Stepwise Preparation of Spherical Gold Nanoparticles Passivated with Cationic Amphiphiles.

Spherical gold nanoparticles with cationic surfaces were prepared in hexadecyltrimethylammonium (CTA(+)) chloride (CTAC) and CTA(+) bromide (CTAB) solutions. In a CTAC solution, ascorbic acid reduction of gold ions (AuCl4(-)) induced spontaneous nucleation of gold clusters, which resulted in the formation of small gold nanoparticles (<5 nm). In a CTAB solution, the combination of ascorbic acid and AuBr4(-) induced low spontaneous nucleation, and therefore controllable crystal growth of seed particles was possible.

Molecular shape recognition through self-assembled molecular ordering: evaluation with determining architecture and dynamics.

The relationship between molecular gel-forming compound-based double-alkylated L-glutamide-derived functional group-integrated organic phase (Sil-FIP) structure and chromatographic performance is investigated and compared with widely used alkyl phases (C(30), polymeric and monomeric C(18)) as references. The functional group-integrated molecular gel on silica is chemically designed newly in a way that the weak interaction sites are integrated with high orientation and high selectivity can be realized by multiple interactions with the solutes. Its functions can be emphasized by being immobilizable with a terminal carboxyl group and the fact that five amide bonds including β-alanine subunit are integrated per molecule.

Molecular-shape selective high-performance liquid chromatography: stabilization effect of polymer main chain by alternating copolymerization.

This work aims to clarify that stabilization or increased rigidity of polymer main chains as an organic stationary phase can lead the selectivity enhancement in high-performance liquid chromatography (HPLC). For this purpose, the alternating copolymer of octadecyl acrylate (ODA) with a cyclic monomer (N-octadecylmaleimide, OMI) as a rigid segment was synthesized and compared with the ODA homopolymer. Both of the polymer-grafted silicas (Sil-poly(ODA-alt-OMI) and Sil-poly(ODA), respectively) were prepared by radical polymerization on 3-mercaptopropyltrimethoxysilane-modified silica.

New surface-confined ionic liquid stationary phases with enhanced chromatographic selectivity and stability by co-immobilization of polymerizable anion and cation pairs.

Polymerizable ionic liquid monomer pairs were designed and copolymerized on silica as a new strategy to prepare multifunctional hybrid materials in hydrophobic and hydrophilic interaction chromatographies with enhancements of selectivity and stability.

Molecular-shape selectivity by molecular gel-forming compounds: bioactive and shape-constrained isomers through the integration and orientation of weak interaction sites.

A molecular gel system was assembled on carrier particles and the integrated effect of weak interaction sites enabled highly efficient separation of the bioactive and shape-constrained isomers of tocopherols, β-carotene, and polycyclic aromatic hydrocarbons (PAHs) by multiple interaction mechanisms.

New strategy for drastic enhancement of selectivity via chemical modification of counter anions in ionic liquid polymer phase.

A new strategy for the design of a new chromatographic stationary phase via simple modifications of the counter anions in poly(ionic liquid)-grafted silica phase based on ionic self-assembly technology is proposed. The phase with methyl orange dye as counter anions exhibits ultra-high selectivity towards shape-constrained isomers.

Preparation of high-selective HPLC packing materials based on alternating copolymer-grafted silica.

Three alternating copolymer-grafted silica stationary phases for use in high-selective RP-HPLC were prepared from two vinyl monomers selected from styrene, N-methylmaleimide, N-octadecylmaleimide, and octadecyl acrylate; they were characterized by elemental analyses, thermogravimetric analysis, diffuse reflectance infrared Fourier transform spectroscopy, and (13)C cross-polarization magic-angle spinning NMR spectroscopy. Aspects of molecular-shape selectivity were evaluated for three different columns using Standard Reference Material 869b, Column Selectivity Test Mixture for Liquid Chromatography. The best selectivity for isomer separations was obtained for the stationary phase prepared with a copolymer of octadecyl acrylate and N-octadecylmaleimide, which was able to separate 16 polycyclic aromatic hydrocarbons (Standard Reference Material 1647e) in an isocratic elution.

Novel approach for the separation of shape-constrained isomers with alternating copolymer-grafted silica in reversed-phase liquid chromatography.

This paper describes a novel packing material for high selective reversed-phase high-performance liquid chromatography (RP-HPLC). The organic phase on silica is chemically designed in a way that the weak interaction sites are integrated with high orientation along the polymer main chain and high selectivity can be realized by multiple interactions with solutes. For the above purpose, we synthesized poly(octadecyl acrylate-alt-N-octadecylmaleimide)-grafted silica (Sil-poly(ODA-alt-OMI)) stationary phase.

Complete chromatographic separation of steroids, including 17alpha and 17beta-estradiols, using a carbazole-based polymeric organic phase in both reversed and normal-phase HPLC.

Poly(2-N-carbazolylethyl acrylate) with terminal trimethoxysilyl groups was prepared as an organic phase and immobilized onto silica. The retention behavior of the column packed with this carbazole-based polymer-immobilized silica (Sil-CEA) was investigated by using various estrogenic steroids and corticoids in both reversed-phase and normal-phase liquid chromatography. As a result, complete separation was confirmed for eight kinds of steroids with Sil-CEA.

Versatile chiroptics of peptide-induced assemblies of metalloporphyrins.

Zinc porphyrin functionalized with double long-chain alkylated L-glutamide (GTPP-Zn) was synthesized for the first time, and its self-assembling behaviour was investigated in nonpolar organic solvents. The uniqueness of this functionalized porphyrin is characterized by its drastic colour change from dark green to purple via the formation of chirally stacked structures through selective axial coordination on zinc with pyridine derivatives. In this paper, we report the versatility of the GTPP-Zn assembly process as a stimuli-responsive chiroptical switching system and describe the remarkable ligand-specific induction of secondary chirality accompanied by aggregation morphological change.

Amphiphilic molecular gels from omega-aminoalkylated L-glutamic acid derivatives with unique chiroptical properties.

Self-assembling amphiphiles with unique chiroptical properties were derived from L-glutamic acid through omega-aminoalkylation and double long-chain alkylation. These amphiphiles can disperse in various solvents ranging from water to n-hexane. TEM and SEM observations indicate that the improvement in dispersity is induced by the formation of tubular and/or fibrillar aggregates with nanosized diameters, which makes these amphiphiles similar to aqueous lipid membrane systems.

Poly(2-N-carbazolylethyl acrylate)-modified silica as a new polymeric stationary phase for reversed-phase high-performance liquid chromatography.

Poly(2-N-carbazolylethyl acrylate) having terminal trimethoxysilyl groups was newly synthesized by radical polymerization and immobilized onto the silica surface (Sil-CEA). The chromatographic property of Sil-CEA was examined by applying polycyclic aromatic hydrocarbons as solutes. Poly(4-vinylpyridine)-modified silica (Sil-VP) and monomeric octadecylated silica (ODS) columns were used as the reference columns.

Thermodynamic investigations on shape selective separation behaviors of poly(4-vinylpyridine)-grafted silica for polycyclic aromatic hydrocarbons in both normal-phase and reversed-phase high-performance liquid chromatography.

With the successful implementation of poly(4-vinylpyridine)-grafted silica prepared by grafting-from approach (GF-VP(n)) as a stationary phase for the separation of polycyclic aromatic hydrocarbons (PAHs) in normal-phase HPLC, this paper describes the chromatographic retention behaviors of PAHs with GF-VP(n) in reversed-phase HPLC. Significantly higher retention factor along with enhanced shape selectivity were observed with GF-VP(n). Thermodynamic study on the retention behaviors of PAHs with GF-VP(n) in normal-phase and reversed-phase HPLC revealed that retention of PAHs was exothermic in both phases.

Enhancement of retentivity and selectivity for PAHs in NP-HPLC by high-density immobilization of poly(4-vinylpyridine) as an organic phase on silica.

Poly(4-vinylpyridine)-modified silica with high grafting density have been prepared by a grafting-from (g-from) approach through radical chain-transfer reactions. The widely used silane coupling agent 3-mercaptopropyltrimethoxysilane was used to prepare thiol-terminated silica. Chain-transfer reaction and polymerization of 4-vinylpyridine was carried out using alpha,alpha'-azobisisobutyronitrile as an initiator.

Novel calixarene hemisphere synthesized via pinacol rearrangement of [2.1.2.1]metacyclophane.

[reaction: see text] Tetramethoxy[2.1.2.

Lewis Acid Catalysis in the Oxidative Cycloaddition of Thiophenes(1).

Thiophenes 1 were treated with m-chloroperbenzoic acid (m-CPBA) under BF(3).Et(2)O catalysis to afford thiophene S-monoxides. These could be reacted in situ as intermediary species with a number of dienophiles to provide arenes (with alkynes as dienophiles) or 7-thiabicyclo[2.

Quadruple Decker [3.3][3.3][3.3]Orthocyclophane Acetal-An Orthocyclophane Ladder.

Through clever bridging of orthocyclophanes (in this case by acetalization), molecules such as 1 can be formed with four benzene rings in a stacked face-to-face arrangement. UV/Vis spectroscopic and electrochemical properties of 1 are governed by π-π through-space interactions within the molecule.