Deperturbation and assignment of the vibronically tangled spectrum of pyrene in a biphenyl matrix

We apply the technique of the Green's function to the vibronically tangled spectrum of pyrene in a biphenyl matrix. We can deperturb the spectrum mathematically and readily assign the resulting weighted density of states. The analysis is reasonably successful and agrees with ground-state data and estimates of the excited-state frequencies previously made by others.     

The role of magnetite in Fischer-Tropsch synthesis

Mössbauer spectroscopy studies of iron catalysts from a Fischer-Tropsch (FT) Pilot Plant run at different time-on-stream periods were carried out. Magnetite Fe₃O₄ was found to be active for the water-gas-shift (WGS) reaction which accompanies the FT synthesis reaction over Fe-based catalysts. A correlation between the ratio of the occupancy of octahedral sites to the tetrahedral sites in magnetite to the WGS activity was found. Cation-deficient magnetite gave higher WGS activity as compared to the stoichiometric phase.     

Ultrasonic attenuation in the intermediate state of indium

Ultrasonic attenuation has been measured in the intermediate state of high purity single crystals of indium of different sizes over the frequency range 10–30 MHz. Oscillations in the temperature dependence of attenuation of longitudinal ultrasound have been observed and are discussed here in the light of a recent theory.     

Interaction of humic acid with plutonium/III/

The stability constants of the complex of Pu/III/ with a humic acid at pH 2.9 and 5.0 were measured using solvent-extraction technique. The organic extractant was dinonyl naphthalene sulphonic acid in sodium form /NaD/ in benzene while the humate aqueous phase had a constant ionic strength of 0.5M /NaClO₄/. The total carboxylate capacity of the humic acid was determined by direct potentiometric titration to be 6.201 Meq g^–1. The apparent pKa increased as the degree of ionization // increased. The 1g ₁ values of the complex of Pu/III/ with humic acid have been determined to be 2.8 and 3.11 at pH 2.9 and 5.0, respectively.     

Peracid oxidation and photooxygenation reactions of silacyclopentadienes

1-Methyl-1,2,3,4,5-pentaphenyl-1-silacyclopentadiene on treatment with perbenzoic acid afforded a mixture of products consisting of tetraphenylfuran, cis-dibenzoylstilbene, cis-dibenzoylstilbene epoxide, 2,5-dihydro-2,3,4,5-tetraphenylfuran, 1,2,3-triphenyl-1,3-propanedione, 1-methylphenylhydroxysilyl-1,2,3,4-tetraphenyl-1,3-butadiene and cis, cis-1,2,3,4-tetraphenyl-1,3-butadiene. Similarly, hexaphenylsilacyclopentadiene reacted with perbenzoic acid to give a mixture comprising tetraphenylfuran and cis-dibenzoylstilbene. Photooxygenation of 1-methyl-1-vinyl-2,3,4,5-tetraphenyl-1-silacyclopentadiene has been found to give a mixture of products including cis-dibenzoylstilbene, trans-dibenzoylstilbene and isodidesyl. Possible mechanistic pathways for these reactions have been suggested.     

Photochemical myers-saito and C2-C6 cyclizations of enyne-allenes: direct detection of intermediates in solution

Several examples of the photochemical Myers-Saito and C2-C6 cyclization of enyne-allenes are described. The presence of a triplet sensitizing unit at the allene terminus and laser flash photolysis results suggest that the cyclization proceeds along the triplet manifold. An intermediate with tau = 33 +/- 5 mus was tentatively assigned to a singlet biradical.     

A study on the fluoride complexes of plutonium(III), samarium(III) and bismuth(III) using fluoride ion-selective potentiometry

Stability constants of the fluoride complexes of Pu(III), Sm(III) and Bi(III) in 1.0M NaClO₄/HClO₄ medium at 23±1°C have been determined by potentiometry using a fluoride ion-selective electrode. Plutonium was reduced to the trivalent state using quinhydrone with an excess to serve as holding reductant. The log values of concentration stability constants log ₁, log ₂, and log ₃ are 3.58, 6.40 and 12.61 for Pu(III), 3.23, 5.81 and 10.54 for Sm(III) and 3.69, 6.13 and 11.04 for Bi(III), respectively. The log ₂ values in all these cases have very large deviation and may be taken only as rough estimates.     

Nanohybrids from liquid crystalline extended amphiphilic dendrimers

A novel extended amphiphilic dendrimer with linear poly(ethylene oxide) (PEO) attached to a PEO-like dendritic core as hydrophilic fraction and eight docosyl chain branches as hydrophobic fraction has been prepared for the use as structure-directing agent for silica-type materials. The extended dendrimer exhibits a hexagonal columnar liquid crystalline phase in the melt. Organically modified inorganic precursors and the extended dendrimer co-assemble into nanostructured hybrids. Hybrids with 0.44 weight fraction (fw) of aluminosilicate show a lamellar morphology, while hybrids with 0.21 fw exhibit a cylindrical structure. Nanostructures were characterized by a combination of small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The results suggest that dendrimer-based amphiphiles may provide an exciting platform for the formation of multifunctional organic-inorganic nanostructured hybrid materials with unique structural characteristics.