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DEVELOPMENT OF MOLECULE-BASED FERROMAGNETS UTILIZING STABLE ORGANIC RADICALS OR PYRIMIDINE-TRANSITION METAL COMPLEXES

利用稳定的有机自由基或嘧啶过渡金属络合物开发基于分子的铁磁体

基本信息

批准号：
08454218
负责人：
NOGAMI Takashi
金额：
$ 5.06万
依托单位：
THE UNIVERSITY OF ELECTRO-COMMUNICATIONS
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

(1) Magnetic Properties of Organic RadicalsMagnetic properties of 165 kinds of TEMPO derivatives (ArCH=N-TEMPO,Ar=aryl group) were studied by SQUID Intermolecular ferromagnetic interactions were found for 52 radicals. Thus, the intermolecular ferromagnetic interaction were found to be not a rare phenomenon. Eight kinds of radicals showed bulk ferromagnetic transitions below 0.4 K.We proposed that the ferromagnetic interaction was caused by the spin-polarization mechanism via beta-hydrogens. This mechanism was supported by MO calculations and NMR measurements. Spontaneous magnetization was observed below T_c by means of zero-field muSR measurements. In order to elevate the transition temperatures, magnetic properties of pi-conjugated NO radicals were studied. NO radicals possessing acridine skeleton showed the intermolecular ferromagnetic interaction which was caused through the overlaps of pi-electron clouds (McConell model).(2) Magnetic Properties of Pyrimidine-Transition Metal ComplexesIn order to study the magnetic interactions of transition-metal ions coordinated to meta-positions of an aromatic ring, magnetic properties of various pyrimidine-transition metal complexes were studied. It was found that coordination modes rather than coordination positions (meta-position) determine the magnetic interactions. In the case of Cu^<2+> an axial/equatorial coordination gave rise to the ferromagnetic interaction, and an equatorial/equatorial coordination did the antiferromagnetic interaction. When we adopted inorganic anions of small sizes, sevral complexes showed the behavior of a weak ferromagnetism. (pyrimidine)_2CoX_2 (X=Cl, Br) has a chiral crystal structure, and showed the behavior of the weak ferromagnetism.

(1)用SQUID研究了165种克里思衍生物（ArCH=N-TEMPO，Ar=芳基）的磁性，发现其中52种有分子间铁磁相互作用。因此，分子间的铁磁相互作用并不是一个罕见的现象。8种自由基在0.4K以下表现出体铁磁相变。我们认为铁磁相互作用是由β-氢的自旋极化机制引起的。分子轨道计算和核磁共振测量支持了这一机理。通过零场muSR测量，在低于T_c的温度下观察到自发磁化。为了提高转变温度，研究了π共轭NO自由基的磁性。具有吖啶骨架的NO自由基表现出由π电子云重叠引起的分子间铁磁相互作用（McConell模型）。(2)嘧啶-过渡金属配合物的磁性为了研究配位到芳香环间位的过渡金属离子的磁相互作用，研究了各种嘧啶-过渡金属配合物的磁性。结果发现，协调模式，而不是协调位置（间位）决定的磁相互作用。在Cu^2+的情况下，轴向/赤道配位产生铁磁相互作用，赤道/赤道配位产生反铁磁相互作用。当采用小尺寸无机阴离子时，一些配合物表现出弱铁磁性。（嘧啶）_2CoX_2（X=Cl，Br）具有手性晶体结构，表现出弱铁磁性。