Marine organisms combat bacterial colonization by biohalogenation of signaling compounds that interfere with bacterial communication. These reactions are catalyzed by haloperoxidase enzymes, whose activity can be emulated by nanoceria using...

A Guinier camera equipped with an imaging plate is used to investigate and eliminate the sources of instrumental errors affecting the quality of the obtained scanned Guinier data. A program with a graphical user interface is presented which converts the data of the scanned images into different standard file formats for powder X-ray patterns containing intensities, their standard deviations and the diffraction angles. The program also allows for manual and automatic correction of the 2θ scale against a known reference material. It is shown using LaB6 that the exported X-ray diffraction patterns provide a 2θ scale reproducible enough to allow for averaging diffractograms obtained from different exposures of the imaging plate for the same sample. As shown on a mixture of NaCl and sodalite, the quality of the produced data is sufficient for Rietveld refinement. The software including source code is made available under a free software license.

The molecule 4,4′-azobis­(3,5-dimethyl-1H-pyrazole) (H2azbpz) can exist in different planar conformers that differ in the relative orientation of the NH atoms with respect to the central azo bond and are related by azo-pedaling, rotation of the pyrazolyl group around the C4–N­(azo) bond, or N1–H to N2–H proton transfer. In the two polymorphs H2azbpz-I and H2azbpz-II, the two symmetrical forms 4,4′-a,a-E (I) and 4,4′-s,s-E (II) assemble in their own solid-state packing as a case of conformational polymorphism. Lattice energy and gas-phase conformer calculations point to the harder-to-obtain polymorph H2azbpz-II, as the thermodynamic more stable form at lower temperatures but having the higher energy conformer form II. Both polymorphs H2azbpz-I and H2azbpz-II were reproducibly obtained by their own crystallization experiments which initially included ball milling to transform H2azbpz-I into -II. The polymorph structures were established by single-crystal and powder X-ray diffraction in combination with Raman spectroscopy and solid-state 13C­{1H} cross-polarization magic angle spinning NMR. The supramolecular assembly of H2azbpz in its two polymorphs features supramolecular honeycomb sheets (hcb topology) in a staggered AA′-packing (in H2azbpz-I) or in an eclipsed AB-fashion (in H2azbpz-II). In addition, the hemihydrate H2azbpz·0.5H2O crystallized reproducibly from water-containing solutions, based on a tetrahedral (T d) {H2O­(pz)4}-subunit with pseudo T d-water molecules, thereby giving a network structure with dia-topology, which can be regarded as a supramolecular analogue of the cubic ice polymorph Ic.

Polycrystallinepowder and single crystals of Na 2 [Zn(NH 2 ) 4 ] • (NH 3 ) 0.24 and Na 2 [Zn(NH 2 ) 4 ] • (H 2 O) 0.37 were obtained under ammonobasic conditions at 823 K and 200 MPa. Upon substituting the constituent ammonia by water, the space group (C2/c) and crystal structure remain generally unchanged. Nevertheless, the presence of water during the ammonothermal synthesis has a fundamental impact on the transport direction, changing from exothermic for the pure ammonia system to an endothermic material transport for the hydrate formation under essentially the same experimental conditions. That indicates that even a small amount of oxygen can have a fundamental influence on the solubility and its temperature dependence of dissolved species during ammonobasic synthesis. Chemical analysis, Raman spectroscopy and thermal analysis consistently support the composition assignment. Solid-state NMR measurements back up the exchange of exclusively ammonia by water, rather than introduction of hydroxide ions. A minor enhancement of the thermal stability of the hydrate compared to the ammoniate is observed.