Volume 74, Issue 1 - Special Issue: Dedicated to Professor Wolfgang Bensch of the Christian-Albrechts-Universität Kiel

Natural orthorhombic sulfur ( α -S 8 ), grown on galena crystals from Cap Garonne, Mine du Pradet, France, were studied by single crystal X-ray diffraction at 150 K: Fddd , a =1036.75(5), b =1273.54(7), c =2437.85(13) pm, wR =0.0380, 1433 F 2 values (all data) and 37 variables. Refinements of the occupancy parameters along with EDX data indicate pure sulfur.

The crystal structure of struvite-type KMgAsO 4 (H 2 O) 6 has been redetermined from single crystal X-ray diffraction data at room temperature. The previous structure model based on powder X-ray diffraction data was confirmed with higher precision and accuracy and with all hydrogen atoms located. KMgAsO 4 (H 2 O) 6 undergoes a reversible phase transition of the continuous type at 263(2) K, changing the symmetry from orthorhombic to monoclinic. The corresponding Pnm 2 1 → P 112 1 symmetry reduction is of a translationengleiche type with index 2 and was monitored by temperature-dependent powder X-ray diffraction measurements. Such a phase transition is unprecedented for struvite-type compounds. The crystal structure of the monoclinic polymorph was determined from a two-domain crystal at 100 K. Except for the motion of one of the water molecules towards stronger hydrogen-bonding interactions, structural changes between the two polymorphs are small.

The ZrNiAl-type (space group P 6̅2 m ) gallides T IrGa ( T =Zr, Nb, Hf, Ta), ZrNiGa and ScPdGa were obtained by arc-melting of the elements, followed by annealing in sealed silica tubes. The samples have been characterized through their Guinier powder patterns. The structures of ZrNiGa, NbIr 1.08 Ga 0.92 and TaIr 1.10 Ga 0.90 were refined from single-crystal X-ray diffractometer data. Refinements of the occupancy parameters indicate the formation of solid solutions for the niobium and the tantalum compound. Within the huge family of ZrNiAl-type phases, NbIr 1.08 Ga 0.92 and TaIr 1.10 Ga 0.90 have the smallest c / a ratios; however, no structural distortions or superstructure formation have been observed. Electronic structure calculations were exemplarily carried out for NbIrGa, substantiating the dominance of the Ir–Ga and Nb–Ir bonding interactions. Temperature dependent magnetic susceptibility measurements of LT-ScPdGa, ZrIrGa, NbIrGa and HfIrGa have shown Pauli paramagnetism. ScPdGa is dimorphic with an orthorhombic TiNiSi-type high-temperature modification (arc-melting and quenching; space group Pnma ) which transforms to the hexagonal ZrNiAl-type low-temperature modification upon annealing at 1023 K. Both structures were refined from single-crystal X-ray diffractometer data. HT-ScPdGa exclusively shows Pd–Ga bonding within the three-dimensional [PdGa] polyanionic network, while additional weak Pd–Pd and Ga–Ga interactions occur in LT-ScPdGa.

The reaction of Ni(OH) 2 and methanetrisulfonic acid trihydrate CH(SO 3 H) 3 ·3H 2 O (H 3 MTA·3H 2 O) in N -methyl-pyrrolidone (NMP) leads to the trinuclear complex {Ni 3 [MTA] 2 (NMP) 8 } (triclinic, P 1̅, Z =1, a =946.25(3), b =1073.24(3), c =1518.27(4) pm, α =72.193(2), β =87.398(2), γ =89.389(2)°, V =1466.49(7)×10 6 pm 3 ). The structural features of the methanetrisulfonate anions are tripodal as well as chelating coordination of the Ni 2+ ions. The thermal analysis has shown that the compound is first losing NMP molecules and that the solvent-free methanetrisulfonate finally decomposes yielding Ni 3 S 2 .

The high-temperature polymorph of the trisulfide Cs 2 S 3 , which has been synthesized from Cs 2 S 2 and elemental sulfur, crystallizes in a new structure type (monoclinic, space group P 2 1 / c , a =999.97(4), b =1029.30(5), c =2642.07(12) pm, β =90.083(2)°, Z =16, R 1=0.0324). The structure contains four crystallographically independent angled S32−${\rm{S}}_3^{2 - }$ trisulfide ions with S–S distances of 205.7–208.3 pm. The distorted b.c.c. packing of the anions and their insertion in the five-membered rings of 3.5 3 +3.5.3.5. (1:1) Cs nets are similarly found in the r.t. form ( Cmc 2 1 , K 2 S 3 -type structure) and the two polymorphs differ mainly in the orientation of the S 3 groups. The second title compound, K 37 Te 28 , was synthesized from stoichiometric melts of the elements. It forms a complex (3+1)D modulated tetragonal structure (space group I 4 1 / amd (00 σ 3 ) s 0 s 0, q =(0, 0, 0.5143), a =1923.22(2), c =2626.66(4) pm, Z =4, R 1 all =0.0837). According to K 37 Te 28 =K 37 [Te(1 X )] 8 [Te(2 X ) 2 ] 6 [Te(3 X ) 8 ] the structure contains three different types of Te anions: The two crystallographically different isolated telluride anions [Te(1 X )] 2− are coordinated by 9/10 K + cations. Three [Te(2 X ) 2 ] 2− dumbbells ( d Te-Te =277.9/286.4 pm) are arranged to ‘hexamers’. The Te(31) and Te(32) atoms are located in columns of face-sharing K square antiprisms. Their z position modulation, which is accompanied by a smaller shift of the surrounding K + cations, results in the decomposition of the [Te(3 X ) 8 ] 2 chain in a sequence |:Te 3 –Te 2 –Te 2 –Te 3 –Te 2 –Te 2 –Te 2 :| of dumbbells Te 2 2− ( d Te–Te =304 pm) and hypervalent linear trimers Te 3 4− ( d Te–Te =325 pm).

Reaction of Cd(NCS) 2 with 4-methoxypyridine leads to the formation of four new compounds, of which one crystallizes in two different polymorphs. In Cd(NCS) 2 (4-methoxypyridine) 4 ·(4-methoxypyridine) 2 ( 1 ) and Cd(NCS) 2 (4-methoxypyridine) 4 ( 2-I and 2-II ) discrete complexes are found, in which the Cd cations are octahedrally coordinated by four 4-methoxypyridine co-ligands and two terminally N-bonded thiocyanate anions. For the polymorphs 2-I and 2-II no single crystals are available and therefore, the corresponding Mn(II) compound ( 2-I-Mn ) was prepared, which is isotypic to 2-I , as proven by a Rietveld refinement. The crystal structure of 2-II was solved and refined from XRPD data. In [Cd(NCS) 2 (4-methoxypyridine) 2 ] n ( 3 ), the Cd cations are also octahedrally coordinated but linked into linear chains by pairs of thiocyanate anions with all ligands in trans -position. {[Cd(NCS) 2 ] 3 (4-methoxypyridine) 5 } n ( 4 ) also consists of chains but two different Cd coordination modes are observed. Two of the three crystallographically independent Cd cations show an octahedral coordination with a trans- or cis -arrangement of the N and S atoms of the anionic ligands, whereas the third one is in a distorted square-pyramidal coordination, with cis- coordination of the thiocyanate N and S atoms. Measurements using simultaneous thermogravimetry and differential scanning calorimetry of 2-I and 2-II show different heating rate dependent mass steps, in which the co-ligands are removed. In some of the residues obtained after the respective TG steps compound 3 was detected but no phase pure samples could be obtained.

Crystalline orthorhombic rare earth carbonate hydroxides Ln [CO 3 ][OH] ( Ln =La, Pr, Nd, Sm, Eu, Gd) were synthesised as phase pure powders via a simple hydrothermal reaction. CO 2 from air acted as natural carbonate source and cetyltrimethylammonium bromide was added as templating agent to an aqueous rare earth nitrate solution. Single-crystal X-ray structure determination was performed on La[CO 3 ][OH] ( Pnma , a =7.4106(5), b =5.0502(3), c =8.5901(6) Å, 563 independent reflections, 38 refined parameters, wR 2=0.037), Pr[CO 3 ][OH] ( Pnma , a =7.2755(4), b =4.9918(3), c =8.5207(5) Å, 744 independent reflections, 38 refined parameters, wR 2=0.04), Eu[CO 3 ][OH] ( Pnma , a =7.1040(4), b =4.8940(3), c =8.4577(5) Å, 1649 independent reflections, 38 refined parameters, wR 2=0.05) and Gd[CO 3 ][OH] ( Pnma , a =7.069(7), b =4.874(5), c =8.464(9) Å, 431 independent reflections, 38 refined parameters, wR 2=0.051). These findings are supported by powder XRD, infrared spectroscopy, UV/Vis spectroscopy and, for Pr[CO 3 ][OH] and Eu[CO 3 ][OH], by measurements of the non-linear optical properties. Thermal analysis could demonstrate the possible use of the Ln [CO 3 ][OH] phases as precursors for rare earth carbonate dioxides Ln 2 [CO 3 ]O 2 and rare earth oxides Ln 2 O 3 . The decomposition products inherit the precursor’s morphology. The lattice parameters of Pr 2 [CO 3 ]O 2 were refined from high-temperature powder XRD data.

The importance of the synthesis conditions on the structural and photocatalytic properties of tantalum oxide nitride was investigated by comparing two variants of phase-pure β -TaON obtained from application of two different synthesis routes, leading to one unstrained and one heavily anisotropically microstrained β -TaON as shown by XRD-based Rietveld refinement. HRTEM images reveal the origin of the strain to be lattice defects such as stacking faults. The strained β -TaON was found to be the clearly less active semiconductor in photochemical and photoelectrochemical water oxidation. The lattice defects are assumed to act as charge carrier traps hindering the photo-generated holes to be displaced to the reaction sites at the surface.

Applying a nematic liquid crystalline phase of a synthetic Na-hectorite with layer separations >100 nm, the reaction time for pillaring with Al 13 Keggin oligocation could be reduced to seconds ensuring that cation exchange is controlled by thermodynamics. With this material at hand we are able to resolve the long-standing dispute regarding the charge of intercalated Keggin oligocations. Micropore sizes as determined by physisorption isotherms, adsorption isotherms obtained via elemental analysis, and results of 27 Al solid-state NMR and pyridine probe IR spectroscopy favor a charge of +7 for the Al 13 pillars intercalated into hectorite unaltered.

The electronic structure and magnetic properties of the compound 2H-NbS 2 intercalated by 3 d elements from Cr to Ni, have been investigated using the Korringa–Kohn–Rostoker electronic structure method. Here, we consider the phases with 33% of intercalation within the ordered phase having a 3×3$\sqrt 3 \times \sqrt 3 $ arrangement of the magnetic atoms. We analyze the relationship of the magnetic and electronic properties on the structural parameters dependent on the intercalant. The exchange coupling parameters calculated from first principles have been used for subsequent Monte Carlo simulations. Within these investigations, the FM order was found for the Cr and Mn intercalated phases as ground state configuration with a Curie temperature being in good agreement with the experiment. According to the Monte Carlo simulation, Fe 1/3 NbS 2 has a complicated noncollinear magnetic structure with a noncompensated total magnetic moment, whereas Co 1/3 NbS 2 and Ni 1/3 NbS 2 are found to be antiferromagnetic, all in line with experimental observations.

By the oxidation of terbium metal with sulfur and tellurium in the presence of cesium bromide as flux at 850°C for 10 days, the first quaternary cesium terbium chalcogenides with ordered S 2− and Te 2− anions could be obtained as main products. The new compounds CsTb 3 STe 4 and CsTb 5 S 2 Te 6 occur as black needles. While CsTb 3 STe 4 crystallizes in the orthorhombic space group Pnma with a =1924.08(16), b =433.61(3) and c =1493.47(13) pm for Z =4, CsTb 5 S 2 Te 6 adopts the monoclinic space group C 2/ m with a =2146.17(18), b =431.42(3), c =1049.68(9) pm and β =102.064(3)° for Z =2. Both crystal structures are characterized by parallel cationic and anionic strands ({[STb3]7+}∞1${}_\infty ^1\{ {[{\rm{ST}}{{\rm{b}}_{\rm{3}}}]^{7 + }}\} $ and {[CsTe4]7−}∞1${}_\infty ^1\{ {[{\rm{CsT}}{{\rm{e}}_4}]^{7 - }}\} $ for CsTb 3 STe 4 as well as {[S2Tb5]11+}∞1${}_\infty ^1\{ {[{{\rm{S}}_{\rm{2}}}{\rm{T}}{{\rm{b}}_{\rm{5}}}{\rm{]}}^{11 + }}\} $ and {[CsTe6]11–}∞1${}_\infty ^1\{ {[{\rm{CsT}}{{\rm{e}}_6}]^{11-}}\} $ for CsTb 5 S 2 Te 6 ), all running along [010]. The cationic chains result from vertex-connected [STb 4 ] 10+ tetrahedra ( d (S 2− –Tb 3+ )=271–277 pm), whereas face-sharing bicapped trigonal or square prisms [CsTe 6+2 ] 15− or [CsTe 8+2 ] 19− , respectively, form their anionic counterparts.

The reaction of the 3d transition metal dichlorides MCl 2 (M=Mn, Fe, Co, Ni, Cu, Zn) with the silver salts of substituted tetracyanocyclopentadienides Ag + [C 5 (CN) 4 X] − (X=CN, H, NH 2 NO 2 ) gives the complexes [M(MeOH/H 2 O) 4 {C 5 (CN) 4 )X} 2 ]. Nine of these complexes were characterized by X-ray diffraction and it shows that they all are mononuclear with an octahedral M(N) 2 (O) 4 coordination sphere. In the structures, extensive hydrogen bonding leads to dense three-dimensional network structures.

The title compounds C 13 H 26 N + Cl − ( N,N -dicyclohexylmethylammonium chloride), C 13 H 26 N + Br − ( N,N - dicyclohexylmethylammonium bromide) and C 13 H 26 N + I − ( N,N -dicyclohexylmethylammonium iodide) are isostructural and crystallize in the orthorhombic space group Pna 2 1 with the lattice parameters a =7.580(1), b =19.072(1), c =9.165(1) Å, V =1324.9(1) Å 3 for X =Cl, a =7.765(1), b =19.054(1), c =9.270(1) Å, V =1371.5(1) Å 3 for X =Br, and a =8.102(1), b =19.084(1), c =9.535(1) Å, V =1474.2(1) Å 3 for X =I with Z =4 for each compound. Their cyclohexyl groups are aligned along [010] while their halide ions are coordinated along [100] by a strong linear N–H··· X ( X =Cl, Br, I) hydrogen bond. Fourier-transform infrared spectra show a decreasing hydrogen bond acceptor strength from the chloride to the iodide.

The rare earth metal-rich RE 14 T 3 Al 3 series ( RE =Y, Gd–Tm, Lu; T =Co, Ni) have been prepared by arc-melting the rare earth metals with appropriate amounts of T Al precursors. All compounds crystallize in the tetragonal crystal system with space group P 4 2 / nmc in the Gd 14 Co 3 In 2.7 -type structure. Two structures (Y 14 Co 2.78(1) Al 3.22(1) : a =952.99(4), c =2292.98(10) pm, wR 2=0.0423, 2225 F 2 values, 63 variables; Y 14 Ni 3.07(2) Al 2.93(2) : a =955.06(5), c =2298.77(10) pm, wR 2=0.0416, 2225 F 2 values, 63 variables) have been refined from single-crystal data, indicating T /Al mixing on one crystallographic site. The lattice parameters of all members have been refined from powder X-ray diffraction experiments. The Y and Lu containing compounds for T =Co and Ni exhibit Pauli paramagnetic behavior, indicating that the Co and Ni atoms exhibit no localized magnetic moment in line with a filled 3 d band. The other compounds show paramagnetism, in line with the rare earth atoms in the trivalent oxidation state. Detailed magnetic investigations, however, were impossible due to the presence of e.g. RE 3 T trace impurities.

The structural properties of modulated SrGe 6− x ( x ≈0.45) were investigated by means of single-crystal and powder X-ray diffraction combined with quantum chemical calculations. The framework compound SrGe 6− x adopts a defect variant of the EuGa 2 Ge 4 -type crystal structure. Samples of the binary compound with nominal compositions 0≤ x ≤0.5 were synthesized at pressures from 5 to 6 GPa and a temperature of typically 1400 K. The product reveals diffraction peaks of the EuGa 2 Ge 4 -type subcell plus additional reflections indicating an ordered superstructure. Detailed crystal structure analysis evidences the incommensurate nature of the superstructure and a modulation of the vacancy ordering in the germanium network. The computations have shown that the non-stoichiometric composition of the framework with its local defect organization affects the calculated charge of the strontium anions. Although the chemical composition is close to a charge-balanced situation, temperature-dependent resistivity measurements showed metal-type conductivity. At ambient pressure SrGe 6− x decomposes exothermally and irreversibly at T =680(10) K into SrGe 2 and germanium, indicating its metastable nature at ambient pressure.

Ionic liquids (ILs) offer the remarkable possibility of the direct synthesis of Eu 2+ -doped nanophosphors in solution, under atmospheric conditions, without the necessity of a high-temperature post-synthetic reduction from its trivalent oxidation state. This work uses for the first time in situ luminescence measurements for monitoring the solvation process of Eu 2+ from the solid salt to the IL and its stability against oxidation under atmospheric conditions. Upon the addition of EuBr 2 to 1-butyl-3-methyl-imidazolium tetrafluoroborate, the formation of the solvation shell is detected by the shift of the emission band at approximately 24 100 cm −1 assigned to the 5 d →4 f electronic transitions of Eu 2+ within EuBr 2 to approximately 22 000 cm −1 , assigned to Eu 2+ within BminBF 4 , tracking the time-dependent influence of the Eu 2+ coordination environment on the crystal field splitting of its d orbitals. Even though the solubility of EuBr 2 was demonstrated to be improved by reducing the concentration and increasing the temperature to 60°C, the performance of reactions at room temperature is recommended for future synthesis of Eu 2+ materials in ILs due to the slight oxidation to Eu 3+ observed upon heating.