Straightforward Synthesis,Electrochemical Properties,and Gel Formation of Thiacalix[n]thiophenes

A facile synthetic approach toward thiacalix[n]thiophene homologues (n=4–6) is presented herein. Pd‐catalyzed coupling of 2,5‐dibromothiophene derivatives with stannyl sulfide gave various thiacalix[n]thiophenes in good yields. The optical and electrochemical properties of the produced cavitands were investigated. Furthermore, gelation was observed in some solvents.     

Bis(dipyrrinato)metal(ii) coordination polymers: crystallization,exfoliation into single wires,and electric conversion ability

One-dimensional coordination polymers (1D-CPs) tend either to dissociate into constitutive ligands and metals readily in solution, or to aggregate randomly and amorphously, which prevents them from widespread application. In the present research, 1D-CPs comprising bridging dipyrrin ligands and divalent metal ions (Zn²⁺, Ni²⁺, and Cu²⁺) are synthesized. A liquid/liquid interfacial reaction gives rise to single crystals suitable for X-ray diffraction analysis: A dichloromethane solution of the ligand is layered with aqueous metal(ii) acetate, such that the coordination reaction proceeds at the liquid/liquid interface. Isolated single fibers of the zinc coordination polymer may be exfoliated from the single crystal or bulk solid upon ultrasonication. Atomic force microscopy (AFM) detects the isolated fibers with lengths of more than several μm. The exfoliated 1D-CP wires feature good processability, realizing a conjugate with single-wall carbon nanotubes (SWCNTs), and a thin film on a transparent SnO₂ electrode. The processed materials show electric conversion ability: For example, the modified SnO₂ electrode serves as a photoanode for a photoelectric conversion system. The designability and tunability of the present 1D-CPs is demonstrated by a ligand modification, affording a luminescent property and an extension of the photoelectric conversion response to longer wavelengths.     

Dehydrative Direct CH Allylation with Allylic Alcohols under [Cp*CoIII] Catalysis

The unique reactivity of [Cp*Co^III] over [Cp*Rh^III] was demonstrated. A cationic [Cp*Co^III] catalyst promoted direct dehydrative C? H allylation with non‐activated allyl alcohols, thus giving C2‐allylated indoles, pyrrole, and phenyl‐pyrazole in good yields, while analogous [Cp*Rh^III] catalysts were not effective. The high γ‐selectivity and C2‐selectivity indicated that the reaction proceeded by directing‐group‐assisted C? H metalation. DFT calculations suggested that the γ‐selective substitution reaction proceeded by C? H metalation and insertion of a C? C double bond, with subsequent β‐hydroxide elimination. The [Cp*Co^III] catalyst favored β‐hydroxide elimination over β‐hydride elimination.     

Benzylic C(sp3)H Perfluoroalkylation of Six‐Membered Heteroaromatic Compounds

Successful benzylic C(sp³)? H trifluoromethylation, pentafluoroethylation, and heptafluoropropylation of six‐membered heteroaromatic compounds were achieved as the first examples of a practical benzylic C(sp³)? H perfluoroalkylation. In these reactions, BF₂C_nF_2n+1 (n=1–3) functioned as both a Lewis acid to activate the benzylic position and a C_nF_2n+1 (n=1–3) source. The perfluoroalkylation proceeded at both terminal and internal positions of the alkyl chains. Perfluoroalkylated products were obtained in moderate to excellent yields, even on gram scale, and in a sequential procedure without isolation of the intermediates. By using this method, trifluoromethylation of a bioactive compound, as well as introduction of a CF₃ group into a bioactive molecular skeleton, proceeded regioselectively.     

Simple Surfactant Concentration‐Dependent Shape Control of Polyhedral Fe3O4 Nanoparticles and Their Magnetic Properties

The shape and size of monodisperse Fe₃O₄ nanoparticles (NPs) are controlled using a chemical solution synthesis in the presence of the surfactant cetylpyridinium chloride (CPC). Cubic Fe₃O₄ NPs surrounded by six {100} planes are obtained in the absence of CPC. Increasing the CPC content during synthesis causes the shape of the resulting Fe₃O₄ NPs to change from cubic to truncated cubic, cuboctahedral, truncated octahedral, and finally octahedral. During this evolution, the predominantly exposed planes of the Fe₃O₄ NPs vary from {100} to {111}. The shape control results from the synergistic effect of the pyridinium cations, chloride anions, and long‐chain alkyl groups of CPC, which is confirmed by comparison with NPs synthesized in the presence of various related cationic surfactants. The size of the cubic Fe₃O₄ NPs can be tuned from 50 to 200 nm, by changing the concentration of oleic acid in the reaction solution. The Fe₃O₄ NPs exhibit shape‐dependent saturation magnetization, remanent magnetization, and coercivity.     

Development of dispersive XAFS system for analysis of time‐resolved spatial distribution of electrode reaction

Apparatus for a technique based on the dispersive optics of X‐ray absorption fine structure (XAFS) has been developed at beamline BL‐5 of the Synchrotron Radiation Center of Ritsumeikan University. The vertical axis of the cross section of the synchrotron light is used to disperse the X‐ray energy using a cylindrical polychromator and the horizontal axis is used for the spatially resolved analysis with a pixel array detector. The vertically dispersive XAFS (VDXAFS) instrument was designed to analyze the dynamic changeover of the inhomogeneous electrode reaction of secondary batteries. The line‐shaped X‐ray beam is transmitted through the electrode sample, and then the dispersed transmitted X‐rays are detected by a two‐dimensional detector. An array of XAFS spectra in the linear footprint of the transmitted X‐ray on the sample is obtained with the time resolution of the repetition frequency of the detector. Sequential measurements of the space‐resolved XAFS data are possible with the VDXAFS instrument. The time and spatial resolutions of the VDXAFS instrument depend on the flux density of the available X‐ray beam and the size of the light source, and they were estimated as 1 s and 100 µm, respectively. The electrode reaction of the LiFePO₄ lithium ion battery was analyzed during the constant current charging process and during the charging process after potential jumping.     

Evidence for a weakening ‘dead zone’ in Tokyo Bay over the past 30?years

Weakened hypoxia in the past 30?years at a dredged area in Tokyo Bay was proven by the existence of amorphous hematite (α-Fe2O3) in sediments. The chemical states of iron in sediments can become a proxy for the scale of anoxia at the time of sedimentation. In 2009, we collected core sediments from a dredged area off Makuhari in Tokyo Bay that is very strongly anoxic in the summer. Every layer of the sediments was analysed by ⁵⁷Fe M?ssbauer spectroscopy and excess 210Pb dating, and amorphous hematite was identified in the sediments from the 1976–1979, 1986–1989 and 2006–2009 layers. Using an estimate based on the Eh-pH diagram optimized for the sedimental environment, the existence of hematite in the dredged area proves that the scale of hypoxia/anoxia is decreasing, and these results agree well with the observed dissolved oxygen level of the seawater mass.