| Project/Area Number |
15350078
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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 |
Functional materials chemistry
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| Research Institution | The University of Tokyo |
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Principal Investigator |
KOJIMA Norimichi The University of Tokyo, Graduate School of Arts and Science, Professor, 大学院・総合文化研究科, 教授 (60149656)
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| Co-Investigator(Kenkyū-buntansha) |
ENOMOTO Masaya The University of Tokyo, Graduate School of Arts and Science, Research Associate, 大学院・総合文化研究科, 助手 (70345065)
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| Project Period (FY) |
2003 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥14,600,000 (Direct Cost: ¥14,600,000)
Fiscal Year 2004: ¥3,800,000 (Direct Cost: ¥3,800,000)
Fiscal Year 2003: ¥10,800,000 (Direct Cost: ¥10,800,000)
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| Keywords | charge transfer phase transition / spin-crossover / ferromagnetism / mixed-valence complex / photo-isomerization / photo-control / organic-inorganic hybrid complex / charge transfer interaction / 有機。無機複合錯体 / 配位子場 / スピンエントロピー / 非対称配位子 |
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| Research Abstract |
In this project, we have synthesized dithiooxalato-bridged iron mixed-valence complexes, (n-C_nH_<2n+1>)_4N[Fe^<II>Fe^<III>(dto)_3] (n=3-6, dto=C_2O_2S_2) and investigated a spin-entropy driven charge transfer phase transition around 120 K, where the electrons of Avogadro's constant transfer cooperatively between the Fe^<II> and Fe^<III> sites, and a ferromagnetic transition at 6.5 K for (n-C_3H_7)_4N[Fe^<II>Fe^<III>(dto)_3]. The charge transfer phase transition takes place for n=3 and 4, while it does not take place between 300 K and 4 K for n=5 and 6. The charge transfer phase transition and the ferromagnetic transition remarkably depend on the hexagonal ring size in the two-dimensional honeycomb network structure of [Fe^<II>Fe^<III>(dto)_3]_∞. The increase of cation size expands the honeycomb ring, which stabilizes the higher temperature phase with Fe^<II> (S=2) and Fe^<III> (S=1/2). Contrary, the contraction of the honeycomb ring stabilizes the lower temperature phase with Fe^<II> (S=0) and Fe^<III> (S=5/2), which was supported by the external pressure effect on the charge transfer phase transition.
In order to control the magnetic properties and the electronic state in the dto-bridged iron mixed-valence system by means of photo-irradiation, we have synthesized a photo-sensitive organic-inorganic hybrid system, (SP)[Fe^<II>Fe^<III>(dto)_3] (SP=spiropyran), and investigated the photo-induced effect on the magnetic properties. The UV irradiation changes the structure of spiropyran from the closed form to the open one in (SP)[Fe^<II>Fe^<III>(dto)_3]. The photochromism in spiropyran induces the charge transfer phase transition in the two-dimensional honeycomb network structure of [Fe^<II>Fe^<III>(dto)_3]_∞, and changes the ferromagnetic transition temperature.
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