Die Verbindungen Ta3Ga2 und IrGa

Ohne Zusammenfassung     

Determination of the pyrites content of bauxites by thermal methods

A derivatographic method has been developed for the identification and determination of the pyrites content of bauxites and clay minerals. If the sample contains at least 0.2% of pyrite, then at 400–450° a weight increase is indicated on the DTG curve, while a heat liberation is shown on the DTA curve. The amplitude of or the area under, these maxima is proportional to the pyrites content of the sample, although the correlation is not linear. In addition, the effect of experimental conditions on the thermal decomposition of pyrites has been studied.     

Unusual coordination of the in(3+) atom in the decahydrated complex Na3{In[N(CH2COO)3]2}·9H2O

All-Union Scientific-Research Institute of Chemical Reagents and Ultrapure Chemical Substances. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 2, pp. 163–166, March–April, 1991.     

Discrimination ofn=2→2 UV transitions of he-like ions in a recoil light source

Neon and argon recoil ions were produced by collisions with 5.9 MeV/amu uranium projectiles andΔn=0 ultraviolet transitions from the metastable 1s2p ³ P _0,2 levels of the target ions were measured in delay to the pulsed projectile beam.     

Lifetimes of bacteriochlorophyll fluorescence in Rhodopseudomonas viridis and Heliobacterium chlorum at low temperatures

Fluorescence lifetimes of isolated membranes of Rhodopseudomonas viridis were measured in the temperature range of 77 K to 25 K. At room temperature, the main component of the fluorescence decay of bacteriochlorophyll (BChl) b had a time constant of 50 ps. In contrast to other purple bacteria, the emission at low temperature was spectrally homogeneous and showed essentially single lifetimes of 140 ps at 77 K and 180 ps at 25 K, with the primary electron donor in the oxidized state. Taking into account the relative fluorescence yields with open and closed reaction centers, we arrive at numbers of 125 ps and 215 ps, respectively, for open reaction centers. These numbers are significantly smaller than expected on the basis of measurements of the efficiency of charge separation, perhaps suggesting that the excitation decay in the absence of reaction centers is considerably faster at low temperature than at room temperature. At least four different spectral components with different lifetimes were observed at 25 K in the emission of Heliobacterium chlorum, a short-wavelength component of about 30 ps and three longer-wavelength components of about 100 ps, 300 ps, and 900 ps. This indicates a strong heterogeneity in the emitting pigment, BChl g-808. The component with the shortest lifetime does not appear to be affected by the redox state of the reaction center and might reflect energy transfer to BChl g species which are connected to the reaction center.     

New synthetic and structural aspects in the chemistry of alkylaluminum fluorides. The mutual influence of hard and soft ligands and the hybridization as rigorous structural criterion

A general synthetic strategy starting from metal alkyls is reported based on the hydrogen difluoride anion as a suitable reagent for obtaining organometallic fluorides. The newly prepared compounds are [Me(4)N][(i-Bu)(2)AlF(2)] (1), [Ph(4)P][(i-Bu)(2)AlF(2)] (2), and [Ph(4)P][AlF(4)] (3), containing the tetrahedral anions [(i-Bu)(2)AlF(2)](-) and [AlF(4)](-). The actual structures are prototypes that allowed a comparison of inorganic and organometallic fluorides in the frame of the hard and soft acid and base principle, by means of ab initio calculations. A new theoretical model is designed to put in equation form the qualitative statements of the Bent rule. The model allows the rationalization of the tendencies of bond angle variation in [R(2)MX(2)] systems containing a main group metal (M), in terms of hybridization of the central atom and the reciprocal influence of hard and soft ligands.     

Investigation of the state of a symmetrical tert-butyl-substituted macroheterocyclic compound in solution by PMR spectroscopy

The PMR spectra of the macroheterocyclic compound obtained by the reaction of 5-tert-butyl-1,3-diiminoisoindoline with 1,3-phenylenediamine in refluxing butyl alcohol and purified by chromatography on aluminum oxide were recorded. It is shown that the compound does not contain a unified conjugated macroring system. The dependence of the chemical shift of the protons of the endocyclic imino groups on the nature of the solvent was investigated. It is shown that the formation of compound-solvent intermolecular hydrogen bonds is complicated by steric factors.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 62–64, January, 1981.     

Exact solution (within a double-zeta basis set) of the schrodinger electronic equation for water

Using recently developed theoretical techniques it has been possible to achieve an exact variational solution of the Schrödinger equation within a modest basis set or one-eleltron functions. The full configuration interaction for this system included a total of 256473 ¹A₁ spin-and space-adapted configurations. Comparison with many-body perturbation theory proves to be quite interesting.     

Electron spin resonance of radicals in γ-irradiated ethylene-propylene-polyene terpolymers

The ESR spectra resulting from γ-irradiation of the following terpolymers: ethylene-propylene-5-ethylidene-2-norbornene (EPENB), ethylene-propylene-l-isopropylidendicyclopentadiene (EPIPDCP) and ethylene-propylene-tricyclo-5.2.1.0^2.6-deca-2.5.8-triene (EPDDCP) have been investigated. Measurements with ethylene-propylene copolymer and isotactic polypropylene have been made for comparison. The results suggest that, during the irradiation at 77 K, most of the radicals can be accounted for in terms of loss of hydrogen atoms from the main EP chains. On warming above the glass transition temperature, some of the primary radicals react with termonomer units yielding new allyl type radicals. The dominant mechanism of reaction seems to be double bond addition in the case of EPIPDCP and EPDDCP and hydrogen abstraction in the case of EPENB.