Publications by authors named "Ryohei Kameyama"

Article Synopsis
  • Mixed-stack complexes made up of alternating donor and acceptor materials generally have poor electrical conductivity due to either being neutral or highly ionic, leading to a lack of conductive carriers.
  • This study successfully synthesized mixed-stack complexes at the neutral-ionic boundary, using specific donors and acceptors with compatible energy levels and orbital symmetry.
  • The resulting single-crystal complexes displayed greatly enhanced room-temperature conductivity, which is the highest reported for this type under normal conditions, and revealed significant changes in their electrical and optical properties based on temperature.
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Article Synopsis
  • - Conductive polymers, like doped PEDOT, are widely used in organic electronics but suffer from structural inhomogeneity, making it hard to control their conductivity and structure.
  • - Low-molecular-weight materials have well-defined structures but limited conductivity control, leading researchers to create oligomer-based conductors that blend the benefits of both polymers and low-molecular-weight materials.
  • - By studying various oligoEDOT analogs, the researchers developed conductors with tunable conductivities, including some reaching metallic states at room temperature, while identifying charge-transfer interactions as the key factor influencing conductivity.
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Article Synopsis
  • Modern organic conductors can be classified into low-molecular-weight and polymer-based materials, each with their own challenges in controlling conductive properties due to structural limitations.
  • Research focused on using single-molecular-weight oligomers as an alternative, specifically modeling a structure similar to doped poly(3,4-ethylenedioxythiophene) (PEDOT) to optimize electrical conductivity.
  • By creating a tetramer with a specific mixed sequence, the researchers achieved a significant increase in conductivity (36 S cm), the highest reported for single-crystalline oligomer conductors, and observed metallic behavior above room temperature for the first time in oligoEDOT.
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The conjugation length is a unique structural factor for oligomer-based π-conjugated conductors as it modulates their electronic structures. Herein, we demonstrated the conjugation length effects on conductivity by comparing a dimer and trimer of single-crystalline oligo(3,4-ethylenedioxythiophene) radical cation salts. The dimer showed a uniform-stacked columnar structure, while the trimer showed stacked columns of the π-dimerized donor and weaker intracolumnar interactions.

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Invited for the cover of this issue is the group of Tomoko Fujino and Hatsumi Mori at the University of Tokyo. The image depicts the structural information of doped PEDOT uncovered by the single-crystalline EDOT dimer model. Read the full text of the article at .

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Although doped poly(3,4-ethylenedioxythiophene) (PEDOT) is extensively used in electronic devices, their molecular-weight distributions and inadequately defined structures have hindered the elucidation of their underlying conduction mechanism. In this study, we introduce the simplest discrete oligomer models: EDOT dimer radical cation salts. Single-crystal structural analyses revealed their one-dimensional (1D) columnar structures, in which the donors were uniformly stacked.

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Anthracene, a simple planar building block for organic semiconductors, shows strong intermolecular interactions and exhibits strong blue fluorescence. Thus, its derivatives have a great potential to integrate considerable charge carrier mobility and strong emission within a molecule. Here, we systematically studied the influence of alkyl chain length on the crystal structures, thermal properties, photophysical characteristics, electrochemical behaviors, and mobilities for a series of 2,6-di(4-alkyl-phenyl)anthracenes (C-Ph-Ants, where represents the alkyl chain length).

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This report details a new method for site-selective methylene oxidation adjacent to azaheterocycles. A dual catalysis approach, utilizing both an iron Lewis acid and an organic hydroxylamine catalyst, proved highly effective. We demonstrate that this method provides complementary selectivity to other known catalytic approaches and represents an improvement over current heterocycle-selective reactions that rely on stoichiometric activation.

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A method for the reductive cross-coupling of conjugated arylalkenes and aryl bromides with hydrosilanes by cooperative palladium/copper catalysis was developed, thus resulting in the highly regioselective formation of various 1,1-diarylalkanes, including a biologically active molecule. Under the applied reaction conditions, high levels of functional-group tolerance were observed, and the reductive cross-coupling of internal alkynes with aryl bromides afforded trisubstituted alkenes.

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