One-Step Synthesis of Cyclobutene-Annulated Fullerenes through a Cascade Reaction

The physicochemical properties of fullerene-based materials typically vary depending on the type and mode of addition of functional groups; therefore, developing fullerene derivatives with novel structures is imperative for further progress in materials science. In this study, we develop an efficient one-step strategy for synthesizing cyclobutene-annulated fullerene derivatives (cyclobutenofullerenes) and characterize their electronic properties. Despite the steric strain, cyclobutenofullerenes can be easily prepared via a one-step reaction of C₆₀ with a secondary propargylic phosphate. Structural analysis of the reaction intermediates suggests that the cascade reaction proceeds through a formal [2+2] cycloaddition of C₆₀ with an allene, caused by the 1,3-migration of the propargylic phosphate, followed by an additional 1,3-migration and the subsequent 1,2-elimination of the phosphodiester moiety.     

An M2L4 Molecular Capsule with a Redox Switchable Polyradical Shell

Preparation of molecular nanostructures with polyradical frameworks remains a significant challenge because of the limited synthetic accessibility which is entirely different from that of neutral and ionic ones. Herein we report the quantitative formation of a new M₂L₄ molecular capsule from metal ions and dihydrophenazine‐based ligands. The capsule has a spherical nanocavity (ca. 1 nm in diameter) enclosed by eight redox‐active, dihydrophenazine panels. Electrochemical oxidation of the capsule leads to the generation of multiple radical cations on the shell framework. Moreover, a stable tetra(radical cation) capsule can be reversibly obtained by chemical as well as electrochemical oxidation.     

Dirhodium(II)-catalyzed C-H amination reaction of (S)-3-(tert-butyldimethylsilyloxy)-2-methylpropyl carbamate: a facile preparation of optically active monoprotected 2-amino-2-methyl-1,3-propanediol

Dirhodium(II)-catalyzed C-H amination reaction of (S)-3-(tert-butyldimethylsilyloxy)-2-methylpropyl carbamate, which was easily prepared from methyl (S)-2-methyl-3-hydroxypropanoate, proceeded more smoothly than those of their 2-(methoxycarbonyl)propyl derivative to give the corresponding oxazolidinone in excellent yield. The resulting oxazolidinone was converted efficiently into both (R)-monoprotected and (S)-monoprotected 2-amino-2-methyl-1,3-propanediols.     

AC susceptibility of magnetic markers in suspension for liquid phase immunoassay

AC susceptibility of magnetic markers in solution was studied for biosensor applications. First, frequency dependence of the susceptibility was measured, and size distribution of the markers was estimated by analyzing the experimental result with the so-called singular value decomposition (SVD) method. The size distribution estimated with the magnetic measurement agreed with that obtained from conventional optical measurement. Next, susceptibility measurement was applied to the liquid-phase immunoassay without bound/free (B/F) separation. We performed the detection of biotin-coated polymer beads in suspension using avidin-coated magnetic markers. Changes of the susceptibility and the size distribution caused by the binding reaction were shown.     

Sound propagation in soundproofing casement windows

Casement windows consisted of two wooden frames that can be opened and closed at various angles are widely used in developing countries with tropical climates. However, an annual increase in a number of motorcycles and automobiles and traffic noise level these countries have rendered these windows to be useless. In this paper, we present a model for manufacturing windows which are suitable for the developing tropical countries. These windows are capable of ventilating, regulating sunlight, protecting against coldness, and reducing traffic noise and fumes from motor vehicles. The ventilation and soundproofing unit hold an importance place in the design of the windows and are calculated using the wave equation and observations of higher-order mode waves. In order to maximize the soundproofing ability, the selection of size and placement of input and output openings in such a way that would minimize the effects of higher-order mode waves are considered in details.     

Colored Turaev-Viro invariants of twist knots

In the present paper we give a formula for colored Turaev-Viro invariants of twist knots using special polyhedra derived from (1,1)-decomposition of the knots.     

Synthesis, structural characterization, and catalytic performance of dititanium-substituted gamma-Keggin silicotungstate

A novel titanium-substituted silicotungstate cluster of [{gamma-SiTi2W10O36(OH)2}2(mu-O)2]8- (1) is synthesized by the introduction of titanium(IV) ions into a divacant lacunary gamma-Keggin-type silicotungstate of [gamma-SiW10O36]8-. This titanium-substituted polyoxometalate, 1, exhibits a dimeric structure. One half of the gamma-Keggin fragment of 1 contains a dinuclear titanium center bridged by two hydroxo groups, and the resulting Ti2(mu-OH)2 core connects to the other Ti2(mu-OH)2 core of the paired gamma-Keggin subunit through Ti-O-Ti linkages. The Ti2(mu-OH)2 core of 1 reacts with MeOH to form the corresponding alkoxo derivative, [{gamma-SiTi2W10O36(OH)(OMe)}2(mu-O)2]8- (2). Two of four hydroxo groups of the Ti2(mu-OH)2 cores in 1 are replaced by methoxo groups to give the Ti2(mu-OH)(mu-OMe) core, and the Ti-O-Ti linkages connecting two gamma-Keggin subunits are maintained in 2. The gamma-Keggin dititanium-substituted silicotungstate 1 catalyzes mono-oxygenation reactions, such as the epoxidation of olefins and sulfoxidation of sulfides with hydrogen peroxide under mild conditions, while the monotitanium-substituted silicotungstate, [alpha-SiTiW11O39]4- (3), and the fully occupied silicododecatungstate, [gamma-SiW12O40]4-, are inactive. The epoxidation with 1 is stereospecific; the configurations around the C=C double bonds of the cis- and trans-olefins are completely retained in the corresponding epoxides. For the competitive epoxidation of cis- and trans-2-octenes, the ratio of the formation rate of cis-2,3-epoxyoctane to that of the trans isomer (R(cis)/R(trans)) is relatively high (21.3) in comparison with those observed for the tungstate catalysts, including [gamma-SiW10O34(H2O)2]4-. The epoxidation of 3-methyl-1-cyclohexene is highly diastereoselective and gives the corresponding epoxide with an anti configuration. The molecular structure of 1 is preserved during the catalysis because the 29Si and 183W NMR spectra of the catalyst recovered after completion of the oxidation are consistent with those of as-prepared compound 1. All these facts suggest the contribution of rigid nonradical oxidants generated on the multinuclear titanium center of 1.     

Homogeneous and disordered assembly of densely packed titanium oxide nanocrystals: an approach to coupled synthesis and assembly in aqueous solution

A homogeneous and disordered assembly of densely packed nanocrystals 2-3 nm in size was synthesized at room temperature in an aqueous solution without the assistance of any organic molecules. The assembled nanocrystals of titanium oxides, such as anatase titanium dioxide, sodium titanate, and a solid solution with rutile tin dioxide, formed macroscopic transparent objects 2-5 mm in size. In general, it is not easy to obtain homogeneous and disordered assembly of nanocrystals without assistance of any organic molecules for the inhibition of inhomogeneous and disordered aggregation. In the present work, the formation of the hydrated layer on the surface of nanocrystals facilitated the homogeneous and disordered assembly. The crystal phases and the compositions of the nanocrystals were controlled by the tuning of the synthetic conditions, such as the initial pH and metal source concentration. Based on the formation processes and mechanisms, this approach for the coupled synthesis and assembly can be applied to a variety of nanomaterials for preparation of homogeneous but disordered assembly.