A novel and efficient route to diarylmethanes catalyzed by nickel(II) ion on nanoporous carbon

Much improved catalytic carbon-carbon bond-forming reactions between aryl chlorides and Grignard reagents has been achieved using nickel(II) ion on nanoporous carbon.     

Possible large magnetic moments in 4d transition metal clusters

The electronic structure and magnetism of 13 atom clusters of ruthenium, rhodium and palladium having face centered cubic(fcc) geometry has been studied using a Gaussian orbital basis and the local spin density approximation. Calculations were done for the lattice spacings relevant to the bulk crystal lattice. Using the fixed moment states as input potentials, as many as 3 self-consistent states were obtained for these clusters. The 3 converged states of Rh₁₃ cluster is found to have magnetic moments of 0.69 _μB , 1.00 _μB and 1.46 _μB . Out of these states, 0.69 _μB moment state is found to be the ground state. But the total energy difference between the 0.69 _μB and 1.00 _μB state is very small. The 1.46 _μB moment state coincides with the state reported previously by other authors which was obtained using the discrete variational method. The experimentally observed moment was around 0.47 _μB . Our calculated moment is closer to the experimentally observed moment than the previously reported moment, but is still a bit larger. Ru₁₃ cluster is also found to have large moments, and 3 self-consistent states are also obtained for this cluster. The 3 magnetic moments of the Ru₁₃ cluster are 0.46 _μB , 0.62 _μB and 1.08 _μB . Out of these states, 0.62 _μB moment state is found to be the ground state. For the Pd₁₃ cluster, in addition to the nonmagnetic state previously reported, a state with magnetic moment of 0.46 _μB is also found to exist indicating possible magnetism in cluster phase.     

Dicobalt octacarbonyl-catalyzed tandem

Novel 5-5-6 tricyclic compounds containing cyclopentenone have been constructed by the dicobalt octacarbonyl catalyzed tandem [2 + 2 + 1] and [2 + 2 + 2] cycloaddition reaction between a diyne and two phenylacethylene under CO pressure.     

Intermolecular coupling in nanometric domains of light-harvesting dendrimer films studied by photoluminescence near-field scanning optical microscopy (PL NSOM)

Near-field scanning optical microscopy (NSOM) has been used to investigate the photophysical characteristics of first- to fourth-generation (G1 to G4) light-harvesting dendrimer thin films containing coumarin-343 and coumarin-2 as the core and peripheral chromophores, respectively. Thin film photoluminescence (PL) spectra exhibit a significant red shift in the lower generations (G1, G2, and G3) as compared to their respective solution PL spectra, implying the formation of excimers. Spatially resolved PL NSOM images exhibit pronounced nanoscopic domains in G1, which become more homogeneous in higher generations due to site-isolation of the core chromophore. G4 exhibits complete site-isolation for these light-harvesting dendrimer films.     

The 2-(4-trifluoromethylphenylsulfonyl)ethoxycarbonyl (Tsc) amino-protecting group: use in the solid-phase synthesis of pyrrole-imidazole polyamides

The development of the 2-(4-trifluoromethylphenylsulfonyl)ethoxycarbonyl (Tsc) function, a novel base-sensitive amino-protecting group, and its application to the preparation of DNA-binding polyamides are described. Pyrrole-imidazole polyamides were synthesized by an efficient solid-phase method under conditions compatible with Fmoc chemistry using two Tsc-protected amino acids, Tsc-Py-OH 1a and Tsc-Im-OH 1b.     

Preparation and application of cryptand-coated piezoelectric crystal gas-chromatographic detector

A re-usable and sensitive cryptand-22-coated quartz-crystal membrane piezoelectric sensor with a homemade computer interface for signal acquisition and data processing was prepared and applied as a gas-chromatographic (GC) detector for various organic molecules. The oscillating frequency of the quartz crystal decreased due to the adsorption of organic molecules on cryptand-22. Effects of functional group, molar mass, steric hindrance and polarity of organic molecules on frequency responses of the cryptand-coated piezoelectric crystal detector were investigated. The cryptand-coated piezoelectric crystal GC detector had demonstrated high sensitivity for various polar organic molecules and good reproducibility when re-used. The frequency responses of the cryptand-coated crystal for various molecules were in the following order: carboxylic acids (RCOOH)primary amines (R-NH₂)>alcohols (ROH)>secondary amines (R₂NH)>tertiary amines (R₃N)>ketones. More polar molecules exhibited better frequency responses. The effect of temperature and amount of coating on the frequency responses of cryptand-coated crystal GC detector were also investigated. The cryptand-coated piezoelectric crystal GC detector compared well with the commercial thermal conductivity detector (TCD).     

Relationship between microhardness and fluorine contents on tooth enamel determined by PIGE analysis

The remineralization effect of fluoride has been measured by surface microhardness on tooth enamel. The purpose of this study was to investigate the relationship between microhardness and fluorine concentration on tooth enamel. Twelve sound bovine enamel specimens were prepared and immersed in 0.05% NaF solution for 1, 3, 6, 24 and 36 hours, respectively. The concentration of fluorine in specimens were measured by PIGE analysis and surface microhardness of each specimen was measured by surface microhardness tester. Fluorine concentration was increased by immersing time. There was no change in microhardness of each specimen by fluorine content. The results of this study suggest that there was no relationship between the fluorine concentration and surface microhardness in sound tooth enamel. PIGE analysis can be used effectively to assess the remineralization effect of fluorine content in tooth enamel.     

Convergent synthesis of PAMAM dendrimers using click chemistry of azide-functionalized PAMAM dendrons

Azide-functionalized PAMAM dendrons containing an azidopropylamine focal point were synthesized by the divergent method and applied for the construction of symmetric PAMAM-like dendrimers containing 1,2,3-triazole rings as connectors via stitching with two different multi-terminal alkynes. The stitching method was based on the click chemistry protocol, i.e., the copper-catalyzed cycloaddition reaction between an alkyne and an azide.     

Metalloporphyrin-capped calix[4]pyrroles: heteroditopic receptor models for anion recognition and ligand fixation

Diametrically strapped calix[4]pyrrole-metalloporphyrin conjugates, potential hosts for anionic guests, have been synthesized and characterized. The syntheses rely on the acid-catalyzed condensation of two dipyrromethane bearing Ni(II) porphyrins with acetone. An (1)H NMR spectroscopic titration experiment indicated that the resulting receptors selectively trapped fluoride anions in organic media but not other, larger halide anions. The experimental results from titration and Job plots indicated that the bound fluoride anion must reside inside the cavity. The current systems provide a well-defined illustration of how size-selective anion receptors may be synthesized by incorporating recognition functions, such as Lewis acidity, hydrogen bonding, and encapsulating moieties into established recognition motifs, calix[4]pyrrole in the present instance.     

Application of Iodide Ion Selective Electrode to the Study of Stepwise Formation Constant and Solubility Product of Lead Iodide

Iodide ion-selective electrode were studied, prepared and applied for the complex formations and solubility product determination. The thermodynamic formation constant of PbI⁺ and the solubility product of PbI₃ were found to be 54 and 9.2 × 10^?9, respectively. The formation constant of PbNO₃⁺ was calculated to be 4.6 from the different formation constant of PbI⁺ in perchlorate and nitrate media.