Effect of Solvent Diols and Ligands on the Properties of Sol-Gel Alumina-Silicas

Amorphous alumina-silicas were prepared from a tetra-alkoxysilane and anhydrous aluminum trichloride or an aluminum alkoxide by a sol-gel process using 2-methyl-2,4-pentanediol, pinacol, 1,2-propanediol, 2,3-butanediol or ethylene glycol as the solvent or complexing agent, and the effect of diols and alkoxy groups on the physical and chemical properties of the alumina-silicas was examined. When the diol or the alkoxy group was bulky, the alumina-silicas had relatively larger micropores, a larger pore volume and higher surface areas. In the conversion of methanol catalyzed by the alumina-silicas, the bulkier diols and alkoxides gave catalysts that produced dimethyl ether in higher yield and hydrocarbons in lower yield. Thus, when ethylene glycol was used as the diol, the best catalyst for the production of hydrocarbons, especially the production of olefins such as ethylene, propylene and butene, was obtained. Furthermore, in comparison with alumina-silica prepared by a traditional kneading process, it was found that the sol-gel alumina-silica could efficiently convert methanol to dimethyl ether and hydrocarbons, but the material prepared by kneading had a very low conversion of methanol to other compounds.     

Photoinduced supramolecular chirality in amorphous azobenzene polymer films

Supramolecular chirality was optically induced in amorphous and achiral azobenzene polymer films by irradiation of a laser beam with elliptical polarization. The chirality resulted from helical orientation of azobenzene chromophores by a combined process of circular and linear polarization. The helix-handedness could be controlled by incident light-handedness.     

Synthesis of allyl cyanamides and N-cyanoindoles via the palladium-catalyzed three-component coupling reaction

The palladium-catalyzed three-component coupling reaction (TCCR) of aryl isocyanides, allyl methyl carbonate, and trimethylsilyl azide was conducted in the presence of Pd(2)(dba)(3).CHCl(3) (2.5 mol %) and dppe (1,2-bis(diphenylphosphino)ethane) (10 mol %). Allyl aryl cyanamides with a wide variety of functional groups were obtained in excellent yields. This palladium-catalyzed TCCR was further utilized for the synthesis of N-cyanoindoles. The reaction of 2-alkynylisocyanobenzenes, allyl methyl carbonate, and trimethylsilyl azide in the presence of Pd(2)(dba)(3).CHCl(3) (2.5 mol %) and tri(2-furyl)phosphine (10 mol %) at higher temperatures afforded N-cyanoindoles in good to allowable yields. (eta(3)-Allyl)(eta(3)-cyanamido)palladium complex, an analogue of the bis-pi-allylpalladium complex, is a key intermediate in the TCCR, and a pi-allylpalladium mimic of the Curtius rearrangement is involved to generate the (eta(3)-allyl)(eta(3)-cyanamido)palladium intermediate.     

Arteminolides B,C, and D,new inhibitors of farnesyl protein transferase from Artemisia argyi

Arteminolides B-D (2-4), new farnesyl protein transferase inhibitors, were isolated together with a known arteminolide A (1) and new regioisomers (5-7) of the compounds from the aerial parts of Artemisia argyi. Structures of these compounds were elucidated by spectroscopic methods and chemical conversion. Arteminolides inhibited the farnesyl protein transferase with IC(50) values of 0.7-1 microM, while the regioisomers 5-7 were inactive. In addition, it was proved that the exocyclic double bond of sesquiterpene lactone did not affect the inhibitory activity of arteminolide. The effects of compound 2 on H-Ras processing and cellular growth in H-ras-transformed cells were also evaluated.     

Tunable metallization by assembly of metal nanoparticles in polymer thin films by photo- or electron beam lithography

The technique of patterning of surfaces with metal-rich structures on micro- or nanoscales was developed by assembling metal nanoparticles into a thin film of polymer in a controllable way. Palladium (Pd) nanoparticles were incorporated into a thin film of poly(methyl methacrylate) (PMMA) using palladium (II) bis(acetylacetonato), Pd(acac)(2), as a precursor vaporized in a nitrogen atmosphere. Depending upon its dose, the irradiation of a PMMA film by UV light or an electron beam (EB) enhances its reducing capability against Pd(acac)(2). This dependency on dose can be used to control the formation and assembly of Pd nanoparticles. Using this technique, binary patterns consisting of metal-rich and metal-poor regions in the polymer film can be created simply by irradiating the surface of the polymer through a binary photomask. Besides the creation of binary patterns, it is also possible to create grayscale patterns where the density of Pd nanoparticles can be tuned to provide shades of gray by the use of light with continuously modulated intensity. Because the electron beam also enhances the reducing power of PMMA against Pd(acac)(2), it is thus possible to obtain highly metallized films with nanoscale pattern features. The PMMA film can be selectively removed by oxygen plasma treatment or by pyrolysis. Thus, highly metallized surfaces with binary or grayscale patterns can be obtained by selective removal of the PMMA films. The metallized regions possess relatively high resistivity against CF(4) plasma compared to the bare silicon surface; therefore, the metallized surface patterns can be transferred onto the underlying silicon substrate by CF(4) plasma treatment. Because of the nanosize effect of metal nanoparticles, the thermal treatment at 900 degrees C, which is significantly lower than the melting temperature of the bulk Pd, yields continuous metallic features by binding the assembled nanoparticles.     

Spectroscopic and chemical characterizations of molecular size fractionated humic acid

A sample of humic acid was divided by ultrafiltration into five fractions of different molecular size (F1; 300 000: F2; 100 000-300 000: F3; 50 000-100 000: F4; 10 000-50 000: F5; 1000-10 000 daltons). Characterization by IR, and CPMAS C-13 NMR spectroscopy indicated that the molecules of the fraction of >/=100 000 daltons were primarily aliphatic, while the smaller molecules of the >/=10 000 dalton fraction were predominantly aromatic. Titration (pH) data were consistent with an increase in the number of carboxylate groups per unit mass as molecular size became smaller. A comparative study with unpurified and purified (by treatment with ion exchange elution, acid precipitation and alkaline dissolution) humic acid samples showed chemical alteration with some loss of carboxyl groups in the humic acid.     

Synthesis and structural characterization of PHP[(C(5)Me(4))(2)], a monodentate chiral phosphine derived from intramolecular C-C coupling of tetramethylcyclopentadienyl groups: an evaluation of steric and electronic properties

The chiral monodentate phosphine PhP[(C(5)Me(4))(2)] is readily obtained by oxidation of the lithium complex Li(2)[PhP(C(5)Me(4))(2)] with I(2), which couples the two cyclopentadienyl groups to form a five-membered heterocyclic ring. The steric and electronic properties of PhP[(C(5)Me(4))(2)] have been evaluated by X-ray diffraction and IR spectroscopic studies on a variety of derivatives, including Ph[(C(5)Me(4))(2)]PE (E = S, Se), Cp*MCl(4)[P[(C(5)Me(4))(2)]Ph] (M = Mo, Ta), Ir[P[(C(5)Me(4))(2)]Ph](2)(CO)Cl, and CpFe(CO)[PhP[(C(5)Me(4))(2)]]Me. For comparison purposes, derivatives of the related phospholane ligand PhP[Me(2)C(4)H(6)] have also been investigated, including Ph[Me(2)C(4)H(6)]PS, Ir[Ph[Me(2)C(4)H(6)]](2)(CO)Cl, Ir[Ph[Me(2)C(4)H(6)]](2)(CO)Me, Ir[PPh[Me(2)C(4)H(6)]](COD)(Cl), and Pd[P[Me(2)C(4)H(6)]Ph][eta(2)-C(6)H(4)C(H)(Me)NMe(2)]Cl. The steric and electronic properties of PhP[(C(5)Me(4))(2)] are determined to be intermediate between those of PPh(2)Me and PPh(3). Thus, the crystallographic cone angles increase in the sequence PPh(2)Me (134.5 degrees) < PhP[(C(5)Me(4))(2)] (140.2 degrees) < PPh(3) (148.2 degrees), while the electron donating abilities decrease in the sequence PPh(2)Me > PhP[(C(5)Me(4))(2)] > PPh(3). Finally, PhP[(C(5)Me(4))(2)] has a smaller cone angle and is less electron donating than the structurally similar phosphine, PhP[Me(2)C(4)H(6)].     

Effect of silane coupling agents on the performance of RO membranes

This study investigates the effect of silane coupling agents on the performance of reverse osmosis (RO) membranes on the basis of sol–gel coating method. The surfaces of the RO membranes were chemically modified with four different alkoxysilanes in order to reduce their hydrophilicity. The objective of this study is to superpose hydrophobic polysiloxane layer on the surface of a polyamide TFC RO membrane and to increase the extent of salt rejection by the modified membranes. A commercial composite RO membrane (SWC1) was treated with silane coupling agents in ethanol at three different concentrations: 1.0, 1.5, and 2.0% (w/v). The silane coupling agents contain one alkyl or phenyl and three alkoxy groups (e.g., methyltriethoxysilane, octyltriethoxysilane, octadecyltrimethoxysilane and phenyltriethoxysilane). In addition, the effect of alkyl or phenyl group hydrophobicity on the permeability and salt rejection of the modified membrane was examined. The surfaces of the modified membranes were characterized by SEM, AFM, contact angle analyzer, and XPS in order to confirm successful sol–gel methods. The modified membranes showed significantly enhanced salt rejection without a decrease in flux. From the surface analysis results, we can observe the changes in the surface roughness, elemental composition, electron energy, and hydrophilicity.     

Structure determination of a sildenafil analogue contained in commercial herb drinks

It was found from HPLC analysis that a commercial herb drink contains a putative sildenafil analog. In order to identify the sildenafil-like compound, separation and purification were carried out. The structure determination was performed based on routine 1D and 2D NMR experiments. Unlike sildenafil, the compound contains an ethylpiperazine instead of a methylpiperazine group. In addition, the piperazine and phenyl groups are connected through an acetyl group instead of the sulfonyl group of sildenafil.