Photochemical stitching of a tubularly assembled hexabenzocoronene amphiphile by dimerization of coumarin pendants

A coumarin-appended amphiphilic hexa-peri-hexabenzocoronene (1) self-assembled to form graphitic nanotubes. Upon irradiation of lambda > 300 nm, the nanotubes in the solid state and suspension both underwent dimerization of the coumarin pendants, affording covalently stitched nanotubes, which were hardly soluble in CHCl3, a good solvent of 1. In contrast, a thin film cast from a homogeneous solution of 1 was intact to photoirradiation. Owing to the reversible nature of the photochemical stitching, both negative and positive patterns of the graphitic nanotubes were developed on a silicon substrate by a lithographic post processing.     

Hyosgerin, a new optically active coumarinolignan, from the seeds of Hyoscyamus niger

Hyosgerin, a new optically active coumarinolignan, has been isolated and characterized along with three other coumarinolignans, venkatasin, cleomiscosin A and cleomiscosin B, from the seeds of Hyoscyamus niger L. The structure was determined on the basis of spectroscopic analysis and chemical conversion. The optical properties and absolute stereochemistry of these coumarinolignans have also been studied and discussed.     

Linear-type S-bridged triruthenium complexes with aliphatic aminothiolate ligands: synthesis, characterization, and properties

Treatment of [RuCl(2)(DMSO)(4)] with 2-aminoethanethiol (Haet) in ethanol gave a dicationic triruthenium complex, [Ru[Ru(aet)(3)](2)]Cl(2) ([1]Cl(2)). Complex [1]Cl(2) was also obtained by treatment of RuCl(3).nH(2)O with excess Haet in water. When [1](2+) was chromatographed on a cation-exchange column of SP-Sephadex C-25, meso (DeltaLambda) and racemic (DeltaDelta/LambdaLambda) isomers of the corresponding tricationic complex, [Ru[Ru(aet)(3)](2)](3+) ([2](3+)), were eluted with aqueous NaNO(3). The racemic isomer of [2](3+) was optically resolved into DeltaDelta and LambdaLambda isomers by using [Sb(2)(R,R-tartrato)(2)](2-) as a resolving agent. The molecular structures of DeltaLambda- and DeltaDelta/LambdaLambda-[2](NO(3))(3) were determined by X-ray crystallography. In these complexes, the central Ru atom is coordinated by six thiolato groups from two terminal fac-(S)-[Ru(aet)(3)] units in an octahedral geometry, forming a linear-type S-bridged triruthenium structure. The spectroelectrochemical studies on the electronic absorption and CD spectra, together with the electrochemical studies, demonstrated that [1](2+) and [2](3+) are interconvertible with each other through a one-electron redox process, retaining the chirality of the triruthenium structure. Their electronic structures were investigated on the basis of EPR and magnetic susceptibility measurements, which indicated that [1](2+) and [2](3+) have spin ground states of S(t) = 0 and S(t) = 1/2, respectively. The corresponding L-cysteinato complex, [Ru[Ru(L-cys-N,S)(3)](2)](3-), which was formed from RuCl(3).nH(2)O and excess L-cysteine (L-H(2)cys) in water followed by air oxidation, is also presented.     

A short and efficient asymmetric synthesis of komaroviquinone

An asymmetric total synthesis of komaroviquinone (1), which is a natural product isolated from Dracocephalum komarovi and shows novel potent trypanocidal activity, was achieved in five steps from the known starting materials. The synthetic route is shorter and more efficient than the reported methods and also useful for the scale-up synthesis.     

Use of Side‐Chain Incompatibility for Tailoring Long‐Range p/n Heterojunctions: Photoconductive Nanofibers Formed by Self‐Assembly of an Amphiphilic Donor–Acceptor Dyad Consisting of Oligothiophene and Perylenediimide

To tailor organic p/n heterojunctions with molecular‐level precision, a rational design strategy using side‐chain incompatibility of a covalently connected donor–acceptor (D–A) dyad has been successfully carried out. An oligothiophene–perylenediimide dyad, when modified with triethylene glycol side chains at one terminus and dodecyl side chains at the other ( 2 Amphi ), self‐assembles into nanofibers with a long‐range D/A heterojunction. In contrast, when the dyad is modified with dodecyl side chains at both termini ( 2 Lipo ), ill‐defined microfibers result. In steady‐state measurements using microgap electrodes, a cast film of the nanofiber of 2 Amphi displays far better photoconducting properties than that of the microfiber of 2 Lipo . Flash‐photolysis time‐resolved microwave conductivity measurements, in conjunction with transient absorption spectroscopy, clearly indicate that the nanofiber of 2 Amphi intrinsically allows for better carrier generation and transport properties than the microfibrous assembly of 2 Lipo .     

Synthesis and characterization of lithium manganese oxides with core-shell Li4Mn5O12@Li2MnO3 structure as lithium battery electrode materials

By a facile LiNO₃ flux method, lithium manganese oxide composites (xLi₄Mn₅O₁₂? yLi₂MnO₃) were synthesized using a hierarchical organization precursor of manganese dioxide. Li₄Mn₅O₁₂ and Li₂MnO₃ have spinel and rocksalt structures, respectively. The lithiation and structural transformation from the precursor to the composites occurred topotactically from exterior toward interior in the precursor particle with the increase of reaction time, and the composites had core-shell spinel@rocksalt structures in addition to the original hierarchical core-shell organization. The electrochemical measurements at 50 °C after 50 cycles confirmed that a typical spinel@rocksalt cathode had higher capacity retention (87.1%) than that with the composition close to the stoichiometric spinel (64.6%), indicating the Li₂MnO₃ shell can improve cycling stability for the composite electrode at elevated temperature.     

Detection of malignant hepatic tumors with ferumoxide-enhanced MR imaging: usefulness of multishot and single-shot fast spin echo sequences

The purpose of our study was to assess whether respiratory-triggered multishot fast spin echo (MS-FSE) and breath-hold half-Fourier single-shot fast spin echo (SS-FSE) images, in addition to breath-hold T(2)*-weighted gradient recalled echo (GRE) images, increase observer performance in the detection of malignant hepatic tumors with ferumoxide-enhanced magnetic resonance (MR) imaging. Ferumoxide-enhanced MR images obtained from 48 patients with 83 malignant hepatic tumors were retrospectively reviewed by three independent off-site readers. In the first image review, GRE images alone were reviewed. Then, MS-FSE images were added for the first combination review. Finally, SS-FSE images were added for the second combination review. Observer performances were tested by McNemar's test and receiver-operating-characteristic analysis for the clustered data. Sensitivity for hepatocellular carcinomas, metastases, and malignant hepatic tumors overall was significantly (p < 0.05) higher with GRE and MS-FSE combined and GRE, MS-FSE and SS-FSE combined than with GRE alone. For metastases, the Az value was significantly (p < 0.05) higher with GRE and MS-FSE combined, and GRE, MS-FSE and SS-FSE combined than with GRE alone. We confirmed the incremental value of ferumoxide-enhanced MR imaging by obtaining MS-FSE and SS-FSE images in addition to GRE images in the detection of malignant hepatic tumors.     

Photo-Degradable Protein-Polymer Hybrid Shells for Caging Living Cells

There is growing demand for the precise remote control of cellular functions in various fields. Herein, a method for caging mammalian cells by coating with photodegradable protein-polymer hybrid shells to photo-control their functions without genetic engineering is reported. A layer-by-layer assembly of photocleavable synthetic materials through biotin-streptavidin (SA) binding was employed for cell coating. The cell surfaces were first biotinylated with photocleavable biotinylated poly(ethylene glycol)(PEG)-lipid and then coated by repeatedly layering SA and micelles of the PEG-lipid and photocleavable biotinylated four-arm PEG. The cell extension and adhesion were suppressed with the shells and then triggered with the degradation of the shells by light exposure. Macrophage phagocytosis was also stopped by caging with the shells and restarted by light-guided uncaging. This study provides the first proof of principle that cellular functions can be remotely controlled by steric hinderance of cell surfaces with photodegradable materials.     

Theoretical studies on Josephson π states

The Josephson effect under particle-number restriction is investigated based on the Feynman two-state model. The existence of new dynamical states of the Josephson phase inherent in such a restricted situation is shown. The new state describes a number of features recently observed in a superfluid³He weak-link system. Quantum decay from Josephsonπ states is also investigated. Since the π state has two different decay paths, they can interfere during the decay processes by quantum tunneling due to a topological phase originating from total particle-number restriction, and result in a parity effect for tunneling.     

Development and optimization of water treatment reactors using TiO2-modified polymer beads with a refractive index identical to that of water

Optical Review - Various water purification reactors were constructed using beads of TiO2-coated MEXFLON, which is a fluoropolymer exhibiting a refractive index identical to that of water. The...