DSC study of stabilizing effect of antioxidant mixtures in styrene-butadiene rubber

The type of cooperation between antioxidants in the binary mixtures of four substituted diphenylamines and phenotiazine in the stabilization of styrene-butadiene rubber has been tested. Thermooxidation of the samples has been studied by differential scanning calorimetry under non-isothermal conditions. The protection factors of the individual stabilizers and their mixtures were determined. The synergy factors were applied to asses the type of cooperation of antioxidants in the mixtures. From their values it can be concluded that the type of cooperation depends on temperature. The highest synergistic effect has been observed for the mixture of phenotiazine and [4-(1-methyl-1-phenyl-ethyl)-phenyl]-phenylamine.     

The magnetic properties and anisotropy of the linear chain compound TlFe3Te3

The magnetic properties of TlFe₃Te₃ are studied on powdered samples and single crystals. Below 220 K TlFe₃Te₃, is a very anisotropic ferromagnet, the crystallographic c axis being the easy axis of magnetization. While in the easy direction saturation is achieved below 0.5 kOe, in the hard direction saturation is reached at 64 kOe. The angular dependence of the magnetization follows closely a cos ¦?¦ law. The magnetic transition is very abrupt at low external fields, suggesting a first order phase transition. It is accompanied by a small anomaly in the thermal dilatation of the c axis. The magnetization shows an anomalous increase below 50 K suggesting a phase transition.     

A Computational Study of CIONO2H+: Structure and Vibrations

Two protonated forms of chlorine nitrate, HClONO⁺ ₂ and ClONO₂H⁺, are treated ab initio by the Hartree-Fock and the second order Møller-Plesset perturbation approach with the standard 6–31G* basis set. Both minimum energy structures are planar (C ₃ symmetry) and their structural, energy, and vibrational parameters are reported. The computations conclude that the proton attacks the chlorine nitrate at its central, not end, oxygen atom. The protonation causes a considerable elongation of the central ON bond which becomes most probable place of cleavage. The dissociation should yield the neutral HOCl and NO⁺ ₂. These quantum-chemical findings well agree with the previous experimental indications.

     

The ferromagnetic and paramagnetic properties of heusler alloys (Ni1−xCox)2MnSn

Mixed Heusler alloys with composition (Ni_1?xCo_x)₂MnSn (x = 0–1). were prepared. They were single phase with L2₁ structure. Magnetic measurements were undertaken in the ferromagnetic and paramagnetic regions. Magnetic parameters, such as Curie temperature, paramagnetic Curie temperature, and spontaneous moment μ₀₀ depend linearly on the composition. The linear variation of μ₀₀ is phenomenologically interpreted by a linear variation of the magnetic moment of manganese between 4.0 μ_B for Ni₂MnSn to 3.6 μ_B for Co₂MnSn, cobalt having a constant moment of 0.75 μ_B over the whole concentration range.     

Synthesis of aluminum hydrazides by hydroalumination of 2,3-diazabutadienes--formation of an Al4(N2)3 cage compound and an Al3(N2)3 macrocyclic ligand

Treatment of 1,1,4,4-tetramethyl-2,3-diazabutadiene with the alane adduct [AlH3(NMe2Et)] yielded the hydrazine derivative (AlH2)2-(AlH)2(N2iPr2)3 (1) by the hydroalumination of both C N double bonds. Compound 1 has a complicated cage structure formed by three hydrazido groups and four aluminium atoms. As a particularly interesting structural motif it contains a N-N group side-on-coordinated to one aluminium atom through its lone pairs of electrons. Sublimation of 1 gave a heterocubane-type compound (HAlNiPr)4 (2) by the complete cleavage of all N-N bonds, one face of which is bridged by weakly coordinated diisopropyldiazene with a N-N double bond. Repeated sublimation gave the pure, unsupported heterocubane molecule 3. Heating of the rough product of the reaction of alane and diazabutadiene to 90 degrees C in a closed vessel yielded another product Al(AlH2)3(N2iPr2)3 (4), which contains a cyclic chelating ligand formed by three hydrazido groups and three aluminium atoms. This heterocycle coordinates a fourth aluminum atom in the molecular center by close contacts to all six nitrogen atoms. A strongly flattened, distorted octahedral coordination sphere results for the inner metal atom.     

Genome-based proteomics

Protein-protein interactions play crucial roles in various biological pathways and functions. Therefore, the characterization of protein levels and also the network of interactions within an organism would contribute considerably to the understanding of life. The availability of the human genome sequence has created a range of new possibilities for biomedical research. A crucial challenge is to utilize the genetic information for better understanding of protein distribution and function in normal as well as in pathological biological processes. In this review, we have focused on different platforms used for systematic genome-based proteome analyses. These technologies are in many ways complementary and should be seen as various ways to elucidate different functions of the proteome.     

GROUP 13 CLUSTER CHEMISTRY: ORGANOGALLIUM AND -INDIUM SUBHALIDES AND RADICALS

Organogallium or-indium subhalides are easily available by the halogenation of the corresponding tetrahedral clusters E ₄ [C(SiMe ₃ ) ₃ ] ₄ . Three types of compounds are formed that retain the tetrahedral arrangement of In atoms or give chains with two or three Ga or In atoms connected by E─E bonds. These subhalides are suitable starting compounds for the synthesis of secondary products containing the elements in low oxidation states. Carboxylato derivatives or transition metal complexes were obtained on such a route. A persistent radical anion was formed on electron transfer to Ga ₉ (CMe ₃ ) ₉ .     

Sterically Constrained Bicyclic Phosphines: A Class of Fascinating Compounds Suitable for Application in Small Molecule Activation and Coordination Chemistry

Bicyclic phosphines with two annulated, electronically unsaturated five-membered heterocycles are available through facile routes. In most cases, their phosphorus atoms are bound to heteroatoms such as oxygen or nitrogen (PN₃ or PN₂O), whereas homoleptic coordination by three sp²-hybridized carbon atoms has been reported only recently. Steric strain causes unique reactivity. Oxidative addition of halogens, N−H or O−H bonds have afforded phosphoranes as valuable materials for secondary processes. Ring opening was identified as an important step for the understanding of these reactions and has been observed experimentally with a diphosphorus-based ring system. A PH₂ derivative has been considered as a model system for small molecule activation, and hydrogen transfer to a diazo compound was observed experimentally. Several of these phosphines are excellent ligands for the coordination of transition-metal atoms. The very bulky PC₃ compound has a basicity similar to that of PPh₃ and may allow the synthesis of complexes with unusually low coordination numbers at the metal atoms. These phosphines found recently renewed interest as promising reagents in various secondary transformations such as the activation of σ-bonds or in coordination chemistry.