New homochiralortho-palladated matrix bearing a bulky substituent at the carbon stereocenter

A new homochiral dimericortho-palladated complex bearing a bulkytert-butyl substituent at the carbon stereocenter was synthesized from optically activeN,N-dimethyl-α-tert-butylbenzylamine. Regioselective activation of only the aromatic C−H bond was shown to occur during the cyclometallation process proceeding under very mild conditions due to steric effects. Spectral characteristics of mononuclear derivatives of the new dimeric complex indicate that the five-membered palladacycle exists predominantly in one of two possible chiral conformations with the axial position of thetert-butyl substituent. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1375–1384, July, 1997.     

Aggregation processes of biomolecules in presence of trehalose

Among disaccharides, trehalose, a naturally-occurring glass-forming disaccharide, is particularly effective in terms of its ability to preserve several organisms under stress conditions. The present work is aimed to investigate the bioprotective action of trehalose on lysozyme as a function of temperature. In order to extract quantitative information about the dimensional changes of the proteins, we performed Small Angle Neutron Scattering measurements on lysozyme/D₂O solutions in absence and in presence of the disaccharide. The findings emphasise the capability of trehalose to stabilise the protein, activating aggregation processes.     

Sulfonated polypropylene ionomers

Polypropylene ionomers have been prepared by sulfonation of copolymers of propene and 7 methyl, 1-6 octadiene, followed by neutralization to cesium salts. Both WAXS and SAXS were used to study the morphology of the samples, while their thermal properties were studied by DSC and their mechanical properties by DMTA. The sulfonation process is shown to cause a further drop in crystallinity in addition to the effect of comonomer incorporation. Ion clustering is observed when the extent of sulfonation is high enough, the limit being dependent on the copolymer composition. The ion pairs which are not incorporated into the cluster cause a small-angle upturn in the WAXS pattern. The mechanical properties are strongly affected by the drop in crystallinity, but may be partly recovered due to ion clustering. No disruption of the ion clusters is observed before thermal decomposition of the polymer.     

Synthesis, properties, and structure of dimethylgold(III) complexes [(CH3)2AuI]2 and (CH3)2AuS2CN(C2H5)2

Volatile diethyldithiocarbamate of dimethylgold(III) was prepared by the interaction of dimethylgold(III) iodide with sodium diethyldithiocarbamate. The complex is examined by the elemental analysis, DTA, IR and electronic spectroscopy. The starting dimeric complex [(CH₃)₂AuI]₂ and a novel monomeric volatile gold(III) complex (CH₃)₂AuS₂CN(C₂H₅)₂ with the AuC₂S₂ coordination core were investigated by single crystal X-ray diffraction for the first time.     

Studies of sodium humate/polyacrylamide/clay hybrid hydrogels. I. Swelling and rheological properties of hydrogels

A type of novel hybrid hydrogels from sodium humate (SH), polyacrylamide (PAM), and hydrophilic Laponite clay were prepared using potassium persulfate (KPS) as the initiator and N,N′-methylenebisacrylamide (MBA) as the cross-linker. The structures of the hydrogels were characterized by field emission scanning electron microscope and FTIR. Their swelling properties, swelling mechanism and rheological properties were also investigated. Experiments show that the composite is heterogeneous in the PAM/SH hydrogel system, while the clay collaborates with SH and improves the network structure of PAM/SH/clay hydrogel. High water-absorbing capability is shown for both hydrogel systems. Han plot proves that clay and SH are compatible with PAM for PAM/SH/clay hydrogels.     

Die Reaktion von SeCl4 mit Übergangsmetalltetrachloriden. Synthese und Kristallstrukturen von (SeCl3)2MCl6 mit M = Zr,Hf, Mo,Re

The Reaction of SeCl₄ with Transition Metal Tetrachlorides. Synthesis and Crystal Structures of (SeCl₃)₂MCl₆ with M = Zr, Hf, Mo, Re The transition metal tetrachlorides ZrCl₄, HfCl₄ and MoCl₄ react with SeCl₄ in closed ampoules at temperatures of 140°C to (SeCl₃)₂MCl₆ (M = Zr, Hf, Mo) which are all isotypic and crystallize in the (SeCl₃)₂ReCl₆ structure type (orthorhombic, Fdd2, Z = 8, lattice constants for M = Zr: a = 1165.7(1)pm, b = 1287.2(2)pm, c = 2180.2(2)pm; for M = Hf: a = 1162.9(2)pm, b = 1285.0(2)pm, c = 2178.2(3)pm; for M = Mo: a = 1153.8(1)pm, b = 1267.7(1)pm, c = 2147.4(2)pm). The Cl^? ions form a hexagonal closest packing with one fourth of the octahedral holes filled by Se⁴⁺ and M⁴⁺ in an ordered way. The MCl₆ octahedra are regular, the SeCl₆ octahedra are distorted with 3 short and 3 long Se? Cl bonds (mean 215 pm and 287 pm). The structures can thus be regarded as built of SeCl₃⁺ and MCl₆^2? ions. Magnetic susceptibility measurements show for M = Zr the expected diamagnetic behavior, for M = Mo and Re paramagnetic behavior according to the Curie-Weiss law with magnetic moments of 2.5 B. M. for M = Mo and 3.7 B. M. for M = Re corresponding to 2 and 3 unpaired electrons respectivly.     

X‐Ray Single Crystal Refinement and Superconductivity of La3Ni2B2N3

Crystalline samples of La₃Ni₂B₂N₃ were synthesized using solid state metathesis reactions from combinations of La, LaCl₃, NiCl₂ together with Li₃BN₂. The structure was determined by single crystal X‐ray diffraction (I4/mmm (No. 139), a = 372.95(2) pm, c = 2056.3(2) pm, R₁ = 0.027, wR₂ = 0.062) and confirmed earlier results from neutron powder diffraction. La₃Ni₂B₂N₃ contains BN units capping square planar Ni layers. Isolated nitrogen atoms reside in La₆ octahedra. Magnetic measurements on several bulk samples exhibit superconductivity at temperatures below 14.6 K.     

Preparation and Characterization of a Sol-Gel Prepared Ferroelectric Sandwich Structure

A novel silicon-based PbTiO₃/Pb(Zr,Ti)O₃/PbTiO₃ (PT/PZT/PT) sandwich structure has been prepared using a sol-gel method. The annealing temperature is greatly reduced compared with those structures without PT layers. Capacitance-voltage (C-V), leakage current-voltage (I-V), polarization-field (P-E), dielectric-frequency response and polarization fatigue of the sandwich structure are examined. The relative dielectric constant, the coercive field and the remanent polarization of the PZT films are measured to be about 900, 18 kV/cm and 16 C/cm² respectively. The current density is less than 5 × 10^–9 A/cm² below 200 kV/cm. The dielectric constant of the structure remains constant at low frequency, and decreases to some degree at high frequency. The retained polarization does not change significantly after 8 × 10⁹ read/write cycles. The PZT films are proved to have very good dielectric and ferroelectric properties. The new PT/PZT/PT sandwich structure can be valuable for memory devices and other applications.     

Synthesis, Crystal Structure Determination, and Physicochemical Study of the Nickel(II) Complex of 4-(Pyridyl-2)-1,2,4-triazole

A new trinuclear nickel(II) complex with 4-(pyridyl-2)-1,2,4-triazole (pytrz), [Ni₃(pytrz)₆(H₂O)₆](NO₃)₆, has been synthesized, and its crystal structure has been determined. The compound was studied by X-ray phase analysis (XRPA), magnetochemical measurements, and electronic and IR spectroscopy.