Crystal Structures of {[Cd(phen)](C6H8O4)3/3} and {[Cd(phen)](C7H10O4)3/3} · 2H2O with C6H10O4 = Adipic Acid and C7H12O4 = Pimelic Acid

Two coordination polymers {[Cd(phen)](C₆H₈O₄)_3/3} ( 1 ) and {[Cd(phen)](C₇H₁₀O₄)_3/3} · 2H₂O ( 2 ) were structurally characterized by single crystal X‐ray diffraction methods. In 1 (C2/c (no. 15), a = 16.169(2)Å, b = 15.485(2)Å, c = 14.044(2)Å, β = 112.701(8)°, U = 3243.9(7)ų, Z = 8), the Cd atoms are coordinated by two N atoms of one phen ligand and five O atoms of three adipato ligands to form mono‐capped trigonal prisms with d(Cd‐O) = 2.271‐2.583Å and d(Cd‐N) = 2.309, 2.390Å. The [Cd(phen)] moieties are bridged by adipato ligands to generate {[Cd(phen)](C₆H₈O₄)_3/3} chains, which, via interchain π—π stacking interactions, are assembled into layers. Complex 2 (P1¯(no. 2), a = 9.986(1)Å, b = 10.230(3)Å, c = 11.243(1)Å, α = 66.06(1)°, β = 87.20(1)°, γ = 66.71(1)°, U = 955.7(2)ų, Z = 2) consists of {[Cd(phen)](C₇H₁₀O₄)_3/3} chains and hydrogen bonded H₂O molecules. The Cd atoms are pentagonal bipyramidally coordinated by two N atoms of one phen ligand and five O atoms of three pimelato ligands with d(Cd‐O) = 2.213—2.721Å and d(Cd‐N) = 2.329, 2.372Å. Through interchain π—π stacking interactions, the {[Cd(phen)](C₇H₁₀O₄)_3/3} chains resulting from [Cd(phen)] moieties bridged by pimelato ligands are assembled in to layers, between which the hydrogen bonded H₂O molecules are sandwiched.     

One‐dimensional Cadmium(II) Coordination Polymers: Syntheses and Crystal Structures of [Cd(H2O)3(C5H6O4)]·2H2O,Cd(H2O)2(C6H8O4), and Cd(H2O)2(C8H12O4)

[Cd(H₂O)₃(C₅H₆O₄)]·2H₂O ( 1 ) and Cd(H₂O)₂(C₆H₈O₄) ( 2 ) were prepared from reactions of fresh CdCO₃ precipitate with aqueous solutions of glutaric acid and adipic acid, respectively, while Cd(H₂O)₂(C₈H₁₂O₄) ( 3 ) crystallized in a filtrate obtained from the hydrothermal reaction of CdCl₂·2.5H₂O, suberic acid and H₂O. Compound 1 consists of hydrogen bonded water molecules and linear {[Cd(H₂O)₃](C₅H₆O₄)_2/2} chains, which result from the pentagonal bipyramidally coordinated Cd atoms bridged by bis‐chelating glutarato ligands. In 2 and 3 , the six‐coordinate Cd atoms are bridged by bis‐chelating adipato and suberato ligands into zigzag chains according to {[Cd(H₂O)₃](C₅H₆O₄)_2/2} and {[Cd(H₂O)₂](C₈H₁₂O₄)_2/2}, respectively. The hydrogen bonds between water and the carboxylate oxygen atoms are responsible for the supramolecular assemblies of the zigzag chains into 3D networks. Crystallographic data: ( 1 ) P1¯ (no. 2), a = 8.012(1), b = 8.160(1), c = 8.939(1) Å, α = 82.29(1)°, β = 76.69(1)°, γ = 81.68(1)°, U = 559.6(1) ų, Z = 2; ( 2 ) C2/c (no. 15), a = 16.495(1), b = 5.578(1), c = 11.073(1) Å, β = 95.48(1)°, U = 1014.2(1) ų, Z = 4; ( 3 ) P2/c (no. 13), a = 9.407(2), b = 5.491(1), c = 11.317(2) Å, β = 95.93(3)°, U = 581.4(2) ų, Z = 2.     

Die Kristallstrukturen der hexagonalen Elpasolithe Ba3NiSb2O9 und Ba3CuSb2O9 – röntgenographische und spektroskopische Ergebnisse

The Structures of the Hexagonal Elpasolite-Type Compounds Ba₃NiSb₂O₉ and Ba₃CuSb₂O₉ The results of an X-ray single crystal study of the hexagonal elpasolite Ba(NiSb₂)⁽⁶⁾O₉ are given. (Space group: C; a = b = 5.837 Å, c = 14.392 Å; Z = 2). The structure can be described by close-packed BaO₃ layers alternating in the sequence c c h c c h … (hex. BaTiO₃ type). Groups of two octahedra with common faces are connected by SbO₆ octahedra via common corners. They are occupied alternately by Ni and Sb. The final reliability index was R = 3.0%. The Cu²⁺-compound is of the same structural type. The ligand field and EPR spectra are discussed in comparison with related Ni²⁺ and Cu²⁺ compounds.     

Synthesis,Crystal Structure,Bonding, and Properties of (Ba6O)(OsN3)2

The new barium nitridoosmate oxide (Ba₆O)(OsN₃)₂ was prepared by reacting elemental barium and osmium (3:1) in nitrogen at 815–830 °C. The crystal structure of (Ba₆O)(OsN₃)₂ as determined by laboratory powder X‐ray diffraction ( , No 148: a=b=8.112(1) Å, c=17.390(1) Å, V=991.0(1) ų, Z=3), consists of sheets of trigonal OsN₃ units and trigonal‐antiprismatic Ba₆O groups, and is structurally related to the “313 nitrides” AE₃MN₃ (AE=Ca, Sr, Ba, M=V–Co, Ga). Density functional calculations, using a hybrid functional, likewise indicate the existence of oxygen in the Ba₆ polyhedra. The oxidation state 4+ of osmium is confirmed, both by the calculations and by XPS measurements. The bonding properties of the OsN₃^5? units are analyzed and compared to the Raman spectrum. The compound is paramagnetic from room temperature down to T=10 K. Between room temperature and 100 K it obeys the Curie–Weiss law (μ=1.68 μ_B). (Ba₆O)(OsN₃)₂ is semiconducting with a good electronic conductivity at room temperature (8.74×10^?2 Ω^?1 cm^?1). Below 142 K the temperature dependence of the conductivity resembles that of a variable‐range hopping mechanism.     

Ein neues Kupfercobaltboratoxid mit isolierten B2O5-Baugruppen: Cu2Co(B2O5)O

On a New Copper Cobalt Borate Oxide with Isolated B₂O₅ Units: Cu₂Co(B₂O₅)O Single crystals of a new compound with the empirical formula Cu₂CoB₂O₆ were obtained by using a B₂O₃ flux technique. X-ray single crystal technique led to a new structure type. Cu₂CoB₂O₆ crystallizes monoclinic, space group C-P2₁/c (No. 14); a = 3.2250(6); b = 14.847(1); c = 9.1171(6) Å; β = 93.67°; Z = 4. All metal sites are octahedrally coordinated and form a two dimensional framework consisting of edge sharing octahedra ribbons. In addition one observes isolated B₂O₅-units and oxygen which is not coordinated to boron. The far relation to the crystal structure of the mineral Warwickite is illustrated.     

Über hexagonale Perowskite mit Kationenfehlstellen. XIV Die rhomboedrischen 12 L-Stapelvarianten Ba2La2BII(W□O12)

On Hexagonal Perovskites with Cationic Vacancies. XIV. The Rhombohedral 12 L-Stacking Polytypes Ba₂La₂B^II(W □O₁₂) Rhombohedral 12 L-stacking polytypes with cationic vacancies of type Ba₂La₂B^II-(W□O₁₂) are reported for B^II = Mg, Zn (white), Ni(light brown) and Co(brown). They crystallize in the space group R3 m, sequences (3 )(1) ? (hhcc)₃. For B^II = Cu, as a consequence of the Jahn Teller effect, a triclinic distorted lattice is observed.     

Ba4Ca(B2O5)2F2: π-conjugation of B2O5 in the planar pentagonal layer achieving large second harmonic generation of pyro-borate

The nonlinear optical (NLO) crystals that can expand the wavelength of the laser to the deep-ultraviolet (DUV) region by the cascaded second harmonic generation (SHG) are of current research interest. It is well known that borates are the most ideal material class for the design of new DUV NLO crystals owing to the presence of good NLO genes, e.g., BO₃ or B₃O₆ groups. However, the NLO pyro-borates with the B₂O₅ dimers as the sole basic building units are still rarely reported owing to their small SHG responses. In this communication, by constructing a planar pentagonal [Ca(B₂O₅)]_∞ layer, the NLO pyro-borate Ba₄Ca(B₂O₅)₂F₂ with a large SHG response (∼2.2 × KDP, or ∼7 × α-Li₄B₂O₅) and a DUV transparent window has been designed and synthesized. The first-principles calculations show that the large SHG response of Ba₄Ca(B₂O₅)₂F₂ mainly originates from the better π-conjugation of the coplanar B₂O₅ dimers in the [Ca(B₂O₅)]_∞ layer. In addition, the planar pentagonal pattern in the [Ca(B₂O₅)]_∞ layer provides an ideal template for designing the new DUV NLO crystals, apart from those in known DUV borates, e.g., the [Be₂BO₃F₂]_∞ layer in KBe₂BO₃F₂ (KBBF).

A new deep-UV NLO pyro-borate Ba₄Ca(B₂O₅)₂F₂ was synthesized by solid-state reactions. The better π-conjugation of B₂O₅ dimers in the planar pentagonal layer achieves a large SHG response (∼2.2 × KDP), which is the largest among all the known DUV transparent borates with B₂O₅ units.

Deep-ultraviolet (DUV, λ < 200 nm) coherent lights with high photon energy, high spatial resolution, and a small heat-affected zone are of significance for applications in photolithography, high-resolution spectroscopy, laser cooling, and scientific equipment.^1–4 However, it is difficult or well-nigh impossible for solid-state lasers to directly radiate the DUV coherent lights. In contrast, relying on the process of second harmonic generation (SHG) of nonlinear optical (NLO) crystals is a more effective way to generate the DUV coherent lights and causes much attention.^5,6 Therefore, the NLO crystal has become an important material basis of solid-state lasers, which seriously affects the development of all-solid-state laser technology. However, it is still a great challenge to rationally design and synthesize DUV NLO crystals because of the extremely rigorous requirements of structural symmetry and properties.^7–10 Structurally, the DUV NLO crystals must crystallize in the noncentrosymmetric (NCS) space groups which are the prerequisite for the materials to exhibit SHG responses. Moreover, it should possess a broad transparency window, a largely effective NLO coefficient (d_eff ≥ 0.39 pm V⁻¹), and a moderate birefringence (0.05–0.10@1064 nm) to achieve the phase-matching (PM) conditions in the DUV region.¹⁰ Based on these requirements, borates have been considered as the ideal material class for DUV NLO crystals because of their special structure and properties'' virtues, including the rich acentric structural types, large band gaps, and stable physical and chemical properties.⁸ To date, the commercialized borate-based UV NLO crystals consist of β-BaB₂O₄ (BBO), LiB₃O₅ (LBO), CsLiB₆O₁₀ (CLBO),^9,10 and the practical DUV NLO crystal KBe₂BO₃F₂ (KBBF). Especially for KBBF, it has become the sole material that can generate DUV coherent laser light (177.3 nm) by a direct SHG method.⁷ Other excellent borate-based UV NLO crystals also consist of K₃B₆O₁₀Cl,¹¹ SrB₅O₇F₃,¹² Li₂B₆O₉F₂,⁵ CsAlB₃O₆F,¹³ M₂B₁₀O₁₄F₆ (M = Ca, Sr),¹⁴ NH₄B₄O₆F,¹⁵ NaSr₃Be₃B₃O₉F₄,¹⁶ AB₄O₆F (A = K, Rb, and Cs),¹⁷etc.The above borate-based materials have achieved great success as UV and DUV NLO crystals, which are mainly attributed to the ability of boron atoms to coordinate with three or four oxygen anions forming trigonal-planar or tetrahedral building blocks.^18,19 For example, the first borate-based NLO crystal, KB₅O₈·4H₂O (KB₅), has the basic building units (BBUs) of [B₅O₁₀], while the BBUs of β-BBO, LBO, and KBBF are [B₃O₆], [B₃O₇], and isolated [BO₃], respectively.^7,8 Remarkably, although various borate crystals with different types of borate groups have been explored during the past decades, the pyro-borate NLO crystals with B₂O₅ groups as the sole BBUs are rarely reported owing to their weak SHG responses.^20–23 For example, the SHG response of the DUV transparent α-Li₄B₂O₅ (ref. 23) is only ∼0.3 × KDP, which is far smaller than the expected value (0.39 pm V⁻¹, 1 × KDP).Actually, the flexible B₂O₅ groups which are composed of two π-conjugated BO₃ units through corner-sharing may also be capable of generating excellent optical performance if they have benign arrangements. In recent research, Pan''s group has indicated that the B₂O₅ dimers are perfect for the design of DUV birefringent crystals. By the synergistic combination, they have successfully designed a potential pyro-borate birefringent crystal, Li₂Na₂B₂O₅, with a short UV cut-off edge (181 nm) and large birefringence (0.095@532 nm).²¹ And they have also grown Ca(BO₂)₂ crystals exhibiting a short UV cut-off edge and larger birefringence (169 nm; 0.2471@193 nm). Based on the analysis of the structure–property relationship of Ca(BO₂)₂, they stated that the polymerized planar B_nO_2n+1 groups, e.g., B₂O₅, could generate a larger anisotropy than isolated BO₃.²² However, their opposite arrangements of B–O groups make them crystallize in the centrosymmetric (CS) space groups, which limit their further development as NLO compounds. Thus, it is clear that pyro-borates exhibiting a large birefringence and a short UV cut-off edge would also be promising DUV NLO crystals if their SHG responses can be enhanced.Based on the above-mentioned ideas, a systematical investigation has been performed on DUV pyroborates. And finally, we successfully synthesized a new NCS pyro-borate, Ba₄Ca(B₂O₅)₂F₂, which can exhibit not only a large SHG response (∼2.2 × KDP and ∼7 × α-Li₄B₂O₅) but also a short UV cut-off edge (<190 nm). Analyzing its structure, one can find that its excellent NLO properties mainly originate from the unique planar pentagonal [Ca(B₂O₅)]_∞ layer, where the B₂O₅ groups adopt the almost coplanar configurations that favor the structure to generate large SHG response and birefringence,²¹ meanwhile the terminal O atoms of B₂O₅ groups are also linked by the Ca²⁺ cations, which eliminate the dangling bonds of B₂O₅ groups and further blue-shift the UV cut-off edge. More importantly, the adjacent [Ca(B₂O₅)]_∞ layers in Ba₄Ca(B₂O₅)₂F₂ are linked by other B₂O₅ groups to form a 3D framework, which will be favorable for the material to avoid the layer habit that KBBF suffers from. In this sense, the planar pentagonal [Ca(B₂O₅)]_∞ layer is similar to the [Be₂BO₃F₂]_∞ layer in KBBF, and it can be seen as a new structure template for the design of new DUV NLO crystals, especially for the DUV pyro-borates. Herein, we will describe the synthesis, experimental and computational characterization as well as the functional properties of the new DUV NLO material, Ba₄Ca(B₂O₅)₂F₂.A polycrystalline sample of Ba₄Ca(B₂O₅)₂F₂ was synthesized by the conventional solid-state reaction and the purity was confirmed by powder X-ray diffraction (XRD) (Fig. S1^†). With the polycrystalline sample, the thermal behavior of Ba₄Ca(B₂O₅)₂F₂ was studied by the thermogravimetric (TG) and differential scanning calorimetry (DSC) measurements. The heating DSC curve shows a sharp endothermic peak at 815 °C with no obvious weight loss in the TG curve (Fig. S2^†), suggesting that Ba₄Ca(B₂O₅)₂F₂ has good thermal stability. To further investigate the thermal behavior of Ba₄Ca(B₂O₅)₂F₂, the polycrystalline sample was calcined at 840 °C and the XRD analysis showed that the calcined sample was Ba₄Ca(B₂O₅)₂F₂, Ba₂Ca(BO₃)₂ (PDF #01-085-2268), Ba₂CaB₆O₁₂ (PDF #01-075-1401) and other unknown phases (Fig. S3^†). These results illustrate that Ba₄Ca(B₂O₅)₂F₂ melts incongruently and the suitable flux is necessary for the crystal growth.With the Na₂O–PbF₂–B₂O₃ as the flux, millimeter-sized block crystals of Ba₄Ca(B₂O₅)₂F₂ were grown for the single-crystal XRD structure determination. Ba₄Ca(B₂O₅)₂F₂ crystallizes in the NCS and polar space group, P2₁ (Table S1^†). In the asymmetric unit, there are four unique Ba, one Ca, four B, ten O, and two F atom(s), which all fully occupy the 2a Wyckoff positions (Table S2^†). All B atoms are coordinated to three oxygen atoms to form the BO₃ triangles with the B–O distances ranging from 1.312(17) to 1.460(16) Å and O–B–O angles varying from 108.0(13) to 130.2(15)°. The BO₃ triangles are further connected to form two types of B₂O₅ dimers, i.e. plane B(1,3)₂O₅ and twisted B(2,4)₂O₅, which are the BBUs of Ba₄Ca(B₂O₅)₂F₂. The Ca atoms are coordinated to six oxygen atoms to form CaO₆ octahedra with the Ca–O distances ranging from 2.285(9) to 2.325(13) Å. For the Ba²⁺ cations, they exhibit three different coordination environments, Ba(1,2)O₆F₂, Ba(3)O₈F₂, and Ba(4)O₇F₂ (Fig. S4^†) with the Ba–O distances ranging from 2.585(9) to 3.250(11) Å and the Ba–F bond lengths ranging from 2.635(8) to 2.736(8) Å. Remarkably, for the F⁻ anions, each unique fluorine atom serves as a common vertex for four Ba atoms to form the FBa₄ polyhedra (Fig. S5a^†), which could be treated as fluorine-centered secondary building units (SBUs). The Ba–F–Ba angles vary from 99.0 (2) to 120.2 (3)°. The bond valence sum (BVS) calculations show the values of 1.67–1.97, 2.45, 2.88–3.10, 1.78–2.13, and 0.95–1.09, for Ba²⁺, Ca²⁺ B³⁺, O²⁻, and F⁻, respectively (Table S2^†). The BVSs of atoms are consistent with their expected oxidation states except the one from the Ca²⁺ cations. The larger BVSs of Ca²⁺ cations can be attributed to six shorter Ca–O bond lengths, which are also observed in other Ca²⁺-containing borates, such as YCa₃(VO)₃(BO₃)₄ (2.44),²⁴ Rb₂Ca₃B₁₆O₂₈ (2.29), and Cs₂Ca₃B₁₆O₂₈ (2.30).²⁵The structure of Ba₄Ca(B₂O₅)₂F₂ is shown in Fig. 1. In the structure, the plane B(1,3)₂O₅ dimer is first connected with four CaO₆ octahedra, meanwhile, each CaO₆ octahedron is also linked by four B(1,3)₂O₅ dimers through sharing their four equatorial O atoms to form a unique planar pentagonal [Ca(B₂O₅)]_∞ layer in the b–c plane (Fig. 1a, b). Then, these [Ca(B₂O₅)]_∞ layers are further linked by the twisted B(2,4)₂O₅ dimers to construct a 3D framework with Ba²⁺ cations maintaining the charge balance (Fig. 1c). Remarkably, for the arrangements of the Ba²⁺ cations and the F⁻ anions, the fluorine-centered SBU FBa₄ polyhedra are linked to construct the 2D [F₂Ba₄] infinite layer (Fig. S5b^†) with the same orientation, which further fills the apertures in the [Ca(B₂O₅)₂] framework (Fig. S5c^†). The existence of fluorine-centered SBUs would certainly have a strong influence on the local coordinate environments, and finally on the whole structure.²⁶Open in a separate windowFig. 1(a) The [Ca(B₂O₅)] layer is composed of B₂O₅ dimers and CaO₆ octahedra. (b) The planar pentagonal topology layer. The comparison of structures between (c) Ba₄Ca(B₂O₅)₂F₂ and (d) KBBF.It is very interesting that Ba₄Ca(B₂O₅)₂F₂ contains a planar pentagonal [Ca(B₂O₅)]_∞ layer, which is similar to the [Be₂BO₃F₂]_∞ layer in KBBF. The structural evolution from KBBF to Ba₄Ca(B₂O₅)₂F₂ is also shown in Fig. 1c and d. In KBBF, the BBUs are the planar BO₃ triangles, which are connected with BeO₃F in the a–b plane by strong covalent bonds to form the [Be₂BO₃F₂]_∞ layers (Fig. S6c^†) and the [Be₂BO₃F₂]_∞ layers have achieved excellent NLO properties of the KBBF crystal.⁷ However in Ba₄Ca(B₂O₅)₂F₂, the BO₃ triangles are changed into the B₂O₅ dimers, and the BeO₃F tetrahedra are substituted by the CaO₆ polyhedra. These B₂O₅ dimers are also connected by the CaO₆ polyhedra to form the interesting planar pentagonal [Ca(B₂O₅)]_∞ layer (Fig. S6d^†). More importantly, in KBBF, the adjacent [Be₂BO₃F₂]_∞ layers are connected by the weak K⁺-F⁻ ionic bonds that results in the strong layer habit of the KBBF crystals, whereas in Ba₄Ca(B₂O₅)₂F₂, the [Ca(B₂O₅)]_∞ layers are bridged by the strong covalent B–O bonds to form a stable 3D framework, which will greatly overcome the layering tendency of the KBBF crystal and facilitate the crystal growth.In addition, we also notice that the planar pentagonal [Ca(B₂O₅)]_∞ layer maybe helpful for enhancing the SHG responses of pyro-borates because small SHG responses of pyro-borates are attributed to the typical twisted configurations of the B₂O₅ groups, which are unfavorable for forming the π-conjugation and the superposition of the microscopic SHG response. For example, α-Li₄B₂O₅, a DUV transparent pyro-borate with sole B₂O₅ units as the BBUs, has a weak SHG response, which may be derived from the twisted B₂O₅ groups and non-planar arrangements (Fig. S7a^†). However, in Ba₄Ca(B₂O₅)₂F₂, the planar configuration of the pentagonal layers can assist the B₂O₅ groups to adopt a nearly coplanar arrangement (Fig. S7b^†) and effectively enhance the π-conjugation of B₂O₅ groups. The better π-conjugation of the planar B₂O₅ groups in the planar pentagonal [Ca(B₂O₅)]_∞ layer has also been confirmed by the electron orbital calculation based on the first-principles calculations.²⁷ The calculated result is shown in Fig. 2. Clearly, the prominent conjugated interactions are observed in the nearly coplanar B(1,3)₂O₅ dimers of Ba₄Ca(B₂O₅)₂F₂ (Fig. 2a), whereas it does little in the twisted B(2,4)₂O₅ dimers of Ba₄Ca(B₂O₅)₂F₂ (Fig. 2b) and two types of twisted B₂O₅ dimers in α-Li₄B₂O₅ (Fig. 2c and d). It can be expected that the nearly coplanar B₂O₅ dimers are more conducive to the large SHG response than the twisted B₂O₅ dimers. Remarkably, the similar pentagonal layers are also observed in other pyro-phosphates, such as Ba₂NaClP₂O₇, K₂Sb(P₂O₇)F, Rb₃PbBi(P₂O₇)₂, and Rb₃BaBi(P₂O₇)₂. Clearly, as pyro-phosphates are the non-π-conjugated systems, the planar pentagonal layers are only helpful for the orientation of anion groups.^28–31 However, they cannot form the better π-conjugation. Therefore, the better π-conjugation of the nearly coplanar B₂O₅ groups in planar pentagonal layers of pyro-borate Ba₄Ca(B₂O₅)₂F₂ would have a different contributing mechanism to the SHG effect with other non-π-conjugated pyro-phosphates.Open in a separate windowFig. 2The orbitals of the nearly coplanar B(1,3)₂O₅ (a) and twisted B(2,4)₂O₅ dimers (b) in Ba₄Ca(B₂O₅)₂F₂. The orbitals of two twisted B₂O₅ dimers (c and d) in α-Li₄B₂O₅.The presence of BO₃ triangles in Ba₄Ca(B₂O₅)₂F₂ is confirmed by the IR spectral measurements (Fig. S8^†). The peaks at 1362 cm⁻¹ and 1208 cm⁻¹ can be attributed to the asymmetric stretching of BO₃ groups.³² A strong band at 1069 cm⁻¹ in the IR spectrum may be associated with the stretching vibration of B–O–B in B₂O₅.^33,34 The weak absorption bands at 950, and 810 cm⁻¹ correspond to the symmetrical stretching vibrations of BO₃ and B–O–B in B₂O₅, respectively. The peaks at 751 and 615 cm⁻¹ can be attributed to the out-of-plane bending of the BO₃ groups.³⁴ Further, the UV-vis-NIR diffuse reflectance spectrum was also measured (Fig. S9^†), which shows that Ba₄Ca(B₂O₅)₂F₂ is transparent down to the DUV region with a UV cut-off edge less than 190 nm (corresponding to a large band gap of 6.2 eV), which is comparable to the newly developed NLO-active borates, such as RbB₃O₄F₂ (<190 nm), CsZn₂BO₃X₂ (X₂ = F₂,Cl₂, and FCl)) (<190 nm) and so on.^35–38 The short cut-off edge demonstrates the potential application of Ba₄Ca(B₂O₅)₂F₂ as a DUV NLO crystal.As Ba₄Ca(B₂O₅)₂F₂ crystalizes in the NCS space group P2₁, it possesses the SHG response, which was measured by the Kurtz-Perry method with the well-known NLO material KH₂PO₄ (KDP) as a reference.³⁹ As shown in Fig. 3, the SHG intensities of Ba₄Ca(B₂O₅)₂F₂ increase with the increase of particle sizes, indicating that Ba₄Ca(B₂O₅)₂F₂ is type-I phase-matchable. The SHG intensity of Ba₄Ca(B₂O₅)₂F₂ at the particle size of 150–212 μm is about 2.2 times that of KDP, and is larger than that of KBBF (1.2 × KDP) or comparable with those newly reported UV NLO crystals, i.e. γ-Be₂BO₃F (2.3 × KDP),⁶ β-Rb₂Al₂B₂O₇ (2 × KDP),⁴⁰ Li₄Sr(BO₃)₂ (2 × KDP),⁴¹ CsB₄O₆F(∼1.9 × KDP).² In addition, as we know, the SHG response of Ba₄Ca(B₂O₅)₂F₂ is the largest among all the known DUV transparent borates with B₂O₅ units (Table S4^†). Its SHG response (2.2 × KDP) is about seven times larger than that of α-Li₄B₂O₅ (0.3 × KDP), another DUV transparent pyro-borate with sole B₂O₅ units.Open in a separate windowFig. 3(a) Phase-matching curve, i.e., particle size vs. SHG intensity, data for Ba₄Ca(B₂O₅)₂F₂ and KH₂PO₄ (KDP) as reference. The solid curve is a guide for the eye, not a fit to the data. (b) Oscilloscope traces showing SHG intensities for Ba₄Ca(B₂O₅)₂F₂ and KDP.To understand the origin of the excellent optical properties of Ba₄Ca(B₂O₅)₂F₂, we also carried out the first-principles calculations.²⁷ It shows that Ba₄Ca(B₂O₅)₂F₂ has an indirect band gap of 6.34 eV (Figures S10a^†), which is in accordance with the experimental results. The valence band maximum (VBM) of Ba₄Ca(B₂O₅)₂F₂ is mainly composed of the orbitals in Ba, and O atoms, while the conduction band minimum (CBM) is dominantly composed of the orbitals in Ba, B, and O atoms. Therefore, the band gap of Ba₄Ca(B₂O₅)₂F₂ is mainly determined by Ba atoms and B₂O₅ groups. Based on the calculated electron structure, the NLO coefficients of Ba₄Ca(B₂O₅)₂F₂ are also calculated. The largest NLO coefficient of Ba₄Ca(B₂O₅)₂F₂ is d₂₂ = −0.524 pm V⁻¹, which is about 5 times lower than that of α-Li₄B₂O₅ (d₂₄ = −0.102 pm V⁻¹) (Table S5a^†), which is matched with the experimental one. Further, the SHG-weighted density maps of Ba₄Ca(B₂O₅)₂F₂ are shown in Fig. 4. These reveal that B₂O₅ dimers make the dominant contribution (72.7%) to the total SHG effect (Table S5b^†). The band-resolved SHG analysis can also conclude that B–O orbitals in Ba₄Ca(B₂O₅)₂F₂ contribute more to the SHG response than those in α-Li₄B₂O₅ (Fig. S10b, S10c^†), indicating that the arrangements of B₂O₅ dimers in Ba₄Ca(B₂O₅)₂F₂ is more beneficial for the large SHG response. And different from α-Li₄B₂O₅, F-centered secondary building units (SBUs) exist in the structure of Ba₄Ca(B₂O₅)₂F₂, and they are further linked to construct 2D [F₂Ba₄]_∞ infinite layers, which could help B₂O₅ groups arrange in a planar pattern (Fig. S5^†).²⁶ So, based on the above analysis, we can conclude that the nearly coplanar B₂O₅ dimers in the planar pentagonal layer and the SBU FBa₄ tetrahedra make a significant contribution to the SHG response of Ba₄Ca(B₂O₅)₂F₂.Open in a separate windowFig. 4The SHG-weighted density maps of the virtual electron process (a) and virtual hole process (b) of d₂₂ for Ba₄Ca(B₂O₅)₂F₂.     

(Ba6O)(ReN3)2: Synthesis,Crystal Structure and Physical Properties

The reaction of a mixture of barium and rhenium (3:1) at 850 °C under flowing nitrogen yielded the nitride‐oxide (Ba₆O)(ReN₃)₂ (R (No. 148); a = 8.1178(2) Å, c = 17.5651(4) Å; V = 1002.43(5) Å³; Z = 6). According to a structure refinement on X‐ray powder diffraction data, this compound is isostructural to a recently described nitride‐oxide of osmium of analogous composition. The structure consists of sheets of trigonal ReN₃ units and trigonal antiprismatic Ba₆O groups. The Ba–O distance of 2.73 Å is close to the sum of the respective ionic radii. The trigonal ReN₃^5– nitride anion displays a Re–N bond length of 1.94 Å, and is planar within the limits of experimental error. The constitution of the anion was confirmed by IR and Raman spectroscopy. The nitride‐oxide is stable up to 1000 °C, semiconducting (σ = 4.57 × 10^–3 Ω^–1 · cm^–1 at RT), and paramagnetic down to 25 K. A Curie–Weiss analysis resulted in a magnetic moment of μ = 0.68 μ_B per rhenium atom.     

Molybdänhalogenidcluster mit zwei terminalen Alkoholatliganden: Synthese und Kristallstrukturen von (C18H36N2O6Na)2[Mo6Cl12(OCH3)2] und (C18H36N2O6Na)2[Mo6Cl12(OC15H11)2] · 2C4H6O3

Molybdenum(II) Halide Clusters with two Alcoholate Ligands: Syntheses and Crystal Structures of (C₁₈H₃₆N₂O₆Na)₂[Mo₆Cl₁₂(OCH₃)₂] and (C₁₈H₃₆N₂O₆Na)₂[Mo₆Cl₁₂(OC₁₅H₁₁)₂] · 2C₄H₆O₃ . Reaction of Mo₆Cl₁₂ with two equivalents of sodium methoxide in the presence of 2,2,2-crypt yields (C₁₈H₃₆N₂O₆Na)₂[Mo₆Cl₁₂(OCH₃)₂] ( 1 ), which can be converted to (C₁₈H₃₆N₂O₆Na)₂[Mo₆Cl₁₂(OC₁₅H₁₁)₂] · 2C₄H₆O₃ ( 2 ) by metathesis with 9-Anthracenemethanole in propylene carbonate. As confirmed by X-ray single crystal structure determination ( 1 : C2/m, a=25.513(8) Å, b=13.001(3) Å, c=10.128(3) Å, β=100.204(12)°; : C2/c, a=15.580(5) Å, b=22.337(5) Å, c=27.143(8) Å, β=98.756(10)°) the compounds contain anionic cluster units [Mo₆ClCl(OR^a)₂]^2? with two alcoholate ligands in terminal trans positions ( 1 : d(Mo—Mo) 2.597(2) Å to 2.610(2) Å, d(Mo—Clⁱ) 2.471(3) Å to 2.493(4) Å, d(Mo—Cl^a) 2.417(8) Å and 2.427(8) Å, d(Mo—O) 2.006(13) Å; 2 : d(Mo—Mo) 2.599(3) Å to 2.628(3), d(Mo—Clⁱ) 2.468(8) Å to 2.506(7) Å, d(Mo—Cl^a) 2.444(8) Å and 2.445(7) Å, d(Mo—O) 2.012(19) Å).     

Über hexagonale Perowskite mit Kationenfehlstellen. XXVI. Ba12Ba2 2/3M 1/3□2O33□3 (MV = Nb,Ta) – die ersten Stapelvarianten eines rhomboedrischen 36 L-Typs

On Hexagonal Perovskites with Cationic Vacancies. XXVI. Ba₁₂Ba_{2 2/3}M _1/3□₂O₃₃□₃ (M^V = Nb, Ta) – the First Stacking Polytypes of a Rhombohedral 36 L-Type In the systems BaO? MO₅(M^V = Nb, Ta) for a Ba:M^V ratio of 2:1 polymorphism is observed. Here the low temperature modifications are described. They crystallize in a rhombohedral 36 L structure with three formula units Ba₁₂Ba_{2 2/3}M _1/3□₂O₃₃□₃ for the trigonal setting (M^V = Nb: a = 5.92₂ Å; c = 93.₂₅ Å; Ta: a = 5,92₂ Å; s = 93.4 Å).     

Über Verbindungen des Typs Ba2BIIIOsVO6

Compounds of Type Ba₂B^IIIOs^VO₆ The black perovskites of type Ba₂B^IIIOs^VO₆ crystallize cubic (B^III ? Pr, Nd, Sm—Lu, Y) and rhombohedral (B^III ? La) respectively; the cell volumina decrease linearily with (r_BIII)³. Intensity calculations on powder data for Ba₂YOsO₆ (space group Fm3m—O) and Ba₂LaOsO₆ (space group R3m—D) gave the intensity related R′ values of 4.6% and 5.0% respectively. The results of the vibrational spectroscopic investigations are reported in common with the bond orders, M? O distances and mean amplitudes and compared with the corresponding values of the series Ba₂B^IIIIr^VO₆ and Ba₂B^IIIRu^VO₆.     

Zur Kenntnis von Ba6La2Co4O15

About Ba₆La₂Co₄O₁₅ Ba₆La₂Co₄O₁₅ were prepared and investigated by X-ray single crystal work. It crystallizes with hexagonal symmetry, space group C–P6₃mc; a = 11.8082; c = 7.0019 Å; Z = 2. Ba²⁺ show face connected BaO₆-octahedra and larger polyhedra of C.N. = 10 and 12. Co³⁺ is surrounded by four and six (tetrahedra, octahedra) oxygen. The Ba²⁺ and La³⁺ ions occupy one point position statistically.     

Über Sauerstoffperowskite des fünfwertigen Rutheniums ABIIIRuVO6 mit AII = Ba,Sr

On Oxygen Perovskites with Pentavalent Ruthenium A B^IIIRu^VO₆ with A^II = Ba, Sr The perovskites Ba₂B^IIIRu^VO₆ with B^III = La, Nd, Sm, Eu, Gd, Dy, Y, are cubic (B^III = La: a = 8,54₄ Å; Y: a = 8,33₇ Å); with a partial order for B^III and Ru^V. The Sc compound, Ba₂ScRuO₆, has a hexagonal 6 L structure (a = 5.79₅ Å; c = 14.22₉ Å; sequence (hcc)₂)₂. The lattice of the Sr perovskites, Sr₂B^IIIRu^VO₆, with B^III = Eu, Gd, Dy, Y is rhombic distorted. The IR and FRI spectra are discussed.     

Die Kristallstruktur der Hexagonalen Verbindungen BaMeIISbO9. II. Ba3CuSb2O9

Crystal Structure of the Hexagonal Compounds Ba^II₃Me^IISb^v₂O₉. II. Ba₃CuSb₂O₉ The crystal structure of the compound Ba₃CuSb₂O₉ was determined from single crystal X-ray diffraction data and refined down to R = 0.03. Ba₃CuSb₂O₉ crystallizes in the hexagonal space group P6₃mc (C) with a = b = 5.809 Å, C = 14.321 Å and Z = 2. The structure can be described by close–packed BaO₃ layers in the sequence cchcchcch…?(hex. BaTiO₃ type). Groups of two octahedra with common faces are connected by SbO₆ octahedra via common corners. They are occupied alternately by Cu and Sb. In agreement with the EPR spectra the CuO₆-octahedra present no static Jahn-Teller distortion at room temperature. However the thermal ellipsoids of the oxygen atoms indicate the presence of adynamic Jahn-Teller-effect.     

Über Das System Ba2Gd2/3□1/3U1−xWxO6 sowie hexagonale Perowskite vom 18-

On the System Ba₂Gd_2/3□_1/3U_1?xW_xO₆ and Hexagonal Perovskites of an 18-Layer Type In the system Ba₂Gd_2/3□_1/3U_1?xW_xO₆ the formation of a continuous solid solution series is observed. With x ? 0.9 the mixed crystals have a cubic 1:1 ordered perovskite structure. With x ≥ 0.95 the compounds are polymorphic: besides an cubic 1:1 ordered perovskite type for x = 0.95; 0.99 and 1.00 one hexagonal layer structure exists. This lattice is in all cases rhombohedral (space group R3 m) and represents an 18 L-type. Likewise the compounds Ba₂B□_1/3W^VIO₆ with B^III = Tb-Lu and Y belong to the 18 L-type.     

CuTb[B5O10]: Das erste „Metaborat”︁ mit einem [B5O10]5− -Anion

CuTb[B₅O₁₀]: The first “Metaborate” with a [B₅O₁₀]^5? Anion Single crystals of the new compound CuTb[B₅O₁₀] were obtained by a B₂O₃ flux-technique. They crystallize in a so far unknown structure. X-ray investigations on single crystals led to the space group C–I ba2 (Nr. 45); a = 6.294(1) Å; b = 8.406(8) Å; c = 12.733(2) Å; Z = 4. The structure contains [B₅O₁₀]^5? chains isolated from each other. These chains include twelf membered rings of boron and oxygen. Each ring consists of two tetrahedral BO₄ and two planar B₂O₅ groups and is connected with the next one via the BO₄ units. Tb³⁺ is eightfold- and Cu²⁺ elongated octahedraly coordinated by oxygen.     

Über hexagonale Perowskite mit Kationenfehlstellen. VII. Schwingungsspektroskopische Untersuchungen an rhomboedrischen 12 L-Stapelvarianten vom Typ Ba4BII(Re2 □ O12) and Ba4B □1/3 (Re2 □ O12)

On Hexagonal Perovskites with Cationic Vacancies. VII. Vibrational Spectroscopie investigations on the Rhombohedral 12 L-Stacking Polytypes Ba₄B^II(Re₂□O₁₂) and Ba₄B □_1/3 (Re₂ □ O₁₂) For the rhombohedral 12 L stacking polytypes Ba₄B^II(Re₂□O₁₂) and Ba₄B□_1/3(Re₂□O ₁₂), space group R3 m, sequence (3)(1), the lattice consists of groups of three face sharing octahedra with the composition Re₂□O₁₂. They are isolated from each other by the Ba and B ions.The vibrational spectra are interpreted according to the factor group analysis. For the Re₂□O₁₂ unit (symmetry D_3d) the results of a complete vibrational analysis and the calculation of the force constants are reported.     

Cadmium in tetragonal pyramidaler Koordination im Barium-Cadmium-Oxovanadat: Ba2Cd3(VO4)2(V2O7)

Cadmium in Square Pyramids of Oxygen in the Barium Cadmium Oxovanadate: Ba₂Cd₃(VO₄)₂(V₂O₇) Single crystals of Ba₂Cd₃(VO₄)₂(V₂O₇) have been prepared by crystallization of a melt of BaCO₃, CdO and V₂O₅. It shows orthorhombic symmetry, space group D? P2₁2₁2₁, a = 7.206(2), b = 9.978(1), c = 19.617(3) Å, Z = 4. The crystal structure is characterized by (VO₄)^3? and (V₂O₇)^4? groups, CdO₆ octahedra, BaO₁₂ and BaO₉ polyhedra and with respect to Cd containing oxides unusual square pyramids of O^2? around Cd²⁺. The observed [CdO₄] zickzack chains are connected by VO₄ tetrahedra, V₂O₇ double tetrahedra and CdO₅ pyramids, forming a tunnel structure along [100]. The tunnels are filled by barium.     

The Mixed Valence Tungsten(IV,V) Compound Na[W2O2Br6]

The reaction of W₆Br₁₂, NaBr, and WO₂Br₂ in the presence of Br₂ in a sealed silica tube yields Na[W₂O₂Br₆] together with WOBr₄ and WO₂Br₂ in the low temperature zone (temperature gradient 1030/870 K). Na[W₂O₂Br₆] crystallizes orthorhombically in the space group Immm (no. 71) with a = 3.775 Å, b = 10.400 Å, c = 13.005 Å and Z = 2. Pairs of condensed trans-[WO₂Br₄] octahedra with a common Br₂ edge form along [100] double chains [W₂O_4/2Br₆]^1– via the oxygen atoms. The mixed valent tungsten atoms are bonded to W₂ pairs with a 2 c–3 e bond (d(W–W) = 2.946 Å, d(W–O) = 1.888 Å, d(W–Br^b) = 2.537 Å, d(W–Br^t) = 2.535 Å, ∢O–W–O = 177.4°, ∢Br^b–W–Br^b (endocyclic) = 109.0°). The Na⁺ cations connect the anionic double chains to form two-dimensional layers parallel (001), which interact by van der Waals forces. The cations are eightfold coordinated by a cube of the terminal Br^t ligands of the polymeric anions (d(Na–Br) = 3.138 Å). Na[W₂O₂Br₆] may be discussed as an intercalation compound of the oxide bromide WOBr₃.     

LixNayBa14LiN6: New Representatives of the Subnitride Family

Three new metal‐rich phases, Li₄Na₁₁Ba₁₄LiN₆, Li₅Na₁₀Ba₁₄LiN₆ and Na₁₄Ba₁₄LiN₆ have been prepared and their crystal structure determined. According to single crystal and powder X‐ray diffraction data, all compounds crystallize with cubic unit cells (Li₄Na₁₁Ba₁₄LiN₆: , a = 17.874(2) Å, Z = 4, V = 5710(1) ų; Li₅Na₁₀Ba₁₄LiN₆: , a = 17.799(1) Å, Z = 4, V = 5638.7(6) ų; Na₁₄Ba₁₄LiN₆: , a = 17.7955(5) Å, Z = 4, V = 5635.6(2) Å). The last mentioned compound crystallizes in the Na₁₄Ba₁₄CaN₆ type, and both Li₄Na₁₁Ba₁₄LiN₆ and Li₅Na₁₀Ba₁₄LiN₆ have related structures. These compounds open a series of metal‐rich Ba nitrides, containing the new Ba₁₄LiN₆ cluster.