sulfuric acid molecules. The crystal structure consists of alternating layers of [K₂(S₂O₇)] slabs and H₂SO₄ molecules. Hydrogen bonds between hydrogen atoms of sulfuric acid molecules and oxygen atoms of the neighboring disulfate anions are observed.     

一个多酸簇合物[Cu4(PPh3)6][Mo8O26]的合成、晶体结构和非线性光学性质

本文报道了一个多酸簇合物[Cu4(PPh3)6][Mo8O26]的合成、X-射线单晶结构分析及IR、XRD表征.单品结构表明中心对称的[Mo8O26]4-是由8个共边的MoO6八面体组成.该化合物具有较好的三阶非线性光学性质,其三阶非线性吸收和折射系数分别为12.9×10-11 MKS和3.13×10-11 esu.