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

我们建议合成由许多顺磁性过渡金属中心（如Mn2+， Cu2+, Co2+, Fe3+）取代的新型多氧钨酸盐分子。我们的重点是过渡金属离子与“超空腔”和不稳定的多氧阴离子配体[a-H2P2W12O48]12-的相互作用。材料将通过x射线衍射、单晶SQUID磁强计、热容测量、变频高场EPR和NMR以及光谱学，结合理论计算进行表征。这是第一个旨在详细了解这种相互作用的研究。我们期望从根本上发现具有同样新颖磁性质的新型多氧阴离子结构。过渡金属与空腔多金属氧酸盐的相互作用使得磁性金属离子簇的结合成为可能。多氧阴离子与几个顺磁性过渡金属离子接近，表现出交换偶联，可能导致大的自旋基态。在这类化合物中，多金属酸氧基质可被认为是包裹并因此隔离过渡金属的磁性团簇的抗磁性宿主。

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.