High-Spin Building Blocks for Molecule Based Magnets with Ferromagnetic Interaction based on Double Exchange

为了建立一类新的基于分子的磁体，需要能够在顺磁中心之间实现强铁磁相互作用的分子构建块(合成子)。这个研究项目是基于双交换的概念，它在混合价系统中传播强的铁磁相互作用。混合价面共享八面体中电子离域的概念将从双核和三核(零维)络合物扩展到一维链状化合物。选择新的配体2，6-二羟甲基苯酚和硫衍生物合成以面共享方式桥联的两个金属离子的双核分子合成子。这种新型的金属配位体能够通过一组O_3或S_3配位体在两侧与其他金属离子配位，从而形成一维链。在混合价系统中，基态的电子在整个链上离域。这种非定域化应该通过伴随一维电导的双交换机制导致强的铁磁相互作用。磁性和电性的转换行为的可能性是由金属到金属的电荷转移吸收给出的，该吸收对应于在没有铁磁相互作用和导电性的情况下激发到局域电子态。

In order to build a new class of molecular based magnets, molecular building blocks (synthons) which allow for strong ferromagnetic interactions between their paramagnetic centers are needed. This research project is based on the concept of double exchange which is known to propagate strong ferromagnetic interactions in mixed valence systems. The concept of electron delocalization in mixed valence face-sharing octahedra will be extended from bi- and trinuclear (zero-dimensional) complexes to one-dimensional chain compounds. The new ligand motive 2,6-dihydroxymethylphenol and the sulfur derivatives is chosen in order to synthesize binuclear molecular synthons with two metal ions bridged in a face sharing fashion. This novel metallo-ligand is capable to coordinate on both sides to other metal ions by a O3- or S3-ligand set to build one-dimensional chains. In the mixed valence systems, a ground state is expected with electrons delocalized over the whole chain. This delocalization should lead to a strong ferromagnetic interaction by a double exchange mechanism accompanied by one-dimensional electric conductivity. The possibility of a switching behaviour of the magnetic and electrical properties is given by the metal-to-metal charge transfer absorption which corresponds to an excitation into a localized electronic state without ferromagnetic interactions and electrical conductivity.