Synthetic procedure for various selenium-containing electron donors of the bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) type

Six selenium variants of BEDT-TTF have been successfully synthesized by a newly developed synthetic method that involves a combination of two key reactions for the construction of two kinds of heterocyclic rings: the first is a one-pot formation of 1,3-dichalcogenole-2-chalcogenones from a common starting material, THP-protected 2-(ethynylthio)ethanol, leading to the inner five-membered rings, and the other is the annelation of the outer six-membered heterocyclic ring onto the inner ring by an intramolecular transalkylation reaction on a chalcogen atom. This method turned out to be widely applicable to the syntheses of the electron donors of bis(ethylenedithio)- and bis(ethyleneselenothio)-substituted types. However, synthetic attempts to form analogous donors of the bis(ethylenediseleno)-substituted type from THP-protected 2-(ethynylseleno)ethanol were unsuccessful. This is attributable to the predominance of side-reactions via a seleniranium (episelenonium) salt over the desired six-membered ring formation by transalkylation via a seleninium salt.     

Studies on the syntheses of azole derivatives. Part IV. Novel Syntheses of 1-Benzylbenzimidazolines by Photolysis of N-Aryl-N-benzylcarbamoyl Azides [Studies on the Syntheses of Heterocyclic Compounds. Part CCCLXXVIII

Photolysis of N-benzyl-N-(4-substituted-phenyl)carbamoyl azides (Ia and Ib) afforded N-benzylidene-N′-benzylhydrazines (XIIa and XIIb) and the debenzylated benzimidazolines (XIIIa and XIIIb).     

Rheology and UV-protecting properties of complex suspensions of titanium dioxides and zinc oxides

Ultra-fine particles of titanium dioxide (TiO(2)) and zinc oxides (ZnO) are very attractive as UV-protecting ingredients in cosmetic products. The UV-scattering behavior of complex suspensions in a silicone oil is studied in relation to rheological properties. To control the dispersion stability of suspensions, three polyoxyethylene (POE)-modified silicones of branch-type, (AB)(n)-type, and ABA-type are used as dispersants. Irrespective of molecular structure, the dispersants can stabilize the TiO(2) and ZnO particles and the flow of both single suspensions is Newtonian with low viscosity. However, the Newtonian flow profiles and high dispersion states are maintained only for complex suspensions prepared with ABA-type dispersant. Since the POE groups which are incorporated between terminal silicones groups attach to the particle surfaces, the steric stabilization is responsible for low viscosity and high dispersions. Because the UV scattering of suspensions is determined by the sizes of flocculated structures, the high transmittance in the visible ranges and low transmittance in the UVA and UVB ranges can be achieved in the presence of ABA-type dispersant.     

Syntheses, structures, spectroscopic properties, and pi-dimeric interactions of [n.n]quinquethiophenophanes

A cyclophane-type of dimeric quinquethiophenes (4a-e) with the bridge chains consecutively varying from two to six methylenes has been synthesized and studied as ideal pi-dimer models. The double-decker structures of these compounds are verified by upfield shifts for the proton NMR signals of the inside thiophenes, as compared to those of monomeric dimethylquinquethiophene (3). The electronic absorption and emission spectra of 4a-e are perturbed by through-space pi-electronic interactions involving exciton-exciton coupling between the two overlapped quinquethiophenes, which become marked with shortening of the bridged alkylene chains. One-electron oxidation of 4a-e with FeCl(3) in dichloromethane results in the appearance of specific polaronic bands in the near-infrared region of the electronic absorption spectra, due to the generation of a radical cation species (polaron) on one of the quinquethiophenes, which electronically interacts with the remaining neutral species. Two-electron oxidation of 4a-e introduces spectral changes, revealing that the resulting two quinquethiophene radical cations readily form an intramolecular pi-dimer, thanks to their close stacking, in contrast to the difficult formation of an intermolecular pi-dimer from 3. The pi-dimeric spectra of 4b-e are comprised of two strong absorption bands, similar to that of 3, the low-energy band of which is considerably red-shifted by an effective pi-dimeric interaction depending on the lengths of the bridged alkylene chains. Quite different is the spectrum of 4a with three absorption bands inherent in pi-dimer, presumably because the two short bridging chains of 4a force the pi-dimer to take a constrained, strongly interactive structure.     

Solid–solvent molecular interactions observed in crystal structures of β-chitin complexes

Three β-chitin structures [anhydrous, di-hydrate, mono-ethylenediamine (EDA)] recently determined by synchrotron X-ray and neutron fiber diffraction were reviewed from the viewpoint of molecular interactions. Both water and EDA molecules interact with the chitin chains through multiple hydrogen bonds. When water complexes with chitin, the hydrogen bonding pattern rearranges with the replacement of an intrachain chitin hydrogen bond by a stronger hydrogen bond between chitin and water, with an associated reduction in the degrees of freedom; the water oxygen is a much stronger acceptor than the O5 ring atom. The behavior of hydrogen exchange by deuterium supports this interpretation. EDA-molecules change the conformation of hydroxymethyl group from gg to gt, accompanied by changes in hydrogen bonds due to the strong accepting ability of the EDA nitrogen atoms. Some important interactions are in common with experimental crystallographic results of cellulosic crystals and of molecular dynamics studies. These new insights into solid–solvent interactions are valuable in understanding molecular interactions in other polysaccharides-solvents system in solution or on surface.     

Studies on the syntheses of azole derivatives. Part III. Syntheses of 1-Phenyl-Δ2-1,2,4-triazolin-5-one and 4-Phenyl-Δ2-1,3,4-oxadiazolin-5-one Derivatives by Fusion of 1-Phenyl-2-acylhydrazine with Urea

Fusion of 1-phenyl-2-acylhydrazine (III) with urea gave Δ²-1,2,4-triazolin-5-one and Δ²-1,3,4-oxadiazolin-5-one derivatives together with various by-products. Furthermore, various derivatives were synthesized for the purpose of examination in a pharmacological screening test.     

Three-vessel study of cerebral blood flow using phase-contrast magnetic resonance imaging: Effect of physical characteristics

The development of phase-contrast magnetic resonance imaging (P-C MRI) provides a noninvasive method for measurement of volumetric blood flow (VFR). We performed P-C MRI to study the effects of physical characteristics on cerebral blood flow. VFR of the left and right internal carotid arteries and basilar artery were measured using P-C MRI and total cerebral blood flow (tCBF) was calculated by summing up the VFR values in the three vessels. Moreover, we investigated the changes in these blood flows as influenced by age, head size, height, weight, body surface area, and handedness. The blood flows were 142 ± 58 ml/min (mean ± standard deviation) in the basilar artery; and 229 ± 86 ml/min in the left, and 223 ± 58 ml/min in the right internal carotid artery; and tCBF was 617 ± 128 ml/min. Significant increases were observed in head size-related change of VFR in the basilar artery (p = .028) and height-related change of tCBF (p = .045). The other characteristics did not significantly influence any VFR. The results suggest that head size and height may reflect CBF, and that these effects should be considered when changes of CBF are diagnosed. Phase-contrast MRI is useful for a noninvasive and rapid analysis of cerebral VFR and has potential for clinical use.