The structure of new lignans from the seeds of phytolacca americana

From the seeds of Phytolacca americana two new lignans, Americanin B and D, have been isolated and their structures elucidated mainly by spectroscopic methods     

Fabrication of nanoscale metallic spirals using phospholipid microtubule organizational templates

We describe the fabrication of metallic Cu spiral/helical nanostructures prepared via selective electroless metallization of a phospholipid microtubule template. The metallization template is created through selective, sequential adsorption of the oppositely charged polyelectrolytes, sodium poly(styrenesulfonate) (PSS) and poly(ethyleneimine) (PEI), onto nanoscale seams naturally occurring on the microtubule surface. A negatively charged Pd(II) nanoparticle catalyst is bound to the terminal cationic PEI layer of the multilayer film and initiates selective template metallization to form the helical Cu nanostructures. Details of the process are presented, and a mechanism and factors affecting the control of the feature critical dimensions are discussed.     

Thermochromism in nickel(II) complexes: thermal, solid state H NMR and single crystal X-ray analysis of bis-(N,N-dimethyl-1,2-ethanediamine) nickel(II) perchlorate

The complex bis-(N,N-dimethyl-1,2-ethanediamine) nickel(II) perchlorate undergoes a first-order thermochromic phase transition at ca. 476 K, changing its color from orange to red. The room temperature X-ray crystal structure determination showed that the nickel ion possesses a square-planar geometry with two five membered chelate rings, in the δλ conformation, forming the NiN₄ chromophore. The broad-line ¹H NMR indicates the onset of a dynamic disorder of diamine chelate rings at the phase transition temperature region, while T₁ measurement of ¹H affords the activation energy of the puckering metal chelate rings to be 26 kJ mol⁻¹. The electronic spectrum revealed that a weakening of ligand field around the nickel is associated with the phase transition.     

A method for the purification of bulk amount of thorium from its daughter products

A method has been developed to purify bulk amounts of natural thorium from its daughter products. The method is based on anion exchange separation of Th from Pb, Bi, Tl, Ra using Dowex 1 X 8 anion exchange resin conditioned to 2M HCl. The method has several advantages over other methods, namely the decontamination is quite high, Th separation is quantitative and it is suitable for the purification of bulk amounts of Th in a reasonably short time.     

Synthesis of thiadiazoles,triazoles and oxadiazoles from sulfonyl acetic acids via a common route

A new class of five membered heterocycles, thiadiazoles, triazoles and oxadiazoles were prepared from sulfonyl acetic acids via acid hydrazides.     

Reduction of Z-2-chlorostilbene with lithium aluminum hydride: evidence for an electron transfer radical mechanism

$\text{Z}$-2-Chlorostilbene undergoes uncatalyzed LiAlH₄ reduction giving phenanthrene and $\text{Z}$-stilbene. An electron transfer radical mechanism is proposed. LiAlH₄ induced isomerization of $\text{Z}$-stilbene produces $\text{E}$-stilbene.     

Luminescence of Ce3+ in Y2SiO5 nanocrystals: Role of crystal structure and crystal size

Here, we report the role of crystal structure and crystal size on the photoluminescence properties of Ce3+ ions in Y2SiO5 nanocrystals. The emission at 430 nm (5d1 --> 4f1) and lifetime of the excited state of Ce3+ ion doped Y2SiO5 nanocrystals are found to be sensitive to the crystal structure, crystal size, and dopant concentration. It is found that the overall lifetime tau of 0.5 mol % Ce doped Y2SiO5 nanocrystals are 8.78 and 3.45 ns for 1000 and 1100 degrees C heat-treated samples with the same crystal structure (X1-Y2SiO5 phase), respectively. However, a significant increase in the overall lifetime (35.21 ns) is observed for the 1300 degrees C annealed 0.5 mol % Ce doped Y2SiO5 sample having a different crystal structure (X2-Y2SiO5 phase). We found that the decay kinetic is biexponential. It is explained that the fast component arises due to sequential hole-electron capture on the luminescent ions and the slow component arises from isolated ions. Our analysis suggests that modifications of radiative and nonraditive relaxation mechanisms are due to local symmetry structure of the host lattice and crystal size, respectively.     

Reaction of sulphate radical anion (SO<Superscript>.</Superscript><Subscript>4</Subscript><Superscript>-</Superscript>) with hydroxy-and methyl-substituted pyrimidines: a pulse radiolysis study

Reactions of sulphate radical anion (SO·₄ ^-) with 4,6-dihydroxy-2-methyl pyrimidine (DHMP), 2,4-dimethyl-6-hydroxy pyrimidine (DMHP), 6-methyl uracil (MU) and 5,6-dimethyl uracil (DMU) have been studied by pulse radiolysis at pH 3 and at pH 10. The transient intermediate spectra were compared with those from the reaction of hydroxyl radical (·OH). It is proposed that SO·₄ ^- produces radical cations of these pyrimidines in the initial stage. These radical cations are short-lived except in the case of DMHP where a relatively longer lived radical cation is proposed to be formed. When there is a hydrogen atom attached to the N(1) or N(3) position, a deprotonation from these sites is highly favored. When there is no hydrogen attached to these sites, deprotonation from a substituted methyl group is favored. At acidic pH, deprotonation from nitrogen is observed for DHMP, MU and DMU. At basic pH, the radical cation reacts with OH^- leading to the formation of OH adducts.