The selenite-capped polyoxo-4-aurate(iii), [Au(III)(4)O(4)(Se(IV)O(3))(4)](4-)

The discrete heteropolyaurate [Au(III)(4)O(4)(Se(IV)O(3))(4)](4-) () represents only the second member of this class ever reported, and was synthesized via one-pot room temperature condensation in aqueous medium. was structurally characterized in the solid state and in solution by single-crystal XRD, TGA, FT-IR, (77)Se NMR, mass spectrometry and electrochemistry.     

A tubular macrocycle from covalently linked anthracenes and meta-phenylene spacers

A novel tubular macrocycle containing four anthracene panels covalently linked by meta-phenylene spacers was synthesized. The tube is approximately 1 nm long with anthracene panels delimiting a columnar cavity with a diameter of ~1 nm and exhibits strong blue fluorescence.     

Synthesis of fluorinated N-aminoaziridines: access to new CF3-peptidomimetics

A series of fluorinated N-aminoaziridines have been synthesized by the PhI(OAc)₂-mediated aziridination procedure. The reaction was carried out with various protected hydrazides and fluorinated alkenes. The reaction was extended to alkenes bearing an amino acid and the ring opening of the CF₃–N-aminoaziridines has been investigated.     

Colorless poly(ester imide)s derived from hydrogenated trimellitic anhydride

Tetracarboxylic dianhydrides were synthesized from hydrogenated trimellitic anhydride (HTA) and some diols to obtain novel poly(ester imide)s (PEsIs). The HTA-derived tetracarboxylic dianhydrides showed much higher reactivity with various diamines than conventional cycloaliphatic tetracarboxylic dianhydrides and led to PEsI precursors with high molecular weights (M_w). The results can be explained in terms of a spacer effect. The PEsI films were essentially colorless regardless of diol and diamine components owing to inhibited charge-transfer interactions. The HTA-derived PEsIs also exhibited excellent combined properties: relatively high glass transition temperatures (T_g), relatively low water absorption (W_A), and relatively low dielectric constants. The outstanding processability (thermoplasticity and solubility) observed for the HTA-derived PEsIs was discussed on the basis of a non-planar/bent structure at the HTA-based imide units. The use of a fluorene-containing diol component was effective for enhancing T_g’s by restricted internal rotation and for reducing W_A by a decreased imide group content. On the other hand, the use of 4,4′-biphenol as another diol gave rise to a prominent toughening effect without sacrificing other target properties. One of the HTA-derived PEsI systems can be a promising candidate as plastic substrates because of its excellent combined properties: a high T_g close to 300 °C, high optical transparency, significant toughness (elongation at break > 100%), and good thermo- and solution-processability.     

Crystalline Complex of Syndiotactic Polystyrene with Poly(ethylene Glycol) Dimethyl Ethers

It has been clarified that syndiotactic polystyrene (sPS) forms co‐crystalline structures with polyethylene glycol dimethyl ethers (PEGDMEs) with molecular weights ranging from 178 to 1 000 g · mol⁻¹ through a guest exchange procedure assisted by a plasticizing agent. The PEGDME molecules are incorporated into the spaces between sPS polymer sheets consisting of (T₂G₂)₂ helices. The results of X‐ray diffraction and gravimetric measurements suggest that one or less molecules are included per unit cell for PEGDME with average molecular weight of 1 000 g · mol⁻¹, which indicates the possibility that longer polymeric molecules can be introduced into sPS lattices with multiple site occupation.

     

[Zr0.72Y0.28]Al4C4: A new member of the homologous series (MC)l(T4C3)m (M=Zr, Y and Hf, T=Al, Si and Ge)

A new layered carbide, [Zr_0.72(3)Y_0.28(3)]Al₄C₄, has been synthesized and characterized by X-ray powder diffraction, transmission electron microscopy and energy dispersive X-ray spectroscopy (EDX). The atom ratios [Zr:Y] were determined by EDX, and the initial structure model was derived by the direct methods, and further refined by Rietveld method. The crystal is trigonal (space group , Z=1) with lattice dimensions of a=0.333990(5) nm, c=1.09942(1) nm and V=0.106209(2) nm³. This compound shows an intergrowth structure with [Zr_0.72Y_0.28C₂] thin slabs separated by Al₄C₃-type [Al₄C₄] layers. It is a new member with l=1 and m=1 of the homologous series, the general formula of which is (MC)_l(T₄C₃)_m (l=1, 2 and 3, m=1 and 2, M=Zr, Y and Hf, T=Al, Si and Ge).     

Rheology of self-assembled monolayers on solid-liquid interface oscillating at MHz frequency

The rheology properties (viscosity and elasticity) of chemisorbed soft matters on a solid-liquid interface oscillating at MHz were investigated using a quartz crystal microbalance (QCM). As a chemisorbed soft matter, we employed the self-assembled monolayers (SAMs) of mercapto oligo(ethylene oxide) methyl ethers, HS(CH₂CH₂O)_nCH₃ (n?=?5, 11, 12, 19, 27, 35 and 43), where those molecular weights had unity. The systematical analyses on the basis of the Voight model revealed the relationships of $\eta \propto M_n^{0.180}$ and $\mu \propto M_n^{0.344}$, where η and μ are the viscosity and elasticity of the SAM, and M_n is the molecular weight of HS(CH₂CH₂O)_nCH₃. As a result, we found that the SAM consisting of the oligomer followed the formula of polymer.     

Coherent control of spin precession motion with impulsive magnetic fields of half-cycle terahertz radiation

Coherent control of the precession motion of magnetizations in a single crystal YFeO3 with double half-cycle pulse terahertz waves was demonstrated. Quasiferromagnetic (0.299 THz) and quasiantiferromagnetic (0.527 THz) precession modes were selectively excited by choosing an appropriate interval of two pulses and were observed as free induction decay (FID) signals from the spin system. By observing the circularly polarized FID signals due to ferromagnetic resonance, we also succeeded in confirming directly the energy storage in the spin system and recovery from that to the electromagnetic radiation.     

Viscosity behavior of poly(glyceryl methacrylate) in the presence of borate and phenylboronate ions

The viscosity behavior of polyelectrolyte solutions induced by borate or phenylboronate complexation with poly(glyceryl methacrylate) (PGM) has been investigated. In dilute solutions borate ions can form monodiol (1/1) complexes and didiol (2/1) intramolecular complexes. Both types of complex are anionic. Thus, the polymer is characterized by the existence of charged sites on the chain and loops formed by intramolecular complexation. On the contrary, phenylboronate can only give monodiol 1/1 complexes. In the presence of passive salt, the charges are screened. By addition of borate ion to a PGM solution, a decrease of the initial polymer viscosity due to loop formation is first observed, then the anionic charges fixed on the chain by complex formation induce an expansion of the polyelectrolyte and the viscosity of the solution increases. The situation is different for the PGM-phenyl boronate system, where no intramolecular crosslink is present. In this case the viscosity of the solution increases with phenyl boronate concentration. But for a fixed complexing ion concentration it will tend to that of the neutral polymer when NaCl is added. ©1995 John Wiley & Sons, Inc.