Volume 233, Issue 6

Results of combined synchrotron X-ray diffraction and pair distribution function experiments performed on the layered compound CrTe 3 provide evidence for a short range structural distortion of one of the two crystallographically independent CrTe 6 octahedra. The distortion is caused by higher mobility of one crystallographically distinct Te ion, leading to an unusual large Debye Waller factor. In situ high temperature X-ray diffraction investigations show an initial crystallization of a minor amount of elemental Te followed by decomposition of CrTe 3 into Cr 5 Te 8 and Te. Additional experiments provide evidence that the Te impurity (<1%) cannot be avoided. Analyses of structural changes in the temperature range 100–754 K show a pronounced anisotropic expansion of the lattice parameters. The differing behavior of the crystal axes is explained on the basis of structural distortions of the Cr 4 Te 16 structural building units. An abrupt distortion of the structure occurs at T ≈250 K, which then remains nearly constant down to 100 K. The structural distortion affects the spin exchange interactions between Cr 3+ cations. A significant splitting between field-cooled ( fc ) and zero-field-cooled ( zfc ) magnetic susceptibility is observed below about 200 K. Applying a small external magnetic field results in a substantial spontaneous magnetization, reminiscent of ferro- or ferrimagnet exchange interactions below ~240 K. A Debye temperature of ~150 K was extracted from heat capacity measurements.

The crystal structure of [Cu 2 ( μ- O)( μ -I) 2 (CNXyl) 4 ]·I 2 ( 2 ·I 2 ) was determined from single-crystal X-ray diffraction data. The adduct 2 ·I 2 represents the first example of structurally characterized isocyanide-copper(II) complexes. In the structure of 2 ·I 2 , 2 forms independent chains connected through molecular iodine via I···I–I···I halogen bonding. The DFT calculations and topological analysis of the electron density distribution within the formalism of Bader’s theory (QTAIM method) were performed for model complex 2 ·I 2 and the obtained results allowed the attribution of these contacts to moderate strength (3.8–5.3 kcal/mol) non-covalent contacts exhibiting some covalent character.

The low-temperature polymorph β -Ca 11 B 2 Si 4 O 22 crystallizes as a monoclinic structure [space group is P 2 1 / c , a =14.059(9), b =6.834(5), c =10.597(7) Å, β =100.735(8)°]. The crystal investigated by single-crystal X-ray diffraction was a twin composed of six individuals. The crystal structure is similar to that of mineral spurrite, Ca 5 (SiO 4 ) 2 CO 3 , and can be described as a framework of [CaO 5 ] and [CaO 6 ] polyhedra, the cavities of which are filled with [SiO 4 ] and [BO 3 ] groups. The orientation relationship of twin domains was investigated by electron backscatter diffraction (EBSD). Thermal expansion was studied by high-temperature X-ray powder diffraction. It is slightly anisotropic: α 11 =10, α 22 =16, α 33 =12×10 −6 °C −1 at 200°C.

The first uranyl beryllophosphate, [(UO 2 ) 2 {Be(H 2 O) 2 (PO 4 ) 2 }]·(H 2 O), has been synthesized under hydrothermal conditions at 200°C. The monoclinic unit-cell parameters are: a =9.3361(1), b =8.8545(4), c =9.6592(10) Å, β=93.211(1)°, V =797.21(6) Å 3 , space group P 2 /n , Z =2. The crystal structure has been solved by direct methods and refined to final R 1 =4.92% using 1294 I >3σ( I ) reflections in the anisotropic approximation. The structure consists of sheets of Ur O 5 pentagonal bipyramids and PO 4 tetrahedra. Ur O 5 bipyramids are linked by edge-sharing to form infinite chains. Adjacent chains of Ur O 5 bipyramids are connected by sharing alternating edges of uranyl bipyramids with PO 4 tetrahedra. The resulting sheets are based on the well-known uranophane anion-topology. Be atoms are tetrahedrally coordinated by two oxygen atoms of PO 4 tetrahedra and two water molecules in the interlayer space. One isolated water molecule also occurs in the interlayer space, where it is held in position by H bonds. The connection between the phosphorus and beryllium tetrahedra leads to formation of an unbranched trimer [BeP 2 O 8 (H 2 O) 2 ] 4− observed for the first time in inorganic oxysalts.

Hydrogenation products of the Zintl phases AeTt ( Ae = alkaline earth; Tt = tetrel) exhibit hydride anions on interstitial sites as well as hydrogen covalently bound to Tt which leads to a reversible hydrogenation at mild conditions. In situ thermal analysis, synchrotron and neutron powder diffraction under hydrogen (deuterium for neutrons) pressure was applied to Ba Tt ( Tt =Ge, Sn). Ba Tt H y (1<y<1.67, γ-phases) were formed at 5 MPa hydrogen pressure and elevated temperatures (400–450 K). Further heating (500–550 K) leads to a hydrogen release forming the new phases β-BaGeH 0.5 ( Pnma , a =1319.5(2) pm, b =421.46(2) pm, c =991.54(7) pm) and α-BaSnH 0.19 ( Cmcm , a =522.72(6) pm, b =1293.6(2) pm, c =463.97(6) pm). Upon cooling the hydrogen rich phases are reformed. Thermal decomposition of γ-BaGeH y under vacuum leads to β-BaGeH 0.5 and α-BaGeH 0.13 [ Cmcm , a =503.09(3) pm, b =1221.5(2) pm, c =427.38(4) pm]. At 500 K the reversible reaction α-BaGeH 0.23 (vacuum)⇄β-BaGeH 0.5 (0.2 MPa deuterium pressure) is fast and was observed with 10 s time resolution by in situ neutron diffraction. The phases α-Ba Tt H y show a pronounced phase width (at least 0.09<y<0.36). β-BaGeH 0.5 and the γ-phases appear to be line phases. The hydrogen poor (α- and β-) phases show a partial occupation of Ba 4 tetrahedra by hydride anions leading to a partial oxidation of polyanions and shortening of Tt – Tt bonds.

A new borate compound K 3 GdB 6 O 12 has been prepared using a high temperature flux method and structurally characterized by single crystal X-ray diffraction analysis. The structure can be described as a three-dimensional framework that is composed of [B 5 O 10 ] 5− groups, K + ions and Gd 3+ ions. In this structure, one crystallographic distinct site is mixed occupied by K and Gd atoms at the molar ratio of 1:1. Furthermore, Sm 3+ ion was used as the activator to test primary of K 3 GdB 6 O 12 to be used as a luminescent host matrix. A series of phosphors K 3 Gd 1−x B 6 O 12 :xSm 3+ were synthesized by conventional solid-state reaction. The photoluminescence properties and concentration quenching of the prepared phosphors were investigated. The results show that K 3 Gd 1−x B 6 O 12 :xSm 3+ can be efficiently excited by near-UV light. K 3 Gd 1−x B 6 O 12 :xSm 3+ might be a promising candidate for visual display and solid-state lighting as an orange emission phosphor.

Four indole-based compounds have been synthesized and their crystal structures determined using high-resolution synchrotron powder X-ray diffraction. In vacuo density function theory (DFT) optimization has been used in building initial molecular models for structure solution with the help of the Cambridge structure database. All four compounds were found to crystallize in the monoclinic space group P 2 1 / c . Dispersion-corrected DFT (DFT-D) has been used for experimental crystal structure validation with acceptable agreement found between the DFT-optimized and final refined structures. Three of the compounds exhibit bronchodilation properties with potency comparable to the theophylline (standard reference).

The ordered structure of the guest-free microporous metal-organic framework zinc 5-tert-butyl isophthalate {Zn[(CH 3 ) 3 CC 6 H 3 (CO 2 ) 2 ]} has been determined and shown to be easily loaded with methanol to form {Zn[(CH 3 ) 3 CC 6 H 3 (CO 2 ) 2 ]}·CH 3 OH. The methanol forms a S 6 -symmetric hexamer within the pores of the material that is uniquely defined by the void space and exerts a subtle structural effect on the framework structure of the host. The work demonstrates the use of this type of metal-organic framework as a matrix to isolate unique molecular clusters in a facile manner.