Band 75, Heft 11 - Special issue dedicated to Professor Robert Glaum of the University of Bonn on the occasion of his 60th birthday

The intermetallic solid solution CePd 1− x Au x Al ( x  = 0.1–0.9) has been synthesized from the elements by arc-melting and subsequent annealing in induction followed by tube furnaces. The samples were characterized using the Guinier powder diffraction technique and the structures of the nominal compositions CeAuAl and CePd 0.2 Au 0.8 Al were refined from single crystal X-ray diffractometer data. For small values of x  = 0.1–0.3, the compounds crystallize in the hexagonal ZrNiAl-type structure (space group P 6‾$‾{6}$2 m ), while for x  = 0.5–0.9 the orthorhombic TiNiSi-type structure (space group Pnma ) was observed. In both structure types, the transition metal and aluminum atoms form a complex polyanionic network with the cerium atoms filling the respective cavities. The transition metal atoms are in both cases surrounded in the shape of a tri-capped trigonal prism, the connectivity of these units, however, is different. Temperature-dependent magnetic susceptibility measurements of all compounds indicated a stable trivalent oxidation state for the cerium atoms along with antiferromagnetic ordering around T N  ∼ 3 K.

The plumbides Ca T Pb 2 ( T  = Rh, Pd), Eu T Pb 2 ( T  = Rh, Pd, Pt), Sr T Pb 2 ( T  = Rh, Pd, Pt) and Ba T Pb 2 ( T  = Pd, Pt) were obtained by direct reactions of the elements in sealed tantalum tubes in an induction furnace. The moisture sensitive polycrystalline samples were characterized by X-ray powder diffraction. They crystallize with the orthorhombic MgCuAl 2 -type structure, space group Cmcm . The structures of CaRhPb 2 ( a  = 433.78(3), b  = 1102.06(8), c  = 798.43(6) pm, wR  = 0.0285, 432 F 2 values and 16 variables) and EuPdPb 2 ( a  = 457.24(5), b  = 1158.27(13), c  = 775.73(8), wR  = 0.0464, 464 F 2 values and 16 variables) were refined from single crystal X-ray diffractometer data. The characteristic structural motif is the distorted tetrahedral substructure built up by the lead atoms with Pb–Pb distances of 326–327 pm in CaRhPb 2 and of 315–345 pm in EuPdPb 2 . With increasing size of the alkaline earth (Eu) cation, the lead substructure becomes more anisotropic with a shift of the [ T Pb 2 ] polyanions from three- to two-dimensional, leading to significantly increased moisture sensitivity. Temperature dependent magnetic susceptibility studies reveal Pauli paramagnetism for SrRhPb 2 , SrPtPb 2 , BaPdPb 2 and BaPtPb 2 . EuRhPb 2 and EuPdPb 2 are Curie–Weiss paramagnets with stable divalent europium as is also evident from 151 Eu Mössbauer spectra. EuRhPb 2 is a ferromagnet with T C  = 17.7(2) K, while EuPdPb 2 orders antiferromagnetically at T N  = 15.9 K. This is in agreement with the full magnetic hyperfine field splitting of the 151 Eu Mössbauer spectra at T  = 6 K.

Since the 1970s, high-resolution transmission electron microscopy (HRTEM) is well established as the most appropriate method to explore the structural complexity of niobium tungsten oxides. Today, scanning transmission electron microscopy (STEM) represents an important alternative for performing the structural characterization of such oxides. STEM images recorded with a high-angle annular dark field (HAADF) detector provide not only information about the cation positions but also about the distribution of niobium and tungsten as the intensity is directly correlated to the local scattering potential. The applicability of this method is demonstrated here for the characterization of the real structure of Nb 7 W 10 O 47.5 . This sample contains well-ordered domains of Nb 8 W 9 O 47 and Nb 4 W 7 O 31 besides little ordered areas according to HRTEM results. Structural models for Nb 4 W 7 O 31 and twinning occurring in this phase have been derived from the interpretation of HAADF-STEM images. A remarkable grain boundary between well-ordered domains of Nb 4 W 7 O 31 and Nb 8 W 9 O 47 has been found that contains one-dimensionally periodic features. Furthermore, short-range order observed in less ordered areas could be attributed to an intimate intergrowth of small sections of different tetragonal tungsten bronze (TTB) based structures.

The new sulfochloride FeBiS 2 Cl is obtained as a black powder following a mechanochemical synthesis procedure. The product crystallizes in the orthorhombic space group Cmcm (no. 63) with lattice parameters a  = 3.82142(7), b  = 12.2850(2) and c  = 9.2911(2) Å. While the iron atom has an octahedral coordination environment, the bismuth atom is coordinated in the form of a bicapped trigonal prism. Both cation polyhedra form alternating layers, for iron built up of corner sharing octahedra along the c axis and edge sharing ones along the a axis. The bismuth polyhedra are connected through shared faces along the c axis and common edges along the a axis. Because of the distribution of sulfur and chlorine on a mixed anion site, the bismuth atoms occupy split positions. Experimental observations are supported by theoretical calculations.

Three thallium(I) diphosphates with compositions Tl 4 P 2 O 7 , Tl 2 H 2 P 2 O 7 , Tl 2 H 2 P 2 O 7 (H 2 O) 0.5 and the mixed-valent thallium(I,III) diphosphate Tl 2 P 2 O 7 (= Tl I Tl III P 2 O 7 ) were obtained from aqueous solutions using an ion-exchange resin (Tl 4 P 2 O 7 ), through thermal treatment of TlH 2 PO 4 at 190 °C and subsequent crystallization from aqueous solutions (Tl 2 H 2 P 2 O 7 , Tl 2 H 2 P 2 O 7 (H 2 O) 0.5 ), and from a phosphate flux at 220 °C (Tl 2 P 2 O 7 ). The crystal structures of monoclinic Tl 4 P 2 O 7 ( C 2/ c , Z  = 4) and orthorhombic Tl 2 H 2 P 2 O 7 ( Pbca , Z  = 8) are unique, whereas monoclinic Tl 2 H 2 P 2 O 7 (H 2 O) 0.5 ( C 2/ c , Z  = 8) is isotypic with its potassium analogue, and triclinic Tl 2 P 2 O 7 ( P 1‾$‾{1}$, Z  = 4) crystallizes in the TlInAs 2 O 7 structure type. The crystal structure of Tl 2 P 2 O 7 is related to that of In 2 P 2 O 7 (= In I In III P 2 O 7 ; P 2 1 / c , Z  = 4) by a translationengleiche group-subgroup relationship ( t 2). IR spectra of Tl 4 P 2 O 7 , Tl 2 H 2 P 2 O 7 and Tl 2 P 2 O 7 are reported and discussed.

The solution behavior of beryllium halides and triflate in acetonitrile was studied by NMR, IR and Raman spectroscopy. Thereby mononuclear units [(MeCN) 2 Be X 2 ] ( X  = Cl, Br, I, OTf) were identified as dominant species in these solutions. The solid state structure of [(MeCN) 2 Be(OTf) 2 ] has been determined by X-ray diffraction. If only one equivalent of MeCN is used the dinuclear compounds [(MeCN)Be X 2 ] 2 ( X  = Cl, Br, I) are formed. Partial halide and triflate dissociation into the monomeric complexes as well as the formation of hetero-halide complexes [(MeCN) 2 BeClBr], [(MeCN) 2 BeClI] and [(MeCN) 2 BeBrI] was observed.

Colorless crystals of the barium rare earth hydrogarnets Ba 3 [ RE (OH) 6 ] 2 ( RE  = Sc, Y, Ho–Lu) were synthesized under hydroflux conditions with KOH at about T  = 200 °C starting from the respective RE 2 O 3 and Ba (NO 3 ) 2 . Single-crystal X-ray diffraction analysis on these distorted rhombic dodecahedra revealed the cubic space group Ia 3‾$‾{3}$ d (no. 230). The crystal structures of the hydrogarnets Ba 3 [ RE (OH) 6 ] 2 are discussed and compared with those of other hydrogarnets. The occurrence of additional reflections, which do not fulfill the reflection conditions of Ia 3‾$‾{3}$ d , is analyzed and described by Renninger or λ /2 effects. A correlation is established between the space group adopted by a hydrogarnet and characteristic interatomic distances. In addition, single-crystal structure data of the strontium indium hydrogarnet Sr 3 [In(OH) 6 ] 2 are provided.

Three new compounds of the Cs Ln [P 2 Se 6 ] family with Ln  = Ce, Sm and Er have been prepared and structurally characterized. Plate-shaped, amber-colored single crystals of these cesium lanthanoid(III) hexaselenodiphosphates(IV) were obtained by heating stoichiometric amounts of Ln , P and Se with CsCl as a reactive flux in fused silica ampoules at 800 °C for four days. CsCe[P 2 Se 6 ] crystallizes monoclinically in space group P 2 1 / c with a  = 1297.86(9), b  = 776.24(5), c  = 1198.43(8) pm, β  = 106.589(3)° and Z  = 4. The structure is isotypic with that of KLa[P 2 Se 6 ], the Cs + cations being ten-fold coordinated by selenium atoms to form double layers of condensed [CsSe 10 ] 19− polyhedra. Ce 3+ resides in a nine-fold coordination and the [CeSe 9 ] 15− polyhedra also form double layers parallel to (100). CsSm[P 2 Se 6 ] crystallizes in the orthorhombic space group P 2 1 2 1 2 1 with a  = 688.67(5), b  = 754.48(5), c  = 2215.21(15) pm and Z  = 4. Its structure is isotypic with that of KY[P 2 Se 6 ] and the Cs + cations reside in an eleven-fold coordination of selenium atoms constituting monolayers of condensed [CsSe 11 ] 21− polyhedra within the (001) plane. Sm 3+ exhibits an eight-fold coordination sphere of selenium atoms and the [SmSe 8 ] 13− polyhedra are also linked to build up parallel monolayers. CsEr[P 2 Se 6 ] crystallizes in the monoclinic space group P 2 1 / c again, but forms its own structure type with the lattice parameters a  = 753.81(5), b  = 1281.92(9), c  = 1276.47(9) pm and β  = 106.898(3)° and Z  = 4. The Cs + cations are twelve-fold coordinated by selenium atoms and erects a three-dimensional framework of condensed [CsSe 12 ] 23− polyhedra. The Er 3+ cations show seven selenium atoms as neighbors and the [ErSe 7 ] 11− polyhedra are edge-connected to form discrete dimers [Er 2 Se 12 ] 18− . All three structures have similar ethane-like [P 2 Se 6 ] 4– anions in staggered conformation with bond lengths of 219–226 pm for d (P1–P2) and 213–222 pm for d (P–Se), which connect the Cs + and Ln 3+ coordination polyhedra into three-dimensional crystal structures.

Many Laves phases take up considerable amounts of hydrogen to form metallic Laves phase hydrides. They frequently undergo phase transitions driven by ordering phenomena for the hydrogen atom distribution. The cubic Laves phase ZrCr 2 takes up hydrogen to form a hydride with almost four hydrogen atoms per formula unit, which undergoes a phase transition to a monoclinic modification at a critical temperature T c  = 250.2 K. Its crystal structure was refined based on neutron powder diffraction data on the deuteride (ZrCr 2 D 3.8 type [ T  = 1.6 K, C 2/ c ]) at four temperatures in the range 50 K ≤  T  ≤ 200 K. The monoclinic low-temperature modification features a strongly distorted square anti-prism ZrD 8 and three CrD 4 polyhedra with almost fully occupied deuterium sites in saddle-like, distorted tetrahedral and planar configurations. Zr–D distances are in the range 201.4(7) pm ≤  d (Zr–D) ≤ 208.5(8) pm and Cr–D distances in the range 172.9(7) pm ≤  d (Cr–D) ≤ 182.4(8) pm.

Orthorhombic HP-Al 2 B 3 O 7 (OH) was synthesized in a Walker-type multianvil apparatus under high-pressure/high-temperature conditions of 12.4 GPa and 1200 °C, respectively. Its structure is isotypic to that of Ga 2 B 3 O 7 (OH) and has been determined via single-crystal X-ray diffraction at room temperature. HP-Al 2 B 3 O 7 (OH) crystallizes in the space group Cmce ( Z  = 8) with the lattice parameters a  = 10.3124(4), b  = 7.3313(3), c  = 10.4801(5) Å, and V  = 792.33(6) Å 3 . The compound has also been characterized by IR and Raman spectroscopy.

The new supertetrahedral compounds M SiAs 2 , M GaSiAs 3 and mC / tI - M 4 Ga 5 SiAs 9 ( M  = Sr, Eu) have been synthesized by solid-state reactions at high temperatures. The structures were determined by single crystal or powder X-ray diffraction. M SiAs 2 and M GaSiAs 3 crystallize in the monoclinic TlGaSe 2 - and RbCuSnS 3 -type structures, respectively (space group C 2/ c ). These are topologically hierarchical variants of the tetragonal HgI 2 -type structure with stacked layers of T2 or T3 supertetrahedra. The T4 compounds M 4 Ga 5 SiAs 9 are dimorphic and form new structure types in the space groups C 2/ c and I 4 1 / amd , respectively. The latter exhibits coinciding layer stacking as known from tetragonal HgI 2 . The T4 compounds close the gap between the longer known T2 types and the recently reported compounds with T5 and T6 supertetrahedra. Measurements of the optical band gap, electrical resistivity and Hall Effect support the semiconducting nature of M 4 Ga 5 SiAs 9 . Magnetization measurements confirm Eu 2+ in Eu 4 Ga 5 SiAs 9 and indicate ferromagnetism below T  = 2 K.

The excited state properties of Pt(II) complexes are strongly influenced by their microenvironment and by intermolecular interactions. In this work, we investigated the photoluminescence of six Pt(II) complexes adsorbed onto a layered nanoclay, namely Laponite ® ( LAP ). The excellent water dispersibility and gel-forming nature of the LAP was exploited to achieve a class of versatile materials. In particular, we report on the comparative photophysics of the dry powders and the hydrogels. Steady-state and time-resolved photoluminescence spectroscopy were used to assess the role of structural features at molecular level on the interaction between the nanodiscs, which in turn affects the intermolecular coupling of the coordination compounds in the excited state.

Carbon subsulfide C 3 S 2 can be produced on a preparative scale by flash vacuum pyrolysis (FVP). The precursor 5-(methylthio)-3 H -1,2-dithiole-3-thione (C 4 H 4 S 4 ) proved to be particularly suitable and yields up to 8% could be achieved on evaporation at T  = 180 °C and pyrolysis of the vapour at 950 °C. The other precursors tested, C 4 S 6 and C 6 S 8 , were far less productive. Insight into the thermal conversion of C 4 S 6 was gained by isolation and structure determination of a new isomer of the sulur-carbon compound C 8 S 8 , which is formed on thermal treatment of C 4 S 6 at T  = 330 °C. The formation of C 8 S 8 can be interpreted by sulfur cleavage from C 4 S 6 . Crystal growth by sublimation below 0 °C allowed for the determination of the crystal structure of C 3 S 2 . The five-atomic molecules are linear and arranged in a typical pattern analogous to the crystal structures of I 2 , CS 2 and CSe 2 . The reaction of C 3 S 2 with bromine is known to give C 3 Br 6 S 2 of yet unknown structure. By sublimation of C 3 Br 6 S 2 in air, 4,5-dibromo-1,2-dithiol-3-one (C 3 Br 2 OS 2 ) was obtained, representing the product of bromine abstraction and oxidation. This substantiates the former suggestion for C 3 Br 6 S 2 to have the structure of a hexabromodithiolane.