"Development of Low Energy-gap and Architecturally Well-defined pi-Conjugated Heterocyclic Highly Oligomers"

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1 : Development of New Building Units for Multi-functional Single Molecular WiresThe emerging field of single-molecular electronics is the final frontier of molecular materials in this century.In this project we have developed various types of heterocyclic building blocks for high-performance single molecular wires.From the selective coupling reactions of these blocks, we have synthesized "architecturally precisely-controlled" heterocyclic highly-oligomers (up to 11 unit-system, MW-3000 ) containing various functional units (a low energy-gap pi-conjugated backbone for high efficiency of long-distance and steady-state electron transport, an insulating mantle to prevent unfavorable inter-chain hopping of the charge carries, donor/acceptor sites, multi-stage redox sites, and alligator clips for the connection to an electrode).The structure-property relationships of the obtained molecular wires have been elucidated based on the spectral properties combined with the results of MO calculations.2 : Design of Novel 4-Terminal Molecular Switching UnitMulti-terminal molecular switching unit will be the key components to construct "molecular computer". As a novel candidate for switching unit, I have designed and synthesized a novel "4-terminal" non-classical thiophene derivative (1,3,5,7-tetrathienyldithieno[3,4-b : 3', 4'-e]pyrazine).This molecule contains a pyrazine-dihydropyrazine multi-stage redox center, and the electronic structure can be switchable between low and high energy-gap states by electrical or electrochemical reactions.I have elucidated the molecular and electronic features of this novel switching system based on the experimental and theoretical data.We have been developing synthetic methods to connect various molecular wires with each terminal (unsubstituted alpha or beta-positions of the thiophene rings) to realize a molecular-scale transistor.