Barium titanate is the most general ferroelectric material which is widely studied in physics and application. The origin of large ferroelectricity is known to be the strong Ti-O covalency of perovskite-type BaTiO3. Therefore, the substitution of oxygen by fluorine which has the largest electronegativity can control the Curie temperature. In the present article, we show “the large annealing effect on TC due to the evaporation of fluorine from the crystal” and “Critical phenomena in KF-substituted BaTiO3 probed by inelastic light scattering”.
Controlled intramolecular electron transfers were demonstrated in a series of cyanide-bridged Fe-Co molecular squares, [Co2Fe2(CN)6(L1)2(L2)4](PF6)2. The electronic structures of the molecular squares can be varied between [FeIIILS2CoIIHS2] and [FeIILS2CoIIILS2] state by intramolecular electron transfers, which were significantly affected by the redox potential differences between metal ions. Chemical modifications of the capping ligands allowed the systematic control of the electronic states, and the occurrence of a novel two-step thermal electron transfer-coupled spin transition (ETCST). The two-step ETCST was originating from three thermodynamically stable phases, LT, IM, and HT phases. The electronic structure of each phase was investigated by X-ray structural analyses, and the IM phase showed long-range order of [FeIIILS2CoIIHS2] and [FeIILS2CoIIILS2] species. In addition, novel thermal and protonation-induced ETCST in the solution state were found using variable temperature UV-vis absorption spectroscopy.
BiNiO3 is a perovskite compound with unique Bi3+0.5Bi5+0.5Ni2+O3 oxidation state. Neutron powder diffraction and synchrotron X-ray absorption studies revealed the intermetallic charge transfer between Bi5+ and Ni2+ on pressurization or on heating at a moderate pressure leading to the shrinkage of the unit cell volume. Partial substitution of La3+ for Bi shifts the phase boundary between Bi3+0.5Bi5+0.5Ni2+O3 and Bi3+Ni3+O3 to the low pressure, low temperature side. Bi0.95La0.05NiO3 shows a negative thermal expansion with a dilatometric thermal coefficient of −82×10−6/K, three times as large as the existing compound.
Powder samples of lead zirconate titanate Pb(Zr,Ti)O3 with several Zr/Ti composition ratio have been prepared by mixed-oxide and sol-gel routes. Their crystal structures were determined by the Rietveld refinement using a high resolution time-of-flight neutron diffraction. It is found that the best refinement results have been obtained with mixture-phase models at all compositions and temperatures below the cubic phase. Anisotropic peak broadening and coherent scatterings of domains were considered in the refinement. The existence of monoclinic Cm phase suggests that there is no definite phase boundary known as the morphotropic phase boundary.
Kainate receptors (KARs) are members of the ionotropic glutamate receptors (iGluR) that play variety of roles in the mammalian brain. Because KARs are comprised of five different isoform proteins, isoform selective compounds are indispensable tools in physiological researches. Dysiherbaine (DH) and neodysiherbaine A (NDH), natural toxins found from marine sponges, were shown to be potent and isoform-selective agonists for KARs. To understand structure-activity relationship of DH and NDH, numbers of analogues are synthesized, and their pharmacological activities have been evaluated in detail. Here, we determined the crystal structures of human KAR isoforms, GluK1 and GluK2, ligand-binding domain in complex with the DH analogues at high resolution. From these structures, we elucidated the relationships between the binding affinity and the molecular structure of the compounds. We also demonstrated differential recognition by some of the DH analogues of closely related isoforms GluK1 and GluK2. Further, we found that neither degree of the domain closure nor twist motion of domains directly correlated to agonist efficacy of the ligands.
Recent developments on thermally convertible soluble precursors of copper phthalocyanine (CuPc), which can be potentially useful for fabrication of a variety of organic devices, have been reviewed. Reaction of phthalonitrile with lithium alkoxides under mild conditions successfully yielded a series of soluble CuPc precursors (4a–4d). X-ray crystallography clarified that the conjugated skeletons of these are all isostructural, and have two alkoxy groups in a syn-conformation fashion, leading to highly bent structures. Thermal analyses demonstrate that these precursors are quantitatively converted into insoluble CuPc with increasing the temperature, in which the conversion temperatures are dependent on the crystal structures of the samples.
Two-dimensional (2D) nanosheets with a thickness of less than 1 nm and lateral dimensions up to a few μm are the thinnest self-standing 2D nanostructures; they are just about one unit cell thick. Research in 2D systems has recently intensified as a result of the emerging progress in graphene—a carbon nanosheet, as well as the successful exfoliation of transition-metal oxide nanosheets. Such exotic 2D nanosheets have been emerging as important new nanomaterials owing to their unique physical properties. Here, we present structures and properties of 2D oxide nanosheets, highlighting emerging functionalities in electronic applications.
Fully automated data collection and processing system has been developed on macromolecular crystallography beamlines at the Photon Factory. In this system, the sample exchange, centering and data collection are sequentially performed for all samples stored in the sample exchange system at a beamline without any manual operations. Data processing of collected data sets is also performed automatically. These results are stored into the database system, and users can monitor the progress and results of automated experiment via a Web browser.