Unknown Structure Type Research Articles

Targeted Discovery of Low-Coordinated Crystal Structures via Tunable Particle Interactions

Particles interacting via isotropic, multiwell pair potentials have been shown to self-assemble into a range of crystal structures, yet how the characteristics of the underlying interaction potential give rise to the resultant structure remains largely unknown. We have thus developed a functional form for the interaction potential in which all features can be tuned independently. We perform continuous parameter space searches by systematically changing pairs of parameters, controlling the various features of the interaction potential. By enforcing a repulsive first well (controlling particle interactions of the first neighbor shell), we stimulate the formation of low-coordinated assemblies. We report the self-assembly of 20 previously unknown crystal structure types, 14 of which have low coordination numbers. Despite limiting the search to a small region of the vast parameter space of possible particle interactions, a wealth of complexity and symmetry is apparent within these crystal structures, which include clathrates with empty cages and low-symmetry structures. Our findings suggest that an unknown number of previously undiscovered crystal structure configurations are possible through self-assembly, which can serve as interesting design targets for soft condensed matter synthesis.

An Efficient Access to 5‐(1,2,3‐Triazol‐1‐yl)isoxazoles – Previously Unknown Structural Type of Triazole‐isoxazole Hybrid Molecule

AbstractSince isoxazole and triazole have significant applications in pharmaceutical chemistry, the synthesis of hybrid isoxazole‐triazole molecules has attracted great attention. In the present study, an efficient method for the synthesis of 5‐azidoisoxazoles has been developed via chemoselective nitro‐group substitution of 3‐EWG‐5‐nitroisoxazoles with sodium azide through the aromatic nucleophilic substitution reaction. The resulting 5‐azidoisoxazoles are employed in CuACC‐reaction with a variety of alkynes, providing a straightforward approach for the synthesis of previously unknown structure type of biologically relevant 5‐(1,2,3‐triazol‐1‐yl)isoxazoles. Both reactions proceed with excellent yields and functional group tolerance under mild conditions.

2D crystal structure and anisotropic magnetism of GdAu6.75−xAl0.5+x (x ≈ 0.54)

Exploration of the gold-rich part of the ternary Gd–Au–Al system afforded the intermetallic compound GdAu6.75−xAl0.5+x (x ≈ 0.54) which was structurally characterized by single crystal X-ray diffraction (Pnma, a = 18.7847(4) Å, b = 23.8208(5) Å, c = 5.3010(1) Å). GdAu6.75−xAl0.5+x crystallizes in a previously unknown structure type featuring layers of Gd2(Au, Al)29 and Gd2(Au, Al)28 clusters which are arranged as in a close-packing parallel to the ac plane. The Gd substructure corresponds to slightly corrugated 36 nets (dGd–Gd = 5.30–5.41 Å) which are stacked on top of each other along the b direction with alternating short (5.4, 5.6 Å, within layers) and long distances (6.4 Å, between layers). The title compound has been discussed with respect to a quasicrystal approximant (1/1 AC) GdAu5.3Al in the same system. The magnetic properties of GdAu6.75−xAl0.5+x were found to be reminiscent to those of some ternary ACs, with sharp peaks in the temperature dependent magnetization, and metamagnetic-like transitions. The material becomes antiferromagnetic below 25 K; magnetometry results suggest that the antiferromagnetic state is composed of ferromagnetic ac planes, coupled antiferromagnetically along the b direction.

Research on Coil Identification Algorithm of Wireless Power Transfer System Based on Magnetic Field Features

In the practical application of wireless power transfer (WPT), the identification of the secondary coil and the analysis of the space magnetic field of the coil will affect the matching scheme of the coil, which will further affect the performance of energy transmission. At present, the establishment of the coil space magnetic field model mainly adopts the finite element method (FEM). The accuracy of the results is limited by the computer performance and the specific settings during calculation, which usually takes a long time. Additionally, it can only analyze and establish the space magnetic field of the coil with specific parameters. Especially when the coil structure and parameters change, it is difficult to quickly establish the spatial magnetic field. This paper presents a secondary side coil identification method of a wireless charging system based on the magnetic field cloud image characteristics. The image feature extraction algorithm is used to extract features of a certain height magnetic field cloud image of an unknown structure type coil obtained by FEM. Further, by matching with the characteristics of the magnetic field cloud image of the known coil, the identification of the unknown coil structure type is realized. The effectiveness and accuracy of the proposed method is verified by an example. This algorithm is helpful to extract the characteristics of the coil space magnetic field, and can establish coil space magnetic field models with different structure types and different coil parameters combined with deep learning to guide the matching scheme of the primary and secondary coils, and realize efficient energy transmission.

CRYSTAL STRUCTURES OF POLYNUCLEAR ANTIMONY BROMIDECOMPLEXES (Et(n-Pr)3N)3[Sb3Br12] AND (2,2′-bipyH)4[Sb4Br20

Trinuclear (Et(n-Pr)3N)3[Sb3Br12] (1) and tetranuclear (2,2′-bipyH)4[Sb4Br20] (2) bromoantimonates(III) are obtained by the reaction of solutions of bromides of the respective organic cations and Sb2O3 in HBr. The structures of 1 and 2 are studied by single crystal XRD. The [Sb3Br12]3– (1) anions belong to a previously unknown structure type of halide Sb(III) complexes.

Investigation on the 773 K Isothermal Section of the Er-Ni-Si Ternary Phase Diagram by X-ray Powder Diffraction

The isothermal section phase diagram of Er-Ni-Si ternary system at 773 K was created by x-ray powder diffraction (XRD) analysis in this paper. Seventeen known ternary compounds ErNiSi, ErNi2Si2, ErNiSi2, Er2Ni3Si5, ErNiSi3, Er3Ni6Si2, ErNi10Si2, Er3NiSi2, ErNi2Si, ErNi5Si3, ErNi4Si, ErNi6Si6, Er33.3Ni18.7−10.7Si48−56 (Er2NiSi3), Er3Ni2Si4, Er33.3Ni8.7−4.7Si58−62 (Er4NiSi7), Er8Ni31Si11, and Er5Ni2Si3 (unknown structure type, similar to Dy5Ni2Si3) have been testified. A new compound Er37Ni3Si60 (unknown structure type) has been confirmed by excluding its XRD pattern as a superposition of nearby phase patterns. Part diffraction peaks have obvious movement with the change of Si content in Er2NiSi3 solid solution, and more moving directions are not consistent, especially at (002) and (110) planes. At the same time, quasi–binary solid solutions were detected in Er2Ni17−xSix, ErNi5−xSix, Er2Ni7−xSix, ErNi3−xSix, ErNi2−xSix, ErNi−xSix, and ErSi−xNix compounds. Other binary compounds of the Er-Ni-Si system do not show any visible solubility of the third element. If the mixture of α-ErSi2 and β-ErSi2 phases is regarded as one ErSi2 phase, the 773 K isothermal section of the phase diagram of Er-Ni-Si system consists of 55 three phase regions and ten solid solution lines.

BaCuSiTe3: A Noncentrosymmetric Semiconductor with CuTe4 Tetrahedra and Ethane-like Si2Te6 Units.

BaCuSiTe3 was prepared from the elements in a solid-state reaction at 973 K, followed by slow cooling to room temperature. This telluride adopts a new, hitherto unknown structure type, crystallizing in the noncentrosymmetric space group Pc with a = 7.5824(1) Å, b = 8.8440(1) Å, c = 13.1289(2) Å, β = 122.022(1)°, and V = 746.45(2) Å3 (Z = 4). The structure consists of a complex network of two-dimensionally connected CuTe4 tetrahedra and ethane-like Si2Te6 units with a Si-Si bond. This semiconducting material has an optical band gap of 1.65 eV and a low thermal conductivity of 0.50 W m-1 K-1 at 300 K. Calculations of its optical properties revealed a moderate birefringence of 0.23 and a second-order harmonic generation response of deff = 3.4 pm V-1 in the static limit.

The First Quinary Rare Earth Thiophosphates: Cs5Ln3X3(P2S6)2(PS4) (Ln = La, Ce, X = Br, Cl) and the Quasi‐Quaternary Cs10Y4Cl10(P2S6)3

We report the first examples of quinary rare earth thiophosphates with a fully ordered cation and anion distribution, Cs5Ln3X3(P2S6)2(PS4), (Ln = La, Ce and X = Br, Cl) as well as the quasi‐quaternary Cs10Y4Cl10(P2S6)3. These four new compounds crystallize in three different, unknown structure types. The yellowish, transparent, brittle Cs5Ce3Br3(P2S6)2(PS4) crystallizes in the orthorhombic space group Pnma (no. 62) with a = 13.276(3), b = 14.891(3), c = 19.593(4) Å, and V = 3873(1) Å3 in a novel structure type. Colorless crystals of Cs5La3Br3(P2S6)2(PS4) and Cs5La3Cl3(P2S6)2(PS4) are isotypic and were obtained in the monoclinic space group P21/m (no. 11) with a = 9.715(2), b = 14.310(3), c = 13.685(3) Å, β = 100.16(3)° and V = 1873(1) Å3 and a = 9.513(2), b = 14.182(3), c = 13.699(3) Å, β = 99.39(3)° and V = 1823(1) Å3, respectively. Both structures contain isolated hexathiohypodiphosphate(IV) [P2S6]4– and thiophosphate [PS4]3– units that are arranged alternately in layers. Cs10Y4Cl10(P2S6)3 crystallizes in colorless transparent platelets in the orthorhombic space group Pnnm (no. 58) with a = 13.153(3), b = 28.964(6), c = 7.780(2) Å, and V = 2964(1) Å3. The structure is composed of isolated [P4/2S6]4– octahedra containing four half occupied P positions surrounded octahedrally by sulfur. We show with Raman scattering that this disordered thiophosphate anion shows a Raman spectrum that is distinct from spectra published for other literature‐known thiophosphate anions.

ScPd2Al3 – New polymorphic phase in Al-Pd-Sc system

We have discovered a new compound of the composition ScPd2Al3 crystallizing in unknown structure type. Moreover, ScPd2Al3 reveals polymorphism. We have found an orthorhombic crystal structure at room temperature and a high temperature cubic phase. The polymorphic phases are separated by a reversible first order transition at 1053°C with a hysteresis of 19°C. ScPd2Al3 exists as a very stable intermetallic phase just in the vicinity of the icosahedral quasicrystal Tsai-type i-phase Al54Pd30Sc16.

Structural Characterization of Intermetallic Compounds by 27Al Solid State NMR Spectroscopy.

Intermetallic compounds are of broad interest for solid state chemists, condensed matter physicists, and material scientists due to their intriguing crystal chemistry, their physical properties, and their potential applications, ranging from lab curiosities to everyday objects. To characterize and understand the properties of new compounds and novel materials, the availability of structural information, particularly single-crystal X-ray diffraction data, is a mandatory prerequisite. Especially when it comes to the formation of compounds with deficient or mixed site occupancies, superstructures, or representatives crystallizing in other, thus far unknown structure types, a complementary method for structural analysis is of great value. Solid state nuclear magnetic resonance spectroscopy has been a valuable tool in many areas of chemistry, being an element-selective, site-specific, and inherently quantitative tool for detailed structural characterization. Magic-angle spinning conditions eliminate or reduce the effect of anisotropic interactions in the solid state, producing high-resolution spectra. Until recently, 27Al NMR studies of intermetallic aluminum compounds have been relatively sparse and mostly limited to binary systems. In this Account, we will summarize the current state of the art of high-resolution 27Al NMR in intermetallic compounds focusing on recent research efforts in our laboratories and the interpretation of NMR parameters in terms of the structural details of the compounds investigated. Besides theoretical aspects of 27Al NMR spectroscopy, short paragraphs on experimental details and the crystal chemistry of the discussed compounds are given. In the main part of this Account, we focus on three key aspects: (i) crystal structure validation, (ii) structural disorder and mixed site occupancies, and (iii) the electronic structure, all of which can be investigated by spectroscopic means. For the first part, we have chosen the ternary equiatomic compounds CaAuAl (TiNiSi type), BaAuAl (LaIrSi type), and Ba3Pt4Al4 (own type). Structural disorder and mixed site occupancies have been probed in the ScTAl series (T = Cr, Ru, Ag, Re) crystallizing in the TiNiSi, HfRhSn, and MgZn2-type structures. Also Na2Au3Al and the Heusler compounds, Sc(T0.5T'0.5)2Al (T = T' = Ni, Pd, Pt, Cu, Ag, Au), have been used for structure validation purposes, based on the number and signal area ratios of the resonances observed and on the comparison between experimental and theoretically calculated nuclear electric quadrupolar interaction parameters. Electronic structure information available from 27Al magnetic shielding will be discussed based on experimental data obtained for the RET5Al2 series (RE = Y, Lu; T = Pd, Pt), the extended RE10TAl3 series (RE = Y, Lu; T = Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt), and the ordered Heusler compounds ScT2Al (T = Ni, Pd, Pt, Cu, Ag, Au).

Flux synthesis, crystal structures, and physical properties of new lanthanum vanadium oxyselenides.

The new lanthanum vanadium oxyselenides LaVSe2O, La5V3Se6O7, La5V3Se7O5, La7VSe5O7, and La13V7Se16O15 were synthesized in eutectic NaI/KI fluxes, and their crystal structures were determined using single-crystal and powder X-ray diffraction experiments. LaVSe2O and La5V3Se6O7 adopt known structure types, whereas La5V3Se7O5, La7VSe5O7, and La13V7Se16O15 crystallize in hitherto unknown structure types. The main building blocks of these compounds are chains of edge-sharing VSe6, VSe5O, and/or VSe4O2 octahedra, linked together by edge-sharing OLa4 and/or OLa3V tetrahedra forming fluorite-like ribbons. LaVSe2O, La5V3Se7O5, and La7VSe5O7 contain only V(iii) ions, whereby La5V3Se6O7 and La13V7Se16O15 contain mixtures of either V(iii)/V(iv) or V(iii)/V(v) cations. Magnetic measurements indicate Curie-Weiss paramagnetism and magnetic ordering of the vanadium moments at low temperatures. More precisely, we observe antiferromagnetism for La5V3Se6O7, metamagnetism for La5V3Se7O5, ferromagnetism for La7VSe5O7 and a complex magnetic structure for La13V7Se16O15.

Single-crystal X-ray diffraction study of Cs2Er[Si6O14]F and Cs2Er[Si4O10

Abstract Single-crystal growth experiments in the system CsF-Er2O3-SiO2 resulted in the simultaneous crystallization of two chemically related compounds within the same run: Cs2Er[Si6O14]F (phase I) and Cs2Er[Si4O10]F (phase II). They represent the first examples for cesium erbium silicates containing fluorine. Basic crystallographic data are – phase I: space group Cmca, a=17.2556(6) Å, b=24.6565(7) Å, c=14.4735(5) Å, V=6157.9(3) Å3, Z=16; phase II: space group Pnma, a=22.3748(7) Å, b=8.8390(2) Å, c=11.9710(4) Å, V=2367.5(1) Å3, Z=8. The structures were determined by direct methods and refined to residuals of R(|F|)=0.0229 for 2920 (phase I) and 0.0231 for 2314 (phase II) independent observed reflections with I>2σ(I). The structure of phase I represents a previously unknown structure type with a three dimensional tetrahedral framework consisting of Q3 and Q4 groups in the ratio 2:1. Basic building units of the network are unbranched sechser single-chains running parallel to [001]. The network can be conveniently built up from the condensation of tetrahedral layers parallel to (010) or (100), respectively. The crystal structure of phase II can be classified as a tubular or columnar chain silicate indicating that the backbones of the structure are multiple chains of silicate tetrahedra. This structure is isotypic to a Cs2Y[Si4O10]F, a compound that has been characterized previously. Alternatively, both compounds can be described as mixed octahedral-tetrahedral frameworks, which can be classified according to their polyhedral microensembles. A topological analysis of both nets is presented.

Searching for “LiCrIIPO4”

The two new phosphates LiCrII4(PO4)3 and Li5CrII2CrIII(PO4)4 are discovered as equilibrium phases (ϑ=800°C) in the quarternary system Li/Cr/P/O. Their crystal structures have been determined from single-crystal X-ray diffraction data {LiCrII4(PO4)3: violet-blue, Pnma (no. 62), Z=4, a=6.175(1)Å, b=14.316(3)Å, c=10.277(2)Å, 100 parameters, R1=0.028, wR2=0.08, 2060 unique reflections with Fo>4σ(Fo); Li5CrII2CrIII(PO4)4: greyish-green, P1¯ (no. 2), Z=1, a=4.9379(7)Å, b=7.917(2)Å, c=8.426(2)Å, α=109.98(2)°, β=90.71(1)°, γ=104.91(1)°, 131 parameters, R1=0.022, wR2=0.067, 1594 unique reflections with Fo>4σ(Fo)}. Li5CrII2CrIII(PO4)4 adopts an hitherto unknown structure type. The crystal structure of LiCrII4(PO4)3 is isotypic to that of NaCdII4(PO4)3 and related to that of the mineral silicocarnotite Ca5(PO4)2(SiO4). Significant disorder between Li+ and Cr2+ is observed for both crystal structures. The oxidation states assigned to chromium in these two phosphates are in agreement with UV/vis/NIR absorption spectra and magnetic susceptibility data recorded for both compounds.Instead of “LiCrIIPO4” mixtures of LiCrII4(PO4)3, Li5CrII2CrIII(PO4)4, Cr2O3, and CrP are observed at equilibrium. Instead of “Li2CrIIP2O7” four-phase mixtures consisting of Li9CrIII3(P2O7)3(PO4)2, Li3CrIII2(PO4)3, LiCrP2O7, and CrP were obtained.

Unique seven-node rare-earth octacyanomolybdate(IV) three-dimensional molecular frameworks: {[Er(H2O)5(Er(H2O)4)3][Mo(CN)8]3·11H2O}n and {[Eu(H2O)5(Eu(H2O)4)3][Mo(CN)8]3·11H2O}n

The crystal structure analyses of {[Er(H2O)5(Er(H2O)4)3][Mo(CN)8]3·11H2O}n (1) and {[Eu(H2O)5(Eu(H2O)4)3][Mo(CN)8]3·11H2O}n (2), show that they are not only new neutral three-dimensional rare-earth octacyanomolybdate(IV) molecular frameworks, but that they also belong to an unknown structure type having seven different nodes. To the best of our knowledge this is different to any other known molybdenum(IV) octacyanide complexes published to date. Both compounds crystallize in the triclinic system, space group P-1, and are isostructural and isotypic. The coordination polyhedra of the molybdenum atoms in the three different [Mo(CN)8]4− anions are trigonal prisms, with two additional atoms. A new bridging mode for octacyanometallates is also observed with five of the eight cyanide groups involved in bridging either three or four rare-earth atoms, while the three remaining cyanide groups are terminal and are involved in hydrogen bonding. The four rare-earth atoms in 1 and 2 have different coordination polyhedra in the form of trigonal prisms with two additional atoms. The three-dimensional structures are made up of infinite two-dimensional slabs linked by one of the rare-earth metal atoms. In both compounds, apart from the 17 coordinated water molecules, there are 11 lattice water molecules of crystallization present in the cavities of the three-dimensional frameworks. The 28 water molecules and the terminal CN− groups are involved in an extensive O–H⋯O and O–H⋯N hydrogen bonding network.

The ternary system Au–Ba–Si: Clathrate solution, electronic structure, physical properties, phase equilibria and crystal structures

We report on (i) the phase relations at 800°C within the ternary system Au–Ba–Si up to 33.3at.% Ba, (ii) on the crystallographic data of new ternary compounds, (iii) on details of the clathrate type I solid solution, (iv) on electrical and thermal transport measurements for Ba8Au5.1Si40.9 supported by (v) density functional theory calculations. The clathrate type I solid solution Ba8AuxSi46−x at 800°C extends from Ba8Au4Si42 (a=1.039nm) to Ba8Au6Si40 (a=1.042nm). The cubic primitive symmetry (space group Pm3¯n) was confirmed by X-ray powder diffraction in the whole homogeneity region. The lattice parameters of the solid solution show an almost linear increase with increasing gold content and site preferences from X-ray refinement confirm that gold atoms preferably occupy the 6d site in random mixture with Si atoms. The phase equilibria at 800°C are characterized by seven ternary phases in the investigated region up to 33.3at.% Ba. The homogeneity range has been established for Ba(Au1−xSix)2 (AlB2 type, extending from BaAu0.4Si1.6 to BaAu0.9Si1.1). BaAu2+xSi2−x (unknown structure type) exhibits a very small homogeneity range (x=0.6–0.7) and two other ternary phases exist at about 22at.% Ba, 52at.% Au and 28at.% Si and 20at.% Ba, 58at.% Au and 22at.% Si (structure types for both unknown). The crystal structures of two further novel phases in the gold-rich part have been determined from single crystal X-ray data: BaAu3+xSi1−x of BaAu3Ge type (x=0–0.3, space group P4/nmm, x=0: a=0.6488(2), c=0.5305(2) nm) and BaAu5−xSi2+x (x=0–0.2, own structure type, space group Pnma, x=0: a=0.8935(2), b=0.6939(2), c=1.0363(2)nm). The proximity of Ba8AuxSi46−x to a metal to insulator transition is corroborated by density functional theory electronic structure calculations. A gap in the electronic density of states, located near the Fermi energy, gives rise to distinct features of the temperature-dependent electrical resistivity and Seebeck effect.

Superconductivity up to 35 K in the Iron Platinum Arsenides (CaFe1−xPtxAs)10Pt4−yAs8 with Layered Structures

We report the synthesis and crystal structures of three new superconducting iron-platinum arsenides (CaFe1-xPtxAs)10Pt4-yAs8 (x = 0-0.15, y = 0-0.4). The structures are stacking variants of FeAs- and slightly puckered Pt4-yAs8-layers with square coordinated platinum separated by calcium-layers, respectively. Arsenic atoms in the Pt4-yAs8-layers form (As2)4- dumbbells according to Zintl's concept, providing charge balance in (Ca2+Fe2+As3-)10(Pt2+)3[(As2)4-]4. Superconductivity was observed at 13-35 K. We suggest that the highest Tc above 30 K occurs in the 1048 phase with clean FeAs-layers that are indirectly electron-doped according to (Ca2+Fe2+As3-)10(Pt2+)4[(As2)4-]4*2e-. We also suggest that the lower critical temperatures occur in the 1038- and a-1048 phases due to Pt-doping at the Fe-site. DFT band structure calculations indicate that the contribution of the Pt4-yAs8-layers to the Fermi surface is small and that the Fermi energy is slightly either below or above a quasi-gap in the Pt-states. The new platinum-iron compounds represent the first iron-based superconductors with so far unknown structure types and can serve as a new platform for further studies that go beyond the known systems.

A new polymorph of Ba(AsO 3OH): Synthesis, crystal structure and vibrational spectra

A new monoclinic polymorph of Ba(AsO 3OH) was synthesized under hydrothermal conditions. It represents a previously unknown structure type. Its crystal structure was determined from a racemic twin using single-crystal X-ray diffraction data collected at 120 and 293 K [space group P2 1, a=7.2149(14)/7.2370(2), b=7.7028(15)/7.7133(2), c=21.7385(43)/21.8079(5) Å, β=95.95(3)/96.073(1)°, V=1201.6(4)/1210.51(5) ų, Z=12]. The crystal structure of P2 1-Ba(AsO 3OH) has a layered character and is built up of four types of regularly alternating layers parallel to (0 0 1). Every AsO 3OH tetrahedron is chelating to two Ba atoms and bridged by another two Ba atoms. Each OH group acts as hydrogen bond donor toward the oxygen atoms positioned in the same or adjacent layers. Although the H atoms could not be located, no ambiguities are present in the hydrogen-bonding scheme. Single-crystal vibrational spectroscopy (FTIR and Raman) was used to describe the vibrational behavior of the hydrogen bond system; particularly the spectroscopic manifestation of the very short and short hydrogen bonds (2.462(7)–2.575(7) Å). In order to complement spectroscopic data on protonated orthoarsenates, infrared spectra of triclinic F1¯-Sr(AsO 3OH) and the orthorhombic variety of Pbca-Ba(AsO 3OH) were recorded and discussed. Furthermore, structural features of other alkaline earth hydrogen arsenates are discussed.

Einfaches System, vielfältige Strukturen: Eine Neuuntersuchung der (Amin)halogenidosilber(I)-Komplexe/ A Simple System with many Structural Variants: A Reexamination of (Amine)halogenidosilver(I) Complexes

We report the structures of nineteen new amine silver halide complexes, some of them featuring previously unknown structure types, stoichiometries (such as L4Ag5X5) and coordination numbers. Known structures have been included and analysed for non-classical hydrogen bonds. We have identified three important factors for the formation of certain structure types. First, Ag-X bonds that form a central framework, typically staircase-shaped. Secondly, hydrogen bonds or other secondary interactions competing with these leading to a weakening or disappearance of some of the central Ag-X bonds. Finally, the polarity of the substituent at nitrogen and the silver halides influence the stoichiometry of the complex.

RbGa3S5 und CsGa3S5 – Zwei neue Strukturtypen

RbGa3S5 and CsGa3S5 – Two New Structure TypesThe title compounds RbGa3S5 and CsGa3S5 were synthesized by a solid state reaction starting from GaS, S and MN3 (M = Rb, Cs) as alkaline metal source. They crystallize in the space group P21/c with comparable lattice parameters but with completely different structures (RbGa3S5: a = 7,1530(6), b = 12,715(1), c = 10,1282(9) Å, β = 102,43(1)°, Z = 4; CsGa3S5: a = 10,6717(8), b = 12,763(1), c = 6,9265(6) Å, β = 91,168(9)°, Z = 4). In RbGa3S5 Rb together with S shows the topology of a hexagonal close packing in which Ga occupies 3/12 of the tetrahedral holes. The GaS4 tetrahedra are connected by common corners and edges forming a 3D‐network. The structure of CsGa3S5 is characterized by corrugated layers of edge‐ and corner‐sharing GaS4‐tetrahedra. Both compounds represent so far unknown structure types and thus two further structural alternatives for compounds with the composition MM3′Ch5.

Synthesis, crystal structure, infrared and Raman spectra of Sr 4Cu 3(AsO 4) 2(AsO 3OH) 4·3H 2O and Ba 2Cu 4(AsO 4) 2(AsO 3OH) 3

The two new compounds, Sr 4Cu 3(AsO 4) 2(AsO 3OH) 4·3H 2O (1) and Ba 2Cu 4(AsO 4) 2(AsO 3OH) 3 (2), were synthesized under hydrothermal conditions. They represent previously unknown structure types and are the first compounds synthesized in the systems SrO/BaO–CuO–As 2O 5–H 2O. Their crystal structures were determined by single-crystal X-ray diffraction [space group C2/ c, a=18.536(4) Å, b=5.179(1) Å, c=24.898(5) Å, β=93.67(3)°, V=2344.0(8) Å 3, Z=4 for 1; space group P4 2 /n, a=7.775(1) Å, c=13.698(3) Å, V=828.1(2) Å 3, Z=2 for 2]. The crystal structure of 1 is related to a group of compounds formed by Cu 2+–( X O 4) 3− layers ( X=P 5+, As 5+) linked by M cations ( M=alkali, alkaline earth, Pb 2+, or Ag +) and partly by hydrogen bonds. In 1, worth mentioning is the very short hydrogen bond length, D···A=2.477(3) Å. It is one of the examples of extremely short hydrogen bonds, where the donor and acceptor are crystallographically different. Compound 2 represents a layered structure consisting of Cu 2O 8 centrosymmetric dimers crosslinked by As1 φ 4 tetrahedra, where φ is O or OH, which are interconnected by Ba, As2 and hydrogen bonds to form a three-dimensional network. The layers are formed by Cu 2O 8 centrosymmetric dimers of CuO 5 edge-sharing polyhedra, crosslinked by As1O 4 tetrahedra. Vibrational spectra (FTIR and Raman) of both compounds are described. The spectroscopic manifestation of the very short hydrogen bond in 1, and ABC-like spectra in 2 were discussed.