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

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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.