K8Gd3Si12O32Cl · 2H2O,a new member of the family of porous silicates with K and RE elements

Crystals of K₈Gd₃Si₁₂O₃₂Cl · 2H₂O (space group $P\bar 1$ ), a new member of the family of porous silicates containing rare earths, are obtained under hydrothermal conditions. The structure retains the main features of the family in which original one-story layers of Si-tetrahedra formed by 6-membered rings of two types and large-in-diameter 8-membered and 12-membered rings are bound by Gd-octahedra to form a framework. Large pores in the interlayer space of the mixed framework are filled with K⁺ ions. The penetration of Cl^? ions from a concentrated mineralizing solution into the centers of the eight-membered rings of the layer corroborates the ion-exchanging properties of the crystals of this structural type. The filling of rings and pores of different types in different members of the family by K⁺ and Cl^? ions, hydroxyl groups, and water molecules is analyzed.     

Large spontaneous polarization and clear hysteresis loop of a room-temperature hybrid ferroelectric based on mixed-halide [BiI3Cl2] polar chains and methylviologen dication

The search for hybrid organic-inorganic materials, which have the great advantage that they can be synthesized at moderate temperature (T < 200 °C), remains a great challenge in the field of ferroelectrics. Here, a room-temperature ferroelectric material with interesting characteristics, (MV)[BiI(3)Cl(2)] (MV(2+) = methylviologen), is reported. Its structure is based on polar inorganic chains resulting from a remarkable Cl/I segregation induced by methylviologen entities, which coincide with the fourfold polar axis of the tetragonal structure. Of great importance is that this room-temperature hybrid ferroelectric displays a clear electrical hysteresis loop with a large spontaneous polarization (>15 μC·cm(-2)).     

Improvement of technology for producing fine-grained activated carbon AG-5

The investigations of carbons of varying degrees of metamorphism and prepared based on of them coal resin compositions were carried out. An effect of coal resin composition on the parameters of the formed porous structure of activated carbon was demonstrated.     

Synthesis and anti-influenza activity of 2-cyanoethoxy and 2-(1<Emphasis Type="Italic">H</Emphasis>-tetrazol-5-yl)ethoxy derivatives of dammarane-type triterpenoids

A series of 3-(2-1Н-tetrazol-5-ylethoxy- and 2-1Н-tetrazol-5-ylethoxyimino) derivatives of dammarane triterpenoids was synthesized by azidation of 3-(2-cyanoethoxy- and 2-cyanoethoxyimino)-dammaranes. The anti-influenza activity of the prepared tetrazolyldammaranes and intermediate compounds against influenza virus А H1N1 was tested. A considerable antiviral activity was observed for 20(S)-3-(2-1Н-tetrazol-5-ylethoxyimino)-25,26,27-trinor-20,24-olidedammarane (SI 26).     

A general synthetic strategy for the design of new BODIPY fluorophores based on pyrroles with polycondensed aromatic and metallocene substituents

BODIPYrrole: A general strategy for the design of novel BODIPY fluorophores based on pyrroles with polycondensed aromatic and metallocene substituents has been developed. The strategy involves the acylation of the condensed substituent and treatment of the acylated derivative (as oxime) with acetylene in MOH/DMSO (M = alkali metal) to give pyrroles that were then used for assembly of the BODIPY fluorophores (see scheme).     

Unusual Photoinduced Response of mTHPC Liposomal Formulation (Foslip)

Liposomal formulations of meso-tetra(hydroxyphenyl)chlorin (mTHPC) have already been proposed with the aim to optimize photodynamic therapy. Spectral modifications of these compounds upon irradiation have not yet been investigated. The objective of this study was to evaluate photobleaching properties of mTHPC encapsulated into dipalmitoylphosphatidylcholine (DPPC) liposomes, Foslip. Fluorescence measurements in DPPC liposomes with different DPPC:mTHPC ratios demonstrated a dramatic decrease in fluorescence anisotropy with increasing local mTHPC concentration, thus suggesting strong interactions between mTHPC molecules in lipid bulk medium. Exposure of Foslip suspensions to small light doses (<50 mJ/cm²) resulted in a substantial drop in fluorescence, which, however, was restored after addition to the sample of a non-ionic surfactant Triton X-100. We attributed this behavior to photoinduced fluorescence quenching. This effect depended strongly on the molar DPPC:mTHPC ratio and was revealed only for high local mTHPC concentrations. The results were interpreted supposing energy migration between closely located mTHPC molecules with its subsequent dissipation by the molecules of photoproduct acting as excitation energy traps. We further assessed the effect of photoinduced quenching in plasma protein solution. Relatively slow kinetics of photoinduced Foslip response during incubation in the presence of proteins was attributed to mTHPC redistribution from liposomal formulations to proteins. Therefore, changes in mTHPC distribution pattern in biological systems would be consistent with changes in photoinduced quenching and would provide valuable information on mTHPC interactions with a biological environment.     

Synthesis and Optical Properties of 2‐(Benzo[b]thiophene‐3‐yl)pyrroles and a New BODIPY Fluorophore (BODIPY=4,4‐Difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene)

The light fantastic : Two new 2‐(benzo[b]thiophene‐3‐yl)pyrroles have been synthesized, and are shown to exhibit optical properties that are promising for optoelectronic materials and devices such as highly efficient fluorescent sensors (see scheme). In addition a new BODIPY fluorophore, derived from 2‐(benzo[b]thiophene‐3‐yl)pyrrole, was also isolated and shows good spectroscopic properties in solution which are fully preserved in the solid state.

     

Structural phase transition in crystals of the molecular conductor α′-(BDH-TTP)<Subscript>6</Subscript>[Hg(SCN)<Subscript>3</Subscript>][Hg(SCN)<Subscript>4</Subscript>]

Single crystals of the organic conductor α′-(BDH-TTP)₆[Hg(SCN)₃][Hg(SCN)₄] are studied by low-temperature X-ray diffraction at 100–300 K. It is shown that, in the temperature range 250–200 K, the compound undergoes a phase transition, which is accompanied by the appearance of superstructure reflections and a rapid increase in their intensity due to the partial anion and cation ordering. The superstructure is observed down to a temperature of 100 K, at which the set of diffraction data is collected. The temperature dependence of the electrical resistance exhibits a minimum in the range of the structural transition temperature. Under a pressure of up to 10 kbar, the general behavior of the dependence remains unchanged and only the minimum is shifted toward the low-temperature range. The phase transition is completely reversible.     

Concerning the first-order phase transition in the low-dimensional organic superconductor (BEDO—TTF)2ReO4 · H2O. Crystal and electronic band structures below the phase transition (T = 170 K)

The effect of the first-order phase transition occurring around 220 K on the crystal and electronic structure of the molecular superconductor (BEDO-TTF) has been studied. The crystal structure at 170 K has been determined and it is found that the main structural change resulting from the phase transition is connected with a rotation of the anions. This rotation leads to changes in the SS and SO intermolecular contacts within the BEDO-TTF donor layers. How these structural changes affect the electronic structure of the salt is studied by comparing the transfer integrals for the different donordonor intermolecular interactions calculated for the room temperature and 170 K crystal structures. It is shown that Fermi surfaces for the 170 K and room temperature structures are very similar, do not exhibit nesting properties, and can be described as resulting from the hybridization of superposing ellipses. Received: 4 September 1997 / Received in final form: 2 December 1997 / Accepted: 3 December 1997     

Effect of mechanical treatment on the aggregative stability of latex and on consumption of coagulants in rubber recovery

The effect that mechanical treatment of SKS-30 ARK latex by mixing in a gap between coaxial cylinders exerts on the latex resistance to an electrolyte and on the polymer yield in coagulation with two types of coagulants, sodium chloride and N,N-dimethylaminopropyl carboxy betaines derived from vegetable oil fatty acids, was studied. Such treatment decreases the rapid coagulation threshold and increases the coagulum yield. The effect is caused by partial breakdown of hydrate shells of particles as a result of mechanical action in a shear stress field.