Rubidium Compounds Research Articles

Formation of solid RbCl from aqueous solutions through membrane crystallization

Rubidium (Rb) is a very precious alkali metal with a high economic value. Of the rubidium compounds, RbCl is probably the most widely used. In the present work, RbCl crystals were obtained by vacuum membrane crystallization (V-MCr). Two different membranes were utilized: (i) one in polypropylene (PP) and (ii) one in poly(vinylidene fluoride)(PVDF). The membranes differ in material but have equal pore and porosity, and the experiments with the two membranes were conducted at the same temperature, vacuum pressure and flow rate values. While RbCl crystals were not obtained with the PVDF membrane due to wetting, good crystals were achieved from experiments with the PP membrane, with dispersion of crystal size distribution around of the average size of just 33.6 %. Another important result is that, in addition to the operating conditions, the membrane material is decisive for the success or failure of the membrane crystallization operation.

Double molybdates of silver and monovalent metals

The Ag2MoO4–Cs2MoO4 system was studied by powder X-ray diffraction, the formation of a new double molybdate CsAg3(MoO4)2 was established, its single crystals were obtained, and its structure was determined. CsAg3(MoO4)2 (sp. gr. P3¯, Z = 1, a = 5.9718(5), c = 7.6451(3) Å, R = 0.0149) was found to have the structure type of Ag2BaMn(VO4)2. The structure is based on glaserite-like layers of alternating MoO4 tetrahedra and Ag1O6 octahedra linked by oxygen vertices, which are connected into a whole 3D framework by Ag2O4 tetrahedra. An unusual feature of the Ag2 atom environment is its location almost in the centre of an oxygen face of the Ag2O4 tetrahedron. Caesium atoms are in cuboctahedral coordination (CN = 12).We determined the structures of the double molybdate of rubidium and silver obtained by us previously and a crystal from the solid solution based on the hexagonal modification of Tl2MoO4, which both are isostructural to glaserite K3Na(SO4)2 (sp. gr. P3¯m1). According to X-ray structural analysis data, both crystals have nonstoichiometric compositions Rb2.81Ag1.19(MoO4)2 (a = 6.1541(2), c = 7.9267(5) Å, R = 0.0263) and Tl3.14Ag0.86(MoO4)2 (a = 6.0977(3), c = 7.8600(7) Å, R = 0.0174). In the case of the rubidium compound, the splitting of the Rb/Ag position was revealed for the first time am ong molybdates. Both structures are based on layers of alternating MoO4 tetrahedra and AgO6 or (Ag, Tl)O6 octahedra linked by oxygen vertices. The coordination numbers of rubidium and thallium are 12 and 10

High-resolution atomic structures of rubidium compounds in L X-ray spectral lines: a promising exploration for chemical analysis

X-ray fluorescence (XRF) spectroscopy has made a significant impact on the chemical profile analysis of various materials used for industrial and medical purposes.

Evaluation of the Technological Parameters of a Solution Target for 82Sr Production

The concept of a solution target for obtaining the radioisotope 82Sr via the reaction Rb(p, xn)82Sr is propounded. A computational estimate of the main technological parameters of a solution target is made. The 82Sr yield in a solution target is calculated for solutions of certain compounds of rubidium and initial proton energy 70 MeV. It is shown that the highest 82Sr yield 7.44 MBq/(μA·h) in a solution target can be obtained by using a saturated solution of RbF. The solution fl ow rate in the circulation loop of the target allowing the operation of a target without boiling-up in a 100 μA proton beam is obtained for a target solution with RbF. The mass/size parameters of the heat-exchanger allowing the solution to be cooled tothe initial temperature in a single pass are calculated. The infl uence of radiolysis of the proton-irradiatedsolution on the operation of the target is determined. It is shown that on the whole radiolysis of the solution target is not large but does require defi nite efforts to utilize the hydrogen.

Syntheses, structural variants and characterization of A2CdSn2S6 (A = Cs, Rb and K) compounds

Four new A2CdSn2S6 (A = Cs(1), Rb(2), K(3-β) and K(3-α)) compounds have been synthesized and characterized by X-ray diffraction and spectroscopic methods. The isostructural cesium(1) and rubidium(2) compounds have noncentrosymmetric three-dimensional tetrahedral [CdSn2S6]2- framework structure and show second-harmonic-generation response. The layered potassium compounds, 3-β and 3-α, have centrosymmetric tetrahedral and octahedral [CdSn2S6]2- framework structures respectively and the compound 3-β, on heating, transforms to compound 3-α. The compound 3-α undergoes facile potassium ion-exchange in aqueous medium with various mono-, di- and tri- valent cations at room temperature.

ASc[SeO3]2 (A = Na – Cs): Pure Alkali‐Metal Scandium Oxoselenates(IV) and Their Representatives With Mixed Alkali‐Metal Occupation

Alkali‐metal scandium oxoselenates(IV) ASc[SeO3]2 (A = Na – Cs) are known since a few years and a hydrothermal synthesis was used to obtain them. In our new studies we applied a flux‐supported solid‐state reaction and produced colorless single crystals as well. All representatives ASc[SeO3]2 with A = Na – Cs crystallize in the orthorhombic space group Pnma, in contrast to earlier reports for hexagonal RbSc[SeO3]2. Furthermore we have extended this field with some crystals showing a mixed occupation on the alkali‐metal site, namely (K,Na)Sc[SeO3]2, (Rb,K)Sc[SeO3]2, and (Cs,Rb)Sc[SeO3]2. Since all of them contain [ScO6]9– octahedra and [SeO3]2– ψ1‐tetrahedra the diverse connectivity of the distinct alkali‐metal centered oxygen polyhedra differentiates the compounds with the smaller alkali metals (A′ = Na and K) from those with the bigger ones (A′′ = Rb and Cs). For the mixed crystals the amount of smaller or bigger alkali metal is responsible, which design is chosen by the system. This forces the mixed crystal (Rb,K)Sc[SeO3]2 with a higher amount of potassium instead of rubidium to crystallize isotypically with KSc[SeO3]2 and NaSc[SeO3]2, whereas the pure rubidium compound RbSc[SeO3]2 adopts the CsSc[SeO3]2‐type structure. These findings are supported by single‐crystal Raman spectroscopy.

Synthesis and Structural Characterization of the layered Selenogallate RbGaSe2

The chalcogenogallate RbGaSe2 was synthesized by thermal decomposition of rubidium azide in the presence of gallium selenide and selenium. RbGaSe2 crystallizes in the monoclinic space group C2/c (no. 15) with the lattice parameters a = 10.954(1) Å, b = 10.949(1) Å, c = 16.064(1) Å, β = 99.841(4)°, V = 1898.2(2) Å3, and Z = 16 (single‐crystal data, 20 °C) in the TlGaSe2 structure type. Its crystal structure features anionic layers 2∞[Ga4Se84–] with a van der Waals distance of 3.30(1) Å. Thermal analysis revealed a melting point of about 930 °C. Using UV/Vis diffuse reflectance spectroscopy, a wide bandgap of 3.16 eV was determined for the colorless semiconductor. The bonding situation in the compound was further compared with the isotypic cesium phases based on the results from Raman spectroscopy and DFT calculations. The slight shifts of the Raman bands suggest a slightly higher covalency of the rubidium compound.

Towards Polysulfuric Acids: The Hydrogentrisulfate Anion [HS3 O10 ]- in A[HS3 O10 ] (A=Na, K, Rb).

The reaction of Na2 SO4 and K2 SO4 with fuming sulfuric acid (65 % SO3 ) yielded colorless extremely sensitive crystals of Na[HS3 O10 ] (monoclinic; P21 /n (No. 14); Z=4; a=707.36(2), b=1378.56(4), c=848.10(3) pm; β=94.817(1)°; V=824.09(4)⋅106 pm3 ) and K[HS3 O10 ] (orthorhombic; Pccn (No. 56); Z=4; a=1057.16(3), b=807.81(2), c=897.57(2) pm; V=766.51(3)⋅106 pm3 ). The analogous rubidium compound Rb[HS3 O10 ] (orthorhombic; Pnma (No. 62); Z=4; a=891.43(3), b=1095.34(4), c=839.37(3) pm; V=819.58(5)⋅106 pm3 ) originates from the reaction of Rb2 CO3 and SO3 . All of the different structures contain the hitherto unknown anion [HS3 O10 ]- and are stamped by strong hydrogen bonds linking the anions either to dimers or chains. Theoretical investigations by DFT methods give further insight in the structural characteristics of [HS3 O10 ]- . The preparation of the [HS3 O10 ]- anion can be seen as an important milestone on our way to the still elusive polysulfuric acids.

Synthesis and crystal structure of new K and Rb selenido/tellurido ferrate cluster compounds

Abstract In the course of a systematic study of alkali iron chalcogenido salts containing clusters [Fe4 Q 8] a series of new mixed-valent potassium and rubidium selenido and tellurido ferrates(II/III) was synthesized by carefully heating the pure elements enclosed in sample tubes under an argon atmosphere up to maximum temperatures of 800–900 °C. Their crystal structures have been determined by means of single crystal X-ray diffraction. The mixed-valent FeII/III tellurido ferrates A 7[Fe4Te8] form three different structure types. All structures contain tetramers of four edge sharing [FeTe4] tetrahedra, which are connected by common edges to form only slightly distorted tetrahedral [Fe4Te8]7− anions (‘stella quadrangula’) with a [Fe4Te4] cubane core. In all cases, these anions are surrounded by 26 alkali cations, which are located at the eight corners and the midpoints of the six faces and 12 edges of a cube. The three crystal structures can thus be described by three different packings of cuboid moieties: The monoclinic rubidium compound Rb7[Fe4Te8] (space group C2/c, a = 2000.16(7), b = 897.79(3), c = 1768.12(6) pm, β = 117.4995(10)°, Z = 4, R1 = 0.0296) is isotypic to the known cesium tellurido and sulfido ferrates Cs7[Fe4(S/Te)8]. Depending on the temperature, K7[Fe4Te8] forms two different but closely related new structure types: The tetragonal r.t. modification (space group P42/nmc, a = 1222.25(14), c = 872.1(2) pm, Z = 2, R1 = 0.0583) crystallizes in a supergroup of the orthorhombic l.t. (100 K) form (space group Pbcn, a = 1715.5, b = 866.76(3), c = 1715.50(7) pm, Z = 4, R1 = 0.0160). In all structures, the cluster centered cubes are stacked to form columns along the short (≈870 pm) axis. These columns are themselves densely packed with 4 (both K compounds) and 6 (A = Rb) adjacent face-sharing columns. According to these arrangements of cluster-centered cubes, a relation of the packing of K/Rb cations and cluster anions with the simple cubic packing can be established applying the crystallographic group-subgroup formalism. Attempts to synthesize the corresponding selenium compound K7[Fe4Se8] resulted in the formation of the likewise mixed-valent compound K6[Fe4Se8]. Despite the modified composition, the new orthorhombic structure (space group Pbcn, a = 1632.62(6), b = 821.10(3), c = 1592.75(6) pm, Z = 4, R1 = 0.0540) is almost isotypic to the l.t. form of K7[Fe4Te8], the only difference being a missing K site. K5Fe2Te5 crystallizes in a new structure type (cubic, space group Pa3̅, a = 1709.02(5) pm, Z = 4, R1 = 0.0594). According to K5Fe2Te5=K15[Fe3Te7]2(Te), its structure contains mixed-valent cuboidal trimers [Fe3Te7](6/7)− and isolated telluride ions, which are coordinated by cubes of K+ cations.

Isotropy of Some Potassium, Sodium and Rubidium Compounds

The norm of elastic constant tensor and the norms of the irreducible parts of the elastic constants of potassium, Sodium and Rubidium compounds are calculated. The relation of the scalar parts norm and the other parts norms and the anisotropy of these compounds are presented. The norm ratios are used to study anisotropy of these compounds.

Risk assessment visualization of rubidium compounds: comparison of renal and hepatic toxicities, in vivo.

Rubidium has been considered to be nontoxic. Its use includes thin film on glass deposition and as medical contrast medium. Recent technology innovations also involve the use of rubidium, but there is limited information about the biological effects of its various compounds. In the present risk assessment study, a series of rubidium compounds with different counter anions-acetate, bromide, carbonate, chloride, and fluoride-were orally administrated in a single dose to several groups of rats. Cumulative 24-h urine samples were obtained, and the levels of rubidium, fluoride, N-acetyl-β-D-glucosaminidase and creatinine were measured to evaluate possible acute renal effects. Daily samples of serum were also obtained to determine the levels of aspartate and alanine aminotransferases to assess possible acute hepatic effects. Urinary rubidium excretion recovery of 8.0-10.5% shows that urine can be a useful diagnostic tool for rubidium exposure. The present results reveal that rubidium shows different biological effects depending on the counter anion. A pattern of large significant NAG leakage and elevation of ALT observed in rats treated with anhydrous rubidium fluoride indicates renal and hepatic toxicities that can be attributed to fluoride. The techniques reported in this study will be of help to assess the potential risks of toxicity of rubidium compounds with a variety of anions.

Thermal and luminescent properties of M2Zn(VO3)4 (M = Rb, Cs)

We have developed processes for the synthesis of the Rb2Zn(VO3)4 and Cs2Zn(VO3)4 tetrametavanadates. Rb2Zn(VO3)4 has been prepared by solid-state reaction (350°C) between presynthesized RbVO3 and ZnV2O6 powders, and Cs2Zn(VO3)4 has been prepared by the Pechini method (sol-gel process). Both metavanadates crystallize in monoclinic symmetry (sp. gr. P21/m). Thermochemical characterization results demonstrate that the vanadates undergo complex transformations during heating to 450°C and subsequent cooling. As a result, the materials are in a nonequilibrium state at room temperature and consist of both the parent double metavanadates and their peritectic decomposition products. We believe that the formation of the structure of the M2Zn(VO3)4 compounds from their melts is a kinetically hindered process. These compounds are structurally stable only at temperatures below 369 (Rb2Zn(VO3)4) or 420°C (Cs2Zn(VO3)4). We have measured for the first time the diffuse reflectance and photoluminescence excitation spectra of the two tetrametavanadates in their emission range and their photoluminescence spectra at various excitation wavelengths and determined their chromaticity coordinates. Their X-ray luminescence and scintillation decay characteristics have been determined for the first time under pulsed electron beam excitation. The electron excitation dissipation processes in the cesium and rubidium compounds are shown to be similar. We discuss the origin of the emission bands in the mixed vanadates and their potential application areas.

Synthesis and Crystal Structure of the Partially Oxidized Cyanoplatinates Rb1.75[Pt(CN)4]·1.25H2O and Cs1.75[Pt(CN)4]·0.5H2O

AbstractCrystal structures of partially oxidized cyanoplatinates were determined by single crystal analysis. Rb1.75[Pt(CN)4]·1.25H2O crystallizes monoclinic in the space group P21/c [a = 1171.4(2) pm, b = 3315.3(6) pm, c = 1054.4(2) pm, β = 114.253(2)°, V = 3733.2(11)·106 pm3, Z = 16, Ntotal = 31567, R(F)N = 0.0858]. The compound was obtained by mixing aqueous solutions of Rb2[Pt(CN)4]·1.5H2O and Rb2[Pt(CN)4]Br2. Cs1.75[Pt(CN)4]·0.5H2O crystallizes in the space group Ibam [a = 1266.1(3) pm, b = 1347.5(3) pm, c = 580.4(1) pm, V = 990.2(3)·106 pm3, Z = 4, Ntotal = 5997, R(F)N = 0.0807]. Crystals of the latter were grown by slow electrochemical oxidation of Cs2[Pt(CN)4]·H2O in aqueous solution using platinum wires as electrodes. In both compounds platinum is partially oxidized to Pt+2.25 and the nearly square‐planar tetracyanoplatinate groups are arranged to columns in a staggered conformation. The rubidium compound features a large unit cell with nonlinear chains of platinum atoms and short alternating Pt–Pt distances of 292 and 294 pm, the cesium compound crystallizes more symmetrically with Pt–Pt distances of c/2 = 290 pm. The two compounds were also characterized by differential thermal analysis, thermogravimetry, infrared, and Raman spectroscopy.

Synthesis, crystal structure, and vibrational spectra of MVO(SO4)2 (M = Rb, Cs, or Tl)

A series of MVO(SO4)2 vanadium complexes, where M = Rb, Cs, or Tl, were prepared, and their crystal structures and physicochemical properties studied. The rubidium and thallium compounds of this series were found to be isostructural to each other and to crystallize, like KVO(SO4)2 and NH4VO(SO4)2, in orthorhombic system (space group P212121, No. 19, Z = 4) with the unit cell parameters a = 4.9735(2) A, b=8.7894(4) A, c = 16.6968(8) A, V = 729.88 A3 (Rb); and a = 4.9636(1) A, b = 8.7399(2) A, c = 16.8598(4) A, V = 731.39 A3 (Tl). The cesium compound was found to crystallize in monoclinic system (space group P21/a, No. 14-2, Z = 4): a = 10.0968(6) A, b = 8.9131(4) A, c = 9.8675(5) A, β = 114.640(2)°, V = 807.16 A3. The MVO(SO4)2 crystal structure is built of VO6 octahedra, which are linked into layers by bridging SO4 groups. At the apex of each VO6 octahedron, there is a short V-O terminal bond having a length of 1.54(1) A (Rb), 1.57(2) A (Tl), and 1.52(4) A (Cs).

Die neuen Alkalimetall‐Sulfidoferrate K9[FeIIIS4](S2)S, (K/Rb)6[FeIII2S6], Rb8[FeIII4S10] und K7[FeII/IIIS2]5

AbstractA series of new potassium and rubidium sulfido ferrates were synthesized from iron and sulfur using elemental potassium and Rb2S as alkali element sources. The structures of all title compounds were determined by means of single‐crystal X‐ray data. Isolated ortho anions [FeIIIS4]5–, together with disulfide and sulfide anions, are the structure elements in K9[FeS4](S2)S (monoclinic, space group P21/c, a = 1068.58(2), b = 787.480(10), c = 2372.96(3) pm, β = 102.9670(10)°, Z = 4, R1 = 0.0325). The diferrates A6[FeIII2S6], among which only the sodium and the cesium salts were known so far, contain dimers of two edge‐sharing [FeS4] tetrahedra. The potassium and the monoclinic form of the rubidium compound (monoclinic, space group P21/c, a = 772.50(1)/796.06(5), b = 1251.24(2)/1291.35(8), c = 1002.80(1)/1032.40(6) pm, β = 127.5260(10)/127.163(4), Z = 2, R1 = 0.0356/0.0466) crystallize with the Cs3GaSe3 structure type. The second, orthorhombic form of Rb6[FeIII2S6] is isotypic to the cesium ferrate (orthorhombic, space group Cmca, a = 1884.36(3), b = 695.660(10), c = 1296.09(2) pm, Z = 4, R1 = 0.0220) forming the Ba3AlSb3 structure type. The rubidium ferrate Rb8[Fe4S10] crystallizes with a new structure type (triclinic, space group P$\bar{1}$, a = 744.65(3), b = 851.21(3), c = 1042.77(4) pm, α = 77.990(2), β = 85.244(2) γ = 81.051(2)°, Z = 1, R1 = 0.0537). The structure exhibits novel tetrameres [Fe4S10]8– of edge‐sharing tetrahedra, which represent segments of the well‐known chain compounds A[FeS2]. K7[FeII/IIIS2]5 (monoclinic, space group C2/c, a = 2790.1(3), b = 1153.74(13), c = 720.17(8) pm, β = 102.746(8)°, Z = 4, R1 = 0.0407) exhibits SiS2 analogous chains of edge‐sharing [FeS4] tetrahedra and contains iron in oxidation states II and III in a 2:3 ratio. This compound is an interesting “intermediate” inbetween the ferrate(III) K[FeIIIS2] and K3[FeII/IIIS2]2, with a 1:1 ratio of FeII:FeIII.

Adding Rubidium and Cesium to the Homologous Series of Alkali Metal Compounds of (Trimethylsilyl)methanides and 2,2,6,6‐Tetramethylpiperidides

Abstract(Trimethylsilyl)methylrubidium [RbCH2SiMe3] (1) and (trimethylsilyl)methylcesium [CsCH2SiMe3] (2) were prepared by metathesis reactions of (trimethylsilyl)methyllithium [LiCH2SiMe3] with rubidium or cesium tert‐butoxide in n‐hexane. Both new compounds are pyrophoric powders which were characterised by NMR spectroscopy and elemental analyses. They can be used as deprotonating agents towards secondary amines such as 2,2,6,6‐tetramethylpiperidine (TMPH). The resulting amides [RbTMP] (3) and [CsTMP] (4) form temperature‐sensitive, n‐hexane‐insoluble orange solids. Treatment with the bidentate donor N,N,N′,N′‐tetramethylethylenediamine (TMEDA) produces the corresponding n‐hexane‐soluble complexes. The crystal structures of [(TMEDA)RbTMP] (3a) and [(TMEDA)CsTMP] (4a) were determined to be closely related to that of [(TMEDA)KTMP]. Thus they are dimers with frameworks that consist of four‐membered M–N–M–N rings (M = Rb, Cs or K, N = TMP). The versatility and stability observed should make these (trimethylsilyl)methyl and TMP compounds of rubidium (1, 3a) and cesium (2, 4a) valuable starting points for further exploration of the chemistry of these heavy alkali metals.

Crystal and molecular structure of ammonium beryllium sulfate dihydrate, (NH4)2Be(SO4)2·2H2O

In this paper we report the crystal and molecular structure of the title compound, (NH4)2Be(SO4)2·2H2O, as determined by single-crystal X-ray diffraction and vibrational spectroscopy data.(NH4)2Be(SO4)2·2H2O crystallizes in the monoclinic space group P21/c (a=11.448(2), b=11.876(2), c=7.439(1)Å, β=96.64(1)°, V=1004.6Å3, Z=4, R1=0.036 for 3753 Fo>4σ(Fo) and 185 variables), and is isotypic with the respective potassium and rubidium sulfates and the potassium selenate. The crystal structure is built from three-membered tetrahedral chain fragments, consisting of a central BeO2(H2O)2 group and two adjacent SO4 tetrahedra. These building blocks are linked by rather strong hydrogen bonds of the water molecules (O⋯O=2.66–2.77Å) and by moderate to weak hydrogen bonds of the NH4 groups (N⋯O≥2.78Å) to a three-dimensional framework structure.The infrared bands corresponding to the stretching modes ν3 and ν1 as well as the Raman band corresponding to ν1 of the SO42- ions are observed in the spectra as doublets, thus reflecting the existence of two crystallographically different sulfate ions. The spectroscopic experiments reveal that the sulfate tetrahedra exhibit a remarkably large extent of energetic distortion as deduced from the values of Δν3 (site group splitting) and Δνmax (the difference between the highest and the lowest wavenumbered component of the stretching modes) (111 and 183.5cm−1, respectively), which could not be predicted from the structural data. The comparison of the spectral region widths of the stretching and bending modes of the SO42- ions allows us to assume that these ions undergo a stronger energetic distortion with respect to the SO bond lengths than that with respect to the OSO bond angles. The water librations couple intensively with both the translatory modes of the Be2+ cations (BeO4 skeleton vibrations) and the normal modes of the sulfate ions, thus producing small isotopic shifts (for example, the ratio νr(H2O)/νr(D2O) has value of 1.12). The strength of the hydrogen bonds formed by the water molecules in the title compound is also commented in comparison with that of the hydrogen bonds in the respective isomorphous potassium and rubidium compounds.

Alkali metal halogenides coordination compounds with hexamethylenetetramine

Six coordination compounds: [Li(H2O)4]+·hmta·Cl−, [Li(H2O)4]+·hmta·I−, [Na(H2O)4(hmta)] 2 2+ ·2H2O·2Br−, [Na(H2O)4(hmta)] 2 2+ ·2H2O·2I−, [K(H2O)(hmta)I] n and [Rb(H2O)(hmta)I] n , have been synthesized and characterised by IR spectroscopy, thermogravimetry coupled with differential thermal analysis, elemental analysis and X-ray crystallography. Both the sodium compounds are isostructural in a solid state, an isostructurality is also observed between compounds containing potassium and rubidium iodides. The sodium compounds exist as dimers (dinuclear core of the complex ion is created by two sodium cations and two water molecules). The molecules of potassium and rubidium compounds are assembled to the two dimensional hybrid nets. The each potentially multifunctional ligand (the hmta) exists in the outer coordination sphere in lithium compounds, acts in a monodentate mode in sodium compounds and in bidentate-bridging modes in potassium and rubidium compounds. The lithium ions are four coordinated, and the sodium, potassium and rubidium ions are six coordinated. Thermal analyses show that the investigated compounds decompose gradually with the formation of alkali metal halides which, during the further heating, are totally removed or they undergo partial decomposition to oxides.

Synthesis, crystal structure, and vibrational spectra of M4V2O3(SO4)4 (M = K, Rb, Cs)

Synthesis was performed and physicochemical properties were studied for the M4V2O3(SO4)4 complexes, where M = K, Rb, or Cs. Their crystal structures were determined using the set of data from X-ray diffraction and neutron diffraction studies. All compounds crystallize in a triclinic lattice (space group \( P\bar 1 \) , Z = 2) with the parameters: a = 7.7688(2), 7.8487(1), 8.1234(1) A; b = 10.4918(3), 10.8750(2), 11.1065(1) A; c = 11.9783(4), 12.1336(2), and 11.8039(1) A; α = 76.600(2)°, 77.910(1)°, 79.589(1)°; β = 75.133(2)°, 75.718(1)°, 87.939(1)°; γ = 71.285(2)°, 72.189(1)°, 75.567(1)°; V = 881.78(5), 945.42(3), 1014.34(2) A3 for K, Rb, Cs, respectively. The structure of M4V2O3(SO4)4 was found to be formed by discrete complex anions V2O3(SO4)44− incorporating two oxygen-bridged vanadium atoms in a distorted octahedral oxygen environment. The sulfate groups are coordinated by the vanadium atoms in the chelating mode with a large scatter of S-O interatomic distances and OSO angles. Every VO6 octahedron has a short terminal vanadium-oxygen bond with a length of about 1.6A. The V2O3(SO4)44− complex anions in potassium and rubidium compounds differ from that in Cs4V2O3(SO4)4 in the type of symmetry and mutual spatial orientation. The vibrational spectra were presented and interpreted in line with the structural analysis data.

Non‐Centrosymmetric Ammonium Rare Earth Nitrates (NH4)2Ln(NO3)5·4H2O – Crystal Structure, Crystal Growth and Optical Properties

AbstractFor crystals of (NH4)2Ln(NO3)5·4H2O (Ln = La, Ce, Pr, Nd), the piezoelectric and the pyroelectric effect was demonstrated unambiguously. X‐ray structure determination shows that all four compounds are isomorphic, with monoclinic, non‐centrosymmetric space group Cc, and are further isomorphic to the related rubidium compounds Rb2Ln(NO3)5·4H2O. Large single crystals of the colourless compounds (NH4)2La(NO3)5·4H2O and (NH4)2Ce(NO3)5·4H2O were grown. On the basis of determined precise refractive indices and their dispersion in the wavelength region 0.365–1.083 μm, phase‐matching conditions for collinear second harmonic generation were analyzed. In both crystals, type I phase matching can be realized for wavelengths from 0.893 μm (La) or 0.892 μm (Ce) to the near IR, where first absorption bands appear.