Spin-crossover behavior and electrical conduction property in iron(II) complexes with tetrathiafulvalene moieties

Iron(II) complexes with neutral and oxidized tetrathiafulvalene (TTF) moieties were prepared and X-ray crystallographic analyses, magnetic and electrical resistivity measurements suggested an interaction of spin transition and electrical conductivity.     

Spontaneous and selective CO2 sorption under ambient conditions in seemingly nonporous molecular crystal of azacalix[5]arene pentamethyl ether

Described are the syntheses, crystal structures, and solid-gas adsorption behaviors of azacalix[4]arene tetramethyl ether and azacalix[5]arene pentamethyl ether. While the former compound exhibited no adsorption of four main atmospheric components, the latter selectively and rapidly adsorbed CO(2) at ambient temperature and pressure. X-ray crystallographic and potential energy distribution analysis revealed that azacalix[5]arene created an energetically favorable space for CO(2) in its seemingly nonporous crystal, leading to the observed selective CO(2) uptake under ambient conditions.     

Application of α-alkoxy bridgehead radical for coupling of oxygenated carbocycles

A new coupling methodology for assembly of highly oxygenated carbocycles was developed. An α-alkoxy bridgehead radical was employed as the key reactive intermediate due to its potent reactivity, minimum steric interaction, and predestined stereochemical outcome. The radical of the trioxadamantane structure, generated from the O,Se-acetal, was reacted with electron-deficient cyclic olefins of various ring sizes. Intermolecular formation of sterically congested linkages between two tetrasubstituted carbons and application of the method to a three-component coupling were two significant achievements.     

Enzymatic epoxide-opening cascades catalyzed by a pair of epoxide hydrolases in the ionophore polyether biosynthesis

Our recent findings of the first epoxide hydrolase Lsd19, involved in lasalocid A biosynthesis, led us to investigate a long-standing controversial issue on the mechanism of enzymatic epoxide-opening cascades. The site-directed mutagenesis and domain dissection analysis to reveal the mechanism of the reaction catalyzed by Lsd19 is examined, especially in the role of acidic amino acid pair and catalytic domains.     

Orthogonal wavelet analysis of turbulent wakes behind various bluff bodies

The multi-scale structures of turbulent wakes generated by three kinds of bluff body, i.e. circular cylinder, square cylinder and compound of cylinder and square (CS) cylinders, have been experimentally investigated in this paper. Firstly, the instantaneous velocity fields and vorticity were measured by the high-speed PIV technique in a circulating water channel. The instantaneous streamlines and corresponding normalized vorticity contours are obtained at a Reynolds number of 5600. Then one- and two-dimensional wavelet multi-resolution technique was used to analyze the instantaneous velocities and vorticity measured by the high-speed PIV. The turbulence structures were separated into a number of subsets based on their central frequencies, which are linked with the turbulence scales. The instantaneous vorticity and Reynolds shear stresses of various scales were examined and compared between the three generators. It is found that the large-scale turbulent structure makes the largest contribution to the vorticity and Reynolds shear stresses for the three wake generators and exhibits a strong dependence upon the initial conditions or the wake generators. The large-scale vorticity and the sizes of vortex in the circular and square cylinders are larger than those in the CS cylinder wake. The contributions to the Reynolds shear stresses from the large-scale turbulent structures account for 90-96% to the measured maximum Reynolds shear stresses for the three wakes. However, the small-scale structures make less contribution to the vorticity and Reynolds shear stresses.     

Photoinduced charge carrier dynamics of Zn-porphyrin-TiO2 electrodes: the key role of charge recombination for solar cell performance

Time resolved absorption spectroscopy has been used to study photoinduced electron injection and charge recombination in Zn-porphyrin sensitized nanostructured TiO(2) electrodes. The electron transfer dynamics is correlated to the performance of dye sensitized solar cells based on the same electrodes. We find that the dye/semiconductor binding can be described with a heterogeneous geometry where the Zn-porphyrin molecules are attached to the TiO(2) surface with a distribution of tilt angles. The binding angle determines the porphyrin-semiconductor electron transfer distance and charge transfer occurs through space, rather than through the bridge connecting the porphyrin to the surface. For short sensitization times (1 h), there is a direct correlation between solar cell efficiency and amplitude of the kinetic component due to long-lived conduction band electrons, once variations in light harvesting (surface coverage) have been taken into account. Long sensitization time (12 h) results in decreased solar cell efficiency because of decreased efficiency of electron injection.     

Platinadithiolene-conjugated pyrylium salt with strong intramolecular donor-acceptor interaction

Protonation of a new platinum complex, Pt(1-pdtAq)((t)Bu(2)bpy), where 1-pdtAq is 1-(phenyldithiolenethynyl)anthraquinone, afforded a cyclized structure, [Pt(1-pdtPyl)((t)Bu(2)bpy)](+), with a unique electronic structure due to intense intramolecular charge transfer.     

Development of a High-Efficiency Decomposition Technology for Volatile Chemical Warfare Agent Sarin Using Dielectric Barrier Discharge

Plasma Chemistry and Plasma Processing - High-efficiency decomposition technology for volatile chemical warfare agent sarin was developed using a dielectric-barrier discharge (DBD). The power...     

Synthesis of Ahod Moiety of Ralstonin A Using Amino Acid Schiff Base Ni(II)-Complex Chemistry

Reported here is the asymmetric synthesis of N-Boc-protected (2S,3S)-3-amino-2-hydroxyoctadecanoic acid, a component of ralstonin A and ralstoamide A. Key synthetic steps include alkylation of chiral Ni(II) complex of glycine Schiff base, conversion of COOH to keto acid (CO−COOH) and reduction of the carbonyl group to generate α-hydroxy functionality. The structure and absolute configuration of (2S,3S)-N-Boc-3-amino-2-hydroxyoctadecanoic acid was shown to be identical to that of the naturally occurring compound.     

Simultaneous separation of water‐ and fat‐soluble vitamins in isocratic pressure‐assisted capillary electrochromatography using a methacrylate‐based monolithic column

A method of simultaneous separation of water‐ and fat‐soluble vitamins using pressure‐assisted CEC with a methacrylate‐based capillary monolithic column was developed. In the proposed method, water‐soluble vitamins were mainly separated electrophoretically, while fat soluble‐ones were separated chromatographically by the interaction with a methacrylate‐based monolith. A mixture of six water‐soluble and four fat‐soluble vitamins was separated simultaneously within 20 min with an isocratic elution using 1 M formic acid (pH 1.9)/acetonitrile (30:70, v/v) containing 10 mM ammonium formate as a mobile phase. When the method was applied to a commercial multivitamin tablet and a spiked one, the vitamins were successfully analyzed, and no influence of the matrix contained in the tablet was observed.