Electronic interactions and their influence on the conformational stability of trans-2-halocyclopentanol

Conformational preferences and electronic interactions of trans-2-fluorocyclopentanol (1), trans-2-chlorocyclopentanol (2), and trans-2-bromocyclopentanol (3) were analyzed using experimental and theoretical (3)J(HH) coupling constants, theoretical calculations, and natural bond orbital (NBO) analysis. The conformational equilibria of compounds 1-3 can be represented by their diaxial and diequatorial conformers as supported by theoretical calculations. From (3)J(HH) coupling constant values, it can be found that the diequatorial conformer is present in the equilibrium as 55% for compound 1 and as 60% for compounds 2 and 3. This behavior is in agreement with orbital interaction analyses obtained from NBO.     

Formation of metallic Ni nanoparticles on titania surfaces by chemical vapor reductive deposition method

Metallic Ni nanoparticles were successfully prepared on the surface of titania thin film substrate by a novel method, named as chemical vapor reductive deposition (CVRD) method. The growth of the nanoparticles was based on the specific adsorption and heterogeneous nucleation on the surface of substrate, not via vapor-phase formation and subsequent sedimentation. The nanoparticle size was found to be well controllable between 10 and 30 nm by the preparation time and vapor pressure of metal complex precursor. ESCA and electron diffraction results clearly demonstrated Ni nanoparticles as metallic. Titania thin film with metallic Ni nanoparticles on its surface showed high efficiency in their photocatalysis of hydrogen evolution from decomposition of ethanol.     

Polymer modification of colloidal particles by spontaneous polymerization of surface active monomers

Adsorption and spontaneous polymerization of head- or tail-type surface active monomers having long methylene chains on colloidal silica and δ-alumina were investigated. Both head-type and tail-type ammonium monomers on silica in chloroform or tetrahydrofuran had the maximum adsorption on the respective adsorption isotherm. Above the monomer concentration giving the maximum adsorption, it was observed that the monomer formed micelles or clusters in bulk solution with removal of adsorbed water molecules from the silica surface. At the monomer concentration giving the maximum adsorption, heating the silica suspension containing the monomer at 40°C or 60°C in tetrahydrofuran or chloroform solution resulted in spontaneous polymerization. The composite particles formed by polymerization were observed to have many spots consisting of polymer on the surface. Therefore, it is suggested that the monomers are concentrated by micelle-like aggregation on the silica surface and consecutively spontaneous polymerization takes place. Adsorption of an anion-type monomer having a carboxyl group on δ-alumina, which exhibited a positive ζ potential in neutral aqueous solution, was higher than that on colloidal silica, but did not spontaneously polymerize on alumina. Received: 13 June 1998 Accepted in revised form: 19 August 1998     

Cyclopalladation of mono-, di- and tribenzylamine by palladium(II) acetate: Influence of bulkiness around the nitrogen atom of benzylamine upon internal metallation

Cyclopalladation of mono-, di- and tribenzylamine has been investigated by reacting the corresponding amines with an equimolar amount of palladium(II) acetate (reaction i), or by heating the corresponding bis-amine complexes [Pd(O₂CMe)₂{(PhCH₂)_nNH_3−n}₂] (n=1, 2) (reaction ii). By the reaction i, all the three amines undergo cyclopalladation. However, in the case of the reaction ii, only the dibenzylamine complex [Pd(O₂CMe)₂{(PhCH₂)₂NH}₂] has been converted into a cyclopalladated complex. The reactivity of the three benzylamines towards cyclopalladation has been discussed in terms of the co-ordinating ability influenced by the bulkiness around the nitrogen atom. Temperature-dependent ¹H-NMR spectra are observed for mononuclear cyclopalladated complexes [Pd(O₂CMe){C₆H₄CH₂N(CH₂Ph)₂–C¹, N}L] (L=PPh₃, AsPh₃) and are attributed to the dissociation of the nitrogen atom in the cyclopalladated chelate ring. A heteroleptic bis-cyclopalladated complex [Pd[C₆H₄CH₂N(CH₂Ph)₂–C¹, N](C₆H₄CH₂NMe₂–C¹, N)] has also been prepared. X-ray crystallographic studies on [{Pd(O₂CMe)[C₆H₄CH₂N(CH₂Ph)₂–C¹, N]}₂] and [Pd[C₆H₄CH₂N(CH₂Ph)₂–C¹, N](C₆H₄CH₂NMe₂–C¹, N)] have been reported.     

Improved Mutual Separation of Some Metal Ions by Introducing Sulfur Atom in Bis(l,l,3,3-tetramethylbutyl)phosphinic Acid

Hard and Soft Acids and Bases Principle (HSAB Principle) of Pearson, Jensen, Davies and Hartley, which consider a metal ion as a Lewis acid and a monodentate ligand as a Lewis base, had been used to evaluate the interaction between a central metal ion and the donor atom of a ligand.     

Chemiluminescence assay for quinones based on generation of reactive oxygen species through the redox cycle of quinone

A sensitive and selective chemiluminescence assay for the determination of quinones was developed. The method was based on generation of reactive oxygen species through the redox reaction between quinone and dithiothreitol as reductant, and then the generated reactive oxygen was detected by luminol chemiluminescence. The chemiluminescence was intense, long-lived, and proportional to quinone concentration. It is concluded that superoxide anion was involved in the proposed chemiluminescence reaction because the chemiluminescence intensity was decreased only in the presence of superoxide dismutase. Among the tested quinones, the chemiluminescence was observed from 9,10-phenanthrenequinone, 1,2-naphthoquinone, and 1,4-naphthoquinone, whereas it was not observed from 9,10-anthraquinone and 1,4-benzoquinone. The chemiluminescence property was greatly different according to the structure of quinones. The chemiluminescence was also observed for biologically important quinones such as ubiquinone. Therefore, a simple and rapid assay for ubiquinone in pharmaceutical preparation was developed based on the proposed chemiluminescence reaction. The detection limit (blank + 3SD) of ubiquinone was 0.05 μM (9 ng/assay) with an analysis time of 30 s per sample. The developed assay allowed the direct determination of ubiquinone in pharmaceutical preparation without any purification procedure. Figure Chemiluminescence generated through the redox cycle of quinone     

Total synthesis of lamellarins D, L, and N

Total synthesis of cytotoxic marine alkaloids, lamellarins D, L, and N, has been achieved by using Hinsberg-type pyrrole synthesis and palladium-catalyzed Suzuki-Miyaura coupling of the 3,4-dihydroxypyrrole bistriflate 6 as the key reactions. The total yields of lamellarins D, L, and N from the common intermediate 6 are 54, 58, and 50%, respectively.     

Properties of hadron and quark matter studied with molecular dynamics

We study the hadron-quark phase transition in a molecular dynamics (MD) of quark degrees of freedom. The hadron state at low density and temperature, and the deconfined quark state at high density and temperature are observed in our model. We investigate the equations of state and draw the phase diagram at wide baryon density and temperature range. We also discuss the transport property, e.g. viscosity, of $q\bar q$ matter. It is found that the ratio of the shear viscosity to the entropy density is less than one for quark matter.