A new n-channel semiconductor class for organic field-effect transistors (OFETs) based on thienoquinoidal structures is reported. A newly employed terminal group, the ((alkyloxy)carbonyl)cyanomethylene moiety, plays two important roles in the thienoquinoidal compounds: i.e., as an electron-withdrawing group to keep the LUMO energy level sufficiently low for acting as an n-channel organic semiconductor and as a solubilizing group to facilitate solution processability. For the construction of this class of compounds, a new, straightforward synthetic method was established and applied to oligothienoquinoidal and fused thienoquinoidal systems. When both core and alkyl groups in the ester moiety were tuned, the thienoquinoidals exhibited good solubility, stability in the atmosphere, and electron-accepting properties, as well as solution processability. Solution-processed FETs based on the terthienoquinoid derivative with ((n-alkyloxy)carbonyl)cyanomethylene moieties exhibit good electron mobilities (mu approximately 0.015 cm(2) V(-1) s(-1)) and I(on)/I(off) approximately = 10(5) under ambient conditions. Vapor-processed FETs using the benzodithienoquinoidal derivative showed similar n-channel FET characteristics.

A reversibly switchable electromagnetic oxide device is demonstrated by using a thin-film transistor structure with a newly developed "leakage-free electrolyte" as a gate insulator. The electrical and magnetic behavior of the device can be switched from antiferromagnetic insulation to ferromagnetic metal electrically under DC voltage of ±3 V at room temperature.The result provides a novel design concept for practical memory device.

A new class of oligothienoquinoidal derivatives with newly employed (acyl)cyanomethylene termini are reported. For the synthesis of (acyl)cyanomethylene-substituted thienoquinoidals, similar methods successfully employed for the synthesis of related dicyanomethylene-or ((alkyloxy)carbonyl)cyanomethylene-substituted thienoquinoidals were not applicable, and thus a new synthetic route was developed. The introduced (acyl)cyanomethylene terminal groups act both as a solublizing group to facilitate solution processability and an electron-withdrawing group to keep the LUMO energy levels sufficiently low for n-channel organic semiconductors. The LUMO energy levels estimated from their reduction potential are ∼4.2 eV below the vacuum level, which just falls in between those for the corresponding dicyanomethylene-and ((alkyloxy)carbonyl)cyanomethylene-substituted thienoquinoidals. This qualitatively agrees with the electron-withdrawing nature of the terminal groups; the order of the electron withdrawing nature is cyano-> acyl-> (alkyloxy)carbonyl-groups. Spin-coating chloroform solutions of (acyl)cyanomethylene-substituted thienoquinoidals gave homogeneous thin films on the Si/SiO 2 substrates, and the thin films based on the terthienoquinoidal derivatives became highly crystalline upon thermal annealing. The annealed film acted as the active semiconducting channel in the FET devices under ambient conditions, and the electron mobilities extracted from the saturation regime were ∼0.06 cm 2 V -1 s -1 . These n-channel FET characteristics are nearly the same or slightly better than those of the FETs based on the related ((alkyloxy)carbonyl)cyanomethylene-terminated terthienoquinoidal, indicating that the (acyl)cyanomethylene moiety is a useful terminal group on the thienoquinoidals for the development of soluble n-channel organic semiconductors.

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Although peripheral nerves can regenerate, clinical outcomes after peripheral nerve injuries are not always satisfactory, especially in cases of severe or proximal injuries. Further, autologous nerve grafting remains the gold standard for the reconstruction of peripheral nerves, although this method is still accompanied by issues of donor-site morbidity and limited supply. Cell therapy is a potential approach to overcome these issues. However, the optimal cell type for promoting axon regeneration remains unknown. Here, we report a novel experimental model dedicated to elucidation of the axon-promoting effects of candidate cell types using simple and standardized techniques. This model uses rat sciatic nerves and consists of a 25 mm-long acellular region and a crush site at each end. The acellular region was made by repeated freeze/thaw procedures with liquid nitrogen. Importantly, the new model does not require microsurgical procedures, which are technically demanding and greatly affect axon regeneration. To test the actual utility of this model, red fluorescent protein-expressing syngeneic Schwann cells (SCs), marrow stromal cells, or fibroblasts were grafted into the acellular area, followed by perfusion of the rat 2 weeks later. All types of grafted cells survived well. Quantification of regenerating axons demonstrated that SCs, but not the other cell types, promoted axon regeneration with minimum variability. Thus, this model is useful for differentiating the effects of various grafted cell types in axon regeneration. Interestingly, regardless of the grafted cell type, host SCs migrated into the acellular area, and the extent of axon regeneration was strongly correlated with the number of SCs. Moreover, all regenerating axons were closely associated with SCs. These findings suggest a critical role for SCs in peripheral nerve axon regeneration. Collectively, this novel experimental model is useful for elucidating the axon-promoting effects of grafted cells and for analyzing the biology of peripheral nerve axon regeneration.