| Co-Investigator(Kenkyū-buntansha) |
NISHINAGA Tohru Tokyo Metropolitan Univ, 理工学研究科, Associate Professor (30281108)
KUWATANI Yoshiyuki Tokyo Metropolitan Univ, 理工学研究科, Associate Professor (00234625)
三宅 由寛 東京都立大学, 理学研究科, 助手 (00347270)
吉田 正人 島根大学, 医学部, 助教授 (50137030)
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| Budget Amount *help |
¥46,800,000 (Direct Cost: ¥36,000,000、Indirect Cost: ¥10,800,000)
Fiscal Year 2005: ¥6,240,000 (Direct Cost: ¥4,800,000、Indirect Cost: ¥1,440,000)
Fiscal Year 2004: ¥15,210,000 (Direct Cost: ¥11,700,000、Indirect Cost: ¥3,510,000)
Fiscal Year 2003: ¥25,350,000 (Direct Cost: ¥19,500,000、Indirect Cost: ¥5,850,000)
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| Research Abstract |
Self-assembly of organic π-conjugated systems into complex, organized supramolecular structures via specific intermolecular interactions is a promising way to realize functional molecular materials. Many intermolecular interactions such as hydrogen bonding, metal coordination, CT interaction, and π-π stacking have been utilized recently to construct desired supramolecular architectures such as fibers, ribbons, tapes, nanotubes, and nanoparticles. Recently, we have developed a new concept of self-assembly by the use of cooperative S…S and π-π stacking interactions. Although S…S interaction is a weak attractive force in solution, it plays an important role in packing of molecules in crystals. Thus, organic conductors and superconductors based on tetrathiafulvalenes (TTF) are constructed using cooperative S…S and π-π stacking interactions
Crystal engineering of organic conductors suggests that van der Waals and dipole-dipole interactions between neutral sulfur atoms give rise to an attract
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ive force in crystals. The corresponding interactions in the oxidation state are also energetically favorable. Therefore, two TTF molecules tend to align face-to-face to produce a stacking structure in crystals. Although the closely located dimeric TTF/TTF is weakly stable in the neutral, state, the dimeric TTF/TTF^+ is strongly stabilized in the cationic state to produce a mixed valence form and hence the appearance of conductivity in the solid state. Moreover, two cation-radicals TTF^+/TTF^+ also interact attractively (π-dimer formation) in solution leading to the formation of a Mott-insulating semi-conductor in the solid state.
It is known that π-conjugated molecules with either electron-withdrawing or large π-circles and disks self-aggregate in solution, while the surface organization of π-conjugated molecules is frequently used by material scientists employing organic materials as molecular switches and devices. To design a π-donor molecules with these applications, detailed knowledge of the structures of self-aggregates in solution or in mesophase is required, because pre-aggregation of conjugated π-systems may control the arrangement of the molecules on the solid surface. With this in mind, construction of a redox-active nanoscale architecture in solution and in the solid state has been achieved, and structures of neutral and cationic aggregates based on TTF oligomers and macrocyclic oligothiophenes have been investigated as a sulfur-rich π-system. Finally, we suceeded to construct conductive helical donors, conductive nanofibers having hexagonal arrangement, and thermochromic TTF systems. Less
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