Oxidative Polymerization of Silylthioketene Dimer

Summary: The first π‐conjugated poly(thioketene dimer) was synthesized via the homopolymerization of a silylthioketene dimer by a chemical oxidation‐reduction process. The polymerization of trimethylsilylthioketene dimer in the presence of FeCl₃ (in CHCl₃ at 70 °C for 24 h) gave the corresponding doped poly(thioketene dimer). After treatment of the doped polymer with an aqueous solution of ammonia, the neutral poly(thioketene dimer) was obtained with an incidental desilylation. The polymer obtained was soluble in DMF and DMSO. From gel permeation chromatographic analysis (DMF, polystyrene standards), the number‐average molecular weight of the polymer was found to be 7 460. The polymer showed low oxidation potentials derived from the thioketene dimer unit. An effective extension of the π‐conjugation was observed in the polymer.

Synthesis of π‐conjugated poly(thioketene dimer).     

Soluble and film-formable homopolymer tethering side-opened cage silsesquioxane pendants

Cage silsesquioxane, denoted as polyhedral oligomeric silsesquioxane (POSS) has high crystallinity to readily cause aggregation when it is induced into polymer side chain. In this work, side-opened POSS was employed to construct a bifunctional monomer for cyclopolymerization. The collapsed symmetry of the POSS core effectively reduced the crystallinity to realize homogeneous films, while a traditional POSS homopolymer formed turbid and brittle films. The obtained film showed high transparency and thermal stability.     

Intramolecular C−H Amination of N-Alkylsulfamides by tert-Butyl Hypoiodite or N-Iodosuccinimide

1,3-Diamines are an important class of compounds that are broadly found in natural products and are also widely used as building blocks in organic synthesis. Although the intramolecular C−H amination of N-alkylsulfamide derivatives is a reliable method for the construction of 1,3-diamine structures, the majority of these methods involve the use of a transition-metal catalyst. We herein report on a new transition-metal-free method using tert-butyl hypoiodite (t-BuOI) or N-iodosuccinimide (NIS), enabling secondary non-benzylic and tertiary C−H amination reactions to proceed. The cyclic sulfamide products can be easily transformed into 1,3-diamines. Mechanistic investigations revealed that amination reactions using t-BuOI or NIS each proceed via different pathways.     

Millimeter-wave spectroscopy of the internal rotation hot band (j=2-1) of the Ar-HCN complex

Millimeter-wave absorption spectroscopy combined with a pulsed jet expansion technique was applied to measure the internal rotation j=2-1 hot band of the Ar-HCN complex in the frequency region of 147-287 GHz. In total 153 rovibrational lines, split into hyperfine components due to the nitrogen nucleus, were assigned to the Σ₂-Σ₁, Σ₂-Π₁, Π₂-Σ₁, Π₂-Π₁, Δ₂-Σ₁, and Δ₂-Π₁ subbands. A set of molecular constants for the Σ₂, Π₂, and Δ₂ internal rotation substates, including subband origins, rotational constants, nuclear quadrupole coupling constants, and Coriolis interaction constants, was determined. The internal rotation energy for the Σ₂ state, 412.8949 GHz, is higher than those for the Π₂ and Δ₂ states, 392.3974 and 355.9570 GHz, by 20.498 and 56.938 GHz, respectively, in contrast to the Σ₁ state located by 17.094 GHz lower than the Π₁ state, the anisotropy of potential energy surface affecting the j=2 and j=1 states differently. The rotational and quadrupole coupling constants in the j=2 excited state are quite different from those in the ground state, indicating drastic change in the average structure in the j=2 state from the ground state. The determined molecular constants were compared with those calculated from the potential energy surface computed at the CCSD(T) level.     

Estimation of Electrical Source Localization Using the Temporal Correlation between Magnetic Field Measurements

It is well known that an inverse problem of biomagnetic imaging is generally ill-posed. Recently several attempts using biocoherence have been reported, but the ill-condition is not considered in these previous methods. If the conventional reconstruction formula is under the ill-condition, the reconstruction problem is also ill-posed and the ill-posedness cannot be improved. In this paper, we propose an approach to estimate the location of current sources under the condition that sources of different positions have little or weak correlation. Our method is based on a well-known regularization method, the truncated SVD method. Compared with the conventional method, our technique allows accurate determination of the location of current sources because it improves the ill-posedness of the inverse problem. We carried out computer simulations using the half-space conducting model and confirmed the effectiveness of our method.     

Formation processes of the integrated ordered mesostructure of silica at liquid-liquid interface using synchrotron radiation X-rays

The formation processes of the integrated ordered mesostructure of silica at the liquid-liquid interface in laurylamine/tetraethoxysilane system were elucidated by measuring the small-angle X-ray scattering pattern every second during the formation processes using strong synchrotron radiation X-rays. Cylinders of silica were formed in random configurations in the very early stage of reactions at the liquid-liquid interface. Since these cylinders were restricted in a two-dimensional liquid-liquid interface, they aligned easily with each other and made an ordered structure composed of aligned cylinders at the interface. These ordered structures then accumulated with each other, making an integrated ordered structure, such as a hexagonal array.     

Photochemistry of Flavins in Micelles: Specific Effects of Anionic Surfactants on the Monomerization of Thymine Cyclobutane Dimers Photosensitized by Tetra-O-acyl Riboflavins*

It was found that tetra-o-acyl riboflavins efficiently photosensitize the monomerization of the cis, syn-cyclobutane dimers of 1,3-dimethylthymine and 1,3-dimethyluracil in aqueous solution in the presence of such anionic surfactants as sodium dodecyl sulfate and sodium hexadecyl sulfate at concentrations higher than their critical micelle concentration, while little monomerization of the dimers was photosensitized by the flavins in the absence of the surfactants and even in the presence of cationic and nonionic surfactants.     

A molecular dynamics study of sodium chenodeoxycholate in an aqueous solution

Hydration structure and dynamics of sodium chenodeoxycholate (CDC) in water are studied by a long-time molecular dynamics calculation. Strong hydration shell around the hydrophobic region of this large solute and strong hydrogen bonds of water with both hydroxyl and carboxyl oxygen atoms have been identified. The rotation of CDC around its longitudinal axis is found to be particularly active in comparison with that around other axes of the molecule. The diffusion coefficient of CDC calculated from the slope of the mean-square displacement, 0.95 × 10⁻⁹ m²/s, is only 1/6 of that for water in the solution, 5.4 × 10⁻⁹ m²/s.     

Synthesis and properties of superconductors prepared from ethylenediaminetetraacetic acid (EDTA)-ethylenediamine (ED) polyamide YBC chelate

Single-phase Y₁Ba₂Cu₃O_7-x has been synthesized by a polymer-metal chelate precursor technique. Ethylenediaminetetraacetic acid (EDTA)-ethylenediamine (ED) polyamide was used as chelating polymer for Y, Ba, and Cu. The titration curves of the polymer in the absence and presence of each metal ion showed the chelate formations. The polymer was dissolved in water and the metal nitrates of Y, Ba, and Cu (1:2:3 in mole ratio) were stoichiometrically added to form a homogeneous molecular complex. The clear polymermetal chealate film was obtained by removal of the solvent without phase separation. This precursor was dried, calcined, and sintered to develop the superconducting (1,2,3) phase. The 1,2,3 phase produced was found to be pure according to x-ray diffraction pattern and it possessed good superconducting properties, i.e., the onset of superconductivity was seen at 90.0 K and the resistance rapidly decreased with decreasing temperature, reaching substantially zero at 88.6 K. Scanning electron microscope (SEM) and face and point analyses by electron probe microanalysis (EPMA) showed that Y, Ba, and Cu elements were uniformly dispersed at least micron order. © 1994 John Wiley & Sons, Inc.