Morphospecific polymer from the copolymerization of trioxane and ethylene oxide

Recently, we have observed the following phenomena during the copolymerization of trioxane and ethylene oxide using a boron trifluoride initiator. In almost all of the polymerization cases, all polymers were soluble in a p-chlorophenol-tetrachloroethane mixed solvent at 90°C. However, in some polymerization cases, a small portion of the polymer was insoluble at this temperature, and this mixed solvent-insoluble fraction showed a higher melting point than that of the other fractions. Scanning electron microscope (SEM) photographs of the polymer showed that a highly fibrous structure was formed for the mixed solvent-insoluble fraction, and this highly packed structure is thought to be the origin of the high melting fraction. The nature of this high melting fraction was further examined using X-ray diffraction and Raman spectra. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2479–2486, 1997     

Novel synthesis of 2-aryl and 2,3-disubstituted indoles by modified double elimination protocol

[reaction: see text] Syntheses of 2-aryl and 2,3-substituted indoles were realized by modified double elimination protocol. Under basic conditions, vinyl sulfones derived from the reaction of 2-aminobenzyl sulfone with benzaldehydes underwent cyclization and alkylation followed by elimination of sulfinic acid to afford 2,3-substituted indoles.     

Synthesis of nitrogen-bridged terthiophenes by tandem Buchwald-Hartwig coupling and their properties

The first synthesis of nitrogen-bridged terthiophenes (NBTTs) has been achieved by a tandem Buchwald-Hartwig coupling of 3,3',3",4'-tetrabromo-2,2':5',2"-terthiophene. Several NBTT derivatives bearing aryl or alkyl moieties on the N-atoms could be synthesized. Their fundamental electrochemical characteristics and HOMO-LUMO levels were found to be influenced by the substituents on the N-atoms.     

High resolution quantum cascade laser studies of the ν3 band of methyl fluoride in solid para-hydrogen

Spectra of solid para-H(2) doped with CH(3)F at 1.8 K are studied in the ν(3) region (~1040 cm(-1)) using a quantum cascade laser source. As shown previously, residual ortho-H(2) in the sample (~1000 ppm) gives rise to distinct spectral features due to clusters of the form CH(3)F-(ortho-H(2))(N), with N = 0, 1, 2, 3, etc. Brief annealing at 7 K is found to give narrower spectral lines (≥0.006 cm(-1)) than conventional (5 K) annealing, and causes the N = 3 and 4 lines to fragment into two or more components. The N = 3 line is observed to be particularly stable and persistent. The N = 0 line (no ortho-H(2) neighbors) is resolved into two closely spaced (≈0.007 cm(-1)) components which are assigned to the K = 0 and 1 states of CH(3)F rotating around its C(3v) symmetry axis (ortho- and para-CH(3)F, respectively). Similar K-structure is also evident for other lines. Weak but persistent features ("N = 1/2 lines") are observed mid way between N = 0 and 1.     

Infrared photochromism in a quantum crystal: laser pumping and probing in solid para-H2 doped with CH3F

Solid para-H(2) doped with CH(3)F at 1.8 K is studied in the ν(3) region (～1040 cm(-1)) using a quantum cascade laser source. Residual ortho-H(2) gives rise to distinct spectral features due to CH(3)F-(ortho-H(2))(N) clusters with N = 0, 1, 2, etc. The laser power (～30 mW) is sufficient to significantly affect the sample, enabling novel photochromism experiments to be performed on a solid para-H(2) matrix-isolated sample. It is found that population can be reversibly transferred between the N = 1 line and satellite features close to the N = 0 line.     

Stereoselective Self‐Aggregation of 31‐Epimerically Pure Amino Analogs of Zinc Bacteriochlorophyll‐d in an Aqueous Micelle Solution

Zinc bacteriochlorophyll‐d analogs possessing an amino group instead of the original hydroxy group at the C3¹ position were prepared by chemical modification of naturally occurring chlorophyll‐a. The synthetic 3¹‐epimers were successfully separated by reverse phase HPLC to give diastereomerically pure samples. The stereochemistry of the chiral C3¹‐center in the separated amines was determined by NMR analysis of their diastereomeric amides as well as by their asymmetric synthesis from authentic stereoisomers. Both the epimers were monomeric in tetrahydrofuran to give sharp electronic absorption bands, while they self‐aggregated to form chlorosomal oligomers with the redshifted bands in an aqueous Triton X‐100 micelle solution (pH = 6.9). The resulting oligomers deaggregated by addition of p‐toluenesulfonic acid to give monomeric N‐protonated ammonium species. The aggregation and deaggregation were dependent on the 3¹‐stereochemistry, indicating that each epimer produced supramolecularly different self‐aggregates.     

Time-dependent changes in the carotenoid composition and preferential binding of spirilloxanthin to the reaction center and anhydrorhodovibrin to the LH1 antenna complex in Rhodobium marinum

Carotenoids were isolated from the cells of Rhodobium marinum, and their structures were determined by mass spectrometry and 1H nuclear magnetic resonance spectroscopy; the carotenoids include lycopene, rhodopin, anhydrorhodovibrin, rhodovibrin and spirilloxanthin. Time-dependent changes in the carotenoid composition in the reaction center (RC) and the light-harvesting complex 1 (LH1) were traced by high-performance liquid chromatography analysis of the extracts. The carotenoid composition changed according to the spirilloxanthin biosynthetic pathway. However, spirilloxanthin having the longest conjugated chain was always preferentially bound to the RC, and anhydrorhodovibrin and other precursors to the LH1.     

Mixing of low-frequency Raman-active phonons studied by femtosecond pump–probe spectroscopy

We report an optical study of the superconducting transition in the YBa₂Cu₃O_7−x films on MgO substrate carried out by femtosecond pump–probe spectroscopy. In both the normal and the superconducting state, we have observed the transient time-resolved reflectivity caused by the oscillations associated with two A_1g metal-ion modes. Temporal interference between the modes is modified below the phase transition, which also appeared in an altered relative intensity of the modes in the Fourier transformed spectra.     

Opto-electronic polymers for advanced computer and communication technologies

This paper describes reviews about the characterization of optical and electronic (opto-electronic) organic materials including polymers, and their applications for advanced key devices used for computers and communications technologies. On the basis of the author's recent investigations, discussions are made on organic electroluminescent thin film materials for emissive display devices, polymer-dispersed liquid crystal materials for passive display devices, organic photo-conductive materials for electrophotographic printer devices, and highly electroconductive polymers for solid tantalum capacitors. Finally, technical issues and development prospects for the opto-electronic organic materials in the 21st century are suggested.