Synthesis and Structural Characterization of Transition Metal-Substituted Polyoxoanions and Investigation of Their Unique Magnetic Properties

我们建议合成新型的多钨酸盐分子取代的许多顺磁性过渡金属中心（如Mn 2+，Cu 2+，Co 2+，Fe 3+）。我们的重点是过渡金属离子与“超缺位”和不稳定的多氧阴离子配体[a-H2 P2 W12 O 48]12-的相互作用。这些材料将通过X射线衍射、单晶SQUID磁力测定、热容测量、变频高场EPR和NMR以及光谱学与理论计算相结合来表征。这是第一项旨在详细了解这种相互作用的研究。我们期望发现具有同样新颖磁性的新型多氧阴离子结构。过渡金属与缺位聚氧乙烯酸盐的相互作用允许并入磁性金属离子的簇。聚氧阴离子与几个顺磁性过渡金属离子在密切接近表现出交换耦合，可能导致大自旋基态。在这样的化合物中，聚氧乙烯酸盐基质可以被认为是抗磁性主体，其包封并由此隔离过渡金属的磁性簇。

We propose to synthesize novel polyoxotungstate molecules substituted by numerous paramagnetic transition metal centers (e.g. Mn2+, Cu2+, Co2+, Fe3+). Our focus is on the interaction of transition metal ions with the 'super-lacunary' and labile polyoxoanion ligand [a-H2P2W12O48]12-. The materials will be characterized by x-ray diffraction, single crystal SQUID magnetometry, heat capacity measurements, variable frequency-high-field EPR and NMR, and optical spectroscopy, combined with theoretical calculations. This is the first study aimed at a detailed understanding of this kind of interaction. We expect to discover fundamentally novel polyoxoanion structures with equally novel magnetic properties. Interaction of transition metals with lacunary polyoxometalates allows to incorporate clusters of magnetic metal ions. Polyoxoanions with several paramagnetic transition metal ions in close proximity exhibit exchange-coupling, possibly leading to large spin ground states. In such compounds the polyoxometalate matrix may be considered a diamagnetic host encapsulating and thereby isolating magnetic clusters of transition metals.