The crystal structure of π-ErBO3: New single-crystal data for an old problem

Single crystals of the orthoborate π-ErBO₃ were synthesized from Er₂O₃ and B₂O₃ under high-pressure/high-temperature conditions of 2 GPa and 800 °C in a Walker-type multianvil apparatus. The crystal structure was determined on the basis of single-crystal X-ray diffraction data, collected at room temperature. The title compound crystallizes in the monoclinic pseudowollastonite-type structure, space group C2/c, with the lattice parameters a=1128.4(2) pm, b=652.6(2) pm, c=954.0(2) pm, and β=112.8(1)° (R₁=0.0124 and wR₂=0.0404 for all data).     

Effect of temperature on the polarization distribution in BTS functional gradient ceramics

The effect of the chemical composition gradient in barium titanate-stannate (BTS) piezoelectric ceramic on the depth distribution of the effective pyroelectric coefficient was investigated. A correlation between the coordinate dependence of polarization in the sample and the polarization temperature is demonstrated.     

Synthesis of Er5(BO3)2F9 and Properties of RE5(BO3)2F9 (RE = Er,Yb)

Er₅(BO₃)₂F₉ was synthesised under conditions of 3 GPa and 800 °C in a Walker‐type multianvil apparatus. The crystal structure was determined on the basis of single‐crystal X‐ray diffraction data, collected at room temperature. Er₅(BO₃)₂F₉ is isotypic to the recently synthesised Yb₅(BO₃)₂F₉ and crystallises in C2/c with the lattice parameters a = 2031.2(4) pm, b = 609.5(2) pm, c = 824.6(2) pm, and β = 100.29(3)°. The physical properties of RE₅(BO₃)₂F₉ (RE = Er, Yb) including high temperature behaviour and single crystal IR‐ / Raman spectroscopy were investigated.     

High-pressure synthesis and crystal structure of the mixed-valent titanium borate Ti5B12O26

The new titanium borate was synthesized under high-pressure/high-temperature conditions in a Walker-type multianvil apparatus at 7.5 GPa and 1350 °C. Ti₅B₁₂O₂₆ is built up exclusively from corner-sharing BO₄-tetrahedra and shows a structural relation to the Zintl phase NaTl. Consisting of B₁₂O₂₆-clusters as fundamental building blocks, the structure of Ti₅B₁₂O₂₆ can be described via two interpenetrating diamond structures as in NaTl, where each atom corresponds to one B₁₂O₂₆-cluster. The tetragonal titanium borate crystallizes with eight formula units in the space group I4₁/acd and exhibits lattice parameters of a=1121.1(2) pm and c=2211.5(4) pm. Ti₅B₁₂O₂₆ is a mixed-valent compound with Ti^III and Ti^IV cations. The environment of the titanium cations, as well as charge distribution calculations, leads us to the assumption that Ti^III and Ti^IV are located on different crystallographic sites.     

Synthese von 1,3-Dithiol-2-thion-Derivaten durch Phasentransfer-Dithiocarboxylierung von CH-aciden O-Alkyl-dithiokohlensäurediestern

Summary CH-Acidic O-alkyl dithiocarbonates1 react with carbon disulfide in a one-pot synthesis under basic conditions (NaH inDMF or phase transfer conditions) and S-alkylation to novel 1,3-dithiole-2-thiones3–6. The structure of these compounds and supporting n.m.r., ir and mass spectra are discussed.

     

Congresses,conferences, symposia,consultations, and seminars in the field of chemical sciences held with participation of the russian academy of sciences

Information

Congresses, conferences, symposia, consultations, and seminars in the field of chemical sciences held with participation of the russian academy of sciencesVI International Frumkin Symposium Fundamental Aspects of Electrochemistry*     

Explicit attention interferes with selective emotion processing in human extrastriate cortex

Background  

Brain imaging and event-related potential studies provide strong evidence that emotional stimuli guide selective attention in visual processing. A reflection of the emotional attention capture is the increased Early Posterior Negativity (EPN) for pleasant and unpleasant compared to neutral images (~150–300 ms poststimulus). The present study explored whether this early emotion discrimination reflects an automatic phenomenon or is subject to interference by competing processing demands. Thus, emotional processing was assessed while participants performed a concurrent feature-based attention task varying in processing demands.     

Homogeneous free‐radical polymerization of styrene in supercritical CO2

The free‐radical polymerization of styrene has been studied in the homogeneous phase of supercritical (sc) CO₂ at 80°C and pressures between 200 and 1 500 bar. 2,2'‐Azobisisobutyronitrile is used as initiator and CBr₄ as chain‐transfer agent. The polymerization is monitored by means of online FT‐IR/NIR spectroscopy. In the presence of CO₂ a solution polymerization may be carried out up to a considerable degree of monomer conversion. At 500 bar, for example, maximum styrene conversions of 34.4 and 11.9% may be reached in homogeneous phase at CO₂ contents of 16.8 and 44.5 wt.‐%, respectively. Analysis of the measured conversion‐time profiles yields termination rate coefficients, k_t, which are by one order of magnitude larger than k_t for styrene bulk polymerizations at identical temperature and pressure. The enhanced termination rate in fluid CO₂ is assigned to the poor solvent quality of scCO₂ for polystyrene.