2003 Fiscal Year Final Research Report Summary
Realization of superconductivity in tetrathiapentalene-type molecular conductors
| Project/Area Number |
13440209
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
機能・物性・材料
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
YOHJI Misaki Kyoto University, Molecular Engineering, Associate professor, 工学研究科, 助教授 (90202340)
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| Co-Investigator(Kenkyū-buntansha) |
ITO Akihiro Kyoto University, Molecular Engineering, Research associate, 工学研究科, 助手 (90293901)
FUENO Hiroyuki Kyoto University, Molecular Engineering, Research associate, 工学研究科, 助手 (30212179)
TANAKA Kazuyoshi Kyoto University, Molecular Engineering, Professor, 工学研究科, 教授 (90155119)
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| Project Period (FY) |
2001 – 2003
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| Keywords | Tetrathiapentalene / Donor / Organic conductor / Superconductivity / Cyclic voltammetry / X-Ray structure analysis / Electrical conductivity |
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| Research Abstract |
(1) Several radical cation salts based on SMEO-ST-TTP have been prepared. X-Ray structure analyses reveal that (SMEO-ST-TTP)_2PF_6 has the so-called β-type donor packing, in which the donors are strongly dimerized in a stack. This salt showed metallic conductivity down to "22 K, below which resistivity increases a little. While, (TMEO-ST TTP)2PF6 exhibited simple metallic behavior down to 1.5 K. The above results indicates that metallic state of (SMEO-ST-TTP)_2PF_6 is destabilized compared with (TMEO-ST TTP)_2PF_6.
(2) Structures and properties of molecular conductors based on BDT-TTP analogues containing pyran-4-ylidene, PDS-TTP have been investigated. X-Ray structure analyses of (PDS-TTP)_2AsF_6 revealed that the donor array is the so-called β-type similar to (BDT TTP)_2X (X = ClO_4, BF_4, PF_6, SbF_6 etc). The intrastack overlaps of the present salt should be smaller compared with those of BDT TTP salts, because the unsymmetrical PDS-TTP molecules are stacked the head-to-tail manner. (PDS-TTP)_2AsF_6 shows metallic conductivity down to 4 K, although the resisitivity increased a little at low temperature owing to formation of microcracks.
(3) Several derivatives of TTP type donor inserted with cyclohexane ring, CHADTDT, have been synthesized. Cyclic voltammetry of CHADTDT derivatives revealed that they exhibited four pairs of one-electron redox waves, and that on-site coulomb repulsion in the dication state is increased as expected. The molecular orbital calculation suggests that the molecular orbital coefficients in the 1,3-dithiole ring at the cyclohexane terminal is negligible. Therefore, the metallic state could be destabilized by formation of narrow band if the donors are stacked in the head-to-tailed manner.
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Research Products
(12 results)
