Desymmetric hydrogenation of a meso-cyclic acid anhydride toward biotin synthesis

Catalytic reactivity in the hydrogenation of a cyclic anhydride to a biotin synthetic intermediate has been investigated on the basis of Lyons’ original method using Wilkinson Ru complex, revealing the high performance of DPPF and XANTPHOS diphosphines possessing wide bite angles. The results have shown a new trail for design of the corresponding asymmetric catalysts, and the potential utility of (S,S)-Et-FerroTANE and (S,S)-(R,R)-Ph-TRAP has been demonstrated.     

Morphological Investigation of Midblock‐Sulfonated Block Ionomers Prepared from Solvents Differing in Polarity

Recent developments regarding charged multiblock copolymers that can form physical networks and exhibit robust mechanical properties herald new and exciting opportunities for contemporary technologies requiring amphiphilic attributes. Due to the presence of strong interactions, however, control over the phase behavior of such materials remains challenging, especially since their morphologies can be solvent‐templated. In this study, transmission electron microscopy and microtomography are employed to examine the morphological characteristics of midblock‐sulfonated pentablock ionomers prepared from solvents differing in polarity. Resultant images confirm that discrete, spherical ion‐rich microdomains form in films cast from a relatively nonpolar solvent, whereas an apparently mixed morphology with a continuous ion‐rich pathway is generated when the casting solvent is more highly polar. Detailed 3D analysis of the morphological characteristics confirms the coexistence of hexagonally‐packed nonpolar cylinders and lamellae, which facilitates the diffusion of ions and/or other polar species through the nanostructured medium.

     

Numerical simulation of cyclic voltammetry for reversible systems with complex stoichiometry

Reversible waves of voltammetry with complex non-unity stoichiometry are studied here based on theory. Numerical simulations were performed for various stoichiometric systems in which coefficients m and q were independently varied from 1 to 4 in a general reaction scheme, mO + ne⁻ ai qR. The calculation results indicate that the peak current function at complex stoichiometry differs from that at simple unity stoichiometry. The relation between the half-wave potential and the formal potential has been partially corrected from that previously reported in the literature. Parameters in the relation between the peak potential and the half-wave potential are unique for each stoichiometric system. The parameter in the relation between the peak potential and the half-peak potential is also presented here.     

Triangular ruthenium acetate clusters containing the bis(pyridyl)propane ligand and their inclusion chemistry with β-cyclodextrin

The triruthenium carboxylate cluster [Ru₃O(OAc)₆(py)₂(bpp)]⁺ (OAc = acetate) containing the bridging 1,3-bis(4-pyridyl)propane (bpp) ligand, and its dimeric species [{Ru₃O(OAc)₆(py₂)}₂(μ-bpp)]²⁺ were synthesized in order to investigate their inclusion compounds with β-cyclodextrin (β-CD). Characterization of the complexes was carried out based on spectroscopic, electrochemical and spectroelectrochemical techniques, while the formation of inclusion complexes was evaluated using ¹H NMR/NOESY spectroscopy. Since bpp is a flexible ligand, a DFT study was carried out in order to characterize its conformational isomers and their possible role in the host–guest chemistry with β-CD. Instead of observing the formation of inclusion compounds with different stoichiometries, we observed the formation of 1:1 bpp/β-CD compounds in which the bpp ligand assumes different conformations. The assembly of polymetallic rotaxane species was successfully demonstrated by monitoring the ¹H NMR spectra of the monomeric cluster species in the presence of aquapentacyanoferrate(II) ions and β-CD.     

Effect of iron acetylacetonate on physico-chemical properties of waterglass based aerogels by ambient pressure drying

The effect of iron acetylacetonate on the physico-chemical properties of waterglass based silica aerogels by ambient pressure drying has been investigated. Doping the gels with iron acetylacetonat (FeAA) facilitates in the diminution of the density of the aerogels. The well established silica network provides effective confinement of FeAA nanoparticles which resists the collapse of silica network during ambient pressure drying. Therefore, in the present paper, the effects of FeAA on the physico-chemical properties of the aerogels have been studied by varying the FeAA:Na₂SiO₃ molar ratio from 3 × 10⁻⁴ to 6 × 10⁻⁴. The aerogels were prepared via ambient pressure drying and characterized by the bulk density, thermal conductivity and water contact angle. The aerogel’s surface morphology, elemental analysis and pore structure were characterized by means of EDAX and FTIR, TEM and N₂ adsorption- desorption analyzer. The high temperature hydrophobicity of these aerogels was checked by heating them in temperature controlled furnace. Silica aerogels with low density ~0.050 g/cc have been obtained using the molar ratio of Na₂SiO₃:H₂O:FeAA:Citric acid:TMCS at 1:146.67:3 × 10⁻⁴:0.54:9.46, respectively. EDAX and FTIR studies show that the iron species are entrapped in the mesoporous framework and not took part in the bonding with silica.     

Spatiotemporal Dynamics of Aggregation-Induced Emission Enhancement Controlled by Optical Manipulation

We present spatiotemporal control of aggregation-induced emission enhancement (AIEE) of a protonated tetraphenylethene derivative by optical manipulation. A single submicrometer-sized aggregate is initially confined by laser irradiation when its fluorescence is hardly detectable. The continuous irradiation of the formed aggregate leads to sudden and rapid growth, resulting in bright yellow fluorescence emission. The fluorescence intensity at the peak wavelength of 540 nm is tremendously enhanced with growth, meaning that AIEE is activated by optical manipulation. Amazingly, the switching on/off of the activation of AIEE is arbitrarily controlled by alternating the laser power. This result means that optical manipulation increases the local concentration, which overcomes the electrostatic repulsion between the protonated molecules, namely, optical manipulation changes the aggregate structure. The dynamics and mechanism in AIEE controlled by optical manipulation will be discussed from the viewpoint of molecular conformation and association depending on the laser power.     

The electronic band structure analysis of OLED device by means of in situ LEIPS and UPS combined with GCIB

Low-energy inverse photoelectron spectroscopy (LEIPS) and ultraviolet photoelectron spectroscopy (UPS) incorporated into the multitechnique XPS system were used to probe the ionization potential and the electron affinity of organic materials, respectively. By utilizing gas cluster ion beam (GCIB), in situ analyses and depth profiling of LEIPS and UPS were also demonstrated. The band structures of the 10-nm-thick buckminsterfullerene (C₆₀) thin film on Au (100 nm)/indium tin oxide (100 nm)/glass substrate were successfully evaluated in depth direction.     

“非保护型”金属胶体纳米簇形成机理研究

碱-乙二醇法制备的"非保护型"金属及合金纳米簇由表面吸附的溶剂分子和简单离子实现稳定化,它们被广泛用于制备高性能复相催化剂和研究复相催化剂中的尺寸、组成、载体表面基团以及修饰剂对催化性能的影响。关于此类非保护金属纳米簇的形成过程及机理的认识尚有待进一步深化。本文采用原位快速扫描X射线吸收精细结构谱(QXAFS)、原位紫外-可见(UV-Vis)吸收光谱、透射电子显微镜和动态光散射技术研究了碱-乙二醇法合成中非保护型金属胶体纳米簇的形成过程与机理。结果表明,在碱-乙二醇法合成非保护型Pt金属纳米簇的过程中,室温下即有部分Pt(IV)被还原至Pt(II)。随着反应温度的升高,OH-逐渐取代与Pt离子配位的Cl-,在Pt―Pt键形成之前,反应体系的UV-Vis吸收光谱中可观察到明显的纳米粒子的散射信号,原位QXAFS分析表明Pt纳米簇是由Pt氧化物纳米粒子还原所形成的;在Ru金属纳米簇的形成过程中,OH-首先取代了Ru Cl_3中的Cl~-,形成羟基配合物Ru(OH) _6~(3-),后者进一步缩合形成氧化钌纳米粒子,最终Ru金属纳米簇由乙二醇还原氧化钌纳米粒子形成。由于先形成了氧化物纳米粒子,后续的还原反应被限制在氧化物纳米粒子内,使最终得到的非保护型金属纳米簇具有尺寸小、分布窄的特点。本工作所获得的知识对发展高性能能源转化催化剂、精细化学合成催化剂、传感器等功能体系具有重要意义。     

A new method to improve validity range of Lie canonical perturbation theory: with a central focus on a concept of non-blow-up region

Validity ranges of Lie canonical perturbation theory (LCPT) are investigated in terms of non-blow-up regions. We investigate how the validity ranges depend on the perturbation order in two systems, one of which is a simple Hamiltonian system with one degree of freedom and the other is a HCN molecule. Our analysis of the former system indicates that non-blow-up regions become reduced in size as the perturbation order increases. In case of LCPT by Dragt and Finn and that by Deprit, the non-blow-up regions enclose the region inside the separatrix of the Hamiltonian, but it may not be the case for LCPT by Hori. We also analyze how well the actions constructed by these LCPTs approximate the true action of the Hamiltonian in the non-blow-up regions and find that the conventional truncated LCPT does not work over the whole region inside the separatrix, whereas LCPT by Dragt and Finn without truncation does. Our analysis of the latter system indicates that non-blow-up regions do not necessarily cover the whole regions inside the HCN well. We propose a new perturbation method to improve non-blow-up regions and validity ranges inside them. Our method is free from blowing up and retains the same normal form as the conventional LCPT. We demonstrate our method in the two systems and show that the actions constructed by our method have larger validity ranges than those by the conventional and our previous methods proposed in Teramoto and Komatsuzaki (J Chem Phys 129:094302, 2008; Phys Rev E 78:017202, 2008).