Rare Earth Carbodiimide Silicates: RE2(CN2)(SiO4)

Rare earth carbodiimide silicates RE₂(CN₂)(SiO₄) with RE = Y, La, and Pr were synthesised by solid state metathesis reactions of RECl₃, Li₂(CN₂), and SiO₂ or Li₂SiO₄, respectively, in silica tubes at 550 °C. All three compounds crystallise with different structures, although all of them represent distorted derivatives of the sodium chloride type structure. The structure of Y₂(CN₂)(SiO₄) was refined monoclinically (C2/m, Z = 2, a = 1301.382(5) pm, b = 377.630(1) pm, c = 527.656(2) pm, β = 93.9816(2) °) from X‐ray powder data. The crystal structure of La₂(CN₂)(SiO₄) was refined in a different monoclinic space group (P2₁/c, Z = 4, a = 660.3(1) pm, b = 1282.0(2) pm, c = 656.2(1) pm, β = 105.23(2) °), and the structure of Pr₂(CN₂)(SiO₄) was refined triclinically (P\bar{1} , Z = 2, a = 646.7(2) pm, b = 669.2(2) pm, c = 671.8(2) pm, α = 86.18(3) °, β = 73.22(3) °, γ = 74.08(3) °) from X‐ray single crystal data.     

New Ternary Boride Carbides RE10B9+xC10–x (RE = Gd,Tb; x ≈︁ 0.2): Infinite Boron Carbon Branched Chains

New ternary rare earth metal boride carbides with compositions close to RE₁₀B₉C₁₀ (RE = Gd, Tb) were prepared from the elements by melting around 1800 K followed by annealing in silica tubes at 1270 K for one month. The crystal structure of the terbium compound was solved by single‐crystal X‐ray diffraction. It crystallizes in a new structure type in the monoclinic space group P2₁/c, a = 7.937(1), b = 23.786(2), c = 11.172(1) Å, β = 133.74(1)°, Z = 4, R1 = 0.045 (wR2 = 0.11) for 5713 reflections with I_o > 2σ(I_o). In the structure BC₂ units and single carbon atoms are attached to a zigzag boron chain forming the unprecedented B₁₈C₁₈ branching unit with a B–B distance of 2.42(2) Å between these units. In addition isolated carbon atoms occupy the centres of elongated octahedra formed by rare earth metal atoms. Disorder in the terbium position together with anomalous displacement ellipsoids for carbon atoms except of those in the BC₂ fragments can be rationalized in terms of a slight deviation in stoichiometry, Tb₁₀B_9+xC_10–x (x ≈? 0.2). The terbium compound is ferromagnetic below T_C ≈? 45 K. Due to the presence of moderately narrow domain walls the magneto‐crystalline energy is small.     

Completing the Series: New Coordination Networks of Composition 3∞[RE2(ADC)3(H2O)6]·2H2O with RE = Pr,Nd, Sm,Eu, Tb,Dy, Ho,Er, Y and ADC2– = Acetylenedicarboxylate (–O2C–C≡C–CO2–)

The crystal structures of ³_∞[RE₂(ADC)₃(H₂O)₆] · 2H₂O (RE = Pr, Nd, Sm, Eu, Tb, Dy) were solved and refined from X‐ray single crystal data. They crystallize in a structure type already known for RE = La, Ce and Gd (P1 , no. 2, Z = 2), which is characterized by REO₉ polyhedra forming dimeric units being the nodes of a 3D framework structure linked by ADC^2– anions (^–O₂C–C≡C–CO₂^– = acetylenedicarboxylate). From synchrotron powder diffraction data it was shown that isostructural coordination networks are formed for RE = Ho, Er, Y, whereas for RE = Tm, Yb, Lu a new structure type crystallizing in a highly complex crystal structure with a large orthorhombic unit cell is found. All compounds are obtained by slow evaporation of an aqueous solution containing RE(OAc)₃ · xH₂O and acetylenedicarboxylic acid (H₂ADC). The coordination networks of composition ³_∞[RE₂(ADC)₃(H₂O)₆] · 2H₂O were thoroughly investigated by thermal analysis and for RE = Eu, Tb, a strong red and green photoluminescence was observed and investigated by means of UV/Vis spectroscopy.     

Thermal,Magnetic, Electronic,and Superconducting Properties of Rare‐Earth Metal Pentagermanides REGe5 (RE = La,Nd, Sm,Gd) and Synthesis of TbGe5

A series of isotypic rare‐earth metal pentagermanides including the new compound TbGe₅ were prepared by high‐pressure synthesis. They crystallize in the orthorhombic space group Immm [No. 71; a = 395.70(9) pm; b = 611.1(2) pm, and c = 983.6(3) pm for TbGe₅]. The crystal structure is isotypic to LaGe₅ and consists of puckered germanium slabs, which sandwich a second germanium species and the rare‐earth metal atoms. At ambient pressure, the thermal decomposition of the phases REGe₅ (RE = La, Nd, Sm, Gd, and Tb) proceeds via discrete intermediate steps into Ge(cF8) and thermodynamically stable germanium‐poorer phases. The investigated compounds REGe₅ are paramagnetic metallic conductors, which order antiferromagnetically at low temperatures. Specific heat measurements reveal that the superconducting state of LaGe₅ below T_c = 7.1(1) K is characterized by a critical field of μ₀H_c2 = 0.2 T and weak electron‐phonon coupling. Density‐functional based band‐structure calculations yield a very similar electronic structure for all the isotypic REGe₅ compounds. Besides a slight increase in the width of the valence band for smaller RE atoms, only minor differences are found for the two different germanium environments.     

Die Kristallstrukturen der Cyanidofluoridoborate K[BFx(CN)4–x], x = 0–4

The crystal structure of K[BF₃(CN)] (Pbcn (Nr. 60) with a = 13.3486(15) b = 6.5239(7) c = 10.0085(11) Å, and eight formula units per unit cell) has been determined and the one of K[BF₂(CN)₂] was confirmed and improved. The different networks in the complete series of borates K[BF_x(CN)_4–x], x = 0–4 are compared and discussed.     

Orthorhombic HP‐REOF (RE = Pr,Nd, Sm – Gd) – High‐Pressure Syntheses and Single‐Crystal Structures (RE = Nd,Sm, Eu)

High‐pressure modifications of the rare earth oxide fluorides REOF (RE = Pr, Nd, Sm – Gd) were successfully synthesized under conditions of 11 GPa and 1200 °C applying the multianvil high‐pressure/high‐temperature technique. Single crystals of HP‐REOF (RE = Nd, Sm, Eu) were obtained making it possible to analyze the products by means of single‐crystal X‐ray diffraction. The compounds HP‐REOF (RE = Nd, Sm, Eu) crystallize in the orthorhombic α‐PbCl₂‐type structure (space group Pnma, No. 62, Z = 4) with the parameters a = 632.45(3), b = 381.87(2), c = 699.21(3) pm, V = 0.16887(2) nm³, R₁ = 0.0156, and wR₂ = 0.0382 for HP‐NdOF, a = 624.38(3), b = 376.87(2), c = 689.53(4) pm, V = 0.16225(2) nm³, R₁ = 0.0141, and wR₂ = 0.0323 for HP‐SmOF, and a = 620.02(4), b = 374.24(3), c = 686.82(5) pm, V = 0.15937(2) nm³, R₁ = 0.0177, and wR₂ = 0.0288 for HP‐EuOF. Calculations of the bond valence sums clearly showed that the oxygen atoms occupy the tetrahedrally coordinated position, whereas the fluorine atoms are fivefold coordinated in form of distorted square‐pyramids. The crystal structures and properties of HP‐REOF (RE = Nd, Sm, Eu) are discussed and compared to the isostructural phases and the normal‐pressure modifications of REOF (RE = Nd, Sm, Eu). Furthermore, results of investigations by EDX and Raman measurements including quantum mechanical calculations are presented.     

Synthesis,Crystal Structure,Thermal and Explosive Properties of [Cd(SCZ)3(H2O)](PA)2·3H2O (SCZ = Semicarbazide,PA = Picrate)

The heptacoordinate transition metal coordination compound [Cd(SCZ)₃(H₂O)](PA)₂ · 3H₂O ( 1 ) with the ligand semicarbazide (SCZ) and the counteranion picrate (PA) was synthesized and characterized by elemental analysis and FTIR spectroscopy. Single‐crystal X‐ray diffraction analysis revealed that 1 crystallizes in the monoclinic space group P21/c. The Cd²⁺ ion is heptacoordinated by three SCZ groups and a water molecule. SCZ presents typical bidentate coordination modes. The thermal decomposition mechanism of 1 was studied by differential scanning calorimetry (DSC), which revealed that complex 1 exhibits three small endothermic and two large exothermic processes. The non‐isothermal kinetics parameters were calculated by the Kissinger's method and Ozawa‐Doyle's method, respectively. The heat of combustion was measured by oxygen bomb calorimetry. The enthalpy of formation, the critical temperature of thermal explosion, the entropy of activation (ΔS^≠), the enthalpy of activation (ΔH^≠), and the free energy of activation (ΔG^≠) were also calculated. Sensitivity tests revealed that 1 is insensitive to mechanical stimuli.     

Synthesis,Crystal Structures,and Optical Properties of AM2(OH)(SeO3)2 (A = Na,Rb; M = Mg,Zn)

Sodium magnesium selenite NaMg₂(OH)(SeO₃)₂ and rubidium zinc selenite RbZn₂(OH)(SeO₃)₂ were prepared by hydrothermal reactions. The crystal structures of the title compounds were determined by single‐crystal X‐ray diffraction. NaMg₂(OH)(SeO₃)₂ crystallizes in the orthorhombic space group Pnma (no. 62) with lattice parameters a = 13.1919(10), b = 6.0415(4), c = 8.2182(6) Å, and Z = 4 and RbZn₂(OH)(SeO₃)₂ crystallizes in the triclinic space group P$\bar{1}$ (no. 2) with lattice parameters a = 4.8698(5), b = 7.3446(8), c = 11.7796(12) Å, α = 82.554(3), β = 78.456(2), γ = 71.603(3)°,and Z = 2. The structure of NaMg₂(OH)(SeO₃)₂ is a three‐dimensional framework consisting of edge‐sharing MgO₆ octahedra and trigonal pyramidal SeO₃^2– groups, whereas the structure of RbZn₂(OH)(SeO₃)₂ is a two‐dimensional layers structure consisting of corner‐sharing [Zn₂O₇] dimers linked by trigonal pyramidal SeO₃^2– groups. The compounds were characterized by the solid state UV/Vis/NIR diffuse reflectance, and FT‐IR spectroscopy.     

Inverse Perovskites (Eu3O)E with E = Sn,In – Preparation,Crystal Structures and Physical Properties

The cubic inverse Perovskites (Eu₃O)In and (Eu₃O)Sn were prepared from the metals and Eu₂O₃ or SnO₂, respectively. For (Eu₃O)In the crystal structure analysis was performed on single crystal X‐ray diffraction data (space group , a = 512.79(3) pm, Z = 1, R_gt(F) = 0.022, wR(F²) = 0.044). The data indicated full occupancy on all sites and a fully ordered structure. According to magnetic susceptibility measurements and X‐ray absorption spectroscopic data at the Eu L_III edge both compounds contain europium in the 4f⁷ (Eu²⁺) electronic state. (Eu₃O)In orders ferromagnetically at 185(5) K, (Eu₃O)Sn shows antiferromagnetic order at 31.4(2) K. Both compounds behave as metallic conductors in electrical resistivity measurements. However, (Eu₃O)In may be classified a metal, while (Eu₃O)Sn is more likely a heavily doped degenerated semiconductor or semimetal according to the absolute values of the resistivity.     

High‐Pressure Synthesis,Crystal Structure,and Properties of GdS2 with Thermodynamic Investigations in the Phase Diagram Gd–S

Gadolinium disulfide was prepared by high‐pressure synthesis at 8 GPa and 1173 K. It crystallizes in the monoclinic space group P12₁/a1 (No. 14) with lattice parameters a = 7.879(1) Å; b = 3.936(1) Å, c = 7.926(1) Å and β = 90.08(1)°. The crystal structure is a twofold superstructure of the aristotype ZrSSi and consists of puckered cationic [GdS]⁺ double slabs that are sandwiched by planar sulfur sheets containing S₂^2– dumbbells. The thermal decomposition of GdS₂ proceeds via the sulfur‐deficient polysulfides GdS_1.9, GdS_1.85 and GdS_1.77 and eventually results in the sesquisulfide Gd₂S₃. GdS₂ is a paramagnetic semiconductor which orders antiferromagnetically at T_N = 7.7(1) K. A metamagnetic transition is observed in the magnetically ordered state.     

Correlation between Luminescence and EPR Spectroscopy as Evidence of Ytterbium Pair Formation in Li6Ln(BO3)3:Yb3+ (Ln=Gd,Y) Borate Single Crystals

Synthesized powders and grown single crystals of nominal compositions Li₆Ln(BO₃)₃:Yb³⁺ (Ln=Y, Gd) were investigated by means of powder and single‐crystal X‐ray diffraction (XRD), as well as optical near‐IR spectroscopy in conjunction with electron paramagnetic resonance (EPR) spectroscopy. The appearance of two distinct zero‐phonon lines suggests the existence of two kinds of Yb³⁺ ions in the single crystals. The XRD results exclude the possibility of a phase transition occurring between room and low temperatures. EPR spectra of single crystals show the presence of both isolated ions and pairs of ytterbium ions substituted for Y³⁺. A strong temperature dependence of the intensity of Yb–Yb pairs resonance lines coincides with temperature dependence of emission peak at 978 nm, confirming a common origin of the defect giving rise to these spectra. Calculated from EPR spectra, the distance between pairs of Yb³⁺ is in good agreement with crystallographic ones: R=3.856 Å, R_cryst=3.849 Å.     

Synthesis,Characterization, and Properties of Pentanitrobenzene C6H(NO2)5

The synthesis of the polynitroaromatic compound pentanitrobenzene was re‐examined by modern spectroscopic, structural and physicochemical methods. Originally prepared in 1979, this material could exhibit interesting properties as an oxygen‐rich energetic building block. The energies of formation were calculated with the GAUSSIAN program package and the detonation parameters were predicted using the EXPLO5 computer code. The performance data were determined and compared to the common oxidizer ammonium perchlorate. The crystal structure of pentanitrobenzene was determined by X‐ray crystallography, and those of 2,3,4,6‐tetranitroaniline and styphnic acid (trinitroresorcinol) were re‐determined.     

Dimers of Ag2+ Ions – Synthesis and Characterization of the Quaternary Silver Fluoride Ag2ZnZr2F14 with [Ag2F7]3– Units

Deep blue‐violet colored powder samples of Ag₂ZnZr₂F₁₄ were synthesized by heating Zn(NO₃)₂·4H₂O, Ag and ZrOCl₂·8H₂O at 300 °C under fluorine atmosphere. The crystal structure of Ag₂ZnZr₂F₁₄ was refined from X‐ray powder diffraction data using the Rietveld method (C2/m, a = 9.0206(1) Å, b = 6.6373(1) Å, c = 9.0563(1) Å, β = 90.44(1)°, Z = 2). The structure is derived from the isotypic Ag₃Zr₂F₁₄ by replacing only one of the two crystallographically different Ag²⁺ ions with Zn²⁺ ions, thus leading to discrete Ag₂F₇ dimers. These dimers are connected via nearly linear Ag–F···F–Ag bridges with short F···F distances of 2.33 Å to form two‐legged ladders. Magnetic susceptibility measurements and density functional calculations show that the two Ag²⁺ ions in each Ag₂F₇ dimer are strongly coupled antiferromagnetically.     

Synthesis,Persistent Luminescence,and Thermoluminescence Properties of Yellow Sr3SiO5:Eu2+,RE3+ (RE=Ce,Nd, Dy,Ho, Er,Tm, Yb) and Orange‐Red Sr3−xBaxSiO5:Eu2+, Dy3+ Phosphor

Sunlight‐excitable orange or red persistent oxide phosphors with excellent performance are still in great need. Herein, an intense orange‐red Sr_3?xBa_xSiO₅:Eu²⁺,Dy³⁺ persistent luminescence phosphor was successfully developed by a two‐step design strategy. The XRD patterns, photoluminescence excitation and emission spectra, and the thermoluminescence spectra were investigated in detail. By adding non‐equivalent trivalent rare earth co‐dopants to introduce foreign trapping centers, the persistent luminescence performance of Eu²⁺ in Sr₃SiO₅ was significantly modified. The yellow persistent emission intensity of Eu²⁺ was greatly enhanced by a factor of 4.5 in Sr₃SiO₅:Eu²⁺,Nd³⁺ compared with the previously reported Sr₃SiO₅:Eu²⁺, Dy³⁺. Furthermore, Sr ions were replaced with equivalent Ba to give Sr_3?xBa_xSiO₅:Eu²⁺,Dy³⁺ phosphor, which shows yellow‐to‐orange‐red tunable persistent emissions from λ=570 to 591 nm as x is increased from 0 to 0.6. Additionally, the persistent emission intensity of Eu²⁺ is significantly improved by a factor of 2.7 in Sr_3?xBa_xSiO₅:Eu²⁺,Dy³⁺ (x=0.2) compared with Sr₃SiO₅:Eu²⁺,Dy³⁺. A possible mechanism for enhanced and tunable persistent luminescence behavior of Eu²⁺ in Sr_3?xBa_xSiO₅:Eu²⁺,RE³⁺ (RE=rare earth) is also proposed and discussed.     

Crystal Structure,Synthesis, and Properties of tri‐Calcium di‐Citrate tetra‐Hydrate [Ca3(C6H5O7)2(H2O)2]·2H2O

From hydrothermal synthesis needle‐shaped crystals of [Ca₃(C₆H₅O₇)₂(H₂O)₂] · 2H₂O were obtained. The crystal structure was determined by single‐crystal X‐ray experiments and confirmed by powder data (P$\bar{1}$ (no. 2) a = 5.9466(4), b = 10.2247(8), c = 16.6496(13) Å, α = 72.213(7)°, β = 79.718(7)°, γ = 89.791(6)°, V = 947.06(13) Å³, Z = 2, R1 = 0.0426, wR2 = 0.1037). The structure was obtained from pseudo merohedrically polysynthetic twinned crystals using a combined data collection approach and refinement processes. The observed three‐dimensional network is dominated by eightfold coordinated Ca²⁺ cations linked by citrate anions and hydrogen bonds between two non‐coordinating crystal water molecules and two coordinating water molecules.     

Syntheses and Crystal Structures of the Cyclotriphosphate Hydrates Nd(P3O9)·3H2O,Nd(P3O9)·4.5H2O,RE(P3O9)·5H2O (RE = Pr,Nd), and Na3RE(P3O9)2·6H2O (RE = Pr,Nd)

Several rare‐earth cyclotriphosphate hydrates were obtained from mixtures of sodium cyclotriphosphates and the respective rare‐earth chlorides. Nd(P₃O₉) · 3H₂O [P$\bar{6}$ , Z = 3, a = 677.90(9), c = 608.67(9) pm, R₁ = 0.016, wR₂ = 0.038, 312 data, 36 parameters] was obtained by a solid state reaction and is isotypic with respective rare‐earth phosphate hydrates, while all the others adopt new structure types. Nd(P₃O₉) · 4.5H₂O [C2/c, Z = 8, a = 1644.6(3), b = 756.11(15), c = 1856.1(4) pm, β = 97.25(3)°, R₁ = 0.032, wR₂ = 0.081, 1763 data, 194 parameters], Nd(P₃O₉) · 5H₂O [P2₁/c, Z = 4, a = 773.75(15), b = 1149.1(2), c = 1394.9(3) pm, β = 106.07(3)°, R₁ = 0.042, wR₂ = 0.082, 1338 data, 194 parameters], Pr(P₃O₉) · 5H₂O [P$\bar{1}$ , Z = 2, a = 745.64(15), b = 889.07(18), c = 934.55(19) pm, α = 79.00(3), β = 80.25(3), γ = 66.48(3), R₁ = 0.059, wR2 = 0.089, 1468 data, 193 parameters], Na₃Nd(P₃O₉)₂ · 6H₂O [P2₁/n, Z = 4, a = 1059.78(18), b = 1207.25(15), c = 1645.7(4) pm, β = 99.742(17), R₁ = 0.047, wR₂ = 0.119, 1109 data, 351 parameters] and Na₃Pr(P₃O₉)₂ · 6H₂O [P2₁/n, Z = 4, a = 1061.42(16), b = 1209.0(2), c = 1635.5(3) pm, β = 99.841(13), R₁ = 0.035, wR₂ = 0.062, 1323 data, 350 parameters] were obtained by careful crystallization at room temperature. A thorough structure discussion is given. The infrared spectrum of Nd(P₃O₉) · 4.5H₂O is also reported.     

Synthesis and X‐ray Crystal Structures of Ru3(CO)9(μ‐arphos)(L) [L = AsPh3, As(m‐C6H4Me)3, As(p‐C6H4Me)3]

Three new triruthenium clusters, Ru₃(CO)₉(μ‐arphos)AsPh₃ ( 1 ), Ru₃(CO)₉(μ‐arphos)As(m‐C₆H₄Me)₃ ( 2 ), and Ru₃(CO)₉(μ‐arphos)As(p‐C₆H₄Me)₃ ( 3 ) were synthesized via thermal reactions of Ru₃(CO)₁₀(μ‐arphos) with different tertiary arsine ligands [AsPh₃, As(m‐C₆H₄Me)₃, As(p‐C₆H₄Me)₃]. All these complexes were fully characterized by elemental analysis, FT‐IR, NMR spectroscopy, and single‐crystal X‐ray diffraction.     

Co‐MOFs Containing Flexible α,ω‐Alkane‐dicarboxylates and Bis(imidazole) Ligands: Synthesis,Structure, and Properties

Three structurally related flexible bis(imidazole) ligands reacted with Co(NO₃)₂ · 6H₂O and succinic acid (L₁) to yield three new metal‐organic frameworks {[Co(L₁)(L₂)] · (H₂O)}_n ( 1 ) [L₂ = 2‐bis(imidazol‐1‐yl)ethane], {[Co(L₁)(L₃)](H₂O)}_n ( 2 ) [L₃ = 1,4‐bis(imidazol‐1‐yl) butane], and {[Co(L₁)(L₄)] · (H₂O)}_n ( 3 ) [L₄ = 1,4‐bis(2‐methyl‐imidazol‐1‐yl)butane], respectively. These complexes were synthesized under solvothermal conditions and characterized by elemental analysis, IR spectroscopy, single‐crystal and powder X‐ray diffraction, as well as thermal analyses. Interestingly, the ligands in these complexes exhibit different conformations and further cause three different configurations. Complex 1 shows a three‐dimensional (3D) framework, which is connected by two‐dimensional (2D) layer structures through hydrogen bonds. Complex 2 is a diamond structure with threefold interpenetration. Complex 3 is a 3D framework linked by hydrogen bonds like complex 1 .