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

我们建议合成被众多顺磁性过渡金属中心（例如 Mn2 、 Cu2 、 Co2 、 Fe3 ）取代的新型多钨酸盐分子。我们的重点是过渡金属离子与“超空间”且不稳定的多氧阴离子配体 [a-H2P2W12O48]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 以及光谱学以及理论计算进行表征。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的磁性的根本新颖的多氧阴离子结构。过渡金属与缺位多金属氧酸盐的相互作用允许结合磁性金属离子簇。多氧阴离子与几个靠近的顺磁过渡金属离子表现出交换耦合，可能导致大的自旋基态。在此类化合物中，多金属氧酸盐基质可被认为是封装并由此隔离过渡金属磁性簇的抗磁性主体。

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.