Preparation and thermal reactivity of some rare earth and uranyl hydrazinesulfinates and sulfite hydrazinates

Hydrazinesulfinate and sulfite hydrazinate derivatives of rare earth elements of composition Ln(N₂H₃SOO)₃(H₂O) and Ln₂(SO₃)₃(N₂H₄)_x(H₂O)_y, respectively, where Ln=La, Ce, Pr, Nd and Sm, have been prepared and characterized by chemical analysis and infrared spectra. The uranyl complexes of the composition UO₂(N₂H₃SOO)₂, UO₂(N₂H₃SOO)₂(N₂H₄) and UO₂SO₃(N₂H₄)(H₂O) have also been prepared under different reaction conditions and studied by different physicochemical techniques. Thermal properties of all these complexes have been studied by thermogravimetry, and differential scanning calorimetry. The hydrazinesulfinate derivatives of rare earth elements undergo thermal decomposition in multisteps to give the respective metal sulfate as the residue. The other series of complexes, viz., rare earth sulfite hydrazinates gave a mixture of metal sulfate and metal oxide as the end products. However, all the uranyl complexes undergo decomposition in air to give UO₂SO₃ as the final product.     

Investigation of double sulfates of lithium and rare earth elements

Compounds in the system Li₂SO₄R₂(SO₄)₃, where R is a rare earth element, have been investigated. Only compounds of the type LiR(SO₄)₂ are formed. The existence of three structural types has been established. X-Ray parameters from Nd to Er have been determined. The thermal stability of the compounds has been investigated.     

Synthesis,Luminescence and Nonlinear Optical Properties of Homoleptic Tetracyanamidogermanates ARE[Ge(CN2)4] (A = K,Cs, and RE = La,Ce, Pr,Nd, Sm,Eu, Gd)

Two new series of tetracyanamidogermanates were prepared by solid‐state reaction of appropriate amounts of REF₃ (RE = rare earth), A₂[GeF₆] (A = alkaline), and Li₂(CN₂) in evacuated silica tubes. Powder X‐ray diffraction patterns of crystalline samples of KRE[Ge(CN₂)₄] and CsRE[Ge(CN₂)₄] were indexed isotypically to KRE[Si(CN₂)₄] and RbRE[Ge(CN₂)₄], respectively. Luminescence properties of Ce³⁺, Eu³⁺, and Tb³⁺ doped compounds and non‐linear optical properties (NLO) of KRE[Ge(CN₂)₄] are reported.     

Syntheses, crystal structures and vibrational spectra of KLn(SO4)2·H2O (Ln=La, Nd, Sm, Eu, Gd, Dy)

The potassium lanthanide double sulphates KLn(SO₄)₂·H₂O (Ln=La, Nd, Sm, Eu, Gd, Dy) were obtained by evaporation of aqueous reaction mixtures of rare earth (III) sulphates and potassium thiocyanate at 298 K. X-ray single-crystal investigations show that KLn(SO₄)₂·H₂O (Ln=Nd, Sm, Eu, Gd, Dy) crystallise monoclinically (Ln=Sm: P2₁/c, Z=4, a=10.047(1), b=8.4555(1), c=10.349(1) Å, wR2=0.060, R1=0.024, 945 reflections, 125 parameters) while KLa(SO₄)₂·H₂O adopts space group P3₂21 (Z=3, a=7.1490(5), c=13.2439(12) Å, wR2=0.038, R1=0.017, 695 reflections, 65 parameters). The coordination environment of the lanthanide ions in KLn(SO₄)₂·H₂O is different in the case of the Nd/Sm/Gd and the Eu/Dy compounds, respectively. In the first case the Ln atoms are nine-fold coordinated in contrast to the latter where the Ln ions are eight-fold coordinated by oxygen atoms. The vibrational spectra of KLn(SO₄)₂·H₂O and the UV-vis reflection spectra of KEu(SO₄)₂·H₂O and KNd(SO₄)₂·H₂O are also reported.     

Phase ratios in the K2O-V2O4-SO3 system at high sulfur trioxide concentrations

Phase ratios in the three-component oxide system K₂O-V₂O₄-SO₃ in the region of the sulfur trioxide concentrations corresponding to its concentrations in the active component of vanadium catalysts for SO₂ to SO₃ conversion have been studied using powder X-ray diffraction, IR spectroscopy, microscopy, and chemical analysis. Four individual compounds (K₂VO(SO₄)₂, K₂(VO)₂(SO₄)₃, K₂VO(SO₄)₂S₂O₇, and K₂(VO)₂(SO₄)₂S₂O₇) and K₂(VO)₂(SO₄)₂S₂O₇ and VOSO₄-base solid solutions of composition K₂(VO)_2+x (SO₄)_2+x S₂O₇ (0 ≤ x ≤ 1.5) were found in the system. K₂VO(SO₄)S₂O₇ and K₂(VO)₂(SO₄)₂S₂O₇ lose their sulfur trioxide when heated above 350°C under an inert atmosphere, and convert to K₂VO(SO₄)₂ and K₂(VO)₂(SO₄)₃, respectively. This implies that K₂VO(SO₄)₂S₂O₇ and K₂(VO)₂(SO₄)₂S₂O₇, as well as K₂(VO)_2+x (SO₄)_2+x S₂O₇ solid solution, cannot exist in the active component of real industrial catalysts.     

Enthalpies of formation of rare earth orthovanadates, REVO4

Rare earth orthovanadates, REVO₄, having the zircon structure, form a series of materials interesting for magnetic, optical, sensor, and electronic applications. Enthalpies of formation of REVO₄ compounds (RE=Sc, Y, Ce-Nd, Sm-Tm, Lu) were determined by oxide melt solution calorimetry in lead borate (2PbO·2B₂O₃) solvent at 1075 K. The enthalpies of formation from oxide components become more negative with increasing RE ionic radius. This trend is similar to that obtained for the rare earth phosphates.     

Structural and vibrational studies of Li[Kx(NH4)1−x]SO4 and Li2KNH4(SO4)2 mixed crystals

Mixed crystals of Li[K_x(NH₄)_1−x]SO₄ have been obtained by evaporation from aqueous solution at 313 K using different molar ratios of mixtures of LiKSO₄ and LiNH₄SO₄. The crystals were characterized by Raman scattering and single-crystal and powder X-ray diffraction. Two types of compound were obtained: Li[K_x(NH₄)_1−x]SO₄ with x?0.94 and Li₂KNH₄(SO₄)₂. Different phases of Li[K_x(NH₄)_1−x]SO₄ were yielded according to the molar ratio used in the preparation. The first phase is isostructural to the room-temperature phase of LiKSO₄. The second phase is the enantiomorph of the first, which is not observed in pure LiKSO₄, and the last is a disordered phase, which was also observed in LiKSO₄, and can be assumed as a mixture of domains of two preceding phases. In the second type of compound with formula Li₂KNH₄(SO₄)₂, the room-temperature phase is hexagonal, symmetry space group P6₃ with cell-volume nine times that of LiKSO₄. In this phase, some cavities are occupied by K⁺ ions only, and others are occupied by either K⁺ or NH₄⁺ at random. Thermal analyses of both types of compounds were performed by DSC, ATD, TG and powder X-ray diffraction. The phase transition temperatures for Li[K_x(NH₄)_1−x]SO₄x?0.94 were affected by the random presence of the ammonium ion in this disordered system. The high-temperature phase of Li₂KNH₄(SO₄)₂ is also hexagonal, space group P6₃/mmc with the cell a-parameter double that of LiKSO₄. The phase transition is at 471.9 K.     

A new potassium rare earth oxyborate K2La2(BO3)2O

A series of potassium rare earth oxyborates, K₂RE₂(BO₃)₂O (RE = La, Nd, Sm and Eu), have been synthesized. Single crystal of the first member of the series, K₂La₂(BO₃)₂O, has been grown by the flux method. Its structure, determined by single crystal X-ray diffraction, shows that it belongs to the monoclinic system, space group P2₁/c with unit cell parameters of a = 11.422(2) Å, b = 6.6803(13) Å, c = 10.813(2) Å, β = 17.23(3)° and Z = 4. Optical transmission spectrum shows that the K₂La₂(BO₃)₂O crystal is highly transparent from 215 nm to 2750 nm.     

Raman spectroscopy evidence of 1:1:1 complex formation during dissolution of WO3 in a melt of K2S2O7:K2SO4

Highly inert yellow solid WO₃ was found to be soluble in considerable amounts in molten K₂S₂O₇ at elevated temperatures (∼650 °C), if only similar molar amounts of sulfates were also present. The dissolution reaction of WO₃ into a melt consisting of a 1:1 molar mixture of K₂S₂O₇ and K₂SO₄ was studied in detail, and Raman spectroscopy was used to characterize the products. In combination with single crystal X-ray crystal structure determination, it was shown that a new dimeric compound, K₈[{W^VIO₂(SO₄)₂}₂(μ-SO₄)₂], was formed and its assigned Raman spectrum at room temperature is given. The WO₂²⁺ cores of the dimeric complex have their symmetrical and antisymmetrical stretching modes ν₁(WO₂²⁺) and ν₃(WO₂²⁺) at around 1054 (strong) and 1042 (weak), and the bending mode ν₂(WO₂²⁺) at around 292 (medium intensity), respectively (positions given in cm⁻¹).     

New Structure Type among Octahydrated Rare‐Earth Sulfates, β‐Ce2(SO4)3·8H2O,and a new Ce2(SO4)3·4H2O Polymorph

Syntheses, crystal structures and thermal behavior of two new hydrated cerium(III) sulfates are reported, Ce₂(SO₄)₃·4H₂O ( I ) and β‐Ce₂(SO₄)₃·8H₂O ( II ), both forming three‐dimensional networks. Compound I crystallizes in the space group P2₁/n. There are two non‐equivalent cerium atoms in the structure of I , one nine‐ and one ten‐fold coordinated to oxygen atoms. The cerium polyhedra are edge sharing, forming helically propagating chains, held together by sulfate groups. The structure is compact, all the sulfate groups are edge‐sharing with cerium polyhedra and one third of the oxygen atoms, belonging to sulfate groups, are in the S–Oμ₃–Ce₂ bonding mode. Compound II constitutes a new structure type among the octahydrated rare‐earth sulfates which belongs to the space group Pn. Each cerium atom is in contact with nine oxygen atoms, these belong to four water molecules, three corner sharing and one edge sharing sulfate groups. The crystal structure is built up by layers of [Ce(H₂O)₄(SO₄)]_nⁿ⁺ held together by doubly edge sharing sulfate groups. The dehydration of II is a three step process, forming Ce₂(SO₄)₃·5H₂O, Ce₂(SO₄)₃·4H₂O and Ce₂(SO₄)₃, respectively. During the oxidative decomposition of the anhydrous form, Ce₂(SO₄)₃, into the final product CeO₂, small amount of CeO(SO₄) as an intermediate species was detected.     

Aqueous solubilities of praseodymium,europium, and lutetium sulfates

The aqueous solubilities of finely divided Pr₂(SO₄)₃·8H₂O(cr), Eu₂(SO₄)₃·8H₂O(cr), and Lu₂(SO₄)₃·8H₂O(cr) have been measured as a function of time at 25°C using isothermal saturation. Solubilities of the latter two salts showed a steady decrease with time, whereas Pr₂(SO₄)₃·8H₂O(cr) showed no such variation within the accuracy of the determinations. The turbidities of these filtered saturated solutions also decreased with time, and indicate that some colloidal rare earth sulfates were present. These colloidal particles (<0.2 m) have a large surface area, which contributes to the Gibbs energy of the solid phase, thus giving rise to enhanced solubilities. The micro-particles also grow with time, thereby reducing the surface area contribution to the Gibbs energy and also leaving fewer particles to pass through the filters. Extrapolation of solubilities to infinite time gives the solubilities of macrocurstalline Eu₂(SO₄)₃·8H₂O and Lu₂(SO₄)₃·8H₂O. Previous solubility data for Lu₂(SO₄)₃, at 20 and 40°C, yield an interpolated value at 25°C that is about 30% low. Densities were also measured at several concentrations of each salt.     

Synthesis, identification and thermal decomposition of double sulfates of La, Ce, Pr or Nd with ethanolammonium

On evaporation at room temperature of an aqueous reaction mixture of Ln(III) sulfate and ethanolammonium sulfate in a molar ratio higher than 1∶16, crystal products with a waxy feel were obtained. They were identified by means of the X-ray powder diffraction patterns and it was concluded that they are isostructural. The results of elemental analysis and the mass losses by TG analysis indicated the formation of double sulfates with general formula: (HOCH₂CH₂NH₃)₄Ln₂(SO₄)5·4.5H₂O (Ln=La, Ce, Pr or Nd) Their thermal decompositions in static atmosphere in the temperature range from ambient up to 1173 K took place in a similar way, and mainly Ln₂O₂SO₄ was obtained as final product. The exception was the Ce compound, which decomposed to CeO₂. The double sulfates decomposed in many not well-differentiated steps. From the mass losses occurring during thermal decomposition, the mode of thermal decomposition was presumed. The X-ray powder diffraction patterns of Ln₂O₂SO₄ (Ln=La, Pr and Nd) show that they are also isostructural.     

K<Subscript>3</Subscript>VO<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>2</Subscript>: Formation conditions,crystal structure,and physicochemical properties

Potassium oxosulfatovanadate(V) K₃VO₂(SO₄)₂ has been obtained by solid-phase synthesis from K₂SO₄, K₂S₂O₇, and V₂O₅ (2: 1: 1), and its formation conditions, crystal structure, and physiochemical properties have been studied. The conversions of K₃VO₂(SO₄)₂ in contact with potassium vanadates and other potassium oxosulfatovanadates(V) are considered in terms of phase relations in the K₂O-V₂O₅-SO₃ system, which models the active component of vanadium catalysts for sulfur dioxide oxidation into sulfur trioxide. The X-ray diffraction pattern of K₃VO₂(SO₄)₂ is indexed in the monoclinic system (space group P2₁) with unit cell parameters of a = 10.0408(1) Å, b = 7.2312(1) Å, c = 7.3821(1) Å, β = 104.457(1)°, Z = 2, and V = 519.02 ų. The crystal structure of K₃VO₂(SO₄)₂ is built from [VO₂(SO₄)₂]^3? complex anions, in which the vanadium atom is in an octahedral oxygen environment formed by two terminal oxygen atoms (V-O(6) = 1.605(7) Å, V-O(10) = 1.619(7) Å and four oxygen atoms of the two chelating sulfate anions. The vibrational spectra of K₃VO₂(SO₄)₂ are analyzed using these structural data.     

A pseudo‐merohedrally twinned rare‐earth sulfate: K6[Ce(HSO4)2(SO4)4]·H2O,a novel structure type

A novel structure type of an acidic rare‐earth sulfate, hexa­potassium cerium dihydrogensulfate tetra­sulfate monohydrate, is reported. The crystal is twinned, mimicking tetra­gonal symmetry. The Ce^IV atom is nine‐coordinate, connecting to one corner‐sharing and four edge‐sharing sulfate groups. One of the potassium ions is disordered over two general positions. The compound is unique as it contains rare‐earth monomers, [Ce(HSO₄)(SO₄)₄]⁵⁻. The structure is composed of these monomers, water mol­ecules, discrete hydrogensulfate ions and potassium ions held together by ionic inter­actions. There are two types of alternating layers in the structure, with compositions [K₄Ce(HSO₄)(SO₄)₄]⁻ and [K₂(HSO₄)(H₂O)]⁺.     

Syntheses and crystal structures of RE3MnSn5−x (RE=Tm, Lu) with 3D Mn-Sn framework

Four new isostructural rare earth manganese stannides, namely RE₃MnSn_5−x (x=0.16(6), 0.29(1) for RE=Tm, x=0.05(8), 0.21(3) for RE=Lu), have been obtained by reacting the mixture of corresponding pure elements at high temperature. Single-crystal X-ray diffraction studies revealed that they crystallized in the orthorhombic space group Pnma (No. 62) with cell parameters of a=18.384(9)-18.495(6) Å, b=6.003(3)-6.062(2) Å, c=14.898(8)-14.976(4) Å, V=1644.3(14)-1679.0(9) Å³ and Z=8. Their structures belong to the Hf₃Cr₂Si₄ type and feature a 3D framework composed of 1D [Mn₂Sn₇] chains interconnected by [Sn₃] double chains via Sn-Sn bonds, forming 1D large channels based on [Mn₄Sn₁₆] 20-membered rings along the b-axis, which are occupied by the rare earth atoms. Electronic structure calculations based on density functional theory (DFT) for idealized “RE₃MnSn₅” model indicate that these compounds are metallic, which are in accordance with the results from temperature-dependent resistivity measurements.     

Cyanide‐Bridged Tetranuclear REIII2FeIII2 (RE = Y,Tb, Dy) Molecular Squares with 2, 2′:6′,2′′‐Terpyridine as a Capping Ligand

Self‐assembly reaction between hydrated rare‐earth (RE) nitrates RE(NO₃)₃ · 6H₂O with K₃Fe(CN)₆ in H₂O/DMF solution by employing the tridentate ligand 2, 2′:6′,2′′‐terpyridine (terpy) as a capping ligand has yielded three cyanide‐bridged compounds [RE(terpy)(DMF)(H₂O)₂][Fe(CN)₆] · 6H₂O [RE = Y ( 1 ), Tb ( 2 ), Dy ( 3 )]. FT‐IR spectra confirmed the presence of terpy ligands and cyanide groups in compounds 1 – 3 . Single‐crystal X‐ray structural analysis indicated that these compounds are isomorphous and adopt neutral [RE₂Fe₂] molecular squares, which are further linked through hydrogen bonding interactions to generate a three‐dimensional supramolecular network. Magnetic susceptibility measurements revealed that significant single ion magnetic anisotropy dominates the properties of these compounds.     

An optical investigation of Ho2(SO4)3 ·8H2O

The optical absorption spectra of Ho³⁺ in single crystals of Ho₂(SO₄)₃·8H₂O have been studied between 2500 A and 9000 A at 4.2 and 77 K. The microscopic crystal structure has been related to the macroscopic shape of the crystals. From the polarization of the optical transitions it is found that the point symmetry of the crystalline electric field (CEF) at the site of the rare earth ions in the sulfate lattice is well described by C_1h. The CEF parameters associated with this symmetry were derived from the observed Stark splitting of the [SL]?J levels and the polarization of the optical transitions. We suggest that the magnetically inequivalent sites observed in Tm₂(SO₄)₃·8H₂O are due to triclinic distortions of the monoclinic CEF.     

RE4[P1–x(C2)x]3 (RE = La–Nd): the Mixed Anionic Substructure Formed by Phosphorus and Carbon

The rare‐earth phosphide carbides RE₄[P_1–x(C₂)_x]₃ (RE = La, Ce, Pr, Nd) represent the first example of a mixed anionic substructure formed by phosphorus and carbon, being the first step toward the formation of the mixed inorganic P–C species. The peculiarities of the crystal structure, magnetic properties, XAS data, and quantum chemical calculation results confirm the ionic nature of the interaction between the rare‐earth cations RE and phosphorus anions, while complex interaction of π states of the C₂ anions and d (and/or f) states of the RE components is indicated. Thus, despite the extensive chemical analogy between the phosphide carbides and phosphide silicides, the atomic interactions stabilizing the structural motif are slightly different.     

Synthesis and characterization of monodisperse spherical SiO2@RE2O3 (RE=rare earth elements) and SiO2@Gd2O3:Ln (Ln=Eu, Tb, Dy, Sm, Er, Ho) particles with core-shell structure

Spherical SiO₂ particles have been coated with rare earth oxide layers by a Pechini sol-gel process, leading to the formation of core-shell structured SiO₂@RE₂O₃ (RE=rare earth elements) and SiO₂@Gd₂O₃:Ln³⁺ (Ln=Eu, Tb, Dy, Sm, Er, Ho) particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL), and cathodoluminescence spectra as well as lifetimes were used to characterize the resulting SiO₂@RE₂O₃ (RE=rare earth elements) and SiO₂@Gd₂O₃:Ln³⁺ (Eu³⁺, Tb³⁺, Dy³⁺, Sm³⁺, Er³⁺, Ho³⁺) samples. The obtained core-shell phosphors have perfect spherical shape with narrow size distribution (average size ca. 380 nm), smooth surface and non-agglomeration. The thickness of shells could be easily controlled by changing the number of deposition cycles (40 nm for two deposition cycles). Under the excitation of ultraviolet, the Ln³⁺ ion mainly shows its characteristic emissions in the core-shell particles from Gd₂O₃:Ln³⁺ (Eu³⁺, Tb³⁺, Sm³⁺, Dy³⁺, Er³⁺, Ho³⁺) shells.     

第二结构导向剂诱导形成的二维有机模板稀土硫酸盐

水热条件下合成了具有超大孔道和层状结构的有机模板稀土硫酸盐。超大孔道的稀土硫酸盐（1）的分子式为[（CH₃）₂NH₂]₉[Pr₅（SO₄）₁₂]·2H₂O,它展现出有趣的交叉二十元环孔道结构。层状的稀土硫酸盐的分子式为[H₃O]₃[（CH₃）₂NH₂]₃[Ln₂（SO₄）₆]（Ln=Pr,2;Nd,3）,它可以被看作是由双链和八元环结合而成。这3种化合物的合成揭示了大的有机胺（三聚氰胺）可能用作为第二结构导向剂,阻止形成高维数的无机骨架,从而诱导了二维层状结构稀土硫酸盐晶体的生长。对化合物1和3的磁性进行了研究,测试的温度范围在2~300 K。