Hiroki Muraoka

Triacylated peonidin 3-sophoroside-5-glucosides from the purple flowers of Moricandia ramburii Webb.

Triacylated peonidin 3-sophoroside-5-glucosides were isolated from the purple flowers of Moricandia ramburii Webb. (Family: Brassicaceae), and determined to be peonidin 3-O-[2-O-(2-O-(trans-feruloyl)-glucosyl)-6-O-(trans-p-coumaroyl)-glucoside]-5-O-[6-O-(malonyl)-glucoside] (1), peonidin 3-O-[2-O-(2-O-(trans-feruloyl)-glucosyl)-6-O-(cis-p-coumaroyl)-glucoside]-5-O-[6-O-(malonyl)-glucoside] (2) and peonidin 3-O-[2-O-(2-O-(trans-sinapoyl)-glucosyl)-6-O-(trans-p-coumaroyl)-glucoside]-5-O-[6-O-(malonyl)-glucoside] (3), respectively, by chemical and spectroscopic methods. In addition, one known acylated cyanidin glycoside, cyanidin 3-O-[2-O-(2-O-(trans-feruloyl)-glucosyl)-6-O-(trans-p-coumaroyl)-glucoside]-5-O-[6-O-(malonyl)-glucoside] (4), was also identified in the flowers. Peonidin glycosides have not been reported hitherto in floral tissues in to Brassicaceae.

Synthesis and electrochemical properties of ferrocene dimers and trimers bridged by an oligothiophene spacer

We describe the design and synthesis of ferrocene dimers and trimers bridged by an oligothiophene spacer as both cathodic and anodic multiple redox-active organic–organometallic hybrid molecules. The electrochemical properties of all compounds were examined by cyclic voltammetry (CV). The voltammograms showed different multi-step, multi-electron redox reactions derived from multi-ferrocene fragments and the organic spacer. The results indicate that a number of thiophene rings in the spacer can be attuned to the redox potentials and the electron-transfer processes.

Development and Application of a Multielectron-Accepting Organic Oxidant for the Catalytic Transition-Metal-Free Oxidative Homocoupling of Grignard Reagents in Air

Heptafluorotolyl-substituted perfluorocyclopentene acts as a four-electron oxidant for the homocoupling of Grignard reagents. It can also be used for catalytic homocoupling with a low catalyst loading (up to 2 mol %) in the presence of atmospheric oxygen. The organocatalytic cycle involves the generation of an organic radical and a perfluorocyclopentadienyl anion.

Synthesis of highly refractive and highly fluorescent rigid cyanuryl polyimines with polycyclic aromatic hydrocarbon pendants

A series of rigid cyanuryl polyimines, polyguanamines (PGs) bearing polycyclic aromatic hydrocarbon pendants were successfully synthesized from 2-substituted 4,6-dichloro-1,3,5-triazine and aromatic diamine monomers used in conventional solution polymerization. In addition, their thermal and optical properties were also investigated. All polymers showed high thermostabilities (Tg ∼ 320 °C, Td5 (N2) ∼ 466 °C, residue at 800 °C under nitrogen ∼69.0%) and adequate solubilities in polar organic solvents. Films prepared by the solvent-cast method showed good transparencies, which mainly depended on the diamine structure as opposed to the dichloride moiety. The refractive indices at the D-line (589 nm) of the PG films were unexpectedly high, between 1.677 and 1.800, compared to those of common organic optical polymeric resins. The incorporated melamine moieties afforded effective dense packing with the polycyclic aromatic hydrocarbon groups filling the free spaces between rigid polymer chains, resulting in unusually high refractive indices. The PG polymer solution in N-methylpyrrolidone showed strong blue fluorescence (371–471 nm) with a quantum yield of up to 98%.

A Comparative Study of the Electronic Property of a Series of 2,4,6-Tri(5-Aryl-2-Thienyl)-1,3,5-Triazines Controlled by the Electronic Nature of Aryl Groups

GRAPHICAL ABSTRACT Abstract A series of 2,4,6-tri(5-aryl-2-thienyl)-1,3,5-triazines with a star-shaped π-conjugated system as a wide variety of aryl-functionalized 2,4,6-tri(2-thienyl)-1,3,5-triazines were designed and systematically synthesized. The electronic properties of these compounds in the solution state were identified by ultraviolet-visible infrared absorption and emission spectroscopies, and cyclic voltammetric studies. The results of the experimental observations demonstrated that the changing electronic nature of terminal aryl groups helps to efficiently tune the optical and redox properties of the 2,4,6-tri(5-aryl-2-thienyl)-1,3,5-triazines. Interestingly, 5-(p-N,N-dibutylaminophenyl-2-thienyl)-1,3,5-triazine exhibits solvatochromic properties and a proton-sensibility due to its intramolecular charge transfer and basic characters, which can be confirmed visually from changes in the color of the solution and emission.

Synthesis, structure, and electrochemical properties of [2.2]paracyclophane[4,5-d]trithiole

A novel five-membered trithiole with sulfur–sulfur linkages bound to a [2.2] paracyclophane framework with low-redox potential has been synthesized. Characterization of the new trithiole was performed by X-ray crystallographic analysis. The cyclic voltammogram of the trithiole showed well-defined reversible electrochemical redox coupled with low-oxidation potential. Novel radical cation salt was isolated in quantitative yield in the one-electron oxidation of the trithiole with one equivalent of NOPF6 as a one-electron oxidant. The structure of the radical cation salt was analyzed by 31P NMR and EPR spectroscopies and elemental analysis. The salt underwent one-electron reduction on treatment with one equivalent of samarium(II) iodide to give the neutral starting trithiole quantitatively.

Synthesis, Structure, and Redox Properties of 1,1'-Bis(aryloligothienyl)ferrocenes

Abstract We succeeded in the synthesis of 1,1′-bis{2-(5-arylthienyl)}ferrocenes as both cathodic and anodic multiple-redox active organic-organometallic hybrid molecules. Characterization of the molecules was performed by physical and spectroscopic means and X-ray crystallographic analyses. The electrochemical properties were examined by cyclic voltammetry. The voltammograms of all compounds showed two oxidation steps derived from the ferrocenium cation and the 5π thiophene radical cation, and two reduction steps derived from 7π thiophene radical anions separated from each other by a bridging ferrocene fragment.

Characterization of aryl-functionalized 2,4,6-tris(2-thienyl)-1,3,5-triazine thin films and their application to organic field-effect transistors

Aryl-functionalized 2,4,6-tris(2-thienyl)-1,3,5-triazine derivatives were applied as thin films via thermal vacuum deposition to investigate properties and potential of the thin films for use as active layers in organic field-effect transistors. All derivatives deposited on quartz substrates produced amorphous films. Ultraviolet–visible absorption spectra of the films resemble those of the molecules in solution, and fluorescence spectra depend largely on the aryl groups. When used in organic field-effect transistors, only the N,N-dibutylamino derivative could display the appropriate device characteristics under p-type operation, but it showed low mobility of charge carriers. The origin of the low mobility is discussed in terms of the electronic structure and film structure of the derivatives in the devices.

Ring Size Controlled Synthesis and Structure of Cyclic Polysulfides Fused to Substituted Benzene Ring

We succeeded in the ring size controlled synthesis of stable cyclic benzopolysulfides with five, six, and seven-membered rings. Each sulfur heterocycle has three, four, and five sulfur atoms with S–S bonding. The cyclic structures are characterized by spectroscopic means and X-ray crystallographic analyses.