Design and Preparation of an Organic Magnetic Metal using Novel pi-Electron System

有机磁性金属的开发是分子磁学研究的热点之一。在这样的自旋系统中，需要传导电子和局域自旋之间的自旋关联。我们设计了一系列作为候选分子的开壳给体作为这种自旋系统的组成部分。开壳施主是由一个施主和一个自由基单元构成的，当发生单电子氧化时，它们相互连接，形成一个交叉共轭的pi-体系。通过碘处理，在四氢呋喃溶液中生成了开壳供体的阳离子自由基。对它们的ESR光谱测定表明，阳离子二自由基均为基态三重态。分子轨道计算显示了它们独特的电子结构：它们有两个不同轨道能量的正交单占据分子轨道(SomOS)。其中一个自组织元的系数分布在整个分子上，而另一个自组织元的系数只集中在自由基单元上。人们认为，在保持两个索莫人的系数的网站上出现了巨大的正向交流互动。我们还制备了以两个硝基氮氧化物为自由基单元，以四苯基苯二胺为给体单元的开壳给电子体。ESR研究表明，它们通过单电子氧化将基态的多重数从单态转变为四态。这些结果表明，这些开壳供体满足有机磁性金属组分的要求之一。

Development of organic magnetic metals is one of the most interest investigation for molecular magnetism. In such spin system, it is required a spin correlation between conduction electrons and local spins. We designed a series of open shell donors which are candidate molecules as components of such spin system. The open shell donors are constructed with a donor and a radical unit and they are connected so as to become a cross-conjugate pi-system when one-electron oxidation takes place. Cationdiradicals of the open-shell donors were generated in THF solution by treating with iodine. ESR spectra measurement of them indicated the cationdiradicals are all ground state triplet species. Molecular orbital calculation appeared an unique electronic structure of them to us as follows : They have two orthogonal singly occupied molecular orbitals (SOMOs) with different orbital energies. While coefficients of one SOMO of them distribute over the whole molecule, that of the other one localize only on the radical unit. It is considered that large positive exchange interaction arises at the site hold the coefficients of two SOMOs. We prepared also an open-shell donor composed of two nitronyl nitroxides as the radical unit and tetraphenylphenylenediamine as the donor unit. The ESR study showed that they changed the ground state multiplicity from singlet to quartet through one-electron oxidation. These results indicate that these open-shell donors satisfy one of the required conditions for the components of organic magnetic metals.