Trimethylsilyl-group containing polyphenylacetylenes for oxygen and ethanol permselective membranes

Phenylacetylenes having one or two trimethylsilyl groups at their benzene ring were synthesized, and polymerized by [Rh(cyclooctadiene) (PPh₃)₂]PF₆, [Rh(norbornadiene)Cl]₂, or WCl₆ to afford high molecular-weight polymers in high yields. These poly(phenylacetylene)s were soluble in many kinds of solvents and were fabricated to tough membranes by the solvent casting method. The oxygen permselectivities of these membranes were very good. The oxygen permeability coefficients (P_o2) and oxygen separation factors (α = P_o2/P_N2) of poly[2,4-(o,p)-bis(trimethylsilyl)phenylacetylene] [poly ( o-1-p-1 )] and poly[(4(p)-trimethylsilyl)phenylacetylene] [poly( p-1 )] membranes were 4.73 × 10^?8 cc(STP) cm/cm² s cmHg and 2.65, and 1.52 × 10^?8 cc(STP) cm/cm² s cmHg and 3.39, respectively. In the case of poly( o-1-p-1 ), P_o2 was comparable to that of polydimethylsiloxane (PDMS) and α was higher than that of PDMS. However, the P_o2 value reduced to 48% of its initial value in about 1 year. In the case of poly( p-1 ), the P_o2 value did not change in about 1 year. Ethanol permeated preferentially through these membranes (α^EtOH > 1) in pervaporation of aqueous ethanol solution, whereas poly(phenylacetylene) [poly( PhA )] showed water permselectivity (α^EtOH < 1). These favorable effects of trimethylsilyl groups on the oxygen and ethanol permselectivities were discussed on the basis of comparison with those of poly( PhA ), other poly(substituted phenyl-acetylene)s, and trimethylsilyl-group containing polystyrenes. © 1994 John Wiley & Sons, Inc.     

Conical support for double-stage diamond anvil apparatus

ABSTRACT

Both micro-paired and conical support type double-stage diamond anvil cells (ds-DAC) were tested using a newly synthesized ultra-fine nano-polycrystalline diamond (NPD). Well-focused X-ray sub-micron beam and the conically supported 2nd stage anvils (micro-anvils) with 10?μm culet enable us to obtain good quality X-ray diffraction peaks from the sample at around 400?GPa. The relationship between confining pressure and sample pressure depends heavily on the initial height (thickness) of micro-anvils, the difference of a few micrometers leads to a quite different compression path. The conical support type is a solution to retain both enough thickness and strength of micro-anvils at higher confining pressure conditions. All conical support ds-DAC experiments terminated by the failure of the 1st stage anvil instead of 2nd one. The combination of ultra-fine NPD 2nd stage anvil and NPD 1st stage anvil opens a new frontier for measurement of the X-ray absorption spectrum above 300?GPa.     

Multi-frequency ESR study of the polycrystalline phenoxyl radical of alpha-(3,5-di-tert-butyl-4-hydroxyphenyl)-N-tert-butylnitrone in the diamagnetic matrix

Multifrequency (X-, Q-, and W-band) electron spin resonance (ESR) spectroscopy has been used to characterize the phenoxyl radical produced from alpha-(3,5-di-tert-butyl-4-hydroxyphenyl)-N-tert-butylnitrone, which is a new spin-trapping reagent. The X-band measurement did not resolve the powder-pattern ESR spectrum. Because of its higher resolution with g value, the Q-band ESR study revealed that the g factor has an axial-like symmetry and that the observed hyperfine structure in the Z-direction is caused by the nitrogen nucleus at the para-position. Furthermore, the results of the W-band ESR experiment more clearly distinguished the perpendicular components from the parallel component, resolving the perpendicular components into x and y components. The X-band powder spectrum was similar to the X-band ESR spectrum of the radical in a frozen solution of toluene. The computer simulation spectra performed using the obtained parameters fitted the experimental spectra well. A comparison of the amplitude of g( perpendicular)(gx, gy) with that of gz showed that the unpaired electron is delocalized over the pi-conjugated framework. Considering the hyperfine coupling constant, it was concluded that about 16% of the unpaired electron distributed over the nitrogen nucleus at the para-position. This study thus showed the significant potential of a multifrequency ESR approach to a powder sample radical in terms of its high resolution with g value.     

A new method for the conversion of allyl alcohol into pi-allyl species promoted by nucleophilic interaction with a CO ligand

Upon treatment with an iridium carbonyl complex, [(PN)Ir(CO)2]+, allyl alcohol can be smoothly converted into pi-allyliridium species at ambient temperature via nucleophilic interaction of the alcohol with a CO ligand followed by C(allyl)-O bond cleavage in the resultant protonated allyloxycarbonyl intermediate.     

Amplified optical window for three-dimensional images

A proposed amplified optical window can form an observable three-dimensional image of an object in darkness. The window comprises two gradient-index (GRIN) lens arrays with an image intensifier between them. The length of the individual GRIN lenses that constitute the arrays is three fourths of the cycle of the meandering optical path on the input side and one fourth of the cycle on the output side. A primitive experimental result proved that the method produces three-dimensional images to be observed. This device would be used as a viewer for observing three-dimensional objects in a dark space without a camera and display equipment.     

High-resolution analysis of (Sc3C2)@ C80 metallofullerene by third generation synchrotron radiation X-ray powder diffraction

The X-ray structure of Sc(3)C(82) is redetermined by the MEM/Rietveld method by using synchrotron radiation powder data at SPring-8, where the C(2) encapsulated structure available to discuss the Sc-Sc interatomic distances has been determined. The encapsulated three scandium atoms form a triangle shape. A spherical charge distribution originating from the C(2) molecule is located at the center of the triangle. Interatomic distances between Sc and Sc are 3.61(3) A in the triangle. The distance between Sc and the center of the C(2) molecule is 2.07(1) A.     

Ladderlike ferromagnetic spin coupling network on a pi-conjugated pendant polyradical

A poly(9,10-anthryleneethynylene)-based polyradical with two pendant stable phenoxyls in one anthracene skeleton was newly synthesized via polymerization of the corresponding bromoethynylanthracene monomer using a Pd(0) catalyst. The average molecular weight of the polymer reached M(n) = 5 x 10(3) and was soluble in common organic solvents. The polyradical was prepared from the corresponding hydroxyl precursor polymer and was appropriately stable at room temperature. The ESR spectrum of the corresponding monomeric radical suggested an effectively delocalized spin density distribution on the backbone anthracene. The magnetization and the static magnetic susceptibility of the polyradical were measured using a SQUID magnetometer. The large average spin quantum number (S = (5)/(2)) of the polyradical indicated that the ferromagnetic spin coupling network of the polyradical had spread throughout the pi-conjugated chain and that it was considerably insensitive to spin defects.     

A helical amplification system composed of artificial nucleic acids

Herein we report an amplification system of helical excess triggered by nucleic acid hybridization for the first time. It is usually impossible to prepare achiral nanostructures composed of nucleic acids because of their intrinsic chirality. We used serinol nucleic acid (SNA) oligomers for the preparation of achiral nanowires because SNA oligomers with symmetrical sequences are achiral. Nanowire formation was confirmed by atomic force microscopy and size exclusion chromatography. When a chiral nucleic acid with a sequence complementary to SNA was added to the nanostructure, helicity was induced and a strong circular dichroism signal was observed. The SNA nanowire could amplify the helicity of chiral nucleic acids through nucleobase stacks. The SNA nanostructures have potential for use as platforms to detect chiral biomolecules under aqueous conditions because SNA can be readily functionalized and is water-soluble.

Herein we report an amplification system of helical excess triggered by nucleic acid hybridization for the first time.     

Stable metallic behavior and antiferromagnetic ordering of Fe(III) d spins in (EDO-TTFVO)2.FeCl4

We report the crystal structure and physical properties of the 2:1 FeCl4- salt of a new donor molecule, EDO-TTFVO. Crystal structure analysis of this salt revealed that the donor molecules formed a beta' '-type two-dimensional conducting layer, and there is a short S...Cl contact between the donor molecules and the FeCl4- ions, which is expected to mediate a strong pi-d interaction. This salt showed a stable metallic conducting behavior down to 0.3 K and an antiferromagnetic ordering at TN approximately 3.0 K, indicating that this salt becomes a new antiferromagnetic molecular metal at ambient pressure. The appearance of the magnetic ordering is considered to originate from the strong pi-d interactions between the donor molecules and the FeCl4- ions because the field dependence of magnetoresistances was remarkably affected below the antiferromagnetic transition temperature.