Syntheses and new development of nano scale magnetic molecules

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High spin molecules with an easy-axis type anisotropy are attracted much interest because they show very slow thermal relaxation of magnetization at very low temperature, and behave as single-domain magnet. Such molecules are classified as single-molecule magnets (SMMs). Furthermore, it is possible to observe macroscopic quantum tunneling of magnetization (QTM) due to their discreet spin energy levels. The relaxation phenomenon via quantum process was first observed in dodecanuclear manganese cluster ([Mn12]) as steps with constant intervals of magnetic field in a magnetic hysteresis roop. The study of QTM is important for not only fundamental and theoretical study of quantum physics, but also for the possible applications for quantum computing. We have studied to prepare multinuclear metal complexes with high-spin ground states. In this research project, we applied our synthetic strategies to the preparation of SMMs and prepared following complexes. (1) Hetero-metal SMMs : Syntheses o … More f hetero-metal complexes have been believed to prepare bridging ligands having coordination sites suitable for different metal ions. We have found that reactions of tridentate Schiff bases with two different metal ions yielded hetero-metal complexes in one-pot syntheses. [Mn^<III>Cu^<II>], [Mn^<III>_2M_2] (M=Cu and Ni), and [Mn^<III>_2Tb^<III>_2] have high-spin ground states and have been proven to be SMMs by ac magnetic susceptibility measurements. (2) Mixed valent manganese oxide with a Perovskite structure showed interesting physical properties due to itinerant electrons in solids. We have found that reactions of pentacoordianted Schiff base ligands with Mn and Cu ions yielded homo and hetero-metal large cluster molecules having oxide bridged metal cores. A homo-metal complex of [Mn^<III>_<12>Mn_V] has mixed valent thirteen manganese ions some of which are bridged by oxide ions. This molecule show quasi-reversible four-steps four-electron redox waves and one and two oxidation states were isolated, and their structures and magnetic properties were studied. The systems are unique methods to prepare oxide molecular clusters, and this synthetic methods help to explore new complex molecule which might show interesting solid state properties due to mixed valence. Less