Regioselective synthesis of bis(silyl enol ethers) and bis(conjugated enones) through electron transfer from Mg metal

Treatment of α,β-unsaturated ketones with Mg metal in the presence of trimethylsilyl choride (TMSCl) brought about facile and regioselective reductive dimerization to give the corresponding bis(silyl enol ethers), 1,6-bis(trimethylsilyloxy)-1,5-dienes. Similar Mg-promoted reductive dimerization of 1,3-cyclic diketones in the presence of TMSCl followed by acid-catalyzed hydrolysis led to selective formation of the corresponding 1,6-diketo-2,4-dienes in moderate to good yields.     

Microelectrochemical approach to induce local cell adhesion and growth on substrates

The nature of an albumin-coated substrate that blocks protein adsorption and cell adhesion was rapidly switched to cell-adhesive by exposure to an oxidizing agent such as HBrO. This finding has enabled cellular pattern drawing even on a single-cell level by closely scanning a microelectrode above the substrate and electrochemically producing the agent at the tip of the electrode. The present microelectrochemical cell patterning is applicable even for a previously cell-patterned substrate and for a grooved substrate. These unique technical features will have impacts on a variety of cell-based studies that require the analysis of heterotypic cell-cell interactions and cellular arrangement on an uneven surface such as semiconductor devices.     

Thermoresponsive conductivity of poly(N‐isopropylacrylamide)/potassium chloride gel electrolytes

A series of thermoresponsive polymer gel electrolytes (PGEs) based on poly(N‐isopropylacrylamide) in aqueous potassium chloride was synthesized by radiation‐induced polymerization and gelation using γ rays from a ⁶⁰Co source. The electric conductivity and swelling properties of the PGE were determined as a function of temperature. It was found that the electric conductivity of the PGE depended strongly on the swelling ratio; most notably, it changed drastically near the volume phase‐transition temperature of the PGE. The temperature/conductivity profile of the PGE exhibits a maximum peak at a certain temperature that is defined as the maximum conductivity temperature (T_max). The T_max of all of the PGEs prepared by low‐dose irradiation agreed with the temperature, near the end of the volume phase transition, where the PGE was completely shrunken. Consequently, the conductivity of gels should provide a good method with which the totally shrunken temperature of the thermoresponsive gels can be monitored with good temperature precision. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 134–141, 2002     

Synthesis and properties of rhodium(III) porphyrin cyclic tetramer and cofacial dimer

Rhodium(III) porphyrin complexes, [Rh(4-PyT(3)P)Cl](4) (1) and [Rh(2-PytB(3)P)Cl](2) (2) (4-PyT(3)P = 5-(4-pyridyl)-10,15,20-tritolylporphyrinato dianion, 2-PytB(3)P = 5-(2-pyridyl)-10,15,20-tri(4-tert-butyl)phenylporphyrinato dianion), were self-assembled and characterized by (1)H nuclear magnetic resonance spectroscopy, infrared spectroscopy, and electron spray ionization-mass spectroscopy methods. The spectroscopic results certified that the rhodium porphyrin complexes 1 and 2 have a cyclic tetrameric structure and a cofacial dimeric structure, respectively. The X-ray structure analysis of 1 confirmed the cyclic structure of the complex. The Soret bands of both oligomers were significantly broadened by excitonic interactions between the porphyrin units, compared to those observed for a corresponding analogue of Rh(TTP)(Py)Cl (TTP = 5,10,15,20-tetratolylporphyrinato dianion, Py = pyridine). Stepwise oxidation of the porphyrin rings in the oligomers was observed by cyclic voltammetry. The oligomers 1 and 2 are very stable in solution, and they slowly undergo reactions with pyridine to give corresponding monomer complexes only at high temperatures (approximately 80 degrees C).     

PHYTOCHROME-MEDIATED PHOTOTROPISM AND DIFFERENT DICHROIC ORIENTATION OF Pr AND Pfr IN PROTONEMATA OF THE FERN ADIANTUM CAPILLUS-VENERIS L.

Abstract— Single-celled protonemata of Adiantum capillus-veneris were cultured under continuous red light for 6 days and then in the dark for 15 h. Brief local exposure of a flank (5 times 20 /mi) of the subapical region of a protonema to a microbeam of red light effectively induced a phototropic response toward the irradiated side. The degree of the response was dependent upon the fluence of the red light. Red/far-red reversibility was typically observed in this photoreaction, showing that phytochrome was the photo-receptive pigment. When the flank was irradiated with a microbeam of linearly polarized red and far-red light, red light with an electrical vector parallel to the cell surface was most effective. However, the far-red light effect was most prominent when its electrical vector was normal to the cell surface. These polarized light effects indicate the different dichroic orientation of P_r (red-light-absorbing form of phytochrome) and P_r (far-red-light-absorbing form of phytochrome) at the cell flank.     

Exchange interaction in covalently bonded biradical-monoradical composite molecules

As a novel molecular designing for genuinely organic molecule-based ferrimagnets, we have proposed a strategy of "single-component ferrimagnetics". When a pi-biradical with an S = 1 ground state and a pi-monoradical with S = (1)/(2) are united by sigma-bonds, the pi-conjugation between the biradical and the monoradical moieties should be truncated in the resultant triradical. This gives magnetic degrees of freedom for both S = 1 and (1)/(2) in the single molecule, serving as a building block for organic molecule-based ferrimagnets under favorable conditions (single-component ferrimagnetics). We have designed and synthesized a triradical, 3-(1'-oxyl-3'-oxido-4',4',5',5'-tetramethylimidazolin-2-yl)benzoic acid 2,4-bis(1' '-oxyl-3' '-oxido-4' ',4' ',5' ',5' '-tetramethylimidazolin-2-yl)phenyl ester (4), as a model compound for the novel approach to genuinely organic ferrimagnets. In the triradical 4, a m-phenylene-bis(nitronyl nitroxide) biradical with a triplet (S = 1) ground state is united with a phenyl nitronyl nitroxide monoradical (S = (1)/(2)) by an ester coupler. Solution-phase ESR spectra from 4 exhibited a complex hyperfine splitting due to (14)N and (1)H nuclei. The analysis of the hyperfine structure based on perturbation calculations has revealed that the exchange interaction within the biradical moiety is much larger than those between the biradical and the monoradical moieties and the magnetic degrees of freedom for both S = 1 and (1)/(2) are retained in 4. An X-ray crystal structure analysis showed that the triradical molecules are arranged in a one-dimensional molecular chain in the crystal. The magnetic susceptibility in a crystalline solid state is consistent with the crystal structure.     

Angular heterocycles. A convenient synthesis of azabenzophenothiazines

The acid-catalysed reaction of substituted 1,4-naphthoquinones with o-aminoheterocyclic thiones in alcoholic solution afforded substituted monoazabenzo[a]phenothiazin-5-ones 4,5 and substituted benzo[a][1,4]diazabenzothiazino[3,2-c]phenothiazin-5-one ( 6 ). Some of the resulting compounds were subjected to dehalogenation. The structures of the products were assigned by elemental analysis, ¹H-nmr, and other spectral analysis.     

An application of MNDO calculation to borate polyhedra

MNDO, a semiempirical SCF-MO method, was applied to study the structure of the borate glass. The clusters, B(OH)₃, H₃B₃O₆, B₃O₆^3?, (HO)₂BOB (OH)₂, (HO)₂B₃O₃OB₃O₃ (OH)₂, BO₃[B(OH)₂]₃ and BO₃[B₃O₃(OH)₂]₃ were treated and their geometries, the heats of reactions, the π electron systems and electronic structures were discussed. The geometry and the electronic structures show a good correspondence with the experimental data. The resonance stabilization effect of the π electron system is not so large as to control the geometries and reactions.     

An Approach to Optical Reflection Tomography along the Geometrical Thickness

We propose and demonstrate a novel optical reflection tomography along the geometrical thickness. This technique is based on simultaneous measurement of refractive index n and thickness t of a sample using the combination of a low coherence interferometer and confocal optics. The interferometer provides optical coherence tomography (OCT) of the dimension of the optical thickness (=n × t) along the optical axis, while the confocal optics gives us another type of reflection tomography, having the thickness dimension of nearly t/n along the optical axis. This sort of tomography can be called confocal reflection tomography (CRT) and has not yet been demonstrated, to our knowledge. Simple image processing of OCT and CRT results in the desired reflection tomographic image, showing two-dimensional refractive index distribution along the geometrical thickness.     

Determination of Critical Micelle Concentration of Surfactant in Organic Solvent by Capillary Electrophoresis

In this work, some uncharged hydrophobic compounds, such as p-arylacetophenones, polycyclic aromatic hydrocarbons and steroids have been separated by micellar electrokinetic chromatography (MEKC) using organic solvents and surfactants.